Combustion Of High Sulfur Coal Research Articles

Desulfurisasi Batubara Dengan Metode Leaching Menggunakan Naoh Dan HCL Di PT. Anugerah Krida Utama, Kutai Kartanegara, Kalimantan Timur

The utilization of coal as a fossil fuel causes several ecological problems, as for the consequences of the coal combustion process, namely pollution and emissions. Combustion of high sulfur coal produces sulfur dioxide gas (SO2). This sulfur dioxide (SO2) will become H2SO4 (sulfuric acid) which can directly or indirectly disrupt human life, such as causing acid rain, causing tightness in the respiratory tract and causing corrosion and shortening the life of factory equipment. To reduce SO2 gas, a reduction in sulfur content is carried out before combustion which is called desulfurization. This research was conducted using the leaching method with variations in leaching agent and solution concentration. Leaching agents used in this study are NaOH and HCl. The coal to be desulfurized is coal from PT Anugerah Krida Utama with an initial total sulfur content of 4,05% adb. 10 grams of coal with a size of 0,212 mm was leached with 250 ml of chemical solution using a hot plate stirrer at 80˚C and 250 rpm for 1 hour. The results showed that the optimum condition for leaching agent NaOH occurred at a concentration of 8 M showing the initial total sulfur content of 4,05% adb decreased to 1,69% adb with a maximum percentage decrease of 58,27% and at leaching agent HCl the optimum condition occurred at a concentration of 1 M showing the initial total sulfur content of 4,05% adb decreased to 2,91% adb with a maximum percentage decrease of 28,14%.

Study on the experiment and reaction kinetics of sulfur removal from coal by microorganisms.

To solve the safety problem of spontaneous combustion of high-sulfur coal, applied microbiology, physical chemistry, reaction kinetics theory, combined with the SEM, FTIR and TG-DTG-DSC experiments and analysis of testing methods, the microbial desulfurization experiments were carried out, and the change law of the desulfurization reaction of coal before and after the element composition, main physical and chemical properties, the coal spontaneous combustion point was studied. The results show that when the temperature is 30°C, the coal particle size is 120 mesh, the initial pH value is 2.0 and the bacteria liquid amount is 15 mL, the desulfurization effect of the coal sample is the best, and the maximum desulfurization rate can reach 75.12%. There is obvious erosion on the surface of the coal sample after microbial desulfurization, the pyrite in the coal is obviously reduced, and the molecular structure in the coal is basically unchanged. Under the action of microorganism, part of inorganic sulfur in coal is removed, the spontaneous combustion point of coal is increased by 50°C, the activation energy of coal has increased more than three times, and the possibility of spontaneous combustion of coal is reduced. By analyzing the reaction kinetics of the microbial desulfurization process, it can be seen that the microbial desulfurization reaction is controlled by external diffusion, internal diffusion and chemical reaction, among which internal diffusion is the main influencing factor.

Influence of Organic Sulfur on Low-Temperature Oxidation of Coal and its Transition Characteristics.

The low-temperature oxidation spontaneous combustion of coal was caused by the active groups in its structure. The oxidation mechanism of carbon and oxygen functional groups in coal had been extensively studied, but there were few reports on the study of sulfur functional groups initiating the coal spontaneous combustion. To investigate the influence of organic sulfur functional groups on the spontaneous combustion of high-sulfur coal and explore its transformation characteristics, the low-temperature oxidation experimental system was used to study the spontaneous combustion tendency of coal with similar metamorphic degrees and different organic sulfur contents. The variations of element forms and organic sulfur functional groups were analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy during low-temperature oxidation of coal and model compounds. The results showed that the forms of organic sulfur in coal mainly included mercaptans, thioethers, thiophenes, sulfones (sulfoxides), and sulfates, and the low-temperature oxidation of coal was not only related to the content of organic sulfur but also related to its type. The coal samples, which possess a low content of total sulfur and a small proportion of active organic sulfur groups such as mercaptans and thioethers, had a lower concentration of indicator gas and a smaller tendency to coal spontaneous combustion. After low-temperature oxidation, the content of mercaptan, thioether, thiophene, methyl(methylene), and pyridine in coal decreased, and the content of oxygen-containing groups such as sulfone (sulfoxide), sulfate, carboxyl, and nitrogen oxide increased. The elements of S, C, and N all changed to a high-valent state. In the oxidation reaction of model compounds, mercaptans were more reactive than thiophenes in the low-temperature region, and the oxidation of thiophene could direct form sulfone (sulfoxide), while the oxidation of mercaptan formed disulfide first. It is speculated that low-valence sulfur migrated to a high-valent state by providing sulfhydryl radicals (•SH) and sulfur radicals (C-S•) combined with active oxygen atoms. After the low-temperature oxidation reaction of model compounds, some organic sulfur existed in the form of aromatic sulfur or sulfur oxides and a small part of sulfur escaped as SO2 and H2S gases in the solid oxidation product.

Experimental research on the spontaneous combustion of Yangquan coal induced by electrochemical oxidation of pyrite

The 15# coal seam of Yangmei No.5 Mine, which produces anthracite, which is the least prone to spontaneous combustion, has a serious hidden danger of spontaneous combustion due to the high sulfur content in the coal. Based on the better conductivity of anthracite, we designed an electrolysis experiment to accelerate the electrochemical oxidation of pyrite in coal. Through experiments and analysis of thermodynamic characteristic parameters, it is obtained that the electrochemical oxidation of pyrite and its main products Fe3+ and Fe2+ have a coupled catalytic effect on the spontaneous combustion of high-sulfur coal in Yangquan. Combined with the FTIR test and analysis, it is found that the electrochemical process causes spatial polarization in the coal, so that polar groups such as –OH undergo spatial diversion and increase the activity. Due to the high content of –OH in Yangquan anthracite, the electrochemical process has the greatest effect on promoting –OH oxidation. Fe3+ and Fe2+ act as strong oxidants and free radicals to promote the –CH2– reaction to generate C=O and promote the generation of CO. This research provides a new direction for the exploration of the spontaneous combustion mechanism of high-sulfur anthracite.

Sulfur release and migration characteristics in chemical looping combustion of high-sulfur coal

Chemical looping combustion of coal has attracted great attention due to its advantage in carbon capture. Sulfur in coal may have negative impacts on this process including deteriorating the reactivity of oxygen carrier and generating gaseous sulfur species. In this research, the release and migration characteristics of sulfur in the chemical looping combustion of Xinzhou coal with two synthetic oxygen carriers, CuO/SiO2 and NiO/Al2O3, were investigated by experiments and thermodynamic simulation. The thermodynamic analysis showed that sulfur in coal mainly migrated to metal sulfides at lower temperatures and peroxide coefficients, but the formation of SO2 was favored at higher temperatures and peroxide coefficients. Experimental results showed that the sulfur conversion efficiencies (XS,g) during the reduction stage reached 62.34 % and 61.25 % under Cu- and Ni-based oxygen carriers, respectively, and XS,g during the reoxidation stage were 6.25 % and 7.44 %, respectively. For both oxygen carriers, the share of H2S and SO2 in the sulfurous gases exceeded 96 % during the reduction stage, while SO2 was the only sulfurous gas when air was introduced. Even though the metal sulfides (Cu2S, Ni3S2 and NiS) were observed in the reduced samples, those two oxygen carriers showed satisfactory regeneration performance after one redox process.

Optimization of NOx emission control based on high sulfur coal combustion

Combined with the operation of an 800MW supercritical boiler burning high sulfur coal, in order to control the emission of nitrogen oxides, the optimization adjustment of ammonia injection and NOx emission reduction based on combustion adjustment is proposed. According to the test of the inlet and outlet of denitration system under 800 MW condition, the parameters of NOx, O2, NH3, wind speed and so on at the inlet and outlet of denitration system are tested, and the ammonia injection manual valve is adjusted according to the test results. After adjustment, the NOx distribution at the outlet of denitration system is uniform, and the ammonia injection quantity is reduced. After adjustment, the flow field under 800 MW and 500 MW conditions is tested, and the flow field distribution under the two conditions is uniform. The adjustment test has achieved the expected effect.

Removal of sulfur element from high-sulfur coal by superconducting HGMS technology

Coal is the most abundant fossil fuel on Earth and is used in a wide range of applications. The direct combustion of high-sulfur coal produces a large amount of sulfur dioxide, which is a toxic and corrosive gas. A new superconducting high gradient magnetic separation (HGMS) technology was studied to remove sulfur from high sulfur coal. The magnetic separation concentrate was obtained under the optimum parameters, such as a particle size of -200 mesh, a magnetic field strength of 2.0 T, a slurry concentration of 15 g/L, and a slurry flow rate of 600 ml/min. The removal rate of sulfur is up to 59.9%. The method uses a magnetic field to remove sulfur-containing magnetic material from a pulverized coal solution. It is simple process with, high efficiency, and is a new way.

BACTERIAL DESULPHURIZATION OF COALS

The review contains literature data about the amount of various forms of sulfur in coals and its impact on the qualitative characteristics of coal. The technological and environmental problems resulting from the combustion of high-sulfur coals are shown. The problems of coal enrichment are considered and an overview of modern methods for their desulfurization are presented. Particular attention is paid to the biotechnological methods with using microorganisms of various taxonomic groups. Data about the reduction of sulphur content in the coals, mainly pyrite, under the action by representatives of mesophilic and moderately thermophilic acidophilic chemolithotrophic bacteria are given. A comparative analysis of the ability of the bacteria of the genera Pseudomonas, Bacillus, Brevibarterium and others to destroy the sulfur-containing heteroatom included in the structural matrix of coal are else given. The data on the role of heterotrophic bacteria in the oxidation of organic sulfur are shown.

Effect of vibration on the separation efficiency of high-sulfur coal in a compound dry separator

The direct combustion of high-sulfur coal can cause serious problems such as the formation of acid rain; therefore, the desulfurization of high-sulfur coal before combustion can reduce environmental pollution. On the basis of an analysis of raw coal, the use of a compound dry separator is proposed in this paper to separate high-sulfur coal across the full size range of 80–0mm. The effects of the vibration amplitude (A), frequency (f), and angle (θ) on the separation results were systematically analyzed in this study. The results showed that when the high-sulfur coal was separated using the compound dry separator under the optimal vibration parameters of f=38Hz, A=2.6mm, and θ=46.5°, the yields of the concentrate and tailings were 71.24% and 28.76%, respectively, with corresponding sulfur contents of 0.93% and 28.59%. The probable error (E) was 0.145 with the largest degree of sulfur content segregation. Under these separation conditions, the acceleration at a clean coal segment increased by 58.06% compared with that at a gangue area; moreover, the material stratification at the clean coal segment was apparent, and the clean coal area was the main separation area. The stratification of dense material at the gangue area was poor, and the gangue area was mainly used to transport and discharge gangue.

Chemical looping combustion of high-sulfur coal with NiFe2O4-combined oxygen carrier

Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its attractive advantage in the inherent separation of CO2. In relative to the single metal oxide-based oxygen carrier (OC), combined OC owned superiority for CLC of coal. In this research, combined NiFe2O4 OC was synthesized using sol–gel combustion synthesis method, and its reaction with a typical Chinese high-sulfur coal as Liuzhi (LZ) coal was performed in a thermogravimetric analyzer (TG). And then, systematic investigation was carried out to explore the evolution of sulfur species and minerals involved in coal and their interaction with the reduced NiFe2O4 OC through different means, including fourier transform infrared (FTIR), field scanning electron microscopy/energy-dispersive X-ray spectrometry, X-ray diffraction, and thermodynamic simulation. TG–FTIR analysis of LZ reaction with NiFe2O4 indicated that two reaction stages were experienced at 350–550 and 800–900 °C, respectively, far different from LZ pyrolysis, and SO2 occurred mainly related to oxidization of H2S with NiFe2O4 over 550 °C. Meanwhile, lattice oxygen transfer rates of NiFe2O4 involved at the two reaction stages were higher than that of directly mixed NiO with Fe2O3 OC and thus more beneficial for LZ coal conversion. Both experimental means and thermodynamic simulation of the solid-reduced residues of NiFe2O4 with LZ coal indicated that the main-reduced counterparts of NiFe2O4 were Ni and Fe3O4. In addition, though good regeneration of the reduced NiFe2O4 was reached, the side products Ni3S2 and Ni2SiO4 should be noted as well for its detrimental effect on the reactivity of NiFe2O4 OC.

Materials Flow Analysis on the System of Flue Gas Desulfurization and Denitration with Pyrolusite Slurry

Circular economy promotes the establishment of recycling-oriented society and recycling-based businesses. Circular economy is characterized by eco-efficiency improvement and materials recycle, furthermore, it also has provided a practical and feasible way for the sustainable development of human society. Materials flow analysis (MFA) has provided a new and simple way to study the development of circular economy. MFA is based on materials inputs and outputs, and then creates materials inputs and outputs account to manage materials flow. The process using pyrolusite for FGD produces manganese, high-purified manganese carbonates and slag used for cement production as byproducts. Electrolytic manganese production process, high-sulfur coal combustion process and cement production process are studied in the research. Materials flows of these processes are studied. The new production patterns are compared with the traditional ones basing on MFA. The results show that these processes are more environment-friendly and resource-saving in the comparison. To evaluate the circular economy efficiency of the complementary system, the evaluation index system of the circular economy construction is created.

Thermodynamic Analysis of Ash Mineral Phases in Combustion of High-Sulfur Coal with Lime

When high-sulfur coal is burnt with lime, the mineral phases of fly ash may be discussed within a SiO2−Al2O3−CaO−CaSO4 system. By obtaining the absent thermochemical property data of the key mineral 3CaO·3Al2O3·CaSO4, the quaternary system was studied thermodynamically. It has been concluded that 2CaO·SiO2 and 3CaO·3Al2O3·CaSO4 may become the dominant minerals of the fly ash if sufficient solid phase reactions can be ensured. Because 3CaO·3Al2O3·CaSO4 and 2CaO·SiO2 are both important cement minerals, there will be great potential to improve the ash characteristics in combustion of high-sulfur coal. This finding gives substantial support to our previous studies of cement clinker cogeneration in pulverized coal combustion boilers. The results will also be very helpful to study the sulfur fixation in high-temperature combustion for which the formation of 3CaO·3Al2O3·CaSO4 is critical. In addition, the knowledge of the mechanism for involved chemical reactions may benefit the production of sulfoaluminate cement as well as the modification of portland cement.

Progression in sulfur isotopic compositions from coal to fly ash: Examples from single-source combustion in Indiana

Abstract Sulfur occurs in multiple mineral forms in coals, and its fate in coal combustion is still not well understood. The sulfur isotopic composition of coal from two coal mines in Indiana and fly ash from two power plants that use these coals were studied using geological and geochemical methods. The two coal beds are Middle Pennsylvanian in age; one seam is the low-sulfur ( 5%) Springfield Coal Member of the Petersburg Formation. Both seams have ash contents of approximately 11%. Fly-ash samples were collected at various points in the ash-collection system in the two plants. The results show notable difference in δ34S for sulfur species within and between the low-sulfur and high-sulfur coal. The δ34S values for all sulfur species are exclusively positive in the low-sulfur Danville coal, whereas the δ34S values for sulfate, pyritic, and organic sulfur are both positive and negative in the high-sulfur Springfield coal. Each coal exhibits a distinct pattern of stratigraphic variation in sulfur isotopic composition. Overall, the δ34S for sulfur species values increase up the section in the low-sulfur Danville coal, whereas they show a decrease up the vertical section in the high-sulfur Springfield coal. Based on the evolution of δ34S for sulfur species, it is suggested that there was influence of seawater on peat swamp, with two marine incursions occurring during peat accumulation of the high-sulfur Springfield coal. Therefore, bacterial sulfate reduction played a key role in converting sulfate into hydrogen sulfide, sulfide minerals, and elemental sulfur. The differences in δ34S between sulfate sulfur and pyritic sulfur is very small between individual benches of both coals, implying that some oxidation occurred during deposition or postdeposition. The δ34S values for fly ash from the high-sulfur Springfield coal (averaging 9.7‰) are greatly enriched in 34S relative to those in the parent coal (averaging 2.2‰). This indicates a fractionation of sulfur isotopes during high-sulfur coal combustion. By contrast, the δ34S values for fly-ash samples from the low-sulfur Danville coal average 10.2‰, only slightly enriched in 34S relative to those from the parent coal (average 7.5‰). The δ34S values for bulk S determined directly from the fly-ash samples show close correspondence with the δ34S values for SO4− 2 leached from the fly ash in the low-sulfur coal, suggesting that the transition from pyrite to sulfate occurred via high-temperature oxidation during coal combustion.

Reduction of Sulfur and Ash from Tabas Coal by Froth Flotation

Tabas mines in Iran have coal sources which are suitable for use in metallurgy industries as coking coal. But the high sulfur content of this coal imposes severe limitations on its utilization as the sulfur oxide gases evolved from the combustion of high sulfur coals result in acid rains and corrosion of equipments. In this work, attempts have been made to reduce sulfur from high sulfur coal of Tabas by froth flotation. Laboratory tests were carried out in order to investigate the influence of various collectors, frothers, pyrite depressants and their consumption dosages on ash and sulfur reduction of Tabas coal. The use of kerosene as a collector and pine oil as a frother has decreased ash and sulfur content of coal more than other collectors and frothers. Although use of sodium polyacrylic acid as a pyrite depressant improved the total recovery of coal concentrate but did not enhance the reduction of sulfur.

Partitioning of sulfur and calcium during pyrolysis and combustion of high sulfur coals impregnated with calcium acetate as the desulfurization sorbent

Combustion of two Chinese coals, without and with the impregnation of calcium acetate, was carried out in a drop tube furnace. Coal pyrolysis was first conducted to study the morphology of the resultant chars, the mode of occurrence of calcium, sulfur and their association within char were studied as well. Secondly, combustion of chars was carried out to reveal the emission of sulfur, transformation of char structure and that of calcium- and sulfur-based compounds in this process. The combustibility of two coals was investigated. Yanzhou high sulfur (YZHS) coal combusted quickly and a portion of the emitted sulfur were captured by the inherent calcium oxide during its combustion. Datong coal (DT) combusted relatively slowly and its sulfur emission was continued until all the carbon burnt out. A thin walled porous structure was formed for the pyrolyzing YZHS char while a relatively thick wall was formed for the pyrolyzing DT char. SO 2 emission during combustion of impregnated coals was decreased considerably compared to that in the cases of raw coals. More than half the emitted sulfur was captured by added calcium in coal pyrolysis. Sulfur removal in the following char compounds varied with both reaction temperature and coal type. Almost all the emitted sulfur was captured at 1000 °C; increasing temperature to 1200 °C, however, decreased its removal efficiency. During coal pyrolysis, the added calcium, which penetrated into coal due to the impregnation, moved to the surface of porous char, where it met the emitted sulfur, capturing it quickly. Little calcium reacted with the inherent aluminosilicate in this step. In the beginning of char combustion, the reaction of oxygen with volatile and char led to the increase of char temperature, as a result, the sulfation of calcium was inhibited to certain extent, whereas the formation of calcium aluminosilicate was facilitated. With char combustion progressed, a porous calcium network was formed, which reacted with SO 2 readily, and hence, the sulfur removal efficiency was increased eventually.

03/01613 In situ desulfurization during combustion of high-sulfur coals added with sulfur capture sorbents: Zhang, L. et al. Fuel, 2003, 82, (3), 255–266

03/01613 In situ desulfurization during combustion of high-sulfur coals added with sulfur capture sorbents: Zhang, L. et al. Fuel, 2003, 82, (3), 255–266

In situ desulfurization during combustion of high-sulfur coals added with sulfur capture sorbents

Two Chinese coals, added with two types of sulfur capture sorbents, were combusted in a drop tube furnace to investigate effect of reaction temperature on sulfur removal during coal combustion. Limestone was used as sorbent and mixed with coal physically for sulfur removal. In addition, another sorbent, calcium acetate, synthesized from natural limestone, was also used for in situ removal of sulfur; it was impregnated into raw coals before combustion. The first series of experiments were carried out in the furnace having downside temperature of 1173 K (the upper side of furnace was at 1573 K). The results proved that calcium acetate captured more sulfur than limestone. In order to understand the effect of reaction temperature on in situ sulfur removal of sorbents, the second series of experiments were carried out at the uniform furnace temperature ranged from 1373 to 1673 K. Moreover, the sulfur removal capability of ashes, taken from combustion of coal with sorbents in drop tube furnace, was studied at 1173 K using thermogravity. The calcium distribution in ashes was analyzed using a novel calcium-based compounds CCSEM category. The results indicated that at certain temperature, higher sulfur removal efficiency was obtained for calcium acetate than that for natural limestone, which is mainly due to the fine dispersion of calcium in impregnated coal so that a good contact was obtained between calcium and sulfur-containing coal particles; increasing the temperature lowered the sulfur removal capabilities of sorbents since the sorbents were captured by inherent aluminosilicate; the sulfur content in raw coal affects the utilization of sorbents significantly in coal combustion. In addition, ashes, rich in calcium, can adsorb SO 2 at 1173 K; the sulfur removal efficiency of fly ash is at least the same as that of natural limestone.

An investigation of a thermochemical process for conversion of gypsum and pyrite wastes into useful products

Pre-combustion coal cleaning and post-combustion flue gas desulfurization (FGD) using lime or limestone are the primary methods employed to reduce sulfur dioxide (SO 2) emission from high-sulfur coal combustion. These processes generate voluminous pyrite and gypsum solid wastes that are usually landfilled, occupying thousands of acres of land and creating serious land and water pollution problems due to the release of acids and toxic substances. An integrated thermochemical process has been developed for the combined utilization of gypsum and pyrite wastes by converting them into useful products including lime, sulfur, and direct reduced iron (DRI). The process includes four major steps. The first step is to concentrate pyrite from coal tailings using flotation or gravity separation. The second is the thermal decomposition of pyrite to pyrrhotite and sulfur. This is followed by the reduction of pyrrhotite with carbon in the presence of lime to produce iron and calcium sulfide. The fourth step involves the reaction of calcium sulfide with gypsum to regenerate lime. The chemical reactions involved in the process were studied using thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. Process variables studied included reaction temperature, time, reactant composition, and the purity of reactants.

00/02180 Environmental aspects of combustion of high-sulfur coals in a recirculating fluidized bed

00/02180 Environmental aspects of combustion of high-sulfur coals in a recirculating fluidized bed

A Comparison of Flue Gas Desulfurization Processes

As coal becomes more and more important as a power plant fuel in this time of energy shortage and the combustion of high-sulfur coals that would impair air quality, efforts have been made to devise efficient processes to control sulfur dioxide emission. Besides desulfurization before combustion, flue gas desulfurization is considered the most promising method that could also be applicable to all other fossil fuels. In this article, the flue gas desulfurization processes are briefly reviewed, and processes with highest use and with high potential for future use are compared from technical and economical points of view. In the selection of a desulfurization process, it is very important to consider the capacity of the plant, fuel type and fuel-to-sulfur ratio, availability and price of the reagent to be used, type, price, and market of side products, disposal problems of wastes, and environmental factors.