A boiler system with multiple furnaces arranged in parallel

Abstract

The present application provides a kind of boiler system of parallel arrangement multi hearth, including at least two groups of boiler subsystem, at least one hearth communication flue and total flue;Boiler subsystem includes hearth, branch flue and first flue gas damper door, branch flue is connected to the top of hearth, and first flue gas damper door is provided in branch flue;The branch flue of each group of boiler subsystem is connected with total flue;The hearth of adjacent two groups of boiler subsystem is connected by a hearth communication flue, and second flue gas damper door is provided on hearth communication flue.By setting at least two groups of boiler subsystem, and each group of boiler subsystem can be operated independently, one group of boiler subsystem or multiple groups of boiler subsystem can be opened to meet the depth requirement of power plant boiler;Also, according to fuel type, the boiler subsystem of corresponding combustion mode can be opened to ensure that fuel and the combustion mode of boiler subsystem match, prevent the problems such as hearth coking, heating surface overtemperature, partial burning in furnace of boiler subsystem.

Description

Technical Field

[0001] This invention belongs to the field of power generation system technology, specifically relating to a boiler system with multiple furnaces arranged in parallel. Background Technology

[0002] Currently, almost all coal-fired power plant boilers are single-furnace arrangements, meaning each boiler has only one furnace. The combustion method of power plant boilers is based on the designed fuel. When the actual coal quality deviates slightly from the designed coal quality, the boiler can burn safely and stably. However, when the deviation is large, problems arise that cause a mismatch between the coal type and the furnace type. These problems manifest as furnace coking, overheating of heating surfaces, uneven burning within the furnace, flameout, insufficient or excessive steam temperature, high combustible content in ash and slag, insufficient top load capacity, and poor stable combustion capacity at low loads. These issues severely impact the unit's ability to operate under load, maintain stable operation, and perform deep peak shaving.

[0003] With the increasing installed capacity of new energy sources year by year, the attributes of thermal power units as both basic and regulating power sources have been established and will continue for a long time. To reduce fuel costs, the coal types used in the boilers of most thermal power plants deviate significantly from the design values. At the same time, to further reduce fuel costs and absorb low-carbon and zero-carbon fuels, some power plants have begun to blend biomass fuels such as sludge, straw, and wood chips. Meanwhile, due to the large fluctuations in new energy sources such as solar and wind power, in order to maximize the absorption of new energy sources, power plant boilers are required to meet frequent peak-shaving requirements. However, the large-capacity, single-furnace design makes it difficult for existing power plant boilers to meet the requirements of large-scale deep regulation. More flexible furnace settings are needed to solve the current problems faced by power plant boilers in terms of fuel adaptability and load regulation capabilities.

[0004] Therefore, there is an urgent need for a boiler system that can match boiler fuel with boiler type and meet the requirements of deep peak shaving. Summary of the Invention

[0005] The embodiments of the present invention aim to at least solve one of the technical problems existing in the prior art, and provide a boiler system with multiple furnaces arranged in parallel.

[0006] An embodiment of the present invention provides a boiler system with multiple furnaces arranged in parallel, including at least two boiler subsystems, at least one furnace connecting flue, and a main flue; The boiler subsystem includes a furnace, a flue, and a first flue gas damper. The flue is connected to the top of the furnace, and the first flue gas damper is located inside the flue. The branch flue of each group of the boiler subsystems is connected to the main flue; The furnaces of two adjacent boiler subsystems are connected by a furnace connecting flue, and a second flue gas damper is provided on the furnace connecting flue.

[0007] In some embodiments of the present invention, the boiler subsystem further includes a burner; The burner is located on the wall of the furnace, and the connection between the furnace flue and the furnace is located above the corresponding burner.

[0008] In some embodiments of the present invention, the boiler subsystem further includes a burnout air nozzle; Along the height direction of the furnace, the burnout air nozzle is located above the burner, and the connection between the furnace flue and the furnace is located below the corresponding burnout air nozzle.

[0009] In some embodiments of the present invention, the boiler subsystem further includes a heat exchanger; The heat exchanger is located in the flue gas duct.

[0010] In some embodiments of the present invention, the heat exchanger is located downstream of the first flue gas damper along the flow direction of the flue gas.

[0011] In some embodiments of the present invention, a denitrification device, a dust removal device, and a desulfurization device are also included; Along the flow direction of the flue gas, the denitrification device, the dust removal device, and the desulfurization device are sequentially arranged in the main flue.

[0012] In some embodiments of the present invention, at least one induced draft fan is also included; Each of the induced draft fans is connected to the flue gas outlet of the main flue.

[0013] In some embodiments of the present invention, the combustion mode of each group of boiler subsystems is one of the following: tangential combustion mode, opposed combustion mode, W-flame combustion mode, fluidized bed combustion mode, and fixed bed combustion mode.

[0014] In some embodiments of the present invention, the heat load of each group of boiler subsystems is allocated according to the total heat load, peak demand, fuel type, and fuel supply of the boiler system.

[0015] In some embodiments of the present invention, the first flue gas damper and the second flue gas damper are electrically driven or pneumatically driven.

[0016] The boiler system with parallel arrangement of multiple furnaces according to embodiments of the present invention includes at least two sets of boiler subsystems. The branch flues of the two adjacent sets of boiler subsystems are respectively connected to the main flue, and the furnaces of the two adjacent sets of boiler subsystems are connected through a furnace connecting flue. The first flue gas damper on the branch flue of each boiler subsystem can control the connection between the branch flue and the main flue. When demand is high, more boiler subsystems can be activated, and when demand is low, fewer boiler subsystems can be activated to meet the deep requirements of the power plant boiler. This enables physical isolation between the shut-down furnace and the operating furnace, preventing flue gas backflow. The second flue gas damper on the furnace connecting flue can control the connection between two adjacent furnaces, enabling the redistribution of flue gas and heat load between the two adjacent furnaces. When one furnace in an adjacent furnace is started, the other furnace in the adjacent furnace provides a start-up heat source through the furnace connecting flue, reducing the amount of fuel used for ignition during startup. Boiler subsystems with corresponding combustion methods can also be activated according to the fuel type to ensure that the combustion method of the fuel and the boiler subsystem is matched, preventing problems such as furnace coking, overheating of heating surfaces, uneven burning in the furnace, flameout, insufficient steam temperature, overheating, and high combustible content in ash and slag from occurring in the boiler subsystem. Attached Figure Description

[0017] Figure 1 This is an overall assembly diagram of a boiler system with multiple furnaces arranged in parallel, according to an embodiment of the present invention.

[0018] The labels in the attached diagram are as follows: 1. First furnace; 2. Second furnace; 3. Third furnace; 4. Burner; 5. Combustion air nozzle; 6. Diversion flue; 7. First flue gas damper; 8. Heat exchanger; 9. Denitrification device; 10. Dust removal device; 11. Desulfurization device; 12. Exhaust fan; 13. Furnace connecting flue; 14. Second flue gas damper; 15. Main flue. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit disclosure. The described embodiments are some, but not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0020] Currently, almost all coal-fired power plant boilers are single-furnace arrangements, meaning each boiler has only one furnace. Power plant boilers are classified into five main types based on their combustion method: tangential combustion, opposed combustion (front and rear walls), W-flame combustion, circulating fluidized bed combustion, and fixed bed combustion. Tangential combustion boilers and opposed combustion (front and rear walls) primarily burn bituminous coal; W-flame combustion boilers primarily burn anthracite; circulating fluidized bed combustion boilers primarily burn coal gangue and low-calorific-value fuels; and fixed bed combustion boilers primarily burn biomass and general industrial solid waste. During the design process of power plant boilers, the selection of parameters such as furnace size and combustion method is based on the design fuel. When the actual coal quality deviates slightly from the design coal quality, the boiler can burn safely and stably. However, when the deviation is large, the coal type and furnace type will be mismatched, resulting in many problems that affect the boiler's safety, economy, and environmental protection, such as furnace coking, overheating of heating surfaces, uneven burning in the furnace, flameout, insufficient or excessive steam temperature, high combustible content in ash and slag, insufficient top load capacity, and poor stable combustion capacity at low loads. These problems seriously affect the unit's ability to carry loads, operate stably, and perform deep peak shaving.

[0021] With the increasing installed capacity of new energy sources year by year, the attributes of thermal power units as both basic and regulating power sources have been established and will continue for a long time. To reduce fuel costs, the coal types used in the boilers of most thermal power plants deviate significantly from the design values. At the same time, to further reduce fuel costs and absorb low-carbon and zero-carbon fuels, some power plants have begun to blend biomass fuels such as sludge, straw, and wood chips. Meanwhile, due to the large fluctuations in new energy sources such as solar and wind power, in order to maximize the absorption of new energy sources, power plant boilers are required to meet frequent peak-shaving requirements. However, the large-capacity, single-furnace design makes it difficult for existing power plant boilers to meet the requirements of large-scale deep regulation. More flexible furnace settings are needed to solve the current problems faced by power plant boilers in terms of fuel adaptability and load regulation capabilities.

[0022] To address the mismatch between power plant boiler fuel and boiler type, and the mismatch between combustion method and load-bearing and deep-adjustment capabilities, the main methods currently employed are as follows: (1) Coal blending: Prepare high-quality coal, low-quality coal and peak-shaving coal in advance. Based on the unit's adaptability to coal quality and blending experience, use various methods such as coal yard stacking, silo blending and compartment blending to maximize the matching of coal type with furnace type.

[0023] (2) Operation adjustment: By conducting adjustment and optimization tests on the main operating parameters of the pulverizing system and the combustion system, the adjustment potential of the boiler is explored; (3) Equipment modification: Improve the boiler’s adaptability to fuel and load response by means of increasing the output of the pulverizing system, modifying the fuel flexibility, modifying the heating surface, and modifying the burner.

[0024] Based on the above, seeking a power plant boiler technology that can simultaneously burn bituminous coal, anthracite, coal gangue, low-calorific-value organic matter, and biomass is an urgent requirement to improve the boiler equipment's adaptability to a wide range of fuels and its load response capability.

[0025] An embodiment of the present invention provides a boiler system with multiple furnaces arranged in parallel, including at least two boiler subsystems, at least one furnace connecting flue, and a main flue. Each boiler subsystem includes a furnace, a branch flue, and a first flue gas damper. The branch flue is connected to the top of the furnace, and the first flue gas damper is located in the branch flue. The branch flue of each boiler subsystem is connected to the main flue. The furnaces of two adjacent boiler subsystems are connected through a furnace connecting flue, and a second flue gas damper is provided on the furnace connecting flue.

[0026] According to an embodiment of the present invention, a boiler system with multiple furnaces arranged in parallel includes at least two sets of boiler subsystems, wherein the branch flues of two adjacent sets of boiler subsystems are respectively connected to the main flue, and the furnaces of two adjacent sets of boiler subsystems are connected through a furnace connecting flue. The first flue gas damper on the branch flue of each boiler subsystem can control the connection between the branch flue and the main flue. When demand is high, more boiler subsystems can be activated, and when demand is low, fewer boiler subsystems can be activated to meet the deep requirements of the power plant boiler. This enables physical isolation between the shut-down furnace and the operating furnace, preventing flue gas backflow. The second flue gas damper on the furnace connecting flue can control the connection between two adjacent furnaces, enabling the redistribution of flue gas and heat load between the two adjacent furnaces. When one furnace in an adjacent furnace is started, the other furnace in the adjacent furnace provides a start-up heat source through the furnace connecting flue, reducing the amount of fuel used for ignition during startup. Boiler subsystems with corresponding combustion methods can also be activated according to the fuel type to ensure that the combustion method of the fuel and the boiler subsystem is matched, preventing problems such as furnace coking, overheating of heating surfaces, uneven burning in the furnace, flameout, insufficient steam temperature, overheating, and high combustible content in ash and slag from occurring in the boiler subsystem.

[0027] In some embodiments of the present invention, the boiler subsystem further includes a burner; the burner is disposed on the wall of the furnace, and the connection between the furnace connecting flue and the furnace is located above the corresponding burner. The design of the furnace connecting flue follows the natural upward trend of high-temperature flue gas, optimizes airflow organization, and extends residence time, promoting complete fuel combustion. Simultaneously, this structure effectively removes localized high-temperature heat above the burner, improves the temperature field distribution, and inhibits localized coking.

[0028] In some embodiments of the present invention, the boiler subsystem further includes a burnout air nozzle; along the height direction of the furnace, the burnout air nozzle is located above the burner, and the connection point between the furnace connecting flue and the furnace is located below the corresponding burnout air nozzle. The design of the furnace connecting flue ensures that the burnout air nozzle can independently and fully inject air into the upper part of the furnace, ensuring efficient oxidation of unburned materials in the burnout zone and maintaining good air-staged combustion effect. Secondly, the connecting flue being located below the burnout air nozzle effectively avoids suction or crossflow interference from the connecting port, thus ensuring the stability of the airflow organization within the furnace.

[0029] In some embodiments of the present invention, the boiler subsystem further includes a heat exchanger located in a branch flue. By installing a heat exchanger in each branch flue, the heat of the high-temperature flue gas flowing through the branch flue can be transferred to other fluids that require heat, thereby improving energy utilization. Specifically, along the flow direction of the flue gas, the heat exchanger in the same branch flue is located downstream of the first flue gas damper.

[0030] In some embodiments of the present invention, a denitrification device, a dust removal device, and a desulfurization device are also included; the denitrification device, dust removal device, and desulfurization device are sequentially arranged in the main flue along the flue gas flow direction. By sequentially arranging the denitrification device, dust removal device, and desulfurization device in the main flue, the flue gas discharged from the main flue can be treated, dust removed, and desulfurized to reduce the pollution of the discharged flue gas to the atmosphere.

[0031] In some embodiments of the present invention, at least one induced draft fan is further included; each induced draft fan is connected to the flue gas outlet of the main flue. Specifically, one, two, three, or more induced draft fans can be provided to vent the flue gas discharged from the main flue to the atmosphere. In this embodiment, providing two induced draft fans is preferred to meet the requirement of venting the flue gas in the main flue while avoiding increased costs due to an excessive number of induced draft fans.

[0032] In some embodiments of the present invention, the combustion modes of each of the at least two boiler subsystems can be completely different or completely the same, or some of the boiler subsystems in the at least two boiler subsystems may have the same combustion mode while others may have different combustion modes. The combustion modes of different boiler subsystems are set according to the total boiler load to flexibly control the heat load, start-up, and shutdown of different boiler subsystems.

[0033] Each boiler subsystem employs one of the following combustion methods: tangential combustion, opposed combustion, W-flame combustion, fluidized bed combustion, or fixed bed combustion. Based on the actual fuels used and blended in the power plant boilers, the boiler subsystems are designed differently. Specifically, the furnace of each subsystem can be designed for tangential combustion, opposed combustion, W-flame combustion, fluidized bed combustion, or fixed bed combustion.

[0034] In some embodiments of the present invention, the heat load and combustion mode of each boiler subsystem are controlled according to the total heat load of the boiler, the type of fuel, the fuel supply, and the peak-shaving requirements. Specifically, the total heat load of the boiler is allocated to each boiler subsystem and the combustion mode of each boiler subsystem is determined according to the total heat load of the boiler, the type of fuel used by the boiler, the fuel supply, and the peak-shaving requirements of the boiler, so as to meet the heat load requirements and peak-shaving requirements of different boiler operating conditions.

[0035] In some embodiments of the present invention, an air supply device (not shown in the figures) is also included, with each boiler subsystem having a separate air supply device. By providing a separate air supply device for each boiler subsystem, individual air supply control for each boiler subsystem can be achieved, meeting the independent operational needs of each boiler subsystem.

[0036] In some embodiments of the present invention, the first flue gas damper and the second flue gas damper are electrically driven or pneumatically driven. Electric or pneumatic driving allows for remote control of the first and second flue gas dampers.

[0037] like Figure 1 As shown, the boiler system of the present invention, which has multiple furnaces arranged in parallel, includes a first furnace 1, a second furnace 2, a third furnace 3, three burners 4, three burnout air nozzles 5, three branch flues 6, three heat exchangers 8, three first flue gas dampers 7, a denitrification device 9, a dust removal device 10, a desulfurization device 11, two induced draft fans 12, two furnace connecting flues 13, two second flue gas dampers 14, and a main flue 15.

[0038] The boiler system of the present invention, which is a multi-furnace boiler arranged in parallel, is an overall boiler that is adaptable to safe and stable combustion of multiple coal types, wide load regulation, and peak and deep peak shaving capabilities. Specifically, the first furnace 1, the second furnace 2, and the third furnace 3 are each connected to a corresponding branch flue 6, and each branch flue 6 is connected to the main flue 15. Each of the first furnace 1, the second furnace 2, and the third furnace 3 is equipped with a burner 4 and a burnout air nozzle 5. The position of the burner 4 is determined according to the combustion mode of each furnace. Each of the three branch flues is equipped with a heat exchanger 8 and a first flue gas damper 7. Along the flue gas flow direction in the branch flue, the heat exchanger 8 is located downstream of the flue gas damper. One end of the main flue 15 is connected to three branch flues 6, and the other end of the main flue 15 is connected to two induced draft fans 12. Along the direction from the branch flues to the induced draft fans 12, the denitrification device 9, the dust removal device 10 and the desulfurization device 11 are sequentially installed in the main flue 15, that is, the main flue 15 connects the denitrification device 9, the dust removal device 10 and the desulfurization device 11 in series.

[0039] One furnace connecting flue 13 connects to the first furnace 1 and the second furnace 2 at its two ends. The connection point between the furnace connecting flue 13 and the first furnace 1 is located below the burner 4 of the first furnace 1 and above the burnout air nozzle 5. The other end of the furnace connecting flue 13 connects to the second furnace 2 at its lower end and above the burnout air nozzle 5. Another furnace connecting flue 13 connects the second furnace 2 and the third furnace 3.

[0040] The operation steps of the parallel-arranged multi-furnace boiler system according to an embodiment of the present invention are as follows: 1) Before starting the boiler, keep all flue gas dampers fully closed; 2) Determine which furnaces need to be put into operation after startup. If multiple furnaces need to be put into operation, the startup sequence of the furnaces needs to be determined and they should be started one by one. 3) The burner 4, burnout air nozzle 5, first flue gas damper 7, heat exchanger 8, denitrification device 9, dust removal device 10, desulfurization device 11, induced draft fan 12, and second flue gas damper 14 all meet the boiler start-up conditions. 4) Open the first flue damper 7 at the outlet of the furnace to be started; 5) Under the condition that the negative pressure of the furnace to be started is -50 to -100 Pa, gradually increase the opening of the suction fan 12 and put the furnace to be started into operation. 6) After the furnace temperature and other parameters meet the conditions for the operation of burner 4, fuel is introduced through burner 4 and the furnace heat load is gradually increased. 7) When it is necessary to put other furnaces into operation, repeat steps 4) to 6) in sequence according to the preset furnace start-up sequence; 8) When it is necessary to adjust the heat load distribution between the furnaces, it can be done by adjusting the fuel quantity of the burners 4 in each furnace; or, according to the requirements of the boiler heat load, the furnaces can be selected to start or stop for adjustment. 9) When it is necessary to balance the flue gas volume and heat load distribution of each furnace, the second flue gas damper door 14 on the corresponding furnace connecting flue 13 can be opened for adjustment as needed and according to equipment operation requirements.

[0041] 10) Adjust the fuel supplied to the burners 4 of each furnace according to the combustion operation status of each furnace in the boiler. 11) When the boiler is shut down, reverse the steps from 1) to 6) in sequence.

[0042] The key point of this invention is that each boiler is equipped with two or more furnaces, which are arranged in parallel to ensure that the boiler has sufficient load capacity and achieves stable combustion at low load.

[0043] The key point of this invention is that the combustion mode of each furnace can be flexibly selected from the four-corner tangential combustion mode, the opposing combustion mode, the W-flame combustion mode, the fluidized bed combustion mode, and the fixed bed combustion mode, so as to flexibly control the load of each furnace.

[0044] The key point of this invention is that the boiler heat load of the device is equal to the sum of the heat loads of all individual furnaces, and the heat load of each furnace can be flexibly allocated to meet the different load requirements of the boiler.

[0045] The key point of this invention is that the outlets of all the furnaces of the boiler are connected in parallel and eventually merge into a main flue, sharing a set of environmental protection devices such as denitrification device, dust removal device, and desulfurization device to treat the flue gas and reduce the pollution of the exhaust gas to the atmosphere; in addition, the outlet of the main flue is connected to an induced draft fan, which can be one or more fans arranged in parallel to discharge the flue gas from the main flue into the atmosphere.

[0046] The key point of this invention is that the adjacent furnaces of the boiler are connected by a furnace connecting flue to achieve the redistribution of flue gas and heat load among multiple furnaces.

[0047] The key point of this invention is that each flue gas outlet of the boiler is equipped with a first flue gas damper to control the start and stop of each flue gas outlet separately.

[0048] The key feature of this invention is that the actuator of the first flue gas damper door is driven by electric or pneumatic means and can be controlled locally or remotely.

[0049] The key point of this invention is that each furnace of the boiler can operate individually or in multiple simultaneous operations, so as to flexibly control the operation or shutdown of each furnace according to the total load of the boiler.

[0050] The key point of this invention is that the combustion system (such as burner), ash removal system (such as cold ash hopper), and air supply device of each furnace of the boiler can be designed and set up independently. This design realizes independent and precise control of each furnace, has extremely strong operational flexibility, supports deep peak shaving and on-demand start-up and shutdown, facilitates staged combustion, and synergistically achieves high efficiency, energy saving and ultra-low emissions.

[0051] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A boiler system with multiple furnaces arranged in parallel, characterized in that, It includes at least two boiler subsystems, at least one furnace connecting flue, and a main flue; The boiler subsystem includes a furnace, a flue, and a first flue gas damper. The flue is connected to the top of the furnace, and the first flue gas damper is located inside the flue. The branch flue of each group of the boiler subsystems is connected to the main flue; The furnaces of two adjacent boiler subsystems are connected by a furnace connecting flue, and a second flue gas damper is provided on the furnace connecting flue.

2. The boiler system with multiple furnaces arranged in parallel according to claim 1, characterized in that, The boiler subsystem also includes a burner; The burner is located on the wall of the furnace, and the connection between the furnace flue and the furnace is located above the corresponding burner.

3. The boiler system with multiple furnaces arranged in parallel according to claim 2, characterized in that, The boiler subsystem also includes a burnout air nozzle; Along the height direction of the furnace, the burnout air nozzle is located above the burner, and the connection between the furnace flue and the furnace is located below the corresponding burnout air nozzle.

4. The boiler system with multiple furnaces arranged in parallel according to claim 1, characterized in that, The boiler subsystem also includes a heat exchanger; The heat exchanger is located in the flue gas duct.

5. The boiler system with multiple furnaces arranged in parallel according to claim 4, characterized in that, Along the flow direction of the flue gas, the heat exchanger is located downstream of the first flue gas damper.

6. The boiler system with multiple furnaces arranged in parallel according to claim 1, characterized in that, It also includes denitrification devices, dust removal devices, and desulfurization devices; Along the flow direction of the flue gas, the denitrification device, the dust removal device, and the desulfurization device are sequentially arranged in the main flue.

7. The boiler system with multiple furnaces arranged in parallel according to claim 1, characterized in that, It also includes at least one induced draft fan; Each of the induced draft fans is connected to the flue gas outlet of the main flue.

8. The boiler system with multiple furnaces arranged in parallel according to claim 1, characterized in that, The combustion mode of each boiler subsystem is one of the following: tangential combustion, opposed combustion, W-flame combustion, fluidized bed combustion, or fixed bed combustion.

9. The boiler system with multiple furnaces arranged in parallel according to claim 1, characterized in that, The heat load of each boiler subsystem is allocated according to the total heat load, peak demand, fuel type, and fuel supply of the boiler system.

10. The boiler system with multiple furnaces arranged in parallel according to claim 1, characterized in that, The first flue gas damper and the second flue gas damper are driven by electricity or pneumatics.

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