Primary application of the `In-bed-deNOx' process using Ca-Fe oxides in iron ore sintering machines

Abstract

To decrease NOx emission from iron ore sintering machines inexpensively, a new process removing NOx within the sintering bed, named `In-bed-deNOx', was studied. This process utilizes the effect of Ca-Fe oxides, named CF, on NOx elimination reaction. This report describes the reaction behavior of NO on mainly the CF liquid surface and the application study of `In-bed-deNOx' to actual sintering process. The effect of CF on the NO elimination reaction was investigated in the crucible experiments. Reaction gas containing about 400 ppm NO was blown onto the specimen in reaction tube. The NO concentration in outlet was measured in the range of 800 °C to 1 400 °C, and 0.2 to 10-17 mole fraction of oxygen. The CF, including ferrous oxide, shows the higher NOx elimination ratio. The NOx elimination ratio increases with increasing temperature and decreasing oxygen potential. To verify the `In-bed-deNOx' process, some pot tests and experimental operations in the Kakogawa sintering plant were carried out. Firstly, the sintering pot tests were carried out by means of charging the CF pellets prepared in advance. NOx emission decreases with the increasing CF pellets addition. Secondly a sintering pot test was carried out by means of using limestone powder. NOx emission from the case of using limestone powder is as little as the case of charging CF pellets. An actual plant test was made by means of using fine limestone. Decreased NOx emission was achieved during the test period.