☆After the direct connection modification of the catalytic cracking ☆ settler, the properties of the slurry deteriorated; how to adjust it?
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As the title suggests, we carried out a direct connection modification on the settler during this maintenance work. The original design featured a rough spin + top spin soft connection; for safety reasons, the soft connection was removed and replaced with an open design. However, as the quality of the raw materials deteriorated, severe coking occurred in the settler; therefore, this maintenance work was carried out in a direct connection configuration. After operation began, it was observed that the properties of the slurry worsened significantly – its density was over 1130, and its solid content (without the addition of chloroform) was above 10, while it dropped to less than 1.6 after the addition of chloroform. Please offer some suggestions and help analyze the reasons behind this and suggest ways to make adjustments
Reduce the catalyst circulation rate and calculate the inlet flow velocity of the centrifuge
It’s due to the manufacturing process; the process parameters need to be adjusted. Reaction adjustment should involve reducing the reaction depth, increasing the gas injection volume, and raising the reagent-to-oil ratio. The shunt adjustment should increase the discharge volume of the slurry, pushing the medium oil and reprocessed oil components downward. Raw materials can be added to the bottom of the tower if necessary. These are just general procedures; the details need to be adjusted accordingly based on the product distribution, manufacturing processes, and equipment available.
There are two reasons for this: one is the deterioration of raw materials, which leads to increased catalyst loss, and the other is the change from a flexible connection to a direct connection. Personally, I think the latter reasons account for a larger proportion; similar phenomena usually occur after changing from a soft connection to a direct connection. In such cases, it is generally recommended to increase the amount of external oil slurry or the volume of oil slurry used for reprocessing!
Besides the catalyst, what other substances cause a high solid content in the slurry?
Analyze the solid content to determine whether it is a catalyst; generally, no other substances are present that could affect the solid content
There are two values for the solid content: one before the addition of the solvent, and the other after its addition. In our case, the solid content is high before adding the solvent, usually exceeding 10; it drops after adding the solvent to a level of ≤1.6. This indicates that most of the substances affecting the solid content are organic compounds that can be dissolved. However, we don’t know what these organic compounds are – is there any information available on this?
Why does changing a soft connection to a direct connection lead to severe catalyst wear? Direct connection should result in less loss, right?
Since the high solid content in the slurry, as determined by analysis, is not caused by the catalyst, it is likely due to large-molecule polycyclic aromatic hydrocarbons such as asphaltenes; this means that the issue is not caused by agent leakage. It appears that the fluidization is working properly, the centrifugation is efficient, and the quick separator still plays a significant role in suppressing secondary reactions. This is mainly due to the poor properties of the crude oil being processed, which makes cracking difficult; it may also be related to issues in the process operations. Generally, this can be addressed by adjusting the ratio of oil to catalyst and the reaction temperature, reducing the degree of reaction, increasing the amount of crude oil that goes to the bottom of the fractional distillation tower, and enhancing the removal of slurry from the system. It is also important to ensure that the pumps, heat exchangers, valves, and other equipment in the slurry system operate properly, so as to prevent the situation from worsening. Wait until better quality crude oil becomes available.