Apr 3, 2012 16:29
Masaru Yoshida, Nikkei Monozukuri
Hitachi Ltd developed a solid adsorbent material made by using cerium oxide for collecting and accumulating carbon dioxide (CO2) produced by coal fired power generation.
Compared with zeolitic solid adsorbents, which are commercially available and commonly used for collecting CO2, the amount of CO2 adsorbed by the new material is about 13 times larger, the company said.
Traditional solid adsorbent materials preferentially adsorb moisture that exists in exhaust gas, making it difficult to efficiently separate CO2. The cerium oxide employed for the new solid adsorbent material can efficiently adsorb CO2 even when there is moisture.
In addition, Hitachi increased the number of adsorption sites of the new adsorbent material by using its exhaust purification catalyst technologies so that more CO2 can be adsorbed. Specifically, to increase adsorption efficiency, a second component that attracts CO2 was added to the surface of the adsorbent material.
Also, by using a template method for forming pillar-shaped fine pores on cerium oxide, the company developed the adsorbent material in which there are regular hollow structures. As a result, CO2 molecules are dispersed inside the fine pores and more likely to contact with the adsorption sites.
For coal fired power generation, there is a need to reduce the amount of CO2 released in the air from the viewpoint of prevention of global warming. And many organizations are engaged in the development and field tests of devices capable of collecting CO2 after exhaust gas treatment that removes nitrogen oxides (NOx), sulfur oxides (Sox), etc.
Thus far, Hitachi has been engaged in the development of a chemical absorption technique that uses an amine fluid as a material for collecting CO2. The technique enables to reduce the amount of energy consumed by collecting CO2 by about 30%, compared with traditional absorbing solutions. And the company is planning to conduct a field test of the technique in the aim of commercializing it.
However, the chemical absorption technique using the amine fluid requires energy for reheating a liquid containing CO2 with vapor from a steam turbine and separating/collecting CO2. Therefore, to reduce the energy required for collecting CO2, Hitachi developed a collection technique using a solid material that has a low specific heat and enables to reduce the amount of vapor.
Currently, for collecting CO2, the new method using the solid adsorbent material requires an amount of energy equivalent to that required by the chemical absorption technique using the amine fluid. But Hitachi plans to further reduce the required amount of energy by 20% or more by improving the solid adsorbent material and building an optimal system in the aim of commercializing the new material in or after 2025