Discussion on some issues regarding the commissioning of the wax oil cracking unit
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Gentlemen, for the paraffin oil cracking unit, what temperature should be chosen as the inlet temperature point when it starts up? What is that temperature approximately? I attended a discussion on a plan. Some people say that in their units, hydrogen is heated to 280–290°C before being fed directly into the wax oil; this temperature is used to prevent the nitrogen present in the oil from affecting the cracking catalyst. Some say that at 260°C, low-nitrogen oil can be introduced directly; the temperature is then raised to 280–290°C, or even up to 330°C, before switching to crude wax oil as the feedstock. I’m seeking help from everyone here.
Is this your first time starting work? If it is the first time starting up, the feedstock can be switched once wet sulfiding is completed; otherwise, if the oil inlet temperature is too low, the cracking depth will not be sufficient, which may result in an inability to send the material to the bottom of the distillation tower. This is a difficult situation to handle. If the temperature is too high, it becomes hard to keep it under control. Generally, an inlet temperature of around 280 is suitable. It is also possible to start using diesel first and then switch to wax oil. For exact details, refer to the data provided in the process package – it will be pretty accurate
Isn’t there a plan that has been developed, along with personnel support? P
If it’s started for the first time, it can be raised to 280 at that point, but once operations begin, won’t the catalyst be reduced by high temperatures in the absence of hydrogen sulfide?
Before H2S penetrates the bed, the reactor temperature (at any point) must not exceed 230°C; even if it is not the first start-up, sulfur needs to be added in appropriate amounts, with the dosage adjusted based on the H2S content in the recycled hydrogen.
For dry catalysts, the temperature at which low-nitrogen oil wets the catalyst should not be too high; 260°C is a suitable temperature. This is because there is an adsorption heat when dry catalysts are wetted, which is generally around 20°C. In cases of emergency shutdowns or when resuming operations after an interruption in feed supply, it’s acceptable to introduce wax oil at 290°C directly. The difference lies in the concept of adsorption heat
It’s now difficult to reduce catalysts in a short time; it’s not a big problem, as catalyst technology is already quite mature