The Research Of The Process Routes For Recycling Benzene From Light Benzene

Light benzene,which is chemical-waste,is the overhead product of the cumene production facility.Light benzene is consist of benzene,propane,butane and other alkane,after determination contains the benzene quality score is about 55.0%.This paper has studied three different separation process routes of recycling benzene,which will be used as synthetic source of cumene,from light benzene.The method of using melt crystallization for recycling benzene from light benzene has been proved to be feasible.This paper has researched the operating conditions of the melt crystallization by using single-factor experiment.Having the results of the effect of the freezing rate,final freezing temperature and crystallization time on mass fraction and purity of the crude crystal.Having the results of the sweating rate,final sweating temperature and sweating time on mass and purity of the product.Researching the multistage melt crystallization for recycling benzene from light benzene.Having done two-stage or three-stage melt crystallization of light benzcene,and getting that the benzene quality score of the product is more than 99.50%and the benzenet recovery is 25.0%to 35.0%.The purity of product completely accords with the synthetic source of the cumene.Using Aspen Plus to simulate the process route of continuous rectification to recycle benzene from light benzene and getting the final process parameters,such as that the number of the theoretical plate is 70,the optimal feed plate is 56th,the distill rate is 885.00 kg/h and the reflux ratio is 6.0.Having used the process parameters mentioned,and finally getting that the benzene quality score of the bottom product is more than 99.50%and the benzene quality score of the overhead product is less than 1.0%.Combining bath fractionating and melt crystallization to build a new process route for recycling benzene from light benzene.Firstly using the bath fractionating to separate the light benzene and getting crude benzene solution of which the benzene quality score is more than 92.0%.Then using the melt crystallization to purify benzene from the crude benzene solution,and getting the final product which will accord with the synthetic source of the cumene.Using Aspen Plus to simulate the batch fractionating tower,and getting the final process parameters,such as that the number of the theoretical plate is 25,the distill rate is 500.00 kg/h,the reflux ratio is 6.0 and the operating time is 6000s to 6300s.Simulating the process by using the parameters and finally getting that the benzene quality score of the bottom product is more than 90.00%and the benzene quality score of the overhead product is less than 3.0%.Then using single-melt crystallization to recycle benzene from the crude benzene solution of which the benzene quality score is about 92.0%.From the experiments,getting the optimal operating conditions,such as that the freezing rate is 2.0,freezing final temperature is-7.0?,crystallization time is over 60min,sweating rate is 0.10?/min,sweating final temperature is-4.0? and sweating time is over 120 min.Having done the experiments under the operating conditions mentioned above,finally getting that the benzene quality score of the bottom product is more than 99.50%and the benzene recovery is over 65.0%.Comparing the three process routes,finding that the method,which combines the bath fractionating and melt crystallization,has many advantages,such as high operating flexibility,low equipment investment and high product recovery.So this paper confirms that this method is the optimal process route for recycling benzene from light benzene.