Bottom Blown Steel Converter And Means For Controlling Injection Of Powdered Material With Process Gasses Therein

Abstract

In connection with the bottom blown oxygen method of making steel, gases and powdered materials such as fluxes and additives are injected into the hot metal of the converter through tuyeres in the bottom of the vessel. The powdered materials are stored in pressure vessels and selectively transported to the converter by entraining the materials in high pressure process gases such as oxygen. Means are provided for maintaining constant material flow rates independent of gas pressure and flow variations. A rotary metering valve assembly is adapted for preventing back-flow of materials when gases are injected without entrained materials or when a second material is injected through a common entrainment point.

Parent Case Text

This is a continuation of application Ser. No. 207,889, filed Dec. 14, 1971 and now abandoned.

Description

BACKGROUND OF THE INVENTION

In the original basic oxygen method for converting impure ferrous hot metal to steel, the hot metal scrap and/or iron ore are placed in a converter vessel and oxygen is blown into the mixture through the top of the vessel with a lance. The oxygen reacts with silicon, manganese, carbon and phosphorus and converts these elements to oxides.

The original basic oxygen steelmaking method, also known as the LD process, has several metallurgical and economical shortcomings. Hot metals with high contents of silicon produce slopping and foaming of slag/metal mixtures and this results in operational problems as well as high metal loss. High phosphorus contents in the hot metals require a two slag practice with the result of longer steelmaking times and higher costs for raw materials. A modification of the LD process is well known as the LD/AC method. A part of the lime requirement, usually less than one half, is added in form of powdered lime through the oxygen lance from the top. For the low phosphorus/high silicon hot metal compositions commonly produced in the United States, for instance, this lime blowing method would not be of advantage. Another problem with the LD method is the sequence of oxidation of elements: silicon, carbon and manganese and finally phosphorus. It is therefore difficult to produce medium and high carbon steels with low phosphorus contents without special and costly efforts involving excessive use of fluxes or removing most of the carbon first and then re-carburizing the steel once the low desired phosphorus level has been achieved.

A new process for refining hot metal which overcomes the above described disadvantages is one which involves injecting fluxes and other powdered materials into tuyeres in the bottom of the converter vessel. The injected materials are entrained in oxygen, and other gases such as nitrogen and argon. The gas and the powdered material is diffused through the melt within the vessel and effects an immediate reaction between the material and the melt contents. This reaction results in evolution of various gases such as carbon monoxide and the formation of oxides such as SiO.sub.2, MnO and P.sub.2 O.sub.5 which are taken into the slag. To flux oxides formed and to remove them to the slag, lime is injected into the bottom. The total lime requirement is added through the bottom tuyeres at a high oxygen rate for rapid steelmaking. Slopping and foaming is minimal and does not require careful control of the oxygen and lime rates. It has also been found that phosphorus is removed simultaneously with carbon provided that the proper lime amounts are added at the proper time. Sulphur can be removed using the tuyere system for bottom blowing of lime or other desulphurizing materials together with a non-oxidizing gas. Oxide material can be bottom blown to oxidize the slag for even more efficient phosphorus removal as will be understood by those familiar with the art. Fluxes such as aluminum oxide or fluorspar can also be added through the bottom tuyeres. Finally, coolants such as iron ore or limestone powder can be added to control the liquid metal temperature while oxygen blowing.

In connection with the process outlined above, it is imperative that accurate control be maintained over the quantity of materials injected with respect to time and independent of the volume of process gas flow.

The bottom blown oxygen process used for direct processing of high phosphorus pig irons has shown substantial advantages over existing LD/AC practices. The process however, still requires an after-blow for phosphorus removal after silicon, manganese and carbon are oxidized. The process, when used directly with high silicon, low phosphorus basic irons as conventionally available in the United States and elsewhere is often subject to rather violent slopping due to the unstable slag conditions largely brought about due to the presence of high silicon. This condition requires cut-back of oxygen rates and increases heat times. The use of powdered material injection, and specifically powdered lime, results in early solution of lime and consequent stabilization of slag reactions resulting in nearly complete suppression of slopping even at extremely high oxygen input rates in the range of 150 scfm per ton of molten steel capacity. This injection of powdered materials has thus become a major advantage to achieve significant increases in metal yield, production rate, and also to greatly improve metallurgical control. A particular advantage obtained is the production of high carbon steels with the so-called "catch carbon" method; the blowing process is stopped when the desired carbon level is reached in the molten metal. At the same time, however, phosphorus and sulphur contents must be low enough to meet final specifications. This is achieved by properly timed and sized bottom blown lime techniques.

In the new bottom blown process for steelmaking, burnt lime, limestone, iron ore, bauxite, soda ash, flurospar and other fine grade injection materials are added together with the process oxygen or inert gas through a plurality of tuyeres. For metallurgical control it is desirable that the quantity of solid powders added with the process gas be regulated efficiently for a constant desired rate in terms of feed weight per unit time, independent of variations in volume of process gas flow and back pressure changes associated therewith.

In the bottom blown process, there is a variable back pressure originating from the variable bath depth in the steelmaking vessel, by intentional variation in charge size, vessel refractory wear and bath agitation during the steelmaking process and through pressure variations due to the change in number of tuyeres in operation.

A system of pneumatic transport used in the conventional LD/AC process used in connection with high phosphorus iron in Europe is based on entrainment of solids in the main oxygen process gas. Material is stored in a pressurized storage tank; a powdered material fluidizing means, a metering valve with automatic position control and an entrainment jet are used. In the LD/AC process where the powdered material is injected through the top blowing oxygen lance, the problem of regulating flow was not difficult to solve because back pressure on the lance remained essentially constant and only a single material was injected; furthermore, the average flow rate for the duration of the oxygen blow was not subject to variations which would affect the back pressure.

To obtain the full advantages of the bottom blown process, it is necessary to provide means for accomodating marked differences in injected material flow rates and back pressures. The present invention is directed to solving this and other problems.

SUMMARY OF THE INVENTION

A general object of this invention is to provide means for accurately controlling the introduction of gases and entrained powder materials in connection with the bottom blown oxygen steelmaking process.

Another object of this invention is to make powder material flow rate entirely independent of intentional variations of process gas flow rate and pressure and also of unintentional variations of process gas back pressure stemming from process variables, so that solid material flow rate is controlled exclusively by control of a valve through which the powdered material is delivered from a reservoir to the converter vessel.

Further object of this invention is to provide means for automatically adapting to variations in delivery pressure and back pressure which would result from variations of flow rates of the gases into the system and any variations in back pressure due to changes in the process characteristics in the converter vessel.

A still further object of the invention is to adapt the system for injection of powdered materials from different reservoirs under process gas pressure. This object is achieved by use of a special sealing device which prohibits pressure which is being applied to any one of the metering valves from being fed back through the sealing device to any of the other pressure reservoirs.

A further object of the invention is to adapt the metering valve construction to enable injection of powdered materials from various sources to a single point without permitting back-flow to the source of powdered materials which are not being actively metered.

A further object of the invention is to conduct the steelmaking method in such a manner that the various metallic and non-metallic constituents of the melt can be held to desired specifications so that the duration of the steelmaking process will be minimized.

Another object of this invention is to provide a materials control system which permits rapid response in either the flow rate of the gases or the metering and injection rate of the materials.

Another object of the invention is to avoid use of any valves between the chamber in which the powdered materials are accelerated to high velocity by the gas nozzle so that no parts of the system are subject to undue erosive action with consequently high maintenance costs. An adjunct to the object is that in the new system the valve which meters the powdered materials is subjected only to flow of materials at low velocity, in which case, errosive effects are minimized.

How the foregoing and other more specific objects of the invention are achieved will appear in a more detailed description of a preferred embodiment of the invention which will be set forth shortly hereinafter.

In accordance with the invention, fluxes and other additives which are to be introduced into the bottom of molten metal within a converter vessel are stored in pressurized vessels. Each vessel is equipped with a chamber in which there is a powdered material metering valve. The metering valve is subject to being controlled to produce a powder material flow rate corresponding with the pre-set process requirements. Means are provided to fluidize the powdered materials on the intake side of the valve and in the bottom region of the pressure reservoir.

Means are also provided to ensure that there is only one variable, namely, the position of the valve which controls the quantity and free flow of the powdered material through the valve opening. Means are provided to make such metered powdered material flow independent of gas flow and back pressure variations. Several discharge chambers from different vessels are connected so as to enable delivery of metered quantities of powdered materials to a single nozzle chamber for entrainment of the powdered material for delivery to the converter bottom. Specific means are established to seal the metering valve from pressure leakages in both directions.

A further object of the invention is to adapt the metering valve and associated regulation equipment to provide a means to meter a wide range of powdered material flow rates from a single pressure storage reservoir. This is an important process requirement. For example, a rapid change in material flow rate must be available. Hitherto, systems controlled by pressure alone could not respond rapidly to a sudden increase or decrease in material flow rate demand.

An illustration of the invention will now be set forth in reference to the drawings:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a steel converter vessel in connection with which the apparatus shown in FIG. 2 may be used;

FIG. 2 is an elevation view of a pressure vessel with parts broken away and parts shown schematically for use with a steel converter vessel in accordance with the inventions;

FIG. 3 is a partial vertical section of the material flow control valve assembly and associated chamber which is shown in FIG. 1;

FIG. 4 shows fragments of several reservoirs and their associated powdered material flow control valves, one of the valves being shown in Section taken on a line corresponding with 4--4 in FIG. 3, each of the valves being connected to a common entrainment chamber with a nozzle.

FIG. 5 is an enlarged vertical section of the material flow control valve assembly shown in FIG. 3, the valve being rotated 180.degree.and shown associated with a cassette which holds the sealing gaskets; and

FIG. 6 shows a fragmentary side elevation view of the material flow control valve assembly.

DESCRIPTION OF A PREFERRED EMBODIMENT

In FIG. 1, the converter vessel is generally designated by the reference numeral 10. The vessel has a metal shell 11 and is lined inside with refractory materials 12. The shell is supported within a trunnion ring 13 that has laterally extending shafts 14 and 15. These shafts are respectively supported in bearing housings 16 and 17 in accordance with conventional design. The top of vessel 10 has an open mouth which, during operation, is covered with a hood 18 to which is connected a gas exhaust duct 19. Extending through hood 18 is a temperature probe 20 which is supported on a mechanism 21 that allows probe 20 to be advanced and retracted through hood 18 into the center of the melt within the vessel.

The bottom of vessel 10 is equipped with a powdered materials distributor 22 to which are attached a plurality of tuyeres 23 which extend through refractory material 12 and communicate with the interior of vessel 10. Finely divided materials entrained in the process gas are brought into distributor 22 through a pipe 24. The pipe leads to a swivel joint, not shown, which is in the vicinity of trunnion shaft 15. Connected with the swivel joint is a stationary conduit 25 through which the powdered materials and entraining process gas are supplied from the pressure reservoir which is shown in FIG. 2.

In FIG. 2, the pressure vessel from which finely divided materials are delivered to converter vessel 10 is generally designated by the reference numeral 26. This vessel may be filled to the desired level with finely divided powdered materials through a valve assembly 27 on the top of the vessel. The valve assembly has a seat 28 and a movable valve element 29 which may be swung to the position 30 in which it is shown in dash-dot lines thus representing the valve in open position. The top of the vessel is also equipped with a level indicator 31 which provides an indication of the depth to which the pressure vessel 26 has been filled with finely divided materials. A pipe 32 leading from the top of vessel 26 has a valve 33 in it for venting the vessel as required. A pressure relief safety valve 34 is provided to relieve any excess pressure which may be developed in tank 26. The pressure vessel 26 is supported on load cells 54 and 55.

Near the bottom of conically shaped pressure vessel 26 there is an annular chamber 35 which is supplied with gas under pressure from a pipe 36. Interposed between chamber 35 and the interior of vessel 26 is a porous element 37 which permits gas to permeate into the finely divided powdered materials in the bottom of vessel 26 to thereby maintain the material in a fluidized state.

The discharge conduit 38 leading from reservoir 26 connects with a chamber 39 in which there is another porous element 40. Underneath this element, the same pressure is applied through a pipe 41 which is applied to the porous element 37 through the agency of pipe 36. The gases which permeate porous material 40 also contribute toward maintaining the finely divided material which drops into chamber 39 in a fluidized state. It is desirable that the pressure, P2, in vessel 26 be nearly equal to the pressure which exists in the vicinity of porous element 37 and in chamber 39. This facilitates free flow of powdered material through a rotary metering valve 42 into entrainment chamber 39'. It is necessary to account for the pressure drop which occurs in porous elements 37 and 40. Consequently, it is necessary to apply a higher pressure through pipes 36 and 41 than the pressure P.sub.2 which exists at the entrance of nozzle 46 and inside vessel 26. This higher pressure is obtained by connecting pipes 36 and 41 through a check valve 43 and a shut-off valve 44 to a high pressure line 45 in which P.sub.1 exists. Connected between line 45 and nozzle 46 as well as line 52 is a differential pressure reducing regulator 47. Regulator 47 maintains a constant pressure differential between P.sub.1 and P.sub.2 independent of various gas flow rates and pressures. If P.sub.3 rises, P.sub.2 will also rise. The rise in P.sub.2 will also cause a corresponding rise in P.sub.1 and the natural effect of a rise in P.sub.1 would be a drop in the process gas flow. The automatic flow control valve 48 is preset for a given flow rate. The decrease in P.sub.1 will cause flow control valve 48 to open up until the flow value is equal to the preset amount to which the flow control valve 48 is set. If P.sub.3 drops, the opposite sequence of events will occur until stability is reached.

To obtain material flow from pressure reservoir 26 to entrainment chamber 39' it is necessary to have pressure P.sub.2 higher than P.sub.3. This is achieved trhough a pressure drop in nozzle 46.

Power material flow rates entirely independent of variations of process gas flow rate and back pressure stemming from process variables can be then be obtained by utilizing, well known means familiar in the art to make the pressure difference in entrainment chamber 39, P.sub.1 relatively constant with respect to pressure P.sub.2 in pressure reservoir 26. This will permit calibrated discharge of powdered material for each fixed open position of metering valve 42 from pressure reservoir 26 to entrainment chamber 39' and conduit 25.

Alternatively, the bottom blown process, may be practiced in conjunction with sophisticated instrumentation in which the opening and closing of metering valve 42 will be controlled by means of special instrumentation based on integrating signals from load cells 54 and 55 with a pre-set rate of material flow per unit time from control console 49. Additional control in respect to other process variables will be obtained by integrating the metering valve 42 position movements with a pre-set rate of material per unit of process gas or gas flow per unit of material through control console 49'. These features will permit automation of the process material injection system and the establishment of operating procedures for various metallurgical controls, for instance, desulfurization and dephosphorization of the melt.

When it is desired to switch from one gas to another gas at higher pressure, everything in the system stays as it is. However, when it is desired to operate with process gas at a lower pressure than that in use, it is necessary to prevent back-flow of the gases from vessel 26 into the process gas feed system. To permit this function the check valve 50 is used in conjunction with check valve 43. If there is an increase in pressure on vessel 26, check valves 43 and 50 remain closed until the pressure on both sides of the check valve becomes equalized. Until equalization is reached, there is a flow of gas at the excess pressure from vessel 26 through the rotary metering valve 42 and through line 52, valve 53 and nozzle 46 out to discharge pipe 25. After pressure equalization is attained, check valves 43 and 50 open and the system is again on the line and functioning to deliver finely divided powdered materials at whatever pressure prevails in vessel 26. When check valves 43 and 50 open, the relationship between pressures P.sub.2 and P.sub.3 is re-established at the levels which existed prior to the input pressure change.

During periods where direct feed of process gas without entrainment of powdered material is required, rotary metering valve 42 is closed. Simultaneously, shut-off valves 44 and 53 will close and thus maintain pressure in pressure reservoir 26. If powdered material is again required, rotary metering valve 42 is re-opened with simultaneous opening valves 44 and 53 to bring the powdered material feeding system into operation. Additionally, in event that powdered material input for a specific heat is complete, the rotary metering valve 42 is closed with simultaneous closure of valves 44 and 53; at which time pressure in pressure reservoir 26 can be released through the vent valve 33 and brought to atmospheric pressure for re-loading of the pressure reservoir through filling aperture 28, even though process gas is still being conveyed to the steelmaking converter to the steelmaking converter. Necessary interlocks will be provided to prevent opening of rotary metering valve 42 and shut-off valves 44 and 53 when pressure is vented from reservoir 26.

Before departing from the description of FIG. 2, it will be noted that a shut-off valve 51 is provided and that this may be closed when it is desired to maintain the equipment. Note also that a pipe 52 connects the process gas supply at pressure P.sub.2 to the interior of vessel 26 through a shut-off valve 53. This line is used to pressurize vessel 26 to pressure P.sub.2 under operating conditions and to discharge excess gas pressure during a switch of one process gas to another.

It should also be noted in FIG. 2 that the rotary valve 42 which will be described in greater detail hereinafter, is operated by a linkage 60 which is merely symbolized by a dash-dot line. Linkage is driven by a mechanical operator 61 which is powdered by an electric motor or cylinder 62. The motor responds to control signals which are otherwise introduced in the system by driving linkage 60 and thereby opening or closing rotary metering valve 42 as required. On the input side of the rotary metering valve 42 is a valve seat assembly which is generally designated by the reference numeral 63 and which will be described in greater detail in connection with other figures. There is also a pressure line 64 connecting a pressure source higher than P.sub.3 to the valve seat assembly 63 for purposes which will be described in connection with the other figures.

Attention is now invited to FIGS. 3 thru 6 for a more detailed description of how the rotary metering valve and the nozzle arrangement is constructed. In FIG. 3, pressure vessel 26 is seen to be in communication with chamber 39 in which the finely divided powdered material is maintained in a fluidized state by gas pressure provided to pipe 41 permeating porous element 40. Finely divided powdered materials pass through valve seat assembly 63 under the control of the rotary metering valve 42. After passing through the rotary metering valve, the powdered materials continue into an entrainment chamber 39' where they are propelled by high velocity gas ejected from nozzle 46. The process gas and entrained finely divided powdered materials are then propelled into pipe 25 which conducts them to the bottom of converter vessel 10. The rotary metering valve 42 is essentially spherical but is flat on one side as indicated by the reference numeral 71. As can be seen in FIG. 4, the rotary metering valve is provided with a central V-shaped groove opening 72 which can be adjusted angularly in respect to an aperture 73 in valve seat assembly 63. The amount of the triangular shaped opening which is exposed to aperture 73 governs the amount of powdered material that will pass through rotary metering valve 42. The spherically shaped rotary metering valve 42 is supported by a shaft 74, as can be seen in FIG. 4, and it is this shaft which is driven by linkage 60 which appears in FIG. 1. As shown in FIG. 3, the apex 75 of the V-shaped groove opening through rotary or ball metering valve 42 is at such angle with respect to aperture 73 that full flow of powdered material through the rotary metering valve is permitted. If, in FIG. 3, rotary metering valve 42 is rotated counterclockwise the closed part of this arcuate surface 76 is presented to aperture 73 in which case no finely divided material may flow.

The ball shaped rotary metering valve 42 cooperates with an annular gasket 77. This gasket 77 constitutes the essential part of the valve seat, which has an interior peripheral corner 78 that presses firmly against the periphery of the ball shaped rotary metering valve 42. Gasket 77 is preferably made of pliable elastomeric material.

Gasket details can be seen best in FIG. 5. Pliable gasket or valve seat 77 has another annular pliable gasket 79 mounted immediately next to it. Gasket 79 is provided with an annular recess 80. The two gaskets 77 and 79 are set in plates 81 and 82, respectively, as can be seen in FIG. 5. Plates 82 and 81 are secured together to hold the gaskets by means of screws 83. Plate 81 and 82 are secured in position by a pair of oppositely spaced clamping members 84 and 85. These clamping members may be removed and the whole valve seat assembly including holding plates 81 and 82 and gaskets 77 and 79 may be removed bodily for replacment of the gaskets as required. Leading into annular space 80 associated with gaskets 79 is a duct 86 as can be seen in FIG. 5. This duct communicates with a tube 64 which was previously mentioned in connection with FIG. 2. In the latter figure, tube 64 was explained as having the purpose of connecting a pressure source higher than P.sub.3 with annular chamber 80 in the valve seat assembly 63. The purpose of this construction is to assure that there will be no back flow through the ball valve 42 when there is a higher pressure on its discharge side than the interior pressure of vessel 26. In other words, it is imperative that rotary ball metering valve 42 shut off tightly under these conditions. Thus, pressure is applied to annular chamber 80 in gasket 79 through tube 64 as to pressurize the annular chamber and thereby augment the pressure between gasket or valve seat 77 and rotary metering valve 42. Note in FIG. 3 and 5 that the rotary metering valve is turned for exemplary purposes at such angle that its flat side 71 is in parallelism with the valve seat assembly. The purpose of this is to permit easy retraction of the gasket holding assembly for replacement of the valve seats as described earlier.

The valve assembly shown in FIG. 5 is seen to be a cross-section of the valve which is shown in elevation in FIG. 6. The section is taken on a line corresponding with 5--5 in FIG. 6. In the latter figure one may readily see how the pressure line 64 is connected to plate 85 so as to supply pressure through duct 86 to annular space 80 in gasket 79. Plate 85 is provided with a plurality of clamping bolts 89 which can be removed to enable removal of the valve seat holding assembly 63 bodily for maintenance purposes as described above. 39'

FIGS. 2 thru 6 show how gas entrained finely divided powdered materials may be delivered from a reservoir 26 through the rotary metering valve structure to pipe 25 through which they are conveyed to the bottom of converter vessel 10. In most installations, it is necessary to supply a variety of finely divided materials to a single converter vessel by means of various gases at various pressures. How this can be done is illustrated in FIG 4. In this figure, the center pressure reservoir 26 corresponds with the reservoir shown in FIG. 2. In FIG. 4, however, there is a pipe 96 leading from the rotary metering valve 42 to the entrainment chamber 39'in which nozzle 46 is located and connected to converter vessel feed pipe 25. On each side of reservoir 26 there are additional pressure vessels 97 and 98 which are respectively connected with valves 99 and 100. Valve 99, for example, is connected with the entrainment chamber 39' with nozzle 46 by means of a conduit 101. Valve 100 is connected to the nozzle chamber by means of a conduit 102. Conduits 101 and 102 preferably make an angle of at least 50.degree. with respect to horizontal when directly connected to entrainment chamber 39'. In cases where conduit connections 101 and 102 are required with inclinations of less than 50.degree. to the horizontal special high pressure air slides and/or pressure screws will be used for connections to entrainment chamber 39'. This angular disposition of conduits 101 and 102 assures that powdered materials will remain in suspension during transport from their valves to the entrainment chamber. The entrainment chamber 39' shown in FIG. 4 serves as a means for entraining the powdered materials from each of the reservoirs 97, 26 and 98.

In the arrangement shown in FIG. 4, each pressure reservoir 97, 26 and 98, would be supplied through a pair of valves corresponding with valves 44 and 53 in FIG. 2. When any one of the pressure reservoirs is in use and is supplying finely divided powdered materials to the entrainment chamber, its valves corresponding with valves 53 and 44 would be open and the corresponding valves associated with the other pressure vessels would be closed at that time to prevent feed-back of finely divided materials from one pressure reservoir to another. The specific sealing device construction detailed in FIG. 5 to be used to ensure that the rotary metering valves 99, 100 and 42 can be used as shut-off valves when not in operation.

It should be further noted that before start of a process heat blow, all pressure reservoirs 97, 26 and 98 have to be loaded with material and then pressurized to P.sub.2 shown in FIG. 2. This will enable any pressure reservoir to be used during the bottom blown process without effecting back pressure P.sub.3.

Claims

What is claimed is:

1. For use in a system which is adapted to convey finely divided materials from a pressurizable storage vessel through a material flow metering valve and then a nozzle chamber in which pressure is maintained relatively constant over a range of process gas flows and back pressures, and in which the material is entrained by gas from the nozzle and thence conveyed to tuyeres which allow injection of the gas and material beneath the surface of molten metal in a vessel for converting ferrous metal to steel, the improvement comprising:

a. said material flow metering valve means has a rotary element with a flow-through opening therein,

b. pliable valve seat means in sealing engagement with said rotary element and cooperating therewith, said valve seat means having a cavity means that responds to gas pressure therein by increasing the sealing pressure between said seat means and said rotary element, and

c. a high pressure source, gas conducting means intercommunicating said cavity to said high pressure source means, the pressure of said source being in excess of pressure in said nozzle chamber means whereupon if the pressure in said nozzle chamber exceeds the pressure in said storage vessel said cavity will be pressurized to enhance said sealing engagement.

2. The invention set forth in claim 1 including:

a. means holding and supporting said pliable valve seat means in proximity with said rotary valve means,

b) said holding means being removable to facilitate removal of said valve seat means therewith.

3. The invention set forth in claim 2 including:

a. a plurality of pressurizable storage vessels and load cells on which said vessel react, respectively, and

b. metering valve means interposed between each of said storage vessels and said nozzle chamber.

4. The invention set forth in claim 3 wherein there are:

a. individual conduit means directly connecting the said metering valve means to said single nozzle chamber, said conduit means being disposed at an angle of not less than 50.degree. with respect to a horizontal plane.

5. The invention set forth in claim 1 including:

a. a first pressure chamber means and a gas permeable means associated therewith for fluidizing the finely divided material in the bottom region of said pressurizable vessel means

b. a second pressure chamber means and a gas permeable means associated therewith for fluidizing the finely divided material near the inlet to said metering valve mean,

c. high pressure gas feed pipe means,

d. means including a shut-off valve and a check valve communicating said feed pipe means to both of said first and second pressure chamber means,

e. differential-pressure reducing regulator means and check valve means serially connected between said feed pipe means and said nozzle means,

f. means including another shut-off valve communicating a point intermediate said last named check valve means and said nozzle means with the top of said pressure vessel above the uppermost level of the finely divided material therein, and

g. means for operating said metering valve means, said shut-off valves each being adapted to operate in response to operation of said metering valve means, whereby to selectively permit or prevent flow of gas through said nozzle chamber with or without entraining finely divided material.

6. The invention set forth in claim 5 including:

a. pressure relief means adapted to relieve pressure in said storage vessel when said metering valve means and said shut-off valves are closed, whereby to permit loading of said storage vessel with finely divided material without discontinuing gas feed through said nozzle.

7. The invention set forth in claim 1 including:

a. load responsive means receiving a force from said storage vessel and producing signals functionally related to said force and regulation and control means for controlling the position of said material flow metering valve and thereby the rate of material flow to the process, using for control purposes signals from said load responsive means on said pressurizable storage vessel that are integrated with pre-set requirements of material flow set in a control console in terms of material weight per unit time.

8. The invention set forth in claim 1 including:

a. load responsive means receiving force from said storage vessel and producing signals which are functionally related to said force and regulation and control means for controlling the position of said material flow metering valve and thereby the rate of material flow to the process, using for control purposes signals from said load responsive means on said pressurizable storage vessels that are integrated with pre-set requirements of material flow set in a control console in terms of material weight per unit volume of process gas.

9. The invention set forth in claim 8 wherein:

a. said regualtion and control means in which said pressure responsive means are integrated include signals indicative of pre-set requirements of material flow in terms of process gas volume per unit weight of material.

10. Apparatus for use with a metallurgical vessel wherein the apparatus delivers gas or finely divided material to an entrainment chamber subject to variations of process gas flow and back pressure, for entrainment in gas for injection into the vessel below the level of molten metal therein whereby said gas and materials may diffuse through molten metal in the converter vessel, said apparatus comprising:

a. material storage reservoir means adapted to be pressurized,

b. means for fluidizing finely divided material and means for discharging material from said vessel adjacent said fluidizing means,

c. a finely divided material entrainment chamber means communicated with said discharging means and including a nozzle means for projecting gas therein,

d. metering valve means interposed between said fluidizing means and said entrainment chamber means, said entrainment chamber means being constructed and arranged for communicating with said converter vessel,

e. a gas feed line adapted to be connected with a source of high pressure gas,

f. gas flow regulating means coupled to said gas feed line and to said fluidizing means and to said material entrainment chamber and being constructed and arranged to provide a higher gas pressure to said fluidizing means than to said entrainment chamber,

g. said metering valve means comprises a rotary valve element having a notch extending chordally therethrough,

h. an apertured pliable valve seat means positioned for cooperating with said rotary valve element to regulate the flow of finely divided material from said storage vessel means to said entrainment chamber,

i. an apertured pliable element juxtaposed to said valve seat means and having a cavity which is subjected to be pressurized to enhance the sealing pressure between said seat means and said rotary valve element, and

j. said gas flow regulating means communicating gas pressure with said cavity whereby when said rotary valve element is closed and the pressure is lower in said storage vessel than in said entrainment chamber the pressure in said cavity will effect said sealing pressure enhancement.

11. The apparatus set forth in claim 10 including:

a. regulation and control means for controlling the position of said material flow metering valve and thereby the rate of material flow to said metallurgical vessel independent of process gas flow rate and back pressure variations, means for producing signals representative of the weight of the contents of said pressurizable storage vessel means responsive to said signals for operating said control means to produce a predetermined material flow rate.

12. The apparatus set forth in claim 10 wherein:

a. there are a plurality of finely divided material storage reservoir means each of which has a said metering valve means associated therewith,

b. pipe means communicating each of said valve means with the same said entrainment chamber, said metering valve means being selectively operable to close all but one of them and to let one remain open and subject to variable control without feed back of gas pressure from said entrainment chamber to any of the inactive storage reservoirs.

13. The invention set forth in claim 10 including:

a. regulation and control means for controlling the position of said material flow metering valve means and thereby the rate of material flow to said converter vessel independent of the process gas flow rate and back pressure variations, using for control purposes signals representative of the weight of the material contents of said pressurizable vessel which signals are integrated with signals indicative of pre-set requirements of material flow in terms of process gas volume per unit weight of material.

14. A system for conveying gas entrained finely divided material from a material storage vessel to apparatus for converting ferrous metal to steel, comprising:

a. a chamber having an inlet communicating with said storage vessel and an outlet communicable with said apparatus,

b. metering valve means interposed between said vessel and said chamber inlet for regulating the flow of finely divided material from the vessel to the chamber, and including a movable element,

c. nozzle means having an inlet and an outlet at least the latter of which is disposed in said chamber for producing a gas stream to entrain said material,

d. said storage vessel means having a material discharge opening communicating with said metering valve means,

e. gas permeable means in said vessel near said discharge opening and an enclosure for said gas permeable means, and

f. gas distribution means for providing gas at a first pressure to said nozzle and a higher pressure to said gas permeable means for fluidizing said material,

g. pliable valve seat means in sealing engagement with said movable element, said seat means having a cavity coupled to said gas distribution means for receiving gas at a pressure in excess of said first pressure to enhance the sealing force between said seat means and said movable element.

15. For use in a system for conveying finely divided material from a pressurizable storage vessel to apparatus for converting ferrous metal to steel in which system material is conducted through a conduit means from said vessel to a chamber wherein said material is entrained in gas projected by a nozzle, the improvement comprising:

a. metering valve means including a rotary valve element interposed between said vessel and chamber,

b. pliable valve seat means in sealing engagement with said rotary element, said seat means having a cavity for receiving pressurized gas to enhance the sealing force between said seat means and said rotary element.

16. The invention set forth in claim 15 including:

a. means for intercommunicating the inlet of said nozzle and the interior of said vessel for enabling substantially the same gas pressure to be applied thereto,

b. means for connecting said cavity to a source of gas pressure greater than said same pressure, whereupon if the pressure in said nozzle chamber exceeds the pressure in said storage vessel, said cavity will be pressurized to said greater pressure to enhance sealing engagement and inhibit flow from said chamber to said vessel.

17. The invention set forth in claim 15 including:

a. rigid means in said conduit means for supporting said pliable valve seat means in proximity with said rotary valve means, said rigid means being mounted for removal from said conduit means jointly with said valve seat means.

18. The invention set forth in claim 15 including:

a. means for determining the weight of material in said storage vessel and means responsive to said determining means by regulating the flow of material through said metering valve means.

19. The invention set forth in claim 18 wherein:

a. said weight determining means is at least one load cell on which at least the weight of said storage vessel means reacts.

20. A system for selectively transporting gas and gas entrained finely divided material to a vessel for converting ferrous metal to steel characterized by said vessel having a refractory lining and tuyere means for conducting said gas and material into said vessel for permeation through a melt contained therein, comprising:

a. at least one pressurizable material storage vessel,

b. a first chamber for communicating with said tuyere means,

c. nozzle means for projecting a gas stream in said chamber to selectively entrain material received from said storage vessel,

d. conduit means having an inlet communicating with said storage vessel and an outlet communicating with said nozzle chamber,

e. metering valve means interposed in said conduit means between said storage vessel and first chamber, said metering valve means including a movable valve element and pressure responsive valve seat means disposed between said valve element and the inlet of said conduit, said pressure responsive valve seat means including a pliable valve seat having one side engagable with said movable valve element and means defining a pressurized fluid receiving space on the other side of said valve seat, said space being isolated from said storage vessel and chamber,

f. first gas permeable means communicating with a space in said conduit means between said valve means and said storage vessel and including a first enclosure for enabling application of pressurized gas to said first permeable means for agitating said material,

g. a second gas permeable means adjacent the exit of said vessel and entrance of said conduit means and including a second enclosure for enabling application of pressurized gas to said second permeable means to agitate said material,

h. gas supply means for providing gas under a first pressure to said nozzle chamber and at a higher pressure to said first and second gas permeable means, said gas supply means also being coupled to said pressurized fluid receiving space seat means for providing a gas thereto at a pressure higher than said first pressure to enhance the sealing engagement between said valve element and said valve seat whereby said valve seat is urged into positive engagement with said valve element regardless of pressure variations in said storage vessel or chamber.

21. The invention set forth in claim 20 including:

a. pressure relief means adapted to relieve pressure in said storage vessel when said metering valve means and said shut-off valves are closed, whereby to permit loading of said storage vessel with finely divided material without discontinuing gas feed through said nozzle.

22. The invention set forth in claim 20 including:

a. load sensitive means on which a force is applied by said storage vessel means in accordance with the weight thereof and which produces corresponding signals,

b. regulation and control means to control position of said material flow metering valve and thereby control the rate of material flow to the process, using for control purposes said signals from said load sensitived means which signals are integrated with pre-set requirements of material flow in terms of material weight per unit time.

23. The invention set forth in claim 20 including:

a. load sensitive means on which a force is applied by said storage vessel means in accordance with the weight thereof and which produces corresponding signals,

b. regulation and control means to control said material flow metering valve and thereby the rate of material flow to the converter vessel, using for control purposes signals from said load sensitive means which signals are integrated with pre-set requirements of material flow in terms of material weight per unit volume of process gas.

24. Apparatus for use with a vessel adapted for converting impure molten ferrous metal to steel wherein the apparatus delivers gas or finely divided material to an entrainment chamber subject to variations of process gas flows and back pressures, for entrainment in gas and injection into the vessel below the level of molten metal therein whereby said gas and materials may diffuse through molten metal in the converter vessel, said apparatus comprising:

a. material storage reservoir means adapted to be pressurized,

b. means for fluidizing finely divided material discharging from the bottom of said vessel,

c. a finely divided material entrainment chamber means including a nozzle means adapted to project gas therein,

d. metering valve means disposed on the inlet side of said entrainment chamber means, said entrainment chamber means being constructed and arranged for communicating with said converter vessel,

e. a gas feed line adapted to be connected with a source of high pressure gas,

f. said metering valve means comprises a rotary valve element having a notch extending chordally therethrough,

g. an apertured pliable valve seat means positioned for cooperating with said rotary valve element to regulate the flow of finely divided material from said storage reservoir means to said entrainment chamber,

h. an apertured pliable element juxtaposed to said valve seat means and having a cavity which is subjected to be pressurized to enhance the sealing pressure between said seat means and said rotary valve element.

25. The apparatus set forth in claim 24 wherein:

a. there are a plurality of finely divided material storage vessel means each of which has a said metering valve means associated therewith,

b. pipe means communicating each of said valve means with the same said entrainment chamber, said metering valve means being selectively operable to close all but one of them and to let one remain open and subject to variable control without feed back of gas pressure from said entrainment chamber to any of the inactive storage vessels.

26. A system for conveying finely divided materials from a pressurizable storage vessel to a metallurgical vessel, the combination of, a material flow metering valve, first means for entraining said material in a pressurized gas stream to a metallurgical vessel, said valve being disposed between said storage vessel and said first means, said valve including a movable valve element, pressure responsive valve seat means sealingly engageable with said valve element and cooperating therewith, said valve seat means including a pressure responsive pliable valve seat having one side in engagement with said valve element, pressurizable means associated with the other side of said valve element and including pressurized fluid receiving space isolated from the storage vessel and said first means, said pressurizable means urging said valve seat into engagement with said movable valve element when said space is pressurized for increasing the sealing pressure with said valve element, and pressurized fluid conducting means connecting said pressurized fluid receiving space to a high pressure source means, the pressure of said source being in excess of pressure in said first means whereby said valve seat is urged into positive engagement with said valve element regardless of pressure variations in said storage vessel or first means.

27. The system set forth in claim 26 wherein said first means comprises a nozzle chamber connected to receive material from said vessel and passing said valve, a nozzle disposed in said chamber and connected to receive a pressurized gas stream for entraining said material, said pressurized gas creating a pressure in said chamber.

28. The system set forth in claim 26 wherein said movable valve element comprising a rotary valve element in sealing engagement with said valve seat.