Vol 61, No 11 (2018)

The interaction of complex esters of linear and aromatic structure with the surface of Kuznetsk Basin gas coal is analyzed. The interacting coal particles and the molecules of the collecting agent are studied in terms of chemical, physicochemical, and quantum-chemical characteristics. Analysis of chemical and structural-group composition of Komsomolets colliery coal, as well as quantum-chemical entity descriptors modeling the structure of the organic unmined coal, indicates the presence of electrophilic adsorption centers on the coal surface formed due to the presence of oxygen-containing groups in their composition. It is shown that the coal surface hydration is due to the adsorption of water molecules on the electrophilic centers of the organic unmined coal. The results indicate that compounds with more pronounced nucleophilic properties than water may be effective flotation reagents. On account of the displacement of the electron density toward the oxygen atoms, complex ester molecules contain nucleophilic centers capable of electrostatic interaction with electrophilic sections of the coal surface by a charge-controlled mechanism. By analysis of the quantum-chemical characteristics of such compounds, as well as their adsorbing and flotation properties and their ability to induce hydrophobic behavior, it is established that the electronegativity of complex esters is correlated with the physicochemical characteristics of the coal surface.

The comprehensive fuel characterization of newly discovered coals is critical to efficient energy recovery and effective utilization in various applications. Over the years, numerous coal deposits have been discovered in Nigeria, which has reignited interest in coal utilization. However, lack of comprehensive data on the new coals and their coking potential has hampered progress in the coal, iron, and steel industries in Nigeria. Therefore, this study examined the coke and energy recovery potential of a newly discovered lignite coal from Ogboligbo (OGB) in Kogi state of Nigeria through carbonization in a muffle furnace reactor. The pH, FTIR and TGA analyses of OGB and the derived cokes were subsequently examined in detail. The results demonstrated that temperature significantly influenced the carbonization process resulting in a coke yield, energy yield, higher heating value, and thermal properties markedly different from OGB. The pH analysis revealed weakly to strongly acidic cokes indicating their limited application to energy, steel, and iron manufacturing. The FTIR analysis showed that OGB and cokes structures consist of clay and silicate minerals such as kaolinite and illite. Lastly, the results showed that the carbonization process adversely affected the thermochemical reactivity of the cokes due to low moisture and volatile matter. However, the risks of self-ignition or spontaneous combustion are minimised after carbonization.

Attention focuses on how the thermal oxidation of hydrocarbon mixtures by air injection at elevated temperatures affects the microstructure of the isotropic coke formed on subsequent carbonization. Specifically, the residue from the atmospheric distillation of shale tar is considered; this hydrocarbon mixture serves as the industrial raw material for the production of isotropic coke. In thermal oxidation at high (350°C) and low (250°C) temperatures, samples are taken for fractionation and coking. In the course of thermal oxidation, the γ fraction of the distillation residue is converted to the α + β fraction. The means size of the structural elements in the coke from the thermally oxidized distillation residue declines. However, for coke produced from the γ and α + β fractions, the opposite changes are observed: decrease in mean size for the α + β fraction, and increase for the γ fraction. For the high-temperature samples, this difference is more pronounced. Thus, the formation of isotropic coke microstructure is due to the conversion of the γ fraction to the α + β fraction and also to the changes in properties of the fractions associated with the thermal-oxidation temperature. In this paper the next denotations are made: isooctane-soluble fraction is denoted as γ fraction, isooctane-insoluble-toluene-soluble is denoted as β fraction, toluene-insoluble-quinoline-soluble is denoted as α fraction, the fraction insoluble in quinoline, pyridine and carbon disulfide is denoted as α-1 fraction. Note that in the domestic literature, the designations of the pitch factions were adopted which differ from the designations used in the English-language literature.

The thermal-destruction products of hexane-insoluble asphaltenes from coal pitch and petroleum asphaltenes are compared. The volatile thermal-decomposition products of the asphaltenes are studied by thermal analysis and gas–liquid chromatography and mass spectroscopy. The morphology and structure of the solid residue is investigated by scanning electron microscopy and X-ray phase analysis. By that means, the analysis of the thermal-decomposition products permits assignment of the asphaltenes to known structural types and prediction of the coke residue’s morphology. The volatile thermal-decomposition products from coal pitch are aromatic polycondensed compounds with 3–7 aromatic nuclei, including N- and S-bearing compounds. The thermal decomposition of petroleum asphaltenes is accompanied by the liberation of alkanes, alkenes, and O-bearing compounds, with chain length from C₁₁ to C₃₀. The content of arenes and polyaromatic hydrocarbons in the volatile thermal-decomposition products from petroleum asphaltenes is considerably less than the content of aliphatic hydrocarbons. Morphological data indicate that the solid thermolytic residues of the asphaltenes differ in structure. For petroleum asphaltenes, the structure is porous and, according to X-ray phase analysis, shows no signs of graphite-like structure. For the asphaltenes from coal pitch, the residue contains graphite-like structure and has a distinctive luster.

The creation of a single shop for the capture of coking byproducts at PAO NLMK in place of the two existing shops is considered. This involves the construction of a common sulfate system and the development of models of the ammonium-sulfate store and equipment by means of 3D design. The 3D models of the ammonium-sulfate store permit ongoing solution of problems arising in its construction.