| While crude oil processed by refineries is becoming heavier and more inferior,improving the sulfur removal purification effect of dry gas and liquefied petroleum gas(LPG)in refineries is of particular importance to upgrade the quality of oil and gas products and meet the emission standards under the increasingly strict environmental protection laws and regulations.Developed by East China University of Science and Technology,the UDS,a kind of formulated desulfurization solvent with high removal efficiency,has excellent removal effect on H2S and organosulfur,thus having been widely used in the purification of highly acidic natural gas,oilfield gas and refinery gas.According to the new requirements of desulfurization specification in refineries,improving removal efficiency based on the good desulfurization perfonnance of UDS solvent is an effective way to realize the quality upgrading of refinery gas products and qualified discharge of heating furnace flue gas.Firstly,COSMO-RS method was applied to calculate the solubility of methanethiol in different solvent components,and corresponding Henry constants were obtained.Based on the calculation results of solubility,DEAPA,which had better solubility to MeSH,was selected as the component to improve the desulfurization performance of UDS solvent,so as to further improve solubility of UDS solvent to mercaptan while maintaining high removal efficiency of H2S and COS.Results showed that the solubility of MeSH in DEAPA was the best,and corresponding Henry constant was 26.1 kPa·L/mol,far less than that in MDEA,which was 85.4 kPa·L/mol.The improved UDS solvent is helpful to meet the organosulfur removal requirements of refinery dry gas and LPG with lower absorption pressure and higher organosulfur content.Then,by using the simulated refinery coking dry gas as raw material which contained H2S 2.15 v%,COS 518 mg-S/m3,MeSH 1015 mg-S/m3 and EtSH 411 mg-S/m3,the absorption process conditions of the improved UDS solvent were investigated and optimized in the atmospheric absorption experimental equipment,and the desulfurization performance of the improved UDS solvent was compared with that of MDEA solvent and original UDS solvent.Density,viscosity and surface tension of the improved UDS solvent were also measured.The anti-foaming perfonnance was investigated and a mathematical model for predicting the anti-foaming performance of UDS solvent was established.Results showed that the removal efficiency of mercaptan compounds was significantly improved while that of COS remained high by improved UDS solvent.Under the absorption conditions of 40℃,gas-liquid ratio 150,solvent ratio 4:6 and solvent concentration 50 wt%,the removal efficiency of COS by MDEA,original UDS and improved UDS solvent were 36.8%,98.2%and 99.98%,respectively.Compared with the original UDS solvent,the removal efficiency of MeSH,EtSH and total sulfur by improved UDS solvent were increased by 31.2,27.8 and 22.7 percentage points,respectively,and 38.6,29.7 and 43.3 percentage points higher than that of MDEA solvent,respectively.The model established for predicting the anti-foaming performance of solvent has good prediction effect.Based on the good results of atmospheric absorption experiments in the laboratory,industrial application tests were carried out in AQSH and GQSH.Results showed that the organosulfur removal efficiency of the refining unit in AQSH was significantly improved after the application of UDS solvent.Under similar operation conditions of industrial plant,the total sulfur content of catalytic dry gas,coking dry gas and coking LPG products after purification were reduced by 20.6%,30%and 15%,respectively,compared with MDEA solvent.The average removal efficiency of COS,MeSH and total organosulfur in coking dry gas by UDS solvent were about 63%,55%and 52%,respectively.The content of SO2 in atmospheric and vacuum furnace flue gas was kept below 42 mg/m3.The regeneration effect of lean liquid is good.After the process optimization of desulfurization plant in GQSH,the total sulfur content of coking LPG can be controlled within the technical specification range of 300 mg/m3,the average is about 145mg/m3.The total sulfur content of the coking dry gas can be reduced to 30～50 mg/m3 and the SO2 content of the flue gas discharged from the heating furnace can be reduced to 10～15 mg/m3,meeting the emission standard steadily. |
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