Influence of a Direct Firebed Cooling in a Residential Wood Pellet Boiler with an Ash-Rich Fuel on the Combustion Process and Emissions

Abstract

The crucial point in inorganic particle formation from biomass combustion is the temperature-dependent release of inorganic compounds, especially potassium (K). Currently common wood fuels comprise a comparatively low amount of K, but the increased usage of wood energy requires new feedstocks in the future. Potentially new feedstocks like short-rotation-coppice (SRC), fuels from agriculture (e.g. straw) or wood from broad-leafed trees of low rotation contain usually high ash contents and/or high potassium concentrations. Apparently, these feedstocks will cause increased inorganic particle emissions from biomass combustion processes. The principle of a decreased firebed temperature as primary measure aiming at a retention of K in the ashes of the firebed is a common approach for particle emission reduction and was investigated in several previous studies. The present study describes the usage of an ash-rich fuel from SRC-pellets made from willow in a residential pellet boiler modified with an unique protot...