Production method of melamine by slow cooling crystallization

Abstract

The invention provides a production method of melamine by slow cooling crystallization. The method changes the crystallization process of melamine in a reaction gas and chooses scientific and reasonable multi-functional professional equipment to eliminate a cold air preparation process that has high power consumption and has great influence on production stability. Also, at the same time of reaction gas cooling and melamine crystallization, higher value recovery of reaction gas waste heat is realized, and all production equipment can operate stably for a long period. Thus, the product can have lower power consumption, coal consumption and production cost, and investment in device construction can drop significantly.

Description

technical field [0001] The invention belongs to the technical field of chemical production, in particular to a production method of melamine. Background technique [0002] At present, there are two main dry production processes of melamine: one is the gas phase quenching process; the other is the solid phase quenching crystallization process. [0003] The gas phase quenching process is as follows: the molten urea is pumped to the urea adding port of the reactor through the urine, atomized under the action of the atomizing gas and enters the reactor, and reacts to form melamine under a certain pressure and temperature through the action of a catalyst. . The heat required for the reaction is provided by a molten salt system. The fluidized bed carrier gas entering the reactor comes from ammonia and carbon dioxide mixed gas that is preheated after separation and purification, liquid urine washing and cooling, and compressor boosting. The reacted gas enters the hot gas cooler ...

AI Technical Summary

Problems solved by technology

There are the following problems in production: First, the amount of air-conditioning is generally 4 times the amount of carrier gas, and the preparation of a large amount of air-conditioning requires a lot of power, which seriously affects the power consumption of the product; A large amount of ammonia, carbon dioxide, and a small amount of melamine and urea residues are entrained. The harsh environment can easily cause unstable operation of the fan and frequent shutdowns; third, the cooling and crystallization process of the reaction gas reduces the heat recovery amount and heat recovery grade of the reaction gas. , Improper use of waste heat causes high consumption of bituminous coal; Fourth, the reactor is prone to dead bed, high silica gel breakage rate, uneven bed temperature, and many reaction by-products; Fifth, equipment and pipelines are easy to block, and the operating time of the device is short, and the time for parking and repairing Sixth, there are many online equipment, long process flow, and large system resistance; Seventh, the amount of civil engineering is large, the area is large, and the investment in equipment is large

[0006] This process has the concept of shortening the process and reducing investment, but when melamine is crystallized, the problems of blocked pipelines and equipment have not been fundamentally solved, making the production impossible to continue, and the temperature of melamine particles at about 180 ° C is used as a cooling medium to cool down , transportation and other preparation processes will waste a lot of electricity, the sensible heat of solid particles is not easy to recover, and the waste heat of melamine reaction will cause a lot of waste, so this process technology has not been industrialized

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