Method of operation of a solid oxide electrolysis cell stack; system for carrying it out

Abstract

The invention relates to a method of operating a solid oxide electrolysis cell (SOEC) stack for producing hydrogen, and to a system for carrying out the method, wherein said SOEC stack comprises at least one solid oxide electrolysis cell (SOEC), and said at least one SOEC comprises an electrolyte layer interposed between a fuel side and an oxygen side, and the method comprises transient operation, wherein the transient operation comprises: - operating the SOEC stack under open-circuit voltage (OCV); - supplying a feed gas containing ammonia; supplying at least a portion of said feed gas containing ammonia to a protective bed reactor, said protective bed reactor comprising a catalyst active in the cracking of ammonia to nitrogen and hydrogen; and extracting from said protective bed reactor a formation gas containing nitrogen and hydrogen;supplying at least a portion of the forming gas comprising nitrogen and hydrogen to the fuel side of at least one of the solid oxide electrolysis cells (SOECs) of the SOEC stack; and extracting from said at least one of the SOECs of the SOEC stack a first fuel-side outlet gas.