Experimental Study of Spark-Ignition Combustion using the Anode-off Gas from a Solid Oxide Fuel Cell 2020-01-0351
Worldwide energy demands have been drastically increasing in recent decades causing accelerated depletion of fossil fuel resources and thus increasing the generation of air pollutants and greenhouse gases. Solid oxide fuel cells (SOFC) have attracted attention in recent years as a novel, innovative and more environmentally friendly energy conversion technology for electrical energy generation. SOFCs can generate electrical power with high net conversion efficiency while emitting relatively low pollutant emissions in comparison to other distributed energy generation systems used today, but they have also exhibited limited robustness and versatility and load following capability. Recent studies have explored hybridized systems, which combine a SOFC with another energy conversion device, e.g. gas turbines or internal combustion engines, to increase the global efficiency of the system. This study is focused on exploring a hybrid SOFC-internal combustion engine system that can use the anode off-gas as a fuel for the engine. The engine can be used to provide additional power to the system and also serve as a means for balance of plant. Although this concept appears to be very promising, there have been limited studies – either theoretical or experimental – that have explored its operational characteristics. This study explored the feasibility of using anode off-gas as a fuel in internal combustion engines to generate additional power for the SOFC hybrid system and compared it with spark-ignition combustion using natural gas. The anode off-gas was simulated using a mixture of H2, CO, CO2 and water vapor at the exact composition of the anode exit. A single-cylinder CFR engine was used in spark-ignition combustion mode, and a comparison between anode off-gas and natural gas was performed. The experimental results showed that the anode-off gas is a fuel conducive to spark-ignition combustion, as it helped the engine to achieve good load levels, with high combustion and thermal efficiencies, as well as low CO and NOx emissions.