According to the different methods of pyrolysis, it is divided into solid phase melting method and liquid phase method. The solid phase method heats the urea to 200~300 °C, pyrolyzes the crude cyanuric acid, then adds 15-20% sulfuric acid (or nitric acid, hydrochloric acid), cooks, and is filtered, washed and dried to obtain the finished product. This is the main method of industrial production of cyanuric acid. The purity of industrial products is ≥95%, and the consumption of urea per ton is 1200kg. The liquid phase method is carried out in an aromatic hydrocarbon or mineral oil solvent, the reaction is completed, the solvent is separated, washed, and dried to obtain a finished product, the reaction conditions are moderate, and the corrosion is small, but the yield is low.
(2) Semi-circulation method: Put cyanuric acid powder into the ball plate, gradually add urea, the molar ratio is 1.7~2, heat up to 190 °C, continue for half an hour, stop heating, continue rolling until no ammonia is formed. . A small portion is taken out, pulverized, dissolved in sulfuric acid, boiled, centrifuged, washed and dried to obtain a finished product. The rest continues to circulate.
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