AU632953B2 - Slurry burner - Google Patents

Description

6329 3 AUSTRALIA Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: SLURRY BURNER.

The following statement is a full description of this invention, including the best method of performing it known to me:-

I

SLURRY BURNER Field of the Invention and Related Art Statement The present invention relates to a burner wherein slurry such as a mixture of coal and water (CWM) is used as fuel.

As shown in Fig. 3, a conventional slurry burner includes a burner plug i, a burner plate 4, a burner tip 7, and a tip nut wherein the tip nut 10 fitsaround the the burner plug i, the burner plate 4, and the burner tip 7 to secure them together (see, for example, Japanese laid-open utility model publication No. 204133/87). The burner plug 1 includes a central fuel supply bore 2, and a 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 the fuel supply bore 2, and a plurality of first mixing chambers 6 defined to mix the fuel fed from the fuel distribution ciamber 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 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 i U- 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 i. 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 5 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.

SUMMARY OF THE INVENTION The present invention provides a slurry burner comprising: a burner plug including a fuel supply bore through which a fuel in slurry state 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 for distributing the fuel, and a plurality of first mixing chambers for mixing the fuel supplied from said fuel distribution chamber with the spraying medium supplied from said spraying medium supply bores of the burner plug; and a burner tip including a second mixing chamber, between the burner tip and said burner plate, for mixing a mixture of fuel and spraying medium received from said I':i t~ o 3 first mixing chambers of said burner plate, and a plurality of nozzles through which the mixture is sprayed out of the slurry burner; and said first mixing chambers having respective axes along which the mixture flows, said axes being inclined to intersect with one another in said 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 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 chamber. This results in a substantial decrease in wear of the burner tip.

Additionally, full 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 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 PREFERRED 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 in 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 e L is 0.5 to 0.8, where V is the distance between the point C and an end surface of the burner tip 7, and L is the inner length of the burner tip 7.

A burner tip 7 has eight nozzles 9 in a circumferentially equally spaced relationship.

In this embodiment, a burner plug 1 includes a central or inner tube 1A and an outer tube lB which these tubes are coaxial. A flange la extends radially outwardly from one end of the inner tube 1A to contact with the burner plate 4.

The inner tube 1A 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 1A 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 7 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.

7 _iA rj ~i 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 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 and 36 are connected through a pair of strainers 37 and 38 to the burners 20. The mixture thus flows from the pumps and 36 through the strainers 37 and 38 to the burners 20. 39 and 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 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.

Claims (6)

1. 2. A slurry burner according to claim i, wherein k L is 0.5 to 0.8, where Z is the axial distance between the inner surface of said burner tip and a point at which said axes of the first t mixing chambers intersect, and L is the axial distance between an end surface of said burner plate and the inner surface of said burner tip.
2. 3. A slurry burner according to claim 1 or 2, wherein said fuel distribution chamber is centrally defined in one side of said burner plate, and said plurality of first mixing chambers are defined around said fuel distribution chamber in a circumferentially equally spaced relationship, and wherein said fuel distribution chamber and said first mixing chambers are communicated with one another through conduits.
3. 4. The slurry burner according to any one of claims 1 to 3, wherein said burner plate includes at least six first mixing chambers. A slurry burner according to any one of claims 1 to 4, wherein said burner tip includes at least eight nozzles.
4. 6. A slurry burner according to any one of claims 1 to 5, wherein said nozzles are defined in said burner tip in a circumferentially equally spaced relationship.
5. 7. A slurry burner according to claim 6, wherein said nozzles of the burner tip are greater in number than said first mixing chamber of the burner plate.
6. 8. A slurry burner according to any one of claims 1 to 3, wherein the slurry is a mixture of coal and water. Dated this 6th day of November 1992 UBE INDUSTRIES, LTD. By Its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. 1- (I ABSTRACT OF THE DISCLOSURE A slurry burner comprises a burner plug including a fuel supply bore through which a 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 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. The first mixing chambers has respective axis along which the mixture flows, the axis of which is inclined to intersect with one another in the second mixing chamber. I