Carbon Mass Fraction Research Articles

Evolution of solid residue composition during inert and oxidative biomass torrefaction

Biomass torrefaction is a thermochemical pretreatment that can be used to improve biomass properties, contributing to the energy densification of biomass or increasing its grindability, burning and gasification characteristics, porous structure, etc. While it is typically carried out under inert conditions, oxygen-lean torrefaction of biomass can reduce the process cost and complexity. This work proposes a novel extended 2-step kinetics mechanism capable of accurately predicting the evolution of the chemical composition of torrefied biomass. The model parameters are obtained from data collected from an extensive experimental campaign in which the chemical composition of torrefied biomass was measured at different temperatures, residence times, and oxygen fractions. The carbon mass fraction of the torrefied products was found to increase by up to 50 % under severe inert torrefaction conditions, i.e., high temperatures and long residence times, whereas the hydrogen fraction decreased. In the presence of oxygen during torrefaction, the carbon and hydrogen contents in the solid residue decrease compared with those produced under inert torrefaction. The extended 2-step model can also be used to determine the high heating value and energy densification of the torrefied biomass, with the latter ranging from 1 to 1.4 for the operating conditions tested.

Physysichemical Properties of Quaternary Ammonium Salts Formed by Undecanoic and Tetradecanoic Acids with Trietanolamine

Abstract The article presents the results of the study of the oil collecting and oil dispersing properties of the quaternary ammonium salts formed by undecanoic and tetradecanoic acids, which are monobasic carboxylic acids, with triethanolamine (TEA) in distilled, drinking, and sea waters contaminated with Balakhani Oil. The surface activity property of the products of different concentrations of these complexes was calculated using a tensiometer, and the elemental composition was calculated using the calculation method. A comparative study of the element composition of the salts of both acids formed with TEA shows that the mass fraction of carbon in the complex formed by tetradecanoic acid with TEA is higher than in the other complex. Comparison of the surface activity property of the complexes formed by undecane and tetradecanoic acid with TEA shows that the complex compound formed by tetradecanoic acid with TEA shows more surface activity property. Therefore, as the mass fraction of carbon element increases in the complexes formed by undecane and tetradecanoic acid with TEA, the complex compound shows more surface activity properties.

Methods for Measuring Organic Carbon Content in Carbonate Soils (Review)

In world practice, the measurement of the mass fraction of carbon of organic compounds (Corg) in soils containing carbonates is carried out in various ways. An analysis of methods that allow solving this problem was carried out, including the latest approaches: thermogravimetry, differential scanning calorimetry, spectroscopy. It has been shown that the presence of CaCO3 does not prevent the use of the dichromatometric method (Tyurin, Walkley-Black) for determining Corg. The disadvantages of the method boil down to the laboriousness of the analysis, the need for constant presence of the operator, incomplete oxidation of organic compounds and environmental pollution. The method of measuring soil mass loss-on-ignition (LOI) is economical and rapid, but it gives an overestimated Corg content, which is associated with the inadequacy of the conversion factor of 1.724, the presence of adsorbed and chemically bound water, as well as mineral components decomposing at T = 105–550°С. The most relevant solution for finding Corg in carbonate soils is to use an analyzer and a calcimeter, although the accuracy of Corg measurements in the presence of carbonates is significantly reduced due to the quadratic summation of the errors of the two methods. The high cost of the device, maintenance, verification and repair limit its widespread use in soil laboratories. To measure the content of soil carbonates, it is possible to use both gravimetric (LOI) and volumetric (calcimeter) methods. The use of the latter is preferable for soils with a predominance of CaCO3 in carbonate composition. Preliminary removal of carbonates from soil samples is labor-intensive and can lead to partial loss of Corg due to acid extraction. The high cost of instruments and the lack of libraries of soil spectra hinder the development of vis-NIR and MIR spectroscopy as an alternative to “wet” chemistry methods. Continuing comparative studies will improve the understanding of the spatial patterns of distribution of carbon in soil organic compounds.

Numerical investigation of the physical-thermal-chemical behaviours of particles during coal combustion and desulfurization processes in a CFB combustor

The desulfurization process has been practised for the clean utilization of coal in chemical engineering fields, yet the physical, thermal, and chemical characteristics of particles are still lacking understanding. In this work, a comprehensive numerical model based on the Eulerian-Lagrangian framework was established to study the particle behaviours during coal combustion and desulfurization processes in a pilot-scale circulating fluidized bed (CFB) combustor. After model validation, the effects of several crucial operation parameters (e.g., excess air ratio, calcium to sulphur ratio, and calcium oxide size) on particle behaviours are illuminated. The results show that density-induced segregation causes coal particles to accumulate in the upper part of the riser. The sand, coal, and CaO particles have time-averaged Reynolds numbers of 15, 6.5, and 0.5, respectively. The particle temperature is higher in areas with lower solid concentrations. Increasing excess air ratio (ϕg) decreases the temperature of sand particles but elevates that of coal and CaO particles. The average particle heat transfer coefficients (HTCs) for sand, coal, and CaO particles are 205 W/m2·K, 172 W/m2·K, and 275 W/m2·K, respectively. With the increase in ϕg, the HTC of sand particles increases but that of CaO particles remains unchanged, additionally, the mass of coal particles decreases and the mass of carbon in coal particles decreases along with the riser. The influence of the Ca/S ratio and CaO size on the axial distribution of coal particle mass and carbon mass fraction is negligible. For each particle species, the axial dispersion coefficient (Dz) is two orders of magnitude greater than the radial ones (Dx, Dy), indicating that the vertical introduction of the fluidizing gas dominates the dense gas-solid flow in the riser.

Analysis of Longitudinal Cracking and Mold Flux Optimization in High-Speed Continuous Casting of Hyper-Peritectic Steel Thin Slabs

Longitudinal crack defects are a frequent occurrence on the surface of thin slabs during the high-speed continuous casting process. Therefore, this study undertakes a detailed analysis of the solidification characteristics of hyper-peritectic steel thin slabs. By establishing a three-dimensional heat transfer numerical model of the thin slab, the formation mechanism of longitudinal cracks caused by uneven growth of the initial shell is determined. Based on the mechanism of longitudinal crack formation, by adjusting the performance parameters of the mold flux, the contradiction between the heat transfer control and lubrication improvement of the mold flux is fully coordinated, further reducing the incidence of longitudinal cracks on the surface of the casting thin slab. The results show that, using the optimized mold flux, the basicity increases from 1.60 to 1.68, the F- mass fraction increases from 10.67% to 11.22%, the Na2O mass fraction increases from 4.35% to 5.28%, the Li2O mass fraction increases from 0.68% to 0.75%, and the carbon mass fraction reduces from 10.86% to 10.47%. The crystallization performance and rheological properties of the mold flux significantly improve, reducing the heat transfer performance while ensuring the lubrication ability of the molten slag. After optimizing the mold flux, a surface detection system was used to statistically analyze the longitudinal cracks on the surface of the casting thin slab. The proportion of longitudinal cracks (crack length/steel coil length, where each coil produced is about 32 m long) on the surface of the thin slab decreases from 0.056% to 0.031%, and the surface quality of the thin slab significantly improves.

Study on the influence of coal on coal-to-ethylene glycol process considering the integration of reactor, distillation column, and heat exchanger network

The ethylene glycol (EG) process has low energy efficiency and high emissions. The raw coals purchased from different mines have different compositions and affect the reactor/column parameters and the integration of the heat exchanger network (HEN). An integrated reactor-distillation column-HEN model is built for optimizing the coal-to-ethylene glycol (CTEG) process considering the variation of raw coal. The particle swarm optimization (PSO) algorithm is used to solve this model and target the optimal raw coal for the CTEG process based on the interaction of MATLAB and Aspen Plus software. The influence of raw coal is obtained based on the sensitivity analysis performed for key reactor parameters and energy consumption. For the identified optimal raw coal, the mass fraction of carbon, hydrogen, oxygen, and ash are 84.02%, 6.80%, 1.00%, and 5.00%, respectively; the water added in the coal-water slurry is 62.15 t·h−1, and the water-gas ratio is 0.32, the corresponding energy consumption and the CO2 emission per unit product are 0.093 kgce⋅kmol−1 and 0.247 kgCO2⋅kmol−1, both decreased by 32.61%. The proposed method can be used to optimize the design and operation of the CTEG process and extended to optimize the other coal-based processes to achieve cleaner production.

A sensitive NH3 chemiresistive sensor with wide detection range: Employing a MOF-derived mesoporous carbon composite with polyaniline

Designing sensing materials with effective porous structure and compositions is a crucial strategy for constructing high-performance gas-sensitive devices. Herein, a dodecahedral mesoporous carbon derived from metal-organic frameworks (CMOF), e.g. Zeolitic Imidazolate Framework-8 (ZIF-8) derived porous carbon (ZIF-8-C) was prepared, and subsequently, three-dimensional (3D) hollow dodecahedral ZIF-derived carbon-polyaniline (PANI) based (ZCPx, x representing the mass fraction of ZIF-derived carbon) hierarchical hybrid materials were constructed by introducing protonated polyaniline on the surface of MOF carbon via in-situ oxidative polymerization. The MOF-derived structure provides a substantial interface surface area for the hybrid material, enabling rapid adsorption and charge transfer, along with essential structural stability. The 3D hollow ZCP50 hybrid material prepared exhibits a wide detection range (0.1–500 ppm), repeatability, acceptable long-term stability, and an 8.3 times response enhancement versus PANI. The above performance is attributed to the significant synergistic effect between ZIF-8-C and PANI. The unique design of this 3D framework holds promising potential for the commercial application of room-temperature gas sensors.

Adsorption of Radioactive Iodine Using Nanocarbon on ETS-10 as Adsorbent

Laboratory-synthesized nanocarbon pelletized with titanosilicate (ETS-10) as a support matrix has been investigated for the capture of radioactive iodine present as methyl iodide (CH3I) in the off-gas streams produced during aqueous reprocessing of used nuclear fuel. The mass fraction of carbon in the sorbent matrix was 0.10. The effects of residence time and CH3I concentration were investigated using a continuous flow column setup to quantify the adsorption and desorption capacities of adsorbent under dynamic conditions from an air stream containing CH3I present at concentrations representative of those expected in the off-gas streams. Air with CH3I gas as a source in the column resulted in quantifiable CH3I adsorption with 0.98 mg/g of adsorption capacity. Laboratory-made nanocarbons had a larger adsorption capacity than those of the other carbons reported in the literature. Additionally, the adsorption capacity of nanocarbon on ETS-10 is compared to that of nanocarbon coated on cordierite in previous studies.

Measurement report: Evaluation of the TOF-ACSM-CV for PM1.0 and PM2.5 measurements during the RITA-2021 field campaign

Abstract. The recently developed time-of-flight aerosol chemical speciation monitor with a capture vaporizer and a PM2.5 aerodynamic lens (TOF-ACSM-CV-PM2.5) aims to improve the collection efficiency and chemical characterization of aerosol particles with a diameter smaller than 2.5 µm. In this study, comprehensive cross-comparisons were performed between real-time online measurements and offline filter analysis with 24 h collection time. The goal was to evaluate the capabilities of the TOF-ACSM-CV-PM2.5 lens, as well as the accuracy of the TOF-ACSM-CV-PM2.5. The experiments were conducted at Cabauw Experimental Site for Atmospheric Research (CESAR) during the RITA-2021 campaign. The non-refractory fine particulate matter (PM1.0 and PM2.5) was measured by two collocated TOF-ACSM-CV-PM2.5 instruments by placing them behind a PM2.5 and PM1.0 inlet, respectively. A comparison between the ACSMs and PM2.5 and PM1.0 filter samples showed a much better accuracy than ±30 % less given in the previous reports, with average differences less than ±10 % for all inorganic chemical species. In addition, the ACSMs were compared to the Monitoring Instrument for Aerosol and Gas (MARGA) (slope between 0.78 and 0.97 for inorganic compounds, R2≥ 0.93) and a mobility particle size spectrometer (MPSS), measuring the particle size distribution from around 10 to 800 nm (slope was around 1.00, R2= 0.91). The intercomparison of the online measurements and the comparison between the online and offline measurements indicated a low bias (< 10 % for inorganic compounds) and demonstrated the high accuracy and stability of the TOF-ACSM-CV-PM2.5 lens for the atmospheric observations of particle matter. The two ACSMs exhibited an excellent agreement, with differences less than 7 %, which allowed a quantitative estimate of PM1.0 vs. PM2.5 chemical composition. The result showed that the PM1.0 accounted for about 70 %–80 % of the PM2.5 on average. The NO3 mass fraction increased, but the organic carbon (OC) mass fraction decreased from PM1.0 to PM2.5, indicating the size dependence on chemical composition.

Combustion Enhancement of Gel Propellant Containing High Concentration Aluminum Particles Based on Carbon Synergistic Effect.

The addition of aluminum particles to gel propellants can improve combustion performance. However, the agglomeration of aluminum during the combustion process can result in a series of negative effects. In this paper, the aluminum agglomeration inhibition method of gel propellant based on carbon synergistic effect is proposed. Carbon particles exhibit excellent combustion properties, and the gaseous product CO2 generated during combustion can mitigate the agglomeration of aluminum. The research demonstrates that incorporating carbon particles into aluminum-containing gel effectively reduces the incomplete combustion of aluminum particles and increases the volumetric calorific value of the gel. When the mass fraction of carbon is 5 wt%, the volume calorific value of the gel reaches the highest. Meanwhile, the rheological experiments show that the addition of carbon particles can improve the shear-thinning properties of the gel, which is beneficial to the atomization and combustion processes of the gel.

Исследование реагентного режима флотации одного из золоторудных месторождений Восточного Забайкалья

The relevance of the problem is that the final product of flotation of the Eastern Transbaikalia deposit to be sold, has a low content. The object of the research is as follows: technological sample of the original ore of the gold deposit in Eastern Transbaikalia. The purpose of the research includes the search for the optimal reagent regime during the flotation process to improve technological performance. The research objectives are to study the chemical and mineral composition and to investigate the possibility of using reagents based on alcohols and C4-C8 esters “KETGOL”, “KETGOL improved”, “KON-92”. The research methodology is based on studying the properties of the components and their influence on the flotation process. The material composition of the ores has been studied by methods of atomic emission spectral quantitative analysis, X-ray fluorescence, phase atomic absorption analyzes and atomic emission analysis with inductively coupled plasma ICP-AES. The mass fraction of total and organic carbon is determined by the infrared absorption method. The gold content in the original ore is based on assay data. When conducting flotation experiments, the equipment of JSC Irgiredmet has been used. As a result of the research, the material composition is studied and laboratory studies of flotation enrichment of the ore sample are carried out. Conclusions on the material composition are as follows: the studied ore sample belongs to the primary gold-quartz, moderate sulfide mineral type of ore. The gold content is 3.12 g/t, silver – 6.9 g/t. The gold in the ore is mostly small and thin, its fineness is 708. The results of flotation enrichment have showed that the use of the KETGOL reagent as an additional collector to potassium butyl xanthate (BX) in a 2:1 ratio with a total consumption of 90 g/t is an effective means of increasing gold recovery to ~87–89 %, with In this case, the quality of the main flotation concentrate remains at the level of ~15.5–16.5 g/t.

Оптимизация технологии обогащения бедной технологически упорной золото-углеродсодержащей руды

The processing of refractory gold ores is a challenging task. Refractory ores include ores that cannot be easily processed due to the fine dissemination of gold in sulphide minerals and the presence of preg-robbing carbonaceous matter. Two processes have been studied: flotation of low-grade double refractory gold ore ­using new carbon depression reagents; gravity – cleaner flotation of rougher flotation concentrate followed by pressure oxidation and the CIL treatment of POX cakes. The study is aimed to optimize the processing of low-grade (Au 0.6 g/t) refractory gold ore and achieve high process parameters. The study included the following steps: the reduction of organic carbon mass fraction (< 0.6 %) in concentrates reporting to hydrometallurgical treatment; experiments on the hydrometallurgical treatment of flotation concentrates using two process options: pressure oxidation (POX) of the initial flotation concentrate followed by the CIL treatment of POX cakes and preliminary gravity – cleaner flotation of the initial flotation followed by pressure oxidation and the CIL treatment of POX cakes. The research methodology is based on studying the influence of carbon depressant reagents on the flotation properties of organic carbon during the flotation process. When carrying out flotation experiments, the equipment of JSC Irgiredmet was used, installed at the semi-industrial testing site (laboratory mills, mechanical flotation machines and auxiliary equipment). The study is carried out in accordance with generally accepted methods of ore preparation and flotation concentration. The mass fraction of organic carbon in the flotation concentrate decreased from 2.0 to 0.5 %. It has been achieved by the use of new reagents for carbon depression (carbon depression reagents). The products of refractory gold ore flotation using new reagents for carbon depression were flotation concentrates suitable for further hydrometallurgical treatment. According to the experiments on rougher flotation concentrate pressure oxidation and subsequent POX cake cyanide leaching, the recovery of gold on the carbon adsorbent was 83.5 %. Preliminary gra­vity – cleaner flotation of the concentrate before pressure oxidation improved the loading of gold on the carbon adsorbent to 96.6 %.

The Impacts of Dust Storms With Different Transport Pathways on Aerosol Chemical Compositions and Optical Hygroscopicity of Fine Particles in the Yangtze River Delta

AbstractAerosol physicochemical properties during two dust storms (DS1: March 30–31, and DS2: May 7–8) are measured in 2021 in Nanjing, aiming to investigate the impacts of dust storms on aerosol chemical compositions and optical hygroscopicity in the Yangtze River Delta (YRD). During DS1, the dust air masses are transported in the lower atmosphere and pass through the inlands and sea areas before reaching the YRD region. During DS2, the dust air masses are transported in the upper atmosphere and pass through the inlands only. Both of them are accompanied by an increase in black carbon (BC) mass fraction and a decrease in nitrate mass fraction in fine particles (PM2.5, particles with diameters less than 2.5 μm) near the surface. However, the impacts on the mass fractions of organics or sulfate are adverse between DS1 and DS2. During dust‐influence periods the enlarged mass ratios of sulfate to nitrate (greater than 4) promote the occurrence of deliquescent behavior of ambient aerosols although dust aerosols can significantly suppress aerosol optical hygroscopicity. To improve model simulations of aerosol optical hygroscopicity, it is necessary to use a segment parameterization to describe aerosol light scattering enhancement factor during dust‐influence periods. The closure study of optical hygroscopicity parameters with two different methods reveals the impact of aerosol scattering Ångström exponent on the estimation of optical hygroscopicity parameter. The results highlight that the impact of dust storms on aerosol chemical compositions and optical hygroscopicity are different for DS events with different transport pathways.

Controlling the Coke Formation in Dehydrogenation of Propane by Adding Nickel to Supported Gallium Oxide

AbstractAtomic layer deposition was applied on mesoporous silica to synthesize a highly dispersed gallium oxide catalyst. This system was used as starting material to investigate different loadings of nickel in the dehydrogenation of propane under industrially relevant, Oleflex‐like conditions. The formation of NiGa alloys was confirmed by X‐ray diffraction analysis and electron microscopy. Surprisingly, the nanoalloys enhanced the selectivity towards C3H6 while decreasing the tendency for coking. Herein, in situ thermogravimetry, and measured mass fractions of carbon revealed that the coking rate was reduced by over 50 % compared to the pristine gallium oxide. Generally, the increased selectivity can be explained by the partial hydrogenation and reduction of the gallium oxide surface. The optimum temperature for the removal of deposited carbon was evaluated by a temperature programmed oxidation. Finally, the best‐performing Ni−GaOx catalyst was employed in a cycled experiment with periodic reaction and regeneration tests. After regeneration, the selected Ni−GaOx catalyst provided a higher yield of propylene compared to the unmodified gallium oxide.

Total Organic Carbon Logging Evaluation of Shale Hydrocarbon Source Rocks in the Shan 1 Section of the Sulige Gas Field, Ordos Basin, China

The mass fraction of total organic carbon (TOC) is one of the key indicators for evaluating the hydrocarbon generation potential of shale source rocks. Experimental measurements to evaluate the TOC content require significant cost and time. Furthermore, the experimental data are often fragmented and may not provide an accurate depiction of the source rocks throughout the entire block. To solve the above problems, this paper proposes to use the combination of conventional logging data and experimental data after an in-depth study of the geophysical characteristics of hydrocarbon source rocks in the Ordos Basin. A quantitative model between logging data and source rocks is established, and then the continuous distribution value of the TOC content in the hydrocarbon source rock interval is calculated. Firstly, the mud shale formation of the Permian–Shanxi Formation in the Upper Paleozoic, located in the Jingbian area of the Ordos Basin, is selected as the research target using the “Jinqiang method”. The model is constructed by selecting appropriate logging curves (acoustic time difference logging, resistivity logging, and density logging) and experimental results based on the response relationship between logging data and TOC data. This method provides more accurate and comprehensive data for source rock studies, combining experimental sampling to contribute to a better evaluation of TOC in source rock. The shale hydrocarbon source rock logging data from 10 wells are selected, and the model is used to realize the full-well section of the logging data to find the hydrocarbon source rock TOC, which is compared with the TOC data from the experimental core tested at a sampling point. The results demonstrate that the model is highly effective and accurate, with a mere 2.7% percentage error observed across 185 sample data points. This method greatly improves the accuracy and completeness of TOC evaluation compared with the results of previous studies and provides a guide for subsequent TOC logging evaluation of source rocks in other areas. With the study in this paper, continuous TOC values of source rocks are obtained, discarding the TOC values representing the whole set of hydrocarbon source rocks with a limited number of sample averages. This method can reflect the contribution of the layers with high and low organic matter abundance, and the calculated reserves are more accurate. By utilizing the measured TOC values of the study area to invert the model to find the parameters, this study contributes to the decision-making of hydrocarbon exploration in domestic and international basins.

Reliability Analysis of HHV Prediction Models for Organic Materials Using Bond Dissociation Energies.

The purpose of this study is to analyze the reliability of predictive models for higher heating values related to organic materials. A theoretical model was developed, which utilizes bond dissociation energies (BDEs) to establish correlations between elemental composition and calorific values. Our analysis indicates that the energy contribution of one mole of hydrogen atoms is approximately equal to -144.4 kJ mol-1. Further investigation reveals significant variations in the bond dissociation energies of carbon atoms within organic compounds, resulting in a range of energy outputs from -414.30 to -275.34 kJ mol-1 per mole of carbon atoms. The presence of oxygen atoms in organic compounds has a negative impact on the magnitude of combustion heat, with values ranging from 131.1 to 207.17 kJ mol-1. The combustion mechanism imposes certain constraints, leading to the equation HHVg = -31.34·[C] - 144.44·[H] + 10.57·[O] for organic compounds. Based on the parameter sensitivity analysis, the coefficient associated with carbon mass fraction exhibits a significantly greater impact on result prediction accuracy, demonstrating a sensitivity value of 92.65%. The results of further analysis indicate that empirical correlations involving the mass fractions of the elements N and S in lignocellulosic materials may be prone to over-fitting, with sensitivity indices of 1.59% and 0.016%, respectively.

Production of pyrolytic carbon from waste of rubber-containing products for use in foundry

The paper deals with the processing of rubber‑containing products by pyrolysis in order to obtain pyrolytic carbon, which is of practical interest for the needs of the foundry. It has been established that the process of gas phase evolution during rubber pyrolysis proceeds in the temperature range of 50–550 °C, the maximum release peaks for all detected substances are in the range of 375–500 °C, the total release is over 140 mg per kg of feedstock. It was found that the concentration and temperature of the exhaust gases make it possible to neutralize them in an autocatalytic mode using the principle of filtration combustion. It is shown that the optimal temperature for obtaining a solid carbonaceous residue (target product) is 320–380 °C, an increase in temperature above 500 °C leads to a decrease in the mass fraction of pyrolytic carbon from 64.8 to 31.9 %, respectively, the proportion of exhaust gases increases from 5 to 8 %, and heating oil yield from 30.2 to 60.1 %.

Comparison of methodological approaches to the determination of organic carbon in wastes of mining, processing and combustion of coal

The content of organic carbon is one of the key indicators in determining the areas of using waste of mining, processing and combustion of coal. The measurement results obtained by existing measurement methods are often incomparable to each other, which does not allow obtaining a reliable information about the waste composition. The goal of this study is to generalize current methodological approaches and choose the most effective one for determining the content of organic carbon in samples of waste of mining, processing and combustion of coal. Three most appropriate methods were selected proceeding from the analysis of the methods used for determining organic carbon in various natural and technogenic objects. Method No. 1 is based on the calculation of organic carbon content as the difference between total carbon measured by a CHN analyzer and carbonate carbon determined by the gravimetric method. In method No. 2, the determination of organic carbon content is carried out through the determination of the ash, moisture and carbonate carbon content. Method No. 3 includes demineralization of the sample with hydrochloric acid, drying, and calcination of the resulting residue. The samples of waste of mining, processing and combustion of coal with mass fraction of organic carbon from 0 to 60% were used as objects of the research. According to the results of experimental studies and taking into account possible limitations, measurement procedure based on method No. 3 for determining the content of unburned carbon in ash and slag from a thermal power plant was chosen. The applicability of the newly developed measurement procedure was verified for an extended area of objects, which includes, in addition to the samples of coal combustion waste, the samples of waste of their mining and processing. The comparability of the results obtained by other methods was demonstrated, and a preliminary assessment of the metrological characteristics was performed. The measurement procedure can be used in analysis of the reference samples used for construction of the calibration characteristics in the determination of organic carbon by instrumental methods, as well as in the determination of the metrological characteristics of the reference materials of the composition of waste of mining, processing and combustion of coal.

Ore composition and native gold characteristics of an ore occurrence in Eastern Transbaikalia

The article deals with the characteristics of the ores of an ore occurrence of the Munginsky cluster located on the western flank of one of the commercial fields of Eastern Transbaikalia. The ores of this promising ore occurrence are underexplored, especially in the technological aspect, which served the basis for studying their composition and characterizing native gold as their main commercial component. The composition of ores and altered rocks was studied by the following methods: atomic emission spectral quantitative analysis, X-ray fluorescence, as well as phase atomic absorption and atomic emission analysis with inductively coupled plasma ICP-AES. The mass fraction of total and organic carbon was determined in the Central Fire Assay Laboratory of JSC Pokrovsky Rudnik, Blagoveshchensk. The proportion of carbonate carbon dioxide was determined by the method of titrimetric determination of carbon dioxide. The content of gold was given according to the data of assay melting, the content of silver – according to the data of atomic absorption analysis. Petrographic and mineragraphic studies were carried out using an optical microscope Olympus BX-51. The mineral composition of the ore sample was also estimated based on the results of X-ray diffraction analysis. The quantitative mineral composition was studied on the crushed material of the original ore with a particle size of -2 mm using the microscopic study data of transparent and polished thin sections on a microscope Nikon Eclipse LV 100 POL. The content of iron hydroxides was determined from the weight difference after the sample was treated with a 10 % oxalic acid solution in a water bath. Comparison of the results obtained on the ore occurrence with the materials on the ore composition of the closest deposit located in 30 km demonstrates that on the one hand they are similar and uniform, and on the other hand they feature some differences. Their common parameters include a rather high degree of sulfide content of ores and similar chemical and mineral composition with the predominance of arsenopyrite, an increased role of bismuth as well as the predominance of fine gold and its similar morphological characteristics. This fact allows to consider the ore occurrence under investigation as an integral part of a single ore system of the closest deposit.

Microwave assisted and conventional hydrothermal treatment of waste seaweed: Comparison of hydrochar properties and energy efficiency

Waste seaweed is a valuable source for converting into value-added carbon materials. In this study, the production of hydrochar from waste seaweed was optimized for hydrothermal carbonization in a microwave process. The produced hydrochar was compared with hydrochar synthesized by the regular process using a conventional heating oven. The results show that hydrochar produced with a holding time of 1 h by microwave heating has similar properties to the hydrochar produced in a conventionally heated oven for 4 h (200 °C and water/biomass ratio 5): carbon mass fraction (52.4 ± 3.9 %), methylene blue adsorption capacity (40.2 ± 0.2 mg g−1) and similar observations on surface functional groups and thermal stability were made between hydrochars produced by both methods. The analysis of energy consumption showed microwave assisted carbonization consume higher energy in compare to conventional oven.The present results suggest that hydrochar made from waste seaweed and using the microwave technique could be an energy-saving technology for producing hydrochar with similar specifications to hydrochar produced by conventional heating methods.