(240c) Chemical Looping Processes: An Example for Process Intensification

The concept of chemical looping reactions has been widely applied in chemical industries, e.g., the production of hydrogen peroxide (H₂O₂) from hydrogen and oxygen using 9,10-anthraquinone as the looping intermediate. Fundamental research on chemical looping reactions has also been applied to energy systems, e.g., the splitting of water (H₂O) to produce oxygen and hydrogen using ZnO as the looping intermediate. Fossil fuel chemical looping applications had been used commercially with the steam-iron process for coal from the 1900s to the 1940s and had been demonstrated at a pilot scale with the carbon dioxide acceptor process in the 1960s and 1970s. There are presently no chemical looping processes using fossil fuels in commercial operation. A key factor that hampered the continued use of these earlier processes for fossil energy operation was the inadequacy of the reactivity and recycleability of the looping particles. This factor led to higher product costs for using the chemical looping processes, compared to the other processes that were petroleum or natural gas based. With CO₂ emission control now being considered as a requirement, interest in chemical looping technology has resurfaced. In particular, chemical looping processes are appealing due to their unique ability to generate a sequestration-ready CO₂ stream while yielding high energy conversion efficiency. Renewed fundamental and applied research since the early 1980s has emphasized improvement over the earlier shortcomings. New techniques have been developed for direct processing of coal or other solid carbonaceous feedstock in chemical looping reactors. Significant progress is underway in particle design, reactor development, and looping system integration, as demonstrated by the operation of several pilot or sub-pilot scale units worldwide, making it possible that chemical looping technology may be commercially viable in the future for processing carbonaceous fuels.

This presentation will describe the fundamental and applied aspects of modern chemical looping technology that utilizes fossil and biomass as feedstock and involve both the metal ? metal oxide and metal oxide ? metal carbonate as reactive looping systems. The presentation will focus on looping reactor and system engineering and its feature of process intensification schemes in the context of the conventional processes. Comparisons of the process efficiencies for the intensified system versus the conventional system will be presented and illustrated.