WO2020088567A1

WO2020088567A1 - Pulverized coal boiler with bottom-arranged combustor, and control method therefor

Info

Publication number: WO2020088567A1
Application number: PCT/CN2019/114598
Authority: WO
Inventors: 朱建国; 刘敬樟; 欧阳子区; 李诗媛; 吕清刚
Original assignee: 中国科学院工程热物理研究所
Priority date: 2018-11-01
Filing date: 2019-10-31
Publication date: 2020-05-07
Also published as: CN111121002A

Abstract

Disclosed are a pulverized coal boiler with a bottom-arranged combustor, and a control method therefor. The coal boiler comprises a furnace (1) and at least one combustor, wherein each combustor is provided with a fuel spout (2), and primary air carries pulverized coal to pass through the fuel spout (2) and go upwards into the furnace (1); and the combustor is arranged at the bottom of the furnace (1). The boiler further comprises secondary air distribution apparatuses arranged at the bottom of the furnace (1) and surrounding the combustor, wherein the secondary air distribution apparatuses are used for injecting secondary air upwards; and the secondary air distribution apparatuses comprise an annular secondary air distribution apparatus (4) arranged surrounding a spout of the combustor, and a distributed secondary air distribution apparatus arranged between the annular secondary air distribution apparatus (4) and a side wall of the furnace (1). The control method for the pulverized coal boiler involves injecting fuel of pulverized coal upwards into the furnace (1) by means of the at least one combustor arranged at the bottom of the furnace (1), and injecting the secondary air upwards into the furnace by means of the secondary air distribution apparatuses arranged at the bottom of the furnace (1) and surrounding the combustor.

Description

Pulverized coal boiler placed at the bottom of the burner and its control method

Technical field

The embodiments of the present invention relate to the field of boilers, and particularly to a pulverized coal boiler and its control method.

Background technique

China has 467 thousand coal-fired industrial boilers, which consumes approximately 700 million tons of raw coal annually, accounting for more than 18% of the country ’s total coal consumption. Industrial boilers are important thermal power equipment, which are widely used in various aspects such as factory power, building heating, and people's lives. In 2015, the National Energy Administration issued the “Coal Clean and Efficient Utilization Action Plan (2015-2020)” to vigorously promote the development and market application of high-efficiency pulverized coal industrial boiler technology.

However, the existing coal-fired industrial boilers have the following technical defects:

(1) There is a tendency of deflagration at the moment of pulverized coal ignition: the main reason is that the pulverized coal fed into the furnace is mostly cold pulverized coal. The pulverized coal needs to go through the preheating, volatile analysis and ignition stages in the furnace. Long ignition time and increased deflagration tendency;

(2) There is a risk of vibration in the boiler: the main reason is that the combustion stability of the pulverized coal deteriorates, and the pressure in the furnace continues to fluctuate. Especially during low-load operation, the temperature level in the furnace is low, the flame of pulverized coal combustion cannot continue to spread, and the boiler vibration risk Increase

(3) high NOx raw emission level of pulverized coal combustion: NOx raw emission levels in multiple 200mg / m ³ or more, a high NOx removal tail cost, and risk of secondary pollution.

Summary of the invention

In order to alleviate or solve at least one of the above problems of the pulverized coal boiler, the present invention is proposed.

According to an aspect of an embodiment of the present invention, the present invention provides a pulverized coal boiler at the bottom of a burner, including: a furnace; and at least one burner, each burner having a fuel nozzle, through which the primary air Carrying coal powder upward into the furnace, where:

The burner is set at the bottom of the furnace;

The boiler further includes a secondary air distribution device disposed at the bottom of the furnace around the burner, and the secondary air distribution device is used to inject secondary air upward;

The secondary air distribution device includes an annular secondary air distribution device arranged around the burner nozzle, and a distributed secondary air distribution device arranged between the annular secondary air distribution device and the furnace side wall.

Optionally, the boiler further includes a tertiary air nozzle, which is arranged in the middle or upper middle of the furnace in the height direction of the furnace. Further optionally, the annular secondary air distribution device is an annular secondary air nozzle.

Or further optionally, the annular secondary air distribution device includes an annular secondary air chamber, an annular secondary air distribution panel, and a wind cap provided on the annular secondary air distribution panel; or the annular two The secondary air distribution device includes an air distribution pipe arranged annularly around the burner nozzle, and a wind cap provided on the air distribution pipe.

Further optionally, the distributed secondary air distribution device includes a distributed secondary air chamber, a distributed secondary air distribution panel, and a wind cap provided on the distributed secondary air distribution panel; or The distributed secondary air distribution device includes a plurality of air distribution tubes distributed on the bottom of the furnace, and a wind cap arranged on the air distribution tube.

Optionally, the equivalent ratio of annular secondary wind is 0.1-0.3; the equivalent ratio of distributed secondary wind is 0.3-0.6, and the total equivalent ratio of secondary air of distributed secondary wind and annular secondary wind is 0.7-0.9 .

Optionally, the air supply control device separately controls the annular secondary air and the distributed secondary air.

Optionally, the fuel nozzle, the annular secondary air outlet and the distributed secondary air outlet are at the same level.

Optionally, the speed of fuel ejected from the fuel nozzle is 10-30m / s; the jet velocity of the annular secondary air is 10-30m / s; the jet velocity of the distributed secondary air is 5-10m / s.

Optionally, the burner is a preheated burner.

The embodiment of the present invention also relates to a method for controlling a pulverized coal boiler, which includes the steps of injecting pulverized coal fuel upward into the furnace through at least one burner provided at the bottom of the furnace; The secondary air distribution device sprays secondary air upward into the furnace, wherein the secondary air distribution device includes an annular secondary air distribution device arranged around the burner nozzle, and the annular secondary air distribution device and the furnace Distributed secondary air distribution device between the side walls.

Optionally, the method includes the steps of: controlling the equivalent ratio of the annular secondary wind to be 0.1-0.3; and controlling the equivalent ratio of the distributed secondary wind to be 0.3-0.6, and the two of the distributed secondary wind and the annular secondary wind The total equivalent ratio of secondary air is 0.7-0.9.

BRIEF DESCRIPTION

1 is a schematic front view of a pulverized coal boiler according to an exemplary embodiment of the present invention;

2 is a top view of the pulverized coal boiler in FIG. 1;

3 is a schematic front view of a pulverized coal boiler according to another exemplary embodiment of the present invention;

4 is a top view of the pulverized coal boiler in FIG. 3;

5 is a schematic front view of a pulverized coal boiler according to still another exemplary embodiment of the present invention;

Fig. 6 is a top view of the pulverized coal boiler in Fig. 5.

detailed description

The technical solutions of the present invention will be further specifically described below through the embodiments and the accompanying drawings. In the description, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the drawings is intended to explain the general inventive concept of the present invention, and should not be construed as a limitation of the present invention.

1 to 2 show a schematic front view and top view of a pulverized coal boiler according to an exemplary embodiment of the present invention.

As shown in Figure 1-2, the illustrated pulverized coal boiler includes furnace 1, preheated fuel nozzle 2, annular secondary air nozzle 3, annular secondary air distribution device 4, distributed secondary air nozzle 5, distributed Secondary air chamber 6, distributed secondary air chamber air distribution plate 7, distributed secondary air hood 8 and furnace tertiary air nozzle 9.

The furnace chamber 1 may have a square columnar structure, and the side walls are enclosed by four membrane walls, including a front wall 11, a rear wall 12, a left side wall 13 and a right side wall 14. The furnace chamber may also have a cylindrical structure or other columnar structures.

In the pulverized coal boiler shown in Figure 1-2, the preheated fuel nozzle 2 is located at the bottom of the furnace, the periphery of the preheated fuel nozzle 2 is an annular secondary air distribution device 4, and the annular secondary air nozzle 3 is located in the annular secondary air channel At the bottom of the bottom, around the annular secondary air distribution device 4, there is also a distributed secondary air distribution device distributed substantially uniformly on most of the bottom surface of the furnace. The distributed secondary air hood 8 can be divided into multiple layers (diameter Direction), the hood 8 of the distributed secondary air is arranged on the air distribution plate 7 of the distributed secondary air chamber 6, and the distributed secondary air take-over 5 is connected to the side of the distributed secondary air chamber 6 .

In an alternative embodiment, the control of distributed secondary air and annular secondary air is completely separate and does not affect each other. The annular secondary air is arranged around the preheated fuel nozzle, and the distributed secondary air is arranged around the annular secondary air.

In an alternative embodiment, the preheated fuel nozzle 2, the annular secondary air outlet and the distributed secondary air outlet are in the same cross-section or the same horizontal plane.

The annular secondary air distribution device can be a ring seam nested outside the fuel nozzle, or a group of air caps with air distribution plates and air chambers or a group of air caps on the air distribution tube.

The distributed secondary air distribution device may include a set of air caps arranged on the air distribution plate with the air chamber, or a set of air caps arranged on the air distribution tube; the foregoing air caps are distributed substantially uniformly at the bottom of the furnace.

A tertiary air nozzle 9 is provided in the middle of the furnace, and the tertiary air nozzles can be arranged in a hedging arrangement at the front and rear walls of the furnace or tangentially at four corners.

The operation of the example shown in Figs. 1-2 will be exemplarily described below.

The primary air and preheated fuel are ejected from the preheated fuel nozzle 2 with an injection speed of between 10-30 m / s. The annular secondary air is ejected from the annular secondary air distribution device 4 through the annular secondary air connection 3 The injection speed of the annular secondary air is between 10-30m / s. The annular secondary air is tightly wrapped around the periphery of the preheated fuel nozzle to speed up the mixing with the primary air. The distributed secondary air enters the secondary through the secondary air take-over 5 The air chamber 6 and the air plate 7 are sprayed by the wind cap 8 after passing through the air chamber cloth plate 7. The distributed secondary air is evenly distributed. The full-section air supply mode can delay the rapid mixing and reaction of a large amount of secondary air and preheated fuel, weakening Preheat the high temperature area where the fuel burns, and at the same time, the bottom is fed with secondary air to prevent the deposition of coal powder particles on the bottom of the furnace.

Furnace tertiary air injection speed is related to the furnace cross section, which is generally between 10-20m / s. The whole of the furnace below the tertiary air nozzle is a uniform reducing atmosphere, and the area above the tertiary air nozzle is the burnout area. The preheated fuel is a mixture of high-temperature coal gas and high-temperature coke. The high-temperature coal gas is the gas produced by the reaction between the coal powder and the primary air during the preheating of the coal powder. The high-temperature coke is the solid material converted after the coal powder reacts during the preheating of the coal powder. The ratio of annular secondary air is related to the preheated fuel composition, preheated fuel temperature and furnace temperature. If the preheated fuel gas has a high calorific value, the preheated fuel will ignite rapidly. Proportion of secondary air or increase annular secondary air injection speed. The equivalent ratio of annular secondary air is generally between 0.1 and 0.3. The distributed secondary air needs to be organically combined with the annular secondary air. The annular secondary air mainly guarantees the rapid ignition and stable combustion of the fuel. The distributed secondary air provides the combustion-supporting gas for the even combustion of the fuel in the entire space of the furnace chamber and protects the fuel. Combustion share and heat release. The ratio of distributed secondary air is higher than that of annular secondary air. The ratio of the distributed secondary air to the secondary air can be controlled to 5: 1-2: 1. The total equivalent ratio of secondary air and distributed secondary air can be controlled between 0.7 and 0.9. During the combustion of preheated fuel, the temperature of the furnace is controlled between 1000-1200 ° C to achieve stable, efficient and low-nitrogen combustion of the preheated fuel.

In the above embodiment, the secondary air at the bottom of the furnace is provided with an annular secondary air and distributed secondary air surrounding the preheated fuel nozzle, and the air volume of the annular secondary air and the distributed secondary air volume can be controlled independently. The annular secondary air is the control air and regulating air for the stable combustion of fuel. The distributed secondary air is the main wind used for fuel combustion. It has the dual functions of adjusting the furnace temperature and controlling the furnace atmosphere. The whole of the furnace below the tertiary air vent is a reducing atmosphere, that is, the air equivalent coefficient below the tertiary air vent is less than 1.0.

The annular secondary air around the preheated fuel nozzle can achieve rapid mixing and contact of the preheated fuel and the secondary air, avoiding the preheating of the preheated fuel due to the slow mixing with the secondary air or the cooling effect of the water wall of the furnace. The fuel flameout or combustion is unstable, and the amount of annular secondary air volume is related to the preheated fuel composition, preheated fuel temperature and furnace temperature.

Distributed secondary air is the main wind used for fuel combustion. After the gasification reaction between the preheated fuel and the annular secondary air, the furnace temperature rises, and the gasified gas and ungasified coke expand outward from the center. In contact with distributed secondary air, because the entire section of the furnace bottom is supplied with a wind hood, the flow field in the furnace is uniform, and the material after the reaction between the preheated fuel and the annular secondary air reacts in the entire furnace space, and because the furnace is below the tertiary air vent The air equivalent ratio is less than 1.0, and there is no oxygen-rich atmosphere below the furnace tertiary air nozzle. Combined with the reaction between the preheated fuel and the annular secondary air, the precipitation of nitrogen-containing substances is strengthened. The precipitated nitrogen-containing substances are integrated under the furnace tertiary air nozzle. In a uniform reducing atmosphere, it is easy to convert to nitrogen, which reduces the nitrogen oxide emission level of preheated fuel combustion.

3 is a schematic front view of a pulverized coal boiler according to another exemplary embodiment of the present invention; FIG. 4 is a top view of the pulverized coal boiler in FIG. 3.

As shown in Figure 3-4, the pulverized coal boiler includes a furnace 1, a preheated fuel nozzle 2, an annular secondary air connection 3, an annular secondary air chamber 4, an annular secondary air chamber air distribution plate 5, an annular secondary air hood 6. Distributed secondary air takeover 7. Distributed secondary air chamber 8, distributed secondary air distribution plate 9, distributed secondary air hood 10 and furnace tertiary air vent 11.

The annular secondary air surrounds the periphery of the preheated fuel. The annular secondary air can also be supplied in the form of a hood to speed up the mixing of the preheated fuel and the annular secondary air to ensure rapid ignition and stable combustion of the preheated fuel. Distributed secondary The wind ensures the uniform flow field and composition in the furnace. The main space below the furnace's tertiary air nozzle is a reducing atmosphere, and the local oxygen-rich atmosphere is small, which reduces the nitrogen oxide emission level of preheated fuel combustion.

5 is a schematic front view of a pulverized coal boiler according to still another exemplary embodiment of the present invention. Fig. 6 is a top view of the pulverized coal boiler in Fig. 5.

As shown in Figures 5-6, the pulverized coal boiler includes a furnace 1, a preheated fuel nozzle 2 and a preheated fuel nozzle 5, the periphery of the preheated fuel nozzle 2 is an annular secondary air connection pipe 3 and an annular secondary air distribution device 4, The periphery of the preheated fuel nozzle 5 is an annular secondary air duct 6 and an annular secondary air duct device 7. The distributed secondary air duct device includes a secondary air duct 8, a secondary air duct 9, an air duct plate 10 and Hood 15.

The furnace is equipped with 2 (or more) preheated fuel nozzles. Each preheated fuel nozzle is equipped with a controlled and controlled annular secondary air around the preheated fuel nozzle. Style secondary wind. The number of annular secondary air chambers is the same as the number of preheated fuel nozzles, and the distributed secondary air chamber may be only one or multiple, all within the protection scope of the present invention. The annular secondary air and distributed secondary air can share the same air distribution plate.

It should be pointed out that, in the present invention, the “ring-shaped” in the “ring-shaped secondary air distribution device” may be, for example, that the air distribution device is a ring-shaped nozzle as a whole, or may be a plurality of nozzles or wind caps arranged around the fuel nozzle These are all within the protection scope of the present invention.

It should also be noted that in the present invention, "distributed" in the "distributed secondary air distribution device" means that the air outlets (spouts or hoods) of the air distribution device are distributed, for example, it may be similar to The uniform distribution of the array may also be an annular arrangement (s) surrounding the annular secondary air distribution device, which are within the protection scope of the present invention.

Based on the above, the present invention provides a pulverized coal boiler with a burner at the bottom, including:

Hearth; and

At least one burner, each burner has a fuel nozzle, through which the primary air carries coal powder upward into the furnace,

among them:

The burner is set at the bottom of the furnace;

The above-mentioned boiler may include a tertiary air nozzle, which is arranged in the middle or upper middle of the furnace in the height direction of the furnace.

More specifically, the secondary air distribution device includes: an annular secondary air distribution device arranged around the burner nozzle; and a distributed secondary air arranged between the annular secondary air distribution device and the furnace side wall Cloth installation.

Correspondingly, the present invention also proposes a method for controlling a pulverized coal boiler, which includes the steps of injecting pulverized coal fuel upward into the furnace through at least one burner provided at the bottom of the furnace; and The secondary air distribution device sprays secondary air upward into the furnace.

In the present invention, after the fuel (such as preheated fuel) is injected into the furnace, it can be quickly and timely mixed with the secondary air, which shortens the ignition time of the preheated fuel, strengthens the combustion stability of the preheated fuel, and avoids or reduces Pre-heated fuel ignition and deflagration tendency and combustion process occurred boiler vibration problems.

In the present invention, through the organic combination and joint control of the annular secondary air and distributed secondary air, the premature conversion of nitrogen-containing substances in the blending of the preheated fuel and the annular secondary air is accelerated, and the primary air outlet below the furnace is mainly The area is an overall uniform reducing atmosphere, basically eliminating local oxygen-rich areas, increasing the degree of reduction of nitrogen-containing substances, and reducing the NOx emission level of preheated fuel combustion.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that these embodiments can be changed and combined without departing from the principle and spirit of the present invention. The scope of is defined by the appended claims and their equivalents.

Claims

A pulverized coal boiler with a burner at the bottom includes:

Hearth; and

At least one burner, each burner has a fuel nozzle, through which the primary air carries coal powder upward into the furnace,

among them:

The burner is set at the bottom of the furnace;

The boiler further includes a secondary air distribution device disposed at the bottom of the furnace around the burner, and the secondary air distribution device is used to inject secondary air upward;

The secondary air distribution device includes:

An annular secondary air distribution device arranged around the burner nozzle; and

A distributed secondary air distribution device arranged between the annular secondary air distribution device and the side wall of the furnace.
The boiler according to claim 1, further comprising:

The tertiary air nozzle is arranged in the middle or upper middle of the furnace in the height direction of the furnace.
The boiler according to claim 2, further comprising:

Air supply control device is used to control the supply ratio of primary air, secondary air and tertiary air.
The boiler according to claim 1, wherein:

The annular secondary air distribution device is an annular secondary air nozzle.
The boiler according to claim 1, wherein:

The annular secondary air distribution device includes an annular secondary air chamber, an annular secondary air distribution panel, and a wind cap provided on the annular secondary air distribution panel; or

The annular secondary air distribution device includes an air distribution tube arranged annularly around the burner nozzle, and a wind cap provided on the air distribution tube.
The boiler according to claim 1, wherein:

The distributed secondary air distribution device includes a distributed secondary air chamber, a distributed secondary air distribution panel, and a hood provided on the distributed secondary air distribution panel; or

The distributed secondary air distribution device includes a plurality of distribution tubes distributed at the bottom of the furnace, and a wind cap provided on the distribution tube.
The boiler according to claim 1, wherein:

The equivalent ratio of annular secondary air is 0.1-0.3;

The equivalent ratio of distributed secondary wind is 0.3-0.6, and the total equivalent ratio of distributed secondary wind to annular secondary wind is 0.7-0.9.
The boiler according to claim 1, wherein:

The air supply control device separately controls the annular secondary air and the distributed secondary air.
The boiler according to claim 1, wherein:

The fuel nozzle, the annular secondary air outlet and the distributed secondary air outlet are at the same level.
The boiler according to claim 1, wherein:

The speed of fuel ejected from the fuel nozzle is 10-30m / s;

The jet velocity of annular secondary air is 10-30m / s;

The spray velocity of distributed secondary air is 5-10m / s.
The boiler according to any one of claims 1-10, wherein:

The burner is a preheated burner.
A control method of pulverized coal boiler, including steps:

Pulverized coal fuel is injected upward into the furnace through at least one burner provided at the bottom of the furnace; and

Through the secondary air distribution device arranged at the bottom of the furnace around the burner, the secondary air is injected upward into the furnace,

among them:

The secondary air distribution device includes an annular secondary air distribution device arranged around the burner nozzle, and a distributed secondary air distribution device arranged between the annular secondary air distribution device and the furnace side wall.
The method according to claim 12, which comprises the steps of:

The equivalent ratio of the control loop secondary air is 0.1-0.3; and

Controlled distributed secondary air equivalent ratio is 0.3-0.6, and the total secondary air equivalent ratio of distributed secondary wind and annular secondary wind is 0.7-0.9.