Coke and Chemistry最新文献

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.

The following characteristics of molecularly oriented coke domains are investigated as a function of their position within the coke and the distance from the coke oven’s heating wall: their height L_c and width L_a, the interplane distance d₀₀₂, the domain density ρ, and the number of layers N within the domain. It is found that L_c and L_a decrease nonlinearly with increase in the distance from the coke oven’s heating wall. The coke’s structural strength Π_c (State Standard GOST 9521–2017) is greater for positions near the wall than for the central region of the coke. The ash content and chemical composition of coke samples in the >0.1 mm and <0.1 mm size classes are determined after crushing in a mill. On the basis of the results of this research and literature analysis, it is established that there is no reliable mathematical model relating the high-temperature characteristics CRI and CSR with the cold mechanical strength M₁₀ and M₂₅. Hence, in broad coke ovens, with constant batch composition, the coke produced may be regarded as of high quality in terms of M₁₀ and M₂₅ but of low quality in terms of CRI and CSR. If the variation in the characteristics of the molecularly oriented domains and the strength of the coke after reaction with CO₂ (CSR) are compared as a function of the distance from the coke oven’s heating wall, it is clear that the parameters L_c, L_a, and d₀₀₂ may be used to create a model capable of predicting CSR.

The benefits of coke production from low-grade coal by stamp charging of the batch are discussed. The influence of production conditions on the formation of dust fractions (≤0.5 mm) after reaction with carbon dioxide is studied. The quantity of dust fractions formed is linearly related to the coke strength CSR after reaction with carbon dioxide. The batch composition and design features of the coke battery have no significant influence on this relationship. The formation of dust fractions (≤0.5 mm) is 1.68 times greater when using traditional coke in the blast furnace than when using coke produced from stamp-charged batch.

The adsorption kinetics of Mn²⁺ ions by AG-3 activated carbon granules is investigated. It is found that the pseudo–first-order Lagergren kinetic model describes manganese adsorption for only 300 min. By contrast, the pseudo–second-order model proposed by Ho and McKay describes the entire process. The role played by diffusion through the sorbent pores in limiting the rate of Mn²⁺ ion extraction is estimated by the Weber–Morris method, on the basis of the isotherms of Mn²⁺ ion adsorption by activated carbon granules. With a high degree of correlation (R² ~ 0.96–0.99), the equilibrium of Mn²⁺ ion adsorption is described by the Langmuir equation. The limiting adsorption capacity of a sorbent monolayer is calculated at various temperatures. When using the adsorptional equilibrium temperature, the thermodynamic parameters of the process are determined. The sorptional extraction of metal ions is greater at higher temperatures. The adsorption of metal ions at the carbon surface is described by means of IR spectroscopic data.