Synthesis And Characteristic Investigation Of Cu-based And Mn-based Oxygen Carriers For Chemical Looping Combustion

Chemical looping combustion is a novel technology considered promsing in reducing the cost of CO₂ capture with inherent CO₂ seperation,in which the oxidation and reduction of metal oxide?oxygen carrier?occurred separately.This dissertation focused on the development of Cu-based and Mn-based oxygen carriers.The research was conducted from four aspects,that is methods to inhibit agglomeration of Cu-based oxygen carriers,reactivity enhancement of Mn ore as oxygen carriers,continuous test in the dual fluidized bed reactor and methods to eliminate the unconverted gas.The Cu-based oxygen carrier was easily agglomerated at high temperatures,which led to defluidization.A new method of manufacturing Cu-based oxygen carriers was proposed by mixing cement with copper oxide power with water added.This method made the manufacture of oxygen carriers much easier and could inhibit agglomeration effectively.At the same time,the reactivity and stability of oxygen carriers maintained high.The mechanism of inhibiting agglomeration by adding inert materials was discussed.The reactivity of manganese ore was greatly improved by adding a small amount of copper?0.5-2.0 wt.%?by wet impregnation.Different ores were tested in a batch-scale fluidized bed reator with CO as the reducing gas.The performance can be enhanced 2-100 times by impregnating copper.BET,XRD,SEM analysis were carried out on the ores and copper-mangansese oxides to interperet the performance enhancement.The enhancement was ascribed to the pore development by copper ion and the caltalytic effect of Cu-Mn compound.Long-term continuous operation was conducted using manganese ore and Cu-modified manganese ore as oxygen carriers to investigate the reactivity and the attrition property of the oxygen carriers.Both Mn-based oxygen carriers showed stable performance during the continuous run.It was found that the attrition rate was not influenced by copper impregnation.The attrition rate was high initially and became much smaller afterwards.The stable attrition rate was0.13 wt.%/h for both oxygen carriers.A low temperature chemical looping process and a direct chemical looping process were proposed to eliminate the unburnt gaseous components from the off-gas.The performance of cement-supported Cu-based oxygen carriers and Cu-modified manganese ore were tested at low temperatures?300-400oC?in TGA,batch-scale fluidized bed reactor and a dual fluidized bed reactor.It was found that these two oxygen carriers showed high reactivity at low temperatures and can highly mitigate the unburnt gaseous components at low temperatures without using extra pure oxygen which was needed in the conventional oxygen polishing step.