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With increased co-firing of coal and different biomasses in power plants, there is a growing need to study and characterize the produced, often heterogeneous ashes and to assess their utilization as secondary raw materials. In this work, we compare different methods for characterizing the ash compositions. These methods include scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDS), X-ray fluorescence (XRF) and inductively coupled plasma emission spectroscopy (ICP-OES). The content of carbonaceous residues in the ashes was measured with CHNS analyzer. The methods and the pretreatment required for each of the analysis were studied in detail for three ashes: (1) coal, (2) peat and wood, (3) peat and wood residue with dolomite addition. The limitations of each method will be discussed. This work gives guidelines for selecting a rapid and reliable method for analyzing the suitability of the ash for a particular application.

Gypsum (CaSO4 2H2O) and anhydrite (CaSO4) are the most common sulfate minerals. The predominant part of gypsum and anhydrite is used as raw materials for the production of gypsum binders (construction gypsum) and additives in various types of cements, to a lesser extent–for the production of hard-burnt, high-strength, molding and medical gypsum, sulfuric acid, ammonium sulfate, and paper and for soil gypsuming. In addition, gypsum and anhydrite are used in small quantities as decorative and ornamental materials. In each deposit of natural gypsum, the distinctive features are its composition and structure, which directly affects the production conditions and construction and technical properties of gypsum binders. This paper is aimed at evaluating the influence of various impurities present in gypsum and anhydrite stones on the properties of the binder. In this work, the selected samples for each case were subjected to chemical and mineralogical analysis, passed the roasting stage, and then samples-beams are formed and tested for bending and compression on laboratory equipment. In summary, the conclusion was made about the ability of impurities to influence the indicators of setting time, strength values.

The object of the paper is Lower-Permian sulphate-carbonate deposits in Shumovskoye oil field. The secondary transformations of the rocks (in this case, dolomitization and sulphatization) disrupt the correlation links between the permeability and porosity, while a rock’s solid phase with its multi-component nature complicates its petrophysical model. A lack of lithological composition in defining the porosity and permeability of the reservoir rocks could result in unreliable evaluation of the oil reserves, non-trustworthy lithology determined evaluation of porosity could reach 8%. An innovation approach to defining the porosity algorithm as regards the lithological composition of the rocks represented by Shumovskoye sulphate-carbonate oil deposits is proposed. Geophysical methods (acoustic, neutron-neutron and gamma-gamma density logging) help find the (total) porosity of the rocks and the content of isolated lithological variations in the rocks by the system of linear equations additively connecting the data from different well logging methods in a structurally complicated reservoir rock. In case the selected geophysical methods lack any variables the system of equations turns out to be undetermined. We propose using the values illustrating the ratios between different variables. For example, the ratio between dolomite and limestone contents Kdol/Kls could be obtained from core analysis. The results obtained with the proposed approach and the traditional methodology differ by 17%. Sulfated dolomites exert the greatest impact on the porosity. The relative error in defining the porosity has been decreased by 23% for the dolomitized variations of the rocks and by 37% for the sulfated variations with the proposed approach.

Magnesite and its main associated mineral dolomite are with a small floatability difference because of similar crystal structure and surface properties, which results in low flotation recovery of magnesite from dolomite. In order to solve the problem, a new mixed collector of sodium oleate (NaOL) for magnesite was proposed in this paper. The effects of flotation behaviors of magnesite and dolomite were investigated by flotation experiments, and the mineral wettability was characterized by contact angle testing. The results show that the mixed collector could greatly reduce the hydrophobicity of dolomite and improve the floatability difference between magnesite and dolomite. The Gaudin’s selectivity index of two minerals increased from 1.75 to 3.78.

Carbide slag is a kind of industrial waste produced from the calcium carbide industry, which is difficult to treat and cannot be used reasonably. In this paper, carbide slag as a calcium source for extracting magnesium was proposed, i.e., carbide slag was directly mixed with low-grade magnesite instead of dolomite as raw material for extracting magnesium without pretreatment. The process is simple to operate and can obtain metal magnesium while reducing nearly 50% of CO2 emissions in the process of extracting magnesium. In the work, the strength of pellets, the effects of Ca/Mg ratio, and calcination temperature on the recovery rate of Mg were investigated. The results showed that low temperature calcination was beneficial to reduction and the recovery rate of Mg increased with the increase of Ca/Mg ratio, and the reduction rate was 87.95% when the Ca/Mg ratio was 1.2.

In blast furnace smelting, MgO can play a role in improving slag performance. In the production process of pellets, the suitable MgO content is easy to reduce the strength of pellets, but other metallurgical properties of pellet can be improved. In this paper, dolomite is used as the main additive of MgO, and the effects of 0, 1, 3, 8, and 11% different magnesium additive contents on the metallurgical performance of pellets are studied. The results show that with the increase of magnesium additive, the drop strength of the green ball increases, and it increases to 8.3 times when the magnesium additive content is 1.5%. The compressive strength of the green ball first decreases and then rises. When the content is 1.5%, the highest value of 1.5N was reached. The strength of the finished ball gradually decreased to 1990N. The highest reduction degree increased to 80%, and reduction swelling index decreased 10.02%. Meanwhile, the softening and smelting properties of magnesium pellets are improved. The softening and smelting temperature range of single magnesium pellets and mixed burden becomes narrow.