Method for indirectly preheating a fluid upstream of a furnace, wherein the fluid is preheated by indirect heat exchange with fumes discharged from the furnace through a medium in a chamber, and wherein the flow rate of the medium in the chamber is adjusted on the basis of at least one of the following temperatures: the temperature of the discharged fumes, the temperature of the medium in the chamber, the temperature of the preheated fluid, and the temperature of the wall separating the discharged fumes from the medium in the chamber.

Method for indirectly preheating a fluid upstream of a furnace, wherein the fluid is preheated by indirect heat exchange with fumes discharged from the furnace through a medium in a chamber, and wherein the flow rate of the medium in the chamber is adjusted on the basis of at least one of the following temperatures: the temperature of the discharged fumes, the temperature of the medium in the chamber, the temperature of the preheated fluid, and the temperature of the wall separating the discharged fumes from the medium in the chamber.

A method for improving effectiveness of a steam generator system includes providing air to an air preheater at a mass flow such that the air preheater has a cold end outlet temperature defined by the improved air preheater operating with increased heat recovery (HR) of at least 1% calculated according to the equation: HR=100%?((Tgi?TgoAdvX)/(Tgi?TgoSTD)?1). The method requires either reducing the amount of heat that flows into the air preheater from the flue gas and/or increasing the amount of heat extracted from the flue gas. The method includes mitigating SO.sub.3 in the flue gas which is discharged directly from the air preheater to a particulate removal system and then directly into a flue gas desulfurization system. The method includes extracting heat from the Flue gas to create equipment preheat and/or flue gas stack reheat air with the latter being fed to heat the flue gas prior to entering a discharge stack to raise the temperature of the flue gas to mitigate visible plume exiting and to mitigate corrosion in, the discharge stack.

A method for improving effectiveness of a steam generator system includes providing air to an air preheater in excess of that required for combustion of fuel and providing the air at a mass flow such that the air preheater has a cold end metal temperature that is no less than a water dew point temperature in the air preheater and such that the cold end metal temperature is less than a sulfuric acid dew point temperature. The method includes mitigating SO.sub.3 in the flue gas which is discharged directly from the air preheater to a particulate removal system and then directly into a flue gas desulfurization system. Flue gas reheat air is fed from the air preheater to heat the flue gas prior to entering a discharge stack to raise the temperature of the flue gas to mitigate visible plume exiting and to mitigate corrosion in the discharge stack.

A method for improving effectiveness of a steam generator system includes providing a steam generator system including a steam generator vessel, an air supply system and an air preheater. The air supply system is in communication with the steam generator vessel through the air preheater and the steam generator vessel is in communication with the air preheater. The air supply system provides a first amount of air to the air preheater. At least a portion of the first amount of air is provided to the steam generator vessel. A flue gas mixture is discharged from the steam generator vessel. At least a portion of the flue gas mixture flows into the air preheater. SO.sub.3 in the flue gas mixture is mitigated before the flue gas mixture enters the air preheater.

The invention relates to a unit and method for melting in a furnace comprising a combustion-heated melting chamber, in which the air is heated by means of heat exchange with the fumes generated by combustion. The heated air is used in a gas turbine in order to generate electrical and/or mechanical energy. In addition, the effluent from the gas turbine is used to pre-heat the combustion oxygen and/or gaseous fuel upstream of the melting chamber.

A heater includes a radiant section with a bottom wall and a side wall. A burner is provided on the bottom wall and a primary fuel stream and a primary combustion air stream are provided through the burner to support a primary combustion reaction local to the burner. The primary combustion air stream may be less than the air needed to burn all of the primary fuel stream, resulting in the primary combustion reaction being sub-stochiometric and reducing NOx formation. A remote air pipe injects remote air into the radiant section distal to the burner, and in some cases, spaced from the burner by at least two meters. The remote air addition supports a lean secondary combustion reaction that further minimizes NOx emissions concentration. The heater is suitable for use with high H2 fuel or preheated air, or both, to lower CO2 emissions while meeting NOx emission targets.