“Daily Share 4.23”: Why is the slurry sent back to the tower in two stages, upper and lower?

Thread Content

After the reaction gases and oils enter the tower, the oil slurry is used for reflux to remove excess heat and wash the catalyst powder; at the same time, it causes a small amount of the heaviest fractions – residue – to condense into a liquid state, which then flows to the bottom of the tower along with the catalyst powder. This residue is continuously extracted for reprocessing or use as a product. Therefore, under normal circumstances, to ensure overheating prevention and the flushing of the catalyst slurry, it is necessary for the fluid to enter the tower from above the chevron baffle, which is the upper inlet. The temperature at the bottom of the tower must be strictly controlled depending on the density of the feedstock; otherwise, coking will occur. In addition to controlling the volume and temperature of the slurry circulation, the adjustment measures also involve injecting a small amount of slurry returning to the tower directly into the liquid level at the bottom of the tower, thereby utilizing the cooler slurry to mix with the slurry at the bottom and reduce the temperature. At this point, the oil slurry should be used at the inlet. If cooling is achieved by increasing the amount of circulating slurry supplied from above, it will simultaneously increase the condensation of residue, causing the liquid level at the bottom of the tower to rise.