Comparison of Flotation and Screening as Separation Method in Coal Recovery From Tailings by Agglomeration

Dependency of Turkey on foreign energy adversely affects the economy of the country and may cause energy shortage in the near future. As a primary domestic energy source, coal is used for energy production in addition to imported oil and gas. However, significantamount of fine coal is lost together with tailings in coal washeries. Recovering of fine coals from these tailings will make an economiccontribution to country. In the present study, fine coals were recovered from tailings of a coal washery in Turkey by using oil agglomeration method. Flotation was used in agglomerate separation stage of oil agglomeration. Results were compared with that of previousstudy in which agglomerates were recovered by screening. The performance of the process increased sharply when flotation was usedinstead of screening in agglomerate separation stage. A clean coal with 28% ash was recovered from the washery tailings containing55% ash by 85% combustible recovery.

Effects of Chemical Properties and Inherent Mineral Matters on Pyrolysis Kinetics of Low-Rank Coals

The kinetics during the pyrolysis process depend on both chemical structure and inherent mineral matters in coal, but normally, only one of these components is investigated in literature. In the present work, four low-rank coals were pyrolyzed in a thermogravimetric analyzer at a heating rate of 10 K/min in a constant nitrogen stream at a temperature up to 900 °C to study the pyrolysis behavior and kinetics. Two of the samples were raw coal (R-YL) and clean coal (C-YL) obtained through the washing process. The results showed that the coal-washing process mainly affected the inorganic part (mineral matters) and structure in coal, which did not largely change the chemical properties. The pyrolysis behavior in primary stage (before 550 °C) was mainly affected by the chemical properties of coal, while the pyrolysis behavior in higher temperature also depended on inherent mineral matters. The kinetics of four coals were obtained using the Coats–Redfern (CR) method with five theoretical models. The difference of E value was almost negligible for R-YL and C-YL, also showing that the coal-washing process did not largely change the chemical properties. The higher frequency factor A for clean coal C-YL showed a more porous structure due to the coal-washing process. The apparent activation energy E in the third stage was affected by the thermodynamic property of inherent minerals.

Enhancement of Flotation Performance of Oxidized Coal by the Mixture of Laurylamine Dipropylene Diamine and Kerosene

Conventional hydrocarbon oil cannot adhere effectively to oxidized coal, resulting in a low yield of clean coal. In this study, a high-speed homogenizer was used to emulsify LDD (laurylamine dipropylene diamine) and kerosene, which enhanced the flotation efficiency of oxidized coal. The flotation results showed an increase from 4.12% (only kerosene) to 23.33% (emulsified oil). An increase in contact angle indicated that the mixture reagent can increase the hydrophobicity of coal particles, which is attributed to the adsorption of LDD onto the coal particle surface and the decrease of the oil droplet A lower surface tension of LDD allows it to produce a stable layer of froth than the layer generated by kerosene alone.

Multi-Attribute Rating METHOD for Selecting a CLEAN COAL Energy Generation Technology

The process of technology management contains various stages, such as the identification, selection, acquisition, implementation, and maintenance of technologies. In the case of power generation companies, a key aspect of the selection stage is the choice of generation technologies for newly commissioned units. The investment decision depends on many factors, primarily economic, environmental, social, technological, and legal, and represents a complex multi-criteria problem. Currently, the decision is further complicated by the often unpredictable tightening of environmental standards, forcing the closure of conventional sources, on which many countries have so far based their energy security. The paper analyzes the problem of choosing one of the so-called clean coal technologies to be implemented in conditions of transformation of the power sector. In this paper, five selected clean coal technologies are characterized, and the SMART method is adopted to technology selection. The following technologies were considered: supercritical coal-fired power plant (with and without CCS), IGCC power plant (with and without CCS), and IGCC power plant with CCS and integrated hydrogen production. Nine practical criteria (in three main groups: environmental, technological, economic) for comparing technologies are defined, computational experiments performed, and conclusions from the research presented. The work was based on the literature study of multi-criteria decision support and an analysis of power sector needs based on the example of the Polish power sector. The conducted research, apart from the technology recommendation, led to the conclusion that the chosen method may be applied to decision-making in the field of power generation technology management. The study also indicated the potential direction of the development of a power generation structure in a situation where a component of ensuring energy security is the use of available coal fuels.

Hybrid inorganic-organic membranes in the service of clean coal technologies

Clean coal technologies (CCT) are all technological solutions that are designed to increase the efficiency of coal combustion, processing and extraction. They are therefore, all the technologies that will help to reduce its environmental nuisance during the production and use of coal and can be introduced at various stages of coal application. Earlier was stated that none of the energy sources (natural gas, crude oil and renewable energy sources), their native resources, the used technologies and the sources of imports are not able to eliminate hard coal from the energy mix of Poland in the near future. That is why the authors began research to create a new clean-coal technology based on the hybrid inorganic-organic membranes, which can be used for elimination of harmful substances generated during coal combustion, especially CO2. This work concerns the study of the inorganic-organic hybrid membranes based on few modified polymer matrices and various inorganic fillers. It was found that incorporation of zeolite 4A into the polymer matrix had significantly changed the gas transport parameters (D, P, S and α). In turn, the mechanical (Rm and E) parameters have increased with the filler content. The application allows the initial selection of ingredients from which the final membrane will be created. The designed technology does not require high financial expenditures, and it is also highly universal. It can be used both in households, heating plants and, above all, in power plants.

New Approach Study on Dry Coal Cleaning System with Two-Stage Corona Electrostatic Processes for High-Sulfur Low-Grade Fine Coals

Corona electrostatic separation can remove inorganic materials from coal, reduce coal ash content and sulfur content and improve coal quality, reduce air pollution caused by smoke dust, SOX, and COX. The performance of corona electrostatic separation technology in cleaning a middle ash medium-ash, high-sulfur coal was experimentally investigated. The electrode voltage, drum rotational speed, and feeding speed were tested, whereas other parameters were maintained constant during the experiment. The results indicate that the performance of this technology in cleaning medium-ash, high-sulfur coal can be improved by optimizing the process parameters. The results demonstrate that corona electrostatic separation is effective for the beneficiation of this grade coal. In addition, the efficiency of coal cleaning is significantly improved by adding the second stage beneficiation to clean the middlings out from the first stage beneficiation. In this study, the first stage of beneficiation recovered 38.00% (by weight) of clean coal (ash content below 20%), and the second stage recovered 48.58% (by weight) of clean coal, improving the overall separation efficiency from 0.69 to 1.74. Furthermore, the sulfur content was reduced from 4.71% (raw coal) to 3.53% (clean coal). Our result show that corona electrostatic separation can effectively reject inorganic sulfur from raw coal, and the two-stage separate is also very helpful for coal purification.

Effects of organic sulfur on oxidation spontaneous combustion characteristics of coking coal

Research on the spontaneous combustion of coal caused by sulfur has always been focused on pyrite in coal but has rarely considered the influence of organic sulfur. In this paper, coal samples, rather than model compounds, were used to study the influence of organic sulfur content in coal on its spontaneous combustion process. The results of X-ray photoelectron spectroscopy and thermogravimetry, differential scanning calorimetry, and mass spectrometry indicate that organic sulfur in Shuiyu clean coal exists in forms of mercaptan, thioether, sulfone (sulfoxide), and thiophene. With the decrease of organic sulfur content, the characteristic temperature points and the peak values of the exothermic curves in the process of coal oxidation spontaneous combustion all shifted toward higher temperatures. The ignition activation energy of coal also increased, and the initial and peak gas evolution temperatures of the oxidation products shifted toward higher temperatures. These findings suggest that the reduction of organic sulfur content can inhibit the oxidation process and spontaneous combustion tendency of coal. This effectively reveals the mechanism of the spontaneous combustion of coal and is of great significance to future studies in this field.