# Commission Implementing Decision of 26 March 2013 establishing the best available techniques (BAT) conclusions under Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions for the production of cement, lime and magnesium oxide (notified under document C(2013) 1728) (Text with EEA relevance) (2013/163/EU), Division 1.5.2: NOx emissions Extent: E+W+S+N.I. Technique Description a Primary measures/techniques I Flame cooling The addition of water to the fuel or directly to the flame by using different injection methods, such as injection of one fluid (liquid) or two fluids (liquid and compressed air or solids) or the use of liquid/solid wastes with a high water content reduces the temperature and increases the concentration of hydroxyl radicals. This can have a positive effect on NOx reduction in the burning zone II Low NOx burners Designs of low NOx burners (indirect firing) vary in detail but essentially the fuel and air are injected into the kiln through concentric tubes. The primary air proportion is reduced to some 6 – 10 % of that required for stoichiometric combustion (typically 10 – 15 % in traditional burners). Axial air is injected at high momentum in the outer channel. The coal may be blown through the centre pipe or the middle channel. A third channel is used for swirl air, its swirl being induced by vanes at, or behind, the outlet of the firing pipe. The net effect of this burner design is to produce very early ignition, especially of the volatile compounds in the fuel, in an oxygen-deficient atmosphere, and this will tend to reduce the formation of NOx. The application of low NOx burners is not always followed by a reduction of NOx emissions. The set-up of the burner has to be optimised III Mid kiln firing In long wet and long dry kilns, the creation of a reducing zone by firing lump fuel can reduce NOx emissions. As long kilns usually have no access to a temperature zone of about 900 – 1 000 °C, mid-kiln firing systems can be installed in order to be able to use waste fuels that cannot pass the main burner (for example tyres). The rate of the burning of fuels can be critical. If it is too slow, reducing conditions can occur in the burning zone, which may severely affect product quality. If it is too high, the kiln chain section can be overheated – resulting in the chains being burned out. A temperature range of less than 1 100 °C excludes the use of hazardous waste with a chlorine content of greater than 1 % IV Addition of mineralisers to improve the burnability of the raw meal (mineralised clinker) The addition of mineralisers, such as fluorine, to the raw material is a technique to adjust the clinker quality and allow the sintering zone temperature to be reduced. By reducing/lowering the burning temperature, NOx formation is also reduced V Process optimisation Optimisation of the process, such as smoothing and optimising the kiln operation and firing conditions, optimising the kiln operation control and/or homogenisation of the fuel feedings, can be applied for reducing NOx emissions. General primary optimisation measures/techniques, such as process control measures/techniques, an improved indirect firing technique, optimised cooler connections and fuel selection, and optimised oxygen levels have been applied b Staged combustion (conventional or waste fuels), also in combination with a precalciner and the use of optimised fuel mix Staged combustion is applied at cement kilns with an especially designed precalciner. The first combustion stage takes place in the rotary kiln under optimum conditions for the clinker burning process. The second combustion stage is a burner at the kiln inlet, which produces a reducing atmosphere that decomposes a portion of the nitrogen oxides generated in the sintering zone. The high temperature in this zone is particularly favourable for the reaction which reconverts the NOx to elementary nitrogen. In the third combustion stage, the calcining fuel is fed into the calciner with an amount of tertiary air, producing a reducing atmosphere there, too. This system reduces the generation of NOx from the fuel, and also decreases the NOx coming out of the kiln. In the fourth and final combustion stage, the remaining tertiary air is fed into the system as ‘top air’ for residual combustion c SNCR Selective non-catalytic reduction (SNCR) involves injecting ammonia water (up to 25 % NH3), ammonia precursor compounds or urea solution into the combustion gas to reduce NO to N2. The reaction has an optimum effect in a temperature window of about 830 to 1 050 °C, and sufficient retention time must be provided for the injected agents to react with NO d SCR SCR reduces NO and NO2 to N2 with the help of NH3 and a catalyst at a temperature range of about 300 – 400 °C. This technique is widely used for NOx abatement in other industries (coal fired power stations, waste incinerators). In the cement industry, basically two systems are considered: low dust configuration between a dedusting unit and stack, and a high dust configuration between a preheater and a dedusting unit. Low dust flue-gas systems require the reheating of the flue-gases after dedusting, which may cause additional energy costs and pressure losses. High dust systems are considered preferable for technical and economical reasons. These systems do not require reheating, because the waste gas temperature at the outlet of the preheater system is usually in the right temperature range for SCR operation --- Source: https://www.legislation.gov.uk/eudn/2013/163/annex/division/6/division/1.5/division/1.5.2 (the official version) Page: https://openlegislation.uk/eu-decision-2013-163/annex/division-6/division-1.5/division-1.5.2 Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.