Hydrocracking, post-furnace hydrogen mixing understood. .

Where did you see it? I also want to go and take a look and learn

The issue of hydrogen mixing before and after the furnace is not clearly explained in many books; neither \"Technical Questions and Answers on Hydrogenation Refining Units\" nor \"Operators of Hydrogenation Units for Gasoline (Coal, Diesel)\" specifies whether the furnace in the hydrogen mixing process after the furnace is used to heat the feed oil or the recycled hydrogen. However, I’ve heard that in the post-furnace hydrogen mixing process for oils in Qingdao and Dalian, the heating furnace is used to heat the recycled hydrogen; therefore, in practical applications, the furnace used for post-furnace hydrogen mixing is essentially a hydrogen heating furnace. If the medium flowing inside the furnace tube is pure hydrogen, then compared to furnace tubes with a two-phase gas-oil mixture as the flow medium, the likelihood of coking is much lower, as factors such as uneven mixing and flow deviation of the mixed medium within the furnace tube are less of an issue.

I came across a statement saying that the hydrogen heater in the post-furnace hydrogen mixing process can reduce the occurrence of coking in the furnace tubes. How to understand it? I am extremely grateful here! I read your words carefully: in the hydrogen mixing process behind the furnace, the hydrogen heater is used to heat only the hydrogen, and it is only after the hydrogen has been heated that it mixes with the feed oil. Compared to heating the feed oil along with hydrogen in front of the furnace, this approach certainly reduces the likelihood of coking in the furnace tubes

Yes, many places are written very unclearly! Is what’s used in Qingdao specifically called post-furnace oil mixing? !

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That makes a lot of sense, thank you! I have another question for you regarding hydrogen blending in hydrocracking – are there four different ways to blend hydrogen in the furnace? First, in front of the furnace. Second, behind the furnace. Third, some in front of the furnace, some behind it. Fourth, post-furnace oil mixing.

No, isn’t post-furnace hydrogen mixing a type of hydrogen mixing method similar to post-furnace oil mixing?

Furnaces with post-furnace hydrogen mixing are used to heat hydrogen, and since there is no carbon in hydrogen, coking does not occur easily. On the other hand, when heavy oil is heated in the furnace tubes, wax oil and residue oil are prone to coking when there is localized overheating. It’s the difference in the heating medium

As the name implies, the hydrogen mixing zone is where the feed oil and hydrogen are mixed, and after mixing they enter the reactor. Mixing the feed oil and hydrogen before entering the reactor is known as pre-reactor hydrogen mixing. After being heated by the furnace, hydrogen is mixed with the feed oil behind the furnace, which is known as post-furnace hydrogen mixing.

Hydrogen mixing behind the furnace reduces the cost of the furnace tubes, but it lowers the flow rate of the feed oil (especially heavy oil) within these tubes, increases its residence time, and raises the risk of coking; hydrogen mixing in front of the furnace can prevent this from happening.