NO_x emissions and the abatement potential of SNCR technology in a kiln plant with calciner

摘要

A large number of measurements and calculations confirm that even in their immediate vicinity cement plants make only a small contribution to the ambient NP_x pollution. In spite of this, the implementation of the European IED (Industrial Emissions Directive) in German law is leading to further tightening of the NO_x limit that is already very ambitious today. This means that the SNCR (Selective Non-Catalytic Reduction) technology used so far for NO_x abatement will come up against its limits. The German cement industry therefore envisages capital costs of around € 300 million in the coming years and a significantly higher electrical power demand. Justifiable hopes that the new limit can also be met with SNCR technology are likely to be confined to plants that have already achieved a relatively low NO_x emission level through primary measures - essentially kiln plants with calciners. Corresponding trials were carried out at the Rudersdorf kiln plant in which an emission level of about 250 mg/m~3 was achieved using SNCR technology. As far as its emission levels and the NO_x abatement technology used are concerned the kiln plant would therefore be fully compliant with the requirements of "Best Available Techniques" (BAT) in the relevant European reference document (BREF) for the cement industry issued in 2012. Although the kiln plant could still be expected to have a certain optimization potential, especially through spatial separation of the CO abatement in the calciner and the injection of ammonia water, compliance with a limit of 200 mg/m3 as the daily average value does not seem feasible. This contradiction occurs if no distinction is made between an average emission level (from the BREF document) and a limit value. Compliance with the NO_x limit would make an appropriate safety margin absolutely essential because the initial level is subject to relatively large fluctuations due to the nature of the process. Longer reference periods, such as a month or a year, would be more realistic for evaluation of the measurements from the emission monitoring.