A combustion system operated at low cost is provided. A combustion system 1 includes a combustion device 10 that burns fuel, an exhaust line L1 through which exhaust gas flows, the exhaust gas being generated through combustion of the fuel in the combustion device 10, a dust collector 50 that is disposed in the exhaust line L1 and that collects dust in the exhaust gas, and a denitration device 90 that is disposed in the exhaust line L1 and that removes nitrogen oxide from the exhaust gas using a denitration catalyst. The denitration device 90 is disposed downstream from the dust collector 50 in the exhaust line L1. The denitration catalyst contains 43 wt % or more of vanadium pentoxide and has a BET specific surface area of 30 m.sup.2/g or more.

A catalytic converter having a honeycomb structure for the aftertreatment of exhaust gases of an internal combustion engine and having an electrically heatable heating plate, wherein the heating plate is formed from a plurality of metal foils which are stacked on top of one another to form a layer stack and are finally wound to form a honeycomb structure having a plurality of flow ducts, wherein the heating plate has arranged therein an insulating means via which electrical insulation is formed between at least two mutually adjacently arranged wound metal foils.

A catalyst apparatus is disposed in an exhaust passage for exhaust gas discharged from an internal combustion engine and includes a catalyst section for purifying the exhaust gas, and a heater section disposed upstream of the catalyst section in the exhaust passage and adapted to heat the exhaust gas. The heater section is configured such that a plurality of metal thin plates and insulators are stacked alternatingly are wound. The heater section contains a pair comprising a positive electrode and a negative electrode for energizing and heating the metal thin plates. The positive and negative electrodes are joined to each of the metal thin plates in such a manner that the positive electrode is located away from the negative electrode in a winding direction of the metal thin plates.

There is provided a catalyst that exhibits a high denitration efficiency at a relatively low temperature and does not cause oxidation of SO.sub.2 in a selective catalytic reduction reaction that uses ammonia as a reducing agent. A denitration catalyst molded in a block shape contains 43 wt % or more of vanadium pentoxide. The denitration catalyst has a BET specific surface area of 30 m.sup.2/g or more and is used for denitration at 200 C. or lower.

A metal substrate for catalytic converter for purifying an exhaust gas includes a honeycomb core with metal flat foil and corrugated foil stacked in layers, and an oxide film having a thickness of 0.1 m or more and 10 m or less is formed in a predetermined range including an exposed end surface exposed toward the gas inlet side. The oxide film contains at least a first alumina including -alumina and a Fe oxide. The -alumina contains -alumina with solid-solved Fe and -alumina with no solid-solved Fe. In the oxide film, the content of the first alumina is 30% by mass or more and 99.5% by mass or less, the content of the Fe oxide is 0.5% by mass or more and 40% by mass or less, and the content of Fe is more than 7% by mass and 35% by mass or less.

A metal substrate for catalytic converter for purifying an exhaust gas includes a honeycomb core with metal flat foil and corrugated foil stacked in layers, and an oxide film having a thickness of 0.1 m or more and 10 m or less is formed in a predetermined range including an exposed end surface exposed toward the gas inlet side. The oxide film contains at least a first alumina including -alumina and a Fe oxide. The -alumina contains -alumina with solid-solved Fe and -alumina with no solid-solved Fe. In the oxide film, the content of the first alumina is 30% by mass or more and 99.5% by mass or less, the content of the Fe oxide is 0.5% by mass or more and 40% by mass or less, and the content of Fe is more than 7% by mass and 35% by mass or less.

There is provided a catalyst that exhibits a high denitration efficiency at a relatively low temperature and does not cause oxidation of SO.sub.2 in a selective catalytic reduction reaction that uses ammonia as a reducing agent. A denitration catalyst is obtained by coating a substrate with a catalyst component. The catalyst component contains 43 wt % or more of vanadium pentoxide and has a BET specific surface area of 30 m.sup.2/g or more. The denitration catalyst is used for denitration at 200 C. or lower.

A combustion system operated at low cost is provided. A combustion system 1 includes a combustion device 10 that burns fuel, an exhaust line L1 through which exhaust gas flows, the exhaust gas being generated through combustion of the fuel in the combustion device 10, a dust collector 50 that is disposed in the exhaust line L1 and that collects dust in the exhaust gas, and a denitration device 90 that is disposed in the exhaust line L1 and that removes nitrogen oxide from the exhaust gas using a denitration catalyst. The denitration device 90 is disposed downstream from the dust collector 50 in the exhaust line L1. The denitration catalyst contains 43 wt % or more of vanadium pentoxide and has a BET specific surface area of 30 m.sup.2/g or more.

A catalyst apparatus is disposed in an exhaust passage for exhaust gas discharged from an internal combustion engine and includes a catalyst section for purifying the exhaust gas, and a heater section disposed upstream of the catalyst section in the exhaust passage and adapted to heat the exhaust gas. The heater section is configured such that a plurality of metal thin plates and insulators are stacked alternatingly are wound. The heater section contains a pair comprising a positive electrode and a negative electrode for energizing and heating the metal thin plates. The positive and negative electrodes are joined to each of the metal thin plates in such a manner that the positive electrode is located away from the negative electrode in a winding direction of the metal thin plates.

A combustion system operated at low cost is provided. A combustion system 1 includes a combustion device 10 that burns fuel, an exhaust line L1 through which exhaust gas flows, the exhaust gas being generated through combustion of the fuel in the combustion device 10, an air preheater 30 that is disposed in the exhaust line L1 and that recovers heat from the exhaust gas, and a denitration device 40 that is disposed in the exhaust line L1 and that removes nitrogen oxide from the exhaust gas using a denitration catalyst. The denitration device 40 is disposed downstream from the air preheater 30 in the exhaust line L1, and the denitration catalyst contains 43 wt % or more of vanadium pentoxide and has a BET specific surface area of 30 m.sup.2/g or more.