Division 72

United Kingdom

BAT is to reduce NO_X emissions from the melting furnace by using one or a combination of the following techniques:

Technique^f1	Applicability
A description of the technique is given in Section 1.10.2.
(i) Minimising the use of nitrates in the batch formulation In the frits production, nitrates are used in the batch formulation of many products in order to obtain the required characteristics	The substitution of nitrates in the batch formulation may be limited by the high costs and/or higher environmental impact of the alternative materials and/or the quality requirements of the final product
(ii) Reduction of the parasitic air entering the furnace The technique consists of preventing the ingress of air into the furnace by sealing the burner blocks, the batch material feeder and any other opening of the melting furnace	The technique is generally applicable
(iii) Combustion modifications
(a) Reduction of air/fuel ratio	Applicable to air/fuel conventional furnaces. Full benefits are achieved at normal or complete furnace rebuild, when combined with optimum furnace design and geometry
(b) Reduced combustion air temperature	Applicable only under installation-specific circumstances due to a lower furnace efficiency and higher fuel demand
(c) Staged combustion: Air staging Fuel staging	Fuel staging is applicable to most conventional air/fuel furnaces. Air staging has very limited applicability due to its technical complexity
(d) Flue-gas recirculation	The applicability of this technique is limited to the use of special burners with automatic recirculation of the waste gas
(e) Low-NO_X burners	The technique is generally applicable. Full benefits are achieved at normal or complete furnace rebuild, when combined with optimum furnace design and geometry
(f) Fuel choice	The applicability is limited by the constraints associated with the availability of different types of fuel, which may be impacted by the energy policy of the Member State
(iv) Oxy-fuel melting	The maximum environmental benefits are achieved for applications at the time of a complete furnace rebuild

Table 62

BAT-AELs for NO_X emissions from the melting furnace in the frits glass sector

Parameter	BAT	Operating conditions	BAT-AEL^f2
The ranges take into account the combination of flue-gases from furnaces applying different melting techniques and producing a variety of frit types, with or without nitrates in the batch formulations, which may be conveyed to a single stack, precluding the possibility of characterising each applied melting technique and the different products.
The conversion factors of 5 × 10^–3 and 7,5 × 10^–3 have been used for the determination of the lower and higher values of the range. However, a case-by-case conversion factor may have to be applied based on the type of combustion (see Table 2).
The achievable levels depend on the quality of the natural gas and oxygen available (nitrogen content).
Parameter	BAT	Operating conditions	mg/Nm³	kg/tonne melted glass^f3
NO_X expressed as NO₂	Primary techniques	Oxy-fuel firing, without nitrates^f4	Not applicable	< 2,5 – 5
		Oxy-fuel firing, with use of nitrates	Not applicable	5 – 10
		Fuel/air, fuel/oxygen-enriched air combustion, without nitrates	500 – 1 000	2,5 – 7,5
		Fuel/air, fuel/oxygen-enriched air combustion, with use of nitrates	< 1 600	< 12

Annotations

Footnotes

f1: A description of the technique is given in Section 1.10.2.
f2: The ranges take into account the combination of flue-gases from furnaces applying different melting techniques and producing a variety of frit types, with or without nitrates in the batch formulations, which may be conveyed to a single stack, precluding the possibility of characterising each applied melting technique and the different products.
f3: The conversion factors of 5 × 10^–3 and 7,5 × 10^–3 have been used for the determination of the lower and higher values of the range. However, a case-by-case conversion factor may have to be applied based on the type of combustion (see Table 2).
f4: The achievable levels depend on the quality of the natural gas and oxygen available (nitrogen content).