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

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

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Chapter 33.2.7 Production of concentrated nitric acidDirect processes for the production of concentrated nitric acid are based on the production ofliquid N 2 O 4 , which reacts under pressure with oxygen and dilute nitric acid to form HNO 3 .2 N 2 O 4 + O 2 + 2 H 2 O f 4 HNO 3Nitrogen oxides, which are formed in an ammonia combustion unit operated at low pressure, arecompletely oxidised into NO 2 (oxidation step and post-oxidation step). NO 2 is washed out withconcentrated nitric acid (absorption step) and by process condensate and dilute nitric acid (finalabsorber step). NO 2 (or its dimer N 2 O 4 ) is stripped from the concentrated acid (bleaching) andliquefied. Concentrated acid is formed from liquid N 2 O 4 , oxygen and dilute nitric acid (from thefinal absorption step) in a reactor at a pressure of approximately 50 bar. Concentrated nitric acidis recirculated to the absorption and final oxidation steps, part of nitric acid is withdrawn asproduct acid. Waste gas is discharged from the final absorption step. NO x concentration of thewaste gas depends on the temperature of the final absorption step. Process condensates anddilute nitric acid arising from catalytic ammonia oxidation, oxidation and post oxidation step arere-used. However, more process condensate is formed than can be used for production ofconcentrated acid. A part of the process condensates has to be used for other production ortreated as waste water.Indirect processes are based on extractive distillation and rectification of weak nitric acid.Sulphuric acid or magnesium nitrate is used as the dehydrating agent. With sulphuric acidprocesses, weak nitric acid is preheated and distilled with H 2 SO 4 . With magnesium nitrateprocesses, a solution of Mg(NO 3 ) 2 is used to extract water from the nitric acid. Dehydratingagents are restored under vacuum. Process condensates which demand an adequate waste watertreatment arise from concentrating the dehydrating agent. Vapour withdrawn from the head ofthe distillation or extraction column is condensed to form concentrated nitric acid. Waste gasescontain nitric acid vapour and are scrubbed with dilute nitric acid.100 December 2006 BS/EIPPCB/LVIC-AAF_BREF_FINAL

Chapter 33.3 Current emission and consumption levelsTable 3.5 and Table 3.6 give an overview/examples for consumption levels of HNO 3 production. Figure 3.3 shows the empirical correlation between specific N 2 Oemission levels and N 2 O concentrations in tail gases. Table 3.7 shows the reported N 2 O levels and Table 3.8 the reported NO x levels.M/M H/H M/H UnitOperating pressure 6 10 4.6/12 barAmmonia 286 290 283 kg/tonne 100 % HNO 3Electrical power 9 13 8.5 kWh/tonne 100 % HNO 3Platinum primary losses 0.15 0.26 0.13 g/tonne 100 % HNO 3Heating steam 8 bar, saturated 0.05 0.35 0.05 tonnes/tonne 100 % HNO 3Excess steam, 40 bar, 450 ºC 0.75 0.58 0.65 tonnes/tonne 100 % HNO 3Cooling water x 100 125 105 tonnes/tonne 100 % HNO 3x jT = 10 K, including water for steam turbine condenserTable 3.5: Examples for consumption levels for steam turbine-driven HNO 3 plants and tail gas containing

Chapter 33.3 Current emission and consumption levelsTable 3.5 and Table 3.6 give an overview/examples for consumption levels of HNO 3 production. Figure 3.3 shows the empirical correlation between specific N 2 Oemission levels and N 2 O concentrations in tail gases. Table 3.7 shows the reported N 2 O levels and Table 3.8 the reported NO x levels.M/M H/H M/H UnitOperating pressure 6 10 4.6/12 bar<strong>Ammonia</strong> 286 290 283 kg/tonne 100 % HNO 3Electrical power 9 13 8.5 kWh/tonne 100 % HNO 3Platinum primary losses 0.15 0.26 0.13 g/tonne 100 % HNO 3Heating steam 8 bar, saturated 0.05 0.35 0.05 tonnes/tonne 100 % HNO 3Excess steam, 40 bar, 450 ºC 0.75 0.58 0.65 tonnes/tonne 100 % HNO 3Cooling water x 100 125 105 tonnes/tonne 100 % HNO 3x jT = 10 K, including water for steam turbine condenserTable 3.5: Examples for consumption levels for steam turbine-driven HNO 3 plants and tail gas containing

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