Analysis of dissolved gas in the application of liquid piston gas compression

Liquid piston compression technology is being explored as a way to achieve high-pressure gas compression in Compressed Air Energy Storage (CAES) systems. When combined with a porous medium, a liquid piston compressor is able to provide near-isothermal compression, and high efficiency. However, the gas being compressed can dissolve into the liquid resulting in loss of compressed gas output. Also, the dissolved gas in the liquid lines can cause aeration that causes damage to pumps and valves. To understand this gas transport phenomenon in the liquid and to evaluate the total amount of gas dissolved, a numerical model was developed. Dispersion due to the porous medium is found to be the dominant mode of mass transfer. The dispersion coefficient is calculated based on an experimental correlation that is given in terms of flow velocity, porous medium geometry and molecular diffusion coefficient. The numerical model is used to investigate a case study in which a water liquid piston is used for air compression. The amount of dissolved gas under various conditions is calculated, such as gas concentration of the inlet flow to the compressor and discharge pressure to the storage tank at the end of compression. The effects of different types of liquids are also quantified by applying in the model the different solubility values of gases in liquids.