Amidst the continuous growth of global industry and rising energy demand, energy efficiency and environmental protection have become core issues in industry development. During industrial production, a significant amount of energy is directly discharged as waste heat, resulting in significant energy waste and increasing environmental burdens. Industrial waste heat boilers, as highly efficient waste heat recovery equipment, can convert waste heat generated during industrial production into usable steam or hot water, achieving secondary energy utilization. They play a vital role in improving corporate energy efficiency, reducing production costs, and promoting sustainable development. A thorough understanding of the operating principles, application scenarios, and advantages of industrial waste heat boilers, particularly solutions to common operational issues, is crucial for industrial enterprises to optimize their energy structure and achieve green production.
An industrial waste heat boiler is a heat exchange device specifically designed to recover waste heat generated during industrial production and convert it into steam, hot water, or other forms of thermal energy. Its core operating principle is based on heat conduction and convection. When high-temperature waste heat carriers generated during industrial production flow through the heating surface of a waste heat boiler, the heat in the waste heat carrier is transferred through the heating surface to the water or other working fluid within the boiler. As the working fluid absorbs the heat, its temperature gradually rises. When it reaches a certain pressure and temperature, the water vaporizes to produce steam. This steam can be used for various purposes, such as heating in industrial production, driving steam turbines for power generation, and heating, thereby effectively recovering and reusing waste heat energy. Unlike traditional boilers that consume fuel to generate heat, industrial waste heat boilers primarily rely on recovering industrial waste heat to operate, resulting in significant energy savings.
Industrial waste heat boilers are widely used across multiple industrial sectors due to their efficient waste heat recovery capabilities. In the metallurgical industry, blast furnace gas, converter gas, and high-temperature flue gas from steel mill heating furnaces during steel production contain significant amounts of waste heat. waste heat boilers recover this heat, generating steam for power generation, heating the steel mill's rolling mills, and heating the factory floor. In the chemical industry, various chemical reactors, cracking furnaces, and synthesis towers generate high-temperature waste heat during operation. waste heat boilers utilize this waste heat to generate steam, providing thermal energy for the chemical production process or driving generators, while reducing energy consumption and carbon emissions. In the power industry, thermal power plants emit large amounts of high-temperature flue gas. Installing waste heat boilers in the flue ducts can recover this waste heat to heat feedwater, improving boiler efficiency and reducing fuel consumption. In the building materials industry, cement production generates significant amounts of heat from high-temperature flue gas from rotary kilns and preheaters. waste heat boilers recover this heat to generate steam that drives steam turbines, providing power for cement production and reducing energy costs.
Energy conservation, environmental protection, and sustainable development are the core advantages of industrial waste heat boilers. By recycling waste heat from industrial production, waste heat boilers significantly reduce enterprises' consumption of traditional energy sources such as coal and natural gas, significantly reducing energy procurement costs. The energy-saving benefits of equipment can quickly offset investment costs, enhancing enterprise competitiveness. Furthermore, they reduce fossil energy use, effectively lower emissions of pollutants such as carbon dioxide and sulfur dioxide, and reduce thermal pollution, helping enterprises meet environmental standards. Furthermore, waste heat boilers improve energy efficiency, promote the transition to a cleaner energy structure, support the achievement of carbon peak and carbon neutrality goals, promote the coordinated development of industrial production and environmental protection, and achieve unified economic, social, and environmental benefits.
Non-combustion waste heat boilers are one of the most common types of industrial waste heat boilers. Their most notable feature is that they operate without a combustion device and rely entirely on recycled waste heat generated during industrial production to heat the working fluid. The heating surface design and layout of this type of waste heat boiler are specifically optimized based on parameters such as the temperature, flow rate, and composition of the waste heat carrier to ensure maximum waste heat absorption. Uncombustion-free waste heat boilers are suitable for industrial applications where the waste heat carrier temperature is relatively stable and the waste heat supply is sufficient and continuous, such as recovering waste heat from blast furnace flue gas in steel mills and recovering waste heat from continuous reactions in chemical plants. Because they do not require fuel combustion, uncombustion-free waste heat boilers not only have low operating costs but also avoid pollutant emissions generated by fuel combustion, resulting in excellent energy-saving and environmental benefits. However, their operational performance is significantly affected by fluctuations in waste heat carrier parameters. When the waste heat carrier temperature is too low or the flow rate is insufficient, it may not meet the working medium heating requirements, resulting in a decrease in steam production or hot water temperature.
Supplementary-fired waste heat boilers, based on uncombustion-free waste heat boilers, incorporate a supplementary combustion device. When the waste heat generated during industrial production is insufficient to meet the working medium heating requirements, or when the waste heat carrier parameters fluctuate significantly, the supplementary combustion device can burn a small amount of fuel to supplement the heat, ensuring the boiler can stably output steam or hot water that meets the requirements. The supplementary combustion volume of supplementary-fired waste heat boilers can be flexibly adjusted according to changes in the waste heat supply, ensuring stable and reliable boiler operation. This type of waste heat boiler is suitable for industrial applications with low waste heat carrier temperatures and unstable or intermittent waste heat supply, such as waste heat recovery in certain intermittent chemical reaction processes and waste incineration power plants. Supplementary-fired waste heat boilers can fully utilize industrial waste heat while also compensating for insufficient waste heat through supplementary firing, expanding the application range of waste heat boilers. However, compared to non-fired waste heat boilers, they consume a certain amount of fuel during operation, increasing operating costs and also generating small amounts of pollutant emissions. However, their overall energy efficiency and environmental benefits are still superior to traditional boilers.
Waste heat boilers for power generation are specifically designed for use with steam turbine power generation systems. Their primary function is to generate superheated steam at high pressure and temperature to drive the turbine, which in turn drives the generator. The design of this type of waste heat boiler places strict requirements on steam parameters, ensuring that the steam generated meets the operating requirements of the steam turbine to achieve high power generation efficiency. Waste heat boilers for power generation are often used in conjunction with industrial production equipment to recover large amounts of high-temperature waste heat generated during industrial production processes, such as waste heat from converter flue gas in the metallurgical industry and waste heat from cement rotary kilns in the building materials industry. In some large industrial enterprises, waste heat power generation systems composed of waste heat boilers, steam turbines, and generators can provide a large amount of electricity, not only meeting the company's own electricity needs but also allowing excess electricity to be sold to the grid, generating additional economic benefits. The use of waste heat boilers for power generation converts industrial waste heat into electricity, further enhancing the utilization value of waste heat resources. They are a key way for industrial enterprises to achieve energy cascade utilization and improve overall energy efficiency.
Over the long term, industrial waste heat boilers are prone to a range of operational problems due to factors such as the composition of the waste heat carrier, operating conditions, and maintenance. These problems not only reduce the heat transfer efficiency of the waste heat boiler and lead to unstable steam production and quality, but can also damage equipment components, increase equipment maintenance costs, and even cause safety incidents, disrupting normal industrial production. Common operational challenges include scaling and ash accumulation, corrosion, flue gas flow and pressure drop issues, unstable steam quality and output, mechanical wear and component damage, and control and monitoring failures. Thoroughly analyzing the causes, consequences, and impact of these issues on equipment operation, and implementing effective preventive and remedial measures, is crucial to ensuring the safe, stable, and efficient operation of industrial waste heat boilers.
Causes and Consequences
Scaling primarily occurs on the water-side heating surfaces of waste heat boilers (HRSBs). Its cause is primarily related to the quality of the boiler water. When boiler water contains hardness components such as calcium and magnesium ions, as well as dissolved bicarbonates and sulfates, these substances react chemically during heating to form insoluble precipitates such as calcium carbonate and magnesium hydroxide. Over long-term boiler operation, these precipitates gradually deposit on the water-side heating surfaces, forming scale. Furthermore, improper operation of the boiler water treatment system, which fails to effectively remove impurities and hardness components from the water, or unstable boiler water level control, which leads to localized overheating of the heating surfaces, can accelerate scale formation. Ash accumulation primarily occurs on the flue gas-side heating surfaces of waste heat boilers (HRSGs). It is caused by solid particles such as dust and fly ash contained in the waste heat carrier (e.g., high-temperature flue gas). During industrial production, high-temperature flue gas carries large amounts of dust and fly ash. As the flue gas flows through the flue gas-side heating surfaces, these solid particles deposit on the surfaces due to inertia and diffusion, forming an ash layer. If the flue gas contains highly viscous substances (such as tar and asphalt found in some chemical flue gases) or if the flue gas velocity is too low, solid particles are more likely to adhere to and accumulate on the heating surfaces, exacerbating ash accumulation.
Scale and ash accumulation can have serious consequences for the operation of HRSGs. The thermal conductivity of scale and ash layers is much lower than that of metal heating surfaces, creating thermal resistance on the heating surfaces, hindering heat transfer and reducing the boiler's heat transfer efficiency. At the same time, scaling reduces the effective heat exchange area of the water-side heating surface, leading to uneven local heating and potentially causing safety hazards such as overheating, bulging, and even tube bursts. Ash accumulation blocks the flue gas passages, increasing flue gas flow resistance, increasing induced draft fan energy consumption, and even disrupting the proper exhaust of industrial equipment, ultimately affecting the stable operation of the entire production process.
Impact on Heat Transfer Efficiency
Heat transfer efficiency is a key metric for measuring waste heat boiler performance, and scaling and ash accumulation have the most direct and significant impact on this efficiency. During the heat transfer process in a waste heat boiler, heat must be transferred from the flue gas side or other waste heat carrier side through the heating surface to the water side or other working fluid side. When scale or ash deposits form on the heating surface, due to their extremely low thermal conductivity, they create significant thermal resistance on both sides of the heating surface.
For scaling on the water side, the scale layer hinders heat transfer from the metal of the heating surface to the water or steam, causing the metal temperature to rise while reducing the amount of heat absorbed by the water or steam, resulting in reduced evaporation capacity. Even if the heat provided by the waste heat carrier remains constant, the increased heat transfer resistance reduces the effective heat absorbed by the working fluid, significantly decreasing the boiler's heat transfer efficiency.
As for soot accumulation on the flue gas side, the ash layer hinders the transfer of heat from the high-temperature flue gas to the metal heating surface, causing the flue gas outlet temperature to rise and a large amount of heat to be discharged into the atmosphere with the flue gas, resulting in a waste of waste heat resources. Furthermore, the presence of the ash layer alters the flow of flue gas through the heating surface, reducing the effective contact area between the flue gas and the heating surface, further reducing heat transfer efficiency. According to relevant data, when the scale thickness on the heating surface reaches 1mm, the boiler's heat transfer efficiency decreases by 5%-10%. When the soot thickness on the flue gas side reaches a certain level, the heat transfer efficiency can decrease by 10%-20%, seriously affecting the energy efficiency and operating economy of the waste heat boiler.
High-Temperature Corrosion
High-temperature corrosion primarily occurs in the high-temperature areas of the flue gas-side heating surfaces of waste heat boilers. High-temperature corrosion is most likely to occur when flue gas temperatures exceed 400°C. This phenomenon is primarily caused by corrosive components in the flue gas. For example, in certain industrial processes, sulfur in the fuel produces sulfur dioxide upon combustion. Under the influence of high temperatures and catalysts, some of this sulfur dioxide further oxidizes to sulfur trioxide. Sulfur trioxide combines with water vapor in the flue gas to form sulfuric acid vapor. When sulfuric acid vapor comes into contact with the hotter heating surfaces, it forms a sulfuric acid film on the surface. This film is highly corrosive and chemically reacts with the metal, causing corrosion damage. Furthermore, elements such as chlorine and vanadium in the flue gas also react with the metal at high temperatures, exacerbating the severity of high-temperature corrosion.
High-temperature corrosion can gradually reduce the thickness and strength of the metal walls of the heating surfaces. In severe cases, it can lead to perforations and leaks, impacting the normal operation of the waste heat boiler and even causing safety accidents. At the same time, corrosion products adhere to the heated surface, further increasing thermal resistance and reducing heat transfer efficiency. The occurrence of high-temperature corrosion is closely related to factors such as flue gas composition, heated surface temperature, and metal material properties. High-temperature corrosion is particularly prominent in industrial environments with high sulfur content, such as those burning oil and coal.
Low-temperature acid dew-point corrosion
Low-temperature acid dew-point corrosion occurs in the low-temperature region of the heated surface on the flue gas side of a waste heat boiler (HRSG). This corrosion typically occurs when the heated surface temperature falls below the flue gas's acid dew-point temperature. Its mechanism is similar to that of high-temperature corrosion: acidic gases in the flue gas combine with water vapor to form acidic liquids. These acidic liquids adhere to the heated surface, corroding the metal.
The flue gas's acid dew point temperature depends on the flue gas's acid gas concentration, particularly sulfur trioxide. A high sulfur trioxide concentration in the flue gas increases the acid dew point temperature accordingly. During waste heat boiler operation, to improve waste heat recovery efficiency, the flue gas outlet temperature is typically kept as low as possible. This causes the heating surface temperature in the low-temperature area to fall below the acid dew point, creating conditions for low-temperature acid dew point corrosion.
Low-temperature acid dew point corrosion causes severe corrosion on the heating surface, forming pits. As corrosion progresses, the metal gradually deteriorates, leading to problems such as perforations and leaks. Furthermore, corrosion products mix with dust and other substances in the flue gas, forming sticky deposits on the heating surface, further hindering heat transfer and reducing heat transfer efficiency. Low-temperature acid dew point corrosion is common in waste heat boilers in industries such as the chemical and power industries, and is particularly severe when using fuels with high sulfur content or processing flue gases with high sulfur content.
Blockage, Leakage, and Reduced Efficiency
During the operation of industrial waste heat boilers, flue gas flow and pressure drop are significant factors affecting the proper operation and efficiency of the boiler. Poor flue gas flow or excessive pressure drop often leads to a range of problems, with blockage and leakage being the most common. Blockages are primarily caused by the deposition of solid particles such as dust, fly ash, and corrosion products in the flue gas, which settle in the flue ducts, between heating surface tube bundles, or on flue baffles. Over time, these deposits gradually accumulate, reducing the cross-sectional area of the flue ducts and increasing the resistance to flue gas flow, leading to blockage. Blockages prevent flue gas from flowing smoothly through the heating surfaces, reducing the effective contact time and area between the flue gas and the heating surfaces, and thus reducing waste heat recovery efficiency. Blockages also prolong the flue gas's residence time within the boiler, raising local temperatures and exacerbating high-temperature corrosion and ash accumulation on the heating surfaces. Furthermore, blockages increase the load on the induced draft fan, leading to increased energy consumption. Insufficient induced draft fan output can even affect the normal exhaust of industrial production equipment, disrupting the stable operation of the entire production process.
Leaks primarily occur in the flue ducts, expansion joints, flange connections, and welds on the heating surface tubes of the waste heat boiler. Causes of leakage may include quality defects during equipment manufacturing, damage to seals or cracking of pipes due to vibration and thermal expansion and contraction during operation, and thinning and perforation of pipe walls caused by corrosion. When flue gas leaks occur, cold air is drawn into the flue, causing the flue gas temperature to drop, diluting the residual heat in the flue gas and reducing waste heat recovery efficiency. Furthermore, if the leaked flue gas contains corrosive components, it can corrode and damage surrounding equipment and buildings, potentially posing a health risk to operators. Furthermore, flue gas leaks can lead to uneven pressure distribution within the flue, further impacting proper flue gas flow, increasing pressure drop, and reducing the efficiency of the induced draft fan.
Both blockages and leaks significantly reduce the heat transfer efficiency of the waste heat boiler, increasing energy waste and operating costs. They also shorten the equipment's lifespan and increase the frequency of equipment repairs and replacements, resulting in significant financial losses for the company.
Pipeline Leakage, Erosion, and Fatigue Damage
Pipelines are a crucial component of industrial waste heat boilers, transporting waste heat carriers, such as water or steam. Over long-term operation, pipelines are prone to leakage, erosion, and fatigue damage, seriously impacting the safe and stable operation of the boiler.
Pipeline leakage is one of the most common mechanical damage issues, and its causes are complex. First, corrosion is the primary cause of pipeline leakage. High-temperature corrosion and low-temperature acid dew-point corrosion, as mentioned above, gradually reduce the pipe wall thickness. When the wall thickness decreases to a certain extent, the pressure of the medium causes the pipe to leak. Second, defects in pipeline welding quality are also a significant factor in leaks. Welding defects such as incomplete penetration, slag inclusions, and porosity can act as stress concentration points. Over long-term operation, as medium pressure and temperature fluctuate, these defects can gradually expand, ultimately leading to pipeline leakage. Furthermore, improper pipeline installation, such as loose connections between the pipeline and equipment and inadequate pipe support, can cause additional stress during operation, potentially leading to leaks over time. Pipe erosion primarily occurs in areas with high flow velocities and sudden changes in flow direction. It's caused by solid particles in the medium or the high-speed flow of the medium itself, which scours and abrades the pipe's inner wall. In industrial waste heat boilers, the flue gas ducting contains high dust levels and typically high flue gas velocities. Dust particles continuously scour the pipe's inner wall, causing gradual wear and thinning. If solid impurities are present in the water-side pipe, the high-speed flow of the working fluid will also cause erosion on the inner wall. Pipe erosion can lead to uneven thinning of the pipe's wall thickness, reducing its load-bearing capacity and damaging the protective film on the inner wall, exacerbating corrosion and further shortening its service life.
Pipe fatigue failure is caused by the cyclical stress changes experienced by the pipe during long-term operation. The operating conditions of industrial waste heat boilers typically fluctuate with industrial production loads, leading to frequent fluctuations in the temperature and pressure of the medium within the pipe. This causes cyclical thermal expansion and contraction, as well as pressure fluctuations, which in turn generate alternating stresses within the pipe. When the amplitude of alternating stress exceeds the fatigue limit of the pipe material and the number of times it occurs reaches a certain level, fatigue cracks will form within the pipe. As the cracks continue to expand, they eventually lead to fatigue fracture. Pipeline fatigue failure is highly hidden and sudden, often occurring without obvious warning signs, easily leading to serious safety accidents.
Heating Surface Wear and Deformation
The heating surface is the core component for heat exchange in industrial waste heat boilers, primarily including the economizer, evaporator, and superheater. During operation, the heating surface is prone to wear and deformation, affecting the boiler's heat transfer efficiency and safe operation.
Heating surface wear primarily occurs on the flue gas side of the heating surface. Its cause is similar to pipe erosion, primarily due to the erosion and impact of solid particles such as dust and fly ash carried by high-temperature flue gas on the heating surface. Dust particles in flue gas have a certain hardness and kinetic energy. When flue gas flows through the heating surface, the dust particles collide and rub against the surface, gradually wearing away the metal layer. The extent of heating surface wear is closely related to flue gas flow rate, dust concentration, dust particle hardness, and the heating surface structure. The higher the flue gas flow rate, the greater the kinetic energy of the dust particles, and the more severe the wear. The higher the dust concentration, the more particles collide with the heating surface per unit time, and the more severe the wear. The harder the dust particles, the stronger the scraping effect on the heating surface. Furthermore, the arrangement of the heating surface tube bundles can affect the flue gas flow. Staggered tube bundles can cause more turbulent flue gas flow, exacerbating dust particle wear on the heating surface. Heating surface wear can lead to reduced wall thickness and strength, increasing the risk of leakage and reducing the effective heat exchange area, thereby lowering the boiler's heat transfer efficiency.
Heating surface deformation is primarily caused by localized overheating or uneven temperature distribution. When scale or ash accumulates on the heating surface, it creates thermal resistance, hindering heat transfer and causing the metal temperature of the heating surface to rise. If the scale or ash accumulation is uneven, it can cause significant temperature differences between different parts of the heating surface, generating thermal stress. Over time, this can lead to deformation of the heating surface. Furthermore, improper boiler water level control, such as a low water level that exposes part of the heating surface to high-temperature flue gas, can cause the heating surface to heat up rapidly due to dry combustion, leading to deformation. During boiler startup or shutdown, if the heating rate is increased or decreased too quickly, the temperature difference between the inner and outer walls of the heating surface can be significant, generating significant thermal stress and easily causing deformation. Heating surface deformation can undermine the structural integrity of the heating surface, leading to uneven tube bundle spacing, affecting the flow of flue gas and working fluid, and further reducing heat transfer efficiency. Furthermore, the deformed heating surface may collide with other components, causing more serious equipment damage.
Automation and Instrumentation Issues
With the continuous advancement of industrial automation, industrial waste heat boilers generally use automated control systems and various instruments to monitor and control boiler operating parameters to ensure safe and stable operation. However, during actual operation, automated systems and instruments are prone to failure, resulting in inaccurate monitoring and effective control of boiler operating parameters, which in turn affects boiler operating efficiency and safety.
Automation control system failures primarily include controller failures, actuator failures, and communication failures. The controller is the core of the automation control system, responsible for receiving monitoring signals from instruments, calculating control commands based on preset control logic, and sending them to the actuators. A controller failure prevents it from properly receiving signals, calculating commands, or sending commands, rendering the control system inoperative and unable to adjust boiler operating parameters. The actuator is responsible for executing the control commands issued by the controller, adjusting parameters such as flow and pressure of the medium. A failure in the actuator prevents the effective execution of control commands. Even if the controller is functioning properly, the boiler operating parameters cannot be controlled. Communication failures refer to problems with signal transmission between the controller and the instruments and actuators. This prevents signal transmission, preventing the control system from obtaining accurate monitoring data or sending control commands, leading to a paralyzed state.
Instrument problems primarily manifest as inaccurate or ineffective instrumentation. The main causes include the following: First, improper instrument selection. If the instrument's range, accuracy, operating temperature, and pressure range don't match the boiler's actual operating conditions, the instrument will be unable to accurately measure parameters. For example, a temperature instrument with a range that is too large will increase measurement errors in the low-temperature range. Second, improper instrument installation. For example, if the temperature measuring point of a temperature instrument isn't installed where the medium's temperature is uniform, if there are air or liquid plugs at the pressure tapping point of a pressure instrument, or if the flow meter isn't installed in the correct position for a straight pipe section, all of these factors can affect the instrument's measurement accuracy. Third, instrument aging or damage. Over extended operation, the instrument's sensors, electronic components, and other components gradually age and degrade, leading to increased measurement errors. If subjected to harsh operating conditions such as vibration, corrosion, and high temperatures, instrument components may also be damaged, causing instrument failure. Fourth, untimely instrument calibration. Over long-term operation, the instrument's measurement accuracy will gradually deviate from the standard value. Failure to perform calibration at the prescribed intervals will result in inaccurate measurement data and a failure to provide a reliable basis for the control system. Automation and instrumentation failures can pose serious operational risks to industrial waste heat boilers. On the one hand, inaccurate or failed instruments fail to reflect the boiler's true operating status, potentially leading operators and control systems to make incorrect judgments and operations based on erroneous information. For example, if the water level meter indicates a low reading, operators may blindly increase the feedwater, causing the boiler water level to overshoot and causing steam to carry water. Inaccurate pressure meter readings can cause the boiler to operate at overpressure, leading to safety accidents. On the other hand, failures in the automated control system can render the boiler unable to automatically adjust, forcing it to rely on manual operation. This not only increases the operator's workload but can also exacerbate fluctuations in boiler operating parameters due to lags and errors in manual operation, impacting boiler efficiency and safety.
Preventive maintenance is a key measure to avoid operational problems in industrial waste heat boilers, extend equipment life, and ensure safe and stable operation. By taking proactive measures, potential faults can be eliminated and the probability of failure reduced.
Using Corrosion-Resistant Materials and Coatings
Selecting corrosion-resistant materials and applying anti-corrosion coatings are effective preventative measures against common corrosion problems in industrial waste heat boilers. During boiler design and manufacturing, appropriate corrosion-resistant materials should be selected based on the composition of the waste heat carrier, temperature, pressure, and other operating conditions. For example, heat-resistant alloy steels containing elements such as chromium, nickel, and molybdenum can be used for flue gas heating surfaces, which are subject to severe high-temperature corrosion. These materials offer excellent high-temperature strength and corrosion resistance, effectively resisting corrosion from acidic gases and harmful elements in high-temperature flue gases. For low-temperature heating surfaces, which are subject to severe low-temperature acid dew point corrosion, materials resistant to sulfuric acid corrosion can be used.
In addition to selecting corrosion-resistant materials, applying anti-corrosion coatings to susceptible components such as heating surfaces and piping is also a cost-effective protective measure. Commonly used anti-corrosion coatings include ceramic coatings, metal-ceramic coatings, and organic polymer anti-corrosion coatings. Ceramic coatings offer high-temperature resistance, wear resistance, and corrosion resistance, making them suitable for high-temperature flue gas heating surfaces. Metal-ceramic coatings combine the toughness of metal with the corrosion resistance of ceramic, offering excellent bonding strength and corrosion resistance. Organic polymer anti-corrosion coatings are suitable for low-temperature, less corrosive environments, such as boiler water-side piping. Anti-corrosion coatings form a dense protective film on component surfaces, isolating the corrosive medium from the metal surface, thereby preventing corrosion.
Water Treatment System Optimization
Optimizing the water treatment system is a key measure to prevent boiler scaling, corrosion, and poor steam quality. First, appropriate water treatment processes, such as ion exchange, reverse osmosis, and chemical precipitation, should be selected based on the boiler's water quality requirements and the characteristics of the water source. This ensures that the boiler water's hardness, salinity, impurities, and dissolved oxygen levels meet operational requirements. For example, for water sources with high hardness, ion exchange can be used to remove calcium and magnesium ions to prevent scale formation. For water sources with high salinity, reverse osmosis can be used for desalination to reduce the salt content in the steam. Secondly, strengthen the operational management of the water treatment system, regularly inspecting, cleaning, and regenerating water treatment equipment (such as ion exchange resins, reverse osmosis membranes, and filters) to ensure stable performance. For example, regularly check the exchange capacity of ion exchange resins and regenerate them when capacity drops below a certain level. Regularly clean reverse osmosis membranes to remove surface contaminants, prevent clogging, and ensure desalination efficiency. At the same time, strengthen monitoring of boiler feed water and boiler water quality, regularly sample and analyze water quality indicators, and adjust water treatment chemical dosages based on the results to ensure consistent water quality.
Furthermore, implementing advanced water quality monitoring and control systems to enable real-time monitoring and automated control of water quality parameters is also a key aspect of optimizing the water treatment system. Installing online water quality analyzers allows for real-time monitoring of feed water parameters such as hardness, pH, dissolved oxygen, and conductivity. When parameters exceed specified limits, automatic alarms are triggered and adjustments to the operating status of water treatment equipment or chemical dosages are made to prevent boiler failures caused by water quality issues.
Maintenance Best Practices
Advanced monitoring and diagnostic technologies enable real-time monitoring of the operating status of industrial waste heat boilers, enabling timely identification of potential faults and hidden dangers. This provides a scientific basis for preventive maintenance and is crucial for ensuring safe and efficient boiler operation.
Regular inspection and cleaning are fundamental to best maintenance practices. Regularly conduct comprehensive inspections of the boiler's heating surfaces, piping, flue, valves, instrumentation, and other components to check for scaling, dust accumulation, corrosion, wear, and leaks. For scaling and dust accumulation, appropriate cleaning methods, such as mechanical, chemical, or physical, should be employed based on the type and thickness of the scale and dust. For example, scale on the water-side heating surface can be removed by pickling. During pickling, the appropriate pickling solution and corrosion inhibitor should be selected based on the scale composition, and the pickling temperature and duration should be controlled to avoid corrosion. For dust accumulation on the flue gas-side heating surface, pulse soot blowers can be used for regular cleaning. Pulse soot blowers use pulsed compressed air to effectively remove dust from the heating surface with minimal damage. Real-time performance tracking uses various sensors and monitoring equipment to collect real-time boiler operating parameters and transmit these parameters to a monitoring center for real-time analysis and processing. Real-time performance tracking can promptly detect abnormal changes in boiler operating parameters, such as a sudden increase in heating surface temperature, an abnormal increase in flue gas pressure, or a decrease in steam production. These abnormal changes are often early signs of a fault. Based on the analysis results, the monitoring center issues a timely warning signal, alerting operators to conduct inspections and address the problem, preventing further escalation. Furthermore, by analyzing historical operating data, performance trends can be identified, and the remaining service life of the equipment can be predicted, providing a basis for formulating a reasonable maintenance plan.
Employee training and operating procedures are crucial for ensuring the effective application of advanced monitoring and diagnostic technologies and the safe operation of boilers. Strengthen training for operators and maintenance personnel to familiarize them with the operating principles, structural characteristics, operating parameter requirements, and the use of monitoring and diagnostic equipment, thereby improving their operational skills and fault diagnosis capabilities. Develop comprehensive operating procedures and maintenance procedures to clearly define the responsibilities and operational processes of operators and maintenance personnel. For example, these procedures should include defining the procedures for boiler startup, shutdown, and load adjustment, and specifying the frequency and methods for regular inspection, cleaning, and calibration. Standardized operations and regular training can reduce malfunctions caused by human error and ensure that the boiler always operates at optimal conditions.
Upgrading the waste heat recovery system is a key approach to improving the energy efficiency of industrial waste heat boilers. By optimizing the system structure and adding waste heat recovery equipment, the waste heat generated during industrial production can be recovered to the maximum extent possible, reducing energy waste.
The waste heat recovery system's process design can be optimized based on the characteristics of the waste heat carrier and the differences in waste heat quality. For high-quality waste heat, a superheater or reheater can be added to the existing waste heat boiler to further heat the generated saturated steam into high-temperature, high-pressure superheated steam. This increases the steam's enthalpy, making it more suitable for driving steam turbines for power generation or meeting high-parameter industrial steam requirements, thereby increasing the waste heat's utilization value. For low- and medium-grade waste heat, if the existing system only recovers heat for hot water or low-pressure steam generation, economizers and air preheaters can be added to utilize this waste heat to heat boiler feed water or combustion air, reducing the boiler's external energy consumption while also lowering the final flue gas discharge temperature and minimizing waste heat loss.
Secondly, high-efficiency heat exchange components and equipment can be used to improve the heat transfer efficiency of waste heat boilers. Traditional waste heat boilers often use bare tube bundles for their heating surfaces, which have a low heat transfer coefficient. These can be upgraded with high-efficiency heat exchange tubes such as finned tubes, spirally grooved tubes, and transversely corrugated tubes. Finned tubes, by adding fins to the bare tube surface, increase the heat transfer area. This is particularly suitable for applications with low flue gas heat transfer coefficients, significantly improving heat transfer efficiency. Spiral grooved and transversely corrugated tubes modify the flow state of the fluid within the tube, increasing turbulence and reducing boundary layer thickness, thereby improving the heat transfer coefficient inside and outside the tube. Furthermore, for flue gases with high dust content, wear-resistant, high-efficiency heat exchange tubes can be used. This improves heat transfer efficiency while reducing dust wear on heating surfaces, extending equipment life.
Furthermore, for intermittent waste heat or large fluctuations in waste heat parameters found in industrial production processes, heat storage devices, such as high-temperature heat storage tanks or phase-change heat accumulators, can be added to the waste heat recovery system. When the waste heat supply is sufficient, the heat storage device stores excess heat; when the waste heat supply is insufficient or interrupted, the stored heat is released, ensuring continuous and stable operation of the waste heat boiler and avoiding sudden drops in steam production or frequent equipment starts and stops caused by waste heat fluctuations. For example, in the glass production industry, periodic maintenance of furnaces can lead to interruptions in waste heat supply. Installing a phase-change heat accumulator can store sufficient heat before maintenance, maintaining basic operation of the waste heat boiler during the maintenance period and ensuring a stable steam supply to subsequent steam-consuming equipment.
Integrating industrial waste heat boilers with cogeneration and combined cycle systems is a key strategy for achieving cascaded utilization of waste heat energy and improving overall energy efficiency, particularly for large industrial enterprises or industrial parks.
Cogeneration systems simultaneously generate electricity and heat through a single unit, improving energy efficiency by 15%-30% compared to traditional separate power and heat generation methods. When integrating a waste heat boiler with a cogeneration system, the steam generated by the waste heat boiler first drives a steam turbine to generate electricity, meeting part or all of the enterprise's electricity needs. The low-pressure steam or exhaust steam discharged from the turbine after power generation is then used for heating, drying, and cooking processes in industrial production, or to provide heating and cooling services within the industrial park, achieving a cascaded "electricity-heat" utilization model. For example, in petrochemical plants, the high-temperature flue gas from the catalytic cracking unit first enters a waste heat boiler (HRSG) to generate high-pressure steam, which drives a steam turbine generator to generate electricity. The resulting low-pressure steam is then used for processes such as crude oil heating and chemical feedstock pretreatment. The remaining low-temperature waste heat is then used in a heat exchanger to heat circulating water, providing domestic hot water for the plant. This creates a complete energy cascade chain and minimizes energy waste.
A combined cycle system combines HRSGs with gas turbines and steam turbines to create a dual power generation model: "gas turbine generation - HRSG steam generation - steam turbine generation." This system is suitable for scenarios with both gas energy and industrial waste heat. In this system, the gas turbine first generates electricity using a gaseous fuel such as natural gas or blast furnace gas. The high-temperature exhaust gas then enters the HRSG, which absorbs the flue gas heat to generate steam. This steam then drives the steam turbine to generate electricity again. Some of the steam can also be used for industrial steam or heating as needed. Compared to single gas turbine or waste heat power generation, combined cycle systems can improve energy efficiency to 55%-65%. They can also simultaneously recover waste heat from gas turbine exhaust and other waste heat from industrial processes, further reducing energy consumption and carbon emissions. For example, in steel plants, blast furnace gas is used as fuel for gas turbines. The exhaust from the gas turbines, along with waste heat from the steel rolling furnace, is fed into waste heat boilers (HRSGs). The steam generated drives steam turbines for power generation, while also providing steam for the steelmaking and rolling processes, achieving synergistic utilization of multiple energy sources.
Infrared thermal imaging technology detects infrared radiation from surfaces and converts it into thermal images, enabling rapid measurement of the temperature distribution of waste heat boiler components. During routine inspections, it can precisely locate problems such as dust accumulation on heated areas and pipe blockages. During leak detection, it can quickly identify small leaks. It can also be used to detect insulation damage, reduce heat loss, and improve thermal efficiency.
Vibration and acoustic monitoring technology analyzes equipment operating signals to identify faults. Vibration monitoring of rotating and fixed components can proactively detect problems such as bearing wear and loose tube bundles. Acoustic monitoring, by analyzing sound characteristics, can locate pipe leaks, identify dust accumulation on heated surfaces, and detect unusual impact noises to prevent equipment damage.
Online water quality chemical analysis monitors key indicators such as pH and conductivity in feedwater, boiler systems, and other systems to prevent scaling, corrosion, and steam quality issues. For example, real-time pH control and conductivity monitoring can be used to detect water treatment faults, and dissolved oxygen control can be used to prevent corrosion, ensuring stable boiler water quality.
Integrating multiple detection technologies with the intelligent monitoring platform enables real-time monitoring, data analysis, fault warnings, and remote management. The platform integrates multi-source data to improve fault diagnosis accuracy, automatically provides warnings and alerts based on thresholds, and provides recommended solutions. It also supports remote viewing and report generation, improving equipment management efficiency and reliability.
Industrial waste heat boilers face challenges such as reduced heat transfer efficiency, equipment corrosion, and operational fluctuations during operation. By adopting corrosion-resistant materials, optimizing water treatment processes, and deploying advanced monitoring and diagnostic technologies and intelligent management systems, a comprehensive solution encompassing prevention, detection, and optimization has been established. As key equipment for efficient energy utilization and sustainable development in enterprises, future efforts require a focus on the development of efficient heat exchange technologies, multi-energy collaborative innovation, in-depth intelligent applications, and improved policies and standards to better promote global energy structural transformation and achieve a win-win situation for economic development and environmental protection.
