排序方式: 共有90条查询结果,搜索用时 328 毫秒
11.
主要研究不同质量比的Fe_2O_3-NiO在氢气气氛下还原过程的非等温动力学。根据热分析动力学研究方法,结合样品的质量损失曲线,获得了样品在非等温还原过程中的动力学曲线,并确定Fe_2O_3-NiO体系在氢气气氛下还原过程的最佳机理函数(G(α)=[-ln(1-α)]~4),过程受随机成核和随后生长机理控制。结果表明:当样品中Fe_2O_3-NiO质量比从1:2变化到2:1时,还原反应过程的活化能从249.821 kJ/mol增加至390.074 kJ/mol;随着体系中NiO含量增加,还原反应开始的温度逐渐降低,还原产物物相由铁纹石相(Fe,Ni)和镍纹石相(Fe,Ni)逐渐转变为镍铁合金相(FeNi_3),产物微观颗粒尺寸变得不均匀。通过建立数学模型,验证了反应过程中反应分数的模型计算值与实验测量值具有良好的相关性。 相似文献
12.
采用还原焙烧-磁选工艺, 对氯化钙作用下镁质贫镍红土矿选择性富集镍进行了研究, 考察了还原温度、还原时间、还原剂用量和氯化钙用量对富集镍的影响。结果表明, 在还原温度1 200 ℃、还原时间40 min、还原剂和氯化钙用量均为8%的条件下, 可获得镍品位8.67%、回收率92.01%的镍铁精矿; 相比于直接还原焙烧-磁选, 加入8%氯化钙后使镍的富集比由3增加到11, 显著提高了镍的富集效果。磁选产品物相分析显示, 镍主要以铁纹石形式存在于精矿中, 通过磁选实现了对镍铁精矿与脉石的有效分离。 相似文献
13.
采用非等温热分析法对红土镍矿固相还原动力学进行了研究,由热失重曲线确定了红土镍矿固相还原的反应机理函数f(a),在此基础上求解出动力学参数,并对建立的动力学模型进行了验证,分析了红土镍矿固相还原机理. 结果表明,红土镍矿失重率与加热温度密切相关,而升温速率对其影响很小;模型计算值与实测值具有良好的相关性;固相还原过程可分为473~773和773~1223 K两个阶段,反应活化能分别为171.91和52.75 kJ/mol,与挥发分的析出和镍、铁氧化物的还原对应;反应属随机成核和随后生长型机理函数,其微分形式为f(a)=1/4(1-a)[-ln(1-a)]-3,反应速率主要由碳气化反应控制. 相似文献
14.
15.
Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temperature programmed reduction test, Ce-Fe oxide behaved complete oxidation at the lower temperature and selective oxidation at higher temperatures. Ce-Fe mixed oxides with the Fe content in the range of 0.1–0.5 was able to produce syngas with high selectivity in high-temperature range(800–900 °C), and a higher Fe amount over 0.5 seemed to depress the CO formation. In isothermal reaction, complete oxidation occurred at beginning following with selective oxidation later. Ce1–xFexO2–δ oxygen carriers(x≤0.5) were proved to be suitable for the selective oxidation of methane. Ce-Fe mixed oxides had the well-pleasing reducibility with high oxygen releasing rate and CO selectivity due to the interaction between Ce and Fe species. Strong chemical interaction of Ce-Fe mixed oxides originated from both Fe*activated CeO2 and Ce3+ activated iron oxides(FeOm), and those chemical interaction greatly enhanced the oxygen mobility and selectivity. 相似文献
16.
Chemical-looping steam methane reforming (CL-SMR) is a novel process towards the production of pure hydrogen and syngas, consisting ofa syngas production reaction and a hydrogen production reaction. Macroporous CeQ-ZrO2 oxygen carders with different pore sizes prepared by colloidal crystal templating method and characterized by techniques of scalming electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and temperature pro- grammed reduction (H2-TPR) were tested in CL-SMR process. For comparison, nonporous CeO2-ZrO2 oxygen carrier prepared by precipitation method was also investigated. It was found that macroporous CeO2-ZrO2 oxygen carriers owned higher reducibility and reactivity in CL-SMR process than nonporous samples. For the macroporous CeO2-ZrO2 sample, the decline of pore size could im- prove the reducibility and reactivity. The macroporous sample with a pore size of 100 nm (labeled as Ce-Zr-100) showed the highest performance for the co-production of syngas and hydrogen during the successive CL-SMR redox cycles. After 10 redox cycles, it still retained good porous structure and reducibility. It was found that the porous structure could accelerate the oxygen release from bulk to surface, leading to a good mobility of oxygen and higher reducibility. In addition, it was also favorable for diffusion and penetration of methane and water steam into the sample particles to accelerate the reaction rate. 相似文献
17.
针对传统的甲烷转化制合成气及金属锌制备技术的缺陷,提出了一种新型的熔融盐反应体系,在熔融盐反应器中以熔融盐(质量比为1:1的Na2CO3/K2CO3)为反应介质对CH4与ZnO反应同时生成金属锌和合成气作了实验研究,利用气相色谱对气体组分进行了分析. 结果表明,反应尾气组分主要是H2, CO和CH4,未检测到CO2,其中合成气的量及H2/CO比例随反应温度的升高而增加,在1198 K左右获得了H2/CO比为2的合成气. 合成气和金属锌分别从气相和熔融盐中获得. 用XRD, SEM及EDS对金属锌产品和熔融盐进行了表征,发现反应后的熔融盐含有少量Na2O和NaOH,来自于CH4与熔融盐之间的微弱反应,由此推断熔融盐还具有消碳功能. 相似文献
18.
设计了一种生物质气在固体氧化物燃料电池堆(SOFCs)中的循环流程.在本技术中,生物质气的主要成分甲烷首先被熔融盐中的晶格氧部分氧化为H2和CO,生物质气中的杂质S和重金属被熔融盐吸收;CO和H2在SOFCs阳极室被电化学氧化为CO2和H20,反应释放的大部分能量转化为电能;大部分CO2在特定温度下,经可再生材料Li4SiO4吸收、解吸被提纯回收.少量CO2和H2O被循环到熔融盐池与甲烷发生重整反应,反应所需要的热量由甲烷部分氧化释放的热量提供.本系统中SOFCs抗积碳及对含S和N燃料的容忍性比较好;整个系统能量利用率高,可以实现CO2的零排放. 相似文献
19.
20.
镍是一种重要的战略金属,随着优质硫化镍矿日益匮乏,资源丰富的红土镍矿成为重要的提镍原料。本文以红土镍矿为研究对象,甲烷为还原剂,硫化钠为添加剂,考察了还原温度、甲烷浓度、还原时间及添加剂用量对镍、铁金属化率的影响,并通过扫描电子显微镜与能量色散光谱(SEM-EDS)分析对还原产物中镍铁的聚集情况进行了研究。结果表明:在还原温度900℃、还原时间60min、甲烷浓度20%、硫化钠添加量10%的条件下,还原产物中的镍、铁金属化率可分别达到89.05%、5.10%。硫化钠的加入促进了镍铁颗粒的聚集长大,有利于镍铁颗粒与杂质的分离,同时生成的FeS抑制了铁的深度还原,实现了镍的选择性还原。 相似文献