Determination Of Sulfur In Coal Research Articles

Assessment of microwave-induced combustion in disposable vessels as a low-cost approach for sulfur determination in coal

The determination and removal of sulfur from coal has become important to the industry and the environment for the pollution control. Therefore, the microwave-induced combustion in disposable vessels (MIC-DV) for sulfur determination in coal by inductively coupled plasma optical emission spectrometry (ICP-OES) was proposed. The parameters that could influence in the combustion, such as sample mass (5 to 30 mg), influence of pressurization (1.0 to 1.8 bar), and type (H2O and HNO3), concentration (1.0 to 14.4 mol L−1) and volume (2.5 to 12.5 mL) of absorbing solution were evaluated. The proposed method was compared with microwave-assisted digestion (MAD), microwave-induced combustion (MIC) and direct solid sampling elemental analysis (DSS-EA) and the agreement was better than 91, 82 and 91%, respectively. The limits of detection and quantification for sulfur in coal after optimized MIC-DV and determination by ICP-OES were 11 and 37 µg g−1. It is important to mention, that the MIC-DV employs low cost and environmental friendly materials and instrumentation. Moreover, the speed of the sample preparation process was increased comparing to MAD, MIC and DSS-EA, since sample combustion was achieved in less than 30 s in a rotor containing 5 positions. Last, but not least, the MIC-DV method is based on the single vessel principle, using the same vessel comprising the sample preparation and quantification, avoiding the use of additional vessels for dilution, reducing the risk of contamination by excessive handling.

Direct Determination of Sulfur in Coal by Electrothermal Vaporization Coupled with Optical Emission Spectrometry

AbstractDie direkte Feststoff‐Multielementanalytik von Kohle und deren Konversionsprodukten mittels elektrothermischer Verdampfung in Verbindung mit einem Atomemissionsspektrometer mit induktiv gekoppeltem Plasma (ETV‐ICP OES) wird am Beispiel der Schwefelbestimmung dargestellt. Zusätzlich zur Gesamtgehaltsbestimmung ist eine Aussage über das Freisetzungsverhalten des Schwefels, basierend auf der kontrollierten thermischen Zersetzung der Probe in Argonatmosphäre und unter Normaldruck möglich. Dies könnte die Grundlage für eine temperaturabhängige Schwefelspeziation darstellen.

Determination of sulfur in coal by solid sampling graphite furnace high-resolution molecular absorption spectrometry

An analytical procedure for quantitative analysis of sulfur in coal by direct solid sampling graphite furnace high-resolution continuum source molecular absorption spectrometry (HR-CS GF MAS) is described, which is based on the molecular absorption of tin sulfide. The heating program is optimized, and a series of chemical modifiers (Ir, Mg, Pd, Ru, W, Zr) are tested. All measurements are accomplished with an Ir coated platform and Pd as modifier, because the best results are achieved.Accurate results are obtained using the central SnS line of the band found at 271.578nm with precision values between 1 and 6%. A limit of detection of 10ngS absolute is achieved. Furthermore, the trueness of the procedure is verified by analysis of certified reference materials. Several coal samples with a concentration range from 0.8 to 21.7mgg−1S and three certified reference materials are analyzed. In all cases, simple calibration with aqueous standards is found to be possible and the sample throughput is 2–3 samples per hour (6 replicates per sample).

Determination of sulfur in coal and ash slurry by high-resolution continuum source electrothermal molecular absorption spectrometry

We propose a procedure for the determination of sulfur in coal slurries by high resolution continuum source electrothermal molecular absorption spectrometry. The slurry, whose concentration is 1mgmL−1, was prepared by mixing 50mg of the sample with 5% v/v nitric acid and 0.04% m/v Triton X-100 and was homogenized manually. It sustained good stability. The determination was performed via CS molecular absorption at 257.592nm, and the optimized vaporization temperature was 2500°C. The accuracy of the method was ensured by analysis of certified reference materials SRM 1632b (trace elements in coal) and SRM 1633b (coal fly ash) from the National Institute of Standards and Technology, using external calibration with aqueous standards prepared in the same medium and used as slurry. We achieved good agreement with the certified reference materials within 95% confidence interval, LOD of 0.01% w/w, and RSD of 6%, which confirms the potential of the proposed method.

Determination of sulfur in coal using direct solid sampling and high-resolution continuum source molecular absorption spectrometry of the CS molecule in a graphite furnace

An analytical method has been developed for the determination of sulfur in coal using direct solid sample analysis in a graphite tube furnace and high-resolution continuum source molecular absorption spectrometry (HR-CS GF MAS). The molecular absorbance of the carbon monosulfide molecule (CS), which is formed in the vaporization stage, has been measured using the rotational line at 258.033nm. Several chemical modifiers were tested and Ru, applied as permanent modifier was chosen, because it exhibited the best performance. The optimum pyrolysis and vaporization temperatures were found to be 500°C and 2200°C, respectively. Aqueous standard solutions prepared from l-cysteine were used for calibration, as the linear regression obtained for this standard was not significantly different from that for a certified coal reference material (CRM) according to a Student t-test. The results obtained for sulfur in three coal CRM and six additional samples also showed no significant difference for the two calibration techniques according to the same statistical test. The sulfur concentration in the coal samples was found between 3.5mgg−1 and 33.7mgg−1 with a typical repeatability around 10%. The limit of detection for the direct analysis of solid coal samples was better than 0.1μgS.

Analytical Methods for Sulfur Determination in Glasses, Rocks, Minerals and Fluid Inclusions

The analytical techniques that are normally utilized to determine the concentration of sulfur in geologic materials can be divided into bulk analytical methods that require sample powders and microanalytical methods done in situ . The most common method of bulk sulfur analysis is accomplished using combustion methods followed by detection of SO2 in an infrared cell. A similar method involves an elemental analyzer coupled to a mass spectrometer where the mass 64 ion beam is monitored and compared to a standard. X-ray fluorescence is another method of bulk powder analysis that is well established for the determination of sulfur in coal and plant materials, but is only rarely used for the analysis of rocks due to a relatively high detection limit and difficulties with sample fusion. Micro-analytical techniques normally involve individual minerals or glasses. The most commonly used method is electron microprobe analysis (EMPA), but ion microprobe (SIMS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) methods are useful for some samples. Nuclear methods of sulfur analyses are useful for some materials largely because of their very low detection limits. A relatively new technique is the application of LA-ICP-MS to determine the concentration of sulfur in fluid inclusions contained within glasses and minerals. In this chapter we review how these methods may be used to measure the concentration of sulfur in a variety of geologic materials. We emphasize the types of materials that can be analyzed, sample preparation, standardization techniques, detection limits and uncertainties that are associated with each of the methods. Elsewhere in this volume, the determination of sulfur species in glasses is discussed (Chapter 2 -- Wilke et al. 2011) and methods of isotopic analyses are treated (Chapter 15 -- Marini et al. 2011). ### Total sulfur concentration in minerals, rocks and glasses using elemental analyzer – infrared absorption technology Automated, high-temperature combustion, carbon-sulfur analyzers utilize solid state infrared (IR) absorption for the …

Sulfur determination in coal using molecular absorption in graphite filter vaporizer

The vaporization of sulfur containing samples in graphite vaporizers for atomic absorption spectrometry is accompanied by modification of sulfur by carbon and, respectively, appearance at high temperature of structured molecular absorption in 200–210nm wavelength range. It has been proposed to employ the spectrum for direct determination of sulfur in coal; soundness of the suggestion is evaluated by analysis of coal slurry using low resolution CCD spectrometer with continuum light source coupled to platform or filter furnace vaporizers. For coal in platform furnace losses of the analyte at low temperature and strong spectral background from the coal matrix hinder the determination. Both negative effects are significantly reduced in filter furnace, in which sample vapor efficiently interacts with carbon when transferred through the heated graphite filter. The method is verified by analysis of coals with sulfur content within 0.13–1.5% (m/m) range. The use of coal certified reference material for sulfur analyte addition to coal slurry permitted determination with random error 5–12%. Absolute and relative detection limits for sulfur in coal are 0.16μg and 0.02mass%, respectively.

99/02913 Improvement of determination of total sulfur in coal by Eschka gravimetric method

99/02913 Improvement of determination of total sulfur in coal by Eschka gravimetric method

97/00688 Determination of ash and sulfur in coal via off-line calibration of XRF

Highly precise and accurate sulphur analyses are required to establish material balance for sulphur in utility boilers where sulphur is present at low levels in the fly ashes. Sulphur determinations using the established methods depend on quantitative extraction of sulphur from some form of sample decomposition residuum. Errors from incomplete extractions can lead to results which are as much as 30% low. The total sample dissolution-X-ray fluorescence procedure developed in this study, yields results which have the precision and accuracy required for material balance calculations. Using this method, fly ash samples containing less than 1% sulphur can be determined with a relative standard deviation of about 3%. Most importantly, the new procedure eliminates the negative bias inherent in the established methods. It is important to note that the procedure is not applicable to the analysis of sulphur in coal, since the organic sulphur would escape detection. However, standard analysis procedures for the determination of sulphur in coal also have a relative standard deviation of about 3%.

96/06768 A new method for the determination of combustible sulfur in coal

96/06768 A new method for the determination of combustible sulfur in coal

95/06648 Direct determination of sulfur in coal by X-ray fluorescence analysis

In chloroplast photosystem II, the extrinsic polypeptide of 33 kDa is involved in the stabilization the Mn cluster in charge of water splitting and in the fulfillment of the Ca2+-cofactor requirement for oxygen evolution. The conformational analysis of the purified 33 kDa extrinsic polypeptide was carried out using FTIR spectroscopy with its self-deconvolution and second derivative resolution enhancement as well as curve-fitting procedures. The FTIR spectroscopic results showed that the isolated polypeptide is characterized by a major proportion β-sheet conformation (36%) with 27% α-helix, 24% turn, and 13% β-antiparallel structures.

On-line sulfur determination in coal with prompt gamma neutron activation

The prompt gamma neutron activation method has been found to be a useful technique for the on-line industrial measurements of bulk media. Based on this method, a system was developed for the on-line sulfur determination in coal. A 252Cf source is used for the production of neutrons and a high purity germanium (HPGe) detector is used for the detection of the gamma rays emitted. The system has been found to be linear over the range tested (0.5–6% in weight sulfur). Neutron-absorbing trace elements in coal such as Cl, were found to have no influence on the sulfur determination of the samples.

Determination of sulphur in coal products by inductively coupled plasma atomic emission spectrometry

A method for the determination of both the soluble and total sulphur in coal products has been devised. The procedure adopted for extracting the soluble sulphates from test materials was based on refluxing samples with hot, dilute HCl and H2O2, whereas the total sulphur content could be quantified after combustion with V2O5 in an O2 flow. The analytical determinations were accomplished by using inductively coupled plasma atomic emission spectrometry. The reproducibility (on average between 3.8 and 1.4%), linear dynamic range (4–5 orders of magnitude) and detection power (1 µg g–1 of sample) were found to be more than adequate for the stated purpose, thus providing a flexible and convenient tool for the determination of sulphur in coal and fly ash.

Sulphur determination by proton-induced prompt gamma emission: The effect of the matrix and its importance in coal analysis

The determination of sulphur through γ-ray spectrometry induced by 5 MeV protons was chosen to study the effect of dilution and spike addition on the stopping power of the matrix and applied to the determination of sulphur in coal. Changes in the matrix cannot be ignored even for the spiking technique.

A simple method for pyritic sulfur determination in coal, using Mössbauer spectroscopy

A simple method for pyritic sulfur determination in coal, using Mössbauer spectroscopy

Development of an X-ray fluorescence method for on-line determination of sulphur in coal

An XRF method for determining sulphur content in coal via iron fluorescence measurement has been investigated. Factors limiting accuracy have been assessed and quantified. Results for 0.2 mm-0 coal on a laboratory analyser and for 5 mm-0 coal on a commercial on-line analyser show calibration accuracies (1σ) of ±0.02% to ±030% sulphur for individual coal types. Many of the values obtained, particularly for low ash coals, are acceptable for on-line monitoring purposes.

Substoichiometric Isotope Dilution Analysis of Sulphur in coal

Abstract Substoichiometric radioisotope dilution analysis has been applied to the determination of sulfur in coal. The experimental procedure involved the combustion of coal samples labelled with 35S as sodium sulfate in a flowing oxýgen stream, collection of the combustion gases in hydrogen peroxide and substoichiometric precipitation of barium sulfate. Samples of 0.2–10.0% sulfur were accurately determined with ±2% RSD by measuring the activity of the precipitates thus obtained and with comparison to standard samples carried through the same procedure. Analysis times of 15 minutes per sample were typical.

Sulfur determination in coal by 14 MeV neutron activation analysis

A procedure involving the irradiation of coal samples with 14 MeV neutrons and subsequent gamma-ray spectrometry of the irradiated sample for the estimation of solfur in coal, has been outlined. The samples were irradiated with 14MeV neutrons from a Cockroft-Walton type generator for one minute and then subjected to gamma-ray spectrometry for another minute using an automated transfer cyclic system. Ten such cycles were repeated for accumulating events under the 2130 keV gamma ray photopeak belonging to34P (T=12.4 s) produced by the34S(n, p)34P reaction for assessing the lower level of detection, LLD, of Sulfur. Interferences due to the presence of other elements in coal were also determined. Sulfur can be determined at LLD of 0.25% in coal provided a 5 g sample of the coal is irradiated with a neutron flux of 5·109 n·cm−2·sec−1 assayed with a gamma ray spectrometer having a large hollow core Ge(Li) detector and an anti-Compton shield.

Analysis for sulphur in coal ash

Highly precise and accurate sulphur analyses are required to establish material balance for sulphur in utility boilers where sulphur is present at low levels in the fly ashes. Sulphur determinations using the established methods depend on quantitative extraction of sulphur from some form of sample decomposition residuum. Errors from incomplete extractions can lead to results which are as much as 30% low. The total sample dissolution-X-ray fluorescence procedure developed in this study, yields results which have the precision and accuracy required for material balance calculations. Using this method, fly ash samples containing less than 1% sulphur can be determined with a relative standard deviation of about 3%. Most importantly, the new procedure eliminates the negative bias inherent in the established methods. It is important to note that the procedure is not applicable to the analysis of sulphur in coal, since the organic sulphur would escape detection. However, standard analysis procedures for the determination of sulphur in coal also have a relative standard deviation of about 3%.

The rapid determination of sulfur in coal

The rapid determination of sulfur in coal