Development Of Combined Calcium And Copper Chemical Looping Process Using Composite Cao/CuO-Based Materials

Among post-combustion CO₂ capture technologies,the calcium looping cycle?CaL?is particularly interesting for its abundant cheap sorbent precursors and the potential high CO₂ carrying capacity.Despite those distinctive advantages,CaL technology faces one problem that extra energy is always required for the regeneration of CaO-based sorbent.Oxy-fuel combustion has been proposed to provide the required energy,however the air separation unit is energy intensive and costly,which largely affect the economics of CaL process.Integration of chemical looping combustion into calcium looping process is a possible method to eliminate the air separation unit.The concept of the new combined process?Combined Ca-Cu chemical looping,CaCuCL?is based on the idea of energy supply for decomposition of CaCO₃ by reduction reaction of oxygen carrier with fuel gas.The primary development of Ca-CuCL was focused on modeling design of process and performance of CaO and CuO composites,however,the potential technical routes of Ca-CuCL process were hardly experimently investigated.Thus,considering the presence of small amount of oxygen in the feed flue gas,the thesis discusses the cyclic performance of both two CaO-CuO composites through characterization methods?SEM,EDS,crushing strength measurement included?and cyclic tests which are conducted using a thermalgravimetric analyzer two schemes,i.e.a two-step cycle and a three-step cycle.Besides,the tested composites are prepared via a impregnation method.In two-step process,CaO-CuO/MgO exhibits relatively stable CO₂ uptake though reaction decay is observed in both composites.Two kinds of sorbents possess excellent oxygen uptake that ensures the energy balance during calcination/reduction step.In three-step process,as for CaO-CuO/MgO composite,the reaction efficiency of integrated carbonation and oxidation step is above 70%during the whole cycles,while rapid decay of CO₂ uptake is still found for CaO-CuO.In general,CaO-CuO/MgO behaves excellent and stable cyclic performance,and it appears that the reaction efficiency of CaO-CuO/MgO in two-step process is distinctly higher than that in three-step process.