Combined solid oxide electrolyzer cell and polymer electrolyte electrolyzer cell hydrogen generation system and method of operating thereof

Abstract

A method of operating an electrolyzer system includes electrolyzing water into oxygen and inlet hydrogen using a polymer electrolyte cell (PEC) module including PECs, providing the inlet hydrogen to solid oxide electrolyzer cell (SOEC) modules that each include at least one SOEC stack, providing steam to the SOEC modules, and electrolyzing the steam to generate oxygen and a main product stream containing hydrogen.

1 . An electrolyzer system, comprising:
 solid oxide electrolyzer cell (SOEC) modules configured to convert steam into a main product stream comprising hydrogen, each SOEC module comprising at least one SOEC stack;   a polymer electrolyte cell (PEC) module comprising PECs and configured to generate inlet hydrogen by electrolysis of water;   an inlet conduit configured to fluidly connect an outlet of the PEC module to inlets of the SOEC modules; and   a product conduit fluidly connected to outlets of the SEOC modules and configured to collect the main product stream from the SOEC modules.   
     
     
         2 . The electrolyzer system of  claim 1 , wherein each of the SOEC modules further comprises:
 a steam conduit configured to provide the steam to the SOEC modules;   a mixer fluidly connected to the steam conduit and configured to mix the inlet hydrogen with the steam;   a hydrogen inlet conduit fluidly connecting the inlet conduit to the mixer; and   a first flow control orifice located on the hydrogen inlet conduit configured to control a mass flow rate of the inlet hydrogen from the inlet conduit to the mixer.   
     
     
         3 . The electrolyzer system of  claim 2 , wherein each of the SOEC modules each further comprises:
 a second flow control orifice configured to control a mass flow rate of the inlet hydrogen to the mixer, wherein the first flow control orifice has a different diameter than the second flow control orifice;   a first valve configured to control the inlet hydrogen flow from the hydrogen inlet conduit to the first flow control orifice; and   a second valve configured to control the inlet hydrogen flow from the hydrogen inlet conduit to the second flow control orifice.   
     
     
         4 . The electrolyzer system of  claim 1 , wherein the PECs comprise proton exchange membrane (PEM) electrolyzer cells. 
     
     
         5 . The electrolyzer system of  claim 1 , wherein the PECs comprise anion exchange membrane (AEM) electrolyzer cells. 
     
     
         6 . The electrolyzer system of  claim 1 , further comprising:
 a heat exchanger configured to cool the product stream in the product conduit; and   a hydrogen pump comprising electrochemical hydrogen pumping cells and having an inlet fluidly connected to an outlet of the heat exchanger by a hydrogen pump conduit, wherein the hydrogen pump is configured to separate water from product hydrogen in the product stream and to pressurize the product hydrogen.   
     
     
         7 . The electrolyzer system of  claim 6 , further comprising:
 a consumer conduit fluidly connected to an outlet of the hydrogen pump and configured to provide pressurized product hydrogen output from the hydrogen pump to a hydrogen consumer;   a return conduit fluidly connecting the consumer conduit to the inlet conduit; and   a diversion valve configured to control diversion of the pressurized product hydrogen from the consumer conduit to the inlet conduit.   
     
     
         8 . The electrolyzer system of  claim 1 , wherein the PEC module comprises a combined PEC module and hydrogen pump which is fluidly connected to the product conduit and configured to separate water from product hydrogen in the product stream and to pressurize the product hydrogen. 
     
     
         9 . The electrolyzer system of  claim 8 , further comprising:
 a heat exchanger configured to cool the product stream in the product conduit;   a pump inlet conduit fluidly connecting the heat exchanger to the combined PEC module and hydrogen pump and configured to recycle the cooled product stream from the heat exchanger to the combined PEC module and hydrogen pump;   a consumer conduit;   a hydrogen supply conduit fluidly connecting an outlet of the combined PEC module and hydrogen pump to the consumer conduit and to the inlet conduit, and configured to recycle the pressurized product hydrogen to the inlet conduit; and   a diversion valve configured to control diversion of the product hydrogen from the hydrogen supply conduit to the consumer conduit.   
     
     
         10 . The electrolyzer system of  claim 1 , wherein the SOEC modules exclude a recycling conduit configured to recycle the hydrogen from the product stream back to the at least one SOEC stack. 
     
     
         11 . A method of operating an electrolyzer system, comprising:
 electrolyzing water into oxygen and inlet hydrogen using a polymer electrolyte cell (PEC) module comprising PECs;   providing the inlet hydrogen to solid oxide electrolyzer cell (SOEC) modules that each comprise at least one SOEC stack;   providing steam to the SOEC modules; and   electrolyzing the steam in the SOEC modules to generate oxygen and a main product stream comprising hydrogen.   
     
     
         12 . The method of  claim 11 , further comprising mixing the inlet hydrogen and the steam, wherein the providing the inlet hydrogen to the SOEC modules and the providing the steam to the SOEC modules comprises providing the mixed inlet hydrogen and steam to the SOEC stacks located in the respective SOEC modules, wherein the step of mixing the inlet hydrogen and the steam occurs at least during a start-up mode of the SOEC modules. 
     
     
         13 . The method of  claim 11 , wherein:
 the providing the inlet hydrogen to the SOEC modules occurs during a start-up mode, a shut-down mode and during an emergency mode of the SOEC modules; and   the SOEC modules do not generate the main product stream comprising the hydrogen during the emergency mode.   
     
     
         14 . The method of  claim 13 , wherein:
 the inlet hydrogen is not provided to the SEOC modules during a steady-state operating mode of the SOEC modules; and   the steam is provided to the SOEC modules during the steady-state operating mode of the SOEC modules.   
     
     
         15 . The method of  claim 11 , wherein the PECs comprise proton exchange membrane (PEM) electrolyzer cells. 
     
     
         16 . The method of  claim 11 , wherein the PECs comprise anion exchange membrane (AEM) electrolyzer cells. 
     
     
         17 . The method of  claim 11 , further comprising:
 cooling the main product stream in a heat exchanger;   electrochemically separating water from product hydrogen in the main product stream and electrochemically pressurizing the product hydrogen; and   providing at least a first portion of the pressurized product hydrogen to a hydrogen consumer.   
     
     
         18 . The method of  claim 17 , further comprising recycling at least a second portion of the product hydrogen into the steam provided to the SOEC modules. 
     
     
         19 . The method of  claim 17 , wherein the electrochemically separating water from product hydrogen in the main product stream and the electrochemically pressurizing the product hydrogen occur in the PEC module which comprises a combined PEC module and hydrogen pump. 
     
     
         20 . The method of  claim 17 , wherein the product hydrogen is not recycled back to the at least one SOEC stack.