CN111947133A

CN111947133A - Boiler, combustion system thereof and use method

Info

Publication number: CN111947133A
Application number: CN202010899741.3A
Authority: CN
Inventors: 赵振宁; 程通锐; 李金晶; 李媛园
Original assignee: State Grid Corp of China SGCC; North China Electric Power Research Institute Co Ltd
Current assignee: State Grid Corp of China SGCC; North China Electric Power Research Institute Co Ltd
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2020-11-17
Anticipated expiration: 2040-08-31
Also published as: CN111947133B

Abstract

The invention discloses a boiler and a combustion system and a using method thereof, wherein the system comprises: the device comprises a separator, a primary air-powder pipeline, a waste gas utilization pipeline and a multi-layer thick and thin combustor; the separator includes: the separation body is provided with an inlet communicated with the primary air powder pipeline, a first outlet communicated with the multi-layer thick and thin combustor and a second outlet communicated with the exhaust gas utilization pipeline; the multi-layer thick and thin burner comprises: the gas-solid separation device comprises a communication mechanism with a gas-solid separation function, a plurality of isolated circulation cavities and an adjusting piece, wherein one end of the communication mechanism is communicated with a first outlet, the communication mechanism is communicated with the other end of the communication mechanism, the adjusting piece is arranged along the gravity direction, and at least part of the adjusting piece is positioned in the circulation cavities; the exhaust gas utilization pipeline comprises a first exhaust gas outlet valve used for controlling the on-off of the exhaust gas utilization pipeline. The invention can flexibly adjust the concentration of the pulverized coal according to the load requirement and ensure the stable combustion property of the combustor.

Description

Boiler, combustion system thereof and use method

Technical Field

The invention relates to the technical field of pulverized coal combustion, in particular to a boiler, a combustion system and a using method thereof.

Background

At present, thermal power generating units in China have the characteristics of surplus structural performance and higher flexible operation requirements. For this reason, many thermal power plants have to consider the stable combustion performance of the boiler at low load and ultra-low load of the unit.

The thermal power generating unit largely adopts a direct-current pulverized coal burner. Specifically, one coal mill is provided with four burners in one layer. When the coal pulverizer is used, the combustors and the coal mills are arranged in multiple layers, and the change of load can be adapted by switching one or more layers of the coal mills and the combustors.

However, the inventors found that: the existing technology for adjusting the layer number of the switching coal mill and the burner is restricted by the requirement of a primary air pipe on primary air speed. The main reasons are: in order to keep the coal dust carried by the primary air from depositing, the primary air velocity must be greater than a critical value. When the load of the unit is reduced, the flow rate of the pulverized coal and the primary wind speed are required to be reduced simultaneously according to the requirement of combustion. However, the primary wind speed threshold value is limited such that the wind speed cannot be reduced after the wind speed is reduced to the threshold value, that is, the primary wind speed is always required to be greater than or equal to the threshold wind speed. Under the condition that the primary air speed can not be reduced any more, the primary air volume ratio (air volume/(air volume + pulverized coal volume)) is higher and higher along with the reduction of the pulverized coal flow, so that the flameout of a burner is easily caused, namely, the ignition and combustion stabilizing performance is reduced, and even the environmental protection performance is gradually reduced due to the increase of NOx emission. In general, the lower limit of the performance of the burner (including ignition stability and environmental protection) limits the peak shaving depth of the boiler load. For a peak shaving unit, the peak shaving capacity of the peak shaving unit is limited by the adaptability of a boiler to high and low loads, and the lowest operation load is one of the most important indexes of the unit peak shaving.

In the history of burner technology development, a PM burner, a wide turn ratio pulverized coal burner and an A-PM burner have appeared, and the lower limit of load adjustment can be reduced to a certain extent. However, such adjustment techniques belong to passive adjustment, the passively adjusted burners still appear to be insufficient in the load variation range of the current thermal power generating unit, and the performance lower limit of a single burner still limits the peak shaving depth of the boiler load.

At present, Chinese patent CN108413387A provides a bidirectional double-staged combustion technology for pulverized coal fired boilers. The technology adds a baffle plate for adjusting the flow area on a thick-thin type combustor, and improves the low-load stable combustion capacity of the boiler. However, the inventors have found through analysis that the patent has the following disadvantages: through setting up the baffle after, not only do not reduce the percentage of once the amount of wind, owing to reduced the flow cross section area, can lead to the wind speed to increase substantially moreover, make the steady ability of burning of combustor worse on the whole.

Disclosure of Invention

In order to overcome at least one defect in the prior art, the invention provides a boiler, a combustion system and a using method thereof, which can flexibly adjust the concentration of pulverized coal according to load requirements and ensure the stable combustion of a combustor.

The above object of the present invention can be achieved by the following technical solutions:

a combustion system, comprising: the device comprises a separator, a primary air-powder pipeline, a waste gas utilization pipeline and a multi-layer thick and thin combustor;

the separator includes: the separation body is provided with an inlet communicated with the primary air powder pipeline, a first outlet communicated with the multilayer thick and thin burner and a second outlet communicated with the exhaust gas utilization pipeline;

the multi-layer thick and thin burner includes: the communicating mechanism is provided with a gas-solid separation function, one end of the communicating mechanism is communicated with the first outlet, the communicating mechanism is communicated with the other end of the communicating mechanism, a plurality of isolated circulation cavities are arranged along the gravity direction, and the adjusting piece is at least partially positioned in the circulation cavities and can at least adjust the circulation area of the uppermost circulation cavity of the multilayer shade burner;

the exhaust gas utilization pipeline comprises a first exhaust gas outlet valve used for controlling the on-off of the exhaust gas utilization pipeline, and when the first exhaust gas outlet valve is in an open state, part of air powder separated by the separator flows through the exhaust gas utilization pipeline and can flow to the hearth.

Further, the exhaust gas utilization line comprises a main line section connected to the second outlet of the separator, the first exhaust gas outlet valve is disposed on the main line section along an exhaust gas flow path, and the exhaust gas utilization line further comprises at least one branch line capable of directly or indirectly introducing exhaust gas into the furnace.

Furthermore, the branch pipe comprises an exhaust gas recirculation branch pipe communicated with the main pipe section, one end of the exhaust gas recirculation branch pipe is connected with the main pipe section, the other end of the exhaust gas recirculation branch pipe is connected to the uppermost circulation cavity of the multilayer shade burner, and the connection position of the exhaust gas recirculation branch pipe and the circulation cavity is located at the downstream of the adjusting part.

Furthermore, the branch pipe comprises an exhaust gas guide branch pipe communicated with the main pipe section, one section of the exhaust gas guide branch pipe is connected with the main pipe section, and the other end of the exhaust gas guide branch pipe is an exhaust gas direct-combustion nozzle used for guiding exhaust gas to the hearth.

Further, the communicating mechanism is arranged at a turning inlet section between the first outlet of the separator and the inlet of the multilayer thick-thin combustor, the whole flowing cavity of the separator extends along the horizontal direction, and a preset included angle is formed between the whole extending direction of the turning inlet section and the horizontal direction.

Furthermore, the combustion system also comprises a secondary air main path and a secondary air branch path communicated with the secondary air main path, and the outlet end of the secondary air main path is a secondary air nozzle; one end of the secondary air branch is communicated with the secondary air main path, and the other end of the secondary air branch is at least communicated with the circulation cavity of the multi-layer thick and thin burner which is positioned at the lowest part.

Furthermore, a mixer is arranged in the main secondary air path, a secondary air nozzle is arranged at the tail end of the main secondary air path, an extension section extending to the mixer is arranged at one end, far away from the separator, of the main tube section, a second exhaust gas outlet valve is arranged on the extension section, and when the second exhaust gas outlet valve is opened, exhaust gas entering the mixer from the main tube section and the extension section and wind energy entering the mixer from the main secondary air path are mixed and then are sprayed to a hearth through the secondary air nozzle of the main secondary air path.

Further, the thick and thin combustor of multilayer is including being located the utmost point dilute phase layer of the top, and being located the dilute phase layer of utmost point dilute phase layer below, utmost point dilute phase layer with be provided with the separator between the dilute phase layer at the juncture that is close to the spout.

Furthermore, a first safety valve is arranged on the exhaust gas recirculation branch pipe and close to the multilayer thick and thin combustor, and a first switch valve is arranged between the first safety valve and the main pipe section.

A boiler, comprising: a plurality of coal mills, at least one outlet for the grinding media being connected to a combustion system as described in any of the above.

A use method based on the boiler comprises the following steps:

when the power generation load is higher than a first preset value, the input of fuel quantity and the flow of primary air and secondary air are adjusted by adjusting the output of the grinding machine and the air quantity of the fan so as to match the load of the unit;

when the power generation load is higher than the second preset value and lower than the first preset value, adjusting the output of the grinding machine, and adjusting the regulating member of the thick-thin multi-layer combustor and the exhaust air volume proportion of the first outlet and the second outlet of the separator to match the load of the machine set;

and when the power generation load is lower than a second preset value, adjusting the using number of the coal mills, the number of layers of the burners and the flow of primary air and secondary air in corresponding proportion to match the load of the unit.

The combustion system that provides in the embodiment of this application, during the use, the primary air powder flows to the separator through the primary air powder pipeline, and the very low wind powder of buggy content is isolated as the exhaust gas. After the part of air powder with very low coal powder content is separated from the primary air powder, the air volume ratio can be effectively reduced. In addition, the flow area of the air powder is not directly reduced, so that the flow velocity of the air powder cannot be increased, and the stable combustion performance of the multilayer thick-thin combustor cannot be influenced.

The concentrated coal powder airflow of the separator flows through the turning inlet section with a certain inclination angle and is respectively led into the flow cavities corresponding to the multi-layer shade separation burner according to the difference of concentration, wherein an extremely dilute phase layer of the multi-layer shade separation burner is provided with an adjusting piece (baffle) for adjusting the flow area, and the adjusting piece is used for adjusting the flow area under the condition of low load, so that the flow speed of gas-solid two-phase flow at a nozzle of the burner and the rigidity of flame can be kept, and the burning effect is improved.

In addition, an exhaust gas guide branch pipe is communicated with the downstream of the baffle plate in an extremely dilute phase layer of the multi-level dense-dilute combustor; when the unit is in low load, a part of exhaust gas separated by the separator returns to the uppermost circulation cavity through the exhaust gas recirculation branch pipe for purging the corresponding circulation cavity and reburning the exhaust gas, and meanwhile, the jetted exhaust gas can generate acting force on flame jetted from an adjacent area to prevent the flame of the adjacent area from backfiring to the uppermost circulation cavity (extremely dilute phase layer).

And a secondary air branch inlet is also arranged on the wall surface of the turning section facing the concentrated phase layer. The secondary air is introduced into the concentrated phase layer through the secondary air branch, so that the problems that the concentration of the pulverized coal on the concentrated phase layer is too high, the deposition and the combustion are insufficient in a circulation cavity and the like can be prevented.

Drawings

The invention is further described with reference to the following figures and embodiments.

FIG. 1 is a schematic illustration of a combustion system according to an embodiment of the present disclosure;

FIG. 2 is a schematic block diagram of another combustion system provided in an embodiment of the present application;

FIG. 3 is a flow chart illustrating steps of a method for using a boiler according to an embodiment of the present disclosure.

Description of reference numerals:

1. a primary air-powder pipeline;

2. a separator;

3. a turn entrance section;

4. a multi-layer thick and thin burner; 40. a primary air nozzle; 41. a concentrated phase layer; 42. a dilute phase layer; 43. a very dilute phase layer;

5. a baffle plate;

6. an exhaust gas recirculation branch;

7. a first on-off valve;

8. a first safety valve;

9. a waste gas guide branch pipe; 90. the exhaust gas directly burns the spout; 91. a second on-off valve;

10. a mixer;

11. a secondary air main road;

12. a secondary air nozzle;

13. a secondary air branch;

14. a second relief valve;

15. a third on-off valve;

16. a first exhaust gas outlet valve;

17. a second exhaust gas outlet valve.

Detailed Description

The technical solutions of the present invention will be described in detail with reference to the accompanying drawings and specific embodiments, it should be understood that these embodiments are merely illustrative of the present invention and are not intended to limit the scope of the present invention, and various equivalent modifications of the present invention by those skilled in the art after reading the present invention fall within the scope of the appended claims.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1 to fig. 2, in the embodiments of the present disclosure, a combustion system is provided, which can be applied to the field of combustion of a gas-solid two-phase mixed fluid, such as pulverized coal combustion, but the combustion system can also be applied to other situations of gas-solid two-phase mixed fluid. In the present application, pulverized coal combustion is taken as an example for illustration, and other scenarios can be referred to by analogy, and the present application is not illustrated one by one.

The combustion system provided by the present application generally includes: a separator 2, a primary air-powder pipeline 1, a waste gas utilization pipeline and a multi-layer thick and thin combustor 4.

In the present embodiment, the separator 2 may include: separating the body. The separation body is provided with an inlet communicated with the primary air-powder pipeline 1, a first outlet communicated with the multilayer thick-thin combustor 4 and a second outlet communicated with the exhaust gas utilization pipeline.

In particular, the separator 2 may be in the form of: cyclone separator 2, louver separator 2, trough separator 2, etc. Wherein, the cyclone separator 2 has very good separation function and can even completely separate the gas-solid two-phase flow. Since in this application it is not necessary to completely separate the gas and solid phases, the present invention is not so applicable to cyclone separators 2 that have too good a separation effect. The separating effect of the louvered separator 2 is inferior to that of the cyclone separator 2. After entering the shutter separator 2, the gas-solid two-phase flow (i.e. pulverized coal and air) can be divided into different fluids according to the content of solid particles, for example, can be divided into two streams of dilute phase fluid and concentrated phase fluid; and the concentrated phase is not too concentrated (too high a solid particle content). Because the coal powder is difficult to burn due to oxygen deficiency caused by over-concentration. Preferably, the air volume ratio of the first outlet and the second outlet of the separator 2 can be adjusted according to the requirement, so as to better use the requirement of the load adjustment of the unit.

In the present embodiment, the primary air-powder pipeline 1 is connected to the inlet of the separator 2 at one end and to the coal mill outlet at the other end, so that the primary air-powder flowing out from the coal mill outlet is introduced into the separator 2.

In the present embodiment, the multi-layer rich-lean burner 4 may include: a communicating mechanism with the gas-solid separation function. One end of the communicating mechanism is communicated with the first outlet, the other end of the communicating mechanism is communicated with the communicating mechanism and is provided with a plurality of isolated circulation cavities along the gravity direction, and at least part of the communicating mechanism is positioned on the regulating part of the circulation cavities, and the regulating part can at least regulate the flow area of the uppermost circulation cavity of the multilayer shade burner 4.

The multilayer thick and thin combustor 4 can be communicated with the first outlet of the separator 2 through a communication mechanism with a gas-solid separation function, so that gas-solid fluid flowing out of the first outlet of the separator 2 is layered according to different solid particle concentrations and is guided into corresponding circulation cavities. For example, a turning inlet section 3 is arranged between the first outlet of the separator 2 and the inlet of the multi-layer thick-thin burner 4, the whole flow-through cavity of the separator 2 extends along the horizontal direction, and a predetermined included angle is formed between the whole extending direction of the turning inlet section 3 and the horizontal direction. The size of the preset included angle can be correspondingly designed according to specific use requirements, and the turning inlet section 3 with the preset included angle is arranged to ensure that the proportion of the pulverized coal and the wind is sequentially increased along the gravity direction when the pulverized coal enters each isolated circulation cavity, and prevent the concentration of the pulverized coal in the circulation cavity at a lower position from being too high.

The number of the specific layers (i.e. the number of the flow-through cavities) of the multi-layer thick and thin burner 4 can be adaptively designed according to the actual use requirement, and can be, for example, 2 layers, 3 layers or even more. As shown in fig. 1 or fig. 2, the multi-layer gradation burner 4 may include, along the gravity direction: extremely dilute phase layer 43, dilute phase layer 42, and concentrated phase layer 41. The inlet end of each layer of circulation cavity is connected with the turning inlet section 3 and used for receiving the air powder separated by the turning inlet section 3, and the outlet end is provided with a primary air nozzle 40 and used for spraying the air powder to the hearth for combustion.

In the present embodiment, an adjusting member may be provided in at least a part of the flow-through chamber of the multi-layer rich-lean burner 4. The adjusting piece can at least adjust the flow area of the uppermost flow cavity of the multi-layer thick and thin burner 4. For example, as shown in fig. 1 or fig. 2, the adjusting member may be movably disposed in the extremely dilute phase layer 43. Of course, in other embodiments, it is not excluded that the adjusting member can be movably arranged in both the extremely dilute phase layer 43 and the dilute phase layer 42. In particular, the adjustment member may be in the form of a baffle 5. The baffle 5 is movably arranged in the flow-through chamber to change the flow-through area of the flow-through chamber. Specifically, the multi-layer thick and thin burner 4 can be further provided with a driving mechanism for driving the baffle 5, and when the number of the circulation cavities needs to be reduced, the position of the baffle 5 can be changed through the driving mechanism, so that the circulation cavities can be blocked. The driving mechanism may drive the baffle 5 by rotating or moving, and the specific structure and driving manner of the driving mechanism are not limited in this application.

In this embodiment, the exhaust gas utilization circuit includes a first exhaust gas outlet valve 16 for controlling the opening and closing of the exhaust gas utilization circuit. When the first control valve is in an open state, part of the air powder separated by the separator 2 can flow to the hearth through the exhaust gas utilization pipeline.

The gas stream separated by the separator 2 is referred to as off-gas. The part of the air flow is air powder with very low coal dust content obtained by separating primary air powder through the separator 2. After a part of air powder with very high coal powder content is separated from the primary air powder, the air volume ratio can be effectively reduced. In addition, the flow area of the wind powder is not directly reduced, so that the flow velocity of the wind powder is not increased.

In one embodiment, the waste gas utilization line may comprise a primary waste gas pipe section connected to the second outlet of the separator 2. The first exhaust gas outlet valve 16 is arranged on the main exhaust gas pipe section and is used for controlling the opening and closing of the main exhaust gas pipe section. Along the exhaust gas flow path, the exhaust gas utilization line further comprises at least one branch which can direct exhaust gas directly or indirectly into the furnace.

Wherein for embodiments in which the branch indirectly conducts exhaust gas to the furnace, the branch comprises an exhaust gas recirculation branch 6 communicating with the main segment. One end of the exhaust gas recirculation branch pipe 6 is connected with the main pipe section, and the other end of the exhaust gas recirculation branch pipe is connected to the uppermost circulation cavity of the multilayer thick-thin combustor 4.

At low load of the unit, a part of the exhaust gas separated by the separator 2 is returned to the uppermost circulation cavity through the exhaust gas recirculation branch pipe 6, for example, as the extremely-lean layer 43 in fig. 1 or fig. 2, for purging the extremely-lean layer 43 and re-combusting the exhaust gas, and the injected exhaust gas can generate force on the flame injected from the adjacent region (for example, the rich layer 41 and the primary air nozzle 40 of the lean layer 42) to prevent the flame from being tempered to the extremely-lean layer 43.

Two valves are arranged on the exhaust gas recirculation pipeline. Wherein, the valve close to the multilayer rich-lean burner 4 is a first safety valve 8, and the first safety valve 8 can be specifically a stop valve or a check valve for intercepting fluid and even preventing backflow of pulverized coal. The valve far away from the multi-layer thick and thin combustor 4 is a first switch valve 7 which is mainly used for controlling the on-off of the exhaust gas recirculation pipeline. Of course, the first on-off valve 7 is not limited in this application, and may be an electric on-off valve that is automatically opened or closed upon receiving an electric control signal, or a manually adjustable on-off valve that is operated to adjust the flow area of the exhaust gas recirculation line.

In the embodiment where the branch ducts direct the exhaust gas into the furnace, the branch ducts comprise exhaust gas guiding branch ducts 9 communicating with the main duct section. One section of the exhaust gas guide branch pipe 9 is connected with the main pipe section, and the other end of the exhaust gas guide branch pipe is an exhaust gas direct-combustion nozzle 90 for guiding exhaust gas to the hearth. The exhaust gas guide branch pipe 9 is provided with a second switch valve 91, and the second switch valve 91 is mainly used for controlling the on-off of the exhaust gas guide branch pipe 9. Specifically, the form of the second on-off valve 91 may refer to the form of the first on-off valve 7, and the present application is not limited thereto.

In one embodiment, the combustion system further comprises: a secondary air main path 11 and a secondary air branch 13 communicated with the secondary air main path 11. The outlet end of the secondary air main path 11 is a secondary air nozzle 12; one end of the secondary air branch 13 is communicated with the secondary air main path 11, and the other end is at least communicated with the lowest circulation cavity of the multi-layer thick and thin burner 4.

Two valves may also be provided on the secondary air branch 13. Wherein, the valve close to the multi-layer rich-lean burner 4 is a second safety valve 14, and the second safety valve 14 can be specifically a stop valve or a check valve for intercepting fluid and even preventing backflow of pulverized coal. The valve far away from the multi-layer thick and thin burner 4 is a third on-off valve 15 which is mainly used for controlling the on-off of the secondary air branch 13. Of course, the third on-off valve 15 is not limited in the present application, and may be an electric on-off valve that is automatically opened or closed upon receiving an electric control signal, or a manually adjustable on-off valve that can be operated to adjust the flow area of the exhaust gas recirculation line.

Preferably, the third on/off valve 15 is an opening-adjustable regulating valve. The secondary air flows to the secondary air nozzle 12 through the secondary air main path 11, and the secondary air branch 13 can lead the secondary air to an adjusting valve near a flow cavity (such as a dense-phase layer 41) with high pulverized coal concentration of the multi-layer rich-lean combustor 4, and lead air with a certain flow rate into the corresponding flow cavity (such as a dense-phase layer 41) through the opening and closing state or opening degree adjustment of the adjusting valve, so that the secondary air is used for adjusting the pulverized coal concentration of the dense-phase layer 41, and the pulverized coal concentration of the dense-phase layer 41 is prevented from being too high, and the secondary air is prevented from being deposited and combusted insufficiently in the flow cavity.

As shown in fig. 2, in one embodiment, a mixer 10 is provided in the main secondary wind path 11. The tail end of the secondary air main pipeline 11 is provided with a secondary air nozzle 12, one end of the main pipeline section, which is far away from the separator 2, is provided with an extension section which extends to the mixer 10, and the extension section is provided with a second exhaust gas outlet valve 17. When the second exhaust gas outlet valve 17 is opened, the exhaust gas entering the mixer 10 from the main pipe section and the extension section is mixed with the wind energy entering the mixer 10 from the secondary air main path 11 and then is sprayed to the hearth through the secondary air nozzle 12 of the secondary air main path 11.

In the embodiment, the separator 2 separates primary air powder, the separated exhaust gas in an extremely dilute phase state during coal powder concentration has 3 flow directions, one flow direction is led to the exhaust gas recirculation branch pipe 6 and returns to the extremely dilute phase layer 43 at the downstream of the adjusting baffle 5 of the multi-layer thick and thin combustor 4, the other flow direction is led to the exhaust gas direct combustion nozzle 90 through the exhaust gas guide branch pipe 9, and the other flow direction is mixed with secondary air through the mixer 10 and flows to the secondary air nozzle 12. The branch of the exhaust extending section where the exhaust guide branch pipe 9 and the mixer 10 are located is two different flow paths of exhaust, and when the exhaust guide branch pipe is used, one branch can be selectively opened according to needs so as to convey redundant exhaust to a hearth.

In one embodiment, the multi-layered rich-lean burner 4 includes an uppermost extremely dilute-phase layer 43 and a dilute-phase layer 42 below the extremely dilute-phase layer 43, and a separator is disposed between the extremely dilute-phase layer 43 and the dilute-phase layer 42 at a boundary near the nozzle.

In the present embodiment, taking the multi-layer rich-lean burner 4 as an example of a three-layer rich-lean burner, a single separator may be provided at the boundary between the outlets of the extremely-dilute-phase layer 43 and the dilute-phase layer 42. The separating piece is mainly used for preventing flame sprayed by burning of the concentrated phase and the dilute phase from channeling to the extremely dilute phase nozzle and burning out the extremely dilute phase nozzle. In addition, the separating piece can also be used for preventing the flue gas from flowing back and improving the stable combustion performance. Specifically, the separating member may be in the form of a Y-shaped separating cone, and of course, the separating member may also be in other forms, and the application is not limited in particular.

When the device is used, primary air powder at the outlet of the coal mill flows to the separator 2 through the primary air powder pipeline 1, and air powder with very low coal powder content is separated out as exhaust gas. After a part of air powder with very high coal powder content is separated from the primary air powder, the air volume ratio can be effectively reduced. In addition, the flow area of the air powder is not directly reduced, so that the flow velocity of the air powder cannot be increased, and the stable combustion performance of the multilayer thick and thin combustor 4 cannot be influenced.

The concentrated coal powder airflow of the separator 2 flows through the turning inlet section 3 with a certain inclination angle and is respectively led into the flow cavities corresponding to the multi-layer shade separation burners according to the difference of concentration, wherein an extremely dilute phase layer 43 of the multi-layer shade separation burners 4 is provided with an adjusting piece (baffle 5) for adjusting the flow area, and the adjusting piece is used for adjusting the flow area under low load, so that the flow speed of gas-solid two-phase flow at the nozzle of the burner and the rigidity of flame can be kept, and the stable combustion capacity and the combustion effect of the boiler can be improved. In addition, an exhaust gas guiding branch pipe 9 is communicated with the extremely dilute phase layer 43 of the multi-layer thick and thin burner 4 and is positioned at the downstream of the baffle 5; at low load of the unit, a part of the exhaust gas separated by the separator 2 is returned to the uppermost circulation cavity through the exhaust gas recirculation branch pipe 6, for example, as the extremely-lean layer 43 in fig. 1 or fig. 2, for purging the extremely-lean layer 43 and re-combusting the exhaust gas, and the injected exhaust gas can generate force on the flame injected from the adjacent region (for example, the rich layer 41 and the primary air nozzle 40 of the lean layer 42) to prevent the flame from being tempered to the extremely-lean layer 43.

On the wall of the turning section facing the concentrated phase layer 41, there is also a secondary air branch 13 inlet. The secondary air is introduced into the concentrated phase layer 41 through the secondary air branch 13, so that the problems that the concentration of the pulverized coal of the concentrated phase layer 41 is too high, the deposition and the combustion are insufficient in a circulation cavity and the like can be solved.

Based on the combustion system provided in the above embodiment of the present application, the present application also provides a boiler provided with the above combustion system. The boiler is also provided with a plurality of coal mills. Each coal mill may be provided with the combustion system of the above embodiment, and in addition, the combustion system may also be provided for several coal mills, and the specific configuration of the combustion system may be selected and set according to the unit load condition, which is not limited in this application.

The utility model provides a be provided with this combustion system's boiler can be better adapt to the operating mode of unit low-load to boiler load's peak shaver degree of depth has been enlarged.

When the load of the unit is reduced, the output of the coal mill can be reduced firstly; in addition, the reduction of ignition heat requirement, the improvement of volatile component concentration and the enhancement of local heat release intensity can be passively realized in a small range through the multi-layer thick and thin combustor 4, so that the stable combustion of the combustor is passively realized; furthermore, the opening degree of the multilayer thick and thin burner 4 can be adjusted by adjusting the baffle 5 of the multilayer thick and thin burner 4, and a part of redundant primary air is separated by the separator 2 and the exhaust gas by the exhaust gas recirculation branch pipe 6, the exhaust gas guide branch pipe 9 and the mixer 10, and the load reduction requirement of reducing the coal burning quantity is continuously matched; when the unit load continues to decrease, the fuel regulation requirement under low load can be achieved by reducing the number of coal mills and the number of corresponding burners.

On the whole, the combustion system can passively adapt to the reduction of load within a small range through the multi-layer thick and thin combustor 4, and on the other hand, the stable combustion performance of the combustion system can be actively adjusted through the baffle 5 and the exhaust gas recirculation branch pipe 6, the exhaust gas guide branch pipe 9 and the mixer 10 of the multi-layer thick and thin combustor 4, so that the reduction of unit load can be adapted in an active and passive level.

As shown in fig. 3, based on the boiler provided in the embodiment of the present application, the present application also provides a using method of the boiler, which may include the following steps:

step S10: when the power generation load is higher than a first preset value, the input of fuel quantity and the flow of primary air and secondary air are adjusted by adjusting the output of the grinding machine and the air quantity of the fan so as to match the load of the unit;

step S12: when the power generation load is lower than a second preset value, adjusting the output of the grinding machine, and adjusting the adjusting piece of the thick-thin multi-layer combustor and/or the exhaust air volume ratio of a first outlet and a second outlet of the separator 2, wherein the first preset value is larger than the second preset value;

step S14: and when the power generation load is lower than a third preset value, adjusting the using number of the coal mills, the number of layers of the burners and the flow of primary air and secondary air in corresponding proportion to match the unit load, wherein the third preset value is smaller than the second preset value.

In the present embodiment, when the power generation load is high, higher than the first preset value, the input of the fuel amount may be adjusted by first considering the adjustment of the output of each coal mill. Specifically, the first preset value may be determined comprehensively according to the adjustment capability of the coal mill output, the lower limit of the primary wind speed, and the like after practice, and the value is not specifically limited in this application. For example, the first preset value may be 70%.

In the present embodiment, when the power generation load is reduced to a certain degree, for example, higher than the first preset value and higher than the second preset value, and the lower limit of the primary wind speed is influenced, the load-variable adaptive adjustment can be performed by adjusting the baffle 5 of the extremely dilute phase of the rich-lean multi-layer combustor and adjusting the ratio of the exhaust air volume of the first outlet and the second outlet of the separator 2; the specific value of the second preset value can be comprehensively determined according to specific scenes.

In the present embodiment, when the power generation load is lower than the second preset value, for example, to a value close to the lower limit of the use of the multi-layer rich-lean burner 4, the load variation adjustment is performed by adjusting the number of coal mills used and the number of burners.

On the whole, to the power generation load condition of difference, adjust through above-mentioned three kinds of modes, the operating mode of adaptation unit low-load that can be better to boiler load's peak shaver degree of depth has been enlarged.

It should be noted that, in the description of the present application, the terms "first", "second", and the like are used for descriptive purposes only and for distinguishing similar objects, and no precedence between the two is intended or should be construed to indicate or imply relative importance. In addition, in the description of the present application, "a plurality" means two or more unless otherwise specified.

The above embodiments in the present specification are all described in a progressive manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment is described with emphasis on being different from other embodiments.

The above description is only a few embodiments of the present invention, and although the embodiments of the present invention are described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A combustion system, comprising: the device comprises a separator, a primary air-powder pipeline, a waste gas utilization pipeline and a multi-layer thick and thin combustor;

2. The combustion system of claim 1, wherein the exhaust gas utilization conduit comprises a main conduit section connected to the second outlet of the separator, the first exhaust gas outlet valve being disposed on the main conduit section along an exhaust gas flow path, the exhaust gas utilization conduit further comprising at least one branch conduit capable of directing exhaust gas directly or indirectly into the furnace.

3. The combustion system of claim 2, wherein the branch pipe comprises an exhaust gas recirculation branch pipe communicated with the main pipe section, one end of the exhaust gas recirculation branch pipe is connected with the main pipe section, the other end of the exhaust gas recirculation branch pipe is connected to the uppermost circulation cavity of the multi-layer thick-thin burner, and the connection position of the exhaust gas recirculation branch pipe and the circulation cavity is located at the downstream of the adjusting member.

4. The combustion system of claim 2, wherein the branch pipe comprises a waste gas guide branch pipe communicated with the main pipe section, one section of the waste gas guide branch pipe is connected with the main pipe section, and the other end of the waste gas guide branch pipe is a waste gas direct-fired nozzle for guiding waste gas to the hearth.

5. The combustion system of claim 1, wherein the communication mechanism is a turning inlet section disposed between the first outlet of the separator and the inlet of the multi-layer burner, the flow-through cavity of the separator extends entirely along a horizontal direction, and the turning inlet section extends entirely at a predetermined angle from the horizontal direction.

6. The combustion system of claim 2 further comprising a main overfire air path and an overfire air branch communicating with said main overfire air path, said main overfire air path having an outlet end in the form of an overfire air jet;

one end of the secondary air branch is communicated with the secondary air main path, and the other end of the secondary air branch is at least communicated with the circulation cavity of the multi-layer thick and thin burner which is positioned at the lowest part.

7. The combustion system of claim 6, wherein a mixer is arranged in the main secondary air path, the end of the main secondary air path is a secondary air nozzle, an extension section extending to the mixer is arranged at the end of the main section far away from the separator, a second ventilation air outlet valve is arranged on the extension section, and when the second ventilation air outlet valve is opened, the ventilation air entering the mixer from the main section and the extension section is mixed with the wind energy entering the mixer from the main secondary air path and then is sprayed to the furnace cavity through the secondary air nozzle of the main secondary air path.

8. The combustion system of claim 6, wherein the multi-layered lean burner includes an uppermost very lean layer and a lean layer below the very lean layer, and a separator is disposed between the very lean layer and the lean layer at an interface near the ports.

9. The combustion system of claim 3, wherein a first relief valve is disposed in the exhaust gas recirculation branch adjacent the multi-stage lean burner, and a first on-off valve is disposed between the first relief valve and the main pipe section.

10. A boiler, characterized in that it comprises: a plurality of coal mills, at least one outlet for abrasive being connected to a combustion system according to any of claims 1 to 9.

11. A method for using the boiler according to claim 10, comprising: