# Commission Implementing Decision of 28 February 2012 establishing the best available techniques (BAT) conclusions under Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions for the manufacture of glass (notified under document C(2012) 865) (Text with EEA relevance) (2012/134/EU), Division 1.10.2: NOX emissions

Extent: E+W+S+N.I.

Technique
Description
Combustion modifications
(i)
Reduction of air/fuel ratio
The technique is mainly based on the following features:
minimisation of air leakages into the furnace
careful control of air used for combustion
modified design of the furnace combustion chamber
(ii)
Reduced combustion air temperature
The use of recuperative furnaces, in place of regenerative furnaces, results in a reduced air preheat temperature and, consequently, a lower flame temperature. However, this is associated with a lower furnace efficiency (lower specific pull), lower fuel efficiency and higher fuel demand, resulting in potentially higher emissions (kg/tonne of glass)
(iii)
Staged combustion
— Air staging involves substoichiometric firing and the addition of the remaining air or oxygen into the furnace to complete combustion.
— Fuel staging a low impulse primary flame is developed in the port neck (10 % of total energy); a secondary flame covers the root of the primary flame reducing its core temperature
(iv)
Flue-gas recirculation
Implies the reinjection of waste gas from the furnace into the flame to reduce the oxygen content and therefore the temperature of the flame.
The use of special burners is based on internal recirculation of combustion gases which cool the root of the flames and reduce the oxygen content in the hottest part of the flames
(v)
Low-NOX burners
The technique is based on the principles of reducing peak flame temperatures, delaying but completing the combustion and increasing the heat transfer (increased emissivity of the flame). It may be associated with a modified design of the furnace combustion chamber
(vi)
Fuel choice
In general, oil-fired furnaces show lower NOX emissions than gas-fired furnaces due to better thermal emissivity and lower flame temperatures
Special furnace design
Recuperative type furnace that integrates various features, allowing for lower flame temperatures. The main features are:
specific type of burners (number and positioning)
modified geometry of the furnace (height and size)
two-stage raw material preheating with waste gases passing over the raw materials entering the furnace and an external cullet preheater downstream of the recuperator used for preheating the combustion air
Electric melting
The technique consists of a melting furnace where the energy is provided by resistive heating. The main features are:
electrodes are generally inserted at the bottom of the furnace (cold-top)
nitrates are often required in the batch composition of cold-top electric furnaces to provide the necessary oxidising conditions for a stable, safe and efficient manufacturing process
Oxy-fuel melting
The technique involves the replacement of the combustion air with oxygen (> 90 % purity), with consequent elimination/reduction of thermal NOX formation from nitrogen entering the furnace. The residual nitrogen content in the furnace depends on the purity of the oxygen supplied, on the quality of the fuel (% N2 in natural gas) and on the potential air inlet
Chemical reduction by fuel
The technique is based on the injection of fossil fuel to the waste gas with chemical reduction of NOX to N2 through a series of reactions. In the 3R process, the fuel (natural gas or oil) is injected at the regenerator entrance. The technology is designed for use in regenerative furnaces
Selective catalytic reduction (SCR)
The technique is based on the reduction of NOX to nitrogen in a catalytic bed by reaction with ammonia (in general aqueous solution) at an optimum operating temperature of around 300 – 450 °C.
One or two layers of catalyst may be applied. A higher NOX reduction is achieved with the use of higher amounts of catalyst (two layers)
Selective non-catalytic reduction (SNCR)
The technique is based on the reduction of NOX to nitrogen by reaction with ammonia or urea at a high temperature.
The operating temperature window must be maintained between 900 and 1 050 °C
Minimising the use of nitrates in the batch formulation
The minimisation of nitrates is used to reduce NOX emissions deriving from the decomposition of these raw materials when applied as an oxidising agent for very high quality products where a very colourless (clear) glass is required or for other glasses to provide the required characteristics. The following options may be applied:
Reduce the presence of nitrates in the batch formulation to the minimum commensurate with the product and melting requirements.
Substitute nitrates with alternative materials. Effective alternatives are sulphates, arsenic oxides, cerium oxide.
Apply process modifications (e.g. special oxidising combustion conditions)

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Source: https://www.legislation.gov.uk/eudn/2012/134/annex/division/5/division/10/division/1.10/division/1.10.2 (the official version)
Page: https://openlegislation.uk/eu-decision-2012-134/annex/division-5/division-10/division-1.10/division-1.10.2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.