Lignite Research Articles

Biogenic Degradation of Lignite Coal from Pakistani Coal Mine and Extraction of Humic Acid through Pretreatment Strategies by Fungal Isolate

The utilization of white rot fungal strain for degradation of low rank coal from coal environments is considered to be the best choice for converting raw coal into different kinds of valuable by products. NF-1, a fungal strain was isolated from coal mine of Thar region of Pakistan. For enhancing the process of biodegradation, the indigenous fungal isolate was used in the study. The lignite (low rank) coal sample degradation initiated by NF-1 strain were undergone through optimization process and had shown considerable production of organics at 1.5% Glucose, 1% coal loading ratio and 7 days of incubation period. The FTIR analysis of untreated coal and treated coal after solubilization was performed in order to observe changes in structural pattern by NF-1 fungal isolate. NF1 has the ability to break down the aromatic side linkages and attacking the amine and carboxyl groups. Scanning electron microscopy (SEM) of the coal treated by NF-1 strain was analyzed to investigate the attachment and adherence of the fungal mycelium on the coal surface. At 200µm the NF-1 isolate hyphae has clearly entrapped the coal particles showing erosion and up to 50µm colonization and visible changes on the coal surface can be observed clearly. Moreover, the residual coal after fungal pretreatment was processed for extraction of humic acid as a byproduct for defining the effect of such biological pretreatments. The produced humic acid was analyzed on the basis of E4/E6 ratio and FTIR. The fungal pretreated humic acid has shown more improvement in E4/E6 ratio as well as presence of functional groups related to humic acid through FTIR. This explains that the isolate NF1 have ability to speed up the biodegradation process and shows an aptitude of producing valuable by products i.e. humic acid as an alternative fuel.

Comparison of properties of brown coal and bio-mass-based substitute fuels

Due to the EU climate change strategy, there are many coal-fired heating plants looking for new fuel. One of the possibilities is biomass-based fuels. This term is quite general because the final technology can be different because of properties of different types of biomasses. The sustainable solution can be the use of biomass residues. This article is about long-term monitoring of the properties of brown coal, agglomerated herbaceous biomass from agricultural residues, and wood chips from harvesting residues. 702 samples of brown coal, 715 samples of plant pellets and 607 samples of wood chips were analyzed, which were supplied do commercial heating plant between the years 2021-2023. The water and ash content, lower heating value (LHV) and higher heating value (HHV), were analyzed. The mineral composition of the fuels was determined quarterly from mixed samples. In the case of water content, the lowest values were achieved for herbaceous pellets (11.35%), due to their previous drying. The moisture content of the wood chips fluctuated. The average was 36.34%, with a maximum deviation of up to 49.9%. The average water content in brown coal was around 28.63%. In detail, there is a seasonal influence of the weather. In the case of ash content determination, the values for brown coal and herbaceous pellets are similar (slightly above 5%), wood chips contain less ash (2.2%). The results for the wood chip samples fluctuated again. There were samples consisting of chipped logs (0.33% ash) and samples with a large proportion of forest soil (4.37%). The highest average HHV values were achieved for brown coal (18.98 MJ/kg), followed by herbaceous pellets (15.84 MJ/kg) and wood chips (11.02 MJ/kg). These differences may cause a decrease in steam output due to a limitation of space in the combustion chamber of the boiler after the retrofit. In the case of the content of nonmetallic elements, a different character of the biomass is evident, consisting of a higher oxygen content (38% vs 19%) and a lower carbon content (48% vs 68%). Biomass also contains less sulfur, but the high chlorine content of 0.12% compared to 0.02% in wood chips was determined in herbaceous pellet samples. For a heating plant, this means intensive chlorine corrosion or exceeding the emission limits of HCl. The solution can be in DSI technology. Brown coal contains more Ti, V, Li, Sr, Be, Na, Fe, and Al. The biomass contains more biogenic elements, especially Ca, K, P, and Zn, which allows the ash to be used for land application. For the combustion process, a significantly higher content of alkali has an adverse effect, causing a decrease of the melting temperature of ash, which can lead to technological problems, such as the formation of a material based on alkaline glass, which decreases heat transfer and combustion efficiency. Most often, this complication is solved by micro detonations and more frequent maintenance. The contents of Hg, Cd, and Tl in the samples were below the detection limit.

ISOLATION OF FULVIC ACID FROM COAL AND STUDY OF PHYSICAL AND CHEMICAL PROPERTIES

Due to its high solubility and low molecular weight, fulvic acid is a very active participant in natural chemical processes. Due to its smaller molecule size than humic acid, it can act both inside and outside the cell. The work presents the method of isolation and purification of fulvic acid obtained from oxidized brown coal and the analysis of its physical and chemical properties by the methods of IR, NMR spectroscopy, and the amount of carboxyl and hydroxyl groups studied. Conducted work on calculation of equilibrium constant (pK) and concentration (C). Stages of purification: adsorption, ion purification and dialysis, where adsorbents obtained from brown ("Shoptykol") and hard ("Shubarkol") coal and coconut activated carbon were used as adsorbents.

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.

Impact of N-Methyl-2-pyrrolidone Erosion on Surface Functional Groups and Pore Evolution in Coals of Different Ranks.

In low-permeability coal reservoirs, utilizing the organic solvent N-methyl-2-pyrrolidone (NMP) has emerged as an effective approach to improving the coal pore structure and enhancing coalbed methane productivity. However, the exact mechanisms of how solvent erosion alters functional groups and develops pores remain incompletely understood. This study utilized Fourier transform infrared spectroscopy and low-field nuclear magnetic resonance to assess the impact of NMP on the functional groups and pore structures of lignite, bituminous coal, and anthracite. The results indicate that a 6 h treatment with NMP led to an increased proportion of oxygen-containing functional groups in all coal samples, accompanied by a decrease in hydroxyls and aliphatic hydrocarbons. The aromaticity of the coal samples was enhanced to varying degrees, most notably for lignite. In terms of pore modification, the porosity of lignite and bituminous coal increased by 84.82 and 43.56%, while anthracite experienced a porosity increase of 3.04%, indicating a diminished effectiveness of NMP as the coal rank increased. These findings suggest that NMP selectively dissolves specific organic molecules in coals, thereby enhancing pore connectivity and promoting a transition from micro- to meso- and macropores. These findings highlight the potential of NMP in enhancing coalbed methane production and advance our understanding of the mechanisms behind solvent erosion.

Migration characteristics of constant elements in the process of coal dissolution by liquid CO2

The effect of liquid CO2 on coal dissolution plays a key role in improving coal bed methane (CBM) recovery and CO2 geological storage. In order to study the effect of liquid CO2–H2O reaction on the migration of mineral constant elements in coal, three kinds of coal samples (lignite, bituminous coal, and anthracite) with different degrees of metamorphism were selected as the research objects. The one-factor experiments of dissolution of liquid CO2 and water-bearing coal samples were carried out by simulating the temperature and pressure of the stratum. X-ray fluorescence spectroscopy (XRF) was used to test the changes in the relative content of constant elements in coal samples after liquid CO2 injection under different pressure conditions. Scanning electron microscopy (SEM) was utilized to observe the evolution pattern of the surface features of the coal before and after the dissolution of liquid CO2. A quantitative analysis of coal pore development characteristics was conducted based on low-temperature N2 adsorption/desorption experiments, and isothermal adsorption experiments were carried out before and after etching the coal samples to understand the adsorption characteristics of CH4 and CO2 by coal under different pressure conditions. The research results indicated that the migration ability of constant elements in coal showed a trend of first decreasing and then increasing with the increasing degree of coal metamorphism. Among the three selected coal samples, the migration ability of constant elements was found to be strongest in anthracite, followed by lignite and bituminous coal. Most of the element migration in coal was carried out through chemical reactions (hydrolysis, carbonation, redox), while some elements were primarily transported through physical means (such as the low-temperature impact of liquid CO2). The dissolution process expands the original pore space of coal and generates new pores, greatly increasing the coal's capacity for CO2 adsorption. These findings deepen our understanding of mineral dissolution in coal by liquid CO2 and provide important insights for achieving efficient and long-term coalbed CO2 geological storage and enhanced methane recovery techniques.

Experimental simulation of water-coal interactions during liquid CO2 injection into coal beds

Injection of liquid CO2 (LCO2) into coal reservoirs is an extremely effective way to enhance coalbed methane recovery and storage. This study aimed to investigate the changes in mineral composition and content during the chemical reaction between coal samples and weakly acidic fluids dissolved in LCO2. Therefore, in this study, simulating the formation temperature (30 °C), three types of coal samples with different metamorphic degrees (lignite, anthracite, and bituminous coal) were selected for CO2–H2O-coal interaction leaching experiments under various pressure conditions (1 MPa, 3 MPa, 5 MPa). X-ray diffraction analysis (XRD) was used to test coal samples' mineral composition and content before and after LCO2 injection under different pressure conditions. Scanning Electron Microscope (SEM) was used to observe the evolution pattern of surface characteristics before and after the dissolution of the coal body by LCO2. The results showed that minerals such as kaolinite, illite, quartz, and potassium feldspar in the three coal samples underwent mineral transformation during the reaction process at different dissolution pressures, and the content changed significantly in the early stage of the reaction. The initial content of kaolinite in the bituminous coal (16.5%) increased to 23.8%, 26.7%, and 25.2% respectively under different leaching pressures of 1 MPa, 3 MPa, and 5 MPa. Carbonate minerals dissolved rapidly in the initial stages of the reaction, the initial content of calcite, a carbonate mineral in the anthracite (9.8%), decreased to 4.2%, 3.8%, and 2.4% respectively under different leaching pressures of 1 MPa, 3 MPa, and 5 MPa. Similarly, the initial content of siderite decreased from 6.8% to 2.8%, 2.3%, and 1.6% respectively. LCO2 pressure had a significant influence on the reaction. These results advance our understanding of LCO2 dissolution of minerals in coal.

Methods for obtaining humate-containing fertilizers from brown coal

ABSTRACT The purpose of the study is to examine the main methods of obtaining fertilizers and optimizing processes. Using methods of analysis, comparison, and experimentation, three main approaches to obtaining fertilizers were identified: grinding and mixing with potassium hydroxide (KOH), ultrafine grinding with chemical additives, and a complex method for processing caustobioliths. Comparative analysis of the investigated methods allowed for identifying their advantages, disadvantages, and effectiveness. The key result was the ability to determine the most effective method for producing humate-containing fertilizers from brown coal, depending on specific production conditions and requirements. The results of the study showed that the ultrafine grinding process with chemical additions, such as urea and alkali metal hydroxides, showed promising potential for creating highly effective humate-containing fertilizers from brown coal, in addition to the comparative analysis. After thorough optimization, this technique showed improved fertilizer utilization and superior plant uptake, making it a strong contender for sustainable farming methods. Nevertheless, achieving optimal results requires detailed process parameter optimization. The study underscores the importance of using brown coal in humate-containing fertilizer production as an environmentally safe and sustainable approach. The results can contribute to further development and improvement of humate-containing fertilizer production methods, promoting sustainable agriculture and increased crop productivity.

Trace Elements in Pernik Sub-Bituminous Coals and Their Combustion Products Derived from the Republika Thermal Power Station, Bulgaria

The contents of 49 trace elements in sub-bituminous Pernik coals and their waste products from preparation and combustion processes were investigated. The studied coals have trace element contents higher than the respective Clarke values for brown coals and some of them may pose environmental concerns. The elements Li, Rb, Cs, Ba, Sc, Y, La, Ce, Nd, Sm, Eu, Er, Ga, Zr, Sn, V, Nb, Ta, W, F, Cu, Zn, In, Pb, Cr, Co, Ni, and Th in the feed coals have concentrations that exceed twice the Clarke values. Most element contents in bottom ash are enriched compared with those in feed coal. Some of the volatile elements are equal or significantly depleted including Sn, Mo, Sb, F, Bi, Cd, Ge, and Pb. Fly ash has higher contents of Ga, Zr, Hf, Sn, V, Nb, Mo, and F in comparison with bottom ash. Most elements have a significant positive correlation with ash yield, indicating their inorganic association. The mixed wastes (coal slurry, bottom ash, and fly ash) in the disposal pond are slightly depleted of most of the elements studied with the exclusion of Cl, Ba, and Br. The Pernik coals and their waste products are unpromising for the extraction of REY due to their low element contents.

Static-dynamic wetting characteristics and microscopic synergistic mechanism of compound surfactant on coal dust with different metamorphic degrees

The compound surfactant has a synergistic effect on the wetting ability of coal dust. In the study, the wettability of compound surfactant on coal dust with different metamorphic degrees was studied from static wetting experiment, dynamic wetting experiment, and micro molecular simulation. The results showed that the contact angle of the anionic-nonionic compound surfactant solution on any coal sheet was significantly smaller than that of the single component, which was 14.04%～63.31% lower than that of the single component. The contact angle of the anionic-anionic compound surfactant on the six kinds of coal dust test pieces was not smaller than the contact angle of each single component, only a compromise of contact angle of single component. The dust suppression efficiency of the gas coal in 0.025 wt% fatty acid methyl esters ethoxylate sulfonate (FMES) and 0.025 wt% coconutt diethanolamide (CDEA) compound solution was the highest, which was 78.4%. Lignite coal, long flame coal, non-caking coal, coking coal, and anthracite all have the highest dust suppression efficiency when sprayed with 0.025 wt% sodium alcohol ether sulphate (AES) and 0.025 wt% CDEA, which were 91.53%, 88.24%, 85.7%, 73.25%, and 80.57%, respectively. For any metamorphic degree of coal sample dust, the anionic-nonionic compound surfactant shows obvious synergistic effect on improving the wettability of coal dust. Furthermore, when the surfactant is adsorbed on the surface of coal molecules, the concentration of water molecules on the surface of coal molecules is increased, the hydrophilicity of the solid–liquid interface is improved, and the water molecules are more intensely diffused on the surface of coal dust. And the absolute value of the adsorption energy of the surfactant on the surface of the coal dust is higher, and the more hydrogen bonds formed by the hydrophilic groups, the better the wettability of the coal dust surface.

Evaluation of brown coal fly ash for stabilising expansive clay subgrade: A sustainable solution for pavement construction

Brown coal fly ash (BCFA) is a lower-quality type of fly ash produced through brown coal combustion, and its disposal in landfills raises environmental concerns. This study, for the first time, evaluates the feasibility of using BCFA for stabilising expansive clay subgrade in pavement construction. Various engineering tests were conducted, including unconfined compressive strength (UCS), repeated load triaxial (RLT), soaked California bearing ratio (CBR), direct shear, and shrink-swell tests. The results indicated that adding BCFA increased UCS, resilient modulus, soaked CBR, and cohesion while reducing shrinkage-swell index and shrinkage/swell strain. The highest resilient modulus (82.52 MPa) and soaked CBR (3.41 %) were achieved with 3 % BCFA content. These findings recommend using 3 % BCFA as the optimum content for stabilising expansive clay subgrade. This research fills a gap by assessing the application of BCFA for stabilising expansive clay soil, providing insights for sustainable utilisation of this abundant waste material in construction.

Features of rare earth elements geochemistry in coals of Central Kazakhstan

AbstractThis research presents the results of a comprehensive study of mineralogical and geochemical features of REE distribution in coals of Central Kazakhstan deposits—Karaganda coal basin and Shubarkol deposit, which have large hard coal reserves and are industrially important for the coal industry of Kazakhstan; the research is based on 205 samples of clayey interlayers and coal seams. It shows basic patterns of distribution and features of concentration for impurity elements, gives an estimate of the impurity elements concentration, including REE, defines conditions and factors of their accumulation, and studies features of their forms in coal and coal-bearing rocks, which allows estimating the mechanisms of their migration and conditions of accumulation. According to the results of geochemical indicators, the article establishes the factors of REE dislocation, reveals the composition of margin rocks that have influenced REE concentration in coal seams, and the presented latest data on mineralogy allowed to establish the ways of their transportation to the paleobasin during the syn- and epigenetic periods of formation of the coal deposits of Central Kazakhstan being researched. It was found that the coals are insignificantly enriched with heavy lanthanides from Ho to Lu. The distribution curves of UCC normalized REE values in the coals are similar and coincide, but they are less than the average value for world coal, and amount to only one-third of the UCC. It was found that the highest concentrations of all REE are characteristic of clayey interlayers and oxidized coals. The La/Yb ratio in this case increases upwards along the section, indicating mainly clastogenic mechanism of REE delivery to the coals. In coal and clay samples, the predominant mineral form of REE is light lanthanide phosphates. Identified particles of REE from minerals and their composition peculiarities suppose autigene nature of their formation. The formation of the bulk of autigene minerals occurred during the maturation of brown coals and their transformation into hard ones.

Use of Lignite Processing Products as Additives to Road Petroleum Bitumen

It is known that there are significant deposits of lignite (brown coal) in Ukraine, particularly in categories A + B + C1. At the same time, certain technical and legal obstacles limit its use as an energy carrier. Therefore, new methods of using lignite and processing its products are necessary. The latter includes humic acids. It was suggested that these acids could be used to stop road bitumens from breaking down. This is because they are antioxidants that contain functional phenolic and carboxyl groups. In particular, this article analyses the nature of the influence of humic acids on the physical and mechanical properties of road petroleum bitumen and its resistance to technological aging. It was found that at a modification temperature of 120 °C (duration-60 min., consumption of humic acids-2.0 wt.%), this additive has a slight negative effect (changes are within permissible limits) on the plastic properties of bitumen and slightly improves its elasticity. The main reason for adding humic acids to road bitumen under the specified conditions is to improve its resistance to technological aging compared to the original binder.

Powering through Challenges: Analyzing the Energy Crisis in the Western Balkans during the Pandemic Context

This paper examines the current challenges in the energy sector of the Western Balkan countries, focusing on the energy sector of Kosovo as a case study during the pandemic. These countries are at crucial stages of their development, marked by significant achievements but with ongoing challenges in the energy sector as a factor for sustainable development. The region remains highly vulnerable to energy crises and geopolitical tensions, particularly due to its heavy dependence on fossil fuels such as brown coal for energy production. Our research focuses on the energy system in Kosovo, highlighting its historical reliance on a fragile energy sector, particularly characterized by inflexible thermal power plants using outdated technology and a lack of additional, more flexible capacity. The purpose of this study is to examine Kosovo's energy system, assess the challenges it encounters, and identify the factors that have contributed to the energy crisis from 2021 to 2023. Doi: 10.28991/HIJ-2024-05-01-08 Full Text: PDF

Combustion in a chamber furnace with a tangentially swirling vortex

Relevance. The need to analyze the furnace processes in boiler units with vertical vortex when arranging pulverized coal combustion with the enhancement of environmental parameters through the installation of tertiary blast nozzles. Despite the carbon-free policy in modern power engineering coal remains one of the main sources of energy, so the reconstruction of boiler units in order to reduce harmful emissions is very relevant. Aim. To study aerodynamics and combustion processes of pulverized coal fuel in the furnace chamber of a boiler unit with a tangential arrangement of burner devices using a combustion scheme with tertiary air blowing. Methods. The Eulerian–Lagrangian approach was applied to numerical study of flow characteristics, heat transfer and combustion in a furnace with a tangential burner arrangement. Also, k-ε model of gas turbulence, particle-turbulence interaction, diffusion model of particle dispersion, P-1 radiation modeling method and pulverized coal particle combustion model based on global particle kinetics and experimental data were used for numerical calculations. Results. Based on numerical calculations and analysis, the dependences of combustion product concentrations, temperature, hydrodynamics at combustion of Kuznetsky coal grade D in the furnace chamber with tangential arrangement of burners for brown coal, as well as at installation of tertiary blast nozzles have been obtained. Insufficient redistribution of air between burners and tertiary nozzles is revealed, as for maintenance of stable twist of vertical vortex and accordingly presence of high values of velocities at the outlet of burner devices it is not possible to increase the portion of tertiary air without reconstruction of burners. It is also established that the volume of the furnace chamber below the burners is poorly involved in heat exchange.

Thermokinetics and synergistic effect analysis of peat-lignite coal co-pyrolysis

ABSTRACT In this study, the synergistic effect between peat and lignite coal was investigated in terms of kinetic energy and mass loss trends using a thermogravimetric analyzer. Thermogravimetric non-isothermal studies were conducted at different heating rates under inert nitrogen atmosphere. Kinetic analysis was performed using model-free KAS, OFW, and Starink methods and the average activation energies varied between 88.62 kJ/mol and 204.28 kJ/mol. Differential mass loss trends were determined using experimental and theoretical data. An obvious deviation was obtained at a blend ratio of PT:CL40:60. Thus, results revealed that the PT and CL co-pyrolysis has synergistic effects, especially for sample PT:CL40:60. SEM and BET analyses were performed on the coke sample of peat, coal, and PT:CL40:60 blend ratio samples for further analysis. The surface area of peat and coal was determined to be 416 m2/g and 83.06 m2/g, respectively. It was concluded that the porosity and surface area of coal (187.02 m2/g) increased with the addition of peat. The results are expected to be useful in the design of peat biomass and coal co-pyrolysis systems.

Changes in the Physicochemical Characteristics of Humic Acids in a Hydrodynamic Rotor-Pulsation Apparatus

The work presents research results of the change comparison of brown coals and the study of the physicochemical properties of humic substances obtained from brown coals of the Karazhyra, Ekibastuz, and Kyzyl-Kiya deposits after hydrodynamic treatment in a rotary-pulsation apparatus. It is shown that the hydromechanical effect on humic acids leads to a change in their composition, accompanied by a decrease in the degree of aromaticity and an increase in the content of oxygen-containing fragments. Mechanical treatment of brown coals under oxidizing conditions maximizes the efficiency of extraction of water-soluble components and humic acids. The structural parameters and functional composition of humic acid molecules during the treatment of brown coals under oxidation-reduction conditions change depending on the conditions. The elemental and functional composition (using IR spectroscopy and potentiometry) of humic substances in brown coals and their molecular weight distribution using size-exclusion chromatography were studied. The influence of the content of metal-binding centers, dispersity, and ash content of humic substances was studied before and after treatment. At a temperature of 70 ºC a rotation time of 10 s, 98.7% of humic acids passes into the solution, which is the best indicator.

Technology for Producing Heat From Composite Coal Fuels in Advanced Oven for Municipal and Household Use

The problem of rational use of coal remains relevant; currently, various technologies have been developed for producing composite solid fuels, briquettes with various binding materials from brown coal deposits in Kyrgyzstan. The widespread use of composite solid fuels (CSF) and coal briquettes in industry, everyday life and public utilities, in our opinion, is limited by two reasons: excessively inflated requirements of existing standards for the physical and mechanical characteristics of briquettes as a product; poor knowledge of optimal conditions for burning briquettes. Our research shows that compressive strength in the range of 15-20 kgf/cm2 provides the necessary strength for the degree of abrasion during transportation and storage of large-sized rectangular CSFs. Reducing the strength requirement to the value indicated above makes it possible to form briquettes from unsorted culm. Among the numerous known binders for briquetting, inorganic types of clays and loams, which are ubiquitous, deserve special attention. It has been established that clays and loams provide the strength of the CSF over 20 kgf/cm2. For the purpose of beneficial use of low-grade fine coal, we carried out briquetting and combustion testing of the resulting briquettes. It has been established that when briquetting coals from the Zhatan and Kumbel deposits with a clay binder, with an increase in the content of fine coals in the composition, the burning time of the briquette increases, as well as the combustion of the combustible mass increases, and the temperature in the combustion space increases. It has been shown that with the help of appropriate minor modifications of standard household stoves it is possible to significantly increase the combustion efficiency of all types of low-grade fuel, including lignite high-ash CSF.

Low Grade Coal Quality With Up Graded Brown Coal Technology

The aim of this research is to increase the calorific value of coal. In this way, coal which has a calorific value of 3500 kCal/kg can be increased to 6500-7000 kCal/kg. Apart from that, by carrying out this up grading, a number of volatile meters will disappear as a result of the heating and pressure process. The knock-on impact is an increase in the economic value of coal and thus the selling price will be more competitive. After the data was collected, the data was analyzed using descriptive methods. The descriptive method is used to describe the upgraded brown coal (UBC) process. Findings that can be obtained in this research include: 1) Potential company profits can be increased, 2) Increased local government income through taxes, 3) Many mining areas can be exploited, 4) Reduction of unemployment by expanding employment opportunities in the mining sector, 5) Reducing environmental damage by mining power by mining wisely. 6) Reducing environmental pollution due to the combustion process. 7) With this process, investment in the coal mining sector can be increased. This research concludes that the economic value of low quality coal will increase and the profits that can be obtained will be better.

Method of hydrothermal treatment for coal spontaneous combustion inhibition and its application

The use of coal combustion inhibitors, which are mostly sprayed on the surface of the coal that remains in the mining region (post-mining inhibition), has a significant effect on preventing spontaneous burning of coal, although their duration of action is limited. Pre-inhibition (pre-mining inhibition) prolong the inhibition duration and offers the chance to change the temperature of the inhibition fluid. This results in the suggestion of a hydrothermal inhibition strategy that emphasises the influence of inhibition fluid temperature on the inhibitory effect in order to achieve accelerated inhibition. Infrared tests and temperature-programmed oxidation are used to explore the inhibition law and mechanism of inhibition temperature on the spontaneous combustion of different coal orders. The findings demonstrated that when the inhibition temperature increased to 30 °C, 40 °C, 50 °C, 60 °C and 70 °C, the average inhibition rate and cross point temperature increased dramatically while the rates of oxygen consumption, exothermic rate, and CO production continuously dropped. Simultaneously, the coal's content of more reactive groups, such methyl and methylene, dropped, and the coal's risk to self-heat reduced. At the 70 °C inhibition temperature, the lignite coal showed the maximum inhibition rate (65.28%). This research is crucial to advancing the inhibitor's application technology and efficiency of inhibition.