CN101109507A - Low-oil ignition level rich-lean enrichment type DC pulverized coal burner - Google Patents

Abstract

The utility model relates to a direct-flow pulverized coal burner of low-oil ignition horizontal rich-lean enrichment type, which relates to a pulverized coal thick-lean burner arranged tangentially at four corners. The feature of the present invention is that after the primary air pulverized coal airflow is separated from the thicker and thinner horizontally, a concentrated strand primary separation block and a concentrated strand secondary separation block are provided at the outlet of the concentrated strand airflow channel to divide the concentrated powder airflow into upper and middle , Lower three strands; the nozzle structure adopts the thick-strand enrichment type nozzle structure, and a small ignition oil gun is provided at the thick-strand enrichment type nozzle. The invention not only reduces the ignition heat required for ignition, is beneficial to ignition and combustion, but also solves the problem of low-load deoiling and stable combustion when large unit boilers of 300-600 MWe level burn difficult-to-combustible coals; and can greatly save ignition and combustion-supporting costs Oil, especially suitable for 100, 200, 300 and 600MWe grade boilers burning inferior bituminous coal, lean coal, semi-anthracite and anthracite burners and their transformation.

Description

Low-oil ignition level rich-lean enrichment type DC pulverized coal burner

technical field

The invention relates to a low-oil ignition DC pulverized coal burner, in particular to an oil-less ignition technology of a four-corner tangentially arranged pulverized coal burner, which belongs to the field of combustion technology and equipment technology.

Background technique

Power plant boilers consume a large amount of fuel oil during ignition and low-load stable combustion. With rising oil prices and tight resources, reducing this part of oil consumption has become an urgent task to achieve economical operation of power plant boilers.

The traditional ignition and fuel stabilization guns of power plant boilers are usually arranged in the secondary air nozzle, and the oil gun arranged in the secondary air nozzle is called a large oil gun. This arrangement has many advantages, but its thermal power is generally relatively large. In the boiler ignition start-up or stable combustion stage, the large oil gun first increases the temperature of the high-temperature flue gas in the furnace, and the high-temperature flue gas then transfers heat to the primary air jet through convection. For a single pulverized coal nozzle, about 1/ The calorific value of 4 participates in the heat exchange of the primary air pulverized coal jet, so the efficiency of ignition and stable combustion of large oil guns is not high.

The ignition technology of the small oil gun is to arrange the oil gun in the nozzle of the primary air, and the heat generated by the oil gun is all used to raise the temperature of the pulverized coal airflow. This kind of oil gun has the best stable combustion effect, and the capacity of the oil gun can be compared The grease gun in the secondary air nozzle is much smaller (hence the name). The small oil gun is only put into use when it is started in a cold state or when the boiler is under low load and stable combustion. If the design of the heat load of the small oil gun meets the ignition heat of the primary air powder jet, the pulverized coal flow can be stably and fully ignited to form a pulverized coal flame. The mutual support with the oil flame produces the combustion effect of replacing oil with coal. This combustion device is called a small oil gun pulverized coal burner.

The levels of ignition oil and low-load oil are directly related to the low-load stable combustion characteristics of the parent burner. In recent years, new pulverized coal burners with low-load stable combustion or low-quality coal have been developed. Through reasonable organization of pulverized coal airflow, the local concentration of pulverized coal has been changed, and the ignition point of pulverized coal has been reduced, making it easy to ignite and stable. The ignition characteristics have been improved, thereby saving fuel for ignition and low-load stable combustion. The better the ignition and stable combustion performance of the parent burner, the smaller the energy of the external heat source required during the ignition stage and the low-load operation of the boiler, and the less fuel oil is used. Therefore, it is necessary to improve the ignition performance and combustion performance of the low-oil ignition burner. In order to save fuel, we must first improve the ignition stability of the parent burner, and then reasonably set the position of the small oil gun.

In pulverized coal boilers, thick-lean combustion (or poor-rich powder combustion) technology is often used, that is, the pulverized coal/air (primary air) airflow entering the furnace is inertially separated, divided into two streams, thick and thin, and then sent to the furnace respectively. Since the pulverized coal concentration of the concentrated strand is significantly higher than that of the original primary air, its ignition characteristics have been significantly improved. The horizontal thick-lean combustion technology is a kind of thick-lean combustion technology. The two airflows after the separation of the thick and thin air are sent into the furnace in the same horizontal direction, and the dense coal powder airflow is sent to the high-temperature area on the fire side where the coal powder is easy to catch fire. The burners used are called horizontal rich-lean burners. Our country now has a variety of horizontal thick-thin burners.

For power plant boilers burning bituminous coal, the existing horizontal thick-lean combustion technology has been proven in theory and practice to solve the problem of stable combustion of pulverized coal boilers in power plants, realize oil cut-off and peak regulation at low loads, reduce NO _x generation, and prevent slagging in the furnace And an effective way to improve the adaptability of coal types. However, for power plant boilers burning low-quality bituminous coal, lean coal, semi-anthracite and anthracite and other difficult-to-combust fuels, the existing horizontal thick-lean combustion technology cannot fully achieve the above-mentioned effects, and it is difficult to meet production requirements. The reason is that for difficult-to-combustible fuels, even if the concentration separation effect of the primary air before entering the furnace is good, the dense pulverized coal airflow in the furnace may still not be heated to the required ignition temperature by the entrained hot flue gas, and cannot be quickly Good realization of pulverized coal airflow ignition and stable combustion. For example, in a horizontal thick-lean burner called "Multi-enrichment Direct-flow Pulverized Coal Burner" (Patent No. 02100688.1), a zigzag multi-strand nozzle structure is adopted at the outlet of the thick-strand pulverized coal. When burning bituminous coal with high volatile content, it shows good stable combustion and low-load operation performance, and has excellent low _NOx combustion characteristics. However, when burning difficult-to-combustible fuels, the combustion-stabilizing effect is reduced. It is difficult to meet the strict low-load stable combustion requirements.

An effective way to solve the above contradictions is to use a special burner outlet structure to more reasonably organize the flow field of the pulverized airflow after it is injected into the furnace, realize the spatial concentration of pulverized coal particles in the furnace, and greatly enhance the space of pulverized coal. Concentration, so that part of the pulverized coal burns in a small space, releases heat, and then transfers the heat to another part of the unignited particles in the thick strand, prompting more particles to ignite and burn. The enrichment burner uses the gas-solid separation element in the primary air channel to separate the primary air for the first stage of thick-lean separation, and arranges a separation block at the outlet of the burner to carry out a concentrated airflow after the first-stage separation into the second stage. Stage gas-solid separation, two concentrated streams with different flow rates are obtained, and the small pulverized coal airflow (concentrated stream) is deflected at a large angle (sharp turn) at the burner outlet, and then forms a high-temperature recirculation zone, and the pulverized coal In this high-temperature recirculation zone, stagnant enrichment (space concentration), rapid temperature rise, release of volatiles and ignition, form a stable small flame on duty, and then ignite the entire primary air pulverized coal flame from this small fire on duty.

Although the existing enrichment burners have been applied to dozens of power plant boilers, and have shown very strong ignition and stable combustion capabilities when burning low-quality bituminous coal, lean coal, anthracite and other difficult-to-combustible fuels, those boilers correspond to The maximum single-unit capacity of the company is only 200MWe, and encountered a technical bottleneck problem when it was promoted to the existing main large-unit boilers in my country with a level of 300MWe～600MWe. The reason is that the existing enrichment burner is a kind of upper and lower thick-lean burner, and its nozzle is large, so it is often necessary to use two primary air nozzles in combination, and the large unit boiler often needs to swing the whole group when the burner is adjusted. , there are great technical difficulties in merging two spouts or using an oversized spout.

With the development of low-oil ignition technology, the placement position of the ignition oil gun has developed from pointing the entire primary air powder-containing air flow to pointing a part of the primary air flow. However, there are still disadvantages of excessively large airflow and excessive fuel consumption, especially when burning non-combustible fuels and reducing the load greatly, this disadvantage is more prominent. Studies have shown that the entire primary air flow can be realized only by igniting the coal powder carried by 7-15% of the primary air, so by improving the parent burner and placing the ignition oil gun more reasonably, there is still a lot to be done in the prior art Expansion capacity.

Contents of the invention

The purpose of the present invention is to provide a kind of direct-flow pulverized coal burner of low-oil ignition level rich-lean enrichment type. The nozzles are equivalent. This burner can be used not only for boilers below 200MWe, but also for large unit boilers of 300MWe to 600MWe. At the same time, it can greatly save ignition oil, which is suitable for burning bituminous coal and low-quality Refractory fuels such as bituminous coal, lean coal, semi-anthracite and anthracite have broad prospects for production and application.

The purpose of the present invention is achieved through the following technical solutions: a direct-flow pulverized coal burner with low-oil ignition level rich-lean enrichment type, which includes a square-circle joint, a primary air channel connected to the square-circle joint, and a separation baffle arranged in the primary air channel. block and separation partition, the concentrated air flow channel and the light air flow channel formed by the separation partition, the dense air flow spout, and the light air flow spout, it is characterized in that: set There is a first-level separation block for concentrated strands and a second-level separation block for concentrated strands; the first-level separation block for concentrated strands separates the concentrated-strand airflow into two airflows, upper and lower, in the vertical direction, the upper airflow is a small airflow, and the lower airflow is a large airflow , the concentrated-strand secondary separation block is located at the outlet of the lower large-strand airflow, and separates the lower-part large-strand airflow into upper and lower two. The thick strand enrichment type nozzle formed by the thick strand lower nozzle is provided with a small ignition oil gun between the thick strand upper nozzle and the thick strand center nozzle.

The horizontal thick-lean enrichment type direct-flow pulverized coal burner according to the present invention is further characterized in that: the small airflow ejected from the upper nozzle of the concentrated strand accounts for 1/4 to 1/3 of the mass flow rate of the total dense strand airflow; The airflow ejected from the concentrated stream central nozzle accounts for 1/6-1/7 of the total mass flow rate of the concentrated stream.

Compared with the prior art, the present invention has the following advantages and benefits: (1) the present invention realizes a four-stage ignition process of a small fire point and a large fire, that is: use a small oil gun to ignite the on-duty at the outlet of the thick stock enrichment type spout structure Small flame, go to ignite thick pulverized coal flame by small flame on duty again and go to ignite whole primary air pulverized coal flame by thick pulverized coal flame. Compared with the common low-oil ignition technology, the heat required to ignite the small flame on duty is much less, thus greatly saving the ignition oil; (2) In normal operation, the low-oil ignition level thick-lean enrichment DC pulverized coal combustion The small oil gun of the burner is out of the working position. At this time, the structure and function of the burner are exactly the same as the horizontal rich-lean enrichment type DC pulverized coal burner, that is: (a) has a strong ignition and stable combustion capability, and is suitable for 100MWe , 200MWe, 300MWe, and 600MWe level unit boilers burn low-quality bituminous coal, lean coal, semi-anthracite and anthracite, and low-load deoiling and stable combustion are required; (b) The temperature on the fire side is high, the concentration of coal powder is large, and there is a large amount of volatile matter released At high temperature, the volatile matter will reduce the generated NO _x to N ₂ , thereby reducing the emission of NO _x ; (c) the concentration of pulverized coal in the outlet area of the burner toward the fire side is thick, and the concentration of pulverized coal in the backfire side is light, thereby improving Or eliminate the reducing atmosphere near the water wall in the burner area, improve or eliminate water wall slagging and high-temperature corrosion; (3) When necessary, small oil guns can also be put into operation to meet the needs of deep peak regulation and low load stable combustion , compared with other low-oil ignition technologies, the fuel-saving rate during deep peak regulation is higher; (4) The low-oil ignition level density-light enrichment DC pulverized coal burner has a compact structure, which is conducive to burner transformation, installation, and Operation and Maintenance.

Description of drawings

Figure 1 is a schematic diagram of the four-corner tangential circle arrangement structure of the low-oil ignition horizontal density-lean enrichment type DC pulverized coal burner.

Fig. 2 is a schematic diagram of the implementation structure of the low-oil ignition level rich-lean enrichment type once-through pulverized coal burner.

Fig. 3 is a cross-sectional view of A-A in Fig. 2, showing the structure of the thick strand side of the low-oil ignition horizontal rich-lean enrichment type once-through pulverized coal burner.

Fig. 4 is the front view of the nozzle of the low-oil ignition horizontal rich-lean enrichment type once-through pulverized coal burner.

Detailed ways

In the figure: 1- square and round joint; 2- primary air channel; 3- separation block; 4- separation partition; 5- concentrated air flow channel; 6- light air flow channel; 7- total concentrated air flow nozzle; 8- Light air flow nozzle; 9-concentrated pulverized coal flame; 10-primary air pulverized coal flame; 11-concentrated primary separation block; 12-concentrated secondary separation block; 13-small flame on duty; 14-concentrated upper nozzle ; 15-the center nozzle of the thick stock; 16-the lower nozzle of the thick stock; 17-the small oil gun for ignition; 18-the flame of the small oil gun.

Detailed ways

The principle and specific structure of the present invention will be further described below in conjunction with the accompanying drawings. The low-oil ignition horizontal rich-lean enrichment type DC pulverized coal burner provided by the present invention adds a small oil gun in the dense stock enrichment nozzle structure of a horizontal thick-lean enrichment type DC pulverized coal burner. The horizontal thick-lean enrichment type direct-flow pulverized coal burner is the parent burner of the present invention, and mainly includes a square-circle joint 1, a primary air channel 2 connected with the square-circle joint, a separation block 3 and a separation partition 4 arranged in the primary air channel , the dense stream airflow channel 5, the light stream airflow channel 6 and the dense stream airflow spout 7 and the light stream airflow spout 8 (as shown in Figure 2) that are divided by the separation partition; Concentrated strand primary separation block 11 and concentrated strand secondary separation block 12 (as shown in Figure 3); concentrated strand primary separation block 11 separates the concentrated strand airflow into two airflows of upper and lower sizes in the vertical direction, and the upper airflow is a small airflow. The lower part of the airflow is a large strand; the dense strand secondary separation block 12 is located at the outlet of the lower large strand of airflow, and separates the lower large strand of airflow into two upper and lower strands; the upper small strand of airflow separated by the dense strand primary separation block It is ejected from the upper nozzle 14 of the thick strand, and the upper and lower two airflows divided into the upper and lower airflows by the secondary separation block 12 of the thick strand are ejected from the central nozzle 15 of the thick strand and the lower nozzle 16 of the thick strand respectively. The total thick-strand airflow nozzle 7 is a thick-strand enrichment type nozzle formed by the thick-strand upper nozzle 14, the thick-strand center nozzle 15 and the thick-strand lower nozzle 16. In this structure, the small airflow ejected from the upper nozzle of the concentrated strand accounts for 1/4/~1/3 of the mass flow rate of the total concentrated airflow; the airflow ejected from the central nozzle of the concentrated strand accounts for 1/6 to 1/7 of the mass flow rate of the air stream. Small oil gun 17 is located in the dense stock enrichment type spout structure.

From Figure 2, Figure 3 and Figure 4, we can clearly see the ignition and combustion process of the parent burner: after the primary air pulverized coal airflow enters the square and round joint 1, it flows through the separation block 3 and the separation gear arranged in the primary air channel 2 Block 4 is divided into thick and thin streams (the amount of pulverized coal in the thick stream accounts for 3/4 of the primary air flow, and the air flow accounts for 1/5 to 1/3 of the primary air flow). Enrichment nozzle 7, the light strand enters the light strand airflow nozzle 8 through the light strand air flow channel 6; the dense strand primary separation block 11 and the concentrated strand secondary separation block 12 are arranged at the exit of the concentrated strand air flow channel 5, and the concentrated strand The primary separation block 11 first separates the entire concentrated airflow into two large (lower) and small (upper) strands in the vertical direction, and the secondary separation block 12 further separates the large airflow into two upper and lower strands, and the upper one is the small one. share. Concentrated strand enrichment nozzle 7, concentrated strand primary separation block 11 and concentrated strand secondary separation block 12 form a concentrated strand enrichment nozzle structure. In this structure, the dense powder air flow is divided into upper, middle and lower three streams, and the middle one is a small stream (accounting for about 1/7-1/6 of the flow rate of the dense stream, and 1/3 of the amount of pulverized coal in the dense stream. ), the lower side adjacent to it is a large airflow, these two airflows together account for about 2/3 of the dense airflow, and another jet is arranged on the upper side of the burner, accounting for about 1/3 of the total airflow . On the fire side, the large airflow sucks the small airflow, causing it to deflect at a large angle (sharp turn) in the furnace, and then form a high-temperature recirculation zone, and the pulverized coal with high inertia enters this high-temperature recirculation zone, where Stagnant enrichment (space concentration), rapid heating, release of volatile matter and ignition, form a small flame 13 (i.e. a small flame on duty), use it to ignite the thick coal powder flame 9, and then go to ignite the entire coal powder flame by the thick coal powder flame Primary air pulverized coal flame 10. The ignition process of pulverized coal in the parent body burner is completed in three stages, that is, light the thick pulverized coal flame 9 with the small flame 13 on duty, and then go to light the whole primary air pulverized coal flame 10 by the pulverized coal flame of the thick strand. The primary air flow carrying pulverized coal in the burner is separated in the horizontal direction in the pipeline. The separated dense air flow is sent to the fire side of the furnace, and the light air flow is sent to the back fire side of the furnace. The amount of pulverized coal in the concentrated airflow accounts for about 3/4 of the primary air, and the air flow accounts for 1/5 to 1/3 of the primary air.

Because the pulverized coal airflow entering the dense-strand enrichment nozzle structure is not the whole of the primary air pulverized coal gas flow, but the dense coal pulverized airflow after the thick-lean separation, it only accounts for 1/5~ of the primary air pulverized coal gas flow. 1/3, thereby greatly reducing the structure size of the thick-strand-enriched nozzle and the total size of the burner nozzle. Therefore, the horizontal thick-lean enrichment type pulverized coal once-through burner is suitable for large unit boiler burners of 300MWe to 600MWe and their transformation, and of course, it is also suitable for boiler burners and their transformation of boilers below 300MWe.

In the present invention, a small oil gun 17 is arranged in the thick stock enrichment nozzle, that is, between the thick stock upper nozzle 14 and the thick stock center nozzle 15. After the small oil gun is set, the ignition process of the burner is a four-stage ignition process: ignition After the small oil gun is put in, a small oil gun flame 18 is formed. Because the temperature of the small flame is very high, in the special structure of the horizontal thick-lean enrichment type burner, after a small amount of primary wind coal powder is put in, the small flame 13 on duty can be ignited. Light the dense coal powder (middle) flame 9 by the small flame on duty again, and then light the whole primary wind coal powder flame 10. Since the small oil gun ignites a small flame on duty, the fuel consumption for ignition is greatly reduced. The capacity of the small oil gun can be made very small, because what it ignites is the carefully organized small flame on duty in the thick jet, which is only a very small part of the primary air flow. When necessary, a small oil gun can also be put into operation to meet the needs of deep peak-shaving and low-load stable combustion. Compared with other low-oil ignition technologies, the fuel-saving rate of deep peak-shaving is higher. The invention has a stronger low-load stable combustion function, and is especially suitable for burning difficult-to-burn fuels such as low-quality bituminous coal, lean coal, semi-anthracite and anthracite.

Claims (2)

1. little oil ignition horizontal dense-dilute concentration type direct flow coal burner, contain circumference joint (1), a wind passage (2) that links to each other with the circumference joint, be arranged on one time in the wind passage separating block (3) and separates dividing plate (4), by the dense strand of gas channel (5) that separates that dividing plate is split to form and thin airflow passage (6), dense strand of air-flow spout (7), thin airflow spout (8), it is characterized in that: be provided with dense thigh one-level explant (11) and dense thigh secondary explant (12) in the exit of described dense thigh gas channel (5); Described dense strand of one-level explant is separated into two strands of air-flows of size up and down with dense strand of air-flow in vertical direction, upper air is a shallow bid, lower stream of airflow is big strand, described dense strand of secondary explant (12) is positioned at the exit of the big strand of air-flow in bottom, again the big burst of flow separation in bottom become big or small two strands up and down, described dense strand of air-flow spout (7) is to go up spout (14) by dense strand, dense burst of center nozzle (15) and dense thigh be dense strand of concentration type spout of spout (16) formation down, is being provided with an igniting small oil gun (17) on described dense strand between spout (14) and the dense thigh center nozzle (15).

2. according to the described horizontal dense-dilute concentration type direct flow pulverized coal burner of claim 1, it is characterized in that: the draft that described dense strand of last spout (14) sprayed accounts for 1/4/～1/3 of total dense strand of flow quality flow; The air-flow that described dense burst of center nozzle (15) sprayed accounts for 1/6～1/7 of total dense strand of flow quality flow.

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