TH31838B - Thermally active carbon for use in denitration, processes for the production of the same substance, denitration methods using the same substance, and denitration systems using the same substance. - Google Patents

Abstract

This invention concerns a technique for the removal of nitrogen oxides (BOx) present in discharge gases supplied from boilers and similar facilities. When the discharge gas temperature is 100°C or lower, the preferred method is to use thermally activated active carbon produced by heating crude active carbon to 600 to 1,200°C in a non-oxidizing atmosphere, which removes oxygen-containing functional groups present on the surface of the substance by reducing the surface oxygen atom/carbon ratio to 0.05 or less. When the discharge gas temperature exceeds 100°C, the preferred method is to use thermally activated active carbon produced by heating crude active carbon to 600 to 1,200°C in a non-oxidizing atmosphere and activating the surface of the substance with sulfuric acid or nitric acid to oxidize the oxygen-containing functional groups of the substance.

Claims (9)

1. Method of using heat-treated carbon fibers for denitration: This method involves using heat-treated carbon fibers obtained by heat-treating raw carbon fibers at 600 to 1200°C in a non-oxidizing atmosphere. This removes oxygen-containing functional groups from the surface and reduces the surface oxygen/atomized carbon ratio to 0.05 or less. The discharge gas temperature is 100°C or less. The heat-treated carbon fibers for denitration consist of heat-treated carbon fibers obtained by heat treatment. With activated carbon fibers at temperatures of 600 to 1,200 °C, and surface activation of the material with sulfuric acid or nitric acid to induce oxygen-oxidizing functional groups, the discharge gas temperature is managed at 100 °C or higher; and the discharge gas containing nitrogen oxides and no more than 80% water vapor, and NH3 gas with the same concentration as nitrogen oxides, are exposed to the heat-treated activated carbon fibers for denitration to selectively reduce the oxides, and thus decompose those gases into nitrogen and water. 2. The denitration method is characterized by the fact that heat-treated carbon fibers, consisting of heat-treated active carbon obtained by heating crude active carbon at 600 to 1,200 °C in a non-oxidizing atmosphere, are removed, and the surface oxygen-containing functional groups are reduced to 0.05 or less. The fibers are then exposed to an emission gas containing nitrogen oxides and no more than 80% water vapor and NH3 gas at the same concentration as nitrogen oxides to selectively reduce the nitrogen oxides. The fibers are then decomposed into nitrogen and water at temperatures ranging from the initial temperature up to 100 °C. 3. The denitration method, as claimed in claim 2, involves the application of a higher level of denitration of nitrogen oxides at low temperatures and low concentrations at the outlet of the exhaust gas handling device or the boiler outlet. 4. The denitration method using active carbon fibers is characterized by a first compaction reactor, which is packed with heat-treated active carbon fibers produced by heat treatment of the raw active carbon fibers at temperatures between 600 and 1,000 °C. A second compaction reactor is located at the end of this process, also packed with heat-treated active carbon. A discharge gas is released at a temperature of 100 °C or less, and ammonia may be introduced into the second compaction reactor. Nitrogen oxides present in the discharge gas are then exposed to the ammonia, and the nitrogen oxides are separated out by continuous selective reduction of the gases to nitrogen. Any excess ammonia can be recovered by re-compression in the second compaction reactor. 5. A denitration system utilizing active carbon fibers as proposed in claim 4, which alternately releases gas into a first and second compression reactor, thereby repeatedly performing denitration and ammonia adsorption operations. 6. Active Carbon Fiber Denitration System: This denitration system consists of a denitrator packed with heat-treated active carbon fibers, produced by heat treatment of raw active carbon at temperatures ranging from 600 to 1,000 °C, and first and second ammonia adsorbents placed before and after the denitrator, respectively. The discharge gas, at temperatures below 100 °C, containing nitrogen oxides, is alternately passed through one of the first and second ammonia adsorbents. Ammonia (NH3) is introduced between the first or second ammonia adsorbents, and the denitrator brings the nitrogen oxides (NOx) present in the discharge gas into contact with the heat-treated active carbon fibers placed in the denitrator, where they are separated by continuous selective reduction. It is converted to nitrogen (N2), and any excess ammonia is recovered by adsorption in the adsorbent at the end of the aforementioned denitrate. 7. Denitration system using active carbon fibers, as claimed under any one of claims 4 through 6, in which the aforementioned active carbon fibers are composed of carbon fibers derived from polyacrylonitrile or pitch rubber. 8. Denitration System Using Heat-Treated Carbon Fibers: This denitration system consists of a first compactor packed with heat-treated carbon fibers, which are produced by heating the carbon fibers at 600 to 1,200 °C in a non-oxidizing atmosphere. This removes the oxygen-containing functional groups present on the surface of the material and reduces the surface oxygen/atomized carbon ratio to 0.05 or less. A second compactor is located at the end of the material, also packed with heat-treated carbon fibers. In this second compactor, the discharge gas at 100 °C or less and ammonia are introduced into the supercompact reactor, removing the nitrogen oxides (NOx) present in the discharge gas. It comes into contact with ammonia and separates nitrogen oxides by selective and continuous reduction of these gases to nitrogen (N2), and any excess ammonia is recovered by adsorption in the second compact reactor mentioned earlier. 9. Denitration system, as claimed in claim 8, in which the aforementioned crude active carbon fibers are composed of carbon fibers derived from polyacrylonitrile or gluten.