MXPA99005608A - Gas jet supersonic coherent to provide gas to a liquid - Google Patents

Abstract

A system for establishing and maintaining a (supersonic coherent gas jet, effective either with an oxidizing gas or an inert gas, which employs a convergent / divergent nozzle for the establishment of an initial supersonic velocity without interruptions, and a flame cover of three layers ned, slower motion, coaxial with the jet for the effective maintenance of supersonic speed O. The invention is particularly useful for providing a gas to a liquid mixture.

Description

GAS JET SUPERSONIC COHERENT TO PROVIDE GAS TO A LIQUID Technical Field This invention relates generally to a method for producing and maintaining a supersonic gas flow. The invention is particularly advantageous when the composition of the gas changes. The invention can be used to supply gas to a liquid.

Background of the Invention It is generally desired to establish a gas flow. For example, a gas flow can be injected into a liquid for one or more of several reasons. A reactive gas can be injected into a liquid to react with one or more liquid components, such as, for example, the injection of oxygen to molten iron to react with carbon within the molten iron to decarburize the iron and provide heat to the molten iron. . The oxygen can be injected to other molten metals such as copper, lead and zinc for smelting or refining purposes to an aqueous liquid or hydrocarbon liquid to perform an oxidation reaction. A non-oxidizing gas, such as an inert gas, can be injected into a liquid to agitate the liquid in order to promote, for example, a better temperature distribution or a better component distribution through liquid. Usually! the liquid is contained in a container tai such as a reactor or a casting container, wherein the liquid forms a combination within the container conforming to the bottom and to a certain length of the side walls of the container, and having a top surface. When gas is injected into the liquid combination, it is desirable to have as much gas flow as possible in the liquid to perform the gas injection attempt. Accordingly, the gas is injected from a gas injection device into the liquid below the surface of the liquid. If the nozzle for a normal gas jet was separated some distance above the surface of the liquid, then much of the gas that hits the surface will be diverted to the liquid surface and will not enter the liquid combination. In addition, said action causes splashing of the liquid, which can result in the loss of material and operational problems. The submerged injection of gas into the liquid using gas injection devices mounted on the bottom or on the side wall. although very effective, they have operational problems when the liquid is a corrosive liquid or is at a very high temperature, since these conditions can cause a rapid deterioration of the gas injection device and localized wear of the container liner resulting in both the need of sophisticated external cooling systems as frequent interruptions for maintenance and high operating costs A "need" is to bring the tip or nozzle of the gas injection device close to the surface of the liquid combination, while avoiding contact with the surface of the liquid and to inject the liquid from the gas injection device at a high speed, so that a significant portion of the gas passes into the liquid. However, this need remains unsatisfactory, since the proximity of the tip of the injection gas device to the surface of the liquid can result in all through significant damage to this equipment In addition, in cases where the surface of the liquid is not stable, the nozzle could be constantly moving representing the moving surface, so that gas injection occurs from the desired location and distance required between the spearhead and the bath surface could be maintained For electric arc furnaces, this requires hydraulically driven, complicated lance manipulators, which are expensive and require extensive maintenance. Another advantage is to use a pipe that is introduced. through the surface of the liquid combination For exampleIn general, waterless chilled pipes are used to inject oxygen into the molten steel bath in an electric arc furnace. However, this need is not satisfactory either, since the rapid wear of the pipe requires hydraulically operated pipe manipulators, which are complicated as a pipe feeding equipment to compensate for rapid wear of the pipe. In addition, the loss of pipe, which must be replaced continuously, is costly. These problems can be solved if a coherent jet could be established. coherent retains its diameter and velocity, after being ejected from a nozzle, more than a normal gas jet does With a coherent jet, the injection tip can be placed significantly farther from the liquid surface, while still allowing that virtually all the gas within the coherent gas jet penetrates the liquid surface. It is known that a The coherent jet of an oxidizing gas can be established by surrounding the oxidation gas jet after its ejection from a nozzle with a flame cover formed by an annular fuel stream around the oxidant gas jet and a stream of annular oxidant at the fuel stream The fuel and oxidant burn to form the flame cover, which flows coaxially with the oxidizing gas stream and keeps it coherent for a long distance after ejection from the nozzle. However, this provision of flame cover does not work well if the gas is an inert gas. In such situations, the velocity of the gas jet is rapidly reduced and the coherence of the inert gas jet deteriorates rapidly. This is a particular problem when it is desired to commute from an oxidizing gas to an inert gas since this requires the alteration of the gas ejection system. Therefore, it is an object of this invention to provide a method for maintaining the speed and coherence of a gas jet without considering whether the gas jet is a jet of oxidizing or inert gas. It is another object of this invention to provide a method for maintaining the speed and coherence of a gas jet, while allowing the composition of the gas jet to be changed.

SUMMARY OF THE INVENTION The above objects and others, which will be apparent to those skilled in the art upon reading this description, are obtained through the present invention, one aspect of which is: A method for establishing a current of high velocity coherent main gas, comprising: (A) ejecting a main gas from a lance having a converging / diverging nozzle to form a main gas stream having a supersonic velocity; (B) expelling a flow of a first oxidant from the lance annularly into the main gas stream, said flow of first oxidant having a velocity less than that of the main gas stream; (C) ejecting a flow of fuel from the lance annularly into the flow of the first oxidant, said fuel flow having a velocity less than that of the main gas stream; (D) expelling a flow of a second oxidant from the lance annularly to the fuel flow, said flow of the second oxidant having a lower velocity than that of the main gas stream; (E) burning the fuel with at least one of the first oxidant and the second oxidant to form a flame cover around the main gas stream. Another aspect of the invention is: An apparatus for establishing a high velocity coherent main gas stream, comprising: (A) a lance having a main gas passage communicating with a converging / diverging nozzle to eject a main gas to a expulsion space; (B) first passage means within the lance to eject a flow of a first oxidant into the ejection space annularly to the main gas stream; (C) second passage means within the lance to eject a flow of fuel into the ejection space annularly towards the flow of the first oxidant: and (D) third passage means within the lance to eject a flow of second oxidant towards the ejection space annularly towards the fuel flow. A further aspect of the invention is: A method for providing gas to a liquid, comprising.

(A) ejecting a main gas from a lance having a converging / diverging nozzle to form a main gas stream having a supersonic velocity; (B) expelling a flow of a first oxidant from the lance annularly into the main gas stream, said first oxidant flow having a lower velocity than that of the main gas stream; (C) expelling a fuel flow from the spear anuously into the flow of the first oxidant, the fuel flow having a velocity less than that of the main gas stream; (D) ejecting a flow of the second oxidant from the lance annularly to the fuel flow, said flow of the second oxidant having a lower velocity than that of the main gas stream; (E) burning the fuel with at least one of the first oxidant and the second oxidant to form a flame cover around the main gas stream; and (F) passing the gas from the main gas stream to a liquid. - As used herein, the term "annularly" represents the shape of a ring. As used herein, the term "inert gas" means a pure gas or gas mixture having an oxygen concentration, which is less than 5 mol%. As it is meant herein, the term "oxidizing gas" represents a pure gas or gas mixture having an oxygen concentration of at least 5 mol%. As used herein, the term "flame cover" means an annular combustion stream substantially coaxial with the main gas stream.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of an embodiment of the tip section of a lance, which can be used in the practice of this invention. Figure 2 is a spearhead section head view illustrated in Figure 1. Figure 3 is a representation of the spear shown in Figure 1 during operation. Figure 4 is a cross-sectional view of another embodiment of the tip section of a lance, which can be used in the practice of this invention. The numbers in the drawings are the same for common elements.

Detailed Description The invention allows the establishment and maintenance of a coherent gas jet regardless of whether the gas is an oxidizing gas or is an inert gas and also allows the gas to change, such as from an oxidant jet to an inert, or vice versa , without any significant deterioration of the coherence and without requiring any change of equipment more than that necessary to supply the different main gas. In addition, the invention allows the oxygen concentration of a changing oxidizing main gas without encountering any significant loss of coherence in the main gas jet. The invention will be described in detail with reference to the drawings. Referring now to Figures 1 and 3, a lance tip section 1 of a lance that can be used to practice the invention is shown in cross section. The spearhead section 1 includes a main gas passage 2, which communicates with a main gas source (not shown). The main gas can be an oxidizing gas or an inert gas. Examples of an oxidizing gas include air, oxygen-rich air having an oxygen concentration of at least 30 mol%, particularly at least 90 mol%, and technically pure oxygen having an oxygen concentration of 99.5 mol% or more. Examples of an inert gas include nitrogen, argon, carbon dioxide, hydrogen, helium, gaseous hydrocarbon and mixtures comprising two or more of the same. The main gas passage 2 communicates with the converging / diverging nozzle 3 at the nozzle inlet 4. The nozzle has an outlet 5. which communicates with the ejection space 6 where the gases are injected. The nozzle outlet 5 has a diameter that is generally within the range of 0.254 to 7.62 cm, preferably within the range of 1.27 to 5.08 cm.

Preferably, as illustrated in Figures 1 and 3, the ejection space 6 is initially confined by an extension section of the lance tip 7 and then opened to a larger volume downstream of the extension section 7. The section of extension 7 typically has a length of 1.27 to 10.16 cm and serves to stabilize combustion of the annular fuel and oxidant to form a flame cover 11 having a greater stability in the initial stages after ejection from the tip section of the tire. Launches that could be the case without the use of the extension section to form the initial confined expulsion space. The main gas passes from the main gas source through the main gas passage 2 and towards the nozzle 3 through the inlet 4. The gas accelerates in the diverging portion of the nozzle, so that it is at a supersonic velocity when it is ejected from the outlet nozzle 5 towards the ejection space 6. The convergent / divergent nozzle allows the initial obtaining of supersonic velocity without interruption. A straight-bore nozzle could cause gas expansion to achieve supersonic velocity to occur after the gas leaves the nozzle causing several cycles of expansion and contraction pulsation before reaching a steady state somewhere downstream of the outlet The velocity of the main gas stream 12 ejected from the bounce outlet 5 is supersonic, that is, it exceeds Mach 1 and preferably is on the Mach 1 2 scale at Mach 3 O, when the main gas is ejected. an atmosphere at an atmospheric pressure Radially separated from the main gas passage 2 is a first annular passage 8, radially separated from the first annular passage 8 is a second annular passage 9, and radially separated from the second annular passage 9 there is a third passage annular 10 The first annular passage 8 communicates with a source of a first oxidant (not shown), which preferably is a fluid that e has an oxygen concentration of at least 30 mol%, very preferably at least 90 mol%, and can be technically pure oxygen. The first oxidant passes through the first annular passage 8 and is injected from the lance into the ejection space 6 in an annular flow to the main gas stream and having a velocity less than that of the main gas stream. Generally, the flow of the first oxidant will have a velocity within the range of 91 44 to 457 2 m per second (mps). The second annular passage 9 communicates with a fuel source ( not shown) The fuel can be any fluid fuel such as methane, propane butylene, natural gas, hydrogen coke oven oil or oil The fuel can be diluted with a diluent, such as, for example, nitrogen The fuel passes through the second annular passage 9 and is ejected from the lance into the ejection space 6 in an annular flow to the first oxidant flow having a lower velocity than that of the primary gas stream. ncipal. Generally, the fuel flow will have a speed within the range of 91.44 to 457.2 m per second. Preferably, the fuel flow will have a velocity approximately equal to the flow rate of the first oxidant. The third annular passage 10 communicates with a source of a second oxidant (not shown), which may be the same source of the first oxidant. That is, the second oxidant can have, and preferably has, the same composition as the first oxidant. Preferably, the second oxidant is a fluid having an oxygen concentration of at least 30 mol%, most preferably at least 90%, and may be technically pure oxygen. The second oxidant passes through the third annular passage 10 and is expelled from the lance into an ejection space 6 in an annular flow to the fuel flow and having a lower velocity than that of the main gas stream and preferably smaller than that of the flow of the first oxidant. Preferably, the flow of the second oxidant has a lower velocity than that of the fuel flow. Generally, the flow of the second oxidant will have a speed within the range of 30.48 to 457.2 m per second and preferably within the range of 30.48 to 152.4 m per second. Each of the first, second and third annular passages communicates with the ejection space 6 preferably, as illustrated in Figures 1 and 3, even or flooded at the outlet 5 of the converging / diverging nozzle 3. Preferably, as shown in Figure 2, each of the first, second and third annular passages becomes a plurality of individual passages, so that each of the first, second and third annular passages communicates with the expulsion space 6 as a ring of holes around the outlet 5. Alternatively, one or more of the first, second and third ring passages can communicate with the injection volume 6 as a circular ring towards the outlet 5 After the expulsion towards the ejection space, the fuel is mixed and burned with at least one, and preferably both, of the first and second oxidants to form a flame cover 11 around the main gas stream. invention is employed in a hot environment such as a metal melting furnace, no separate ignition source is required for the fuel and the oxidant if the invention is not to be employed in an environment where the fuel and the oxidant have self-ignition, an ignition source such as a spark generator will be required The flame cover will have a speed lower than the main gas stream velocity, and will generally be within the range of 15-24 to 304 8 m per second The triple layer slows down the flame cover 11 around the initially supersonic gas flow 12 from the diverging converging nozzle and serves to keep the gas stream coherent, that is, with little loss of speed and with little expansion of the width of the main gas stream, for a significant distance from the nozzle, generally at least 20 nozzle outlet diameters (d) and up to 100d or more while the supersonic speed continues to be maintained This allows the placement of the lance so that the spear point is separated at a greater distance from where the main gas hits or otherwise couples a liquid or a solid, thus improving safety and conserving better the integrity of the lance Preferably, the main gas impacts on the target liquid or solid at a supersonic velocity, and preferably, the flame cover extends substantially from the lance tip towards the surface of the target liquid or solid. amount of fuel and oxidant provided from the lance will be adjusted enough to form an effective flame cover for the longit However, there are many times when you want significantly more fuel and oxidant to pass from the lance so that the flame cover not only serves to protect the main gas stream from the introduction of ambient gas. In addition, it also serves to provide a significant heat in the injection volume. In other words, the lance may, in some embodiments of this invention, also function as a lance. the spearhead of the invention, wherein the first annular passage communicates with the third annular passage within the lance, so that the first annular passage receives the oxidant to be expelled towards the expulsion volume from the third annular passage to through an internal connection passage 13. The connection passage 13 is dimensioned to ensure that the speed difference between the first oxidant stream and the second stream oxidant is maintained in the preferred embodiment of the invention. The invention will find particular utility for the injection of a gas into a liquid, wherein it is desired to keep the spear tip out of the liquid and, in addition, significantly separate from the surface of the liquid. For example, the invention can be used to provide a gaseous reactant to a hydrocarbon or aqueous liquid, such as for an oxidation, hydroxidation or nitrogenation reaction. It will be particularly useful when the liquid is a corrosive liquid, such as a highly acidic or basic liquid, or when the liquid has a very high temperature, such as a molten metal. A particularly effective use of the invention is to provide oxygen, the main gas, to the molten metal to react with carbon in the molten metal to decarburize the metal and provide heat to the molten metal. Then, the main stream can be changed to be an inert gas such as argon, without any other change in the equipment or flowing into the annular passages, to provide the argon to the molten metal to stir the molten metal and distribute the heat better. This change it can be carried out relatively and quickly and without the loss experienced so far in the efficiency of establishing the coherent main gas jet. A particularly advantageous use of this invention is to inject gases having different concentrations of oxygen into a liquid such as a molten metal, without the need for any other major change when the oxygen concentration of the main gas is changed. For example, to make stainless steel, the invention can be used to provide a main gas stream coherent to the molten metal from a lance having a separate tip at a significant distance from the surface of the molten metal. Said injection by lance can be used in place of conventional gas injection through submerged nozzles. During the initial stages of the stainless steel process, the main gas stream is composed of an oxidizing gas such as pure oxygen or a fluid mixture having an oxygen concentration of about 75 mol%, where the remainder is nitrogen, argon or carbon dioxide. As the refining process continues, the oxygen concentration in the main gas is reduced in a programmed manner. Finally in the final portion of the refining process, the main gas becomes an inert gas. The invention and its advantages will be further illustrated in relation to the following examples and comparative examples. The examples are presented for illustrative purposes and are not intended to be limiting.

In order to demonstrate known systems, a lance having a spear point similar to that illustrated in Figures 1 and 3, but without the third annular passage, was employed. The converging / diverging nozzle had a throat diameter of 0 909 cm and an outlet diameter of 1 336 cm Pure oxygen was expelled from the nozzle to form a main gas stream having an initial velocity of 524 2 mps Natural gas was passed to the injection volume from the first annular passage to a speed of 185 9 mps and pure oxygen was passed to the injection volume from the second annular passage at a speed of 124 9 mps forming a flame cover around the main oxygen gas stream The velocity of the main gas stream on its axis it was measured at a distance of 91.44 cm from the nozzle outlet and it was found to be only a small drop in its initial velocity The normalized velocity of the gas stream oxygen main, that is, its jet axis velocity of 91 44 cm from the nozzle outlet divided by its initial jet axis velocity, was 0 95 or 95% However when the test was repeated using pure nitrogen a an initial velocity of 560 8 mps as the main gas, its normalized speed was only 43% The deterioration of the velocity of the nitrogen gas jet was reduced a little by changing the order of the fuel and the oxidant which form the flame cover That is, oxygen is provided through the first annular passage and natural gas was provided through the second annular passage. In this test, the normalized nitrogen velocity improved up to 74%. However, when this test was repeated using oxygen as the main gas, the normalized oxygen velocity deteriorated to 81%. A similar spearhead, but with a third annular passage, such as that illustrated in Figures 1 and 3, was used to demonstrate the invention. The procedure was similar to that previously described, except that pure oxygen was expelled into the ejection space from the first annular passage at a speed of 185.9 mps, natural gas was expelled into the ejection space from the second annular passage to a speed of 185.9 mps, and pure oxygen was expelled into the ejection space from the third annular passage at a speed of 82.29 mps to form the flame cover. When oxygen was used as the main gas, its normalized speed was 90%, which was a significant improvement over the 81% previously obtained when the main gas was an oxidizing gas and the flame envelope gas closest to the gas main was an oxidant. Further. when the main gas was changed to nitrogen, its normalized speed was 89%, which was a significant improvement over all known arrangements and demonstrates that the invention can be used with good effectiveness to establish and maintain a coherent jet using either an oxidizing gas or an inert gas for the coherent jet.

Although not intended to be held by any theory, the applicants believe that the advantageous results obtained with their invention are due to, at least in part, the maintenance of the flame cover closest to the main gas jet. The ring oxidant current low speed external, which is in contact with the middle annular fuel stream, serves to stabilize a flame on the nozzle face The stability of the flames is achieved by providing an extension causing some of the hot combustion gases to circulate near the nozzle face acting as a source of continuous ignition The current internal annular oxidant mixes with the average annular fuel current, providing a fuel rich in oxygen-oxygen mixture very close to the perimeter of the main gas jet This oxygen-rich atmosphere keeps the flame cover near the perimeter of the main gas jet The presence of a current or Internal ring xidant is especially effective when the main gas is an inert gas that contains little or no oxygen Now through the use of this invention, a jet of coherent supersonic gas with approximately the same effectiveness can be established and maintained over a long distance without considering whether the gas jet is an oxidizing gas or an inert gas Although the invention has been described in detail with reference to certain preferred embodiments those skilled in the art will recognize that other embodiments of the invention exist within the spirit and scope of the appended claims.

Claims (2)

1. - A method for establishing a coherent mainstream gas stream at high speed comprising: (A) ejecting a main gas from a lance having a converging / diverging nozzle to form a main gas stream having a supersonic velocity; (B) expelling a flow of a first oxidant from the lance annularly into the main gas stream, said flow of first oxidant having a velocity less than that of the main gas stream; (C) eject a flow of fuel from the lance annularly to the flow of the first oxidant, said fuel flow having a velocity less than that of the main gas stream: (D) expelling a flow of a second oxidant from the throws annularly towards the fuel flow, said flow of the second oxidant having a speed lower than that of the main gas stream; (E) burning the fuel with at least one of the first oxidant and the second oxidant to form a flame cover around the main gas stream.

2. The method according to claim 1, wherein the main gas is an oxidizing gas. 3 - The method according to claim 1, wherein the main gas is an inert gas. 4. The method according to claim 1, wherein the main gas contains oxygen and the concentration of oxygen in the main gas changes with time. 5. The method according to claim 1, wherein the main gas changes from an oxidizing gas to an inert gas. 6. An apparatus for establishing a high velocity coherent main gas stream, comprising: (A) a lance having a main gas passage communicating with a converging / diverging nozzle to eject a main gas into an ejection space; (B) first passage means within the lance to eject a flow of a first oxidant into the ejection space annularly to the main gas stream; (C) second passage means within the lance to eject a flow of fuel into the ejection space annularly towards the flow of the first oxidant: and (D) third passage means within the lance to eject a flow of second oxidant towards the ejection space annularly towards the fuel flow. 7. The apparatus according to claim 6. characterized in that it further comprises an extension on the lance to form the ejection space d - The apparatus according to claim 6. characterized by J e further comprises a connection passage within the lance allowing the first means of passage to communicate with the third means of passage 9.- A method to provide gas to a liquid, comprising: (A) ejecting a main gas from a lance having a converging nozzle / divergent to form a main gas stream having a supersonic velocity; (B) expelling a flow of a first oxidant from the lance annularly towards the main gas stream, said first oxidant flow having a lower velocity than that of the main gas, (C) eject a flow of fuel from the lance annularly to the flow of the first oxidant, the flow of fuel having a lower velocity than here she of the main gas stream; (D) ejecting a flow of the second oxidant from the lance annularly to the fuel flow, said flow of the second oxidant having a lower velocity than that of the main gas stream; (E) burning the fuel with at least one of the first oxidant and the second oxidant to form a flame cover around the main gas stream; and (F) passing the gas from the main gas stream to a liquid. 10. The method according to claim 9, wherein the liquid is a target! molten.