APPLICATION OF EXPANDED PTFE MEMBRANE FILTER AND ELECTRICAL SENSING ZONE METHOD TO IN-STACK PARTICLE SIZE MEASUREMENT (AIR POLLUTION, SOURCE TEST, CASCADE IMPACTOR).

摘要

A particle size distribution measurement method using an in-stack filter and measuring with the electrical sensing zone (ESZ) method has been studied experimentally. An expanded polytetrafluoroethylene (PTFE) membrane filter has been shown to meet the requirements for in-stack sampling. Its collection characteristics for submicrometer aerosol filtration have been determined using sodium chloride aerosol and coal-fired fly ash particles in the 0.075-1.00 um diameter range, with the face velocity varying between 4 and 26 cm/sec. The results of the filter characteristics measurement have been compared with the available theories and data and are in reasonable agreement.;A variety of electrolytes for use with the ESZ method have been selected based on the chemical properties of the sample and tested to determine which are best for measuring the size distribution. Chemical and physical dispersants have been tested to determine their behavior in removing particles from the filter. The collected particles have been shown to be easily removed from the filter and redispersed into the electrolyte for analysis with the ESZ method.;A direct comparison was made of particle size distributions obtained from a coal-fired power plant by a cascade impactor and by the in-stack filter and ESZ method. A good agreement was found in the particle size distributions obtained by these two methods at a site on a coal-fired boiler upstream of the inlet of an electrostatic precipitator (ESP) using a 30 micrometer ESZ aperture. The agreement is less satisfactory at the outlet of the ESP, where a smaller aperture is required.;It is concluded that the in-stack filter and ESZ method involves a much simpler, well established and relatively inexpensive technique for collecting and analyzing a particulate matter sample. The method can yield results with a high degree of confidence.