[월간수소경제 박상우 기자] A research team led by Dr. Shin-Geun Lee of the High Temperature Energy Conversion Laboratory at the Korea Energy Research Institute (hereinafter referred to as the Korea Energy Research Institute) has succeeded in producing high-purity hydrogen of more than 99.99% by developing an integrated membrane reactor that can decomp. ammonia into hydrogen and purify it at the same time.
The low-temperature membrane-catalyst composite ammonia reforming technology developed this time is a technology that can produce green hydrogen from ammonia using a palladium membrane reactor at a low temperature of less than 500°C. Specifically, the separator developed by the research team is meaningful as it managed to localize it after years of research and development.
Among the different methods for producing clean hydrogen, a method of producing hydrogen using ammonia, which is liquid at low pressure and high temperature, and which is easy to store and transport in liquid form, is attracting attention.
In order to extract hydrogen from ammonia, a decomposition method using a catalyst is used. In general, this reaction decomposes 95% or more at 400 ° C or higher, but the activity of a commercial catalyst is low, so the temperature to 600 ° C or higher to increase the decomposition rate. . In addition, nitrogen is removed by PSA (pressure swing adsorption) for the production of high purity, but the production of high purity is difficult due to the limitation of adsorption which can only adsorb nitrogen.
Accordingly, the research team succeeded in developing an integrated membrane reactor capable of decomposing 98% or more of ammonia at temperatures below 100°C and purifying it at the same time using a palladium membrane and an ammonia decomposition catalyst.
The current reactor for hydrogen extraction based on ammonia consists of a reactor that decomposes ammonia and technology for its refinement with PSA (pressure swing adsorption) and TSA (temperature swing adsorption).
Here, the researchers made it possible to purify hydrogen simultaneously with hydrogen production using a hydrogen separation membrane without PSA or TSA purification technology. By refining hydrogen at the same time as production, the decomposition temperature decreased and made it possible to produce high purity hydrogen at the same time by Le Chatelier’s principle due to the effect of removing products from the equilibrium reaction.
The most important thing in a membrane reactor is the performance and price of the membrane, and the research team improved the ‘electroless plating method’ to overcome the problems of high price and precision manufacturing, which were recognized as limitations of the current palladium membrane. Through this, it was confirmed that hydrogen extraction is possible at a low temperature of 500°C or less while reducing the amount of palladium to less than half.
As a result of testing by installing a number of separation membranes developed by the research team in the reactor, it has been certified that it can produce more than 99.99% of high purity hydrogen 2kg/d or more with a decomposition rate of 98% and a 93% hydrogen recovery rate up to aged when the temperature of the reactor is lowered by more than 100 ℃. The agency has completed the verification.
In particular, the advanced separator has a large area and more than twice the hydrogen production per area, which is the highest level in the world.
“The technology of extracting hydrogen from ammonia using a membrane reactor can integrate the decomposition reaction and purification of hydrogen into one,” said Dr. “To become a country with advanced technology, Korea also needs a lot of interest and support for membrane and process-intensive separation. research,” he said.
