Air cooling circulating water flow direction switching device and indirect air cooling system energy saving method

Abstract

The invention relates to the technical field of thermal power plant indirect cooling towers, in particular to an air cooling circulating water flow direction switching device and an indirect air cooling system energy saving method. The switching valve body comprises an I-shaped shell, the I-shaped shell is connected with a water inlet pipe and a water return pipe in a flange mode and used for communicating the water inlet pipe with the water return pipe, an outer shell is arranged on the outer wall of the I-shaped shell, double-cross-shaped channels are formed in the I-shaped shell, a rotatable switching valve element is arranged in each cross-shaped channel, and the two ends of each switching valve element are communicated with the water inlet pipe and the water return pipe. The switching valve elements are synchronously controlled through fluid transmission pieces. Water flow direction switching devices are installed on an existing water inlet pipe and an existing water return pipe, so that when the indirect air cooling tower enters the working condition in winter, displacement of a switching valve element is accurately commanded through a hydraulic control system which is arranged on the indirect air cooling tower and is responsible for regulating and controlling the opening degree of a side shutter of the indirect air cooling tower; and the conversion of the system from a conventional countercurrent heat exchange mode to a downstream heat exchange mode is realized.

Description

Technical Field

[0001] The invention relates to the technical field of intercooling towers in thermal power plants, in particular to an air-cooling circulating water flow direction switching device and an energy-saving method for an indirect air-cooling system. Background Art

[0002] See also Figure 1 In the field of indirect cooling systems, the Harmon indirect air cooling system has become the preferred solution for many power plants and industrial cooling applications due to its excellent heat exchange efficiency, low plant power consumption rate, small number of equipment and relatively simple system structure. Compared with the direct air cooling system, the indirect air cooling system effectively reduces the direct consumption of water resources and the risk of environmental pollution by using cooling water and steam for heat exchange in a closed cycle, showing obvious environmental friendliness and economic benefits.

[0003] However, due to the special climatic conditions in northern my country, the indirect air cooling system faces severe challenges. The temperature difference between the four seasons in this region is significant, with extreme low temperatures in winter reaching -31°C, which is about 60 to 70°C lower than the high temperatures in summer. This poses a double challenge to the operating efficiency and safety of the indirect air cooling system. According to the principles of thermodynamics, the reduction in the temperature of the cold source can theoretically increase the vacuum degree, thereby enhancing the working capacity and efficiency of the unit. However, operation in an extremely low temperature environment may cause the cooling triangle area of ​​the air cooling system to face serious risks of freezing damage, especially when the cooling water temperature is too low, which will increase the probability of freezing and blockage inside the system, threatening the safety of the equipment.

[0004] To cope with the severe winter cold, the current response measures are mostly to adjust the shutter opening, increase the exhaust steam pressure and temperature by reducing the air circulation, so as to prevent the cooling water from being overcooled and frozen. For example, the shutter opening of the winter fan section of Unit 1 needs to be maintained at 35% to 40%, and that of Unit 2 is about 32%. Although this approach can effectively avoid freezing damage, it sacrifices some of the unit's operating efficiency and economy, resulting in reduced energy utilization efficiency in winter and increased operating costs. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the fact that operation in extremely low temperature environment mentioned above or in the prior art may cause the cooling triangle area of ​​the air cooling system to face serious risk of freezing damage, especially when the cooling water temperature is too low, which will increase the probability of freezing and blockage inside the system, threatening the safety of the equipment. Although the existing countermeasures can effectively avoid freezing damage, they sacrifice part of the operating efficiency and economy of the unit, resulting in reduced energy utilization efficiency and increased operating costs in winter, the present invention is proposed.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: an air-cooling circulating water flow direction switching device, comprising a radiator main pipe, including a water inlet pipe and a water return pipe arranged in parallel;

[0008] The switching valve body comprises an I-shaped shell, wherein the I-shaped shell is connected to the water inlet pipe and the water return pipe in the form of a flange, and is used to connect the water inlet pipe and the water return pipe, and an outer shell is arranged on the outer wall of the I-shaped shell, and a double cross channel is arranged inside the I-shaped shell, and a rotatable switching valve core is arranged inside each of the cross channels, and each of the switching valve cores is synchronously controlled by a fluid transmission member.

[0009] As a preferred solution of the air-cooled circulating water flow direction switching device of the present invention, the I-shaped shell includes two parallel first vertical channels and second vertical channels connected to the water inlet pipe and the water return pipe, a transverse channel is arranged between the first vertical channel and the second vertical channel, the intersection of the first vertical channel and the transverse channel is a first cross channel, the intersection of the second vertical channel and the transverse channel is a second cross channel, and the outer shell is sleeved on the outside of the transverse channel and is connected to it.

[0010] As a preferred solution of the air-cooled circulating water flow direction switching device of the present invention, wherein: the switching valve core includes two groups of valve plates rotatably arranged at the diagonals of the first cross channel or the second cross channel, the two groups of valve plates respectively include a first plate and a second plate, a notch is set on one side of the first plate, and another notch is set on the other side of the second plate, and the notches of the first plate and the second plate correspond to each other.

[0011] As a preferred solution of the air-cooled circulating water flow direction switching device of the present invention, the fluid transmission component includes a cylinder that is arranged through the center of the first cross channel or the second cross channel, and the upper and lower ends of the cylinder are both provided with raised protrusions, and the edges of the first plate and the second plate are fitted therewith.

[0012] As a preferred solution of the air-cooled circulating water flow direction switching device of the present invention, the first plate and the second plate are both rotatably installed in the I-shaped shell through a rotating member, and the rotating member is connected to the cylinder.

[0013] As a preferred solution of the air-cooled circulating water flow direction switching device of the present invention, wherein: the rotating part includes a cavity arranged inside the shell, and an L-shaped rod body located in the cavity, a screw groove is arranged on the outer wall of the L-shaped rod body, a protrusion is arranged in the cavity, the protrusion slides along the screw groove, and the upper end of the L-shaped rod body is lifted and lowered along the inner limit position of the side surface of the first plate or the second plate.

[0014] As a preferred solution of the air-cooled circulating water flow direction switching device of the present invention, wherein: a lock buckle is provided at the notch of the first plate or the second plate, and a retractable lock core is provided at the outer wall of the first plate or the second plate located in the notch, the lock core is plugged into the lock hole, and the lock core is located in the connecting hole.

[0015] As a preferred solution of the air-cooled circulating water flow direction switching device of the present invention, wherein: a vent hole is arranged in the L-shaped rod body, the vent hole is connected with the cavity, and the connecting hole is connected with the vent hole inside the rotating part.

[0016] In order to solve the above technical problems, the present invention also provides the following technical solutions: an energy-saving method for an indirect air cooling system, comprising the air cooling circulating water flow direction switching device, and comprising the following steps:

[0017] Pipeline modification and device installation: During the non-operating period of the system (i.e., the window period), the existing water inlet pipe and return pipe are partially cut off, and the above-mentioned air-cooled circulating water flow direction switching device is installed at the cut-off end to lay the foundation for the flexible adjustment of the subsequent heat exchange mode;

[0018] Operation mode adjustment: In winter, the hydraulic control system is used to accurately control the movement of the switching valve core, thereby switching the indirect air cooling tower system from countercurrent heat exchange mode to cocurrent heat exchange mode, and also adjusting the opening of the shutters on the side of the indirect air cooling tower.

[0019] As a preferred solution of the indirect air cooling system energy-saving method of the present invention, further, under the premise of ensuring the safety and stability of the system, one main circulating water pump is shut down and the operating frequency or working efficiency of another circulating water pump is improved.

[0020] The beneficial effects of the present invention are as follows: the existing water inlet pipe and water return pipe are partially cut, and a special water flow switching device is installed at the cut interface. This modification builds a hardware foundation for the flexible adjustment of the subsequent heat exchange mode. When entering the winter working condition, the hydraulic control system equipped with the indirect air cooling tower itself is used to accurately command the displacement of the switching valve core to realize the transformation of the system from the conventional countercurrent heat exchange mode to the downstream heat exchange mode. This transformation is intended to adapt to the low temperature environment in winter, reduce the heat loss of cooling water in the low temperature section outside the tower, and prevent the risk of freezing. At the same time, the hydraulic system is also responsible for regulating the opening and closing degree of the side shutters of the indirect air cooling tower to further optimize the air flow and heat exchange efficiency.

[0021] In order to improve energy efficiency while ensuring the safety and stability of system operation, a strategy of streamlining the operation of circulating water pumps was adopted, that is, stopping one circulating water pump and increasing the operating frequency or enhancing the working efficiency of the remaining water pumps. This move aims to reasonably allocate power resources, avoid energy waste, and achieve overall operating cost reduction and efficient energy use. This series of measures is jointly committed to significantly improving the antifreeze ability, energy saving and emission reduction effect, and overall operating performance of the indirect air cooling system under winter conditions by minimizing the transformation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0023] Figure 1 This is the overall schematic diagram of the indirect air cooling system.

[0024] Figure 2 It is an overall schematic diagram of the air-cooled circulating water flow switching device.

[0025] Figure 3 Schematic diagram of the internal structure of the air-cooled circulating water flow switching device Figure 1 .

[0026] Figure 4 Schematic diagram of the internal structure of the air-cooled circulating water flow switching device Figure 2 .

[0027] Figure 5 This is a schematic diagram of the internal flow direction after the air-cooled circulating water flow direction switching device is switched.

[0028] Figure 6 for Figure 5 Schematic diagram of the AA section structure.

[0029] Figure 7 for Figure 6 Enlarged schematic diagram of the structure at point B in the middle.

[0030] Figure 8 Schematic diagram of the temperature changes of the internal and external media before and after the optimization and transformation of the intercooling tower.

[0031] Fig. 9 This is the influence of circulating water inlet temperature on condenser vacuum.

[0032] In the figure:

[0033] 100, radiator main pipe; 101, water inlet pipe; 102, water return pipe;

[0034] 200, switching valve body; 201, I-shaped shell; 201a, first vertical channel; 201b, second vertical channel; 201c, transverse channel; 202, outer shell; 203, cross channel; 203a, first cross channel; 203b, second cross channel; 204, switching valve core; 204a, valve plate; 204a-1, first plate; 204a-2, second plate; 204b, notch; 204c, lock core; 204d, lock hole; 204e, connecting hole; 205, fluid transmission part; 205a, cylinder; 205b, protrusion; 205c, rotating part; 205c-1, shell; 205c-2, cavity; 205c-3, L-shaped rod; 205c-4, vent. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0038] Example 1

[0039] Reference Figure 1-Figure 7, which is the first embodiment of the present invention, and provides an air-cooling circulating water flow direction switching device, including a radiator mother pipe 100, including a water inlet pipe 101 and a water return pipe 102 arranged in parallel; a switching valve body 200, including an I-shaped shell 201, the I-shaped shell 201 is connected to the water inlet pipe 101 and the water return pipe 102 in the form of a flange, and is used to connect the water inlet pipe 101 and the water return pipe 102, and an outer shell 202 is arranged on the outer wall of the I-shaped shell 201, and a double cross channel 203 is arranged inside the I-shaped shell 201, and a rotatable switching valve core 204 is arranged inside each cross channel 203, and each switching valve core 204 is synchronously controlled by a fluid transmission member 205.

[0040] In the strategy of optimizing the indirect air cooling system to improve energy efficiency and antifreeze performance, the present application first partially cuts off the existing water inlet and return pipes 102 during the system maintenance window, that is, the non-operating period, and installs a special water flow direction switching device at these cut-off points. This transformation provides the system with a basis for flexibly adjusting the water flow direction in different seasons or working conditions. When winter comes, the existing shutter hydraulic control system is used to achieve precise control of the switching valve core 204, thereby completing the transition from the countercurrent heat exchange mode to the downstream heat exchange mode. This conversion strategy effectively adjusts the flow path of the cooling water through the precise operation of the hydraulic system, ensures that the temperature in the circulating water pipe at the outer end of the tower is increased by at least 10°C, significantly reduces the risk of freezing caused by low temperature, and ensures the safety and stable operation of the system in extreme weather. At the same time, this strategy reduces the additional energy consumption required for antifreeze, and effectively promotes the realization of energy conservation and emission reduction goals.

[0041] In addition, in order to further improve the operating efficiency, the strategy also includes the optimization of the operation of the circulating water system pump group. Under the premise of ensuring the overall safety and stability of the system operation, measures were taken to stop using one main circulating water pump and increase the operating frequency or improve the working efficiency of another circulating water pump. This approach not only balances the load of the pump group, but also effectively reduces the overall energy consumption, achieving a more economical and efficient operation mode.

[0042] Example 2

[0043] Reference Figure 2-Figure 7, which is the second embodiment of the present invention. Different from the previous embodiment, this embodiment provides an I-shaped shell 201 including two parallel first vertical channels 201a and second vertical channels 201b connected to the water inlet pipe 101 and the water return pipe 102, a transverse channel 201c is arranged between the first vertical channel 201a and the second vertical channel 201b, the intersection of the first vertical channel 201a and the transverse channel 201c is a first cross channel 203a, the intersection of the second vertical channel 201b and the transverse channel 201c is a second cross channel 203, and the outer shell 202 is sleeved on the outside of the transverse channel 201c and is connected to it. The switching valve core 204 includes two sets of valve plates 204a that are rotated and arranged at the diagonal positions of the first cross channel 203a or the second cross channel 203. The two sets of valve plates 204a include a first plate 204a-1 and a second plate 204a-2, respectively. A notch 204b is arranged on one side of the first plate 204a-1, and another notch 204b is arranged on the other side of the second plate 204a-2. The notches 204b of the first plate 204a-1 and the second plate 204a-2 correspond to each other. A through cylinder 205a is arranged at the center of the first cross channel 203a or the second cross channel 203. Both the upper and lower ends of the cylinder 205a are provided with raised protrusions 205b, and the edges of the first plate 204a-1 and the second plate 204a-2 are in contact with them. The first plate 204a-1 and the second plate 204a-2 are both rotatably mounted in the I-shaped housing 201 via a rotating member 205c, and the rotating member 205c is in communication with the cylinder 205a.

[0044] It should be noted that, in the conventional water flow mode, the first plate 204a-1 closes the channel entrance connecting the first cross channel 203a or the second cross channel 203 with the outer shell 202, while the second plate 204a-2 closes the interface between the first cross channel 203a or the second cross channel 203 and the transverse channel 201c. In this way, the circulating water first enters the first vertical channel 201a through the water inlet pipe 101, passes through the central area of ​​the first cross channel 203a, and then passes through the other end of the first vertical channel 201a, and then enters the next stage of the air cooling cycle process, and finally passes through the second vertical channel 201b and the center of the second cross channel 203, and flows back to the return pipe 102 to complete the cycle. This process ensures a straight path for water circulation and maintains high heat exchange efficiency. When the heat exchange mode needs to be switched, the first plate 204a-1 and the second plate 204a-2 are rotated alternately in the center area of ​​the same cross channel 203, thereby opening the path to the transverse channel 201c and directly connecting with the outer shell 202. This change changes the water flow path. Now the water starts from the water inlet pipe 101 and directly enters the transverse channel 201c. After air cooling operation through the optimized path, it returns through the return pipe 102, realizing the adjustment of the water flow direction. This adjustment has significant energy-saving and optimization effects for the indirect air cooling system.

[0045] It should be noted that a cylinder 205a is arranged on the central axis of the first cross channel 203a or the second cross channel 203, and the upper and lower terminals of the cylinder 205a are specially designed with protrusions 205b, which coincide with the contours of the edges of the first plate 204a-1 and the second plate 204a-2. Since the two plates are in the shape of circular discs, when they are rotated to overlap in the center of the channel, a triangular space is formed in the middle. At this time, the protrusions 205b structures at both ends of the cylinder 205a play a key role. They just fill this potential leakage gap, effectively preventing circulating water or other fluids from leaking therefrom, and ensuring the sealing. The cylinder 205a not only plays a sealing role, but also plays a role in firmly supporting the first plate 204a-1 and the second plate 204a-2 when the water flow is strong. Even when the water flow is strongly pushed, the two disc-shaped valve plates 204a can be fixed in the designed central position, avoiding displacement caused by external force impact, ensuring the accurate execution and stable maintenance of the heat exchange channel switching. Such a design not only improves the system's anti-leakage performance, but also enhances the overall stability and reliability, ensuring that the switching valve core 204 can accurately control the water flow path under various working conditions, achieving the goals of energy saving and optimized operation.

[0046] The rotating member 205c includes a cavity 205c-2 arranged inside the shell 205c-1, and an L-shaped rod body 205c-3 located in the cavity 205c-2. A screw groove is arranged on the outer wall of the L-shaped rod body 205c-3, and a protrusion is arranged in the cavity 205c-2. The protrusion slides along the screw groove, and the upper end of the L-shaped rod body 205c-3 is limited and lifted along the inner side of the first plate 204a-1 or the second plate 204a-2.

[0047] A lock buckle is provided at the notch 204b of the first plate 204a-1 or the second plate 204a-2, and a retractable lock core 204c is provided at the outer wall of the first plate 204a-1 or the second plate 204a-2 located in the notch 204b. The lock core 204c is plugged into the lock hole 204d, and the lock core 204c is located in the connecting hole 204e, which is connected to the inside of the rotating part 205c.

[0048] When in use, gas is injected into the cylinder 205a through the hydraulic system, and the gas enters the rotating member 205c connected thereto along the channels inside the cylinder 205a and the shell 205c-1, and pushes the L-shaped rod 205c-3 to move upward in the cavity 205c-2 inside the rotating member 205c. Since the outer wall thereof is provided with a screw groove, the cavity 205c-2 is provided with a convex block, and the convex block moves along the screw groove, the L-shaped rod 205c-3 moves upward and rotates at the same time. Since the upper end cross bar of the L-shaped rod 205c-3 is limited and lifted in the inner groove of the first plate 204a-1 or the second plate 204a-2, the L-shaped rod 205c-3 drives the first plate 204a-1 or the second plate 204a-2 to rotate, thereby the first plate 204a-1 and the second plate 204a-2 are connected. 2 rotates and merges at the cylinder 205a, and further the upper end cross bar of the rod body is located at the uppermost end of the inner groove of the first plate 204a-1 or the second plate 204a-2, and is connected with the inner cavity connecting hole 204e, and then the gas will enter the connecting hole 204e from the cavity 205c-2 of the rotating member 205c and the L-shaped rod body 205c-3, and push the lock core 204c located in the connecting hole 204e to move outward, so that the lock core 204c of the first plate 204a-1 is inserted into the lock hole 204d of the second plate 204a-2, and the lock core 204c of the second plate 204a-2 is inserted into the lock hole 204d of the first plate 204a-1, completing the interlocking process, and then locking the entire switching valve core 204, realizing the switching of the internal flow line, and realizing the countercurrent and downstream heat exchange switching of water and cold air.

[0049] On the contrary, when unlocking, the lock core 204c in the connecting hole 204e is withdrawn by vacuum, and the L-shaped rod body 205c-3 is lowered and rotated to be retracted, and the first plate 204a-1 and the second plate 204a-2 are rotated to be retracted, and finally the valve core is rotated to switch to the normal state.

[0050] Example 3

[0051] Reference Figure 1 or Figure 8 , which is the third embodiment of the present invention. Different from the previous embodiment, this embodiment provides an energy-saving method for an indirect air-cooling system, including an air-cooling circulating water flow direction switching device, and includes the following steps: Pipeline modification and device installation: During the non-operating period of the system (i.e., the window period), the existing water inlet pipe and the return pipe are partially cut off, and the above-mentioned air-cooling circulating water flow direction switching device is installed at the cut-off end, laying the foundation for the flexible adjustment of the subsequent heat exchange method; Operation mode adjustment: Entering winter, the hydraulic control system is used to accurately control the movement of the switching valve core, so as to switch the indirect air-cooling tower system from the countercurrent heat exchange mode to the downstream heat exchange mode, and the shutter opening on the side of the indirect air-cooling tower is also adjusted. Furthermore, under the premise of ensuring the safety and stability of the system, one main circulating water pump is deactivated, and the operating frequency or work efficiency of another circulating water pump is improved.

[0052] Renovation plan: Without changing the original system operation mode of the existing intercooler, add an air-cooled circulating water flow direction switching device to the circulating water inlet and outlet pipelines of the renovated fan section to achieve countercurrent and cocurrent heat exchange switching between circulating water and cold air.

[0053] This project mainly carries out the research on the switching of circulating water of intercooler tower between downstream and upstream, and the antifreeze research on the heat dissipation tube bundle of intercooler tower, and develops the optimized operation scheme of circulating water of intercooler tower.

[0054] 1 Antifreeze safety analysis:

[0055] 1.1 The phase change temperature of water is +4℃. Since the first antifreeze research of intercooler in China in 1993, taking into account the influence of freezing speed, the Fengzhen Power Plant conducted a study on air cooling antifreeze in 1996 and found that the system is safer if the circulating water return temperature is not lower than +12℃. In actual operation, the meteorological changes are taken into consideration and the circulating water return temperature is increased to above +30℃ in winter. Comparing the three working conditions with the same external ambient temperature of -30℃, -20℃ and -10℃, the secondary heat exchange after optimization will become the heat exchange between cold water and heated cold air, and the temperature gradient between the circulating water outlet and the cooling air will be significantly reduced. Under the same conditions, the antifreeze capacity of the circulating water will be greatly improved. In the past, for antifreeze safety, the return water temperature of the intercooler was adjusted to above 30℃ in winter. After optimization, the return water temperature can be adjusted to above 25℃, which still has a large safety margin. For details, please refer to Figure 8 .

[0056] Table 1 Comparison of relevant parameters of countercurrent and cocurrent heat exchange in intercooler at ambient temperature -30℃

[0057]

[0058] Table 2 Comparison of relevant parameters of countercurrent and cocurrent heat exchange in intercooler at ambient temperature -20℃

[0059]

[0060] Table 3 Comparison of relevant parameters of countercurrent and cocurrent heat exchange in intercooler at ambient temperature -10℃

[0061]

[0062] 1.2 From the current calculation results and the test experience of Fengzhen Power Plant, it can be determined that the prerequisite for switching the circulating water of the intercooler from countercurrent heat exchange to cocurrent heat exchange is: when the shutters are fully open, the circulating water return temperature is lower than 12℃ (for safety reasons, the switching condition after this optimization is 20℃). According to local meteorological conditions, the optimized switching time schedule can be preliminarily determined as shown in the following table:

[0063] Table 4 Dual-process intercooler optimization switching schedule

[0064]

[0065] 2. Optimize some sectors of the indirect air-cooling tower, that is, according to the current operating experience of withdrawing a maximum of four sectors in winter and the calculation of circulating water flow, it is planned to optimize 4 of the 8 sectors of the intercooling tower of Unit 2, with the function of switching between forward and reverse flow, and finally realize the forward flow operation of the optimized 4 downstream heat exchange sectors throughout the winter, that is, the unit's full load to 25% load operation with flexibility optimization while ensuring the antifreeze safety of the intercooling tower, and achieve a larger opening of the shutters throughout the year, with the set value of circulating water outlet ≥12℃ (increased to 20℃ for safety), and with good unit economy and winter antifreeze safety.

[0066] 3. Effect: The construction of a switchable device for circulating water in the intercooling tower in the forward and reverse flow will reduce the circulating water temperature of the main unit by 5°C and the circulating water flow by 50%. There is no risk of freezing of the cooling tube bundle of the intercooling tower, and the unit can operate continuously, safely and stably in winter. Through the study of the antifreeze method of the dual-process indirect air-cooling system, the winter antifreeze problem of the dual-process indirect air-cooling tower can be well solved by switching between forward and reverse flow, and the antifreeze ability of the dual-process indirect air-cooling tower in cold areas has been greatly improved; in-depth exploration and utilization of natural cold source conditions can further reduce the circulating water volume and circulating water temperature of the unit in winter, further improving the energy-saving potential of the dual-process indirect air-cooling system, achieving less fan investment and reducing the power consumption rate of the plant. Through post-optimization testing and in-depth analysis, the optimization scheme and optimization method will be promoted and applied to more indirect air-cooling units, including units of different capacities and models, to achieve a wider range of energy-saving and antifreeze effects, and provide more reliable and efficient solutions for the energy industry in the northern region. Through the optimization and experimental testing of the heat exchange mode of indirect air-cooling units in winter, new design ideas can be provided for manufacturers, and safer and more energy-saving operation measures can be provided for indirect air-cooling units that have been put into operation, filling the gap in indirect air-cooling technology. Through continuous research and practice, the design and operation of indirect air-cooling systems will be continuously improved and optimized, which will provide more advanced and reliable technical solutions for the energy industry in northern China and achieve the goals of energy conservation, emission reduction and sustainable development.

[0067] Beneficial effects:

[0068] 1 Economic Benefits

[0069] 1.1 The influence of circulating water temperature change on vacuum:

[0070] The surface condenser separates the working medium and cooling water in the thermal cycle system of the steam turbine by a cooling surface. The cooling water does not need to be deoxygenated, and the water quality can be adjusted according to the requirements of the pipes in the closed circulation system. The hybrid condenser connects the thermal cycle system of the steam turbine with the cooling circulation loop.

[0071] Basis for quantitative calculation:

[0072] The main task of quantitative calculation is to determine the new exhaust pressure after the circulating water inlet temperature changes. In the thermal calculation of the condenser, the basic heat transfer calculation formula is: Dγ=k·AΔt av From this formula, we can see that: as long as we find out the exhaust steam ratio (vaporization latent heat) of the condenser, we can look up the exhaust pressure from the water vapor property table. However, in the above calculation formula, there are exhaust latent heat (γ), heat transfer coefficient (k), heat transfer logarithmic temperature difference (Δt av )3 unknowns, so this equation cannot be solved. However, if we carefully analyze this basic formula, it is not difficult to see that the above 3 unknowns are all related to the exhaust pressure.

[0073] Therefore, we can first assume an exhaust pressure, and then the other three unknowns can be determined accordingly. At this time, we can use the heat transfer formula to calculate the steam turbine exhaust flow rate D, and then compare it with the original exhaust flow rate Do (the exhaust flow rate before the circulating water temperature changes). If the exhaust pressure is correct, it is considered that the exhaust pressure we assumed is correct, that is, the actual exhaust pressure after the circulating water temperature changes. Otherwise, the assumed calculation should be repeated until it meets the requirements.

[0074] 1.2 Determination of basic working conditions and their parameters

[0075] To determine the impact of changes in the condenser circulating water inlet temperature on its exhaust pressure, the original operating conditions (basic operating conditions) should be selected first before calculation and comparison can be performed. Here we select the operating condition when the condenser circulating water inlet temperature is 20℃ as the basic operating condition.

[0076] (1) Parameters related to calculation

[0077] Circulating water inlet temperature 20

[0078]

[0079] (2) Calculation of condenser cooling ratio

[0080] Calculation formula: Cooling ratio m = circulating water flow / exhaust steam flow, substituting the relevant values ​​into the above formula, we get:

[0081] m = 36000 / 599.46 = 60.0

[0082] (3) Calculation of heat transfer coefficient (k0)

[0083] k0=D0γ0 / Δt av0 A (1)

[0084] Δt av0 =Δt0 / ln[(Δt0+δ l ) / δ l ] (2)

[0085] Where Δt av0 1. Heat transfer temperature difference;

[0086] Δt0 is the circulating water temperature rise;

[0087] δ l —Difference in heat transfer end of condenser.

[0088] δ l =t p -t w20 =34.3-29.51=4.79℃

[0089] Substituting the relevant values ​​into formula (2), we get:

[0090] Δt av0 =9.51 / 1n[(9.51+4.79) / 4.79]=8.70℃

[0091] Substituting the relevant values ​​into formula (1), we get:

[0092] k0=(D0γ0) / (Δt av0 A) =599567x2420.76 / 8.70x16700 =9989.73kJ / hm 2 ℃

[0093] (4) Calculation of circulating water temperature correction coefficient

[0094] β t0 =1-(0.42×β0 0.5 / 1000)×(35-20) 2 (3)

[0095] Where β0 is the cleaning factor

[0096] Substituting the relevant values ​​into formula (3), we get:

[0097] β t0 =1-(0.42×0.8 0.5 / 1000)×(35-20) 2 =0.9155

[0098] 1.3 Calculation of other working conditions and their parameters

[0099] The circulating water inlet temperature is 25℃ (and other parameters remain unchanged). From the above analysis, it can be seen that the exhaust pressure is assumed and then checked by the calculated exhaust flow rate. Therefore, the calculation of the exhaust pressure is actually the determination of the exhaust flow rate.

[0100] From formula (1), it can be deduced that:

[0101] D1=k1×A×Δt av1 / γ1 (4)

[0102] Note: The lower corner code 1 represents the value when the circulating water inlet temperature is 25℃.

[0103] Calculation of heat transfer coefficient k1,

[0104] k=14652ββ w β t β z βd (5)

[0105] Where β w - Correction factors for cooling water velocity and pipe diameter;

[0106] β z ——Correction factor of cooling water flow;

[0107] β d ——Steam load rate correction factor.

[0108] In the above calculation formula, when only the circulating water inlet temperature changes, the heat transfer coefficient k and the circulating water temperature correction coefficient β t It is a proportional relationship. That is: k1=(k0 / β t0 )×β t1 (6)

[0109] Circulating water temperature correction coefficient β t1 Calculation:

[0110] β t1 =1-(0.42×β1 0.5 / 1000)×(35-t w ) 2

[0111] =1-(0.42×0.8 0.5 / 1000)×(35-25) 2

[0112] =0.9624

[0113] Substituting the relevant values ​​into formula (6), we can obtain: k1=(k0 / β t0 )β t1

[0114] =(9989.73 / 0.9155)x0.9624

[0115] =10501.49kJ / h·℃

[0116] Heat transfer logarithmic temperature difference Δt av1 Calculation:

[0117] After the circulating water inlet temperature changes to 25°C, assuming that its exhaust steam pressure changes to 6.97 kPa, it can be found from the water vapor table: the exhaust steam temperature t p =38.942℃; exhaust steam latent heat value 2409.40kJ / kg.

[0118] Circulating water temperature rise Δt1=γ1 / (C p × m)=2409.40 / (4.1868×60.0)=9.591℃

[0119] Condenser heat transfer end difference δ1=38.942-25-9.591=4.351℃

[0120] Heat transfer logarithmic temperature difference

[0121] Δt av1 =Δt / ln[(Δt+δ1) / δ1]=9.591 / ln[(9.591+4.351) / 4.351]=8.236℃

[0122] Substituting the relevant values ​​into (4), we obtain:

[0123] D1=k1×A×Δt av1 / γ1=10501.49x16700x8.236 / 2409.40

[0124] =599 480kg / h

[0125] Check of exhaust steam flow:

[0126] ΔD=|D0-D| / D0=1599567-5994801 / 599567=0.00015≤0.002

[0127] By checking the exhaust flow rate, it can be considered that the exhaust pressure assumed in the above calculation is correct. That is, when the condenser circulating water inlet temperature is 25℃ (and other parameters remain unchanged), the exhaust pressure value is 6.97kPa

[0128] According to the relevant steps in the above calculation process, it is very convenient to calculate the corresponding exhaust pressure when the condenser circulating water inlet temperature is 5℃, 10℃, 15℃, 30℃, and 33℃. The calculation results of each working condition are shown in Fig. 9 shown.

[0129] 1.4 Estimation of the impact of changes in condenser circulating water inlet temperature on unit economic performance

[0130] From the above calculation results, it can be concluded that when the condenser circulating water inlet temperature rises from 20℃ to 25℃, the corresponding exhaust pressure change rate is 0.32kPa / ℃; when the inlet temperature rises from 25℃ to 30℃, it is 0.40kPa / ℃.

[0131] According to the curve provided by the relevant data, it is calculated that for every 1kPa increase in the exhaust pressure of the unit, the coal consumption of the unit will increase by about 1.65g / (Kw.h). Based on this, the impact of the change in the circulating water inlet temperature on the coal consumption of the unit can be calculated, and the specific results are shown in Table 5.

[0132] Table 5 Relationship between circulating water inlet temperature change and coal consumption

[0133]

[0134] It can be concluded from Table 1 that when the circulating water inlet temperature rises from 20℃ to 33℃, the unit coal consumption increases by an average of 0.635kg / kW.h for every 1℃ change in the circulating water temperature.

[0135] If the energy saving and optimization of the indirect air cooling system is completed, the co-current heat exchange switching research will be implemented on the 4 cooling fan sections on the windward side of the intercooling tower of Unit 2. In winter, the indirect air cooling tower system will be changed from the current countercurrent heat exchange mode to the co-current heat exchange mode, so that the temperature inside the pipe on the outlet side (outer end of the tower) of the originally easy-to-freeze area will be increased by an average of more than 10°C, eliminating the hidden danger of ice formation in the easy-to-freeze area of ​​the cooling pipe outside the tower. The return water temperature of the cooling tower can be controlled at 20-25°C, which is 5°C lower than the original operating mode. The average exhaust back pressure in winter is conservatively estimated to be reduced by about 0.5kPa. The exhaust back pressure can be reduced by about 1kPa during the peak cold period and the fin tube bundle will not freeze. The operation for 4 months in winter can save about 780t of coal and about 440,000 yuan in fuel costs. The circulating water flow rate is reduced by half (the two variable frequency main engine circulating water pumps maintain 32Hz operation, and the average operating frequency for the current four months is 40Hz, or one main engine circulating water pump is shut down and the other one is operated at a higher frequency. The specific operation plan is to be determined by the test). The four-month operation in winter can save 1.13 million kWh of electricity, about 360,000 yuan. After the intercooler circulating water system reverses the flow in winter, a total of 800,000 yuan can be saved.

[0136] 2 Social benefits (including safety benefits and environmental benefits)

[0137] After optimization, the risk of freezing damage to the intercooler tower can be greatly reduced, the safety of the intercooler tower equipment can be improved, the back pressure of the unit can be reduced, the plant power consumption rate can be reduced, and carbon emissions can be reduced.

[0138] 3Industry Value

[0139] It can be promoted and applied in intercooled power generating sets in the north.

[0140] 4. Achievement promotion plan (market conditions, application environment and promotion plan for the promotion / transformation of research results after the project research is implemented)

[0141] In recent years, most thermal power units in northern my country have adopted indirect air cooling systems. There is a problem in the northern region, that is, the meteorological conditions vary greatly throughout the year, and the ambient temperature difference between winter and summer can reach about 60 to 70 ° C. From the basic principles of thermodynamics, for vacuum systems, lower cold end temperatures are very beneficial to improving the functionality and efficiency of the unit. However, in order to avoid freezing damage accidents in the cooling triangle, the exhaust steam pressure and temperature must be increased by manually closing the shutters in winter. This causes the unit to operate at a higher back pressure, thereby reducing the unit's power generation capacity and operating economy. After the project research and implementation, it can effectively reduce the risk of freezing damage in the cooling triangle, make full use of the low temperature environment conditions in winter, reduce the back pressure of the unit, and improve the efficiency of the generator set, so it has a good prospect for promotion and application.

[0142] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to several modifications still falling within the scope of the appended claims.

[0143] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0144] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0145] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An air-cooling circulating water flow direction switching device, characterized in that: include, The radiator main pipe (100) comprises a water inlet pipe (101) and a water return pipe (102) arranged in parallel; The switching valve body (200) comprises an I-shaped shell (201), wherein the I-shaped shell (201) is connected to the water inlet pipe (101) and the water return pipe (102) in the form of a flange, and is used to connect the water inlet pipe (101) and the water return pipe (102), and an outer shell (202) is arranged on the outer wall of the I-shaped shell (201), and a double cross channel (203) is arranged inside the I-shaped shell (201), and a rotatable switching valve core (204) is arranged inside each of the cross channels (203), and each of the switching valve cores (204) is synchronously controlled by a fluid transmission member (205).

2. The air-cooling circulating water flow direction switching device according to claim 1, characterized in that: The I-shaped housing (201) comprises two parallel first vertical channels (201a) and second vertical channels (201b) connected to the water inlet pipe (101) and the water return pipe (102); a transverse channel (201c) is arranged between the first vertical channel (201a) and the second vertical channel (201b); the intersection of the first vertical channel (201a) and the transverse channel (201c) is a first cross channel (203a); the intersection of the second vertical channel (201b) and the transverse channel (201c) is a second cross channel (203b); and the outer housing (202) is sleeved on the outside of the transverse channel (201c) and is in communication with the transverse channel (201c).

3. The air-cooling circulating water flow direction switching device according to claim 2, characterized in that: The switching valve core (204) includes two groups of valve plates (204a) rotatably arranged at the diagonals of the first cross channel (203a) or the second cross channel (203b), and the two groups of valve plates (204a) respectively include a first plate (204a-1) and a second plate (204a-2), a notch (204b) is provided on one side of the first plate (204a-1), and another notch (204b) is provided on the other side of the second plate (204a-2), and the notches (204b) of the first plate (204a-1) and the second plate (204a-2) correspond to each other.

4. The air-cooling circulating water flow direction switching device according to claim 3, characterized in that: The fluid transmission component (205) includes a through-tube (205a) arranged at the center of the first cross channel (203a) or the second cross channel (203b), and the upper and lower ends of the tube (205a) are both provided with raised protrusions (205b), and the edges of the first plate (204a-1) and the second plate (204a-2) are in contact with the protrusions.

5. The air-cooling circulating water flow direction switching device according to claim 4, characterized in that: The first plate (204a-1) and the second plate (204a-2) are both rotatably mounted in the I-shaped housing (201) via a rotating member (205c), and the rotating member (205c) is connected to the cylinder (205a) via an air passage.

6. The air-cooling circulating water flow direction switching device according to claim 5, characterized in that: The rotating member (205c) comprises a shell (205c-1), a cavity (205c-2) arranged inside the shell (205c-1), and an L-shaped rod body (205c-3) located in the cavity (205c-2); a screw groove is arranged on the outer wall of the L-shaped rod body (205c-3); a convex block is arranged in the cavity (205c-2); the convex block slides along the screw groove; and the upper end of the L-shaped rod body (205c-3) is limitedly lifted and lowered along the inner side of the first plate (204a-1) or the second plate (204a-2).

7. The air-cooling circulating water flow direction switching device according to claim 6, characterized in that: A lock hole (204d) is provided at the notch (204b) of the first plate (204a-1) or the second plate (204a-2), and a retractable lock core (204c) is provided at the outer wall of the first plate (204a-1) or the second plate (204a-2) located in the notch (204b), and the lock core (204c) is inserted into the lock hole (204d), and the lock core (204c) is located in the connecting hole (204e).

8. The air-cooling circulating water flow direction switching device according to claim 6, characterized in that: A vent hole (205c-4) is provided in the L-shaped rod body (205c-3), the vent hole (205c-4) is connected to the cavity (205c-2), and the connecting hole (204e) is connected to the vent hole (205c-4) inside the rotating member (205c).

9. An energy-saving method for an indirect air cooling system, characterized in that: The invention comprises the air-cooling circulating water flow direction switching device according to any one of claims 1 to 7, and comprises the following steps: Pipeline modification and device installation: During the non-operating period of the system (i.e., the window period), the existing water inlet pipe and return pipe are partially cut off, and the above-mentioned air-cooled circulating water flow direction switching device is installed at the cut-off end to lay the foundation for the flexible adjustment of the subsequent heat exchange mode; Operation mode adjustment: In winter, the hydraulic control system is used to accurately control the movement of the switching valve core, thereby switching the indirect air cooling tower system from countercurrent heat exchange mode to cocurrent heat exchange mode, and also adjusting the opening of the shutters on the side of the indirect air cooling tower.

10. The energy-saving method for an indirect air cooling system according to claim 9, characterized in that: Furthermore, under the premise of ensuring the safety and stability of the system, one main circulating water pump is shut down and the operating frequency or working efficiency of another circulating water pump is increased.

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