The challenge for the pump technology is the medium CO2, which is gaseous under normal ambient conditions. It has to be constantly kept in a liquid state through precise monitoring of the process parameters to prevent cavitation damage in the pump. Poor lubrication properties and the high compressibility of liquid CO2 require specially developed pumps with a high level of process reliability. Specifically this means that the pump has to be specially developed for the CO2 application: The power end has to be able to withstand the rod forces resulting from the high suction pressure and optimum lubrication of the bearing points has to be ensured. At the same time, pressure increases up to 1,000 bar create a correspondingly higher temperature increase: This requires effective cooling of the fluid section with cooling channels in the stuffing boxes and valve blocks.
As some components cannot be cooled directly, it is important to adapt the materials and the design so that as little as possible of the generated compression heat is absorbed. Because the CO2 is alternately subjected to compression and expansion, it is necessary to minimise or avoid the temperature rise and the resulting losses.
Another keyword here is the optimisation of dead space in the fluid section of the pump: The optimisation always ensures a high volumetric efficiency. This volumetric efficiency is becoming increasingly important due to the rising processing pressure. Volumetric efficiency influences the flow rate and therefore the function of the entire pump.
Particularly with very high pressures up to 1,000 bar, a design with optimised dead space volume in the fluid section is crucial to the general function of the pump. Incorrectly designed liquid end components can not only cause the pump to cease pumping but also merely to compress and expand without discharging the desired volume of the medium.