Numerical Simulation Study Of Gas-solid Two-phase Coupling And Flue Gas Cleaning Reaction Processes For Flue Gas Purification In Spouted Bed

With the improvement of people’s living standards,the country is paying more and more attention to environmental issues.The concept of"building and practicing green water and green mountains is the silver mountain of gold"was written into the report of the Party Congress.One of the priorities of today’s energy sector is how to make flue gas emissions from power plants harmless.The main pollutants in flue gas are SO₂,NO_x,HF and fine particulate matter.Separate equipment is available for both desulphurization and denitrification.However,there is no solution for HF removal from flue gas.Although the level of HF is not high compared to the first two,the human body is several or even dozens times more harmful to both.It is better for the environment if SO₂ and HF are removed in the same unit.This also does not increase the proportional area of the removal unit.Therefore,we study the wet particle fluidization characteristics from the basic theory of gas-solid two-phase flow in the spray bed.Then,on this basis,we study the key influencing factors to improve the multi-component removal efficiency of semi-dry flue gas to achieve clean flue gas emission.In this paper,a numerical simulation method considering the two-phase transfer of gas and solids and the synergetic removal of multiple components is established to analyze the fluidization of wet particles in the bed and the efficiency of exhaust gas cleaning,and to study the influence of the water content and contact angle of wet particles on their fluidization properties,using a single-port spray bed as the research object and aiming at a semi-dry exhaust gas cleaning reaction with high efficiency.At the same time,it provides theoretical support and guidance for actual industrial production flue gas cleaning by integrating it with semi-dry spray dynamic bed flue gas cleaning based on the optimum fluidization factor of wet particles.The main results of this research are as follows:（1）To study the mathematical model required for wet particle fluidization in a jet bed,including discrete phase mathematical models such as liquid bridging force,contacting force,rolling friction,etc.The particle collision model and the large vortex model are added and modified in the gas phase motion using the gran rolling＿friction cdt model code in the LIGGGHT software.In addition,the reliability of the model used was verified by comparison with existing experimental data and its reliability was analyzed in terms of z-direction velocity,bed pressure drop and minimum jet gas velocity.Thus,a numerical simulation method for the fluidization of a wet particle system with non-idealized contact angle and water content was established.（2）To analyze the effect of different water content and contact angle on the fluidization characteristics of wet particles.It was found that compared to dry particles,wet particles would show obvious agglomeration in the fountain region,and the higher the water content,the more obvious the agglomeration would be and the more it would hinder particle fluidization.At the same time,the contact angle has an effect on particle velocity fluctuations,and a contact angle ofθ=30°helps prevent particles from escaping the spouted bed and avoids particle agglomeration at the junction of the spouted region and fountain region.（3）To study the effect of the key factors on the reaction efficiency of the multi-component cleaning of the semi-dry flue gas.The semi-dry flue gas purification technology with the physical model of spray bed must first consider the expansion angle of the nozzle in the bed,the size of the angle affects the spray slurry distribution area,too large expansion angle,although the spray distribution area is wide,but there is wear and tear on the wall,10°range for single-port spouted bed flue gas purification efficiency is the best.Secondly,the spray particle is an important factor to improve the desulfurization and defluorination efficiency of the spray bed semi-dry method,the particle diameter is related to the import fluidization gas velocity and fluidization effect in the bed,research shows that when the spray particle diameter and spray slurry droplet diameter ratio of 15,the bed air flow smoothly,the best desulfurization efficiency and defluorination efficiency.Third,for the spray slurry,the spray speed in the ratio of 2-3 to the spray gas speed,Ca（OH）₂ in the spray slurry of the ratio of 0.005-0.01,when the most cost-effective desulfurization and defluorination efficiency.Fourthly,the Ca/S in the spray bed is the most influential factor on the desulphurization efficiency and defluorination efficiency,the higher the Ca/S,the higher the flue gas desulphurization efficiency.Considering the actual production economy,the best Ca/S is 2.5,the desulphurization efficiency is 93.55%and the defluorination efficiency is 99.79%.