Circulating fluidized bed boiler system with sorting and feeding unit and control method of circulating fluidized bed boiler system

Abstract

The invention relates to a circulating fluidized bed boiler system with a sorting and feeding unit, comprising: a circulating fluidized bed boiler comprising a hearth, a first separator and a return feeder which are in pairwise communication, the return feeder is communicated with a dense-phase region or a corresponding region of the hearth through a return pipe, and the hearth is provided with a fuel supply inlet and a conventional fluidized air inlet; the sorting and feeding unit is suitable for sorting fuel into first fuel in a first particle size range and second fuel in a second particle size range, the first particle size range is larger than the second particle size range, the first fuel is suitable for being introduced into a fuel supply inlet, and the second fuel is suitable for being introduced into a peak regulation feeding opening of the circulating fluidized bed boiler based on pneumatic conveying. The invention further relates to a control method of the circulating fluidized bed boiler system.

Description

Technical Field

[0001] The invention relates to the technical field of combustion equipment, in particular to a circulating fluidized bed boiler system with a sorting feeding unit and a control method for the circulating fluidized bed boiler system. Background Art

[0002] The circulating fluidized bed (CFB) boiler is a type of coal clean combustion utilization equipment with a large operating adjustment range, stable combustion, and low pollutant emission levels. However, there is also a problem of large thermal inertia, which leads to a slow rate of load change. When the CFB boiler is operated for peak load regulation or in conjunction with the variable process of industrial production, especially when the load is less than 30% (this data is not absolute and may fluctuate up and down depending on the specific situation of the boiler), there is an operating risk. At low load, the amount of circulating material in the furnace is reduced, the bed temperature is difficult to maintain, the heat load of the furnace cross section is greatly reduced, and the hydrodynamic safety of the working fluid in the heating surface is at risk. Therefore, the depth of low-load operation is difficult to continue to explore, and it is impossible to adapt to the needs of new power systems that accept renewable energy on a large scale.

[0003] High-temperature bed is the key to maintaining stable operation of circulating fluidized bed boilers. On the one hand, when circulating fluidized bed boilers are running at ultra-low load, a large amount of fluidizing air needs to be introduced to ensure fluidization. However, the amount of fuel is small, the material circulation volume is small, and the combustion rate of granular coal is slow, resulting in the fluidizing air taking away more bed heat than the supplementary bed heat. Therefore, it is often difficult to maintain the bed temperature, which limits the low-load stable operation of the CFB boiler. Summary of the invention

[0004] The present invention is proposed to solve or alleviate at least one aspect of the technical problems in the prior art.

[0005] According to an embodiment of the present invention, a circulating fluidized bed boiler system is proposed, comprising:

[0006] A circulating fluidized bed boiler comprises a furnace, a first separator and a returner which are connected in pairs, the returner is connected to a dense phase area or a corresponding area of ​​the furnace via a return pipe, and the furnace is provided with a fuel supply inlet and a conventional fluidizing air inlet; and

[0007] The sorting feeding unit is suitable for sorting fuel into a first fuel in a first particle size range and a second fuel in a second particle size range, the first particle size range is larger than the second particle size range, the first fuel is suitable for being introduced into a fuel supply inlet, and the second fuel is suitable for being introduced into a peak-shaving feeding port of a circulating fluidized bed boiler based on pneumatic conveying.

[0008] According to another aspect of an embodiment of the present invention, a control method for a circulating fluidized bed boiler system is proposed, the boiler system comprising: a circulating fluidized bed boiler, comprising a furnace, a first separator and a returner connected in pairs, the returner communicating with a dense phase area or a corresponding area of ​​the furnace via a return pipe, the furnace being provided with a fuel supply inlet and a conventional fluidizing air inlet; and a sorting and feeding unit, adapted to sort the fuel into a first fuel in a first particle size range and a second fuel in a second particle size range, the first particle size range being larger than the second particle size range, the method comprising the steps of:

[0009] The first fuel is introduced into the fuel supply inlet, and the second fuel is introduced into the peak-shaving feed port of the circulating fluidized bed boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following description and accompanying drawings may better help understand these and other features and advantages of various embodiments disclosed by the present invention, in which the same reference numerals always represent the same components, wherein:

[0011] Figure 1 A schematic structural diagram of a sorting and feeding unit of a circulating fluidized bed boiler system according to an exemplary embodiment of the present invention;

[0012] Figure 2 A schematic structural diagram of a circulating fluidized bed boiler system according to an exemplary embodiment of the present invention, wherein the position of a peak-shaving feed port is shown;

[0013] Figure 3 A schematic structural diagram of a sorting and feeding unit of a circulating fluidized bed boiler system according to another exemplary embodiment of the present invention;

[0014] Figure 4 It is a schematic structural diagram of a circulating fluidized bed boiler system according to an exemplary embodiment of the present invention, wherein the pneumatic conveying position of fine coal particles is shown.

[0015] Reference numerals:

[0016] 100 circulating fluidized bed boiler, 101 furnace, 102 separator, 103 return feeder;

[0017] 200 sorting and feeding unit, 201 coal crusher, 202 sorting device, 203 separation device, 204 fuel storage bin, 205 fine powder storage bin DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further specifically described below by examples and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0019] Figure 1 is a schematic structural diagram of a sorting and feeding unit of a circulating fluidized bed boiler system according to an exemplary embodiment of the present invention, Figure 2 It is a schematic structural diagram of a circulating fluidized bed boiler system according to an exemplary embodiment of the present invention, wherein the position of the peak-shaving feed port is shown.

[0020] like Figure 1-Figure 2 As shown, the present invention provides a CFB fine powder peak shaving system, comprising:

[0021] The circulating fluidized bed boiler 100 includes a furnace 101, a separator 102, and a material returner 103, which are connected to each other; and

[0022] The sorting and feeding system 200 includes a coal crusher 201, a sorting device 202, a separation device 203 and a fuel storage bin 204, wherein the dense phase area at the bottom of the boiler furnace and / or the return device are provided with peak-shaving feeding ports, which are respectively a first peak-shaving feeding port and a second peak-shaving feeding port, the solid material outlet of the separation device 203 is connected to the peak-shaving feeding port, and the exhaust gas outlet of the separation device 203 is connected to the secondary air outlet of the boiler furnace.

[0023] The particle size of coal entering the circulating fluidized bed boiler is generally in the range of 0 to 10 mm. Generally, a two-stage crusher is used. 50 ≈1mm. After the granular coal from the coal crusher is sorted by the sorting device 202, the part with a particle size less than 1mm is sent to the separation device 203, and after the solid is captured by the separation device, exhaust gas and fine coal particles are formed. The large coal particles remaining in the sorting device 202 enter the fuel storage bin 204.

[0024] In the case of a three-stage or four-stage crusher, d 50 It is often lower, and the fuel sorting particle size can also be fine coal with a particle size of 0 to 0.1 mm.

[0025] The exhaust gas enters the furnace from the secondary air inlet, and is burned in the boiler furnace to utilize the combustibles therein, while also replenishing the heat in the upper part of the boiler furnace.

[0026] Fine coal particles can be fed into the bottom of the furnace through the peak-shaving feed port to participate in low-load operation.

[0027] In a further embodiment, the boiler system further comprises a fine powder storage bin 205 (e.g. Figure 3 The fine coal particles from the separation device 203 can be fed only into the storage bin 205 or into the peak-shaving feed port when fed into the storage bin 205.

[0028] The coarse coal particles formed by the sorting device 202 are fed into the furnace feed port as the feed coal under normal operating conditions. Since the distribution of the coarse coal particles changes significantly after sorting, in order to reduce the possible impact on normal operating conditions, the coarse coal particles in the fuel storage bin 204 can be mixed with the crushed coal from the coal crusher 201 and then fed into the furnace (in actual applications, the coarse coal particles can be added to the conveyor belt).

[0029] See also Figure 1 The sorting and feeding unit further comprises a coal crusher 201, and the fuel outlet of the coal crusher is communicated with the sorting device 202, the storage bin 204, and the fuel supply inlet or the boiler feed port. In an optional embodiment, the fuel outlet of the coal crusher 201 is communicated with the sorting device 202 and the fuel supply inlet or the boiler feed port, but not with the storage bin 204.

[0030] Figure 4 FIG. 1 is a schematic structural diagram of a circulating fluidized bed boiler system according to an exemplary embodiment of the present invention, wherein the pneumatic conveying position of fine coal particles is shown. Figure 4 The present invention can also be provided with an air distribution device for fine coal particles, which is used to deliver the fine coal particles to the bottom of the boiler furnace by pneumatic conveying, and under the fluidizing air, on the one hand, maintain the normal fluidization of the bed layer, and on the other hand, when the fine coal particles pass through the bed material at the bottom of the furnace, the high temperature of the bed material is used to increase the fuel temperature, and part of the combustion releases heat to heat the bed layer, thereby improving the combustion characteristics of the fuel, thereby efficiently burning in the furnace. Figure 4 As shown, the fluidizing air distribution device is connected to a plurality of conventional fluidizing air inlets arranged at the bottom of the furnace; the fine coal particle distribution device is connected to a plurality of second feeding ports arranged at the bottom of the furnace so as to transport the fine coal particle into the furnace by pneumatic conveying.

[0031] In an alternative embodiment, Figure 1-Figure 4 The storage bin 204 may not be provided, so that the coarse coal particles from the sorting device 202 can be directly fed to the boiler feed port.

[0032] exist Figure 1-Figure 4 In the illustrated embodiment, the exhaust gas of the separation device 203 is directed to the secondary air port of the boiler, but this may not be the case in the present invention. For example, the exhaust gas may be directed to another furnace inlet instead of the secondary air port.

[0033] In the present invention, the so-called coarse particles and fine particles are relative concepts, indicating that after the fuel particles are sorted by the sorting unit, there are different particle size ranges, namely the first particle size range and the second particle size range. The coarse particles in the first particle size range are introduced into the boiler feed port, and the fine particles in the second particle size range are introduced into the peak shaving feed port.

[0034] Based on the above, the present invention proposes a peak-shaving method using the above CFB fine powder peak-shaving system:

[0035] (1) When the boiler is reducing load or operating stably at low load (e.g. below 30% load),

[0036] When the boiler drops from high load (for example, higher than 70% load) to low load (for example, lower than 30% load), the sorting feeding unit is started, fine-grained coal is fed from the peak-shaving feeding port, the conventional coal feeding at the feeding port is reduced (completely shut down if necessary), the secondary air in the furnace is shut down, the exhaust gas is introduced into the secondary air port or into the middle and upper part of the furnace, and the primary air volume is reduced to only maintain the fluidization state of the bed material and be used for the combustion of the fine-grained coal.

[0037] (2) When the boiler is operated at ultra-low load and the load is increased, the fine-particle coal supply is maintained and conventional coal supply is put into operation. After the boiler reaches the predetermined load, the sorting and separation system is cut off and only coarse-particle coal is put into operation to enter conventional operation.

[0038] In the above-mentioned embodiments of the present invention, coal is used as an example of fuel. As can be understood by those skilled in the art, other solid fuels that can be sorted into different particle sizes can also be applied to the technical solution of the present invention.

[0039] In the present invention, by setting up a sorting feeding unit and a corresponding fan (based on pneumatic conveying), the boiler fuel at low load is regulated, and fine coal particles are used to ensure combustion at low load, without the need to add a coal mill, thereby reducing the investment cost of transformation. In addition, the exhaust gas can also supplement the combustion of fuel in the upper part of the furnace, supplement the heat in the upper part of the furnace, and improve the hydrodynamic safety of the boiler at low load.

[0040] In the present invention, each numerical range includes the endpoint value unless explicitly stated. In addition, the numerical range also includes the midpoint value, one-third value and two-thirds value, all of which are within the protection scope of the present invention.

[0041] Based on the above, the present invention proposes the following technical solutions:

[0042] 1. A circulating fluidized bed boiler system, comprising:

[0043] A circulating fluidized bed boiler comprises a furnace, a first separator and a returner which are connected in pairs, the returner is connected to a dense phase area or a corresponding area of ​​the furnace via a return pipe, and the furnace is provided with a fuel supply inlet and a conventional fluidizing air inlet; and

[0044] The sorting feeding unit is suitable for sorting fuel into a first fuel in a first particle size range and a second fuel in a second particle size range, the first particle size range is larger than the second particle size range, the first fuel is suitable for being introduced into a fuel supply inlet, and the second fuel is suitable for being introduced into a peak-shaving feeding port of a circulating fluidized bed boiler based on pneumatic conveying.

[0045] 2. The boiler system according to item 1, wherein:

[0046] The peak-shaving feed port comprises a first feed port arranged on a return pipe; and / or

[0047] The peak-shaving feed port includes a second feed port arranged in a dense phase area or a corresponding area of ​​the furnace.

[0048] 3. The boiler system according to item 1, wherein:

[0049] The boiler system includes a fluidizing air distribution device, which is communicated with a plurality of conventional fluidizing air inlets arranged at the bottom of the furnace;

[0050] The boiler system also includes a pneumatic conveying air distribution device, which is communicated with a plurality of second feed ports arranged at the bottom of the furnace so as to transport the second fuel into the furnace in a pneumatic conveying manner.

[0051] 4. The boiler system according to any one of 1 to 3, wherein:

[0052] The sorting and feeding unit includes a sorting device and a separating device. The sorting device includes a first outlet and a second outlet. The first fuel is suitable for coming out of the first outlet. The second outlet is communicated with the separating device. The separating device includes a lower outlet and an upper outlet. The second fuel is suitable for coming out of the lower outlet.

[0053] 5. The boiler system according to claim 4, wherein:

[0054] The sorting and feeding unit further includes a first storage bin communicated with the first outlet and used for storing the first fuel; and

[0055] The lower part of the first storage bin is provided with a delivery pipeline communicating with the fuel supply inlet, and / or the first outlet is provided with a delivery pipeline communicating with the fuel supply inlet.

[0056] 6. The boiler system according to 5, wherein:

[0057] The sorting and feeding unit further comprises a fuel pulverizer, and a fuel outlet of the fuel pulverizer is in communication with the sorting device and the first storage bin; or

[0058] The sorting and feeding unit further comprises a fuel pulverizer, and a fuel outlet of the fuel pulverizer is in communication with the sorting device, the first storage bin and the fuel supply inlet.

[0059] 7. The boiler system according to claim 4, wherein:

[0060] The sorting and feeding unit further includes a second storage bin communicated with the lower outlet for storing a second fuel; and

[0061] The lower part of the second storage bin is provided with a conveying pipeline connected to the peak-shaving feeding port, and / or the lower outlet is provided with a conveying pipeline connected to the peak-shaving feeding port.

[0062] 8. The boiler system according to claim 4, wherein:

[0063] The furnace of the boiler is provided with secondary air vents;

[0064] The upper outlet of the separation device is an exhaust gas outlet and is provided with a pipeline communicating with the secondary air outlet.

[0065] 9. A control method for a circulating fluidized bed boiler system, the boiler system comprising: a circulating fluidized bed boiler, comprising a furnace, a first separator and a returner connected in pairs, the returner communicating with a dense phase area or a corresponding area of ​​the furnace via a return pipe, the furnace being provided with a fuel supply inlet and a conventional fluidizing air inlet; and a sorting and feeding unit, adapted to sort the fuel into a first fuel in a first particle size range and a second fuel in a second particle size range, the first particle size range being larger than the second particle size range, the method comprising the steps of:

[0066] The first fuel is introduced into the fuel supply inlet, and the second fuel is introduced into the peak-shaving feed port of the circulating fluidized bed boiler based on pneumatic transportation.

[0067] 10. The method according to 9, wherein:

[0068] The peak-shaving feed port comprises a first feed port arranged on a return pipe; and / or

[0069] The peak-shaving feed port includes a second feed port arranged in a dense phase area or a corresponding area of ​​the furnace.

[0070] 11. The method according to 9 further comprises the steps of:

[0071] When the load of the boiler decreases toward below 30%, the sorting feeding unit is started, the second fuel is fed from the peak-shaving feeding port, the supply of the first fuel to the fuel supply inlet is reduced or shut down, and the primary air volume is reduced to only maintain the fluidization state of the bed material and for the combustion of the second fuel.

[0072] 12. The method according to 11, wherein:

[0073] The sorting and feeding unit comprises a sorting device and a separating device, the sorting device comprises a first outlet and a second outlet, the first fuel is suitable for coming out from the first outlet, the second outlet is communicated with the separating device, the separating device comprises a lower outlet and an upper outlet, the second fuel is suitable for coming out from the lower outlet, the furnace of the boiler is provided with a secondary air port, the upper outlet of the separating device is an exhaust gas outlet and is provided with a pipeline communicated with the secondary air port;

[0074] The method also includes the steps of shutting down the furnace secondary air, and passing the exhaust gas from the upper outlet into the secondary air port or passing the exhaust gas from the upper outlet into the middle and upper part of the furnace.

[0075] 13. The method according to 9 further comprises the steps of:

[0076] When the load of the boiler increases from less than 30% load to more than 70% load, supplying the first fuel while maintaining the supply of the second fuel;

[0077] After the boiler reaches a predetermined load, the fuel sorting device is cut off and only the first fuel is supplied.

[0078] 14. The method according to claim 9, wherein:

[0079] The boiler system includes a fluidizing air distribution device, which is communicated with a plurality of conventional fluidizing air inlets arranged at the bottom of the furnace;

[0080] The boiler system also includes a pneumatic conveying air distribution device, which is communicated with a plurality of second feed ports arranged at the bottom of the furnace so as to transport the second fuel into the furnace in a pneumatic conveying manner.

[0081] In the present invention, a boiler load lower than 30% is defined as a low load, and a load higher than 70% is defined as a high load. However, as those skilled in the art will appreciate, the definitions of low load and high load vary based on different boilers. At this time, based on different practical applications, the claims "lower than 30% load" includes the low load condition of the actual boiler, and "greater than 70% load" includes the high load condition of the actual boiler.

[0082] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A circulating fluidized bed boiler system, comprising: A circulating fluidized bed boiler comprises a furnace, a first separator and a returner which are connected in pairs, the returner is connected to a dense phase area or a corresponding area of ​​the furnace via a return pipe, and the furnace is provided with a fuel supply inlet and a conventional fluidizing air inlet; and The sorting feeding unit is suitable for sorting fuel into a first fuel in a first particle size range and a second fuel in a second particle size range, the first particle size range is larger than the second particle size range, the first fuel is suitable for being introduced into a fuel supply inlet, and the second fuel is suitable for being introduced into a peak-shaving feeding port of a circulating fluidized bed boiler based on pneumatic conveying.

2. The boiler system according to claim 1, wherein: The peak-shaving feed port comprises a first feed port arranged on a return pipe; and / or The peak-shaving feed port includes a second feed port arranged in a dense phase area or a corresponding area of ​​the furnace.

3. The boiler system according to claim 1, wherein: The boiler system includes a fluidizing air distribution device, which is communicated with a plurality of conventional fluidizing air inlets arranged at the bottom of the furnace; The boiler system also includes a pneumatic conveying air distribution device, which is communicated with a plurality of second feed ports arranged at the bottom of the furnace so as to transport the second fuel into the furnace in a pneumatic conveying manner.

4. The boiler system according to any one of claims 1 to 3, wherein: The sorting and feeding unit includes a sorting device and a separating device. The sorting device includes a first outlet and a second outlet. The first fuel is suitable for coming out of the first outlet. The second outlet is communicated with the separating device. The separating device includes a lower outlet and an upper outlet. The second fuel is suitable for coming out of the lower outlet.

5. The boiler system according to claim 4, wherein: The sorting and feeding unit further includes a first storage bin communicated with the first outlet and used for storing the first fuel; and The lower part of the first storage bin is provided with a delivery pipeline communicating with the fuel supply inlet, and / or the first outlet is provided with a delivery pipeline communicating with the fuel supply inlet.

6. The boiler system according to claim 5, wherein: The sorting and feeding unit further comprises a fuel pulverizer, and a fuel outlet of the fuel pulverizer is in communication with the sorting device and the first storage bin; or The sorting and feeding unit further comprises a fuel pulverizer, and a fuel outlet of the fuel pulverizer is in communication with the sorting device, the first storage bin and the fuel supply inlet.

7. The boiler system according to claim 4, wherein: The sorting and feeding unit further includes a second storage bin communicated with the lower outlet for storing a second fuel; and The lower part of the second storage bin is provided with a conveying pipeline connected to the peak-shaving feeding port, and / or the lower outlet is provided with a conveying pipeline connected to the peak-shaving feeding port.

8. The boiler system according to claim 4, wherein: The furnace of the boiler is provided with secondary air vents; The upper outlet of the separation device is an exhaust gas outlet and is provided with a pipeline communicating with the secondary air outlet.

9. A control method for a circulating fluidized bed boiler system, the boiler system comprising: A circulating fluidized bed boiler comprises a furnace, a first separator and a returner connected in pairs, the returner is connected to a dense phase area or a corresponding area of ​​the furnace via a return pipe, the furnace is provided with a fuel supply inlet and a conventional fluidizing air inlet; and a sorting and feeding unit, which is suitable for sorting the fuel into a first fuel in a first particle size range and a second fuel in a second particle size range, wherein the first particle size range is larger than the second particle size range, and the method comprises the steps of: The first fuel is introduced into the fuel supply inlet, and the second fuel is introduced into the peak-shaving feed port of the circulating fluidized bed boiler based on pneumatic transportation.

10. The method according to claim 9, wherein: The peak-shaving feed port comprises a first feed port arranged on a return pipe; and / or The peak-shaving feed port includes a second feed port arranged in a dense phase area or a corresponding area of ​​the furnace.

11. The method according to claim 9, further comprising the steps of: When the load of the boiler decreases toward below 30%, the sorting feeding unit is started, the second fuel is fed from the peak-shaving feeding port, the supply of the first fuel to the fuel supply inlet is reduced or shut down, and the primary air volume is reduced to only maintain the fluidization state of the bed material and for the combustion of the second fuel.

12. The method according to claim 11, wherein: The sorting and feeding unit comprises a sorting device and a separating device, the sorting device comprises a first outlet and a second outlet, the first fuel is suitable for coming out from the first outlet, the second outlet is communicated with the separating device, the separating device comprises a lower outlet and an upper outlet, the second fuel is suitable for coming out from the lower outlet, the furnace of the boiler is provided with a secondary air port, the upper outlet of the separating device is an exhaust gas outlet and is provided with a pipeline communicated with the secondary air port; The method also includes the steps of shutting down the furnace secondary air, and passing the exhaust gas from the upper outlet into the secondary air port or passing the exhaust gas from the upper outlet into the middle and upper part of the furnace.

13. The method according to claim 9, further comprising the steps of: When the load of the boiler increases from less than 30% load to more than 70% load, supplying the first fuel while maintaining the supply of the second fuel; After the boiler reaches a predetermined load, the fuel sorting device is cut off and only the first fuel is supplied.

14. The method of claim 9, wherein: The boiler system includes a fluidizing air distribution device, which is communicated with a plurality of conventional fluidizing air inlets arranged at the bottom of the furnace; The boiler system also includes a pneumatic conveying air distribution device, which is communicated with a plurality of second feed ports arranged at the bottom of the furnace so as to transport the second fuel into the furnace in a pneumatic conveying manner.

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