Coke and Chemistry最新文献

The ability of some samples of coal enrichment waste to adsorb oxygen is investigated. The incubation period of self-ignition (spontaneous combustion) is determined, as well as the likelihood of self-ignition of coal-bearing rock. Some of the samples are susceptible to spontaneous combustion and their presence in tailings heaps may result in endogenous fires. Self-ignition of coal slurry is unusual because of its high moisture content. However, laboratory research shows that slurry may rapidly lose moisture in summer, and the incubation period is significantly shortened. That may lead ultimately to spontaneous combustion hot spots. To prevent endogenous fires, the incubation period must be determined for coal enrichment waste in rock tailings.

Coal tar pitch is derived from coal tar. It is used as a binder for electrodes and anode mass. It is mainly produced as the <360°C fraction in the distillation of coal tar. However, the coal tar pitch obtained by this means does not always meet the requirements for binder pitch. It may be characterized by low softening point and insufficient content of binder fractions (β and α₂). Thermal oxidation is used to improve pitch quality. The present article describes experiments on the oxidation of low-temperature pitch (59°C) produced by the distillation of coal tar (from EVRAZ ZSMK) and medium-temperature grade B electrode pitch (71°C) in a thin layer. Such oxidation is not often used and requires further investigation. Thermal oxidation in a thin layer is studied on laboratory apparatus in a 4-L reactor. Air is supplied by a pipe of 9-mm diameter. The mass of the pitch samples is selected so that they sit in a thin layer on the reactor floor. The range of oxidation temperature is 260–300°C. The rate of air supply is 4800 L/kg h for low-temperature pitch and 2400 L/kg h for medium-temperature grade B electrode pitch. The oxidation product (pitch) is collected. The pitch yield, its softening temperature, and its content of components insoluble in toluene and quinoline are determined. The fractional composition of the oxidation products is analyzed. The products are compared with the initial pitch samples. For medium-temperature grade B electrode pitch, the dependence of the softening point and fractional composition of the oxidation products on the duration of oxidation is considered. The conditions in which the content of the α₁ fraction may increase on low-temperature oxidation are identified. The increase in the content of α₂ and α₁ fractions in the oxidation products is estimated. It is found that oxidation in a thin layer increases the yield of carbonized pitch. For the given pitch samples, the yield of carbonized pitch–coke mixture is higher than the yield of carbonized pitch–coke mixture based on grade C electrode pitch.

The coal residues (CR) obtained after the removal of humic matter from lignite is characterized by infrared (IR), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR). The structural groups present in the residues differ from those in the initial lignite. The sorption of copper and lead cations by the coal residues is studied. The sorptional capacity of the residues is greater for copper than for lead. Two mechanisms are involved in the interaction of the residues with copper and lead cations: ion exchange of the metal cations for protons of the carboxyl groups; and complex formation. The ligands involved may be oxygen-bearing structural groups such as carboxyl and phenol hydroxyl groups.

The optimal time for applying 1 M nitric acid solution to carbonized sapropelic coal that is intended for use in supercapacitor electrodes is determined: modification for 10 min at 100°C is required. This approach increases the specific capacitance of the resulting electrode material by 20%, on average, with different potential scanning rates. Sorption measurements establish that modification of the carbonizate by nitric acid increases the mean mesopore size. In turn, in the production of Co₃O₄/C nanocomposite by an absorption method, with subsequent thermal decomposition of the precursor—cobalt(II) nitrate—at the surface and within the pores of the carbonizate, the optimal time for modification of the carbon matrix by nitric acid is 15 min at 100°C. The specific capacitance of the resulting nanocomposite is ~359 F/g. That is 1.25 times the value for the initial electrode material.

In order to study the effect of microwave reforming process on the organic functional group structure (the way of organic combination of elements such as C, H and O) and carbon structure (carbon orderliness, microcrystalline structure, etc.) of different coking coals. Pre-treatment of coking coal (100, 200, 300 W) was carried out by 100s radiation treatment at different power, and the temperature was controlled below 200°C to prevent the coking coal from cracking. The functional group structure and carbon structure of coking coal before and after microwave treatment were analyzed using infrared spectroscopy, Raman spectroscopy methods. The results showed that with the prolongation of the microwave radiation treatment time, the overall trend of aroma fa first decreased, then increased and then decreased. The variation of DOC, the degree of aromatic ring polymerisation, varied considerably from one coal sample to another, and the ratio of the length of the main chain of the aliphatic chain to the length of the branched chain, A(CH₂)/A(CH₃), showed a U- or W-shaped variation. The oxygen-containing functional group structural parameter C' shows an overall increasing trend. The peak position difference PG-D between the D and G peaks ended up showing an overall decreasing trend, and the area ratio I_D/I_G between the D and G peaks showed a decreasing trend or the final result was basically the same as the beginning. The physical and chemical properties of coking coal were elucidated to characterize the reactive carbonaceous base point during the gasification reaction and to provide basic theoretical support for the preparation of low reactivity-high quality coke.

The air pollutants emitted in coke production that must be regulated and monitored are determined. The analysis is based on the characteristics of the equipment in the main production shops and departments, taking account of the physicochemical transformations of the coal and existing information regarding the sources of atmospheric emissions.

The composition of distillates from coal extracts obtained by thermal solution in high-boiling hydrocarbon fractions—specifically, the processing products of oil and coal—is studied by means of FTIR spectroscopy and ¹H NMR spectroscopy. The results obtained by these two methods are very similar. The distillates consist mainly of aromatic hydrocarbons with admixtures of oxygen- and nitrogen-bearing compounds. The distillate yield increases if heavy catalytic cracking gas oil is added to the solvent. The hydrocarbons present are characterized by a small content of aromatic carbon and hydrogen and a large content of substituents bound to aromatic rings. It is established that these distillates may be used to produce needle coke, since their composition resembles that of the traditional raw materials in this process.

This review of the literature on research into bitumens (waxes and resins) and humic matter in China shows that China has sufficient reserves of lignite suitable for the production of bitumens and humic matter. Most research is devoted to the composition and properties of the waxy component of bitumens (bitumen wax) and the most representative fractions of humic matter (humic and fulvic acids). The resinous component of bitumens (bitumen resin) and the derivatives of humic acids (humous and hymatomelanic acids) have not been studied enough to permit their effective and safe practical application. Data on the composition and properties of Chinese lignite indicate promising applications in cosmetology, medicine, the food industry, and the chemical industry. Convincing evidence shows that humic and fulvic acids are very effective as plant growth stimulators and as reagents for soil reclamation and water treatment, with applications also in animal husbandry. Promising and widely used technologies are noted. Enterprises in the Chinese market are characterized, along with their notable bitumen and humic products. The review indicates that two-step extraction of bitumens and humic matter, with subsequent separation into narrower fractions, makes more complete use of the chemical potential of lignite and is more economical.