Research And Development Of Oxalic Acid Production Process

Oxalic acid is a very important chemical intermediate.At present,domestic enterprises mostly use sodium formate method and polysaccharide oxidation method to produce oxalic acid.However,due to the low efficiency,serious pollution and so on,these two methods will be eliminated in the future.The most promising method of oxalic acid production is the gas phase coupling method of carbon monoxide,which is mainly divided into two steps:firstly,diethyl oxalate is produced by the reaction of carbon monoxide with ethyl nitrite in an oxidative coupling reactor.Then diethyl oxalate is hydrolyzed to oxalic acid.In this paper,the production process of oxalic acid by gas phase coupling method of carbon monoxide is designed and studied by Aspen Plus,and the heat transfer network of the process system is designed and optimized.Aspen Plus was used to estimate the physical properties of ethyl nitrite,and the model of reaction distillation was established for the regeneration tower of ethyl nitrite and the hydrolysis tower of diethyl oxalate.The NRTL-RK physical property method is used to simulate the whole process.The operation parameters of ethyl nitrite regeneration tower were optimized.After optimization,the conversion rate of O₂ in reactants was close to 100%,and the recovery rate of ethyl nitrite at the top of tower was 99.99%.The synthesis and separation process of diethyl oxalate were optimized to match the regeneration reaction with the coupling reaction.And the diethyl oxalate with mass fraction of 99.99%was obtained through distillation operation,which was used for the next hydrolysis reaction.Simulation and optimization process of diethyl oxalate hydrolysis preparation of oxalic acid.For the by-product ethanol generated during the reaction,an alcohol water separation tower is designed to recycle it as raw material for regenerative reaction.The ethanol recovery rate of ethanol water separation tower top is 98.4%and the mass fraction is 94.3%.Almost pure oxalic acid solution was obtained from the distillation column of hydrolysis reaction column,and the oxalic acid product with mass flow rate of 6375.22kg/hr was obtained after crystallization and separation.Compared with the optimized production,the yield was increased by 252.5kg/hr.Using the Aspen Energy Analyzer to design and optimize the heat exchanger network of the whole system process.After optimization,the utility consumption of the system can be reduced by 32.30%,which achieves the requirement of energy saving.