Method and apparatus for fractionating measurement of aerosols

摘要

In the method for determining the particle size distribution in an aerosol-loaded gas stream, the gas stream (3) is fed through a separation-stage cascade (1) with stepped separation limits and the aerosol concentration is measured before and after each separation stage (2n). From the difference in the two measured values belonging to a separation stage (2n) the respectively deposited particle fraction for neighbouring separation limits is then determined. The method is, in particular, carried out such that the individual separation stages (2n) are connected up stepwise after one another in series, the measurement gas flowing through the separation stages (2n) already connected up, the aerosol concentration being in each case measured with the aid of a photometer after the last separation stage connected up. The corresponding apparatus consists of a separation-stage cascade (1), in which, after each separation stage (21...5), a connection line (41...5) which can be closed by a remote-controlled valve (61...5) leads to a collection tube (5). The aerosol concentration remaining in each case after a selected separation stage (2n) is measured with the aid of a continuous (through-flow) photometer (8) which is arranged downstream of the collection tube (5). A computer-supported evaluation and control unit actuates the valves (6n) in the connection lines (4n) and determines the particle size distribution and total concentration of the aerosol on the basis of the photometer signals measured after the separation stages (2n). <IMAGE>