Patent Description:
A boiler typically includes a furnace in which fuel is burned to generate heat to produce steam. The combustion of the fuel creates thermal energy or heat, which is used to heat and vaporize a liquid, such as water, which makes steam. The generated steam may be used to drive a turbine to generate electricity or to provide heat for other purposes. Fossil fuels, such as pulverized coal, natural gas and the like are typical fuels used in many combustion systems for boilers. For example, in an air-fired pulverized coal boiler, atmospheric air is fed into the furnace and mixed with the pulverized coal for combustion. In an oxy-fired pulverized coal boiler, concentrated levels of oxygen are fed into the furnace and mixed with pulverized coal for combustion.

Boiler/piping/turbine thermal masses lend themselves well to the power markets that are capacity and base loaded to maintain operational efficiencies and component lifecycles. Today's power market is shifting from base load to cyclic and peak loading brought on by increasing participation of renewable energy sources. The emerging challenge facing many grid systems is grid stability associated with the sudden and cyclic electrical production profile of such renewable energy sources. As more and more renewable energy sources are added to the grid, there will be a greater need for operation of fossil fuel-fired power plants at low power and/or improve fast starting to assist stabilizing the grid.

Currently, large coal-fired plants take <NUM> to <NUM> hours from cold to be at <NUM>% of their rating. There are at least two main challenges to making large plants more responsive for electrical generation requirements. Namely, when the load of a steam turbine is reduced, pressure in the reheat system drops in direct proportion to the steam flow. In most steam power plants, the highest feed water heater is connected to the cold reheat system. The cold reheat pressure is directly related to the feed water temperature at the boiler inlet. Thus, when the cold reheat pressure is reduced, the feed water temperature at the boiler inlet is also reduced. Further, with a reduced reheat pressure, the temperature at the outlet of the hot reheat system will drop resulting in reduced cycle efficiency and longer reheat cycles. Secondly the temperature cycling of steam boiler component can impact design lifecycle and tolerances particularly for components exposed to large temperature variations e.g., high pressure steam turbine and piping, super heater configurations and the like. As a result, it is common to maintain temperatures and the reheat pressure at high levels in the plant in order to avoid imposing temperature related stresses on the boiler and turbine components. Therefore, it is desirable to maintain boiler system components at higher temperatures to reduce plant restart, warm-up, and even hot restart cycle times, while reducing stresses on plant components. <CIT> discloses a method for starting and loading a combined cycle turbine of the type having a gas turbine with a fuel flow control valve and a steam turbine with at least one steam control valve both disposed on a single shaft and having a heat recovery steam generator heated by said gas turbine and connected to supply steam to the steam control valve, the combined cycle turbine having a unified control system and driving a load and also having an auxiliary steam source connected to the steam control valve. <CIT> discloses s system configuration and operating method for a single shaft combined cycle plant comprising a gas turbine, an exhaust heat recovery boiler for generating steam using exhaust heat discharged from the gas turbine; and a steam turbine driven by steam generated from the exhaust heat recovery boiler, rotors of the gas turbine and rotors of the steam turbine being coupled, and the steam turbine comprising a high pressure turbine being supplied with and driven by high pressure steam generated at a superheater of the exhaust heat recovery boiler and a reheating turbine supplied with and driven by steam that passes through the high pressure turbine and is reheated by a reheater of the exhaust heat recovery boiler.

The system according to the invention is described in claim <NUM>. In an embodiment, a system for reheating a steam driven power generation system is described. The system includes a boiler system including a main boiler with a combustion system, the boiler system operative to generate steam when the combustion system is operative and a mixer with an input fluidly coupled to the boiler. The system also includes a plurality of steam pipes, the plurality of steam pipes including a first steam pipe and a second steam pipe and a turbine having at least a first section the turbine operable to receive steam, wherein an input to the first section of the turbine is fluidly connected via the first steam pipe to an output of at least one of the boiler and the mixer and operable to carry steam from the boiler system at a first temperature to the first section of the turbine, wherein an output of the first section of the turbine is fluidly connected to the second steam pipe, and the second steam pipe is operable to carry heated steam at a second temperature from an output of the turbine to an at least one of an input to the boiler and an input of the mixer. In addition, the system includes a first flow control valve operable to control a flow of steam through the first section of turbine, a sensor the sensor operable to monitor at least one operating characteristic in the boiler system. The system includes a control unit configured to receive information associated with the monitored operating characteristic and control at least the first flow control valve, to control the amount of steam directed through the turbine under selected conditions and when the main boiler system is not generating steam.

The method according to the invention is described in claim <NUM>. In another embodiment, described herein is a method of reheating a power generation system, having a boiler system including a main boiler and a mixer, the main boiler operative to generate steam when the combustion system is operating, and the mixer with an input fluidly coupled to the main boiler. The method including operably connecting a flow of steam at a first temperature from the mixer or the main boiler to a at least a first section of a turbine operable to receive steam, operably connecting an output of the first section of the turbine to at least one of an input to the boiler and an input of the mixer to carry heated steam at a second temperature therefrom, operably connecting a first flow control valve, the first flow control valve operable to control a flow of steam through the first section of the turbine. The method also includes monitoring at least one operating characteristic in the boiler system, receiving information associated with the monitored operating characteristic with a controller, and controlling at least the flow control valve to control the amount of steam directed through the first section of the turbine under selected conditions when the main boiler system is not generating steam to warm the boiler.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings.

The described embodiments will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:.

Reference will be made below in detail to exemplary embodiments as described herein, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference characters used throughout the drawings refer to the same or like parts. While the various embodiments as described herein are suitable for use with heat recovery steam generation systems that include combustion system, generally, a pulverized coal boiler such as for use in a pulverized coal power plant has been selected and described for clarity of illustration. Other systems may include other types of boilers, furnaces and fired heaters utilizing a wide range of fuels including, but not limited to, coal, oil and gas. For example, contemplated boilers include, but are not limited to, may both T-fired and wall fired pulverized coal boilers, circulating fluidized bed (CFB) and bubbling fluidized bed (BFB) boilers, stoker boilers, suspension burners for biomass boilers, including controlled circulation, natural circulation and supercritical boilers and other heat recovery steam generator systems.

Embodiments as described herein relate to a power generation system having a heat recovery steam generation system including a combustion system and method and control scheme therefor that provides for improving and reducing startup times in boiler systems. In particular embodiments are related to a system and method that provides a controlled shut down of the power generation system and boiler and way to pre-warm and sustain warmth in a boiler/turbine/steam piping system when starting a power plant from cold conditions and maintains the pressure/temperature of the boiler/turbine/steam piping when re-starting a power plant from hot conditions. Maintaining warmth/pre-warming the boiler system components facilitates a much shorter time period to restart the boiler/steam piping/turbine allowing the typical coal-fired power plant to be more responsive to sudden electrical grid demands. Furthermore, in periods of low grid energy demand, e.g., when grid demand is low (renewable energy contribution is high), it may be possible/desirable for some fossil fueled boilers to be required to reduce load or even discontinue operation as part of an effort to maintain and balance the electrical grid. In such cases, in accordance with one or more of the described embodiments, instead of cycling coal-fired plants to minimum load, a shutdown process is initiated and carried out with the intention to restart the plant within a span of several hours, e.g., <NUM> hours up to several days.

Immediately following furnace purge and furnace isolation, the boiler pressures and temperature will slowly decay over time, however the described embodiments include a method and system of recovering this inevitable decay by providing warming steam via a controlled admittance of steam into the steam drum/boiler. In one embodiment warming is accomplished with recovering heat generated as a result of turbine ventilation or partial ventilation. In another embodiment, warming may be accomplished with small steam flows from an auxiliary boiler/secondary steam source. Steam is supplied by a smaller auxiliary (aux. ) boiler or by a secondary steam source to generate a steam drum (or equivalent) pressure of approximately <NUM> bar without requiring the main boiler to be fired.

<FIG> illustrates a power generation system <NUM> including a heat recovery steam generation system with combustion system <NUM> having a boiler <NUM> as may be employed in power generation applications. The boiler <NUM> may be a tangentially fired boiler (also known as a T-fired boiler) or wall fired boiler. Fuel and air are introduced into the boiler <NUM> via the burner assemblies <NUM> and/or nozzles associated therewith. The combustion system <NUM> includes a fuel source such as, for example, a pulverizer <NUM> that is configured to grind fuel such as coal to a desired degree of fineness. The pulverized coal is passed from the pulverizer <NUM> to the boiler <NUM> using primary air. An air source <NUM> provides a supply of secondary or combustion air to the boiler <NUM> where it is mixed with the fuel and combusted, as discussed in detail hereinafter. Where the boiler <NUM> is an oxy-fired boiler, the air source <NUM> may be an air separation unit that extracts oxygen from an incoming air stream, or directly from the atmosphere.

The boiler <NUM> includes a hopper zone <NUM> located below a main burner zone <NUM> from which ash can be removed, the main burner zone <NUM> (also referred to as a windbox) where the air and an air-fuel mixture is introduced into the boiler <NUM>, a burnout zone <NUM> where any air or fuel that is not combusted in the main burner zone <NUM> gets combusted, a superheater zone <NUM> with superheater <NUM> where steam can be superheated by the combustion flue gases. The boiler <NUM> also includes an economizer zone <NUM> with an economizer <NUM> where water can be preheated prior to entering a steam drum <NUM> or a mixing sphere (<NUM>) to feed water to the waterwall <NUM>. Pumps <NUM> may be employed to aid in circulating preheat water to the waterwall <NUM> and through boiler <NUM>. Combustion of the fuel with the primary and secondary air within the boiler <NUM> produces a stream of flue gases that are ultimately treated and exhausted through a stack downstream from the economizer zone <NUM>. As used herein, directions such as "downstream" means in the general direction of the flue gas flow. Similarly, the term "upstream" is opposite the direction of "downstream" going opposite the direction of flue gas flow.

Generally, in operation of the power generation system <NUM> and combustion system <NUM>, the combustion of fuel in the boiler <NUM> heats water in the waterwalls <NUM> of the boiler <NUM>, which then passes through the steam drum (or equivalent), hereinafter referred to as drum <NUM> to the superheater <NUM> in the superheater zone <NUM> where additional heat is imparted to the steam by the flue gases. The superheated steam from the superheater <NUM> is then directed via a piping system shown generally as <NUM> to a high pressure section <NUM> of turbine <NUM>, where the steam is expanded and cooled to drive turbine <NUM> and thereby turn a generator <NUM> (<FIG>) to generate electricity. The expanded steam from the high pressure section <NUM> of the turbine <NUM> may then be returned to a reheater <NUM> downstream from the superheater <NUM> to reheat the steam, which is then directed to an intermediate pressure section <NUM> of turbine <NUM>, and ultimately a low pressure section <NUM> of the turbine <NUM> where the steam is successively expanded and cooled to drive turbine <NUM>.

As illustrated in <FIG>, the combustion system <NUM> includes an array of sensors, actuators and monitoring devices to monitor and control the combustion process and the resulting consequences with respect to low excess air operation. For example, temperature and pressures monitors shown generally as <NUM> are employed throughout the system to ensure proper control, operation and ensure that operational limits are not exceeded. In another example, the combustion system <NUM> may include a plurality of fluid flow control devices <NUM> that supply secondary air for combustion to each fuel introduction nozzle associated with the burner assemblies <NUM>. In an embodiment, the fluid flow control devices <NUM> may be electrically actuated air dampers that can be adjusted to vary the amount of air that is provided to each fuel introduction nozzle associated with each burner assembly <NUM>. The boiler <NUM> may also include other individually controllable air dampers or fluid flow control devices (not shown) at various spatial locations around the furnace. Each of the flow control devices <NUM> is individually controllable by a control unit <NUM> to ensure that desired air/fuel ratios and flame temperature are achieved for each nozzle location.

The combustion system <NUM> may also include a flame scanning device <NUM> associated with each individual fuel introduction nozzle or burner assembly <NUM>. The flame scanning devices <NUM> are configured to assess the local stoichiometry (air/fuel ratio) at each respective the nozzle location within the main burner zone <NUM>. In addition to detecting the respective quantities of air and fuel at each nozzle location, the flame scanning devices <NUM> are also configured to sense the flame temperature adjacent to each burner assembly <NUM>.

<FIG> also illustrates that the backpass <NUM> of the boiler <NUM> downstream from the superheater <NUM>, reheater <NUM>, and economizer <NUM> in economizer section <NUM> is fitted with a monitoring device <NUM>. The monitoring device <NUM> is configured for measurement and assessment of gas species such as carbon monoxide (CO), carbon dioxide (CO<NUM>), mercury (Hg), sulfur dioxide (SO<NUM>), sulfur trioxide (SO<NUM>), nitrogen dioxide (NO<NUM>), nitric oxide (NO) and oxygen (O<NUM>) within the backpass <NUM>. SO<NUM> and SO<NUM> are collectively referred to as SOx. Similarly, NO<NUM> and NO are collectively referred to as NOx.

Continuing with the operation of the boiler <NUM>, in operation, a predetermined ratio of fuel and air is provided to each of the burner assemblies <NUM> for combustion. As the fuel/air mixture is combusted within the furnace and flue gases are generated, the combustion process and flue gases are monitored. In particular, various parameters of the fireball and flame, conditions on the walls of the furnace, and various parameters of the flue gas are sensed and monitored. These parameters are transmitted or otherwise communicated to the combustion control unit <NUM> where they are analyzed and processed according to a control algorithm stored in memory and executed by a processor. The control unit <NUM> is configured to control the fuel provided to the boiler <NUM> and/or the air provided to the boiler <NUM>, in dependence upon the one or more monitored combustion and flue gas parameters and furnace wall conditions.

Furthermore, the power generation system <NUM> also includes an array of sensors, actuators and monitoring devices to monitor and control the heating processes associated with steam generation, and reheating in accordance with the described embodiments. For example, the power generation system <NUM> may include a plurality of fluid flow control devices e.g., <NUM> (<FIG>), that control the flow of water or steam in the system <NUM>. In an embodiment, the fluid flow control devices <NUM> may be electrically actuated valves that can be adjusted to vary the amount of flow there through. Each of the flow control devices e.g., <NUM> is individually controllable by a control unit <NUM>. The power generation system <NUM> may also include a plurality of sensors operable to monitor various other operational parameters of the power generation system <NUM> for example temperature and pressure sensors may by employed as needed to monitor the operation and effect in numerous parts of the system <NUM>. In an embodiment, the temperature and pressure sensors may each be operably connected to the control unit <NUM> or another controller as needed to implement the methodologies and functions described herein.

<FIG> depicts a simplified schematic of system for heat loss reduction and prewarming at least a portion of a power generation system <NUM> in accordance with an embodiment. The system and associated methodology provides a way to optionally reduce heat loss in the boiler <NUM> and to warm and sustain operational characteristics, including, but not limited to temperature and pressure in at least the turbine <NUM> and steam piping system <NUM> interconnecting the boiler <NUM>. It may readily be appreciated that when starting a power generation system now denoted <NUM> from cold conditions any prewarming will help reduce the overall warming, steam generation, power generation startup time, hereinafter referred to collectively as startup time. In addition, with the boiler <NUM> inoperative, each of the components of the power generation system <NUM> will slowly begin to lose heat to the ambient. The rate of heat loss can vary significantly based on the ambient temperature, exterior temperature, the particular components, as well as how well they are insulated. To that end, naturally, efforts taken to delay and reduce heat loss in the power generation system <NUM> while the boiler <NUM> is inoperative will improve the overall recovery capability and thereby start up time.

In an embodiment, a system configuration and methodology is described that provides for reducing heat losses and employing warming steam to maintain the operational characteristics, including, but not limited to temperature of the boiler <NUM>, interconnecting steam piping <NUM>, and turbine when the boiler is at least initially inoperative to facilitate re-starting a boiler <NUM> and power generation system <NUM>. Warming facilitates a quicker restarting of the boiler <NUM> and ultimately the turbine <NUM>, allowing the coal-fired power plant to be more responsive to sudden electrical grid demands. To address periods of low energy demand on the grid <NUM>, some fossil fueled power plants may be required to reduce load or even discontinue operation to maintain balance the grid <NUM>. In the latter case, the described embodiments provide for reductions of heat losses and ensure the provision of warming steam, thereby heating of the boiler <NUM>, and main steam piping e.g., <NUM> to the steam turbine <NUM>. Such warming facilitates transitioning the boiler <NUM> to producing steam more rapidly, and thereby transitioning the power generation system <NUM> to electricity production more rapidly than conventional systems.

In an embodiment the boiler <NUM> is shut down and not producing steam. It will be appreciated that an operator may employ various efforts to delay and reduce heat loss in the power generation system <NUM>. For example, once the flue gases have been sufficient purged, optionally, the circulation pump(s) <NUM> are stopped/slowed to prevent further heat losses throughout the power generation system <NUM>. Furthermore, damper <NUM> is optionally employed and closed to avoid further heat losses through draft effects in the combustion system <NUM>. In an embodiment, the damper <NUM> is selected and configured to provide tight sealing of the exhaust flue of the boiler <NUM> to minimize draft losses.

Continuing with <FIG>, during periods of low grid energy demand, when a fossil fueled power plants has reduced load or even discontinued, the described embodiments are employed to warm the power generation system <NUM>. In an embodiment, power is drawn from the grid <NUM> power the generator <NUM> as a motor. Pulling power from the grid <NUM> under such conditions (e.g., low grid demand, high contribution to the grid from renewables and the like) helps to balance and stabilize the grid <NUM>. The generator <NUM>, operating as a motor turns the turbine <NUM>. Turning the turbine <NUM> under such conditions is known in some instances as turning or motoring, and may result in ventilation of some or portions of the turbine stages, which, as a result of the work imparted upon the steam and friction in the turbine, particularly the high pressure section <NUM> of the turbine <NUM>, adds heat to the steam in the turbine <NUM>. As a result, in some embodiments, the temperature T2 downstream of the high pressure section <NUM> of the turbine <NUM> will be higher than the temperature T1 at the inlet to the high pressure section <NUM> of the turbine. In addition, there will be a small pressure drop in the high pressure section <NUM> of the turbine <NUM> as the steam expands. In an exemplary embodiment the heat generated may be captured and utilized to reheat/maintain the temperature of the boiler <NUM>. In an embodiment, about <NUM>%=<NUM>% for the rating of the power generation system <NUM> may be generated and employed for heating. However, it should also be appreciated that based on the operating conditions and the mass flow of the steam in the turbine <NUM> complete ventilation may not be necessary. In some instances, and selected optional configurations of the system, particularly when auxiliary heaters are employed, as described herein, less work need be expended in the turbine <NUM> in order to facilitate warming/maintaining the boiler <NUM> at desired temperatures and pressures. Moreover, in some embodiments, it may be possible for a portion of the turbine <NUM> or even a portion of a section e.g., the high pressure section <NUM> of the turbine <NUM> to be in ventilation, while another portion e.g., the intermediate pressure section <NUM> or low pressure section <NUM> of the turbine is generating work e.g.to drive the generator <NUM>.

Continuing with <FIG>, in an embodiment, as the turbine <NUM> is spun by the generator <NUM>, steam in the steam pipe <NUM> and high pressure section <NUM> of the turbine is warmed or at least additional energy is absorbed by virtue of the work imparted by the turbine <NUM>. The heated steam is then directed back to the mixer <NUM> and boiler <NUM>. In an embodiment the temperature(s) and pressure(s) entering and leaving the high pressure section <NUM> of the turbine <NUM> are monitored and directed to the control unit <NUM> to aid in the control. One or more of the circulation pumps <NUM> may be operated to ensure mixing and circulation of water through the boiler <NUM> and drum. In embodiments with other boiler types, including natural circulation boilers, a small auxiliary circulation pump <NUM> may be incorporated to aid in water circulation in the waterwall <NUM> of the boiler.

In an embodiment, flow control valve <NUM> is employed to control the heating/cooling of the turbine <NUM> by directing permitting the flow of more or less steam through the high pressure section <NUM> of the turbine <NUM>. In an embodiment the steam may be heated by the high pressure section <NUM> of the turbine <NUM> to a target temperature of about <NUM>, but not to exceed the temperature limits of the blades of the high pressure section <NUM> of the turbine <NUM>. In an embodiment the not to exceed temperature for the high pressure section <NUM> of the turbine <NUM> is about <NUM>. The heating of the steam in the high pressure section <NUM> of the turbine <NUM> is directly controlled by the mass flow going through it. In cases where the steam temperature approaches the maximum allowable, flow control valve <NUM> is adjusted to direct additional steam to the high pressure section <NUM> of the turbine <NUM> (thereby cooling it). Temperature measurements are made at the inlet and outlet to the high pressure section <NUM> of the turbine <NUM>. Control unit <NUM> monitors the temperatures and pressures and adjusts the flow of steam via flow control valve <NUM> to control the warming of the boiler and yet ensure protect the turbine <NUM> from exceeding high temperature limitations.

In an embodiment, the heated steam is sparged with the water in the mixer/drum <NUM>. The heated steam heats the water in the boiler <NUM> to maintain the temperatures and pressures in the boiler <NUM>. In addition, some of the higher temperature steam passes to the intermediate pressure section <NUM> and then low pressure section <NUM> of the turbine <NUM> to ensure that design temperatures limitations are adhered to for the intermediated pressure section <NUM> and low pressure section <NUM> of the turbine. Optionally some of the heating from these sections may also be captured to facilitate heating of the boiler <NUM> as described herein. Ultimately the remaining steam passes to the condenser <NUM> and on to the hot well (not shown) to be recirculated in the boiler <NUM>.

It will be appreciated that while the examples provided are described with respect to a controlled circulation boiler, such descriptions are merely illustrative. Other configurations for the boiler <NUM> as are employed in steam generation heat recovery systems are possible, including, but not limited to natural circulation boilers, and supercritical boilers. For example, in application to once through boilers (since they do not have any drum), the injection of the hot steam coming from turbine may take place at a water wall inlet or similar locations. The effect will be similar to a steam injection in a drum.

Continuing with <FIG>, in an embodiment, steam from the outlet of the high pressure section <NUM> of the turbine <NUM> may have lost sufficient pressure that it may be desirable to compress the steam to achieve a higher pressures and temperatures to aid in the sparging/mixing for reheating and maintaining temperatures and pressures for the boiler <NUM>. In addition, the mixer/boiler is generally at a higher pressure than the outlet side of the high pressure section <NUM> of the turbine <NUM>. To that end, in an embodiment an electrically driven compressor <NUM> may be employed and controlled by the control unit <NUM> to pressurize the heated steam, heating it further, and increasing its pressure as needed to facilitate mixing in the mixer <NUM>. The increase in temperature and pressure aid in maintaining targeted pressures in the mixer <NUM> and boiler <NUM>. In an embodiment, the compressor <NUM> increases the pressure to slightly higher than the current pressure in the drum <NUM>, with a temperature slightly higher than the corresponding saturation temperature experienced by the water in the drum <NUM>. To facilitate such control, the temperature and pressure in the drum <NUM>, are monitored with sensors <NUM> that are operably connected to the control unit <NUM>. In an embodiment the compressor increases the pressure to the drum pressure and maintain the boiler <NUM> warm. In an embodiment, the compressor increases the pressure to a target drum pressure of exceeding the drum pressure of <NUM> bar psi with a targeted temperature increase in excess of the saturation for the steam at that pressure. It should be appreciated that the target pressure and temperature may vary depending on where the steam is injected. It will be readily appreciated that the operation of the electrically driven compressor is advantageous in another way in that it provides for further balance and stabilization on the grid <NUM>. In examples where indirect mixing is employed, the target pressure and temperature would be based on the difference between flow and the component limitation in the system.

In another embodiment, as a result of the work imparted upon the steam and friction in the turbine in the high pressure section <NUM> of the turbine <NUM>, optionally, some of the heated steam is directed to the intermediate pressure section <NUM> and even optionally the low pressure section <NUM> of the turbine <NUM>. As a result of the continued ventilation in the intermediate pressure section <NUM> of the turbine <NUM>, heat is also added to the steam in the turbine <NUM>. As a result, the temperature T4 downstream of the intermediate pressure section <NUM> of the turbine <NUM> will be higher than the temperature T3 at the inlet to the intermediate pressure section <NUM> of the turbine <NUM>. In addition, there will be a small pressure drop in the intermediate pressure section <NUM> of the turbine <NUM> as the steam expands. In an exemplary embodiment the heat generated may be captured and utilized to reheat/maintain the temperature of the boiler <NUM>. In an embodiment the steam may be heated by ventilation of the intermediate pressure section <NUM> of the turbine <NUM> to a target temperature of about <NUM>, but not to exceed the temperature limits of the blades of the intermediate pressure section <NUM> of the turbine <NUM>. In an embodiment the not to exceed temperature for the intermediate pressure section <NUM> of the turbine <NUM> is about 400C. Furthermore, in yet another embodiment, steam from the outlet of the intermediate pressure section <NUM> of the turbine <NUM> may have lost sufficient pressure that it may be desirable to compress the steam to achieve a higher pressures and temperatures to aid in the sparging/mixing for reheating and maintaining temperatures and pressures for the boiler <NUM>. To that end, in an embodiment an electrically driven compressor <NUM> may be employed and controlled by the control unit <NUM> to pressurize the heated steam from the intermediate pressure section <NUM> of the turbine <NUM>, heating it further, and increasing its pressure. The increase in temperature and pressure aid in maintaining targeted pressures in the mixer <NUM> and boiler <NUM>. In an embodiment, the compressor <NUM> increases the pressure to slightly higher than the current pressure in the drum <NUM>, with a temperature slightly higher than the corresponding saturation temperature experienced by the water in the drum <NUM>. To facilitate such control, the temperature and pressure in the drum <NUM>, are monitored with sensors <NUM> that are operably connected to the control unit <NUM>. n an embodiment the compressor <NUM> increases the pressure to a target pressure as described herein with a targeted temperature increase at least the saturation temperature associated with the target pressure as described herein. It will be readily appreciated that the operation of the electrically driven compressor <NUM> is advantageous in that it provides for further balance and stabilization on the grid <NUM>. In an embodiment, flow control valve <NUM> is employed to control the heating/cooling of the turbine <NUM> by directing permitting the flow of more or less steam through the intermediate pressure section <NUM> of the turbine <NUM>. In an embodiment the steam may be heated by ventilation of the intermediate pressure section <NUM> of the turbine <NUM> to a target temperature of about <NUM>, but not to exceed the temperature limits of the blades of the high pressure section <NUM> of the turbine <NUM>. In an embodiment the not to exceed temperature for the intermediated pressure section <NUM> of the turbine <NUM> is about <NUM>.

In yet another embodiment, optionally, while the high pressure section <NUM> of the turbine <NUM> is operating in ventilation, or partial ventilation, steam is directed to the intermediate pressure section <NUM> and even optionally the low pressure section <NUM> of the turbine <NUM>. In this instance, the steam is employed to drive the intermediate pressure section <NUM> and/or low pressure section <NUM> and thereby provide the work needed to drive the generator <NUM>. As a result of the continued ventilation in the high pressure section <NUM> of the turbine <NUM>, heat is also added to the steam in the turbine <NUM>, while simultaneously providing motive power for at least the turbine. As a result, in this instance, the temperature T4 downstream of the intermediate pressure section <NUM> of the turbine <NUM> will be lower than the temperature T3 at the inlet to the intermediate pressure section <NUM> of the turbine <NUM>. In addition, there will be a pressure drop in the intermediate pressure section <NUM> of the turbine <NUM> as the steam expands providing work. In an exemplary embodiment the power generated may be captured and utilized to drive the turbine <NUM> to support the ventilation, or partial ventilation of the high pressure section <NUM> of the turbine <NUM> and/or to drive the generator <NUM> and direct a small amount of power to the grid. For example, if an auxiliary heater <NUM> (<FIG>) is employed, there may be there excess heat available for the heating of the boiler, such that some of the steam generated may be employed in the turbine.

To facilitate such control, the temperature and pressure in the system <NUM>, are monitored with sensors <NUM> that are operably connected to the control unit <NUM>. In an embodiment, at least the flow control valves <NUM> and <NUM> may be employed to control the heating/cooling of the turbine <NUM> by directing permitting the flow of more or less steam through the high pressure section <NUM> of the turbine <NUM> for ventilation, and through the intermediate pressure section <NUM> of the turbine <NUM> for ventilation or for power generation, while the generator <NUM> may be controlled to operate as a generator or a motor. Once again, it will be appreciated that as described herein the high pressure section <NUM> of the turbine <NUM> is employed for ventilation, while the intermediate pressure section <NUM> and low pressure section <NUM> are employed for ventilation or power generation. Such description is merely illustrative, and the system configuration is not so restrictive, any section of the turbine <NUM> could be employed for ventilation, and any other section could be utilized for power generation or ventilation if desired. That is, for example, the high pressure section <NUM> of the turbine <NUM> could be employed for power generation or ventilation, while the intermediate pressure section <NUM> of the turbine is employed for ventilation.

Turning now to <FIG> as well, <FIG> depicts another simplified schematic of system for heat loss reduction and prewarming at least a portion of a power generation system <NUM> in accordance with an embodiment. The system is the same as that described with respect to <FIG> with the exception that in the following embodiments additional components are included. Once again, the system and associated methodology provides a way to optionally reduce heat loss in the boiler, <NUM> and to warm and sustain operational characteristics, including, but not limited to temperature and pressure in at least the turbine <NUM> and steam piping system <NUM> interconnecting the boiler <NUM>. In an embodiment, a system configuration and methodology is described that provides for reducing heat losses and employing warming steam to maintain the operational characteristics, including, but not limited to temperature of the boiler <NUM>, interconnecting steam piping <NUM>, and turbine when the boiler is at least initially inoperative and not producing steam to facilitate re-starting a boiler <NUM> and power generation system <NUM>. Warming facilitates a quicker restarting of the boiler <NUM> and ultimately the turbine <NUM>, allowing the coal-fired power plant to be more responsive to sudden electrical grid demands.

Once again, in an embodiment the boiler <NUM> is shut down and not generating steam. It will be appreciated that an operator may employ various efforts to delay and reduce heat loss in the power generation system <NUM> as described herein. In an embodiment, once again power is drawn from the grid <NUM> power the generator <NUM> as a motor as described herein, turning the turbine <NUM> and generating heat therein as described herein. In an exemplary embodiment the heat generated may be captured and utilized to reheat/maintain the temperature of the boiler <NUM>. In an embodiment, the heated steam from the turbine <NUM> is then directed to the optional compressor <NUM> through a heat exchanger <NUM> to exchange its heat back to the mixer <NUM> and boiler <NUM>. In this case, since the heated steam from the high pressure section <NUM> of the turbine <NUM> is not directly mixed with the water in the mixer drum <NUM>, the compressor <NUM> is optional and may not be needed to equalize the pressure between the turbine high pressure section <NUM> and the mixer <NUM>. The hot steam is routed to the heat exchanger <NUM>, which warm up the water into the mixer <NUM> and/or the boiler <NUM> and then recirculated to the turbine <NUM>. In yet another optional embodiment compressor <NUM> may be installed downstream of the heat exchanger to add pressure to the now cooled steam as it is redirected to the turbine <NUM> to be reheated, or a different optional compressor <NUM> may be employed depending upon the configuration of the system <NUM>. Furthermore, in yet another configuration, the heat exchanger may be installed with the downtube of the boiler <NUM>. Once again, reheating is targeted to pressurize the high pressure section <NUM> of the turbine <NUM> and provide desirable target high temperatures out of the turbine <NUM> to facilitate the warming of the boiler <NUM> and facilitate a warm/hot start-up of the boiler <NUM> and ultimately the turbine <NUM>. This threshold pressure depends on plant specific characteristics, since the amount of steam flow needed to achieve targeted heating in the high pressure section <NUM> of the turbine <NUM> depends on the initial temperatures, pressures, turbine geometry and materials and the like. In an embodiment the targeted heating in the turbine <NUM> is <NUM> while the pressure from the compressor is selected to be just higher than the pressure in the drum. In an embodiment the targeted drum pressure is about <NUM> bar, though other pressures are possible depending on the design constraints of the system. The heat exchanger <NUM> can be of any configuration suitable for the exchange heat between the heated compressed steam and the mixer <NUM>. It should be appreciated that employing heat exchanger <NUM> add flexibility in the configuration of the system for reheating in that pressures between the output of the high pressure section <NUM> of the turbine and the mixer <NUM> need not be addressed. That is, the heat exchanger <NUM> facilitates permitting a pressure difference between the two. Likewise, heat exchanger <NUM> may readily be employed to directly heat the water in the boiler <NUM>.

Continuing with <FIG>, in yet another embodiment the heated steam from the high pressures section <NUM> of the turbine <NUM> is directed to the mixer <NUM> as described herein. In addition, a flash tank electric heater <NUM> may be employed in addition or as an alternative to further heat the water/steam in the mixer <NUM>. The heated steam heats the water in the boiler <NUM> to maintain the temperatures and pressures in the boiler <NUM>. In an embodiment, the steam may be heated by the high pressure section <NUM> of the turbine <NUM> to a target temperature of <NUM>, but not to exceed the temperature limits of the blades of the high pressure section <NUM> of the turbine <NUM>. In an embodiment the not to exceed temperature for the high pressure section <NUM> of the turbine <NUM> is about <NUM>. In an embodiment, the steam may be heated by the auxiliary heater to a target temperature of <NUM>, but once again not to exceed the temperature limits of the drum <NUM> or the blades of the high pressure section <NUM> of the turbine <NUM>. In an embodiment the not to exceed temperature for the high pressure section <NUM> of the turbine <NUM> is about <NUM>. The actual target temperatures and pressures may vary depending on the design and configuration of the system. For example, the temperatures may depend on the on the location of the auxiliary heater <NUM> (if employed). In case of auxiliary heater <NUM> is on the exhaust or outlet side of the high pressures section <NUM> of the turbine <NUM>, then target temperatures of <NUM>-<NUM> "nominal design temperature of the unit. " There need be any additional constraint about blades because it is located downstream. However, in an embodiment where the auxiliary heater <NUM> is located before the inlet to the high pressure section <NUM> of the turbine <NUM>, then <NUM> is employed as a target to ensure that turbine design constraints are not exceeded. In an embodiment, the auxiliary heater may be employed in addition to or in the alternative to the full ventilation of the turbine <NUM>. For example, depending on the design and construction of a given power generation system <NUM> including the boiler12 and turbine, and the losses in the steam pipes <NUM>, varying amounts of added heat may be sufficient to maintain the desired temperatures and pressures in the boiler. Under such conditions, a reduced heating from the turbine <NUM> may be sufficient. In yet another embodiment, compressor <NUM> may be employed between the boiler <NUM> and the auxiliary heater <NUM> and the input to the high pressure section <NUM> of the turbine <NUM>. In this embodiment the compressor <NUM> may be employed to ensure that the pressure of the steam being directed to the high pressure section <NUM> of the turbine <NUM> is of sufficient pressure and temperature for driving the turbine under selected conditions.

Turning now to <FIG> as well for description of a method <NUM> of operation for the employing the turbine <NUM> in ventilation mode for preheating the steam generation system <NUM> in accordance with an embodiment. In an embodiment a control system is implemented to control the operation of the generator <NUM> for turbine ventilation, auxiliary boiler/flash tank <NUM>, compressors <NUM>, <NUM>, control valves <NUM>, <NUM> and any isolation valves (not shown), and the like to execute the described methodologies. In an embodiment such control functions may be implemented in wholly or in part in control unit <NUM> or in another controller. In an embodiment multiple modes of operation are envisioned. It should be appreciated that while two modes of operation are described, such description in only for the purpose of example. Various other and additional modes of operation may readily be envisioned and it should be well understood that variations and other modes operation are possible. In an embodiment, a mode of operation for employing the turbine <NUM> for preheating/warming the steam generation system <NUM> is directed to warm-up/maintaining boiler temperatures and pressures as may typically be required to facilitate a hot start. Other modes of operation may be directed to maintaining a power generation system operational characteristics, including, but not limited to temperature and pressures at selected temperatures and pressures for longer durations.

<FIG> depicts a method <NUM> for reducing heat losses in a boiler and warming the boiler <NUM> in accordance with an embodiment. Under such conditions, the boiler <NUM> and its waterwall <NUM> as well as the mixer <NUM> and at least one steam pipe <NUM> are maintained warm as desired to facilitate starting. Under such conditions, at process step <NUM>, the operational characteristics, including, but not limited to temperature and/or pressures of the boiler <NUM>, and/or mixer drum <NUM>, turbine inlet(s) and outlet(s) are monitored. As depicted at process step <NUM>, if the temperature is less than a selected threshold, the reheating process is initiated, otherwise the monitoring continues. It will be appreciated that the particular selected temperature can vary depending on the particular boiler <NUM>, mixer, <NUM>, steam pipes <NUM>, turbine <NUM>, ambient temperatures and the like. In an embodiment, the boiler <NUM> is reheated if the temperature falls below about <NUM>, though other temperature selections are possible. In an embodiment, it is desired to maintain at least one of the boiler <NUM>, mixer <NUM>, steam pipes <NUM>, and/or turbine <NUM> at temperatures just sufficiently to maintain their pressures.

Continuing with the method <NUM>, as depicted at process step <NUM>, the reheating process is initiated by directing steam to at least the high pressures section <NUM> of the turbine <NUM>, the generator <NUM> is activated as a motor to drive the turbine <NUM> and begin imparting work to at least the high pressure section <NUM> of the turbine <NUM>. The flow control valve <NUM> is controlled to permit the flow of heated steam to mixer <NUM>. As depicted at process step <NUM>, optionally, in an embodiment the compressor <NUM> (if employed) is operated to further compress the heated steam and match the pressures in the boiler <NUM>/mixer <NUM>. Optionally, in yet another embodiment the auxiliary heat source <NUM> (if employed) is operated, further heating the steam from the mixer <NUM> as depicted at process step <NUM>. Optionally it should be understood, that the auxiliary heat source <NUM> may be firing and warmed prior to directing hot water to the boiler <NUM>, though warming the auxiliary heat source <NUM> is not required. In yet another option, as depicted at process step <NUM>, intermediate section heating may also be employed to further facilitate boiler reheating. It should be appreciated that while various steps of the method <NUM> are depicted in a particular order, they need not be, and are described in such order merely for the purposes of illustrating the examples of the embodiments. Some steps may of discussion, some steps may readily be conducted in different order. Continuing with the method <NUM>, as depicted at process step <NUM>, the flow of steam through at least the high pressure section <NUM> of the turbine <NUM> is controlled via the flow control valve <NUM> to obtain the desired rise in temperatures without exceeding turbine constraints. Continuing with <FIG> and the method <NUM> reiterates with monitoring the temperature during reheating until a selected operational characteristics, including, but not limited to reheating temperature or pressure is achieved or the boiler <NUM> is restarted as depicted at process step <NUM>. As depicted at process step <NUM>, in an embodiment, when it is desired to restart the boiler <NUM> to return to service, the flow control valve <NUM> (and any other optionally employed equipment are closed), the generator is unexcited and connected to operate as a generator. The boiler <NUM> and associated equipment are started (e.g., start fans, light-off ignitors and oil/NG burner firing). Advantageously, the firing rate for the boiler <NUM> may be increased quickly to the highest rate possible, as each of the components is prewarmed. When about steam flow has been established as depicted at process step <NUM>. The auxiliary heat source <NUM> may be maintained in continuous operation to continuing aiding the warming and restarting if desired. The power generation system and control therefor provided by the described embodiments provide financial, emissions and operational benefits to operators. In particular, fuel savings and emissions reductions can be achieved by optimizing the reheating time of the boiler. The power generation system <NUM> provides for main boiler shut down and restart by precision control of turbine ventilation, optional compressors, and an optional auxiliary heat source and a selective boiler/mixer reheating process. For example, significant savings may be realized for each boiler in operation by facilitating main boiler shut down and restart permitting the power generation system to be more responsive to variations in grid demand. These cost savings can be achieved as a result of the lower amount of fuel and emissions associated with efficiently operating the generator to use the turbine to facilitate system warming and restarts. The reduction also results in improved emissions as operation of the main boiler at inefficient conditions of reduced power are avoided. Furthermore, employing the turbine ventilation for reheating while the main boiler is inoperative avoids the need to operate or use auxiliary power that is needed to operate the downstream equipment, including fans and pumps for the required air quality control equipment. The reduction in auxiliary power translates into the need for less fuel and steam to achieve a given production level which, in turn, further reduces the fuel requirements and increases efficiency.

In addition to operational savings, the power generation system of the described embodiments provides for capital cost savings on new plant or boiler design and constructions. In particular, with the control system disclosed herein, it is possible to design/plan equipment for lower boiler restart constraints. Furthermore, the power generation system of the described embodiments provides for capital and recurring cost savings on existing retrofitted plant or boiler designs and constructions. In particular, with the system and methodology disclosed herein, it is possible to modify existing equipment for lower restart constraints while achieving faster restarts.

While the power generation system of the described embodiments allows for the real-time monitoring of numerous operational parameters that are utilized by a controller to precisely control turbine ventilation and boiler reheating, the described embodiments are not so limited in this regard. In particular, the various sensor feedbacks, in addition to being used in boiler reheating process control, can be stored and compiled for use in diagnostic and predictive analytics for asset performance and maintenance assessments of the process and equipment. That is, the data obtained from the various sensors and measurement devices can be stored or transmitted to a central controller or the like so that equipment and process performance can be assessed and analyzed. For example, the sensor feedbacks can be utilized to assess equipment health, for use in scheduling maintenance, repairs and/or replacement.

In an embodiment, a system for reheating a steam driven power generation system is described. The system includes a boiler system including a main boiler, the boiler system operative to generate steam and a mixer with an input fluidly coupled to the boiler. The system also includes a plurality of steam pipes, the plurality of steam pipes including a first steam pipe and a second steam pipe and a turbine having at least a first section the turbine operable to receive steam, wherein an input to the first section of the turbine is fluidly connected via the first steam pipe to an output of at least one of the boiler and the mixer and operable to carry steam from the boiler system at a first temperature to the first section of the turbine, wherein an output of the first section of the turbine is fluidly connected to the second steam pipe, and the second steam pipe is operable to carry heated steam at a second temperature from an output of the turbine to an at least one of an input to the boiler and an input of the mixer. In addition, the system includes a first flow control valve operable to control a flow of steam through the first section of turbine, a sensor the sensor operable to monitor at least one operating characteristic in the boiler system and a generator operably connected to the turbine, the generator operable as a motor and configured to receive power from the grid and drive the turbine. The system includes a control unit configured to receive information associated with the monitored operating characteristic and control at least one of the generator and first flow control valve, to control the amount of steam directed through the turbine under selected conditions and when the main boiler system is not generating steam.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the at least one operating characteristic is measured in the at least one of the plurality of steam pipes, the main boiler, the mixer, and the turbine.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the at least one operating characteristic is measured at the outlet of the first section of the turbine.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the at least one operating characteristic includes at least one of a temperature and a pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the amount of steam supplied to the first section of the turbine is controlled to maintain selected constraints of at least one of the first section of the turbine.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the selected constraints include at least one of a temperature, temperature gradient, and a pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the selected constraints include at least one of a temperature of <NUM>, and a pressure of <NUM> bar.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include a first compressor, the first compressor operably connected between the output of the first section of the turbine and at least one of the input to boiler and the input to the mixer, the first compressor controllable by the controller and operable to receive the heated steam from the first section of the turbine and increase at least one of a pressure or a temperature thereof.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first compressor increases a pressure of the heated steam to at least a pressure of that in the at least one of the boiler and the mixer.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include an auxiliary heat source operative to provide steam to at least one of the boiler, the mixer, the steam pipes, and the first section of the turbine and wherein the controller is operable to control the auxiliary heat source so that steam heated and directed to the at least one of the boiler, the mixer, and the first section of the turbine.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the auxiliary heat source provides sufficient heat with the turbine to maintain at least one of the boiler, the mixer, the steam pipes, and the turbine at a desired temperature or pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include the turbine having at least a second section, wherein an input to the second section of the turbine is fluidly connected and operable to receive steam at a third temperature from at least one of an output of the first section of the turbine, an output of the boiler and an output the mixer; wherein an output of the second section of the turbine is fluidly connected and operable to carry steam at a fourth temperature from an output of the second section turbine to an at least one of an input to the boiler and an input of the mixer.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include a second flow control valve operable to control a flow of steam through the second section of turbine; and wherein the control unit is configured to receive information associated with another monitored operating characteristic and control the second flow control valve, to control the amount of steam directed through the second section of turbine.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the heated steam at a fourth temperature from an output of the intermediate pressure section turbine is at a higher temperature than the steam at a third temperature from at least one of an output of the first section of the turbine, an output of the boiler and an output the mixer.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include a second compressor, the second compressor operably connected between the output of the second section of the turbine and at least one of the input to boiler and the input to the mixer, the second compressor controllable by the controller and operable to receive the heated steam from the second section of the turbine and increase at least one of a pressure or a temperature thereof.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the second compressor increases a pressure of the heated steam to at least a pressure of that in the at least one of the boiler and the mixer.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that a heat exchanger operably connected to receive the heated steam from the first section of the turbine at a first pressure and transfer heat to at least one of water and steam in the boiler or the mixer at another pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that an amount of steam directed through the turbine under selected conditions is configured to provide sufficient heating to at least one of the boiler, the steam pipes, the mixer and the turbine to maintain each at a selected temperature or pressure.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the at least one operating characteristic is measured at the main boiler, the mixer, or the turbine.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the amount of steam supplied to the firsts section of the turbine is controlled to maintain selected constraints of at least one of the first section of the turbine the steam pipes, or the connections thereof.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that at least one of the first section and the second section of the turbine is operating in a ventilation or partial ventilation mode.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first section of the turbine is a high pressure section, and second section of the turbine is an intermediate power section.

In another embodiment, described herein is a method of reheating a power generation system, having a boiler system including a main boiler and a mixer, the main boiler operative to generate steam when operating, and the mixer with an input fluidly coupled to the main boiler. The method including operably connecting a flow of steam at a first temperature from the mixer or the main boiler to a at least a first section of a turbine operable to receive steam, operably connecting an output of the first section of the turbine to at least one of an input to the boiler and an input of the mixer to carry heated steam at a second temperature therefrom, operably connecting a first flow control valve, the first flow control valve operable to control a flow of steam through the first section of the turbine, and operably connecting a generator to the turbine, the generator operable as a motor and configured to receive power from the grid and drive the turbine. The method also includes monitoring at least one operating characteristic in the boiler system, receiving information associated with the monitored operating characteristic with a controller, and controlling at least one of the flow control valve and the generator to control the amount of steam directed through the first section of the turbine under selected conditions when the main boiler system is not generating steam to warm the boiler.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include, that the at least one operating characteristic is a temperature measured at least one of the main boiler, the mixer, the steam pipe and the turbine.

Finally, it is also to be understood that the system <NUM> and control unit <NUM> may include the necessary electronics, software, memory, storage, databases, firmware, logic/state machines, microprocessors, communication links, displays or other visual or audio user interfaces, printing devices, and any other input/output interfaces to perform the functions described herein and/or to achieve the results described herein. For example, as previously mentioned, the system may include at least one processor and system memory/data storage structures, which may include random access memory (RAM) and read-only memory (ROM). The at least one processor of the system <NUM> may include one or more conventional microprocessors and one or more supplementary co-processors such as math co-processors or the like. The data storage structures discussed herein may include an appropriate combination of magnetic, optical and/or semiconductor memory, and may include, for example, RAM, ROM, flash drive, an optical disc such as a compact disc and/or a hard disk or drive.

Additionally, a software application that adapts the controller to perform the methods disclosed herein may be read into a main memory of the at least one processor from a computer-readable medium. Thus, embodiments of the present invention may perform the methods disclosed herein in real-time. The term "computer-readable medium," as used herein, refers to any medium that provides or participates in providing instructions to the at least one processor of the system <NUM> (or any other processor of a device described herein) for execution. Such a medium may take many forms, including but not limited to, non-volatile media and volatile media. Non-volatile media include, for example, optical, magnetic, or opto-magnetic disks, such as memory. Volatile media include dynamic random access memory (DRAM), which typically constitutes the main memory. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive (SSD), magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, a RAM, a PROM, an EPROM or EEPROM (electronically erasable programmable read-only memory), a FLASH-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read.

While in embodiments, the execution of sequences of instructions in the software application causes at least one processor to perform the methods/processes described herein, hard-wired circuitry may be used in place of, or in combination with, software instructions for implementation of the described methods/processes. Therefore, embodiments as described herein are not limited to any specific combination of hardware and/or software.

As used herein, "electrical communication" or "electrically coupled" means that certain components are configured to communicate with one another through direct or indirect signaling by way of direct or indirect electrical connections. As used herein, "mechanically coupled" refers to any coupling method capable of supporting the necessary forces for transmitting torque between components. As used herein, "operatively coupled" refers to a connection, which may be direct or indirect. The connection is not necessarily being a mechanical attachment.

Claim 1:
A system for reheating a steam driven power generation system (<NUM>), comprising:
a boiler system including:
a main boiler (<NUM>), the main boiler (<NUM>) operative to generate steam; and
a mixer (<NUM>) with an input fluidly coupled to the boiler (<NUM>);
a plurality of steam pipes (<NUM>), the plurality of steam pipes (<NUM>) including a first steam pipe (<NUM>) and a second steam pipe;
a turbine (<NUM>) having at least a first section (<NUM>) operable to receive steam, wherein an input to the first section (<NUM>) of the turbine (<NUM>) is fluidly connected via the first steam pipe (<NUM>) to an output of at least one of the main boiler (<NUM>) and the mixer (<NUM>) and operable to carry steam from the boiler system at a first temperature (T1) to the first section (<NUM>) of the turbine (<NUM>), wherein an output of the first section (<NUM>) of the turbine (<NUM>) is fluidly connected to the second steam pipe, and the second steam pipe is operable to carry heated steam at a second temperature (T2) from an output of the turbine (<NUM>) to at least one of an input to the boiler (<NUM>) and an input of the mixer (<NUM>);
a first flow control valve (<NUM>) operable to control a flow of steam through the first section (<NUM>) of the turbine (<NUM>);
a sensor (<NUM>), the sensor (<NUM>) operable to monitor at least one operating characteristic in the boiler system;
a generator (<NUM>) operably connected to the turbine (<NUM>), characterized in that the generator is operable as a motor and configured to receive power from the grid (<NUM>) and drive the turbine (<NUM>); and
a control unit (<NUM>) configured to receive information associated with the monitored operating characteristic and control at least the first flow control valve (<NUM>) and the generator, to control the amount of steam directed through at least the first section (<NUM>) of the turbine (<NUM>) under selected conditions and when the boiler system is not generating steam.