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ANNEX U.K.BAT CONCLUSIONS FOR THE PRODUCTION OF PULP, PAPER AND BOARD

ACRONYMS U.K.

1.2. BAT CONCLUSIONS FOR KRAFT PULPING PROCESS U.K.

1.2.2. Emissions to air U.K.

1.2.2.2. Reduction of emissions from a recovery boiler U.K.

NO_x emissions U.K.

BAT 22. In order to reduce NO_x emissions from a recovery boiler, BAT is to use an optimised firing system including all of the features given below. U.K.

	Technique
a	Computerised combustion control
b	Good mixing of fuel and air
c	Staged air feed systems, e.g. by using different air registers and air inlet ports

Applicability U.K.

Technique (c)is applicable to new recovery boilers and in the case of a major refurbishment of recovery boilers, as this technique requires considerable changes to the air feed systems and the furnace.

BAT-associated emission levels U.K.

See Table 4.

Table 4

BAT-associated emission levels for NO_x emissions from a recovery boiler

a Increasing the DS content of the black liquor results in lower SO2 emissions and higher NOx emissions. Due to this, a recovery boiler with low emission levels for SO2, may be on the higher end of the range for NOx and vice versa.
b The actual NOx emission level of a recovery boiler depends on the DS content and the nitrogen content of the black liquor, and the amount and combination of NCG and other nitrogen containing flows (e.g. dissolving tank vent gas, methanol separated from the condensate, biosludge) burnt. The higher the DS content, the nitrogen content in the black liquor, and the amount of NCG and other nitrogen containing flows burnt, the closer the emissions will be to the upper end of the BAT-AEL range.
c If a recovery boiler were to burn black liquor with a DS > 83 %, then NOx emission levels should be reconsidered on a case-by-case basis.
DS = dry solid content of black liquor.
Parameter		Yearly averageamg/Nm3 at 6 % O2	Yearly averageakg NOx/ADt
NOx	Softwood	120 – 200b	DS < 75 %: 0,8 – 1,4 DS 75 – 83 %c: 1,0 – 1,6
	Hardwood	120 – 200b	DS < 75 %: 0,8 – 1,4 DS 75 – 83 %c: 1,0 – 1,7