FIELD OF THE TECHNIQUE

The present invention relates to an improved cooling apparatus, in particular for cooling the white slag, the residue of the ladle bottom and/or the black slag. The apparatus in question is in particular of the tubular/cylindrical rotating reactor type, to be used preferably in a plant and/or method for cooling and recovering the white slag, the residue of the ladle bottom and/or the black slag that it generates/they generate during the steel production, in particular the slag deriving from a refining phase that normally takes place outside the furnace, in particular in the ladle.

Therefore, the cooling apparatus according to the present invention finds advantageous use in the technical sector of steel production and more particularly in the technical sector of the recovery and/or disposal of slag produced during the aforementioned steel production.

BACKGROUND OF THE INVENTION

In the technical sector of steel production, it is known that the main waste generated therein substantially includes smoke abatement powders, exhausted refractory materials and slag in general. In particular, during the steel refining process it is known to add a composition (rich in lime) that can be partially recovered/disposed of at the end of the refining process (known as "white slag").

To date, one of the major problems remains that relating to the recovery and/or disposal of the so-called "white slag", deriving from the steel refining processes.

The white slag, as it is very rich in lime, has been the subject of many attempts for its recovery over time, although its tendency to hydration and to withering processes make it a highly unstable material and, therefore, difficult to recover.

This involves considerable problems in the management of an outdoor storage of the material and in the prevention of its dispersion into the environment.

More in detail, the recovery of the aforementioned white slag would allow two important advantages to be achieved: on the one hand, reducing the use of raw materials in steel production, such as in particular basic slag, and on the other hand reducing the disposal of waste in landfill, to the benefit of the ecological/environmental aspect. This is of fundamental importance if we consider that white slag constitutes over 90% of the waste byproducts potentially recoverable in a steel plant.

In order to make it usable, it is necessary to cool the white slag leaving the steel production plant before subjecting it to any other recovery process. As is known, the white slag generated during steel production reaches temperatures above 1400°C in a variable quantity depending on the production capacity of the steel refiner.

In this situation, for the cooling of about 1 m3/hour of white slag, or to bring it from about 1400°C to about 70°C, it is required an amount of water or cooling fluid that goes from 50 to 100m ³ / now, based on the aforementioned amount of slag to be cooled.

Generally, the white slag generated by traditional steel production plants varies from 3 to 6% of the quantity of steel produced.

It is therefore evident that the demand in terms of energy and water by the cooling apparatuses of the known type defines a very important problem that has been felt for a long time.

The main compound of the white slag is the dicalcium silicate whose molecule is characterized by a crystalline structure that varies according to the temperature.

During the cooling process of the white slag, at temperatures below about 500°C the dicalcium silicate is subjected to phase transitions that involve an increase in volume which, due to the different crystalline structure and density, gives rise to a fragmentation of the matrix, so-called "withering".

The "controlled" reduction of the temperature of the white slag in a "protected" environment therefore allows its recovery by generating a powder rich in lime that can find a new use in the furnace or in other different applications.

JP5213493 and JP5217388 describe a method and an apparatus for cooling and for the recovery of the white slag which is based on the withering process, in which there is an open tubular reactor in which the white slag is inserted. In this case, the cooling of the white slag is obtained indirectly by cooling the external surface of the reactor by means of water which is sprayed on the upper part of the reactor itself and then collected in a suitable tank, located below the reactor.

WO2016/116884 describes an indirect cooling and recovery system for the white slag in which a rotating drum is intended for the indirect cooling of the white slag thanks to a cooling fluid circulating in a cavity formed in the shell of the drum.

However, these apparatuses and methods have proved to be not free from drawbacks in practice. The main drawbacks encountered in these solutions are represented by the dispersion and high water consumption.

In particular, a drawback of the aforementioned known art lies in the fact that the water normally used for cooling the aforementioned tubular reactor derives directly from the steel production plant in which the cooling apparatus is installed. This water can be at a higher pressure (in particular much higher, for example it is greater than 8 bar) than that necessary to guarantee the required and sufficient flow rate for cooling the tubular reactor.

For this purpose, known-type apparatuses normally provide for a laminating valve, normally a gate valve, placed upstream of the supply ducts which carry the water towards the cooling means of the cylindrical reactor.

Obviously, the aforesaid valve, in combination with a flow meter, effectively regulates the water flow rate, however incurring the drawback of wasting potential energy stored by the pressurized water.

Therefore, known types of equipment have a very low energy efficiency, affecting the efficiency of the entire steel production chain.

ITVE20100055 describes a reactor for cooling the ladle slag; the reactor has a tubular shape and rotates around its horizontal axis, and is equipped with means for cooling its walls with water, thus allowing indirect cooling of the material passing through the reactor. In particular, the cooling circuit comprises a water collection tank used to cool the reactor walls and a pump, which is powered by an inverter motor to thus control the flow of water in circulation.

CN202126194 describes a tubular development reactor which comprises an external cooling cavity and a tube heat exchanger.

GB2078708 describes a solution with two cooling rollers connected to a first circuit that crosses a heat exchanger so that the water circulating in said first circuit cools by exchanging heat with the water circulating in a second circuit, thus transforming it into steam; in particular, the water in the first circuit, when it leaves the heat exchanger, is cold and is sent by a pump to the cooling roller, while the high-pressure steam that comes out of the heat absorption section of the exchanger is sent to a turbine which thus powers an electric generator.

JPS60195309 describes a solution which provides for sending the output steam, and generated by the heating of the slag, through an exchanger in order to drive a turbine. OBJECTS OF THE INVENTION

The object of the invention is to propose an improved cooling apparatus which allows to overcome, at least in part, the drawbacks of the known solutions.

The purpose of the present invention is to obviate the problems of known techniques by proposing an improved cooling apparatus for the white slag, the residue of the ladle bottom and/or the black slag, which it generates/they generate in the steel production and refining phase, able to increase energy efficiency, while maintaining high quality standards of the material obtained and safety for operators and equipment. Another object of the invention is to propose an improved cooling apparatus which allows to obtain a high energy efficiency.

Another object of the invention is to propose an improved cooling apparatus which is constructively completely reliable.

Another object of the invention is to propose an improved cooling apparatus that allows to cool the white slag, the residue of the ladle bottom and/or the black slag in an optimal way, or that obtains an optimal cooling of the white or black slag, or of the ladle bottom, obtaining at the same time the aforementioned high energy efficiency.

Another object of the invention is to propose an improved cooling apparatus which is resistant and robust.

Another object of the invention is to propose an improved cooling apparatus which is capable of treating the entire bottom of the ladle, including steel.

Another object of the invention is to propose an improved cooling apparatus which can be easily implemented and with low costs.

Another object of the invention is to propose an apparatus capable of treating white or black slag in the various and possible physical conditions in which it can occur, for example in the solid, semisolid-pasty or liquid state, depending on the requirements and necessity.

Another purpose of the invention is to propose an apparatus which is quick and easy to maintain and which, at the same time, allows to improve the energy efficiency in the recovery of the white or black slag or the ladle bottom, while maintaining high levels of quality standards of the material obtained.

Another object of the invention is to propose an improved cooling apparatus which is an alternative and an improvement with respect to known solutions.

SUMMARY OF THE INVENTION

All these objects, both individually and in any combination thereof, and others which will result from the following description, are achieved, according to the invention, with an apparatus with the characteristics indicated in claim 1.

DESCRIPTION OF THE FIGURES

The present invention is further clarified hereinafter in one of its preferred embodiments and in some executive variants, reported purely by way of non-limiting example with reference to the attached drawings, in which:

Figure 1 shows a perspective view of a detail of the improved cooling apparatus according to the present invention, figure 2 shows a schematic view of the cooling apparatus according to the present invention. DETAILED DESCRIPTION OF THE INVENTION AND OF SOME OF ITS PREFERRED EMBODIMENTS

The present invention relates to an improved cooling apparatus 1 for cooling a material, in particular for cooling white slag, ladle bottom residue and/or black slag.

In particular, the term “white slag” hereinafter refers to a waste deriving from the refining processes of a metal alloy, in particular of steel, during the production chain of the alloy itself, in particular of steel. In particular, white slag is a waste material very rich in lime and/or other binders and therefore advantageously recoverable.

The term "black slag" refers to the slag that forms above the steel melting bath as a result of the oxidation of the scrap and of the compounds generated by the additives inserted in the charge of the electric furnace to produce steel starting from the scrap; suitably, this slag is discharged at the outlet from the electric furnace to be treated in a separate and dedicated way with respect to the liquid steel.

The term "ladle bottom residue" means the material formed/found at the bottom of a ladle furnace, said material comprising white slag containing lime or lime-based compounds and also comprising a metal alloy, preferably steel, in the molten or semi-molten/viscous state. Conveniently, the ladle furnace receives the liquid steel (called "tapped") which is formed in an electric furnace, preferably an arc furnace (also known as "EAF"), which is used in the steel industry to produce steel starting mainly from scrap ferrous, as well as from highly alloyed iron-based materials, such as direct reduced iron (called “DRI” or “sponge iron”), liquid steel and other precursors of iron.

Advantageously, the apparatus 1 according to the present invention can be operatively associated with a steel production plant and/or its derivatives or variants.

Advantageously, the apparatus 1 can be positioned at the outlet of a ladle furnace or at the outlet of an electric furnace, preferably an arc furnace (also known as "EAF").

Conveniently, the cooling apparatus 1 is suitable for use in a plant for the recovery of the white or black slag that is generated in the steel production and refining phase.

The improved cooling apparatus 1 object of the present invention comprises at least one rotating reactor (or drum) 2, substantially tubular (preferably cylindrical), equipped with at least one wall 3 which internally delimits a chamber 4 for receiving and passing through the material to be cooled, extending between an inlet opening for the material to be cooled and an outlet opening 5 for the cooled material.

Advantageously, the apparatus 1 according to the invention can comprise a rotating reactor 2 for the treatment of the white or black slag or the ladle bottom which can be of any traditional type and, for example, can be of the type described in EP3247811 or in EP3323898 or in the Italian patent application 102021000012812. Conveniently, the apparatus 1 comprises cooling means 18 acting on the reactor 2 and configured to cool, directly or indirectly, by means of a cooling fluid, the material that passes through said chamber 4.

Preferably, the apparatus 1 comprises cooling means 18 of the wall 3 which delimits the chamber 4 inside it, to thus indirectly cool the material passing through said chamber.

Conveniently, the apparatus 1 comprises means 18 for indirect cooling of the material passing through said chamber and, in particular, these means may comprise:

- means (for example nozzles) for spraying a cooling fluid (preferably a cooling liquid and, more preferably, water) on the external surface of said wall 3, and/or

- cooling plates fixed to said wall and comprising ducts for the circulation of a cooling fluid (preferably a cooling liquid and, more preferably, water), and/or

- at least one cavity, possibly made using modular panels, which is defined externally around said wall and which defines a chamber permeated by a cooling fluid (preferably a cooling liquid and, more preferably, water) and, in particular, a chamber in which said refrigerant fluid circulates.

Operationally, the cooling fluid acts on the wall 3 of the chamber 4 in such a way as to cool said wall, and consequently also indirectly cool the material to be cooled contained in said chamber.

Conveniently, in a possible embodiment not shown, the cooling means 18 are configured to send the cooling fluid directly into contact with the material passing through the chamber 4.

Advantageously, the apparatus 1 according to the invention further comprises supply means 10 of at least one cooling fluid (preferably a cooling liquid and, more preferably, water) to the cooling means 18 of the rotary reactor.

Conveniently, the supply means 10 are fluidically connected at the inlet to the cooling means 18 to thus supply the latter with the cooling fluid, preferably a cooling liquid and, more preferably, water.

Preferably, said cooling means 18 can comprise at least one distribution circuit 6 of the cooling fluid arranged at least partially around a reactor 2 and configured to receive a cooling fluid (preferably water) from the supply means 10.

Preferably, the supply means 10 comprise at least one fluidic feed circuit which at the inlet is connected to an external feed 9, in particular mains water, of the cooling fluid, while at the outlet it is connected to the cooling means 18 of the reactor 2.

Conveniently, in in correspondence with the fluidic circuit for feeding the supply means 10, a hydraulic machine 11 is installed which is connected to an electric machine 12. Preferably, said hydraulic machine 11 is connected to the electric machine 12 so as to transform the mechanical energy deriving from the fluid cooling liquid - and in particular from the cooling fluid - circulating in said power supply means 10, in electrical energy, or vice versa. More in detail, the hydraulic machine 11 is mechanically connected to the electric machine 12 so as to operate the latter.

Preferably, the hydraulic machine 12 is fed at the inlet with a cooling liquid, in particular with water, and not with steam or gas, and is configured to transform the mechanical energy of said cooling liquid into electrical energy.

Conveniently, said hydraulic machine 11 is configured to regulate the flow rate, in particular by decreasing/increasing the pressure, of the cooling fluid - and in particular of the cooling liquid - entering the cooling means 18.

Conveniently, the hydraulic machine 11 is positioned upstream with respect to the cooling means 18 acting on the reactor 2.

Conveniently, the supply means 10 and the cooling means 18 do not comprise any heat exchanger.

Conveniently, the assembly of said hydraulic machine 11 with said electric machine 12 is configured to operate from:

- flow/flow meter of the cooling fluid in the supply circuit of the supply means 10,

- regulator of the flow rate and/or pressure of the cooling fluid in the circuit of the supply means 10, and therefore at the inlet to the cooling means 18,

- generator of electric energy, and in particular of electric current, to be then advantageously used for powering a user, preferably the cooling apparatus itself, and/or to be fed into the network.

Conveniently, the use of a hydraulic machine 11 makes it possible to avoid the use of a dedicated valve to reduce the pressure by dissipating energy.

In particular, suitably, the regulation of the flow rate of the cooling fluid is carried out by controlling/setting the number of movements (revolutions/strokes) per minute of the moving parts of the hydraulic machine 11.

In particular, suitably, the regulation of the pressure of the cooling fluid is carried out by controlling the driving torque of the hydraulic machine 11 by setting the current produced at the output of the electric machine 13.

Conveniently, said hydraulic machine 11 can comprise a dynamic machine, such as for example an impeller or turbine. In particular, in this case, for a limited measuring range (for example 60-100 m ³ /h), the dynamic machine itself can act as a flow rate/flow measurement device. Conveniently, the dynamic machine can be combined with an external and dedicated flow rate/flow measurement device (for example a flow meter), to detect the flow rate/flow in the circuit of the supply means 10.

Preferably, said hydraulic machine 11 comprises a volumetric machine, such as a gear or piston pump. In particular, the use of a volumetric machine makes it possible to have a greater precision in measuring the flow rate/flow and, moreover, it can be used in a wider measuring range, for example from 0 to 100 m ³ /h. Conveniently, said electric machine 12 can comprise an electromechanical generator, of the alternator or dynamo/motogenerator type.

Conveniently, the electric energy - and in particular the electric current - coming out of the electric machine 12 can be sent to an inverter, for its introduction into the grid.

Advantageously, the assembly of said hydraulic machine 11 with said electric machine 12, provided and acting in correspondence with the power supply means 10, allows, if necessary, by sending electric current to the electric machine 12, to act by means of said hydraulic machine 11 on the cooling fluid entering the same hydraulic machine in such a way as to correspondingly vary its flow rate and/or pressure (for example to increase the flow rate or pressure), thus guaranteeing a fluid with suitable or sufficient flow rate and pressure at the inlet to the cooling means 18.

Advantageously, in the circuit of said supply means 10, downstream of the hydraulic machine 11 , a further safety valve can be provided; preferably, this further safety valve is provided in the case of a dynamic hydraulic machine 11 . Conveniently, however, in the case of a volumetric hydraulic machine 11 , this additional safety valve may not be necessary since it is the same hydraulic machine 11 which can operate to completely stop the passage of the cooling fluid.

Preferably, therefore, the hydraulic machine 11 entering the cooling means 18 intercepts the cooling fluid circulating in the supply means 10 to lower the pressure, and therefore control the flow rate, of the cooling fluid before it enters the cooling means 18. Conveniently, moreover, the combination of the hydraulic machine 11 with the electric machine 12 allows a fluid with suitable flow rate and pressure to be sent to the cooling means 18, to thus cool the material inside the chamber 4 and in particular white or black slag or the bottom of the ladle, and at the same time allows to produce recovered electric energy that can be used for any purpose, such as for example the supply of users or for its introduction into the network.

Advantageously, the supply means 10 receive the cooling fluid from the same water network that feeds a steel production plant and/or the like.

The cooling fluid advantageously comprises water, in particular already used or usable in the steel production plant. Advantageously, the cooling fluid of the supply means 10 upstream of the hydraulic machine 11 has a pressure of between 6 bar and 10 bar and in particular of about 8 bar.

Conveniently, the pressure of the cooling fluid downstream of the hydraulic machine 11 has a pressure of between 0.1 bar and 4 bar and in particular of about 1 bar.

Conveniently, if the cooling fluid of the supply means 10 upstream of the hydraulic machine 11 has a pressure of about 6 - 10 bar, said hydraulic machine 11 is configured to decrease the pressure of the cooling fluid entering the cooling means 18, thus powering said electric machine 12 and generating electric energy to be used for powering a user, preferably the cooling apparatus itself, and/or to be fed into the network.

Conveniently, if the cooling fluid of the supply means 10 upstream of the hydraulic machine 11 has a pressure lower than about 0.1 - 4 bar, said hydraulic machine 11 is configured to increase, using the electrical energy supplied by said electric machine 12, the pressure of the cooling fluid entering the cooling means 18.

More specifically, the supply means 10 take the high-pressure cooling fluid from an upstream plant, in particular a steel production plant and convey towards the cooling means 18 of the apparatus 1 through the hydraulic machine 11 , which together with the electric machine 12, operates as a flow rate/flow meter, as a flow rate/pressure regulator of said cooling fluid (preferably by lowering the pressure of said fluid) and electricity generator.

Advantageously, the chamber 4 of the reactor 2 is configured to advance the material to be cooled (ie the white or black slag or the ladle bottom) in a first direction of movement. Conveniently, the cooling means 18 can be configured to move the cooling fluid from an inlet section to said outlet section in a second direction at least partially opposite to said first direction. In particular, the cooling fluid acts externally on the chamber 4 crossing it along its longitudinal development according to a direction which is opposite to that with which the material to be cooled crosses/advances inside said chamber 4.

In accordance with the preferential embodiment illustrated in the accompanying figures, the reactor 2 preferably has a substantially cylindrical shape and extends along a main axis X between a first end (not shown), in which the inlet opening is made, and a second end, in which the outlet opening 5.

Preferably, the first direction of movement of the material to be cooled is substantially parallel to the main axis X and facing from the inlet opening towards the outlet opening 5.

Advantageously, the reactor 2 is made of thermally conductive material, in particular it is made of metallic material, such as for example steel.

Conveniently, in order to cool the material in an optimal manner, the reactor 2 is rotatably mounted on a support structure 15 and can be operated in rotation around the main axis X by motorization means 16. Advantageously, the support structure 15 is intended to be resting on the ground and comprises at least a lower support base 15', and is preferably made of metallic material.

Preferably, the support structure 15 supports the reactor 2 in such a way that its main axis X is substantially horizontal, or more precisely that it is at least partially inclined, from a higher level in correspondence with the inlet opening, to a lower level in correspondence with the outlet opening 5. Conveniently, further motorization means (not shown) can be provided to vary the inclination of the reactor 2 with respect to the horizontal.

Conveniently, the apparatus 1 comprises at least one electronic control unit (not shown) electronically connected to the motorization means and programmed to control them to vary the rotation speed of the reactor 2 and/or the inclination of the reactor with respect to the horizontal.

The electronic control unit is programmed to control the rotation of the reactor 2 according to a first direction of rotation, for example clockwise, or counterclockwise.

Otherwise, the electronic control unit can be programmed to rotate the reactor 2 in more than one direction of rotation, alternately, in order to mix the material inside the chamber 4 and increase the cooling efficiency of the apparatus 1 according to the invention.

Conveniently, the apparatus 1 comprises at least one temperature sensor operatively associated with the reactor 2, electronically connected to the electronic control unit and configured to detect at least one temperature measurement of the reactor 2 and/or of the material to be cooled.

The electronic control unit is advantageously configured to receive the temperature measurement and correspondingly control the motorization means for varying the rotation speed of the reactor 2 and/or the inclination of the reactor.

The electric machine 12 is electronically connected to the electronic control unit to send to the latter the data relating to the measurement of flow rate/flow carried out by the hydraulic machine 11 and to receive from the electronic control unit the commands for varying the flow and/or the pressure of the cooling fluid sent to the cooling means 18.

Conveniently, if provided separately from the hydraulic machine, the sensor for measuring the flow rate/flow of the cooling fluid through the supply means 10 is electronically connected to the electronic unit of control and is configured to send the flow rate /flow measurement to the electronic control unit.

Advantageously, the electronic control unit comprises at least one microcontroller, such as for example a PLC (programmable logic controller) or the like.

Preferably, the electronic control unit further comprises at least one processing module programmed to process the temperature measurement and the flow rate/flow measurement and generate a corresponding first control signal for the drive means and a second control signal for the electric machine 12 connected to the hydraulic machine 11.

Conveniently, the electronic control unit also comprises at least one control module, electronically connected to the processing module and to the motorization means and to the electric machine 12 associated with the hydraulic machine 11 and programmed to send the first command signal and the second command signal.

Obviously, the electronic control unit can be connected to the sensors and to the motorization means and to the regulating device in any itself known manner to the person skilled in the art and therefore not described in detail below.

For example, the electronic control unit may provide a wired connection or a wireless connection (wireless) without thereby departing from the protection scope of this patent.

As is clear from what the cooling apparatus according to the invention is particularly advantageous, in that:

- it allows to overcome the drawbacks of the known solutions;

- is able to increase energy efficiency, while maintaining high quality standards of the material obtained and safety for operators and equipment;

- it allows to obtain a high energy efficiency;

- it is constructively completely reliable;

- it allows to cool the white slag, the residue of the ladle bottom and/or the black slag in an optimal way, or obtain an optimal cooling of the white slag while obtaining the aforementioned high energy efficiency;

- it is easy to implement and with low costs.

- is able to treat white or black slag in the various and possible physical conditions in which it can occur, for example in the solid, semisolid-pasty or liquid state, according to requirements and needs;

- it is quick and easy to maintain and, at the same time, allows to improve the energy efficiency in the recovery of the white or black slag or the ladle bottom, while maintaining high quality standards of the material obtained;

- it is an alternative and an improvement with respect to the known solutions.

In particular, the present solution differs from the solutions described in ITVE20100055, CN202126194, GB2078708 and JPS60195309 in that the hydraulic machine 11 for driving the electric machine 12 is mounted on the means 10 which feed, at the inlet, the cooling means of the reactor. More in detail, the present solution differs from the solutions described in ITVE20100055 and CN202126194 in that it provides for the presence of a hydraulic machine 11 for driving the electric machine 12, while it differs from the solutions described in GB2078708 and JPS60195309 (which provide for the use of a turbine which is driven by the steam leaving a heat exchanger) since the hydraulic machine 11 is mounted on the means which feed the cooling means 18 with the cooling fluid and, in particular, with the cooling liquid.

This is particularly advantageous in that the combination of the hydraulic machine 11 with the electric machine 12 and the positioning of the hydraulic machine 11 at the inlet to the cooling means 18 allows the latter to be sent a fluid with suitable flow rate and pressure, to thus cool the material inside the chamber 4 and in particular white or black slag or the bottom of the ladle, and at the same time allows the production of electric recovery energy that can be used for any purpose, such as for example the power supply of users or for its introduction into net.

The present invention has been illustrated and described in some of its preferred embodiments, but it is understood that executive variations may be applied to them in practice, without however departing from the scope of protection of the present patent for industrial invention.