Promising use of waste coal in the production of insulating material without the use of traditional natural materials

Abstract

It is shown that one of the promising directions for the production of thermal insulation materials are waste coal (waste of the fuel and energy complex). Insulation materials (ceramic lightweight bricks) with the density not higher than 1250 kg/m³ were derived from waste coal without using the traditional natural raw materials. The innovative proposals for the use of waste coal in the manufacture of insulation materials were developed and their novelty was confirmed by four RF Patents. The investigated coal waste is characterized by high calorific value (1800–2800 kcal/kg); thus, such waste should be used not only as nonplastic materials but also as combustible additives so as to exclude the use of anthracite, coke breeze, etc., in the compositions of ceramic masses. Combustible additives containing increased amounts of organic compounds (the loss of ignition of >15%) and iron oxide (Fe₂O₃ of more than 3%) not only increase the porosity of ceramic products but also facilitate the uniform sintering of a ceramic crock. It was shown that there are three types of pores that mainly occur in samples of insulation materials: slitlike ones, isothermal ones, and bizarre pores. In addition, the samples contain relatively large oval pores and “channel” isometric pores. These pores determine the water absorption of ceramic materials. The presence of pores and, consequently, the heterogeneity of the material adversely affect the properties of ceramic products, and the harmful effect on the mechanical strength of the elongated (slitlike) pores is estimated at about 5 times higher than that for round ones. In addition, the presence of slit-shaped pores indicates the incompleteness of the sintering processes. The use of waste from the fuel and energy complex in the production of ceramic materials makes it possible to efficiently utilize industrial waste, to save scarce traditional natural materials, to expand the range of raw materials for construction materials, and to make a significant contribution to environmental protection.