Desulphurization Of Coal Research Articles

Rapid total sulphur reduction in coal samples using various dilute alkaline leaching reagents under microwave heating: preventing sulphur emissions during coal processing.

Currently in South Africa, online flue gas desulphurisation (FGD) is being utilized as one of the most effective methods for total sulphur reduction in coal samples during the combustion process. However, the main disadvantage associated with FGD is the formation of its by-products (FGD gypsum). The latter is mostly formed in low grade quality, thereby bringing secondary pollution problems and extra disposal costs. Therefore, the current study describes the development of total sulphur extraction in coal under microwave heating using different dilute alkaline solutions such as NaOH, NaOH-H2O2, NH4OH, and NH4OH-H2O2. The experimental conditions were as follows: 150°C, 5min and 10% (m/v or v/v) for temperature, extraction time and reagent concentration, respectively. The most effective alkaline reagent for coal desulphurisation was observed to be NaOH-H2O2 with total sulphur reduction of 55% (from the inductively coupled plasma-optical emission spectrometry (ICP-OES) results). The NaOH-H2O2 reagent also showed significant morphological changes in coal as observed from the SEM images and effective demineralisation as revealed by the powder X-ray diffractometer (P-XRD) results. Additionally, desulphurisation results obtained from the developed microwave-assisted dilute alkaline extraction (MW-ADAE) method were quite comparable with the published work. The proposed total sulphur reduction method is advantageous as compared to some of the literature reported coal desulphurisation methods as it requires a short period (5min) of time to reach its completion. Additionally, the proposed method shows excellent reproducibility (% RSD from 0.5 to 1); therefore, it can be utilized for routine analysis. Graphical abstract ᅟ.

Coal desulphurization and conditions optimization through response surface methodology, Khushab mines, Pakistan

ABSTRACTThe study aims at coal desulphurization prior to its combustion to reduce the environmental hazards. The process of desulphurization was performed by using microwave-assisted technology in alkaline medium. Response surface methodology (RSM) was employed for the optimization of the removal of sulfur from coal samples by microwave treatment in order to study the interactive and simple effects of operational variables. The parameters, that is, coal particle size, power of microwave, and time of irradiation, were examined. Precipitation method with barium chloride was used for the estimation of sulfur removal. Samples of coal were ground into different particle sizes and then slurries of coal were made in aqueous media and finally irradiated with microwaves in the presence of KOH medium. The measured response was sulfur reduction up to 60%. Time of irradiation and power of microwave have significant effect on desulphurization of coal.

Fine coal desulphurization and microwave energy absorption behaviour by microwave magnetic separation

AbstractMicrowave energy has been used to improve the coal‐pyrite magnetism, while magnetic medium has been added to enhance the microwave energy. Hence, there will be a secondary gradient magnetic chain, which can improve the desulphurization process through magnetic separation. Microwave energy and medium synergistic effects are able to readily improve the magnetic desulphurization process for fine coal. The present paper has studied the impact of microwave energy on the magnetic desulphurization process for fine coal. Intrinsic electromagnetic parameters of different materials were used to analyze and predict the equivalent dielectric parameters of the fine coal layer. The electromagnetic parameter according to the effective medium theory equation for fine coal was established. Coal specific susceptibility is related to pyrite content and pyrrhotite content in pyrite. The specific susceptibility values for the three types of coals were found to be in the following order: Lu'an (LA) coal > Weinan (WN) coal > Yiluo (YL) coal. The most suitable value for LA high‐sulphur coal's sulphur content after being separated by dry type rare earth roll strong magnetic separator appeared to be 60 s delayed in nitrogen atmosphere compared to the corresponding value in an air atmosphere. LA fine coal sulphur content reduced to 2.05 % from 3.66 %, and the microwave magnetic separation desulphurization rate was 44 %.

DOLOMITE DESULFURIZATION BEHAVIOR IN A BUBBLING FLUIDIZED BED PILOT PLANT FOR HIGH ASH COAL

Although fluidized bed in situ desulphurization from coal combustion has been widely studied, there are aspects that remain under investigation. Additionally, few publications address Brazilian coal desulphurization via fluidized beds. This study used a 250 kWth bubbling fluidized bed pilot plant to analyze different aspects of the dolomite desulphurization of two Brazilian coals. Superficial velocities of 0.38 and 0.46 m/s, flue gas recycling, Ca/S molar ratios and elutriation were assessed. Results confirmed the influence of the Ca/S molar ratio and superficial velocity - SO2 conversion up to 60.5% was achieved for one coal type, and 70.9% was achieved for the other type. A recycling ratio of 54.6% could increase SO2 conversion up to 86.1%. Elutriation and collection of ashes and Ca-containing products did not present the same behavior because a lower wt. % of CaO was collected by the gas controlled mechanism compared to the ash.

Determination of reaction areas for the sulfur conversion during low-metamorphosed coal oxidative desulphurization

Taken into account the global trends of metallurgy, in order to save energy, new technologies in blast furnaces are actively developed in Ukraine, namely, substitution of natural gas for pulverized coal (PC). However, use of this technique is complicated by inconsistencies of characteristics of a large part of domestic coal with requirements that apply to PC raw materials, primarily because of the high sulfur content in it.To solve this problem, it is proposed to use the method of coal oxidative desulphurization that consists in selective conversion of pyritic sulfur by vapor-air mixture. However, the content of sulfur in coal is not the only requirement, so the task of research is determination of process parameters that will enable to minimize the destruction and burning of organic carbon that occurs during its oxidative desulphurization.Series of experiments on detailed determination of patterns for high-sulfur low-metamorphosed coal oxidative desulphurization to produce raw materials for PC are began in this article. The effect of linear velocity of the oxidant and the grain size of raw materials on the process is determined and the values of these factors when oxidative desulphurization isn't limited to diffusion velocity of the oxidant to the coal grain surface are established. The dependence of the process stages from parameters of fluidized bed and mass transfer criteria of the reagent is shown.

Effect of regeneration atmosphere on the properties of an iron oxide desulphurisation sorbent for high-temperature coal gas desulphurisation

Desulphurisation sorbent properties, including desulphurisation activity and mechanical strength, are important in the sulphidation/regeneration cycle for high-temperature coal gas desulphurisation. In this paper, α-Fe2O3 desulphurisation sorbent was prepared and the changes in its mechanical strength and the surface morphology after regeneration in O2, SO2 and SO2–O2 atmospheres were measured with a particle strength tester and by scanning electron microscopy. The mechanical strength of the sorbent was generally higher after regeneration, although the formation and decomposition of sulphate during regeneration decreased the mechanical strength of the sorbent. The sulphate formation and decomposition depended on the O2 and SO2 concentration and the regeneration temperature. The mechanical strength was also increased by the sorbent sintering.

Evaluation of different microwave-assisted dilute acid extracting reagents on simultaneous coal desulphurization and demineralization

Coal combustion is one of the largest anthropogenic contributors to SOx and some other volatile elemental emissions to the atmosphere. Therefore, the current study investigated the effect of different dilute acidic reagents (HCl, HNO3, HCl–HNO3, HCl–H2O2, HNO3–H2O2 and HCl–HNO3–H2O2) on simultaneous coal demineralization and desulphurization under microwave irradiation. The applied conditions for microwave-assisted dilute acid extraction (MW-ADAE) process were as follows: 180°C, 5min, 3molL−1, 3molL−1, 0.1g and 2:1 for microwave temperature, extraction time, acid concentration, [H2O2], coal amount and acid-hydrogen peroxide volume ratios, respectively. The leachate solutions obtained from the MW-ADAE process were then analysed by using ICP–OES for multi-element determination. The ICP–OES analysis was performed in order to investigate the acidic reagent that resulted in highest extraction recoveries of the examined multi-element. All extracting reagents that contained HNO3 showed accepted extraction efficiencies (% R⩾80%) as indicated by the ICP–OES results. The proposed MW-ADAE procedure with HNO3–H2O2 reagent showed excellent desulphurization efficiency parallel to the other literature reported methods. The raw and acid treated coals were then characterized by Elemental analyser (CHNS), FT-IR, SEM, P-XRD and TGA to examine the influence of different acids on the coal structure. The FT-IR, SEM and P-XRD results showed insignificant changes throughout all the studied acidic reagents. However, the CHNS results of HNO3–H2O2 treated coal revealed sufficient coal desulphurization as compared to the other investigated acids. Alternatively, thermal studies of raw coal (A) showed high quantity of unburned mineral matter. In addition, most of the acid treated coals such as B (HCl), C (HNO3), E (HCl–H2O2 and F (HNO3–H2O2) indicated moderate removal of mineral matter while aqua-regia based extracting reagents (G (HCl–HNO3–H2O2) and D (HCl–HNO3)) caused drastic extraction of both carbon and mineral content. Therefore, the mixture of HNO3–H2O2 was selected as the potential extracting reagent for the proposed simultaneous coal desulphurization and demineralization process as it showed moderate attack on the carbon content of the coal and sufficient desulphurization (102%) and demineralization (70–115%).

Desulphurization and Usage of Medium-Metamorphized Black Coal. 2. Desulphurized Coal Used as an Additive for the Production of Special Types of Coke

Desulphurization and Usage of Medium-Metamorphized Black Coal. 2. Desulphurized Coal Used as an Additive for the Production of Special Types of Coke

Desulphurization and Usage of Medium-Metamorphized Black Coal. 1. Determination of the Optimal Conditions for Oxidative Desulphurization

The conditions providing proceeding of the reactions between pyrite sulphur of medium-metamorphized coal and air-steam mixture in the kinetic area have been found. Experimental-statistical mathematical model has been designed. The optimal factors of mediumcoalificated coal oxidative desulphurization have been determined on its basis. Under optimal conditions two samples of coking coal have been desulphurized. These samples will be used as components of the coal charge in the production of special types of coke.Знайдено умови, які забезпечують перебіг реакцій у кінетичній області між піритною сіркою середньометаморфізованого вугілля і паро-повітряною сумішшю. Розроблено експериментально-статистичну математичну модель та на її основі встановлено оптимальні значення чинників процесу оксидаційного знесірчення кам’яного вугілля середнього ступеня вуглефікації. У знайдених оптимальних умовах здійснено знесірчення двох зразків коксівного вугілля, які будуть використані як компоненти вугільної шихти у виробництві спеціальних видів коксу.

Effect of native bacteria Sinomonas flava 1C and Acidithiobacillus ferrooxidans on desulphurization of Meghalaya coal and its combustion properties

Coal collected from Meghalaya state situated in northeastern (NE) region of India contains about 6.17% total sulphur (4.7% organic) with a gross calorific value of 26,208J/g. In the present study, the coal sample was subjected to biodesulphurization along with optimization of various process parameters using a bacteria isolated from the native coal mine site. The native bacterium was identified to be Sinomonas flava 1C and reported first time for the capability to remove about 40% of sulphur from the coal. An innovative two-step sequential leaching using S. flava 1C followed by Acidithiobacillus ferrooxidans was used in the present study to enhance desulphurization. Sequential leaching resulted in 50–53% of sulphur removal from the coal sample. Sequential leaching reduced the sulphur content to 3.08% (organic 2.15%+pyritic 0.1% and 0.85% of sulphate sulphur) in −500+300μm size fraction of coal. Analytical characterization indicated that the energy value of coal was not affected adversely due to the biodesulphurization process rather its calorific value increased from 26,208J/g to 29,481J/g.

Study of enhanced low-quality coal oxidative desulphurization and deashing by using HNO3 and microwave pretreatment

In this paper, the effect of urea-hydrogen peroxide (UHP) solution on desulphurization and demineralization of coal with high sulphur and high ash by using HNO3 and microwave pretreatment was investigated. The oxidation process is strongly dependent on irradiation power and time for microwave pretreatment, UHP concentration, leaching time and temperature of the UHP solution. X-ray diffraction and Fourier transform infrared technique have been performed for the raw and treated coals. Compared with the UHP alone, successive treatments with HNO3 and microwave pretreatment resulted in the significant removal of total sulphur and mineral matter from the coal. The proposed experimental method has the meaning of practical guide to the desulphurization and deashing of coal by microwave.

Experimental Study on SO2 and NOx Removal during Briquette Combustion

In this paper, the desulphurization of coals prepared briquettes using lime based products (calcium hydroxide and calcium carbonate) and sodium hydroxide as desulphurizing agents (DSA) was investigated in a vertically integrated experimental furnace. Meanwhile, the effect of sodium hydroxide on the denitrification was also studied. The results indicated that calcium carbonate as a DSA is more efficient for SO2 removal during the char combustion, whereas hydrated lime and NaOH are efficient in both char and volatile combustion. For most of the coals, the desulfurization efficiencies in case of lime hydrated reaches over 80 %, whereas desulfurization efficiencies is below 70% when calcium carbonate is used as DSA. It was also found that NaOH can be used as denitrifying agent as well as desulphurizing agent, and the maximum denitrifying efficiencies by using NaOH denitrifying agents for coal A and coal B are 59% and 54%, respectively.

Optimization of Oxidation Desulphurization of Power-generating Coal

An experimental statistic model of powergenerating coal oxidative desulphurization has been developed and its adequacy has been proved. On the basis of the proposed model the desulphurization optimal conditions for three samples of power-generating coal were determined. The low-sulphur solid fuel with the content of general sulphur of 1.0–1.5 mas % was obtained under established optimal conditions. Створено експериментально-статистичну модель процесу оксидаційного знесірчування кам'яного енергетичного вугілля та доведено її адекватність. З використанням запропонованої моделі знайдено оптимальні умови проведення знесірчування трьох зразків кам'яного енергетичного вугілля. Проведення процесу за цих оптимальних умов дозволило отримати низькосірчисте тверде паливо (вміст загальної сірки не перевищував 1.0-1.5% мас.).

Desulphurization of High Sulfur Coal by Mild Pyrolysis Combination with Magnetic Separation

In this work, a new desulfurization process of high sulfur coal was designed and examined. The novel process involved pyrolysis of high sulfur coal at low temperature and then a dry magnetic separation. For testing the cleaning coal process, a Chinese high sulfur coal, Baisu coal was pyrolyzed in a fixed bed reactor from 400 to 700°C for 30min, and then separated by a dry magnetic separator. The results showed that under optimum conditions, a remarkable reduction of sulfur content in coal was achieved, and more importantly, almost all pyrite sulfur in coal was removed.

Desulphurization of High Sulfur Coal by Mild Pyrolysis Combination with Magnetic Separation

In this work, a new desulfurization process of high sulfur coal was designed and examined. The novel process involved pyrolysis of high sulfur coal at low temperature and then a dry magnetic separation. For testing the cleaning coal process, a Chinese high sulfur coal, Baisu coal was pyrolyzed in a fixed bed reactor from 400 to 700°C for 30min, and then separated by a dry magnetic separator. The results showed that under optimum conditions, a remarkable reduction of sulfur content in coal was achieved, and more importantly, almost all pyrite sulfur in coal was removed.

Gamma Irradiation of Pyrite in Egyptian Coal as Studied by Means of Mössbauer Spectroscopy at Room Temperature

A well characterized coal sample from Egypt was irradiated using 60Co source for different dwell times starting from 10 to 100 h in the first experiment and from 7 to 28 days for the second one. The constant dose rates of both were 9.12 and 7.61 Gray/min, respectively. Mossbauer results obtained from the first irradiation process have shown oxidation of pyrite to jarosite. While ferrous sulfates resulted from pyrite oxidation is clearly evidenced in the irradiated coals from 7 to 28 days. Gamma irradiation as a method for coal desulphurization is discussed.

Effect of complexing agents in the desulphurization of coal by H2SO4 and H2O2 leaching

The pyritic sulphur extraction from a sub-bituminous coal in an oxidizing aqueous media was examined. The results show that the pyritic coal desulphurization in H2SO4 solutions and in presence of H2O2 could be effectively increased to 89% by the addition of complexing agents such as quercetin, phosphoric, oxalic and citric acids. According to the above, the current study might contribute to establish a new alternative process to eliminate pyritic sulphur from coal concentrates.

Organosulfur Compounds in CS<sub>2</sub> Extractable-Fractions from Four Chinese Coals Oxidized with NaOCl

Four Chinese coals were oxidized with NaOCl aqueous solution under mild conditions. The reaction mixture was extracted with diethyl ether, carbon disulfide, petroleum ether, acetic ester and benzene sequentially. A series of organosulfur compounds (OSCs) were identified in the carbon disulfide fraction from the oxidized coals by GC/MS analysis but no OSCs were detected from other fractions except for 3 thiophene polycarboxylic acids found in ether-extraction. Some new types of sulfur function groups were also detected in the coal oxidation products which were not previously reported from coals. The results revealed that macromolecule OSCs in coals can be effectively degraded to water soluble small molecules with NaOCl aqueous solution, which can be enriched by carbon disulfide. Understanding the distribution of OSCs forms in coals matrix is useful in high value-added utilization of coals and coal desulphurization technologies.

Electric discharge disintegration and coal desulphurization in the manufacture of water-coal fuel

The results of monitoring the sulfur content in the components of water-coal fuel at their disintegration with the use of electric discharges were summarized, and a scheme of the desulphurization process was proposed.

Chemical and biological desulphurization of boiler coal

Chemical and biological desulphurization of boiler coal