granulation process of urea with an acid scrubbing system and the subsequent integration of ammonium salt in urea granules

摘要

urea granulation process with an acid scrubbing system and the subsequent integration of ammonium salt in urea granules. the invention relates to a urea granulation process with a purification system including several residual streams for removing dust and ammonia from the exhaust gas of a urea granulation unit comprising a urea granulator (1), a stage of urea granulator scrubber dust (2), a granulator scrubber acid stage (3), product coolers (5), a product cooler deputy dust stage (4), an evaporation unit (6), and a condenser unit (7). In this way, a first stream of fresh air (8), passing through a first sequence of process steps, is sent to the urea granulator (1), through which the air charged with dust and ammonia (9) is removed from the granulator (1) and transported in a granulator scrubber dust stage (2), followed by a granulator scrubber acid stage (2), followed by a granulator scrubber acid stage (3), this stage in that the air loaded with ammonia (12) is contacted with an acid in the liquid phase (22) and the ammonia is purified from this air by the generation of an ammonium salt. a second stream of fresh air (15), passing through a second sequence of process steps, is used to cool the product removed from the sand granulator (1), by means of which said cooling is carried out in product coolers (5 ), in this way the said air is heated, and later it is transported to a dust stage of the product cooler debugger (4). the clean exhaust gas (13) taken from the acid stage of the granulator scrubber (3), and the clean exhaust gas (18) taken from the dust cooler stage of the product cooler (4), are released into the atmosphere ( 19). therefore, the purification system is passed, which in itself is a complete closed system, and totally separated from urea synthesis, by means of which the ammonium salt solution stream (23) of the acid stage of the purifier is granulator (3), is fed into said dust stage of the product cooler debugger (4), whereby the ammonia from the air stream charged with dust (17) leaving the product coolers (5) is removed, and the liquid substance released (24) from the dust stage of the product cooler scrubber (4) and the liquid substance released (11) from the dust stage of the granulator scrubber (2) are sent to the evaporation unit (6). the vapor stream (29) of the evaporation unit (6), which contains ammonia is supplied in the condenser unit (7), which releases a liquid process condenser (30), and said liquid process condensate (30) is supplied with concentrated liquid substance (28) from the evaporation unit (6), containing urea and ammonium salt, and a melt of urea (26) from a synthesis unit (27) are transported in the urea granulator (1), separately . in this way, the ammonium salt contained in the concentrated liquid substance stream (28) is integrated into the granulated urea product.