The Measurement of Concentration Stability of the Fluidized Bed Aerosol Generator by Measuring the Pressure Drop of Sampling Membrane Filter
用滤膜压力降法研究气溶胶发生器输出浓度的稳定性

The fluidized bed aerosol generator, which can produce dry particles with a wide micron size distribution and high concentration, is an important instrument in aerosol research. The generator has been designed for our studies, such as the improvement of the PM10 impactor and the character of aerosol collection, and the powder reservoir was appended to feed the powder into the fluidized bed continuously. But its stability of outlet aerosol concentration was not satisfied well in the past applications, and it was mainly affected by the stability of powder entrancing into the bed, so the feeding system of generator needed improving. Based on the relation between the collected mass of an aerosol and the pressure drop of sampling membrane filters, the stability was characterized by measuring the pressure drop in this work. By this method, the parameters affecting feeding system were discussed firstly, and then a method putting some silica gel into the powder reservoir in order to improve powder feeding system stability was put forward. In the tests, the number of silica gel layer was changed from 1 to 4, the flow rate was varied from 600 to 1000 L/h, and the stability of generator under these conditions was tested respectively. Finally, it can be concluded that the stability of this generator is below 30% with 1 to 3 silica gel layers in the powder reservoir and 800 to 1000 L/h flow rates. As a result, the generator can meet the aerosol research well.