Red Mud Is Used For The Modification Research Of Coal Chemical Chain Combustion

Chemical looping combustion（CLC）technologyis an energy conversion system that can simultaneously achieve energy efficient cascade utilization and separation within CO₂.Among them,the oxygen carrier is the key of CLC technology.There is a great demand on oxygen carrier in CLC,especially for solid fuels.Therefore,it is particularly important to select oxygen carriers with low price and good reactivity.Because the composition of red mud is very similar to Fe-based oxygen carrier and RM is abundant in storage,it has the advantage of low price.In this paper,the new idea of using red mud as oxygen carrier for CLC of coal is put forward.And the red mud can be used as iron making material to realize the real meaning of red mud resource utilization.The performance of the reaction of red mud（RM）and other oxygen carriers with lignite was compared in fixed bed reactor and bubbling bed reactor,respectively.The feasibility of red mud as oxygen carrier for CLC of coal was verified and the factors affecting the reactivity of red mud and coal were discussed in detail.The results show that compared with Ce-Fe-Zr-O、Mn Co₂O₄、La Fe O₃ and Cu ore oxygen carriers,red mud can maintain better activity in both reactors.High purity of CO₂ and carbon capture rate can be obtained in the reaction process,which indicated that red mud is very suitable as an oxygen carrier for chemical looping combustion.of coal.On this basis,the factors affecting the reaction performance of red mud oxygen carrier are discussed.It is found that the most suitable reaction temperature is 900℃,the ratio of OC/Coal is the best at 50:1,and the Coal particle size is best controlled at 20～40 mesh.Under these conditions,when red mud reacts with lignite at 900℃,the purity of CO₂ in tail gas is70.55%and the carbon capture rate is 42.41%.A small amount of Cu O was added to the red mud oxygen carrier to significantly enhance the reducibility of red mud,the reduction temperature of iron oxide in H₂atmosphere is transferred to a lower temperature.The reaction performance between the oxygen carrier and coal was the best when the amount of Cu O was 20wt%.After10 cycles,the CO₂ purity and carbon capture rate were above 92%and 60%respectively.A small amount of Ni O and Mn O_x were added to red mud to modify it,and their effects on the reactivity of modified oxygen carrier and lignite were investigated.The results showed that the addition of Ni O could significantly improve the reducibility of red mud to chemical looping combustion of coal.Among them,15Ni-RM samples showed the best reaction performance.The addition of inert component Mg O has little effect on the reactivity of red mud based oxygen carrier,but it significantly improves the cycling stability of oxygen carrier.Ni and Mg elements were added to the red mud simultaneously,and the synergistic effect of Ni O and Mg O enhanced the reactivity and cycling stability of the RM-based oxygen carrier and lignite.After a long redox cycles,the staggered distribution of most elements（i.e.,Ni,Mg,Al,Si,and Ca）is promoted,which enhances the interaction between Ni and Fe oxides and contributes to the high activity and stability of oxygen carriers in the continuous chemical cycle combustion process.