Waste heat recovery device, gas turbine plant provided with same, and waste heat recovery method

A waste heat recovery device comprising:

• a low-boiling-point medium Rankine cycle in which a low-boiling-point medium circulates while the low-boiling-point medium is repeatedly condensed and evaporated;
• a heated water line that guides heated water in liquid form to the low-boiling-point medium Rankine cycle from a boiler configured to heat the water by using high-temperature gas;
• a water recovery line that returns the water, which has been led from the heated water line to the low-boiling-point medium Rankine cycle, and passed through the low-boiling-point medium Rankine cycle, to the boiler;
• a water supply line that supplies the water to the boiler;
• and
• a heat exchanger that exchanges heat between a medium apart from the high-temperature gas and at least one of the water flowing in the water recovery line, the water flowing in the heated water line, and the water flowing in the water supply line,
• wherein the low-boiling-point medium Rankine cycle includes a heater that heats the low-boiling-point medium by exchanging heat between the low-boiling-point medium in liquid form, and the water, which is the liquid having passed through the heated water line.

A waste heat recovery method comprising:

• a Rankine cycle-performing step of circulating a low-boiling-point medium in a low-boiling-point medium Rankine cycle such that the low-boiling-point medium is repeatedly condensed and evaporated;
• a heated water-introducing step of guiding heated water in liquid form to the low-boiling-point medium Rankine cycle from a boiler that heats the water by high-temperature gas;
• and
• a water recovery step of returning the water, which has been guided to the low-boiling-point medium Rankine cycle and has passed through the low-boiling-point medium Rankine cycle, to the boiler,
• a water supply step of supplying the water to the boiler;
• and
• a heat-exchange step of exchanging heat between a medium apart from the high-temperature gas and at least one of the water flowing in the heated water-introducing step, the water flowing in the water recovery step, and the water flowing in the water supply step,
• wherein the Rankine cycle-performing step includes a heating step of heating the low-boiling-point medium by exchanging heat between the water, which is the liquid introduced to the low-boiling-point medium Rankine cycle, and the low-boiling-point medium that is a liquid.