WO2004070298A1

WO2004070298A1 - Method and apparatus for solidifying a pumpable mass

Info

Publication number: WO2004070298A1
Application number: PCT/NL2004/000072
Authority: WO
Inventors: Peter Willem Carolus Van Der Schoot
Original assignee: Van Der Schoot Engineering B.V.
Priority date: 2003-02-05
Filing date: 2004-02-02
Publication date: 2004-08-19
Also published as: NL1022588C2

Abstract

A method and apparatus for solidifying a pumpable mass by providing the mass in a gap (6) between a first, movable contact surface (7a) of a first guide element (7) and a second contact surface (2a), movable relative to the first contact surface (7a), of a second guide element (2). The temperature of the guide element (2,7) is controllable. The mass is displaced in the gap (6) over a path where solidifying takes place, the relatively narrow gap having such a height that the mass solidifying and solidified off the two contact surfaces (2a,7a), forced through the gap (6), is exposed, as a result of the movement of the two guide elements (2,7) relative to each other, to a frictional treatment before leaving the gap (6).

Description

Title: Method and apparatus for solidifying a pumpable mass

The invention relates to a method for solidifying a pumpable mass by applying the mass onto a first, movable contact surface of a first guide element whose temperature is controlled by contacting a surface facing away from the first contact surface with a medium influencing the temperature of the first contact surface, wherein the mass, at a place of application, is brought onto the first contact surface, is displaced along a path where the solidification takes place, and at the end of the path is removed from the first contact surface, as well as to an apparatus for carrying out such a method. For thus solidifying a pumpable mass, different methods are known, solidifying being understood to mean both drying by means of heating, for instance with the aid of a roller dryer, a paddle dryer or a disc dryer, and congealing by means of cooling, for instance with the aid of a cooling roller, a cooling belt or a disc cooler, whereby the pumpable mass is transformed into a mass which, depending on the -residual degree of moisture, is, to a greater or lesser extent, dry, granular or powdered.

Drying with the aid of a roller means having to use a relatively expensive and complicated overall construction, which is extremely laborious to clean, and, further, a drying process. Garried out with a roller is difficult to automate. The mass to be processed is applied to the upper side of the horizontally arranged roller of a relatively large diameter. To enable a layer to be applied to the roll with a uniform and desired thickness, a separate roller system is used, which can be accurately positioned and set with respect to the roller. The mass drying and setting during the rotation of the roller will stick onto the roller. surface and^'is to be scraped -off it with a squeegee, after which the. loosened material, if desired, is to be comminuted during a subsequent processing operation. Any vapors and gases escaping from the drying mass are to be- collected and removed, .whilst the scraping off and possible further crumbling leads to dust formation. As a result of these factors, the working space in which work is done gets rapidly polluted. This can be prevented with an encasing which, however, because of the large dimensions of the roller, should be rather sizeable. For the same reasons, providing a vacuum construction is costly and much heat loss occurs through radiation and through heating up of the ambient and transport air. In an apparatus provided with paddles or discs, no sticky products can be processed. In this case too, a voluminous construction requiring much space is involved, entailing relatively much heat loss. Moreover, especially the construction of paddle shafts is rather expensive and delicate. Cooling belts are extremely sensitive to wear, entail major maintenance problems, are subject to a relatively large heat loss and require a relatively large set-up surface.

The object of the invention is to improve a method of the type described in.the opening paragraph hereof, such that the pumpabl&mass" can solidify in a compact, enclosed and shielded space utilizing a relatively small number of relatively, simple means.

This is achieved according to the invention if at the location of said path, with the first guide element and a second guide element provided with a second contact surface, of which the second contact surface moves substantially parallel to and relative to the first contact surface, and of which the temperature is controlled by contacting a surface facing away from the second contact surface with a medium influencing the temperature of the second contact surface, a relatively narrow gap is formed through which the mass to be processed is pressed from the place of application, the relatively narrow gap having such a height that the mass solidifying and solidified off the two contact surfaces, forced through the gap, is exposed, as a result of the movement of the two guide elements, relative to each other, to a factional treatment before leaving the gap. Through these measures, in a relatively small space, a relatively large contact surface for effecting^' the solidification is provided. Here, the layer thickness, the residence time, the eventual moisture content and the extent of solidification can be accurately set and controlled, whilst such setting and such control can be automated in a relatively simple manner. Since for the heating or for the cooling, processing energy is supplied from both contact surfaces to the mass to be treated, this mass can be processed extremely intensely and the energy losses can be reduced to a minimum due to the enclosed character of the narrow gap. Subjection to the frictional treatment can result in grinding or crumbling within the gap, in which case the dust formation polluting the environment is limited to a minimum.

In order for the process conditions to be influenced as optimally and variedly as possible, according to further embodiments of the invention, a number of supplemental measures may be provided. Thus, for instance, the temperature of the first guide element can be controlled independently of that of the second guide element for obtaining an optimum temperature gradien in the layer of mass to be solidified and subsequently to be exposed to the frictional treatment. For materials of mutually different properties to be successively processed optimally, it may be preferred to enlarge or reduce the gap between the two guide elements moving relative to each other. If work is to be done with a sticky mass, then it may be preferred for the gap - between the two guide elements moving relative to each other to be reduced locally and/or temporarily. In that case, the two contact surfaces can be ■ locally or temporarily brought towards each other so far that between those contact surfaces a clean-scraping action occurs, which action can be maximized by reducing the gap to virtually zero. By further providing that at least in the gap a reduced pressure prevails, it is possible, in the solidification by means of heating so as to abstract water from the mass, to work with lower temperatures than at atmospheric pressure, which provides advantages inter alia in the processing of temperature-sensitive products. The invention further relates to an apparatus for carrying out a method for solidifying a pumpable mass. To that end, in an apparatus which is provided with a housing in which a first guide element is situated, which is provided with a movably arranged first contact surface and with means for controlling the temperature of the first contact surface, whilst further means are present to enable, at a first place, mass to be treated to be supplied to the first contact surface and to enable, at a second place, situated at a distance from the first place, solidified mass to be removed from the first contact surface, as known in the apparatuses discussed above, it is proposed, according to the invention, that a second guide element, which is provided with a second contact surface and with means for controlling the temperature of the second contact surface, with its second contact surface facing towards and substantially parallel to the firδt Cόϊ-.ta<_t- surface, is so arranged that the two contact surfaces, form a gap_; the second contact surface being arranged to be movable substaiitially parallel to an relative to the ^'first contact surface, and at the second^place collecting means for solidified mass are arranged. Thus, with relatively simple means, an extremely compact apparatus with a relatively large contact surface can be realized, whilst through the combination of the mass becoming more viscous and the movement of the two contact surfaces relative to each other, automatically a frictional processing, such as a crumbling or grinding of the solidifying and solidified layer is obtained.

It is particularly preferred that the apparatus is further characterized in that the first and the second guide element both have a rotation- symmetrical contact surface with each a centerline, the first place being situated at the location of the centerline of at least one of the rotation- symmetrical contact surfaces, the second place being the outer circumference thereof and at least one of the two rotation-symmetrical contact surfaces being drivable for rotation around its centerline. Thus the apparatus can be realized in a relatively simple manner, while the mass is displaced between and along the contact surfaces by the pumping pressure under which the mass is supplied, supported by the centrifugal action as a result of one or both contact surfaces being driven in rotation.

To make it possible that different masses to be treated are taken into account, it may be arranged that the distance between the two rotation- symmetrical contact surfaces is adjustable.

The centerlines may then extend substantially both vertically and horizontally. Vertical then means a promoting of the uniform flow -through; horizontal gives better exhaust possibilities for any escaping vapors and gases. Naturally, if desired, an arrangement of the centerlines at any suitable angle between vertical and horizontal is possible.

The contact surfaces can be formed by flat, plane disc surfaces. It is preferred, however, that the rotation-symmetrical contact surfaces have a cone shape with a divergence that may or may not vary. In the latter case, a conceivable cone shape would be one with a stepped divergence or a flowingiy increasing divergence. With a cone shape, in contrast with a flat disc, the extent to which the diameter of the circumferential gap increases depending on the distance to the supply can in many ways be varied and optimized by modification of the apical angle of the cone. In the use of a cone shape for the contact surfaces, in an advantageous and relatively simple manner, a self-cleaning action can be obtained if according to a further elaboration of the invention the centerline of one rotation-symmetrical contact surface extends parallel to and at a short distance from the centerline of the other rotation-symmetrical contact surface and can rotate about that centerline. Thus, a varying gap can be obtained and the mass can thereby be prevented from sticking to the contact surfaces. This effect can be optimized if, further, the short distance between the two centerlines is such that the two rotation-symmetrical contact surfaces all but touch each other, or touch each other very lightly. Further, it is also possible that the first and the second guide element both have an elongated contact surface, with at least one of the contact surfaces forming part of a drivable conveyor belt.

If desired, it may be further arranged that at least one of the contact surfaces is provided with guide strips for the mass to be treated. This feature may have advantages for transporting the mass and determining the residence time of the mass.

If during the treatment vapors or gases are released from the mass to be solidified, it is preferred that the housing is provided, beyond the second place, with vapor and gas exhaust means. If desired, these means could be combined with means for creating a reduced pressure in the housing in order to enable lower temperatures to be employed in drying.

Referring to embodiments schematically represented in the drawing, though exclusively by way of non-limiting examples, the method and apparatus for solidifying a pumpable mass according to the invention will presently be further elucidated. In the drawing:

Fig. 1 shows a first embodiment with horizontal rotation axis; Fig. 2 shows a second embodiment with vertical rotation axis; Fig. 3 shows a third embodiment with rotation body bearing-mounted on two sides; and

Fig. 4 shows a fourth embodiment with horizontal rotation axis. The apparatus represented schematically in Fig. 1 is. provided with a housing 1, of whioh only a single wall is represented; but which may further comprise various elements to provide for encasement and support in any- desired and suitable manner. A cone-shaped body 2 is fixedly arranged in_. the housing 1. The cone-shaped body 2 is of double -walled design and defines an enclosed space 3 with a supply branch 4 and a discharge branch 5. Within the cone-shaped body 2, while leaving clear a relatively narrow gap 6, a hollow cone 7 is arranged which is held in place by means of a hollow shaft end 8 which is. mounted rotatably in a bearing 9. Connected to the hollow shaft end 8 is a fixedly arranged inlet duct 10, while an outlet duct 11 extends from the hollow cone 7 via the hollow shaft end 8 and the inlet duct 10, breaking through the latter. The cone-shaped body 2 has an open top to which is connected a pipe stub 12 through which the hollow shaft end 8 extends and which has a product inlet 13 radially connected thereto, which is in open communication with the gap 6. The space between the hollow shaft end 8 and the pipe stub 12, viewed from the hollow cone 7, is closed off, beyond the product inlet 13, by a sealing ring 14. At its side remote from the pipe stub 12, the gap 6 terminates in an enclosed housing space 15, which is provided with a vapor discharge 16 and a product discharge 17.

The procedure for solidifying a pumpable mass with the above- described apparatus may be as follows.

By supplying the cone-shaped body 2 with steam via the supply branch 4, the inner wall 2a is adjusted to the desired temperaturer^To minimize heat losses, the outer wall 2b will be suitably insulated. Cooled and/or condensed steam is abstracted from the cone-shaped body 2 via the discharge branch 5. Similarly, the outer wall 7a of the hollow cone 7 is adjusted to the desired temperature by means of steam supplied via the inlet duct 10, whilst the basic wall 7b may be insulated to prevent heat losses as much as possible. Steam cooled and/or condensed in the hollow cone 7 is discharged via the outlet line 11. As the hollow cone 7 and the cone-shaped body 2 can be supplied independently of each other, if desired, the outer wall 7a, which bounds the gap 6 on one side, can have a different temperature than the inner wall 2a, which bounds the gap 6 on the other side. Further, during the heating process, the hollow cone 7 is caused to rotate by driving means, not shown.

When the temperature in the gap 6 and the speed of the hollow cone 7 have reached the desired value, then, via the product inlet 13, under pressure, by a pump not shown, a mass to be treated is pressed into the gap 6, thereby filling it up completely, while the rotating hollow cone 7 provides for a uniform distribution of the mass supplied. The heated inner wall 2a and the heated outer wall 7a in combination with the relatively narrow gap 6 form a relatively large contact surface, so that the mass to be solidified is heated intensely and uniformly. As a result, the water evaporates from the mass, which becomes more and more viscous as a result, and at some point the viscosity becomes such that, as a result of the narrow gap 6 and the surfaces of the inner wall 2a and the outer wall 7a bounding the narrow gap 6 and moving relative to each other, discrete rolls of material are formed, in which form the mass leaves the gap 6 and falls down to be discharged from the housing 1 via the product discharge 17. Vapors and/or gases generated during this process rise and are removed from the housing 3 via the vapor discharge 16.

The above-described process can be managed in various ways through control of a number of parameters. It has already been noted that the inner wall 2a ean have a different temperature .than the quter wall 7a. The - temperature of an inner wall can be tuned to the optimal conditions through corresponding control of the pressure and the temperature of the steam supply. A further control factor is the speed of the hollow cone 7. Further, in the interior of the housing 1, a reduced pressure can be applied, so that water to be separated starts to evaporate at a lower temperature, which may be preferred in the processing of temperature-sensitive materials. An important parameter is the height of the gap 6. It can be- influenced by arranging the cone-shaped body 2 and the hollow cone 7 to be adjustable with respect to each other, for instance by arranging the cone-shaped body 2 to be movable and securable in horizontal direction. A likewise important parameter is the pressure at which the mass is supplied to the gap 6,' which allows the residence time of the mass in the apparatus to be influenced in conjunction with inter alia the speed and the height of the gap. Depending on inter alia the properties of the mass to be processed and the. desired residual moisture content therein upon processing, for each instance of use, optimum parameters can be determined, set and, automatically or not, (fine)-adjusted.

If sticky or caking material is to be processed, an automatic and, if desired, continuous clean-scraping of the contact surfaces of the walls 2a and 7a can be accomplished by arranging for the centerlines of the hollow cone 7 and the cone-shaped body 2 not to coincide but to extend parallel to and at a short distance from each other, for instance in such a way that the hollow cone 7 and the cone-shaped body 2, in the form of a line, all but touch, or touch very lightly. This can be realized by adjusting the cone- shaped body 2 in vertical direction. If it is then deemed undesired that the scraping area is always situated at the same place, it may be provided that the centerline of the cone-shaped body 2 rotates about the centerline joJ.^"ther hollow cone 7, so that a moving scraping area is ;obtaine^*d: The apparatus shown in Fig. 2 is provided, with a housing 21, in which a fixed cone-shaped body 22 is situate^, which^by a hollow design, forms an enclosed space 23 and envelops a hollow cone 27. while leaving clear a gap 26. To the top of the hollow cone 26 connects a shaft end 28 which is bearing-mounted in a bearing 29. To the top of the hollow cone- shaped body 26 connects a pipe stub 32, which is provided with a product - inlet 33.. A sealing ring 34 is situated, viewed from the hollow cone 27,. beyond the product inlet 33 in the annular space between the shaft end 28 and the pipe stub 32. The gap 26 terminates at the base of the hollow cone 27 in a funnel- shaped housing space 35 including, in addition to the hollow cone-shaped body 22, a vapor discharge 36 and, in the lower funnel end, a product discharge 37. The hollow cone-shaped body 22 and the hollow cone ^'27 can be supplied with a heating medium in the manner as, for instance, represented in Fig. 1 and discussed above. The operation of this apparatus is substantially identical to that as described hereinabove with reference to Fig. 1. In Fig. 3, the parts that are the same as those in Fig. 1 are designated with the same reference numerals. Compared with Fig. 1, both the shape of the hollow cone-shaped body 2' and that of the hollow cone 7' have been modified. Instead of a cone shape of constant divergence, the cone shape chosen in the embodiment according to Fig. 3 involves an initial wide divergence followed by an appreciably lesser divergence, which, if desired, could even be zero. Thus, for instance, the gap 6' can be designed with a different height in different areas, and in the area of slight divergence gravity has less influence on the distribution of the mass in circumferential direction. Further, the hollow cone 7', instead of being bearing-mounted on one side, has been bearing-mounted on two sides by providing, perpendicularly to the base plane 7b' in line with the shaft end 8, an axle journal 18 which is supported by a bearing 19.

In Fig. 4, again, those parts that are the same as those in Fig. 1 are designated with the same reference numerals. In the embodiment according to Fig..4, the hollow cone-shaped body 2 of Fig. 1 has been replaced with a hollow, substantially disc-shaped body 42, and the hollow cone 7 with a hollow, substantially disc-shaped body 47. The bodies 42 and 47 each have a flat, planar contact surface, which, directed towards each other, define a gap 46. A product supply 53 extends centrally through the disc-shaped body 42. Through the arrangement and design of the gap 46, the solidified mass leaving the gap 46 is collected and guided to a product discharge 58, while gases and vapors can be removed from the housing via the vapor discharge 59. It will be evident that within the scope of the invention as laid down in the appended claims, many other modifications and variants are possible. Thus, for instance, steam has been mentioned as a heating medium. This can also be any other medium, or a cooling medium. It is also possible to heat in a different manner, for instance electrically. The fixed cone-shaped body may also be rotatably arranged and driven; Instead of arranging for the centerline of one cone to rotate about the centerline of the other cone, it is also conceivable to arrange for one or both cones to vibrate, or to have an eccentric perform a reciprocating movement. Further, a variety of other cone shapes than shown in the drawing are possible. Thus, instead of the sharp transition shown in Fig. 3, a transition of flowing configuration can be chosen, and also there may be more transitions present. If desired, it is also possible to provide guide ribs on the surfaces bounding the gap.

Claims

1. A method for solidifying a pumpable mass by applying the mass onto a first, movable contact surface of a first guide element whose temperature is controlled by contacting a surface facing away from the first contact surface with a medium influencing the temperature of the first contact surface, wherein the mass, at a place of application, is brought onto the first contact surface, is displaced over a path where the solidification takes place, and at the end of the path is removed from the first contact surface, characterized in that at the location of said path, with the first guide element and a second . guide element provided with a second contact surface, of which the second contact surface moves substantially parallel to and relative to the first contact surface, and of which the temperature is controlled by contacting a surface facing away from the second contact surface with a medium influencing the '^temperature of the second contact surface, a relatively narrow gap is formed *. through which the mass to be processed is pressed from the place of . application, the relatively narrow gap having such a height that the mass solidifying and solidified off the two contact surfaces, forced through the gap, is exposed, as a result of the movement of the two. guide elements relative to each other, to a frictional treatment before leaving the gap.

2. A method according to claim 1, characterized in that a guide element is heated.

3. A method according to claim 1, characterized in that a guide element is cooled.

4. A method according to claim 2 or 3, characterized in that the temperature of the first guide element is controlled independently of that of the second guide element.

5. A method according to any one of the preceding claims, characterized in that the gap between the two guide elements moving relative to each other is reduced locally.

6. A method according to any one of the preceding claims, characterized in that the gap between the two guide elements moving relative to each other is reduced temporarily.

7. A method according to claim 5 or 6, characterized in that the gap is reduced to virtually zero.

8. A method according to any one of the preceding claims, characterized in that at least in the gap a reduced pressure prevails.

9. An apparatus for solidifying a pumpable mass, provided with a housing in which a first guide element is situated, which is provided with a movably arranged first contact surface and with means for controlling the temperature of the first contact surface, whilst further means are present to enable, at a first place, mass to be treated to be supplied to the first contacfsurface and to enable, at a second place situated at a distance from the first place, solidified mass to be removed from the first contact surface, characterized in that a second guide element, which is provided with a second contact surface and with means for controlling the temperature of the second contact sμrface, with its second contact surface facing towards and substantially parallel to the first contact surface, is so arranged that the two contact surfaces form a gap, the second contact surface being arranged to be movable substantially parallel to and relative to the first contact surface, and at the second place collecting means for solidified mass are arranged. ' ^'

10. An apparatus according to claim 9, characterized in that the first and the second guide element both have a rotation- symmetrical contact surface with each^'a centerline, the first place being situated adjacent the centerline of at least one of the rotation-symmetrical contact surfaces, the second place being the outer circumference thereof, and at least one of the two rotation- symmetrical contact surfaces being drivable for rotation about its centerline.

11. An apparatus according to claim 10, characterized in that the distance between the two rotation-symmetrical contact surfaces is adjustable.

12. An apparatus according to claim 10 or 11, characterized in that the centerlines extend substantially vertically.

13. An apparatus according to claim 10 or 11, characterized in that the centerlines extend substantially horizontally.

14. An apparatus according to any one of claims 10-13, characterized in that the rotation-symmetrical contact surfaces have a cone shape.

15. An apparatus according to claim 14, characterized in that the cone shape has a varying divergence.

16. An apparatus according to any one of claims 10-15, characterized in that the centerline of one rotation-symmetrical contact surface extends parallel to and at a short distance from the centerline of the other rotation- symmetrical contact surface and can rotate about-triat centerline.

17. An apparatus according to claim 16, characterized in that the short distance between the two centerlines is such hat the two rotation- symmetrical contact surfaces all but touch, or touch very lightly.

18. . An apparatus according to claim 9, characterized in that the first and the second guide .element both have an elongated contact surface, with at least one of the contact surfaces forming part of a drivable conveyor belt.

19. An apparatus according to any one of claims 9-18, characterized in. that at least one of the contact surfaces is^' provided with guide strips for the mass to be treated.

20. An apparatus according to any one of claims 9-19, characterized in that the housing is provided, beyond the second place, with vapor and gas exhaust means.

21. An apparatus according to any one of claims 9-20, characterized in that means are present to create a reduced pressure in the housing.