CN112108260B - A pulverizing system and method suitable for high-moisture coal types - Google Patents

Abstract

The invention discloses a pulverizing system and method suitable for high-moisture coal, comprising a primary fan, an air preheater, a hot primary air pipe, a cold primary air pipe, a hot air adjusting door, a cold air adjusting door, a heating device, a coal mill, a controller, a hot primary air volume measuring device, a coal mill outlet temperature measuring device and a primary air powder pipe. The cold air at the outlet of the primary air blower is divided into two paths: one path of the air enters the inlet pipeline of the coal mill directly through the cold primary air pipe; the other path of the hot primary air enters an air preheater for heating, the heated hot primary air enters an inlet pipeline of the coal mill for mixing with cold primary air after being heated again by a heating device, and the mixed hot air enters the coal mill for drying coal dust, so that the aim of improving the drying output of the coal mill is fulfilled. The system can effectively improve the temperature of hot primary air, improve the drying output of the coal mill, strengthen the adaptability of the coal mill to the moisture of coal types, prevent the coal dust condensation from blocking pipes caused by the excessively low outlet temperature of the coal mill, enable the unit to burn high-moisture coal types, reduce the unit price of standard coal, reduce the operation cost, be favorable for the safe and stable operation of the unit, and have better economic benefit.

Description

A pulverizing system and method suitable for high-moisture coal types

【Technical field】

The invention belongs to the technical field of pulverizing systems in thermal power plants, and relates to a pulverizing system and method suitable for high-moisture coal types.

【Background technique】

my country is rich in coal resources, and thermal power generation still occupies a dominant position in the energy power generation market. With the rapid growth of my country's economy, coal consumption will become larger and larger, coal supply will become increasingly tight, and coal prices will continue to rise. . In recent years, due to the overcapacity of installed coal-fired units, the continued rise in coal prices, and the continuous reduction in power generation utilization hours, coal-fired power plants have experienced reduced profits or even losses. In order to reduce operating costs, the company has implemented the strategy of “reducing costs, increasing efficiency, and turning losses into profits.” To achieve the goal, some power plants have begun to mix economical coal with high moisture content and low calorific value.

The hot primary air temperature at the air preheater outlet of a bituminous coal-burning boiler unit is generally designed to be between 280°C and 320°C. With the increase in the blending ratio of economical coal with high moisture and low calorific value, it is common in pulverizing systems that the coal mill inlet air temperature cannot be achieved. To meet the drying needs, when the cold air door of the coal mill is fully closed, the drying capacity of the hot primary air is still insufficient, resulting in insufficient drying output of the coal mill and affecting the boiler's load capacity.

In order to improve the drying output of the coal mill, it can be appropriately alleviated by increasing the primary air volume, but it cannot be solved fundamentally. Moreover, the primary air rate of the boiler operation is high and the secondary air rate is low, resulting in improper combustion air distribution in the furnace. A series of problems such as overheating of the heating surface, high power consumption of the primary fan, and increased wear of the primary air duct have seriously affected the safe and stable operation of the unit.

In order to increase the temperature of the hot primary air, improve the drying output of the coal mill, enhance the adaptability of the pulverizing system to the moisture content of coal types, and ensure the safe and economical operation of the pulverizing system, a pulverizing system and method suitable for high-moisture coal types are urgently needed.

[Content of the invention]

The purpose of the present invention is to solve the above-mentioned problems in the prior art and provide a pulverizing system and method suitable for high-moisture coal types, which can effectively increase the temperature of the hot primary air, increase the drying output of the coal mill, and enhance the efficiency of the coal mill on coal. The adaptability of this kind of moisture prevents the outlet temperature of the coal mill from being too low, causing condensation of pulverized coal to block the pipe. It allows the unit to burn high-moisture coal, reduces the unit price of standard coal, reduces operating costs, and is conducive to the safe and stable operation of the unit. , has better economic benefits.

In order to achieve the above objectives, the present invention adopts the following technical solutions to achieve:

A pulverizing system suitable for high-moisture coal types, including:

Primary fan, the outlet of the primary fan is divided into two paths, one path is connected to the hot primary air duct, and the other path is connected to the cold primary air duct; the hot primary air duct and the cold primary air duct are merged and connected to the coal mill;

Coal mill, the outlet of the coal mill is connected to the primary air powder pipe;

A control unit, which is used to collect the coal mill outlet temperature and the hot primary air volume, and control the temperature of the hot primary air according to the coal mill outlet temperature and the hot primary air volume.

Further improvements of the present invention include:

The hot primary air duct is provided with an air preheater, a hot air regulating door and a heating device in sequence.

A cold air regulating door is provided on the cold primary air duct.

The control unit includes a temperature measuring device, a controller and a hot primary air volume measuring device. The temperature measuring device is arranged in the primary air powder pipe near the coal mill outlet; the temperature measuring device is connected to the controller and sends the temperature signal to the control unit. The hot primary air volume measuring device is installed on the hot primary air duct and connected to the controller to send the air volume signal of the hot primary air to the controller; the controller adjusts the heating device according to the temperature signal and primary air volume signal.

The heating device adopts a steam heater, a flue gas heater or an electric heater, and the temperature of the heated primary air can be increased by more than 50°C.

The steam heater is a surface heater, and the heating heat source is taken from the steam at the outlet of a screen superheater, a high-temperature superheater or a high-temperature reheater, and the steam heater drains water back to the inlet of the high-pressure heater;

The flue gas heater is a surface heater or a hybrid heater. The heating source is taken from the flue gas at the outlet of the high-temperature superheater or high-temperature reheater; the cold flue gas passing through the surface flue gas heater returns to the inlet of the air preheater.

A pulverizing method suitable for high-moisture coal types, including the following steps:

When the coal mill is running, the hot primary air volume measuring device collects the air volume signal S1 of the hot primary air, the temperature measuring device collects the coal mill outlet temperature to obtain the temperature signal S2, and sends the air volume signal S1 and temperature signal S2 to the controller respectively;

The controller performs feedforward adjustment on the heating amount of the heating device based on the air volume signal S1, and performs feedback adjustment on the heating amount of the heating device based on the temperature signal S2.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention arranges a heating device on the hot primary air duct at the outlet of the air preheater, which can effectively increase the temperature of the hot primary air, meet the requirements of the pulverizing system for burning high-moisture and low-calorific coal types, and enhance the adaptability of the coal mill to the moisture content of the coal types. , to prevent the outlet temperature of the coal mill from being too low, causing condensation of pulverized coal to block the pipe, reducing the operating cost of the power plant, which is conducive to the safe and stable operation of the unit, and has good economic benefits. The heating source of the heating device of the invention has three types: steam, flue gas and electricity. It has high heating efficiency for hot primary air, large temperature rise range, flexibility and reliability, and wide application range. This invention adopts feedforward-feedback closed-loop control, uses the coal mill hot primary air volume signal as feedforward, and uses the coal mill outlet temperature signal as feedback to control the heating amount of the heating device, while ensuring the drying output of the coal mill. Under the premise, the energy consumption of system operation is reduced.

[Picture description]

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic diagram of a pulverizing system suitable for high-moisture coal types used in coal-fired power plants according to the embodiment of the present invention.

In the picture: 1 is the primary fan, 2 is the air preheater, 3 is the hot primary air duct, 4 is the cold primary air duct, 5 is the hot air regulating door, 6 is the cold air regulating door, 7 is the heating device, and 8 is the coal grinder. machine, 9 is the controller, 10 is the hot primary air volume measuring device, 11 is the coal mill outlet temperature measuring device, and 12 is the primary air powder pipe.

【Detailed ways】

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, rather than all embodiments. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Therefore, the following detailed description of the embodiments of the invention provided in the appended drawings is not intended to limit the scope of the claimed invention, but rather to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

It should be noted that similar reference numerals and letters represent similar items in the following figures, therefore, once an item is defined in one figure, it does not need further definition and explanation in subsequent figures.

In the description of the embodiments of the present invention, it should be noted that if the terms “upper”, “lower”, “horizontal”, “inner”, etc. appear to indicate an orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. , or the orientation or positional relationship in which the product of the invention is usually placed when used, is only for the convenience of describing the invention and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific orientation or be constructed in a specific orientation. and operation, and therefore cannot be construed as limitations of the present invention. In addition, the terms "first", "second", etc. are only used to differentiate descriptions and are not to be understood as indicating or implying relative importance.

In addition, if the term "level" appears, it does not mean that the component is required to be absolutely horizontal, but may be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical". It does not mean that the structure must be completely horizontal, but can be slightly tilted.

In the description of the embodiments of the present invention, it should also be noted that, unless otherwise clearly stated and limited, the terms "setting", "installation", "connecting" and "connecting" should be understood in a broad sense. For example, they can It can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, or it can be an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be an internal connection between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

The present invention will be described in further detail below in conjunction with the accompanying drawings:

Refer to Figure 1. As shown in Figure 1, a pulverizing system suitable for high-moisture coal types used in coal-fired power plants includes a primary fan 1, an air preheater 2, a hot primary air duct 3, a cold primary air duct 4, and a hot air regulator. Door 5, cold air regulating door 6, heating device 7, coal mill 8, controller 9, hot primary air volume measuring device 10, coal mill outlet temperature measuring device 11, primary air powder pipe 12.

The cold air from the outlet of primary fan 1 is divided into two paths: one path passes through the cold primary air duct 4 and directly enters the inlet pipe of the coal mill; the other path enters the air preheater 2 for heating. The heated primary air is heated again by the heating device 7 before entering. The inlet pipe of the coal mill mixes with the cold primary air, and the mixed hot air enters the coal mill 8 to dry the pulverized coal. By further increasing the hot primary air temperature, the hot air temperature requirements for grinding high-moisture coal in the pulverizing system can be met, and the drying output of the coal mill can be increased.

Hot primary air duct 3 and cold primary air duct 4 are installed with hot air regulating door 5 and cold air regulating door 6 respectively. When the drying output of the coal mill is insufficient, priority is given to closing the opening of the cold air regulating door 6 to increase the drying output of the coal mill.

The heating device 7 is arranged on the hot primary air duct 3 at the outlet of the air preheater. The heating device includes three types: one is a steam heater, the other is a flue gas heater, and the third is an electric heater. After passing through the heating device 7 The hot primary air temperature can be increased by more than 50℃.

The steam heater is a surface heater. The heating heat source can be taken from the outlet steam of a screen superheater, a high-temperature superheater or a high-temperature reheater. The steam heater drains water back to the inlet of the high-pressure heater.

The flue gas heater is a surface heater or a hybrid heater. The heating source can be taken from the flue gas at the outlet of the high-temperature superheater or high-temperature reheater; the cold flue gas passing through the surface flue gas heater returns to the inlet of the air preheater. .

The hot primary air volume signal S1 and the coal mill outlet temperature signal S2 are obtained through the hot primary air volume measuring device 10 and the coal mill outlet temperature measuring device 11. The controller 9 uses the hot primary air volume signal S1 as a feedforward to heat the heating device 7 Pre-adjusting is performed, and the coal mill outlet temperature signal S2 is used as feedback to accurately adjust the heating amount of the heating device 7 to achieve closed-loop control of the system.

In this implementation example, by adding a hot primary air heating device at the outlet of the air preheater, the temperature of the hot primary air is effectively increased, the drying output of the coal mill is increased, the adaptability of the coal mill to the moisture content of the coal type is enhanced, and the outlet temperature of the coal mill is prevented. If it is too low, condensation of pulverized coal will cause pipe blockage. Through closed-loop control, the energy consumption of the system operation can be reduced while ensuring the drying output of the coal mill.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (5)

1. A coal pulverizing system suitable for high moisture coal, comprising:

the air conditioner comprises a primary air fan (1), wherein the outlet of the primary air fan (1) is divided into two paths, one path is connected with a hot primary air pipe (3), and the other path is connected with a cold primary air pipe (4); the hot primary air pipe (3) and the cold primary air pipe (4) are connected with a coal mill (8) after being converged; an air preheater (2), a hot air regulating door (5) and a heating device (7) are sequentially arranged on the hot primary air pipe (3); a cold air adjusting door (6) is arranged on the cold primary air pipe (4);

the outlet of the coal mill (8) is connected with a primary air-powder pipe (12);

the control unit is used for collecting the outlet temperature of the coal mill (8) and the hot primary air quantity, and controlling the temperature of the hot primary air according to the outlet temperature of the coal mill (8) and the hot primary air quantity.

2. The coal pulverizing system applicable to high-moisture coal according to claim 1, wherein the control unit comprises a temperature measuring device (11), a controller (9) and a hot primary air quantity measuring device (10), and the temperature measuring device (11) is arranged at the position, close to the outlet of the coal mill (8), of the primary air duct (12); the temperature measuring device (11) is connected with the controller (9) and sends a temperature signal to the controller (9); the hot primary air volume measuring device (10) is arranged on the hot primary air pipe (3) and is connected with the controller (9) to send an air volume signal of the hot primary air to the controller (9); the controller (9) adjusts the heating device (7) according to the temperature signal and the primary air quantity signal.

3. The coal pulverizing system for high-moisture coal according to claim 1 or 2, wherein the heating device (7) adopts a steam heater, a flue gas heater or an electric heater, and the temperature of the heated primary air can be increased by more than 50 ℃.

4. A coal pulverizing system for high-moisture coal as defined in claim 3, wherein the steam heater is a surface heater, the heating source is steam from the outlet of a screen superheater, a high-temperature superheater or a high-temperature reheater, and the steam heater is drained back to the inlet of the high-pressure heater;

the flue gas heater is a surface heater or a hybrid heater, and the heating heat source is selected from the high-temperature superheater or the flue gas at the outlet of the high-temperature reheater; the cold flue gas passing through the surface flue gas heater is returned to the air preheater inlet.

5. A method of milling a suitable high moisture coal using the system of claim 4, comprising the steps of:

when the coal mill (8) operates, the hot primary air volume measuring device (10) collects an air volume signal S1 of hot primary air, the temperature measuring device (11) collects the outlet temperature of the coal mill (8) to obtain a temperature signal S2, and the air volume signal S1 and the temperature signal S2 are respectively sent to the controller (9);

the controller (9) performs feedforward adjustment of the heating amount of the heating device (7) according to the air volume signal S1, and performs feedback adjustment of the heating amount of the heating device (7) according to the temperature signal S2.