Multi-stage heating system of thermodynamic circulating fluidized bed boiler

Abstract

The invention discloses a multistage heating system of a thermodynamic circulating fluidized bed boiler, and relates to the field of boiler machinery, the multistage heating system comprises a water supply pipeline, a primary fan, a boiler body and a flue communicated with the boiler body, the boiler body is provided with a steam pocket and a primary air port, and the inner wall surface of the flue is provided with a plurality of superheaters; in the flue, the projection of the circulation direction of the steam channel in the circulation direction of the gas channel is opposite to the circulation direction of the gas channel. A plurality of superheaters are arranged on a cavity of a flue, so that water vapor can be heated for multiple times, in the flue, the projection of the circulation direction of a steam channel in the circulation direction of a gas channel is opposite to that of the gas channel, reverse flow type heat exchange is achieved, the temperature difference between fluids is kept large in the heat exchange mode, and heat exchange efficiency is improved. Therefore, heat can be effectively transferred from the high-temperature fluid to the low-temperature fluid, water vapor can be heated to a higher temperature, and it can be ensured that the water vapor is fully heated in different stages.

Description

Technical Field

[0001] The invention relates to the field of boiler machinery, in particular to a multi-stage heating system of a thermal circulating fluidized bed boiler. Background Art

[0002] The circulating fluidized bed boiler uses the most industrialized clean coal combustion technology. The existing circulating fluidized bed boiler uses solid fuel (coal) and desulfurizer (limestone) in the furnace for fluidized combustion. The main structure includes two parts: the combustion chamber and the circulating furnace (including the high-temperature gas-solid separator and the return system). At present, the circulating fluidized bed boiler technology has been widely used in the power, chemical, metallurgical and other industries. Due to its high efficiency and low pollution, it has become an important part of modern industry.

[0003] However, existing circulating fluidized bed boiler systems have obvious deficiencies in the subsequent heating of water vapor and are unable to achieve multi-stage heating, which limits their use in certain high-demand industrial applications.

[0004] To this end, we propose a multi-stage heating system for a thermal circulating fluidized bed boiler. Summary of the invention

[0005] The object of the present invention is to provide a multi-stage heating system for a thermal circulating fluidized bed boiler, which can ensure that water vapor is fully heated at different stages and increase the temperature of water vapor to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a multi-stage heating system of a thermal circulating fluidized bed boiler, comprising a water supply pipe, a primary fan, a boiler body and a flue connected to the boiler body, the boiler body is provided with a steam drum and a primary air port, and a plurality of superheaters are provided on the inner wall surface of the flue; The water supply pipe is connected to the steam drum, the steam drum is connected to a plurality of superheaters in sequence, and the superheaters are connected to the outside of the flue to form a steam channel; The primary fan is connected to the primary air port, the primary air port is connected to the cavity of the boiler body, the cavity is connected to the flue, and the flue is connected to the chimney to form a gas channel; Wherein, in the flue, a projection of a flow direction of the steam channel on a flow direction of the gas channel is opposite to the flow direction of the gas channel.

[0007] Specifically, it also includes a secondary fan, which is connected to a secondary air port arranged on the side wall of the boiler body and is used to introduce secondary air to introduce oxygen into the boiler body. The primary air port is arranged at the bottom of the boiler body, and the primary fan is used to introduce primary air to keep the fuel in a fluidized state.

[0008] Specifically, it includes a control module and a gas detector arranged on the inner side of the chimney, the gas detector is used to detect the composition of the flue gas, the control module is connected to the gas detector, the primary fan and the secondary fan, and when the gas detector detects that the content of nitrogen oxides in the flue gas exceeds a monitoring threshold, the rotation speed of the primary fan and the secondary fan is controlled to increase the proportion of the primary air in the total air volume.

[0009] Specifically, it also includes a coal bunker and several groups of conveyor belts arranged on the lower side of the coal bunker, the conveyor belts are driven by a drive motor, when the gas detector detects that the oxygen content in the flue gas exceeds the monitoring threshold, the control module controls the operating speed of the drive motor to increase or controls the rotation speeds of the primary fan and the secondary fan to decrease, when the gas detector detects that the oxygen content in the flue gas is lower than the monitoring threshold, the control module controls the operating speed of the drive motor to decrease or controls the rotation speeds of the primary fan and the secondary fan to increase.

[0010] Specifically, it also includes a temperature sensor arranged on the inner wall of the boiler body. When the temperature sensor detects that the temperature inside the boiler body exceeds a monitoring threshold, the control module controls the operating speed of the drive motor to decrease. When the temperature sensor detects that the temperature inside the boiler body is lower than the monitoring threshold, the control module controls the operating speed of the drive motor to increase.

[0011] Specifically, the oxygen content of the primary air is lower than the oxygen content of the secondary air.

[0012] Specifically, it also includes a separator, which is arranged between the boiler body and the flue and respectively connects the boiler body and the flue, and is used to separate the gas and the large-particle coal ash.

[0013] Specifically, an air preheater is further provided in the flue, and the air preheater is connected to the boiler and the primary air fan and the secondary air fan respectively. The air preheater exchanges heat with the gas in the flue to preheat the primary air and the secondary air.

[0014] Specifically, an economizer is further provided in the flue, and the economizer is connected to the water supply pipe and the steam drum. The economizer exchanges heat with the gas in the flue to heat the water supply of the water supply pipe.

[0015] Specifically, it also includes a dust collector, which is arranged between the flue and the chimney and connects the flue and the chimney, and is used to filter and remove dust from the gas flowing out of the flue, wherein part of the gas after filtering and dust removal is mixed with air as primary air, and the secondary air is air.

[0016] The present invention has at least the following beneficial effects: the present invention arranges a plurality of superheaters on the cavity of the flue so that the water vapor can be heated multiple times, and in the flue, the projection of the flow direction of the steam channel on the flow direction of the gas channel is opposite to that of the gas channel, and countercurrent heat exchange is performed. In this heat exchange method, the temperature difference between the fluids is kept large, which is conducive to the effective transfer of heat from the high-temperature fluid to the low-temperature fluid, and the water vapor can be heated to a higher temperature, ensuring that the water vapor is fully heated at different stages. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the workflow of the present invention; Figure 2 It is a schematic diagram of the control principle of the present invention.

[0018] In the figure: 1. water supply pipe; 2. primary fan; 3. boiler body; 31. steam drum; 32. primary air outlet; 33. cavity; 34. secondary air outlet; 4. flue; 41. superheater; 42. air preheater; 43. economizer; 5. secondary fan; 6. control module; 7. gas detector; 8. coal bunker; 9. drive motor; 10. temperature sensor; 11. separator; 12. dust collector; 13. chimney. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] This application provides a technical solution: like Figure 1As shown, a multi-stage heating system of a thermal circulating fluidized bed boiler is provided, comprising a water supply pipe 1, a primary air fan 2, a boiler body 3 and a flue 4 connected to the boiler body 3, the boiler body 3 is provided with a steam drum 31 and a primary air outlet 32, the steam drum 31 is connected to the steam pipe of the boiler and is mainly used for collecting, distributing and storing steam, and a plurality of superheaters 41 are provided on the inner wall surface of the flue 4; the water supply pipe 1 is connected to the steam drum 31, the steam drum 31 is connected to the plurality of superheaters 41 in turn, and the superheaters 41 are connected to the outside of the flue 4 to form a steam channel; The secondary fan 2 is connected to the primary air port 32, the primary air port 32 is connected to the cavity 33 of the boiler body 3, the cavity 33 is connected to the flue 4, and the flue 4 is connected to the chimney 13 to form a gas channel; wherein, in the flue 4, the flow direction of the steam channel is projected on the flow direction of the gas channel opposite to the flow direction of the gas channel, and the steam passes through the superheater 41 through the arrangement of multiple superheaters 41 so that the temperature of the superheater 41 is exchanged with the gas in the flue 4 to heat the steam, and by placing the flow direction of the steam channel in the flow direction of the gas channel The projection on the drum 31 is opposite to the flow direction of the gas channel to realize countercurrent heat exchange, that is, the low-temperature steam exchanges heat with the low-temperature gas, and the high-temperature steam exchanges heat with the high-temperature gas. The high-temperature flue gas flowing out of the boiler body 3 is passed into the flue gas inlet of the flue 4, and passes through a plurality of superheaters 41 in the flue 4 for heat exchange in sequence. After the flue gas temperature gradually decreases, it flows out from the flue gas outlet of the flue 4. The steam with a lower temperature flowing out of the steam drum 31 is first passed into the superheater 41 arranged near the flue gas outlet of the flue 4 to realize temperature The lower temperature steam exchanges heat with the flue gas with a lower temperature near the flue 4, and then the steam is passed into the superheater 41 which is gradually away from the flue gas outlet. Since the flue gas temperature is higher when the superheater 41 is gradually away from the flue gas outlet, the flue gas temperature passing through the superheater 41 after the steam is heated to a higher temperature is also higher, and the steam is continuously heated. In this way, it is ensured that the water vapor is fully heated at different stages, and the maximum temperature of the steam can be increased. In some embodiments, the superheater 41 is set to be a screen superheater 41.

[0021] In some embodiments, a desuperheater is provided between different superheaters 41 to control the temperature of the steam. When the steam passes through multiple superheaters 41, the steam temperature is relatively high, which may easily cause excessive thermal stress to the equipment in the system (such as pipes, valves, turbine blades, etc.). The temperature of the steam is controlled within a reasonable range to avoid damage to the equipment caused by excessive temperature. The desuperheater can stabilize the temperature of the steam and improve the uniformity and stability of the steam flow, thereby improving the operating efficiency and safety of the system.

[0022] Preferably, the present application also includes a secondary fan 5, which is connected to a secondary air port 34 provided on the side wall of the boiler body 3, and is used to introduce secondary air to introduce oxygen into the boiler body 3. The primary air port 32 is provided at the bottom of the boiler body 3, and the primary fan 2 is used to introduce primary air to keep the fuel in a fluidized state. By providing the secondary fan 5, oxygen can be delivered to the furnace in batches, and the supply amount and timing of oxygen can be controlled to further optimize the combustion process, thereby avoiding problems such as incomplete combustion and pollutant emissions caused by excessive or insufficient oxygen.

[0023] like Figure 2 As shown, in some embodiments, a control module 6 and a gas detector 7 arranged on the inner side of the chimney 13 are included. The gas detector 7 is used to detect the composition of the flue gas. Specifically, the gas detector 7 is a fixed NOx concentration detector. The fixed NOx concentration detector can specifically be Emerson Rosemount 951, which can be installed at the outlet of the flue 4 to detect the NOx concentration of the flue gas. The control module 6 is connected to the gas detector 7, the primary fan 2 and the secondary fan 5. When the gas detector 7 detects that the content of nitrogen oxides in the flue gas exceeds the monitoring threshold, the rotation speed of the primary fan 2 and the secondary fan 5 is controlled to control the proportion of the total air volume of the primary fan 2 to increase. When the air supply to the boiler or burner is too much and the oxygen concentration is high, the nitrogen in the air will react with oxygen to increase the generation of NOx. By controlling to reduce the primary air that first enters the boiler body 3 and increase the input of the secondary air, the oxygen provided by the primary air can be reduced while the total oxygen amount remains unchanged. Since the oxygen consumption is low in the initial stage of combustion of the boiler, oxygen enrichment is prone to occur, resulting in the production of nitrogen oxides. The generation of nitrogen oxides can be reduced by controlling the ratio of the primary and secondary air.

[0024] Preferably, the oxygen content of the primary air is lower than that of the secondary air. Since the fluidized bed boiler requires a certain amount of primary air to ensure the fluidization state of the combustibles, and too much primary air may result in excessive oxygen content, by setting the primary air to a low oxygen content, the fluidization state of the combustibles can be achieved while reducing the generation of nitrogen oxides. By real-time monitoring and regulation of the combustion process parameters, the generation of harmful substances such as NOx can be effectively controlled to meet environmental protection standards.

[0025] Preferably, the present application also includes a coal bunker 8 and a plurality of conveyor belts arranged at the lower side of the coal bunker 8, the conveyor belts are connected to the pulleys, the pulleys are connected to the rotating shaft, and the rotating shaft is driven to rotate by the driving motor 9 to drive the conveyor belt to move. The specific gas detector 7 includes a fixed oxygen concentration detector in addition to the fixed NOx concentration detector. The fixed oxygen concentration detector can be specifically selected from GfG G460 can be installed at the outlet of the flue 4 to detect the oxygen content of the flue gas. When the gas detector 7 detects that the oxygen content in the flue gas exceeds the monitoring threshold, the control module 6 controls the operating speed of the drive motor 9 to increase or controls the rotation speed of the primary fan 2 and the secondary fan 5 to decrease. When the gas detector 7 detects that the oxygen content in the flue gas is lower than the monitoring threshold, the control module 6 controls the operating speed of the drive motor 9 to decrease or controls the rotation speed of the primary fan 2 and the secondary fan 5 to increase. When the oxygen content in the flue gas is too low, it means that the oxygen intake is too low, which may cause incomplete combustion. The oxygen consumption can be reduced by slowing down the transportation speed of the drive motor 9 for coal or by increasing the primary and secondary air intake to increase the oxygen supply. When the oxygen content is too high, the opposite operation is performed, which will not be repeated here. The system can automatically adjust the fuel supply and air ratio to ensure the best combustion state and reduce energy waste.

[0026] Preferably, the present application further includes a temperature sensor 10 arranged on the inner wall of the boiler body 3. When the temperature sensor 10 detects that the temperature inside the boiler body 3 exceeds the monitoring threshold, the control module 6 controls the operating speed of the drive motor 9 to decrease. When the temperature sensor 10 detects that the temperature inside the boiler body 3 is lower than the monitoring threshold, the control module 6 controls the operating speed of the drive motor 9 to increase. The coal intake is controlled by controlling the operating speed of the drive motor 9 to adjust the temperature of the boiler body 3. When the coal intake increases, the supply of primary air and secondary air is increased synchronously. In the present application, the temperature control is set as the first priority in the control module 6. When there is a conflict in the actions executed by other indicators, the action of controlling the temperature is executed first, and the control of the oxygen content is the second priority, and the control of the nitrogen oxide content is the third priority. When a conflict of instructions occurs, it is preferred to execute the instruction with the higher priority. For example, when the oxygen concentration is too high and the temperature is too high, the speed of the drive motor 9 is reduced, and the actions with the secondary priority continue to be executed if there is no conflict. Therefore, the speed of the primary fan 2 and the secondary fan 5 is also increased.

[0027] Preferably, the present application further includes a separator 11, which is disposed between the boiler body 3 and the flue 4 and connects the boiler body 3 and the flue 4 respectively, and is used to separate the gas and the large-particle coal ash.

[0028] Preferably, an air preheater 42 is also provided in the flue 4, and the air preheater 42 is respectively connected to the boiler and the primary fan 2 and the secondary fan 5. The air preheater 42 exchanges heat with the gas in the flue 4 to preheat the primary air and the secondary air. The preheated air can lower the temperature required for combustion, reduce the moisture content of the flue gas, and improve the calorific value conversion efficiency of the fuel combustion, thereby enhancing the overall combustion efficiency of the boiler, and the heat energy in the flue gas can be recovered to achieve the effect of energy saving and emission reduction.

[0029] Preferably, an economizer 43 is also provided in the flue 4, and the economizer 43 is connected to the water supply pipe 1 and the steam drum 31. The economizer 43 exchanges heat with the gas in the flue 4 to heat the water supply pipe 1, and the heat energy in the flue gas can be recovered to achieve the effect of energy saving and emission reduction.

[0030] Preferably, the present application also includes a dust collector 12, which is arranged between the flue 4 and the chimney 13 and connects the flue 4 and the chimney 13, and is used to filter and remove dust from the gas flowing out of the flue 4, wherein part of the gas after filtering and dust removal is mixed with air as primary air, and the secondary air is air. The gas after filtering and dust removal is mixed with air as primary air. Since the gas is exhaust gas discharged after combustion and has less oxygen, there is no need to specially prepare primary air with a low oxygen content. It is convenient and can recover part of the heat energy in the exhaust gas to save energy and reduce emissions.

[0031] The implementation principle of a multi-stage heating system of a thermal circulating fluidized bed boiler is as follows: feed water is introduced into an economizer 43 arranged in a flue 4 through a feed water pipe 1, and the feed water exchanges heat with the flue gas in the flue 4 in the economizer 43 to increase the feed water temperature, and then the feed water is introduced into a steam drum 31, and the steam drum 31 is connected to a steam pipe in a boiler body 3, and the feed water is heated through the steam pipe to become steam, and the steam is then introduced into a plurality of superheaters 41 arranged in the flue 4 in sequence from low to high according to the temperature of the flue gas passing through the superheater 41, so that the steam temperature is further increased, and finally the steam is introduced into a steam using device, and the primary air and the secondary air are provided with power by the primary fan 2 and the secondary fan 5 to flow into the flue 4 arranged The air preheater 42 exchanges heat with the flue gas in the flue 4 to heat the primary air and the secondary air. The primary air is introduced into the bottom of the boiler body 3 to provide air power and oxygen for the fuel entering the boiler body 3, so that the fuel forms a fluidized state for combustion, while the secondary air is introduced into the side of the boiler body 3 to supplement oxygen to prevent excessive oxygen from being introduced at one time to cause an oxygen-rich environment to produce excessive nitrogen oxides. The primary and secondary air introduced become high-temperature flue gas after combustion and are introduced into the entrance of the flue 4, and are successively passed through multiple superheaters 41, economizers 43 and air preheaters 42 for heat exchange, so that the temperature of the flue gas is reduced and the heat of the flue gas is recovered, and then the low-temperature flue gas is introduced into the chimney 13 and discharged into the atmosphere.

[0032] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A multi-stage heating system for a thermal circulating fluidized bed boiler, characterized in that: It comprises a water supply pipe (1), a primary air fan (2), a boiler body (3) and a flue (4) connected to the boiler body (3), the boiler body (3) being provided with a steam drum (31) and a primary air outlet (32), and a plurality of superheaters (41) being provided on the inner wall surface of the flue (4); The water supply pipe (1) is in communication with the steam drum (31), the steam drum (31) is in communication with a plurality of superheaters (41) in sequence, and the superheaters (41) are in communication with the outside of the flue (4) to form a steam channel; The primary fan (2) is connected to the primary air port (32), the primary air port (32) is connected to the cavity (33) of the boiler body (3), the cavity (33) is connected to the flue (4), and the flue (4) is connected to the chimney (13) to form a gas passage; Wherein, in the flue (4), a projection of the flow direction of the steam channel on the flow direction of the gas channel is opposite to the flow direction of the gas channel.

2. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 1, characterized in that: The boiler body (3) further comprises a secondary fan (5), the secondary fan (5) being in communication with a secondary air port (34) provided on a side wall of the boiler body (3) and being used for introducing secondary air to introduce oxygen into the boiler body (3); the primary air port (32) being provided at the bottom of the boiler body (3); and the primary fan (2) being used for introducing primary air to keep the fuel in a fluidized state.

3. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 2, characterized in that: The invention comprises a control module (6) and a gas detector (7) arranged inside the chimney (13), wherein the gas detector (7) is used to detect smoke components, and the control module (6) is connected to the gas detector (7), the primary fan (2) and the secondary fan (5). When the gas detector (7) detects that the content of nitrogen oxides in the smoke exceeds a monitoring threshold, the rotation speeds of the primary fan (2) and the secondary fan (5) are controlled to increase the proportion of the primary air in the total air volume.

4. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 3 is characterized in that: It also includes a coal bunker (8) and a plurality of conveyor belts arranged at the lower side of the coal bunker (8), wherein the conveyor belts are driven by a drive motor (9); when the gas detector (7) detects that the oxygen content in the flue gas exceeds a monitoring threshold, the control module (6) controls the driving motor (9) to increase its operating speed or controls the primary fan (2) and the secondary fan (5) to decrease their rotating speeds; when the gas detector (7) detects that the oxygen content in the flue gas is lower than the monitoring threshold, the control module (6) controls the driving motor (9) to decrease its operating speed or controls the primary fan (2) and the secondary fan (5) to increase their rotating speeds.

5. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 4, characterized in that: The boiler also comprises a temperature sensor (10) arranged on the inner wall of the boiler body (3); when the temperature sensor (10) detects that the temperature inside the boiler body (3) exceeds a monitoring threshold, the control module (6) controls the operating speed of the drive motor (9) to decrease; and when the temperature sensor (10) detects that the temperature inside the boiler body (3) is lower than the monitoring threshold, the control module (6) controls the operating speed of the drive motor (9) to increase.

6. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 2, characterized in that: The oxygen content of the primary air is lower than the oxygen content of the secondary air.

7. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 1, characterized in that: It also comprises a separator (11), which is arranged between the boiler body (3) and the flue (4) and respectively connects the boiler body (3) and the flue (4) and is used to separate the gas and the large-particle coal ash.

8. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 2, characterized in that: An air preheater (42) is also provided in the flue (4), and the air preheater (42) is connected to the boiler and the primary air fan (2) and the secondary air fan (5) respectively. The air preheater (42) exchanges heat with the gas in the flue (4) to preheat the primary air and the secondary air.

9. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 1, characterized in that: An economizer (43) is also provided in the flue (4); the economizer (43) is connected to the water supply pipe (1) and the steam drum (31); the economizer (43) exchanges heat with the gas in the flue (4) to heat the water supply of the water supply pipe (1).

10. The multi-stage heating system for a thermal circulating fluidized bed boiler according to claim 6, characterized in that: It also includes a dust collector (12), which is arranged between the flue (4) and the chimney (13) and connects the flue (4) and the chimney (13) and is used to filter and remove dust from the gas flowing out of the flue (4), wherein part of the gas after filtering and removing dust is mixed with air as primary air, and the secondary air is air.

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