MXPA00008671A - Blasting lance with a gas/liquid mixing chamber and a method for the expansion cooling thereof - Google Patents

Abstract

The invention relates to a method for cooling a lance provided for converting a medium into a molten mass and/or for measuring the properties of the molten mass. A gas/liquid mixture is fed as a cooling medium into a cooling circuit which is closed up to the lance end (2) situated on the melting side. The invention provides that the gas/liquid mixture or the components thereof is/are fed and permitted to expand under pressure up to the area of the lance end (2) situated on the melting side. The invention also relates to a lance which has a mixing chamber (5, 6) connected to the cooling circuit. The mixing chamber has the connections (3, 7) for a gas and liquid supply which is designed to produce the gas/liquid mixture, whereby the mixing chamber (5, 6) is connected via a pressure line (10) to at least one two-component nozzle (11) arranged in the area of the lance end (2) which is situated on the melting side.

Description

BLOCKING LANCET WITH A MIXED C MARA GAS / LIQUID AND METHOD FOR COOLING WITH EXPANSION OF THE SAME The invention relates to a method for cooling a lancet provided for the introduction of a medium into a melt and / or for measuring the properties of the melt, and a suitable lancet for carrying out this method according to the preambles in claims 1 to 3. Lancets are known for blowing media (particularly solids and / or gases) into the interior of metallurgical vessels such as furnaces or converters and as carriers of instruments for measuring properties of the melt. For example, they are used for the refining of oxygen from a cast iron melt, for blowing in the medium during the steel treatment (for example coal for foaming the slag) and for measuring the temperature of the melt. The region of the end of this lancet that faces the melt is subjected to a high thermal stress. From the previous public use, it is known to use tubular steel lancets, the end of the melt side of which burns continuously in operation, whereby the lancet has to be moved, accordingly. In addition, cooled lancets with closed cooling circuits with water are known. The operation of these lancets is dangerous because, in the case of a leak in the cooling circuit, a contact of the melt with the cooling water can lead to explosive reactions. If the water is enclosed by the melt, the evaporation and expansion of the water that then takes place can break the melt in an explosive manner. Neither the chemical dissolution of the water nor a subsequent reaction of the oxyhydrogen gas will be excluded. Therefore, it has already been suggested (DE 35 43 836 C2) to use two lancets that move alternately in the operating position. The lancet located in the operating position is cooled with a gas. Because sufficient cooling action is not achieved in this way, the lancet moves away from an oven after a certain period of operation and is re-cooled with water in this position which is separated from the melt. During this period, the second lancet continues the operation. This alternative operation with the two lancets is expensive. From WO-A-92/07965 a lancet having a closed cooling circuit which is supplied with a diphasic mixture is known. The fundamental object of the invention is to create a method and a lancet of the type named in the introduction, which makes possible the effective and reliable cooling of the lancet. The method according to the invention is characterized in that the gas / liquid mixture or its constituents are conducted under pressure to and in the region of the lancet on the side of the melt and allowed to spread thereon. The end of the lancet on the side of the melt denotes that the end of the lancet which, in operation, faces the melt or optionally falls into it. It is the end of the lancet subjected to a high thermal stress. The cooling circuit is closed towards the end of the lancet that gives the side of the melt. In this region the refrigerant outlet takes place, the coolant instead returning to a region of the lancet which is separated from the melt and which leaves the lancet at that location. The refrigerant circuit as a whole can be completely closed, but an open cooling circuit can also be used, where the heated cooling medium, which leaves the lancet and is separated from the end of the melt side, does not it is used again. The gas content of the mixture used according to the invention is preferably air or an inert gas (for example nitrogen or argon), the liquid content is preferably water. The gas / liquid mixture is conducted according to the invention under pressure up to and towards the region of the end of the lancet on the side of the melt. The term "region of the lancet end of the melt side" denotes a region that is in the vicinity of the appropriate end of the lancet, region that is already highly subjected to a thermal stress in the operation. The pair of terms "driving under pressure to and to the region of this end and the subsequent permission to expand" will be understood to mean that in the named region, a sudden pressure drop of the gas / liquid mixture occurs. Accordingly, the embodiment of the invention only depends on an appropriate pressure difference, not on the absolute levels of the respective pressures. Allowing an expansion (preferably by allowing the outlet of an appropriate nozzle in an area of less pressure) has the effect of the liquid phase of the mixture. it breaks into fine drops and / or evaporates. Both effects substantially increase the cooling power because, on the one hand, evaporation requires considerable amounts of heat and on the other hand, finely dispersed droplets as a result of large surface area can further remove heat in a fast and effective manner (with evaporation). The expansion, provided according to the invention, of the cooling mixture, the region of the end of the lancet on the side of the melt thus effects a clear increase in the cooling power compared to the prior art. On the other hand, it ensures a clear increase in safety because, as a result of the expansion procedure in the region of this lancet end, there is little or no liquid phase. In the case of operational disturbances, the melt that penetrates this region therefore can not close large amounts of water and thus cause thermal explosions. Within the scope of the invention. The diphasic liquid gas mixture can be produced away from the end of the lancet on the melt side and can be supplied as a finished mixture under pressure to this end and allowed to expand there. Likewise, it is possible to conduct the gas and liquid separately under pressure to and to the region of the end of the lancet on the side of the melt, and either only to mix it together shortly before the scanning process or on the other hand, allow it to expand by means of separate nozzles which are arranged in such a way that the gas / liquid mixture is produced in situ during the expansion process. For example, separate nozzles can be arranged in such a way that the outgoing liquid is removed by the expansion gas and broken to form a fine aerosol. The method according to the invention requires considerably smaller amounts of liquid for cooling with water, known in the prior art. The gas / liquid flow is adjusted in such a way that the liquid content in the region of the end of the lancet on the side of the melt, is subjected particularly to thermal stress evaporates for the most part or completely as a result of the expansion. This has two advantages. First, in this manner for cooling, not only the thermal capacity of the liquid (water) is used, but also the heat and evaporation substantially greater for the liquid-vapor phase transition, and even with relatively small liquid flows, It gets a high cooling power. If, in the case of operating disturbances, in the region of the end of the melt side, a leak in the refrigerant line results, the large surface area of the gas / liquid mixture supplied as an aerosol has the effect that in any In this case, a very rapid evaporation of liquid content results, even before the melt can enclose the drops of liquid. The liquid portion of the cooling medium used according to the invention is usually water. If the operating conditions are chosen where the water content in the lancet region on the melt side, part is evaporated for the most part or completely, the cooling circuit is preferably supplied with demineralized water in order to avoid calcareous deposits in the corresponding region of the cooling area. If demineralized water is not available and if the cooling circuit should be supplied with usual tap water or untreated water, the gas / liquid flow is preferably adjusted in such a way that a smaller portion of the water evaporates in the region of the end of the lancet on the side of the melt, the remainder being retained as a finely distributed aerosol. The calcareous deposits unwanted in this way are greatly avoided. The flow velocity of the diphasic mixture, which is high as a result of the expansion process, does not entrain evaporated water, with the result that stationary water can not be collected in the region of the tip of the lancet, water that could lead to an danger of explosion in the event of a penetration of the melt. The gas / liquid mixture can be produced outside the lancet and fed to the lancet already as a mixture. However, within the scope of the invention, it is preferred that the lancet have a mixing chamber connected to the cooling circuit, the mixing chamber having connections for a supply of liquid gas and being constructed for the production of a mixture of gas / liquid. The mixing chamber is arranged separately from the end of the lancet on the side of the melt. It is preferably located on the part of the lancet projecting out of the furnace or the converter. The gas / liquid mixture is preferably conducted from the mixing chamber at a pressure of 2 to 6 bar, then preferably around 3 bar, through a pressure tube towards the end of the lancet on the side of the melt. A region of this end, a two-component nozzle is arranged, of which the mixture expands in a region of cooling arranged in the region of the tip of the lancet. Within the scope of the invention, the term "two-component nozzle" denotes any device that allows a passage of a gas / liquid mixture and, in the process, can maintain a pressure difference between the supply side and the supply side. output in such a way as to result in a nozzle action, ie, a division of the mixture supplied in the region of lower pressure that is after the nozzle. At the outlet of the nozzle, the liquid content of the mixture is broken into fine drops. The expanded and heated mixture is conducted away from the end of the lancet on the side of the melt by means of a second tube and leaves the lancet again in a connection which is arranged preferably outside the converter. The pressure of the mixture after the exit of the two-component nozzle or nozzles is preferably somewhat below atmospheric pressure. If the lancet is used in an immersion operation, it must be greater than the back pressure of the liquid melt that surrounds the tip of the lancet. First, as a result of the operation disturbances, a melting of the tip of the lancet results and a penetration of the melt into the cooling area, the excess pressure prevailing therein prevents further penetration of the melt and possibly the scum. Advantageously, the mixing chamber has two annular chambers which are mutually abutting and enclose the lancet tube, in the radial dividing wall of which annular chamber connection holes or connection openings are arranged. The term lancet tube denotes the inner tube of the complete arrangement of the lancet, which is provided for the introduction of gas and / or solids from the melt. The inner annular chamber can receive water, for example, from its end surface, the outer annular chamber which receives compressed air from the circumference. Compressed air is mixed in the water through the holes in the radial division wall. The mixture produced is removed on the surface of the melt side end of the mixing chamber and carried out. The pressure tube for connecting the mixing chambers and the two component nozzle is preferably a closed circular pipe surrounding the lancet tube concentrically. The return of the expanded mixture from the end of the lancet on the side of the melt also takes place by means of a circular pipe, closed that can be constructed as a second circular, closed pipe that concentrically surrounds the pressure tube.

A second embodiment of a lancet according to the invention of separate pressure tubes for the supply of gas, on the one hand, and liquid, on the other hand, towards the end of the lancet on the side of the melt. These pressure tubes can be constructed as closed circular pipes that concentrically surround the lancet tube. In the region of the end of the lancet on the side of the melt, the pressure tubes end in nozzle arrangements, from which gas, on the one hand and liquid, on the other hand, and, in the on-site process, which , that is to say during the expansion process, are mixed to form an aerosol of fine particles. The action of suction of the expansion gas drags the liquid out and divides it into fine drops. The flow velocity of the aerosol produced in situ is thus high so that considerable quantities of water do not remain in the region of the end of the lancet on the melt side. Therefore, there is no, or there is only a small safety risk in the case of melt penetration. The operating pressures of this lancet can be clearly below 3 bar. The excess pressure required in the gas line (compressed air line) accounts for, for example, 1 to 2 bar, preferably approximately 1.5 bar. The liquid (water) only needs to be supplied at a low excess pressure of below 1 bar, preferably around 0.5 bar, because during the aerosol formation, it is dragged by the compressed expansion air and divided. A preferred field of use of the invention is the treatment of, or measurement of, metallurgical melts, for example cast iron or steel melts. However, the invention is not restricted to use with metal melts, but can be used for additional flows of high temperature melts (eg, glass melts). The exemplary embodiments of the invention will be explained in the following with reference to the drawings. Figure 1 shows a longitudinal section through a lancet according to the invention. Figure 2 shows a cross section along plane A-A of Figure 1.

Figure 3 shows a longitudinal section through a second embodiment of a lance according to the invention. Figure 4 shows a cross section along plane AA of Figure 3. The lancet according to the invention according to Figures 1 and 2 has an inner lancet tube 1, through which solids and / or gases are supplied. of the melt. The exit of these media in the melt takes place at the end 2 of the lancet on the side of the melt. The lancet tube 1 is surrounded by a cooling device which is described in more detail in the following. By means of a connecting piece 3, cooling water is supplied to an annular chamber 4 surrounding the lancet tube 1. The end surfaces of the annular chamber 4 and the inner chamber 5 of the axial connection mixing chamber are connected to each other, with the result that this inner annular chamber 5 is supplied with water from the annular chamber 4. The annular chamber 5 inside is encircled by an outer, annular chamber 6 which is supplied with compressed air by means of a connecting piece 7.

The two annular chambers 5, 6 together form the mixing chamber. The radial dividing wall 8 between the annular chambers 5 and 6 has connection holes indicated in 9. The compressed air and the water mixture between each other and the mixture is conducted through the closed circular pipe (pressure tube) 10, which is connected axially in the inner annular chamber 5 towards the end of the lancet on the side of the melt. The pressure of the mixture in the pressure tip 10 accounts for approximately 3 bar. The closed circular pipe 10 is formed in the region of the end two on the side of the melt of the lancet in 6 nozzles 11 of two components evenly distributed over the circumference of the lancet. The water / air mixture expands at the outlet of the two-component nozzles in the cooling area 12, cancel. The water is broken into very fine droplets by this expansion processing. The large surface of the supplied water favors a rapid heat absorption and therefore a high cooling power. The formation of the circular pipe 10 closed in 6 nozzles 11 of two components allows the operation of the lancet with tap water or process water as a constituent of the cooling medium. The inner diameter of the nozzles 11 of two components makes possible the passage of impurities and particles, and the latter possibly being contained in the process water. If the lancet is to be operated exclusively with demineralized water, the closed circular pipe 10 can be narrowed in the region of the cooling chamber of the cooling area 12 to form an annular gap with an inner diameter of about 0.5 mm, with the separation ring surrounding the lancet tube 1 in a rotationally symmetric manner. This annular gap forms a single two component nozzle. The formation of the various discrete nozzles 11 of two components is not necessary in this case. On the opposite end surface (on the side of the melt) of the cooling chamber 12, the mixture exiting the two-component nozzles 11 encounters a curved cooling surface 13, by means of which its direction is deflected and movement and is supplied to the refrigerant removal line constructed as the second circular, closed pipe 14. The water content of the supplied mixture is evaporated in the cooling chamber 12 in a preferably complete manner. Under particular operating conditions, if unusually high temperatures result in the cooling chamber 12, the cooling action can possibly be supported by the largely endothermic division of a portion of the water into hydrogen and molecular oxygen. If, in the case of operational disturbances, the lancet is burned in the region of the end 2 on the melt side of the cooling chamber 12 it opens towards the melt, as a result of the use of the fine aerosol as the medium For cooling, there is virtually no danger that water that is still liquid will be enclosed by the melt and will subsequently evaporate in an explosive manner. In the cooling area 12, an access pressure is preferably established, which, during the immersion operation of the lancet, is sufficient in order to force back the molten metal or slag possibly entering the cooling chamber 12. and in order to prevent further penetration.

The cooling medium flowing back through the closed circular pipe 14 is removed in the lancet by means of an annular chamber 15 and a connecting piece 16. Either it can be discharged (open cooling circuit) or, on the other hand part, return again the cooling circuit. The annular chamber 15 has a second connection 17 which is connected to a pressure control safety valve, not shown in the drawing. In addition to being used to introduce media into the melt, the lancet can also be used to measure properties of the melt. For this purpose, the measuring instruments can be arranged in the region of end 2 on the side of the melt, the measuring instruments that are not shown in the drawing. For example, the temperature of the melt can be measured by a radiation pyrometer. With a steel melt, an analysis of several elements can be carried out, for example, by means of laser induced emission spectroscopy. In this way, for example, a steel refining process can be carried out metrologically and finish in the desired state. To perform these measurements, the lancet is guided with the measuring instrument arranged thereon in the region of the surface of the steel bath. Preferably, the compressed air or an inert gas such as nitrogen is blown through the lancet tube 1, which, on the one hand, keeps the opening of the lancet clean, and on the other hand, releases the slag to the lancet. surface of the steel bath. The lancet according to the invention is introduced through an opening in the wall or cover in the converter or furnace. The connections for the supply and removal of the cooling medium and the cooling chamber are preferably located outside the converter in an appropriately colder region. Figures 3 and 4 show a second embodiment of the invention, where the gas and liquid are conducted in a separate manner to the end 2 of the lancet on the side of the melt and where the gas / liquid mixture is produced during the process of expansion only in situ. Here, the same reference numerals denote functionally identical components as compared to the embodiment according to Figures 1 and 2. The substantial difference compared to the embodiment according to Figures 1 and 2 is that three closed circular pipes, concentric between Yes, they are arranged around inner lancet tube 1. The circular, closed, interior pipe 18 conducts cooling water to the end 2 of the lancet on the side of the melt, which is connected to the annular chamber 4 for this purpose. The closed, intermediate circular pipe 19 is supplied with compressed air by means of the connection 7 and the annular chamber 6 provided with the connection holes 9. As in the first embodiment, the closed, outer circular pipe 14 is used to return the medium of cooling heated to the annular chamber 15 and the associated connection 16. The water and the gaseous medium (compressed air) flow through the pipes 18, 19, circular, closed separately to the end 2 of the lancet on the side of the melt. At the outlet of the compressed air in the annular chamber 12 and the accompanying expansion, the cooling water outlet is entrained and divided to form a fine aerosol. The diphasic mixture used according to the invention is produced in situ. Surprisingly, the present operation of this embodiment can be clearly reduced compared to the lancet according to Figures 1 and 2. Therefore, to achieve an aerosol of fine particles, which passes through the annular chamber 12 to a high flow rate and subsequently removed, it is sufficient to supply the water in the circular pipe 18 closed at a pressure in excess of 0.5 bar and the compressed air in the circular pipe 19 closed to a pressure in excess of 1.5 bar.

Claims (10)

1. CLAIMS 1. A method for cooling a lance provided for the introduction of a medium in a melt and / or for measuring properties of the melt, wherein a cooling circuit closed towards the end of the lancet on the side of the mass When a molten gas is molten, a gas / liquid mixture is conducted as a cooling medium, characterized in that the gas / liquid mixture or its constituents are conducted under pressure to and towards the end region of the lancet on the melt side. let it expand there. The method according to claim 1, characterized in that the gas / liquid mixture is produced in a mixing chamber of the lancet which is arranged separate from the end of the lancet on the side of the melt. The method according to claim 1 or 2, characterized in that the gas / liquid mixture is conducted under a pressure of 2 to 6 bar, preferably about 3 bar, to the end of the lancet on the side of the melt . 4. The method according to claim 1, characterized in that the gas and liquid are led separately to the end of the lancet on the side of the melt and allowed to expand there, wherein during the operating procedure a gas / liquid mixture. The lancet for carrying out the method according to claim 2 or 3 with a cooling circuit closed towards the end of the lancet on the side of the melt, characterized by a mixing chamber arranged separately from the end of the lancet on the side of the melt and connected to the cooling circuit, the mixing chamber having connections for a supply of liquid gas and being constructed to produce a gas / liquid mixture, wherein the mixing chamber is connected by means of of a pressure tube at least one two-component nozzle arranged in the region of the end of the melt side of the lancet. 6. The lancet according to claim 5, characterized in that the mixing chamber has two annular chambers that are concentric with each other and surround the lancet tube, with connection holes that are arranged in the radial direction wall of the annular chambers. . 7. The lancet according to claim 6 or 7, characterized in that the pressure tube is a closed circular pipe that surrounds the lancet tube concentrically. The lancet according to claim 7, characterized in that in order to return the expanded gas / liquid mixture from the lancet end of the melt side to the exit of the mixture out of the lancet, a second circular pipeline is provided. closed, circling the pressure tube concentrically. The lancet for carrying out the method according to claim 4, with a cooling circuit closed towards the end of the lancet on the side of the melt, characterized by two pressure tubes connected to connections for a supply of gas and liquid . The pressure tubes are constructed for the separate supply of gas, on the one hand the liquid, on the other hand, towards the end of the lancet on the side of the melt and ending at the region of the end of the lancet and on the side of the lancet. the melt in nozzle arrangements, whereby a gas / liquid mixture is produced in situ. 10. The lancet according to claim 9, characterized in that the pressure tubes are closed circular tubes that concentrically surround the lancet tube.