Study On The Mechanism Of The Synergy Of Magnetic Field And Magnetic Particles To Strengthen The Absorption Of CO₂ By Ammonia

The combustion of fossil fuels is the main cause of the increase of atmospheric CO2 concentration,which leads to global climate change.The effective way to reduce carbon emissions is to implement carbon capture and storage technology in coal-fired power plants.At present,the vast majority of carbon capture and storage technologies are still in the research stage.Developing new and efficient carbon capture technologies for coal-fired flue gas and mastering its reaction mechanism and operation law have important practical significance and engineering practice value for achieving carbon emission reduction.Chemical absorption carbon capture technology is a common carbon capture technology for coal-fired flue gas.As an absorbent,ammonia water has the advantages of low cost,large absorption capacity,non-degradation,no corrosion to equipment,low energy consumption of regeneration and combined removal of multiple pollutants.In this paper,magnetic field and nanoparticles were used to enhance the absorption process of CO2 in ammonia water,and the mechanism of the process was studied.The specific research contents and results are as follows.Firstly,the effects of magnetic field and particles on the reaction mechanism of ammonia and CO2 were studied.Before and after adding 8mT magnetic field and 1g/L Fe3O4 nanoparticles,CO2 absorption experienced two stages:stable absorption(constant decarbonization efficiency)and slow-down absorption(decarbonization efficiency decline).In the stable absorption stage,ammonium carbamate formation was the main reaction,while in the slow absorption stage,ammonium carbamate hydrolysis was the main reaction.With the addition of magnetic field and particles,the stable absorption period of ammonia water with different initial concentration(2%-3%)can be prolonged for 2-3 minutes,the decarbonization efficiency can be increased by 1%-4%,and the maximum temperature can be increased by 0.3%-0.9%.Before and after adding particles and magnetic field,the degree of carbonization at the end of stable absorption stage is about 0.45 and 0.55,respectively.Under the action of magnetic field,the Brownian motion and micro-convection motion of nanoparticles in solution intensify,the diffusion resistance of liquid molecules decreases,and ammonia molecules are easier to diffuse to liquid film,and the stable absorption period prolongs.Secondly,the influence of magnetic field and particle on mass transfer of CO2 was studied.Four kinds of particles:TiO2,Fe3O4,AI2O3 and SiO2 can increase the total volumetric mass transfer coefficient of CO2,and the former two have the strongest effect.Adding 0.2g/L and 20nm Fe3O4 particles alone can increase the total volumetric mass transfer coefficient by 5.4%.Adding 40mT magnetic field alone can increase the total volumetric mass transfer coefficient by 4.8%.Adding 40 mT magnetic field and 0.2 g/L 20 nm Fe3O4 particles can increase the total volumetric mass transfer coefficient by 13.0%.Before and after adding magnetic field and particles,the change trend of total volumetric mass transfer coefficient with ammonia concentration,CO2 concentration and flue gas flow rate will not change.With the increase of ammonia concentration,the decrease of CO2 concentration and the decrease of flue gas flow rate,the total volumetric mass transfer coefficient of CO2 increases.With the addition of particles and magnetic field,the total volume mass transfer coefficient of CO2 is higher when the temperature is lower than 35?.Without the addition of particles nor magnetic field,the total volumetric mass transfer coefficient of CO2 is higher when the temperature is higher than 35?.Adding magnetic field and particles can improve the interface area.The addition of magnetic field and nanoparticles increases the mass transfer coefficient of liquid phase,decreases the volume of bubbles and increases the interface area.Through the above two reasons,the total volumetric mass transfer coefficient is improved.Finally,the feasibility of removing SO2 and CO2 from flue gas by ammonia water is discussed.CO2 has no effect on desulfurization efficiency,and the increase of SO2 concentration will lead to the decrease of decarbonization efficiency.When the concentration of ammonia water is high enough,the effect of SO2 on decarbonization efficiency is obviously weakened.The decarbonization efficiency was improved by adding magnetic field and particles.