Note: Descriptions are shown in the official language in which they were submitted.
- 20467~30
The present invention relates to a burner wherein
slurry such as a mixture of coal and water (CWM) is used as
fuel.
A conventional slurry burner includes a burner
plug, a burner plate, a burner tip, and a tip nut, wherein
the tip nut fits around the burner plug, the burner plate
and the burner tip to secure them together (see, for
example, Japanese laid-open utility model publication No.
204133/87). The burner plug includes a central fuel supply
bore, and a plurality of spraying medium supply bores
defined around the fuel supply bore in a circumferentially
spaced relationship. The burner plate includes a fuel
distribution chamber communicated with the fuel supply bore
and including passages to distribute a fuel fed from the
fuel supply bore, and a plurality of first mixing chambers
defined to mix the fuel fed from the fuel distribution
chamber through conduits with a spraying medium fed from the
spraying medium supply bores. The burner tip includes a
second mixing chamber communicated with the first mixing
chambers to further mix the fuel and spraying medium, and a
plurality of nozzles formed in one end of the burner tip
remote from the burner plate to spray the mixture out of the
slurry burner.
A fuel such as high density coal-water slurry and
a spraying medium such as compressed air are introduced into
the burner plug. The fuel and the spraying medium then flow
from the fuel supply bore and the spraying medium supply
bores respectively into the burner plate. In the burner
plate, the fuel flows from the fuel distribution chamber
toward the first mixing chambers and is mixed with the
spraying medium. A mixture is then introduced into the
burner tip. The mixture is well mixed in the second mixing
A
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chamber. Thereafter, the mixture is sprayed out of the
slurry burner through nozzles.
The high density coal-water slurry is highly
abrasive. To this end, the burner plate and the burner tip
are protected with a material which has resistance to wear.
SUMMARY OF THE INVENTION
It is an object of the present invention to
provide a slurry burner wherein a mixture of the fuel and
spraying medium fed from a plurality of first mixing
chambers is evenly distributed in a second mixing chamber as
a result of impingement and flows at a reduced speed toward
the inner surface of the second mixing chamber (or burner
tip), and wherein the mixture is well mixed in the second
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of the burner tip and spray the mixture in homogeneous state.
It is another object of the present invention to provide
a slurry burner wherein fuel is subjected to shear while it
flows along the inner wall of the second mixing chamber so as
to eliminate large droplets of fuel in spraying.
According to the present invention, there is provided
a slurry burner comprising a burner plug including a fuel
supply bore through which fuel slurry is supplied, and
a plurality of spraying medium supply bores through which a
spraying medium is supplied, a burner plate including a fuel
distribution chamber defined to distribute the fuel, and a
plurality of first mixing chambers defined to mix the fuel
supplied from the fuel distribution chamber with the spraying
medium supplied from the spraying medium supply bores of
the burner plug; and a burner tip including a second mixing
chamber defined between the burner tip and the burner plate to
further mix a mixture of fuel and spraying medium received from
the first mixing chambers of the burner plate, and a plurality
of nozzles through which the mixture is sprayed out
of the slurry burner, wherein the first mixing chambers has
respective axis along which the mixture flows, the axis of
which are inclined to intersect with one another in the second
mixing chamber.
With the slurry burner of the present invention, fuel
in slurry state is first fed from the fuel supply bore of the
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burner plug to the first mixing chambers through the fuel
distribution chamber of the burner plate. Spraying medium is
also fed from the spraying medium supply bores of the burner
plug to the first mixing chambers of the burner plate for
mixture with the fuel. A resultant mixture is then fed to
the second mixing chamber of the burner tip. After the mixture
has been mixed further in the second mixing chamber, it is
sprayed from the nozzles for combustion purposes. When mixtures
flow out of the first mixing chamber, they intersect in the
second mixing chamber. This results in impingement of the
mixtures and thus, even dispersion of the mixtures. After
the mixtures are fully mixed in the second mixing chamber,
they are sprayed out of the slurry burner.
Even dispersion in the second mixing chamber allows
the mixtures to impinge against the inner surface of the burner
tip at a slower speed than when the mixtures flow out of the
first mixing ch~her. This results in a substantial decrease
in wear of the burner tip.
Additionally, ful~ mixture in the second mixing chamber
results in homogeneous state of the spraying fuel.
The fuel is fully agitated as a result of impingement
upon introduction into the second mixing chamber from the
first mixing chambers. The fuel is subject to shear while
it flows along the inner wall of the second mixing chamber.
This produces a thin film of fuel to eliminate large droplets
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of fuel in spraying.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional view of a slurry burner
according to one embodiment of the present invention;
Fig. 2 is a sectional view showing the slurry burner
in use;
Fig. 3 is a sectional view of a conventional slurry
burner; and
Fig. 4 is a view showing a boiler system incorporating
the burner of the present invention.
DESCRIPTION OF THE PK~ K~:~ EMBODIMENT
The present invention will now be described by way of
example with reference to the accompanying drawings.
Fig. 1 illustrates one embodiment of the present
invention. Like elements are designated by like reference
numerals as used ln Fig. 3.
In this embodiment, six first mixing chambers 6 are
defined in a burner plate 4 in a circumferentially equally
spaced relationship. These first mixing chambers 6 are inclined
inwardly toward a second mixing chamber 8 and intersect with another
at the point C. Preferably, the position of the point C is
such that Q / L is 0.5 to 0.8, where Q is the distance between
the point C and an end surface of the burner tip 7, and L is
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the inner length of the burner tip 7.
A burner tip 7 has eight nozzles 9 in a circumferen-
tially equally spaced relationship.
In this embodiment, a burner plug 1 includes a central
or inner tube lA and an outer tube lB which these tubes are
coaxial. A flange la extends radially outwardly from one
end of the inner tube lA to contact with the burner plate 4.
The inner tube lA defines a fuel supply bore 2 to receive a
mixture of coal and water (CWM) through a conduit 12.
A plurality of bores formed in the flange la of the inner tube
lA is spraying medium supply bores 3 through which steam flows.
In the embodiment shown in Fig.l, a portion of the first
mixing chamber 6 which is upstream of the conduit 5a is smaller
in diamter than the rest of the first mixing chamber 6.
The structure of the remaining components is similar
to that shown in Fig. 3 with the exception of the material
which has resistance to wear.
With the slurry burner thus constructed, fuel in slurry
state is fed from the fuel supply bore 2 of the burner plug
1 to the first mixing chamber 6 through a fuel distribution
chamber 5. Spraying medium flows from the spraying medium
supply bores 3 to the first mixing chamber 6 of the burner
plate 4 to mix with the fuel. The fuel and the spraying
medium are further mixed in the second mixing chamber 8. The
fuel is then sprayed from the nozzles 9 for combustion
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purposes. The mixtures flow from the first mixing chambers 6
and then intersect with one another in the second mixing
chamber 8. By this arrangement, the mixtures can evenly be
dispersed as a result of impingement before they are sprayed
from the nozzles 9.
Even dispersion in the second mixing chamber 8 allows
the mixtures to impinge against the inner surface of the burner
tip 7 at a slower speed than when the mixtures flow out of the
first mixing chamber 6. This results in a substantial decrease
in wear of the burner tip 7.
Additionally, full mixture in the second mixing chamber
results in homogeneous state of the spraying fuel.
As shown in Fig. 2, the fuel is fully agitated as a
result of impingement upon introduction into the second mixing
chamber 8 from the first mixing chambers 6. The fuel is
subject to shear while it flows along the inner wall of the
second mixing chamber 8. This produces a thin film of fuel
to eliminate large droplets of fuel in spraying.
The burner tip 7 as well as the burner plate 4 is
vulnerable to wear and preferably, made of ceramic (such as
silicon nitride) to provide resistance to wear.
In the present invention, after combustion is completed
it is preferable to feed water, steam or air to the fuel SUpply
bore 2 in the slurry burner so as to purge or remove
any residue.
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Fig. 4 shows a fuel system for use in a boiler 21
incorporating the burners 20 thus far described.
A mixture of coal and water (CWM) is supplied to
a tank 32 through a pipe 31. The mixture is then supplied
5 from the tank 32 to two single screw fuel injection pumps 35
and 36 through a corresponding pair of lines 33 and 34. The
pumps 35 and 36 are connected through a pair of strainers 37
and 38 to the burners 20. The mixture thus flows from the
pumps 35 and 36 through the strainers 37 and 38 to the
burners 20. 39 and 40 are lines through which an extra
amount of CWM is returned to the tank 32. 41 is a heavy oil
burner mounted to the boiler 21. 42 is a heavy oil feed
line. The strainers 37 and 38 are operable to separate
granule which is, in turn, disintegrated in a CWM sludge
15 mixer 43. The granule thus disintegrated is then returned
to the tank 32. 44 iS an automatic combustion controller
(ACC) operable to control the amount of CWM to be supplied
in response to the load of the boiler.
The prior art is shown in Fig. 3, which shows a
20 conventional slurry burner which includes a burner plug 1,
a burner plate 4, a burner tip 7, and a tip nut 10, wherein
the tip nut 10 fits around the burner plug 1, the burner
plate 4, and the burner tip 7 to secure them together. The
burner plug 1 includes a central fuel supply bore 2, and a
25 plurality of spraying medium supply bores 3 defined around
the fuel supply bore 2 in a circumferentially spaced
relationship. The burner plate 4 includes a fuel
distribution chamber 5 communicated with the fuel supply
bore 2 and including passages to distribute a fuel fed from
30 the fuel supply bore 2, and a plurality of first mixing
chambers 6 defined to mix the fuel fed from the fuel
distribution chamber 5 through conduits 5a with a spraying
medium fed from the spraying medium supply bores 3. The
burner tip 7 includes a second mixing chamber 8 communicated
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with the first mixing chambers 6 to further mix the fuel and
spraying medium, and a plurality of nozzles 9 formed in one
end of the burner tip remote from the burner plate 4 to
spray the mixture out of the slurry burner.
A fuel such as high density coal-water slurry and
a spraying medium such as compressed air are introduced into
the burner plug 1. The fuel and the spraying medium then
flow from the fuel supply bore 2 and the spraying medium
supply bores 3 respectively into the burner plate 4. In the
burner plate 4, the fuel flows from the fuel distribution
chamber S toward the first mixing chambers 6 and is mixed
with the spraying medium. A mixture is then introduced into
the burner tip 7. The mixture is well mixed in the second
mixing chamber 8. Thereafter, the mixture is sprayed out of
the slurry burner through nozzles 9.
The high density coal-water slurry is highly
abrasive. To this end, the burner plate 4 and the burner
tip 7 are protected with a material which has resistance to
wear.
8a
