Edge seals for molten carbonate fuel cell stacks

A vertical reactant manifold seal assembly in a molten carbonate fuel cell stack for limiting electrolyte migration vertically through the stack, said seal assembly comprising:

• a) a layer of spheroidal lithium aluminate grains having a diameter in the range of about 45 microns to about 75 microns, said grains being bonded together by a glass layer formed on the surface of said lithium aluminate grains, said lithium aluminate-glass layer extending vertically along an outer edge of the stack;
• b) a layer of fine pore zirconia cloth extending vertically of the stack, said zirconia cloth layer contacting said lithium aluminate-glass layer and being operable to remove from the latter any electrolyte which may migrate thereto from the stack interior so as to keep said lithium aluminate-glass layer essentially dry;
• c) an electrically insulating ceramic layer disposed on said zirconia cloth layer;
• and
• d) a reactant manifold mounted on said stack, said three layers being interposed between said manifold and active areas of the stack.

A method for forming a lithium aluminate seal member in a molten carbonate fuel cell stack, said method comprising the steps of:

• a) pretreating a supply of lithium aluminate particles by drying said particles so as to remove absorbed water from said particles;
• b) screening said pretreated lithium aluminate particles on a preheated screen to remove particles below about 40 microns in size;
• c) screening said pretreated lithium aluminate particles on a preheated screen to remove particles above about 75 microns in size;
• and
• d) bonding said screened and dried particles into a self-sustaining porous seal member.

A method for forming a lithium aluminate seal member in a molten carbonate fuel cell stack, said method comprising the steps of:

• a) pretreating a supply of lithium aluminate particles by drying said particles so as to remove absorbed water from said particles;
• b) screening said pretreated lithium aluminate particles on a preheated screen to remove particles below about 40 microns in size;
• c) screening said pretreated lithium aluminate particles on a preheated screen to remove particles above about 75 microns in size;
• and
• d) mixing said screened and dried particles with an alcohol santicizer and boric acid mixture to form a pasty caulk;
• e) heating said caulk to convert the boric acid to boron and reacting the boron with the lithium aluminate particles to form a glassy bonding phase on the surface of said particles thereby forming a porous self-sustaining seal member having an internal capillarity which will not support significant electrolyte migration.