Coal Density Research Articles

Optimization method for predicting coal reservoir fractures in the Laochang area of Eastern Yunnan using paleotectonic stress inversion

IntroductionCoal reservoir fractures serve as critical storage spaces and migration pathways for coalbed methane (CBM), significantly influencing CBM enrichment. The characteristics of coal reservoir fracture development can be obtained using traditional simulation methods, but these still have shortcomings. This work presents an optimization approach for the traditional method.MethodsThis study introduces an optimization approach for traditional methods with two novel contributions. This study integrates the simulation of tectonic stress fields with fracture prediction, using surface sandstone fractures as constraints to reconstruct the paleostress field of the coal seam, while also accounting for the influence of coal thickness on fracture development to calculate fracture density.ResultsThe predicted fracture density results were validated against measured values from the Bailongshan mine and Xiongdong coal mine with a relative error of approximately 12%, suggesting a reasonable degree of reliability.DiscussionBased on the results of the fracture simulation predictions, it is believed that the coal seam fracture density in the study area is mostly 10–20 lines/m and that the sweet spot for CBM development is located in the Yuwang block.

Numerical simulation of an externally heated fixed bed reactor for coal pyrolysis based on porous media

A cutting-edge three-dimensional transient model utilizing porous media has been developed to accurately simulate the pyrolysis process of externally heated coal. This innovative model comprehensively considers the evaporation and condensation of water, as well as the release of volatiles. In addition, it meticulously examines the change in coal seam porosity and the interphase heat transfer between pyrolysis gas and solid coal seam. The model's precision has been appropriately confirmed through validation against the central temperature evolution inside the experimental reactor. Notably, this model systematically illustrates various aspects, including the evolution of coal layer temperature, evaporation and moisture density, changes in coal layer density, porosity distribution, volatile release, and interphase heat transfer. The obtained results reveal that the heat absorption by moisture phase change causes the coal seam temperature to relatively stabilize at around the water boiling point for a period, thus delaying the initiation of the coal pyrolysis reaction. The pyrolysis gas released by center coal seam pyrolysis tends to flow radially toward the heating wall before flowing out of the reactor. Additionally, the change in coal seam porosity increases the heat transfer rate by an average of 1.5 °C/min during the rapid heating stage. The analysis also highlights the significant occurrence of interphase heat transfer throughout the pyrolysis process and elucidates its mechanism in various stages. Ultimately, this work offers essential theoretical guidance for the design, optimization, and scaling of subsequent externally heated fixed-bed coal pyrolysis reactors.

Response Patterns of Acoustic Wave Characteristics to Reservoir Petrophysical Parameters in Different Bedding Directions: A Case Study of Low- and Middle-Rank Coals in Xinjiang, China.

The physical properties of coal reservoirs, important parameters for evaluating the production potential of coalbed methane (CBM) resources, can be assessed nondestructively and in real-time using acoustic wave technology. In this study, we collected 48 low- and middle-rank coal samples oriented in different bedding directions from seven typical coal mines, encompassing the Zhunan, Tuha, and Kuqa-Bay coalfields in Xinjiang, China. We clarified the characteristics of the physical parameters (apparent density, fracture, porosity, and permeability) and acoustic wave of coal variations through acoustic wave, porosity, and permeability experiments, revealing the response law of acoustic wave characteristics to the physical parameters of coal. The results indicated that the acoustic wave velocity and dynamic elastic modulus (E d) of coal samples oriented in the perpendicular bedding direction are larger than those oriented in the parallel bedding direction; however, the dynamic Poisson's ratio (μd) of coal samples oriented in different bedding directions does not significantly differ. The existence of fractures significantly reduces the acoustic wave velocity and E d of the coal. The greater the apparent density of coal, the tighter its structure, resulting in a faster acoustic wave velocity. The larger the porosity of coal, the greater its internal voids, leading to a more pronounced attenuation of acoustic energy and a slower acoustic wave velocity. The more developed and interconnected the bedding fractures of coal bodies oriented in the parallel bedding direction, the higher their permeability, resulting in a smaller decrease in acoustic wave velocity. Conversely, the more developed the bedding fractures of coal bodies oriented in the perpendicular bedding direction, the more pronounced their attenuation of acoustic wave velocity. Finally, the regression equations for E d with the square of P-wave velocity (V P 2) and μd with the square ratio of V P to S-wave velocity (V P 2/V S 2) were established for coal. The study findings can help evaluate and predict the reservoir quality of coal seams, assess CBM, and improve the safety and efficiency of its extraction.

Study on particle size and density segregation law in the separating process of poor quality coal with high gangue content under the action of composite force field

ABSTRACT Thin-seam mining frequently captures a significant proportion of gangue and interbedded coal in surface coal mines. Consequently, raw coal has a broad range of particle size distributions and a high percentage of components with intermediate densities, which are complex and challenging to separate. This study aims to determine the method of product division and the segregation law of particle size and density of raw coal during the separation process using a vibration and airflow composite force field. A difference in the particle size segregation of the coal particles was evident. Particle-size segregation primarily occurs in the separation area. Large-particle-size coal has a wide distribution range, spreading over the entire bed and fully utilizing the bed to achieve separation. The material becomes increasingly displaced into the separation area as its particle size decreases, thereby weakening the separation effect. Large coal particles can undergo density segregation in the vertical direction, with low-density material placed in the upper layer. This ensures that low-density material is incorporated into the refined coal product. Regardless of density, the coal tended to tilt more toward the bottom layer as the particle size decreased. This results in a poor density stratification effect with refined coal products mixed with gangue and an increase in the mismatch content. The extent of fine coal discharge was determined to be two-fifths of the entire length of the discharge side. This ensures that the majority of refined coal is recovered and that there is no excessive gangue mixing with the refined coal output. Achieving a 55.54% yield, refined coal lowers its ash content by 16%, increases its calorific value by 1400 kcal/kg, and effectively separates coal with a high gangue concentration.

Study on the rigid-discrete coupling effect of scraper conveyor under different chain speed-load conditions

The complexity of the underground environment in coal mines often leads to varying load conditions during the operation of the scraper conveyor, which can affect the lifespan of its components and result in unnecessary energy consumption. A test platform for the scraper conveyor was constructed based on the similarity theory to measure torque, speed, chain tension, and scraper acceleration during transportation. A DEM-MBD model of the scraper conveyor was developed and validated through transport tests and similarity theories to analyze the rigid-discrete coupling effect under different chain speed-load conditions. The results revealed a stratification phenomenon and a Brazilian fruit effect in the movement of coal. The average velocity of the upper and lower coal layers gradually increased during the transportation, while the difference between them gradually decreased. As the load increased, the stacking density and height of coal between scrapers also increased, leading to a higher force exerted on the scraper and chain. As the chain speed increased, the stacking density and height of coal between scrapers decreased, along with a decrease in the force applied to the scraper and chain. The formation of three-body wear necessitates a specific positional condition. When the scraper (chain)- coal-deck plate (chute liner) forms a particle stagnation state, severe wear occurs on the parts. This study provides a foundation for analyzing the transport mechanism of scraper conveyor from the particle perspective, offers a simulation reference for analyzing the mechanical and tribological characteristics of the line pan and scraper chain, and serves as a guideline for the future development of transportation state monitoring and the optimization and enhancement of components under different working conditions.

Decoding wettability in coal-water-CO2 system for enhanced sequestration security

The injection of CO2 into deep unminable coal seam is a most promising carbon storage method that can simultaneously achieve the dual objectives of mitigating CO2 emission and enhancing coalbed methane recovery. In this context, the wettability of the coal-water-CO2 system plays an important role in the CO2 injection rate, storage capacity, and sequestration security. However, the factors affecting wettability alternation in the coal-water-CO2 system are still unclear until now. In this study, the sessile drop method was used to measure the contact angle (CA) in the coal-water-CO2 system under different pressures (3 – 8 MPa) and temperatures of (40–70 °C) with four different rank coals. Results indicate that with increasing pressure, the CA shows a steady increase below 5 MPa followed by a rapid increase at 5 – 8 MPa. The CA decreases with increasing temperature and coal rank. The CA is negatively correlated with the mes- and macro-pores, but positively correlated with micropores. It was found that these relationships are attributed to the CO2 density and CO2 adsorption capacity of coal. As the CO2 density increases, the coal-CO2 interaction force intensifies, leading to a tendency towards CO2 wetting for the coal-water-CO2 system. The adsorption capacity illustrates the strength of the coal-CO2 interaction, where the affinity of polar adsorption sites for CO2 molecules exceeds that of nonpolar adsorption sites. Finally, we conducted a comprehensive assessment of the wettability of the coal-water-CO2 system as it varies with burial depth by developing an integrated model that considers four influential factors, including pressure, temperature, coal rank, and pore structure. The findings of this study can be utilized to determine the optimal CO2 injection pressure in CO2-ECBM projects and enhance sequestration safety.

3D modeling of cryogenic cracking by liquid nitrogen in coal under true triaxial stresses

Coalbed methane (CBM) plays an indispensable role in total natural gas production and consumption, and for the bottlenecks encountered in stimulating CBM reservoirs by conventional fracturing methods, studying more environment-friendly and efficient stimulation methods is imperative. Cryogenic fracturing using liquid nitrogen has been trialed for the development of coalbed methane, demonstrating great significance as more and more research corroborated. This study extended our previous coupled thermo-mechanical-damage (TMD) numerical procedure to investigate the cryogenic fracturing or damage process in 3D coal cubes. The cryogenic fractures on concrete cubes along with analytical solutions of temperature and first principle stress distributions for the borehole cooling process were first employed to verify the correctness and feasibility of this method, which incorporates the boundary conditions affected by the Leidenfrost effect at the initial stage. Then sensitivity analyses of cryogenic fracture generation including the maximum fracture cross-sectional area and the fractured volume were carried out. Results show that the coal rock with a high modulus of elasticity and coefficient of thermal expansion is more prone to be damaged in terms of the cross-sectional area and volume than other parameters within the parameter range analyzed. Damage cross-sectional area and damage volume expand with both the increasing coefficient of thermal expansion and the increasing modulus of elasticity, while they shrink with increasing heat capacity and coal density. Cryogenic fractures are relatively less sensitive to the thermal conductivity, density, and heat capacity of coal. This 3D modeling study provides a technical route and a panorama of the cryogenic fracturing process under varied conditions in opaque coal rocks.

On methods for determining the true density of coals to predict the outburst hazard of coal seams

On methods for determining the true density of coals to predict the outburst hazard of coal seams

A spatio-temporal temperature prediction model for coal spontaneous combustion based on back propagation neural network

Coal spontaneous combustion (CSC) occurs with the change of temperature and gas concentration which is useful for early warning. To explore the intrinsic correlation between temperature evolution and gas distribution, a Back Propagation Neural Network (BPNN) model of coal temperature - gas composition - spatial distance was constructed, which is based on the gas characteristics and spatial distribution of coal temperature in large-scale coal spontaneous combustion experiments. The results showed that the O2 concentration reached the lowest value (8.058%) at 45 cm on Day 52 with the time. CO and CO2 also formed concentration peaks at 45 cm, and the gas distribution continuously moved towards the inlet position. The hydrocarbon gas components showed periodic increases, with values below 100 ppm. When the supply air time increased, the temperature rise rate in the initial stage of oxidation was slow but relatively uniform. Affected by ventilation conditions and coal density, two high-temperature zones were observed at 45 cm and 85 cm in the experimental furnace. With the inclusion of spatial distance parameters in coal temperature prediction, the BPNN model exhibits accurate predictive capability, with a total error of 0.94997. This can provide a method for predicting temperature changes in coal mine.

Mechanism of measuring ash with low-energy gamma rays for equal coal seam thickness

ABSTRACT Considering the issues related to significant fluctuations and errors in the measured data of the dual-energy gamma-ray online ash analyzer caused by various external factors, this study investigates the impact of factors such as the distance between the detector and the radioactive source, coal seam thickness, moisture content, and particle size range on ash measurements. Additionally, a novel low-energy gamma-ray online ash measurement device is proposed, which ensures uniform coal seam thickness. By utilizing this device, the coal samples subjected to measurement exhibit characteristics such as small particle size, a narrow range of particle sizes, a smooth coal flow surface, consistent coal flow density, a fixed distance between the coal seam and the detector surface, and constant coal seam thickness. These conditions collectively provide optimal circumstances for accurate low-energy gamma-ray ash content measurement. Experimental results indicate that during the separation of Suntuan: Tongting raw coal, the average discrepancy between the measured ash content and the assay ash content was only 0.33%, and the standard deviation of the measured ash content was significantly lower than that of the assay ash content. Specifically, when separating Suntuan: Tongting raw coal, the standard deviation reached its minimum at 0.16%. Comparatively, the low-energy gamma-ray online ash measurement device outperforms the dual-energy gamma-ray online ash analyzer, exhibiting enhanced accuracy and stability in ash measurements, thereby better fulfilling the requirements of daily production.

Gas pressure, in-situ stress and coal strength effects on the evolution process of coal and gas outbursts based on the experimental data

ABSTRACT This paper investigated the effects of gas pressure, in-situ stress, and coal strength on coal and gas outbursts (CGO) based on the laboratory CGO experimental data. Based on the hypothesis of the comprehensive of CGO, the single-factor control variable method was used to analyze and evaluate the relative outburst intensity, the characteristics of outburst holes, the distribution of pulverized coal, the drops of outburst gas pressure, and the pulverized coal density under different outbursts experimental condition. The improved CGO energy equation and instability criterion are proposed as a direction to study the occurrence of CGO as an energy evolution direction. Furthermore, the results shows that the initial outburst gas pressure was 0.45 MPa during the experimental conditions of in-situ stress was 5 MPa, and the coal strength was 0.24 MPa. The gas pressure is directly proportional to the relative outburst intensity, while the in-situ stress and coal strength are inversely proportional to the relative outburst intensity. After the CGO occurred, the outburst coal always show spallation and pulverization characteristics. The results highlight that the gas pressure plays a key role in pulverizing and throwing out the pulverized coal, and the in-situ stress mainly plays a role in destroying the coal, and the coal strength plays a resistance role during the CGO occurs. It is also found that pulverized coal particles size less than 0.28 mm can be used to represent the distribution pattern of the total weight of outburst pulverized coal particles in the different outburst interval. These results clearly illustrate that using effective methods to control gas pressure, in-situ stress, and coal strength has an important role in preventing and controlling CGO on coal mining sites.

Paleotectonic Stress and Present Geostress Fields and Their Implications for Coalbed Methane Exploitation: A Case Study from Dahebian Block, Liupanshui Coalfield, Guizhou, China

The macroscopic structural fractures (joints) and geostress distribution characteristics of coal reservoirs are important factors affecting the exploitation of coalbed methane (CBM). In this study, the joints in the sedimentary strata of the Dahebian block in Liupanshui area, Guizhou Province were investigated. Directional coal samples were collected for observation and statistical analysis of coal microfractures, the paleotectonic stress fields of the study area were reconstructed, and the tectonic evolution was elucidated. The geostress distribution characteristics of the target coal seam (coal seam No. 11, P3l) in the study area were analyzed using the finite element numerical simulation method. The results indicate that the structural evolution of the Dahebian syncline in the study area can be divided into two stages. The Late Jurassic–Early Cretaceous stage (Early Yanshanian) is the first stage. Affected by the sinistral strike slip of the Weining–Ziyun–Luodian (WZL) fault zone, the derived stress field in the study area exhibits maximum principal stress (σ1) in the NEE–SWW direction. The Late Cretaceous stage (Late Yanshanian) is the second stage. Affected by the dextral strike slip of the WZL fault zone, the derived stress field exhibits σ1 in the NNW–SSE direction. The folds and faults formed in the first stage were modified by the structural deformation in the second stage. The dominant strikes of joints in the sedimentary strata are found to be in the NW–NNW (300°–360°) and NE (30°–60°) directions, with dip angles mostly ranging from 60° to 90°. The dominant strikes of coal microfractures are in the NW (285°–304°) and NE (43°–53°) directions. The distribution of geostress in the study area is characterized by high levels of geostress in the syncline center, decreasing towards the surrounding periphery. The overall trend of the geostress contour line is similar to the shape of the syncline and is influenced by folds and faults. The σ1 of coal seam No. 11 is vertical stress. The prediction results show that the joint density of coal seam No. 11 in the block is 36–50 joints/m, and the shape of the joint density contour line is also affected by the axial direction of the Dahebian syncline and the surrounding faults. The variation in coal seam joint density and the control effect of geostress on joints opening or closing affects the permeability of coal reservoirs. The study results provide significant guidance for the exploitation of CBM.

Effect of temperature on thermal properties and residual strength of coal gangue concrete

Key factors for assessing the high-temperature resistance of coal gangue concrete are high-temperature residual strength and thermal properties. The high-temperature residual strength, high-temperature thermal conductivity, high-temperature specific heat capacity, and high-temperature density of concrete with various coal gangue coarse aggregate replacement ratios were tested using experimental methods in this paper to study the high-temperature resistance of coal gangue concrete. Thermal density and high-temperature residual strength tests took into account influencing factors like the water-cement ratio (0.50, 0.45, 0.40), aggregate replacement ratio (0, 25 %, 50 %, 75 %, 100 %), and temperature variation (room temperature, 200 °C，300 °C，400 °C，500 °C，600 °C，700 °C，800 °C), while thermal properties tests considered the effects of various coarse aggregate replacement ratios and temperatures. The study showed that when the temperature rises, coal gangue concrete's thermal density falls, mass loss rises, residual strength declines, thermal conductivity rises, and its specific heat capacity fluctuates. At temperatures between 20 °C and 400 °C, concrete's residual strength decreases with an increase in the coal gangue coarse aggregate replacement ratio, while thermal conductivity and specific heat capacity increase. At temperatures between 500 °C and 800 °C, however, concrete's residual strength slightly improves with an increased coal gangue coarse aggregate replacement ratio, while mass loss changes more. The research finally provides the formulae for calculating the high-temperature residual strength and thermal properties of coal gangue concrete based on the test results.

Study on wettability model of coal particles based on composition

ABSTRACT In order to assess coal floatability, it is necessary to understand how different coal compositions affect particle-wetting behavior. In this study, the influence of different sizes and densities of particles on coal wettability was conducted, respectively. For this purpose, the coal compositions were explored via XRF and the wetting rising velocity experiment of each coal composition was investigated based on the capillary force. The contact angle decreases obviously with the decrease in particle size. The contact angle decreases as the coal particle density increases. The larger the contact angle, the worse the wettability. The coal compositions had a significant effect on the coal-wetting behavior. The content of organic substances decreased with the decrease in powder size. SiO2 had the highest content and the lowest contact angle among the inorganic oxygen-containing. Hydrogen bonds were created between the hydrogen and oxygen atoms on the surface. The stronger the hydrogen bonding force, the more tightly the water molecules adsorbed. Furthermore, the organic content decreased as the coal density increased. The increase in contaminants could be responsible for this phenomenon. The predictive wetting model between the coal compositions and the contact angle was established and its accuracy was evaluated. The predictive model is reliable at larger coal sizes and lower densities due to an average error at 7.2% of 0.35 mm and 10.61% of 1.35 g/cm3. The results provide some valuable insight into the efficient clean utilization of technology and pre-flotation feedback for coal processing.

Non-invasive density and porosity fraction mapping of bituminous coal using ultrasound

The principle of the conventional ultrasound test states that the detectable voids cannot be smaller than the acoustic wavelength. However, by using effective medium approximation, the fraction of small voids can be estimated by the variation of the effective density. In this study, a non-contacting ultrasound-based porosity fraction mapping methodology is developed for estimated small voids in coal with long operating wavelength in air. This novel ultrasonic technique based on the mechanical properties of coal offers a rapid scan of the effective density mapping and distribution of void fraction over a large sample area, which overcame the limitation of small voids detection in the conventional ultrasound testing.

Ignition of Coals with Continuous-Wave Lasers at Wavelengths of 450 and 808 nm

The kinetic and energy characteristics of the ignition of microparticle powders of coals of G (gas), Zh (fat), and K (coking) grades with a bulk density of 0.4 g/cm3 under the action of continuous-wave laser radiation at wavelengths λ = 450 and 808 nm with an exposure time of 1 s were measured. Coals were ignited only under irradiation, and the effect of flame propagation was absent. Ignition delay times were measured as a function of the radiation power density, and the critical values of the coal ignition energy density were determined. Energy consumption for the ignition of coals with radiation at λ = 808 nm was greater than that at λ = 450 nm for all grades of coals. It was established that the absorption of laser radiation by coal samples had a quantum character.

Effect of coal particle density on combustion kinetics of Indian coal

ABSTRACT This work presents the combustion behavior of different mean relative densities (MRD) of Indian thermal coal. Coal of different MRD in the range of 1.25 to 2.20 was prepared using the density separation method. Essential characterization of all MRD fraction coals was done by proximate analysis, ultimate analysis, gross calorific value, BET analysis, and ash analysis. The combustion behavior of all coal samples was carried out by a thermogravimetric analyzer (TGA). Combustion characteristics parameters such as ignition temperature (TIG), peak temperature (Tmax), burnout temperature (TBT) and maximum combustion rate (DTGmax) were evaluated using TGA-DTG data. Results show that with the increase of MRD from 1.25 to 2.20, TIG and Tmax increase from 324°C and 451°C to 426°C and 462°C, respectively, while DTGmax reduces from 9.52 to 1.68 mass%/min. The kinetic analysis demonstrates that coal combustion follows the first-order reaction model and can be separated into two stages. The thermodynamic parameters signify that lighter MRD coal requires lower endothermic energy than heavier MRD coal.

Investigation on the Fragmentation and Outburst Mechanism of Coal Sample with Pore Gas Using CDEM

In this paper, using the continuum-discontinuum element method (CDEM), the fragmentation and outburst process of coal specimen are simulated, and the main factors affecting coal breaking and outburst are explored. The results show that after the coal seam is uncovered, coal generates obvious failure and outburst trend. Near coal-free surface, the fracture coal blocks generate significant displacement, resulting in larger opening widths of coal cracks. Coal deep generates the cracks without an obvious opening width. The crack density of coal with pore gas is larger than those of coal without gas, and it is larger than those of coal without pores. However, in the early stage of coal failure, the obvious separation and outburst ranges of coal with gas are smaller than those of coal without gas, and are smaller than those of coal without pores. The numbers of fracture coal blocks show an increase with the growth of in situ stress, pore ratio and gas pressure. The effect of in situ stress on fracture coal block number (517–10,203) is larger than the effect (7589–15,170) of pore ratio and is larger than the effect (5803–6836) of gas pressure. The effect of in situ stress on a maximum size (0.0387–0.138 m) of fracture blocks is larger than the effect (0.0342–0.0733 m) of pore ratio and is larger than the effect (0.0454–0.0578 m) of gas pressure. The coal outburst velocity and range show an increase with the growth of gas pressure and in situ stress (3.77–5.65 m/s); however, the coal outburst shows a slow decrease with a growth of pore ratio. The effect of gas pressure on the coal outburst velocity (11.51–21.9 m/s) is larger than the effect (3.77–5.65 m/s) of in situ stress and is larger than the effect (4.52–5.23 m/s) of pore ratio. This investigation is beneficial to understand the mechanisms of coal–gas outburst in coal mining and roadway excavation.

Coal bed methane gas in-place estimation for the North-Western region of Zimbabwe

Coal Bed Methane (CBM) is natural gas occurring in coal seams. It can be used for domestic (heating and cooking) and industrial purposes, electricity generation, transportation (as compressed natural gas or liquefied natural gas), and in boilers supporting mining operations. It is established that Zimbabwe has CBM in the North-Western region. At the time of this study, only one organization (Industrial Development Corporation) has reported an Original Gas in Place (OGIP) estimate for the region as 765 Bm3. In this study we use Monte Carlo Simulation (MCS) to estimate the range of OGIP values for the region. MCS is a widely used probabilistic method, preferred over deterministic methods in which only best-estimate values of parameters are used to predict a single OGIP value. This single OGIP value may be either positively (overestimated) or negatively skewed (underestimated). However, the probabilistic approach using MCS accounts for the uncertainty in values of parameters. This is done by incorporating appropriate range and probability distributions (e.g. triangular, normal, uniform, etc.) of input parameters (e.g. target area, formation thickness, coal bulk density, and adsorbed methane content), and repeating calculations to generate a cumulative distribution curve for the OGIP. The generated curve provides statistical confidence levels represented as probability distributions, i.e. P10, P50, and P90 represents low, mid, and high probability estimates, respectively. Our results show that P10, P50, and P90 values for the North-Western region OGIP are 5699 Bm3, 2347 Bm3, and 706 Bm3, respectively. The Resource Density (RD) estimation is found to range from 0.015 Bm3/km2 to 0.113 Bm3/km2 over the geographic area. This range is comparable to Alberta plains shallow and deep basins in Canada which boosts a higher level of confidence for CBM potential in Zimbabwe. The results are encouraging for further exploration and planning of exploitation of CBM in Zimbabwe.

Stamp-Charged Coke-Making Technology—An Empirical Model for Prediction of Coal Charge Density for Stamp Charging Coke Oven Batteries

Coke-making technology utilises two systems for charging the coke oven chambers with coal—a stamp-charged system (stamp-charging) and a gravity charged system (top charging). The presented study examines the impact of selected coal properties on the effectivity of the stamping operation by measuring the bulk density of the obtained stamped coal cake. An empirical mathematical model was developed that allows the forecasting of the coal cake density based on the most frequently assessed coal parameters, such as volatile matter, ash, moisture and particle size parameters, as well as the stamping operation parameter—cumulative stamping energy. The obtained results showed that the density of the stamped coal cake increases with the increase in the stamping energy (53.3 kg/m3 increase, for increase in natural logarithm value of 1), RRSB specific coal particle diameter d′ (6.4 kg/m3 increase, for each 0.1 mm increase in d′), ash content (8.9 kg/m3 increase, for 1% point increase) and moisture content (4 kg/m3 increase, for 1% point increase), and decreases with the increase in volatile matter content (3.82 kg/m3 decrease, for 1% point increase).