Control method and control device for exhaust heat recovery system for marine vessel

A control device for an exhaust heat recovery system which comprises an exhaust gas economizer to which exhaust gas generated in a main engine of a vessel is introduced via a turbocharger, a steam turbine powered by steam generated in the exhaust gas economizer, a gas turbine driving a generator together with the steam turbine, an auxiliary generator compensating for a decline in electricity based on power generation by the generator and a portion of the exhaust gas generated in the main engine is supplied to the gas turbine so as to discharge (amount of heat of) the exhaust gas from the gas turbine to the exhaust gas economizer, the control device comprising:

• an acquiring unit which estimates or calculates a current reserve heat amount (Q) based on a heat energy detection signal of the exhaust gas economizer;
• an acquiring unit which obtains, based on an operation state of the auxiliary generator and power demand within the vessel, a reference heat amount (Qmin) which is required to maintain requisite power until the auxiliary generator is actuated;
• and
• a control unit which controls the auxiliary generator by selecting an operation state of the auxiliary generator from a shutoff state, a standby state and a driving state so that the current reserve heat amount (Q) becomes greater than the reference heat amount (Qmin).

The control device for the exhaust heat recovery system, further comprising:

• a bypass line which bypasses the gas turbine to supply a portion of the exhaust gas generated in the main engine to the exhaust gas economizer;
• a bypass valve which is arranged in the bypass line and changes a flow rate of the exhaust gas;
• and
• a bypass valve adjusting unit which adjusts an opening of the bypass valve so that the current reserve heat amount (Q) reserved in the exhaust gas economizer becomes greater than the reference heat amount (Qmin).