Study On Chemical Looping Combustion Performance Of Oxygen Carrier Modified By Solid Construction Waste Doping In Bayan Obo Iron Concentrate

Chemical Looping Combustion（CLC） is a new type of combustion technology that differs from conventional combustion in that the traditional direct contact reaction between fuel and air is broken down into two gas-solid reactions with the aid of an oxygen carrier（OC）,which transfers oxygen from the air to the fuel without contacting the fuel.With the advantages of low price,large reserves and environmental friendliness,Baiyun Ebo iron ore concentrate is an ideal raw material for the preparation of oxygen carriers,therefore,a chemical chain combustion study was carried out using Baiyun Ebo iron ore concentrate as an oxygen carrier.The literature shows that iron-based oxygen carriers have the disadvantages of dense surface,low reactivity and easy sintering agglomeration,etc.For addressing the problems of average reactivity and weak resistance to sintering caused by the dense structure of dolomitic iron ore as an oxygen carrier when it is involved in chemical chain combustion,Considering that the main components of construction solid waste-red brick are inert oxides such as Al₂O₃and Si O₂,and the structure is loose and porous,the specific surface area of the dolomite iron ore concentrate oxygen carrier was increased by adding red brick powder to provide support for it to form a loose and porous structure,thus making it react more rapidly and completely with CO and improving its cyclic reaction capacity.Feasibility studies by Thermogravimetric analyser and tube furnace,followed by characterisation by XRD,SEM and TED,led to the following conclusions:（1）The reaction temperature of dolomite oxygen carriers with CO is basically higher than 800℃,and the DTG curve shows that the higher weight loss rate is between 800℃and 950℃,thus the experimental temperature is divided into 800℃,850℃,900℃and950℃.Through the constant temperature experiments at different temperatures of the specific thermogravimetric analyser,combined with the TED test results of the original ore and different ratios of red brick modified oxygenate,it can be seen that the effect of 2.5%red brick powder addition modified oxygen carrier is better than other ratios,and the reaction effect at 800℃is much lower than the other three temperatures,so the subsequent experimental temperature is adjusted to 850℃,900℃and 950℃.（2）Through the kinetic analysis of the programmed warming experimental data,it was found that the oxygen carrier modified by red brick powder belongs to the chemical reaction model（n=3）in the temperature range of 790.2～822.2°C with a correlation coefficient of 0.99403,while the temperature range of 920.1～962.3°C belongs to the three-dimensional diffusion model（Jander）with a correlation coefficient of 0.99981,after which the oxygen carriers’s The lower the apparent activation energy,the faster the reaction rate,so the red brick powder modified oxygen carriers can shorten their reaction time with CO and speed up the reaction process.（3）Considering that the oxygen carriers may need to be recycled several times after it is put into practical application,the cyclic reaction ability and sintering resistance is also one of the important properties of the oxygen carriers,so 51 reduction-oxidation cycle experiments were carried out at 850°C,900°C and 950°C for the raw and modified oxygen carriers,and the analysis was compared.The cumulative oxygen carriers conversions were 22%～63%,42%～67%and 69%～87%at 850°C,900°C and 950°C respectively,which showed that the cumulative oxygen carriers conversions increased with increasing temperature.（4）XRD and SEM analyses of the oxygen carriers before and after cycling of the original and red brick modified ore showed that the influence mechanism of the red brick powder modified iron ore concentrate oxygen carriers was to increase the specific surface area of the oxygen carriers and to form a loose and porous morphological structure,so that the oxygen carriers formed a good internal pore structure,which was conducive to the reaction between CO and the internal oxygen carriers,as well as to enhance the sintering resistance and cycling reaction ability of the oxygen carriers.