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

Abstract

A method for controlling an amount of seawater supplied to a scrubber that purifies sulfur oxide contained in exhaust gas by bringing the sulfur oxide into contact with seawater, includes calculating a minimum amount of seawater necessary for an absorption reaction of the sulfur oxide by the seawater, from an engine output, a sulfur content of fuel oil, and a predetermined alkalinity of the seawater, calculating a corrected amount of seawater as an amount of seawater at which the sulfur oxide 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 in the exhaust gas, calculating a set amount of seawater by summing the minimum amount of seawater and the corrected amount of seawater and implementing control such that seawater corresponding to the set amount is supplied to the scrubber.

What is claimed is: 
     
         1 . An amount of seawater control method for a scrubber, which controls an amount of seawater supplied to a scrubber that purifies sulfur oxide contained in exhaust gas by bringing the sulfur oxide into contact with seawater, comprising the steps of:
 calculating 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 an engine output, a sulfur content of fuel oil and a predetermined alkalinity of the seawater;   calculating 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;   calculating a set amount of seawater by summing the minimum amount of seawater and the corrected amount of seawater; and   implementing control such that seawater corresponding to the set amount of seawater is supplied to the scrubber.   
     
     
         2 . The amount of seawater control method for a scrubber according to  claim 1 , further comprising the steps of:
 calculating an alkali injection amount from an amount of an alkali component which is contained in seawater corresponding to the set amount of seawater; and   implementing control in such a manner that an alkali agent corresponding to the alkali injection amount is injected into recycled seawater which is supplied to the scrubber.   
     
     
         3 . A method, comprising:
 calculating a first amount of seawater for obtaining an absorption reaction with a first amount of sulfur oxide in an exhaust gas;   calculating a second amount of seawater based on processing variables including a second amount of sulfur oxide in scrubbed exhaust gas that is discharged by a scrubber for scrubbing the exhaust gas;   calculating a third amount of seawater based on the first amount of seawater and the second amount of seawater; and   supplying the third amount of seawater to the scrubber.   
     
     
         4 . The method of  claim 3 , wherein:
 the calculating the first amount of seawater comprises processing variables including an engine output value, a sulfur content of fuel oil and a predetermined alkalinity of the seawater; and   the calculating the second amount of seawater comprises processing variables including a measured value of the sulfur oxide in the exhaust gas.   
     
     
         5 . The method of  claim 4 , wherein the calculating the second amount of seawater further comprises processing variables including a CO 2  concentration in the scrubbed exhaust gas and a designated emission ratio. 
     
     
         6 . The method of  claim 5 , wherein the calculating the second amount of seawater further comprises performing PID (proportional, integral and derivative) control based on:
 a set variable corresponding to an amount of sulfur oxide to be purified based at least partly on the designated emission ratio and the CO 2  concentration; and   the second amount of sulfur oxide in the scrubbed exhaust gas.