1996 Volume 45 Issue 9 Pages 540-545
An electrochemical method for monitoring hydrogen content permeated through steel pipe at elevated temperatures (-673 K) was, first time, applied to an actual hydrodesulfurizing plant for light oil. The monitoring equipments include a molten sodium hydroxide electrolyte, a stabilized zirconia reference electrode, Pt-wire counter electrode, a high-purity alumina cell, potentiostat and recorder. The monitoring of ionic current of permeated hydrogen was performed with high reliability during over one month. The measuring currents were fundamentally similar values as ones calculated from the assumption that the process flow was pure hydrogen gas. But, after several days, the permeation currents decreased to 1/2-1/5 of the calculated value. This decrease is closely related to the formation of FeS film at the inner surface of pipe.