Effect of Prussian Blue on Organic Sulfur of Coal in Aqueous Medium

Abstract

This study is an attempt to desulfurize organic sulfur from coal samples with ferric hexacyanoferrate (II), Fe₄ [Fe(CN)₆], as the desulfurization agent. Effect of temperature, particle size and concentration of ferrocyanide ion on desulfurization from the coal samples has been investigated. The temperature and stirring time are the most important parameters for the level of desulfurization of organic sulfur. Removal of organic sulfur content increased continuously with increasing temperature from 298 to 368 K. The organic sulfur removal rate sharply increases from 10 min to 30 min stirring time. After 30 min, it reaches a value of plateau. Particle size between ?100 mesh and ?200 mesh slightly affects the amount of organic sulfur removal. Gradual increase in the concentration of ferric hexacyanoferrate (II) raised the magnitude of desulfurization, but at higher concentration, the variation is not significant.     

微波脱硫的研究进展与存在问题

综述了煤中含硫分分类及其存在的形式,阐述了微波对煤中含硫组分的作用原理。总结了微波直接脱硫法、微波与气体联合脱硫法、微波与碱液联合脱硫法等脱硫方法的应用,并分析了上述方法的优势及不足,提出了对微波脱硫研究工作的展望。     

Investigation on the mechanism of coal desulfurization by ultrasonic with peroxyacetic acid

This investigation reports the exploration of the mechanism for coal desulfurization utilizing ultrasonic (US) with peroxyacetic acid. Changes in surface and pore diameter for coal samples were determined before and after US treatment. To study its chemical effect, production regularities of hydroxyl radical under US field was analyzed by the iodine release method. Experimental results showed that the specific surface area, total pore volume and average pore size of treated samples were improved compared to untreated coal. In addition, the production rule of hydroxyl radical was consistent with that of desulfurization rate. XPS analysis results indicated that the removals of pyrite, mercaptan, and sulfur ether from coal were more than 60%, while thiophene, sulfoxide and sulfone were difficult to remove from coal. The further oxidation of sulfur-containing groups in coal was obtained due to the physical and chemical effects of the ultrasonic. These findings confirmed that the synergistic action of physical and chemical effects of the US played an important role in this desulfurization process, which could serve as a reference for further optimizing the coal desulfurization process.     

Experimental research on two-stage desulfurization technology in traveling grate boilers

In order to promote the desulfurization efficiency of calcium-based sorbents during coal combustion in traveling grate boilers, the influences on sulfur removal of the thermal conditions and the sorbents were discussed in this paper. It was found that the SO₂ concentration first rises, then declines along the traveling grate and reaches the peak near the midpoint of the grate. The fluctuation of the SO₂ concentration over time in the flue gas is mainly affected by the flame temperature. When the particle size of the sorbents decreases from 75 to 0.1 μm, the sulfur removal efficiency will increase slightly. A reasonable Ca/S molar ratio is about 2 when sorbents are blended with the coal on the grate and its further increase has little benefit to desulfurization. A new, so-called two-stage desulfurization process — sulfur capture firstly in the coal bed and secondly in the combustion gas — is suggested as it can greatly promote the sulfur removal efficiency up to 70∼80%. By X-ray powder diffraction analysis, some thermal stable phases were identified in the sulfur retention cinder obtained from the on-grate process.     

Oxidative Desulfurization of Aşkale Coal by Nitric Acid Solution

Abstract

Efficient use of fossil fuels is of utmost importance in a world that depends on these for the greatest part of its energy needs. Although lignite is a widely used fossil fuel, its sulfur content limits its consumption. This study aims to capture combustible sulfur in the ash by oxidizing it with solution of nitric acid solution. Thus, the combustible sulfur in the coal was converted to sulfate form in the ash. Parameters affecting the conversion of sulfur were determined to be nitric acid concentration, reaction time and mean particle size at constant (near room) temperature and shaking rate. The maximum desulfurization efficiency reached was 38.7% of the original combustible sulfur with 0.3 M nitric acid solution, 16 h of reaction time and 0.1 mm mean particle size.     

Oxidative Desulfurization of Tufanbeyli Coal by Hydrogen Peroxide Solution

Abstract

It is becoming popular to use fossil fuels efficiently since the necessary energy is mostly supplied from fossil fuels. Altough there are high lignite reservoirs, high sulfur content limits the efficient use of them. In this article, we aimed to convert combustible sulfur in coal to non-combustible sulfate form in the ash by oxidizing it with a hydrogen peroxide solution. The parameters affecting the sulfur conversion were determined to be: hydrogen peroxide concentration, reaction time, mean particle size at constant room temperature and shaking rate. The maximum desulfurization efficiency reached was 74% of the original combustible sulfur with 15% (w/w) hydrogen peroxide solution, 12 hours of reaction time, and 0.25 mm mean particle size.     

Retention of SO2 Emission of Coal Combustion by Using Lime in Briquetting

In this study, the effect of lime on control of SO₂ emissions was investigated by briquetting of coal particles with various lime contents. The influence of the added lime was determined not only from the view of its contribution to environmental aspects but also in terms of effects on the thermal features and reaction kinetics of coal. The extent of improvement was determined by detailed sulfur analysis. Thermal qualification and reaction kinetics of the coal briquettes with varying lime contents were performed by evolved gas analysis and its complementing kinetic model based on Arrhenius principles. At the end of experiments, utilization of lime was seen to contribute considerably to desulfurization process. However, lime addition had an adverse effect both on the effectiveness of combustion and the liability of the coal briquettes to oxidize.     

Effects of temperature and limestone on sulfur release behaviors during fluidized bed gasification

Gaseous sulfur is released during fluidized bed coal gasification, and control the yield of gaseous sulfur or the conversion between gaseous organic sulfur and inorganic sulfur at source is necessary, because it can economically satisfy the requirements of industrial production and protect the environments. In this study, sulfur release behaviors of a middle-sulfur coal called Guizhou coal were quantitatively determined through controlled experiments in a lab-scale fluidized bed during oxygen rich-steam gasification. The measured gaseous sulfur species were H₂S, SO₂, COS and CS₂. The effects of temperature (850^OC-950^OC) and limestone (Ca/S = 2) on the sulfur release behaviors were investigated. Among the above four gaseous sulfur, the yield of H₂S is the highest, followed by COS, while only less than 1.5% of sulfur in coal is released as SO₂ and CS₂. With the increase in temperature, the yield of H₂S increases while that of SO₂ decreases, and the change of COS yield and CS₂ yield is not obvious. The molar ratio of H₂S/COS increases with increasing temperature, which is qualitatively matched by thermodynamic analysis. The addition of limestone reduces the released sulfur but not change the distribution of gaseous sulfur forms. Meanwhile, the molar ratio of H₂S/COS increases after adding limestone, while the trend with temperature of H₂S/COS does not change. The removal rate of H₂S is between 23% and 28%, which increases with temperature. The distributions of sulfur in bottom char and fly ash are similar. The main sulfur species in the bottom char is organic sulfur, and thiophene dominates the organic sulfur. The increase of temperature and the addition of limestone will both promote the increase of inorganic sulfur content, and the decrease of organic sulfur content.     

炉内喷钙及尾部增湿活化脱硫的中间试验研究

对炉内喷钙及尾部增湿活化脱硫技术进行了中间试验研究,株洲烟煤的含硫量较低,当钙硫比为2．67,增湿量为18．6kg/h时,脱硫率达到75％,吸收剂利用率为28．1％。可以满足目前燃煤锅炉脱硫的需要。     

Biodesulfurization of Cayirhan Lignites

In this study, the lignite was improved oxidizing sulfur compounds by Thiobacillus thiooxidans and Thiobacillus ferrooxidans bacteria. Experiments in the batch reactors have been carried out 20% aqueous suspension of coal samples. Sugar beet molasses was used as the bacterial substrate. The maximum removal of combustible sulfur was obtained as 78.2% under the following conditions; addition 5% of T. thiooxidans and 5% T. ferrooxidans into coal suspension, 0.2 g molasses/g coal change, pH value of 3, at shaking rate of 70 rpm and at 40°C for 5 days.     

Hydrocarbon Desulfurization to Clean Fuels by Selective Oxidation Versus Conventional Hydrotreating

Abstract

Environmental concerns have driven the need to remove sulfur-containing compounds to an extremely low level for transportation fuels. Conventional hydrodesulfurization catalysts can be used to remove a significant portion of the sulfur from petroleum distillates for the blending of refinery transportation fuels. Removing the last traces of sulfur compounds where the sulfur atom is sterically hindered, as in multi-ring aromatic sulfur compounds, is a significant challenge. One recent area of innovation to remove sulfur from upgraded crude is oxidative desulfurization, a process that can operate under mild conditions and without the need for external H₂. In this article, the mechanism, process, and the new inventions of selectively oxidative desulfurization are reviewed.     

高硫煤脱硫技术及展望

高硫煤的直接燃烧会产生严重的环境污染,为此需要开发有效的高硫煤脱硫技术。介绍了我国高硫煤中硫的赋存状态和分布规律,分析了目前高硫煤脱硫的物理方法、化学方法和生物方法及目前各种脱硫方法存在的关键问题,最后对高硫煤脱硫技术的发展方向进行了阐述。     

Comparing product distribution and desulfurization during direct pyrolysis and hydropyrolysis of Longkou oil shale kerogen using reactive MD simulations

The product distribution and organic sulfur removal during direct pyrolysis and hydropyrolysis of oil shale kerogen were investigated via reactive molecular dynamics (RMD) simulations with reactive force field (ReaxFF). Two structural models for direct pyrolysis and hydropyrolysis of kerogen were constructed about kerogen extracted from Longkou oil shale to investigate the impact of H₂ at different temperatures on the product distribution and reaction processes of oil shale. The experimental results show that hydropyrolysis could increase light shale oil (the most important product in shale oil industry), and improve the removal rate of organic sulfur simultaneously. It was found that comparing to the direct pyrolysis, hydropyrolysis can provide more H free radicals to participate in the reaction and therefore promoting the pyrolytic reaction of kerogen. In addition, hydropyrolysis greatly promoted the desulfurization due to the contribution to the production of H₂O molecules, and the transfer of sulfur to the gas products requires the participation of H₂O molecules. This work is an intensive study on hydropyrolysis mechanism at different temperatures at the atomic level. These conclusions could be helpful for the clean utilization technology of oil shale industry.     

环境友好型原油脱硫剂效果评价与现场应用

JH6011环境友好型原油脱硫剂是一种油溶性-水中分散的复合有机化合物,其作用于原油中硫化物的脱硫条件为反应时间6~12h,脱硫温度50~70℃,脱硫剂与硫化物质量比为1∶1~2∶1。利用碘量法测定脱硫剂在模拟油(柴油)、原油中的脱硫率,结果显示其在模拟油中的脱硫率高于85%,在原油中的脱硫率高于80%。利用能量色散X-射线荧光光谱法测定其对原油中有机硫的脱除效果,平均脱除率为21.73%(主要为噻吩类)。现场应用时,总脱硫率也可达到80%以上,但需要根据原油硫含量、酸值、运动黏度等因素确定合适的添加量、脱硫温度和反应时间。硫含量较高或酸值较大时,可适当加大添加量,黏度较大时可适当提高脱硫温度或延长反应时间。     

Comparison of oil extraction methods,energy analysis and biodiesel production from flax seeds

In recent years, the commercial potential of oil extraction and biodiesel production derived from vegetable seed is being realized. The process energy input requirements are important factors in oil extraction and biodiesel production. This research work investigated oil extraction from flax seeds and compared extraction yield with the energy load. The effect of moisture content on the oil yield was compared between a mechanical oil expeller, organic solvent extraction, organic solvent and microwave assisted, organic solvent and ultrasonic assisted, and combined microwave and ultrasonic with organic solvent. The maximum oil yields % wt/wt from these techniques was 22.6%, 36.3%, 10.0%, 42.0% and 27.8%, respectively. The moisture content had a significant effect on oil yield with the mechanical oil expeller, organic solvent method and ultrasonic assisted extraction, whereas no or little effect was found on microwave‐assisted extraction. The microwave‐assisted extraction showed better results compared with the ultrasonic‐assisted and combined treatment methods. The relative energy consumption of these processes was experimentally investigated; energy ratios were calculated based on the amount of energy recovered to the amount of energy supplied to the flax seed for oil extraction. The net energy ratios showed that microwave‐assisted extraction had the highest (25.21%), followed by organic solvent method (14.04%), ultrasonic method (6.33%) and lowest was with combined ultrasonic and microwave assisted treatment (5.73%). These results showed that flax seed oil can be extracted using microwave‐assisted methods efficiently and in an energy feasible manner. In situ ultrasonic transesterification was applied to powdered samples with 4%, 8% and 12% moisture content (on % dry basis) within an ultrasonic bath having an intensity of 0.124 W/cm². The flax seed biodiesel produced showed a highest conversion yield of 93%, and the effect of different moisture content on the yield showed that 4% moisture content sample produced the greatest biodiesel yield. Copyright © 2013 John Wiley & Sons, Ltd.     

Fueling power plants with high sulfur coal in compliance with emission standards

We compare the economics of the two most advanced strategies for meeting current SO₂ emission standards in power plants fueled with high sulfur coal. One strategy calls for converting high sulfur coals to clean synfuels before combustion. The other involves direct coal burning, followed by fuel gas desulfurization (FGD). Our results show that the FGD route is preferable.Advantages of FGD over the coal conversion route are the following. The total capital and operating costs for FGD are almost an order of magnitude lower, thermal efficiencies are higher, and utility requirements are lower. The FGD systems have been in operation since 1968 and, after initial problems, have been operated reliably and at availability acceptable to the utility industry. About 80% of existing power plants, according to one survey, can be retrofitted with FGD. Even with possible breakthroughs in coal-conversion technologies, it appears that FGD will remain the economically preferred route to desulfurization.     

440t_h CFB锅炉掺烧石油焦二氧化硫排放特性研究

在440 t/h大型循环流化床锅炉上进行了燃烧不同比例煤和石油焦混合燃料时二氧化硫排放特性的试验研究。研究了燃烧不同比例的混合燃料、炉膛温度、过量空气系数和钙硫摩尔比对二氧化硫排放特性的影响。研究结果表明,过量空气系数和钙硫摩尔比的增加可以降低二氧化硫排放浓度。存在一个最佳脱硫温度,二氧化硫排放浓度最低,对于各种混合燃料最佳脱硫温度应在830～850℃之间。     

Chemical looping combustion of lignite with the CaSO4–CoO mixed oxygen carrier

Chemical looping combustion (CLC) has well developed as a novel combustion technology for simultaneous completion of the coal combustion and CO₂ capture with a low energy penalty. Among all the oxygen carriers available, CaSO₄ has gained great attention as a promising oxygen carrier (OC) in CLC due to its high oxygen capacity and low price. But further application of CaSO₄ OC also suffers the problems of low reactivity and even deactivation due to the sulfur loss via the side reactions of CaSO₄, which should be well addressed. In this research, the CaSO₄–CoO mixed OC was prepared firstly, and experiments based on thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR) were conducted to evaluate the reaction characteristics and evolution of the gaseous products during the reaction of the prepared CaSO₄–CoO mixed OC with lignite (abbreviated as YN). Both the higher reaction rate of the prepared mixed OC with YN coal and the elevated CO₂ concentration fully reflected the enhanced reactivity of the prepared mixed OC for YN coal conversion. Furthermore, the micromorphology of the solid reaction products was analyzed by the field emission scanning electron microscopy spectrometry (FESEM). Good sintering resistance of the prepared CaSO₄–CoO mixed OC during its reaction with YN was verified, which was ascribed to the temporary inert support role played by the CaSO₄ substrate. In order to further study the desulfurization ability of CoO in the mixed OC, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermodynamic simulation were used for in-depth analysis. The gaseous sulfur species released by the CaSO₄ side reactions were mainly fixed as solid CoS, Co₉S₈ and CaS, with the total content higher than 99.8%. And the sulfided OC could be completely regenerated to its original state at the oxidation stage according to the X-ray diffraction (XRD) result. Overall, the prepared CaSO₄–CoO mixed OC not only has the enhanced reactivity and good sintering resistance, but also owns the potential to control sulfur released from the CaSO₄ side reactions, which has broad application prospect to simultaneously achieve decarbonization and desulfurization in the CLC process.     

煤洁净燃烧添加剂技术的研究

从研究煤中硫的析出规律入手,分析了钙基吸收剂在高温下固硫率低的原因,及有机硫和无机硫的不同析出规律,选择具有促进或催化作用的工业废料,与钙基固硫剂按比例掺混,形成一毓既可直接在燃烧过程中脱硫,又有一定催化燃烧作用所洁净燃料添加剂。     

Experimental study on desulfurization efficiency and gas–liquid mass transfer in a new liquid-screen desulfurization system

This paper presents a new liquid-screen gas–liquid two-phase flow pattern with discarded carbide slag as the liquid sorbent of sulfur dioxide (SO₂) in a wet flue gas desulfurization (WFGD) system. On the basis of experimental data, the correlations of the desulfurization efficiency with flue gas flow rate, slurry flow rate, pH value of slurry and liquid–gas ratio were investigated. A non-dimensional empirical model was developed which correlates the mass transfer coefficient with the liquid Reynolds number, gas Reynolds number and liquid–gas ratio (L/G) based on the available experimental data. The kinetic reaction between the SO₂ and the carbide slag depends on the pressure distribution in this desulfurizing tower, gas liquid flow field, flue gas component, pH value of slurry and liquid–gas ratio mainly. The transient gas–liquid mass transfer involving with chemical reaction was quantified by measuring the inlet and outlet SO₂ concentrations of flue gas as well as the characteristics of the liquid-screen two-phase flow. The mass transfer model provides a necessary quantitative understanding of the hydration kinetics of sulfur dioxide in the liquid-screen flue gas desulfurization system using discarded carbide slag which is essential for the practical application.