WO2022074573A1

WO2022074573A1 - System and method for determining the chemical composition of metallurgical or iron and steel materials

Info

Publication number: WO2022074573A1
Application number: PCT/IB2021/059151
Authority: WO
Inventors: Nicola GAGLIARDI; Matteo GIORDANO
Original assignee: Danieli & C. Officine Meccaniche S.P.A.
Priority date: 2020-10-07
Filing date: 2021-10-06
Publication date: 2022-04-14
Also published as: IT202000023611A1

Abstract

The invention relates to a neutron activation analysis system and method (10; 110; 210), particularly PGNAA or PFTNA, for determining the chemical composition of bulk steel or metallurgical material (14), in particular scrap. The neutron activation zone (20; 120; 220) is located between one or more neutron sources (12; 230) and one or more gamma ray (γ) detector(s) (16; 234) and in particular is represented by a container of the transport container type as used on lorries, trains or ships. Difference measurements of the chemical composition of the container (20; 120; 220) with and without bulk material (14) allows the determination of the percentage chemical composition of the bulk material (14) and, in combination with a weighing of the bulk material (14), the determination of the absolute weight of the individual components of interest of the bulk material (14). The analysis is carried out on the entire volume of the material to be analysed.

Description

TITLE: SYSTEM AND METHOD FOR DETERMINING THE CHEMICAL COMPOSITION OF METALLURGICAL OR IRON AND STEEL MATERIALS

Applicant: DANIELI & C. Officine Meccaniche S.p.A., Via Nazionale 41, 33042 Buttrio (UD), Italy

TECHNICAL FIELD

The invention relates to a system and a method for determining the chemical composition of bulk iron, steel or metallurgical material, in particular the bulk analysis of the scrap entering a steel plant, for example a steel mill, using neutron activation technology with measurement of the gamma rays emitted by the atoms excited by a neutron bombardment.

BACKGROUND ART

On average, scrap accounts for almost 40% of the production cost of semi-finished steel products, reaching 60% (for the production of special steels), but also 70% (for reinforcements or rebar) of the production cost if limited to the steps of melting, refining and casting, setting itself as the main cost item in a steel mill. Currently the scrap entering the production plant, transported by lorries or train cars, is weighed and checked at a visual and radiative level. The chemical analysis techniques applied so far are surface techniques, such as XRF spectrophotometry (X-ray fluorescence), which analyse only the exposed surface. Therefore, no information is obtained on the composition of the entire volume of material purchased. For the proper management of the production process and in order to obtain control over suppliers, it would be important to determine whether the scrap entering exceeds thresholds, in terms of quantity of certain components, for example copper, tin and inert, corresponding to qualitative terms of the product to be manufactured or even deriving from Community regulations.

Furthermore, determining the composition of the volumes of scrap purchased allows to know the actual amount of iron present in the scrap, in order to only pay for the amount of actual ferrous material and not also the impurities which contribute to the total weight of the material purchased, but which are discarded (when possible). The art known so far has not satisfactorily solved the need to determine the bulk composition of the scrap, which would also be useful to be able to optimize the mixtures of the scrap loads which feed the melting furnaces. The American documents 8,138,480 B2, US 2016/0011126 Al and US 2018/0297091 Al disclose a neutron activation analyser of bulk material on a conveyor belt, while Mannanal S. J. et al. describe in "On-line bulk composition analysis of steel scrap using PGNAA/Scrap Probe" in the final report of the Research Fund for Coal and Steel of the European Commission (https://op.europa.eu/en/publication-detail/-/publication/lfe9c2b5-21b6-4d69-al0a- cca0213e9c29) on the analysis of scrap with neutron activation in lorries and train cars. The use of neutron-activation analytical methods in the field of recycling metal materials is known from Brooks, Leslie et al. ("Ferrous and non-ferrous recycling: Challenges and potential technology solutions",' Waste Management, vol. 85 (2019), pp. 519-528) and in the analysis of reference materials by Sudarshan, K. et al. (Analysis of reference materials by prompt y-ray neutron activation analysis and evaluation of sample -dependent background", ANALYTICA CHIMICA ACTA, vol. 535 (2005), pp. 309-315).

DISCLOSURE OF THE INVENTION

The object of the invention is to overcome the aforementioned drawbacks and to propose a system and a method for determining the chemical composition, both qualitative and quantitative, of bulk iron, steel or metallurgical material, in particular of scrap entering a steel plant.

A further object of the present invention is to provide a system and a method for analysing the composition of the entire mass of metallurgical or iron/ steel material, in particular ferrous scrap, quickly, without handling the material, and without having to take samples, without simultaneously damaging the material to be analysed.

Another object of the present invention is to propose a system and a mass analysis method which provides information on the entire analysed material and not only on the surface or exposed composition thereof. Further objects or advantages of the invention will be apparent from the following description.

The object is achieved in a first aspect of the invention by a neutron activation analysis system, in particular PGNAA or PFTNA, for determining the chemical composition of bulk iron, steel or metallurgical material, in particular scrap, comprising:

(a) at least one neutron source;

(b) at least one gamma ray detector; (c) an activation zone adapted to contain/containing the bulk material to be analysed;

(d) one or more shields for capturing unwanted neutrons and gamma rays, and

(e) a control unit for managing said at least one neutron source and said at least one gamma ray detector and determining, from the measured gamma rays, the elemental composition of the bulk material, wherein said activation zone is located between said at least one neutron source and said at least one gamma ray detector.

The implementation of neutron activation technology, in particular PGNAA technologies (Prompt Gamma Ray Neutron Activation Analysis) or PFTNA technology (Pulsed Fast Thermal Neutron Activation) allows firstly to verify the chemical composition of the metallurgical or iron/ steel material on a bulk scale, in particular the scrap entering the steel mill, and then indirectly know the quantity of inert materials, non-ferrous, oxides and ferrous materials further contained in the supply. The analysis concerns the entire volume or mass of the material to be analysed, and is therefore a sort of bulk analysis. In the present disclosure reference will therefore be made to a bulk (chemical) analysis as a type of analysis which affects the entire mass of the material, as opposed to the superficial analysis which characterizes only a limited exposed layer. The bulk analysis in this sense provides information on the chemical composition of the analysed material, having analysed it as a whole (the entire mass/the entire volume) and not in single more or less representative spot samples. The determination of the chemical composition of the metallurgical or iron/steel material, according to the invention, therefore occurs with a bulk analysis on the entire volume/the entire mass of the material to be analysed. The result obtained is therefore representative for the entire material.

Advantageously, the output obtained is an analysis report comprising the indication in percentage form of the elements present in the entire volume of scrap analysed. It goes without saying that it is possible to indicate the individual fractions of the elements as mass, weight or molar values, easily convertible therebetween. In exemplary form, an analysis result can be expressed as: 94.26% Fe, 2.89% Si, 1.07% Al, 0.29% Cu, etc.

The analysis of instant or ready gamma rays through neutron activation is a non-contact and non-destructive analytical technique which can be used in online analysis systems to determine the elemental composition of bulk materials. The neutrons interact with the atoms of the elements in the bombarded materials, which then emit gamma rays which can be revealed and detected. Each element emits a photon of characteristic energy when it returns to a stable state after the excitation caused by the absorption of a neutron in the nucleus. When a thermal neutron, or rather a low energy neutron (< 0.025 eV) approaches or collides with a nucleus of an atom, an interaction occurs between the neutron and the nucleus. The atom then absorbs a neutron and increases the mass number by +1 , passing to the excited state. During its disexcitation, the atom emits a photon in the range of gamma rays which is characteristic of each element. The photon is called "ready", as it is emitted at the instant of the nuclear reaction.

The emitted gamma ray has a defined energy associated with the atom from which it was released. In essence, the gamma ray emitted is like a "fingerprint" of the element. The emitted gamma rays are detected and an energy spectrum is generated which gives information about the elements present and their amount.

Online PGNAA and PFTNA analysers detect gamma rays using, for example, scintillation detectors. These detectors are composed of a high-purity crystal structure which, when exposed to gamma rays, produces photons proportional in energy to the energy of the gamma rays which enter the crystal. A photo-multiplier tube coupled to the crystal converts light pulses into electrical signals. The electrical pulses produced are amplified and analysed to obtain information on specific elements.

The neutron activation process is a radio-analytical method capable of identifying in any sample, whether in solid, liquid or gaseous state, practically all the elements of the periodic table. The detection limits for individual elements are usually very low and therefore it is a very suitable analysis method also to determine traces of elements in large volumes of materials, even if these limits vary within the periodic table.

From the energy of the photon emitted, the qualitative result is obtained (identification of the element present) and from the count of the photons of this energy it is possible to extract the quantitative result (the amount of the element present in the scrap). The result is expressed in an energy spectrum which represents the "count" of photons as a function of the energy with a peak for each element.

The neutrons used in the analysis technique are alternatively provided by a radioisotope, often Californium 252 (²⁵²Cf), or by a neutron generating system. The radioisotope undergoes spontaneous fission and produces neutrons which are used in the analysis process. The neutrons of a neutron generator are produced electrically in an accelerator. Compact solutions already on the market consisting of small accelerators which exploit the nuclear fusion reaction of deuterium-deuterium (D + D — n + ³He) or deuterium-tritium (D + T — n + ⁴He) to make neutrons can be used as a source of neutrons. Consequently, through materials called moderators (such as water, heavy water or graphite) it is possible to reduce the speed of the neutrons until they are thermalized (energies of about 0.025 eV). Or this phenomenon can occur after many interactions with the examined material, because for each interaction the neutron loses energy until it becomes "thermal". The use of these types of sources (compared to the more common source ²⁵²Cf) allows to create a pulsed beam, while the radioisotope produces a continuous neutron flow.

While PGNAA uses dangerous radioactive isotopes to generate a continuous stream of neutrons, the PFTNA-based system generates neutrons electrically in a pulsed manner, allowing the gamma-ray detector to differentiate between neutron-nucleus interactions. A high frequency pulse can only be obtained with an electric neutron source. The PGNAA technique uses a continuous neutron flux, while the PFTNA technique generates a pulsed neutron flux.

Being electrically operated, the PFTNA ensures the highest level of safety: unlike the PGNAA, the neutron emission can be stopped, thus lowering the user's exposure to the analytical system. For example, neutrons emitted by PFTNA generators in a deuterium-tritium interaction have a high energy of up to 14 MeV compared to only 2.5 MeV in PGNAA which emanates from the weaker ²⁵²Cf. The higher energy of the neutron brings a number of analytical advantages. The most important is the ability to also reveal carbon and oxygen. Higher neutron energy also results in an overall improvement in sensitivity. The ability to handle wide variations of mass in the activation zone and independence from particle sizes are some added advantages of PFTNA-based analysers.

Neutron gamma -activation detectors penetrate the entire cross-section of the analysed material, providing a uniform measurement of the entire material, not only of its surface. Surface analysis technologies such as XRF, X-ray diffraction, and other spectral analysis technologies measure limited depths and surfaces that may not be representative of the entire amount of material. The technique DGNNA (Delayed Gamma Neutron Activation Analysis) is practically already contained within the PFTNA, as it analyses both prompt and delayed photons which derive from two different processes, disexcitation by neutron capture in the first case and disexcitation by beta decay in the second case.

The utility of neutron activation techniques lies in some peculiar features, which are listed below:

• Simultaneous qualitative identification of several elements (position of the peak in the energy spectrum) and also the assessment (at least approximate) of the amount of the same (peak area).

• It is a non-destructive technique, which does not require direct contact with the sample or the collection of a portion of the sample, and therefore the sample analysed is not damaged. A preparation of the sample with a relative waste of time is also avoided.

• Since it is not a charged particle, the neutron can further penetrate into the target material, as it is not affected by Coulomb repulsion. This feature distinguishes it from the techniques of XRF and hyperspectral images which instead only carry out a surface analysis.

A problem with neutron activation analysis is that the neutrons emitted from the neutron source also excite materials outside the material to be analysed, which in turn generate gamma rays which are detected by the detectors. To counteract this phenomenon, several shields are provided within the measurement system for capturing neutrons, so that the neutron radiation preferably affects only the material to be measured and therefore no "foreign gamma rays" are generated which contaminate the desired gamma rays. The shielding materials can be plastic materials provided with neutron poisons such as boron or lithium. Choosing the shield thickness allows to adjust the attenuation of neutrons, for example by a factor of 8. The use of lithium or boron epoxy resin coatings is also useful. Patent disclosure US 8,138,480 B2 teaches possible shields. In some cases a shield is not possible, for example for structural elements of the activation zone, in which case the gamma rays produced by these structural elements are preferably subtracted with differential measurements, as will be explained below. In a very preferred embodiment of the invention, the bulk material is scrap. Given the very heterogeneous origin of scrap, it is very difficult to know its chemical composition. Given the nature of the analysis, however, it can also be used to verify other materials in the metallurgical or iron and steel sector, such as coke, ferroalloys, lime, solidified slag, etc.

In a very advantageous embodiment of the invention, the activation zone can be a container of the transport container type, such as a crate or a box of a lorry, a train car or a shipping container. This allows to analyse the volume of bulk material, in particular the scrap, directly at the entrance to the steel mill or the iron making/steel or metallurgical plant in a practical and fast manner, without having to take samples, thus reducing the time and handling. Conveniently saving time and energy, the transport containers can be used directly as an activation zone for the analysis of the bulk material being supplied which reaches the iron making/steel or metallurgical plant. The analysis technique as mentioned is not destructive, so the container will not be damaged.

In this regard, and in order to obtain information on the individual masses of the elements contained in the bulk material, it is very advantageous that the neutron activation analysis system further comprises a scale, on which the container of the transport container type can be positioned. With the percentage chemical composition obtained from the neutron activation analysis and information on the total weight of the bulk material, it is possible to obtain absolute values on the composition of the volume of processed material, thus generating a ratio of the amounts of the elements present.

Preferably, the analysis system according to the invention further comprises cameras for the visual control of the bulk material, so that a visual/dimensional analysis of what has been analysed can also be connected to the analytical report.

A second aspect of the invention relates to a neutron activation analysis method, in particular PGNAA or PFTNA, for determining the chemical composition of bulk iron, steel or metallurgical material, in particular scrap, comprising the following steps:

(i) providing a neutron activation analysis system with at least one neutron source and at least one gamma ray detector, preferably an analysis system according to the invention;

(ii) positioning the bulk material in the activation zone between said at least one neutron source and said at least one gamma -ray detector; (iii) irradiating the activation zone with neutrons generated by said at least one neutron source and measuring said gamma rays emitted by the atoms exited in the activation zone with said at least one gamma ray detector for a period T and determining the elemental composition of the bulk material.

Advantageously, the bulk material is scrap.

Particularly preferred is an activation zone which corresponds to a container of the transport container type, such as a crate or a box of a lorry, a train car or a shipping container in which the problem of detecting the gamma rays emitted by structural parts of the activation zone is solved by applying differential measurements, in which the neutron activation analysis method further comprises the following steps:

(iv) emptying said container of the transport container type;

(v) repeating step (iii) with the same measurement period T;

(vi) subtracting the elemental composition obtained in the second measurement from the elemental composition obtained in the first measurement, providing as a result the elemental composition of the bulk material.

To allow to know also absolute values of the quantity of the elements of interest contained in the analysed bulk material, it is preferable to include a weighing of the bulk material and in particular during steps (iii) and (v) the container of the transport container type is weighed and in step (vi) the weight difference between the container of the transport container type containing the bulk material and the container of the empty transport container type is also determined, so as to derive the net weight of the bulk material so as to be able to calculate from the elemental composition percentage of the bulk material the absolute weight of the individual components of interest of the bulk material.

Advantageously, to save time, the analysis of the scrap occurs simultaneously with the dead times of weighing. The analysis time required for neutron analysis is highly dependent on the technology selected (PGNAA or PFTNA) and the number and type of neutron sources and y- ray detectors used.

The allignment of the neutron activation analysis with the weighing process masks the analysis time at least partially from the weighing time, usually about two minutes, in each case carried out at the entrance to the metallurgical or iron making/steel plant. Advantageously, during step (iii) a visual check of the bulk material is simultaneously carried out with cameras. The visual inspection can also occur before or after step (iii). The visual inspection allows to determine the dimensions of part of the scrap, its size and, in a qualitative way, the presence of evident non-compliant materials.

In an advantageous embodiment of the neutron activation analysis method according to the invention, during step (iii) said at least one neutron source and/or said at least one gamma ray detector are moved in the longitudinal and/or vertical direction of said activation zone. Movements without and with interruptions of the irradiation are conceivable. For example, the movements can be managed based on determinations of the fill level of the activation zone.

A further aspect of the invention concerns a metallurgical or iron making/steel plant, in particular a steel mill, which comprises a neutron activation analysis system according to the invention upstream of an arc or induction melting furnace, for example also upstream of an oxygen converter of the BOF (Basic Oxygen Furnace) type of the Linz-Donawitz process.

In a preferred embodiment of the invention, the detectors of photons or gamma rays suitably cover the entire irradiated zone. An array of N y -detectors is used. Due to the complexity of the PGNAA/PFTNA spectra and the need to resolve even very close peaks, germanium detectors are preferred for this type of analysis, as they have a high resolution, but are very expensive. A valid alternative are scintillation detectors with lanthanum bromide activated with cerium, LaBrs(Ce), as they have excellent energy resolution at a lower cost. Another alternative are the traditional but inexpensive Nal(Tl) scintillators, which are however limited by low resolution in energy.

Preferably, the number of detectors exceeds the number of sources, e.g., 50 - 75 detectors are opposed by 5 sources. A preferred ratio of the number of sources to that of the detectors is advantageously greater than or equal to 10 to 1. With the number and configuration of the sources and detectors it is possible to optimize the result obtained in terms of homogeneity, i.e. receiving representative information on the composition of the entire material.

A plurality of point sources are present in a preferred embodiment of the neutron activation analysis system according to the invention. Unlike the linear source described by Mannanal et al., a matrix of point sources can be more effective in capital cost and system versatility. Mannanal et al. instead describe as an optimal solution a container with detectors arranged on all the walls of the activation zone and a linear source which crosses inside the whole length of the container. Such an arrangement is not feasible for arriving lorries/train cars. Thus, in a design for lorries, the linear source follows the entire load in one of the walls longitudinally.

In an advantageous embodiment of the invention, the neutron activation analysis system comprises movement means for moving said at least one neutron source or a plurality of neutron sources, preferably point sources, and/or said at least one gamma ray detector or a plurality of gamma ray detectors in the longitudinal direction of the activation zone and/or in the vertical direction of said activation zone.

Since the neutron sources (the so-called "cannons") produce rather concentrated neutron beams, it is useful to adjust not only the electrical parameters, but also the spatial ones. In the case of a linear source arranged along a lorry at a medium height and detectors instead arranged on the entire height of the load, the arrangement could be suitable, but if the lorry were only half full, neither the source nor the detectors would be optimally positioned. The same principle applies when the lorry is higher, lower, or with different fill levels, or if the same activation zone is to be used to analyse train cars and lorries which have different heights.

It would therefore be advantageous to be able to change the position of the source(s) and/or detector(s).

In this regard, it is particularly advantageous not only to be able to activate individual sources and/or detectors which cover the entire length and height of the activation zone, but also to be able to envisage the possibility of changing the position of the source(s) and/or detector(s).

Advantageously, the neutron activation system comprises a plurality of neutron sources (multiple neutron sources), in particular localized neutron sources with known beam concentration, and preferably also a plurality of detectors to achieve a higher degree of adjustment. The term "localized" is understood as a synonym for tip or point.

In an advantageous variant of the analysis system according to the invention, one or more neutron sources and/or one or more gamma ray detectors are respectively arranged on a first and a second movable plate. Advantageously, said movable plates are provided with movement means for moving said source(s) and/or said detector(s) in the direction of the length of the activation zone and/or in the vertical direction, i.e., the height of the activation zone.

Those skilled in the art easily identify the movement means with their general knowledge, such as rack or cart/trolley systems. The movement allows the adaptation of the system to different types of containers, crates, train cars, lorries, etc. and to different fill levels thereof, in order to best exploit the expensive chemical analysis system, optimizing the neutron-scrap interaction and the gamma-ray capture/detector.

The use of a movement system of sources and detectors and therefore the adjustment of the length and height of the convoy optimizes the count, also made possible by the use of a plurality not only of detectors but also of sources. The use of cannons, thus point sources, allows to calibrate the collimation of the beam and consequently to adjust the penetration of the neutron beam. It can then be decided whether to analyse in a concentrated or a space-mediated manner. Advantageously, the analysis system control unit is connected to a visual control of the system, e.g., cameras, and configured to receive information on the distribution of the material within the lorry, train car or the like and calculate a suitable path of the source(s) and/or the detector(s) during the analysis.

As already mentioned, shields, for example in concrete, are necessary to shield the system from photons and neutrons. Concrete blocks with an appropriately sized thickness can be used, advantageously around 1 to 2 metres.

In the literature it is possible to find estimates on the concentration limits of the various elements of the periodic table measurable with such a technology analysing the sample for a few minutes, for example 10 minutes. The following detection levels are reported: nickel < 0.01%, iron, chromium, copper and sulphur 0.01 to 0.1%, aluminium and silicon 0.1 to 0.3%, molybdenum 0.3 to 1%, while a value of 3 to 10% is found for tin considering a measurement time of 10 min. The elements of greatest interest in the scrap analysis therefore generally have a good level of detectability.

Of particular interest for the analysis of scrap are elements with atomic numbers Z < 30, in particular C, Al, Si, Ca, Cr, Mn, Fe, Ni, Cu, and also Mo and Sn.

The system according to the invention provides information on the qualitative and quantitative composition of the scrap, using measurement values taken on the entire volume of the material analysed, and also ensuring several economic advantages:

The chemical composition measured, compared with the regulatory limits, can prove that the entering material exceeds or does not exceed the contents established by the relevant Community legislation, allowing the classification of the material. Consider that detecting and then removing 1% of inert/non-ferrous material (beyond the limits allowed by the legislation) in scrap can lead to savings of around 3 euros/ton on the material sent to casting or the melting furnace.

Knowing the net amount of ferrous material, it becomes possible to verify how much ferrous material is supplied, paying only the actual quantity of ferrous material. The possibility of demonstrating non-compliance with the quantities of the regulation or low iron contents gives the manager of the iron making/steel or metallurgical plant the means to reject the scrap supplied.

Having the analysis system available, it is also possible to carry out periodic analyses on nonferrous materials (checking the ferrous content of the transport container bottom, performing bulk anthracite analysis to check the level of residues or of sulphur, checking the content of impurities in ferroalloys to optimize their use, checking the level of impurities in lime). This increases the analytical capacity within the iron making/steel or metallurgical plant, in particular in steel mills and promotes more conscious production processes.

With a view to tracing the material in the scrapyard, this analysis completes the traceability of the material directly at the supply level, knowing for example which materials carry the most tramp elements or traces. Tramp describes an item which is not "specified" in the alloy grade, but which in an acceptable amount (trace) can be present without any adverse effect on the performance of the alloy or the required quality. Increasing the content of these elements can worsen the quality of the molten product, and therefore are often present in a regulated or otherwise limited amount in steel. The analyses according to the invention allow to determine, also as a function of to the supplier, to what extent tramp elements/traces are present in order to have a lever in the purchase of the bulk material, such as scrap, and to be able to modify the material in the compositions in the basket to adjust and correct the content in metals and non- metals.

With the system and method of analysis according to the invention it is possible to determine the bulk composition of large quantities of bulk material, of around tens of tons in approximately a few minutes.

The features and advantages described for one aspect of the invention may be transferred mutatis mutandis to the other aspects of the invention. The industrial applicability is obvious from the moment when it becomes possible to determine the composition of the bulk material fed for melting, allowing both the classification of the material according to regulatory aspects, or based, for example, on the content in tramp or trace elements, the most accurate determination of the purchase price of the scrap based on the actual iron content. In addition to the control of the material when being supplied, the possibility of integrating bulk visual and chemical analysis with weighing would therefore facilitate a conscious and optimized use of metallurgical/iron/steel material in processes.

Said objects and advantages will be further highlighted during the description of preferred embodiment examples of the invention provided by way of example, without limitation.

Variants and further features of the invention are the object of the dependent claims. The description of preferred exemplary embodiments of the neutron activation analysis system and method according to the invention is given by way of example and not of limitation, with reference to the attached drawings. In particular, unless specified otherwise, the number, shape, size and materials of the analysis system and of the individual components can vary and equivalent elements can be applied without deviating from the inventive concept.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 illustrates, in a sectional diagram, an embodiment of an analysis system according to the invention.

Fig. 2 illustrates, in a perspective view, another embodiment of a measurement system according to the invention.

Fig. 3 illustrates, in a block diagram, an embodiment of an analysis method according to the invention.

Fig. 4 illustrates, in a perspective view, a third embodiment of an analysis system according to the invention.

Figure 1 shows a possible embodiment of a scrap analysis system 10 based on PGNAA or PFTNA technology, in a sectional diagram in which a source 12 produces thermal neutrons n which, by interacting with the atoms of the scrap 14, generate photons (gamma rays) y which are collected from an array of photodetectors 16 allowing the identification of the chemical species present in the sample and the relative percentage amounts. The analysis times are in the order of a minute. Concrete blocks 18 of adequate thickness can be used to shield the photons y and attenuate neutron rays. The scrap 14 is contained in a container 20 of the type used in trains or on lorries. The analysis system 10 depicted is applicable, in a preferential but not exhaustive manner, to the scrap entering the steel mill coming from these lorries or trains.

Figure 2 shows in a perspective view a further possible embodiment of an analysis system 110 according to the invention with a geometry consistent with that presented in the previous figure. A train car 120 is located within a parallelepiped-shaped chamber in which a wall 126 is a combination of a shielding cover and an array of photo -detectors (not depicted), for example of the LaBrs(Ce) type, and the opposite wall 128 is a combination of a shielding cover and an array of neutron source of the deuterium-tritium type (not depicted). Another shielding cover is the ceiling 119 of the chamber. Of course, the remaining three walls can also be made as shielding elements. The floor 121 comprises a train car weighing system as currently already widely used in the iron making/ steel industry. The two cameras 123 allow photographing the scrap for a visual check. Alternatively, cameras can be provided in the radiation control gate. Fig. 3 illustrates, in a block diagram, an embodiment of an analysis method according to the invention. In a first step 30, a train car containing scrap is positioned between a neutron source and an array of gamma ray detectors and on a scale, thus in the case of the system according to figure 2 between the walls 126 and 128 and on the floor with scale system 121. Next, in step 32, the train car with the scrap is weighed and irradiated with neutrons, preferably simultaneously. The gamma rays generated by the atoms present in the train car and in the scrap are detected and measured together for a period T. As a result, the weight Pi "train car + scrap" and the qualitative and quantitative elemental composition (percentage) Ci "train car + scrap" are obtained. When the measurement and weighing are complete, the train car is emptied (step 34). Now, in the following step 36, the empty train car is repositioned on the scale between neutron source and gamma ray detectors to weigh the empty train car, irradiate it with neutrons, and measure the gamma rays emitted by its excited atoms. Therefore, in step 38 the weight P2 of the empty train car and the elemental composition percentage C2 thereof is obtained. Finally, in the last step 40, it is possible to calculate from the differences [Pi - P2] and [Ci - C2], the net weight of the scrap and its percentage elemental composition and from these data also the individual masses of the individual determined elements of interest.

Fig. 4 illustrates, in a perspective view, a third embodiment of an analysis system according to the invention. In the above drawing a train car 220 is visible which is located within a parallelepiped-shaped chamber in which a wall 226 with a shielding cover is provided with an array of photo-detectors 234 arranged on a first movable plate 236, for example of the LaBrs(Ce) type, and the opposite wall 228 with a shielding cover is provided with an array of neutron sources 230 of the deuterium-tritium type arranged on a second movable plate 232. Another shielding cover is the ceiling 219 of the chamber. Of course, the remaining three walls can also be made as shielding elements. The floor 221 comprises a train car weighing system as currently already widely used in the iron making/ steel industry. The two cameras 223 allow photographing the scrap for a visual check. Alternatively, the photo cameras/video cameras can be provided in the radiation control gate. The movable plates 232 and 236 are movable in the longitudinal direction L of the chamber or train car. The two drawings below show a detail of the drawing above in which the sources 230 are movable in the direction of the height A of the chamber or of the train car. The same movement can be achieved for the detectors (not depicted). The initial situation is on the left, with the sources in a lowered position on the right, for example in the case of a train car fdled with little material, thus obtaining a better interaction of the neutrons with the material and a better capture of the gamma rays emitted.

The movements could be controlled by automatic systems for measuring the level of the content in the convoy or manually or with systems based on artificial intelligence and vision.

Instead of equipping the entire container with the measuring system, only a small part (the two movable plates 232 and 236) is equipped. The sensitive elements are reduced and concentrated. The costs in terms of detectors and sources are reduced. When performing the analysis, the two plates move consistently along the length of the convoy and analyse the entire train car. The length of the section to be analysed can also be set, if it varies for different types of material entering the system. The sources 230 and the detectors 234 also move along the vertical axis A of the respective plates on which they are mounted. This is to manage the different heights or the different fill levels of the convoys (train cars or lorries). The result of the measurement is the integration over time of the measured gamma photons, at the level of automation it is necessary to have additional control of the movement, a one-directional movement L and along the vertical axis A, for example a rack system. Very high precision movements are not necessary.

Consider for example analysing a train car containing material from vehicle demolition: the system of sources 230 and detectors 234 is positioned in an optimal default geometry for train cars, where it will analyse all the volume of the material contained, since in the demolition there could be a copper content which could also come for example from windings of engines thrown into the train car and which could worsen the yield of steel since copper is difficult to remove chemically. Later on, however, a lorry 220 will have to be analysed which contains mixed scrap: in this case, the sources and detectors are repositioned to the original position and the desired stroke for the lorry is automatically adapted. After repositioning the sources to the default, the operator or the system or the artificial vision model which uses the cameras will decide to move the analysis towards the bottom of the train car, as it wants to verify the presence of dissolved copper in the load, which reasonably will be in contact with the platform. A fast passage can alternatively be performed with upper sources and a slower and more precise passage with lower sources.

During implementation, further parts and/or modifications or variants not described herein can be added to the analysis system and method object of the invention, without thereby departing from the scope of the invention. If such modifications or such variants should fall within the scope of the following claims, they should all be considered protected by the present patent. In practice, the materials used, as well as dimensions, numbers and shapes, as long as they are compatible with the specific and not otherwise specified use, may be different, according to requirements. Although the present invention has been described with reference to specific examples, those skilled in the art will certainly be able to produce many other equivalent forms of analysis systems and methods, having the features expressed in the claims and therefore all of which falling within the scope of protection defined by them.

The invention has achieved the aim of proposing a fast and non-destructive system and method for determining the percentage elemental composition of bulk steel or metallurgical material, in particular of the scrap entering the steel mill which provides information on the entire analysed material and not only on the surface composition thereof.

Claims

1) Neutron activation analysis system (10; 110; 210), in particular PGNAA or PFTNA, for determining the chemical composition of bulk iron, steel or metallurgical material (14), in particular scrap, comprising:

(a) at least one neutron source (12; 230);

(b) at least one gamma -ray detector (16; 234);

(c) an activation zone (20; 120; 220) adapted to contain/containing the bulk material to be analysed;

(d) one or more shields (18; 113, 126, 128; 219, 226, 228) for capturing unwanted neutrons and gamma rays, and

(e) a control unit for managing said at least one neutron source (12; 230) and said at least one gamma ray detector (16; 234) and determining, from the measured gamma rays (y), the elemental composition of the bulk material (14), wherein said activation zone (20; 120; 220) is located between said at least one neutron source (12; 230) and said at least one gamma ray detector (16; 234).

2) Neutron activation analysis system (10; 110; 210) according to claim 1, characterized in that said bulk material (14) is scrap.

3) Neutron activation analysis system (10; 110; 210) according to claim 1 or 2, characterized in that said activation zone (20; 120; 220) is a container of the transport container type, such as a crate or a box of a lorry, a train car or a shipping container.

4) Neutron activation analysis system (10; 110; 210) according to claim 3, characterized in that it further comprises a scale (121) on which said container of the transport container type (20; 120; 220) is positionable/positioned.

5) Neutron activation analysis system (10; 110; 210) according to any one of the preceding claims, characterized in that it further comprises cameras (123; 223) for the visual control of the bulk material (14). 6) Neutron activation analysis system (10; 110; 210) according to any one of the preceding claims, characterized in that it comprises a plurality of point neutron sources (230).

7) Neutron activation analysis system (10; 110; 210) according to any one of the preceding claims, characterized in that it further comprises

(f) movement means for moving said at least one neutron source or a plurality of neutron sources (12; 230), preferably point sources, and/or said at least one gamma ray detector or a plurality of gamma ray detectors (16; 234) in the longitudinal direction (L) of the activation zone (220) and/or in the vertical direction (A) of said activation zone (220).

8) Neutron activation analysis system (10; 110; 210) according to any one of the preceding claims, characterized in that it comprises a plurality of neutron sources (230), in particular localized neutron sources with known beam concentration, and a plurality of detectors (16; 234).

9) Neutron activation analysis system (10; 110) according to any one of the preceding claims, characterized in that one or more neutron sources (12; 230) and/or one or more gamma ray detectors (16; 234) are arranged on a first (232) and a second (236) movable plate, respectively.

10) Neutron activation analysis system (10; 110) according to any one of the preceding claims, characterized in that the analysis system control unit is connected to a visual control of the system, for example cameras (223), and is configured to receive information on the distribution of the material inside the lorry, train car or the like (20; 220) to calculate a suitable path of the source(s) (12; 230) and/or the detector(s) (16; 234) during the analysis.

11) Neutron activation analysis method, in particular PGNAA or PFTNA, for determining the chemical composition of bulk iron, steel or metallurgical material (14), in particular scrap, comprising the following steps: 19

(i) providing a neutron activation analysis system (10; 110; 210) with at least one neutron source (12; 230) and at least one gamma ray detector (16; 234), preferably an analysis system (10; 110; 210) according to any one of claims 1 to 10;

(ii) positioning said bulk material (14) in the activation zone (20; 220; 320) between said at least one neutron source (12; 230) and said at least one gamma ray detector (16; 234);

(iii) irradiating the activation zone (20; 120; 220) with neutrons (n) generated by said at least one neutron source (12; 230) and measuring said gamma rays (y) emitted by the atoms excited in the activation zone (20; 120; 220) with said at least one gamma ray detector (16; 234) for a period T and determining the elemental composition of the bulk material (14).

12) Neutron activation analysis method according to claim 11, characterized in that said bulk material (14) is selected from scrap, coke, ferroalloys, lime, solidified slag, and preferably is scrap.

13) Neutron activation analysis method according to claim 11 or 12, characterized in that said activation zone (20; 120; 220) is a container of the transport container type, such as a crate or a box of a lorry, a train car or a shipping container and in that said neutron activation analysis method further comprises the following steps:

(iv) emptying said container (20; 120; 220) of the transport container type;

(v) repeating step (iii) with the same measurement period T;

(vi) subtracting the elemental composition obtained in the second measurement from the elemental composition obtained in the first measurement, providing as a result the elemental composition of the bulk material (14).

14) Neutron activation analysis method according to one of claims 11 to 13, characterized in that during steps (iii) and (v) the container (20; 120; 220) of the transport container type is weighed and in step (vi) the weight difference between the container (20; 120; 220) of the transport container type containing the bulk material (14) and the empty container (20; 120;

20 is also determined so as to allow the absolute weight of the individual components of interest of the bulk material (14) to be calculated from the percentage elemental composition of the bulk material. 15) Neutron activation analysis method according to any one of claims 1 1 to 14, characterized in that during step (iii) a visual check of the bulk material is simultaneously carried out with cameras (123; 223).

16) Neutron activation analysis method according to any one of claims 1 1 to 15, characterized in that during step (iii) said at least one neutron source (12; 230) and/or said at least one gamma ray detector (16; 234) are moved in the longitudinal (L) and/or vertical (A) direction of said activation zone (20; 120; 220).

17) A metallurgical or iron making/steel plant, in particular a steel mill, comprising a neutron activation analysis system (10; 110; 210) according to any one of claims 1 to 10 upstream of a melting furnace, in particular an arc or induction furnace, or upstream of an oxygen converter.