Working principle and function of the flash tank

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1. Flashing occurs when saturated water at high pressure enters a container at lower pressure; the sudden drop in pressure causes this saturated water to turn into saturated steam and saturated water at the pressure of that container. 2. The boiling point of a substance increases as pressure rises and decreases as pressure falls. This allows the high-pressure, high-temperature fluid to be depressurized, thereby lowering its boiling point and allowing it to enter the flash tank. At this point, the fluid temperature is higher than the boiling point at that pressure. The fluid rapidly boils and vaporizes in the flash tank, resulting in two-phase separation. The device that brings a fluid to vaporization is not a flash tank, but a pressure relief valve. The function of a flash tank is to provide a space for rapid vaporization of the fluid and separation of the vapor from the liquid. Working principle: The principle of a flash tank relies on the difference in saturated vapor pressures of substances at different temperatures; by reducing the pressure, liquid substances evaporate rapidly, thereby enabling the conversion of liquid substances into gaseous ones. Structure of the flash tank: The structure of a flash tank generally consists of a tank body, feed pipes, discharge pipes, steam pipes, exhaust pipes, etc. Among these, the tank body is the main component of the flash tank; it is usually made of stainless steel, which provides good corrosion resistance, as well as resistance to high temperatures and pressures. The feed pipe and discharge pipe are used to introduce and remove liquid substances from the flash tank, respectively; steam is used to introduce steam into the tank, while the exhaust pipe is used to release the gases inside the flash tank. When the liquid substance enters the flash tank, high-temperature and high-pressure steam is introduced through steam pipes, causing the pressure inside the tank to rise rapidly. At this point, the saturated vapor pressure of the liquid substance also increases, but due to the low temperature of the liquid substance, its saturated vapor pressure remains low. Therefore, when the pressure inside the tube reaches a certain value, the saturated vapor pressure of the liquid substance will be lower than the pressure inside the tank; at this point, the liquid substance will evaporate rapidly and transform into a gaseous state. The advantage of a flash tank is its ability to rapidly convert liquid substances into gaseous ones, thereby improving production efficiency. In addition, flash tanks offer advantages such as energy savings and environmental protection; they are able to convert liquid substances into gaseous ones at lower temperatures, thereby reducing energy consumption and environmental pollution. November 10-14 – TÜV-HAZOP Leader Training Course – Shangyu, Shaoxing. For example, when water is heated under atmospheric pressure, 100°C is the maximum temperature that liquid water can reach at that pressure. Reheating cannot increase the temperature of water; it can only turn the water into steam. The heat absorbed by water as it is heated to its boiling point is called \"sensible heat,\" or specific heat of saturated water. The heat required to convert saturated water into steam at the same atmospheric pressure is called \"latent heat\". However, if water is heated under certain pressure, its boiling point is higher than 100°C, which requires more sensible heat. The higher the pressure, the higher the boiling point of water, and the greater its heat content as well. As the pressure decreases, some of the sensible heat is released; this excess heat is then absorbed in the form of latent heat, causing some of the water to be \"vaporized\" into steam. Points to note: Care should be taken in the design and use of flash tanks. First of all, appropriate liquid substances and steam should be selected to ensure uniform evaporation rates and quality within the flash tank. Secondly, advanced control systems should be employed to monitor and adjust parameters such as pressure, temperature, and flow rate within the flash tank in real time, in order to ensure the safe and stable operation of the equipment. It is necessary to strengthen the training of operators to ensure they can operate the flash tank correctly.