CONTINUOUS LONG-TERM OPERATION OF BUBBLING-BUBBLING BEDS TYPE CHEMICAL-LOOPING COMBUSTOR BY USING NATURAL GAS AS FUEL

摘要

The power plant is a major stationary source of CO2 emission. Thus, the CO2-free power generation will help to solve the greenhouse problem. Chemical-looping combustion is a novel concept of NGCC (Natural Gas Combined Cycle) and is a combustion technology with in-situ separation of CO2 and no NOx emission without additional treatment systems. The system is composed of two interconnected reactors, an air reactor (oxidizer) and a fuel reactor (reducer). A metal oxide is used as an oxygen carrier which transfers oxygen from the oxidizer to the reducer. The purpose of this study is to demonstrate inherent CO2 separation, no NOx emission, high CO2 selectivity, high fuel conversion, and no carbon deposition in the chemical-looping combustion system by continuous long-term operation in a novel 50kWth chemical-looping combustor. This process consists of two bubbling fluidized beds without loopseals, horizontal pneumatic transport line or transport reactor for solid circulation and/or conveying. To investigate the feasibility of the process in realistic operating conditions, natural gas and air were used as reacting gases. We measured NO, NO2 and N2O concentration to clarify whether NOx are formed during oxidation and measured CO2, CO, CH4, H2 concentration to certify an inherent CO2 separation and no carbon deposition during reduction. Total operating times were more than 50 hours. Pressure drop profiles in the system loop were maintained steadily throughout total operation time and solid circulation between the oxidizer and the reducer was smooth and stable. By analysis of gas concentration in the exit streams from the system, we could conclude that inherent CO2 separation and NOx-free combustion are possible in the chemical-looping combustion system.