Study On Gas-solid Flow Behaviors Of Spouted Bed At Elevated Temperature/Elevated Pressure

Dense gas-solid flow gains its popularity in the field of multiphase flow. As a commonly used gas-solid reactor, the spouted bed has an advantage in the case of dealing with the Geldart D particles. In many applications, the spouted bed should be operated at the elevated temperature and pressure. The previous researches mainly focused on the chemical reaction mechanism, reaction characteristics and the reaction modelling. The studies on the gas-solid flow behaviors at the elevated temperature and pressure were insufficient. The present work investigates the spouting behaviors of the spouted bed at elevated temperature and pressure. The aim of the present work is to give references to the design and structure optimization of spouted beds used at high temperature and pressure, and to improve the cognitive level of the scientific problems in the dense gas-solid reaction system at high temperature and pressure.A multifunction experimental system combined with a pressurized spouted bed, a high-resolution digital image acquisition and processing system and a high-precision multi-channel pressure signal real-time acquisition and processing system was established. The macro-scale spouting behaviors were investigated on this system. The differences of the pressure drop under the ascending process and descending process were pointed out. The changing rule of the pressure drop with the operating parameters and physical parameters was also studied. The relationships of the operating parameters and physical parameters with the maximum pressure drop and the minimum spouting velocity were investigated, and new correlated equations were given by take the pressure into consideration. Based on the multifunction experimental system, the changing law of particles flow structures with increasing velocity under different pressures was investigated. The flow patterns of the pressurized spouted bed were divided into different classes. By the modern signal processing technologies, the standard deviation analysis, the power spectrum analysis and the Hurst analysis methods, were applied to study the switching rules of the flow patterns. The extractive characteristic parameter was applied to represent and identify the flow regimes.A CFD-TFM numerical simulation platform was established for the pressurized spouted bed. The instantaneous flow patterns colored with the particle volume fraction with increasing operating pressure were given. The changing rule of the minimum spouting velocity with the varied pressure was studied. The main advantages of the pressurized spouted bed over the normal spouted bed were stated by analyzing the fountain height under elevated pressure. The particle concentrations and the particle velocities in the pressurized spouted bed were given, which were hard to get by the experimental methods. In addition, the changing law of the spout diameter was investigated.Based on the CFD-TFM numerical simulation platform of pressurized spouted bed, the gas-solid flow characteristics of spouted bed at elevated temperature and pressure were studied by adding a Sutherland model to calculate the gas viscosity. The influences of the temperature on the flow behaviors under high pressure condition were studied. The instantaneous flow patterns with increasing the temperature were given. By taking the vertical particle velocity as the judgment standard, the changing rule of the jet shape with the increasing temperature was studied. The influence of the temperature on the minimum spouting velocity was changed with the particle diameter, and the critical diameter was given by investigating varying particles. The particle concentrations and the particle velocities in the spouted bed at elevated temperature and pressure were investigated. Moreover, the influences of pressure on the gas-solid spouting behaviors including flow patterns and jet shape of the spouted bed under high temperatures were studied.