Ammonia production by Haldor Topsoe process Ammonia production by Haldor Topsoe process
Naphtha obtained from the distillation of petroleum crude is used as the source of Naphtha obtained from the distillation of petroleum crude is used as the source of hydrogen which acts as the reactant for the production of ammonia. One mole of hydrogen which acts as the reactant for the production of ammonia. One mole of Ammonia requires one mole of nitrogen and three moles of hydrogen as per Ammonia requires one mole of nitrogen and three moles of hydrogen as per stoichiometry equation. Natural gas is the better option for hydrogen source and stoichiometry equation. Natural gas is the better option for hydrogen source and advantages over the naphtha process as most of the unit operations are reduced getting advantages over the naphtha process as most of the unit operations are reduced getting down the installation and production cost.
down the installation and production cost.
Many variations of the Haber’s process are now being used for the
Many variations of the Haber’s process are now being used for the manufacture ofmanufacture of synthetic ammonia some varying to such an extent that they are identified by a name synthetic ammonia some varying to such an extent that they are identified by a name often that of the group of men developing them. Important among these are the often that of the group of men developing them. Important among these are the modified Haber Bosch, Haldor Topsoe, Claude, Casale, Fauser and Mount Cenis modified Haber Bosch, Haldor Topsoe, Claude, Casale, Fauser and Mount Cenis processes.
processes.
All of them are fundamentally the same in that nitrogen is fixed with hydrogen as All of them are fundamentally the same in that nitrogen is fixed with hydrogen as ammonia in the presence of a catalyst but have variations in the construction of ammonia in the presence of a catalyst but have variations in the construction of equipment their arrangement, the composition of catalyst and temperature and equipment their arrangement, the composition of catalyst and temperature and pressure used but
pressure used but an ideal process flow sheet an ideal process flow sheet becomes the platform for improvement inbecomes the platform for improvement in the process. A simple block di
the process. A simple block diagram shows the Haber’s processagram shows the Haber’s process -:-:
1.
1. Naphtha gas supply:Naphtha gas supply: Naphtha is used as feedstock and fuel for Ammonia plant and is Naphtha is used as feedstock and fuel for Ammonia plant and is supplied at the offsite Gas Metering station at a pressure of 44 kg/
supplied at the offsite Gas Metering station at a pressure of 44 kg/cmcm22. After metering. After metering at offsite, the naphtha gas for
at offsite, the naphtha gas for process feed is directly received at Ammonia plant batteryprocess feed is directly received at Ammonia plant battery limit at 40 kg/
limit at 40 kg/cmcm22 and and 4040℃℃. Fuel gas is used for burners of feedstock preheater,. Fuel gas is used for burners of feedstock preheater, primary Reformer, Auxiliary superheater and start-up heater in Ammonia plant-Feed gas primary Reformer, Auxiliary superheater and start-up heater in Ammonia plant-Feed gas goes to the Desulphurization unit for sulphur removal, if any and subsequently goes to the Desulphurization unit for sulphur removal, if any and subsequently processed to produce synthesis gas for Ammonia production.
processed to produce synthesis gas for Ammonia production.
2.
2. Desulphurization:Desulphurization: Raw naphtha contains high sulphur which harms the catalyst in Raw naphtha contains high sulphur which harms the catalyst in the reforming reactor and even consumes hydrogen by undesired side reactions. A the reforming reactor and even consumes hydrogen by undesired side reactions. A packed bed reactor is utilized for the removal of sulphur. Zinc oxide based bed absorbs packed bed reactor is utilized for the removal of sulphur. Zinc oxide based bed absorbs the sulphur.
the sulphur.
3.
3. Primary reformer:Primary reformer: Naphtha contains carbon and hydrogen compounds to separate Naphtha contains carbon and hydrogen compounds to separate hydrogen all the carbon
hydrogen all the carbon is converted to carbon dioxide and his converted to carbon dioxide and hydrogen by means of steamydrogen by means of steam at high temperature with the p
at high temperature with the presences of the nickel based catalyst.resences of the nickel based catalyst.
4.
4. Secondary reformer:Secondary reformer: Nitrogen required for the synthesis reaction is obtained from Nitrogen required for the synthesis reaction is obtained from the air so, the carbon dioxide and hydrogen stream is mixed with the air.
the air so, the carbon dioxide and hydrogen stream is mixed with the air.
5.
5. Shift conversion:Shift conversion: Carbon monoxide which is formed in the previous process is Carbon monoxide which is formed in the previous process is converted to carbon dioxide by using steam which results in shift reaction producing converted to carbon dioxide by using steam which results in shift reaction producing hydrogen. High and low shift
hydrogen. High and low shift reactors are arranged for this conversion process.reactors are arranged for this conversion process.
6.
6. removal: removal: All the carbon dioxide p All the carbon dioxide produced is removed by the absorption process.roduced is removed by the absorption process.
Absorption and stripping towers recover the most of the gas which is used in the urea Absorption and stripping towers recover the most of the gas which is used in the urea production.
production.
7.
7. Methanation:Methanation: The traces of carbon dioxide and carbon monoxide are converted to The traces of carbon dioxide and carbon monoxide are converted to methane by means of hydrogen on the catalyst like nickel in methanation reactor. Heat methane by means of hydrogen on the catalyst like nickel in methanation reactor. Heat is produced due
is produced due to the exothermic reaction.to the exothermic reaction.
8.
8. Ammonia synthesis reactor:Ammonia synthesis reactor: Iron acts as the catalyst at temperature 400 Iron acts as the catalyst at temperature 400℃℃ and and pressure 142 kg/
pressure 142 kg/22 the reaction proceeds for the formation of ammonia. the reaction proceeds for the formation of ammonia.
9.
9. Chilling system:Chilling system: A compression absorption refrigeration system is used for A compression absorption refrigeration system is used for liquefaction of ammonia. At 1 atm the boiling
liquefaction of ammonia. At 1 atm the boiling point of ammonia is -33point of ammonia is -33℃℃..
The
The advantagesadvantages of this process are: of this process are:
1.
1. Greater compactness, simplicity in case of converter design since under high-Greater compactness, simplicity in case of converter design since under high- pressure gases have a smaller volume.
pressure gases have a smaller volume.
2.
2. Elimination of expensive heat exchanger required in processes operated at lowElimination of expensive heat exchanger required in processes operated at low pressure.
pressure.
3.
3. Removal of ammonia with water cooling alone.Removal of ammonia with water cooling alone.
The
The disadvantagesdisadvantages of this process are: of this process are:
1.
1. Shorter life of Shorter life of converters.converters.
2.
2. High apparatus upkeep in the High apparatus upkeep in the high-pressure operation.high-pressure operation.
3.
3. Efficiency loss in approximately 20% of making up gas, which Efficiency loss in approximately 20% of making up gas, which is unconverted.is unconverted.
In comparison, Haldor Topsoe process operates at the pressures lower than Claude In comparison, Haldor Topsoe process operates at the pressures lower than Claude process and against the disadvantage of using a heat exchanger for heat recovery and process and against the disadvantage of using a heat exchanger for heat recovery and less compactness in converter design. Recovery of 20% of
less compactness in converter design. Recovery of 20% of unconverted gas and unconverted gas and recyclingrecycling it to increase the efficiency and conversion of the complete process and the large and it to increase the efficiency and conversion of the complete process and the large and massive compressors which are used in Claude process are required to maintaining 900 massive compressors which are used in Claude process are required to maintaining 900 atm which cost millions of dollars are avoided in Haldor Topsoe and is thus more atm which cost millions of dollars are avoided in Haldor Topsoe and is thus more economical and good especially for large capacity process. Also, the
economical and good especially for large capacity process. Also, the life of the converterlife of the converter is very long and ammonia is removed by water-cooling and by knock out the drum.
is very long and ammonia is removed by water-cooling and by knock out the drum.
A Table of Process Design Modifications in Ammonia Production:
A Table of Process Design Modifications in Ammonia Production:
Ever-evolving technologies are been adopted by the modern industries to improve the Ever-evolving technologies are been adopted by the modern industries to improve the conversion rate with efficiency and less energy consumption for complete process, conversion rate with efficiency and less energy consumption for complete process, some of the competitive designed techniques are given and much more are to be some of the competitive designed techniques are given and much more are to be introduced.
introduced.
Process Pressure
Process Pressure(atm)(atm) TemperatureTemperature(℃)(℃) ConversionConversion (%) (%) Mont
Mont Cenis Cenis 120 120 400 400 8-208-20 Stami
Stami Carbon Carbon 310 310 500 500 10-3010-30 Fauster-Monteca
Fauster-Montecatini tini 220-230 220-230 500 500 10-3010-30 Casale
Casale 500-700 500-700 500 500 15-2515-25 Clued
Clued 330-630 330-630 540-590 540-590 15-2515-25 Haber
Haber Bosch Bosch 330 330 500-550 500-550 10-3010-30 Nitrogen
Nitrogen Eng. Eng. Corp. Corp. 200-300 200-300 500-550 500-550 10-3010-30 Lummus
Lummus 270-330 270-330 500-510 500-510 10-10-2525 Kellogg
Kellogg 300-350 300-350 500-510 500-510 10-3010-30 Du
Du Pont Pont 900-1000 900-1000 500-600 500-600 40-8040-80
