GLASS-CRYSTALLINE SURFACES FOR BUILDING CERAMICS FROM POWER STATION WASTE

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1 Journal of Yakov Chemical Beliy, Technology Yaroslava and Kol tsova, Metallurgy, Sergey 50, Nikitin 1, 2015, GLASS-CRYSTALLINE SURFACES FOR BUILDING CERAMICS FROM POWER STATION WASTE Yakov Beliy, Yaroslava Kol tsova, Sergey Nikitin Ukrainian State Chemical Technological University, 8, Gagarina str., 49000, Dnepropetrovsk, Ukraine Received 31 March 2014 Accepted 28 November 2014 ABSTRACT The possibility of using thermoelectric power station waste for obtaining free-pigmentary colour glass-crystalline surfaces for building ceramics are shown. The regularity of changing colour of compositions breakage glass - slag and breakage glass - fly-ash depending on the concentration of the introduced waste and burning temperature are established. Their phase structures are given. Keywords: colour glass-crystalline surfaces, breakage glass, slag, fly ash. INTRODUCTION As a rule, for colored glaze surfaces, overcoated on building ceramics, expensive ceramic pigments are used [1]. At the same time in the industrial enterprises there is a lot of different waste containing oxides of transition metals, which can give one or another colour to vitrosurfaces. To our opinion thermoelectric power station waste is a promising material for obtaining colour glass surfaces. Slag and powder-like residua (fly ash) are formed when solid fuel is burnt in the fire-chambers of thermoelectric power stations [2]. They are the products of high-temperature treatment of the mineral part of the fuel. Fly ash is characterized by high specific surface (particle size mkm) and trivalent iron. Its chemical mineralogical structure depends on the mineral part of burnt fuel. Slag is characterized by increased content of amorphous mainly bivalent iron. The possibility of using silicate waste and slags in the production of building materials has been studied by many authors. The aim of our investigations is to obtain coloured glass-crystalline surfaces on the base of cullet with waste of the Pridneprovskaya thermoelectric power station (TPS): slag and fly ash from burning bituminous coal, using as chromophores the contained therein oxides of metals of variable valency. In the modern scientific and technical literature there are no data on the use of waste like the mentioned components which can give color to glass-crystalline surfaces. Taking into account the fact that the chemical and mineralogical composition of the slag and fly ash from a TPS is significantly different, depending on the region, these studies are relevant and will allow widening the raw resources of ceramics production sufficiently, to decrease production price and to improve the environment at the expense of utilization of such waste. Chemical compositions of the wastes are shown in Table 1. 97

2 Journal of Chemical Technology and Metallurgy, 50, 1, 2015 Table 1. Chemical compositions of waste from the Pridneprovskaya TPS,. Waste name SiO 2 Al 2 O 3 Fe 2 O 3 Oxide name FeO CaO MgO K 2 O+Na 2 O TiO 2 SO 3 Slag Fly-ash EXPERIMENTAL Since glaze surfaces are complex multicomponent systems, the agglomeration of which is accompanied by different physical and chemical processes, we previously have investigated compositions breakage glass - slag and breakage glass -fly ash in order to establish the peculiarities of their behavior at thermal treatment. For doing that samples, after drying were burnt at temperature of C, and formed by half-dry pressing from the investigated powder compositions (passing through the sieve 0063), containing from 20 to 100 of slag or fly ash and from 80 to 20 of breakage glass, respectively. Their visual marks are shown in Table 2. It can be noted that lots of slag and lots of the fly ash compositions (60-80 of waste) were baked and not fused at the investigated temperature. That is why later on they were burnt at higher temperatures and C (Table 2). As a result of our studies we have established changing of the samples colours from vinous to green, depending on quantity of the introduced waste and the burning temperature. This may be caused by changing of the phase structure of the baked glasscompositions at the expense of their crystallization. For investigation of the crystal phase structures of the compositions, those with fuel slag and more contrasting colours have been chosen. The composition and visual colour marks (after burning at C) are shown in Table 3, and the chemical composition - in Table 4. Table 2. Visual mark of the samples containing cullet and waste of TPS. Content of waste, Visual mark (colour, lustre, degree of agglomeration) T = С T = С T = С Slag 80 Vinous, dim, baked Vinous, dim, closely baked with lustre Pearl vinous with metal lustre, baked Slag 60 Vinous, dim, baked Dark vinous, closely baked, crystallized Dark vinous, fused Slag 40 Vinous, dim, baked Light green, fused Dark vinous, foamed Slag 20 Light green, fused, with small pores Fly-ash 80 Brown-orange, dim, baked Dark-brown, closely baked Dark-brown, lustre, fused, big shrinking Fly-ash 60 Brown, dim, baked Dark green with impregnations, fused Light green, fused, big shrinking Fly-ash 40 Grey, fused Fly-ash 20 Grey-green, with lustre, fused 98

3 Yakov Beliy, Yaroslava Kol tsova, Sergey Nikitin Table 3. Material compositions and visual colour mark of the compositions breakage glass - slag. Components content, composition Breakage glass Fuel slag Visual colour mark Orange brown Vinous Green with vinous insertions Light green Table 4. Chemical compositions of the investigated glass-slag mixtures,. Oxide name Composition SiO 2 Al 2 O 3 Fe 2 O 3 FeO CaO MgO K 2 O Na 2 O SO X-ray phase analysis of raw materials and the samples was carried out according to the method of powder on a DRON-3.0 diffractometer with Cu-Kα radiation. The identification of the crystalline phases was carried out using data from ASTM tables [3]. The analysis of the phase composition (Fig. 1a) indicates that in the fuel slag after treatment at C, there are phases as asmonticellite, helenite and hematite, which gives orange-brown tint to the samples. In the compositions of slag and breakage glass not only changing of colour is seen but also crystalline phases: when supported 60 of the breakage glass Fig. 1. XRD analysis of the investigated glass-slag compositions with supporting fuel slag, : a) 100; b) 40; c) 30; d)

4 Journal of Chemical Technology and Metallurgy, 50, 1, 2015 cristobalite, pyroxene and monticellite mainly are crystallized (Fig. 1b); the quantity of iron oxides (Table 4) is lower than in the slag. The ions of iron are mainly concentrated in the glass phase and this gives to the samples an wine colour; when the supporting cullet is increased to more than 70, the main crystalline phases of the investigated compositions are pyroxene, cristobalite and devitrite (Fig. 1с,d). The obtained data (Fig. 1) are indicative of the greatest degree of crystallizing, after burning at temperature C, of samples with 40 of fuel slag. When the temperature of these glass-slag compositions is increased up to C, the colour changes from vinous to light-green (Table 2). According to XRD data (Fig. 2), after burning, the degree of crystallizing of the samples is decreased. The basic crystalline phases are diopside, quartz and anorthite. Microphotography of the sample 100 Fig. 2. XRD analysis of the investigated glass-slag compositions No 2 (Table 3) after burning at 1100 C. Fig. 3. SEM analysis of sample No 2 (Table 3). with 40 of fuel slag obtained on the raster electron microscope is shown in Fig. 3. On the SEM photo the short prismatic crystals of diopside, which is not soluble in acids, and will contribute acid resistance to glass crystal surface are well distinguished. RESULTS AND DISCUSSION Following the revealed opportunity to obtain coloured glass-crystalline compositions with glass and waste from TPS, such wastes were introduced in the composition of a surface containing 67 of cullet and 33 of loamy components (fire-clay from the Polozhskiy deposit of the Zaporozhskaya region, clay and loam - of Sursko- Litovskiy deposit of Dnepropetrovskiy region) [4]. It should be mentioned that introducing fuel waste in quantity from 2.5 to 67.0 % mass was done at the expense of partial or full changing the cullet in the surface composition. The crushed raw materials were mixed in their combined wet milling in a ball-mill down to the test sieve 0063 not more than 0,03 % passing through. After ageing, during the a sunny day, the investigated suspensions were spread on ceramic tile of scrap burned by the watering method. Coated samples after drying were burnt, in a muffle electrical furnace at 1000 and C. On the investigated surfaces with the help of a photoelectrical lustre measuring device FB - 2 and colour comparator CC-3 [5, 6] the optical-colour characteristics: coefficient of mirror reflection (lustre, %), colour tone (wave length, nm) and colour purity (%)

5 Yakov Beliy, Yaroslava Kol tsova, Sergey Nikitin Fig. 4. Differential thermal analysis of the raw mixtures with content of 67 of fly ash (a) and fuel slag (b). were determined. The visual mark of their quality was also estimated. For raw mixtures containing 67 of fuel waste, differential thermal analysis was carried out (Fig. 4). It had been established that maximal intensities of the crystallizing processes were observed for mixtures with fly ash at the temperature C (Fig. 4a) and for those with slag - at C (Fig. 49b). It is necessary to note that for the mixture containing fly ash at C there is an exoeffect accompanying mass loss in accordance with the TG curve. This effect is connected with burning-out carbon which in the fly ash is from 12 to 20 %. After burning at 1000 and C the investigated surfaces did not have any defects, their colour changed from beige to dark-brown in accordance with the quantity of the introduced additions and burning temperature (Tables 5, 6). The colour tone of the surfaces was in the range nm and the colour purity with increasing Table 5. Visual mark of colour and optical colour characteristics of the investigated surfaces containing fuel slag. Quality of addition, length, nm Burning temperature С С Visual mark of colour length, nm Visual mark of colour Light-beige Light-beige Grey-beige with small 2, brown inclusions or marble Grey-beige with a lot of brown inclusions or marble , Beige-gray with lilac brown inclusions Grey with lilac-brown inclusions Lilac-brown Marbleized Brow Dark vinousbrown Dark-brown Dark orangebrown Dark-brown Dark orangebrown 101

6 Journal of Chemical Technology and Metallurgy, 50, 1, 2015 Table 6. Visual mark of colour and results for the optical colour characteristics of the investigated surfaces containing fly ash. Quality of addition length, nm Burning temperature С С Visual mark of colour length, nm Visual mark of colour 2, Beige Light-beige Beige Light-beige 7, Dark-beige Light-beige Dark-beige Light-beige Light-brown Dark-beige with dotty inclusions Terracotta Brown Terracotta Terracotta Terracotta Terracotta waste quality was raised from 10 to 60 %. For all surfaces containing fuel slag lustre absence has been observed at both burning temperatures. Only the surface with 2.5 % of the slag after burning at C had a lustre (13 %). For surfaces with fly ash the lustre absence was characteristic only after burning at C. Burning at C leads to indices of lustre up to 16 %. Visually mark the addition to the surfaces of fly ash causes Fig. 5. XRD analyses of surfaces containing: a) 64 of breakage glass; b) 20 of fuel slag and 47 of breakage glass; c) 67 of fuel slag. 102

7 Yakov Beliy, Yaroslava Kol tsova, Sergey Nikitin changes the colour from light-cream (at ash concentration of 7.5 ) to dark-brown (67 ) and for slag - from light-beige (at ash concentration of 7.5 % mass) to brown-red (67 ) (Tables 5, 6). It has been established that slag changing surfaces colour with beige to brown-red at burning temperature1000 o C occurs at the lower concentrations (from 7.5 ) in comparison with samples burnt at 1100 o C (from 20 ). This can be explained by changing the phase surfaces composition when using different quantities of slag. This has been confirmed by the results from the investigation of presented above. According to the XRD phase analysis (Fig. 5), addition to the original surface of 20 fuel slag increases its crystallization degree but does not essentially influence the forming of crystalline phases. Both for the original surface and for the one containing the mentioned quantity of slag the presence of diopside, quartz and tridymite is typical (Fig. 5a, b). The complete change of the cullet to fuel slag leads to crystalline phases as quartz, anorthite and hematite, the presence of which promotes coloration into orange-brown. CONCLUSIONS Mixtures breakage glass - fuel slag and breakage glass - fly-ash change their colour from vinous to greenish, depending on the quantity of the introduced additions. X-ray phase analyses show a complex character of the crystalline processes for the baked compositions breakage glass - fuel slag. Optimal proportions (60 of breakage glass and 40 of fuel slag), allowing to increase crystallization degree, have been established. As a result of the presented studies opportunities for obtaining coloured surfaces for building ceramics using slag and fly ash of TPS are shown. Depending on the quantity of the introduced waste, beige, marbleized, terra-cotta, brown and dark-brown surfaces, without using expensive pigments, can be obtained. REFERENCES 1. G.V. Lisachuk, M.I. Pyshchenko, L.A. Belostotskaya and others, Vitrocrystalline surfaces on ceramics, 2008, (in Russian). 2. L.I. Dvorkin, O.L. Dvorkin, Building materials from industrial waste: training and information aids, Rostovon-Don, Fenix, 2007, (in Russian). 3. ASTM diffraction data cards and alphabetical and grouped numerical index of X-ray diffraction data, Philadelphia, Y.I. Beliy, Y.I. Koltsova, N.V. Shepotko, Pat Ukraine, C03C8/02.Number: Filing Date: Date: comparater-3. Technical description and instruction on exploitation to,1990, (in Russian). 6. Photoelertrical lustre measure of type-2, Passport.- M.- Ministry of instrument-making, means of automation and operational systems, 1979, (in Russian). 103