Difficult to feed the riser pipe into place

There are so many reasons! If the differential pressure, valve status, stripping steam, and circulation rate are all fine, there may be an obstruction caused by foreign objects.

It just finished a shutdown for maintenance; the shutdown was due to this issue. The same thing is happening now that operations have resumed – it’s not clear how severe the impact of the loosening is

The impact of loose points is quite significant; it depends on the density of the risers, and it’s necessary to determine which section is not unobstructed. 1. It’s possible that the plug valve was left closed for an extended period during startup, resulting in wet catalyst accumulating above the valve; after heating and drying, this material blocked the upper part of the valve. Try moving the plug valve vigorously – attempt this several times. 2. Check the pressure drop across the plug valve and the density of the slurry; if the pressure drop is low and the density is high, try increasing the fluidization air flow for the sleeve ； (Also, it is not clear whether the blockage of the sleeve catalyst distributor was checked during maintenance.) 3. If the densities in all the feedstock risers are low while the density in the stripping section is high, there is a problem with the stripping section; issues such as blockages in the grids may be present. 4. If the density in the feedstock risers is high, the loosening points can be adjusted from bottom to top, and the bypass valves at those loosening points can be slightly opened to observe whether the density decreases and to check the material flow ；

During the shutdown for maintenance, was it checked whether there were any breaks at the loose points of the standpipe?

If it becomes loose, the impact is limited; there are orifice plates available, and even if it’s strained, the amount affected won’t be significant. Since it has just been overhauled, everything should have been checked, right?

Uneven temperature rise causes the lining to peel off, resulting in poor material discharge?

I just connected all the broken parts, but didn’t check whether they worked or not; when I started using them, I found that several of them didn’t function

After the maintenance of a device is completed or when a new device is put into operation, any loose areas must be cleared by using a toothpick to ensure they are unobstructed. The loosening of individual key points is crucial for the fluidization in inclined tubes; for example, the sections with changing diameters, elbows, horizontal sections, and the areas before and after the slide valve are all important points where loosening can occur. It is recommended to start with loosening first.