The main function of the condenser in the vacuum system is to condense the vapor part of the mixed gas above 100 °C from the vacuum tank into a liquid below 25 °C at one time, so the cooling capacity is particularly strong, and the condensation effect is particularly good. Generally, the condensing power should reach more than 3/4 of the rated power of the VPD equipment (ie, the evaporator power).

The structure of the condenser is a shell and tube heat exchanger. There are multi-layer baffles in the shell side of the airflow to ensure that the airflow is fully condensed. The total inlet and outlet pipes are divided into multiple branches in the condenser to form a sufficient condensation area. Due to the large amount of cooling water, VPD equipment needs to build a special cooling water station or chiller to supply circulating cooling water for it.

The temperature of the cooling water has a great influence on the working performance of the condenser. Generally, the maximum water vapor partial pressure that the leakage pump can withstand is about 3kPa, and the corresponding water vapor saturation temperature is 24°C, that is, the temperature of the oil-water-gas mixture at the outlet of the condenser should not exceed 24°C, otherwise there will be too much water vapor. Entering the dump pump will affect its normal operation; and the temperature of the cooling water needs to be lower. This is difficult to guarantee in many areas in summer in our country. In recent years, in order to effectively strengthen the condensation effect, the main condenser of the existing VPD equipment is cooled by a chiller. Or a small condenser provided with cooling water by a chiller is connected in series between the collection tank and the leakage pump to further reduce the residual gas Partial pressure of water vapour and kerosene vapour.

The working pressure of the condensing system is also very critical. Obviously. If the total pressure in the condenser and the collection tank is lower than the saturated vapor pressure of water at the current temperature by 3kPa, the water vapor cannot condense at all, and all of it will be dumped by the pump. draw away. For water vapor to be sufficiently condensed, the condensing pressure must be higher than the saturated vapor pressure. However, the pressure of the condensing system should not be too high. Because the pressure of the condensing system is too high, the gas pressure in the vacuum tank is required to be higher, otherwise the mixed gas cannot flow into the condenser naturally under the action of the pressure difference, and the pressure in the vacuum tank is too high. Directly affects the outward diffusion of water vapor in the insulating material. Taking into account the above two factors, and taking into account the existence of permanent gas components in the residual gas, the working pressure in the condenser is selected to be 4.5kPa, which can not only ensure that the water swallow gas is fully condensed, and will not be regenerated, but also can make the vacuum The pressure in the tank should be as low as possible.

In the relatively complete VPD equipment, there is also an auxiliary condenser in the condensing system, which is specially designed to receive the high-temperature kerosene vapor discharged in the later stage of the kerosene purification process in the distillation room. The structure of the auxiliary condenser is the same as that of the main condenser. The power of the condenser corresponds to the power of the distillation chamber, and the condensed kerosene liquid is also discharged to the collection tank.