Patent ID: 6398848
Filing Date: 2002-06-04
Classification: B03C,C04B,Y02W

Abstract:
A method of separating a low density fly ash fraction from an overall group of fly ash entrained in a gas stream comprising the steps of:passing the gas through a duct having a first area; passing the gas stream from the duct through an expansion nozzle; passing the gas stream through the expansion nozzle and into a hollow body having a second area, whereby the second area is larger than the first area; decelerating the gas stream as it enters the expansion nozzle to separate out low density ash particles; collecting the low density ash particles from a hopper positioned adjacent the expansion nozzle; wherein the expansion nozzle is positioned adjacent an electrostatic precipitator; the electrostatic precipitator collects ash from the overall gas stream having a first ash density, and in which the low density ash collected in the hopper positioned adjacent the expansion nozzle is at least 10 percent lower in density than the first ash density produced by the electrostatic precipitator; the low density ash that is collected has a specific gravity of 2.0 or less; the low density ash that is collected in the hopper positioned adjacent the expansion nozzle has a particle size distribution that is predominantly in the range of from between 30 microns to 400 microns; and the low density ash that is collected includes a major amount of frothy, semi-solid particles with both internal and external porosity and a minor amount of hollow particles with thick walls containing internal and external pores.