Hypoxic temperature-regulated drying gasless direct discharge type intermediate silo type pulverizing system

Abstract

The application discloses a low-oxygen temperature-regulating dry gas direct-discharge type intermediate silo type coal pulverizing system, relates to the field of coal preparation of thermal power plants, and comprises the following: an intermediate silo type coal pulverizing system body, a furnace flue gas fan, a heat exchanger and a dust collector; the furnace flue gas fan is connected with a coal mill in the intermediate silo type coal pulverizing system body through a pipeline; an input end of the furnace flue gas fan is connected with an exhaust pipe of a boiler; the heat exchanger is arranged on the pipeline between the furnace flue gas fan and the coal mill in the intermediate silo type coal pulverizing system body; the dust collector is arranged between a fine powder separator and a powder discharger in the intermediate silo type coal pulverizing system body; and an output end of the powder discharger is communicated with the atmosphere. The intermediate silo type coal pulverizing system can use coal with high moisture content and high volatile matter, and the transformation cost is low and the transformation cycle is short. Moreover, the temperature of the drying gas is adjustable, the oxygen content is low, unsafe accidents are avoided, the dry gas is directly discharged into the atmosphere without entering the air bellow, and the boiler combustion efficiency is not affected.

Description

Technical Field

[0001] This application relates to the field of coal production in thermal power plants, and in particular to a low-oxygen, temperature-regulating, drying, exhaust gas direct discharge intermediate storage pulverizing system. Background Technology

[0002] Lignite has extremely high reserves, but its high moisture content (35-50% on an as-received basis), low calorific value, high volatile matter, and tendency to spontaneously combust limit its use as fuel, resulting in a relatively low price. With the continuous increase in installed capacity of new energy sources, older thermal power plants have begun to use lignite. Because of the high moisture content of lignite, drying requires more energy, necessitating higher drying temperatures. This makes older thermal power plant units more prone to accidents, especially those with intermediate storage pulverizing systems. Figure 1 As shown, power plants with traditional intermediate storage pulverizing systems generally use hot air pulverizing, which cannot grind high volatile matter. If the entire pulverizing system is replaced, the modification cycle is long and the modification cost is high. Summary of the Invention

[0003] The purpose of this application is to provide a low-oxygen, temperature-controlled, drying, and direct-discharge intermediate storage pulverizing system, which can use coal with high moisture and high volatile matter content, and is a low-cost and short-cycle intermediate storage pulverizing system that is based on the traditional intermediate storage pulverizing system.

[0004] To achieve the above objectives, this application provides the following solution: This application provides a low-oxygen temperature-regulating drying exhaust gas direct discharge intermediate storage pulverizing system, including: an intermediate storage pulverizing system body, a flue gas fan, a heat exchanger, and a dust collector; The flue gas blower is connected to the coal mill in the intermediate storage pulverizing system via a pipeline; the input end of the flue gas blower is connected to the boiler's exhaust pipe; a heat exchanger is installed on the pipeline between the flue gas blower and the coal mill in the intermediate storage pulverizing system. The dust collector is located between the fine powder separator and the powder discharger in the main body of the intermediate storage pulverizing system; the output end of the powder discharger is connected to the atmosphere.

[0005] Optionally, the flue gas blower is used to pass the high-temperature flue gas discharged from the boiler into the coal mill to dry the coal powder during the process of crushing the raw coal into coal powder in the coal mill; The heat exchanger is used to regulate the temperature of the flue gas entering the coal mill.

[0006] Optionally, the dust collector is used to collect coal dust from the pulverizing exhaust gas discharged from the fine powder separator; The powder discharge machine is used to discharge the exhaust gas from powder making into the air after it has passed through the dust collector.

[0007] Optionally, the output end of the dust collector is also connected to the coal powder inlet of the intermediate coal powder silo in the intermediate storage pulverizing system body; the dust collector is also used to transport the coal powder in the pulverizing exhaust gas discharged from the fine powder separator to the intermediate coal powder silo.

[0008] Optionally, the dust collector may employ an electrostatic precipitator.

[0009] Optionally, an oxygen content detection mechanism is also installed on the pipeline between the flue gas fan and the coal mill in the intermediate storage pulverizing system; the oxygen content detection mechanism is used to detect the oxygen content in the flue gas introduced into the coal mill.

[0010] Optionally, the input end of the flue gas fan is connected to the air preheater of the boiler flue gas duct.

[0011] Optionally, the intermediate storage pulverizing system may also include: a raw coal bunker, a coarse powder separator, and a bellows. The output end of the raw coal bunker is connected to the input end of the coal mill; the output end of the coal mill is connected to the coarse powder separator; the first output end of the coarse powder separator is connected to the input end of the coal mill, and the second output end of the coarse powder separator is connected to the input end of the fine powder separator; the first input end of the air box is connected to the coal powder outlet of the intermediate coal powder bunker, the second input end of the air box is connected to the air preheater of the boiler, and the output end of the air box is connected to the furnace of the boiler.

[0012] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a low-oxygen, temperature-regulating, and direct-discharge intermediate storage pulverizing system for exhaust gas. A boiler exhaust fan draws in the flue gas, which has a low oxygen concentration and high temperature. This effectively dries the moisture in the pulverized coal in the coal mill and prevents oxygen from mixing with the coal, thus avoiding potential safety hazards. A heat exchanger is added to the duct downstream of the exhaust fan to regulate the flue gas temperature, ensuring thorough drying of the pulverized coal. A dust collector is introduced between the fine powder separator and the exhaust fan to collect small amounts of fine pulverized coal from the exhaust gas. The high-humidity exhaust gas does not need to enter the air box; it is discharged into the atmosphere through the exhaust fan, improving boiler combustion efficiency. This intermediate storage pulverizing system can use coal with high moisture and high volatile matter content and is a modification of a traditional intermediate storage pulverizing system, requiring low modification costs and a short modification cycle. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1A schematic diagram of a traditional intermediate storage pulverizing system is provided for this application; Figure 2 This is a schematic diagram of the structure of an intermediate storage pulverizing system for flue gas drying and mixing powder feeding provided in an embodiment of this application; Figure 3 This is a schematic diagram of a low-oxygen temperature-controlled drying exhaust gas direct-discharge intermediate storage pulverizing system provided in an embodiment of this application. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] The entire working process of a traditional intermediate storage pulverizing system is as follows: (1) Raw coal (low moisture, low volatile matter, not easy to spontaneously combust) enters the coal mill from the raw coal bunker and is circulated with hot air at 270°C (a mixture of 320°C hot air from the boiler's air preheater and ambient air). The function of the hot air is to dry and transport the coal powder. (2) Drying and crushing: The raw coal is crushed in a coal mill and turned into coal powder. The water inside the coal powder is heated and vaporized. (3) Separation: The hot air gradually cools down in the coal mill, and the air temperature at the coal mill outlet eventually becomes 75°C. The hot air carries small coal particles into the coarse powder separator. Coal particles with larger diameters are blocked and sent back to the coal mill. Coal particles with the required diameter are sent into the fine powder separator. In the fine powder separator, most of the coal particles are separated and enter the intermediate coal powder bin. A small portion of the coal particles (in the pulverizing exhaust gas) is sucked into the exhaust fan and finally sent to the air box. (3) Combustion: The hot air from the boiler's air preheater, which is introduced into the wind box, sends the pulverized coal from the intermediate pulverized coal bin into the boiler's furnace for combustion.

[0018] Traditional intermediate storage pulverizing systems require more capacity for drying high-moisture, high-volatile-content bituminous coal and lignite. Increased drying temperatures can easily lead to accidents. Traditional intermediate storage pulverizing systems are not suitable for grinding coal with high moisture and high volatile-content.

[0019] In one exemplary embodiment, in such Figure 1Based on the traditional intermediate storage pulverizing system shown, a new intermediate storage pulverizing system structure combining flue gas drying and mixed powder feeding is proposed, as follows: Figure 2 As shown, the ambient air introduced in the traditional intermediate storage pulverizing system has been replaced with flue gas discharged from the boiler. A flue gas fan is installed to extract the 450°C hot flue gas from the boiler combustion as a substitute for hot primary air as a drying medium. This gas is mixed with hot air from the boiler's air preheater and sent into the subsequent pulverizing structure. After being dried by the fine powder separator, the powder-containing moisture gas re-enters the boiler. Figure 2 In this process, the high-temperature, low-oxygen flue gas from boiler combustion is utilized ( Figure 2 The flue gas (450℃) replaces the high-temperature, oxygen-rich hot air in the coal mill. The higher temperature results in better drying, and because of the low oxygen content, the pulverized coal will not burn or explode during the pulverization process, thus avoiding unsafe accidents.

[0020] Figure 2 In intermediate storage pulverizing systems, the powder-containing moisture gas, after drying in the fine powder separator, re-enters the boiler, affecting combustion efficiency. Furthermore, the temperature of the flue gas entering the coal mill is not adjustable, resulting in poor flexibility. To address this, a low-oxygen, temperature-regulating, drying, and direct-discharge intermediate storage pulverizing system is proposed, such as... Figure 3 As shown, it includes: the main body of the intermediate storage pulverizing system, the flue gas fan, the heat exchanger, and the dust collector.

[0021] The flue gas blower is connected to the coal mill in the intermediate storage pulverizing system via a pipeline; the input end of the flue gas blower is connected to the boiler's exhaust pipe; flue gas inlets are opened on both sides of the boiler air preheater inlet, flue gas pipes are arranged, and a new flue gas blower is added. After the flue gas is pressurized by the flue gas blower, it is sent to the hot air pipe and then enters the coal mill.

[0022] A heat exchanger is installed on the pipeline between the flue gas fan and the coal mill in the intermediate storage pulverizing system. The heat exchange medium is generally condensate or feedwater to facilitate energy recovery, and the flue gas temperature is regulated by controlling the flow rate of the heat exchange medium.

[0023] The dust collector is located between the fine powder separator and the pulverizer in the main body of the intermediate storage pulverizing system; the output end of the pulverizer is connected to the atmosphere. The pulverizing exhaust gas discharged from the fine powder separator passes through the dust collector, the separated coal powder enters the intermediate coal powder silo, and the dust-free exhaust gas is discharged into the atmosphere through the pulverizer.

[0024] Among them, the flue gas fan is used to pass the high-temperature flue gas discharged from the boiler into the coal mill to dry the coal powder during the process of crushing the raw coal into coal powder in the coal mill.

[0025] The heat exchanger is used to regulate the temperature of the flue gas entering the coal mill.

[0026] The dust collector is used to collect coal dust from the pulverizing exhaust gas discharged from the fine powder separator.

[0027] The powder discharge machine is used to discharge the exhaust gas from powder making into the air after it has passed through the dust collector.

[0028] The dust collector's output end is also connected to the coal powder inlet of the intermediate coal powder silo in the intermediate storage pulverizing system body; the dust collector is also used to transport the coal powder in the pulverizing exhaust gas discharged from the fine powder separator to the intermediate coal powder silo.

[0029] As an example, the dust collector can be an electrostatic precipitator.

[0030] Among them, an oxygen content detection mechanism is also installed on the pipeline between the flue gas fan and the coal mill in the intermediate storage pulverizing system; the oxygen content detection mechanism is used to detect the oxygen content in the flue gas introduced into the coal mill.

[0031] The intermediate storage pulverizing system also includes: a raw coal bunker, a coarse powder separator, and a bellows. The output end of the raw coal bunker is connected to the input end of the coal mill; the output end of the coal mill is connected to the coarse powder separator; the first output end of the coarse powder separator is connected to the input end of the coal mill, and the second output end of the coarse powder separator is connected to the input end of the fine powder separator; the first input end of the air box is connected to the coal powder outlet of the intermediate coal powder bunker, the second input end of the air box is connected to the air preheater of the boiler, and the output end of the air box is connected to the furnace of the boiler.

[0032] The intermediate storage pulverizing system in this application has the following advantages: (1) Using a flue gas fan to extract the high-temperature flue gas discharged from the boiler as a heat source and power source, the traditional intermediate storage pulverizing system is transformed into a pulverizing system that can use coal with high volatile matter and high moisture content. This allows thermal power plants (300MW, 600MW) using the traditional intermediate storage pulverizing system to safely grind high-moisture and high-volatile bituminous coal and lignite into coal powder without replacing the entire pulverizing system.

[0033] (2) Install a heat exchanger on the flue gas duct and use condensate / feed water to adjust the temperature of the flue gas to a suitable range for grinding, prevent oxygen from entering, reduce the oxygen concentration during grinding, and ensure the safety of grinding.

[0034] (3) Install a dust collector to send the remaining low-temperature and high-humidity gas after coal powder drying into the atmosphere after dust removal and other measures. A large amount of high-humidity and low-temperature exhaust gas will no longer enter the furnace of the boiler, thus improving the combustion efficiency of the boiler.

[0035] (4) A large amount of high humidity and low temperature exhaust gas no longer enters the boiler furnace, which improves the service life of the boiler system. Taking a 300MW unit as an example, the amount of water entering the furnace is reduced by as much as 2,500 to 4,000 tons per day (calculated based on a 300MW unit).

[0036] (5) Due to the significant reduction in moisture content entering the furnace, the flue gas volume is greatly reduced, the power of equipment such as induced draft fans is reduced, and the power plant's self-consumption of electricity is reduced. The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A low-oxygen, temperature-controlled, drying, exhaust gas direct-venting intermediate storage pulverizing system, characterized in that, include: The intermediate storage pulverizing system body, flue gas fan, heat exchanger and dust collector; The flue gas blower is connected to the coal mill in the intermediate storage pulverizing system via a pipeline; the input end of the flue gas blower is connected to the boiler's exhaust pipe; a heat exchanger is installed on the pipeline between the flue gas blower and the coal mill in the intermediate storage pulverizing system. The dust collector is located between the fine powder separator and the powder discharger in the main body of the intermediate storage pulverizing system; the output end of the powder discharger is connected to the atmosphere.

2. The low-oxygen temperature-controlled drying exhaust gas direct-discharge intermediate storage pulverizing system according to claim 1, characterized in that, The flue gas fan is used to pass the high-temperature flue gas discharged from the boiler into the coal mill to dry the coal powder during the process of crushing the raw coal into coal powder in the coal mill. The heat exchanger is used to regulate the temperature of the flue gas entering the coal mill.

3. The low-oxygen temperature-controlled drying exhaust gas direct-discharge intermediate storage pulverizing system according to claim 1, characterized in that, Dust collectors are used to collect coal dust from the pulverizing exhaust gas discharged from the fine powder separator; The powder discharge machine is used to discharge the exhaust gas from powder making into the air after it has passed through the dust collector.

4. The low-oxygen temperature-controlled drying exhaust gas direct-discharge intermediate storage pulverizing system according to claim 1, characterized in that, The dust collector's output end is also connected to the coal powder inlet of the intermediate coal powder silo in the intermediate storage pulverizing system body; the dust collector is also used to transport the coal powder in the pulverizing exhaust gas discharged from the fine powder separator to the intermediate coal powder silo.

5. The low-oxygen temperature-controlled drying exhaust gas direct-discharge intermediate storage pulverizing system according to claim 1, 3, or 4, characterized in that, The dust collector uses electrostatic precipitator.

6. The low-oxygen temperature-controlled drying exhaust gas direct-discharge intermediate storage pulverizing system according to claim 1, characterized in that, An oxygen content detection device is also installed on the pipeline between the flue gas fan and the coal mill in the intermediate storage pulverizing system; the oxygen content detection device is used to detect the oxygen content in the flue gas introduced into the coal mill.

7. The low-oxygen temperature-controlled drying exhaust gas direct-discharge intermediate storage pulverizing system according to claim 1, characterized in that, The flue gas fan has a flue gas inlet located at the air preheater of the boiler exhaust duct.

8. The low-oxygen temperature-controlled drying exhaust gas direct discharge intermediate storage pulverizing system according to claim 4, characterized in that, The intermediate storage pulverizing system also includes: a raw coal bunker, a coarse powder separator, and a bellows; The output end of the raw coal bunker is connected to the input end of the coal mill; the output end of the coal mill is connected to the coarse powder separator; the first output end of the coarse powder separator is connected to the input end of the coal mill, and the second output end of the coarse powder separator is connected to the input end of the fine powder separator; the first input end of the air box is connected to the coal powder outlet of the intermediate coal powder bunker, the second input end of the air box is connected to the air preheater of the boiler, and the output end of the air box is connected to the furnace of the boiler.

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