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 propane
is of interest to the U.S. Army and the U.S Department of Homeland
Security as secure power source for critical power operations. The abil-
ity to operate continuously on HD-5 propane also provides a valuable
proposition to islands, remote sites, national parks, data centers, military
bases, hotels, and hospitals. HD-5 propane, as opposed to other grades
of propane, was selected as the back-up fuel of choice because of its
availability (even in remote areas), cost, and ease of processing in the
fuel cell power plant. Although natural gas distribution through utility
pipelines is convenient, it is vulnerable to natural disaster, threats of
terrorism, and simple repair outages. Propane, however, is routinely
transported and stored as a liquid at ambient temperatures and offers
a convenient and secure option for fuel cell operations. An adequate
quantity 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. Army
Engineer Research and Development Center’s Construction Engineering
Research Laboratory (ERDC-CERL), is working with FuelCell Energy
(FCE) to test an internally reforming 250 kW carbonate fuel cell. Previous
to the demonstration at CTC, FCE operated a 250 kW carbonate direct
fuel cell for 1500 hours, which generated 300,000 kilowatt-hours (kWh)
net AC electricity using HD-5 propane as fuel. Among the challenges
addressed, lessons learned by FCE during initial operation on HD-5
propane included: 1) avoiding carbon deposition during pre-reforming
of propane into a methane rich gas, 2) metering and controlling propane flow to account for variations in fuel composition, 3) removing sulfur
from the propane, and 4) increasing the steam required for operation
on propane. Peripheral issues that required additional investigation
included identifying the number and volume of propane tanks and a
vaporization system to deliver the required rate and quantity of fuel.