NO_x-Reduction by SNCR with alternative reagents for rotary kilns in cement plants

摘要

In order to reduce the NO_x emission of a long dry rotary kiln for the production of cement clinker at the ENCI cement works, a DeNO_x installation was developed and tested. The main goal was to reduce the NO_x emission by 40% with a minimum of secondary emissions and no extreme ammonium cycles. To reach this goal the SNCR process was chosen as the suitable one. The data required to design the plant, such as the available residence time, temperature and degree of mixing, were obtained by CFD calculations, performing pilot-plant experiments, and preliminary field tests with the long kiln at the ENCI site, Maastricht/the Netherlands. Thus the position of injection of the reducing agent into the kiln burning process as well as the type of the reducing agent could be determined. Finally, a test program was carried out on an industrial scale to be able to fine-tune the operational settings of the SNCR process, to optimize the NO_x reduction and to minimize the consumption of the reducing agent and the emissions of secondary components. The plant was tested on site and a reduction of NO_x of 40-50% is now obtained by injection of urea grains into the kiln inlet. Alternatively, with limited process adaptations other solid reagents, such as chicken manure, can be applied with the developed DeNO_x plant.