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Current developments in emission abatement technologies – Part 2

World Cement,

Read part 1 here

Dust abatement systems

Electrostatic precipitators, fabric filters and also hybrid filters are established technologies, which exhibit high dedusting efficiencies to meet the current environmental requirements. A new approach in emission abatement technologies is the combination of dust and NOx abatement. Ceramic or fabric filter bags containing catalysts for NOx reduction could be an interesting alternative to SCR facilities. However, this technology is still in a very early stage of development and not yet ready for commercial application.

Another emerging technology is the installation of high-temperature bag filters (HT filters), which can be used, for example, for the dedusting of cooler exit air without cooling it. Afterwards the exit air can be used for different waste heat utilisation options.

TOC emissions

Basically, the linker burning process possesses inherent and appropriate conditions to destroy organic compounds, which are fed with fuels or raw materials into the hot section of the kiln system. However, organic constituents in the raw material can be evaporated on its way down the preheater, resulting in corresponding emissions. In this context the utilisation of alternative raw materials and the right feeding points are of particular importance.

The BAT for the limitation of TOC emissions is to avoid the feeding of raw materials with high contents of volatile organic compounds into the kiln systems via the raw mill route and to carefully control the  input of organic compounds via the  raw materials. However, in individual cases further measures have to be applied. An emerging emission abatement technology in the cement sector is the so-called Regenerative Thermal Oxidation (RTO) (Figure 2), by which the emissions of CO, total organic carbon and odour can be significantly reduced. Furthermore, the integration of a SNCR or SCR facility is possible, which can lead in addition to a reduction in NOx emissions.

SCR facility in a cement works.

Mercury reduction

Mercury emissions are the subject of global environmental discussions and binding obligations to further reduce these are being discussed at UN level. European emission limit values can be met by process-integrated measures (e.g. input control or dust shuttling); further measures could be required in specific cases. In this case, alternative measures for mercury abatement would be applied, e.g. the improvement of the efficiency of the dust shuttling through the injection of appropriate sorbents into the flue gas stream. As there are only limited operational experiences available – mainly for limiting emissions peaks during direct operation – research projects are being carried out in the cement industry aiming at significant mercury abatement.

This is part 2 of a 2-part article that was originally published in Newsletter 2/2015 of the European Cement Research Academy and is reproduced by kind permission of ECRA.

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