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7/22/2019 ammoniaproduction-131113173051-phpapp02

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National Fertilizers Ltd.Bathinda


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Sections

Ammonia Plant

Urea Plant

Steam Generation Plant

Bagging Plant


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Ammonia Plant

Desulphurization Section

Reforming Section

Shift Section

Carbon Dioxide Removal Section

Methanation Section

Ammonia Synthesis Section


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HYDROGENATOR: Reactions involved in Hydrogenator are:

RSH + H 2 RH + H 2S

R 1SSR 2 + 3H 2 R 1H + R 2H + 2H 2S

R 1SR

2 + 2H

2 R

1H + R

2H + H

2S

COS + H 2 CO + H 2S If some content of CO 2 is also exist in Natural Gas feed then:

CO + H CO + H O

CO + H S COS + H O CoMo or NiMo based catalyst is used in Hydrogenator.


Natural Gas Feed

Recycle Hydrogen

Feed Gas Preheater

Hydrogenator

Sulphur

AbsorberNo. 1

400 oC38 Kg/cm 2

395 oC


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H S ABSORBER: The Hydrogenated Natural Gas is fed to the Sulphur Absorbers.

Zinc oxide catalyst is in the form of 4 mm cylindrical extrudates.

Operating temperature is approx. 395C.

ZnO + H S ZnS + H O

ZnO + COS ZnS + CO

Sulphur content in the natural gas is less than 0.1 ppm by weight.


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Reforming Section

Desulphurized gas is converted into synthesis gas by catalytic reforming of thehydrocarbon mixture with steam and the addition of air.

Reactions involve in Reformer Section:

CnH2n+2 + 2H O Cn-1H2n + CO + 3H - heat

CH + 2H O CO + 4H - heat

CO + H CO + H O heat

Reactions take place in two steps

1. Primary reforming

2. Secondary reforming


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Primary Reformer

Desulphurized Gas

Process Steam

Preheater

PrimaryReformer

785-795 o

520 oC

34 - 31 kg/cm2 g

Steam Carbon Mole Ratio=3/1

Composition of catalyst (% w/w)1. Nickel Monoxide, NiO (17)2. Calcium Oxide, CaO (7)3. Potassium oxide, K2O (4)4. Aluminum Oxide , Al 2O 3 (Balance)

Composition : (Mole%)(At Inlet of CatalystTubes)Ar 0.02CH4 79.68CO 2 ppm

CO2 0.24H2 4.09N2 2.54C2H6 6.48C3H8 2.63C4H10 1.88C6H12 - 0.24

As we have seen that we are getting around

12.86 mole % of methane and we dont want

it to be exist in stream just because it will be

acting as inert in whole further processes.

So we have to remove it.

`For removing this access of methane we

use Secondary Reformer.

P r o

d u c t

S t r e a m

o f P r i m a r y

R e f o r m e r


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Secondary Reformer

The process gas is mixed with air with keeping theratio of H2/N2 Ratio: 3.0.

Partial combustion takes place in the top of reactor. Methane concentration is 0.60 mole%. Outlet gas contains about 13.05mole% CO and

7.24mole% CO that are removed further becausecatalyst may get poisioned.

791 oC

30 kg/cm2 g

Catalystcomposition(%mole):

NiO = 8 10%Al2O3 = 87 90 %Cao = < 0.05 %

Gas inletcomposition (mole%)Ar 47 ppmCH4 12.86CO 9.5CO2 10.70

H2 66.20 N2 0.74


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CO Shift Section

Exothermic reaction which occurs in this section is:

CO + H 2O H2 + CO 2 + heat

Shift reaction takes place in the two CO converters:

1. HT CO-Converter.

2. LT CO- converter with process gas cooling after each converter.


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Methanator trimheater

HT/LT CO Convertors

Process gas from Reformer Section

HT CO

Convertor

Waste heatboiler BFW Preheater 1 BFW

360 oC29.6kg/cm 2

432 oC205 oC

205 oC28.6kg/cm 2

227 oC

LT COConvertor

Catalysts composition(mole%) which isavailable in pellet form.Fe2O3 - 85- 95 %Cr 2O3 - 7-9 %CuO - 1-2%Al2O3 - 1.0%

Catalyst cooxides of CAl, Which

active in be250 oC.

Composition (mole%)of inlet stream of HTCO Converter is:Ar 0.27, CH4 0.60,CO 13.37, CO2 7.65 , H2 55.61, N2 22.47

Composition (mole%)of outlet stream of HTCO Converter is:Ar 0.24, CH4 0.55CO 3.22, CO2

15.94H2 59.59, N2 20.48

CoCAC1H

340 oC


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CO 2 Removal Section

Outlet gas from CO converter contain 18.32 mole% CO2 Based on two stage activated MDEA process The solvent used for CO2 absorption is aMDEA(40%) Consists of a two stage CO2 absorber, a CO2 stripper and

two flesh vessels.

These are the reactions occurs in CO 2 removal section.R 3 N + CO2 + H 2O R 3 NH + + HCO 3-

2R 2 NH + CO 2 R 2 NH 2+ + R 2 N-COO -


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CO2 to Urea

Condensate

StripperReboiler

HEL S Pump

Cooler

Chiller

L PFlash

HPPump

BFW

Preheater

Semilean Sol n

Lean Solution

Stripper160C 27.8 Kg/cm2

131C

65

50C 5.1 Kg/cm2

72C 0.59 Kg/cm2

95C


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Methanation Section

Methanation, a process in which the residual Carbon Oxides (CO, CO 2) are converted intoMETHANE because it acts as inert in Ammonia Synthesis Section.

Reactions involve in Methanator are:

CO + 3H 2 CH 4 + H 2O + heat

CO2 + 4H 2 CH 4 + 2H 2O + heat

As we can see these reactions are exothermic so Low temperature, high pressure and alow water vapour content favours the methanation equilibrium.

After converting all Carbon Oxides into METHANE, product stream is pressurised from25Kg/cm 2 to 187Kg/cm 2 by using compressors and gas boosters and for maintainingtemperature, chillers are being used.


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Gas/GasHE

Trimheater

Process gas fromHT CO Converter

Process gas forLT CO Converter

Synthesis Gas FroCO 2 Removal Se

Methanator

Synthesis gas to loop

60C 26.8 Kg/cm2

285 C

300 C

322 C

90C 25 Kg/cm2

Nickel based catalystis used here in methanatorwhich consist around 27%wt Nickel. (280-420 C)

Composition(%at inlet is:

Ar- 0.29, CH4- CO2-0.05,CO-0H2- 74.29,N2- 2

Composition(%mole)at inlet is:

Ar- 0.29, CH4- 1.08,H2- 73.95, N2- 24.88


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High pressure and low temperature favourable equilibrium conditions of ammoniareaction.

About 20% of N2 and H2 is converted into ammonia at given operating conditions. Unconverted remainder is recycled back.

There are three beds we use in Ammonia Convertor:First bed : 370-510 C Second bed: 425-480 C Third bed: 420-460 C

Ammonia Synthesis Section

3H 2 + N 2 = 2NH 3 + heat ( H = 92.4 kJ/mol) 130C 187 Kg/cm

Feed gas inlet

Feed gas in

Fe Oxied (Fe3O4) % wt 93 2 CaO, Al 2O 4, K2O, SiO 2, % wt 7 2With the irregular shape beadswith the size of 1.5-3mmBulk density 2.8kg/l


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130C 187Kg/cm 2

StartupHeater

Product letDown tank

AmmoniaSeparator

Purg

Makeup SynthesisGas

Ammonia

Converter

Cooler

SynthesisHotHeatExchanger

SteamBoiler HE

Chiller

Compressors

10C

10C

11

27

12

25

10C 178.9Kg/cm 2

354C 270C 180C

Composition(mole%) atOutlet of AmmoniaConverterAr- 2.11, CH4- 7.14 H2- 52.84, N2- 17.61

NH3- 20.30

ComPurConAr-H2

NH

CoDCoAH

N

ComStreAr-H2-

NH

Composition(mole%) atInlet of AmmoniaConverterAr- 1.82, CH4- 6.18 ,

H2- 65.95, N2- 21.99, NH3- 4.06


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Ammonia Recovery

AmmoniaReflux

AmmoniaOH Drum

DistillationColumn

Reboiler

Purge GasAbsorber

Lean Sol n Cooler

Circulation Pump

Purge Gas

Let Down Gas

Steam

RichleanSol n

Exchanger

Fuel

248C

11C 27Kg/cm 2

10C 178.9Kg/cm 2

61C 20Kg/cm 2

45C 25Kg/cmComposition(mole%) of

Purge Gas:Ar- 2.49, CH4- 8.38

H2- 82.48, N2- 20.82 NH3- 5.82

Composition(mole%) ofLet Down Gas:Ar- 3.16, CH4- 16.12 H2- 38.06, N2- 15.76

NH3- 26.88


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Conclusion

National Fertilizer Ltd. Bhatinda is producing 99.80% pure Ammoniaby Using Natural Gas with the help of helder tropsch method forfurther production of Urea.


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Thank You !!!

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