The pre-sulfidation issue in hydrogenation reactors
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Hello everyone. Our facility is designed to produce hydrogen from natural gas and desulfurized dry gas; at the start of operation, pure natural gas was used. The hydrogenation reactor has not been put into use yet. It has been operating for over a month now. The sulfurization method discussed back then was natural sulfurization using the small amount of sulfur present in natural gas. However, with the system currently operating at around 40% load, the temperature at the inlet of the hydrogenation reactor reaches around 400 degrees, which makes it impossible to use this reactor. How can this problem be solved?
There are two questions: 1. Why raise the reactor inlet temperature so much? Is it to ensure the converter inlet temperature? 2. Is the reduction of the conversion catalyst also carried out using pure natural gas, without any external hydrogen being used?
1. Since the gas flow rate is currently low, the temperature coming out of the first coil is very high (natural gas has two heating coils, with the second one being part of a bypass line). 2. The conversion and reduction were carried out using natural gas as a reducing agent; at that time, the hydrogenation reactor was not in use.
What the poster means is that if the feedstock is changed while the plant is operating, the hydrogenation reactor will overheat. . I don’t understand what it means to refrain from using a hydrogenation reactor; these days, hydrogenation reactors are hardly used for natural gas. Did you just proceed directly without using one?
1. Is it impossible to control the outlet temperature of the first heating coil? If that’s not possible, try reducing the flow rate to lower the temperature. 2. Was hydrogen added during the natural gas reduction process as a converting agent?
The amount of natural gas cannot be increased at the moment; it’s impossible to control it. During the conversion and reduction process, no hydrogen is used – natural gas is used for reduction directly!
Our plant is designed to produce hydrogen using natural gas and desulfurized dry gas; currently, since there is no desulfurized dry gas available, pure natural gas is being used. The hydrogenation reactor has been taken out of service at the moment! But there is no sulfidation.
What is the heating medium for the coil? Is it steam? Control the amount of steam. If it cannot be controlled, the production of new hydrogen has to be temporarily halted; the temperature must be lowered, dry gas must be introduced until it meets the required standards, and then hydrogen production can resume.
How can trace amounts of sulfur in natural gas be fully sulfided? It is possible to start using natural gas and then gradually switch to dry gas, while closely monitoring the temperature rise and the hydrogen sulfide content at the reactor outlet. Initially, there will be no hydrogen sulfide, as it has already been consumed by the catalyst. When the hydrogen sulfide content at the outlet increases, it indicates the effectiveness of the catalyst in carrying out the sulfidation process. Regarding the high reactor temperature you mentioned, you can introduce natural gas to control the temperature; it’s not easy to control it solely by adjusting the hydrogen supply. Once the temperature stabilizes, gradually increase the proportion of dry gas.
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