Abstract
Integrated gasification fuel cell (IGFC) systems that combine coal gasification and solid oxide fuel cells (SOFC) are promising for highly efficient and environmentally sensitive utilization of coal for power production. Most IGFC system analysis efforts performed to-date have employed non-dimensional SOFC models, which predict SOFC performance based upon global mass and energy balances that do not resolve important intrinsic constraints of SOFC operation, such as the limits of internal temperatures and species concentrations. In this work, a detailed dimensional planar SOFC model is applied in IGFC system analysis to investigate these constraints and their implications and effects on the system performance. The analysis results further confirm the need for employing a dimensional SOFC model in IGFC system design. To maintain the SOFC internal temperature within a safe operating range, the required cooling air flow rate is much larger than that predicted by the non-dimensional SOFC model, which results in a larger air compressor design and operating power that significantly reduces the system efficiency. Options to mitigate the challenges introduced by considering the intrinsic constraints of SOFC operation in the analyses and improve IGFC design and operation have also been investigated. Novel design concepts that include staged SOFC stacks and cascading air flow can achieve a system efficiency that is close to that of the baseline analyses, which did not consider the intrinsic SOFC limitations.
Highlights
Coal-based power plants with low criteria pollutant emissions and carbon capture capability are essential for satisfying the ever increasing global energy demand while protecting the earth from pollution and climate change
To provide a system level background to carry on the discussions, an Integrated gasification fuel cell (IGFC) system consisting of catalytic hydro-gasification and hybrid pressurized solid oxide fuel cells (SOFC) – gas turbine power block, which is one of the most promising system configurations obtained in previous non-dimensional SOFC model based design and analysis [12], has been chosen as a “baseline” case in this work
This work focuses upon the additional insights provided by this dimensional model in an IGFC system analysis work and the changes in system design that must be considered due to the insights produced by the dimensional model
Summary
Coal-based power plants with low criteria pollutant emissions and carbon capture capability are essential for satisfying the ever increasing global energy demand while protecting the earth from pollution and climate change. As an electrochemical energy conversion device, the performance and safe operation of SOFC are significantly affected by the internal distributions of temperature and species concentrations, which are beyond the resolution capability of non-dimensional SOFC models. To clarify this issue, a detailed dimensional model for planar SOFC has been previously developed for use in such IGFC system analysis work [14]. To provide a system level background to carry on the discussions, an IGFC system consisting of catalytic hydro-gasification and hybrid pressurized SOFC – gas turbine power block, which is one of the most promising system configurations obtained in previous non-dimensional SOFC model based design and analysis [12], has been chosen as a “baseline” case in this work. TVhij j0 p r xiı area, m2 effective diffusivity of species i in porous materials, m2 s−1 ideal potential of H2 oxidization at ambient pressure activation energy, kJ mol−1 convective heat transfer coefficient, W m−2 K−1 equilibrium constant ohmic resistance, ̋ or: heat conduction resistance, W K−1 temperature, K voltage, V specific enthalpy of species, J mol-1 electric current, A electric current density, A m−2 exchange current density, A m−2 pressure, bar rate of reaction, mol s−1 molar fraction of species i electron transfer coefficient pre-exponential factor in exchange current density calculation thickness, m
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