The coal fed to gravity enrichment consists of coals coming from different deposits and exploitation fronts. These coals differ in quality parameters, especially the amount of gangue (stone) changing over time. This results in the instability of work, especially jiggers, which have a relatively low accuracy assessed by probable scattering or imperfection rates. This deteriorates the quality of the concentrate obtained, the quality parameters of which change over time. The improvement of jiggers work would be possible by averaging the feed. This process is practically impossible due to the failure to design such a node during plant construction, which are, in most cases, directly related to the shaft. In the article, the authors propose to solve the process of averaging the feed before directing it to the enrichment process in jiggers by introducing its deshaling in vibratory- air separators of the FGX type.
The article presents current state of the structure of hard coal enrichment plants in Poland, taking the capacity, the range of grain enrichment and the type of equipment used into account. This data were presented in a tabular format for each Polish Coal Company operating on the Polish market. The article was also present simplified: flow sheet of the steam and coking coal enrichment system. Based on the presented data, the planned needs and trends were described in terms of increasing production efficiency, minimizing water consumption and safety of work. A list of research and development works which must be undertaken were also presented as well as factors determining the technological development of the processing plants.
Work is being carried out on possibilities of limiting the content of mercury in hard coal products by gravity concentration of run-of-mine coal in the Branch of the Institute of Mechanized Construction and Rock Mining in Katowice and on the Faculty of Energy and Fuels of the AGH University of Science and Technology in Krakow. Under domestic industrial conditions, gravity concentration is carried out with heavy medium liquids and in jigs. Preliminary - pilot studies have shown the possibility of mercury removal also by using the dry deshaling method involving vibratory air separators. Mercury is mainly found in the pyrite and the rubble formed by the mineral carbon, but also in the organic carbon. Some of it is located in layers of coal roof fields, which in the course of their exploitation go to coal. The mercury removal efficiency during the gravity concentration process will depend on the decomposition of the listed components in the density fractions. The paper presents the results of investigations of total mercury and total sulphur content in the separated coal fractions from four mines. These contents were determined in fractions: –1.5 g/cm3 (conventionally clean coal – concentrate), 1.5–1.8 g/cm3 (conventionally middlings) and +1.8 g/cm3 (conventionally rock – waste). The results are summarized in Tables 3–5 and in Charts 1–4. Conversely, graphs 5-8 show the relationship between mercury content and total sulphur content in the tested coal samples. The study, which can be called a preliminary analysis of the susceptibility of the coals to gravity concentration, showed that the dry deshaling method on the vibratory air separators would allow significant amounts of mercury accumulated in the middlings and waste fractions to be removed.
Nowadays, actions allowing for a reduction of anthropogenic mercury emission are taken worldwide. Great emphasis is placed on reducing mercury emission from the processes of energochemical coal conversion, mainly from the coal combustion processes. One of the methods which enable a reduction of anthropogenic mercury emission is the removal of mercury from coal before its conversion. It should be pointed out that mercury in hard coal may occur both in the organic and mineral matter. Therefore, a universal method should allow for the removal of mercury, combined in both ways, from coal. In the paper, a concept of the hybrid mercury removal process from hard coal was presented. The idea of the process is based on the combination of the coal cleaning process using wet or dry methods (first stage) and the thermal pretreatment process at a temperature in the range from 200 to 400 °C (second stage). In the first stage, a part of mercury occurring in the mineral matter is removed. In the second stage, a part of mercury occurring in the organic matter as well as in some inorganic constituents characterized by a relatively low temperature of mercury release is removed. Based on the results of the preliminary research, the effectiveness of the decrease in mercury content in coal in the hybrid process was estimated in the range from 36 to 75% with the average at the level of 58%. The effect of the decrease in mercury content in coal is much more significant when mercury content is referred to a low heating value of coal. So determined, the effectiveness was estimated in the range from 36 to 75% with the average at the level of 58%.
Węgiel kamienny wydobywany w kopalni (węgiel surowy) tworzy substancja organiczna i mineralna. Przed bezpośrednim wykorzystaniem urobek musi być poddany procesom wzbogacania. Stosowane procesy wzbogacania mają na celu usunięcie skały płonnej, pirytu, a także przerostów. Do wzbogacania węgla kamiennego stosowane mogą być zarówno metody wzbogacania na mokro, jak i na sucho. W pracy przedstawiono wybrane ekologiczne i ekonomiczne aspekty procesu suchego odkamieniania węgla kamiennego przy wykorzystaniu separatora powietrzno-wibracyjnego i separatora optyczno-rentgenowskiego. Zastosowanie nowoczesnych urządzeń do suchego odkamieniania, tj. separatory powietrzno-wibracyjne i separatory optyczno-rentgenowskie, umożliwią obniżenie emisji pierwiastków ekotoksycznych ze spalania węgla kamiennego. Wydzielenie pirytu pozwala na obniżenie zawartości siarki, a także innych pierwiastków ekotoksycznych, m.in. rtęci, arsenu, talu, czy ołowiu. Generalnie pod względem ekonomicznym technologia suchego odkamieniania cechuje się niższymi nakładami inwestycyjnymi i kosztami eksploatacyjnymi w porównaniu do metod wzbogacania na mokro. Instalacje suchego odkamieniania są dobrym rozwiązaniem dla inwestycji o krótkim okresie planowanej eksploatacji i/lub dla instalacji o małej wydajności, a także w przypadku ograniczonej dostępności do wody. Dla instalacji o dłuższym okresie eksploatacji i o wyższych wydajnościach, efektywność inwestycji jest wyższa dla metod wzbogacania na mokro. Istnieje również możliwość suchego odkamieniania węgla na dole w kopalni przy użyciu tzw. kruszarek Bradforda. Wydzielony produkt w postaci grubych kamieni może znaleźć zagospodarowanie na dole kopalni, np. do podsadzania wyrobisk.