A dry quenching waste heat boiler feed water deoxidization and economizer anticorrosion energy saving system

Abstract

The embodiment of the application provides a dry quenching waste heat boiler feed water deoxidization and economizer anticorrosion energy-saving system, which comprises a membrane deoxidizer, a temperature raising assembly, a boiler feed water pump and an economizer, the temperature raising assembly raises the output feed water temperature to above 90 DEG C; the boiler feed water pump is connected to the outlet of the temperature raising assembly, used for pressurizing the feed water after temperature raising, and conveying the pressurized feed water to the economizer of the dry quenching waste heat boiler. The membrane deoxidization is used to reduce the deoxidization energy consumption, and the temperature raising assembly is used to raise the feed water temperature to above 90 DEG C, effectively improving the problem that the pipe wall temperature of the low temperature section of the economizer is lower than the acid dew point of the flue gas. The economizer is segmented into a low temperature section and a high temperature section along the feed water flow direction; the low temperature section adopts a finless light pipe structure, eliminating the high corrosion position of the fin root, and the light pipe structure is not easy to accumulate the condensed liquid, facilitating the inspection and maintenance, and improving the corrosion problem of the low temperature section of the economizer.

Description

Technical Field

[0001] This application relates to the field of dry quenching technology, and in particular to a dry quenching waste heat boiler feedwater deoxygenation and economizer corrosion prevention and energy saving system. Background Technology

[0002] Dry quenching technology utilizes the sensible heat of red-hot coke to generate steam that drives a steam turbine for power generation, making it an important method for waste heat utilization in coking plants. The feedwater system of the dry quenching waste heat boiler undertakes key functions such as deoxygenation, heating, and water supply, and its operating efficiency directly affects the overall economic efficiency of the power generation system.

[0003] Traditional thermal deoxygenation methods consume large amounts of steam, typically requiring about 50 to 60 kg of steam per ton of boiler feedwater for heating and deoxygenation. This results in high energy consumption and complex systems. In recent years, membrane deoxygenation technology has begun to be applied in boiler feedwater treatment. Membrane deaerators utilize the microporous structure of hydrophobic hollow fiber membranes, allowing dissolved oxygen to pass through the membrane pores while water is retained on the outside of the membrane, thus achieving physical deoxygenation. Compared to thermal methods, membrane deoxygenation consumes only 3% to 5% of the energy required for thermal methods, and the dissolved oxygen level in the effluent can be controlled below 1 μg / L, demonstrating significant energy-saving advantages.

[0004] The existing technology has the following problems:

[0005] (1) Problem of reduced feedwater temperature after the introduction of membrane deoxygenation

[0006] Traditional thermal deaerators heat feedwater to around 104°C. The feedwater enters the economizer at a relatively high temperature, and the economizer tube wall temperature remains consistently above the flue gas acid dew point, eliminating the risk of low-temperature condensation corrosion. However, membrane deaerators operate at ambient temperature, with outlet water temperatures ranging from 20°C to 50°C. If the feedwater directly enters the economizer, the economizer tail tube wall temperature will drop below the flue gas acid dew point (typically 110°C to 130°C). This causes sulfuric acid vapor and moisture in the flue gas to condense on the heated surfaces, resulting in severe low-temperature corrosion.

[0007] (2) Low-temperature corrosion has a particularly prominent impact on finned tube economizers.

[0008] Economizers for dry quenching coke waste heat boilers typically use spiral finned tubes as heat exchange elements to increase the heat exchange area and improve waste heat recovery efficiency. However, the small fin spacing of spiral finned tubes (usually 6mm to 12mm) makes the fin roots highly susceptible to the accumulation of low-temperature sulfuric acid condensate. Once sulfuric acid condenses on the fin surface, not only does the fin itself rapidly corrode and perforate, but the accumulated sulfuric acid also blocks the channels between the fins, significantly increasing flue gas resistance and severely affecting the normal operation of the boiler.

[0009] (3) Matching problem between existing membrane deoxygenation and waste heat recovery systems

[0010] Patent CN120947015A discloses a feedwater system and heating method for a dry quenching waste heat boiler. It employs a membrane deaerator followed by a series of heat pipe heat exchangers (using boiler flue gas waste heat to heat the feedwater to 40°C to 60°C) and a plate heat exchanger (using coke oven desulfurization flue gas to heat to 60°C to 80°C). Finally, the feedwater is heated to 80°C to 100°C via steam from a heating tank before being fed into the boiler economizer. This scheme achieves a feedwater temperature of 80°C to 100°C through staged heating, mitigating low-temperature corrosion to some extent, but it has the following shortcomings:

[0011] First, even if the feedwater is heated to 80°C to 100°C, the tube wall temperature at the very end of the economizer (feedwater inlet section) may still be close to or below the acid dew point. This design does not include any specific anti-corrosion measures for the economizer itself, leaving a risk of corrosion even with long-term use. Second, the economizer uses a uniform tube type (spiral finned tube) throughout, meaning the fin surface still faces corrosion risks in the low-temperature section. Summary of the Invention

[0012] The purpose of this application is to provide a deaeration and economizer corrosion prevention and energy-saving system for feedwater of a dry quenching waste heat boiler, so as to improve the problem of corrosion risks in the low-temperature section of the economizer. The specific technical solution is as follows:

[0013] A dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy saving system includes:

[0014] Membrane deaerators are used to deoxygenate demineralized water, reducing the dissolved oxygen in the demineralized water to ≤5μg / L;

[0015] The heating component is connected to the outlet pipeline of the membrane deaerator and is used to perform gradient heating treatment on the deaerated demineralized water to raise the output feed water temperature to above 90°C.

[0016] A boiler feedwater pump, connected to the outlet of the heating component, is used to pressurize the heated feedwater and deliver the pressurized feedwater to the economizer of the dry quenching waste heat boiler.

[0017] An economizer is installed in the tail flue of a dry quenching waste heat boiler. The economizer is divided into a low-temperature section and a high-temperature section along the feedwater flow direction. The low-temperature section adopts a finless tube structure, while the high-temperature section adopts a finned tube structure.

[0018] In some embodiments, the heating component includes a primary heating component and a secondary heating component connected in series along the water flow direction;

[0019] The first-stage heating component uses the waste heat from the flue gas of the dry quenching coke boiler as a heat source to preheat the demineralized water output from the membrane deaerator.

[0020] The secondary heating component is used to further heat the feedwater that has been preheated by the primary heating component, so that the final output feedwater temperature reaches above 90°C.

[0021] In some embodiments, an inlet water temperature sensor and a controller are also included;

[0022] The inlet water temperature sensor is installed at the economizer inlet and is used to collect the economizer inlet feedwater temperature in real time.

[0023] The secondary heating component includes a hot water tank with a built-in steam heating coil or a heating pipe with a built-in electric heating element.

[0024] The controller is connected to the inlet water temperature sensor and the secondary heating component, and is configured to increase the steam supply of the steam heating coil or increase the heating power of the electric heating element when the economizer inlet feedwater temperature is detected to be lower than the preset low temperature threshold.

[0025] In some embodiments, the low temperature threshold is configured to be 90°C.

[0026] In some embodiments, the primary heating component is any one of a heat pipe heat exchanger, a shell-and-tube heat exchanger, or a plate heat exchanger, and the primary heating component preheats the demineralized water to 50°C to 75°C, while the secondary heating component heats the demineralized water to 90°C to 98°C.

[0027] In some embodiments, the material of the tube in the low-temperature section of the economizer is one of 09CrCuSb steel, 09CuPCrNi steel, or weathering steel.

[0028] In some embodiments, the economizer low-temperature section tube is made of carbon steel substrate, and the outer surface of the carbon steel substrate is provided with an acid-resistant protective coating.

[0029] In some embodiments, the diameter d1 of the low-temperature section light tube is 32mm to 38mm, and the wall thickness δ is 4mm to 6mm; the ratio of the transverse pitch S1 to the diameter d1 of the low-temperature section light tube is 2.0 to 2.5, and the ratio of the longitudinal pitch S2 to the diameter d1 is 1.8 to 2.0; the light tubes are arranged in a sequential or staggered manner.

[0030] In some embodiments, the high-temperature section finned tube is a spiral finned tube with a base tube diameter d2 of 32mm to 38mm, a fin height h of 12mm to 16mm, a fin thickness of 1.0mm to 1.5mm, and a fin pitch of 6mm to 10mm; the ratio of the transverse pitch S3 of the high-temperature section finned tube to the base tube diameter d2 is 2.0 to 2.5, and the ratio of the longitudinal pitch S4 to the base tube diameter d2 is 1.5 to 1.8.

[0031] In some embodiments, the low-temperature section and high-temperature section of the economizer adopt an integrated upper and lower segmented arrangement structure, or adopt a split structure in which two sets of independent economizer modules are installed in series.

[0032] In some embodiments, the secondary heating component includes a hot water tank with a built-in steam heating coil or a heating pipeline with a built-in electric heating element;

[0033] The temperature measurement and control system calculates the inlet pipe wall temperature of the economizer and compares the calculated pipe wall temperature with the acid dew point of the flue gas in the economizer. When the pipe wall temperature is lower than the acid dew point, the system increases the steam supply of the steam heating coil or increases the heating power of the electric heating element.

[0034] In some embodiments, the membrane deaerator is configured with a membrane module, which is a hydrophobic PVDF hollow fiber membrane or a PP hollow fiber membrane; the hollow fiber membrane has an inner diameter of 100μm to 400μm, an outer diameter of 200μm to 800μm, an average pore size of 0.01μm to 0.1μm, and a membrane porosity of 40% to 80%; the membrane module has a packed specific surface area of ​​not less than 4000m² / m³.

[0035] In some embodiments, an inlet pipe wall temperature sensor is also included;

[0036] The inlet pipe wall temperature sensor is installed on the economizer inlet pipe wall and is used to collect the economizer inlet pipe wall temperature in real time.

[0037] The controller is also connected to the inlet pipe wall temperature sensor and is configured to: compare the collected economizer inlet pipe wall temperature with a preset acid dew point; when the collected economizer inlet pipe wall temperature is lower than the preset acid dew point, increase the steam supply of the steam heating coil or increase the heating power of the electric heating element accordingly.

[0038] Beneficial effects of the embodiments in this application:

[0039] The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system provided in this application includes a membrane deaerator, a heating component, a boiler feedwater pump, and an economizer. Typically, the flue gas acid dew point is 110℃~130℃. When the flue gas temperature is lower than the acid dew point, sulfuric acid condensation and precipitation are likely to occur, forming an ash shell that affects the circulation of gas in the dry quenching boiler. Simultaneously, the heating component raises the temperature of the deaerated feedwater to above 90℃. At this temperature, the temperature of the economizer tail flue pipe wall is typically about 20℃ higher than the feedwater temperature, meaning the economizer tail flue pipe wall temperature can be higher than 110℃. At this temperature, sulfuric acid condensation and precipitation are less likely to occur in the flue gas, and condensate is less likely to accumulate on the economizer pipe wall. This improves the problem of condensate easily combining with sulfur trioxide in the flue gas to form liquid sulfuric acid, thereby reducing the formation of an ash shell that affects the circulation of gas in the dry quenching boiler. This approach retains the energy-saving advantages of membrane deoxygenation (saving a significant amount of steam compared to traditional thermal deoxygenation) while mitigating low-temperature corrosion through a reasonable heating strategy.

[0040] Furthermore, the economizer is divided into a low-temperature section with a finless tube structure and a high-temperature section with a finned tube structure along the feedwater flow direction. The low-temperature section uses a tube structure, which has several advantages: first, it eliminates the weak point at the fin root, where condensate easily accumulates and corrosion is prone to occur; second, because the surface of the tube is smooth, even if a small amount of sulfuric acid condenses, it is not easy to accumulate, and the condensate can flow smoothly down the tube wall; and third, the tube is easy to inspect and maintain, and corrosion can be detected in time. This allows for targeted solutions to the corrosion problem in the low-temperature section of the economizer in the dry quenching waste heat boiler, while ensuring the heat exchange efficiency of the high-temperature section, achieving comprehensive optimization of deoxygenation, corrosion prevention, and energy saving.

[0041] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0043] Figure 1 A schematic diagram of the process flow of a dry quenching waste heat boiler feedwater deoxygenation and economizer corrosion prevention and energy saving system is provided for the embodiments of this application.

[0044] Figure 2 for Figure 1 The diagram shows the structural layout of the economizer in a dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy saving system.

[0045] Figure 3 for Figure 1 The diagram shows an electrical connection structure of a dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy saving system.

[0046] Figure 4 for Figure 1 The diagram shows the structural layout of the low-temperature section of the economizer in a dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy saving system.

[0047] Figure 5 for Figure 1 The diagram shows the structural layout of the high-temperature section of the economizer in a dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy saving system.

[0048] Figure 6 for Figure 1 The diagram shows another electrical connection structure of a dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy saving system.

[0049] The attached figures are labeled as follows:

[0050] Membrane deaerator 1, heating component 2, primary heating component 21, secondary heating component 22, boiler feed pump 3, economizer 4, bare tube structure 41, finned tube structure 42, inlet water temperature sensor 5, controller 6, inlet pipe wall temperature sensor 7. Detailed Implementation

[0051] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0052] Traditional dry quenching waste heat boiler feedwater systems have limitations in deoxygenation and corrosion prevention. Thermal deoxygenation is energy-intensive, while membrane deoxygenation, although energy-saving, can easily lead to low-temperature corrosion of the economizer, especially in finned tubes, where the corrosion risk is particularly prominent in the low-temperature section. Existing solutions have certain corrosion risks in the low-temperature section of the economizer.

[0053] like Figure 1 and Figure 2As shown, this application proposes a deoxygenation and economizer corrosion prevention and energy-saving system for feedwater of a dry quenching waste heat boiler, including a membrane deaerator, a heating component, a boiler feedwater pump, and an economizer. The membrane deaerator is used to deoxygenate the demineralized water, reducing the dissolved oxygen to ≤5μg / L. The heating component is connected to the outlet pipeline of the membrane deaerator and is used to perform gradient heating treatment on the deoxygenated demineralized water, raising the output feedwater temperature to above 90℃. The boiler feedwater pump is connected to the outlet of the heating component and is used to pressurize the heated feedwater and deliver the pressurized feedwater to the economizer of the dry quenching waste heat boiler. The economizer is installed in the tail flue of the dry quenching waste heat boiler and is divided into a low-temperature section and a high-temperature section along the feedwater flow direction. The low-temperature section adopts a finless tube structure, and the high-temperature section adopts a finned tube structure.

[0054] The demineralized water is stored in a demineralized water tank and can be pumped to the membrane deaerator by a demineralized water pump.

[0055] For example, the demineralized water tank is a storage container for demineralized water, made of carbon steel lined with rubber, and equipped with a level gauge and a temperature sensor. The outlet of the demineralized water tank is connected to the inlet of the demineralized water pump to receive makeup water from the plant's demineralized water system.

[0056] For example, the demineralized water pump is a horizontal multistage centrifugal pump, with two units (one in operation and one on standby). The rated flow rate is selected based on the maximum feedwater volume of the boiler, and the head is sufficient to overcome the resistance of the subsequent pipeline and the operating resistance of the membrane deaerator. The pump body is equipped with frequency converter control to automatically adjust the flow rate according to the demineralized water tank level and system load.

[0057] Demineralized water is stored in a demineralized water tank. Upon system startup, the demineralized water pump delivers it to the membrane deaerator. Inside the membrane deaerator, the demineralized water flows on the outside of the hollow fiber membrane, while a vacuum system continuously draws gas from the membrane pores. Dissolved oxygen permeates through the membrane pores and is discharged to the vacuum side. The dissolved oxygen in the deaerated feedwater is ≤5 μg / L.

[0058] For example, this membrane deaerator can utilize a vacuum system or an ejector (steam jet) to draw dissolved oxygen away through the membrane pores; alternatively, it can employ a purging method, introducing an inert gas (such as N2) into the membrane module housing to remove dissolved oxygen. Its outlet water temperature ranges from ambient to 50°C. Using this membrane deaeration technology avoids the large steam consumption required by traditional thermal deaeration.

[0059] The heating element is configured to provide a gradient temperature increase to the deoxygenated brine, raising the output feedwater temperature to above 90°C. Exemplarily, this temperature increase can be achieved by using one or more heat exchangers to stage the heating of the demineralized water with an external heat source. This heat source can be boiler flue gas waste heat, steam, hot water, or electric heating, etc. By gradually increasing the feedwater temperature, corrosion problems caused by excessively low temperatures when the feedwater directly enters the economizer can be effectively mitigated.

[0060] The boiler feedwater pump is configured to pressurize the heated feedwater and deliver it to the economizer of the dry quenching waste heat boiler to maintain normal boiler operation. For example, the boiler feedwater pump is a horizontal multistage centrifugal pump, with two units (one in operation and one on standby). It draws water from the heating components, pressurizes the feedwater, and then sends it to the boiler economizer. A thermometer and pressure gauge are installed at the pump inlet, and the pump body is equipped with frequency converter control.

[0061] The economizer is installed in the boiler's tail flue to recover waste heat from the flue gas and preheat the boiler feedwater. The economizer is divided into a low-temperature section and a high-temperature section along the feedwater flow direction. The low-temperature section refers to the area where the feedwater initially enters the economizer and has a relatively low temperature; the high-temperature section refers to the area where the feedwater is further heated within the economizer and has a relatively high temperature. The low-temperature section uses a finless tube structure, meaning no fins are installed on the outer surface of the tubes, to reduce the risk of acidic substances in the flue gas condensing and accumulating at the fin roots. The high-temperature section uses a finned tube structure; in areas with higher feedwater temperatures and lower corrosion risk, fins are installed on the surface of the heat exchange tubes to increase the heat exchange area and improve waste heat recovery efficiency.

[0062] For example, along the feedwater flow direction, the economizer has a bare tube structure of three or more layers in the low-temperature section and a finned tube structure of three or more layers in the high-temperature section.

[0063] The feedwater, heated by the economizer, enters the boiler drum and exchanges heat with the high-temperature circulating flue gas from the dry quenching furnace to generate steam.

[0064] After the waste heat is recovered by the economizer, the temperature of the boiler flue gas drops to 120℃~140℃ before being discharged through the chimney.

[0065] This system effectively reduces deoxygenation energy consumption by using a membrane deaerator.

[0066] Typically, the acid dew point of flue gas is 110℃~130℃. When the flue gas temperature is below the acid dew point, sulfuric acid condensation and precipitation are likely to occur. Furthermore, when condensate is present on the economizer tube walls, this condensate easily combines with sulfur trioxide in the flue gas to form liquid sulfuric acid, creating an ash shell on the economizer tube walls that affects the circulation of the circulating gas in the dry quenching boiler. Simultaneously, the feedwater after deoxygenation is heated to above 90℃ using a heating element. At this temperature, the temperature of the economizer tail flue tube walls is typically about 20℃ higher than the feedwater temperature, keeping the economizer tail flue tube wall temperature above 110℃. This reduces the likelihood of sulfuric acid condensation and precipitation in the flue gas, and minimizes condensate retention on the economizer tube walls. This mitigates the problem of condensate easily combining with sulfur trioxide in the flue gas to form liquid sulfuric acid, thus reducing the formation of an ash shell that affects the circulation of the circulating gas in the dry quenching boiler. This approach retains the energy-saving advantages of membrane deoxygenation (saving a significant amount of steam compared to traditional thermal deoxygenation) while mitigating low-temperature corrosion through a reasonable heating strategy.

[0067] Furthermore, the economizer is divided into a low-temperature section with a finless tube structure and a high-temperature section with a finned tube structure along the feedwater flow direction. The use of a tube structure in the low-temperature section eliminates the weak point at the root of the fins, which is prone to condensate accumulation and corrosion. Secondly, because the surface of the tube is smooth, even if a small amount of sulfuric acid condenses, it is not easy to accumulate, and the condensate can flow smoothly down the tube wall. Thirdly, the tube is easy to inspect and maintain, and corrosion can be detected in time. This can specifically solve the corrosion problem in the low-temperature section of the economizer of the dry quenching waste heat boiler, while ensuring the heat exchange efficiency of the high-temperature section, and achieving comprehensive optimization of deoxygenation, corrosion prevention and energy saving.

[0068] like Figure 1 As shown, in some possible embodiments, the heating component includes a primary heating component and a secondary heating component connected in series along the feedwater flow direction; the primary heating component uses the waste heat from the flue gas of the dry quenching coke boiler as a heat source to preheat the demineralized water output from the membrane deaerator; the secondary heating component is used to further heat the feedwater preheated by the primary heating component, so that the final output feedwater temperature reaches above 90°C.

[0069] Specifically, the deoxygenated brine first enters the primary heating element for initial heating, and then enters the secondary heating element for further temperature enhancement. This allows the system to flexibly configure and optimize the heating process according to different heat source characteristics and heating requirements.

[0070] The primary heating element uses waste heat from the flue gas of the dry quenching coke boiler as a heat source to preheat the demineralized water output from the membrane deaerator. This element can be implemented using various heat exchange devices, such as shell-and-tube heat exchangers, plate heat exchangers, or heat pipe heat exchangers designed for flue gas-water heat exchange.

[0071] For example, a heat pipe heat exchanger is installed after the dry quenching circulating fan to preheat the demineralized water using waste heat from the boiler flue gas. The heat pipe heat exchanger consists of multiple gravity-type heat pipes. The evaporation section is placed in the flue to absorb heat from the flue gas, and the condensation section is placed on the water side to release heat to heat the feedwater. No external power is required, and the temperature of the demineralized water can be increased by approximately 25°C to 35°C (for example, from 20°C to 40°C to 50°C to 70°C). The outlet water then enters the secondary heating element.

[0072] The secondary heating element further heats the feedwater after preheating by the primary heating element, ensuring the final output feedwater temperature reaches above 90℃. The function of the secondary heating element is to precisely raise the feedwater temperature to the target value of above 90℃, building upon the preheating by the primary heating element. The secondary heating element can employ steam heating or electric heating, and by adjusting the steam supply or electric heating power, precise control of the feedwater temperature can be achieved, ensuring that the feedwater entering the economizer remains within the temperature range required for corrosion prevention.

[0073] The embodiments of this application employ a two-stage heating chain, resulting in lower system complexity, lower equipment investment, and no need to introduce coke oven desulfurization flue gas as a heat source, thus reducing the coupling complexity between systems.

[0074] like Figure 3 As shown, in some possible embodiments, an inlet water temperature sensor and a controller are also included; the inlet water temperature sensor is set at the economizer inlet to collect the economizer inlet feedwater temperature in real time; the secondary heating component includes a hot water tank with a built-in steam heating coil or a heating pipeline with a built-in electric heating element; the controller is connected to the inlet water temperature sensor and the secondary heating component respectively, and is configured to: when the economizer inlet feedwater temperature is detected to be lower than a preset low temperature threshold, increase the steam supply of the steam heating coil or increase the heating power of the electric heating element accordingly.

[0075] Specifically, the inlet water temperature sensor is used to monitor the feedwater temperature entering the economizer in real time. For example, this sensor typically uses a temperature measuring element such as a resistance temperature detector (RTD) or a thermocouple, and is installed on the feedwater pipe at the economizer inlet. It can convert temperature information into an electrical signal and transmit it to the controller.

[0076] The controller is responsible for receiving the temperature signal transmitted by the inlet water temperature sensor and adjusting the secondary heating component according to the preset control logic.

[0077] The controller can be a programmable logic controller (PLC) or a dedicated microprocessor controller, capable of outputting corresponding control commands based on the comparison between the real-time temperature and the preset low-temperature threshold.

[0078] The heating method of the secondary heating component can be flexibly selected. For example, a hot water tank with a built-in steam heating coil uses steam as a heat source and transfers heat to the water supply in the hot water tank through the coil. The steam supply can be controlled by adjusting the opening of the steam valve, thereby controlling the water supply temperature.

[0079] Steam sources can be extracted from the steam turbine or supplied from the desuperheating and pressure reducing station. The design output of the steam heating coil is calculated based on heating water from 50°C to 90°C under maximum feedwater flow conditions, with an appropriate margin.

[0080] The hot water tank outlet temperature is controlled between 90℃ and 98℃, and automatic temperature control is achieved by adjusting the steam output of the steam heating coil. A temperature control loop consisting of a temperature sensor and a regulating valve is set up. When the outlet water temperature is lower than the lower limit (e.g., 90℃), the steam supply is automatically increased, and when the water temperature is higher than the upper limit (e.g., 98℃), the steam supply is reduced.

[0081] In the embodiments of this application, the amount of steam required for heating the hot water tank is much less than the steam consumption of traditional thermal deaeration. Traditional thermal deaeration requires heating water from room temperature to 104°C, consuming approximately 15 kg to 20 kg of steam per ton of water; in the embodiments of this application, the water only needs to be heated from 50°C to 70°C to 90°C, consuming approximately 5 kg to 8 kg of steam per ton of water, reducing steam consumption by approximately 60% to 70%.

[0082] Alternatively, the heating pipe with built-in electric heating element can directly heat the electric heating element with electrical energy, and then transfer the heat to the water flowing through the pipe. The heating power can be controlled by adjusting the voltage or current to regulate the water temperature.

[0083] The controller is configured to issue an adjustment command when it detects that the economizer inlet feedwater temperature is lower than a preset low-temperature threshold (e.g., 90°C; the economizer tail flue pipe wall temperature is typically about 20°C higher than the feedwater temperature, meaning the economizer tail flue pipe wall temperature can be between 110°C and 120°C, making it less likely for sulfuric acid condensation to occur in the flue gas). If the secondary heating element is a hot water tank using a steam-heated coil, the controller will increase the steam supply, allowing more high-temperature steam to enter the coil, thereby increasing the feedwater temperature. If the secondary heating element is a heating pipeline using electric heating elements, the controller will increase the heating power of the electric heating elements, increasing heat output to raise the feedwater temperature above the safe range.

[0084] Through the above technical solution, this application can monitor the economizer inlet feedwater temperature in real time and intelligently adjust the secondary heating components according to the actual situation. When the feedwater temperature is detected to be lower than the preset low-temperature threshold, the controller can respond promptly and automatically increase the heating capacity of the secondary heating components, for example, by increasing the steam supply or increasing the electric heating power, thereby quickly raising the feedwater temperature to a safe range. This proactive temperature control strategy effectively avoids the risk of acid dew point corrosion in the low-temperature section of the economizer caused by excessively low feedwater temperature, significantly extends the service life of the economizer, ensures the long-term stable operation of the dry quenching waste heat boiler system, and reduces maintenance costs.

[0085] In some possible embodiments, the primary heating component is any one of a heat pipe heat exchanger, a shell-and-tube heat exchanger, or a plate heat exchanger. The primary heating component preheats the demineralized water to 50°C to 75°C, and the secondary heating component heats the demineralized water to 90°C to 98°C.

[0086] The primary heating element preheats the demineralized water to 50℃~75℃. This temperature range is designed to fully utilize the waste heat from the dry quenching boiler flue gas to preheat the demineralized water, maximizing waste heat recovery.

[0087] Based on this, the secondary heating element heats the demineralized water to 90℃~98℃. Within this temperature range, the temperature of the flue gas duct at the economizer's tail end is typically about 20℃ higher than the feedwater temperature, and the flue gas duct temperature can be between 110℃ and 120℃, making it less likely for sulfuric acid to condense and precipitate in the flue gas.

[0088] In some possible embodiments, the material of the light tube in the low-temperature section of the economizer is one of 09CrCuSb steel, 09CuPCrNi steel, or weathering steel.

[0089] 09CrCuSb steel, commonly known as ND steel, is a low-alloy steel resistant to sulfuric acid dew point corrosion. By adding alloying elements such as Cr, Cu, and Sb, it effectively prevents the penetration of corrosive media, thereby significantly improving the steel's resistance to low-temperature acid corrosion.

[0090] 09CuPCrNi steel is another low-alloy steel with excellent weather resistance and acid corrosion resistance. Through the synergistic effect of elements such as Cu, P, Cr, and Ni, this steel can effectively resist corrosion and acidic media, making it particularly suitable for environments with a risk of low-temperature acid corrosion.

[0091] Using 09CrCuSb steel, 09CuPCrNi steel, or weathering steel as the material for the bare tubes in the low-temperature section of the economizer can significantly improve the low-temperature acid corrosion resistance of the economizer, thereby extending the service life of the equipment, reducing maintenance costs, and ensuring the long-term stable operation of the dry quenching waste heat boiler system.

[0092] In some possible embodiments, the economizer's low-temperature section tube uses a carbon steel substrate with an acid-resistant protective coating on its outer surface. By using a cost-effective carbon steel substrate and applying an acid-resistant protective coating to its outer surface, the economizer's low-temperature section tube can effectively solve the problem of low-temperature acid corrosion.

[0093] like Figure 4 As shown, in some possible embodiments, the diameter d1 of the low-temperature section light tube is 32mm to 38mm, and the wall thickness δ is 4mm to 6mm; the ratio of the transverse pitch S1 to the diameter d1 of the low-temperature section light tube is 2.0 to 2.5, and the ratio of the longitudinal pitch S2 to the diameter d1 is 1.8 to 2.0; the light tubes are arranged in a sequential or staggered manner.

[0094] The technical solution sets the tube diameter d1, wall thickness δ, ratio of transverse pitch S1 to tube diameter d1, and ratio of longitudinal pitch S2 to tube diameter d1 for the bare tube in the low-temperature section of the economizer. Reasonable transverse and longitudinal pitch ratios can effectively enhance convective heat transfer and improve heat recovery efficiency.

[0095] like Figure 5 As shown, in some possible embodiments, the high-temperature section finned tube is a spiral finned tube, with a base tube diameter d2 of 32mm to 38mm, a fin height h of 12mm to 16mm, a fin thickness of 1.0mm to 1.5mm, and a fin pitch of 6mm to 10mm; the ratio of the transverse pitch S3 of the high-temperature section finned tube to the base tube diameter d2 is 2.0 to 2.5, and the ratio of the longitudinal pitch S4 to the base tube diameter d2 is 1.5 to 1.8.

[0096] Through the above technical solution, the tube diameter d2, fin height h, fin thickness, fin pitch, ratio of transverse pitch S3 to base tube diameter d2, and ratio of longitudinal pitch S4 to base tube diameter d2 of the finned tube in the high-temperature section of the economizer are set. Reasonable transverse and longitudinal pitch ratios can effectively enhance convective heat transfer and improve heat recovery efficiency.

[0097] In some possible embodiments, the low-temperature section and the high-temperature section of the economizer are arranged in an integrated upper and lower segmented structure, or in a split structure in which two independent economizer modules are installed in series.

[0098] Specifically, the integrated upper and lower segmented arrangement structure refers to the economizer's low-temperature section and high-temperature section being physically designed as a single unit, but internally divided into two or more regions along the height direction, corresponding to the low-temperature section and the high-temperature section respectively. For example, the finless tube bundles of the low-temperature section can be arranged in the lower region within a common shell or frame, while the finned tube bundles of the high-temperature section can be arranged in the upper region. This integrated design helps reduce the footprint, simplifies the installation process, and may reduce manufacturing costs by sharing structural components.

[0099] A split-type structure with two independent economizer modules connected in series refers to an economizer where the low-temperature section and high-temperature section are designed as two or more independent modular units. Each module can be manufactured and installed separately. For example, there can be a dedicated module for the low-temperature section, containing a finless tube structure; and a dedicated module for the high-temperature section, containing a finned tube structure. These two independent modules are connected in series in the field via piping to allow feedwater to flow sequentially through the low-temperature and high-temperature sections.

[0100] In some possible embodiments, the physical spatial division between the low-temperature section and the high-temperature section is defined by the isotherm of the feedwater temperature inside the economizer tube; under the first actual thermal operating conditions, the temperature range of the dividing line is between 110°C and 120°C; under the second actual thermal operating conditions, the temperature range of the dividing line is between 125°C and 135°C; and under the third actual thermal operating conditions, the temperature range of the dividing line is between 140°C and 150°C.

[0101] First actual thermal operating conditions (full load condition)

[0102] The boiler load is 100% of its rated load. The economizer flue gas inlet temperature is 390℃ to 400℃, the economizer feedwater inlet temperature is 90℃, and the economizer feedwater outlet temperature is 280℃. The water content in the circulating gas is 5% to 7%, and the sulfur dioxide concentration in the circulating gas is 100 to 300 ppm. Based on a conversion rate of 1% to 3%, the equivalent sulfur trioxide concentration is 1 to 9 ppm. According to the Verhoff equation, the corresponding flue gas acid dew point is approximately 105℃ to 135℃. Under this operating condition, the feedwater temperature range corresponding to the boundary between the low-temperature and high-temperature sections of the economizer is 110℃ to 120℃. The corresponding tube wall temperature is slightly higher than the acid dew point, ensuring that the tube wall temperature in the low-temperature section remains above the acid dew point to prevent low-temperature corrosion.

[0103] Second actual thermal operating conditions (80% load condition)

[0104] The boiler load is 80% of its rated load. The economizer flue gas inlet temperature is 370℃ to 390℃, the economizer feedwater inlet temperature is 90℃, and the economizer feedwater outlet temperature is 275℃. The water content in the circulating gas is 5% to 7%, and the sulfur dioxide concentration in the circulating gas is 100 to 300 ppm. Based on a conversion rate of 1% to 3%, the equivalent sulfur trioxide concentration is 1 to 9 ppm. According to the Verhoff equation, the corresponding flue gas acid dew point is approximately 105℃ to 135℃. Under this operating condition, because the flue gas temperature is slightly lower than that under full load conditions, the overall temperature distribution within the economizer shifts downwards. The feedwater temperature range corresponding to the dividing line is 125℃ to 135℃. The position of the dividing line is adjusted accordingly towards the high-temperature section to ensure that the tube wall temperature is higher than the acid dew point.

[0105] For example, combined Figure 2 As shown, when the dividing line is 130℃, the water temperature in the low-temperature section is between 90℃ and 130℃, and the water temperature in the high-temperature section is greater than 130℃.

[0106] Third actual thermal operating conditions (45% load condition)

[0107] The boiler load is 45% of its rated load. The economizer flue gas inlet temperature is 330℃ to 340℃, the economizer feedwater inlet temperature is 90℃, and the economizer feedwater outlet temperature is 265℃. The water content in the circulating gas is 5% to 7%, and the sulfur dioxide concentration in the circulating gas is 100 to 300 ppm. Calculated based on a conversion rate of 1% to 3%, the equivalent sulfur trioxide concentration is 1 to 9 ppm. According to the Verhoff equation, the corresponding flue gas acid dew point is approximately 105℃ to 135℃. Under this operating condition, because both the flue gas temperature and flow rate decrease under low load conditions, the overall temperature distribution within the economizer shifts downwards. To ensure that the tube wall temperature in the low-temperature section is higher than the acid dew point, the boundary line is shifted towards the high-temperature section. The feedwater temperature range corresponding to the boundary line is 140℃ to 150℃, and the proportion of the low-temperature section increases accordingly.

[0108] like Figure 6 As shown, in some possible embodiments, an inlet pipe wall temperature sensor 7 is also included; the inlet pipe wall temperature sensor 7 is disposed on the inlet pipe wall of the economizer 4 and is used to collect the inlet pipe wall temperature of the economizer 4 in real time; the controller 6 is also connected to the inlet pipe wall temperature sensor 7 and is configured to: compare the collected inlet pipe wall temperature of the economizer 4 with a preset acid dew point, and when the collected inlet pipe wall temperature of the economizer 4 is lower than the preset acid dew point, correspondingly increase the steam supply of the steam heating coil or increase the heating power of the electric heating element.

[0109] Specifically, the inlet pipe wall temperature sensor 7 is used to monitor the temperature of the inlet pipe wall of the economizer 4 in real time. For example, this sensor typically uses a temperature measuring element such as a resistance temperature detector (RTD) or a thermocouple, and is installed on the feed water pipe wall at the inlet of the economizer 4. It can convert temperature information into an electrical signal and transmit it to the controller 6.

[0110] The controller 6 is responsible for receiving the temperature signal transmitted by the inlet pipe wall temperature sensor 7 and adjusting the secondary heating component 22 according to the preset control logic.

[0111] The controller 6 is configured to compare the collected inlet pipe wall temperature of the economizer 4 with a preset acid dew point (e.g., 110°C). When the collected inlet pipe wall temperature of the economizer 4 is lower than the preset acid dew point, the controller 6 will issue an adjustment command to increase the steam supply of the steam heating coil or increase the heating power of the electric heating element.

[0112] If the secondary heating component 22 is a hot water tank with a steam heating coil, the controller 6 will increase the steam supply to allow more high-temperature steam to enter the coil, thereby increasing the water supply temperature. If the secondary heating component 22 is a heating pipe with an electric heating element, the controller 6 will increase the heating power of the electric heating element to increase the heat output and raise the water supply temperature above the safe range.

[0113] Through the above technical solution, this application can monitor the inlet pipe wall temperature of the economizer 4 in real time and intelligently adjust the secondary heating component 22 according to the actual situation. When the inlet pipe wall temperature is detected to be lower than the preset acid dew point, the controller 6 can respond promptly and automatically increase the heating capacity of the secondary heating component 22, for example, by increasing the steam supply or increasing the electric heating power, thereby quickly raising the feedwater temperature to a safe range. This proactive temperature control strategy effectively avoids the risk of acid dew point corrosion in the low-temperature section of the economizer 4 caused by excessively low feedwater temperature, significantly extends the service life of the economizer 4, ensures the long-term stable operation of the dry quenching waste heat boiler system, and reduces maintenance costs.

[0114] In some possible embodiments, the membrane deaerator is equipped with a membrane module, which is a hydrophobic PVDF hollow fiber membrane or a PP hollow fiber membrane; the hollow fiber membrane has an inner diameter of 100μm to 400μm, an outer diameter of 200μm to 800μm, an average pore size of 0.01μm to 0.1μm, and a membrane porosity of 40% to 80%; the membrane module has a packed specific surface area of ​​not less than 4000m² / m³. Compared with traditional thermal deaeration, membrane deaeration consumes only 3% to 5% of the energy of thermal methods, eliminating the large amount of steam consumed by thermal deaerators.

[0115] In some possible embodiments, the vacuum system of the membrane deaerator maintains a vacuum level of 0.08 MPa to 0.095 MPa inside the membrane module housing.

[0116] The embodiments of this application have at least one of the following advantages:

[0117] (1) Significant energy saving. Membrane deoxygenation replaces traditional thermal deoxygenation, reducing steam consumption per ton of water from 15-20 kg to 5-8 kg (steam heating only for hot water tank), a reduction of approximately 60%-70%. Simultaneously, the power consumption of membrane deoxygenation is only 3%-5% of that of thermal deoxygenation. Overall, this patented system can reduce the energy consumption of the water supply system by approximately 50%-65% compared to traditional thermal deoxygenation methods.

[0118] (2) The system is simple and the investment is low. Compared with the three-stage heating link (heat pipe + plate heat exchanger + steam heating water tank) disclosed in patent CN120947015A, this patent only requires two stages of heating, eliminating the plate heat exchanger and its supporting coke oven desulfurization flue gas pipeline system, which greatly reduces equipment investment and operation and maintenance costs.

[0119] (3) The low-temperature section of the economizer is safe and reliable. The low-temperature section at the bottom of the economizer uses ND steel bare tubes, which eliminates the risk of low-temperature sulfuric acid corrosion from both material and structural perspectives: the corrosion resistance of ND steel is far superior to that of ordinary carbon steel, and the bare tube form eliminates the root of the fins, a high-risk area for corrosion. Even if the operating conditions fluctuate and the feedwater temperature drops temporarily, the ND steel bare tubes can still withstand the pressure safely.

[0120] (4) The heat exchange efficiency of the high-temperature section is not affected. The upper high-temperature section of the economizer (water temperature > 130℃) adopts spiral finned tubes, which have a large heat exchange area and high heat exchange efficiency, ensuring the full recovery of waste heat from boiler flue gas, and the flue gas temperature can be reduced to 120℃~140℃.

[0121] (5) Convenient operation and maintenance. The low-temperature section of the economizer adopts a bare tube design with a smooth surface and no fins, making daily inspection and maintenance convenient. Even if slight corrosion occurs after long-term operation, the inspection and replacement of bare tubes is much simpler than that of finned tubes. The finned tubes in the high-temperature section have a very low risk of corrosion and a long service life because their wall temperature is higher than the acid dew point.

[0122] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A deaeration and economizer corrosion prevention and energy-saving system for feedwater of a dry quenching waste heat boiler, characterized in that, include: Membrane deaerators are used to deoxygenate demineralized water, reducing the dissolved oxygen in the demineralized water to ≤5μg / L; The heating component is connected to the outlet pipeline of the membrane deaerator and is used to perform gradient heating treatment on the deaerated demineralized water to raise the output feed water temperature to above 90°C. A boiler feedwater pump, connected to the outlet of the heating component, is used to pressurize the heated feedwater and deliver the pressurized feedwater to the economizer of the dry quenching waste heat boiler. An economizer is installed in the tail flue of a dry quenching waste heat boiler. The economizer is divided into a low-temperature section and a high-temperature section along the feedwater flow direction. The low-temperature section adopts a finless tube structure, while the high-temperature section adopts a finned tube structure.

2. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 1, characterized in that, The heating component includes a primary heating component and a secondary heating component connected in series along the water flow direction; The first-stage heating component uses the waste heat from the flue gas of the dry quenching coke boiler as a heat source to preheat the demineralized water output from the membrane deaerator. The secondary heating component is used to further heat the feedwater that has been preheated by the primary heating component, so that the final output feedwater temperature reaches above 90°C.

3. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 2, characterized in that, It also includes an inlet water temperature sensor and controller; The inlet water temperature sensor is installed at the economizer inlet and is used to collect the economizer inlet feedwater temperature in real time. The secondary heating component includes a hot water tank with a built-in steam heating coil or a heating pipe with a built-in electric heating element. The controller is connected to the inlet water temperature sensor and the secondary heating component, and is configured to increase the steam supply of the steam heating coil or increase the heating power of the electric heating element when the economizer inlet feedwater temperature is detected to be lower than the preset low temperature threshold.

4. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 3, characterized in that, The low temperature threshold is configured to be 90°C.

5. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 2, characterized in that, The primary heating component is any one of a heat pipe heat exchanger, a shell-and-tube heat exchanger, or a plate heat exchanger. The primary heating component preheats the demineralized water to 50°C to 75°C, and the secondary heating component heats the demineralized water to 90°C to 98°C.

6. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 1, characterized in that, The material of the light tube in the low-temperature section of the economizer is one of 09CrCuSb steel, 09CuPCrNi steel, or weathering steel.

7. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 1, characterized in that, The economizer's low-temperature section tube uses a carbon steel substrate, and an acid-resistant protective coating is applied to the outer surface of the carbon steel substrate.

8. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 1, characterized in that, The diameter d1 of the low-temperature section optical tube is 32mm to 38mm, and the wall thickness δ is 4mm to 6mm. The ratio of the transverse pitch S1 to the diameter d1 of the low-temperature section optical tube is 2.0 to 2.5, and the ratio of the longitudinal pitch S2 to the diameter d1 is 1.8 to 2.

0. The optical tubes are arranged in a sequential or staggered manner.

9. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 1, characterized in that, The high-temperature section finned tube is a spiral finned tube with a base tube diameter d2 of 32mm to 38mm, a fin height h of 12mm to 16mm, a fin thickness of 1.0mm to 1.5mm, and a fin pitch of 6mm to 10mm. The ratio of the transverse pitch S3 of the high-temperature section finned tube to the base tube diameter d2 is 2.0 to 2.5, and the ratio of the longitudinal pitch S4 to the base tube diameter d2 is 1.5 to 1.

8.

10. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 1, characterized in that, The economizer's low-temperature section and high-temperature section adopt an integrated upper and lower segmented arrangement structure, or a split structure in which two independent economizer modules are installed in series.

11. The dry quenching waste heat boiler feedwater deaeration and economizer corrosion prevention and energy-saving system according to claim 3, characterized in that, It also includes an inlet pipe wall temperature sensor (7); The inlet pipe wall temperature sensor (7) is installed on the inlet pipe wall of the economizer (4) to collect the inlet pipe wall temperature of the economizer (4) in real time. The controller (6) is also connected to the inlet pipe wall temperature sensor (7) and configured to: compare the collected economizer (4) inlet pipe wall temperature with the preset acid dew point; when the collected economizer (4) inlet pipe wall temperature is lower than the preset acid dew point, increase the steam supply of the steam heating coil or increase the heating power of the electric heating element accordingly.

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