Division I Primary or process-related techniques, such as:

United Kingdom

Technique	Description	Applicability
(i) Selection or treatment of fuel
(a) Use of gas to replace liquid fuel	Gas generally contains less nitrogen than liquid and its combustion leads to a lower level of NO_X emissions. See Section 1.20.3	The applicability may be limited by the constraints associated with the availability of low sulphur gas fuels, which may be impacted by the energy policy of the Member State
(b) Use of low nitrogen refinery fuel oil (RFO) e.g. by RFO selection or by hydrotreatment of RFO	Refinery fuel oil selection favours low nitrogen liquid fuels among the possible sources to be used at the unit. Hydrotreatment aims at reducing the sulphur, nitrogen and metal contents of the fuel. See Section 1.20.3	Applicability is limited by the availability of low nitrogen liquid fuels, hydrogen production and hydrogen sulphide (H₂S) treatment capacity (e.g. amine and Claus units)
(ii) Combustion modifications
(a) Staged combustion: air staging fuel staging	See Section 1.20.2	Fuel staging for mixed or liquid firing may require a specific burner design
(b) Optimisation of combustion	See Section 1.20.2	Generally applicable
(c) Flue-gas recirculation	See Section 1.20.2	Applicable through the use of specific burners with internal recirculation of the flue-gas. The applicability may be restricted to retrofitting external flue-gas recirculation to units with a forced/induced draught mode of operation
(d) Diluent injection	See Section 1.20.2	Generally applicable for gas turbines where appropriate inert diluents are available
(e) Use of low-NO_X burners (LNB)	See Section 1.20.2	Generally applicable for new units taking into account, the fuel-specific limitation (e.g. for heavy oil). For existing units, applicability may be restricted by the complexity caused by site-specific conditions e.g. furnaces design, surrounding devices. In very specific cases, substantial modifications may be required. The applicability may be restricted for furnaces in the delayed coking process, due to possible coke generation in the furnaces. In gas turbines, the applicability is restricted to low hydrogen content fuels (generally < 10 %)

Notes on Division

Footnotes

f1: BAT-AEL refers to combined emissions from the gas turbine and the supplementary firing recovery boiler, where present.
f2: For fuel with high H₂ content (i.e. above 10 %), the upper end of the range is 75 mg/Nm³.
f3: For an existing unit using high air pre-heat (i.e. > 200 °C) or with H₂ content in the fuel gas higher than 50 %, the upper end of the BAT-AEL range is 200 mg/Nm³.
f4: For existing units < 100 MW firing fuel oil with a nitrogen content higher than 0,5 % (w/w) or with liquid firing > 50 % or using air preheating, values up to 450 mg/Nm³ may occur.
f5: The lower end of the range can be achieved by using the SCR technique.