Amount of seawater control device for scrubber, amount of seawater control method for scrubber, and amount of alkali control device and amount of alkali control method

An amount of seawater control device for a scrubber, which controls an amount of seawater supplied to a scrubber that purifies sulfur oxide contained in exhaust gas from an engine by bringing the sulfur oxide into contact with seawater, comprising:

• a minimum amount of seawater converter connected to the engine, the minimum amount of seawater converter being configured to
• receive an engine output from the engine and an input indicating a sulfur content of fuel oil, and
• calculate a minimum amount of seawater which is a minimum amount of seawater necessary for an absorption reaction of the sulfur oxide by the seawater, from the engine output, the sulfur content of fuel oil and a predetermined alkalinity of the seawater;
• an amount of seawater correction converter connected to the minimum amount of seawater converter, the amount of seawater correction converter being configured to
• receive the minimum amount of seawater from the minimum amount of seawater converter, and
• calculate a corrected amount of seawater which is an amount of seawater at which the sulfur oxide contained in the exhaust gas discharged into atmosphere from the scrubber is equal to or less than a set variable based on a measured value of the sulfur oxide contained in the exhaust gas;
• and
• a pump control device connected to the minimum amount of seawater converter and the amount of seawater correction converter, the pump control device being configure to control the amount of seawater supplied to the scrubber in accordance with a set amount of seawater that is a sum of the minimum amount of seawater calculated by the minimum amount of seawater converter and the corrected amount of seawater calculated by the amount of seawater correction converter.