New carbon dioxide utilization technology - supercritical carbon dioxide extraction
Supercritical carbon dioxide extractionequipment - a new type of carbon dioxide utilization technology, is currentlycommitted to the development of this technology at home and abroad. Thetechnology can produce high value-added products, extract substances that cannot be extracted by chemical methods in the past, and is cheap, non-toxic, safeand efficient. It is suitable for chemical, pharmaceutical, food and other industries.Carbon dioxide is a very common gas, but excessive carbon dioxide will causethe "greenhouse effect", so it is important to make full use ofcarbon dioxide. Traditional carbon dioxide utilization technology is mainlyused to produce dry ice (fire extinguishing) or as food additives.
In the supercritical state, CO2 fluid hasthe dual characteristics of gas-liquid two-phase. It not only has the same highdiffusion coefficient and low viscosity as gas, but also has the similardensity and good solubility with liquid. Its density is very sensitive totemperature and pressure changes, and is proportional to the solubility withina certain pressure range, so the solubility of the substance can be changed bycontrolling temperature and pressure.
When the temperature is higher than thecritical temperature Tc=31.26 C and the pressure is higher than the criticalpressure Pc=7.2 MPa, the properties of carbon dioxide will change. Its densityis close to the liquid, its viscosity is close to the gas, and its diffusioncoefficient is 100 times that of the liquid, so it has an amazing solubility.It can dissolve many kinds of substances and extract effective components. Ithas wide application prospects.
Supercritical carbon dioxide (CO2) iscommonly used as an extractant at present.
1, the critical temperature of CO2 is 31.1C, the critical pressure is 7.2MPa, and the critical condition is easy toachieve.
2, CO2 chemical properties of inactivewaves, colorless, tasteless, non-toxic, safe.
3, cheap, high purity, easy to obtain.
The principle of supercritical carbondioxide extraction and separation process is that supercritical carbon dioxidehas a special dissolving effect on some special natural products, and therelationship between the dissolving ability of supercritical carbon dioxide andits density is utilized, that is, the influence of pressure and temperature onthe dissolving ability of supercritical carbon dioxide. In the supercriticalstate, the supercritical carbon dioxide is contacted with the substance to beseparated, so that it can selectively extract the components with differentpolarity, boiling point and molecular weight. Of course, the extracts obtainedunder different pressure ranges can not be single, but the mixed components canbe obtained under controlled conditions. Then the supercritical fluid can betransformed into ordinary gas by means of decompression and heating, and theextracted material can be completely or basically precipitated, so as toachieve the purpose of separation and purification.