Heat exchanger for a hot fuel cell

1. A heat exchanger for operating at an outlet of a hot fuel cell feeding the heat exchanger with oxidizer gas and with fuel gas, the heat exchanger comprising:

a first flow circuit for oxidizer gas;

a second flow circuit for fuel gas;

a pre-mixer chamber fed both with oxidizer gas and with fuel gas from at least the second circuit;

a combustion chamber fed with the gaseous mixture from the pre-mixer chamber and with oxidizer gas from the first circuit;

a flow circuit for flue gas, receiving the flue gas coming from the combustion chamber;

a first enclosure including the flow circuit for flue gas and the combustion chamber, and a second enclosure including the first flow circuit for oxidizer gas and the second flow circuit for fuel gas, the first and second enclosures configured to communicate with each other such that a cooling fluid flows in both enclosures; and

an inner cylindrical wall and an outer cylindrical wall,

wherein the first flow circuit for oxidizer gas, the second flow circuit for fuel gas, the combustion chamber, and the flow circuit for flue gas are immersed in a common cooling fluid,

wherein the second enclosure is defined between the inner cylindrical wall and the outer cylindrical wall, and the first enclosure is defined by the inner cylindrical wall, and

wherein the first and second flow circuit present ducts arranged for spiral coils which are placed inside the second enclosure around the first enclosure.

2. A heat exchanger according to claim 1 , wherein the oxidizer gas feeding the pre-mixer chamber is taken from the first circuit.

3. A heat exchanger according to claim 1 , wherein the oxidizer gas feeding the pre-mixer chamber is taken from an external flow circuit for the oxidizer gas.

4. A heat exchanger according to claim 1 , further comprising a third flow circuit for fuel gas feeding the pre-mixer chamber and immersed in the cooling fluid.

5. A heat exchanger according to claim 4 , further comprising an external flow circuit for fuel gas feeding the pre-mixer chamber.

6. A heat exchanger according to claim 1 , wherein the pre-mixer chamber is separated from the combustion chamber by an injection grid.

7. A heat exchanger according to claim 6 , wherein the oxidizer gas taken directly from the first circuit is fed to the combustion chamber in an annular manner around the injection grid.

8. A heat exchanger according to claim 1 , wherein the oxidizer gas taken directly from the first circuit and feeding the combustion chamber passes via a dilution air chamber formed around the combustion chamber.

9. A heat exchanger according to claim 1 , wherein the cooling fluid is water.

10. A heat exchanger according to claim 1 , wherein the spiral coils of the first and second flow circuits are placed in alternation.

11. A heat exchanger according to claim 1 , wherein an inlet for the cooling fluid is disposed at a bottom portion of the outer cylindrical wall and an outlet for the cooling fluid is disposed in a top portion of the outer cylindrical wall.

12. A boiler for operating at an outlet from a hot fuel cell, the boiler comprising a heat exchanger according to claim 1 .

13. A system for cogeneration of heat energy and of electrical energy, the system comprising:

a hot fuel cell; and

a heat exchanger according to claim 1 and fed with oxidizer gas and fuel gas by the hot fuel cell.

14. A system according to claim 13 , further comprising a reformer, the heat exchanger including the second flow circuit and a third flow circuit for fuel gas, the second and third flow circuits being fed respectively by the hot fuel cell and by the reformer.