Method and continuous casting plant for operating a cooling chamber

Abstract

The invention relates to a method and a continuous casting plant (100) for operating a cooling chamber (1) in a strand guide device (10) of the continuous casting plant. The continuous casting plant (100) comprises a mold (8) for casting a cast strand (13) and a strand guide device (10) for guiding the cast strand (13) after it has left the mold. The strand guide device (10) comprises a cooling chamber for cooling the freshly cast cast strand. In the cooling chamber (1), the cast strand (13) is subjected to a coolant, forming a steam-air mixture (5) at an actual pressure. The steam-air mixture (5) is sucked out of the cooling chamber (1) with the aid of a suction device (20). In order to avoid, on the one hand, “energy waste” during operation of the extraction device and, on the other hand, to prevent too much steam-air mixture from remaining within the cooling chamber (1) or even the steam-air mixture from escaping from the cooling chamber, the present invention provides a pressure control circuit (30) for the continuous casting plant (100) for controlling the actual pressure of the steam-air mixture (5) in the cooling chamber (1) to a predetermined target pressure (P-target) by varying the power of the extraction device (20).

Description

The invention relates to a method and a continuous casting installation for operating a cooling chamber in a strand guiding device of the continuous casting installation. The continuous casting plant is typically constructed in a casting hall of a steel mill.Continuous casting plants are fundamentally known from the prior art. They typically comprise a mold for casting a casting strand, for example made of metal. A strand guide device is arranged downstream of the mold for transferring the cast strand into the horizontal after leaving the mold. Within the strand guiding device, the cooling strand is typically cooled by spraying with a coolant. This takes place in a cooling chamber in which a steam-air mixture having an actual pressure and an actual temperature is formed by spraying the hot casting strand with the coolant. The vapor-air mixture is extracted from the cooling chamber by means of an extraction device. In this respect, a method for operating the cooling chamber in a strand guiding device is also known from the prior art.The cooling chamber is typically not hermetically sealed with respect to its environment, in particular with respect to the air in the casting hall or with respect to the air outside the casting hall, so that such external air penetrates into the cooling chamber via inevitably present openings in the cooling chamber, referred to below as second openings, and is therefore necessarily part of the steam-air mixture in the cooling chamber. In this respect, this external air, referred to below as second air, influences the actual temperature and the actual pressure of the steam-air mixture in the cooling chamber.The amount of steam which forms in the cooling chamber can likewise vary because it is dependent on a respectively operated operating state of the continuous casting plant during the casting operation, the temperature of the cast cast continuous casting and the respectively used coolant and the temperature thereof. The actual pressure of the steam in the cooling chamber also varies with the quantity of steam.The suction device is traditionally operated at constant high, typically maximum power, in particular at constant speed, for which reason the quantity of the vapor-air mixture sucked out of the cooling chamber is traditionally likewise constant. Apart from the desired case, in which the quantity of the steam-air mixture sucked off by the suction device corresponds exactly to the quantity of the steam-air mixture in the cooling chamber, a distinction must be made between two undesired cases:In a first undesirable case, the output of the suction device is too great for the quantity of the vapor-air mixture to be sucked off in the cooling chamber. Then, the vacuum in the cooling chamber increases and energy is "wasted" because, as said, the output of the suction device is set too high.In a second undesirable case, the power of the suction device is too low for the amount of the steam-air mixture to be sucked off in the cooling chamber. Steam can then emerge from the cooling chamber and lead to poor visibility for the operating personnel of the continuous casting installation on the casting platform arranged above the strand guide. In addition, the remaining vapor-air mixture can locally condense inside and outside the cooling chamber, resulting in water accumulation. On the floor of the plant, the water accumulation leads to a risk of slipping for the operating personnel and a water accumulation in the vicinity of the melt can lead to a buffer.The object of the invention is to further develop a known method and a known continuous casting installation for operating a cooling chamber in a continuous guide device of the continuous casting installation to the effect that the described two undesirable cases during operation of the cooling chamber with the disadvantages resulting therefrom are avoided. In other words, the development takes place according to the invention in such a way that, on the one hand, energy waste during operation of the suction device is avoided and, on the other hand, the suction of a sufficient quantity of the vapor-air mixture is nevertheless ensured.This object is achieved by the method claimed in claim 1. Accordingly, the method according to the invention is characterized by a regulation of the actual pressure of the steam-air mixture in the cooling chamber to a predefined desired pressure by varying the power of the suction device for suction and extraction of the steam-air mixture from the cooling chamber.With this claimed pressure regulation, it is advantageously possible to keep the pressure of the steam-air mixture in the cooling chamber constant at the level of the predetermined desired pressure. The desired pressure in the cooling chamber is always a negative pressure. An overpressure is expressly undesirable, which would lead to an escape of the steam-air mixture from the cooling chamber, with the disadvantages described above. With the claimed pressure control, the output of the suction device is always adapted to the quantity of vapor-air mixture to be sucked off present in the cooling chamber, whereby the above-described disadvantages are advantageously avoided.In addition to the actual pressure, the actual temperature of the steam-air mixture in the cooling chamber is also subject to certain fluctuations during the casting operation. These fluctuations result on the one hand from different operating states of the continuous casting plant, in particular possibly differently operated coolings of the cast strand. On the other hand, the actual temperature also depends on the second air quantity which is inevitably drawn into the cooling chamber and the temperature of which differs in summer and in winter. With the variable output of the suction device within the scope of the pressure regulation according to the invention, the quantity of the second quantity of air drawn in also fluctuates, and thus the actual temperature of the steam-air mixture in the cooling chamber also fluctuates.According to an embodiment of the invention, the present invention therefore also provides, in addition to the pressure control, a temperature control for the steam-air mixture in the cooling chamber. The actual temperature of the steam-air mixture is regulated to a predetermined setpoint temperature or kept constant at this. This offers the following advantages: a constant or unified temperature of the steam-air mixture surrounding the casting strand in the cooling chamber is firstly advantageous for the quality of the casting strand, because the uniform temperature of the steam-air mixture does not influence the active strand cooling. The constant temperature is also advantageous for the function of a pollutant separator which separates a maximum of many pollutants from the steam-air mixture only if the steam-air mixture has a temperature which is as favourable as possible for condensation when it is passed through the separator. The setpoint temperature of the steam-air mixture is preferably set to the optimum (operating) temperature for the functioning of the pollutant separator. The pollutant separator is optionally arranged in the outlet of the cooling chamber upstream of the suction device.Further advantageous embodiments of the invention, in particular specific embodiments of the claimed pressure and / or temperature control, are the subject matter of the dependent claims.The above-mentioned object of the invention is achieved in terms of apparatus by the continuous casting plant claimed in claim 8. The advantages of this solution correspond to the advantages mentioned above with reference to the claimed method.The description is appended with FIG. 1 which shows the continuous casting plant according to the invention.The invention is described in detail below with reference to this single FIG. 1 in the form of exemplary embodiments.FIG. 1 shows a continuous casting plant 100 which is arranged in a casting shop 1000. The continuous casting plant 100 has a mold 8 for casting a cast strand 13, for which purpose the mold 8 is fed with liquid melt, typically molten metal, from an intermediate container 6 via a dip tube 7. The intermediate container 6 is in turn fed with the melt from a ladle 4.After casting, the as yet non-solidified casting strand is pulled out of the mold 8 and is typically transferred to the horizontal in a strand guide device 10, which is likewise a component of the continuous casting plant 100. Within the strand guiding device 10, the casting strand also passes through a cooling chamber 1. The steam-air mixture has an actual pressure and an actual temperature in the cooling chamber.In order to keep the pressure of the steam-air mixture 5 in the cooling chamber constant, the present invention provides a pressure control circuit 30. This pressure chamber is designed to regulate the actual pressure of the steam-air mixture 5 in the cooling chamber 1 to a predefined setpoint pressure P-Soll, that is to say to keep it constant at this setpoint pressure level. For this purpose, the pressure control circuit 30 provides that the output of a suction device 20 for drawing on and off the steam-air mixture 5 from the cooling chamber 1 is varied in a suitable manner.To carry out this pressure regulation, the pressure regulating circuit 30 has the following components: the suction device 20 with a power controller M 20 as actuator for variably producing the power or the rotational speed of the suction device and a pressure sensor P 1 for detecting the actual pressure in the cooling chamber 1. furthermore the pressure regulating circuit 30 has a pressure comparison device D 1 for determining a pressure regulating deviation as the difference between the setpoint pressure and the actual pressure of the steam-air mixture 5 in the cooling chamber 1. finally the pressure regulating circuit 30 comprises as central element a pressure regulator C 1 for generating an actuating signal for the power controller M 20 of the suction device in accordance with the pressure regulating deviation so, the pressure control deviation becomes zero. If the pressure control deviation is zero, this means that the actual pressure of the steam-air mixture in the cooling chamber 1 corresponds to the predefined setpoint pressure. In addition, the output of the suction device 20 is then adjusted such that a necessary quantity of the steam-air mixture 5 is always also sucked out of the cooling chamber 1. "Necessary quantity" means that neither too much nor too little steam-air mixture is sucked out of the cooling chamber 1, so that the associated disadvantages, as are known from the prior art and have been described in the introduction, are effectively avoided by this pressure control according to the invention.The vapor-air mixture extracted by the extraction device 20 is discharged into the environment of the casting hall 1000 after any pollutants contained therein have been separated beforehand with the aid of the pollutant separator 22.According to one exemplary embodiment, the cooling chamber 1 has a first opening O 1, through which a first air quantity L 1 can enter the cooling chamber 1 in a controlled manner. This first air quantity L 1 is air from the casting hall 1000, in which the continuous casting plant 100 is constructed and operated, or ambient air from outside the casting hall or a combination of these two vents. The first air quantity L1 is sucked into the cooling chamber 1 by the suction device 20, for which reason the vapor-air mixture 5 in the cooling chamber 1 also contains the first air quantity L1. In this situation, the actual temperature of the steam-air mixture 5 in the cooling chamber 1 is a mixing temperature which depends not only on the operating state of the continuous casting plant 100 and in particular on a respective currently carried out cooling of the continuous casting 13, but also on the temperature of the first air quantity L 1 drawn in.In order to optimize the function of the separator 22 so that a maximum amount of pollutant can be separated from the vapor-air mixture, the present invention provides, in addition to the claimed pressure control, a temperature control which is realized with the aid of a temperature control circuit 40. The temperature control circuit serves for controlling the actual temperature T1 of the steam-air mixture in the cooling chamber to a predetermined desired temperature T-Soll by varying the position of an air control element Z12, for example in the form of a flap in the feed duct for the first air quantity L1. The temperature control is effected by suitable variations of the position of the air control element and thus by suitable settings control of the first air quantity L 1 that can be drawn into the cooling chamber by the suction device 20. Specifically, the air control circuit 40 has, in addition to the air actuator Z 12, a first temperature sensor E 1 for measuring the respectively present actual temperature T 1 of the steam-air mixture 5 in the cooling chamber 1, a temperature comparison device D 2 for ascertaining a temperature control deviation as the difference between the setpoint and the actual temperature of the steam-air mixture, and a temperature controller C 2 for generating a control signal for the air actuator Z 12 in accordance with the temperature control deviation in such a way that the temperature control deviation becomes zero. If the temperature control deviation becomes zero, the actual temperature corresponds to the setpoint temperature, which, as already mentioned above, is preferably set such that the pollutant separator 22 functions optimally.According to a further advantageous exemplary embodiment of the invention, the actual temperature TL of the first air quantity L 1 is taken into account in the calculation of the output signal of the temperature controller C 2, that is to say of the actuating signal for the air actuator Z 12. For this purpose, the temperature TLof the first air quantity L 1 is detected or measured with the aid of a second temperature sensor E 2 and then output as an influence or disturbance variable to the temperature controller C 2, so that the latter can take into account the temperature TLin the calculation of the actuating signal for the air actuator Z 12.According to a further exemplary embodiment, the continuous casting plant 100 according to the invention can have a heating device 42 for heating the first air quantity L 1 before it is drawn into the cooling chamber 1. Said second temperature sensor E2 is arranged downstream of the heating device 42 in the flow direction of the first air quantity in this case, in order that the actual temperature TL of the first air quantity L1 is correctly detected, i.e. is detected as it reaches the cooling chamber 1. The heating device 42 is preferably designed in the form of a heat exchanger which can further preferably be operated with the warm steam-air mixture extracted from the cooling chamber 8 as heat medium.In general, the continuous casting plant just described with reference to FIG. 1 is designed to carry out the method according to the invention for operating the cooling chamber 1 in the strand guiding device 10 in the continuous casting plant 100, as has been described in claims 1 to 7 and above within the scope of the description of the continuous casting plant according to the invention with reference to FIG. 1 and its function.All that needs to be added is that the cooling chamber 1 is typically not hermetically sealed with respect to external air, as is known from the prior art and has been described above. In the cooling chamber according to the invention, it is therefore also to be assumed that, in addition to the opening E 1 for supplying the first air quantity L 1 which is intentionally provided in terms of design, various undesired openings O 2 are also present, which make possible the uncontrolled penetration of a second air quantity L 2 into the cooling chamber 1. The air quantity L2 is also external air in the form of air from the casting hall 1000 and / or from the environment thereof, which, however-unlike the first air quantity L1-passes uncontrolled through said openings O2 into the cooling chamber 1. This second air quantity L 2 is also typically sucked into the cooling chamber 1 by the negative pressure exerted by the suction device 20 of the cooling chamber 1. The vapor-air mixture 5 in the cooling chamber 1 therefore typically also comprises the second air quantity L2in addition to said first air quantity L1. Just like the first air quantity, this second air quantity L2 also has an influence on the actual temperature of the steam-air mixture 5 in the cooling chamber 1, which is, as stated, a mixing temperature. Analogously to the first air quantity L 1, the second air quantity L 2 also influences the actual pressure of the steam-air mixture 5 in the cooling chamber 1.List of reference characters1 Cooling chamber 4 Ladle 5 Steam-air mixture 6 Intermediate container 7 Immersion pipe 8 Chill mould 10 Strand guiding device 13 Casting strand 20 Extraction device 22 Pollutant separator 30 Pressure control circuit 40 Temperature control circuit 42 Heating device 100 Continuous casting installation 1000 Casting hall C1 Pressure controller C2 Temperature controller D1 Pressure comparison device E1 Temperature sensor E2 Temperature sensor L1 Air quantity L2 Air quantity M20 Power controller O1 Opening O2 Opening P1 Pressure sensor P-Target pressure R Casting direction T1 Actual temperature TL Temperature T-Target temperature Z2 Air quantity Z12 Air actuator

Claims

Method for operating a cooling chamber (1) in a strand guiding device (10) of a continuous casting installation (100), comprising the following steps: guiding a cast strand (13) cast in a mold (8) of the continuous casting installation (100), preferably in the horizontal, after leaving the mold in the strand guiding device (10); cooling the cast strand (13), as it passes through the cooling chamber (1) within the strand guiding device (10), by spraying the cast strand (13) with a coolant, forming a steam-air mixture with an actual pressure and an actual temperature; and aspirating and removing the steam-air mixture (5) from the cooling chamber (1) with the aid of an extraction device (20); characterized regulating the actual pressure of the vapor-air mixture (5) in the cooling chamber (1) to a predefined setpoint pressure (P-setpoint) by varying the power of the suction device (20).Method according to Claim 1, characterized in that the regulation of the pressure has the following substeps: - detecting the actual pressure in the cooling chamber (1); - determining a pressure control deviation as the difference between the desired pressure and the actual pressure; - aspirating and extracting the steam-air mixture (5) from the cooling chamber (1) with the aid of the extraction device (20); and - generating an actuating signal for the power controller (M20) of the extraction device (20) in accordance with the pressure control deviation in such a way that the pressure control deviation becomes zero.Method according to one of the preceding claims, characterized in that a first quantity of air (L1) is sucked into the cooling chamber (1) by the suction device (20) through at least one first opening (O1) in accordance with the performance of the suction device, for which reason the steam-air mixture (5) in the cooling chamber (1) also contains the first quantity of air (L1); in that the first quantity of air (L1) is air from a casting hall (1000) in which the continuous casting installation (100) is constructed, or ambient air from outside the casting hall or a combination of both vents; in that the actual temperature of the steam-air mixture in the cooling chamber is a mixing temperature which also depends on the temperature of the first quantity of air (L1) sucked in; and / or that the actual pressure of the vapor-air mixture in the cooling chamber is a mixing pressure which also depends on the drawn-in first air quantity (L1).Method according to Claim 3, characterized bycontrolling the actual temperature of the steam-air mixture in the cooling chamber (1) to a predefined desired temperature by varying the position of an air actuator (Z12), for example in the form of a flap, for variable setting and monitoring of the first air quantity (L1) which is drawn into the cooling chamber (1) by the suction device (20).Method according to Claim 4, characterized in that the regulation of the actual temperature of the steam-air mixture has the following substeps: - measuring the actual temperature (T1) of the steam-air mixture in the cooling chamber (1); - determining a temperature control deviation as the difference between the setpoint temperature and the actual temperature of the steam-air mixture; and - generating a control signal for the air actuator (Z12) in accordance with the temperature control deviation in such a way that the temperature control deviation becomes zero.Method according to Claim 5, characterized in that the temperature (TL) of the first air quantity (L1) is measured and fed to the temperature controller (C2) as an influencing variable for consideration in the calculation of the actuating signal for the air actuator (Z12).Method according to one of the preceding claims, characterized in that a second air quantity (L2) is sucked into the cooling chamber (1) by the suction device (20) through a second opening (O2), for which reason the steam-air mixture (5) in the cooling chamber (1) contains not only the first air quantity (L1) but also the second air quantity (L2); and in that the actual temperature of the steam-air mixture in the cooling chamber is a mixing temperature which also depends on the temperature of the second air quantity (L2) sucked in.Continuous casting plant (100) comprising: a mold (8) for casting a cast strand (13); and a strand guiding device (10) having a cooling chamber (1) for guiding and cooling the cast strand (13) after leaving the mold (8), wherein the cast strand (13) is supplied with a coolant for cooling in the cooling chamber (1) with formation of a steam-air mixture having an actual pressure and an actual temperature; and a suction device (20) for suction and suction of the steam-air mixture (5) from the cooling chamber (1); characterized in that a pressure control circuit (30) is provided for controlling the actual pressure of the steam-air mixture (5) in the cooling chamber (1) to a predetermined desired pressure (P-desired) by varying the output of the suction device (20).Continuous casting plant (100) according to Claim 8, characterized in that the pressure control circuit (30) has the following components: - the suction device (20) having a power controller (M20) as actuator for variably setting the power of the suction device (20); - a pressure sensor (P1) for detecting the actual pressure in the cooling chamber; - a pressure comparison device (D1) for determining a pressure control deviation as the difference between the setpoint pressure and the actual pressure of the steam-air mixture in the cooling chamber (1); and - a pressure regulator (C1) for generating a control signal for the power controller (M20) of the suction device (20) in accordance with the pressure control deviation in such a way that the pressure control deviation becomes zero.Continuous casting plant (100) according to claim 8 or 9, characterised in that the cooling chamber (1) has a first opening (O1), through which a first quantity of air (L1) can pass into the cooling chamber (1); that the first quantity of air (L1) is air from a casting hall (1000) in which the continuous casting plant (100) is constructed, or ambient air from outside the casting hall or a combination of both vents; that the first quantity of air (L1) is suctioned into the cooling chamber (1) by the suction device (20), for which reason the steam-air mixture (5) in the cooling chamber (1) also contains the first quantity of air (L1); and that the actual temperature of the vapor-air mixture in the cooling chamber is a mixing temperature which also depends on the temperature of the drawn-in first air quantity (L1).Continuous casting plant (100) according to claim 10, characterised bya temperature control circuit (40) for controlling the actual temperature (T1) of the steam-air mixture (5) in the cooling chamber (1) to a predetermined desired temperature (T-desired) by varying the position of an air control element (Z12), for example in the form of a flap, as part of the temperature control circuit (40) for variably setting and controlling the first air quantity (L1) which can be sucked into the cooling chamber (1) by the suction device (20).Continuous casting plant (100) according to Claim 11, characterized in that the temperature control circuit (40) has: - a first temperature sensor (E1) for measuring the actual temperature (T1) of the steam-air mixture in the cooling chamber (1); - a temperature comparison device (D2) for determining a temperature control deviation as a difference between the setpoint temperature and the actual temperature of the steam-air mixture; - the air actuator (Z12); and - a temperature controller (C2) for generating an actuating signal for the air actuator (Z12) in accordance with the temperature control deviation in such a way that the temperature control deviation becomes zero.Continuous casting plant (100) according to Claim 12, characterized in that a second temperature sensor (E2) is provided for measuring the actual temperature (TL) of the first air quantity (L1) and for supplying the actual temperature as an influence variable to the temperature controller (C2) for consideration in the calculation of the actuating signal for the air actuator (Z12).Continuous casting plant according to one of Claims 10 to 13, characterized bya heating device (42) for heating the first air quantity (L1) before it is drawn into the cooling chamber (1), wherein the heating device is preferably designed in the form of a heat exchanger which is further preferably operated with the steam-air mixture drawn out of the cooling chamber (8) as heat medium.

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