Lakhra Coal Research Articles

Land Subsidence Detection Using SBAS- and Stacking-InSAR with Zonal Statistics and Topographic Correlations in Lakhra Coal Mines, Pakistan

The adverse combination of excessive mining practices and the resulting land subsidence is a significant obstacle to the sustainable growth and stability of regions associated with mining activities. The Lakhra coal mines, which contain some of Pakistan’s largest coal deposits, have been overlooked in land subsidence monitoring, indicating a considerable oversight in the region. Subsidence in mining areas can be spotted early when using Interferometric Synthetic Aperture Radar (InSAR), which can precisely monitor ground changes over time. This study is the first to employ the Small Baseline Subset (SBAS)-InSAR and stacking-InSAR techniques to identify land subsidence at the Lakhra coal mines. This research offers critical insights into subsidence mechanisms in the study area, which has never been previously investigated for ground deformation monitoring, by utilizing 150 Sentinel-1A (ascending) images obtained between January 2018 and September 2023. A total of 102 deformation spots were identified using SBAS-InSAR, while stacking-InSAR detected 73 deformation locations. The most extensive cumulative subsidence in the Lakhra coal mine was −114 mm, according to SBAS-InSAR, with a standard deviation of 6.63 mm. In comparison, a subsidence rate of −19 mm/year was reported using stacking-InSAR with a standard deviation of 1.17 mm/year. The rangeland covered 88.8% of the total area and exhibited the most significant deformation values, as determined by stacking and SBAS-InSAR techniques. Linear regression showed that there was not a strong correlation between subsidence and topographic factors. As detected by optical remote sensing data, the subsidence locations were near or above the mines in the research area, indicating that widespread mining in Lakhra coal mines was the cause of subsidence. Our findings suggest that SAR interferometric time series analysis is helpful for proactively identifying and controlling subsidence difficulties in mining regions by closely monitoring activities, hence reducing negative consequences on operations and the environment.

Identification of the Most Critical Health and Safety Hazard in the Lakhra Coal Field

Identification of the Most Critical Health and Safety Hazard in the Lakhra Coal Field

Numerical Simulations of Gasification of Low-Grade Coal and Lignocellulosic Biomasses in Two-Stage Multi-Opposite Burner Gasifier

Thermochemical processes utilizing biomass demonstrate promising prospects for the generation of syngas. In this work, a gasification process employing combination of an indigenous low-grade coal with two distinct biomass sources, namely rice husk (RH) and wood sawdust (WS), was explored. The gasification of the selected feedstock was performed using a double-staged multi-opposite burner (MOB) gasifier. A 3D computational fluid dynamics (CFD) model was employed to analyze the effect of kinetic and diffusion rates on the overall gasification performance of an entrained flow biomass gasifier. DPM was employed to track the particles’ trajectory, while the gas phase was treated as the continuous phase, and its behavior was predicted using a standard k-epsilon turbulent model. To calculate both the homogeneous and heterogeneous reaction rates, the finite rate/eddy dissipation model was implemented. The findings indicate that the char conversion efficiency exceeded 95% across all instances. Among the different reaction schemes, scheme E (which involved complete volatile and char combustion reactions) produced better results in comparison with published results, with less than 1% error. Hence, scheme E was validated and utilized for the rest of the simulated cases. The feeding rate has an inverse effect on the overall performance of the gasifier. An increase in feed rate decreases the CO and H2 composition in syngas. The maximum CO value was observed to be 57.59% at a 1.0 O/C ratio with a 0.005 kg/s feed rate, and the maximum H2 value was observed to be 16.58% in the same conditions for Lakhra coal samples. In summary, Lakhra coal exhibited better performance than other biomass samples due to its better fixed carbon and volatiles in its composition.

A physical coal cleaning approach for clean energy production from low grade Lakhra coal of Pakistan using diester table

In this work coal from Lakhra (coal mine in Pakistan) was subjected to a physical technique for mineral matter and sulfur reduction by using diester table. Effect of particle size and coal-to-water ratio of slurry were studied. A reduction of 85% in sulfur content and 88% in ash content for 500 µm coal sample was observed. While at 300 µm size sulfur and ash content were reduced about 77% and 80% respectively. At 150 µm size, the reduction in sulfur and ash was observed to be lesser (54% and 55% respectively) due to the decrease in specific gravity difference of coaland impurity (i.e. sulfur and ash). GCV increased from 17.2 MJ/kg of the raw coal to 23.3 MJ/kg of cleaner fraction obtained at 500 µm. Based on the results of this study, diester table can be proposed to be a simpler however an effective physical coal cleaning method to reduce sulfur and ash content. Besides other parameters, particle size is a crucial parameter to impact the cleaning efficiency and because of the greater difference in specific gravity of coal and impurity, higher particles size used in this study resulted in the cleanest product.

Alkali leaching in dissolved oxygen for efficient desulphurization of low-grade Lakhra coal

ABSTRACT Coal is still a great source of energy, but its high sulfur content causes environmental pollution and problems in its processing. This study used a method of combined oxidation and alkali leaching to desulfurize low-grade, high-sulfur Lakhra coal at different ranges of temperature, alkali concentration, leaching time, partial pressure of oxygen, and agitation speed. The optimum values for the leaching reaction were observed to be an alkali (NaOH) concentration of 0.8 mM, a leaching time of 1.5 h, an oxygen partial pressure of 150 psi, and an agitation speed of 800 rpm. The ash content of the coal initially increased at higher values of reaction time and temperature, and then became saturated at a certain peak. The raw coal was characterized for ultimate and proximate analysis, and the product was characterized for ash content and total sulfur content.

Chemical association and combustion behaviour of cadmium in coal of different mining fields using sequential and single step extraction methods

ABSTRACT This work sought to conduct the chemical association of a toxic metal (cadmium) in coal samples of various origins in Pakistan. For that purpose, a sequential extraction scheme recommended by the Community Bureau of Reference (BCR) has been carried out to know the chemical fractionation of Cd in different coal samples. Simultaneously a time saving vortex-assisted single-step extraction (VA-SSE) via the same experimental parameters conditions used in each fraction steps of BCR sequential extraction procedure (BCR-SE). The coal samples were collected from Thar coal (TCF) and Lakhra coal fields (LCF) of Sindh, Pakistan. The validity of BCR-SE and VA-SSE were checked by applying spiking standard addition procedure on real coal samples. The BCR-SE and VA-SSE were completed in 51 h and 1.0–2.0 min, respectively. In second phase determined the combustion behaviour of Cd or/amount of Cd in coal samples volatilise after heating in an electric furnace in laboratory at three temperature interim (200°C, 400°C and 900°C). The coal ash obtained at 900°C was put to three step sequential extraction method. The evaluated result showed that the total values of Cd in coal samples of block II of Thar coal field (TCF), Site I and Site II of Lakhra coal field (LCF) were found in the range of 3.42–4.43, 2.02–2.82 and 2.91–3.92 mg/kg, correspondingly. The final result indicated that the major chemical fraction of Cd was bound with organic phase of coal samples of both origins (about 40%). The evaluated data showed that 60–71% of Cd in coal samples was found in first three fractions, whilst about 29–40% of Cd was observed in residual. The extracted Cd concentrations in various chemical fractions of coal samples obtained through VA-SSE were 1.6–2.6%, higher than those values gained via BCR-SE (p < 0.04). The resulted data indicated that, after burning of coal samples at 900°C, about 63–69% of total Cd in coal samples of both mining areas was found in residual ash, while 31–34% was vaporised/volatilised out into the atmosphere.

Bioprocess development and optimization of parameters for enhancing bio-assisted method for sulfur removal from lakhra coal using rhodococcus sp SL-9

ABSTRACT The burning of coal releases toxic gases that disturb the environmental conditions. It is imperative to use this energy as much as possible. Due to its characteristics, it is possible to manipulate unused loss reserves. In this case, it is necessary to continue research emphasizing clean coal technology from an energy perspective, safety, and environmental sustainability problem. It wants to be implemented that 50% of the world’s coal reserves are low grades. In this regard, the current work is related to removing sulfur obtained from coal using newly isolated bacteria sl-9. It was determined that different process parameters might be used to remove Sulfur. There is a reduction of 45% of the total Sulfur in unprocessed coal when several parameters are controlled, such as 20% (w/v) pulp density, 180 rpm, 20 mesh (850 microns), and pH 7. So, Sl-9 has the potential to lower coal’s sulfate content.

Chemical association of copper and selenium in coals of Sindh by time saving single step strategy and their impact on groundwater.

The aim of the present study is to estimate the different chemical fractionations of copper (Cu) and selenium (Se) in coal samples of different coal mining areas. The Cu and Se bound to various chemical fractions of coal collected from two mining fields of Sindh, Pakistan, have been determined by BCR sequential extraction scheme (BCR-SES). The long duration of the BCR sequential scheme (51h) was reduced by a time-saving shaking device (ultrasonic bath) termed as ultrasonic-assisted extraction (USE) depending on the same operating conditions and extracting solutions used for BCR sequential extraction scheme. The both trace elements were determined in aquifer water, sampled from different depth of both coal mining fields. In addition, the groundwater of dug well in the vicinity of coal mining areas were also analyzed for Cu and Se using reported extraction methodologies. The partitioning of Cu and Se bound with different chemical fractions of coal was successfully made by proposed USE, within 2h as compared to long duration of BCR-SES (51h). The Cu and Se concentrations in acid-soluble fractions of coal samples were > 10%, enhanced by USE extraction procedure than those values gained via BCR-SES (p < 0.01). About 67 to 69% of Cu were found in the first three fractions, whereas their remaining amount corresponding to 31 to 33%, respectively bound with crystalline/residual fraction, while up to 66.1 to 71.1% of total Se contents extracted in three extractable phases, followed up to 28.9 to 33.8% of it was bound with residual phase. The concentrations of Cu and Se in groundwater of different aquifers were found in decreasing order as AQ1 > AQII > AQIII; the same trend was observed for two aquifers of Lakhra coal mining, whereas the groundwater samples have two to three folds higher levels of Se than WHO limit. The Cu levels in water samples were significantly lower than the recommended limit of WHO for drinking water (p < 0.01).

Facile application of used engine oil in high sulfur coal briquetting to reduce the hazardous emission gases

ABSTRACT Non-hazardous coal briquettes were prepared from the blend of indigenous Lakhra coal containing high sulfur, slaked lime, used engine oil and bentonite clay. Briquettes were prepared with different compositions to observe the respective behavior of components. Raw coal and coal briquettes were characterized with ultimate and proximate analysis, TGA, emission gas analysis, mechanical strength, and smoke number. The optimized briquetting composition was observed as 72% raw coal, 16% bentonite clay as binder, 6% slaked lime and 6% used engine oil. Ignition time of this composition was reduced from 12 minutes to 6 minutes. Testo smoke number of coal briquette was much lower than that of raw coal, and higher amount of smoke in raw coal was reduced by briquetting. The heating value in optimized briquette batch 4 was higher as compared to other briquetting batches. TGA test showed that temperature rise per unit time was similar for both in raw coal as well as in coal briquettes, while the weight reduced per unit time was less for coal briquettes as compared to raw coal. Also the mechanical Strength was achieved up to 17.96 MPa. It was observed that mechanical strength was increased in coal briquettes with increase in amount of oil.

Evaluation of Work-related Musculoskeletal Injuries Among Coal Miner

Mining work is quite tedious, and it takes the whole body into account. Underground mine environment has sensory issues, and working conditions are not ideal. It results in maximum chances for the occurrence of work-related musculoskeletal injuries (WRMSIs). WRMSIs are the conditions which affect muscles, bones, joints, nerves, vessels, and supporting system. These are the significant cost occurring disorders in the workplace. This research aims to assess the WRMSIs in Lakhra coal mines to identify critical issues. Fifty operational workers completed the self- administrated questionnaire survey. Data related to personal and work information, physical activities age, nature of job, and WRMSIs was collected. A physical wellbeing checklist and Body Part Diagram were used to know the response of the worker. The research findings show that shoulder and knee disorders occur more frequently among workers. Almost 54% of cases were reported knee pain, whereas 44% reported toe/foot disorders, 38% for a wrist disorder, 36% stuck with shoulder pain, 16% had neck pain, 10% were with elbow pain, and only 2% have the hip disorder. The study is a positive addition in the research area to carry out better health and safety measures for the miners.

Analysis of Lakhra Coal by Calibration Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) and Comparison of Self-Absorption Correction Procedures

The analysis of Lakhra Coal to determine its total carbon content and ash content is reported by calibration-free laser-induced breakdown spectroscopy (CF-LIBS). The total carbon content and ash content in coal are key parameters for efficient energy u in sepower plants. The optical emission spectrum of coal contains spectral lines of Ca, Si, Fe, Ti, Mg, Na, K, Li, Al, and C together with traces of Ba and Sr. The excitation temperature and electron number density of the laser-produced plasma were estimated using a Boltzmann plot and Stark broadened Hα line, respectively. The self-absorption correction in the emission intensities of the spectral lines were performed using the internal reference self-absorption correction (IRSAC) and the density correction. The analysis of the coal was performed by CF-LIBS, CF-LIBS with IRSAC, and CF-LIBS with density correction which were then compared with the certified composition reported by the Lakhra Coal Development Company. The results revealed that IRSAC with a fixed slope is more easily applicable and reliable than the number density correction for analyzing the total carbon content, ash content, and trace elements.

Calcium and Lead Levels in the Biological Samples and Their Effect on the Biochemical Parameters of Indoor and Outdoor Workers of Five Zonal Areas of Coal Mining Field

Workers of the Lakhra coal mining Sindh Pakistan were affected by a multi-factorial exposure of heavy metals. The prevalence of lead (Pb) exposures in work-related symptoms among workers of indoor and outdoor mining of Lakhra coal mining was evaluated in detail. The biological samples (scalp hair and blood) of 270 workers of Lakhra coal mining {official and control subjects} (indoor and outdoor) 18 to 55 years age group and 70 referent subjects of same age-groups were examined. The biological samples (blood and scalp hair) of workers of Lakhra coal mining and referent subjects were analyzed for calcium (Ca) and lead (Pb). Flame atomic absorption spectrometry was applied for the determination of the Ca in digested samples of studied subjects by the microwave oven whereas, the Pb contents were measured by electrothermal atomic absorption spectrometry. The validity of the methodology was checked by using the certified human hair material (BCR 397) and lyophilized human blood (Clincheck). The results indicated the higher contents of Pb in biological samples of indoor and outdoor mining workers than referents. However, the levels of Ca were found to be lower in indoor and outdoor mining workers than those of referents. It can be concluded that immediate action should be taken by recommended authorities to improve the ventilation and hygiene practices inside the industries, mines, and other workplaces.

Investigation of Performance for Entrained Flow Gasifier Through Simulations

Pakistan has proven huge coal reserves but still unable to harvest the energy due to unavailability of ingenious technology. Coal gasification is robust, efficient and environmental friendly technology but it is highly sensitive to the coal characteristics. Scant literature is available on the development of the coal gasification technology which suits the characteristics of indigenous coal reserves. This papers presents the simulation of entrained flow gasifier for using indigenous coal through process modeling software namely Aspen Plus® to evaluate various system flow steps within an entrained flow gasifier. General techniques have also been discussed for creating the equilibrium-bases simulations of gasification systems. Peng-Robinson equation was used to correlate the volume of species with respect to state variables (temperature and pressure). The effects of composition of different indigenous coals like Thar, Lakhra and Sonda were investigated through simulations along with O/C (Oxygen-to-Carbon) ratio. Parametric study revealed that the O/C ratio along with other related system parameters have great influence on the performance. Sulfur could be available in different forms in coal like pyrite, sulfate or organic sulfur so appropriate form of sulfur in feedstocks should be corrected for better accuracy of model results. The highest percentages of CO i.e. 44.2, 37.8, and 46.6% were obtained from Thar coal (air dried form), Lakhra coal and Sonda coal respectively at the 0.3 O/C ratio. The decrease in LHV and HHV (Lower and Higher Heating Values) of syngas was observed on increase of O/C ratio for all coal types. The composition of as received Thar coal gave maximum LHV (1.5x104 KJ/Kg) and HHV (1.78x104 KJ/Kg) at the 0.3 O/C ratio. The future work could be extended by simulating biomass composition in the developed model of gasifier in transient simulations.

Pyrolysis–Gas Chromatography of Lakhra Coal: Effect of Temperature and Inorganic Matter on the Product Distribution

The objective of this article was to study the effect of pyrolysis temperature and mineral matter on the distribution of the products of C1-C6 hydrocarbons. Pakistani lignite named Lakhra 6B was used to study the effect of inorganic substances on the reactivity of coal. The experiments were performed using pyrolysis gas chromatography to investigate the activity of virgin coal, HCl acid-washed coal, and acid-washed coal with (Ca(C2H3O2)2, Mg(C2H3O2)2, NaC2H3O2, KC2H3O2), added respectively. The products obtained were monitored by a gas chromatograph. The main products identified were methane, ethane, ethylene, propane, 1-butene, n-butane, 1-pentene, n-pentane, and benzene. The results showed that coal conversion to methane increased with an increase in temperature and the amount of this hydrocarbon was high among all the hydrocarbons formed. It was observed that the addition of metal ions affected the yields of the products selectively. The yield of benzene was observed to be high in the case of calcium and magnesium form coals. The other cations form coals produced a smaller quantity of benzene in the temperature range studied. From the results, it can be concluded that metal ions played a selective role in controlling the yield of C1-C6 hydrocarbons products from coal pyrolysis in general and benzene yield in particular.

Proximate analysis of Lakhra coal power plant and its health and environmental impact

ABSTRACT Pakistan is one of the coal rich countries but only adds 10% of electricity to the national grid from coal fired power plants while major sources are, Hydel, LNG, Furnace oil, and natural gas. Prior to the discovery of Thar coal reservoirs, Lakhra was the largest coal field of Brown Lignite coal with high ash and sulfur contents, i.e. 30% and 7%, respectively. The power generation capacity of the plant is 150 MW. Study conducted revealed that all the existing values of un-washed coal found (High Ash, Low Moisture, Low Fixed Carbon, High Sulfur, and Low Calorific value) while the washed coal values found (Low Ash, Low Moisture, High Fixed Carbon, Low Sulfur, and High Heating value). The emission of hazardous gases and particles by using unwashed coal adversely affect the environment and human health whereas washed coal exhibited relatively low level emissions of these pollutants. It was observed that the washed coal of Lakhra is more feasible to save the environment as well as Cost Benefit for production of electricity.

Desulfurization of Lakhra coal by combined leaching and catalytic oxidation techniques

ABSTRACT Desulfurization of the Lakrah coal was investigated by combined leaching and catalytic oxidation. For leaching various concentrations of different acidic and base solutions including H2SO4, HCl, HNO3, KOH, NaOH, and Na2CO3 were used. Among acids, 0.4 N HNO3 at room temperature and 30 min stirring time, provided about 19.3% of sulfur removal, whereas the base solution of 0.4 N KOH was most effective, decreasing the total sulfur by 29%. The leached coal was subjected to oxidative desulfurization using H2O2 as oxidant. The optimum conditions were found to be 70°C temperature, 60 min reaction time and using toluene as a solvent, which led to decrease in the total sulfur upto 50%. The oxidative desulfurization was further investigated in the presence of Fe loaded on bentonite catalyst. The oxidative desulfurization of the Lakhra coal in the presence of 3% Fe loaded on bentonite clay was enhanced to about 83%.

Numerical Study of Coal Composition Effects on the Performance of Gasification Through Computational Fluid Dynamic

Abstract Pakistan is very rich in coal reserves specifically after exploration of Thar coal reserves. At the same time country is facing energy crises due to shortage or unavailability of sustainable fuel supply at a cheaper rate. One potential solution is coal gasification which gives clean synthetic gas usually called syngas for use as an alternative fuel source for electricity production at a cheaper rate as well as a source of recovering different chemicals used as basic raw materials in other industries. Numerical simulations have been performed in this work for the gasification process of indigenous coal on a 2D computational fluid dynamic (CFD) model of downdraft entrained-flow gasifier using commercial CFD software FLUENT®6.3.26. Navier-stokes equations along with transport equations for species have been solved using eddy-dissipation combustion model. The compositions of indigenous coals (Thar, Lakhra, and Sonda) were used in simulations as gasification feedstock. Rich oxidant conditions 95 % O2 and 5 % N2 were set for gasification. The gasification performance was studied by comparing efficiencies of gasification and quality of syngas produced for three types of coal feedings. The temperature and pressure profiles inside the gasifier were also studied. From simulation results, the great influence of coal composition was observed in the performance of gasification. Lakhra coal produced syngas with a maximum heating value of 20.55 MJ/kg whereas sonda coal produced syngas with a minimum heating value of 17.96 MJ/kg.

Fractionation of Manganese in Soil Samples Collected From the Lakhra Coal Field in Pakistan Using Two Modes of Atomic Absorption Spectrometry

Fractionation of Manganese in Soil Samples Collected From the Lakhra Coal Field in Pakistan Using Two Modes of Atomic Absorption Spectrometry

Effect of rice husk co-combustion with coal on gaseous emissions and combustion efficiency

ABSTRACTInvestigation on co-combustion of Lakhra coal and rice husk blends was carried out in a drop tube furnace to measure its impact on flue gas emissions and carbon burnout. According to experimental results, the emissions of NO and SO2 were higher in case of combustion of Lakhra coal compared to coal​–rice husk blends combustion. The emissions of CO decreased rapidly at higher furnace temperatures beyond 900°C. Minimum of CO emissions were nearly 45 ppm while SO2 and NO emissions were found to be 554 and 120 ppm, respectively, for 15% biomass blending ratio and at exit furnace temperature of 1000°C. The unburnt carbon was found to be reduced significantly with an increase in furnace temperature and blending ratio. The study has shown that blending of rice husk would be a useful option to minimize SO2 and NO emissions during combustion of Lakhra coal.

Reverse flotation of cut-of-grade of Lakhra coal

ABSTRACTThe selective mining activities have generated a huge quantity of poor grade coal that is rich in mineral matter and sulfur content and has piled up in whole mining site at Lakhra. This highly oxidized and mineral matter rich coal has been upgraded by reverse floatation. Three process parameters such as pH (7, 8, 9, 10, 11), particle mesh size (60, 100, 150, 200), and % solids (10, 15, 20, 25, 30) in flotation pulp have been investigated with respect to their effect on sulfur and ash reduction. According to results of this study, parameters such as particle size of 100 mesh (150 µm), pH 9 and 20% solids were found to be optimum removing 63.7% of ash and 72.9% of sulfur from coal and coal recovery of 61.3%. Moreover, the heating value of coal also improved from 3924 kcal/kg to 5500 kcal/kg ~ 40.16% enhancement. The recovery of combustibles and gangue at optimum conditions was found to be 60.31% and 39.1% respectively. The clean coal thus obtained containing 12.7% ash, 1.5% sulfur, and 5500 kcal/kg heating value can be used as an energy source for cement manufacturing, in utility boilers, and production of smokeless briquettes for domestic and industrial use.