The nature of iron tailings and the feasibility of its utilization

First, the nature of iron tailings

Most of the iron ore in Tangshan is a Presinian Anshan metamorphosed sedimentary iron deposit, the upper part is poor hematite, magnetite lower part is poor. The gangue minerals are quartz , chlorite, tremolite, and the like. The iron ore tailings chemical composition of SiO ₂ is 65% to 75%, TFe 8% to 14%, is a high-silicon high-iron tailings, generally does not contain valence associated elements. The main components are quartz, a small amount of amphibole, chlorite, biotite , calcite and dolomite. They are generally broken and graded. The particles are finer, the gradation is good, and some have certain chemical activity due to a certain degree of calcination or chemical treatment. According to relevant information, the requirements for the chemical composition of raw materials for the production of building products are: SiO ₂ >65%, Al ₂ O ₃ >15%, Fe ₂ O ₃ <15%, MgO<5%, Na ₂ O<2%, K ₂ O < 2.5%, SO ₂ < 4%. The chemical composition of iron tailings in large and medium-sized factories in Tangshan area is shown in Table 1.

Table 1 Chemical composition of iron tailings (%)

It can be seen from Table 1 that the iron tailings in Tangshan area are low in addition to Al ₂ O ₃ . All other ingredients meet the requirements. It can be used in construction materials with proper adjustment of its composition.

Second, the feasibility of iron tailings utilization

Research and application at home and abroad have proved that there are some mineral colloids in tailings, which have certain electrical properties, absorption and huge surface energy. Under alkaline excitation, this colloidal substance can be hydrated with cement slurry. Ion exchange occurs to form new aggregates. These aggregates are network structures that rely on relatively strong chemical bonds. At the same time, since the building products are formed under a certain pressure, the tightness of the contact surface between the cement particles and the minerals is increased, and the hydration reaction is enabled to strongly gel the quartz particles and other substances. Studies have shown that cement can be tightly combined with quartz particles during hydration, second only to limestone and dolomite.

At the same time, the main chemical composition of the siliceous iron tailings is SiO ₂ , and the solubility in the neutral water is about 1.6×10 ^{-6 in the} form of opal, gangue, diatomite and siliceous shale . However, in an alkaline aqueous environment spontaneously with a basic metal ion generating compound, zeolite, or generating insoluble calcium silicate hydrate minerals. Quartz, which exists in crystalline form, must have this property in a high-pressure hydrothermal environment. When such tailings are subjected to high temperatures, their main physicochemical properties are characterized by homogeneous polymorphic transformation of quartz. Under high pressure, various high temperature variants of quartz, although the performance difference in the tailings building materials structure is not obvious, but the volume effect of the phase change, but the production process plays a restrictive role. For purer quartz sand or quartzite tailings. Due to its high melting point, it can be used as an acidic refractory material and can also be melted into high temperature resistant quartz glass.

For the development and research of tailings building materials, foreign countries started earlier. As early as the early 1960s, the former Soviet Union began research and production of tailings building materials. For example, the Krivorog iron ore mine used fine-grained aggregates in addition to the appropriate classification of tailings. tailings silicate building products; Kursk tailings is built in the main raw material and cement glass;卡齐卡纳尔Kovdor mining and also containing a large amount of magnesium silicate Magnesium cement and cement products were developed from beneficiation tailings. In addition to the study of tailings wall materials in Canada, the Quebec mine also uses fired tailings to produce refractory silica bricks. In addition to the recovery of fluorite , feldspar , quartz, etc. from waste rock in the United States, most of the tailings are currently used as concrete fillers and paving materials, and some people use iron meteorite tailings to make lightweight bricks with adjustable density. Some people in Japan mixed iron tailings with 10% diatomaceous earth and burned them into lightweight aggregates. In Ukraine, quartzite tailings are classified, >0.14mm for construction sand, <0.04mm for stomata glass and foam glass, 0.14 to 0.04mm for concrete fillers and foam concrete. Many metal mines abroad have optimized secondary resources and used the remaining tailings for the manufacture of tailings bricks and building materials.

Shan Institute of Mining Tailings using Qidashan added certain ingredients (gravel, sand, clay and pulverized coal ash) and lime, after some processing as a road base material, and to a winding of Shenyang road 12km Industrial tests, as measured by the highway department. The strength requirements of the secondary road to the subgrade have been met. The institute also used the Qidashan and Shantoushan fine tailings to develop unburned bricks and facing bricks, and its performance reached the 100# standard.

An anhydrous or depleted tailings mineral, which undergoes a hydration reaction in an aqueous (including steam) environment and produces an aqueous mineral complex that is chemically stable under conditions of use and has a certain mechanical strength. . The building material product thus obtained is called hydrated synthetic tailings building material.

(III) Characteristics of tailings building materials utilization

Characteristics of the use of tailings in the Tangshan area: 1) Wide range of uses. At present, iron tailings can be applied to almost all areas of building materials production; 2) large utilization. With the improvement of the comprehensive utilization technology and process equipment of iron tailings in recent years, the utilization of iron tailings in the field of building materials has been increasing year by year; 3) the degree of utilization has been continuously improved; 4) the effect of saving energy and reducing costs.

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