| Gasoline desulphurization by pervaporation (PV) membrane process is a newly-emerged desulphurization technology. And this process has the following advantages: low investment and operating cost, depth desulphurization, modular design, easily magnification and construction etc. The technology has attracted wide attention of petrochemical field. In this study, based on the scale-up experiment in the laboratory, the process simulation has been done according to the established pervaporation mathematical model. Then, the pilot tests were conducted on the pilot plant to investigate the performance of PEG/PVDF composite membrane. Based on the pilot test results, the economic evaluation of this technology was done.The results of the simulation showed that, the compensation of increased temperature on the decline of membrane performance caused by increased pressure is very obvious; The optimization of operating parameters can reduce the required membrane area, but meanwhile increase the load of the vacuum system and the condensation cost; Within certain ranges, the rate of the retentate product increased when the permeate pressure decreased as well as the feed temperature increased; High feed sulfur content and low target sulfur content enhanced the difficulty of the separation. With the separation difficulty enhanced, the required membrane area increased, and the retentate rate decreased. The simulation of the pilot experiment with a 1 BPD scale showed that, the retentate rate was 67%, when the required membrane area was 1.4 m2, the feed and target sulfur content were 1080μg/g and 500μg/g respectively.Pilot tests have been proceeded using the pilot plant. The optimal operating conditions for pilot plant were 388K of feed temperature, 350 Pa of permeate pressure in vacuum shell and 25 L/h of feed flow rate.The pilot tests under above conditions showed that the sulfur content of FCC gasoline was reduced from 1080μg/g to 400μg/g and 500μg/g to 150μg/g respectively, when the retentate rate was above 70%. The study of the longer inner run lasting for 1000 h showed that the performance of the membranes were very steady. According to total sulfur analysis of feed and permeate samples, it was found that PEG/PVDF composite membrane exhibited high rich factor of thiophene,especially of polysubstitution thiophene. According to hydrocarbon series analysis, it was found that the content of aromatic hydrocarbon in retentate sample was deeply declined,while the content of alkene, isoalkane and cycloalkane was increased. Analysis on the octane number showed that, the octane number of retentate sample decreased with the extent of desulfurization, while the octane number of permeate stream was a little higher than those of feed sample.The economic evaluation on the technology of membrane process for FCC gasoline desulfurization has been made based on pilot tests. The advantages of this technology lied in four fields: First, the loss of the octane number is low; Second, the consumption of the hydrogen gas is low; Third, the wastage of the gasoline in the process of desulfurization is low; Fourth, the cost of the apparatus and the energy consumption is low. Take the technology with a 1.0×106 t/a scale for instance, the cost of the apparatus is about 30%-40% percent less than conventional hydrodesulfurization technology, and the expenses can also be saved by 25% per year. These dates demonstrated that the technology of FCC gasoline desulfurization by membrane process has a favourable foreground. |
PDF Full Text Request