Quick flexible powder distribution device and method for direct-fired coal-fired unit coupled with middle storage powder supply

Abstract

The application discloses a kind of quick flexible powder distribution device and method of direct blowing medium storage system powder coupling coal-fired unit, device includes raw coal bin through coal feeder and connects medium speed coal mill, primary air pipe road access medium speed coal mill;Medium speed coal mill is divided into medium storage mill group, direct blowing mill group, medium storage mill group is sequentially communicated with pulverized coal separator, gas lock, pulverized coal buffer bin, powder feeder, air-powder mixer and combustor, pulverized coal separator exhaust gas outlet is connected with exhaust gas header through powder exhaust fan, primary air powder feeding pipe road access exhaust gas header, and the discharge end of direct blowing mill group is directly connected with combustor.The scheme adopts four mills direct blowing, two mills medium storage double branch coupling layout, realizes that powder is made with powder supply decoupling, utilizes buffer bin storage powder regulation, improves unit variable load response rate, realizes low load two mills high concentration pulverized coal stable combustion, independent powder adjustment improves furnace balanced combustion, relieves water-cooled wall high temperature corrosion and local overheating surface fault.

Description

Technical Field

[0001] This invention belongs to the technical field of coal-fired power generation equipment, specifically relating to a rapid and flexible pulverized coal distribution device and method for a coal-fired unit with direct-fired, centrally stored, controlled-supply, and coupled pulverized coal supply. Background Technology

[0002] As the proportion of new energy installed capacity in the new power system continues to increase, coal-fired units are gradually transforming from basic power sources to peak-shaving power sources. Rapid load changes and deep peak shaving have become the norm, which has led to technical problems such as high-temperature corrosion of boiler water-cooled walls, local overheating of heating surfaces, and poor stability of pulverized coal flames under low-load conditions.

[0003] Currently, coal-fired boilers generally adopt medium-speed coal mill direct-fired pulverizing systems. The pulverizing process is directly and rigidly coupled with the burner's pulverized coal supply, resulting in significant lag in pulverized coal delivery and severely restricting the unit's load response speed. Simultaneously, the large and unadjustable deviation in pulverized coal distribution at the mill outlet pipes easily leads to skewed combustion within the furnace, uneven heat load distribution, and increased risk of damage to heating surfaces. During low-load operation, multiple coal mills need to operate simultaneously near their minimum output to ensure operational safety, resulting in a high primary air-to-coal ratio, excessively low pulverized coal concentration at the burner outlet, and poor flame stability. Using oil guns or plasma combustion for stable combustion would significantly increase energy consumption.

[0004] Existing technologies cannot fundamentally solve the above problems by simply optimizing coal feeding and primary air control, and cannot break through the bottlenecks of delayed pulverization, uneven distribution, and stable combustion under low load. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid and flexible pulverization device and method for coal-fired power units with direct-fired pulverization and coal storage coupling, in order to solve the technical defects of existing direct-fired pulverization systems, such as sluggish coal powder transportation, slow load response, uneven coal powder distribution in pipelines leading to uneven burning in the furnace, and corrosion and overheating of heating surfaces.

[0006] To achieve the above objectives, this application provides the following technical solution: The first aspect of this application provides a rapid and flexible pulverized coal distribution device for a coal-fired unit with direct-fired coal storage and pulverized coal supply coupling, characterized in that it comprises: The raw coal bunker has its outlet connected to the feed inlet of the coal feeder, the outlet of the coal feeder is connected to the feed inlet of the medium-speed coal mill, and the primary air duct is connected to the air inlet of the medium-speed coal mill. The medium-speed coal mill includes a medium storage mill group and a direct-fired mill group. The discharge port of the medium storage mill group is connected in sequence to the inlet of the coal powder separator, the air lock and the inlet of the coal powder buffer bin. The outlet of the pulverized coal buffer silo is connected in sequence to the pulverizer, the air-pulverizer mixer and the burner; The exhaust gas outlet of the pulverized coal separator is connected in sequence to the exhaust fan, the exhaust gas header and the air-powder mixer, and the primary air conveying pipeline is connected to the exhaust gas header. The discharge port of the direct-fired mill is connected to the burner, forming a powder distribution structure that couples the direct-fired powder supply branch and the central storage powder supply branch. The coal powder buffer silo maintains a continuous dynamic circulation of coal powder while storing and supplying it, and the rated effective storage volume of the coal powder buffer silo matches the total amount of coal powder produced per hour under continuous rated operation of the medium-speed coal mill.

[0007] In one optional embodiment, the medium-speed coal mill is configured as six units, of which two constitute the medium storage mill group and the other four constitute the direct-fired mill group. The intermediate storage mill group is connected to the corresponding pulverized coal separator, pulverized coal buffer bin and burner respectively, and the direct-fired mill group is connected to the corresponding burner to form a coupled pulverization structure of four mills directly-fired pulverized coal supply and two mills intermediate storage pulverized coal supply.

[0008] In one optional embodiment, the two direct-fired mill groups and one intermediate storage mill group are connected to the burners arranged on the front wall of the boiler, and the other two direct-fired mill groups and one intermediate storage mill group are connected to the burners arranged on the rear wall of the boiler. The intermediate storage mill group corresponds to the burners in the middle layer area, and the direct-fired mill groups correspond to the burners in the upper layer area and the lower layer area, respectively.

[0009] In one optional embodiment, the pulverized coal buffer chamber is configured as a closed cavity structure with a volume of 80-110 m³, and the internal space of the pulverized coal buffer chamber forms a pulverized coal storage cavity that can accommodate the continuous dynamic flow of pulverized coal. The upper part of the pulverized coal buffer silo is provided with a feeding port, which is connected to the outlet of the airlock. The lower part of the pulverized coal buffer bin is provided with a discharge port, which is connected to the feed port of the pulverized coal feeder. The pulverized coal buffer silo is equipped with a material level detection device, which is used to monitor the pulverized coal level in the silo in order to maintain a dynamic balance in the operation of pulverized coal storage and supply.

[0010] In one optional embodiment, the bottom outlet of the pulverized coal buffer silo is connected to the inlet of multiple pulverized coal feeders, and the outlet of each pulverized coal feeder is connected to the corresponding air-pulverized coal mixer and burner, so as to realize independent adjustment of the pulverized coal supply of each pulverized coal supply branch.

[0011] In one optional embodiment, the primary air conveying pipeline is connected to the exhaust gas header inlet, and when the intermediate storage mill is shut down, primary air is supplied to the exhaust gas header to replace the exhaust gas and complete the coal powder conveying.

[0012] In one optional embodiment, the air inlet of the air-coal mixer is connected to the air outlet of the exhaust gas header, and the powder inlet of the air-coal mixer is connected to the powder outlet of the powder feeder, so as to fully mix the exhaust gas and pulverized coal to form an air-coal mixture that meets the conveying requirements.

[0013] In one optional embodiment, the coal powder outlet of the coal powder separator is connected to the feed inlet of the airlock, and the discharge outlet of the airlock is connected to the feed inlet of the coal powder buffer silo. The exhaust gas outlet of the pulverized coal separator is connected to the air inlet of the exhaust fan, and the air outlet of the exhaust fan is connected to the air inlet of the exhaust gas header.

[0014] In one optional embodiment, the discharge port of the intermediate storage mill is connected to the inlet of the pulverized coal separator via a pulverized coal silo pipeline, and the discharge port of the air-pulverized coal mixer is connected to the inlet of the burner via a burner pipeline.

[0015] A second aspect of this application provides a rapid and flexible pulverized coal distribution method for a coal-fired unit with a direct-fired, centrally stored, and coupled pulverized coal supply system. This method is implemented using the rapid and flexible pulverized coal distribution device for a coal-fired unit with a direct-fired, centrally stored, and coupled pulverized coal supply system as described above, and includes: The air-powder mixture produced by the medium-storage mill is sent to the pulverized coal separator for air-powder separation. The separated coal powder is temporarily stored in the coal powder buffer silo, and the exhaust gas generated during separation is sequentially sent to the air-coal mixer through the exhaust fan and exhaust gas header as the coal powder conveying medium. The coal powder buffer silo is equipped with a coal powder feeder at the bottom to independently supply coal powder to each corresponding burner, and the direct-fired mill maintains the operation mode of direct coal powder supply to the corresponding burner. Synchronously adjust the pulverizing output of the intermediate storage mill group and the output of each pulverizing pipeline feeder to achieve decoupling of the pulverizing process from the furnace pulverizing process; Based on the decoupling of pulverization and pulverization supply, and combined with the operating conditions of rapid load change, balanced combustion in the furnace, and stable combustion under low load, a matching pulverization operation mode is switched.

[0016] Furthermore, the step of temporarily storing the separated coal powder in a coal powder buffer silo specifically includes: The target material level, upper limit and lower limit of the pulverized coal buffer silo are preset, and the real-time material level of the pulverized coal buffer silo is collected in real time. When the real-time material level is within the set range formed by the upper limit of the material level and the lower limit of the material level, the amount of pulverized coal entering the storage mill group and the amount of pulverized coal exiting the feeder are kept matched. When the real-time material level is lower than the lower limit of the material level, the pulverizing output of the medium storage mill is increased to increase the amount of pulverized coal entering the silo. When the real-time material level is higher than the upper limit of the material level, reduce the pulverizing output of the medium storage mill to reduce the amount of pulverized coal entering the silo. By controlling the amount of pulverized coal entering and leaving the silo in a closed loop within different zones, the pulverized coal buffer silo can maintain a dynamic circulation condition of pulverized coal being stored and supplied simultaneously, thus avoiding long-term static accumulation of pulverized coal.

[0017] Furthermore, based on the decoupling of pulverization and pulverization supply, and combined with the operational requirements of rapid load changes, balanced combustion in the furnace, and stable combustion under low loads, the matching pulverization operation mode is switched, specifically including: Based on the target load change rate of the unit, calculate the load change time corresponding to the unit completing the load adjustment. Based on the number of feeders involved in load regulation, the target output increment and output change rate of a single feeder are calculated. Based on the calculations of the variable load duration, the target output increment of a single pulverizer, and the rate of output change, under the condition of unit load increase, the speed of the pulverizer in the high-storage branch is preferentially adjusted to rapidly increase the total amount of pulverized coal supplied to the furnace. Under the condition of reduced unit load, the speed of the pulverized coal feeder in the central storage branch should be reduced first to quickly reduce the total amount of pulverized coal supplied to the furnace; When the unit load approaches the preset target value, adjust the output of the direct-fired mill and adjust the coal powder supply of the intermediate storage mill so that the coal powder buffer silo level returns to the preset range.

[0018] Furthermore, based on the decoupling of pulverization and pulverization supply, and combined with the operational requirements of rapid load changes, balanced combustion in the furnace, and stable combustion under low loads, the matching pulverization operation mode is switched, specifically including: Pulverized coal distribution deviation tests were conducted on each pulverized coal pipeline of the direct-fired mill under different output conditions; Based on the test data of the powder distribution deviation test, a powder distribution deviation database for each direct-blown mill group corresponding to different output conditions is established. For the output conditions in the powder pipe powder quantity deviation database that have no measured data, the powder pipe powder quantity deviation data corresponding to the condition is solved by linear interpolation using two adjacent sets of known output parameters. Using the pulverized coal quantity deviation data of the pulverized coal pipe, the total amount of pulverized coal fed into the furnace of each row of burners along the width of the furnace on the front and rear walls of the boiler is calculated respectively. With the goal of equal total pulverized coal quantity in each row of burners along the width of the furnace, the required compensation pulverized coal quantity for each feeder in the central storage pulverized coal supply branch is calculated based on the difference in pulverized coal quantity in each row. By adjusting the pulverized coal supply to the burner corresponding to the central storage pulverized coal supply branch, the deviation in pulverized coal distribution in the direct-fired pipeline is compensated, making the heat load distribution in the width direction of the furnace more uniform.

[0019] Furthermore, based on the decoupled operation of pulverization and pulverized coal supply, and combined with the operational requirements of rapid load changes, balanced combustion in the furnace, and stable combustion under low load, a matching pulverized coal distribution operation mode is switched, specifically including: When the coal-fired power unit is operating at a low load of 20% to 30% of its rated load, all direct-fired mill units shall be shut down. Based on the aforementioned low-load operating conditions, the two medium-sized storage mills are kept running continuously to replace the conventional low-load three-mill redundant operation mode, thereby improving the pulverized coal concentration and flame stability of the burners corresponding to the medium-sized storage mills. Based on the aforementioned low-load operating conditions, when one of the two intermediate storage mill units fails and stops operating, air is supplied to the exhaust gas header through the primary air duct to feed pulverized coal to the burner, and preparation is made to start up one direct-fired mill unit, thus avoiding the unit tripping accident caused by the failure and shutdown of one of the two conventional direct-fired mill units.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention adopts a coupled arrangement of direct-fired and intermediate-storage coal mills. While retaining some of the direct-fired coal mill characteristics, it forms an adjustable buffer supply branch through the intermediate-storage mill group, coal powder buffer silo, and multiple feeders. This structure does not require changes to the original coal mill and burner body. Only partial modifications are needed to the existing direct-fired coal mill system to balance the reliability of the original system operation and the flexible coal powder adjustment capability of the newly added intermediate-storage branch.

[0021] 2. This invention adopts a continuous dynamic flow buffer coal powder silo with simultaneous storage and supply. The coal powder level in the silo is monitored in real time by a material level detection device, and the pulverizing output of the intermediate storage mill and the output of the feeder are adjusted in conjunction to keep the coal powder level in the buffer silo within a set range. This ensures the coal powder adjustment margin required for rapid load changes and reduces the safety risks of coal powder remaining in the conventional intermediate storage mill for a long time, accumulating powder, agglomerating, and oxidizing and heating up.

[0022] 3. This invention constructs a pulverizing and feeding system that couples the direct-fired pulverized coal feeding branch with the intermediate storage pulverized coal feeding branch, flexibly decoupling the pulverizing process of part of the coal mill from the pulverizer feeding process. When the unit load changes, the output of the pulverized coal buffer silo can be quickly adjusted by the feeder to directly change the amount of pulverized coal entering the furnace. Then, the pulverizing output of the intermediate storage mill group and the intermediate storage mill group are adjusted in a coordinated manner to restore the material level balance in the pulverized coal buffer silo. This reduces the impact of the pulverizing lag of the coal mill in the traditional direct-fired pulverizing system on the unit's load response and improves the unit's ability to quickly increase and decrease load.

[0023] 4. This invention features multiple independent pulverized coal feeders at the bottom of the pulverized coal buffer silo. Each feeder corresponds to a different pulverized coal supply branch or burner, allowing for independent adjustment of the pulverized coal quantity in each branch. By combining the pulverized coal flow rate deviation of each pulverized coal pipe in the direct-fired mill group, the pulverized coal supply rate of the central storage branch is compensated and adjusted. This ensures that the total pulverized coal quantity of each row of burners along the furnace width on the front or rear wall of the boiler tends to be consistent, thereby improving the uniformity of furnace heat load distribution and reducing the risks of localized uneven burning, high-temperature corrosion of water-cooled walls, and localized overheating of heating surfaces.

[0024] 5. This invention is applicable to low-load stable combustion conditions; when operating at low load, the direct-fired mill can be shut down, while the intermediate storage mill can be kept running in a relatively high output range; compared with the traditional low-output redundant operation mode of three coal mills, this method is conducive to reducing the primary air-coal ratio, increasing the coal powder concentration at the burner outlet, enhancing the stability of coal powder flame at low load, and reducing the dependence on fuel oil or plasma-assisted stable combustion. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This invention provides a fast and flexible coal pulverizer for a coal-fired unit with direct-fired coal storage and coal pulverizer supply coupling. Figures 2-3 A schematic diagram of a rapid and flexible pulverized coal distribution device for a coal-fired unit with direct-fired central storage and pulverized coal supply coupling, provided by the present invention, in operation throughout the furnace; In the diagram: 1. Raw coal bunker; 101. Front wall; 102. Rear wall; 103. Burner mounting port; 104. Burner fixing support assembly; 2. Coal feeder; 3. Medium-speed coal mill; 3a. First medium-speed coal mill; 3b. Second medium-speed coal mill; 3c. Third medium-speed coal mill; 3d. Fourth medium-speed coal mill; 3e. Fifth medium-speed coal mill; 3f. Sixth medium-speed coal mill; 4. Pulverized coal silo pipeline; 5. Pulverized coal separator; 6. Airlock; 7. Pulverized coal buffer silo; 8. Pulverized coal exhaust fan; 9. Pulverized coal feeder; 10. Air-coal mixer; 11. Exhaust gas pulverized coal delivery pipeline; 12. Exhaust gas header; 13. Primary air pipeline; 14. Primary air pulverized coal delivery pipeline; 15. Pipeline to burner; 16. Burner. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] To address the technical deficiencies mentioned in the background section, this embodiment provides a rapid and flexible pulverized coal mixing device and method for a coal-fired unit with direct-fired coal storage and pulverized coal supply coupling.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1 As shown, in a first aspect of the present invention, a rapid and flexible coal pulverizing device for a coal-fired unit with direct-fired coal storage and coal pulverizing coupling is provided, comprising: a raw coal bunker 1, a coal feeder 2, six medium-speed coal mills 3 (a first medium-speed coal mill 3a, a second medium-speed coal mill 3b, a third medium-speed coal mill 3c, a fourth medium-speed coal mill 3d, a fifth medium-speed coal mill 3e, and a sixth medium-speed coal mill 3f), a coal pulverizing silo pipeline 4, a coal pulverizer 5, an airlock 6, a coal pulverizing buffer silo 7, a coal exhaust fan 8, a coal feeder 9, an air-coal pulverizer mixer 10, a waste gas coal pulverizing pipeline 11, a waste gas header 12, a primary air pipeline 13, a primary air coal pulverizing pipeline 14, a burner pipeline 15, and a burner 16. In this embodiment, there are six medium-speed coal mills 3, two of which form a medium-storage mill group and the other four form a direct-fired mill group. The medium-storage mill group is connected to the corresponding coal powder separator 5, coal powder buffer silo 7 and burner 16 respectively, and the direct-fired mill group is directly connected to the corresponding burner 16 to form a coupled coal powder distribution structure of four direct-fired coal powder supply and two medium-storage coal powder supply.

[0032] The intermediate storage mill is arranged in the middle layer area of ​​the boiler burner 16, and the direct-fired mill is arranged in the upper and lower layers of the boiler burner 16 respectively; the outlet of each medium-speed coal mill 3 is connected to the burner 16 in the corresponding elevation area.

[0033] In this embodiment, the raw coal supply chain structure is such that the bottom outlet of each raw coal bunker 1 is sealed to the inlet of the corresponding coal feeder 2. The outlet of the coal feeder 2 is fixedly connected to the raw coal inlet of the medium-speed coal mill 3 with the same number. Raw coal enters the coal feeder 2 from the raw coal bunker 1, and after metering, it is continuously transported to the medium-speed coal mill 3. The primary air duct 13 is branched from the hot primary air main pipe of the boiler air preheater. Each branch duct is independently connected to the air inlet of a single medium-speed coal mill 3. The primary air duct 13 is equipped with electrically adjustable baffles in sections, which can independently control the air volume and air pressure of a single medium-speed coal mill 3. In this embodiment, the pulverizer outlet of the medium storage mill is sealed to the inlet flange of the corresponding pulverized coal separator 5 via the de-pulverizing silo pipeline 4; the pulverized coal separator 5 has two media outlets, one at the bottom and one at the top, with the lower end being the pulverized coal outlet and the upper sidewall being the exhaust gas outlet. The pulverized coal outlet of the pulverized coal separator is sealed to the top inlet of the pulverized coal buffer silo 7 via an airlock 6, and the airlock relies on the weight of the valve body to achieve unidirectional air lock; the bottom conical discharge port of the pulverized coal buffer silo 7 is connected to multiple parallel discharge branch pipes, each... The branch pipes are connected to the feed inlet of the independent pulverizer 9, and the discharge outlet of a single pulverizer is connected to the pulverized coal inlet of the air-pulverizer mixer 10. The finished product outlet of the air-pulverizer mixer 10 is connected to the pulverized coal inlet of the corresponding burner 16 through the burner-to-burner pipeline 15. This completes the closed medium-speed coal mill 3, the pulverized coal silo pipeline 4, the pulverized coal separator 5, the air lock 6, the pulverized coal buffer silo 7, the pulverizer 9, the air-pulverizer mixer 10, the burner-to-burner pipeline 15, and the burner 16 to form a closed medium-storage pulverized coal supply channel.

[0034] In this embodiment, the exhaust gas outlet of the pulverized coal separator 5 is connected to the air inlet of the exhaust fan 8 via the exhaust gas delivery pipeline 11. After the exhaust fan 8 completes the exhaust gas pressurization, the outlet main pipe of the exhaust fan 8 is connected to the air inlet of the exhaust gas header 12. The exhaust gas header 12 adopts a large-diameter cylindrical structure. Multiple branch pipelines are led out from the side wall of the cylinder according to the number of air-powder mixers 10. Each branch pipeline is individually connected to the exhaust gas inlet of the corresponding air-powder mixer 10. The exhaust gas flows at high speed in the cavity of the mixer 10 to form a negative pressure to suck up the pulverized coal falling from the pulverizer 9. The two are fully mixed to form an air-powder mixture with uniform concentration, qualified flow rate, and meeting the pipeline transportation conditions. One end of the primary air conveying pipeline 14 is sourced from the boiler hot primary air main pipe, and the other end is connected to the outlet side pipeline of the exhaust fan 8 or the side wall of the exhaust gas header 12. The pipeline is equipped with an electric shut-off valve and an air volume regulating baffle. When the storage mill group fails and is shut down for maintenance, or when the medium-speed coal mill 3 stops, resulting in insufficient exhaust gas, the control system automatically opens the valve of the primary air conveying pipeline 14, and the high-temperature primary air enters the exhaust gas header 12, directly replacing the exhaust gas of the original coal powder separator 5 as the conveying medium.

[0035] In this embodiment, all four direct-fired mill units retain the original direct-fired pipeline layout. The air-coal mixture produced by the medium-speed coal mill 3 is directly transported to the burner 16 through the original primary air-coal pipeline. The pulverizing output is equal to the coal powder supply of its corresponding burner 16, maintaining the traditional instant pulverizing and instant combustion operation mode.

[0036] Using the above-mentioned differentiated pipeline layout scheme, the entire pulverizing unit forms a pulverizing and supplying structure with four direct-fired mill groups and two intermediate storage mill groups operating in parallel. The physical decoupling of the pulverizing process and the combustion pulverizing process of the intermediate storage branch is achieved through the pulverized coal buffer silo 7. Under the premise of minimal unit modification, the rapid and balanced pulverizing supply of coal-fired units under variable load is fully optimized.

[0037] In the preferred detailed implementation structure of this scheme, the pulverized coal buffer silo 7 adopts a closed cavity structure with a volume of 80-110m³. Its rated effective storage volume is determined according to the pulverization rate of a single medium-sized storage mill unit under continuous rated operating conditions for about one hour. The pulverized coal buffer silo 7 mainly undertakes the short-term pulverized coal buffering and dynamic adjustment functions between the medium-sized storage mill unit and the burner 16. During normal operation, the pulverized coal in the silo maintains a continuous circulation state of simultaneous storage and supply.

[0038] This embodiment abandons the traditional large-capacity warehouse (greater than 300m³). 3 The coal powder storage design concept is based on the functional positioning of intermediate dynamic buffering, continuous coal powder circulation, and short-term reserve, matching the geometric volume of the silo with the coal powder storage duration. Volume parameter calculation process: Using the theoretical pulverizing capacity of a single medium-speed coal mill 3 running continuously for 1 hour under the rated operating condition of the boiler's maximum continuous evaporation capacity (BMCR) as the basis for calculating the maximum coal storage, it can be obtained through material balance that the pulverizing capacity of a single medium-speed coal mill 3 under rated operating condition is approximately 55.4t per hour.

[0039] The industry-standard design selects a bulk density of pulverized coal of 0.684 t / m³ and sets the effective filling coefficient of the pulverized coal silo at 0.8. The formula for calculating the effective volume of the silo is as follows: The effective volume of the silo = total weight of pulverized coal stored ÷ pulverized coal bulk density ÷ filling coefficient. Substituting the parameters, we get 55.4 ÷ 0.684 ÷ 0.8 = 101 m³. Therefore, the geometric volume of a single pulverized coal buffer silo 7 in this embodiment is determined to be 101 m³. In optional embodiments, the volume of the pulverized coal buffer silo 7 can be flexibly adjusted within the range of 80 m³ to 110 m³, all of which fall within the protection scope of the capacity buffer silo design in this invention.

[0040] Furthermore, this embodiment uses a 660MW front and rear wall opposed combustion boiler as the application carrier, with three layers of burners arranged vertically in the boiler furnace: lower, middle, and upper layers; for example... Figure 2 and Figure 3As shown, the six medium-speed coal mills 3 are arranged in a layered and paired manner along the front wall 101 and rear wall 102 on both sides of the boiler body. The six pieces of equipment are sequentially identified as the first medium-speed coal mill 3a, the second medium-speed coal mill 3b, the third medium-speed coal mill 3c, the fourth medium-speed coal mill 3d, the fifth medium-speed coal mill 3e, and the sixth medium-speed coal mill 3f.

[0041] This scheme preferably selects the second medium-speed coal mill 3b and the fifth medium-speed coal mill 3e arranged in the middle layer to form the medium storage mill group to carry out the transformation of the medium storage pulverized coal supply branch, and sets up two independent pulverized coal buffer silos 7, and matches them with corresponding pulverized coal separators 5, air locks 6, exhaust fans 8 and a complete set of pipelines and pulverized coal feeding equipment.

[0042] It is important to emphasize that selecting two medium-speed coal mills in the middle layer for modification is only the optimal implementation method of this invention, and does not limit the modification target to a single one. The selection and position of the middle storage mill can be flexibly adjusted according to the actual boiler structure, on-site equipment installation space, original pulverized coal pipeline laying path, and on-site safety management regulations. This leads to multiple feasible alternative implementation methods, such as upper-layer double-mill modification and lower-layer double-mill modification. Any of the above pairing methods conforms to the two-storage-four-direct-fired coal mill architecture design concept of this invention. As long as the two selected medium-speed coal mills are equipped with complete middle storage pulverized coal supply branches, and the remaining four coal mills retain their original direct-fired pulverized coal supply structure, they all fall within the protection scope of this invention.

[0043] The second aspect of this invention provides a rapid and flexible pulverized coal distribution method for a coal-fired unit with direct-fired coal storage and pulverized coal supply coupling. The method is implemented using the aforementioned rapid and flexible pulverized coal distribution device and includes system commissioning, dynamic pulverized coal buffer silo level control, rapid load increase / decrease control, furnace balanced combustion control, low-load stable combustion control, and abnormal operating condition handling. Specifically, it includes the following steps: Step 1: Equipment check and parameter initialization before system startup.

[0044] Before the unit is ignited and started up and the central storage and pulverized coal distribution system is put into operation, check the equipment status of the following components: raw coal bunker 1, coal feeder 2, medium-speed coal mill 3, pulverized coal discharge pipeline 4, pulverized coal separator 5, air lock 6, pulverized coal buffer 7, pulverized coal exhaust fan 8, pulverized coal feeder 9, air-pulverized coal mixer 10, exhaust gas pulverized coal delivery pipeline 11, exhaust gas header 12, primary air pipeline 13, primary air pulverized coal delivery pipeline 14, burner pipeline 15, and burner 16.

[0045] Confirm that the equipment, valves, pipelines, material level detection devices and unit control system meet the commissioning requirements, and set the target material level, upper limit and lower limit of the pulverized coal buffer silo 7 in the unit control system, set the output range of each feeder 9, the adjustment range of the exhaust fan 8, the exhaust gas adjustment range and the interlock protection parameters of each branch.

[0046] Step 2: Start-up of raw coal conveying and input of coal mill pulverizer.

[0047] The feeders 2 of each branch are started in sequence. Raw coal enters the feeder 2 from the raw coal bunker 1 and is continuously fed into the corresponding medium-speed coal mill 3 after being metered by the feeder 2. At the same time, the primary air pipeline 13 is opened to send primary air into the medium-speed coal mill 3 to complete the drying, grinding and coal powder carrying of the raw coal.

[0048] Step 3: Commissioning of the central storage branch line and gas-powder separation.

[0049] The air-coal mixture generated by the medium-sized storage mill enters the coal powder separator 5 for air-coal separation. The separated coal powder is then conveyed to the coal powder buffer bin 7 by its own gravity through the airlock 6.

[0050] The exhaust gas generated by the pulverized coal separator 5 is pressurized by the exhaust fan 8 and enters the exhaust gas delivery pipeline 11, which then flows into the exhaust gas header 12.

[0051] Step 4: Establish the initial material level of the pulverized coal buffer silo.

[0052] When the system is first put into operation, the amount of pulverized coal entering the central storage mill is greater than the total amount of pulverized coal exiting each feeder 9 at the bottom of the pulverized coal buffer silo 7, so that the amount of pulverized coal stored in the pulverized coal buffer silo 7 gradually increases.

[0053] When the coal powder buffer silo 7 reaches the preset target level, the pulverizing output of the intermediate storage mill and the total output of each feeder 9 are adjusted to maintain a dynamic balance between the amount of coal powder entering and leaving the silo, and the system switches to a state of simultaneous storage and supply.

[0054] Step 5: Start-up of the exhaust gas delivery channel and distribution of air volume.

[0055] Start the exhaust fan 8 of the coal powder supply branch to pressurize the exhaust gas generated by the coal powder separator 5 and send it into the exhaust gas header 12.

[0056] Based on the coal powder delivery volume of each central storage coal powder supply branch, the exhaust gas flow rate of each exhaust gas header 12 is adjusted to match the air intake volume of each air-coal mixer 10 with the coal powder output volume of the corresponding coal feeder 9, thereby maintaining the required air-coal ratio and delivery speed for coal powder pipeline transportation.

[0057] Step 6: Start the powder feeder and supply powder to the central storage branch.

[0058] Start the coal feeder 9 at the bottom of the coal powder buffer silo 7, so that the coal powder enters the air-coal mixer 10 after being metered by the coal feeder 9, and mixes with the exhaust gas provided by the exhaust gas header 12 to form an air-coal mixture.

[0059] The air-coal mixture is transported to the corresponding burner 16 via the burner-to-burner pipeline 15, thereby forming a coupled coal supply state in which the direct-fired coal supply branch and the intermediate storage coal supply branch operate in parallel.

[0060] Step 7: Dynamic level control of pulverized coal buffer silo.

[0061] During normal operation, the pulverized coal buffer silo 7 maintains a state of simultaneous storage and supply. The material level in the silo is jointly determined by the amount of pulverized coal entering the silo from the intermediate storage mill and the total amount of pulverized coal exiting the silo from each feeder 9.

[0062] The amount of pulverized coal entering the silo is mainly affected by the coal feeder 2 of the medium-speed coal mill and the pulverizing output of the medium-speed coal mill 3; the amount of pulverized coal exiting the silo is jointly determined by the operating output of each pulverizer 9 at the bottom of the pulverized coal buffer silo 7.

[0063] The coal powder level is continuously collected by a level detection device installed on the coal powder buffer silo 7, and the level signal is transmitted to the unit control system. The unit control system adjusts the pulverizing output of the intermediate storage mill and the operating status of the feeder 9 according to the relationship between the real-time level and the target level, the upper limit of the level and the lower limit of the level.

[0064] When the real-time material level is within the set range formed by the upper and lower limits of the material level, the amount of pulverized coal entering the central storage mill group and the total amount of pulverized coal exiting each feeder 9 are dynamically matched to keep the material level in the pulverized coal buffer silo 7 stable near the target material level.

[0065] When the real-time material level is lower than the lower limit, increase the coal feed rate of the coal feeder 2 of the medium storage mill and the pulverizing output of the medium-speed coal mill 3 to increase the amount of pulverized coal entering the silo; if necessary, under the condition of not affecting the pulverized coal supply demand of the boiler, restrict all or part of the pulverizers 9 from continuing to increase their output, or appropriately reduce the total pulverized coal output of the pulverizers 9 so that the material level of the pulverized coal buffer silo 7 gradually rises back to the set range.

[0066] When the real-time material level is higher than the upper limit, reduce the coal feed rate of the coal feeder 2 of the medium storage mill and the pulverizing output of the medium-speed coal mill 3 to reduce the amount of pulverized coal entering the silo; if necessary, under the condition that the boiler load allows, appropriately increase the output of all or part of the pulverized coal feeders 9 so that the material level of the pulverized coal buffer silo 7 gradually falls back to the set range.

[0067] Before implementing rapid load increase and rapid load decrease control, the target output change and output change rate of each feeder 9 are calculated based on the unit's current load, target load, target load change rate, and the number of feeders 9 involved in the regulation.

[0068] Assume the rated load of the unit is The total fuel supply of the system under BMCR conditions is During the process of adjusting the unit from the current load to the target load, the difference in the total powder feed rate of the system is:

[0069] When the target load change rate is When the unit is %Pe / min, the required load change time is:

[0070] If n powder feeders participate in rapid adjustment and are required to complete the adjustment within time T, then the target output increment and output rate change rate of a single powder feeder are:

[0071] Meanwhile, in order to maintain the safety of powder feeding and the required air-to-powder ratio, the primary air volume entering the mill should be adjusted simultaneously.

[0072] Step 8: Rapid load increase control.

[0073] After receiving the load increase command, the unit adopts an adjustment method of first increasing the powder supply of the central storage powder supply branch and then increasing the powder production output of the central storage mill.

[0074] The first step is to increase the operating speed of the coal feeder 9 in the central storage coal supply branch, which is involved in the regulation, according to the increase in coal powder required for load increase, so as to quickly release the stored coal powder in the coal powder buffer bin 7 and increase the total amount of coal powder entering the furnace.

[0075] After the incremental pulverized coal is output by the pulverizer 9, it is mixed with exhaust gas in the air-coal mixer 10 and then transported to the burner 16 through the burner pipeline 15. The increase in the amount of pulverized coal entering the furnace at this stage is mainly accomplished by the pulverizer 9, without waiting for the pulverizing output of the intermediate storage mill to increase simultaneously.

[0076] The second step is to simultaneously increase the output of the pulverizer 9 and the exhaust fan 8 according to the increase in output of the pulverizer 9, and adjust the pulverizer supply air volume of each pulverizer supply branch of the exhaust gas header 12 so that the pulverizer supply gas flow rate matches the increased pulverized coal volume.

[0077] The third step is to increase the coal feed rate of the coal feeder 2 of the medium-speed coal mill and the pulverizing output of the medium-speed coal mill 3, increase the amount of pulverized coal entering the silo, and replenish the pulverized coal consumed by the pulverized coal buffer silo 7 during the load increase process.

[0078] The pulverizing output of the intermediate storage mill is gradually adjusted according to the decrease in the material level of the pulverized coal buffer silo 7, so that the intermediate storage mill can undertake the task of replenishing pulverized coal after the load is increased.

[0079] The fourth step is to gradually adjust the output of each feeder 9 to a steady-state value that matches the target load when the unit load approaches the target value. Continue to adjust the pulverizing output of the intermediate storage mill to restore the coal powder buffer silo 7 to the set range. The system will then re-enter a stable operating state of simultaneous storage and supply. If necessary, the pulverizing output of the direct-fired mill will be appropriately increased.

[0080] Step 9: Rapid load reduction control.

[0081] After receiving the load reduction command, the unit adopts an adjustment method that first reduces the coal feed rate of the central storage coal supply branch, then reduces the coal grinding output of the central storage mill, and uses the coal powder buffer bin 7 to receive the surplus coal powder.

[0082] The first step is to reduce the operating speed of the coal feeder 9 in the central coal storage branch, which is involved in the regulation, according to the amount of coal powder reduction required for load reduction, so as to quickly reduce the amount of coal powder output from the coal powder buffer silo 7 to the furnace and reduce the amount of fuel entering the furnace.

[0083] In the second step, during the initial load reduction phase, the pulverizing output of the medium-speed coal mill 3 cannot immediately decrease due to the inertia of the coal stored inside the mill and the pulverizing process. The excess pulverized coal generated during this stage continues to enter the pulverized coal buffer silo 7, which temporarily absorbs the deviation between the pulverizing output of the medium-speed coal mill and the pulverized coal supply from the burner.

[0084] The third step is to simultaneously reduce the output of the pulverizer 9 and the pulverized coal delivery air volume of each branch of the exhaust gas header 12, based on the reduction in the output of the pulverizer 9, so that the pulverized coal delivery air volume matches the reduced pulverized coal volume.

[0085] The fourth step is to reduce the coal feed rate of the coal feeder 2 and the pulverizing output of the medium-speed coal mill 3 when the unit load approaches the target value, and to coordinate and adjust the pulverizing output of the coal feeder 9 and the pulverizing output of the coal feeder 9 according to the real-time material level of the coal powder buffer silo 7.

[0086] When the coal pulverized buffer silo 7 rises during the load reduction process, the pulverizing output of the intermediate storage mill group is further reduced, and the output of the feeder 9 is appropriately increased under the condition that the boiler load allows, so that the coal pulverized buffer silo 7 gradually recovers to the set range, and the pulverizing output of the direct-fired mill group is appropriately reduced when necessary.

[0087] Step 10: Control of balanced combustion in the furnace.

[0088] Multiple coal feeders 9 are installed at the bottom of the coal powder buffer silo 7. Each coal feeder 9 corresponds to an independent coal powder supply pipeline and burner 16. The coal powder supply of each coal powder supply branch can be adjusted independently.

[0089] Under different output conditions of the direct-fired mill, a pulverized coal distribution deviation test was conducted on each pulverized coal pipeline to obtain the pulverized coal flow rate and distribution ratio of each pulverized coal pipeline under different outputs of medium-speed coal mills. Based on the test data, a database of pulverized coal pipeline deviation under different output conditions of each direct-fired mill was established.

[0090] For the medium-speed coal mill 3 output condition where there is no measured data in the coal powder quantity deviation database, the coal powder quantity deviation data of the coal powder pipes of two adjacent known output conditions are used, and the coal powder quantity deviation of each coal powder pipe under the corresponding condition is determined by linear interpolation.

[0091] Based on the real-time output of the direct-fired mill and the corresponding deviation of the pulverized coal quantity in the pulverized coal pipe, the pulverized coal quantity supplied by the direct-fired pulverized coal supply branch to each row of burners 16 along the furnace width direction of the boiler front wall 101 and rear wall 102 is calculated, and the total pulverized coal quantity fed into the furnace to each row of burners 16 is further calculated.

[0092] With the goal of ensuring that the total amount of pulverized coal in each row of burners 16 along the width of the furnace wall is consistent, the compensation amount of pulverized coal required by each feeder 9 in the central storage pulverized coal supply branch is calculated based on the difference between the total amount of pulverized coal in each row of burners 16.

[0093] When the amount of pulverized coal supplied to a certain burner 16 by the direct-fired pulverized coal supply branch is too low, the operating output of the corresponding intermediate storage pulverized coal feeder 9 of that burner 16 is increased, thereby increasing the amount of pulverized coal to be compensated by the intermediate storage pulverized coal supply branch; when the amount of pulverized coal supplied to a certain burner 16 by the direct-fired pulverized coal supply branch is too high, the operating output of the corresponding intermediate storage pulverized coal feeder 9 of that burner 16 is decreased, thereby reducing the amount of pulverized coal to be compensated by the intermediate storage pulverized coal supply branch.

[0094] The coal powder quantity is calculated and compensated for on the front wall 101 and rear wall 102 of the boiler, respectively. By independently adjusting the output of each coal feeder 9, the deviation of the coal powder quantity in the direct-fired coal tube is compensated, so that the total coal powder quantity of each row of burners 16 along the width of the furnace wall tends to be balanced. This helps to improve the combustion skew and uneven heat load distribution along the width of the furnace, and reduces the risk of localized uneven burning, high-temperature corrosion of water-cooled walls, and localized overheating of heating surfaces.

[0095] Step 11: Low-load stable combustion control.

[0096] When the unit is operating at an ultra-low load of 30% or below, all direct-blown mill units will be reduced and shut down in sequence, while the two intermediate storage mill units will continue to operate continuously.

[0097] The output of each of the two medium-speed coal mills is higher than that of a single mill under low-load operation of three conventional medium-speed coal mills. The two medium-speed coal mills maintain a relatively stable pulverizing output, and each feeder independently adjusts the coal powder supply according to the actual fuel demand of the unit, so that the pulverizing output of the medium-speed coal mills is no longer directly limited by the instantaneous coal powder demand of the burner.

[0098] As the output of the pulverizer 9 decreases, the output of the exhaust fan 8 and the pulverized coal delivery air volume of each branch of the exhaust gas header 12 are reduced simultaneously, so that the pulverized coal delivery gas flow rate matches the pulverized coal supply, reducing the primary air-to-coal ratio and increasing the pulverized coal concentration at the burner 16 outlet.

[0099] Simultaneously, the total pulverizing output of the two intermediate storage mills is adjusted based on the real-time material level in the pulverized coal buffer silo 7. When the material level in the pulverized coal buffer silo 7 is lower than the set range, the total pulverizing output of the intermediate storage mills is increased; when the material level in the pulverized coal buffer silo 7 is higher than the set range, the total pulverizing output of the intermediate storage mills is decreased, so that the pulverized coal buffer silo 7 is maintained at a certain material level.

[0100] By using the above control methods, the number of medium-speed coal mills 3 that are put into operation under low load conditions is reduced, the operating output of a single medium-speed coal mill group is increased, and the corresponding coal powder delivery air volume is reduced, thereby improving the ignition conditions of pulverized coal and the stability of the flame under low load, and reducing the dependence on auxiliary combustion stabilization methods such as fuel oil or plasma.

[0101] Step 12: Handling Abnormal Operating Conditions.

[0102] When the pulverized coal storage unit fails and stops operating, the primary air conveying pipeline 14 is opened to send primary air into the exhaust gas header 12 to replace the exhaust gas as the pulverized coal conveying medium.

[0103] The pulverized coal in the pulverized coal buffer silo 7 continues to enter the air-coal mixer 10 via the pulverizer 9, and is carried by the primary air and transported to the corresponding burner 16 via the burner pipeline 15, providing continuous pulverized coal supply time for operation mode switching and fault handling.

[0104] When the unit is under low-load stable combustion conditions and one medium-sized storage mill unit fails and stops operating, the other medium-sized storage mill unit continues to produce pulverized coal, and the pulverized coal stored in the pulverized coal buffer silo 7 and the primary air conveying channel are used to maintain the pulverized coal supply.

[0105] Simultaneously, a direct-fired mill unit will be started to gradually increase its pulverizing output and bear the corresponding fuel load, avoiding a continuous decrease in the amount of pulverized coal fed into the unit due to a single intermediate storage mill unit failure. After the intermediate storage mill unit failure is resolved, pulverizing will be restarted and the dynamic material level in the pulverized coal silo will be gradually restored. The started direct-fired mill unit will then be shut down at an appropriate time.

[0106] This method, while retaining the original pulverized coal supply mode of the four direct-fired mills, achieves rapid pulverization, balanced pulverization, and stable combustion under low load by using two intermediate storage mills, pulverized coal buffer silos 7, and independent pulverized coal feeding branches. It is suitable for the flexible modification of existing direct-fired pulverizing systems.

[0107] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rapid and flexible pulverized coal distribution device for a coal-fired unit with direct-fired central storage and pulverized coal supply coupling, characterized in that: include: The raw coal bunker has its outlet connected to the feed inlet of the coal feeder, the outlet of the coal feeder is connected to the feed inlet of the medium-speed coal mill, and the primary air duct is connected to the air inlet of the medium-speed coal mill. The medium-speed coal mill includes a medium storage mill group and a direct-fired mill group. The discharge port of the medium storage mill group is connected in sequence to the inlet of the coal powder separator, the air lock and the inlet of the coal powder buffer bin. The outlet of the pulverized coal buffer silo is connected in sequence to the pulverizer, the air-pulverizer mixer and the burner; The exhaust gas outlet of the pulverized coal separator is connected in sequence to the exhaust fan, the exhaust gas header and the air-powder mixer, and the primary air conveying pipeline is connected to the exhaust gas header. The discharge port of the direct-fired mill is connected to the burner, forming a powder distribution structure that couples the direct-fired powder supply branch and the central storage powder supply branch. The coal powder buffer silo maintains a continuous dynamic circulation of coal powder while storing and supplying it, and the rated effective storage volume of the coal powder buffer silo matches the total amount of coal powder produced per hour under continuous rated operation of the medium-speed coal mill.

2. The rapid and flexible pulverized coal distribution device for direct-fired, centrally stored, and coupled coal-fired power units according to claim 1, characterized in that, The medium-speed coal mill is configured with six units, two of which constitute the medium storage mill group and the other four constitute the direct-fired mill group. The intermediate storage mill group is connected to the corresponding pulverized coal separator, pulverized coal buffer bin and burner respectively, and the direct-fired mill group is connected to the corresponding burner to form a coupled pulverization structure of four mills directly-fired pulverized coal supply and two mills intermediate storage pulverized coal supply.

3. The rapid and flexible pulverized coal distribution device for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 2, is characterized in that, The two direct-fired mill groups and one intermediate storage mill group are connected to the burners arranged on the front wall of the boiler, and the other two direct-fired mill groups and one intermediate storage mill group are connected to the burners arranged on the rear wall of the boiler. The intermediate storage mill group corresponds to the burners in the middle layer area, and the direct-fired mill groups correspond to the burners in the upper layer area and the lower layer area, respectively.

4. The rapid and flexible pulverized coal distribution device for a direct-fired, centrally stored, and coupled coal-fired power unit according to claim 1, characterized in that, The pulverized coal buffer chamber is configured as a closed cavity structure with a volume of 80-110 m³. The internal space of the pulverized coal buffer chamber forms a pulverized coal storage cavity that can accommodate the continuous dynamic flow of pulverized coal. The upper part of the pulverized coal buffer silo is provided with a feeding port, which is connected to the outlet of the airlock. The lower part of the pulverized coal buffer bin is provided with a discharge port, which is connected to the feed port of the pulverized coal feeder. The pulverized coal buffer silo is equipped with a material level detection device, which is used to monitor the pulverized coal level in the silo in order to maintain a dynamic balance in the operation of pulverized coal storage and supply.

5. The rapid and flexible pulverized coal distribution device for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 1, characterized in that, The bottom outlet of the pulverized coal buffer silo is connected to the inlet of multiple pulverized coal feeders, and the outlet of each pulverized coal feeder is connected to the corresponding air-pulverized coal mixer and burner, so as to realize independent adjustment of the pulverized coal supply of each pulverized coal supply branch.

6. The rapid and flexible pulverized coal distribution device for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 1, characterized in that, The primary air conveying pipeline is connected to the exhaust gas header inlet. When the intermediate storage mill is shut down, primary air is supplied to the exhaust gas header to replace the exhaust gas and complete the coal powder conveying.

7. The rapid and flexible pulverized coal distribution device for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 1, characterized in that, The air inlet of the air-coal mixer is connected to the air outlet of the exhaust gas header, and the powder inlet of the air-coal mixer is connected to the powder outlet of the powder feeder, so as to fully mix the exhaust gas and coal powder to form an air-coal mixture that meets the conveying requirements.

8. The rapid and flexible pulverized coal distribution device for a coal-fired unit with direct-fired, intermediate-storage, and pulverized coal supply coupling as described in claim 1, characterized in that, The coal powder outlet of the coal powder separator is connected to the feed inlet of the air lock, and the discharge outlet of the air lock is connected to the feed inlet of the coal powder buffer silo. The exhaust gas outlet of the pulverized coal separator is connected to the air inlet of the exhaust fan, and the air outlet of the exhaust fan is connected to the air inlet of the exhaust gas header.

9. The rapid and flexible pulverized coal distribution device for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 1, characterized in that, The discharge port of the intermediate storage mill is connected to the inlet of the pulverized coal separator through a pulverized coal silo pipeline, and the discharge port of the air-pulverized coal mixer is connected to the inlet of the burner through a burner pipeline.

10. A rapid and flexible pulverized coal blending method for a coal-fired unit with direct-fired, centrally stored, and coupled pulverized coal supply, characterized in that: The rapid powder dispensing device according to any one of claims 1 to 9 is used, comprising: The air-powder mixture produced by the medium-storage mill is sent to the pulverized coal separator for air-powder separation. The separated coal powder is temporarily stored in the coal powder buffer silo, and the exhaust gas generated during separation is sequentially sent to the air-coal mixer through the exhaust fan and exhaust gas header as the coal powder conveying medium. The coal powder buffer silo is equipped with a coal powder feeder at the bottom to independently supply coal powder to each corresponding burner, and the direct-fired mill maintains the operation mode of direct coal powder supply to the corresponding burner. Synchronously adjust the pulverizing output of the intermediate storage mill group and the output of each pulverizing pipeline feeder to achieve decoupling of the pulverizing process from the furnace pulverizing process; Based on the decoupling of pulverization and pulverization supply, and combined with the operating conditions of rapid load change, balanced combustion in the furnace, and stable combustion under low load, a matching pulverization operation mode is switched.

11. A rapid and flexible pulverized coal blending method for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 10, characterized in that, The process of temporarily storing the separated coal powder in a coal powder buffer silo specifically includes: The target material level, upper limit and lower limit of the pulverized coal buffer silo are preset, and the real-time material level of the pulverized coal buffer silo is collected in real time. When the real-time material level is within the set range formed by the upper limit of the material level and the lower limit of the material level, the amount of pulverized coal entering the storage mill group and the amount of pulverized coal exiting the feeder are kept matched. When the real-time material level is lower than the lower limit of the material level, the pulverizing output of the medium storage mill is increased to increase the amount of pulverized coal entering the silo. When the real-time material level is higher than the upper limit of the material level, reduce the pulverizing output of the medium storage mill to reduce the amount of pulverized coal entering the silo. By controlling the amount of pulverized coal entering and leaving the silo in a closed loop within different zones, the pulverized coal buffer silo can maintain a dynamic circulation condition of pulverized coal being stored and supplied simultaneously, thus avoiding long-term static accumulation of pulverized coal.

12. A rapid and flexible pulverized coal blending method for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 10, characterized in that, Based on the decoupling of pulverization and pulverization supply, and combined with the operational requirements of rapid load change, balanced combustion in the furnace, and stable combustion under low load, the system switches to a matching pulverization operation mode, specifically including: Based on the target load change rate of the unit, calculate the load change time corresponding to the unit completing the load adjustment. Based on the number of feeders involved in load regulation, the target output increment and output change rate of a single feeder are calculated. Based on the calculations of the variable load duration, the target output increment of a single pulverizer, and the rate of output change, under the condition of unit load increase, the speed of the pulverizer in the high-storage branch is preferentially adjusted to rapidly increase the total amount of pulverized coal supplied to the furnace. Under the condition of reduced unit load, the speed of the pulverized coal feeder in the central storage branch should be reduced first to quickly reduce the total amount of pulverized coal supplied to the furnace; When the unit load approaches the preset target value, adjust the output of the direct-fired mill and adjust the coal powder supply of the intermediate storage mill so that the coal powder buffer silo level returns to the preset range.

13. A rapid and flexible pulverized coal blending method for a direct-fired, centrally-fed, coupled coal storage and pulverized coal supply coal-fired unit according to claim 10, characterized in that, Based on the decoupling of pulverization and pulverization supply, and combined with the operational requirements of rapid load change, balanced combustion in the furnace, and stable combustion under low load, the system switches to a matching pulverization operation mode, specifically including: Pulverized coal distribution deviation tests were conducted on each pulverized coal pipeline of the direct-fired mill under different output conditions; Based on the test data of the powder distribution deviation test, a powder distribution deviation database for each direct-blown mill group corresponding to different output conditions is established. For the output conditions in the powder pipe powder quantity deviation database that have no measured data, the powder pipe powder quantity deviation data corresponding to the condition is solved by linear interpolation using two adjacent sets of known output parameters. Using the pulverized coal quantity deviation data of the pulverized coal pipe, the total amount of pulverized coal fed into the furnace of each row of burners along the width of the furnace on the front and rear walls of the boiler is calculated respectively. With the goal of equal total pulverized coal quantity in each row of burners along the width of the furnace, the required compensation pulverized coal quantity for each feeder in the central storage pulverized coal supply branch is calculated based on the difference in pulverized coal quantity in each row. By adjusting the pulverized coal supply to the burner corresponding to the central storage pulverized coal supply branch, the deviation in pulverized coal distribution in the direct-fired pipeline is compensated, making the heat load distribution in the width direction of the furnace more uniform.

14. A rapid and flexible pulverized coal blending method for a direct-fired, centrally stored, coupled coal-fired power unit according to claim 10, characterized in that, Based on the decoupling of pulverization and pulverized coal supply, and considering the requirements of rapid load changes, balanced combustion in the furnace, and stable combustion under low load, the appropriate pulverized coal distribution operation mode is switched, specifically including: When the coal-fired power unit is operating at a low load of 20% to 30% of its rated load, all direct-fired mill units shall be shut down. Based on the aforementioned low-load operating conditions, the two medium-sized storage mills are kept running continuously to replace the conventional low-load three-mill redundant operation mode, thereby improving the pulverized coal concentration and flame stability of the burners corresponding to the medium-sized storage mills. Based on the aforementioned low-load operating conditions, when one of the two intermediate storage mill units fails and stops operating, air is supplied to the exhaust gas header through the primary air duct to feed pulverized coal to the burner, and preparation is made to start up one direct-fired mill unit, thus avoiding the unit tripping accident caused by the failure and shutdown of one of the two conventional direct-fired mill units.

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