EP4337455A1

EP4337455A1 - Method and device for pressing

Info

Publication number: EP4337455A1
Application number: EP22723021.6A
Authority: EP
Inventors: Moritz VÖLTZER
Original assignee: Harburg Freudenberger Maschinenbau GmbH
Current assignee: Harburg Freudenberger Maschinenbau GmbH
Priority date: 2021-05-11
Filing date: 2022-05-04
Publication date: 2024-03-20
Also published as: DE112022002524A5; WO2022237935A1; DE102021112308A1

Abstract

The invention relates to a method and a device for pressing. According to the invention, air or nitrogen, preferably in liquid form, is introduced as a coolant into the pressing chamber of a press such that the temperature of the oil cake and/or of the liquid that has been pressed out decreases during the pressing process.

Description

Method and device for pressing

The invention relates to a device for pressing, in particular in the sense of a screw press.

In addition, the invention relates to a method for pressing.

Methods and devices of this type are used to squeeze liquids out of a press cake, for example oil from oil-bearing seeds. For this purpose, the material to be pressed is fed to a pressing device, for example designed as a screw press, in which liquid is removed from the press cake by mechanical pressing, so that solid and liquid components of the material to be pressed are separated from one another.

Screw presses have a screw shaft that is rotatably mounted in a press chamber. The pressing chamber is delimited by a so-called sieve basket in a tubular shape, with the material to be pressed being fed in at a first end and the press cake being ejected at the second end. The sieve basket has peripheral openings, which are generally designed as slots running parallel to the axis of rotation of the screw shaft and through which the pressed liquid can escape from the press chamber. These slits are usually formed by the spaces between strainer rods arranged next to one another.

Due to the mechanical friction and the high pressure, very high temperatures sometimes occur during the pressing process, which affect both the quality of the press cake and the pressed liquid and the operational reliability of the press.

1 Limiting the temperature during the pressing process has a positive effect on product quality, both on the press cake itself and on the liquid to be pressed out.

After pressing, the press cake is used, for example, as animal feed or as a food supplement, so that certain quality requirements are met.

For example, it is a requirement in this respect to obtain the highest possible PDI value (protein dispersibility index) in the press cake. This value represents the solubility of the proteins in the press cake, which is negatively influenced by the protein denaturation that occurs at high temperatures.

With regard to the quality of pressed liquids, it is an aim, for example in the case of mustard oil pressed from mustard seeds, to obtain the highest possible allyl isothiocyanate content (AITC content) in this, since the AITC content causes the pungent taste.

The AITC content also decreases with increasing temperatures during the pressing process.

For both of the aforementioned goals with regard to the product quality of press cake and pressed liquid, it is therefore of considerable importance to keep the temperature as low as possible during the pressing process.

However, especially with regard to oils as pressed liquids, the cooling of the press cake during the pressing process has disadvantageous effects on the viscosity, so that it is more difficult to drain off.

DE 10 2007 014 775 A1 proposes methods and devices of the aforementioned type that enable an improvement in the product quality of the oil obtained, in particular for use in the production of edible oil, which is achieved in particular by limiting the temperature of the extract to a maximum of 60° C. throughout extraction process is achieved through the use of supercritical CO2 as the extractant.

The addition of supercritical CO2 during the pressing process thus acts on the one hand as a coolant and on the other hand as an extraction agent in the true sense of the word. Applying this teaching to a seed oil extraction occurs by dissolving the carbon dioxide in the oil

2 significant reduction in viscosity and thus significant liquefaction, so that the adverse effect of cooling on the viscosity of the oil is at least compensated.

However, disadvantages of using CO 2 as a cooling medium for screw presses are the comparatively high costs of liquid CO 2 , the complex construction of the pressing device itself required for this, and safety aspects. The use of CO 2 requires elaborate sealing of the press with an enclosed chamber and the use of gas detectors by personnel working in the press area to prevent and/or detect a suffocating atmosphere in the press area. The closed chamber also prevents the pressed liquid from draining away in this area, so that the entire length of the press chamber cannot be used to its full extent.

It is therefore an object of the invention to specify a device for pressing with which the material to be pressed and/or the pressed liquid can be cooled during pressing without the disadvantages occurring when using supercritical CO 2 .

According to the invention, this object is achieved by a device for pressing according to claim 1 .

A further object of the invention is to specify a method for pressing with which the material to be pressed and/or the pressed liquid can be cooled during pressing without the disadvantages occurring when using supercritical CO 2 .

According to the invention, this object is achieved by a method for pressing according to patent claim 14 .

The features of a device for pressing and a method for pressing disclosed below are part of the invention both individually and in all executable combinations.

A pressing device according to the invention is designed as a mechanical pressing device, in particular as a screw press, and has means for supplying a coolant into the pressing chamber.

In another embodiment of the invention, the coolant is directed onto the strainer basket exclusively or additionally from the outside, at least in certain areas.

3 According to the invention, air or nitrogen is used as the coolant, with the respective coolant being able to be fed in liquid form into the compression chamber of the device for compression in preferred embodiments of the invention.

In preferred embodiments of the invention, nitrogen is used as a coolant compared to air, since this, in addition to the cooling effect, also contributes to a better product quality of press cake and pressed liquid, since oxidation of the products during pressing is avoided, and the risk of fire due to the displacement of oxygen is eliminated of the bale chamber is reduced.

Since the nitrogen escaping into the interior of the press can be regarded as harmless and it is also completely soluble in air, which consists of 80% nitrogen, there is no potential risk as long as the press is connected to a sufficiently dimensioned aspiration system and the hall in which the press is set up, is well ventilated. Flap seals can be used for additional security.

Flap seals are seals for flaps that form part of a housing or casing of a pressing device. These flaps serve to provide accessibility to the strainer basket of a device for pressing, for example for maintenance purposes, and at the same time shield the interior of the device for pressing from the environment. A sealing of the flaps supports this shielding, so that the escape of gases from the device for pressing into the surrounding work area is avoided. In embodiments of the invention, the flap seals are designed as rubber lips which are arranged on the edges of the flaps.

In preferred embodiments of the invention, flap seals are combined with aspiration of the press interior.

In embodiments of the invention, sensors are installed on the side doors and cake flap to prevent the doors or flaps from opening during operation of the device for pressing or during the supply of coolant.

In embodiments of the invention, the sensors are in the form of proximity switches or inductive switches, with which it is possible to detect whether the doors and/or flaps are closed.

4 In a preferred embodiment of the invention, the sensors are integrated into a process control with which the supply of the coolant and/or the operation of the press can be stopped when a door and/or flap is opened.

In liquid form, the temperature of the respective coolant is lower compared to the gaseous state at ambient pressure, so that the cooling effect on the press cake and/or the pressed liquid is higher.

The means for supplying a coolant include at least one coolant source and at least one coolant outlet, which is arranged on the pressing device in such a way that the coolant can be introduced into the pressing chamber.

In embodiments of the invention, the coolant source can be designed, for example, as a coolant container or reservoir in which coolant is stored under ambient pressure or possibly at a higher pressure, or as a device for generating the coolant.

The pressing device particularly preferably has a plurality of coolant outlets.

In embodiments of the invention, the at least one coolant source and the at least one coolant outlet are connected to one another via at least one coolant line.

At least one coolant valve is preferably provided, via which the supply of coolant into the pressing chamber of the pressing device can be controlled.

In preferred embodiments of the invention, the at least one coolant outlet is arranged close to the worm shaft or in the worm shaft itself, so that the coolant is injected close to the worm shaft. This maximizes the path that the coolant has to take through the press cake before leaving the press chamber, so that the effect of the heat exchange between the coolant and the press cake is maximized.

Depending on the temperature of the coolant supplied, the injection must not be too close to the worm shaft, as the shaft could otherwise be damaged due to the low temperatures.

5 In embodiments of the invention, at least one coolant outlet is arranged on the worm shaft.

In one embodiment of the invention, the coolant is injected from inside the worm shaft through a coolant outlet.

In other embodiments of the invention, the coolant is injected through coolant outlets projecting into the press chamber from the outside. This arrangement of the coolant outlets allows for easier retrofitting of conventional devices for pressing compared to injection from the screw shaft.

Basically, the injection of the coolant from nozzles that are not arranged in the worm shaft has the advantage that the material of the worm shaft is not adversely affected by direct contact with the coolant at the feed temperature. For example, the worm shaft can become brittle if the temperatures are too low.

Temperatures of less than or equal to 5°C are critical for the material of the worm shaft, temperatures of less than or equal to 0°C are particularly critical.

In advantageous embodiments of the invention, at least one temperature sensor is arranged in the screw shaft in the area where the coolant is introduced into the press chamber. With this, the local temperature of the worm shaft can be measured.

In particularly preferred embodiments of the invention, at least one measured temperature value of the temperature sensor arranged in the worm shaft is used to control the feed quantity and/or the feed temperature of the coolant in such a way that the temperature of the worm shaft is kept above a temperature limit value in order to prevent damage to the worm shaft due to thermal stresses avoid.

In embodiments of the invention, the injection of the coolant from the inside of the worm shaft through a coolant outlet and the injection of the coolant through coolant outlets projecting into the press chamber from the outside are combined with one another.

When the coolant is injected through coolant outlets protruding from the outside into the press chamber, in embodiments of the invention these are arranged in areas in the conveying direction of the press behind throttle rings. In these relaxation and

6 Mixing zones allow the coolant introduced to optimally come into contact with the press cake.

Since the aggregate state of coolants introduced in liquid form changes from liquid to gaseous in the press chamber of the press, a good mixing effect and high heat exchange are achieved.

An additional mixing effect to the mixing of press cake and coolant caused by the press as such is realized in the case of coolant outlets protruding into the press chamber due to the associated flow resistances in the region of the coolant outlets for the press cake.

In embodiments of the invention, this has a sealed area of the strainer basket in the area of the coolant outlets and/or in an area directly behind it in the conveying direction, in which area the coolant cannot escape. As a result, the coolant is conveyed longer together with the press cake in the conveying direction of the press, so that better cooling of the press cake is achieved. This reduces the escape of trub, i.e. press cake as a solid content in the pressed liquid.

In embodiments of the invention, the means for introducing the coolant are arranged entirely or partially in a cooling ring which forms part of the press chamber. Depending on the installation length of the cooling ring, the length of the strainer rods in the installation area is adjusted accordingly in embodiments according to the invention.

Due to the introduction of the coolant in the area of the worm shaft, entrainment effects occur when the press cake flows through from the coolant outlet to the openings of the press chamber, so that parts of the liquid to be pressed flow with the coolant. As a result, the increased viscosity of the pressed liquid that is associated with the cooling of the press cake and the resulting impaired drainage of the pressed liquid can be at least partially compensated. Depending on the pressure, temperature and direction of flow of the coolant, it may even be possible to achieve improved yields of the pressed liquid.

Due to the loosening of the press cake with evaporating coolant and the flow resistance of the nozzles or coolant outlets, there is improved mixing of the press cake in the strainer in the relaxation zones after the throttling rings of the press. This enables better mass transport of the pressed

7 Allows liquid (eg the oil) from the press cake out of the strainer, since there is now press cake with an increased liquid content on the inside of the strainer.

In addition to the location and type of coolant, the amount of coolant supplied also plays a role in relation to the achievement of the effects according to the invention, in particular in relation to the throughput of the press cake.

With an increase in the amount of coolant supplied, at least the cooling effect also increases.

In embodiments of the invention, the pressing device has a measuring device for measuring the exit temperature of the press cake from the pressing device. With the aid of a corresponding dosing device, the amount of coolant supplied can be adjusted to set a target temperature for the press cake emerging from the press.

A pressing method according to the invention comprises at least the following method steps:

Provision of air or nitrogen as a coolant using a coolant source Supplying the coolant from the coolant source into the press chamber of a screw press and/or at least in some areas on the outside of the strainer basket of the screw press

Cooling the press cake and/or the pressed liquid using the coolant

In this case, a material to be pressed or a press cake is introduced through a feed opening into a screw press and transported through a press chamber with the aid of a screw shaft and pressed in the process, so that a liquid is pressed out of the press cake. The pressed liquid exits the press chamber through openings.

The coolant is preferably supplied to the screw press in the liquid state, as this is colder and the cooling effect is greater.

The coolant is preferably injected into the press chamber in the area of the worm shaft, so that the cooling effect is improved and, if necessary, entrainment effects are achieved with regard to the pressed liquid.

Preferably, nitrogen is used as the coolant, particularly preferably liquid nitrogen.

8th In embodiments of the invention, the method for pressing according to the invention is designed to implement part or all of the functions of a device for pressing according to the invention.

In advantageous embodiments of the method according to the invention, the coolant is supplied in such a way that the screw shaft is locally cooled to a maximum temperature greater than 0°C, in particularly preferred embodiments to a maximum temperature greater than 5°C.

In a preferred embodiment of a method for pressing according to the invention, a device for pressing according to the invention is used.

Conversely, a device according to the invention for pressing in embodiments is also designed to implement the method according to the invention in all disclosed variants. In a method for pressing according to the invention or with a device for pressing according to the invention, the following operating parameters are used in embodiments of the invention:

The inlet pressure of the coolant is atmospheric pressure in embodiments of the invention. In other embodiments, a pressure below 100 bar is provided. In different embodiments of the invention, the coolant is injected under high pressure. In any case, the inlet pressure of the coolant is so high that it can be pumped into the strainer basket in corresponding embodiments of the invention.

In embodiments of the invention, 100-1000 t/d seed equivalent for pre-pressing, 90-170 t/d seed equivalent for post-pressing and 30-100 t/d seed equivalent for finishing presses can be set as the mass flow for the press cake. In other embodiments, however, lower mass flows can also be covered.

In preferred embodiments of the invention, the ratio of the supplied mass fraction of the coolant to the total mass flow of the press (press cake and coolant) is between approximately 0 and 25%. Excessive coolant input consumes an unnecessarily large amount of coolant and cools the press cake to an unnecessarily large extent. The press cake or the pressed liquid is preferably only cooled to such an extent that the process specifications with regard to the specified product quality are just achieved.

9 The essential advantage in the product quality of the press cake that can be achieved according to the invention is the higher PDI value, which indicates the percentage of water solubility based on the total amount of protein in the product.

Due to the lower temperature, fewer phosphatides go into the pressed oil, so that the degumming of the oil is less complex, or when mixing the now higher-quality post-press oil with pre-press oil, it may be completely unnecessary.

When pressing mustard seeds, the allyl thiocyanate content is crucial for the product quality. A value of 0.3 meq is aimed for for high-quality products, with a value of up to 0.26 meq being considered acceptable. The content of allyl thiocyanate decreases with higher temperatures, so that the target value of 0.3 meq can be expected in the range of an oil temperature in the range of about 70 °C. In contrast, the usual oil temperature of conventional squeezing is approximately 100° C., so that a temperature reduction according to the invention is accompanied by a significant improvement in the oil quality.

Another advantage of the invention is the use of inexpensive coolants. Liquid carbon dioxide is typically slightly more expensive than liquid nitrogen. Obtaining nitrogen from the ambient air yourself is even more economical when there is a high demand. Savings of 40 to 75% can be achieved depending on the cost of purchasing and delivery in an area. It is therefore a case-by-case decision as to whether delivery of liquid nitrogen or on-site generation, which requires a higher initial investment, makes more financial sense. This also applies to air as a coolant.

Furthermore, compared to the use of supercritical CO2 as a coolant, existing conventional presses can be converted much more easily for use in accordance with the teaching according to the invention, since only a few structural adjustments to the presses are absolutely necessary.

With a classic shaft cooling, in which a coolant is only passed through the worm shaft, the required temperature reductions cannot be achieved anywhere near.

In embodiments of the invention, a multi-stage pressing is realized by the serial arrangement of at least two cooled pressing stages. As a result, lower residual fat contents in the press cake can be achieved compared to single-stage presses / pressing processes.

10 Exemplary embodiments of the invention are shown in the figures explained below. Show it:

Figure 1: A schematic representation of a longitudinal section through a device according to the invention for pressing,

Figure 2: A detailed view of a section in the area of a coolant outlet,

FIG. 3: A detailed view of a section in the area of a further embodiment of a coolant outlet,

FIG. 4: A table with comparative values for parameters of a device according to the invention

Process for pressing and

Figure 5: A graphic representation of the cooling effect of two coolants in comparison.

FIG. 1 shows a schematic representation of a longitudinal section through a pressing device (1) according to the invention.

The embodiment shown of a pressing device (1) according to the invention is designed as a screw press and has a pressing chamber (2) which extends like a tube in the longitudinal direction of the pressing device (1). The pressing chamber (2) is delimited in the radial direction by a strainer basket (3) which has a large number of openings through which a pressed liquid (8) can escape from the strainer basket (3).

A worm shaft (4) is rotatably mounted in the press chamber (2) and can be driven by means of a press drive (5). At a first end, the pressing device (1) has a feed opening (6) for the material to be pressed/press cake, which can then be conveyed through the pressing chamber (2) with the aid of the worm shaft (4). In the longitudinal direction of the pressing device (1), the worm gear formed between the worm shaft (4) and the sieve basket (3) becomes narrower and narrower, so that a continuously high pressure is exerted on the material to be pressed / the press cake. At the second end of the pressing device (1), it has an outlet (7) for the press cake.

The device for pressing (1) also has a strainer basket section designed as a cooling ring (9). In the area of the cooling ring (9), the device for pressing (1) has a plurality of coolant outlets (10) through which a coolant enters the pressing chamber (2).

11 Device for pressing (1) can be initiated. The coolant outlets (10) are connected to a coolant source (12) via a coolant line (11).

Furthermore, the device for pressing (1) has a coolant valve (13) via which the supply of coolant into the pressing chamber (2) can be regulated in relation to the quantity supplied per unit of time (e.g. volume flow) or at least switched on and off.

In addition, the illustrated embodiment of a device for pressing (1) has a coolant pump (14) with which the coolant can be conveyed from the coolant source (12) to the coolant outlets (10). Depending on the embodiment of the coolant source (12) and/or the coolant valve (13), variants without such a coolant pump (14) are also embodiments according to the invention of a device for pressing (1). For example, the amount of coolant fed into the press chamber (2) can be adjusted with the aid of a coolant pump (14). In other embodiments, this can be adjusted via the pressure of the coolant source (12) and/or a corresponding activation of the coolant valve (13), which is embodied, for example, as a proportional valve.

In the illustrated embodiment of the invention, the cooling ring (9) is arranged behind a throttle ring (15) in the conveying direction of the screw press, so that the coolant is supplied in an expansion zone.

Figure 2 shows a detailed view of an embodiment according to the invention of a device for pressing (1) in the area of a coolant outlet (10), the coolant line (11) running at least in some areas in the worm shaft (4) and the coolant outlet (10) on the worm shaft (4) is arranged. Screw parts (16) are arranged on the screw shaft (4) and form different pressure zones, relaxation zones and conveying areas.

FIG. 3 shows an alternative embodiment of a coolant outlet (10) of a pressing device (1) according to the invention, the coolant outlet (10) extending from the outside through the strainer basket (3) into the pressing chamber (2). The opening of the coolant outlet (10) is arranged close to the worm.

Close to the worm in the sense of this document means in a spatial immediate proximity to the outer surface of the worm shaft (4) or worm parts (16) arranged on the worm shaft. The illustration in FIG. 3 is not true to scale for all dimensions of devices for pressing (1) according to the invention with regard to the distance from the worm shaft (4) and coolant outlet (10).

12 In embodiments of the invention, an arrangement of a coolant outlet (10) close to the screw means that it is located at a distance of less than 1 cm, in particularly preferred embodiments at a distance of about 3 mm to 10 mm, from the outer surface of the screw shaft ( 4) or worm parts arranged on the worm shaft.

A table is shown in Figure 4 showing the cooling effect of supplying nitrogen (N 2 ) as a refrigerant at two different levels of supply of refrigerant compared to supercritical CO 2 . Due to the significantly lower inlet temperature of the liquid nitrogen of -196 °C compared to the inlet temperature of 72.3 °C for supercritical CO2, the press cake cools down more with the same mass flows of the pressing aids or coolants when using liquid nitrogen, since the enthalpy difference of the pressing aid is more than three times as large. With an increase in the mass flow of liquid nitrogen from 111 kg/h to 219 kg/h, there is also a significant increase in the cooling effect. In the present example, the temperature difference achieved in the cooled press cake is increased from 16.5 °C to 32.7 °C.

Assuming a press cake outlet temperature of approx. 140° C., which is usual in two-stage finishing presses, after the repressing, a calculated temperature curve results as a function of the supplied quantities of CO 2 or N 2 as shown in FIG.

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Claims

Device for pressing (1) designed as a screw press having a pressing chamber (2) in which a material to be pressed or press cake can be pressed using a screw shaft (4) and the pressing chamber (2) being delimited in the radial direction by a strainer basket (3). , characterized in that it comprises means for supplying a coolant into the press chamber (2) and/or onto the strainer basket (3) from the outside, the coolant being air or nitrogen. Apparatus for pressing (1) according to Claim 1, characterized in that the means for supplying a coolant are designed for supplying the coolant in the liquid state. Press device (1) according to one of Claims 1 and 2, characterized in that the means for supplying a coolant comprise at least one coolant source (12) and at least one coolant outlet (10). Device for pressing (1) according to Claim 3, characterized in that the coolant source (12) is designed as a coolant container or as a device for generating the coolant. Device for pressing (1) according to one of Claims 3 and 4, characterized in that the means for supplying a coolant comprise a coolant valve (13) and/or a coolant pump (14) which is/are arranged in the region of a coolant line (11).

14 is / are, which connects the coolant source (12) with the at least one coolant outlet (10). Device for pressing (1) according to one of Claims 1 to 3, characterized in that at least one coolant outlet (10) is arranged for introducing the coolant into the pressing chamber (2). Pressing device (1) according to Claim 6, characterized in that the at least one coolant outlet (10) arranged to introduce the coolant into the press chamber (2) is designed in such a way that the coolant can be introduced into the press chamber (2) close to the screw. Device for pressing (1) according to Claim 7, characterized in that at least one coolant outlet (10) arranged for introducing the coolant into the press chamber (2) is arranged on the screw shaft (4). Device for pressing (1) according to one of Claims 6 to 8, characterized in that at least one coolant outlet (10) arranged to introduce the coolant into the pressing chamber (2) extends from the outside through the strainer basket (3) into the pressing chamber (2 ) extends. Device for pressing (1) according to any one of the preceding claims, characterized in that the at least one coolant outlet (10) is arranged in a coolant ring (9) which is part of the strainer basket (3). Device for pressing (1) according to one of the preceding claims, characterized in that the at least one coolant outlet (10) is arranged in the conveying direction of the screw press in an area behind a throttle ring (15). Pressing device (1) according to one of the preceding claims, characterized in that it has a sealed area of the strainer basket (3) behind coolant outlets (10) in the conveying direction of the pressing device (1). Device for pressing (1) according to any one of the preceding claims, characterized in that it has a sealed flap in the housing.

15 Method for pressing, in which a material to be pressed or a press cake is introduced into a screw press through a feed opening (6) and transported through a pressing chamber (2) with the aid of a screw shaft (4) and is thereby pressed, so that a liquid (8) is extracted from the material to be pressed or Press cake is pressed and the pressed liquid (8) exits through openings from the press chamber (2), comprising the following process steps:

Providing a coolant using a coolant source (12)

Supplying a coolant from a coolant source (12) into the press chamber (2) of the screw press and/or at least in some areas on the outside of the strainer basket (3) of the screw press

Cooling of the press cake and/or the pressed liquid using the coolant, characterized in that air or nitrogen is used as the coolant. Pressing method according to Claim 14, characterized in that the coolant is supplied under atmospheric pressure. Pressing method according to either of Claims 14 and 15, characterized in that the coolant is liquid when it is fed. Pressing method according to one of Claims 14 to 16, characterized in that the coolant is introduced into the press chamber (2) close to the screw. Pressing method (1) according to one of Claims 14 to 17, characterized in that a pressing device (1) according to one of Claims 1 to 13 is used.

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