decompression

It refers to the saturated vapor pressure of the target product; that is, under specific temperature conditions, the operating pressure is lower than the saturated vapor pressure of the target product, which enables the separation of this product.

Reduced pressure is relative to normal pressure; it is an operating pressure (vacuum) lower than atmospheric pressure, achieved through vacuum pumping equipment

Vacuum distillation is part of the atmospheric and vacuum distillation unit. At atmospheric pressure, the heavy oil is heated to around 410°C in a heating furnace, and then fed into a vacuum distillation tower where it is distilled at an absolute pressure of approximately 8.799 kPa (60 mmHg). The lubricant feedstock for cracking is obtained as the distillate, while the residue is vacuum residue.

:handshake :loveliness:

I agree with the opinion on the 3rd floor: pressure reduction is relative to normal pressure, and it is achieved by using vacuum systems to create an operating pressure that is lower than atmospheric pressure

Vacuum distillation is a unit for distilling crude oil under conditions of near vacuum. The pressure at the top of a distillation column in normal-pressure distillation is 10–40 KPa higher than atmospheric pressure, whereas the operating pressure at the top of a distillation column in vacuum distillation ranges from a few thousand pascals to twenty–thirty thousand pascals, which is much lower than atmospheric pressure. The purpose of using vacuum is to allow the fractions in crude oil with boiling points above 350–530 degrees to be separated at lower temperatures (generally below 400 degrees; in our two units for normal and vacuum distillation, the temperature at the exit of the vacuum distillation furnaces is kept around 380 degrees). Since the boiling point of substances decreases as pressure drops, if these fractions were to be separated through normal-pressure distillation, temperatures of over 500 degrees would be required, leading to cracking or condensation of the oil. Vacuum distillation is divided into wet vacuum distillation, dry vacuum distillation, and semi-wet distillation. In wet distillation, steam is injected at the bottom of the tower to reduce the partial pressure of the oil vapor; this method requires relatively high energy consumption, and the operating pressure at the top of the tower is also high. Dry vacuum distillation, on the other hand, does not require steam injection, resulting in lower operating pressures, which can drop below 1 KPa (absolute pressure). We use vacuum towers based on dry vacuum distillation, whose operating pressures are generally below 2 KPa, essentially in a vacuum condition.