Oxygen-fuel burner with cavity-actuated mixing
An oxy-gaseous fuel burner ( 400, 500 ) or a solid fuel burner ( 700 ) having an annular cavity ( 404, 504, 704 ) upstream from and proximate to an outlet plane ( 416, 516, 716 ) and a converging ( 434, 734 ) or converging-diverging nozzle ( 537 ) located upstream from and proximal to the cavity ( 404, 504, 704 ). The solid fuel burner ( 700 ) also is preferably operated so that the velocity of gas exiting a second annulus ( 730 ) is less than the velocity of gas exiting a central conduit ( 710 ).
1. A burner comprising:
a first annular conduit in fluid flow communication with a supply of an annular gas, the annular gas comprising one of oxygen and a gaseous fuel, the first annular conduit having a first inner wall and a first outer wall;
a central conduit located within the first annular conduit and being in fluid flow communication with a supply of a central gas, the central gas comprising the other of oxygen and a gaseous fuel, the central conduit having a central outer wall and an outlet plane; and
a symmetric cavity formed in at least one of the central outer wall, the first inner wall, and the first outer wall, the cavity being positioned proximal to and a non-zero distance upstream of the outlet plane of the central conduit, the cavity having a length, a depth, and an aspect ratio defined as the length divided by the depth, the depth being at least 10% of the hydraulic diameter of the conduit bounded by the wall in which the cavity is formed, the aspect ratio being from 1 to 10;
wherein the cavity has an upstream wall, a bottom wall, and a downstream wall, and wherein the upstream wall and the downstream wall each adioin the bottom wall at the same relative angle to render the cavity symmetric in the upstream-downstream direction, and wherein the length is a distance between the upstream wall and the downstream wall, and wherein the depth is a height of one of the upstream wall and the downstream wall; and
wherein the cavity is formed in the central outer wall.
2. The burner of claim 1 , wherein the central gas consists of oxygen and the annular gas consists of the gaseous fuel.
3. The burner of claim 1 , wherein the central gas consists of the gaseous fuel and the annular gas consists of oxygen.
4. The burner of claim 1 , wherein the cavity has an aspect ratio of between 1 and 4.
5. The burner of claim 1 , wherein the cavity is formed in the central outer wall.
6. The burner of claim 1 , wherein the cavity extends continuously through a 360 degree circumference of the cavity-containing wall.
7. The burner of claim 1 , wherein the cavity comprises a plurality of cavities spaced along a 360 degree circumference of the cavity-containing wall.
8. The burner of claim 1 , further comprising a converging nozzle located upstream from and proximal to the cavity.
9. The burner of claim 1 , further comprising a converging-diverging nozzle located upstream from and proximal to the cavity.
10. The burner of claim 1 , wherein the cavity upstream wall and the cavity downstream wall are each perpendicular to a direction of flow in the central conduit and the first annular conduit.
11. The burner of claim 1 , further comprising a second annular conduit configured to discharge a mixture of solid fuel and a transport gas, the second annular conduit surrounding the first annular conduit.
12. A method of combusting gas using the burner of claim 1 , comprising:
(a) flowing one of oxygen and gaseous fuel through the central conduit;
(b) flowing the other of oxygen and gaseous fuel through the first annular conduit that surrounds the central conduit; and
(c) flowing one of the oxygen and gaseous fuel across the cavity.
13. The method of claim 12 , the aspect ratio being between 1 and 4.
14. The method of claim 12 , wherein the cavity is located in an outer wall of the central conduit.
15. The method of claim 12 , wherein the cavity extends continuously through a 360 degree circumference of the cavity-containing wall.
16. The method of claim 12 , further comprising:
(d) flowing one of the oxygen and gaseous fuel through a converging nozzle located upstream from and proximal to the cavity.
17. The method of claim 12 , further comprising:
(d) flowing one of the oxygen and gaseous fuel through a converging-diverging nozzle located upstream from and proximal to the cavity.
18. The method of claim 12 , further comprising:
(d) flowing a mixture of solid fuel and a transport gas through a second annular conduit that surrounds the first annular conduit.
19. A burner comprising:
a central conduit configured to discharge a central gas comprising one of oxygen and a gaseous fuel, the central conduit being bounded by a central outer wall;
an annular conduit configured to discharge an annular gas comprising the other of oxygen and a gaseous fuel, the annular conduit surrounding the central conduit and being bounded by an annular inner wall and an annular outer wall; and
a symmetric cavity formed in at least one cavity-containing wall selected from the group consisting of the central outer wall, the annular inner wall, and the annular outer wall, the cavity being positioned proximal to and a non-zero distance upstream of an outlet plane of the central conduit, the cavity having a length, a depth, and an aspect ratio defined as the length divided by the depth, the depth being at least 10% of the hydraulic diameter of the conduit bounded by the wall in which the cavity is formed, the aspect ratio being from 1 to 10;
wherein the cavity has an upstream wall, a bottom wall, and a downstream wall, and wherein the upstream wall and the downstream wall each adjoin the bottom wall at the same relative angle to render the cavity symmetric in the upstream-downstream direction, and wherein the length is a distance between the upstream wall and the downstream wall, and wherein the depth is a height of one of the upstream wall and the downstream wall; and
wherein the cavity is formed in the central outer wall.