Sulfur Retention Research Articles

Combined effects of Fenton peroxidation and CaO conditioning on sewage sludge thermal drying

Joint application of Fenton’s reagent and CaO can dramatically enhance sludge dewaterability, thus are also likely to affect subsequent thermal drying process. This study investigated the synergistic effects of the two conditioners on the thermal drying behavior of sewage sludge and the emission characteristics of main sulfur-/nitrogen-containing gases. According to the results, Fenton peroxidation combined with CaO conditioning efficiently promoted sludge heat transfer, reduced the amounts of both free and bound water, and created porous structure in solids to provide evaporation channels, thus producing significant positive effects on sludge drying performance. In this case, the required time for drying was shortened to one-third. Additionally, joint usage of Fenton’s reagent and CaO did not increase the losses of organic matter during sludge drying process. Meanwhile, they facilitated the formation of sulfate and sulfonic acid/sulfone, leading to sulfur retention in dried sludge. Both of Fenton peroxidation and CaO conditioning promoted the oxidation, decomposition, and/or dissolution of protein and inorganic nitrogen in sludge pre-treatment. As a consequence, the emissions of sulfurous and nitrogenous gases from dewatered sludge drying were greatly suppressed. These indicate that combining Fenton peroxidation with CaO conditioning is a promising strategy to improve drying efficiency of sewage sludge and to control sulfur and nitrogen contaminants during sludge thermal drying process.

Sulfur retention in an oxy-fuel bubbling fluidized bed combustor: Effect of coal rank, type of sorbent and O2/CO2 ratio

In this work, SO2 retention via calcium-based sorbents added in a continuous bubbling fluidized bed combustor (∼3kWth) operating in oxy-fuel combustion mode is analyzed. Tests were performed at different operating temperatures with three sorbents, two limestones and one dolomite, and with three coals, ranging from lignite to anthracite, to analyze the influence of coal rank, type of sorbent, sorbent particle size, and O2/CO2 feeding ratio on the sulfation process.It was found that the combustor temperature had a strong influence on the limestones sulfur retention with a maximum at 900–925°C. The behavior of the limestones was qualitatively similar with the three coals, attaining the highest sulfur retention values working with the lignite and the lowest working with the bituminous coal. On the contrary, with the dolomite the sulfur retention was hardly affected by the combustion temperature and the sulfur retentions attained were higher than with the limestones. The sulfur retention increased with diminishing the Ca-based sorbent particle size, and it was hardly affected by the O2/CO2 ratio fed into the combustor.

Study of the Size Distribution of Sulfur, Vanadium, and Nickel Compounds in Four Crude Oils and Their Distillation Cuts by Gel Permeation Chromatography Inductively Coupled Plasma High-Resolution Mass Spectrometry

The size distribution of sulfur, vanadium, and nickel was determined for four crude oils and their distillation cuts using gel permeation chromatography (GPC) coupled to inductively coupled plasma high-resolution mass spectrometry (ICP HR MS). The results show a trimodal distribution of vanadium and nickel compounds in the crude oils, the atmospheric residues, and the vacuum residues and, for sulfur compounds, either a mono- or bimodal distribution depending upon the distillation cut considered. A correlation exists between the sulfur fraction retention times and the temperature cuts of the distillation for a temperature below 560 °C and also between the viscosity of the crude oils and the proportion of trapped sulfur compounds in a higher boiling temperature fraction. The thermic treatment applied for the distillation increases the aggregation of low- and medium-molecular-weight compounds of vanadium and nickel into higher molecular weight aggregates between the crude oil on the one hand and the atmospheric residue and vacuum residue on the other hand, especially when the crude oil has a high total sulfur content.

Co-combustion of biomass and gaseous fuel in a novel configuration of fluidized bed: Combustion characteristics

Experimental study on co-combustion of rice straw and natural gas has been performed in a bubbling fluidized bed. The used combustor allows a novel jetting-fountain configuration and the conventional operation as well. In the jetting-fountain configuration, natural gas premixed with the air sufficient for combustion proceeds through the jet pipe to create a jet-fountain zone. Whereas only the air required for rice straw combustion passes through the gas distributor. The findings of the experiments confirm that smooth combustion of natural gas with rice straw can be performed in the novel jetting-fountain fluidized bed. This avoids acoustic effects and explosions of burning bubbles that occurs in the conventional operation. Natural gas contribution had a major impact on combustion characteristics and the performance of the combustor has been found to be much better when applying the jetting-fountain configuration. There are considerable reductions (up to 64%, 28% and 34%) in CO, NOx and SO2 emissions, respectively. The fixed carbon loss reduces (up to 65%) as well. Combustion efficiency records generally higher values with the jetting-fountain configuration. Combustion efficiency steadily improves with increasing natural gas contribution (up to 99.8%). Increasing bed temperature (up to 900°C) is beneficial for reducing CO, decreasing fixed carbon loss and improving combustion efficiency. The existence of an optimum bed temperature for sulfur retention has been confirmed. As normal, NOx increases with bed temperature.

Solid state NMR study of chemical structure and hydrothermal deactivation of moderate-temperature carbon materials with acidic SO3H sites

Hydrothermal stability of carbon based acid catalysts synthesized by sulfonating carbohydrates pyrolyzed at moderate temperatures (300–600°C) has been reported previously. To test the effect of carbon structure on hydrothermal stability, we produced catalysts by dry pyrolysis at 350°C and 450°C or by hydrothermal carbonization, followed by sulfonation with fuming sulfuric acid, as well as by direct sulfonation of glucose. The catalysts were characterized by BET, titration, Raman spectroscopy, TGA, XPS, reaction testing, and 13C solid state NMR. Catalysts were hydrothermally treated and then analyzed for sulfur retention and catalytic activity. The lower temperature carbon catalysts showed the best stability, however all showed significant activity loss. Solid state NMR of materials made from 13C-glucose was used to characterize the structural details in an attempt to correlate functional groups to hydrothermal stability of catalyst active sites. Structural models generated from NMR data showed that the most stable catalysts contained a significant fraction of furan rings and hardly any polycondensed aromatic rings.

On the use of a highly reactive iron ore in Chemical Looping Combustion of different coals

Coal combustion using the Chemical Looping technology can be carried out under different configurations. This paper focuses on the in situ gasification Chemical Looping Combustion (iG-CLC). In this technology, it is especially important the selection of the oxygen carrier as there may be losses in the drainage of coal ashes. Finding low-cost oxygen carriers has become a relevant research focus. Several Fe-based materials have been tested including minerals and industrial residues. In this work, a highly reactive iron ore that had already shown promising characteristics for coal combustion was used in a continuous 500Wth CLC unit. Its performance in the combustion of anthracite, bituminous coal and lignite was evaluated and compared with the results for other Fe-based materials, such as ilmenite or a bauxite waste. The combustion efficiency obtained with the Tierga iron ore was the highest reported to date which makes this carrier a promising candidate for further scale-up. Moreover, the high CaO content of this material led to analyze its relevance for sulphur removal during the first hours of operation. High sulphur retention capacity was observed but this capacity decreased with time as the calcium oxide was both saturated and lost as fines during operation.

Study on Sulfur Retention Characteristics for Bio-Briquette

The sulfur retention mechanism of bio-briquette combustion is analyzed in the paper. The experimental research is carried out on the influence factors of biomass content, with inclusion of combustion temperature, Ca/S ratio, sulfur retention additives. The results indicate that when Ca/S ratio is equal to 2 and the combustion temperature is 850°C,the sulfur retention efficiency of low sulfur bio-briquette exceeds 60%.The rising trend becomes slow when Ca/S ratio is higher than 2.The sulfur retention effect will be reduced over 950°C. Using Fe2O3 as sulfur retention additive can significantly improve the sulfur retention capability of bio-briquette.

XANES spectroscopic study of sulfur transformations during co-pyrolysis of a calcium-rich lignite and a high-sulfur bituminous coal

Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy was applied to determine the sulfur forms in a calcium-rich lignite coal (L coal) and a high-sulfur bituminous coal (B coal), and to investigate their transformations during the co-pyrolysis of two coals. Calcium K-edge XANES spectroscopy was used for examining the occurrence modes of calcium in two coals and their transformation during the coal pyrolysis. Sulfur was present in L coal in the form of thioether, thiophene, sulfate and sulfonate, and in B coal in the form of thiophene, pyrite, thioether and sulfate. Most calcium in L coal was organically associated. The co-pyrolysis was found to synergistically facilitate the progressive decomposition of pyrite and also result in the virtually complete elimination of thioether from the char, with the promoted retention of sulfur as CaS and CaSO4. It was evident that the calcium in L coal was an important factor underlying the synergistic effects on the sulfur transformations during the co-pyrolysis.

Effect of some natural minerals on transformation behavior of sulfur during pyrolysis of coal and biomass

The effect of tourmalines, Na-bentonite and medical stone on the retention of total sulfur, pyritic sulfur, sulfate sulfur and organic sulfur were investigated in a fixed bed reactor. The result shows that during Longma coal pyrolysis, adding tourmalines, Na-bentonite and medical stone all make the total sulfur retention and organic sulfur retention increase obviously. Interestingly, the results also indicate that adding tourmaline 1 (T1), tourmaline 2 (T2), Na-bentonite and medical stone all could make sulfate sulfur retention decrease obviously. Furthermore, when temperature is below 650°C during coal pyrolysis, adding tourmaline1 (T1) makes pyritic sulfur retention higher; while adding Na-bentonite, tourmaline 2 (T2) or medical stone makes pyritic sulfur retention lower. Besides that, the results also show that adding tourmaline 2 (T2) is beneficial for sulfur to convert into H2S and then escape, while adding medical stone is not only good for sulfur to turn into H2S, but also is good to turn into COS during LM coal pyrolysis. For co-pyrolysis of LM coal and biomass, the results show that during co-pyrolysis of LM coal and wheat straw or sawdust, adding tourmaline 1 (T1) influences the total sulfur retention differently with temperature increases. Furthermore, adding tourmaline 1 (T1) also could influence the emission of H2S and COS to a certain degree during co-pyrolysis of coal and biomass.

Promotion of cashmere growth by sulfur supplements in cashmere goats

This study was conducted to investigate effects of inorganic and organic sulfur supplements on cashmere growth and their differences. Thirty-six six-month-old female Liaoning cashmere goats with a body weight of approximately 25 kg and good health were randomly assigned to three treatments: control, ZnSO4 and HMBi (2-hydroxy-4-(methylthio) butyric acid isopropyl ester). The three groups were fed a basal diet, a ZnSO4 diet (supplemented with 0.63% ZnSO4.H2O) and an HMBi diet (supplemented with 1.27% HMBi), respectively. Blood and cashmere samples were collected at the end of the three-month experimental period. The plasma concentrations of total protein, urea nitrogen, ammonia and amino acids; the cashmere content of amino acids and sulfur contents; the cashmere growth rates; and the diameter of the cashmere fibres were determined. The results indicated that dietary supplementation with ZnSO4 or HMBi can decrease the plasma urea nitrogen concentration and increase concentrations of total protein and methionine in plasma. In addition, the two types of sulfur supplements appeared to increase the methionine, cysteine and sulfur contents in cashmere fibres. Furthermore, the supplements can accelerate cashmere growth, with no significant effect on cashmere fineness. The promotion of cashmere growth probably stems from the improvement in the protein metabolic balance, sulfur retention and sulfur-containing amino acids synthesis in cashmere goats following the ZnSO4 or HMBi supplementation. In general, the ZnSO4 supplement promotes greater cashmere growth than the HMBi supplement under the experimental conditions.

Effects of Temperature and Flue Gas Recycle on the SO2 and NOx Emissions in an Oxy-fuel Fluidized Bed Combustor

Oxy-fuel combustion consists in burning a fuel with a mixture of nearly pure oxygen and a CO2-rich recycled flue gas resulting in a product flue gas from the boiler containing mainly CO2 and H2O.In this work, the effect of combustion temperature and flue gas recycle composition on pollutant emissions and on the sulfation process, in order to optimize the SO2 retention in circulating fluidized beds (CFBC), were analyzed.The experimental work was carried out with an anthracite coal in a 3 kWth continuous bubbling fluidized bed (BFB) combustor operating in oxy-fuel conditions. It was found that in oxy-combustion conditions in BFB an increase of combustor temperature produced an increase on NO emission and a decrease in the CO and N2O emissions. The optimum temperature to reach the highest sulphur retention was at 900-925°C.Flue gas recirculation was simulated by mixing different gases (CO2, SO2, NO, and steam) in different concentrations. It was observed that SO2 recycle produced an increase on the sulfur retention as a consequence of the higher SO2 concentration existing in the bed. About 65% of the recycled NO was reduced to N2, being the NO converted to N2O lower than 5vol.%. Wet recycle produced an important reduction on NO emission in comparison with dry recycle.

Pollutant emissions in a bubbling fluidized bed combustor working in oxy-fuel operating conditions: Effect of flue gas recirculation

In this work, pollutant emissions in a continuous bubbling fluidized bed combustor (∼3kWth) at oxy-firing conditions were measured. An anthracite coal was used as fuel and a limestone was added for sulfur retention. Flue gas recirculation was simulated by mixing different gases (CO2, SO2, steam, and NO) and the effect of varying the gas composition of the recycled flow on the pollutant emissions was analyzed. It was observed that the most important effect of CO2 recirculation was the increase of the optimum temperature for SO2 retention from ∼850°C (conventional air combustion) to 900–925°C. SO2 recirculation increased the Ca-based sorbent utilization and did not affect the N2O emissions at any temperature. In addition, at 850°C the CO emission increased and the NO emission decreased, however, at 925°C the CO variation was negligible and the NO reduction was low. About 60–70% of the recycled NO was reduced to N2 and N2O, being the NO converted to N2O lower than 5%. Steam recirculation mainly led to a sharp decrease in NO emission. A synergetic effect among the different recycled gases was not found in any case.

Effect of Coal Fly Ash as Additive on the Sulfur Retention of Coal Briquette

Clean coal briquette is one of the most effective techniques to remove SO2 from coal combustion by using sulfur-retention agent to retain sulfur in coal residuals. Ca(OH)2 has been proved to be an effective sulfur-retention agent. CaSO4 as the primary sulfur-containing product, however, is thermal unstable at high temperatures. It has been reported that SiO2, Al2O3, Fe2O3 etc. are excellent sulfur retention additives, those are abundant in coal fly ash. In this study coal fly ash was used to the additive to improve the sulfur retention of coal briquette. The results showed that the addition of coal fly ash can improve the sulfur retention. The modified coal fly ash obtained by calcinations assisted with Ca(OH)2 can improve the sulfur retention more noticeable. The SEM and XRD results further indicated that coal fly ash promoted the formation of the sulfur-containing products such as Ca-Si-S-O compounds with high thermally stability.

Optimum temperature for sulphur retention in fluidised beds working under oxy-fuel combustion conditions

Oxy-fuel combustion is one of the leading options for power generation with CO2 capture. The process consists of burning the fuel with a mixture of nearly pure oxygen and a CO2-rich recycled flue gas, resulting in a product flue gas from the boiler containing mainly CO2 and H2O. Among the possible boiler types, fluidised bed combustors are very appropriate for the oxy-fuel process because they allow the in situ desulphurisation by feeding Ca-based sorbents into the combustor.In this work, the effect of the temperature of the combustor on the retention of the SO2 generated in the combustion of two coals with very different sulphur content (a lignite and an anthracite) has been studied. The experimental facility used was a bubbling fluidised bed (BFB) combustor of ∼3kWth. Tests were conducted under oxy-fuel combustion mode and also under enriched-air combustion mode for comparison reasons. A Spanish limestone “Granicarb” was used as Ca-based sorbent for sulphur retention. The temperatures tested were between 800 and 970°C using Ca/S molar ratios between 0 and 3.It was found that in BFB combustors operating under oxy-fuel combustion conditions the optimum temperature to achieve the highest sulphur retention was 900–925°C, whereas operating with enriched air the optimum combustion temperature was 850–870°C. Working at the optimum temperature, the SO2 retentions were lower in oxy-fuel combustion than in enriched air combustion conditions. It was also observed that working with lignite there was 10–15% of sulphur retention by coal ashes, however, working with anthracite the sulphur retention by coal ashes was negligible. This finding was independent of the combustion mode used, oxy-fuel or enriched air.

Synergistic effects on co-pyrolysis of lignite and high-sulfur swelling coal

Co-pyrolysis of a lignite coal and a bituminous coal was carried out on a fixed-bed reactor. The lignite was enriched with calcium, and the bituminous coal featured in high sulfur and strong swelling. Experiments were also conducted for the blends using the acid-washed lignite and/or the acid washed bituminous coal to address the influences of calcium in the lignite on the synergistic behaviors. Calcium in the lignite exhibited some aspects of synergy including the catalytic cracking reactions of tar, the retention of sulfur in the char, and the catalyzed polyaromatization and gasification of char. These synergies impacted the differences in the product distribution and gas composition between the co-pyrolytic results and the additive ones. Moreover, there appeared to be a synergistic effect on the cross-linking reaction of volatile matter, resulting in an increase in the char yield irrespective of coal demineralization. The co-pyrolysis was also observed to destroy the swelling of coal. This synergistically increased the tar yield due to less resistant escaping of tar from the intra-particles of coal.

Genomic Insights into Bacterial DMSP Transformations

Genomic and functional genomic methods applied to both model organisms and natural communities have rapidly advanced understanding of bacterial dimethylsulfoniopropionate (DMSP) degradation in the ocean. The genes for the two main pathways in bacterial degradation, routing DMSP to distinctly different biogeochemical fates, have recently been identified. The genes dmdA, -B, -C, and -D mediate the demethylation of DMSP and facilitate retention of carbon and sulfur in the marine microbial food web. The genes dddD, -L, -P, -Q, -W, and -Y mediate the cleavage of DMSP to dimethylsulfide (DMS), with important consequences for ocean-atmosphere sulfur flux. In ocean metagenomes, sufficient copies of these genes are present for approximately 60% of surface ocean bacterial cells to directly participate in DMSP degradation. The factors that regulate these two competing pathways remain elusive, but gene transcription analyses of natural bacterioplankton communities are making headway in unraveling the intricacies of bacterial DMSP processing in the ocean.

Influence of different electrode compositions and binder materials on the performance of lithium–sulfur batteries

The specific capacity and cycling stability of lithium sulfur batteries have been investigated with respect to the chemical composition and fabrication process of the sulfur electrode. Three different kinds of electrode compositions (containing Nafion, polyacrylonitrile/carboxymethylcellulose, and Teflon, respectively, as binder materials) have been tested. For the electrodes containing Nafion as the binder material, an additional Nafion coating has been deposited on top of the electrodes to enhance the sulfur retention and to suppress the polysulfide shuttle. Both SEM images before cycling and post mortem are presented in order to shed light on the influence of the composition of the electrode on its electrochemical performance. Good cycling performance can be attained based on relatively simple and therefore cost-effective electrode setups and production methods.

Thermal transformations of organic and inorganic sulfur in Type II kerogen quantified by S-XANES

Sulfur X-ray Absorption Near Edge Structure Spectroscopy (S-XANES) was used to quantify the thermal transformations of organic and inorganic sulfur forms in pyrite-containing Type II kerogens and kerogen chars after open system pyrolysis for a series of well-defined times and temperatures. These results are compared to identical experiments conducted on the same kerogens treated to be pyrite-free. No significant differences were found in the thermal transformations of organic sulfur between the pyrite-containing and pyrite-free kerogen. The loss of aliphatic sulfur forms occurs early (equivalent Ro<1.5%) while there is a relative increase in thiophenic sulfur over aromatic sulfide at higher maturity (Ro>1.5%). In pyrite-containing kerogens, the complete conversion of pyrite (FeS2) into pyrrhotite (Fe1−xS) occurs by a laboratory equivalent Ro=1.5%, followed by the conversion of pyrrhotite into troilite (FeS) at higher maturity. The availability of hydrogen from hydrocarbons generated from kerogen accelerates the initial decomposition of pyrite resulting in pyrrhotite and H2S evolution. H2S evolution up to Ro=2.4% corresponds to the sulfur loss associated with pyrrhotite and troilite formation and aliphatic sulfur loss, indicating that sulfur from pyrite results almost exclusively in H2S evolution with no significant incorporation and retention of sulfur into the organic matter of the kerogen chars under the current set of open system pyrolysis conditions.

Preparation of Coal Briquette by Using Coal Waste and Coal Slurry

Coal waste and coal slurry are the largest industrial waste generated from coal preparation plants. This paper describes a method to make clean coal briquette with coal waste and coal slurry. Two binders were used during the coal briquette making process. In addition, a mixture of cacium hydroxide and coal fly ash was added into the formulation acting as a sulfur retention agent. The results show that coal briquette strength and sulfur retention were significantly improved. For example, both wet strength and falling strength reached 99%. The sulfur retention is about 55.41%.

Sulfur dioxide and primary carbonaceous aerosol emissions in China and India, 1996–2010

Abstract. China and India are the two largest anthropogenic aerosol generating countries in the world. In this study, we develop a new inventory of sulfur dioxide (SO2) and primary carbonaceous aerosol (i.e., black and organic carbon, BC and OC) emissions from these two countries for the period 1996–2010, using a technology-based methodology. Emissions from major anthropogenic sources and open biomass burning are included, and time-dependent trends in activity rates and emission factors are incorporated in the calculation. Year-specific monthly temporal distributions for major sectors and gridded emissions at a resolution of 0.1°×0.1° distributed by multiple year-by-year spatial proxies are also developed. In China, the interaction between economic development and environmental protection causes large temporal variations in the emission trends. From 1996 to 2000, emissions of all three species showed a decreasing trend (by 9 %–17 %) due to a slowdown in economic growth, a decline in coal use in non-power sectors, and the implementation of air pollution control measures. With the economic boom after 2000, emissions from China changed dramatically. BC and OC emissions increased by 46 % and 33 % to 1.85 Tg and 4.03 Tg in 2010. SO2 emissions first increased by 61 % to 34.0 Tg in 2006, and then decreased by 9.2 % to 30.8 Tg in 2010 due to the wide application of flue-gas desulfurization (FGD) equipment in power plants. Driven by the remarkable energy consumption growth and relatively lax emission controls, emissions from India increased by 70 %, 41 %, and 35 % to 8.81 Tg, 1.02 Tg, and 2.74 Tg in 2010 for SO2, BC, and OC, respectively. Monte Carlo simulations are used to quantify the emission uncertainties. The average 95 % confidence intervals (CIs) of SO2, BC, and OC emissions are estimated to be −16 %–17 %, −43 %–93 %, and −43 %–80 % for China, and −15 %–16 %, −41 %–87 %, and −44 %–92 % for India, respectively. Sulfur content, fuel use, and sulfur retention of hard coal and the actual FGD removal efficiency are the main contributors to the uncertainties of SO2 emissions. Biofuel combustion related parameters (i.e., technology divisions, fuel use, and emission factor determinants) are the largest source of OC uncertainties, whereas BC emissions are also sensitive to the parameters of coal combustion in the residential and industrial sectors and the coke-making process. Comparing our results with satellite observations, we find that the trends of estimated emissions in both China and India are in good agreement with the trends of aerosol optical depth (AOD) and SO2 retrievals obtained from different satellites.