Steam supply system and method for guaranteeing safety of low-load water cooling wall of fluidized bed boiler
The design of a dual steam supply system and a dual economizer in parallel solves the hydrodynamic safety issue of the water-cooled wall during low-load operation of the fluidized bed boiler, ensuring safe and efficient operation of the water-cooled wall under low load and meeting industrial steam parameter requirements.
Patent Information
- Application Number
- CN202510985217.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-17
- Publication Date
- 2025-09-23
AI Technical Summary
During low-load operation of existing fluidized bed boiler units, the hydrodynamic safety of the water-cooled wall is difficult to ensure, especially when the steam extraction scheme design does not match user needs, which affects the safety of the water-cooled wall heating surface and reduces the unit efficiency.
A dual steam supply system is adopted, including feed water pump, high-pressure heater, economizer, bypass economizer, water-cooled wall and steam-water separator. The working medium is heated by high-temperature flue gas and the dual economizers are arranged in parallel and adjusted by valve group to achieve precise control of the water-cooled wall inlet temperature, ensuring the safety of the water-cooled wall under steam supply and non-steam supply conditions.
Under the ultra-low load condition of 30% THA, the mass flow rate of the water-cooled wall exceeds the critical value, preventing boiling stagnation and backflow, achieving safe protection of the water-cooled wall, and avoiding energy loss through the dual-path steam supply design to meet the industrial steam parameter requirements.
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Figure CN120684703A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of coal-fired power generation, and in particular relates to a steam supply system and method for ensuring the safety of low-load water-cooled walls of fluidized bed boilers. Background Art
[0002] With the development of new energy power generation capacity, the proportion of grid access is gradually increasing. In order to meet the needs of this new type of power system and the rapid development of economy and urbanization, some generators are actively exploring the heating market to fully utilize the advantages of cogeneration. The demand for industrial steam is increasing. According to the surrounding environmental conditions of the generator set, measures are taken according to local conditions. At the same time, based on the customer's industrial steam parameter requirements and unit operation safety, a variety of different heating methods can be flexibly selected, such as high-exhaust heating, heat reheating or extraction steam with a pressure matcher for heating. There are many factors that affect the unit's power generation, heat supply and heating method.
[0003] Conventional steam extraction schemes are designed based on the user's steam usage parameter requirements. However, with the diversification of steam usage parameter requirements, the extraction point parameters set on the fluidized bed boiler side or the steam turbine side cannot fully match the steam usage parameters required by the user. For example, the pressure and temperature can only match the previous one unilaterally. In order to meet the steam usage parameter requirements, the conventional design is to change the extraction point to a higher temperature parameter or mix steam with higher temperature parameters to meet the steam supply temperature requirements. This method has the following shortcomings: when supplying steam or not supplying steam, it affects the safety of the heating surfaces of each level of the fluidized bed boiler; at the same time, using high-quality steam parameters reduces the efficiency of the unit. Summary of the Invention
[0004] In view of this, the present invention aims to propose a steam supply system and method for ensuring the safety of the water-cooled wall of a fluidized bed boiler at low load, so as to solve the problem of hydrodynamic safety of the water-cooled wall during the low-load operation of the existing fluidized bed boiler unit participating in the deep peak regulation of the unit.
[0005] To achieve the above object, the present invention adopts the following technical solutions: A steam supply system for ensuring the safety of the low-load water-cooled wall of a fluidized bed boiler includes a feed water pump, a high-pressure heater, an economizer, a bypass economizer, a water-cooled wall and a steam-water separator. The feed water pump includes two water outlet pipes, one of which is connected to the input end of the high-pressure heater, the output end of the high-pressure heater is connected to the input end of the water-cooled wall through the economizer outlet pipe, the output end of the water-cooled wall is connected to the input end of the steam-water separator, the output end of the steam-water separator is connected to the industrial steam supply pipe, and the other water outlet pipe is connected to the input end of the bypass economizer, and the output end of the bypass economizer is connected to the economizer outlet pipe.
[0006] Furthermore, the outlet of the steam-water separator is connected to two pipelines, one is connected to the industrial steam supply pipeline, and the other is connected to the input end of the bypass superheater, and the output end of the bypass superheater is connected to the industrial steam supply pipeline.
[0007] Furthermore, valve groups are installed on the pipes between the feed water pump and the bypass economizer, the pipes between the steam-water separator and the bypass superheater, the pipes between the steam-water separator and the industrial steam supply pipe, and the pipes between the bypass superheater and the industrial steam supply pipe.
[0008] Furthermore, the economizer is installed in the economizer bypass flue behind the tail flue of the fluidized bed boiler, and the bypass superheater is installed in the superheater bypass flue behind the tail flue of the fluidized bed boiler.
[0009] Furthermore, the economizer bypass flue and the superheater bypass flue are provided with a rear flue rear wall behind them, and the inlets of the economizer bypass flue and the superheater bypass flue are both connected to the economizer outlet flue.
[0010] Furthermore, an economizer outlet header and an economizer inlet header are respectively installed at the upper and lower ends of the economizer, and the economizer outlet header and the economizer inlet header are both connected to the bypass economizer flue. A first closing baffle is provided on the bypass economizer flue above the economizer, and a first adjusting baffle and a first expansion joint are provided on the bypass economizer flue below the economizer. The bypass economizer flue is connected to the economizer outlet flue.
[0011] Furthermore, bypass superheater flues are installed at both upper and lower ends of the bypass superheater. The upper bypass superheater flue is provided with a second closing baffle and a superheater outlet header in sequence along the direction of flue gas flow, and the lower bypass superheater flue is provided with a superheater inlet header, a second regulating baffle and a second expansion joint in sequence along the direction of flue gas flow. The lower bypass superheater flue is connected to the economizer outlet flue.
[0012] A method for a steam supply system for ensuring the safety of a low-load water-cooled wall of a fluidized bed boiler utilizes high-temperature flue gas in the furnace to heat the working medium in the water-cooled wall under steam supply and non-steam supply conditions, so that the working medium temperature meets the steam supply requirements. The method specifically comprises the following steps: Step 1: Water flows through the outlet of the feed water pump and the high-pressure heater into the economizer; Step 2: Then it passes through the economizer outlet pipe and enters the water-cooled wall; Step 3: Another stream of water enters the bypass economizer through the feed water pump for heat exchange and then merges with the economizer outlet pipe to enter the water-cooled wall; Step 4: The working medium heated in the water-cooled wall is supplied with steam through the steam supply pipe.
[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts a dual-path design of "feedwater flow + extraction steam flow". Under the ultra-low load condition of 30% THA, the water wall mass flow rate can exceed the critical value, effectively preventing hydrodynamic instability phenomena such as boiling stagnation and backflow.
[0014] 2. The present invention adopts a dual economizer parallel system, and realizes precise control of the water-cooled wall inlet temperature through the dual adjustment mode of the flue gas damper and the pipeline regulating valve.
[0015] 3. The separator outlet of the present invention is provided with a dual steam supply pipeline, which can directly output industrial steam at 300-550°C, or be secondary heated through a bypass superheater, avoiding the energy loss caused by mixing high-grade steam in the traditional solution. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of a steam supply system for ensuring the safety of a low-load water-cooled wall of a fluidized bed boiler according to the present invention; Figure 2 This is a schematic diagram of the smoke and air flow of a steam supply system for ensuring the safety of a low-load water-cooled wall of a fluidized bed boiler according to the present invention; Figure 3 This is a schematic diagram of the structure of the economizer bypass flue and the superheater bypass flue.
[0017] In the picture: 1-feedwater pump, 2-high-pressure heater, 3-economizer, 4-bypass economizer, 5-economizer outlet pipe, 6-water-cooled wall, 7-steam-water separator, 8-bypass superheater, 9-valve group, 10-bypass economizer flue, 11-first closing damper, 12-economizer outlet header, 14-economizer inlet header, 15-first regulating damper, 16-first expansion joint, 17-economizer outlet flue, 18-bypass superheater flue, 19-second closing damper, 20-superheater outlet header, 22-superheater inlet header, 23-second regulating damper, 24-second expansion joint, 25-rear wall of rear flue. DETAILED DESCRIPTION
[0018] The following will clearly and completely explain the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. It should be noted that the embodiments of the present invention and the features therein can be combined with each other without conflict, and the embodiments described are only part of the embodiments of the present invention, not all of them.
[0019] Specific implementation 1: See Figure 1-3 This embodiment describes a steam supply system for ensuring the safety of the low-load water-cooled wall of a fluidized bed boiler, comprising a feed water pump 1, a high-pressure heater 2, an economizer 3, a bypass economizer 4, a water-cooled wall 6, and a steam-water separator 7. The feed water pump 1 comprises two water outlet pipes, one of which is connected to the input end of the high-pressure heater 2, the output end of the high-pressure heater 2 is connected to the input end of the water-cooled wall 6 through the economizer outlet pipe 5, the output end of the water-cooled wall 6 is connected to the input end of the steam-water separator 7, the output end of the steam-water separator 7 is connected to the industrial steam supply pipe, and the other water outlet pipe is connected to the input end of the bypass economizer 4, and the output end of the bypass economizer 4 is connected to the economizer outlet pipe 5.
[0020] Under steam supply conditions and non-steam supply conditions, the high-temperature flue gas in the furnace is used to heat the working medium in the water-cooled wall 6 so that the working medium temperature reaches the steam supply requirement. One path of water passes through the outlet of the feed water pump 1 and enters the economizer 3 through the high-pressure heater 2, and then enters the water-cooled wall 6 through the economizer outlet pipe 5. The other path of water passes through the feed water pump 1 and enters the bypass economizer 4 for heat exchange, and then merges with the economizer outlet pipe 5 to enter the water-cooled wall 6. The working medium heated in the water-cooled wall 6 is supplied with steam through the steam supply pipe.
[0021] like Figure 2 As shown, economizer 3 is arranged at the lower part of the right tail flue, with a flue gas temperature range of 430°C-540°C, which is in the low-temperature flue gas area. The bypass economizer operates in a flue gas temperature range of 610°C-760°C, which is in the high-temperature flue gas area.
[0022] In this embodiment, the water-cooled wall 6 adopts a membrane wall form and adopts a spiral water-cooled wall + vertical water-cooled wall structure. In the high-load area, the spiral water-cooled wall adopts an internal threaded tube form, which can enhance the heat exchange of the fluid in the tube, effectively reduce the wall temperature of the water-cooled wall, and improve the safety margin of the water-cooled wall. This partitioned setting of the internal threaded tube reduces the water-cooled wall resistance to a certain extent.
[0023] In this embodiment, the flow rate through the water wall 6 under the steam supply condition is the feed water flow rate + the extraction steam flow rate. The high-temperature radiation heat exchange in the fluidized bed boiler furnace is used to make the steam meet the steam supply requirements. In particular, under the ultra-low load condition of 30% THA, the water wall mass flow rate can be increased to be greater than the critical mass flow rate (~400kg / m 2 s), ensuring the hydrodynamic safety of water-cooled wall 6, which can effectively prevent the occurrence of boiling stagnation, backflow, multiple values, pulsation and other phenomena, especially ensuring the hydrodynamic safety of water-cooled wall 6 under low load conditions. Under non-steam supply conditions, the flow through the water-cooled wall is the feed water flow, and the high-temperature radiation heat exchange in the fluidized bed boiler furnace is used to make the steam meet the superheated steam requirements and enter the superheated steam system.
[0024] Under steam supply conditions, the flow through water-cooled wall 6 is the feed water flow + extraction steam flow. High-temperature radiation heat exchange in the fluidized bed boiler furnace is used to ensure that the steam meets the steam supply requirements. In particular, under ultra-low load conditions below 30% THA, the water-cooled wall mass flow rate can be increased to a value greater than the critical mass flow rate (~400kg / m2s) at this time, ensuring the hydrodynamic safety of the water-cooled wall.
[0025] The normal feed water flow is heated by the high-pressure heater 2 and then enters the economizer 3 and then the water-cooled wall 6. The extraction steam flow is heated by the bypass economizer 4 and then merged through the economizer outlet pipe 5 and then enters the water-cooled wall 6. When steam supply is not needed, the bypass economizer 4 can be freely removed to ensure the normal operation of the original unit.
[0026] In this embodiment, the economizer 3 and the bypass economizer 4 are arranged in parallel, arranged in two flues on the flue gas side, and connected by parallel pipes on the steam-water side. A dual adjustment mechanism is implemented on the flue gas side and the steam-water side, which can effectively control the temperature entering the water-cooled wall 6.
[0027] Specific implementation method 2: See Figure 1-3 To illustrate this embodiment, the outlet of the steam-water separator 7 is connected to two pipelines, one is connected to the industrial steam supply pipeline, and the other is connected to the input end of the bypass superheater 8, and the output end of the bypass superheater 8 is connected to the industrial steam supply pipeline.
[0028] In order to match the diversity of industrial or heating steam demands, two pipelines are arranged at the outlet of the steam-water separator 7. One pipeline is directly connected to the industrial steam pipeline. When the parameters are met, it is directly utilized. When the temperature does not meet the parameters, it enters the bypass superheater 8 for heating. When the steam supply parameters are met, steam is supplied through the industrial steam supply pipeline.
[0029] Specific implementation 3: See Figure 1-3 To illustrate this embodiment, a valve group 9 is installed on the pipeline between the water feed pump 1 and the bypass economizer 4, the pipeline between the steam-water separator 7 and the bypass superheater 8, the pipeline between the steam-water separator 7 and the industrial steam supply pipeline, and the pipeline between the bypass superheater 8 and the industrial steam supply pipeline. The valve group 9 can accurately control the flow rate of the fluid in each pipeline so that the industrial steam supply meets industrial needs.
[0030] Specific implementation 4: See Figure 1-3 To illustrate this embodiment, the economizer 3 is installed in the economizer bypass flue behind the tail flue of the fluidized bed boiler, and the bypass superheater 8 is installed in the superheater bypass flue behind the tail flue of the fluidized bed boiler. The inlets of the economizer bypass flue and the superheater bypass flue are connected to the flue rear wall 25, and the economizer bypass flue and the superheater bypass flue are both connected to the economizer outlet flue 17.
[0031] The coal burner bypass flue and the superheater bypass flue are arranged in parallel, both arranged behind the tail flue of the fluidized bed boiler, with the inlet connected to the flue rear wall 25 and the outlet connected to the economizer outlet flue 17.
[0032] In this embodiment, an economizer outlet header 12 and an economizer inlet header 14 are respectively installed at the upper and lower ends of the economizer 3. Both the economizer outlet header 12 and the economizer inlet header 14 are connected to the bypass economizer flue 10. A first closing baffle 11 is provided on the bypass economizer flue 10 above the economizer 3, and a first regulating baffle 15 and a first expansion joint 16 are provided on the bypass economizer flue 10 below the economizer 3. The bypass economizer flue 10 is connected to the economizer outlet flue 17. The economizer 3 is arranged in the bypass economizer flue 10 and exchanges heat with the flue gas in countercurrent. According to the flue gas flow direction, the main components include the first closing baffle 11, the economizer outlet header 12, the economizer 3, the economizer inlet header 14, the first regulating baffle 15, and the first expansion joint 16. The first regulating baffle 15 is used to adjust the amount of flue gas passing through the bypass economizer flue 10 to achieve the purpose of regulating heat exchange.
[0033] In this embodiment, bypass superheater flues 18 are installed at the upper and lower ends of the bypass superheater 8. The upper bypass superheater flue 18 is provided with a second closing baffle 19 and a superheater outlet header 20 in sequence along the flue gas flow direction, and the lower bypass superheater flue 18 is provided with a superheater inlet header 22, a second regulating baffle 23 and a second expansion joint 24 in sequence along the flue gas flow direction. The lower bypass superheater flue 18 is connected to the economizer outlet flue 17. The bypass superheater 8 is arranged in the bypass superheater flue 18 and exchanges heat with the flue gas in countercurrent. According to the flue gas flow direction, it mainly includes the second closing baffle 19, the superheater outlet header 20, the bypass superheater 8, the superheater inlet header 22, the second regulating baffle 23 and the second expansion joint 24. The second regulating baffle 23 is used to adjust the amount of flue gas passing through the economizer bypass flue to achieve the purpose of regulating heat exchange.
[0034] Specific implementation 5: See Figure 1-3 This embodiment describes a method for a steam supply system for ensuring the safety of a low-load water-cooled wall of a fluidized bed boiler. The method utilizes high-temperature flue gas in the furnace to heat the working medium in the water-cooled wall 6 under steam supply and non-steam supply conditions, so that the working medium temperature reaches the steam supply requirement. The method specifically includes the following steps: Step 1: One channel of water passes through the outlet of the feed water pump 1, passes through the high-pressure heater 2 and enters the economizer 3; Step 2: Then it passes through the economizer outlet pipe 5 and enters the water-cooled wall 6; Step 3: Another stream of water enters the bypass economizer 4 through the feed water pump 1 for heat exchange and then merges with the economizer outlet pipe 5 to enter the water wall 6; Step 4: The working medium heated in the water-cooled wall 6 is supplied with steam through the steam supply pipeline.
[0035] The temperature of the high-temperature flue gas in the furnace ranges from 800 to 1050°C.
[0036] The specific embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The specific embodiments do not describe all details in detail, nor do they limit the invention to the specific embodiments described. Numerous modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.
Claims
1. A steam supply system for ensuring the safety of the low-load water-cooled wall of a fluidized bed boiler, characterized by: The invention comprises a feed water pump (1), a high-pressure heater (2), an economizer (3), a bypass economizer (4), a water-cooled wall (6) and a steam-water separator (7), wherein the feed water pump (1) comprises two water outlet pipes, wherein one water outlet pipe is connected to the input end of the high-pressure heater (2), the output end of the high-pressure heater (2) is connected to the input end of the water-cooled wall (6) through the economizer outlet pipe (5), the output end of the water-cooled wall (6) is connected to the input end of the steam-water separator (7), the output end of the steam-water separator (7) is connected to the industrial steam supply pipe, the other water outlet pipe is connected to the input end of the bypass economizer (4), and the output end of the bypass economizer (4) is connected to the economizer outlet pipe (5).
2. The steam supply system for ensuring the safety of low-load water-cooled walls of fluidized bed boilers according to claim 1, characterized in that: The outlet of the steam-water separator (7) is connected to two pipelines, one of which is connected to the industrial steam supply pipeline, and the other is connected to the input end of the bypass superheater (8), and the output end of the bypass superheater (8) is connected to the industrial steam supply pipeline.
3. The steam supply system for ensuring the safety of low-load water-cooled walls of fluidized bed boilers according to claim 2, characterized in that: A valve group (9) is installed on the pipeline between the feed water pump (1) and the bypass economizer (4), the pipeline between the steam-water separator (7) and the bypass superheater (8), the pipeline between the steam-water separator (7) and the industrial steam supply pipeline, and the pipeline between the bypass superheater (8) and the industrial steam supply pipeline.
4. The steam supply system for ensuring the safety of low-load water-cooled walls of fluidized bed boilers according to claim 1, characterized in that: The economizer (3) is installed in the economizer bypass flue behind the tail flue of the fluidized bed boiler, and the bypass superheater (8) is installed in the superheater bypass flue behind the tail flue of the fluidized bed boiler.
5. The steam supply system for ensuring the safety of low-load water-cooled walls of fluidized bed boilers according to claim 4, characterized in that: The rear of the economizer bypass flue and the superheater bypass flue is a rear flue rear enclosure wall (25), and the inlets of the economizer bypass flue and the superheater bypass flue are both connected to the economizer outlet flue (17).
6. The steam supply system for ensuring the safety of low-load water-cooled walls of a fluidized bed boiler according to claim 5, characterized in that: An economizer outlet header (12) and an economizer inlet header (14) are respectively installed at the upper and lower ends of the economizer (3). The economizer outlet header (12) and the economizer inlet header (14) are both connected to the bypass economizer flue (10). A first closing baffle (11) is provided on the bypass economizer flue (10) above the economizer (3). A first regulating baffle (15) and a first expansion joint (16) are provided on the bypass economizer flue (10) below the economizer (3). The bypass economizer flue (10) is connected to the economizer outlet flue (17).
7. The steam supply system for ensuring the safety of low-load water-cooled walls of a fluidized bed boiler according to claim 5, characterized in that: The bypass superheater (8) is provided with a bypass superheater flue (18) at both upper and lower ends. The upper bypass superheater flue (18) is provided with a second closing baffle (19) and a superheater outlet header (20) in sequence along the flue gas flow direction. The lower bypass superheater flue (18) is provided with a superheater inlet header (22), a second regulating baffle (23) and a second expansion joint (24) in sequence along the flue gas flow direction. The lower bypass superheater flue (18) is connected to the economizer outlet flue (17).
8. A method for a steam supply system for ensuring the safety of a low-load water-cooled wall of a fluidized bed boiler according to any one of claims 1 to 7, characterized in that: Under steam supply and non-steam supply conditions, the high-temperature flue gas in the furnace is used to heat the working medium in the water-cooled wall (6) so that the working medium temperature reaches the steam supply requirement. Specifically, the following steps are included: Step 1: Water flows through the outlet of the feed water pump (1) and enters the high-pressure heater (2) into the economizer (3); Step 2: Then it passes through the economizer outlet pipe (5) and enters the water-cooled wall (6); Step 3: Another stream of water enters the bypass economizer (4) through the feed water pump (1), and after heat exchange, it merges with the economizer outlet pipe (5) and enters the water-cooled wall (6); Step 4: The working medium heated in the water-cooled wall (6) is supplied with steam through the steam supply pipe.
9. The method for a steam supply system for ensuring the safety of a low-load water-cooled wall of a fluidized bed boiler according to claim 8, characterized in that: The temperature of the high-temperature flue gas in the furnace ranges from 800 to 1050°C.