IFFCO kalol energy saving

7/29/2019 IFFCO kalol energy saving

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Sucess Story of Implementation of Energy Saving Project atIFFCO Phulpur Unit

- Mr. M. Rajashekharaiah- Mr. Y. Narula- Mr. I.C.Jha- Mr. R. Maiti

Abstract: IFFCO Phulpur unit is committed to use the energy in the most

efficient way. "Energy Conservation " is a major objective for IFFCO as such, and

more so, for Phulpur Unit. This has enabled to run the 1980 vintage Naphtha

based Ammonia Plant of Phulpur-I with better performance level even after 25

years of operation. Ammonia plant of Phulpur-II, a new generation Naphtha

based plant of late nineties, has been continuously improving its performance by

implementing several modifications and by adopting best operating philosophy.

IFFCO Phulpur Unit is continually striving to be the lowest energy consumer in

the fertilizer industry. To achieve its goal, a number of energy conservation

schemes have been identified and planned to implement in stages under the

Energy Saving Project (ESP). Phase-I of ESP was successfully implemented &

envisaged savings were achieved. Phase-II of ESP will be implemented in the

forth-coming annual turnaround. The ESP has also contributed in reducing Green

House Gas Emission. This paper highlights the schemes implemented in Phase-I

& schemes to be implemented in Phase-II and also describes in details the

experiences gained during project execution and implementation.


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Introduction:

IFFCO Phulpur Unit is a modern fertilizer complex originally having a 977 MTPD

Ammonia Plant based on Naphtha Steam reforming process of Kellogg, a 1670

MTPD Urea Plant based on ammonia stripping process of Snamprogetti-Italy,

three coal fired boiler having 125 MT/hr capacity each and 12.5 MW

TurboGenerator. This unit of IFFCO Phulpur plant started commercial production

in March 1981.

Second unit consisting of 2 streams of 1310 MTPD Urea Plant based on

ammonia stripping process of Snamprogetti-Italy, 1520 MTPD Ammonia Plant

based on Naphtha-Steam reforming of HTAS Denmark, a LSHS fired High

pressure boiler of 200 MT/Hr capacity and 18 MW power generator alongwith

necessary Offsites facilities was also commissioned in December1997.

The salient energy saving features of Ammonia Plant of Unit-II are:

9 Gas Turbine Drive (with Naphtha as fuel) for process Air compressor.

9 Heat Recovery Unit connected to the Gas Turbine for generating HP

steam to meet the requirement of Urea Plant.

9 Medium pressure Process Condensate Stripper.

9 GV-CO2 removal system.

The aim of IFFCO has been to achieve maximum production with high on stream

efficiency, consuming minimum energy in an eco friendly environment. IFFCO

Phulpur unit has focused its attention on various aspects of productivity along

with energy conservation, right from the very beginning.

In general as plant grows old, it is seen that there is decline in its performance

due to aging, wear & tear in the plant & machinery. But at IFFCO Phulpur Energy

management and Energy saving are among the top priority items in the list of

organizational objectives. The major steps followed to this effect are:


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a) Regular energy audit of the plant and identification of the sources of

energy wastage, if any.

b) Selection and implementation of suitable schemes to eliminate energy

losses.

c) Maintaining good house keeping through periodic monitoring.d) Increasing awareness among plant engineers and operators by regularly

conducting seminar / talks and by providing literature on energy

conservation.

With the help of the above strategy coupled with effective & efficient maintenance

program, IFFCO Phulpur unit has been able to achieve the excellence in energy

efficiency.

Specific energy consumption per MT of Ammonia Produced in Phulpur-I was at a

high level of 10.22 Gcal/MT of NH3 during initial years. As a result of sincere

implementation of above policy coupled with sincere and dedicated efforts by all,

it has become possible to operate the 1980 vintage Naphtha based plant at an

energy level of 9.2 Gcal / MT.

Being a new generation plant of late nineties, Ammonia Plant of Phulpur-II is

comparatively energy efficient. Specific Energy consumption per MT of Ammonia

produced in Phulpur -II was 7.82 Gcal/MT.

Energy Saving Project:

In the present market scenario, there have been obvious requirement of

upgradation of existing plant technology and reduction of specific energy

consumption. At IFFCO Phulpur, in order to make the plant as a viable unit, a

study to find out the possibility of improving plant performance was carried out. It

was observed that in Ammonia Plant maximum energy (70-80%) loss was in the

form of dumping to cooling water system through coolers & turbine condensers.

Special efforts were made to maximize heat recovery from the system, to

minimize steam consumption in turbines and also to improve the level of heat

recovery from the system. In order to achieve this, various schemes were


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envisaged for implementation under the Energy Saving Project (ESP). The

schemes, which were finalized for implementation, are:

Sl.

No.

Description

Phulpur-I

1.0 Improvement in outlet systems for LT Shift Converter

2.0 New LT shift guard, BFW Preheater and Separator

3.0 Revamp of CO2 removal system to a modern 2-stage GV process

layout

4.0 Installation of S-50 radial flow Synthesis Converter and MP Boiler

5.0 Drying of Make-up gas and Synthesis Loop Re-piping

6.0 Synthesis Gas Compressor LP & HP case internal replacement

7.0 Installation of Final Gas Chiller

Phulpur-II

1.0 New LT shift guard and BFW Preheater

2.0 Installation of S-50 radial flow Synthesis Converter and HP Boiler

3.0 Installation of Final Gas Chiller

Project Execution Philosophy:

Successful completion of any project, grass-root or revamp, entirely depends on

efficient planning. IFFCO Phulpur unit has enough project execution experience

and this has been explicit in completion of Phulpur Expansion Project one month

before the schedule. Though ESP is a revamp project, its quantum of job is only

slightly less than any other project as all the new equipments and pipeline are to

be erected near the existing equipments & within the available space. Moreover,

hooking up the new installation is to be carried out during plant turn around

without affecting normal plant operation

In order to have smooth execution of the project, the entire jobs have been split

into three stages.


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Relocation of existing equipment and rerouting of existing pipeline

to make space available for developing the best possible

equipment layout.

Implementation of schemes broadly covering the front-end of theAmmonia Plant viz Modification of CO2 Removal System at

Phulpur-I along with LTS Guard Bed with BFW pre-heater etc. in

both Phulpur-I & Phulpur-II termed as ESP: Phase-I.

Implementations of schemes covering the back-end of the

Ammonia Plant viz S-50 Converter and Boiler, Make-up Gas

Chiller, Make-up gas Drying in both Phulpur-I & Phulpur-II,

Modification/Re-rotoring of Synthesis Compressor in Phulpur-I -

termed as ESP: Phase-II.

ESP Phase-I schemes have been commissioned in the annual turnaround of

2005 & ESP Phase-II schemes are planned to be commissioned in March-April

2006.

It was decided that all three phase of works would be carried out during annual

turn around. In order to minimize the execution time further, entire fabrication /

erection jobs have been subdivided in three groups.

Erection of new equipments, wherever possible, before annual turn

around.

Pre-fabrication and erection of piping, new control valves &

instruments, to the extent possible before annual turn around.

Modification of existing pipelines for hooking up the schemes and

modification of existing DCS & ESDS system to facilitate the

installation of new graphics & control logics during annual turn

around.

Brief description of the schemes of both Phulpur-I & Phulpur-II, which was

implemented during annual turn around of 2005, is given below.


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PHULPUR-I: ESP-Phase-I

Improvement in outlet systems for LT Shift Converter

Original Elephant Stool Shift Reactor Outlet system

The outlet system of the LT shift reactors was changed to decrease the pressure drop

across the reactor. In the originally designed LT Shift Reactor of Kellog Design,

elephant stool outlet system was installed.

However, by modifying to an HTAS proven outlet system, the pressure drop in the

reactor decreased to 0.5 Kg/cm2. The lower pressure drop resulted in a higher suction

pressure for the synthesis gas compressor and thereby reducing the power consumption

of the compressor.

New HTAS Proven Shift Reactor Outlet system

New LT Shift guard, BFW Preheater and Separator

The main objective of introducing changes in the shift section was to lower the pressure

drop created by the reactor outlet systems and to reduce the CO slippage from the


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section. Furthermore, additional heat was expected to be recovered at a higher energy

level in this section by installing an HP BFW preheater.

With the installation of LT Shift Guard before LT Shift Converter, it was possible

to short load the existing LT Shift converter and reduce the pressure drop. The

new BFW preheater improved the heat gain in BFW for the production of HP

Steam and subsequent temperature control in LT Shift Converter. On an

LT Shift guard, BFW Preheater and Separator : Phulpur-Iaverage, the CO slip at the outlet of LT Shift Converter, after the installation of LT

Shift Guard, lowered to 0.15 % as against 0.25-0.30% without LT Shift Reactor.

Lower CO slip resulted in additional ammonia production due to reduction in

consumption of Hydrogen in Methanator otherwise required for converting all

residual carbon oxides in gas mixture into methane before entering Ammonia

Synthesis loop. In other way, with same level of ammonia production, feed

naphtha requirement was reduced which also translated in subsequent reduction

in steam consumption.

Revamp of CO2 removal system to a modern 2-stage GV process layout

In the original design, CO2 removal system of was Benfield process with a

design regeneration heat requirement of 1056 KCal/NM3 of CO2. In 1993, the

Lo-Heat benfield modification employing multistage flash tank & steam ejectors

with design energy of 960 Kcal/NM3 was implemented.


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For further reduction of energy consumption, revamp of CO2 removal system to

2-stage GV Process layout was the best option taking into consideration the

limitation in space and utilization of existing towers with efficient packing.

The main features of 2-stage GV process, were the high pressure and low

pressure stripping process occurring in two strippers using same Benfieldsolution with activator ACT-1, with HP CO2 Strippers operating at 1.1 Kg/cm2g &

LP Stripper operating at 0.14 Kg/cm2g. Rich / loaded solution was introduced to

both HP & LP Strippers in parallel and semi lean and lean solution from HP

Stripper to LP Stripper before going to the respective circulating pump suction. In

order to compress the CO2 generated in LP Stripper to required supply pressure

of CO2 to Urea, OH CO2 System comprising of condenser, separator,

condensate pump & CO2 blower was installed. Packing of absorber bottom bed

was replaced with IMTP 40 and discharged packing (Hy-Pak no. 2) was utilized

to replace the bottom bed of HP Stripper.

Modification in CO2 removal system to a modern 2-stage GV Process

In the new process layout total solution (both semilean & lean) was flushed to a

pressure of 0.14 Kg/cm2 whereas in Lo-Heat process only semilean solution was


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flushed. This resulted in lower regeneration heat requirement. With this a more

pure CO2 product was available with lower regeneration energy.

PHULPUR-II: ESP-Phase-I

New LT Shift guard, BFW Preheater:

The purpose of installing LT Shift Guard before LT Shift Converter was to reduce

the CO slippage from the section without increasing pressure drop. A new BFW

LT Shift guard, BFW Preheater : Phulpur-IIPreheater was installed at down stream of new LT Shift Guard in order to control

the inlet temperature to LT Shift Converter and to recover the exothermic heat of

reaction. Knockout Drum was not installed because the BFW temperature inlet to

BFW Preheater was kept higher than that of Phulpur-I. This resulted in higher

tube wall temperature and thereby possibility of condensation was eliminated.

Impact of the scheme was same as described for Phulpur-I scheme. Only

difference was that after installation of LT Shift Guard, CO slip from LT Shift

Converter reduced to 0.12 % from the existing value of 0.20 %.


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PHULPUR-I: ESP-Phase-II

Brief description of schemes of Phulpur-I that will be implemented during forth-

coming annual turn around of 2006 are given below:

Installation of S-50 radial flow Synthesis Converter and MP Boiler:

In Phulpur-I, the design ammonia content at the outlet of Synthesis Converter is

only 15.5 % whereas the new generation plants are designed with ammonia

content as high as 24%. In order to get higher conversion, a new S-50 converter

with a lower heat exchanger and an internal electrical start-up heater is to be

installed at the down stream of existing Ammonia Synthesis Converter. The new

converter will increase the ammonia conversion per pass and reduce the gas

circulation through the synthesis loop and thereby will reduce the overall steam

consumption in the Synthesis Compressor Turbine. As a result of higher

conversion in the S-50 converter, Synthesis Converter outlet temperature is

expected to increase beyond the design temperature of the existing BFW Heater.

Therefore, it is planned to install a New Boiler downstream of converter before

existing BFW Heater. Medium Pressure steam generation from the new boiler

has been chosen to optimize the overall steam balance of the plant.

Drying of Make-up gas and Synthesis Loop Re-piping

It is observed that refrigeration compressor load in Phulpur-I is very high in

comparison with that of Ammonia-II. This is only because of high recycle rate in

the synthesis loop. With the intension of reducing synthesis loop circulation rate

and pressure drop further, the piping around the synthesis gas compressor

recycle stage will be rearranged in such a manner that ammonia present in


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Schematic Diagram of Modified Back-end of Ammonia Plant : Phulpur-I

Converter effluent will get condensed and separated before going to the recycle

stage of the compressor. The recycle gas will then mix with make-up gas and get

compressed in the recycle stage of the compressor and directed to the Synthesis

Converter through the converter feed / effluent exchanger. This system has adisadvantage because oxides of carbon and hydrogen present in the make-up

gas are directly fed to Synthesis Converter by which catalyst gets deactivated.

After this loop re-piping, the existing water cooler will not be used to cool kick-

backed gas. Hence one Kick-Back Cooler will be installed at the discharge of

Synthesis Compressor

In order to send oxide free make-up gas directly to the converter, an ammonia

wash unit will be installed between LP & HP case of Synthesis Compressor. The

make up gas will be washed with an ammonia stream from ammonia separator to

remove the oxides. Installation of Ammonia Wash Unit and Synthesis loop re-

piping will reduce the circulation rate in the synthesis loop and thereby will

reduce the power consumption in the Synthesis Gas Compressor.


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Synthesis Gas Compressor LP & HP case internal replacement:

The present compressor is of mid 1970 design and the operating conditions have

changed largely after the Synthesis Converter retrofit in which Kellogg design 4-

bed axial flow quench type reactor was modified to Casale design axial-radialflow reactor. Moreover, after the installation of S-50 Converter and Loop re-

piping, operating condition, particularly circulation rate, will change drastically.

This will decrease the operating pressure of Synthesis loop. The new internals of

LP & HP case will be designed to meet the new operating condition and better

efficiency. The combined efforts of matching the system & operating conditions,

improvement in efficiency leads to less steam consumption in the Synthesis

Compressor Turbine.

Installation of Final Gas Chiller:

After the installation of S-50 Converter & Ammonia Wash Unit, Synthesis

Converter effluent gas will be cooled and chilled successively in three Ammonia

chillers. Due to higher loop pressure and higher ammonia concentration, vapor

generated in the first chiller, which is operated at a pressure corresponding to 3 rd

stage suction of Refrigeration Compressor, will be high. This will cause improper

distribution of ammonia vapor among the different stage of Refrigeration

Compressor which may lead to condition of running the Refrigeration

Compressor very close to surge limit even with a small kick back flow.

The additional load on the 1st stage and subsequent stages of the refrigeration

compressor will improve its operation and reduce the wastage of power by the

kickback flow.

With the intention of increase in load on the 1st stage of the refrigeration

compressor, Final Gas Chiller is introduced to cool down the make-up gas to 6

deg.C from the present level of 27 deg.C. This will increase the volumetric

efficiency due to lower inlet temperature of make-up gas leading to reduction in

steam consumption in the synthesis gas compressor for the same work output.


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PHULPUR-II: ESP-Phase-II

Brief description of the schemes to be implemented during annual turn around of

2006 are given below:

Installation of S-50 radial flow Synthesis Converter and HP Boiler:

For energy reduction in ammonia synthesis loop, installation of a HTAS S-50

ammonia synthesis converter and a new HP-WHB is found to be the most

beneficial option. The S-50 converter & New HP Boiler will be located in series in

between the existing converter and existing HP Synloop Boiler. The S-50

converter will increase the conversion and reduce the circulation and thereby will

reduce the pressure drop in the loop. Furthermore, To make an optimum overall

steam balance, high pressure steam will be generated from the waste heat boiler

to control the inlet temperature to the new converter.

S-50 radial flow Synthesis Converter and HP Boiler


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Installation of Final Gas Chiller:

In the existing system, make-up gas is cooled to 35 deg.C before being

compressed in the synthesis gas compressor. Final Gas Chiller will be introduced

to cool down the make-up gas to 6 deg.C from the present level of 35 deg.C.This will increase the volumetric efficiency due to lower inlet temperature of

make-up gas leading to reduction in steam consumption in the synthesis gas

compressor for the same work output.

Experience in Revamp Equipment Layout:

Inclusion of new equipments and piping in Kellogg Ammonia Plant layout of 1980

vintage was a very difficult task. In last 25 years of operation, many

improvements for energy saving and plant reliability have been incorporated.

These modifications already added some equipments and space available in

original plant layout has already been used. New LT Shift Guard and BFW

Preheaters were quite big in size in comparison to

LT Shift guard, BFW Preheater and Separator : Phulpur-I

existing equipments. Some radical decisions were taken. Existing LT Shift

Converter inlet Knockout drum was relocated to new place and piping revamped

during the annual turn around 2004. This made space available for LT Shift

Guard. BFW Preheater and new Knockout drum were planned to be located at


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higher elevations. With location of BFW Preheater and Knockout Drum at higher

elevation, movement of crane boom to be used later for maintenance / catalyst

loading in HT / LT Shift Converter was expected to be restricted. The location

and elevation of BFW Preheater and Knockout Drum was optimized for smooth

operation of crane by analyzing with the help of various views of layout option.

CO2 removal system with a modern 2-stage GV Process: Phulpur-I

Similar layout problem due to space limitation also propped in modification of

CO2 Removal system, which required relocating of 105-CB near the existing105-CA to have both the re-boilers connected with HP Stripper. Making civil

foundation for 105-CB near existing 105-CA was not possible due to limitation of

space in adjacent area and interference between existing and proposed

foundations. It was decided to keep the Process Gas Reboilers at their original

locations. But this resulted in long 30 size piping from Process Gas Reboiler

(located near to LP Stripper) to HP Stripper. Due to two-phase fluid flow in piping,

vibration was also expected during operation. During normal stress analysis

results, two loops were provided by the consultant, which could have resulted in

higher vibration. With the help of finite element analysis by specialists and taking

cue from vibration free operation of existing piping arrangement for last 25 years,

new piping without loops were finalized. This resulted in compact piping layout

suiting to space limitation problem. Location of CO2 Blower and new Acid Gas

Separator were finalized after lot of permutation and combinations.


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New LT shift guard, BFW Preheater of Phulpur-IIEnough space between the equipments is provided in HTAS Ammonia Plant of

Phulpur-

II, still finalization of layout was difficult task in order to satisfy insurance

guidelines for minimum distance between control room and nearest piping /

equipment and also to provide space for movement of tractors etc. for loading /

unloading of shift converter catalyst. But as Knock-out Drum was not there,

finalization of layout was comparatively easier than Phulpur-I.

Problem in Erection:

ESP Phase-I has already been executed and commissioned. Some of the

problem faced during fabrication and erection are listed below:

The first job of modification of shift outlet system was taken up in

the annual turnaround of 2004. The complete fabrication and

erection was executed through in house expertise and resources.

The fabrication and erection job inside the vessel in a limited time


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period was a tough task. This was completed successfully with

micro-planning of activities outside and inside the vessel.

The piping items in quantities were less in comparison to any

grass-root project and this led to get very little response from

foreign bidders for pipe & pipefitting. Indigenous vendors delayed the supply and many items had to be

directly unloaded to job site as there was no time available for

prefabrication.

Many materials had to be replaced with alternate available material.

The ESP piping layout was finalized after consideration of as-built

isometric drawings of the existing piping. As it happens in revamp

jobs, at number of places as-built dimensions in the drawing were

not matching with site dimensions. So, modifications in pre-

fabricated spools at the last moment were required to be done.

Modification of Strippers was a challenging job. The additional

nozzles, modification in size of the existing nozzle, welding and

heat treatment was deliberated and may options were thought off.

After all these deliberations, total modification of Strippers including

its internals was done in house with out taking any assistance from

outside agencies.

During execution of Strippers modification, it was also observed

that draw-off pan was having stress corrosion cracks. As repair by

welding was to cause further damage, the cracks were not repaired

but a SS sheet was laid over it at the places where cracks were

visible.

For nozzle modification in HP & LP Strippers, new reinforcement

pads on dished ends could not be welded, as shape of dished ends

could not be formed. The existing reinforcement pads only were

used for these nozzles.


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Experience in Pre-commissioning and Commissioning

In ESP Phase-I of Phulpur-I, two schemes that have been implemented during

the annual turn around 2005 are installation LT Guard & BFW Preheater and

Revamp of CO2 removal system to a modern 2-stage GV process layout. Natureof these schemes was completely different. First one was an add-on unit

whereas second one was the modification of the existing unit. Based on the

nature of the schemes it was decided that pre-commissioning activity of CO2

section revamp would be carried out along with the normal plant start-up, but LT

Guard system would be stream lined after completion of start-up activities.

Activities, which were carried during pre-commissioning and commissioning of

CO2 Removal section, are:

Card board Blasting of all CO2 lines.

DM Water Washing of all Benfield Solution and condensate lines.

Tightness test / Leak testing of overall system by blocking the

system at normal pressure level for 8 hours.

Water washing of the complete system by circulating washing

liquid.

Alkaline Washing of the system by circulating 3.5 wt % NaOH

solution at a temperature of 80 deg C.

Washing with hot DM Water for 8 hours.

Cleaning of all pump strainers.

Passivation of the system by circulating 23.5 wt % K2CO3 and 0.4

wt % of V2O5 solution at a temperature of 140 deg C for 24 hours.

Introduction of Process Gas to CO2 Absorber after the formation of

passivation layer. Formation of Passivation layer is confirmed by

analyzing V2O5 concentration in solution, which remains at more

than 4 g/l.


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Activities, which were carried during pre-commissioning and commissioning of LT

Guard System, are:

Card board Blasting of all Process Gas lines.

Steam Blowing of all Steam and Condensate line.

Catalyst Loading, Purging and Catalyst heating with hot nitrogen

Reduction of LT Guard Catalyst as per suppliers procedure.

Lined-up LT Shift Guard with the main LT Shift Converter.

Problem Faced during Pre-commissioning & Commissioning

a) Maintaining solution temperature during passivation of the system

In Lo-Heat Benfield Process, four re-boilers, two Process Gas Reboilers and two

Steam Reboilers supplied heat to both the Strippers running in parallel. After

modifying the system to 2-stage GV process lay out, one steam reboiler was

removed and all other three reboilers were connected to HP Stripper to supply

total regeneration heat.

During passivation of the system, Steam Reboilers were used to maintain the

desired K2CO3 solution temperature at about 80 -100 deg C. But after the

modification, only one Steam Reboiler was available because heat from Process

Gas Reboilers was not available at this stage of plant start-up. Heat supplied by

only Steam Boiler became insufficient to maintain the solution temperature.

Solution temperature could only be maintained after the Process Gas Reboilers

were taken in line, which caused 24 hours delay in production. To eliminate the

problem permanently, required necessary changes have already been planned

and are described below in Future Planning section of the article.

b) Controlling Level of HP Stripper

In the modified system, diverting rich solution to both HP Stripper & LP Stripper

controls level of CO2 Absorber, feeding semi lean & lean solution from HP


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Stripper to LP Stripper controls level of LP Stripper and level of HP Stripper gets

controlled automatically. During commissioning, the level indication of HP

Stripper was erratic. Indicated level was much less than the actually prevailed.

After introduction of process gas in the Process Gas Reboilers, it was observed

that lean & semi lean solution temperature in HP Strippers gradually increasedand level of LP Strippers gradually decreased, which led to reduction in

circulation rate and finally stoppage of circulation.

After analyzing the phenomena, it was concluded that flow of liquid from HP

Stripper to LP Stripper was restricted due to flashing of liquid occurring across

the level control valve. Reason for the flashing was higher solution temperature.

In fact, the control valve is designed for handling liquid only. Although heat was

being supplied by process gas, proper boiling of liquids was not taking place due

to higher level of liquid and thereby causing non-availability of vapor space.

Finally, it was concluded that level indication of HP Stripper was erratic. All the

tappings of level troll were checked and instrumentation loop in DCS for the level

indication was checked. Solution was drained from HP Stripper. Level indication

was recalibrated and reconfirmed from the local level gauge. After ensuring the

reliability of level indication in all aspects, circulation was established and total

system was taken in line with out any hindrance.

c) Higher process gas temperature at the inlet of Process Gas Reboilers

As per process design, before entering to Process Gas Reboilers, process gas is

cooled down to a temperature of 173 deg C by generating steam in Condensate

Reboiler (501-C). Steam generated in Condensate Reboiler is directly fed to HP

Stripper as live steam. Process gas temperature at the inlet of Process Gas

Reboilers is controlled via a side stream flow control valve, which bypasses a

fraction of process gas.

After stabilizing the total plant, optimization of parameters in modified system

was started. But LP steam supplied to Steam Reboilers could not be reduced

beyond 3.5 MT/hr against the guaranteed figure of 1.5 MT/hr. Further reducing

steam to Steam Reboiler below 3.5 MT/hr, overall water balance with in the


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system got disturbed and level in Condensate Reboiler could not be maintained

with out taking DM Water from outside. This was because of lesser amount of

condensate formed in the Over Head Condensate system.

After analyzing the problem, it was found that heat load of Condensate Reboiler

was more than design value, which demanded more condensate for maintainingthe desired level. Temperature of process gas at the inlet of Process Gas

Reboilers was 162 deg C against the design value of 173 deg C though the by-

pass flow control valve was full open. Theoretical estimations based on the

design pressure drop of the control valve indicated that only half of the process

gas would flow through the by-pass control valve even at full open condition. In

order to solve the problem, it has been planned to replace the by-pass control

valve with a new one having lower pressure drop in next annual turnaround.

Performance Evaluations

Phulpur-I

a) New LT shift guard, BFW Preheater and Separator

Phase-I of Energy Saving Project in Phulpur-I, consisting of LT Guard Scheme

and CO2 Section Revamp to 2-Stage GV Process, was commissioned during

Annual Turnaround of March-April 2005.

Implementation of LT Guard Scheme resulted in decrease in CO slip from CO-

Conversion Section to 0.15 mol-% from 0.21 mol-% earlier. This resulted in

decrease in specific consumption of all inputs (due to decrease in loss of H2 in

Methanator), increase in heat recovery but slight increase in pressure drop in the

front end due to addition of new equipments & piping.

b) Revamp of CO2 removal system to a modern 2-stage GV process layout

CO2 Removal Section in Phulpur-I Ammonia Plant was revamped from Lo-Heat

Benfield System to 2-Stage GV Process retaining Lo-Heat Benfield Solution for

CO2 removal. The heat supplied in Reboilers for regeneration of Benfield


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solution has reduced from 35.2 Gcal / hr. to 27.76 Gcal / hr. The power

consumption in CO2 Blower (110-J) installed to boost CO2 pressure from LP

Regenerator 102-EB, is 378 kWH. The net Regeneration Energy of CO2

Removal Section has reduced from 1049 k cal / Nm3 of CO2 to 872 k cal / Nm3

of CO2 on implementation of the Scheme.

Phulpur-II:

New LT shift guard and BFW Preheater

Phase-I of Energy Saving Project in Phulpur-II, consisting of LT Guard Scheme,

was commissioned during Annual Turnaround of Feb-March 2005. The CO slip

from CO-Conversion Section was reduced from 0.20 mol-% to 0.12 mol-%. This

resulted in decrease in specification consumption of all inputs (due to decrease in

loss of H2 in Methanator), increase in heat recovery but slight increase in

pressure drop in the front end (due to addition of new equipments & piping). The

heat recovery increased by 0.15 Gcal / hr.

Future Planning

Problems that have been faced during commissioning of ESP Phase-I schemes

and major problem that have been envisaged during finalization of equipment

layout are listed below:

Provision for using MP steam in Process Gas Reboilers

In order to save start-up time as well as additional expenditure on account of

venting of Process Gas, provision for MP Steam connection in 105-CA/CB for

heat input during passivation has been planned. As per the scheme, MP Steam

is, first of all, desuperheated to a temperature of 160 deg C and then fed to

Process Gas Reboilers, which will give heat to the circulating K2CO3 solution to

maintain the required temperature. The proposed scheme consists of one flow

control valve, and one spray nozzle temperature control valve and other

instruments & piping. The same will be implemented during annual turn around of

2006.


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Utilization of Existing Foundation of Process Gas Reboiler of CO2 Removal

system for Final Gas Chillers.

The space limitation in Ammonia-I provided various ideas of utilizing space.

Finalization of Final Gas Chiller location was again a difficult task. Even utilizingthe space, after removal of Steam Reboiler of CO2 Removal System in ESP

Phase-I, was not possible as dismantling of old foundation and making new

foundation in a running plant in such a congested area was not possible. As such

it was decided to make structure on the existing foundation suitable for the Final

Gas Chiller and place it on the same.

Relocation of Converter Effluent Exchanger (121-C) by modifying existing

foundation to facilitate Synthesis Loop Repiping

Presently, converter feed gas, after separating ammonia in Ammonia Separator,

is heated in the tube side of Converter Feed / Feed Recycle Gas Exchanger

(120-C) and then further heated in the tube side of Converter Feed/ Effluent

exchanger (121-C). In order to keep the tube side of both the exchangers in

series, tube side channel covers are directly connected through nozzles.

After the Loop Repiping, tube side out let of 120-C will be routed to recycle stage

of Synthesis Compressor and final discharge of Synthesis Compressor will be

routed to tube side inlet of 121-C. To accommodate this two 14 pipeline between

two adjacent exchanger, it was planned earlier to modify the exchangers by

cutting the shell to channel joint and re-welding in an orientation where those

tube side nozzles are opposite in direction. Later after considering the criticality

of cutting & re-welding of an equipment, it has been decided that 120-C is to be

placed at a higher elevation at the same location on the same foundation with a

structure on the foundation. To elevate 120-C it has been planned to construct a

structure of required height on the same foundation so that space is created to

accommodate 14 90 deg. 1.5 D elbow between the two exchangers.


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Conclusion

Energy conservation is a continuous process and it is very much essential for

energy intensive industry like fertilizer. Improvements keeping pace with

technology advancement are the key for survival and progress. ESP: Phase-Ihas been implemented in time and expected energy savings has also been

realized except for some minor deviation, which will be realized after some

modification. IFFCO Phulpur firmly believes that Energy Saving Project: Phase-II

is expected to be completed before the scheduled time and that will in turn add

up to Phulpur unit being more energy efficient & cost effective.

Documents

IFFCO kalol energy saving