What is the impact of the high-temperature inlet temperature on operation?
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The higher the temperature in the high-temperature section, the easier it is for gases to evaporate. When the temperature drops, hydrogen sulfide and ammonia remain in the liquid phase, which can lead to pipe blockages. At the same time, the hydrogen sulfide concentration in the liquid phase becomes too high. Is this understanding correct? Thank you
Speaking of catalytic cracking, the high-temperature range is around 250 degrees. At this temperature, ammonium salts will not precipitate, so there is no pipeline blockage as you mentioned. For hydrogen sulfide, there is usually a hydrogen sulfide removal stripping tower in the distillation section, and the removal of hydrogen sulfide from the product is primarily controlled by this stripping tower.
My temperature here is currently between 210–220°C – is that too low?
Energy consumption is lower at lower temperatures, but the temperature should not be set too low, as ammonium salt crystallization can occur and block the pipelines; ultimately, it depends on the nitrogen content of the raw materials
I don’t know what your design temperature is. I think it’s relatively low. The temperature of hot high-grade oil is high; only by raising the temperature of low-grade oil entering the hydrogen sulfide removal tower can the load on the reboiler or distillation column be reduced. The temperature of the general high-temperature process is usually controlled through heat exchange between the raw materials and the reaction products. We also need to check the load of the reactor and the temperature of the raw materials. (Of course, I’m not sure what your process is like; these analyses are based on the process of my own device.)
At low temperatures, hydrogen sulfide and ammonia are removed through thermal low-pressure flashing, and the stripping tower downstream also serves to remove hydrogen sulfide. It’s not clear whether you are referring to that section of pipeline being blocked and whether there is a water injection process. Personally, I think the key is whether the product quality is up to standard and whether the process parameters are within acceptable limits.
The crystallization temperature of ammonium chloride NH4Cl is around 200 degrees, while that of ammonium hydrosulfide NH4S is approximately 130°C; to prevent the crystallization of ammonium salts, the temperature should be increased slightly