Biurea production process through urea method

Abstract

The invention discloses a biurea production process through a urea method. The process comprises the following steps: mixing a urea solution with sodium hypochlorite, performing reaction to generate a crude solution containing hydrazine hydrate, and removing sodium carbonate in the crude solution; adding 10-15% hydrochloric acid recovered in an ADC oxidation process into the crude solution without sodium carbonate to neutralize to enable the PH value to be 2-3, performing multi-effect evaporation and concentration to obtain a hydrazine dihydrochloride solution of which the concentration is 20-30%, conveying precipitated sodium chloride to a centrifuger to enable solid sodium chloride to be separated out, conveying the hydrazine dihydrochloride solution to a concentration kettle, adding solid urea to react to produce biurea, and performing centrifugation, washing and drying to obtain the biurea product. The biurea production process provided by the invention has the benefits that a rectification procedure in a conventional hydrazine hydrate production process through evaporation, rectification and concentration of a crude solution is eliminated, and a defect that multiple-effect evaporation cannot be realized in the conventional evaporation, rectification and concentration process as hydrazine hydrate is likely to decompose at high temperature is overcome, so that plenty of steam can be saved, and single kettle yield of the condensation kettle is greatly improved.

Description

technical field [0001] The invention relates to the technical field of biurea, in particular to a process for producing biurea by a urea method. Background technique [0002] The crude solution for producing hydrazine hydrate by urea method contains hydrazine hydrate, sodium carbonate, urea, sodium chloride and water. The content of sodium carbonate is 110-150g / L. The conventional method is to pre-cool the crude solution of hydrazine hydrate and send it to the crystallization kettle, and cool it down to -2°C--0°C; centrifuge to remove 60--70% of sodium carbonate decahydrate , to obtain a hydrazine hydrate solution containing 35-60 / L sodium carbonate. If this solution is added to the hydrochloric acid recovered in the ADC oxidation process, after adding urea, the condensation reaction is carried out to produce biurea, because the freezing method adopted for condensation can only remove part of the sodium carbonate, and the hydrazine hydrate solution still contains sodium car...

AI Technical Summary

Problems solved by technology

If this solution is added to the hydrochloric acid recovered in the ADC oxidation process, after adding urea, the condensation reaction is carried out to produce biurea, because the freezing method adopted for condensation can only remove part of the sodium carbonate, and the hydrazine hydrate solution still contains sodium carbonate, which requires a large amount of recovery. Hydrochloric acid to neutralize the remaining sodium carbonate, and because the concentration of recovered hydrochloric acid is only low, after the hydrazine hydrate solution is neutralized by recovered hydrochloric acid, the hydrazine content in it is only 35-40g / L, and the single-pot yield of the condensation reactor decreases. Larger or more condensation vessels

If the hydrazine hydrate solution after removing part of the sodium carbonate is produced by evaporation and rectification to produce 20-40% hydrazine hydrate, a large amount of steam will be consumed. Because of the existence of sodium carbonate, sodium carbonate monohydrate will be formed during the evaporation process. There is a The existence of sodium carbonate in water will block the heat exchange tube of the heater. It is often necessary to stop the production and discharge the material, and add water to clean the heater, which is not conducive to the continuous production of evaporation and rectification. Cleaning the heater consumes a large amount of steam and causes material loss. Loss, if multi-effect evaporation is used, in concentrated-effect evaporation, it is evaporation under pressure, the concentration of hydrazine hydrate is high, and the temperature is high. Because hydrazine hydrate begins to decompose at 140 ° C, explosion accidents are prone to occur