Division BAT 56 In order to prevent or reduce NOX emissions to air while limiting CO emissions to air from the combustion of process fuels from the chemical industry, BAT is to use one or a combination of the techniques given below.

United Kingdom

Technique		Description	Applicability
a.	Low-NO_X burners (LNB)	See descriptions in Section 8.3	Generally applicable
b.	Air staging	See descriptions in Section 8.3
c.	Fuel staging	See description in Section 8.3. Applying fuel staging when using liquid fuel mixtures may require a specific burner design
d.	Flue-gas recirculation	See descriptions in Section 8.3	Generally applicable to new combustion plants. Applicable to existing combustion plants within the constraints associated with chemical installation safety
e.	Water/steam addition		The applicability may be limited due to water availability
f.	Fuel choice		Applicable within the constraints associated with the availability of different types of fuel and/or an alternative use of the process fuel
g.	Advanced control system		The applicability to old combustion plants may be constrained by the need to retrofit the combustion system and/or control command system
h.	Selective non-catalytic reduction (SNCR)		Applicable to existing combustion plants within the constraints associated with chemical installation safety. Not applicable to combustion plants operated < 500 h/yr. The applicability may be limited in the case of combustion plants operated between 500 h/yr and 1 500 h/yr with frequent fuel changes and frequent load variations
i.	Selective catalytic reduction (SCR)		Applicable to existing combustion plants within the constraints associated with duct configuration, space availability and chemical installation safety. Not applicable to combustion plants operated < 500 h/yr. There may be technical and economic restrictions for retrofitting existing combustion plants operated between 500 h/yr and 1 500 h/yr. Not generally applicable to combustion plants of < 100 MW_th

Table 34

BAT-associated emission levels (BAT-AELs) for NO_X emissions to air from the combustion of 100 % process fuels from the chemical industry in boilers

Fuel phase used in the combustion plant	BAT-AELs (mg/Nm³)
For plants operated < 1 500 h/yr, these BAT AELs do not apply.
For plants operated < 500 h/yr, these levels are indicative.
For existing plants of ≤ 500 MW_th put into operation no later than 27 November 2003 using liquid fuels with a nitrogen content higher than 0,6 wt-%, the higher end of the BAT-AEL range is 380 mg/Nm³.
For existing plants put into operation no later than 7 January 2014, the higher end of the BAT-AEL range is 180 mg/Nm³.
For existing plants put into operation no later than 7 January 2014, the higher end of the BAT-AEL range is 210 mg/Nm³.
	Yearly average		Daily average or average over the sampling period
	New plant	Existing plant^f1	New plant	Existing plant^f2
Mixture of gases and liquids	30–85	80–290^f3	50–110	100–330
Gases only	20–80	70–100^f4	30–100	85–110^f5

As an indication, the yearly average CO emission levels for existing plants operated ≥ 1 500 h/yr and for new plants will generally be < 5–30 mg/Nm³.

Annotations

Footnotes

f1: For plants operated < 1 500 h/yr, these BAT AELs do not apply.
f2: For plants operated < 500 h/yr, these levels are indicative.
f3: For existing plants of ≤ 500 MW_th put into operation no later than 27 November 2003 using liquid fuels with a nitrogen content higher than 0,6 wt-%, the higher end of the BAT-AEL range is 380 mg/Nm³.
f4: For existing plants put into operation no later than 7 January 2014, the higher end of the BAT-AEL range is 180 mg/Nm³.
f5: For existing plants put into operation no later than 7 January 2014, the higher end of the BAT-AEL range is 210 mg/Nm³.