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A
TRAINING REPORT
ON
UREA- PLANT
TRAINING DURATION: 6 th JUNE 2011 TO 2 nd JULY 2011
SUBMITTED TO SUBMITTED BY
Dr. D. N. VERMA SAUMYA TIWARI
D. G. M.-TRAINING 3rd yr, B. Tech. (CHEMICAL ENGG.)
IFFCO PHULPUR, ALLAHABAD H.B.T.I. KANPUR
1
CERTIFICATE
This is to certify that the Training Report on UREA-1 plant has been prepared by Saumya
Tiwari d/o Rakesh Tewari ( 3rd yr B.Tech, Chemical Engineering) of HBTI Kanpur
(G.B.T.U Lucknow) and she has taken keen interest in completion of her assignment under
my guidance .
Mr. R.B. Rai Mr. A. K. Chaturvedi Mr. S.K. Mishra
D.G.M.(Urea-1) Chief manager(Urea-1) Sr. Manager(Urea-1)
IFFCO ,Phulpur, IFFCO,Phulpur, IFFCO, Phulpur,
Allahabad Allahabad Allahabad
2
ACKNOWLEDGEMENT
Industrial training is a part of our academic activities and every student has to attach
himself with any one of the leading industries for getting insight of this subject. The entire
period of training, I wish to express my gratitude to the management of IFFCO Phulpur,
Allahabad, especially its management and training department who gave me this opportunity
by permitted to me to work under their kind supervision.
I would like to express my thanks to Dr. D. N. Verma who provided me an
opportunity to do training. I wish sincerely thanks to Mr. Rajan Singh for all outwork
rendered to me for completing this training report.
At the submission of this project we take the opportunity to express our deep sense of
gratitude to Mr. R.B. Rai, Mr. A. K. Chaturvedi, Mr. S.K. Mishra and Mr. V. P. Singh for
supporting and guiding us.
We would also like to appreciate all the plant operators and engineers of this
organization who helped us enough in quenching our thirst to smallest queries.
3
TABLE OF CONTENTS:
SR. NO.
BRIEF DESCRIPTION OF CONTENTS Pg. no.
1 Introduction of IFFCO 52 Introduction of IFFCO Phulpur unit 73 Ammonia plant 103.1 Brief description of ammonia plant 113.2 Brief process description of ammonia plant 134 Urea plant 184.1 Brief description of urea plant 194.2 Urea : physical and chemical properties 204.3 Process technology 214.4 Uses of urea 224.5 Brief process description of urea plant 234.6 Effect of process variable in urea plant 294.7 Urea production performance 314.8 Equipment details 324.9 Corrosion in urea plant 364.10 Offsite description 374.11 Power distribution 424.12 DCS System 425 Environment and pollution control 436 Fire and safety 447 Conclusion 468 References 48
4
INTRODUCTION
Indian Farmers Fertilizers Co-operative Limited (IFFCO) was registered on November 3,
1967 as a Multi-unit Co-operative Society. On the enactment of the Multistate Co-operative
Societies act 1984 & 2002, the Society is deemed to be registered as a Multistate Co-
operative Society. The Society is primarily engaged in production and distribution of
fertilizers.
IFFCO commissioned an ammonia - urea complex at Kalol and the NPK/DAP plant at
Kandla both in the state of Gujarat in 1975. Another ammonia - urea complex was set up at
Phulpur in the state of Uttar Pradesh in 1981.
As part of this vision, IFFCO has acquired fertilizer unit at Paradeep in Orissa in
September 2005. As a result of these expansion projects and acquisition, IFFCO's annual
capacity has been increased to 3.69 million tons of Urea and NPK/DAP equivalent to 1.71
million tones. In pursuit of its growth and development, IFFCO had embarked upon and
successfully implemented its Corporate Plans, ‘Mission 2005’ and ‘Vision 2010’. These
plans have resulted in IFFCO becoming one of the largest producer and marketer of
Chemical fertilizers by expansion of its existing Units, setting up Joint Venture Companies
Overseas and Diversification into new Sectors.
5
IFFCO has now visualized a comprehensive plan titled ‘ Vision-2015 ’ which is presently
under implementation. IFFCO has made strategic investments in several joint ventures.
Godavari Fertilizers and Chemicals Ltd (GFCL) & Indian Potash Ltd (IPL) in India. As
part of strategic diversification, IFFCO has entered into several key sectors. IFFCO-Tokio
General Insurance Ltd (ITGI) is a foray into general insurance sector. Through ITGI,
IFFCO has formulated new services of benefit to farmers. 'Sankat Haran Bima Yojana'
provides free insurance cover to farmers along with each bag of IFFCO fertiliser purchased.
IFFCO is also behind several other companies with the sole intention of benefitting farmers.
The distribution of IFFCO's fertilizer is undertaken through over 39824 Co-operative
Societies. In addition, essential agro-inputs for IFFCO has promoted several institutions and
organizations to work for the welfare of farmers, strengthening cooperative movement,
improve Indian agriculture. Indian Farm Forestry Development Cooperative Ltd
(IFFDC), Cooperative Rural Development Trust (CORDET), IFFCO Foundation,
Kisan Sewa Trust belong to this category. An ambitious project 'ICT Initiatives for Farmers
and Cooperatives' is launched to promote e-culture in rural India. IFFCO obsessively
nurtures its relations with farmers and undertakes a large number of agricultural extension
activities for their benefit every year.
At IFFCO, the thirst for ever improving the services to farmers and member co-operatives is
greedy, commitment to quality is insurmountable and harnessing of mother earths' bounty to
drive hunger away from India in an ecologically sustainable manner is the prime mission.
IFFCO, today, is a leading player in India's fertilizer industry and is making substantial
contribution to the efforts of Indian Government to increase food grain production in the
country.
Awards & Milestones Safety Innovation Award - 2010
Greentech Gold Award for Training Excellence
ICWAI Award for Excellence in Cost Management - 2009 for IFFCO
IFFCO Shines at Public Relation Society of India, Grabbed 2 prestigious awards
IFFCO Aonla Wins "Gold Award“ - 10th Annual Greentech Environment Excellence
Award 2009
IFFCO bagged First ever dotCoop Global Award for Cooperative Excellence
IBM Awards First Prize to IFFCO for Innovation
6
IFFCO Phulpur Unit-I bagged "First Prize" by FAI.
CIO 100 & IT Awards
Microsoft Felicitates IFFCO
National Energy Conservation 2008 - 1st Award Conferred on Phulpur Unit
IFFCO bags three FAI Awards
IFFCO bags Energy conservation award
Phulpur Unit bags National Energy Award from Honorable President of India
Best Managed Work Force Award for IFFCO
IFFCO PHULPUR UNIT
Head of the Unit : Mr. Surjit Singh (Sr. Executive Director)
Total Area 1068 acres
Area Under plant 321 acres
Area under Township Area under township, cordet, agricultural farms, green belt, ash ponds, roads, Open space: 747 acres.
IFFCO Phulpur is a large scale modern fertilizer complex having two ammonia plants and
two urea plants. A turbo generator set has been provided to insulate the plant operations from
the effects of unreliable imported electric power. Coal handling, ash handling, inert gas
generation plant naphtha fuel oil and diesel storage and handling facilities. 10000 tons
capacity of atm ammonia storage and loading facility bagging and material handling etc are
often auxiliary units of ammonia and urea complex. Consultants for ammonia, urea and
offsite facilities were respectively Pullman Kellog, Snam Progetti and Development
consultants.
LOCATION:
Unit is located in the heartland of gangetic zone which is India’s prime agriculture belt at
Phulpur district Allahabad in the state of U.P. The site is located in U.P. highway no. 7
connecting Allahabad to Jaunpur and Gorakhpur Phulpur, which is a tehsil, is about 5 km.
7
away from the site and linked with broad gauge line on the Varanasi- Allahabad railway
route.
Phulpur I Process Licensor Date of Commercial production
Ammonia Plant MW Kellog, U.S.A Urea Plant Snamprogetti, Italy 28th MAR 1981
Phulpur II Process Licensor Date of Commercial production
Ammonia Plant HTAS, Denmark Urea Plant Snamprogetti, Italy DEC 22nd , 1997
PHULPUR PRODUCTION CAPACITY:
PLANT PRODUCTION IN MTPD
PHULPUR-1
AMMONIA : 1215
UREA : 2115
PHULPUR-2
AMMONIA
UREA
:
:
1740
3030
8
Phulpur Unit - Records & Achievements
Highlights of 2009-2010 of Phulpur Unit has Achieved Highest ever Yearly Production with Lowest ever Yearly Energy in All Plants. Longest Accident free period of 1721 days till March 31,’10 is continuing since 15th July, 2005. Golden Jubilee Award in Recognition & Appreciation of Extraordinary Accomplishment and Contribution to the Nation from Chamber of Commerce & Industry, (Eastern U.P., Allahabad)
Phulpur Unit: Records & Achievements
Unit-I 1. Fifteen million tonne of Urea Production have been achieved in a period of 568 days on 20.07.2009. 2. Eight million tons of Ammonia production has been achieved in a period of 1064 days on 02.10.2007.3. Fifteen million tons of Urea Dispatch (By road & rail) achieved in a period of 568 days on 20.07.2009.
Unit-II
1. Ten million tons of Urea Production has been achieved in a period of 392 days on 07.08.2009. 2. Six million tons of Ammonia production has been achieved in a period of 717 days on 01.12.09.3. Ten million tons of Urea Dispatch (By road & rail) achieved in a period of 387 days on 06.08.09.
9
AMMONIA- PLANT
10
Brief Description of Ammonia Plant
The Ammonia plant in Phulpur-I is based on MW Kellogs USA
technology having capacity of 1215 MTPD and in Phulpur-II plant is
based on Haldor Topsoe’s Denmark’s technology with a capacity of 1740
MTPD.
The Ammonia Plant in Phulpur-I and Phulpur-II uses RLNG as raw
material for feed and fuel. But there is a provision of using Naphtha also as
raw material in Phulpur-II.
The main process steps for production of Ammonia in both the plants are
similar and are briefly described below:
Raw material:RLNG is used as main raw material to produce ammonia which has the following
composition:
CH4 : 98.77%
C2H6 : 0.69%
N2 : 0.51%
C3H8 : 0.03%
11
BLOCK DIAGRAM FOR AMMONIA PROCESSING
12
BRIEF PROCESS DESCRIPTION OF AMMONIA PRODUCTION:
DesulphurisationThe Traces of sulphur present in RLNG are removed in the desulphurisation section
before sending to the reforming section following hydrogenation reactions are as under:
1) RSH + H2 = RH + H2S
2) COS + H2 = CO + H2S
3) C4H4S + 4H2 = C4H10 + H2S
The desulphuriser reactor consists of Co, Mo based catalyst and ZnO based catalyst.
The desulphurisation takes place in two steps. The first step is hydrogenation where
organic sulphur is converted into Hydrogen sulphide over the hydrogenation catalyst in
the HDS reactor. The second step is the absorption of the H2S formed which takes
place in 2 nos. ZnO absorbers connected in series.
Reforming Section
In the reforming section consisting of Pre-reformer, Primary reformer & Secondary
reformer, the sulphur free RLNG is reformed with steam and air into raw synthesis gas
(process gas) at a pressure of 30 - 37 kg / cm2. The gas contains mainly hydrogen,
nitrogen, carbon monoxide (CO) and carbon dioxide (CO2).
The steam reforming process can be described by the following reaction:
(i) Cn H2n+2H2O = Cn-1H2nCO2+3H2 - heat
(ii) CH4 +2H2O = CO2 + 4H2 - heat
(iii) CO2 + H2 = CO + H2O - heat
Since the reaction is highly endothermic, RLNG is fired in furnace as fuel to maintain
the temperature at about 800 deg C. The reformed process gas has a temperature of
about 800 deg. C and contains about 9-11 mole% (dry basis) of methane and around 70
% hydrogen.
13
SECONDARY REFORMINGSecondary reforming, which including mixing and combustion of the reformed process
gas with process air, takes place in the secondary reformer. Secondary reformer consists
of Ni based catalyst. The process gas (31.5 kg/cm2g, 800 deg C) enters the Secondary
reformer at the top. The reaction between oxygen and process gas is a combustion
where all the oxygen is utilized, raising the temperature to about 1200 deg C. When
passing the catalyst bed, the temperature decreases to about 975 deg C and the pressure
to 31 kg/cm2 g. The Outlet gas from Secondary Reformer contains about 56 %
hydrogen.
2H2 + Air (O2 + 3.8 N2 ) 2H2O + 3.8 N2 + Heat
CH4 + 5 Air (O2 + 3.8 N2) CO2+2CO + 6H2O + 19 N2 +Heat
Gas Purification SystemThe gas purification section comprises three main process steps:
1) CO conversion
2) CO2 Removal
3) Process Condensate Stripping
4) Methanation
CO-Conversion SectionThe reformed process gas enters into CO-conversion section comprising the two
CO-converters and equipment for process gas cooling and condensate separation.
The main part of the carbon monoxide is converted into carbon dioxide by the shift
reaction:
CO + H2O = CO2 + H2 + Heat
The heat evolved is primarily used for steam production and boiler feed water
preheating.
14
High Temperature CO-Conversion
The high temperature CO-converter comprises two catalyst beds. The process gas
enters the top of the converter and passes the two beds the normal outlet
temperature of the gas is about 424 deg. The outlet gas from HT Shift Converter
contains around 3% CO.
Low Temperature CO conversion
The gas leaving the high temperature CO-converter is cooled in HP waste heat
boiler, in the trim heater and in the boiler feed water preheater. Process gas entering
the low temperature CO converter has a content of 2.98 mole% carbon monoxide.
The gas leaves the converter at about 219 deg C and 29.1 kg/cm2 g.The process gas
is cooled in the boiler feed water preheater. Before entering the CO2 removal
section. The process condensate is separated in the separator inlet reboiler.The
outlet gas from LTshift converter contains around 0.12 % CO
Carbon dioxide Removal Section
Basically, the CO2 removal section comprises of Absorber, where the CO2 content
in the process gas will be absorbed in liquid phase at high pressure. The liquid
containing the CO2 is transferred to tower regeneration unit. Consisting of two
Strippers operating at different pressure. In these two towers the pressure is low and
thereby, due to equilibrium, the CO2 again will be transferred into the gas phase.
Carbondioxide is removed by absorption in hot potassium carbonate solution containing
approx. 27 wt% potassium carbonate. The solution also contains glycine and diethanol
amine as activators and vanadium pentaoxide as corrosion inhibitor. The gas passes the
separator OH absorber and enters the methanation section. The solution enters the top of
1st regenerator column. The solution passes down through the packed beds in the column
in counter current with steam. The steam strips off the carbon dioxide, and a mixture of
15
steam and carbon dioxide leaves the top of the column the CO2 thus evolved is sent to
urea plant and regenerated solution is recirculated back to CO2 absorber.
K2 CO3 + H2O + CO2 2 KHCO3 (ABSORPTION)
2KHCO3 K2CO3 + CO2 + H2O (STRIPPING)
Methanation Section
Following reactions take place in methanator.
(i) CO + 3H2 = CH4 + H2O + Heat
(ii) CO2 + 4H2 = CH4 + 2H2O + Heat
The process gas from carbon dioxide removal section still contains about 0.05 vol%
CO2 and 0.30 vol % CO As the carbon dioxides are poisonous to the ammonia
synthesis catalyst, it is converted in the methanator by use of hydrogen.
The outlet gas from Methanator contains around 73 % H2, 25 % N2, and 0.7 % CH4.
Ammonia Synthesis Section
COMPOSITION OF SYN GASES:
H2 : 73.78%
N2 : 25.39%
Ar : 0.31%
CH4 : 0.59%
The gases after the methanator outlet are sent to synthesis loop for conversion of
N2& H2 into NH3. The gases are introduced in synthesis gas compressor where the
pressure is increased to around 180 Kg/cm2. since ammonia reaction take place at
elevated pressure.
16
Ammonia ConversionThe ammonia conversion is carried out in two converters installed in series. One
original converter and another (S-50) installed during Energy Saving Project (ESP).
Ammonia converter catalyst is promoted Iron.
Reaction: 3H2 + N2 = 2NH3 + Heat
Since the reaction is highly exothermic the waste heat is utilised for generating steam
and Boiler feed water heating. TThe gases are cooled in a series of Chillers and the
ammonia get condensed a series of chillers and the ammonia get condensed and is
separated. The uncondensed gases are recycled back to Synthesis Gas Compressor.
The liquid NH3 separated out in a high pressure separator is taken to a lower
pressure separator where the inerts are separated out. This liquid NH3 is taken to
Another flash drum for removal of inerts and liquid NH3 is sent to Urea plant or
Ammonia Storage Tanks.
17
UREA-1 PLANT
18
Brief Description of Urea Plant
The Urea Plant is based on Snamprogetti’s Ammonia stripping process. The
Phulpur-I plant is having capacity of 2115 MTPD while in Phulpur-II there are
two units with a capacity each of 1515 MTPD.
The process of manufacturing of urea in both the units is same except for Phulpur-II
where all the sections are separate for two streams except for Prilling and waste
water treatment section which are common for both the units.
RECORDS: PRODUCTION IN UREA-1 PLANT
HIGHEST PRODUCTION:
DAILY : 2401.00 MT (14/06/2010)
MONTHLY : 70105.80 MT (OCT 2009)
YEARLY : 745131 MT (2010-2011)
LOWEST ENERGY CONSUMPTION:
MONTHLY : 6.4677 GCAL/MT (2010-11)
YEARLY : 6.6698 GCAL/MT (MARCH’2011)
LOWEST SP. STEAM CONSUMPTION:
MONTH : 1.0700 MT/MT (DEC’2010)
YEAR : 1.0908 MT/MT (2010-11)
19
UREA
PHYSICAL AND CHEMICAL PROPERTIES OF UREA
Molecular weight : 60.05
Melting point : 132.600 C
Boiling point : Decomposes at atm. press. Before
boiling.
Specific Gravity : 1.355
(Crystal) at 200 C
Heat of combustion : 2531 Cal/g
Heat of solution in water : -57.8 Cal/g
Critical Humidity : 70.1%
Viscosity at 1500 C : 2.16 CPS
Crystallization heat : 47 Kcal / kg.
Fusion Heat : 59.95 Kcal/kg.
Thermal conductivity : 0.191 K.cal/cm0 C
Specific heat at 200 C 98.40 C 120.50 C 160.30 C 2200 C
(Cal/gm0C) 0.321 0.158 0.194 0.224 0.288
20
Solubility in at 00C 200C 400C 600C 800C 1000C
Water (wt%) 67 105 163 240 396 725
Urea is a white crystalline chemical product and is readily soluble in water. On heating
beyond it’s m.p. It decomposes leaving CO2, NH3 and other complex compounds of C, N2O.
At 1600 C, it decomposes to yield NH3, biuret and higher condensation product and longer
the Urea is held above it’s m.p. further the reaction process.
PROCESS TECHNOLOGY :
Urea is produced by synthesis from liquid NH3 and gaseous CO2. NH3 & CO2 react to form
ammonium carbamate, a portion of which is dehydrated to form Urea and water.
The fraction of ammonium carbamate that dehydrates is determined by the ratio of the
various reactants, the operating temperature and the residence lime in the reactor.
The reaction to produce Urea from NH3 and CO2 takes place in two stages at elevated
pressure & temperature.
2NH3 + CO2 = NH2COO NH4 + 38.1 K.cal/g.mole (1)
NH2 COONH4 = NH2CONH2 + H2O -7.1 K.cal/g.mole (2)
The first reaction is strongly exothermic, therefore heat is liberated as this reaction occurs.
With excess NH3, the CO2 conversion to carbamate is almost 100%, provided solution
pressure is greater than decomposition pressure of carbamate. The decomposition pressure
is the pressure at which carbamate will decompose back into CO2 and NH3. Decomposition
pressure is a function of NH3 concentration in the feed and solution temperature and
increases if either temp. of NH3 recycle is increased. It is desirable to operate at high
temperature and high ratio of NH3 to CO2 provided reactor pressure is high enough to
prevent carbamate from decomposing into CO2 and NH3. This will maximize CO2
conversion to Urea as shown in the reaction (2)
21
The 2nd reaction is endothermic, therefore heat is required for this reaction to occur. The
heat for this reaction comes from the formation of carbamate. This reaction is a function of
temp. and NH3 concern in feed. The solution effluent from the reactor being a mixture of
Urea solution, ammonium carbamate, unreacted NH3, water and CO2 is extremely corrosive
in nature.
USES OF UREA:
1. As Fertilizer in agriculture; Due to high N-content of Urea demand of Fertilizer grade
Urea is rising rapidly. Urea today accounts for a large percentage of Nitrogenous
Fertilizer.
2. As cattle Feed: Urea is used as cattle feed in western countries – sheep and cattle are
capable of digesting Urea upto about 40% of their protein requirement.
3. As raw material for various industrial products: Urea also is used extensively in
preparation of adhesives, textile, anti-shrink compound, ion-exchange and as an
intermediate in the preparation of pigments.
22
23
BRIEF PROCESS DESCRIPTION OF UREA PLANT
Urea is commercially manufactured by direct synthesis of gaseous CO2 and liquid NH3. Urea
production process consists of the following main operations:
Process Technology
The Urea production process takes place through the following main operations:
a) Urea synthesis and high pressure recovery.
b) Urea purification and low pressure recovery.
c) Urea concentration.
d) Urea prilling
e) Waste Water treatment
a) Urea synthesis and high pressure recovery
CO2 gas mixed with a small measured quantity of air is compressed in a turbine
driven four stage centrifugal compressor to about 160 Ata and fed to the reactor.
The liquid ammonia is pumped at high pressure pumps to a pressure of about 240
Ata through an ejector which drives the carbamate from carbamate separator
into the reactor In the Urea reactor operating at 150 kg/cm2 and 190 deg.c.
Ammonia along with recycle Carbamate, reacts with compressed CO2 to form
Ammonia carbamate, a part of which dehydrates to Urea and water. The oxygen
in the air forms a passive oxide layer on the surface of the vessel to prevent
corrosion by carbamate and urea.
The reaction products from the reactor overflow to HP stripper where most of the
un reacted carbamate get stripped off as gaseous Ammonia and CO2. Heat of
decomposition is supplied by MP steam, admitted into Stripper shell side. Urea
solution thus obtained flows out to the MP section. The vapours produced on
decomposition of carbamate in HP stripper enter the HP carbamate condenser,
along with weak carbamate solution from MP section through a mixer. Gases
condensed to form carbamate again and flow to the HP carbamate separator.
24
During this condensation, LP steam is generated in the HP carbamate condenser
shell side. Condensate required for generating steam is supplied from shell side
of MP decomposer.
b) Urea purification and low pressure recovery
Medium Pressure Section
Urea solution from the bottom of the HP Stripper now enters the bottom of Pre-
Decomposer and then to MP Decomposer for further decomposition. During
expansion much of the remaining Carbamate flashes forming NH3 and CO2
vapours, thereby concentrating urea in the solution. This urea solution is further
let down through a level control valve and enters the LP section.
The vapours from the MP Decomposer are condensed in MP condenser using
ammonium carbonate solution from the LP section, with tempered cooling water
in the tube side. The carbamate solution overflows from the MP Condenser into
MP Absorber where the excess Ammonia and inerts are separated in form the
vapours. These vapours are further purified in the top section of the Absorber
with reflux ammonia. Ammonia with inert gases leaving the top of MP Absorber
is mostly condensed in Ammonia Condenser, with cooling water in tube side.
From Ammonia Condenser both liquid and gas phases are sent to Ammonia
receiver along with incoming liquid Ammonia. The inert gases, saturated with
Ammonia, leaving the receiver enter the Ammonia Recovery Tower, Here
Ammonia is further condensed by direct contact with cold Ammonia from the
Battery limit and flows down the Ammonia Receiver.
The inerts with residual ammonia vapours from the Tower are sent to MP
Ammonia Absorber where later gets absorbed with cold condensate in inert
washing tower and recycled to MP Absorber as ammonia water. The inerts are
released to vent stack.
25
26
Low Pressure Section :
The Urea solution from MP Decomposer bottom enters the LP Decomposer after
let down through a level control valve. As a result of expansion, most of the
remaining carbamate undergoes decomposition. Thus Urea solution is further
concentrated and is then sent to the vacuum concentrators through a level control
valve. The vapours enter the LP condenser shell and get absorbed in a weak
Carbamate solution. LP condenser has cooling water in tube side. The liquid thus
formed goes to the Carbonate Solution Tank from where it is recycled back to
MP Condenser.
The inert gases from the Tank containing ammonia vapours are absorbed with
cold condensate in LP Ammonia Absorber and sent to vent stack. The liquid
flows down to the Tank. The concentration of urea is approx. 70% at the outlet.
Urea concentration section
The liquid from the bottom of LP decomposer is further concentrated in
Preconcentrator and then goes for further in two Vacuum concentrators in series.
Here with the help of Low pressure steam, urea solution is concentrated from
70% to 99.7%. The vacuum is created and maintained by two vacuum systems
consisting of a set of steam ejectors and condensers.
Urea melt thus obtained is then pumped to the prilling tower. The vapours from
the vacuum separators are condensed in the condensers and sent to the waste
water tank.
d) Urea prilling
The melted Urea leaving the second vacuum separator is pumped to the top of
104 meter high natural draft prilling tower and sprayed by means of rotating prill
bucket. The fine droplets, while descending through the tower come into contract
with cold air and solidify to from prills. These prills are conveyed to bagging
plant for bagging or to Urea silo for storage.
27
e) Waste water treatment
Traces of gases present in the condensate from vacuum section are removed in a
Hydrolyser stripper system. Waste water from the Hydrolyser section is sent to
the effluent system. The recovered Ammonia solution is recycled back to the LP
recovery section and Ammonium carbamate from LP section is recycled back to
the MP recovery section.
FCO LIMIT PHULPUR UREA
Total N% (min on dry basis) 46 46.6
Moisture % ( max.) 1.0 0.45
Biuret % (max.) 1.5 1.0
FIG: Schematic view of urea
28
EFFECT OF PROCESS VARIABLE IN UREA PRODUCTION
The equilibrium conversion to Urea will be favored under the following process variables :
I) Higher ammonia concentration.
II) Less H2O concentration.
III) Higher temperature.
IV) Higher pressure.
V) Increased residence time.
I) EFFECT OF NH3 / CO2 RATIO:
Theoretical ratio of NH3 / CO2 is two. But in this condition Urea yield is only around
43.44% at 170 atm. and 1550 C. This low yield can be improved by changing NH3 / CO2
ratio when the excess ratio of NH3 is increased to 279%, Urea yield will change from
43.44% to 85.2%. On the other hand when the excess ratio of CO 2 is changed from 0-300%,
Urea yield will increase only from 43.44% to 46%. The effect of excess CO2 is very small.
More over, in the CO2 rich condition the soln becomes very corrosive. In general, most all
the Urea plants are operated under NH3/CO2 ratio around 2.5 to 5.0.
II) EFFECT OF H 2O/CO2 RATIO: Water is a product of Urea formation, presence of excess H2O shifts the equilibrium reaction
in reverse direction and yield of urea is poor. However water has to be added for recycling
unconverted NH3 and CO2 back to the reactor. Lower the amount of water in reactor higher
is the yield of Urea. Excess H2O in reactor also reduces effective volume for urea formation
and additional energy is required to get rid of this H2O. Study shows that presence of one
mole of excess H2O per mole of carbamate reduces equilibrium yield of urea to half.
III) EFFECT OF PRESSURE AND TEMPERATURE :As per Le-chaterlier’s principal higher pressure favoured carbamate formation. At the
operating condition carbamate formation is almost instantaneous and reaction tends to
29
completion provided reaction heat is removed simultaneously. Lower temperature favoured
carbamate formation, being an exothermic reaction.
In case of Urea formation, higher temperature is favourable, because the reaction is
endothermic. The relation is such that when temperature increases, the conversion increases
proportion only, maximum equilibrium conversion is achieved at around 196-2000 C.
Reactants are highly corrosive at higher temperature.
Operating pressure is totally dependent on the temperature at which conversion takes place.
Urea conversion takes place in liquid phase, so equilibrium pressure becomes increasingly
higher when the temperature rises.
IV) RESIDENCE TIME :Urea conversion reaction is slow and takes 20 mins. To attain equilibrium. Higher residence
time favoured equilibrium. Conversion and normally reactors are designed for residence time
of 30 mins to one hour depending upon there operating parameters.
Residence time in Urea reactor plays an important part on equilibrium conversion. Where
operating parameters including mole ratio are not favourable for a good yield, higher
residence – time compensates to some extent to achieve a better yield. But this is done by
providing higher reactor volume which increases capital investment.
BIURET IN UREA:
The formation of biuret during Urea production is not desirable as it is toxic to the plants and
it should not exceeds more than 1.5% in Urea as per Fertilizer control order. It is produced
when Urea is heated in the absence of free NH3.
NH2CONH2 + NH2CONH2 → NH2 CO NH CO NH2 + NH3
(Urea) (Biuret )
The formation of biuret is favoured by higher temperature, higher concentration of urea
solution, low NH3 content and higher residence time.
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EQUIPMENTS DETAILS:
REACTOR
SUPPLIER: MITSUBISHI HEAVY INDUSTRIES LTD., JAPAN
The liquid mixture of NH3 & carbamate and gaseous CO2 are fed in reactor where these react to form ammonium carbamae, a portion of which dehydrates to form Urea & Water. The reactor is vertically mounted and made of carbon steel. It is internally lined with 5 mm thick stainless steel liner 316-L (Modified). The reactor has 14 nos. sieve trays numbered from top over a length of 35 meter. Serve trays are provided to avoid back mixing & for improvement of contact between gaseous & liquid phase. The liquid & gases flow from bottom top via these sieve plates. Reaction products after leaving the reactor are sent to stripper.
OPERATING DETAILS:Units
Operating Pressure Kg/cm2a 151Operating Temperature 0C 185Design Pressure Kg/cm2a 166Design Temperature 0C 195
MECHANICAL DETAILS:
Length mm 36,000 (Tan to tan)I.D. mm 2,305O.D. mm 2494Internal lining mm 5 mm thick 316-L (Modified)Total nos. of sieve trays Nos. 14
MATERIAL OF CONSTURCTION
Shell : Carbon steel Sieve trays : SS 316-L (Modified)All internal walls & linerIn contact with fluid : SS 316-L (Modified)
Composition of 316 – L (Modified)
Cr -- 22% Ni > 12%
Mo > 2.2% N < 0.2%
C < .03%
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MP DECOMPOSER
SUPPLIED BY : LARSEN AND TOUBRO LTD. BOMBAY
Solution from the stripper is flashed in MP separator (MV-2) at 18 Ata pressure. Due to flashing some Ammonia and CO2 is released from the solution. The rest of the solution is heated in MP decomposer E-2 to decompose carbamate into Ammonia CO2 and water at 18 Ata pressure. MP decomposer is a falling film type heat exchanger.
The solution containing Urea, Water, Unconverted cabamate and Ammonia is fed over the tube sheet. The solution enters the decomposer tubes through a set of four holes.The tube sheet at the top and bottom both have a 10 mm thick overlay of SS-3316-L. Shell side fluid is 26 ata steam condensate (from stripper shell side) as heating medium. Expansion belows are provided for the shell.
OPERATING DETAILS: Units Shell Tube
Fluid Handled - Steam Urea +Condensate Carb+
Water +ammonia
Design Pressure Kg/cm2 28 22
Design Temperature 0C 225 185
Operating Pressure Kg/cm2 25 17
Operating Temperature
In 0C 225 129
Out 0C 161 155
Heat Duty MK Cals/hr – 4.2
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MECHANICAL DETAILS: Units
Material of construction - SS 316L and 10mm thick overlay of SS 316L on tubesheets.
No. of Tubes Nos. 543
Tube O.D. mm 38
Tube I.D. mm 34.8
Heat Transfer Area M2 390
Effective length mm 6,000
LP DECOMPOSER SUPPLIER BY: Larsen and Toubro Ltd., Bombay
LP decomposer is a falling film heat exchanger which decomposes carbamate present in Urea solution. Solution is distributed into the decomposer tubes through the ferrules fitted on them. Each ferrule is provided with 4 holes through which liquid flows down to tubes. The 4 holes are essentially on the same plane and are tangential to the surface of the ferrule. The tangential entry ensures that liquid is in the form of a film flowing along the wall of the tubes. Vapors of water, ammonia and CO2 leave the decomposer tubes top. The heating medium is 4.5 Ata steam. The shell side has an expansion joint for differential expansion.
OPERATING DETAILS: UNITS SHELL TUBE
Fluid Handled --- Steam Urea +
Water some carbamate
Designed:Pressure Kg/cm2g 5.5 5.5Temperature 0C 180 170
Operating:
Pressure Kg/cm2g 3.5 3.5
Temperature:
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In 0C 147 95
Out 0C 147 138
No. of passes No 1 1Heat Duty MKCal/hr. 3.1
MECHANICAL DETAILS FOR TUBES Units
Material of construction --- SS 316-LNo. of rubes Nos. 785O.D. mm 38.0I.D. mm 34.8Effective length m 6
MECHANICAL DETAILS FOR SHEEL:
Material of construction - Carbon steel I.D. MM 1,500Steam inlet Nozzle dia Inches 8Condensate outlet nozzle dia Inches 3
PRILLING TOWER:
ERECTOR: M/s E.C.C., BOMBAY
This is a concrete structure of 96 meter height. The urea melt enters the rotating prill
bucket situated just below the prill tower ceiling. Melt enters at a temperature of
about 1400C and is distributed in fine droplets over the cross section of the tower of
22 meter diameter and having free falling height of 72.5 meters.
It is a natural draft tower where ambient air enters through bottom lower openings
having total area 57 M2.During the fall through bucket, the droplets of urea first
solidify and then cooled to a temperature of about 600C-650C. Hot air outlet windows
are provided at the top having total area 153 M2.
The prill are scraped by a rotating straight double arm scraper and fed to the prill
tower conveyor through openings in the rake floor. The inside wall of the tower is
painted with epoxy painting & bottom floor where prills fall are coated with FRP
coating to resist corrosion. 1,000 mm x 1,000 mm inspection windows with light are
provided every four flights of external stairway. One elevator runs parallel to the prill
tower structure. Over & above the elevator, external staircase is also provided. 35
CORROSION IN UREA PLANT EQUIPMENTS:
Studies of corrosion in urea plant have led to the identification of the following type of
corrosion:
1) Stress corrosion.
2) Inter granular corrosion.
3) Galvanic corrosion.
4) Crevice corrosion.
5) Pitting corrosion.
6) Condensation corrosion.
Most severe corrosion in urea plant occurs at location where urea and carbamate solution are
handled at high temperature and pressure. Studies have shown that major attack occurs at the
bottom. 3 to 10 of the reactor directly; above where NH3, CO2 and ammonium carbamate are
introduced. In view of higher pressure, temperature, cone and two phases mixture in urea
reactor a liner of stainless steel 31 GL is used in the construction. Ti, Zr, and stainless steel
are used as liner material. As to selection of material, corrosion resistance is not the only
factor that determines the choice of material, other factor such as mechanical properties,
workability weld ability and economic consideration are taken into consideration.
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OFFSITES:
SECTIONS:
1. Borewells and Raw Water Distribution System.
2. Cooling Tower.
3. DM and CPU Units.
4. Effluent Treatment Plant
5. Water Softening plant
6. AMF Plant
7. RO Plant
8. IG Plant
EFFLUENT TREATMENT PLANT
INTRODUCTION:
Removal & control of nitrogenous compounds such as NH3 that is present in waste being
discharged from ammonia plant and urea plant is very essential in view of pollution control
and water reuse philosophy. As water is one of the precious natural resources for running any
industry its reuse and conservation is essential for environmental pollution control and to
reduce operating cost of the industry.
To overcome problems associated with disposal of ammonia effluent and making it fit for
reuse the effluent treatment plant is installed in which NH3 present in effluent water is
reduced by stripping process.
BRIEF PROCESS DESCRIPTION
To carry out the stripping process a packed column called steam stripper is provided in which
the raw effluent is fed from the top and the LP steam is introduced from the bottom. The
stripping occurs and the treated water obtained is transferred to softening plant.
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WATER SOFTENING PLANT
Water source of raw water required for the plant is underground sub-soil water containing
salts of sodium, magnesium and calcium, together with bicarbonate, carbonate, sulphates,
chlorides and silica (Major constituents) and Nitrate, Phosphate, Iron, Organic matter and
dissolved gases (Minor constituents). On using the raw water having high hardness as
cooling water make up, these salts break during heat transfer process inside the heat
exchangers and thereby form scales.
To bring down the concentration of calcium and magnesium hardness and also silica in
cooling tower make up water, “cold lime softening process” is adopted. The raw containing
high HCO3 alkalinity is reduced during treatment with lime solution and the treated water
becomes suitable for cooling water make up.
The capacity of the water softening plant under Phase-II is to treat 800 m3/hr. of raw water
and the other design basis is:
Design treated water quality and softening plant Phase-II outlet is following:
pH - 10.4 to 10.7
Total hardness < 50 ppm as CaCO3
Ca hardness < 40 ppm as CaCO3
Turbidity < 12 NTU
REVERSE OSMOSIS PLANT
Normally when 2 solutions are separated by means of semi – permeable membrane, the
solvent flows from dilute solution to concentrated solution. If pressure is applied to
concentrated side and if the pressure is greater than osmotic pressure, then solvent flow is
reversed, i.e., it flow from concentrated solution side. This process is called reverse osmosis.
It is advantageously used to extract water from concentrated solution.
During R.O. process, pressure is continuously applied to the feed stream by a high pressure
pump. Consequently feed stream gets divided into two parts.
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1. Permeate stream (low in dissolved solid content)
2. Reject stream (very high in dissolved solid content)
PROCESS DESCRIPTION:
The water is fed to the R.O. plant from R.O. feed pit. In the feed some chlorine is introduced
in concentration of 1 ppm. This chlorine kills bacteria and algae, which is harmful to
membrane.
From feed pit the water is entered into solid catalyst classifier. In this classifier dolomite and
lime is introduced in solid form (not in fully powdered form). Here 0.1% of a polymer
solution is also added. This polymer coagulates the silica, which is deposited on dolomite and
lime, into large size. Hence the effluent from classifier is reduced in silica and turbidity from
that of water in feed.
To the classifier effluent 10% sodium – hexa-meta phosphate (SHMP) is added. The solution
acts as an anti scalar. The effluent then enters into 4 continuous filters. These filters are
actually sand filters having sands of uniform size. The effluent from these fitters is
maintained at pH 6.5 by addition of 30% HCl and stored in clarified water storage tank. The
rejects from solid contact classifier and 4 continuous filters are sent to sludge – pit where it is
poured and dried. The dried solid material was then sent into ash pond. This classified water
is used as power water and in chemical tanks (dolomite, lime etc). Introducing it in
multigrade filters, in which different sizes of sand layers are used as filter, further purifies
this water. The effluent from multigrade filters then passes through a basket type cartridge
filter. The cartridge filter removes suspended particles from water. When the differential
pressure across the cartridge filter reaches 1 kg/cm2 when the flow rate through cartridge
filter reduces, the cartridge filter must be replaced. The effluent from this filter then enters
into 2 micron cartridge filters, removes suspended particles upto 5 micron. The effluent from
micron cartridge filter then enters into R.O. skid. The R.O. unit consists of single stream 3
stages. There are total 37 pressure tubes each containing 6 No. of membrane modules:-
The 1st stage contains 20 pressure tubes.
The 2nd stage contains 11 pressure tubes.
The 3rd stage contains 6 pressure tubes.
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The membrane elements mainly made of polyamide films, imported from USA. The total
input flow rate to this R.O. unit is 150 m3/hr. the flow rate through each pressure tube is 7
m2 / hr. (approx.)
Hence total product water is (75+35+15) = 125 m3/hr. and reject is 150 m3/hr. The maximum
load can be handled by this R.O. unit is 165 m3/hr.
The product water is stored in product water tank and from there supplied to different plants,
such as DM plant and softening plant inlet.
D.M. PLANT
In the D.M. Plant the deep bore raw water containing various impurities is demineralized i.e.
freed from the various minerals present in it to make it 100% free from particulate matter for
its further usage as the boiler feed water and process water.
The recommended quality of D.M. water being used in high pressure boiler is:
Conductivity (mho/cm) : Less than 0.3 micron
Silica : Less than 0.01 ppm
SiO2 hardness : Nil
Electrical char. due to electrolyte : Nil
pH : 6.8-7.5
Raw water is passed to first sand filter to remove suspended impurities then to SAC (strong
acid cation).
In SAC cation resin is used to remove cationic part of impurities like NaCl, CaHCO3
etc.
Re-H + NaCl → Re-Na + HCl
Re-H + CaHCO3 → Re-Ca + H2CO3
From SAC the process stream is passed to degasser where CO2 is removed from
water by stripping it using air.
H2CO3 → H2O + CO2
Then the stream is passed to weak base anion exchanger (WBA). Here the weak base
resin removes basic ion impurities.40
Re-OH + HCl → Re-Cl + H2O
Then the stream is passed through SBA (strong base anion). Where strong base resin
is used to remove remaining anion impurities.
From this the stream is passed through mixed bed. It contains both anionic and
cationic resins to remove both cation and anion impurities.
Finally this demineralized water stream is passed to D.M. water tank.
Power Distribution in Urea Plants:
T.G.1 - 12.5 MW41
T.G.2 - 18 MW
Total power required 25.17 M
Urea1 - 3.75 MW
Urea 2 - 6.5 MW
DISTRIBUTED CONTROL SYSTEM (DCS)
BRIEF DESCRIPTION OF DCS:
Computer based ‘Distributed Control Systems’ have been used in large quantities instead of
pneumatic control or electronic analogue control system.
In D.C.S. system, three types of distribution exists:
a) Geographical Distribution.
b) Functional Distribution
c) Safety Distribution
DCS is more accurate, fast in operation, more users friendly more informatics and equipped
to take care of start up and shutdown of plants.
In Urea plant of IFFCO Phulpur expansion, DCS model is CENTUM-CS, supplied by M/s
Yokogawa Blue Star Ltd. India. DCS collects the database from various section of the plant
directly for open loop tags for monitoring, recording and control of process parameters.
There are six information and command station comprising of six CRT screens and one
engineering station for maintenance and configuration purpose.
One PC is provided for loop drawing.
One PC is provided with HART maintenance system for maintaining field
instrument working with HART protocol. A transient data Manager (TDM) is
also a part of DCS used for monitoring temperature and vibration of bearing of
turbines, compressor and high pressure carbamate pumps. One PC is also
provided along with TDM for storing, monitoring and analysis of the temperature
and vibration.
Main Function of DCS Are:
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1. Control and monitoring of various process parameters.
2. Data acquisition and storage.
3. Data management, manipulations and report generation etc.
ENVIRONMENT AND POLLUTION CONTROL
At IFFCO Phulpur Unit there has been an emphasis on keeping the environment clean and
safe. Due to a continuous and dedicated efforts in this direction goal of zero discharge of
effluent has been achieved.
Strategy:
Regular monitoring of effluent.
Reduction of effluent generation.
Reuse of liquid effluent generated.
Using the solid waste for useful purpose.
Measures Taken:
Natural draft prill tower of 96 M height for reduced dust emission.
100 M high chimney and ESP in boiler to reduce dust emission.
Cooling tower blow down reduction.
Reuse of steam condensate from ammonia and urea plant in steam generation
plant.
Reuse of inert gas plant effluent in softening plant.
Reuse of waste water from urea plant in cooling tower after treating in Hydrolyser
System.
Reuse of Jacket cooling water of ammonia plant in cooling tower.
Reuse of impure condensate from power plant in cooling tower.
Reuse of raw water pump house ejector water softening plant.
Utilization of Effluent for:
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- Deashing operation in steam generation plant.
- Irrigation in farm land, green belt etc.
- Dust suppression in ash pond and coal yard.
Use of fly ash for making bricks. Fly ash being supplied to cement manufacturing plant.
ACTIONS IN HAND:
In order to reduce the data water consumption further and also to take care of effluent to be
generated in expansion plant, following two major schemes are being implemented.
1) Sewage Treatment Plant is being installed to treat township sewage. This water
after treatment will be used in plant and raw water consumption is expected to
reduce by about 3000 m3/day. It is expected to be completed by June 1997.
2) Reverse Osmosis Plant will be put up with its pretreatment along with DM plant
effluent segregation scheme. The segregated DM plant effluent will be first
treated in pretreatment plant to remove these impurities. Treated H2O from
pretreatment section will be finally treated with the help of R.O. membranes to
get the water quality fit for reuse in the plant. Total cost of the plant is expected
to be Rs. 8.51 crores. Plant completion is expected by March 1998.
FIRE & SAFETY:
IFFCO Phulpur believes in the philosophy of “prevention is better than cure”. All
necessary steps are being taken to avoid accidents. All employees are being given
training to avoid accidents. However, to handle any eventualities a team of qualified and
trained personnel with necessary modern facilities are available round the clock. An
incident occurred on 04.05.96 when Naphtha caught fire in ammonia plant and it could
have caused severe damage to the ammonia plant, being a major fire ancient, however the
fire was brought under control within 25 mins. This speaks volumes about the
preparedness of fire fighting staff.
Facilities Available:
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10 Kms length of fire hydrant line ring with 13 single heated and 13 double
heated ground hydrant and 23 single headed fire escape and internal hydrants.
3 fire tenders equipped with latest fire fighting facilities.
16000 m3 total water storage out of which 8000 m3 water exclusively reversed for
fire fighting only.
3 Motor driven and 2 diesel driven water pumps. Each of 410 m3/h capacity. 1
Motor driven pump of 10m3/h capacity.
Fixed foam system for Naphtha storage area.
Fire jeep and rescue van.
Breathing apparatus – 15
Explosive meter - 10
Gas detectors, O2 meters and smoke detectors.
CONCLUSION
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IFFCO is the world’s largest cooperative sector in production of fertilizers. It was registered
on November 3, 1967 as a Multi-unit Co-operative Society. IFFCO has production units in
the following places Kalol, Kandla, Phulpur, Aonla, Paradeep in India. Ammonia - urea
complex was set up at Phulpur in the state of Uttar Pradesh in 1981.
In Phulpur IFFCO has two ammonia and two urea plants, a power plant and other offsite
planst like DM plant RO plant water softening plant, cooling tower, ammonia and naphtha
storage. Other useful sites are production and quality control, material handling and bagging.
The Ammonia plant in Phulpur-I is based on MW Kellogs USA technology having
capacity of 1215 MTPD and in Phulpur-II plant is based on Haldor Topsoe’s
Denmark’s technology with a capacity of 1740 MTPD.
The Ammonia Plant in Phulpur-I and Phulpur-II uses RLNG as raw material for feed
and fuel. But there is a provision of using Naphtha also as raw material in Phulpur-II.
The main process steps for production of Ammonia in both the plants are similar and
are briefly: desulphurisation, reforming, shift conversion, CO2 removal by absorption,
methanation and ammonia conversion. Following main reaction takes place in ammonia
conversion.
3H2 + 2N2 → 2NH3
The Urea Plant is based on Snamprogetti’s Ammonia stripping process. The
Phulpur-I plant is having capacity of 2115 MTPD while in Phulpur-II there are two
units with a capacity each of 1515 MTPD.
The process of manufacturing of urea in both the units is same except for Phulpur-II
where all the sections are separate for two streams except for Prilling and waste water
treatment section which are common for both the units.
The reaction of Ammonia and Carbon dioxide to produce urea takes place in two stages
at elevated pressure and temperature.
1) 2NH3 + CO2 = NH2COONH4+ 38.1 Kcal/gm.mole
carbamate
2) NH2COONH4 = NH2CONH2 + H2O -7.1 Kcal/gm.mole
carbamate Urea Water
The Urea production process takes place through the following main operations:
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Urea synthesis and high pressure recovery. Urea purification and low pressure
recovery. Urea concentration. Urea prilling. Waste Water treatment. Offsite contains all
the auxiliary units supporting the main process units which are ammonia and urea plants.
Offsite comprises of AMF set, IG plant, RO plant, DM plant, Cooling tower plant, water
softening plant etc. Power plant has two sets of turbo generators: TG1 and TG2. TG 1 has
capacity of 12.5 MW and TG2 has capacity of 18 MW. Total requirement of power is 25.17
MW for the whole campus. Computer based ‘Distributed Control Systems’ have been used
in large quantities instead of pneumatic control or electronic analogue control system. DCS is
more accurate, fast in operation, more users friendly more informatics and equipped to take
care of start up and shutdown of plants.
In Urea plant of IFFCO Phulpur expansion, DCS model is CENTUM-CS, supplied by
M/s Yokogawa Blue Star Ltd. India.
The plant is totally echo friendly and has got many recycling processes such as energy
management unit for minimizing the consumption of energy, water treatment plant,
manufacturing of ash bricks etc. Many features of it had got self dependent factors and
thus are responsible for higher order of recycling and award getting performance thus
had got many awards in this field. IFFCO Phulpur believes in the philosophy of
“prevention is better than cure”. All necessary steps are being taken to avoid accidents.
All employees are being given training to avoid accidents. However, to handle any
eventualities a team of qualified and trained personnel with necessary modern facilities
are available round the clock. Thus IFFCO is one of the best examples of modernized
industry in the world.
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REFERENCES:
INTERNET: WWW.GOOGLE.COM
WWW.WIKIPEDIA.COM
WWW.IFFCO.NIC.IN
BOOKS AND MANUALS:
BASIC TRAINING MANUAL, IFFCO PHULPUR
UREA-1 MANUAL, IFFCO PHULPUR
AMMONIA -2 MANUAL, IFFCO PHULPUR
DRYDEN’S OUTLINES FOR CHEMICAL ENGINEERING.
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