CN105627280B - A kind of lignite semi-coke combustion with meagre oxygen boiler - Google Patents

Abstract

The invention discloses a kind of lignite semi-coke combustion with meagre oxygen boiler, including some cyclone cylinder lean-oxygen burners and boiler body；Boiler body includes dual firing chamber, is arranged at the boiler heating surface and exhaust opening on dual firing chamber top；Cyclone cylinder lean-oxygen burner is an inverted Adiabatic Cyclone separator with central tube；The dual firing chamber of the cyclone cylinder lean-oxygen burner connection boiler body.Lignite semi-coke powder tangentially or is cut to the annular space entered between central tube and cyclone cylinder under primary air effect, be formed as high-temp combustion gasification zone in the bottom of annular space, excess air coefficient is kept to be less than 1 in this region, maintenance reaction is combustion with meagre oxygen atmosphere；Flue gas containing fuel gas enters dual firing chamber, and fully burning generation high-temperature flue gas is up respectively by each heating surface of boiler of tower arrangement, completes heat transfer, flue gas is reduced to certain exhaust gas temperature.Combustion intensity of the present invention is high, retention efficiency is high, pollutant emission is low, load regulation range is wide.

Description

A lignite semi-coke lean oxygen combustion boiler

technical field

The invention relates to the technical field of boilers, in particular to a lignite semi-coke oxygen-poor combustion boiler.

Background technique

Lignite is a low-rank coal with huge reserves in my country and the world. However, lignite has high water content, high volatile matter, easy spontaneous combustion, and is not conducive to transportation, which restricts the large-scale utilization of lignite. It is of great significance for the development of lignite to improve the quality of lignite and comprehensively utilize it by classification and quality.

In the field of lignite utilization, medium and low temperature pyrolysis technology is a more promising technology for the utilization of lignite by classification and quality. The pyrolysis solid product lignite semi-coke is a kind of better fuel due to the reduction of volatile matter, moisture content and calorific value. The high-efficiency and low-pollution utilization of lignite semi-coke plays a pivotal role in improving the comprehensive energy efficiency of lignite classification and utilization.

Lignite semi-coke can be used as raw material for gasifier to produce gas, and can also be used for direct combustion of boiler fuel to produce heat energy. Among them, it is the most direct method to use the boiler to directly burn the heating medium to produce hot water or steam. However, due to the significant reduction of volatile components of lignite semi-coke, its ignition performance is affected. It is very important to develop a lignite semi-coke-fired boiler with stable combustion performance and low pollutant emissions.

At present, there are three main combustion methods of solid fuel coal and coal coke: bed furnace, fluidized bed furnace and pulverized coal furnace. Pulverized coal furnace is the main combustion method of power plant boiler.

Another combustion method, cyclone combustion, has also been widely used. Cyclone combustion is a stable and controllable high-speed rotating flame artificially organized. It has a high degree of fullness of the combustion flame and extremely strong disturbance ability. It is suitable for the combustion process of powder and crumb solid fuels. heat intensity. Since there is a certain accumulation of solid fuel in the combustion chamber, it has a relatively long residence time in the cyclone furnace, which helps to maintain the continuity of the combustion process. The hot slag film accumulates a certain amount of heat and is an extremely stable combustion bed, which can maintain the stability of the combustion process. Cyclone combustion has the advantages of high combustion intensity, high slag collection rate, and stable combustion. However, its application is limited due to problems such as iron precipitation, hydrogen explosion, difficulty in slag removal, and high emissions of pollutants such as nitrogen oxides.

Under the background of energy conservation and emission reduction, coal-fired power plants undertake the important task of power peak regulation, requiring power plant boilers to be able to operate stably and efficiently within a wide load range. The existing utility boilers usually have a contradiction between the stability and high efficiency of combustion and the low-load operation of the boiler. Therefore, it is necessary to propose a new combustion boiler, which can not only achieve high-efficiency and low-pollution combustion, but also achieve greater load regulation.

Contents of the invention

The object of the present invention is to provide a lignite semi-coke oxygen-depleted combustion boiler to solve the problems of low combustion intensity, narrow load adjustment range and excessive pollutant discharge in the existing pulverized coal furnace boiler; the boiler of the present invention has high combustion intensity, slagging It has the advantages of high efficiency, low pollutant emission and wide load regulation range.

To achieve the above object, the present invention is achieved by taking the following technical solutions:

A lignite semi-coke oxygen-depleted combustion boiler, including several cyclone oxygen-lean combustion devices and a boiler body; the boiler body includes a secondary combustion chamber, a boiler heating surface and a smoke exhaust port arranged on the upper part of the secondary combustion chamber; the cyclone oxygen-deficient combustion device It is an inverted adiabatic cyclone separator with a central cylinder; the oxygen-lean combustion device of the cyclone is connected to the secondary combustion chamber of the boiler body.

Further, the cyclone lean oxygen combustion device includes a cyclone, a central tube, a flue gas duct and a secondary wind cyclone; the lower side wall of the cyclone is provided with a primary tuyere; the center of the bottom of the cyclone has a through hole, and the center The cylinder passes through the through hole at the bottom of the cyclone and extends into the inside of the cyclone. The top of the central cylinder is a through hole and is spaced from the inner wall of the top of the cyclone. Slag pool, the bottom of the molten slag pool is provided with a first slag discharge port; the bottom of the central cylinder is provided with a second slag discharge port, one end of the flue gas conduit is vertically connected to the central cylinder, and the other end is connected to the second combustion chamber.

Further, a secondary air swirler for feeding secondary air for supplementary combustion is provided at the entrance of the flue gas duct and the secondary combustion chamber.

Further, the primary tuyere is set on a downward slope.

Further, two primary air outlets for forming a cyclone in the cyclone are provided on the side wall of each cyclone.

Further, the heating surface of the boiler is arranged in tower type.

Further, under the action of the primary air, the lignite semi-coke powder enters the annular space between the central cylinder and the cyclone from the primary air outlet at the lower part of the cyclone along the tangential or cutting direction, and forms a high-temperature combustion gasification zone at the lower part of the annular space. In this area, the excess air ratio is kept less than 1, and the reaction is maintained as an oxygen-lean combustion atmosphere; the generated flue gas is strongly rotated in the cyclone to remove liquid slag, and then the flue gas enters the second combustion chamber through the flue gas duct between the second combustion chamber and the cyclone. The combustion chamber, when entering the secondary combustion chamber, supplements part of the secondary air, and enters the secondary combustion chamber with a rotating jet; the flue gas is fully burned in the secondary combustion chamber and further exothermic, and then generates high-temperature flue gas to pass through the tower-type boilers respectively. The heating surface completes the heat transfer, reduces the flue gas to the exhaust temperature and then discharges it from the exhaust port.

Further, the central cylinder and the cyclone are made of silicon nitride material, and the cyclone combustion chamber formed between the central cylinder and the cyclone is an adiabatic combustion chamber.

Further, the combustion in the secondary combustion chamber is homogeneous combustion, and the excess air ratio is 1.05-1.1.

Further, the temperature of the reaction zone above the molten slag pool is 100-200°C higher than the ash melting temperature.

Further, there are multiple cyclone lean oxygen combustion devices and they are evenly distributed on the periphery of the boiler body.

Compared with prior art, the advantage of the present invention is:

1. Molten oxygen-lean combustion is used in the cyclone to convert most of the fuel nitrogen into nitrogen, and graded air combustion is used in the second combustion chamber to reduce the emission of nitrogen oxides.

2. There are more molten slag in the annular space of the cyclone to form a slag pool. The molten ash in the slag pool catalyzes the gasification and combustion of residual coke and provides heat source, which maintains the stability of combustion and improves the carbon conversion rate. Each cyclone has two symmetrically arranged primary air inlets, forming a strong swirling airflow in the cyclone; above the bottom of the cyclone is a molten slag pool with a certain depth, and large particles of coal chips are quickly heated in the molten slag pool. Decomposition and gasification to achieve high carbon conversion rate; there are slag discharge holes under the slag pool, and the temperature in the cyclone is maintained above the ash melting temperature, which can realize smooth liquid slag discharge.

3. The gasification combustion in the slag pool is mainly a carbon-oxygen exothermic reaction, which keeps the local high temperature in the slag pool, which is conducive to improving the combustion intensity and the fluidity of the molten slag.

4. The strong swirling airflow in the cyclone combustion chamber throws the coke slag to the wall to realize the separation of molten droplets and flue gas, improves the slag filling rate, and greatly reduces the contamination of the subsequent tower boiler heating surface and the follow-up Dust removal burden.

5. There is a second slag separation chamber at the lower part of the central tube between the cyclone and the second combustion chamber. The liquid slag that cannot be separated in the future enters this slag pool and is captured, further reducing the proportion of fly ash in the flue gas to achieve liquid slag Separate as much as possible from gaseous products.

6. There is a supplementary secondary air of rotating jet at the entrance of the second combustion chamber to maintain the overall excess air coefficient at a low level. The main combustion in the second combustion chamber is homogeneous combustion, which reduces the formation of nitrogen oxides.

7. The cyclone, central tube and heat-insulating conduit are all made of silicon nitride, which improves the thermal shock resistance of the equipment.

8. One boiler can be equipped with multiple cyclone lean oxygen combustion equipment.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the structural representation of a kind of lignite semi-coke oxygen-poor combustion boiler of the present invention;

FIG. 2 is a top view of FIG. 1 .

In the figure: 1. Cyclone; 2. Central tube; 3. Boiler heating surface; 4. Smoke outlet; 5. Secondary combustion chamber; 6. Secondary wind cyclone; 7. Flue gas duct; Slag outlet; 9. First slag outlet; 10. Molten slag pool; 11. Primary tuyere.

detailed description

Please refer to Fig. 1, a lignite semi-coke oxygen-depleted combustion boiler of the present invention includes several cyclone oxygen-depleted combustion devices and a boiler body, both of which are arranged in a satellite shape.

The bottom of the boiler body is the secondary combustion chamber 5, the upper part of the secondary combustion chamber 5 is the boiler heating surface 3 arranged in a tower type, and the top of the boiler heating surface 3 is provided with a smoke exhaust port 4.

The cyclone lean oxygen combustion device includes a cyclone 1 , a central tube 2 , a flue gas duct 7 and a secondary air cyclone 6 . The lower side wall of the cyclone 1 is provided with a primary tuyere 11 which is slightly inclined downward; each side wall of the cyclone 1 is provided with two primary tuyeres 11 for forming a cyclone in the cyclone 1 . The center of the bottom of the cyclone 1 has a through hole, and the central tube 2 extends into the interior of the cyclone 1 through the through hole at the bottom of the cyclone 1, and the top of the central tube 2 is a through hole and is spaced from the inner wall of the top of the cyclone 1. The connection with the cyclone 1 is sealed. A molten slag pool 10 is provided in the cyclone 1 below the primary tuyere 11 , and a first slag discharge port 9 is provided at the bottom of the molten slag pool 10 . The bottom of the central cylinder 2 is provided with a second slag outlet 8, one end of the flue gas conduit 7 is vertically connected to the central cylinder 2, and the other end is connected to the secondary combustion chamber 5, and a secondary discharge port is provided at the entrance of the flue gas conduit 7 and the secondary combustion chamber 5. The wind cyclone 6 is used to send secondary air for supplementary combustion.

In order to realize oxygen-lean combustion, lignite semi-coke powder is sent into the annular area above the molten slag pool 10 in the cyclone 1 by the primary air and recirculated flue gas through the slightly downwardly inclined primary tuyere 11. Rapid pyrolysis and combustion under the action of heating, the excess air coefficient of the primary air is maintained within the range of less than 1. Small particles burn rapidly under the action of airflow. Due to the strong turbulent combustion, the molten ash droplets of small particles merge and grow up, and are thrown to the wall of cyclone 1 under the action of centrifugal force, and flow into the molten slag pool under the action of gravity. 10, and the coke powder with large particles also adheres to the molten slag film under the action of centrifugal force, and slowly flows into the molten slag pool 10 under the action of gravity, and the residual coke particles undergo gasification and combustion reactions while flowing, and flow into the molten slag pool After 10, the residence time is significantly increased, which improves the carbon burnout rate. The temperature of the reaction zone above the molten slag pool 10 is controlled by adjusting the excess air coefficient and the recirculation flue gas rate, and is kept 100-200°C higher than the ash melting temperature. The molten slag pool 10 has a large heat capacity, and can quickly complete the gasification and combustion of residual coke. Since there is a layer of molten slag in the molten slag pool 10 , the stability of the temperature of the slag pool and the fluidity of the molten slag can be guaranteed, and excess molten slag is discharged from the first slag discharge port 9 . In the annular reaction zone, the gas-liquid separation of the generated gas product and the slag is completed, and the gas is sent from the reentry zone on the upper part of the cyclone 1 down the central tube 2 and into the secondary combustion chamber 5 through the flue gas duct 7 . At the entrance of the flue gas duct 7 and the secondary combustion chamber 5, the secondary air for supplementary combustion is sent through the secondary air swirler 6, and the complete combustion is completed in the secondary combustion chamber 5 with a small excess air coefficient of 1.05-1.1. The high-temperature flue gas generated after complete combustion goes upward from the second combustion chamber 5 and passes through the heating surfaces 3 of each boiler in turn. A certain amount of exhaust smoke is introduced into the primary tuyere 11 by the flue gas recirculation fan.

The structure and process characteristics of the lignite semi-coke oxygen-poor combustion boiler of the present invention are:

In the annular passage formed by the adiabatic high-temperature cyclone 1 and the central cylinder 2 made of silicon nitride, the ratio of the excess air introduced is lower than 1, forming an oxygen-poor combustion condition, and at the same time, there is a thick molten slag in this area In the pool 10, the residual coke is melted and burned, and the generated flue gas contains more combustible gas. The temperature of the molten slag pool is higher, which is conducive to the complete conversion of residual carbon and smooth slag discharge. The inverted cyclone allows for maximum separation of slag and gaseous products. At the same time, the nitrogen oxides generated due to high-temperature lean oxygen combustion are also significantly reduced. In the secondary combustion chamber, due to the homogeneous combustion, a low excess air ratio can be maintained to reduce the generation of pollutants. The feature of this type of boiler is that each boiler body can be equipped with multiple cyclone oxygen-lean combustion devices, and each cyclone oxygen-lean combustion device can operate independently, thereby improving the load adjustment ratio of the lignite semi-coke oxygen-lean combustion boiler.

Claims (8)

1. a kind of lignite semi-coke combustion with meagre oxygen boiler, it is characterised in that including some cyclone cylinder lean-oxygen burners and boiler sheet Body；

Boiler body includes dual firing chamber (5), is arranged at the boiler heating surface (3) and exhaust opening (4) on dual firing chamber (5) top；

Cyclone cylinder lean-oxygen burner is an inverted Adiabatic Cyclone separator with central tube；The cyclone cylinder oxygen deprivation combustion Burn the dual firing chamber (5) of device connection boiler body；

Cyclone cylinder lean-oxygen burner includes cyclone cylinder (1), central tube (2), smoke tube (7) and Secondary Air cyclone (6)；Rotation The lower sides of air duct (1) are provided with primary air nozzle (11)；The bottom centre of cyclone cylinder (1) is provided with through hole, and central tube (2) passes through It is internal that the through hole of cyclone cylinder (1) bottom stretches into cyclone cylinder (1), at the top of central tube (2) for through hole and with cyclone cylinder (1) top inner wall It is arranged at intervals, central tube (2) seals with cyclone cylinder (1) junction；Lower section in cyclone cylinder (1) positioned at primary air nozzle (11) is provided with Slag bath (10) is melted, the bottom of melting slag bath (10) is provided with the first slag-drip opening (9)；The bottom of central tube (2) is provided with the second deslagging Mouth (8), smoke tube (7) one end vertical connection central tube (2), other end connection dual firing chamber (5)；

Cyclone cylinder lean-oxygen burner is multiple and be uniformly distributed in boiler body periphery.

A kind of 2. lignite semi-coke combustion with meagre oxygen boiler according to claim 1, it is characterised in that smoke tube (7) with The porch of dual firing chamber (5) is provided with the Secondary Air cyclone (6) for being used for being sent into afterburning Secondary Air.

3. a kind of lignite semi-coke combustion with meagre oxygen boiler according to claim 1, it is characterised in that primary air nozzle (11) is downward It is obliquely installed.

A kind of 4. lignite semi-coke combustion with meagre oxygen boiler according to claim 1, it is characterised in that each cyclone cylinder (1) side Wall is provided with two primary air nozzles (11) for being used to form whirlwind in cyclone cylinder (1).

A kind of 5. lignite semi-coke combustion with meagre oxygen boiler according to claim 1, it is characterised in that boiler heating surface (3) tower Formula is arranged.

6. a kind of lignite semi-coke combustion with meagre oxygen boiler according to claim 1, it is characterised in that lignite semi-coke powder is once Tangentially or cut empty to the annular entered from cyclone cylinder bottom primary air nozzle (11) between central tube and cyclone cylinder under air effect Between, be formed as high-temp combustion gasification zone in the bottom of annular space, keep excess air coefficient to be less than 1 in this region, maintain React for combustion with meagre oxygen atmosphere；Flue gas strong rotation removing molten slag in cyclone cylinder is generated, then flue gas passes through dual firing chamber Smoke tube (7) between cyclone cylinder enters dual firing chamber, part auxiliary air is supplemented when entering dual firing chamber, with rotating jet Into dual firing chamber；Flue gas fully burning and further heat release in dual firing chamber, then high-temperature flue gas is up passes through tower respectively for generation The each heating surface of boiler of formula arrangement, completes heat transfer, and flue gas is reduced to after exhaust gas temperature and discharged from exhaust opening.

A kind of 7. lignite semi-coke combustion with meagre oxygen boiler according to claim 1, it is characterised in that central tube and cyclone cylinder by Silicon nitride material is made, and the cyclone combustion chamber formed between central tube and cyclone cylinder is insulated combustion chamber.

A kind of 8. lignite semi-coke combustion with meagre oxygen boiler according to claim 1, it is characterised in that the combustion carried out in dual firing chamber It is 1.05~1.1 to burn for homogeneous combustion, excess air coefficient；The temperature of reaction zone above slag bath (10) is melted than grey melting temperature It is high 100~200 DEG C.