U.S. patent application number 13/808119 was filed with the patent office on 2013-05-09 for dense phase swirl pulverized coal burner.
The applicant listed for this patent is Yuehua Li. Invention is credited to Yuehua Li.
Application Number | 20130112120 13/808119 |
Document ID | / |
Family ID | 48141702 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130112120 |
Kind Code |
A1 |
Li; Yuehua |
May 9, 2013 |
Dense Phase Swirl Pulverized Coal Burner
Abstract
A dense phase swirl pulverized coal burner comprises a primary
air channel, a direct flow secondary air channel and a outermost
swirl secondary air channel; and multiple levels of pulverized coal
concentration rings are arranged axially at intervals along the oil
gun casing in a straight tube section of the primary air channel,
so that pulverized coal air flow is distributed thickly outside and
thinly inside the primary air nozzle. In the invention, dense phase
pulverized coal outside the primary air nozzle passes through guide
vanes, forms disturbed flow, is ejected into a furnace and mixes
with high temperature backflow flue gas rapidly and sufficiently at
an outlet. Meanwhile, dilute pulverized coal air flow at the center
is ejected into the furnace by direct flow, ensuring subsequent
mixing and combustion of pulverized coal flow. The primary air
nozzle and the secondary air nozzle are provided with cone flaring
structures with certain angle to effectively control appropriate
mixing of secondary air and pulverized coal. The invention has
advantages of strong ignition and combustion stability, good coal
adaptability, low nitric oxide emission, simple primary air channel
structure and small resistance, which effectively slows wear rate
of parts.
Inventors: |
Li; Yuehua; (Shanghai,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Li; Yuehua |
Shanghai |
|
CN |
|
|
Family ID: |
48141702 |
Appl. No.: |
13/808119 |
Filed: |
February 16, 2012 |
PCT Filed: |
February 16, 2012 |
PCT NO: |
PCT/CN12/71214 |
371 Date: |
January 3, 2013 |
Current U.S.
Class: |
110/264 ;
110/265 |
Current CPC
Class: |
F23D 1/005 20130101;
F23D 2201/20 20130101; F23D 1/02 20130101 |
Class at
Publication: |
110/264 ;
110/265 |
International
Class: |
F23D 1/02 20060101
F23D001/02; F23D 1/00 20060101 F23D001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2011 |
CN |
20111039317.X |
Claims
1. A dense phase swirl pulverized coal burner, characterized by
comprising a primary air channel (1) provided with the following
parts communicated successively: an elbow section as a pulverized
coal inlet, a straight tube section arranged horizontally and a
primary air nozzle; and an oil gun casing (4) arranged on a central
shaft of the straight tube section and a torch oil gun of the
burner arranged inside the oil gun casing (4); a direct flow
secondary air channel (2) arranged around outer wall of the nozzle
of the primary air channel (1), and a swirl secondary air channel
(3) arranged around outer wall of a nozzle of the direct flow
secondary air channel (2) with the direct flow secondary air
channel (2) and the swirl secondary air channel (3) distributed
with air in a same big wind box; wherein, multiple levels of
pulverized coal concentration rings (6) are arranged axially at
intervals along the oil gun casing (4) in the straight tube section
of the primary air channel (1); and each level of the pulverized
coal concentration rings (6) is a cone flaring structure arranged
around outer edge of the oil gun casing (4), and a cone flaring
opening thereof faces the primary air nozzle so that pulverized
coal air flow is distributed thickly outside and thinly inside the
primary air nozzle after being subject to multiple levels of cone
flaring.
2. The dense phase swirl pulverized coal burner according to claim
1, characterized in that the elbow section of the primary air
channel (1) is provided with a pulverized coal flow equalizing
plate (5) arranged around the central shaft of the elbow section
and divided into two-layer air channels in the elbow section; one
end of the pulverized coal flow equalizing plate (5) is arranged on
an inlet of the elbow section, and the other end thereof extends to
an outlet of the elbow section, i.e. the position communicating the
elbow section with the straight tube section so that the pulverized
coal air flow passes through the elbow section, is distributed
uniformly and circumferentially, and enters the straight tube
section.
3. The dense phase swirl pulverized coal burner according to claim
1, characterized in that the nozzle of the primary air channel (1)
is provided with multiple guide vanes (7) arranged uniformly and
circumferentially around inner wall thereof; positions of the guide
vanes (7) are matched with path field of the dense phase pulverized
coal air flow so that the dense phase pulverized coal air flow
forms disturbed flow and is ejected at a certain swirl angle; and
dilute phase pulverized coal air flow at the center of the nozzle
is ejected into an external furnace directly.
4. The dense phase swirl pulverized coal burner according to claim
1, characterized in that outer walls of the nozzles of the primary
air channel (1), the direct flow secondary air channel (2) and the
swirl secondary air channel (3) are provided with flow expanding
cone structures (8, 9, 10) respectively; and cone flaring openings
of the flow expanding cone structures (8, 9, 10) are respectively
arranged toward the external furnace so as to delay mixing time of
secondary air and primary air.
5. The dense phase swirl pulverized coal burner according to claim
1, characterized in that the oil gun casing (4) of the straight
tube section is provided with 2-3 levels of pulverized coal
concentration rings (6), and size of the pulverized coal
concentration rings (6) is enlarged by levels.
6. The dense phase swirl pulverized coal burner according to claim
5, characterized in that a cone flaring angle (.alpha.) of each
level of the pulverized coal concentration rings (6) is within the
range of 10.degree.-25.degree..
7. The dense phase swirl pulverized coal burner according to claim
3, characterized in that the nozzle of the primary air channel (1)
is provided with 10-20 guide vanes (7) around inner wall
thereof.
8. The dense phase swirl pulverized coal burner according to claim
7, characterized in that an included angle between each of the
guide vanes (7) and axial direction of the primary air channel (1)
is 10.degree.-30.degree., and radial height of the guide vanes (7)
along the primary air channel (1) is 0.05-0.1 time the diameter of
the primary air channel (1).
9. The dense phase swirl pulverized coal burner according to claim
4, characterized in that cone flaring angles (.beta.1, .beta.2,
.beta.3) of the multiple flow expanding cone structures are not
more than 45.degree. respectively.
10. The dense phase swirl pulverized coal burner according to claim
1, characterized in that the direct flow secondary air channel (2)
is provided with a regulating device (11) for regulating air flow;
and the swirl secondary air channel (3) is provided with a
regulating device (12) for regulating swirl air strength.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the technical field of coal fired
boilers in power plants, in particular to a dense phase swirl
pulverized coal burner used for a coal-fired boiler.
DESCRIPTION OF THE RELATED ART
[0002] As nitric oxide emissions from boilers of coal-fired power
plants are strictly controlled in China in recent years, a
supporting low NOx burner technology of full furnace staged
combustion low NOX technology is widely used, particularly various
different low NOx swirl burner technologies in wall-fired
boilers.
[0003] In order to effectively reduce nitric oxides produced from
combustion in a furnace of a wall-fired boiler, for the full
furnace staged combustion technology, part of oxygen that is
delivered from a main combustion zone to realize burning-out in
early technologies (i.e. pulverized coal is sent to a burner zone
of the furnace, hereinafter referred to as the main combustion
zone) is supplied to the furnace through a special air port at the
upper part of the furnace in a delayed manner, thus forming
oxygen-deficient combustion atmosphere when chemical equivalent
ratio of air in the main combustion zone is less than 1 and forming
a reducing atmosphere area between the main combustion zone and the
upper air port (burning-out zone), which allows sufficient
reduction of early nitric oxides. Meanwhile, most of the swirl
burners are subject to rich-lean combustion and multichannel
grading air supply mode so as to control mixing time of air and
pulverized coal, form the reducing atmosphere in the burner zone
and achieve the purpose of reducing nitric oxides in the burner
zone.
[0004] However, 3 issues exist for application of the burner
technology: 1, in order to divide pulverized coal air flow in the
primary air channel into dense flow and thin flow
circumferentially, uniformly and effectively, the burner always has
relatively complex structure, which may increase system resistance,
increase fan load and house supply, wear the channel, shorten life
cycle of equipment and increase operation and maintenance cost of
power plants; 2, due to poor adaptability of coal, particularly
poor steam coal in China, actual coal ignition and combustion
stability can not reach original design requirements, and flame at
outlet of the burner is always unstable during peak regulation of
the boiler; and 3, due to poor subsequent mixing performance of
primary air pulverized coal air flow and secondary air pulverized
coal air flow at the nozzle of the burner, coal in the burner
cannot be burnt out, possibly increasing loss.
SUMMARY OF THE INVENTION
[0005] The purpose of the invention is to provide a dense phase
swirl pulverized coal burner used for a coal-fired boiler of a
power plant. The dense phase swirl pulverized coal burner can
enhance mixing of dense phase pulverized coal air flow and outlet
high temperature backflow with the help of dense phase pulverized
coal disturbed flow at a nozzle to realize rapid ignition and
stable combustion of pulverized coal, and control appropriate
mixing of secondary air and primary air so as to enhance subsequent
mixing and burning-out of the pulverized coal air flow. Besides, a
pulverized coal concentration ring inside a primary air channel has
simple structure and small resistance, effectively slowing wear
rate and extending use and maintenance period of equipment.
[0006] In order to achieve the purpose, the technical solution of
the invention is to provide a dense phase swirl pulverized coal
burner which comprises:
[0007] a primary air channel provided with the following parts
communicated successively: an elbow section as a pulverized coal
inlet, a straight tube section arranged horizontally and a primary
air nozzle; and an oil gun casing arranged on a central shaft of
the straight tube section and an torch oil gun of a burner arranged
inside the oil gun casing;
[0008] a direct flow secondary air channel arranged around outer
wall of a nozzle of the primary air channel, and a swirl secondary
air channel arranged around outer wall of a nozzle of the direct
flow secondary air channel with the direct flow secondary air
channel and the swirl secondary air channel distributed with air in
a same big wind box; a regulating device arranged in the direct
flow secondary air channel for regulating air flow; and a
regulating device arranged in the swirl secondary air channel for
regulating swirl air strength.
[0009] The elbow section of the primary air channel is provided
with a pulverized coal flow equalizing plate arranged around the
central shaft of the elbow section and divided into two-layer air
channels in the elbow section; one end of the pulverized coal flow
equalizing plate is arranged at an inlet of the elbow section and
the other end thereof extends to an outlet of the elbow section,
i.e. the position communicating the elbow section with the straight
tube section, so that the pulverized coal air flow passes through
the elbow section to be distributed uniformly and
circumferentially, and enters the straight tube section.
[0010] Multiple levels of pulverized coal concentration rings are
arranged axially at intervals along the oil gun casing in the
straight tube section of the primary air channel; and each level of
pulverized coal concentration ring is a cone flaring structure
arranged around outer edge of the oil gun casing, and a cone
flaring opening thereof faces the primary air nozzle so as to allow
the pulverized coal air flow to be distributed thickly outside and
thinly inside the primary air nozzle after being subject to
multiple levels of cone flaring.
[0011] Preferably, the oil gun casing of the straight tube section
is provided with 2-3 levels of pulverized coal concentration rings,
and size of the pulverized coal concentration rings is enlarged by
levels. Cone flaring angle of each level of pulverized coal
concentration rings is within the range of
10.degree.-25.degree..
[0012] The nozzle of the primary air channel is provided with
multiple guide vanes arranged uniformly and circumferentially
around inner wall thereof; the guide vanes have positions matched
with path field of dense phase pulverized coal air flow outside the
nozzle, and disturb peripheral dense phase pulverized coal only,
thus allowing the dense phase pulverized coal air flow to eject at
a certain swirl angle; and dilute phase pulverized coal air flow at
center of the nozzle will be ejected into an external furnace
directly.
[0013] Preferably, the nozzle of the primary air channel is
provided with 10-20 guide vanes (7) around inner wall thereof An
included angle between each of the guide vanes and axial direction
of the primary air channel is 10.degree.-30.degree., and radial
height of the guide vanes along the primary air channel is 0.05-0.1
time diameter of the primary air channel.
[0014] Outer walls of the nozzles of the primary air channel, the
direct flow secondary air channel and the swirl secondary air
channel are respectively provided with the flow expanding cone
structures, and cone flaring openings thereof are respectively
arranged toward the external furnace to delay mixing time of
secondary air and primary air.
[0015] Preferably, the cone flaring angles of the multiple flow
expanding cone structures are not more than 45.degree..
[0016] Compared with the prior art, the dense phase swirl
pulverized coal burner of the invention has advantages that the
primary air passes through the pulverized coal flow equalizing
plate and forms relatively uniform two layers around the air
channel; due to effect of the multiple levels of pulverized coal
concentration rings in the horizontal straight tube section, the
primary air can distribute thickly outside and thinly inside the
primary air nozzle under the action of cone flaring.
[0017] As the flow expanding cone structures are arranged on the
primary air nozzle and the secondary air nozzle respectively,
mixing time of the secondary air and the primary air is delayed
under the action of cone flaring. Based on reasonable control of
the cone flaring angles, an oxygen-deficient atmosphere is formed
in the primary air during initial ignition, which allows sufficient
reduction of early nitric oxides. Appropriate mixing of the primary
air and the secondary air can keep water cooled walls of the
nozzles to be in an oxidizing atmosphere for a long time,
effectively preventing clogging and high temperature corrosion of
the water cooled wall of the burner zone.
[0018] Besides, due to cone flaring effect of the primary air
nozzle, a high temperature flue gas backflow area is formed around
the nozzle; and multiple guide vanes are arranged on the inner wall
of the nozzle of the primary air channel to disturb the dense phase
pulverized coal before being ejected into the furnace and eject the
dense phase pulverized coal into the high temperature flue gas
backflow area at a certain swirl angle for strong mixed combustion,
thereby achieving the purpose of rapid ignition and enhancing
stable combustion.
[0019] In addition, dilute phase pulverized coal at the center of
the primary air nozzle is ejected into the furnace by direct flow,
which keeps rigidity of the primary air and allows thorough mixing
and burning-out of the subsequent primary air and secondary
air.
[0020] Therefore, the invention can be strongly adaptable to
various types of coal. For different coal types, the cone flaring
angles and grading arrangement of the pulverized coal concentration
rings can be designed to control dense and dilute separation degree
of pulverized coal; radial height of the guide vanes and size of
the included angles between the guide vanes and the axial direction
can be designed to control disturbed flow of dense phase pulverized
coal; and the flow expanding cone structure of the primary air
nozzle can be used to control size of the high temperature backflow
area. According to change of coal quality during operation, swirl
intensity of the secondary air can be regulated by the regulating
device to adapt to ignition and stable combustion requirements of
different types of coal.
[0021] The invention is characterized by simple primary air channel
structure, good wear resistance, strong overall ignition and stable
combustion, good coal adaptability, high efficiency and low nitric
oxide emission.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a sectional view of an overall structure of the
dense phase swirl pulverized coal burner in the invention; and
[0023] FIG. 2 is a schematic diagram of structural layout of guide
vanes of a nozzle of the dense phase swirl pulverized coal burner
in the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] The invention will be described in combination with
accompanied drawings.
[0025] As shown in FIG. 1, the dense phase swirl pulverized coal
burner of the invention (hereinafter referred to as the burner)
comprises a primary air channel 1, a direct flow secondary air
channel 2 arranged around outer wall of a nozzle of the primary air
channel 1, and a swirl secondary air channel 3 arranged around
outer wall of a nozzle of the direct flow secondary air channel 2.
The direct flow secondary air channel 2 and the swirl secondary air
channel 3 are distributed with air in a same big wind box.
[0026] The primary air channel 1 is provided with the following
parts communicated successively: an elbow section as a pulverized
coal inlet, a straight tube section arranged horizontally and a
primary air nozzle. An oil gun casing 4 is arranged on a central
shaft of the straight tube section of the primary air channel 1,
and a torch oil gun of the burner is arranged inside the oil gun
casing 4.
[0027] The elbow section of the primary air channel 1 is provided
with a pulverized coal flow equalizing plate 5 arranged around the
central shaft of the elbow section and divided into interior and
exterior two-layer air channels near and far from a turning center
in the elbow section; one end of the pulverized coal flow
equalizing plate 5 is arranged on an inlet of the elbow section,
and the other end thereof extends to an outlet of the elbow
section, i.e. the position communicating the elbow section with the
straight tube section. Therefore, when primary air pulverized coal
air flow passes through the elbow section of the primary air
channel 1, the pulverized coal flow equalizing plate 5 and the
horizontal straight tube section to form upper and lower two-layer
uniform air flow, thus ensuring that pulverized coal is relatively
circumferential and uniform at the outlet of the elbow section.
[0028] Further, 2-3 levels of pulverized coal concentration rings 6
are arranged axially at intervals along the oil gun casing 4 in the
horizontal straight tube section of the primary air channel 1; and
each level of pulverized coal concentration rings 6 is a cone
flaring structure arranged around outer edge of the oil gun casing
4, a cone flaring opening thereof faces the nozzle, and cone
flaring angles .alpha. of the pulverized coal concentration rings
is within the range of 10.degree.-25.degree.; and size of the
pulverized coal concentration rings 6 is enlarged by levels. After
the pulverized coal air flow uniformly distributed in the straight
tube section under the action of the pulverized coal flow
equalizing plate 5 successively passes through the cone flaring
structures of each of pulverized coal concentration rings 6, most
pulverized coal air flow will be kept in the straight tube section
of the primary air channel 1 due to inertia, flow from the
periphery of the central shaft, and finally be distributed thickly
outside and thinly inside the nozzle of the primary air channel
1.
[0029] As shown in FIG. 1 and FIG. 2, the nozzle of the primary air
channel 1 is provided with multiple guide vanes 7 arranged
uniformly and circumferentially around inner wall thereof (10-20
vanes); an included angle between each of the guide vanes 7 and
axial direction of the primary air channel 1 is
10.degree.-30.degree., and radial height of the guide vanes along
the primary air channel 1 is 0.05-0.1 time diameter of the primary
air channel 1. That is, THE multiple guide vanes 7 are arranged on
an area at the periphery of the channel where the dense phase
pulverized coal flows; dense phase flow is disturbed to eject at a
certain swirl angle before being ejected into the furnace, and the
dilute phase pulverized coal air flow at the center is still
ejected into the furnace along the axis of the channel by direct
flow.
[0030] Flow expanding cone structures facing one end of the furnace
and corresponding to serial number 8, 9 and 10 in FIG. 1 are
arranged on outer walls of the nozzles of the primary air channel
1, the direct flow secondary air channel 2 and the swirl secondary
air channel 3 respectively, thus delaying mixing time of the
secondary air and the primary air under the action of cone flaring.
Based on reasonable control of the cone flaring angles, an
oxygen-deficient atmosphere can be formed in the primary air during
initial ignition, which allows sufficient reduction of early nitric
oxides. The preferred cone flaring angles .beta.1, .beta.2 and
.beta.3 corresponding to the flow expanding cone structures 8, 9
and 10 are not more than 45.degree. respectively.
[0031] In addition, negative pressure is produced due to
arrangement of the flow expanding cone structure 8 in the burner,
and the nozzle of the primary air channel 1 entrains high
temperature flue gas to form an annular high temperature flue gas
backflow area. Thus, the dense phase pulverized coal air flow at
the periphery of the primary air nozzle is disturbed by the guide
vanes 7 and ejected into the high temperature flue gas backflow
area to strongly mix with air there, which can cause rise
temperature of the pulverized coal sharply due to great heat and
ignite the pulverized coal for a moment.
[0032] In addition, according to arrangement of the flow expanding
cone structures 8 and 9, the direct flow secondary air channel 2
and the swirl secondary air channel 3 are provided with regulating
devices 11 and 12 respectively for controlling air flow and swirl
air strength to control mixing time of the secondary air and the
primary air. Appropriate mixing of the primary air and the
secondary air can allow water cooled walls of the nozzles to be in
an oxidizing atmosphere for a long time, effectively preventing
clogging and high temperature corrosion of the water cooled wall of
the burner zone.
[0033] Besides, the dilute phase pulverized coal air flow at the
center of the primary air nozzle is directly ejected into the
furnace along the axis of the channel without disturbed flow, which
can keep rigidity of the primary air and ensure that the primary
air is ejected into a certainly deep position in the furnace.
Subsequently, due to disturbed flow of the swirl secondary air, the
pulverized coal air flow is strongly mixed to ensure subsequent
mixing and combustion of the pulverized coal air flow, reduce
nitric oxides in the burner during initial oxygen-deficient
combustion and achieve the purpose of efficient burning-out of the
pulverized coal.
[0034] Therefore, the invention can be strongly adaptable to
various types of coal. For different types of coal, the cone
flaring angle and grading arrangement of the pulverized coal
concentration rings 6 can be designed to control dense and dilute
separation degree of the pulverized coal; radial height of the
guide vanes 7, and size of the included angle between the guide
vanes 7 and the axial direction can be designed to control
disturbed flow of the dense phase pulverized coal; and the flow
expanding cone structure 8 of the primary air nozzle can be used to
control the size of the high temperature backflow area. According
to changes of coal quality during operation, swirl intensity of the
secondary air can be regulated by the regulating devices 11, 12 to
adapt to ignition and stable combustion requirements of different
types of coal.
[0035] The invention is characterized by simple structure, good
wear resistance, strong ignition and stable combustion, good coal
adaptability, high efficiency and low nitric oxide emission.
[0036] While the invention has been described in detail and with
reference to the preferred embodiment, it is to be understood that
the invention is not restricted thereto. It is apparent to those
skilled in the art that various changes and modifications can be
made therein in accordance with the disclosure. Therefore, scope of
the invention is to be restricted only by the appended claims.
* * * * *