Due to the wide variety of utilization of entrained-bed coal gasification for chemicals production, hydrogen production and fuel for industry, technology has been developed worldwide. Gasification plants consist of several key technologies such as coal feeding, gasification, dust removal etc. The understanding of solid-gas flow in these fields is required in order to optimize the device configuration. This article introduces the recent R&D activities concerning two phase flow; coal feed rate and void fraction in a transportation tube, particle residence time in a swirl-flow type gasifier, high temperature dust removal technologies.
Fully developed liquid-solid two-phase flow in a vertical pipe has been investigated in this paper. Experiments were carried out in a vertical pipe of 26mm I. D. using water and uniform-sized spherical particles of 6.12mm in diameter. The particles were made of ceramics having a density of 2540kg/m3. The volumetric fluxes of water and the particles varied within the ranges of 0≤jL≤1.5m/s and 0.0075≤js≤0.060m/s. The velocity of the particles was determined by a tracer method, i. e. the velocity of a tracer particle of aluminum was measured using a pair of metal detectors. The frictional pressure drop of the flow was also obtained. A simple model to correlate the velocity of coarse particles with the two-phase flow rates, diameter, density and drag coefficient of the particle is proposed. The model is compared with the experimental data of other investigators as well as the present authors and shows better agreement than other correlations tested. As to the frictional pressure drop, the present data are well correlated by the correlations of Durand, Oedjoe et al. and Weber et al. In addition to those, a modified correlation of the Durand's is proposed to correlate the data at a relatively higher concentration of solid particles.
Fully developed three-phase flow in a vertical pipe was investigated. The experiments were carried out by using air, water and spherical particles of 6.12mm in diameter. The ceramic particles and the 26 mm I.D. test pipe used were the same as those used in Part 1 of this study. The ranges of volumetric fluxes of air, water and particles were 0.50≤jG≤8.0 m/s, 0.50≤jL≤1.2m/s and 0.0075≤jMs≤0.060m/s, respectively. Measurements of the particle velocities and large gas bubbles were recorded, and the volume fractions of each phase were determined. The pressure drop was also measured. Regarding the particle velocity, an empirical model was proposed to correlatethe velocity of coarse particles with the three-phase flow parameters, i.e., such as the particle size, the volumetric fluxes and the densities of each phase, and so on. This model, together with some correlations suitable for gas-liquid or liquid-solid two-phase flow, can lead to a prediction of the volume fractions of each phase and to the determination of the three-phase pressure drop. Concerning the volume fractions and the pressure drop, comparisons were made between the experimental data and calculations not only for the above-mentioned data and model of the authors but also for those of other investigators.
The behavior of the uniform-field electromagnetic flowmeter with air-watertwo phase flow was studied both experimentally and theoretically. The gas holdup couldbe measured quite accurately in a bubbly flow. It can be considered that there is no effectof the axisymmetric gas holdup profile and liquid velocity profile on the output signal. Butin a slug flow, the sensitivity is lowered heavily. The largest case for the error is the violent fluctuation of the liquid velocity and gas holdup. The sensitivity is unit in a churn turbulent flow, because the intensity of the fluctuation is decreased rapidly with an increase of column diameter. It is assumed that the droplets, ripples and disturbance waves give rise to a decrease of sensitivity in an annular flow.