Hydrocracking shutdown
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Why is the shutdown of hydrocracking for diesel replacement carried out at 290 degrees? Can other temperatures be used?
In my opinion, there are upper and lower limits for the temperature at which diesel is used to replace heavy oil (paraffin oil or residue): 1. Upper temperature limit: the material should no longer react; 2. Lower temperature limit: the subsequent heating with hydrogen steam requires a certain high temperature (above 300 degrees), and the temperature does not need to drop too quickly. Any value within this temperature range should work, and 290°C can also serve as a reference value
Low-nitrogen diesel should be used to prevent nitrogen poisoning of the catalyst; is that correct?
But what I’m really asking about is the temperature
But what I’m really asking about is the temperature
We just checked our installation plan: low-nitrogen oil is introduced at 320°. To shut down the reaction system, hydrogen removal is required at a constant temperature of 250° and 6 Mpa for 36 hours. So I think a temperature of over 250 is fine, but it shouldn’t be too close to that value, as otherwise it’s difficult to control the process; if it’s too high, energy is wasted. Therefore, I think 290° would be a reasonable choice for you. At the same time, due to heat exchange considerations, our equipment has limitations on the flow rate of low-nitrogen oil; there is also a concern about blockages caused by the residue oil, which is why a higher temperature is used to help the low-nitrogen oil carry away this heavier oil. It’s my own understanding; if there are mistakes, we can discuss them.