Experimental and theoretical investigation of instationary bubble flow and mass transfer in a bubble column

In many chemical processes, chemical reactors and storage vessels are used under high pressure and temperature conditions. In case of a sudden decrease of the pressure a large amount of steam and gas is generated by flashing of the liquid and re-volatilisation of dissolved gaseous substances. As a result, the liquid level inside the vessel swells and a two-phase blowdown from the vessel may occur. In the present work a water-carbon dioxide system is examined. The time dependent pressure, the axial profile of the void fraction and its distribution over the cross sectional area at different axial positions are measured by electric tomography. For the simulation of the pressure relief an improved mathematical model compared to common calculation methods for pressure relief systems is used. A new method for calculating the maximum possible mass flow of the liquid at the entrance of the blowdown pipe is developed. The calculated values of the pressure and the two-phase mass flow rate agree well with the experimental data.