Coal feeding system and method for a circulating fluidized bed

Abstract

The present application relates to a coal feeding system and method for a circulating fluidized bed, the coal feeding system for a circulating fluidized bed comprising: a furnace, a coal feeding device and a decoupling return pipe. The coal feeding device is used for conveying coal, the upper end of the decoupling return pipe is connected with the coal feeding device, the lower end of the decoupling return pipe is connected with the furnace, the upper end of the decoupling return pipe has a return port, the decoupling return pipe has at least two bending sections, the length direction of the two bending sections is provided with an included angle alpha with the height direction of the furnace, and the included angles alpha of the two bending sections are not equal. The coal feeding system for a circulating fluidized bed has a simple structure design, is convenient to transform, can realize coal decoupling combustion at the same time, and can reduce the emission of NO x , and reduce environmental pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal feeding, in particular, to a coal feeding system and method for a circulating fluidized bed. BACKGROUND

[0002] NO x is one of the important culprits causing acid rain, haze and other environmental problems, and its main source is the combustion process of various fuels, especially the emissions from power plants and industrial boilers. According to the latest revised "Standard for Air Pollutants Discharge of Thermal Power Plants" (GB13223-2011), the NO x emission requirement of new boilers is <100mg / m 3 , and in recent years, the ultra-low emission index requires NO x emission <50mg / m 3 (based on the oxygen content of 6%). Due to the characteristics of medium-temperature combustion (800-900℃) and a large amount of reducing materials in the furnace, the original NO x emission of circulating fluidized bed boilers is low, and usually can meet the environmental protection standards of most countries. However, to achieve the original ultra-low emission, it still faces great challenges, and it is still necessary to deeply explore the low-nitrogen combustion potential of circulating fluidized bed technology.

[0003] At present, the methods for reducing the NO x emission of boilers mainly aim at the NO x generated after combustion, and the methods such as selective non-catalytic reduction (SNCR), selective catalytic reduction (SCR) or combination of the two (SNCR+SCR) are used. However, this kind of post-combustion NO x treatment method needs to install additional equipment in the tail flue, which will inevitably increase the complexity of the operation of the circulating fluidized bed boiler and the overall economy, so it is necessary to introduce the technology of reducing NO x emission before or during combustion.

[0004] Among them, the decoupled combustion of coal is a promising technical solution. The decoupled combustion of coal is essentially to decouple and match the pyrolysis and combustion processes of coal, on the one hand to realize the efficient combustion of volatile matter and semi-coke, and on the other hand to utilize the reducing property of pyrolysis products to inhibit the generation and emission of NO x as much as possible.

[0005] However, in the related art, in order to realize the decoupled combustion of coal in the circulating fluidized bed, a pyrolysis chamber is usually separately arranged in series with the furnace, but due to the fluid introduction, coal feeding, coal pyrolysis, separation of volatile matter and tar, and return of bed material and coke in the pyrolysis chamber, there are certain difficulties and challenges in design and modification. SUMMARY

[0006] The present application aims to at least partially solve one of the technical problems in the related art.

[0007] To this end, embodiments of the present application provide a coal feeding system for a circulating fluidized bed, which has a simple structure, is easy to modify, and can realize decoupled combustion of coal while reducing NO x emissions and environmental pollution.

[0008] The coal feeding system for a circulating fluidized bed according to embodiments of the present application comprises a furnace, a coal feeding device for conveying coal, and a decoupling return pipe, the upper end of the decoupling return pipe being connected to the coal feeding device, the lower end of the decoupling return pipe being connected to the furnace, the upper end of the decoupling return pipe having a return port, and the decoupling return pipe having at least two bending sections, the length direction of each of the two bending sections being at an angle a with the height direction of the furnace, and the two bending sections having different angles a.

[0009] The coal feeding system for a circulating fluidized bed according to embodiments of the present application can prolong the contact time of coal and return material, improve the thermal uniformity of return material, and further improve the thermal uniformity of the furnace. In addition, the decoupling of the coal feeding and combustion process can strengthen the reduction atmosphere in the dense phase zone of the circulating fluidized bed, reduce the NO x emissions in the furnace, achieve ultra-low emission standards and environmental protection requirements, and reduce environmental pollution.

[0010] In some embodiments, the decoupling return pipe comprises a first bending section and a second bending section, the upper end of the first bending section being connected to the coal feeding device, the lower end of the first bending section being connected to the upper end of the second bending section, the lower end of the second bending section being connected to the furnace, the first bending section gradually approaching the furnace in a top-to-bottom direction, the angle between the length direction of the first bending section and the height direction of the furnace being a1, wherein a1 is greater than or equal to 0° and less than 90°, the angle between the second bending section and the height direction of the furnace being a2, and a1≠a2.

[0011] In some embodiments, the lower end of the furnace has a necking portion, the cross-sectional area of the necking portion gradually decreasing in a top-to-bottom direction, the angle between the furnace wall surface of the necking portion and a horizontal plane orthogonal to the height direction of the furnace being g, and the angle between the lower end of the decoupling return pipe and the horizontal plane orthogonal to the height direction of the furnace being b, wherein b is less than g.

[0012] In some embodiments, g is greater than or equal to 70° and less than or equal to 76°.

[0013] In some embodiments, the decoupling return pipe has a length of W in a horizontal plane perpendicular to the height direction of the furnace, and a length of H in the height direction of the furnace, wherein W / H is greater than or equal to 0.5 and less than or equal to 1.3.

[0014] In some embodiments, the coal feeding device comprises a coal hopper, a first coal feeder, a second coal feeder, an expansion joint, and a coal feeding pipe, the coal hopper is connected to the first coal feeder, the first coal feeder is connected to the second coal feeder, the second coal feeder is connected to the expansion joint, the coal feeding pipe extends in the height direction of the furnace, the upper end of the coal feeding pipe is connected to the expansion joint, and the lower end of the coal feeding pipe is connected to the upper end of the decoupling return pipe.

[0015] The coal feeding method for a circulating fluidized bed according to another embodiment of the present application is applied to the coal feeding system for a circulating fluidized bed in any of the above embodiments, and the coal feeding method comprises:

[0016] feeding coal into the decoupling return pipe through the coal feeding device;

[0017] feeding return material into the decoupling return pipe through the return material port;

[0018] mixing the coal and the return material through the decoupling return pipe, decoupling combustion of the coal and the return material through the plurality of bending sections, and feeding the coal and the return material into the furnace.

[0019] The coal feeding method for a circulating fluidized bed according to the embodiments of the present application can prolong the contact time of the coal and the return material, improve the thermal uniformity of the return material, and further improve the thermal uniformity of the furnace by setting the decoupling return pipe to the above structure. In addition, the coal can be strengthened in the pyrolysis behavior in the decoupling return pipe, so that the coal is pyrolyzed to generate coke, volatile matter, etc. in advance, and the burnout of the coal is improved. In addition, the reaction chain of the decoupling coal combustion process can strengthen the reducing atmosphere in the dense phase zone of the circulating fluidized bed, reduce the NOx emission in the furnace, and achieve the original emission, ultra-low emission standard and environmental protection requirements, and reduce environmental pollution. x The original emission, ultra-low emission standard and environmental protection requirements are achieved, and environmental pollution is reduced.

[0020] In some embodiments, the mass flow ratio of the coal and the return material is greater than or equal to 0.04 and less than or equal to 0.06.

[0021] In some embodiments, a sealing air interface is formed on the coal feeding device, sealing air is fed into the coal feeding device and the decoupling return pipe through the sealing air interface, and / or return material air is fed into the decoupling return pipe through the return material port.

[0022] In some embodiments, a purge air interface is formed on the decoupling return pipe, and anti-blocking air or loosening air is introduced into the decoupling return pipe through the purge air interface; and / or, the coal feeding system further comprises a vibrating device connected to the decoupling return pipe, and the vibrating device is used to loosen the material in the decoupling return pipe. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a general view of a coal feeding system for a circulating fluidized bed according to an embodiment of the present application.

[0024] Figure 2 is a partial view of a coal feeding system for a circulating fluidized bed according to the related art.

[0025] Figure 3 is a partial view of a coal feeding system for a circulating fluidized bed according to a first embodiment of the present application.

[0026] Figure 4 is a partial view of a coal feeding system for a circulating fluidized bed according to a second embodiment of the present application.

[0027] Figure 5 is a partial view of a coal feeding system for a circulating fluidized bed according to a third embodiment of the present application.

[0028] Figure 6 is a partial view of a coal feeding system for a circulating fluidized bed according to a fourth embodiment of the present application.

[0029] Figure 7 is a partial view of a coal feeding system for a circulating fluidized bed according to a fifth embodiment of the present application.

[0030] Figure 8 is a coal particle size distribution diagram of a coal feeding system for a circulating fluidized bed according to an embodiment of the present application.

[0031] Figure 9 is a return material particle size distribution diagram of a coal feeding system for a circulating fluidized bed according to an embodiment of the present application.

[0032] REFERENCE NUMERALS:

[0033] 1, furnace; 11, necking portion;

[0034] 2, coal feeding device; 21, coal hopper; 22, first coal feeder; 23, second coal feeder; 24, expansion joint; 25, coal feeding pipe; 26, sealing air interface; 27, control valve;

[0035] 3, decoupling return pipe; 31, bending section; 311, first bending section; 312, second bending section; 313, third bending section; 32, return material port; 33, sealing return valve. DETAILED DESCRIPTION

[0036] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0037] The following is a reference appendix. Figures 1 to 9 A coal feeding system and method for a circulating fluidized bed are described according to embodiments of the present invention.

[0038] like Figure 1 As shown, the coal feeding system for a circulating fluidized bed according to an embodiment of the present invention includes: a furnace 1, a coal feeding device 2, and a decoupled return pipe 3. The coal feeding device 2 is used to transport coal. The upper end of the decoupled return pipe 3 is connected to the coal feeding device 2, and the lower end of the decoupled return pipe 3 is connected to the furnace 1. The upper end of the decoupled return pipe 3 has a return port 32. The decoupled return pipe 3 has at least two bent sections 31. The length direction of the two bent sections 31 is provided with an angle α between it and the height direction of the furnace 1, and the included angle α of the two bent sections 31 is not equal.

[0039] Understandably, the decoupling return pipe 3 adopts a bent design, and the decoupling return pipe 3 can be composed of two or more bent sections 31. For example, the decoupling return pipe 3 includes a first bent section 311, a second bent section 312, and a third bent section 313.

[0040] According to an embodiment of the present invention, the coal feeding system for a circulating fluidized bed, by configuring the decoupled return pipe 3 with the above-described structure, can extend the contact time between the coal and the return material, improve the thermal uniformity of the return material, and thus improve the thermal uniformity of the furnace 1. Furthermore, it can enhance the pyrolysis behavior of the coal in the decoupled return pipe 3, causing it to pyrolyze earlier to generate coke, volatile matter, etc., thereby improving the coal's combustibility. In addition, the decoupled coal feeding combustion process can strengthen the reducing atmosphere in the dense phase region of the circulating fluidized bed, reducing NO in the furnace 1. x The original emissions meet ultra-low emission standards and environmental protection requirements, thus reducing environmental pollution.

[0041] It is understood that the coal feeding system for circulating fluidized beds in the embodiments of the present invention fully utilizes the characteristics of the reducing atmosphere in the dense phase region of the circulating fluidized bed and its feeding system. Through the design of the decoupled return pipe 3 and its matching sealing and anti-clogging measures, the "segmented" decoupled combustion of coal is achieved under the premise of ensuring safe operation.

[0042] Based on the "segmented" decoupling method, it is generally believed in related technologies that an independent pyrolysis chamber needs to be set up. The pyrolysis chamber is usually located close to the furnace wall, at the sealed return valve 33 below the riser, or at the external bed heat exchanger. However, due to the complex physicochemical processes required to be realized in the independent pyrolysis chamber, such as fluid introduction, coal feeding, coal pyrolysis, separation of volatiles and tar, and return of bed material and coke, it is difficult to design and modify it based on the existing circulating fluidized bed.

[0043] Therefore, the coal feeding system for circulating fluidized beds in embodiments of the present invention can be modified from the original return coal feeding system to the aforementioned decoupled return pipe structure. This allows coal and return material (circulating ash or limestone, etc.) to mix under high temperature and low oxygen conditions. Furthermore, it enables partial or complete pyrolysis of the coal before it enters the furnace during the coal's residence time, further achieving decoupled combustion of the coal.

[0044] Meanwhile, the coal feeding system for circulating fluidized beds in the embodiments of the present invention also achieves the following technical effects:

[0045] (1) Since the coal and the return material are fully premixed in the decoupled return pipe 3, it is equivalent to increasing the reaction time of the coal and improving the combustibility of the coal.

[0046] (2) Since the coal and the return material are fully premixed in the decoupled return pipe 3, the thermal uniformity of the return material is improved, which further improves the temperature uniformity of the furnace 1.

[0047] In some embodiments, such as Figure 1 As shown, the decoupling return pipe 3 includes a first bend section 311 and a second bend section 312. The upper end of the first bend section 311 is connected to the coal feeding device 2, and the lower end of the first bend section 311 is connected to the upper end of the second bend section 312. The lower end of the second bend section 312 is connected to the furnace 1. The first bend section 311 gradually approaches the furnace 1 from top to bottom. The angle between the length direction of the first bend section 311 and the height direction of the furnace 1 is α1, where α1 is greater than or equal to 0° and less than 90°. It can be understood that the first bend section 311 can be the first bend section 31 of the decoupling return pipe 3 from top to bottom. By setting the first bend section 311 to the above structure, the coal feeding system for circulating fluidized beds in the embodiments of the present invention can reduce the overall size of the coal feeding system and allow the coal and return material to be fully premixed in the decoupling return pipe 3.

[0048] Furthermore, the angle between the second bending segment 312 and the height direction of the furnace 1 is α2, and α1≠α2. It can be understood that the bending angle of the second bending segment 312 is different from that of the first bending segment 311. In other words, the axial direction of the first bending segment 311 is not collinear with the axial direction of the second bending segment 312.

[0049] The angle between the second bending section 312 and the height direction of the furnace 1 is a2, a2 is greater than or equal to -90° and less than or equal to 90°. It can be understood that the second bending section 312 can gradually approach the furnace 1 in the direction from top to bottom, or gradually move away from the furnace 1 in the direction from top to bottom, thereby further increasing the residence time of the coal and the return material in the decoupling return material pipe 3, and improving the heat uniformity of the return material.

[0050] In some embodiments, as shown in Figure 1 The lower end of the furnace 1 has a necked portion 11, the cross-sectional area of the necked portion 11 gradually decreases in the direction from top to bottom, and the angle between the wall surface of the necked portion 11 and the horizontal plane perpendicular to the height direction of the furnace 1 is γ. The angle between the lower end of the decoupling return material pipe 3 and the horizontal plane perpendicular to the height direction of the furnace 1 is β. In other words, the furnace inclination angle of the furnace 1 is γ, and the furnace entry angle of the decoupling return material pipe 3 is β, and β is less than γ. It can be understood that the furnace entry section of the decoupling return material pipe 3 is directly connected to the furnace 1, and the furnace entry section of the decoupling return material pipe 3 is made of hard material to avoid flexible connection between the furnace entry section of the decoupling return material pipe 3 and the furnace 1. The coal feeding system for the circulating fluidized bed of the embodiments of the present application can improve the anti-blocking effect of the decoupling return material pipe 3 and make the discharge of the decoupling return material pipe 3 more smooth by satisfying the above relationship between the furnace inclination angle γ and the furnace entry angle β.

[0051] Specifically, γ is greater than or equal to 70° and less than or equal to 76°. The inventors of the present application have found through experimental research that when the furnace inclination angle γ satisfies the above relationship, the anti-blocking effect of the decoupling return material pipe 3 can be further improved.

[0052] In some embodiments, as shown in Figure 1 The projection length of the decoupling return material pipe 3 on the horizontal plane perpendicular to the height direction of the furnace 1 is W, and the length of the decoupling return material pipe 3 in the height direction of the furnace 1 is H, wherein W / H is greater than or equal to 0.5 and less than or equal to 1.3.

[0053] Optionally, W is selected in the range of greater than or equal to 6.5m and less than or equal to 8.5m, and H is selected in the range of greater than or equal to 6.5m and less than or equal to 12m. The inventors of the present application have found through experimental research that when the width W and the length H of the decoupling return material pipe 3 satisfy the above range, the production material of the decoupling return material pipe 3 can be reduced, and the coal and the return material can be fully premixed in the decoupling return material pipe 3, thereby making the structural design of the coal feeding system for the circulating fluidized bed more reasonable.

[0054] In some embodiments, as shown in Figure 1As shown, the coal feeding device 2 includes a coal hopper 21, a first coal feeder 22 and a second coal feeder 23, an expansion joint 24 and a coal feeding pipe 25, the coal hopper 21 is connected with the first coal feeder 22, the first coal feeder 22 is connected with the second coal feeder 23, the second coal feeder 23 is connected with the expansion joint 24, the coal feeding pipe 25 extends along the height direction of the furnace 1, the upper end of the coal feeding pipe 25 is connected with the expansion joint 24, and the lower end of the coal feeding pipe 25 is connected with the upper end of the decoupling return pipe 3. It can be understood that the coal can be transported to the first coal feeder 22 through the coal hopper 21, the first coal feeder 22 can be transported to the second coal feeder 23, the second coal feeder 23 transports the coal to the coal feeding pipe 25 through the expansion joint 24, and then the coal feeding pipe 25 can transport the coal into the decoupling return pipe 3. For example, the coal feeding pipe 25 is provided with a control valve 27 to control the flow rate of the coal entering the decoupling return pipe 3.

[0055] The coal feeding method for the circulating fluidized bed according to another embodiment of the present application is applied to the coal feeding system for the circulating fluidized bed of the embodiment of the present application, and the coal feeding method for the circulating fluidized bed comprises the following steps:

[0056] The coal feeding device 2 transports the coal into the decoupling return pipe 3;

[0057] The return material is transported into the decoupling return pipe 3 through the return material port 32;

[0058] The coal and the return material are mixed through the decoupling return pipe 3, the coal and the return material are decoupled and combusted through the multiple bending sections 31, and are introduced into the furnace 1.

[0059] The coal feeding method for the circulating fluidized bed according to the embodiment of the present application can prolong the contact time of the coal and the return material, improve the thermal uniformity of the return material, and further improve the thermal uniformity of the furnace 1 by setting the decoupling return pipe 3 as the above structure. Moreover, the coal pyrolysis behavior in the decoupling return pipe 3 can be strengthened, so that the coal is pyrolyzed in advance to generate coke, volatile matter and the like, and the coal burnout is improved. In addition, the reaction chain of the decoupling coal combustion process can strengthen the reducing atmosphere in the dense phase zone of the circulating fluidized bed, reduce the NO x The original emission meets the ultra-low emission standard and environmental protection requirements, and reduces environmental pollution.

[0060] Optionally, the mass flow ratio of the coal and the return material is greater than or equal to 0.04 and less than or equal to 0.06. It can be understood that the mass flow ratio of the coal and the return material is related to the boiler operation load. Generally, the flow rate of the coal is selected in the range of 18 kg / s-22 kg / s, and the flow rate of the return material is selected in the range of 360 kg / s-450 kg / s. The present inventors have found through experimental research that when the mass flow ratio of the coal and the return material meets the above relationship, the premixing uniformity of the coal and the return material is better, and the coal burnout is improved.

[0061] Optionally, a sealing air interface 26 is arranged on the coal feeder 2, and sealing air is introduced into the coal feeder 2 and the decoupling return pipe 3 through the sealing air interface 26. Specifically, the coal feeder pipe 25 is provided with a coal feeding port, and the first coal feeder 22 and the coal feeding port are both provided with the sealing air interface 26, through which the sealing air can be introduced into the coal feeder 2 and the decoupling return pipe 3. The sealing air can be primary air or normal temperature air.

[0062] Specifically, the flow rate of the sealing air at the coal feeding port is greater than or equal to 1.0u mmf Relatedly, generally, the flow rate of the sealing air is selected in a range of greater than or equal to 1.0u mmf and less than or equal to 2.0u mmf .

[0063] Optionally, a purge air interface is arranged on the decoupling return pipe 3, and anti-blocking air or loosening air is introduced into the decoupling return pipe 3 through the purge air interface. The coal feeding system further comprises a vibrating device connected to the decoupling return pipe 3, and the vibrating device is used to dredge the material in the decoupling return pipe 3, thereby improving the smoothness of the material flow in the decoupling return pipe 3.

[0064] Further, the return port 32 is provided with a sealing return valve 33, and return air can be introduced into the decoupling return pipe 3 through the return port 32. The flow rate of the return air and the loosening air is greater than or equal to 1.0u hmf Relatedly, generally, the flow rate of the return air and the loosening air is selected in a range of: 1.0u hmf < loosening air flow rate < return air flow rate ≤ 4.0u hmf .

[0065] It can be understood that the design and operation of the coal feeding system for the circulating fluidized bed in the embodiments of the present application need to meet the following requirements:

[0066] (1) The coal material has sufficient residence time in the decoupling return pipe 3, and sufficient heat exchange is performed between the fluid, other return materials and the wall surface. Specifically, the following aspects can be controlled: ① design reasonable decoupling return pipe structure parameters to prolong the flow process of the coal material; ② control the operating parameters of the decoupling return pipe 3, including but not limited to the mass flow ratio of the coal material and the return material, the flow rate of the sealing air at the coal feeding port, the flow rate of the return air and the loosening air at the sealing return valve 33; ③ strengthen the heat exchange of the coal particles.

[0067] (2) Prevent gas from backflowing from the coal feeding port. Specifically, this can be achieved by arranging the sealing air above the first coal feeder 22 and the coal feeding port.

[0068] (3) Preventing material from blocking the decoupling return pipe 3. Specifically, the blocking prevention device can be installed at the corner of the decoupling return pipe 3, which is prone to be blocked. The blocking prevention measures include, but are not limited to, wind blowing or mechanical vibration.

[0069] (4) Ensuring that the decoupling return pipe 3 is in a strict anaerobic environment. Specifically, the gas composition and inlet flow rate of the sealing air, the anti-blocking air, the return air or the loosening air can be adjusted to achieve this purpose.

[0070] In addition, the inventors of the present application conducted the following control experiments, the specific contents of which are as follows.

[0071] The comparative example of the present application is based on the simulation study of the internal coal residence time of the conventional return pipe structure:

[0072] Comparative Example 1: The conventional return pipe structure as shown in Figure 2 is adopted, and the structural parameters are as follows: pipe diameter D = 1.5 m, valve angle a = 32°, furnace angle b = 58°, bending number N = 0, and center segment length L0 = 13.15 m.

[0073] The coal particle size distribution is as shown in Figure 8 , the return material particle size distribution is as shown in Figure 9 , the return air gas composition is 79% N2, 15% O2, 4% CO2 and 2% CO, the return air flow rate is 0.3 m / s, and the coal / return material mass flow ratio is 20 kg / s:440 kg / s. Under this working condition, the maximum residence time of coal particles in the decoupling return pipe 3 is about 39 s.

[0074] The embodiment of the present application is based on the simulation study of the internal coal particle residence time of the decoupling return pipe structure of the present application:

[0075] Embodiment 1: The decoupling return pipe structure as shown in Figure 3 is adopted, and the structural parameters are as follows: pipe diameter D = 1.5 m, valve angle a = 60°, furnace angle b = 75°, bending number N = 1, bending angle a1 = 15°, and center segment length L1 = 5.57 m, L2 = 9.45 m.

[0076] The coal particle size distribution is as shown in Figure 8 , the return material particle size distribution is as shown in Figure 9 , the return air gas composition is 79% N2, 15% O2, 4% CO2 and 2% CO, the return air flow rate is 0.3 m / s, and the coal / return material mass flow ratio is 20 kg / s:440 kg / s. Under this working condition, the maximum residence time of coal particles in the decoupling return pipe 3 is about 57 s, which is increased by 18 s compared with Comparative Example 1.

[0077] Embodiment 2: The decoupling return pipe structure as shown in Figure 4The decoupling return pipe structure shown, the structural parameters are respectively: pipe diameter D = 1.5 m, valve angle α = 60°, furnace angle β = 73°, bending number N = 2, bending angle α1 = 44°, α2 = 17° and center section length L1 = 2.88 m, L2 = 3.58 m, L3 = 8.38 m.

[0078] The coal particle size distribution is shown as Figure 8 The return material particle size distribution is shown as Figure 9 The return material wind gas composition is 79% N2, 15% O2, 4% CO2 and 2% CO, the return material wind flow rate is 0.3 m / s, the coal / return material mass flow ratio is 20 kg / s:440 kg / s, under this working condition, the maximum residence time of coal particles in the decoupling return pipe 3 is about 55 s, which is increased by 16 s compared with the comparative example 1.

[0079] Example 3: using the decoupling return pipe structure shown as Figure 5 The structural parameters are respectively: pipe diameter D = 1.5 m, valve angle α = 15°, furnace angle β = 28°, bending number N = 1, bending angle α1 = 28° and center section length L1 = 9.63 m, L2 = 5.68 m.

[0080] The coal particle size distribution is shown as Figure 8 The return material particle size distribution is shown as Figure 9 The return material wind gas composition is 79% N2, 15% O2, 4% CO2 and 2% CO, the return material wind flow rate is 0.3 m / s, the coal / return material mass flow ratio is 20 kg / s:440 kg / s, under this working condition, the maximum residence time of coal particles in the decoupling return pipe 3 is about 46 s, which is increased by 7 s compared with the comparative example 1.

[0081] Example 4: using the decoupling return pipe structure shown as Figure 6 The structural parameters are respectively: pipe diameter D = 1.5 m, valve angle α = 15°, furnace angle β = 16°, bending number N = 2, bending angle α1 = 52°, α2 = 74° and center section length L1 = 9.69 m, L2 = 3.16 m, L3 = 2.6 m.

[0082] The coal particle size distribution is shown as Figure 8 The return material particle size distribution is shown as Figure 9 The return material wind gas composition is 79% N2, 15% O2, 4% CO2 and 2% CO, the return material wind flow rate is 0.3 m / s, the coal / return material mass flow ratio is 20 kg / s:440 kg / s, under this working condition, the maximum residence time of coal particles in the decoupling return pipe 3 is about 52 s, which is increased by 13 s compared with the comparative example 1.

[0083] Example 5: using the decoupling return pipe structure shown as Figure 7The structure parameters of the decoupling return pipe structure are as follows: pipe diameter D = 1.5 m, valve outlet angle a = 62°, furnace inlet angle b = 28°, bending number N = 2, bending angles a1 = -62° and a2 = 62°, and center segment lengths L1 = 7.87 m, L2 = 7.87 m, and L3 = 7.87 m.

[0084] The coal particle size distribution is as shown in Figure 8 The return material particle size distribution is as shown in Figure 9 The return material wind gas composition is 79% N2, 15% O2, 4% CO2, and 2% CO, the return material wind flow rate is 0.3 m / s, the coal feeding / return material mass flow rate ratio is 20 kg / s:440 kg / s, and under this working condition, the maximum residence time of the coal particles in the decoupling return pipe 3 is about 90 s, which is increased by 51 s compared with the comparative example 1.

[0085] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0086] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0087] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing", and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or can be integrated; can be mechanical connection, can also be electrical connection or communication with each other; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0088] 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.

[0089] In the present application, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material or characteristic is included in at least one embodiment or example of the present application. In the present specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any suitable manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0090] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and cannot be construed as limiting the present application, and changes, modifications, replacements and variations of the above embodiments made by those skilled in the art are within the scope of the present application.

Claims

1. A coal feeding system for a circulating fluidized bed, characterized by, The application relates to a coal feeding system for a circulating fluidized bed, which comprises the following components: a furnace; a coal feeding device for feeding coal; a decoupling return pipe, which comprises a first bending section and a second bending section, the upper end of the first bending section is connected with the coal feeding device, the lower end of the first bending section is connected with the upper end of the second bending section, the lower end of the second bending section is connected with the furnace, the first bending section gradually approaches the furnace in the direction from top to bottom, the angle between the length direction of the first bending section and the height direction of the furnace is alpha 1, wherein alpha 1 is greater than or equal to 0 DEG and less than 90 DEG, the angle between the second bending section and the height direction of the furnace is alpha 2, and alpha 1 is not equal to alpha 2; the upper end of the decoupling return pipe is provided with a return port.

2. The coal feeding system for a circulating fluidized bed according to claim 1, characterized by, the lower end of the furnace is provided with a necking portion, the cross-sectional area of the necking portion gradually decreases in the direction from top to bottom, the angle between the furnace wall surface of the necking portion and the horizontal plane perpendicular to the height direction of the furnace is gamma, and the angle between the lower end of the decoupling return pipe and the horizontal plane perpendicular to the height direction of the furnace is beta, wherein beta is less than gamma.

3. The coal feeding system for a circulating fluidized bed according to claim 2, characterized by wherein, gamma is greater than or equal to 70 DEG and less than or equal to 76 DEG.

4. The coal feeding system for a circulating fluidized bed according to claim 1, characterized by, the projection length of the decoupling return pipe on the horizontal plane perpendicular to the height direction of the furnace is W, and the length of the decoupling return pipe in the height direction of the furnace is H, wherein W / H is greater than or equal to 0.5 and less than or equal to 1.

3.

5. The coal feeding system for a circulating fluidized bed according to claim 1, characterized by, the coal feeding device comprises a coal hopper, a first coal feeder and a second coal feeder, an expansion joint and a coal feeding pipe, the coal hopper is connected with the first coal feeder, the first coal feeder is connected with the second coal feeder, the second coal feeder is connected with the expansion joint, the coal feeding pipe extends in the height direction of the furnace, the upper end of the coal feeding pipe is connected with the expansion joint, and the lower end of the coal feeding pipe is connected with the upper end of the decoupling return pipe.

6. A coal feeding method for a circulating fluidized bed, characterized by, The application relates to a coal feeding method applied to the coal feeding system for a circulating fluidized bed, and the coal feeding method comprises the following steps: feeding coal into the decoupling return pipe through the coal feeding device; feeding return material into the decoupling return pipe through the return port; mixing the coal and the return material through the decoupling return pipe, decoupling combustion of the coal and the return material through the two bending sections, and feeding the coal and the return material into the furnace.

7. The coal feeding method for a circulating fluidized bed according to claim 6, characterized by, The mass flow ratio of the coal and the return material is greater than or equal to 0.04 and less than or equal to 0.

06.

8. The coal feeding method for a circulating fluidized bed according to claim 6, characterized by, a sealing air interface is arranged on the coal feeding device, and sealing air is fed into the coal feeding device and the decoupling return pipe through the sealing air interface; and / or, return material air is fed into the decoupling return pipe through the return port.

9. The coal feeding method for a circulating fluidized bed according to claim 6, characterized by, a purging air interface is arranged on the decoupling return pipe, and anti-blocking air or loosening air is fed into the decoupling return pipe through the purging air interface; and / or, the coal feeding system further comprises a vibrating device, the vibrating device is connected with the decoupling return pipe, and the vibrating device is used for dredging the material in the decoupling return pipe.

Images