Fluidized bed mother pipe pressure multi-furnace joint control method

Abstract

The application discloses a fluidized bed mother pipe pressure multi-furnace joint control method, and relates to the technical field of fluidized bed boiler production control, which comprises the following steps: selecting one of multiple boilers as a main boiler for main pressure control; setting an upper limit of load increment of the main boiler as Delta Fmax according to historical data and field investigation; judging whether the load fluctuation of the main boiler is greater than or equal to Delta Fmax, if yes, controlling the load fluctuation of the main boiler as Delta Fmax, and distributing the load difference between Delta F and Delta Fmax to the remaining boilers; if no, controlling the load fluctuation of the main boiler as Delta F. The fluidized bed mother pipe pressure multi-furnace joint control method can effectively improve the control effect of the boiler combustion system.

Description

Technical Field

[0001] The present invention relates to the technical field of fluidized bed boiler production control, and more particularly to a method for controlling multiple fluidized bed main pipe pressures. Background Art

[0002] The process control of the boiler combustion system is relatively complex. Except for a few loops that can be automatically controlled, other control loops are still mainly operated by manual experience. The overall automation level is relatively low. Due to external load fluctuations, key process indicators such as flue gas oxygen content, main steam pressure, and main steam flow are difficult to be well controlled, and there is still room for improvement in operational stability.

[0003] In existing technology, for boiler systems, manufacturers generally use a DCS system, with a conventional control strategy primarily based on PID single-loop control and equipment interlock protection. This means that PID is used for automatic control of some loops (such as the drum liquid level), while manual control is used for the majority of loops (main steam pressure). However, manual pressure control requires high operator coordination and is labor-intensive (up to 1,500 operations per unit). It is prone to errors, has poor safety, and can easily lead to back-end pressure fluctuations. Furthermore, because the production unit includes multiple boilers in parallel operation, improper operation of a single boiler can cause fluctuations in the product unit of back-end users, affecting the quality of the final product.

[0004] In summary, how to improve the control effect of the boiler combustion system is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a fluidized bed main pipe pressure multi-furnace joint control method, which can effectively improve the control effect of the boiler combustion system.

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

[0007] A method for controlling multiple furnaces of a fluidized bed main pipe pressure, comprising:

[0008] Select one of the multiple boilers as the main boiler for controlling the pressure;

[0009] Setting the load increment upper limit ΔFmax of the main boiler based on historical data and on-site investigation;

[0010] Determine whether the load fluctuation ΔF of the main boiler is greater than or equal to ΔFmax. If so, control the load fluctuation of the main boiler to ΔFmax, and distribute the load difference between ΔF and ΔFmax to the remaining boilers; if not, control the load fluctuation of the main boiler to ΔF.

[0011] In one embodiment, the allocating the load difference between AF and AFmax to the remaining boilers comprises allocating the load difference to the remaining boilers in proportion to their loads, wherein the proportion to the load can be set and modified in advance.

[0012] In one embodiment, the controlling the load fluctuation of the main boiler as AF comprises individually increasing the coal quantity of the main boiler to increase the pressure and load of the main boiler.

[0013] In one embodiment, the main boiler and the remaining boilers are each provided with a load distribution switch.

[0014] In one embodiment, the main boiler and the remaining boilers are each provided with a first selection switch for selecting the steam flow controlled by the main boiler and a second selection switch for selecting the steam pressure controlled by the main boiler.

[0015] In one embodiment, the main boiler and the remaining boilers are each provided with a load increase and decrease controller for increasing or decreasing the load of the boiler to the latest set value at a specified speed.

[0016] In one embodiment, the selected one of the plurality of boilers as the main boiler for controlling the pressure further comprises,

[0017] determining whether the coal feeder of each boiler is in a coal outage state, if yes, controlling the coal feeder in the coal outage state to be disconnected, and distributing the total coal quantity required by the boiler to the normal coal feeders, and if no, distributing the total coal quantity required by the boiler to the normal coal feeders.

[0018] In one embodiment, the determining whether the coal feeder of each boiler is in a coal outage state comprises,

[0019] reading the coal quantity of each coal feeder in real time;

[0020] determining whether the coal quantity is abnormal, if yes, the coal feeder is in a coal outage state, and if no, the coal feeder is normal.

[0021] In one embodiment, the controlling the coal feeder in the coal outage state to be disconnected further comprises voice alarm when the coal feeder in the coal outage state is disconnected.

[0022] In one embodiment, the distributing the total coal quantity required by the boiler to the normal coal feeders comprises distributing the total coal quantity required by the boiler to the normal coal feeders in proportion to their coal feeding, wherein the proportion to the coal feeding can be set and modified in advance.

[0023] In the method for controlling multiple fluidized bed boilers by using the mother pipe pressure, first, one of the boilers is selected as the master boiler for controlling the pressure. Then, according to the historical data and the field investigation, the upper limit of the load increment of the master boiler is set. Finally, it is determined whether the load fluctuation of the master boiler is greater than or equal to the upper limit of the load increment. If yes, the load fluctuation of the master boiler is controlled to be the upper limit of the load increment, and the load difference between the load fluctuation and the upper limit of the load increment is distributed to the remaining boilers. If no, the load fluctuation of the master boiler is controlled to be the load fluctuation. In addition, when the selected master boiler reaches the load requirement, other boilers can be selected as the master boiler, and the above method is used for load adjustment operation. By using the method, the load adjustment operation of the boilers can be automatically controlled, so that the boilers can reach the required load.

[0024] By using the method, the load adjustment operation of the boilers can be automated and standardized, so as to reduce the labor intensity of the operators, avoid the mistakes caused by the non-uniform manual operation methods, make the boilers operate properly, avoid the product unit fluctuation of the end users, and affect the quality of the final products. In addition, the upper limit of the load increment is set according to the historical data and the field investigation, which helps to improve the self-control safety of the boilers.

[0025] In summary, the method for controlling multiple fluidized bed boilers by using the mother pipe pressure can effectively improve the control effect of the boiler combustion system. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0027] Fig. 1 The flowchart of the method for controlling multiple fluidized bed boilers by using the mother pipe pressure;

[0028] Fig. 2 The structural diagram of the circulating fluidized bed boiler;

[0029] Fig. 3 The use diagram of the method for controlling multiple fluidized bed boilers by using the mother pipe pressure.

[0030] Figs. 1-3 In the figure:

[0031] 1 is the furnace, 2 is the gas-solid separator, 3 is the solid material recycling device, 4 is the heat exchanger, 5 is the convection flue, 6 is the coal feeder, 7 is the feeder, 8 is the primary air fan, 9 is the secondary air fan, 10 is the dust collector, 11 is the induced draft fan, and 12 is the chimney. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0033] The core of the present application is to provide a fluidized bed mother pipe pressure multi-furnace joint control method, which can effectively improve the control effect of the boiler combustion system.

[0034] Please refer to Figs. 1 to 3 , Fig. 1 The flowchart of the fluidized bed mother pipe pressure multi-furnace joint control method provided by the present application is shown in the figure; Fig. 2 The structural schematic diagram of the circulating fluidized bed boiler is shown in the figure; Fig. 3 The use schematic diagram of the fluidized bed mother pipe pressure multi-furnace joint control method is shown in the figure.

[0035] The specific embodiment provides a fluidized bed mother pipe pressure multi-furnace joint control method, which comprises the following steps:

[0036] Step S1, one of multiple boilers is selected as a main boiler for main control pressure;

[0037] Step S2, the load increment upper limit ΔFmax of the main boiler is set according to historical data and field investigation;

[0038] Step S3, it is judged whether the load fluctuation amount ΔF of the main boiler is greater than or equal to ΔFmax, if yes, the load fluctuation amount of the main boiler is controlled to be ΔFmax, and the load difference amount of ΔF and ΔFmax is distributed to the remaining boilers; if no, the load fluctuation amount of the main boiler is controlled to be ΔF.

[0039] It should be noted that the boiler of the present application refers to a circulating fluidized bed boiler, which is usually composed of a furnace 1, a gas-solid separator 2, a solid material recirculation device 3, a heat exchanger 4 and a convection flue 5, and the structure is shown in Fig. 2 During use, fuel and limestone desulfurizer are crushed into particles of appropriate size, and then fed from the upper part of the air distribution plate of the furnace 1 of the circulating fluidized bed boiler by the coal feeder 6 and the feeder 7, and the primary air and the secondary air required for combustion are respectively fed from the bottom and the side wall of the furnace 1 by the primary air fan 8 and the secondary air fan 9. Under the action of the primary air, the fuel and the desulfurizer are blown up to a fluidized state. The fluidized state refers to that the solid particles rise and float up under the action of air with a certain flow rate, and then fall down under the action of gravity, forming a state similar to liquid boiling.

[0040] The fluidized state of the bed material greatly intensifies the strength of combustion, the entire furnace 1 is in a state of combustion, and a large amount of solid particles are carried out by the gas flow, after being separated by the cyclone separator, the solid material is sent back to the furnace 1 by the solid material recycling device 3 to circulate and burn until it is burned out, thereby forming a circulation of the bed material. And, water-cooled pipes are arranged around the furnace 1 for absorbing part of the heat generated by combustion. The flue gas exchanges heat with the convection heating surface in the tail flue, and finally passes through the dust collector 10 and the induced draft fan 11 and is discharged into the atmosphere through the chimney 12.

[0041] It should be further pointed out that the boiler load refers to the total amount of steam required to be provided by the boiler to meet the needs of the downstream users; the main pipe pressure is a key indicator of the boiler device, which needs to be ensured stable for the boiler to supply heat and power. The "setting the load increment upper limit ΔFmax of the main boiler according to historical data and field investigation" of the present application can refer to using advanced control software to store boiler operation data to make a database, when setting the load increment upper limit ΔFmax of the main boiler, the data of the database can be viewed, the historical behavior and data of the main pipe pressure are analyzed and arranged, and combined with artificial experience, the main control pressure of which boilers and the load of the other boilers are summarized according to the characteristics of the boiler, to provide a basis for joint control and load distribution.

[0042] In the use of the fluidized bed main pipe pressure multi-boiler joint control method provided by the present application, first, a boiler is selected as the main boiler for main control pressure in the multiple boilers. Then, the load increment upper limit ΔFmax of the main boiler is set according to historical data and field investigation. Finally, it is judged whether the load fluctuation ΔF of the main boiler is greater than or equal to ΔFmax, if yes, the load fluctuation of the main boiler is controlled to be ΔFmax, and the load difference between ΔF and ΔFmax is distributed to the remaining boilers; if not, the load fluctuation of the main boiler is controlled to be ΔF. In addition, when the selected main boiler reaches the load demand, other boilers can be reselected as the main boiler, and the above method is continued to be used for load adjustment operation. By using the method, automatic control of each boiler load adjustment can be realized, so that the boiler reaches the required load.

[0043] By using the method, the load adjustment operation of the boiler can be automated and standardized, so as to reduce the labor intensity of the operator, avoid mistakes caused by non-uniform manual operation, make the boiler operate properly, avoid the fluctuation of the product unit of the downstream user, and affect the quality of the final product. Moreover, the set load increment upper limit ΔFmax is summarized from historical data and field investigation, which helps to improve the self-control safety of the boiler operation.

[0044] In summary, the fluidized bed main pipe pressure multi-boiler joint control method provided by the present application can effectively improve the control effect of the boiler combustion system.

[0045] In one embodiment, the load difference between AF and AFmax is distributed to the remaining boilers, including distributing the load difference to the remaining boilers in proportion to the load, wherein the proportion to the load can be set in advance and modified. That is, when the external disturbance increases, the load fluctuation AF of the main boiler increases, resulting in a decrease in the pressure of the main boiler, and when the load fluctuation AF is greater than or equal to the upper limit of the load increment AFmax, the load distribution operation is triggered to distribute the upper limit of the load increment AFmax to the main boiler and distribute the load difference between AF and AFmax to the remaining boilers in proportion to the load.

[0046] In one embodiment, the load fluctuation AF of the main boiler is controlled, including separately increasing the coal quantity of the main boiler to increase the pressure and load of the main boiler. That is, when the external disturbance increases, the load fluctuation AF of the main boiler increases, resulting in a decrease in the pressure of the main boiler, and when the load fluctuation AF is less than the upper limit of the load increment AFmax, the load distribution operation is triggered to distribute the load fluctuation AF only to the main boiler.

[0047] In one embodiment, the main boiler and the remaining boilers are each provided with a load distribution switch. When the load distribution operation is triggered, the upper limit of the load increment AFmax can be distributed to the main boiler running in proportion to the load by starting the load distribution switch.

[0048] In one embodiment, the main boiler and the remaining boilers are each provided with a first selection switch for selecting the main boiler to control the steam flow and a second selection switch for selecting the main boiler to control the steam pressure. That is, each boiler needs to have a selection switch for the main steam flow and the main steam pressure to select which boiler or boilers to control the pressure (main steam pressure) and which boiler or boilers to control the flow (main steam flow) according to the characteristics of the boilers.

[0049] In one embodiment, the main boiler and the remaining boilers are each provided with a load increase and decrease controller for increasing or decreasing the load of the boiler to the latest set value at a specified speed. That is, the load increase and decrease controller is provided with a control program designed to achieve a smooth change in the set value of the main steam flow. By adding the load increase and decrease controller, the entire adjustment process can be realized without the intervention of operating personnel, achieving fully automatic operation. Furthermore, after the load distribution operation is completed, automatic modification of the load set value can be realized.

[0050] In order to further illustrate the fluidized bed mother pipe pressure multi-boiler control method provided by the present application, an example is given as follows.

[0051] Taking three boilers as an example, first, it is determined which boiler is the main boiler to control the pressure, and the remaining boilers are determined to control the flow. Fig. 3For example, the main boiler is designated as boiler 1, and the remaining boilers are designated as boilers 2 and 3. The load F of boilers 1, 2, and 3 is 140 kg / h, the pressure inside the boilers is P, and the ΔFmax of boiler 1 is 10 kg / h.

[0052] Then, based on historical data and on-site investigations, the load increment limit ΔFmax for Boiler 1 was set. Whether the fluctuation is internal or external is determined by whether ΔF is greater than ΔFmax. If insufficient air-fuel ratio leads to insufficient boiler gas flow (indicating this fluctuation is internal), causing a drop in P (ΔF < ΔFmax), then Boiler 1, which controls the pressure, will increase the coal flow alone to raise the pressure.

[0053] When the external load demand (assuming that the external load demand at this time is 20kg / h) increases, causing the pressure P to drop, at this time ΔF≥ΔFmax (that is, this fluctuation is an external disturbance), when the load fluctuation ΔF is greater than the set load increment upper limit ΔFmax, the load distribution operation is triggered, which can control the load of furnace 1# to increase by 10kg / h, so that the load F of furnace 1# increases to 150kg / h. The load difference between ΔF and ΔFmax is proportionally distributed to furnaces 2# and 3#. For example, the load difference of 10kg / h can be evenly divided into furnaces 2# and 3#, so that the load F of furnaces 2# and 3# increases to 145kg / h. Fig. 3 When load sharing is triggered, the boiler flow setpoint of the master flow control will be automatically modified by the load increase / decrease controller (such as APC controller), and the load will be pulled to the new setpoint at a specified speed.

[0054] In one embodiment, before selecting one of the multiple boilers as the main boiler for controlling the pressure, the method further includes:

[0055] Determine whether each coal feeder 6 of each boiler has a coal shortage phenomenon (that is, the flow rate of the coal feeder 6 of the boiler changes suddenly or even returns to zero due to moisture in the coal or other physical reasons),

[0056] If so, the coal feeder 6 that is out of coal is disconnected and the total coal supply required by the boiler is distributed to all normal coal feeders 6. If not, the total coal supply required by the boiler is distributed to all normal coal feeders 6. The above-mentioned coal-out operation can be regarded as an automatic accident detection and automatic handling program module for the coal-out problem that may occur during the boiler combustion process to ensure the safety of the combustion process.

[0057] In one embodiment, determining whether each coal feeder 6 of each boiler has a coal shortage phenomenon includes reading the coal supply amount of each coal feeder 6 in real time; determining whether the coal supply amount is abnormal, if so, the coal feeder 6 has a coal shortage phenomenon, if not, the coal feeder 6 is normal.

[0058] That is, when the boiler breaks coal under normal working conditions, the main steam flow will decrease significantly, affecting the normal operation of the boiler, and leading to unstable user indicators. By using the method, the coal feeder 6 can be automatically judged which coal feeder 6 breaks coal through the abnormal fluctuation of the coal feeding amount and the oxygen content on the corresponding side, so as to automatically and quickly handle the coal breaking phenomenon and effectively avoid the fluctuation of the working condition.

[0059] In one embodiment, the control of the coal feeder 6 breaking coal also includes voice alarm when the coal feeder 6 breaking coal is disconnected, so as to remind the operator to check the abnormal coal feeder 6 on site through voice alarm.

[0060] In one embodiment, the total coal feeding amount required by the boiler is distributed to each normal coal feeder 6, including distributing the total coal feeding amount required by the boiler to each normal coal feeder 6 according to the coal feeding ratio, wherein the coal feeding ratio can be set and modified in advance. For example, the distribution button for setting the coal feeding ratio can be provided on the coal feeder 6 of the boiler, so as to remind the operator through voice alarm when any one or more coal feeders 6 break coal, and automatically distribute the total coal demand according to the ratio to other normal coal feeders 6.

[0061] Under normal working conditions, the breaking of coal will cause the main steam flow of the boiler to decrease significantly, affecting the normal operation of the boiler, and leading to unstable user indicators. In the case of normal use of APC (advance process control), the coal feeder 6 can be automatically judged which coal feeder 6 breaks coal through the abnormal fluctuation of the coal feeding amount and the oxygen content on the corresponding side, so as to automatically and quickly handle the coal breaking problem and effectively avoid the fluctuation of the working condition.

[0062] The above automatic accident judgment / automatic handling program module starts to run in a loop to judge whether multiple coal feeders 6 break coal. Once the coal feeder 6 breaks coal, the coal feeding program control switch of the coal feeder 6 is cut off, and the total coal feeding amount is distributed to other coal feeders 6 according to the coal feeding ratio in time, so as to reduce the pressure of handling the coal breaking of the coal feeder 6 and avoid the interference of personnel under the APC automatic state. The operator is reminded to check the state of the coal feeder 6 on site through voice alarm, and the coal feeding program control switch of the coal feeder 6 is opened after the normal state is restored, and the total coal feeding amount is automatically distributed to all coal feeders 6.

[0063] The present application can standardize, unify and program the multi-boiler control process of the mother pipe pressure through APC software, and has the following advantages compared with the original manual control:

[0064] ①The automatic program reduces the labor intensity of the operator, and the number of operations in the automatic control range is reduced from about one thousand times to a single digit.

[0065] ② It has wide applicability, and is more advantageous for devices with more boilers. The same and standardized steps are summarized and concluded from the historical behavior data of excellent operators, so that the automatic control safety achieved is higher, that is, the control of multiple boilers uses the model predictive control technology in the APC software. Through the steps of historical data analysis-establishing mathematical models-automatic control controller construction, an APC controller for multiple boiler combustion is established, which realizes single-unit control during small load fluctuations and multi-unit joint control during large load fluctuations, ensuring stable control of main steam pressure under different conditions; and it is equipped with automatic judgment / automatic processing program modules for possible coal outage accidents, that is, the automatic processing of coal outage uses the script control in the APC controller, and the safety of automatic processing of coal outage can be further improved through real-time judgment of the coal outage status of coal feeder 6;

[0066] ③ More precise and stable automatic control operation has replaced the manual extensive adjustment method. The load adjustment range has been reduced, which effectively reduces the impact on back-end users and ensures the stability and uniformity of back-end product quality.

[0067] It should be noted that, in the present invention, the first selection switch and the second selection switch are referred to as first and second only to distinguish the positions, and there is no order of precedence.

[0068] In addition, it should be noted that the orientation or positional relationship indicated by the "bottom" and the like in the present invention is based on the orientation or positional relationship shown in the accompanying drawings and is only for the purpose of simplifying the description and facilitating understanding, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0069] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. Any combination of all the embodiments provided by the present invention is within the scope of protection of this invention and will not be described in detail here.

[0070] The above is a detailed introduction to the fluidized bed main pipe pressure multi-furnace joint control method provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above examples is only intended to help understand the method and core concept of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A fluidized bed mother pipe pressure multi-furnace joint control method, characterized by, The application relates to a coal feeding system for multiple boilers, which comprises: determining whether the coal feeding machine (6) of each boiler is in a coal interruption state, if yes, the coal feeding machine (6) in the coal interruption state is controlled to be disconnected, and the total coal feeding amount required by the boiler is distributed to the normal coal feeding machines (6), if no, the total coal feeding amount required by the boiler is distributed to the normal coal feeding machines (6); selecting one of the multiple boilers as a main boiler for controlling pressure; According to historical data and field research to set the load increment upper limit of the main boiler It includes using the model predictive control technology in the APC software, through the historical data analysis - mathematical model - automatic controller building steps to establish the APC controller of the multiple boilers, to make the database, when setting the load increment upper limit of the main boiler , view the data of the database, analyze and arrange the historical behavior and data of the main pipe pressure, and combine with artificial experience, according to the characteristics of each boiler, summarize and arrange the main control pressure of a certain boiler and the main control load of another boiler; judging whether the load fluctuation amount of the main boiler is greater than or equal to judging whether the load fluctuation amount of the main boiler is greater than or equal to , if yes, controlling the load fluctuation amount of the main boiler to be , and distributing the load difference amount of and to the remaining boilers, the distributing the load difference amount of and to the remaining boilers comprising distributing the load difference amount to the remaining boilers in proportion to the load, wherein the load proportion can be set and modified in advance; if no, controlling the load fluctuation amount of the main boiler to be .

2. The fluidized bed mother pipe pressure multi-furnace joint control method according to claim 1, characterized by, controlling an amount of load fluctuation of the main boiler to be , the coal feeding amount of the main boiler is separately increased to increase the pressure and load of the main boiler.

3. The fluidized bed mother pipe pressure multi-furnace joint control method according to claim 1 or 2, characterized by, The main boiler and the rest of the boilers are provided with load distribution switches.

4. The fluidized bed mother pipe pressure multi-furnace joint control method according to claim 1 or 2, characterized by, The main boiler and the rest of the boilers are provided with first selection switches for selecting the main steam flow of the boilers and second selection switches for selecting the main steam pressure of the boilers.

5. The fluidized bed mother pipe pressure multi-furnace joint control method according to claim 1 or 2, characterized by, The main boiler and the rest of the boilers are provided with load increase and decrease controllers for increasing or decreasing the load of the boilers to the latest set value at a specified speed.

6. The fluidized bed mother pipe pressure multi-furnace joint control method according to claim 1 or 2, characterized by, The determination of whether the coal feeding machine (6) of each boiler is in a coal interruption state comprises: real-time reading of the coal feeding amount of each coal feeding machine (6); determination of whether the coal feeding amount is abnormal, if yes, the coal feeding machine (6) is in a coal interruption state, if no, the coal feeding machine (6) is normal.

7. The fluidized bed mother pipe pressure multi-furnace joint control method according to claim 1 or 2, characterized by, The control of the disconnection of the coal feeding machine (6) in the coal interruption state further comprises voice alarm when the coal feeding machine (6) in the coal interruption state is disconnected.

8. The fluidized bed mother pipe pressure multi-furnace joint control method according to claim 1 or 2, characterized by, The distribution of the total coal feeding amount required by the boiler to the normal coal feeding machines (6) comprises distribution of the total coal feeding amount required by the boiler to the normal coal feeding machines (6) according to a coal feeding ratio, wherein the coal feeding ratio can be set and modified in advance.

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