WO2005110070A1

WO2005110070A1 - Method and device for separating solid from milk or a milk product

Info

Publication number: WO2005110070A1
Application number: PCT/NL2005/000376
Authority: WO
Inventors: Herbert Zeevalkink; Meindert Keizer; Henk Van Oosten
Original assignee: Hovap International (Holland) B.V.
Priority date: 2004-05-19
Filing date: 2005-05-18
Publication date: 2005-11-24
Also published as: NL1026231C2

Abstract

The invention relates to a device for separating a selected solid, such as fat cream, lactose, salt, sugar or protein, from milk or a milk product, for instance whey, such as whey concentrate and whey permeate, comprising: an inlet (2) for the milk or the milk product; at least one separating stage (7) ; and at least two outlets (3, 6) for at least partially separate discharge of the selected substance and a residue, wherein the separating stage comprises a hydrocyclone.

Description

METHOD AND DEVICE FOR SEPARATING SOLID FROM MILK OR A MILK PRODUCT

The present invention relates to a device for separating a selected solid, such as fat cream, lactose or protein, from milk or a milk product, for instance whey such as whey concentrate and whey permeate, comprising: an inlet for the milk or the milk product; at least one separating stage; and at least two outlets for at least partially separate discharge of the selected substance and a residue. The present invention also relates to a method for the same purpose, comprising of: providing the milk or the milk product; subjecting the milk or the milk product to at least one separating stage; and at least partially separately discharging the selected substance and a residue at least at two outlets. Such devices and methods are generally known in the art. Use is normally made here, as the separating stage, of at least one decanter. It is particularly the use of such decanters which results in a number of drawbacks of the known art. Decanters are renowned for being difficult to clean. This is particularly a disadvantage in the case of milk products or milk in which whey contains for instance lactose, sugar, salt and protein. The process of separating or isolating has to be interrupted for a long time when a determined degree of contamination, which is clearly associated with decanters, results in a need for cleaning. Decanters are moreover also particularly difficult to clean per se because of the configuration and structure thereof. It is noted in this respect that lactose in particular is an exceptionally expensive substance, certainly when it can be provided in a particularly pure form, for which purpose the separating process must be especially effective. Contamination by protein, when the raw material is whey, results in unacceptably high levels of contamination by protein in the lactose after the process. Considerable improvements are in any case desirable in the efficiency of separating solids from milk and/or milk products. The present invention has for its object to provide an improvement in respect of the known art and to obviate or at least considerably reduce the drawbacks of the known art, for which purpose according to the present invention use is made in the separating stage of at least one hydrocyclone. Such hydrocyclones can be cleaned rapidly and efficiently and furthermore have a considerably higher efficiency in the separation of solids. The operation of hydrocyclones can moreover be better controlled and individual separating stages, each with a hydrocyclone, can be coupled in efficient manner, whereafter the assembly can in turn also be well controlled, at least during operation thereof. A large number of separating stages can also be chosen such that the purity of the obtained solids can be increased to a very high level. The dependent claims 2-19 relate to preferred embodiments of devices (and methods) within the scope of the present invention as defined in the main claim 1 and independent claim 20. Claim 2 thus relates to the use of additional separating stages which likewise comprise a hydrocyclone. Through a suitable choice of the number of separating stages a desired purity of the selected solid to be ultimately obtained can thus be achieved. The device herein preferably has the features of claim 3, and additionally or alternatively such a device has the features of claim 4. A device according to the invention preferably has a feed for washing liquid. This can serve to bring to and hold at a desired level the fluidity, and therefore the transportability, of the selected solid through the device. According to claim 6, such a washing liquid can comprise water. In an embodiment with at least two separating stages in series according in any case to claim 4, also having a feed for washing liquid according to claim 5, the device preferably has the features of claim 7. It is favourable if the washing liquid with residue is carried through the device in opposite direction to the movement of the selected solid, precisely because in the later separating stages of the process a higher concentration of the selected solid is provided which then becomes progressively more difficult to transport, and the washing liquid is therefore introduced at a point where it is the most effective. The features of claim 8 are preferably also realized in a device with a feed for washing liquid according to the invention. The control and the measuring means control the device in a manner such that a throughfeed, and therefore output, of the selected solid can be effected that corresponds to the capacity of the separating stages. Controllable pump means are preferably used here as defined in claim 9, which are controlled by the control of claim 8 for the purpose of adjusting the feed of the washing liquid, likewise in accordance with the throughfeed capacity of the separating stages used. The outlet of the final separating stage in the process is preferably coupled to pump means as according to claim 10 for forced and controlled discharge of the selected solid from the outlet of the device, so that the throughfeed capacity of the individual and combined separating stages is thereby also influenced in a favourable manner. A filter can herein be connected to the pump means as defined in claim 11. Such a filter can be used to separate washing liquid and the selected solid from each other, wherein the washing liquid is thus in fact used in the movement toward the filter as medium for transporting the selected solid. Measuring means can be arranged from the pump to the filter in order to determine whether sufficient washing liquid is being supplied as carrier for the selected solid. In response to a finding of such measuring means a liquid conduit connected to the pump means can be opened as according to claim 13 so as to provide a required quantity of liquid, in particular washing liquid, for a safe transport of the selected solid toward the filter. At the filter the selected solid and the liquid, in particular washing liquid, are then separated and the liquid can flow to a reservoir as defined in claim 14. The reservoir can further be connected to a branch of the liquid conduit for selective opening, which can be opened when a low level of liquid is found in the reservoir . In an embodiment which in any case has a feed for washing liquid, the measure of claim 16 is favourable because washing liquid can thus be extracted from the reservoir. In an additional or alternative embodiment there is provided a control which comprises measuring means at the inlet of the device, as defined in claim 17. It is thus possible to check whether a quantity of milk or milk product is being introduced that corresponds to the throughfeed capacity of the device. Preferably arranged here on the inlet is a controllable pump which is sensitive to such a finding for the purpose of harmonizing the inlet flow with the processing capacity. A return conduit can be or is here arranged from the outlet to the inlet, in order to in any case harmonize the feed rate of selected solid with this processing capacity. The invention will be elucidated hereinbelow on the basis of two exemplary embodiments thereof which are shown in the accompanying drawing, in which: fig. 1 shows a schematic view of a first embodiment of a device according to the present invention; and fig. 2 shows a schematic view of a second embodiment . Fig. 1 shows a first embodiment of a device 1 according to the present invention with which a corresponding method is implemented. The device comprises an inlet 2 and two outlets 3, 6. Inlet 2 is connected to a tank 4 having therein milk or a milk product, for instance whey, such as whey concentrate and whey permeate, having therein solid such as fat cream, lactose, salt, sugar or protein. The milk or the milk product will be referred to as raw material 5. The device comprises a first separating stage 7, a second separating stage 8 and, connected therebetween, a third separating stage 9. Each of these separating stages 7, 8 and 9 comprises a hydrocyclone 10. The inlet of the hydrocyclone of separating stage 7 is connected to tank 4. The first outlet 11 of hydrocyclone 10 of the first separating stage 7 is connected to the inlet of hydrocyclone 10 of the third separating stage 9, and the first outlet 12 thereof is in turn connected to the inlet of hydrocyclone 10 of the second separating stage 8. The outlet 13 of hydrocyclone 10 of the second separating stage 8 is connected to outlet 3 of device 1. A second outlet 14 of hydrocyclone 10 of the second separating stage 8 is connected to the inlet of hydrocyclone 10 of the third separating stage 9, the second outlet 15 of which is in turn connected to the inlet of hydrocyclone 10 of the first separating stage 7. The second outlet 16 of the first separating stage 7 simultaneously forms the second outlet 6 of device 1. The other outlet 3 of device 1 is connected to a filter 17, from which liquid is carried via a conduit 19 to a reservoir 18 and from which solid is fed to a dryer 20. The selected solid for separating which must be obtained from raw material 5 comes available after being subjected to the action of the dryer. The device further comprises a liquid feed 21 which runs to the first outlet 13 of the second separating stage 8 and from which a branch 22 runs to reservoir 18. A conduit 23 further runs from reservoir 18 to the inlet of hydrocyclone 10 of the second separating stage 8. Liquid in reservoir 18 thus comes from conduit 19 or branch 22 and is provided at the inlet of the second stage 8, from where it is carried via the second outlet 14 to the inlet of the third stage 9 and subsequently via the second outlet 15 of stage 9 to the inlet of the first stage 7, from where the liquid is carried via the second outlet 16 or outlet 6 of the device to another additional hydrocyclone 24 and is discharged from a second outlet 25 thereof. This path of liquid from reservoir 18 is indicated in fig. 1 with dash-dot-dot lines . Raw material 5 from tank 4 is supplied to inlet 2 of device 1 and follows the serial path from an inlet of a hydrocyclone 10 of a stage via the first outlet thereof to the inlet of the subsequent hydrocyclone 10 in the following stage. This is at least the case for the selected solid to be separated from the raw material 5 subject to the setting parameters of the diverse components, more explanation of which follows below. The path of the selected solid to be separated is indicated with dotted lines in fig. 1, and this shows that the selected solid to be separated and the liquid from reservoir 18 follow opposing paths through device 1. It should be noted here that at the second outlet 14, 15 or 16 of a hydrocyclone 10 in each of the stages 7, 8 and 9 not only is the liquid discharged from reservoir 18, but also as much of the residues as possible, i.e. as much as possible of the liquids and substances in raw material 5 other than the selected solid to be separated. To the extent that a determined quantity of this selected solid to be separated is still present at outlet 6 of the device in the combined materials presented to hydrocyclone 24 at the inlet 27 thereof, this quantity can still be fed back via conduit 26 into device 2 at the inlet thereof. Arranged at the inlet of hydrocyclone 10 in the first stage 7 is a meter which generates a control signal for a pump 29 which is connected to tank 4 for regulating the infeed flow of raw material 5 from tank 4. Meter 28 carries out a more or less accurate analysis of the quantities of liquid, residue and selected solid for the purpose of controlling pump 29 in accordance with the throughfeed capacity of the assembly of stages 7, 8 and 9, herein taking into account the feedback of selected substance via conduit 26, the throughfeed of liquid and residue from outlet 25 of the third stage 9 and the supply of raw material 5 via inlet 2. A very efficient fine adjustment of device 1 and the quantities of raw material supplied thereto can thus be realized. Arranged at outlet 3 of the device is a similar meter 30 which measures the discharge from the first outlet 13 of hydrocyclone 10 in the second separating stage 8, which is substantially selected solid to be separated. In accordance with the measurements of meter 30 there follow a number of control actions. Measurement signals from meter 30 are used to control a pump 31 connected to outlet 13. A valve 32 in liquid feed 21 can likewise be controlled with the signal from meter 30 in order to dilute the slurry released at outlet 13 and enable transport thereof to filter 17 with pump 31. If the supplied quantity of liquid from liquid feed 21 is not sufficient at any given moment, this is detected by a further meter 35 which in fact therefore signals emergency situations and further controls valve 32 for supply of more liquid. The signal from meter 30 is also used to control a valve 33 which is arranged in conduit 23 for the purpose of providing liquid from reservoir 18 to the inlet of hydrocyclone 10 in the second separating stage 8. Control of pump 31, valve 32 and valve 33 on the basis of measurement signals from meter 30 therefore serves the purpose of harmonizing the system conditions for optimizing the parameters to each other so as to obtain the highest possible output of selected solid to be separated, while taking into account the processing capacity of separating stages 7, 8 and 9, the quantities of raw material supplied and so on. Meters 28, 30 and 35 are described in the foregoing as generating signals on the basis of which other components in device 1 can be controlled. It is noted that controls are therefore formed which can all form part of a single control for the process or the method performed with device 1. such a control or such a number of controls can comprise individual data-processing units, such as computers. It is further noted that in the system of device 1 there is provided a further feed for washing liquid 36 with which an efficient cleaning of device 1 can be effected. Feed 36 runs to inlet 2 of device 1 as well as to reservoir 18. Use is made for this purpose of valves 37, which are opened when the system of device 1 according to the invention is not in operation in order to clean the device 1. The cleaning liquid herein runs through all aspects and flows and an effective and efficient cleaning of device 1 can be provided. Fig. 2 shows an alternative embodiment of a device 38 according to the present invention. This once again comprises the three separating stages 7, 8 and 9 and is substantially the same as device 1 shown in fig. 1, with the following exception. In the device 1 shown in fig. 1 the signal from meter 28 is used to control a controllable pump 29. The throughfeed capacity of the assembly of separating stages 7, 8 and 9 and the supply of raw material 5 are hereby adjusted to each other. In the embodiment of fig. 2 the signal from meter 28 is used to control a valve 39 in a conduit 40, which conduit 40 runs from outlet 3 back to inlet 2 to in any case harmonize the supply of selected solid to be separated to the outlet of the first separating stage 7 with said throughfeed capacity. As already noted, the configuration of the device of fig. 2 is otherwise the same as that of device 1 in fig. 1. After perusal of the foregoing, many alternative and additional embodiments will occur to the skilled person, all of which must be deemed as falling within the scope of protection of the present invention as defined in the appended claims and to the extent such embodiments do not differ appreciably from in any case the essence of the thus defined invention. More or fewer stages can for instance be used than the three in the embodiments shown in the figures. A cleaning system can be omitted, and although not essential, it is deemed very desirable. There are diverse other control options for setting parameters and adjusting throughfeed and feedback flows in relation to the processing capacity of a device according to the present invention. Such control options are well within the reach of the person with ordinary skill in the art in the field of the present invention, and are therefore not discussed further here. Data-processing units, such as computers, can be used as components of the controls used and applied in such systems and devices, although such data- processing devices are not shown in the drawings and there are moreover many other possibilities for controlling the progress of the flows. It is thus possible to connect directly to a discharge the outlets of each of the stages 7, 8 and 9 intended for the liquid and the residue, although there is then a great chance of much of the selected solid to be separated being lost, which is precisely what can be avoided with the cycles shown in fig. 1 and 2.

Claims

1. Device for separating a selected solid, such as fat cream, lactose, salt, sugar or protein, from milk or a milk product, for instance whey, such as whey concentrate and whey permeate, comprising:

- an inlet for the milk or the milk product;

- at least one separating stage; and - at least two outlets for at least partially separate discharge of the selected solid and a residue; wherein the separating stage comprises a hydrocyclone.

2. Device as claimed in claim 1, wherein the separating stage is a first separating stage and the device further comprises at least one second separating stage with a hydrocyclone between the inlet and the outlets .

3. Device as claimed in claim 2, wherein the first and second separating stages are connected in series and the outlet for substantially the selected solid from the first separating stage and the inlet of the second separating stage are connected to each other.

4. Device as claimed in claim 2 or 3, wherein the first and second separating stages are connected in series and the outlet for substantially the residue from the second separating stage and the inlet of the first separating stage are connected to each other.

5. Device as claimed in at least one of the foregoing claims, further comprising a feed for washing liquid.

6. Device as claimed in claim 5, wherein the washing liquid comprises water.

7. Device as claimed in claim 4 and either of the claims 5 and 6, wherein the feed is connected to the inlet of the second separating stage and washing liquid with residue is carried through the device in opposite direction to the movement of the selected solid.

8. Device as claimed in claim 5, 6 or 7, further comprising a control which comprises measuring means at the outlet for determining a momentary discharge flow of the selected solid to be separated.

9. Device as claimed in claim 8, further comprising controllable pump means at the feed for controlled feed of washing liquid, wherein the control is adapted to control the pump means for the purpose of adjusting the momentary feed flow of washing liquid in accordance with the processing capacity of at least the separating stage on the basis of the discharge flow.

10. Device as claimed in at least one of the foregoing claims, further comprising pump means at the outlet for discharge of the selected solid to be separated.

11. Device as claimed in claim 10, wherein a filter is connected to the pump means.

12. Device as claimed in claim 11, wherein measuring means are arranged between the pump means and the filter in order to determine the flow of solid out of the pump means.

13. Device as claimed in claim 12, further comprising a liquid conduit which is connected to the pump means and which can be opened selectively, and which can be opened in response to a signal from the measuring means, said signal being an indication of the need for more liquid.

14. Device as claimed in claim 11, 12 or 13, wherein a reservoir for liquid is connected to the filter.

15. Device as claimed in claims 13 and 14, wherein the reservoir is further connected to a branch of the liquid conduit to be opened selectively, which can be opened in the case of a low level of liquid in the reservoir.

16. Device as claimed in at least one of the foregoing claims 5-15, wherein the feed for washing liquid is connected to a or the reservoir.

17. Device as claimed in at least one of the foregoing claims, comprising a control which comprises measuring means at the inlet for determining a momentary inlet flow of the milk or the milk product.

18. Device as claimed in claim 17, further comprising controllable pump means at the inlet for controlled infeed of the milk or the milk product, wherein the control is adapted to control the pump means for the purpose of adjusting the momentary inlet flow in accordance with the processing capacity of at least the separating stage.

19. Device as claimed in claim 17 or 18, further comprising a return conduit from the outlet to the inlet, which can be selectively opened and closed and along which, under the influence of the control, selected solid can be carried selectively to the inlet of the separating stage in accordance with the processing capacity of the separating stage.

20. Method for separating a selected solid, such as fat cream, lactose, sugar, salt or protein, from milk or a milk product, for instance whey, such as whey concentrate and whey permeate, comprising of:

- providing the milk or the milk product;

- subjecting the milk or the milk product to at least one separating stage; and

- at least partially separately discharging the selected substance and a residue at least at two outlets; wherein the separating stage comprises a hydrocyclone.

21. Method as claimed in claim 20, further comprising at least one step for implementing a task of a component of a device as claimed in at least one of the foregoing claims 1-19.