Coal Mixture Research Articles

Study on road performance of asphalt mixture based on surface modification of coal gangue

In order to solve the problem of coal gangue environmental pollution and the shortage of aggregate resources in road engineering, this paper studies the feasibility of using waste coal gangue as coarse aggregate of asphalt mixture. Through the physical and mechanical properties test, the difference between coal gangue and natural aggregate was compared and analyzed. The surface modification and strengthening treatment of coal gangue aggregate was carried out by using methyl sodium silicate solution, and the best modification scheme was determined. The influence of different content and surface modification on the road performance of coal gangue asphalt mixture was studied by laboratory test. With the help of scanning electron microscope test, the change characteristics of the microstructure of coal gangue asphalt mixture before and after surface modification were explored. The results show that although the indexes of coal gangue are inferior to those of natural aggregate, it can be used to prepare asphalt mixture within the scope of specification requirements. The modification effect of sodium methyl silicate solution with modification time of 6h is the best, which can significantly improve the water absorption, density and crushing value of coal gangue. When the content of coal gangue is controlled within 30%, the performance of asphalt mixture meets the requirements of the specification, and the amount of coal gangue in asphalt mixture can be increased after surface modification. After surface modification, the surface pores and cracks of coal gangue asphalt mixture are reduced, and the surface micro-damage under high temperature immersion and freeze-thaw cycle conditions is improved.

Modification mechanism of caking property of polystyrene waste using low-temperature pyrolysis and its use in coal-blending coking

Polystyrene (PS) waste was depolymerized using a low-temperature pyrolysis treatment (LTPT) to increase its caking index. The mechanism of caking index modification was revealed by using Fourier transform infrared spectroscopy, thermogravimetric (TG) analysis, pyrolysis-gas chromatography with mass spectrometric detection, and solid-state 13C nuclear magnetic resonance spectroscopy. The crucible coal-blending coking tests were carried out using an industrial coal mixture and the treated-PS with the highest caking index (PS300) or raw PS. Some properties of the resultant cokes were also analyzed. It was demonstrated that the caking index of PS dramatically increased by LTPT; however, exceeding 300 °C did not yield any benefit. The caking index increased due to the formation of the caking components, whose molecules are medium in size, caused by LTPT. Additionally, the coke reactivity index of the coke obtained from the mixture containing PS300 decreased by 5.1% relative to that of the coke made from the mixture with PS and the coke strength after reaction index of the former increased by 7.3% compared with that of the latter, suggesting that the ratio of depolymerized PS used for coal-blending coking could increase relative to that of PS.

Effect of moisture content on pyrolysis product yield from lignite and lignite-peanut shell mixtures using slow pyrolysis

ABSTRACT The conversion of biomass-coal mixtures into energy using thermal conversion systems offers a more environmentally sustainable alternative to conventional coal consumption. A reactor with an internal compartment is proposed to improve the pyrolysis performance of lignite coal and mixtures of lignite coal with peanut shells. The study investigates lignite coal with varying moisture contents and peanut shell proportions (0%, 10%, 25%, and 50%) at a temperature of 500°C, using a heating rate of 0.1°C/s. The results indicated that dry mixtures demonstrated higher overall productivity compared to wet mixtures, particularly in terms of charcoal production. The weight of charcoal increased by 4.83%, 4.71%, 4.02%, and 2.61% across the mixtures. The total conversion rates for dry mixtures were 24.59%, 29.27%, 34.36%, and 40.44%, while for wet mixtures, the conversion rates were 29.42%, 33.98%, 38.38%, and 43.05%, respectively. The results revealed that moisture content during pyrolysis significantly influenced the productivity of lignite and lignite-peanut shell mixtures. The conversion rates in dry mixtures were lower compared to those in wet mixtures. The novelty of this work lies in its pioneering investigation of the impact of moisture on the slow pyrolysis of Turkish lignite mixed with peanut shells. It offers novel insights into optimizing the thermal conversion process for these materials by uniquely examining the effects of moisture on productivity and conversion rates.

Combustion behavior of solid waste fuels in the vertical tube reactor under different oxy-fuel environments

Oxy-fuel combustion technology has been recognized as one of the promising ways for cost-effective CO2 capture. The co-combustion characteristics of flax straw biomass/bituminous coal mixture (FS/BC) and flax straw biomass/sewage sludge mixture (FS/SS) under air, oxy-fuel (21%/79% O2/CO2) and oxygen-enriched oxy-fuel (30%/70% and 40%/60% O2/CO2) conditions were investigated in the vertical tube reactor. In particular, the study focused on the burning characteristics, the effect of blending ratio, and flue gas emissions. The findings indicated that flax straw biomass exhibited superior ignition performance compared to its blends with sewage sludge and bituminous coal. A higher O2 concentration from 21% to 40 led to a reduction in ignition delay time by 4s at 850 ℃ and by up to 10s at 950 ℃. Moreover, char combustion time was reduced by 50% for FS/SS blends due to the lower fixed carbon content compared to FS/BC blends. Additionally, increasing the O2 concentration resulted in lower emissions of CO by ∽40% and N2O by ∽45% for both blends. However, this also led to a slight increase in SO2 and NO emissions by ∽15% and ∽26%, respectively. The optimal conditions for the tested samples in oxy-fuel environment were found to be 30% O2/70 CO2, which enhanced combustion performance while lowering flue gas emissions.

Experimental Study of Agglomeration Formation during Co-Combustion of Coal and Palm Kernel Shell in Fluidized Bed

Abstract Co-combustion of biomass and coal in Indonesia power plants are a key element of the path towards achieving net-zero emissions. However, introducing biomass into a coal-boiler furnace may pose operational challenges. Therefore, this study aims to assess the potential of agglomeration when mixing biomass with a fluidized bed boiler. Complementation simulation tests were conducted by combining coal with various fractions of palm kernel shell (PKS) in a furnace capacity of 5kWth maintained at 850°C within an hour. The initial fuel was 100% coal, gradually increasing the biomass mixture by 5%, 10%, 15%, 20%, and 25%. The results indicated that de-fluidization occurred at 25% of the biomass mixture and to prevent agglomeration, the temperature of the bed was kept below 850°C. The agglomeration test of coal and PKS mixtures was successfully performed in a 5kW lab-scale facility, and the result will be useful for predicting agglomeration phenomena in power plants.

Experimental investigation of OH* emission spectrum characteristics and transient ignition dynamics in methane and coal dust mixtures explosions

Combustible gases, dusts and their mixtures are widely present in human production and life，and the fire and explosion disasters caused by them pose a serious threat to the field of energy security applications. Studying the ignition process of mixtures is essential for disaster risk assessment and safety protection. In this work, the explosion characteristics and OH* emission spectra of the mixtures were experimentally tested by varying the fuel equivalence ratio ( ER ≈ 0.79 ~ 1.71), and the evolution of the transient flow field structure during the ignition process was quantitatively analyzed using the schlieren image velocimetry method. The results indicate that the emission spectrum of OH* is closely correlated with the maximum explosion pressure, and the spectral intensity of OH* at 306.4nm is consistent with the maximum rate of explosion pressure rise. The flow field during the ignition process of the mixtures shows that a small amount of coal dust (concentration≤30g/m3) can significantly promote flame acceleration and instability as the methane concentration is in lean combustion or stoichiometric ratio. However, when the concentration of coal dust increases (concentration≥40g/m3), coal dust will suppress flame acceleration and instability. For methane concentration in fuel-rich combustion state, coal dust always suppresses flame acceleration and instability. The experimental results contribute to a further understanding of gas and coal dust mixed explosions and provide a verification database for the construction of chemical kinetic mechanisms.

Study on preparation and performance of bagasse/sodium carboxymethyl cellulose gel for inhibiting coal spontaneous combustion

In order to effectively prevent and control coal spontaneous combustion and improve the safety of coal mining, bagasse carboxymethy cellulose (BCC) prepared from bagasse (BS) and sodium carboxymethyl cellulose (CMC) were used as the substrates. A gel (BCC-CMC) for inhibiting coal spontaneous combustion was prepared using a chemical crosslinking method involving zirconium citrate crosslinking and glucono-delta-lactone (GDL) modification. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were utilized to characterize both the crystal and molecular structure of bagasse and its derived bagasse carboxymethyl cellulose. The results indicated that new carboxymethyl groups were introduced into bagasse during the treatment, facilitating the successful extraction and preparation of sodium carboxymethyl cellulose. The results of viscosity and bonding tests demonstrated that the concentration and dosage of CMC had the most significant influence on the gel viscosity, which remained higher and more stable at room temperature. The coal bonded by the gel coal mixture can effectively seal surface cracks, with a bonding degree of up to 70.72 %. TG-DTG, temperature-programmed oxidation experiment and FTIR analyses revealed that, compared to raw coal, coal samples treated with gel exhibited improved stability, fewer active groups, and fewer oxygen-containing functional groups, effectively inhibiting coal’s low temperature oxidation and reducing the risk of spontaneous combustion. The gel is environmentally friendly, cost-effective, and exhibits good flame retardant properties. This study is of great significance for preventing and controlling coal spontaneous combustion, effectively ensuring the safe production of coal resources and the safety of mine workers, achieving the green sustainable development of the mine.

Experimental study on characteristics of methane-coal dust explosions and the spatiotemporal evolution of flow field in early flame

To understand the explosion characteristics of methane-lignite coal dust mixtures and the spatiotemporal evolution of the early flame flow field, explosion pressure, OH* emission spectra, and early flame schlieren images were captured in a 60L constant volume combustion bomb. Schlieren image velocimetry was used to obtain the instantaneous velocity distribution of the methane-coal dust flame front. The results indicate that adding coal dust causes a nonlinear increase in explosion pressure, particularly at low methane concentrations. At a 5 % methane concentration, adding coal dust can increase the maximum explosion pressure by up to 39 % (190 kPa). The trend of the OH* emission spectra corresponds with the maximum explosion pressure. A slight increase in coal dust significantly enhances the OH* emission spectra, especially at lower concentrations, potentially increasing it by nearly five times. However, at higher coal dust concentrations, the OH* emission spectra are significantly reduced. Additionally, within the considered concentration range (≤58.14 g/m³), larger turbulent integral length scales in initial conditions consistently result in the fastest flame acceleration. These findings provide experimental evidence for further exploration of the explosion mechanisms of methane-coal dust mixtures and the development of chemical reaction kinetic models.

Optimizing Combustion Efficiency in Blast Furnace Injection: A Sustainable Approach Using Biomass Char and Coal Mixtures

Optimizing Combustion Efficiency in Blast Furnace Injection: A Sustainable Approach Using Biomass Char and Coal Mixtures

Mechanical behavior of calcareous tuff and coal mine tailings mixture as an embankment material for road construction

The construction of embankments requires available and suitable material that sounds to the imposed load. The selection of materials that provide slope stability and maintain pavements is made through specific test control. This research aims to analyze the mechanical behavior of a mixture of 75% calcareous tuff and 25% coal mine tailings (CMTs) used on embankment foundations. the impact of particle size characteristics and the compaction on the mechanical behavior of the mixture are studied. The direct shear test was conducted on different material states, granular and uncompressed states, compaction at the Maximum Practical Optimum (MPO), and MPO compaction post a 30-day curing period at 40 degrees Celsius. the normal stress applied ranging from 50 to 500 KPa, with a constant shear rate displacement of 0.5 mm/min. The results show a substantial influence of compaction on both friction angle (φ) and cohesion (C) values. a remarkable increase in cohesion values after the curing period, attributed to the cementitious compound formation from the interaction between calcareous tuff and coal mine tailings. This investigation emphasizes coal mine tailings potential as a sustainable and cost-effective embankment material for road construction, especially in arid regions. The material exhibits significant shear strength, with a marked increase in cohesion values post-curing state. These results are conducted to consider coal mine tailings as an appealing alternative to traditional materials of road engineering.

Mechanical Properties and Durability of Steel Slag-mineral Powder-coal Gangue Mixture by Uniform Design for Pavement Base

To realize the utilization of industrial solid waste resources and solve the shortage problem of pavement materials, this paper uses steel slag, mineral powder, and coal gangue to prepare a mixture. A uniform test with 2 factors and 6 levels was designed. Through regression analysis, response surfaces were established to study the mechanical properties of the coal gangue mixture. The hydrated products at different ages were microscopically analyzed by XRD and SEM. The durability including freeze-thaw cycles, dry and wet cycles, and immersion expansion rate were researched. The results show that the 7d unconfined compressive strength of the mixture reaches 2.14 – 6.46 MPa, with a 180d resilience modulus of 954 – 1098 MPa, and a 180d splitting tensile strength of 0.66 – 0.83 MPa. With the increase of steel slag content, the 7d unconfined compressive strength of the mixture first decreases and then increases. The content of mineral powder is positively correlated with the 7d unconfined compressive strength. The 180d compressive resilience modulus decreases first and then increases with the increase of steel slag and mineral powder content. The 180d splitting tensile strength is positively correlated with the content of steel slag and mineral powder. The mixture is less affected by freeze-thaw cycles, with mass loss rates of only 1.77 % – 2.13 %. The mass loss rate of the admixture is 0.87 % – 0.99 % after 10 dry and wet cycles, and the strength is slightly improved. The maximum expansion rate of the mixtures immersed in water for 10d is only 0.28 %. The hydrated reaction between steel slag, mineral powder and coal gangue promotes the formation of more hydration products such as AFt, C-S-H, CaAl2(SiO4), and Ca(OH)2. The C-S-H and CaAl2(SiO4) are intertwined into a dense network to wrap Ca(OH)2, which improves the compactness of the mixture and effectively resists the freeze-thaw expansion stress. The steel slag-mineral powder-coal gangue mixture meets the requirements of relevant norms and can be well used in pavement bases.

Carboxymethyl β-Cyclodextrin Assistance for the 4-Nitrophenol Reduction Using Cobalt-Based Layered Double Hydroxides.

Cobalt-aluminum-layered double hydroxides containing carboxymethyl β-cyclodextrin (CMβCD) were synthesized by coprecipitation and evaluated as a cobalt source for the 4-nitrophenol reduction in an aqueous medium. Several physicochemical techniques (XRD, FTIR, TGA) indicated the intercalation of the anionic cyclodextrin without damages to the hydrotalcite-type structure. These lamellar cobalt-aluminum hybrid materials (CoAl_CMβCD) were evaluated in the 4-nitrophenol reduction and showed higher activities in comparison with the CMβCD-free standard material (CoAl_CO3). To rationalize these results, a set of experimental controls going from physical mixtures of CoAl_CO3 with different cyclodextrins to other cobalt-based materials were investigated, highlighting the beneficial effects of both the layered double hydroxide and CMβCD-based hybrid structures. CMβCD also showed a beneficial effect as an additive during the 4-nitrophenol reduction. CoAl_CO3, dispersed in a fresh CMβCD solution could be re-used for five successive cycles without the loss of activity.

Ash Properties and Environmental Impact of Coal and Its Blend with Patent Fuel for Climate Sustainability

Fossil fuels are still widely used today, and exploring more sustainable ways of using coal is crucial. One promising approach is to develop a patented fuel with reduced harmful gas emissions during combustion. This study aims to investigate the properties of the ash produced by burning steam coal mixed with various ratios of patent fuel. The combustion process was carried out using a standard solid fuel boiler with a power output of 70 kW. The ash samples were analyzed using various analytical methods, and ash leaching tests were conducted. The study found that adding patent fuel to coal affects combustion and ash composition. Determining the thermal stability of ash samples showed that adding patent fuel to coal results in decomposition starting earlier and in stronger combustion. The ash produced by patent fuel–coal mixtures contains lower concentrations of Ba, Cr, Ga, Li, Mn, V, and Zn than pure coal combustion. Leaching tests showed that coal ash leachates had higher concentrations of environmental pollutants, such as As, Cd, Co, Mn, Mo, Sb, and U, than patent fuel leachates. Adding patent fuel to coal affects combustion, ash properties, emissions, and disposal. Understanding these implications can help to develop sustainable coal usage and reduce environmental impact.

Features of ignition and combustion of low-grade coal mixed with pyrolysis liquid

THE RELEVANCE of the study lies in the need to use pyrolysis liquid from wood processing for combustion in boilers of medium and low power as part of mixtures with coal. The unpredictability of the ignition and combustion properties of such mixtures, as well as the lack of calculation methods, predetermined a predominantly experimental approach to the study of these processes. At the same time, for the widespread implementation of such technological solutions in practice, it is necessary to have relatively simple methods for assessing the ignition and combustion characteristics of these components. THE PURPOSE. Synthesize samples of pyrolysis liquid from two different sorts of wood and perform their characterization. Develop an experimental method for studying ignition and combustion characteristics of pyrolysis liquid mixed with low-reactivity coal. Perform research on ignition delay times and the composition of released gas-phase products. Determine the main mechanisms of action of the components in the mixture of low-grade coal with pyrolysis liquid they’re during ignition and combustion. METHODS. The study was carried out using an experimental technique based on a high-temperature muffle furnace equipped with a high-speed video camera and a once-through gas analyzer. RESULTS. The article presents the dependences of the ignition delay times and the concentration curves of gas-phase products released during combustion of mixtures of low-grade coal and two types of pyrolysis liquid in the temperature range of the heating medium 600-800 °C and additive concentrations from 0 to 20 wt.%. Linear approximation dependences of ignition delay times on additive concentrations were obtained, and the mechanism of action of the additive during combustion was formulated. CONCLUSION. It was found that an increase in the concentration of the additive in the mixture leads to a stable decrease in the ignition delay times, while the amount of gas-phase products formed varied additively with respect to the composition of the mixture. The shape of the concentration curves for the release of CO and NOx indicates the independent action of the components of the mixture. The mechanism of action of additives was proposed. It was based on significant contribution of their evaporation process followed by combustion in the gas phase, which, in turn, initiats the ignition of coal.

Porous carbon prepared by thermal dissolution of coal and biomass for high-performance supercapacitors

Porous carbon materials have been considered a kind of promising materials for supercapacitors due to high specific surface area and excellent electronic conductivity. Soluble portions (SPs) acquired from thermal dissolution of carbon-based raw materials have been used as the carbon source for hierarchical porous carbons (HPC). In this work, mixtures of rice straw and coal at different mass ratios were selected as the raw materials for co-thermal dissolution to obtain SPX. The variation of soluble proportions and subsequent impacts on the electrochemical properties of HPCX were investigated. During thermal dissolution, the addition of rice straw increased the content of nitrogen-containing compounds in SPX. Therefore, the specific capacitance of HPC1/4 is 355 F/g. The specific capacitance of activated carbon material without rice straw is only 299 F/g. The relationship between the molecular characteristics of carbon source and the performance of supercapacitors has been determined. In addition to oxygen-containing compounds, the presence of nitrogen-containing compounds can also lead to a higher electrochemical property for porous carbon materials.

Studies on increased utilization of high-ash Indian coal in coke-making

ABSTRACT Due to low-ash coking coal scarcity, India depends on high-cost imported coal for coke making. The present work aims to increase the Indian coal input in the original coal blend for coke making. One typical Indian high-ash and one imported low-ash coal were used as reference materials, presently used in coal blend for coke production in IISCO Steel Plant Burnpur (ISP), West Bengal, India. Coal samples were ground, changing various parameters. The ash distribution in different particle sizes was evaluated. It is observed that decreasing the particle size up to −88 µs can reduce ash content from (18–23%) to (12–14%), which is generally considered suitable for the blended coal mixture used for coke making in the coke-oven battery in ISP. Reduced ash containing fraction of high- ash coal was utilized to evaluate the dilatation behavior and economics of the coking process by considering blending with different percentages of beneficiated Indian coal. From the behavioral study, it was observed that 20% blending would be economical for coke making without hampering the original blend property. The improved dilatation behavior was observed by incorporating 20% dry beneficiated Indian coal in the original blend. The CRI, CSR, and Micum index properties are identical with the normal blend and within the acceptable limit.

Effects of methane concentration on flame propagation mechanisms and dynamic characteristics of methane/coal dust explosions

The study explores the flame propagation and explosion dynamic behavior of gas/powder two-phase compound explosions, taking methane and coal dust mixture as the research object. The influence of different methane concentrations on the compound explosion characteristics was researched. The vertical pipeline, high-speed camera, ion current probe, and pressure sensor be used to test the propagation behaviors, microstructure characteristics, and explosion dynamics of compound explosion flames. The function of methane concentration on the propagation behaviors, combustion reaction zone thickness, flame temperature, propagation velocity, and explosion pressure of compound flame was revealed, and the propagation mechanisms of gas/powder compound explosion flames were explained. The experimental research discovered that the compound flame of methane/coal dust explosion presents a white luminous zone with uniform distribution and appears to have an approximate homogeneous combustion state. The explosion dynamics parameters all showed a trend of first increased and then decreased as the methane concentration increased, but the reaction zone thickness of the combustion first reduced and then increased. In addition, the dominant position of homogeneous or heterogeneous combustion in the combustion reaction zone will also switch with the change in methane concentration. The compound flame is similar to premixed gas combustion under optimal methane concentration, the combustion zone thickness (δ) and preheating zone thickness (β) are the smallest, and the compound explosion shows powerful performance. In addition, the flame propagation mechanisms of methane/coal dust compound explosion were elucidated based on the theory of heat.

Agglomeration of coal and polyethylene mixtures during fixed-bed co-gasification

The article presents the results of experimental studies on the gasification of mixtures of brown coal and polyethylene (up to 20 wt% fraction) in a laboratory reactor. The work aims to study the agglomeration process during the heating and oxidation of the mixtures. The measurement results (gas composition, pressure drop) provide indirect information on the dynamics of thermal decomposition and structural changes in the fuel bed. We have shown that the interaction between polyethylene and a coal surface leads to the formation of dense agglomerates, in which the molten polymer acts as a binder. Clinkers form as a result of interfacial interactions between components and filtration flow rearranging. The hydrogen/carbon ratio in the solid residue of coal-polyethylene co-gasification increases from 0.07–0.2 to 1.11, indicating the formation of stable hydrocarbon compounds on the carbon surface. The conducted research makes it possible to identify possible interactions between chemical reactions and transfer processes that lead to agglomeration in mixtures of coal with polyethylene.

Numerical Analysis of the Coal Mixture Composition Effects on Combustion and Gas Emissions in CFB Boiler

The combustion system in the CFB boiler had a high complexity, in order to identify and understand the combustion process that occurs in the CFB boiler, CFD analysis was applied. This study was conducted to analyze the combustion and gas emissions produced in a CFB boiler with several variations of coal mixture. Coal particles injected into the furnace were modeled with DPM, specifically the Euler-Lagrange approach. The coal used came from two coal mining industries and mixed with the percentages of 20% : 80%, 30% : 70% and 40% : 60%. The amounts and conditions of combustion air and coal had been determined. The simulation process in the CFB boiler was carried out at a maximum load (110 MWe) without involving bed material. The results showed that the energy and combustion temperature produced in the mixture of 20% : 80% reached the highest value, the mixture of 40% : 60% produced the highest concentration of H2O and produced the lowest concentrations of CO2, O2, NO and SO2. On the other hand, the distribution of pressure and gas velocity had relatively the same value in each mixture. This could be caused by the characteristics of coal mixture, the amount of air and coal injected, and the absence of bed material.

Effect of co-combustion of coal with biomass on the morphology of soot

This study performed an experimental investigation to explore the effect of co-combustion of coal with biomass on the morphological parameters and nanostructure of soot. Three types of soot, namely Shenghua coal (SH) soot, Pinewood biomass (PW) soot, and Co-combustion of SH and PW (CC) soot, were collected from the combustion flames of Shenhua coal, Pinewood biomass, and a mixture of coal and biomass. Thereafter, the soot samples were observed and analyzed by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) to obtain their morphological parameters and nanostructure characteristics. The TEM results showed that the size of nascent soot particles generated in co-combustion flame is the largest, rather than between the sizes of PW and SH soot. The nanostructure of the three types of soot primary particles is mainly composed of straight parallel crystal stripes. The separation distance of crystal stripes in SH soot was measured to be larger than that in PW soot, indicating that the crystal structure of soot generated in Pine biomass combustion flame is more compact. It was also observed that both coal-derived primary soot particles and biomass-derived primary soot particles were formed in the co-combustion flame. SEM results indicated that PW soot agglomerates have stronger aggregation performance and more compact structure then SH soot and CC soot. The primary particle size of SH and CC soot agglomerates was mainly concentrated between 50 and 70 nm, while that of PW soot agglomerates was relatively uniform. Furthermore, the number of primary particles in SH soot and CC soot was distributed over a wide range compared to PW soot.