Abstract: A once-through steam generator comprises a duct having an inlet end in communication with a source of a hot gas; and a tube bundle installed in the duct and comprising multiple heat transfer tubes. The tube bundle has an economizer section, an evaporator section, and a superheater section. A steam separating device may be positioned between the evaporator section and the superheater section, wherein, as part of a wet start-up, hot water collected by the steam separating device is delivered from the steam separating device to mix with cold feedwater before it is introduced into the economizer section. A start-up module may be positioned in the duct near the inlet end, wherein, as part of a dry start-up, cold feedwater is delivered into the start-up module to generate hot water that is then mixed into the feedwater stream before it is introduced into the economizer section.

Abstract: A once-through steam generator comprises a duct having an inlet end in communication with a source of a hot gas; and a tube bundle installed in the duct and comprising multiple heat transfer tubes. The tube bundle has an economizer section, an evaporator section, and a superheater section. A steam separating device may be positioned between the evaporator section and the superheater section, wherein, as part of a wet start-up, hot water collected by the steam separating device is delivered from the steam separating device to mix with cold feedwater before it is introduced into the economizer section. A start-up module may be positioned in the duct near the inlet end, wherein, as part of a dry start-up, cold feedwater is delivered into the start-up module to generate hot water that is then mixed into the feedwater stream before it is introduced into the economizer section.

Abstract: A once-through steam generator comprises a duct having an inlet end in communication with a source of a hot gas; and a tube bundle installed in the duct and comprising multiple heat transfer tubes. The tube bundle has an economizer section, an evaporator section, and a superheater section. A steam separating device may be positioned between the evaporator section and the superheater section, wherein, as part of a wet start-up, hot water collected by the steam separating device is delivered from the steam separating device to mix with cold feedwater before it is introduced into the economizer section. A start-up module may be positioned in the duct near the inlet end, wherein, as part of a dry start-up, cold feedwater is delivered into the start-up module to generate hot water that is then mixed into the feedwater stream before it is introduced into the economizer section.

Abstract: An increased efficiency boiler is provided, which, instead of trying to eliminate steaming in the economizer, designs the economizer to permit steaming, and a control is provided for the boiler which takes into account the heat input to the boiler as well as the water level in the steam drum and the reliability of the economizer.