Departamento de Ingeniería Química y Tecnología del Medio

Ambiente

GLASS

GROUP 5Alba Calvo García

Javier Caramazana Sánchez

Alberto Nicolás Herrero

Ricardo Treviño Mediavilla

‘GLASS MANUFACTURING INDUSTRY’

EUROPEAN COMMISSION

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Commission

1. GENERAL INFORMATION

Glass Industry: extremely diverse (Products & Manufacturing techniques)

Major companies: Saint-Gobain, Danone, United Glass, AVIR.

- Production EU: 29 million tonnes (1996).- Steady growth in the overall volume of sales over the last decade.

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Glass Industry

Spain:Fourth European producer : 3.742.902 Tonnes of glass (2003, FEVE)Companies: Grupo Vidrala, BA Vidrio, Group Gobain, OI Europe, PPG IndustriesMost of the companies are integrated in ‘Vidrio España’

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The term glass does not have a convenient simple definition.

GLASS: ‘is a hard material, transparent and fragile that ordinarily is obteined by melting silica (SiO2), sodium carbonate (Na2CO3) and limestone (CaCO3)’.

- Glasses are divided into two categories

- Depending on their chemical composition, glasses are clasified in

(f = thermal expansion coefficient, α)

Hard glasses

Soft glasses

four main groups:

GLASS

Soda-lime glasses (bottles, jars, tableware, window glass… ) Lead crystal and crystal glass (decorate items, drinking glasses…)Borosilicate glasses (laboratory equipment, lighting, cookware…)Special glasses (optical glasses, glass solders, electrodes…)

Soda-lime glasses, lead crystal and crystal glass, and Borosilicate glasses represent more than 95 % of all the glasses produced.

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2. APPLIED PROCESS AND TECHNIQUES

Wide range of raw materials diversity of the Glass IndustryMaterials: Silica sand, process cullet, post consumer cullet, sosa ash,colouring agents, feldspar, dolomite, alumina...

Melting: is the central phase in the production of glass. There are numerousways to melt glass depending on the desired product, its end use, the scale of

of operation and commercial factors. Melting technique, fuel choice and furnace

size will all depend on these factors.

Melting techniques:- Regenerative furnaces

- Recuperative furnaces

- Oxy-fuel melting

- Electric melting

- Combined fossil fuel and electric melting

- Discontinuous batch melting

- Special melter desing

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Types of glass

Container Glass.

Flat Glass.

Continuous Filament Glass Fibre.

Domestic Glass.

Special Glass.

Mineral Wool.

Ceramic Fibre.

Frits.

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Raw materials for the Glass Industry are naturally occurring minerals or manmade inorganic substances.

• No major environmental issues associated. Emissions to Air.

• Dust emissions to below 5 mg/m3.• Melting

• The products of fossil fuel combustion and the high temperature oxidation of nitrogen in the combustion atmosphere.

• Volatilisation and subsequent condensation of volatile batch materials.

• Gases emitted from the raw materials and melt during the melting processes.

3. CONSUMPTION AND EMISSION LEVELS

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Emission to Air in the differents types of glass.

• Container glass.

• Flat glass

• Continuous filament glass fibre

• Domestic glass

• Special glass

• The higher temperatures favour higher rates of volatilisation and NOx formation, and the greater use of nitrate refining agents can result in

higher NOx, SO2, and metal emissions.

3. CONSUMPTION AND EMISSION LEVELS

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Emission to Air in the differents types of glass.

• Mineral wool.

• Ceramic fibre• Emissions from melting are generally very low consisting

mainly of dust from raw materials. Dust emissions are generally below 20 mg/m3.

• Frits

3. CONSUMPTION AND EMISSION LEVELS

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Emission to water.

• Water pollution is not a major issue for most installations within the glass industry.

Energy. The theoretical energy requirements for :

• Heat of reaction to form the glass from the raw materials

• Enthalpy, to raise the glass temperature from 20 °C to 1500 °C.

• Heat content of the gases (principally CO2).

3. CONSUMPTION AND EMISSION LEVELS

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Energy in the differents types of glass.

• Container glass• 4.5 to 7.0 GJ/tonne of glass melted and 6.5 to 9.0 GJ/tonne of finished

products.• Flat glass

• Energy levels for melting are typically 5.5 to 8.0 GJ/tonne of glass melted.

• Continuous filament glass fibre• Energy consumption for melting is usually 18 to 33 GJ/tonne of product.

• Domestic glass• As high as 60 GJ/ tonne of finished product.

• Mineral wool• 3.0 to 5.5 GJ/tonne of finished product.

• Ceramic fibre• The energy consumption ranges from 6.5 - 16.5 GJ/tonne of melt.

• Frits • Approximately 13 GJ/tonne.

3. CONSUMPTION AND EMISSION LEVELS

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4. TECHNIQUES IN THE DETERMINATION OF BAT

The main environmental impact as a whole arises due to emissions to air from melting activities.

primary techniques are those which reduce or avoid the formation of the pollutants.

secondary techniques are those which act on the pollutants to render them less harmful or collect them in a form that can be reused, recycled or disposed of.

Major changes affecting melting technology are usually most economically implemented if coincided with furnace rebuilds.

Regenerative Furnaces. Recuperative Furnaces. Combined Fossil Fuel and Electric Melting. Discontinuous Batch Melting. Stone Wool Melting.

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4. TECHNIQUES IN THE DETERMINATION OF BAT

Electric Melting.

Electric melting has important effects on pollutant emissions. Complete replacement of fossil fuels

• Eliminates oxides of sulphur, thermal NOx, and carbon dioxide.• Dust emissions can be controlled by extraction to a dust abatement

system. Not in use for production (>300 tonnes per day).

Techniques for Controlling Emissions to Air from Melting Primary techniques

• Raw material modifications.• Temperature reduction at melt surface.• Burner positioning.• Conversion to gas firing (or very low sulphur oils).

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Main techniques for controlling each substance emitted from melting activities and from downstream operations.

Emissions to air as these are generally the most significant emissions from glass processes.

4. TECHNIQUES IN THE DETERMINATION OF BAT

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MELTING TECHNIQUE SELECTION

The environmental performance of a furnace is a result of a combination

of the choice of melting technique, the method of operation and the

provision of secondary abatement measures. The final choice should be an optimised balance of economic and

environmental advantages.

Regenerative furnaces Recuperative furnaces Combined Fossil Fuel and Electric Melting Discontinuous Batch Melting Electric Melting

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TECHNIQUES FOR MATERIALS HANDLING

Emissions of powder materials can be minimised by using enclosed silos

Collected material can be returned to the silo or recycled to the furnace Fine materials can be stored in enclosed containers Dusty materials can be stored under cover Where materials are transported by conveyors, enclosure to provide

wind

protection is necessary.

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TECHNIQUES FOR CONTROLLING EMISSIONSTO AIR:

These techniques include emissions related to each sector in the Glass Industry.

Emissions and techniques are:

Particulate matter • Primary techniques: raw material changes and

furnace/firing modifications.

• Electrostatic Precipitators

• Bag filters

• Mechanical Collectors

• High Temperature Filter Media

• Wet Scrubbers

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Oxides of Nitrogen (NOx) • Combustion Modifications:reduce air/fuel ratio, reduce preheat

temperature, staged combustion...• Batch Formulation• Special furnace Designs• The FENIX Process: combustion optimisation package based on

primary measures• Oxy-Fuel Melting: replacement of the combustion air with oxygen• Chemical Reduction by Fuel (CRF): Fuel is added to the waste gas

stream to chemically reduce NOx to N2

• Selective Catalytic Reduction (SCR): involves reacting NO with

ammonia in a catalytic bed• Selective Non-Catalytic Reduction (SNCR): The same basis as SCR

but higher temperatures

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Oxides of Sulphur (SOx)• Fuel Selection

• Batch Formulation

• Dry or Semi-dry Scrubbing

Fluorides (HF) and Chlorides (HCl)• Reduction at Source

• Scrubbing Techniques

Oxides of Carbon• CO is rarely emitted from Glass Industry installations at a

level to cause environmental concern• Reduction in emission of CO2 by reducing fuel usage

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TECHNIQUES FOR CONTROLLING EMISSIONSTO WATER Emissions to the water environment are relatively low and not specific

to the Glass Industry. Water can be recycled or treated using standard techniques:

• Physical/Chemical Treatment

. Screening Neutralisation

. Skimming Aeration

. Settlement Precipitation

. Centrifuge Coagulation and Flocculation

. Filtration • Biological Treatment

. Activated sludge

. Biofiltration

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TECHNIQUES FOR MINIMISING OTHER WASTES

Most of the activities in the Glass Industry produce relatively

low levels of solid waste. The main process residues are:

Unused raw materials, Melt not converted into product Waste product dust collected from waste gas streams Solid waste from waste water system

Techniques for minimising wastes are: wherever practicable,

prevention, minimisation of waste by primary means

and recycling

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ENERGY

Glass making is a very energy intensive process The choices of energy source, heating technique and heat recovery

method are central to the economic performance, environmental

performance and energy efficiency. The main techniques for reducing energy usage are:

Melting technique and furnace design Combustion control and fuel choice Cullet usage Waste heat boilers Cullet/batch preheating

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5. BAT CONCLUSIONS

• Principal characteristics• Periodic rebuild of the furnaces• Age of the furnace

• Principal emissions• Dust• Oxides of Nitrogen• Oxides of Sulphur• Other emissions from melting• Downstream processes

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DUST

Is considered to be the use of an electrostatic precipitator or bag filter operating, in conjunction with a dry or semi-dry acid gas scrubbing system

• Container glass Less than 0.1 kg/tonne of glass melted

• Flat glass

• Continuous filament glass fibre

• Domestic glass Level associated: 5 – 30 mg/Nm3

• Special glass Level associated: 5 – 30 mg/Nm3

• Mineral wool Level associated: 5 – 30 mg/Nm3

• Frits Less than 0.1 kg/tonne of glass melted

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OXIDES OF NITROGEN

• Container glass Less than 1000 mg/Nm3. Generally equates to less than 3.0 kg/tonne of glass melted.

• Flat glass 500 - 700 mg/Nm3 which generally equates to 1.25 - 1.75 kg/tonne of glass melted.

• Continuous Filament Glass Fibre Generally higher than 1000 mg/Nm3 and greater than 4.5 kg/tonne of glass melted.

• Domestic Glass In air-fuel fired furnaces are generally in the range 1500 - 2000 mg/Nm3 which generally equates to 3.75 - 5 kg/tonne of glass melted.

• Special glass 500-700 mg/Nm3.

• Mineral Wool 500 - 700 mg/Nm3 which generally equates to 0.5 - 1.4 kg/tonne of glass melted.

• Frits 0.5 - 1.5 kg/tonne of glass melted or alternatively 500 - 700 mg/Nm3.

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OXIDES OF SULPHUR• Container glass For natural gas firing up to 800 mg/Nm3 which generally equates to 1.2 kg/tonne of glass melted. For oil firing up to 1500 mg/Nm3 which generally equates to 2.25 kg/tonne of glass melted.

• Flat glass For natural gas firing up to 800 mg/Nm3 which generally equates to 2 kg/tonne of glass melted. For oil firing up to 1500 mg/Nm3 which generally equates to 3.75 kg/tonne of glass melted.

• Continuous filament glass fibre For natural gas firing less than 200 mg/Nm3 which generally equates to less than 0.9 kg/tonne of glass melted. For oil firing 500 - 1000 mg/Nm3 which generally equates to 2.25 to 4.5 kg/tonne of glass melted.

• Domestic glass For natural gas firing 200 - 500 mg/Nm3 which generally equates to 0.5 – 1.25 kg/tonne of glass melted. For oil firing 500 - 1300 mg/Nm3 which generally equates to 1.25 – 3.25 kg/tonne of glass melted.

• Special glass Similar to domestic glass.

• Mineral wool less than 600 mg/Nm3 which generally equates to less than 1.5 kg/tonne of glass melted.

• Frits 0.1 - 0.5 kg/tonne of glass melted which generally equates to less than 200 mg/Nm3.

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6. EMERGING TECHNIQUES

1. Low Nox burner systems

- The reducing conditions above the melt or batch blanket could affect glass quality and may cause early surface descomposition. Required extra sulfate which may lead to increased SOx emissions.

2. Oxy-fuel melting

- The exiting installations are still based on a conventional recuperative style cross-fired furnace.

3. Cullet and batch preheating

4. Batch formulations

- Two main air emission components: particulates and fluorides.

5. Integration of frit processes

6. Flue gas recirculation

- “Synthetic air”, based on the combination of flue gas recirculation and the use of oxygen firing.

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6. EMERGING TECHNIQUES

7. Glasulin research program

- Joint project between 17 glass companies and 4 research institutes and has the objetive for developing new methods for the reduction of sulphate levels in the batch.

7. New melter designs

8.1. The seg melter

- Batch is charged into an all-electric pre-melting furnace capable of converting 75% of the raw material into glass.

8.2. The advanced glass melter

- Potencial for low NOx emissions.

8.3. The plasma melter

- The composition and colour of the glass can very rapidly be altered. SOx, NOx and dust emissions are negligible.

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7. CONCLUDING REMARKS

Identify those techniques which are most likely to be appropriate for a given sector.

Develop a methodology for assessing the relative effects on the environment taken as a whole of emissions to different media and to the same medium.

The application of oxy-fuel firing is at a relatively early stage. Some issues can only be assessed with information from the long-term use of the technique. Also the direct costs of the technique should be reassessed particularly with regard to the balance between energy savings and the cost of oxygen.