Latent heat of evaporation
Since the latent heat of evaporation of CO2 is the lowest among known solvents (for example, the latent heat of evaporation of CO2 is 175.56J/g, the corresponding latent heat of evaporation of water is 2.26kJ/g, and the latent heat of evaporation of ethanol is 852.7J/g), therefore, supercritical The energy consumption of the CO2 fluid extraction process should be relatively low, which has always been the advantage of this technology.
However, the energy consumption of the supercritical CO2 fluid extraction process is affected by the process flow and operating parameters, so it is difficult to compare, so there are few reports on the energy consumption comparison between the supercritical CO2 fluid extraction process and the traditional separation process.
Ethanol extraction process vs. supercritical CO2 extraction process
So we take the ethanol extraction process as an example to compare the energy consumption of the supercritical CO2 extraction process.
The process of concentrating organic compounds such as ethanol from ethanol dilute aqueous solution using supercritical CO2 fluid requires much less energy than conventional rectification.
Starch fermentation is used to produce ethanol, and the ethanol content in the fermented liquid is usually 6%~10% (mass). Generally, the distillation concentration method is used, and the ethanol can be concentrated to a purity of 95% through two-stage rectification. The whole concentration process can consume more.
Using supercritical CO2 extraction technology, from the analysis of phase equilibrium data, the phase equilibrium composition of CO2 fluid added to ethanol aqueous solution, compared with the gas-liquid equilibrium relationship of distillation, ethanol has a higher selectivity and is easier to separate, and industrialization has great advantages.