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

Chapter 77.4.10 Combined treatment of exhaust gases from neutralisation/evaporation and granulationDescriptionThe example plant renewed its NPK fertiliser production and a new combined waste gasscrubber was installed for treating exhaust gases/vapours from neutralisation/evaporation andexhaust gases from two spherodisers. The former setup (venturi scrubber and co-condensationof the neutralisation/evaporation exhaust vapours, scrubbing of NH 3 loaded gases) was replaced.Figure 7.6 illustrates the combined treatment.Instead of condensing the vapours from neutralisation/evaporation, they are combined with thehot exhaust gas from the spherodiser (about 100 ºC, not saturated with H 2 O) and the added heatleads to additional evaporation of H 2 O in the scrubber. The additional H 2 O removal enables therecycling of all scrubber liquids (and the contained nutrients) to the production process.In the example, the total gas volume flow is about 250000 Nm 3 /hour and about 1800 m 3 /hourscrubbing liquor is circulated. An amount of about 1 m 3 /hour scrubbing liquor is drawn off forrecycling to the NPK production and contains about 25 % w/w AN. The scrubber is fed withliquid effluents from NPK production. The scrubber is equipped with a demister located abovethe scrubber packing and requires periodic cleaning, because insoluble compounds in theexhaust gases, e.g. dolomite, CaSO 4 and Ca 3 (PO 4 ) 2 can cause clogging.Emission to airPeriodicalwashing withHNO 3andfresh waterDemisterExhaust vapoursfromneutralisation/evaporationBufferProcess waterfrom NPKproductionCycloneCycloneExhaust gasfrom spherodisersLiquor to NPKproductionBufferReturns to NPKproductionFigure 7.6: Combined treatment of exhaust gases from NPK productionFigure based on [9, Austrian UBA, 2002]314 Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers