An oxygen-enriched pulverized coal burner and a combustion method based on pumping and ejection thereof

Abstract

The invention discloses an oxygen-enriched pulverized coal burner and a combustion method based on suction and injection. The burner includes a primary air duct, an adjustment air duct, a pre-combustion chamber and a nozzle. The primary air duct and the adjustment air duct are eccentrically arranged at the inlet end of the pre-combustion chamber. The pre-combustion chamber is arranged at the inlet end of the nozzle and is coaxially arranged with the nozzle. A pure oxygen duct is also arranged at the inlet end of the nozzle and is arranged on the outside of the pre-combustion chamber. A circulating flue gas duct is sleeve-typely arranged outside the pure oxygen duct. The primary air carries the pulverized coal through the primary air duct and enters the pre-combustion chamber to form an eccentric jet and local entrainment. The adjustment air introduced by the adjustment air duct causes the pulverized coal to be partially pyrolyzed and burned in the pre-combustion chamber, forming a mixed fuel wind that enters the nozzle. The high-speed pure oxygen is wrapped in the circulating flue gas, which delays the combustion of the mixed fuel wind and forms the entrainment of flue gas in the furnace to reduce the peak value of the flame temperature. The invention has the advantages of promoting the combustion of pulverized coal while ensuring the safety of the heating surface.

Description

Technical Field

[0001] The invention relates to an oxygen-enriched coal powder burner and a combustion method thereof based on pumping and jetting, belonging to the technical field of combustion. Background Art

[0002] Greenhouse gas emissions are a hot topic of concern to the international community today. The combination of oxygen-enriched combustion technology and carbon dioxide capture and storage technology can effectively control carbon dioxide emissions from coal-fired power plants. Oxygen-enriched combustion technology refers to a combustion method in which pure oxygen obtained from an air separation unit is mixed with recycled flue gas and then used as an oxidant to replace air. Oxygen-enriched combustion technology enriches carbon dioxide in the tail gas, facilitating subsequent separation and capture. However, due to the differences in physical and chemical properties between carbon dioxide and nitrogen, problems such as delayed ignition and low flame temperature will occur in oxygen-enriched combustion. On the other hand, since the circulating flue gas requires the use of additional fans, the plant power consumption rate is increased and the overall efficiency of the power plant is reduced. Therefore, a more economical and environmentally friendly technical route is: while reducing the amount of recycled flue gas, increase the inlet oxygen concentration, and at the same time control the flame temperature not to be too high to ensure the safety of the heating surface. In this context, the development of a new type of oxygen-enriched pulverized coal burner is an urgent need for coal-fired power generation companies.

[0003] The existing technologies cannot solve the above problems at the same time. For example, the existing oxygen-enriched coal-fired boilers usually adopt the method of increasing the inlet oxygen concentration from 21% to 30% to alleviate the problems of ignition delay, low flame temperature, and high energy consumption of flue gas circulation fans. However, the ignition time at this time is still longer than that of air-fired coal-fired boilers, the energy consumption of the circulation fan is still large, and the efficiency of the power plant is still low. If the inlet oxygen concentration is further increased, although the above problems can be solved, it will cause the peak heat flux density in the furnace to be too large, which will seriously threaten the safety of the heating surface and cannot meet the production needs.

[0004] In view of this engineering background, the research and development of oxygen-enriched pulverized coal combustion technology that can be applied to high oxygen concentration conditions has become a technical problem that urgently needs to be solved. Its successful development can ensure the ignition characteristics and flame temperature of oxygen-enriched combustion, which is beneficial to combustion stability and heat exchange in the furnace; at the same time, it can reduce the energy consumption of the flue gas circulation fan, which is beneficial to improving the overall efficiency of the power plant and achieving good economic benefits. Summary of the invention

[0005] The present invention aims to provide an oxygen-enriched pulverized coal burner and a combustion method based on extraction and injection. On the one hand, the eccentric primary air is sucked in the pre-combustion chamber to promote the heating of the pulverized coal jet, thereby shortening the ignition distance; on the other hand, the high-speed secondary air is sucked to make the temperature in the furnace more uniform, and the peak heat flux density can be guaranteed not to be too high even under higher oxygen concentrations.

[0006] The present invention is achieved through the following technical solutions:

[0007] An oxygen-enriched pulverized coal burner comprises a primary air duct, an adjusting air duct, a pre-combustion chamber and a nozzle; the nozzle is arranged in a furnace as the outlet end of the burner; the primary air duct and the adjusting air duct are eccentrically arranged at the inlet end of the pre-combustion chamber; the pre-combustion chamber is arranged at the inlet end of the nozzle and is coaxially arranged with the nozzle; a pure oxygen duct is also arranged at the inlet end of the nozzle, and the pure oxygen duct is arranged outside the pre-combustion chamber.

[0008] In the above technical solution, two pure oxygen pipelines are provided, which are symmetrically arranged at the inlet end of the nozzle.

[0009] In the above technical solution, the burner further comprises a circulating flue gas duct, which is arranged in a sleeve-like manner on the outer periphery of the pure oxygen duct and is arranged in a concentric circle with the pure oxygen duct.

[0010] In the above technical solution, the cross-sectional area of ​​the circulating flue gas pipeline is 2 to 5 times the cross-sectional area of ​​the pure oxygen pipeline.

[0011] In the above technical solution, the cross-sectional area of ​​the nozzle is 10 to 20 times the cross-sectional area of ​​the pre-combustion chamber; the cross-sectional area of ​​the pre-combustion chamber is 2 to 10 times the cross-sectional area of ​​the adjustment air duct.

[0012] In the above technical solution, the cross-sectional area of ​​the pre-combustion chamber is 10 to 40 times the cross-sectional area of ​​the circulating flue gas duct.

[0013] In the above technical solution, the distance from the central axis of the circulating flue gas duct to the central axis of the pre-combustion chamber is 2 to 6 times the radius of the pre-combustion chamber.

[0014] A combustion method of an oxygen-enriched pulverized coal burner based on pumping and jetting, comprising:

[0015] The primary air carries the pulverized coal through the primary air duct and enters the pre-combustion chamber. With the help of the eccentric jet of the primary air in the pre-combustion chamber, local entrainment is formed in the pre-combustion chamber and at its outlet, which promotes the heating and ignition of the pulverized coal.

[0016] A proper amount of air is introduced into the pre-combustion chamber as adjustment air through the adjustment air duct, so that the pulverized coal is partially pyrolyzed and burned in the pre-combustion chamber, and the mixed fuel air is formed and enters the nozzle;

[0017] Pure oxygen is injected into the nozzle from the pure oxygen pipeline at a speed of 100 to 200 m / s, which not only serves as secondary air to further burn the mixed fuel air, but also forms smoke entrainment in the furnace to reduce the peak flame temperature.

[0018] In the above technical solution, the method further comprises:

[0019] Pure oxygen is injected into the nozzle from the pure oxygen pipeline at a speed of 100-200m / s. At the same time, the circulating flue gas is injected through the circulating flue gas pipeline to entrain and dilute the pure oxygen. The secondary air formed by the pure oxygen and the circulating flue gas delays the combustion of the mixed fuel air and forms flue gas entrainment in the furnace to reduce the peak flame temperature.

[0020] The present invention has the following advantages and beneficial effects: the entrainment of the biased primary air in the pre-combustion chamber can promote the heating of the coal powder jet by the high-temperature flue gas and shorten the ignition distance. The secondary air composed of the circulating flue gas and pure oxygen is sprayed at high speed on the upper and lower sides of the pre-combustion chamber, causing a large amount of flue gas entrainment in the furnace, which can ensure that the peak heat flux density will not be too high even under high oxygen concentration conditions, thereby ensuring the safety of the heating surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the oxygen-enriched pulverized coal burner involved in the present invention.

[0022] In the figure: 1-primary air duct; 2-adjusting air duct; 3-precombustion chamber; 4-pure oxygen duct; 5-circulating flue gas duct; 6-nozzle; 7-refractory material; 8-furnace. DETAILED DESCRIPTION

[0023] The specific implementation manner and working process of the present invention will be further described below in conjunction with the accompanying drawings.

[0024] The terms such as up, down, left, right, front and back in this application document are based on the positional relationships shown in the drawings. If the drawings are different, the corresponding positional relationships may also change accordingly, so they cannot be understood as limiting the scope of protection.

[0025] like Figure 1 As shown, an oxygen-enriched pulverized coal burner includes a primary air duct 1, an adjusting air duct 2, a pre-combustion chamber 3 and a nozzle 6. The outlet end of the nozzle 6 burner is arranged in the furnace 8. The primary air duct 1 and the adjusting air duct 2 are eccentrically arranged at the inlet end of the pre-combustion chamber 3. The pre-combustion chamber 3 is arranged at the inlet end of the nozzle 6 and is coaxially arranged with the nozzle 6, and the two are connected by flanges or welding. The cross-sectional area of ​​the nozzle 6 is 10 to 20 times the cross-sectional area of ​​the pre-combustion chamber 3. The cross-sectional area of ​​the pre-combustion chamber 3 is 2 to 10 times the cross-sectional area of ​​the adjusting air duct 2.

[0026] A pure oxygen pipeline 4 is also provided at the inlet end of the nozzle 6, and the pure oxygen pipeline 4 is arranged outside the pre-combustion chamber 3. As an optimized technical solution, two pure oxygen pipelines 4 are provided, which are symmetrically arranged at the inlet end of the nozzle 6.

[0027] A circulating flue gas duct 5 is also arranged on the outer periphery of the pure oxygen duct 4. The circulating flue gas duct 5 is arranged in a sleeve-like manner and is arranged concentrically with the pure oxygen duct 4. The cross-sectional area of ​​the circulating flue gas duct 5 is 2 to 5 times that of the pure oxygen duct 4.

[0028] The cross-sectional area of ​​the pre-combustion chamber 3 is 10 to 40 times the cross-sectional area of ​​the circulating flue gas duct 5. The distance from the central axis of the circulating flue gas duct 5 to the central axis of the pre-combustion chamber 3 is 2 to 6 times the radius of the pre-combustion chamber 3.

[0029] The primary air carrying the coal powder is passed into the pre-combustion chamber 3 through the primary air duct 1. Due to the eccentric arrangement of the primary air duct 1, the primary air is an eccentric jet in the pre-combustion chamber, so that local suction is formed in the pre-combustion chamber 3 and its outlet, which promotes the heating and ignition of the coal powder.

[0030] By adjusting the air duct 2, an appropriate amount of air is introduced into the pre-combustion chamber 3 as the adjustment air, so that the coal powder is partially pyrolyzed and burned in the pre-combustion chamber 3. At this time, the combustion of the coal powder is in the form of a faint spark, rather than an obvious flame. This can ensure good ignition performance and avoid excessive combustion temperature in the pre-combustion chamber 3. The partially pyrolyzed and burned coal powder, primary air, adjustment air, pyrolysis gas, and combustion flue gas form a mixed fuel air and enter the nozzle 6.

[0031] Pure oxygen is injected from the pure oxygen pipe 4 into the nozzle 6 at a speed of 100-200m / s, and the circulating flue gas is injected through the circulating flue gas pipe 5 to entrain and dilute the pure oxygen. At this time, the circulating flue gas envelops the pure oxygen, delaying the mixing of the secondary air oxygen and the mixed fuel air; the high-speed jet of the secondary air causes a strong entrainment of the flue gas in the furnace, controlling the peak value of the flame temperature. Therefore, even under high oxygen concentration conditions, the combustion intensity can be effectively controlled to ensure the safety of the heating surface.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An oxygen-enriched pulverized coal burner, the burner being capable of being arranged in a furnace (8), characterized in that: The burner comprises a primary air duct (1), an adjusting air duct (2), a pre-combustion chamber (3) and a nozzle (6); the nozzle (6) is arranged in a furnace (8) as the outlet end of the burner; the primary air duct (1) and the adjusting air duct (2) are eccentrically arranged at the inlet end of the pre-combustion chamber (3); the pre-combustion chamber (3) is arranged at the inlet end of the nozzle (6) and is coaxially arranged with the nozzle (6); a pure oxygen duct (4) is also arranged at the inlet end of the nozzle (6), and the pure oxygen duct (4) is arranged outside the pre-combustion chamber (3) so as to allow pure oxygen to flow in from the pre-combustion chamber (3) The pure oxygen pipe (4) is sprayed into the nozzle (6) at a speed of 100 to 200 m / s as secondary air; the cross-sectional area of ​​the nozzle (6) is 10 to 20 times the cross-sectional area of ​​the pre-combustion chamber (3); the cross-sectional area of ​​the pre-combustion chamber (3) is 2 to 10 times the cross-sectional area of ​​the adjustment air pipe (2); the burner further comprises a circulating flue gas pipe (5), the circulating flue gas pipe (5) is arranged in a sleeve-like manner on the outer periphery of the pure oxygen pipe (4), and is arranged concentrically with the pure oxygen pipe (4), and the cross-sectional area of ​​the circulating flue gas pipe (5) is 2 to 5 times the cross-sectional area of ​​the pure oxygen pipe (4).

2. The oxygen-enriched pulverized coal burner according to claim 1, characterized in that: Two pure oxygen pipelines (4) are provided, and are symmetrically arranged at the inlet end of the nozzle (6).

3. The oxygen-enriched pulverized coal burner according to claim 1, characterized in that: The cross-sectional area of ​​the pre-combustion chamber (3) is 10 to 40 times the cross-sectional area of ​​the circulating flue gas duct (5).

4. The oxygen-enriched pulverized coal burner according to claim 3, characterized in that: The distance from the central axis of the circulating flue gas duct (5) to the central axis of the pre-combustion chamber (3) is 2 to 6 times the radius of the pre-combustion chamber (3).

5. A combustion method of an oxygen-enriched pulverized coal burner based on pumping and jetting, which uses the oxygen-enriched pulverized coal burner as claimed in claim 1, characterized in that: The method comprises: The primary air carrying the pulverized coal is passed through the primary air duct (1) into the pre-combustion chamber (3), and an eccentric jet of the primary air in the pre-combustion chamber is used to form a local entrainment in the pre-combustion chamber (3) and at its outlet, thereby promoting heating and ignition of the pulverized coal; A proper amount of air is introduced into the pre-combustion chamber (3) through the adjusting air duct (2) as adjusting air, so that the pulverized coal is partially pyrolyzed and burned in the pre-combustion chamber (3), forming a mixed fuel air which enters the nozzle (6); Pure oxygen is injected from the pure oxygen pipeline (4) into the nozzle (6) at a speed of 100-200 m / s, which not only serves as secondary air to further burn the mixed fuel air, but also forms smoke entrainment in the furnace to reduce the peak flame temperature.

6. The combustion method based on pumping and jetting of an oxygen-enriched pulverized coal burner according to claim 5 is characterized in that: The burner further comprises a circulating flue gas pipeline (5), wherein the circulating flue gas pipeline (5) is arranged in a sleeve-like manner on the outer periphery of the pure oxygen pipeline (4) and is arranged concentrically with the pure oxygen pipeline (4); the method further comprises: Pure oxygen is injected from the pure oxygen pipeline (4) into the nozzle (6) at a speed of 100-200 m / s, and at the same time, the circulating flue gas is injected through the circulating flue gas pipeline (5) to entrain and dilute the pure oxygen. The secondary air formed by the pure oxygen and the circulating flue gas delays the combustion of the mixed fuel air, and the flue gas in the furnace is entrained to reduce the peak value of the flame temperature.

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