The Use of Metal Hydrides for Hydrogen Recovery from Industrial Off-Gas Streams

Abstract

This paper describes the development of a concept to utilize metal hydrides to recover hydrogen from industrial off-gas streams. The activity included a survey of industrial waste streams a selection of metallic hydriding alloys, testing of alloys for poison tolerance and life, a conceptual design and an economic analysis. Of the nine alloys tested, only the lanthanium-nickel-aluminum type proved to have the durability to be used in this concept. A fixed bed reactor system, using LaNi4 25Alo75 in pelletized form, that was the only concept that was technically feasible. The cost of delivered hydrogen ranged from $1.31 to $1.72/MSCF for a refinery hydrotreater and an ammonia purge gas stream based on an alloy life of a year. These costs, though lower than that for hydrogen produced from steam reforming of natural gas, are at best marginal relative to the competing technologies such as cryogenic, membrane and pressure swing adsorption systems.