| In the face of the heavy pressure of crude oil and the strict pressure of fuel standards,hydrocracking and other processes of crude oil have been developing rapidly.These processes require hydrogen,which leads to dramatically increases in hydrogen consumption,and the hydrogen cost has become the second largest cost of raw materials in the refining process.At the same time,the tail gas with hydrogen is used as fuel gas in the processing of crude oil,or the recovery efficiency is low,which resulting in a great waste of hydrogen in refinery tail gas.At present,the coupling technology of membrane separation and pressure swing adsorption is often used in industry to achieve high yield and high purity recovery of hydrogen from refinery tail gas.However,due to the separation characteristics of membrane separation and pressure swing adsorption,H2 S enrichment occurred in the process of hydrogen recovery by HM/PSA recovery.Most of the H2 S and H2 O in the refinery exhaust gas were recycled in the process,and the concentration of H2 S is much higher than the allowable presence in the refinery,resulting in corrosion of equipment and pipelines,which is not conducive to the safety and stability of the device.In this paper,aiming at the phenomenon of H2 S enrichment in the process of hydrogen recovery by HM/PSA,the HM/PSA coupling process was designed to analyze the concentration of H2 S in the process system,on the basis of the process,the absorption unit was coupled to remove the H2 S enriched in the HM/PSA process,which can ensure the high purity and high efficiency hydrogen recovery,reduce the equipment corrosion caused by H2 S enrichment in refinery gas,achieve a high efficiency and safe recovery of hydrogen refinery.According to the different standard of determining the location of the H2 S absorption removal section,two different separation sequences of the refinery hydrogen recovery process were designed,which is HM/PSA/Absorption process and HM/Absorption/ PSA process.In order to solve the problem of the highest concentration of H2 S in the desorption gas of PSA in HM/PSA process,the HM/PSA/ absorption coupling process was designed,and the H2 S of the HM/PSA coupling process system was maximized removal.So that the H2 S content in the PSA desorption gas was reduced from 297 ppm in the original HM/PSA process to 110 ppm.The results show that the HM/PSA/Absorption process can obtain high hydrogen recovery rate and furthest decrease the content of H2 S in the system.The H2 S content?14 ppm?in theresidual gas of the hydrogen membrane separation section is smaller than the combustion standard?20 ppm?of the fuel pipe network,and can be sent directly to the fuel pipe network.However,because PSA desorption gas is required to be pressurized before feeding to the absorption section and the liquid water is generated in the process of compression,the H2 S which own most serious degree of enrichment in PSA desorption gas will dissolve in liquid water,causing serious corrosion of the compressor in the high temperature and high pressure environment.Aiming at the problems in HM/PSA/Absorption process,the HM/Absorption/PSA process was designed.The absorption section is used to treat the permeate gas with more severe H2 S enrichment in the system..Before the H2 S has not reached the maximum degree of enrichment in the HM/PSA process,removal of H2 S which is suddenly enrich in the permeate gas,so that the content of H2 S in the permeate gas is reduced from 140 ppm in the original HM/PSA process to 58 ppm.By this way,we can not only reduce the degree of H2 S enrichment,but also ensure the safety of subsequent PSA equipment production.In addition,the content of H2 S in the residual gas decreases to 20 ppm,which accords with the standard of fuel gas combustion and can be sent directly to the fuel pipe network. |
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