High yields, high purity melamine manufacturing process
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United States of America Patent
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May 10, 2005
Grant Date -
May 29, 2003
app pub date -
Dec 7, 2000
filing date -
Dec 22, 1999
priority date (Note) -
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Abstract
The process to recover both melamine and oxyaminotriazines (OAT) from the mother liquors of melamine crystallisation comprising the following steps: a) addition to a melamine and OAT containing aqueous solution at high temperature of an alkaline agent until the solution pH reach a value equal or higher than 11; b) most of melamine crystallisation by solution cooling; c) separation and recovery of precipitated melamine; d) acidification of the obtained solution, after precipitated melamine separation, in order to reach a pH of about 7; e) the suspension obtained in d) above after precipitated melamine recovery, is subject to filtration according to tangential filtration technique obtaining a clear permeate which contains as a solution all melamine which did not precipitate in step b) and a retentate comprising of OAT dispersion; f) OAT deprived mother liquors from e) are recycled to row melamine solution preparation step; in such a way almost the total amount of melamine, which did not precipitate in step b), is recovered; g) OAT are recovered from step e) retentate by using any conventional separation technics.
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