Problems in vacuum distillation of oils
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The company is a small refinery, and its process involves using two vacuum distillation columns (without stripping columns) to separate the oil products. At present, the first vacuum distillation tower can only remove water and produce a small amount of overhead oil and diesel; the oil coming out of the bottom of this tower is sent to the second vacuum distillation tower, where diesel, wax oil, and residue are produced. Due to the poor quality of the product, we now want to make improvements. The main problem is that the oil has turned black, giving it an unsatisfactory color; the possibility of a leak in the heat exchanger has been ruled out. The wax oil and diesel cannot be separated clearly; wax oil is mixed in with the diesel. Quality control of diesel and residue often suffers from neglecting one aspect while focusing on another. The tower top uses a water-cycle vacuum pump, which often suffers from corrosion and fails to rotate during operation. Dear experts, please share your valuable suggestions on how to make improvements.
The main reason for poor separation is that the trays and packing need to be modified； Corrosion can be addressed by replacing certain materials or by introducing appropriate corrosion inhibitors.
Why use two pressure reduction towers? Convert the first one into an atmospheric pressure tower and replace its trays. The inability to rotate the vehicle is due to corrosion issues
If the product quality is poor, it indicates that there are issues with the separation precision of the tower, which is quite troublesome. Using the existing equipment, it’s better to have a design institute redo the design!
Poor product quality is due to issues with separation accuracy; for packed towers, it depends on the quality of the distributor. The most likely reason is that operations deviate from the design parameters, and this is the case in many factories, where operations are not carried out according to the design at all. If the drive shaft won’t rotate, it’s likely a problem with the vacuum pump, as the content of light components in the crude oil fluctuates and deviates from the designed values ； The corrosion problem is likely due to the lack of desalination during the previous dehydration process, as well as low-temperature corrosion; using only corrosion inhibitors is not sufficient. Improvements can be made to the process, such as carrying out flash evaporation for dehydration after heat exchange