The circulation pump of the exhaust gas absorption tower fails to deliver fluid
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Our company has two ester production units, each equipped with an exhaust gas absorption tower made of fiberglass; the two towers share one DN200 vent outlet. The diameter of the tower is 500 mm, and its height is 3.5 meters; it contains bulk packing inside. The exhaust gas circulation pump we use has a head of 12 meters and a flow rate of 5 cubic meters per hour. The pump’s inlet has a diameter of DN40, while its outlet has a diameter of DN25. The piping inlet has a diameter of DN80, and the outlet has a diameter of DN65. But now there is a problem: the material at the pump outlet does not reach the top of the tower. Our material is a mixture of ester and water, with a density of 0.93 kg/cm3. The pump is a magnetic pump, and the inlet and outlet pipes of the pump are very hot, estimated to be around 70 degrees. The temperature of the gas entering the exhaust tower is around 45 degrees; in hot summer weather, it can sometimes exceed 50 degrees. The main reasons for our own analysis are as follows: 1. The temperature of the circulating liquid is too high, causing vaporization and thus pump cavitation, which prevents material from being pumped out ； 2. The pump’s outlet pipe is too large; the pump is not able to generate sufficient power, so the outlet pipe needs to be reduced in size. 3. The power of the pump is insufficient; it is too low. 4. The exhaust gas absorption tower is very small, and the material inside it is essentially stagnant. The magnetic pump relies on that material to cool the mechanical seal, which quickly heats up the material within the tower. At the beginning of operation, some fluid could be pumped into the tower; the inlet pipe of the tower went from cold to hot, and there was also a pressure of 0.1 MPA at the pump outlet. However, after a while it stopped working, with the outlet pressure dropping to zero. I would appreciate it if the experts could analyze what exactly caused this result. Thank you!
With high temperatures, the packing may partially dissolve; moreover, there are esters in the exhaust gases. Try replacing the packing or use a different absorption tower
If it has vaporized, we’ll know once the exhaust is released. It is recommended to use a jacket for cooling.
Based on the poster’s description, the fourth reason is considered the most likely. Insufficient material, prolonged cycling, and rising temperature lead to the evacuation of the vaporization pump. Additionally, an enlarged outlet of the magnetic pump can also cause it to fail to feed material.
Why don’t you consider the installation height of the pump?
Personally, I think first of all, the diameter of the pump outlet pipe, DN65, is too large; the motor does not have sufficient power – the current can be measured to check this. It is recommended to make the pump outlet pipe smaller. The tower in question uses a DN500 pipe, while the pump outlet pipe is DN32; the spraying density is sufficient. Using a DN65 pipe would result in lower kinetic energy of the material at the tower inlet. Second, the temperature is a bit high; has it been demagnetized? Third, at high temperatures, the material vaporizes, and gases are present inside.
Have you removed the pump’s inlet pipe? Check whether the packing in the tower is blocking the pump’s inlet, causing the pump to run idle I guess there are significant reasons for this
That makes sense; at 70 degrees Celsius, the saturated vapor pressure is around 30 kPa