System Process Intensification Of High Temperature/Low Temperature Fischer- Tropsch Synthesis And Product Design

The integrated HTFT-LTFT system integrated high temperature Fischer-Tropsch synthesis and low temperature Fischer-Tropsch synthesis together,has the flexibility to produce high quality fuels,which has an important strategic sigificance for ensuring energy security and oil products quality upgrading.However,the indirect coal-to-liquid process suffers from poor economic performance especially at low oil price.The poor economic performance is largely because of the unproperly utilization of FT syncrude.FT syncrude can be further refined not only to transportation fuels,but also to high value chemicals.High value chemicals production represents a valuable solution to increase the economic profitability on an industrial scale.So the novel HTFT-LTFT system for high value chemicals is proposed to improve the FT syncrude utilization efficiency and add the products value.Supported by the National High Technology Research and Development Program（863 program,2011AA05A204）,we focus on the design of high temperature/low temperature fischer-tropsch polygeneration system and product processing.The main results and conclusions are as follows.Higher olefin content and high olefin to paraffin ratio can be found in the carbon range of C2-C4 and C5-C10 in FT products under different combined ratio of HTFT and LTFT synthesis,which will benefit the olefin seperation as chemicals and follow up utilizing.Base on the product selection framework firstly established for HTFT-LTFT system,the ethylene,propylene,alpha-olefin and lubricating oil base oil is confirmed as the target product of HTFT-LTFT systems after the market research.The alternative system processes from coal to final product are established and modeled in Aspen Plus software.System evaluation is performed to guide technology selection and research efforts towards more efficient HTFT-LTFT systems.The integrated HTFT-LTFT coproduction of both olefins and base oils simultaneously presents an excellent economic performance with internal rate of return of 15.21%,and net present value of 107.83×10⁸ RMB with the proportion of chemicals in the product structure of 0.86.But the chemical income in the income structure accounts for 68%,so it improves the overall economic efficiency by high value utilization of products.The system has high ability against raw material and product prices fluctuation.It is indicated that the integrated HTFT-LTFT with olefins and base oils coproduction technology is an enticing choice for high added value utilization of FT syncrude,and has great potential applicability in coal-to-liquid industry.In the global optimization procedure for the integrated HTFT-LTFT with olefins and base oils coproduction system,the total investment is decreased by9.3%when the Texaco coal gasification technology is switched to the multi-nozzle oppositely coal-water slurry gasification technology.The olefin chemicals production is always with high energy consumption to meet the high purity requirements.To reduce the energy consumption,the effect of cryogenic separation process structure on the energy consumption is investigated and compared under the same product purity and recovery.The sequential cryogenic separation process is the optimal cryogenic separation process for HTFT-LTFT system with lowest condenser duty of 131.37 GJ·h^-1 and total energy duty of 343.5GJ·h^-1.Furthermore,the olefins purity in sequential separation process can meet the requirements for polymerization,and is not influenced by the scale ratio of HTFT and LTFT.To increase the purity ofα-olefins,it is difficult to removal iso-olefins with similar boiling point toα-olefins because the isoamylene conversion is limited to chemical equilibrium.The design method of reaction distillation column based on equilibrium model is established and applied to guide the design of reaction distillation column in etherification process.The isoamylenes conversion reached to 95%,which will benefit theα-olefins recovery.