Method for refining metal and corresponding station

Abstract

Method and corresponding station (10) for refining metal in steel plants comprising a degassing apparatus (11) and a monitoring apparatus (100), having a gas analyzer (101), one or more pressure detectors (103), possibly one or more flow detectors (104) and a processing unit (102).

Description

[0001] METHOD FOR REFINING METAL AND CORRESPONDING STATION

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a method and a corresponding station for refining metal, which can find application in the steel industry and steel production sector, such as for example in the field of steel secondary metallurgy processes, or also in sectors that process other metals, in which there are ladle furnaces, refining furnaces, vacuum degassing treatment stations or suchlike.

[0004] BACKGROUND OF THE INVENTION In the context of secondary metallurgy processes, especially for producing so- called special steels, it is known to carry out refining treatments, a part of which in an electric arc furnace (EAF) but more often directly in a subsequent ladle furnace (LF) and possibly in an additional vacuum degassing treatment station.

[0005] The LF furnace is equipped with a lid through which, in the refining completion station, electrodes are lowered to heat the metal, while the degassing station comprises a hermetically isolatable chamber inside which the ladle is positioned, or it provides a lid with which to hermetically isolate the ladle, in order to generate a vacuum condition inside it.

[0006] Refining treatments often include deoxidation, alligation, desulphurization, vacuum degassing (VD), vacuum oxygen decarburization (VOD) and removal of inclusions, to refine the chemical composition in order to fall within the composition ranges of the various chemical species indicated in the technical specifications of the type of steel to be produced. Refining requires a high degree of homogenization of the liquid metal, both in terms of chemical composition and also temperature.

[0007] Homogenization is guaranteed by a continuous stirring which can be carried out through the injection of inert gas, for example argon or nitrogen, using submerged lances or porous plugs located on the bottom of the ladle and connected to a gas injection line, with the aim of continuously stirring the liquid metal bath and bringing the solid and / or gaseous inclusions and impurities present therein up to the surface.

[0008] The desired chemical composition is reached, starting from the initial one, through operating procedures (for example additions of ferroalloys, vacuum treatment and suchlike), carried out on the basis of statistical analyses on previous production or on test campaigns.

[0009] Since the thermo-chemical process is influenced by many parameters and characterized by non-negligible variability, it is necessary to verify any deviation from the expected values of the concentration of the chemical species in the metal by collecting subsequent samples, and possibly correct any following actions.

[0010] The application of correlations, reported in the literature and / or in the aforementioned operating procedures, does not always allow to calculate the current values of the chemical composition in a refining process, due to the high number of independent parameters and to the fact that they contain calibration parameters that are strongly dependent on the plant examined and not necessarily constant over time. It therefore becomes necessary to use physical and / or statistical models that help to estimate, in real time, the concentration values of chemical species in the metal. Usually, the aforementioned models are based on process data, such as pressure at the surface of the metal bath, flow of gasses from the porous plugs or from the submerged lances, and data on the measurements of the chemical concentrations of the various elements dissolved in the bath, collected over time. The chemical concentrations reached are usually measured “spotwise” (not continuously), for example in the laboratory, a method that involves the use of consumable materials (sampling cartridges) and the use of human time, even if the measurement is carried out using automated samplers.

[0011] The measurement of the content of the chemical species dissolved in the liquid steel is carried out by taking samples of liquid steel, solidifying them and measuring them in the laboratory using a mass spectrometer. Mass spectrometry allows to recognize certain elements and chemical compounds, such as carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, sulfur, titanium, vanadium, chromium, manganese, iron, nickel, copper and others. Instead, the measurement of the hydrogen content in the liquid steel is usually carried out with instruments based on TCD (Thermal Conductivity Detector) technology, using instrumentation equipped with appropriate consumables that is introduced into the liquid bath. In the latter case, the collection of material samples is not provided, and the analysis is carried out by field instrumentation. However, due to the nature of vacuum treatment plants (for example VD, VOD and suchlike), it is difficult to carry out the measurement of the chemical species dissolved in the liquid steel during the vacuum phase, since the ladle is inserted into a chamber which is hermetically insulated with a lid, or the ladle is directly hermetically insulated by a lid thereof.

[0012] The measurement can be carried out directly in the event that the steel plant is equipped with vacuum samplers, which however involve higher costs, both for the plant itself (CAPEX costs) and also for the greater maintenance and higher use of consumable products (OPEX costs). In addition, in these cases the efficiency of the plant is lower due to greater false air leaks.

[0013] US 2012 / 0266722 describes a method and apparatus for degassing molten metal in a melting chamber, in which it is provided to measure a concentration profile of gas in a furnace, in particular CO and CO2, using an adjustable laser source, an optical detector and a reference detector. There is therefore the need to perfect a method and a corresponding apparatus for refining liquid metal that can overcome at least one of the disadvantages of the state of the art.

[0014] To do this, it is necessary to determine the progress status of the degassing process, estimating the content of hydrogen, nitrogen, carbon, sulfur and possibly other chemical species dissolved in the metal bath in real time.

[0015] One purpose of the present invention is to perfect a method and provide a station for refining metal capable of estimating the content of hydrogen, nitrogen, carbon, sulfur and possibly other chemical species dissolved in the metal bath in real time in a sufficiently precise manner. Another purpose of the present invention is to perfect a method and a corresponding station for refining metal capable of reducing the variability of the refining treatment, by knowing its status before interrupting the treatment process.

[0016] One purpose of the present invention is to provide a monitoring apparatus for metal refining stations. Another purpose of the present invention is to interrupt or prolong the process of a vacuum treatment on the basis of a reliable estimate of the process status, with a time / energy saving and reducing production costs compared to current refining treatments. Another purpose of the present invention is to reduce the cost of the hardware for the analysis of process gasses in the vacuum treatment.

[0017] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

[0018] SUMMARY OF THE INVENTION

[0019] The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea. In accordance with the above purposes and to resolve the technical problem described above in a new and original way, also achieving considerable advantages compared to the state of the prior art, the following discloses a method according to the present invention for refining metal in a refining station in steel plants.

[0020] In accordance with one aspect of the present invention, the refining station comprises a degassing apparatus. The degassing apparatus can be under vacuum.

[0021] In accordance with one aspect of the present invention, the refining station can comprise one or more vacuum chambers.

[0022] In accordance with one aspect of the present invention, the method provides to:

[0023] - position, downstream of a dust separator of a dust filtering unit of the degassing apparatus, a gas analyzer of a monitoring apparatus;

[0024] - detect, by means of the monitoring apparatus, the chemical concentration of one or more chemical species in process gasses drawn into the degassing apparatus;

[0025] - detect the ambient pressure in proximity to the surface of a metal bath;

[0026] - estimate, in real time, the concentration of one or more chemical species dissolved in the metal bath by means of the abovementioned concentration of one or more chemical species in the process gasses and the abovementioned pressure.

[0027] By doing so, compared to operating practices of state of the art that provide treatment instructions based on treatment times and parameters defined on the basis of statistical considerations, this method advantageously allows to estimate the content of one or more chemical species, such as hydrogen and nitrogen for example, in the metal bath in real time, by means of the chemical concentration, measured in real time, of the one or more chemical species in the process gasses. In this way, it is possible to conclude the degassing process at the appropriate time, estimating with good reliability that the concentration of the chemical species in the metal is the desired one.

[0028] Treatment times can therefore be reduced. More significantly, it is possible to avoid having to restore the vacuum in the event that one realizes that the desired concentration values have not been reached, which entails a considerable lengthening of treatment times (at least 10-15 min on a treatment of about half an hour), a greater energy consumption to bring the metal bath back to low pressure and a reduction in the time for the decantation step.

[0029] In accordance with another aspect of the present invention, the method can provide that the analyzer is positioned downstream of a pump unit of the degassing apparatus. Advantageously, after the pump unit the process gasses are essentially at ambient pressure and at a temperature below 100°C. Furthermore, the dust content in the process gasses is at a minimum.

[0030] In accordance with another aspect of the present invention, the method can provide that the analyzer is selected from a mass spectrometer, a Fourier Transform

[0031] Infrared Spectroscopy (FTIR) spectrometer, a RAMAN spectrometer, a Thermal Conductivity Detector (TCD).

[0032] In accordance with another aspect of the present invention, the method can provide that the analyzer is a Raman spectroscopy gas analyzer. Advantageously, using a gas analyzer based on RAMAN technology allows to analyze most of the process gasses in a metal refining process with high reliability. For example, CO, CO2, H2, N2, 02, CH4 can be measured.

[0033] Furthermore, the use of an analyzer as above allows to keep costs, both of the plant and also for maintenance, low when compared to, for example, a mass spectrometer. In fact, mass spectrometers have very high costs that are hard to amortize over time.

[0034] In accordance with another aspect of the present invention, the method can provide to use, in order to calculate the concentration of the one or more chemical species dissolved in the metal, a calculation model having as input parameters the chemical concentration of one or more chemical species in the process gasses and the ambient pressure in correspondence with the surface of a metal bath.

[0035] In accordance with another aspect of the present invention, the method can provide that the calculation model is defined, in a preliminary step, on the basis of data resulting from a punctual analysis of the concentrations of chemical species dissolved in a metal bath and of concentration values of one or more chemical species in corresponding process gasses calculated on the basis of measurement data detected by the gas analyzer. In accordance with another aspect of the present invention, the method can provide to detect a flow of stirring gas in the metal bath and use it, together with the concentration of one or more chemical species and the pressure, to estimate the concentration of the one or more chemical species dissolved in the metal.

[0036] In accordance with another aspect of the present invention, the method can provide that the chemical species are one or more of either hydrogen or nitrogen.

[0037] In accordance with another aspect of the present invention, the method can provide an extraction mode of the sample of the process gasses, which provides its extraction from a suction line of the plant. In this way, the gasses can be conditioned, if necessary, with regard to their temperature, dustiness and / or humidity.

[0038] In accordance with another aspect of the present invention, the method can alternatively provide an in situ mode, which provides that the measurement is performed directly on the flow of process gasses in the suction line through a coupling element. For example, in the case of a Raman spectrometer, the coupling element allows monochromatic and measurement electromagnetic radiations to pass.

[0039] In this way, it is possible to carry out a measurement directly in correspondence with the suction line, without needing to take samples of the process gasses.

[0040] In accordance with another aspect of the present invention, the station for refining metal in steel plants comprises a degassing apparatus and a monitoring apparatus.

[0041] The monitoring apparatus comprises a gas analyzer positioned downstream of the dust separator of the dust filtering unit of the degassing apparatus.

[0042] The apparatus is configured to detect the concentration of one or more chemical species in process gasses drawn into the degassing apparatus and the ambient pressure in correspondence with the surface of a metal bath, and to estimate, in real time, the concentration of one or more chemical species dissolved in the metal bath by means of this concentration of one or more chemical species in the process gasses and such pressure.

[0043] In accordance with another aspect of the present invention, the monitoring apparatus comprises one or more pressure detectors and a processing unit.

[0044] In accordance with another aspect of the present invention, the analyzer can be a Raman spectroscopy gas analyzer, comprising a coupling element which allows the passage of electromagnetic radiations exciting a Raman spectrum and of measurement electromagnetic radiations to perform a measurement directly on a flow of process gasses in a process gasses suction line.

[0045] In accordance with another aspect of the present invention, a secondary steel making steel plant, for refining metal, comprises one or more LF furnaces and one or more metal refining stations, or VD / VOD stations.

[0046] DESCRIPTION OF THE DRAWINGS

[0047] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restr ictive example with reference to the attached drawings wherein:

[0048] - fig. 1 is a schematic representation of a metal refining station, according to the present invention;

[0049] - fig. 2 is a schematic representation of a monitoring apparatus of the metal refining station of fig. 1 ; - fig. 3 shows the Raman spectrum obtained from a gas analyzer of the monitoring apparatus of fig. 2.

[0050] We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

[0051] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications.

[0052] DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION

[0053] With reference to fig. 1, a station 10 according to the present invention, for refining metal in steel plants for the production of metal materials, for example steel, comprises a degassing apparatus 11 and a monitoring apparatus 100, configured to determine the progress status of a metal degassing process.

[0054] The station 10 can comprise one or more vacuum chambers 12.

[0055] The one or more vacuum chambers 12 can each comprise a receptacle 13 with an upper aperture 14, inside which a ladle 50 is housed, and a lid 15 able to be hermetically associated with the receptacle 13. In an alternative embodiment not shown here, the vacuum chamber can comprise a lid mating with the aperture of the ladle and able to close it hermetically, during use, thus not requiring a receptacle. The ladle 50 is a cylindrical shaped receptacle, with its lower based closed, lined internally with refractory material, intended to house the metal bath M produced in a furnace, for example an electric arc furnace EAF, and to transport it downstream for the subsequent refining treatments and finally toward continuous casting. The ladle 50 is provided with an open upper part 51 and at least one porous plug, or a submerged lance 52, passing through a bottom wall 53 of the ladle 50, through which a gas, preferably inert, is blown, able to determine a stirring of the metal bath M contained.

[0056] The degassing apparatus 11 is able to draw process gasses present in the environment in correspondence with the metal bath M, for example in correspondence with its surface or in its vicinity. For example, the degassing apparatus 11 is able to draw the process gasses of the one or more vacuum chambers 12.

[0057] The degassing apparatus 11 can be under vacuum. It can therefore be suitable to perform a vacuum treatment, that is, to create, during use, a pressure much lower than the ambient pressure inside the vacuum chambers 12. In this case, the pressure in correspondence with the surface of the metal bath M can be negative with respect to the ambient pressure, at least in some of the processing steps.

[0058] The vacuum treatment can be carried out, during the refining, in order to reach the desired temperature of a metal bath M being processed, to reach the content of the dissolved chemical species, for example hydrogen and nitrogen, and the content of elements such as sulfur and carbon required for the metal bath M.

[0059] The degassing apparatus 11 can comprise a dust filtering unit 20 to separate the dusts from the process gasses. The dust filtering unit 20 can comprise a dust separator 21 and possibly additional filtering devices 22, such as a cyclone and / or a bag filter for example.

[0060] The degassing apparatus 11 can comprise a plurality of ducts 25, 26, 27, 28 to form a suction line 29 for the fluidic communication of the various components of the degassing apparatus 11. It can also comprise a vacuum pump unit 30, for example mechanical pumps or steam ejectors, to create the vacuum and evacuate the process gasses.

[0061] Respectively, a duct 25 can connect one or more vacuum chambers 12 with the dust separator 21 ; a duct 26 can connect the dust separator 21 with any subsequent filtering device(s) 22 or with the pump unit 30; a duct 27 can connect the filtering devices 22 with the pump unit 30; a duct 28 can connect the pump unit 30 with the outlet of the process gasses.

[0062] The degassing apparatus 11 can also comprise:

[0063] - a diverter 31, which allows to select the vacuum chamber 12 on which to operate in the event more than one vacuum chamber 12, generally two, is required;

[0064] - a main shut-off valve 32, which divides the vacuum chamber 12 side from the pump unit 30 side, in order to reduce the times required to reach vacuum;

[0065] - a cooler, which cools the fumes.

[0066] The apparatus 100 is used to determine the progress status of a degassing process of the metal bath M, by estimating in real time the content of one or more chemical species dissolved in the metal, in particular gasses, such as for example hydrogen, nitrogen, but also oxygen, carbon, sulfur and / or suchlike.

[0067] The apparatus 100, or at least a measuring part thereof, is positioned downstream of the dust separator 21. The apparatus 100 can therefore be positioned in correspondence with the duct 26 at exit from the dust separator 21.

[0068] According to one embodiment, in the event additional filtering devices 22 are present, the apparatus 100 can be positioned downstream of the dust filtering unit 20.

[0069] According to another embodiment, the apparatus 100 can be positioned downstream of the pump unit 30.

[0070] The apparatus 100 comprises a gas analyzer 101 and a data processing unit 102.

[0071] The apparatus 100 can comprise one or more pressure detectors 103 for detecting the ambient pressure in correspondence with the metal bath M. For example, the pressure detector 103 can be positioned in such a way as to detect the pressure in the one or more vacuum chambers 12 or in proximity to the ladle 50. The data detected by the one or more pressure detectors 103 can be acquired by the processing unit 102.

[0072] The apparatus 100 can comprise one or more flow detectors 104 for measuring the flow of stirring gasses. The data detected by the one or more flow detectors 104 can be acquired by the processing unit 102.

[0073] The apparatus 100 can comprise one or more temperature detectors for detecting the temperature of the metal bath M. The data detected by the one or more temperature detectors can be acquired by the processing unit 102.

[0074] The analyzer 101 can be selected from a mass spectrometer, a Fourier Transform Infrared Spectroscopy (FTIR) spectrometer, a RAMAN spectrometer, a Thermal Conductivity Detector (TCD), or suchlike. Preferably, the analyzer 101 is a Raman spectroscopy gas analyzer. In this case, the analyzer 101 can comprise, in a known manner, a laser apparatus 120 for generating a stimulus electromagnetic radiation R1 (fig. 2). The electromagnetic radiation R1 can be monochromatic and collimated.

[0075] In a known manner, the electromagnetic radiation R1 is in the frequency field of visible light or IR (Infrared), preferably in the visible field.

[0076] The wavelength of the electromagnetic radiation R1 can be defined on the basis of the chemical species to be detected, for example it can be 532 or 785 nm.

[0077] The analyzer 101 can comprise an optical fiber, not shown in the drawings, for transporting the electromagnetic radiation R1 to a measurement point, where the process gasses to be measured are located.

[0078] The analyzer 101 is configured to illuminate, by means of the electromagnetic radiation Rl, the process gasses drawn into the degassing apparatus 11. Following the stimulation by means of the electromagnetic radiation Rl, the process gasses can emit a measurement electromagnetic radiation R2. The analyzer 101 can comprise a spectrometer 121 (fig. 2) for analyzing the measurement electromagnetic radiation R2 and generating a Raman spectrum SR (fig. 3).

[0079] The analyzer 101 can comprise an optical fiber, not shown in the drawings, for transporting the measurement electromagnetic radiation R2 from the process gasses to the spectrometer 121.

[0080] The measurement radiation R2 comprises the Raman scattering electromagnetic radiation. The analyzer 101 can comprise (fig. 2) a plurality of optical elements for the treatment of the radiations R1 and R2, such as filters 125, 126 for filtering the wavelength bands of interest of the radiations R1 and R2, focusing lenses 127, 128, dichroic mirrors 129, collimation mirrors 130, diffraction gratings 131 for separating the radiation R2 into its constituent wavelengths, focusing mirrors 132 and CCD (Charge-Coupled Device) detectors 133.

[0081] The analyzer 101 can comprise a containing chamber 135 (fig. 2) for containing a sample to be analyzed, in an extraction measurement mode that provides the extraction of a gas sample and its transport into the containing chamber 135. The analyzer 101 can therefore comprise, or cooperate with, a sampler (not shown in the drawings), for taking and transporting the sample of the process gasses.

[0082] The gas sample can be extracted in correspondence with the ducts 26 or 27 and conditioned to be brought to the temperature, dustiness and humidity conditions suitable for the measurement. Alternatively, it can be advantageously extracted downstream of the pump unit 30, in correspondence with the duct 28. Alternatively and as shown in fig. 1, the analyzer 101 comprises a coupling element 136 for coupling with the suction line 29, for in situ analysis. The coupling element 136 can be an optical window that allows the passage of the stimulus radiation R1 and the measurement radiation R2.

[0083] The analyzer 101 provides at output digital measurement data relating to the Raman spectrum SR, which can for example be represented through a graph of the

[0084] Raman spectrum SR (fig. 3). The aforementioned measurement data can be acquired by the processing unit 102.

[0085] In particular, to each chemical species (for example hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide) there correspond one or more peaks on the Raman spectrum SR. Each peak corresponds to a mode of vibration of the molecule of the corresponding chemical species.

[0086] The processing unit 102 is configured to estimate the gas content in the metal bath M. The processing unit 102 can comprise a processing module 140 and a storage module 141. It can also comprise a module 142 for interfacing with components of the station 10 and / or devices 143 for interfacing with an operator.

[0087] The processing module 140 can be a microcontroller, microprocessor, processor or suchlike, local or remote, for example in the cloud.

[0088] The processing module 140 can be able, as a whole, to implement algorithms for the acquisition, management and processing of the measurement data.

[0089] For example, the aforementioned algorithms can be configured for the acquisition, management and processing of the Raman spectrum SR. The data processing algorithms are able to calculate, on the basis of the measurement data, the chemical concentrations of one or more chemical species in the process gasses. For example, and preferentially, they are able to calculate the chemical concentration of hydrogen and nitrogen, but they can also calculate the concentration of oxygen, carbon monoxide, carbon dioxide, methane and suchlike. In another embodiment, the chemical concentrations of one or more chemical species in the process gasses on the basis of the measurement data can be calculated by the analyzer 101, for example in a data processing module of the analyzer 101.

[0090] The data processing algorithms can comprise a calculation model having as input parameters the chemical concentration of the chemical species in the process gasses and the ambient pressure in correspondence with the metal bath M. The flow of stirring gas and / or the temperature can also be input parameters of the model.

[0091] The calculation model can be defined, in a preliminary step, on the basis of data resulting from a punctual analysis of the concentrations of chemical species dissolved in the metal bath M and of values of chemical concentration of one or more chemical species in the process gasses, calculated on the basis of corresponding measurement data.

[0092] By the term “corresponding” we mean that it is related to the metal bath M for which the punctual analysis is carried out. Punctual analysis is understood as being carried out by taking one or more samples of the material of the metal bath M and analyzing them, for example with field or laboratory instrumentation. The preliminary step can be an experimental step or, preferably, it can be carried out during one or more previous processing cycles. The processing module 140 can also be able, as a whole, to implement algorithms for the automatic management and control of functionalities of the station 10, by means of the interface module 142. For example, on the basis of the results of the measurement data processing, it can command the end of a vacuum treatment when the estimated concentrations of the chemical species (for example hydrogen, nitrogen) in the metal bath M have reached the desired values. As a further example, it can provide data to an operator through the interface devices 143.

[0093] The storage module 141 can be one or more of the commercially available memories, such as a random access memory (RAM), a read-only memory (ROM), a floppy disk, a hard disk, a mass memory, or any other form of digital storage whatsoever, local or remote.

[0094] The storage module 141 can be able to store the aforementioned data acquisition, management and processing algorithms and the aforementioned management and command algorithms, as well as the acquired and estimated data.

[0095] The module 142 for interfacing with components of the station 10 can comprise data transmission devices, actuation systems and / or suchlike.

[0096] The devices 143 for interfacing with an operator can comprise a screen, an audio apparatus, a keyboard, a mouse or suchlike. The operation of the apparatus 10 described heretofore, which corresponds to the method according to the present invention, comprises the steps of:

[0097] - positioning the gas analyzer 101 downstream of the dust separator 21 ;

[0098] - detecting, by means of the monitoring apparatus 100, the chemical concentration of one or more chemical species in process gasses drawn into the degassing apparatus 11 ;

[0099] - detecting the ambient pressure in proximity to the surface of the metal bath M;

[0100] - estimating, in real time, the concentration of one or more chemical species dissolved in the metal bath M by means of the aforementioned concentration of one or more chemical species in the process gasses and the aforementioned pressure.

[0101] The method can provide to position the gas analyzer 101 downstream of the pump unit 30.

[0102] The method can provide that the analyzer 101 is a Raman spectroscopy gas analyzer.

[0103] The method can provide to use, for the aforementioned estimation, the calculation model having as input parameters the aforementioned chemical concentration of one or more chemical species in the process gasses, ambient pressure in correspondence with the surface of the metal bath M and possibly flow of stirring gas and / or temperature.

[0104] The method can therefore provide to carry out, preliminarily, a punctual analysis of the chemical species dissolved in the liquid metal bath M, calculate the concentration values of one or more chemical species in the process gasses on the basis of the measurement data of the analyzer 101, and define the model by correlating the values obtained from the aforementioned punctual analysis and from the aforementioned concentration values in the process gasses.

[0105] The method can provide to calibrate the analyzer 101.

[0106] It is clear that modifications and / or additions of parts and / or steps may be made to the station 10, to the apparatus 100 and to the method as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims.

[0107] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of method and corresponding station for refining metal, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0108] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

CLAIMS1. Method for refining metal in a refining station (10) in steel plants comprising a degassing apparatus (11), characterized in that it provides to:- position, downstream of a dust separator (21) of a dust filtering unit (20) of said degassing apparatus (11), a gas analyzer (101) of a monitoring apparatus (100);- detect, by means of said monitoring apparatus (100), the chemical concentration of one or more chemical species in process gasses drawn into said degassing apparatus (11);- detect the ambient pressure in proximity to the surface of a metal bath (M), by means of one or more pressure detectors (103);- estimate, in real time, the concentration of one or more chemical species dissolved in said metal bath (M) by means of said concentration of one or more chemical species in said process gasses and said pressure.

2. Method as in claim 1, characterized in that it provides that said analyzer (101) is positioned downstream of a pump unit (30) of said degassing apparatus (11).

3. Method as in claim 1 or 2, characterized in that said analyzer (101) is selected from a mass spectrometer, a Fourier Transform Infrared Spectroscopy (FTIR) spectrometer, a RAMAN spectrometer, a Thermal Conductivity Detector (TCD).

4. Method as in claim 1 or 2, characterized in that it provides that said analyzer ( 101 ) is a Raman spectroscopy gas analyzer.

5. Method as in any claim from 1 to 4, characterized in that it provides to use a calculation model having as input parameters said chemical concentration of one or more chemical species in said process gasses and said ambient pressure in correspondence with the surface of said metal bath (M), and in that said calculation model is defined, in a preliminary step, on the basis of data resulting from a punctual analysis of the concentrations of dissolved chemical species in a metal bath and of concentration values of one or more chemical species in corresponding process gasses.

6. Method as in any claim from 1 to 5, characterized in that it provides to detect a flow of stirring gas in said metal bath (M) and use it to estimate the concentration of said one or more chemical species dissolved in said metal bath (M) together with said concentration of one or more chemical species in said process gasses and said pressure.

7. Method as in any claim from 1 to 6, characterized in that it provides that said chemical species are one or more of either hydrogen or nitrogen.

8. Method as in any claim from 1 to 7, characterized in that it provides a choice of an extraction mode of a sample of the process gasses, which provides its extraction from a suction line (29) of said degassing apparatus (11), or an in situ mode, which provides that the measurement is performed directly on the flow of process gasses in said suction line (29).

9. Station (10) for refining metal in steel plants comprising a degassing apparatus (11) and a dust separator (21) of a dust filtering unit (20) of said degassing apparatus (11), characterized in that it also comprises, downstream of said dust separator (21), a monitoring apparatus (100) comprising a gas analyzer (101) positioned downstream of a dust separator (21) of a dust filtering unit (20) of said degassing apparatus (11), said apparatus (100) comprising a gas analyzer (101) configured to detect the concentration of one or more chemical species in process gasses drawn from said degassing apparatus (11) and one or more pressure detectors (103) configured to detect the ambient pressure in correspondence with the surface of a metal bath (M) and estimate, in real time, the concentration of one or more chemical species dissolved in said metal bath (M) by means of said concentration of one or more chemical species in process gasses and said pressure.

10. Station (10) as in claim 9, characterized in that said analyzer (101) is aRaman spectroscopy gas analyzer, comprising a laser apparatus (120) for generating an electromagnetic radiation (Rl) that stimulates a measurement electromagnetic radiation (R2) emitted by the process gasses and a spectrometer ( 121 ) for detecting and analyzing said measurement electromagnetic radiation (R2) and generating a corresponding Raman spectrum (SR), and in that said processing unit (102) is configured to command said analyzer (101) to illuminate, by means of said electromagnetic radiation (Rl), said process gasses; extract, from said measurement electromagnetic radiation (R2) detected, a said corresponding Raman spectrum (SR); calculate, on the basis of said Raman spectrum (SR), the concentration of said one or more chemical species in said process gasses.

11. Monitoring apparatus (100) for refining metal in steel plants, characterized in that it comprises a gas analyzer (101) configured to detect the concentration of one or more chemical species in process gasses deriving from secondarymetallurgy treatments, one or more pressure detectors (103) configured to detect the ambient pressure in correspondence with the surface of a metal bath (M), and a processing unit (102) configured to estimate, in real time, the concentration of one or more chemical species dissolved in said metal bath (M) by means of said concentration of one or more chemical species in process gasses and said pressure.

12. Apparatus (100) as in claim 11, characterized in that said analyzer (101) is a Raman spectroscopy gas analyzer.

13. Apparatus (100) as in claim 11 or 12, characterized in that said analyzer (101) comprises a coupling element (136) which allows the passage of stimulus electromagnetic radiations (Rl) and of measurement electromagnetic radiations (R2) to perform a measurement directly on a flow of process gasses in a process gasses suction line (29).

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