The process of purification consists of three main stages. On the first stage the gas from the source cylinder (Source CO2) is being transferred in the measuring cylinder through the block of drying (H2O adsorber) with a NaX zeolite. An amount of the dried gas can be defined by a pressure drop in the Measuring cylinder by manometer PI1. It’s rationally to have maximum possible pressure, comparable with the pressure in the source cylinder, in the measuring cylinder. When performing these conditions Measuring cylinder is capable to contain before 2 m3 (on normal conditions basis) of liquefied CO2. The rate of filling of the Measuring cylinder can be established by the valve MV8b (valves MV7,8,8a are completely opened) and must not exceed 1 bar/min.
On the second stage the gas by portions of 240-280 normal litres is being transferred to the Freezer1, is included in 50-liter capacity (Dewar). Dewar is filled by the liquid nitrogen. Valves MV1,1a,6,7 must be open, MV8 – is initially closed. CO2 in the Freezer1 moves to a solid state. The amount of frozen CO2 can be defined by the drop of pressure in the Measuring cylinder by the PI1 manometer. After the moving the sufficient amount of the gas, valve MV7 must be closed. An achievement of full freezing of the portion of CO2 is being defined by the display of the mechanical vacuum gauge VI2 at the valve MV4 is opened. Admixtures remaining in the gas phase are being evacuated by the adsorption vacuum pump (Adsorber), which is filled by the active carbon “CKT”. Process of evacuation lasts until the residual pressure not exceed 8*10-3 Torr. The rate of residual vacuum is being controlled by the ionisation vacuum gauge VI1. The efficiency of Adsorber increased by placing it with the Freezer1 in Dewar.
On the third stage it’s necessary to carry out the additional removing of O2 from CO2 by the absorbing oxygen in H2O & O2 adsorber. First, Freezer1 is connected to the electric heater (Heater), for warming up to room temperature (valves MV1,1a,1b,6 are opened). Warming process is controlled by the pressure changing which is displaying on PI1 manometer. After that gaseous CO2 is being dosed through the H2O & O2 adsorber right into prepared steel 40-liter cylinders (valves MV9, 9a are opened) or into the cylinder for the clean gas (Pure CO2), or is translated to the initially frozen Freezer2 (valves MV3, 3a are opened). Freezer2 is placed in the reservoir with liquid N2 (Reservoir). The volume of CO2 accumulated in Freezer2 must not exceed 1 m3 (at normal conditions). H2O & O2 adsorber is equipped by active copper, carried by the silica gel; process of O2 absorbing occurs at increased temperature. This block has additional zeolite cartridge for the fine drying. Rate of the gas passing through the H2O & O2 adsorber must not exceed 40 litres/min (at normal conditions). After the removing of CO2 from the Freezer1, the last is being cooled to the room temperature, and then put in Dewar again and cooled to the temperature of liquid nitrogen. Hereon it is ready to be filled by the next portion of CO2.