Blending combustion bamboo reed system of coal-fired circulating fluidized bed boiler

Abstract

The invention relates to the technical field of circulating fluidized bed boilers, and particularly discloses an arundo donax blending combustion system of a coal-fired circulating fluidized bed boiler, which comprises a circulating fluidized hearth, a first feeding device and a second feeding device, the circulating fluidized hearth comprises a coal feeding port, a secondary tuyere, a dense-phase region and a dilute-phase region, the coal feeding port is positioned on one side, far away from the dilute-phase region, of the dense-phase region, and the secondary tuyere is positioned on the other side of the dense-phase region; the secondary tuyere is located on the side, close to the dilute-phase area, of the dense-phase area. The first feeding device is used for crushing coal and conveying the coal to the dense-phase area; the second feeding device comprises a crushing mechanism, a washing and drying mechanism, a baking and forming mechanism and a conveying mechanism, the crushing mechanism crushes the bamboo reed, the washing and drying mechanism washes and dries the bamboo reed powder, and the baking and forming mechanism bakes the dried bamboo reed powder into bamboo reed particles; and the conveying mechanism conveys the arundo donax particles into the dense-phase area through the secondary tuyere. And the washing and drying mechanism is used for washing and drying the bamboo reed powder to remove most alkali metal, chlorine and sulfur elements in the bamboo reed, reduce the ash content and relieve contamination and corrosion.

Description

Technical Field

[0001] The invention relates to the technical field of circulating fluidized bed boilers, in particular to a coal-fired circulating fluidized bed boiler system mixed with arundo donax. Background Art

[0002] Biomass energy is the fourth largest energy source after coal, oil, and natural gas, and is globally recognized as a "zero-carbon" energy source. Its green, low-carbon, and clean characteristics make it crucial for addressing energy and environmental challenges. Among them, Phragmites australis is a high-yield energy plant that can be cultivated in concentrated areas. Its long life cycle, short harvesting cycle, strong environmental adaptability, and high volatile content make it a promising new approach to the widespread utilization of biomass. Blending biomass with coal has garnered widespread attention as a key approach to effectively utilizing biomass energy and achieving low-carbon development of coal-fired power generation.

[0003] Circulating fluidized bed boilers have the characteristics of low-temperature combustion, stable combustion, strong load regulation capability, strong fuel adaptability, and low pollutant emissions. They are expected to provide a feasible solution for the combustion utilization of reed bamboo.

[0004] However, due to the high content of alkali metals, chlorine and sulfur in Phragmites australis, serious ash and slagging corrosion problems are likely to occur on the heated surface when Phragmites australis is mixed with Phragmites australis in large proportions.

[0005] Therefore, it is urgent to use a coal-fired circulating fluidized bed boiler mixed with austria to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a coal-fired circulating fluidized bed boiler system for burning reed bamboo, so as to solve the problem in the related art that reed bamboo has high contents of alkali metals, chlorine and sulfur, and serious ash and slagging corrosion of the heated surface is easily caused when burning reed bamboo in large proportions.

[0007] The present invention provides a coal-fired circulating fluidized bed boiler system for burning reed bamboo, the coal-fired circulating fluidized bed boiler system for burning reed bamboo comprising:

[0008] A circulating fluidized bed furnace, comprising a coal feed port, a secondary air port, a dense phase zone, and a dilute phase zone, wherein the coal feed port is located on a side of the dense phase zone away from the dilute phase zone, and the secondary air port is located on a side of the dense phase zone close to the dilute phase zone;

[0009] a first feeding device, for crushing coal and delivering the crushed coal to the dense phase zone through the coal feeding port;

[0010] The second feeding device includes a crushing mechanism, a water washing and drying mechanism, a baking and molding mechanism, and a conveying mechanism. The crushing mechanism is used to crush the reed bamboo, the water washing and drying mechanism is used to wash and dry the crushed reed bamboo powder in sequence, the baking and molding mechanism is used to bake the dried reed bamboo powder into reed bamboo particles, and the conveying mechanism is used to deliver the reed bamboo particles into the dense phase zone through the secondary air port.

[0011] As a preferred technical solution for the coal-fired circulating fluidized bed boiler system for burning reed bamboo, the secondary air inlet is divided into a lower secondary air inlet and an upper secondary air inlet spaced apart in the vertical direction, and the reed bamboo particles are fed into the dense phase zone through the lower secondary air inlet;

[0012] It also includes a limestone supply device, including a coarse lime supply mechanism and a fine lime supply mechanism. The coarse lime supply mechanism supplies coarse lime to the dense phase area through the coal feeding port, and the fine lime supply mechanism supplies fine lime to the dense phase area through the upper secondary air port.

[0013] As a preferred technical solution for the coal-fired circulating fluidized bed boiler system for burning reed bamboo, the system further includes a cyclone separator and a material return device, wherein the smoke inlet of the cyclone separator is connected to the side of the dilute phase zone away from the dense phase zone, the material inlet of the material return device is connected to the material outlet of the cyclone separator, and the material outlet of the material return device is connected to the dense phase zone;

[0014] It also includes an SNCR mechanism, including a first SNCR nozzle and a second SNCR nozzle, the first SNCR nozzle is arranged in the dense phase zone and close to the upper secondary air port, and the second SNCR nozzle is arranged at the smoke inlet of the cyclone separator.

[0015] As a preferred technical solution of the coal-fired circulating fluidized bed boiler system for burning reed bamboo, it also includes a tail flue, the smoke inlet of the tail flue is connected to the smoke outlet of the cyclone separator, and an afterburning chamber is provided at the smoke inlet of the tail flue;

[0016] It also includes an afterburning air blower, which is used to blow air into the afterburning chamber.

[0017] As an optimal technical solution for the coal-fired circulating fluidized bed boiler co-firing reed system, it also includes a heat treatment device, which includes a high-temperature superheater, a low-temperature superheater and an economizer. Along the flow direction of the flue gas in the tail flue, the high-temperature superheater, the low-temperature superheater and the economizer are arranged in the tail flue in sequence.

[0018] As a preferred technical solution for the coal-fired circulating fluidized bed boiler system with the burning of reed bamboo, the heat treatment device further comprises an air preheater, which is arranged on a side of the economizer away from the low-temperature superheater;

[0019] It also includes a primary fan and a secondary fan. The primary fan is used to heat the air through the air preheater and send it into the primary air chamber. The secondary fan is used to heat the air through the air preheater and send it into the dense phase zone through the lower secondary air port and the upper secondary air port respectively.

[0020] As an optimal technical solution for the coal-fired circulating fluidized bed boiler co-firing reed system, it also includes a variable frequency speed regulation induced draft fan and a chimney, the air inlet of the variable frequency speed regulation induced draft fan is connected to the smoke outlet of the tail flue, and the air outlet of the variable frequency speed regulation induced draft fan is connected to the chimney.

[0021] As an optimal technical solution for the coal-fired circulating fluidized bed boiler system mixed with reed, part of the flue gas flowing out of the outlet of the variable frequency speed regulation induced draft fan flows into the chimney, and the other part flows into the primary air chamber.

[0022] As an optimal technical solution for the coal-fired circulating fluidized bed boiler system mixed with reed, it also includes a dust collector, which is connected in series between the variable frequency speed regulation induced draft fan and the tail flue.

[0023] As a preferred technical solution for the coal-fired circulating fluidized bed boiler system with the burning of reed bamboo, the circulating fluidized furnace includes an air distribution plate, which is arranged between the primary air chamber and the dense phase zone;

[0024] Blast furnace slag is arranged on the air distribution plate.

[0025] The beneficial effects of the present invention are:

[0026] The present invention provides a coal-fired circulating fluidized bed boiler co-firing system for reed bamboo, which includes a circulating fluidized furnace, a first feeding device and a second feeding device. The circulating fluidized furnace includes a coal feeding port, a secondary air port, a dense phase zone and a dilute phase zone. The coal feeding port is located on a side of the dense phase zone away from the dilute phase zone, and the secondary air port is located on a side of the dense phase zone close to the dilute phase zone; the first feeding device is used to crush coal and send the crushed coal to the dense phase zone through the coal feeding port; the second feeding device includes a crushing mechanism, a water washing and drying mechanism, a baking and molding mechanism and a conveying mechanism, the crushing mechanism is used to crush the reed bamboo, the water washing and drying mechanism is used to wash and dry the crushed reed bamboo powder in sequence, the baking and molding mechanism is used to bake the dried reed bamboo powder into reed bamboo particles, and the conveying mechanism is used to send the reed bamboo particles into the dense phase zone through the secondary air port. When the system is working, since reed bamboo contains alkali metals, chlorine and sulfur elements at high content, the reed bamboo powder is washed and dried through the water washing and drying mechanism, thereby effectively removing the alkali metals, chlorine and sulfur elements in the reed bamboo, reducing the ash content and alleviating the problems of contamination and corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural diagram of a coal-fired circulating fluidized bed boiler system mixed with arundo donax in an embodiment of the present invention.

[0028] In the picture:

[0029] 1. Circulating fluidized furnace; 11. Coal feed port; 12. Secondary air inlet; 121. Lower secondary air inlet; 122. Upper secondary air inlet; 13. Dense phase zone; 14. Dilute phase zone; 15. Primary air chamber; 16. Air distribution plate;

[0030] 21. Coal hopper; 22. Coal mill; 23. Pulverized coal feeder;

[0031] 31. Crushing mechanism; 311. Shearing crusher; 312. Pulverizer; 32. Washing and drying mechanism; 33. Baking and forming mechanism; 34. Conveying mechanism;

[0032] 4. Limestone supply device; 41. Coarse lime supply mechanism; 42. Fine lime supply mechanism;

[0033] 5. Cyclone separator; 6. Material return device; 71. First SNCR nozzle; 72. Second SNCR nozzle;

[0034] 8. Tail flue; 81. Afterburning chamber; 9. Afterburning air blower;

[0035] 101. High-temperature superheater; 102. Low-temperature superheater; 103. Economizer; 104. Air preheater;

[0036] 20. Primary fan; 30. Secondary fan; 40. Variable frequency speed-regulating induced draft fan; 50. Chimney; 60. Dust collector. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature being "above", "above" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0039] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0040] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0041] like Figure 1As shown, this embodiment provides a coal-fired circulating fluidized bed boiler system for burning aconite mixed with bamboo. The coal-fired circulating fluidized bed boiler system for burning aconite mixed with bamboo includes a circulating fluidized furnace 1, a first feeding device and a second feeding device. The circulating fluidized furnace 1 includes a primary air chamber 15, a dense phase zone 13 and a dilute phase zone 14. An air distribution plate 16 is provided between the primary air chamber 15 and the dense phase zone 13. The primary air port is connected to the primary air chamber 15. The secondary air port 12 and the coal feeding port 11 are both located in the dense phase zone 13. The coal feeding port 11 is located on the side of the dense phase zone 13 away from the dilute phase zone 14, and the secondary air port is located on the side of the dense phase zone 13 close to the dilute phase zone 14; the first feeding device is used to crush the coal and send the crushed coal to the dense phase zone 13 through the coal feeding port 11; the second feeding device includes a crushing mechanism 31, a water washing and drying mechanism 32, a baking and molding mechanism 33 and a conveying mechanism 34. The crushing mechanism 31 is used to crush the reed, the water washing and drying mechanism 32 is used to wash and dry the crushed reed powder in sequence, the baking and molding mechanism 33 is used to bake the dried reed powder into reed particles, and the conveying mechanism 34 is used to send the reed particles into the dense phase zone 13 through the secondary air port 12. When the system is in operation, the first feeding device is used to pulverize the coal and deliver the pulverized coal to the dense phase zone 13 through the coal feeding port 11. The conveying mechanism 34 is used to deliver the reed pellets into the dense phase zone 13 through the secondary air port 12. The primary air enters the primary air port and is injected into the dense phase zone 13 through the air distribution plate 16, maintaining the fluidization of the bed material and providing the basic combustion oxygen, maintaining an oxygen-deficient reducing atmosphere, and suppressing the generation of NOx. The secondary air enters the dense phase zone 13 through the secondary air port 12. On the one hand, it can increase the mixing degree of the coal powder and the reed pellets. On the other hand, it can supplement the combustion oxygen so that the coal powder and the reed pellets can be fully burned. The reed pellets are fed at the secondary air port 12. In the early stage of combustion, a large amount of volatile matter is precipitated from the reed pellets, which helps to reduce the NOx generated by the combustion of the coal powder.

[0042] Optionally, the crushing mechanism 31 includes a shearing crusher 311 and a pulverizer 312 . The shearing crusher 311 is used to adapt to the characteristics of Arundo donax that it is relatively tough and not easily broken.

[0043] Since the content of alkali metals, chlorine and sulfur in reed bamboo is relatively high, the reed bamboo powder is washed and dried by the washing and drying mechanism 32, thereby effectively removing the alkali metals, chlorine and sulfur in the reed bamboo, reducing the ash content, and alleviating the contamination and corrosion problems.

[0044] The baking and forming mechanism 33 bakes and forms the bamboo, which is more conducive to storage and transportation, promotes the release of slag-causing and corrosive elements, alleviates the problems of contamination and corrosion, and can also increase the calorific value and density of the bamboo, and prevent the bamboo from being carried by the flue gas in the circulating fluidized furnace 1 and directly leaving the coal-fired circulating fluidized bed boiler mixed with bamboo system.

[0045] Optionally, the first feeding device includes a coal hopper 21 , a coal mill 22 and a pulverized coal feeder 23 . The coal is processed into pulverized coal from the coal hopper 21 through the coal mill 22 , and then passes through the pulverized coal feeder 23 and enters the dense phase zone 13 from the coal feeding port 11 .

[0046] Optionally, the coal-fired circulating fluidized bed boiler system for burning reed bamboo further includes a cyclone separator 5 and a return device 6, wherein the smoke inlet of the cyclone separator 5 is connected to the side of the dilute phase zone 14 away from the dense phase zone 13, the feed port of the return device 6 is connected to the discharge port of the cyclone separator 5, and the discharge port of the return device 6 is connected to the dense phase zone 13. In this embodiment, a large amount of unburned coal powder and reed bamboo particles still exist in the flue gas wafting out from the dilute phase zone 14. At this time, after the flue gas enters the cyclone separator 5, the unburned coal powder and reed bamboo particles enter the return device 6 under the action of centrifugal force, and the return device 6 sends this part of the coal powder and reed bamboo particles back to the dense phase zone 13, thereby improving the utilization rate of energy.

[0047] Optionally, the secondary air inlet 12 is divided into a lower secondary air inlet 121 and an upper secondary air inlet 122, spaced vertically apart. Phragmites australis particles are fed into the dense phase zone 13 through the lower secondary air inlet 121. The coal-fired circulating fluidized bed boiler system for co-firing Phragmites australis also includes a limestone supply device 4, comprising a coarse lime supply mechanism 41 and a fine lime supply mechanism 42. The coarse lime supply mechanism 41 supplies coarse lime to the dense phase zone 13 through the coal feed port 11, while the fine lime supply mechanism 42 supplies fine lime to the dense phase zone 13 through the upper secondary air inlet 122. In this embodiment, the staggered design of the upper and lower secondary air layers is a core technical approach to optimizing combustion efficiency and environmental performance. The primary function of the lower secondary air layer is to provide sufficient oxygen for combustible gases such as CO and H2, as well as unburned coke particles, rising from the dense phase zone 13, thereby increasing the burnout rate from 90% to >98%. This oxygen supplement moderately raises the local temperature (50–100°C) and accelerates coke combustion.

[0048] At the same time, coarse limestone particles with a particle size of 1 to 2 mm are sprayed into the coal feeding port 11, and fine limestone particles with a particle size of 200 to 500 μm are sprayed into the upper secondary air port 122. The simultaneous addition of limestones of different particle sizes can not only give full play to the characteristics of small-particle limestone, such as large specific surface area, many pores, and fast reaction rate, but also allow larger-particle limestone to re-enter the furnace with the circulating ash in the cyclone separator 5, thereby extending the limestone residence time and improving the limestone utilization rate and desulfurization efficiency.

[0049] Optionally, the coal-fired circulating fluidized bed boiler system co-firing reed bamboo also includes an SNCR mechanism, comprising a first SNCR nozzle 71 and a second SNCR nozzle 72. The first SNCR nozzle 71 is positioned in the dense phase zone 13 near the upper secondary air inlet 122, and the second SNCR nozzle 72 is positioned at the smoke inlet of the cyclone separator 5. In this embodiment, the first SNCR nozzle is added at the upper secondary air inlet 122 of the circulating fluidized bed. This location is in the dense phase zone 13 of the boiler, where the combustion reaction is intense and the temperature is high. Even during low-load operation, the temperature can be maintained at the optimal SNCR reaction temperature, which is conducive to the SNCR denitrification reaction during variable load operation. Furthermore, the high concentration of fuel particles near the secondary air inlet promotes the NOx reduction reaction. The second SNCR nozzle 72 is positioned at the smoke inlet of the cyclone separator 5, thereby further denitrifying the flue gas before it enters the cyclone separator 5.

[0050] Optionally, the coal-fired circulating fluidized bed boiler system for co-firing asparagus further includes a tail flue 8, the smoke inlet of which is connected to the smoke outlet of the cyclone separator 5, and an afterburning chamber 81 is provided at the smoke inlet of the tail flue 8. The coal-fired circulating fluidized bed boiler system for co-firing asparagus further includes an afterburning air blower 9 for blowing air into the afterburning chamber 81. In this embodiment, air is introduced into the afterburning chamber via the afterburning air blower 9, thereby completely combusting unburned coal powder, asparagus particles, hydrogen, and carbon monoxide in the flue gas.

[0051] Optionally, the coal-fired circulating fluidized bed boiler system co-firing reed bamboo further includes a heat treatment device comprising a high-temperature superheater 101, a low-temperature superheater 102, and an economizer 103. The high-temperature superheater 101, the low-temperature superheater 102, and the economizer 103 are sequentially arranged within the tail flue 8 along the flow direction of the flue gas within the tail flue 8. In this embodiment, after the flue gas flows through the high-temperature superheater 101, the low-temperature superheater 102, and the economizer 103 in sequence, most of the heat in the flue gas is removed by the high-temperature superheater 101, the low-temperature superheater 102, and the economizer 103, thereby achieving energy recovery and utilization.

[0052] Optionally, the heat treatment device further includes an air preheater 104, which is disposed on a side of the economizer 103 away from the low-temperature superheater 102. The coal-fired circulating fluidized bed boiler system co-firing reed bamboo also includes a primary fan 20 and a secondary fan 30. The primary fan 20 is used to heat the air through the air preheater 104 and deliver it to the primary air chamber 15. The secondary fan 30 is used to heat the air through the air preheater 104 and deliver it to the dense phase zone 13 through the lower secondary air port 121 and the upper secondary air port 122, respectively. In this embodiment, the air preheater 104 can heat the passing air, which can reduce the energy loss of the fuel used to heat the gas and improve the boiler thermal efficiency by 3%-8%. The high-temperature combustion-supporting gas accelerates the ignition of the fuel and promotes complete combustion of the fuel.

[0053] Optionally, the coal-fired circulating fluidized bed boiler system for co-firing astragalus further includes a variable frequency speed-regulating induced draft fan 40 and a chimney 50. The air inlet of the variable frequency speed-regulating induced draft fan 40 is connected to the smoke outlet of the tail flue 8, and the air outlet of the variable frequency speed-regulating induced draft fan 40 is connected to the chimney 50. In this embodiment, the variable frequency speed-regulating induced draft fan 40 can accelerate the exhaust of flue gas from the tail flue 8 through the chimney 50. Because this embodiment uses a mixture of coal and astragalus, which produces relatively large amounts of flue gas, the speed of the variable frequency speed-regulating induced draft fan 40 is adjustable to accommodate flue gas generated by varying coal and astragalus mixture ratios.

[0054] Optionally, a portion of the flue gas flowing out of the outlet of the variable frequency speed regulating induced draft fan 40 flows into the chimney 50, and another portion flows into the primary air chamber 15. In this embodiment, mixing a portion of the flue gas flowing out of the outlet of the variable frequency speed regulating induced draft fan 40 with the primary air can reduce the oxygen concentration and temperature in the dense phase 13, which is beneficial for reducing the generation of pollutants such as NOx, while also ensuring the fluidization air velocity at low loads.

[0055] Optionally, the coal-fired circulating fluidized bed boiler system co-firing reed bamboo also includes a dust collector 60, which is connected in series between the variable frequency speed control induced draft fan 40 and the tail flue 8. In this embodiment, the dust collector 60 can remove particulate matter from the flue gas flowing out of the tail flue 8, thereby preventing the particulate matter from entering the environment and from re-entering the circulating fluidized bed furnace 1.

[0056] Optionally, the circulating fluidized furnace 1 includes an air distribution plate 16 disposed between the primary air chamber 15 and the dense phase zone 13. Blast furnace slag is disposed on the air distribution plate 16. In this embodiment, blast furnace slag is used as the bed material. Slagging caused by alkali metals is related to the interaction between the fuel ash and the bed material. Quartz sand bed material has a more pronounced slagging tendency, while blast furnace slag is less likely to slag, which helps alleviate the problem of ash accumulation and slagging.

[0057] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A coal-fired circulating fluidized bed boiler system with mixed burning of reed bamboo, characterized in that: include: A circulating fluidized bed furnace (1) comprises a coal feeding port (11), a secondary air port (12), a dense phase zone (13) and a dilute phase zone (14), wherein the coal feeding port (11) is located on a side of the dense phase zone (13) away from the dilute phase zone (14), and the secondary air port (12) is located on a side of the dense phase zone (13) close to the dilute phase zone (14); a first feeding device for crushing coal and delivering the crushed coal to the dense phase zone (13) through the coal feeding port (11); The second feeding device comprises a crushing mechanism (31), a water washing and drying mechanism (32), a baking and forming mechanism (33) and a conveying mechanism (34), wherein the crushing mechanism (31) is used for crushing the reed bamboo, the water washing and drying mechanism (32) is used for washing and drying the crushed reed bamboo powder in sequence, the baking and forming mechanism (33) is used for baking the dried reed bamboo powder into reed bamboo particles, and the conveying mechanism (34) is used for conveying the reed bamboo particles into the dense phase zone (13) through the secondary air port (12).

2. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 1, characterized in that: The secondary air inlet (12) is divided into a lower secondary air inlet (121) and an upper secondary air inlet (122) arranged at intervals in the vertical direction, and the reed particles are fed into the dense phase zone (13) through the lower secondary air inlet (121); The invention also includes a limestone supply device (4), comprising a coarse lime supply mechanism (41) and a fine lime supply mechanism (42). The coarse lime supply mechanism (41) supplies coarse lime to the dense phase zone (13) through the coal feeding port (11), and the fine lime supply mechanism (42) supplies fine lime to the dense phase zone (13) through the upper secondary air port (122).

3. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 2, characterized in that: It also includes a cyclone separator (5) and a return device (6), wherein the smoke inlet of the cyclone separator (5) is communicated with the side of the dilute phase zone (14) away from the dense phase zone (13), the feed port of the return device (6) is communicated with the discharge port of the cyclone separator (5), and the discharge port of the return device (6) is communicated with the dense phase zone (13); The invention also includes an SNCR mechanism, comprising a first SNCR nozzle (71) and a second SNCR nozzle (72), wherein the first SNCR nozzle (71) is arranged in the dense phase zone (13) and close to the upper secondary air port (122), and the second SNCR nozzle (72) is arranged at the smoke inlet of the cyclone separator (5).

4. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 3, characterized in that: It also includes a tail flue (8), the smoke inlet of the tail flue (8) is connected to the smoke outlet of the cyclone separator (5), and a post-combustion chamber (81) is provided at the smoke inlet of the tail flue (8); It also includes an afterburning air blower (9), and the afterburning air blower (9) is used to blow air into the afterburning chamber (81).

5. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 4, characterized in that: The invention also includes a heat treatment device, which includes a high-temperature superheater (101), a low-temperature superheater (102) and an economizer (103). Along the flow direction of the flue gas in the tail flue (8), the high-temperature superheater (101), the low-temperature superheater (102) and the economizer (103) are sequentially arranged in the tail flue (8).

6. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 5, characterized in that: The heat treatment device further comprises an air preheater (104), wherein the air preheater (104) is arranged on a side of the economizer (103) away from the low-temperature superheater (102); The invention also includes a primary air fan (20) and a secondary air fan (30), wherein the primary air fan (20) is used to heat the air through the air preheater (104) and send the air to the primary air chamber (15), and the secondary air fan (30) is used to heat the air through the air preheater (104) and send the air to the dense phase zone (13) through the lower secondary air port (121) and the upper secondary air port (122).

7. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 6, characterized in that: It also includes a variable frequency speed regulating induced draft fan (40) and a chimney (50), wherein the air inlet of the variable frequency speed regulating induced draft fan (40) is connected to the smoke outlet of the tail flue (8), and the air outlet of the variable frequency speed regulating induced draft fan (40) is connected to the chimney (50).

8. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 7, characterized in that: A portion of the smoke flowing out of the air outlet of the variable frequency speed regulating induced draft fan (40) flows into the chimney (50), and the other portion flows into the primary air chamber (15).

9. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 7, characterized in that: It also includes a dust collector (60), which is connected in series between the variable frequency speed regulating induced draft fan (40) and the tail flue (8).

10. The coal-fired circulating fluidized bed boiler system mixed with arundo donax according to claim 1, characterized in that: The circulating fluidized bed furnace (1) comprises an air distribution plate (16), and the air distribution plate (16) is arranged between the primary air chamber (15) and the dense phase zone (13); Blast furnace slag is arranged on the air distribution plate (16).

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