Properties of RE–W cathode and its application in electrostatic precipitation for high temperature gas clean-up

In this paper, three rare earth tungsten (RE–W) electrostatic precipitation cathodes (cerium–tungsten (Ce–W), lanthanum–tungsten (La–W) and yttrium–tungsten (Y–W)) were prepared by powder metallurgy. The microstructure and the electron emission properties of the three cathodes were examined. The application of the Y–W cathode in high temperature electrostatic precipitation was investigated. Results show that the addition of the rare earth reduces the tungsten crystal size, with yttrium (Y) affecting the crystal size more significantly than lanthanum (La) and cerium (Ce). The rare earth (cerium, lanthanum or yttrium) exists, in the form of crystalline tungstates, at the tungsten (W) crystal boundary. The effective work function of the La–W cathode has the lowest value of 2.88 eV at vacuum condition, but the Y–W cathode shows the best emission properties at atmosphere pressure. The collection performance of an electrostatic precipitator (ESP) using the Y–W cathode was investigated by ash particles with various resistivity and size distribution at various temperatures. The particles with higher resistivity tend to be collected effectively at high ambient temperature, and the collection efficiency rise with the increase in temperature. If the resistivity of dusts is not high enough, corresponding to the highest collection efficiency, there exists an optimum temperature value. As in a conventional corona ESP, the larger particles are collected more effectively in an ESP with Y–W cathode.