Elevated pressure operation of molten carbonate fuel cells with enhanced CO
Molten carbonate fuel cells (MCFCs) are operated at elevated pressure to provide increased operating voltage and/or enhanced CO 2 utilization with a cathode input stream having a low CO 2 content. It has been discovered that increasing the operating pressure of a molten carbonate fuel cell when using a low CO 2 -content cathode input stream can provide unexpectedly large increases in operating voltage while also reducing or minimizing the amount of alternative ion transport and/or enhancing CO 2 utilization.
1. A method for producing electricity, the method comprising:
introducing an anode input stream into an anode of a molten carbonate fuel cell;
introducing a cathode input stream comprising O 2 , H 2 O, and CO 2 into a cathode of the molten carbonate fuel cell; and
operating the molten carbonate fuel cell at a cathode pressure of 1 kPa-g or more, an average current density of 80 mA/cm 2 or more, and a measured CO 2 utilization of 70% or more to generate electricity, an anode exhaust comprising H 2 , CO, and CO 2 , and a cathode exhaust comprising CO 2 , 1.0 vol % or more O 2 , and 1.0 vol % or more H 2 O, wherein a calculated CO 2 utilization calculated based on the average current density is greater than the measured CO 2 utilization by 5.0% or more.
2. The method of claim 1 , wherein the cathode input stream comprises 5.0 vol % or less of CO 2 , or wherein the cathode exhaust comprises 1.0 vol % or less of CO 2 , or a combination thereof.
3. The method of claim 1 , wherein the molten carbonate fuel cell is operated at an anode pressure of 1 kPa-g or more, or wherein the cathode pressure is 10 kPa-g or more, or a combination thereof.
4. The method of claim 3 , wherein the anode pressure is 1 kPa-g to 300 kPa-g, or wherein the cathode pressure is 1 kPa-g to 300 kPa-g, or a combination thereof.
5. The method of claim 3 , wherein the anode pressure is 10 kPa-g to 500 kPa-g, or wherein the cathode pressure is 10 kPa-g to 500 kPa-g, or a combination thereof.
6. The method of claim 1 , wherein a fuel utilization in the anode is 60% or more, or wherein a fuel utilization in the anode is 55% or less.
7. The method of claim 1 , wherein an anode pressure and the cathode pressure differ by 0.5 kPa-g or less.
8. The method of claim 1 , wherein a voltage drop across the cathode is 0.4 V or less, or wherein the electricity is generated at a voltage of 0.55 V or more, or a combination thereof.
9. The method of claim 1 , wherein a H 2 concentration in the anode exhaust is 5.0 vol % or more, or wherein a combined concentration of H 2 and CO in the anode exhaust is 6.0 vol % or more, or a combination thereof.
10. The method of claim 1 , wherein the molten carbonate fuel cell is operated at a thermal ratio of 0.25 to 1.0.
11. A method for producing electricity, the method comprising:
introducing an anode input stream into an anode of a molten carbonate fuel cell;
introducing a cathode input stream comprising O 2 and 5.0 vol % or less CO 2 into a cathode of the molten carbonate fuel cell; and
operating the molten carbonate fuel cell at a cathode pressure of 1 kPa-g or more, an average current density of 80 mA/cm 2 or more, and a measured CO 2 utilization of 70% or more to generate electricity, an anode exhaust comprising H 2 , CO, and CO 2 , and a cathode exhaust comprising a CO 2 content of 1.0 vol % or less, wherein a calculated CO 2 utilization calculated based on the average current density is greater than the measured CO 2 utilization.
12. The method of claim 11 , wherein the calculated CO 2 utilization is greater than the measured CO 2 utilization by 2.0% or more.
13. The method of claim 11 , wherein the molten carbonate fuel cell is operated at an anode pressure of 1 kPa-g or more, or wherein the cathode pressure is 10 kPa-g or more, or a combination thereof.
14. The method of claim 13 , wherein the anode pressure is 1 kPa-g to 300 kPa-g, or wherein the cathode pressure is 1 kPa-g to 300 kPa-g, or a combination thereof.
15. The method of claim 13 , wherein the anode pressure is 10 kPa-g to 500 kPa-g, or wherein the cathode pressure is 10 kPa-g to 500 kPa-g, or a combination thereof.
16. The method of claim 11 , wherein an operating voltage of the molten carbonate fuel cell at a cathode pressure of 0 kPa-g is 0.75 V or less, when operated at an average current density of 80 mA/cm 2 or more with a difference of 1.0% or less between calculated CO 2 utilization and measured CO 2 utilization, and wherein the cathode pressure is 100 kPa-g to 500 kPa-g.
17. The method of claim 11 , wherein a fuel utilization in the anode is 60% or more, or wherein a fuel utilization in the anode is 55% or less.
18. The method of claim 11 , wherein an anode pressure and the cathode pressure differ by 0.5 kPa-g or less.
19. The method of claim 11 , wherein a voltage drop across the cathode is 0.4 V or less, or wherein the electricity is generated at a voltage of 0.55 V or more, or a combination thereof.
20. The method of claim 11 , wherein a H 2 concentration in the anode exhaust is 5.0 vol % or more, or wherein a combined concentration of H 2 and CO in the anode is exhaust is 6.0 vol % or more, or a combination thereof.