High pressure method for producing pure melamine in a vertical synthesis reactor

Abstract

The invention relates to a high pressure method for producing pure melamine by pyrolyzing urea in a vertical synthesis reactor. The invention is characterized in that the synthesis reactor has three stages vertically arranged above one other, whereby: a) in the first i.e. uppermost stage, the smaller portion of the total amount of urea is introduced into the central tube of a first tank reactor whereby forming a first melamine-containing reaction medium; b) in the second i.e. middle stage, the first melamine-containing reaction medium as well as the larger portion of the total amount of urea is introduced into the central tube of a second tank reactor whereby forming a second melamine-containing reaction medium, after which; c) in the third i.e. lowermost stage, the second melamine-containing reaction medium is introduced into a vertical tubular flow reactor whereby forming a raw melamine melt that is subsequently processed in any manner whereby obtaining pure melamine. This makes it possible to achieve a more uniform conversion of urea, a more mild and corrosion-reducing supply of reaction heat, and for the reaction to be optimally carried out as well as to achieve a complete reaction of the urea in the melamine synthesis reactor. In comparison to other melamine methods, the invention provides a more compact, economical and efficient synthesis of melamine.

Description

technical field [0001] The invention relates to a high-pressure process for the production of pure melamine by pyrolysis of urea in a vertical synthesis reactor and to a reactor for carrying out the process. Background technique [0002] In the high-pressure process for the preparation of melamine, urea melt and optionally gaseous ammonia are usually reacted in the absence of a catalyst at a temperature of about 325 to 450° C. and a pressure of 50 to 250 bar to form liquid melamine and off-gas, The exhaust gas consists mainly of ammonia and carbon dioxide. The liquid melamine, which contains besides unreacted urea also by-products, is subsequently treated, for example, by quenching with water, by sublimation or by decompression under specific conditions, and the pure melamine is subsequently separated off. [0003] Melamine reactors known from the conventional melamine process are generally vertical tank reactors of the loop reactor type, as described, for example, in AT 40...

AI Technical Summary

Problems solved by technology

In this process the same disadvantages as in the one-stage loop reactor arise with regard to the synthesis of melamine

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