• Energy Research

Abstract Derived and discussed are empirical relationships that describe dependencies of the true density and yield of coal chars on carbonization temperature in the 550–1000°C range. They include formulae for the determination of mass and true density changes with temperature for both organic matter and mineral matter in the coal chars. The relationships are based on results of investigations of laboratory-scale made coal chars under comparable conditions to industrial-scale carbonization processes and, therefore, should also be valid for coke products. Additionally, technological parameters such as a bulk density of coal blend and specifics of grinding process are found not to influence significantly the true density and yield of the coal chars.

This paper presents investigative results of the energy efficiency of hot water production for sanitary uses by means of gas-fired water heaters with the combustion chamber sealed with respect to the room in single-family houses and multi-story buildings. Additionally, calculations were made of the influence of pre-heating the air for combustion in the chimney and air supply system on the energy efficiency of hot water production. CFD (Computational Fluid Dynamics) software was used for calculation of the heat exchange in this kind of system. The studies and calculations have shown that the use of gas water heaters with a combustion chamber sealed with respect to the room significantly increases the efficiency of hot water production when compared to traditional heaters. It has also been proven that the pre-heating of combustion air in concentric chimney and air supply ducts essentially improves the energy efficiency of gas appliances for hot water production.

Passive methods, which are used for the purification of flue gases, can often be insufficient in the case of the emission of mercury and other ecotoxic elements into the environment. Therefore, it may often be necessary to introduce additional methods of reducing the emission of these pollutants, for example, the injection of powdered activated carbon or coke dust into flue gas ducts. The efficiency of coke dust has been confirmed by tests in the laboratory and a demo plant scale. In accordance with the proposed solution, coke dust is dosed before the electrostatic precipitator and then separated fully along with fly ashes. Before injection, coke dust contains negligible amounts of mercury (4.8–10.5 μgHg/kg, depending upon the size of the fraction), which is a value several times lower than the Hg content in sub-bituminous coals and lignites. However, it can also be a carrier of other ecotoxic elements, such as nickel and chromium. Their contents in coke dust are often much higher than in coal used for po...

During the cokemaking process, a significant amount of mercury occurring in a coal blend is released to the atmosphere. One of the ways of reducing this emission is to reduce mercury content in a coal blend. This could be obtained through the coal washing process. The optimization of this process requires the knowledge of mercury occurrence in coal, especially in its inorganic constituents. A qualitative analysis of mercury occurrence in the inorganic constituents of Polish coking coals was performed using an electron probe microanalyzer (EPMA). For that purpose, selected samples of rejects and middling products derived from the washing process in dense media separators and jig concentrators were examined. The obtained results have confirmed a strong connection between mercury occurrence and the presence of sulfides (pyrite, marcasite, and chalcopyrite) in Polish coking coals. Significant amounts of mercury were also noticed for barite, siderite, and aluminosilicates. The highest value of mercury content, at the level of 0.100%, was obtained for marcasite. For the analyzed coals, the effectiveness of mercury removal in the washing process was determined by the forms of pyrite occurring in coal. The highest values of effectiveness of mercury removal were obtained in the case of coals for which the large framboidal pyrite aggregates with chalcopyrite overgrowths were noticed. It was also found that middling products were characterized by the occurrence of the Hg-rich overgrowths of pyrite on organic matter. To achieve a significant reduction in mercury content in clean coal, it is necessary to develop an effective method of removing this form of pyrite from hard coal.

Coke is an integral component of the blast furnace charge; therefore, it plays an important role in the integrated steelmaking process. Achieving the required coke quality parameters by producers requires the use of a high proportion of the highest quality coking coals (hard coking coals) in the coking blends, which significantly increases the unit production costs. Approximately 75% of these costs are constituted by the cost of the coal blend’s preparation. There is a deficit in the best quality coking coals on the world market and their supply are characterized by large fluctuations in quality parameters. Therefore, from the point of view of the economics of coke production, it is advantageous to produce high-quality coke from a coke blend with the highest possible content of cheaper coals. The paper presents the results of the influence of coal charge bulk density and semi-soft coking coal content in the coking blend on the textural and structural parameters of coke, which determine its quality. Research has shown that the application of increased density influences the parameters of the texture and structure of the coke, which shape its quality parameters. The use of stamp-charging technology contributes to the improvement of the coke quality or enables the production of coke of a predetermined quality from blends containing cheaper semi-soft coals.

Abstract In recent years, the literature on HVAC has been predominantly devoted to the problems of increasing the efficiency of buildings, reduction of CO2 emission or ensuring user-friendly indoor air quality. However, in many countries, including Poland, ensuring safety for the users of gas appliances is a key issue. That particularly concerns the gas-fired water heaters with open combustion chamber (Type B). The problem can be solved by replacing the traditional heaters with combustion chamber sealed with respect to the room (Type C) equipped with air supply and combustion product ducts systems. Two pilot plants were built, corresponding with the conditions of a typical Polish multi-storey residential building. During the designing process, the CFD Fluent software was used, making it possible to optimally select the dimensions and configuration of the tested plants. The tests were conducted for different operation variants, during which the appropriate functioning of the appliances was evaluated as well as the energy efficiency of hot water production. Moreover, selected ways of enhancing the operation of such appliances as well as the impact of wind on their work were examined. The experimental results presented in the paper should make it easier to implement gas-fired instantaneous water heaters Type C, particularly in the already-existing multi-storey residential buildings.

The aim of the study was to evaluate the content, occurrence, and leachability of arsenic (As), lead (Pb), and thallium (Tl) in wastes from coal cleaning processes with respect to the safe management of this waste. The study focused on wastes resulting from the wet gravitation and flotation processes employed for the purposes of coking coal cleaning in four coal mines situated in the Upper Silesian Coal Basin (Poland). The scope of the study included (i) determination of the content of these elements in the investigated wastes using atomic absorption spectrometry, (ii) evaluation of their mode of occurrence using electron microprobe analysis, and (iii) preliminary assessment of their leachability in deionized water. The content of the analyzed elements in the examined samples of coal waste was twice as high as the average content of these elements in the Earth's crust. The contents of As and Pb, however, did not exceed their permissible contents in inert waste in accordance with Polish legal regulations based on EU directives. The limit on the content of Tl is not specified by these regulations, but its amount in the examined samples was similar to that occurring in the soils. Moreover, leaching tests have shown that these elements are hardly eluted from the analyzed material. Their content in the water leachates was generally lower than the detection limit of the analytical method, complying with the standards for good and very good water quality. Low leachability of these elements most probably results from their mode of occurrence in the investigated wastes. The chemical analysis using an electron microprobe and the analysis of the correlation between these elements, e.g., total and pyritic sulfur, have shown that Pb, As, and Tl are mainly found in sulfide minerals which are characterized by negligible solubility. In conclusion, the investigated hard coal processing waste does not constitute a threat to the environment and can be commercially used or safely neutralized, e.g., by landfilling.

Abstract Equations are derived for calculation of real density and total pore volume of hard coals from their ultimate and proximate analyses. Generalized solutions are obtained for organic matter and mineral matter contents in coals. In the case of organic matter a simplified structural model of coal is utilized. Coefficients and final mathematical expressions are determined by application of statistical methods.