BOILER PLANT AND BOILER PLANT OPERATING METHOD

摘要

A boiler plant, which improves efficiency due to having a simple structure, and which reliably recovers waste heat from exhaust gas and heats combustion air, is provided. The boiler plant is provided with: a circulation flow path (33) in which hot water converges in a water supply system after having branched off midway through the water supply system; a water-heating-type air preheater (37), which is disposed on the circulation flow path (33), and which exchanges heat with combustion air; a hot water economizer (39), which is disposed downstream from the water-heated-type air preheater (37) in the direction in which the hot water flows, and which exchanges heat with the exhaust gas of the boiler; a flow regulating means which regulates the flow of hot water that flows through the circulation flow path (33); a hot water temperature gauge (45), which detects the temperature of hot water discharged from the water-heating-type air preheater (37); an exhaust gas temperature gauge (47), which detects the temperature of exhaust gas discharged from the hot water economizer (39); and a controller (49), which controls the flow of hot water by regulating the flow regulating means in such a manner that the hot water temperature remains lower than a first predetermined temperature, and in such a manner that the exhaust gas temperature remains higher than a second predetermined temperature, which is set higher than the first predetermined temperature.