Solid Fuel Chemistry最新文献

In order to determine the chemical composition of peat, the individual composition of lowland peat from the Bolshoi Kaltus 1 deposit (Arkhangelsk oblast) was characterized. The chemical composition of pyrolysis products of the test peat sample was determined using pyrolytic gas chromatography (GC–MS). Chromatograms of peat were obtained at temperatures from 200 to 600°C. The paper presents the results of a study of the peat pyrolysis process. The properties of products obtained on its basis by thermochemical treatment were described.

The composition, structure, and morphology of dehydrated sewage sludge, a by-product of pulp and paper production, were studied. The thermal characteristics of sewage sludge were investigated. An elemental analysis of the sewage sludge was carried out, the results of which revealed a large number of noncombustible elements (5.5%), including heavy metals (vanadium, chromium, nickel, zinc, and strontium), compared to other types of fuel. Thermogravimetric studies on the thermal decomposition of dehydrated sediment were carried out. The thermogravimetric and differential thermogravimetric curves were described, and the temperature ranges of drying, release of volatile substances, and combustion of coke residue were determined. Microscope photos showed that the particle size of the sediment varied from 0.5 and 350 nm, and amorphous flakes and crystalline inclusions were the main elements of its structure.

Exploring the optimal experimental conditions and mechanism of a novel functionalized ionic liquid 1-ethyl-3-methylimidazolium bromide ([EMIM][Br]) for enhancing the wettability of coal powder is of great significance for reducing the harm of coal dust. This study determined the critical micelle concentration of [EMIM][Br] aqueous solution through ultraviolet(UV) absorption spectroscopy, and analyzed the mechanism of the influence of [EMIM][Br] aqueous solution on the wettability of coal using characterization methods such as contact angle, scanning electron microscope(SEM), automated surface area and porosity analyzer(BET), and fourier transform infrared spectroscopy(FTIR). The results showed that the critical micelle concentration of [EMIM][Br] aqueous solution was 0.005 mol/L, and the optimal experimental conditions were reaction temperature of 40°C, soaking time of 8 hours, and ratio of 1 g to 20 ml. After the action of [EMIM][Br] aqueous solution, the coal dust stomatal layer zone was developed, wedge-shaped stomata and sheet-filled cracks appeared, and the number of mesopores was increased. The content of hydrophilic functional groups such as C–O, carboxyl(–COOH), hydroxyl ether hydrogen bonds(OH…O), and hydroxyl self-consolidating hydrogen bonds(OH…OH) in the pulverized coal was increased, and the content of hydrophobic functional groups such as aryl hydrocarbons –CH₃ and–CH₂ was decreased, which improved the wettability of the pulverized coal.

To investigate combustion thermodynamics and kinetics for different coal rank, TG-DSC test was conducted on long-flame coal (LFC), gas-fed coal (GFC), and coke coal (CC) under different heating rates. Based on the DSC curve, the combustion process of coal can be divided into five stages: dehydration and desorption stage, chemical adsorption stage, transition stage, combustion stage, and burnout stage. With the increase in heating rate, the combustion characteristic parameters and the exothermic quantity show an upward trend. Under the consistent condition of the heating rate, the coal rank is positively correlated with its characteristic temperature, and negatively correlated with the maximum exothermic quantity. The kinetics experimental results show that the differential method exhibited higher fitting coefficients compared to the integral method, indicating its greater reliability in calculating results. Moreover, the activation energy increased with the increase of the coal rank under the same heating rate. CC has the highest activation energy, followed by GFC and LFC. These findings provide data support for the combustion law of similar coal types.

The samples of humic acids (HAs), hymatomelanic acids (HmAs), humus acids (HuAs), and fulvic acids (FAs) and residual coals were obtained by extraction from brown coals of the Kansk-Achinsk and South Ural coal basins. The fractions of humic substances were studied using Fourier transform IR and ¹³C NMR (CPMAS) spectroscopy, technical analysis, and elemental analysis. It has been established that all fractions of humic substances had individual elemental and structural group compositions.

The re-engineered feedstock technique converts low-quality coal into high-quality coal using physical processing on AFBC boiler under full scale with coal as primary fuel. The physical feedstock mixing was adapted as it is identified as having the potential to improve the quality, environmental impact, and energy efficiency of coal combustion. The addition of 6.3% of limestone significantly reduced the SO₂ emissions by 34% and the structural stability was ensured by the retained Fe. The erosive corrosive studies ensures no degradation to the structural material due to the introduction of the limestone particulates. The reduced concentration of sulphur content in the flue gas and passivation of surfaces with the limestone together synergetically reduced the erosion-corrosion effect on the rifle tube section.

A change in the structure of the pyrolytic carbon coating deposited on the surface of a graphite substrate was shown depending on the time the substrate remained in the reaction zone. A multilayer spherical structure of the pyrolytic carbon has been revealed; according to experimental data, is formed on a layer of already formed pyrolytic carbon. A mechanism for the formation of a multilayer spherical structure is proposed.

To study the effect of pyrite on coal spontaneous combustion characteristics in low-rank coal under an oxygen atmosphere in goaf, this paper selected PZ brown coal impregnated with pyrite and its reaction products and monitored the changes in the generation of characteristic gases CO and CO₂ during the programmed heating process of coal samples. The experiment found that oxygen concentration has the greatest impact on the spontaneous combustion characteristics of coal with added Fe³⁺. When the oxygen concentration in goaf coal increases to 9%, the promotion rate of high sulfur coal spontaneous combustion is the highest, which easily increases the range of goaf spontaneous combustion risk areas. When the temperature rises to 60°C, the catalytic effect of pyrite reaction products on coal spontaneous combustion is greatly enhanced. Through FTIR testing, it was found that Fe³⁺ ions, as strong oxidative free radicals, promote the reaction of –CH₂–, –COOH, and –OH in coal at low oxygen concentrations, leading to a further increase in the tendency of coal to self ignite at low oxygen concentrations.

The results of derivatographic studies of the decomposition of oil shale and thermolysis processes in the presence of oil shale are presented. It was found that the addition of oil shale to brown or hard coal intensified the process of thermal dissolution of coal, and the solubility of the organic matter of coal increased with the amount of added oil shale; gas formation decreased and the yield of liquid products increased. The activating role of oil shale was also revealed in the processes of thermolysis of oil residues, gasification (high-temperature thermolysis) of fuel oil and tar emulsions, and preparation of bitumen compositions for road construction.

Results of approbation of the methodology developed at NUST MISIS for assessing the long-term leachability of major and trace elements out of coal mining wastes are presented. This methodology is used to assess the impact of such wastes on the environment when they are placed in dumps or used for reclamation. Three coal mining wastes of various mineral and chemical compositions have been tested. The results have demonstrated that the prolonged treatment of waste with a high sulphur content leads to the oxidation of sulphur-containing compounds, resulting in a significant increase in concentration of water-soluble forms of sulphur, calcium, iron, potassium, sodium and magnesium after the 6th week of treatment, as well as in a decrease in the total sulphur content after the 9th week of processing.