Valuable Recycling of waste glass generated from the liquid crystal display panel industry

Accepted Manuscript Valuable Recycling of Waste Glass generated from the Liquid Crystal Display Panel Industry

Kicheol Kim, Kidong Kim PII:

S0959-6526(17)32618-5

DOI:

10.1016/j.jclepro.2017.10.326

Reference:

JCLP 11118

To appear in:

Journal of Cleaner Production

Received Date:

12 June 2017

Revised Date:

21 October 2017

Accepted Date:

29 October 2017

Please cite this article as: Kicheol Kim, Kidong Kim, Valuable Recycling of Waste Glass generated from the Liquid Crystal Display Panel Industry, Journal of Cleaner Production (2017), doi: 10.1016/j. jclepro.2017.10.326

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ACCEPTED MANUSCRIPT

Highlights Recycling of LCD process waste glasses (LPWG) in E-glass was examined. Source of B2O3 such as colemanite was replaced by LPWG. Effect of contaminants coated to the surface of LPWG was negligible. Two important melt properties for LPWG content showed an opposite behavior. Replacement of E-glass with LPWG up to 50 % in glass batch was suggested.

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Valuable Recycling of Waste Glass generated from the Liquid Crystal Display Panel Industry Kicheol Kim, Kidong Kim* Department of Materials Science and Engineering, Kunsan National University, Kunsan, Chunbuk 54150, Republic of Korea. Abstract Due to the drastic growth of the liquid crystal display (hereafter LCD) industry in the last decade, lots of waste glass is being produced. There are three types of waste glass derived from LCD glass manufacturers, LCD panel manufacturers and end-oflife LCD devices. Among them cullet from LCD glass is being recycled into a raw material for commercial electric continuous fiber glass (hereafter E-glass). However, the recycling of waste glass from LCD panel (LPWG) and end waste glass is limited due

to

various

reasons

such

as

contaminants,

toxic

components

and

inhomogeneous glass compositions etc. Despite use of LPWG in the cement industry, it is not an effective form of recycling, considering the characteristics of LCD glass. In this work, to examine the possibility of recycling LPWG in the E-glass industry, several glass batches containing LPWG were prepared. First, some optical properties of the prepared and commercial E-glass were examined. Then, the viscosity and liquidus temperature (TL) were determined. The effect of LPWG was

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negligible in the transmission and color of the resultant glasses, considering that commercial bulk E-glass has an emerald-green color due to refractory corrosion. With an increase in the LPWG content, the isoviscosity and liquidus temperatures showed opposite behaviors; the temperature (TW) corresponding to the fiber forming viscosity (103 dPas) decreased, whereas the TL increased. Based on TW-TL, the replacement of 50 wt% of the original E-glass with LPWG was recommended. Additionally, economic and environmental effects were discussed. Keywords: LCD waste glass, recycling, E-glass, viscosity, liquidus temperature

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1. Introduction The manufacturing of LCD panels for information display devices, such as televisions, monitors, and mobile phones, only occurs in four Asian countries, that is, Korea, Japan, Taiwan and China. A large amount of waste glass is being generated from the LCD industry. This waste glass can be divided into three categories: 1) LCD cullet from LCD glass manufacturers, 2) LCD process waste glass (hereafter designated LPWG) from LCD panel manufacturers, and 3) end LCD waste glasses from end-of-life LCD devices. Among them, LCD cullet is recycled as a raw material for commercial alkali-free borosilicate fiber glass, so-called E-glass, and has been used for alkali borosilicate glass wool and soda lime silicate container glass in Korea (Kim and Hwang, 2011; Kim et al., 2014). LCD cullet is the main raw material to supply B2O3 to E-glass and glass wool and can also be used to supply Al2O3 to soda lime silicate container glass. In end LCD waste glass, however, toxic components, such as arsenic and antimony oxide, contained in most LCD glass produced before 2010 (Ellison and Cornejo, 2010) preclude their recycling, and thus they are disposed of as waste material (Bihlmaier and Völker, 2013). Approximately 80 kt/y of LPWG is produced by LCD panel manufacturers. Furthermore, about half of that value, approximately 40 kt/y, is produced by Korean manufacturers, who in 2015, had a share of approximately 50 % in the global LCD

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panel market (IEEE GlobalSpec, 2015). LPWG can be divided into two groups: one originates from the edge trimming of the combined two glass substrates before application of the polarizing film, while the other originates from the inspection of the finished panels before injection of the liquid crystal. The reuse of LPWG as a raw material for LCD glass is impossible due to contaminates such as coatings on its surface. The introduction of LPWG to batch of the original LCD glass or other colorless glass produces a slightly grayish color. Besides, the LPWG composition fluctuates considerably depending on the glass supplier, and thus, LPWG recycling is difficult in a process that is sensitive to composition change. However, if each LCD manufacturer tended to favor a specific glass manufacturer, fluctuations in the LPWG composition could be remarkably improved. Several studies have introduced LPWG as raw material in the development of glass-ceramics (Lin, 2007; Lin et al., 2009; Fan and Li, 2013; Fan and Li, 2014), traditional sintered ceramics (Kim et al., 2015; Kim et al., 2016), insulating foamed glass (Lee, 2013) and cement (Lin et al., 2009; Wang, 2011; Ling et al., 2013). In Korea, approximately 80 % of LPWG is now being recycled for use as a raw material in cement. Considering the composition and components of LPWG, however, this is not an effective form of recycling. LCD glass is alkali-free and composed of SiO2, Al2O3, B2O3, and alkaline earth oxides. As described in detail in a review literature (Ellison and Cornejo, 2010), LCD

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glass is produced by stirrer melting above 1600 ℃, using high-purity raw materials to guarantee the display quality and thus the LPWG itself, excluding surface coatings, has excellent homogeneity. Moreover, unlike LCD glasses produced before 2010, current LCD glasses contain no toxic components, which indicates that the resulting waste glass, such as LPWG, is environmentally friendly. Therefore, LPWG could be a raw material for other commercial E-glasses through the addition of a proper amount to the glass batches, under the condition that there is little influence on the production process and the properties of the original glass. If such an application of LPWG is realized, the following more valuable effects are expected: 1) raw material conservation, especially for the expensive B2O3 supplier, and 2) energy conservation accompanied by the reduction of CO2 emissions. In the present work, edge trimming waste glass, i.e., one of LPWG, was introduced to commercial E-glass batches, and its influence on important melt properties for the production of fiber glass was examined. The results were discussed from the viewpoint of production, economic and environmental effects. 2. Materials and methods 2.1. LPWG source Edge trimming waste glass obtained from LCD panel production processes at the LG Display Co. plant in Gumi, Korea, was used as the LPWG source. As shown

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in Fig. 1, only one surface of the waste glass fragments is patterned by Cu and Mo coatings, which serve as electric circuits, and their concentration in oxide form in remelted LPWG is under 150 ppm. LPWG fragments were used as a raw material without refining. 2.2. Glass preparation Table 1 contains the experimental batch compositions of E-glass containing LPWG, which was introduced to the batch in contents up to approximately 70 wt% of the total glass. The chemical formula of each raw material is also given in parenthesis. The chemical analysis results of the raw materials, including LPWG, are provided in Table 2. The original batch composition of E-glass is denoted E0LPWG. Approximately 300 g of the glass batch described in Table 1 was melted at 1500 ℃ in a Pt/20Rh crucible for two hours, and the bubble-free melts were homogenized by a Pt/20Rh stirrer. The glass was cast on graphite plates and annealed near its transition temperature (695 ℃). The theoretical compositions of the resulting glasses calculated from the experimental batches are presented in Table 3. 2.3. Visible transmission To examine the effect of contaminates, such as Cu and Mo, coated on the LPWG surface on the final color of the bulk glass, the spectrum and color of the prepared glasses were compared with those of commercial bulk E-glass without

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LPWG produced at the KCC Co. plant in Sejong, Korea. The transmission spectrum and color chromaticity of the glasses with dimensions of 20×30×4 mm were measured in the visible wavelength range of 340-850 nm using a UV-Vis spectrophotometer (UV-2401PC, Shimadzu, Japan). 2.4. Process properties The commercial production line of E-glass fiber consists of a melting furnace, a forehearth and bushing. A brief description of the typical production process is presented in Fig. 2. The production process of E-glass fiber is divided into batch melting for a phase transition from the mixed crystalline raw materials to melts, refining to remove bubble, conditioning for proper viscosity to fiberize and fiber forming at the bushing. In this process, the two most important properties of the melts are the viscosity (η) and liquidus temperature (TL), which must be estimated when applying new raw materials (Wallenberger and Bingham, 2010). The melts derived from batch melting are conditioned in a forehearth to optimize the material for continuous fiber formation. Viscosity is an index describing the fluidity of melts, which must have an optimal viscosity for the fining, homogenization of the melt and fiber formation (Wooley, 1991; Varshneya, 1994; Martlew, 2005). In particular, fiber formation by Pt alloy bushing, i.e., fiberization, is sensitive to the melt viscosity at working temperature (Tw) (Wallenberger et al., 2001; Wallenberger and Bingham,

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2010). TL is the maximum temperature at which crystallization (strictly called devitrification) occurs in the glass itself at equilibrium. To guarantee glass formation without devitrification in E-glass, TL should be lower than Tw corresponding to 103 dPas. The value of η in the melt state was determined over a glass temperature range of 1100-1500 ℃ using a vertical precision tube furnace in which a rotating viscometer (VT-550 Haake Viscotester, Thermo Scientific, Germany) based on DIN 52312 was installed. The viscometer was calibrated using standard glass I from DGG (Deutsche Glastechnische Gesellschaft) in a Pt/20Rh crucible by the rotation of a Pt/20Rh spindle (Meerlender, 1974). The temperatures corresponding to three viscosity points, logη=2, 2.5 and 3 (η in dPas), were calculated by the Vogel-FulcherTamann (VFT) equation based on the measured viscosity at high temperatures as follows, logη=A+B/(T-T0) where A, B and T0 are constant and T is the temperature in ℃ (Scholze, 1988). To determine the TL of the glasses, the glass powder was sieved under 20 mesh (850 μm), placed in a Pt/5Au boat and soaked for 8 hours in a gradient temperature furnace over a temperature range of 800-1200 ℃, following ASTM C829-81. The temperature was controlled within 1 ℃, and TL was first determined for a standard

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glass sample (NIST/NBS SRM 773). A crystalline shape existing near the surface of the quenched glass was observed by a polarizing microscope (DM-EP, Leica, USA), and TL was determined. The viscosity at TL was also calculated by the aforementioned VFT equation. Detailed descriptions of both the melt viscosity and the liquidus temperature are given elsewhere (Hwang et al., 2000). The densities of the annealed glasses were also measured by the Archimedes method using a density determination kit (77402, Ohaus, USA). 3. Results and discussion 3.1. Color and transmission. Photographs of the four glass samples are presented in Fig. 3. The bulk E0LPWG and E70LPWG glasses melted in a laboratory Pt alloy crucible were light green and colorless, respectively. In contrast, the bulk glass (E0LPWGInd) produced in an industrial melting furnace was emerald green. However, fiber produced with diameter of 10 µm, so-called chopped strand glass, has white color. There is a remarkable difference in color between the laboratory glasses, the industry glass and fiber glass. Fig. 4 shows the spectral transmission of the E0LPWG~E70LPWG series, including E0LPWGInd. The transmittance increases upon the addition of LPWG. However, the emerald-green industry bulk glass, E0LPWGInd, shows a relatively low

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transmittance in the visible range. The chromaticity coordinates (x, y, z) of the color slightly shift in the blue direction with an increase in LPWG. However, the color coordinates of E0LPWGInd (0.3107, 0.3223, 0.3670) are somewhat different from those of E0LPWG (0.3136, 0.3244, 0.3620) and the other samples. Additional details concerning the chromaticity coordinates of all glass samples are provided in Table 4. The Fe2O3 concentration in LCD glass is controlled due to the deep and broad absorption bands of Fe2+ at 1050 nm (Ellison, 2012). The present LPWG contains 500 ppm Fe2O3. Pyrophyllite, which is often replaced by LPWG in the raw materials of E-glass, as shown in Table 1, contains a much higher Fe2O3 concentration of 3500 ppm (see Table 2). Therefore, the Fe2O3 concentration in the prepared glass decreases with an increase in the LPWG content (see Table 3), which results in an increase in the transmittance of the glasses containing LPWG, as shown in Fig. 4 (see also average transmittance in Table 4). However, the surface thin-film materials on LPWG shift the color chromaticity very slightly toward the blue direction, as these materials may behave as multivalent ions (for example, Cu2+) as a constituent of glass (Bamford, 1977). In fact, the color difference between E0LPWG and E70LPWG could not be visibly distinguished, excluding the effect of Fe2O3 concentration. E0LPWGInd collected from the industrial plant, however, has an emerald-green color, as mentioned above, unlike the other LPWG-series glasses

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prepared in the laboratory. Industrial melting furnaces for E-glass are constructed of various kinds of refractory. In particular, the refractory in contact with the melt must be anticorrosive, and thus, a special refractory cast by the electric fusion of Cr2O3doped AZS (Al2O-ZrO2-SiO2) is normally installed in the area that contacts the melt as indicated in Fig. 2 (Velez et al., 1997). Therefore, Cr ions from the refractory diffuse into the melt, resulting in the emerald-green color of the final glass due to the absorption of Cr3+ (see Fig. 3) (Boymanns et al., 1997). According to ICP analysis (iCAP7400DUO, Thermo Scientific, USA), the concentration of Cr in E0LPWGInd is 27 ppm (converted value to Cr2O3: 39.4 ppm). Finally, the slight color change in the glasses containing LPWG prepared in the laboratory is negligible because the final color of industrial E-glass is strongly influenced by Cr3+ from the refractory in the melting furnace. In other words, contaminants coated on the edge trimming waste glass of LPWG, such as Cu, Mo, etc., do not prevent LPWG from being recycled as a raw material for E-glass. Furthermore, when formed into thin fibers, the emeraldgreen glass is seen as white. 3.2. Viscosity, liquidus temperature and glass forming ability Based on the temperature dependence of the viscosity (Fig. 5) of the LPWGseries glasses, in Fig. 6 the temperature corresponding to viscosities of logη=2, 2.5, 3 and TL are plotted as a function of the LPWG content. These isoviscosity curves

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show that the temperature decreases with an increase in the LPWG content; in other words, the addition of LPWG to the glass batch induces a decrease in the melt viscosity. However, this effect is mitigated by an increase in the melt viscosity, according to the temperature difference (ΔTη) between E0LPWG and E70LPWG at constant viscosity, for example, ΔTη=55 ℃ at logη=2, 43 ℃ at logη=2.5 and 39 ℃ at logη=3. The polarizing microscopy images of the LPWG-series glasses thermally treated for 8 hours show that at low temperature, there are many needle-shaped crystals (see Fig. 7(a)) whose frequency decreases with increasing temperature. Photographs of E0LPWG taken between 818 and 1124 ℃ are presented in Fig. 7(b). The maximum temperature at which crystals exist is TL. The TL of the prepared glasses increases with an increase in the LPWG content, as shown in Fig. 6. The TL of E0LPWG and E70LPWG is 1097 and 1144 ℃, respectively. The TL of E70LPWG deviates by +47 ℃ from the original E-glass (E0LPWG). TW, TL and related parameters are summarized in Table 5. The decrease in the temperature, including TW, at fixed viscosity with increased LPWG content (see also Fig. 6) may be due to the addition of glass network modifying components, such as SrO and BaO, derived from LPWG. Considering the crystallization mechanisms, however, the contaminants derived from the surface coatings of LPWG would play a

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greater role in increasing TL than the composition change of E-glass upon the introduction of LPWG itself. The glass forming ability is defined in terms of a melt’s resistance to crystallization during cooling (Shelby, 2005) and is proportional to the cooling rate and viscosity of the melt. TL is of practical importance since devitrification near TW during formation is highly undesirable. Therefore, the difference (ΔT=TW-TL) can be an indirect indicator of the cooling rate for glass formation; in other words, at the same cooling rate, a greater ΔT provides a more desirable glass formation (Wallenberger and Smrček, 2010). In general, a reduction in the viscosity by compositional change results in an increase in the material diffusion, which enhances the crystallization rate of a glass. Therefore, the viscosity at liquidus temperature, namely, log at TL, can also be an indicator to depress the devitrification, and thus, the glass forming ability is enhanced by an increase in log at TL (Hlaváč, 1983). The decrease in T and logη at TL with an increase in the LPWG content, as shown in Table 5, clearly indicates that the introduction of LPWG is unfavorable for fiber forming processes. However, it is not easy to determine the amount of LPWG that would be accepted by the E-glass industry, because the production technology depends on each manufacturer. Considering that the ΔT of the other two commercial E-glasses with different B2O3 concentrations (<1.5 and 0

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wt%) is 58 and 85 ℃, respectively (Wallenberger and Bingham, 2010), it is tentatively suggested that the introduction of up to 50 % LPWG (E50LPWG) is possible for the present E-glass batch. The density (d) of the resulting glass, given in the last column of Table 5, increases almost linearly with an increase in the LPWG content due to the introduction of heavy-molecular-weight components, such as SrO and BaO. This increased density of a new batch containing LPWG in the initial input to the melting furnace is rather desirable because mixing with the previous melts in the melting furnace will proceed faster, resulting in a good homogeneity of the final melts (Chopinet et al., 2010). 3.3. Economic and environmental effects. Comparing the LPWG composition with that of the original E-glass (E0LPWG), it is recognized that SiO2, Al2O3 and B2O3 can be largely supplied from LPWG (see Tables 2). Fig. 8 created based on Table 1 clearly demonstrates the amount of raw materials (pyrophyllite and colemanite) that can be reduced by the introduction of LPWG. With an increase in the LPWG content, the input of pyrophyllite (supplier of Al2O3 and SiO2) and colemanite (supplier of CaO and B2O3) to the batch can be greatly decreased. In particular, a remarkable reduction in the most expensive material, colemanite, which supplies B2O3, is observed; for example, the input of

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colemanite in the batch for E50LPWG is reduced to approximately 23 % of the initial amount, namely E0LPWG. Here, 77 % of the B2O3 concentration required in E-glass is supplied from LPWG, and the rest comes from colemanite. In the batch for E70LPWG, the total B2O3 content can come from LPWG, without the need for colemanite. These results imply that a large amount of natural raw materials in the Eglass industry could be conserved by the application of LPWG. B2O3 plays several important roles in the production of alkali-free E-glass, for example, lowering the batch melting temperature by the formation of the liquidus with SiO2 (FToxide-Oxide Phase Diagrams) as well as the viscosity by the formation of [BO3] coordination in the melt structure (Gupta et al., 1985). Despite these positive effects, crystalline raw materials containing B2O3, such as colemanite and boric acid, have serious disadvantages, such as high batch cost and high volatilization of B2O3 during melting, resulting in hazardous particulates through waste gas (Wallenberger et al., 2007). However, these problems can be solved to some extent by the introduction of LPWG. Since LPWG is a recycled waste glass, its cost is lower than colemanite or any source of B2O3, and unlike traditional raw materials, it only reverts to a viscous liquid during heating, without any chemical reactions that cause B2O3 volatilization or refractory corrosion.

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In relation to energy conservation, the use of LPWG can significantly lower the energy cost of operating a glass melting furnace. In general, the required energy can be reduced by 3 % for each 10 wt% cullet in the total glass product consisting of soda lime silica such as bottle glass and flat glass (Fleischmann, 1997; Beerkens et al., 2004; Masanet et al., 2008). This also applies to waste glass, such as LPWG, and thus, an energy savings of approximately 15 % can be expected for the E50LPWG batch. Furthermore, the temperature at constant melt viscosity, as shown in Fig. 6, decreases with the LPWG content. Considering that glass production processes, including melting, depend on the melt viscosity, the energy demand for the operation of the melting furnace would be much lower due to both the introduction of waste glasses (LPWG) and the decrease in the isoviscosity temperature. In addition, this energy savings is very desirable for reducing CO2 emissions, as every ton of postconsumer cullet recycled in a glass furnace saves 270 kg of CO2 from being emitted during the production of glass fibers (Vieitez et al., 2011). These data indicate the effect of LPWG on the reduction of CO2 emissions. This CO2 reduction effect is also valid in the clay brick production in which waste glass is used as raw material and thus results in decrease of the firing temperature (Layman’s Report, 2017). Moreover, other toxic gas emissions, such as NOx, will be reduced because less fuel is used (Enneking, 1994). In Table 6 an approximate

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relative comparison between E0LPWG and E50LPWG is summarized from the view

point of raw material cost, energy cost and CO2 emission. The results show that the introduction of 50% LPWG to glass batch makes it possible to save 28% and 15% in raw material and energy cost, respectively and to reduce 18% in CO2 emission. There is another advantage in using glass cullet. In particular, the furnace life can be prolonged up to 30 % due to the decreased melting temperatures and use of a less corrosive batch by the introduction of glass cullet (Ruth and Dell'Anno, 1997). This leads to a reduction in the furnace depreciation cost, which contributes to cost savings in glass production. Such economic and environmental effects have been proven by the application of LCD cullet to E-glass batches in industrial plants (Kim and Hwang, 2011).

4. Conclusions In the present work, a recycling possibility of LCD process waste glasses (LPWG) in E-glass industry was examined. It is clarified that contaminants coated to the surface of LPWG such as Cu and Mo are not obstacle in recycling of LPWG as a raw material for E-glass because the final color of industrial E-glass depends strongly on Cr3+ derived from refractory corrosion in the melting furnace. The two most important process properties in industrial E-glass production, viscosity and

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liquidus temperature showed an opposite behavior in their dependence on LPWG content. Especially, the liquidus temperature showed an unfavorable tendency for fiber forming process. Nevertheless it was suggested that a replacement of E-glass by LPWG is possible up to 50 % considering the cases of the other commercial Eglasses. Those results were filed as patent. From the view point of economics and environment the effects of LPWG were also discussed. Contribution of LPWG to the conservation of natural raw materials, emission reduction of polluting materials and CO2, saving of batch cost and energy, and even extension of furnace life was treated in detail. An attempt to use LPWG of edge trimming waste glass is now running in Korean E-glass industry. At the same time, a process for the refining of LPWG generated from the inspection of the finished panels is being also developed.

Acknowledgments We thank LG Display Co. and KCC Co. for supplying the LCD waste glasses and Eglasses, respectively. This study was supported by the R&D Center for Valuable Recycling in the Institute for Advanced Engineering (Global-Top Environmental Technology Development Program) and was funded by the Ministry of Environment, Republic of Korea (Project No. 2016002250005).

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Martlew, D., 2005. Viscosity of molten glasses, in: Pye, L. D., Montenero, A., Joseph, I. (Eds), Properties of Glass Forming Melts. CRC Press, Boca Raton, FL, pp. 75-141. Masanet, E., Worrell, E., Graus, W., Galitsky, C., 2008. Energy Efficiency Improvement and Cost Saving Opportunities for the Fruit and Vegetable Processing Industry: An ENERGY STAR® Guide for Energy and Plant Managers. Ernest Orlando Lawrence Berkeley National Laboratory, University of California Berkeley, CA 94720. Meerlender, G., 1974. Viskositäts-temperaturverhalten des standardglases I der DGG. Glastechn. Ber., 47, 1-3. Ruth, M., Dell'Anno, P., 1997. An industrial ecology of the US glass industry. Resour. Policy, 23, 109-124; DOI 10.1016/S0301-4207(97)00020-2. Scholze, H., 1988. Glass: Nature, Structure, Properties. Springer-Verlag, Berlin, Heidelberg. Shelby, J. E., 2005. Introduction to Glass Science and Technology. Royal Society of Chemistry, Cambridge. Varshneya, A. K., 1994. Fundamentals of Inorganic Glasses. Academic Press, San Diego.

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Velez, M., Smith, J., Moore, R. E., 1997. Refractory degradation in glass tank melters.

A

survey

of

testing

methods.

Cerâmica,

43,

180-184;

DOI.org/10.1590/S0366-69131997000400006 Vieitez, E. R., Eder, P., Villanueva, A., Saveyn, H., 2011. End-of-Waste Criteria (EoW) for Glass Cullet: Technical Proposals. European Commission Joint Research Centre Institute for Prospective Technological Studies, Seville Spain. Wallenberger, F. T., Bingham, P. A., 2010. Fiber Glass and Glass Technology: Energy-Friendly Compositions and Applications. Springer, New York. Wallenberger, F. T., Smrček, A., 2010. The liquidus temperature; its critical role in glass manufacturing. Int. J. Appl. Glass Sci., 1, 151-163; DOI 10.1111/j.20411294.2010.00015.x. Wallenberger, F. T., Hicks, R. J., Simcic, P. N., Bierhals, A. T., 2007. New environmentally and energy friendly fibreglass compositions (E-glass, ECRglass, C-glass and A-glass)-advances since 1998. Glass Technol.: Eur. J. Glass Sci. Technol., Part A, 48, 305-315. Wallenberger, F. T., Watson, J., Li, H., 2001. Glass fibers, in: Miracles, D. B., Donaldson, S. L. (Eds), ASM Handbook, Vol. 21, Composites. ASM International: Materials Park, OH, pp. 27-34.

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Wang, H. Y., 2011. The effect of the proportion of thin film transistor–liquid crystal display (TFT–LCD) optical waste glass as a partial substitute for cement in cement mortar. Construction and Building Materials, 25, 791-797; DOI 10.1016/j.conbuildmat.2010.07.004. Wooley, F. E., 1991. Melting/Fining, in: Jr. Schneider, S. J. (Eds), Engineered Materials Handbook, Vol. 4: Ceramics and glasses. ASM International, Materials Park, OH, pp. 386-393

25

Fig. 1. Appearance of edge trimming waste glass fragments in LPWG. Coatings serving as electric circuits are visible on the surface of waste glass fragments.

Fig. 2. Typical commercial production process of E-glass fiber and two important process properties (η and TL)

Fig. 3. Appearance of two glass bulk samples (E0LPWG, E70LPWG) melted in laboratory Pt alloy crucible, E-glass bulk (E0LPWGInd) and E-glass called chopped strand fiber produced in industry melting furnace.

Transmittance (%)

90

80

70

60

400

450

500

550

600

650

700

750

Wavelength (nm)

Fig. 4. Spectral transmission in visible range: E0LPWG (—), E10LPWG (—), E30LPWG (—), E50LPWG (—), E70LPWG (—), and E0LPWGInd (—).

5.0

log (dPas)

4.5 4.0 3.5

log  

3.0

(Tw)

2.5 2.0 900

1000

1100

1200

1300

1400

1500

o

Temperature ( C Fig. 5. Temperature dependence of viscosity of five melts. E0LPWG; (■), E10LPWG; (●), E30LPWG; (▲), E50LPWG; (▼), E70LPWG; (◆).

1450

1350

o

Temperature ( C)

1400

1300 1250 1200 1150 1100 1050

0

10

30

50

70

LPWG content (wt%)

Fig. 6. Dependence of temperature on the LPWG content at logη=2 (▲), 2.5 (●), and 3 (■) (η in dPas) and TL (▼).

(a)

TL=1097℃

818℃

1124℃ (b)

Fig. 7. (a) Observed needle-shaped crystals for E0LPWG. (left: 40x, right: 100x) (b) Photographs by polarizing microscope for E0LPWG surface treated thermally for 8 hours between 818 and 1124℃ in gradient furnace and determination of TL (40x)

Unit: kg

Fig. 8. Amount of pyrophyllite and colemanite reduced by introduction of LPWG in batch for 1000kg glass.

Table 1. Experimental batches containing LPWG for E-glass preparation (kg) Raw material pyrophyllite (Al2O34SiO2H2O) calcite (CaCO3) colemanite (2CaO3B2O35H2O) sodium sulfate (Na2SO4) soda ash (Na2CO3) LPWG weight of total batch weight of total produced glass

E0LPWG

E10LPWG

E30LPWG

E50LPWG

E70LPWG

707.2

628.2

471.1

315.4

159.9

304.0

304.1

304.1

304.1

296.8

156.9

132.4

83.8

35.6

-

3.6

4.1

5.2

6.3

7.2

0

0

0.96

2.28

3.62

0 1171.7

96.8 1165.6

288.9 1154.0

479.0 1142.7

663.7 1131.2

1000

1000

1000

1000

1000

Table 2. Chemical analysis of raw materials (weight fraction) Raw material

SiO2

Al2O3

pyrophyllite (Al2O34SiO2H2O) calcite (CaCO3) colemanite (2CaO3B2O35H2O) sodium sulfate (Na2SO4) soda ash (Na2CO3)

0.7300

LPWG

0.6010

B2O3

Fe2O3

Na2O

K2 O

MgO

CaO

0.2000

0.0035

0.0080

0.0080

0.0200

0.0200

0.0042

0.0011

0.0011

0.0005

0.0081

0.5481

0.0467

0.0014

0.0001

0.0210

0.2638

0.4174

0.0003

0.0005

SrO

BaO

0.0005

0.0030

0.0070

0.0033 0.5620

0.5810 0.1050

TiO2

0.0001

0.4363

0.1690

SO3

0.0035

0.0780

0.0470

0.0054

Table 3. Theoretical compositions of E-glass containing LPWG (wt%) Glass code　 E0LPWG (E-glass) E10LPWG

SiO2

Al2O3

B2O3

Fe2O3

Na2O

K2O

MgO

CaO

SrO

BaO

SO3

TiO2

52.48

14.20

6.55

0.29

0.73

0.58

1.99

22.22

0　

0　

0.47

0.50

52.37

14.24

6.53

0.26

0.69

0.52

1.81

22.17

0.45

0.05

0.46

0.44

E30LPWG

52.10

14.30

6.50

0.20

0.67

0.39

1.46

22.05

1.34

0.15

0.46

0.33

E50LPWG

51.83

14.36

6.47

0.14

0.66

0.27

1.12

21.94

2.23

0.26

0.46

0.22

E70LPWG

51.29

14.34

6.90

0.09

0.65

0.14

0.79

21.71

3.09

0.35

0.46

0.11

Table 4. Chromaticity co-ordinate (x, y, z) and average transmittance of six glasses including Industrial melted Glass Color and transmittance color x chromaticity y coordinate z average transmittance (%)

E0LPWG

E10LPWG

E30LPWG

E50LPWG

E70LPWG

E0LPWGInd

0.3136 0.3244 0.3620 81.59

0.3129 0.3229 0.3642 83.09

0.3121 0.3218 0.3661 83.45

0.3113 0.3203 0.3684 84.98

0.3104 0.3188 0.3708 88.14

0.3107 0.3223 0.3670 82.05

Table 5. Working temperature (TW) and liquidus temperature (TL) of five melts, density (d) of five glasses Properties

E0LPWG

E10LPWG

E30LPWG

E50LPWG

E70LPWG

TW (℃)

1223

1219

1211

1203

1184

TL (℃)

1097

1099

1114

1129

1144

ΔT(TW-TL) (℃)

126

120

97

74

40

logη at TL (η in dPas) d (g/cm3)

3.93

3.94

3.73

3.55

3.28

2.5977

2.6094

2.6332

2.6491

2.6765

Table 6. Relative comparison of economic and environmental effects between E0LPWG and E50LPWG per ton of glass (unitless) Glass code

Raw material cost

Energy cost

CO2 emission

E0LPWG

100

100

100

E50LPWG

72

85

82

Price per ton of LPWG: 134 US$ CO2 emission per ton of glass: 0.78 kg (Ecofys, 2009)