A boiler system for realizing flexible depth peak shaving

Abstract

The present application relates to a kind of boiler systems of realizing flexible depth peak shaving, including coal mill, burner, primary air fan, secondary air fan, first separator, second separator, fine coal hopper, air-powder mixer, exhaust air fan, air preheating system and flue gas recirculation system, coal mill is connected first separator, first separator is connected burner, first separator is also sequentially connected second separator, fine coal hopper, air-powder mixer and burner, second separator is sequentially connected exhaust air fan and burner, burner is installed in the hearth of boiler body, primary air fan is sequentially connected air preheating system and air-powder mixer, primary air fan is also sequentially connected air preheating system and coal mill, secondary air fan is sequentially connected air preheating system and burner, the flue gas inlet of flue gas recirculation system is connected the main flue of boiler body, and flue gas outlet is connected coal mill, burner and hearth lower part.Advantages: solve the problem of boiler safety and low load economy under the condition of flexible depth peak shaving.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal-fired boilers, in particular to a boiler system for realizing flexible and deep load regulation. BACKGROUND

[0002] To realize flexible and deep load regulation, the invention patent 202210594006.0 discloses a flexible mixed type pulverized coal supply system based on online monitoring of coal flow and coal quality, and the core is the fine coal bunker technology. By using the fine coal bunker technology, stable combustion and rapid load variation capability under low load can be ensured. However, the fine coal bunker technology has the following defects: 1) the furnace heat load fluctuates greatly when the load is changed and low, combined with the unstable characteristics of water power under low flow and low pressure, which easily causes the water-cooled wall temperature to fluctuate sharply and the local water-cooled wall to overheat; 2) when the load is low, the main steam temperature is generally higher than the reheat steam temperature, and the smoke baffle adjustment and the burner swing adjustment cannot be reversed, and the current common solution is to use desuperheating water, but this will cause the cycle efficiency to decrease greatly, and even if the desuperheating water is fully opened, it cannot completely reverse the situation, and the system can only run below the rated temperature, further reducing the efficiency.

[0003] Therefore, in order to solve the above technical problems, it is necessary to develop a new boiler system for realizing flexible and deep load regulation. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a boiler system for realizing flexible and deep load regulation, which effectively overcomes the defects of the prior art.

[0005] The technical solution of the present application to solve the above technical problems is as follows:

[0006] A boiler system for realizing flexible and deep load regulation, comprising a coal mill, a burner, a primary air fan, a secondary air fan, a primary separator, a secondary separator, a fine coal hopper, a wind-powder mixer, a flue gas fan, a boiler body, an air preheating system and a flue gas recirculation system, the coal mill is connected to the primary separator through a coal outlet, the primary separator is connected to the burner through a pipeline, the primary separator is further connected to the secondary separator, the fine coal hopper, the wind-powder mixer and the burner in sequence through a pipeline, the flue gas outlet of the secondary separator is connected to the flue gas fan and the wind-powder mixer in sequence through a pipeline, the burner is installed on the side wall of the furnace of the boiler body, the primary air fan is connected to the air preheating system and the burner in sequence through a pipeline, the primary air fan is further connected to the air preheating system and the coal mill in sequence through a pipeline, the secondary air fan is connected to the air preheating system and the burner in sequence through a pipeline, the flue gas inlet of the flue gas recirculation system is connected to the main flue of the boiler body, and the flue gas outlet thereof is connected to the flue gas inlet of the coal mill, the burner and the lower part of the furnace of the boiler body through pipelines respectively.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the aforementioned air preheating system includes a low-temperature air preheater and a high-temperature air preheater installed in the main flue. The low-temperature air preheater has two air-side inlets, a primary air outlet, and a secondary air outlet. The high-temperature air preheater has an air-side inlet and an air-side outlet. The primary air fan is connected to one of the air-side inlets of the low-temperature air preheater via a pipeline. The primary air outlet of the low-temperature air preheater is connected to the burner and the air-coal mixer via pipelines. The air-side inlet and outlet of the high-temperature air preheater are connected to the secondary air outlet of the low-temperature air preheater and the burner via pipelines. The secondary air fan is connected to the other air-side inlet of the low-temperature air preheater via a pipeline.

[0009] Furthermore, a dust collector and an induced draft fan are sequentially connected to the tail end of the flue of the boiler body.

[0010] Furthermore, an auxiliary flue is installed on the side wall of the main flue of the boiler body. An economizer is provided in the middle section of the flue of the boiler body. The auxiliary flue is located at the location of the economizer and is independent of the main flue. The front end of the auxiliary flue is connected to the main flue, and the rear end of the auxiliary flue is provided with an auxiliary flue opening connected to the main flue. A secondary flue gas baffle is provided at the auxiliary flue opening. The high-temperature air preheater is installed in the auxiliary flue and has a flue gas inlet and a flue gas outlet that are connected to the front and rear ends of the auxiliary flue. The low-temperature air preheater is located in the rear section of the main flue and is located behind the economizer.

[0011] Furthermore, the aforementioned flue gas recirculation system includes a recirculation fan. Air inlets are respectively provided on the main flue near the secondary flue gas baffle, at the end of the main flue, and on the pipeline between the dust collector and the induced draft fan. The air inlet of the recirculation fan is connected to the three aforementioned air inlets through three fan pipelines. The air inlet of the recirculation fan constitutes the flue gas inlet of the aforementioned flue gas recirculation system, and its air outlet constitutes the flue gas outlet of the aforementioned flue gas recirculation system.

[0012] Furthermore, in the main flue, a main flow channel and a secondary flow channel are arranged in parallel in front of the economizer. The main flow channel and the secondary flow channel are respectively provided with a main heat-receiving surface structure and a secondary heat-receiving surface structure. A primary flue gas baffle is provided at the rear end between the main flow channel and the secondary flow channel for simultaneously adjusting the flue gas flow of both.

[0013] Further, a first air door is arranged on the three above-mentioned fan pipelines, a second air door is arranged on the pipeline connecting the air side primary air outlet of the low-temperature air preheater with the above-mentioned air-pulverized coal mixer, and a control valve is arranged on the pipeline connecting the above-mentioned fine coal hopper with the air-pulverized coal mixer.

[0014] Further, when the unit is in high-load operation, the second air door and the control valve are closed, the exhaust gas fan is operated, and the fine coal hopper starts to store the fine coal powder provided by the secondary separator; when the boiler load decreases, the angle of the burner and the primary flue gas damper are adjusted to make the main / reheated steam temperature reach the rated value; when the boiler load further decreases, the air volume of the recirculation fan is adjusted to make the main / reheated steam temperature reach the rated value; when the boiler load is lower than 40%-50%, the second air door and the control valve are opened, the direct coal supply amount of the primary separator decreases, and the burner starts to mix the fine coal powder for combustion; when the boiler load is lower than 40%-50%, the secondary flue gas damper is adjusted to make the secondary air temperature at the flue gas outlet of the high-temperature air preheater reach 400-600℃; when the unit is in rapid load increase, the second air door and the control valve are opened to ensure that the coal powder heat increase amount matches the load increase rate, and after the load is stable, the coal supply amount of the fine coal hopper is gradually reduced, and the direct coal supply amount of the primary separator is increased.

[0015] Further, the coal feeding system is connected with the coal feeding inlet of the coal mill.

[0016] The present application has the advantages that: the complementary coupling and optimal design of the fine coal bunker, flue gas recirculation and high / low-temperature air preheater are adopted, the technical effect of the system as a whole is much greater than that of the three alone, and the safety and economy of the boiler under the condition of flexible and deep load regulation are effectively solved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is a structural schematic diagram of the boiler system for realizing flexible and deep load regulation of the present application.

[0018] In the figure, the components represented by the numbers are listed as follows:

[0019] 1, coal mill; 2, burner; 3, primary air fan; 4, secondary air fan; 5, primary separator; 6, secondary separator; 7, fine coal hopper; 8, air-pulverized coal mixer; 9, exhaust gas fan; 10, boiler body; 30, coal feeding system; 40, dust collector; 50, induced draft fan; 53, primary flue gas damper; 60, recirculation fan; 61, first air door; 62, control valve; 81, second air door; 101, auxiliary flue; 103, secondary flue gas damper; 201, low-temperature air preheater; 202, high-temperature air preheater. DETAILED DESCRIPTION

[0020] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] Example: Figure 1 As shown, the boiler system for flexible deep peak shaving in this embodiment includes a coal mill 1, a burner 2, a primary air fan 3, a secondary air fan 4, a primary separator 5, a secondary separator 6, a clean coal hopper 7, an air-coal mixer 8, a waste gas fan 9, a boiler body 10, an air preheating system, and a flue gas recirculation system. The coal outlet of the coal mill 1 is connected to the primary separator 5. The primary separator 5 is connected to the burner 2 via a pipeline. The primary separator 5 is also connected to the secondary separator 6, the clean coal hopper 7, the air-coal mixer 8, and the burner 2 in sequence via pipelines. The waste gas outlet of the secondary separator 6 is connected to the waste gas fan 9 (air inlet) and the burner 2 (waste gas outlet) in sequence via pipelines. The air outlet of the blower 9 is connected to the burner 2), the burner 2 is installed on the side wall of the furnace of the boiler body 10, the primary air blower 3 is connected to the air preheating system and the burner 2 in sequence through pipelines, the primary air blower 3 is also connected to the air preheating system and the coal mill 1 in sequence through pipelines, the secondary air blower 4 is connected to the air preheating system and the burner 2 in sequence through pipelines, the flue gas inlet of the flue gas recirculation system is connected to the main flue of the boiler body 10, and its flue gas outlet is connected to the flue gas inlet of the coal mill 1, the burner 2 and the lower part of the furnace of the boiler body 10 through pipelines (wherein, the height of the part where the lower part of the furnace is connected to the flue gas outlet is lower than the installation height of the burner 2).

[0022] In this embodiment, the air preheating system includes a low-temperature air preheater 201 and a high-temperature air preheater 202 installed in the main flue. The low-temperature air preheater 201 has two air-side inlets, an air-side primary air outlet, and an air-side secondary air outlet (the low-temperature air preheater 201 and the high-temperature air preheater 202 each have a flue gas inlet and a flue gas outlet, and the flue gas in the flue enters through the flue gas inlet and flows out through the flue gas outlet). The high-temperature air preheater 202 has an air-side inlet and an air-side outlet. The primary air fan 3 is connected to one of the air-side inlets of the low-temperature air preheater 201 through a pipeline. The air-side primary air outlet of the low-temperature air preheater 201 is connected to the burner 2 and the air-coal mixer 8 through pipelines. The air-side inlet and air-side outlet of the high-temperature air preheater 202 are connected to the air-side secondary air outlet of the low-temperature air preheater 201 and the burner 2 through pipelines. The secondary air fan 4 is connected to the other air-side inlet of the low-temperature air preheater 201 through a pipeline.

[0023] It should be noted that: Appendix Figure 1The low-temperature air preheater 201 marked outside the main flue actually refers to the part of the low-temperature air preheater 201 in the flue penetrating out of the flue, and similarly, the high-temperature air preheater 202 marked outside the main flue actually refers to the part of the high-temperature air preheater 202 in the flue penetrating out of the flue. Figure 1 The high-temperature air preheater 202 marked outside the main flue actually refers to the part of the high-temperature air preheater 202 in the flue penetrating out of the flue.

[0024] In this embodiment, the tail end of the flue of the boiler body 10 is sequentially connected with a dust collector 40 and an induced draft fan 50.

[0025] According to the structural design of the conventional boiler system, in this embodiment, the heating surface structure, the economizer (s in the figure), the high-temperature air preheater, and the low-temperature air preheater (all of the above designs belong to the conventional arrangement in the existing boiler system) are sequentially arranged in the flue of the boiler from the front end to the rear end. In this embodiment, on the basis of the existing boiler design, an auxiliary flue 101 is additionally installed on the side wall of the main flue of the boiler body 10. The middle section of the flue of the boiler body 10 is provided with an economizer. The auxiliary flue 101 is arranged at the position of the economizer and is independent of the main flue. The front end of the auxiliary flue 101 is in communication with the main flue. The rear end of the auxiliary flue 101 is provided with an auxiliary flue opening in communication with the main flue. A two-stage flue baffle 103 is arranged at the auxiliary flue opening. The high-temperature air preheater 202 is installed in the auxiliary flue 101. Generally, the high-temperature air preheater and the low-temperature air preheater both have a flue gas inlet and a flue gas outlet in communication with the flue. The low-temperature air preheater 201 is arranged at the rear section of the main flue and is located behind the economizer.

[0026] It should be particularly noted that in the main flue, the heating surface structure can be a superheater, a reheater, a bypass heat exchanger, an economizer, etc.

[0027] In this embodiment, the flue gas recirculation system includes a recirculation fan 60. Air inlets are respectively arranged on the part of the main flue close to the two-stage flue baffle 103, the tail end of the main flue, and the pipelines between the dust collector 40 and the induced draft fan 50. The air inlet of the recirculation fan 60 is connected to the three air inlets through three fan pipelines. The air inlet of the recirculation fan 60 constitutes the flue gas inlet of the flue gas recirculation system, and the air outlet thereof constitutes the flue gas outlet of the flue gas recirculation system of the recirculation fan 60.

[0028] The air outlet of the recirculation fan 60 is connected to the flue gas inlet of the coal mill 1, the burner 2, and the lower part of the furnace of the boiler body 10 through three pipelines, respectively. Air dampers e, f, and g are respectively arranged on the three pipelines.

[0029] It should be further noted that:

[0030] In the embodiment, the main flue and the auxiliary flue are arranged in parallel in front of the economizer, the main flue and the auxiliary flue are respectively provided with the main heating surface structure 51 and the auxiliary heating surface structure 52, and the rear end between the main flue and the auxiliary flue is provided with the primary flue gas damper 53 for simultaneously adjusting the flue gas flow of the main flue and the auxiliary flue. The primary flue gas damper 53 is swingably arranged on the side wall shared by the rear ends of the main flue and the auxiliary flue, and the swing to either side can simultaneously adjust the output air flow of the main flue and the auxiliary flue, and the operation is relatively flexible.

[0031] In the embodiment, the primary flue gas damper 53 and the secondary flue gas damper 103 are both flue gas dampers (electric) commonly used in the boiler system, and the specific structure is not described herein.

[0032] In the embodiment, the first air door 61 is arranged on the three air fan pipelines, the second air door 81 is arranged on the pipeline connecting the air outlet of the air side of the low-temperature air preheater 201 and the air-pulverized coal mixer 8, and the control valve 62 is arranged on the pipeline connecting the pulverized coal bunker 7 and the air-pulverized coal mixer 8 (that is, the control valve 62 is arranged at the outlet of the pulverized coal bunker 7).

[0033] In the embodiment, the coal feeding system 30 is connected to the coal inlet of the coal mill 1, and the coal feeding system 30 is a product of the prior art commonly used in the boiler, and the specific structure is not described herein.

[0034] According to different working conditions of the boiler system, the specific use process is as follows:

[0035] When the boiler load decreases, the angle of the burner 2 and the primary flue gas damper 53 are adjusted to make the main / reheated steam temperature reach the rated value; when the boiler load further decreases, the air volume of the recirculating air fan 60 is adjusted to make the main / reheated steam temperature reach the rated value; when the boiler load is lower than 40%-50%, the second air door 81 and the control valve 62 are opened, the direct coal supply of the primary separator 5 decreases, and the burner 2 starts to mix fine coal powder for combustion; when the boiler load is lower than 40-50%, the secondary flue gas damper 103 is adjusted to make the secondary air temperature of the flue gas outlet of the high-temperature air preheater 202 reach 400-600℃; when the unit rapidly increases the load, the second air door 81 and the control valve 62 are opened to ensure that the increase amount of the pulverized coal heat matches the load increase rate, and after the load is stable, the coal supply of the pulverized coal bunker 7 is gradually reduced, and the direct coal supply of the primary separator 5 is increased.

[0036] In addition, when the boiler rapidly decreases the load, the coal feeding amount entering the coal mill 1, the opening degrees of the dampers and valves on the pipelines of the entire system such as the coal mill 1 and the burner 2 (such as the opening degrees of the first air door 61, the second air door 81, the control valve 62, the air door e, the air door f, the air door g, etc.) are flexibly adjusted to ensure that the decrease amount of the pulverized coal heat matches the load decrease rate.

[0037] Need to be added:

[0038] When the boiler is in basic load stable operation, only the pipeline access between the first separator 5 and the burner 2 can be opened, and the pipeline access between the first separator 5 and the second separator 6 can be closed, and air dampers (air damper a and air damper b) are arranged on the above two pipeline accesses respectively, and the pipeline access is kept open or closed by adjusting the air dampers (air damper a and air damper b);

[0039] When the coal entering the coal mill 1 is low-moisture, high-volatile, and easy-to-ignite and burn bituminous coal, the pipeline access between the first separator 5 and the burner 2 is kept open, while the pipeline access between the first separator 5 and the second separator 6 is closed, the pipeline between the primary air fan 3 and the wind-powder mixer 8 is closed (that is, the second air damper 81 is closed), and the discharge port of the fine coal bucket 7 is closed (that is, the pipeline between the fine coal bucket 7 and the wind-powder mixer 8 is disconnected), while the pipeline between the primary air fan 3 and the coal mill 1 is kept open, and the second channel enters the pulverizing operation mode. At this time, part of the coal powder enters the burner 2 through the pipeline access between the first separator 5 and the burner 2, and part of the coal powder enters the fine coal bucket 7 for storage through the pipeline access between the first separator 5 and the second separator 6;

[0040] When the boiler is load shedding, the pipeline access between the first separator 5 and the burner 2 is kept open, while the pipeline access between the first separator 5 and the second separator 6 is closed, the pipeline between the primary air fan 3 and the wind-powder mixer 8 is closed, and the discharge port of the fine coal bucket 7 is closed, and the pipeline access between the first separator 5 and the second separator 6 enters the pulverizing operation mode. At this time, part of the coal powder enters the burner 2 through the pipeline access between the first separator 5 and the burner 2, and part of the coal powder enters the fine coal bucket 7 for storage through the pipeline access between the first separator 5 and the second separator 6;

[0041] When the boiler needs to quickly increase the load, the pipeline access between the first separator 5 and the burner 2 is kept open, the pipeline access between the first separator 5 and the second separator 6 is kept open, the pipeline between the primary air fan 3 and the wind-powder mixer 8 is kept open, and the discharge port of the fine coal bucket 7 is opened, and the pipeline access between the first separator 5 and the second separator 6 enters the powder feeding operation mode, and the air volume of the pipeline access between the first separator 5 and the second separator 6 is adjusted. At this time, the coal powder in the fine coal bucket 7 enters the burner 2 through the wind-powder mixer 8, the exhaust gas of the second separator 6 enters the burner 2 through the exhaust air fan 9, the coal feeding amount entering the boiler is increased, and the load of the boiler is quickly increased. An air damper d is arranged on the pipeline between the primary air fan 3 and the wind-powder mixer 8, and the air volume of the pipeline is adjusted by operating the air damper d;

[0042] When the coal quality in the coal mill 1 is poor, in order to prevent the boiler load from decreasing, the pipeline passage between the primary separator 5 and the burner 2 is unblocked, the pipeline passage between the primary separator 5 and the secondary separator 6 is closed, the pipeline between the primary air fan 3 and the wind-powder mixer 8 is kept unblocked, and the discharge opening of the clean coal bucket 7 is opened, and the pipeline between the primary separator 5 and the secondary separator 6 enters the powder feeding mode. At this time, the coal powder in the clean coal bucket 7 enters the burner 2 through the wind-powder mixer 8, the exhaust gas of the secondary separator 6 enters the burner 2 as the tertiary air through the exhaust air fan 9, the coal supply to the boiler is increased and the coal quality is improved, and the boiler load is maintained stable;

[0043] When the boiler is in low load operation, the pipeline passage between the primary separator 5 and the burner 2 is unblocked, at the same time, the pipeline passage between the primary separator 5 and the secondary separator 6 is closed, the pipeline between the primary air fan 3 and the wind-powder mixer 8 is kept unblocked, and the second channel enters the powder feeding mode. At this time, the coal powder in the clean coal bucket 7 enters the burner 2 through the wind-powder mixer 8, the exhaust gas of the secondary separator 6 enters the burner as the tertiary air through the exhaust air fan 9, and the boiler is realized low load stable operation.

[0044] It needs to be specially pointed out that: in the boiler flue, the structure of the heating surface, the distribution of the main flow channel and the secondary flow channel, the arrangement of the primary flue gas baffle 53, the economizer and the design of the internal air preheater M in the flue all belong to the prior art.

[0045] The boiler system of the embodiment solves the four key problems of stable combustion, rapidness, economy and safety of flexible and deep peak regulation, and has at least the following beneficial effects:

[0046] 1) The clean coal bunker adopts the mode of storing high-quality coal, ensuring stable combustion and rapid load change under low load.

[0047] 2) The flue gas recirculation solves the problems of boiler safety and low load economy under the condition of flexible and deep peak regulation, and the main reasons are as follows: (1) The flue gas recirculation delays the ignition, the spatial distribution of the coal powder in the furnace is more uniform, the uniform combustion similar to the MILD mode is realized, the local peak heat load is weakened, and the furnace safety is ensured; the flue gas recirculation reduces the heat absorption of the furnace and increases the heat absorption of the convection heating surface, adjusts the main / reheat steam temperature, ensures that the main / reheat steam temperature reaches the rated value, reduces the amount of desuperheating water, and improves the economic efficiency of the cycle; (2) The flue gas recirculation enters the furnace in the form of mixing with the primary air, reduces the oxygen content of the primary air, and realizes high-temperature hot air powder feeding at the position of the coal mill, avoids irreversible loss after mixing with cold air, and improves the efficiency.

[0048] 3) The high-temperature air preheater solves the problem of stable combustion caused by flue gas recirculation and further improves the economy. The main reasons are: the high-temperature air preheater 202 preheats the secondary air temperature to above 500°C before injecting it into the furnace for combustion, ensuring stable combustion under low load under flue gas recirculation; the high-temperature air preheating utilizes the waste heat of the tail flue, reduces the exhaust gas temperature, and increases boiler efficiency.

[0049] The entire system adopts a complementary and optimized design of clean coal bins, flue gas recirculation, and high and low temperature air preheaters. The effect of this design on the entire system is far greater than the sum of the effects of using clean coal bins, flue gas recirculation, and high and low temperature air preheaters individually, achieving a "1+1+1>3" effect and solving the four key issues of stable combustion, speed, economy, and safety in flexible and deep peak shaving.

[0050] It should be noted that the technical solution of this embodiment is applicable to most boilers, such as Π-type, tower-type, four-corner tangent, counter-flow, steam boilers, supercritical carbon dioxide boilers, etc.

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0053] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0054] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "over", "above" and "on top of" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature "under", "below" and "underneath" the second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0055] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0056] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A boiler system for achieving flexible deep peak shaving, characterized in that: The system includes a coal mill (1), a burner (2), a primary air fan (3), a secondary air fan (4), a primary separator (5), a secondary separator (6), a clean coal hopper (7), an air-coal mixer (8), a waste gas fan (9), a boiler body (10), an air preheating system, and a flue gas recirculation system. The coal outlet of the coal mill (1) is connected to the primary separator (5). The primary separator (5) is connected to the burner (2) via a pipeline. The primary separator (5) is also connected to the secondary separator (6), the clean coal hopper (7), the air-coal mixer (8), and the burner (2) in sequence via pipelines. The waste gas outlet of the secondary separator (6) is connected to... The exhaust gas fan (9) and the burner (2) are mounted on the side wall of the furnace of the boiler body (10). The primary air fan (3) is connected to the air preheating system and the air-coal mixer (8) in sequence through pipelines. The primary air fan (3) is also connected to the air preheating system and the coal mill (1) in sequence through pipelines. The secondary air fan (4) is connected to the air preheating system and the burner (2) in sequence through pipelines. The flue gas inlet of the flue gas recirculation system is connected to the main flue of the boiler body (10), and its flue gas outlet is connected to the flue gas inlet of the coal mill (1), the burner (2), and the lower part of the furnace of the boiler body (10) through pipelines. The air preheating system includes a low-temperature air preheater (201) and a high-temperature air preheater (202) installed in the main flue. The low-temperature air preheater (201) has two air-side inlets, an air-side primary air outlet, and an air-side secondary air outlet. The high-temperature air preheater (202) has an air-side inlet and an air-side outlet. The primary air fan (3) is connected to one of the air-side inlets of the low-temperature air preheater (201) via a pipeline. The air-side primary air outlet of the low-temperature air preheater (201) is connected to the burner (2) and the air-coal mixer (8) via pipelines. The air-side inlet and air-side outlet of the high-temperature air preheater (202) are connected to the air-side secondary air outlet of the low-temperature air preheater (201) and the burner (2) via pipelines. The secondary air fan (4) is connected to the other air-side inlet of the low-temperature air preheater (201) via a pipeline. The flue tail end of the boiler body (10) is sequentially connected to a dust collector (40) and an induced draft fan (50). An auxiliary flue (101) is installed on the side wall of the main flue of the boiler body (10). An economizer is provided in the middle section of the flue of the boiler body (10). The auxiliary flue (101) is located at the location of the economizer and is independent of the main flue. The front end of the auxiliary flue (101) is connected to the main flue. The rear end of the auxiliary flue (101) is provided with an auxiliary flue opening connected to the main flue. A secondary flue gas baffle (103) is provided at the auxiliary flue opening. The high-temperature air preheater (202) is installed in the auxiliary flue (101) and has a flue gas inlet and a flue gas outlet that are connected to the front end and rear end of the auxiliary flue (101) respectively. The low-temperature air preheater (201) is located in the rear section of the main flue and is located behind the economizer. The flue gas recirculation system includes a recirculation fan (60). Air inlets are provided on the main flue near the secondary flue gas baffle (103), at the end of the main flue, and on the pipeline between the dust collector (40) and the induced draft fan (50). The air inlet of the recirculation fan (60) is connected to the three air inlets through three fan pipelines. The air inlet of the recirculation fan (60) constitutes the flue gas inlet of the flue gas recirculation system, and its air outlet constitutes the flue gas outlet of the flue gas recirculation system. The main flue has a main flow channel and a secondary flow channel arranged in parallel in front of the economizer. The main flow channel and the secondary flow channel are respectively provided with a main heat-receiving surface structure (51) and a secondary heat-receiving surface structure (52). A primary flue gas baffle (53) for simultaneously adjusting the flow rate of the two flues is provided at the rear end between the main flow channel and the secondary flow channel. The three fan pipelines are equipped with a first damper (61), the air side primary air outlet of the low temperature air preheater (201) is connected to the air-coal mixer (8) pipeline with a second damper (81), and the fine coal hopper (7) is connected to the air-coal mixer (8) pipeline with a control valve (62). When the unit is running at high load, the second damper (81) and control valve (62) are closed, the exhaust gas fan (9) is running, and the clean coal hopper (7) begins to store the clean coal powder provided by the secondary separator (6); when the unit load decreases, the angle of the burner (2) and the primary flue gas damper (53) are adjusted to bring the main / reheat steam temperature to the rated value; when the unit load decreases further, the air volume of the recirculation fan (60) is adjusted to bring the main / reheat steam temperature to the rated value; when the unit load is below 40%, the second damper (81) and control valve (62) are closed. When the unit load is increased, the direct coal supply of the primary separator (5) decreases, and the burner (2) begins to mix in fine coal powder for combustion. When the unit load is less than 40%, the secondary flue gas damper (103) is adjusted so that the secondary air temperature at the flue gas outlet of the high-temperature air preheater (202) reaches 400-600℃. When the unit load increases rapidly, the second damper (81) and control valve (62) are opened to ensure that the increase in coal powder heat matches the rate of load increase. After the load stabilizes, the coal supply of the fine coal hopper (7) is gradually reduced to increase the direct coal supply from the primary separator (5).

2. The boiler system for flexible deep peak shaving according to claim 1, characterized in that: It also includes a coal feeding system (30) connected to the coal inlet of the coal mill (1).

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