OXY-FUEL BURNER FOR BURNING PULVERISED FUEL

Abstract: The wall (5) of a tube (2) for delivering pulverised fuel to the outlet (4) of an oxy-fuel burner (1) forms part of a chamber (6) which is pressurized or evacuated. The pressure in the chamber is continuously monitored. If the pressure in the chamber (6) changes in a way indicative that the wall (5) of the oxy-fuel burner (1) has failed the oxy-fuel burner (1) is automatically shut down.

Description: TECHNICAL FIELD This invention relates to oxy-fuel burners for burning pulverised fuel. BACKGROUND ART Oxy-fuel burners for burning pulverised fuel generally comprise a central tube through which pulverised fuel, for example pulverised coal is blown by a stream of air. Oxygen is introduced in a passageway circumjacent the central tube and mixes with the pulverised fuel at the tip of the oxy-fuel burner. One of the problems with this arrangement is that the pulverised fuel can be very abrasive. As a result the wall of the central tube, which is usually made from stainless steel, has to be checked frequently. If the wall of the central tube fails in an oxy-fuel burner then the pulverised fuel may mix with the oxygen inside the burner and explode with very serious consequences. This problem can be mitigated to some extent in an oxygen/natural gas/pulverised fuel burner by surrounding the central tube with the natural gas supply passageway. However, both the wall of the central tube and the natural gas supply passageway can erode to bring both the natural gas and pulverised fuel into direct contact with the oxygen. DISCLOSURE OF INVENTION The present invention aims to provide an oxy-fuel burner for burning pulverised fuel in which failure of the pulverised fuel supply tube can be easily detected. According to the present invention there is provided an oxy-fuel burner for burning pulverised fuel, which burner comprises a tube for delivering pulverised fuel to the outlet of the burner, and one or more passageways circumjacent said tube for delivering oxygen or oxygen enriched air to said outlet, characterised in that the wall of said tube forms one side of a chamber which extends circumjacent said tube and separates said tube from said passageway(s), said chamber being provided with a connection so that the pressure therein can be monitored. Preferably, said chamber is provided with means to automatically monitor the pressure in said chamber. Such monitoring may be carried out continuously or intermittently. In such an arrangement means are preferably provided which automatically shut down the oxy-fuel burner if a pressure change in said chamber is detected which indicates that the wall of the tube has failed. In one embodiment of the invention a second wall bounding said chamber defines the or an inner wall of the or one of said passageways for supplying oxygen or oxygen enriched air to the outlet of said burner. In another embodiment of the invention a second wall bounding said chamber is spaced from the or an inner wall of the or one of said passageways for supplying oxygen or oxygen enriched air to the outlet of the burner. For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings in which: BRIEF DESCRIPTION OF DRAWINGS Figures 1A and 1B together show a plan view, partly in cross-section, of an experimental oxygen/natural gas/pulverised fuel burner in accordance with the present invention; and Figure 2 is an end view looking in the direction of line II-II in Figure 1. Referring to the drawings there is shown an oxygen/natural gas/pulverised fuel burner which is generally identified by reference numeral 1. The burner 1 comprises a central tube 2 which extends from the inlet 3 to the outlet 4 of the burner 1. The wall 5 of the central tube 2 forms one side of a chamber 6 which is formed between the central tube 2 and an outer tube 7 which is concentric with the central tube 7. The gap between the central tube 2 and the outer tube 7 is closed by a weld bead 8 at the outlet 4 and by a seal 9 adjacent the inlet 3. A connection 10 provides communication with the chamber 6. The outer tube 7 extends through a tube 19 which forms the inner wall of an oxygen supply passage 11 which is disposed circumjacent the central tube 2. Twelve pipes 12 extend through the oxygen supply passage 11 and communicate at their inlet ends with a header 13. In use pulverised fuel is blown through the central tube 2. Oxygen is introduced through oxygen inlet 14 and passes through the oxygen supply passage 11. The oxygen and pulverised fuel mix at the outlet 4 of the burner 1 and burn. If desired natural gas may be introduced into the burner 1 through natural gas inlet 15. The natural gas is distributed to pipes 12 via header 13 and travels through the pipes 12 to the outlet 4 of the burner 1. A small volume of natural gas also flows to the outlet 4 of the burner 1 between the outer tube 7 and the tube 19. The front of the burner 1 is provided with a water jacket 16. In use, cooling water enters through water inlet 17 and leaves through water outlet 18. Prior to commencing firing the burner 1 chamber 6 is pressurized to about 4 bar A with air. Burner 1 is then fired. As the temperature of the burner increases the pressure in chamber 6 increases. If the wall 5 of the central tube 2 fails the air pressure in chamber 6 drops to the pressure inside the central tube (typically not more than 2 bar). A pressure sensor (not shown) detects the drop in pressure below 4 bar and automatically shuts down the burner by cutting off the oxygen supply and then the pulverised fuel. Various modifications to the burner shown are envisaged, for example the natural gas supply system may be omitted. In such an embodiment the outer tube 7 could form the inner wall of the oxygen supply passage circumjacent the central tube 2. Attention is drawn to our co-pending application of even date.

Claims: 1. An oxy-fuel burner for burning pulverised fuel, which burner comprises a tube (2) for delivering pulverised fuel to the outlet (4) of the burner, and one or more passageways (11) circumjacent said tube (2) for delivering oxygen or oxygen enriched air to said outlet (4), characterised in that the wall (5) of said tube (2) forms one side of a chamber (6) which extends circumjacent said tube (2) and separates said tube (2) from said passageway(s) (11), said chamber (6) being provided with a connection (10) so that the pressure therein can be monitored. 2. An oxy-fuel burner as claimed in Claim 1, characterized in that said chamber (6) is provided with means to automatically monitor the pressure in said chamber (6). 3. An oxy-fuel burner as claimed in Claim 2, characterized in that it includes means which automatically shut down the oxy-fuel burner if a pressure change in said chamber (6) is detected which indicates that the wall (5) of the tube (2) has failed. 4. An oxy-fuel burner as claimed in any preceding claim, characterized in that a second wall bounding said chamber defines the or an inner wall of the or one of said passageways for supplying oxygen or oxygen enriched air to the outlet of said burner. 5. An oxy-fuel burner as claimed in any one of Claims 1 to 3, characterized in that a second wall (7) bounding said chamber (6) is spaced from the or an inner wall (19) of the or one of said passageways (11) for supplying oxygen or oxygen enriched air to the outlet (4) of the burner.

Inventors: YOUNG, PHILIP JOHN
Applicants: AIR PRODUCTS AND CHEMICALS, INC.
Application year: 1988
Main classification: F23D1
IPC codes: F23D1, F23L7, F23D17