An exhaust gas cooler includes: a steam drum containing first water; an economizer for heat exchange between exhaust gas and the first water supplied from the steam drum; and a feedwater pipe for supplying the first water with second water having a lower temperature than the first water. The exhaust gas cooler is configured such that the first water flowing out of the economizer is introduced into the steam drum. The second water is divided and supplied to the first water flowing out of the economizer and the first water flowing into the economizer.

An economizer having a structure capable of efficiently warming water and facilitating inspection and cleaning is obtained. In an economizer for warming water by combustion exhaust gas generated by a boiler, to a cylindrical water pipe in which an inflow port and an outflow port are formed on a side surface and through which the water passes, a plurality of gas pipes erected for circulating the combustion exhaust gas are arranged in corresponding fan-shaped portions of the water pipe. The combustion exhaust gas introduced from a bottom surface side of the water pipe folds back at an upper part of the water pipe and flows downward, then folds back at a lower part of the water pipe, flows upward, and flows out from an upper surface side of the water pipe, whereby the plurality of gas pipes efficiently warms the water in the water pipe.

An economizer having a structure capable of efficiently warming water and facilitating inspection and cleaning is obtained. In an economizer for warming water by combustion exhaust gas generated by a boiler, to a cylindrical water pipe in which an inflow port and an outflow port are formed on a side surface and through which the water passes, a plurality of gas pipes erected for circulating the combustion exhaust gas are arranged in corresponding fan-shaped portions of the water pipe. The combustion exhaust gas introduced from a bottom surface side of the water pipe folds back at an upper part of the water pipe and flows downward, then folds back at a lower part of the water pipe, flows upward, and flows out from an upper surface side of the water pipe, whereby the plurality of gas pipes efficiently warms the water in the water pipe.

Heat recovery steam generator-method, comprising a casing, upstream coils of heat exchanger tubes downstream from casing inlet, one or more feedwater heater coils in casing downstream from upstream coils, one or more low temperature heat exchanging coils in casing downstream from upstream coils, one or more low temperature heat exchanging coils within casing comprising corrosion-resistant, thermally conductive graphite component-thermoplastic polymer component composite material, a first flow conduit extending from low temperature heat exchanging coil to feedwater heater coil for water to flow from low temperature coil to feedwater heater coil; and second conduit extending from one or more feedwater heater coils to one or more of the upstream coils for flow from feedwater heater coil to one or more upstream coils, so gas passing through inlet passes through upstream coils through one or more feedwater heater coils and then through one or more low temperature coils.

Heat recovery steam generator-method, comprising a casing, upstream coils of heat exchanger tubes downstream from casing inlet, one or more feedwater heater coils in casing downstream from upstream coils, one or more low temperature heat exchanging coils in casing downstream from upstream coils, one or more low temperature heat exchanging coils within casing comprising corrosion-resistant, thermally conductive graphite component-thermoplastic polymer component composite material, a first flow conduit extending from low temperature heat exchanging coil to feedwater heater coil for water to flow from low temperature coil to feedwater heater coil; and second conduit extending from one or more feedwater heater coils to one or more of the upstream coils for flow from feedwater heater coil to one or more upstream coils, so gas passing through inlet passes through upstream coils through one or more feedwater heater coils and then through one or more low temperature coils.

A steam generation apparatus includes: a heat medium flow passage through which a heat medium flows; a primary economizer disposed in the heat medium flow passage; a secondary economizer disposed in the heat medium flow passage at an upstream side of the primary economizer with respect to a flow direction of the heat medium; a primary evaporator disposed in the heat medium flow passage at an upstream side of the secondary economizer with respect to the flow direction of the heat medium; a first flash tank for generating flash steam; a first feed water line configured to supply water heated by the primary economizer to the secondary economizer; and a second feed water line disposed so as to branch from the first feed water line and configured to supply the water heated by the primary economizer to the first flash tank.

A steam generation apparatus includes: a heat medium flow passage through which a heat medium flows; a primary economizer disposed in the heat medium flow passage; a secondary economizer disposed in the heat medium flow passage at an upstream side of the primary economizer with respect to a flow direction of the heat medium; a primary evaporator disposed in the heat medium flow passage at an upstream side of the secondary economizer with respect to the flow direction of the heat medium; a first flash tank for generating flash steam; a first feed water line configured to supply water heated by the primary economizer to the secondary economizer; and a second feed water line disposed so as to branch from the first feed water line and configured to supply the water heated by the primary economizer to the first flash tank.

A water heater includes a water tank and a flow-through heating element. The water tank contains heated water. The flow-through heating element is located in the lower portion of the water tank and heats water as water is passed through an interior channel of the heating element. In another configuration, the water heater further includes a recirculation line and the heating element further includes an input end external of the water tank to receive water to be heated and an output end to output heated water into the water tank. The recirculation line transports water from the water tank to the input end of the heating element that is external of the water tank.

A water heater includes a water tank and a flow-through heating element. The water tank contains heated water. The flow-through heating element is located in the lower portion of the water tank and heats water as water is passed through an interior channel of the heating element. In another configuration, the water heater further includes a recirculation line and the heating element further includes an input end external of the water tank to receive water to be heated and an output end to output heated water into the water tank. The recirculation line transports water from the water tank to the input end of the heating element that is external of the water tank.

An exhaust gas cooler includes: a steam drum containing first water; an economizer for heat exchange between exhaust gas and the first water supplied from the steam drum; and a feedwater pipe for supplying the first water with second water having a lower temperature than the first water. The exhaust gas cooler is configured such that the first water flowing out of the economizer is introduced into the steam drum. The second water is divided and supplied to the first water flowing out of the economizer and the first water flowing into the economizer