CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2020-040120, filed on Mar. 9, 2020, and the entire contents of which are incorporated herein by reference.

FIELD

The presented embodiment is related to the acid gas removal apparatus and the acid gas removal method of acid, separating and removing acid gases, such as carbon dioxide, from the acid gas absorbent which absorbed acid gases, and regenerating the acid gas absorbent.

BACKGROUND

The technology to allow acid gases, such as carbon dioxide, to be absorbed by an amine-containing acid gas absorbent is used in industrial plants, such as thermal power plants, with CCS (carbon dioxide capture and storage), and is considered as a most promising candidate for stopping global warming. The acid gas absorbent which absorbed acid gases is generally heated in a regeneration tower to be released the acid gases, and thereby regenerated for repeated use. The temperature used in this process is generally 140° C., and huge energy is consumed for this process, which is called heat duty or energy penalty. Therefore, if acid gases can be efficiently released even when the heating temperature is set to a lower temperature, the amount of energy consumption can be reduced, which potentially facilitates the wide use of the technology as a means of preventing global warming.

Additionally, it is also known that a switchable polarity solvent, whose solubility is converted upon a certain stimulus, is used as the acid gas absorbent. The switchable polarity solvent includes a water-insoluble amine that is made soluble in water upon absorption of acid gases, such as carbon dioxide. Even if such a switchable polarity solvent is used, the heat treatment is needed to regenerate the acid gas absorbent, and energy saving is also required as in the case of CCS.

In general, when a strong acid is added to an acid gas absorbent with acid gas, the weak acid gas, such as carbon dioxide, is released according to acid strength. Heating is less required in this method, but the strong acid should be separated from the acid gas absorbent to avoid undesirable circulation of the strong acid within the industrial plants. Thus, this method is not suitable for regeneration of the absorbent. In addition, the acid gases are released by a stoichiometric reaction, which is completed in a short period of time and does not provide a continuous release of acid gas.

Therefore, the method mentioned above is not suitable for CCS plants, which is desired continuous operation.

Meanwhile, although the alternative method using a solid acid, a nitride, or an oxide have been developed for absorbent regeneration, further research have been required for efficient acid gas separation and removal at low temperature.

