Patent Application
20070175297
This technology relates to a launder for conveying a stream of molten metal.
A vertical shaft melting furnace is a particular type of furnace that is used to melt metal. Pieces of metal are dropped into the furnace shaft to form a load of pieces that are piled upward from the bottom of the shaft. Burners fire into the shaft to melt the load of metal pieces, and the molten metal drains outward through a tap hole at the bottom of the shaft. A launder is a trough-shaped structure that extends from the tap hole to convey the stream of molten metal from the furnace to a holding vessel.
The claimed invention includes a burner that is arranged to fire in a direction extending upstream through a launder toward and into a vertical shaft melting furnace through the tap hole in the furnace. In this arrangement, the burner can preheat both the furnace and the launder.
The invention further provides a method of pretreating a vertical shaft melting furnace by firing a burner in a direction extending upstream through the launder toward and into the shaft through the tap hole.
Additionally, the invention provides a method of retrofitting a vertical shaft melting furnace by installing the burner on the launder. It follows that the invention includes a retrofitted apparatus as well as an originally constructed apparatus with such a burner.
The apparatus shown schematically in the drawings has parts that are examples of the elements recited in the apparatus claims, and can be operated in steps that are examples of the elements recited in the method claims. The following description thus includes examples of how a person of ordinary skill in the art can make and use the claimed invention. It is presented here to meet the requirements of enablement and best mode without imposing limitations that are not recited in the claims. The various parts as shown, described, and claimed, may be of either original or retrofitted construction as required to accomplish any particular implementation of the claimed invention.
The parts that are shown schematically in
In use of the furnace 10, metal pieces are dropped into the shaft 18 through the charge entrance 14 and are piled upward from the hearth 20 to form an irregularly shaped load with a height that reaches past the burners 24. Molten metal drops to the hearth 20 and flows outward through the tap hole 16 as the pile of metal pieces is melted downward through the shaft 18. The molten metal then flows through the launder 12 from the furnace 10 to a ladle (not shown) or other holding vessel.
The launder 12 includes a trough 30 with a bottom wall 32 and a pair of opposite side walls 34. The launder 12 further has cover portions 36 that can be installed and removed separately from each other along the length of the trough 30. Burners (not shown) can be mounted on the covers 36 to maintain the launder 12 at or above the melting temperature of the metal load. Such burners may have any suitable structure and arrangement known to those of ordinary skill in the art. Additionally, the launder 12 is equipped with a burner 40 that is arranged to fire in a direction extending upstream through the launder 12 toward and into the furnace 10 through the tap hole 16.
The burner 40 at the launder 12 preferably is a high velocity burner with a central nozzle axis 45 along which a flame is projected from the burner 40. Examples of suitable burners include premix burners and nozzle mix burners. In the illustrated example, the burner 40 is a nozzle mix burner that is mounted on a side wall 34 of the trough 30 in a position above the level at which a stream of molten metal is expected to flow through the launder 12, with the central nozzle axis 45 extending into the shaft 18 through the center of the tap hole 16. More specifically, the launder has a first section 50 extending in a straight line from the tap hole 16, and has a second section 52 extending at an angle from the first section 50. The second section 52 of the launder 12 is oriented to provide a location from which the burner axis 45 can project through the first section 50 of the launder 12 and further through the tap hole 16 so that the burner 40 can preheat both the first section 50 of the launder 12 and the shaft 18 inside the furnace. This is preferably accomplished by firing the burner 40 in a fuel-rich condition to avoid excess oxidant in the shaft 18 which, in turn, avoids oxidation of copper in the load to be melted in the shaft 18.
This written description sets forth the best mode of carrying out the invention, and describes the invention to enable a person of ordinary skill in the art to make and use the invention, by presenting examples of the elements recited in the claims. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples, which may be available either before or after the application filing date, are intended to be within the scope of the claims if they have structural or process elements that do not differ from the literal language of the claims, or if they have equivalent structural or process elements with insubstantial differences from the literal language of the claims.
