Study On Flue Gas Desulfurization Technology By Activated Carbon In Fixed Bed

Atmospheric environmental pollution has attracted wide attention.Sulfur oxide is an important pollutant that affects the quality of the atmospheric environment.The exploration and research of its efficient emission control technology has attracted the attention of domestic researchers.Activated carbon has been widely used as the main adsorption/catalytic material for flue gas purification due to its abundant microporous structure,large specific surface area,and stable physicochemical properties.The research and development of activated carbon flue gas desulfurization technology is of great significance for promoting the development of domestic air pollution prevention,ultra-low emissions from coal-fired boilers,and the improvement of urban air quality.In this paper,the activated carbon adsorption/catalysis of SO₂is the research center,and the fixed bed reactor is used to study the influencing factors and reaction mechanism of activated carbon adsorption/catalysis of low concentration SO₂in flue gas,and the activated carbon is modified and desulphurized after regeneration.The performance test,the specific content and conclusions of the research are as follows:（1）Through the single factor test,the type of activated carbon,simulated flue gas system,flue gas air velocity,carbon layer height,flue gas temperature,flue gas relative humidity,activated carbon particle size,intake SO₂concentration and flue gas O₂Activated carbon flue gas desulfurization control test was carried out with variables such as concentration.The test results show that the desulfurization performance of activated carbon is in the order of AC1>AC2>AC3>AC4>AC5.The participation of O₂and H₂O in the flue gas components can cause chemical adsorption of SO₂,and increase the equilibrium adsorption capacity and breakthrough time of SO₂.When the space velocity increases,the SO₂adsorption capacity and penetration time decrease,and the initial dynamic adsorption capacity and initial adsorption/catalytic rate increase.The SO₂equilibrium adsorption capacity,breakthrough time,dynamic adsorption capacity and adsorption/catalysis rate increased with the increase of carbon layer height and O₂concentration,but decreased with the increase of bed temperature and activated carbon particle size.Excessive thickness will increase the gas-solid contact time and system mass transfer resistance;the increase in the equilibrium adsorption of SO₂in the low concentration area is weaker than that in the high concentration area;there is a synergistic adsorption effect between SO₂and O₂;physical adsorption may be SO₂adsorption/catalysis The rate control step of the process;when the particle size is larger,the internal diffusion resistance of the activated carbon is also larger.When the intake SO₂concentration increases,the SO₂equilibrium adsorption capacity,dynamic adsorption capacity and initial adsorption/catalytic rate increase,while the breakthrough time decreases.Properly increasing the relative humidity is beneficial to the improvement of the desulfurization performance of the activated carbon.Too high water vapor content will form a liquid film to block the pores and inhibit the adsorption of SO₂and O₂.Within the scope of this experiment,the desulfurization performance of the simulated flue gas is the best when the relative humidity is55RH%.（2）Scanning electron microscope（SEM）,specific surface area and pore size distribution determination（BET）,X-ray fluorescence element analysis（XRF）,thermogravimetric test（TGA）,Fourier transform infrared spectroscopy（FT-IR）were used for the five activated carbons,p H measurement,Boehm titration basic characterization experiments,the results show that:5 kinds of activated carbon are microporous activated carbon,the element content of more than 90%is composed of C,H,O,N,the ash content is less,and the surface has Abundant functional groups,p H test is alkaline,activated carbon has anion exchange adsorption characteristics.The relationship between the physical and chemical properties of activated carbon and SO₂equilibrium adsorption capacity and penetration time was analyzed by quantitative correlation method.There is a positive linear correlation between the content of capacity and basic functional groups,and the correlation is good.（3）The adsorption/catalysis process and mechanism of SO₂on activated carbon were explored by the analysis methods of adsorption kinetics,adsorption isotherm and adsorption thermodynamics.The effect of different apparent kinetic models on the dynamic adsorption process of SO₂is from good to bad:Bangham pore diffusion model>Elovich kinetic model>MorrisⅡintraparticle diffusion model>Ho quasi-second-order kinetic model.The fitting effects of Langmuir and Freundlich adsorption isotherm models are both good,and the Freundlich model is better than the Langmuir model in predicting SO₂adsorption equilibrium.Thermodynamic parameters reflect that the process of activated carbon adsorption/catalysis of SO₂is a spontaneous,exothermic and system disorder reduction process,and physical adsorption has a greater impact on activated carbon adsorption/catalysis of SO₂than chemical adsorption.（4）The modified activated carbon was prepared by impregnation modification with different concentrations of KMn O₄solution and impregnation and loading modification with metal Fe,Zn,Mg,Cu nitrate solution.The desulfurization rate,SO₂adsorption capacity and breakthrough time of KMn O₄modified activated carbon increased with the increase of the concentration of modified reagent KMn O₄solution.The desulfurization rate,SO₂adsorption capacity and breakthrough time of the metal-supported modified activated carbon were ranked as AC1-Fe>AC1-Zn>AC1-Mg>AC1-Cu>AC1.The effects of water washing time and water temperature on the regeneration rate of activated carbon were studied by the water washing regeneration method,and the effects of regeneration-cycle times on the regeneration rate and mass loss rate of conventional activated carbon and modified activated carbon were investigated.The regeneration rate of AC1 increased with the increase of washing time and washing temperature,and the increase of regeneration rate gradually slowed down with the increase of washing time and washing temperature.With the increase of desulfurization-regeneration cycle times,the regeneration rates of AC1,AC1-0.04Mn and AC1-Fe gradually decreased,the decline rate of regeneration rate became slower obviously with the increase of regeneration times,and the loss rate of mass loss rate decreased with the increase of regeneration times.increase gradually.