Plant and method for classifying scrap

Abstract

The invention relates to a plant for sorting scrap according to its chemical composition. The plant comprises a shearer (10; 110) adapted to cut the scrap; an analysis device (28; 128) downstream of the shearer for analyzing the chemical composition of the sheared material; transport means (20, 26; 109, 126, 140, 142, 144, 146) for transporting the sheared material to the analysis device (28; 128), including a plurality of vibrating feeders and conveyors; and a discharge system (26; 32, 34, 36, 38; 150) adapted to separate the analyzed material (30; 145) according to its chemical composition. In a related method, the shearing (101) is followed by a chemical analysis of the sheared material (107), which allows the separation of the sheared scrap into fractions with different chemical compositions. The invention serves to optimize the feeding of various types of scrap, differentiated for example by their copper content, to a smelting furnace.

Description

Technical Field

[0001] The present invention relates to a plant and a method for classifying shredded scrap that enables different types of scrap, distinguished by their chemical composition, in particular by their copper content, to be separated into different fractions. The plant and method can use various forms of shearing and are not limited to scrap of a given size or weight.

Background Art

[0002] In steelworks, scrap is the basis of the production process, its purchase is one of the main cost items, and alone it accounts for approximately 40% of the final products sold.

[0003] Generally, scrap is sorted into various subclasses according to weight, size and origin and is very diverse in terms of purity (and thus price) depending on the proportion of iron it contains. The lower the proportion of iron, the lower the quality of the scrap. Secondly, some elements, mainly copper and tin, must be removed from the metal bath as much as possible. The reason is that their concentrations above certain thresholds cause product defects and quality degradation. Thus, two characteristics of purity are incorporated into the geometric and dimensional characteristics of the scrap, and the second of these characteristics affects the so-called "melting loss".

[0004] From a dimensional point of view, iron-based scrap can be sorted into at least four categories, each category being useful for balancing the basket when the melting furnace is fed. Generally, the classification of scrap is complex and depends on the local market. Thus, the following disclosure is based on a general and simplified case study.

[0005] The first group that can be considered is the group of shredded scraps, usually of small size, containing inert inclusions and a very diverse residue. Thus, it is characterized by a high density when loaded into the basket and is usually used to form the bottom of the basket. This type of scrap mainly comes from the scrap treatment and crushing of automobiles, household appliances, and urban metal waste. Generally, crushing is carried out in a hammer mill or a shredder, which crushes all components simultaneously with the treatment. This fragmentation results in a large number of small components, which are sorted using separation systems such as magnetic drums, eddy current carpets, air blow devices, etc.

[0006] Thus, the output is mainly divided into ferrous materials and non-ferrous materials, and if possible, separated among inert materials including copper, aluminum, and if possible, light plastics and heavy plastics.

[0007] The second category of scrap is scrap resulting from the demolition of buildings, where mixtures of materials of various sizes are variously aggregated with debris such as concrete, which is cut into transportable parts but can also be very large. This category may also include materials from stored or otherwise obsolete scrap. This material is not particularly valuable and should be sized down (if necessary) to be mixed with other more valuable materials to enable proper filling of the basket.

[0008] The third category of scrap is scrap resulting from molding and processing waste. In this case, the quality is high, the contaminants are limited, and as a result, the melting loss is low, and the remaining problem is the size of the fragments. Generally, molding plates have a rather large size in order to maximize the number of pieces that can be made from each plate. Therefore, they must first be cut up to be easily transportable.

[0009] The fourth of the main categories of scrap is scrap metal waste of a fairly large size, such as pylons, rails, structural beams, steel plates and other materials of a fairly heavy weight, which requires cutting by high-performance machines. Again, in this case, the quality of the scrap is generally good, but the difficulty of transportation is considerable. These are usually materials of a homogeneous and clearly defined category that must be processed in order to allow easy loading into the furnace.

[0010] As is well known, steelworks use different numbers of baskets (on average 2 - 3) per casting. Alternatively, continuous loading by conveyor or vibrating belt is used.

[0011] However, the scrap supplied to the melting furnace is not always of the same type or, in any case, is heterogeneous. In order to dispose of the scrap as uniformly as possible and keep the charging mixture in a non-biased state to achieve a certain melting time, it is common to mix the various categories of scrap in various proportions. The charging material must have the following characteristics. - Facilitate the furnace charging process by reducing the downtime associated with basket loading as much as possible; - Be able to be dispersed in the basket in such a way as to minimize furnace collapse and damage during the charging and arc piercing stages; - Have a content of residual elements (Cu, Sn) that is compatible with the composition limits of the steel to be produced; - Have a competitive average cost, taking into account the strong influence of iron-based scrap on the finished product.

[0012] The following examples describe the concept of basket composition with various types of scrap and illustrate how each category of scrap can perform an effective function for the success of casting.

[0013] To maintain the integrity of the furnace bottom and reduce the scattering of molten iron residues (hot heel), light scrap is placed at the bottom, and then, to avoid damage to the graphite electrode, heavy scrap (about 0.90 t / m 3) Place the layer of 3 ) at this lower position and cover it with an average scrap layer (about 0.70 t / m

[0014] The basket is usually composed of removing various types of scrap from the scrap yard by a crane, which means that it is important to separate various types of scrap and in particular to identify scrap stocks containing impurities (such as copper). The reason is that the impurities will ultimately remain in the metal bath and must be removed or diluted in some way.

[0015] Currently, scrap is transported to the steelworks by trucks or container wagons. After the net weight is confirmed, it is classified and transported to the storage area. The various incoming materials often require a grading process carried out by experienced operators according to their seniority.

[0016] The procedure leading to the purchase of the load requires the entire truck to be weighed. Then the scrap is unloaded into the area of the scrap yard and the truck is reweighed to measure its tare weight. The price is then determined based on the weight difference and then on the actual material unloaded. It is clear that this weight includes most of the suitable scrap, but often also includes some unsuitable scrap and other materials that are useless or harmful to the melting process, such as plastics, soil, paper, etc.

[0017] This collection of scraps, also composed of very different dimensions, often clusters into lumps formed during transport between the material loaded by crane and the folded and bundled material, which means that it is not easy to loosen. Another significant part of the scrap may be too large to allow easy loading into the basket. For this reason, many plants tend to use special shears to cut these scrap piles. However, the problem that remains unresolved by all these processes is the purity of the scrap to be processed. In fact, the shears cut whatever is given to them, whether it is more or less pure iron or contains more or less significant traces of other unwanted substances. The composition of this scrap is unknown, and purely dimensional sorting can be carried out in the scrap yard or, at most, based on a more superficial visual analysis of the scrap, with the risk that significant amounts of unwanted elements will be melted and cause a decline in product quality.

Summary of the Invention

Problems to be Solved by the Invention

[0018] The object of the present invention is to propose a plant and method that eliminate the aforementioned drawbacks and enable classification according to not only the weight or size of the scrap but also its chemical composition.

[0019] A further object of the present invention is to provide a plant and method for classifying scrap used by a steelworks that can constitute a scrap amount for casting that is optimized as much as possible and contains only minimal traces of unwanted elements, and can meet the quality and regulatory requirements of the finished product at the end of the production process. Another object of the present invention is found in the need to find a plant and method for classifying significant parts of the scrap that can reduce the uncertainty regarding the residual elements, especially copper, used in the melting process, and thus further optimize the management of the charge mixture.

[0020] Other objects and advantages of the present invention will become apparent from the following detailed description.

Means for Solving the Problems

[0021] In a first aspect of the present invention, the object is (a) a shearing machine suitable for cutting scrap; [[ID=1(1)]]](b) an analytical device downstream of the shearing machine for analyzing the chemical composition of the sheared material; (c) transport means for transporting the sheared material to the analytical device; and (d) a discharge system adapted to separate the analyzed material according to its chemical composition determined by the analytical device is achieved by a plant for classifying scrap according to its chemical composition, the transport means including a plurality of vibrating elements and a conveyor.

[0022] Naturally, the plant may include a plurality of analytical devices.

[0023] These shearing machines are usually composed of a container into which chunks of scrap are dropped by a mechanical arm. The container generally has several movable walls and is usually compressed along three axes. The side walls are crushed towards the inside of the container, the lid is pushed down, and the material is crushed through a piston from the bottom and pushed towards the outlet side.

[0024] Note: There seems to be a formatting issue in the original text where "[[ID=1(1)]]" is an incorrect tag format. It should probably be "" as per the sequential numbering. The translation has been adjusted accordingly for the sake of a more logical flow.A shearing machine is usually installed at the outlet from a compression container and has a linear or inclined blade that hydraulically moves up and down (guillotine type to disperse the acting force along the cutting edge). When the product is pushed towards the outlet, it is usually cut into agglomerates of various lengths between 40 cm and 1.2 m. To facilitate cutting, a counter blade is often mounted on the opposite side of the shearing blade. The shearing machine is designed for low-speed cutting. That is, it can perform several cuts per minute (usually 300 cutting cycles per hour). Some shearing machines are arranged in a mobile mode on wheels or trucks to load materials from various parts of the scrap yard; otherwise, the shearing machine is stationary, in which case the scrap has to be transported to the shearing machine. When the required cutting force is small, i.e., in the case of small machines, mechanical mobility is preferred. Most mobile shearing machines have a horizontal container and are particularly suitable for handling lightweight and low-density scrap.

[0025] Normally, a horizontal shearing machine for cutting scrap includes a container for loading the material and a supply cylinder for transporting the scrap to the outlet and discharging the processed scrap (restricted in such a way that the scrap is cut just before the outlet by a shearing cylinder having a cutting blade). Everything is controlled by a hydraulic control unit.

[0026] Alternatively, for the processing of larger and heavier scrap metal, an inclined type of stationary shearing machine is used. This shearing machine can utilize gravity to eliminate the need for rear and side and / or upper cylinders and instead use surplus oil to provide shearing with a greater cutting pressure. The presence of a jaw to hold the material at the outlet of the shearing machine during and between cuts of the material can facilitate cutting. These machines generally have a hydraulically actuated plug to close the outlet area of the container.

[0027] Particularly suitable are shearing machines that have a movable blade inclined (i.e., at an angle of about 10°) in combination with an inclined (i.e., at about 30°) bottom, preferably having a lateral compression element with a force of, for example, about 560 tons and no thrust cylinder. Also, the shearing force reaches a value of 2,000 tons, and cutting dimensions of width 1,200 mm and length 400 - 1,200 mm can be obtained. This type of shearing machine operating in a continuous automated form reaches a productivity level of over 100 tons per hour. The scrap slides, due to gravity, along the inclined bottom in the direction of the inclined blade, and the bottom and the blade realize an angle of about 140° between them. Lateral and vertical reducers densify the material and adapt its dimensions.

[0028] The values exemplified above are stated throughout the text but are preferred values and not exclusive in any case.

[0029] Therefore, these shearing machines make it possible to cut the amount of mixed scrap into compact-sized pieces or chunks suitable for feeding into a continuous casting basket or conveyor belt and then into a melting furnace.

[0030] Conveniently, the plant starts from a shearing machine similar to the above, preferably a shearing machine of the inclined container and blade category. The reason is that this enables cutting all types of scrap and has a simplified hydraulic circuit compared to horizontal shearing machines. However, this concept can also be realized with horizontal shearing machines or other shearing machines known in the art.

[0031] In an embodiment of the present invention, the analyzer can be located directly at the outlet of the shearing machine. In this case, the means for transporting the sheared material to the analyzer will coincide in location with the means provided in the shearing machine for transporting the material to the outlet. However, a preferred variant of the present invention provides that the analyzer is located at a distance from the shearing machine and that the transport means define a connection of the distance between the shearing machine and the analyzer. In this case, the analyzer may be arranged on the transport means, in other words along the transport means, or at the end of the transport means.

[0032] Analysis of the chemical composition of the sheared scrap enables its classification based on the elements present and their concentrations, optimizing its subsequent use, and this occurs precisely during scrap shearing. The results of such analysis will serve to perform a preliminary classification of the scrap entering the shearing machine and will allow for further subdivision in the plant of the present invention.

[0033] Preferably, a conveyor belt or carpet adapted to receive the sheared material is arranged as transport means downstream of the shearing machine. The conveyor carpet can also be moved by a motor or vibrated, for example by an eccentric mass system, the sum of their rotational movements generating the resulting feed. The conveyor carpet is preferably arranged below the opening of the shearing machine container such that the material falls onto it by gravity. This fall, combined with the operation of the conveyor and / or vibration (in the case of a vibrating carpet), helps to remove dust from the scrap. An intake system can also be provided around the conveyor belt to facilitate cleaning of the area. It is preferred to arrange the suction below it. Also, the vibration disperses the material more evenly, better preparing it for possible magnetic separation into ferrous and non-ferrous materials.

[0034] In a highly advantageous embodiment of the present invention, the scrap sorting plant includes a magnetic separation device disposed between the shearing machine and the analysis device for separating the sheared material into a magnetic material and a non-magnetic material. In this case, advantageously, the transport means includes a first transport means for transporting the sheared material from the shearing machine to the magnetic separation device and a second transport means for transporting at least the magnetic material from the magnetic separation device to the analysis device.

[0035] In this variant, the path that the scrap follows after shearing is a path that undergoes separation of the magnetic material from the non-magnetic material, i.e., separation into an iron-based fraction and a non-iron-based fraction. Preferably, the magnetic separation device is a rotating magnetic drum system disposed downstream of the first transport means, such as a simple conveyor carpet or more preferably a vibrating table. Preferably, the non-iron-based material is removed from the relative transport means, for example, where it falls directly from the drum and lands.

[0036] In a preferred embodiment, the diameter of the magnetic drum is larger than the minimum length of the scrap that can be cut out from the shearing machine. For example, if the shearing machine cuts out sections of at least 40 cm, the magnetic drum has a diameter of at least 40 cm. However, the optimal ratio is a drum with a diameter that is 1 to 2 times the maximum length achievable by the shearing machine. Thus, for a 1.2 m shear, the optimal drum has a diameter of 1.5 m. This is because one dimension, i.e., the dimension of the shearing machine opening, remains fixed and equal between 1 and 1.5 m.

[0037] Therefore, a preferred system for preparing and sorting scrap for melting preferably comprises a shearing assembly having a shearing machine with an inclined blade and a bottom, a unit for separating inert, powdery, and non-iron-based materials from iron-based materials, and an analysis unit for determining the chemical composition of the separated iron-based materials with respect to at least some elements.

[0038] In a further alternative form of the invention, the plant provides third transport means adapted to transport the sheared material directly to the analyzer while bypassing the magnetic separation device. Alternatively, it is also conceivable to move the magnetic separation device out of the process flow by means of the respective moving means and to close the resulting gap, for example with a chute.

[0039] This embodiment is suitable when the scrap loaded into the shearing machine has a considerable size and weight and can therefore be substantially pure. In order to act on scraps of various sizes and weights in the plant, it is useful to take measures to exclude the magnetic separation device from service and replace it with alternative means. In fact, large materials and / or weights cannot be lifted and may clog and damage the separation device.

[0040] The transport means, in the case of a second transport means after the magnetic separation device, can include a radial / swing type conveyor belt, i.e., a conveyor belt that moves around the radius of a circle (the center of which coincides with the scrap loading point) and creates various destinations for the material to be transported depending on the angle of rotation. If the analyzer is located upstream of the radial conveyor, the destinations can correspond to various fractions of materials having different chemical compositions. The radial conveyor can act as a discharge system. The transport system is preferably inclined, lifts the material from the loading point located at the bottom, and drops the material onto a pile arranged under the circumference along which it rotates. Each of the said piles is characterized by being homogeneous from the point of view of the composition of the material contained therein. In that case, the second transport means can coincide in location with a discharge system adapted to subdivide the material analyzed according to point (d).

[0041] In other cases, a radial conveyor can be used to send the material flow, if desired, to the next analyzer or to a destination that does not require analysis.

[0042] Alternatively, the discharge system can also be realized by a conveyor belt, preferably an inclined conveyor belt, which supplies a plurality of dual-track belts. Both solutions are disclosed in more detail with reference to the two exemplary embodiments shown in FIGS. 1 and 2. These types of transport means enable the sheared material to be placed on these second transport means or alternatively on a third transport means after being lowered and separated into separate fractions, according to the chemical composition determined by an analyzer disposed thereon. Another solution for the discharge system is the swivel chute, which will be described later with reference to FIG. 3.

[0043] Preferably, the transport means (first and / or second) includes a vibrating feeder for uniformly dispersing the material on the transport means. Conveniently, the transport means further includes metering means. In a highly preferred variant of the invention, the speed of the transport means is adjustable in order to be able to adapt to the requirements of the analyzer according to the measurement time.

[0044] The transport means, particularly the second transport means, is advantageously a composite of several vibrating elements and inclined conveyors arranged in a cascade in order to optimize the precise fine-tuning of the flow rate according to the requirements of the analyzer.

[0045] Preferably, the transport means includes a conveyor, preferably an inclined conveyor, where the analyzer is located. Advantageously, a further, faster conveyor, which always forms part of the transport means, follows, and this further conveyor transports the analyzed material to a discharge system adapted to separate the various fractions of the material based on the results transmitted by the analyzer.

[0046] Two embodiments particularly suitable for preparing materials for analysis are defined in claims 9-11, and the related exemplary embodiments are described below with reference to FIGS. 3 and 6. The inventors have combined a plurality of vibratory feeders and conveyors in a given order that has been found to be particularly suitable for the purpose. Particularly advantageous was the length selected for the individual elements. Also, the inclination of the individual elements: horizontal (parallel to the plant floor), upward (inclined upward along the transport direction), downward (inclined downward along the transport direction) or cascading (the start of one transport means is below the end of the previous transport means) played an important role.

[0047] An analyzer of the above type can in particular detect the elements Cu, Sn, Zn, P, Mo, Ni, Cr and Mn and classify the material with respect to the presence of impurities rather than the iron content.

[0048] In another embodiment of the present invention, a system is provided for weighing material from a shearing machine that has been pre-purified as much as possible from non-magnetic contamination in terms of scrap loading. Such a weighing system can use, for example, a load cell or a calibrated spring, and this measurement, in combination with the belt conveyor speed data, makes it possible to calculate the flow rate of the material over time. In addition to the weight, each pile is characterized by the presence or absence of a particular chemical element or a threshold value of that element.

[0049] Taking copper and tin, which are undesirable components during melting, as application examples, for example, it is possible to have piles of scrap with a composition of copper and / or tin of less than 0.2%, less than 0.4%, less than 1%, etc. In an advantageous variant of the present invention, the classification of the material results in fractions characterized by copper contents of <0.20% (m / m), 0.20 - 0.35% (m / m) and >0.35% (m / m), respectively. This makes it possible to create a more information-based composition of the scrap feed material for the melting process.

[0050] In order to obtain this separation, it must preferably be possible to analyze the composition of the scrap being processed "online", i.e., while it is passing along the transport means. In this regard, the plant according to the invention provides a chemical analysis device. Preferably, the chemical analysis device is an XRF analyzer, a LIBS analyzer or a neutron activation analyzer, preferably a neutron activation analyzer, in particular a PGNAA system.

[0051] X-ray fluorescence analysis (XRF) is an X-ray emission spectroscopy technique that enables the identification of the chemical elements present in or constituting the sample being examined. The principle used is as follows. It is possible to create a vacancy in the inner shell of the atoms of an element using X-rays of appropriate energy and intensity. This position is then re-occupied by an electron belonging to one of the outermost shells, which, upon de-excitation, generates a photon having an energy equal to the difference in energy of the electrons between the initial and final positions. Such a technique will preferably be used not by locally (by instantaneously / locally analyzing the material composition), but by integrating the compositional information of a given mass of scrap. Characteristic peaks of the various elements are clearly distinguishable in the emission spectrum. This technique is non-destructive but provides information only about the surface composition of the scrap.

[0052] A laser-induced breakdown spectroscopy (LIBS) analyzer uses short pulses of a laser to generate a microplasma on the surface of the sample, causing ablation of a small mass of the sample. The light emitted from the plasma is collected and analyzed by a spectrometer. Each element of the periodic table corresponds to a specific spectral peak.

[0053] Next, for example, an analyzer arranged along a section of an inclined conveyor examines the stream of sheared material passing beneath it and counts the various chemical composition elements. A transmitted light phosphor can be placed under (or above) the material, and a light receiver is installed on the opposite side. The state of the art and the market provide a wide range of analysis systems that can be used for this purpose, and therefore a more detailed description is not required here.

[0054] An exemplary system operation is as follows. Based on data regarding the conveyor speed and the weight of the material, or after a given period, when a certain amount (i.e., 1 ton) of material passes under the analyzer, the count ends, and depending on the result, the inspected amount is discharged into the optimal pile in terms of elemental commonality. Since the measurement requires a minimum duration (i.e., 1 minute), it is necessary to wait for a certain amount of scrap to pass.

[0055] Therefore, a discharge system suitable for sorting the analyzed material according to the chemical composition determined by the analyzer preferably comprises a transport means suitable for dropping the outgoing material at different positions, a weighing means, calculating the flow rate from the weight, sorting the material flow into parts of a specific weight, and further chemically characterizing them based on the data received from the analyzer and sending them to different piles / fractions through the commands of the transport means, in combination with a control unit.

[0056] To assist in the reading and analysis of the material, it is recommended to reduce the height of the layer under analysis and avoid overlapping as much as possible. For this reason, a system for "scooping" the material, such as a blade or spike, is provided in the transport means upstream of the analyzer, and it is recommended that the system loosen the material as it passes through. After shearing, the size of the material is smaller, so it is easier to process with this system.

[0057] Alternatively, the same transport means may be provided with embossed elements adapted to perform this operation while transporting the material to the analyzer.

[0058] In a preferred embodiment of the present invention, on the other hand, the first and / or second transport means comprises a table, a belt and / or a vibrating feeder. Such a vibrating element serves to homogenize the material dispersion, that is to say, to convert a non-uniform material flow into a uniform flow suitable for chemical analysis and magnetic separation. The vibrating element compresses the material in the sense of closing the gap formed between one batch and the next.

[0059] The market offers a wide range of vibrating elements, which usually have a plane with wear-resistant aspects and a vibrating motor below that plane.

[0060] Very advantageously, the analyzer is located on the transport means, in particular on the second transport means if a magnetic separation device is present. This enables in-situ and in-transit analysis to the destination, saves time and provides information about the destination of the material before it is unloaded.

[0061] Very advantageously, a neutron activation analysis system, in particular prompt gamma-ray neutron activation analysis (PGNAA) or pulsed fast thermal neutron activation (PFTNA) can also be used for this purpose.

[0062] Immediate or prompt gamma-ray analysis by neutron activation is a non-contact and non-destructive analytical technique that can be used in an on-line analysis system to determine the chemical composition of bulk materials.

[0063] Neutrons interact with the elements within the material they collide with and then emit measurable gamma rays. Each element emits photons of characteristic energy when returning to a stable state after excitation caused by the absorption of neutrons by the atomic nucleus. When thermal neutrons, or more precisely low-energy neutrons (<0.025 eV), approach or collide with the atomic nucleus, an interaction occurs between the neutron and the nucleus. Then, the atom absorbs the neutron, increasing its mass number by +1 and becoming excited. During its de-excitation, the atom emits photons in the range of gamma rays characteristic of each element. Since this photon is emitted at the instant of the nuclear reaction, it is called "prompt".

[0064]

Number

[0065] The emitted gamma rays have a unique energy corresponding to the emitting atom. Essentially, the emitted gamma rays are like the "fingerprint" of the element. When the emitted gamma rays are detected and an energy spectrum is generated, that energy spectrum provides information about the elements present and their amounts.

[0066] PGNAA and PFTNA online analyzers detect gamma rays using, for example, scintillation detectors. These detectors consist of a high-purity crystal structure that, when exposed to gamma rays, generates photons of energy proportional to the energy of the gamma rays incident on the crystal. A photomultiplier tube coupled to the crystal converts the light pulse into an electrical signal. The generated electrical pulse is amplified and analyzed to obtain information about specific elements. State-of-the-art technology is aware of several alternative detectors that those skilled in the art can easily identify.

[0067] The neutron activation process is a radiation analysis method that can identify virtually all elements in the periodic table in any sample, regardless of whether it is in a solid, liquid, or gaseous state, but the limits of element detectability and quantification are not the same for all elements.

[0068] Qualitative results (identification of the elements present) can be obtained from the emitted photon energy, and quantitative results (the amount of elements present in the scrap) can be obtained from the photon count of this energy. The results are represented by an energy spectrum that shows the "count" of photons as a function of energy with peaks for each element.

[0069] The neutrons used in the analytical technique are provided by radioactive isotopes, often californium 252 ( 252 Cf), or by neutron generation systems. The radioactive isotopes undergo spontaneous nuclear fission and generate the neutrons used in the analysis process. The neutrons from a neutron generator are electrically generated in an accelerator. Compact solutions that are already commercially available can be used as neutron sources. These consist of small accelerators that generate 2.5 MeV neutrons using the deuterium-deuterium fusion reaction (D+ → n+ 3 He), or 14.5 MeV neutrons using the deuterium-tritium fusion reaction (D+T → n+ 4 He). It is possible to reduce the speed of the neutrons to their thermalization point (an energy of about 0.025 eV) via a substance called a modulator (such as water, heavy water, or graphite), or via the collision of the neutrons themselves with the sample. The use of these types of sources (compared to the more common source 252 Cf) makes it possible to create a pulsed beam, while the radioactive isotope generates a continuous neutron flux.

[0070] The dangerous radioactive isotope generates a continuous neutron flux, but the systems based on the above reactions generate neutrons electrically in pulses, enabling the gamma-ray detector to distinguish neutron-nucleus interactions. High-frequency pulses can only be obtained from an electrical neutron source.

[0071] An electrically operated system ensures the highest level of safety that can stop neutron emission, thus reducing the exposure of the users of the analysis system. The increase in neutron energy brings several analytical advantages. The most important advantage is the ability to analyze carbon and oxygen as well. Higher neutron energy also results in an overall improvement in sensitivity. The ability to handle a wide range of mass variations in the activation zone and the independence from particle size are additional advantages of the PFTNA-based analyzers.

[0072] The gamma-ray activation chemical neutron analyzer penetrates the entire cross-section of the material to be analyzed and provides a uniform measurement not only of its surface but also of the whole material. Surface analysis techniques such as XRF, LIBS, X-ray diffraction and other spectral analysis techniques measure only a limited depth and surface and cannot represent the total amount of the material. They require multiple sensors but have higher accuracy and integration time.

[0073] The usefulness of neutron activation techniques lies in several special features shown below. - (At least approximate) evaluation of the simultaneous qualitative identification (position of peaks in the energy spectrum) and quantity (scaling area of peaks) of several elements. - It is a non-destructive technique that does not require direct contact with the sample or collection of a part of the sample, and thus the sample to be analyzed is not damaged. Also, time-consuming sample preparation is avoided. - Since neutrons are not charged particles, they are not affected by Coulomb repulsion and can penetrate deeper into the target material. This is different from XRF, LIBS and hyperspectral imaging techniques that perform only surface analysis.

[0074] The problem with neutron activation analysis is that neutrons emitted from a neutron source also excite substances outside the material being analyzed, which then generate gamma rays whose presence is identified by a detector. To counter this phenomenon, conveniently, various shields for capturing neutrons are provided within the measurement system so that the neutron beam preferably affects only the material being measured, and thus no "extraneous gamma rays" that contaminate the desired gamma rays are generated. The shielding material can consist of plastics containing neutron poisons such as boron or lithium. The choice of shield thickness makes it possible to adjust the attenuation of neutrons, for example, to 1 / 8. Also, the use of lithium or boron epoxy resin coatings is useful. Patent specification US8,138,480B2 provides possible shields and solutions, such as directly determining the composition of bulk materials on a conveyor belt.

[0075] The chemical composition can also be expressed as a percentage or, if information regarding the material flow rate is available, as an absolute value indicating a mass, molar, or weight value.

[0076] In the literature, by analyzing a sample for several minutes (i.e., 10 minutes), it is possible to find estimated values of the concentration limits of various elements in the periodic table that can be measured using this technique. In the case of nickel, the detection level is reported as <0.01%; for iron, chromium, copper, and sulfur, the detection levels are reported as 0.01 - 0.1%; for aluminum and silicon, the detection levels are reported as 0.1 - 0.3%; for molybdenum, the detection level is reported as 0.3 - 1%; for tin, values of 3 - 10% are seen with a measurement time of 10 minutes. Thus, the most targeted elements in scrap analysis generally exhibit good detectability levels.

[0077] The system of the present invention provides information regarding the qualitative and quantitative composition of scrap, offering important advantages.

[0078] When compared to regulatory limits, the measured chemical composition can prove whether the input materials exceed or do not exceed the content required by the applicable EU law, and can also enable the classification of materials for the purpose of constituting mixtures of various scrap fractions for melting furnaces or oxygen converters in the Linz-Donawitz process. This provides a means for modifying the materials in the basket and adjusting and correcting the metal and non-metal contents through dilution.

[0079] A second aspect of the invention is the following steps: (I) Shearing of the scrap; (II) Analysis of the chemical composition of the sheared material; and (III) Sorting of the analyzed material into fractions according to the chemical composition determined in step (II) which involves a method for classifying scrap, wherein the scrap is transported on a plurality of vibrating feeders and conveyors prior to its analysis.

[0080] Advantageously, the sorting in step (III) occurs by the respective control of the discharge transport means that create the various fractions of the sheared scrap according to the determined chemical composition and flow rate (if measured). Alternatively, it is possible to divide the transported material into slices corresponding to specific advance periods of the transport means.

[0081] The analysis is preferably carried out by the XRF, LIBS or neutron activation method described above with respect to the plant of the invention, preferably during transport.

[0082] Advantageously, if the incoming scrap has been reduced in size and weight, between steps (I) and (II), magnetic separation of the sheared material occurs, separating it into a magnetic fraction and a non-magnetic fraction, and during step (II) only the magnetic fraction is analyzed and the non-magnetic fraction is discarded. In this way, much of the purely non-ferrous material is discarded. Based on information about the size or weight of the scrap obtainable from weighing or visual inspection, for example by means of a camera, it is possible to send the sheared material either to a route including magnetic separation or to a bypass route. Preferably, the fractions produced by constantly accumulating inside during the application of the method parts of sheared scrap of similar chemical composition contain various amounts of iron and / or unwanted elements, such as copper, in the steel.

[0083] Before being analyzed, the material is preferably subjected, preferably in the plant of the invention, to vibrations, in particular inclined transport and specific speed conditions, in order to adapt the material to the requirements of the analyzer, in particular to correspond to the required measurement time. In this regard, combinations of conveyors of different specific lengths are also useful.

[0084] Using the plant and method for scrap classification according to the invention, it is possible to determine the chemical composition of large amounts of bulk material (on the order of dozens of tons) in a short time (on the order of minutes), classify it and separate it. Preferably, the analysis takes place along the transport means that removes the sheared scrap from the shearing machine. In a preferred variant of the invention, the sorting in step (III) takes place by instructing the transport means downstream of the analyzer to drop parts of the sheared scrap of the same or at least similar chemical composition into the same fraction. For this purpose, it is useful to use a radial conveyor belt or a dual-track multi-conveyor belt or a swivel chute.

[0085] The features and advantages disclosed with respect to one aspect of the invention can also be transferred to other aspects of the invention with the necessary modifications.

Industrial Applicability

[0086] Industrial applicability becomes apparent from the moment it becomes possible to classify sheared scrap according to regulatory aspects based on, for example, the content of iron and / or impurities or trace elements, in particular copper, and consequently the intended handling of the composition in a basket for use in a refining furnace or similar furnace.

[0087] The above objectives and advantages will be further emphasized in the disclosure of the preferred embodiments of the present invention provided by way of example only.

[0088] Modifications and further features of the present invention are the subject of the dependent claims. The description of the preferred exemplary embodiments of the plant and method for scrap classification according to the present invention is given only by way of non-limiting example with reference to the accompanying drawings. In particular, unless otherwise specified, the number, shape, dimensions and materials of the plant and individual components can be different, and equivalent elements can be applied without departing from the concept of the present invention.

Brief Description of the Drawings

[0089]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0090] Detailed Description of the Preferred Embodiment Figure 1 shows, in a block diagram, the concept of a scrap sorting plant according to the present invention. For example, a horizontal shearing machine 10 includes a container 12 into which scrap can be loaded, in the direction of arrow a, by means of a device 14 such as a crane. The shearing machine 10 includes an extrusion device 16 for advancing scrap (not shown) towards a cutting device 18 at the outlet of the shearing machine 10. Alternatively, an inclined shearing machine can also be used as described above. The sheared material (not shown) leaves the shearing machine 10 on a conveyor belt 20 facing a magnetic drum 22 for magnetic separation of the material. The separated non-magnetic material is diverted from the plant on a conveyor belt 24, and the magnetic material continues to flow in the direction of flow b of the material on a further conveyor belt 26 equipped with an analyzer 28 for directly analyzing the chemical composition of the material on the conveyor belt 26.

[0091] After attracting the ferromagnetic scrap to itself, the magnetic drum 22 empties it into a chute (not shown) opposite the magnetic drum and sends it to the belt 26. The non-magnetic material falls from the conveyor belt without being attracted by the drum 22 and finally reaches a second conveyor belt 24 suitable for sending it to a special pile not used for melting and reaching a hopper (not shown).

[0092] For example, a control unit located within the analyzer itself identifies, based on the data received from the analyzer, the type of scrap currently present in a given section on the belt and classifies it into relative fractions F1 and F2. Depending on the type of fraction detected, the control unit instructs the conveyor belt 26 to change its position, in the direction of arrow c (between the position shown by the solid line and the position shown by the dashed line), and to drop the incoming material onto the piles corresponding to the determined fractions F1, F2. This is a very simplified system that combines the transport means and the discharge system in a radial conveyor and, of course, can also be implemented in such a way that the discharge system follows the transport means.

[0093] Figure 2 shows a variant of the transport means and discharge system downstream of the shearing machine for physically separating the various fractions (F1 - F4) of the sheared and analyzed material, replacing the belt 26 of Figure 1 (including the analyzer not shown). In this case, a control unit (not shown) selects the direction of travel of belt 34 depending on the chemical composition of the material 30 when the sheared and analyzed material 30 reaching the non - rotatable inclined conveyor belt 32 is placed on the dual - track conveyor belt 34 (arrow x), and then sends it onto the subsequent dual - track belts 36 or 38 (arrows y1 and y2), from where the material is sent towards the respective piles containing fractions F1 - F4 (arrows z1, z2, z3, z4) while constantly setting the relative movement direction of the respective belts 36, 38. The criteria for determining to which fraction the sheared and analyzed material belongs can be the iron content and / or the presence of undesirable elements.

[0094] Details regarding suitable shearing machines, suitable transport means, and available magnetic separation devices can be found in the description part of the present invention. The method of loading the shearing machine can also be various as described above, and of course, the number of fractions can also be various. Instead of dropping the separated material into a scrap yard, it can also be directly transported to different plants (such as melting furnaces) where it can be used, or loaded onto wagons or trucks and transported to other locations. The transport means can be composed of various types of conveyors and advantageously can also include a vibrating feeder, etc.

[0095] FIG. 3 shows a preferred embodiment of a scrap sorting plant providing an inclined shearing machine 110, followed by a vibrating table 109 for homogenizing the sheared material and preparing it for magnetic separation in a subsequent permanent magnet magnetic drum 122 (i.e., having a diameter of 1,220 mm and a width of 2,100 mm). Non-ferrous materials are removed by conveyor 124. Downstream of drum 122, a radial conveyor 126 is disposed for transporting ferrous materials to an analyzer or dropping them to the ground, depending on the position taken by rotation in the direction of arrow y. Ferrous materials fall from radial conveyor 126 onto a first vibrating feeder 140, then from there onto a second vibrating feeder 142, which further reduces the height of the material and homogenizes its dispersion. Then conveyor 144 follows, which transports the material to an inclined conveyor 146 equipped with an analyzer 128 for determining the composition of the material online. After passing through analyzer 128, the analyzed material falls onto a high-speed conveyor 148, and when this high-speed conveyor drops the material onto a swivel chute 150 by gravity, this swivel chute pours the materials sorted according to various concentrations of specific metals, particularly copper, into different containers 152 based on the values received from analyzer controller 128. The lengths of the conveyors and feeders can vary from several meters in the case of the first feeder, for example about 2.75 meters, to 20 meters in the case of the high-speed conveyor. The length is selected by those skilled in the art based on the timing and degree of homogenization of the material required by the analyzer. The adjustable speed of the transport means, the inclination of the transport means, and the metering of the material being transported also help to optimize the analysis time.

[0096] FIG. 4 shows an analyzer 128 located on a transport means 146 carrying ferrous material 145 as shown in FIG. 3. Frame 129 supports a neutron source 170, which emits neutrons (arrow x) that penetrate ferrous material 145, then that ferrous material emits rays (arrow y), and those rays are identified by detector 172 and analyzed in an analyzer control unit.

[0097] Container 152 can be movable while being conveniently placed on the weighing table. The container filled in this way is clearly defined in terms of chemical composition and weight and can be sent to the corresponding basket for supply to the melting furnace.

[0098] For example, in the arrangement of the containers in FIG. 3, it is possible to obtain copper fractions containing >0.30% (m / m), 0.20 - 0.30% (m / m), and <0.20% (m / m) of copper. The analysis system integrates the concentrations of the detected elements at the correct timing to provide the total average concentration for each container set within the desired limits.

[0099] FIG. 5 shows in block diagram an embodiment of the scrap classification method according to the present invention. After the 100 - step scrap shearing, magnetic separation 101 of the sheared material follows by separating the non - magnetic material 103 from the main material flux b1 (arrow b2). The magnetic material 105 continues to be analyzed (107) with respect to its chemical composition. The detected data reaches the control unit 109 (arrow v), and this control unit determines whether the analyzed material belongs to each fraction and commands the transport means 111 supplied along the main flux direction b1 to send the material to different piles corresponding to different fractions F1, F2, F3, F4 (b z ) as shown. In this regard, it can be said that a rotatable conveyor belt (shown in FIG. 1) or a dual - track multi - conveyor belt (shown in FIG. 2) or the swivel chute shown in FIG. 3 or other equivalent means are useful. Those skilled in the art will be able to find other solution means for discharging and separating the material.

[0100] Figure 6 shows a side view of another detailed embodiment of the scrap sorting plant according to the present invention. A shearing machine and a magnetic drum, particularly a magnetic drum having permanent magnets (not shown), are disposed upstream of the radial conveyor 226. The radial conveyor 226 conveys iron-based materials to the analyzer 228 or drops them into the pile NF in the surrounding area. The iron-based materials fall from the inclined radial conveyor 226 onto the first horizontal vibrating feeder 240 (in the direction of the analyzer), and then from there onto the second horizontal vibrating feeder 242, which further reduces the height of the materials and equalizes their dispersion. Then, a horizontally disposed conveyor 244 follows, and this conveyor conveys the materials to a further horizontal conveyor 246 equipped with two analyzers 228 for determining the composition of the materials online. A system 245 is disposed at the starting end of the conveyor 246 for blocking bulky parts and / or for weighing. After passing through the analyzer 228, the analyzed materials fall onto the conveyor 248, and when this high-speed conveyor drops the materials onto the swivel chute 250 at high speed by gravity, this swivel chute pours the sorted materials according to the target concentration level of a specific metal, particularly copper, received from the analyzer controller 228 into different piles F1, F2.

[0101] The lengths of the conveyors and feeders in the embodiments shown in FIGS. 3 and 6 are in the following ranges in an exemplary form. For the radial conveyor, it is 14 - 18 m; for the first vibrating feeder, it is 4 - 6 m; for the second vibrating feeder, it is 2 - 4 m; for the conveyor connecting to the conveyor equipped with the analyzer (itself with a length of 10 - 30 m), it is 5 - 7 m; for the high-speed conveyor, it is 16 - 22 m; and for the swivel chute, it is 6 - 8 m.

[0102] At the implementation stage, without departing from the object of the present invention, parts may be added to the plant and method for scrap classification included in the present invention, or further modifications or changes not described may be added to the plant and method for scrap classification. If such modifications or such changes fall within the following claims, they should all be considered to be protected under this patent. In fact, the materials used as well as the dimensions, numbers and shapes can vary according to requirements as long as they are compatible with the specific use and unless otherwise specified. Although the present invention has been described with reference to specific examples, those skilled in the art will be able to create numerous other equivalent forms of analysis plants and methods that have the features described in the claims and thus fall within the scope of protection defined by all the claims.

[0103] The present invention has achieved the objective of proposing an effective plant and method for classifying scrap exiting a shearing machine such as to enable the production of a scrap mixture that is separated according to specific criteria related to the chemical composition and which is thereby optimized and standardized, in particular with regard to the copper content, for the melting furnace basket (which enables the identification of larger parts with a lower copper content).

Claims

1. A plant for classifying scrap according to its chemical composition, comprising: (a) a shearing machine (10; 110) adapted to cut the scrap; (b) an analysis device (28; 128) downstream of the shearing machine (10; 110) for analyzing the chemical composition of the sheared material (145); (c) transport means (20, 26; 126, 140, 142, 144, 146, 148) for transporting the sheared material (145) to the analysis device (28; 128); and (d) a discharge system (26; 32, 34, 36, 38; 150; 250) adapted to separate the analyzed material (30; 145) according to its chemical composition determined by the analysis device (28; 128), wherein the transport means includes a plurality of vibrating elements and conveyors, the plant for classifying the scrap comprises the following machines arranged in the following order: - a shearing machine (110), - a vibrating table (109), - a drum magnet (122), - a radial conveyor (126; 226) for transporting the iron-based material separated from the drum magnet (122) to the analysis device (128; 228) or for dropping the non-iron-based material into the surrounding area, - a first vibrating feeder (140; 240), - a second vibrating feeder (142; 242), - a first conveyor (144; 244), - a second conveyor (146; 246) provided with an analysis device (128; 228), - a third, faster conveyor (148; 248), - a discharge system (26; 32, 34, 36, 38; 150; 250) wherein the vibrating table (109), the radial conveyor (126; 226), the first vibrating feeder (140; 240), the second vibrating feeder (142; 242), the first conveyor (144; 244), and the second conveyor (146; 246) form the transport means including a plurality of vibrating elements and conveyors, a plant for classifying scrap.

2. The plant for classifying scrap according to claim 1, comprising means for moving the drum magnet out of the process flux and a chute or the like adapted to block the path of the material in place of the drum magnet.

3. The plant for classifying scrap according to claim 1 or 2, wherein the analysis device (28; 128) is an XRF analysis device, a LIBS analysis device or a neutron activation analysis device.

4. A plant for classifying scrap according to claim 1 or 2, wherein the analysis device (28; 128) is a PGNA system.

5. A plant for classifying scrap according to claim 3 or 4, wherein the second conveyor where the analysis device is located is an inclined conveyor or a horizontal conveyor.

6. A system adapted to loosen the transported material, selected from blades, spikes and embossing elements, is disposed upstream of the analysis device in the transport means, for the plant for classifying scrap according to any one of claims 1 to 5.

7. The radial conveyor (126; 226) is inclined upward or ascending, the third conveyor (148; 248) is inclined upward or ascending, the first vibrating feeder (140; 240), the second vibrating feeder (142; 242) and the first conveyor (144; 244) are arranged in a cascade manner, the first conveyor (144; 244) is horizontal, and the discharge system (150; 250) is inclined downward or descending, (I) the first vibrating feeder (240), the second vibrating feeder (242) and the second conveyor (246) are horizontal; or (ii) the first vibrating feeder (240) and the second vibrating feeder (142) are inclined downward or descending, and the second conveyor (146) is inclined upward or ascending, for the plant for classifying scrap according to any one of claims 1 to 6.

8. The discharge system for separating the analyzed material according to its chemical composition determined by the analysis device is a transport means selected from a radial conveyor belt (26), a multi-conveyor belt (32, 34, 36, 38) having a plurality of dual-track conveyor belts, or a swivel chute (150; 250), for the plant for classifying scrap according to any one of claims 1 to 7.

9. The length of the conveyor and the vibrating feeder is 14 to 18 m in the case of the radial conveyor; 4 to 6 m in the case of the first vibrating feeder; 2 to 4 m in the case of the second vibrating feeder; 5 to 7 m in the case of the first conveyor; 10 to 30 m in the case of the second conveyor; 16 to 22 m in the case of the third conveyor; and 6 to 8 m in the case of the swivel chute, for the plant for classifying scrap according to any one of claims 1 to 8.

10. The shearing machine is an inclined shearing machine, for the plant for classifying scrap according to any one of claims 1 to 9.

11. A method for classifying scrap in the plant according to any one of claims 1 to 10, comprising: The following steps: (I) Shearing of the scrap (100); (II) Analysis (107) of the chemical composition of the sheared material (107) during its transportation; and (III) Sorting (111) of the analyzed material into fractions (F1, F2, F3, F4) depending on the chemical composition determined in step (II) by means of transportation means including that the scrap is subjected to transportation on a plurality of vibrating feeders and conveyors before its analysis, A method for classifying scrap, wherein magnetic separation (101) of the sheared material occurs between step (I) and step (II) to separate the material into a magnetic fraction (105) and a non-magnetic fraction (103), and during step (II), only the magnetic fraction (105) is analyzed and the non-magnetic fraction (103) is discarded.

12. The transportation of the sheared material to the analyzer provides homogenization of the sheared material and / or a reduction in its height on the transportation means, for the method for classifying scrap according to claim 11.

13. The fractions (F1, F2, F3, F4) contain various amounts of iron and / or unwanted elements in the steel, for the method for classifying scrap according to claim 11 or 12.

14. The various amounts of the unwanted elements are various amounts of copper, for the method for classifying scrap according to claim 13.

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