What good methods do you have to deal with the vacuum condition caused by the top circulation pump in catalytic fractionation?
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What good methods do you have to deal with the vacuum condition caused by the top circulation pump in catalytic fractionation?
Control the temperature of the constant-peak recycle tower so that it is not too high; increase the stability difference between extraction and return in the constant-peak recycle process in order to reduce the circulation volume of this process.
The extraction temperature can be appropriately increased to increase the top load. Remove the fine mesh of the pump inlet filter.
If nothing else works, it’s necessary to add a little cold reflux.
Ensure that the temperature of the top recirculation tower is not too low; it is generally around 80°C. A withdrawal temperature of around 130°C is suitable. At the same time, it is necessary to control the volume of material in the top recirculation tower. The reaction feed and pressure must be stable, with strict control over the pressure at the top of the distillation tower. Based on experience, when the top temperature of the tower is too low, the extraction temperature drops as well; in such cases, timely adjustments should be made by raising the top temperature appropriately. Once the extraction temperature returns to normal levels, the top temperature can then be reduced gradually until it remains within the specified range.
If time is available continuously after starting operation, should we consider the option of installing a liquid collection tank at the outlet?
This issue was also discussed in a previous conversation, and it turned out that the best solution is to increase the height of the oil collection tank – it’s simple and practical, requires little investment, and yields quick results!
A few suggestions: 1. Based on the results of the heat balance calculation, it is necessary to take into account that the heat taken from the upper part should be in the range of 25–30%; if this value is too low, the heat extraction point can be moved upward. 2. Analyze the composition of the material circulating at the top to determine whether any moisture is present An online dehydrator can be installed during maintenance ； 3. If the device is running for a long enough time, consider whether the oil collection tank is leaking Then the only option is to stop operations for maintenance and replace the bottom plate.
Is it the low processing capacity and the lower temperature control at the top of the fractionation tower, which result in water being carried in the overhead stream and causing the pump to experience vacuum? Also, could it be an internal leak in the heat exchanger, which causes water to enter the top circulation and leads to the pump running dry?
The most likely cause is water carried in the top stream. The measures are: first, to increase the extraction temperature and control the pressure at the top of the tower; second, to install dehydration facilities – there seem to be articles on this topic in oil refining engineering and design.
The evacuation caused by the top circulation pump is essentially due to water being carried along with the circulation flow; the solution is to increase the top temperature appropriately. If the top temperature is controlled too low, salt deposition at the top of the distillation tower can occur. The person asking the question also needs to determine whether the blockage at the discharge port is caused by salt deposition. The solution to salt formation is to carry out washing. Each refinery has mature experience