Equipment and process for producing melamine under low pressure

Abstract

The invention discloses equipment and a process for producing melamine under a low pressure. The process comprises the following steps of: (1) atomizing molten urea, introducing into a reactor, and reacting by taking gas ammonia as a reaction carrier gas in a reactor under the condition that the temperature is 380-410 DEG C and the pressure is 0.1-1.4MPa to generate melamine, carbon dioxide, ammonia and a deamination product of melamine; (2) after reacting, crystalizing the deamination product, filtering, cooling the filtered gas with a quenching medium, and separating to obtain a finished product; (3) absorbing the gas left after separation with water to form a methylamine solution and a mixed gas; and (4) rectifying the mixed gas under the condition that the temperature is between 30 DEG C below zero and 30 DEG C to form ammonia gas, and returning the ammonia gas to the step (1) for serving as a reaction carrier gas or/and returning to the step (2) for serving as quenching medium. The invention further discloses equipment for producing melamine under a low pressure. The equipment and the process have the advantages of good product quality, high production efficiency, low energy consumption, environmental friendliness, simple process, and the like.

Description

technical field [0001] The invention relates to a melamine production process, in particular to a low-pressure melamine production process, and also relates to low-pressure melamine production equipment. Background technique [0002] The production process of melamine usually includes three main processes such as polymerization reaction, quenching separation and tail gas treatment. [0003] Polymerization reaction: urea is used as raw material, converted into melamine at a certain temperature and pressure, and NH is released at the same time 3 and CO 2 . [0004] Quenching separation: divided into liquid phase quenching method and gas phase quenching method. The liquid phase quenching method usually quenches the reaction product with water or an aqueous solution containing melamine, so that the melamine is completely dissolved in the aqueous solution, or partially dissolved and partially crystallized; the gas phase quenching method is usually used to contain NH 3 and CO ...

AI Technical Summary

Problems solved by technology

[0006] The problems of the common low-pressure liquid-phase quenching method for melamine are: the process is long and the operation is complicated; there are a lot of equipment and the volume is relatively large, and some equipment has high requirements on materials and large investment; product purification needs steam, and energy consumption is relatively high. High; the tail gas pressure is low and contains a lot of water, etc., so it is not easy to use directly; the filter residue is difficult to handle, and there are environmental protection risks

[0007] The problem with the low-pressure gas-phase quenching method is that the quenched gas needs to be washed with molten urea, and the entrained urea mist is easy to foul in the process pipeline, thereby blocking the system and affecting long-term operation; The heat exchanger is blocked; it needs to be equipped with a compressor unit that can withstand higher temperature and high power; the tail gas is difficult to deal with due to its low pressure

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