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Why does the pressure in the reaction system drop when the cold hydrogen flow to the reactor increases in a diesel hydrotreating unit?
Is it because the hydrogen consumption increased that the system pressure dropped?
As cold hydrogen increases, the temperature drops. Could it be a drop in pressure caused by the temperature decrease?
I really can’t figure this out. Logically, it’s a closed system; when the temperature drops due to the addition of cold hydrogen, hydrogen consumption should decrease as well, so how can it still go down? How much cryogenic hydrogen have you used to cause the pressure drop? Is it one or two valve positions, or how many? I think it’s because the temperature of cold hydrogen is low, which reduces the volume of the gas phase that needs to be cooled inside the reactor. I’m not sure; it’s just an idea I have.
If the source of cold hydrogen is the outlet of the recycle hydrogen compressor, an increase in cold hydrogen will inevitably lead to a decrease in system pressure, and the pressure in the reaction system will also drop as a result
This shouldn’t make much of a difference, right? Cold hydrogen is also part of the circulating hydrogen; if you don’t use cold hydrogen, then you use it at the reactor inlet, and the amount remains the same. A decrease in system pressure definitely indicates that there is less hydrogen in the system.
That won’t happen; a decrease in temperature only leads to reduced hydrogen consumption, and the same amount of hydrogen continues to circulate within the system, so there is no drop in pressure. Introducing a large amount of cold hydrogen should result in a short-term increase in pressure.
Shouldn’t increasing the amount of cold hydrogen lead to an increase in the temperature of the reaction bed above normal levels, an increase in the reaction depth, and a higher hydrogen consumption during the reaction? I’m not sure about hydrocracking, but the pressure in the hydrorefining system should be the pressure of hydrogen; it has little to do with the reaction conversion rate or the degree of cracking. When the amount of fresh hydrogen remains constant, a higher consumption of hydrogen leads to a decrease in pressure, while lower hydrogen consumption results in an increase in pressure.
Yes. By examining the operation curve carefully, it can be seen that the amount of new hydrogen added under normal conditions is constant; before adding quench hydrogen, it is definitely because the temperature rise in the bed increases, which leads to a drop in pressure within the system. After adding rapidly cooled hydrogen, the temperature recovered very quickly; this bed does not require that much hydrogen, and the pressure in the system rose swiftly. What you said is correct.
If the amount of cold hydrogen is large, it definitely has an impact; when the amount of circulating hydrogen remains constant, more cold hydrogen flowing away will surely result in a decrease in the amount of material circulating within the system. 1. Will the reaction system remain at a low pressure due to the increased amount of cold hydrogen, or is this only temporary? 2. Once the amount of cold hydrogen returns to its normal level, will the pressure in the reaction system be the same as before?
Both cyclic hydrogen and cold hydrogen enter the reaction system, so there is no need to distinguish between them. Viewing the system as a whole or a container, as long as the amount of material entering remains constant, the pressure will increase or decrease depending on the amount of hydrogen consumed.