Division 49

United Kingdom

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

I..

primary techniques, such as:

Technique^f1	Applicability
A description of the techniques is given in Section 1.10.2.
(i) 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 (i.e. use of recuperative furnaces in place of regenerative furnaces)
(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 the 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. The achieved environmental benefits are generally lower for applications to cross-fired, gas-fired furnaces due to technical constraints and a lower degree of flexibility of the furnace. 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
(ii) Electric melting	Not applicable for large volume glass productions (> 300 tonnes/day). Not applicable for productions requiring large pull variations. The implementation requires a complete furnace rebuild
(iii) Oxy-fuel melting	The maximum environmental benefits are achieved for applications at the time of a complete furnace rebuild

II..

secondary techniques, such as:

A description of the techniques is given in Section 1.10.2.
Technique^f2	Applicability
(i) Selective catalytic reduction (SCR)	The application may require an upgrade of the dust abatement system in order to guarantee a dust concentration of below 10 – 15 mg/Nm³ and a desulphurisation system for the removal of SO_X emissions Due to the optimum operating temperature window, the applicability is limited to the use of electrostatic precipitators. In general, the technique is not used with a bag filter system because the low operating temperature, in the range of 180 – 200 °C, would require reheating of the waste gases. The implementation of the technique may require significant space availability
(ii) Selective non-catalytic reduction (SNCR)	Very limited applicability to conventional regenerative furnaces, where the correct temperature window is difficult to access or does not allow a good mixing of the flue-gases with the reagent It may be applicable to new regenerative furnaces equipped with split regenerators; however, the temperature window is difficult to maintain due to the reversal of fire between the chambers that causes a cyclical temperature change

A description of the techniques is given in Section 1.10.2.

Technique^f2

Applicability

(i)

Selective catalytic reduction (SCR)

The application may require an upgrade of the dust abatement system in order to guarantee a dust concentration of below 10 – 15 mg/Nm³ and a desulphurisation system for the removal of SO_X emissions

Due to the optimum operating temperature window, the applicability is limited to the use of electrostatic precipitators. In general, the technique is not used with a bag filter system because the low operating temperature, in the range of 180 – 200 °C, would require reheating of the waste gases.

The implementation of the technique may require significant space availability

(ii)

Selective non-catalytic reduction (SNCR)

Very limited applicability to conventional regenerative furnaces, where the correct temperature window is difficult to access or does not allow a good mixing of the flue-gases with the reagent

It may be applicable to new regenerative furnaces equipped with split regenerators; however, the temperature window is difficult to maintain due to the reversal of fire between the chambers that causes a cyclical temperature change

Table 39

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

Parameter	BAT	BAT-AEL
The conversion factors of 2,5 × 10^–3 and 4 × 10^–3 have been used for the determination of the lower and upper value of the BAT-AEL range (see Table 2), with some values being approximated. However, a case-by-case conversion factor needs to be applied based on the type of production (see Table 2).
The higher values are related to a special production of borosilicate glass tubes for pharmaceutical use.
The achievable levels depend on the quality of the natural gas and oxygen available (nitrogen content).
Parameter	BAT	mg/Nm³	kg/tonne melted glass^f3
NO_X expressed as NO₂	Combustion modifications	600 – 800	1,5 – 3,2
	Electric melting	< 100	< 0,25 – 0,4
	Oxy-fuel melting^f4 ^f5	Not applicable	< 1 – 3
	Secondary techniques	< 500	< 1 – 3

Annotations

Footnotes

f1: A description of the techniques is given in Section 1.10.2.
f2: A description of the techniques is given in Section 1.10.2.
f3: The conversion factors of 2,5 × 10^–3 and 4 × 10^–3 have been used for the determination of the lower and upper value of the BAT-AEL range (see Table 2), with some values being approximated. However, a case-by-case conversion factor needs to be applied based on the type of production (see Table 2).
f4: The higher values are related to a special production of borosilicate glass tubes for pharmaceutical use.
f5: The achievable levels depend on the quality of the natural gas and oxygen available (nitrogen content).