Particulate size distribution and carbon conversion during oxidation of biomass from livestock farming

Agriculture greatly contributes to the annual emissions atmospheric pollutants. Cow manure is a lignocellulosic material, which higher heating value (HHV) typically varies between 15 and 20 MJ/kg on dry basis. As solid biofuels it shows relatively low coke content, at the expense of the relative mass fraction of moisture, ash and volatile matter. Although animal manure utilization has been widely studied during the last decades it has not gained significant attention in Bulgaria, due to the availability of other fossil and renewable resources. However, considering the pollution control and the circular economy perspectives the potential utilization of this type of solid residue matter deserves extensive research. Preliminary in-house studies on solid biomass residue confirmed the direct relation between the high volatiles content and the emissions of gaseous and particulate matter (PM) in the exhaust. The present work aimed to study the rate of carbon conversion and the size segregated PM in the flue gases, obtained during direct oxidation of cow manure. The experiment was carried out in a tubular flow furnace, capable for providing well controlled operation conditions, such as: atmospheric pressure, temperatures of 950 °C, partial pressure of the oxygen (O 2 ) in the air supply flow of 21 vol. % at an inlet air flow rate of 10 l/min. The temperature dependence of the carbon conversion and the gaseous pollutants was obtained along with the size distribution curve of the PM, considering particulates of size from 0.016 to 10 microns. As expected, the fractions of PM with aerodynamic diameter equal to or smaller than 1 micron were the dominant one.