KR101024824B1 - Method and device for cooling blowing lances - Google Patents

Abstract

The invention relates to a method for cooling blowing lances that, in order to treat liquid metal melts contained in metallurgical vessels, particularly a steel contained in RH vessels and optionally being subjected to a vacuum, and/or in order to heat metal melts (optionally under a vacuum), can be introduced into and withdrawn from the inside of the vessel by means of a lifting device. A blowing lance comprises at least one inner guiding tube, which serves to guide gases, particularly oxygen, and which has a head-end lance mouth for blowing the gas onto the metal melt, and comprises a cooling jacket, which extends over the length of the lance and which serves to lead a cooling medium therethrough. The cooling jacket is provided in the form of a double-walled jacket tube, which has an inner and an outer cooling channel and which is provided with a redirecting tube in the area of the head end. The metallurgical vessel is connected to a vacuum pump in order to lower the pressure. According to the invention, the instantaneously available suction capacity of the pump limits the maximum flow rate of the gas serving as the cooling medium.

Description

Method and device for cooling blowing lances

The invention relates to the treatment of liquid metal molten metal in metallurgical vessels, in particular for use in vacuumed steel optionally in reflux degassing (RH) vessels and / or inside the vessel which can be raised or lowered. A method of cooling a blow lance used for heating a metal melt (optionally under vacuum) by means of a lift device, wherein the blow lance comprises at least one internal guide tube for injecting gas, in particular oxygen, into the metal melt Headend lance mouth for blowing gas and a cooling jacket extending over the entire length of the lance for the passage of refrigerant, the cooling jacket being formed of a double wall jacket tube and having internal cooling The metallurgical vessel has a vacuum pump with an inner cooling passage, an outer cooling passage and a rerouting tube in the head end region. It is connected to reduce the internal pressure.

The present invention also relates to an apparatus for carrying out the above-described method on a metallurgical vessel, in which a blowing lance can be inserted and withdrawn inside the vessel by a lifting device, the blow lance having an inner guide tube having a head end lance inlet. And at least a cooling jacket, wherein the cooling jacket has an internal cooling passage and an external cooling passage, connected by a redirection passage, wherein the metallurgical vessel is loaded with a pump connected to the metallurgical vessel by means of a vacuum fitting. Discharged.

Blown lances of the type described above are basically known in the art. The refrigerant is typically water and is blown through the lance at a high flow rate under pressure to the lance head while blowing gas or solids onto the molten steel. In particular, at the end of the lance head part, a burn spot on the surface of the bath is radiated towards the lance head part to form an extremely high temperature, which causes an overall increase in wear and crack formation in the lance head part. As a result, the wall thickness of the cooling chamber formed in the lance head becomes thinner, softer and ruptures over time. The leaked water can then evaporate and exceed the suction capacity of the vacuum pump, resulting in extremely high pressure in the vessel.

To prevent the risk of water breakthrough during the operation of the blown lance on the one hand and to cool the lance internally on the other hand, the blown lance is molten as proposed in German patent application DE 35 43 836 C2. In another process submerged, two blown lances are used which are alternately used to cool with cooling water. Only those submerged in the melt in the blown state at any point in the two blow lances are cooled by air, and those outside the melt at any point in time are concentrated by the coolant. However, alternating use of two blow lances is relatively complex. Therefore, for water-cooling blown lances, the German patent application DE 35 43 836 C2 shows that the temperature detected by the temperature sensors in thermal contact with the wall of the lance head part is characterized by water cooling and / or oxygen injection and / or Or it is proposed to be used for controlling the injection of additives and / or the separation of the lance head portion from the melt solution bath.

So far, the disadvantages associated with water cooling of the blown lances, namely defects (ruptures or cracks) in the area of the cooling jacket of the lances and the ingress of water into the vessels associated with them, are characterized by The rapid expansion of the freed water, which turned to steam in the reaction space above it, and the possibility of separation of hydrogen gas from water vapor were not eliminated. In particular for RH containers having only a limited free space in the container, there is a serious risk that the temperature inside the container can reach 1800 ° C. When the cooling water circulating through the lance is converted to steam at a flow rate of 30 m ³ / h to 50 m ³ / h, the ratio of the suction rate to the amount of steam produced when this amount of cooling water breakthrough is 1:20 to At 1: 100, only a limited amount of vacuum pumps can be used with current vacuum pumps.

In the RH vessel, from the point of view of the device, two submerged or raised tubes (siphon tubes) extending to the molten steel form a siphon-like closure, a pressure relief opening (expansion flap). Since it is not possible to introduce)), under these circumstances the closure acts as one pressure equalization opening. In case of unfavorable situations in case of water breakthrough to the RH vessel through the defect of the oxygen lance, the subsequent expansion can reach a final expansion pressure of approximately 14 × 10 ⁵ Pa. In the case of an expansion rate of 2 × 10 ⁷ Pa / s and pressure relief only through the siphon tubes, a large amount of molten steel can be forced out of the area surrounding the device.

It is an object of the present invention to further develop the method of the type mentioned at the outset in order to limit the above-mentioned drawbacks in case of cooling jacket leakage from the lance, to improve the safety of the operator and to make the whole apparatus safer.

This object is achieved by the method according to the first invention. Its first feature is the use of gas as the coolant, which can dramatically reduce the amount of leaked coolant in the case of a defect in the lance. Preliminary calculations indicate that a 1000 kg / h cooling steam jet is sufficient for the oxygen blowing process under a pressure of 1 × 10 ⁴ to 2 × 10 ⁴ Pa in a RH vessel, and VCD under a pressure of 70 Pa to 4 × 10 ³ Pa In the case of vacuum circulation degassing, 360 kg / h of cooling steam jet was shown to be sufficient. This amount of steam is significantly reduced compared to a device that can be made of cooling water, and in the case of a crack in the lance or a rupture of the lance does not create a dangerous expansion in the vessel and can be immediately aspirated by the suction pump without special technology. . The ratio of the suction power of the (vacuum) pump to the amount of steam generated is approximately 2: 1 to 6: 1, whereby steam development accompanied with expansion through the siphon tube is effectively prevented. Another feature of the present invention is that the flow rate of the gas used as the refrigerant is controlled by the intensively available suction force of the pump. If the suction power of the pump decreases or is smaller or smaller for other reasons, the cooling gas flow will be minimized correspondingly so that the ratio of the suction power of the pump to the amount of cooling gas that must be discharged in case of breakage will remain at least one.

Other features have been described in the second to eighth inventions.

According to another feature of the method of the present invention, the instantaneously available pump suction rate additionally controls the lance feed, whereby preferably the amount introduced for lance cooling By measuring the difference in the amount consumed, the lance inlet can immediately block the gas inlet. The first feature serves to prevent further damage to the lance by rapid temperature rise as the lance approaches the surface of the solution bath. Another feature ensures that only the amount of gas present in the lance's cooling jacket can flow out.

Preferably superheated steam is used as the refrigerant, in particular superheated steam heated 20 ° C. above the boiling point of water. For cooling with steam, the volume flow rate will correspond to other refrigerants used, in particular nitrogen or argon, depending on the state of the art. Because of the small volume flow rate required for cooling, the width of the cooling passages can be minimized.

According to another feature of the invention, during oxygen injection, the refrigerant is introduced into the internal cooling passage and discharged through the external cooling passage. This, with maximum heat adsorption, ensures that the superheated steam entering the lance is discharged directly from the lance in the region of the external cooling channel or external cooling passage. Furthermore, the lance has the advantage that the oxygen introduced through the inner guide tube is heated by the amount of steam flowing along the inner guide tube and thus blown into the molten steel in the vessel which is already heated. As a result, the temperature loss in the molten steel is reduced, more intense carbon reactions occur during oxygen blow decarbonization, not only oxygen efficiency or utilization is improved, but also more intense aluminum reactions during chemical heating, and finally oxygen consumption This decreases.

If the lance is located at the upper point between suction states during VCD operation, steam is introduced through the channels of the external cooling passages or cooling jackets and redirected at the heat end and then through the internal cooling channels or internal cooling passages. Provided for discharge. In this case, to the extent that the lance ambient temperature is smaller than the temperature during the oxygen blowing operation, the steam supply to the cooling jacket initially heats the region of the external cooling channel or the external cooling passage, thereby consequently in the region of the cooling channel or the cooling passage. It is ensured that the steam is cooled to prevent condensate from forming.

In order to prevent overheating of the cooling jacket and to optimize the amount of refrigerant required for different lance passages and operating conditions, another feature of the present invention is that the amount of refrigerant entering the cooling jacket, i.e. steam or water vapor, is the outer jacket of the lance. Control depending on the temperature measured at and / or at the lance position at that moment. In order to prevent condensate formation occurring in the head region of the lance, the lance is not initially cooled but is preheated at the start of its operation, the lance is inserted into an already heated metallurgical vessel, and only after that steam cooling begins.

In the use of steam, the refrigerant is preferably provided at a temperature of 160 ° C. to 210 ° C. at a pressure of at least 7 × 10 ⁵ Pa.

The object of the present invention is further achieved with a device according to the ninth invention, which comprises the overall flow of gas acting as a refrigerant, the lance position at that moment, the suction power of the available vacuum pump, A control unit that adjusts as a function of external wall temperature. The lance inlet is preferably also adjusted via the control unit. In order to better detect the temperature load of the lance and the resulting abrasion effect, the measuring lances are arranged at different longitudinal axial spacings on the blowing lance head and the outer wall of the blowing lance, which are connected to the control unit. do. Depending on the measured temperature, the flow rate of the refrigerant through the control unit can be increased or decreased. In order to prevent condensate formation in the cooling passages in the region of the lance head, a condensate separator is preferably provided and guided through the condensate separator before the refrigerant enters the cooling passages of the blown lance.

Improved heat adsorption is ensured when the inner surface of the outer cooling jacket tube facing the cooling passages has radially projecting ribs in the cooling passages or cooling channels.

Preferably the inlet of the lance consists of a Laval nozzle.

Embodiments as well as other advantages of the invention are shown in the drawings.

1 is a schematic cross sectional view of a blown lance;

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1.

3 is a cross-sectional view of the RH vessel in which the lance is introduced, including a schematic illustration of the control unit.

4 through 7 are cross-sectional views of respective RH vessels having different lance positions or in different operating states.

8 to 11 are respective time-temperature graphs of temperatures calculated according to FIGS. 4 to 7 under process conditions.

Basically known in the art, the lance 10 has an inner guide tube 11 which ends at the head end with a nozzle 20, preferably at the lance inlet 12 with a Laval nozzle open. . Gas, in particular oxygen, can be introduced through this inner guide tube. The inner guide tube 11 is surrounded by a cooling jacket 13, which is a redirection tube 14 in which the inner space is inserted into the inner cooling passage 15 and the outer cooling passage 16 surrounding the inner guide tube 11. It has an outer tubular cooling jacket tube 13a subdivided by. The redirecting tube 14 extends to the head region of the lance 10 but ends before the nozzle 20, so that the redirecting region 17 connects between the internal cooling passage 15 and the external cooling passage 16. Is formed. Each of the two cooling passages 15, 16 is connected at the foot end of the lance with respective openings 18 that can be interchanged depending on the desired refrigerant flow direction between the inlet and outlet.

As shown in FIG. 2, in order to promote heat transfer to the refrigerant passing through the cooling jacket, the surface of the cooling jacket tube 13a directed toward the cooling passage 16 projects radially into the cooling passage 16. It is formed to have ribs 19.

In order to cool the lance to an operable state, as described in more detail later, the cooling gas, which is a superheated steam, preferably heated 20 ° C. to 50 ° C. more than the boiling point, is provided with cooling passages 15, 15, of the cooling jacket 13. 16) is introduced. In order to prevent condensate formation in the cooling channel of the cooling jacket of the lance, cross switching of the inlet and outlet of steam can be achieved between the internal cooling passage 15 and the external cooling passage 16. Thus, for example, when the temperature of the lance becomes higher during the oxygen blowing operation, the inflow of cooling steam is effected through the opening 18 connected with the internal cooling passage 15, so that the steam initially cools along the inner guide tube 11. It flows into the redirection area 17 of (13) and from there it exits through an external cooling passage 16 in contact with the lance surrounding the reaction space of the vessel in the tubular jacket 13. However, if the lance is located at an upper point between the processing steps of the individual loads, the thermal effect on the cooling jacket 13 will be significantly reduced. In this case steam is initially blown into the external cooling passage 16. Vapor is discharged through the internal cooling channel and its headside release opening 18. The corresponding flow also applies in the case of VCD operation.

The same applies to the start-up operation, ie when the lance is cold and initially lance 10 is introduced into the metallurgical vessel 200 without steam cooling to heat the lance. The same cooling inflow is switched immediately after preheating the lance.

As shown in greater detail in FIG. 3, the metallurgical vessel 200 may have a submerged or immersed tube or siphon tube 21 inserted into a molten metal 29 filled with ladle 23. . The metallurgical vessel 200 may have its contents discharged by the pump 30 through the connecting part 22. The pump 30 and the lance drive 24 are connected to the control unit 27. In order to determine the lance position at that moment, an encoder 25 is provided.

Moreover, along the lance jacket and at the lance inlet at different longitudinal axial spacings, temperature sensors are provided, in which only one temperature sensor 26 is shown. The temperature measured by this sensor and other temperature sensors is transmitted to the control unit 27. The control unit 27 controls the amount of cooling gas introduced into the jacket through the controller 28 as a function of the suction force of the pump 30 and the temperature measured by the temperature sensor. An apparatus (not shown) for measuring the flow rate may be provided, which may detect the rate at which cooling steam is supplied, and any deviation acts as a sign that there is a leak and sends a signal to the control unit 27. To pass. In the case of a leak, the lance inlet and additional cooling gas supply are stopped or the lance recovery from the metallurgical vessel 200 begins.

4 shows a lance inserted into a metallurgical vessel 200. In the state shown, the pressure inside the vessel is standard or normal, ie the pump 30 is not working. Both the inner guide tube 11 and the cooling passages 15, 16 are not yet supplied with gas. The temperature of the container interior space in the practical application under this assumption leads to a temperature of 1500 ℃ (T _i). The temperatures T ₁ , T ₂ , T ₃ , T ₄ measured in the lance within the first 2 minutes are shown in FIG. 8. In practical applications a temperature increase up to 1060 ° C. at the head of the lance can be measured. After 2 minutes, the steam refrigerant is activated to supply steam at a temperature of 160 ° C. and a pressure of 7 × 10 ⁵ Pa. The temperatures T ₁ , T ₂ measured at the lance head are lowered to 260 ° C and 215 ° C. The amount of steam introduced through the cooling passages 15, 16 amounts to approximately 179 kg / h.

5 shows the lance 10 during the oxygen blowing operation. In the vessel pressure was 2 × 10 ⁴ Pa, and the temperature (T _i) amounts to 1800 ℃. Oxygen is blown over the inlet via the inner guide tube 11 in an amount of, for example, 1000 Nm ³ / h. During lance cooling, a steam of 7 × 10 ⁵ Pa at a temperature of 160 ° C. is used. The temperature T ₁ , T ₂ , T ₃ , T ₄ change and steam outlet temperature is shown in FIG. 9.

FIG. 6 shows the lance introduced into the metallurgical vessel 200 during the VCD process, ie without oxygen inflow through the inner guide tube 11. The pressure adjusted inside the vessel is between 70 Pa and 4 × 10 ³ Pa. The lance is cooled with steam (7 × 10 ⁵ Pa, 160 ° C.). The internal temperature T ₁ in the vessel reached 1200 ° C. The amount of steam passing through the cooling passages 15, 16 has reached 360 kg / h. The change in temperature T ₁ to T ₄ and the vapor release temperature T _DA can be seen from FIG. 10.

7 shows a lance located at an upper point. The metallurgical vessel 200 has a siphon tube submerged in the molten metal. As can be seen from FIG. 11, while the vapor discharge amount reaches 1464 kg / h, the temperature of the lance submerged represents 20 ° C. to 160 ° C. or 200 ° C. for a short time.

Each of the described and investigated operating situations includes a pressure of 0.5 × 10 ⁴ Pa to 2 × 10 ⁴ Pa, an amount of vapor refrigerant discharge of 1000 kg / h, and a vacuum of 70 Pa to 4 × 10 ³ Pa during VCD operation. The operation under shows that it can have a vapor refrigerant emissions of 360 kg / h. In comparison to liquid water cooling, very small amounts of steam are used and are prevented from being generated and safely discharged by the vacuum pump in the case of cracks or rupture of the lance, ie no dangerous expansion occurs in the metallurgical vessel 200. .

The measurement of the difference between the incoming and outgoing vapor volume by flow and pressure measurement, and the supply and discharge lines immediately indicate any lance leaks. To prevent condensate formation at the upper point of the lance, the vapor flow direction is reversed (inverted) by the switching of the valves.

When the lance is cracked or the lance ruptures, the amount of refrigerant leaking is significantly reduced than before, so that the lance can be used in a safer lance manufacturing field.

Claims (16)

A method of cooling a blow lance for at least one of treatment of a liquid metal melt contained in a metallurgical vessel and heating of the metal melt, the blow lance being movable to be inserted and discharged into the metallurgical vessel by a lance drive. At least one internal guide tube for injection of gas or solids with a headend lance mouth for gas injection onto the molten metal, and over the length of the lance for the passage of refrigerant It has an extended cooling jacket, the cooling jacket has a double wall jacket tube forming inner and outer cooling passages with a redirecting tube at the head end region, the metallurgical vessel is connected with a pump for reducing the pressure therein, Blown lance cooling, wherein the instantaneously available suction force of the pump limits the maximum flow of gas used as the refrigerant Way. The method of claim 1, Blown lance cooling method characterized in that the treatment of the liquid metal molten metal in the metallurgical vessel is carried out in a vacuum. The method of claim 1, Blowing lance cooling method characterized in that the heating of the molten metal is carried out in a vacuum. The method according to any one of claims 1 to 3, Blown lance cooling method characterized in that the liquid metal molten metal is a molten steel processed in a metallurgical vessel which is an RH vessel. The method of claim 1, The instantaneously available pump suction force limits the maximum allowable cooling gas flow rate by flow measurement and stops the cooling gas flow when the instantaneously available pump suction force is exceeded. The method according to claim 1 or 5, A blow lance cooling method, characterized in that a superheated steam superheated to 20 ° C. to 50 ° C. above the boiling point of water is used as the refrigerant. The method according to claim 1 or 5, The at least one inner guide tube for gas injection supplies oxygen, and during oxygen injection, the refrigerant flows into the internal cooling passage and is discharged through the external cooling passage. The method according to claim 1 or 5, A blow lance cooling method characterized in that when the blow lance is positioned between processing steps and during a vacuum circulation degassing (VCD) operation, the refrigerant is introduced into the external cooling passage and discharged through the internal cooling passage. The method according to claim 1 or 5, And the flow rate of the refrigerant is controlled according to at least one of a temperature measured around the outside of the blown lance and a blown lance position at that moment. The method according to claim 1 or 5, Blown lance cooling method, characterized in that the start-up blow lance is initially preheated without cooling, the lance is introduced into the already heated metallurgical vessel and the steam cooling starts only thereafter. The method of claim 1, A blow lance cooling method, characterized in that at least a pressure of 7 × 10 ⁵ Pa and steam at a temperature of 160 ° C. to 210 ° C. are introduced as a refrigerant. A blow lance cooling apparatus having a metallurgical vessel (200) for carrying out the method according to claim 1, wherein the blow lance (10) is movable by the lance drive (24) to be inserted into and discharged from the inside of the vessel. The lance has at least one inner guide tube 11 with a head end lance inlet 12, an internal cooling passage 15 and an external cooling passage 16 connected via a redirection tube 14 at the head end region. It has a cooling jacket (13) having a lance also has a pump (30) for discharging the contents of the metallurgical vessel (200) through the connecting part (22), And a control unit 27 for adjusting the flow rate of the gas used as the refrigerant, The control unit (27) regulates the flow rate of the refrigerant according to the instantaneous lance position, the suction force of the pump (30) and the measured external wall temperature of the blown lance. The method of claim 12, Blown lance cooling device, characterized in that the blow lance head and the temperature measuring sensors on the cooling jacket (13) of the blow lance are arranged with longitudinal axial spacing and connected to the control unit (27). The method according to claim 12 or 13, Blown lance cooling apparatus characterized by a condensate separator through which the refrigerant passes before entering the internal cooling passage or the external cooling passage. The method according to claim 12 or 13, Blown lance cooling apparatus, characterized in that the inner surface of the cooling jacket tube (13a) facing the outer cooling passage (16) has ribs (19) projecting radially into the outer cooling passage (16). The method according to claim 12 or 13, Blown lance cooling device, characterized in that the lance inlet is composed of Laval nozzle.

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