I used wood pellet as a fuel and automatic ignition system fitted there. Actually, tar produce due to incomplete combustion, but the boiler is highly efficient design. I find in some paper, above 1000 degree PAH (polycyclic aromatic hydrocarbon) form, which stains in wall of boiler and act as resisting device. My goal is to remove tar while operating the boiler, if there is any chemist please help me to find the chemical/catalyst which reduce/remove tar production. Thanks for reply Baryon.