Treatment method for reducing carbon dioxide emission of combustion exhaust gas

A treatment method for reducing carbon dioxide emission of combustion exhaust gas using a caustic soda aqueous solution as a carbon dioxide absorbing liquid, the method comprising:

• a caustic soda synthesis step;
• and
• a treatment step of reducing carbon dioxide emission of combustion exhaust gas,
• wherein the caustic soda synthesis step is a step in which a caustic soda aqueous solution and calcium carbonate precipitate are generated by a causticization reaction by adding slaked lime to a natural sodium carbonate aqueous solution prepared by dissolving refined powder of natural sodium carbonate ore in water, and are subjected to solid-liquid separation or a natural sodium carbonate aqueous solution obtained by filtering an aqueous solution in which pulverized sodium carbonate ore powder is dissolved in a caustic soda aqueous solution to convert the sodium bicarbonate as a component into sodium carbonate, and removing and refining water insoluble components to obtain a synthetic caustic soda aqueous solution,
• the treatment step of reducing carbon dioxide emission of combustion exhaust gas is a step in which the synthetic caustic soda aqueous solution generated in the caustic soda synthesis step and purified combustion exhaust gas are brought into gas-liquid countercurrent contact so that carbon dioxide in the exhaust gas is reduced by being absorbed by the synthetic caustic soda aqueous solution and immobilized as sodium carbonate, and
• in the caustic soda synthesis step, the calcium carbonate precipitate obtained by solid-liquid separation of the caustic soda aqueous solution and the calcium carbonate precipitate produced by the causticization reaction is set as light calcium carbonate by washing the attached caustic soda with water and drying, and alkaline drainage generated by a water washing treatment is recycled to in the aqueous solution preparation step of sodium carbonate ore.

A treatment system for reducing carbon dioxide emission of combustion exhaust gas using a caustic soda aqueous solution as a carbon dioxide absorbing liquid, the system comprising:

• a caustic soda synthesis apparatus;
• and
• a treatment apparatus for reducing carbon dioxide emission of combustion exhaust gas,
• wherein the caustic soda synthesis apparatus is an apparatus in which a caustic soda aqueous solution and calcium carbonate precipitate are generated by a causticization reaction due to slaked lime by using a natural sodium carbonate aqueous solution prepared by dissolving refined powder of natural sodium carbonate ore in water or a natural sodium carbonate aqueous solution obtained by filtering an aqueous solution in which pulverized sodium carbonate ore powder is dissolved in a caustic soda aqueous solution to convert the sodium bicarbonate as a component into sodium carbonate, and are subjected to solid-liquid separation to obtain a synthetic caustic soda aqueous solution,
• the treatment apparatus of reducing carbon dioxide emission of combustion exhaust gas is an apparatus in which the synthetic caustic soda aqueous solution generated in the caustic soda synthesis apparatus and purified combustion exhaust gas are brought into gas-liquid countercurrent contact so that carbon dioxide in the exhaust gas is reduced by being absorbed by the synthetic caustic soda aqueous solution and immobilized as sodium carbonate, and
• in the caustic soda synthesis apparatus, the calcium carbonate precipitate obtained by solid-liquid separation of the caustic soda aqueous solution and the calcium carbonate precipitate produced by the causticization reaction is set as light calcium carbonate by washing the attached caustic soda with water and drying, and alkaline drainage generated by a water washing treatment is recycled to in the aqueous solution preparation step of sodium carbonate ore.