Fine pore enthalpy exchange barrier for a fuel cell power plant

A fuel cell power plant that generates electrical energy from a process oxidant stream and a reducing fluid stream, the plant comprising:

• a. at least one fuel cell means for producing the electrical energy from the oxidant stream and reducing fluid stream;
• and,
• b. a direct mass and heat transfer device secured in fluid communication with both a primary oxidant inlet line that directs the process oxidant stream into the fuel cell means and also with the plant exhaust passage that directs the plant exhaust stream out of the fuel cell means, the device including a structure that secures a fine pore enthalpy exchange barrier in mass transfer relationship between the oxidant and exhaust streams passing through the device so that the process oxidant stream passes adjacent an inlet surface of the barrier, and the plant exhaust stream passes adjacent an opposed exhaust surface of the barrier and the structure secures the barrier between the oxidant and exhaust streams to prevent bulk mixing of the streams within the device, wherein the barrier includes a self-supporting flexible support matrix means for defining hydrophilic pores having a pore-size range of between about 0.1 to about 100 microns and for being chemically stable in the presence of a liquid transfer medium so that whenever the liquid transfer medium fills the pores the barrier has a bubble pressure greater than 0.2 pounds per square inch, and wherein the structure includes a first flow guide means secured adjacent the first mesh layer for guiding the process oxidant stream to flow adjacent the first mesh layer, and a second flow guide means secured adjacent the second mesh layer for guiding the plant exhaust stream to flow adjacent the second mesh layer.

A method of exchanging water and heat from a plant exhaust stream leaving a fuel cell power plant into a process oxidant stream entering a fuel cell of the fuel cell power plant, comprising the steps of:

• a. securing a fine pore enthalpy exchange barrier between an exhaust chamber and an oxidant chamber of a direct mass and heat transfer device, wherein a flexible support matrix of the barrier defines hydrophilic pores having a pore-size range of between about 0.1 to about 100 microns, so that whenever a liquid transfer medium wets the pores defined within the support matrix of the barrier, the barrier restricts bulk mixing of fluids between the exhaust and oxidant chambers;
• b. passing the plant exhaust stream through the exhaust chamber adjacent an exhaust surface of the fine pore enthalpy exchange barrier, and passing the process oxidant stream through the oxidant chamber adjacent an inlet surface of the barrier opposed to the exhaust surface so that a pressure differential between the exhaust and oxidant fluids is less than 0.2 pounds per square inch;
• and,
• c. then directing the process oxidant stream from the direct mass and heat transfer device into the fuel cell.