Patent Application
20120006238
The present invention relates to a pulverized coal concentrator for a pulverized coal burner of a pulverized-coal fired boiler, in particular a pulverized coal concentrator for an internal-combustion type pulverized coal burner, and to a pulverized coal burner comprising such a pulverized coal concentrator.
Around the world, the conventional power plants and many industrial pulverized coal boilers burn heavy oil, diesel oil or natural gas, for the starting ignition and low-load combustion stabilization thereof, to achieve the ignition of pulverized coal. So in each year, a plenty of fuel oil is consumed. Recently, the developed plasma ignition and combustion stabilizing technique save fuel oil to a large extent and realize starting of pulverized coal boiler without oil. The Chinese patent CN03268412.6 discloses a staged igniting burner, as shown in
The Chinese patent CN200720146244.6 discloses a plasma burner, as shown in
The above patents discloses the multi-stage chamber structure of plasma pulverized coal burner which contains the following drawbacks: insufficient adaptability of the plasma pulverized coal burner to coal quality, air velocity and pulverized coal density, and insufficient ignition stabilization and reliability.
The present invention aims to providing a pulverized coal concentrator and a pulverized coal burner using such a pulverized coal concentrator, particularly suitable for a pulverized coal burner of internal combustion ignition and stabilization type, so as to increase adaptation of the pulverized coal burner to coal quality, air velocity and pulverized coal density.
In accordance with the present inventive pulverized coal concentrator, it is fixedly arranged inside a pulverized coal burner and comprises a front part and a rear part, characterized in that, the front part is designed as a bowl-shaped structure, for guiding and concentrating a gas-solid two-phase flow consisted of concentrated pulverized coal and air (hereinafter referred to as “air-pulverized coal flow”), and the rear part is designed as a cylinder-shaped structure, for maintaining a proper extension of the dense phase zone of the air-pulverized coal flow.
Preferably, the present inventive pulverized coal concentrator is designed as an integral structure, that is, the front part and the rear part are made integrally and the front part and/or the rear part are arranged fixedly; or, the present pulverized coal concentrator is designed as a split structure, that is, the front part and the rear part are made separately respectively, wherein the front part is connected with the rear part and the front part and/or the rear part are arranged fixedly; or the front part and rear part are arranged apart in a distance one from another and the front part and the rear part are arranged fixedly respectively.
Herein, the above distance can be particularly determined according to the coal quality, the structural size of component parts, the requirements on the pulverized coal ignition and combustion stabilization as well as the aerodynamic field inside boiler furnace and so on.
In the present inventive pulverized coal concentrator, by dense-weak separation of pulverized coal via the bowl-shaped structure of the front part, a portion of dense coal air pulverized coal flow enters the bowl-shaped structure, and the thin coal air pulverized coal flow enters a next stage of burner chamber, so that the air-pulverized coal flow inside the bowl-shaped structure is concentrated to a density level suitable for ignition; and at the same time due to the flow guidance of the bowl-shaped structure, the pulverized coal is forcedly introduced into the plasma flame area (or other heat ignition source), producing a heat temperature ignition effect, so that the pulverized coal volatile component and the coke particles are ignited simultaneously, to realize non-homogenous combustion in the earlier ignition process and the pulverized coal particles are rapidly ignited. At the same time, by the cylinder-shaped structure of the rear part, a proper extension of the pulverized coal dense phase zone (with respect to pulverized coal density, there is a dense phase zone and a thin phase zone, wherein the zone in which pulverized coal occupies a large proportion in the air pulverized coal flow is called the dense phase zone, and the rest zone is called the thin phase are) can be held, so as to realize a heat collection effect, so that the effective flame source is controlled into a narrow zone to prevent heat dissipation of flame source, which facilitates forming of a steady flame and then igniting coal particles outside the concentrator.
According to a preferable embodiment of the present invention, the front part has a bowl opening and a bowl bottom opening, an inlet of the rear part is connected with the bowl opening or the bowl bottom opening, or the inlet of the rear part is connected to a wall between the bowl opening and the bowl bottom opening of the front part.
According to a preferable embodiment of the present invention, a bowl bottom opening of an additional bowl-shaped component is connected to an outlet of the cylinder-shaped rear part, and the bowl opening of the bowl-shaped front part is facing away from a bowl opening of the additional bowl-shaped component. In adjacency of the additional bowl-shaped structure an eddy zone will form to intensify the pulverized coal flame combustion.
According to a preferable embodiment of the present invention, the size of the bowl opening is larger than that of the bowl bottom opening.
According to a preferable embodiment of the present invention, through holes are made in the bowl-shaped wall of the front part, in particular in adjacency to the bowl bottom.
According to a preferable embodiment of the present invention, the axial length of the front part is smaller than that of the rear part.
According to a preferable embodiment of the present invention, the bowl-shaped front part is formed by connection of several planes or is consisted of a camber or is the combination of the both. The bowl-shaped front part is preferably consisted of a circular camber.
According to a preferable embodiment of the present invention, the cylinder-shaped rear part is formed by connection of several planes or is consisted of a camber or is the combination of the both. The bowl-shaped front part is preferably consisted of a circular camber.
According to a preferable embodiment of the present invention, the cylinder-shaped rear part is a horizontal straight cylinder, a gradually expanding cylinder or a gradually narrowing cylinder or their combination. Herein, the rear part is preferably a gradually expanding structure, which can decrease the flow velocity of air-pulverized coal flow and increase the residence time of pulverized coal in the firing section. Of course, as for coal having low volatile component and high water and ash component, the gradually narrowing structure can be used for increasing fire collection capability. Thus, the rear part preferably comprises at least a gradually expanding cylinder and/or gradually narrowing cylinder.
According to a preferable embodiment of the present invention, through holes are made in the bowl wall of the bowl-shaped front part. Preferably, through holes are made in adjacency to the bowl bottom of the bowl-shaped front part. Through the holes in the bowl wall of the bowl-shaped structure, weak phase air-pulverized coal flow can be concentrated and shunted to retain dense phase air-pulverized coal flow, balance pressure difference, decrease air velocity and depress the negative influence on firing due to augmentation of flow velocity, so that at the same time of increasing of pulverized coal density, the flow velocity of air pulverized coal flow does not increase in a same proportion.
According to a preferable embodiment of the present invention, the rear part is provided at its outlet edge with a tooth-like structure or a petal-like structure. Preferably, the tooth-like or petal-like structure has an angle of 0°-90° (that is, the teeth or petal extends outwards perpendicularly to the chamber axis, it is 90°, or the teeth or petal extends parallel to the chamber axis, it is 0°). Through the tooth-like structure or the petal-like structure at the outlet edge of the rear part, a firing front edge disturbance of pulverized coal can be increased to form a backflow and an eddy so as to improve combustion. Such a structure can be used in case of slightly poor coal quality.
According to a preferable embodiment of the present invention, the wall of the cylinder-shaped rear part is also provided with through holes. Through these holes, pressure difference can be balanced to decrease the air velocity inside the rear part so as to improve firing. The quantity, shape and size of the holes can be set as practically demanded. Herein the holes can be inclined holes or straight holes, wherein inclined holes have better concentrating and shunting effect than straight holes.
According to a preferable embodiment of the present invention, the inlet of the bowl-shaped front part is of a square or circular structure or is of an angled tooth-like or petal-like structure (similar to the tooth-like or petal-like structure at the outlet/nozzle of the rear part). Through this embodiment, concentration and uniform flow can also be realized.
According to a preferable embodiment of the present invention, an additional cylinder is arranged at the inside of or outside of the rear part, and an interlayer space is formed between the additional cylinder and the cylinder-shaped rear part. The additional cylinder is arranged in such a manner that the holes in the wall of the front part is housed inside by the interlayer space and thus there is air-pulverized coal flow in the interlayer space, or that the holes in the wall of the front part is not housed inside by the interlayer space and thus there is no air-pulverized coal flow in the interlayer space. Through this interlayer space, the effects can be achieved, such as heat preservation and collection, separation of hot-cold medium, forming of central dense phase are as well as secondary firing front edge oxygen-supplementation and disturbance etc.
According to a preferable embodiment of the present invention, a multiple-stage combination structure of the pulverized coal concentrators is provided, wherein the rear part of the previous stage of concentrator is nested with the front part of the next stage of concentrator consequently. Thus the effect of single stage of concentrator can be strengthened so that all the advantages of the present inventive concentrator are more prominent, and the adaptability to coal quality, air velocity and pulverized coal density is stronger.
According to a preferable embodiment of the present invention, the front part is arranged coaxially to the rear part.
In accordance with the present inventive pulverized coal burner, particularly an internal combustion type burner (in the conventional burners, pulverized coal is ejected into furnace and then is ignited by oil gun, herein the coal is gradually ignited by means of radiation heat of furnace and the convection heat of high temperature flue gas, but in the internal combustion type burners, the pulverized coal is partially ignited inside the burner to begin fire and burn, and then is conveyed into furnace for combustion), it comprises the above-mentioned pulverized coal concentrator.
According to a preferable embodiment of the present invention, the pulverized coal burner also comprises at least one stage of burner chamber and an ignition source.
According to a preferable embodiment of the present invention, the pulverized coal concentrator is arranged between the ignition source and a first stage of burner chamber, the ignition source projects into the bowl-shape structure of the concentrator, and/or the outlet of the concentrator, i.e., the outlet of the cylinder-shaped rear part projects into the first stage of burner chamber.
In the burner, due to the application of said pulverized coal concentrator, the ability of heat-collection is increased and the strength of combustion flame is also improved.
According to a preferable embodiment of the present invention, the ignition source, the pulverized coal concentrator and the burner chambers are arranged coaxially relatively to one another.
According to a preferable embodiment of the present invention, the ignition source is a plasma generator or small oil gun or high-temperature air.
According to a preferable embodiment of the present invention, the plasma generator is arranged in a distance of 10-100 mm from the bowl bottom opening of the front part.
In the present inventive pulverized coal burner, coal particles are forcedly introduced into the present concentrator, through dense-weak separation of pulverized coal via the bowl-shaped structure, denser pulverized coal having lower velocity enters the bowl-shaped structure, and weaker pulverized coal flows into the next stage burner chamber, so that the air-pulverized coal flow is concentrated into a density level necessary for ignition of various types of coal. Preferably, small holes are made in the bowl-shaped structure, the weaker air-pulverized coal flow reaches outside of the concentrator through the holes, so the air velocity inside the concentrator is decreased, also decreasing the negative influence on firing due to enlargement of flow velocity The rear cylinder-shaped structure of the concentrator maintains a proper extension of the dense phase zone of pulverized coal, to avoid insufficient combustion by preventing the pulverized coal entering the bowl-shaped structure from contacting with outside cool air-pulverized coal flow too early during the initial of firing, the ignited pulverized coal will not ignite the outside pulverized coal until it forms a stable flame. The glowing flame expands rapidly at the outlet of the concentrator to mix intensively with the pulverized coal in the outer chamber, producing energy larger than the ignition source to ignite the next stage of pulverized coal.
The present invention produces the following effects:
In the following, the present invention is described in detail with reference to drawings and embodiments, in which:
In the present invention, the pulverized coal concentrator can be designed as an integral structure, that is, the front part 102 and the rear part 101 are made integral, such as by casting or mold injection method, or, the pulverized coal concentrator can also be designed as a split structure, wherein the front part 102 and the rear part are made respectively separately, and the front part and the rear part can be connected together or be arranged apart from one another.
It can also be that the bowl-shaped front part 102 consisted of a camber in
In the present inventive pulverized coal burner, after the starting of the plasma generator 301, high-temperature, high-enthalpy value plasma flame is produced, and the pulverized coal and air flow (also “air-pulverized coal flow”) comes from the bowl opening 109 into the front part 102 of the concentrator, a portion of the air-pulverized coal flow reaches outside of the concentrator via small holes 105 of the bowl-shaped structure, the dense phase air-pulverized coal flow is retained in the concentrator, so the air velocity inside the concentrator is decreased. The small holes 105 may reduce air velocity and decrease the negative influence on firing due to enlargement of flow velocity. Through the guidance and concentration effect of the bowl-shaped structure (with big bowl opening and small bowl bottom opening), the coal particles are forcedly introduced into the central arc area of the plasma flame with higher temperature, the air pulverized coal flow is concentrated to a density level suitable for ignition, the pulverized coal is rapidly ignited at the initial stage after it is ignited by the plasma flame. The air pulverized coal flow enters via the bowl bottom opening 103 into the rear part 101 to be continuously guided, and finally the glowing flame expands rapidly at the outlet of the concentrator to mix intensively with the pulverized coal in the next stage chamber, producing energy larger than the ignition source to ignite the pulverized coal entering the first chamber 201. After the pulverized coal inside the first stage chamber 201, it then ignites the pulverized coal inside the second stage chamber 202 i.e. the outer chamber, and finally ejects into furnace for combustion.
Of course, the present invention is already described in detail based on the present inventive embodiment; however, the present invention is not limited thereto. The present inventive concentrator has the key point of concept that, the front part of the concentrator is designed as a bowl-shaped structure, for guiding and concentrating a gas-solid two-phase flow consisted of concentrated pulverized coal and air, and the rear part is designed as a cylinder-shaped structure, for maintaining a proper extension of the dense phase zone of the air pulverized coal flow, the combination of both realizes the invention object. The front part and the rear part are referred to with respect to the flow direction of the air pulverized coal flow, in the flow direction, the part located front is a front part and the part located rear is a rear part. The person skilled in the art can easily apply the present inventive pulverized coal concentrator to other related technical field, such as industrial furnace, without exercising inventive skills, as practically required. Furthermore, the present inventive pulverized coal concentrator can also be used to concentrate other fluids, such as other gas-solid two-phase flow. These modification variants and other equivalent variants should be deemed to fall within the protection scope of the present patent application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200910119640.3 | Mar 2009 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN10/00354 | 3/23/2010 | WO | 00 | 9/19/2011 |
