Solid Fuel Chemistry最新文献

The influence of a gas atmosphere during sample preparation, granulometric composition, the duration of contact with air, and the stage of metamorphism on the sorption of oxygen by coals from the atmosphere was established. It was shown that sample preparation performed in an atmosphere of air led to the primary oxidation of the outer surface of coals, which introduced an error in the subsequent determination of the rate of oxygen sorption. Fine coal fractions (0–0.2 mm) with a more developed outer surface exhibited increased oxygen absorption activity. The rate of oxygen sorption was maximal at the initial moment of the interaction of native coals with air, and it decreased with the duration of contact. The least metamorphosed hard coals of the D brand with a high concentration of reactive functional groups and a developed porous structure were characterized by the greatest chemisorption activity.

The results of experimental studies on the influence of the initial moisture content of cedar needles on the time characteristics of ignition of coal–water suspensions (CWSs) based on D-grade thermal coal are presented. Biomass (fallen and freshly cut cedar needles) was used as an additive accelerating the ignition process. The effect of the initial moisture content of the plant additive in the composition of coal–water suspensions on the ignition delay times was analyzed. It has been established that the initial moisture content of cedar needles did not have a significant effect on the time characteristics of the fuel ignition process (the difference did not exceed 4%), but the addition of the needles led to a significant decrease in the ignition delay times (the CWS ignited faster on average by 15%).

Since Ethiopia relies on biomass resources for about 90% of its energy sources, problems such as deforestation and soil degradation have been intensified more than ever. To mitigate these problems, a possibility of using excess aquatic biomass such as water hyacinth as alternative energy is being investigated. In this study, fuel characteristics of biochar briquettes made from combination of water hyacinth biochars, different binders, and organic matter used in Ethiopia were evaluated. Water hyacinth was dried and pyrolyzed at 400 and 800°C (WHB400 and WHB800, respectively). Water hyacinth biochar was mixed with different binders (molasses and Ethiopian soil) at a ratio of [6:4:0] without organic matter, or at a ratio of [6:3:1] with organic matter ([water hyacinth biochar:binder:organic matter]). The experimental results showed that WHB400 with molasses as binder without organic matter [6:4:0] was the best mixing ratio as biochar briquette with the highest higher heating value and the greatest compressive strength among all other biochar briquettes. Therefore, this study showed water hyacinth biochar could be a great potential as an alternative fuel to conventional acacia charcoal.

The composition and characteristics of high-molecular-weight components of the thermolysis products of petroleum residue asphaltenes obtained in supercritical water with and without a catalyst based on iron oxides have been studied. The experiments were carried out in an autoclave at a temperature of 450°C for 60 min; the catalyst was prepared in situ from iron(III) tris(acetylacetonate). The use of supercritical water and the in situ prepared catalyst made it possible to increase the yield of saturated and aromatic hydrocarbons by a factor of more than 9.5 compared to that in a control experiment (thermolysis without water and a catalyst) and decrease the yield of solid products insoluble in chloroform. The properties of high-molecular-weight components isolated from the thermolysis products were characterized using structural group analysis and IR spectroscopy. High-molecular-weight components obtained by thermolysis in supercritical water in the presence of the catalyst, in comparison with the products obtained in the control experiment, were characterized by higher H/C ratios and concentrations of oxygen-containing groups and lower average molecular weights.

The antioxidant activity of resin–asphaltene components isolated from two crude oils of different compositions was analyzed before and after exposure to a magnetic field using the voltammetric method of oxygen electroreduction. The antioxidant activity of the test asphaltenes and weakly polar and polar resins increased or decreased with increasing sample concentration in a supporting electrolyte solution. Petroleum antioxidants are part of a complex colloidal structural system, and they are associated with it by associative interactions that arise as a result of changes in the size and activity of associates in the petroleum system as a whole.

The interaction of humic acids (HAs) isolated from oxidized brown coal with the polyaromatic hydrocarbon naphthalene has been studied. The electron-donating properties of HAs were evaluated based on the intensity of electronic transitions in the UV region and calculated descriptors. The modification of the HA structure was carried out by mechanical activation (MA) under alkaline and oxidative conditions. A significant increase in the fraction of aromatic and oxidized fragments in the HA structure after MA under oxidative conditions increased the intensity of binding HAs to naphthalene. A significant increase in the adsorption capacity of mechanically activated HAs in a dispersive aqueous medium with naphthalene was demonstrated.

Samples of cryogels based on aqueous solutions of polyvinyl alcohol were investigated. The molecular weights of the cryogel samples varied from 25⋅10³ to 60⋅10³. It has been found that the ultimate strength of dry briquettes increased from 1.2 to 3.7 MPa with an increase in the polymer molecular weight. The resulting briquettes can be used, for example, as a proper domestic or industrial fuel.

The effect of an inhibitory composition based on an amphiphilic polymer of polyacrylate and stearic acid on the composition of paraffinic hydrocarbons in asphalt–resin–paraffin deposits (ARPDs) of high-paraffin oil was studied. It was shown that the molecular weight distributions of paraffinic hydrocarbons in the ARPDs were different upon the addition of the amphiphilic polymer and the composition to oil. The action of the polymer led to a decrease in the total concentration of C₁₆–C₂₁ hydrocarbons and an increase in the fraction of high-molecular-weight C₂₂–C₃₄ hydrocarbons. On the contrary, the use of stearic acid as a surfactant in the composition decreased the amount of high-molecular-weight paraffin hydrocarbons.

The influence of ultrasonic treatment, a polymer additive, and their combined effect on the structural and rheological properties of highly paraffinic, low-resin oil and the composition of separated sediments was studied. The oil was processed in an ultrasonic field (field intensity, 6 W/cm²; frequency, 22 kHz; and time, 1–10 min). The sedimentation process was carried out at a medium temperature of 30°C and a cold rod temperature of 5°C. Viscosity–temperature parameters of oil were determined using a Brookfield DV-III ULTRA rotational viscometer. Ultrasonic treatment for 1 min and a polymer additive (0.05 wt %) led to a decrease in the viscosity by a factor of 5 and in pour point by 8°C. The introduction of the additive and the complex effect contributed to changes in the molecular weight distribution of n-alkanes in sediments: a shift of the second distribution maximum to the region of higher molecular weight components and an increase in the concentration of n-alkanes ΣC₁₇H₃₆–C₃₃H₆₈.

Changes in the composition of oil compounds in a vertical section of peat soil on the territory of the Mamontovskoye oilfield (KhMAO, Western Siberia) 6, 12, and 18 years after oil pollution were studied using gas chromatography–mass spectrometry (GC–MS). The distribution of individual compounds in the surface soil layer after an oil spill was largely determined by biodegradation reactions progressing with time. In the underlying layers at a depth of 10–50 cm, the composition and concentration of oil components indicated the influence of migration processes on their differentiation.