2. Paper on Soot Blowing Optimization Field Experience

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Analysis of Two-Output Inverter For Induction Heating Application Analysis of Two-Output Inverter For Induction Heating Application

SOOTBLOWING OPTIMIZATION: FIELD EXPERIENCE

1YASHPAL SAHU,

2AMIT PANDEY,

3MD SHAHABUDDIN,

4POOJA AGRAWAL

Jindal Power Limited, Tamnar

Abstract—Furnace and convective pass slagging and fouling have a negative effect on boiler performance and emissions. The purpose of soot blowers is to keep the heat transfer surface clean so as to contribute towards optimal performance of the boiler. Excessive soot blowing can cause increased maintenance in fossil-fired boilers. Soot blowers perform on-line cleaning of localized areas consuming substantial amounts of costly high pressure Main Steam; this cost motivates the study of soot blowers and development of improved soot blowing strategies. Boiler

operators typically follow one continuous soot blowing sequence. Most rely on manufacturer’s recommendations, while some try to improve soot blower activation strategy by employing a trial-and-error approach. Considering the importance of soot blowing on plant operations and availability, soot blower operations need more attention. The Jindal Power Limited – different Dept. teamed up and has taken the initiative to perform a study on soot blower optimization by implementing pattern wise blowing. For this, different combination of tiers wise SB was done and the requirement and effectiveness of each tier was observed by studying different parameters and developed a pra ctical, knowledge-based approach to soot blowing optimization and has implemented it in Unit # 3 & Unit # 1 of 4 x 250 MW, OPJSTPP. This approach can deal with the reduction of soot blower activation frequency, and steam temperature

control. This paper describes the approach; implementation on a 250 MW tangentially fired boiler, operating experience, and benefits to the plants.

Keywords— Soot Blower, slagging

I. INTRODUCTION

All coals contain mineral matter in coal ash. Furnace

slagging occurs as molten or sticky fly ash particles

come in contact with the furnace walls or other

radiant surfaces and form deposits due to the

quenching effect of the tube wall. Slag deposits

reduce heat transfer to the furnace walls, and increase

the amount of heat available to the convection pass.

This results in a higher furnace exit gas temperature

(FEGT) and, for subcritical boilers, in a higher steam

temperature, desuperheating spray flows and NOx emissions. Deposition of ash on tubes or heat transfer

surfaces in the convective pass reduces heat transfer

in that part of the boiler. The convective pass fouling

results in less heat is transfer to the working fluid, a

decrease in steam temperature and desuperheating

spray flows, and in an increase in flue gas temperature

at the boiler exit.

The challenge in sootblowing optimization is to

determine which sections of the boiler to clean and on

what schedule, considering the factors such as tube

life, sootblower steam or steam consumption and

maintenance cost. For best boiler performance, it is important to maintain an optimal balance between

furnace and convective pass heat transfer.

A. BASICS OF SOOT BLOWING

Sootblowing controls the level of ash and slag

deposits on heat transfer sections. Sootblowers

perform on-line cleaning of localized areas using

high-pressure steam or air. Wall blowers and water

cannons remove slag from furnace water walls, while

retractable blowers clean the convective pass of the boiler (including the air preheater). Furnace cleaning

increases radiation heat transfer to water walls and

reduces the FEGT. This decreases the amount of heat that is available to the convective pass.

Therefore, over-cleaning of furnace walls can result

in low steam temperatures (below design level) with

resulting heat rate penalties and increased moisture

levels and erosion damage in last stages of the low-

pressure turbine. Reduced reheat steam temperature

also results in lower turbine and unit power output.

II. JPL APPROACH TO SOOT BLOWING

OPTIMIZATION

JPL has developed a sootblowing optimization

approach, described in References [1 to 47], for

balancing furnace and convection pass heat transfer to improve boiler performance, reduce NOx

emissions, and minimize disturbances caused by

sootblower activation.

The JPL sootblowing optimization approach

depends on a database describing the effects of

sootblower activation on parameters, such as

cleanliness of heat transfer surfaces, steam

temperatures, attemperating sprays, and other

parameters of interest. The sootblower

characterization database (SBCD), created from a

series of sootblower characterization tests, contains of the effect of one sootblower or sootblower group

at a time on parameters of interest.


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III. SOOT BLOWERS OPTIMIZATION IN

BOILERS

There are many methods used for optimization of wall

blower operation in boiler furnace, like the manual

method, heat flux measurement method, and the automated method. The manual method is discussed

as this will bring out the philosophy involved in

optimizing wall blower operation.

Wall blowers are provided in boilers to clean the

furnace wall deposits. They seldom find use in

oil and gas fired boilers. The deposition and

slagging in boiler furnace is required to be

removed from the furnace walls at regular

intervals. The interval period will depend on the

area of deposition and the severity of deposition.

Steam wall blowers are found to be very efficient

in removing the furnace wall deposits.

In JPL Stage-I boiler of around 825t/hr capacity,

the total number of soot blowers are 90. In this,

around 56 numbers are wall blowers. The

frequency of soot blowing depends upon the type

of coal being fired. However the operating group

must remember that the initial suggested

sequence and frequency is more general and has

to be adapted to each boiler. The purpose of these

soot blowers is to keep the heat transfer surface

clean so as to contribute towards optimal

performance of the boiler.

A. EFFECT OF THE SOOT BLOWER ON

BOILER PERFORMANCE

Removes the deposits on the furnace wall and

ensures good heat transfer in the furnace region

The furnace outlet temperature slowly ramps up

after wall blowing as time lapses

Superheater spray quantity is seen to increase

with time lapse after wall blowing

Increases the bottom ash quantity depending

upon the deposition on furnace walls

Increases furnace tube material loss if blowing

is done too frequently without any deposits.

This leads to boiler outage or increased

maintenance.

In the case of water lancers for removing molten

slag, while operating there will be a large dip in

generation for the same heat input. This is mainly

due to the increased boiler losses

B. MEASURES TO BE CONSIDERED

Before taking up wall blower optimization, the

following has to be ensured:

All wall blowers are set to the right steam

pressure recommended by the designer

Check the alignment of the wall blower with

respect to the furnace walls

Ensure at least 50 degree centigrade of super

heat in the steam being used. This is to prevent

damage of the furnace walls due to wet team

impingement.

All wall blowers are operational

It is of great help if the boiler furnace walls are

photographed just after a planned shutdown.

Before shutting down the boiler, do not wall

blow the furnace for one full sequence. This

ensures deposit collection on the walls between

the adopted frequencies. While shutting down

the boiler ensure minimal thermal shock, by

slowly lowering the load. This ensures deposits

stay on the walls. Take the photograph from a

convenient man hole. But take all safety

precautions as anytime the deposit can fall

down due to cooling or thermal gradient.

There are many methods used for optimization of

wall blower operation, like the manual method, heat

flux measurement method, and the automated

method. The manual method is discussed as this is

bringing out the philosophy involved in optimizing wall blower operation.


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C. NEED FOR SOOT BLOWER

OPTIMIZATION

To improve consistency in efficient operation of

boiler

To reduce steam wastage by identifying those

areas of low or no deposits

To reduce damage on furnace wall tubes due to

excessive blowing

The change in SH spray & RH Spray without change in other parameters indicates that the furnace deposits

are increasing. If the superheater or reheater sprays

increases above a particular level (to be determined

for each boiler), operate all wall blowers. These are

two basic things to adhere to while optimizing wall

blowers.

IV. OPTIMISATION STRATEGY ADOPTED

A. EARLIER OPERATION OF WALL

BLOWER

In every 8-hr shift, wall blowing used to be done once. It takes around 1 hour 30 min for complete

blowing. All blowers (1 to 56) were operated at a

pressure of about 22 kgf/cm2 & temperature of about

240 deg. C.

B. TECHNIQUE ADOPTED

There are 56 wall blowers in a boiler furnace wall, the

steps for optimization is listed.

Operate all 56 blowers

See the effect on superheater spray and note all

operating parameters of boiler

Wait for the superheater spray to ramp up to the

initial level and stay almost steady

Wall blow each row - study effect

Watch superheater spray drop and regain time

The interval between blowers is to be maintained

constant

Repeat if required each row independently,

waiting each time for the spray to reach the

original level with other parameters of boiler

remaining constant

Repeat the study for two adjacent rows

Repeat the study for two alternate rows

Repeat the study for blowers in front, rear, left

and right sides of furnace walls separately and

study the effect on superheater spray flow.

The blowing having the least effect on the

superheater spray indicates low or no deposit on

the walls.

A plot of superheater spray drop when each

blower is operated will give a good idea of

deposition in that area

Use the photograph of the furnace wall to

validate the effectiveness of blowers

Decide which blowers can be skipped during

blowing as well as the effectiveness of the row

The procedure for wall blower operation can be

evolved after the study and data analysis for the most effective way of wall blowing.

The use of heat flux meter by embedding

thermopiles at appropriate location in the furnace

walls to understand whether the tube in the region is

clean or with deposition the operation of the wall

blower requirement can be decided.

In the case of fully automated intelligent wall blower

system, the need to wall blow each blower is

understood from the effective heat flux falling on the

tubes. Designers use different methods to establish

this.

Day

Shift Remarks

A B C

1 Current operation for data capturing

2 1 to 14 All 56 All 56

3 1 to 14 All 56 All 56 For data

validation

3 15 to

28 All 56 All 56

4 15 to

28 All 56 All 56

For data

validation

5 29 to

42 All 56 All 56

6 29 to

42 All 56 All 56

For data

validation

5 43 to

56 All 56 All 56

6 43 to

56 All 56 All 56

For data

validation


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C. OBSERVATION

Following are the observations taken under notice with the data collected:

D. PRESENT SCENARIO

A Shift B Shift C Shift

Tiers operated 1st

, 2nd

& 3rd.

2nd

and 3rd.

All four tiers

Soot Blowers to be

operated 1 to 42 15 to 42 1 to 56

Number blowers not

operated 14 28 0

So the number of blowers which will not operate in a day is 42 blowers

Parameter

1 to 56 Blower 1 to 14 Blower 15 to 28 Blower 29 to 42 Blower 43 to 56 Blower

Effect on

SH Spray

Spray just before

SB > 52 TPH > 50 TPH > 46 TPH > 48 TPH > 50 TPH

Reduced by 10 to 11 TPH 6 to 8 TPH 16 to 18 TPH ~ 15 TPH

No noticeable

change recorded Deteriorated to

same condition

after around

2 hr 1 and 1/2 hr 2 hr 2 hr

Effect on

RH Spray

Spray just before SB

5 TPH < 3 TPH < 2 TPH 2 TPH 5 TPH

Reduced by 5 3 2 2

No noticeable

change recorded Starts

deteriorating

slowly after

around

1 and 1/2 hr 2 hrs 2- 3 hrs 2- 3 hrs

Effect on

Burner Tilt

Deteriorated to

same condition

after around

1 and 1/2 hr No noticeable

change

No noticeable

change

No noticeable

change

Tilt position

remains same


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E. COMPILED DATA BEFORE & AFTER OPTIMIZATION

F. SH & RH TREND

Parameter May Jun Jul Aug Sep Oct Nov

Load 251.8 248.7 250.3 250.2 249.9 252.2 250.5

Avg MS Temp 534.0 534.6 534.2 534.3 534.6 534.7 534.6

Avg HRH Temp 535.7 535.5 535.8 535.8 536.0 536.0 535.7

Total SH Spray 44.6 45.6 52.1 51.3 53.8 43.9 46.1

Total RH Spray 4.3 2.9 9.2 9.1 10.2 5.7 4.9

O2 at APH-A I/L 3.2 3.2 3.0 2.5 2.6 2.9 3.1

O2 at APH-B I/L 3.0 3.3 3.6 3.0 3.0 3.0 3.1

Avg O2 3.1 3.3 3.3 2.7 2.8 3.0 3.1

FGT after PSH (L) 822.9 818.9 843.5 840.3 834.5 817.7 817.5

FGT after PSH (R) 774.7 776.4 786.4 757.4 802.4 782.7 764.7

SH & RH trends before & after Wall Blowing Optimization


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V. FINANCIAL ASPECT OF CASE

A. Quantity of DM Water Saved

Total quantity of steam consumed during wall blowing

(1 to 56):- 5 tones i.e. 5000 Kg of steam

=> The steam consumed per blower is = 5000/ 56 =

89.2 kg of steam

By adopting above mentioned combination amount of

steam consumption reduction

= (89 X 14) + (89 X 28) = 3738 kg of steam per day

Steam consumption reduction in a year (taking 97%

PLF) = 3738 x 0.97 x 365 = 13, 23,439 kg = 1323

tonnes in a year

DM water cost = 100 Rs per m3 = 100 Rs per tonne

Total cost of DM water lost = 1323 x 100= 132300 Rs = 1.32 Lacs

B. Amount of Heat Energy Saved in terms

of Coal by throttling of steam

Steam condition at Super heater header a throttling for supplying steam to wall blowers: - Pr. -165 Kg/cm2 &

Temp. – 420 degree C

Enthalpy of steam = 724 Kcal/kg

Quantity of steam saved = 1323 tonnes

Total savings = 1323 X 724 = 975852000 kcal

Taking coal GCV 3500 kcal/kg, Quantity of coal saved

= 975852000/3500 = 273672 kg = 273.6 tonnes

Amount saved = 273672 (assuming cost of coal 1000 Rs

per tonne)

= 2.73 lacs

Total amount saved = 1.32 +2.73 = 4.05 lacs in a year.

VI. CONCLUSION

A series of upgraded steps at the JPL have been coupled

with optimization systems to gain performance benefits

in the form of fuel savings, reduced emissions,

increased net power generation and improved dispatch

capability along with financial saving. The combination

of a flexible and capable toolset, application expertise

and the power of continuous improvement are now

Providing continuous and significant performance benefits to the station.

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R., Henrikson, J., Cylwa, W. and Luk, J.,

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Cleanliness,” Presented at Combustion Canada

2003 Conference, September 21-24, 2003,

Vancouver, BC, Canada.

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About Author:

Yashpal Sahu

Education qualifications: ME- Mechanical, BIT, Mesra Ranchi

BE-Mechanical, GRKIST, Jabalpur

Certified Energy Auditor

Certfied BOE

Work Exp: 10 yrs 8 months with Jindal Power Limited,

- Project Monitoring of 250 MW

- Commissioning & Operation of 250MW

- Efficiency and CEEPI department

- Commissioning of 600 MW unit

Cell no: +91 9329445005

Email: [email protected]

Md Shahabuddin

Education: B.Tech in Electrical & Electronics

Engineering (EEE)

From Bengal College of Engineering & Technology ,

Durgapur

PGDC in Thermal Power Plant from NPTI, Guwahati

Work Exp: 1. Since Aug 2009 to Jul 2012 as a Desk Operation Engineering (Asst Manager) in Vedanta

Aluminium Ltd. , Jharsuguda.

2. Currently working as a CEEPI TEAM

(Asst Manager) in Jindal Power Ltd. , Tamnar.

Cell no: +91 7898905434


Amit Kumar Pandey

Education qualification:

B.E. Mechanical (Honours)

PGD in Thermal Power Plant Engg. NPTI Nagpur (M.S.)

Work Exp: Associated with Jindal Power Ltd. since

Aug 2007,

Currently working as Manager (Operation).

M- + 91 7898905225


Pooja Agrawal

Education: B.Tech in Electrical Engineering (EE)

From Indian School of Mines, Dhanbad

Work: Currently working as a CEEPI TEAM (Asst

Manager) in Jindal Power Ltd. , Tamnar.

Cell no: +91 7898902697


mailto:[email protected]



Documents

2. Paper on Soot Blowing Optimization Field Experience