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

Chapter 22.2 Applied processes and techniquesNote: process parameters presented in the following sections, such as temperatures andpressures, might deviate in specific cases.2.2.1 OverviewAmmonia is synthesised from nitrogen and hydrogen by the following reaction:N 2 + 3H 2 d 2NH 3The best available source of nitrogen is from atmospheric air. The hydrogen required can beproduced from various feedstocks but currently it is derived mostly from fossil fuels. Dependingof the type of fossil fuel, two different methods are mainly applied to produce the hydrogen forammonia production: steam reforming or partial oxidation.For a detailed description of conventional steam reforming, see Section 2.2.3.For a detailed description of partial oxidation, see Section 2.2.4.About advanced conventional steam reforming, processes with reduced primary reforming, andheat exchange autothermal reforming, see Sections 2.4.1, 2.4.2, 2.4.3.For a description of ammonia production using water electrolysis, see Section 2.4.26.As it can be seen from Table 2.2, currently, about 80 % of the ammonia production capacityworldwide is provided by the well-developed steam reforming process. High level processintegration, innovative equipment design and improved catalysts are the main characteristics ofammonia plants today.Feedstock Process % of world capacityNatural gas Steam reforming 77Naphtha, LPG, refinery gas Steam reforming 6Heavy hydrocarbon fractions Partial oxidation 3Coke, coal Partial oxidation 13.5Water Water electrolysis 0.5Table 2.2: Applied processes and feed stocks in the production of ammoniaThe third column shows the related share of world capacity (1990)[3, European Commission, 1997]There has been limited development work of the partial oxidation process in integrated plantconcepts. At present, a typical plant is a blend of techniques offered by different licensorsassembled by the selected contractor. The achieved energy consumptions reported in Table 2.3suggest that, compared to the steam reforming process, there is a potential for improvement ofthe energy efficiency of partial oxidation processes.FeedstockProcessNet primary energyconsumption GJ/t NH 3 (LHV)RelativeinvestmentNatural gas Steam reforming 28 x 1Heavy hydrocarbons Partial oxidation 38 1.5Coal Partial oxidation 48 2 – 3x Best achieved dataTable 2.3: Cost differences and total energy demands for ammonia production[3, European Commission, 1997]Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers 37