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Comparison Analysis of the Advantages and Disadvantages of 8 Cleaning Methods for Condensers: Online Cleaning vs. Cleaning During Shutdown. Summary: By analyzing the impact of scale formation on the operational safety and economic efficiency of power generation units, as well as by comparing the advantages and disadvantages of existing condenser cleaning methods in the thermal power industry, and through case studies of online chemical cleaning of condensers in thermal power plants, a comparative analysis of the performance data of these condensers before and after cleaning was conducted. This shows that online chemical cleaning of condensers holds significant potential for adoption in the thermal power industry. Keywords: condenser scaling ； Condenser shutdown cleaning ； Online condenser cleaning ； High condenser exhaust temperature ； Drop in condenser vacuum ； Large condenser terminal difference ； Application of energy-saving technologies I. Common problems caused by scaling in power plant condensers Severe scaling in condensers usually leads to an increase in the temperature difference at the turbine side of the condenser, a deterioration of the vacuum level, and a rise in the exhaust pressure of the condenser. This results in a decrease in the available heat for the turbine, a reduction in the turbine’s output, and a decline in power generation efficiency ； The exhaust temperature of the condenser increases, causing components such as the exhaust cylinder and bearing housings to expand due to heat, which leads to a change in the bearing’s position and results in vibration in the turbine ； An increase in exhaust temperature can also cause the flanges of the heat exchange tubes in the condenser, such as those made of copper, stainless steel, or titanium, to become loose, thereby compromising the seal integrity of the condenser ； Furthermore, a decrease in the condenser vacuum leads to a reduction in the volumetric flow rate of the exhaust steam. Operating the unit under low vacuum for an extended period can cause flow separation and swirls in the last stage blades of the turbine; at the same time, it generates significant excitation forces in certain areas of these blades, which can easily damage them. This may result in the breakage of the last stage blades, leading to turbine damage and shutdown, and even safety accidents. II. Five online condenser cleaning technologies and three shut-down condenser cleaning technologies are available to address the issue of scaling in the condensers of steam turbine generators. Currently, the eight common condenser cleaning technologies are divided into two categories: shut-down cleaning and online cleaning. Common techniques for cleaning condenser fouling that causes shutdowns in steam turbine generator sets include traditional chemical cleaning during shutdown, high-pressure water cleaning, and shot blasting ； Common online cleaning methods for fouling in the condensers of steam turbine generators include rubber ball cleaning, ultrasonic cleaning, robotic cleaning, spiral ribbon cleaning, and online chemical cleaning. ▲Figure 1: Comparative analysis of the advantages and disadvantages of 8 techniques for online cleaning and shutdown cleaning of condensers. Condenser scaling removal via shutdown cleaning technique 1 – Traditional chemical cleaning: In the case of traditional chemical cleaning of condensers, the cleaning efficiency of the tube walls of the heat exchange tubes is high, resulting in thorough cleaning. Traditional chemical cleaning of condenser fouling in copper tubes, stainless steel tubes, and titanium tubes requires shutting down the unit; the cleaning process takes a long time, which affects the normal operation of the unit ； Traditional chemical cleaning for condenser scaling requires the use of effective corrosion inhibition techniques, as well as manual operation, monitoring, and maintenance, in order to prevent corrosion and leakage in the copper, stainless steel, and titanium tubes used for heat exchange, which could otherwise lead to the failure and disposal of these tubes. Technology for stopping the unit for cleaning due to condenser scaling 2 – High-pressure water cleaning of condenser scaling. High-pressure water cleaning is a mechanical method that uses power tools and other equipment to clean the condenser. The disadvantages of this cleaning method include the need to stop the unit, which affects its normal operation; it can also damage the inner surfaces of copper tubes, stainless steel tubes, and titanium tubes. In addition, mechanical scratches appear to varying degrees on the inner surfaces of these heat exchange tubes, and corrosion can occur at these spots, forming crack nuclei that continue to spread inward, leading to damage to the copper tubes, stainless steel tubes, and titanium tubes in the condenser. Technique 3 for shutting down a condenser due to scaling and cleaning it – projectile cleaning of condenser scaling. The advantages and disadvantages of projectile cleaning are similar to those of high-pressure water cleaning; both are mechanical methods that use tools and equipment to clean the condenser. Sometimes, in order to thoroughly clean the walls of the condenser’s heat exchange tubes, both projectile cleaning and high-pressure water cleaning are used alternately. Online cleaning technology for removing scale from condensers without shutting down the plant – 1. Online rubber ball cleaning. There are various types of rubber balls used for this purpose, including ordinary rubber balls, peeled rubber balls, and silicone balls. Rubber ball cleaning is widely used in many thermal power plants; however, the effectiveness of such cleaning systems is limited. Issues such as uneven distribution of rubber balls, low recovery rates, loss of balls, blockages in the heat exchange tubes caused by balls, and high resistance in the secondary filters lead to uneven cleaning and poor results. Shutting down the plant in order to carry out cleaning is necessary to ensure a proper cleanliness level of the condensers. Figure 2: Online rubber ball cleaning for power plant condensers – issues such as blockage by balls, low recovery rate of balls, balls escaping from the system, and low cleaning efficiency due to scaling. Online cleaning technology that allows cleaning of condenser scaling without shutting down the plant: 2 – Online ultrasonic cleaning. Ultrasonic cleaning is a method commonly used for cleaning the copper tubes in condensers; it utilizes ultrasonic vibrations generated by high-frequency sound waves to clean and remove surface dirt. Online ultrasonic cleaning cannot remove severe fouling from condensers without shutting down the unit; it is suitable for removing mild to moderate levels of fouling. However, for severe fouling or deposits inside the copper tubes of the condenser, ultrasonic cleaning may not be effective enough, and other more powerful cleaning methods are required ； Online ultrasonic cleaning of the condenser without shutting it down may cause mechanical damage; the impact force generated by ultrasonic vibrations is considerable. Careful operation is required when using ultrasonic cleaning, and it is essential to select the appropriate frequency and power level. Improper handling can lead to scratches, corrosion, or damage on the surface of the condenser’s copper tubes ； Online ultrasonic cleaning of the condenser to remove scale without shutting down the unit takes a long time; compared to traditional cleaning methods, ultrasonic cleaning usually requires more time to achieve an optimal level of cleanliness ； It requires high costs and energy consumption, and its cleaning efficiency is poor in the latter part of the pipeline. Online cleaning technology for removing scale from condensers without shutting down the system – 3: Online robotic cleaning. This online robotic cleaning system is installed within the water chamber of the condenser; servo motors and reducers are used to control the arms, enabling precise delivery of high-pressure water streams to clean the tube bundles. It can be combined with various other cleaning methods to achieve better cleaning results. However, it has issues such as long cleaning cycles, low efficiency, rapid decay of high-pressure water kinetic energy, poor cleaning performance in the rear section of the tube bundle, a complex system, a high potential failure rate, high investment costs, and high maintenance expenses. Online cleaning technology for condenser scaling without shutdown – 4: Online spiral link cleaning. In this method, a spiral link that can rotate around an axis is placed inside the cooling tubes; the cooling water flowing through these tubes causes the link to rotate and swing, thereby removing dirt. Additionally, this movement improves the heat exchange efficiency within the tubes. This system has advantages such as simple equipment and the ability to operate continuously. However, the connectors increase the frictional loss along the flow path, raising the power consumption of the circulation pump and increasing production costs. Moreover, these connectors can easily cause wear on the tube bundle or lead to their own breakage, which in turn may result in blockages and damage to the tube bundle. Online cleaning technology for condenser scaling without shutdown – 5: Online chemical cleaning. The advantage of traditional shutdown-based chemical cleaning for condenser scaling is thorough cleaning and a high cleaning efficiency. The disadvantage is the need to shut down the system for cleaning, which results in a loss in power generation efficiency ； Cleaning processes that take a long time, and require manual operation, monitoring, and maintenance ； High cost investment and significant losses in the economic efficiency of power generation. Online chemical cleaning of condenser fouling without shutting down the plant is a cleaning technique that has evolved from the traditional method of performing chemical cleaning while the plant is shut down. Online chemical cleaning of the condenser can be carried out without shutting down the plant; it takes a short amount of time and does not require any downtime, thereby reducing losses resulting from power generation interruptions. The HS-186 multi-functional agent, which includes properties for sterilization, removal of sludge, cleaning of scale, and metal passivation, is used in this process. This results in low cleaning costs and short processing times. Online cleaning can be performed for around 10 hours, during which moss, other microorganisms, sludge, and dust are removed, while scale in the tubes is cleared and corrosion of metal components is prevented ； Online chemical cleaning of the condenser fouling can be carried out at any time without shutting down the unit, eliminating the need to wait for major or minor maintenance periods. Online chemical cleaning of the condenser without shutting it down ensures a high cleanliness level. After the cleaning is completed, the key performance indicators of the condenser reach the following values: A. Vacuum level increases by ≥1.0–2.0 kPa; B. The temperature difference decreases by ≤3.0 degrees Celsius; C. The exhaust gas temperature decreases by ≤2.0°C; D. Power generation increases by ≥2% under the same air supply conditions as before. While there are advantages and disadvantages associated with condenser scaling cleaning methods, the online chemical cleaning technique developed from traditional shutdown-based cleaning methods allows for better results in terms of operation, safety, and cost-efficiency, with minimal modifications to existing equipment. Colleagues and students, aside from these 8 condenser cleaning techniques – traditional chemical cleaning, high-pressure water cleaning, projectile cleaning, online gel ball cleaning without shutting down the system, online ultrasonic cleaning without shutdown, online robotic cleaning without shutdown, online spiral ribbon cleaning without shutdown, and online chemical cleaning without shutdown – what other condenser cleaning techniques are you aware of? Which condenser cleaning technology do you think offers the best overall performance at present? Regarding issues such as corrosion and scaling in condensers, red-colored wastewater from boilers, adjustment of the pH value of boiler feed water, red-colored boiler water, hardness in steam condensation water, tube failures due to corrosion and scaling in boilers, corrosion in steam systems, excessive iron content in steam condensation water, yellow-colored steam condensation water, as well as online cleaning and descaling techniques that allow operations to continue without interruption for condenser scaling problems, and similar online descaling methods for boiler scaling without shutting down the boiler – Beijing University of Chemical Technology’s Yan Hui at I86OO475З86 is always available to discuss these issues, exchange experiences and insights. Students are also welcome to share new technologies related to condenser cleaning, as well as their experience in managing and using boiler equipment, so that we can learn from each other in addressing various practical problems associated with boilers. Figure 3: Comparative analysis of the advantages and disadvantages of 8 cleaning methods for condensers – online cleaning versus cleaning during shutdown. Comparison of the condition of the heat exchange tubes in the condensers of steam turbine generators in thermal power plants before and after online chemical cleaning. III. Application examples of online chemical cleaning for removing scale from condensers without shutting down the plant. Operational conditions of the condenser in the Xuzhou Tongshan biomass cogeneration project before online chemical cleaning without shutdown. The Xuzhou Tongshan biomass cogeneration project is equipped with 35 MW high-temperature, ultra-high pressure reheated steam turbine generators, along with a 130 t/h high-temperature, ultra-high pressure reheated circulating fluidized bed biomass boiler. This project uses agricultural straws and forestry waste as primary raw materials; it processes over 600,000 tons of straws per year and generates around 300 million kWh of electricity annually. It provides enterprises in the equipment manufacturing industrial park with combined supply of cooling, heating, electricity, and compressed air. Figure 4: In the condenser of the thermal power plant, online rubber ball cleaning is affected by issues such as ball blockage, low recovery rate of balls, ball loss, and scaling, resulting in a low cleaning efficiency. At 2:58 p.m. on April 14, 2023, in the control room of the biomass cogeneration project’s thermal power plant in Tongshan, Xuzhou, a screenshot showing the condition of the condenser before online cleaning was displayed on the control panel, as shown in Figure 5. The boiler’s gas supply rate is 114.5 t/h, the vacuum level is -87.4 kPa, the exhaust steam temperature is 51.6°C, and the terminal difference is 17.1 degrees Celsius. The power generation capacity is 30.69 MW/H. Scaling on the condenser clearly leads to a low vacuum level in the condenser as well as a large terminal difference; this reduces the thermal efficiency of the turbine unit, increases the standard coal consumption for power generation, and results in a significant decrease in power output. Figure 5 shows the operating conditions of the condenser in the turbine generator set’s control room at the thermal power plant before performing online chemical cleaning without shutting down the unit; it also shows the operating conditions after carrying out semi-sided online chemical cleaning without shutting down the unit. At 5:01 a.m. on April 23, 2023, in the control room of the biomass cogeneration project’s thermal power plant in Tongshan, Xuzhou, a screenshot was taken of the condenser’s semi-sided area after approximately 5 hours of online chemical cleaning without shutting down the unit, as shown in Figure 6. The boiler’s steam supply rate is 118 t/h; the vacuum level increased to -96.0 kPa, while the exhaust steam temperature dropped to 36.2°C. The terminal difference decreased from 17.1 degrees Celsius to 6.5 degrees Celsius, returning to normal levels. The power generation capacity increased to 33.71 MW/H, with a net increase of 3.020 MW per hour – representing a 10% increase in power output. This results in an additional About 72,000 kWh of electricity generated per day. At a cost of 0.7 yuan per kWh, this translates to an additional profit of about 50,000 yuan per day. All operating parameters of the condenser have returned to normal. Figure 6 shows the operational status of the condenser in the turbine generator set at the control room of the thermal power plant, after semi-online chemical cleaning without shutting down the unit; it also shows the operational status after full chemical cleaning of both sides of the condenser without any shutdown. At 4:21 a.m. on April 24, 2003, the control panel in the control room of the biomass cogeneration project in Tongshan, Xuzhou, displayed a screenshot showing the condition of the other half of the condenser after approximately 5 hours of online chemical cleaning without shutting down the unit, as shown in Figure 7. The steam supply rate of the boiler is 115.4 t/h; the vacuum level increased to -97.6 kPa, the exhaust steam temperature dropped to 31.8°C, and the terminal difference narrowed to 3.7 degrees Celsius. It became necessary to stop one of the circulation pumps, as otherwise overcooling would also affect power generation efficiency. As a result, the power generation capacity increased only to 32.75 MW per hour. Figure 7: Operation status of the turbine generator set’s condenser after full chemical cleaning on both sides without shutting down the plant in a thermal power plant. IV. Conclusion: The application of the online cleaning technique for condensers without shutting down the plant to 35MW high-temperature, ultra-high-pressure reheated turbine generator sets shows that scaling in the circulating water of the condenser’s heat exchange tubes has a significant impact on power generation. This online cleaning technique enables the resolution of issues such as increased exhaust temperature, reduced vacuum level, and increased terminal difference in the plant’s condenser within 10 hours. Compared to the chemical or mechanical/physical cleaning methods that require shutting down the traditional condenser due to scaling, the online chemical cleaning technology for condensers that allows operation to continue enables maintenance of the condenser’s cleanliness and prevention of corrosion within it. It achieves good results in terms of operation, safety, and cost-effectiveness, with minimal modifications to existing equipment, within a relatively short period of time. It is proven that the online chemical cleaning technology for condensers without shutdown has practical significance for adoption and promotion in the thermal power industry. Comparative Analysis of the Advantages and Disadvantages of 8 Techniques for Online and Shutdown Cleaning of Condensers (Yan Hui)