Low Sulfur Levels Research Articles

Distribution Characteristics of Sulfur and the Main Harmful Trace Elements in China's Coal

Abstract: To promote the rational development and use of clean coal resources in China, data on the regional and age distribution of sulfur, arsenic and other harmful elements in Chinese coal was broadly collected, tested for content, and analyzed. Coal in northwestern China is characterized by low to extremely low levels of sulfur; the coal of the Taiyuan Formation in northern China mainly has high‐sulfur content; that of the Shanxi Formation is mainly characterized by low sulfur coal; and the Late Permian coal in southern China has overall higher sulfur content; other regions have low sulfur coal. The average content of harmful trace elements in the bulk of China's coal is similar to the corresponding content in the coal of the North America and the rest of the world, whereas the content of various elements (Hg, Sb and Se) is different in magnitude to the corresponding percentage in the crust. The average content of the elements Cr, Se, Co, Be, U, Br in Late Permian coal in S China ranks first in the country whereas the average content of Hg and CI in the coals of Late Carboniferous to Early Permian age in N China are the highest. The average content of Mn in Early and Middle Jurassic coal is higher in NW China. The high content of harmful elements in some coal should cause particular concern both in the development and utilization of coal.

Rapid Determination of Low-Level Sulfur Compounds in Beer by Headspace Gas Chromatography with a Pulsed Flame Photometric Detector

Off-flavors in beer are frequently due to the presence of sulfur compounds. A simple and sensitive method for the analysis of volatile sulfur compounds in beer at trace levels was developed using headspace gas chromatography with a pulsed flame photometric detector. Different capillary columns were tested, and a 60-m nonpolar DB-1 capillary column was found to be the most appropriate. Four sulfur compounds, including hydrogen sulfide, methanethiol, ethanethiol, and dimethyl sulfide, could be quantified simultaneously using ethyl methyl sulfide as the internal standard. Calibration curves were established in a 4% (vol/vol) ethanolic solution with pH adjusted to 4.0; linear correlation coefficients (r) were greater than 0.99 for all target compounds. This method enables four sulfur compounds in beer to be determined at trace levels, with recoveries greater than 96%, a repeatability error of less than 5%, and limits of detection between 0.1 and 2 μg/L. The overall method was successfully applied to the determination of sulfur compounds studied in several beers.

Determination of sulfur in steels by radiochemical neutron activation analysis with liquid scintillation counting

A method has been developed for the determination of low-level sulfur in steels by radiochemical neutron activation analysis. During sample irradiation, 35S is produced by the 34S(n,γ)35S reaction. Irradiated steels are mixed with sulfur carrier and dissolved in HCl/HNO3. Sulfur is reduced to H2S by reaction with HI/H3PO2/HCl. The evolved H2S is absorbed in dilute NaOH, which is mixed with scintillation cocktail for the measurement of 35S by liquid scintillation counting. Sulfur carrier yield is determined by iodometric titration. Chlorine is also determined by RNAA in order to correct for 35S produced via the 35Cl(n,p)35S reaction. Sulfur has been determined at mass fractions as low as ≈5 mg/kg in ultra-high-purity iron using this method.

INTEGRATING ALBEMARLE RESOLVE DESULFURIZATION TECHNOLOGY WITH NOVEL PETRO-CANADA PROCESS CONCEPTS IN COMMERCIAL FCCU OPERATIONS

The gasoline and distillate sulfur regulations promulgated throughout the world to reduce tail-pipe emissions are now strongly impacting refinery operations and investments. FCC gasoline is recognized as the principal contributor of sulfur to the gasoline pool and has become the focus for meeting the new specifications. The difficulty in removing sterically hindered sulfur species in the fluid catalytic cracking unit (FCCU) cycle oil drives up the hydrogen and investment costs for treating the distillates. Although installation of pre- and post-treatment facilities is planned by many refiners, other non-capital approaches such as undercutting are being evaluated to meet interim and future sulfur levels. Even when expensive treatment facilities are installed, operating costs can be lowered and the flexibility of the facility increased with improvements in the ability to remove sulfur in the FCCU. In this article, we detail Petro-Canada's experience in integrating Albemarle's RESOLVE sulfur reduction technology with a combination of innovative process ideas. These concepts include heavy naphtha recycle, coprocessing of hydrogen donor feeds, and recycle of light cycle oil (LCO) to a specially designed stripper reactor. Special attention is paid to the interaction of deep FCC feed hydrodesulfurization with the FCC performance. The results demonstrate that very low FCC gasoline sulfur levels can be achieved without significant capital investment through novel approaches to recycle, creative integration of cat feed hydrotreating unit (CFHTU)-FCCU designs and operations, and application of state-of-the-art sulfur reduction additive technology. An added benefit of the RESOLVE 950 sulfur reduction technology is the substantial elimination of sulfur oxides in the FCC flue gas. This has been observed in Petro-Canada operations and numerous other RESOLVE 950 applications around the world.

Trickle bed reactor model to simulate the performance of commercial diesel hydrotreating unit

A two phase mathematical model was developed to simulate the performance of bench scale and commercial hydrotreating reactors. Major hydrotreating reactions, namely, hydrodesulphurization, hydrodearomatization and olefins saturation were modeled. Experiments were carried out in a fixed bed reactor to study the effect of different process variables and these results were used for estimating kinetic parameters. Significant amount of feed vaporization (20–50%) was estimated under normal operating conditions of DHDS suggesting the importance of considering feed vaporization in DHDS modeling. The model was validated with plant operating data, under close to ultra low sulphur levels by correctly accounting for feed vaporization in heat balance relations and appropriate use of hydrodynamic correlations. The model could predict the product quality, reactor bed temperature profiles and chemical hydrogen consumption in commercial plant adequately.

Silica-Catalyzed tert-Butyl Hydroperoxide Oxidation of Dibenzothiophene and Its 4,6-Dimethyl Derivative: A Route to Low-Sulfur Petroleum Feedstocks

Silica catalyzes the tert-butyl hydroperoxide (TBHP, t-BuOOH) oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-Me2DBT) to their oxides at 50−90 °C. Sulfur concentrations in simulated hydrotreated petroleum feedstock solutions containing 374 ppm of sulfur as DBT or 4,6-Me2DBT can be reduced to 1 ppm within 40 min at 90 °C. As an inexpensive, stable, and recyclable catalyst, silica has several advantages over other catalysts for the oxidation of DBTs to their easily separated oxides as a means of achieving low sulfur levels in petroleum feedstocks.

An investigation of the thermal stability and sulphur tolerance of Ag/γ-Al2O3 catalysts for the SCR of NOx with hydrocarbons and hydrogen

The sulphur tolerance and thermal stability of a 2wt% Ag/γ-Al2O3 catalyst was investigated for the H2-promoted SCR of NOx with octane and toluene. The aged catalyst was characterised by XRD and EXAFS analysis. It was found that the effect of ageing was a function of the gas mix and temperature of ageing. At high temperatures (800°C) the catalyst deactivated regardless of the reaction mix. EXAFS analysis showed that this was associated with the Ag particles on the surface of the catalyst becoming more ordered. At 600 and 700°C, the deactivating effect of ageing was much less pronounced for the catalyst in the H2-promoted octane-SCR reaction and ageing at 600°C resulted in an enhancement in activity for the reaction in the absence of H2. For the toluene+H2-SCR reaction the catalyst deactivated at each ageing temperature. The effect of addition of low levels of sulphur (1ppm SO2) to the feed was very much dependent on the reaction temperature. There was little deactivation of the catalyst at low temperatures (≤235°C), severe deactivation at intermediate temperatures (305 and 400°C) and activation of the catalyst at high temperatures (>500°C). The results can be explained by the activity of the catalyst for the oxidation of SO2 to SO3 and the relative stability of silver and aluminium sulphates. The catalyst could be almost fully regenerated by a combination of heating and the presence of hydrogen in the regeneration mix. The catalyst could not be regenerated in the absence of hydrogen.

The interactive effects of phosphorus, sulfur and cultivar on the early growth and condensed tannin content of greater lotus (Lotus uliginosus) and birdsfoot trefoil (L. corniculatus)

Although soil phosphorus and sulfur influence the establishment and condensed tannin (CT) content of perennial Lotus species, previous field responses to superphosphate fertiliser applications have been confounded by moisture stress and weed competition, and the association of CT content with soil fertility has not been consistent between sites and species. In a glasshouse experiment, 2 cultivars of L. uliginosus (Grasslands Maku and Sharnae) and 1 cultivar of L. corniculatus (Grasslands Goldie) were grown in sand culture under 3 levels of phosphorus (0.1, 0.2 and 0.7 mmol/L) and 3 levels of sulfur (2.6, 6.4 and 92.4 mmol/L), applied as nutrient solutions, to examine the interaction of cultivar, phosphorus and sulfur on dry weight, CT content and mineral nutrient concentrations. Dry weight of the Lotus cultivars 68 days after sowing was significantly increased by increasing levels of phosphorus and sulfur, and there was a significant phosphorus × sulfur interaction, characterised by a much smaller response to increasing phosphorus at low levels of sulfur compared with the response at intermediate and high levels. Results indicated that positive responses to superphosphate applications at establishment can be expected if weed competition is controlled and that both soil phosphorus and sulfur should be monitored in order to predict responses to superphosphate applications at sowing. In L. corniculatus cv. Grasslands Goldie, low levels of CT were maintained at increasing phosphorus and sulfur treatment levels, whereas the CT content of the L. uliginosus cultivars increased with increasing levels of phosphorus and sulfur and was positively correlated with dry weight accumulation. This result, allied to measurements of CT in grazed swards, suggests that a management strategy of frequent cutting or grazing during the active growth phase will maintain optimal CT levels for grazing in L. uliginosus cultivars.

Rapid Determination of Sulfur in Liquid Hydrocarbons for At-Line Process Applications Using Combustion/Oxidation and UV-Fluorescence Detection

Abstract With the reduction in sulfur levels in gasoline and diesel products, it is necessary to have a method available which can precisely and accurately measure the very low levels of sulfur in these fuels. ASTM test method D 5453, Sulfur by Combustion and Ultraviolet Fluorescence (UVF), is a laboratory-based technology that has been widely used in the industry for such purposes for more than a decade. An on-line/at-process version of this technique is described which can complete a fast analysis in less than one minute. Thus, near real-time data can be obtained when refineries and terminals need to make rapid determinations of sulfur levels for process control and pipeline distribution decisions involving the new generation “clean” hydrocarbon fuels. Particularly discussed is the advantage gained for decision making involving detection of transport boundaries and related custody transfer issues.

Low-Level Sulfur in Fuel Determination Using Monochromatic WD XRF—ASTM D 7039-04

Abstract A monochromatic wavelength dispersive X-ray fluorescence (MWDXRF) technique has been successfully developed for measuring low-level sulfur in fuel. In this technique, two doubly curved crystal (DCC) optics were used to provide monochromatic excitation and fixed channel wavelength dispersive analysis. Using highly efficient DCC optics, compact bench top MWDXRF analyzers for sulfur analysis have been successfully produced. A new ASTM standard test method for low-level sulfur determination in diesel and gasoline, D7039-04, has been developed based on this technique. Data for ultra-low-sulfur fuel were collected and analyzed using this new method. In this paper, the results of repeatability, reproducibility, and bias are presented and discussed. The repeatability for 10-ppm sulfur fuel was shown to be around 1 ppm. The pooled limit of quantification (PLOQ) for ultra-low-sulfur diesel was found to be less than 1.5 ppm in this study. The reproducibility of 15-ppm sulfur diesel fuel was determined to be better than 3 ppm (95 % confident level). The limit of detection for a single analyzer was found to be 0.36 ppm. The effect of matrix composition was investigated. The correction due to matrix for low-level sulfur diesel and gasoline is generally not significant.

Deep HDS on doped molybdenum carbides: From probe molecules to real feedstocks

Deep HDS on phosphorus and nickel–alumina-supported molybdenum oxycarbides was studied, first, with probe molecules then with real feedstocks. Catalysts were characterized by elemental analysis, X-ray diffraction, CO chemisorption, transmission electron microscopy, X-ray photoelectron spectroscopy and infrared spectroscopy. Propene and tetralin hydrogenation were used to probe the activity of the doped materials. Hydrodesulfurization of 4,6-dimethyldibenzothiophene was investigated as a probe for the deep HDS of diesel fuel. For contact times ranging from 0 to 0.4 s, the HDS of 4,6-DMDBT is zeroth-order with respect to the reactant and proceeds via two parallel routes, direct desulfurization and hydrogenation pathways, the former being preponderant. Phosphorus and nickel modify the catalytic behaviour and induce the highest HDS activity. Deep hydrodesulphurization (HDS) of diesel fuels was carried out on promoted or non-promoted Mo 2C-supported γ-Al 2O 3 and on bulk Mo 2C under standard industrial conditions. The effect of the promoter was investigated for different feedstocks on HDS and hydrogenation (HDA) with very low levels of sulfur. The HDS conversion indicated that P-doped alumina supported carbide catalysts were as active as a commercial Co–Mo/Al 2O 3 catalyst for low level of sulfur in the feed. Furthermore, the refractory compounds, such as 4,6-DMDBT were only transformed on molybdenum carbide catalyst under industrial conditions for hydrotreated gas oils. For feeds containing less than 50 wt. ppm in sulfur, P-doped carbides were more active than commercial catalysts for HDA, as well as deep HDS or HDN.

A Comparative Study of the HDS Kinetics of Straight Run and Coker Gas Oils Under Deep Desulfurization Conditions

Deep desulfurization of diesel blending streams has gained considerable importance in the petroleum refining industry in recent years due to environmental regulations which limit the sulfur content of diesel fuel to very low levels. Among the various factors influencing deep desulfurization of diesel to lower and lower sulfur levels, the quality of the feedstock plays an important role. In the present work, the degree of desulfurization of two different feedstocks, namely, coker gas oil (CGO) and straight run gas oil (SRGO) and their blends was investigated under different operating severities. The distributions of different types of sulfur compounds in both feeds were examined by GC-SCD. Kinetics of desulfurization of both feeds under deep desulfurization conditions was also studied. The results revealed that SRGO, in spite of having a significantly larger amount of total sulfur, desulfurized more easily and produced diesel fuel with low sulfur levels in the desired range (< 350 ppm) at lower temperatures compared with CGO. More severe operating conditions (higher temperature, lower LHSV etc.) were found necessary to bring about deep desulfurization of CGO and its blends with SRGO to the same sulfur level. Kinetic experiments showed a reaction order of 1.5 for the overall HDS of both types of feeds, but the activation energy was higher for CGO (30 kcal/mole) than SRGO (24 kcal/mole). The results are explained on the basis of the differences in the concentrations of nitrogen and refractory sulfur compounds present in the two feeds.

DP-SCD and LTMGC for Determination of Low Sulfur Levels in Hydrocarbons

Abstract A novel measurement technique has been developed for the rapid determination of low levels of sulfur in hydrocarbon matrices. The technique employs low thermal mass gas chromatography (LTMGC) and a dual plasma sulfur chemiluminescence detector (DP-SCD). Highly sensitive total volatile sulfur measurement can be made in less than 30 s with detection limits in the 20–30 parts per billion range. Response is linear over at least three orders of magnitude sulfur with excellent repeatability. By taking advantage of LTMGC's rapid temperature programming and cool down time, it is also possible to measure individual sulfur species, analogous to ASTM D 5623. Conditions have also been developed using the same analytical apparatus to detect the major elemental sulfur allotropes (S2, S3, S6, S7, and S8) in gasoline at levels that can cause silver corrosion.

Engine Lubricant Trends Since 1990

A review is undertaken of the important trends in engine lubricant performance tests that have taken place over the last 10-15 years. Lubricant formulations are driven by industry standard specifications, original equipment manufacturer requirements, and consumer needs. A review is given of the important specifications and associated performance tests, and how these have impacted on lubricant development. The key trends are, firstly, the need for improved fuel economy, secondly, the need for improved oxidation stability, thirdly, the need for improved handling of contaminants (e.g. soot), and, fourthly, the recent move to lubricants containing low levels of sulphur, phosphorus, and sulphated ash, for after-treatment device compatibility reasons.

A comparison of high accuracy isotope dilution techniques for the measurement of low level sulfur in gas oils

A comparison of high accuracy methods for the analysis of total sulfur in gas oils by three metrology institutes is described. The work contains a comparison of three different aspects of the analysis: sample digestion, instrumental measurement and isotope dilution strategies. Thermal ionisation mass spectrometry (TIMS) in combination with high pressure asher (HPA) or Carius tube digestion has traditionally been used for such high accuracy analysis. However, this paper demonstrates that the faster, less laborious technique of ICP-MS in combination with microwave digestion is equally capable. Results from the comparison experiments show excellent agreement for fuel samples containing sulfur concentrations in the range 11–200 μg g −1. This excellent agreement across the different sample preparation, measurement and isotope dilution techniques has been exploited in the certification of two new diesel fuel reference materials.

Elemental Analysis of Soft Plaque and Calcified Plaque Deposits from Human Coronary Arteries and Aorta

Twenty-five samples of soft plaque and calcified plaque deposits from human hearts or aorta were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The determined elements were Ca, P, Na, K, Mg, Zn, Cu, Ba, Pb, Fe, Al, Si, and S. Results showed that the concentration of all elements in the soft plaque was at the micromolar level. In the calcified deposits, the concentrations of Ca and P were at least an order of magnitude higher than the soft plaque, but the other elements were at the same order of magnitude. In the calcified plaque the molar ratios of Ca/P suggested that a significant portion existed as hydroxyapatite Ca10(PO4)6(OH)3. However, their absolute concentrations indicated that this compound was not a major component of the plaque although it may play a major role in determining the crystal structure of the deposit. In some samples the Ca/P ratio was too high to conform to hydroxyapatite. In others it was too low. This indicated that both the calcium and phosphorus existed in other chemical forms which varied from sample to sample. In the soft tissue the P level was high indicating it existed primarily in chemical forms other than hydroxyapatite. The presence of homocysteine is often associated with heart disease. However, the low levels of sulfur indicate that although it may be present, it is not a major component of the plaque, but may nevertheless play an important role in its formation.

Deep hydrodesulphurization and hydrogenation of diesel fuels on alumina-supported and bulk molybdenum carbide catalysts

Deep hydrodesulphurization (HDS) of diesel fuels has been carried out on P (Ni)-promoted or non-promoted Mo 2C-supported γ-Al 2O 3 and bulk Mo 2C under standard industrial conditions (613 K, 3 MPa). The effect of the promoter was investigated for different feedstocks on HDS and hydrogenation (HYD) with very low levels of sulfur. The temperature effect was also followed. The HDS conversion indicates that phosphorus promoted alumina supported carbide catalysts are as active as a commercial Co–Mo/Al 2O 3 catalyst for low levels of sulfur in the feed. Furthermore, the refractory compounds such as 4,6-dimethyldibenzothiophene are only transformed on molybdenum carbide catalyst in industrial conditions for hydrotreated gas oils. With gas oils with less than 50 wt ppm in sulfur, phosphorus promoted molybdenum carbide catalysts become more active than commercial catalysts for the HYD of the aromatic compounds and the HDS or the HDN of the feedstock.

Effect of zirconium on structure and properties of high carbon Fe - 10.5 wt-%Al alloy

The effects of zirconium additions on the structure and properties of high carbon Fe - 10.5 wt-%Al alloy have been investigated. Three different alloys with nominal compositions, Fe - 10.5Al - 0.7C (base), Fe - 10.5Al - 0.7C - 0.1Zr and Fe - 10.5Al - 0 7C - 0.17Zr were prepared. Processing of these alloys through a combination of air induction melting with flux cover (AIMFC) and electroslag remelting (ESR) yielded sound ingots free from gas and microporosity with very low levels of sulphur, oxygen, and nitrogen. This process route also resulted in excellent recovery of aluminium and zirconium. The ESR ingots were hot forged and hot rolled at 1375 K and the hot rolled alloys were examined using scanning electron microscopy, electronprobe microanalysis, and X-ray diffraction to understand the microstructure of these alloys. The ternary, Fe - 10.5Al - 0.7C (base) alloy exhibited a two phase microstructure consisting of a large volume fraction of Fe3AlC0.5 precipitates in an Fe - Al (α) matrix. Addition of zirconium (0.1 and 0.17%) resulted in the precipitation of a very small volume fraction of fine zirconium oxycarbide particles in the Fe - Al ( α ) matrix in addition to a large volume fraction of Fe3AlC0.5 precipitates. Tensile and creep rupture tests were performed on all three alloys in the hot rolled condition. The base Fe - 10.5Al - 0.7C alloy exhibited poor room temperature ductility and creep properties. Addition of 0.1%Zr to the base alloy resulted in significant improvement in room temperature and high temperature ductility and creep properties. However, further increase in Zr addition from 0.1 to 0.17% was not beneficial.

Model of Desulphurization of Steel Melts in Ladles - Deoxidation and Slag Formers Calculation

The authors present their own model applicable for effective desulphurization of steel by ladle treatment. The model is based on a thermodynamic approach (equilibrium data) and technological data (correction factors). It consists of two parts. In the first part the authors present the formulae derived for estimation of the additions of deoxidation agents which ensure sufficiently low oxygen level prior to the desulphurization process, while the other part gives a qualitative and quantitative selection of slag formers to achieve low final levels of sulphur in steel. For the deoxidation process two variants were considered: (i) with Al only (for low silicon steels) or (ii) Al-Si (for silicon steels) as deoxidizers. For the desulphurization process three variants were assumed as to ladle slag composition: (i) slag consisting of a fraction of furnace slag, lime addition and deoxidation products, (ii) slag made of synthetic CaO-Al 2 O 3 and (iii) slag based on lime and fluorspar. The model formulae for desulphurization were derived using the sulphide capacity concept which relies on the optical basicity. In addition, rough estimates of the slag liquidus temperatures are given. A numeric example of the model application and the model algorithm (appendix) are enclosed.

Effect of rare earth elements and sulfur on microstructure and chilling tendency in flake graphite cast iron

A flake graphite cast iron was produced to determine the effect of rare earth (RE) additions on the microstructure and chilling tendency of low (0.01–0.03%S) and high (0.03–0.1%S) sulfur level content. Cooling curves and microstructures of base iron and RE-added flake graphite cast iron were also investigated. In this study, various ratios of RE/S were used to find stoichiometric balance of RE/S for optimum condition of type A graphite forming range and maximum chill reduction. To clearly identify the chilling tendencies, high quality pig iron was used. All experiments were conducted without post inoculation in order to clarify the effects of rare earth in the cast iron. It is clear that RE/S ratio about 2.5 showed type A graphite and chill depth at minimum level. It is considered that this RE/S favors the formation of RE-sulfides which act as substrates for graphite nucleation and thus decrease chilling tendency.