Vacuuming of the bottom pump in the vacuum distillation column of the atmospheric and vacuum distillation unit
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The bottom pump of the vacuum distillation column in the atmospheric and vacuum distillation unit is designed to handle a flow rate of 400 tons per hour; currently, it operates at a rate of 250 tons per hour. But currently, only 170 tons per hour can be extracted. The liquid level at the bottom of the tower has reached 90%. The processing capacity is limited. Is it caused by coking? There is no problem with the vacuum furnace.
1. To identify the root causes of problems, analysis can be conducted from two aspects: the equipment itself and changes in process parameters. 2. A sealing failure in the equipment’s mechanical seal leads to internal leakage, causing the sealing oil to enter the machine body. Light-weight sealing oil tends to vaporize when in contact with high-temperature media, resulting in evacuation. 3. Insufficient exhaust within the pump body, inadequate preparation before starting the pump, improper filling of the pump, vacuum conditions, and insufficient outlet flow. 4. Any obstruction in the pipeline system, including issues with the inlet manual valve, outlet manual valve, outlet control valve, or the backflow valve, can lead to a reduction in outlet flow and cause the pump to run dry. 5. Both excessive vacuum level in the vacuum tower and high temperature at the bottom of the tower can cause the material at the bottom of the tower to vaporize, leading to pump cavitation and insufficient flow stability.
The analysis upstairs is quite thorough; let’s take another look at the corrosion condition of the impeller
The inlet or inlet pipeline is blocked. Find out the reason.
If 170 t/h can be consistently excluded and the pump outlet pressure is normal, the possibility of the pump running dry should be ruled out, as well as the factor of excessive vacuum. Priority should be given to checking for any obstructions in the pipeline system – including the inlet manual valve, outlet manual valve, outlet control valve, or return valve – as such obstructions can lead to a reduction in outlet flow and cause the pump to run dry. Corrosion of the impeller and blockages in the flow channels should also be considered.
There is also a possibility of blockage on the rear side; check this during maintenance, and examine the coking condition of the first heat exchanger for residue oil.
Check whether the cavitation head of the bottom pump meets the requirements; increase the operating liquid level appropriately to see if this improves the situation