Discussion On Optimization Of DMF Production With Annual Output Of 100,000 Tons

As an important organic chemical raw material,dimethylformamide is widely used in the fields of leather,synthetic fiber,medicine,petrochemical,electronics,fuel,coating,metal processing and so on,and thus it is necessary to study the influences of operation conditions on DMF synthesis reaction and the influences of impurities on the production process.Analysis and improvement of the process as well as the key equipment can make the production process more reasonable and the advantages more obvious,which is very important for the guidance of production process.In this paper,DMF production device of 100,000 tons per year designed by the sixth design institute of the ministry of chemical industry was utilized as test system and sodium methanol was selected as the catalyst in order to study the effects of temperature,pressure,raw material ratio,catalyst concentration on DMF synthesis.The results showed that temperature could affect the selectivity and yield of DMF and the optimal reaction temperature was in the range of 105-115 ^oC;increase of pressure was beneficial to the yield of DMF and the most economical operation pressure was 1.8 MPa?g?,depending on the comprehensive consideration on several factors,such as equipment investment,product yield and energy saving;the ratio of CO to DMA affected conversion and the balanced yield of DMF was highest when the ratio of CO to DMA was 1:1;with constant flow-rate of catalyst solution,the lower the concentration of sodium methanol,the higher the conversion of CO,but the DMF synthesis reaction would be terminated if catalyst concentration was too lower,while If the amount of sodium methanol was too high,crystallization would occur easily,as a result,the optimal concentration of sodium methanol in catalyst solution was 25%.The synthetic process and product purity were susceptible to the impurities brought by the raw material,including H₂O,CO₂ and methylenemide.Both H₂O and CO₂ could react with the catalyst which could deactivate the catalyst,and methylenemide could react with CO which may lead to that content of recombinant fraction rise up.Impurities introduced by the raw materials of DMF could be strictly controlled by the methods of keeping operation stability of dimethylamine distillation tower,combining methanol washing and membrane separation of coarse water gas and strictly controlling methanol purity in raw material for synthesis of dimethylamine.Optimizing production process,stabilizing process control and reducing raw material consumption were realized through the improvement of synthetic heat exchanger system,evaporation system and distillation system,the equipment of reactor member nozzles,filter device and DMF slurry shielding pump.Based on the above measures,production index was further optimized,the consumption of dimethylamine decreased to 0.66 t/tDMF,carbon monoxide consumption decreased to 410Nm³/tDMF,and catalyst consumption decreased to 3 kg/tDMF.