Solid Fuel Chemistry最新文献

The combination of denitrogenation pretreatment and deep hydrotreatment was examined to produce clean transportation fuel from nitrogen-rich coal liquid. Heavier fraction (recovery yield; 13.1 wt%) of coal liquid was separated by distillation and denitrogenated by extractions with CuCl₂ · 2H₂O, sulfuric acid, furfural and their combinations. Effectiveness of the treatments for nitrogen reduction was increased as following; H₂SO₄ (48.0%) < CuCl₂ ⋅ 2H₂O (75.0%) < furfural (80.0%) < H₂SO₄/furfural (85.0%) < CuCl₂ ⋅ 2H₂O/furfural (92.0%). The hydrotreatment tests using a batch-type autoclave showed that the hydrodenitrogenation of the heavier oil was promoted by the denitrogenation pretreatment with an order of furfural < H₂SO₄ < CuCl₂ ⋅ 2H₂O < H₂SO₄/furfural < CuCl₂ ⋅ 2H₂O/furfural. The combined treatment with CuCl₂·2H₂O and furfural was the most effective for both its nitrogen reduction and enhancement of the following hydrodenitrogenation. As a result, the first-order hydrodenitrogenation rate increased by 4.4, and the nitrogen content was reduced to 11 wtppm or 230-fold compared with those of the untreated heavier oil. Mixtures of refined heavier oils and heavier-cut coal liquid were also hydrotreated and similar tendencies were obtained.

A method for producing granular carbon adsorbent by stirring a suspension of carbon black in a solution of naphthalene (in heptane) in the presence of sulfuric acid was proposed. Experimental research together with mathematical processing of the results made it possible to propose a mechanism for the formation of spherical carbon granules from carbon black and naphthalene: in the course of intense mixing in the presence of concentrated sulfuric acid, a binder material was formed from naphthalene, and it was adsorbed on the surface of carbon black particles. The resulting particles with a thin layer of binding material on their surface stuck together in the field of centrifugal forces to form larger particles, which ultimately acquired a spherical shape and had a size of up to 5 mm. A comparison of the resulting carbon granules (from carbon black and synthetic pitch) with granules prepared by mixing carbon black and petroleum pitch showed that the proposed adsorbent had specific surface area and mechanical strength greater by factors of 1.5–2.

The reactions of humic acids in a pure form and in the composition of coal with sodium percarbonate occurring on solid-phase mechanochemical treatment were compared. Analysis for CHNO, IR spectroscopy, and potentiometric titration were used to study changes in the composition of humic acids mechanochemically treated after isolation from brown coal. The sorption properties in relation to heavy metal ions (Zn²⁺, Cu²⁺, and Cd²⁺) and their changes as a result of the treatment were studied. The results were correlated with data similar to those for humic acids in coal that underwent mechanochemical treatment. It was demonstrated that, at present, an increase in the yield of humic acids and the concentrations of phenolic and carboxyl groups in brown coal as a result of treatment with sodium percarbonate can be explained by the oxidation of fractions other than humic acids in the organic matter of brown coal.

A series of experiments on the leaching of rare earth elements (REEs) from Miocene brown coals of the Sergeevskoe deposit with water and alkaline and acid solutions was carried out. Using a set of methods (ICP MS, XRD analysis, heavy concentrate analysis, SEM EDS, and IR spectrometry), it was revealed that acid leaching was the most effective: 72–99% of REEs was extracted with a 1 M solution of hydrochloric acid in 24–48 h. This fact indicates that most of the REEs in the brown coals of the Sergeevskoe deposit were associated with the organic matrix in the form of complexes with the carboxyl groups of humic and fulvic acids. The high percentage of REE extraction indicates the possibility of using coals from the Sergeevskoe deposit as an easily enriched source of REEs.

The pyrolysis of two types of raw materials of plant origin (sawdust and sunflower husks), components of the organic matter of biomass (hemicellulose, cellulose, and lignin), and model mixtures prepared from components in accordance with their fractions in the raw materials was studied. Pyrolysis of the materials was carried out using TGA and a laboratory setup with a fixed bed reactor. The distribution and composition of the products were determined at pyrolysis temperatures of 350, 425, 500, and 575°C. Experimental data obtained with the biomass samples and model mixtures were compared with calculated values obtained based on the pyrolysis of individual components and their fractions in the biomass. The possibility of predicting the distribution of pyrolysis products depending on the component composition was investigated. The influence of intercomponent interaction in biomass on the yield and composition of pyrolysis products was revealed.

In order to optimize the arrangement parameters of gas extraction in the downhole layer, the transport level of gas-containing coal was studied through industrial tests and low-temperature liquid nitrogen tests, and the heat-fluid-solid coupling model of the coal-rock deformation field, gas seepage and diffusion field, and temperature field was established, and numerically solved by using COMSOL. The optimal borehole diameter was determined by the single-hole gas extraction capacity, effective radius and extraction impact radius, based on which the superimposed extraction mechanism of neighboring boreholes and the change of gas extraction capacity under multi-hole extraction were studied, and the spacing of boreholes was finally determined. The study shows that: the test coal samples have high adsorption level of gas, the pressure difference between matrix and fissure under the influence of Klinkenberg effect leads to the decrease of gas seepage rate and extraction to a fixed value, the decreasing trend of coal body temperature decreases with the increase of extraction time, the decreasing rate of coal body permeability rises with the increase of attenuation coefficient, and the decreasing rate of gas extraction is accelerated accordingly. The reasonable drill hole diameter of 172403 working face in Dashucun Mine is 114mm, and the spacing of the holes is 6m, which has a good effect of on-site extraction and ensures the safe production of the mine and the sustainable development of the resources.

The properties and efficiency of a solid–liquid suspension based on ground blast furnace slag, which is used to deactivate the processes of oxidation and spontaneous combustion of coals, have been studied. It has been established that sequential impregnation of coal with water-soluble and thickened components of the slag suspension promotes uniform passivation and a decrease in the oxidative activity of the external contacting surface. The results obtained justify the effectiveness of using slag waste as a constituent of technological suspensions for the insulation plugging of a coal seam.

The effect of treatment of a freshly reduced cobalt catalyst with oxygen and ammonia on its properties in the Fischer–Tropsch synthesis was studied. It was shown that treatment with small amounts of catalytic poisons helped to increase the selectivity of the catalyst with respect to the formation of target products, linear C₅₊ hydrocarbons. The observed effect can be explained by partial blocking of the sites of direct CO hydrogenation to methane and modification of Lewis acid sites. The data obtained were consistent with the concept of the two-center surface model of Co catalysts for the Fischer–Tropsch synthesis and the theory of astoichiometric components of catalytic reactions.

The results of an analysis of the state of developments in the field of gasification of coal and biomass mixtures are presented. It is shown that this is a promising direction for diversifying the areas of coal application and a new area for using biomass as a renewable natural resource. The specific features of the process of gasification of coal and biomass mixtures are considered. A comparison of gasifiers of various types was carried out, and the technology and the type of gasifiers that are of particular interest for the production of synthesis gas from the mixtures of coal and biomass were identified.