Energy Consumption Comparison Of Typical Operation For Binary Stripping Batch Distillation And Preparation Of High Purity Octamethylcy-clotetrasiloxane

Distillation is a widely used industrial operation for liquid mixtures separation in industry.Batch distillation also called process distillation,whose equipment in small quantities of chemicals.In the dissertation,the energy consumption of three typical operation strategies for the constant reflux ratio,constant distillate composition and optimal reflux ratio is compared through the process simulation calculation.The results showed that the method of stripping batch distillation separation Polymethylsilane for preparing the high purity octamethylcy-clotetrasiloxane is feasible.The results are as follows.(1)The numerical calculation method for the constant reflux ratio's constant distillate composition in binary stripping batch distillation is introduced.The computation program is tested by the theory of the total amount of vaporization reaching the minimum vaporization with the number of theoretical plates is increasing.The deviation of the calculation method is explained by comparing the analytical results of the minimum vaporization and the numerical results.(2)The limit function calculation of the unconstrained function is computed by using the penalty function method to solve the total vaporization calculation of optimal operation in the binary conventional batch distillation under the ideal operating condition.After the function is discrete,the fixed two-step factorial gradient method is used to calculate the limit value of the unconstrained function.The selection of the penalty term in the unconstrained function which is constructed is discussed.The influence of the various parameters on the calculation process and the result and the principle of determining the computed end are also discussed.(3)The concept of mean recurrent liquid efficiency and average total mass transfer driving of binary stripping batch distillation are introduced.The energy consumption of the process is characterized by analyzing the essence of mean recurrent liquid efficiency which is obtained by the simulation results with the operation strategy of constant distillate composition.The irreversibility of the batch distillation process is characterized by the total mass transfer momentum of the whole column which is gained by analyzing the simulation results with the combined operation strategy(the first simple distillation operation and then the constant concentration operation).The conclusion is that the more amount of distillate,the less degree of irreversibility of the process.(4)Depending on the simulation results,the energy consumption between the constant reflux ratio operation and constant distillate composition in the binary constant batch distillation is compared.The results are as follows:(1)In general,the energy consumption of the constant distillate composition is lower than that of the constant reflux ratio.The reasons are as follows:(a)The lower mean recurrent liquid efficiency is caused by the lower recurrent liquid efficiency in the beginning of the distillation of constant reflux ratio operation;(b)The top distillate with different concentrations of constant reflux ratio operation are mixed,which increases the irreversibility of the distillation process;(c)The amount of distillate in the constant distillate composition operation is greater than that in the constant reflux ratio operation,which reduces the irreversibility of the distillation process.(2)For the constant reflux ratio(N1??+)of the batch distillation process,which the constant concentration area is always kept at the bottom of the separation task.When the number of theoretical plates is very close to the minimum number of theoretical plates required for binary conventional batch distillation of the constant distillate composition strategy,the result is that the energy consumption of constant distillate composition strategy may be higher than that of the constant reflux ratio operation strategy.(5)According to the simulation results,the energy consumption between the operation of optimal reflux ratio and constant content of distillate in the conventional binary batch distillation is compared.The conclusions are as follows:(1)The energy consumption of the optimal reflux ratio is lower than that of the constant distillate composition.For a given separation task,there is a minimum point in energy consumption between the two operation strategies under some theoretical plate.The reasons may be that when the number of theoretical plates is relatively small(the number is close to the minimum theoretical plate required for the operation of the distillate composition),the reflux ratio is optimized to improve the reflux efficiency by controlling the reflux ratio of the process;(2)When the number of theoretical plates is relatively large,the optimization operation is done by controlling the reflux ratio of the process,ensuring that the process is highly efficient,the material is removed from the system as quickly as possible and the irreversibility of the process is reduced.(3)Under a certain number of theoretical plates,the reason thata minimum point in the energy consumption existsbetween the optimal reflux ratio and constant top concentration is that the difference between the energy consumption and the irreversible degree is minimized.(6)The methyl-silicone is used as the raw material,of which the main contentsare Hexamethylcyclotrisiloxane 42.23%;Octamethyl cyclotetrasiloxane 32.24%;Decamethylcyclopentasiloxane 25.53%.The high purity octamethylcy-clotetrasiloxane can be obtained after batch distillation for twice.Results showed that the content of as-prepared high purity octamethylcy-clotetrasiloxane is 99.668% and the total yield is about 70%.