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

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

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Chapter 22.2.3 Conventional steam reformingFigure 2.1 gives an overview of conventional steam reforming. The individual process stagesare described in the following subsections.Natural gasZnODesulphurisationZnSH 2 O, fuelPrimary reformerFlue-gasAir, powerSecondary reformerHeatShift conversionHeatHeat, powerCO 2 removalCondensate, CO 2MethanationPowerCompressionPowerNH 3 synthesisPurge/flash gasNH 3Figure 2.1: NH 3 production by conventional steam reforming[1, EFMA, 2000]2.2.3.1 DesulphurisationThe catalyst used in the steam reforming process is highly sensitive to any sulphur compounds,therefore these compounds need to be reduced to a concentration of less than 0.15 mg S/Nm 3feed gas. To achieve this, the feed gas is preheated up to 350 – 400 °C. Thereafter, the sulphurcompounds are hydrogenated to H 2 S, typically using a cobalt molybdenum catalyst, and thenfinally adsorbed on pelletised zinc oxide (R = alkyl group):R-SH + H 2 f H 2 S + RHH 2 S + ZnO f ZnS + H 2 OThe hydrogen required for the reaction is usually recycled from the synthesis section of theplant.<strong>Large</strong> <strong>Volume</strong> <strong>Inorganic</strong> <strong>Chemicals</strong> – <strong>Ammonia</strong>, Acids and Fertilisers 39

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