Ammonia

Basic Flowsheet Elements

Chemistry of the Ammonia Process

Simplified Block Diagram of a Typical 1000 t/d Ammonia Plant

Simplified Block Diagram of a 2000 MTPD Methanol Flowsheet

Methanol

Purification

Reforming

Compression Distillation

Synthesis

Steam Raising

Feedstock (CH ) 4

Water

VHT-S103 20 m³

VSG-EZ200

VSG-Z101 40 m³ VSG-Z101 40 m³

VSG-A101 200 m³

Simplified Block Diagram of a Hydrogen Flowsheet

Desulfurization

Primary Reforming

High Temperature CO Shift

VHT-S101

VSG-Cl101

VSG-EZ200

VSG-Z101

VSG-F101

PSA

etc

Steam Natural Gas Feed

Hydrogen

Simplified Flowsheet for a Typical Ammonia Plant

Natural Gas

Steamsuperheater

AirSteam

30 bar

Steam

Steamraising

350 C 200 C

Heat Recovery

Steamraising

Cooling

Cooling

Reboiler

CO

Cooling

Preheater

HeatRecovery

Steam

Boiler

Process Condensate

Quench

Quench

Liquid Ammonia

H

Hydrodesulphuriser Primary Reformer

SecondaryReformer

High Temperature

Shift

Low Temperature

Shift

Ammonia SynthesisMethanator

Carbon DioxidePurge Gas

Cooling

400 Co

390 Co

2

790 Co

550 Co

1000 Co

o

420 Co

150 Co

400 Co

470 Co

o

220 Co

290 Co

330 Co

2

CO Removal2

220 bar

Refrigeration

CondensateCooling

AmmoniaCatchpot

Modern Conventional Flowsheets

Main process steps are the same for all plants Main differences in equipment design

Uhde Top fired reformer Proprietary exit header design Secondary reformer has a riser HP loop with radial flow converter

Modern Conventional Flowsheets

HKBR Primary reformer with manifold/riser

Haldor Topsøe Side fired reformer Radial flow converter S-200 S-250

Other Flowsheet Options

Braun Purifier ICI AMV ICI LCA Dual Pressure Uhde Process HKBR KAAP (with/without purifier) Linde LAC H2 Recovery is used on most

modern plants

Braun Purifier Process

Primary reformer exit temperature is 700°C Excess air is added to the secondary reformer Methane slip typically around 2-2.5 mol % Excess nitrogen (and methane) cryogenically

removed downstream of methanator Also removes water - ammonia synthesis catalyst

poison Improved synthesis lives Can reduce SC ratio to 2.7-3.0 Small primary

Braun Purifier Process

Cold Box

Purified Syn Gas Waste Gas

Raw Syn Gas

Feed Effluent Exchangers

ICI AMV Process

As with Braun - utilizes excess air to secondary Excess nitrogen is passed to the loop Loop runs at low pressure (80-110 bara) Use ICI LP Catalyst (74- Series) Uses a saturator to saturate feed gas This raises around 50% of the required steam Can use SC ratio of 2.8 H2 Recovery in loop at loop pressure

ICI LCA Process

Aim at small plant capacities (500 mtpd) Uses the GHR-Secondary concept Excess air is utilized to close heat balance Utilizes an ITS rather than HTS and LTS A saturator for steam raising A PSA system to remove the CO2 and excess N2 A low pressure loop (80 bara) A tube cooled converter or Casale converter No longer actively marketing

Dual Pressure Uhde Process

PGR Unit

Make up gasfrom frontend

H2O

Ammonia from once through conversion

HP-steam

C.W.NH3NH3

C.W.

C.W.

C.W.

HP-steam

NH3 NH3

Off-Gas

Ammoniafrom

HP loop

HPcasing

LPcasing

Firstammoniaconverter

Secondammoniaconverter

Once throughammoniaconverter

HP-steam

Note: Molecular Sieves not shown

Dual Pressure Uhde Process

Benefits of such a scheme realised at 3,000 mtpd +

Although this is large capacity - all equipment is proven

Note the low pressure converter between stages of synthesis gas machine

Makes machine smaller Makes loop pipework 24” Uses Comp. J catalyst

HKBR Purifier and KAAP

Primary Reformer

Secondary Reformer

Shift & CO2 Removal

Purifier

Compression KAAP

Meth’n Dryers

Recycle Purge

To Fuel

Feed

Linde LAC

Key features are No secondary reformer Nitrogen is generated cryogenically and

added after a PSA unit No HTS/LTS - only Isothermal (ITS) shift No methanation

Linde LAC Desulfurization

Primary Reformer

Isothermal Shift

PSA

Nitrogen Unit

Ammonia Synthesis

Other Flowsheet Options

Use Gas Turbine to drive process air compressor

Can use effluent as combustion air Has 16-17% O2 and is at 500°C Braun plants Install pre reformer HT Retrofit Many other reasons Remove heat from duct Uprate plant

Other Flowsheet Options

Synthesis Gas driers Reduces H2O in syn gas H2O is a poison Activity increases Ammonia Wash As per Syn Gas driers Booster converters Drop load on loop and allow overall output

increase Quenches in Shifts

Ammonia Flowsheet Data Analysis Tool - VULCAN CERES

Looks at all catalytic unit operations Highlights potential issues/in-correct data

items Functionality to address flowsheet options Kellogg risers Differential flowsheet conditions (Braun) Use as a basis for Predictions of future performance Predictions of new catalyst options Uprates