System and method for producing melamine

Abstract

The invention belongs to the technical field of melamine preparation, and relates to a system and a method for producing melamine. The system comprises a fluidized bed reactor, wherein mixed gas generated by the fluidized bed reactor goes into a hot gas cooler, a hot gas filter, a crystallizer, a catcher, a urea scrubber, a gas-liquid separator and a demister successively; the demister is connected with the crystallizer; a molten salt bath is successively connected with a molten salt furnace and the fluidized bed reactor to provide a heat transfer medium; a carrier gas preheater is connected with the fluidized bed reactor and the molten salt bath; molten salt enters the molten salt furnace, the fluidized bed reactor and the carrier gas preheater successively from the molten salt bath and then returns to the molten salt bath; granular urea outside a boundary area enters the lower part of the urea scrubber; part of molten urea flowing from the bottom of the urea scrubber partly enters the upper and middle parts of the urea scrubber through a circulating pump and the rest enters the fluidized bed reactor. The urea is added in a granule form of during the production of melamine, and reduces the energy consumption of the molten urea with less environmental pollution.

Description

technical field [0001] The invention belongs to the technical field of melamine preparation, and in particular relates to a melamine production system and method. Background technique [0002] At present, most of the production of melamine is based on urea as raw material, and the reaction formula is: [0003] 6CO(NH 2 ) 2 →C 3 N 6 h 6 +3CO 2 +6NH 3 [0004] This reaction is an endothermic reaction and requires heating, generally using molten salt heating. Melamine has the characteristics of sublimation and desublimation. At present, the domestic fluidized bed catalytic reaction process uses this characteristic of melamine to cool the melamine in the reaction gas to below the desublimation temperature through the cooling medium, so that the melamine has gas Condensate into a solid, the existing gas phase quenching process of producing melamine with granular urea as raw material is as follows: [0005] Granular urea is first added to the urea melting tank, and the g...

AI Technical Summary

Problems solved by technology

[0007] First, the use of heat is unreasonable: foreign granular urea needs to be melted into a liquid at about 140°C with steam or other heat, and then enters the urea scrubber, which increases energy consumption

[0008] Second, there is pollution to the environment: when urea is heated and melted, ammonia and carbon dioxide gas are released, and the released ammonia and carbon dioxide gas are directly discharged into the atmosphere, which will cause air pollution. processing, also increases energy consumption

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