Bazı Türk linyitlerinin mineral içerikleri

Abstract

Kömürün mineral madde veya inorganik bileşenleri, kömürün organik yapısının parçası olmayan elementlerin toplamı dır, içerdiği mineral madde kömürün üretimini, hazırlanmasını ve kullanımını etkiler. Kullanılan kömürün mineral maddesinin bileşimi ve miktarı; koklaştırma, gazlaştırma, sıvılaştırma ve yakma süreçlerinin başarısını belirleyici rol oynar. Bu çalışmada, Türkiye'nin 25 değişik yöresinden toplanmış olan linyit kömürlerinin mineral maddeleri araştırılmıştır. Linyit numunelerinin, toplam mineral madde ve kül içerikleri kullanılarak, "mineral madde faktörleri" belirlenmiştir. Kömürlerin organik kısımları performik asit ile oksitlenerek uzaklaştırılmış ve izole edilen mineraller x- ışınları tekniği ile analiz edilmiştir. Kömürün mineral maddesi içinde bulunabilen birçok bileşik performik asitten etkilenmeden yapısını korumuş ve analiz sonucunda saptanabilmiştir.

Mineral matter is generally considered to be the sum of all inorganic minerals (discrete phases) and elements that are present in coal. Thus, all elements in coal except organically combined. C, H, 0, N, and S are classified by this definition as mineral matter. This adequately classifies most inorganic elements in coals, those that are structurally bound within various minerals, but some other elements are also combined in the organic matter. For bituminous coals such elements include B, Be, Br, Ge, Sb, and V; for lower rank coals much of the Ca is combined as an organic salt. In addition, many other elements are combined in both the organic and the mineral matter fractions. The minerals in coal can be classified as to: a) Origin, b) Time of emplacement, c) Relative abundance. The classif iciation of minerals in coal according to origin, can be subdivided into three categories: 1- Detrital, 2- Vegetal, 3- Chemical. A detrital origin implies that the mineral was derived from a source external to the peat-forming swamp and was transported as particulate matter into the swamp VI by water or wind. It is generally held that the most abundant minerals in coal-clay minerals and quartz- are detrital in origin, being introduced into the swamp as overbank deposits of streams during times o-F flood. Certainly, mineral matter principally o-F detrital origin occurs in coals that formed from peat accumulated adjacent to stream channels or in peat accumulated in portions of the swamp invaded by crevasse splays. Detrital materials carried by the wind could be de posited throughout the swamp, but except for unusual cases, wind-born detritus could not be considered a ma jor contribution to the total mineral-matter content of coal. Minerals of vegetal origin from the inorganic constituents of swamp plants. All plants contain inor ganic material with the abundance and composition of the inorganic material depending upon the kind of plant, the type of plant tissue, the climate, and the soil-bedrock geology of the site upon which the plant grew. Woody tissue generally has the lowest concentration of inor ganic material, averaging <1-2'A on a dry weight basis. Minerals of chemical origin are those formed from ingredients once in aqueous solution. The individual minerals could have formed by direct chemical precipita tion from solution or from chemical reactions between the solutions and inorganic or organic materials already present in the peat or the coal A variety of sources exist for the dissolved ions. One source is external to the swamp-the weathering of rocks in the surrounding highland, with the ions trans ported into the swamp as the dissolved load of surface streams or groundwater. A second source of dissolved material is within the swamp itself-the decomposing plant materials. Watec - soluble materials exist within the plant tissue as part of the plant ash. Also, other ions orginally held as part of the organic components of the plants are released into solution as organometal 1 ic bonds are. destroyed during decomposition. A similar Vll source o-F dissolved ions is provided later, in the early coal if ication stage, as -fundamental changes in the organic composition o-F the early -formed coal take place and various ionic materials are released into solution. Minerals are emplaced into coal throughout its en tire history, beginning in the earliest peat-accumula tion stage and continuing up to the most recent times. Howewer, there do appear to be two distinct episodes o-f mineral emplacement Coal minerals are subdivided into two basic categories: a) Syngenetic, b) Epigenetic. According to this classi-f ication, the syngenetic minerals would include those that were incorporated into coal -from the very earliest peat-accumulation stage up to the early diagenetic stage o-f coal i-f ication. Which would be be-fore the so-ft lignite stage. By this defini tion, most o-f the minerals in coal are syngenetic. It is also during this interval of time that the organic components of the coal are undergoing major diagenetic modifications. It appears from petrographic data that the syngenetic phase of mineral emplacement ends before the development of cleat. Syngenetic minerals exhibit draping structures, indicating continued compaction. Following the development of cleat, the final or epigenetic phase of mineral enhancement begins. The development of major fractures throughout the coal bed allows the movement of graundwater solutions of mineral- forming ions through the coal bed. The process of geochemical coal if icat ion has by now proceeded to the point where the organic portion of the coal has become relatively inert and therefore no longer serves as a major source of ionic contribution to the groundwater solutions or reacts with groundwater solutions. The most common epigenetic minerals are the car bonates, pyrite, and kaolinit. Calcite is the vx 1 1 dominant cleat-filling carbonate, although dolomite is not uncommon. Pyrite is by far the dominant disulfide found in epigenetic mineralization, although some of the marcasite occurrences are quite impressive. Most classifications of coal minerals make some reference to their relative abundance. Descriptive terms and corresponding to another. Relative abundance is designated as major, minor, or trace. A major concentration is one>10 wt.% of the low- temperature ash, minor is any concentration from 1-2 to 10 wt.%, and trace abundance refers to any occurrence of <1 wt.%. In most cases, concentrations of trace minerals are in the ppm range. The problems with the commercial use of coal are usually due to the mineral matter present in the coal. The problems Bre often associated with deposits in boilers. The sticky material may accumulate on the walls of the large furnace cavity. This process is usually referred to as slagging. The large furnaces have suspended tubes in them. Deposits form and grow on these tubes in a process called fouling. Sometimes these deposits grow to a point at which the operation of the boiler must be terminated, called a forced outage, for cleaning of the walls and/or tubes. Mineral matter in coal is not always a deleterious material for a process. In coal liquefaction, it has been observed that the rate is increased in the presence of pyrite. In gasification, the rate is increased in the presence of alkalies. The conversion of solid coal to liquid fuels has been a very demanding process in terms of the pressures and, to some extent, the temperatures that have been used. Catalysts have been poisoned by the sulphur and other species in the mineral matter. As a result, catalyst costs and replacement rates can be quite high. A cheap, naturally occuring catalyst that came with the coal would be of significant interest. Pyrite seems to be such a material. IX The purpose of this study was to examine the mine ral matter of some Turkish lignites. The ligqite samples are forms 4 5 6 7 8 9 10 11 12 13 14 15 16 17 ia 19 20 21 22.£.**.»' 24 25 Cayır han- Ankara Askale-Erzurum BaCjyaka-MuQla Merkesler-Bolu Çan-Çanakkale Dodurga-Çorum Ak pınar- İstan bul Çif ta lan- İstanbul Ged i 2 -Kütahya Ilgın-Konya Mengen-Bolu Mihalıccık-Eskisehir Hilas-MuÇla Orhanel i-Bursa Sey i tömer-Kü tahy a Soma-Hanisa Tepebası- Konya Tmaz-MuÇla Karakaya-TekirdaQ Tünebil ek-Kütahya YataQan-MuQla Mersi fon-Amasya Sorgun-Yozgat Yeniköy-îstanbul El bistan-Kahramanmaraş All coal samples studied were prepared as for the ASTIİ standard proximate analysis, i.e. less then 0.25 mm. The moisture content of the lignite samples varies between 2.0-43.0 "/.; the ash content between 6.2-40.6 7.; the volatile matter content between 22.2-46.4 %: and the heat content between 10.3-27.7 MJ/kg. The mineral matter content of the lignite samples was determined according to ISO-602 standard, which varies between 7.68-46.22 "A on dry. basis. From the ash and the mineral matter content, the mineral matter factor of the lignite samples was calculated, which varies between 0.91-1.72. Isolation of the mineral matter of the lignite samples by performic acid oxidation via complete removal of organic matter was carried out at about 323-333 K. A 4 gr sample and 100 ml formic acid were taken together in a İ000 ml conical flask, which was placed in a temperature controlled water bath. Hydrogen peroxide was allowed to fall drop by drop in the flask until the complete oxidation. The isolated minerals were separated by filtration and washed with distilled water. The washed minerals were dried at 303 K and analyzed by X- ray technic. The ash samples prepared according to ASTM standard were also analyzed by X-ray for comparison. 19 different mineral species were found in the isolated minerals of the lignite samples, but only S species were determined in the ash samples. Carbonate and sulphide minerals are likely to be decomposed in acid medium and they are difficult to isolate in their original forms. Therefore, pyrite content of the lignite samples was determined by ASTM standard procedure. All of the lignite samples contain pyrite. The most common minerals were found to retain their original structure after performic acid treatment. Isolation of mineral matter by performic acid oxidation is a suitable quick method for low carbonized coals.