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)

1.2.6.1 NO_x emissions

19. In order to reduce the emissions of NO_x from the flue-gases of kiln firing and/or preheating/precalcining processes, BAT is to use one or a combination of the following techniques:

a A description of the techniques is provided in Section 1.5.2.
	Techniquea	Applicability
a	Primary techniques
	I. Flame cooling	Applicable to all types of kilns used for cement manufacturing. The degree of applicability can be limited by product quality requirements and potential impacts on process stability
	II. Low NOx burners	Applicable to all rotary kilns, in the main kiln as well as in the precalciner
	III. Mid-kiln firing	Generally applicable to long rotary kilns
	IV. Addition of mineralisers to improve the burnability of the raw meal (mineralised clinker)	Generally applicable to rotary kilns subject to final product quality requirements
	V. Process optimisation	Generally applicable to all kilns
b	Staged combustion (conventional or waste fuels), also in combination with a precalciner and the use of optimised fuel mix	In general, can only be applied in kilns equipped with a precalciner. Substantial plant modifications are necessary in cyclone preheater systems without a precalciner. In kilns without precalciner, lump fuels firing might have a positive effect on NOx reduction depending on the ability to produce a controlled reduction atmosphere and to control the related CO emissions
c	Selective non-catalytic reduction (SNCR)	In principle, applicable to rotary cement kilns. The injection zones vary with the type of kiln process. In long wet and long dry process kilns it may be difficult to obtain the right temperature and retention time needed. See also BAT 20
d	Selective catalytic reduction (SCR)	Applicability is subject to appropriate catalyst and process development in the cement industry

BAT-associated emission levels

See Table 2.

Table 2

BAT-associated emission levels for NO_x from the flue-gases of kiln firing and/or preheating/precalcining processes in the cement industry

a The upper level of the BAT-AEL range is 500 mg/Nm3, if the initial NOx level after primary techniques is > 1 000 mg/Nm3.
b Existing kiln system design, fuel mix properties including waste and raw material burnability (e.g. special cement or white cement clinker) can influence the ability to be within the range. Levels below 350 mg/Nm3 are achieved at kilns with favourable conditions when using SNCR. In 2008, the lower value of 200 mg/Nm3 has been reported as a monthly average for three plants (easy burning mix used) using SNCR.
c Depending on initial levels and NH3 slip.
Kiln type	Unit	BAT-AEL(daily average value)
Preheater kilns	mg/Nm3	< 200 – 450a b
Lepol and long rotary kilns	mg/Nm3	400 – 800c

20. When SNCR is used, BAT is to achieve efficient NO_x reduction, while keeping the ammonia slip as low as possible, by using the following technique:

	Technique
a	To apply an appropriate and sufficient NOx reduction efficiency along with a stable operating process
b	To apply a good stoichiometric distribution of ammonia in order to achieve the highest efficiency of NOx reduction and to reduce the NH3 slip
c	To keep the emissions of NH3 slip (due to unreacted ammonia) from the flue-gases as low as possible taking into account the correlation between the NOx abatement efficiency and the NH3 slip

Applicability

SNCR is generally applicable to rotary cement kilns. The injection zones vary with the type of kiln process. In long wet and long dry process kilns it may be difficult to obtain the right temperature and retention time needed. See also BAT 19.

BAT-associated emission levels

See Table 3.

Table 3

BAT-associated emission levels for NH₃ slip in the flue-gases when SNCR is applied

a The ammonia slip depends on the initial NOx level and on the NOx abatement efficiency. For Lepol and long rotary kilns, the level may be even higher.
Parameter	Unit	BAT-AEL(daily average value)
NH3 slip	mg/Nm3	< 30 – 50a