National Fertilizers Ltd.Bathinda

AJAY NAGAR

10112001

Sections

Ammonia Plant

Urea Plant

Steam Generation Plant

Bagging Plant

Ammonia Plant

Desulphurization Section

Reforming Section

Shift Section

Carbon Dioxide Removal Section

Methanation Section

Ammonia Synthesis Section

HYDROGENATOR:

• Reactions involved in Hydrogenator are:

RSH + H2 → RH + H2S

R1SSR2 + 3H2 → R1H + R2H + 2H2S

R1SR2 + 2H2 → R1H + R2H + H2S

COS + H2 → CO + H2S

• If some content of CO2 is also exist in Natural Gas feed then:

CO₂ + H₂ ↔ CO + H₂O

CO₂ + H S₂ ↔ COS + H₂O

• CoMo or NiMo based catalyst is used in Hydrogenator.

Desulphurization Section

Natural Gas Feed

Recycle Hydrogen

Feed Gas Preheater

Hydrogenator

Sulphur Absorber No. 1 Sulphur

Absorber No. 2

400oC38 Kg/cm2

395oC

351oC395oC

Natural Gas With Recycle Hydrogen

Desulphurization Section

H₂S 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. 395˚C.

ZnO + H₂S ↔ ZnS + H₂O

ZnO + COS ↔ ZnS + CO₂

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

Reforming Section

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

Reactions involve in Reformer Section:

CnH2n+2 + 2H₂O ↔ Cn-1H2n + CO₂ + 3H₂ - heat

CH₄ + 2H₂O ↔ CO₂ + 4H₂ - heat

CO₂ + H₂ ↔ CO + H₂O – heat

Reactions take place in two steps

1. Primary reforming

2. Secondary reforming

Primary Reformer

Desulphurized Gas

Process Steam

Preheater

PrimaryReformer

SecondaryReformer

Process Air

785-795oC

520oC

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, Al2O3 (Balance)

Composition : (Mole %)(At Inlet of Catalyst Tubes)Ar – 0.02CH4 – 79.68CO – 2 ppmCO2 – 0.24H2 – 4.09N2 – 2.54C2H6 – 6.48C3H8 – 2.63C4H10 – 1.88C6H12 - 0.24

Composition: (Mole %)(At Outlet of Catalyst Tubes)Ar – 47 ppmCH4 – 12.86CO – 9.5CO2 – 10.70H2 – 66.20N2 – 0.74Higher HC – Neglegible

As we have seen that we are getting around

12.86 mole % of methane and we don’t 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.

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Process Gas

Secondary Reformer

• The process gas is mixed with air with keeping the ratio 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% CO₂ that are removed further because catalyst may get poisioned.

550oC791oC

1100-1200oC

958oC

30 kg/cm2 g

Catalyst composition(%mole):NiO = 8 – 10%Al2O3 = 87 – 90 %Cao = < 0.05 %

Gas inlet composition (mole%)Ar – 47 ppmCH4 – 12.86CO – 9.5CO2 – 10.70H2 – 66.20N2 – 0.74

Gas outlet composition (mole%)Ar – 0.27CH4 – 0.60CO – 13.37CO2 – 7.65H2 – 55.61N2 – 22.47

CO Shift Section

• Exothermic reaction which occurs in this section is:

CO  +  H2O   ↔  H2  +  CO2 + 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.

Methanator trimheater

HT/LT CO Convertors

Process gas from Reformer Section

HT COConvertor

Waste heatboiler

BFW Preheater 1 BFW Preheater 2

360oC29.6kg/cm2

432oC205oC

205oC28.6kg/cm2

227oC 160oC

LT COConvertor

Catalyst’s composition (mole%) which is available in pellet form. Fe2O3 - 85- 95 % Cr2O3 - 7-9 % CuO - 1-2% Al2O3 - 1.0%

Catalyst consist the oxides of Cu, Cr and Al, Which is most active in between 170-250oC.

Composition (mole%) of inlet stream of HT CO 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 HT CO Converter is:Ar – 0.24, CH4 – 0.55CO – 3.22, CO2 – 15.94H2 – 59.59, N2 – 20.48

Composition (mole%) of outlet stream of LT CO Converter is:Ar – 0.24, CH4 – 0.53CO – 0.30, CO2 – 18.32H2 – 60.73, N2 – 19.88

340oC

CO2 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 CO2 removal section.

R3N + CO2 + H2O ↔ R3NH+ + HCO3-

2R2NH + CO2 ↔ R2NH2+ + R2N-COO-

CO2 to Urea

Condensate

StripperReboiler

HEL S Pump

Cooler

Chiller

L PFlash

HPPump

BFWPreheater

Semilean Soln

Lean Solution

Process gassaparator

CO2 Absorber

Output after CO2Absorption

Flash gas/ Inerts

Stripper160˚C27.8 Kg/cm2

131˚C

65˚C

65˚C

65˚C27.8 Kg/cm2

60˚C26.8 Kg/cm2

50˚C5.1 Kg/cm2

72˚C0.59 Kg/cm2

95˚C

Methanation Section

Methanation, a process in which the residual Carbon Oxides (CO, CO2) are converted into METHANE because it acts as inert in Ammonia Synthesis Section.

Reactions involve in Methanator are:

CO + 3H2 ↔ CH4 + H2O + heat

CO2 + 4H2 ↔ CH4 + 2H2O + heat

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

After converting all Carbon Oxides into METHANE, product stream is pressurised from 25Kg/cm2 to 187Kg/cm2 by using compressors and gas boosters and for maintaining temperature, chillers are being used.

Gas/GasHE

Trimheater

Process gas fromHT CO Converter

Process gas forLT CO Converter

Synthesis Gas From CO2 Removal Section

Methanator

Synthesis gas to loop

60˚C26.8 Kg/cm2

285˚C

300˚C

322˚C

90˚C25 Kg/cm2

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

Composition(%mole) at inlet is:Ar- 0.29, CH4- 0.65,CO2-0.05,CO-0.36,H2- 74.29,N2- 24.36

Composition(%mole) at inlet is:Ar- 0.29, CH4- 1.08, H2- 73.95, N2- 24.88

• High pressure and low temperature favourable equilibrium conditions of ammonia reaction.

• 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

3H2 + N2 = 2NH3 + heat (ΔH = −92.4 kJ/mol) 130˚C187 Kg/cm2

354˚C183.6 Kg/cm2

Feed gas inlet

Feed gas inlet Outlet

Feed gas inlet

Fe Oxied (Fe3O4) % wt 93 ± 2CaO, Al2O4, K2O, SiO2, % wt 7 ± 2With the irregular shape beads with the size of 1.5-3mm Bulk density 2.8kg/l

130˚C187Kg/cm2

StartupHeater

Ammonia(Product)

Let DownGas

Product letDown tank

AmmoniaSeparator

Purge Gas

Makeup SynthesisGas

AmmoniaConverter

Cooler

SynthesisHotHeatExchanger

SteamBoiler HE

Chiller

Compressors

10˚C

10˚C

11˚C27Kg/cm2

12˚C25Kg/cm2

10˚C178.9Kg/cm2

354˚C 270˚C 180˚C

Composition(mole%) atOutlet of AmmoniaConverterAr- 2.11, CH4- 7.14H2- 52.84, N2- 17.61NH3- 20.30

Composition(mole%) ofPurge Gas of AmmoniaConverterAr- 2.49, CH4- 8.38H2- 82.48, N2- 20.82NH3- 5.82

Composition(mole%) of LetDown Gas of AmmoniaConverterAr- 3.16, CH4- 16.12H2- 38.06, N2- 15.76NH3- 26.88

Composition(mole%) of ProductStream of Ammonia ConverterAr- 0.01, CH4- 0.16H2- 0.06, N2- 0.04NH3- 99.73

Composition(mole%) atInlet of AmmoniaConverterAr- 1.82, CH4- 6.18, H2- 65.95, N2- 21.99, NH3- 4.06

Ammonia Recovery

Ammonia

AmmoniaReflux

AmmoniaOH Drum

DistillationColumn

Reboiler

Purge GasAbsorber

Lean Soln Cooler

Circulation Pump

Purge Gas

Let Down Gas

Steam

RichleanSoln

Exchanger

Fuel Gas

248˚C

11˚C27Kg/cm2

10˚C178.9Kg/cm2

61˚C20Kg/cm2

45˚C25Kg/cm2Composition(mole%) of

Purge Gas:Ar- 2.49, CH4- 8.38H2- 82.48, N2- 20.82NH3- 5.82

Composition(mole%) ofLet Down Gas:Ar- 3.16, CH4- 16.12H2- 38.06, N2- 15.76NH3- 26.88

Composition(mole%) ofFuel Gas:Ar- 2.71, CH4- 9.46H2- 65.73, N2- 22.08NH3- 0.01

Composition(mole%) ofProduct Gas:Ar- 64ppm, CH4- 0.03H2- 0.06, N2- 0.02NH3- 99.88

Conclusion

National Fertilizer Ltd. Bhatinda is producing 99.80% pure Ammonia by Using Natural Gas with the help of helder tropsch method for further production of Urea.

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Thank You !!!