Fluid handling – Processes – Affecting flow by the addition of material or energy
Patent
1993-08-17
1995-04-18
Chambers, A. Michael
Fluid handling
Processes
Affecting flow by the addition of material or energy
137340, 137828, F17D 116, F15C 104
Patent
active
054069696
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to regulating the flowrate of a liquid furnace product and in particular to an apparatus for regulating such flow. While the invention will be described with reference to the metallurgical industry, the flowrate control technique is applicable to other industries which exhibit flowrate control problems similar to those stipulated.
BACKGROUND OF THE INVENTION
Flowrate control of liquid furnace products leaving metallurgical vessels and transport to the next process location in launders is very important to the overall performance of such vessels.
In the extractive metallurgy industry, tapping of furnaces is a very difficult, labour intensive and hazardous operation. Conventional tapping of furnaces is carried out periodically through a water cooled breast tapping hole. The hole is opened with an oxygen lance and closed by freezing in the tapping hole assisted by a clay plug or water cooled restrictor bars.
The problems associated with conventional tapping systems include delay in tapping due to difficulties in opening the taphole, no control of tapped liquid flowrate, wear and erosion of taphole due to oxy-lancing and difficulties in closing the taphole. As a result improved tapping techniques are required to overcome these difficulties. One such technique is the continuous tapping concept.
The development of continuous tapping began as early as 1899, when an external forebay for continuous tapping of iron blast furnaces was suggested. This idea was developed further to essentially the present day furnace/forebay relationship. Initially continuous tapping was limited to copper blast furnaces. The next development was the Roy type tapper in which the major differences from earlier developments were the use of an adjustable weir height by means of a deep V-notch and the installation of a burner in the forebay. The Roy type tapper is now conventional technology on lead blast furnaces.
The operation of the Roy type tapper is based on the principle of the liquid in the forebay counterbalancing the majority of the internal pressure of the furnace. The excess furnace pressure is the driving force for liquid flow out of the furnace. The advantages of the Roy type tapper over conventional tapping are the greater utilisation of the furnace for higher production and better control of composition than with intermittent tapping. However the Roy type tapper is an equilibrium system and cannot be controlled from a remote location. Consequently this type of tapper cannot handle a feed of variable composition and changes in flowrate must be made by weir or furnace head adjustments.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the inadequacies of the Roy type continuous tapper.
Accordingly, the invention provides a method for for controlling the flow of a liquid material in a conduit, said conduit having a means to transfer heat from said liquid material, which method comprises: heat transfer from the liquid material flowing through the conduit which will provide a given flow rate of liquid material through the conduit, said rate of heat transfer being determined from a relationship between heat transfer rate from said liquid material and the flow rate through the conduit, through said conduit to provide the given flowrate through the conduit, wherein the heat transfer from said conduit causes a layer of material solidified from said liquid material to form on the inner surface of said conduit thereby constricting the passage for fluid flow through said conduit and changing the liquid flow accordingly.
Preferably, the heat transfer rate is regulated by changing the flowrate of coolant through a heat exchange jacket around said conduit.
The invention controls the flow of liquid furnace products by controlling the thickness of a solidified crust which forms in the taphole. Consequently, the flow of liquid furnace products can be controlled in the hostile environment where known control valves cannot be used.
In accordance with another aspect
REFERENCES:
patent: 2714622 (1955-08-01), McMullen
patent: 4392509 (1983-07-01), Siddall
patent: 5002480 (1991-03-01), Gellert et al.
Gray Neil B.
Pitsillos John S.
Chambers A. Michael
The University of Melbourne
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