CN111520737A - Coal mill outlet temperature control method and system based on furnace smoke inerting - Google Patents
Coal mill outlet temperature control method and system based on furnace smoke inerting Download PDFInfo
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- CN111520737A CN111520737A CN202010491478.4A CN202010491478A CN111520737A CN 111520737 A CN111520737 A CN 111520737A CN 202010491478 A CN202010491478 A CN 202010491478A CN 111520737 A CN111520737 A CN 111520737A
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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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C25/00—Control arrangements specially adapted for crushing or disintegrating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L11/00—Arrangements of valves or dampers after the fire
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
- F26B21/06—Controlling, e.g. regulating, parameters of gas supply
- F26B21/10—Temperature; Pressure
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Abstract
The invention discloses a coal mill outlet temperature control method and system based on furnace smoke inerting, and aims to reduce oxygen content of a coal pulverizing system by using flue gas at the tail of a boiler and inerting the coal pulverizing system to improve explosion-proof capability starting from a deflagration generation mechanism of the coal pulverizing system. And the concentration of combustible gas CO thermally resolved from the pulverized coal at the outlet of the coal mill and the wind speed at the outlet of the coal mill are monitored, a strategy is provided for adjusting the oxygen content, the wind temperature and the wind quantity of inert media of a powder preparation system, and the temperature level at the outlet of the coal mill in actual operation is determined. Compared with the traditional method for determining the outlet temperature of the coal mill according to the empirical formula and needing a large amount of cold air, the method has the advantages of obvious coal type adaptation and safety guarantee, and can effectively improve the comprehensive output of the coal pulverizing system, reduce the power consumption of coal pulverizing and improve the boiler efficiency.
Description
Technical Field
The invention belongs to the technical field of coal-fired power generation, and particularly relates to a coal mill outlet temperature control method and system based on furnace smoke inerting.
Background
The temperature control of the coal mill outlet of the coal pulverizing system is always a key factor for explosion prevention of the coal pulverizing system, the overhigh temperature of the coal mill outlet reduces the safety of the coal pulverizing system, easily causes unsafe events of explosion of the coal pulverizing system, and threatens the running safety of a unit; the temperature control of the outlet of the coal mill is too low, so that the drying and ventilation output of a coal pulverizing system are insufficient, the running power consumption of the coal pulverizing system is increased, the output is reduced, cold air is doped into the coal pulverizing system, the exhaust gas temperature is increased, the boiler efficiency is reduced, and the coal consumption for generating power of the boiler is increased.
At present, the control standard of the outlet temperature of a coal mill of a coal pulverizing system of a power system in China is mainly determined according to the volatile content of fire coal, and the deflagration characteristics of coal with the same volatile content are remarkably different due to the great difference of coal quality characteristics such as heat productivity, moisture, ash content, coal rank and the like, and the structural types of different coal mills also have great influence on the deflagration characteristics of raw coal in the coal mill. However, the outlet temperature of the coal mill specified by the relevant regulations and standards at present is mainly determined according to the function of the single index of the volatile component of the coal quality, so that the method is difficult to adapt to the actual application requirements of variable coal quality and large coal characteristic difference in China, and the common problems that the outlet temperature of the coal mill is controlled to be at a lower level to avoid explosion of a coal pulverizing system, and a large amount of cold air needs to be doped into the coal pulverizing system at the present stage are caused, so that the output of the coal pulverizing system is seriously influenced, the power consumption of pulverized coal is increased, the exhaust gas temperature is increased, the boiler efficiency is reduced, and a method and a control system which can adapt to the current variable coal quality situation in China and can determine the outlet temperature of the coal mill according to the coal quality characteristic.
Disclosure of Invention
The invention aims to solve the problems of insufficient output power of a coal pulverizing system, low economy and the like caused by the fact that a large amount of cold air is mixed into the coal pulverizing system due to a conventional coal pulverizer outlet temperature method, and provides a coal pulverizer outlet temperature control method and system based on furnace smoke inerting. Starting from a mechanism of explosion occurrence of a coal pulverizing system, the method and the system for reducing oxygen content of the coal pulverizing system by using flue gas at the tail of a boiler, inerting the coal pulverizing system and improving explosion-proof capability of the system are provided, and a method and a system for monitoring the concentration of CO thermally resolved from coal powder at an outlet of a coal mill and the wind speed at the outlet of the coal mill are combined, so that a control strategy is provided for determining the temperature, the oxygen content and the flow of an inert medium of the coal pulverizing system, and the temperature level of the outlet of the coal mill in actual operation is. Therefore, the operation safety of the powder making system can be ensured, and the adverse effect caused by the cold air input into the powder making system can be avoided.
The invention is realized by adopting the following technical scheme:
the coal mill outlet temperature control system based on the furnace smoke inerting comprises a boiler, a tail flue heat exchanger, an air preheater, a primary fan, an induced draft fan, a furnace smoke fan, a coal mill, a coal powder separator, a coal bunker, a coal feeder and a combustion system; wherein the content of the first and second substances,
a high-temperature furnace smoke air door and a high-temperature furnace smoke temperature measuring point are arranged on a high-temperature furnace smoke pipeline at the inlet of the furnace smoke fan, a low-temperature furnace smoke air door and a low-temperature furnace smoke temperature measuring point are arranged on a low-temperature furnace smoke pipeline, a furnace smoke fan inlet air door and a mixed furnace smoke temperature measuring point are arranged on a furnace smoke fan inlet converging pipeline, and a furnace smoke fan outlet air door is arranged on a furnace smoke fan outlet pipeline; a hot primary air door and a hot primary air temperature measuring point are arranged on a hot primary air pipeline at the outlet of the air preheater; a coal mill inlet air door, a coal mill inlet oxygen amount measuring point and a coal mill inlet temperature measuring point are arranged on a mixed medium pipeline at the coal mill inlet; a pulverized coal pipeline between the outlet of the pulverized coal separator and the inlet of the combustion system is provided with a pulverized coal pipe wind speed measuring point, a pulverized coal pipe wind temperature measuring point and a pulverized coal pipe CO concentration measuring point;
the boiler smoke outlet of the boiler is connected with the inlet of the tail flue heat exchanger, the outlet of the tail flue heat exchanger is connected with the inlet of the air preheater, the outlet flue of the air preheater is connected with the inlet of the induced draft fan, the inlet of the low-temperature boiler smoke air door is provided with two paths, one path is connected with the outlet of the induced draft fan, and the other path is connected with the flue of the tail flue heat exchanger area;
the inlet of the coal mill is divided into two paths, one path is a drying medium inlet, the other path is a raw coal inlet, wherein the drying medium inlet is divided into two paths, one path is connected with the outlet of the flue gas blower, the other path is connected with the outlet of the air preheater, and the inlet of the air preheater is connected with the outlet of the primary air blower; a raw coal inlet of the coal mill is connected with an outlet of the coal feeder, and an inlet of the coal feeder is connected with an outlet of the coal bunker; the outlet of the coal mill is connected with the inlet of the coal powder separator, and the outlet of the coal powder separator is connected with the coal powder airflow inlet of the combustion system through a coal powder pipeline.
The invention is further improved in that the drying medium at the inlet of the coal mill comprises three components of hot primary air, high-temperature furnace smoke and low-temperature furnace smoke, wherein the hot primary air is from a primary fan and is heated by an air preheater, the high-temperature furnace smoke is from a tail flue heat exchanger area, the low-temperature furnace smoke is from an outlet of a furnace draught fan, and the mixed furnace smoke consisting of the high-temperature furnace smoke and the low-temperature furnace smoke is mixed with the hot primary air after being pressurized by a furnace smoke fan to form the grinding drying medium.
The invention has the further improvement that the flow of the high-temperature furnace smoke from the heat exchanger area of the tail flue of the boiler is adjusted through a high-temperature furnace smoke air door, and the temperature of the high-temperature furnace smoke is monitored through a high-temperature furnace smoke temperature measuring point; the flow of low-temperature furnace smoke from the outlet of the induced draft fan is adjusted through a low-temperature furnace smoke air door and passes throughMonitoring the temperature of the low-temperature furnace smoke by a low-temperature furnace smoke temperature measuring point; the temperature of the mixed furnace smoke entering the furnace smoke fan is monitored through a mixed furnace smoke temperature measuring point, and the flow of the mixed furnace smoke is regulated through an outlet air door of the furnace smoke fan; hot primary air from a primary fan and heated by an air preheater is used for regulating the flow through a hot primary air door, and the temperature of hot air is monitored through a hot primary air temperature measuring point; the total flow of the mixed furnace smoke and the hot primary air is adjusted through an air door at the inlet of the coal mill, and the O of the grinding medium is measured through an oxygen measuring point at the inlet of the coal mill2The concentration, temperature of the mill-entering mixed media is measured by a mill inlet temperature measurement station.
The invention has the further improvement that the drying medium of the coal pulverizing system is a mixture of furnace smoke and hot air, the oxygen concentration of the drying medium is adjustable, the oxygen concentration of the drying medium entering the mill is monitored through a mill inlet oxygen amount measuring point during adjustment, then the ratio of the furnace smoke and the hot air of the drying medium entering the mill is adjusted through the adjusted opening of a furnace smoke fan outlet air door and a hot primary air door, the aim of controlling the oxygen concentration of the medium entering the mill is achieved, and the explosion-proof capability of the coal pulverizing system in the coal pulverizing process can be obviously improved by the low-oxygen coal pulverizing medium.
The invention has the further improvement that the drying medium of the powder making system can adapt to the flexible regulation and control of the coal quality characteristics of the coal types, and the drying medium is composed of three media of high-temperature furnace smoke, low-temperature furnace smoke and hot primary air according to a set proportion or is one of the media; under the condition of stable coal quality, the system structure can be simplified into the combination of hot air and high-temperature furnace smoke or the combination of two mediums of hot air and low-temperature furnace smoke.
The invention has the further improvement that the control of the outlet temperature of the powder preparation system is determined based on the monitoring results of a mill inlet oxygen amount measuring point, a powder pipe wind speed measuring point and a powder pipe CO concentration measuring point; when the CO concentration is too high, the deflagration risk of the powder making system is increased, the regulation and control are carried out by flexibly adopting a method of reducing the oxygen content of an inlet of the powder making system or the temperature of a mixed medium, and the corresponding measures are to regulate the opening degrees of air doors corresponding to hot air and high-temperature and low-temperature furnace smoke; when the air speed of the powder pipe is too low, the flow of the smoke or hot air of the powder making system is adjusted to adjust the powder feeding air speed.
The method for controlling the outlet temperature of the coal mill based on the furnace smoke inerting comprises the following steps:
the furnace smoke for reducing the oxygen content of the powder making system is formed by mixing low-temperature furnace smoke from an outlet of an induced draft fan and high-temperature furnace smoke from a heat exchanger area at the tail part of a boiler, the mixed furnace smoke is mixed with hot primary air after the pressure of the furnace smoke fan is increased, and finally, a drying medium which is formed by the low-temperature furnace smoke, the high-temperature furnace smoke and the hot primary air and can monitor and regulate three variables of oxygen content, temperature and flow is formed, and a proper inerting drying medium is provided according to the actual coal quality characteristic of entering the boiler; the flow control of the three media is realized by regulating and controlling a low-temperature furnace smoke air door, a high-temperature furnace smoke air door, a furnace smoke fan inlet air door, a hot primary air door and a coal mill inlet air door which are arranged in the system.
The invention has at least the following beneficial technical effects:
the invention is based on the chain reaction mechanism of the coal powder airflow deflagration generation of the coal pulverizing system, and utilizes a method for monitoring and controlling key indexes such as oxygen quantity, propagation speed, combustible gas concentration and the like which are necessary for the deflagration reaction to form a set of system for controlling the outlet temperature of a coal pulverizer of the coal pulverizing system of a coal pulverizing boiler. In order to adapt to the condition that coal quality of the boiler burning coal of the power station boiler is changeable in China, boiler tail flue gas with different temperature levels is selected, the boiler tail flue gas is low-oxygen-content drying medium which is easily obtained in a power station boiler system, the oxygen concentration in the flue gas is usually in a range of 2% -6%, and the boiler tail flue gas is an excellent inert drying medium. The proper temperature flue gas and the hot primary air of the conventional coal pulverizing system are combined to form a flue gas and hot air mixed drying medium, the oxygen content level in the coal pulverizing process of the coal pulverizing system can be effectively reduced, the inerting coal pulverizing system grinding process is achieved, the deflagration risk of the coal pulverizing system is remarkably reduced, good conditions are created for improving the outlet temperature of a coal pulverizer, cold air is prevented from being doped in the running process of the coal pulverizing system, the existing primary air system is also prevented from being greatly changed, the balance imbalance of the flue gas system is caused, and the adaptability and the reliability of the system are reduced. On the other hand, the concentration of CO at the outlet of the pulverizing system is an important index for well reflecting that combustible substances begin to be separated out in the pulverized coal grinding process, and the abnormal rise of the concentration of CO shows that the combustible substances in the pulverized coal are obviously separated out and the deflagration risk of the system rises, so that the concentration of CO can be used as a monitoring index for preventing deflagration of the pulverizing system. Moreover, the reasonable ventilation speed of the pulverizing system is also the main index of the pulverized coal airflow deflagration chain reaction, the airflow speed exceeding the flame propagation speed can block the propagation and aggravation of the deflagration reaction, the through-flow speed in the system is properly increased under necessary conditions, and the method also has an important effect on preventing deflagration of the pulverizing system. The coal mill outlet temperature control method and system based on the furnace smoke inerting are provided by combining the monitoring and control of three key indexes of the oxygen content of the coal milling system, the CO concentration of the coal mill outlet and the wind speed of the coal milling system, and have important practical significance for reducing the amount of doped cold air of the coal milling system, improving the output of the coal milling system, reducing the power consumption of coal milling and improving the boiler efficiency while ensuring the running safety of the coal milling system.
Specifically, according to the coal mill outlet temperature control method and system based on the furnace smoke inerting, provided by the invention, the drying medium of the coal pulverizing system is composed of three media of hot primary air, high-temperature furnace smoke and low-temperature furnace smoke, the flow rates of the three media can be respectively adjusted through a hot primary air door, a high-temperature furnace smoke air door and a low-temperature furnace smoke air door on corresponding pipelines, and the free adjustment of the oxygen amount, the temperature and the flow rate of the grinding drying medium can be realized. The oxygen amount adjustment, the temperature adjustment of a drying medium at the inlet of the coal pulverizing system and the adjustment of the ventilation flow of the coal pulverizing system are important advantages which are not possessed by the existing boiler mainly adopting hot air as the drying medium, and the explosion-proof capability of the coal pulverizing system and the adaptation and regulation capability under the condition of facing changeable coal quality are greatly enhanced. The method comprises the steps of setting measuring points of CO concentration, temperature and wind speed at an outlet of a coal mill, utilizing monitoring results to realize real-time evaluation of explosion-proof capacity, drying output and ventilation output of a coal pulverizing system, determining the liftable outlet temperature of the coal mill, replacing calculation results of a traditional empirical formula, and using the results as feedback indexes to regulate and control the flow and proportion of three media entering the coal pulverizing system to form the integral closed-loop control of the system.
Compared with the traditional method for determining the outlet temperature of the coal mill according to the empirical formula by the coal pulverizing system and needing to mix a large amount of cold air, the method provided by the invention has the advantages of obvious coal type adaptability, and the system avoids mixing the cold air, and can improve the comprehensive output of the coal pulverizing system, reduce the power consumption of coal pulverizing and improve the boiler efficiency.
In summary, the invention provides a coal mill outlet temperature control method and system based on smoke inerting, which aims to realize a monitoring and control system for explosion-proof capability, drying output and ventilation output of a coal pulverizing system by forming a drying medium consisting of low-temperature smoke, high-temperature smoke and hot primary air and respectively installing oxygen quantity, temperature, CO concentration, speed and other measuring points on the coal pulverizing system, and perform closed-loop control on the composition and flow of the drying medium of the coal pulverizing system according to the change of coal types and real-time data required by control, so that the outlet temperature of the coal mill is increased, and the aim of effectively improving the running economy of the coal pulverizing system and a boiler under the condition of ensuring the safety of the coal pulverizing system is fulfilled.
Drawings
FIG. 1 is a schematic diagram of the configuration of a coal mill outlet temperature control system based on the inerting of the flue gas of the present invention.
Description of reference numerals:
1. boiler, 2, tail flue heat exchanger, 3, air preheater, 4, primary fan, 5, induced draft fan, 6, low temperature smoke damper, 7, low temperature smoke temperature measuring point, 8, high temperature smoke damper, 9, high temperature smoke temperature measuring point, 10, smoke blower inlet damper, 11, mixed smoke temperature measuring point, 12, smoke blower, 13, smoke blower outlet damper, 14, primary hot air damper, 15, primary hot air temperature measuring point, 16, coal mill inlet damper, 17, mill inlet oxygen amount measuring point, 18, mill inlet temperature measuring point, 19, coal mill, 20, coal dust separator, 21, coal bunker, 22, coal feeder, 23, coal pipe air speed measuring point, 24, coal pipe air temperature measuring point, 25, coal pipe CO concentration, 26, combustion system.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Referring to fig. 1, the coal mill outlet temperature control method and system based on furnace smoke inerting of the invention comprises a boiler 1, a tail flue heat exchanger 2, an air preheater 3, a primary air fan 4, an induced draft fan 5, a low-temperature furnace smoke air door 6, a low-temperature furnace smoke temperature measuring point 7, a high-temperature furnace smoke air door 8, a high-temperature furnace smoke temperature measuring point 9, a furnace smoke air fan inlet air door 10, a mixed furnace smoke temperature measuring point 11, a furnace smoke air fan 12, a furnace smoke air fan outlet air door 13, a primary hot air door 14, a primary hot air temperature measuring point 15, a coal mill inlet air door 16, a mill inlet oxygen amount measuring point 17, a mill inlet temperature measuring point 18, a coal mill 19, a coal dust separator 20, a coal bunker 21, a coal feeder 22, a coal pipe air speed measuring point 23, a coal pipe air temperature measuring point 24, a coal pipe CO concentration measuring.
The boiler smoke outlet of the boiler 1 is connected with the inlet of the tail flue heat exchanger 2, the outlet of the tail flue heat exchanger 2 is connected with the inlet of the air preheater 3, the outlet flue of the air preheater 3 is connected with the inlet of the induced draft fan 5, the inlet of the low-temperature boiler smoke damper 6 is provided with two paths, one path is connected with the outlet of the induced draft fan 5, and the other path is connected with the flue in the tail flue heat exchanger 2 area;
the inlet of the coal mill 19 is divided into two paths, one path is a drying medium inlet, the other path is a raw coal inlet, wherein the drying medium inlet is divided into two paths, one path is connected with the outlet of the flue gas blower 12, the other path is connected with the outlet of the air preheater 3, and the inlet of the air preheater 3 is connected with the outlet of the primary air blower 4; the raw coal inlet of the coal mill 19 is connected with the outlet of a coal feeder 22, and the inlet of the coal feeder 22 is connected with the outlet of a coal bunker 21; the outlet of the coal mill 19 is connected to the inlet of a coal dust separator 20, and the outlet of the coal dust separator 20 is connected to the coal dust airflow inlet of the combustion system 26 through a coal dust pipeline.
In addition, a high-temperature furnace smoke air door 8 and a high-temperature furnace smoke temperature measuring point 9 are arranged on a high-temperature furnace smoke pipeline at the inlet of the furnace smoke fan 12, a low-temperature furnace smoke air door 6 and a low-temperature furnace smoke temperature measuring point 7 are arranged on a low-temperature furnace smoke pipeline, a furnace smoke fan inlet air door 10 and a mixed furnace smoke temperature measuring point 11 are arranged on a converging pipeline at the inlet of the furnace smoke fan 12, and a furnace smoke fan outlet air door 13 is arranged on an outlet pipeline of the furnace smoke fan 12. And a hot primary air door 14 and a hot primary air temperature measuring point 15 are arranged on a hot primary air pipeline at the outlet of the air preheater 3. And a coal mill inlet air door 16, a mill inlet oxygen measuring point 17 and a mill inlet temperature measuring point 18 are arranged on a mixed medium pipeline at the inlet of the coal mill 19. And a powder pipe air speed measuring point 23, a powder pipe air temperature measuring point 24 and a powder pipe CO concentration measuring point 25 are arranged on a coal powder pipeline between the outlet of the coal powder separator 20 and the inlet of the combustion system 26.
The low-temperature furnace smoke air door 6, the high-temperature furnace smoke air door 8 and the hot primary air door 14 respectively realize the adjustment of the flow ratio of the low-temperature furnace smoke, the high-temperature furnace smoke and the hot primary air, and realize the control of the dry medium component at the inlet of the coal mill; and a mill inlet oxygen amount measuring point 17 and a mill inlet temperature measuring point 18 are used for monitoring the oxygen amount and the temperature of the mixed media entering the mill, and a mill inlet air door 16 is used for regulating and controlling the total amount of the drying media entering the mill. The powder pipe wind speed measuring point 23 monitors the powder pipe wind speed and reflects the ventilation output condition of the powder making system, the powder pipe wind temperature measuring point 24 is an important monitoring index of the drying output of the coal mill, and the powder pipe CO concentration is a key index for evaluating the deflagration condition of the powder making system and is also an important basis for participating in the drying medium flow ratio regulation and temperature control of the powder making system.
The invention provides a coal mill outlet temperature control method based on furnace smoke inerting, which utilizes a coal mill outlet temperature control system based on furnace smoke inerting and comprises the following steps:
the boiler smoke for reducing the oxygen content of the powder making system is formed by mixing low-temperature boiler smoke from an outlet of an induced draft fan 5 and high-temperature boiler smoke from an area of a boiler tail heat exchanger 2, the mixed boiler smoke is mixed with hot primary air after the pressure of the boiler smoke fan is increased, and finally, the low-temperature boiler smoke, the oxygen content formed by three media of the high-temperature boiler smoke and the hot primary air together is formed, the temperature and the flow of the drying media can be monitored and regulated, the flexible and various regulating means can adapt to the changeable coal source condition in China, and the inerting drying media suitable for being provided according to the actual coal quality characteristics entering the boiler are provided. The flow control of the three media is realized by regulating and controlling a low-temperature furnace smoke air door 6, a high-temperature furnace smoke air door 8, a furnace smoke fan inlet air door 10, a hot primary air door 14 and a coal mill inlet air door 16 which are arranged in the system.
The regulation and control method and the strategy of the air door are determined based on the monitoring data of three aspects of explosion prevention, drying and ventilation output of a coal pulverizing system, and specifically are determined by the monitoring data of a CO concentration measuring point 25, a temperature measuring point 24 and a speed measuring point 23 which are arranged on an outlet coal powder pipe of a coal mill. If the CO concentration is lower, the larger safety margin of the powder making system is reflected, and the outlet temperature of the coal mill can be increased; when the actually measured temperature of the outlet of the powder making system is lower, the drying output of the powder making system is relatively lower, and the heat input into the powder making system is increased by adopting a mode of increasing the temperature or flow of a drying medium of the powder making system; when the wind speed at the outlet of the coal mill is low, the ventilation output of the coal pulverizing system is low, and the total medium flow of the coal pulverizing system needs to be increased. After the results are obtained, a command for adjusting the corresponding air door can be sent out according to the requirement, and the closed-loop control of the system is formed.
In summary, the coal mill outlet temperature control method and system based on furnace smoke inerting provided by the invention start with a deflagration mechanism of a coal pulverizing system, reduce oxygen content of the coal pulverizing system by using smoke at the tail of a boiler, inertize the coal pulverizing system, improve explosion-proof capability, monitor the concentration of combustible gas CO thermally resolved from coal powder at the outlet of the coal mill in a heating process and the air speed at the outlet of the coal mill, provide a strategy for adjusting the control of oxygen content, air temperature and air quantity of inert media of the coal pulverizing system, and determine the temperature level at the outlet of the coal mill in actual operation.
Specifically, the drying medium of the powder preparation system is composed of three media of hot primary air, high-temperature furnace smoke and low-temperature furnace smoke, the flow of the three media can be respectively adjusted through a hot primary air door, a high-temperature furnace smoke air door and a low-temperature furnace smoke air door on corresponding pipelines, and free adjustment of oxygen quantity, temperature and flow of the grinding drying medium can be achieved. The oxygen amount adjustment, the temperature adjustment of a drying medium at the inlet of the coal pulverizing system and the adjustment of the ventilation flow of the coal pulverizing system are important advantages which are not possessed by the existing boiler mainly adopting hot air as the drying medium, and the explosion-proof capability of the coal pulverizing system and the adaptation and regulation capability under the condition of facing changeable coal quality are greatly enhanced. The method comprises the steps of setting measuring points of CO concentration, temperature and wind speed at an outlet of a coal mill, utilizing monitoring results to realize real-time evaluation of explosion-proof capacity, drying output and ventilation output of a coal pulverizing system, determining the liftable outlet temperature of the coal mill, replacing calculation results of a traditional empirical formula, and using the results as feedback indexes to regulate and control the flow and proportion of three media entering the coal pulverizing system to form the integral closed-loop control of the system.
Compared with the traditional method for determining the outlet temperature of the coal mill according to the empirical formula and needing to mix a large amount of cold air, the method provided by the invention has the obvious coal type adaptation advantages, and can effectively improve the comprehensive output of the coal pulverizing system, reduce the power consumption of coal pulverizing and improve the boiler efficiency.
Claims (7)
1. The coal mill outlet temperature control system based on the furnace smoke inerting is characterized by comprising a boiler (1), a tail flue heat exchanger (2), an air preheater (3), a primary air fan (4), an induced draft fan (5), a furnace smoke air fan (12), a coal mill (19), a coal powder separator (20), a coal bunker (21), a coal feeder (22) and a combustion system (26); wherein the content of the first and second substances,
a high-temperature furnace smoke air door (8) and a high-temperature furnace smoke temperature measuring point (9) are arranged on a high-temperature furnace smoke pipeline at the inlet of a furnace smoke fan (12), a low-temperature furnace smoke air door (6) and a low-temperature furnace smoke temperature measuring point (7) are arranged on a low-temperature furnace smoke pipeline, a furnace smoke fan inlet air door (10) and a mixed furnace smoke temperature measuring point (11) are arranged on a converging pipeline at the inlet of the furnace smoke fan (12), and a furnace smoke fan outlet air door (13) is arranged on an outlet pipeline of the furnace smoke fan (12); a hot primary air door (14) and a hot primary air temperature measuring point (15) are arranged on a hot primary air pipeline at the outlet of the air preheater (3); a coal mill inlet air door (16), a coal mill inlet oxygen measuring point (17) and a coal mill inlet temperature measuring point (18) are arranged on a mixed medium pipeline at the inlet of the coal mill (19); a pulverized coal pipeline between the outlet of the pulverized coal separator (20) and the inlet of the combustion system (26) is provided with a pulverized coal pipe wind speed measuring point (23), a pulverized coal pipe wind temperature measuring point (24) and a pulverized coal pipe CO concentration measuring point (25);
a furnace smoke outlet of the boiler (1) is connected with an inlet of a tail flue heat exchanger (2), an outlet of the tail flue heat exchanger (2) is connected with an inlet of an air preheater (3), an outlet flue of the air preheater (3) is connected with an inlet of an induced draft fan (5), an inlet of a low-temperature furnace smoke air door (6) is provided with two paths, one path is connected with an outlet of the induced draft fan (5), and the other path is connected with a flue in the tail flue heat exchanger (2) area;
the inlet of the coal mill (19) is divided into two paths, one path is a drying medium inlet, the other path is a raw coal inlet, the drying medium inlet is divided into two paths, one path is connected with the outlet of the flue gas blower (12), the other path is connected with the outlet of the air preheater (3), and the inlet of the air preheater (3) is connected with the outlet of the primary air blower (4); a raw coal inlet of the coal mill (19) is connected with an outlet of a coal feeder (22), and an inlet of the coal feeder (22) is connected with an outlet of a coal bunker (21); the outlet of the coal mill (19) is connected with the inlet of the coal powder separator (20), and the outlet of the coal powder separator (20) is connected with the coal powder airflow inlet of the combustion system (26) through a coal powder pipeline.
2. The system for controlling the outlet temperature of the coal mill based on the inerting of the smoke as claimed in claim 1, wherein the drying medium at the inlet of the coal mill (19) is composed of three components of hot primary air, high-temperature smoke and low-temperature smoke, wherein the hot primary air is from a primary air fan (4) and is heated by an air preheater (3), the high-temperature smoke is from the area of a rear flue heat exchanger (2), the low-temperature smoke is from the outlet of a furnace draught fan (5), and the mixed smoke composed of the high-temperature smoke and the low-temperature smoke is mixed with the hot primary air to form the grinding drying medium after being pressurized by a smoke fan (12).
3. The coal mill outlet temperature control system based on flue gas inerting of claim 1, characterized in that the high temperature flue gas from the boiler (1) back pass heat exchanger (2) area is flow regulated by a high temperature flue gas damper (8) and its temperature is monitored by a high temperature flue gas temperature measurement point (9); the flow of low-temperature furnace smoke from the outlet of the induced draft fan (5) is adjusted through a low-temperature furnace smoke air door (6), and the temperature of the low-temperature furnace smoke is monitored through a low-temperature furnace smoke temperature measuring point (7); the temperature of the mixed furnace smoke entering the furnace smoke fan (12) is monitored through a mixed furnace smoke temperature measuring point (11), and the flow of the mixed furnace smoke is regulated through a furnace smoke fan outlet air door (13); hot primary air from the primary air fan (4) and heated by the air preheater (3) passes through the hot primary air door (14) to adjust the flow, and the temperature of hot air is monitored by a hot primary air temperature measuring point (15); mixing ofThe total flow of the combined furnace smoke and the hot primary air is adjusted through an inlet air door (16) of the coal mill, and the O of the grinding medium is measured through a grinding inlet oxygen measuring point (17)2The concentration, temperature of the mill-entering mixed media is measured by a mill inlet temperature measurement (18).
4. The system of claim 1, wherein the drying medium of the coal pulverizing system is a mixture of furnace smoke and hot air, and the oxygen concentration of the drying medium is adjustable, the oxygen concentration of the drying medium entering the mill is monitored through a mill inlet oxygen amount measuring point (17) during adjustment, and then the proportion of the furnace smoke and the hot air entering the milling medium is adjusted through adjusting the opening degrees of a furnace smoke fan outlet air door (13) and a primary hot air door (14), so that the aim of controlling the oxygen concentration of the milling medium is achieved, and the explosion-proof capability of the coal pulverizing system in the coal pulverizing process can be remarkably improved by the low-oxygen pulverizing medium.
5. The system of claim 4, wherein the drying medium of the pulverizing system is flexibly adjusted and controlled according to the coal quality characteristics of the coal, and is composed of three media, namely high-temperature flue gas, low-temperature flue gas and hot primary air, according to a set proportion, or is one of the media; under the condition of stable coal quality, the system structure can be simplified into the combination of hot air and high-temperature furnace smoke or the combination of two mediums of hot air and low-temperature furnace smoke.
6. The coal mill outlet temperature control system based on furnace smoke inerting of claim 1, wherein the control of the outlet temperature of the coal pulverizing system is determined based on the monitoring results of a mill inlet oxygen amount measuring point (17), a pulverized pipe wind speed measuring point (23) and a pulverized pipe CO concentration measuring point (25); when the CO concentration is too high, the deflagration risk of the powder making system is increased, the regulation and control are carried out by flexibly adopting a method of reducing the oxygen content of an inlet of the powder making system or the temperature of a mixed medium, and the corresponding measures are to regulate the opening degrees of air doors corresponding to hot air and high-temperature and low-temperature furnace smoke; when the air speed of the powder pipe is too low, the flow of the smoke or hot air of the powder making system is adjusted to adjust the powder feeding air speed.
7. Method for controlling the outlet temperature of a coal mill based on the inerting of the flue gases, characterized in that it uses a system for controlling the outlet temperature of a coal mill based on the inerting of the flue gases according to any of the claims from 1 to 6, comprising the following steps:
the furnace smoke for reducing the oxygen content of the powder making system is formed by mixing low-temperature furnace smoke from an outlet of an induced draft fan and high-temperature furnace smoke from a heat exchanger area at the tail part of a boiler, the mixed furnace smoke is mixed with hot primary air after the pressure of the furnace smoke fan is increased, and finally, a drying medium which is formed by the low-temperature furnace smoke, the high-temperature furnace smoke and the hot primary air and can monitor and regulate three variables of oxygen content, temperature and flow is formed, and a proper inerting drying medium is provided according to the actual coal quality characteristic of entering the boiler; the flow control of the three media is realized by regulating and controlling a low-temperature furnace smoke air door, a high-temperature furnace smoke air door, a furnace smoke fan inlet air door, a hot primary air door and a coal mill inlet air door which are arranged in the system.
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