PROFILE

Nestling in the sylvan environs of the Brahmaputra valley where the beautiful

rendezvous of water and land throws up myriad colours, Numaligarh Refinery

Limited (NRL), which was set up at Numaligarh in the district of Golaghat (Assam)

in accordance with the provisions made in the historic Assam Accord signed on 15th

August 1985, has been conceived as a vehicle for speedy industrial and economic

development of the region.

The 3 MMTPA Numaligarh Refinery Limited was dedicated to the nation by the

erstwhile Hon'ble Prime Minister Shri A. B. Vajpayee on 9th July, 1999. NRL has

been able to display creditable performance since commencement of commercial

production in October, 2000. With its concern, commitment and contribution to

socio-economic development of the state combined with a track record of continuous

growth, NRL has been conferred the status of Mini Ratna PSU.

The present authorized capital of the company is Rs. 1000 crores and paid up capital

is Rs. 735.63 crores. The shareholding pattern as on 31-03-2006 is given below :

 

Bharat Petroleum Corporation Limited :: 61.65%

Govt. of Assam :: 12.35%

Oil India Limited :: 26.00%

Total :: 100%

 

Product Range : Our product range includes LPG, Naphtha, Motor Spirit ( MS),

Aviation Turbine Fuel ( ATF)Superior Kerosene Oil ( SKO)High Speed Diesel

(HSD), Raw Petroleum Coke ( RPC ) Calcined Petroleum Coke ( CPC) & Sulphur.

Retail Segment : Strategic decision was taken to enter into the Retail Distribution

segment. Permission was received from Govt. of India to market MS & HSD through

a chain of 510 Retail Outlets in a phased manner. Hitherto, scores of retail outlets,

aptly christened 'Energy Stations' have already been commissioned in the North East

and other parts of India and the process continues.

Commitment to the community : NRL is conscious of the fact that the ongoing

process of economic reforms is irreversible and the challenge of change on all facets

of business and environment is inevitable. So is the fact that the real purpose of

business is human well being. This dictum remains the driving force of all our social

commitments. In keeping with this ideology, the company has both spawned and

sponsored a succession of social initiatives which entail such diverse activities as

providing relief to upgrading skill and productivity of the beneficiaries

 

 GENESIS

 

Proposal for a Refinery included in "Assam

Accord" as a part of Government of India's

offered economic package

:: August 15, 1985

IBP Co. Limited appointed as implementing

agency

(Equity Structure IBP : 51%, GOA: 10%,

Public : 39%)

:: June 23, 1989

Environmental clearance received :: May 31, 1991

EIL Appointed as Prime Consultant :: August 28, 1992

Foundation stone laid by former Prime Minister

Shri P V Narasimha Rao

:: July 3, 1992

CCEA( Cabinet Committee of Economic

Affairs) approval

Accorded

:: July 15, 1992

Numaligarh Refinery incorporated :: April 22, 1993

BPCL inducted as major promoter BPCL : 32%,

IBP:19%, GOA : 10%, Public : 39%

:: June 2, 1995

Approved Commissioning :: April, 1999

Numaligarh Refinery dedicated to the Nation by

Hon'ble Prime Minister Shri A. B. Vajpayee

:: July 9, 1999

Commencement of Commercial Operations :: October, 2000

NRL becomes subsidiary of BPCL :: March, 2001

 

 LOCATION

 

::Numaligarh Refinery and its township are well connected by air, road and

rail.

:: The nearest airport is Jorhat, 70 km away from NRL site. Indian Airlines

and Jet Airways operate from/to Jorhat, four days a week.

:: Road distance from Guwahati to Numaligarh is 250 km through NH-37

towards east. It takes around 5 hours by luxury coaches that operate daily

in the morning and afternoon.

:: The nearest railhead is at Furkating Jn, 35 km from NRL which is

approachable by a hired taxi.

:: Temperature ranges from 7 to 24 degree celsius during winter and 18 to 35

degrees celsius in summer.

 

 CORPORATE VISION

To be a vibrant, growth oriented energy company of national standing and global

reputation having core competencies in Refining and Marketing of petroleum

products committed to attain sustained excellence in performance, safety standards,

customer care and environment management and to provide a fillip to the

development of the region.

 

 CORPORATE MISSION

 

Develop core competencies in Refining and Marketing of petroleum

products with a focus on achieving international standards on safety,

quality and cost.

Maximize wealth creation for meeting expectations of stakeholders.

Create a pool of knowledgeable and inspired employees and ensure their

professional and personal growth.

Contribute towards the development of the region.

 

 CORPORATE OBJECTIVE

 

To excel in its performance, NRL would strive to:

Maximise refinery capacity utilisation and optimise product pattern by

efficient refinery operation.

Ensure smooth and timely evacuation of products, create a sound customer

base and necessary marketing infrastructure.

Achieve highest standards in product quality, safety, health and

environment protection.

Manage and operate the facilities in an efficient and cost effective manner

for generation of adequate internal resources.

Inculcate best business practices through the use of ERP and E-

Commerce.

Focus on development and growth of Human Resource through proper

training and career planning.

Plan for production and marketing of low volume, high value products.

Remain at the technological forefront by continuous upgradation of in-

house expertise and absorption of the latest technologies.

Establish strong corporate identity and brand equity.

Facilitate economic and industrial development of the region.

 

 MAJOR UNITS

 

Crude & Vacuum Distillation

CDU Capacity :: 3.0 MMTPA

Designed By ::Engineers India

Limited

Commissioned :: April’1999

VDU Capacity :: 1.32 MMTPA

Designed By ::Engineers India

Limited

Commissioned :: April’1999

Delayed Coker Unit

Capacity :: 0.306 MMTPA

Designed By ::Engineers India

Limited

Commissioned :: Sept’1999

Hydrogen Unit

Capacity :: 38000 TPA

Licensor ::

HALDOR

TOPSOE,

Denmark

Commissioned :: Feb’2000

Hydrocracker Unit

Capacity :: 1.1MMTPA

Licensor :: CHEVRON,USA

Commissioned :: June’2000

Sulfur Recovery Block

Capacity :: 4000 TPA

Designed By ::Engineers India

Limited

Commissioned :: July’ 2000

Coke Calcination Unit

Capacity :: 0.104 MMTPA

Licensor :: SVEDALA,USA

Commissioned :: May 2004

Motor Spirit Plant

Capacity :: 225 TMTPA

Process licensor :: M/s AXENS France

Consultant ::Toyo Engineering (I)

Ltd.

Commissioned ::

Naptha hydrotreating

unit : June 2006

Catalytic Reforming

unit : July 2006

KILN

The function of kiln is to calcine powdered coke.

The rotary kiln is 2895 mm diameter inside of shell, 53350 mm long and was shipped

in 3 sections for field welding.

The kiln is supported on two carrying station.

The feed end of the shell has a conical end and is fitted with a segmented leaf air seal.

The discharge end of the shell has a straight end fitted with a segmented leaf air seal

and an air cooled nose ring.

The kiln is driven by a spur ring gear and reducer powered by an AC variable

frequency motor.

The kiln is equipped with an emergency drive powered by a diesel engine. The

emergency drive includes a coupling which limits the rollback speed of the drive

components.

The kiln speeds are 1.25 RPM normal and 1.80 RPM maximum at full production.

The kiln is sloped 30 mm per meter (5.5% grade).

The kiln rotation is counter-clockwise as viewed from the discharge end.

COMPONENT DESCRIPTION OF KILN

Tires

o Pier no. 1, Plain 3595 mm OD X 560 mm Wide

o Pier no. 2, Thrust 3595 mm OD X 560 mm Wide

Carrying Rollers

o Piers nos. 1 and 2 1130 mm X 610 mm Wide

Carrying Station Bearings

o Piers nos. 1 and 2 410 in Diameter X 480 in Long

Thrust Rollers

o Pier no. 2 914 mm Diameter X 152 mm Face

Thrust Roller Bearings Spherical Roller

Ring Gear Spur

217 Teeth, Module 20

203 mm Face

4340 mm Pitch Diameter

2400 mm Center Distance

Pinion Spur

23 Teeth, Module 20

203 mm Face

460 mm Pitch Diameter

Main Reducer Parallel Shaft

Triple Reduction

Main Motor 30 kW, 1000 RPM

AC Variable Frequency

Emergency Drive 3 kW, 1800 RPM

Electric Motor

COOLER

The function of the cooler is to cool the Calcined petroleum coke.

The rotary cooler is 2.59 m diameter inside of shell, 24.384 m long and was shipped

in two (2) sections.

The cooler is supported on two carrying stations.

The feed end of the shell has a straight end.

The discharge end of the shell has a straight end and a trammel section.

The cooler is driven by a spur ring gear and reducer powered by an AC variable

frequency motor that will be furnished by purchaser.

The cooler is suggested to be equipped with an emergency drive powered by an

electric motor connected to an emergency power net. The emergency drive shall

include a coupling that limits the rollback speed of the drive components.

The cooler speeds are 3.5 RPM normal and 4.25 RPM maximum at full production.

The cooler is sloped 41.67 mm per 1000 mm (2.386° degree).

The cooler rotation is counterclockwise as viewed from the discharge end.

COMPONENT DESCRIPTION OF COOLER

Tires

o Pier no. 1, Plain 2983 mm OD X 241 mm Wide

o Pier no. 2, Thrust 2983 mm OD X 241 mm Face Wide

Carrying Rollers

o Piers nos. 1 and 2 610 mm X 292 mm Wide

Carrying Station Bearings

o Piers nos. 1 and 2 Spherical Roller Bearing

Thrust Rollers

o Pier no. 2 305 mm Diameter X 76 mm Face

Thrust Roller Bearings Spherical Roller

Ring Gear Spur

202 Teeth, 1.5 Diametral Pitches

104 mm Face

3420.53 mm Pitch Diameter

1862.665 mm Center Distance

Pinion Spur

18 Teeth, 1.5 Diametral Pitches

140 mm Face

304.8 mm Pitch Diameter

Main Reducer Parallel Shaft

Triple Reduction ratio

Main Motor 22 kW HP, 1000 RPM

AC Variable Frequency

Emergency Drive 1.1 kW, 1450 RPM

Electric Motor

INCINERATOR

The function of the incinerator is to burn any volatile matter, products of combustion,

and particulates carried out of the kiln.

The stationary incinerator is a 5486 mm inside diameter by 30937 mm long carbon

steel welded fabrication and was shipped in two sections for field welding.

The incinerator is provided with the following features:

o Two combustion air shrouds with flanged connections for the fan ducts.

o Combustion air inlet pipes welded to the inside of the shell and arranged to

enhance mixing of the combustion air with the kiln exhausts gases.

o Two duct Hoppers one near each end of the incinerators.

o Two access doors.

o Two flanged burner openings.

o Two observation ports.

o Two saddle type supports, one fixed and one free.

o Provision for an infrared pyrometer and thermocouples.

o Provision for outlet draft connection.

o Oxygen analyzer probe.

COMPONENT DESCRIPTION OF INCINERATOR

Supports

o Pier no. 1, Held 4838 mm Long X 600 mm Wide

o Pier no. 2, Free 4838 mm Long X 600 mm Wide

Support Rollers

o Pier nos. 2 180 mm OD X 4594 mm Long

RPC YARD

ROLLER CRUSHER

VIBRATING FEEDER

ROTARY COOLER

ROTARY KILN

SILO

BUNKER HOUSE

BAGGING HOUSE

FLUE GAS

CPC WAREHOUSE

CALCINER OPERATION PROCESS FLOW DIAGRAM

CALCINER OPERATION PROCESS DESCRIPTION

Sized (crushed and screened) Raw Petroleum Coke (RPC) from the storage silos is

fed to the kiln feed bin. The RPC feed rate from the feed bin to the kiln is controlled

by a weight feeder. The weight feeder discharges the RPC into the duplex air seal/gate

which is turn discharges it through the feed pipe and into the rotary kiln. The RPC

feed rate to the rotary kiln can be controlled and varied from the main control room to

suit operating requirements.

CALCINATION-

The rotary kiln is where calcinations and densification of the RPC take place and

product quality is controlled. The interior of the rotary kiln is refractory lined. It is

rotated through an ACVF drive which allows the operator to vary the speed to suit

Calcined coke quality and capacity. The rotary kiln includes the following equipment:

a. Refractory

b. Riding Rings

c. Support Roller Station

d. Drive Train including

i. Ring Gear

ii. Pinion

iii. Parallel Shaft Speed Reducer

iv. Motor

v. ACVF Drive Unit

vi. Auxiliary drive for Start Up, Maintenance and Emergencies

e. Feed and Discharge End Air Seals

Rotary kiln coke calciners give the operator the flexibility of controlling operation

conditions such as residence or retention time, temperature gradient and heat up rate.

The process heat for the rotary kiln system is from 2 sources:

a) The kiln firing system Gas or Oil Firing.

b) Burning a percentage of the evolved volatile matter in rotary kiln.

Air required for the complete combustion of the fuel (gas or oil), is provided by the

primary and shape air fans introduced through the kiln burner. Additional fuel

combustion air, if required, is provided by secondary air fan introduced through the

firing hood.

Air for the partial combustion of volatile matter in kiln is provided by the secondary

air fan introduced through the firing hood.

Calcined coke is discharged from the kiln through the firing hood and transfer chute

into the rotary cooler.

CALCINED COKE COOLING-

The Calcined coke is cooled in the rotary coolers which consist of the following:

a. Refractory

b. Riding Rings

c. Support Roller Stations

d. Drive Train including

i. Ring Gear

ii. Pinion

iii. Parallel Shaft Speed Reducer

iv. Motor

v. ACVF Drive Unit

e. Feed and Discharge End Air Seals

Coke cooling in the rotary cooler is via direct water quenching provided by the

quenching water cooling system. Two (2) spray lances are located at the feed end of

the cooler, one having six (6) spray nozzles capable of delivering 20 LMP of water at

240 kPa each, the second having six (6) spray nozzles capable of delivering 8 LMP of

water at 240 kPa each. A third spray lance having two (2) nozzles capable of

delivering 10 LMP of water at 240 kPa each is located downhill from the feed end

lances and a fourth spray lance having one (1) nozzle capable of delivering 25 LMP

of water at 240 kPa is located at the discharge end of the cooler.

An optical pyrometer aimed into a thermowell through the cooler shell, senses coke

temperature in the cooler 5484 mm from the feed end and controls the amount of

water from the feed end spray lances. A second optical pyrometer aimed into a

thermowell through the cooler shell, senses the coke temperature in the cooler 14934

mm from the feed end and controls the amount of water from the third spray lance

located 11889 mm from the feed end of the cooler. A thermocouple located in the

cooler discharge hood senses coke temperature being discharged from the cooler and

control the fourth spray lance mentioned above located 610 mm from the discharge

end.

Calcined coke from the rotary cooler is generally in the 93 to 148°C range and is

discharged into the product material handling system.

The cooling gas stream from the rotary cooler is continually exhausted from the

cooler discharge hood by the cooler exhaust fan. Gases pulled from the cooler pass

through the multiclone dust collector, through the cooler exhaust fan and delivered to

the incinerator. Particulates collected by the multiclone dust collector are discharged

to the product material handling system.

Incinerator and WHRB Gas Handling System Flow Diagram

FLUE GAS

SCREEN

INCINERATOR

EVAPORATOR

SECONDARY SUPER HEATER

PRIMARY SUPER HEATER

ECONOMIZER

BAG FILTER HOUSE

STACK

Incinerator and Gas Handling System-

Unburned volatile matter, process gasses and airborne solids (coke dust) are drawn

from the rotary kiln, through the kiln feed hood and into the incinerator by the ID Fan

or by natural draft. Natural draft through the system is controlled by adjusting the by-

pass guillotine damper position, if the waste heat boiler is to be by-passed. If the

waste heat boiler is utilized, the ID Fan must be used to vent the system gases to the

stack. In this case, the by-pass guillotine damper is closed, the guillotine damper in

the duct to the waste heat boiler open and either the ID Fan speed or fan damper

setting used to control the negative pull of gases from the system.

Volatile matter and coke dust are burned in the incinerator. Air is required for

combustion in the incinerator is provided by the combustion air fans. The incinerator

is equipped with two (2) (gas or oil) burner firing systems. Combustion air for the

burners is provided by the incinerator primary air fans. The firing systems are used to

help bring the incinerator up to process temperatures and must be used when coke

feed is started to the rotary kiln to insure the ignition and combustion of volatile

matter and coke dust being drawn into the incinerator.

Hot gases leaving the incinerator can either be vented to atmosphere through the stack

or drawn through the waste heat boiler for steam generation prior to being vented

through the stack. As mentioned above, at times when the waste heat boiler is not

operational, the system is vented by natural draft through the stack by modulating the

by-pass guillotine damper. During this time, the guillotine damper in the duct to the

waste heat boiler is closed. When the waste heat boiler is operational, the system draft

is maintained by the ID Fan speed or fan damper setting. During this time, the

guillotine damper in the duct to the waste heat boiler is open, the by-pass guillotine

damper closed.

NORMAL START-UP OPERATION

During system shutdowns, and prior to re-starting the calcinations system, a complete

mechanical inspection of all equipment (including refractory) should be carried out, as

well as a check that all instrumentation and control loops are functioning properly.

Until system start-up air flow and pressures, flue gas flows, and material and gas

stream temperatures are established, it is recommended that the following automatic

control loops remain in the manual mode:

a. Firing Hood Draft Indication Controller (PIC3514), which control the I.D.

Fan speed or damper position, or in by-pass guillotine damper position.

b. Gas Stream Indication Controller (AIC3901), which control the position of

the Incinerator Combustion Air Fan Damper (FCV3901 & 3902), and in

turn, the Excess Oxygen Level (AI3901) at incinerator outlet.

c. Temperature Indication Controller (TIC3901), which controls the position

of Kiln Secondary Air Fan Damper (TCV3501), and in turn, the

Incinerator Inlet Temperature (TI3901).

d. Temperature Indication Controller (TIC3902), which controls the position

of Incinerator Primary Air Fan Damper (FCV3502 & FCV3503), and in

turn, the Incinerator Outlet Temperature (TI3902).

1. Start the following equipment:

a. Guillotine damper Cooling Fan.

b. Feed Pipe Cooling Fan.

c. Closed Loop Water Cooling System Pumps if applicable.

Before, starting, the valve in the line of pump should be open, and the valve in

line of the redundant/off-line pump should be closed.’

2. If the through the waste heat boiler, raise the Guillotine Damper to the waste heat

recovery boiler and close the by-pass Guillotine Damper. Start the I.D. Fan and adjust

the fan speed or fan damper, as required, to create -0.03 kPa Firing Hood Draft.

3. Start Kiln Burner System selecting gas firing. The Primary Air Fan, Secondary Air

Fan and Shape Air Fan will start automatically after 10 and 20 second delays and take

the system through the purge cycle. Following the purge cycle low fire burner ignition

will take place. Adjust I.D. Fan speed or fan damper to maintain 0.01 to -0.02 kPa

Firing Hood Draft.

4. Making slight increase in Kiln Primary Air Flow and Kiln Burner Gas Flow, raise

the Kiln Exit Gas Temperature 20°C/h to 300°C. The I.D. Fan speed or fan damper

must be adjusted while making these changes, to maintain a -0.01 to -0.02 kPa Firing

Hood Draft. The system exit gas must be monitored throughout the start-up and Kiln

Secondary Air Fan Damper open when and as required, to maintain a minimum 1.0%

excess O2 at the outlet of the incinerator. As air flow from the Kiln Secondary Air

Fan is increased to maintain the required excess O2, the I.D. Fan speed or fan damper

is adjusted to maintain the -0.01 to -0.02 kPa Firing Hood Draft.

5. When the 300°C Kiln Exit Gas Temperature is reached, start intermittent rotation

of the rotary Kiln, rotating it 90° every 15 minute.

6. Continue increasing the Kiln Exist Gas Temperature at a rate of 20°C/h, by

effecting incremental change Kiln fuel gas flow, and to the kiln primary and

secondary air flow. Upon reaching 500°C Kiln Exit Gas Temperature, start Kiln Feed

and Discharge End Nose Ring Cooling Fans. At the same time, being continuous

rotation of kiln at the slowest possible speed, using the main drive electric motor.

Maintain -0.01 to -0.02 kPa Firing Hood Draft, and the minimum of 1.0% Excess O2

at the incinerator outlet.

7. When the kiln exist temperature reaches 560°C, adjust the Kiln Secondary Air Fan

Damper, and the I.D. Fan speed or damper to maintain 1.0% Excess O2 and -0.03 kPa

Firing Hood Draft. Start the Incinerator Primary Air Fan, and adjust Dampers to 20%

open. Start the Incinerator Air Fans, and adjust Dampers open, if required, to increase

the Excess O2 to 4.0 to 6.0%. Adjust the I.D. Fan speed or damper, as required,

maintain a -0.03 kPa Firing Hood Draft.

8. Ignite the Incinerator Burner and increase the Incinerator Exit Gas Temperature

45°C/h. Adjust Incinerator Combustion Exit Air Fan Dampers as required to maintain

4.0 to 6.0% excess O2. Adjust I.D. Fan speed or fan damper to maintain -0.03 kPa

Firing Hood Draft. Increase Kiln speed to 0.5 rpm.

9. Start the Feed Duplex Air Seal. Start the kiln feed belt conveyor. Start the green

coke weigh feeder with a feed rate of 2.0 T/h. adjust the Incinerator Combustion Air

Fan Dampers to maintain 4.0 to 6.0% excess O2 and the I.D. Fan speed or fan damper

to maintain -0.03 kPa Firing Hood Draft. Continue increasing the Kiln Exit Gas

Temperature at the rate of 45°C/h and increase the green coke feed at the rate of 1.0 to

2.0 T/h. Green coke feed increases must be made so that the 45°C/h Kiln Exist Gas

Temperature increases can be maintained.

10. Start the following equipment:

a. Calcined coke takes away conveyor.

b. Cooler Discharge Airlock.

c. Cooler Dust Collector Airlock.

d. Start rotary cooler, and set cooler speed at 0.5 rpm. Ensure that the cooler

quench water r system is available, when required, to cool product discharging

from the Rotary Kiln.

11. When Calcined coke begins to discharge from the Rotary Kiln into the Rotary

Cooler, the Water Quench spray at the cooler feed end must be opened. Typically,

during system start up, the feed end quench water is controlled manually. In this case,

it’s controlled manually from the DCS, where the Remote/Manual Feed End Control

Valve can be opened, and the flow of quench water regulated to control the coke

temperature. The Cooler Product Discharge Temperature should be maximum 150°C.

after the coke calcining system has reached capacity, and normal operating

conditions, cooling of the coke by the cooler quench water system will be

automatically controlled by temperature Indicating Controllers.

12. Fully Open (100%)Tempering Air Damper, between Cooler Discharge Hood and

Dust Collector.

13. When coke starts discharging from the Rotary Cooler, start the Cooler Exhaust

Fan and close the Tempering Air Damper. Adjust the Cooler Discharging Hood Draft

to -0.05 kPa. At this time the Cooler Discharge Hood Draft Controller should be

placed in the “automatic” mode, and set at -0.05 kPa. The Cooler Dust Collector

Outlet Temperature should be maintained at a minimum 150°C with a maximum of

250°C. as the Cooler Exhaust Fan draws air from the Cooler Discharge Hood, and

exhausts it into the incinerator, the Incinerator Combustion Air Fan Dampers must be

adjusted to maintain the 4.0 to 6.0% Excess Oxygen and if necessary, the I.D. Fan

speed or fan damper adjusted to maintain -0.03 kPa Firing Hood Draft.

14. The approximate Rotary Kiln Speeds, Green Coke Feed Rates and Rotary Cooler

Speeds that are anticipated during start up and normal operation, are as follows:

S.No

.

GREEN COKE

FEED

RATE (T/H)

ROTATION

KILN

SPEED

ROTARY

COOLER

SPEED

1 Start Feed 2.0 0.50 0.50

2 3.0 0.55 0.60

3 4.0 0.60 0.75

4 5.0 0.65 1.00

5 6.0 0.70 1.25

6 7.0 0.75 1.50

7 8.0 0.80 1.75

8 9.0 0.90 2.00

9 10.0 1.00 2.25

10 11.0 1.05 2.40

11 12.0 1.10 2.50

12 13.0 1.15 2.75

13 14.0 1.20 3.00

14 15.0 1.25 3.25

15 16.0 1.30 3.50

16 18.0 1.35 3.75

17 20.0 1.40 4.00

15. When the Kiln Exist Gas Temperature Reaches 800°C, further temperature

increases should be at the rate of 50°C/h, until the normal operation temperature 850

to 1000°C is reached. During this same time period, the Green Coke Feed Rate

increased at the rate of 1.0 to 2.0 T/h, with the Kiln Speed increased per the above

chart. Green Coke Feed increases again should be such that the 50°C/h increase in

Kiln Exit Gas Temperature, Incinerator Outlet Gas Temperature and Incinerator

Outlet Excess Oxygen must be monitored during this period, and adjustments made to

fuel, air flows and the I.D. Fan speed or fan damper, as required, to maintain the

Excess Oxygen Level at 4.0 to 6.0%, and the Firing Hood Draft at -0.03 kPa.

16. After reaching the expected operating temperature ranges for the system, the

Green Coke Feed Rate is increased continually 2.0 t/h, until the desired operating

capacity is reached. As the Green Coke Feed Rate is increased, the Rotary Kiln Speed

should be increased accordingly per above chart.

17. Expected normal operating Parameters with the system producing quality

Calcined coke at capacity, are as follows:

TEMERATURES-

a. Incinerator Outlet Gas Temp. 1050 to 1200°C

b. Incinerator Inlet Gas Temp. 850 to 1000°C

c. Kiln Exit Gas Temp. 850 to 1000°C

d. Firing Hood Temp.(Coke) 1350 to 1450°C

e. Cooler Dust Collector Exit Gas Temp. 170 to 250°C

f. Cooler Product Temp. 120 to 150°C

PRESSURES-

a. Firing Hood Draft -0.02 to -0.03kPa

b. Kiln Exit Draft -0.06 to -0.08kPa

c. Cooler Exit Draft -0.12 to -0.17kPa

d. Dust Coll. Diff. -0.50 to -0.70kPa

SPEED/RATES-

a. Kiln Speed 1.0 to 1.3 rpm

b. Cooler Speed 2.5 to 3.5 rpm

c. Green Coke Feed Rate 14.0 to 16.0 T/h

EXCESS OXYGEN-

a. O2 at Incinerator Outlet 4.0 to 6.0%

18. Upon reaching the expected operating values for the process control variables, all

control loops can be placed in the “automatic” mode. The “actual” operating values,

covering all variables, can only be established once the system has been balanced, and

is producing anode grade quality coke, at rated capacity. To achieve this quality test

results of Calcined coke samples, taken hourly at the cooler discharge, must be

returned to the control room with one hour of sampling. Capacity of the Calcined

coke must be confirmed. With review of this quality/capacity information,

adjustments can be made to the control variables to achieve optimum system

operating conditions.

KILN

DISCUSSION-

This outline is prepared to develop a maintenance program that will avoid the serious

problem which can occur when equipment is not properly maintained. Daily

inspections are by far the most critical items in the plan. The responsibility for these

inspections should be assigned to the same man each day, so he can easily spot

changes in the Klin’s and Rotary Cooler operation which are signs of impending

problems. If a change is noted, the cause should be determined and corrective action

taken.

DAILY INSPECTIONS-

Motor Amperage- Is it within normal range? A gradual increase can be a sign of a

bearing problem or heavy thrusting of one or more roller assemblies. Large

fluctuations can indicate a wrapped Kiln shell.

Discharge End Seal- Check for gaps and lose hardware.

Nose Ring Refractory- It’s worn damaged or missing sections.

Kiln Shell- To check any obvious distortion, discoloration or hot spots.

Carrying Rollers Axial Position- Are the rollers thrusting against the downhill thrust

face of the kiln bearing? This can be observed by opening the pipe plug in the side of

the bearing house. An indicator mounted on each down hill roller bearing housing

12mm from the roller face can be used to monitor the thrust face wear on the carrying

roller bearing.

Carrying Rollers Bearings Temperature- Feel the housings. If any housing is

abnormally warm, check and record the shaft temperature and oil sump temperatures

at regular intervals.

Carrying Rollers Bearings- Check the oil distribution on the roller shaft through the

bearing housing inspection cover and bearing housing oil level.

Carrying Rollers Bearings Seals – Check the shaft for oil and the seals for any sign

of damage. If a problem is noted, frequently check the housing oil level until the seal

is repaired.

Cooling Water Flow and Temperature- Check flow indicators and thermometers. If

the water temperature rises, closely monitor bearing shaft temperatures.

Carrying Roller O.D. – Check the roller spalling, crowned, developing groves or

tapered surfaces.

Tire O.D. - Check the tire spalling.

Tire and Roller- Check the contact pattern and their adequate lubrication.

Tire Retainer Blocks- Check for wear and cracked welds.

Thrust Roller Surface Conditions – Check the wear pattern even across the face.

Kiln Shell Axial Position- Check the Kiln floating properly or thrusting against one

of the thrust roller.

Gear contact Pattern – Check the contact pattern.

Gear Lubrication- Is it even across the full face.

Driver Sound- Check the change in sound.

Feed End Seal- Check the gap and loose hardware.

Emergency Drive- Test runs the drive.

WEEKLY INSPECTION

Bolts – Check for tightness.

Gear- Check the oil level.

MONTHLY INSPECTION

Gear and Pinion Pitch Line Separation- Check the separation between the scribed

gear and pinion pitch lines. If the two lines overlap, make an immediate alignment

correction to prevent damage to gear set.

Tire Creep- After the kiln has reached operating temperature, mark the tire and the

kiln shell at a point. After 60 revolutions of the kiln, measure the distance between the

two marks. Divide the distance by (60 * 3.14) to obtain the hot diametral clearance

between the tire pads and the bore of the tire. A diametrical clearance in excess of

0.1% of kiln diameter is not acceptable.

A large hot clearance can cause refractory problem. The high clearance and resulting

shell ovality are usually caused by over heating the kiln shell under the tire.

Gear Tangent Plates- Check for cracked weld.

Pinion Bearing Lubrication- Add grease to each pinion bearing pillow block.

Thrust Roller Bearing Lubrication- Add grease.

QUARTERLY SERVICE

Tire Bore- Check the lubrication.

SEMI-ANNUAL SERVICE

Carrying Roller Bearing—Change oil.

Gear Guard - Change oil.

Pinion Bearing – Change grease.

ANNUAL INSPECTIONS

Rotary kilns and cooler are rugged, relatively simple machines, and as such are best

suited to a preventive maintenance program than to a remedial one. The most

important objective of such a maintenance effort is to assure that the equipment has

not been misaligned by settling or tipping of the foundation which, if not corrected,

will create problems with the kiln or cooler shell, the tires, the carrying and thrust

rollers, and with the main gear and pinion.

PIERS, CHECK ELEVATION AND ALIGNMENT-

Proper shutdown procedure should be followed until the kiln or cooler is cold.

Alignment checks should start with the top machined surfaces of the carrying station

frames. The frames at each pier should be examined to determine that the elevation is

the same as when initially installed, that the slope is still correct, and that the frame is

level in the transverse direction. If deviations in slope and transverse level are found,

tipping of pier is indicated. Depending upon the degree of deviation, through should

be given to resetting the station frame to the proper slope and level.

After carrying station frame elevations have been checked, the longitudinal centerline

of the frames should be confirmed.

KILN, CHECK ALINGNMENT-

Each carrying roller’s position should be checked in relationship to the kiln centerline.

Measurements are taken from the carrying roller face on both the high and low sides,

to the true centerline of the frame that have been previously confirmed or established.

A straight edge is laid across the frame centerline for taking these measurements

which are recorded for use in the final alignment of the roller.

Next, the kiln should be raise off the carrying roller at each station and the diameter of

the tires and rollers measured. The clearance between the O.D of the tire pads and the

I.D of the tire should also be measured. If this clearance is excessive, shimming of the

tire pads is recommended.

Find the horizontal center of the tires and carrying rollers on both sides and measure

the vertical centre distance between all tires and rollers. Record these reading.

The thrust carrying station is always used as the control point. Check the mesh of the

gear and pinion to determine whether the present kiln or cooler elevation at this

station is satisfactory or if the kiln shell should be raised or lowered to correct

unsatisfactory gear and pinion meshing. Required adjustment in elevation can be

determined from roller and tire diameters, vertical distance between centers of tire and

rollers and the distance between the face of the roller and the kiln centerline.

All carrying roller bearing should be checked for shims previously inserted between

the bearing housing and the station frame. Because these shims change elevation their

thickness must be recorded.

After all above measurements taken, simple calculation are carried out to determine

the proper setting dimension between each carrying roller face and the kiln centerline.

Comparing these calculated dimensions with the measured dimension will give the

distance each roller will have to be adjusted. Normally this adjustment would be made

after the kiln can be jacked off the rollers at each pier and the roller adjusted prior to

resuming operation. Dial indicators are used to verify high and low side adjustments

made to each carrying roller. If the carrying rollers require large adjustments be made

in small increments to all rollers rather than pushing each roller the full amount at one

time.

In addition, a visual inspection of the clearance between the tire and the tire retainer

bars should be made. If the clearance is excessive, the tire may have to be

repositioned and new retainer bars installed.

Measure the clearance between the thrust rollers and the thrust tire. Excessive

clearance is an indication that the thrust roller will have to be repositioned or

replaced.

CARRYING ROLLERS, CHECK ADJUSTMENT

With the kiln shell now on centerline and slope, the carrying rollers should be

checked and aligned if necessary.

A perfectly aligned carrying roller is one whose axis is parallel to the axis of rotation

of the kiln shell. Misalignment of the carrying rollers introduces accelerated wear

between the rollers and tires. The degrees of wear, of course, depend on the degree of

misalignment.

The thrust rollers on a kiln are a safety feature. The downhill thrust of the kiln is

absorbed by skewing the carrying rollers and floating the kiln between the thrust

rollers.

When a carrying roller is aligned parallel to the axis of rotation of the kiln, the

carrying roller and shaft will be downhill due to its own weight. The downhill thrust

collar of the carrying roller shaft will bear against the thrust face of the downhill

bearing. If a carrying roller is skewed at all it should be in such a manner that will

relive the load on the thrust roller, and not add to it. Since this means that the carrying

roller must attempt to move the kiln uphill, it follows that the carrying roller must be

forced downhill.

From these two facts, we can see that carrying roller thrust collars should always be

against the thrust face of the down hill bearings. Any shaft not seating against its

downhill thrust face is either floating or is possibly applying downhill thrust to the

kiln which counteracts the uphill thrust being applied by other roller.

All rollers should be thrusting downhill as lightly as possible. However, to adjust the

roller to achieve this condition, the direction of the thrust of each carrying roller

should first be determined. This can be done bye removing the pipe plug in the front

of the bearing housing and observing the thrust collar location relative to the bronze

bearing insert thrust face. Adjust the appropriate bearing inward to force the roller to

move uphill. Back off the outboard nut 0.4mm and the hydraulic jack to push in the

adjusting screw until the nut and washer make contact with the adjusting block.

Tighten the inboard nut after each adjustment to hold the adjusting screw in place.

Wait for 2 or 3 minutes to see if the roller is moving up hill. This would be indicated

by an increase in the clearance between thrust collar and the bronze thrust face.

Continue adjusting in 0.4 mm increments until the roller moves uphill.

To verify that the bearing is actually moving during each adjustment, set the dial

indicators against the bearing housings to physically record the bearing movement. If

the roller does not move uphill after 3mm movement of the bearing, adjustment

should be shifted to the other bearing which should be moved outward. The purpose

of this is to prevent excessive movement of the kiln or cooler centerline alignment.

This can be accomplished by using the hydraulic jack to hold the adjusting screw in

place while backing off the inboard nut using the same incremental movement as

before. When the pressure in the hydraulic jack is removed the horizontal force on the

roller from the tire should be sufficient to push the bearing out. Tighten the outboard

nut when complete.

Make the final adjustment to the bearing that will move the roller downhill with an

inward movement of the bearing. Back off the nut approximately 0.2 mm and use the

hydraulic jack to push in the adjusting screw until the roller moves downhill. If the

coarse adjustment has been done carefully the roller will move downhill with 0.4 mm

bearing movement or less. After final adjustment is completed, make sure to tighten

both nut to hold the adjusting screw position.

When the carrying roller is very close to parallel with the axis of kiln or cooler

rotation, roller response to adjustment could be slow. A dial indicator can be used

against the sides of the carrying roller detecting movement of the roller as soon as it

occurs.

After all rollers have been adjusted, the kiln should float between thrust rollers. Under

these conditions the carrying rollers should be absorbing minimum load and

experiencing the minimum wear possible. Movement of all bearings should be

recorded during the adjustment process. These records will be an aid in maintaining

proper kiln alignment.

It should be noted that all alignment and adjustment work can be carried out while

the kiln is in operation, if the main gear and pinion have been provided with scribed

pitch lines. The pitch line serve as a rough guide to maintain proper engagement while

the alignment is being completed.

Gear Joint Bolts – Check tightness.

Gear and Pinion – Check radial and axial alignment.

Drive - Check alignment.

Gear and Pinion Teeth – Condition.

Carrying Station Frames - Condition.

Refractory - Condition.

Carrying and Thrust Mechanism - Condition.

Thrust Roller Bearings- Change grease.

Water Cooling Coils- Inspect.

INCINERATOR

DISCUSSION

This outline is prepared to develop a maintenance program that will avoid the

serious problem which can occur when equipment is not properly maintained. Daily

inspections are by far the most critical items in the plan. The responsibility for these

inspections should be assigned to the same man each day, so he can easily spot

changes in the Incinerator operation which are signs of impending problems. If a

change is noted, the cause should be determined and corrective action taken.

Refractory- It’s worn damaged or missing sections.

Incinerator Shell- To check any obvious distortion, discoloration or hot spots.

Rollers Axial Position- To check the roller positioned properly to accommodate

incinerator expansion.

WEEKLY INSPECTIONS

Bolts- Check for tightness.

ANNUAL INSPECTIONS

Stationary Incinerator is rugged, relatively simple piece of equipment, and as

such is better suited to a preventive maintenance program than to a remedial one. The

most important objective of such a maintenance effort is to be assuring that the

equipment has not been misaligned by setting or tripping of the foundation which, if

not corrected, will create problems with the incinerator shell, the rollers, support

saddles and refractory.

As a minimum an inspection of the support bases and piers must be carried out

on an annual basis or as frequently as required to insure that the following limitations

are not exceeded before corrective action is taken.

Pier Slope

The maximum axial deviation of the top of the support bases from designated

slope must not exceed 3.0 mm per meter.

If these limitations are exceeded regrouting of the support bases will be

required.

Vertical Pier Displacement

Deviations from specified elevation of any support base must not exceed +/- 6

mm.

If these limitations are exceeded corrections can be made by shimming

between the support saddle weldment and the spacer weldment to raise the

settled support as required.

Piers, Check Elevation and Alignment

Proper shutdown procedure should be followed until the incinerator is cold.

Alignment checks should start with the top surfaces of the support bases. The base at

each pier should be examined to determine that the elevation is the same as when

initially installed, and that is level in all directions. If the deviations in level are found,

tipping of the pier is indicated. Depending upon the degree of deviation, through

should be given to resetting the base plate.

After the base elevations have been checked, the longitudinal centre line of the

supports should be confirmed. To do this, establish on offset centre line along the side

of the incinerator from the first to last support. The offset of the center line should be

at a distance that allows unobstructed visibility along the line, and is equal distant

from the centre lines of the base plates of the two extreme incinerator supports.

Measurement should be taken and recorded from the offset center line to the base

plate center lines of all intermediate supports.

Measurements for the intermediate supports should normally equal the offset

distance at the extreme supports of the incinerator. If all the measurements are not

equal, one or more piers have shifted or an original error in center line makings has

been uncovered. A plot of the offset measurements versus axial spacing of the

supports will indicate which center line marks are out of line. The plot should confirm

the shifted piers found during the elevation check or should indicate the center line

marks that were in error. After any pier corrections or base resetting, new center line

marks should be plainly scribed to replace those which were out of line.

If the center line markings for the two extreme supports were true, any new

marks can be located by measuring the assumed offset distance from the line. If they

were not true, a new offset line should be established, using the two furthest apart

supports having true markings. Or distance can be calculated from the plot using

proportions determined by the similar triangles created between the converging offset

line and the true center line.

Saddle Supports- Conditions

Refractory- Conditions

LUBRICATION

Kiln lubrication-

Ring Gear-

The suggested method of lubricating the ring gear and pinion consists of an oil sump

built into the gear guard with on oiling pinion which meshes with the drive pinion and

transfers the lubricant to the drive gear.

A high grade synthetic lubricant with a polyalphaolefin base stock and a

sulfur/phosphorus extreme pressure (EP) additive and meeting the following

specifications should be used:

AGMA number EP

Viscosity @ 100 °F 12600 to 15400 SSU

Viscosity @ 210 °F 700 to 900 SSU

Pour point (°F) max. -4

Flash point (°F) min. 428

The lubricant must meet all requirements of AGMA 9005 D94 specifications for

extreme pressure lubricants.

After a new kiln has been in service for one month, the oil should be drained and the

reservoir cleaned. Thereafter, the oil should be changed at least every six months.

Carrying Roller Bearings-

The carrying roller bearings are bronze journal type bearings. They are lubricated

with series of oil dippers that lift the oil from the bearing reservoir and drop it on an

oil pan which distributes it over the roller shaft.

Kiln bearings inherently operated at low speeds, high loading and high temperatures,

requiring a heavy duty lubricant. Extreme pressure (EP) gear oils should be avoided

due to potential damage to bronze at high temperatures. Use a high grade synthetic

lubricant with a polyalpholefin base stock and a phosphorus additive with the

following specification:

ISO Viscosity Grade 680

Viscosity @ 100°F 2840 to 3600 SSU

Viscosity @ 210°F 250 to 320 SSU

Pour point (°F) max. -20

Flash point (°F) min. 445

Maximum operation temperature of 250°F.

After a new kiln has been in service for one month, the oil should be drained and the

reservoir cleaned. Thereafter, the oil should be changed at least every six months.

Thrust Roller Bearings-

These anti friction, spherical roller bearings should be lubricated at high grade

synthetic grease that combines a polyalphaolefin base fluid with a lithium complex

soap thickener and a zinc anti-wear additive and meeting the following specifications:

NLGI Consistence No. 1

Penetration, Wkd. @ 77°F 310-340

Drop point 455-490°F

Type soap: Lithium complex

Type oil: Synthetic Base

1500 cSt @ 40°c, 8000 SSU @100°F.

110 cSt @ 100°c, 510 SSU

@210°F.

Lubricate the bearing on a monthly basis. Clean out grease and repack bearings every

12 months.

Pinion Shaft Bearings-

These anti-friction, spherical roller bearings should be lubricated with high grade

lithium complex grease with the following specifications:

NLGI Consistence No. 2 EP

Penetration, Wkd. @ 77°F 265-295

Drop point 400-475°F

Type soap: Lithium

Type oil: Mineral

150 cSt @ 40°c, 750 SSU @100°F.

13 cSt @ 100°c, 70 SSU @ 210°F.

Keep pillow blocks packed from 1/3 to ½ full of grease by adding grease about every

month. At least every three months remove pillow block caps and examine the grease.

If the grease is in good condition it can be used for another three months. Clean out

old grease and repack bearings every six months.

Tire Bore-

When the kiln initially begins operation, the tire bore may be lubricated with a

colloidal graphite and water emulsion system. Description of this method is as

follows:

Lubricants:

Acheson colloids Co. lubricant RD-5, or Castrol Industrial North America, Inc.

Molub-Alloy 491-C, or equalent.

The RD-5 lubricant (or equivalent) is a colloidal graphite water emulsion with a

wetting agent additive, which makes it possible for the lubricant to adhere to the hot

metal surface.

Application: The graphite-water emulsion can be applied with, for example, a

portable pressure tank system which includes an extended nozzle. The lubricant must

be agitated before each application to insure a uniform mixture.

Initially, dilute one part of RD-5 lubricant (or its equivalent) to five part of water.

Apply by spray two times per week on each tire. At each application, spray in the

space between the tire bore and the kiln shell and form both sides of the tire. Spray as

high as possible on the up-turning side of the kiln in the area between 7 o’clock and

12 o’clock positions. Each application is to be continued as the kiln rotates for one

revolution.

After one to two weeks, change the ratio of the lubricant to one part RD-5 (or

equivalent) to ten parts water. Apply two times per week.

Tire and Roller Contact surface-

To reduce the wear between the tire and roller surfaces, a 25mm thick solid graphite

block is set in the lubricator weldment provided for each tire. The blocks are set on

the rollers running on the down side of each tire. The weight of each block is

sufficient to transfer adequate lubricant to the rollers and tire. The lubrication is

continuous and should be checked daily and replaced as required. Use Dixon H-80-D

graphite blocks or Ohio Carbon W-201 or their equivalent.

Low Temperature Operation-

Provisions must be made for below normal temperature by using heating units or

applying lubricants of lower viscosity. Below normal temperatures are those that are

below the pour points of the lubricants being used.

Lubricant condition-

The above lubrication schedule sets minimum requirements. If the lubricant shows

sign of contamination or general deterioration then it should be replaced immediately.

COOLER LUBRICATION

Ring Gear-

The suggested method of lubricating the ring gear and pinion consists of an oil

sump built into the gear guard with on oiling pinion which meshes with the drive

pinion and transfers the lubricant to the drive gear.

A high grade synthetic lubricant with a Polyalphaolefin base stock and a

sulfur/phosphorus extreme pressure (EP) additive and meeting the following

specifications should be used:

AGMA number EP

Viscosity @ 100 °F 12600 to 15400 SSU

Viscosity @ 210 °F 700 to 900 SSU

Pour point (°F) max. -4

Flash point (°F) min. 428

The lubricant must meet all requirements of AGMA 9005 D94 specifications for

extreme pressure lubricants.

After a new cooler has been in service for one month, the oil should be drained and

the reservoir cleaned. Thereafter, the oil should be changed at least every six months.

Carrying Roller Bearings-

These bearings should be lubricated with high grade grease with the following

specification:

NLGI Consistence No. 2 EP

Penetration, Wkd. @ 27°C 265-295

Drop Point 135-150°C

Type Soap Lithium, Soda or Soda Lime

Type Oil 110-260cSt @ 40°C

15-21 cSt @ 100°C

Keep pillow blocks packed from 1/3 to ½ full of grease by adding grease

about every month. At least every three months remove pillow block caps and

examine the grease. If the grease is in good condition it can be used for another three

months. Clean out old grease and repack bearing every six months.

Thrust Roller Bearings-

These anti friction, spherical roller bearings should be lubricated at high grade

synthetic grease that combines a polyalphaolefin base fluid with a lithium complex

soap thickener and a zinc anti-wear additive and meeting the following specifications:

NLGI Consistence No. 1

Penetration, Wkd. @ 77°F 310-340

Drop point 455-490°F

Type soap: Lithium complex

Type oil: Synthetic Base

1500 cSt @ 40°c, 8000 SSU @100°F.

110 cSt @ 100°c, 510 SSU

@210°F.

Lubricate the bearing on a monthly basis. Clean out grease and repack bearings every

12 months.

Pinion Shaft Bearings-

These anti-friction, spherical roller bearings should be lubricated with high grade

lithium complex grease with the following specifications:

NLGI Consistence No. 2 EP

Penetration, Wkd. @ 77°F 265-295

Drop point 400-475°F

Type soap: Lithium

Type oil: Mineral

150 cSt @ 40°c, 750 SSU @100°F.

13 cSt @ 100°c, 70 SSU @ 210°F.

Keep pillow blocks packed from 1/3 to ½ full of grease by adding grease about every

month. At least every three months remove pillow block caps and examine the grease.

If the grease is in good condition it can be used for another three months. Clean out

old grease and repack bearings every six months.

Tire Bore-

When the kiln initially begins operation, the tire bore may be lubricated with a

colloidal graphite and water emulsion system. Description of this method is as

follows:

Lubricants:

Acheson colloids Co. lubricant RD-5, or Castrol Industrial North America, Inc.

Molub-Alloy 491-C, or equalent.

The RD-5 lubricant (or equivalent) is a colloidal graphite water emulsion with a

wetting agent additive, which makes it possible for the lubricant to adhere to the hot

metal surface.

Application: The graphite-water emulsion can be applied with, for example, a

portable pressure tank system which includes an extended nozzle. The lubricant must

be agitated before each application to insure a uniform mixture.

Initially, dilute one part of RD-5 lubricant (or its equivalent) to five part of water.

Apply by spray two times per week on each tire. At each application, spray in the

space between the tire bore and the kiln shell and form both sides of the tire. Spray as

high as possible on the up-turning side of the kiln in the area between 7 o’clock and

12 o’clock positions. Each application is to be continued as the kiln rotates for one

revolution.

After one to two weeks, change the ratio of the lubricant to one part RD-5 (or

equivalent) to ten parts water. Apply two times per week.

Tire and Roller Contact surface-

To reduce the wear between the tire and roller surfaces, a 25mm thick solid graphite

block is set in the lubricator weldment provided for each tire. The blocks are set on

the rollers running on the down side of each tire. The weight of each block is

sufficient to transfer adequate lubricant to the rollers and tire. The lubrication is

continuous and should be checked daily and replaced as required. Use Dixon H-80-D

graphite blocks or Ohio Carbon W-201 or their equivalent.

Low Temperature Operation-

Provisions must be made for below normal temperature by using heating units or

applying lubricants of lower viscosity. Below normal temperatures are those that are

below the pour points of the lubricants being used.

Lubricant condition-

The above lubrication schedule sets minimum requirements. If the lubricant shows

sign of contamination or general deterioration then it should be replaced immediately.

SYSTEM DESCRIPTIN

1.1 General

Waste Heat Recovery boiler:

The unit, located downstream of the incinerator and petroleum coke calciner,

is designed to cool 95,866 kg/h of the flue gases from the incinerator from 1075°C to

200°C, generating 37,200 kg/h of steam at 40.5 kg/cm²g and 464 +/- 5°C from

demineralized, deaerated feed water entering at 105°C.

Salient feature of the design are:

1. Evaporative screen (generating tubes) to protect the superheater from

incinerator radiation.

2. Fully drainable evaporator and economizer section.

3. Waterwall enclosure for the superheater and evaporator sections to prevent

acid condensation, a typical problem with refractory lined casing.

4. Extremely insulated carbon steel casing for the economizer to prevent acid

condensation.

5. Preheating of the incoming feedwater in a drum coil to 160°C before entering

the economizer, to prevent acid corrosion of the economizer tubes.

6. Designing the economizer gas outlet temperature to 200°C to protect

downstream ducts from acid corrosion.

7. Use of Retractable steam sootblowers in the superheater section and rotary

stem sootblowers in the Evaporator & Economizer sections for on-load

cleaning of the heating surfaces.

8. Use of reasonably high flue gas velocities through the boiler to keep the

particulates in suspension, so that the majority of them are captured in

downstream flue gas cleaning system.

9. Provision of through/pyramidal hopers beneath the evaporator and economizer

heating surfaces to catch any fall-out of particulates. The hoppers are

externally insulated to provide hot casing.

1.2 SCREEN

An evaporator screen made up of four (4) rows of 2” OD tubes, is provided

as the first heat-absorbing surface to protect the downstream section from the

radiation in the refractory lined incinerator duct upstream of the unit. The refractory in

the gas inlet is a composite two layer refractory, the hot face castable backed up by an

insulating castable with low thermal conductivity. Further, the penthouse region over

the superheater area is lined with insulating castable.

1.3 SUPERHEATER

A two-stage superheater is provided at the next heating surface with the

primary stage made up of six (6) rows and the secondary stage made up of four (4)

rows of 44.5 mm OD X 4.06 mm” tube wall. The tubes are SA 213T11 and SA 213-

T22 material, depending on the tube wall temperatures. The two stage superheater is

arranged with the secondary superheater downstream of the primary superheater, on

the gas side. This cross parallel flow arrangement with the colder steam in the hotter

flue gas section and the hotter steam in the colder flue gas zone provides lower tube

metal temperature control. This arrangement, coupled with interstage desuperheater,

using feedwater as the spray medium, will ensure constant steam outlet temperature

leaving the boiler to the turbine without overheating the superheater tubes.

The super heater tubes are oriented vertically with the flue gases flowing

horizontally over them. The tubes are welded to the inlet and outlet headers located at

the top. The sidewalls of the superheater enclosure are made up of membrane welded

waterwall panels, which are part of the steam generation circuit.

The roof of the superheater section is formed by the evaporator tubes. A

refractory lined and externally insulated, carbon steel cover box with removable cover

will form the seal. This arrangement will keep the carbon steel at practically the same

temperature as the waterwall tubes, thus preventing stress due to differential

expansion and preventing acid condensation. The roof tubes are bent to make a single

row screen after the secondary superheater and again bent at the bottom to form a

waterwall floor for the superheater region.

1.4 EVAPORATOR

A two-section evaporator is located downstream of the superheater section.

This heating surface is made up of 2” OD tubes and is housed inside a membrane

welded waterwall enclosure, also part of the evaporator circuits. The evaporator and

the side all tubes are connected at top to the Steam drum and at the bottom to the

lower headers. Connection of the tubes to the drum/headers is by rolling. A manway

is provided between the two sections of the evaporator for access and maintenance.

An externally insulated carbon steel through is provided at the bottom between the

two section to catch any particulate fall out.

1.5 ECONOMIZER

The flue gases leaving the evaporator section will flow into the fully drainable

economizer section. This section is made up of 51 mm OD tubes, with pyramidal

hoppers to collect particulate fall out and baffles in the hoppers to prevent gas by-

passing. The heating surfaces will be located inside a carbon steel casing, externally

insulated and lagged.

To minimize acid condensation, deaerated feedwater at 105°C is preheated to

160°C in a coil in the steam drum, before entering the economizer.

1.6 EXPANSION JOINT

A fabric type expansion joint is provided in the flue duct, between the

evaporator and economizer, to absorb the thermal expansion between the two

sections.

1.7 STEAM DRUM

A single steam drum, 1650 mm ID, is provided, giving water storage in excess of

3 minutes, adequate to switch from one feed pump to the other. The drum is providing

with connections for:

Feedwater

Continuous blow down

Pressure gauges

Level transmitter

Water column with alarm probes

Safety valves

Vent

Drain

Chemical feed

Steam water separation internals inside the drum will ensure a maximum of 0.5

PPM total dissolved solids in the steam when the boiler is maintained at levels

corresponding to a maximum of 2% continuous blow down.

1.8 BOILER VALVES & FITTINGS

All the necessary valves, gauges, pressure, temperature, level and flow

elements and transmitters are provided from the feedwater booster pumps to the main

steam stop valve. All incoming piping between these terminals points are also in the

scope of supply.

All the valves will have either butt-weld or socket weld ends, expect drum and

superheater safety valves, which will be flanged.

1.9 DESUPERHEATER (ATTEMPERATOR)

To provide constant final superheat temperature of 464°C, an interstage

desuperhearter is provided between the primary and secondary sections of the

superheater. Feedwater is used as the spray medium.

If the superheater absorbs more heat than required, the spray water will cool

the steam entering the secondary superheater to maintain a constant final steam outlet

temperature.

The spray water is injected into the steam through a mechanical atomizer with

nozzles. The desuperheater is flanged and mounted in the steam piping, between the

primary and secondary superheater.

1.10 SOOT BLOWING SYSTEM

To facilitate on-load cleaning of the superheater tubes, four (4) retractable

electric motor driven steam sootblowers are provided. Two (2) are provided in the

lane between the screen and primary superheater and two (2) in the lane between the

secondary superheater and Evaporator. 1. Additional eight (8) electric motor operated

rotary sootblowers will be provided, two (2) in the lane between evaporator 1&2, two

(2) in the lane after evaporator 2, and four (4), with the lances vertically oriented, in

the lanes in the economizer section.

Steam from the superheater outlet will be used and distributed to the

individual sootblowers, by piping.

2.0 DATA SHEET

Duty Conditions of Waste Recovery System

Numaligarh Refinery WHRB

o Steam Generation 37.2T/h

o Pressure @ Superheater Outlet 40.5 kg/cm²g

o Temperature @ Superheater Outlet 464°C

o Flue Gas Inlet Temperature 1075°C

o Economizer Exit Gas Temperature 200°C

Composition & Flow of Flue Gases

(100% flow)

Component Flow Rate (kg/h)

CO² 9529.0

H²O 16,169.0

N² 63770.0

O² 6341.0

SO² 55.0

Ash 1.74

C 14.22

S 0.16

Total 95,880.

UNIT Screen Primary

Superheate

r

Secondary

Superheate

r

Evaporato

r I

Evaporato

r II

Economize

r

Fluid Flue

Gases

Flue Gases Flue Gases Flue Gases Flue Gases Flue Gases

Flow

Rate(Kg/h)

95,86

6

95,866 95,866 95,866 95,866 95,866

Inlet Temp(C) 1075 962 813 764 408 305

Outlet Temp(C) 962 813 764 408 305 200

Inlet Pressure

(mm W.C)

-61.00 -69.00 -77.00 -81.00 -131.00 -167.00

Outlet Pressure

(mm W.C)

-69.00 -77.00 -81.00 -131.00 -167.00 -345.00

Pressure Drop

(mm W.C)

8.00 8.00 4.00 50.00 36.00 178.00

Heat Loss (%) 1.0 1.0 1.0 1.0 1.0 1.0

Gas

Velocity(m/s)

18.74 15.19 13.36 21.66 14.43 19.46

Heated Side

Fluid Sat.

Steam

Steam Steam Sat. Steam Sat. Steam Feed Water

Flow Rate(kg/h) - 35,047 37,237 - - 35,792

Blowdown(Kg/

h

- 745

Attemperator

Spray(#/h)

2,190

Inlet Temp(C) 258 258 391 258 258 160

Outlet Temp(C) 258 466 464 258 258 232

Inlet Pressure

(kg/cm²g)

45 45 43.1 45 45 46.2

Outlet Pressure

(kg/cm²g)

45 43.1 40.5 45 45 45

Pressure Drop

(kg/cm²g)

0 1.9 2.6 0 0 1.2

Velocity(m/sec) - 22.73 27.25

Heated

Transfer Data

Heat Absorbed

(mm Kcal/h)

3.643 4.716 12.6 10.610 2.900 2.910

Overall K

(Kcal/m²h C)

62.65

2

67.043 38.225 68.399 63.979 68.700

Log Mean

Temp. Diff.

759.1 524.9 357.5 292.8 88.8 54.9

Heating

Surface(m²)

77 134 919 530 511 772

PERFORMANCE DATA SHEET

Flue Gases @ 1075C (100%)

3.0 Initial Water Treatment Precautions

Oxygen

Oxygen is highly corrosive when dissolved in water. Even small

concentrations of this gas can serious problems.

Makeup water can introduce appreciable amount of oxygen into the system.

Other major sources of oxygen in the system are through leakage of air at the suction

sides of pumps and the breathing action of receiving tanks.

One of the most serious aspects of oxygen corrosion is that it occurs as pitting.

This type of corrosion can produce tube failures even though only a relatively

small amount of metal has been lost.

Mechanical desertion of the feedwater is most important step in eliminating

dissolved oxygen and other corrosive gases such as ammonia, carbon dioxide and

hydrogen sulfide.

For complete oxygen removal mechanical desertion requires chemical

assistance.

At operating pressure of 60 Kg/Cm²g and over, hydrazine is the most commonly used

reducing agent, which will remove dissolved oxygen by the following reaction:

N2H4 + O2 = 2H2O + N2

Hydrazine + Oxygen = Water + Nitrogen

Because the products of this reaction are water and nitrogen, the reaction adds

no solids to the boiler water.

In theory, 1PPM of hydrazine is required to react with 1PPM of oxygen.

However in practice, 1.5PPm to 2.0PPm of hydrazine are required per 1PPM of

oxygen.

Blowdown

Boiler water Blowdown is the removal of the boiler water concentrated with

impurities, from the system.

Its purpose is to maintain boiler water control parameters within prescribed

limits to minimize potential for scale, carryover and other specific problems. It can be

used to remove suspended solids present in the system.

In effect, some of the concentrated water is removed and replaced with

feedwater. The percentage of Blowdown water varies from plant to plant dependent

on the quality of feedwater.

3.1 FEEDWATER TREATMENT

In cases of new plant start-up, it’s not always possible to obtain good

deaerated water and city water must be used. In this case, chemical desertion must be

employed. For unit that will operate at pressure over 60 kg/cm²g, desertion should be

accomplished by the use of hydrazine. This benefit in two ways – the hydrazine

reaction ties up the oxygen, and the hydrazine has the ability to form the desired

magnetite protective film inside of the tubes.

GENERAL

Of extreme importance to the life of any boiler is that the proper feedwater

treatment be established as soon as the unit begins its operational life.

Care should be taken in choosing a component feedwater consultant who can

help monitor the treatment and give advice for improvement.

The most common causes of corrosion in boiler systems are dissolved

corrosive gases, chemical agents, concentration cells and low pH. Corrosion problems

can develop in any part of the steam generation system.

3.2 BOILER BLOWDOWN

All dissolved and suspended solids entering a boiler with its feedwater remain

in the drum and tubes a steam are generated. Continued addition of makeup produces

increasingly higher solids concentration in the boiler drum. Finally a point is reached

beyond which operation is completely unsatisfactory. Tables show limits for various

impurities at different drum pressures.

Every boiler has a limit for total solids above which priming and carryover

occur. Low pressure units with large drums, operating at comparatively low steaming

at high rates can tolerate 2500 to 5000 PPM total solids. But high pressure boilers,

operating at high steaming rates, can tolerate concentration of only 500 PPM or less to

produce steam of acceptable purity. To keep within those limits, some of the boiler

water with concentrated impurities must be removed from the drum. For this

reason, boilers are equipped with Blowdown connections.

INTERMITTENT BLOWDOWN

Intermittent Blowdown should be taken from the lowest point in the

circulating system. The blowoff valve is opened manually to remove accumulated

sludge.

The main disadvantage of intermittent Blowdown is the waste of hot water.

Also, control of the boiler water concentrations is irregular at best. Keeping within

safe limits means the operator must maintain a rigid Blowdown schedule; otherwise,

it is possible to have foaming and printing in the boiler with the resulting carryover to

the Superheater.

CONTINUOUS BLOWDOWN

Continuous Blowdown keeps boiler water within desired analysis limits.

Continuously removing a small quantity of water keeps the concentrations almost

constant. Savings also can accrue from incorporation of heat recovery. Connection for

continuous Blowdown is taken from the part of boiler circulation system with the

most concentrated water. In modern units, most of the solids are in solution and are

taken from the drum at a point below the water level.

With this arrangement, blowoff valves need only to be opened occasionally

(but on a regular basis) to discharge sludge from the lower headers.

4.0 NORMAL START-UP

(NORMAL START-UP COLD) assume the complete boiler steam generating sub-

system is devoid of boiler water. This sub-system comprises of steam drum,

evaporators, Economizer and associated inlet and outlet piping to each component and

simultaneously open all vents and valves as follows:

1) Steam drum vents.

2) Economizer vents.

3) Open feed water pump’s suction and discharge valves.

4) Open feedwater level control isolation valves.

Start the boiler feed pump and fill the system by opening and feedwater stop

valve, downstream of the check valve, and the feedwater level control valve. Adjust

the feedwater control valve as necessary, to prevent cavitations.

As the system fills and entrapped air is removed, close respective vent valves

when water starts issuing out of the vents. Continue filling the system until the water

level is established in the steam drum at 1” visibility in the steam drum water level

gages. Close the feedwater level control valve.

Caution

Before lightning Off the Incinerator (or opening the valve between the

incinerator & the boiler, if the incinerator is already in operation), the following

valves should be in the closed position:

Chemical feed stop valve.

Level transmitter vents.

Saturated sample valves.

Continuous Blowdown isolation valve.

Continuous Blowdown valve.

Before lightning off the incinerator, the following valves should be in the fully open

position:

Steams drum level.

Remote level element isolation.

Level transmitter isolation

Superheater- vents.

- Drains.

- Start-up vents.

- Attemperator water blocks valves.

Now the boiler system is now ready to be operated.

1) Light off incinerator and start raising flue gas temperature.

2) During this period the following should be adhered to for safe operation of the

boiler.

a. As steam begins to generate, steam will exhaust from the drum vent

valves. When steam pressure rises to 2 kg/cm²g as evidenced on the

drum pressure gauge, close drum vent valves.

b. Steam will now flow through the steam drum crossover line and into

the superheater and will exhaust to atmosphere through the superheater

vent and drains.

c. When steam escapes from the primary and secondary superheater

header vents, close the respective vent valves.

d. Steam pressure is raised by combination of increasing firing (heat

input) and manipulation of main superheated steam start-up vent.

e. Once significant flow of steam is venting through the start-up vent, all

superheater drains cab be closed.

f. It is mandatory that sufficient steam flows through the superheater so

that the outlet steam temperature does not exceed 464°C.

g. If the superheater outlet temperature cannot be maintained at 464°C.

With the start-up vent wide open, activate the Attemperator by placing

the Attemperator spray on automatic.

h. Raise steam pressure by adjusting the superheater vents and auxiliary

fuel firing, so that the saturation temperature increases at a rate not

exceeding 55°C/hr.

i. The superheater start-up vent remains in full open position until the

main steam stop valve is opened and normal steam flow is established.

At this, time start-up vent valve can be closed.

j. Set continuous Blowdown valve to necessary Blowdown rate.

Saturated

4.1COLD START UP PROCEDURE OF BOILER:

1. Check drums level. Before filling the system with feed water, close the following

Drains.

a. All feed water line drains

b. Evaporator drain

c. Economizer drain

d. IBD

e. CBD

2. Open the following drains.

a. Main steam line drain

b. Super heater drain

3. Open the following vents

a. Stream drum vents.

b. Super heater vents

c. Attemperator vent

d. Economizer vent

e. Start up vent

4. Also open the following valves

a. Feed water booster pump suction & discharge valves

b. Feed water level control isolating valves

5. Start the boiler water feeding slightly opening the feed water control valve.

6. Close economizer vent when water comes out of it.

7. Fill up the feed water upto 40% of the drum level gauge. Check and tally with the

LI at DCS

8. Start ID fan with minimum speed and minimum opening of inlet control damper.

9. Crack open the boiler side guillotine damper. Flue gas will enter the boiler pass.

10. When steam pressure rises to 2 kg/cm², close the steam drum vents.

11. When steam starts escaping from Attemperator, primary and secondary super

heater vents sufficiently, throttle the vents.

12. Saturation temperature should be increased at a rate not exceeding 55°C/hr.

13. Throttle super heater and main steam drain valves when steam starts coming

sufficiently out of the drain.

14. Start the booster feed water pump. Control drums level such that it is at normal

level. Put drum level controller into Auto mode.

15. Line up Attemperator control. Super heater outlet temperature should not exceed

464°C. Put Attemperator control into Auto mode.

16. The start up vents will remain in open condition till main steam stop valve is

opened and steam flow is established. After opening the main steam stop valve,

close the start up vents. Close the main steam drain and vents fully.

17. Start chemical dozing pump. Adjust dozing.

18. Open continuous blow down valve to necessary blow down rate.

19. Line up the sample coolers.

20. Steam and Boiler water parameters should be maintained as followed:

CBD: Ph : 9.5 to 10.5

Phosphate : 20 to 30 ppm

Silica : < 2.5 ppm

Saturated Steam: Ph : 7.5 – 8.5

Silica : < 0.01

Superheated steam: Ph : 7.5 – 8.5

Silica : < 0.01

4.2WARM START UP OF BOILER

1. Start up vents and super heater vents should be in open condition.

2. Raise the steam drum pressure & temperature. Increase in saturation steam

temperature should not exceed 55º C.

3. Maintain drum level.

4. When steam pressure rises to 2 kg/cm², close the steam drum vents.

5. When steam starts escaping from Attemperator, primary and secondary super

heater vents sufficiently, throttle the vents.

6. Throttle super heater and main steam drain valves when steam starts coming

sufficiently out of the drain.

7. Start the booster feed water pump. Controls drum level such that it is at

normal level. Put drum level controller into Auto mode.

8. Line up attemperation control. Super heater outlet temperature should not

exceed 464°C. Put attemperation control into Auto mode.

9. The start up vents will remain in open condition till main steam stop valve is

opened and steam flow is established. After opening of main steam stop valve,

close the start up vents. Close the main steam drain and vents fully.

10. Start chemical dozing pump. Adjust dozing.

11. Open continuous blow down valve to necessary blow down rate.

12. Maintain drum level.

13. Operate Attemperator control such that superheated steam temperature does

not exceed 464º C.

Steam Synchronization

1. See that SH steam pressure & temperature are above network pressure &

temperature.

2. Inform CPP control room about steam synchronization programme.

3. Open Main steam stop valve and close the super heater vents and start up vent.

4. Regulate SH steam control valve to maintain SH pressure.

5. See that drum level is maintained.

6. Slowly push steam to the network as per requirement.

SHUT DOWN PROCEDURE OF WHRB

7. Reduce boiler steaming by reducing the fuel at incinerator burner, keeping at

least 4 to 6% of oxygen content at the flue gas.

8. Close the boiler side guillotine damper. Adjust draft at the kiln firing hood

within –0.1 to –0.3 mmwc by opening the boiler by-pass damper.

9. Close Main steam control valve and the MSSV. Open Start up vent and

superheated vents.

10. Drop in saturated steam temperature should not exceed 55º C

11. Maintain drum level.

12. The boiler will continue to generate steam due to heat storage at its inlet duct

refractory. Filling of water is to be continued to control the drum level.

13. Crack open the super heater drains.

14. Close inlet damper of ID fan. Stop ID fan.

15. Close CBD.

16. Open the drum vents when drum pressure reaches 2 kg/cm².

17. Stop FW booster pump.

5.0 TUBE FAILURE

Operating a boiler with a known tube leak is not recommended. Steam or

water escaping from a small leak can cut other tubes by impingement and set up a

chain reaction of the tube failures. By the loss of water or steam, a tube failure can

alter boiler circulation or flow and result in other circuits being overheated.

Small leaks can sometimes be detected by the loss of water from the system,

the loss of chemicals from a drum-type boiler, or by noise made by the leak. If a leak

is suspected, the boiler should be shutdown as soon as normal operating procedures

permit. After the leak is located by hydrostatic testing, it should be repaired by

replacing the tube or a section of it with new tubing.

Several items must be considered when a tube failure occurs. One of the first

things is the decision whether or not to continue the flow of feedwater, even though

the steam drum water level cannot be maintained. In general, the feedwater flow

should be continued as long as the temperature of the waste heat gases entering the

units hot enough to damage the unit.

After the unit has been cooled, make a complete inspection for evidence of

overheating and for incipient cracks, especially to headers and drums.

As investigation of tube failure can be eliminated and future failures

prevented. This investigation should include a careful inspection of the failed tube. In

some cases, a laboratory analysis or consideration of background information leading

up to the failure is required.

This information should include the location of the failure, the length of time

the unit has been in operation, load conditions, start-up and shutdown conditions, and

feedwater treatment.

TUBE LEAKS

Causes:

1. Can be either design or operation oriented.

2. Object is to decide which the problem is and apply remedy.

Classify:

1. Mechanical problems

2. Excessive temperatures

3. Corrosion mechanism

6.0 HYDROSTATIC TESTING

Upon completion of the field erection of any boiler, the unit must be

hydrostatically tested to one and one half times the design pressure to ensure the water

and steam tightness integrity of all components, shop and field welds, that make up

the unit.

The water to be used in test must be the best quality available. However, if

untreated water is all that is available, then it must be treated with oxygen scavengers.

The water should be heated up to approximately 25°C. Introducing cold water

to the unit will form condensation on the outside of the tubes, making spotting of any

leaks very difficult.

The water should be introduced to the boiler as quickly as possible, so that the

heat does not dissipate. On new units, the drum and superheater safety valves should

be left off and the connections blind flanged. In any subsequent hydros, the safety

valves may be gagged.

When first introduction water to the unit, all drum, superheater, convective

evaporator and economizer vents should be left open until water appears to ensure the

pressure parts are being purged of air.

After water appears at the various at the various vents, they should be closed

and the hydrostatic test pump connected and the unit pressurized to one and one half

times the design pressure. This pressure should be held for one (1) hour.

The pressure is then dropped to the normal design pressure and a complete

inspection of the unit made. If any leaks appear, the unit must be depressurized, drain

and repair is made, the unit must once again be hydro-tested.

Once the unit has been proved sound, the water should be drained and a fresh

fill prepared. At this time on a new unit, the blind flanges should be removed and the

safety valves mounted.

Depending on the time frame between the hydro test and boil-out, the unit may

have to be laid up in either wet or dry storage. If the boil out follows immediately, the

unit should be filled to one (1) inch of water showing in the gauge glass, and boil-out

chemicals added.

In the event that the time between hydro and boil-out is two (2) weeks to a

month, the unit should be laid up in wet storage. This means again treating with

oxygen scavengers, filling the unit to ¾ gauge glasses and adding a nitrogen blanket.

If the time frame is longer than a month, the unit should be laid up in dry storage. In

this case, all the water must be drained from the unit including superheater. If the

superheater is of the non-drainable type, the water may have to force out using

compressed air.

7.0 HOT ALKALINE FLUSH

After the hydrostatic test and prior to the boil out, the feedwater/condensate

system should be subjected to a hot alkaline flush to prevent contaminants from this

area fouling up the boiler surfaces.

Pre-operational contaminants include mill scale, weld scale, corrosion

products, oil, grease, dust and dirt, protective coatings, and other contaminants

remaining after fabrication and construction.

Its preferable to have a professional cleaning company performs this

operation, since they can supply the required chemicals and can dispose of the spent

flush water. With the use of high pressure hoses, a closed loop should be made of the

feedwater/condensate system. Items such as the feedwater pumps, recalculating

pumps, deaerator and condenser should be bypassed. In conjunction with the flush,

such equipment as the condenser (where possible), hotel, deaerator, and deaerator

storage tank should be hand cleaned.

Condensate/feedwater systems and corrosion products can be carried to the

boiler where they deposit on the heating surfaces. The insulating effect of a corrosion

deposit can lead to tube overheating and failure.

Removal of contaminants has advantages other than minimizing failures.

Cleaning may also reveal stress area and cracks resulting from fatigue, embrittlement,

or corrosion.

8.1 BOILER MAINTENANCE

Outage Preparation

Outage preparation requires proper securing of furnace and boiler pressure

parts so that no danger exists for plant personnel. The unit can be cleaned of loose

flyash by blowing all sootblowers in a progressive sequence to the convection pass

outlet.

When the unit is in service, data, including boiler and air preheater

temperature, gas side pressure drops and the frequency of soot blowing, should

indicated problem areas of ash accumulation.

Outage Objectives

During the outage, the entire unit should be thoroughly inspected with the

following objectives:

1. To detect any possible signs of overheating of tubes, particularly if

thermocouples have indicated this possibility. Tubes should be examined for

signs of erosion, it may be necessary to gauge tubes either by mechanical or

ultrasonic methods to establish the amount of wall thinning. Superheater,

evaporators and economizers should be inspected for swelling, blistering or

warping.

2. To discover any possible signs of erosion or corrosion, a thorough inspection

of heat absorbing surfaces should be given added importance if any unusual

operating conditions have precluded the outage.

Erosion appears as a smooth, sometimes shiny, loss of metal on the superheater,

evaporator and economizer.

Corrosion associated with ash deposits may be hidden and sandblasting of surfaces

may be required for detection and measurement.

3. To locate deposits of ash or slag that interferes with heat transfer or free gas

flow through the unit

Any heavy deposits that block a major portion of gas lanes can

indirectly contribute to erosion problems by creating channels of heavy velocity in

remaining open areas. The presence of deposits indicates the need to check the

operation of the Burners.

4. To check that any airflow regulating or adjustment equipment such as

dampers, and free of warpage or overheating and operate freely over the

control range. The fuel distribution system should be inspected for any sign of

erosion.

5. To determine the condition of any refractory exposed to flue gases,

particularly if operating conditions have been unusually severe as when

operating intermittently. The outage inspection and past operating occurrences

or problems should be correlated to take corrosive steps to prevent the re-

occurrence of problems. For example: the overheating of superheater tubes

may have occurred from too rapid a start-up or tube internal deposits. A must

during every outage is recalibration, reconditioning, cleaning and maintenance

of the overall control system.

Outage Objectives

Boiler Maintenance programs

The maintenance of boiler equipment should be controlled by a

planned program. The program should consist of the following basic parts:

1. inspection and overhaul procedures

2. overhaul scheduling

3. equipment histories and spare parts inventories

4. personnel training

5. equipment improvement

8.2 CARDINAL RULES OF BOILER MAINTENANCE

1. Be familiar with the equipment.

2. Maintain accurate and complete records.

3. Analyze and identify the root cause of the problems.

4. Determine maintenance cycles and plan future labor and material

requirements.

8.3 OPERATING CHECKS RELATING TO MAINTENANCE

1. Check for any flue gas, steam or water leaks.

2. Check for steam leaks at superheater headers and tube joints.

3. Check for air leaks around doors, seals and furnace.

4. Check for slag build-up on refractory.

5. Check for missing insulation on header and drum.

6. Check for change in pressure drop through the superheater indicating internal

condition of the tubes.

7. Check for quality at the drum. This will indicate the condition of steam

scrubbers and separators.

8. Check for noises in the drum. This may be caused by loose piping.

9. Check for a variation in temperature differences over the economizer at

constant load indicating deposits or by-passing.

10. Check for an increase in pressure drop over any part of the system at constant

load indicating deposits or build-up.

11. Check the extent of expansion and contraction of pressure parts during start-up

and shutdown.

12. Check exit gas temperature and compare with steam temperature at normal

loading to determine any fouling of the heat exchange surfaces.

13. Whenever possible, check the operation of safety features on combustion

controls and water level.

8.4 SAFETY CHECKLIST FOR INSPECTION AND MAINTENANCE

1. Before entering the boiler, lock out and tag all equipment items with movable

parts connected to the boiler and fuel system and place a sign at the control

panel indicating a workman is in the boiler.

2. Before entering the boiler, make sure its properly isolated at all fuel, flue gas,

steam and water sources, make sure it’s properly vented. Use low power lights

or explosion-proof flashlights.

3. Notify shift supervisor when beginning and upon completion of the inspection.

4. Always inspect in pairs, so if assistance is required, help will be close at hand.

5. Always be aware of the nearest escape routes.

6. Before closing drum manholes and furnace doors, it is essential to ensure that

all personnel are out of the boiler.

8.5 TUBE FAILURE ANALYSIS

Failure Mechanisms

Small pitting corrosion on the waterside of tubes in economizer is

noticeable due to the lower level of protective chemical such as hydrazine which is

normally present in feedwater. Proper deaeration of feedwater is absolutely for

protection of the Economizer.

Failure to Scale and Long-Term Creep

A build-up of internal scale which leads to a gradual rise in

temperature of the tube metal. The tube appears swollen with blister or bulge. The

outside surface may have an “elephant hide” appearance. Ruptures are a thin opening

along the axis of the tube. The edges of the failure are generally thick.

Short-Term Overheat Failure

A rapid elevation of temperature of the tube metal caused by a

starvation of water flow to the tube results in a wide rupture. The edges of the rupture

are thin and sharp. In superheater, a short term overheat could result from a blockage

of the steam flow.

Oxygen Pitting (Superheater)

Usually found in the tight loops of the superheater and is the result of

the exposure to condensate that forms in the bends at shutdown with oxygen in the air.

Exfoliation (Superheater)

Generally exfoliation is found in tubing that has been exposed to

temperatures above 480°C. Exfoliation appears as flaking of metal scale on the inside

of the tube.

Pluggage of Tight Bends of Superheater

Flakes of exfoliation metal from the superheater, lodge in the tight

loops and tend to plug the area. When loops are plugged, flow will be restricted and

the tube metal will probably experience a swelling and a overheat type failure.

Chelant Corrosion

Chelant corrosion or attack develops when the sodium salts are kept at

high concentrations over a period of many months. The attacks are of a dissolving or

thinning nature and not of pitting. The attack concentrates on threaded members,

baffle edges and other unrelieved stressed areas.

Tube Failure Analysis-

How to remove a tube sample:

1. The tube sample should be saw-cut to prevent any slag flowing into the

sample or the good section of tubing.

2. The sample should be cut approximately 8 to 10 inches above and below the

affected area.

3. The exact location should be documented as follows:

a. Tubes should be numbered and counted from east to west and north to

south.

b. The elevation should be noted and marked on the tubes.

8.6 SAFETY VALVE INSPECTION AND MAINTENANCE

Periodic inspection, testing and maintenance program is recommended

to ensure proper valve function. This program should include valve removal to a

shop-testing environment for:

1. Verification of set pressure.

2. Valve tightness test.

Valve inspection should include factor which could affect valve

performance. Important among these are:

1. Temperature variation, both system and ambient.

2. Vibration.

3. Residue on internal parts.

4. Valve body mechanical stress.

5. Line turbulence.

6. Sizing and configuration of discharge piping.

7. Sizing and configuration of inlet piping.

8. Bore diameter.

Any program of troubleshooting or preventive maintenance should

consider each of the above of each valve.

Lift and Blowdown

Lift is an important characteristic because full relieving capacity of the

valve can only be achieved at full rated lift. Blowdown is the difference between the

set pressure and the closing pressure of the valve.

Valve internal dimension have critical relationships and the surface

finish must be carefully maintained as recommended by the manufacturer for the

valve to perform properly.

Any part repair should be approved by the manufacturer who

understands the valve design, construction and application and who meets the original

manufacturer’s specification.

Valve Tightness

There should be limited leaks after a valve lifts and reseats. Refer to

the valve manufacturer’s instruction manual for test pressure, duration of test and

acceptable leakage rate for each type and size.

Testing

A safety valve should always be tested after any maintenance work.

This testing can be accomplished on a test stand. Upon conclusion of repair and

testing, a repair name tag should be attached identification that repaired the valve and

the date of the repair. The valve should be final tested on the equipment it services

and any required final adjustment made.

Installation

The valve should not be replaced on its side after assembly and test, as this can

disturb the vertical alignments of the valve. Special attention should be given to the

proper torque of inlet and outlet nuts and bolts. Uniform torque valves should be used

and done in such a way that will not impart internal stress to the valve body.

8.7 FEEDWATER CONTROL VALVES

During each annual boiler inspection, the condition of the feedwater

control valve and feedwater piping should be determined. Typical conditions to look

for include:

1. Accumulation resulting in the chemical treatment into the system upstream of

the feedwater control valve.

2. Wire drawing of the control valve. This is caused by the valve operating in the

nearly-closed position. In this case, the valve rarely opens to its design

position and water level control can be erratic.

Boiler Appliances

Boiler appliances such as gauge glasses, gauge cocks, water columns,

water level controls, high or low alarms or cut-offs, non-return valves, should be

inspected at regular intervals.

All controls and interlocks should be checked and re-calibrated each

year.

Pressure Gauges

Pressure gauges should be inspected and recalibrated on a routine basis

whenever there is any question of accuracy. The normal cycle for removal, inspection

and recalibration is once every twelve months. Since gauges are instruments, they

should be handled carefully.

Always use a wrench on the shank of the gauge. Never apply force

against the gauge case. Hold a wrench on the socket flats to screw a fitting to place.

Do not twist against the gauge socket screw which holds the gauge mechanism in the

case.

Valves

All valves associated with the boiler system should be checked for

leakage, stem erosion and that they are operable to give a positive shut-off.

8.8 DAILY LOG

A daily log for scheduling and recording work performed and

maintenance, testing and inspection is recommended. The routine work normally

performed on power boilers is listed. As each portion of the work is completed, the

person performing the work should enter the date and his initials in the appropriate

spaces. The plant inspector should recommend immediate correction of any unsafe or

undesirable practices that may be discovered.

A system of worksheets should be made available for the shift opening

personnel, so that any defect that may be discovered during the shift can be noted and

brought to the immediate attention of the maintenance supervisor. Defects discovered

on shift should also be noted in the operation log book.