EP1346067B1 - Cooling system for a metallurgical smelting furnace - Google Patents

Abstract

The invention relates to a cooling system for a metallurgical smelting furnace, containing a cooling element (16i; i=1, 2, 3, 4) which is integrated into a wall in the metallurgical smelting furnace and which contains at least one internal cooling refrigerating channel (18i; i=1, 2, 3, 4). A predetermined cool water volume flow (Qi; i=1, 2, 3, 4) passes through said channel, guaranteeing the required cooling performance. The cooling system is embodied in such a way that a static absolute pressure which is less than the atmospheric pressure at the place of installation of the metallurgical smelting furnace is produced in the greater part of the at least one internal cooling channel (18i; i=;1, 2, 3, 4) of said predetermined cooling water flow (Qi; i=1, 2, 3, 4). A preliminarily container (24) for cooling water is arranged at a higher position than the cooling element(s) (16i; i=;1, 2, 3, 4) so that the geodesic superrelevation thereof determines the rest pressure in the cooling circuit.

Description

The present invention relates to a cooling system for a metallurgical Melting furnace.

State of the art

Mostly cooling systems for metallurgical melting furnaces, both crucible-shaped as well as shaft-shaped construction, are today as closed Cooling water systems trained. They include cooling elements in the furnace walls are integrated and provided with cooling channels. A pump pumps the cooling water through the cooling channels of the cooling elements. A static pressure maintenance device such as. a container with a gas cushion ensures that there is a static pressure of a few bars at every point of the cooling channels is present. Such cooling systems are referred to below as "pressure circuits". On the one hand, the overpressure in the cooling channels increases the evaporation temperature of the cooling water, which has a positive effect on the Security of the cooling system affects, since a vapor formation the cooling capacity greatly reduced and consequently local overheating of a cooling element can lead. On the other hand, it has long been known that the Use of such pressure circuits in metallurgical furnaces is not without risk. Even with a small leak, relatively large amounts of cooling water introduced into the furnace, causing damage to a refractory lining and may even lead to violent explosions if e.g. Cooling water accumulates in the melting furnace and then liquid metal is covered.

To rule out these risks, metallurgical ones are still used today Ovens used sprinkler cooling systems, as they have been used for more than have been known for a hundred years. However, the latter can never have the same cooling capacity how cooling elements integrated into the furnace wall provide and are extremely problematic in terms of their maintenance.

Splash water cooling systems were used as a "modern" alternative for pressure circuits developed. The latter include cooling boxes in the furnace walls are integrated and have spray nozzles in an inner chamber, which the Spray cooling water on the inside wall of the chamber facing the inside of the oven. The majority of the excess pressure in the spray nozzles is reduced here, so that there is only a slight excess pressure in the coolers. Such Splash water cooling systems are, however, quite complex to manufacture and claim also a lot of space in the furnace wall.

It should also be noted that some parts of metallurgical For safety reasons, melting furnaces are still not cooled at all become. For example, this is the case for the bottom of an arc furnace such as it is used in electrical steel plants.

It has also already been proposed in a metallurgical cooling system To produce a vacuum. This is to prevent that in the event of a small leak in the cooling element cooling water can penetrate into the furnace. One such solution is for example already in 1984 in US 4,603,423 in connection with wall cooling an arc furnace. This cooling system includes one Feed pump, a reservoir for cooling water, a pressure reducing valve, parallel cooling elements, a suction pump and a gas separator. The feed pump pumps the cooling water from the storage tank over the Pressure reducing valve in the cooling elements, the pressure behind the pressure reducing valve should be less than atmospheric pressure. The suction pump should then suck the cooling water through the cooling elements and then over press the gas separator back into the storage container. A similar Vacuum cooling system is described in JP 09 287733.

That such vacuum cooling systems are found in metallurgical melting furnaces haven't been able to get through until now, most likely because that you question their safety. In fact, small pressure fluctuations can occur lead to overheating in the cooling elements.

Object of the invention

The object of the present invention is a reliable cooling system to propose for a metallurgical melting furnace, the larger one Security than known pressure circuits has a greater cooling capacity than Classic sprinkler cooling ensures the use of more compact ones and simpler cooling elements than known spray water cooling systems enabled and safer than the vacuum cooling systems proposed so far is. This object is achieved by a cooling system according to claim 1.

Characterization of the invention

A cooling system according to the invention for a metallurgical melting furnace comprises at least one cooling element in a furnace wall of the metallurgical Melting furnace is integrated. The term "furnace wall" includes both the side walls of the melting furnace and the floor or the furnace lid. The at least one cooling element has at least one internal cooling channel on a predetermined Cooling water volume flow is flowed through, which the required cooling capacity guaranteed. The cooling system also includes at least one Reservoirs for cooling water; and at least one cooling water pump sucks the cooling water heated in the cooling element and into the reservoir pumps it back. The cooling system is designed hydraulically in such a way that in most of the at least one internal cooling channel at the predetermined Cooling water flow a static pressure is present which is less than the atmospheric Pressure at the location of the metallurgical melting furnace. In in other words, there is no excess pressure in the at least one cooling element of the cooling water compared to the ambient pressure. This means that in the event of a small leak in the cooling element, no cooling water in the Melting furnace can penetrate. Rather, it becomes ambient air or furnace gas sucked into the internal cooling channel of the cooling element due to the leak. Direct leakage monitoring can be caused by the suction of furnace gas by means of gas detectors. This will make general security significantly improved for man and machine. By the forced management of the Cooling water through internal cooling channels of the cooling elements are the known Disadvantages of sprinkler cooling eliminated. The for the invention Cooling elements required are also much more compact and cheaper to produce than splash water coolers. It remains to be noted that the cooling system according to the invention for metallurgical melting furnaces of both crucible-shaped, as well as shaft-shaped design is suitable. It is here possible to design only part of the furnace cooling as a vacuum system. For example, furnace cooling in a particularly vulnerable area metallurgical melting furnace as a vacuum system according to the invention, the remaining part of the furnace, however, be designed as a classic overpressure system. The cooling system according to the invention also has a flow tank for Cooling water arranged above the at least one cooling element is and prevails in the atmospheric pressure. This flow tank supplies the at least one cooling element with cooling water and gives, through its geodetic exaggeration, the idle pressure, or pre-pressure, in the cooling circuit before. He also forms an expansion tank for the cooling water. Through the Static determination of the form will result in dangerous pressure fluctuations largely avoided in the cooling system. This will ensure the security of the cooling system according to the invention, in comparison to known vacuum cooling systems, significantly improved.

With a cooling system according to the invention, it is possible, for example to provide safe floor cooling for a metallurgical arc furnace. A cooling system according to the invention can also advantageously be used as a lid cooling system of such a metallurgical arc furnace. At the The cooling system according to the invention is suitable for a blast furnace, among others. beneficial to the Underfloor cooling. In all of these cases, the great security against leakage is that of the invention Cooling system of particular importance.

The cooling system is normally designed as a closed circuit. This means that it has a recooling device and at least one cooling water pump on. The latter sucks the cooling water heated in the cooling element and pumps it into the flow tank via the at least one recooling device back. However, it is also possible to use the cooling system as an open cooling circuit to operate, that is to supply the flow tank with fresh water and to drain the warm return.

Between the cooling water pump (s) and the cooling element (s) is advantageous Degassing container arranged. A gas detection device makes it possible Detect furnace gases that are in the degassing tank from the cooling water separate and that a leak in the cooling system in the furnace area indicate.

In a preferred embodiment, this degassing container comprises a gas space above the cooling water and a vacuum pump for Generating an atmospheric negative pressure in this gas space.

Solid cooling plates are advantageous in a cooling system according to the invention made of copper or cast iron can be used as cooling elements. tube panels and coils are in some areas of a melting furnace, however not excluded and also particularly inexpensive.

piece placement

FIG. 1:

ein Schaltschema eines erfindungsgemäßen Kühlsystems;

FIG. 2:

ein schematische Darstellung einer Ausgestaltungsvariante eines Entgasungsbehälters für das Kühlsystems nach FIG. 1.

An embodiment of the invention will now be described with reference to the accompanying figures. Show it:

FIG. 1:

a circuit diagram of a cooling system according to the invention;

FIG. 2:

a schematic representation of an embodiment variant of a degassing container for the cooling system according to FIG. 1.

Description of a preferred embodiment of the invention using the characters

FIG. 1 shows a greatly simplified circuit diagram of a cooling system for a metallurgical melting furnace. The reference number 10 denotes a cooling circuit of the melting furnace. This cooling circuit 10 comprises a cooling water flow collector 12 and a cooling water return collector 14. Between the cooling water flow collector 12 and the cooling water return collector 14, a plurality of cooling elements 16 _i (i = 1, 2, 3, 4) are connected. The cooling elements 16 _i (i = 1, 2, 3, 4) shown are, for example, solid cooling plates made of copper or cast iron with integrated cooling channels 18 _i (i = 1, 2, 3, 4) for the cooling water. These cooling plates 16 _i (i = 1, 2, 3, 4) are mounted inside an outer furnace shell and are mostly covered by a furnace lining made of a refractory material. It should be noted that those skilled in the art also know such cooling elements 16 _i (i = 1, 2, 3, 4) as so-called "staves".

Each cooling element 16 _i (i = 1, 2, 3, 4) has a valve 20 _i (i = 1, 2, 3, 4) in its flow connection and a valve 22 _i (i = 1, 2, 3) in its return connection , 4) on. These valves 20 _i and 22 _i make it possible to isolate the corresponding cooling element 16 _i from the cooling circuit 10. At least one of the two valves 20 _i and 22 _i is also designed to enable fine tuning of the pressure losses in the corresponding cooling element 16 _i (i = 1, 2, 3, 4). In FIG. 1, the cooling elements 16 _i (i = 1, 2, 3, 4) are all connected in parallel. However, it is not excluded that the cooling circuit 10 can also comprise cooling elements connected in series.

Reference numeral 24 denotes a supply tank for cooling water which is arranged above the cooling water flow collector 12. This Flow tank 24 is in via a ventilation line 25 with the atmosphere Connection so that 24 atmospheric pressure above the cooling water in the flow tank prevails in the. The cooling water can be supplied via a flow line 26 from the flow tank 24 into the lower lying cooling water flow collector 12 flow in. An emptying line 27 enables the flow tank 24 to drain into a drain channel 28 if necessary. In this drain line 27 also leads to an overflow device 29.

Reference numeral 30 in FIG. 1 denotes a closed degassing container into which the cooling water flows from the return collector 14. A vacuum pump 32 is connected to this degassing container 30. The latter creates an atmospheric negative pressure in a gas space 33 above the cooling water. It should also be emphasized that the degassing tank 30 through a partition 34 into a decanting basin 36 and a Suction basin 38 is divided. The cooling water flows into the decanting basin 36 via a return line 40, with a large part of the cooling water transported solid particles settled in the decanting basin 36. Because the cooling water level in the degassing container 30 is slightly higher than the partition 34, the cooling water flows into the suction basin 38 and can flow into one Flow in suction line 42. The vacuum pump 32 can e.g. around a jet pump operated with compressed air. Reference numeral 44 denotes a source of compressed air (i.e. an air compressor or a Compressed air distribution network) to which the jet pump 32 for the purpose of generating a Suction air jet is connected. This suction air jet sucks a vacuum in the degassing tank 30. As further shown in FIG. 1, the Output of the jet pump 42 by means of an exhaust air line 46 to a water separator 48 are connected, in which the degassing tank 30 entrained cooling water is separated from the exhaust air. This water separator 48 can e.g. be arranged above the flow container 24, so that the separated cooling water via a line 50 by gravity in the flow tank 24 can be returned.

The suction line 42 is at a lower pressure increasing station 52 connected, for example two pumps 54 and 56 connected in parallel comprises, each of the pumps 54, 56 is in operation and the other in Reserve is. If the pumps 54, 56 are centrifugal pumps, the existing one NPSH value of the system is of course greater than the required NPSH value of the Centrifugal pumps. For this reason, the centrifugal pumps may need a certain amount Height below the degassing container 30 may be arranged. To a deep one However, pumps can also be used to avoid the pump shaft will be less prone to cavitation.

The pumps 54, 56 are therefore also on the suction side via the suction line 42 the degassing tank 30 connected. They are on the pressure side via a pressure line 58 connected to the flow tank 24. In this pressure line 58 is a recooler 60 installed for the cooling water. Pumps 54, 56 pump consequently, the cooling water from the degassing tank 30 through the recooler 60 back into the pre-reservoir 24. With the reference numeral 62 is one Fresh water pipe referred to, by means of which water losses are compensated can be or a water exchange can be made.

According to an important aspect of the present invention, the cooling system is designed hydraulically in such a way that in the majority of the cooling channels 18 _i, with a predetermined cooling water flow, a static pressure is present which is lower than the atmospheric pressure at the installation site of the metallurgical melting furnace. In FIG. 1 denotes Q _i (i = 1, 2, 3, 4) in each case the predetermined cooling water flow which is required in the respective cooling element 16 _i (i = 1, 2, 3, 4) by the desired amount of heat at a predetermined flow and return temperature of the cooling water. The supply lines to the individual cooling elements 16 _i are designed such that a slight negative pressure is present in the inlet of the cooling channels 18 _i . The cooling water crosses the cooling channels 18 _i from top to bottom. In the cooling channels 18 _i , the static pressure can be influenced by local and linear pressure losses (loss energy), the channel cross section (speed energy) and the gradient (position energy). It should be noted that pressure losses and a reduction in the cross-section of the duct increase the negative pressure (ie the static absolute pressure decreases), but a slope causes the negative pressure to decrease (ie the static absolute pressure increases). In order to cause a slow rise in the vacuum from the flow connection to the return connection with a constant duct cross-section, the energy loss must increase slightly faster than the position energy decreases.

A very precise calculation of the existing statistical pressure at every point of the cooling circuit 10 is absolutely necessary in order to get the cavitation problem under control. With modern computer programs for the calculation of flows in pipelines, however, this is no problem for the person skilled in the art. In order to achieve sufficient security against cavitation in the cooling channels, the static absolute pressure should not be lower than kP _D at any point in the cooling circuit 10, where k is a safety factor greater than 1 and P _{D is} the evaporation pressure of the cooling water at the maximum cooling water temperature. For example, one can assume that at a maximum return temperature of the cooling water of 40 ° C, the static absolute pressure should not be lower than 0.4 bar at any point in the cooling circuit.

The negative pressure in the cooling elements 16 _i (i = 1, 2, 3, 4) ensures that if there is a small leak in the cooling circuit 10, no cooling water will escape into the melting furnace. Rather, air or furnace gases are sucked into the cooling circuit 10 through the leak. The reference number 70 in FIG. 1 denotes a gas detector which responds to furnace gases which collect in the gas circuit 33 of the degassing container 30 in the event of a leak in the cooling circuit 10. Via this gas detector 70, the furnace operator receives reliable information relatively quickly that a leak has formed in the cooling circuit 10.

If the degassing tank 30 is significantly lower than the return collector 14 can be arranged, optionally on the vacuum pump 32 to be dispensed with. Fig. 2 shows such a degassing tank 130. It is a certain geodetic height H is arranged under the return collector 14 and with this via a return line 40 with low pressure losses connected so that the static absolute pressure of the cooling water in the return line 40 rises sharply and in the return collector 14 slightly larger than that Atmospheric pressure. The degassing of the degassing container 30 can consequently to the atmosphere via a simple vent valve 132. With reference numeral 134 is shown in FIG. 2 denotes a gas detector based on Furnace gases that respond in the event of a leak in the cooling circuit 10 before Collect vent valve 132 of degassing container 130 until the vent valve opens. The furnace operator also receives this gas detector 132 Relatively quickly a reliable indication that there is a leak in the cooling circuit 10 has formed.

Claims (7)

1. Cooling system for a metallurgical melting furnace comprising:

   at least one cooling element (16_i; i = 1, 2, 3, 4), which is integrated in a furnace wall of the metallurgical melting furnace and has at least one internal cooling duct (18_i; i = 1, 2, 3, 4), through which passes a predetermined volumetric cooling water flow (Q_i; i = 1, 2, 3, 4), which ensures the required cooling capacity;

   at least one storage tank for cooling water; and

   at least one cooling water pump (54, 56) which sucks up the cooling water which has been heated in the cooling element (16_i; i = 1, 2, 3, 4) and pumps it back into the storage tank;

   the cooling system being hydraulically designed in such a way that a static absolute pressure, which is smaller than the atmospheric pressure at the place of installation of the metallurgical melting furnace, prevails in the largest part of the at least one internal cooling duct (18_i; i = 1, 2, 3, 4) with the predetermined cooling water flow (Q_i; i = 1, 2, 3, 4);

   characterized in that
   the storage tank for the cooling water is formed by a feed tank (24) for cooling water, which is arranged above the at least one cooling element (16_i; i = 1, 2, 3, 4).
2. Cooling system as claimed in claim 1, characterized by
   a recooling system (60) which is arranged hydraulically between the at least one cooling water pump (54, 56) and the feed tank (24).
3. Cooling system as claimed in claim 1 or 2, characterized by
   a degassing tank (30, 130) arranged hydraulically between the cooling water pump (54, 56) and the at least one cooling element (16_i; i = 1, 2, 3, 4); and
   a gas detection device (70, 134) for detection of furnace gases which are separated from the cooling water in the degassing tank (30, 130).
4. Cooling system as claimed in claim 3, characterized by
   a gas space (33) above the cooling water in the degassing tank (30); and
   a vacuum pump (32) for generation of an atmospheric vacuum in the gas space (33) above the cooling water.
5. Cooling system as claimed in one of claims 1 to 4, characterized in that the at least one cooling element (16_i, i = 1, 2, 3, 4) is a solid cooling plate made from copper or cast iron.
6. Metallurgical melting furnace comprising at least one cooling system as claimed in one of the preceding claims.
7. Metallurgical melting furnace as claimed in claim 6, wherein at least one cooling system is formed according to any of the preceding claims as bottom cooling of the melting furnace.

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