What is the reason why the sulfur level at the outlet is higher than that at the inlet in precise desulfurization?

Precise desulfurization mainly involves converting organic sulfur into inorganic sulfur before removal. The reason why the sulfur content at the outlet is higher than that at the inlet is that the catalysts in each tank have reached the end of their useful life and the temperature of the catalysts in those tanks is too low

There are two aspects: 1: The activity of the precision desulfurization agent is lost, so this agent needs to be replaced, as the sulfur that was previously adsorbed is released. 2: The temperature of the fine desulfurization agent is too low; it is necessary to increase the temperature of fine desulfurization, primarily by using a steam heater before the fine desulfurization process. 3: An oxygen pump is installed at the inlet for precise desulfurization to promote oxidation; the flow rate of this oxygen pump is 10 m3/h. Special attention must be paid when starting up or shutting down the operation with oxygen added at this point.

My humble opinion: 1. The sulfur content increases slightly after hydrogenation; the total amount of sulfur remains unchanged. What changes is the unit of measurement, expressed in grams or kilograms per hour； 2. The standard unit for measurement is typically NM3; changes in the volume of gas before and after the hydrogenation reactor lead to changes in this measurement standard ； 3. Hydrogenation reactions are usually reactions that result in a reduction in volume; as the basis for measurement decreases, the total sulfur content on the surface increases.

1. To remain active, iron-molybdenum hydrogenation catalysts need to be sulfided during reduction and heating. 2. When the inlet hydrogen sulfide level is too low, sulfur release occurs, which is mainly manifested in the secondary hydrogenation stage

Deactivation due to anti-sulfidation, low level of H2S in the inlet gas, large fluctuations in temperature and water vapor concentration – re-sulfidation treatment is required

Generally, the higher sulfur level at the outlet of cobalt-molybdenum hydrogenation organic sulfur conversion catalysts compared to the inlet level is mainly due to fluctuations in the sulfur content at the inlet, which leads to desulfurization of the catalyst. This is because there is a dynamic equilibrium between sulfidation and desulfidation on the active surface of cobalt-molybdenum hydrogenation catalysts.

1. The cobalt-molybdenum hydrogenation tank should be the last hydrogenation tank in the process. The gas entering this tank may have a very low sulfur content; if it is less than 10PPM, it could reduce the catalyst, leading to the release of sulfur. This would result in higher levels of total sulfur and hydrogen sulfide at the outlet compared to the inlet. Therefore, a bypass line is usually installed between the iron-molybdenum outlet and the cobalt-molybdenum inlet to prevent the gas entering the cobalt-molybdenum tank from having an excessively low sulfur content. 2. Consider the reasons for testing. There are many forms of organic sulfur in gas, and many of these forms do not have corresponding testing instruments available in ordinary enterprises. After conversion through cobalt-molybdenum processes, they turn into H2S; as a result, it appears that the total sulfur content increases, but in reality some forms of organic sulfur remain undetected. 3. The reason given on the fifth floor is also a factor.

Do you have a spare cable there? Thank you

Ours is on the primary hydrogenation outlet pipeline, connected to the secondary hydrogenation inlet

The sulfur level at the inlet and outlet of the secondary hydrogenation catalyst is maintained in a dynamic equilibrium. If the amount of sulfur entering the catalyst was previously relatively high but has now dropped suddenly, then the secondary hydrogenation catalyst will definitely release some sulfur in order to reach a new equilibrium. Therefore, the higher level of sulfur exported compared to that imported is only a temporary phenomenon.