CN117109024A - Coal-fired unit ultra-low load stable operation pulverizing system and control method - Google Patents
Coal-fired unit ultra-low load stable operation pulverizing system and control method Download PDFInfo
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- 238000010298 pulverizing process Methods 0.000 title claims abstract description 77
- 238000000034 method Methods 0.000 title claims abstract description 33
- 239000003245 coal Substances 0.000 claims abstract description 328
- 239000000843 powder Substances 0.000 claims abstract description 264
- 238000009826 distribution Methods 0.000 claims abstract description 11
- 238000010521 absorption reaction Methods 0.000 claims abstract description 9
- 239000000446 fuel Substances 0.000 claims description 28
- 238000000227 grinding Methods 0.000 claims description 15
- 238000007664 blowing Methods 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 10
- 238000004064 recycling Methods 0.000 claims description 10
- 230000006870 function Effects 0.000 claims description 7
- 238000011217 control strategy Methods 0.000 claims description 5
- 238000012937 correction Methods 0.000 claims description 5
- 238000004880 explosion Methods 0.000 claims description 5
- 239000000295 fuel oil Substances 0.000 claims description 5
- 238000005457 optimization Methods 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 4
- 230000010354 integration Effects 0.000 claims 1
- 238000002485 combustion reaction Methods 0.000 abstract description 19
- 230000004048 modification Effects 0.000 abstract description 3
- 238000012986 modification Methods 0.000 abstract description 3
- 230000008878 coupling Effects 0.000 abstract description 2
- 238000010168 coupling process Methods 0.000 abstract description 2
- 238000005859 coupling reaction Methods 0.000 abstract description 2
- 230000008859 change Effects 0.000 description 4
- 238000004590 computer program Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 239000002817 coal dust Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000010977 unit operation Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- FKLFBQCQQYDUAM-UHFFFAOYSA-N fenpiclonil Chemical compound ClC1=CC=CC(C=2C(=CNC=2)C#N)=C1Cl FKLFBQCQQYDUAM-UHFFFAOYSA-N 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K1/00—Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K3/00—Feeding or distributing of lump or pulverulent fuel to combustion apparatus
- F23K3/02—Pneumatic feeding arrangements, i.e. by air blast
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N1/00—Regulating fuel supply
- F23N1/02—Regulating fuel supply conjointly with air supply
- F23N1/025—Regulating fuel supply conjointly with air supply using electrical or electromechanical means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K2201/00—Pretreatment of solid fuel
- F23K2201/10—Pulverizing
- F23K2201/1006—Mills adapted for use with furnaces
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K2201/00—Pretreatment of solid fuel
- F23K2201/10—Pulverizing
- F23K2201/103—Pulverizing with hot gas supply
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K2201/00—Pretreatment of solid fuel
- F23K2201/30—Separating
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Abstract
The invention belongs to the field of coal-fired power plant pulverized coal boiler equipment, and particularly relates to a coal pulverizing system and a control method for ultralow-load stable operation of a coal-fired unit, wherein the coal pulverizing system comprises the following components: the device comprises a medium-speed coal mill, a burner, a boiler, an air box, a fine powder separator, a first explosion-proof door, a second explosion-proof door, a moisture absorption pipe, a powder discharge fan, a coal powder bin, a powder feeder, a coal powder mixer, a first valve, a second valve, a third valve and a fourth valve. Under the ultralow load working condition of the unit, the coupling degree of the coal mill and the boiler is reduced, and compared with a medium-speed mill direct-fired pulverizing system, the influence of the instability of the pulverizing of the coal mill on the low-load stable combustion of the boiler is avoided. The invention improves the air-powder distribution balance, improves the powder supply flexibility and improves the running economy and safety of the powder making system. The invention can effectively solve the problems of the direct-fired pulverizing system under the ultralow load of the unit, does not influence the running states of other load working conditions, and has small modification amount.
Description
Technical Field
The invention belongs to the field of coal-fired power plant pulverized coal boiler equipment, and particularly relates to a coal pulverizing system for ultralow-load stable operation of a coal-fired unit and a control method.
Background
At present, most coal-fired units with the capacity of 300MW and above adopt a direct-fired pulverizing system, however, under the increasing deep peak-shaving requirement of the coal-fired units, the defects of the direct-fired pulverizing system under the ultralow-load working condition of the units are gradually prominent: on the one hand, under the ultralow load, the adverse effects of wind powder concentration, wind powder balance and coal quality disturbance on boiler combustion are amplified in a nonlinear way, but in a direct-blowing type pulverizing system, the wind powder distribution balance of an outlet pipeline of a coal mill is poor, the compensation and leveling adjustment of the coal powder quantity of a primary air pipeline cannot be performed, and the low-load combustion stability of a unit is reduced; on the other hand, due to the consideration of system safety, two coal mills on the bottom layer still need to be kept to operate under ultra-low load, and the total fuel amount requirement is little, so that the coal mills are seriously deviated from rated output operation, the consequences of high power consumption and poor economy are caused, the safe operation and the service life of the coal mills are influenced, and in order to ensure enough wind ring wind speed, the wind powder concentration is low.
Through the above analysis, the problems and defects existing in the prior art are as follows:
1. the coal mill has high power consumption, poor economy, large operation noise and unsafe performance: under the ultralow load, two coal mills at the bottom layer need to be kept to run in order to ensure the safety of the system, but the fuel demand is small, so that the coal mills deviate from rated output running seriously, the electricity consumption is increased, and the economical efficiency is reduced; and simultaneously affects the safe operation and the service life of the coal mill.
2. The wind powder concentration is low: under the ultralow load, under the running condition of two coal mills, in order to ensure the wind speed, the wind-coal ratio is reduced, and the wind powder concentration is reduced.
3. The wind powder distribution balance is poor: under ultralow load, the influence on combustion can be amplified by the change of wind powder concentration and coal quality, and the wind powder distribution balance of an outlet pipeline of a direct-fired pulverizing system is poor, so that effective compensation cannot be performed, and the combustion stability is influenced.
4. The low-load combustion stability of the unit is reduced: the change of wind powder concentration and balance and the disturbance of coal quality can be amplified in a nonlinear way under ultralow load, so that the low-load combustion stability of the unit is reduced.
Therefore, under the ultralow load working condition, the technical problems to be solved in the existing direct-blowing pulverizing system are mainly to improve the economy (reduce the power consumption), improve the air-powder distribution balance and the air-powder concentration and improve the low-load combustion stability of the unit. This also provides technical direction and design ideas for the subsequent invention patents.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a coal pulverizing system and a control method for ultralow-load stable operation of a coal-fired unit, which are used for modifying a medium-speed mill direct-fired pulverizing system, wherein a coal powder bin is connected in series on a coal mill powder outlet pipeline connected with a bottom-layer combustor, the coal mill is modified into a middle warehouse-type pulverizing system, and the structures of other coal mills are unchanged. Therefore, under the ultralow load, only one coal mill can be kept to operate due to the existence of the powder bin, the output of the coal mill can approach the economic output of the coal mill, the number of powder feeding pipelines is reduced, the required air quantity is reduced, and the air powder concentration is improved; meanwhile, powder is supplied to the burner by the powder feeder, and the uniform distribution of wind and powder can be realized by adjusting the rotating speeds of different powder feeders. Therefore, the running stability and economy of the unit under the ultra-low load can be effectively improved, and the ultra-low load stable combustion of the boiler is realized.
The coal pulverizing system for the ultralow-load stable operation of the coal-fired unit is realized by combining a medium-speed coal mill with a fine powder separator, and realizing the middle warehouse type coal powder treatment by utilizing a coal powder warehouse, so that the stable supply of coal powder in ultralow load is ensured; the system connects the pulverized coal bin with a plurality of coal hoppers and a pulverized coal feeder, allowing finer pulverized coal distribution; in the control strategy, the total fuel quantity synthesizes the coal quantity of a plurality of parts, adopts a mode of exhausting and powder feeding, realizes the accurate control of the powder feeding air quantity by adjusting each valve, and ensures the stable operation under the ultralow load.
Further, the coal-fired unit ultra-low load steady operation's pulverizing system includes: the device comprises a medium-speed coal mill, a burner, a boiler, an air box, a fine powder separator, a first explosion-proof door, a second explosion-proof door, a moisture absorption pipe, a powder discharge fan, a coal powder bin, a powder feeder, a coal powder mixer, a first valve, a second valve, a third valve and a fourth valve;
the medium speed coal mill is integrally built by the coal mill, the coal powder separator and the coal powder distributor, an outlet of the medium speed coal mill is connected with the first bellows through the first valve, and the converging moisture absorption pipe is connected with the coal powder separator. The upper end of the fine powder separator is provided with a first explosion door, the lower end of the fine powder separator is connected with a coal powder bin, the coal powder bin is provided with a moisture absorption pipe which is connected with an inlet pipeline of the fine powder separator, an outlet at the upper end of the fine powder separator is connected with a powder discharge fan, and the outlet of the fan is divided into two paths: one path of the air is fed into a powder falling pipe at the inlet of the coal mill and is a recycling pipe, and a baffle plate on the pipe is a hot air recycling air door; the other route is distributed by the second air box and then is connected with the burner through a third valve and the coal powder mixer, the lower end of the coal powder bin is connected with the powder feeder, and the powder feeder is connected with the coal powder mixer. The primary air is connected with the third valve and the middle pipeline of the pulverized coal mixer through the fourth valve.
Further, the fine powder separator and one pulverized coal bin are respectively connected, an air-powder pipeline at the outlet of a certain bottom coal mill (hereinafter referred to as a mill A) is connected with the fine powder separator, and the lower end of the fine powder separator is connected with the pulverized coal bin; the other 5 mills are direct-blowing pulverizing systems, and the mill outlet air-powder pipeline is directly connected with the burner.
Further, the lower end of the pulverized coal bin is provided with 6 coal hoppers, each coal hopper is connected with 1 pulverized coal feeder, and 6 pulverized coal feeders are respectively connected with 6 pulverized coal mixers.
Further, the total working process is as follows: the full load process of the coal mill pulverizing system keeps the middle storage type, namely pulverized coal pulverized by the coal mill enters a pulverized coal bin, and the pulverized coal bin supplies powder to a boiler through a powder feeder; the whole load process of other mills (B\C\D\E\F mill) keeps direct blowing, namely the coal powder ground by the coal mill directly enters the burner; the mill group is switched according to the original scheme under medium and high load, and only the bottom layer A mill is reserved and operated in the form of a middle warehouse type pulverizing system under the ultra-low load (20% THA and below).
Further, the general control principle is as follows: the total fuel quantity consists of four parts, namely the coal quantity of the exhaust gas primary air powder pipe, the coal quantity of the powder feeder, the coal quantity of the B\C\D\E\F coal mill and the fuel oil converted coal quantity. The fuel main control instruction is the coal feeding quantity of the B\C\D\E\F coal feeder and the coal feeding quantity of the powder feeder respectively; the powder position of the powder bin is controlled in intervals, and the coal feeding amount of the coal feeder A is controlled; the powder feeding mode is exhaust gas powder feeding, the powder feeding air quantity of the primary air powder pipe is controlled by adjusting the opening of the hot air recirculation second valve, and the fourth valve is used for air reversing control.
The invention further aims to provide a control method of the coal pulverizing system applied to the ultralow-load stable operation of the coal-fired unit, wherein the powder level control logic of the coal powder bin is that three powder level measuring points of the coal powder bin obtain powder level feedback of the coal powder bin through a median selector, and the difference value between the powder level feedback and a powder level set value is subjected to PID operation, manual/automatic station and speed limitation to obtain a coal feeding quantity instruction of the A coal feeder, wherein the total fuel quantity instruction is divided by the automatic quantity to serve as feedforward of a PID controller. The output command of the A coal feeder is not larger than the maximum output of the A mill.
Further, for the coal feeding amount of the B\C\D\E\F coal feeder and the coal feeding amount control logic of the powder feeder is as follows: the coal feeding amount of the coal feeder A is added with the hot air recirculation coal amount after being delayed to obtain the coal output amount of the coal mill A; multiplying the outlet coal quantity of the coal mill A by the separation coefficient of the fine powder separator to obtain the quantity of coal dust carried in the exhaust gas; the amount of coal powder carried in the exhaust gas is multiplied by a correction coefficient formed by the opening degrees of the second valve and the third valve to obtain the amount of coal powder of the exhaust gas primary air powder pipe, and the difference value between the amount of coal powder in the exhaust gas and the amount of coal powder of the exhaust gas primary air powder pipe is the amount of hot air recycling coal. The sum of the coal amount of the powder feeding machine and the coal amount of the primary air powder pipe removed by the exhaust gas is the coal amount of the primary air powder pipe of the grinding A; the sum of the coal quantity of the primary air powder pipe of the A mill, the coal quantity of the B\C\D\E\F coal mill and the fuel oil converted coal quantity is multiplied by a coal quality correction coefficient to obtain the actual total fuel quantity. The total fuel quantity command from the main control of the boiler is used as a set value to be compared with the actual fuel quantity, the deviation of the total fuel quantity command is subjected to PID operation and manual/automatic station to form a fuel main control command for controlling the rotating speed of the B\C\D\E\F coal feeder in parallel, and the difference between the fuel main control command and the coal quantity of the exhaust primary air powder pipe is subjected to speed limiting to obtain the rotating speed command of the powder feeder. Considering that the automatic numbers of the B\C\D\E\F coal feeders and the powder feeders are different, the control gains of the control loops are different, and the automatic numbers of the coal feeders are obtained by two different broken line functions to obtain the proportional gains and the integral times of different PID controllers.
Further, the primary air quantity control in the primary air powder pipe of the mill A is realized by adjusting the opening degree of the second valve, and the control logic is as follows: the coal quantity of the primary air-powder pipe of the mill A is converted into a primary air-powder pipe air quantity demand set value through a function device, and a second valve opening instruction is obtained after PID operation, manual automatic switching and speed limiting after the comparison with the actual air quantity of the main pipe.
Another object of the present invention is to provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and the computer program when executed by the processor causes the processor to execute the steps of the data synchronization optimization method between chips connected in series.
Another object of the present invention is to provide an information data processing terminal, where the information data processing terminal is used to implement the data synchronization optimization system between the serial chips.
In combination with the technical scheme and the technical problems to be solved, the technical scheme to be protected has the following advantages and positive effects:
first, the invention reduces the coupling degree of the coal mill and the boiler under the ultralow load working condition of the unit, and compared with a medium-speed mill direct-fired pulverizing system, the invention avoids the influence of the instability of the pulverizing of the coal mill on the low-load stable combustion of the boiler.
Secondly, the coal mill A is changed into a medium-storage type pulverizing mode, namely, the powder is supplied to the combustor by the powder feeder, so that the air-powder distribution balance is improved, and the powder supply flexibility is improved; only one coal mill is kept to operate, so that the coal mill is operated close to economic output, the operation economy and safety of the pulverizing system are improved, and meanwhile, the wind powder concentration is improved. The invention can effectively solve the problems of the direct-fired pulverizing system under the ultralow load of the unit, does not influence the running states of other load working conditions, and has small modification amount.
Thirdly, the existing direct-blowing pulverizing system has obvious defects under the ultralow load of the unit due to the structural characteristics of the existing direct-blowing pulverizing system. On the one hand, the pulverized coal of the medium-speed coal mill in the direct-fired pulverizing system is separated by the separator and distributed by the distributor and then enters into 6 (or 4) primary air-powder pipes respectively. However, the uniformity of pulverized coal distribution of the pulverized coal distributor has certain deviation precision, which is generally +/-10% -20%, and the relative deviation of the pulverized coal amount sometimes reaches +/-40% along with the pressure change in each air-pulverized coal pipe in the running process. When the coal-fired unit operates under ultra-low load, the influence of the pulverized coal quantity deviation of each burner on the combustion stability of the boiler is amplified; on the other hand, under ultralow load, the required fuel quantity of the boiler is very little, but for unit operation safety, at least two coal mills need to be ensured to operate, so that the output of the coal mills deviates from the economic output seriously, the operation of a coal pulverizing system is uneconomical, the service life of the coal mills is even influenced, and meanwhile, the concentration of wind powder is low because of ensuring a certain wind ring wind speed. Both the two aspects are inherent problems of the structure of the direct-fired pulverizing system, can not be solved by an operation optimization means, and are exposed prominently under the condition of lower and lower unit operation load under the background of deep peak regulation requirements, so that the direct-fired pulverizing system is gradually valued by people.
Therefore, the invention changes a certain bottom coal mill into a middle-storage type pulverizing mode, other coal mills keep the original direct-blowing pulverizing mode, and on one hand, because the powder storage amount of the coal powder bin is buffered and guaranteed, only one coal mill can be kept to operate, thereby improving the economical efficiency and the wind powder concentration of a pulverizing system; on the other hand, the non-uniformity of the pulverized coal distribution of the primary air and powder pipe at the outlet of the coal mill will not affect the side of the boiler, and the powder is directly supplied to the burner by a plurality of powder supplying machines, and the pulverized coal quantity of each air and powder pipe is regulated by the pulverized coal quantity regulating means, so that the uniformity of the pulverized coal quantity among each air and powder pipe can be ensured.
Fourth, the following is a significant technical improvement from each claim:
1. the requirement of claim 1 describes the whole framework of a coal-fired unit ultra-low load stable operation pulverizing system. The technology is advanced in that a composite system of a medium speed coal mill, a fine powder separator, a pulverized coal bin and a pulverized coal feeder is constructed, so that pulverized coal can be stably supplied under ultralow load, and the combustion requirement of a boiler is met.
2. The method of claim 2 is characterized in that a direct connection mode of the grinding A and the fine powder separator is established, and other 5 grinding adopts a direct blowing type pulverizing system. The technological progress is that the coal powder treatment process of the A mill is simplified, and meanwhile, a high-efficiency direct-blowing pulverizing system is provided for other mills.
3. In claim 3, 6 coal hoppers are added and connected with 6 powder feeders. The technical progress is that the configuration enables the system to distribute and supply pulverized coal more finely, and improves the stability of powder supply.
4. This requirement describes the operation under different loads as claimed in claim 4. When the unit works under ultra-low load, the system works by keeping the bottom layer A mill and adopting the form of an intermediate warehouse pulverizing system. The technical progress is that a new working mode is provided for ultra-low load operation, and stable operation under the working condition is ensured.
5. This requirement defines the overall control principle of the system as claimed in claim 5. The technical progress is to clearly control each part of the pulverized coal supply and how to precisely control the powder feeding quantity. By means of exhaust gas powder feeding and adjusting the valves, the running stability under ultra-low load is further enhanced.
In summary, each of these claims provides critical technical support for stable operation of the coal-fired unit under ultra-low load, and significant technical advances are made from system configuration to control strategies.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a connection structure between an A mill, a pulverized coal bin and a burner provided by an embodiment of the invention;
FIG. 2 is a logic diagram of the control of the coal feeding amount of the A coal feeder provided by the embodiment of the invention;
FIG. 3 is a logic diagram of the control of the coal feed amount of the B\C\D\E\F coal feeder and the coal feed amount of the powder feeder according to the embodiment of the invention;
FIG. 4 is a logic diagram of primary air quantity control of the primary air powder pipe of the mill A provided by the embodiment of the invention;
FIG. 5 is a temperature cloud provided by an embodiment of the present invention; (a) is unbiased; (b) is ± 10% offset; (c) a deviation of + -20%;
FIG. 6 is a velocity cloud provided by an embodiment of the present invention; (a) is unbiased; (b) is ± 10% offset; (c) a deviation of + -20%;
in the figure: 1. a first valve; 2. a second valve; 3. a third valve; 4. a fourth valve; 5. a first explosion vent; 6. a second explosion vent; 7. a first bellows; 8. a second bellows.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Aiming at the problems in the prior art, the invention provides a method, a system, equipment and a terminal for optimizing data synchronization among serial chips, and the invention is described in detail below with reference to the accompanying drawings.
Taking a 660MW ultra-supercritical unit and a 20% THA stable working condition as an example, the total fuel amount requirement of the unit under the 20% THA stable working condition is 58t/h, the direct-fired pulverizing system adopts a coal mill of which the model is an HP-1003 medium-speed coal mill, the maximum output is 85.9t/h, and for safety, two mills at the bottom layer need to be kept to operate, the actual output of each mill is 29t/h, the economic working condition of the coal mill is seriously deviated, the power consumption of the coal mill is increased, and the safe operation of the coal mill is influenced; after being distributed by a coal powder distributor, the outlet of the medium-speed coal mill has larger deviation of the coal powder quantity among different coal powder pipelines, and a means for adjusting the coal powder of each air powder pipeline again is not provided, so that the combustion stability of the unit under the load of 20% THA and lower load of the boiler is seriously affected. Therefore, in order to improve the stability and economy of ultralow-load operation of the unit, the invention integrates the characteristics of the direct-fired pulverizing system and the medium-storage pulverizing system, the bottom layer A mill is transformed into the medium-storage pulverizing system, and the rest coal mills (B\C\D\F\E mill) keep the original system structure unchanged.
As shown in FIG. 1, the pulverizing system suitable for the ultralow-load stable operation of the coal-fired unit provided by the embodiment of the invention comprises a medium-speed coal mill, a burner, a boiler, a first air box 7, a second air box 8, a fine powder separator, a first explosion-proof door 5, a second explosion-proof door 6, a moisture absorption pipe, a powder discharge fan, a coal powder bin, a powder feeder, a coal powder mixer, a first valve 1, a second valve 2, a third valve 3 and a fourth valve 4.
The outlet of the medium speed coal mill is connected with a first air box 7 through a first valve 1, and the converging moisture absorption pipe is connected with the fine powder separator. The upper end of the fine powder separator is provided with a first explosion door 5, the lower end of the fine powder separator is connected with a coal powder bin, the coal powder bin is provided with a moisture absorption pipe which is connected with an inlet pipeline of the fine powder separator 6, an outlet of the upper end of the fine powder separator is connected with a powder discharge fan, and the outlet of the fan is divided into two paths: one path of the air is fed into a powder falling pipe at the inlet of the coal mill and is a recycling pipe, and a baffle plate on the pipe is a hot air recycling air door; the other path is distributed by a second air box 8 and then is connected with a burner through a third valve 3 and a coal powder mixer, the lower end of the coal powder bin is connected with a powder feeder, and the powder feeder is connected with the coal powder mixer. The primary air is connected with the third valve 3 and the middle pipeline of the pulverized coal mixer through the valve 4.
The boiler furnace is a hedging type combustion furnace and is divided into a front wall and a rear wall, each wall is provided with 3 layers of burners and 2 layers of over-fire air nozzles, each layer of 6 burners is provided with 36 burners and 24 over-fire air nozzles.
The number of the coal mills is 6, namely, an A mill, a B mill, a C mill, a D mill, an E mill and an F mill, wherein the F mill is a standby coal mill, and powder outlet pipelines of the A mill, the B mill and the C mill are respectively connected with the lower, middle and upper layers of the front wall of the boiler furnace; and the powder outlet pipelines of the grinding D, the grinding E and the grinding F are respectively connected with the lower layer, the middle layer and the upper layer of the rear wall of the boiler furnace.
The fine powder separator and the pulverized coal bin are respectively connected with an air-powder pipeline at the outlet of a certain bottom coal mill (hereinafter referred to as a mill A), and the lower end of the fine powder separator is connected with the pulverized coal bin; the other 5 mills are direct-blowing pulverizing systems, and the mill outlet air-powder pipeline is directly connected with the burner.
The lower end of the pulverized coal bin is provided with 6 coal hoppers, each coal hopper is connected with 1 pulverized coal feeder, and 6 pulverized coal feeders are respectively connected with 6 pulverized coal mixers.
As shown in fig. 1, the embodiment of the invention provides a pulverizing system suitable for the ultralow-load stable operation of a coal-fired unit, which has the following general working procedures: the full load process of the coal mill pulverizing system keeps the middle storage type, namely pulverized coal pulverized by the coal mill enters a pulverized coal bin, and the pulverized coal bin supplies powder to a boiler through a powder feeder; the whole load process of other mills (B\C\D\E\F mill) keeps direct blowing, namely the coal powder ground by the coal mill directly enters the burner; the mill group is switched according to the original scheme under medium and high load, and only the bottom layer A mill is reserved and operated in the form of a middle warehouse type pulverizing system under the ultra-low load (20% THA and below).
The embodiment of the invention provides a control method of a coal pulverizing system suitable for ultralow-load stable operation of a coal-fired unit, which has the following general control principle: the total fuel quantity consists of four parts, namely the coal quantity of the exhaust gas primary air powder pipe, the coal quantity of the powder feeder, the coal quantity of the B\C\D\E\F coal mill and the fuel oil converted coal quantity. The fuel main control instruction is the coal feeding quantity of the B\C\D\E\F coal feeder and the coal feeding quantity of the powder feeder respectively; the powder position of the powder bin is controlled in intervals, and the coal feeding amount of the coal feeder A is controlled; the powder feeding mode is exhaust gas powder feeding, the powder feeding air quantity of the primary air powder pipe is controlled by adjusting the opening of the second valve 2, and the valve 4 is used for air reversing control.
As shown in fig. 2, in the control method of the coal pulverizing system suitable for the ultralow-load stable operation of the coal-fired unit provided by the embodiment of the invention, the powder level control logic of the coal powder bin is that three powder level measuring points of the coal powder bin obtain powder level feedback of the coal powder bin through a median selector, and the difference value between the three powder level measuring points and a powder level set value is subjected to PID operation, manual/automatic station and speed limitation to obtain a coal feeding quantity instruction of the coal feeder A, wherein the total fuel quantity instruction is divided by the automatic quantity to serve as feedforward of a PID controller. The output command of the A coal feeder is not larger than the maximum output of the A mill.
As shown in fig. 3, the control method of the coal pulverizing system suitable for the ultralow-load stable operation of the coal-fired unit disclosed by the invention is characterized in that for the coal feeding quantity of the b\c\d\e\f coal feeder and the coal feeding quantity control logic of the coal feeder are as follows: the coal feeding amount of the coal feeder A is added with the hot air recirculation coal amount after being delayed to obtain the coal output amount of the coal mill A; multiplying the outlet coal quantity of the coal mill A by the separation coefficient of the fine powder separator to obtain the quantity of coal dust carried in the exhaust gas; the difference between the amount of coal powder in the exhaust gas and the amount of coal powder in the exhaust gas going to the primary air powder pipe is the amount of hot air recycling coal. The sum of the coal amount of the powder feeding machine and the coal amount of the primary air powder pipe removed by the exhaust gas is the coal amount of the primary air powder pipe of the grinding A; the sum of the coal quantity of the primary air powder pipe of the A mill, the coal quantity of the B\C\D\E\F coal mill and the fuel oil converted coal quantity is multiplied by a coal quality correction coefficient to obtain the actual total fuel quantity. The total fuel quantity command from the main control of the boiler is used as a set value to be compared with the actual fuel quantity, the deviation of the total fuel quantity command is subjected to PID operation and manual/automatic station to form a fuel main control command for controlling the rotating speed of the B\C\D\E\F coal feeder in parallel, and the difference between the fuel main control command and the coal quantity of the exhaust primary air powder pipe is subjected to speed limiting to obtain the rotating speed command of the powder feeder. Considering that the automatic numbers of the B\C\D\E\F coal feeders and the powder feeders are different, the control gains of the control loops are different, and the automatic numbers of the coal feeders are obtained by two different broken line functions to obtain the proportional gains and the integral times of different PID controllers.
As shown in fig. 4, in the control method of the pulverizing system suitable for the ultralow-load stable operation of the coal-fired unit provided by the embodiment of the invention, the primary air quantity control in the primary air-powder pipe of the grinding a is realized by adjusting the second valve 2, and the control logic is as follows: the coal quantity of the primary air-powder pipe of the mill A is converted into a primary air-powder pipe air quantity demand set value through a function device, and the primary air-powder pipe air quantity demand set value is compared with the actual air quantity of a main pipe, and then the opening instruction of the second valve 2 is obtained through PID operation, a manual automatic switcher and speed limitation.
The application embodiment of the invention provides a computer device, which comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of a control method of a coal pulverizing system of a coal-fired unit, which stably operates under ultra-low load.
The application embodiment of the invention provides an information data processing terminal which is used for realizing a coal-fired unit ultra-low load stable operation coal pulverizing system.
The experimental procedure and data of the present invention are further described below:
the uniformity of pulverized coal distribution of a pulverized coal distributor adopted by a medium-speed mill direct-fired pulverizing system has certain deviation precision, which is generally +/-10% -20%, and the relative deviation of the pulverized coal quantity sometimes reaches +/-40% due to the pressure change in each air powder pipe in actual operation. In order to compare and explore the influence of different pulverized coal quantity deviations on the combustion stability of a boiler under the ultralow load of a unit, a geometric model of a 660MW supercritical unit opposed combustion furnace is established through modeling software such as Gambit, and a speed field and a temperature field on a specific section (z= 12.8635m section) near a bottom layer combustor are obtained by performing thermal state numerical simulation on different air powder tube coal quantity deviation working conditions (no deviation, 10% deviation and 20% deviation) of the furnace, which only remain the combustion of a front wall bottom layer combustor, under the ultralow load working condition, under the condition of the 20% ultralow load on FLUENT software.
Fig. 5 and 6 show temperature cloud patterns and velocity cloud patterns of different pulverized coal amounts in specific cross sections near the bottom layer burner, respectively, and it can be seen that the combustion is stable and the flow velocity of the pulverized coal is uniform under the condition that only the bottom layer burner is kept without deviation, and the outlet temperature peak value of each burner is near 2000 ℃. With the increase of the deviation of wind powder, the problems of large difference of outlet temperature peaks of the burners, inconsistent burning flame length, uneven wind powder speed value and the like occur, and even under the deviation condition of +/-20 percent, the situation of fire extinguishment of part of the burners occurs. The numerical simulation results show that the wind-powder balance of each wind-powder pipe is an important factor influencing the stable combustion of the low load of the boiler under the ultra-low load, and the pulverizing system and the control method provided by the invention can effectively adjust the wind-powder balance of the wind-powder pipe, only maintain the running mode of one mill, also promote the wind-powder concentration, and realize the stable running of the unit under the ultra-low load.
The following are two specific embodiments and implementations thereof:
example 1: coal pulverizing system of small coal-fired unit
1. System configuration:
the main structure is composed of 1 medium speed coal mill, 1 fine powder separator, 1 coal powder bin and 1 powder feeder.
The air-powder pipeline at the outlet of the grinding A is directly connected to the fine powder separator, and the lower end of the fine powder separator is connected with the coal powder bin, so that a simplified flow is formed.
2. The implementation scheme is as follows:
during ultra-low load operation, only the mill a is used for operation of the intermediate bin type pulverizing system to ensure stable pulverized coal supply.
The control strategy is carried out according to claim 5, and the exhaust gas is used for powder feeding, and the hot air recirculation second valve is regulated to control the powder feeding quantity of the primary air powder pipe.
Example 2: large coal-fired unit pulverizing system
1. System configuration:
6 medium speed coal mills are used, wherein 1 mill is configured as a mill, and the other 5 mills are direct-fired pulverizing systems.
And 6 coal hoppers are arranged and connected with 6 powder feeders, so that high-efficiency and rapid coal powder supply is ensured.
2. The implementation scheme is as follows:
when the device runs under medium and high load, the original grinding set switching scheme is maintained, and when the device runs under ultra-low load, only the bottom layer A grinding is maintained, and the device runs in a form of a middle warehouse type pulverizing system.
The control strategy is also carried out according to claim 5, wherein the pulverized coal supply of mill a is controlled in intervals by the powder level of the powder bin, and the other 5 mills directly feed the pulverized coal into the burner.
These two embodiments are suitably adapted for different sizes of coal-fired units to ensure stability and efficiency under various operating conditions.
The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention will be apparent to those skilled in the art within the scope of the present invention.
Claims (10)
1. The coal pulverizing system is characterized in that the system adopts a combination of a medium-speed coal mill and a fine powder separator, and utilizes a coal powder bin to realize coal powder treatment of a middle bin type, so that stable coal powder supply under the condition of ultralow load is ensured; the system connects the pulverized coal bin with a plurality of coal hoppers and a pulverized coal feeder, allowing finer pulverized coal distribution; in the control strategy, the total fuel quantity synthesizes the coal quantity of a plurality of parts, adopts a mode of exhausting and powder feeding, realizes the accurate control of the powder feeding air quantity by adjusting each valve, and ensures the stable operation under the ultralow load.
2. The coal-fired unit ultra-low load stable operation pulverizing system according to claim 1, comprising:
the outlet of the medium-speed coal mill is connected with a first bellows through a first valve, and the converging moisture absorption pipe is connected with a fine powder separator; the upper end of the fine powder separator is provided with a first explosion door, the lower end of the fine powder separator is connected with a coal powder bin, the coal powder bin is provided with a moisture absorption pipe which is connected with an inlet pipeline of the fine powder separator, an outlet at the upper end of the fine powder separator is connected with a powder discharge fan, and the outlet of the fan is divided into two paths: one path of the air is fed into a powder falling pipe at the inlet of the coal mill and is a recycling pipe, and a baffle plate on the pipe is a hot air recycling air door; the other route is distributed by a second air box and then is connected with a burner through a third valve and a coal powder mixer, the lower end of the coal powder bin is connected with a powder feeder, and the powder feeder is connected with the coal powder mixer; the primary air is connected with the third valve and the middle pipeline of the pulverized coal mixer through the fourth valve.
3. The coal-fired unit ultra-low load stable operation pulverizing system according to claim 2, wherein the fine powder separator and the pulverized coal bin are respectively connected, an outlet air-powder pipeline of the A mill is connected with the fine powder separator, and the lower end of the fine powder separator is connected with the pulverized coal bin; the other 5 mills are direct-blowing pulverizing systems, and mill outlet air-powder pipelines are directly connected with a burner; the lower end of the coal powder bin is provided with 6 coal hoppers, each coal hopper is connected with 1 powder feeder, and 6 powder feeders are respectively connected with 6 coal powder mixers.
4. The coal-fired unit ultra-low load stable operation pulverizing system according to claim 2, wherein the total working process is as follows: the full load process of the coal mill pulverizing system keeps the middle storage type, namely pulverized coal pulverized by the coal mill enters a pulverized coal bin, and the pulverized coal bin supplies powder to a boiler through a powder feeder; the other full-load grinding process keeps direct blowing, namely, the pulverized coal ground by the coal mill directly enters the burner; the grinding group is switched according to the original scheme under medium and high load, and only the bottom layer A grinding is reserved under the ultralow load and is operated in the form of a middle warehouse type pulverizing system.
5. The coal-fired unit ultra-low load stable operation pulverizing system according to claim 2, wherein the general control principle is as follows: the total fuel quantity consists of four parts, namely the coal quantity of a primary air powder pipe from the exhaust gas, the coal quantity of a powder feeder, the coal quantity of a B\C\D\E\F coal mill and the fuel oil converted coal quantity; the fuel main control instruction is the coal feeding quantity of the B\C\D\E\F coal feeder and the coal feeding quantity of the powder feeder respectively; the powder position of the powder bin is controlled in intervals, and the coal feeding amount of the coal feeder A is controlled; the powder feeding mode is exhaust gas powder feeding, the powder feeding air quantity of the primary air powder pipe is controlled by adjusting the opening of the hot air recirculation second valve, and the fourth valve is used for air reversing control.
6. A control method applied to the coal-fired unit ultra-low load stable operation pulverizing system according to any one of claims 1 to 5, which is characterized in that the high-precision and high-stability control of the coal-fired unit pulverizing system under the ultra-low load working condition is realized by adopting multi-parameter comprehensive control and optimization.
7. The control method of the coal-fired unit ultra-low load stable operation pulverizing system according to claim 6, wherein the method of measuring powder level at three points of the pulverized coal bin to obtain the median value is adopted to feed back the actual powder level of the pulverized coal bin, PID control is carried out on the actual powder level of the pulverized coal bin and a set value, and stable pulverized coal bin powder supply control is realized;
calculating according to parameters such as the coal quantity at the outlet of the mill A, the separation coefficient of the fine powder separator, the correction coefficient of the opening degree of the second valve and the third valve, and the like to obtain the optimal coal quantity of each coal mill and each powder feeder;
comparing the total fuel quantity instruction of the main control of the boiler with the actual fuel quantity, and obtaining the rotating speed control instructions of the B-F coal feeder and the powder feeder through PID control;
according to the different numbers of automatic input of the B-F coal feeder and the powder feeder, two broken line functions are adopted to obtain different PID parameters, and the control performance of a control loop is improved;
the coal quantity at the outlet of the grinding A is subjected to hysteresis compensation and added with the hot air recycling coal quantity, and the influence of the hot air recycling coal quantity is considered.
8. The method for controlling a coal pulverizing system for ultra-low load stable operation of a coal-fired unit according to claim 6, wherein for the b\c\d\e\f coal feeder, the coal feeding amount and the coal feeding amount control logic of the coal feeder are as follows:
and a plurality of key parameters are integrated, including the outlet coal quantity of the coal mill A, the separation coefficient of the fine powder separator and the opening correction coefficient of the valve. The integration method ensures that the coal pulverizing system can still realize the accurate control of each coal mill and the coal feeder under the ultralow load working condition, and ensures the stable supply of the coal.
9. The method for controlling a coal-fired unit ultra-low load stable operation pulverizing system according to claim 8, further comprising:
two broken line functions are adopted, and different operation conditions are adapted by adjusting the proportional gain and the integral time of the PID controller.
10. The control method of the coal-fired unit ultra-low load stable operation pulverizing system according to claim 6, wherein the primary air quantity control in the primary air-powder pipe of the A mill is realized by adjusting the opening degree of the second valve, and the control logic is as follows: the coal quantity of the primary air-powder pipe of the mill A is converted into a primary air-powder pipe air quantity demand set value through a function device, and a second valve opening instruction is obtained after PID operation, manual automatic switching and speed limiting after the comparison with the actual air quantity of the main pipe.
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| CN117823934A (en) * | 2024-01-03 | 2024-04-05 | 南方电网电力科技股份有限公司 | Powder preparation system for direct-blowing coal-fired unit and monitoring control method thereof |
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| CN117823934A (en) * | 2024-01-03 | 2024-04-05 | 南方电网电力科技股份有限公司 | Powder preparation system for direct-blowing coal-fired unit and monitoring control method thereof |
| CN117823934B (en) * | 2024-01-03 | 2024-07-12 | 南方电网电力科技股份有限公司 | Powder preparation system for direct-blowing coal-fired unit and monitoring control method thereof |
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