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Oxidation of hydrogen in a helium stream by copper oxide: Analysis of combined film and pore diffusion with rapid irreversible reaction in a fixed‐bed process
Author(s) -
Scott Charles D.
Publication year - 1969
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690150126
Subject(s) - mass transfer , hydrogen , chemistry , diffusion , copper , reaction rate , helium , oxide , thermodynamics , coolant , analytical chemistry (journal) , chromatography , organic chemistry , physics , catalysis
Differential equations were derived to describe the system characterized by a rapid, irreversible reaction of a fluid species in a flowing fluid with a fixed bed of solids in which the reaction rate was controlled by mass transfer of the reacting fluid from the bulk fluid to the reaction site in the solid. Two kinds of mass transfer resistances were assumed, external or film diffusion resistance, and internal pore diffusion resistance. The set of differential equations were solved by a finite‐difference method for both the generalized case and for the specific case of reaction of hydrogen in a stream of helium with fixed beds of copper oxide pellets. The hydrogen‐copper oxide reaction is one step in a proposed method for removal of hydrogen as a contaminant in the helium coolant of nuclear reactors. This reaction was experimentally investigated in tests with both differential and deep beds of copper oxide in the temperature range of 400 to 600°C., at pressures of 10.2 to 30.0 atm., with gas mass flow rates of 0.0050 to 0.050 g./sq.cm.‐sec, and with inlet hydrogen concentrations of 0.0008 to 1.21 vol. %. These tests showed that the system could be described by the two rate‐limiting steps: film and pore diffusion of hydrogen. Differential‐bed tests were used to establish hydrogen transport properties within the porous copper oxide pellets, and tests with deep beds were used to establish external mass transport properties. Generalized breakthrough curves were determined by a computer solution of the mathematical model. These curves can be the basis for design of fixed‐bed copper oxide oxidizers for gas‐cooled, nuclear reactor purification systems and for design of any fixed‐bed system which follows the assumed reaction mechanism.