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Micro-Channel Fabrication and Evaluation to Remove Mercaptan from Gas Streams

Hosseinpour, Vahid | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53178 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Kazemeini, Mohammad; Mohammadi, Ali Asghar; Rashidi, Alimorad
  7. Abstract:
  8. Due to the potential risk of sulfur compounds in fossil fuels and according to today’s regulations, sulfur content should be kept as low as possible, e.g., below 5 ppm. Mercaptans are one of the sulfur components in natural gas. Scope of this research defined as catalytic removal of ethyl mercaptan from the gas stream. For this purpose, two microreactor systems placed in series. In the first microreactor, catalytic decomposition of ethyl mercaptan has been investigated. In the first step of this survey, a microreactor with 24 microchannels with a newly designed distributor has been developed with a computational fluid dynamic technique. in comparison to the conventional triangular distributor, this newly designed distributor reduces 230% distribution index. Therefore, a uniform flow distribution observed in this case. based on the results of the simulation with the aid of laser ablation and machinery, microreactor fabricated on stainless steel (316) plate with 3 mm thickness. application of a temporary and permanent binder led to a good coating of the H-ZSM-5 catalyst on the wall of the microreactor. well established coating proved by less than 3.7% weight loss in ultrasonic tests. catalytic decomposition of ethyl mercaptan in the microreactor shows that in this reactor we need 50 ℃ lower temperature for complete conversion relative to the conventional fixed bed reactor. due to enhancement in the heat and mass transfer lower by-products have been formed in the microreactor. Hydrogen sulfide and ethylene picked as main products of the reaction. In the second microreactor hydrogen sulfide converted to the elemental sulfur by the selective oxidation reaction. Catalytic decomposition ethyl mercaptan take place at about 400 ℃, while required temperature for selective oxidation reaction with carbon-based catalyst is about 200 ℃. Then for temperature reduction of gas stream between two microreactors a micro heat exchanger has been designed and fabricated by selective leaser melting method. With the aid of computational fluid dynamic joint with design of experiments effect of geometrical and operational condition on the performance of finned micro heat exchanger have been studied. Among of four type of microfins, e.g., cylindrical, pyramid, conical and cubic, pyramidal microfins best performance. Based on the optimized geometric of finned microchannel, a micro heat exchanger with 20 microchannel with 325 μm width and 650 μm height has been constructed. In the final step of mercaptan removal from gas stream selective oxidation of hydrogen sulfide in the presence of N-CNT catalyst has been investigated. Microreactor show complete conversion of H2S in the 190 to 230 ℃. Behavior of this reaction in the microreactor shows higher conversion and selectivity relative to plug flow reactor. With increasing in the reaction temperature causes 22% decrease in selectivity in fixed bed reactor, while this reduction in the microreactor is less than 11%. Promising results of individual section motivated us to perform continues mercaptan removal from gas stream. Analysis of outlet stream from second reactor shows no ethyl mercaptan and hydrogen sulfide
  9. Keywords:
  10. Selective Oxidation ; Hydrogen Sulfide ; Ethyl Mercaptan ; Experimental Design ; Microreactor ; Micro Heat Exchanger

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