Carbonate Direct Fuel Cell Operation on Dual Fuel

Abstract

The ability to operate highly-ef ficient, pollution-free, distributed-generation power plants on either natural gas or HD-5 grade propaneis of interest to the U.S. Army and the U.S Department of HomelandSecurity as secure power source for critical power operations. The abil-ity to operate continuously on HD-5 propane also provides a valuableproposition to islands, remote sites, national parks, data centers, militarybases, hotels, and hospitals. HD-5 propane, as opposed to other gradesof propane, was selected as the back-up fuel of choice because of itsavailability (even in remote areas), cost, and ease of processing in thefuel cell power plant. Although natural gas distribution through utilitypipelines is convenient, it is vulnerable to natural disaster, threats ofterrorism, and simple repair outages. Propane, however, is routinelytransported and stored as a liquid at ambient temperatures and offersa convenient and secure option for fuel cell operations. An adequatequantity of propane can be stored on site to sustain operations for sev-eral days in a variety of weather climates.In response to the interest for a fuel flexible power plant, Concur-rent Technologies Corporation (CTC), under contract to the U.S. ArmyEngineer Research and Development Center’s Construction EngineeringResearch Laboratory (ERDC-CERL), is working with FuelCell Energy(FCE) to test an internally reforming 250 kW carbonate fuel cell. Previousto the demonstration at CTC, FCE operated a 250 kW carbonate directfuel cell for 1500 hours, which generated 300,000 kilowatt-hours (kWh)net AC electricity using HD-5 propane as fuel. Among the challengesaddressed, lessons learned by FCE during initial operation on HD-5propane included: 1) avoiding carbon deposition during pre-reformingof propane into a methane rich gas, 2) metering and controlling propane flow to account for variations in fuel composition, 3) removing sulfurfrom the propane, and 4) increasing the steam required for operationon propane. Peripheral issues that required additional investigationincluded identifying the number and volume of propane tanks and avaporization system to deliver the required rate and quantity of fuel.