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Pakistan is the world largest lignite bearing country in the world due to the Thar coal reserves. Sulfur contained in this coal need to be removed prior to combustion. Oxidative alkali leaching in dissolved oxygen technique was used to remove the sulfur from Thar coal. This method removed enough all three types of sulfur; about 90% pyretic sulfur, 78% organic sulfur and 50% sulfate sulfur and more than 82S% of total sulfur removal was achieved. Effect of various reaction parameters were observed, it was investigated that reaction time and partial pressure of oxygen has positive effect on the desulfurization, higher the reaction time and oxygen partial pressure higher the degree of desulfurization, also the desulfurization increased with increase in reaction temperature and alkali concentration till some optimum value and then decreases with further increase in value of temperature and concentration of alkali, although desulfurization was observed maximum with minimum particle size. Coal was also characterized with Thermogravimetric Analysis (TGA) and Testo smoke number to investigate the combustion behavior of processed coal. It was observed that combustion properties of processed coal were improved and black smoke in processed coal was reduced.

This study was performed to investigate feasibility of employing enhanced gravity separator for beneficiation of pyritic limestone. Limestone sample primarily constituted of calcite, dolomite, quar...

Large quantities of fine coal have been produced during mining and processing activities of coals. Use of these fine coals after cleaning is important in terms of recovering of economically valuable energy source and prevention of environmental pollution. In the present study, amenability of a high ash-sulfur coal sample to flotation process was investigated. Coal particle size and collector dosage were selected as variables. Increasing coal particle size affected sulfur and ash rejections adversely. On the other hand, more combustible matter was recovered at coarser particle sizes. Maximum combustible recovery, ash rejection, pyritic sulfur rejection and sulfate sulfur rejection were achieved to be 82.56%, 82.84%, 90.04% and 81.45%, respectively. Polished section examinations and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis confirmed the rejection of significant level of ash and sulfur from the coal.

The spatial distribution of fine high-sulfur lean coal under different backwash water pressures and rotational frequencies in enhanced gravity field using the Falcon concentrator was invest...

Eight density separates of Permian Highveld (#4) coal were investigated for partitioning of Hg and trace elements. The separates include float fractions obtained in heavy media having densities of 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 g/cm 3 , and the sink fraction for 2.0 g/cm 3 . Bulk analysis of the separates shows strong (R 2 ≥ 0.80) positive correlations between pyritic sulfur and mercury, and between ash yield and both pyritic sulfur and mercury. Laser ablation (LA) ICP-MS analysis of individual pyrite grains in the separates confirms association of Hg and As with pyrite as indicated by bulk analysis. Other elements detected in pyrite by LA-ICP-MS include Mn, Co, Ni, Tl, and Pb. Results for the separates allow prediction of Hg, trace elements, and ash yields expected in specific South African coal products. These range from 0.06 ppm Hg and an ash yield of 11.5% ash for the export fraction to 0.47 ppm Hg and an ash yield of 60.9% for the discard (stone) fraction (dry basis). Results show pronounced differences expected between coal used for domestic power generation and coal which is exported.

Wet high gradient magnetic separation (WHGMS) of an Egyptian coal sample was carried out to minimize its pyritic-sulfur content reaching 1.60% (2.9% total sulfur). Optimization of the process using the Boxmag Rapid separator included feeding rate, pulp density, applied magnetic field, and the canister loading %. This was conducted through the CCRD and RSM, using Design Expert 6.0 software. Results showed that, at the optimum separation conditions, i.e., 10 l/h feeding rate, 5% pulp density, 2200 Gauss, and 0.6% canister loading, a coal concentrate assaying 0.57% pyritic sulfur was obtained with a recovery 58% and separation efficiency 79.34%.

Similarities concerning the occurrence of mercury and sulfur in coal are the reasons for studying the correlation between mercury content and the content of the various forms of sulfur such as: total sulfur, pyritic sulfur, sulfate sulfur, and organic sulfur. For this purpose a wide range of different coals and rejects were used. Selected samples differed significantly in the content of ash, mercury, sulfur and its various forms. In the examinations, both steam and coking coals were studied. For coking coals, samples of raw coals, clean coals, middling products and rejects derived from coal preparation plants were examined. To verify the correlation a statistical analysis was performed. The Spearman’s rank correlation coefficient and the correlation coefficients R for polynomial functions of degree 1 and 2 were determined. Based on the obtained results, it can be concluded, that mercury occurs in Polish hard coals both in the organic matter and the inorganic constituents. For the organic matter a significant correlation between the content of mercury and the content of total sulfur and organic sulfur was obtained for subset of examined samples characterized by a relatively low ash yield (clean coals derived from the coal cleaning process). In the case of the inorganic constituents a significant correlation between the content of mercury and the content of pyritic sulfur was obtained for the examined subset of samples characterized by a very high ash yield (rejects derived from the coal cleaning process). An analysis of the subsets of samples derived from individual mines showed that the modes of occurrence of mercury in coal were different for various Polish mines. These differences may be explained by the genetic diversity of coal i.e. various diagenetic, coalification and post-diagenetic conditions, including such phenomena as mineralization that post-dates coal formation and magmatic intrusion, etc. In order to explain the mercury and sulfur behavior in the analyzed processes of coal cleaning the percentage share of those elements in rejects in relation to raw coal was also determined. The mercury removal efficiencies recorded for the cleaning process of Polish hard coals ranged from about 33% to as much as 67%. Results of the statistical analyses did not, however, provide necessary evidence allowing for the formulation of final conclusions regarding the modes of occurrence of mercury in Polish coals, its association with sulfur present in coal as well as proportioning of mercury in the processes of coal cleaning. The results did make it possible, though, to identify the major scientific problems, which, if solved by relevant methods (e.g. XRD, SEM, EPMA), will facilitate the understanding of the Hg-modes of occurrence in various Polish hard coals. The results of the statistical analyses will also make it easier to appropriately select samples in order to explain these scientific problems.

Research on coal desulfurization is very important for economic, social, and environmentally sustainable development. In this study, three batches of shake flask experiments were conducted for coal bio-desulfurization using Acidithiobacillus ferrooxidans to explore the relationship between microbial nutrients (iron-free M9 K medium) supply and coal bio-desulfurization efficiency. The results showed that the removal rates of pyritic sulfur and total sulfur from coal effectively increased following reintroduction of coal into the filtrate from previous batch. The removal rates of pyritic sulfur and total sulfur were 55.6% and 10.0%, 77.1% and 16.1%, and 86.5% and 28.2%, respectively, in the three batch experiments without iron-free M9 K medium addition. In contrast, the removal rates of pyritic sulfur and total sulfur reached 87.5% and 28.2%, 89.1% and 31.6%, and 92.0% and 29.1%, respectively, in the three batch experiments with 6.7% iron-free M9 K medium addition. However, addition of excessive iron-free M9 K medium was detrimental to coal bio-desulfurization because of the synthesis of jarosite (MFe3(SO4)2(OH)6, M = K+, NH4+) and gypsum (CaSO4·2H2O), which further declined the pyritic sulfur bio-oxidation efficiency and total sulfur removal efficiency.

Bu tez kapsamında Türkiye'nin 10 farklı kömür sahasından alınan kömür numuneleri ile çalışılmıştır. Numunelerin karakterizasyonu için; kimyasal analizleri (nem, kül, uçucu madde, sabit karbon, üst ısıl değer ve alt ısıl değer), elementel analizleri (C, H, O ve N) yapılmıştır. Kükürt (S) çeşitleri (toplam kükürt, pritik kükürt, sülfat kükürdü, yanabilir kükürt ve organik kükürt) belirlenmiştir. Numunelerin öğütülebilirlikleri, HGI değerleri belirlenerek incelenmiştir. 1,40 gr/cm3 ve 1,60 gr/cm3 yoğunluklu ağır ortamlarda Yüzdürme-Batırma Testleri yapılmıştır. 1,60 gr/cm3 yoğunlukta yüzen ürünlerin elementel analizleri, toplam kükürt içerikleri, HGI değerleri belirlenmiştir. Hem tüvenan kömür örneklerinde, hem de 1,60 gr/cm3 yoğunlukta yüzen ürünlerde petrografik çalışmalar yapılmıştır. Yüzen ürünlerin küllerinin kül ergime dereceleri ve mineralojik bileşimleri belirlenerek, Slagging İndeksleri ve Fouling İndeksleri tespit edilmiştir.Mikrodalga uygulamalarında; mikrodalga enerjisinin 1,60 gr/cm3 yoğunlukta yüzen ürünlerin toplam kükürt içeriğine etkisi incelenmiştir. Mikrodalga çalışmaları sonunda Çayırhan numunesinin toplam kükürdü %5,30'dan %2.31'e düştüğü, %6,50 toplam kükürt içerikli Milas-Ekizköy numunesinin mikrodalga uygulaması sonrası toplam kükürdünün %3,18'e indiği, mikrodalga uygulaması ile Çayırhan ve Milas-Ekizköy numunelerinin toplam kükürt içeriklerinde %52,64 ve %51,08 kükürt giderimi sağlanmıştır. In this thesis study, coal samples from different 10 locations in Turkey were investigated. In order to characterize the coal samples, they were analyzed in terms of chemical analysis (moisture, ash, volatile matter, fixed carbon, gross and ultimate calorific value) and elemental analysis (C,H and N). Coal samples were investigated in terms of sulphur content and sulphur types (total sulphur, pyritic sulphur, combustible sulphur and organic sulphur). Coal samples were also analyzed in terms of their grindability (HGI). In the first step of this study, float and sink analysis with 1.40 and 1.60 g/cm3 density medium was carried out on the coal samples. Floated coal samples were analyzed in terms of their total sulphur content, elemental analysis and HGI grindability measurements. Beside these, petrographic studies were carried out on the run of mine and cleaned coal samples. Ash samples of floated coal samples were obtained and their ash melting degrees and mineralogic compositions were analyzed. With the help of these abovementioned ash melting degrees and mineralogic composition analysis, Slagging and Fouling indices of the samples were determined. In the scope of this study, also microwave application was realized on the floated coal samples. The aim of the microwave application was to observe the effect of microwave on total sulphur content within the 1.60 g/cm3 density floated coal samples. Microwave studies resulted as total sulphur content of Çayırhan coal sample decreased down from 5.3 % to 2.31 % while total sulphur content of Milas-Ekizköy coal sample decreased from 6.5 % to 3.18 %. Removal percentages of total sulphur content of Çayırhan and Milas-Ekizköy coal samples were 52.64% and 51.08, respectively. 131

Pyritic sulfur separation of El-Maghara coal ore was studied using Falcon concentrator model SB40-VFD as an enhanced centigugal gravity separator. The coal sample was ground to below 100 µm to reach liberation between pyrite and coal. Optimization of the separation process has been studied using central composite rotatable design (CCRD) and response surface method (RSM). The studied working factors were the back-water pressure (psi) and rotation frequency (Hz) and their interactions, where the feeding rate and pulp density were kept constant through all experiments. A model describing the relation between pyritic sulfur separation efficiency percentage and the previously mentioned operating variables and their interactions, have been designed. Results showed that maximum separation efficiency reached 70.61%, with decreasing total sulfur, and pyritic sulfur contents reaching 1.72% and 0.48% from original assays reaching 2.90% and 1.60%, respectively. That maximum separation efficiency was attained at 78.38...

Emulsification is one of the most important stages in coal cleaning by using oil agglomeration. Reduction in size of oil droplets and increase in total surface area provided by emulsification result in coverage of entire coal surface with oil, thereby reducing the oil dosage and affecting rapid agglomeration. Ultrasonic emulsification which has been used recently in many sectors such as pharmaceutical, cosmetic, food, chemical industries may be a beneficial and promising operation in oil agglomeration of coal. In the present study, an oxidized fine coal with high ash and pyritic sulfur content was cleaned by oil agglomeration process after ultrasonic emulsification and the effects of power level and time of ultrasonic treatment on the performance of the agglomeration process were determined. Ash and pyritic sulfur rejections that was found to be 50.38% and 85.28%, respectively, at agglomeration test without ultrasonic emulsification was increased to maximally 56.89% and 88.69% by using ultrasonic emulsification before agglomeration. While increase in power of ultrasonic treatment did not affect ash and pyritic sulfur removals considerably, ultrasonic treatment time had positive affect at higher power levels. Contrary to expectations, ultrasonic emulsification affected the combustible recovery and separation efficiencies adversely.

WOS: 000311801900009, This article is concerned with removing the pyritic and total sulfur contents from Dursunbey and. Iskilip lignites by means of trona, which is a natural mineral. The experiments were performed at 20, 50, and 90 degrees C for periods ranging from 15 to 180 minutes using trona solutions with concentrations in the 2.50-15.00% range, and the optimal conditions for sulfur removal were determined. The effect of variable temperature (20, 50, and 90 degrees C), concentrations of distilled water (0%) and trona solution concentration (1.25-15.00%), and experimental duration (15-180 minutes) on sulfur removal was investigated under the optimal conditions determined. It has been established that trona affects sulfur removal in thermal atmosphere and it reduces the pyritic sulfur contents of Dursunbey and. Iskilip lignites by 41 and 31% and the total sulfur contents by 41 and 38%, respectively., Bulent Ecevit University Scientific Research FundBulent Ecevit University [2004-13-02-04], The writers should like to express their gratitude to the Bulent Ecevit University Scientific Research Fund (Project No: 2004-13-02-04) for their financial assistance at the project level.

Hava kirliliğinde büyük paya sahip olan kömür; yakıt olarak kullanıldığında çevresel açısından zararlı ve yüksek oranda kirletici bileşenler ortaya çıkarır. Kömür kullanımında çevreyi etkileyen faktörler; partiküler madde, SOX, NOX ve diğer gaz ürünlerle birlikte atıkların salınması problemidir. Kömürden kükürt giderimi için günümüze kadar birçok yöntem geliştirilmiştir. Bu çalışmada uygulama, maliyet ve işletim açısından uygun ve yenilik getirebilecek meşe külü kullanılarak kömürden kükürt giderimi amaçlanmıştır. Bu amaçla kükürt içeriği farklı olan dört adet kömürde farklı miktarlarda meşe külü kullanılarak kükürt giderim verimleri tespit edilmiştir. Numunelerin organik kükürt analizleri de yapılmış fakat meşe külünün organik kükürt giderimi üzerine önemli bir etkisinin olmadığı gözlenmiştir. Ayrıca karbon ve kalori değerleri de belirlenmiş ve bu değerlerin çok fazla değişim göstermediği belirlenmiştir.İki farklı miktardaki meşe külü uygulamasında kükürt giderim veriminin meşe külünün miktarı ile arttığı belirlenmiştir. Ermenek kömürü toplam kükürt giderim veriminin, meşe külü miktarına bağlı olarak %17 ile % 47 arasında olduğu yapılan analizler sonucunda tespit edilmiştir. Piritik kükürt giderim veriminin ise %13 ile % 60 arasında olduğu tespit edilmiştir. Analizler sonucunda meşe külünün organik kükürtü önemli miktarda etkilemediği görülmüştür. Aynı şekilde meşe külünün karbon değerlerini de pek fazla etkilemediği gözlemlenmiştir.Tunçbilek kömürü toplam kükürt giderim veriminin %8 ile % 59 arasında olduğu belirlenmiştir. Piritik kükürt giderim verimi ise uygulanan meşe külü miktarına bağlı olarak %15 ile %28 arasında değişim göstermiştir. Organik kükürtün meşe külü ile yapılan analiz sonucu önemli düzeyde etkilenmediği tespit edilmiştir. Karbon değerlerinde pek fazla değişim gözlenmemiştir ve meşe külünün, kömürün kalori değerini etkilemediği de tespit edilmiştir.Sorgun kömürü toplam kükürt giderim veriminin % 20 ile % 29 arasında olduğu tespit edilmiştir. Piritik kükürt giderim veriminin ise % 42 ile % 58 arasında olduğu belirlenmiştir. Organik kükürt değerlerini, meşe külünün anlamlı düzeyde etkilemediği de tespit edilmiştir. Burdur kömürü toplam kükürt giderim verimi %26 ile %41 arasında olduğu belirlenmiştir. Piritik kükürt giderim verimi ise % 25 ile % 54 arasında olduğu tespit edilmiştir. Meşe külünün, kömür bünyesindeki organik kükürtü ve kömürün karbon değerlerini dikkate değer düzeyde etkilemediği tespit edilmiştir. Bir diğer yönden ilave edilen potasyum hidroksitin kükürt giderim verimi üzerinde daha etkili olduğu tespit edilmiştir. Bu nedenle potasyum hidroksitin meşe külü ile birlikte uygulamasının kükürt giderimini arttırdığı sonucuna varılmıştır. Anahtar Kelimeler: Kömür, Kükürt, Meşe Külü, Karbon, Giderim, SUMMARYCoal which have big role in air pollution when used as fuel environmentally exposes harmful and highly pollutant components. With the usage of coal the factor effect environment are dust, SOX, NOX and disposal problem wastes with the other gas products.One of the reason of the air pollution is sulfur which exist with the usage of coal as fuel. Coal used in many areas such as heating so coal pollution must be decraesed in minumum levels with developing alternative technologies. Many methods have been developed up to now for the removal of sulfur from coal. In this study trying different techniques and methods, such as oak ashes worked which have implement, cost and processing terms for removal sulfur from the coal thougt as most suitable and newest method. Result of study Show that oak ash have big effect to remove pyritic sulfur in coal.Analysis with Ermenek (Karaman) coal total amount of sulfur the removal efficiency depending on the amount oak ash has been found to between % 17 and % 47. Pyritic sulfur amount the removal efficiency depending on the amount oak ash has been found to between % 13 and % 60.Organic sulfur analysis of samples were performed but there was no effect on oak ash for organik sulfur. Likewise carbon values was no effect on oak ash. Tunçbilek (Kütahya) coal total amount of the removal efficiency depending on the amount oak ash has been found to between % 8 and % 59. Pyritic sulfur amount the removal efficiency depending on the amount oak ash has been found to between % 15 and % 28. Organic sulfur values were no effect on oak ash for organik sulfur. Likewise carbon and caloric values were no effect on oak ash. Sorgun (Yozgat) coal total amount of the removal efficiency depending on the amount oak ash has been found to between % 20 and % 29. Pyritic sulfur amount the removal efficiency depending on the amount oak ash has been found to between % 42 and % 58. Organic sulfur analysis of samples were no effect of oak ash. Burdur coal total amount of sulfur the removal efficiency depending on the amount oak ash has been found to between % 26 and % 41. Pyritic sulfur amount the removal efficiency depending on the amount oak ash has been found to between % 25 and % 54. Organic sulfur analysis of samples were no effect of oak ash. Also was measured carbon and caloric values. It was observed that didn't show much change.On the other way, it has been found to be more effective oak ash added potassium hydroxide. Therefore, it was concluded oak ash apply with potassium hydroxide increased sulfur removal.Key words: Coal, Sulfur, Oak ash, Carbon, Removal 63

The present article discusses the results of measurements carried out to assess the distribution of different sulfur types in lignite samples deriving from two opencast lignite mines near the villages of Bukkabrany and Visonta. These mines ensure the continuous supply of fuel for one of Hungary's largest thermal power plant. According to our findings no significant differences could be identified between the samples of the two mines based on their total sulfur (St) content. Both lignite types were classified as coals with medium-sulfur content according to the system of Chou (1990). A majority of total sulfur is accumulated in lignite, while in the intercalated carbonaceous shale total sulfur is present in minor amounts. Usually the sequence of the distribution of sulfur among the different bond forms in lignite collected from opencast mine of Visonta is as follows: pyritic sulfur (Sp) > organic sulfur (Sorg) > sulfate sulfur (SSOorg). In the samples collected from Visonta and Bukkabrany quantiti...

Existing standard test methods for determining forms of sulfur take a long time, consume a significant amount of reagents, and generate waste. Faced with this problem, an alternative screening method is proposed using hydrogen peroxide in acid medium for the desulfurization of coal and estimation of forms of sulfur in Brazilian raw coal. The detailed characterization of the extracts and the solids was performed at different reaction times. Hydrogen peroxide solutions at different concentrations (3, 10, and 30%) were tested in the presence and absence of the HCl or HNO3 (0.1 mol L–1). Best results were obtained using 10% H2O2/0.1 mol L–1 HCl with removals of 88–98% of pyritic sulfur and 3.5–18% of ash present in the coal samples. The concentration of total dissolved iron measured in extracts approaches the maximum concentration of iron expected for total oxidation of pyrite to sulfate at the end of reaction (240 min). Thus, it can be used to estimate the content of pyritic sulfur, with maximum percent erro...

The goal of this project was to develop and test an innovative coal cleaning process to reduce the ash content of coal and produce ultra clean coal (UCC). Coal samples that were prepared from concentrates of Iran's Zirab and Tabas coal preparation plants were found to have initial ash contents of 8.31 and 10.36%, respectively. These coals were demineralized with the combination of microwave irradiation pretreatment and dual acid leaching processes with HF followed by HNO3 in a batch reactor. For samples that were microwaved and leached with HF, the reduction in ash ranged from 22 to 76% and from 22 to 82% for Zirab and Tabas coal samples, respectively, depending on leaching conditions. Microwave irradiation pretreatment had a positive effect on demineralization with HF, especially for the coarse size fractions. For the fine size fractions, reduced leaching times were found to enhance the effect of microwave irradiation. The microwave-irradiated, HF-leached product was leached further using a 1.4 M HNO3 solution at a leaching temperature of 65 °C to remove fluoride sediments and pyritic sulfur. The ash content of the Zirab coal was reduced from 2.57 to 0.69% by leaching with the HNO3 solution for 1 h. The ash content of the Tabas coal was reduced from 2.44 to 0.39% by leaching with the HNO3 solution for 3 h. The results show that microwave irradiation can be considered as a pretreatment process in the chemical leaching of coal to produce UCC.

This paper presents a neural network model to predict the effects of operational parameters on the organic and inorganic sulfur removal from coal by sodium butoxide. The coal particle size, leaching temperature and time, sodium butoxide concentration and pre oxidation time by peroxyacetic acid (PAA) were used as inputs to the network. The outputs of the models were organic and inorganic sulfur reduction. Feed-forward artificial neural network with 5-7-10-1 arrangement, were capable to estimate organic and inorganic sulfur reduction, respectively. Simulated values obtained with neural network correspond closely to the experimental results. It was achieved quite satisfactory correlations of R 2 = 1 and 0.96 in training and testing stages for pyritic sulfur and R 2 = 1 and 0.97 in training and testing stages, respectively, for organic sulfur reduction prediction. The proposed neural network model accurately reproduces all the effects of operational variables and can be used in the simulation of Tabas coal desulfurization plant.

Mercury emissions from US coal-fired power plants will be regulated by the US Environmental Protection Agency (USEPA) before the end of the decade. Because of this, the control of Hg in coal is important. Control is fundamentally based on the knowledge of the amounts of Hg in mined, beneficiated, and as-fired coal. Eastern Kentucky coals, on a reserve district level, have Hg contents similar to the USA average for coal at mines. Individual coals show greater variation at the bench scale, with Hg enrichment common in the top bench, often associated with enhanced levels of pyritic sulfur. Some of the variation between parts of eastern Kentucky is also based on the position relative to major faults. The Pine Mountain thrust fault appears to be responsible for elemental enrichment, including Hg, in coals on the footwall side of the thrust. Eastern Kentucky coals shipped to power plants in 1999, the year the USEPA requested coal quality information on coal deliveries, indicate that coals shipped from the region have 0.09 ppm Hg, compared to 0.10 ppm for all delivered coals in the USA. On an equal energy basis, and given equal concentrations of Hg, the high volatile bituminous coals from eastern Kentucky would emit less Hg than lower rank coals from other USA regions.

In this study, desulfurization and deashing of Hazro coal via a flotation method were studied. For this purpose, experimental studies were conducted on the coal sample with ash, sulfur, volatile matter, and fixed carbon contents of 24.77%, 6.90%, 35.18%, and 38.06%, respectively, and two groups of flotation experiments were made. The effects of pH, collector amount, and various frothers (MIBC, AF 76, pine oil, DF 250) on the depressing and floating pyrite from Hazro coal were investigated in the first and second group flotation experiments, respectively. Flotation results indicated that, when compared to various frothers, the following order for the depressing of pyrite was obtained: MIBC > pine oil > AF 76 > DF 250. For the floating of pyrite, the following order was obtained: DF 250 > pine oil > AF 76 > MIBC. A concentrate containing 1.12% pyritic sulfur and 13.02% ash with a pyritic sulfur reduction of 66.86% was obtained from a feed that contained 4.95% pyritic sulfur and 24.77% ash. The flotation m...

The purpose of this study was to determine the cause of the experimentally noticed decrease of sulfate sulfur during a thermal treatment of coal. In the case of the pyrolysis of the investigated six coals of different rank and with a widely differing sulfur contents, the decrease of the amount of sulfate sulfur was often GT 50% and, in some cases, GT 80%. The analysis of the obtained results indicates that this effect may be attributed to the overrated values of the sulfate sulfur in coal, which are the result of certain erroneous effects of the hydrochloric acid (HCl) treatment of coal, which is used during the standard procedures for sulfate sulfur determination. It is shown that, because of the HCl treatment, a portion of the organic and/or pyritic sulfur is identified as sulfate sulfur. This effect may be expected to be more pronounced in the case of low-rank coals, as well as in coals that have a relatively large content of pyritic sulfur.

Inorganic materials of coal contain a number of inorganic constituents, especially sulfur, which plays an important role in almost all coal utilization systems. Some methods have been applied to coal to remove its inorganic materials from the organic part. Coal before utilization is subjected to some physical, chemical and biological desulfurization methods. However, physical and biological methods are ineffective and time consuming and they can be applied only on the bench scale. Most of the effective coal desulfurization techniques are based on chemical methods. Main desulfurization methods are chemical desulfurization, leaching, extraction, flotation, oxydesulfurization and biodesulfurization. The alkaline desulfurization is more effective in removing the pyritic sulfur from the coal, which is the less abundant form than the organic sulfur.

In considering with morphological physicochemical transformations of the coal samples pyrolysed in CO 2 atmosphere at different temperatures, the change of their adsorptive capacities have been investigated. It was seen that the change occurred in the monolayer adsorption capacities as parallel to morphological transformations of the coal surface is particularly connected with the amount of organic sulfur present in the coal matrix. Adsorption capacity is not affected from the contents of pyritic sulfur and ash of coal samples. The measurements of zeta potential of the pyrolysed coal samples also showed that pyrolysis modified the functional groups on surface of the coal, depending on the pyrolysis temperature.

Cyclo-microbubble flotation column (CMFC) is an advanced column flotation technology for fine coal cleaning developed by China University of Mining and Technology (CUMT). It combines cyclone separation with column flotation to enhance pyritic sulfur rejection and separation efficiency. A specially designed external bubble generator is employed to efficiently precipitate fine bubbles on particle surface. A set of screen plates inside the column produces nearly plug-flow condition, which is preferred for flotation process. The CMFC technology has been successfully employed to recover fine coal from discarded waste ponds and replace conventional mechanical cells. Typical commercial testing results are described and analyzed. The column is very effective in cleaning particles down to 45 μm. Laboratory- and pilot-scale testing of CMFC has also demonstrated that the CMFC process can produce a superclean coal product of 1.5∼1.6% ash content from a 9.8% ash feed.

The removal of pyritic sulfur from a Turkish lignite in aqueous suspension by nitric acid was investigated. The effects of particle size (−60, −100 and −200 mesh), reaction time (0–10 800 s), nitric acid concentration (5–30 wt.%), temperature (25–103 °C) and speed of stirring (0.75–20 s −1 ) were studied. The pyritic sulfur was quantitatively removed at boiling temperature (≈103 °C in Erzurum) in 25% HNO 3 solution.

The aim of this work was to identify and quantify by means of Mossbauer spectroscopy the amount of pyritic sulfur in coal samples of the Guachinte mine, Valle, Colombia. For the quantification a calibration curve for pyritic sulfur content vs. relative spectral area ratio of sulfur and pure (99.99%) Fe-powder was obtained, using Mossbauer spectroscopy. The samples used in the calibration were the representative ones of the fractions obtained after one and two hydrocyclonic removal processes of a homogeneous sample of raw coal. A linear relationship was obtained and used to determine the amount of pyritic sulfur of the original coal.

Alkaline desulfurization is more effective in removing pyritic sulfur from coal, which is the less abundant form than the organic sulfur. Lignite and coal samples from Turkish resources were extracted with an aqueous alkaline solution obtained from the water-soluble fraction of biomass ash. By this method, high sulfur removal from lignites was possible. The effect of temperature, the amount of biomass ash used, and stirring speed were studied in the ranges 10 to 50 g, 350 to 550 K, 0.042 to 1.8 MPa, 15 to 60 min, and 300 to 600 rpm, respectively. The effect of pyritic and organic sulfur removal were investigated. This process removed 33.1, 35.3, and 37.2% of total sulfur content; 52.3, 53.6, and 60.7% of pyritic sulfur content; and 4.6, 22.1, and 18.0% of organic sulfur content from the lignite samples, respectively.