Coal Type Research Articles

Study on radiation characteristics of coal fired boiler changing with burnout rate

The burnout rate is an important parameter in the combustion of pulverized coal. During the process of pulverized coal burnout, its radiation characteristics and the entire coal-fired boiler vary with the burnout rate, which is a very complex process and current research is not clear enough. This study proposes a new single particle pulverized coal burnout model, which incorporates pore volume correction to fit the density ratio and diameter ratio of multiple coal types with varying burnout rates as the theoretical basis. Using Mie theory, Jiaozuo coal particles are calculated average absorption and scattering efficiency in the band of 0.39 ∼ 16 μm, which is used as the basis for correcting particle emissivity and scattering factor. Then, through user defined function (UDF) in the simulation software, the particle radiation characteristics are modified from the original constants of 0.9 and 0.6 to linear and polynomial models that vary with the burnout rate. Not only do the spatial distribution rules of the coal-fired boilers radiation characteristics with the burnout rate of the furnace be obtained, but also the temperature distribution of the furnace under different particle radiation characteristics models is compared. The results show that the pulverized coal burnout model is consistent with the experimental results in literatures. High burnout rate corresponds to low mass concentration of furnace particles, and low absorption and scattering coefficients. Using the above model to calculate the particle emissivity and scattering factor that vary with the burnout rate, after UDF embedding, the error between the simulation results and the on-site cross-sectional temperature and thermal imaging detection decreases from 4.81 % to 2.59 %, reflecting the high accuracy and rationality of the burnout model and particle radiation characteristic correction method.

Effect of calcium-based additives on NO release of coals under different combustion modes

The nitrogen oxides and sulfur oxides released from coal combustion pose serious environmental hazards, but there exists a contradiction between low-nitrogen combustion and efficient desulfurization, necessitating a deeper understanding of the impact of calcium-based desulfurization agents on NOx release. Based on one-stage and two-stage horizontal furnaces, the effects of temperature, coal types and CaO on the release of NO were explored under the coupled combustion and the separated combustion. The experimental results indicate that: under both conditions, the NO emissions of coals decrease with the increase of temperature. The reaction time of separated combustion is shorter than that of coupled combustion. Under the coupled combustion, the order of NO emissions is: anthracite (AC) > bituminous coal (BC) > lignite (LC) > high chlorine coal (HC), and the order are mainly affected by the content of N in coal. At 800 °C, the fuel-N conversion rates of BC, AC, LC, and HC are all the highest, and the rates are 20.52 %, 25.93 %, 14.90 %, and 15.34 %, respectively. As the temperature rises, both volatile-N and char-N emissions show a downward trend. The NO emissions in the separated combustion are greater and the fuel-N conversion rates of BC, AC, LC, and HC are 44.11 %, 47.31 %, 40.44 % and 32.21 %, respectively. The reduction reaction between char and NO plays a crucial role. After the addition of CaO, there is a significant increase in NO release, indicating that CaO has a catalytic effect on the release of volatile-N and char-N. Under the separated combustion, the impact of CaO on NO emissions is relatively minor, and sometimes it leads to a reduction in NO emission. The role of CaO on the NO release is multifaceted.

Quality management in a 3D geological model – reliability of predicted hard coal quality parameters

This paper presents some of the results of the project undertaken in JSW SA, which aim was to create a three-dimensional model of the deposits that make up the company and schedule company’s production. The assessment of the quantity of coals without analysis of qualitative data, i.e. physicochemical parameters, coking parameters, and optical petrographic analysis is not suitable for obtaining commercial contractors. To obtain information on the quality of the coal seam, the geological service of the mine takes coal samples. In the stratigraphic model and quality model, dedicated interpolators are used for interpolation and extrapolation. In the seam quality model, the most optimized interpolators are Inverse and Height. Modelled parameters such as volatile parts content and random vitrinite reflectivity were analysed in detail. The Height interpolator looks for both a random and a linear dependency. It extracts random changes locally while searching for linear dependencies and extrapolates them to a deposit area that does not have qualitative data. There is a risk of extrapolating a given value to infinity. Nevertheless, the amount of data and the area modelled allows you to close its scope at an acceptable level. A separate POLYGON interpolator based on mxl express surfaces was created to map coal type range. It uses interpolated quality parameters at a given location, generating a range of a particular type of coal. Setting the trend of variability makes it possible to predict higher coal types in deeper, unrecognized batches of deposits according to documented variability in parameters.

Key Bearing Structure Instability Mechanism: A Case Study in Mining Under Close‐Distance Coal Pillar

This study is aimed at solving the issue of mining under the boundary coal pillar of the close‐distance coal seam that causes roof falling. This study established a new key bearing structure model for analyzing the structural instability mechanism when mining under the coal pillar at the working face by taking Shaping Coal Mine as an example. The purpose of this study is to analyze the formation process, load transfer mechanism, and two failure types of the key bearing structure using theoretical analysis and numerical simulation. Additionally, this study discussed the timing and method of roof control for different key bearing structure failure types. Research shows that the instability of the key bearing structure composed of the coal pillar, interlayer rock, and lower coal body is the important reason behind the roof falling. The instability types of key bearing structures include the coal pillar instability type and the cantilever beam instability type. The stability width of the interlayer rock cantilever beam and the coal pillar jointly ascertain the failure type of the key bearing structure. In the 9204 working face, the key bearing structure was destroyed when the coal pillar was 14 m wide, resulting in the roof stress being as high as 31.81 MPa. The stress drop phenomenon can be used as a boundary to divide the failure process of the key bearing structure into three stages. The pressure relief of the coal pillar and interlayer rock cantilever beam is an effective way to deal with this problem, and the coal pillar instability type needs to be pressure relieved earlier than the cantilever beam instability type. The research findings offer new insights into the roof stability control of mining under the coal pillar.

Dual-energy X-ray transmission identification method for coal and gangue with different thicknesses and densities

To reduce the thickness effect influence of dual-energy X-ray transmission (DE-XRT) and solve the problem of identifying coal and gangue with different thicknesses and densities, this paper proposes a method based on the Bayesian optimisation KNN model to classify the pixels of images. The gray feature I and R-values are used to train the classifier to recognize unknown classification pixels. The proportion of classified pixels in the images of a single target is used as the classification parameter. This method reduces the effect of thickness in R-I two-dimensional space. Considering the change in the density of different coal types and taking the density at the boundary between the coal and gangue as 1.8 g/cm3, the recognition rate reached 97.74 %. For raw coal with a 5–150 mm thickness range, the accuracy of identifying predischarged gangue reached 99.16 %. Our study provides a new method and practical guidance for DE-XRT coal preparation.

Optimization of extrinsic parameters for beneficiation of coal with the help of Cronobacter sp

ABSTRACT Beneficiation increases the calorific value of low-grade coal and extracts environmentally sensitive elements. Bacteria may be used as eco-friendly coal cleaning tool, but the treatment is influenced by several extrinsic and intrinsic factors. This study examined five extrinsic factors, namely particle size of coal, pulp density, bacterial biomass concentration, number of bacterial beads (immobilized bacterial cells) and the duration of treatment. For optimization, the test runs were designed using Taguchi L16 orthogonal array, determining optimal values through S/N ratio analysis and individual parameter contribution using ANOVA. The optimal conditions obtained for sub-bituminous coal beneficiation using Cronobacter sp. are 80–120 mesh particle size, 30% pulp density, 750 mg bacterial biomass/g coal, 25 bacterial beads, and six days of treatment resulting in 13.36% ash yield reduction. Particle size had the highest impact (69.4%), followed by treatment duration (13.1%), pulp density (6.3%), bacterial biomass (6.3%), and bacterial bead number (4.8%). A regression model attributed only 42% influence of these extrinsic factors on inorganic removal from coal. Therefore, further research on other factors, particularly intrinsic ones, in inorganic matter liberation is imperative. These findings can be used for designing experiments that optimize the extraction of cleaner fuel from various types of low-grade coal.

Effect of Kaolin Addition on Combustion Behavior of Zhundong Coal Pellet Using Flame Emission Spectroscopy

ABSTRACT Kaolin, as an adsorbent, has been proven to be effective in inhibiting sodium release during high alkali coal combustion thereby alleviating severe slagging and fouling problems. Understanding the co-firing behavior of Zhundong coal with kaolin additives is essential for Zhundong coal utilization. In this study, the effect of kaolin additive on the combustion behavior of two Zhundong coals with different Na contents was investigated based on image analysis and flame emission spectroscopy (FES) method. Spectral and image results were able to distinguish the three stages of coal combustion. The addition of kaolin impacted all combustion stages for both types of coal. The results show the volatile combustion time of the blended coal sample was shortened, while the char burnout time was prolonged, which was attributed to the ash suppression effect. The two coals presented similar decrease trends with different blending ratios in terms of sodium concentration, pellet surface temperature, and thermal radiation. However, the changes were no longer evident after the blending ratio reached 8% and 12%. The replacement of combustible components in the coal by the kaolin altered the mineral fraction of the ash and thus affected the heat and mass transfer. Combining the online measurement results and the analysis of the ash fusion characteristics, the suggested addition of kaolin was 8% and 12% respectively.

Experimental study on the effect of room temperature pre-oxidized time on spontaneous combustion characteristics of coal

The presence of different types of coal at room temperature can lead to self-heating of coal, potentially resulting in spontaneous combustion. To investigate the effect of ambient temperature pre-oxidation (BL) time on the self-combustion characteristics of different coal types, synchronous thermal analysis (STA) and Fourier-transform infrared spectroscopy (FTIR) experiments were conducted. The results of the synchronous thermal analysis experiments indicate that ambient temperature pre-oxidation for 3 months (BL3), BL6, and BL9 coals exhibit faster oxidation reactions compared to the original coal, while BL12 coal shows slower oxidation than the original coal. Among these, BL9 coal demonstrates the most significant changes in oxidation reaction characteristics, with the fastest oxidation reaction time being 35.36 min, which is 1.38 min faster than the original coal. To support this observation, a comparison was made between the relative content of active functional groups in the original coal and BL coal. The study revealed that the BL process affects the relative content of hydroxyl groups, aromatic hydrocarbons, aliphatic hydrocarbons, and oxygen-containing functional groups, thereby influencing the coal-oxygen reaction process. This suggests that pre-oxidized coal, compared to the original coal, has a larger pore structure, which plays a dominant role in promoting coal self-combustion in the first 9 months of the BL process. As BL time continues to increase, the continuous reaction of active functional groups at room temperature leads to excessive consumption, resulting in a more significant role in inhibiting coal self-combustion. The research results provide valuable insights for predicting the spontaneous combustion risk of oxidized coal.

Study on the catalysis of copper-based compounds on coal spontaneous combustion and its mechanism

ABSTRACTTo study the effect of the copper element in coal on the spontaneous combustion process of coal, corresponding copper-containing compounds were added to the coal-based on their occurrence state, and thermodynamic experiments and in-situ diffuse reflectance infrared spectroscopy experiments were conducted. Thermodynamic oxidation experiments have shown that the catalytic effects of Cu (NO3)2, CuCl2, CuCl, and Cu2O on three types of coal with different degrees of metamorphism are mainly reflected in the accelerated oxidation stage. After adding copper-containing compounds, the ignition temperature of coal decreased by 22.1°C to 134.4°C, the heat release increased by 1.33 to 3.19 times, and the CO emission and oxygen consumption rate also increased. CuCl has the greatest impact on the ignition point temperature of coal and increases the oxygen consumption rates of DNH and TS by 2.32 and 1.51 times that of raw coal. CuCl2 has the strongest catalytic effect on coal oxidation heat release. Through in-situ diffuse reflectance infrared spectroscopy experiments, it was found that the reaction rate of fatty hydrocarbons in the oxidation process of three types of coal with the addition of copper-containing compounds increased to 1.3–3 times that of raw coal, and the oxidation rate of oxygen-containing functional groups also significantly increased, while the cracking temperature of aromatic structures significantly decreased. This is because copper ions, as strong free radicals, induce free radical chain reactions in coal and exhibit a strong promoting effect on the coal oxygen reaction process.

Structural changes and product distribution of typical Xinjiang coals and chars during pyrolysis

AbstractThis study used micro‐Raman spectroscopy, gas chromatography–mass spectrometry (GC–MS), and gas chromatography–flame ionization detector/thermal conductivity detector (GC–FID/TCD) to analyze the structure and pyrolysis reactions of nine typical coals and chars from Xinjiang. The study fitted 10 Gaussian bands of typical Xinjiang coal and investigated the changes in coal structure during coalification and pyrolysis. The results indicated that the reduction degree of CO structures in coal during coalification had a rough linear relationship with the Vdaf (dry ash‐free volatile matter) content. During coalification, the condensation of aromatic rings is accompanied by a continuous decrease of CO structures, while the contents of cross‐linking and substitution structures decrease persistently relative to the large aromatic ring structures. The influence of coal type on char yield for typical Xinjiang coal is within 15 wt.%; the influence on tar yield is within 8.5%, with a greater impact on the yield of alkanes and phenols in tar; the influence on CO yield in pyrolysis gas is within 6.3%. The relative content of large aromatic ring structures in coal is relatively stable during pyrolysis, while the relative content of small aromatic ring structures declines as coal transforms into char. The study inferred that small aromatic rings might decompose and transform into tar after pyrolysis reaction, which also resulted in a high selectivity of phenolic products in tar from most coal pyrolysis above 40%. This study revealed the structural changes and pyrolysis product distribution of nine typical coals and chars from Xinjiang, providing useful information for their utilization.

Preliminary study of the methanol production process from coal to support the coal downstream program

Coal downstreaming is a government program to create a comparative and competitive advantage of coal and its various derivative products. Coal derivative products are expected to be economically competitive with oil and natural gas. One of the coal downstream programs is the production of methanol from coal through the gasification process. The development of the methanol industry will support the government’s program of the transfer from fuel-based oil to biodiesel and will reduce dependence on imports. All types of coal in this study can be used as raw material for the methanol production. The coal with high mositure content ((>40%), prior to the gasification process, a dewatering process is required. The dewatering process chosen is the steam tube drying process, the gasification process with a fixed bed gasifier type, the Davy or Johnson Matthey low pressure methanol synthesis technology and the copper – zinc oxide with aluminum oxide or chromium oxide (Cu – ZnO – Al2O3/Cu – ZnO – Cr2O3) catalyst type.

Utilization of Calliandra calothyrsus and Gliricidia sepium as co-firing fuel with consideration of ash-related issues

Biomass can be utilized as co-firing fuel in existing power plants. Woody biomass such as Calliandra calothyrsus and Gliricidia sepium, which can be planted in degraded land, have short cycle, good survivability, and high energy potency, are potential to be utilized. However, adding biomass to existing power plant fuel may cause ash deposition problems such as slagging, fouling, abrasion, corrosion, and agglomeration. This study investigates the ash-related problems of co-firing C. calothyrsus and G. sepium with different type of coal using theoretical indices. The results show that addition of C. calothyrsus and G. sepium up to 50 wt.% has insignificant effect to the risk of slagging, fouling, abrasion, and agglomeration of co-firing fuel. Since the chlorine content in these biomasses increases the corrosion risk to high, the addition of C. calothyrsus is recommended up to 10 wt.% while G.sepium up to 15 wt.% for co-firing fuel.

Degradative solvent extraction of low rank coal: Structural evolution of extraction products

The degradative solvent extraction method was proposed to convert low rank coals into carbon-enriched products under mild condition. However, limitations in the understanding of the structure evolution of products and reaction mechanism of the extraction process hinder the targeted regulation of the products. Therefore, in this work the structural evolution of products during the extraction for different types of coals and by different types of solvents were investigated. Synthesized molecular structural models of the products were constructed and the reaction mechanism was then discussed. Results show that the industrial compounding solvent (ICS) is capable of extracting more single-ring aromatic organics from coals and increasing the yields of the main products by approximately 10% compared to 1-methylnaphthalene. During the extraction process, the main reaction of the sub-bituminous coal is the breakage of unstable chemical bonds and functional groups, while the reaction of lignite is the thermal decomposition and deoxygenation of massive small molecules in the coal. Moreover, the ICS promotes aromatization reactions during the extraction, which indicates that the ICS is the appropriate industrial solvent for the degradative solvent extraction. This research proved a theoretical guidance for the industrialization of DSE technology and the targeted regulation of the products.

Investigation of the smashing characteristics induced by energy distribution of CO2 BLEVE for coalbed methane recovery

Failure in the near field of coal by liquid CO2 phase transition blasting (LCO2-PB) is the major reason for fracturing performance and enhancing coalbed methane (ECBM) recovery. Features to clarify this failure are of significant importance for the field projects. Some studies have revealed that the energy of LCO2 releasing can determine the damage feature to some extent. This study was therefore initiated to investigate the effect of BLEVE energy on the fracturing performance of LCO2-PB in coal. A series of LCO2-PB fracturing tests was carried out on hard and soft coal to examine the effect of CO2 BLEVE energy on fracture morphology. It was obtained that, compared with fractal dimension of hard coal under lower import energy (623.48 kJ) is around 2.17, the higher import energy (831.36 kJ) provides a larger fractal dimension (2.32), especially for high rupture pressure (95 MPa), which make fragments smash into a smaller radial. Although higher input energy favours a large superfluous energy density for any coal types, soft coal represents a stronger tendency to fracture in the stress drop stage. Lower input energy in hard coal seam products a longer main fracture, and excellent fracturing in soft coal prefers the higher import energy.

Study on mechanical characteristics and energy accumulation and release law of coal samples with different saturation and creep damage

ABSTRACT Under the long-term influence of overburden load and water infiltration, coal undergoes creep damage, and the disturbance caused by mining activities can lead to sudden instability, triggering geological disasters such as mine flooding. Therefore, this study prepared four types of coal samples with different saturations under creep damage conditions and conventional coal samples. A comparative study was conducted using uniaxial compression tests to examine the deterioration characteristics of physical and mechanical parameters, failure modes, and energy evolution patterns in these two types of coal samples. Additionally, a microscopic deterioration model of coal samples under the combined influence of water and creep damage was constructed to elucidate the mechanism of creep damage on the deterioration of mechanical properties in water-containing coal samples. The research findings indicate that coal samples affected by creep damage and conventional coal samples exhibit significant consistency in mechanical parameters and energy evolution patterns. Specifically, an increase in saturation is positively correlated with peak stress, elastic modulus, and dissipated energy. Conversely, peak strain, total input energy, and elastic strain energy are negatively correlated with rising saturation levels. Under the same saturation conditions, the change in mechanical parameters and energy characteristics is more pronounced in creep-damaged coal samples. Furthermore, the stress-strain curves of both coal sample types exhibit prolonged compaction stages, shortened elastic stages, and more significant yield stages. Under equivalent saturation levels, the stress-strain trends in creep-damaged coal samples show more substantial variations. Upon loading and failure, the conventional coal sample transitions from single inclined plane shear failure to tension-shear mixed failure as the saturation increases. Conversely, the creep-damaged coal sample shifts from “X”-type conjugate shear failure and tension-shear mixed failure to tension failure, signifying a tendency toward more complex failure modes. In cases where the coal sample has a water saturation of 41%, the deterioration of its mechanical parameters is primarily attributed to creep damage. However, when the water saturation reaches 41–100%, water plays a dominant role in the deterioration of the coal sample’s mechanical parameters. After experiencing creep damage, the internal micro-cracks of the coal sample are extensively developed, which is also the primary factor contributing to the deterioration of the coal sample’s mechanical properties and an increased proportion of dissipated energy.

Atomization of composite liquid fuels in experimental setup with variated gas temperature and pressure

The efficiency of slurry fuel combustion can be improved by developing a predictive mechanism to estimate fuel atomization characteristics. However, no data are available on slurry fuel atomization behavior under near-real conditions. This paper presents the experimental research findings on the combined and separate effect of gas temperature and pressure on slurry fuel atomization characteristics. The experiments involved composite liquid fuels based on water and filter cake (typical coal processing waste) in variable concentrations. These conditions are the same as in advanced fuel slurry preparation units involving pre-combustors, swirlers, and other elements. In this research we have recorded such spray characteristics as droplet sizes and velocities, volume fraction of droplets with given sizes, jet angle, as well as the angle its deviation from the original trajectory. As has been observed, an increase in the ambient gas temperature leads to a 30% increase in the jet velocity and a 40–60% increase in the volume fraction of small droplets, whereas a pressure increase, on the contrary, reduces these parameters by 11–32% and 100%, respectively). Combined effects of chamber gas pressure and temperature on atomization characteristics have been identified: the variation of atomization characteristics did not exceed 18%. Mathematical expressions have been obtained to predict the atomization characteristics of composite liquid fuels in power-generating units with the known gas temperature and pressure. Maps have been plotted using a set of dimensionless parameters that can help control droplet size, velocity, jet angles, and angles of its deviation from its original path.

Mechanical performance assessment of sustainable coal plastic composite building materials

This paper presents a study for developing a high filler content coal plastic composite (CPC) for use in building and construction applications as a substitute for the state-of-the-art wood-plastic composites (WPCs). The influence of coal type (bituminous, sub-bituminous) and content (up to 70 wt%) on the mechanical performance was characterized and compared with predominant commercially available WPC products. SEM micrographs revealed good adhesion between coal and the polymer at the interface with less porosity than WPCs. Additionally, particle fracture and particle pull-out failure mechanisms were evident in the SEM micrographs, with the latter being more dominant. DSC thermal analyses revealed potential chemical reactions between the coal and HDPE interfaces, resulting in enhanced composite performance. Results indicate the tensile strength for CPC material had inverse proportionality with coal content. Despite the reduction, tensile strength for CPC with 60 wt% bituminous coal was not significantly different from a typical WPC formulation. Flexural strength increased to a maximum value, at 60 wt% for bituminous coal and 50 wt% for sub-bituminous coal, followed by a decrease. CPC with 60 wt% bituminous coal possessed higher flexural strength and, in some cases, comparable flexural modulus as compared to WPC products. Flexural properties indicated that a composite deck made from the CPC material could meet or exceed the loading and deflection requirements for decking boards. FEA models indicated that a hollow deck profile would potentially have a better load-deflection curve with less localized stresses compared to common decking board profiled sections.

Techno-economic Analysis of a Solid Fuel Testing Facility for Thermal Power Plants in Peninsular Malaysia: A Monte Carlo Approach

Coal-fired thermal power plants in Peninsular Malaysia are expected to remain operational for at least another 20 years, highlighting the need for clean coal technology adoption. The introduction of new coal types necessitates the verification of their technical viability prior to adoption into power plants, which is addressed by the proposed Solid Fuel Testing Facility (SFTF) system. Hence, this study developed a Monte Carlo-based model to examine the economic factors influencing the profitability of the SFTF system as a solid fuel pre-qualification assessment tool. Three critical factors have been identified as contributors to the SFTF system's economic viability uncertainty: the Test Number, Power Purchase Agreements (PPA) Reduction, and Test Cost. In terms of Net Present Value (NPV) valuation, the Test Number has the highest sensitivity. The projected increase in coal demand necessitating the inclusion of a broader spectrum of new coal variants in power plant operations. As a result, the possibility of an expanded Test Number for the SFTF system exists until the PPA's tenure expires. Therefore, the possibility of favourable NPV outcomes remains prominent throughout the term of the PPA. In contrast, the PPA Reduction has the lowest susceptibility to NPV sensitivity. This demonstrates the SFTF system's ability to navigate policy shifts related to PPA tenure reductions, albeit within a range of 3 to 4 years of reduction. It is suggested that a broader range of parameters be considered in order to gain a more holistic understanding of the economic viability of the proposed SFTF system.

Removal of Pyridine from Aqueous Solutions Using Lignite, Coking Coal, and Anthracite: Adsorption Kinetics

A novel coking wastewater treatment technique is proposed based on the principles of the circular economy. By utilizing coal as an adsorbent for organic pollutants in coking wastewater, the treated coal can be introduced into the coking system after the adsorption and flocculation sedimentation processes. This creates a closed-loop system with zero coking wastewater emissions. We investigated the potential of adsorption for the removal of pyridine. Batch experiments were conducted using lignite, coking coal, and anthracite as adsorbents. Both coking coal and anthracite showed favorable adsorption properties for the chosen contaminants. The experimental data were analyzed utilizing various models, including pseudo-first-order and pseudo-second-order kinetic equations, as well as intraparticle diffusion and Bangham. This study aimed to identify the rate-limiting step in the adsorption process. The results revealed that the adsorption of pyridine onto the three coal types followed pseudo-second-order kinetics. The rate-limiting mechanisms may include both boundary-layer diffusion and intraparticle diffusion. The effect of pH on coal adsorption and the activation energy of pyridine adsorption by coking coal were also examined. Adsorption offers a promising approach in advanced wastewater treatment, with coking coal emerging as a cost-effective adsorbent for addressing persistent organic pollutants during the adsorption process.

Petrographic and geochemical analysis of Barmer Basin Paleogene lignite deposits: Insights into depositional environment and paleo-climate

The current study attempts to characterize the samples from Kapurdi, Giral and Sonari lignite mines of Barmer Basin within Rajasthan Tertiary Lignite deposits using petrographic and geochemical techniques. The data generated has been studied in order to better understand the geochemical properties, hydrocarbon potential, depositional environment and paleo-climatic condition of the paleo-mires of these lignites. The proximate analysis of the samples reveals that the average ash content of the Barmer Basin is 11.93 %, the average moisture content is 14.08 %, average volatile matter yield is 42.03 % and the average fixed carbon is 31.95 %, which suggesting that the physical properties of lignite are dominated by volatile matter on dry basis. The ultimate investigation reveals the chemical properties of the lignite with the average carbon content found to be 58.79 wt%, hydrogen value 3.83 wt%, nitrogen percentage 1.60 wt% and sulphur content 2.75 wt%. This clearly indicates high sulphur concentration in Barmer lignite deposits, based on dry basis. The lignite samples subjected to FTIR studies identified aliphatic CH group, aromatic CO group, hydroxyl OH and Aldehyde HCO group. The Rock-Eval pyrolysis studies have been carried out to know the coalification profile of the deposits and hydrocarbon source rock potential. The varying behaviour between brown coal lithotype are primarily reflected by changes in oxygen index values, whereas hydrogen index values demonstrate a more pronounced correlation with coal type rather than the level of maturation. The results show the average total organic carbon (TOC) 47.29 %, S1 peak 2.18 mg HC/g, S2 peak 88.70 mg HC/g, S3 peak 19.22 % mg CO2/g, Tmax 410.53 °C, hydrogen index 219.2 mg HC/g TOC and oxygen index 46.33 mg CO2/g TOC. According to petrographic investigations, the huminite macerals dominate followed by liptinite and inertinite maceral groups in mineral matter-free basis. In all the three different lignite mines, the huminite group dominates with preserved sub-maceral ulminite indicating less transformation of structured plant matter. Reconstruction of depositional environment and paleo-climatic condition of the paleo-mires has been attempted by using organic petrographic indices. The high gelification index (GI) and low tissue preservation index (TPI) values suggest a prolonged wet environment during the decomposition of organic material, accompanied by a gradual subsidence process. The ground water influence index (GWI) and vegetation index (VI) denote ombrotrophic to mesotrophic hydrological conditions of basin at the time of deposition.