How to reduce coking at the bottom of a catalytic fractionator?

Generally, a stream of oil slurry returning to the tower (or reprocessed oil) is introduced near the oil slurry extraction point at the bottom of the tower to facilitate mixing. The introduction of this slurry causes agitation in the area near the bottom slurry extraction port, preventing catalyst particles or other small coke particles from depositing in this relatively flat area and thus avoiding the formation of flow dead zones. Furthermore, since the temperature of the oil slurry returning to the tower in circulation is only around 240°C, this small amount of material also contributes to a relatively lower temperature in this zone of slow flow, which helps to prevent the formation of initial coke in that area. Anti-coking steam is also usually provided at the bottom of the tower. To increase the perturbation in that area.

1. Use superheated steam to enhance stirring. 2. Use slurry reflux for stirring. 3. The temperature at the bottom of the tower should not be too high. 4. Ensure that only a small amount of slurry is discharged externally

To reduce coking at the bottom of the catalytic fractionation tower, it is crucial to prevent the oil slurry at the bottom from staying there for too long. Otherwise, the catalyst powder that has been washed out will deposit in those dead zones, gradually leading to agglomeration and clumping, which in turn blocks the pump used to extract the oil slurry from the bottom of the tower – creating a vicious cycle. Enhanced stirring can be achieved by appropriately increasing the amount of water sent downward and the amount of steam used.

To prevent coking, it should be by increasing the amount of slurry discharged outside

The measures are multi-faceted: 1. Keep the solid content in the slurry within acceptable limits, at 6 grams per liter. 2. Control the temperature at the bottom of the distillation tower so that it does not exceed specified values. 3. Ensure that the viscosity of the slurry is not too high. 4. Prevent the density of the slurry from being too high. 5. Maintain an adequate circulation rate for the slurry to ensure that the flow velocity in the heat exchangers remains sufficient. 6. Keep the liquid level at the bottom of the tower low; this, together with a high circulation rate, helps reduce the time the slurry stays at the bottom of the tower. 7. Install flushing and stirring rings at the outlet where the slurry is drawn off. 8. Allow the slurry to be discharged externally to an appropriate extent. 9. Depending on the properties of the raw materials and the slurry itself, try to avoid or minimize reprocessing of the slurry. 10. Prevent the reaction from going too deep

Control the steam for bottom agitation at an appropriate level, as well as the amount of slurry discharged outside; the density of the slurry should not be too high, and the proportion of components in the slurry with temperatures below 350 degrees should not be too low. The temperature at the lower levels of the distillation tower should not be too high, and scale inhibitors should be added at the slurry extraction point.

1. Control the bottom temperature of the tower to not exceed 340. 2. Add an oil slurry scale inhibitor. Re-refined oil could be considered as a substitute for stirring steam.

One additional point: it is possible to calculate the residence time of the oil slurry at the bottom of the distillation column; this time should not be too long, as coking results from the combination of time and temperature； Therefore, the bottom temperature of the distillation column can be set a bit lower; it should not be too high.

Most importantly, the temperature at the bottom of the distillation tower must be strictly controlled, and the ambient temperature at that location should not be too high

1. Residence time. 2. Return tower temperature. 3. Introduce the stirring medium. 4. Control the solid content. 5. A temperature-regulating oil slurry system can be added to improve the washing effect and control the temperature returning to the tower.

Every time our plant stops operating, severe coking occurs at the bottom of the distillation tower. How can we make modifications to overcome this problem of coking? More specifically, this post was last edited by chengkang on 2009-4-5 06:33.]

This question is too general; many units have distillation towers. Which specific unit’s distillation tower has experienced coking? Coking occurs for two main reasons: high temperature and low flow rate. Is the adjustment range of the valve at the outlet of your distillation tower too large, resulting in varying flow rates of the material inside the tower? When the residence time is too long and the temperature is high, coking takes place inside the tower.

Please refer to the following post: http://bbs.hcbbs.com/thread-417921-1-1.html

It’s simple: keep the temperature at the bottom of the tower from being too high, and avoid the temperature range where the slurry cokes (above 370). . . :lol

1. Steam stirring； 2. The bottom temperature of the tower must not be high ； 3. The density of the slurry should not be too high ； 4. The amount of slurry discharged outside should not be too small ； 5 Add an appropriate amount of slurry scale inhibitor ； 6. The solid content of the slurry oil must not exceed 6.

A few additional suggestions； Because no coking has occurred in my distillation tower since 2006. 1. Add agitation for the oil slurry at the bottom of the tower, or use reprocessed oil for agitation (my plant uses reprocessed oil for agitation). When stirring the slurry, the temperature should not be too low; it is best to keep it above 260 degrees. 2. Regularly test the viscosity of the slurry to maintain proper density. 3. Steam stirring is the best option; switch to an oil slurry return coil. A small amount can also be used; it is recommended not to rely mainly on steam. 4. Reduce the resistance in the slurry system and increase the circulation flow rate of the slurry – ideally to the maximum possible rate – while minimizing the distance the slurry has to travel through the heat exchangers.