Fuel mixing control arrangements are provided for fuel cell power plants (10)
operating on multiple fuels (22, 24, 26). A fuel delivery system (16)
supplies hydrogen-rich fuel (20) to the cell stack assembly (CSA) (12)
after controlled mixing of a primary fuel (22) and at least a secondary
fuel (24), each having a respective "equivalent hydrogen (H2)
content". The relative amounts of the primary fuel (22) and secondary fuel
(24) mixed are regulated (18, 34, 36) to provide at least a minimum
level (LL) of hydrogen-rich fuel having an equivalent hydrogen content sufficient
for normal operation of the CSA (12). The primary fuel (22) is a
bio-gas or the like having a limited, possibly variable, equivalent H2
content, and the secondary fuel (22) has a greater and relatively constant
equivalent H2 content and is mixed with the primary fuel in an economic, constant
relationship that assures adequate performance of the CSA (12). One or more
parameters (IDC, P, V, E. C.) of the operating power plant (10) related
to the equivalent H2 content of at least the primary fuel may be sensed
(72, 26, 78, 84, 176) and used to control (18, 36) the relative amounts
of secondary and primary fuels (22, 24) mixed in response thereto.
