A variable-load and wide-coal-type lean-rich separation combustion device

Abstract

The present invention discloses a variable-load wide-coal-type concentration-dilution separation combustion device. A primary air-powder mixture flow velocity detector is arranged at the inlet of the primary air-powder pipe, and a control baffle for the inlet amount of lean-phase primary air-powder into the furnace and a concentration-dilution separation partition are arranged in the primary air-powder pipe; the outlet of the primary air pipe is communicated with the inlet of the coal mill, the first opening of the three-way flow valve is communicated with the inlet of the coal mill, the second opening of the three-way flow valve is communicated with the primary air and flue gas outlet at the bottom of the primary air-powder pipe, and the third opening of the three-way flow valve is communicated with the burnout air inlet of the furnace; one end of the concentration-dilution separation partition is axially connected to the inner wall at the bottom of the primary air-powder pipe, and the control baffle for the inlet amount of lean-phase primary air-powder into the furnace and the concentration-dilution separation partition are located directly above the bottom opening of the primary air-powder pipe. This combustion device can reduce the generation of NOx, and at the same time, the burner can operate in the optimal state under different loads.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection of power plants and relates to a variable-load and wide-coal-type concentration-dilution separation combustion device. Background Art

[0002] More than 70% of the costs of thermal power plants are used to purchase coal. Currently, due to the impact of the general environment of high coal prices and controlled electricity prices, thermal power plants are generally on the verge of losses and most of them cannot purchase the designed coal types with high coal prices. To control the power generation cost, power plants often purchase nearby coal types with relatively low costs but far from the designed coal quality. For a power station boiler operating under a given condition, its various air volume ratios and the combustion organization in the furnace can only achieve the best state for the designed coal type. Facing the rapidly changing load and variable coal types, the operating boiler cannot quickly make targeted responses to these changes. Moreover, with the increasing emphasis on energy conservation and emission reduction in China, higher requirements are put forward for the load regulation performance, low-load stable combustion ability, and cross-load optimized operation of power station coal-fired boilers. Therefore, when reforming existing burners and designing new burners, it is necessary to focus on the low-load stable combustion of pulverized coal and the optimized organization of the combustion process, and to achieve stable, safe, efficient, and low-pollution combustion as much as possible within a wide load range to ensure the normal operation of the boiler unit under the peak shaving operation state.

[0003] However, when the pulverized coal burner operates at different loads, the amount of pulverized coal carried by the primary air at different loads is different. At this time, if the primary air volume is not changed, the excess air coefficient of the primary air changes, so that the main combustion zone fails to operate under the optimal working condition. While affecting the combustion organization in the boiler, it destroys the original design's inhibition of the generation of nitrogen oxides and deteriorates the low-pollution performance of the burner. If the primary air volume is changed, the flow rate of the primary air-pulverized coal mixture in the primary air pipe changes. At this time, the separation effect deviates from the original design concept, and the concentration-dilution separation ratio deviates from the original design value, which also causes the burner not to operate in the optimal state. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a variable-load and wide-coal-type concentration-dilution separation combustion device, which can reduce the generation of NOx and enable the burner to operate under the optimal state at different loads.

[0005] To achieve the above purpose, the present invention discloses a variable-load and wide-coal-type concentration-dilution separation combustion device, which includes a coal mill, a primary air-pulverized coal pipe, a furnace, and a three-way flow valve;

[0006] The outlet of the coal mill is connected to the inlet of the primary air powder pipe, and the outlet of the primary air powder pipe is connected to the inlet of the furnace. At the inlet of the primary air powder pipe, a detector for the flow velocity of the primary air powder mixture is provided. Inside the primary air powder pipe, a control baffle for the amount of lean-phase primary air powder entering the furnace and a concentration separation baffle are provided.

[0007] The outlet of the primary air pipe is connected to the inlet of the coal mill. The first opening of the three-way flow valve is connected to the inlet of the coal mill. The second opening of the three-way flow valve is connected to the outlet of the primary air exhaust at the bottom of the primary air powder pipe. The third opening of the three-way flow valve is connected to the burnout air inlet of the furnace.

[0008] One end of the control baffle for the amount of lean-phase primary air powder entering the furnace is pivotally connected to the inner wall at the bottom of the primary air powder pipe. The control baffle for the amount of lean-phase primary air powder entering the furnace and the concentration separation baffle are located directly above the opening at the bottom of the primary air powder pipe. At the bottom of the control baffle for the amount of lean-phase primary air powder entering the furnace, a driving device for controlling the tilt angle of the control baffle for the amount of lean-phase primary air powder entering the furnace is provided.

[0009] Inside the primary air powder pipe, a number of blocking blocks are also provided. Among them, the blocking blocks and the concentration separation baffle are distributed in sequence along the air flow direction.

[0010] Along the air flow direction, the height of each blocking block gradually increases.

[0011] The driving device includes a stepping motor and a lead screw nut mechanism. Among them, the output end of the stepping motor is connected to one end of the lead screw in the lead screw nut mechanism. The other end of the lead screw is inserted into the primary air powder pipe and then connected to the lower surface of the control baffle for the amount of lean-phase primary air powder entering the furnace.

[0012] It also includes a data acquisition and controller. The input end of the data acquisition and controller is connected to the output end of the detector for the flow velocity of the primary air powder mixture. The output end of the data acquisition and controller is connected to the control end of the stepping motor and the control end of the three-way flow valve.

[0013] It also includes a concentration detection device for detecting the NOx concentration at the furnace outlet. Among them, the concentration detection device is connected to the data acquisition and controller.

[0014] The third opening of the three-way flow valve is connected to the burnout air inlet of the furnace through a burnout air pipe.

[0015] The first opening of the three-way flow valve is connected to the inlet of the coal mill through a primary air exhaust conveying pipe.

[0016] The length of the control baffle for the amount of lean-phase primary air powder entering the furnace is 2 / 3 of the height of the primary air powder pipe.

[0017] The present invention has the following beneficial effects:

[0018] When the variable-load wide-coal-type pulverized coal concentration-difference separation combustion device described in the present invention is in specific operation, when the boiler unit burns the designed coal type and operates at full load, the burner itself works in the optimal designed state. When the NOx generation at the furnace outlet meets the requirements at this time, the opening degree of the control baffle for the inlet quantity of the lean-phase primary air powder into the furnace is adjusted to zero. When the NOx generation at the furnace outlet is on the high side at this time, the control baffle for the inlet quantity of the lean-phase primary air powder into the furnace is opened, and the three-way flow valve ensures that the primary air exhaust gas enters the furnace as the burnout air, further controlling the NOx generation. When the boiler load decreases, the control baffle for the inlet quantity of the lean-phase primary air powder into the furnace is opened, prompting a part of the lean-phase primary air exhaust gas to return through the primary air exhaust gas conveying pipe to enter the coal mill to carry pulverized coal, ensuring that the flow velocity in the primary air powder pipe is equivalent to the designed flow velocity at a low primary air flow rate under low load and maintaining the designed concentration-difference separation ability. At the same time, the excess primary air exhaust gas required for realizing the concentration-difference separation of pulverized coal is recycled again, without entering the furnace to affect the excess air coefficient in the main combustion area, ensuring that the combustion is in the expected optimized state, ensuring the concentration-difference separation effect of the primary air powder under a wide load range, and at the same time, the oxygen content brought into the furnace by the primary air in the main combustion area under different loads can be maintained, ensuring that the air organization in the furnace during combustion under different loads is similar to the designed working conditions. In addition, when the NOx at the furnace outlet is on the high side, the present invention increases the share of the primary air exhaust gas as the burnout air through the three-way flow valve, reduces the oxygen content in the main combustion area, weakens the generation of NOx, provides guarantee for the ignition of the pulverized coal air flow and low-NOx combustion, and realizes stable, safe, efficient and environment-friendly combustion under a wide load. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0020] Wherein: 1 is a coal mill, 2 is a detector for the flow velocity of the primary air-pulverized coal mixture, 3 is a primary air powder pipe, 4 is a furnace, 5 is an inlet for burnout air, 6 is a primary air pipe, 7 is a primary air exhaust gas conveying pipe, 8 is a three-way flow valve, 9 is a data acquisition and controller, 10 is a lead screw, 11 is a stepping motor, 12 is a burnout air pipe, 13 is a stop block, 14 is a concentration-difference separation partition plate, 15 is a control baffle for the inlet quantity of the lean-phase primary air powder into the furnace. DETAILED DESCRIPTION OF THE INVENTION

[0021] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessarily confusing the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0022] A schematic structural diagram according to an embodiment of the present invention is shown in the accompanying drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are only exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0023] Referring to Figure 1 , the variable-load wide-coal-type concentration-dilution separation combustion device described in the present invention includes a coal mill 1, a primary air-powder mixture flow velocity detector 2, a primary air-powder pipe 3, a furnace 4, a burnout air inlet 5, a primary air pipe 6, a primary air lean gas conveying pipe 7, a three-way flow valve 8, a data acquisition and controller 9, a lead screw nut mechanism, a stepping motor 11, a burnout air pipe 12, a stop block 13, a concentration-dilution separation partition 14, and a control baffle 15 for the inlet amount of lean-phase primary air-powder into the furnace;

[0024] The outlet of the coal mill 1 is connected to the inlet of the primary air-powder pipe 3, and the outlet of the primary air-powder pipe 3 is connected to the inlet of the furnace 4. A primary air-powder mixture flow velocity detector 2 is provided at the inlet of the primary air-powder pipe 3. A control baffle 15 for the inlet amount of lean-phase primary air-powder into the furnace, a concentration-dilution separation partition 14, and several stop blocks 13 are provided in the primary air-powder pipe 3, wherein the stop blocks 13 and the concentration-dilution separation partition 14 are distributed in sequence along the air flow direction;

[0025] The outlet of the primary air pipe 6 is connected to the inlet of the coal mill 1 and one end of the primary air lean gas conveying pipe 7. The other end of the primary air lean gas conveying pipe 7 is connected to the first opening of the three-way flow valve 8. The second opening of the three-way flow valve 8 is connected to the primary air lean gas outlet at the bottom of the primary air-powder pipe 3. The third opening of the three-way flow valve 8 is connected to the burnout air inlet 5 of the furnace 4 through the burnout air pipe 12;

[0026] One end of the lean-phase primary air powder furnace inlet quantity control baffle 15 is pivotally connected to the inner wall of the bottom of the primary air powder pipe 3. The lean-phase primary air powder furnace inlet quantity control baffle 15 and the concentration-difference separation baffle 14 are located directly above the bottom opening of the primary air powder pipe 3.

[0027] The input end of the data acquisition and controller 9 is connected to the output end of the primary air powder mixture flow rate detector 2. The output end of the data acquisition and controller 9 is connected to the control end of the stepping motor 11 and the control end of the three-way flow valve 8. The output end of the stepping motor 11 is connected to one end of the lead screw 10 in the lead screw nut mechanism. The other end of the lead screw 10 is inserted into the primary air powder pipe 3 and then connected to the lower surface of the lean-phase primary air powder furnace inlet quantity control baffle 15.

[0028] During normal operation, the lean-phase primary air powder furnace inlet quantity control baffle 15 closes the primary air lean gas outlet at the bottom of the primary air powder pipe 3 to ensure that no lean-phase primary air lean gas enters the primary air lean gas conveying pipe 7.

[0029] The length of the lean-phase primary air powder furnace inlet quantity control baffle 15 is 2 / 3 of the height of the primary air powder pipe 3.

[0030] Principle and working process of the present invention:

[0031] First, obtain the optimized concentration-difference separation ratio, the velocities of the concentrated-phase and lean-phase primary air powder entering the furnace 4, and the excess air coefficient of the primary air powder under different loads and different coal types according to the historical operation experience data of the boiler. During the actual operation process, according to the different coal types and different load requirements fed in, adjust the opening degree of the lean-phase primary air powder furnace inlet quantity control baffle 15 and the three-way flow valve 8 through the primary air powder mixture flow rate detector 2 to regulate the flow rate of the primary air lean gas entering the primary air powder pipe 3.

[0032] When the boiler unit burns the designed coal type and operates at full load, the burner itself works in the optimal designed state. If the NOx concentration at the outlet of the furnace 4 meets the requirements at this time, the opening of the control baffle 15 for the input amount of lean-phase primary air powder into the furnace is adjusted to zero, and the working state of the present invention is the same as that of the traditional rich-lean separation combustion device. When the generated NOx concentration at the outlet of the furnace 4 is on the high side, the control baffle 15 for the input amount of lean-phase primary air powder into the furnace is gradually opened, and at the same time, the three-way flow valve 8 is adjusted. The primary air exhaust gas is sent into the furnace 4 as overfire air through the three-way flow valve 8 to further control the generation of NOx. When the boiler load drops, taking 50% load as an example, the control baffle 15 for the input amount of lean-phase primary air powder into the furnace is opened at this time, so that part of the lean-phase primary air exhaust gas re-enters the coal mill 1 through the primary air exhaust gas conveying pipe 7 to carry pulverized coal. Ensure that when the primary air flow rate is low under low load, the flow velocity in the primary air powder pipe 3 is equivalent to the designed flow velocity, and maintain the designed rich-lean separation ability. At the same time, the excess primary air exhaust gas required for realizing the rich-lean separation of pulverized coal is recycled again, which does not enter the furnace 4 to affect the excess air coefficient in the main combustion area, and ensures that the combustion is in the expected optimized state.

[0033] In summary, the present invention can ensure the rich-lean separation effect of primary air powder under a wide load range, and at the same time can maintain the oxygen amount brought into the furnace 4 by the primary air in the main combustion area under different loads, ensuring that the air organization in the furnace 4 during combustion under different loads is similar to the designed working condition. In addition, when the NOx concentration at the outlet of the furnace 4 is on the high side, the present invention can also increase the air volume of the primary air exhaust gas as overfire air through the three-way flow valve 8, reduce the oxygen amount in the main combustion area, and weaken the generation of NOx. Therefore, the present invention can provide guarantee for the ignition of pulverized coal air flow and low-NOx combustion, and realize stable, safe, efficient and environmental protection combustion under wide load.

[0034] At the same time, it should be noted that the opening adjustment of the control baffle 15 for the input amount of lean-phase primary air powder into the furnace and the flow distribution of the three-way flow valve 8 have no linear relationship with the boiler or burner load and the change of coal type. To achieve the optimal effect of the application of the present invention, in actual application, first, it is necessary to determine the opening of the control baffle 15 for the input amount of lean-phase primary air powder into the furnace and the flow distribution of the three-way flow valve 8 under different loads according to the actual operation effect of the boiler, and use this as the basis for the subsequent optimized operation and automatic adjustment of the combustion device.

[0035] In summary, the present invention can ensure the rich-lean separation effect of primary air powder under variable load and wide coal type conditions, and at the same time maintain the oxygen amount brought into the furnace 4 by the primary air in the main combustion area under different loads. Part of the primary air exhaust gas enters the overfire area as overfire air and serves as reburning fuel, which can reduce the nitrogen oxides that have been produced in the furnace 4, further reduce the generation of boiler combustion pollutants, and realize stable, safe, efficient and environmental protection combustion under variable load and variable coal type conditions.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A variable load and wide coal type separated rich and lean combustion device, characterized in that, It includes a coal mill (1), a primary air powder pipe (3), a furnace (4) and a three-way flow valve (8); The outlet of the coal mill (1) is communicated with the inlet of the primary air powder pipe (3), and the outlet of the primary air powder pipe (3) is communicated with the inlet of the furnace (4). A primary air powder mixture flow velocity detector (2) is provided at the inlet of the primary air powder pipe (3), and a lean-phase primary air powder inlet control baffle (15) and a lean-rich separation partition (14) are arranged in the primary air powder pipe (3); The outlet of the primary air pipe (6) is communicated with the inlet of the coal mill (1). The first opening of the three-way flow valve (8) is communicated with the inlet of the coal mill (1). The second opening of the three-way flow valve (8) is communicated with the primary air exhaust outlet at the bottom of the primary air powder pipe (3). The third opening of the three-way flow valve (8) is communicated with the burnout air inlet (5) of the furnace (4); One end of the lean-phase primary air powder inlet control baffle (15) is pivotally connected to the inner wall at the bottom of the primary air powder pipe (3). The lean-phase primary air powder inlet control baffle (15) and the lean-rich separation partition (14) are located directly above the bottom opening of the primary air powder pipe (3). A driving device for controlling the inclination angle of the lean-phase primary air powder inlet control baffle (15) is provided at the bottom of the lean-phase primary air powder inlet control baffle (15); The driving device includes a stepping motor (11) and a lead screw nut mechanism. Among them, the output end of the stepping motor (11) is connected to one end of the lead screw (10) in the lead screw nut mechanism. The other end of the lead screw (10) is inserted into the primary air powder pipe (3) and then connected to the lower surface of the lean-phase primary air powder inlet control baffle (15); It further includes a data acquisition and controller (9). The input end of the data acquisition and controller (9) is connected to the output end of the primary air powder mixture flow velocity detector (2). The output end of the data acquisition and controller (9) is connected to the control end of the stepping motor (11) and the control end of the three-way flow valve (8); It further includes a concentration detection device for detecting the NOx concentration at the outlet of the furnace (4). Among them, the concentration detection device is connected to the data acquisition and controller (9).

2. The variable-load wide-coal-type rich-lean separation combustion device according to claim 1, wherein, A number of stoppers (13) are also arranged in the primary air powder pipe (3).

3. The variable-load wide coal type thick-thin separation combustion device according to claim 1, characterized in that Each stopper (13) and the lean-rich separation partition (14) are distributed in sequence along the air flow direction.

4. The variable load wide coal type pulverized coal concentrator separated combustion device according to claim 2, wherein Along the air flow direction, the height of each stopper (13) gradually increases.

5. The variable-load wide coal type thick-thin separation combustion device according to claim 1, characterized in that, The third opening of the three-way flow valve (8) is connected to the burnout air inlet (5) of the furnace (4) through a burnout air pipe (12).

6. The variable-load wide coal type thick-thin separation combustion device according to claim 1, characterized in that, The first opening of the three-way flow valve (8) is connected to the inlet of the coal mill (1) through a primary air exhaust conveying pipe (7).

7. The variable-load wide-coal-type pulverized coal concentrator combustion device according to claim 1, characterized in that, The length of the lean-phase primary air powder inlet control baffle (15) is 2 / 3 of the height of the primary air powder pipe (3).

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