Improvement of hydrogenation process
The distribution of sulfur content at the outlet of hydrogenation reactor, the content of COS and CS2 with simple molecular structure and less side reactions is about 67mg / m3; The content of mercaptan and thiophene with poor hydrogenation * * and prone to side reactions is about 35mg / m3, so targeted removal schemes need to be designed respectively.
2.1cos and CS2 removal scheme
In general, the hydrogenation * * of sulfur-containing compounds is closely related to their structure. The hydrogenation * * of sulfur-containing compounds with complex structure is often poor. Because the structure of COS and CS2 is relatively simple and the hydrogenation reaction speed is very fast, the hydrogenation reaction between COS and CS2 is relatively easy to occur and less disturbed. Therefore, it is only necessary to increase the loading amount of hydrogenation catalyst to meet the process index. However, since the hydrogenation reactor cannot continue to be equipped with catalyst, a pre hydrogenation reactor is added before the first hydrogenation reactor. The electro-hydraulic flue gas baffle door adopts the sealing mode of metal hard seal and graphite soft seal to ensure the air tightness of the valve without internal leakage and external leakage.
2.2 removal scheme of mercaptan and thiophene
To sum up, the removal efficiency mainly depends on the hydrogenation link. Due to the complex structure and relatively poor hydrogenation * *, mercaptan, thiophene and other sulfides are the key steps of hydrogenation reaction. The existence of H2S has two main effects: (1) it reacts with olefins to produce new mercaptans and thiophenes; (2) The hydrogenolysis of thiophene was inhibited. Therefore, it can be inferred that the lower the H2S content, the higher the hydrogenation conversion of mercaptan and thiophene. Therefore, replace the catalyst in iron oxide desulfurization tank a with iron manganese catalyst with both hydrogenation and desulfurization * *, and fill part of iron molybdenum catalyst in the upper half of iron oxide desulfurization tank B to make the gas enter the iron manganese desulfurization tank after one * hydrogenation, remove the converted H2S as much as possible, and then conduct hydrogenation reaction, so as to remove the influence of H2S on mercaptan and thiophene hydrogenation reaction. The electro-hydraulic flue gas baffle door adopts three-layer anti-corrosion design to ensure that the valve body is not easily corroded.
2.3 feed gas purification scheme
In order to prevent the tar and wash oil impurities carried by the feed gas from entering the hydrogenation reactor, causing coking and rising resistance of the catalyst bed, it is decided to add two * * carbon filters before hydrogenation to further remove the oil impurities contained in the gas.
Through the research on the operation data of gas fine desulfurization production unit, the following conclusions are obtained.
(1) The high resistance of hydrogenation reactor is due to the polymerization and coking of tar, wash oil, turbine oil and other substances entrained by feed gas in high temperature environment.
(2) The key link affecting the desulfurization efficiency of the fine desulfurization unit is the hydrogenation process, and the key link controlling the total hydrogenation efficiency is the hydrogenation reaction of mercaptan and thiophene.
(3) The reaction between olefins and H2S affects the removal efficiency of mercaptan and thiophene.
(4) The presence of H2S inhibited the hydrogenation of thiophene.
(5) The lower the H2S content, the higher the hydrogenation conversion of mercaptan and thiophene.
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