Patent Application
20110117507
1. Field of The Invention
This disclosure relates to burners of solid fuel fired furnaces and more specifically to a burner nozzle tip design that allows for easier removal and maintenance.
2. Discussion of Related Art
Solid fuel furnaces have many common uses, such as for firing boilers to produce steam and electricity. The solid fuel typically is pulverized coal. Coal particles of the pulverized coal is entrained in a flowing air stream and blown into a combustion chamber of a furnace where it is burned.
The invention will be described with reference to both
Since the air flow with entrained solid particles passes through the fuel firing compartment 100 subject to erosion effects similar to sand blasting. Anything within the path of the air/fuel flow is eroded.
Since the nozzle tips 200 are located in the combustion chamber, they are also exposed to excessive heat and heat cycling. This can overheat and warp the nozzle tips, and have effects on the moving parts, such as pivot pin 310.
Combustion occurring near the nozzle tips 200 creates constant expansion, contraction and vibration. If the pivot pin is held in place with bolts or nuts, it is possible that they will loosen and vibrate out. This would cause the nozzle tip 200 to fall into the furnace. The furnace has a grinder for grinding up the ashes at the bottom of the furnace. Not only will there be uneven and uncontrolled burning, but the nozzle tip, bolt and nut will become caught in the grinder causing damage and the boiler to become non-operational. This would require time and expense to correct the problem.
For this reason, one end of the pivot pin is typically welded into place. The pins must be ground off to replace them. The inside of the furnace is covered with water tubes that pass close to each of the nozzle tips 200. Therefore, the only way to replace the nozzle tips is to grind or burn off the pivot pins from inside of the nozzle tips 200. There is little access to the nozzle tip 200 openings, making replacement difficult.
The entire fuel firing compartment, except for the nozzle tip 200 is located within a closed windbox compartment (not shown for clarity in
Typically these solid fuel furnaces are used as steam generators to create electricity in power plants. When one of these power plants is ‘down’, the owner is required to buy and supply equivalent power from the power grid to provide an uninterrupted supply of electricity to its customers.
Buying this replacement electricity is much more expensive that generating it. This may amount to significant losses by being out of operation. Therefore, a significant part of the costs are ‘down time’ costs.
Since nozzle tip operate at very high temperatures and in an erosive environment, the nozzle tips 200 tend to have a short life relative to the other parts of the system and have to be replaced often.
Maintenance relative to the remainder of the fuel firing compartment parts, it would be beneficial to be able to quickly and easily replace only the nozzle tip 200. This then results in a furnace that is less costly to operate and service.
The present invention may be embodied as a replaceable nozzle tip assembly 250 within a solid fuel furnace having a stationary nozzle 110. The nozzle tip assembly 250 includes a nozzle tip 200 having with shroud walls 210, 220 and a central opening 230.
A bearing 510, 520, 530 is fixed to the shroud walls 210, 220. The bearing 510, 520, 530 has a central orifice 511, 521, 531.
A pivot pin assembly 410, 420, 430 passes through the bearing orifice 511, 521, 531 and the sidewall of the stationary nozzle 110, to pivotally and removeably attach the nozzle tip 200 to the stationary nozzle 110. The pivot pin assembly 410, 420, 430 acts as a fastener that is accessible from the central opening 230. This allows easy replacement of the nozzle tip.
The present invention may also be embodied as a nozzle tip assembly 250 removeably attached to a stationary nozzle of a solid fuel furnace.
The nozzle tip assembly 250 includes a nozzle tip 200 having at least one outer shroud wall 210, 220 and at least one central opening 230.
A bearing 510, 520, 530 with a bearing orifice 511, 521, 531 is attached to the shroud wall 210, 220 of the nozzle tip 200.
A fastener base 413, 423, 433 is fitted into the bearing orifice 511, 521, 531 and extends at least partially through a sidewall of the stationary nozzle 110 allowing the stationary nozzle 110 to pivot relative to the fastener base 413, 423, 433 and nozzle tip 200.
A set screw 411, 421, 431 is used to secure the fastener base 413, 423, 433 to the bearing 510, 520, 530, the set screw 411, 421, 431 being accessible from the central opening 230 of the nozzle tip 200.
With reference now to the figures where all like parts are numbered alike;
The use of the teens “a” and “an” and “the” and similar references in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.
The most direct way of replacing a nozzle tip 200 would be from the furnace side, if the pivot pin were not welded.
The inside of the furnace is covered with water pipes for collecting the heat and for creating steam. These burners may be many feet from the bottom of the furnace. Therefore, temporary scaffolding must be erected to allow access to the nozzle tips 200. This may be acceptable for light work, but any more involved work may cause accidents that would damage the water pipes and other equipment inside of the furnace. For this reason, it was common to work on the other side of the windbox and remove the entire fuel-firing compartment 100 for maintenance.
The present invention allows for easier and more economical replacement of the nozzle tips 200. A new pivot pin assembly design is used instead of the welded pivot pin design for holding the nozzle tip 200 in place. This new design allows for the pivot pin removal and installation from inside the furnace without grinding or cutting.
The pivot pin assembly 410 remains the same size as the pivot pin 310 currently being used. The pivot pin assembly 410, however, is manufactured to allow it to be removeably held in place using a fastener that is protected from the hazardous conditions.
A fastener base 413 has a cylindrical portion 415 and an expansion portion 417. The expansion portion 417 in its normal resting position is slightly larger diameter than bearing orifice 511. Expansion portion 417 has slits allowing it to be squeezed to make it thinner or released to expand back to make it thicker. The expansion portion 417 also has a snap ridge 419 that protrudes outward from the expansion portion 417. Bearing 510 also has a snap groove 513 that is designed to receive and removeably hold snap ridge 419. Cylindrical portion 415 extends outward enough to pass through a sidewall of stationary nozzle (110 of
For assembly, fastener base 413 is pushed into bearing orifice 511. The leading edge of the extension portion 417 is preferably tapered to the center so as to squeeze expansion portion 417 together making it thinner until snap ridge 419 snaps into snap groove 513, holding fastener base 413 in place.
A set screw 411 has a threaded head section 412 and a body section. It is inserted into the fastener base 413 after the fastener base 413 has been inserted into bearing orifice 511. The body section restricts the expansion section 417 from reducing its thickness and prevents the snap ridge 409 from being removed from the snap groove 513. The head section 412 is threaded to thread into the outer end of the fastener base 413.
A set screw 421 passes through the fastener base 423 and screws into a threaded section fixed within bearing 520. This may be a threaded nut (not shown) welded within bearing orifice 521. The shape of insertion section 427 fitting snugly within bearing orifice 521 stops rotation of fastener base 423 restricting loosening of set screw 421.
A screw cap 429 threads into fastener base 423 thereby providing a corrosion-tight barrier protecting set screw 431 and fastener base 423. This screw cap 429 acts as a plug on the stationary coal nozzle side to seal the inner area from coal intrusion and wear. This also acts to jam against set screw 421 and acts as a lock nut in case set screw 421 begins to loosen.
In an alternative embodiment, cylindrical section 425 of fastener base 423 has internal threads. A screw cap similar to screw cap 429 may be employed and screwed into this cylindrical section 425 to protect fastener base 423 and prevent set screw 421 from loosening.
Cylindrical portion 425 extends outward enough to pass through a wall of the stationary nozzle (110 of
A fastener base 433 has a cylindrical portion 435 and an expansion portion 437. The expansion portion 437 in its normal resting position has a diameter slightly smaller than bearing orifice 531. Expansion portion 437 has slits allowing it to be expanded to make it thicker.
Cylindrical portion 435 extends outward enough to pass through a wall of the stationary nozzle (110 of
A set screw 431 has threads at one end. It is inserted through the fastener base 413 and loosely screwed into the narrower end of a truncated cone shaped expander 438.
The set screw 431, fastener base 433, and expander 438 are inserted into bearing orifice 531. Set screw 431 is then tightened causing expander 438 to be pulled toward set screw 431 thereby expanding expansion portion 437. Expansion portion 437 then becomes tightly held within bearing orifice 531.
A screw cap 439 is screwed into this cylindrical section 435 to protect fastener base 433 and prevent set screw 431 from loosening.
Even though a set screw is described in this embodiment, it is appreciated that the invention covers all types of removable fasteners that will allow the nozzle tip to pivot about the stationary nozzle, and be accessed from the furnace side of the nozzle tip.
As opposed to the prior art designed, with the present invention, a worker will not have to cut out material to replace the nozzle tip. No welding is required to install the present invention.
The present invention is designed to use existing holes in the stationary nozzle and nozzle tips 200. The embodiment of
The present invention may be used to retrofit any existing ‘T fired’ nozzle types. The pivot pin assembly is sealed from wear. Since it attached with fasteners, it may be replaced with hand tools. No special rigging is required.
Even though this invention has its preferred use for solid fuel burner nozzle tips, and more specifically coal-fired burner nozzle tips, it is equally applicable to other nozzle tips that are intended to pivot and are located inside of a furnace. These may be oil burner nozzle tips, natural gas burner nozzle tips, other fuel gas nozzle tips and air inlet tips.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.
