Simulation And Analysis Of Ethylene Oxide Process

As an important chemical raw material,ethylene oxide?EO?is routinely used to produce many kinds of intermediate and fine chemical products,such as ethylene glycol?EG?,ethanolamine and water-reducing agent,etc.In recent years,the production and proportion of high-purity ethylene oxide have been enlarged in EO/EG plants.With the high-purity ethylene oxide being the main product and a small amount of ethylene glycol the by-product.In view of this,we carry out the present research on process having an annual production capacity of 120,000 tons of EO in this work.Based the whole process simulation using Aspen Plus,a comprehensive and thorough analysis of the process was presented via system evaluation index,and an optimal energy utilization efficiency was obtained via optimization of the process and pinch technology.The main research results are as follows:Firstly,the model of the ethylene oxide reaction and scrubbing,removal of CO₂,EO stripping and refining,and purification were developed using Aspen Plus,and the simulated results agree well with the design value.Effects of lean cycle water flow and temperature on scrubbing were analyzed in the EO scrubber section.Equilibrium level model and rate-based non-equilibrium level model of CO₂ absorption by K₂CO₃ were built in removal section,and the distribution of temperature and key component parameters with the packed height were analyzed as well.The mass transfer scheme was further obtained.Effects of Bulk packing?IMTP?and structured packing?Mellapak 250X and Mellapakpl 252Y?on the absorption efficiency of CO₂ showed that Mellapak 250X had the highest efficiency with lowest pressure drop.In EO stripping tower,the optimal reflux flow was determined according to the demand of stripping and refining process.Based on the study of each section,the whole process of production of EO was built,and the simulation value fitted well with design value in 10%error band,which contributed to evaluation and optimization of the process.Secondly,the material,energy and exergy balance were obtained from the whole process simulations.The system evaluation was made in four approaches:effective atomic yield,comprehensive energy consumption,exergy loss and carbon footprint analysis.Results showed that effective atomic yield was 67.95%,comprehensive energy consumption was 591.83 kg-ce-t-prod^-1,and the total carbon emissions was 5889.04 kg-CO₂·t-prod^-1.The energy consumption of steam and carbon emissions were the highest.The total exergy consumption was 41.57 MW,and all the internal exergy consumption in each section was higher than external.Finally,energy utilization efficiency optimization was carried out by optimization of the process and pinch technology.The energy consumption of the cold utilities was reduced through improving internal heat exchange of hot lean cycle water flow in the stripping tower bottom.Further,the energy recovery and utilization efficiency increased.Base on pinch technology of Aspen Energy Analyzer,the energy utilization was analyzed.Through the analyzing of total cost and minimum pinch temperature difference,the optimal pinch temperature difference was specified as 11 ?,and the heat exchanger network was improved.6.68 MW of hot utilities and 6.68 MW of cold utilities were saved by the improvement.The economic feasibility of the optimization was demonstrated.