Article Efficiency Measures R 04 FAI

8/12/2019 Article Efficiency Measures R 04 FAI

1/19

- 1 -

Efficiency Improvement at IFFCO Paradeep

S.K. Gandhi, Executive Director

and

Navin Nath, Chief Manager (Process)

Indian farmers Fertiliser Cooperative Limited,

Paradeep Unit

Distt. Jagatsinghpur,

Paradeep, Orissa

Abstract

In view of high cost of energy it is imperative to conserve

energy to reduce the cost of production. Level of energy

consumpt ion of an operating plant can also provide the insight

of its physical and financial health. Article gives an insight on

how IFFCO Paradeep Unit is continuously improving its

performance in the areas of energy efficiency and

environmental improvement. The measures implemented

involves modification in the existing process and equipments,

changes in the equipment layout, recycling of material and

water, reduct ion of wastage and use of renewable energy. The

details of these measures and resultant savings in energy andwater consumption and improvement in environment etc are

elaborated.

1.0 Introduction

IFFCO Paradeep Unit operates two streams of Sulphuric acid plant (2 x 3500

MTPD), one stream of Phosphoric acid (2650 MTPD as 100% P2O5) and three

streams of complex fertilizer plant (3x2090 MTPD). The main raw materials

such as Rock Phosphate, Sulphur, Sulphuric Acid and Ammonia are imported

from various countries. The electric power requirement is met through Captive

Power Plant (CPP) having two nos. turbo generator (TG) sets, each having

capacity of 55 MW. In addition to the waste heat boilers in Sulphuric Acid

Plant, there are two coal fired 110 TPH capacity Atmospheric Fluidized Bed

Combustion boilers generating steam at a pressure of 61 kg/cm2(g) used for

power generation and other utility requirements.


2/19

- 2 -

The raw materials are transported from Jetty to the plant through 5 kms long

belt conveyors/pipelines. Water required for the plant is supplied from

Taladanda Canal 2 km away from the plant site. Unique Features of Paradeep

Unit :

1) Largest Phosphatic fertilizer complex in India.

2) Worlds largest single stream phosphoric acid plant: 2650 MTPD.

3) Largest Sulphuric acid plants in India: 2 x 3500 MTPD.

4) Captive power generation, hence self reliant.

5) Own jetty for unloading imported raw materials without delays.

2.0 Effic iency Measures Implemented since 2005

Though the Paradeep plant was commissioned in the year 2000 but it wasunder closure by Pollution Control Board when IFFCO took over in 2005.

There were various design and operational drawbacks in the plant. IFFCO

took various systematic measures to improve its operation and energy

efficiency. With the continuous improvement, Electrical as well as thermal

energy has been brought down to the level of just half of its previous levels.

Water consumption of complex has been reduced from 35000 m3/day to

25000 m3/day. Some of the improvements made in the plant are described.

3.0 Efficiency Improvement in Sulphuric Acid Plant

3.1. Installation of Heat Recovery System (HRS)

Lot of heat is generated in the Sulphuric Acid Plant in acid dilution and

absorption. But a large amount of this heat is discarded in the cooling tower.

However in the Heat Recovery System, the low level heat discarded to the

cooling tower is used to generate the LP (4.0 kg/cm2g) steam.

HRS operates at the upstream of existing Intermediate Absorption Tower

(IAT). The HRS consists of a steam injection chamber, a packed heat recovery

tower, a horizontal steam boiler, heater, preheater, diluter, an acid circulating

pump, and two acid drain pumps. The schematic of sulphuric acid plant with

heat recovery system is shown in Figure 1.


3/19

- 3 -

Figure 1: Schematic diagram of Sulphuric acid plant with heat recovery system

The additional steam of about 65 MTPH produced by the heat recovery system

has reduced the steam required from the coal fired boilers. Since the heat

recovery system was installed, coal consumption has decreased by 35%. In

addition to this it has reduced the heat load on cooling tower by 45 Gcal/hr.

Which in turn have stopped the operation of 1 cooling water pumps, two cooling

tower fans and have reduced the evaporation loss from cooling tower. Total

savings attributable to the heat recovery system project are estimated at Rs 25

croreper year.

Figure 2 and 3 shows block diagram illustration of steam balance of the

complex before and after HRS respectively.

Furn

ace

I

II

SH 2

SH 1

IV

III

HRS

HeaterHRS Tower

Demister

FAT

Circulation

DT Circulation

Tank

BoilerConverter 1 Converter 2

Venturi

Scrubber

Hot HE450

oC

341.oC

248.

o

C

Cold HE

Steam DrumHP Steam to export

Stack

Strong acid from IAT tank required

during highhumidity only

IAT Circulation

Tank

240oC

DTFAT IAT

Sulphur

CW

CWCW CW

Air

Blow DownIP Steam

Economizer

HRS

Pre

Heate

r

Boiler feed water

To deaerator

Treated water

from existing

system

0.7 barg steam

HRS

Diluter

HRS Boiler

Steam

Strong

Acid to

common

acid tank

N

New HRS

Product

acid

Blower

Process water


4/19

- 4 -

Figure 2 Steam & Power balance PRE HRS-1

Figure 3 Steam & Power balance Post HRS-1


5/19

- 5 -

3.2. Reduction of Catalyst preheating time during Cold Start-up of Sulphuric

Acid Plant & simultaneous reduction of diesel consumpt ion.

This schemes was designed in-house to preheat the catalyst by utilizing HP

steam from coal fired boilers in the waste heat boiler of Sulphuric Acid Plant

and also providing an interconnection between 1stbed outlet duct to 4th bed

inlet duct in order to achieve 4thbed temperature early, during the cold start-

up. After implementation of the above scheme, diesel consumption has been

reduced from 100 KL to 60 KL thus saving 40 KL per startup per stream and

Cold start-up time has been reduced from 36 hrs to 24 hrs thus saving 12 hrs

of production. Total investment was just Rs. 1.0 lakh. The schematic of

scheme is shown in Figure 4.

Figure 4 Schematic diagram Modification of Start up in Sulphuric acid Plant

3.3. Alkali Scrubber to arrest SOX emission during start-up

Sulphuric acid plant is equipped with an Alkali Scrubber unit for scrubbing

1,20,000 NM3/hr of gas. The scrubbing system controls SO3concentration in

the stack during the plant start-up. Sodium hydroxide solution (15%) is used

as scrubbing media. After absorption of SO3, sodium hydroxide solution gets

converted into sodium sulphite and sodium bisulphate. The tail gas from final

absorption tower enters at the bottom of the scrubber and rises to the top

through polypropylene packing beds.


6/19

- 6 -

The moisture of the gas is removed by 20 Nos. of PPE fiber beds mist

eliminators installed before the packing. The gas leaving the scrubber is

vented in to atmosphere through the stack. The pH of the circulation solution is

maintained at 6.8. A bleed off is taken from the circulating liquor to the final

effluent tank where the aeration takes place. The solution is aerated for 120

hours by a surface aerator to convert sodium sulphite and sodium bisulphate

to sodium sulphate.

3.4. Caesium promoted catalyst

Caesium promoted catalyst has been added to the 4th bed (248 m3) of theconverter bed in Sulphuric Acid Plant. Out of the 248 m3 catalyst 50% is the

caesium promoted catalyst. The conversion temperature with caesium

promoted catalyst is as low as 340C where for normal catalyst its about 400-

420 C. Because of low reaction temperature conversion of SO2 to SO3

during cold start up is attained relatively faster, reduces the plant start-up

duration and also reduces the emission of SO2 during start up.

3.5. Utilization of vent steam from condensate receiver and CBD tank

In sulphuric acid plant, the flash steam from condensate tank and boiler

continuous blow down tank (CBD) were vented to atmosphere. To recover the

loss of energy the flash steam was diverted to the nearby deareator tank with

an investment on Rs 2.6 Lakh. The recovery of steam resulted in subsequent

reduction of 7 ton of LP steam input to deareator. The block diagram of the

scheme is shown in Figure 5.


7/19

- 7 -

Figure 5: Schematic showing Utilisation of Vent Steam

3.6. Reduct ion in Boiler feed water pump discharge pressure from 105kg/cm2g to 90 kg/cm2g in Sulphuric Acid pant

Though the boiler feed water header pressure requirement was about 90

kg/cm2g, discharge of Boiler Feed Water Pumps was maintained at 105

kg/cm2g to with a view that it provides operation flexibility. The detailed review

of the boiler feed water system established that there is no need of keeping

such a high discharge pressure. Reduction in the discharge pressure has

resulted in the stoppage of one pump which was made stand-by, thereby

resulting in power savings of 900 kW.

3.7. Candle Filter to arrest acid mist in sulphuric acid plant

In Sulphuric acid plant at the top of Inter pass Absorption Tower and Final

Absorption Tower, trickling candle filters have been installed. The candle filter

helps in arresting acid mist or droplets present in the outlet gases. The gas

leaving the final absorption tower has an acid mist concentration of 40 mg/Nm3

of SO3as against the norm of 50 mg/NM3, which is discharged through to tail

gas stack of 131 meters height.


8/19

- 8 -

4.0 Efficiency Improvement in Phosphoric Acid Plant

4.1. Modification of evaporators barometric condenser by installation of

single sieve type distribut ion t ray and removal of steam ejector system.

In evaporators, phosphoric acid is concentrated from 28% to 54 % P2O5.There

are seven evaporators. Each evaporator is single stage, forced circulation unit

consisting of rubber lined flash chamber, axial flow circulation pump and

vertical shell and tube Heat Exchanger with impervious graphite tubes. Acid is

re circulated at a high rate by the pump through the heat exchanger and into

the flash chamber where an absolute pressure of about 66 mmHg is

maintained to keep the acid at its boiling point. The vapours from the flashchamber flow under vacuum to the entrainment separator. From the separator

phosphoric acid is returned to flash chamber and the vapour flow continues to

fluorine scrubber. Vapours from the fluorine scrubber will come under direct

contact with cooling water in the barometric condenser and the remaining non

condensable gases are extracted.

Figure 6: Barometric Condenser Before and After Modification


9/19

- 9 -

Earlier System:

In the earlier system the vapors from the fluorine scrubber are condensed in

baffle type barometric condenser where a large amount of cooling water

condenses the partial amount of water vapor. Remaining water vapor and any

non condensable gases are extracted by a two stage Vacuum jet steam

ejector system consisting of two nos. of medium pressure (MP) steam (15

kg/cm2g) ejectors and a water cooled inter condenser. MP Steam

consumption in each ejector system was 2 MTPH. Total MP Steam

consumption in all the seven evaporators was 14 MTPH.

Modified system:

In the modified system, baffle trays of barometric condenser were replaced

with a single sieve tray where cooling water passes through the sieve at the

top and condenses condensable vapours and extracts all the non condensable

gases without vacuum jet ejection system. The modification was carried in-

house with an investment of Rs 84.894 lakh, with savings of 14 TPH of MP

steam equivalent to annual savings of about Rs. 5 crore.

Figure 6 shows the schematic before and after modification.

4.2. Installation of pre scrubber for improving Fluorine scrubbing efficiency

Earlier reactor fumes were scrubbed in a single stage scrubbing system with

pond water. This system was not adequate and was not meeting the norms

fixed by the Pollution Board. After conducting in-house study a pre-scrubber is

installed at the up-stream of the existing scrubber (Figure 7). Additional pre-

scrubber vessel along with an additional scrubber exhaust fan and new stack

with higher diameter was installed. This has improved the scrubbing efficiency,

reduced the fluorine emission to the atmosphere from 20-25 mg/NM3 to 4-5

mg/NM3.


10/19

- 10 -

Figure 7 Fluorine Scrubbing Unit

4.3. Retrofit of Fluorine recovery uni t

Earlier Hydro Fluorosilisic acid recovery system was bypassed. Hydro

fluorosilicic acid produced in evaporator section was not recovered in the

Fluorine Scrubber instead it was getting recovered in the barometric

condenser which in turn lead to rise in the fluoride content in cooling tower and

release of free fluorine in to the atmosphere. Fluorine recovery system was put

into operation by major revamping viz brick lining of the scrubber, installing

reliable pumps, circulation MSRL lines replaced with Poly-propylene lines etc.

Presently about 20 MT / day hydro flurosilisic acid (18% - 20% H2SiF6) is

recovered which in turn reduces emission of Fluorine to the atmosphere. The

schematic in Figure 8 shows the modification.


11/19

- 11 -

Figure 8: Fluorine Recovery Unit

4.4. Provision of a Single cloth wash tank in Phosphoric Acid Plant.

There are seven (7) nos. of belt filters in Phosphoric Acid Plant. Each belt filter

was having its individual cloth wash tank and cloth wash pump. All these 7 cloth

wash tanks and pumps were replaced with common cloth wash tank and pump.

This has reduced the power consumption by 27.5 kW and has also improved

the accessibility & approach to the equipments and house-keeping of the entirearea.

Figure 9: Schematic Diagram of Modification in Wash Tank


12/19

- 12 -

5.0 Effic iency Improvement in Complex Ferti liser Plant

5.1. Steam Air heater in DAP:

To evaporate the moisture of fertilizer, hot gases are supplied into the dryerthrough a duct which is lined with refractory. The hot air was generated byfiring

fuel oil through a burner and a combustion chamber with supply of inlet air.

System was retrofitted with steam heated air system for utilizing the captive

steam of the plant by connecting the hot air duct of this new steam air heater to

the existing discharge duct of combustion chamber as shown in Figure 10.

Total expenditure for all the three trains was Rs. 6.78 crore and with the annualFO saving of 12150KL total monetary savings are about Rs. 51.22 crore.

Figure 10: Steam Air Heater


13/19

- 13 -

5.2. Individual scrubbing system for Dust and Fumes in DAP/NP Plant

There was a common dust and Fume Scrubbing System for scrubbing dust

generated from conveyor, elevators, crushers & screens and Fumes from Pre-

neutralizer and Granulator. Dust being heavier and system not designed for

the combined scrubbing of fumes and dust, it was not able to suck the dust

properly. To overcome the problem separate dust scrubbing system was

installed from the scrap equipment and material (Figure 11). This modification

improved dust scrubbing efficiency reduced the dust escape to the

atmosphere and reduced the ammonia loss to atmosphere from 350 mg/NM3

to 150 mg/NM3.

Figure 11: Dust and Fumes Scrubbing Unit in DAP Plant

6.0 Effic iency Measures in Utilit ies and Offsi te

6.1. Energy savings due to installation of new BFW line from AFBC boiler to

Energy Center

Earlier a dedicated pump of 300 kW motor was supplying Boiler feed water to

PRDS in Energy center. A new line from the discharge of BFW pump of coal

fired boiler was provided to supply the required de-superheating water to thisPRDS. This has stopped the operation of 300 kW motor thus saved 300 kW

power.


14/19

- 14 -

6.2. Installation of lower capacity Pump at Canal pump house

The Canal pump house, which is the source of water supply to Paradeep Unit is

at distance of about two kilometres. From the underground tank of canal pump

house water is pumped to the plant through centrifugal pump of 3000 m3/hr

capacity drive by 450 kW motor. On studying the water supply system, it was

observed that the process requirement could be met with a pump of lower

capacity of 1500 m3/hr only. Pump was replaced with lower capacity pump

driven by motor of 160 kW thus saving 290 kW power.

6.3. Replacement of Cool ing Tower fan blades from sol id FRP to Hollow FRP

Fan blades of cooling tower in Sulphuric Acid Plant and Energy Centre were

replaced from Solid FRP to Hollow FRP. Seven numbers of Fan blades were

replaced in Sulphuric Acid Plant and 10 nos. of fan blades were replaced in

Energy Centre Cooling Tower. Total reduction in power consumption was 300

kW.

6.4. Energy savings in Coal Handling Plant (CHP)

There were 11 nos. of conveying belts were operated in the earlier layout.

However with careful study the conveyor belts have been reduced to 7. This

resulted in a power saving of about 200 kW.

6.5. Trimming of Filter water pump impeller

The filter water pumps are used to pump process water to different plants inside

the complex. Each of the three pumps was designed to give a flow of 1800

m3/hr at a discharge pressure of 6.90 kg/cm2. After an in-house study as per the

requirement of the plant it was observed that the impeller of one pump can be

trimmed for lower flow without any change in the discharge pressure. The

impeller dia. of the pump was trimmed form 540 mm to 520 mm. This resulted in

the power saving of 75 kW.

6.6. Installation of De dusting unit for Product Handling Conveyors

De-dusting units are installed at various locations in the product handling

system to extract the dust and keep the environment dust free Figure 11). The

system was designed in-house using scrap equipment & material.


15/19

- 15 -

Fig-11: De-dusting system for Product Conveyer and Bagging Plant

6.7. Energy savings due to reduct ion in discharge head of Ammonia transfer

pump

A scheme was implemented to reduce the discharge head thus reducing the

power consumption of Ammonia transfer pump by reducing the impeller from

four stage to three stage. After implementation of the scheme, power

consumption has been reduced from 71 kW to 59 kW, thereby saving 12kW of

power consumption.

6.8. Installation of Capacitor banks to increase Power factor

Power factor at Paradeep unit was just 0.71. Capacitor Banks were installed

and power factor improved to 0.90.

6.9. Installation of Steam traps and Condensate recovery system

A total of 387 nos. steam traps were installed in all the plants of the entire

complex. This scheme has resulted in steam savings of about 5%.

6.10. Installation of screw type un-loader

Earlier, there were two Grab type un-loaders each of 1500 TPH capacity at

Jetty for unloading Rock Phosphate & Sulphur from Ship. Unloading the

materials through grab un-loaders, lot of dust was generated.


16/19

- 16 -

Now an additional Screw Type Enclosed Un-loader of 1800 TPH capacity has

been installed to avoid the dust generation and any spillage (Figure 12). This

system was commissioned in July 2013.

Figure 12 Screw Un-loader

6.11. Renewable Energy Measures

As a part of green initiative; lighting of Administrative Building is done by

installing the solar panels of 30 kW (3x10 kW) with an investment of Rs.70 lakh

6.12. Measures for Water Conservation

6.12.1. Water conservation measures in Phosphor ic Acid Plant

a) Reduct ion in Fresh Water Consumption

Previously, around 200 m3/h of fresh water was used in the lubricating oil

coolers of the gypsum pump and ball mills. These coolers are now connected

to the sulphuric acid plant closed loop cooling water circuit, thereby reducing

fresh water consumption.

b) Utilization of Waste Water from utili ty/offsite

The waste water generated during back wash of resin in DM plant, tower blow

down of sulphuric acid and power plant cooling towers of about 350 m3/hr are


17/19

- 17 -

being used in 7 nos. of belt filter condensers, vacuum ring pumps and for rock

phosphate wet grinding. Thus saving about 9000 m3/day of fresh water.

c) Use of pond water as pump seal water

All the centrifugal pumps in phosphoric acid plant, except the pumps in ball

mill section are designed to handle acidic solution; this made us possible to

use acidic pond water as pump seal water instead of fresh process water thus

saving 20 m3/hr of fresh water.

The above modifications lead to zero consumption of process water in

phosphoric plant with only minor consumptions for safety showers and

cleaning purpose.

6.12.2. Water conservation measures in Sulphur ic Acid Plant

a) LP steam condensate recovery

About 25 TPH of low pressure steam is used for melting of sulphur, molten

sulphur storage tank and molten sulphur pipeline. All the steam condensate

from the sulphur melting and storage area earlier drained to the storm water

channel. This condensate is now sent to DM plant polishing unit. As a result of

this about 20 m3/h of DM water is saved.

b) Waste heat boi ler blow down recovery

Earlier blow down from waste heat boilers of around 10 m3/hr was drained in

the storm water channel. This is diverted to Intermediate absorption tower and

Final absorption tower dilution tanks for sulphuric acid dilution thus reducing

the consumption of water by 10 m3/hr.

7.0 Impact of Improvements

Figure 13 and 14 clearly indicate how Electrical Energy and thermal energy

consumption of the plant improved over the years respectively. Specific

consumption of electivity has been reduced from about 958 kWh/ MT of P2O5

in 2006-07 to 568 kWh/MT of P2O5 in 2012-13. In the year 2013-14, it is

expected that this shall be about 500 kWh/MT of P2O5. The water

consumption has reduced significantly.


18/19

- 18 -

958

833806

718

620 616

568

400

500

600

700

800

900

1000

KWH/MTof

P2O5inFertlizer

Overall Specific Consumption of Electricity

Thermal Energy Consumption was reduced from 2.99 Gcal/MT of P2O5 in the

year 2006-07 to 1.71 Gcal/MT of P2O5 in the year 2012-13. Lowest thermal

energy consumption of 1.07 Gcal/MT of P2O5 was achieved in the year 2011-

11. Thermal energy consumption in recent years has gone up due to stoppage

of Sulphuric Acid Plant for revamping the Absorption Towers. The overall

specific consumption of water has been brought down from 12.90 M3 per tonne

product in 2006-07 to 6.01 M3 per tonne of product in 2012-13 (Figure 15).

Gcal/tonneP2O5

1.18

1.71

2.99

2.43

2.04

1.31.07

0

0.5

1

1.5

2

2.5

3

3.5

2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-13

Thermal Energy Consumption per tonne of Complex fertilizer


19/19

Figure 15

8.0 Conclusion

With moderate investment in the energy conservation and environment

improvement measures as on-going process, there is steady decline of energy

consumption and reduction in emission of sulphur dioxide and fluorine.Consumption of electric and thermal energy have come down from 568 kWh/MT

of P2O5 to 500 kWh/MT of P2O5 and 2.99 Gcal/MT of P2O5 to 1.71 Gcal/MT of

P2O5 respectively from 2006-07 to 2012-13. The water consumption has also

been reduced from 12.90 M3/MT of product to 6.01 M3/MT of product during

the same period.

Documents

Article Efficiency Measures R 04 FAI