NL1006806C2 - Method and device for the continuous preparation of granulate mixtures. - Google Patents

Description

975134 / WK / tnke

Short designation: Method and device for the continuous preparation of granulate mixtures.

The present invention relates to a process for preparing granulate mixtures, in particular sand and / or gravel, with predetermined composition or particle size distribution, comprising the steps of: 5 - providing, for example by recovering, a raw starting granulate, in in particular a sand and / or gravel mixture, separating the starting granulate into fractions of different particle size distributions, dosing at least two fractions in a dosed manner into a first granulate final mixture, delivering the first granulate to a first container. final mixture.

Such a method is known from NL-A-8105887. According to NL-A-8105887, a coarse sand mixture is recovered and separated into separate fractions of distinct particle size distribution, after which the fractions are stored in separate silos. A sand mixture of a desired composition can be produced from the stored fractions, without thereby being directly dependent on the composition of the raw raw material obtained.

One of the drawbacks of the method according to NL-A-8105887 is the fact that as soon as too little material of a certain particle size distribution is present in the raw starting material, which material is required for the final mixture to be produced, the relevant stock. exhausted, so that the composition of the mixture should be interrupted. At the same time, the silos, in which material with a different particle size distribution has been incorporated, are filled, so that the separation in fractions must eventually also be stopped. The respective first container, for example a truck or cargo ship, must then be removed by leaving or sailing to make way for another container for receiving a mixture of different composition (formulation), in which the relevant container fraction is not present or is present in a small amount and the fractionation is resumed - •. '' <** · t ^ · 1006806 '2.

The present invention aims to solve the above-mentioned problem and is characterized in that, for preparing a second granulate final mixture with another composition, the dosage of the relevant fractions according to the composition is carried out substantially without interruption of the process. the second mixture is modified and a second granulate end mixture thus formed is delivered to a second container. Since, as already explained above, the composition of a raw starting granulate mixture can vary rapidly in practice, which may lead to shortages of certain fractions, once the composition of the obtained raw starting granulate mixture gives rise to this, the dosage can be changed in order to obtain a to prepare more granular final mixture. By dispensing this second granulate end mixture into a second container, the first container and resp. truck or freighter, not to be removed to make way for a subsequent container for the second final mixture, so that the entire production process need not be interrupted. In addition, the first container may optionally remain in place or near and be replaced by another container and filled again as soon as the raw fraction in question again contains sufficient amounts for the production of the first-mentioned final mixture in the raw starting granulate mixture.

Advantageously, the separate fractions are each temporarily collected in one or more buffer spaces after separation. This makes it possible to absorb fluctuations in the composition of the raw output granulate. By proper dosing, the desired delivery quantity of the relevant fraction from the associated buffer space can be ensured.

The release rate of the granulate final mixture is preferably chosen such that the flow rate with which the fraction, which is formed the least, is collected in the buffer space, is substantially equal to the flow rate with which this fraction is discharged from said buffer space. all this in such a way that a minimal, substantially constant amount of said fraction is present in this buffer space. In this manner, the desired final granulate mixture with the op. w, 40 moment largest possible capacity formed. So one can

Mv 'it 1 0068 06 · -3- for example, in the case of the extraction of sand from a sand pit, the capacity of the method to be reduced to 5-6 tons / at a low supply of a required fraction while maintaining the dosing accuracy. h and increase to 300 ton / h with 5 unlimited supply of all required fractions.

In a filled buffer space, the relevant fraction fed thereto is discharged from said buffer space in a preferred embodiment of the method of the present invention via an overflow. As a result, when the buffer space becomes full, there is no need to interrupt the recovery of the crude granulate mixture and the separation thereof into fractions, because the available buffer space would be full for a certain fraction. Auxiliary buffer spaces of relatively small size will suffice to discharge the at that time superfluous fractions. Sand extraction has proven to be a volume of (approximately 140 m3), whereby the above production capacity could be achieved.

Preferably, the fraction discharged via the overflow is delivered into a third container, so that none of the recovered material has to be lost. In principle, it is possible to use the third container as an additional buffer stock by returning the fraction concerned from it back to the buffer space, although this is not directly preferred.

In a further preferred embodiment of the method according to the present invention, at least one fraction unsuitable for the production of a granulate-final mixture is separated after separation of the fractions and discharged undosed in a fourth container. In the case of sand extraction, for example, much gravel with a particle size distribution above 5 mm is also not used for the production of sand-end mixtures. By separating this fraction and disposing of it in a separate fourth container, this fraction is also not lost and can be used for other purposes.

As already indicated above, the present invention provides the possibility of changing the dosage to a different, likewise desired composition, which composition is delivered in the second container 40, in the case of minor formation of one of the fractions required for the preparation of the desired granulate mixture. .

•> * “'1 006806« «-4-

If, for example, the supply of a certain fraction is so small that the formation of a desired granulate end mixture is necessarily only very slow, while a granulate final mixture with a different composition must also be produced, the dosage can be changed accordingly. after which the new composition is delivered to the second container. The time at which the dosage of each fraction is changed to obtain the desired second final mixture without interrupting the preparation process can be by the "sandwich" principle known in the art, which will be explained in more detail below.

The dosages of the fractions are preferably carried out by means of a control means and which are connected to a data processing unit which is arranged to suitably control the control means. With the help of such an automated system it is possible to enter and call up various desired compositions at any time, as a result of which the dosages will be automatically changed for the relevant composition.

Preferably, the control for dispensing the final mixture in the first or second container is also carried out with the aid of the data processing unit. In this way it is possible to ensure that the new composition is automatically delivered to another container at the right moment, that is to say at the moment that a final mixture of different composition is supplied. It is often not possible to distinguish optically between the different compositions, which makes it virtually impossible to manually change the dispensing in the containers when the different end mixtures according to the method of the present invention are formed essentially without interruption.

The invention further provides an apparatus for preparing granulate mixtures by means of the method according to the invention, comprising: a feed for raw starting granulate, means for separating the starting granulate into fractions with different particle size distributions, 40 means for controlled joining together of at least two 1 rins of the fractions to a first granulate final mixture, a first container, and discharge means for feeding the formed granulate final mixture to the first container, the device being characterized in that it second container, and the discharge means is arranged to optionally feed the first or second container.

The method according to the present invention can be carried out very well with such an apparatus.

Preferably, the device comprises at least one buffer space for each fraction. These buffer spaces are very advantageous for temporary storage of the fractions.

The discharge means advantageously comprise a movable conveyor belt. This conveyor belt can be directed to either the first container or the second container and, if necessary, be directed by pivoting on the other, i.e. the second and the first container, for example when one of the containers is full, or as a final mixture with other composition is supplied. Use can also be made of other means, such as for instance a pivotable valve, which guides the final mixture to one or the other container, optionally through additional conveyor belts.

In order to optimally carry out the method according to the present invention, one or more of the buffer spaces of the device according to the present invention are provided with an overflow and the device comprises a third container, wherein transport means are present for transporting it via the overflow of dispensed material to the third container. These transport means can for instance be designed as a conveyor belt or vibrating chutes or the like. If not all buffer spaces are provided with an overflow, simultaneous continuous fractionation and final mixture composition are not possible.

Preferably, the device according to the present invention comprises a fourth container for receiving a fraction unsuitable for the production of a granulate final mixture. As already described above, said fraction can be collected by the device according to the present invention, so that this fraction need not be lost.

1006806 * -6-

In particular, the device according to the invention comprises means for continuously analyzing the grain size distribution of one or more fractions, from which the respective final mixtures are formed.

Furthermore, there are furthermore preferably present means for continuously analyzing the grain size distribution of the formed final mixture.

It offers considerable advantages for the entire process if the grain size distribution of both the fractions and the mixture ultimately formed therefrom is continuously determined.

With this data, the accuracy of the method can be considerably increased.

The present invention further provides a floating device for preparing granulate mixtures from a raw raw granulate extract, in particular from sand and / or gravel mixtures, which device is characterized in that it comprises an device according to the invention. The containers advantageously comprise vessels to be coupled to the device, which vessels are suitable for receiving the respective mixtures or fractions.

Such a device is particularly suitable for extracting sand from, for instance, sand pits or river or sea beds. Since there are several moorings and the buffer spaces are also provided with an overflow, a continuous preparation of final mixtures is possible, without recovery having to be interrupted, when a final mixture with a different composition has to be produced. All this has already been explained above.

Floating devices for preparing granulate mixtures, in particular due to the continuous supply and discharge of granulate and associated emptying of the buffer spaces, the problem of unbalance of the floating devices may arise, due to the fact that the different storage and buffer spaces are not all the same weight of the fractions concerned. A continuous variation of the filling degree of the buffer spaces will therefore result in a continuous imbalance of the device. The imbalance is counteracted in that, in the first place, the device advantageously comprises an even number of buffer spaces 40 per fraction, which are located on either side of the longitudinal axis of each. - / 1; "4 ·" "RPn -7- vessel. By dispensing the fractions in question in order to dispense a granulate final mixture, the weight of the combined buffer spaces at the end of the longitudinal axis of the floating device is as regards weight 5, when substantially the same amount is delivered as from the common buffer spaces on the other side of said longitudinal axis, the weight distribution, measured transversely to the floating device, remains substantially the same.

The floating device can further be provided on starboard and / or port 10 with one or more balancing repair bodies, which ensure the stabilization of the device in both transverse and longitudinal direction. In this connection reference is made to the applicant's Dutch patent application NL-A-yyyyyyy. Such bodies can be weighting or floating bodies.

The invention will be explained in more detail below with reference to the appended drawing, in which: figures 1A and B schematically show the method according to the present invention by means of flow charts; and Figure 2 is a schematic representation of a device according to the present invention.

Fig. 1A schematically shows the recovery of a raw starting granulate, which is divided at 2 into fractions with different particle size distributions, whereby the individual fractions I, II, III and IV are conveyed to buffer spaces 3a, 3b, 3c, respectively. and 3d, after which the fractions are dosed at 4 and transported via feed means 5 to 6, where the fractions are mixed.

A first final mixture is formed here.

Although two buffer spaces are shown for each fraction, this is not necessarily necessary; one buffer space per fraction is sufficient. However, two buffer spaces per fraction are preferable from the viewpoint of stability if the process is carried out with a floating device, which will be discussed below.

The first final mixture is delivered via a discharge 7 to a first container 8. Without interrupting the extraction and other processes, the dosage at the location of 4 can be changed, so that a different quantity of the 40 different fractions is supplied to the feed means 5, so that a second one. .. ·. . 1006806-8 granulate final mixture is formed. Just before this second granulate mixture with a different composition reaches the outlet 7, this outlet can be moved (dotted arrow) so that the second final mixture is dispensed in a second container 9. The dosage can be controlled in such a way that when changing the composition in this case, first the dosage of the fractions IV, which are located in buffer spaces 3d, is subsequently changed, then the dosage of the fractions III, which are located in buffer spaces 3c, namely at such a later time that the newly dosed fractions III are delivered to the feed means at the moment that the also newly dosed fraction IV reaches the place where fraction III is delivered to the feed means. This creates a new "front" upstream, the composition of fractions III and IV of which corresponds to that desired in the second final mixture.

Downstream of the "front" there is still the complete composition of the first final mixture, albeit still unmixed. The dosing of fractions II can then be adjusted in such a way that the new dosing of this fraction is delivered precisely to the feed means V when the front passes this place, etc. This dosing method is also called the "sandwich". called principle. This means that no materials are lost, nor can a mixture with an incorrect composition be dispensed. After separation 25 at 2, fraction V is discharged undosed to container 11. The sorting methods can for instance be effected by means of vibration and sieving or with running water. Such separation methods are well known in the art.

It should further be noted that additional treatment steps known in the art can be incorporated into the preparation method of the invention. For example, the sorted fractions can still be subjected to a dewatering step or a cleaning step, or the moisture content of the sorted fractions can be determined. In this connection reference is made to the patent application NL-A-xxxxxxx filed by the applicant, in which the moisture content of the weighed material is calculated on the basis of a known dry weight of the fraction concerned by weighing a certain volume on a conveyor belt 40 determined by weighing-drying-weighing of samples. 1006806 * -9-

Figure 1b schematically shows the discharge of a fraction from the buffer spaces via a overflow to a third container 10. As soon as a buffer space 3 has been filled to a certain height, additional material supplied will be discharged via the associated overflow 15 and delivered to the third container 10. Although it is shown here that the materials discharged from the buffer spaces via separate flows to the third container 10, it is also possible that the separate flows first converge on a common transport means, such as a conveyor belt, which then discharge the material to the third container. Mixing of different fractions need not occur, however, if, for example, by suitable dosing, care is taken to ensure that two different fractions are not simultaneously delivered to the common means of transport via the overflows of their respective buffer spaces 3.

When the method is applied in a floating device, it is important to control the balance of the device as much as possible. This can be accomplished by ensuring, computer-controlled or not, that the total metered weight per unit time, metered from buffer spaces 3A1, 3B1, 3C1 and 3D1, is substantially equal to the corresponding weight, metered from buffer fer spaces 3A2, 3B2, 3C2 and 3D2. For example, in order to obtain a certain amount of fraction I, one can dose unequal amounts from both dosing bunkers 3A1 and 3A2, which can compensate for a distribution of weight in buffer space 3C1. All this is feasible with the help of dosing automation.

In Figure 2, a floating device according to the present invention is indicated by A. The reference numbers have been used analogously to Figure 1. A raw starting granulate is collected via a suction nozzle 1 and separated into five fractions of different particle sizes in a sorting device 2.

The first fraction, for example with a particle size distribution between about 50 and 250 µl, is located in buffer spaces 3A1 and 3A2, which are located on either side of the longitudinal axis of the device A, respectively. A second fraction II, with a particle size distribution varying, for example, between about 250 and 500 μπι, is located in buffer spaces 3B1 and -kV · "- - - - 1 0068 0 6- * -10-3B2. Furthermore, buffer spaces 3C1, 3C2 for a third fraction III with a particle size distribution ranging between about 500 and 2,000 μπι and spaces 3D1 and 3D2 for a fourth fraction IV with a particle size distribution ranging between about 2,000 and 5,000 μπι are present. Fraction V, with a particle size distribution above about 5,000 μπι, is removed immediately after separation via a conveyor belt 14 to a vessel 11. The material already belonging to fraction V, which is already removed, is indicated by 12. The feed means are indicated by 5, on which the dosed fractions are transported to a mixing device 6. After mixing, the final mixture is discharged via a conveyor belt 7 which is pivotable about axis 7a. In the drawing, the pivotable conveyor belt is directed above a va Article 8. By pivoting, this conveyor belt can also be directed to a vessel 9, in order to deliver the respective final mixture to the desired vessel 9.

16 shows the transport means for discharging fractions released via the overflows of the buffer spaces. The fractions transported are collected in a vessel 13 via a pivotable conveyor belt 17. This vessel 13 can have separate compartments for collecting separate fractions. However, it is also possible that vessel 13 comprises only 1 compartment, in which 1 or more separate fractions are collected, whether or not separately from each other.

The pivotable conveyor belt 7 could also be replaced by a pivot valve and two additional fixed conveyor belts. The swing valve directs the flow from the mixer 6 either to one or the other conveyor belt, which lead to vessel 8 or vessel 9, respectively.

1006806 '

Claims (18)

Method for preparing granulate mixtures, in particular sand and / or gravel, with predetermined composition or particle size distribution, comprising the steps of: 5. providing, for example by recovering, a raw starting granulate, in particular a sand and / or gravel mixture, separating the starting granulate into fractions of different particle size distribution, - dosing together at least two fractions into a first granulate final mixture, - dispensing the first granulate final mixture to a first container. characterized in that for preparing a second final granulate mixture of a different composition, substantially without interruption of the process, the dosage of the respective fractions is changed according to the composition of the second final mixture and the second granulate thus formed -end mixture is delivered to a second container. Method according to claim 1, characterized in that the separate fractions are each temporarily collected in one or more buffer spaces after separation. 3. A method according to claim 2, characterized in that the release rate of the granulate final mixture is chosen such that the flow rate at which the fraction, of which the least is formed, is collected in the buffer space is substantially equal to the flow rate. with which this fraction is discharged from said buffer space, all this in such a way that a minimum substantially constant amount of said fraction is present in this buffer space. Method according to claim 3, characterized in that with a filled buffer space, the relevant fraction fed in is discharged from said buffer space via an overflow. ,. '.' γ '. * 1006806 '* -12- Method according to claim 4, characterized in that the fraction discharged via the overflow is dispensed in a third container. Method according to one of the preceding claims, characterized in that after separation of the fractions, at least one fraction unsuitable for the production of a granulate-final mixture is separated and removed in a fourth container. 10 7. A method according to any one of the preceding claims, characterized in that when one of the fractions required for the preparation of the desired granulate mixture is formed, the dosage is changed to another, likewise desired composition, which composition is dispensed in the second container. . Method according to any one of the preceding claims, characterized in that the dosages of the fractions are carried out 2. by means of control means, which are connected to a data processing unit, which is arranged to control the control means in an appropriate manner. 9. A method according to any one of the preceding claims, characterized in that the control for dispensing the final mixture in the first or second container is carried out by means of a data processing unit. 10. Apparatus for preparing granulate mixtures by the method according to one or more of the preceding claims, comprising: feed for raw starting granulate, means for separating the starting granulate into fractions with different particle size distributions, 35. means for a regular combination of at least two of the fractions into a first granulate final mixture, a first container, and discharge means for feeding the formed granulate final mixture, 40, characterized by φ · --·· »to the first container. That the device comprises a second holder; and the discharge means are arranged to optionally feed the first or second container. 5 Device according to claim 10, characterized in that the device comprises at least one buffer space for each fraction. 12. Device as claimed in claim 11, characterized in that the adjustable discharge means comprise a movable conveyor belt. Device as claimed in claim 11 or 12, characterized in that one or more buffer spaces are provided with an overflow 15 and the device comprises a third container, wherein transport means are present for transporting the material delivered via the overflow to the third container. . Device as claimed in one or more of the claims 11-13, 2. characterized in that the device comprises a fourth container for receiving a fraction unsuitable for the production of a fraction unsuitable for the granulate final mixture. Floating device for preparing granulate mixtures 25 from an extracted raw starting granulate, in particular sand, characterized in that it comprises a device according to one or more of claims 10-14. 16. Device according to claim 15, characterized in that the containers comprise vessels to be coupled to the device, which vessels are suitable for receiving the relevant mixtures or fractions. 17. Device according to claim 15 or 16, characterized in that the device contains an even number of buffer spaces per fraction, which are in each case located on either side of the longitudinal axis of the vessel. 1006306 -14- 18. Method for operating a floating device according to one or more of claims 15-17, in which the fractions concerned are dosed in such a way that a quantity of granulate-end mixture is dispensed from the joint buffer spaces on one side of the longitudinal axis of the floating device in terms of weight, substantially the same amount is delivered as from the joint buffer spaces on the other side of said longitudinal axis, so that the weight distribution, measured transversely to the floating device, remains substantially the same. 1 0068 06 '