Tomosada Jotaki

The reduction of pressure drop due to dust loading in a conventional cyclone

Abstract Experiments have been conducted to examine the effect of dust loading on pressure drop in a conventional cyclone. The presence of dust in the air stream reduced the cyclone pressure drop by as much as 30%, even at extremely low concentrations, such as 0.2 g/m 3 . In the range of 1.5–50 g/m 3 , the pressure drop ratio (the ratio of the pressure drop of dusty air to that of pure air with the same inlet velocity) was independent of dust concentration, and kept nearly constant; but it decreased as the concentration increased above 50g/m 3 . It was observed that the presence of dust reduced the tangential velocity. However the radii of a cross section of the cyclone, where the pressures are equal to those of the entrance and the exit, did not change noticeably. Calculating the pressure drop by integrating the term due to centrifugal force is also examined.

The calculation of particle deposition efficiency due to inertia, diffusion and interception in a plane stagnation flow

Abstract The particle deposition mechanism in a plane stagnation flow is investigated analytically and numerically. Particle deposition efficiency η TID is obtained theoretically by taking into account particle inertia, diffusion and interception. It is compared with various calculated deposition efficiencies, i.e. η T (due to inertia) + η I (due to interception) + η D (due to diffusion), η TI , (due to inertia and interception) + η D , etc. In the region where all of the three deposition mechanisms, i.e. inertia, interception and diffusion, act at the same time, real deposition efficiency η TID is not accurately expressed by η T + η I + η D . However, η TID is nearly equal to η TI + η D unless the interception parameter is zero. The calculated results of particle concentration indicate that a high concentration region is formed near the deposition plate, and that the concentration becomes higher as particle inertia increases.

Similarity of granular flow in a blow tank solids conveyor

Abstract By measuring velocity profiles of non-cohesive granular material for different feed rates at different times in a blow tank solids conveyor in which the conveying pipe exits at the upper part of the tank, it is found that there is similarity in the vertically downward component of solid velocity in a region distant from the free surface and from the pipe inlet where the particles are not fluidized.

Feed rate characteristics of a blow tank solids conveyor in transport of granular material

Abstract Feed rate characteristics of a blow tank solids conveyor in which the conveying pipe exits at the upper part of the tank are experimentally examined by the use of polyethylene pellets having a large minimum fluidizing velocity. The flow pattern of solid particles in the tank resembles suction flow at the pipe inlet and bears a strong resemblance to that of gravity discharge of solids from an orifice, and there exists a dead solids region on the porous support through which compressed air is blown. Within this region pipe inlet height from the porous support and tank size have no effect on the feed rate. For a given tank, the feed rate increases with an increase in pipe diameter. An empirical equation is proposed to relate these variables.

Pressure drop in vertical pneumatic transport lines of powdery material at high solids loading

Abstract The compressibility of the air flow cannot be neglected in measuring the distribution of static pressure in vertical pipes. Measurements indicate that static pressure decreases almost linearly along the greater part of the pipes length. This area, which has been termed a pseudo-established region by Fortier, shows the same decrease in pressure as a fully established region of incompressible flow. Then it is shown that the pressure drop in the pseudo-established region can be easily obtained in the same way as it is for an incompressible flow if the coefficient for the additional pressure drop due to solids and the Froude number are calculated in terms of atmospheric conditions.

Sudden expansion of gas‐solid two‐phase flow in a pipe

Momentum transfer from particles to gas in the decelerated flow of suspensions is confirmed experimentally in a sudden expansion of the pipe by using different particles, when a flux Richardson number, approximately evaluated at the expansion, exceeds 0.002.

Investigation of the collection mechanism in absorption of aerosols by bubbling through water

Abstract The collection mechanism in absorption of aerosols by bubbling through water, which has the advantage of simple apparatus and high collection efficiency, has been studied both experimentally and theoretically. In consequence, the following has become clear: 1. (a) The mechanism has been explained fairly well by the effect of particle inertia only. 2. (b) Particles with extremely small values of inertia parameter, compared with fibre filter dust collection, have been collected. 3. (c) Dust collection efficiency increased exponentially in proportion to water depth, and an analogous relation to the logarithmic penetration law in fibre filter dust collection exists for this mechanism.

Collection of submicron particles by H2 bubbles

Abstract A theoretical analysis is presented to describe the deposition of Brownian particles onto H 2 bubbles (flotation) by analogy with classical filtration theory. Experimentally, it is shown that submicron and smaller particles of MnO 2 are collected by H 2 bubbles without using the special collector or chemicals usually employed in flotation. The experimental technique for determining the total collection efficiency is described. A comparison between the theory and our experiment makes it clear that there are cases in which the simpler filtration theory is adaptable to a complicated flotation analysis. In addition, we find that the collection mechanisms of submicron particles of MnO 2 is predominantly characterized by interception and Brownian diffusion.