Abstract
Most CO2 mitigation technologies (sequestration or valorization) require a concentrated CO2 stream. However, conventional combustion technologies produce flue gas with a low concentration of CO2, requiring significant energy to concentrate the CO2. In contrast, the chemical looping combustion (CLC) process produces a flue gas that after the condensation of co-constituent H2O delivers a pure CO2 stream. This paper proposes process modifications to confer polygeneration (energy and chemical production) and CO2 valorization capabilities to the CLC process. The design modifications to separate the gasifier and fuel reactor, as well as the employment of hydrogen separators, splitters, partial/complete recycling of flue gas, are shown to result in various CLC-based polygeneration schemes. These schemes have been analyzed for their efficacy toward the aforementioned objectives. A performance assessment metric based on operating cost analysis, termed the relative profit/CO2 emission, has been utilized to evaluate the polygeneration schemes relative to the standalone versions of the conventional CLC and chemical (methanol and DME considered separately) production processes. The effect of varying operational parameters, such as syngas to fuel reactor split fraction, flue gas recycle ratio, and syngas to WGS split fraction, on the performance of the proposed schemes has been evaluated. Simulations conducted in Aspen Plus demonstrate the efficacy of the proposed schemes.
