When water is heated at atmospheric pressure, 100 °C is the highest temperature allowed for liquid water at that pressure. Reheating does not increase the temperature of the water, but only converts it into steam. The heat absorbed by water before it rises to the boiling point is called “sensible heat”, or the saturated water sensible heat. The heat required to convert saturated water into steam at the same atmospheric pressure is called “latent heat.”
However, if the water is heated under a certain pressure, the boiling point of water will be higher than 100 °C, so more sensible heat is required. The higher the pressure, the higher the boiling point of water and the higher the heat content. The pressure decreases and part of the sensible heat are released. This part of the excess heat will be absorbed in the form of latent heat, causing some water to be “flashed” into steam.
Working principle of the flash column: The method of flash column uses the volatility of each component in the liquid mixture, and uses the heat energy as a medium to partially vaporize it, thereby enriching the light component in the vapor phase and enriching the liquid phase in the liquid phase. The principle of using silica gel as stationary phase in flash column is an equilibrium between adsorption and desorption. So if the sample and silica gel adsorption are relatively strong, it is not easy to flow out. This will happen, the back point first out, and the front point after out. Then it’s better to adopt alumina as the stationary phase to prevent samples from leaking and allows the mobile phase passes through.
In fact, in the distillation calculation of the flash column, each theoretical plate must perform such a flash calculation, but at this time the general name is called “equilibrium level” calculation, which is theoretically stricter, and its calculation content is exactly the same Every rigorous or “flash” calculation or “equilibrium level” calculation must meet the following three major balances: mass balance, energy balance, and phase balance.
Therefore, a standard “flash” calculation module can handle both changes in pressure (increasing or decreasing) can also handle heat exchange and work exchange. The internal and external work exchange and heat exchange are mainly reflected in the energy balance, and the mass balance and phase balance mainly determine the vaporization fraction and vapor phase. In addition, there is a very important and difficult task in the “flash” calculation.
Flash column is to determine whether the state you specify is in the vapor-liquid two-phase, or only the vapor-phase or liquid-phase only. Moreover, the calculation of liquid-liquid equilibrium, in general, also requires “flashing” calculations. Of course, some software orders come out because the calculation is more difficult. The above description of “flashing” is only one word, not very rigorous, but relatively more accurate. In short, whether you use PROII, ASPEN or H “YSIS, Flash” calculation is really its most basic core.