Simulation Of Gas-Solid Flow And Heat Transfer Characteristics In A Side-Stirred Fluidized Bed

In order to solve the problem of uneven distribution of gas-solid two phases caused by the phenomenon of adhesion and loss of solid particles in the current fluidized iron making process,a new type of side-stirred fluidization reaction is used here based on the traditional fluidization equipment.The internal gas-solid two-phase flow and temperature distribution characteristics of the reactor were studied by numerical simulation methods,which provided theoretical support for the further development of this new type of bubbling fluidized bed reactor.In this paper,a new type of side agitated bubbling fluidized bed reactor is taken as the research object.Based on the flow characteristics of solid particles in a cold side agitated fluidized bed,the correctness of the numerical model is verified.The commercial CFD software Fluent was used to study the effects of parameters such as the type of agitating paddle,agitation speed,and fluidizing gas velocity on the bubble phase behavior,particle motion and distribution characteristics,and temperature distribution characteristics in a side-stirred bubbling bed reactor The main conclusions are as follows:(1)By comparing the changes in bubble behavior in a traditional bubbling fluidized bed with a new type of side agitated fluidized bed,it was found that the size of the bubble phase in the fluidized bed with side agitation was significantly reduced and eventually disappeared in the bed.Tracing the size change of a single bubble in the bed,it was found that the size of the bubble was reduced by 81.46%and the expansion rate of the bed was reduced by 25%under side agitation.It shows that the large bubbles basically disappeared into the bed under the effect of side agitation.From the evolution of gas-solid flow behavior in the bed over time,it was found that the fluidization period of the side-stirred fluidized bed was 0.9 s.(2)Numerical calculations show that increasing the fluidization rate is beneficial to increase the intensity of the movement of solid particles in the bed,but excessive fluidization speed leads to a decrease in the uniformity of the distribution of solid particles in the bed,but it reduces the gas-solid two-phase Fluidization quality.When the fluidizing gas velocity is 0.424 m/s,the stability in the bed is relatively high.Increasing the stirring speed can promote the strength of the cyclic movement of the solid particles in the bed.However,when the stirring speed is too high,the solid particles in the vicinity of the stirring blade will have an uneven distribution under the centrifugal force generated by the blade.Causes the degree of gas-solid mixing in this area to decrease,thereby reducing the gas-solid fluidization effect.When the stirring speed is 180 rpm,the gas-solid distribution in the side-stirred fluidized bed is more uniform than other simulation conditions.(3)The temperature difference between the gas and solid phases near the distribution plate has a large gradient.This area is an effective area for heat transfer between the gas and solid phases.Increasing the stirring speed increases the circulation speed of the particles,which increases the residence time of the particles in the effective heat transfer area,which is conducive to improving the utilization of gas energy.When the stirring speed is 180 rpm,the effect is better than the other speeds.Increasing the apparent gas velocity significantly increases the heat transfer coefficient and effective heat transfer height between the gas and the solid,and the heat transfer efficiency of the iron ore powder particles increases accordingly.The solid concentration and temperature distribution are more uniform.Comparing the effects of the three types of propellers on the gas-solid temperature distribution,it is found that the three-bladed bladed propeller has the best gas-solid heat transfer effect.Comprehensive analysis shows that the simulation conditions are agitation speed of 180 rpm and an apparent gas velocity of 0.658 m/s.When the three-round blade agitator blade,the particle volume fraction and gas-solid temperature distribution in the bed are more uniform,and the effective area of gas-solid heat transfer And the heat transfer efficiency in this regular distribution is higher than under other conditions.The effective heat transfer height is 42 mm,and the gas-solid heat transfer coefficient is 484.545 W/m2·K.Based on the numerical simulation method,this paper analyzes the flow behavior and heat transfer characteristics of gas and solid phases during fluidization,and obtains basic data and better operation and structure of gas-solid flow characteristics in a side-stirred bubbling fluidized bed.The parameters provide theoretical basis for the subsequent design and scale-up of the new side-stirred bubbling fluidized bed.