Chemical Looping with Oxygen Uncoupling using a Copper-based Solid Oxygen Carrier

摘要

Chemical Looping Combustion of coal provides a pathway for CO_2 enrichment, capture and sequestration while avoiding the energy penalty of an air separation unit as in oxy-combustion. This technology employs a solid metal oxide oxygen carrier in two coupled fluidized beds. The first bed is fluidized using high temperature air, bringing the metal oxide to its highest oxidation state and is referred to as the air reactor. The second bed is fluidized using water, CO_2 and/or syngas from an upstream gasification process and is known as the fuel reactor. Oxidation of the fuel components occur here while reducing the metal oxide. This technology has been demonstrated in numerous locations at bench- and pilot-scale while combusting gaseous fuels. Combustion of solid fuels in this manner is difficult due to slow solid-solid reaction rates. In most instances when solid fuels are utilized in a chemical looping combustor, a gasification step is also required. However to achieve highest efficiency and to minimize complexity, it is desirable to eliminate the gasification step and directly combust solid fuels with oxygen delivered by the metal oxide carrier. The University of Utah has engaged in research over many years to develop a copper based solid oxide carrier that will release oxygen into the gas phase in the fuel reactor. This approach is known as Chemical Looping Combustion with Oxygen Uncoupling (CLOU). The University of Utah has demonstrated this approach at bench scale and has just commissioned a pilot-scale demonstration unit (PDU) at the Industrial Combustion and Gasification Research Facility (ICGRF). The PDU is designed to fire at a rate of 100 kW on coal while producing a nearly pure CO_s stream ready for compression and sequestration. This paper will provide an overview of the state of this technology and the efforts at the University of Utah to demonstrate CLOU at pilot-scale.