Patent ID: 8741028

Claim:
A carbon dioxide separating and recovering system comprising: an absorption tower configured to cause carbon dioxide to be absorbed in an absorbing solution, and exhaust a rich solution as the absorbing solution in which the carbon dioxide is absorbed; a regeneration tower configured to release the carbon dioxide from the rich solution, and exhaust a lean solution as the absorbing solution having a dissolved carbon dioxide concentration lower than a dissolved carbon dioxide concentration in the rich solution; a rich solution transferring pump configured to transfer the rich solution from an outlet of the absorption tower to an inlet of the regeneration tower; a lean solution transferring pump configured to transfer the lean solution from an outlet of the regeneration tower to an inlet of the absorption tower; and at least one measuring apparatus configured to measure an ultrasound propagation speed in the absorbing solution flowing in the system, each of the at least one measuring apparatus comprising: a temperature measuring unit configured to measure a temperature of the absorbing solution; an ultrasound generator configured to generate ultrasound in the absorbing solution; an ultrasound propagation speed measuring unit configured to measure the ultrasound propagation speed by using the ultrasound; and a dissolved carbon dioxide concentration calculator configured to calculate a dissolved carbon dioxide concentration in the absorbing solution, based on the temperature measured by the temperature measuring unit, the ultrasound propagation speed measured by the ultrasound propagation speed measuring unit, and a correlation expression which shows a relationship between the dissolved carbon dioxide concentration and the ultrasound propagation speed in the absorbing solution, and is changed according to the temperature of the absorbing solution, wherein the at least one measuring apparatus comprises first to fourth measuring apparatuses configured to measure the ultrasound propagation speeds in the lean solution flowing in a vicinity of the inlet of the absorption tower, in the rich solution flowing in a vicinity of the outlet of the absorption tower, in the rich solution flowing in a vicinity of the inlet of the regeneration tower, and in the lean solution flowing in a vicinity of the outlet of the regeneration tower, respectively, and wherein the carbon dioxide separating and recovering system is configured to control the system, based on the dissolved carbon dioxide concentrations calculated by the measuring apparatuses.