Division BAT 20 In order to prevent or reduce NOX emissions to air while limiting CO and N2O emissions to air from the combustion of coal and/or lignite, BAT is to use one or a combination of the techniques given below.

United Kingdom

Technique		Description	Applicability
a.	Combustion optimisation	See description in Section 8.3. Generally used in combination with other techniques	Generally applicable
b.	Combination of other primary techniques for NO_X reduction (e.g. air staging, fuel staging, flue-gas recirculation, low-NO_X burners (LNB))	See description in Section 8.3 for each single technique. The choice and performance of (an) appropriate (combination of) primary techniques may be influenced by the boiler design	Generally applicable
c.	Selective non-catalytic reduction (SNCR)	See description in Section 8.3. Can be applied with ‘slip’ SCR	The applicability may be limited in the case of boilers with a high cross-sectional area preventing homogeneous mixing of NH₃ and NO_X. The applicability may be limited in the case of combustion plants operated < 1 500 h/yr with highly variable boiler loads
d.	Selective catalytic reduction (SCR)	See description in Section 8.3	Not applicable to combustion plants of < 300 MW_th operated < 500 h/yr. Not generally applicable to combustion plants of < 100 MW_th. There may be technical and economic restrictions for retrofitting existing combustion plants operated between 500 h/yr and 1 500 h/yr and for existing combustion plants of ≥ 300 MW_th operated < 500 h/yr
e.	Combined techniques for NO_X and SO_X reduction	See description in Section 8.3	Applicable on a case-by-case basis, depending on the fuel characteristics and combustion process

Table 3

BAT-associated emission levels (BAT-AELs) for NO_X emissions to air from the combustion of coal and/or lignite

Combustion plant total rated thermal input(MW_th)	BAT-AELs (mg/Nm³)
These BAT-AELs do not apply to plants operated < 1 500 h/yr.
In the case of coal-fired PC boiler plants put into operation no later than 1 July 1987, which are operated < 1 500 h/yr and for which SCR and/or SNCR is not applicable, the higher end of the range is 340 mg/Nm³.
For plants operated < 500 h/yr, these levels are indicative.
The lower end of the range is considered achievable when using SCR.
The higher end of the range is 175 mg/Nm³ for FBC boilers put into operation no later than 7 January 2014 and for lignite-fired PC boilers.
The higher end of the range is 220 mg/Nm³ for FBC boilers put into operation no later than 7 January 2014 and for lignite-fired PC boilers.
In the case of plants put into operation no later than 7 January 2014, the higher end of the range is 200 mg/Nm³ for plants operated ≥ 1 500 h/yr, and 220 mg/Nm³ for plants operated < 1 500 h/yr.
	Yearly average		Daily average or average over the sampling period
	New plant	Existing plant^f1	New plant	Existing plant^f2 ^f3
< 100	100–150	100–270	155–200	165–330
100–300	50–100	100–180	80–130	155–210
≥ 300, FBC boiler combusting coal and/or lignite and lignite-fired PC boiler	50 – 85	< 85 – 150^f4 ^f5	80 – 125	140 – 165^f6
≥ 300, coal-fired PC boiler	65 – 85	65 – 150	80 – 125	< 85 – 165^f7

As an indication, the yearly average CO emission levels for existing combustion plants operated ≥ 1 500 h/yr or for new combustion plants will generally be as follows:

Combustion plant total rated thermal input (MW_th)	CO indicative emission level (mg/Nm³)
The higher end of the range may be up to 140 mg/Nm³ in the case of limitations due to boiler design, and/or in the case of fluidised bed boilers not fitted with secondary abatement techniques for NO_X emissions reduction.
< 300	< 30–140
≥ 300, FBC boiler combusting coal and/or lignite and lignite-fired PC boiler	< 30–100^f8
≥ 300, coal-fired PC boiler	< 5–100

Annotations

Footnotes

f1: These BAT-AELs do not apply to plants operated < 1 500 h/yr.
f2: In the case of coal-fired PC boiler plants put into operation no later than 1 July 1987, which are operated < 1 500 h/yr and for which SCR and/or SNCR is not applicable, the higher end of the range is 340 mg/Nm³.
f3: For plants operated < 500 h/yr, these levels are indicative.
f4: The lower end of the range is considered achievable when using SCR.
f5: The higher end of the range is 175 mg/Nm³ for FBC boilers put into operation no later than 7 January 2014 and for lignite-fired PC boilers.
f6: The higher end of the range is 220 mg/Nm³ for FBC boilers put into operation no later than 7 January 2014 and for lignite-fired PC boilers.
f7: In the case of plants put into operation no later than 7 January 2014, the higher end of the range is 200 mg/Nm³ for plants operated ≥ 1 500 h/yr, and 220 mg/Nm³ for plants operated < 1 500 h/yr.
f8: The higher end of the range may be up to 140 mg/Nm³ in the case of limitations due to boiler design, and/or in the case of fluidised bed boilers not fitted with secondary abatement techniques for NO_X emissions reduction.