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41.
描述用单光束激光复活制银盐白光显示反射全息图的技术,本技术的关键:1)母全息图的颜色必须恢复到满足其布拉格条件;2)复制所用的光波与记录母全息图时的参考的相同;(3)复制所用的激光采用平行偏振,以减少界面反射;94)采用白糖溶液作为折射率匹配液,取得极佳效果。 相似文献
42.
为了更进一步了解CFB气化能力和碳利用率,本文报道了两种煤焦(西山焦煤飞灰,神木煤)以二氧化碳及氧气混合物为气化介质,在小型鼓泡流化床上进行气化反应的研究,并与相同气化条件下的循环流化床气化数据进行了比较。研究结果表明:在相同直径气化反应装置上,相同的气化条件下,循环流化床(CFB)的气化碳转化率、气化强度远远高于鼓泡流化床(BFB)的气化结果,但BFB的煤气中可燃气组成高于CFB的。CFB气化反应装置更适合于生产中、低热值煤气。 相似文献
43.
Fu-Long Li Yu-Cong Zheng Hao Li Fei-Fei Chen Hui-Lei Yu Jian-He Xu 《Tetrahedron》2019,75(12):1706-1710
An engineered epoxide hydrolase from Vigna radiate (VrEH2M263N) shows near-perfect enantioconvergence in single enzyme mediated hydrolysis of racemic p-nitrostyrene oxide (pNSO). To explore industrial potential of the promising biocatalyst, we tried to immobilize the VrEH2 variant by covalently linking onto a commercially available amino resin ECR8405F. Then a 5-mL packed bed reactor filled with the immobilized VrEH2M263N was connected with macroporous resin NKA-11 for in situ product adsorption, and the product (R)-p-nitrophenyl glycol (pNPG) was harvested by methanol elution, with 91% isolated yield and 97% ee. The continuous reactor was operated stably for more than 100?h with a space time yield of 20?g?L?1?h?1. Subsequently, the β-blocker (R)-Nifenalol was prepared by chemically synthesized from (R)-pNPG, affording the product in an overall yield of 61.3% (1.5?g) and an enantiopurity of 99.9% ee after recrystallization. 相似文献
44.
While circulating fluidized bed (CFB) reactor has many advantages over the more conventional turbulent fluidized bed (TFB) reactor, it does at least have one significant shortcoming-the rather dilute solids volume concentration in CFB reactor gives rise to less ideal reaction intensity. On the other hand, while having higher reaction intensity, TFB reactor has one fatal drawback of particle back-mixing, making it not suitable for certain reactions such as catalytic reaction where the catalyst requires frequent regeneration. This paper describes some key issues in the development of a circulating turbulent fluidized bed (CTFB) reactor that combines the advantages of both TFB and CFB, that is, to have the high reaction intensity as in TFB but and also to have a suppressed solids back-mixing as in CFB due to a continuous net upflow of solids flux through the bed. Experimental results show enough evidence to suggest that a new fluidization regime is formed, the characteristics of which appears to be distinct from those observed in a regular TFB and from those in either the bottom or the upper sections of regular CFB and/or high-density CFB (HDCFB). Fundamentally, the difference is that particle-particle interaction (collision) dominates the motion of particles in CTFB and TFB, while gas-particle interaction (drag force) is the key element that determines the two phase flow in CFB including HDCFB. 相似文献
45.
《Particuology》2017
Multistage fluidized beds are frequently used for product drying in industry. One advantage of these fluidized beds is that they can achieve a high throughput, when operated continuously. In this study, γ-Al2O3 particles were dried in a pilot-scale horizontal fluidized bed, without considering any comminution effects. For each experiment, the particle moisture content distribution and residence time distribution were determined. To take into account particle back mixing in our experiments, a one-dimensional population balance model that considers particle residence time was introduced into a fluidized bed-drying model. Experimental particle residence time distributions were reproduced using a tank-in-series model. Subsequently, the moisture content distribution was implemented, as a second dimension to the population balance in this model. These two-dimensional simulations were able to describe the experimental data, especially the spread in the residual particle moisture distribution, much more accurately than one-dimensional simulations. Using this novel two-dimensional model, the effects of different operating parameters (process gas temperature, solid feed rate, superficial air velocity) on the particle moisture content distribution were systematically studied. 相似文献
46.
《Particuology》2017
This paper analyzes the influence of different coal mass fraction in an air dense medium fluidized bed (ADMFB). The effect of the low density particles layer on heavy sedimentation increased with increasing material layer thickness. The thickness of the low density particles layer also affected the final settling time of the high density particles. Increasing the thickness of the low density particles layer by Δh provoked an increase in the settling of high density particles that was related to their diameter (Δh/D). The pressure gradient across the bed was lower than that observed for the control experiment, which had only the dense material, owing to a decrease in the pressure gradient in Zones 1 and 5 (at the top and bottom of the bed, respectively). Introducing different coal sizes resulted in different fluidization environments, particle accumulation layers, and changes to the surrounding zone. However, the influence of the coal particles on the local bed characteristics was related to its concentration. The feeding mass fraction of 6–13 mm size and 13–25 mm size coal should be limited to10% and 13%, respectively. The ranges of possible deviation were found to be 0.08–0.15 and 0.07–0.10 for the respective samples. 相似文献
47.
《Particuology》2017
In this work, the mixing and segregation of binary mixtures of particles with different sizes and densities in a pseudo-2D spouted bed were studied experimentally. A binary mixture of solid particles including sand, gypsum, and polyurethane was used. To determine the particles mass fraction, and their mixing and segregation in the bed, an image-processing technique was developed and used. Important hydrodynamic parameters, such as the axial and radial segregation profiles of the solid particles, were measured. The effects of air velocity, particle size, and particle mass fraction were also evaluated. The flow regime in the spouted bed and the time required for reaching the equilibrium state of the solid particles were discussed. The results showed that the segregation of solid particles and the time to equilibrium both decreased when the air velocity increased to much larger than the minimum spouting velocity. The axial segregation increased with the diameter ratio of the particles. Upon completion of the test, coarse particles were concentrated mainly in the spout region, while fine particles were aggregated in the annulus region. Examination of the flow pattern in the spouted bed showed that the particles near the wall had longer flow paths, while those near the spout region had shorter flow paths. 相似文献
48.
作为中国聚变工程实验堆(CFETR)候选包层之一的水冷包层(WCCB),拟采用不同尺寸的两元混合增殖球床以增加球床的填充率,从而满足氚增殖比(TBR)要求。采用离散元方法(DEM)建立了满足中子学要求的CFETR水冷包层两元球床填充结构,通过CFD计算分析获取了氦气在球床颗粒间隙之间的流动特性,包括孔隙率分布、速度分布和压降等。 相似文献
49.
Niranjan D. Parab Cang Zhao Ross Cunningham Luis I. Escano Kamel Fezzaa Wes Everhart Anthony D. Rollett Lianyi Chen Tao Sun 《Journal of synchrotron radiation》2018,25(5):1467-1477
The high‐speed synchrotron X‐ray imaging technique was synchronized with a custom‐built laser‐melting setup to capture the dynamics of laser powder‐bed fusion processes in situ. Various significant phenomena, including vapor‐depression and melt‐pool dynamics and powder‐spatter ejection, were captured with high spatial and temporal resolution. Imaging frame rates of up to 10 MHz were used to capture the rapid changes in these highly dynamic phenomena. At the same time, relatively slow frame rates were employed to capture large‐scale changes during the process. This experimental platform will be vital in the further understanding of laser additive manufacturing processes and will be particularly helpful in guiding efforts to reduce or eliminate microstructural defects in additively manufactured parts. 相似文献
50.