Metallurgical apparatus – Means sealing or opening aperture in vessel – By means plugging aperture
Reexamination Certificate
1998-09-22
2001-10-09
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Means sealing or opening aperture in vessel
By means plugging aperture
C266S045000, C266S047000
Reexamination Certificate
active
06299830
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the tapping of molten metal furnaces, and more particularly, to the removal of molten basaltic type slags and metals from high temperature plasma arc furnaces and the confinement of fumes generated during the removal.
BACKGROUND OF THE INVENTION
High temperature plasma arc melters are traditionally utilized for the production of irons and steels and for other extractive metallurgy purposes. Recent developments in the usage of plasma arc melters for the processing of minerals and waste material have generated a need for improved methods of removing molten basalt from the primary melting chamber.
Basaltic slags and reduced metals are produced from waste type arc furnaces at temperatures nominally in the range of 1500° C. to 2000° C. Basaltic slag are generally viscous in nature even at high temperatures and are very corrosive. The viscous nature of these slags presents difficulties in removal of the product from the melter. One standard method to aid in the removal is to add fluxing agents such as alkali metals Na, K etc.) or alkali earth metals (Ca, Mg, etc.) to chemically change the composition and reduce the viscosity for a given temperature range. However, it is often desirable to minimize the addition of fluxing agents to the melt for economic and product specification purposes.
Another method used is raising the temperature of the melt a sufficient amount to ensure a flowable liquid as the liquid progresses through an opening in the melter (removal means). Alternately, heat may be added to the removal means to ensure a flowable liquid stream. The temperature of the melt must be sufficient to provide a flowable fluid through the product removal means (taphole or weir) to remove a generally viscous product. Complications arise due to the fact that basaltic slags generally remain viscous above 1535° C. (melting point of iron) and are very corrosive and acidic. The acidic nature of these slags often precludes the use of standard components generally used in the iron and steel industry which are commonly available.
Electrically fired plasma torches are currently used for the processing of minerals and waste material. These torches tend to operate in the 5,000° C. to 10,000° C. range at the torch with bath temperatures approaching greater than 2500° C. in the hot areas. Graphite electrode plasma arc furnaces may be operated in very short arc or submerged orientations and tend to operate at slightly lower bath temperatures in the range of 1500° C. to 2000° C. Operations with higher bath temperatures provide the ability for greater control of viscosity, but result in energy and maintenance penalties. Operations with a bath temperature just high enough to encourage chemical reactions and the production of basaltic type material provide economic and maintenance advantages but complicate the removal of the basaltic slag product.
Molten material is generally removed from the furnaces by tipping the furnace and pouring the material over a spout, by opening a tap hole located in the side or bottom of the funiace, or by flowing the material under and over weir structures located at the bottom of the furnace. Eccentric bottom tapping is generally standard practice for tapping electric arc furnaces used in the production of steel. Molten material is generally removed from blast furnaces by drilling out a plug of material located in a hole through a sidewall in the furnace.
Typically, the molten material is removed in a batch operation in which nearly all of the molten material is drained from the furnace once the hole is tapped. In industrial use this method provides a relatively simple and inexpensive method for product removal. However, it is often desirable to start and stop the molten stream rather than dispense all of the molten material at one time. This requires opening, closing, and maintenance of the tap hole and difficult control of fugitive emissions from the hole. The hole is generally closed with a disposable plug, ram gun, ramming paste or mixture, or other type of mechanical closures. These closures are often difficult to install and remove and may be susceptible to leaks.
Therefore, there is currently a need for a tapping apparatus and method which creates a tap hole which can be repeatedly opened and closed, and a method for confining fumes generated when the tap hole is opened during the removal of the molten material from the furnace.
SUMMARY OF THE INVENTION
The present invention involves a method and apparatus for removing molten materials from high temperature furnaces and the confinement of flames generated during the removal. The invention provides controlled opening and closing of a tap hole in the furnace and allows for repeated starting and stopping of a molten stream.
An apparatus of the present invention is used for controlling the flow of molten material from a melt container having a tap hole formed in a sidewall of the container. The apparatus generally comprises a tubular insert sized for insertion into the tap hole, a rod receivable within the insert and a cooling device for cooling the rod to a temperature below the temperature of the molten material. The insert has a first end for insertion into the molten material, a second end, and a fluid passageway extending between the first and second ends. The rod is longitudinally movable between a first position wherein the rod is positioned within the tubular insert for cooling a portion of the molten material through the passageway, and a second position wherein the rod is spaced from the first end of the insert to allow the plug to melt and start the flow of molten material through the passageway.
According to one aspect of the invention, the rod is formed of copper and the cooling device comprises a passageway extending along at least a portion of the rod for flowing fluid within the rod. The high thermal conductivity of the copper draws heat away from the molten material to a cooling medium. The continuous cooling of the copper pin by a heat transfer fluid and a heat sink causes the plug to remain intact during the high temperature melting process. The geometry of the rod and insert and penetration of the cooled rod into the insert are important factors in the formation of the plug and a button (body) of solidified material within the higher temperature molten bath. The removal of the rod with subsequent stoppage of cooling of the plug and button within the insert causes the solidified button to heat up and melt back into the molten bath. This causes an initiation of a molten basalt tap stream through the insert.
A tapping system of the present invention generally comprises a melt container for melting a material, a tapping mechanism operable to start and stop flow from the container, a housing interposed between the tapping mechanism and melt container, and a conduit having a first end connected to the housing and a second end connected to an upper chamber of the melt container. The system further comprises a vacuum source connected to the upper chamber of the melt container to draw off gases generated during the melting and tapping processes from the container and housing.
According to another aspect of the invention, a method of controlling flow of molten material from a container comprises inserting a rod into the tubular insert, cooling the rod below the temperature of the molten material, and forming a solid plug from molten material at a first end of the rod assembly by cooling a portion of the molten material, thereby stopping the flow of molten material through the tubular insert in the container. In one embodiment, the method employed utilizes a chilled copper insertion rod to cool and solidify a plug of basalt within the insert.
According to yet another aspect of the present invention, a method of molding an object from a high alumina-chrome plastic refractory comprises: filling a mold with the material; applying pressure to the mold; relieving pressure from the mold; heating the mold to solidify the object; removing the material from the m
Buss Gary V.
Greenhalgh Mitchell R.
Raivo Brian D.
Kastler Scott
MelTran, Inc.
Morrison & Forester LLP
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