What are the reasons for large radial temperature differences after the hydrocracking unit is put into operation?
Thread Content
After the 1.2 million-ton hydrocracking unit was put into operation, a problem arose with the radial temperature difference in Bed 2 of the cracking reactor; this temperature difference reached over 12 degrees. The temperature increased normally during hydrogen circulation, and the pressure drop across the bed was not significant. The bed temperature remained normal after oil was fed in, but once cold hydrogen was introduced, the radial temperature difference increased. It is suspected that there are issues with the cold hydrogen distributor and the lower bubble tray; those who have encountered similar problems are welcome to share their experiences.
The radial temperature difference reflects the fluid distribution; it’s not necessarily due to the catalyst not being installed properly, and issues with the cold hydrogen tray and the distribution tray bubbles could also be the cause. However, it tends to be a problem with the cold hydrogen distribution disk. At least that’s the case in our setup: without cold hydrogen, there is no radial temperature difference, but once cold hydrogen is used, the radial temperature difference becomes quite significant.
There is a problem with the cold hydrogen tank; the catalyst causes channeling, which also results in radial temperature differences when cooling the hydrogen
If the temperature distribution in the bed is normal during oil feeding, there should be no problems with the catalyst packing; it’s likely the cold hydrogen distribution plate that is faulty.
A large radial temperature difference may be caused by uneven catalyst packing density; in areas where the catalyst is more compact, less oil and gas passes through, resulting in locally high temperatures. However, based on past experience, a large radial temperature difference occurs when a newly installed catalyst is first put into use, and this situation gradually improves after it has been operating for some time.
According to what you have said, the quality of the internal components can be assessed from the following two aspects: 1. If no cryogenic hydrogen is used and the radial temperature difference across the bed is no more than 3°C, then there is no problem with the distribution plate； Otherwise, the allocation disk will perform very poorly. 2. The radial temperature difference across the bed is greater when cooling hydrogen is used compared to when it is not, indicating a problem with the cold hydrogen tank. Our company has developed a new set of hydrogenation internal components technology that ensures a radial temperature difference within the bed layer of no more than 2°C (with most values around 1°C); feel free to contact us if you are interested. Email: smartft@sina.com