Pollution Prevention and Abatement Handbook WORLD BANK GROUP Effective July 1998

Glass Manufacturing

Industry Description and Practices Waste Characteristics

This document describes the manufacture of flat Two types of air emissions are generated: those glass and pressed and blown glass. Flat glass in- from the combustion of fuel for operating the cludes plate and architectural glass, automotive glass-melting furnaces, and fine particulates from windscreens, and mirrors. Pressed and blown the vaporization and recrystallization of materi- glass includes containers, machine-blown and als in the melt. The main emissions are sulfur hand-blown glassware, lamps, and television oxides (SOx), nitrogen oxides (NOx), and particu- tubing. In both categories, a glass melt is prepared lates, which can contain heavy metals such as from silica sand, other raw materials such as lime, arsenic and lead. Particulates from lead crystal dolomite, and soda, and cullet (broken glass). The manufacture can have a lead content of 20–60% use of recycled glass is increasing. It reduces the and an arsenic content of 0.5–2%. Certain spe- consumption of both raw materials and energy cialty glasses can produce releases of hydrogen but necessitates extensive sorting and cleaning chloride (HCl), hydrogen fluoride (HF), arsenic, prior to batch treatment to remove impurities. boron, and lead from raw materials. Container, For the manufacture of special and technical pressing, and blowing operations produce a pe- glass, lead oxide, potash, zinc oxide, and other riodic mist when the hot gob comes into contact metal oxides are added. Refining agents include with the release agent used on the molds. arsenic trioxide, antimony oxide, nitrates, and Cold-top electric furnaces, in which the melt sulfates. Metal oxides and sulfides are used as surface is covered by raw material feed, release coloring or decoloring agents. very little particulate matter, as the blanket acts The most common furnace used for manufac- as a filter to prevent the release of particulate turing glass melt is the continuous regenerative matter. Some releases of particulates will take type, with either the side or the end ports con- place in tapping, but furnace releases should be necting brick checkers to the inside of the melter. of the order of 0.1 kilogram per ton (kg/t) when Checkers conserve fuel by acting as heat exchang- operated this way. ers; the fuel combustion products heat incoming Lead glass manufacture may result in lead combustion air. The molten glass is refined (heat emissions of about 2–5 kg/t. conditioning) and is then pressed, blown, drawn, In all cases, the concentration of heavy metals rolled, or floated, depending on the final prod- and other pollutants in the raw flue gas mainly uct. Damaged and broken product (cullet) is re- depends on the type of fuel used, the composi- turned to the process. tion of the feed material, and the portion of re- The most important fuels for glass-melting cycled glass. High input of sulfates or potassium furnaces are natural gas, light and heavy fuel oil, nitrate may increase emissions of sulfur dioxide and liquefied petroleum gas. Electricity (fre- and nitrogen oxides, respectively. Where nitrate quently installed as supplementary heating) is is used, more than two thirds of the introduced also used. Energy requirements range from 3.7 nitrogen may be emitted as nitrogen oxides. The to 6.0 kilojoules per metric ton (kJ/t) glass pro- use of heavy metals as coloring or decoloring duced. agents will increase emissions of these metals.

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The grinding and polishing of flat glass to pro- will reduce energy requirements (for an esti- duce plate glass have become obsolete since the mated 2% savings for each 10% of cullet used in development of the float glass process. The the manufacture of melt) and thus air emissions chemical makeup of detergents that may be used (up to 10% for 50% cullet in the mix). Typical re- in float glass manufacturing can vary signifi- cycling rates are 10–20% in the flat glass indus- cantly—some may contain phosphorus. In blow- try and over 50% for the blown and pressed glass ing and pressing, pollutants in effluents are industries. generated by finishing processes such as cutting, The amount of heavy metals used as refining grinding, polishing, and etching. The pollutants and coloring or decoloring agents, as well as use include suspended solids, fluorides, lead, and of potassium nitrate, should be minimized to the variations in pH. extent possible. Liquid effluents also result from forming, fin- In the furnace, particulates are formed through ishing, coating, and electroplating operations. the volatilization of materials, leading to forma- Heavy metal concentrations in effluents occur tion of condensates and of slag that clogs the fur- where silvering and copperplating processes are nace checkers. Disposal of the slag requires in use. testing to determine the most suitable disposal method. It is important to inspect the checkers Pollution Prevention and Control regularly to determine whether cleaning is required. Oxygen-enriched and oxyfuel furnaces are used Particulate matter is also reduced, for example, in specialty glass operations to reduce emissions by enclosing conveyors, pelletizing raw material, or to make possible higher production rates with reducing melt temperatures, and blanketing the the same size furnace. Although oxyfuel furnaces furnace melt with raw material. may produce higher NOx emissions on a concen- Reductions in wastewater volumes are pos- tration basis, they are expected to yield very low sible through closed cooling water loops and levels of nitrogen oxides on a mass basis (kg/t of improved blowoff techniques. product). Low-NOx furnaces, staged firing, and flue gas recirculation are available to reduce both Target Pollution Loads concentration and the mass of nitrogen oxide emissions. These techniques are also available for Modern plants using good industrial practices air-fuel-fired furnaces. Nitrogen oxide levels can are able to achieve the pollutant loads given here. be controlled to 500–800 milligrams per cubic Because of the lack of nitrogen in the oxidant, meter (mg/m3). using oxyfuel-fired furnaces produces four to five The type of combustion fuel used affects the times less flue gas volume than regenerative fur- amount of sulfur oxides and nitrogen oxides naces. As a result nitrogen oxides are reduced by emitted. Use of natural gas results in negligible 80%, and particulates are reduced by 20–80%. sulfur dioxide emissions from the fuel compared For furnaces that operate with a cover of raw with high-sulfur fuel oils. Fuel oil with a low sul- material, a target of 0.1 kg/t for particulates is fur content is preferable to fuel oil with a high realistic. Reductions in sulfur dioxide are sulfur content if natural gas is not available. achieved by choosing natural gas over fuel oil An efficient furnace design will reduce gaseous where possible. emissions and energy consumption. Examples of improvements include modifications to the Treatment Technologies burner design and firing patterns, higher preheater temperatures, preheating of raw ma- ESPs are the preferred choice for removing par- terial, and electric melting. ticulates, although fabric filters are also used. Dry Changing the composition of the raw materi- scrubbing using calcium hydroxide is used to als can, for example, reduce chlorides, fluorides, reduce sulfur dioxide, hydrogen fluoride, and and sulfates used in certain specialty glasses. The hydrogen chloride. Secondary measures for NOx use of outside-sourced cullet and recycled glass control include selective catalytic reduction 322 PROJECT GUIDELINES: INDUSTRY SECTOR GUIDELINES

(SCR), selective noncatalytic reduction (SNCR), Table 1. Air Emissions from Glass and certain proprietary processes such as the Manufacturing Pilkington 3R process. (milligrams per normal cubic meter) Parameter Maximum value Emissions Guidelines Nitrogen oxides 1,000 (up to 2,000 Emissions levels for the design and operation of may be acceptable, each project must be established through the en- depending on fur- nace technology and vironmental assessment (EA) process on the ba- if justified in the EA) sis of country legislation and the Pollution Prevention Sulfur oxides and Abatement Handbook, as applied to local con- Gas fired 700 ditions. The emissions levels selected must be Oil fired 1,800 justified in the EA and acceptable to the World Particulates 50 (20 where toxic Bank Group. metals are present) The guidelines given below present emis- Lead and cadmium (total) 5 Arsenic 1 sions levels normally acceptable to the World Total of other heavy metals 5 Bank Group in making decisions regarding Fluoride 5 provision of World Bank Group assistance. Any Hydrogen chloride 50 deviations from these levels must be described in the World Bank Group project documenta- tion. The emissions levels given here can be Table 2. Effluents from Glass Manufacturing consistently achieved by well-designed, well- (milligrams per liter, except for pH) operated, and well-maintained pollution con- Parameter Maximum value trol systems. The guidelines are expressed as concentrations pH 6–9 to facilitate monitoring. Dilution of air emissions TSS 50 or effluents to achieve these guidelines is un- COD 150 Oil and grease 10 acceptable. Lead 0.1 All of the maximum levels should be achieved Arsenic 0.1 for at least 95% of the time that the plant or unit Antimony 0.5 is operating, to be calculated as a proportion of Fluorides 20 annual operating hours. Total metals 10

Air Emissions Note: Effluent requirements are for direct discharge to surface waters. The air emissions presented in Table 1 should be achieved. at noise receptors located outside the project property boundary. Liquid Effluents Maximum allowable log The effluent levels presented in Table 2 should equivalent (hourly be achieved. measurements), in dB(A) Day Night Ambient Noise Receptor (07:00–22:00) (22:00–07:00) Residential, Noise abatement measures should achieve either institutional, the levels given below or a maximum increase in educational 55 45 background levels of 3 decibels (measured on the Industrial, A scale) [dB(A)]. Measurements are to be taken commercial 70 70 Glass Manufacturing 323

Monitoring and Reporting • Consider natural gas rather than oil as the fuel of choice. Frequent sampling may be required during start- • Select raw materials to minimize emissions of up and upset conditions. Once a record of con- fluorides and other pollutants such as chlo- sistent performance has been established, rides and sulfates. sampling for the parameters listed in this docu- • Maximize water reuse. ment should be as described below. • For reductions in particulate emissions, pel- Opacity should be monitored continuously. The letize raw materials, enclose conveyors, reduce maximum opacity level should be set to correspond melt temperatures, and blanket the melt sur- to 50 mg/Nm3.Other air emissions parameters face with raw material. should be measured annually. Liquid effluents should be continuously monitored for pH, and Sources other parameters should be tested weekly. Monitoring data should be analyzed and re- Bounicore, Anthony J., and Wayne T. Davis, eds. 1992. viewed at regular intervals and compared with the Air Pollution Engineering Manual. New York: Van operating standards so that any necessary correc- Nostrand Reinhold. tive actions can be taken. Records of monitoring Economopoulos, Alexander P. 1993. Assessment of results should be kept in an acceptable format. The Sources of Air, Water, and Land Pollution: A Guide to results should be reported to the responsible au- Rapid Source Inventory Techniques and Their Use in thorities and relevant parties, as required. Formulating Environmental Control Strategies. Part 1: Rapid Inventory Techniques in Environmental Pollution. Geneva, World Health Organization. Key Issues Sittig, Marshall. 1975. Pollution Control in the Asbestos, The key production and control practices that will Cement, Glass, and Allied Mineral Industries. Park lead to compliance with emissions requirements Ridge, N.J.: Noyes Data Corporation. can be summarized as follows: World Bank. 1996. “Pollution Prevention and Abatement: Glass Manufacturing Plants.” Draft Technical Back- • Consider using oxyfuel-fired furnaces for spe- ground Document. Environment Department, Wash- cialty glass manufacturing. ington, D.C.

• Use low-NOx burners, staged firing, and flue gas recirculation.