Process for producing biurea through optimized urea method

Abstract

The present invention discloses a process for producing biurea through an optimized urea method. The process comprises that: during the biurea preparing, the crude solution of hydrazine hydrate produced through the urea method is adopted as a raw material and is subjected to repeated evaporation concentration and freezing crystallization for a plurality of times to respectively separate out sodium chloride and sodium carbonate so as to obtain a fine hydrazine solution of the hydrazine hydrate; the sodium chloride is separated at the evaporation section and the sodium carbonate decahydrate is separated at the freezing crystallization section during each evaporation, a salt extracting pump is used to extract, and the solid sodium chloride is separated out by a salt separation centrifuge; and the liquid is subjected to freezing crystallization, is separated, and then returns to the cold hydrazine solution at the evaporation section, pre-cooling is performed, and then the obtained material is conveyed to the crystallization kettle. The process of the present invention has the following beneficial effects that: the hydrazine hydrate-containing crude solution produced through the urea method is adopted as the raw material, alkali removing through freezing is performed while the cold energy and the heat energy are recovered, the repeated circulating method is used, the hydrazine hydrate concentration is improved in the low cost manner, and the process has characteristics of less raw material consumption, less energy source consumption, low cost, and high single-kettle yield during condensation.

Description

technical field [0001] The invention relates to the technical field of biurea, in particular to a process for optimizing the production of biurea by a urea method. Background technique [0002] Biurea is white solid or powder, molecular formula: C 2 h 6 N 4 o 2 , Molecular weight: 118, insoluble in water, melting point 247-250°C, biurea is mainly used in the production of ADC foaming agent. [0003] The conventional urea method to produce biurea is divided into two types: acid method and pure hydrazine method. [0004] The conventional acid method mainly adopts the crude solution containing <70g / L hydrazine hydrate produced by the urea method to separate part of the sodium carbonate decahydrate through freezing and crystallization to obtain a dilute hydrazine solution whose concentration of hydrazine hydrate is increased to less than about 10%, adding sulfuric acid or Hydrochloric acid is neutralized and then reacted with urea at a temperature of >100°C to form bi...

AI Technical Summary

Problems solved by technology

In this evaporation process, 0.3-0.5 tons of caustic soda of biurea must be added to evaporate the hydrazine hydrate in the crude solution (the effect of adding caustic soda is that the caustic soda in the evaporator reacts with the unreacted urea in the crude solution to form Sodium carbonate, and keep under the situation of strong alkali to facilitate the evaporation of hydrazine hydrate), thus increasing the consumption of caustic soda