Desulfurization of high sulfur Kütahya-Gediz coal

The role of fossil fuels in world energy production will be important in the future as it was in the past. The negative effects of the fossil fuels to the environment cause the limitation of the usage areas and also economical problems of the location where they are mined. Kütahya-Gediz coals include high amount of sulfur so the mining of this coal is limited although the quality is high in means of caloric value. The aim of this study is to apply various desulphurization methods in order to increase the usability of the Gediz coals.Under the scope of the thesis subject, first of all a detailed characterization study of the Gediz coals was made in order to determine the characteristics. As a result, it was found out that Gediz coals include 7.06% sulfur which is 3.55% pyritic and 2.89% organic. Although it includes high amount of ash (25.99%), the caloric value is very high (5607 kcal/kg). It was also understood that the pyritic sulfur has very small particle size and is distributed within the organic structure of the coal.Some physical (magnetic separation, knelson concentrator, floatation) methods as well as chemical (acidic and alkali chemical, pyrolysis, autoclave, electron transfer) methods were used and also experiments were made by the combination of these methods.As most of the sulfur content is organic and pyritic origin sulfur has very small particle size, it is not possible to removal it by physical methods. Chemical methods are necessary for desulfurization due to the property of the coal.In alkali chemical method experiments, alkali chemicals such as NaOH, KOH, Ethanol-NaOH, Ethanol-KOH, Methanol-NaOH and Methanol-KOH was used and as a result 9-12% sulfur was removed. The desired results could not be achieved from these experiments which were performed under low temperature and pressure. Autoclave method was used under high temperature and pressure, 40% sulfur was removed from the coal. After this experiment, it was understood that high temperature and pressure is effective for the removal of sulfur in coals of this region. The results also showed that acidic chemicals should be used in stead of basic chemicals. For this purpose, various acidic chemicals were applied (Hydrochloric acid (HCl), Nitric acid (HNO3), Hydrogen peroxide (H2O2), Sulfuric acid (H2SO4), Hydrogen fluoride (HF), iron sulphate (Fe2(SO4)3), Peroxyacetic acid (PAA), Acetic acid (CH3COOH), formic acid (HCOOH), performic acid (H2O2-HCOOH), boric acid (H3BO3)). Some of them were very effective in desulfurization but some of them were not. Acidic chemicals were generally more successful in desulfurization. The ratios of desulfurization are as follows for the applied chemicals: HCl+HNO3 66.95%, H2O2 40.38%, H2SO4 8.81%, HF 7.52%, Fe2(SO4)3 20.39%, PAA 55.64%, CH3COOH 9.60%, H2O2-HCOOH 11.73%.Pyrolysis was also used as a chemical desulfurization method. Conventional heating and microwave heating were applied. Microwave heating did not give the desired results but 40% of sulfur was removed from Gediz coal by using conventional heating. It was determined that microwave heating should rather be used as a supporting method in stead of being used by itself. The last chemical desulfurization method was electron transfer method. In this method, the desulfurization effect of various metal salts were examined (CuCl2, CuSO4, CoCl2, NiCl2, HgCl2) and for this purpose both conventional and microwave heating were applied. Metal salts removed 9-12% sulfur with conventional heating while they removed 12-22% sulfur by microwave heating. Microwave heating in electron transfer method was first applied in this PhD study.Finally, different methods were applied in combination. In these studies where physical and chemical methods were used together thermal processing or chemical methods were applied after floatation method and important amount of sulfur was removed as a result. Also thermal processing (microwave) applied before chemical methods converted the coal into more soluble forms during the chemical method application. As a result, three staged systems, respectively floatation, thermal processing and chemical method, was applied and important amount of sulfur was removed from the coal.A detailed study where Gediz region coals were used, was performed in removing sulfur and important results were obtained.As a result, it was determined that it is very difficult to remove the sulfur types in Gediz coal with physical methods and that chemical methods are necessary. It was determined that the products obtained after the application of various methods can be used in secondary or tertiary cities degreed in the notice issued by Ministry of Environment and Forestry according to the air pollution density. Clean coal including 13.67% ash with 47.40% deashing ratio and 1.47% sulfur with 79.05% desulfurization ratio were obtained out of Gediz region coal including 7.06% sulfur and 25.99%ash after applying thermal processing by microwave (800 W, 2 minutes) and then chemical process in basic ambient by using KOH and finally chemical process in acidic ambient by using HCl-HNO3.Keywords: Desulfurization, Chamical Methods, Physical Methods.