Could you help analyze the reasons for building a bridge over the upcoming route?
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For a 600,000 tons/year coaxial heavy oil catalytic cracking unit, after the unit goes into bed rest and during the fluidization test operation of the two reactors, it is not possible to establish a normal inventory level in the stripping section. When the valve is opened wider for circulation, the inventory level in the stripping section gradually increases; once the valve is fully open, this inventory level fails to decrease. Once the valve is fully open and the inventory in the stripping section rises to between 25 and 35 tons, it will drop on its own; sometimes, negative pressure applied to the two vessels is required to reduce the inventory in the stripping section.
1. The fluidization is abnormal; this may be related to the low circulation load after the bed becomes clogged. Try increasing the circulation rate to the normal level； 2. Check whether all the fluidization air is in use and functioning properly ；
Check whether the relief points of the startup riser are in proper operation and whether they remain unobstructed; when fluid cannot flow down, the bypass valves at those relief points can be opened to facilitate flow； Check the operation status and unobstructed condition of the Vertebral body in the stripping section ； What is your catalyst circulation rate? Are the density of the raw material riser and the density of the sleeve normal? Do not use too much fluidization air for the sleeve.
It’s what the two people upstairs said – give it a try.
First and foremost, it is necessary to establish the reserves
Actually, this is also a fairly common issue with coaxial catalysis. Personally, I believe that the setting of the loosening points in this area is closely related to its operation, as the fluidization in this region is very complex; an appropriate setting of the loosening points will facilitate fluidization! Catalytic cracking is an abbreviation for this process; many people overlook the full name, which is fluidized catalytic cracking. Fluidization is a prerequisite – an essential condition that cannot be ignored!
Check each loose steam line of the upcoming standpipe to see if there are any bypass lines open； Also, reduce the amount of stripping steam; maybe it’s the high volume that’s providing support.
This phenomenon should not be bridging; it might be the shedding of coke lumps. The location of the blockage is likely to be at the grid below the stripping section or at the necking area of the plug valve; this can be determined based on the parameters from the vertical pipe instruments. If the situation isn’t serious, it is recommended to keep the process in a fluidized state for some time to grind the gel clumps smaller so that they can fall down and production can resume; if that doesn’t work, then shutdown is the only option
Are there any pictures? Check the density distribution of the riser.
It doesn’t have to be by building a bridge; if a bridge is built, it will be extremely difficult to get down. 1. It’s possible that there are too many large catalyst particles, which leads to poor fluidization. 2. Based on what we’ve observed, fluidization is not very good every time the system is started up; sometimes it’s only possible to maintain circulation with great difficulty. As soon as a little oil is introduced into the system, fluidization returns to normal. During periods when the system stops functioning, much of the coke burns up, and since coke also acts as a lubricant within the catalyst, that’s why such phenomena occur!