铁矿石作为氧载体在熔融盐中催化甲烷燃烧

熔融盐循环热载体无烟燃烧技术（noneflame combustion technology using thermal cyclic carrier of molten salt,NFCT）不会向大气中排放有害气体,是一种清洁燃烧技术。利用XRD、SEM和TG等分析手段对催化剂的性能进行了表征。在质量比为1：1的Na2CO3和K2CO3熔融盐中研究了Fe2O3中的晶格氧对甲烷的催化燃烧性能。铁矿石在熔融盐中分别与甲烷和空气发生反应,用XRD分析生成物表明,作为铁矿石主要成分的Fe2O3可以在熔融盐中失去和恢复晶格氧,这些品格氧可以用来催化氧化甲烷。TG分析结果表明,铁矿石被甲烷还原分为两个阶段,第一个阶段从550℃开始,680℃结束,Fe2O3被还原成Fe3O4,第二个阶段从850℃开始至1050℃结束,第一个阶段生成的Fe3O4在这一阶段大部分被还原成了FeO。被甲烷还原的铁矿石在TG试验中与空气反应时,只出现一个明显的增重段,从350℃开始直到反应温度的上限1100℃,增重速率较快的区间是400～850℃。从燃烧产物的气相色谱分析结果可以看出,甲烷在熔融盐中绝大部分被氧化成了CO2和H2O。因此,铁矿石可以作为氧载体在熔融盐中催化甲烷燃烧。     

铜基氧载体化学链氧解耦的流化床实验研究

采用溶胶-凝胶法制备了CuO/CuAl2O4氧载体,在CO2气氛下和空气气氛下,分别研究了该氧载体的释氧和吸氧性能,研究结果表明,随着温度的升高,氧载体的释氧、吸氧速率不断升高.随后在N2气氛下研究了3种典型煤的化学链氧解耦燃烧过程,结果表明,煤中挥发分的含量直接影响燃烧过程的快慢,在氧解耦燃烧时,高挥发分的褐煤尾气中,CO2体积分数比无烟煤高15%左右,褐煤中碳的平均转化率为无烟煤的2～3倍.     

高硫煤-CuO化学链燃烧特性及硫演化热力学研究

以贵州六枝高硫煤为研究对象,通过热重实验对该典型高硫煤和CuO氧载体的化学链燃烧特性及其与空气直接接触时的燃烧特性加以定性分析和定量评估。为探索煤中硫的演化及其与CuO氧载体作用对CuO氧化活性的影响,进一步采用HSC Chemistry软件,分析了氧载体过量系数Φ对煤中硫分布的影响。研究表明:相比于空气下煤直接燃烧,CuO与六枝煤化学链燃烧的着火温度高,可燃指数和综合燃烧特性指数小,显示CuO氧载体更低的反应活性;在热力学平衡状态下,当0Φ≤1.25及Φ1.25时,系统中硫组分分别以固相Cu_2S和气相SO_2形式存在。基于上述研究结果,提出了一种煤化学链燃烧系统中同时进行脱硫和CO_2捕集的新方案。     

化学链中Cu、Fe基复合氧载体各组分间相互作用的研究进展

化学链燃烧是一种新型的燃烧方式,既可以避免氮氧化物的产生,又可以实现二氧化碳的内分离,近年来受到了国内外研究人员的广泛关注.氧载体的反应性、循环稳定性以及载氧能力等性能,是化学链燃烧系统的重要影响因素.添加惰性载体和制备多活性组分复合氧载体都是可以有效提高氧载体性能的主要方式.为了解决氧载体中各组分之间反应降低氧载体性能的问题,本文就近年来国内外有关Cu基和Fe基复合氧载体的研究进行了总结和分析,发现TiO2和SiO2会与Fe2 O3形成尖晶石,不适合做Fe2 O3的载体;添加活性组分虽然可以使氧载体释氧速率和循环反应性增强,但也会和Fe2 O3或者CuO反应产生复杂物相,使氧载体反应活性下降或者烧结.在此基础上针对活性组分与惰性组分以及活性组分与活性组分之间的相互作用两个方面进行了综述和展望.     

火焰合成Pt修饰CuO氧载体低温化学链燃烧特性

采用火焰喷雾热解方法(FSP)合成了Pt修饰CuO纳米氧载体材料(FSP-Pt/Cu O),首先通过XRD、SEM等表征手段分析了Pt/CuO的结构和组成;通过热重分析仪、化学吸附仪对比研究了FSP合成的CuO、Pt/CuO以及商用CuO纳米颗粒的化学链燃烧反应性能．结果表明,FSP-Pt/CuO氧载体材料与H₂、CO、CH₄的还原反应温度能够分别降低到200℃、105℃、290℃以下．进一步考察了H₂、O₂不同浓度对Pt/CuO氧载体还原、氧化特性的影响,并测试了Pt/CuO氧载体的低温化学链燃烧循环稳定性．最后通过Pt/CuO氧载体颗粒表面的氢溢流原理对低温化学链燃烧过程进行了模型机理解释．     

基于密度泛函理论的CuO氧载体释氧机理研究

化学链氧解耦（CLOU）是基于化学链燃烧（CLC）技术的一种新型燃烧方式,具有CO2内分离的优良特性。具有良好吸氧释氧性能的氧载体是CLOU技术的关键,其宏观层面的反应性决定于其微观层面的晶格氧传输机理,但目前对这种微观机理的研究非常缺乏。本文采用量子化学计算方法——密度泛函理论（DFT）研究CuO氧载体释氧的微观机理,构建了CuO团簇及CuO平板模型,模拟团簇及表面的释氧过程。CuO平板模型释氧包括O原子在CuO内部扩散、表面O2的形成及释放过程。结果表明：CuO(111)表面释氧过程的最高能量势垒为3.16 eV,与实验值3.39 eV接近,低于CuO团簇模型的释氧能量势垒3.51 eV;此外,O原子在CuO(111)内部的扩散势垒仅为0.87 eV,说明CuO(111) 释氧的限制步骤是表面O2的形成过程。     

用于焦炉煤气重整合成气的管式透氧膜反应器的研制及其运行性能

采用热注浆法成功地制备了致密的混合导体BaCo0.7Fe0．2Nb0.1O3-δ（BCFNO）透氧膜管,应用在焦炉煤气中甲烷部分氧化制合成气反应中,可以利用透氧膜以空气为氧源和焦炉煤气中的甲烷反应制合成气,实现膜分离制氧和甲烷部分氧化反应的一体化。试验结果表明,当反应温度在875℃时,膜的透氧量为8．7mL／（cm^2·min）,焦炉煤气中甲烷的转化率可以达到94％以上,H2的选择性在90％左右。试验结果还表明,透氧膜管的性能可靠稳定,经过长时间的运行膜管没有出现破裂,在富氢焦炉煤气气氛下表现出很好的稳定性。     

Ni基和Co基金属载氧体的持续循环能力研究

化学链燃烧技术是一种新颖的二氧化碳分离技术,其中金属载氧体持续循环反应能力的优劣直接关系到该技术的实际应用和推广。以Ni基和Co基金属载氧体为研究对象,用热重分析仪(TGA)、扫描电镜(SEM)和X射线衍射仪(XRD)等工具研究了二者的持续循环能力。结果表明,添加惰性载体后载氧体的反应速率和持续循环能力均有大幅的提升,且Ni基载氧体比Co基载氧体表现出更好的反应特性和持续循环能力。     

以CuO为氧载体处理市政污泥的化学链燃烧

基于双极燃料反应器的化学链燃烧装置,以CuO为氧载体,对污泥化学链燃烧进行实验研究。反应器稳定运行,以反应器温度(750℃～850℃)、不同质量分数的CuO(0～100%)为参数,热重分析法和HSC热力学模拟为方法,探究对污泥化学链燃烧性能的影响。研究表明,温度的增加、碳转化率和CO_2的捕获效率升高,降低了出口烟气中可燃性气体的浓度。污泥的着火温度为Ti=267.5℃,挥发分特性指数为D=2.6×10-5,有效降低了污泥样品反应的初始热解温度,加快污泥样品的处理速度。加入足量的氧载体CuO加快了碳转化速率,有效消耗了产生CO所需的反应物,提高了出口气体中CO_2的含量,占比高达99.8%,未产生副产物有毒有害气体CO。SEM表征显示,氧载体由于释放晶格氧形成了空腔的结构,有利于再次氧化形成新的氧载体,具有较好的循环稳定性。     

甲烷催化燃烧锅炉用催化剂的研究

催化燃烧是一种高效、低排放的新兴技术,可应用于天然气发电。利用共沉淀法制备了系列Ce—Zr复合氧化物,并用XRD和SEM等手段对其进行了表征,测试了其催化甲烷燃烧性能。结果表明,部分铈离子可进入氧化锆晶格中形成锆基固溶体。当游离的CeO2较好地分散在氧化锆基固溶体上时,铈锆催化剂具有较好的催化甲烷燃烧性能。Ce0.6Zr0．4O2催化剂显示了这种协同作用,获得了较低起燃温度（318℃）和完全转化温度（530℃）。     

高温低氧燃烧条件下氮氧化物的生成特性

高温低氧燃烧原理是高温空气燃烧技术赖以发展的基础，使得高温燃烧条件下的氮氧化物的生成与排放受到大大抑制。为了掌握这种非常规燃烧现象及污染物生成的基本规律，采用扩散燃烧模型、热力NO生成模拟与湍流N－S方程，数值研究了燃烧空间中空气氧浓度对燃烧特性和氮氧化物排放浓度的影响，再现了高温与低氧两种条件相结合，形成的稳定的低氮氧化物排放的燃烧特性。计算结果与实验数据吻合，为发展高温空气燃烧技术提供了理论基础。     

Comparison of CuO and NiO as oxygen carrier in chemical looping combustion of a Victorian brown coal

Chemical looping combustion (CLC) is a novel process where an oxygen carrier, preferably oxides of metal, is used to transfer oxygen from the combustion air to the fuel. The outlet gas from the process reactor consists of CO₂ and H₂O, and concentrated stream of CO₂ is obtained for sequestration when water vapour is condensed. Chemical looping has been widely studied for combustion of natural gas; however its application to solid fuels, such as coal, is being studied relatively recently; no work has been done using Victorian brown coal which represents a very large resource, over 500 years at current consumption rate. In this study we carried out an experimental investigation pertaining to CLC of a Victorian brown coal from Loy Yang mine using NiO and CuO as oxygen carrier. The experiments were conducted using a thermogravimetric analyser (TGA) under CO₂ gasification environment with NiO and CuO. The reduction and re-oxidation of NiO in five repeated cycle operations were performed at 950 °C. However, the same cyclic operation for CuO was performed at 800 °C, as it was observed that at 950 °C CuO could not be re-oxidized to its original state due to sintering, which significantly altered the morphology. The extent of coal combustion and re-oxidation of metal oxides resulted in a 4.4-7.5% weight loss of NiO per cycle. No such weight loss was observed in case of CuO at 800 °C. The high reactivity of CuO was observed as compared to NiO during cyclic operation. The percentage of combustion at the end of the 5th cycle with CuO was 96% as compared to 67% with NiO. Fresh oxide particles and solid residues are characterized using SEM to understand surface morphological changes due to combustion. The energy dispersive X-rays (EDX) helped to get surface elemental information, albeit qualitative, of fresh and used metal oxide particles. The current study, for the first time, has generated practical information on the temperature range, approximate time, and percent combustion that can be achieved while using NiO and CuO as oxygen carriers during CLC with Loy Yang brown coal. Based on these results the ongoing work includes long duration experiments with Loy Yang and other Victorian brown coals.     

NiFe2O4为载氧体的生物质半焦化学链燃烧热力学模拟研究

本文建立了以铁酸镍（NiFe2O4）为载氧体的生物质半焦化学链燃烧模型,利用HSC Chemistry 5.0软件对生物质半焦和NiFe2O4载氧体之间的化学链燃烧反应进行了热力学计算,模拟载氧体被半焦还原以及载氧体被空气氧化两个步骤的氧化还原过程,得到燃料反应器的优化操作参数为：载氧体和生物质半焦的摩尔比（O/BC）为1.5,燃料反应器的温度为800℃。热力学分析显示,NiFe2O4在化学链燃烧反应中是按照NiFe2O4→Ni-Fe2O3→ Ni-Fe3O4→Ni-FeO→Ni-Fe的顺序逐级被还原的。氧化过程的模拟说明,在空气气氛中,失去的晶格氧可以恢复到初始的程度,而实验手段得到的氧化产物的X射线衍射图则证明,通过氧化,被还原的载氧体可以大部分恢复到NiFe2O4尖晶石结构。     

An experimental study on high temperature and low oxygen air combustion

ho~cuon,Recently, much attenhon has been paid to uhliZinghidly Preheated air up to l,(XX)"C through waste gas inindustrial furnaces, in which about 15% of totalnational energy in KOrea were consumed, because ofhigh efficiency of energy savings. Moreover, one ofthree major issues in the fiscal 1996," UnderstandingEnhancement of ugh TemP~ Air COmbushon" hasbeen stUdied as successive subject in the Japanesenational Project tO reduce CO, for Protechon of earth.IntrDduction of high regenera…     

空气分级燃烧降低NOx排放技术的研究

利用Fluent数值模拟软件分析了空气分级对高温低氧空气燃烧污染物排放的影响.应用空气分级燃烧技术的燃烧器不仅使燃烧室内具有较高的温度水平,温度场均匀,燃烧效率高,而且NOx的生成量也较低,可以达到节约燃料和降低污染物的综合效果.计算结果分析表明:分级燃烧的二次空气配比对燃烧室内的NOx排放有较大影响.当一次空气占40%左右时,NOx排放最少.     

A mechanistic investigation of a calcium-based oxygen carrier for chemical looping combustion

Chemical looping combustion (CLC) has been suggested as an energy-efficient method for the capture of carbon dioxide from combustion. It is indirect combustion by the use of an oxygen carrier, which can be used for CO₂ capture in power-generating processes. The possibility of CLC using a calcium-based oxygen carrier is investigated in this paper. In the air reactor air is supplied to oxidize CaS to CaSO₄, where oxygen is transferred from air to the oxygen carrier; the reduction of CaSO₄ to CaS takes place in the fuel reactor. The exit gas from the fuel reactor is CO₂ and H₂O. After condensation of water, almost pure CO₂ could be obtained. The thermodynamic and kinetic problem of the reduction reactions of CaSO₄ with CO and H₂ and the oxidization reactions of CaS with O₂ is discussed in the paper to investigate the technique possibility. To prevent SO₂ release from the process of chemical looping combustion using a calcium-based oxygen carrier, thermochemical CaSO₄ reduction and CaS oxidation are discussed. Thermal simulation experiments are carried out using a thermogravimetric analyzer (TGA). The properties of the products are characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD), and the optimal reaction parameters are evaluated. The effects of reaction temperature, reductive gas mixture, and oxygen partial pressure on the composition of flue gas are discussed. The suitable temperature of the air reactor is between 1050 and 1150 °C and the optimal temperature of the fuel reactor between 900 and 950 °C.     

结构化载氧体颗粒化学链燃烧内扩散影响模拟分析

采用有限速率模型对CuO/Al_2O_3结构化载氧体颗粒化学链燃烧进行了数值模拟,考察了不同结构化载氧体颗粒模型和进气速度对载氧体化学反应内扩散的影响。结果表明,相比于球形载氧体,环形结构拉西环载氧体内扩散更为容易,反应快,温升高;相比于全活性载氧体,1/4活性和半活性载氧体气体扩散到活性物质距离短,反应更快;增加进气速度能够加速颗粒内扩散,改善反应速率。     

Comparison of metallic oxide,natural ore and synthetic oxygen carrier in chemical looping combustion process

As one of clean coal combustion ways, chemical looping combustion (CLC) showed high CO₂ capture efficiency with lower energy penalty. But these processes were limited by the low reaction rate between oxygen carriers (OCs) with coal char. This study evaluated the performances of Cu-based OCs with coal in in-situ gasification chemical-looping combustion (iG-CLC) and chemical-looping with oxygen uncoupling (CLOU) process. CuO modified by iron ore and chrysotile were employed as OCs which the addition of chrysolite improved the char gasification and iron ore enhanced the stability of CuO at high temperature. Results showed that CuO supported by ores (chrysolite and iron ore) had better H₂ and CO conversion under H₂O atmosphere than CuO and iron ore. Chrysolite decorated CuO can convert almost all H₂ to H₂O at 850 °C. Synthetic OCs showed better stability and high temperature tolerance during 10 redox cycles.     

Exergy analysis of chemical-looping combustion systems

A power plant based on chemical-looping combustion offers both a possibility of high net power efficiency and separation of the greenhouse gas CO₂. This is due to the way the oxidation of the fuel takes place. Instead of oxidizing the fuel with oxygen from the combustion air, the fuel is oxidized by an oxygen carrier, i.e., an oxygen-containing compound. The oxygen carriers that have been suggested in previous studies are metal oxides like NiO, Fe₂O₃ and Mn₃O₄. The reduced oxygen carrier is in the next step reoxidized by air in a second reactor and then recirculated to the first reactor. In this way, fuel and air are never mixed and the fuel oxidation products CO₂ and water leave the system undiluted by air. All that is needed to get an almost pure CO₂ product is to condense the water vapour and remove the liquid water.Chemical-looping combustion (CLC) is also claimed to reduce the fuel exergy destruction in the overall reaction of combustion of the fuel. This gives a possibility to increase the net power efficiency.This paper gives an introduction to chemical-looping combustion. Results from simulations and a detailed exergy analysis of two different CLC gas turbine (GT) systems are also presented. The first system utilizes methane as a fuel and NiO as oxygen carrier. The second system utilizes a fuel gas mixture consisting mainly of CO and H₂, simulating a fuel gas from for instance coal gasification. Results for this system are given for simulations with both NiO and Fe₂O₃ as oxygen carrier. The two systems are compared to comparable simulated systems with conventional combustion of the same fuel. The exergy analysis shows that the irreversibilities generated upon combustion of the fuel are reduced. The net power efficiency of the CLC–GT systems is similar or higher than for the corresponding GT systems with conventional combustion. The net power efficiency of CLC systems could be even further increased if the exergy remaining in the exhaust could be utilized in an efficient way.