WALL-ARRANGED GIANT RING-SHAPED STRAIGHT-THROUGH PULVERIZED COAL BURNER

Abstract

A wall-arranged giant ring-shaped direct-current pulverized coal burner includes burner nozzles arranged on four side furnace walls of a boiler. The burner nozzles on the four side furnace walls form a wall-tangential combustion mode in the furnace, and the burner nozzles on each side furnace wall are arranged in a ring by a plurality of small nozzles to form a giant ring-shaped combined nozzle. There is a plurality of small nozzles arranged in a ring on each side furnace wall to form a giant ring-shaped combined nozzle. The giant ring-shaped combined nozzles on the four side furnace walls may form a wall- tangential combustion mode in the furnace. Through the mutual entrainments of the multiple airflows in the giant ring-shaped combined nozzle and the mutual support of the fireside and back-fire-side airflows, the stiffness of each airflow may be effectively enhanced.

Description

TECHNICAL FIELD

The present disclosure relates to the technical field of boiler burners, particularly to a wall-arranged straight-through pulverized coal burner.

BACKGROUND

The existing straight-through pulverized coal burners of large pulverized coal boilers in power plants are mainly arranged in a four-comer tangential mode or a four-wall tangential mode. In the four-comer tangential mode and the four-wall tangential mode, all straight-through burners are simply arranged along the same vertical line at four corners or on four furnace walls. For example, Chinese invention patent with No. CN102494333B discloses a single-fireball tangentially-firing boiler for the burning of anthracite; and Chinese utility model patent with No. CN204358718U discloses a nozzle device of a burner of a wall-type tangential firing pulverized coal boiler.

In the existing arrangements, the stiffness of each single airflow is used to resist strong impingement of the synthetic swirling flue gas flow (or upstream gas flow) in the furnace. Furthermore, due to the narrow gap among the vertically arranged nozzles, air supplement condition at the back-fire side of the injected airflow is poor, which further increases the deflection of the injected airflow along the horizontal direction and even leads to the phenomenon of airflow scouring the furnace walls. Therefore, under the condition that the linear arrangement in each burner group remains unchanged, the traditional improvement measures include: grouping burner nozzles along the furnace height direction to increase the distance between burner groups and to improve the problem of insufficient air supplement at the back-fire side of each group of burner nozzles; adopting large-chamfer arrangement to improve air supplement conditions at the back-fire side of the comer-injected airflows: adopting wall-arranged burners to enable the burners to be far away from the downstream wall surfaces, so as to better improve the air supplement conditions on the back-fire side of the airflow. However, all the above improvement measures have limited effects and have failed to completely solve the problem of large deflection of the injected airflows because the single airflow from each burner nozzle cannot resist the strong impingement force of the swirling flue gas and the upstream airflow. So, it is difficult to control the actual combustion tangent circle diameter in the furnace, and the phenomenon of airflow scouring on furnace walls occurs sometimes, resulting in the occurrence of major accidents such as combustion instability, slagging, high-temperature corrosion, flue gas temperature deviation, and over-temperature tube explosion.

SUMMARY

A technical problem to be solved by some embodiments of the present disclosure is to provide a new wall-arranged giant ring-shaped straight-through pulverized coal burner, which is used to solve the problems of airflow deflection and the subsequent flame scouring on the furnace walls caused by the insufficient airflow rigidity in existing boilers, as well as the problems of slagging and high-temperature corrosion on the heating surfaces of the furnace caused by the flame scouring on furnace walls.

In order to solve the above problems, a wall-arranged giant ring-shaped straight-through pulverized coal burner is provided. The burner includes burner nozzles arranged on four side furnace walls of a boiler, and the burner nozzles on the four side furnace walls form a wall-tangential combustion mode inside the furnace. Each burner nozzle on each side furnace wall includes multiple small nozzles arranged along a ring to form a giant ring-shaped combined nozzle.

In some embodiments, the small nozzles forming the giant ring-shaped combined nozzle are arranged along a circular ring, an elliptical ring or a rectangular ring.

In some embodiments, in the main combustion region inside the furnace, a plurality of the giant ring-shaped combined nozzle are installed on each side furnace wall along a furnace height direction.

In some embodiments, on each side furnace wall corresponding to the main combustion region inside the furnace, the giant ring-shaped combined nozzle includes a plurality of small primary air nozzles and a plurality of small secondary air nozzles arranged along a ring.

In some embodiments, the plurality of small primary air nozzles and the plurality of small secondary air nozzles are arranged at intervals with one another along a ring.

In some embodiments, the plurality of small primary air nozzles and the plurality of small secondary air nozzles are arranged on a circular ring, an elliptical ring or a rectangular ring in a two-two or three-three concentrated mode.

In some embodiments, the plurality of small primary air nozzles and the plurality of small secondary air nozzles are arranged on two concentric circular rings, two elliptical rings or two rectangular rings respectively.

In some embodiments, the plurality of small primary air nozzles and the plurality of small secondary air nozzles are respectively arranged on two circular rings which have equal diameters and are not concentric.

In some embodiments, on each side furnace wall corresponding to a burnout area at an upper part of the furnace, the giant ring-shaped combined nozzle includes a plurality of small separated over fire air nozzles arranged in a ring.

In some embodiments, the small nozzles installed on each side furnace wall can be adjusted upward, downward, leftward and rightward.

Compared with the prior art, the present disclosure has the following beneficial effects.

In some embodiments of the present disclosure, on each side furnace wall, the plurality of small nozzles is arranged along the ring to form the giant ring-shaped combined nozzle, and the giant ring-shaped combined nozzles on four side furnace walls can form the wall-tangential combustion mode in the furnace. The giant ring-shaped combined nozzle can effectively enhance the stiffness of each airflow through the mutual entrainment of the airflows within the giant ring-shaped combined nozzle and through the mutual support of the fireside airflows and the back-fire side airflows, thereby alleviating the phenomenon of flame scouring on the furnace walls caused by the rapid attenuation of the airflow stiffness and thus fundamentally reducing the risk of slagging and high-temperature corrosion on the heating surface of the furnace,

Different from the one-level mode in the existing boiler in which a single airflow from the burner nozzle directly interacts with the main flue gas inside the furnace, some embodiments of the present disclosure adopt a two-level mode; more specially, firstly multiple single-burner nozzles are assembled into a giant ring-shaped combined nozzle, and then these combined airflows injected from the giant ring-shaped combined nozzle interact as a whole with the main flue gas inside the furnace. As an intermediate level between the lower level of a single small nozzle and the higher level of the whole furnace burners, the giant ring-shaped straight-through pulverized coal burner makes the combined airflows has a strong overall stiffness and thus the resistance to the transverse impingement of the swirling flue gas inside the furnace, so the scheme of burner present in this disclosure has a stronger constraint on the main swirling flue gas inside the furnace. Therefore, the combined airflows injected from the giant ring-shaped combined nozzle have a strong anti-deflection ability, which better overcomes the huge problem that flow aerodynamic conditions inside the furnace become more and more difficult to be organized with the increase in boiler capacity, and thereby forming a stable and reasonable actual combustion tangential circle. So, the burner in the present disclosure completely overcomes the difficult problem of poor air supplement condition on the back-fire side of the airflows caused by the vertical arrangement of burners in the traditional burner scheme, thus effectively eliminating the phenomenon of flame scouring on furnace walls; as a result, the problem of slagging and high-temperature corrosion on the heating surface of the boiler with large capacity has been fundamentally solved. Furthermore, some embodiments of the present disclosure can also improve the combustion uniformity in the furnace and increase the combustion temperature, which is conducive to promoting combustion stability of low-quality coal and reducing the generation of nitrogen oxides.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a boiler using a wall-arranged giant ring-shaped straight-through pulverized coal burner according to the present disclosure.

FIG. 2 is a schematic diagram of the giant ring-shaped combined nozzle formed by small nozzles with square end sections.

FIG. 3 is a schematic diagram of the giant ring-shaped combined nozzle formed by small nozzles with circular end sections.

FIG. 4 is a schematic diagram of the giant ring-shaped combined nozzle formed by small nozzles with rectangular end sections.

FIG. 5 is a schematic diagram of the giant ring-shaped combined nozzle formed by small nozzles arranged along an elliptical ring.

FIG. 6 is a schematic diagram of the giant ring-shaped combined nozzle formed by small nozzles arranged along a rectangular ring.

FIG. 7 is a schematic diagram showing small primary air nozzles and small secondary air nozzles arranged on two concentric circular rings.

FIG. 8 is a schematic diagram showing the small primary air nozzles and the small secondary air nozzles arranged on two circular rings that have equal diameters and are not concentric.

FIG. 9 is a schematic diagram showing the small primary air nozzles and the small secondary air nozzles arranged in a two-two concentrated mode.

FIG. 10 is a schematic diagram showing the small primary air nozzles and the small secondary air nozzles arranged in a three-three concentrated mode.

FIG. 11 is a comparison diagram showing the velocity distributions in a boiler furnace with traditional burners and a boiler furnace with burners of the present disclosure.

FIG. 12 is a comparison diagram showing the temperature distributions in the boiler furnace with the traditional burners and a boiler furnace with the burners of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The specific embodiments of the present disclosure are further described in detail below in combination with the accompanying drawings. These embodiments are only used to explain the present disclosure, not to limit the present disclosure.

In the description of the present disclosure, the terminology used herein for the purpose of describing particular examples is not intended to be limiting for further examples. Whenever a singular form such as “a”, “an” and “the” is used and using only a single element is neither explicitly or implicitly defined as being mandatory, further examples may also use plural elements to implement the same functionality. It should be noted that orientation or position relationships indicated by the terms “center”, “longitudinal”, “lateral”, “up”, “down”, “inner”, “outer” and so on are based on the orientation or position relationships shown in the drawings, which are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element mentioned must have a specific orientation, be constructed or operated in a specific orientation: therefore, it cannot be understood as a limitation of the present disclosure.

Furthermore, in the description of the present disclosure, unless otherwise stated, “multiple” means two or more.

As shown in FIG. 1, the present disclosure provides a wall-arranged giant ring-shaped straight-through pulverized coal burner. The burner includes burner nozzles arranged on four side furnace walls 100 of the boiler. The burner nozzles on the four side furnace walls 100 can form a wall-tangential combustion mode in the furnace. Different from the prior art, each burner on each side furnace wall 100 is formed by multiple small nozzles arranged along a ring, giant ring-shaped combined nozzles 10, 20, 30, 40 are formed on each furnace wall. These giant ring-shaped combined nozzles 10, 20, 30 and 40 are arranged at different heights of the furnace wall 100. Four giant ring-shaped combined nozzles (such as the four giant ring-shaped combined nozzles 10) on the four side furnace walls 100 at the same height are installed with a certain distance deviated from the centerlines of the furnace walls 100.Therefore, airflows ejected from the four giant ring-shaped combined nozzles interact with one another in the furnace to form a suitable combustion tangential circle, that is, a wall-tangential combustion mode.

A distance from the installation center of each giant ring-shaped combined nozzle to its adjacent downstream furnace wall should be generally greater than 0.7 times of the equivalent diameter of giant ring-shaped combined nozzle, so that there is a certain distance from the small nozzles on the back-fire side of the giant ring-shaped combined nozzle to the adjacent downstream furnace wall, to prevent the injected airflows from adhering to the furnace wall caused by that the airflows on the back-fire side of the giant ring-shaped combined nozzle is too close to the adjacent wall surface.

As shown in FIGS. 2, 3 and 4, the end section of each of the small nozzles 1 and 2 forming the giant ring-shaped combined nozzle may be square, circular or rectangular, or C-shaped as disclosed in the Chinese Patent CN104676585B.

As shown in FIG. 4. 5 and 6, the small nozzles 1 and 2 forming the giant ring-shaped combined nozzle may be arranged along a circular ring (as shown in FIG. 4), an elliptical ring (as shown in FIG. 5) or a rectangular ring (as shown in FIG. 6).

As shown in FIG. 1, the giant ring-shaped combined nozzles on the furnace walls 100 include a plurality of giant ring-shaped combined nozzles 10, 20 and 30 in the main combustion region of the furnace, and a plurality of giant ring-shaped combined nozzles 40 in the burnout area of the furnace. Each giant ring-shaped combined nozzle 40 in the burnout area of the furnace is formed by a plurality of small separated over fire air nozzles arranged in a ring-shaped mode. As shown in FIGS. 2-10, on the furnace walls corresponding to the main combustion region of the furnace, each giant ring-shaped combined nozzle is formed by a plurality of small primary air nozzles 1 and a plurality of small secondary air nozzles 2 arranged in a ring-shaped mode.

In a preferred embodiment, each giant ring-shaped combined nozzle 10, 20 and 30 in the main combustion region includes 6 small primary air nozzles 1 and 6 small secondary air nozzles 2, and each giant ring-shaped combined nozzle 40 in the burnout area includes 12 small separated over fire air nozzles. Small nozzles with square end sections are adopted, in which a side length of each small primary air nozzle 1 is 0.36 meters, a side length of each small secondary air nozzle 2 is 0.44 meters, a side length of each small over-fired air nozzle is 0.36 meters, and an equivalent ring diameter of the giant ring-shaped combined nozzle is 3.6 meters.

An area of the end section of the small primary air nozzle 1 may be less than, equal to or greater than that of the small secondary air nozzle 2.

As shown in FIGS. 2-6, the small primary air nozzle 1 and the small secondary air nozzle 2 are arranged along the ring at intervals: more specially, the small primary air nozzle 1 and the small secondary air nozzle 2 are alternately arranged on the same circular ring, the same elliptical ring or the same rectangular ring to enhance the interactions between the fuel stream and the combustion air to promote their mixing.

As shown in FIG. 7, the small primary air nozzle 1 and the small secondary air nozzle 2 are arranged along two concentric circular rings to form a giant ring-shaped combined nozzle. In some embodiments, the small primary air nozzle 1 and the small secondary air nozzle 2 may also be arranged along two concentric elliptical rings or two concentric rectangular rings to form a giant ring-shaped combined nozzle. FIG. 7 shows that the small primary air nozzles 1 are arranged on the large outer ring, and the small secondary air nozzles 2 are arranged on the small inner ring, which could be exactly opposite in other embodiments.

As shown in FIG. 8, the small primary air nozzles 1 and the small secondary air nozzles 2 may also be arranged along two circular rings that have equal diameters and are not concentric, to form a giant ring-shaped combined nozzle.

As shown in FIG. 9, the small primary air small nozzles 1 and the small secondary air small nozzles 2 may also be arranged on a circular ring, an elliptical ring or a rectangular ring in a two-two concentrated mode; more specially, each two adjacent small primary air nozzles 1 and each two adjacent small secondary air nozzles 2 are alternately arranged along a ring to form a giant ring-shaped combined nozzle.

As shown in FIG. 10, the small primary air nozzles 1 and the small secondary air nozzles 2 may also be arranged along a circular ring, an elliptical ring or a rectangular ring in a three-three concentrated mode; more specially, three adjacent small primary air nozzles 1 and three adjacent small secondary air nozzles 2 are alternately arranged along a ring to form a giant ring-shaped combined nozzle.

The total number of the small primary air nozzles and the small secondary air nozzles in each giant ring-shaped combined nozzle may be not less than 5, which may be increased with increasing boiler capacity. Power of each small primary air nozzle is not less than 3~5 MW. A diameter or an equivalent diameter of each giant ring-shaped combined nozzle is not less than 1 meter, which increases with increasing boiler capacity. The above equivalent diameter refers to a diameter of a circle which has an area equal to the ring. For the giant ring-shaped combined nozzle with the small nozzles arranged along two rings, the equivalent diameter refers to an average value of equivalent diameters of the two rings.

In some embodiments, in order to facilitate installation, the small primary and secondary air nozzles of the giant ring-shaped combined nozzle are installed perpendicular to the furnace wall surface, which reduces the sensitivity to the installation angle compared with the existing four-corner tangential boiler. Furthermore, the small nozzles can be adjusted upward, downward, leftward and rightward; more specially, an angle between the small primary air nozzle and the furnace wall surface and an angle between the small secondary air nozzle and the furnace wall surface can be adjusted upward, downward, leftward and rightward according to the operation requirements, for controlling the size of the actual tangential circle and the adjustment of the flame center position.

The inventor carried out computational fluid dynamics (CFD) numerical simulation on the tangentially-fired pulverized coal boiler with the traditional wall-arranged burners and the pulverized coal boiler with the giant ring-shaped straight-through pulverized coal burners of the present disclosure to analyze the in-furnace flow and combustion differences under such two schemes. The calculation results are shown in FIGS. 11-12, where FIG. 11 shows the velocity contour on cross sections at different heights in the furnace under two burner arrangements, and FIG. 12 shows the temperature field contour on the vertical middle sections in the furnace under the two burner arrangements.

From FIG. 11, it can be seen that, compared with the boiler with the traditional wall-arranged straight-through burners, a better tangential combustion circle is formed in the furnace of the boiler with the burners of the present disclosure, wherein the high-velocity zone near the furnace walls is reduced, and the phenomenon of flame scouring on furnace walls is significantly alleviated. Therefore, the risk of slagging and high-temperature corrosion on the heating surface of the furnace caused by flame scouring on furnace walls is fundamentally reduced, thereby improving the operation reliability of the boiler.

It can be seen from FIG. 12 that, the combustion temperature level in the boiler with the burner of the present disclosure is increased significantly, which indicates that adopting the scheme of burner of the present disclosure is also conducive to the processes of coal combustion and the subsequent heat release, thereby facilitating the improvement on the boiler efficiency. In addition, it can be seen that, compared with the boiler adopting the traditional wall-arranged tangential burners, the area of the low-temperature zone at the furnace center of the boiler using the burner of the present disclosure is smaller, which shows that the traditional near-wall circular flame combustion mode can be transformed into a more uniform volume combustion mode in the present disclosure, which is conducive to improving the combustion uniformity in the furnace.

In the present disclosure, the mutual entrainments of multiple airflows in the giant ring-shaped combined nozzle make it difficult for each individual airflow to diffuse to the external space, thus helping to enhance the overall stiffness of the combined airflows. Furthermore, the swirling flue gas flow and the deflected upstream airflow in the furnace mainly impinge the fire-side airflows from the giant ring-shaped combined nozzle, while the back-fire side airflows can maintain a strong stiffness since they are not directly impinged. The back-fire side airflows with stronger stiffness play a role in supporting the fireside airflows that may be deflected, so it can effectively prevent the large deflection of the fireside airflows.

The present disclosure provides a wall-arranged giant ring-shaped straight-through pulverized coal burner, which is particularly suitable for reconstruction of the existing boilers and design of new boilers with large capacity of 200MW and above and with large size of furnace. The wall-arranged giant ring-shaped straight-through pulverized coal burner can significantly overcome the problems such as airflow scouring on furnace walls caused by the insufficient airflows stiffness, and the subsequent slagging and high-temperature corrosion on the heating surface caused by the airflow scouring on furnace walls in large capacity boilers, which can make the boiler operate more safely and stably. Furthermore, it is beneficial to control the formation of nitrogen oxides during coal combustion process. In conclusion, the present disclosure can effectively overcome the defects in the prior art and improve the safety and stability of boiler operation, so it has high industrial application value.

The above embodiments only illustrate the principle and effect of the present disclosure, not limit the present disclosure. Any person ordinarily skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present disclosure shall still be covered by the claims of the present disclosure.

Claims

1. A wall-arranged giant ring-shaped straight-through pulverized coal burner, comprising burner nozzles arranged on four side furnace walls of a boiler, the burner nozzles on the four side furnace walls form a wall-tangential combustion mode inside the boiler furnace, wherein each burner nozzle on each side furnace wall comprises a plurality of small nozzles arranged along a ring to form a giant ring-shaped combined nozzle.

2. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 1, wherein the small nozzles forming the giant ring-shaped combined nozzle are arranged along a ring selected from a group consisting of a circular ring, an elliptical ring and a rectangular ring.

3. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 1, wherein on each side furnace wall corresponding to a main combustion region inside the furnace, a plurality of the giant ring-shaped combined nozzles are provided along a furnace height direction.

4. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 1, wherein on each side furnace wall corresponding to the main combustion region inside the furnace, the giant ring-shaped combined nozzle comprises a plurality of small primary air nozzles and a plurality of small secondary air nozzles arranged along the ring.

5. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 4, wherein the plurality of small primary air nozzles and the plurality of small secondary air nozzles are arranged at intervals with one another along the ring.

6. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 4, wherein the plurality of small primary air nozzles and the plurality of small secondary air nozzles are arranged on a ring selected from a group consisting of a circular ring, an elliptical ring and a rectangular ring in a mode selected from a group consisting of a two-two concentrated mode and a three-three concentrated mode.

7. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 4, wherein the plurality of small primary air nozzles and the plurality of small secondary air nozzles are arranged on two rings selected from the group consisting of two concentric circular rings, two elliptical rings and two rectangular rings.

8. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 4, wherein the plurality of small primary air nozzles and the plurality of small secondary air nozzles are respectively arranged on two circular rings which have equal diameters and are not concentric.

9. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 1, wherein on each side furnace wall corresponding to a burnout area at an upper part of the furnace, the giant ring-shaped combined nozzle comprises a plurality of small separated over fire air nozzles arranged in a ring.

10. The wall-arranged giant ring-shaped straight-through pulverized coal burner according to claim 1, wherein the small nozzles installed on the side furnace wall are adjusted upward, downward, leftward and rightward.