METHOD AND APPARATUS TO CAST A SHEET OF MATERIAL CONTAINING ALKALOIDS

Abstract

The invention relates to a method for casting a sheet of a material containing alkaloids, the method comprising: —forming a slurry of the material containing alkaloids, the slurry having a viscosity value; —storing the slurry in a first tank; —providing a first flow-path and a second flow-path for fluid communication between the first tank and a casting box, the first flow-path comprising a first pump and the second flow-path comprising a second pump; —directing the slurry either along the first flow-path or along the second flow-path from the first tank to the casting box, defining a flow of slurry through the first flow-path or through the second flow-path, on the basis of the viscosity value of the slurry; and—casting the slurry to obtain a sheet of material containing alkaloids. The invention further relates to a casting apparatus for the production of a sheet of material containing alkaloids.

Claims

1. A method for casting a sheet of a material containing alkaloids, the method comprising: forming a slurry of the material containing alkaloids, the slurry having a viscosity value; storing the slurry in a first tank; providing a first flow-path and a second flow-path for fluid communication between the first tank and a casting box, the first flow-path comprising a first pump and the second flow-paths comprising a second pump; directing the slurry either along the first flow-path or along the second flow-path from the first tank to the casting box, defining a flow of slurry through the first flow-path or through the second flow-path, on the basis of the viscosity value of the slurry; and casting the slurry to obtain a sheet of material containing alkaloids.

2. The method according to claim 1, wherein the step of directing the slurry either along the first flow-path or along the second flow-path from the first tank to the casting box on the basis of the viscosity value of the slurry includes: setting a threshold viscosity value; directing the slurry along the first flow-path if the viscosity value of the slurry is below the threshold viscosity value; directing the slurry along the second flow-path otherwise.

3. The method according to claim 1, wherein the slurry has a composition, and comprising one or more of: measuring the viscosity value of the slurry in the first tank; measuring the viscosity value of the slurry in the casting box; measuring the viscosity value of the slurry in the first flow-path or second flow-path; determining the viscosity value on the basis of the slurry's composition.

4. The method according to claim 3, comprising: measuring or determining the viscosity value of the slurry more than once; switching the flow of slurry from the first flow-path to the second flow-path, or vice-versa, in case of a variation of the viscosity value compared to a previous measurement or determination.

5. The method according to claim 1, comprising: storing the slurry in a second tank; providing a third flow-path for fluid communication between the second tank and the casting box, the third flow-path comprising a third pump; connecting the second flow-path to the second tank, so that the second tank and the casting box are in fluid communication via the second flow-path; and directing the slurry either along the third flow-path or along the second flow-path from the second tank to the casting box on the basis of the viscosity value of the slurry.

6. The method according to claim 5, comprising: measuring or determining the viscosity value of the slurry more than once; switching both flows of slurry from the first flow-path and third flow-path to the second flow-path, or vice-versa, in case of variation of the viscosity value compared to a previous measurement or determination.

7. The method according to claim 4, wherein the flow of slurry entering in the casting box defines a flow-rate, comprising: maintaining the flow rate of the slurry entering in the casting box substantially constant before and after the switching.

8. The method according to claim 1, wherein the first pump defines a first pump speed and the second pump defines a second pump speed, the method comprising: measuring the first pump speed or the second pump speed; measuring a flow rate of the slurry in the first flow-path or in the second flow-path; switching the flow of slurry from the first flow-path to the second flow-path, or vice-versa, in case the measured flow rate of the slurry in the first flow-path or in the second flow-path is outside a given range for the respective measured first pump speed or second pump speed.

9. The method according to claim 1, wherein the first pump defines a first pump speed and the second pump defines a second pump speed, the method comprising: measuring a flow rate of the slurry exiting the casting box or entering the casting box or in the first flow-path or in the second flow-path; and changing the first pump speed or second pump speed on the basis of the measured slurry flow rate.

10. A casting apparatus for the production of a sheet of material containing alkaloids, the apparatus comprising: a first tank to store a slurry of material containing alkaloids; a casting box including a casting device to cast a sheet of material containing alkaloids; a viscosity evaluator to measure or determine a viscosity value of the slurry; a first flow-path fluidly connecting the first tank and the casting box to direct a flow of slurry to the casting box; a second flow-path fluidly connecting the first tank and the casting box to direct a flow of slurry to the casting box; a first pump and a second pump, said first pump being arranged within the first flow-path and second pump being arranged within the second flow-path; a first valve to selectively open either the first flow-path or the second flow-path to allow the flow of slurry from the first tank to the casting box either via the first flow-path or via the second flow-path; and a control element to operate the first valve to select either the first flow-path or the second flow-path on the basis of the viscosity value of the slurry.

11. The apparatus according to claim 10, wherein the first pump or the second pump is a positive displacement pump.

12. The apparatus according to claim 10, wherein the first flow-path or the second flow-path includes piping, the piping having a diameter comprised between about 2.5 centimetres and about 10.5 centimetres.

13. The apparatus according to claim 10, wherein the viscosity evaluator includes a viscosimeter.

14. The apparatus according to claim 10, comprising: a second tank; a third flow-path fluidly connecting the second tank to the casting box to direct a flow of slurry to the casting box; a third pump located within the third flow-path; wherein the second flow-path fluidly connects the second tank and the casting box to direct a flow of slurry to the casting box; a second valve to selectively open either the third flow-path or second flow-path to allow the flow of slurry from the second tank to the casting box either via the third flow-path or via the second flow-path; wherein the control element operates the second valve to select the third flow-path or the second flow-path on the basis of the viscosity value of the slurry.

15. The apparatus according to claim 10, wherein the first pump, second pump or third pump defines a first pump speed, second pump speed or third pump speed, and the apparatus comprising a speed variator to vary the speed of the first pump, or of the second pump or of the third pump.

Description

[0090] Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings in which:

[0091] FIG. 1 shows a schematic lateral view of a casting apparatus for casting a sheet of a material containing alkaloids according to the invention;

[0092] FIG. 2 shows a second embodiment of the casting apparatus of FIG. 1;

[0093] FIG. 3 shows a third embodiment of the apparatus of FIGS. 1 and 2; and

[0094] FIG. 4 shows an enlarged view of a detail of the apparatuses of FIGS. 1-3.

[0095] With reference to FIG. 1, a first embodiment of a casting apparatus for the production of a cast sheet of a material containing alkaloids according to the present invention is represented and indicated with reference number 100. Only a portion of the casting apparatus 100 is shown in FIG. 1.

[0096] In particular, the casting apparatus 100 is adapted for the production of a cast sheet of a material containing alkaloids, such as a homogenized tobacco material 1.

[0097] The casting apparatus 100 comprises a casting box 10 containing slurry 2 and a movable support 20, wherein a casting blade 70 (see FIG. 4) casts the slurry 2 contained in the casting box 10 onto the movable support 20 so as to form the cast sheet 1 of homogenized tobacco material. Instead of casting blade 70, any other casting device can be used as well. The casting apparatus 100 further includes a first tank 3, such as a storage or a buffer tank, from where slurry 2 is transferred into the casting box 10. Casting apparatus 100 includes a first flow-path 4 and a second flow-path 5 connecting casting box 10 to first tank 3, and a first pump 6 and a second pump 7, positioned respectively within the first flow-path 4 and second flow-path 5. Preferably, the first pump 6 and the second pump 7 comprise a control of flow rate to control the amount of slurry 2 introduced in the casting box 10 via the first flow-path or the second flow-path. The first pump 6 and second pump 7 are advantageously designed to ensure that slurry transfer times are kept to the minimum necessary. The first tank 3 is thus fluidly connected, by means of the first flow-path 4 and second flow-path 5, to the casting box 10 so as to feed the same with the slurry 2.

[0098] First pump 6 is different from second pump 7. First pump is suitable to work with a first range of slurry viscosities. Second pump is suitable to work with a second range of slurry viscosities. The first range is different from the second range.

[0099] Each flow-path 4, 5 includes suitable piping 8 and two valves, positioned downstream and upstream their respective first and second pump 6, 7. First valve 21 and second valve 22 are present in the first flow-path 4 upstream and downstream the first pump 6, respectively, and third valve 23 and fourth valve 24 are present in the second flow-path 5, upstream and downstream the second pump 7, respectively. First valve 21 and second valve 22 are used in order to enable the replacement of the first pump 6 from the first flow-path 4 for cleaning or maintenance. Third valve 23 and fourth valve 24 are used in order to enable the replacement of the second pump 7 from the second flow-path 5 for cleaning or maintenance.

[0100] In the embodiment of FIG. 1, first flow-path 4 includes a first outlet 25 formed in the first tank 3 and it extends from the same, while the second flow-path 5 includes a second outlet 26 formed in the first tank 3 and it extends from the same. Thus, for a given section of the first flow-path and a given section of the second flow-path, which includes the first pump and the second pump, the first flow-path is separate from the second flow-path.

[0101] Downstream the first pump 6 and second pump 7, the first flow-path 4 and second flow-path 5 merge so that a single inlet 27 delivers slurry to the casting box 10.

[0102] Further, the casting apparatus 100 includes a control element 50, apt to control the opening and closing of from the first valve to the fourth valve 21, 22, 23, 24. Control element 50 can be a control unit such as a microprocessor or the like, suitably programmed.

[0103] The casting apparatus 100 may also include one or more viscosimeter, all indicated with 60. The viscosimeter may be located in the first flow-path, or in the second flow-path, or in both. The viscosimeter 60 may be located alternatively or in addition in the first tank 3 or in the casting box 10, in order to measure or to determine the viscosity of the slurry. The viscosimeter 60, regardless of its position, is also connected to the control element 50. Control element 50 is also adapted to control first pump 6 and second pump 7 to control a characteristic of the same, for example their pump speed or pump flow rate.

[0104] The casting apparatus 100 also includes a flow rate sensor 80, depicted for example positioned in one of the first flow-path 4 or second flow-path 5. The flow-rate sensor 80 may be placed along one of the flow-paths 4, 5 or at the casting box 10. Flow rate sensor 80 is also connected to control element 50.

[0105] With now reference to FIG. 2, a second embodiment of the casting apparatus 101 is shown. Reference numerals indicating the same or analogue elements of the casting apparatus 100 of the embodiment of FIG. 1 remain unchanged.

[0106] The casting apparatus 101 includes a first tank 3 and a second tank 30. The first tank 3 and second tank 30 may be identical or different. Preferably, first tank 3 and second tank 30 are identical to first tank 3 of the first embodiment of the casting apparatus 100 of FIG. 1.

[0107] The casting apparatus 101 further comprises a casting box 10 identical to that of the first embodiment of the casting apparatus 100 and detailed later with reference to FIG. 4.

[0108] The casting apparatus 101 further includes a first flow-path 4, a second flow-path 5, and a third flow-path 11 to connect casting box 10 to first tank 3 and second tank 30: first flow-path 4 connects the first tank 3 to the casting box 10, the third flow-path 11 connects the second tank 30 to the casting box 10, while the second flow-path 5 connects both first tank 3 and second tank 30 to the casting box 10. Each of first flow-path 4, second flow-path 5 and third flow-path 11 includes a pump, namely, first pump 6, second pump 7 and third pump 9, respectively. Preferably, each of the first pump 6, second pump 7 and third pump 9 comprises a control of flow rate to control the amount of slurry 2 introduced in the casting box 10. The first pump 6, second pump 7 and third pump 9 are advantageously designed to ensure that slurry transfer times are kept to the minimum necessary. The first tank 3 is thus fluidly connected, by means of the first flow-path 4 and second flow-path 5, to the casting box 10 so as to feed the same with the slurry 2. The second tank 30 is thus fluidly connected, by means of the second flow-path 5 and third flow-path 11, to the casting box 10 so as to feed the same with the slurry 2.

[0109] First pump 6 is different from second pump 7. First pump is suitable to work with a first range of slurry viscosities. Second pump is suitable to work with a second range of slurry viscosities. The first range is different from the second range. Third pump 9 is substantially identical to first pump 6. Third pump 9 is suitable to work with a third range of slurry viscosities. The third range is equal to the first range.

[0110] First flow-path 4 and third flow-path 11 are similar to each other. Each of the first flow-path and third flow-path includes two valves, positioned downstream and upstream their respective first pump 6 and third pump 9. First valve 21 and second valve 22 are present in the first flow-path 4 upstream and downstream the first pump 6, respectively. Fifth valve 31 and sixth valve 32 are present in the third flow-path 11 upstream and downstream the third pump 9, respectively. First valve 21 and second valve 22 are used in order to enable the replacement of the first pump 6 from the first flow-path 4 for cleaning or maintenance. Fifth valve 31 and sixth valve 32 are used in order to enable the replacement of the third pump 9 from the third flow-path 11 for cleaning or maintenance.

[0111] In the embodiment of FIG. 2, each of the first flow-path 4 and third flow-path 11 includes an outlet. First flow-path 4 includes an outlet 25 in the first tank 3 and it extends from the outlet. Third flow-path 11 includes an outlet 28 in the second tank 30. Thus, for a given section of the first flow-path and for a given section of the third flow-path, which includes the first pump 6 and the third pump 9, respectively, the first flow-path is separate from the third flow-path. Downstream the first pump 6 and third pump 9, the first flow-path 4 and third flow-path 11 merge so that a single inlet 27 delivers slurry to the casting box 10.

[0112] The second flow-path includes two outlets, one outlet 26 in the first tank 3 and another outlet 29 in the second tank 30. From the two outlets 26, 29, two separate piping 8 extend and they merge upstream the second pump 7. In each piping, a valve is included, seventh valve 33 and third valve 23, located upstream the second pump 7. Downstream the second pump 7, a further valve, fourth valve 24, is positioned. Downstream fourth valve 24, the second flow-path 5 merges with the first flow-path 4 and third flow-path 11 so that a single inlet 27 delivers slurry 2 to the casting box 10. Third valve 23 and seventh valve 33 upstream of second pump 7, and fourth valve 24 downstream second pump 7 are used in order to enable the replacement of the second pump 7 from the second flow-path 5 for cleaning or maintenance. Further, the casting apparatus 101 includes control element 50, apt to control the opening and closing of from the first to the seventh valves 21, 22, 23, 24, 31, 32, 33. Control element 50 can be a control unit such as a microprocessor or the like suitably programmed. In FIG. 2, the connection of control element 50 with the various components is not indicated for clarity purposes.

[0113] The casting apparatus 101 may also include one or more viscosimeters, all indicated with 60. The viscosimeter may be located in the first flow-path or in the second flow-path or in the third flow-path. The viscosimeter may be located in all flow-paths. The viscosimeter may be located in two of the three flow-paths. In addition or alternatively, the viscosimeter may be located in the first tank 3, in the second tank 30, or in the casting box 10, in order to measure or to determine the viscosity of the slurry. The viscosimeter 60, regardless of its position, is also connected to the control element 50.

[0114] Control element 50 is also adapted to control first pump 6, second pump 7 and third pump 9 to control a characteristic of the same, for example their speed or pump flow rate.

[0115] The casting apparatus 101 also includes a flow rate sensor 80, depicted for example positioned in one of the flow-paths. The flow rate sensor 80 may be placed along one of the first flow-path 4, second flow-path 5, or third flow-path 11. The flow rate sensor may be located in all flow-paths. The flow rate sensor may be located in two of the three flow-paths. The flow rate sensor 80 may be located at the casting box 10 so that the flow rate of the slurry at the inlet 27 is measured. Flow rate sensor 80 is also connected to control element 50.

[0116] With now reference to FIG. 3, a third embodiment of the casting apparatus 102 is shown. Reference numerals indicating the same or analogue elements of the casting apparatuses 100, 101 of embodiments of FIG. 1 or 2 remains unchanged.

[0117] The casting apparatus 102 is similar to the casting apparatus 100 of FIG. 1. The casting apparatus 102 comprises a casting box 10 identical to that of the first embodiment and second embodiment of the casting apparatus 100, 101 and detailed later with reference to FIG. 4.

[0118] The casting apparatus 102 differs from the casting apparatus 100 of FIG. 1 in that it includes an additional flow-path to the first flow-path and the second flow-path. The additional flow-path connects the first tank 3 to the casting box 10, as the first flow-path and second flow-paths. Casting apparatus 102 includes a first flow-path 4, a second flow-path 5, and a fourth flow-path 34 to connect casting box 10 to first tank 3. Each of the first flow-path, second flow-path and fourth flow-paths includes a pump, namely, first pump 6, second pump 7 and fourth pump 35. Preferably, the first pump 6, second pump 7 and fourth pump 35 comprise a control of flow rate to control the amount of slurry 2 introduced in the casting box 10. The first pump 6, second pump 7 and fourth pump 35 are advantageously designed to ensure that slurry transfer times are kept to the minimum necessary. The first tank 3 is thus fluidly connected, by means of the first flow-path 4, second flow-path 5 and fourth flow-path 34 to the casting box 10 so as to feed the same with the slurry.

[0119] First pump 6 is different from second pump 7. First pump is suitable to work with a first range of slurry viscosities. Second pump is suitable to work with a second range of slurry viscosities. The first range is different from the second range. Fourth pump 35 is different from first pump 6. Fourth pump 35 is different from second pump 7. Fourth pump 35 is suitable to work with a fourth range of slurry viscosities. The fourth range is different from the first range. The fourth range is different from the second range.

[0120] Each of the first flow-path 4, second flow-path 5 and fourth flow-path 34 includes two valves, positioned downstream and upstream their respective first pump 6, second pump 7 and fourth pump 35. First valve 21 and second valve 22 are present in the first flow-path, upstream and downstream the first pump 6, respectively. Third valve 23 and fourth valve 24 are present in the second flow-path, upstream and downstream the second pump 7, respectively. Eighth valve 36 and ninth valve 37 are present in the fourth flow-path 34, upstream and downstream the fourth pump 35, respectively. First valve 21 and second valve 22 are used in order to enable the replacement of the first pump 6 from the first flow-path 4 for cleaning or maintenance. Third valve 23 and fourth valve 24 are used in order to enable the replacement of the second pump 7 from the second flow-path 5 for cleaning or maintenance. Eighth valve 36 and ninth valve 37 are used in order to enable the replacement of the fourth pump 35 from the fourth flow-path 34 for cleaning or maintenance. In the embodiment of FIG. 3, each of the first flow-path 4, second flow-path 5 and fourth flow-path 34 includes an outlet 25, 26, 38 in the first tank 3, respectively, from which they extend. Downstream the first pump 6, second pump 7 and fourth pump 35, the first flow-path, second flow-path and fourth flow-path merge so that a single inlet 27 delivers slurry to the casting box 10.

[0121] Further, the casting apparatus 102 includes control element 50, apt to control the opening and closing of valves 21, 22, 23, 24, 36, 37. Control element 50 can be a control unit such as a microprocessor or the like suitably programmed. In FIG. 3, the connection of control element 50 with the various components is not indicated for clarity purposes.

[0122] The casting apparatus 102 may also include one or more viscosimeter, all indicated with 60. The viscosimeter may be located in the first flow-path or in the second flow-path or in the fourth flow-path. The viscosimeter may be located in all flow-paths. The viscosimeter may be located in two of the three flow-paths. In addition or alternatively, the viscosimeter may be located in the first tank 3, or in the casting box 10, in order to measure or to determine the viscosity of the slurry. The viscosimeter 60, regardless of its position, is also connected to the control element or unit 50.

[0123] Control element 50 is also adapted to control first pump 6, second pump 7 and fourth pump 35 to control a characteristic of the same, for example their speed or pump flow rate.

[0124] The casting apparatus 102 also includes a flow rate sensor 80, depicted for example positioned in one of the flow-paths. The flow rate sensor 80 may be placed along one of the first flow-path 4, second flow-path 5, or fourth flow-path 34. The flow rate sensor may be located in all flow-paths. The flow rate sensor may be located in two of the three flow-paths. The flow rate sensor 80 may be located at the casting box so that the flow rate at the outlet of one of the flow-paths is measured. Flow rate sensor 80 is also connected to control element 50.

[0125] With now reference to FIG. 4, a detailed view of the casting box 10 is depicted. Casting box of FIG. 4 can be the casting box 10 used in any embodiment of the casting apparatus 100, 101, 102 of FIGS. 1-3.

[0126] The casting box 10 comprises four side walls. The side walls include first and second opposite walls 12, 14 and a third and a fourth opposite walls (not shown in the figures), which connect the first and second opposite walls 12, 14.

[0127] The casting blade 70 is associated to the casting box 10 at the second wall 14. The casting blade 70 is associated to the casting box 10 in order to cast the slurry. The casting blade 70 has a dominant dimension which is its longitudinal width. The casting blade 70 is for example substantially rectangular.

[0128] The casting blade 70 is attached to the casting box 10 preferably by means of an adjustable board operated by an actuator (not shown in the pictures) which allows a precise control of the position of the casting blade 70.

[0129] The amount of slurry 2 in the casting box 10 has a pre-determined level, which is preferably kept substantially constant so that the pressure exerted by the column of slurry 2 remains substantially the same. In order to keep the amount of slurry 2 substantially at the same level, the pumps (either first pump and second pump in the first embodiment of the casting apparatus 100, or the first pump, second pump and third pump in the second embodiment 101 of the casting apparatus, or the first pump, second pump and fourth pump in the third embodiment of the casting apparatus 102) control the flow of slurry 2 to the casting box 10.

[0130] The movable support 20 comprises for example a continuous stainless steel belt including a drum assembly. The drum assembly includes a main drum 41 located below the casting box 10 which moves the movable support 20. Preferably, the casting box 10 is mounted on top of the main drum 41.

[0131] The slurry 2 is cast on the steel belt 20—at the drum 41—through the casting blade 70, which creates a continuous sheet 1 of homogenized tobacco material. In order for the slurry 2 to reach the casting blade 70 and thus the movable support 20, the casting box 10 has an opening or aperture 17 in correspondence of its bottom and the opening 17 extends along a width of the casting box 10. The opening 17 is positioned over and in proximity of the drum 41.

[0132] The movement of the steel belt 20 forwards the slurry 2 towards the casting blade 70 at a front exit 18 of the casting box 10 (at the second wall 14; see curve 13 showing the slurry motion). The casting blade 70 casts a part of the slurry 2 on the steel belt 20, while the remaining majority of the slurry 2 turns back and recirculates inside the casting box 10. The steel belt 20 moves along a casting direction (see the arrow 44).

[0133] Between the casting blade 70 and the steel belt 20 a gap is present, the dimensions of which determine—among others—the thickness of the cast sheet 1 of homogenized tobacco material.

[0134] Casting apparatus 100 operates according to the method of the invention.

[0135] The viscosity of the slurry 2 is evaluated. The viscosity is preferably evaluated using viscosimeter 60 located in the first tank 3 or in the casting box 10 or in the first flow-path 4 or in the second flow-path 5, or in both. More than one viscosimeter can be used. Alternatively, the viscosity of the slurry can be calculated based on the slurry's composition.

[0136] The first flow-path 4 and second flow-path 5 are provided with two different pumps 6, 7 which are suitable for different type of viscosity of the slurry. For example the first pump 6 is preferably used for “low viscosity slurry” and the second pump 7 is preferably used for “high viscosity slurry”. Thus, depending whether the viscosity of the slurry is above or below a given threshold, the control element 50 opens valve 23 and leaves valve 21 closed, or vice versa, respectively, so that the slurry flows from the first tank to the casting apparatus via the second flow-path 5 or via the first flow-path 4, using the second pump 7 or the first pump 6. Thus, the slurry uses only one of the two flow-paths at the time.

[0137] At the casting box 10, slurry 2 preferably maintains the same level. Further, at the casting box, the flow rate of the slurry coming from the first flow-path 4 or the second flow-path 5 is checked via sensor 80. Casting box 10 casts the slurry 2 onto movable support 20 which moves along casting direction 44 via casting blade 70.

[0138] Preferably, the viscosity of the slurry is continuously checked while casting takes place. Therefore, if the viscosity of the slurry varies, or the measured flow rate is outside a given range, the control element 50 may actuate valves 21 and 23, changing the flow-path used by the slurry to reach the casting box 10.

[0139] In the following, the method of operation of the casting apparatuses 101, 102 is outlined, mentioning only the differences with the method of operation of casting apparatus 100.

[0140] Casting apparatus 102 operates as casting apparatus 100, but there are three different flow-paths 4, 5, 34 that can be alternatively selected. There are three different pumps 6, 7, 35, each of which is preferably used for a different set of values of the viscosity of the slurry 2. For example the first pump 6 is preferably used for “low viscosity slurry”, the second pump 7 is preferably used for “high viscosity slurry”, while the fourth pump 35 is used for “intermediate viscosity slurry” comprised in a range of viscosity values between the high viscosity slurry and the low viscosity slurry. Thus, if the viscosity of the slurry is above a first threshold and below a second threshold, the control element 50 opens valve 36 and leaves valves 21 and 23 closed, so that the slurry flows from the first tank to the casting apparatus via the fourth flow-path 34 using the fourth pump 35. If the viscosity of the slurry is above the second threshold, the control element 50 opens valve 23 and leaves valves 21 and 36 closed, so that the slurry flows from the first tank to the casting apparatus via the second flow-path 5 using the second pump 7. If the viscosity of the slurry is below the first threshold, the control element 50 opens valve 21 and leaves valves 23 and 36 closed, so that the slurry flows from the first tank to the casting apparatus via the first flow-path 4, using the first pump 6. Thus, the slurry uses only one of the three flow-paths at the time. Therefore, after the viscosity of the slurry has been evaluated, one of the first flow-path 4, second flow-path 5 or fourth flow-path 34 is selected to direct the slurry from first tank 3 to casting box 10, where it is cast as in casting apparatus 100. A single flow-path is used for the transfer of the slurry from the tank to the casting box.

[0141] In the casting apparatus 101, the slurry is located in two tanks, first tank 3 and second tank 30. The first tank 3 is connected to the casting box 10 via the first flow-path 4 and the second flow-path 5 having first pump 6 and second pump 7, respectively. The second tank 30 is connected to the casting box via the third flow-path 11 and second flow-path 5, having third pump and second pump, respectively. Preferably, the first pump 6 and third pump 9 are suitable to be used for the same ranges of values of the viscosity of the slurry, while the second pump 5 in the second flow-path is suitable to be used with a different range of values of the viscosity of the slurry, for example for higher values of viscosity than the first pump and third pump. Thus, depending whether the viscosity of the slurry is above or below a given threshold, the control element 50 opens valves 21, 31 and leaves valves 23 and 33 closed, or vice versa, respectively, so that the slurry 2 flows from the first tank 3 and second tank 30 to the casting box 10 via the first flow-path 4 and third flow-path 11 using the first pump 5 and third pump 9, or the slurry 2 flows from the first tank 3 and second tank 30 to the casting box 10 via the second flow-path 5 using the second pump 7. Thus, from the two tanks, the slurry can flow to the casting box 10 via a single flow-path, that is, via the second flow-path 5, or via two different flow-paths at the same time, first flow-path 4 and third flow-path 11.