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.

Apparatus and methods for selectively transmitting objects of interest from a first reservoir to a second reservoir are disclosed. The apparatus includes electromagnetic focusing apparatus configured to interact with objects of interest to induce a change in a property of the objects of interest so as to increase the probability that the objects of interest through a throat diffusively coupling the first reservoir and the second reservoir.

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 catalyst powder according to the present invention is a catalyst powder that includes: a core portion that contains ceria and zirconia; and a surface layer portion that is located on the core portion and contains ceria and zirconia. The ratio (M.sub.2/M.sub.1) is 0.30 or more and 0.95 or less, the ratio (M.sub.2/M.sub.1) being the ratio of a mole fraction M.sub.2 (mol %) of cerium in the surface layer portion measured using X-ray photoelectron spectroscopy to a mole fraction M.sub.1 (mol %) of cerium in the entire powder. It is preferable that the ratio (M.sub.4/2/M.sub.3/1) between M.sub.3/1 and M.sub.4/2 is 1.1 or more and 5.0 or less, wherein M.sub.3/1 (=M.sub.3/M.sub.1) represents the ratio between a mole fraction M.sub.3 (mol %) of zirconium in the entire powder and a mole fraction M.sub.1 (mol %) of cerium in the entirety of the powder, and M.sub.4/2 (=M.sub.4/M.sub.2) represents the ratio between a mole fraction M.sub.4 (mol %) of zirconium measured using X-ray photoelectron spectroscopy and a mole fraction M.sub.2 (mol %) of cerium measured using X-ray photoelectron spectroscopy.

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 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.

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.

There is provided a method for recycling 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 method for recycling a denitration catalyst includes a step of removing a used denitration catalyst from a denitration device and then coating the used denitration catalyst 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, and the denitration catalyst after recycling is used for denitration at 200? C. or lower.

There is provided a method for recycling 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 method for recycling a denitration catalyst includes a step of spraying an aqueous solution with a pH of 7 or more onto a used denitration catalyst while the denitration catalyst is set in a denitration device to remove a surface of the denitration catalyst. 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. The denitration catalyst after recycling is used for denitration at 200? C. or lower.