Layout and Setup for a Conversion System of Hydrogen Exhaust Gas Streams into Electricity using a PEM Fuel Cell
In some sectors of industry like coke production, chlorine production or semiconductor manufacturing hydrogen exhaust streams accrue. The hydrogen content can range between 40 – 99 % and represents a huge energy source, which is predominantly not converted into electricity nowadays. A conversion system consisting of a diaphragm compressor, a humidifier and a fuel cell system to convert exhaust gas streams into electricity is presented in this paper. One challenge is to avoid any impact on the process facility and the process itself which is solved by an input pressure control using the compressor and a controlled bypass valve. Furthermore, the influence of nitrogen content in a hydrogen/nitrogen gas mixture on a PEM fuel cell system in flow through mode is investigated on an 8 kW PEMFC. Due to the dilution of hydrogen with up to 60 % nitrogen the maximum output power of the system is dramatically reduced by 55 % to 3.6 kW. The total conversion efficiency depends on exhaust gas conditions, mainly hydrogen concentration and pressure levels, and is expected to be between 10 – 37 %. Another major influence is the fuel cell current density whereby a reduction from 0.5 A/cm2 to 0.2 A/cm2 yields to doubled conversion system efficiency for low hydrogen contents.
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