Reasons for the high solid content in the slurry

The solid content of the slurry is high. http://bbs.hcbbs.com/viewthread.php?tid=316920&highlight=%B9%CC%BA%AC%C1%BF%B8%DF Please take a look~~~~~~~~

The main reason for the high solid content is the malfunction of the cyclone separator; its separation efficiency is poor. One can check the pressure drop across the separator – if it is higher than normal, it indicates that the cyclone separator is blocked. Another factor is the operating method: perhaps the differential pressure control between the two units is set too high

Generally, it’s because the centrifuge is not performing well. If this issue has only appeared recently, it might be caused by coking. Could someone explain how the pressure difference between the two devices mentioned upstairs affects the solid content?

Basically, it’s either that the centrifuge isn’t working properly or there’s a leak

Unstable reserve control or excessively high reserves can also lead to such results

The possibility of coking in the secondary centrifuge is relatively higher; at the initial stage of coking, the valve plates of the wing valves become less responsive, and there are significant fluctuations in the centrifuge pressure drop, the density of the material in the legs, and the amount of material stored. When coking is severe, the valve plate fails to operate, the material legs get blocked, and a large amount of catalyst is lost; at that point, it is necessary to shut down the operation for repairs. Sometimes the thick spiral legs can also get clogged, and in such cases the problem is not an increase in the solid content; in that situation, the slurry can be considered a catalyst.

1. Fault in the compressor governor, resulting in fluctuations in the unit’s rotation speed, or fluctuations in steam pressure and backflow； 2. Fluctuations in the total steam injection volume during the reaction, failure of a certain steam control valve, resulting in back-and-forth variations ； 3. The flow rate of the pre-heating steam or dry gas is malfunctioning or inaccurate; the flow rate is low, resulting in poor pre-heating effects and unstable reactions ； 4. The regenerated inclined tubes are not unobstructed or clogged due to backwashing, resulting in poor fluidization of the inclined tubes. If the leakage is not caused by fluctuations in reaction pressure, then the reasons for leakage from the reactor along with a high solid content are as follows: 1. The installation angle of the flap valve exceeds the allowable deviation; the angle should be set according to the values determined during static tests of the flap valve, with an allowable deviation of 0.3–0.5 degrees. If this range is exceeded, leakage will occur ； 2. The feed rate is too low for an extended period, the steam supply is insufficient, the linear velocity at the inlet of the centrifuge is below the critical value, or the pressure in the centrifuge is below 3.5 Kpa ； 3. Frequent accidents and prolonged fluctuations in the feed rate cause the linear velocity at the separator inlet to remain below the critical value for extended periods, or the pressure drop across the separator to stay below 3.5 Kpa; moreover, the linear velocity at the separator inlet experiences significant fluctuations ； 4. The pressure and reserve of the two devices fluctuate significantly ； 5. The valve for the steam branch line equipped with a orifice plate is not closed, either the steam contains water, there is no orifice plate installed on the reverse blowing steam, the catalyst is severely damaged, or the content of fine powder in the balancing agent is too high ； 6. The regeneration temperature is excessively high, causing thermal degradation of the catalyst ； 7. Leakage in the internal and external heat exchangers; steam is broken down by the high-temperature catalyst ； 8. The catalyst has poor sphericity or strength, and wears out and breaks down during cyclic fluidization; or the wear resistance indices of the two types of catalysts differ significantly, leading to severe mutual wear and breakdown ； 9. The feed nozzle operates at a velocity exceeding the critical value (above 100 m/s), resulting in catalyst fragmentation ； 10. Catalysts suffer from severe heavy metal contamination, which reduces their strength and leads to fragmentation at high temperatures

The coarse swirl separation effect at the riser outlet is not good, right?

A high differential pressure between the two devices can be interpreted as a low pressure in the settler. We know that there is a linear velocity at the inlet of the cyclone; if this linear velocity exceeds a certain value, the catalyst will be carried away, and the solid content in the slurry will increase. And if the pressure in the settler is too low, the linear velocity at the cyclone inlet will increase, which may lead to agent leakage.

The solid content in the slurry is high – by how much? When diagnosing such problems, the separator is the main factor to consider; it is possible to analyze the sieve composition of the solids in the slurry. If there are large particles, it may be a problem with the separator; if everything consists of fine powder, the causes can be more complex, possibly due to an excess of fine catalyst particles. On the surface, a high solid content in the slurry seems to indicate that catalyst is leaking from the settler. However, if catalyst is leaking from both the reactor and the settler, it may be necessary to look for causes related to damage to the catalyst or to the internal components responsible for distributing the catalyst between these two devices.

I’ve learned a lot; with more people around, one’s perspective broadens. What I want to say is that some time should be given for the process of verifying each idea.