Purge gas protected transportable pressurized fuel cell modules and their operation in a power plant

A method of operating a fuel cell generator apparatus comprising the steps of:

• (1) passing oxidant gas and fuel gas, both being pressurized, through inlets and into a plurality of fuel cell assembly modules, each module containing a plurality of fuel cells, each fuel cell having electrolyte between an oxidant electrode and a fuel electrode, where the modules are each enclosed by a module housing capable of withstanding temperatures over 600.degree. C.;
• where the module housings are surrounded by an axially-elongated pressure vessel having two ends, such that there is a purge gas volume between the module housings and the pressure vessel, the oxidant gas and fuel gas also passing through the pressure vessel enclosing the modules;
• (2) passing pressurized purge gas through the pressure vessel to circulate within the purge gas volume, where the purge gas dilutes any unreacted fuel gas flow from the module;
• and
• (3) passing exhaust gas and circulated purge gas and any unreacted fuel gas out of the pressure vessel.