Tanning process with recovery of water and chemical products

Abstract

A tanning process with recovery of water and chemical products comprising at least the steps of: - introducing one or more hides in a containment chamber thermally insulated from the outside, in which temperature, humidity and quantity of liquid inside are constantly monitored; - treating the hides, by feeding to containment chamber a treatment liquid in nebulized form selected from the group comprising water or a mixture thereof with one or more chemical products adapted to give to said hides the desired mechanical, physical and aesthetic properties; - extracting the hides from the containment chamber; characterized in that, subsequently to the step of treating the hides, said process comprises a rinsing procedure comprising at least the steps of: - discharging the treatment liquid not absorbed by the hides from the containment chamber; - accumulating the treatment liquid not absorbed by the hides in a collection tank; - rinsing the containment chamber by feeding a rinsing liquid selected from the group consisting of water or a mixture thereof with one or more detergent products; - discharging the contaminated rinsing liquid after use from the containment chamber; - accumulating the contaminated rinsing liquid after use in the collection tank; - treating the accumulated rinsing liquid in the collection tank in order to separate the water from the chemical products; - recovering the water and the chemicals products generated by the step of treating the liquid accumulated in the collection tank, in order that they can be at least partially reused in the same tanning process or in a subsequent tanning process.

Description

[0001] TANNING PROCESS WITH RECOVERY OF WATER AND CHEMICAL PRODUCTS

[0002] The present invention relates to a tanning process with recovery of water and chemical products.

[0003] More specifically, reference is made to a tanning process in which water and chemical products are recovered from liquid effluents resulting from the various leather tanning and retanning treatments.

[0004] As is well known, tanning is an industrial process that transforms raw animal hides into leather that can be used for various products. Re-tanning, on the other hand, is a further treatment, that is performed after tanning in order to improve the properties of the leather, such as its softness, elasticity, color and water resistance.

[0005] WO2022 / 128033A1 discloses a tanning process equipment including a tanning container, a controller and temperature regulating equipment; the controller controlling the temperature in the tanning container on the basis of temperature setpoint input to or established by the controller; the tanning process comprising the steps of initially determining process parameters, on the basis of animal hide characteristics, the animal hide characteristics including the animal hide type and weight; the process parameters including time, temperature, start pH and end pH or any combination thereof; executing the tanning process of the animals hides on the basis of the process parameters in the tanning container under atmospheric pressure. The tanning process involves addition of tanning agents to the animal hides in the tanning container and addition of water in an amount of less than 10% bw of the animal hides.

[0006] CN111304376A discloses a tanning method and device. The method comprises the steps of raw material pretreatment; tanning treatment, rinsing, neutralizing, and a finishing treatment. The device comprises a base, a fixed frame and a rotating cylinder. The fixed frame is mounted on the base; the rotating cylinder is mounted on the fixed frame and is rotatably connected with the two ends of the fixed frame; a wastewater recycling bin is mounted below the base and communicates with the base. A plant tanning agent, ammonium sulfate and sodium chloride, serve as main components of the tanning liquid; neutralizing is carried out through sodium bicarbonate.

[0007] EP0960948A1 discloses a drum for milling, dyeing and tanning. The tanning drum is supplied with water and liquid chemicals via nozzles positioned near its axis of rotation. Air is circulated via a fan, filter and heater. Temperature probes are used to control operation of the fan and heater.

[0008] The conventional tanning processes require intensive use of water and chemical products, which can have a significant impact on the environment. Therefore, recycling both water and chemical products in tanning processes is crucial to make the industry more sustainable.

[0009] Various techniques are known to remove contaminants and harmful chemicals from water used in tanning processes, including sedimentation, which removes suspended solids, and filtration, which allows further cleaning of the water through filters.

[0010] Wastewater may also undergo biological oxidation processes, which essentially consist of using bacteria to decompose organic materials, and disinfection with chlorine or other methods to eliminate pathogens.

[0011] Treated water can be reused in the various stages of tanning processes, such as leather washing, reducing the demand for fresh water and minimizing environmental impact.

[0012] As for the recovery of chemical products, and in particular chromium, which is one of the main tanning agents used, chemical precipitation is generally employed, effected by adding substances that form insoluble compounds with the chromium, which can then be removed, or the use of membrane technologies that allow advanced filtration to separate the chromium from the water.

[0013] Sulphates and chlorides can be recycled and reused in tanning baths through chemical separation processes, while enzymes and biological products can be recycled and used in further leather treatment cycles.

[0014] The recovery of water and chemicals products in tanning processes varies depending on several factors, including the type of process, the technologies used and the resource management practices adopted by the tanning company.

[0015] In particular, as regards washing water, which accounts for a large portion of the water used in traditional tanning processes, up to 60-70% of the water used can be recovered. Wastewater, on the other hand, can generally be reused in a more significant percentage, often up to 80-90%.

[0016] Up to 98% of the chromium used can be recovered through the precipitation and filtration processes mentioned above.

[0017] The recovery of tannic agents is more complex, but methods can be used to extract and reuse tannic extracts, recovering up to 50-60% of them.

[0018] Other chemical products, such as salts and imbibition agents, can be partially recovered and reused. The recovery percentage varies depending on the type of substance and technology used, but is often around 40-60%.

[0019] From the above, it is clear that there remains ample scope for improving the recycling of water and chemical products in tanning processes, and how this represents a fundamental step towards making this industry more sustainable, reducing environmental impact and optimizing the use of resources.

[0020] The aim of the present invention is therefore to improve the performance, in terms of efficiency, of systems for recovering water and chemical products from the tanning industry, by eliminating the drawbacks of the prior art and thus providing a tanning process with recovery of water and chemicals that is substantially closed-loop, which allows minimizing the use of new resources and maximizing recovery.

[0021] Within the scope of this aim, a particular object of the invention is to provide a tanning process that allows to decrease the amount of chemical waste and contaminated water not reused.

[0022] A further object of the invention is to provide a tanning process that reduces the demand for clean water and new chemical products, thereby decreasing operating costs.

[0023] A further object of the invention is to provide a tanning process that reduces pollution of water bodies and soil, contributing to the sustainability of the tanning industry.

[0024] A further object of the invention is to provide a tanning process that allows for greater flexibility in the use of water and chemical products, with their almost total recoverability.

[0025] A further object of the invention is to provide a tanning process that makes it possible to handle the chemical products used in such a way as to avoid contamination with other products (cross contamination).

[0026] This aim and objects, as well as others that will become better apparent hereinafter, are achieved by a tanning process with recovery of water and chemicals comprising at least the steps of: introducing one or more hides in a containment chamber thermally insulated from the outside, in which temperature, humidity and quantity of liquid inside are constantly controlled; treating said hides, by feeding to said containment chamber a treatment liquid in nebulized form selected from the group comprising water or a mixture thereof with one or more chemical products adapted to give to said hides desired mechanical, physical and aesthetic properties; extracting said hides from said containment chamber; characterized in that, subsequently to said step of treating said hides, said process comprises a rinsing procedure comprising at least the steps of: discharging the treatment liquid not absorbed by the hides from the containment chamber; accumulating the treatment liquid not absorbed by the hides in a collection tank; rinsing said containment chamber by feeding a rinsing liquid selected from the group consisting of water or a mixture thereof with one or more detergent products; discharging the contaminated rinsing liquid after use from the containment chamber; accumulating the contaminated rinsing liquid after use in the collection tank; treating the accumulated rinsing liquid in the collection tank in order to separate the water from the chemical products; recovering the water and the chemicals products generated by the step of treating the liquid accumulated in the collection tank, in order that they can be at least partially reused in the same tanning process or in a subsequent tanning process.

[0027] Further features and advantages will become better apparent from the description of a preferred, but not exclusive, embodiment of a tanning process according to the invention, illustrated by way of non-limiting example the accompanying drawings wherein:

[0028] Figure 1 is a schematic representation of the steps of an embodiment of the tanning process according to the present invention;

[0029] Figure 2 is a schematic representation of an embodiment of a machine for performing the tanning process according to the present invention.

[0030] With reference to the figures, a tanning process 100, with recovery of water and chemical products, is described according to the present invention.

[0031] The tanning process 100 is advantageously implemented by a machine 1 , illustrated in figure 2.

[0032] The tanning process 100 comprises a step 110 of introducing one or more hides inside a containment chamber 2 thermally insulated from the external environment, wherein temperature, humidity and quantity of liquid present inside are constantly monitored.

[0033] For the purposes of the present invention, the term "controlling" refers to the possibility of measuring and regulating temperature and / or humidity and / or quantity of liquid present in the containment chamber 2 by acting on the relevant parameters.

[0034] For example, in the embodiment illustrated in figure 2 of the machine 1 , the containment chamber 2 is formed by an insulating casing 3, rotating around its own axis, within which a perforated wall 4 is placed that is configured to delimit a zone 5 adapted to receive the hides inside.

[0035] The insulated enclosure 3 is provided with a selectively sealable loading / unloading opening by means of a lid. The perforated wall 4 has openings configured to allow the passage of air and liquids. An air handling unit 6 is associated with the insulated enclosure 3 and is subservient to hardware and software means, which are configured to generate and maintain, within the containment chamber 2, an optimal temperature and / or humidity and / or amount of water for performing the tanning process 100.

[0036] The tanning process 100 further comprises a step 120 of treating the hides by feeding a treatment liquid to the containment chamber 2. The treatment liquid may comprise water or a mixture thereof with one or more chemical products suitable to give the desired mechanical, physical and aesthetic properties to said hides.

[0037] The quantity of water and / or chemical products used during the step 120 of treating the hides may vary depending on various aspects; however, this quantity, while being such as to completely wet the hides, remains contained within particularly low values with respect to the known technique. In particular, in the tanning process 100, an amount of water less than 200% by weight of the hides is used, and an amount of chemical products reduced to about 30% by weight, with reference to the weight of the hides, compared to the known art.

[0038] Advantageously, the treatment liquid is fed to the containment chamber 2 in nebulized form, for example by means of feeding means 7 provided with nozzles or other devices capable of delivering said liquid in the form of tiny droplets or aerosols, so as to allow and promote its uniform and cohesive absorption by the hides. This feature makes it possible to avoid immersing the hides in baths of treatment, as is the case with conventional procedures, further reducing the use of water and chemicals compared to the known technique.

[0039] By way of example, the chemical products used in the treatment step 120 come from the group that includes descaling agents, macerating agents, pickling agents, tanning agents, cross-linking agents, soaking agents, degreasing agents, re-tanning agents, neutralizing agents, coloring agents and fat-liquoring agents.

[0040] In carrying out the tanning process 100, the step 120 of treating the hides may be repeated a sufficient number of times in order to obtain the desired result, and each time a different treatment liquid may be employed depending on the type of processing to be carried out.

[0041] For example, according to an embodiment of the invention, the step 120 of treating the hides is performed a first time, taking the name of washing, by employing clean water as treatment liquid, the water being sprayed on the hides in an amount up to 100% of their weight, in order to remove any impurities and residues present.

[0042] After washing, the step 120 of treating the hides is repeated, taking the name of decalcination, by spraying the hides with decalcifying agents that serve to free them from the products used during calcination.

[0043] After decalcination, the step 120 of treating the hides is repeated again, taking the name of maceration, by soaking the hides with macerating agents suitable for removing the keratin degradation products, hair and epidermis residues.

[0044] Following maceration, the step 129 of treating the hides is repeated again, taking the name of re-washing, by using only clean water as treatment liquid, the water being sprayed onto the skins in quantities up to 100% of their weight, in order to eliminate any impurities and residues present.

[0045] When the hides have been re-washed, the step 120 of treating the hides is repeated again, taking the name of "pickling", by soaking the hides with pickling agents, i.e. acidifying agents that have the task of bringing the hides to an optimal pH value for the penetration and fixation in the dermis fibers of the tanning agents used subsequently.

[0046] At this point, the step 120 of treating the hides is repeated once again, taking the name of tanning, by soaking the hides with tanning agents that are irreversibly fixed to the leather proteins, in order to block any possibility of attack by microorganisms.

[0047] Once the hides have been tanned, the step 120 of treating the hides is repeated again, taking the name of cross-linking, by spraying the hides with cross-linking agents that fix the tanning agents permanently onto the hides.

[0048] It should be noted that the steps described above may follow one another in a different order, or certain steps indicated as separate may in practice be grouped together or repeated several times.

[0049] According to a further embodiment of the invention, wherein the tanning process is used to carry out a re-tanning of the hides, the step of treating the hides, taking the name of wetting, is first carried out by spraying clean water on the hides.

[0050] Following wetting, the step 120 of treating the hide is repeated, taking the name of soaking, by soaking the hides with soaking and degreasing agents, in order to free them from the coarsest dirt.

[0051] The step 120 of treating the hides is then repeated once again, taking the name of re-tanning, soaking the hides with re-tanning agents that have the function of improving their appearance, filling the empty spaces, so as to give them the desired fullness and compactness.

[0052] Subsequently, the step 120 of treating the hides is repeated again, taking the name of neutralization, by spraying the hides with neutralizing agents that bring the hides to an optimal pH value for the penetration and fixation of the chemical agents used subsequently.

[0053] At this point, the step 120 of treating the hides is repeated, taking the name of dyeing, by soaking the leathers with dyeing agents.

[0054] The step 120 of treating the hides is then repeated once again, taking the name of fat-liquoring, by soaking the hides with fat-liquoring agents that essentially 'lubricate' their internal fibrous structure, giving them particular organoleptic properties.

[0055] It should be noted that the above-described steps may follow one another in a different order, or some steps indicated as separate may in practice be grouped together or repeated several times.

[0056] The tanning process 100 then comprises a step 130 of extracting the hides from the containment chamber 2.

[0057] Thereafter, the hides are generally spread out on special supports, before undergoing subsequent mechanical actions, such as, for example, splitting and shaving.

[0058] According to the present invention, the tanning process 100 provides that a rinsing procedure 200 is performed following the step 120 of treating the hides.

[0059] Advantageously, the rinsing procedure 200 is implemented by employing suitable rinsing means 8.

[0060] The rinsing procedure 200 comprises a step 210 of discharging the treatment liquid not absorbed by the hides from the containment chamber 2, for example, by means of a pump.

[0061] The rinsing procedure 200 further comprises a step 220 of accumulating the treatment liquid not absorbed by the hides, and drained from the containment chamber 2, in a collection tank 9.

[0062] If necessary, the rinsing procedure 200 further comprises a step 215 of separating a liquid fraction of the treatment liquid not absorbed by the hides and skins from a solid fraction comprising, for example, particulates or other suspended solids.

[0063] Thus, the rinsing procedure 200 comprises a step 230 of rinsing the containment chamber 2 and the treatment liquid supply means 7 by feeding to them a rinsing liquid which may be water or a mixture thereof with one or more cleaning agents appropriate for the purpose.

[0064] Advantageously, the rinsing liquid is fed to the containment chamber 2 in nebulized form, for example by means of the same feed means 7 as the treatment liquid, so that they too are rinsed.

[0065] Thereafter, the rinsing procedure 200 comprises a step 240 of discharging the contaminated rinsing liquid after use from the containment chamber 2 and a step 250 of accumulating such liquid in the collection tank 9.

[0066] If necessary, the rinsing procedure 200 also comprises a step 245 of separating a liquid fraction of the contaminated rinsing liquid after use from a solid fraction.

[0067] The rinsing procedure 200 further comprises a step 260 of treating the liquid accumulated in the collection tank 9 in such a way as to separate the water from the chemical products.

[0068] By way of example only, various embodiments of the rinsing procedure 200 provide that the step 260 of treating the liquid accumulated in the collection tank 9 is implemented, for example, by a filtration procedure (ultrafiltration / nanofiltration, reverse osmosis, etc.) or by an evaporation procedure, or by other known separation techniques.

[0069] If necessary, the rinsing procedure 200 also includes a step 255 of adding one or more additives to the liquid accumulated in the collection tank 9, prior to the step 260 of treating that liquid.

[0070] By way of example, various embodiments of the rinsing procedure 200 provide that the additives used are from the group comprising stabilizing agents, anti-foaming agents, preserving agents, thermal stabilizing agents, anti-scaling agents and pH adjusting agents.

[0071] The rinsing procedure 200 further comprises a step 270 of recovering the water and chemicals generated by the step 260 of treating the liquid accumulated in the collection tank 9, so that they can be at least partially reused in the tanning process 100 or in a subsequent tanning process.

[0072] It should be noted that the amount of water and chemical products generated by the step 260 of treating the liquid accumulated in the collection tank 9 is close to 100% of the amount of liquid contained therein.

[0073] The rinsing procedure 200 also includes a step 280 of disposing, through the intended disposal cycle, the solid fractions generated by the step 215 of filtering the treatment liquid not absorbed by the skins and by the step 245 of filtering the contaminated rinsing liquid after use.

[0074] It should be noted that, if in carrying out the tanning process 100, the step 120 of treating the hides is repeated several times using a different treatment liquid from the previously used treatment liquid, it is preceded each time by the rinsing procedure 200, in such a way as to prevent cross contamination from occurring.

[0075] In practice, it has been seen that the invention achieves its intended aim and objects by providing a substantially closed-loop tanning process, which minimizes the use of new resources and maximizes the recovery of water and chemicals, making hides processing operations decidedly more sustainable.

[0076] In fact, the tanning process according to the invention allows for almost total recovery of the used water and chemicals, reducing the amount of non-reusable chemical waste and contaminated water to almost zero.

[0077] The tanning process according to the invention also makes it possible to considerably reduce the amount of water to be purified.

[0078] This not only results in considerable savings in economic terms, but also protects the environment and the health of the workers.

[0079] This application claims the priority of Italian Patent Application No. 102024000020548, filed on September 16, 2024, the subject matter of which is incorporated herein by reference.

Claims

CLAIMS1. Tanning process (100) with recovery of water and chemical products comprising at least the steps of: introducing (110) one or more hides in a containment chamber (2) thermally insulated with respect to the outside, in which temperature, humidity and quantity of liquid inside are constantly controlled; treating (120) said hides, by feeding, to said containment chamber (2), a treatment liquid in nebulized form, selected from the group comprising water or a mixture thereof with one or more chemical products adapted to give to said hides desired mechanical, physical and aesthetic properties; extracting (130) said leathers from said chamber of containment (2); said process being characterized in that, subsequently to said step of treating (120) said hides, it comprises a rinsing procedure (200) comprising at least the steps of: discharging (210) treatment liquid not absorbed by said hides from said containment chamber (2); accumulating (220) said treatment liquid not absorbed by said hides in a collection tank (9); rinsing (230) said containment chamber (2), by feeding to said containment chamber (2) a rinsing liquid selected from the group consisting of water or a mixture thereof with one or more detergent products; discharging (240) said contaminated rinsing liquid after use from said containment chamber (2); accumulating (250) said contaminated rinsing liquid after use in said collection tank (9); treating (260) said accumulated rinsing liquid in said collection tank (9) in order to separate the water from the chemical products; recovering (270) said water and said chemical products generated by said step (260) of treating the liquid accumulated in said collection tank (9), in order that they can be at least partially reused in said tanning process (100) or in a subsequent tanning process.

2. The tanning process (100) according to claim 1 , characterized in that said step of treating (260) the liquid accumulated in said collection tank (9) is carried out by a method selected from the group consisting of filtration, evaporation or centrifugation.

3. The tanning process (100), according to one or more of the preceding claims, characterized in that, subsequently to said step of discharging (210) the treatment liquid not absorbed by said hides from said containment chamber (2), said process comprises a step of separating (215) a liquid fraction of said treatment liquid not absorbed by said hides from a solid fraction.

4. The tanning process (100) according to one or more of the preceding claims, characterized in that, subsequently to said step of discharging (240) the contaminated rinsing liquid after use from said containment chamber (2), said process comprises a step of separating (245) a liquid fraction of said contaminated rinsing liquid after use from a solid fraction.

5. The tanning process (100), according to one or more of the preceding claims, characterized in that, subsequently to said step of separating (215) a liquid fraction of said treatment liquid not absorbed by said hides from a solid fraction and said step of separating (245) a liquid fraction of said rinsing liquid contaminated after use from a solid fraction, said process comprises a step of disposing (280) said solid fractions.

6. The tanning process (100), according to one or more of the preceding claims, characterized in that, preliminarily to said step of treating (260) the liquid accumulated in said collection tank (9), said process comprises a step of adding (255) one or more additives to said liquid accumulated in said collection tank (9).

7. The tanning process (100), according to one or more of the preceding claims, characterized in that said additives are selected from the group comprising stabilizing agents, anti-foaming agents, preserving agents, thermal stabilizing agents, anti-scaling agents and pH adjusting agents.

8. The tanning process (100), according to one or more of the preceding claims, characterized in that said step of treating (120) said hides is repeated for a selected number of times.

9. The tanning process (100), according to one or more of the preceding claims, characterized in that, if said step of treating (120) said hides is repeated using a treatment liquid different from the previously used treatment liquid, said step of treating (120) said hides is preceded by said rinsing procedure (200), in order to avoid cross contamination.

10. The tanning process (100), according to one or more of the preceding claims, characterized in that said chemical products are selected from the group consisting of de-liming agents, macerating agents, pickling agents, tanning agents, crosslinking agents, soaking agents, degreasing agents, re-tanning agents, neutralizing agents, coloring agents, fat-liquoring agents.

11. The tanning process (100), according to one or more of the preceding claims, characterized in that the amount of treatment liquid fed to said containment chamber (2) in said step of treating (120) said hides is less than 200% of the weight of said hides.

12. The tanning process (100), according to one or more of the preceding claims, characterized in that the amount of water and chemical products generated by said step of treating (260) said liquid accumulated in said collection tank (9) is close to 100% of the amount of liquid accumulated in said collection tank (9).

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