Pressure control issue in electrodialysis tanks

Evaporation of oil and gas in an electrodialysis tank can cause an explosion, as the electrolyte in the tank comes into contact with grease and produces hydrogen gas. As oil and gas evaporate, hydrogen accumulates inside the tank, forming a mixture of flammable gases. If there is a source of ignition (such as sparks or an open flame), it is possible for a combustion reaction between hydrogen and air to occur, leading to an explosion. Furthermore, electrodialysis cells are generally made of metal materials, and under high-pressure conditions, the accumulation of hydrogen gas can lead to corrosion of the metal structure and stress concentration, further increasing the risk of explosion. Therefore, controlling the pressure in the electrodesalination tank can effectively reduce oil and gas evaporation and minimize hydrogen accumulation, thereby preventing explosion accidents. .

The operating pressure has no direct effect on the desalination process; the pressure in the desalination tank is determined by the saturated vapor pressure of the crude oil, the pressure drop at each stage, and the fluid resistance in the process flow after desalination. It serves primarily to prevent water and light oils from vaporizing inside the electrodesalination tank, thereby avoiding fluctuations in the operation of the equipment. It is generally required that the minimum pressure inside the electrodialysis tank should be at least about 0.148 MPa higher than the saturated vapor pressure of oil and water at the desalination temperature. It is generally set at 0.15~0.2 MPa to prevent the desalination process from being affected by the vaporization of crude oil and water. If the pressure at the back of the system decreases for some reason, \"venting\" may occur inside the tank, creating a vaporization zone at the top of the electrodialysis tank. Excessive \"venting\" indicates that the crude oil after dehydration contains too much water, and the desalination effect is poor. The normal operating value of the system back pressure should prevent the occurrence of \"venting\" phenomenon. If the crude oil inside the electrodialysis tank vaporizes, a vaporization zone is formed at the top of the tank; the level switch installed at the top of the tank will then automatically cut off the primary power supply circuit to the transformer, thereby eliminating the high-voltage electric field inside the electrodialysis tank.