Primary techniques for NOx containment in a sustainable glass industry The achievements of the Prime Glass Project The Prime Glass DeNOx solutions in the present scenario of the glass industry NOx containment technologies Francesco Prosperi Stara Glass 1
SUMMARY Nitrogen Oxides and Regulations Strategies for NOx containment Primary measures (Design, A/G ratio, Burner technology, Prime Glass technologies) Secondary measures (SCR, SCNR- Centauro) Conclusions
Nitrogen Oxides Nitrogen oxides are atmosphere pollutants and it is believed that they aggravate the conditions of people suffering of asthma. Some of them, in presence of solar radiation, can react with oxygen forming ozone while others in presence of unburnt hydrocarbons (HC) can form other compounds constituting the photochemical smog. Moreover Nitrogen trioxide and pentoxide, forming nitrous and nitric acid, are mainly responsible for acid rains. The main mechanism of NOx formation is the one defined as thermal NOx, the undesired compounds are generated from the breaking of air molecular nitrogen at high temperature, in presence of oxygen. 3
Regulations To reduce the environmental impact and safeguard the health and life, the industrial legislation is becoming globally more and more restrictive about the permissible levels of NOx, in fact on 28 February 2012, under Directive 2010/75/EU of the European Parliament and of the Council on industrial emissions for the manufacture of glass, the European Commission established the best available techniques (BAT) to reduce the NOx emissions. 4
Primary and secondary measures The reduction of nitrogen oxides emissions can be achieved using two different approaches: Primary measures: reduction of emission at the origin, intervening into the process of NOx generation. Secondary measures: reduction of emission from the system, cutting down, through chemical treatment, the oxides produced during the combustion. Primary measures Secondary measures 5
How to intervene to reduce NOx The reduction of nitrogen oxides involves both glass technicians and technology suppliers, and is the biggest challenge of the future in the environmental performances. Technical choice depending on status/arrangement of plant, applicable technologies, emission limits required Primary measures Secundary measures (*) Preferred solution when applicable. Available: Combustion chamber design Combustion adjustment Burner technology (Low-NOx ) Prime Glass technologies SCR SNCR (Centauro) (*) Primary measures to be applied anyway to reduce inlet level of emission 6
Combustion chamber design The first action that can be taken against the formation of nitrogen oxides is designing, with specific criteria, the combustion chamber. This allow to maintain under control the air velocity, the gas injection and, at the same time, the temperature distribution in the area of ignition, i.e. the NOx birthplace. PLUS MINUS : set in best condition combustion chamber arrangement for application of other technologies : Application for new project in cold conditions 7
Combustion adjustment On the existing furnaces the most immediate action is acting on the fuel/air ratio but the production of CO should also be considered. In fact, while an excess of air causes a higher generation of NOx, the lack of oxygen cause the incomplete oxidation of the fuel, with the consequences of a higher energy consumption and a chemical attack to the heat recovery system. PLUS : quite effective in NOx reduction Applicable during furnace run MINUS : Reduction of energy performances / possible impact on glass quality Dangerous reduced conditions for downstream refractory structures 8
Burner technology - Low-NOx The main principle is the limitation of mixing between fuel and air during the initial stage of combustion. The direction of fuel injection is at an angle to the air stream axis, and the mixing of fuel and air in the primary combustion zone is limited. Therefore a high temperature region is reduced. Fuel which is not burned in this zone gradually mixes with air not used in the initial stages and thus combustion is completed. PLUS : level of efficiency depending on starting point and in combination with furnace design Application during furnace run MINUS : No negative impact. Courtesy of Global Combustion 9
Prime Glass technologies Will be object of detailed explanation in present conference 10
Secondary measures (treatment with Ammonia) The secondary measures for NOx abatement are based on the chemical reaction (for simplification we consider just one reaction) between NOx (acid gas) and Ammonia (alkaline and reducing gas), giving as products nitrogen and water. 6 NO + 4 NH 3 5 N 2 + 6 H 2 O The reaction is thermodynamically favored in all conditions, but the kinetics of reaction is strongly affected temperature. Due to temperature condition of waste gases can be achieved: Thermal reaction Only at high temperature (> 800 C) reaction without catalyst SNCR Catalitic reaction Low temperature reaction with catalyst SCR (< 450 C) 11
SCR (Selective Catalytic Reaction) The catalyst may be comprised of a support, typically ceramic, on which porous surface is dispersed a metal capable of catalyzing the reaction (the one of most common use is Vanadium, as V2O5). The catalyst allows the reaction to occur at lower temperatures (between 240 and 430 C) and with higher reduction yields (about 80%). In glass field practical limitation to use EP for dust removal (for working temperatures) The main impacts of SCR system are: Big initial investment of equipment High Operational costs - Electric Energy - Maintenance (mainly catalyst renewal) 12
SNCR (Selective Not Catalytic Reaction) To have the non catalytic abatement (SNCR) of nitrogen oxides the thermal profile has to allow a temperature between 800-1000 C in the zone of ammonia or, more conveniently, urea injection. Compared to SCR systems: Lower initial investment of equipment (nor catalyst nor complex equipment) No significant maintenance costs When is it possible to install a SNCR system? Unit melter Possible (but recuperative system not future technology for other performances) End Port (single pass) Not possible End Port (double pass) Potentially possible for the process, but not achievable for refractory structures safety and process instability Centauro (End Fired furnace) Possible 13
Centauro (Stara Glass Patent) Waste gas reversal valve Ceramic regenerators Combustion air Waste gas Furnace Metallic recuperators Air reversal valve 14
Centauro SNCR temperature window 1250 1350 C 300 550 C 150-250 C T amb. air air air air waste gas waste gas waste gas waste gas 1450 1550 C 800 1000 C 500 650 C 200 400 C 15
Centauro s SNCR results on application Centauro A - Operation SNCR 3 years Centauro B - Operation SNCR 2 years Level of NOx achievable in continuous after SNCR treatment: < 400 mg/nm3 @8%O2 16
Centauro in Europe Centauro 1 Centauro 2 Centauro 3 17
Centauro in Europe UNDER CONSTRUCTION COMING SOON Centauro 4 Centauro 5 Centauro 6 18
Conclusions NOx is the most complex problem faced in glass industry in the environmental field, and will be the biggest challenge to face in the future both for advanced countries and (later on ) for countries in development. There s no direct and unique solution to face this problems, so that glass makers and engineering /technological company invest big effort to find simpler and less impacting solutions for the management of this issue. Thanks to the results coming from many years of field experience in the treatment of emissions and from Prime Glass LIFE Project, Stara Glass is fully qualified to give conventional and advanced solution to manage NOx containment and to make the glass industry a more sustainable industry. 19
THANKS FOR YOUR ATTENTION 20