Structural glass based on the wastes from the enrichment of the KMA iron quartzites

Abstract

In this paper we consider the feasibility of manufacturing glass based on iron-containing tailings from the enrichment of iron quartzites, and also of stripped KMA rocks (chalk, marl), sodium sulfate (industrial by-product of the Shebekin Chemical Factory), and traditional raw materials. The average statistical chemical composition of the tallings (for the past 13 years), which is given in Table 1, fluctuates within relatively small limits. The mineral position of the tailings is mainly quartz (51-58%) and silicates (22-33%). Present in small quantities are siderite (to 2.6%), hematite (3-6.5%), and magnetite (2-3%). The particle size composition of the tailings is the following: particles less than 0.07 ram, 65-72%; 0.07-0.2 mm, 20-25%; greater than 0.2 mm, 9-11%. The classification of the railings according to particle sizes, necessary for the manufacture of these or other materials, can be done directly at the shops of the mining combines. From Table 1 it is seen that the chemical composition of the tailings is mainly silica and iron oxides (90% total) and apparently can be placed in the binary systems SiO 2 -FeO or SiO 2 -F%O 3. It is well known that iron-containing glasses with satisfactory technological and high technical properties can be obtained in the CaO-FexOy-SiO 2 and the Na20-FexOy-SiO 2 systems and their derivatives [1]. The Na 2 -FeO-SiO 2 system is of greatest interest. Glasses containing Na 20 and FeO are most easily melted [2]. In addition, retaining the iron in the ferrous form is comparably easier than in the ferric since at the usual melting temperatures (1450-1500~ the equilibrium of the dissociation reaction Fe20 3 ~ FeO + �89 O 2 is shifted to the right. The graph points of the glass compositions studied based on tailings and soda (converted to three components) are shown in Fig. 1. The glasses were made in a laboratory Silit furnace at 1300-1400~ A reducing atmosphere was created by introducing carbon into the charge (1%) and into the combustion chamber of the furnace. The FeO/(FeO + Fe2Oa) ratio in the glasses studied varied within the limits of 80-92%. As was expected, the compositions with the best technological properties lay in the region of the boundary line between the SiO 2 and Na20'2SiO 2 primary crystallization fields (see Fig. 1). Also the charge was thoroughly melted at 1350~ the upper limit of crystallization did not exceed 950~ and the water resistance was in the third hydrolytic class. However, the high Na20 content (14-17%) limits the use of the glasses based on tailings and soda primarily because of their low chemical stability. Thus the effect of replacing a part of the Na 20 in glasses Nos. 5-6 by CaO was studied (the soda in the charge was partially replaced by chalk). With an increase in the quantity of CaO the melting temperature, the water stability, and the hardness of the glass were increased; the upper threshold of crystallization changed; and the temperature coefficient of linear expansion was lowered (Fig. 2). The replacement of Na20 by CaO is expedient up to 7-9% Na20 content in the glass; further decrease in the Na 20 noticeably lowers the technological properties of the glass melt.