Coke and Chemistry最新文献

A possible new method for the generation of ozone–hydroxyl mixtures is considered: the use of cold plasma from a corona electric discharge between a point electrode and a plane, with negative voltage at the point electrode. Discharges in air and in water vapor are considered. The lifetime of hydroxyl radicals in these conditions is ~0.12 s; ozone is consumed in sustaining the hydroxyl radicals. The parameters of the power supply circuit for the point electrodes is considered. As an example, the functional configurations of a closed generator (volume of liquid to be treated 50 mL; total discharge current 0.5 mA), a flow-type reactor (discharge current 5 mA; productivity 250 L/h), and a circulatory reactor productivity 25–250 L/h) are presented. The circulatory system permits increase in the dose created in the liquid by decrease in productivity of the water. The energy consumption in generating a single hydroxyl radical in the corona discharge is around 500 eV. It is not economically expedient to process extremely polluted water. To remove impurities that are hard to break down, treatment with ozone–hydroxyl mixture is preceded by regular water treatment. For each reactor, the doses created in the liquid are determined. The advantages and disadvantages of each system are compared.

The influence of preliminary crushing of fly ash and slag from lignite and its firing temperature on its structure is studied by electron microscopy. In addition, the influence of those factors on the bioleaching of scandium and the total quantity of rare earth metals and on the mass loss of the fly ash and slag and the target metals is investigated. Optimal firing conditions are chosen. Decrease in organic content of the fly ash and slag increases the bioleaching of scandium by ~80% and of rare earth elements by ~10%. The mass loss of the fly ash and slag on firing is around 3%. Principles are outlined for the accumulation of scandium in the organic component of the fly ash and slag, regardless of its distribution between the organic and mineral components of the lignite.

The utilization of industrial biomass waste is a priority today. A promising approach is the combustion of biomass with traditional fuels. In the present work, the combustion of lignite and lignin is investigated, with slow heating. Mixtures containing 25, 50, and 75 wt % lignin are considered; the particle size is 100–200 μm. The lignite and lignin are subjected to technical and elemental analysis. Thermal analysis is employed in experiments with heating at 10°C/min an oxidative medium (air flow rate 50 mL/min). By thermal analysis, the heating process may be divided into three stages: removal of moisture and sorbed and occluded materials; thermal decomposition, with the emission and combustion of volatiles; and ignition and combustion of the carbon residue. The basic combustion parameters for the carbon residue are determined from the results of thermal analysis: the ignition and combustion temperatures; the maximum rate of mass loss and the corresponding temperature; and the combustion index. It is established that the ignition temperature of the carbon residue is 15% lower for lignin than for lignite. Therefore adding 25% lignin to lignite lowers the ignition point by 12%. The interaction of the fuel components that synergetically affect the combustion intensity is also analyzed. The results may be used in converting coal-fired boilers for the combustion of lignite–biomass mixtures.

Distillation of coal tar in an ARN-LAB-03 system yields 9% of a light oil fraction (boiling up to 170°C), 12% of a medium oil fraction (boiling at 170–230°C), 10% of a heavy oil fraction (boiling at 230–270°C), 32% of an anthracene fraction (boiling at 270–360°C), and 35% of a solid pitch residue. The anthracene fraction is subjected to coking. After coking the anthracene fraction for 5.5 h under a pressure of 3.5 MPa at 500°C, the yield of coke sample K-3 is 45%. The yield of coke sample K-4 obtained in the same conditions, but at 4.5 MPa, is 50%. On that basis, an effective method is proposed for producing coke from the anthracene fraction of coal tar.

The influence of the manufacturing pressure and the composition of pellets based on sawdust and assorted wastes and low-grade fuels on their density and mechanical characteristics (impact strength, hardness, resistance to vibrational loads) is studied experimentally. The specific additives employed are lignite, straw, and cardboard; in each case, 30 wt % of this component is added. With increase in manufacturing pressure and the use of those additives, the sample density may be increased from 2 to 8%. The pellet composition has a greater influence than the manufacturing pressure on the pellets’ characteristics. Adding cardboard increases the impact strength by 0.3–2.6%. Likewise, at fixed manufacturing pressure, the hardness increases by a factor of 1.5–2.9 on adding cardboard or lignite. The best resistance to vibrational loads is observed for sawdust pellets with no additive. The experiments show that 400 MPa is the optimal manufacturing pressure in terms of density, impact strength, hardness, and resistance to vibrational loads. The experimental results may be used in developing technologies for the production and combustion of pelletized fuels consisting of biomass and industrial waste.

Mutually complementary research methods indicate that an electrode material based on carbonized sapropelic coal filled with silver nanoparticles is very promising for use in supercapacitor electrodes. In identifying the optimal conditions for applying the silver nanoparticles to the surface of the carbon matrix, three options are considered: with no reducing agent; with sodium tetrahydroborate; and with hydrazine hydrate. The option with no reducing agent yields the optimal capacitance. Charge accumulation in the electrodes is mainly due to a double electrode layer. The mean capacitance of the composites (537 F/g) is 20% higher than that of the basic carbon material (435 F/g). Impedance spectroscopy indicates that the capacitance is higher for the composite on account of the overall decrease in the electrical resistance. The decrease in resistance of the nanocomposite is greatest when applying the silver nanoparticles to the surface of the carbon matrix with no reducing agent.

Experiments are conducted on the ignition and combustion of low-grade coal and its processing waste after mechanical and chemical activation. A method is developed for studying the reactivity of coal. On a laboratory test bench, well-known methods for determining the combustion conditions of coal (including lignite, Kuznetsk Basin coal, and Ekibastuz coal) are employed. Calibration of Kuznetsk Basin coal is completed. The axial and tangential combustion rates are determined for analysis and graphical interpretation. The ignition parameters of the coal samples are determined, and a system for monitoring the ignition is developed. The proposed method includes differential scanning calorimetry and mass spectrometric analysis of the gas. An example is given for thermal analysis of coal with differentiation of the stages in the process; curves for mass spectrometric analysis of the ionic currents are presented. The possibility of replacing fuel oil and gas with mechanically activated coal in the ignition and lighting systems of pulverized coal boilers is theoretically and experimentally established. The conclusion is that mechanically activated coal may be used as a universal fuel, with environmental and economic benefits. The proposed method may be used in modernizing and designing thermal power stations.

The current state of the global and Russian coal industry is analyzed, and its prospects are assessed. Global trends in coal extraction and consumption are considered, with an emphasis on the major producing and consuming nations. Attention focuses on Russia’s global position, its contribution to coal extraction and exports, and the problems and prospects associated with the changing global energy balance. The analysis rests on information from open sources, including scientific articles, specialized reports, statistical data, and the predictions of international experts. The variation in the output, exports, and profits of the Russian coal industry between 2012 and 2023 is compared. The key factors affecting the competitiveness of coal are identified, and the basic trends in global prices and demands are noted. The influence of geopolitical factors and environmental requirements on the coal industry is analyzed, and the importance of new technologies and increased production efficiency in ensuring stable development is emphasized. The role of the coal industry in the energy security and economic development of nations is studied, and the need to develop strategies for adaptation to changing market conditions is stressed.

A method is proposed for producing granulated carbon adsorbent from petroleum coke (activated by potassium hydroxide) and isotropic petroleum pitch. Granules with different proportions of filler and binder are prepared. According to the Brunauer–Emmett–Teller (BET) method, the specific surface is greatest for the sample with 90% activated coke and 10% binder (by mass): 1525 m²/g. With increase in binder content from 10% to 40%, the specific surface declines by a factor of two or three. It is established that isotropic petroleum pitch obtained as a byproduct in the production of mesophase petroleum pitch may be used as the binder. In terms of the BET specific surface and strength of the granules, the optimal binder content is 20–30%.