What is Supercritical CO2 Fractionation Column
The supercritical CO2 Fractionation Column uses the difference in volatilities of the components in the liquid mixture to purify substances. In the column, the liquid flows from top to bottom by gravity, while the gas flows counter currently to the liquid from bottom to top by pressure difference.
Two types of Supercritical CO2 Fractionation Column
The good contact of the two-phase fluid is formed by the tray or packing installed in the tower. Therefore, the height of the tower can be divided into a plate tower and a packed tower according to the structure of the internal parts.
The structure of the Supercritical CO2 Fractionation Column equipment determines the fluid dynamics and mass transfer performance of its operation to a certain extent. The plate tower and the packed tower have their own characteristics:
Five differences between plate type and packing type Supercritical CO2 Fractionation Column
Component Concentration Changes
There are a certain number of trays in the plate-type Supercritical CO2 Fractionation Column, and the gas passes through the liquid layer on the trays in the form of a bubbling jet from the bottom of the column to make the two phases contact and carry out mass transfer; the component concentration of the two phases increases along the height. Changes in steps. A certain height of packing is installed in the packing tower, and the gas-liquid two-phase conducts countercurrent mass flow along the packing surface. The component concentrations of the two phases vary continuously along the height of the column.
The pressure drop of the packed supercritical CO2 Fractionation Column is generally smaller than that of the plate column. Less pressure drop means less power consumption and lower operating costs.
Superficial gas velocity
The supercritical CO2 Fractionation Column’s supercritical gas velocity is generally larger than the traditional packed column. A high superficial gas velocity means a large production capacity, and abnormal phenomena such as liquid flooding will not occur even at a relatively high gas velocity. However, the superficial gas velocity of the newly packed tower has been greatly improved.
The plate-type CO2 Fractionation Column has greater operating flexibility and is more suitable for occasions where the gas and liquid loads fluctuate greatly, especially since the operating flexibility of the float valve tower is the largest. Plate towers are also suitable for occasions where the liquid-gas ratio fluctuates greatly.
The efficiency of the plate CO2 Fractionation Column is relatively stable, and the efficiency will increase with the increase of the column diameter. Packed towers have high efficiency when the diameter of the tower is small, and the efficiency will decrease when the diameter of the tower increases, but the new regular packing is an exception. The cost of the plate tower is lower than that of the packed tower when the diameter is large, but for the tower with a diameter of less than ∅800, the cost of the packed tower is lower; the installation and maintenance of the plate tower are easier than that of the packed CO2 Fractionation Column, especially the tower with a larger diameter.
Read More: Supercritical carbon dioxide
How to choose Supercritical CO2 Fractionation Column
When selecting the tower type, various factors should be considered comprehensively, and the appropriate tower type should be selected according to the main contradiction. For corrosive materials, a packed tower should be used, because the filler can be ceramic or other corrosion-resistant materials; a packed tower should be used for materials that are prone to foaming because the filler is not easy to form foam; heat-sensitive materials should operated under reduced pressure to prevent Overheating, so a packed tower with a small pressure drop should be selected; plate towers are suitable for materials with suspended solids or easy scaling because most packed towers are easy to block; if the material system is accompanied by thermal effects in the mass transfer process, heat needs to be extracted A plate tower is suitable.