Recycling system for plaster waste from the general public and recycling process implementing such a system

Abstract

System (1) for recycling gypsum waste from the general public, intended to recover a so-called final fraction comprising particles with a particle size less than or equal to a specified threshold dimension, system (1) comprising: at least one waste preparation unit (2); at least one waste crushing and sorting unit (3) for the waste from the preparation unit (2); at least one recovery unit (5) recovering at least a portion of the fine fraction from the crushing and sorting unit (3); system (1) being characterized in that it further comprises at least one finishing unit (4) receiving at least a portion of the coarse fraction from the crushing and sorting unit (3), the finishing unit (4) comprising at least one rolling mill having a gap less than or equal to the threshold dimension. Figure for the abstract: Figure 1

Description

Title of the invention: Recycling system for plaster waste from the general public and recycling process implementing such a system. FIELD OF THE INVENTION

[0001] The present invention relates to the field of plaster recycling, and more particularly to the field of gypsum recovery from plaster waste from the general public, in particular from the demolition and / or renovation of buildings.

[0002] More specifically, the invention relates to a system for recycling plaster waste to recover gypsum. technological BACKGROUND

[0003] Plaster is a hydraulic binder typically obtained from gypsum, a material found naturally in nature and extracted from quarries. However, operating costs, environmental problems, and the depletion of natural resources are leading to the development of recycling solutions to recover gypsum from plaster waste.

[0004] Plaster waste from the general public comes from various sources and is often intimately mixed with other materials. For example: • simple plaster, for example any gypsum board covered with a paper facing, • plaster tiles • plaster molds, • plaster from ceilings mixed with flax, reeds, wooden lath, etc... • so-called complex plaster, covered for example with glass wool, rock wool, polystyrene, etc... • plaster covered with earthenware, metal, plastic, electrical conduits, etc...

[0005] Plaster recycling processes can be divided into two categories: chemical processes, which generally involve heat treatment and the use of water, and mechanical processes, which are based primarily on grinding and sorting. The invention relates to a type of mechanical process, which is easier to implement and less expensive than chemical processes.

[0006] Mechanical processes face several difficulties. Indeed, the sticky nature of plaster can make it difficult to detach from other materials, and more particularly from paper and cardboard. Thus, during grinding, the paper and Cardboard is also shredded, making it difficult to separate from the gypsum. Furthermore, ambient humidity can promote adhesion between the plaster and the paper and cardboard, as well as clogging of equipment.

[0007] US2016 / 0214895 describes an example of a mechanical recycling process for gypsum from construction materials, which includes a succession of sorting, grinding and screening steps to separate gypsum particles from paper and cardboard.

[0008] In document EP1421995, it is proposed to introduce into a mechanical type plaster recycling process a crushing step in order to make the materials more brittle and promote their detachment in a drum.

[0009] Document US2017 / 341084 also describes an example of a recycling line with a succession of crushing and screening.

[0010] However, these processes do not allow sufficient levels of yield and purity of the recovered gypsum to be achieved, so that the rejects from these processes constitute significant waste that must be treated, increasing the costs of recycling plaster and reducing its ecological value.

[0011] Indeed, in order to achieve a high gypsum purity level at the recycling stage, the materials must be sorted to the smallest possible size. However, the smaller the sorting size, the more difficult it is to extract gypsum with a good yield, as the rejects contain a significant proportion of gypsum. Thus, the result is either a low yield rate, resulting in substantial rejects (which always contain plaster), which are difficult to recycle and must be treated, or a low purity of the recovered gypsum, limiting its use as a replacement for natural gypsum extracted directly from quarries.

[0012] The invention thus aims to remedy in particular the aforementioned disadvantages by proposing a new solution for recycling plaster from the general public, by a process, improving in particular the profitability of recycling by improving the yield rate as well as the purity rate of the recovered gypsum.

[0013] Thus, a first object of the invention is to propose a solution enabling the recovery of gypsum from plaster waste from the general public with increased profitability.

[0014] A second object of the invention is to propose a solution enabling the recovery of gypsum from plaster waste from the general public in a completely mechanical way.

[0015] A third object of the invention is to propose a solution for recovering gypsum from plaster waste from the general public, allowing for a higher purity rate of the recovered gypsum than in the prior art.

[0016] A fourth object of the invention is to propose a solution for recovering gypsum from plaster waste from the general public, allowing the gypsum to be efficiently separated from other materials in order to recover value from these other materials.

[0017] A fifth object of the invention is to propose a solution enabling the recovery of gypsum from plaster waste from the general public and reducing recycling costs.

[0018] A sixth object of the invention is to propose a solution enabling the recovery of gypsum from plaster waste from the general public by using equipment already available on the market. Summary of the invention

[0019] Thus, according to a first aspect, the invention relates to a recycling system for plaster waste from the general public, designed to recover a so-called final fraction comprising elements with a particle size less than or equal to a predetermined threshold dimension. The system includes, in particular: • at least one waste preparation unit, which includes at least one magnetic sorting device enabling the separation, at least in part, of metallic elements from the rest of the waste; • at least one unit for crushing and sorting waste from the preparation unit which includes at least one crushing device and at least one sorting device with a mesh size less than or equal to the threshold dimension, allowing the waste to be separated into a fine fraction and a coarse fraction; • at least one recovery unit recovering at least part of the fine fraction from the crushing and sorting unit.

[0020] The system further comprises at least one finishing unit receiving at least a portion of the coarse fraction from the crushing and sorting unit. The finishing unit comprises at least one rolling mill having a gap less than or equal to the threshold dimension followed by at least one finalizing sorting device with a mesh size less than or equal to the threshold dimension and feeding the recovery unit.

[0021] The set of fine fractions recovered by the recovery unit then corresponds to the final fraction of particle size less than or equal to the threshold dimension.

[0022] The system thus makes it possible to recover a fine fraction with a very small particle size, in order to obtain a high purity level, as well as to extract the gypsum with a high yield. In particular, the use of a rolling mill after the grinding device allows for more efficient sorting.

[0023] Depending on different aspects, it is possible to foresee one and / or the other of the characteristics below taken alone or in combination.

[0024] Thus, the crushing sorting device and the final sorting device may each include at least one flip-flop type screener. The flip-flop type screener notably helps to limit the risk of clogging of the screener, while still providing adequate sorting quality.

[0025] According to one embodiment, at least one rolling mill of the finishing unit includes smooth rolls, i.e. rolls that do not have asperities on the threshold dimension scale.

[0026] For example, the dimension alone is less than or equal to 1.2 mm or even less than or equal to 1 mm, which makes it possible to achieve a recycling rate of up to 99%, as well as a natural gypsum replacement rate of around 60%

[0027] According to one embodiment, the shredding device includes, for example, at least one reject outlet connected to the finalizing unit, so that the finalizing unit receives both a coarse fraction from the sorting and shredding unit and the rejects from the shredding device. Thus, the recycling rate is further improved by processing the rejects from the shredding device.

[0028] More specifically, the finishing unit may comprise at least two successive rolling mills. The reject outlet of the crushing device may then be connected to the finishing unit between the two rolling mills, so that the first rolling mill receives exclusively the coarse portion from the sorting and crushing unit, and the second rolling mill receives a mixture comprising the waste that passed through the first rolling mill and the reject portion from the crushing device. The crushing effect of the waste in the second rolling mill is thus improved, increasing the gypsum extraction rate from the waste, and therefore the recycling rate.

[0029] According to one embodiment, the grinding device includes at least one paddle grinder, which makes it possible to efficiently grind the waste.

[0030] According to one embodiment, the waste preparation unit includes a visual waste sorting table. Waste that is easily identifiable as non-compliant for further processing in the system is thus removed at the beginning, preventing it from obstructing subsequent equipment.

[0031] According to a second aspect, the invention relates to a process for recycling plaster waste from the general public, intended to recover a so-called final fraction comprising elements with a particle size less than or equal to a predetermined threshold dimension, by implementing the system as described above. The process includes, in particular: • the determination of the threshold dimension, • the adjustment of the crushing and sorting unit as well as the finalizing unit with the determined threshold dimension; • The passage of waste through the recycling system.

[0032] It is thus possible to choose a threshold dimension according to the desired results, particularly in terms of recycling rate and purity of the recycled gypsum. Brief description of the drawings

[0033] Embodiments of the invention will be described below with reference to the drawings, briefly described below:

[0034] [Fig-1] represents a diagram of a recycling system conforming to a mode of realization of the invention;

[0035] [Fig.2] schematically represents a waste preparation unit of the [Fig.1] system;

[0036] [Fig.3] schematically represents a sorting and grinding unit and a finalization unit of the system of [Fig.1].

[0037] In the drawings, identical references designate identical or similar objects. DETAILED DESCRIPTION

[0038] Figure 1 schematically represents a system 1 for recycling plaster waste according to an embodiment of the invention. The waste is referred to as "from the general public," meaning it comes from various sources without distinction. This includes, in particular, plaster waste used in construction, demolition, industrial applications, and / or from private individuals.

[0039] System 1 is for example installed on a site near the raw waste storage location.

[0040] Recycling system 1 recovers, from waste, a so-called final fraction comprising elements with a particle size less than or equal to a threshold dimension. Particle size refers here to the dimension of the elements determined by any particle size analysis method. In what follows, the dimension of the elements therefore refers to a dimension determined by any particle size analysis method.

[0041] The threshold dimension is chosen, predetermined, according in particular to the desired result, as characterizing the particle size of the final fraction.

[0042] System 1 comprises a series of three units: a waste preparation unit 2, a crushing and sorting unit 3, and a finalization unit 4. Each unit 2, 3, and 4 comprises a series of stations, one embodiment of which is detailed below. The system further includes a recovery unit 5, which collects fractions generated along system 1 corresponding to the final fraction. Although not explicitly stated, a waste conveying system, for example, a conveyor belt, may be provided between each station and each unit.

[0043] The waste preparation unit 2 has the function of preparing the waste for the crushing and sorting stage which takes place in the crushing and sorting unit 3, in particular by removing raw waste materials which are immediately identifiable.

[0044] More specifically, the preparation unit 2 includes a feed bunker 21, into which the raw waste is poured. The raw waste comprises various materials, in the form of elements of varying dimensions, up to 300 mm (millimeters) or even more. The bunker 21 allows, in particular, for the control and maintenance of a predetermined waste flow rate. It then feeds a first screener 23, for example of the star type, which performs an initial particle size separation around a given value, so as to obtain a so-called fine fraction, smaller than the given value, for which visual sorting is difficult or even impossible, and a so-called coarse fraction, larger than the given value, which can be sent to a sorting table 24. The value given for sorting in the first screener 23 is, for example, less than 100 mm (millimeters), and for example equal to 50 mm.A crusher can be provided upstream of the first screener 23, for example in the case where the waste has dimensions incompatible with the first screener 23. In addition, a metal sorting device, for example of the magnetic overband type, can also be provided upstream of the first screener 23 in order to remove the metal elements that are already accessible.

[0045] In what follows, for each device allowing a particle size separation around a given setting value, a fine fraction is defined corresponding to the particle size elements less than or equal to the setting value of the device concerned and a coarse fraction corresponding to the elements with dimensions greater than the setting value of the device concerned.

[0046] The sorting table 24 allows operators, for example, to perform visual sorting and remove items from the waste that are immediately identifiable as non-compliant, such as wooden or plastic items, bricks, metal parts, or pieces of polystyrene. The sorting table 24 is, for example, located in a closed, air-conditioned cabin 22, providing operators with good working conditions. The non-compliant items are then visually identified, removed manually or using equipment, and conveyed onto an outflow conveyor 25, possibly for recycling in a dedicated circuit 6. The cabin 22 is, for example, a self-supporting structure, elevated above the feed bunker 21.

[0047] The conforming waste elements exiting the sorting table 24 can then be sent to a screw crusher 26, in which the waste is crushed by slow mechanical pressure to reduce its size to a maximum dimension, for example, 200 mm. The screw crusher 26 may comprise a single or several screw rollers, for example three, and allows for efficient grinding of waste.

[0048] The waste exiting the screw crusher 26 can then be mixed with the fine fraction exiting the first star screener 23 before entering a sorting device to remove metallic objects. Indeed, metallic objects that have escaped the operators on the sorting table 24 are preferably removed before the crushing and sorting unit, in order to prevent them from damaging and / or causing premature wear, particularly of the downstream devices, and in particular the crushing device.

[0049] The sorting device includes, for example, a magnetic overband magnetizer 27 for recovering metallic objects. The overband magnetizer may be followed by a sorting device 28 comprising a magnetization device, for example, by generating a magnetic field through which the waste passes and becomes electrically charged by eddy currents. Then, using a magnetic head 29 on the waste, the magnetized elements are extracted.

[0050] The non-conforming elements thus extracted from the waste in the preparation unit 2, and essentially the metallic elements, are removed for example using the exit belt 25, and can possibly be recovered in a separate circuit, such as the dedicated circuit 6.

[0051] The waste, thus freed from the majority of non-conforming elements, is then processed in unit 3 for crushing and sorting. Its maximum dimension is, according to the example detailed here, 200 mm.

[0052] The grinding and sorting unit 3 includes, in particular, at least one grinding device and at least one sorting device, referred to as a grinding device, set to the threshold dimension to recover elements of dimensions corresponding to the final fraction. For example, the threshold dimension is less than 1.5 mm, preferably less than 1.2 mm, and preferably less than or equal to 1 mm.

[0053] To this end, the crushing and sorting unit 3 may include a first crushing and sorting device comprising, for example, a second screener 31, for example of the trampoline type, also called a flip-flop screener, with a mesh size set to the threshold dimension, i.e., whose output mesh is less than or equal to the threshold dimension, and which performs a first separation between a fine fraction, forming part of the final fraction and which is sent to the recovery unit 5, for example on an output belt 51 of the recovery unit 5, and a coarse fraction. The use of a flip-flop type screener makes it possible, in particular, to limit the risk of clogging of the screener openings. The shaking of the flip-flop screener also contributes to the separation between the plaster and the other materials.Optionally, the first crushing sorting device may include a sieve 32, for example of oscillating type, with mesh size set to the threshold dimension, which is interposed between the second screener 31 and the belt 51 of. output, in order to prevent elements of dimensions greater than that of the threshold dimension and which may have passed through the second screener 31 from ending up on the output band 51 and in the final fraction.

[0054] The coarse fraction exiting the second screener 31 is sent to a grinding device 34. The grinding device 34 preferably comprises an impact crusher, and even more preferably a paddle crusher, in which the coarse fraction from the second screener 31 is struck against a screen in order, in particular, to detach the gypsum adhering to paper and / or cardboard facings. According to one embodiment, the screen of the crusher 34 has a mesh size of less than 200 mm, and for example, 40 mm. Thus, the crusher 34 generates a coarse fraction with a size greater than or equal to 40 mm, called the crusher reject, and a fine fraction with a size less than 40 mm, which is sent to a second grinding sorting device, which comprises, for example, a third screener 35, which may be of the same type as the first screener 31, and which has a mesh size set to the threshold dimension.The third screener 35 also has a mesh size set to the threshold dimension, so that it separates a fine fraction from a coarse fraction, as with the second screener 31. The second sorting device may further include a second oscillating sieve 36, similar to the first oscillating sieve 33, through which the fine part exiting the third screener 35 passes, in order to be discharged, for example onto the same outlet belt 32, and to join the fine fraction from the first oscillating sieve 31.

[0055] The grinding and sorting unit 3 may include other successive grinding and sorting devices.

[0056] According to the invention, the crushing and sorting unit 3 is followed by the finalization unit 4 which receives the coarse fraction coming out of the third screener 35, i.e. whose element size is greater than the threshold size.

[0057] The finalization unit 4 comprises at least one rolling mill followed by at least one sorting device called a finalization device.

[0058] More specifically, according to the embodiment illustrated in the figures, the finishing unit 4 may include a fourth screener 41, for example of the star type, which receives the coarse fraction from the third screener 35 of the grinding and sorting unit 3. The fourth star screener 41 further separates and dissociates the materials, and in particular the gypsum from the paper and / or cardboard, into smaller pieces after passing through the grinding and sorting unit 3. The fourth screener 41 is set, for example, to a size larger than the threshold size, for example, a size larger than the threshold size by a factor greater than 1, which may be between 1.2 and 2. For example, when the threshold size is 1 or 1.2 mm, the second star screener 41 may be set to a size of 1.5 or 2 mm. The fourth Screener 41 thus generates a fine fraction, but which does not correspond to the final fraction, and a coarse fraction.

[0059] The finishing unit 4 then comprises at least one first rolling mill 42 which follows the fourth screener 41, and which receives the coarse portion of the fourth screener 41. This coarse portion may include, according to the example presented here, elements with dimensions up to 30 mm, or even 40 mm. The first rolling mill 42 comprises at least two rollers with a smooth surface, so as to crush the elements without shredding or grinding them, thus facilitating the separation of the gypsum from the other materials.

[0060] By smooth, we mean here the absence of patterns and / or roughness on the surface of the rollers which come into contact with the waste, at the scale of the threshold dimension.

[0061] The other materials are mainly paper and / or cardboard, which regain their initial shape and dimensions at the exit of the first rolling mill 42. The gap, or air gap, between the rollers of the first rolling mill 42 is set to a determined minimum value, for example corresponding to the threshold dimension.

[0062] The output of the first rolling mill 42 is then conveyed to a first final sorting device, which includes, for example, a fifth screener 43 and a third sieve 44. The fifth screener 43 is, for example, of the flip-flop type, with the mesh size set to the threshold dimension. The fine fraction from the fifth screener 43 is sent to the third sieve 44, for example, of the oscillating type, in order to feed the output belt 51 with a fine fraction corresponding to the final fraction. The fine fraction from the fourth screener 41 is also sent to the third sieve 44, so as to recover the particle size elements corresponding to the final fraction.

[0063] The coarse fraction from the fifth screener 43 is conveyed to a sixth screener 45, for example a flip-flop type, which also receives the rejects from the shredder 34 of the shredding and sorting unit. These rejects are mixed with the coarse fraction from the fifth screener 43 in the sixth screener 45, which has a mesh size set larger than the threshold size. For example, its mesh size is set to 8 mm. This allows large items, such as paper and cardboard, to pass through, even if gypsum is still attached to them. The coarse fraction from the sixth screener 45 can be recovered, for example, on a dedicated paper conveyor 60. It is assumed at this stage that the coarse fraction from the sixth screener 45 consists almost exclusively of paper and / or cardboard.

[0064] The fine portion from the sixth screener 45 then passes through a second rolling mill 46, also with smooth rollers, in order to crush and not grind or shred the elements. The mixture of the fine portion from the sixth screener 45 and the rejects from the crusher 34, which contain elements larger than the fine portion, increases the rolling efficiency in the second rolling mill 46. The gap of the second rolling mill 46 is set to a value less than or equal to the threshold dimension, of so that the last gypsum elements still attached to paper and / or cardboard and which are in the fine fraction of the sixth screener 45 detach without degrading the papers and / or cardboards.

[0065] The output of the second rolling mill 46 is then sent to a fourth sorting device, comprising, for example, a seventh screener 47 and a fourth sieve 48. The seventh screener 47 is, for example, of the flop type, with a mesh size set to the threshold dimension. The coarse fraction from the seventh screener 47 is sent onto the paper conveyor 60, and the fine fraction is sent to the fourth sieve 48, with a mesh size set to the threshold dimension, before joining the output conveyor 51.

[0066] The set of fine fractions recovered in the recovery unit 5, on the outlet belt 51, then forms the final fraction, comprising elements of particle size less than or equal to the threshold dimension, and containing almost exclusively gypsum.

[0067] The use of one or more rolling mills after grinding allows for the extraction of gypsum stuck to other materials, particularly paper and cardboard, with greater efficiency.

[0068] Indeed, when passing through a rolling mill, an element for example made of paper or cardboard, with plaster glued on it, is then deformed, crushed between the rollers, so that the plaster, being more brittle than the paper or cardboard, detaches and crumbles into smaller elements, while the paper or cardboard returns to its original shape after passing through.

[0069] By carrying out rolling after grinding, on elements of reduced dimensions due to grinding, the setting of the gap between the rollers of the rolling mill can be adapted to the target threshold dimension, allowing the recovery of gypsum in a more efficient manner.

[0070] Thus, the lower the threshold dimension, the more efficient the gypsum recovery. Indeed, thanks to the system described above, up to 99% of the gypsum can be recovered from a plasterboard with a paper backing. Furthermore, the final fraction recovered in the recovery unit 5 has a higher gypsum purity level than in the prior art, so that this final fraction can be used as a replacement for natural gypsum, directly from the quarry, with a replacement rate of approximately 60%.

[0071] As already indicated, the non-conforming elements exiting the preparation unit 2 can be processed in a dedicated circuit 6. Similarly, the coarse fractions exiting the finalization unit 4, and in particular from the screeners 43, 45 and 47, can also be processed in a dedicated circuit 7.

[0072] The system 1 thus described allows the implementation of a process for recycling plaster waste from the general public, in which the threshold dimension is previously determined based in particular on the desired result, then by passing the waste successively in unit 2 for preparation, unit 3 for crushing and sorting and unit 4 for finalization, so as to recover the final fraction in unit 5 for recovery.

Claims

Demands

1. System (1) for recycling plaster waste from the general public intended to recover a so-called final fraction comprising elements with a particle size less than or equal to a specified threshold dimension, the system (1) comprising: • at least one waste preparation unit (2), comprising at least one magnetic sorting device (27, 28, 29) for separating at least some of the metallic elements from the rest of the waste; • at least one waste crushing and sorting unit (3) from the preparation unit (2), comprising at least one crushing device (34) and at least one sorting device (31, 32, 35, 36) with a mesh size less than or equal to the threshold dimension, for separating the waste into a fine fraction and a coarse fraction; • at least one recovery unit (5) recovering at least part of the fine fraction from the crushing and sorting unit (3);the system (1) being characterized in that it further comprises at least one finishing unit (4) receiving at least part of the coarse fraction from the crushing and sorting unit (3), the finishing unit (4) comprising at least one rolling mill (42, 46) having a gap less than or equal to the threshold dimension followed by at least one final sorting device (43, 44, 47, 48) with a mesh less than or equal to the threshold dimension and feeding the recovery unit (5), and in that at least one rolling mill (42, 46) of the finishing unit (4) comprises smooth rollers, the set of fine fractions recovered by the recovery unit (5) corresponding to the final fraction.;

2. Recycling system (1) according to claim 1, wherein the crushing sorting device (31, 32, 35, 36) and the finalizing sorting device (43, 44, 47, 48) each comprise at least one flip-flop type screener (31, 35, 43, 47).

3. Recycling system according to any one of claims 1 or 2, wherein the dimension alone is less than or equal to 1.2 mm.

4. Recycling system according to claim 3, wherein the threshold dimension is less than or equal to 1 mm.

5. Recycling system (1) according to any one of the preceding claims, wherein the grinding device (34) comprises at least one reject outlet connected to the finalizing unit (4), such that the finalizing unit (4) receives both a coarse fraction from the sorting and grinding unit (3) and the rejects from the grinding device (34).

6. Recycling system (1) according to claim 5, wherein the finishing unit (4) comprises at least two successive rolling mills (42, 45), the reject outlet of the grinding device (34) being connected to the finishing unit (4) between the two rolling mills (42, 45), such that a first rolling mill (42) receives exclusively the coarse part from the sorting and grinding unit (3) and the second rolling mill (45) receives a mixture comprising the waste passed through the first (45) rolling mill and the reject part from the grinding device (34).

7. Recycling system (1) according to any one of the preceding claims, wherein the grinding device (34) comprises at least one paddle grinder.

8. Recycling system (1) according to any one of the preceding claims wherein the waste preparation unit (2) comprises a visual waste sorting table (24).

9. A method for recycling plaster waste from the general public intended to recover a so-called final fraction comprising elements with a particle size less than or equal to a determined threshold dimension, by implementing the system (1) according to any one of the preceding claims, the method comprising: • determining the threshold dimension; • setting the crushing and sorting unit (2) and the finalizing unit (4) with the determined threshold dimension; • passing the waste through the recycling system (1).

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