Showing papers in "Journal of Chemical Engineering of Japan in 2015"

Failure mechanism of true 2D granular flows

Abstract: Most previous experimental investigations of two-dimensional (2D) granular column collapses have been conducted using three-dimensional (3D) granular materials in narrow horizontal channels (i.e., quasi-2D condition). Our recent research on 2D granular column collapses by using 2D granular materials (i.e., aluminum rods) has revealed results that differ markedly from those reported in the literature. We assume a 2D column with an initial height of h0 and initial width of d0, a defined as their ratio (a =h0/d0), a final height of h , and maximum run-out distance of d . The experimental data suggest that for the low a regime (a 0.65), the ratio of a to (d-d0)/d0, h0/h , or d/d0 is expressed by power-law relations. In particular, the following power-function ratios (h0/h=1.42a^2/3 and d/d0=4.30a^0.72) are proposed for every a >0.65. In contrast, the ratio (d-d0)/d0=3.25a^0.96 only holds for 0.65 1.5. In addition, the influence of ground contact surfaces (hard or soft beds) on the final run-out distance and destruction zone of the granular column under true 2D conditions is investigated.

Prediction of NOx Emission from Coal Fired Power Plant Based on Real-Time Model Updates and Output Bias Update

Abstract: In order to deal with the nonlinear varying behavior of NOx emissions for long term predictions, a real-time recursively updating model is indispensable. In this paper, new recursively updating models are proposed to predict NOx emissions. The proposed real-time models are equipped with an initial LSSVM model and subsequent updating methods to adapt the models with recent changes to process data. The updating methods include solo Least Squares Support Vector Machines (LSSVM) update, solo output bias update, and the combination of these two termed as the LSSVM-Scheme. These models are applied to NOx emission process data from a coal combustion power plant in Korea. Prediction results obtained from the proposed real-time LSSVM models are compared with their counterpart real-time PLS models, which reveal that real-time LSSVM models outperform their counterpart real-time PLS models. Among other models developed in this work, LSSVM-Scheme and solo output bias update based on LSSVM predicts NOx emissions robustly for a long passage of time with the highest accuracy.

Optimal Structure Synthesis of Internally Heat Integrated Distillation Column

Abstract: A systematic procedure is proposed for designing an internally heat integrated distillation column which separates a binary mixture. In the proposed procedure, the liquid compositions in the column are discretized and each of them is assigned to a stage in a column. The feature of the proposed procedure is that the structure of vapor and liquid paths among the stages are treated as design variables. The combinations of the heat exchange stages in the stripping and rectifying sections are also treated as design variables. As the liquid composition of each stage has been decided in advance, the state variables related to each stage can be calculated before solving the synthesis problem. Thus, the design problem is formulated as a mixed integer linear programming problem, and the optimal column structure is derived by solving it. The proposed method was applied to the problems of separating a benzene-toluene mixture. The results show that the structure of an internally heat-integrated distillation column is systematically derived. Furthermore, an unexpected innovative structure called a stepwise condenser was generated by the proposed procedure.

Models and Applications for Simulating Turbulent Solid–Liquid Suspensions in Stirred Tanks

Abstract: Solid-liquid suspensions in stirred tanks are common in many process industries. The complex flow characteristics such as two-phase turbulence and inter-phase interaction make the corresponding numerical simulations complicated and challenging. In this paper, we review the models dealing with both the continuous and the discrete phases and summarize the applications for simulating such flow phenomena, including velocity and turbulence components, solids concentration, just-suspended speed, cloud height, optimization of geometrical parameters, and particle shape and type. Some perspectives concerning different modeling approaches are presented, and the Eulerian-Lagrangian approach with resolved particles is highlighted to address the underlying suspension mechanisms in stirred tanks.

Acidic Properties of Various Silica Catalysts Doped with Chromium for the Oxidative Dehydrogenation of Isobutane to Isobutene

Abstract: Although previous researchers have found that FSM-16 (#16 Folded Sheet Mesoporous material) doped with chromium and related Cr-doped silica catalysts has shown great activity for the oxidative dehydrogenation of isobutane to isobutene, information on the nature of these catalysts is insufficient. For this study, three types of Cr-doped silica catalysts were prepared by applying the template ion exchange method. CrOx/FSM-16 and CrOx/SiO2 were used as references. These catalysts were used for oxidative dehydrogenation, which was then characterized via various techniques. The most active catalyst was Cr-doped silica, which did not have the hexagonal structure that is characteristic of mesoporous FSM-16. Various characterizations showed that the catalytic activity of the Cr-species, stemmed from a weak acidic nature and a redox nature that originated from the combination of silicate and a Cr cation, as opposed to the hexagonal structure and strong acidic nature of FSM-16.

Statistical Validation of the Mixing Length Concept in Bubble Columns Operated in the Transition Flow Regime

Abstract: A new statistical parameter was de ned in order to determine the range of applicability of the mixing length concept in two bubble columns. Gas holdup time series (60,000 points) were measured in two bubble columns (0.15 and 0.4 m in i.d.) by a conductivity wire-mesh sensors. The new statistical parameter Φ was de ned as the ratio of the mean value of the signal to three times the average absolute deviation (3AAD) and it was correlated to the mixing length. It was found that this new correlation was not valid in all hydrodynamic regimes. It is applicable only in the transition ow regime. Such a clari cation has not been provided in the literature so far. In the narrow bubble column, the results were also conrmed on the basis of the Kolmogorov entropy and another statistical parameter. The new parameter Φ was also used for ow regime identi cation. In the narrow bubble column, the rst transition velocity Utrans was identi ed at 0.034 m/s; whereas, the second Utrans occurred at 0.112 m/s. In the large bubble column, the two Utrans values were identi ed at 0.045 and 0.101 m/s, respectively.

Effect of Aperture Structure of Dutch Weave Mesh on Flow Resistivity

Abstract: Yuichi Yoshida1,2, Yohei Inoue3, Atsuko Shimosaka2, Yoshiyuki Shirakawa2 and Jusuke Hidaka2 1 Technical Section, Kansai Wire Netting Co., Ltd., 2-7-8 Inari, Naniwa-ku, Osaka 556-0023, Japan 2 Department of Chemical Engineering and Materials Science, Faculty of Science and Engineering, Doshisha University, 1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto 610-0321, Japan 3 Department of Mechanical Engineering and Intelligent Systems, Faculty of Informatics and Engineering, e University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182-8585, Japan