羰基硫脱除技术

综述了羰基硫(COS)的性质和各种脱除方法包括胺法、加氢、水解、氧化等技术的原理与特点。胺法多用于处理H2S和COS同时存在的天然气和炼厂气,关键在于提高COS脱除率;加氢转化法将COS转化成H2S的转化率高,在石油炼制中应用较为广泛,但所用Co-Mo-Al2O3催化剂价格昂贵,操作温度较高,并存在一定的副反应。水解转化法反应温度低、不消耗氢源、副反应少,是目前十分活跃的研究领域,重点在于高活性催化剂的研制。指出开发配方优化和系列化的醇胺类溶剂吸收体系及催化剂性能优良的水解转化法有较好的发展前景。     

Cu、Ag改性活性炭常温脱除低浓度羰基硫性能研究

采用等体积浸渍法,以硝酸处理后的活性炭（AC-HN）为载体,AgNO3和Cu(NO3)2为原料制备了Cu/AC-HN和Ag/AC-HN吸附剂。研究了浸渍液、焙烧温度、焙烧时间和负载量对吸附剂常温脱除低浓度羰基硫（COS）性能影响,并通过N2物理吸附、FE-SEM、TG-DTG、XRD、FTIR对吸附剂进行了表征。动态吸附结果表明,改性后的吸附剂吸附COS的能力提升。Ag+在AC表面被还原成Ag0。Cu/AC-HN活性组分以Cu2O存在,表现出更佳的吸附能力。Cu(NO3)2改性后,吸附剂比表面积降低,AC原有官能团没有发生变化。焙烧温度对Cu/AC-HN活性组分物相有较大影响。焙烧温度升高,Cu(NO3)2逐渐分解成CuO,CuO被AC还原成Cu2O,350 ℃时Cu2O的量达到最高。进一步增加温度,Cu2O被还原成Cu0,Cu2O量降低。AC对COS的吸附量为7.5mg/g。当焙烧温度350℃、焙烧时间1.5h、铜负载量5%时,Cu/AC-HN吸附COS的效果最好,吸附量达到14.8mg/g。     

羰基硫脱除技术研究现状及进展

论述了脱除羰基硫的各种方法,包括还原法、水解法、吸收法、吸附法、光解法及氧化法等,展望了COS脱除技术的研究趋势。指出ZrO2与TiO2、Al2O3混合制备新的多组分催化剂,以及引入铁一类助剂来降低催化剂表面的亲水性进而降低催化剂的失活程度是COS脱除技术研究可能的新方向。     

Cu、Ag改性活性炭常温脱除低浓度羰基硫性能

采用等体积浸渍法,以硝酸处理后的活性炭(AC-HN)为载体,Ag NO3和Cu(NO3)2为原料制备了Cu/ACHN和Ag/AC-HN吸附剂。研究了浸渍液、焙烧温度、焙烧时间和负载量对吸附剂常温脱除低浓度羰基硫(COS)性能影响,并通过N2物理吸附、FE-SEM、TG-DTG、XRD、FTIR对吸附剂进行了表征。动态吸附结果表明,改性后的吸附剂吸附COS的能力提升。Ag+在AC表面被还原成Ag0。Cu/AC-HN活性组分以Cu2O存在,表现出更佳的吸附能力。Cu(NO3)2改性后,吸附剂比表面积降低,AC原有官能团没有发生变化。焙烧温度对Cu/AC-HN活性组分物相有较大影响。焙烧温度升高,Cu(NO3)2逐渐分解成CuO,CuO被AC还原成Cu2O,350℃时Cu2O的量达到最高。进一步提高温度,Cu2O被还原成Cu0,Cu2O量降低。AC对COS的吸附量为7.5 mg/g。当焙烧温度350℃、焙烧时间1.5 h、铜负载量5%时,Cu/AC-HN吸附COS的效果最好,吸附量达到14.8 mg/g。     

沼气中羰基硫的深度脱除

沼气深度脱硫对于以沼气为制氢原料的分布式燃料电池电站十分重要。采用浸渍法制备了Zn O/γ-Al2O3、Cu O/γ-Al2O3及Cu/γ-Al2O3,实验研究了上述金属氧化物脱硫剂以及商业Fe2O3脱硫剂对沼气中羰基硫(COS)的深度脱除性能。结果表明,Cu基脱硫剂对COS的脱除性能优于Zn O/γ-Al2O3和Fe2O3,其可在250~400℃的温度下将COS脱除到10 ppb以下,能够满足分布式PEMFC电站对脱硫的要求,并达到在其沼气重整器的原料气体预热段完成深度脱硫的目标。Cu O/γ-Al2O3的硫容在250℃达到了最大的0.185 mmol?g?1。对Cu O/γ-Al2O3的脱硫机理进行了分析。固相产物中Cu S的存在说明了COS在Cu O/γ-Al2O3上的吸附为化学吸附,而Cu2O和Cu的存在则说明了沼气中的CH4与CO2在250℃以上的温度下发生了重整反应,Cu2O和Cu为该反应生成的H2和CO的还原产物。气相产物中检测到的H2S,可能是由COS的加氢反应生成的。还考察了沼气中水分对COS深度脱除的影响。Cu基脱硫剂的性能会受到水分的不利影响,但随着温度的升高,该影响呈减小的趋势。     

改性氧化铁脱硫剂脱除羰基硫性能的研究

制备了一种采用碳酸盐活性组分浸渍改性的氧化铁脱硫剂,考察了活性组分负载量、原料气空速、水汽含量以及氧气含量对改性脱硫剂活性的影响.结果表明,在室温(10～30℃)、常压、原料气空速1000 h-1、原料气中水汽含量1%以及无氧的条件下,改性后氧化铁脱硫荆的COS硫客达到3%,且改性后脱硫剂对硫化氢和二硫化碳的脱除能力也有一定的提高.对新鲜和失活脱硫剂进行红外光谱表征,结果表明,COS在脱除过程中氧化生成的硫酸盐毒化了表面碱性羟基活性住是脱硫剂失活的直接原因.     

高温煤气中羰基硫的加氢脱除研究进展

综述了加氢转化法脱除高温煤气中COS的研究现状,从加氢转化催化剂镍、钴、钼系,具有转化和吸收双功能的脱硫剂(钙系、锌系、铁系、锰系、复合金属氧化物)以及改性活性炭基催化剂等方面进行了分析,并对相应的脱硫反应条件控制和现存问题进行讨论,提出了改进措施。     

变压吸附法脱除变换气中二氧化碳的技术总结

简要介绍变压吸附(PSA)法脱除变换气中二氧化碳装置的工艺流程及运行情况,提出在生产运行中需要注意的问题,并对几种脱除变换气中二氧化碳的工艺进行经济分析比较。     

催化水解法低温脱除煤气中羰基硫的研究

采用等体积浸渍法制备了负载钼酸铵、碳酸钾、氢氧化钠3种活性组分的氧化铝基水解催化剂,考察了氧含量、温度、湿度对羰基硫水解转化率的影响。实验结果表明,随着氧含量的增加,催化剂反应活性降低;随着温度的升高,催化剂反应活性提高。水蒸气在低含量时可促进水解反应进行,但含量过高则会造成催化剂反应活性的下降。该催化剂在80~100℃,湿度25%条件下具有优异的水解活性和稳定性。     

变压吸附分离工业废气二氧化碳的研究进展

概述了未来人类对过量二氧化碳排放的处理办法,即碳的捕获和存储(CCS).简介了4种二氧化碳的分离工艺及特点和工业中二氧化碳的捕获系统.阐述了变压吸附工艺的基本原理和其在捕获工业废气中二氧化碳上的应用,以及变压吸附分离二氧化碳的工艺在循环结构设计、吸附剂材料和数值模拟等方面的研究进展和国内外的工业化应用.分析了目前该工艺仍存在的问题,指出该技术具有广阔的应用前景.     

An evaluation of autotrophic microbes for the removal of carbon dioxide from combustion gas streams

Carbon dioxide is a greenhouse gas that is believed to be a major contributor to global warming. Studies have shown that significant amounts of CO₂ are released into the atmosphere as a result of fossil fuels combustion. Therefore, considerable interest exists in effective and economical technologies for the removal of CO₂ from fossil fuel combustion gas streams. This work evaluated the use of autotrophic microbes for the removal of CO₂ from coal fired power plant combustion gas streams. The CO₂ removal rates of the following autotrophic microbes were determined: Chlorella pyrenoidosa, Euglena gracilis, Thiobacillus ferrooxidans, Aphanocapsa delicatissima, Isochrysis galbana, Phaodactylum tricornutum, Navicula tripunctata schizonemoids, Gomphonema parvulum, Surirella ovata ovata, and four algal consortia. Of those tested, Chlorella pyrenoidosa exhibited the highest removal rate with 2.6 g CO₂ per day per g dry weight of biomass being removed under optimized conditions. Extrapolation of these data indicated that to remove CO₂ from the combustion gases of a coal fired power plant burning 2.4 × 10⁴ metric tons of coal per day would require a bioreactor 386 km² × 1 m deep and would result in the production of 2.13 × 10⁵ metric tons (wet weight) of biomass per day. Based on these calculations, it was concluded that autotrophic CO₂ removal would not be feasible at most locations, and as a result, alternate technologies for CO₂ removal should be explored.     

Separation of carbon dioxide and methane in continuous countercurrent gas centrifuges

The goal of this study is to determine the order of magnitude of the maximum achievable separation for decontaminating a natural gas well using a gas centrifuge. Previously established analytical approximations are not applicable for natural gas decontamination. Numerical simulations based on the batch case show that although the separative strength of the centrifuge is quite good, its throughput is very limited. Both enrichment and throughput are only a function of length and peripheral velocity. A centrifuge with a length of 5 m and a peripheral velocity of approximately 800 m/s would have a throughput of 0.57 mol/s and a product flow of 0.17 mol/s. These numbers are calculated with the assumption that the centrifuge is refilled and spun up instantaneously. The results for the countercurrent centrifuge show how the production rate varies as a function of internal circulation, product-feed ratio, peripheral velocity and centrifuge length and radius. Under conditions similar to those of the batch case the production is approximately half compared to the batch case, i.e., 0.08 mol/s. Optimization can yield a higher production at the cost of lower enrichment. Considering the current natural gas prices and the low production rate of the centrifuge, it is certain that the gas centrifuge will not generate enough revenue to make up for the high investment costs.     

酸性气湿法制酸工艺中SO2转化器数学模拟

根据工业设计与生产操作条件,建立了酸性气湿法直接制酸工艺中SO2转化器的数学模型,用此模型对转化器进行模拟,结果与工业设计和生产数据相吻合。利用此模型分析了转化器进口条件对SO2转化率的影响,对SO2转化器几种操作工况进行了优化,结果表明提高一、二段催化床进口温度、降低第三段催化床进口温度、增大进口气体中O2与SO2摩尔比有利于SO2的转化。在给定的生产工况条件下,SO2最优转化率可达99.01%、酸性气体中SO2质量分数可降至0.06%。     

Gas hydrate formation from hydrogen/carbon dioxide and nitrogen/carbon dioxide gas mixtures

Gas hydrates from CO₂/N₂ and CO₂/H₂ gas mixtures were formed in a semi-batch stirred vessel at constant pressure and temperature of 273.7 K. These mixtures are of interest to CO₂ separation and recovery from flue gas and fuel gas, respectively. During hydrate formation the gas uptake was determined and the composition changes in the gas phase were obtained by gas chromatography. The rate of hydrate growth from CO₂/H₂ mixtures was found to be the fastest. In both mixtures CO₂ was found to be preferentially incorporated into the hydrate phase. The observed fractionation effect is desirable and provides the basis for CO₂ capture from flue gas or fuel gas mixtures. The separation from fuel gas is also a source of H₂. The impact of tetrahydrofuran (THF) on hydrate formation from the CO₂/N₂ mixture was also observed. THF is known to substantially reduce the equilibrium formation conditions enabling hydrate formation at much lower pressures. THF was found to reduce the induction time and the rate of hydrate growth.     

Studies on the deactivation of NOx storage-reduction catalysts by sulfur dioxide

The interaction of sulfur dioxide with a commercial NO_x storage-reduction catalyst (NSR) has been investigated using in situ IR and X-ray absorption spectroscopy. Two pathways of catalyst deactivation by SO₂ were identified. Under lean conditions (exposure to SO₂ and O₂) at 350 °C the storage component forms barium sulfates, which transform from surface to hardly reducible bulk sulfate species. The irreversible blocking of the Ba sites led to a decrease in NO_x storage capacity. Under fuel rich conditions (SO₂/C₃H₆) at 350–500 °C evidence for the formation of sulfides on the oxidation/reduction component (Pt) of the catalyst was found, which blocks the metal surface and thus hinders the further reduction of the sulfides.     

Activation of monolithic catalysts based on diatomaceous earth for sulfur dioxide oxidation

The formation of the active phases during the activation process of monolithic catalysts based on V₂O₅–K₂SO₄ supported on diatomaceous earth for SO₂ to SO₃ oxidation in flue gases, has been shown to be a crucial factor to achieve satisfactory catalytic performance. As the temperature is increased from room temperature to 470°C, SO₂ and SO₃ are taken up by the green catalyst and the precursors are transformed into the active species. The role of each component of the catalyst during the activation was analyzed by studying the behavior towards SO₂ adsorption of four materials, which contained: diatomaceous earth, diatomaceous earth + V, diatomaceous earth + K, and diatomaceous earth + V + K. The influence of the potassium sulfate accessibility in the green catalyst was studied by using two different preparation methods, which gave rise to differences in the catalysts SO₂ adsorption properties and catalytic performance. Furthermore, the influence of the activation atmosphere was studied using nitrogen, oxygen or a flue gas composition. It was shown that pyrosulfate species should be formed at temperatures below 400°C, to keep the vanadium in the active 5+ oxidation state.     

Observed electrochemical oscillations during the oxidation of aqueous sulfur dioxide on a sulfur modified platinum electrode

The electrochemical oxidation of aqueous sulfur dioxide has been investigated on a sulfur modified polycrystalline platinum electrode. It has been found that time and potential-based current oscillations occur on a modified electrode in the oxidation region >0.7 V vs. SHE. The oscillation is specific to catalytic oxidation on sulfur modified platinum and is not observed on an unmodified electrode. Using i–R compensation techniques, the oscillation has been found to stem from electrochemical origins; the interfacial potential being an essential variable. The influence of other controllable variables including holding potential, sulfur dioxide concentration and sulfuric acid concentration have also been investigated for their effects on the oscillation. The electrochemical oscillation is explained here in part by the intermediate formation of dithionate. Two possible mechanisms, including a dual pathway mechanism, are explored.     

Dewatering green sapwood using carbon dioxide cycled between supercritical fluid and gas phase

Green radiata pine sapwood was dewatered through exposure to CO₂, cyclically alternated between supercritical fluid and gas phase. Plots of moisture content against cycle number showed sigmoidal shapes, with the maximum slope showing a linear dependence on the maximum pressure applied in each cycle, over the range 8–20 MPa. The initial slope varied as the square root of the hold time at 40 MPa, as expected for diffusion of CO₂ through water into the wood. The temperature of the vessel showed no influence on the dewatering rate over the range 38–58 °C. Dissection of partly-dewatered specimens showed strong moisture gradients in green wood, changing to a relatively uniform distribution through a cross-section as the moisture content decreased to an end-point of 40% of the oven-dry weight. This end-point was attributed to moisture remaining in cell walls, after the lumens had been emptied.