Dechlorination by reduced pressure is to inject an appropriate amount of hydrochloric acid into dilute brine, adjust the pH to 1.8~2.2, and keep the vacuum at a high level to remove the chlorine and recycle it.

The vacuum dechlorination method can be divided into the following three methods.
1. Medium-pressure steam jet degassing method
The steam jet dechlorination absorption system generally requires the steam pressure to be 1.0~1.3MPa, and a jet pump with a reasonable structure must be selected, and its vacuum degree can reach 0.055~0.070MPa. The high-speed airflow produced by the throttling and expansion of the medium-pressure steam by the jet pump takes away the gas in the dechlorination vacuum device, so that the pressure in the device is continuously stabilized at a low pressure state, so as to destroy the dissolution balance and chemical reaction of free chlorine in the dilute brine Balance, make the precipitated chlorine and steam enter the cooler together, and then use the circulating water for cooling, and the separated chlorine is sent to the chlorine mains.

2. Mechanical DVE vacuum pump method
The mechanical DVE vacuum pump mainly refers to the water ring DVE vacuum pump. It generates vacuum before the pump through the high-speed operation of the water ring and impeller in the water ring pump to suck the gas (including water vapor) in the dechlorination vacuum device. The chlorine gas enters the chlorine gas main pipe, and the excess chlorine water is sent to the dilute brine tank for treatment.

3. Water spray sealing DVE vacuum pump method
The water jet DVE vacuum pump method uses the shearing force of high-speed flowing water and the cooling effect of low-temperature water to extract the gas in the dechlorination vacuum device and merge it into the chlorine water tank, and the swelled chlorine gas is collected into the chlorine gas main pipe.
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