A raw coal bunker structure and deep peak regulation method for a direct-blowing pulverizing system

Abstract

A raw coal bunker structure and deep peak-shaving method for a direct-blowing pulverizing system, the structure includes several groups of raw coal bunker units, different raw coal bunker units store coal types with different levels of volatile matter and calorific value; the raw coal bunker unit includes a storage bunker, the storage bunker is connected to a coal feeder through a distribution bunker, the storage bunker and the distribution bunker are connected through a coal lowering pipe, the distribution bunker and the coal feeder are connected through a coal dropping pipe, and coal gates are provided on the coal lowering pipe and the coal dropping pipe; different raw coal bunker units are connected to the distribution bunker through an auger device. The present invention also provides a deep peak-shaving method for a raw coal bunker structure of a direct-blowing pulverizing system, which can quickly and flexibly distribute coal quality according to changes in unit load and combustion conditions, thereby improving the flexible peak-shaving capability of the unit.

Description

Technical Field

[0001] The invention belongs to the field of coal-fired power station boilers and relates to a raw coal bunker structure of a direct-blowing pulverizing system and a deep peak regulation method. Background Art

[0002] With the clean energy reform, the installed capacity of new energy power stations such as wind power and photovoltaic power has increased rapidly. However, new energy has the characteristics of randomness, intermittency, instability, etc. In response to the problem of new energy consumption, the National Energy Administration proposed to fully tap the peak-shaving capacity of the existing system and enhance the flexibility and adaptability of the system.

[0003] As an important equipment in coal-fired thermal power units, the main factor limiting the flexibility of boilers is the low-load stable combustion performance of the boilers. Different coal qualities entering the furnace correspond to different minimum stable combustion loads without oil addition. If the load is lower than the minimum stable combustion load, it is necessary to add fuel oil to ensure that the boiler can burn stably under this load. For boilers burning high-volatile bituminous coal, the minimum stable load without oil addition shall not be less than 30% to 35% of the rated operating conditions; for boilers burning lean coal, low-volatile bituminous coal, and lignite, the minimum stable load without oil addition shall not be less than 35% to 50% of the rated operating conditions; for boilers burning anthracite, the minimum stable load without oil addition shall not be less than 40% to 50% of the rated operating conditions. The higher the volatile content of the coal entering the furnace, the lower the minimum stable load without oil addition, and the stronger the unit's flexible operation capability. Due to the large deviation between the quality of the coal entering the furnace and the designed coal type, the boiler combustion is unstable and fire extinguishing occurs. Even if the boiler can burn stably, the minimum electric load of the coal-fired power unit under pure condensing conditions is 40% to 50%, which has a great impact on the flexible operation of the unit.

[0004] When the load of coal-fired thermal power units is high, the furnace temperature of the boiler is high, the flue gas volume is large, and the combustion stability is good. At this time, if more volatile matter and coal with lower calorific value can be mixed, the production and operation costs can be reduced on the basis of ensuring the load capacity of the unit; when the load of coal-fired thermal power units is low and close to the lowest stable combustion load without oil injection, the furnace temperature of the boiler is low, the flue gas volume is small, and the combustion stability is poor. At this time, the volatile matter and calorific value of the coal entering the furnace are required to be high to ensure the combustion stability of the boiler and prevent unsafe incidents such as boiler extinguishing due to unstable combustion. However, when coal-fired thermal power units participate in the peak load regulation of the power grid, their load changes are subject to the dispatching requirements of the power grid, and high or low loads may occur at any time. The existing raw coal bunker structure cannot flexibly mix the coal quality entering the furnace according to the changes in the unit load, affecting the peak load regulation capacity and load response speed of the unit. If the raw coal bunker structure can be optimized to improve the flexibility of the coal allocation, the coal entering the furnace can be flexibly mixed according to the unit load and combustion conditions, and the flexible peak load regulation capacity of the unit can be improved on the basis of reducing fuel costs. Summary of the invention

[0005] The purpose of the present invention is to address the problem in the above-mentioned prior art that the raw coal bunker structure cannot flexibly blend the quality of coal entering the furnace according to changes in the unit load, and to provide a raw coal bunker structure and a deep peak-shaving method for a direct-blowing pulverizing system, which can quickly and flexibly adjust the coal quality according to changes in the unit load and combustion conditions, thereby improving the flexible peak-shaving capability of the unit.

[0006] In order to achieve the above object, the present invention has the following technical solutions:

[0007] A raw coal bin structure for a direct-blowing pulverizing system comprises a plurality of raw coal bin units, wherein different raw coal bin units respectively store coal types with different grades of volatile matter and calorific value; the raw coal bin units comprise a storage bin, which is connected to a coal feeder via a blending bin, the storage bin and the blending bin are connected via a coal lowering pipe, the blending bin and the coal feeder are connected via a coal dropping pipe, and coal gates are provided on the coal lowering pipe and the coal dropping pipe; the blending bins of different raw coal bin units are connected via an auger device.

[0008] Preferably, the auger device comprises a main shaft penetrating the distribution bin and connecting the raw coal bin unit, a spiral blade is arranged on the periphery of the main shaft, and the distribution bins of the raw coal bin unit are connected through a material trough, and the material trough is wrapped around the outside of the spiral blade.

[0009] Preferably, an upper coal port and a lower coal port are separated and arranged on the upper and lower sides of the spiral blade in the mixing bin, and both the upper coal port and the lower coal port are rectangular openings, and electric shut-off doors are provided at the upper coal port and the lower coal port; the coal gate is driven by an electric motor.

[0010] Preferably, the auger device is horizontally arranged between the two mixing bins, the main shaft of the auger device is driven by a driving motor, the main shaft speed is 40r / min to 70r / min, and the gap between the spiral outer diameter of the spiral blade and the material trough is 12.5mm to 15mm.

[0011] Preferably, the spiral blade has a nominal spiral diameter of 400 mm to 800 mm and a spiral pitch of 355 mm to 500 mm.

[0012] Preferably, an inert gas interface is provided on the material trough, the inert gas interface is connected to an inert gas source via an inert gas pipeline, and an electric shut-off door is provided on the inert gas pipeline.

[0013] Preferably, the storage bin has a hyperbolic or conical structure, and a coal level monitoring device is provided in the storage bin; when the storage bin contains coal that is prone to blockage, an anti-blocking device is provided in the storage bin; and a lattice fence is provided at the coal inlet of the storage bin.

[0014] Preferably, the structure of the distribution bin is conical, the inner wall of the distribution bin is a smooth and wear-resistant stainless steel plate, an air cannon and an anti-blocking device are provided in the distribution bin; a coal level monitoring device is provided in the distribution bin; the coal storage capacity of the distribution bin is 1 / 4 of that of the storage bin.

[0015] The present invention also provides a deep peak regulation method for a raw coal bunker structure of a direct-blowing pulverizing system, comprising the following steps:

[0016] When the unit load rate is high, the boiler furnace temperature is high, the amount of flue gas generated by combustion is large, and the boiler combustion stability is good. Under this condition, the storage bin of the raw coal bunker unit storing high-volatile matter and high-calorific value coal is closed, and the low-volatile matter and low-calorific value coal falling into the blending bin of the adjacent raw coal bunker unit is transported to the blending bin of the raw coal bunker unit through the auger device to meet the unit's need to blend low-volatile matter and low-calorific value coal under high load;

[0017] When the unit needs to reduce load for peak operation, the unit load rate is low, the boiler furnace temperature is low, the amount of flue gas generated by combustion is small, and the boiler combustion stability is poor. Under this condition, the storage bin of the raw coal bunker unit storing low-volatile matter and low calorific value coal is closed, and the high-volatile matter and high calorific value coal falling into the distribution bin of the adjacent raw coal bunker unit is transported to the distribution bin of the raw coal bunker unit through the auger device, so that the coal entering the furnace under low load can be adjusted to high-volatile matter and high calorific value coal in time, ensuring the combustion stability of the boiler under low load and reducing the minimum load of the boiler for stable combustion without oil addition.

[0018] Compared with the prior art, the present invention has the following beneficial effects: by setting an auger device between two adjacent groups of raw coal bin units, the transportation of stored coal between the two raw coal bin units can be realized, and then the coal quality can be quickly and flexibly adjusted according to the changes in the unit load and combustion conditions, so as to meet the requirements of the peak-shaving capacity and load response speed of coal-fired thermal power units under the deep peak-shaving operation mode. When the unit is under high load and the combustion is stable, the blending ratio of low-volatile matter and low-calorific value coal is increased, and the production and operation costs are reduced on the basis of meeting the load-carrying capacity of the unit; when the unit is under low load and the stable combustion capacity is weak, the blending ratio of high-volatile matter and high-calorific value coal is increased, and the minimum stable combustion load of the boiler without oil injection is reduced, which improves the flexible peak-shaving capacity of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the structure of the raw coal bunker of the direct-blowing pulverizing system of the present invention;

[0020] In the attached figure: 1-storage bin; 2-coal lowering pipe; 3-distribution bin; 4-coal lowering pipe; 5-coal gate; 6-coal feeder; 7-auger device; 8-driving motor; 9-main shaft; 10-spiral blade; 11-material trough; 12-coal upper opening; 13-coal lowering opening; 14-electric shut-off door; 15-inert gas source; 16-inert gas pipeline; 17-electric stop door. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0022] See also Figure 1 The raw coal bin structure of the direct-blowing pulverizing system of the present invention includes several groups of raw coal bin units, and different raw coal bin units store coal types with different levels of volatile matter and calorific value. The raw coal bin unit includes a storage bin 1, and the storage bin 1 is connected to the coal feeder 6 through the distribution bin 3. The storage bin 1 and the distribution bin 3 are connected through a lower coal pipe 2, and the distribution bin 3 and the coal feeder 6 are connected through a coal drop pipe 4. The lower coal pipe 2 and the coal drop pipe 4 are both provided with a coal gate 5, and the coal gate 5 is driven by an electric motor. The distribution bins 3 are connected between different raw coal bin units through an auger device 7, and the auger device 7 is arranged horizontally. The auger device 7 includes a main shaft 9 that penetrates the distribution bin 3 and connects the raw coal bin units. The outer periphery of the main shaft 9 is provided with a spiral blade 10. The distribution bins 3 of the raw coal bin units are connected through a cylindrical or rectangular material trough 11, and the material trough 11 is wrapped around the spiral blade 10.

[0023] In order to prevent the spontaneous combustion of the coal accumulated in the trough 11 of the auger device, an inert gas interface is provided on the trough 11 , and the inert gas interface is connected to the inert gas source 15 through an inert gas pipeline 16 , and an electric shut-off door 17 is provided on the inert gas pipeline 16 .

[0024] The main shaft 9 of the auger device 7 is driven by a driving motor 8. In order to meet the conveying capacity of the auger device 7, the rotation speed of the main shaft 9 is 40r / min to 70r / min, and the gap between the spiral outer diameter of the spiral blade 10 and the material trough 11 is 12.5mm to 15mm.

[0025] The spiral blade 10 has a nominal spiral diameter of 400 mm to 800 mm and a spiral pitch of 355 mm to 500 mm.

[0026] The interior of the blending bin 3 is divided into an upper coal opening 12 and a lower coal opening 13 on the upper and lower sides of the spiral blade 10 , respectively. The upper coal opening 12 and the lower coal opening 13 are both rectangular openings, and are provided with electric shutoff doors 14 .

[0027] The structure of the storage bin 1 is hyperbolic or conical, and a coal level monitoring device is provided in the storage bin 1; when the storage bin 1 contains coal that is prone to blocking, an anti-blocking device is provided in the storage bin 1; and a lattice fence is provided at the coal inlet of the storage bin 1.

[0028] The structure of the distribution bin 3 is conical, and the inner wall of the distribution bin 3 is a smooth and wear-resistant stainless steel plate. The distribution bin 3 is provided with an air cannon and an anti-blocking device; the distribution bin 3 is provided with a coal level monitoring device; the coal storage capacity of the distribution bin 3 is 1 / 4 of that of the storage bin 1.

[0029] The embodiment of the present invention provides a deep peak regulation method for a raw coal bunker structure of a direct-blowing pulverizing system, comprising:

[0030] A single coal-fired thermal power unit is equipped with 4 to 6 sets of direct-blowing pulverizing system raw coal bunker units suitable for deep peak regulation. Among them, the storage bunker and distribution bunker corresponding to the bottom pulverizing system are named A storage bunker and A distribution bunker respectively, and the storage bunkers and distribution bunkers corresponding to the remaining 3 to 5 pulverizing systems are named B storage bunker and B distribution bunker, C storage bunker and C distribution bunker, D storage bunker and D distribution bunker, E storage bunker and E distribution bunker, and F storage bunker and F distribution bunker. High-volatile and high-calorific-value coal is stored in the A storage bunker, and medium-low-volatile and low-calorific-value coal is stored in the remaining B to F storage bunkers.

[0031] When the unit load rate is high, the boiler furnace temperature is high, the amount of flue gas generated by combustion is large, and the boiler combustion stability is good. Under this working condition, it is assumed that four pulverizing systems A, B, C, and D need to be put into operation. Close the coal gate 5 on the lower coal pipe 2 corresponding to the A storage bin (storing high-volatile and high-calorific value coal), and the coal gate 5 on the lower coal pipe 2 and the coal gate 5 on the coal drop pipe 4 corresponding to the adjacent B~D storage bins (storing medium-low volatile and low-calorific value coal) are both in the open state. The medium-low volatile and low-calorific value coal stored in the B~D storage bins falls into the B~D blending bins through the lower coal pipe 2, and then falls into the B~D coal feeder through the coal drop pipe 4, and then is ground into coal powder of qualified fineness by the coal mill and sent to the furnace for combustion. The auger device 7 between the A blending bin and the B blending bin is in operation, the upper coal port 12 in the A blending bin is closed and the lower coal port 13 is opened, the upper coal port 12 in the B blending bin is opened and the lower coal port 13 is closed, when the raw coal stored in the B storage bin falls into the B blending bin through the lower coal pipe 2, a part of it falls into the upper coal port 12 of the auger device 7 in the B blending bin, and under the rotation of the main shaft 9 of the auger device 7, the medium-low volatile matter and low calorific value coal is transported to the A blending bin through the rotating spiral blades 10, and falls into the A blending bin through the lower coal port 13 of the auger device 7 in the A blending bin, the coal gate 5 on the coal drop pipe 4 connecting the A blending bin and the A coal feeder is opened, and the medium-low volatile matter and low calorific value coal in the A blending bin falls into the A coal feeder, and is ground into coal powder of qualified fineness by the coal mill and sent into the furnace for combustion. By operating the auger device 7 between the A blending bin and the B blending bin, the stored coal in the B blending bin is transported to the A blending bin, meeting the unit's need to blend a large proportion of medium-low volatile matter and low calorific value coal under high load, thereby reducing fuel operating costs.

[0032] When the unit is required to be dispatched by load, it is necessary to reduce the load for peak load regulation. Under this condition, two pulverizing systems A and B are put into operation. Because the unit load rate is low, the boiler furnace temperature is low, the amount of flue gas generated by combustion is small, and the boiler combustion stability is poor. If the coal entering the furnace is low-volatile and low-calorific value coal, it is easy to cause the boiler to extinguish due to unstable combustion, or oil needs to be added to assist combustion, resulting in increased operating costs. Under this condition, the coal gate 5 on the lower coal pipe 2 corresponding to the B storage bin is closed, and the coal gate 5 on the lower coal pipe 2 and the coal gate 5 on the coal drop pipe 4 corresponding to the A storage bin are open. The high-volatile and high-calorific value coal stored in the A storage bin falls into the A blending bin through the lower coal pipe 2, and then falls into the A coal feeder through the coal drop pipe 4. After that, it is ground into coal powder with qualified fineness by the coal mill and sent to the furnace for combustion. The auger device 7 between the A blending bin and the B blending bin is in operation, the upper coal port 12 in the B blending bin is closed and the lower coal port 13 is opened; the upper coal port 12 in the A blending bin is opened and the lower coal port 13 is closed; when the raw coal stored in the A storage bin falls into the A blending bin through the lower coal pipe 2, a part of it falls into the upper coal port 12 of the auger device 7 in the A blending bin; under the rotation of the main shaft 9 of the auger device 7, the high-volatile matter and high-calorific value coal is transported to the B blending bin through the rotating spiral blades 10, and falls into the B blending bin through the lower coal port 13 of the auger device 7 in the B blending bin; the coal gate 5 on the coal drop pipe 4 connecting the B blending bin and the B coal feeder is opened, and the high-volatile matter and high-calorific value coal in the B blending bin falls into the B coal feeder, and then is ground into coal powder of qualified fineness by the coal mill and sent into the furnace for combustion. Through the operation of the auger device 7 between the A and B distribution bins, the stored coal in the A distribution bin is transported to the B distribution bin, ensuring that both sets of pulverizing systems grind high-volatile matter and high-calorific value coal. Since the coal entering the furnace under low load can be adjusted to high-volatile matter and high-calorific value coal in time, the combustion stability of the boiler under low load is guaranteed, and the minimum stable combustion load of the boiler without oil injection can be reduced, thereby improving the flexible peak-shaving capacity of the unit.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A raw coal bunker structure of a direct-blowing pulverizing system, characterized in that: The invention comprises a plurality of groups of raw coal bin units, wherein different raw coal bin units store coal types with different levels of volatile matter and calorific value respectively; the raw coal bin unit comprises a storage bin (1), the storage bin (1) is connected to a coal feeder (6) via a distribution bin (3), the storage bin (1) and the distribution bin (3) are connected via a coal lowering pipe (2), the distribution bin (3) and the coal feeder (6) are connected via a coal dropping pipe (4), and coal gates (5) are provided on the coal lowering pipe (2) and the coal dropping pipe (4); the distribution bins (3) are connected to each other via an auger device (7); The auger device (7) comprises a main shaft (9) penetrating the distribution bin (3) and connected to the raw coal bin unit, a spiral blade (10) is arranged on the outer periphery of the main shaft (9), and the distribution bins (3) of the raw coal bin unit are connected through a material trough (11), and the material trough (11) is wrapped around the outside of the spiral blade (10); The auger device (7) is horizontally arranged between the two mixing bins (3). The main shaft (9) of the auger device (7) is driven by a driving motor (8). The main shaft (9) has a rotation speed of 40 r / min to 70 r / min. The clearance between the spiral outer diameter of the spiral blade (10) and the material trough (11) is 12.5 mm to 15 mm. The material trough (11) is provided with an inert gas interface, and the inert gas interface is connected to an inert gas source (15) through an inert gas pipeline (16), and an electric stop door (17) is provided on the inert gas pipeline (16).

2. The raw coal bunker structure of the direct-blowing pulverizing system according to claim 1 is characterized by: The upper and lower sides of the spiral blade (10) are separated and provided with a coal opening (12) and a coal opening (13) in the mixing bin (3). Both the upper and lower coal openings (12) and (13) are rectangular openings. Both the upper and lower coal openings (12) and (13) are provided with electric shutoff doors (14). The coal gate (5) is driven by an electric motor.

3. The raw coal bunker structure of the direct-blowing pulverizing system according to claim 1 is characterized by: The spiral blade (10) has a nominal spiral diameter of 400 mm to 800 mm and a spiral pitch of 355 mm to 500 mm.

4. The raw coal bunker structure of the direct-blowing pulverizing system according to claim 1 is characterized by: The storage bin (1) has a hyperbolic or conical structure, and a coal level monitoring device is provided in the storage bin (1); when the storage bin (1) contains coal that is prone to blockage, an anti-blocking device is provided in the storage bin (1); and a lattice fence is provided at the coal inlet of the storage bin (1).

5. The raw coal bunker structure of the direct-blowing pulverizing system according to claim 1 is characterized by: The structure of the distribution bin (3) is conical, the inner wall of the distribution bin (3) is a smooth and wear-resistant stainless steel plate, an air cannon and an anti-blocking device are arranged in the distribution bin (3); a coal level monitoring device is arranged in the distribution bin (3); the coal storage capacity of the distribution bin (3) is 1 / 4 of that of the storage bin (1).

6. A deep peak regulation method for the raw coal bunker structure of a direct-blowing pulverizing system, characterized in that: The raw coal bunker structure of the direct-blowing pulverizing system according to any one of claims 1 to 5 is adopted, comprising the following steps: When the unit load rate is high, the boiler furnace temperature is high, the amount of smoke generated by combustion is large, and the boiler combustion stability is good. Under this working condition, the storage bin (1) of the raw coal bunker unit storing high-volatile matter and high-calorific value coal is closed, and the low-volatile matter and low-calorific value coal falling into the blending bin (3) of the adjacent raw coal bunker unit is transported to the blending bin (3) of the raw coal bunker unit through the auger device (7), so as to meet the unit's need to blend and burn low-volatile matter and low-calorific value coal under high load; When the unit needs to reduce load for peak-shifting operation, the unit load rate is low, the boiler furnace temperature is low, the amount of smoke generated by combustion is small, and the boiler combustion stability is poor. Under this condition, the storage bin (1) of the raw coal bunker unit storing low-volatile matter and low-calorific value coal is closed, and the high-volatile matter and high-calorific value coal falling into the blending bin (3) of the adjacent raw coal bunker unit is transported to the blending bin (3) of the raw coal bunker unit through the auger device (7), so that the coal entering the furnace under low load can be adjusted to high-volatile matter and high-calorific value coal in time, thereby ensuring the combustion stability of the boiler under low load and reducing the minimum load of the boiler for stable combustion without adding oil.

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