Control of tanning drum temperature during tanning process of animal hide

Abstract

The invention relates to a method for adjusting the internal temperature of a tanning drum during a dry tanning step of a tanning process for tanning a plurality of animal skins. The tanning drum comprises a central axis, a mechanical driver and an animal raw hide inlet. The mechanical drive is connected to an electric motor, wherein the electric motor is configured to rotate the tanning drum via the mechanical drive. The internal temperature is at least partially adjusted by a first temperature adjusting device and / or at least partially adjusted by a second temperature adjusting device. The first temperature regulation device comprises a heating element and the second temperature regulation device comprises the motor and the mechanical drive, which provides heat from the rotation of the tanning drum when the tanning drum comprises the plurality of animal skins.

Description

Technical Field

[0001] The present invention relates to a method of regulating the internal temperature of a tanning drum during the tanning step of a tanning process, and to a tanning system to achieve such temperature control. Background Art

[0002] Known tanning processes usually use large amounts of water during the tanning step of the tanning process. This large amount of water in the tanning drum acts as a huge thermal energy storage, which makes it difficult to perform temperature regulation of the internal temperature of the tanning drum. As a result, the tanned hides may be damaged and the quality may be reduced during the tanning process. Summary of the invention

[0003] The inventors have recognized the above problems and challenges associated with regulating the internal temperature of a tanning drum and have subsequently developed the following invention which benefits from the possibility of regulating the internal temperature of a tanning drum using one of two heating sources when the tanning drum contains no water or very low water content.

[0004] The present invention relates to a method for regulating the internal temperature of a tanning drum during a tanning step of a tanning process for tanning a plurality of animal hides, wherein the tanning drum comprises a central axis, a mechanical drive and an animal hide inlet, wherein the mechanical drive is connected to an electric motor, wherein the electric motor is configured to rotate the tanning drum via the mechanical drive, wherein the method comprises the step of regulating the internal temperature at least partially by a first temperature regulating device and / or at least partially by a second temperature regulating device, wherein the first temperature regulating device comprises a heating element, and wherein the second temperature regulating device comprises the electric motor and the mechanical drive, which provide heat from the rotation of the tanning drum when the tanning drum comprises the plurality of animal hides.

[0005] According to an advantageous embodiment of the invention, said tanning step is a dry tanning step.

[0006] Tanning is understood to be a part of the process of treating animal skins and hides (collectively referred to as hides) to produce leather. The tanning process changes the protein structure of the hide, making it more durable and less prone to decomposition. Therefore, the tanning process includes multiple steps, wherein the tanning step is a step, and during this period, the internal temperature of the tanning drum is regulated by the present invention. The dry tanning step may refer to a tanning step in which no tanning liquid is required to dissolve the tanning agent. During the dry tanning step, a substance in a gaseous state such as water may be introduced to regulate the temperature inside the tanning drum.

[0007] Animal hides are understood to be natural skins and hair from animals such as, for example, cattle. Hides can be products from the cattle food industry and can be processed into leather. Part of this process is the tanning process, the temperature of which is adjusted according to the invention.

[0008] A mechanical drive is understood to be a gear, pulley or similar device fixed to the tanning drum, meshing with a chain, gear, belt or similar device to convert the rotation of the motor into rotation of the tanning drum. Note that the motor may be controlled by a motor drive.

[0009] The central axis is to be understood as the geometrical centre of the tanning drum, ie not necessarily the physical axis of the tanning drum. The central axis may coincide with the centroid of the circular shape of the tanning drum when seen in end view.

[0010] Using both a first and a second temperature regulating device, ie heating from two different heating sources, is advantageous because a reduction in the power required to increase the temperature inside the tanning drum during the tanning step is achieved compared to known tanning processes.

[0011] In addition, since the tanning step is a dry (also known as low water tanning process) tanning step, the temperature inside the tanning drum can be adjusted faster and more accurately, because no liquid is added to the tanning drum before the tanning step. Therefore, the volume of tanning liquid for the tanning step that needs to be heated is reduced. It should be mentioned that the tanning drum may include liquid used in the rawhide processing before the tanning step. In addition, if required in the tanning step, in addition to the tanning agent, a small amount of liquid may be required to dissolve the ingredients. In addition, the rawhide may have absorbed liquid / be wet during the pre-tanning step and therefore contain liquid that can be found at the bottom of the tanning drum.

[0012] Furthermore, the amount of tanning agent required is reduced since it does not have to be dissolved in the tanning liquor, such as water.

[0013] A first temperature regulating device is understood to be a device which regulates the temperature at least indirectly by using a heating element for heating the fluid in the tanning drum or for heating the fluid outside the tanning drum before the fluid is introduced into the tanning drum.

[0014] The second temperature regulating device is understood to regulate the temperature by friction between the animal skin / animal hide and the drum wall as the animal skin / hide rotates in the tanning drum. This contribution to increasing the internal temperature of the tanning drum can be said to be free, because the rotation of the tanning drum is an essential part of the tanning process. Nevertheless, if the friction between the hide and the inner drum surface does not generate heat, a higher rotation speed may be required to promote the generation of heat compared to the operating speed required for the tanning process. Such a higher rotation speed may result in a slight increase in the energy required to rotate the drum. When certain tanning agents such as vegetable tanning agents are used, the heat generated by the drum rotation may be sufficient to reach the required temperature.

[0015] Since the water required in the tanning step is significantly reduced, the temperature control according to the present invention is possible and facilitates sufficiently accurate temperature control and thereby improves the quality of the tanning. In addition, a faster response time to temperature changes is advantageous. In addition, the speed at which the required temperature of the tanning step is reached is increased, resulting in a better tanning process by fixing or bonding the tanning agent to the animal hide. Therefore, the temperature can be increased to fix the chromium, and the pH value can be increased to increase the shrinkage temperature.

[0016] According to an advantageous embodiment of the invention, the tanning drum further comprises a temperature sensor.

[0017] The advantage of the temperature sensor is that a direct measurement of the temperature inside the tanning drum is provided and thereby a more accurate temperature and a faster response time to temperature changes during the tanning step can be obtained. Thus, the risk of reaching a certain temperature during the tanning step which is, for example, too high for a particular hide and which could damage the hide is mitigated.

[0018] According to an advantageous embodiment of the invention, said temperature regulation of said tanning step is automatically controlled by a controller based on the temperature measured by said temperature sensor.

[0019] Providing temperature measurements from the temperature sensor to the controller is advantageous because an automatic temperature control loop is thereby established, based on which the controller can control the injection of temperature regulated fluid into the tanning drum or adjust the rotational speed of the tanning drum and thereby regulate the temperature increase.

[0020] According to an advantageous embodiment of the invention, the tanning drum further comprises at least one, preferably at least two, most preferably at least three air release valves.

[0021] Two or three air release valves are advantageous because during the rotation of the tanning drum there is always one air release valve located in the upper part of the tanning drum / at or above the central axis of the tanning drum. In this way, when the tanning drum rotates, one air release valve always provides a free passage from the inside of the tanning drum to the outside of the tanning drum. Therefore, when fluid is introduced into the tanning drum, the pressure inside the tanning drum does not increase.

[0022] According to an advantageous embodiment of the invention, the tanning drum comprises a fluid inlet valve, which controls the inlet of fluid into the tanning drum.

[0023] The fluid inlet may be located at the central axis of the tanning drum. The fluid may enter a fluid flow guide which may be referred to as a wash plate. From the wash plate the fluid may enter the hide compartment HC of the tanning drum. The wash plate may include two opposite ends connected by a central fluid of the tanning drum. A plurality of holes may be provided in each distal end of the wash plate. These holes may be used as a guide device for distributing the fluid into the tanning drum. The distribution of the fluid is advantageous because the hides within the tanning drum are not in direct contact with fluid or gaseous form which, at a given temperature, may damage the hides during the tanning process.

[0024] In principle, the fluid inlet valve may be located anywhere in the conduit from the fluid source / fluid heater to the tanning drum inlet.

[0025] The advantage of a fluid inlet valve is that it simplifies the control of the input of a fluid such as water in gaseous form such as steam. Thus, the total amount of water introduced can be monitored and controlled and excess water can be avoided. Excess water could further increase the amount of tanning agent required in the tanning step, which is avoided.

[0026] The terms steam and vapor are used interchangeably. As used herein, the term "steam" refers to a substance in a gaseous state. Steam may come from, for example, an organic source, such as ether or water.

[0027] The fluid inlet valve may be implemented as a regulating valve, a solenoid valve, a pneumatic valve, etc. or multiple conduits with different orifices. The latter may result in an additional level of control over the amount of water introduced into the tanning drum.

[0028] According to an advantageous embodiment of the invention, said tanning drum comprises a liquid content without a liquid surface inside said tanning drum.

[0029] The liquid surface is to be understood as the liquid surface from which the liquid column can be measured. Thus, the liquid column is measured from this surface to the lowest point of the tanning drum.

[0030] When the tanning drum rotates, the liquid in the tanning drum may follow the hide up and down and around the inside of the tanning drum due to its rotation. Therefore, during rotation, the liquid inside the tanning drum may not collect, and therefore there may be no visible liquid surface inside the tanning drum.

[0031] Furthermore, the amount of liquid inside the tanning drum may be limited, so that even after half a second or a few seconds, such as for example after the tanning drum has been at rest for 1 to 10 seconds, the liquid inside the tanning drum that is not contained by the hides still does not collect at the bottom of the tanning drum. Therefore, after such a rest period, such as any natural number of rest periods between 1 and 10 seconds, it may not be possible to measure a liquid level of more than 20 cm, such as more than 15 cm, such as more than 5 cm or any natural number of liquid levels between 0 cm and 25 cm. At least this is the case if the hides are removed from the tanning drum before measuring the liquid level.

[0032] According to an advantageous embodiment of the invention, said tanning drum contains a liquid content having a liquid surface inside said tanning drum being below said central axis during said tanning step.

[0033] Since the tanning step of the present invention is a dry tanning step, no tanning liquid is required to dissolve the tanning agent. Therefore, the introduction of the fluid can be used only for temperature regulation. However, as mentioned above, during the tanning step, there may be some carryover liquid (also referred to as liquid) in the tanning drum from the previous process performed inside the tanning drum and contained in the rawhide. Preferably, after the tanning drum does not rotate for a period of time, the surface of this liquid (i.e., the liquid not contained in the rawhide) is lower than the central axis. Such a non-rotating time period can be between 5 and 10 minutes and can be called a sedimentation time.

[0034] According to an advantageous embodiment of the invention, the distance from the liquid surface to the central axis during the stationary state of the tanning drum is at least 25 cm, preferably at least 50 cm, most preferably at least 100 cm.

[0035] Since the tanning drum comprises a plurality of hides, there may be no liquid surface, such as a horizontal liquid surface itself. However, an estimated liquid surface and an estimated liquid surface of the hides in the tanning drum below the central axis can still be determined. Preferably, the distance between this estimated liquid surface and the central axis is at least 100 cm.

[0036] If the hide is removed from the tanning drum, the liquid surface will drop and the distance to the central axis will increase. Therefore, if the estimated liquid surface cannot be determined, the hide can be removed from the tanning drum and a more accurate distance from the then horizontal liquid surface to the central axis can be determined. Preferably, the distance between the estimated liquid surface and the central axis is at least 100 cm.

[0037] Stationary is understood to mean that the tanning drum is not rotating for a period of time sufficient for the liquid inside the tanning drum to settle at a substantially horizontal surface.

[0038] According to an advantageous embodiment of the invention, when said plurality of animal hides are dry, said tanning drum contains a liquid content of less than 10%, 20%, 25%, 30%, 40%, 50% by weight of said plurality of animal hides.

[0039] With regard to this specific method of measuring the water content in the tanning drum, it should be mentioned that this is a measurement with reference to the liquid contained in the hides. Thus, the hides are considered dry when they are considered ready for leather production / considered as a commercial product. Thus, when it is said that a tanning drum contains less than 50% dry hides by weight, the weight of the liquid at the end of the tanning process is 50% less than the weight of the plurality of dry hides in said drum.

[0040] According to an advantageous embodiment of the invention, said tanning drum contains a liquid content of less than 10%, 20%, 25%, 30%, 40%, 50% by weight of said plurality of animal hides when said plurality of animal hides is soaked.

[0041] With regard to this specific method of measuring the liquid content in a tanning drum, it should be mentioned that this is a measurement method with reference to the liquid contained in the hide. Therefore, an animal hide is considered soaked when it can no longer hold liquid. Therefore, when it is said that a tanning drum contains less than 50% by weight of soaked hides, the weight of liquid at the end of the tanning process is 50% less than the weight of a number of soaked hides in the drum.

[0042] According to an advantageous embodiment of the invention, said tanning drum contains a liquid content which is less than 110%, 120%, 130%, 140%, 150% of the liquid contained in said plurality of animal hides.

[0043] With regard to this specific method of measuring the liquid content in the tanning drum, it should be mentioned that this is a measurement with reference to the liquid contained in the hide. Therefore, the liquid content in the tanning drum is 100% when the hide can no longer hold liquid. Therefore, when it is said that the tanning drum contains less than 150% liquid, 100% of the liquid is contained by the hide and the other 50% of this amount is either added during the tanning process or is a holdover from previous steps in the preparation of the hide.

[0044] The percentages are given with reference to the moisture content in the hides. The moisture content in the hides must not exceed 100%. The additional water may come, for example, from the pickling tank hold-up water (e.g. between 10% and 40%, ideally less than 10%), 2% dilution water and possibly a small contribution from the steam inlet.

[0045] According to an advantageous embodiment of the invention, the amount of liquid added during said tanning step is less than the amount of liquid present inside said tanning drum at the beginning of said tanning step.

[0046] When liquid is used to raise or lower temperature, it can be introduced in a gaseous form such as vapor or aerosol. Introducing the fluid in this manner is advantageous because a minimum amount of fluid is required to obtain the desired temperature regulation.

[0047] A common advantage of the above methods of defining a limited content of water in the tanning drum is that it reduces the amount of water used in the tanning step. Thus, reducing the amount of water reduces the amount of tanning required, resulting in a reduced impact on the environment. Furthermore, the amount of waste water is reduced, which means that a lower volume of said waste water needs to be treated, which further reduces the impact of the tanning step on the environment.

[0048] Common to all the above methods of defining the liquid content in the tanning drum is that the amount of liquid is measured at the end of the tanning step. The amount of liquid may be partly carryover from previous steps in the preparation of the hides and partly liquid added during the tanning step.

[0049] For all the above mentioned methods of defining the liquid content in the tanning drum it should be mentioned that the liquid contained in or added to the tanning drum during the tanning step is used to regulate (upwards or downwards) the temperature inside the tanning drum.

[0050] For all of the above methods of defining the liquid content of the tanning drum, it should be noted that the liquid added to the tanning drum may be water and therefore, in this context, the term liquid may be replaced by the term water.

[0051] According to an advantageous embodiment of the invention, said plurality of animal hides comprises a liquid content according to a liquid holding capacity.

[0052] According to an advantageous embodiment of the invention, the moisture content of said plurality of animal hides exceeds the water retention capacity.

[0053] As mentioned above, the term "soaked" refers to the state of the hide in which it retains water in accordance with its maximum water holding capacity. The maximum water holding capacity may vary depending on the animal species from which the animal hide is derived.

[0054] The term "maximum water holding capacity" as used herein refers to the amount of water that can be bound to the hide. Therefore, the water holding capacity does not refer to the amount of water that can drip directly from the hide after soaking.

[0055] In addition, the hides may contain excess water that exceeds the maximum water holding capacity. Excess water that exceeds the maximum water holding capacity may come from direct transfer to the tanning drum from the soaking vessel in which the pre-tanning step is performed, or from incomplete drainage of the drum in which the pre-tanning step is performed. Thus, "exceeding the maximum water holding capacity" is caused by not letting the hides drip or not draining completely before the tanning process. This excess water is sometimes also referred to as held-up water.

[0056] Furthermore, when the animal hide is pickled, this may also result in soaking of the hide. Therefore, before the tanning step, the hide may be acidic. According to the present invention, the animal hide to be tanned may typically be a pickled animal hide.

[0057] According to an advantageous embodiment of the invention, during said tanning step, a fluid is added to the interior of said tanning drum.

[0058] As used herein, the term "fluid" refers to water, for example in a liquid or gaseous state, which can be introduced into the tanning drum in one of these forms, preferably in a gaseous state in the form of steam, to regulate the temperature, preferably to increase the temperature. The fluid can have different physical and chemical properties. Therefore, the term can refer, for example, to an organic solvent, an inorganic solvent or water in a liquid or gaseous state.

[0059] Providing a fluid during the tanning step may be advantageous for regulating or optimizing the tanning of the hides, for example by introducing the tanning agent into the interior of the tanning drum via a fluid or by using a tempered fluid as a temperature regulator. Thus, the temperature of the fluid may be higher or lower than the temperature of the interior of the tanning drum, and thus the introduction of the fluid may regulate the temperature of the interior of the tanning drum upwards or downwards.

[0060] Using the fluid in a gaseous state may be more advantageous because it can reduce the amount of fluid required to reach a specific temperature that is optimal for tanning. Thus, the amount of fluid used can be further reduced, which further reduces the amount of waste water and thereby reduces the environmental impact of the process.

[0061] According to an advantageous embodiment of the invention, said fluid is introduced into said tanning drum while said tanning drum is rotating.

[0062] This is advantageous because it has the effect of even out the tanning of all the hides as they continuously change position in the tanning drum due to the rotation.

[0063] According to an advantageous embodiment of the invention, the fluid is added from the first fluid source or the second fluid source.

[0064] This is advantageous because it has the effect that two different temperatures and / or two different types of fluids can be introduced into the tanning drum. Thus, if the temperature is to be increased, fluid from one source can be introduced, and if the temperature is to be decreased, liquid from a second source can be introduced. The flow of fluids from the two sources can be controlled by a plurality of valves, and therefore only one fluid inlet may be required for fluids from both sources into the tanning drum.

[0065] According to an advantageous embodiment of the invention, said fluid is a tanning liquid.

[0066] As used herein, the term "tanning liquid" refers to a fluid comprising a tanning agent or a pH adjusting agent or a combination thereof. Therefore, the tanning liquid can be a mixture of chemicals and a fluid such as water. It should be mentioned that a third fluid source can be used using a third fluid inlet to the drum. This may be necessary if a tanning agent or additional ingredients required during the tanning step are to be introduced.

[0067] According to an advantageous embodiment of the invention, the fluid is steam, preferably water steam.

[0068] According to an advantageous embodiment of the invention, at the end of said tanning step at least 50%, preferably at least 25%, most preferably at least 10% of the total injected fluid comes from steam.

[0069] The use of steam is advantageous because in this way the maximum heat capacity of the fluid introduced into the tanning drum can be utilized.The introduced fluid may be steam of or from water (H2O).

[0070] According to an advantageous embodiment of the invention, said fluid is introduced in discrete time periods during said tanning step.

[0071] The injection or introduction of fluid is generally 3-5 seconds to several minutes to several hours. According to the temperature difference between fluid and the internal temperature of the tanning drum, the internal temperature can be adjusted upward or downward such as 0-3 degrees per hour. This temperature increase is mainly promoted by injecting fluid, but may also be supported by the heat generated by the drum rotation. Therefore, if the initial temperature is much lower than the desired temperature (such as, between 10 and 25 degrees low) of the tanning step, it is not impossible to increase the temperature by introducing fluid for 10,15,20 minutes or longer to obtain the desired tanning temperature.

[0072] According to an advantageous embodiment of the invention, said discontinuous time period exists during the tanning part of said tanning step.

[0073] The tanning step begins with a mixing and dispensing portion at ambient temperature, which has a duration such as between 4 and 12 hours. The tanning step ends with a tanning portion at a specific temperature, which is generally above ambient temperature, for a duration such as between 6 and 8 hours. It is therefore during the tanning portion that the temperature regulation of the invention is most important.

[0074] According to an advantageous embodiment of the invention, a first of said discontinuous time periods is between 5 and 60 minutes, such as between 5 and 45 minutes, or between 5 and 30 minutes.

[0075] The period of time during which the fluid is introduced into the tanning drum is longest at the beginning of the tanning portion of the tanning step. This is particularly true when the temperature inside the tanning drum is to be raised from ambient temperature to the desired temperature. The flow of hot fluid may then be continuously introduced for more than, for example, five minutes until the measured temperature reaches the desired temperature.

[0076] According to an advantageous embodiment of the invention, the last time period of the discontinuous time periods is between 1 second and 1 minute, preferably between 2 seconds and 30 seconds, most preferably between 3 seconds and 15 seconds.

[0077] Towards the end of the tanning part of the tanning step, the period of time for which fluid is introduced into the tanning drum is the shortest. This is because the desired temperature has been reached and only needs to be maintained, which requires less introduction of tempering fluid.

[0078] According to an advantageous embodiment of the invention, the fluid is introduced continuously, alternating between a temperature-maintaining flow and a temperature-raising flow.

[0079] In the case of changing the flow of steam (such as the volume of steam per unit time) to obtain temperature regulation, the continuous introduction of a fluid such as steam can be introduced. Therefore, steam can be continuously introduced into the drum to maintain the desired temperature. However, if the temperature must be increased, it is necessary to increase the flow of the fluid entering the drum. Similarly, when the upper temperature limit is reached, the flow must be stopped. Therefore, the discontinuous introduction of the fluid can be understood as a flow pulse from a first flow level to a second flow level. Wherein the first flow level is a temperature-maintaining flow and the second flow level is a temperature-raising flow. The second flow level is determined by the temperature increase and the time to reach the temperature increase. During the temperature maintenance period, a temperature maintenance flow of the fluid is provided, and a certain volume of steam is introduced per unit time to ensure that the temperature is maintained between an upper threshold and a lower threshold. During the temperature increase period, a temperature increase flow of the fluid is provided, and the volume of steam introduced per unit time is higher than during the temperature maintenance period.

[0080] It should be mentioned that by introducing X amount of steam, the temperature in the drum will increase by X degrees C per hour. Thus, for example, by fine-tuning the amount of steam introduced or the time to reach the desired temperature, the desired temperature can be obtained.

[0081] The volume and time units may depend on the type of hide to be tanned and are therefore determined individually for a specific tanning process.

[0082] According to an advantageous embodiment of the present invention, the internal temperature is controlled between 20-55 degrees Celsius.

[0083] Temperature regulation is advantageous because the tanning step can be performed in different climates. Thus, in colder climates, it may be necessary to increase the temperature before the tanning step. In warmer climates, it may be necessary to reduce the temperature inside the tanning drum before starting the tanning step. Ultimately, temperature regulation before the tanning process can affect the result and quality of the tanning process. Furthermore, temperature control is advantageous because different types of hides are tanned at different temperatures and / or the tanning step may include steps performed at different temperatures.

[0084] According to an advantageous embodiment of the invention, when said fluid has a temperature lower than said measured temperature inside said tanning drum, said controller reduces said internal temperature by introducing said fluid.

[0085] The controller may control valves to allow passage / passage of, for example, air or aerosol through the cooling system and into the tanning drum and thereby automatically control / lower the internal temperature based on input from the temperature sensor.

[0086] Being able to reduce the temperature inside the tanning vessel is advantageous, particularly when the tanning drum is physically located at an ambient temperature substantially equal to or higher than the temperature required for the tanning process.

[0087] According to an advantageous embodiment of the invention, the temperature of said fluid is controlled by a cooling system fluidically connected to said tanning drum.

[0088] The method of reducing the temperature of the fluid introduced into the tanning drum is to pass it through a heat exchanger of a cooling system. Such a cooling system can be a standard cooling system, such as a cooling system with a compressor, condenser, expansion valve and evaporator / heat exchanger known in the art. The introduction can be controlled by a controller via control of one or more valves in the piping system between the cooling system and the tanning drum.

[0089] The controller may also control cooling systems such as the compressor and expansion valve.

[0090] According to an advantageous embodiment of the invention, said fluid having a temperature lower than said measuring temperature is introduced into said tanning drum in a separate duct.

[0091] The separate conduit system may be a different conduit than the conduit via which the temperature-elevated fluid is introduced into the tanning drum.

[0092] According to an advantageous embodiment of the invention, said measured temperature inside said drum is controlled by a cooling system regulating the temperature of a cooling fluid circulating in the space between the second wall and the first wall of said drum.

[0093] This is advantageous because the temperature inside the tanning drum can be at least partially controlled by such a cooling fluid. Thus, the temperature inside the tanning drum can be controlled by this cooling fluid, by introducing an additional fluid into the tanning drum, or by a combination thereof. It should be mentioned that temperature regulation can also include increasing the temperature, in which case the cooling fluid will be the heating fluid, although the fluids are the same.

[0094] The cooling or temperature regulation system may cause a cooling fluid to circulate in the space between the first and second walls of the double-walled drum. Thus, by regulating the temperature of the cooling fluid (e.g. via a heat exchanger of the cooling system), the temperature inside the drum may be regulated (upwards or downwards) without having to come into direct contact with the hides, open the drum or otherwise interfere with the tanning process. As an alternative, an electric heating or cooling system may be used.

[0095] According to an advantageous embodiment of the invention, when said fluid has a temperature higher than said measured temperature inside said tanning drum, said controller increases said internal temperature by introducing said fluid.

[0096] The controller may control the valve to allow fluid flow, such as, for example, air, water or aerosol, through / through the heater / first temperature regulating device comprising a heating element and into the tanning drum, thereby automatically controlling / increasing the internal temperature based on input from the temperature sensor.

[0097] Typically, the temperature inside the tanning drum is controlled in the range of 20° C. to 45° C. Therefore, the fluid may be above or below ambient temperature.

[0098] According to an advantageous embodiment of the invention, said fluid is introduced into the hide compartment of said tanning drum above said central axis.

[0099] The advantage is that it simplifies the monitoring of the temperature and avoids reaching too high a temperature which could damage the hides being processed in the tanning drum. Furthermore, the provision of an inlet constitutes a further advantage in that it does not require the chemicals to be mixed in solution beforehand. Thus, the total amount of water can be monitored and excess water usage avoided.

[0100] Furthermore, when the fluid is, for example, hot steam, introducing the fluid above the central axis reduces the risk of direct exposure of the hides to the steam which could damage the hides. Preferably, the fluid is introduced into the hide compartment behind the hide shovel (with respect to the direction of rotation), which ensures mixing of the hides with the tanning agent during rotation of the tanning drum.

[0101] According to an advantageous embodiment of the invention, the heating element heats the fluid outside the tanning drum and subsequently introduces the fluid into the tanning drum via a conduit.

[0102] Heating the fluid external to the tanning drum is advantageous because standard off-the-shelf heating systems can be used.

[0103] According to an advantageous embodiment of the invention, the heating fluid is introduced into the tanning drum in gaseous form.

[0104] Introducing a heated fluid such as hot steam as water is advantageous because it has the effect of reducing the amount of fluid required to adjust the temperature upwards compared to using the fluid in its liquid form. This is true whether such a liquid is heated both inside or outside the tanning drum.

[0105] Reducing the liquid inside the tanning drum is advantageous because it is easier to dose the tanning agent correctly since most of the tanning agent is absorbed by the animal hides compared to tanning with a large amount of liquid inside the tanning drum where some tanning agent will remain in the waste water after the tanning process.

[0106] The larger volume of liquid inside the tanning drum may be understood as liquid having a surface located at or above the central axis, such as at or above a distance of 10 cm below the central axis or at or above 50 cm below the central axis.

[0107] According to an advantageous embodiment of the invention, the rotation of said tanning drum is controlled by said controller controlling the frequency and voltage of the power supplied to said electric motor.

[0108] Controlling the power supply to the motor may be performed by connecting the power supply to the motor drive of the motor. The motor drive may be understood as a variable frequency drive for controlling the speed of the motor. Alternatively, a simple start and stop control of the current path of the motor may also be considered as power delivery control to the motor.

[0109] According to an advantageous embodiment of the invention, an increase in the rotational speed of the motor axis of the electric motor contributes to increasing the internal temperature of the tanning drum.

[0110] According to an advantageous embodiment of the invention, the electric motor is a variable speed electric motor.

[0111] In the same way, by reducing the rotational speed of the tanning drum, the contribution of the second temperature regulating device to the temperature regulation, ie the contribution of the tanning drum rotation, can be reduced.

[0112] It should be mentioned that a rotational speed of the tanning drum between 0.5 revolutions per minute (RPM; revolutions per minute) and 10 RPM has proven to be suitable for the tanning process according to the invention.

[0113] Temperature regulation by rotation may be more advantageous, because rotation may cause friction of the surfaces of the hides inside the tanning drum. The friction caused by rotation may lead to temperature changes. Therefore, the temperature may be adjusted according to the rotation speed, so that the temperature can be changed in an additional way. In addition, friction may be used to achieve a specific temperature for the tanning process. Therefore, the need for heating from other sources may be reduced. Other sources may be, for example, warm fluids or steam. Finally, when certain types of tanning agents are used, this may further reduce wastewater (liquids may not be needed to increase the temperature), thereby reducing the impact of the tanning process on the environment.

[0114] It may be advantageous to use limited amounts of water or no water at all. The limited amount of water inside the tanning drum affects the amount of friction between the individual animal hides. Thus, if the water content inside the tanning drum is too high, the heat generated by the friction may be lost.

[0115] According to an advantageous embodiment of the invention, the second temperature regulating device is provided when the liquid surface is less than 10 cm from the tanning drum bottom, such as less than 5 cm from the tanning drum bottom.

[0116] The less liquid is present in the tanning drum, the greater the contribution of the available friction to the heating process of the temperature inside the tanning drum. It is therefore advantageous to only make the humidity inside the tanning drum non-condensable and thereby to build up a volume of liquid at the bottom of the tanning drum which has a measurable / visible liquid surface immediately after stopping the rotation of the tanning drum, such as within 10-30 seconds after stopping the rotation. Providing may be understood as applying, acting or being used to regulate the temperature inside the tanning drum.

[0117] It should be mentioned that the cause of the increase in temperature inside the drum is the increase in speed, or simply the effect of time and friction, the temperature will increase. This is true at least when the drum includes a gearbox drive rather than a belt drive. The adjustment of speed can be done automatically based on experience such as 2 hours of speed 2RPM, 2 hours of speed 3RPM, etc., or it can be done manually based on the temperature increase achieved, so that the RPM (revolutions per minute / speed) is further increased when it is necessary to obtain a higher temperature.

[0118] According to a preferred embodiment of the present invention, the automatically controlled temperature regulation includes the following steps: during the rotation of the tanning drum, detecting the current temperature inside the tanning drum, if the current temperature is lower than the lower threshold temperature, injecting water vapor into the tanning drum through the fluid inlet to increase the current temperature; and if the current temperature is between the lower threshold and a first upper threshold temperature, continuing to rotate the tanning drum without injecting fluid into the tanning drum.

[0119] According to an advantageous embodiment of the invention, said automatic control further comprises the step of injecting fluid into said tanning drum via said fluid inlet in order to reduce said current temperature if said current temperature is above a second upper threshold temperature.

[0120] The advantage of this control mode is that both a reduction and an increase in the internal temperature of the tanning drum can be provided, and it is therefore easier to maintain the internal temperature of the tanning drum between the lower threshold temperature and the first threshold temperature. More accurate temperature control can lead to better tanning and thereby improve the quality of tanned hides. In addition, since the tanning drum can be cooled, the risk of damaging the hides due to excessive temperatures is reduced.

[0121] According to an advantageous embodiment of the invention, the fluid inlet is closed during the detection of the current temperature.

[0122] This is advantageous because flow inside the drum may affect the reading from the temperature sensor and therefore the temperature sensor may not measure the exact temperature.

[0123] According to an advantageous embodiment of the invention, after said tanning step, said plurality of animal hides are washed in a washing process.

[0124] Washing is particularly advantageous when tanning is carried out according to the invention, i.e. without water / with very little water. There may be unabsorbed tanning agent, as well as fibers such as hair from the hides which are not removed from the tanning drum by drainage, such as with the known "wet" tanning processes.

[0125] The washing process is advantageous because it helps to remove excess tanning agents, such as chrome salts in chrome tanning or vegetable tannins in vegetable tanning. Thus, by preventing excess tanning agents, the formation of hard or brittle leather can be avoided. Thus, the washing process involves washing the hides in a container with water, dragging through, spinning, etc.

[0126] According to an advantageous embodiment of the invention, the washing process is carried out outside the tanning drum in a washing container comprising a fiber filtration filter.

[0127] An advantage of the fiber filter is that the fluid used for flushing is continuously filtered and can therefore be used to flush / wash more hides before it needs to be replaced. Therefore, the impact of this process on the environment is further reduced. Compared with the traditional wet tanning process, the amount of fiber in the tanning drum after the tanning step according to the present invention is higher. This is because there is no water (or very little water) in the tanning drum, so no fibers are removed during the drainage process. If the fibers need to be removed before the sammy process (which can be the case in the manufacture of high quality hides), the fibers need to be removed in the washing process between the tanning and sammy processes.

[0128] According to an advantageous embodiment of the invention, the animal hide comprises bovine hide, bovine hide, cow hide or calf hide.

[0129] According to an advantageous embodiment of the invention, during the tanning process the pressure inside the tanning drum is in the range of 0.7-1.3 atmospheres, such as 0.9-1.1 atmospheres.

[0130] In one aspect, the present invention relates to an animal hide tanning system configured for tanning a plurality of animal hides, the tanning system comprising: a tanning drum comprising a central axis, a mechanical drive and an animal hide inlet, wherein the mechanical drive is connected to a motor, wherein the motor is configured to rotate the tanning drum via the mechanical drive; a temperature control system, the temperature control system comprising a temperature sensor, a first temperature regulating device, a second temperature regulating device and a temperature controller, wherein the temperature controller is configured to regulate the internal temperature of the tanning drum by at least partially regulating the internal temperature by the first temperature regulating device and / or at least partially regulating the internal temperature of the tanning drum by the second temperature regulating device during tanning of the plurality of animal hides, wherein the first temperature regulating device comprises a heating element, and wherein the second temperature regulating device comprises the tanning drum, which comprises the plurality of animal hides and is configured to be rotated.

[0131] Note that the heating element may be an electric heating element, and note that the heat from the tanning drum may be friction heat generated by rotating the tanning drum comprising a plurality of animal hides in a reduced / limited amount of water. As mentioned above, during a tanning step (such as a dry tanning step), the temperature inside the tanning drum may be regulated at least in part by introducing a substance in a gaseous state (such as water).

[0132] According to an advantageous embodiment of the invention, the tanning system further comprises a cooling system configured for cooling a fluid, wherein the cooling is configured for introduction into the tanning drum via a conduit.

[0133] This is advantageous because the system also reduces the internal temperature of the tanning drum.

[0134] According to an advantageous embodiment of the invention, during said tanning step, said fluid is introduced in discrete time periods.

[0135] According to an advantageous embodiment of the invention, said discontinuous time period exists during the tanning part of said tanning step (TAN).

[0136] According to an advantageous embodiment of the invention, a first of said discontinuous time periods is between 5 and 60 minutes, such as between 5 and 45 minutes, such as between 5 and 30 minutes.

[0137] According to an advantageous embodiment of the invention, the system according to any of claims 23-24 regulates the internal temperature of the tanning drum by implementing the method according to any of claims 1-22. BRIEF DESCRIPTION OF THE DRAWINGS

[0138] Various embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0139] Figure 1 The various steps of the tanning process are shown,

[0140] Figure 2 shows a tanning drum and a washing container for a tanning step and a washing step according to an embodiment,

[0141] Figure 3 A temperature regulating device according to an embodiment is shown, and

[0142] Figure 4 The relationship between the discontinuous introduction of fluid into the tanning drum and the internal temperature of the tanning drum is shown. DETAILED DESCRIPTION

[0143] Figure 1 The pre-tanning, tanning and post-tanning steps of animal hides are shown. Several steps are required to prepare the hides for the tanning process of the tanning step TAN, and finally obtain the finished leather LE. At least some of these steps are briefly described below, and it should be noted that one or more steps are optional depending on the specific hides, processes and final products. Preparation or pre-tanning PRET raw hide RH is first cured CUR raw hide RH with salt to prevent collagen from rotting due to bacterial growth during the time from purchasing the hides to being processed. Curing CUR can remove moisture from the hides, and bacteria cannot grow. Curing CUR may depend on whether the hides are pickled or fresh, followed by desalination DES.

[0144] Then in a soaking step, the animal hides AH are soaked in clean water SOA which may contain additives such as degreasing, soda, enzymes and / or bactericides, to remove salts left over from the curing process and to increase the moisture in the hides. The soaking is carried out at a pH between 8 and 10.

[0145] In the liming step LIM, sulfur compounds can be added together with lime, enzymes and / or degreasing agents to remove the hair from the hides. Proteins are hydrolyzed at a high pH such as 12 to 13, i.e. become water-soluble, and are washed away. This process is also known as hide opening of the collagen fiber texture (i.e. skin opening and release of tanning active groups) and partial saponification of natural oils.

[0146] After liming, fleshing FLE is performed and during the fleshing step, sharp blade rollers are used to remove the remains of tissue, meat and fat. It should be noted that fleshing and splitting of fresh hides after soaking and before liming LIM process is possible. In order to obtain uniform thick leather of the desired thickness, the hides can be split SPL. Untanned leather is also called pelt. Pelt has a moisture content of 60%-80% and the dry matter contains about 98% collagen.

[0147] Furthermore, fleshing can also be carried out before the liming process.

[0148] Before tanning, the swelling caused by the high alkalinity in the liming process must be eliminated and the pH of the collagen is reduced by the deliming process. During deliming DEL, the calcium hydroxide in the hides is removed by adding weak organic acids, such as aliphatic or aromatic dicarboxylic acids such as, for example, sulfophthalic acid, or by adding weak inorganic salts such as, for example, ammonium sulfate, ammonium chloride or polyphosphates. In the deliming process, the calcium hydroxide in the hides is removed.

[0149] Optionally, depending on the final use of the leather LE, the hides can be treated with enzymes to soften them in a process known as bating BAT. Bating is carried out in a slightly heated float, ie at 30 to 35 degrees Celsius.

[0150] Pickling PIC is a process where the hides are first treated with common salt (sodium chloride) in the case of mineral tanning and then with sulfuric acid. This is done to lower the pH of the collagen to facilitate penetration of the tanning agent. At a pH of 7-9, the bating process may take 45 minutes to 6 hours, and at a pH of 2.8 to 5, such as pH 2.8 to 3.2 for a standard pickling process, the pickling process may take about 5 to 12 hours.

[0151] The hides obtained after bating BAT and pickling are completely saturated with the aqueous solution and are called pickled pelts.

[0152] At this point, the so-called pre-tanning PRET ends. Thereafter, the actual tanning takes place in the tanning step TAN, which generally takes 10 to 20 hours and is generally carried out in a rolling tanning drum TD.

[0153] Tanning TAN of hides AH can be carried out in a tanning solution whose main component is a tanning agent. The tanning agent can be dissolved in the residual water in the tanning drum as a residue of a previous step or the residual water in the hide. Therefore, the tanning agent in powder form can be introduced into the tanning drum without additional water, and the dosage of the tanning agent is calculated according to the weight of the hide. This weight can be determined during or after the last step before the tanning step (which can be a pickling step). It should be noted that if additional ingredients are required in addition to the tanning agent, then these additional ingredients may need to be dissolved in water. The amount of water required for this purpose may be within the range of 1% of the total amount of water added during the tanning step. In fact, in order to ensure the best possible distribution thereof in the drum, these additional ingredients can be introduced via the fluid inlet at the drum axis. This fluid inlet may be different from the fluid inlet for injecting the temperature regulating fluid.

[0154] Thus, the tanning solution may contain, for example, salt, formic acid, sulfuric acid, sodium bicarbonate, and may have additional compounds. During tanning, the adhesive groups on the collagen are cross-linked with the tanning agent. The pH may be increased to a value between 3.6 and 4.2, for example, by adding a base or by using a self-alkalizing tanning agent.

[0155] As an example, alkalization can be performed by introducing 0.4-0.6% (36.5 kg) Feliderm MgO into the tanning, which can be added in several steps, where the alkalization process can be run for eight hours to bind the tanning agent in the animal hides, for example when using chromium salt B as tanning agent.

[0156] The tanning agent may be any suitable tanning agent for tanning animal hides, including but not limited to chromium sulfate and its derivatives, plant extracts, glutaraldehyde, especially fatty oils, and other mineral salts based on aluminum, zirconium, titanium, iron, silicates, etc., and synthetic tanning agents based on acrylic acid, acrylic acid copolymers, triazines, polyphenols, polysulfonic acids and their condensates, etc.

[0157] Tanning agents may also contain additional ingredients, such as bactericides (Busan 1280), or other additives that may provide additional qualities to the tanned hides or tanning process. Tanning agents may include other additives, such as, for example, electrolyte-stable fatting agents, cationic / fatting agents or slip agents. Tanning agents may be provided to the container in any form, wherein each component may be introduced individually or in the form of a mixture, which may be in solid or liquid form. Examples of commercially available tanning agents are Chromosome B and Baychrome A.

[0158] Other compounds may also be used during the tanning process and these may be sodium sulfide, sodium hydroxide, sodium bisulfite, arsenic sulfide, calcium hydrosulfide, dimethylamine and sodium sulfide. Bactericides such as, for example, pentachlorophenol may also be added to prevent bacterial growth.

[0159] After the tanning step TAN, the so-called post-tanning step can be applied. The first post-tanning POSTT step is washing WAS. This step between the tanning TAN and the squeezing SAM step is particularly important for the present invention, because the tanning step TAN is carried out with a very limited amount of water. Because the tanning of the present invention is carried out with a reduced amount of water, and thus compared to conventional "wet" tanning, a reduced amount of waste water and more fibers leave the tanning drum with the hide. In such conventional tanning, the fibers from the hide can be at least partially washed away / removed from the hide by the waste water.

[0160] Therefore, due to the higher amount of fibers, the washing WAS step after the tanning step TAN according to the invention requires more frequent replacement of the water in the washing container WC. Therefore, the water saved by the heating according to the invention at the tanning step TAN can be said to be used or at least partly used in the subsequent washing process, thereby reducing the effect of the heating according to the invention at the tanning step TAN. However, in order to reduce the need to replace the water, as with regard to Figure 2 As described above, the washing container WC is modified.

[0161] The next step is SAM, which is a process where the moisture content of the hide is reduced to 45-65% by passing the hide through rollers etc. Splitting is a process where the hide is passed through a splitter that cuts the thicker hide into two layers. The layer without the grain surface can become suede or an artificial grain surface can be applied to it. Uniform thickness can be achieved by shaving the hide on the non-grain side using a machine with a spiral (helical) blade mounted on a rotating cylinder.

[0162] According to an embodiment of the present invention, the animal hide may be squeezed. Squeezing of the animal hide may help clean the animal hide, wherein squeezing may remove fibers or absorb grease from the animal hide. During the wet process in a tannery, whether it is a wet blue process, a wet white process, or a vegetable process, the squeezing machine absorbs grease and moisture from the hide.

[0163] The step of neutralizing NEU can be applied to remove any residual chemicals and prepare the animal hide for further processing. As an example, this can be a deacidification to remove the remaining acid so as to restore the pH value to neutral. Additional tanning or retanning RET can be applied to add more tanning agents, such as chrome, to provide the hide with the preferred properties required for the finished leather. Then, dyeing the leather DYE into a wide variety of colors plays an important role in the aesthetic appearance and is also an important part of meeting fashion requirements. Fatliquoring FAT is a step in which oil is introduced into the animal hide to lubricate the fibers to keep the hide soft.

[0164] The post-tanning process involves neutralizing the cationic charge of the chrome-tanned animal hides by raising the pH of the animal hides to 4.5-6.5.

[0165] Several finishing steps FIN may then be performed, such as, for example, conditioning, staking, dry rolling / milling, buffing, brushing, surface coating, etc. (not shown).

[0166] Figure 2 A tanning drum TD used during the tanning step TAN and a washing container WC for washing the hides after the tanning step TAN are shown in end view. Furthermore, the tanning drum TD comprises an air release valve ARV to release the pressure.

[0167] The outer end of the drum TD is removed so that the interior of the tanning drum TD can be seen. Inside the tanning drum, four shovels SH are shown. These shovels SH ensure that the hides AH are lifted and put down again during the rotation of the drum TD, thereby mixing.

[0168] The drum TD is shown without any water, only the water contained in the hides (also not shown). If all hides were kept at their maximum capacity, the amount of water in the drum would be 100% according to this document. The invention teaches a regulation control method, applicable to the tanning step TAN, in which the total amount of water, i.e. the water in addition to the 100% water retained by the hides, has a water level below the central axis CA.

[0169] In the illustrated embodiment, at least one fluid inlet is provided at the central axis CA. This inlet fluidically connects the interior of the tanning drum TD (sometimes also referred to as the hide compartment) to the first temperature regulating device 1TRE. The first temperature regulating device 1TRE comprises a fluid supply source FS and a heating element HE. These elements are connected by a conduit CO. The controller CON controls the state of the valve VA in the conduit CO and controls the heating element HE. Thus, the controller CON is controlling the flow of the fluid injected into the tanning drum TD and the temperature of the fluid. As mentioned elsewhere herein, preferably, the fluid is water vapor.

[0170] The fluid is injected into the washboard inlet WBI, which connects the fluid inlet to the washboard WB fluid at the outermost periphery of the internal hide compartment HC of the tanning drum TD. The washboard is a perforated ring that allows the fluid to be distributed inside the drum. In this way, the fluid will not be introduced directly into the drum, thereby without the risk of damaging the hides. Typically, since the fluid is hot steam, it will guide the fluid upwards through the washboard inlet WBI, and the temperature increase will occur from the upper part of the animal hide compartment HC to ensure that there is no direct contact between the high temperature steam and the animal hides.

[0171] Thus, a first temperature regulating device 1TRE can generate a temperature-increasing fluid flow, which first temperature regulating device 1TRE comprises a heating element HE for heating, for example, water, thereby generating steam, which is then introduced into the tanning drum. As mentioned above, the introduction can be controlled by the controller CON via one or more valves VA in the piping system between the heater and the tanning drum. The controller can also control the heating elements of the heating system.

[0172] The control of the fluid flow and fluid temperature may be controlled, for example, based on a predetermined recipe requiring a specific temperature during a specific time period. This temperature may be provided to the controller by an operator via a human machine interface, or preset in a recipe automatically executed by the controller. As shown, the controller CON receives temperature feedback from a temperature sensor TES measuring the temperature inside the tanning drum TD. Note that Figure 2 The location of the temperature sensor is for illustration purposes only and it is preferably located close to the central axis CA.

[0173] As mentioned before, the next step is a washing step WAS where the hides AH are washed to remove the fibers. The washing step is a result of the dry tanning process, during the tanning step TAN there is no water or very little water in the drums and therefore fibers are not removed from the hides when the drums are drained.

[0174] The washing step WAS consists of attaching the hides AH to a suspension and then dipping and / or dragging the hides through a washing container. During these movements through the water, the fibers are removed from the hides. Since the fibers are now in the water, the water needs to be filtered or replaced frequently. Figure 2 The washing container WC is shown with a conduit CO, a filter FI and a pump PU which together ensure clean water for washing the hides.

[0175] Reference Figure 3 , an embodiment of a tanning system TS comprising a process plant PE for a tanning process is shown and will be explained in detail below. Figure 3 A process plant PE for automatic or semi-automatic tanning of animal hides AH is schematically shown in . Furthermore, the tanning drum TD comprises an air release valve ARV to release the pressure.

[0176] The process equipment PE includes a tanning drum TD known from conventional tanning processes, and such equipment can be a container or drum, which can be a large-sized cylindrical machine that rotates horizontally around its central axis CA and is large enough to accommodate multiple hides, such as hundreds of animal hides that can weigh thousands of kilograms. The tanning drum TD has at least one opening for adding animal hides, and this opening or another opening can also be used to add tanning agents to the animal hides in the tanning drum TD. The tanning drum TD can be a drum having an animal hide inlet ANI in the form of a hatch, which can be opened to introduce animal hides, liquids such as aqueous solutions and / or tanning agents. The drum can be configured to maintain ingredients for the tanning process / tanning step TAN. In addition, the process equipment also includes a first temperature regulating device 1TRE and a second temperature regulating device 2TRE. This temperature regulating device establishes the desired temperature in the tanning drum under the control of a temperature controller TEC. The temperature regulating device can generally include at least one heater, preferably also includes a cooler, or any device suitable for heating, optionally cooling or at least setting the desired temperature of the contents in the tanning container or the flow injected into the tanning container.

[0177] exist Figure 3 In the drawings, an auxiliary unit AUX is shown with an additional duct ACO connected to the tanning drum TD in the vicinity of the central axis CA. The purpose of this auxiliary unit AUX is to illustrate that additional components for cooling fluids or related to the tanning step TAN or other steps of the tanning process may be included in the tanning system TS. Such auxiliary functions may be controlled, for example, manually or by a controller CON.

[0178] Thus, fluid can be added from a first source via conduit CO, or from a second source via an additional conduit ACO. This is advantageous because two fluids of different temperatures and / or two different types can be introduced into the tanning drum. Thus, if the temperature is to be increased, a fluid from one source can be introduced, and if the temperature is to be reduced, a liquid from a second source can be introduced. The flow of fluids from the two sources can be controlled by multiple valves, and therefore only one fluid inlet may be required to allow fluids from both sources to enter the tanning drum. However, in some embodiments, the tanning system may also be equipped with one inlet for each source.

[0179] More specifically, the first temperature regulating device 1TRE is based on a heating element HE for heating a fluid provided from a fluid source FS. The fluid may be water and the fluid source may be a container or a conduit that provides water to the heating element HE when needed. The heating element HE may be an electric heating element powered from a power source not shown, such as a utility grid.

[0180] The fluid source FS is fluidically connected to the heating element via the conduit CO, and the heating element is fluidically connected to the tanning drum via the conduit CO. The temperature controller TEC can control the flow of the fluid in the conduit via the valve VA and / or via the heating element HE. This control is based on information such as the current temperature of the animal hide AH and the inside of the tanning drum. This temperature can be provided to the controller CON / temperature control TEC via a temperature sensor TES measuring the temperature inside the tanning drum.

[0181] It should be mentioned that in one embodiment, the first temperature regulating device 1TRE may include a second fluid source (shown as auxiliary unit AUX) or a conduit or cooling system (shown as auxiliary unit AUX) across the heating element (not shown). Via one or more of these elements / configurations of elements, the temperature controller TEC is also able to provide a cooling fluid into the tanning drum. Such a cooling fluid may be the same fluid as the fluid used to heat the internal temperature of the tanning drum, but it is not heated.

[0182] More specifically, the second temperature regulating device 2TRE is based on the rotation of the tanning drum TD. This rotation generates friction between the hides / hides and the drum wall, since there is no or very little water in the drum. The rotation is controlled by a motor driver MOD, such as a variable frequency drive, which supplies power to the motor EM. In this way, based on an input from the controller CON or from the temperature controller TEC, the rotation speed of the drum is controlled, and the higher the rotation speed, the higher the heat generated by the friction between the hides and between the hides and the inside of the tanning drum.

[0183] The electric motor EM is mechanically connected to the drum, for example via a mechanical drive MED, such as a belt drive, or via gears which transmit the rotational force from the electric motor EM to the drum TD.

[0184] The tanning drum may be made of wood, steel or polypropylene or any material that can withstand the material degradation caused by the chemical agents used during the tanning process. An example of a tanning process equipment may be the PPHTT NJ with automatic door PAB / 140 from the manufacturer Hüni.

[0185] The tanning process equipment PE may be equipped with different types of control devices, such as time controllers TIC that control the duration of the process equipment operation, such as the duration of the tanning cycle, the rotation cycle / speed, the heating cycle, etc., and temperature controller devices TEC that control the temperature in the tanning drum of the system. These controllers may all be implemented in a single or distributed controller CON that controls the automatic operation of the tanning process equipment PE, including the temperature inside the tanning drum.

[0186] The tanning process may be controlled based on process parameters. The process parameters related to the execution of the tanning process controlled and monitored by the controller CON must be based on assumptions, measurements or knowledge of certain important data, namely the animal hide characteristics. The animal hide characteristics typically include at least the type / origin of the hide, i.e. a determination or input to the controller which defines whether the hide to be tanned comes from a cow, goat, kangaroo, yak, etc. The tanning process according to an embodiment of the invention depends on the type of animal hide AH to be introduced into the tanning drum. Different types of animal hides AH may be more or less loose, may contain more or less collagen, etc., which must be considered in connection with the control of the tanning process.

[0187] In principle, it is important to include or apply a test device to measure such characteristics and provide the data to the controller CON with little or no human intervention (e.g. calculations), or the characteristics may be determined manually, such as simply as the hide type, and the relevant process parameters may be input into the controller, such as process duration, temperature set point or temperature development, rotation speed of the tanning drum, direction of rotation, etc. Such a processing routine may also be included in or programmed in relation to the controller so that a plurality of preset programs are presented for the user to select based on the animal hide characteristics.

[0188] Another animal hide characteristic that should be considered is the weight of the animal hide to be tanned in the tanning vessel. This weight may be determined manually by a human operator as input into a controller or may be determined automatically at run time based on data received from a weight sensor associated with the tanning drum.

[0189] Other animal hide characteristics may be employed within the scope of the present invention, but the above described characteristics are most commonly used in some manner.

[0190] As mentioned above, the internal temperature of the tanning drum TD may be adapted to be heated under the control of a controller CON or a temperature controller TEC, which may be the same or separate controllers. Temperature control is important for increasing the temperature inside the container to speed up the tanning process and / or to complete the tanning process by fixing tanning agents (e.g. chrome tanning, wet bright / wet white or vegetable tanning) on ​​the animal hides. Depending on the desired tanning temperature, the temperature may be increased from an ambient temperature of approximately 20-22 degrees Celsius (depending on winter / summer and the geographical location of the tanning system TS) to 30-50 degrees Celsius.

[0191] The temperature measurement and control during the tanning process / tanning step TAN according to an embodiment of the present invention can be performed by any suitable temperature controller TEC, which is configured to control the temperature in the tanning drum through the tanning process. Such a controller can work by measuring the temperature or receiving an input representing such a temperature, such as receiving an input from a temperature sensor TES that directly measures the temperature inside the tanning drum, and the controller can communicate the relevant software control signals to a temperature regulating device, such as a motor / motor driver, a valve, a heating element and / or a cooler such as a fluid inlet, to achieve the desired temperature in the tanning drum TD. The temperature can be measured by one or more temperature sensors TES that measure the temperature in the tanning drum or its derivatives, and the sensor is communicatively coupled to the controller, thereby facilitating automatic control of the tanning control parameters based on the measured temperature values ​​and, of course, other optional measurements and process parameters.

[0192] During the tanning process, the time can also be preset and controlled. The time controller can be any suitable programmable time controller and can be connected to the temperature regulating device TRE. Such connection can be wired or wireless. The preset time can cover the entire process, or at least cover the duration until the tanning process is interrupted for the first time, such as measuring the pH value, after which the remaining process time can be determined or the time until the next interruption can be determined. The time controller can also be used to provide a temperature set point to the controller CON, and the controller CON can change the state of the tanning process based on this input. Such a state change can be from a part of a predetermined tanning program with one temperature for a specific period of time to another part of a predetermined tanning program with another temperature for a specific period of time.

[0193] The pH value can be measured by a pH meter or pH tracer connected to the controller CON, they can also be measured manually. An example of a pH meter used in the field of tanning can be a pH tracer (PHT)-ETP. The pH measurement can include measuring the pH in an additive or a combination of additive and hide in a tanning vessel.

[0194] If necessary, the pH of the animal hide is measured during processing, and such pH measurements can often be performed relatively manually, depending on the accuracy and frequency of measurements to be performed.

[0195] The pH can be actively controlled by, for example, adding alkali. An example here would be the addition of Feliderm MgO to a plant where the alkalization process can be run for, for example, 8 hours to bind the tanning agent into the animal hide.

[0196] The pH can also be reactively controlled by using a self-alkalizing tanning agent. An example here would be a self-alkalizing chromium sulfate, such as, for example, Baychrom A. By using a self-alkalizing agent, no additional alkalizing agent may be required. Alkalization can be obtained by increasing the heat inside the apparatus.

[0197] Virtually any compound capable of raising the pH of the tanning solution above 3.5 can be considered a candidate for an alkalizing agent.

[0198] The control of pH may be automatic or at least partially automatic by means of the controller CON. In other embodiments, such control of pH may be achieved by interrupting the tanning process or by programming intervals at which pH measurements and optional supplementary pH control are performed. As mentioned above, such a process is usually achieved by actively controlling the pH.

[0199] Control of pH can also be run as a mixed active and passive process, for example starting with a self-alkalizing tanning agent that includes a pH control agent and then adjusting the pH during the adjustment process by actively adding the pH control agent, such as after measuring the pH in the drum and / or the pH of the hide at intervals during the process.

[0200] The process is carried out at atmospheric pressure, or when the pressure in the container is substantially similar to the pressure around the container. Alternatively, the process can be carried out in a non-pressurized container. This means that during the tanning process, the internal pressure remains similar to the surrounding pressure and does not increase actively. However, it is foreseeable that an increase in the internal temperature of the tanning equipment may slightly change the pressure inside the drum. In addition, the introduction of a fluid for regulating the internal temperature may increase the pressure inside the drum. In order to compensate for such an increase in pressure, at least one drum end is equipped with an air release valve ARV, one of which can be automatically opened when moving upward through the central axis. Preferably, the air release valve ARV does not open before passing through the horizontal plane defined by the central axis CA.

[0201] Alternatively, the tanning equipment is not airtight or has a safety valve that opens if pressure builds up during the process. If the pressure inside the vessel rises above 1.2-2 atmospheres, it can be considered a hazard to the machine and the operators working with the machine.

[0202] According to an embodiment of the present invention, during the tanning process, the drum can be a closed system. The drum can be understood as a container that can hold animal hides, any water and / or aqueous solution used for the tanning process and / or heating, any tanning agent introduced in dry, solid, liquid, wet or any form, without changing the concentration of the ingredients within the tanning equipment.

[0203] The process parameters can be determined based on a preliminary assessment of the animal hide characteristics AHC. Here, several parameters must be considered when setting such process parameters PP, since the starting point may vary greatly and therefore the process parameters for running the optimal tanning process result in a uniform distribution of the tanning agent.

[0204] Such variations can be the weight and / or thickness of the hide, e.g. limed cuts or the whole mass, where thick and dense hides may require longer times or higher temperatures than thinner hides. Furthermore, the characteristics of hides vary greatly between hides of different animals, e.g. cows and alligators, and even hides of the same species, e.g. calf, veal, heavy veal, cow, bull, cattle, etc. Other variations in the starting point of the hide can also be whether the hide is salted, how dehydrated the hide is, how much hair and / or fat is present on the hide, the number of hides to be processed.

[0205] When process parameters are determined based on the above examples of eg animal hide properties, an automatic tanning process or at least a tanning step TAN for tanning animal hides may be started and at least partly performed automatically.

[0206] Then set up the tanning step TAN based on the characteristics of the animal hide, such as a manual for the tanning step TAN operator, including specifications such as the selection and concentration of chemicals, feed inlet temperature, run time, drum speed, rotation direction, etc. Such a tanning step TAM is set to run automatically, however, a control step may be included during the process, such as measuring the pH value on the entire cross section of the animal hide to control whether it is in the correct range. Such pH measurement can be completed by cutting the hide and measuring the pH with a pH indicator of the cross section of layers such as the grain, middle layer and meat layer to ensure that the pH distribution throughout the layer is uniform. Then, the results during the control step can lead to a fixed direction for the next step. Powder can also be added manually to the process. In the following cases, a process control step of checking the pH of the cross-section / layer indicator can be used: phenolphthalein <8.2 colorless>8.2 pink and / or bromocresol green <3.8 yellow>5.4 blue, etc.

[0207] Figure 4 Two diagrams are shown in relation to a tanning step TAN according to the invention. The upper diagram shows the discontinuous time periods during the tanning step TAN during which a fluid is injected into the tanning drum to regulate the internal temperature and the cumulative amount of fluid added. The lower diagram shows the temperature inside the tanning drum due to the injected fluid. As shown, in this example, the fluid is warmer than the internal temperature, so the internal temperature increases due to the injection.

[0208] These figures only describe theoretical tanning steps to facilitate understanding of the principles of the invention. Depending on the specific type of hides to be tanned, the number of hides in the tanning drum, the volume of the tanning drum, the ambient temperature, etc., the diagrams will deviate from the numbers shown, but do not constitute the principles shown.

[0209] As indicated along the X-axis in both figures, the main tanning step TAN depicted in the figures has a duration of 18 hours. As also shown in the above figure, at the start of the tanning step TAN, the percentage of water in the tanning drum is 100%. This means that either the hides AH have reached their maximum water holding capacity and there is no retained water from the previous process. Alternatively, there is some residual water and the hides have not reached their maximum water holding capacity. Therefore, all animal hides may have reached 100% of their maximum water holding capacity and, in addition, there may be additional retained water corresponding to 10%-20% of the weight of the soaked animal hides. In addition, a minimum amount of dilution water may be added.

[0210] Tanning agent is introduced via the animal hide inlet AHI which is subsequently closed, and the tanning step starts at time 0. Tanning step TAN comprises a first part and a second part. In the first part (which can last for 4-12 hours), the tanning agent is distributed and dissolved in the drum during the drum TD rotation process. The temperature is substantially ambient temperature. During the second part (which can last for 6-8 hours), the internal temperature rises during the rotation process. The temperature rise is controlled such as in the continuous steps described below.

[0211] As the drum starts to rotate, the second temperature regulating device 2TRE starts to influence the internal temperature and ensures that the temperature does not rise to the point where the tanning agent is activated, which can be reduced by injecting cooling fluid into the drum. The rotation generates heat through the friction between the hides / skins and the drum wall through the second temperature regulating device 2TRE. Surprisingly, such friction occurs due to the reduction of liquid inside the tanning drum, although liquid may be present and the hides may be soaked in liquid.

[0212] As mentioned above, during the first part, i.e. in this example during the first 10 hours of the tanning step TAN, only the second temperature regulating device 2TRE generates heat. For example, due to the slow rotation of the drum, the thermal influence of the rotation during the first 10 hours is small, but for illustration purposes, the temperature curve on the figure below is shown to be rising during these 10 hours. Thus, in this example, the ambient temperature may be 20°C, and the internal temperature of the tanning drum increases by one degree to 21°C after 10 hours.

[0213] After 10 hours, the first part of the tanning step TAN ends and the second part begins. Therefore, fluid is injected into the tanning drum TD and the temperature starts to rise while the fluid is injected. As shown in the figure above, the fluid is injected for 30 minutes, causing the temperature to rise from 21°C to 24°C, as shown in the figure below. The temperature is maintained at 24 degrees for 30 minutes because this is required by the tanning recipe of this example. This may need to be continued for 10 minutes. 1 / Liquid not shown was injected between 2 hours and 11 hours.

[0214] The recipe then teaches raising the temperature to above 25°C, such as between 25°C and 60°C, such as between 25°C and 45°C, such as between 35°C and 40°C, which is the temperature range required for the remainder of the tanning step TAN. 1 / 2 hours, a fluid in the form of water vapour is introduced to raise the temperature from 24°C to the desired tanning temperature, in this example 31°C.

[0215] As shown, the temperature is between upper and lower threshold temperatures of 29C and 31°C, respectively, which in this particular example are acceptable deviations from the desired temperature for tanning. If the upper threshold is exceeded, fluid is injected at a temperature below 31°C, preferably much lower such as 10 degrees or lower (how much lower determines the amount of fluid required to lower the temperature) to lower the temperature inside the tanning drum.

[0216] Steam (water in this example) is produced by the first thermostat and, together with the heat produced by the second thermostat, raises the internal temperature. Thus, the temperature curve shown in the figure below includes contributions from both the first and second thermostats.

[0217] In this example, over time, when no fluid is injected, the temperature drops. The speed of such a temperature reduction depends on factors such as the ambient temperature, the rotation speed (contribution from the second heater), etc. In this example, after 12 hours, the temperature has dropped to the lower threshold, i.e. 29°C. Therefore, steam is introduced again for a short time to bring the temperature back between the two thresholds. In this way, during the second part, until the 18th hour after the tanning step TAN is completed, the temperature is adjusted by stopping the introduction of steam into the tanning drum and / or by changing the rotation speed of the drum. These discontinuous steam introductions may only be a few seconds, such as 10 seconds, such as 5 minutes, at intervals, because the drum is heated at this time, thereby establishing thermal inertia in the tanning drum structure. Therefore, it is only necessary to maintain the temperature, and there is no need to heat anything from the starting temperature at this time.

[0218] As mentioned above, the temperature changes are shown in the figure below. The figure above shows the liquid accumulated in the tanning drum. From this example, it can be seen that at the end of the tanning process, the total amount of liquid is 130%. This includes the 100% present at the beginning of the tanning process, and then the 30% amount introduced during the tanning as part of the temperature control.

[0219] It should be noted that the temperature control may introduce more fluid than the 30% that can be determined in the tanning drum after introduction into the tanning process. This is because part of the introduced steam escapes from the tanning drum via the air release valve ARV as part of the automatic equalization of the pressure in the tanning drum.

[0220] Thus, in this example, a total of 50% of liquid may be added during the tanning process, but only 30% may be determined at the end of the tanning step TAN. Note that in other examples this (the total amount of added fluid or the portion of added fluid detectable in the drum at the end of the tanning step TAN) may be between 10% and 50%, and note that all of this or at least 50%, 40%, 30%, 20% or 10% of such added liquid may be added as water vapor. Note also that the method of determining the amount of added liquid here is by the weight of the hide including the water retained in the hide. Alternatively, the amount of added liquid may be determined by the weight of the dry hide (before and after the tanning process), by the measurable liquid surface in the tanning drum, etc.

[0221] Therefore, again referring to the above Figure 4 , if the tanning process starts with 100% water in the tanning drum (i.e. no more water than the hide can hold / retain), during the first 10 hours, up to 2% of diluent (calculated based on the water holding capacity of the animal hide) and chemicals such as fat liquid or fungicides can be added. The fluids and chemicals can be added simultaneously or in batches over time. Thus, at the 10th or 11th hour in this particular embodiment, 2% of fluid can be added, resulting in a total amount of fluid in the tanning drum of 102%. In the following hours, such as during the 11th hour, more than 2% of steam can be introduced, but as mentioned above, some of the steam will escape through the air release valve ARV. As a non-limiting example, after 13 hours, the total amount of fluid introduced into the tanning drum can be 7%, resulting in a total amount of liquid in the drum of 107%. At the end of the tanning step TAN, 11% of fluid can be added, resulting in a total amount of fluid in the drum of 111% at the end of the tanning step TAN. Thus, the temperature increase may have started with the introduction of water vapour and therefore the increase in water in the drum may be negligible. If visible water is present in the drum when the hides are unloaded, this may be due to insufficient drainage of the drum after the pickling step, i.e. such water may be water held up from the pickling float.

[0222] It should be noted that Figure 4 The fluid introduced may be water and / or water vapor, and the amount of such fluid may be based on the weight of the animal hide being soaked.

[0223] Therefore, the actual amount of fluid required from the fluid source exceeds the amount that can be determined after the tanning process, i.e. by 11%. Since the steam escapes via the air release valve ARV, the total amount of water introduced during the tanning step TAN can be 17% of the weight of the hide, including the water remaining at the beginning of the tanning process. In this example, 6% may escape via the air release valve ARV and therefore 11% remains in the tanning drum at the end of the tanning step.

[0224] One method of determining the amount of fluid to be added is to compare the weight of the tanning drum or the tanning drum contents before and after the tanning step TAN. Alternatively, the liquid level inside the tanning drum (such as relative to the central axis) is measured before and after the tanning step TAN. At least the latter method may require a settling time after the tanning process so that the fluid inside the tanning drum gathers at the bottom of the tanning drum. Since the weight of a gaseous fluid (such as water vapor) does not change when the phase changes to a liquid state, a settling time may not always be required. However, this may depend on the method for determining the weight of the tanning drum contents.

[0225] Alternatively, the amount of fluid added may be determined based on measurements of a fluid source such as a tank, ambient air or a pipeline supply.By knowing the amount introduced to the first temperature regulating equipment 1TRE, knowledge is also gained about the amount introduced to the tanning drum.

[0226] It should be noted that when determining the amount of liquid introduced during the tanning process, the introduction of the tanning agent should be taken into account. One method is to determine by comparison the starting weight / height of the liquid surface after the tanning agent is introduced into the tanning drum.

[0227] The weight of the hide in a tanning drum with 100% water retention depends on the type of hide and the weight of the hide is determined when there is no additional water in the drum, i.e. no water surface.

[0228] Thus, in the above example, the amount of water introduced is limited and preferably at least partly in the form of steam. In this way, the dosage of the tanning agent is easier, the temperature control is more precise, the contribution of the second heating is increased, and the heating is faster, since no thermal inertia has to be built up in the large volume of water inside the tanning drum.

[0229] The dosage of the tanning agent may result in a reduction of at least 5%, such as at least 10%, such as at least 15%, such as at least 20%, such as at least 25%, such as between 10-30% of the tanning chemicals. Specifically, with respect to chromium, the reduction is at least 2%, such as at least 3%, such as at least 4%, such as at least 5%, such as at least 8%, such as between 2%-8%, such as between 4%-6%.

[0230] List of reference numerals:

[0231] ADC. Additional catheter

[0232] AHI. Animal hides and skins import

[0233] ARV Gas Release Valve

[0234] AUX. Auxiliary unit

[0235] BAT. Soften

[0236] CA. Central axis

[0237] CO. Catheter

[0238] CON.Controller

[0239] CUR.

[0240] DEL.Deashing

[0241] DES. Desalination

[0242] DYE. Dyeing

[0243] EM. Electric motor

[0244] FAT.

[0245] FI.Filter

[0246] FIN. Finishing

[0247] FLE. Remove the flesh

[0248] FS. Fluid source

[0249] HC.Hide compartment

[0250] HE.Heating element

[0251] LE.Leather

[0252] LIM. Liming

[0253] MED. Mechanical Drive

[0254] MOD. Motor Driver

[0255] NEU. Neutralization

[0256] PE.Technology

[0257] PIC. Pickling

[0258] PRET. Pre-tanning step

[0259] POSTT. Post-tanning step

[0260] PU. Pump

[0261] RH. Raw leather

[0262] RET. Retanning

[0263] SAM.Squeeze water

[0264] SH.Shovel

[0265] SHA.Shaving

[0266] SPL. Segmentation

[0267] TAN. Tanning

[0268] TD. Tanning drum

[0269] TEC. Temperature Controller

[0270] TES. Temperature sensor

[0271] TIC.Time Controller

[0272] TS. Tanning system

[0273] VA. Valve

[0274] WAS.Washing

[0275] WB.Washboard

[0276] WBI.Washboard Entrance

[0277] 1TRE. First Temperature Regulation Equipment

[0278] 2TRE. Second temperature regulating equipment

Claims

1. A method for regulating the internal temperature of a tanning drum during a tanning step (TAN) of a tanning process for tanning a plurality of animal hides (AH), wherein the tanning drum (TD) comprises a central axis (CA), a mechanical drive (MED) and an animal hide inlet (AHI), wherein the mechanical drive (MED) is connected to an electric motor (EM), wherein the electric motor (EM) is configured to rotate the tanning drum (TD) via the mechanical drive (MED), wherein the method comprises the step of regulating the internal temperature at least partially by means of a first temperature regulating device (1TRE) and / or at least partially by means of a second temperature regulating device, wherein the first temperature regulating device (1TRE) comprises a heating element (HE), and Wherein said second temperature regulating device (2TRE) comprises said electric motor (EM) and said mechanical drive (MED), which provides heat from the rotation of said tanning drum when said tanning drum comprises said plurality of animal hides (AH).

2. The method according to claim 1, wherein: The tanning step (TAN) is a dry tanning step.

3. The method according to claim 1 or 2, wherein: The tanning drum (TD) further comprises a temperature sensor (TES), wherein the temperature regulation of the tanning step (TAN) is automatically controlled by a controller (CON) based on the temperature measured by the temperature sensor (SES).

4. A method according to any one of the preceding claims, wherein: The tanning drum (TD) comprises a liquid content without a liquid surface inside the tanning drum (TD).

5. The method according to any one of the preceding claims 1 to 3, wherein: The tanning drum (TD) comprises a liquid content having a liquid surface inside the tanning drum (TD) below the central axis (CA) during the tanning step.

6. A method according to any one of the preceding claims, wherein: When said plurality of animal hides (AH) are dry, said tanning drum (TD) comprises a liquid content of less than 10%, 20%, 25%, 30%, 40%, 50% by weight of said plurality of animal hides (AH).

7. A method according to any one of the preceding claims, wherein: When the plurality of animal hides (AH) are soaked, the tanning drum (TD) comprises a liquid content of less than 10%, 20%, 25%, 30%, 40%, 50% by weight of the plurality of animal hides (AH).

8. A method according to any one of the preceding claims, wherein: The tanning drum (TD) comprises a liquid content which is less than 110%, 120%, 130%, 140%, 150% of the liquid contained in the plurality of animal hides (AH).

9. A method according to any one of the preceding claims, wherein: The amount of liquid added during the tanning step is less than the amount of liquid present inside the tanning drum (TD) at the start of the tanning step (TAN).

10. A method according to any one of the preceding claims, wherein: During the tanning step (TAN), fluid is added to the interior of the tanning drum (TD).

11. The method according to claim 10, wherein: The fluid is a tanning liquor.

12. The method according to claim 10, wherein the fluid is steam, preferably water vapor, wherein at the end of the tanning step at least 50%, preferably at least 25%, most preferably at least 10% of the total injected fluid comes from steam.

13. The method according to any one of the preceding claims 10 to 12, wherein: The fluid is introduced in discontinuous time periods during the tanning step, wherein the discontinuous time periods exist during the tanning part of the tanning step (TAN), wherein a first time period of the discontinuous time periods is between 5 and 60 minutes, such as between 5 and 45 minutes, such as between 5 and 30 minutes.

14. A method according to any one of the preceding claims, wherein: The fluid is introduced continuously, alternating between a temperature-maintaining flow and a temperature-raising flow.

15. A method according to any one of the preceding claims, wherein: The temperature inside the drum is controlled by a cooling system regulating the temperature of a cooling fluid circulating in the space between the second wall and the first wall of the drum.

16. Method according to any one of the preceding claims, wherein the heating element (HE) heats the fluid outside the tanning drum (TD), the fluid then being introduced into the tanning drum (TD) via a conduit (CO), wherein, The heated fluid is introduced into the tanning drum (TD) in gaseous form.

17. The method according to any one of the preceding claims 3 to 16, wherein: The rotation of the tanning drum (TD) is controlled by the controller (CON) which controls the frequency and voltage of power supplied to the electric motor (EM), wherein an increase in the rotation speed of the motor axis of the electric motor (EM) helps to increase the internal temperature of the tanning drum (TD).

18. A method according to any one of the preceding claims, wherein: The second temperature regulating equipment (2TRE) is provided when the liquid surface is less than 10 cm from the bottom of the tanning drum (TD), such as less than 5 cm from the bottom of the tanning drum (TD).

19. A method according to any one of the preceding claims, wherein: The temperature regulation of the automatic control comprises the following steps: - during the rotation of the tanning drum (TD), detecting the current temperature inside the tanning drum, - if the current temperature is below a lower threshold temperature, injecting water vapor into the tanning drum (TD) via the fluid inlet in order to increase the current temperature, and - If said current temperature is between said lower threshold temperature and a first upper threshold temperature, continuing the rotation of said tanning drum (TD) without injecting fluid into said tanning drum (TD).

20. A method according to any one of the preceding claims, wherein: The automatic control further comprises the step of injecting fluid into the tanning drum (TD) via the fluid inlet to reduce the current temperature if the current temperature is above a second upper threshold temperature.

21. A method according to any one of the preceding claims, wherein: After the tanning step, the plurality of animal hides (AH) are washed in a washing process, wherein the washing process is performed outside the tanning drum (TD) in a washing container (WC) comprising a fiber filtration filter.

22. The method according to any of the preceding claims, wherein during the tanning process the pressure inside the tanning drum (TD) is in the range of 0.7-1.3 atmospheres, such as 0.9-1.1 atmospheres.

23. An animal hide tanning system (TS) configured for tanning a plurality of animal hides (AH), the tanning system comprising: - a tanning drum (TD), comprising a central axis (CA), a mechanical drive (MED) and an animal hide inlet (AHI), wherein the mechanical drive (MEDI) is connected to an electric motor (EM), wherein the electric motor (EM) is configured to rotate the tanning drum (TD) via the mechanical drive (MED), - a temperature control system comprising a temperature sensor (TES), a first temperature regulating device (1TRE), a second temperature regulating device (2TRE), and a temperature controller (TEC), wherein the temperature controller (TEC) is configured to regulate the internal temperature of the tanning drum (TD) during a process of tanning a plurality of animal hides (AH) by regulating the internal temperature at least partially by the first temperature regulating device (1TRE) and / or at least partially by the second temperature regulating device (2TRE), wherein the first temperature regulating device (1TRE) comprises a heating element, and Wherein said second temperature regulating equipment (2TRE) comprises said tanning drum (TD), which comprises said plurality of animal hides and is configured to be rotated.

24. The system of claim 23, wherein: The tanning system also includes a cooling system, which is configured for cooling a fluid, wherein the cooling is configured to be introduced into the tanning drum (TD) via a conduit (CO), wherein during the tanning step, the fluid is introduced in discrete time periods, wherein a first time period of the discrete time periods is between 5 and 60 minutes, such as between 5 and 45 minutes, such as between 5 and 30 minutes.

25. The system according to any one of claims 23-24, which adjusts the internal temperature of the tanning drum according to the method of any one of claims 1-22.

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