Pollutants formation during single particle combustion of biomass under fluidized bed conditions: An experimental study

Abstract

The present work aimed at investigating the effect of several operating parameters on the experimentally measured primary gaseous products and particulate matter (PM), as well as on the reaction rate and the total conversion, obtained during single particle combustion of biomass in fluidized bed conditions. In focus were the following operating parameters: initial mass of the fuel particle (ranging between 0.1 and 0.5 g), oxygen partial pressure (from 5 to 21 kPa), bed temperature (between 700 and 900 °C) and biomass type. The experiment was carried out at atmospheric pressure, using five different types of solid biofuels. The primary carbon conversion products were carbon dioxide (CO2) and carbon monooxide (CO). The fuel bound nitrogen was converted mainly to nitrogen monooxide (NO). However, biomass having higher nitrogen content showed lower nitrogen conversion to NO, but higher absolute NO emissions. Particulates of submicron size, with unimodal size distribution, were the dominant fraction of particulate emissions for all fuels. The mass normalized PM concentration was reduced by three orders of magnitude during char combustion, thus supporting the hypothesis that PM formation is highly affected by the availability of volatile matter and the ash composition.