Preheating device for shortening start-stop time of gas-steam combined cycle
By using modularly designed finned assemblies and detachable connections with serpentine tubes, the problem of long cold start-up time for gas-fired steam combined cycle units is solved, achieving rapid start-up and reduced maintenance costs.
Patent Information
- Application Number
- CN202520470641.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-18
- Publication Date
- 2026-02-03
- Estimated Expiration
- 2035-03-18
AI Technical Summary
When gas-fired combined cycle units are in a cold state, the startup process and temperature control are difficult, resulting in long startup times and an inability to quickly reach the optimal operating state, which affects the grid's peak-shaving capacity.
A modular preheating device is designed, which uses detachable fin assemblies fixed to a serpentine tube. By setting multiple sets of fin inner rings and heat-conducting fan plates on the outside of the serpentine tube, the heat transfer area is increased, and the detachable connection of the fin assembly is achieved through a fastening mechanism, thereby reducing maintenance costs.
It significantly shortens the start-up and shutdown time of the gas-steam combined cycle, reduces maintenance costs, and improves equipment flexibility and grid peak-shaving capacity.
Smart Images
Figure CN223869861U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of energy-saving device technology, and in particular to a preheating device for shortening the start-up and shutdown time of a gas-steam combined cycle. Background Technology
[0002] In recent years, gas-steam combined cycle units have developed rapidly, gaining popularity in the industry due to their advantages such as rapid start-up, excellent environmental performance, short construction period, and relatively low capital investment. In the field of grid peak shaving, the rapid start-up characteristics of gas turbines make them stand out. Faced with peak and trough changes in electricity load, gas turbines can respond quickly, flexibly adjust power generation, efficiently fill power gaps or reduce excess power, and ensure a dynamic balance between power supply and demand.
[0003] However, thermal equipment such as steam turbines and waste heat boilers pose challenges to the rapid startup of gas turbine units. Especially when the equipment is cold, numerous limitations exist in terms of temperature rise rate, startup procedures, and operational parameter control, making it difficult for gas turbines to start quickly and reach optimal operating conditions, thus failing to meet the grid's peak-shaving demands in a timely manner. This not only reduces the overall flexibility of the power generation system but also inconveniences the grid's balancing and regulation during peak and off-peak periods, slowing down the speed at which power supply adapts to changes in load.
[0004] By installing preheating devices, the cycle start-up time of gas-fired steam combined units can be significantly improved, thereby saving gas costs and plant power costs. Common preheating devices mainly include start-up boilers. The start-up boiler generates steam through internal heat exchangers (such as economizers and evaporators) to provide an initial heat source for the waste heat boiler and drive equipment such as steam turbines to complete the system start-up. Among them, serpentine coils are a common style of heat exchanger. To improve the heat exchange capacity of the coil, some heat exchangers will add fins to the outside of the coil. By increasing the contact area, the heat exchange effect is improved. However, since the fins are mostly fixed to the outside of the coil by welding and are integrated with the coil design, if a problem occurs with the fins or a section of the heat exchanger, the entire coil and the entire set of fins need to be replaced simultaneously, resulting in high maintenance costs. Utility Model Content
[0005] To address the aforementioned problems, this invention proposes a preheating device for shortening the start-up and shutdown time of a combined gas-steam cycle, thereby overcoming the shortcomings of existing devices.
[0006] To achieve the purpose of this utility model, the utility model is achieved through the following technical solution: a preheating device for shortening the start-up and shutdown time of a gas-steam combined cycle, comprising: a start-up boiler, an exhaust pipe on one side of the start-up boiler, an air inlet chamber on the other side of the start-up boiler, an air inlet pipe on the air inlet chamber, and the air inlet pipe being connected to the start-up boiler.
[0007] The start-up boiler is equipped with a heat exchanger, which is fixedly connected to the start-up boiler. The heat exchanger includes a header and a serpentine tube, with the serpentine tube fixedly connected to the lower end of the header.
[0008] Multiple fin assemblies are fitted on the outside of the serpentine tube. Each fin assembly includes multiple inner fin rings fitted on the outside of the serpentine tube. Multiple heat-conducting fan plates are provided on the outside of the inner fin rings. The heat-conducting fan plates are fixedly connected to the inner fin rings. An assembly plate is provided between two adjacent inner fin rings. The assembly plate is fixedly connected to the inner fin rings. A fastening mechanism is provided on the assembly plate. The inner fin rings are detachably connected to the serpentine tube through the fastening mechanism.
[0009] A further improvement is that the inner ring of the fin includes two arc-shaped clamps that fit around the outside of the serpentine tube, with the left and right ends of the arc-shaped clamps aligning with the left and right ends of the other arc-shaped clamp.
[0010] A further improvement is that the assembly plate includes two strip plates, which are fixedly connected to the left and right ends of the arc-shaped hoop plate, and the two strip plates are aligned with each other.
[0011] A further improvement is that the fastening mechanism includes a bolt seat located on the outside of the assembly plate, the bolt seat being fixedly connected to the assembly plate, a fixing bolt being mounted on the bolt seat, the fixing bolt being threadedly connected to a threaded hole in the bolt seat, and a nut being mounted on the bolt seat for fastening the fixing bolt.
[0012] A further improvement is that: one arc-shaped hoop has limiting ridges at both ends, and the other arc-shaped hoop has grooves at both ends that mate with the limiting ridges.
[0013] A further improvement is that the upper and lower surfaces of the heat-conducting fan plate are provided with several strip grooves.
[0014] A further improvement is that the heat-conducting fan plate has several through holes.
[0015] Compared with the prior art, the beneficial effects of this utility model are:
[0016] Water is heated by high-temperature gas inside the heat exchanger. The inner ring of the outer fin of the serpentine tube is fixed by a detachable connection. After the fastening mechanism is released from the inner ring of the fin, the entire fin assembly can be removed. The modular design of the fin assembly means that only the damaged section needs to be replaced when a partial failure occurs, effectively reducing maintenance costs. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a structural diagram of the boiler in this utility model.
[0019] Figure 2 This is a structural diagram of the serpentine tube in this utility model.
[0020] Figure 3 This is a structural diagram of the heat-conducting fan plate in this utility model.
[0021] Figure 4 This is a structural diagram of the assembly plate in this utility model.
[0022] Figure 5 This is a utility model Figure 3 Enlarged view of the structure at point A in the middle.
[0023] The components are: 1. Boiler start-up; 2. Exhaust pipe; 3. Air inlet chamber; 4. Air inlet pipe; 5. Heat exchanger; 51. Manifold; 52. Serpentine tube; 6. Fin assembly; 61. Fin inner ring; 62. Heat-conducting fan plate; 63. Through hole; 64. Strip groove; 65. Assembly plate; 66. Limiting ridge; 67. Groove; 7. Fastening device; 71. Bolt seat; 72. Fixing bolt; 73. Nut. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, 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, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0025] according to Figure 1 , 2 As shown in Figures 3, 4, and 5, this embodiment proposes a preheating device for shortening the start-up and shutdown time of a gas-steam combined cycle, comprising: a start-up boiler 1, an exhaust pipe 2 on one side of the start-up boiler 1, an air inlet chamber 3 on the other side of the start-up boiler 1, an air inlet pipe 4 on the air inlet chamber 3, and the air inlet pipe 4 being connected to the start-up boiler 1.
[0026] The gas discharged from the gas turbine has a temperature as high as 600 degrees Celsius and still has a high energy content. Sending this high-temperature gas to the boiler to heat water into steam to drive the steam turbine, which in turn drives the generator to generate electricity, can significantly improve the power generation capacity and the thermal efficiency of the combined cycle unit.
[0027] The preheating device mainly consists of an air inlet pipe 4, a start-up boiler 1, and an exhaust pipe 2. The start-up boiler 1 has a dense network of pipes. The water pump pressurizes the water to be heated into these pipes. The gas burns in the start-up boiler to produce high-temperature gas, which heats the water in the pipes into high-pressure steam for heating the steam turbine and waste heat boiler.
[0028] The start-up boiler 1 is equipped with a heat exchanger 5, which is fixedly connected to the start-up boiler 1. The heat exchanger 5 includes a header 51 and a serpentine tube 52, which is fixedly connected to the lower end of the header 51.
[0029] The serpentine tube 52 is connected to headers 51 at both ends. The headers 51 are the heating components for starting the boiler 1. Water is heated by high-temperature gas from the outside inside the heat exchanger 5.
[0030] To better transfer heat, multiple sets of fin assemblies 6 are fitted on the outside of the serpentine tube 52. The fin assembly 6 includes multiple sets of inner fin rings 61 fitted on the outside of the serpentine tube 52. Multiple sets of heat-conducting fan plates 62 are provided on the outside of the inner fin rings 61. The heat-conducting fan plates 62 are fixedly connected to the inner fin rings 61. An assembly plate 65 is provided between two adjacent inner fin rings 61. The assembly plate 65 is fixedly connected to the inner fin rings 61. A fastening mechanism is provided on the assembly plate 65. The inner fin rings 61 are detachably connected to the serpentine tube 52 through the fastening mechanism.
[0031] By setting multiple fin assemblies 6 on the outside of the serpentine tube 52, the heat transfer area of the pipe can be significantly increased, and the waste heat recovery effect can be improved. Since the inner fin ring 61 and the heat-conducting fan plate 62 are densely arranged and are fitted on the outside of the serpentine tube 52, the maintenance difficulty of the serpentine tube 52 is increased. Therefore, the inner fin ring 61 is fixed to the serpentine tube 52 in a detachable connection manner. After the fastening mechanism is released from the inner fin ring 61, the entire fin assembly 6 can be removed. The modular design of the fin assembly 6 means that only the damaged section needs to be replaced when a partial failure occurs, which effectively reduces maintenance costs.
[0032] It is worth explaining in detail that the inner ring 61 of the fin includes two arc-shaped hoops that fit around the outside of the serpentine tube 52, with the left and right ends of the arc-shaped hoops matching the left and right ends of the other arc-shaped hoops.
[0033] It is worth explaining in detail that the assembly plate 65 includes two strip plates, which are fixedly connected to the left and right ends of the arc-shaped hoop plate, and the two strip plates are aligned with each other. The inner ring of the fins 61 is composed of two aligned arc-shaped hoop plates, and the heat-conducting fan plate 62 is fixedly connected to the outside of the arc-shaped hoop plate. The upper and lower adjacent arc-shaped hoop plates are fixed by the two strip plates. When the two arc-shaped hoop plates are aligned, the two adjacent strip plates on the left and right sides will also be aligned with each other.
[0034] Regarding the fastening mechanism:
[0035] The fastening mechanism includes a bolt seat 71 located on the outside of the assembly plate 65. The bolt seat 71 is fixedly connected to the assembly plate 65. A fixing bolt 72 is mounted on the bolt seat 71, and the fixing bolt 72 is threadedly connected to a threaded hole in the bolt seat 71. A nut 73 for fastening the fixing bolt 72 is mounted on the bolt seat 71. When disassembling the fin assembly 6 from the outside of the serpentine tube 52, the fixing bolts 72 on each bolt seat 71 are unscrewed one by one from the bolt seat 71, thereby releasing the fixation between the strip plates, and the arc-shaped hoop plate can also be removed.
[0036] To enhance the fit between the two curved hoops, one curved hoop has limiting ridges 66 at both ends, and the other curved hoop has grooves 67 at both ends that mate with the limiting ridges 66. When the two curved hoops are fitted together, the limiting ridge 66 at one end of the curved hoop will engage with the grooves 67 on the other curved hoop, improving the fastening effect.
[0037] To improve the heat conduction effect of the heat-conducting fan plate 62, in a preferred embodiment, several strip grooves 64 are formed on the upper and lower end surfaces of the heat-conducting fan plate 62. The strip grooves 64 on the surface of the heat-conducting fan plate 62 can disrupt laminar airflow, enhance turbulence, and reduce thermal resistance.
[0038] In a preferred embodiment, the heat-conducting fan plate 62 is provided with several through holes 63. The presence of through holes 63 can effectively reduce the support burden on the serpentine tube 52 by reducing the weight of the heat-conducting fan plate 62 without significantly affecting its structural strength, thereby improving the service life of the heat exchanger 5.
[0039] Preheating devices are usually equipped with a preheating system, and the function of the preheating system will be briefly explained here.
[0040] The preheating system uses steam generated by the start-up furnace to heat the steam turbine, bringing it to a warm state and reducing the warm-up waiting time under cold conditions.
[0041] The preheating system can be started and stopped remotely by DCS. After the start-up furnace is started, the high-temperature and high-pressure steam generated is introduced into the waste heat boiler or steam turbine through pipelines to transition its temperature from a cold state to a warm state.
[0042] The preheating system drives the gas turbine shaft to rotate via the gas turbine SFC, and engages with the steam turbine shaft via the 3S clutch to drive the steam turbine to rotate, so as to preheat the steam turbine evenly. The steam produced by the starter boiler enters the steam turbine and reaches 690 rpm under the combined action of the SFC. Once it reaches the temperature, it can be stopped.
[0043] The high-temperature and high-pressure steam generated by the preheating system after the start-up furnace is started is introduced into the waste heat boiler through pipeline to heat the water in the low-pressure steam drum. After the water temperature reaches about 80°C, it is sent into the high and medium-pressure steam drums through the high and medium-pressure feedwater pump.
[0044] By optimizing the startup process, the systems are more tightly integrated, reducing startup waiting time.
[0045] By optimizing the operation process, reducing the probability of human error, and improving overall operation efficiency, the goal of shortening the start-up time can be achieved while ensuring stable unit operation. Improving the start-up speed through preheating will not cause additional life loss and will help extend the service life of the unit.
[0046] The preheating method for combined cycle steam turbines is suitable for cold starts of single-shaft combined cycle units equipped with automatic synchronizing clutches. Here, we supplement information on a commonly used preheating method.
[0047] Specifically, the preheating method includes the following steps:
[0048] Step 1: The gas turbine and steam turbine operate in turning gear mode. That is, before the unit's cold start, the gas turbine and steam turbine operate at turning gear speeds under the drag of the turning gear. At this time, the high-pressure gate valve, intermediate-pressure regulating valve, intermediate-pressure gate valve, high-pressure bypass valve, intermediate-pressure bypass valve, high-pressure exhaust check valve, high-pressure main valve, high-pressure regulating valve, reheat main valve, and reheat regulating valve are all closed. The high-pressure exhaust vent valve is open, the unit is supplied with steam by the shaft sealing system, a vacuum is established, and the oil system is engaged. The boiler-side electric isolation valve is closed, the steam source delivery valve is open, and the high-pressure pneumatic gate valve, intermediate-pressure regulating valve, and intermediate-pressure gate valve 1 (near the intermediate-pressure regulating valve) are opened to allow steam to fill the warm-up system pipelines and warm the high-pressure main steam valve group. The preheating system drain valve and the steam turbine drain system are opened. Based on the measured values of temperature and pressure measuring points, it is determined whether the steam has sufficient superheat (Note: the steam temperature is the smaller value before the high-pressure main valve and on the preheating pipeline, and the steam pressure is the larger value before the high-pressure main valve and on the preheating pipeline).
[0049] Step 2: Use the variable frequency starter SF to increase and stabilize the speed of the gas turbine at 800 rpm.
[0050] Step 3: Open the high-pressure main valve, high-pressure regulating valve, and intermediate-pressure gate valve 2 (near the turbine side) to introduce warm-up steam into the turbine. Use the high-pressure regulating valve and intermediate-pressure regulating valve to adjust the steam intake of the high and intermediate-pressure cylinders, increasing and stabilizing the turbine speed at 800 rpm. When the turbine speed tends to exceed the gas turbine speed, the automatic synchronization clutch will automatically engage. (If the SC trips unexpectedly before the turbine speed reaches 800 rpm, the turbine will trip, all valves will close, and both the turbine and gas turbine will coast down.)
[0051] Step 4: The SFC gradually disengages, and the steam turbine drives the gas turbine and generator to start warming up. The warm-up speed is 800 or 500 rpm. Since the steam turbine is running under load, the steam intake increases, which can significantly enhance the warm-up effect. Adjust the steam intake ratio of the high-pressure and intermediate-pressure cylinders (12) to allow more steam to enter the intermediate-pressure cylinder. After the speed stabilizes, open the reheat valve to allow preheated steam to enter the valve body to warm the valve.
[0052] Step 5: When the intermediate-pressure rotor groove temperature of the steam turbine exceeds 200℃, cut off the warm-up steam and end the warm-up. At this time, close the high-pressure main valve, high-pressure regulating valve, reheat regulating valve, high-pressure gate valve, intermediate-pressure gate valve, intermediate-pressure regulating valve, and high-pressure exhaust valve to cut off the warm-up steam and end the warm-up. The gas turbine and steam turbine will return to the turning gear state, and the speeds of the gas turbine and steam turbine will each decrease to their initial turning gear speeds. When the speed of the steam turbine is lower than that of the gas turbine, the automatic synchronization clutch will automatically disengage.
[0053] Once the warm-up is complete and the speeds of both the gas turbine and steam turbine have returned to the turning gear speed, the combined cycle unit can be started normally using the conventional warm-state or hot-state start-up method.
[0054] It is important to note that:
[0055] 1. Based on the turbine cylinder temperature, rotor temperature, and waste heat boiler boiler water temperature, T... STEAM =0.6*T CASE +0.4 TROTOR The steam temperature of the booster turbine or waste heat boiler is calculated by adding 50 (the coefficient is adjusted on-site according to the actual situation). This temperature is then processed by the PID calculation of the starter furnace to calculate the reasonable required temperature. This temperature is then sent to the control parameters of the starter furnace, and the starter furnace control system is used to achieve the required temperature.
[0056] 2. The steam turbine is driven by the gas turbine SFC to rotate, and the steam enters the steam turbine for preheating. The steam intake and drainage of the steam turbine are controlled to control parameters such as the temperature difference between the upper and lower cylinders, the expansion difference, and the absolute expansion.
[0057] How this application works:
[0058] The preheating device mainly consists of an air inlet pipe 4, a start-up boiler 1, an exhaust pipe 2, and a desuperheating and pressure reducing device. The start-up boiler 1 contains a dense network of pipes. A feedwater pump forces water to be heated into these pipes, and the high-temperature gas discharged from the start-up boiler 1 heats the water in the pipes into high-pressure steam. Both ends of the serpentine tube 52 are connected to headers 51, which are the heat-receiving components of the start-up boiler 1. The water is heated by the external high-temperature gas within the heat exchanger 5. By installing multiple fin assemblies 6 on the outside of the serpentine tube 52, the heat transfer area of the pipe can be significantly increased, improving the waste heat recovery effect. Because the inner fin ring 61 and the heat-conducting fan plate 62 are densely arranged and fitted onto the outside of the serpentine tube 52, the maintenance difficulty of the serpentine tube 52 is increased. Therefore, the header 51 is fixed to the serpentine tube 52 using a detachable connection. After releasing the fastening mechanism from the inner fin ring 61, the entire fin assembly 6 can be removed.
[0059] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.
[0060] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A preheating device for shortening the start-stop time of a gas-steam combined cycle, comprising a start-up boiler (1), one side of the start-up boiler (1) being provided with an exhaust pipe (2), the other side of the start-up boiler (1) being provided with an air inlet bin (3), the air inlet bin (3) being provided with an air inlet pipe (4) in communication with the start-up boiler (1); characterized in that The start-up boiler (1) is provided with a heat exchanger (5) fixedly connected with the start-up boiler (1), the heat exchanger (5) comprising a header (51) and a serpentine pipe (52) fixedly connected to the lower end of the header (51); A plurality of fin assemblies (6) are arranged outside the serpentine pipe (52), the fin assembly (6) comprising a plurality of fin inner rings (61) arranged outside the serpentine pipe (52), a plurality of heat-conducting fan plates (62) being arranged outside the fin inner rings (61) and fixedly connected with the fin inner rings (61), a splicing plate (65) being arranged between two adjacent fin inner rings (61) and fixedly connected with the fin inner rings (61), the splicing plate (65) being provided with a fastening mechanism, and the fin inner rings (61) being detachably connected with the serpentine pipe (52) through the fastening mechanism.
2. The preheating device for shortening the start-stop time of a gas-steam combined cycle according to claim 1, characterized in that: The fin inner ring (61) comprises two arc-shaped hoop plates arranged outside the serpentine pipe (52), the left and right ends of the arc-shaped hoop plates being opposite to the left and right ends of the other arc-shaped hoop plate.
3. The preheating device for shortening the start-stop time of a gas-steam combined cycle according to claim 2, characterized in that: The splicing plate (65) comprises two strip-shaped plates fixedly connected to the left and right ends of the arc-shaped hoop plates, the two strip-shaped plates being opposite to each other.
4. The preheating device for shortening the start-stop time of a gas-steam combined cycle according to claim 3, characterized in that: The fastening mechanism comprises a bolt seat (71) arranged outside the splicing plate (65) and fixedly connected with the splicing plate (65), a fixing bolt (72) being assembled on the bolt seat (71) and threadedly connected with a threaded hole formed in the bolt seat (71), and a nut (73) being assembled on the bolt seat (71) and used for fastening the fixing bolt (72).
5. The preheating device for shortening the start-stop time of a gas-steam combined cycle according to claim 2, characterized in that: The left and right ends of one arc-shaped hoop plate are provided with limiting edges (66), and the left and right ends of the other arc-shaped hoop plate are provided with grooves (67) matched with the limiting edges (66).
6. The preheating device for shortening the start-stop time of a gas-steam combined cycle according to claim 1, characterized in that: A plurality of strip-shaped grooves (64) are formed in the upper end surface and the lower end surface of the heat-conducting fan plate (62).
7. The preheating device for shortening the start-up and shut-down time of a gas-steam combined cycle according to claim 1, characterized in that: A plurality of through holes (63) are formed in the heat-conducting fan plate (62).