Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

Chapter 22.3 Current emission and consumption levels2.3.1 Energy consumptionTable 2.6 shows the reported energy consumption levels for the production of ammonia. Anexample for the breakdown of energy flow is indicated in Table 2.5.Energy flow Share %Product ammonia 71.9Unrecovered process heat 10.5Air compressor turbine 7.8Syngas compressor turbine 5.7Flue-gas heat 2.4Refrigeration compressor turbine 1.8Miscellaneous 0.6Overall 100Table 2.5: Example for energy flows in an ammonia production plant(1350 tonnes/day, fired primary reformer)[13, Barton and Hunns, 2000]2.3.1.1 Comparison of energy consumption figuresThe comparison of energy consumption figures without precise knowledge of design andevaluation criteria can be misleading. First, the state of the ammonia product should be noted.Relative to the delivery of liquid ammonia to battery limits at ambient temperature, theproduction of 3 bar ammonia vapour at the same temperature would save 0.6 GJ/tonne NH 3 ,while delivery as liquid at -33 °C would need an extra 0.3 GJ/tonne NH 3 . The temperature ofthe available cooling medium has a considerable influence. Increasing the cooling watertemperature from 20 to 30 °C increases energy consumption by 0.7 GJ/tonne NH 3 . A detailedenergy balance, listing all imports and exports, together with the caloric conversion factors usedfor steam and power is needed for a fair comparison of plants. Additionally, energy export canhave a beneficial effect on the net energy consumption. Gas composition is also of someimportance. Nitrogen content is marginally beneficial: 10 mol % nitrogen leads to a saving ofabout 0.1 GJ/tonne NH 3 , whereas a content of 10 mol % carbon dioxide would add 0.2 GJ/tonneNH 3 to the total consumption value [15, Ullmanns, 2001].Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers 49