Vacuum, electrochemical, and chemical three in one deaerator

1、 Overview of Vacuum, Electrochemical, and Chemical Deaerators
Deoxygenation is a crucial step in the boiler feedwater treatment process. Oxygen is the main corrosive substance in the water supply system and boiler. The oxygen in the water supply should be quickly removed, otherwise it will corrode the water supply system and components of the boiler. The corrosive substance, iron oxide, will enter the boiler, deposit or adhere to the boiler tube wall and heating surface, forming insoluble and poorly heat transferred iron scale. Moreover, corrosion will cause pitting on the inner wall of the pipeline and increase the resistance coefficient. When pipeline corrosion is severe, pipeline explosion accidents may even occur. According to national regulations, steam boilers with evaporation capacity greater than or equal to 2T/H and hot water boilers with water temperature greater than or equal to 95 ℃ must be deoxygenated. For many years, many boiler feedwater treatment workers have been exploring efficient and economical deoxygenation methods, such as two-stage vacuum, electrochemical, and chemical deoxygenation methods integrated into a deaerator. Suitable for deoxygenation of room temperature water, it has unparalleled advantages over other deoxygenation methods and has a wide range of applicability.

2、 Principles of Vacuum, Electrochemical, and Chemical Deaerators
Step 1: Two stage vacuum deoxygenation
　　　　vacuum deaeratorAdopting a fully enclosed structure, it remains in a vacuum state throughout operation. The water supply first enters the strong rotating membrane device through the electrolytic cell. The working principle of two-stage vacuum deoxygenation is to apply Henry's law and Dalton's law. According to Henry's law, in a closed container, if any gas exists on the water surface at the same time, the solubility of the gas is proportional to its own partial pressure, and the solubility of the gas is only related to its own partial pressure. Under a certain pressure, as the water temperature increases, the partial pressure of water vapor increases, while the partial pressure of air and oxygen decreases. At 100 ℃, the partial pressure of oxygen decreases to zero, and the dissolved oxygen in water also decreases to zero. When the pressure on the water surface is lower than atmospheric pressure, the solubility of oxygen can also reach zero at lower water temperatures. In this way, oxygen molecules on the water surface are released or converted into other gases, resulting in zero partial pressure of oxygen. Oxygen in the water continuously escapes and 90% of dissolved oxygen is removed under negative pressure. Two stage vacuum deoxygenation aims to reduce boiling point and achieve deoxygenation effect under vacuum.
Step 2: Electrochemical Deoxygenation
The entire equipment is equipped with an electrolytic separation cylinder, which is composed of an anode and a cathode to form a decomposition water channel, forming an electrolytic separation assembly. Water passes between the two poles.
3、 Composition of vacuum, electrochemical, and chemical deaerator equipment
Vacuum, electrochemical, and chemical deaerators are mainly composed of deaerators (deaeration heads), high-efficiency membrane devices, continuous reaction electrolytic cylinders, booster pumps, water jet vacuum pump units, water intake pump units, PLC control boxes, and other components.
Vacuum, electrochemical, and chemical deaerators are equipped with electrolytic cylinders and high-efficiency rotating membrane devices. The natural falling membrane is replaced with a strong rotating membrane to increase the renewal of the liquid film and cause the liquid film to rotate strongly along the pipe wall, enhancing dispersion and mass transfer functions; Change the corresponding boiling point to a suspended boiling point. Overcome the overflow (splashing) caused by high water vapor flow velocity in the layer and maintain the vapor (gas) channel; Consolidate the three independent heat and mass transfer methods into one unit of components. Due to its high efficiency and certain special functions, it has surpassed the technical performance of other deaerators. During the operation of vacuum, electrochemical, and chemical deaerators, the deaerator is in a negative pressure state. When installing at a high position, the distance between the outlet of the electrolytic cylinder and the inlet of the boiler feedwater pump should be relatively large, preferably not less than 10 meters; When installed at a low position, the outlet of the electrolytic cylinder is connected to the water intake pump unit to increase the pressure of the negative pressure water before entering the boiler feedwater pump. The water jet vacuum pump unit is equipped with a long throat water jet vacuum pump, which has a compact design structure and extremely low power consumption. And it has high suction efficiency, with a suction volume twice as high as the old model under the same conditions. Low noise, no vibration, and simpler installation and layout. The function of the water intake pump unit is to increase the pressure of negative pressure water through the water intake pump and connect it to the boiler feedwater pump when the deaerator is installed at a low position. The two-stage vacuum, electrochemical, and chemical deaerator is put into operation. The first step is to fill the water level of the deaerator's water injection tank to the overflow port. The valve of the overflow port is open, and the water replenishment port of the water injection tank is also normal to ensure that the water temperature of the water injection tank is at 30 ℃. Close the relevant valves and first fill the water level of the deaerator to the operating standard water level. Start the vacuum water jet pump, open the gate valve on the suction pipeline, and when the vacuum degree of the deaerator reaches -0.075Mpa, open the inlet valve and start the boiler feed water pump. The deoxygenated water enters the membrane separator and forms a high-efficiency water film skirt under a water pressure of 0.2Mpa. Run under high vacuum, increase the water temperature by about 30 ℃ -60 ℃, fully suck out the oxygen, and discharge it into the water jet tank. The deoxygenated feedwater enters the electrolytic cylinder for electrolytic deoxygenation, and then enters the second stage electrolytic cylinder for chemical deoxygenation. The deoxygenated water is discharged into the third stage electrolytic cylinder for chemical deoxygenation and pressurization. The boiler feedwater pump sends the deoxygenated water to the boiler. When the deaerator is stopped, the gate valve on the suction pipeline must be closed first, and then the water injection pump must be stopped. If the water injection pump is stopped first without closing the gate valve on the suction pipeline, the deaerator will be in a vacuum state, and the water in the water injection tank will be sucked back into the deaerator, affecting the deaeration effect.

4、 Automatic control system for vacuum, electrochemical, and chemical deaerators
1. The normal operation of the equipment is fully automated and unmanned. The entire operation of the equipment is intelligently controlled by PLC, and all operating parameters and control points are automatically monitored and adjusted by PLC. All valves and vacuum pump units are automatically controlled to open (can also be manually opened).
2. The vacuum degree of the equipment is controlled above -0.05~-0.06Mpa during online operation. Ensure that the desalinated water enters the deaerator and vigorously rotates within the high-efficiency rotating membrane device to form a water film skirt, allowing for sufficient oxygen release.
Once the vacuum degree becomes unstable, the equipment will automatically sound an alarm, and personnel need to make on-site adjustments.
3. The water level is controlled by an automatic liquid level controller, and if the water level is lower than the design water level, the equipment will automatically alarm.
4. PLC automatically tracks and controls the electric water supply regulating valve and vacuum degree, always controlling the oxygen content of the water supply to be ≤ 0.05~0.1mg/L.