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

Chapter 77.2.3 Direct neutralisation (pipe reactor)Various amounts of H 3 PO 4 , H 2 SO 4 and HNO 3 are neutralised in pipe reactors with gaseous orliquid NH 3 . The pipe reactor is usually fitted in the granulation drum. Another pipe reactor maybe used in the dryer.A wide range of grades can be produced, including ammonium phosphates (DAP/MAP). Theheat of the reaction is used to evaporate the water contained in the phosphoric acid so theprocess can be operated at low recycle ratios and thus with low utilities consumption.7.2.4 Pre-neutralisationThe conventional slurry process is carried out in a series of tanks/reactors, using a preneutraliser.Various amounts of H 3 PO 4 , H 2 SO 4 and HNO 3 are neutralised with NH 3 and theresulting slurry can be partly evaporated to achieve the water content necessary for thesubsequent particle formation. This process can produce NPKs and ammonium phosphates(DAP/MAP) with a good final product quality but yields a slurry with a high water content andhence, a high recycle ratio and increased energy consumption.7.2.5 Drum granulation with ammoniationThis process uses mainly solid raw materials. Some NH 3 is reacted with H 2 SO 4 /H 3 PO 4 /HNO 3within the bed of solid raw and recycle material in the granulation drum. The process is veryflexible and can produce a broad range of grades, including products with a low nitrogencontent.7.2.6 Particle formation and conditioningThe options for particle formation include:• spherodiser, see Section 7.4.2• granulation drum, see Section 7.4.3• prill tower, see Section 7.4.4• pugmill (also called blunger) granulation• pan granulation (for use in CN production, see Section 7.4.8)• compaction.The required temperatures for particle formation and drying with spherodiser or drumgranulation depend also on the composition of the NPK product. For example, for NPK 15-15-15 dryer inlet temperatures of about 320 ºC and for NPK 20-8-8 dryer inlet temperatures