Physical and Chemical Characteristics of Particulate Matter (PM_1) Emitted from Combustion of a Bituminous Coal in Air and Oxy-Fuel Environments

摘要

This work examined the physical and chemical characteristics of submicron particulate emissions (PM_1) from pulverized bituminous coal burning under either conventional air or oxy-fuel conditions. Oxy-fuel combustion is a process that takes place in O_2/CO_2 environments, which are achieved by removing nitrogen from the intake gases and recirculating large amounts of flue gases to the boiler; this is done to moderate the high temperatures caused by the elevated oxygen partial pressure therein. In this study, combustion took place in a laboratory laminar-flow drop-tube furnace (DTF) in environments in either air or oxy-fuel conditions. A Pittsburgh bituminous coal was burned at a DTF temperature of 1400 K. Scanning Electron Microscope (SEM) was used to observe the morphology of the submicron particles and SEM coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS) technique was used for the chemical analysis of the PM_1. Bimodal ash particle size distributions were observed in the submicron region. Mass fractions of the major metal oxides in submicron ash particles also showed a bimodal distribution. Both the submicron emission yield and the major metal oxides in the submicron particles were typically lower in oxy-fuel condition than those in air. S was the preeminent component of the PM_(0.1-0.18) (stage 9) while Si and Al were the greatest component of the PM_(0.56-1) (stage 6). Scanning Electron Microscopy (SEM) revealed that submicron particles were spherical which is attributed to vaporization of minerals followed by condensation and particle growth.