Coke and Chemistry最新文献

Improvement in the efficiency of sludge flotation and processing in coal enrichment by appropriate selection of flocculants and modifiers is considered. Zh coal fines (with a high content of small classes) from the Chertinsk mine (Kuznetsk Basin) enriched at Belovskaya enrichment facility are investigated, with 19.5% ash content. The flocculants employed are acrylamide copolymers: Magnаfloc 380 (М-380), Magnаfloc 10 (М-10), Magnаfloc 525 (М-525), and Magnаfloc 345 (М-345). Their performance is compared with that of widely used flocculants (VPK and KSP polyelectrolytes and Technofloc-TL 1597). Neonol (oxyethylated nonylphenol), which is an effective modifier, is also employed; it consists of a mixture of isomers. The action of flocculants and the subsequent modifier on the coal fines is analyzed on the basis of theoretical and experimental data. Sedimentation analysis shows that anionic Magnаfloc М-10 is the most effective flocculant for positively charged coal dispersions. The flotation efficiency is improved for coal fines treated with Magnаfloc М-10 and then Neonol modifier. Quantum chemical modeling by means of HyperChem software establishes the interaction of Neonol with the polar centers of model compounds in the coal’s organic mass (forming hydrogen bonds) and with the polar centers of Magnаfloc М-10. Analysis of the coal’s flotation properties confirms that the coal surface becomes hydrophobic after flocculation of the coal fines and subsequent treatment with Neonol modifier. After flocculation of the coal sludge and subsequent treatment with Neonol, the concentrate yield in flotation is increased by 2.4%, while its ash content is decreased by 0.3%.

Generally, in underground mining, coking coal beds are gas-bearing and require degassing. Therefore, the gas dynamics of the bed is a key aspect in the development of coal–methane deposits. The prevailing standards are based on sorption theory, but current requirements are associated with new approaches to understanding gas liberation. New results based on the hypothesis of a coal–gas solid solution indicate that the irreversible decomposition of that solid solution due to the relaxation of the mine pressure provokes gas liberation from the bed in the appropriate conditions. Given the steady increase in the speed of face movement, it is clear that ideas from the past (1950s–1970s) regarding the properties of the coal bed and the processes that occur there do not meet current requirements. Since the breakdown of some part of the coal–gas solid solution changes the gas structure of the bed, we may determine the gas flow into the bed’s filtration volume by analysis of that breakdown. The gas balance equation in terms of the forms of methane in the bed takes account of the influence of methane in solid form on the sorptional potential of coal and permits quantitative assessment of changes in the gas structure within the bed under the influence of geomechanical mining processes.

Coke plant tar is oxidized at 220°C in air current at 1.8 L/min for 4.5 h. In this process, elemental sulfur is added in quantities of 20, 30, and 40 wt %. With increase from 20 to 40 wt %, penetration declines from 55 to 38 mm; and the softening temperature (determined by the ring and rod method) declines from 52 to 45°C. The change in the physicomechanical properties of the mixture when adding 20, 30, and 40 wt % S is studied by X-ray phase analysis. With 30 wt % S, the reaction of sulfur with the aromatic rings forms 2-naphthanol-6-sulfonic acid (OHС₁₀Н₆SO₃H).

Abstract

To reveal the molecular structure characteristics of the caking components in coal, three coals with different ranks were treated using a new synthetic ionic liquid (i.e., [N₄₄₄₁][NO₃]), the combination of which is based on the effect degree of different anions and cations of ionic liquids on the caking properties of the coals. Additionally, the raw and treated coals were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman. The results showed that the caking index (G) values of the coals decreased after [N₄₄₄₁][NO₃] treatment, and the destruction degree decreased with increasing coal rank. The decrease in G is related to the removal of some species during [N₄₄₄₁][NO₃] treatment. FTIR and Raman showed that aromatics with 3 or more rings but less than that in graphite and long-chain aliphatics were removed. XRD showed that [N₄₄₄₁][NO₃] treatment decreased the graphitization degrees of the coals. Additionally, a mechanism of destroying the caking property of coal using [N₄₄₄₁][NO₃] is proposed. [N₄₄₄₁][NO₃] treatment could decrease the contents of aromatics with 3 or more rings but less than that in graphite and long-chain aliphatics. Consequently, the caking property of coal is destroyed.

Oxidized and unoxidized coal samples of various ranks are compared, as well as the humic and fulvic acids derived from those materials. Petrographic analysis shows that macerals of the vitrinite group predominate in the coal samples; the oxidized samples belong to oxidation group OK II. B coal (lignite) and D coal (long-flame coal) undergo more profound changes than G coal (gas coal) on oxidation (weathering). Compared to their unoxidized counterparts, the oxidized coal samples are characterized by higher ash content, yield of volatiles, and content of oxygen, nitrogen, and sulfur. The elemental composition of fulvic and humic acids from oxidized and unoxidized B and D coal varies widely but may be regarded as typical. Compared to fulvic acid, all the samples of humic acid are higher in carbon and lower in oxygen, nitrogen, and sulfur. Given the high yield of fulvic and humic acids from oxidized B and D coal, they may be regarded as promising raw materials for humic production. The yield of fulvic and humic acids from oxidized G coal is minimal.

Today, blast furnaces tend to operate with large quantities of injected materials—hydrogen sources. In the 1960s, the introduction of such additives prompted close attention to the chemical processes in the blast furnace. In the last few decades, many researchers have studied the reaction of coke with atmospheres containing H₂ and H₂O. This sharp increase in interest may be attributed to the increasing presence of hydrogen in blast furnaces and to the availability of powerful methods such as X-ray phase analysis and electron microscopy and also software for digital image analysis and thermodynamic analysis. The thermodynamic laws and kinetics of blast furnace processes were studied. The results show that coke reacts with H₂O more intensely and with greater intensity than it reacts with CO₂. That affects the coke strength. Other research has addressed the influence of the H₂ and H₂O content on the porosity of the coke and its disintegration. Recently, thermodynamic analysis of the gasification of carbon from coke in a CO₂ + H₂O atmosphere (solution loss reaction of coke) by various research groups shows that increase in the H₂O content in the initial gas further stimulates gasification. Thermodynamic analysis of the reactions associated with the gasification of coke by CO₂ and H₂O and the reduction of iron oxides (the coupling reaction) indicates that higher hydrogen content in the gas may shift the gasification of carbon to lower temperatures.

Production technologies for carbon-bearing binders with reduced carcinogenic impact (emissions) on carbonization are considered. Information is provided regarding the best-known European binders with reduced benzo[a]pyrene emissions on carbonization that are used in the production of refractories and carbon materials. A method is proposed for the production and use of a carbon binder that may be added to coal tar pitch in order to minimize benzo[a]pyrene emissions on carbonization.

The distribution of iron oxides on firing ceramic brick produced from interstitial shale clay and iron-bearing slag from power plants, with no traditional materials, is studied by means of Mössbauer spectroscopy. A relation between the strength, frost resistance, and iron content is established. The calculated area of the spectral doublets indicates that the reduction of iron oxides by carbon oxides converts the iron compounds at the sample surface, where oxidant predominates, mainly to hematite, whereas those at the center, where reducing agents predominate, are converted to magnetite. The increased Fe²⁺ content in the samples hastens the appearance of liquid, which facilitates mullite formation and strengthens the ceramic structure.

A strategy is proposed for the synthesis of graphene oxide from an intercalated graphite compound. The intercalated graphite compound is based on stage III graphite nitrate, which is graphite with nitrogen compounds introduced between its planes. The modified Hummers method is used for oxidation of the intercalated graphite compound. The initial material and the products are characterized in detail by physicochemical methods: scanning electron microscopy, Raman spectroscopy, and high-temperature catalytic oxidation. As oxidation of the intercalated graphite compound continues, the defect content of the initial carbon framework increases, on account of decrease in size of the crystallites. Raman spectroscopy indicates that the initial intercalated graphite compound is a graphite structure with few defects of the graphene layers. With oxidation of the sample, the disorder of the carbon framework gradually increases. In part, this is due to shrinkage of the graphite-like crystallites, with subsequent reorientation of the graphene layers. After a certain time, the initial structure is modified: we note partial restoration of the graphite-like fragments and simultaneous proliferation of defects.

The theory, practice, and legal foundations of lending to coal mining organizations are considered in an era when the cost of servicing external debt is rising and the distribution of investment capital within the coal industry is unstable. Economic and legal mechanisms for the regulation of credit to coal-mining enterprises are systematized. Improvements in the relevant regulations are recommended: in particular, closer monitoring of national banks, so as to track the use of funds allocated to mining enterprises for environmental upgrades. The need to develop preferential banking schemes for mining activities is emphasized.