Waste water treatment facilities utilize the process of anaerobic decomposition to clean water. A byproduct of this process is called anaerobic digester gas (ADG). The ADG gas has a significantly high impact as a greenhouse gas and is therefore subject to strict emissions regulation standards. UTC Power commercially manufactures a 200 kW phosphoric acid based fuel cell (PureCell^TM Model 200 system) that can use the ADG gas as the fuel. This system serves dual purposes: reduction in overall air emissions due to the usage of ADG, and energy savings due to the generation of power and heat from “free” fuel.

The PureCell^TM Model 200 system running on ADG fuel consists of three major components including: 1) the gas processing unit (GPU), 2) the power module, and 3) the cooling module. The GPU supplier by a vendor is designed to primarily remove hydrogen sulfide from the ADG fuel as its presence is damaging to the fuel cell. It also removes other compounds such as sulphur and volatile organics. The power module uses catalytic steam reforming (CSR) to produce a hydrogen rich reformed fuel stream from the ADG. The CSR reforming process yields higher H2 per unit of fuel compared to other reforming processes, boosting fuel quality and fuel cell efficiency. The fuel cell stack uses a phosphoric acid electrolyte to generate direct current (DC) power from reformate. The spent reformed fuel from the fuel cell stack is sent to the CSR burner to provide heat for the endothermic reforming process. The reformer exhaust is combined in the condenser along with the spent air from the fuel cell stack to recover condensed water. A power conditioner converts DC power from the fuel cell to AC power to be utilized in grid connected and/or grid independent mode of operation. The heat generated from the fuel cell and other mechanisms is captured in the form of two hot water streams. The hot water streams can be used by the customer for various heating and cooling purposes. The cooling module rejects any waste heat not utilized by the customer thereby maintaining overall thermal balance. In this talk, the ADG driven fuel cell system will be presented in more detail. We will highlight our research and development efforts for the next generation fuel cell operating on ADG gas. Our 200 kW fuel cell system has been operating on ADG fuel at several different sites. In this talk, we will present data on the fuel cell performance including efficiency, emissions and durability. Some of the challenges in operating on other renewable fuels will also be presented.