Provided is a combustion system using a catalyst having better denitration efficiency at low temperatures, during a selective catalytic reduction reaction in which ammonia is used as a reducing agent.
This combustion system comprises: a combustion device that combusts fuel; an exhaust path through which flows exhaust gas generated from the combustion of fuel in the combustion device; a dust collection device that is arranged on the exhaust path and collects ash dust/dust in the exhaust gas; and a denitration device that is arranged on the exhaust path and removes nitrogen oxides from the exhaust gas by means of a denitration catalyst, wherein the denitration device is arranged downstream of the dust collection device on the exhaust path, and the denitration catalyst contains vanadium oxide including vanadium pentoxide and has a defect site in which an oxygen atom is deficient in a crystal structure of the vanadium pentoxide.