Study On Recovery Technology Of Ammonia For The Synthesis Device Of DMC By Two-Step Method Of Urea

Dimethyl carbonate(Referred to as DMC)is an Environmentally friendly and green chemical product,it has received extensive attention and researches at home and abroad in recent years,which is known as the the "new block" in the field of organic synthesis.This paper focuses on the engineering technology of the 40,000 tons/year synthesis device of DMC by two-step method of Urea,the running operation of the device found that ammonia released from the dissolved kettle of Urea when urea and propylene glycol,the catalyst were heating dissolved in the dissolved kettle of Urea,this had caused the loss of raw materials,meanwhile environmental pollution was inevitable,while the original process package does not mention this problem.Therefore,the effective control of the urea decomposition of the device and the effective recovery of ammonia release is of great significance.A small test simulated the heating dissolution process of urea, propylene glycol and catalyst in the dissolved kettle of Urea,the results showed that urea and propylene glycol,the catalyst converted to liquid-solid mixture after stirring and dissolving,and no ammonia release in the case of temperature below 60 ℃,at the same time the urea could not be dissolved completely.However,given the faster decomposition of urea under the conditions of temperature more than 800℃,which is not conducive to the follow-up main reaction,while the urea can be completely dissolved after 35 minutes with the temperature above 70 ℃ accompanied by ammonia,also the higher the temperaturee,the faster the reaction.so the solution temperature on the dissolved kettle of urea should be controlled at about 80 ℃.In view of the phenomenon of ammonia release found in the experiment,the industrial dissolved kettle of urea was transformed technically about ammonia recovery,and a device of ammonia recovery was increased,the running results after the technical transformation show that the actual operation results are consistent with the design results of ammonia recovery device,the environmental pollution caused by the ammonia release in the process of urea dissolution has been basically eliminated,simultaneously the annual recovery of ammonia was 1,680,the annual recovery of propylene glycol of was 72 tons,both to protect the environment,but also to increase efficiency for enterprises.