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US 8,709,229 B2Granted
Method to prevent sulfur accumulation in membrane electrode assembly
AssigneeSavannah River Nuclear Solutions, LLC
InventorsJohn L. Steimke, Timothy J. Steeper, David T. Herman
Life of this patent
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Abstract
A method of operating a hybrid sulfur electrolyzer to generate hydrogen is provided that includes the steps of providing an anolyte with a concentration of sulfur dioxide, and applying a current. During steady state generation of hydrogen a plot of applied current density versus concentration of sulfur dioxide is below a boundary line. The boundary line may be linear and extend through the origin of the graph with a slope of 0.001 in which the current density is measured in mA/cm2 and the concentration of sulfur dioxide is measured in moles of sulfur dioxide per liter of anolyte.
Claims12
A method of operating a hybrid sulfur electrolyzer to generate hydrogen, consisting of:
- providing an anolyte to an electrolyzer cell, wherein the anolyte has a concentration of sulfur dioxide;
- and
- applying current to the electrolyzer cell such that a current density is established;
- establishing and maintaining a steady state production of hydrogen generation in which a plot of the applied current density on an X-axis of a graph versus the concentration of sulfur dioxide on a Y-axis of the graph is below a boundary line on the graph, wherein the boundary line is linear and extends through an origin of the graph and has a slope of 0.001 in which the X-axis of the graph is current density measured in mA/cm2 and the Y-axis of the graph is concentration of sulfur dioxide measured in moles of sulfur dioxide per liter of anolyte, wherein the steps of providing an anolyte and applying current occur during the steady state production of the hybrid sulfur electrolyzer, and a start up sequence consisting of:
- loading anolyte that does not have any concentration of sulfur dioxide into an anolyte tank;
- impressing a voltage to the electrolyzer cell that is less than that needed to accomplish water electrolysis of hydrogen;
- heating the electrolyzer cell and the anolyte;
- slowly adding sulfur dioxide to the anolyte such that anolyte pressure is increased and concentration of sulfur dioxide in the anolyte is increased;
- obtaining the amount of concentration of the sulfur dioxide in the anolyte by use of the temperature and pressure of the anolyte, wherein the plot of the applied current density on the X-axis of the graph versus the concentration of sulfur dioxide on the Y-axis of the graph is below the boundary line;
- changing a power supply to the electrolyzer cell to current control once a target current is reached;
- and
- decreasing the concentration of sulfur dioxide in the anolyte until the first indication of an increase in voltage in the electrolyzer cell, wherein the decreasing step is performed only if an increase in concentration of sulfur dioxide in the anolyte does not cause a decrease in voltage of the electrolyzer cell.
9 more elements
A method of operating a hybrid sulfur electrolyzer to generate hydrogen, consisting of:
- loading anolyte that does not have any concentration of sulfur dioxide into an anolyte tank;
- impressing a voltage of 0.9 volt to the electrolyzer cell;
- heating the electrolyzer cell and the anolyte;
- slowly adding sulfur dioxide to the anolyte such that anolyte pressure is increased and concentration of sulfur dioxide in the anolyte is increased;
- obtaining the amount of concentration of the sulfur dioxide in the anolyte by use of the temperature and pressure of the anolyte, wherein the plot of the applied current density and concentration of sulfur dioxide does not cross over the boundary line during the entire start up sequence;
- changing a power supply to the electrolyzer cell to current control once a target current is reached;
- decreasing the concentration of sulfur dioxide in the anolyte until the first indication of an increase in voltage in the electrolyzer cell, wherein the decreasing step is performed only if an increase in concentration of sulfur dioxide in the anolyte does not cause a decrease in voltage of the electrolyzer cell;
- and,
- running at steady state production of hydrogen generation with respect to a boundary line on a graph that has on its axes current density and concentration of sulfur dioxide, wherein the boundary line is linear and extends through an origin of the graph and has a slope of 0.001 in which the X-axis of the graph is current density measured in mA/cm2 and the Y-axis of the graph is concentration of sulfur dioxide measured in moles of sulfur dioxide per liter of anolyte, wherein during the steady state production of hydrogen generation a plot of the current density and concentration of sulfur dioxide does not cross over the boundary line, wherein the boundary line separates a region on the graph where sulfur formation in the electrolyzer cell is expected from a region on the graph where sulfur formation in the electrolyzer cell is not expected or only minimally expected but where higher voltages are needed to generate hydrogen.
6 more elements
Dependencies are inferred from the claim text.