Development And Experimental Study Of A Little Scale Supercritical CO₂ Extraction Device

SCFE(supercritical fluid extraction) is a new chemical separation technology. After the last 30 years development, the SCFE technology already became an energy-saving chemical separation method, which has caused more and more researchers'widespread attention in the world. Whether in basic theory research or application, this technology has all made many progress, but because people's study is not still enough on phase equilibrium in the SCFE process and the transmission fundamental, many difficulties are still remained in the SCFE technology ,such as process, equipment and project respect. So, SCFE application is limited. In this paper, choosing CO2 as the perfectly SCF medium, the solubility parameter theory of SCFE and the mass transfer mechanism of SCF(supercritical fluid) extraction of solid raw material are analyzed. A little scale SC-CO2 fluid extractor is developed and exploited, which is characterized by little system, simply operation, widely application, safety running, and low failure rate, the operation steps of the system, the CO2 filling way, the extract condition control, and the separation way and so on are analyzed and designed. And, a three factors and three dimensions orthogonal test for the extraction of the shelled peanut was carried out by the SC-CO2 fluid density took for the primary control parameter for the first time, and the detailed analysis to the experimental results is carried on;Finally, a comparison between the experimental results of this topic and the literature is provided.The analysis of the solubility parameter theory of SCFE and the mass transfer mechanism of SCF extraction of solid raw material show that:The dissolving capacity of a solute in a SCF is related to the properties and condition of the SCF, and to the properties of solute, especially to its molecular weight, molecular structure and volatility and so on;main influencing factors of the mass transfer rate in the SCFE process include the diffusion coefficient of component A to component B, the size of the solid particle, time, the initial molar density of component B in the solid particle, the molar density of component B and component A in CO2 fluid, the speed of flow of CO2, the viscosity coefficient of CO2 and so on;thereby, it is obvious that the plan of the static secondary extraction as the small test plan have the feasibility, and a conclusion can be drawn that the CO2 density as the primary control parameter of the extraction is more reasonable. The analysis to the result of the three factors and three dimensions orthogonal experiment which is under the main control of parameter with SC-CO2 density show that: Under the present topic experimental condition, the optimum technological conditions for the SC-CO2 fluid static secondary extraction of shelled peanuts are the CO2 density 750kg/m3,the extraction temperature 45℃, the loading 100g;in these factors which affect the SC-CO2 fluid extraction, the CO2 density is the maximal effect on the extraction rates, followed by temperature, and the loading amounts are the minimal effect on the extraction rates;The extraction rate of SC-CO2 extraction of shelled peanut increases with the rise of the CO2 density, increases along with the temperature increases, reduces along with the rise of the loading.The comparative analysis to the experiment result of the present topic and the literature comes to a conclusion: the extraction rates of the static extraction is lower than that of the dynamic extraction;the small test of SC-CO2 fluid extraction experiment adopting the static secondary extraction is reasonable and economy, the static secondary extraction scheme has more superiority as the optimization research scheme of the extraction technological conditions;Compared with the extraction pressure, the SC-CO2 fluid density has more direct effect to extraction rates.