Chemical cleaning system for dirt on heat transfer pipe of steam generator

Abstract

The invention belongs to the field of nuclear power station key equipment maintenance technology research, and particularly relates to a steam generator heat transfer pipe incrustation chemical cleaning system which comprises a cleaning tank, a rinsing tank and a passivation tank which are connected with a thermal state surge tank through make-up pumps. The thermal-state surge tank is sequentially connected with the cooler, the simulator container and the coupon container through the circulating pump, and the coupon container is connected with the thermal-state surge tank to form a main circulation loop; the thermal-state pressure stabilizing tank is used for storing a medium of the main circulation loop, heating circulating fluid and stabilizing the pressure of the main circulation loop; the simulator container and the coupon container are respectively provided with a heat transfer tube assembly simulator and coupon samples of various types of scales; the simulation body container is a natural circulation simulation body or a direct current circulation simulation body in a test research stage; in the engineering application stage, the evaporator is a nuclear power plant actual evaporator. Descaling effect verification can be carried out on different chemical cleaning processes, and meanwhile the chemical cleaning device is applied to chemical cleaning and removal of dirt on the heat transfer tube of the nuclear power plant evaporator.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power plant key equipment maintenance technology research, specifically involving a chemical cleaning system for scale on heat transfer tubes of steam generators. Background Technology

[0002] Steam generators are key equipment for heat exchange between the primary and secondary loops of nuclear power plants. Their performance and operational reliability are directly related to the safety, economy, and reliability of the entire nuclear power plant. Currently, the condition of the fouling on the surface of the heat transfer tubes has the greatest impact on the safe operation and heat exchange capacity of the evaporator.

[0003] The working medium of the evaporator inevitably contains soluble salts. During the evaporation process, water evaporates continuously, causing the concentration of dissolved substances to rise sharply, far exceeding their solubility limit. These substances precipitate and adhere to the surface of the heat transfer tubes, which have the highest temperature. The high temperature of the heat transfer tube wall provides favorable conditions for scale formation processes such as crystallization, polymerization, and sintering. At the same time, the stagnation of fluid in the boundary layer of the tube wall also promotes deposition, which may eventually lead to adverse consequences such as reduced heat transfer efficiency and under-deposit corrosion.

[0004] Therefore, there is an urgent need to develop a system or method for removing fouling from heat transfer tubes in order to solve the current problems associated with fouling in heat transfer tubes. Summary of the Invention

[0005] The purpose of this invention is to provide a chemical cleaning system for heat transfer tube fouling in steam generators. This system (small structural size) can verify the descaling effect of different chemical cleaning processes composed of different cleaning agents and cleaning thermal parameters, helping to screen out the optimal cleaning process. At the same time, this system (large structural size) can be applied to the chemical cleaning and removal of fouling in heat transfer tubes of nuclear power plant evaporators (such as natural circulation, especially direct current circulation), promoting the formation of a fully independent industrial chain from experimental research to formula development and engineering application.

[0006] Technical solution to achieve the purpose of this invention:

[0007] A chemical cleaning system for heat transfer tube fouling in a steam generator is disclosed. The system comprises: a circulating pump, a cooler, a simulated container, a plate container, a hot pressure stabilizing tank, a water pump, a cleaning tank, a rinsing tank, and a passivation tank. The cleaning tank, rinsing tank, and passivation tank are each connected to the hot pressure stabilizing tank via the water pump. The hot pressure stabilizing tank is sequentially connected to the cooler, the simulated container, and the plate container via the circulating pump. The plate container is connected to the hot pressure stabilizing tank, forming a main circulation loop. The hot pressure stabilizing tank is used for storing the medium in the main circulation loop, heating the circulating fluid, and stabilizing the pressure in the main circulation loop. The simulated container and the plate container respectively contain simulated heat transfer tube components and plate samples of various types of fouling. In the experimental research stage, the simulated container is either a natural circulation simulated container or a direct current circulation simulated container. In the engineering application stage, it is an actual evaporator in a nuclear power plant.

[0008] Furthermore, the system also includes: a main loop sampler and a simulated body sampler; a first sampling branch and a second sampling branch are respectively provided at the cooler inlet and the simulated body container; a main loop sampler is provided on the first sampling branch for measuring the oxygen content and pH of the main loop in a time-sharing and segmented manner; a simulated body sampler is provided on the second sampling branch for measuring the oxygen content and pH of the simulated body in a time-sharing and segmented manner.

[0009] Furthermore, the system also includes: an EDTA waste liquid recovery tank and an Fe waste liquid recovery tank; the sewage discharge from the cleaning tank, rinsing tank, passivation tank, hot pressure stabilizing tank, and main circulation loop is all connected to the EDTA waste liquid recovery tank and the Fe waste liquid recovery tank.

[0010] Furthermore, the hot pressure stabilizing tank is provided with an interface at the top for venting or injecting nitrogen; when used for injecting nitrogen, it provides nitrogen protection for the main circulation loop, and provides high-pressure nitrogen driving force during the liquid discharge stage of the loop to prevent the liquid in the loop from contacting oxygen.

[0011] Furthermore, both the simulated container and the hanging container are equipped with key temperature and pressure measuring points to monitor the internal medium status; the inlet and outlet of the simulated container are equipped with multiple valves to achieve forward and reverse fluid switching flushing.

[0012] Furthermore, each of the cleaning tank, rinsing tank, and passivation tank is equipped with a level gauge and a filling port. The cleaning tank has an electric stirrer built in. The water supply pump is a single-stage plunger pump with a filter at the inlet and a flow meter at the outlet for cumulative calculation of the total injection volume. The cooler is a tube-in-tube structure, with the fluid inside the tube being the main circuit medium and the fluid outside the tube being tap water cooling water.

[0013] Furthermore, a regulating valve is provided between the outlet of the circulating pump and the first sampling branch, and the regulating valve works with the frequency converter to regulate the flow rate of the main circulation loop.

[0014] Furthermore, the natural circulation simulator is used to simulate a natural circulation evaporator, including a container upper flange cover A, a container body, a positioning support, and a container lower end cap. The container upper flange cover A and the container lower end cap are detachably connected to the top and bottom of the container body, respectively. The positioning support is installed inside the container body, and a first heat transfer tube sample is mounted on the positioning support. The positioning support positions and supports the first heat transfer tube sample, and both ends of the first heat transfer tube sample are sealed with plugs. Pre-made scale adheres to the outer surface of the first heat transfer tube sample. The circulating fluid of the main circulation loop continuously flushes the outside of the first heat transfer tube sample, while there is no medium flowing inside the tube. After flushing for a period of time, the first heat transfer tube sample is disassembled, and the descaling effect is tested by weighing.

[0015] Furthermore, the DC circulation simulator is used to simulate a DC circulation evaporator, including a container upper flange cover B, a container header, and a container outer sleeve. The container header includes an upper header and a lower header. The two ends of the container outer sleeve are connected to the upper header and the lower header. The container upper flange cover B is detachably connected to the top of the upper header. A second heat transfer tube sample is assembled inside the container outer sleeve. The outer diameter of the second heat transfer tube sample is slightly smaller than the inner diameter of the container outer sleeve. The upper end of the second heat transfer tube sample is fixedly connected to the upper header, and the lower end of the second heat transfer tube sample is placed at the pipe opening where the container outer sleeve connects to the lower header through a clearance fit. Pre-made scale adheres to the inner surface of the second heat transfer tube sample. The circulating fluid in the main circulation loop mainly flushes the inside of the second heat transfer tube sample, and there is no medium flow outside the tube. After flushing for a period of time, the second heat transfer tube sample is disassembled, and the descaling effect is checked by weighing. The DC circulation simulator is equipped with an external heating wire to heat the medium inside the tube when the loop fluid is stationary.

[0016] Furthermore, in the experimental research stage, the heating source of the hot pressure stabilizing tank is an electric heating rod, including a pressure stabilizing tank body, an electric heating rod, and a safety valve. The electric heating rod is fixedly connected to the pressure stabilizing tank body, and an interface is provided at the top of the pressure stabilizing tank body, with a safety valve installed on the interface. In the engineering application stage, the heating source is low-pressure steam supplied by the plant.

[0017] The beneficial technical effects of this invention are as follows:

[0018] 1. The present invention provides a chemical cleaning system for heat transfer tube fouling in a steam generator. Utilizing chemical cleaning technology, it can use specific cleaning agent formulations to carry out efficient descaling for different types of fouling. It thoroughly removes complex internal structures, small tube bundles, and hard or highly adhesive deposits that are difficult to reach by mechanical methods. It is effective for both direct-flow evaporators and natural circulation evaporators.

[0019] 2. This invention designs and constructs an experimental system for chemical cleaning of fouling on the surface of evaporator heat transfer tubes. It studies the fouling removal effects on heat transfer tubes under different cleaning agent formulations and thermal operating parameters for both direct-flow and natural-circulation evaporators. Simultaneously, by proportionally expanding the equipment and loop dimensions and capacity, it can be used as a dedicated chemical cleaning device for nuclear power plants to perform evaporator chemical cleaning. The main loop circulation mode accommodates both application scenarios. In the experimental research phase, the simulated container is a self-made natural-circulation or direct-flow simulation container, mainly used to explore the cleaning effects of different chemical cleaning processes. In the engineering application phase, the simulated container is an actual evaporator from a nuclear power plant, significantly enhancing the system's versatility.

[0020] 3. The present invention provides a chemical cleaning system for the fouling of heat transfer tubes of steam generators, which is equipped with a sampling port in the main circulation loop and a key parameter monitoring interface, such as temperature, pressure, oxygen content, and pH value, to ensure that the chemical cleaning process can be implemented accurately. Since pH value and oxygen content are not easy to measure at high temperatures, they need to be cooled down by the sampler before the actual operating values ​​can be obtained.

[0021] 4. The present invention provides a chemical cleaning system for the fouling of heat transfer tubes of a steam generator, which is equipped with an electrically heated pressure stabilizing tank that integrates storage, heating and pressure stabilization functions. It simultaneously realizes the functions of main circuit medium storage, circulating fluid heating and circuit pressure stabilization. It is also equipped with an interface for venting or injecting nitrogen to provide nitrogen protection for the main circuit and to provide high-pressure nitrogen driving force during the circuit drainage stage to prevent the liquid in the circuit from contacting oxygen. In the experimental research stage, the heating heat source is an electric heating rod. In the engineering application stage, the heating heat source is low-pressure steam supplied by the plant.

[0022] 5. The present invention provides a chemical cleaning system for heat transfer tube fouling in a steam generator, which includes a self-made natural circulation simulator or a direct current circulation simulator for studying the chemical cleaning effect on different stack types. The simulator is equipped with heat transfer tube samples fixed by means of threads, sleeves, etc. The surface of the heat transfer tube samples is pre-configured with standard fouling patterns. During the experimental research phase, the chemical cleaning effect is verified by flushing with circulating fluids with different parameters and formulations, combined with the component weighing method.

[0023] 6. The present invention provides a chemical cleaning system for heat transfer tube fouling of a steam generator, which is equipped with a flange-sealed container for suspending various types of scale samples. The container is located at the outlet end of the simulation container. When the circulating pump stops, the flange cover can be opened to facilitate inspection and evaluation of the descaling effect at different stages of the descaling cycle.

[0024] 7. The present invention provides a chemical cleaning system for heat transfer tube fouling of a steam generator, which includes a waste liquid tank for cleaning agents that cannot meet the direct discharge standards. Through graded sedimentation and acid-base neutralization, EDTA and Fe in the cleaning agent are filtered out step by step so that it can finally meet the direct discharge standards. Attached Figure Description

[0025] Figure 1 A process flow diagram of a chemical cleaning system for fouling heat transfer tubes of a steam generator provided by the present invention;

[0026] Figure 2 A schematic diagram of a simulated container structure in a chemical cleaning system for fouling heat transfer tubes of a steam generator provided by the present invention: Figure 2 'a' represents a natural cycle simulation. Figure 2 b represents a DC cycle simulation;

[0027] Figure 3This is a schematic diagram of the hot pressure stabilizing tank structure in a chemical cleaning system for fouling of heat transfer tubes in a steam generator, as provided by the present invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0029] like Figure 1 As shown, the present invention provides a chemical cleaning system for heat transfer tube fouling in a steam generator. The medium of the system is liquid in a storage tank. The system includes: a storage tank, a circulation pump 1, a cooler 2, a simulated container 3, a plate container 4, a hot pressure stabilizing tank 5, a water replenishment pump 6, a main circuit sampler 12, a simulated sampler 13, an EDTA recovery waste liquid tank 10, and an Fe recovery waste liquid tank 11. The storage tank includes a cleaning tank 7, a rinsing tank 8, and a passivation tank 9.

[0030] The cleaning tank 7, rinsing tank 8, and passivation tank 9 are connected to the hot pressure stabilizing tank 5 via the water replenishment pump 6. The hot pressure stabilizing tank 5 is connected to the cooler 2, the simulated container 3, and the plate container 4 in sequence via the circulation pump 1. The plate container 4 is connected to the hot pressure stabilizing tank 5 to form the main circulation loop. The inlet of the cooler 2 and the simulated container 3 are respectively provided with a first sampling branch and a second sampling branch. The first sampling branch is equipped with a main loop sampler 12, and the second sampling branch is equipped with a simulated sampler 13. The sewage discharge from the cleaning tank 7, rinsing tank 8, passivation tank 9, hot pressure stabilizing tank 5, and the main circulation loop is connected to the EDTA recovery waste liquid tank 10 and the Fe recovery waste liquid tank 11.

[0031] The storage tanks are divided into a cleaning tank (7), a rinsing tank (8), and a passivation tank (9). Each tank is equipped with a level gauge and a filling port. The cleaning tank (7) has a built-in electric stirrer. The lower part of each of the three tanks (cleaning tank 7, rinsing tank 8, and passivation tank 9) is connected to the inlet of the water supply pump (6). The water supply pump (6) is a single-stage plunger pump with a filter at the inlet and a flow meter at the outlet for calculating the total injection volume. The outlet of the water supply pump (6) is connected to the main circulation loop to fill the hot pressure stabilizing tank (5) with liquid. The outlet of the hot pressure stabilizing tank (5) is connected to the circulation pump (1). The circulation pump (1) is a variable frequency magnetic centrifugal pump with a regulating valve at the outlet to regulate the loop flow in conjunction with the frequency converter. After the regulating valve, there is a first sampling branch and a matching main loop sampler (12) to measure the oxygen content and pH of the main loop in stages and at different times. A cooler (2) is connected to the rear end to provide a cooling source for the entire loop. Cooler 2 is a tube-in-tube structure. The fluid inside the tube is the main loop medium, and the fluid outside the tube is tap water cooling water. A simulated container 3 and a plate container 4 are connected after the cooler. The two containers respectively contain a simulated heat transfer tube assembly and a plate sample. Both simulated container 3 and plate container 4 are equipped with key measuring points such as temperature and pressure to monitor the internal medium status. A second sampling branch and a matching simulated sampler 13 are located in the lower part of simulated container 3 to achieve time-segmented measurement of oxygen content and pH within the simulated medium. Multiple valves are installed at the inlet and outlet of simulated container 3 to achieve forward and reverse fluid switching for flushing. The cleaned medium flows through plate container 4 to its outlet and finally returns to the inlet of circulating pump 1 to complete one cycle. Plate container 4 is mainly used to suspend small samples of various types of scale to facilitate inspection and evaluation of the descaling effect at different stages of the descaling cycle. Since the passivating agent and rinsing agent in cleaning tank 7, rinsing tank 8, and passivation tank 9 meet the emission standards, they can be directly discharged into the ditch. However, when discharging the cleaning agent, the liquid in the main circulation loop needs to be pressurized by nitrogen gas at the top of the hot pressure stabilizing tank 5 and then sequentially pumped into the waste liquid pool EDTA recovery waste liquid pool 10 and Fe recovery waste liquid pool 11 through the drain outlet of the circulation pump 1 and the drain outlets of each tank in the main circulation loop. Then, the waste liquid in the EDTA recovery waste liquid pool 10 and Fe recovery waste liquid pool 11 is precipitated by acid and alkali in sequence before it can be discharged into the ditch.

[0032] like Figure 1As shown, the system accommodates a dual-application scenario for its main loop circulation mode. In the experimental research phase, the simulated container 3 is a self-made natural circulation simulated container or a DC circulation simulated container, mainly used to explore the cleaning effects of different chemical cleaning processes. In the engineering application phase, the simulated container 3 is an actual evaporator in a nuclear power plant, greatly enhancing the system's versatility. The system is equipped with a hot-state pressure stabilizing tank 5 that integrates storage, heating, and pressure stabilization functions. It simultaneously realizes the functions of main loop medium storage, circulating fluid heating, and loop pressure stabilization. It is also equipped with an interface for venting or injecting nitrogen to provide nitrogen protection for the main loop and to provide high-pressure nitrogen driving force during the loop drainage phase, thereby preventing the liquid in the loop from contacting oxygen. In the experimental research phase, the heating source is an electric heating rod, while in the engineering application phase, the heating source is low-pressure steam supplied by the plant.

[0033] like Figure 2 As shown, the simulation container 3 is divided into a natural circulation simulation container and a DC circulation simulation container.

[0034] The natural circulation simulator is used to simulate a natural circulation evaporator. It includes an upper flange cover A301, a container body 302, a positioning support 304, and a lower end cap 305. The upper flange cover A301 and the lower end cap 305 are detachably connected to the top and bottom of the container body 302, respectively. The positioning support 304 is installed inside the container body 302, and a first heat transfer tube sample 303 is mounted on the positioning support 304. Pre-made scale adheres to the outer surface of the first heat transfer tube sample 303. The circulating fluid in the main circulation loop continuously flushes the outside of the first heat transfer tube sample 303, while no medium flows inside the tube. After flushing for a period of time, the first heat transfer tube sample 303 is disassembled, and the descaling effect is tested by weighing. The upper flange cover A301 and the lower end cap 305 of the container are detachable flanges to enable free disassembly and assembly of the first heat transfer tube sample 303 and removal of the bottom deposited scale. The positioning support 304 is mainly used for positioning and supporting the first heat transfer tube sample 303. Both the upper and lower ends of the first heat transfer tube sample 303 are sealed with plugs.

[0035] The DC circulation simulator is used to simulate a DC circulation evaporator. It includes a container upper flange cover B306, a container header 307, and a container outer sleeve 309. The container header 307 includes an upper header and a lower header. The container outer sleeve 309 is connected to the upper and lower headers at both ends. The container upper flange cover B306 is detachably connected to the top of the upper header. A second heat transfer tube sample 308 is installed inside the container outer sleeve 309. The container header 307 is used to simulate the upper and lower headers of the actual evaporator heat transfer tubes. The outer diameter of the second heat transfer tube sample 308 is slightly smaller than the inner diameter of the container outer sleeve 309 and is installed inside it with a clearance fit. The upper end of the second heat transfer tube sample 308 is fixed to the upper header by a threaded connection, and the lower end of the second heat transfer tube sample 308 is placed at the pipe opening where the container outer sleeve 309 connects to the lower header with a clearance fit. The pre-made scale adheres to the inner surface of the second heat transfer tube sample 308. The circulating fluid in the main circulation loop mainly flushes the inside of the second heat transfer tube sample 308, and there is no medium flowing outside the tube. After flushing for a period of time, the second heat transfer tube sample 308 is disassembled. During disassembly, the threads between the upper end of the second heat transfer tube sample 308 and the upper header need to be loosened and the whole thing pulled out from bottom to top. The descaling effect is then checked by weighing. The DC circulation simulator is equipped with an external heating wire to heat the medium inside the tube when the loop fluid is stationary (immersion condition). The flange cover B306 on the container is a detachable flange to allow the second heat transfer tube sample 308 to be freely disassembled and assembled.

[0036] like Figure 3 As shown, the hot-state pressure stabilizing tank 5 uses electric heating as its heat source during the experimental research phase. It includes a pressure stabilizing tank body 501, an electric heating rod 502, and a safety valve 503. The electric heating rod 502 is fixedly connected inside the pressure stabilizing tank body 501. An interface is located at the top of the pressure stabilizing tank body 501, and the safety valve 503 is installed on the interface. The hot-state pressure stabilizing tank 5 can simultaneously realize the functions of storing the medium in the main circulation loop, heating the circulating fluid, and stabilizing the pressure in the main circulation loop. The electric heating rod 502 is connected to the pressure stabilizing tank body 501 by a threaded hard seal and is also equipped with an interface for venting or injecting nitrogen, providing nitrogen protection for the main circulation loop and providing high-pressure nitrogen driving force during the loop drainage stage to prevent the liquid in the loop from contacting oxygen.

[0037] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. All contents not described in detail in the present invention can be derived from existing technologies.

Claims

1. A chemical cleaning system for fouling heat transfer tubes in a steam generator, characterized in that, The system includes: a circulating pump (1), a cooler (2), a simulated container (3), a plate container (4), a hot pressure stabilizing tank (5), a water replenishment pump (6), a cleaning tank (7), a rinsing tank (8), and a passivation tank (9); the cleaning tank (7), the rinsing tank (8), and the passivation tank (9) are connected to the hot pressure stabilizing tank (5) via the water replenishment pump (6); the hot pressure stabilizing tank (5) is connected to the cooler (2), the simulated container (3), and the plate container (4) in sequence via the circulating pump (1), and the plate container (4) is connected to the hot pressure stabilizing tank (5) to form a main circulation loop; the hot pressure stabilizing tank (5) is used for storing the medium in the main circulation loop, heating the circulating fluid, and stabilizing the pressure in the main circulation loop; the simulated container (3) and the plate container (4) are respectively filled with heat transfer tube assembly simulated bodies and plate samples of various types of scale; the simulated container (3) is a natural circulation simulated body or a DC circulation simulated body in the experimental research stage; in the engineering application stage, it is an actual evaporator of a nuclear power plant.

2. The chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, The system includes: a main loop sampler (12) and a simulated body sampler (13); the inlet of the cooler (2) and the simulated body container (3) are respectively provided with a first sampling branch and a second sampling branch; the first sampling branch is provided with a main loop sampler (12) for measuring the oxygen content and pH of the main loop in time-sharing and segmented manner; the second sampling branch is provided with a simulated body sampler (13) for measuring the oxygen content and pH of the simulated body in time-sharing and segmented manner.

3. The chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, The system includes: EDTA recovery waste liquid tank (10), Fe recovery waste liquid tank (11); cleaning tank (7), rinsing tank (8), passivation tank (9), hot pressure stabilizing tank (5) and sewage discharge from the main circulation loop are all connected to EDTA recovery waste liquid tank (10) and Fe recovery waste liquid tank (11).

4. The chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, The hot pressure stabilizing tank (5) is provided with an interface on the top for venting or injecting nitrogen. When nitrogen is injected, it provides nitrogen protection for the main circulation circuit and provides high-pressure nitrogen driving force during the liquid discharge stage of the circuit to prevent the liquid in the circuit from contacting oxygen.

5. The chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, Both the simulated container (3) and the hanging container (4) are equipped with key temperature and pressure measuring points to monitor the internal medium status; the simulated container (3) is equipped with multiple valves at the inlet and outlet to achieve forward and reverse fluid switching flushing.

6. The chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, Each of the cleaning tank (7), rinsing tank (8), and passivation tank (9) is equipped with a level gauge and a filling port. The cleaning tank (7) has an electric agitator built in. The water replenishment pump (6) is a single-stage plunger pump with a filter at the inlet and a flow meter at the outlet for calculating the total injection volume. The cooler (2) is a pipe-in-pipe structure with the fluid inside the pipe being the main circuit medium and the fluid outside the pipe being tap water cooling water.

7. A chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, A regulating valve is provided between the outlet of the circulating pump (1) and the first sampling branch. The regulating valve works with the frequency converter to regulate the flow of the main circulation loop.

8. A chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, The natural circulation simulator is used to simulate a natural circulation evaporator. It includes a container upper flange cover A (301), a container body (302), a positioning support (304), and a container lower end cap (305). The container upper flange cover A (301) and the container lower end cap (305) are detachably connected to the top and bottom of the container body (302), respectively. The positioning support (304) is installed inside the container body (302). A first heat transfer tube sample (303) is mounted on the positioning support (304). The positioning support (304) positions and supports the first heat transfer tube sample (303). Both the upper and lower ends of the first heat transfer tube sample (303) are sealed with plugs. Pre-made scale adheres to the outer surface of the first heat transfer tube sample (303). The circulating fluid of the main circulation loop continuously flushes the outside of the first heat transfer tube sample (303). There is no medium flowing inside the tube. After flushing for a period of time, the first heat transfer tube sample (303) is disassembled, and the descaling effect is tested by weighing.

9. A chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, The DC circulation simulator is used to simulate a DC circulation evaporator, including a container upper flange cover B (306), a container header (307), and a container outer sleeve (309). The container header (307) includes an upper header and a lower header. The container outer sleeve (309) is connected to the upper header and the lower header at both ends. The container upper flange cover B (306) is detachably connected to the top of the upper header. A second heat transfer tube sample (308) is assembled inside the container outer sleeve (309). The outer diameter of the second heat transfer tube sample (308) is slightly smaller than the inner diameter of the container outer sleeve (309). 08) The upper end is fixedly connected to the upper header. The lower end of the second heat transfer tube sample (308) is placed at the pipe opening where the outer casing (309) of the container is connected to the lower header through a clearance fit. The pre-made scale adheres to the inner surface of the second heat transfer tube sample (308). The circulating fluid of the main circulation loop mainly flushes the inside of the second heat transfer tube sample (308). There is no medium flowing outside the tube. After flushing for a period of time, the second heat transfer tube sample (308) is disassembled. The descaling effect is tested by weighing. The DC circulation simulator is equipped with an external heating wire to heat the medium inside the tube when the loop fluid is stationary.

10. A chemical cleaning system for heat transfer tube fouling in a steam generator according to claim 1, characterized in that, In the experimental research stage, the heat source of the hot pressure stabilizing tank (5) is an electric heating rod, including a pressure stabilizing tank body (501), an electric heating rod (502), and a safety valve (503). The electric heating rod (502) is fixedly connected inside the pressure stabilizing tank body (501). An interface is provided at the top of the pressure stabilizing tank body (501), and a safety valve (503) is provided on the interface. In the engineering application stage, the heat source is low-pressure steam supplied by the plant.

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