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Solid Waste Source Reduction and Recycling
Published in Charles R. Rhyner, Leander J. Schwartz, Robert B. Wenger, Mary G. Kohrell, Waste Management and Resource Recovery, 2017
Charles R. Rhyner, Leander J. Schwartz, Robert B. Wenger, Mary G. Kohrell
Silica sand, a very pure form of silicon dioxide, is the most common ingredient in glass manufacturing. Sodium oxide, commonly known as soda ash, is used as a fluxing agent to lower the high melting point of sand. Blending limestone, the third major glass ingredient, with the soda ash reduces water solubility. Silica sand, soda ash, and limestone are all available in abundant supplies. By adding alumina, boric oxides, coloring agents, or other minor ingredients, easily formed durable containers can be produced. In addition to these ingredients, the glass container industry has always used in-house cullet in its batches because cullet melts at lower temperatures than the virgin raw materials used to make glass. If significant quantities of cullet are used, its lower melting results in energy savings in the manufacturing process. As noted in Table 4.3, energy savings are likely to be in the range of 4% to 32%.
III Recycling of Glass
Published in Susan E. M. Selke, Packaging and the Environment, 1994
Recycled glass used as a raw material in glass production is known as cullet. The use of a certain amount of cullet is essential in a glassmaking operation. Normally about 10 percent of glass production ends up as in-house cullet due to such factors as manufacturing defects and breakage (Hanlon, 1984). The cullet serves to facilitate the melting of the other raw materials, allowing for operation at a somewhat lower temperature. The lower temperature, in turn, reduces energy use (though the savings is very much smaller than for aluminum), increases production, and increases furnace life. Every 1 percent increase in cullet is estimated to save 0.25 percent of the energy used to make glass containers (Glass Packaging Institute, 1986). It is estimated that use of 50 percent cullet can double furnace life. Air emissions of nitrogen oxides and particulates are also somewhat reduced, with total air pollution reduced 20 percent with recycled glass. Water use is reduced 50 percent (Walsh and O'Leary, 1988). Use of 1 ton of cullet also saves 1.2 tons of virgin raw materials (Pollock, 1987).
Glasses
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
Ordinary ‘soda’ glass is made from a mixture of silica sand, soda ash (crude sodium carbonate) and lime (from limestone). Since glass is an easy product to recycle, large amounts of scrap glass, known as cullet, are used in glass manufacture. Large ‘tank’ furnaces, usually gas-fired and operating at 1590°C, hold up to 250 tonnes of molten glass produced from the raw materials and up to 90% cullet. The cullet comes mainly from ‘bottle banks' operated by municipal authorities. Almost half of bottles find their way to these ‘banks'.
Pilot-scale, on-site investigation of crushed recycled glass as tertiary filter media for municipal lagoon wastewater treatment
Published in Environmental Technology, 2022
Rena D. Salzmann, Joe N. Ackerman, Nazim Cicek
Glass containers are widely used for food, beverage and cosmetics packaging, accounting for approximately 98% of the total waste glass generation [1]. Glass packaging waste can be continually recycled into new glass containers, without any loss of quality or purity. This process requires waste glass to be cleaned, separated by colour and crushed to cullet – crushed recycled glass suitable for remelting. Cullet is then mixed with virgin materials and melted to produce new glass packaging products. The addition of cullet reduces both the amount of raw materials and energy required for container glass production [2–4]. Every tonne of recycled glass remanufactured into container glass saves 315 kg of CO2, which includes transportation and processing emissions [5]. Despite the benefits of closed-loop glass recycling, there are many obstacles to that process.
Prospects and physical limits of processes and technologies in glass melting
Published in Journal of Asian Ceramic Societies, 2019
The earlier decrease (1930–1970) in the above compilation was due chiefly to progress in the field of refractory materials allowing the use of increased processing temperatures. While a glass furnace in 1930 had a lifetime as short as just 1 to 1.5 years, lifetimes well beyond 10 years are now standard. The significant further decrease (1970–1990) was due mainly to systematic use of recycled cullet. Depending on the glass color, 30% to 70% and often up to 90% of cullet is used in the container glass category while 25% is a typical level for flat glass. Thus, both the development of refractory materials and the use of cullet must be considered as the two major milestones in energy saving. Lately [1,2], a benchmark survey on >130 container glass furnaces was presented. Energies were normalized to 50% cullet and to the primary energy equivalent of oxygen production for oxy-fuel furnaces. The ranking yielded the following:
Mechanical performance of cement-stabilised soil containing recycled glass as road base layer
Published in Road Materials and Pavement Design, 2020
Rosalia Pacheco-Torres, Fernando Varela
Regarding the standards and technical considerations, the USA Department of Transportation and the American Association of State Highway and Transportation Officials consider up to 10% of RG content in granular base applications and up to 30% in subbase applications (American Association of State Highway and Transportation Officials, 2000; Federal Highway Administration U.S. Department of Transportation, 2016; Minnesota Department of Transportation, 2005). In Australia and New Zealand just 5% of cullet glass content is permitted in granular products (Arnold, Werkmeister, & Alabaster, 2008).