\"Raw catalyst riser\" of coaxial catalytic cracking unit"

It affects the catalyst, causing it to coking after entering the centrifuge; in some cases, the catalyst can even cause blockages in the material legs of the third and fourth centrifuges

This phenomenon is quite common; there are 8 loose connections in the rising pipe, and the breakage of a few of these connections can affect the proper fluidization of the pipe. A high level of material in the stripping section, along with breaks in the pressure guiding pipes, can cause malfunctions in the instruments used to measure volume and density, which hinders production analysis

This post was last edited by Refiner on 2020-6-26 08:55. If a loose point on the \"raw catalyst riser\" of a coaxial catalytic cracking unit breaks, it will directly affect the smooth feeding of material into the riser, impair fluidization, and lead to an increase in the solid content. In severe cases, the inability of the catalyst to circulate properly will result in unplanned shutdowns； A broken pressure lead can cause the inventory and density instruments to malfunction, making production analysis difficult and affecting normal operations!

Theoretically, it has a certain impact on catalyst fluidization, but in practice the effect is not as significant as imagined. The running risers of our catalytic unit become loose, and several of them break every time there is an emergency repair. It can be seen from the CO2 content in the catalytic gas; generally, this level increases after a break occurs

Reply to 1# 176866346: Wait until the loose point in the raw gas riser is disconnected. If the root part breaks, it may cause perforation at the base of that loose point, leading to backflow of flue gas; this is manifested by an increase in nitrogen content in the dry gas, as well as difficulties in controlling the amount of material accumulated in the settler. Reduce the opening degree of the raw gas plug valve.

This post was last edited by jbcyf on 2012-3-10 at 10:41. It depends on the actual circumstances; it will certainly cause wear at the root of the breakage, and poor vulcanization may also occur. As for the vertical tubes, fluidization isn’t a problem because both components are in vibration (gentle vibration). A few breaks generally won’t affect fluidization. The steam escaping from the vertical tubes is usually symmetrical left and right, with two per layer. Taking our FCC unit as an example: there are 12 such escapes, distributed across 6 layers, with two symmetrical ones per layer. The steam blows downward at a 30-degree angle (in the direction of the plug valve). Since the vertical tubes store a large amount of pressure, there is a dense-phase gas flow inside them, with a density ranging from 500 to 700, with 600 being the most common value. The escaping steam tends to flow toward the regenerator. Generally speaking, the steam escaping from the upper vertical tubes enters the settler, while in many units, the steam escaping from the middle and lower vertical tubes goes along with the catalyst into the regenerator. If the root of an upper vertical tube breaks, it may increase the flue gas content in the gas stream, but it won’t affect the capacity of the stripping section. The situation is similar to that of perforations in our stripping section； If it is in the lower section, it will not lead to gas carrying smoke; however, if the wear and perforations are severe, it will make it difficult to maintain the inventory in the stripping section. Of course, production maintains its own balance and cycle amidst fluctuations, and factors such as the flow of gas in the riser, the pressure difference between the two vessels, and the amount of material stored in the settler play a significant role in this.

If there is a fracture at the lower part, it will also lead to an increase in the dilute-phase density of the regenerator

Will it also cause the dilute-phase density of the regenerator to increase? Will the density in the dilute phase increase? ? ?

In principle, it can cause problems such as poor fluidization, but in practice, the impact is not significant. During the maintenance in 2004 of our 1.8 million tons of heavy oil catalytic feedstock risers, it was found that nearly half of them were clogged or broken, yet operations were not affected in any way. But it may also be related to the location of the loose point.

The catalyst should flow down the standpipe while being confined by a bed layer; subsequently, under the action of the main airflow, some of it is fragmented into a dilute phase. If it comes into contact with the area above the dense phase layer, can its density still not increase?