Method for removing sodium carbonate from hydrazine hydrate crude solution

Abstract

The invention discloses a method for removing sodium carbonate from a hydrazine hydrate crude solution. The method comprises the following steps: 1, a urea solution is mixed with sodium hypochlorite, wherein a molar ratio of the urea solution to sodium hypochlorite is 1-2, such that the crude solution obtained by a reaction does not contain sodium hydroxide; 2, a chloride is added into the hydrazine hydrate crude solution; and centrifugal separation is carried out, such that poorly soluble carbonate is separated; 3, the hydrazine hydrate solution with sodium carbonate removed is subjected to membrane filtration, such that cations in the solution are removed. With the method, sodium carbonate in the hydrazine hydrate crude solution is thoroughly removed. The produced poorly soluble carbonate can be directly sold after certain treatments, and can be subjected to a reaction with hydrochloric acid recovered from an ADC process for producing chloride for recycling. When the sodium-carbonate-removed hydrazine hydrate solution is used in a biurea production process, acidic substance addition can be greatly reduced. When the sodium-carbonate-removed hydrazine hydrate solution is used in a hydrazine hydrate production process through evaporation and rectification, evaporation and rectification continuous production is facilitated.

Description

technical field [0001] The invention relates to the technical field of removing sodium carbonate, in particular to a method for removing sodium carbonate in the thick solution of hydrazine hydrate. 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 used in the process of producing biurea, the remaining sodium carbonate needs to consume a large amount of acidic substances, which increases the consumption of acidic substances. If this solution is used in the process of producing hydrazine hydrate thro...

AI Technical Summary

Problems solved by technology

If this solution is used in the process of producing biurea, the remaining sodium carbonate needs to consume a large amount of acidic substances, which increases the consumption of acidic substances

If this solution is used in the process of producing hydrazine hydrate through evaporation and rectification, sodium carbonate monohydrate will be formed in the evaporation process due to the existence of sodium carbonate, and the existence of sodium carbonate monohydrate in the evaporator will block the heat exchange tube of the heater. It is often necessary to stop production and discharge materials, 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