What are the reasons for insufficient flow rate of the top circulation pump in the catalytic cracking fractionation system?
Thread Content
The flow rate from the top circulation pump is insufficient; therefore, rough gas is used to supplement the top circulation flow. Since the inlet for this rough gas supplementation is located before the pump, the pressure of the top circulation pump remains normal. Even after turning off the rough gas supplementation, the flow meter in the top circulation system still does not show any reading. I seek advice from experts
1. The flow meter of the top circulation system still does not display any readings; please contact the instrumentation team. 2. Check whether the opening degree of the top circulation three-way valve is too small; if it is below 30, the flow rate cannot be increased. 3. Is it to increase diesel production by lowering the dry point of gasoline and raising the 95% point of diesel? If this is done, the load at the top of the fractionation tower can be appropriately increased, thereby eliminating the insufficient top circulation volume.
Reply to 2# aqhjh0159: It’s not a problem with the flow meter; the pump is experiencing vacuum conditions when no heavier gasoline is added； Our top circulation three-way valve remains fully open whenever there are problems with the top circulation system; we use heavy oil catalytic cracking, so the reaction temperature is quite high, and the circulation volume in the middle section isn’t very large either – therefore the third situation you mentioned cannot occur. We now suspect that the extraction point at the top isn’t very unobstructed, but nothing else can be removed by washing the tower!
(1) If evacuation is caused by overload at the top of the tower, it is necessary to increase the flow rate of cold return fluid in a timely and appropriate manner, as well as to increase the heat extraction from stage one or stage two, in order to reduce the temperature at the top. (2) If the load at the top of the tower is too low, resulting in cavitation in the top circulation pump, the cold reflux should be shut off, the heat extraction from stage one or stage two should be reduced appropriately, in order to increase the load at the middle stage.
Is it possible that salt deposition at the pump inlet is the cause? Check whether there have been any significant changes in the salt content of your raw materials, and what is the effectiveness of the electrodialysis process?
1. If the temperature at the top of the distillation column is controlled too low, below 100 degrees Celsius, water accumulation on the tray over time can lead to salt formation, which in turn blocks the trays and pipes and results in a reduced circulation rate. 2. It can be considered from the perspective of equipment failures: check whether there are any abnormal noises at the top of the tower, at the pump inlets and outlets, and within the pipes; issues such as the failure of the outlet check valve or the accumulation of tray components at the pump inlet can reduce the flow area within the pipes, resulting in insufficient circulation volume.
It seems it should still be around 95% higher. It shouldn’t be a device issue.
If the temperature change is minimal and backflow still occurs, it may be due to a problem with the instrument. If the pump makes loud noises and the flow rate is unstable, it could be because of blocked pipes or salt buildup, as corrosion is often severe at the top-of-the-loop position
The temperature of the top circulation extraction is too low, with water accumulation