| 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. |