US3568932A

US3568932A - Ceramic burners

Info

Publication number: US3568932A
Application number: US867988A
Authority: US
Inventors: Jacobus Van Laar; Johannes H W Ouwerkerk
Original assignee: Didier Werke AG
Current assignee: Didier Werke AG
Priority date: 1968-10-19
Filing date: 1969-10-17
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09
Also published as: LU59663A1; GB1290503A; JPS4933373B1; DE1803984B2; AT297905B; DE1803984A1; FR2021086A1; BE740316A

Abstract

A ceramic burner for hot blast stoves for blast furnaces. A ceramic block has a central hole and a crown of holes surrounding it. A vertical conduit feeds gaseous fie; and a second coaxial conduit supplies combustion air. The conduits have their upper ends passing through the holes. The upper surface of the block slants upwardly from the central hole and the holes of said crown are directed toward the prolonged axis of the central hole. The central hole has essentially the shape of a rectangular slot and the sloping part of the upper surface of the block comprising essentially two flat surfaces which comprise an angle of 40*120*, and the crown of holes is subdivided into two rows of holes running parallel to each other and to the longitudinal sides of said central hole. The rectangular shape of the central hole shows a ratio of length versus width between 4:1 and 6:1 and the slot width is less than 600 mm. Each of the two rows of holes has at least four holes the middle axis of which form together with the prolongation of the axis of the central hole an angle ranging from 20* to 70*.

Description

United States Patent [54] CERAMIC BURNERS [5 6] References Cited UNlTED STATES PATENTS 2,437,042 3/1948. Prosser et a1. 239/430X A [72] Invent rs Ja lls Bll 3,185,458 5/1965 Reed 431/190X Santpoort;

Primary Examiner-Carroll B. Dority, Jr. $222: ouwerkerk hmmden Attomey-Wenderoth, Lind and Ponack [21] Appl. No. 867,988 [22] Filed Oct. 17, 1969 4 i g z A G ABSTRACT: A ceramic burner for hot blast stoves for blast s e b d Ge furnaces. A ceramic block has a centralhole and a crown of 32} P :3 many holes surrounding it. A vertical conduit feeds gaseous tie; and nonty a second coaxial conduit supplies combustion air. The cong P 733 4 duits have their upper ends passing through the holes'. The

upper surface of the block slants upwardly from the central hole and the holes of said crown are directed toward the prolonged axis of the central hole. The'central hole has essentially the shape of a rectangular slot and the sloping part of the upper surface of the block comprising essentially two flat surfaces which comprise an angle of 40 1 20, and the crown of holes is subidvided into two rows of holes running parallel to each other and to the longitudinal sides of said central hole. The rectangular shape of the central hole shows a ratio of length versus width between 4:1 and 6:1 and the slot width is less than 600 mm. Each of the two rows of holes has at least four holes the middle axis of which form together with the prolongation of the axis of the central hole an angle ranging from CERAMIC BURNERS The invention refers to a ceramic burner, particularly to be used in .hot blast stoves for blast furnaces comprising a first vertical conduit for the feeding of gaseous combustible fuel and a second coaxial conduit for the feeding of combustion air, whereby the conduits on their upper ends pass into a ceramic block through perforations, namely into a central hole with a crown of holes around it, whereby the upper surface of the block runs inclined from the central hole upwards and theholes of the crown are directed towards the prolonged axis of the central hole.

Ceramic burners of the types mentioned above are presently common construction elements in hot blast stoves for blast furnaces. They constitute a process as compared to the formeily common metal burners which were installed outside the combustion chamber of the hot blast stove. With the ceramic burner being built into the hot blast stove a considerably higher cupola temperature can be attained, without the burner suffering any damage by it. Moreover it is possible to avoid, through a ceramic burner installed vertically inside a combustion chamber the rebounding of the flames on the separation wall between the combustion chamber and the lattice work, particularly inthe place where the difference of temperature between the combustion chamber and the lattice work should be the highest. Thus the separation wall and the lattice work are both greatly spared.

The known ceramic burners have a round or oval-shaped exit opening at the (central hole for the fuel supply. The holes of the surrounding crown are slot'shaped and equal in size. Although the known ceramic burners represent a considerable improvement over the older metal burnersthey can still be improved. On top of the cupola and under the lattice work of the hot blast stove an important amount of unburned gases can be measured, mainly CO and this notwithstanding the fact that a sufficient supply of combustion air has been provided. Even at this, the economy of the installation is not yet optimal. Also the combustion is uneven, particularly in the lower part of the combustion chamber. An object of the present invention is to eliminate these imperfections.

A further object is to secure a better control and mixing of the fuel and air up until it arrives into the flame thereby influencing the evenness and completeness of the combustion.

A further object is to provide a construction wherein the central hole essentially has the shape of a rectangular slot with the sloping part of the upper surface'of the block composed essentially of two flat surfaces making an angle of -l20 and preferably 60-90 and having the crown of holes subdivided into two rows of holes parallel to each other and to the sides of the central hole.

Several devices have been used with metal burners in order to improve the mixing of gas and air. These known constructions cannot be used for ceramic burners for hot blast stoves, due to their dimensions as well as to the restricted construction possibilities with ceramic stones, whereby the oval shape of the combustion chamber poses specific construction conditions to the expert.

Even though greater successes have been achieved with any shape of holes in the ceramic block, it has been proven that the rectangular shape of the central hole according to the invention is particularly advantageous, whereby preferably the relationship of length and width should be between 4:1 and 6:1 and the slot width of the hole less than 600 mm.

Besides it has proven to be advantageous to provide the two rows with at least four holes, whereby their middle axes together with the extension of the axis of the central hole form an angle of 20 to 70.

The advantageous effect of the new burner should be attributed to the very intensive mixing of air and fuel, which because of this shape of the burner can be achieved. The air jets which penetrate the relatively narrow jet of fuel and specifically adapted shape of the upper surface of the block prevent the possibility that fuel and air jets that are unmixed,

or incompletely mixed or mixed in the wrong proportion persist until they reach the flame. It may be assumed, that in the case of the known, coaxial distribution of the air holes around a central circular hole for the introduction of fuel the air mixing ratio over the burner shows a gradient. Therefore theoretically only within a relatively narrow zone of the mixing area good mixing conditions may be expected in the known ceramic burners. a

An object of the invention is also the specific distribution of the holes of both rows to each other. The expert would consider it useful, in order to improve the mixture of gas and air, that the different holes are distributed at different heights. To be sure such a distribution is also covered by the invention, but surprisingly enough, in the burner according to the inven tion better results have been obtained when the holes on both rows are distributed on the same height.

According to the purpose and/or circumstances of utilization it may be advantageous accordingto the invention to distribute every two holes of the two rows across each other or the holes of one row staggered in relation to the other row. The best shaping effect of the ceramic block is obtained, when the distribution of the fuel and the air over the cross section of the central hole, and/or over the different holes is distributed as evenly as possible. In order to promote the evennness of the distribution the two conduits should join shortly before passing over to the holes through the ceramic block. 7

Further objects of the invention and their advantages will be illustrated in the drawings, which represent a schematic form of construction according to the invention, in which:

FIG. 1 shows schematically a hot blast stove with a built in burner in a longitudinal section;

FIG. 2 shows the burner of FIG. 1 at an enlarged scale;

FIG. 3 is a section according to line lII-III in FlG. 2.

In FIG. 1 the housing of a hot blast stove is designated by l and 2 is the bottom on which it stands, forming together a brick entity. The brick housing is surrounded by a steel casing (not shown). A number of pillars 3 projecting out of the bottom 2 support a lattice 4, which in turn serves for supporting the perforated stones piled up on it (not shown) through which is led alternately hot fuel gas from the top down and air to be heated from the bottom upwardsQThis so-called lattice work construction is separated by a wall 5 from the combustion chamber, which towards the outside is limited by a section of the housing 1. The hot blast stove is shut off on the top by a brick cupola 6 and a steel cupola 7.

The gaseous fuel material necessary for the conservation of the hot fuel gases and the air are led through a conduit 8 and/or a ring conduit 9 to the combustion block 10. The burner is indicated only schematically in FIG. 1. Above the burner the fuel material and the air are intimately mixed and the fuel material is burned inxthe combustion chamber.

The hot combustion gases are led over the separation wall 5. Once the piled up stones over the lattice work are conveniently heated, the

feed openings

14 and 15 of the combustion and air conduits 8 and/or 9 are closed.

The air to be heated is then led through opening 11 in an inverse direction through the installation and can escape through opening 12.

FIG. 2 shows the burner and its surroundings in detail and on an enlarged scale.

FIG. 3 shows a detail of it in a longitudinal section, petpendicular to that of FIG. 2. This detail show only half, the other half is symmetrical to it. Central conduit 8 for the fuel material connects to a central hole 16 in block 10.

This block is made of ceramic material the same as the walls of conduits 8 and 9 and the walls 1 and 5 of the combustion chamber. The central hold 16 has a rectangular shape with a ratio of length and width of approximately 5:1. in the upper surface 18 of block 10 two rows of openings 17 discharge, which are connected with conduit 9. These openings 17 have a rectangular shape, with the short sides of the rectangle of the opening aligned head-on, on each row.

Openings 1'7 in each row are placed staggered to the openings of the other row, so that jets of combustion air alternately blow out of the openings beside each other. This can be obtained when the upper surface 18 of the ceramic block is essentially formed by two flat surfaces forming together an angle of about 90.

This shape of the burning block insures an optimal mixture of the fuel material and air, when only the fuel material and the air actually escape uniformly out of the sectional area of hole 16 and/or openings 17. The latter is obtained by having both conduits 8 and 9 provided with a narrowing down as shown at 19 and 20.

We claim:

1. A ceramic burner, to be used particularly in hot blast stoves for blast furnaces comprising a ceramic block having perforations, a vertical conduit for the feeding of gaseous fuel, a second coaxial conduit for the supply of combustion air, said conduits having their upper ends passing through said perforations, said perforations comprising a central hole and a crown of holes on each side of the central hole, the upper surface of said block slanting upwardly from said central hole and the holes of said crown being directed toward the prolonged axis of said central hole, said central hole having essentially the shape of a rectangular slot, the sloping part of the upper surface of said block comprising essentially two flat surfaces which comprise an angle of 40-l20, and said crown of holes being subdivided into two rows of holes running parallel to each other and to the longitudinal sides of said central hole.

2. A ceramic burner according to claim 1 wherein said two flat surfaces comprise an angle of 60to 90.

3. A burner according to claim 1 wherein the rectangular shape of said central hole shows a ratio of length versus width between 4:1 and 6:1 and the slot width is less than 600 mm.

4. Burner according to claim 1 wherein each of said two rows of holes has at least four holes the middle axis of which form together with the prolongation of the axis of said central hole an angle ranging from 20 to 70.

5. Burner according to claim 1 wherein said holes of both rows are aligned on the same height.

6. Burner according to claim 1 wherein said holes of both rows stand opposite each other.

7. Burner according to claim ll wherein said holes of one row are staggered with respect to the other row.

8. Burner according to claim 1 wherein both of said conduits before passage to said holes through said ceramic block are narrowed.

9. Burner according to claim 1 wherein both of said rows of holes of the crown are slot shaped and their greatest dimension is vertically aligned to the longitudinal direction of said central hole.

Claims

1. A ceramic burner, to be used particularly in hot blast stoves for blast furnaces comprising a ceramic block having perforations, a vertical conduit for the feeding of gaseous fuel, a second coaxial conduit for the supply of combustion air, said conduits having their upper ends passing through said perforations, said perforations comprising a central hole and a crown of holes on each side of the central hole, the upper surface of said block slanting upwardly from said central hole and the holes of said crown being directed toward the prolonged axis of said central hole, said central hole having essentially the shape of a rectangular slot, the sloping part of the upper surface of said block comprising essentially two flat surfaces which comprise an angle of 40*-120*, and said crown of holes being subdivided into two rows of holes running parallel to each other and to the longitudinal sides of said central hole.

2. A ceramic burner according to claim 1 wherein said two flat surfaces comprise an angle of 60*to 90*.

4. Burner according to claim 1 wherein eAch of said two rows of holes has at least four holes the middle axis of which form together with the prolongation of the axis of said central hole an angle ranging from 20* to 70*.

7. Burner according to claim 1 wherein said holes of one row are staggered with respect to the other row.