The exhaust gas from a power plant can be recovered and used as a raw reaction material

The research group led by Assistant Professor Hiroshi Machida has developed an unprecedented CO₂capture technology, namely H2 stripping regeneration technology, in which hydrogen (H2) gas is supplied to the regeneration tower (desorber)(2). It is indicated in this research that, with the implementation of this new technology, combustion exhaust gas can be replaced by CO₂/H2 gas at lower temperatures (85 deg.C) than those used in conventional technology. The further reduction of energy can be achieved when it is combined with technologies such as those involved in the promotion of exhaust heat utilization and recovery of reaction heat.

This new technology can exhibit the world's highest energy-saving performance (i.e., separation and collection of energy required is less than 1 GJ/ton-CO₂when a desorber temperature is 60 deg.C) when it is combined with the phase-separation solvent that this research group has also developed.

This technology is expected to be applicable to value-added material production such as the syntheses of methane, methanol, gasoline, etc., from CO₂in the combustion exhaust gas and H2 from renewable energy, and is expected to contribute to carbon recycling.

1) H2 stripping regeneration technology

In the conventional process to synthesize fuel or chemicals from CO₂and renewable H2, pure CO₂is collected and is then mixed with H2 before being supplied to the reduction reactor. In the H2 stripping regeneration technology, H2 gas is supplied at the bottom of the desorber. As a result, CO₂partial pressure in the desorber is lowered, which promotes regeneration and lowers the regeneration temperature. The mixture of CO₂and H2 gases collected from the head of the desorber is supplied directly to the synthesis reactor.

2) Regeneration tower (Desorber)

In the amine absorption method, CO₂absorption and regeneration towers (i.e., absorber and desorber) are used to separate and collect CO₂in the exhaust gas mixture from facilities like power plants. Gases such as N₂and O₂, in addition to CO₂, are included in the combustion exhaust gas from these facilities and pure CO₂gas is collected with this amine absorption method. Only the CO₂gas is absorbed in the absorber by amine solution, and it is then heated in the desorber to regenerate pure CO₂gas. In other words, only CO₂gas can be extracted from the mixture of gases.

This study has been supported by Advanced Low Carbon Technology Research and Development Program (ALCA ) of JST Strategic Basic Research Programs.