The density issue of vapor-liquid mixed feed
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I am manually calculating the gas and liquid phase loads as well as the densities for the methanol-water distillation system. I’m facing a problem: in the case of a mixed vapor-liquid feed, with a feed temperature of 90 degrees Celsius, a top temperature of 64.7 degrees Celsius, and a bottom temperature of 109 degrees Celsius, how can I estimate the average densities of the gas and liquid phases in the rectifying section and the stripping section?
I’ll try to figure it out myself; is there anyone skilled who can help me answer it? Thank you
A binary distillation column? I have a method, but I’m not sure if it will work. The vapor and liquid phase compositions of each tray, including those at the top and bottom of the tower, are determined using the tray-by-tray calculation method; thereafter, the density calculation formulas for gas and liquid mixtures are applied respectively.
I can give you a hint: check out books related to chemical engineering. Calculations related to gas and liquid densities. I have some information here; I’m not sure if it can help you: 2. Calculation of dew point temperature and equilibrium liquid phase composition (given gas phase composition and total pressure). Since: or: Substituting into the above equation gives: This equation can be used to calculate the dew point temperature and equilibrium liquid phase composition of a gas mixture. The trial-and-error method should also be applied in the calculations. The trial-and-error principle is exactly the same as that used for calculating the bubble point temperature. It should be noted that using relative volatility for the aforementioned calculations can yield similar results. 3. Partial vaporization of a multi-component solution: When a multi-component solution is partially vaporized, the amounts and compositions of the two phases change with pressure and temperature. Their quantitative relationships can be derived as follows: By performing a material balance on a given amount of the liquid feedstock, we obtain: Total mass F = V + L (1) For any component (2) Substituting (2) into the equation gives: … (3) By substituting L = F – V from (1) into (3), we obtain equation (4). In this equation, – is the vaporization rate ； – The composition of any component i in the liquid phase mixture ； －Composition and molar fraction of component i in the liquid phase after partial vaporization ； – Composition of component i in the gas phase after partial vaporization. When the temperature and pressure of the system are constant, the above formula can be used to calculate the vaporization rate and the corresponding gas-liquid phase compositions. Conversely, when the gasification rate is constant, the above formula can also be used to calculate the gasification conditions.
It’s more convenient to use ASPEN