Analysis of the HBr-based hydrogen production process as being developed by the SRT Group, Inc. Process study

Abstract

The SRT Group is developing a process that produces hydrogen from the electrolysis of hydrobromic acid. Compared to conventional water electrolysis, HBr electrolysis requires about 25% less electricity per unit of hydrogen produced. The capital and O and M costs are higher though, because of equipment that is required to regenerate HBr from the bromine formed in the electrolyzer (as a comparison a water electrolyzer discards the oxygen product and imports new water feedstock). Exhibit 1 presents summary statistics for the HBr and water electrolysis systems. All else equal, the HBr electrolysis process will be favorable to water electrolysis in situations where electricity is more expensive. A cost model is developed for water and HBr electrolysis systems. It indicates that HBr electrolysis is favored when the average cost of electricity exceeds 5.9 cents/kWh, at which price the cost of hydrogen 2.8 $/kg (20 $/MMBtu). In most cases steam methane reforming would be preferred if electricity costs are higher than 4 cents/kWh, indicating little commercial viability for HBr electrolysis. In 1996, SRT Group proposed a revised concept that addressed the issues associated with the solar-based process. Their idea is to add methane to the reactor with the bromine and water. The methane scavenges the oxygen produced in reaction (1) thus driving a higher conversion of bromine to HBr. Also, the reaction of methane and oxygen provides needed heat. The SRT Group has tested this concept in the laboratory and has demonstrated hydrogen production. The purpose of this analysis is to assess the economic potential of SRT Group`s innovation.