(33f) Advanced Power Generation From Coal Based on An Innovative Design of Solid Oxide Fuel Cell

Among fossil fuels, coal is considered to play a key role in meeting the long-term energy needs of human civilization due to its abundant and widely distributed reserves. However, currently almost all energy derived from coal comes through its combustion resulting in a significant emission of CO₂ and air pollutants including nitrogen oxides (NO_x) and sulfur oxides (SO_x). As a result, there has been an increased attention toward the development clean coal technologies (CCTs) such as integrated coal gasification combined cycle (IGCC) and integrated coal gasification fuel cell (IGFC) that can improve the efficiency of power generation from coal and hence reduce the emissions. To further increase the efficiency of IGCC and IGFC, recently exergy-recuperative advanced IGCC (A-IGCC) and advanced IGFC (A-IGFC) systems have also been proposed. Though IGFC technology is considered to be the ultimate coal-based power generation technology due to its highest power generation efficiency and low environmental impact, existing IGFC designs still rely on low-efficiency combustion process at the gas turbine. To address this issue, the current research proposes a new type of IGFC system, termed as super IGFC (S-IGFC), which employs a novel concept of a fluidized bed to reuse the high-exergy waste heat from solid oxide fuel cell (SOFC) for driving the endothermic coal gasification reaction. The proposed system comprises a gasifier, an SOFC and a steam turbine as the main functional units and its overall efficiency is estimated to be up to 89%. To make the proposed S-IGFC system practically realizable, an innovative design of SOFC based on hollow fibers (HFs) is also put forward. The proposed design consists of a ceramic HF as the structural support and thin layers of cathode, electrolyte and anode are deposited above it, in that order, conforming with the design criterion for application in the S-IGFC system. Besides, a thin porous layer of current collecting material is coated on the HF just below the cathode so that current can be collected efficiently from the entire surface of the cathode, as opposed to the conventional designs where large current collection loss occurs at the inner electrode. The proposed HF-based design is anticipated to increase current collection efficiency from the inner electrode by 2 to 5 folds depending on the cell length.