System and method for heat exchanger control based on real-time corrosion monitoring

Abstract

A system (80) and method (200) for controlling corrosion in a heat exchanger (60) having a hot gas inlet (74) and outlet (76) and a cold-side inlet (68) and outlet (70) includes determining (210) a temperature at a selected first location on the heat exchanger, controlling (220) a temperature of a corrosion detection device (82) to a selected first temperature based on the temperature of the heat exchanger surface, and determining (230) a corrosion rate at the selected first location associated with the heat exchanger surface for the selected first temperature. The method (200) further includes comparing (240) the corrosion rate to a predicted corrosion rate, determining (250) a target temperature for a cold-side fluid inlet of the heat exchanger (60) based at least in part on the determined corrosion and the comparison, and controlling (260) the temperature of the cold-side fluid inlet based at least in part on the determined target inlet temperature, the determined corrosion rate, and the predicted corrosion rate.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments described herein relate generally to heat exchanger evaluation and control methods and systems. More particularly, methods and systems for evaluating data representative of corrosion characteristics of a combustion vessel heat exchanger can be used, among other things, to control the inlet temperature of the heat exchanger. [Background technology]

[0002] A boiler typically includes a furnace that burns fuel to generate heat and produce steam. When the fuel is burned, thermal energy, or heat, is produced, which is used to heat and vaporize a liquid, such as water, to produce steam. The steam produced can then drive a turbine to generate electricity or provide heat for other purposes. Fossil fuels, such as pulverized coal and natural gas, are typical fuels used in many combustion systems in boilers. Burning the fuel produces heat and forms soot and flue gases.

[0003] The walls of a combustion vessel are often composed of a series of heat exchange tubes filled with a heat exchange medium (typically water) and are sometimes referred to as a "water wall." One side of the water wall faces the combustion chamber and is exposed to combustion products, which may include hot gases, ash, and corrosive combustion by-products. Similarly, boiler systems also include other heat exchangers (e.g., superheaters, reheaters, and economizers) that are exposed to combustion flue gases for heating. Burning fuels such as coal can cause soot and ash to deposit on the inner surfaces of the heat exchangers and boiler heat exchange surfaces, impairing heat transfer from the heated gases in the combustion vessel to the water tubes and heat exchangers. The walls of a combustion vessel or heat exchanger can corrode over time as a result of corrosive materials in the ash deposited by the consumed fossil fuels or physical deterioration caused by, for example, solid waste consumed in waste-to-energy power plants. This corrosion reduces the wall thickness of the tubes in the water wall or heat exchanger. The walls of heat exchange surfaces must be maintained at a minimum thickness to reliably withstand the high temperatures and pressures of water / steam pipes or heat exchangers. Because flue gas side corrosion adversely affects boiler materials (such as pressure bearing materials or protective layers / retaining components / sheet metal) or flue gas cleaning, there is a continuous demand for more resistant materials. However, material selection is limited by the boiler's environmental conditions (flue gas temperature, flue gas chemistry, fouling chemistry, corrosion, etc.) and the expected performance and characteristics (lifespan, repairability, functionality within composite materials, etc.). As a result, boiler corrosion, boiler malfunctions, and flue gas cleaning make the relevant environmental conditions highly variable and unstable, making it difficult to predict the performance and characteristics of the materials used.

[0004] Thus, "online" material testing emerged. In this method, a probe is inserted into each boiler at the planned site to record the material's performance and properties. Material probes (e.g., approximately 70 cm long) are used, whose body is dimensionally identical to the actual part (boiler tube, solid material) and, if necessary, equipped with corresponding applications (e.g., protective layers). These large probes are internally cooled to maintain the temperature at the front of the probe body. The temperature is set within a freely selectable range; that is, the "material temperature" is simultaneously recorded over a wide temperature range. Thus, critical temperature thresholds are detected. In these examples, the probe body can often be used for extended periods, which can be freely selected from a few hours to several months. Following on-site use, similar to damage investigations, the probe body is disassembled in the laboratory and subjected to microanalytical tests to document the cause of corrosion, the type and intensity of corrosion (degradation rate), or any adverse effects on the probe body's functionality. Within this temperature range, all relevant temperatures can be examined equally (for example, in the range 250°C to 300°C for the evaporator, in the range 400°C to 500°C for the superheater, and in the range 80°C to 200°C for the economizer or preheater and for the flue gas).

[0005] Proper maintenance of combustion vessels typically requires periodic shutdowns to inspect, clean, and repair critical components. Current diagnostic probes require long-term testing to assess corrosion. To avoid losses associated with plant shutdowns without compromising safety, physical and operating conditions within the combustion vessel must be carefully monitored and evaluated to detect unsafe conditions. For these reasons, it would be desirable to provide a non-intrusive, online monitoring system that evaluates, for example, the physical characteristics of heat exchanger critical sections to determine the corrosion characteristics of a combustion system based on temperature and / or flow in each heat exchanger. Summary of the Invention

[0006] In one embodiment, described herein is a method for controlling corrosion of a heat exchange surface of a heat exchanger having a hot gas inlet and outlet and a cold-side inlet and outlet. The method includes determining a temperature at a selected first location of the heat exchanger, controlling a temperature of a corrosion detection device to a selected first temperature based on the temperature of the heat exchanger surface, and determining a corrosion rate at the selected first location associated with the heat exchanger surface for the selected first temperature. The method further includes comparing the corrosion rate to a predicted corrosion rate, determining a target temperature of a cold-side fluid inlet of the heat exchanger based at least in part on the comparing step, and controlling the temperature of the cold-side fluid inlet based at least in part on the determined inlet target temperature, the determined corrosion rate, and the predicted corrosion rate.

[0007] In another embodiment, described herein is a system for monitoring corrosion of a heat exchange surface of a heat exchanger. The system includes a heat exchanger having a hot gas inlet, a hot gas outlet, a cold-side inlet, and a cold-side outlet; a corrosion detection device disposed at a first selected location on the heat exchange surface of the heat exchanger, the corrosion detection device operable to measure a corrosion rate of the heat exchange surface relative to a first selected temperature; a temperature compensation device controllable and operable to control a temperature of the corrosion detection device; and a temperature detection device disposed proximate the first selected location, the temperature detection device operable to measure a temperature of the heat exchanger at the first selected location. The system further includes a controller operable to control at least one of a flow of heat exchange medium through the heat exchanger to the cold-side inlet and a temperature, and a controller operable to communicate with the corrosion detection device, the temperature compensation device, the temperature sensor, and the controller. At least one of the corrosion detection device and the controller is operable to control the temperature compensation device to maintain the corrosion detection device at the first selected temperature based at least in part on the temperature of the heat exchanger at the first selected location. At least one of the corrosion detection device and the controller is operable to determine a corrosion rate at the first location of the heat exchange surface of the heat exchanger and to execute a process to control a temperature of the cold side inlet of the heat exchanger based at least in part on the measured corrosion at the first location and a predicted corrosion rate of the heat exchanger for a measured temperature at the selected first location of the heat exchanger.

[0008] Additional features and advantages are realized by the techniques of the present disclosure. Other embodiments and aspects of the present disclosure are described in detail herein. For a further understanding of the present disclosure, including its advantages and features, reference may be made to the detailed description and drawings. [Brief explanation of the drawings]

[0009] The described embodiments will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which: [Figure 1] 1 is a simplified schematic diagram of a power generation system having a boiler, according to one embodiment. [Figure 2] 1 is a cross-sectional view of an exemplary heat exchanger according to one embodiment. [Figure 3] 3 is a schematic diagram of the heat exchanger of FIG. 2 including a corrosion detection system according to one embodiment. [Figure 4] FIG. 1 is a schematic diagram of a corrosion sensor module according to one embodiment. [Figure 5] FIG. 2 is a simplified block diagram of a corrosion detection module according to one embodiment. [Figure 6] 1 is a flowchart of a method for determining and controlling corrosion in a heat exchanger according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Exemplary embodiments described herein are described below, and examples of embodiments are illustrated in the accompanying drawings. Wherever possible, the same reference numerals used throughout the drawings represent the same or similar parts. While the various embodiments described herein are generally suitable for use in heat recovery steam generation systems, including combustion systems, for clarity of explanation, a pulverized coal boiler, such as that used in a pulverized coal power plant, has been selected for description. Other systems can include other types of plants with heat exchangers, including chemical plants and power plants, as well as boilers, furnaces, and heaters that utilize a wide range of fuels, including, but not limited to, coal, oil, and gas. For example, possible boilers include T-fired pulverized coal boilers, wall-fired pulverized coal boilers, circulating fluidized bed (CFB) boilers, and bubbling fluidized bed (BFB) boilers, stoker-fired boilers, suspension burners for biomass boilers, forced circulation boilers, natural circulation boilers, supercritical boilers, and other heat recovery steam generation systems.

[0011] The embodiments described herein relate to a power generation system having a combustion system, a corrosion evaluation method, and a control scheme for the power generation system and the corrosion evaluation method, which provide for evaluating data representative of the corrosion characteristics of heat exchange surfaces in a boiler. In particular, a gas-gas or gas-liquid heat exchanger is controlled in response to a corrosion rate measured by a sensor disposed on a probe inserted into the side of the heat exchanger. More specifically, the described embodiments include a system, probe, and control method for operating a heat exchanger at a minimum allowable cold-side inlet temperature, governed by feedback from the corrosion rate of a probe located on the hot side in contact with the gas phase. For example, in one embodiment, the corrosion sensor comprises a real-time temperature-controlled corrosion monitoring sensor, allowing the temperature of the dynamic temperature profile of the surface of the gas-gas or gas-liquid heat exchanger to be optimized for maximum thermal efficiency without operating in a corrosive environment. In one embodiment, a boiler operator can determine a specific or given corrosion behavior of the heat exchanger while optimizing the cold-side inlet temperature or the dynamic temperature profile of the heat exchanger surface. The described embodiments are applicable to all types of boilers having heat exchange surfaces, but more particularly to fossil-fuel boilers and waste boilers, including tangentially fired boilers, as well as bubbling bed boilers, fluidized bed boilers, and circulating fluidized bed boilers.

[0012] FIG. 1 illustrates a power generation system 10 including a boiler wall rating system with a combustion system 11 having a boiler 12, such as may be used in power generation applications according to some embodiments. The boiler 12 may be a tangentially fired boiler (also known as a T-fired boiler) or a wall-fired boiler. Fuel and air are supplied to the boiler 12 by a burner assembly 14 and / or nozzles associated with the burner assembly 14. The combustion system 11 includes a fuel supply, such as a pulverizer 16, which pulverizes a fuel, such as coal, to a desired fineness. The pulverized coal is delivered from the pulverizer 16 to the boiler 12 using primary air. An air source 18 can supply secondary air or combustion air to the boiler 12. In the boiler 12, the secondary air or combustion air is mixed with fuel and combusted, as described in more detail below. If the boiler 12 is an oxy-fuel boiler, the air source 18 can be an air separation unit that extracts oxygen from an incoming air stream or an air separation unit that extracts oxygen directly from the atmosphere.

[0013] The boiler 12 includes a hopper zone 20 located below the main burner zone 22, from which ash can be collected for later removal. The bottom of the boiler 12 is equipped with a grid 32, which introduces combustion gases, floatation gases, or fluidization gases (for floor-type boilers), called primary or combustion air, supplied to the boiler 12 by a fan 34 via an air preheater 17, and removes bottom ash and other debris from the boiler 12. The boiler 12 also includes a main burner zone 22 (also called a windbox), which is supplied with air and an air-fuel mixture; a burnout zone 24, where any air or fuel not combusted in the main burner zone 22 is burned; and a superheater zone 26, which includes a superheater 27 capable of superheating steam with combustion flue gases. The boiler 12 also includes an economizer zone 28, which includes an economizer 31, which can preheat water before it enters the mixing bulb or drum (25) and supply it to the water wall 23. In the main burner zone 22, a controlled flow of primary air, pulverized coal, and secondary air is supplied to the combustion system 11, which can form a rotating fireball. The rotating fireball is a type of combustion process that releases materials that contribute to deposits on the fireside surface of the water wall 23. Carbon-based combustion by-products accumulate as slag and / or ash on the fireside surface of the water wall 23. The boiler feedwater entering the economizer 31 is generated from the steam turbine 50 and utilized in a condenser 57 located downstream of the steam turbine 50. The condensate is first heated by steam in one or more low-pressure preheaters (not shown) before entering the economizer 31. A pump 40 can be used to encourage the water to flow through the water wall 23 and circulate throughout the boiler 12.

[0014] Combustion of fuel with primary and secondary air in boiler 12 produces a flue gas stream that is ultimately treated and discharged through a chimney downstream of economizer zone 28. Much of the final heat collection from the flue gas occurs in combustion air preheater 17, which uses the heat from the flue gas to heat air used as combustion air in combustion system 11. Air preheater 17 is followed in the flue gas path by an electrostatic filter / precipitator or bag filter (not shown), which separates any remaining solid particles from the flue gas before it is discharged to the atmosphere through a chimney. As used herein, directions such as "downstream" refer to the direction of flue gas flow. Similarly, the term "upstream" refers to the opposite direction from "downstream," which is the opposite direction from the direction of flue gas flow.

[0015] Generally, during operation of power generation system 10 and combustion system 11, as fuel is burned in boiler 12, water in water wall 23 of boiler 12 is heated and flows through a steam drum (or steam drum equivalent)—hereinafter referred to as drum 25—to superheater 27 in superheater zone 26, where additional heat is added to the steam by flue gases. Superheated steam from superheater 27 then flows through a piping system, generally indicated by the numeral 60, to high-pressure section 52 of turbine 50, where the steam expands and cools to drive turbine 50, thereby rotating generator 58 and generating electricity. The expanded steam from high-pressure section 52 of turbine 50 then returns to reheater 29, downstream of superheater 27, where the steam is reheated and sent to intermediate-pressure section 54 of turbine 50 and ultimately to low-pressure section 56 of turbine 50, where the steam is continuously expanded and cooled to drive turbine 50.

[0016] As shown in FIG. 1 , combustion system 11 includes an array of sensors, actuators, and monitors for monitoring and controlling the combustion process and the resulting effects of the combustion process on boiler operation. For example, temperature and pressure monitors, generally designated 36, are used throughout the system to ensure proper control and operation and to ensure operational limits are not exceeded. In another example, combustion system 11 can include multiple fluid control devices 30 that supply secondary air for combustion to each fuel introduction nozzle associated with burner assembly 14. In one embodiment, fluid control devices 30 can be electrically operated air dampers that can be adjusted to vary the amount of air supplied to each fuel introduction nozzle associated with each burner assembly 14. Boiler 12 can also include other individually controllable air dampers or fluid control devices (not shown) at various locations around the furnace perimeter. Each of fluid control devices 30 can be individually controlled by control unit 150 to ensure the desired air / fuel ratio and flame temperature is achieved for each nozzle position.

[0017] FIG. 1 also shows a backpath (or backdraft section) 33 of the boiler 12 downstream from the superheater 27, reheater 29, and economizer 31 in the economizer zone 28. The backpath 33 may also be equipped with a monitoring device 37. The monitoring device 37 may optionally be configured to measure and evaluate gas species such as carbon monoxide (CO), carbon dioxide (CO2), mercury (Hg), sulfur dioxide (SO2), sulfur trioxide (SO3), nitrogen dioxide (NO2), nitric oxide (NO), and oxygen (O2) in the backpath 33. SO2 and SO3 are collectively referred to as SOx. Similarly, NO2 and NO are collectively referred to as NOx. Carbon monoxide (CO), carbon dioxide (CO2), mercury (Hg), sulfur dioxide (SO2), sulfur trioxide (SO3), nitrogen dioxide (NO2), nitric oxide (NO), and oxygen (O2) are released into the backpath 33. SO2 and SO3 are collectively referred to as SOx. Similarly, NO2 and NO are collectively called NOx.

[0018] As the boiler 12 continues to operate, optionally, a predetermined ratio of fuel and air is supplied to each of the burner assemblies 14 for combustion. As the fuel and air mixture combusts in the furnace and generates flue gases, the combustion process and the resulting flue gases are monitored. In particular, various parameters of the fireball and flame, the condition of the furnace walls, and various parameters of the flue gases may be sensed and monitored. These parameters are transmitted or communicated to the combustion control unit 150, where they are analyzed and processed according to control algorithms stored in memory and executed by a processor. The control unit 150 controls the fuel supplied to the boiler 12 and / or the air supplied to the boiler 12 based on one or more of the monitored combustion and flue gas parameters and the condition of the furnace walls.

[0019] Additionally, the power generation system 10 also includes an array of sensors, actuators, and monitors, generally designated as 36 and 38, for monitoring and controlling the progression of corrosion associated with steam generation, according to the described embodiment. For example, in one embodiment, the sensor system 80 may be a temperature-controlled / compensated corrosion detection system 80. This detection system 80 is further described herein and hereafter referred to as the corrosion system 80. In other examples, each sensor 36 may be a temperature sensor, a pressure sensor, etc. In one embodiment, the corrosion detection system 80, the temperature sensor, and the pressure sensor 36, etc., may each be operably connected to a control unit 150 or another controller, as appropriate, to perform the methods and functions described herein. Additionally, the power generation system 10 may include, in one example, multiple fluid control devices 66 for controlling the flow of water or steam within the system 10. In one embodiment, the fluid control devices 66 may be electrically actuated valves that can be adjusted to vary the flow rate. Each of the fluid control devices (e.g., 66) is individually controllable by the control unit 150.

[0020] Corrosion can be particularly damaging to boiler components. It occurs primarily as a direct result of combustion by-products of the fuel used. Gas species such as SOx and NOx, produced from fossil fuels and solid waste fuels, are particularly corrosive. Those skilled in the art understand that some combustion vessels, such as those fueled by natural gas, do not experience the same corrosion or deterioration as those fueled by coal or solid waste. In solid waste or coal-fired combustion vessels, corrosion or deterioration of the vessel walls often occurs. It is highly beneficial to measure, evaluate, and minimize such corrosion.

[0021] Thermally efficient operation of the boiler 12 requires heat integration using gas-to-liquid and gas-to-gas non-contact heat exchangers, including but not limited to the water wall 23, superheater 27, reheater 29, or economizer 31. By way of example, the function of an economizer is to raise the water temperature to an "approach" temperature close to the saturation temperature. The approach temperature is typically selected to maximize thermal energy absorption efficiency and operational flexibility. An air preheater (APH) is a device designed to heat air prior to another process (such as combustion in a boiler) with the primary goal of increasing the thermal efficiency of that process.

[0022] FIG. 2 illustrates an exemplary heat exchanger 60, such as a portion of the boiler 12 shown in FIG. 1 , including the water wall 23, superheater 27, reheater 29, or economizer 31. In one example, the heat exchanger 60 is the economizer 31 of the boiler 12 and includes individual water or steam pipes 62 arranged side-by-side and connected by end bends 64 and brackets 66, as shown. The water / steam pipes 62 have a water or steam inlet 68 and an outlet 70. The heat exchanger 60 has a flue gas inlet 74 and a flue gas outlet 76. The water pipes 62 in the illustrated embodiment are oriented generally perpendicular to the longitudinal axis of the boiler 12 and the path of the flue gas. While the heat exchangers 60 referenced herein are described as having water pipes and water inlets and outlets, it should be understood that such description is for illustrative purposes only. The heat exchangers 60 may be of any type and may function with any fluid working medium, as is well understood in the art. For example, the heat exchanger 60 may be gas-gas or liquid-gas without loss of generality.

[0023] In one embodiment, one or more corrosion sensor systems 80 can be located on components of a heat exchanger 60 (e.g., the economizer 31, reheater 29, superheater 27, etc., described herein). Generally, if the hot side of a heat exchanger 60, such as the economizer 31, is in a gas phase containing potentially corrosive species, corrosion can occur; however, high gas temperatures often prevent corrosion. However, as the gas temperature decreases, for example, due to the flue gas donating heat to the heat exchanger medium (e.g., water / steam), corrosion becomes more likely, especially as the flue gas dew point is approached. Because the exact dew point varies depending on many variables, including the exact temperature, fuel composition, flue gas composition, and heat exchanger material, it is difficult to accurately predict the conditions under which corrosion will begin and how the corrosion rate will be affected relative to process conditions. Furthermore, the surfaces of the heat exchanger 60 become fouled over time, and conditions can change over time because process conditions at the surfaces differ significantly from bulk gas-phase conditions. During transient events (such as load changes or maintenance shutdowns of the heat exchanger 60), the conditions experienced can change dramatically over short periods of time in ways that significantly impact the dynamics of corrosion mechanisms. Failure to maintain the heat exchanger 60 under corrosion-free operating conditions can be costly and undesirable. For example, if corrosion develops under acid dew point conditions in a heat recovery steam generator (HRS) power plant 10, the undesirable effects of corrosion can lead to shutdowns and even the loss of permits. Conversely, consistently maintaining heat exchange surfaces above the dew point (to avoid corrosion) reduces the efficiency of the heat exchanger. However, achieving a minimum temperature for safe and economically viable operation is desired. Accordingly, in one embodiment, a system and technique are proposed for assessing the corrosion state of a heat exchanger 60 exposed to flue gas.

[0024] 3, a simplified block diagram of a heat exchanger 60 having a corrosion detection system 80 according to one embodiment is shown. In one embodiment, the corrosion detection system 80 and control process 200 (see also FIG. 4) includes a control unit 150 that operates the heat exchanger 60 to achieve the desired performance optimization (maximum heat exchange with an acceptable corrosion rate). The detection system 80 and control process 200 facilitates determining corrosion characteristics and optimally controls flows in the heat exchanger 60. In particular, fluid flows in the heat exchanger 60 are controlled to achieve an acceptable minimum cold-side inlet temperature based at least in part on corrosion rate feedback from the corrosion detection system 80, which is located on the hot side of the heat exchanger 60 in contact with the gas-phase heat exchange medium (e.g., flue gas).

[0025] In one embodiment, the corrosion detection system 80 employs one or more corrosion detection devices 82 and temperature sensors 86 located in locations of the heat exchanger 60 where condensation / deposition may (or preferably is likely to) occur. For example, more specifically, the corrosion detection devices 82 are located on the hot side of the heat exchanger 60, or more specifically at the hot side outlet 76, where they are in contact with the gas phase of the heat exchange medium (e.g., flue gas at the outlet 76). The corrosion detection devices 82 include a corrosion sensor 84 coupled to the temperature sensor 86 to facilitate monitoring of corrosion at a given selected location for a selected temperature. One possible type of corrosion sensor 84 is an electrical resistance sensor, which is a piece of material 81. The temperature of the piece of material 81 is measured and, furthermore, temperature-controlled, and the metal thickness of the sensor is calculated over time (as the metal corrodes). The changing resistance relative to a selected operating temperature can be easily correlated to the corrosion rate. In one embodiment, the handling conditions of the corrosion sensors 84 and the metal in the sample material 81 are selected to be the same as those of the heat exchanger 60, so that the sensors exhibit the same corrosive environment and characteristics as the heat exchanger 60. Thus, in one embodiment, the corrosion detection system 80 includes corrosion detection devices 82 having electrical resistance / corrosion sensors 84 comprising pieces of material (in one example, made of the same material as the heat exchanger 60) coupled to the heat exchanger, and temperature sensors 86 that measure the temperature of each detection device 82. The electrical resistance can be measured by applying a voltage and measuring the current, or using known techniques such as a Wheatstone bridge. In one embodiment, two or more temperature-controlled corrosion detection devices 82 are used. For example, in one embodiment, two or more corrosion detection devices 82r, 82s are used. The temperature of the corrosion detection device 82r is controlled to a temperature indicated by Tr (e.g., the current operating temperature of the material of the heat exchanger 60) to track corrosion at the surface temperature of the hot gas outlet indicated by Tw of the heat exchanger 60, while the corrosion detection device 82s is set as a "scout" at a different temperature indicated by Ts (e.g., a predicted temperature to improve performance with an acceptable corrosion rate) to evaluate possible corrosion for different temperatures.In another embodiment, the metal handling conditions used for one corrosion detection device 82 (e.g., scout 82s) may differ from the actual metal handling conditions of the existing heat exchanger 60. The use of different handling conditions allows for an evaluation to determine whether the new handling conditions are suitable for use with the heat exchanger. In one embodiment, the temperature Tw is measured at the “coldest” point of the heat exchanger 60, for example, near or at the hot gas outlet 76, but not necessarily near or at the outlet 76. In one embodiment, three or more corrosion detection devices 82 are used, as shown in FIG. 4 . The corrosion detection system 80 of the described embodiment can include multiple temperature-controlled corrosion detection devices 82 (designated 82a, 82b, 82c, 82d, . . . 82n), each including an electrical resistance / corrosion sensor 84 coupled to a temperature monitoring sensor 86.

[0026] Furthermore, in one embodiment, the temperature of the system 80, more specifically, the temperature of one or more corrosion sensing devices 82, is controlled over time to facilitate correlation between temperature and measured corrosion. In one embodiment, the surface temperature of the sensing device 82, more specifically, the surface temperature of the electrical resistance / corrosion sensor 84, can be controlled, and the corrosion rate is monitored in real time based on the controlled temperature. In one embodiment, each corrosion sensing device 82 can have a dedicated or common temperature compensation device (e.g., a cooling system) 90 that allows multiple surface temperatures to be achieved at different corrosion sensing devices 82. In one embodiment, the corrosion sensing system 80 uses individual temperature-compensated corrosion sensing devices 82. In another embodiment, the corrosion sensing system 80 includes a tube 100, preferably made of the same material (e.g., the material of the heat exchanger 60) as the material for which corrosion monitoring is desired, with a distal end 102 closed for insertion into the flue gas. The temperature compensation device 90 (in one example, a cooling device 104) is disposed within the tube 100 and is operable to maintain a selected number of controlled temperatures, which are adjustable / controlled independently of one another. In one embodiment, the cooling device 104 provides cooling air that is delivered by the tube 103. The tube 103 is substantially concentric with the tube 100 and is operable to deliver cooling air to the closed distal end 102 of the tube 100, which then returns toward the open end of the tube 100. In this manner, by delivering a certain amount of air or cooling air, the temperature at the distal end 102 of the tube 100 can be precisely controlled to a selected temperature. The temperature is selected according to the corrosion characteristics corresponding to a given material, location, etc. In another embodiment, the temperature compensation device 90 can be configured as a thermoelectric element, such as a Peltier element, whereby an electric current is passed through a semiconductor material attached to each corrosion detection device 82, establishing a temperature difference across the material that can be utilized to achieve cooling.

[0027] Continuing with FIGS. 3 and 4, in operation, each temperature monitoring sensor 86 is operable to monitor the temperature of the corrosion sensing device 82 or the heat exchanger surface temperature, e.g., Tw and Tc are used as the illustrated measured temperatures of the heat exchanger surface, while Ts and Ts are the temperatures of the respective corrosion sensing devices 82r and 82s. In one embodiment, as described above, one corrosion sensing device 82 (designated as the "reference" sensing device 82r) is temperature controlled to closely track the surface temperature, e.g., Tw, of the heat exchanger 60 whose corrosion is to be monitored. In one embodiment, the reference sensing device 82r preferably experiences similar metal handling conditions as the hot-gas-side surface of the heat exchanger 60 and tracks an exposure history (which results in conditions on the sensor surface that closely resemble those found on the heat exchanger surface). As a result, corrosion at a given time can be ascertained based on changes in electrical resistance monitored during operation as a function of the measured temperature from the temperature sensor 86, and similarly, corrosion rates can be determined over time. In particular, for example, in one embodiment, electrical resistance measurements from sensor 84 can provide metal thickness resolution of less than 1 angstrom, allowing for continuous online monitoring in a filtered air environment. In more challenging environments, establishing the corrosion trend and corrosion rate, as measured by metal thickness between two elapsed times, can take time (ensuring that a measurement period is selected that allows for a sufficient signal-to-noise ratio). In one embodiment, the corrosion rate can be easily determined by measuring the resistance over a selected period of time at a given temperature of heat exchanger 60, as shown in FIG. 4 . If the corrosion rate exceeds a selected threshold, the cold-side inlet temperature can be adjusted to achieve the desired corrosion rate. In some embodiments, the cold-side inlet temperature is monitored and easily correlated to the determined corrosion rate to control the scheme related to the cold-side inlet temperature of the heat exchange medium (e.g., water / steam). In one embodiment, if the corrosion rate is greater than a selected threshold, the cold-side inlet temperature is controlled to decrease slightly to reduce the temperature differential across heat exchanger 60, thereby reducing the expected corrosion to a more acceptable level.

[0028] Optionally, in another embodiment, a second corrosion sensing device 82 (denoted as a “scout” sensing device 82s) is set and controlled to a different target operating temperature or target dynamic temperature profile expected to be applied to the heat exchanger 60 in the future. The corrosion and corrosion rate associated with this scout sensing device 82s can also be determined. In embodiments where a “scout” sensor is selected and controlled at a different temperature, the difference in corrosion rate in the temperature change (relative to the reference sensor) determines the gradient needed to select a preferred temperature setpoint for the cold-side inlet of the heat exchanger. In one embodiment, process 200 is executed on controller 150 to monitor the corrosion rate in real time for both sensing devices 82r and 82s. In one embodiment, feedback regarding the relative or absolute corrosion rate measured from the reference corrosion sensing device 82r and the scout corrosion sensing device 82s is used to determine whether a new temperature setpoint or dynamic temperature profile is appropriate from a corrosion perspective for the heat exchanger 60. In other words, if the corrosion profile is smaller than expected, the cold-side temperature at the inlet 68 of the heat exchanger can be lowered. Conversely, if the measured corrosion is greater than expected, the temperature differential in the heat exchanger 60 should be reduced to slow or control the corrosion rate. Process 200 can be iterated before modifying plant operation, whether related to predicting transients or optimizing thermal efficiency under resulting process conditions. In one embodiment, based on the anticipated demands on the heat exchanger 60, the cold-side inlet temperature, measured in some embodiments as Tc, can be controlled to ensure desired corrosion characteristics. In one embodiment, the target cold-side inlet temperature can be controlled by controlling the temperature and / or flow rate of the heat exchange medium (e.g., water / steam) flowing through the heat exchanger 60.

[0029] In one embodiment, three or more temperature-controlled corrosion sensing devices 82 are used so that different temperature set points or different dynamic temperature profiles can be simultaneously tested and their effect on corrosion measured in real time. For both sensors, corrosion rates are monitored in real time, and feedback on relative or absolute rates is used to determine whether new temperature set points or dynamic temperature profiles are appropriate from an corrosion standpoint. This process is repeated before modifying plant operation, whether related to predicting transients or optimizing thermal efficiency under resulting process conditions.

[0030] 5 , corrosion detection system 80 and / or control unit 150 may include the necessary electronic components, 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 and / or achieve the results described herein. For example, as previously mentioned, in one embodiment, corrosion detection system 80 and / or control unit 150, or both, may be implemented as self-contained or modular components of power generation system 10 and may include at least one processing module 140 and system memory / data storage structures, which may include random access memory (RAM) and read-only memory (ROM). The processor of module 140 may include one or more conventional microprocessors, microcontrollers, one or more auxiliary coprocessors, such as a math coprocessor, or the like. The data storage structures described herein may include any suitable combination of magnetic, optical, and / or semiconductor memory, and may further include, for example, RAM, ROM, flash drives, optical disks (e.g., compact disks and / or hard disks or hard drives). The processing module 140 and / or the control unit 150 may be implemented in the form of an integrated microcontroller, with functions integrated into a single package. Additionally, the corrosion detection system 80 may be implemented as a microcontroller, including an ASIC or FPGA, as needed, to interface with the various modules that perform the functions, processing, and communication described herein. Furthermore, software applications that adapt the corrosion detection system 80 and the modules or control unit 150 included therein to perform the method 200 disclosed herein may be loaded from a computer-readable medium into the main memory of at least one processor. Thus, embodiments of the present invention may perform the methods disclosed herein in real time.As used herein, the term "computer-readable medium" refers to any medium that provides or participates in providing instructions to at least one processor of module 80 or control unit 150 (or other processor of an apparatus described herein) for execution.

[0031] Continuing with the description of FIG. 5 , in one embodiment, each of the sensors (e.g., 84, 86) may be hardwired to the control unit 150. In another embodiment, the sensor interface 130 and processing unit are included in the sensing device 82, which communicates with the electrical resistance sensor / corrosion sensor 84 and the temperature sensor 86, as well as with the control unit 150. In one embodiment, a low-power communication interface 160 is used. The communication interface 160 is configured to connect to an interconnect / network 162. The interconnect / network 162 interconnects the corrosion sensing device 82 and one or more controllers, such as the control unit 150. The network 162 may be a mix of wired and wireless components and may utilize communication networks, including IP networks. It should be understood that the interconnect / network 162 may include wired or wireless components, or a combination thereof. Such wired components may be ordinary network cables, optical fibers, or electrical wires, or any other type of physical structure used by the detection module 80, the control unit 150, and other devices in the boiler system to communicate. Additionally, the network 162 may include wireless components, such as radio, optical, magnetic, or sonic links, or any other type of wireless link used by the corrosion detection device 82 and the control unit 150 to communicate. The communication interface 160 may be wired, wireless, or a combination thereof. In one embodiment, a wireless communication interface 160 and a wireless network 162 are used. For example, the communication interface 160 may use various techniques, technologies, and protocols to facilitate the implementation of the described embodiments, including, but not limited to, those described above. For example, the communication interface 160 and the network 162 may be implemented as Ethernet, Wi-Fi, Bluetooth, NFC, etc.The network 162 can be implemented using a hub-and-spoke type configuration or as a mesh network configuration. In some embodiments, a wireless mesh network can be used to allow multiple corrosion sensing devices 82 positioned around the boiler 12 to communicate with each other, coordinate measurements, and send data back to the control unit 150. Preferably, the wireless local power source 120 is combined with the wireless communication interface 160 and the network 162 to significantly reduce the installation costs of each sensor system 80 and the overall system.

[0032] While boiler 12, and more specifically, integrated corrosion detection system 80 and / or control unit 150, are described as including separate modules for power supply 120, sensor interface 130, processing module 140, and communication interface 160, it should be understood that such description is for illustrative purposes only. In alternative embodiments, the functionality of all or some of the described modules can be readily integrated or combined as desired. For example, in one embodiment, all or some of the functionality of sensor interface 130, processing module 140, and communication interface 160 can be incorporated into a microcontroller, ASIC, FPGA, or the like.

[0033] In the described embodiment, method 200 monitors corrosion of the heat exchange surface of a heat exchanger 60 in a boiler system 12. The method begins by monitoring the temperature, Tw, of the surface of the heat exchanger 60, as shown in process step 210. As described herein, the measurement is preferably made near the hot gas outlet 76, but need not be made at the coldest point or a location where condensation is likely to occur on the heat exchanger 60. Method 200 continues by controlling the temperature of a corrosion detection device 82 (e.g., 82r) at a first location, as shown in process step 220. Corrosion of the corrosion detection device 82 at a selected first location is monitored, as shown in process step 230. In one embodiment, the resistivity measurement is compared and evaluated with resistivity measured at a known constant temperature over a selected measurement period to obtain a known baseline and corrosion rate at the selected location and selected temperature, as shown in process step 240, to determine the corrosion rate. Based on a comparison of the measured corrosion, method 200 determines a target temperature for the cold side inlet of heat exchanger 60 based at least in part on the corrosion rate, in process step 250. Method 200 then controls the inlet temperature of heat exchanger 60 based at least in part on the measured corrosion rate, as shown in process step 260. Method 200 then optionally repeats the above steps for a selected second temperature, as shown in process step 270. Finally, method 200 then controls the inlet temperature of heat exchanger 60 based at least in part on the selected second temperature, the selected first temperature, and the measurements at the selected location, as shown in process step 280.

[0034] While the various steps of method 200 are shown in a particular order, it should be understood that these steps are not necessarily required in the illustrated order and are described in the illustrated order merely for purposes of illustrating an exemplary embodiment. Some steps may require consideration, and some steps may be readily performed in a different order. In addition to operational savings, the power generation system of the described embodiments may save capital costs associated with new heat exchanger design and construction. In particular, the control system disclosed herein may be used to design / plan equipment for more efficient heat exchange operation by maximizing heat exchange efficiency while ensuring corrosion rates are suppressed.

[0035] In one embodiment, described herein is a method for controlling corrosion of a heat exchange surface of a heat exchanger having a hot gas inlet and outlet and a cold-side inlet and outlet. The method includes determining a temperature at a selected first location of the heat exchanger, controlling a temperature of a corrosion detection device to a selected first temperature based on the temperature of the heat exchanger surface, and determining a corrosion rate at the selected first location associated with the heat exchanger surface for the selected first temperature. The method further includes comparing the corrosion rate to a predicted corrosion rate, determining a target temperature of a cold-side fluid inlet of the heat exchanger based at least in part on the determined corrosion, the comparing, and controlling the temperature of the cold-side fluid inlet based at least in part on the determined inlet target temperature, the determined corrosion rate, and the predicted corrosion rate.

[0036] In addition to or as an alternative to one or more of the features above, another embodiment of the method includes controlling the temperature of the corrosion sensing device including providing a temperature compensation device at the first location.

[0037] In addition to or as an alternative to one or more of the features above, another embodiment of the method may include controlling the temperature of the corrosion detection device to a current temperature of the heat exchanger.

[0038] In addition to or as an alternative to one or more of the above features, another embodiment of the method is where determining corrosion is based on measuring electrical resistance at the selected first location.

[0039] In addition to or as an alternative to one or more of the features described above, other embodiments of the method may include comparing the electrical resistance at the selected first location to a baseline electrical resistance measured under selected conditions.

[0040] In addition to or as an alternative to one or more of the features above, other embodiments of the method may include the selected conditions including a first selected location at a first selected temperature at an initial time.

[0041] In addition to or as an alternative to one or more of the features described above, another embodiment of the method is based in part on at least one of controlling the flow rate of heat exchange medium to the cold side inlet of the heat exchanger and controlling the temperature of the heat exchange medium flowing to the cold side inlet of the heat exchanger.

[0042] In addition to or as an alternative to one or more of the above features, another embodiment of the method includes controlling a temperature of a corrosion detection device at a selected first location on the heat exchange surface of the heat exchanger to a selected second temperature; determining a corrosion rate associated with the heat exchange surface of the heat exchanger at the selected second temperature; comparing the determined corrosion rate to a predicted corrosion rate associated with the selected second temperature; determining a target temperature of a cold side inlet of the heat exchanger based at least in part on the measured corrosion rate at the selected second temperature and the comparing; and controlling the temperature of the cold side inlet based at least in part on the measured corrosion rate at the selected second temperature and the determined cold side inlet temperature.

[0043] In addition to or as an alternative to one or more of the features above, another embodiment of the method includes the selected second temperature being selected based at least in part on an improved predicted corrosion rate of the heat exchanger.

[0044] In addition to or as an alternative to one or more of the above features, another embodiment of the method can include the selected first location being based on a location on the heat exchange surface of the heat exchanger where corrosion is likely to occur.

[0045] In addition to or as an alternative to one or more of the features described above, other embodiments of the method may include the selected first location being selected to be proximate to a hot gas outlet of the heat exchanger.

[0046] In another embodiment, a system for monitoring corrosion of a heat exchange surface of a heat exchanger is described. The system includes a heat exchanger having a hot gas inlet, a hot gas outlet, a cold-side inlet, and a cold-side outlet; a corrosion detection device disposed at a selected first location on the heat exchange surface of the heat exchanger, the corrosion detection device operable to measure a corrosion rate of the heat exchange surface relative to a selected first temperature; a temperature compensation device controllable and operable to control a temperature of the corrosion detection device; and a temperature detection device disposed proximate the selected first location, the temperature detection device operable to measure a temperature of the heat exchanger at the selected first location. The system further includes a controller operable to control at least one of a flow of heat exchange medium through the heat exchanger to the cold-side inlet and a temperature, and a controller operable to communicate with the corrosion detection device, the temperature compensation device, the temperature sensor, and the controller. At least one of the corrosion detection device and the controller is operable to control the temperature compensation device to maintain the corrosion detection device at the selected first temperature based at least in part on the temperature of the heat exchanger at the selected first location. At least one of the corrosion detection device and the controller is operable to determine a corrosion rate at the first location of the heat exchange surface of the heat exchanger and to execute a process to control a temperature of the cold side inlet of the heat exchanger based at least in part on the corrosion measured at the first location and a predicted corrosion rate of the heat exchanger for a measured temperature at the selected first location of the heat exchanger.

[0047] In addition to or as an alternative to one or more of the features described above, other embodiments of the system can include a temperature sensor operable to measure the temperature at and around the cold side inlet of the heat exchanger surface.

[0048] In addition to or as an alternative to one or more of the above features, another embodiment of the system is such that at least one of the corrosion detection device and the controller is operable to perform a process to control the temperature of the cold side inlet of the heat exchanger based at least in part on corrosion measured at the first location, a predicted corrosion rate of the heat exchanger for the measured temperature at the selected first location of the heat exchanger, and a measured cold side inlet temperature.

[0049] In addition to or as an alternative to one or more of the features described above, another embodiment of the system may include an electrical resistance sensor operable to measure the electrical resistance of the heat exchange surface and a temperature sensor operable to measure the temperature of the exchange surface in the vicinity of the corrosion detection device.

[0050] In addition to or as an alternative to one or more of the features described above, another embodiment of the system may include a power source operable to provide power to the corrosion detection device, a processor module operable to execute a process for determining corrosion based at least in part on the electrical resistance and the measured temperature, and a communications module operable to communicate with at least the controller.

[0051] In addition to or as an alternative to one or more of the features described above, other embodiments of the system may include a second corrosion detection device disposed at a selected first location on a heat exchange surface of the heat exchanger, the second corrosion detection device operable to measure corrosion of the heat exchange surface at a selected second temperature.

[0052] In addition to or as an alternative to one or more of the features described above, other embodiments of the system may include controlling the temperature of the cold-side inlet based at least in part on the corrosion rate measured at the selected second temperature and the determined cold-side inlet temperature.

[0053] In addition to or as an alternative to one or more of the features described above, other embodiments of the system may be such that the selected second temperature is based at least in part on an improved predicted corrosion rate of the heat exchanger.

[0054] In addition to or as an alternative to one or more of the features described above, other embodiments of the system can include the selected first location being based on a location where corrosion is likely to occur on the heat exchange surface of the heat exchanger.

[0055] In addition to or as an alternative to one or more of the features described above, other embodiments of the system may include the selected first location being selected to be proximate to a hot gas outlet of the heat exchanger.

[0056] Finally, system 10 and control unit 150 may include the necessary electronic components, software, memory, storage, databases, firmware, logic / state machines, microprocessors, communications links, displays or other visual or audio user interfaces, printing devices, and any other input / output interfaces to perform the functions and / or achieve the results described herein. For example, as previously described, the system may include at least one processor and system memory / data storage structures, including random access memory (RAM) and read-only memory (ROM). The at least one processor of system 10 may include one or more conventional microprocessors and one or more auxiliary coprocessors, such as a math coprocessor. The data storage structures described herein may include any appropriate combination of magnetic, optical, and / or semiconductor memory, and may further include, for example, RAM, ROM, flash drives, optical disks (e.g., compact disks and / or hard disks or hard drives).

[0057] Additionally, software applications that adapt the controller to perform the methods disclosed herein may be loaded from a computer-readable medium into the main memory of at least one processor. Thus, embodiments of the present invention may perform the methods disclosed herein in real time. As used herein, the term "computer-readable medium" refers to any medium that provides or participates in providing instructions to at least one processor of system 10 (or other processors of the devices described herein) for execution. Such media may take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media include, for example, optical disks, magnetic disks, or magneto-optical disks (e.g., memory). Volatile media include dynamic random access memory (DRAM), which typically constitutes main memory. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, a hard disk, a solid-state drive (SSD), magnetic tape, any other magnetic media, a CD-ROM, a DVD, any other optical media, RAM, a PROM, EPROM or EEPROM (electronically erasable programmable read-only memory), FLASH®-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read.

[0058] In embodiments, execution of a series of instructions in a software application causes at least one processor to perform the methods / processes described herein, although hardwired circuitry may be used in place of or in combination with software instructions to implement the methods / processes described. Thus, the embodiments described herein are not limited to any specific combination of hardware and / or software.

[0059] As used herein, "electrical communication" or "electrically coupled" means that particular components communicate with one another through direct or indirect exchange of signals by a direct or indirect electrical connection. As used herein, "mechanically coupled" means any connection method capable of supporting the force necessary to transmit torque between parts. As used herein, "operably coupled" means connection, which may be direct or indirect. The connection does not necessarily have to be a mechanical attachment.

[0060] As used herein, the singular reference to an element or step should be understood not to exclude a plurality of such elements or steps, unless such exclusion is expressly stated. Furthermore, references to "one embodiment" of multiple described embodiments are not intended to be interpreted as excluding the existence of additional embodiments that incorporate the recited features. Furthermore, unless expressly stated otherwise, embodiments "including," "comprising," or "having" an element or elements having a particular characteristic may also include additional elements that do not have that characteristic.

[0061] Furthermore, the dimensions and types of materials described herein are intended to define parameters related to the described embodiments, but are by no means limiting, and are exemplary embodiments. Many other embodiments will be apparent to those skilled in the art upon reviewing the above description. The scope of the present invention should be determined with reference to the appended claims. The claims may include other examples that occur to those skilled in the art, and such other examples are intended to be within the scope of the claims if they have elements that do not differ from the literal language of the claims or if they include equivalent elements that differ only insubstantial from the literal language of the claims. In the appended claims, the terms "comprises" and "in" are used as the plain-English equivalents of the respective terms "comprises" and "in." Furthermore, in the following claims, terms such as "first," "second," "third," "upper," "lower," "bottom," "top," etc. are used merely as labels and are not intended to impose numerical or positional requirements on their objects. Moreover, no claim limitation is stated in, and is not intended to be construed as, means-plus-function format unless such claim limitation expressly uses the phrase "means for" followed by a description of the function without further structure.

[0062] [Embodiment 1] A method (200) for controlling corrosion of heat exchange surfaces in a heat exchanger (60) having a hot gas inlet (74) and a hot gas outlet (76) and a cold side inlet (68) and a cold side outlet (70), the method comprising: Determining (210) a temperature at a first location on a surface of the heat exchanger (60); controlling (220) the temperature of a corrosion detection device (82) to a first temperature based on the temperature at the first location on the surface of the heat exchanger (60); determining (230) a corrosion rate at the first location relative to the heat exchange surface of the heat exchanger (60) for the first temperature; comparing (240) the corrosion rate to a predicted corrosion rate associated with the first location and the first temperature; determining (250) a target temperature for a cold fluid inlet of the heat exchanger (60) based at least in part on the comparison of the corrosion rates (240) at the first location; and controlling (260) the temperature of the cold-side fluid inlet (68) based at least in part on the target temperature, corrosion rate, and predicted corrosion rate of the fluid inlet; A method (200) comprising: [Embodiment 2] 2. The method of claim 1, wherein controlling the temperature of the corrosion detection device includes providing a temperature compensation device at the first location. [Embodiment 3] 3. The method of claim 2, wherein controlling the temperature of the corrosion detection device to the first temperature comprises controlling the temperature of the corrosion detection device to a current temperature of the heat exchanger. [Embodiment 4] 3. The method of claim 2, wherein determining the corrosion rate is based on measuring an electrical resistance at the first location. [Embodiment 5] Controlling the temperature of the cold fluid inlet (260) comprises: controlling the flow rate of the heat exchange medium flowing into the cold side inlet of the heat exchanger; and Controlling the temperature of the heat exchange medium flowing into the cold side inlet (68) of the heat exchanger (60). 2. The method (200) of claim 1, wherein the method is based on at least one of: [Embodiment 6] controlling (280) the temperature of the corrosion detection device (82) at the first location on the heat exchange surface of the heat exchanger (60) to a second temperature; determining a second corrosion rate at the second temperature associated with the heat exchange surface of the heat exchanger (60); comparing the second corrosion rate to a predicted corrosion rate associated with the second temperature; determining a target temperature for a second cold side inlet of the heat exchanger based at least in part on the second corrosion rate at the second temperature and the comparing; and controlling the temperature of the cold side inlet based at least in part on a second corrosion rate at the second temperature and a target temperature of the second cold side inlet. 2. The method of claim 1, comprising: [Embodiment 7] 7. The method of embodiment 6, wherein the second temperature is selected based at least in part on an improved predicted corrosion rate of the heat exchanger. [Embodiment 8] A system (80) for monitoring corrosion of a heat exchange surface of a heat exchanger (60), the system (80) comprising: a heat exchanger (60) having a hot gas inlet (74), a hot gas outlet (76), a cold side inlet (68), and a cold side outlet; a corrosion detection device (82) disposed at a first location on a heat exchange surface of the heat exchanger, the corrosion detection device (82) operable to measure a corrosion rate of the heat exchange surface relative to a first temperature; a temperature compensation device (90) controllable and operable to control the temperature of the corrosion sensing device (82); a temperature sensing device (86) disposed proximate the first location, the temperature sensing device (86) operable to measure a temperature of the heat exchanger (60) at the first location; a controller (140, 150) operable to control at least one of the flow and temperature of the heat exchange medium flowing through the heat exchanger to the cold side inlet; and a controller (140, 150) operable to communicate with the corrosion detection device (82), the temperature compensation device (90), the temperature sensor (86), and a control device; Including, at least one of the corrosion detection device (82) and the controller (140, 150) is operable to control the temperature compensation device (82) to maintain the corrosion detection device at the first temperature based at least in part on the temperature at the first location of the heat exchanger (60); At least one of the corrosion detection device (82) and the controller (140, 150) is operable to determine a corrosion rate at the first location of the heat exchange surface of the heat exchanger (60) and to execute a process to control the temperature of the cold side inlet of the heat exchanger (60) based at least in part on the measured corrosion at the first location and a predicted corrosion rate of the heat exchanger (60) for the measured temperature of the heat exchanger (60) at the first location. [Embodiment 9] 9. The system (80) of claim 8, wherein at least one of the corrosion detection device and the controller is operable to execute a process for controlling the temperature of the low-temperature side inlet of the heat exchanger based at least in part on the corrosion rate measured at the first location, the predicted corrosion rate of the heat exchanger for the measured temperature at the first location of the heat exchanger, and the measured low-temperature side inlet temperature. [Embodiment 10] The corrosion detection device (82) an electrical resistance sensor operable to measure the electrical resistance of the heat exchange surface; a temperature sensor (86) operable to measure the temperature of the exchange surface proximate the corrosion detection device; 9. The system (80) of embodiment 8, comprising: [Explanation of symbols]

[0063] 10 Power Generation System 11 Combustion System 12 Boiler 14 Burner Assembly 16. Fine grinder 17 Air preheater 18 Air Source 22 Main Burner Zone 23 Water wall 24 Burnout Zone 25 drums 26 Superheater Zone 27 Superheater 28 Economizer Zone 29 Reheater 30 Fluid control device 31 Economizer 32 grid 33 Back Pass 37 Monitoring equipment 40 Pump 50 Steam Turbine 52 High-voltage section 54 Medium pressure section 56 Low pressure section 57 Condenser 58 Generator 60 heat exchanger 66 Fluid Control Device 68 Entrance 70 exit 74 Flue gas inlet 76 Flue gas outlet 80 Corrosion Detection System 82 Corrosion detection devices 86 Temperature Sensor 90 Temperature Compensation Device 140 Processing Module 150 Control Unit 200 ways 210 Processing Process 220 Processing Process 230 Processing Process 240 Processing Process 250 Processing Steps 260 Processing Process 270 Processing Process 280 Processing Process

Claims

1. A method (200) for controlling corrosion of heat exchange surfaces of a heat exchanger (60) having a hot gas inlet (74) and a hot gas outlet (76) and a cold side inlet (68) and a cold side outlet (70), the method comprising: Determining (210) a temperature at a first location on a surface of the heat exchanger (60); controlling (220) the temperature of a corrosion detection device (82) to a first temperature based on the temperature at the first location on the surface of the heat exchanger (60); determining (230) a corrosion rate at the first location relative to the heat exchange surface of the heat exchanger (60) for the first temperature; comparing the corrosion rate to a predicted corrosion rate associated with the first location and the first temperature (240); determining (250) a target temperature for a cold fluid inlet of the heat exchanger (60) based at least in part on the comparison of the corrosion rates (240) at the first location; and controlling (260) a temperature of the cold-side fluid inlet (68) based at least in part on the target temperature, corrosion rate, and predicted corrosion rate of the cold-side fluid inlet; A method (200) comprising:

2. The method (200) of claim 1, wherein controlling the temperature of the corrosion sensing device (82) comprises providing a temperature compensation device (90) at the first location.

3. 3. The method of claim 2, wherein controlling the temperature of the corrosion detection device to the first temperature comprises controlling the temperature of the corrosion detection device to a current temperature of the heat exchanger.

4. 3. The method (200) of claim 2, wherein determining (230) the corrosion rate is based on measuring an electrical resistance at the first location.

5. Controlling the temperature of the cold fluid inlet (260) comprises: controlling the flow rate of the heat exchange medium flowing into the cold side inlet of the heat exchanger; and The method of claim 1, wherein the method is based on at least one of: controlling a temperature of the heat exchange medium flowing into the cold side inlet of the heat exchanger.

6. controlling (280) the temperature of the corrosion detection device (82) at the first location on the heat exchange surface of the heat exchanger (60) to a second temperature; determining a second corrosion rate at the second temperature associated with the heat exchange surface of the heat exchanger (60); comparing the second corrosion rate to a predicted corrosion rate associated with the second temperature; determining a target temperature for a second cold side inlet of the heat exchanger based at least in part on the second corrosion rate at the second temperature and the comparing; and controlling the temperature of the cold side inlet based at least in part on a second corrosion rate at the second temperature and a target temperature of the second cold side inlet. The method (200) of claim 1, comprising:

7. The method (200) of claim 6, wherein the second temperature is selected based at least in part on an improved predicted corrosion rate of the heat exchanger (60).

8. A system (80) for monitoring corrosion of a heat exchange surface of a heat exchanger (60), the system (80) comprising: a heat exchanger (60) having a hot gas inlet (74), a hot gas outlet (76), a cold side inlet (68) and a cold side outlet; a corrosion detection device (82) disposed at a first location on a heat exchange surface of the heat exchanger, the corrosion detection device (82) operable to measure a corrosion rate of the heat exchange surface relative to a first temperature; a temperature compensation device (90) controllable and operable to control the temperature of said corrosion sensing device (82); a temperature sensing device (86) disposed proximate the first location, the temperature sensing device (86) operable to measure a temperature of the heat exchanger (60) at the first location; a controller (140, 150) operable to control at least one of the flow and temperature of the heat exchange medium flowing through the heat exchanger to the cold side inlet; and a controller (140, 150) operable to communicate with the corrosion detection device (82), the temperature compensation device (90), the temperature sensor (86), and the control device; Including, at least one of the corrosion detection device (82) and the controller (140, 150) is operable to control the temperature compensation device (82) to maintain the corrosion detection device at the first temperature based at least in part on the temperature at the first location of the heat exchanger (60); At least one of the corrosion detection device (82) and the controller (140, 150) is operable to: determine a corrosion rate at the first location on the heat exchange surface of the heat exchanger (60); compare the corrosion rate at the first location with a predicted corrosion rate of the heat exchanger (60) for the measured temperature at the first location on the heat exchanger (60); and execute a process to control a temperature of a cold side inlet of the heat exchanger (60) based at least in part on a comparison result between the measured corrosion rate at the first location and the predicted corrosion rate of the heat exchanger (60) for the measured temperature at the first location on the heat exchanger (60).

9. 10. The system (80) of claim 8, wherein at least one of the corrosion sensing device and the controller is operable to execute a process for controlling a temperature of a cold side inlet of the heat exchanger based at least in part on a measured corrosion rate at the first location and the predicted corrosion rate plus a measured cold side inlet temperature.

10. The corrosion detection device (82) an electrical resistance sensor operable to measure the electrical resistance of the heat exchange surface; a temperature sensor (86) operable to measure the temperature of a surface of the heat exchanger proximate the corrosion detection device; The system (80) of claim 8, comprising:

11. A method (200) for controlling corrosion of a heat exchange surface of a heat exchanger (60) having a hot gas inlet (74) and a hot gas outlet (76) and a cold side inlet (68) and a cold side outlet (70), the method comprising: Determining (210) a temperature at a first location on a surface of the heat exchanger (60); and controlling (220) a temperature of a corrosion detection system to a first temperature based on a temperature at the first location on a surface of the heat exchanger (60), the corrosion detection system including a plurality of corrosion detection devices, each having a corrosion sensor coupled to a temperature sensor; and controlling the temperature of the corrosion detection system includes providing a temperature compensation device integrated with the corrosion detection system at the first location, the temperature compensation device including a first tube having a closed end and an opposite open end, the first tube housing the corrosion detection system, and a second tube disposed within the first tube, the corrosion detection devices of the plurality of corrosion detection devices coupled to an inner wall of the first tube in a spaced-apart arrangement, the second tube being open at a first end and an opposite second end, the second tube configured to deliver cooling air flowing toward the closed end of the first tube, the cooling air reflecting off the closed end of the first tube toward the open end of the first tube, the reflected cooling air being directly cooling each of the plurality of corrosion sensing devices while flowing toward the open end of the first pipe, the temperature compensation device controlling the cooling of each of the plurality of corrosion sensing devices forming the corrosion detection system in response to an amount of cooling air flowing through the first pipe and the second pipe, each corrosion sensing device including a microcontroller, the microcontroller including a communication interface enabling communication with other corrosion sensing devices forming the corrosion detection system and with a control unit operably coupled to the plurality of corrosion sensing devices, a processing module, a sensor interface communicating with a corresponding corrosion sensor and a temperature sensor, and a power source providing power to the communication interface, the processing module, and the sensor interface, the plurality of corrosion sensing devices being configured to communicate with each other, adjust measurements, and send data regarding the adjusted measurements to the control unit; determining a corrosion rate at the first location relative to the heat exchange surface of the heat exchanger (60) for the first temperature; comparing the corrosion rate to a predicted corrosion rate associated with the first location and the first temperature; determining a target temperature for a cold fluid inlet of the heat exchanger (60) based at least in part on the comparison of the corrosion rates at the first location; and controlling a cold-side fluid inlet temperature (68) based at least in part on the cold-side fluid inlet target temperature, corrosion rate, and predicted corrosion rate; A method (200) comprising:

12. A system (80) for monitoring corrosion of a heat exchange surface of a heat exchanger (60), the system (80) comprising: a heat exchanger (60) having a hot gas inlet (74), a hot gas outlet (76), a cold side inlet (68) and a cold side outlet; a corrosion detection system disposed at a first location on a heat exchange surface of the heat exchanger to measure a corrosion rate of the heat exchange surface relative to a first temperature, the corrosion detection system including a plurality of corrosion detection devices, each corrosion detection device having a corrosion sensor coupled to a temperature sensor; a temperature compensation device (90) integrated with the corrosion detection system and controllable and operable to control a temperature of the corrosion detection system, the temperature compensation device including: a first tube having a closed end and an opposite open end, the first tube housing the corrosion detection system; and a second tube disposed within the first tube, each corrosion detection device of the plurality of corrosion detection devices coupled to an inner wall of the first tube in a spaced-apart arrangement; the second tube being open at a first end and an opposite second end; the second tube being configured to deliver cooling air flowing toward the closed end of the first tube, the cooling air reflecting off the closed end of the first tube toward the open end of the first tube, the reflected cooling air directly cooling each corrosion detection device of the plurality of corrosion detection devices as it flows toward the open end of the first tube; a temperature compensation device (90) configured to control cooling of each of the plurality of corrosion detection devices forming the corrosion detection system in response to an amount of cooling air flowing through the first pipe and the second pipe, each corrosion detection device including a microcontroller, the microcontroller including a communication interface that enables communication with other corrosion detection devices forming the corrosion detection system and with a control unit operably coupled to the plurality of corrosion detection devices, a processing module, a sensor interface that communicates with corresponding corrosion sensors and temperature sensors, and a power source that provides power to the communication interface, the processing module, and the sensor interface, the plurality of corrosion detection devices being configured to communicate with each other, adjust measurements, and send data related to the adjusted measurements to the control unit. Including, each temperature sensor associated with a corresponding corrosion detection device is operable to measure a temperature at the first location of the heat exchanger; each processing module associated with a corresponding corrosion detection device and said control unit is operable to control at least one of a temperature and a flow rate of a heat exchange medium flowing to said cold side inlet (68) of said heat exchanger (60); the control unit is capable of communicating with the processing module, a temperature sensor of the plurality of corrosion detection devices, and the temperature compensation device; at least one of the plurality of corrosion detection devices and the control unit is operable to control the temperature compensation device to maintain the corrosion detection system at the first temperature based at least in part on a temperature at the first location of the heat exchanger; At least one of the corrosion detection system and the control unit determines a corrosion rate at a first location on a heat exchange surface of the heat exchanger, and executes a process to control a temperature of a cold side inlet of the heat exchanger based at least in part on the measured corrosion at the first location and a predicted corrosion rate of the heat exchanger for the measured temperature of the heat exchanger at the first location.

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