首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 89 毫秒
1.
Japan started the national project “COURSE 50” for CO2 reduction in the 2000s. This project aimed to establish novel technologies to reduce CO2 emissions with partially utilization of hydrogen in blast furnace-based ironmaking by 30% by around 2030 and use it for practical applications by 2050. The idea is that instead of coke, hydrogen is used as the reducing agent, leading to lower fossil fuel consumption in the process. It has been reported that the reduction behavior of hematite, magnetite, calcium ferrite, and slag in the sinter is different, and it is also considerably influenced by the sinter morphology. This study aimed to investigate the reduction behavior of sinters in hydrogen enriched blast furnace with different mineral morphologies in CO–CO2–H2 mixed gas. As an experimental sample, two sinter samples with significantly different hematite and magnetite ratios were prepared to compare their reduction behaviors. The reduction of wustite to iron was carried out at 1000, 900, and 800°C in a CO–CO2–H2 atmosphere for the mineral morphology-controlled sinter, and the following findings were obtained. The reduction rate of smaller amount of FeO led to faster increase of the reduction rate curve at the initial stage of reduction. Macro-observations of reduced samples showed that the reaction proceeded from the outer periphery of the sample toward the inside, and a reaction interface was observed where reduced iron and wustite coexisted. Micro-observations revealed three layers, namely, wustite single phase in the center zone of the sample, iron single phase in the outer periphery zone of the sample, and iron oxide-derived wustite FeO and iron, or calcium ferrite-derived wustite 'FeO' and iron in the reaction interface zone. A two-interface unreacted core model was successfully applied for the kinetic analysis of the reduction reaction, and obtained temperature dependent expressions of the chemical reaction coefficients from each mineral phases.  相似文献   

2.
NH4HCO3 conversion followed by HCl leaching was performed and proven to be effective in extracting Pb and Sr from zinc extracted residual. The mechanism and operating conditions of NH4HCO3 conversion, including molar ratio of NH4HCO3 to zinc extracted residual, NH4HCO3 concentration, conversion temperature, conversion time, and stirring velocity, were discussed, and operating conditions were optimized by the orthogonal test. Experimental results indicate that NH4HCO3 conversion at temperatures ranging from 25 to 85°C follows the shrinking unreacted core model and is controlled by inner diffusion through the product layer. The extraction ratios of Pb and Sr under optimized conditions reached 85.15% and 87.08%, respectively. Moreover, the apparent activation energies of Pb and Sr were 13.85 and 13.67 kJ·mol?1, respectively.  相似文献   

3.
《矿物冶金与材料学报》2021,28(12):2001-2007
Graphene oxide (GO) wrapped Fe3O4 nanoparticles (NPs) were prepared by coating the Fe3O4 NPs with a SiO2 layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO2 coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO2 on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO2 layer can effectively induce the GO nanosheets to completely wrap the Fe3O4 NPs, forming a core-shell Fe3O4@SiO2@GO composite where Fe3O4@SiO2 NPs are firmly encapsulated by GO nanosheets. The optimized Fe3O4@SiO2@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.  相似文献   

4.
In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile (which have the same general formula Mg3Si2O5(OH)4), and talc (Mg3Si4O10(OH)2) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K2MgSiO4 phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K2MgSiO4 formation. All the materials showed catalytic activity for the transesterification of soybean oil (1:6 of oil : methanol molar ratio, 5wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K2MgSiO4.  相似文献   

5.
《矿物冶金与材料学报》2021,28(9):1397-1412
As the world’s second largest economy experiencing rapid economic growth, China has a huge demand for metals and energy. In recent years, China ranks first, among all the countries in the world, in the production and consumption of several metals such as copper, gold, and rare earth elements. Bioleaching, which is an approach for mining low grade and refractory ores, has been applied in industrial production, and bioleaching has made great contributions to the development of the Chinese mining industry. The exploration and application of bioleaching in China are reviewed in this study. Production and consumption trends of several metals in China over the past decade are reviewed. Technological processes at key bioleaching operations in China, such as at the Zijinshan Copper Mine and Mianhuakeng Uranium Mine, are presented. Also, the current challenges faced by bioleaching operations in China are introduced. Moreover, prospects such as efficiency improvement and environmental protection are proposed based on the current situation in the Chinese bioleaching industry.  相似文献   

6.
《矿物冶金与材料学报》2021,28(12):1940-1948
The evolution of inclusions and the formation of acicular ferrite (AF) in Ca–Ti treated steel was systematically investigated after Mg and La addition. The inclusions in the molten steel were Ca–Al–O, Ca–Al–Mg–O, and La–Mg–Ca–Al–O after Ca, Mg, and La addition, respectively. The type of oxide inclusion in the final quenched samples was the same as that in the molten steel. However, unlike those in molten steel, the inclusions were Ca–Al–Ti–O + MnS, Ca–Mg–Al–Ti–O + MnS, and La–Ca–Mg–Al–Ti–O + MnS in Mg-free, Mg-containing, and La-containing samples, respectively. The inclusions distributed dispersedly in the La-containing sample. In addition, the average size of the inclusions in the La-containing sample was the smallest, while the number density of inclusions was the highest. The size of effective inclusions (nucleus of AF formation) was mainly in the range of 1–3 μm. In addition, the content of ferrite side plates (FSP) decreased, while the percentage of AF increased by 16.2% due to the increase in the number of effective inclusions in the La-containing sample in this study.  相似文献   

7.
The butt welds of 4-mm thick 5A06 aluminum alloy plates were produced by adjustable-gap bobbin-tool friction stir travel with travel speeds of 200, 300, and 400 mm/min in this study. The microstructure was studied using optical microscopy and electron backscatter diffraction (EBSD). Tensile tests and microhardness measurements were performed to identify the effect of the travel speed on the joint mechanical properties. Sound joints were obtained at 200 mm/min while voids were present at different positions of the joints as the travel speed increased. The EBSD results show that the grain size, high angle grain boundaries, and density of geometrically necessary dislocations in different regions of the joint vary depending on the recovery and recrystallization behavior. Specific attention was given to the relationship between the local microstructure and mechanical properties. Microhardness measurements show that the average hardness of the stir zone (SZ) was greater than that of the base material, which was only affected slightly by the travel speed. The tensile strength of the joint decreased with increasing travel speed and the maximal strength efficiency reached 99%.  相似文献   

8.
A high-building multi-directional pipe joint (HBMDPJ) was fabricated by wire and arc additive manufacturing using high-strength low-alloy (HSLA) steel. The microstructure characteristics and transformation were observed and analyzed. The results show that the forming part includes four regions. The solidification zone solidifies as typical columnar crystals from a molten pool. The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100°C, and the typical columnar crystals in this zone are difficult to observe. The partial austenitizing zone forms from the completely austenite zone heated between Ac1 (austenite transition temperature) and 1100°C, which is mainly equiaxed grains. After several thermal cycles, the partial austenitizing zone transforms to the tempering zone, which consistes of fully equiaxed grains. From the solidification zone to the tempering zone, the average grain size decreases from 75 to 20 μm. The mechanical properties of HBMDPJ satisfies the requirement for the intended application.  相似文献   

9.
《矿物冶金与材料学报》2020,27(9):1251-1258
A Monte Carlo Potts model was developed to simulate the recrystallization process of a cold-rolled ultra-thin grain-oriented silicon steel. The orientation and image quality data from electron backscatter diffraction measurements were used as input information for simulation. Three types of nucleation mechanisms, namely, random nucleation, high-stored-energy site nucleation (HSEN), and high-angle boundary nucleation (HABN), were considered for simulation. In particular, the nucleation and growth behaviors of Goss-oriented ({011}<100>) grains were investigated. Results showed that Goss grains had a nucleation advantage in HSEN and HABN. The amount of Goss grains was the highest according to HABN, and it matched the experimental measurement. However, Goss grains lacked a size advantage across all mechanisms during the recrystallization process.  相似文献   

10.
Nano graphene platelet (Gr) reinforced nano composites with a zinc–aluminum alloy (ZA27) matrix were produced by powder metallurgy at four different mass ratios (0.5wt%, 1.0wt%, 2.0wt% and 4.0wt%) and three different sintering temperatures (425, 450, and 475°C). In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure, the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope. Hardness, transverse rupture, and abrasion wear tests were performed to determine the mechanical properties. According to the test results, the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased. However, when the composites produced in different reinforcement ratios were evaluated, the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.  相似文献   

11.
张彤 《科技咨询导报》2009,(13):131-131
叙述了钢厂废水处理的流程和原理,针对钢厂废水量大、时变性强、非线性等特点,提出了模糊自适应PID控制的方法,进行废水处理中PH值的控制,根据PH的偏差值和偏差变化率进行实时调整控制参数,并通过在秦皇岛某钢厂废水处理中实际应用取得了较理想的控制效果。  相似文献   

12.
13.
动态优先级队列能够较好地满足多媒体网络业务流的多种QoS需求。采用离散时间的D-MAP/PH/1排队模型来研究动态优先级队列,并应用矩阵分析的方法,对该排队模型的稳态分布进行分析,得到了系统的主要性能指标:两类业务流的平均队长、阻塞概率和平均延时等结果。  相似文献   

14.
王雪洁  朱喜梅 《科技资讯》2013,(13):204-204,206
测定盐酸地尔硫卓延迟缓释制剂的体外释放行为,为试药翻定释放度质量标准。采用体外释放度检查法,在pH值6.8介质中进行体外释放度测度,利用高效液相色谱进行检测。本制剂释放度复合延迟释放特点,可用于该药释放度质量标准制定。  相似文献   

15.
探讨了有理PH曲线的G1 Hermite插值问题,运用复数表达将问题转化为包含5个复代数方程的方程组,通过求解这个方程组,得到结论:当插值条件形成凸多边形时,插值问题有2个解,其中之一为多项式解;而当插值条件形成非凸多边形时,只有切方向满足一定条件时,插值问题才有一个解.而对于后一种情况,总可以通过加点的方式细分原逼近曲线,进而得到由两段有理三次PH曲线G1拼接而成的4组样条插值曲线.  相似文献   

16.
荷兰科学家HenkVanLubeck提出了在溶液中应用[H+]和[OH-]比值的对数即AG来表示其酸度。关于AG,本文从四个方面论述它的优点及其与pH的关系,并介绍有关AG的计算。  相似文献   

17.
介入医学图像处理意义重大,本文论述了一种医学图像处理技术--峰值保持数字减影技术(PH-DSA),该方法最突出的优点是造影剂用量低,约降到普遍方法用量的1/3。  相似文献   

18.
介绍利用精密PH试纸分别测定肥料中K+和NH+4,该法分析一个样品仅需几分钟,且不需要专门的仪器特别适用于现场快速、简单测定肥料中钾和铵含量。  相似文献   

19.
研究概率多项式时间谱系的结构性质,证明了:(1)如果BP∑_(k+1)~pBP∑_k~P,则PH=BP∑∏_K~P;(2)如果BP∑_k~PBP∏_k~P,则;PH=BP∑_K~PP;(3)对任意n,k≥0,BP∑_K~P(BP∑_n~P)=BP∑_(n+k)~p,BP∑_n~P(BP△_(k+1)~P)=BP∑_(n+k)~n;(4)对任意n,k≥1,BP∑_n~P(BP∑_k~p∩BP∏_k~P)=BP∑_(n+k-1)~P这些结果说明概率多项式时间谱系与多项式时间谱系有相同的结构性盾,但也有差别.  相似文献   

20.
用配位滴定法对混合离子进行分步滴定时,将pH_(?)定为最佳酸度范围的低限是否合理。在最佳酸度范围内有一最佳pH值能否作为一普遍规律的结论,文章从三种不同类型的实例,论证上述结论的局限性。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号