Sulfur Content Of Coal Research Articles

Enrichment and particle size dependence of polonium and other naturally occurring radionuclides in coal ash

Coal fired thermal power contributes 70% of power in India. Coal fired power generation results in huge amounts of fly ash and bottom ash of varying properties. Coal, which contains the naturally occurring radionuclides, on burning results in enrichment of these radionuclides in the ashes. In the present study, coal, bottom ash and fly ash samples collected from six coal-fired power plants in India were measured for 210Po using alpha spectrometry and for natural U, 226Ra, 232Th and 40K by an HPGe γ-ray spectrometer. 210Po in fly ash ranged from 25.7 to 70 Bq/kg with a mean value of 40.5 Bq/kg. The range and mean activities of 238U, 226Ra, 232Th, 40K in fly ash were 38.5–101 (78.1), 60–105.7 (79), 20–125 (61.7) and 43.6–200 (100) Bq/kg respectively. Fly ash and bottom ash contains two to five times more natural radionuclides than feed coal. The results were compared with the available data from earlier studies in other countries. The effect of particle size on enrichment factor of the nuclides in fly ash was studied. 210Po showed the largest size dependence with its concentration favoring the smaller particle size while 232Th showed least size dependence. 238U and 226Ra showed behavior intermediate to that of 210Po and 232Th. Also the correlation between sulfur content of the feed coal and activity of 210Po was investigated. Increased sulfur content in feed coal enhanced enrichment of 210Po in ash.

Biological removal of sulphur and ash from fine-grained high pyritic sulphur coals using a mixed culture of mesophilic microorganisms

Bioleaching of coal’s pyrite is a promising option to reduce sulphur content of high sulphur coals from an economical, technical and environmental point of view. In this research, a mixed culture of acidophilic iron- and sulphur-oxidizing mesophilic microorganisms including Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans was used to remove pyritic sulphur from the high sulphur coal of Mehr Azin, Tabas, Iran. The influence of various parameters, namely nutrient medium type (Norris and 9K), initial pH (1, 1.5 and 2) and the addition of ferrous sulphate on the pyritic sulphur removal and ash content of coal was investigated using an orthogonal array L-18 Taguchi design. Shake flasks experiments were carried out in pulp density of 5% (w/w), particle size of smaller than 500μm, and a stirring rate of 150rpm at 35°C for 30days. Analysis of variance (ANOVA) was used to determine the effects of the variables on sulphur and ash reduction from the coal. The maximum sulphur removal (50.3% total sulphur) was obtained at the initial pH of 1, the ferrous sulphate addition of 0.02M and Norris nutrient medium. Total sulphur and ash content values were decreased from 3.87% to 1.92% and 25.72% to 11.6%, respectively. SEM/EDS and XRD analyses showed that a high level of sulphate and jarosite precipitations could be occurred at the initial pH of 2 when 0.05M ferrous iron addition and 9K nutrient medium were used.

EPR and IR studies on the role of coal genetic type in plastic layer formation

Coal blends with all possible combinations of two pairs of isometamorphic coals of different sulfur levels were pyrolysed in centrifugal field, allowing to be separated into solid, fluid and gaseous products. It has been shown that the replacement of the low-sulfur by the high-sulfur coking coal of the same rank (≈83–88% Cdaf) in blends leads to a substantial increase of fluid product yield which can be of great practical value. Using the EPR and DRIFT-spectroscopy methods the structural peculiarities of the obtained products have been studied. An apparent relation between the content of sulfur in coal, paramagnetic centers in plastic layer and coal coking ability was established. It was demonstrated that the concentration of paramagnetic centers in fluid non-volatile products correlates with the yield of plastic layer responsible for coking ability.

Optimizing Fine Circuit Design to Maximize Pyrite Rejection and Enhance Coal Marketability

Coal sulfur content is a critical property in both coking and thermal coal marketability. Sulfur level reduction in both markets greatly enhances coal value. In the Northern Appalachian region of the United States, sulfur levels in some potential coking coals are often marginal (1.1%–1.5%). On many occasions, much of the sulfur is concentrated in the form of pyrite in the finer sized fractions (1 mm × 0.045 mm). Traditional fine coal processing circuitry (spirals, flotation) tends to produce high levels of product sulfur. Pyrite reaching the flotation circuit typically floats well, producing high-sulfur froth concentrate. Being able to run at lower densities in the 1 mm × 0.25 mm size fraction reduces sulfur levels considerably. Removal of high-density pyrite by a combination of classification and spiraling allows low-sulfur froth concentrates to be produced. Circuit design and plant results for a recently commissioned plant in Northern Appalachia using this technology are discussed. Similarly in the Illinois basin of the United States, the pyrite concentration in the fines has precluded the use of froth flotation in many plants giving rise to significant yield losses. By incorporating a similar approach of classifying out the pyrite and then treating the desulfured fines in flotation, acceptable concentrates can be generated for the lower sulfur market. Once again the flotation yield is supplemented by taking the concentrated pyrite, which flows to the plant's clean coal effluent streams, and removing this by fine spiraling and floating the reduced-sulfur spiral concentrate.

Trends in pulp and paper mill emissions of SO2 and NOx, 1980-2010

Sulfur dioxide (SO2) and oxides of nitrogen (NOx) emissions from U.S. pulp and paper mills have been estimated from industry-wide surveys conducted every five years, beginning in 1980 and continuing through 2010. Between 1980 and 2010, total SO2 emissions declined by over 70%, while paper and paperboard production rose 35%. NOx emissions peaked in 1995, but fell by almost 40% over the next 15 years. Paper and paperboard production only declined 7% over the same period. These downward emission trends resulted from several factors, including reductions in oil and coal use, declining oil and coal sulfur content, increased use of add-on SO2 and NOx control systems on boilers, growing use of combustion modification techniques to minimize emissions, improvements in energy efficiency, and declining pulp, paper, and paperboard production over the past 15 years.

Sulfur and Nitrogen Distributions during Coal Carbonization and the Influences of These Elements on Coal Fluidity and Coke Strength

The present study focuses on examining the fate of coal-S and coal-N during carbonization in detail and making clear the effects of these elements on coal fluidity and coke strength. When eight kinds of caking coals with 80–88 mass%-daf C are carbonized in high-purity He at 3°C/min up to 1000°C with a quartz-made fixed bed reactor, 50–75% of coal-S remains as FeS and organic-S in the coke, and the rest is released as tar-S and H2S. Most of coal-N is also retained in the coke, and the remainder is converted to tar-N, HCN, NH3 and N2. The eight coals give Gieseler maximum fluidity values between 435 and 480°C, and the value tends to be larger at a smaller sulfur content in coal or in the carbonaceous material recovered after carbonization at 450°C. It also seems that the value increases with increasing nitrogen content in coal or total amount of either HCN or NH3 formed up to 450°C. Furthermore, the addition of S-containing compounds to an Australian bituminous coal lowers coal fluidity and coke strength considerably, whereas indole gives the reverse effect on them. On the basis of these results, it is suggested that coal-S or some coal-N has a negative or positive effect on the two properties, respectively.

Increased total sulfur content in coal from Donets and other basins

The ash composition is used to assess the conditions of coal-bed formation in the Donets and L’vovsk-Volynsk basins. The experimental data are inconsistent with some aspects of the hypothesis that pyrite and secondary organic sulfur are formed in the coal. The lack of a relationship between the total sulfur content Std in the coal and the MgO content in its ash does not agree with the notion that sulfates from sea water provide the basis source of nonvegetative sulfur in coal. The actual Std values do not always correspond to the theory that the source of sulfur depends on the alkalinity of the water and the reducing medium where the deposits accumulate. In the conditions that are most favorable to the formation of coal with high total sulfur content (Std > 4 wt %) according to the existing hypothesis, the actual value of Std is no more than 1.5%. The source of pyrite and organic sulfur in coal requires further discussion.

A robust framework to predict mercury speciation in combustion flue gases

Mercury emissions from coal combustion have become a global concern as growing energy demands have increased the consumption of coal. The effective implementation of treatment technologies requires knowledge of mercury speciation in the flue gas, namely concentrations of elemental, oxidized and particulate mercury at the exit of the boiler. A model that can accurately predict mercury species in flue gas would be very useful in that context. Here, a Bayesian regularized artificial neural network (BRANN) that uses five coal properties and combustion temperature was developed to predict mercury speciation in flue gases before treatment technology implementation. The results of the model show that up to 97 percent of the variation in mercury species concentration is captured through the use of BRANNs. The BRANN model was used to conduct a parametric sensitivity which revealed that the coal chlorine content and coal calorific value were the most sensitive parameters, followed by the combustion temperature. The coal sulfur content was the least important parameter. The results demonstrate the applicability of BRANNs for predicting mercury concentration and speciation in combustion flue gas and provide a more efficient and effective technique when compared to other advanced non-mechanistic modeling strategies.

The impacts of the Clean Air Act on production cost, and the substitution between inputs in the electric utility industry

The paper examines how having to comply with Phase 1 of Title IV of the 1990 Clean Air Act affected production cost and the substitution between fuel and non-fuel (labor, capital) inputs. Phase 1 required firms to reduce their sulfur dioxide emissions. Enacting procedures to reduce sulfur dioxide emissions (using lower sulfur content coal or other fuel sources) could lead to higher cost, and impact the substitution between fuel and non-fuel inputs. Using a 1992-2000 panel of 34 U.S. electric utilities, empirical results indicate that the procedures electric utilities enacted to comply with Phase 1 contributed to small increases in both marginal cost and total cost. Firms having to comply with Phase 1 were more willing, than firms not subject to Phase 1, to substitute from fuel to non-fuel (labor, capital) inputs following an increase in the price of fuel. Utilities subject to Phase 1 that had a fuel clause were more willing, than Phase 1 firms without a fuel clause, to substitute from non-fuel inputs to fuel when the price of the non-fuel input increased.

The Distribution Characteristics of Total Sulfur Content of Coals Formatting in Different Geological Age, Guangxi Province, China

The era distribution characteristics of total sulfur content of coals formatting in Early Carboniferous, Later Permian, Early Jurassic and Cenozoic in Guangxi,China, were studied by basing the statistics and analysis of total sulfur content of 19 important coals producing area including 173 exploration area and mining area. The results show that the coals of Early Carboniferous are mainly high sulfur coal and sub-high sulfur coal and the total sulfur content is high around the centered area around Liucheng Guilin - Xinan area and gradually decrease along south and north sides. The sulfur content of Late Permian coals are very high and reach to 5%-8% in some area and there is great difference among sulfur content in different area. The sulfur in Early Jurassic coals have great difference in distribution and are up to 10% in Northeast Guangxi area but less than 0.5% in Southeast Guangxi area. The coals of Cenozoic are low sulfur coal in common.

Removal of Organic Sulfur in Two Coals in Microwave and Ultrasonic Co-Enhanced Oxidative Process

Microwave heating has been used in desulfurization of coal. Removal of organic sulfur and organic sulfur forms alterations of Xishan (XS) coal and Yunnan (YN) coal was investigated under microwave and ultrasonic irradiation. The results showed the optimum conditions for desulfurization were 50 min and 560 W for microwave and ultrasound for both coals. The desulfurization rate was maximum 23.53% for XS coal and 76.58% for YN coal. The effect of combining microwave and ultrasonic irradiation on desulfurization was stronger than simple microwave irradiation. The content of sulphone sulfur in coal was increased from the XPS after microwave and ultrasonic co-enhanced oxidative desulfurization.

Thiophenic Sulfur Compounds Released During Coal Pyrolysis

Thiophenic sulfur compounds are released during coal gasification, carbonization, and combustion. Previous studies indicate that thiophenic sulfur compounds degrade very slowly in the environment, and are more carcinogenic than polycyclic aromatic hydrocarbons and nitrogenous compounds. Therefore, it is very important to study the principle of thiophenic sulfur compounds during coal conversion, in order to control their emission and promote clean coal utilization. To realize this goal and understand the formation mechanism of thiophenic sulfur compounds, this study focused on the release behavior of thiophenic sulfur compounds during coal pyrolysis, which is an important phase for all coal thermal conversion processes. The pyrolyzer (CDS-5250) and gas chromatography-mass spectrometry (Focus GC-DSQII) were used to analyze thiophenic sulfur compounds in situ. Several coals with different coal ranks and sulfur contents were chosen as experimental samples, and thiophenic sulfur compounds of the gas produced during pyrolysis under different temperatures and heating rates were investigated. Levels of benzothiophene and dibenzothiophene were obtained during pyrolysis at temperatures ranging from 200°C to 1300°C, and heating rates ranging from 6°C/ms to 14°C/ms and 6°C/s to 14°C/s. Moreover, the relationship between the total amount of benzothiophene and dibenzothiophene released during coal pyrolysis and the organic sulfur content in coal was also discussed. This study is beneficial for understanding the formation and control of thiophenic sulfur compounds, since it provides a series of significant results that show the impact that operation conditions and organic sulfur content in coal have on the amount and species of thiophenic sulfur compounds produced during coal pyrolysis.

Application of Bacillus subtilis for reducing ash and sulfur in coal

The replacement of coal with other energy sources is due to the presence of harmful impurities such as sulfur that can lead to emission of harmful and corrosive gases such as H2S and SO2. These gases can affect the human health due to its toxicity. Also, the mineral matter (ash) can cause several types of respiratory system diseases due to the presence of heavy metals and formation of hazardous compounds while burning of coal. In order to avoid the production of such emissions, the researchers all over the world were looking for a methodology that can eliminate or reduce these impurities from coal. Therefore, the current study aims at decreasing the sulfur and ash content in Egyptian coal (Maghara coal), using bioflotation technique. The effect of Bacillus subtilis (B. subtilis) on the removal/reduction of sulfur and ash was investigated. The affinity of B. subtilis to coal surface was characterized using zeta-potential, adsorption tests and Fourier transform infrared. The bioflotation results showed that, at optimum conditions, a clean coal contains 0.92 % total sulfur and 1.95 % ash and yield exceeding 72 % was obtained from the starting coal containing 3.3 % sulfur and 6.65 % ash.

Research on the Correlation between Mercury and Sulfur Content in Coals

To reduce mercury emission in the flue gas at coal-fired power plant, it is very important and meaningful to research the mercury content and the existing status of other elements in coal. In this paper, mercury and sulfur content including their relevant relations of existing speciations from five coal samples were studied. Experimental method was based on U.S. EPA Method 7471 and experimental apparatus was automatic mercury analysis system Hydra AA. The results showed that in these 5 coal samples, the range of mercury content was from 0.284μg/g to 0.663μg/g and the average content was 0.401μg/g. The range of sulfur content was from 0.688% to 5.546% and the average content was 2.30% . The existing status of mercury and sulfur in coal was very complex. Under normal circumstances, when there was high sulfur content in coal, there was also high mercury content. However, the low sulfur coal may be of high mercury content.

Air Preheaters Operating Situation and Analysis in Coal-Fired Generators

To prevent and dispose all kinds of problems occurred in the air preheaters of the large coal-fired power plants and improve the performance of the air preheaters, the representative problems of the air preheaters in Henan province was summarized with the statistical method. With specific cases, its adverse impact for boilers and auxiliary machines were analyzed. The main reasons for causing these problems were design flaws, maintain undeserved, poor blowing effect and high sulfur content in coal that can cause acid corrosion to the air preheaters. A series of countermeasures were put forward to resolve the problems.

Environmental externalities and regulation constrained cost productivity growth in the US electric utility industry

This paper examines whether having to comply with Phase 1 of Title IV of the 1990 Clean Air Act, and rate of return regulation, each impacted the rate of total factor productivity (TFP) growth when accounting for the production of good and bad outputs. Phase 1, effective from 1995 to 1999, requires electric utilities to reduce their emissions of sulfur dioxide and nitrogen oxide (bad outputs). Actions undertaken to reduce the emissions (using less sulfur content coal, installing equipment), may have led to higher production costs, and impacted the rate of TFP growth. Rate regulation may impact how the firm produces its selected output level, which could lead to higher cost over time, and biased estimates of TFP growth. Following the work of Ball et al. (Struct Change Econ Dyn 16(3): 374–394, 2005), who developed the standard Malmquist cost productivity (MCP) index, we develop a MCP index for a rate regulated firm (RMCP index) then use the standard and regulated indices to determine whether having to comply with Phase 1 impacted TFP growth. Empirical results indicate that (i) the RMCP index underestimated the rate at which TFP growth occurred, (ii) Phase 1 utilities on average experienced positive TFP growth from 1996 to 2000 (Phase 1 firms experienced higher TFP growth rates than the rates experienced by firms not subject to Phase 1), and operated more allocatively inefficient in complying with the Phase 1 restrictions. Complying with Phase 1 did not affect the rate at which technical change occurred or the rates of change in scale efficiency.

Desulfurization of Lu,an Coal by Ultrasonic and Microwave

In this paper, the desulfurization of LA (Lu,an) coal was carried out by combining the method of ultrasonic and microwave irradiation. The effect of microwave time and combination of ultrasonic and microwave irradiation on the desulfurization of LA coal was investigated. The results showed that the sulfur removal effect of microwave irradiation time is obvious. The removal rate of organic sulfur increased with the microwave irradiation time increased. The effect of ultrasonic before microwave irradiation on desulfurization was greater than simply microwave method. The sulphur form was investigated systematically using X-ray photoelectron spectroscopy (XPS). After microwave and ultrasonic co-enhanced oxidative desulfurization of coal, the content of sulfur in coal was decreased by the XPS analysis.

Characteristics of hydrogen sulfide formation in pulverized coal combustion

Low excess air combustion and two-stage combustion are currently being attempted as a means of reducing NOx emission from the boiler in pulverized coal-fired power plants. However, a strong reducing atmosphere is formed in the region between burners and air ports in the case of two-stage combustion. This atmosphere promotes the formation of hydrogen sulfide (H2S), which causes sulfidation corrosion at the boiler wall. The control of H2S formation and the prevention of corrosion are important in power plants. In this study, the characteristics of H2S formation in two-stage combustion were investigated using a test furnace for pulverized coal combustion. H2S was formed in the case of H2 coexistence. The H2S concentration was affected by the fuel ratio and the sulfur content in coal. The H2S concentration is very low below a H2 concentration of about 2%, above which the H2S concentration has a strong correlation with that of H2. Furthermore, it was found that after the release of sulfur has finished, H2S and SO2 reach equilibrium concentrations in accordance with the equation SO2+3H2=H2S+2H2O.

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.