US 3912237 A
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United States Patent 1191 Ostberg et a1. Oct. 14, 1975 METHOD AND APPARATUS FOR MOVING 522,944 7/1894 Saltsman 1 259/1 13 OF LIQUH) PHASES IN INDUSTRIAL 1,385,205 7/1921 Custer... 259/1 12 1,605,138 11/1926 Parks 68/216 PRocEssEs Inventors: Jan-Erik Ostberg, Bettna; Sven Anders Noren, Brommit, both of Sweden Assignee: Jan-Erik Ostberg, Bettna, Sweden Filed: June 26, 1969 Appl. No: 836,918
 US. Cl. 259/112; 259/47; 259/98; 68/216  Int Cl. B0lF13/00  Field ofSearch 259/112, 113, 114, 71, 259/47, 27, 98', 68/215-219; 417/555 156] References Cited UNITED STATES PATENTS 166,893 8/1875 Rcdheffer 259/113 Primary Examiner-Roy D. Frazier Assistant ExaminerRobert A. Hafer 1 ABSIRACT A body of molten or liquid material within a container is caused to move in a predetermined direction or path by moving back and forth in the container a member which is out of contact with the walls of the container and which has such a shape and motion that it impels the fluid material vigorously when moved in one direction and less vigorously when moved in the other direction so as to produce movement substantially in the first direction The device preferably has two opposed faces, one concave and the other convex with the concave face pointing in the direction of the desired movement.
6 Claims, 15 Drawing Figures N l L N Fig.2
Sheet 1 of 5 Oct. 14, 1975 Fig.1
U.S. Patent INYENTORS' JAN-ERIK O5TBERG, SVEN ANDERS HOQEN I l v r US. Patent 0m 14, 1975 Sheet 2 of5 3,912,237
INVENTORS JAN-ERIK O6TBER SVEN ANDERS HDREN US. Patent 0m. 14, 1975 Sheet 4 of5 3,912,237
INVENTORS am xwizz mr. BY
U.S. Patent Oct. 14, 1975 Sheet 5 of5 3,912,237
Length of travel I NVEN'TQRS -ER\K OSTBER H ANDERS NOREN METHOD AND APPARATUS FOR MOVING OF LIQUID PHASES IN INDUSTRIAL PROCESSES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of producing movement in a predetermined path ofliquid, particularly liquids at high temperature such as metallic melts. The purpose of the flow path selected may be any of a number of purposes, such as mixing or homogenizing of the liquid or melt in order to increase by this means the reaction rate of one or more reaction steps in a production cycle and/or to increase the yield of a reaction by bringing the system closer to thermodynamic equilibrium. The effect of the stirring on the reaction rate may be particularly powerful in case of reactions which are sluggish in nature, and when this is the case the stirring may alter the course of the process entirely. Another purpose of such movement may be to transport the liquid from one position to another in an industrial process, which involves a chain of successive steps.
The invention is particularly adapted to the creation of flow generally or of certain flow patterns in liquid systems, which for some reason or other do not lend themselves either to being handled by conventional pumps or conventional pumping methods.
2. The Prior Art A typical example of such liquid systems are metallurgical melts. The high temperature of these melts eliminates the use of most materials for the design of the pumping equipment and the chemical influence of the surroundings does likewise. The vessels in which the melts are processed are in addition often not easily accessible, in addition to which the flow pattern which would favorably influence the particular process is often very specific. Difficult problems, sometimes comparable to these, may be presented also in other cases, for instance in floating mixtures of true liquids and solid materials, slurries and so forth.
The force of gravity has because of necessity been relied upon in the absence of other satisfactory pumping devices. This is the case in most casting operations, conventional as well as continuous or pressure casting. Even in cases where the object has been to stir a melt, to mix additions into a melt, to homogenize a melt generally, to improve upon a metallurgical procedure by speeding up the movement with phases, by creating large interfaces for reaction, by making turbulent mixing zones and even for the coagulation of nonmetallicinclusions, reladling processes such as the "Perrin- Process" have been used to great advantage. The field of force has also been used for the transport in some recent proposals for continuous metallurgical processes. Professor Howard K. Worner thus describes in the June issue for [961 of "The Australian Engineer" an arrangement for the transportation ofthe melt in inclined channels during a continuous metallurgical process.
A gas passing through a liquid is a familiar method for getting the liquid into a flow. The gas may do this by influencing the apparent specific gravity, or it may transfer material which adheres to the gas-bubbles.
Flow within metallic melts is sometimes brought about by electromagnetic forces. This is the case in electric arc furnaces equipped with so'called inductive stirrers. This is also the case in induction furnaces of all kinds. The same type of forces are sometimes used for a true transport and a process is known in the iron and steel industry in which melts are transported upwards in channels, being driven by alternating electromagnetic fields.
it is sometimes practical to move the liquid indirectly by moving the vessel, which holds the melt. This is an old practice used in rotary kilns of many types and of shaking ladies and similar vessels. which are turned around some vertical, horizontal or inclined axis.
There are also methods known in which metallurgical melts and other difficult liquids are stirred or moved by some tool, which is submerged in the liquid and rotated or caused to make some translatory movement by some crankshaft arrangement. The rotating tools may simultaneously have a pumping action or they may act by creating a vortex of some type.
Continuous processes by their very nature require flow of material. The processes of these kinds, which are being developed in the iron and steel industry for example, are sometimes arranged so that a melt is moved in channels or pipes, which may be open or closed. The melt is subject to a sequence of treatments during the transport. The movement is normally first induced in the metallic melt but it is advantageous to regulate directly or indirectly also the movement of re actants, which may be added to the system or of prod ucts ofthe reaction. The movement of this non-metallic phase may be parallel to the metallic phase or counter current to it. The continuity may be applied to the entire process or to single steps of it and the movement may be induced according to this invention entirely or partly by downward flow or merely by gravity.
SUMMARY OF THE lNVENTlON The present invention relates to a hydrodynamic method of moving particularly difficult liquids such as metallurgical melts according to preset geometrical schemes, particularly in areas which are difficult to access.
The method is carried out by means of a mechanical tool which operates while submerged in the liquid. The tool performs a back and forth or a reciprocating movement. It is called a diode-pump because of its similarity to the well-known electrical components called diodes. The justification for this denomination is that the diode-pump has characteristics analogous to this electrical component.
The electrical diode may obtain its particular effect from any of a number of physical phenomena, but all types of electrical diodes have in common that they produce a high resistance to the electric current in one direction, whereas the resistance to the current is small when the direction of the flow is in the opposite direction. lf thus the electrical diode is part of an alternating electrical circuit, the electrical potential will be insuffi cient to produce an electrical current in one direction, whereas heavy current will flow when the direction of the potential is reversed. Semi-conductors may constitute diodes, obtaining the desired effect because of their inner structure. For that reason, they make a very good analogy to the hydro-mechanical device of a di ode-pump according to the present invention.
The diode-pump is a body moved back and forth in the liquid, which is within a container, the pump element being out of contact with the container walls. The movement is periodic. The length of each stroke and the frequency of the strokes may be set within wide limits, but both quantities must be chosen to suit the geometry of the desired path of movement of the liquid sys tem as well as other practical conditions prevailing. It is well known that the electrical diode calls for similar considerations. The tool must be so shaped that the resistance towards flow of the liquid with respect to the tool is large for one direction of movement but small in the opposite direction. A stroke in the first mentioned direction will thus transfer a large quantity of energy to the liquid and will accelerate the liquid in such first direction. A stroke in the opposite direction will deprive the liquid of only a marginal quantity of energy, because the mutual resistance in this direction is small. Consequently the liquid will be only slightly retarded by the return stroke. The net result is in spite of the fact that the pumping body is moved and giving an impulse in both directions a resultant force and a flow in just one direction, namely the one in which the resistance between the pump and the liquid is large. A substantially straightlined field of force is generated, the direction of which coincides with the direction in which the pumping body is moved.
Force and movement will also be induced more or less completely into the surrounding portions of the whole liquid. The extent of which this takes place is a function of the strength of the original field or force and of the dimensions of the vessel. The direction and the orientation of the flow will primarily be set by the diode-pump proper. Secondly. however, the shape and the dimensions of the vessel will also have an influence. The diode-pump primarily creates a substantially rectilinear, well defined and easily adaptable flow pattern, parts of which may be extended even to parts of the liquids which are not easily reached directly.
Conventional systems of pumping cover a wide range of methods in order to meet requirements in normal surroundings. This also applies to problems for which, when the conditions are severe, the diode-pump is the best answer. To meet the ends, the normal pump may be equipped with valves. The pump-assembly may include pipes for getting the liquid to and from the pump proper or there may be some device of another type in order to guide or to control the operation. Such expedients are difficult to use in the surroundings where the diode-pump should operate. When the ambient temperatures are high, when a corrosive liquid is very demanding upon the materials used for the design or when a very particular flow pattern is desired in difficult places, those conventional methods are not practical. A number of problems encountered is steel furnaces and in metal ladles demonstrate this fact in a drastic way.
A deslagging may for instance be greatly facilitated, if a field of force and a liquid flow can be produced right upon the face of the furnace bank below the working door of an electric arc furnace. The field is preferably strong and the orientation of the flow should be rather exact. No conventional pump could solve this problem. The diode-pump on the other hand is well suited for tasks of this kind, where already the geometry and the choice of material eliminate the use of the normal devices.
The apparatus to carry out this method is a pumping body. It is submerged in the liquid and reciprocates or oscillates therein in two opposite substantially rectilinear directions. In this movement the body acts as a sort ofthrottle when going in one ofthe directions. Various shapes of the pumping body will be specified in the following description and further explained by the figures, in which also reference is made in a schematic way to various practical applications.
The diode effect is particularly obtained because of the shape of the pumping body, usually by the shape of a certain part of it such as a cup-formed body or a hook or some ring or other arrangement attached within an annular body. The diode effect may however even be caused by the character of the movement proper, particularly in cases where a nonuniform movement is used instead ofa uniform one. In those cases a high velocity in the forward direction is followed by a slower movement in the return direction. There may also be a rather distinct maximum in the velocity of the body. The throttling effect may also be obtained by other means, for instance because of different friction between the body and the liquid in the movement in one direction and the other.
The apparatus has a driving member, normally a driving rod or a driving axle. These parts are of course necessary for the operation but are not per se part of the invention. The length of each stroke of the diode-pump and the frequency of the strokes both have great bearing upon the results. Although there is mostly an optimum for each particular case, the choice is a function of the geometrical dimensions of the melt or the liquid and must be settled in each case with care accordingly. The diode-pump is usually a separate and distinct body which is attached to the driving member. In some cases, however, as is indicated in some of the figures, the driving member may form a part of the diode body.
A typical application of the invention deals with the stirring of metallurgical melts in furnace hearths or ladles. The various additions given to or influences exerted upon such a system are as a rule applied to the surface of the system and it is often desired or necessary to distribute the effect by stirring in order to avoid local concentrations of additives or peaks of temperature.
One specific situation of this type occurs during metallurgical processes when slag has to be removed from the surface. Particularly when it is important that this job is done rapidly and completely and accompanied with a minimum of metallic losses, the task is largely facilitated if the surface layers of the metal can be brought to flow towards the area of the furnace or the ladle, where the actual removal of the slag from the system takes place.
A further application of the invention relates to feeding of liquid metal into or out from a container of some sort. This is done in teaming of steel for instance such as in the continuous casting technique. The object may be to regulate the flow rate. The purpose of using the invention may also be to improve upon the quality of the performance of the job, because this invention may make it easier to carry out the job without the trouble which may occur when a nozzle is used or when the metal is flowing freely over lip".
To this list of examples from the metallurgical industry a great number of examples of areas for application could be added and this could be supplemented by examples from other industries, where liquids or melts are processed. There is in fact an abundance of needs for transportation of fundamentally this type in the metallurgical industry as well as in other industries.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to IS show various modifications of a diode pump according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The way in which the diode pump operates may be described in the following way with particular refer ence to FIG. 1. This figure shows the diode pump in a vertically movable arrangement. At the lower end of the shaft or rod 2 is attached a cup-formed pumping body 4 in a position just below the surface of the liquid. The pumping body is moved up and down as indicated by the double arrow, but out of contact with the wall of the container in which the liquid is held. When the pump is going down in the direction of the curved arrows the concave side 6 of the cup pushes the fluid in front ofit forward in the direction of the arrows. The liquid behind the cup joins the cup in its movement and is in turn joined by the material at the periphery of the cup. The primary movement is thus transferred to the surrounding liquid and the flow volume is appreciably reinforced.
During the return stroke the liquid moves into the cavity from around the periphery of the cup and fills this cavity while exerting some, though small resistance. Liquid in the area above the cup is moved back to the sides, likewise with some, though small resistance. The amount of resistance caused by these two factors will tend to create some retardation of the flow, but the effect is small and a continuous forward flow will be generated.
FIG. 2 shows an annular ring structure 10 in an arrangement, which otherwise is similar to that of FIG. 1.
FIGS. 3 and 4 show other modifications. A pumping body 12 which in one way or another is attached to the driving member is formed like a pipe. In this pipe is mounted a cup-formed pumping element 14 (FIG. 3) or an element shaped as an annular ring 16 with crosssection similar to a cup. These cups or annular rings have a throttling effect in the pipe. The exact location within the pipe has an influence upon the effect, the best results sometimes being obtained when the element is located close to the outgoing end of the pipe.
The pipe shape of the FIGS. 3 and 4 has proven suitable for operations in hearth furnaces such as electric arc furnaces. These pumps may be positioned along the incline of the furnace banks in a simple way and the pump may be brought close to the bank without the risk of erosion caused by high velocity of the flow and a nonprotected ceramic surface.
FIG. 5 shows an upwardly convex cup 18 capable of producing upward flow.
The use of pumps in metallurgical apparatus in channels or in ladles or in other containers can require great variation in order to suit the particular needs or the design of the container and for problems of this variety the adaptability of the diode pump is an immense value. FIGS. 6 and 7 show a pump 20 which is given either a linear horizontal movement (FIG. 6) or a circular movement which is only a slight deviation from the preferred straight line movement (FIG. 7). This arrangement is made for metallurgical treatment in countercurrent in a channel. If the channel runs nearly horizontally and ifthe area of the cup perpendicular to the length direction of the channel is at least 10% of the area ofthe channel, it is possible to generate such a vigorous stream that the surface of the metallic melt is raised in the direction of the flow. Because of this a reactant charged upon the surface of the melt at the outlet end of the channel will because of the incline of the surface be forced to flow downhill in the direction opposite to the direction of the main flow of the heavier melt. The melt therefore at the finishing end, where the refining is largely brought to an end, is facing fresh nonused refining reagents. Likewise at the other end of the channel, where the reactant has largely had its effect, it is meeting fresh nonrefined metal, which is not in equilibrium even with this utilized reactant. By this arrangement the reaction may be carried to a fuller degree of refinement than otherwise possible and the reactants will be more fully utilized.
FIG. 8 shows an arrangement with two cups, which is a development of the arrangement of FIG. I.
In the form of FIG. 10, a cylindrical body 24 which penetrates a surface of the liquid such as the top surface is moved up and down in the liquid, The downward movement being rapid and the upward movement being slow. This will cause a substantial downward flow. The effect can also be achieved by using a plunger 26 having a concave bottom end as shown in FIG. 11.
FIG. 12 shows a form having a tubular body 28 with a central opening 30 surrounded by a downwardly facing annular groove 32.
It is sometimes advantageous to combine the effect from two or more pumping bodies. An illustration of this is shown in FIG. 13, which shows a pig iron ladle 34 where two pumping bodies 36 are submerged into the metal, one pumps vertically towards the surface while the other one pumps vertically downward. A rotation is thus generated around a horizontal axle in the ladle. If the main object is to get a reaction with the slag upon the surface, the pumping body which is pumping the iron upward is located near the surface where the slag metal interface is located. If on the contrary the object is to dissolve scull or heavy alloys upon the ladle bottom, the downward directed pumping body is moved closer to the bottom in order to concentrate the turbulent movement in those areas where the mixing is desired. Sometimes it may be more suitable to use two or more pumps. which have the same general arrangement as those just mentioned, cooperating in movement in the same direction. If both are located near the surface and are directed downward, a toroidal whirl is created, which may result in a smooth general mixing combined with a turbulent reaction zone near the surface. The two or more pumps may also be directed upward. By that arrangement the surface is affected so that a cavity is formed in the center of the surface. The slag floats to this cavity and the slag will be kept away from the side walls of the container, which is necessary if the slag is erosive.
The majority of the figures including FIG. 1, shows a sharp edge at the periphery of the pumping body. This makes for the best pumping efficiency. For applications at high temperatures such as metallurgical melts this construction may be hard to achieve because of difficulties in the manufacture of ceramic material and as a practical compromise it will often be necessary to deviate somewhat from the hydrodynamically most desirable shape. FIG. 14 shows rounded edge the diameter which is 1% of the diameter of the cup.
An alternative to a completely ceramic pumping body for a metallurgical application is a body of metallic material, which may be cooled, and which is protected by a ceramic coating of a thickness which is chosen to correspond to the requirements because of the length of stay, the temperature and other factors. A cooling of the interior reinforcement is often advisable also in order to meet the mechanical strains. The ceramic material used for the pumping body must be able to stand temperature shock and have a maximum strength at the operating temperature. Quite a number of ceramic materials will be suitable. Rammed or cast refractory materials are suitable, particularly those cast from the molten state. Plumbago or graphite, where the chemistry allows such a choice, are suitable. It is often a valuable additional feature that these materials lend themselves to the making of smooth surfaces with low coefficients of friction. The friction may also be controlled by filling the pores in the basic material by such materials as clay, graphite or other finely ground materials. Friction is a factor which may contribute in the building up of a one-sided resistance to flow, particularly if the surfaces of the pumping body are so prepared that the friction between pumping body and liquid is different in the two directions of movement and in cases it is advisable to use it in order to accentuate the effects of shape and speed mentioned previously.
When ceramic materials are used, it is advantageous to make the cups or their equivalents exchangeable. If the life is short anyway. it may be economical to use mass-produced exchangeable parts. In such cases sophisticated qualities such as freedom from tendency to cavitate can be omitted in favor of other considerations such as hydrodynamic efficiency.
In FIG. IS an arrangement is shown in which the pumping body has a non uniform speed with each stroke in the two directions, thus demonstrating the effect of speed as compared with shape.
From the fundamental shape shown in FIG. 1 a great number of variations can be developed according to the practical situation and the needs. Some examples are indicated in the drawings. It is not always necessary to use a full cup. Segments of cups may in some situa tions make an acceptable substitute. These may all be put on the same height on the driving member and the final article may look like a cup, which has been split. The hooks" may also be distributed along some length of the axle or the shaft. These shapes are often the solution, when the actual problem requires adaption to a difficult or complicated form of the container, in which the pump operates.
The diode effect may be reinforced by the introduction of a gas into the system. The gas may be introduced outside the pump or within the pump and in such a way that the diode effect of the pump is accentuated. This is often to advantage when the fluid has to be pumped upwards in a vertical or inclined channel. This gas may be introduced directly through a porous pumping body or through the gas cooled reinforcement of the body. The gas in question whether it is introduced in one way or another may be chemically or otherwise physically neutral with respect to the process being carried out or may take an active part in the reaction.
The invention is also of value for liquids which have abnormal qualities such as high viscosity and reduced fluidity. For example, this may be caused by the pres ence in the liquid of substantial quantities of solids in powder or similar form. This includes slurries and similar substances.
A pump according to the invention can also be used for slow propulsion of large vessels in harbors, by the repulsive effect exerted on a vessel from which a pumping member according to the invention is driven into the water at the rear of the vessel.
I. A method for producing a substantially rectilinear and unidirectional flow within a body of liquid in a con tainer, which comprises substantially rectilinearly reciprocating in coincident paths in both directions a liquid propelling member which is immersed in said body of liquid and disposed at a distance from the walls of said container and having a concave face with walls substantially parallel to the direction of reciprocation at their free edges in one direction of movement and a non-concave face facing in the other direction of movement whereby upon the movement of the member in such one direction it produces a substantially larger resistance to said movement, and thereby exerts a larger force on the liquid in said body of liquid, than upon the movement thereof in the opposite direction and that upon the movement in said opposite direction the liq uid flowing in said one direction with respect to said member adjacent the periphery thereof moves inwardly into the concavity of the concave face.
2. A method as claimed in claim 1, in which the nonconcave face is convex.
3. A method as claimed in claim I, in which said liquid propelling member is moved more rapidly in said one direction than in said opposite direction.
4. Apparatus for producing a substantially rectilinear and unidirectional flow within a body of liquid in container, comprising a liquid propelling member immersed in said body of liquid and disposed at a distance from the walls of said container and means for substantially rectilinearly reciprocating said liquid propelling member in coincident paths in both directions within said body of liquid, the liquid propelling member having a concave face with walls substantially parallel to the direction of reciprocation at their free edges facing in one direction of movement and a non-concave face facing in the other direction of movement whereby movement of said member in said one direction produces a substantially larger resistance to said move ment, and thereby exerts a substantially larger force on the liquid in said body of liquid, than upon the movement thereof in the opposite direction and that upon the movement in said opposite direction the liquid flowing in said one direction with respect to said liquid propelling member adjacent the periphery thereof moves inwardly into the concavity of the concave faces in which said liquid propelling member has a central opening therein and has a half-concave face directed in said one direction and a half-convex face directed in said opposite direction.
5. Apparatus as claimed in claim 4, including a tubular part surrounding said liquid propelling member and secured thereto.
6. Apparatus as claimed in claim 4, in which said means for reciprocating said liquid propelling member are adapted to move said member more rapidly in said one direction than in said opposite direction.