Coal Preparation Plant Research Articles

Технология очистки и утилизации поверхностных сточных вод и осадков

Одной из основных экологических проблем является сбор, транспортировка и очистка поверхностных сточных вод. Большинство существующих систем отвода и очистки поверхностных сточных вод уже не справляются с увеличивающимся объёмом стоков или физически изношены. Основными источниками загрязнения поверхностных сточных вод являются продукты смыва почвенного покрова, разрушения асфальтовых и бетонных поверхностей, истирания автомобильных шин, проливы автотоплива и масел, а также строительные и другие материалы, складируемые на открытых площадках хранения. Поверхностные сточные воды загрязняют водоёмы взвешенными, поверхностно-активными веществами, нефтепродуктами, органическими примесями, ионами тяжёлых металлов и другими загрязнителями. Осадки приводят к загрязнению и заилению русел водотоков, нарушают жизнедеятельность живых организмов, микроорганизмов, оказывают негативное влияние на биоценоз и самоочищающую способность водоёмов.
 В статье описывается исследование, целью которого являлась разработка технологии очистки поверхностных сточных вод предприятий угольной промышленности с использованием нового сооружения фильтрования воды - реактора-осветлителя. Экспериментальные исследования проводились в производственных условиях на обогатительной фабрике в Новосибирске. Пилотная установка являлась моделью очистных сооружений ливневых и талых сточных вод предприятия. Изучен состав поверхностных сточных вод предприятия угольной промышленности, разработан проект новой установки очистки сточных вод - реактора-осветлителя. Реагентная очистка ливневой воды проводилась в отстойнике с использованием оксихлорида алюминия в качестве коагулянта. Затем воду осветляли в слое мелкозернистого взвешенной контактной загрузки реактора-осветлителя в скором фильтре, загруженном горелой породой, и на угольном фильтре. Качество очищенной воды соответствовало предъявляемым требованиям. В результате теоретических и экспериментальных исследований была разработана технология очистки ливневых сточных вод промышленных предприятий, которая позволяет сбрасывать их в открытые водоёмы или использовать для утилизации и технического водоснабжения предприятий.

Audio-based fault diagnosis for belt conveyor rollers

In order to monitor the roller states online running on the belt conveyor, one class of fault diagnosis systems based on audio is studied in this paper. Firstly, the audio data is collected from the belt conveyor by sensors, which is analyzed using the stacked sparse encoders and convolutional neural network. Secondly, the fault features are extracted from the audio data by using spectral clustering algorithm. Finally, a real fault diagnosis system is applied on the belt conveyor working in the coal preparation plant. The running result shows that the fault diagnosis system works very well for rollers fault detection with the accuracy rate 96.7%.

Study on noise characteristics of a novel equal-thickness screen

As the key unit in coal preparation and utilization, equal-thickness screens characterized by a large capacity and high efficiency have been extensively applied in coal preparation plants. Recently, the noise pollution caused by the screening of coal has become more and more serious. Reducing the noise of vibrating screens is the key to control the noise of coal preparation plants. In this article, the noise test system was used to measure three-dimensional (3D) sound intensity of the equal-thickness screen. According to the analysis of sound intensity distribution and spectral coherence, the main sources of noise were identified. The main sources of noise of equal-thickness screen were vibration motors, side panel, screen surface and damping supports. A displacement model was fitted to the experimental data, and the kinematics of the sieve body was studied. The results showed that the amplitude of the sieve body decreased as the distance from the feeding end (towards the discharge end). Similarly, the intensity of the noise decreased about 2 dB in the same direction (from the feeding end to discharge end). However, in the direction perpendicular to the movement of the material, the noise distribution was symmetrical. Finally, various noise reduction measures were also put forth. It could be seen that when the composite spring was adopted as the damping support and the structures of vibration motors, screen surface and side panel were changed, the noise could be effectively reduced.

Spatially Allocating Life Cycle Water Use for US Coal‐Fired Electricity across Producers, Generators, and Consumers

There are water consequences across every life cycle stage of coal‐fired electricity consumption, from production and processing to combustion, which have not been studied with regional specificity. There is often a spatial decoupling between where coal is produced and processed versus where it is combusted for power generation, complicating any analysis to estimate the life cycle water implications of electricity consumption. Furthermore, electricity generated by coal‐fired power plants can be consumed within its own balancing authority or exported to another balancing authority. This analysis spatially resolves the water consumed and water withdrawn for coal mining, coal preparation, and power plant cooling from 1) where the coal is mined to where the coal is burned for power production and 2) where the electricity is generated to where the electricity is consumed. Although the largest portion of coal consumed came from the Northern Great Plains province, coal from this region consumes the least amount of water for mining and preparation compared with other provinces. Water withdrawals for cooling power plants within each balancing authority are driven by cooling technology. Due to the interconnected grid, there can be differences between attributing water footprint at the producer level versus the consumer level.

Long-term leaching characteristic study of coal processing waste streams

A study of the mobility of major and potentially hazardous trace elements from coal processing waste materials was conducted using two types of leaching tests. The baseline leaching test simulates stable waste storage under water, whereas the kinetic test models the storage of waste under more variable conditions including intermittent exposure to air and variations in humidity. Coarse and fine refuse materials were obtained from three commercial coal preparation plants that were being used to upgrade US bituminous run-of-mine coal containing low-to-high amounts of pyritic sulfur. X-ray diffraction analyses revealed a large variation in mineralogy between the coarse and fine refuse streams due to the mineral fractionation that occurs in the processing units and plant. The coarse refuse samples contained higher pyrite contents while the fine refuse samples had high clay content and a minor amount of calcite. This variation in mineralogy resulted in relatively large difference in the leaching characteristics of the waste streams. The most acidic pH and highest release of trace elements were observed in the leachate of coarse refuse containing medium-to-high amounts of coal pyrite, while the fine refuse samples released lower amounts of trace elements in their circumneutral leachate. The least amount of trace elements was observed in the leachate of low pyritic refuse streams. The test data suggested that the most effective disposal practice for coal waste material is segregation and isolation of the coal pyrite and co-disposal of the coarse and fine refuse streams.

Rapid detection of the total moisture content of coal fine by low-field nuclear magnetic resonance

Coal total moisture content has an observable influence on its calorific value. In this investigation, a rapid detection method of total moisture of coal fine through 1H low-field nuclear magnetic resonance (LF-NMR) was proposed. The first peak point value and total signal amplitude analyzed by T2 spectrum were used to fit with the total moisture content of coal. The first peak point value and total signal amplitude increased as the total moisture content of coal increased. The fitting results of both first peak point value and total signal amplitude to the total moisture content of coal agreed with the second-order linear equation best. The first peak point value had higher prediction accuracy than the total signal amplitude and hence it is used preferentially to predict coal moisture content. This method provides a new and effective tool for online detecting the moisture content of coal in the coal preparation plant.

Study on ultrasonic-electrochemical treatment for difficult-to-settle slime water.

The treatment of slime water not only has a direct impact on the economic benefits of the coal preparation plant, but also has an important significance for the conservation and utilization of the environment and water resources in the mining area. However, under the background of increasing mechanization level of coal mining, the proportion of fine coal is increasing, and the slime water exhibits fine, high and sticky characteristics in terms of particle size, ash, and viscosity, making it difficult for the slime water to settle. In this paper, research on the treatment of difficult-to-settle slime water by ultrasound-electrochemistry is investigated. The principle of the ultrasonic-electrochemical method for treating difficult-to-settle slime water is discussed. The effects of electrodes, electrolytes, ultrasonic energy density and ultrasonic time on treatment of difficult-to-settle slime water are analyzed. Results show that ultrasound-electrochemical pretreatment for difficult-to-settle slime water is not a simple superposition of the two treatment methods, and ultrasound can promote the electrochemical reaction. The optimal ultrasonic parameters are given: ultrasonic frequency, energy density and ultrasonic time are 29kHz, 0.5W/m3 and 4min respectively. Based on the basic properties of the micro-charge on the surface of coal particles, the flocculation sedimentation can be promoted effectively by the combination of sonochemical and electrochemical methods. Finally, the research status of the new treatment technology for difficult-to-settle slime water is discussed, and the development trend is pointed out.

Designing coal preparation circuit for cleaning high ash and high sulfur Punjab (Pakistan) coal to meet end-user requirements

ABSTRACT Modern coal preparation plants are designed to achieve maximum overall clean coal yield with an acceptable amount of impurities to meet end-user requirements. LIMN is commonly used to design and simulate coal processing circuits based on size and density distribution data of coal. In this study, particle distribution data for size, density, and floatability were established for Punjab coal after crushing it to 38 mm. Punjab coal contains high amounts of ash (34.70%) and sulfur (8.34%). Float-sink tests conducted on several size fractions disclosed that 16% target ash could be achieved at an overall yield of 63% with ash and sulfur rejection values in the range of 72.63–94.18% and 73.01–88.45%, respectively. However, the sulfur limit of 1.0% would be difficult to meet. Dell release analysis performed on – 0.25 mm fraction revealed poor flotation response of Punjab coal. Several process flowsheets were designed and simulated using LIMN to generate data for yield, ash and sulfur. End-User Beneficiation Number (EBN) was introduced and utilized for determining the best processing option that can provide maximum yield while meeting the quality requirements of the end-user. Economic analysis involving CAPEX, OPEX, and payback period validated the merit of EBN.

EDEM技术在选煤厂转载点溜槽设计中的应用

EDEM技术在选煤厂转载点溜槽设计中的应用

Optimizing the tensile strength of concrete containing coal waste considering the cost

Nowadays, removal of the waste from industrial activities is one of the serious problems in the world. Contrarily, needing the development of industrial construction and reduce its costs, with considering the construction quality, are the main priorities of progress. Therefore, in this paper, for the first time, all these issues are considered related to using the waste of coal extraction; also, the application of coal wash rejects in the concrete manufacture and its impact on tensile strength of concrete have been investigated. To this goal, coal waste was prepared from the Central Alborz Coal Preparation Plant in northern Iran. Designing the experiments by the response surface methodology (RSM), the influence of parameters like water/cement (0.4–0.6), cement content (305–445 kg/m3), aggregate volume (0.4–0.6%) and coal waste (0.5–9.75%) on the tensile strength to cost of concrete construction were evaluated. Presenting the model, optimizing and investigating the individual, reciprocal and simultaneous effects of independent variables on the tensile strength to cost of concrete by RSM were conducted for the first time. Based on the results of tensile strength tests and estimating the cost of concrete construction, the highest ratio of tensile strength to cost was obtained by using the cement content of 340 kg/m3, water/cement of 0.45, gravel volume of 0.55% and coal waste of 7.5%. In this case, the response value was 1.29E−6 MPa/USD. These results indicate the high potential of these wastes in the production of concrete in terms of tensile strength and also economic aspect.

Flocculation and sedimentation characteristic of coal slurry in coal preparation plant

Flocculation sedimentation test was carried out on the coal slurry of the selected coal preparation plant. A mathematical correlation model of initial settling velocity, upper clarification turbidity and sediment volume with various influencing factors was established. The results show that: the initial settling velocity increases first and then decreases with the increase of flocculant concentration; when the flocculant concentration is 10g/m3, the initial settling velocity is the largest; the initial settling velocity increases with the increase of the mass ratio of coagulant and flocculant. The upper clarification turbidity decreases first and then increases with the increase of the flocculant concentration; when the flocculant concentration is 10g/m3, the supernatant has the lowest turbidity; the upper clarification turbidity decreases with the increase of the mass ratio of coagulant and flocculant. The volume of sediment increases with the increase of flocculant concentration, and increases with the increase of mass ratio of coagulant and flocculant.

The Use of Pyrite Concentrate and Waste Formed at the Brown Coals Enlargement

The work is devoted to an important environmental and economic problem: the enrichment formed wastes recycling and brown coal processing. If pyrite sulfur (pyrites) is extracted from high-sulfur coal before it is burned, the negative impact on the environment is reduced (sulfur dioxide emissions reduction into atmospheric air) and, as a result, environmental payments, as well as the possibility of obtaining sulfuric acid from pyrite. Waste coal preparation plants can be used in the building materials production (ceramics, cements, concrete aggregates), in the hydraulic structures construction, as well as with the purpose of improving the soil fertility in agriculture.

Rare Earth Elements and Yttrium (REY) in coal mine drainage from the Illinois Basin, USA

The ever-growing demand in the USA and in the modern economy for rare earth elements, defined here as the lanthanide elements plus yttrium (REY), motivates the development of economically feasible and environmentally friendly approaches for domestic REY resources. Non-conventional sources, including coal mine drainage (CMD) hosting elevated concentrations of REY, have been explored as attractive secondary sources for metals recovery. Consequently, in this study we investigate CMD from abandoned coal mines in the Illinois Basin as a potential REY resource.We collected CMD from 35 abandoned coal mine sites in the Illinois Basin and investigated trends in REY enrichment and their association with CMD geochemical characteristics, including pH, the presence of other chemical elements of economic significance (i.e., Zn, Ni, Cr, Cu, V) as well as spatial patterns in relation to Permian magmatic intrusions of the Hicks Dome, a potential source of REY in the Illinois Basin. Additionally, the REY contents in possible source rocks for Illinois CMD were measured including coal from an underground mine and coal preparation plant in southern Illinois, mafic igneous rocks associated with Hicks Dome, and hydrothermal fluorite from Illinois fluorspar district.The REY concentrations in samples of CMD (filtered fraction) and associated coal and non-coal solids were determined by ICP-MS. The total concentration of REY in CMD, ΣREYCMD varied between 1 and 9879 μg/L with an average of 1059 μg/L and critical-ΣREYCMD (Nd, Eu, Tb, Dy, and Y) varied between 0.3 and 7212.5 μg/L with an average of 611 μg/L. Basin-wide, we found no statistical correlation between ΣREYCMD and (1) pH of the CMD, or (2) proximity to the Permian magmatic intrusion at Hicks Dome in southern Illinois. The REYCMD values normalized to North American Shale Composite (NASC) REYCMD/REYNASC exhibit enrichments in middle-REY for all CMD, but also enrichments in light-REY in some CMD. Statistically, we observed that ΣREYCMD displays significant direct correlations with Al, Si, SO4, Zn, Ni, Co, and Cu and no-correlation with Fe, Ca, PO4, Ba, and V.Synthesis of the geochemical data suggests that coal mining sites with the highest ΣREYCMD and critical-ΣREY contents include non-coal bedrock dominated by silicates (high clay content) and coal mine wastes that were impacted by metal-rich hydrothermal solutions, which are predominantly located along the western and northern margins of the Illinois Basin. Particularly, sites with the highest hydrothermal input as approximated by Mississippi Valley-type mineralization (i.e., Zn contents) are prime candidates for REY, as well as other elements of potential economic value such as Al, Ni, Cr, V, and Co. Thus, CMD in the Illinois Basin could become a potential alternative domestic source of extractable REY, especially critical-ΣREY, as well economically valuable metals.

Combustion of Wet Coal Processing Waste and Coal Slime as Components of Fuel Slurries

ABSTRACT Coal processing waste is generated annually in large volumes by the coal exporting countries. More than 70% of run-of-mine coal is enriched. At the same time, typical coal processing waste (slime, flotation waste, mid-coal and tailings) make up at least 10–15% of the raw coal mass. Approximately 220–300 million tons of coal processing waste is generated annually at coal-preparation plants in Russia and China. The results of experimental researches in recent years illustrate the growing interest in such wastes as promising energy components. In this paper, we performed a comparative analysis of the main physical properties, ignition and combustion characteristics of several types of coal processing waste. The comparison is made for typical flotation waste (filter cakes or coal slime) generated in Russia and China. It is shown that for wastes from different countries the ignition delay times differ by no more than 50% and the heat of combustion by 9–15%. Concentrations of main anthropogenic emissions were determined. Generalization is made using criterion expressions to illustrate the advantages and disadvantages of coal processing waste incineration in comparison with pulverized coal combustion.

Optimization of Coal Washery Tailings by Flotation Process

Flotation tailings are by-products of coal preparation plants, which do not only occupy cultivated land but also cause pollution. The high ash content and low calorific value of tailings limit their applications. Deashing is the precondition for the reutilization of flotation tailings. However, it is more difficult to remove ash content from flotation tailings compared with raw coal. Based on the analysis of coal properties, the flotation performance of different collectors was compared in this study. Flotation flows and the mechanism of depressants were explored. The optimized flotation conditions were as follows: pulp concentration of 100 g/L, inflation rate of 0.25 m3/(m2·min), collector (C4) dosage of 300 g/t, frother dosage of 500 g/t, and revolving speed of 2200 rpm. The ash content of clean coal was also reduced by adding a depressant. The flotation performance was best when the amount of sodium hexametaphosphate (used as the depressant) was 4 kg/t; the recovery of clean coal was 71.88%, and the ash content was 10.64%.

Коэффициент полезного действия неэкранированных топок многотоннажных газовых сушильных установок углеобогатительных фабрик

Коэффициент полезного действия неэкранированных топок многотоннажных газовых сушильных установок углеобогатительных фабрик

Comparative Response on Flotation of Coal by Using Process and De-Ionized Water

ABSTRACT Recycling of the process water is an essential aspect for the mineral and coal processing industries to address the challenges on the sustainability of the environment. In this study, the influence of dissolved ions presents in the process water of an Indian coal preparation plant is investigated on flotation behavior of coal by a combination of release analysis, batch flotation tests, dynamic froth stability measurements, surface tension measurements, contact angle measurements, zeta potential measurements, and Fourier-transform infrared spectroscopy measurements. Also, comparison studies are conducted with de-ionized water to float the same coal for the evaluation.

A Field Survey of Rare Earth Element Concentrations in Process Streams Produced by Coal Preparation Plants in the Eastern USA

A field study was undertaken to experimentally measure the concentrations of rare earth elements (REEs) contained in the process streams generated by a group of 20 coal preparation plants located in the eastern USA. For each site, representative samples of clean coal product, coarse refuse, and fine refuse were collected. Each sample was then partitioned into preselected size and density classes by wet screening/sieving and float-sink testing. The resultant products were dried and subjected to laboratory analyses to determine ash contents and rare earth element concentrations including Yttrium and Scandium. A detailed analysis of the database generated by this exercise showed that coal-based products from these preparation plants contained significant quantities of rare earth elements. In particular, the coarse refuse streams currently discarded by the 20 plants examined were found to contain a sufficient tonnage of REEs to satisfy the current domestic demand for these important elements. The data also showed a strong positive correlation between ash content and REE concentration, which suggested that the primary association of REEs in eastern USA bituminous coal sources is likely within fractions containing inorganic impurities. This association was well described using a simple power equation relating ash content and REE concentration. The ratio of heavy-to-light rare earth elements was discovered to be significantly higher in organically rich fractions of clean coal, suggesting that mineral impurities intimately associated with carbonaceous matter have elevated concentrations of heavy rare earth elements. A similar trend was observed for a grouping of rare earth elements (Y, Nd, Eu, Tb, and Dy) that are likely subject to near-term supply shortages. Finally, the database showed that a linear correlation existed between La for many REEs of interest, although there were several notable exceptions for some high-value REEs (Lu, Pr, and Tb).

Separation performance of flotation column with dilution water in pulp zone

ABSTRACT Flotation columns show a good separation performance for fine coal slime and have been widely used in coal preparation plants. In this study, to reduce the ash content of the concentrate, dilution water was added to the pulp zone of the flotation column. Tailings discharge was also correspondingly increased to ensure the balance of coal pulp in the flotation column. The results indicate that ash content and yield of concentrate decrease with the increasing dilution water. The flotation efficiency index increases initially and then decreases as the rate of dilution water increases, and the highest flotation efficiency index is obtained at a dilution water rate of 0.18 cm/s, this indicates that appropriate addition of dilution water in the pulp zone improves the separation performance of the flotation column. In addition, the closer the dilution water is to the bottom of the flotation column, the better the separation performance of the flotation column becomes. Moreover, compared with a conventional flotation column with a feed pulp concentration of 40 g/L, the flotation column with dilution water has a similar pulp concentration in the pulp zone and shows a better separation performance.

Design of intelligent ratio control system for raw coal in coal preparation plant

Design of intelligent ratio control system for raw coal in coal preparation plant