Development of a detailed kinetic model for the combustion of biomass

International audienceIn the context of the growing utilization of biomass to produce energy and of the related need to decrease pollutant emissions from domestic wood combustion devices, this paper presents a new kinetic model of wood combustion considering especially in details the gas-phase reactions related to the combustion of the tars produced by the biomass devolatization. The tar production is predicted using a semi-detailed mechanism of the literature. The tar gas-phase combustion model has been built as a compilation of literature mechanisms already proposed for these species, except for hydroxyacetaldehyde for which a new oxidation mechanism has been written. Experiments on the thermochemical behavior of three types of wood (beech, fir and oak) were also performed in parallel of this work using Thermogravimetric Analysis (TGA). The new detailed kinetic model of wood combustion, BioPOx (Biomass Pyrolysis and Oxidation), has been tested against a wide range of experimental results published in literature. This model fairly reproduces experimental results for pyrolysis and combustion of biomass and its constituents, key produced tars from biomass pyrolysis, and key compounds for Polycyclic Aromatic Hydrocarbons (PAH) formation, for a wide range of experimental devices and operating conditions.

Wood washing: influence on gaseous and particulate emissions during wood combustion in a domestic pellet stove

International audienceNowadays, the use of biomass increasingly replaces the fossil fuels for the domestic heating production. In order to reduce pollutant emissions from biomass combustion, wood was washed at room temperature in order to represent natural rain leaching before burning in a recent pellet stove (2010s) of nominal output of 6.3 kW. Raw and washed woods were combusted for three different types of wood (oak, beech and fir) and the study focused on their particulate and gaseous emissions (Total Suspended Particles (TSP), Particulate Matter with diameter below 2.5 μm (PM2.5), carbon monoxide (CO), nitrogen oxides (NOx) and Total Volatile Organic Compounds (TVOC)). Polycyclic Aromatic Hydrocarbons (PAH), aldehydes and wood tracers as phenols compounds were also measured. In addition, considering the toxic equivalent factor, the human health impact of adsorbed and gaseous PAH is considerably reduced (96%) in the case of washed fir combustion. Emission factors of CO and TSP for washed wood combustion also show a decrease up to 50% depending on the type of wood used. Furthermore, phenolic compounds, Benzene, Toluene, Ethylbenzene, Xylenes and Trimethylbenzene (BTEXT) emissions can also be reduced by the washing of biomass. Washed oak combustion leads to a clear decrease by 60% of the total of BTEXT. In the case of phenols emissions, phenol shows a significant decrease by 91% during the combustion of washed fir wood