In industrial production and power supply, boilers, as core energy conversion equipment, are like the "heart" of the power system. Their operating efficiency and steam quality directly determine the stability, economic efficiency, and environmental performance of the entire production chain. Whether it's large-scale thermal power plants supplying electricity to thousands of households or industrial enterprises like chemical and metallurgy carrying out continuous production, the steam generated by boilers is a critical energy source that drives equipment and ensures process success.
However, when purchasing and operating boilers, many companies face a core question: not every boiler requires both a superheater and a reheater. What are the respective functions of these two devices? What are the differences in their operating principles? And how can one determine whether one is necessary based on their specific needs? This article will start from the basics and systematically analyze the principles, applications, and differences between boiler superheaters and reheaters. It will also focus on the most important customer concerns regarding selection, energy efficiency, and maintenance. This article provides companies with a professional and practical reference, helping them gain a comprehensive understanding of these two key devices and make more informed boiler configuration decisions.
To gain a deeper understanding of superheaters and reheaters, we first need to clarify their core definitions, common configuration scenarios, and key features. This provides the foundation for subsequently assessing their application value.
A boiler superheater is a heat exchange device in a boiler system specifically designed to heat saturated steam output from the drum (steam drum) to superheated steam, exceeding the saturation temperature. Although saturated steam has a certain pressure, its temperature is limited by pressure and contains a small amount of water, making it unsuitable for some demanding industrial scenarios. Superheaters, on the other hand, absorb heat from the high-temperature flue gas in the boiler's tail duct to further heat the saturated steam, thereby raising the steam temperature. Superheaters are widely used in a wide range of configurations. Most medium- and high-pressure industrial boilers (e.g., those with pressures ≥3.82 MPa and temperatures ≥450°C) and nearly all power plant boilers (including pulverized coal boilers and circulating fluidized bed boilers) are equipped with superheaters as standard. Even some low-pressure industrial boilers with special steam temperature requirements (such as high-temperature setting processes in the textile industry) may be equipped with superheaters.
Their most notable feature is that during the heating process, the steam temperature rises significantly (typically by tens to hundreds of degrees Celsius), while the pressure remains essentially constant (due to the low internal flow resistance of the superheater, resulting in negligible pressure loss). This process significantly improves the "quality" of the steam—not only reducing its water content to extremely low levels, but also achieving a higher enthalpy (the amount of heat per unit mass of steam), allowing it to release more energy in subsequent work or heat exchange processes, reducing energy loss.
Unlike a superheater, a boiler reheater is a heat exchange device that reintroduces low-pressure, low-temperature exhaust steam (i.e., steam that has already released some of its energy) from the high-pressure cylinder of a steam turbine after work into the boiler, where it is reheated to a high temperature close to the main steam temperature.
In terms of deployment scenarios, reheater applications are clearly targeted: they are primarily used in large power plant boilers (especially thermal power units with a single unit capacity of 300MW or greater) and are rarely used in ordinary industrial boilers. This is because the core function of a reheater is closely related to the efficiency of the thermodynamic cycle. Its energy-saving benefits can only be fully realized in large-capacity, high-parameter power plant thermal systems. Industrial boilers, on the other hand, primarily use steam for direct heat exchange or to drive small steam turbines, eliminating the need for a complex reheat cycle. The core features of the reheater include two key aspects: First, it significantly improves thermal cycle efficiency by reheating the exhaust steam from the high-pressure cylinder, thereby avoiding energy loss caused by excessive humidity when the low-temperature steam subsequently performs work in the low-pressure cylinder. Second, it protects the steam turbine equipment. The reduced humidity of the heated steam effectively reduces erosion and wear on the turbine blades, extending the turbine's service life and reducing equipment maintenance costs.
Understanding the working principles of superheaters and reheaters helps us understand their energy conversion logic, enabling better parameter control and troubleshooting in actual operation.
The superheater's operating process is essentially an indirect heat exchange between high-temperature flue gas and saturated steam. The specific process can be divided into three steps:
Steam input: Saturated steam generated in the boiler drum enters the superheater tube bank (usually composed of multiple seamless steel tubes connected in parallel) through connecting pipes.
Heat transfer: The superheater tube bank is located in the high-temperature area (flue gas temperature is typically 800-1200°C) at the boiler furnace outlet or tail flue. The high-temperature flue gas flows horizontally or vertically against the superheater tube walls, transferring heat to the saturated steam flowing within the tubes through radiation and convection.
Steam output: After absorbing heat, the saturated steam gradually increases in temperature, eventually becoming superheated steam that meets the design parameters. This steam is then transported through the outlet pipe to the steam turbine (power station boiler) or industrial heating equipment (industrial boiler).
Throughout this process, due to the relatively stable cross-sectional area of the superheater tube bank and the low resistance to steam flow within the tubes, the steam pressure remains essentially unchanged; only the temperature increases. For example, in the chemical industry's ethylene production process, high-temperature steam exceeding 400°C is required as the heat source for the cracking furnace. In this case, the boiler superheater must heat the 10MPa saturated steam (saturated temperature approximately 311°C) output from the drum to 450°C to meet the high-temperature heat source required by the cracking reaction. Without a superheater, relying solely on saturated steam would not be able to meet process requirements, directly impacting product yield and quality.
The reheater's operating principle is similarly based on flue gas heat exchange, but it targets "secondary steam." Its process differs significantly from that of a superheater and can be divided into four steps:
Exhaust Steam Intake: After the turbine's high-pressure cylinder uses the main steam (supplied by the superheater) to perform work, exhaust steam is discharged with a pressure of 2-4 MPa and a temperature of 300-350°C. This exhaust steam is then returned to the boiler's reheater tube bank via dedicated piping.
Reheating: The reheater tube bank is typically located in the flue gas duct after the superheater and before the economizer (flue gas temperature is approximately 600-800°C). The high-temperature flue gas transfers heat to the exhaust steam within the tubes through convection, gradually raising the exhaust steam temperature to a level close to that of the main steam (usually 10-30°C lower than the main steam temperature. For example, if the main steam temperature is 540°C, the reheat steam temperature is approximately 100-200°C). 520°C);
Steam Reuse: After heating, the high-temperature reheated steam is piped to the turbine's intermediate-pressure (or low-pressure) cylinder, where it expands again and performs work, releasing more energy.
The cycle is completed: The steam, having performed work, enters the condenser, condenses into water, and is treated in the heat recovery system before being re-sent to the boiler, completing the entire thermal cycle.
For example, in a 300MW steam turbine generator set at a thermal power plant, without a reheater, exhaust steam from the high-pressure cylinder directly enters the low-pressure cylinder, where its humidity can reach as high as 15%-20%. This not only results in energy loss due to "water carryover" (reducing cycle efficiency by approximately 8%-10%), but also causes severe erosion on the low-pressure cylinder blades, shortening their lifespan. However, with a reheater, the exhaust steam temperature rises to over 500°C and the humidity drops to below 5%, improving cycle efficiency by 3%-5% while effectively protecting the turbine blades and reducing the risk of equipment failure.
The differences in the uses of superheaters and reheaters determine their application boundaries in different industries and equipment. Enterprises need to select the appropriate configuration based on their steam applications.
The core value of superheaters is to "increase steam temperature and optimize steam quality." Therefore, their application scenarios cover almost all areas with high steam temperature requirements, mainly in two major areas:
Power Plant Boilers
Superheaters are essential core components in power plant boilers in thermal and nuclear power plants. The power generation efficiency of steam turbines is directly related to steam temperature—the higher the steam temperature, the higher the internal efficiency of the steam turbine and the lower the coal consumption (or energy consumption) for power generation. For example, the superheater outlet steam temperature of a subcritical power plant boiler (pressure 16.7 MPa) is typically 540°C, while the superheater outlet temperature of a supercritical power plant boiler (pressure ≥ 22.1 MPa) can reach 566°C or even higher. This high-temperature steam drives the high-speed rotation of the steam turbine, driving the generator to generate electricity. Without a superheater, relying solely on saturated steam to drive the steam turbine would not only reduce power generation efficiency by 15%-20%, but also cause turbine blade wear due to high steam humidity, increasing equipment maintenance costs.
Industrial Boilers
Superheaters are widely used in industries such as the chemical, petrochemical, metallurgical, papermaking, textile, and food processing industries, primarily to provide high-temperature, dry steam for production processes:
Chemical and petrochemical industries: The production of synthetic ammonia, methanol, and ethylene requires high-temperature steam as a reaction heat source or heating medium. Superheaters provide superheated steam at 350-450°C to ensure sufficient chemical reactions and improve product yields.
Metallurgical industries: Steel mills require high-temperature steam to heat rolls and dry steel during rolling. Superheaters provide this high-temperature steam. Steam above 400°C prevents oxidation and rusting of steel caused by water carried by steam.
Textile and Papermaking Industries: Fabric shaping in the textile industry and sheet drying in the papermaking industry both require dry, high-temperature steam. Superheaters effectively remove moisture from the steam, preventing fabric moisture and paper deformation.
Food Processing Industry: In processes such as canned food sterilization and milk powder drying, superheated steam not only provides a stable high temperature but also prevents condensate from saturated steam from contaminating food, ensuring food safety.
The core value of reheaters is to "optimize the thermal cycle and protect critical equipment." Their application scenarios are relatively concentrated, primarily in power plant boilers, supplemented by a few specialized industrial installations:
Power Plant Boilers
In large power plant boilers (especially steam turbine generator sets with a single unit capacity of 300 MW or greater), reheaters are a key means of improving thermal cycle efficiency. According to thermodynamic principles, reheating exhaust steam from the high-pressure cylinder in the steam cycle reduces "wet steam loss" (i.e., the loss of energy from water in the steam that cannot be released during work) while also improving the steam's ability to perform work in the intermediate and low-pressure cylinders. Data shows that power plant boilers equipped with reheaters can improve their thermal cycle efficiency by 3%-5%. For example, for a 300MW unit, this can save approximately 15,000 tons of standard coal annually, representing significant economic benefits.
Reheaters also effectively protect steam turbine equipment. If exhaust steam from the high-pressure cylinder enters the intermediate and low-pressure cylinders without reheating, its humidity can reach as high as 15%-25%. Water droplets in the wet steam can impact turbine blades at high speed, causing erosion and corrosion, and in severe cases, even blade breakage, leading to equipment failure. However, after reheating, the steam humidity can be reduced to below 5%, significantly reducing blade damage, extending the turbine's service life, and reducing downtime for maintenance.
Special Industrial Installations
In general industrial applications, reheaters are extremely rare, being deployed only in a few specialized installations with extremely high energy efficiency requirements.
For example:
Large-scale industrial waste heat power generation systems: Some steel and cement plants utilize waste heat generated during production to build waste heat power plants. If the waste heat boiler is paired with a large steam turbine (e.g., ≥50 MW), a small reheater may be deployed to improve power generation efficiency.
Ultra-large compressed air energy storage systems: In the new energy storage sector, ultra-large compressed air energy storage systems generate electricity through steam-driven expanders. If the system capacity reaches hundreds of megawatts, a reheat cycle and reheaters may also be employed.
Overall, however, the demand for reheaters in the industrial sector is far lower than in the power plant sector, and most industrial boilers do not require reheaters.
To more clearly understand the differences between the two, we'll compare them based on 5 key dimensions: target, core function, pressure variation, application scope, and core objectives.
|
Comparison Item |
Superheater |
Reheater |
|
Target Fluid |
Saturated steam from the boiler drum |
Low-pressure exhaust steam from the high-pressure turbine cylinder |
|
Core Function |
Heats saturated steam to superheated steam, increasing its temperature |
Reheats the low-pressure exhaust steam, increasing its temperature and enthalpy |
|
Pressure Change |
Steam pressure remains largely unchanged (pressure loss ≤ 5%) |
Steam pressure has already decreased (typically 2-4 MPa at high-pressure turbine exhaust) |
|
Application Scope |
Widely used in industrial and power plant boilers |
Primarily used in power plant boilers; rarely used in industrial boilers |
|
Primary Objective |
Improves steam quality to meet high-temperature heating or power generation needs |
Enhances thermal cycle efficiency and protects turbine blades |
The above comparison shows that the core of the superheater is "primary quality improvement," targeting saturated steam that has not yet performed work and has a wide range of applications; the core of the reheater is "secondary efficiency enhancement," targeting spent steam that has already performed work and is primarily used in power plants. Although both are heating devices, their positioning and uses differ significantly.
For both boiler purchasers and operators and maintenance personnel, mastering basic technical knowledge of superheaters and reheaters is key to ensuring appropriate equipment selection and safe operation.
This knowledge focuses on five core dimensions: structural type, typical temperature range, material requirements, temperature control methods, and safety risks.
The core structure of both superheaters and reheaters is the "tube bank." Based on their layout and heat transfer method, they are primarily divided into three categories to meet the heat transfer requirements of different boilers:
Radiant Type: The tube bank is located directly within the boiler furnace or in the high-temperature radiant zone at the furnace outlet, with heat primarily harvested through radiation. Its significant advantages include high heat transfer intensity and rapid steam temperature rise, but the tube walls are subjected to the high temperature of the furnace radiation for a long period of time, resulting in high temperatures. Therefore, this design is often used in the "low-temperature section" of a superheater or the "inlet section" of a reheater, allowing for rapid temperature increases during the initial steam heating phase while minimizing the risk of overheating of the tube walls in the high-temperature section.
Convection-type: The tube bank is installed in the boiler's tail flue, absorbing flue gas heat through convection. This design offers uniform and stable heat transfer, with tube wall temperature relatively less affected by flue gas temperature, resulting in enhanced safety. As the mainstream design for superheaters and reheaters, it is often used in the "high-temperature" or "outlet" sections of the equipment, enabling precise control of the final steam outlet temperature to meet stringent steam parameter requirements for process or power generation.
Platform-type: The tube bank is arranged vertically in a "screen" formation at the furnace outlet, absorbing both radiative and convective heat (radiation accounts for approximately 60% and convection for approximately 40%). This design combines the advantages of high heat transfer efficiency with a compact structure, enabling high heat transfer within the limited flue space. It is particularly suitable for superheaters in large-capacity power plant boilers, meeting the high-parameter and high-load steam requirements of power plants.
The choice of different structural types requires a comprehensive consideration of boiler capacity, operating parameters (pressure, temperature), and flue space. For example, small industrial boilers have low capacity and relatively low heat exchange requirements, so their superheaters are often convection-type. Large power plant boilers, on the other hand, have high parameters and large heat demands, so their superheaters often use a combination of radiant, screen, and convection-type superheaters, achieving efficient energy conversion through multi-stage heat exchange.
The outlet temperatures of superheaters and reheaters are not fixed and are determined based on the specific application and operating parameters of the boiler. Typical temperature ranges for different application scenarios are as follows:
Superheater Outlet Temperature:
Industrial boilers are commonly used for process heating in industries such as the chemical and textile industries. Superheater outlet temperatures are typically 350-450°C. When combined with medium- and low-pressure operating parameters (such as the common 3.82 MPa and 450°C combination), they can meet most industrial high-temperature heating needs.
Power plant boilers require higher temperatures to efficiently drive steam turbines for power generation. The superheater outlet temperature of a subcritical power plant boiler is 540°C; supercritical power plant boilers, due to improved parameters, can reach temperatures of 566-600°C; and ultra-supercritical power plant boilers, pursuing higher energy efficiency, have their temperatures further increased to 600-620°C.
Reheater Outlet Temperature:
The core function of the reheater is to restore the exhaust temperature of the high-pressure cylinder. Therefore, its outlet temperature is typically close to the main steam (superheater outlet steam) temperature, generally 10-30°C lower than the main steam temperature. For example, when the main steam temperature is 540°C, the reheat steam temperature is approximately 520-530°C. When the main steam temperature rises to 600°C, the reheat steam temperature is adjusted accordingly to 580-590°C, ensuring that the steam entering the intermediate and low-pressure cylinders still has high work capacity.
Setting the temperature range requires balancing the equipment material's tolerances with actual application requirements. Excessively high temperatures can cause creep failure in the pipes, shortening equipment life. Excessively low temperatures can't meet the heat source requirements of industrial processes or the power generation efficiency requirements of power plants, resulting in energy waste.
Superheater and reheater tubes are exposed to high temperatures and high pressures for extended periods of time and come into direct contact with corrosive flue gases. This places extremely high demands on material properties. Commonly used materials are alloy steels, and the specific choice depends on the tube wall temperature:
Tube wall temperature ≤480℃ Low-alloy heat-resistant steel, such as the Chinese grade 12Cr1MoV, is often used. This material contains alloying elements such as chromium, molybdenum, and vanadium, and offers excellent thermal strength (resistance to deformation at high temperatures) and processability (easily machined and welded). It also offers relatively low cost and is suitable for superheaters in medium- and low-pressure industrial boilers, meeting temperature requirements of 350-450°C.
Tube wall temperatures of 480-580°C: Medium-alloy heat-resistant steel is used, typically the US grade T91 and its Chinese counterpart, P91. This material, based on low-alloy steel, increases the alloying element content, significantly improving its high-temperature creep resistance (the ability to resist slow deformation under prolonged high temperatures) and corrosion resistance. It is suitable for the operating environments of subcritical and supercritical power plant boilers and is the mainstream material for superheaters and reheaters in these boilers.
Tube wall temperature＞580℃: High-alloy heat-resistant steels, such as T122/P122 and HR3C, are required. These materials, with a chromium content exceeding 20%, can operate stably and long-term in ultra-high-temperature environments of 600-650°C, effectively resisting high-temperature oxidation and corrosion. They are primarily used in the high-temperature superheaters and reheaters of ultra-supercritical power plant boilers, meeting the high-power generation requirements.
In addition, all pipes must undergo rigorous quality inspections, including nondestructive testing (UT ultrasonic testing and RT radiography) to identify internal defects such as cracks and pores; mechanical testing (tensile testing and impact testing) to verify material strength and toughness; and metallographic analysis to examine the material's internal structure and ensure the absence of internal defects, ensuring it meets the requirements of long-term high-temperature operation.
Superheater and reheater outlet temperatures must be strictly controlled within the design range (typically within ±5°C). Abnormal temperatures can cause equipment failure: Overheating can lead to pipe creep failure, while undertemperature can affect efficiency or cause wet steam erosion in the turbine. Three common temperature control methods are:
Water Spray Desuperheater: A water spray desuperheater is installed between the superheater or reheater tube banks. A suitable amount of desalted water (or condensate) is injected into the high-temperature steam. The water mixes with the steam, absorbs heat, and evaporates, rapidly reducing the steam temperature. This method offers the advantages of fast response (adjustment lag time of only 10-30 seconds) and high control accuracy. It is currently the most widely used temperature control method, commonly used in the final stage of the superheater and the outlet section of the reheater, enabling precise fine-tuning of the final steam temperature.
Flue gas dampers: Adjustable dampers are installed on both sides of the superheater or reheater area of the boiler's tail flue. By adjusting the damper opening, the flue gas flow rate through the superheater/reheater is adjusted. For example, when the superheater outlet temperature is high, the flue gas damper in the superheater area is closed to reduce the amount of high-temperature flue gas exposed and reduce the heat exchange intensity. When the temperature is low, the damper is opened to increase the flue gas flow rate. This method is suitable for operating conditions with slow load changes and has a long adjustment lag time (approximately 1-3 minutes). It is often used as an auxiliary method for water spray desuperheating to achieve coarse temperature adjustment and stabilization.
Combustion Adjustment: Temperature is indirectly adjusted by altering the boiler's combustion conditions. Common methods include adjusting the burner's swing angle (changing the flame center height), optimizing the primary and secondary air ratios, and matching the fuel-to-air ratio. If the flame center moves upward, the flue gas temperature at the furnace outlet increases, increasing the heat absorbed by the superheater and causing the steam temperature to rise. Conversely, a downward shift in the flame center lowers the superheater temperature. This method is considered "coarse adjustment" and is suitable for pre-regulating temperature during significant boiler load fluctuations. It must be used in conjunction with water spray and flue gas dampers to ensure stable temperature within the design range.
Superheaters and reheaters are core, high-temperature, and high-pressure components of boilers. Improper operation or untimely maintenance can easily lead to safety failures. Three main risks require specific mitigation:
Superheater tube burst: This is the most common type of failure and is primarily caused by three reasons:
① Excessive steam flow (e.g., prolonged low-load operation of the boiler), which prevents adequate cooling of the tube walls and causes temperatures exceeding the material's tolerance limit; ② Substandard feedwater quality leads to scale formation within the tubes. This scale increases thermal resistance and causes localized overheating of the tube walls;
③ Quality defects in the tube material (e.g., weld cracks, uneven wall thickness), which can lead to creep rupture under prolonged high-temperature operation. Tube bursts can cause steam leaks, requiring emergency shutdown for repairs in severe cases, resulting in production interruptions and financial losses.
Insufficient reheater temperature: When the reheater outlet temperature falls below the design value (deviation exceeding 30°C), two major problems can occur:
① Increased steam humidity at the turbine's intermediate and low-pressure cylinder inlets. High-velocity wet steam can erode turbine blades, shortening blade life;
② Decreased thermal cycle efficiency, increased power plant coal consumption, and higher operating costs.
Common causes include:
① Improper flue gas damper opening, insufficient flue gas flow through the reheater, and reduced heat exchange efficiency;
② Malfunctioning water spray desuperheater, resulting in excessive water spray and a significant drop in steam temperature;
③ Low boiler combustion efficiency, resulting in low furnace outlet flue gas temperature, which cannot provide sufficient heat for the reheater.
Tube Corrosion: Corrosion is primarily categorized as low-temperature corrosion and high-temperature oxidation corrosion:
① Low-temperature corrosion: Fuel with a high sulfur content (such as high-sulfur coal) generates corrosive gases such as SO₂ and SO₃ upon combustion. These gases combine with water vapor in the flue gas to form sulfuric acid mist, which adheres to the tube walls at the reheater inlet (where the flue gas temperature is lower), causing corrosion.
② High-temperature oxidation corrosion: When the tube wall temperature exceeds 600°C, the tube reacts with the oxygen in the flue gas, forming an oxide scale. This oxide scale detaches, thinning the tube wall, reducing tube strength and increasing the risk of tube bursts.
During boiler procurement and operation, customers often raise questions about core requirements such as "need for configuration," "economic efficiency," and "safety." The following are professional answers to frequently asked questions:
Determining whether to configure a reheater depends on your specific needs:
Superheater: Recommended if any of the following conditions are met:
① The production process requires high-temperature dry steam (such as chemical reactions or textile finishing);
② Driving a steam turbine for power generation (whether in a power plant or an industrial self-contained power plant);
③ The steam transmission distance is long (superheated steam has a low water content, which reduces pipeline condensation losses). If only low-temperature steam is required (such as for heating or small-scale heating), then a reheater is not necessary.
Reheater: Configuring a reheater is economical only when the requirements of a "large power plant boiler (single unit capacity ≥ 300MW) + high-parameter thermodynamic cycle" are met. For industrial boilers, small waste heat power plants, and other scenarios, the investment cost of configuring a reheater far exceeds the energy savings, so it is not worth considering.
Energy Efficiency and Economics
Superheater Economics: Installing a superheater can increase steam enthalpy, reduce energy losses, and achieve fuel savings of approximately 5%-10%. (For example, a 10t/h industrial boiler can save approximately 300-500 tons of standard coal annually after installing a superheater.) The payback period for industrial boilers is typically 1-2 years, while for power plant boilers, due to their larger capacity, the payback period can be shortened to 0.5-1 year.
Reheater Economics: This is only effective for power plant units above 300MW, improving cycle efficiency by 3%-5%. A 600MW unit can save approximately 30,000 tons of standard coal annually, with a payback period of approximately 2-3 years (due to the complex reheater system and high initial investment).
Operation and Maintenance
Service life: The design life of superheaters and reheaters is typically 15-20 years for power plant boilers and 8-12 years for industrial boilers. The actual service life depends on: ① Material quality (e.g., P91 steel has a longer lifespan than 12Cr1MoV steel); ② Operating parameter control (whether it is subject to chronic overheating); and ③ Maintenance frequency (regular pickling and flaw detection).
Scale and corrosion prevention: ① Strictly control feedwater quality (hardness ≤ 0.03 mmol/L, oxygen content ≤ 7 μg/L) to prevent scale formation in the pipes; ② Select low-sulfur fuel (sulfur content ≤ 0.8%) to reduce the generation of corrosive gases; ③ Regularly inspect the pipe walls (ultrasonic flaw detection every six months) and perform chemical pickling annually to remove scale and oxide scale.
Reputable boiler manufacturers must provide the following quality certifications:
Material Certification: Superheater/reheater tubes must be accompanied by a material certificate (such as a quality assurance certificate issued by the steel mill), clearly specifying the material grade (e.g., T91, 12Cr1MoV), chemical composition, mechanical properties, and other parameters to ensure compliance with standards such as GB/T 5310 "Seamless Steel Tubes for High-Pressure Boilers."
Third-Party Testing: Key components (such as welded joints) must undergo non-destructive testing (UT/RT testing, with a 100% pass rate) and a hydrostatic test (test pressure of 1.25-1.5 times the design pressure, maintained for 30 minutes without leakage) by a third-party testing agency. A test report must also be provided.
Temperature Stability: Boilers equipped with a dual-control system of "water spray desuperheating + flue gas dampers" can control steam temperature fluctuations within ±5°C, meeting process or power generation requirements. Highly automated boilers (equipped with a DCS control system) can automatically adjust temperature without manual intervention.
Overtemperature Protection: Boilers require multiple protection measures: ① Temperature alarm (audio-visual alarm when the temperature exceeds the design temperature by 10°C); ② Automatic desuperheating (automatically increasing the temperature of the water spray desuperheater when overtemperature occurs); ③ Emergency Shutdown (when the temperature exceeds the material limit, the boiler's MFT protection is triggered and the fuel supply is cut off).
To prevent superheater tube bursts: ① Ensure stable boiler load (avoid prolonged operation at low load); ② Regularly clean the tube stack (perform annual acid cleaning); ③ Closely monitor steam flow and tube wall temperature during operation, and make timely adjustments if any abnormalities are detected.
To prevent wet steam erosion of steam turbines: ① Ensure the reheater outlet temperature meets the specified temperature (with a deviation of no more than ±10°C); ② Install a humidity monitoring device at the turbine inlet, triggering an alarm if the temperature exceeds the specified temperature; ③ Regularly inspect turbine blades and promptly repair any signs of erosion.
Although both boiler superheaters and reheaters are high-temperature heat exchangers, they differ significantly in their scope of application and core value. Superheaters are highly versatile and a core component for generating high-temperature steam in industrial and power plant boilers, prioritizing quality improvement. Reheaters are used exclusively in large power plant boilers over 300MW, focusing on efficiency improvement and engine protection. When selecting boiler configurations, industrial applications should evaluate superheater configuration based on process requirements. Power plant operators should standardize both configurations and prioritize the reliability of materials and temperature control systems. This will optimize procurement and operation, achieving safety and energy conservation goals.
