Method and system for improving boiler effectiveness

A method for improving effectiveness of a steam generator system, the method comprising:

• providing a steam generator system comprising a steam generator vessel, an air supply system, an improved air preheater, a particulate removal system, a flue gas desulfurization system and a flue gas discharge stack, with the air supply system being in communication with the steam generator vessel through the air preheater, and with the steam generator vessel being in communication with the discharge stack through the air preheater, the particulate removal system and the flue gas desulfurization system, with the particulate removal system being located downstream of the air preheater, with the flue gas desulfurization system being located downstream of the particulate removal system and with the discharge stack being located downstream of the particulate removal system;
• the air supply system providing a first amount of air to the air preheater at a mass flow sufficient to establish a first temperature of a flue gas mixture exiting the air preheater, the first temperature being 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% as calculated according to the equation:
• HR=100%×((Tgi−TgoAdvX)/(Tgi−TgoSTD)−1);
• mitigating SO3 in the flue gas mixture generated in the steam generator vessel, the mitigating of SO3 occurring before the flue gas mixture enters the air preheater;
• configuring the air preheater to heat the first amount of air to a second temperature of about 288° C. to 399° C. (550° F. to 750° F.);
• supplying a first portion or all of the first amount of air as combustion air to the steam generator vessel for combustion of the fuel;
• discharging all or a portion of the flue gas mixture exiting the steam generator vessel at the first temperature, directly from the air preheater to the particulate removal system thereby removing particulate from the flue gas mixture and creating a first treated flue gas mixture;
• and
• discharging the first treated flue gas mixture from the particulate removal system directly into the flue gas desulfurization system thereby creating in and discharging from the flue gas desulfurization system, a second treated flue gas mixture at a third temperature;
• the third temperature being of a magnitude sufficient to facilitate injection of a second portion of air as preheat air providing heat to at least one of a coal drying facility and to preheat the steam generator vessel.

A system for improving effectiveness of a steam generator system, the system comprising:

• a steam generator vessel;
• an air preheater in communication with the steam generator vessel;
• an air supply system configured to provide air to the steam generator vessel through the air preheater;
• a particulate removal system;
• a flue gas desulfurization system;
• a discharge stack;
• and the steam generator vessel being in communication with the discharge stack through the air preheater, the particulate removal system and the flue gas desulfurization system, with the particulate removal system being located directly downstream of the air preheater, the flue gas desulfurization system being located directly downstream of the particulate removal system and with the discharge stack being located directly downstream of the flue gas desulfurization system;
• the air supply system being configured to provide a first amount of air to the air preheater at a mass flow sufficient to establish a first temperature of a flue gas mixture exiting the air preheater, the first temperature being 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, and the first temperature being from about 105° C. (220° F.) to about 125° C. (257° F.);
• SO3 mitigation means upstream of the air preheater, the SO3 mitigation means being configured to mitigate SO3 in the flue gas mixture generated in the steam generator vessel;
• the air preheater being configured to heat the first amount of air to a second temperature of about 288° C. to 399° C. (550° F. to 750° F.);
• the particulate removal system being configured to convey the flue gas mixture at a third temperature directly to the flue gas desulfurization system;
• an excess air duct in communication with the air preheater and a second duct positioned between the flue gas desulfurization system and the discharge stack, the excess air duct being configured to convey a second portion of the first amount of air as flue gas reheat air fed from the air preheater at the second temperature from the air preheater to the second duct;
• and
• injection means located between the flue gas desulfurization system and the discharge stack, the injection means being configured to discharge the flue gas into the discharge stack at a fourth temperature,
• wherein the third temperature is of a magnitude sufficient to allow the flue gas reheat air to raise the fourth temperature to a magnitude sufficient to mitigate visible plume exiting the discharge stack and to mitigate corrosion in the discharge stack.

A method for retrofitting a steam generator system for improved effectiveness, the method comprising:

• removing at least one heat exchanger positioned downstream of an air preheater:
• reconfiguring an air supply source to the air preheater to supply a first amount of air at a mass flow sufficient to establish a first temperature of a flue gas mixture exiting the air preheater, the first temperature being 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 and the first temperature being from about 105° C. (220° F.) to about 125° C. (257° F.);
• providing SO3 mitigation means in communication with the steam generator vessel, the mitigation means being configured to mitigate the SO3 in the flue gas mixture generated in the steam generator vessel, the mitigating of SO3 occurring before the flue gas mixture enters the air preheater;
• configuring the air preheater to heat the first amount of air to a second temperature being substantially no less than the temperature of combustion air of an original system and being about of 288° C. to 399° C. (550° F. to 750° F.) to maintain or improve boiler efficiency;
• supplying a first portion or all of the first amount of air to the steam generator vessel for combustion of the fuel;
• discharging all or a portion of the flue gas mixture exiting the steam generator vessel at the first temperature, directly from the air preheater to the particulate collection system thereby removing particulate from the flue gas mixture and creating a first treated flue gas mixture;
• discharging the first treated flue gas mixture from the particulate removal system directly into the flue gas desulfurization system thereby creating in and discharging from the flue gas desulfurization system, a second treated flue gas mixture at a third temperature;
• injecting a second portion of the first amount of air as flue gas reheat air with the second flue treated flue gas mixture at the third temperature thereby creating third treated flue gas mixture at a fourth temperature, prior to entering the discharge stack;
• and
• admitting the third treated flue gas mixture to the discharge stack at the fourth temperature,
• wherein the third temperature is of a magnitude sufficient to allow the flue gas reheat air to raise the fourth temperature to a magnitude sufficient to mitigate visible plume exiting the discharge stack and to mitigate corrosion in the discharge stack.

A method for retrofitting a wet stack steam generator system capable of flue gas outlet velocities in the order of 55 to 60 feet per second for improved effectiveness, the method comprising eliminating the wet stack permitting increased flue gas outlet velocities by:

• reconfiguring an air supply source to an air preheater to supply a first amount of air at a mass flow sufficient to establish a first temperature of a flue gas mixture exiting the air preheater, the first temperature being 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% as calculated according to the equation:
• HR=100%×((Tgi−TgoAdvX)/(Tgi−TgoSTD)−1);
• providing SO3 mitigation means in communication with the steam generator vessel, the mitigation means being configured to mitigate the SO3 in the flue gas mixture generated in the steam generator vessel, the mitigating of SO3 occurring before the flue gas mixture enters the air preheater;
• configuring the air preheater to heat the first amount of air to a second temperature being substantially no less than the temperature of combustion air of an original system and being about of 288° C. to 399° C. (550° F. to 750° F.) to maintain or improve boiler efficiency;
• supplying a first portion or all of the first amount of air to the steam generator vessel for combustion of the fuel;
• discharging all or a portion of the flue gas mixture exiting the steam generator vessel at the first temperature, directly from the air preheater to the particulate collection system thereby removing particulate from the flue gas mixture and creating a first treated flue gas mixture;
• discharging the first treated flue gas mixture from the particulate removal system directly into a flue gas desulfurization system thereby creating in and discharging from the flue gas desulfurization system, a second treated flue gas mixture at a third temperature;
• injecting a second portion of the first amount of air as flue gas reheat air with the second flue treated flue gas mixture at the third temperature thereby creating third treated flue gas mixture at a fourth temperature, prior to entering the discharge stack;
• and
• admitting the third treated flue gas mixture to the discharge stack at the fourth temperature,
• wherein the third temperature is of a magnitude sufficient to allow the flue gas reheat air to raise the fourth temperature to a magnitude sufficient facilitate a dry stack to mitigate visible plume exiting the discharge stack and to mitigate corrosion in the discharge stack, and
• wherein the retrofitted steam generator system is capable of running at increased loads at which the flue gas outlet velocities exceeds those previously permitted with a wet stack.

A method for improving effectiveness of a steam generator system, the method comprising:

• providing a steam generator system comprising a steam generator vessel, an air supply system, an air preheater, a first particulate removal system, a second particulate removal system, a flue gas desulfurization system, and a flue gas discharge stack, with the air supply system being in communication with the steam generator vessel through the air preheater, and with the steam generator vessel being in communication with the discharge stack through the air preheater, the first particulate removal system and the flue gas desulfurization system, with the first particulate removal system being located downstream of the air preheater, with the flue gas desulfurization system being located downstream of the first particulate removal system;
• with the discharge stack being located downstream of the flue gas desulfurization system and with the air preheater being in communication with the discharge stack through the second particulate removal system;
• providing a humidity sensor disposed between the steam generator vessel and the air preheater;
• providing an infrared sensor in the air preheater;
• measuring humidity of a flue gas mixture with the humidity sensor to determine a magnitude of a first temperature;
• the air supply system providing a first amount of air to the air preheater at a mass flow sufficient to establish a first temperature of a flue gas mixture exiting the air preheater, the first temperature being 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 and the first temperature being from about 105° C. (220° F.) to about 125° C. (257° F.);
• determining, with the infrared sensor, the cold end metal temperature in the air preheater;
• comparing the cold end metal temperature to the water dew point temperature;
• controlling the cold end metal temperature to be no less than the water dew point temperature;
• mitigating SO3 in the flue gas mixture generated in the steam generator vessel, the mitigating of SO3 occurring before the flue gas mixture enters the air preheater;
• configuring the air preheater to heat the first amount of air to a second temperature of about 288° C. to 399° C. (550° F. to 750° F.);
• supplying a first portion or all of the first amount of air as combustion air to the steam generator vessel for combustion of the fuel;
• discharging all or a portion of the flue gas mixture exiting the steam generator vessel at the first temperature, directly from the air preheater to the particulate removal system thereby removing particulate from the flue gas mixture and creating a first treated flue gas mixture;
• discharging the first treated flue gas mixture from the particulate removal system directly into the flue gas desulfurization system thereby creating in and discharging from the flue gas desulfurization system, a second treated flue gas mixture at a third temperature of 52° C. to 60° C. (125° F. to 140° F.);
• removing particulate contaminants from the second portion of air, the particulate contaminants being introduced to the second portion of air from leakage within the air preheater from the flue gas mixture;
• injecting a second portion of the first amount of air as flue gas reheat with the second flue treated flue gas mixture at the third temperature thereby creating third treated flue gas mixture at a fourth temperature of at least 68° C. (155° F.), prior to entering the discharge stack;
• and
• admitting the third treated flue gas mixture to the discharge stack at the fourth temperature.