Heat transfer enhancement in packed bed reactor is investigated. As a thermal conduction enhancer, carbon fiber brushes with a high thermal conductivity are inserted in the packed bed. In order to achieve higher thermal performance, the carbon fiber brush is attached to the heat transfer wall with a supporting material containing carbon nanotube (CNT). The CNT is particularly used due to its high thermal conductivity. As a result, silicone rubber is suitable for the supporting material because it is so soft that it prevents from increasing local void fractions near the heat exchange wall. In addition, improvement of heat flow in a packed bed is studied using CNT itself. As a result, both the effective thermal conductivity and the heat transfer coefficient between packed bed and reactor wall are improved particularly for larger particles.

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The objective of this paper is to investigate the effect of paddle rotational speed on the mixing behavior in an agitation process of an electrophotographic system by using parallel DEM. The mixing behaviors of beads with different sizes and densities were measured at various paddle rotational speeds by using a high-speed video camera, and were compared with the simulation results. A good agreement in the mixing behavior was obtained and the changes in particle velocity during the mixing were comparable. The simulation for mixing behavior of larger carrier particles suggested that the radial particle mixing was much faster than the axial one. The faster radial mixing is attributed to the fact that there are two radial flows in the system; the one is over the shaft, the other is between the paddle and the shaft. The extent of mixing depended on the number of paddle rotations when the rotational speed is larger than 100 rpm, while the mixing under 50 rpm is completed at a smaller number of rotations.

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Beads motion in a stirred mill filled with a slurry was simulated by the Discrete Element Method (DEM), enabling to calculate the impact energy of beads. Since the specific impact energy of beads is known to be well correlated with the grinding rate constant, it was monitored as an effective index of grinding performance in the simulation work. The present work is to investigate effect of the pin configuration, particularly, the number of pins attached on the agitator and their length on the beads motion as well as the impact energy. The pins were attached on the axis of the agitator equi-interval in the circumference direction and 3-line in the horizontal axis in the mill. We have found that the beads motion is dependent on the number of pins, and the specific impact energy reaches the maximum value at 8 in number of pins under the present condition. In addition, the maximum value under the specific impact energy is shifted towards large number of pins as the beads filling ratio increases. The specific impact energy of beads is increased with an increase in pin length.

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This study experimentally investigated the spouting of fluidized cohesive powder bed of soft wheat flour of 46μm through a circular orifice of 4mm at the bottom of a cylindrical vessel where the air is mainly introduced at the top and bottom of the bed. It is found that the steady flow of the fluidized powder bed as well as mass flow condition is obtained when the same flow rate of air is simultaneously introduced at the top and bottom of the bed. Then, it is confirmed that the total mass of spouting powder decreases with reducing the initial void fraction and the flow rate of air, and that there are critical conditions for the continuous spouting of the powder from an orifice. It is also found that the spouting of powder from an orifice requires a high interstitial air pressure when the initial void fraction is small.

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The effects of mineral content, and mineral distribution in coal, and pulverizing method on characteristics of mineral liberation were investigated in order to develop an efficient de-ashing method for coal. It is found that the effect of mineral content on the characteristics of mineral liberation is significant at a mineral content lower than 10wt%, while it is weak at a mineral content exceeding 10wt%. When the particle size of pulverized coal was 120μm, the minerals in coal were more easily liberated than the mineral particles larger than 120μm. In addition, the mineral liberation during the pulverization of coal containing granular minerals, i.e., locally-distributed minerals, into finer particles was higher than in the coal with linear minerals, i.e., linearly-distributed minerals. A high degree of mineral liberation was attained when the pulverizing methods based on impact force (ball mill and hammer mill) were used for the coals that contained a large amount of granular minerals. On the other hand, for coals that contained linear minerals, it was effective to use the pulverizing method based on compressive force, such as a Roll mill and HGI mill. Consequently it was found that the selection of a suitable pulverizing method depending on the mineral distribution in coal was important for achieving efficient mineral liberation.

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In this study, float-sink of chlorine containing and not-containing plastics in a gas-solid fluidized bed of silica sand was studied with and without joints in the air distributor and by changing the amount of objects loaded on the air distributor. The float-sink was evaluated using three parameters, i.e., recovery, purity and efficiency. The values obtained with the joints are smaller than without the joints, and decreased with increasing the amount of objects on the distributor. Because there is no airflow at the joints, the sand on the joints is not fluidized and circulating flow of the sand is generated over the area other than the joints. A 2D fluidized bed showed that air bubbles are not uniformly generated on the air distributor and the fluidization of the sand becomes intense when the objects are on the distributor. These results indicate that the circulating flow and the sudden intense fluidization disturb the expected float-sink of objects.

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