Theoretical and experimental study on a liquid compression reactor
Industry is continuously looking for cleaner and more energy efficient processes and equipment. Twente University assists in that and studied the pulsed compression reactor(PCR). In this reactor a freely moving piston reciprocates in a cylinder compressing a reaction gas mixture to very high temperatures and pressures. The piston is lubricated by a small very narrow gas layer but this leads to gas leakage and fitting problems due to thermal expansion.
Replacing the solid piston by a liquid column these problems can be solved. Two types of liquid compression reactors based on the water hammer phenomena are proposed and studied both theoretically and experimentally. The first is single gas pocket compression, similar to the PCR. The second is bubbly mixture compression. Abruptly stopping of a bubbly column leads to the formation of high pressure waves propagating through the mixture. This leads to extreme pressures and temperatures in the bubbles during compression expansion cycle.
In a simple experimental setup pressures in the liquid up to 90 bar are measured having only 6 bar driving pressure in a tube with inner diameter of 8 mm.
The chemical reactor studied can be applied to several chemical processes. Production of ethylene, acetylene and hydrogen directly from methane is one of such processes. It was found by modeling that 15 bar pressure waves could already be sufficient for almost 100% methane conversion if it is diluted with argon. If a high density liquid metal used instead of water lower pressures are sufficient and/or argon can be replaced with hydrogen. Formation of solid products i.e. soot is no problem anymore because it can easily be filtered out.
In the modeled chemical process liquid is inert and gas reactive. For other processes both gas and liquid can be reactants. Also solid catalysts can be added to the mixture to enhance some processes. Summarizing, the liquid compression technology gives many opportunities for many processes.