Transmission of Alkali Aerosols through Sampling Systems

In biomass gasification, particles such as condensed alkali salts pose a threat on equipment. Due to high loads of condensable tars in the gases, sampling of these particles to liquids and subsequent analysis of the liquid is frequently the method of choice for measuring the alkali concentration in the gas. However, little is known about the collection efficiency of liquid sampling devices. By measuring the aerosol transmission using a surface ionization detector, two continuous sampling systems are compared with conventional impinger bottles. A low collection efficiency for the latter was found, but down to nearly zero transmission for the continuous sampling systems. The main mechanisms for mass transfer from gas to liquid are discussed with emphasis on particle removal in gas slugs in two-phase flow inside tubes of the sampling system.