EP0921860B1 - Process for controlling a sand and gravel sorting and sizing device - Google Patents

Description

The invention relates to a method for controlling the product composition in a device for classifying and sorting sand and gravel, which consists of a feed arrangement for the raw material feed and at least one chamber serving to separate the light materials from the sand product fraction with a sand product discharge and an overflow for the light materials. the chamber being designed to sort the raw material feed as a sorting area working according to the fluidized bed method for separating the sand fraction from the light materials and a proportion of fine sand. A device for the separation of light materials from sand and gravel corresponding to the aforementioned features is in the brochure "MAB fluidized bed sorter - Hydrosort I" the Schauenburg Maschinen- und Anlagen-Bau GmbH described; In this device, the raw material feed consisting of sand of different grain sizes is introduced into the cylindrical single-chamber container with an essentially flat bottom and discharges for the cleaned sand arranged therein. Upflow water is applied to the single-chamber tank from the bottom, so that a fluidized bed with a very high turbidity density is built up in the single-chamber tank using the fine fractions of sand contained in the raw material feed, which can float organic contaminants contained in the raw material feed, especially heavily carbonized wood , so that the impurities as well as mud-like fines are washed out with the overflow water.

In addition, there is a two-chamber design with an inner chamber serving to separate the coarse sand as a coarse sand room and an outer chamber connected to the coarse sand room via an overflow designed as an inclined surface, which serves to sort the fine sand according to the fluidized bed method as fine sand room and with an overflow assigned to the outer chamber for the Light materials and the fine sand fractions) are described in EP 0 508 335 A2, which works on the same principle with regard to the cleaning of the fine sand, since in a first step the coarse sands are separated off as a product fraction without special cleaning due to a set separation grain size.

In such devices, the requirement is now that the proportion of fine sand in the whole the respective amount of sand product should not exceed a certain percentage, preferably in the range of a certain concentration related to the respective amount of sand product; However, such a requirement cannot be met with the operation of the above-described devices in one or the other embodiment.

The invention is therefore based on the object of specifying a method for controlling the product composition in a device with the aforementioned features, by means of which a predetermined concentration of fine sand in the amount of sand product can be achieved.

This object is achieved, including advantageous refinements and developments of the invention, from the content of the patent claims, which follow this description.

The basic idea of the invention is that a classifying separation of the sand fraction into a quantity of sand product and into a fine sand fraction to be discharged via the overflow takes place in the chamber above the bed height of the fluidized bed in the chamber, and that for setting a predetermined concentration of fine sand in the Amount of sand product, the height of the fluidized bed is regulated in such a way that the proportion of fine sand in the raw material feed quantity can be divided into a proportion of fine sand to be applied in the quantity of sand product and a proportion of fine sand to be discharged via the overflow, depending on the predetermined permissible concentration, whereby For all geometrically similar structural designs of the device, a fixed spreading rate, defined by the ratio of the amount of fine sand to be discharged to the amount of fine sand in the raw material feed amount, is specified as a function of the fluidized bed height in the form of a calibration curve as a machine-specific parameter, and from the calibration curve that as a function of the fine sand amount determined corresponding fluidized bed height is derived as the target value for the bed height control of the fluidized bed in the chamber.

According to this, a first process step is first of all to use this fluidized bed for classification in addition to the sorting effect of the fluidized bed set in the container, and to set a grain size between a fine sand fraction and a fine sand fraction to be discharged via the overflow; While the fine sand fraction is to remain completely in the product discharge, a certain part of the fine sand fraction present in the raw material feed should be introduced as a proportion corresponding to the predetermined concentration into the sand product quantity to be discharged over the bottom of the container, depending on the sand product quantity, the proportion exceeding that Fine sand is to be removed via the overflow. To this end, the method according to the invention takes advantage of the surprisingly recognized effect that the fluidized bed not only adjusts a particle size per se is possible, but that depending on the other structural conditions of the chamber design, a quantitative distribution of the entire fine sand fraction over the layer height of the fluidized bed in the container can be adjusted. For this purpose, according to the method, the spreading of fine sand can be specified as a machine-specific parameter in the form of a calibration, so that after determining the total proportion of fine sand in the raw material task, the fluidized bed height to be set with regard to the fine sand quantity to be applied together with the fine sand can be derived.

Since generally valid, dimensionally analytical test results of geometrically comparable devices can be used for the method according to the invention, there is the advantage from the invention that, on the one hand, the method according to the invention can be carried out independently of the grain composition of the raw material feed quantity and the sand product quantity does not have to be continuously analyzed.

Insofar as the method is used in a single-chamber container with a fluidized bed formed therein, this container results in only a single quantity of sand product as a measurement variable and as the basis for the concentration required with regard to the fine sand fraction. In a two-chamber design according to EP 0 508 335 A2, the amount of sand product is made up of the partial amount withdrawn in the coarse sand area and the partial amount withdrawn from the fine sand area, the amount in the sand product amount fine sand fraction to be introduced is spread over the fine sand area; to this extent the sand product quantity is to be summarized from two part sizes.

According to a first embodiment, the invention provides that the proportion of fine sand in the raw material feed is determined as a starting value by sampling and carrying out a grain size analysis on the sample taken. In alternative procedures, knowing the proportion of fine sand in the raw material feed can then either directly determine the fluidized bed height as the setpoint and, in comparison with a measured actual value for the fluidized bed height, the measure of the required readjustment can be determined, or a set amount of readjustment for the fluidized bed height can be used The measured actual value of the fluidized bed height is approximated to the desired value corresponding to the required spreading distribution.

A further possibility without determining the grain size composition in the raw material feed in one embodiment of the invention is that the spreading distribution as a function of the measured quantities for the raw material feed and / or the sand product quantity and / or the fine sand quantity applied via the overflow and the fluidized bed height as the desired value is derived as a function of the spreading distribution, it being possible for the mass flows to be measured preferably by means of switched-on belt scales.

According to an embodiment of the invention, it is provided that the size of the separating grain between the fine sand fraction and the fine sand fraction is 0.25 mm.

Fig. 1

in einer schematischen Darstellung die Zuordnung der Massenbilanz bei einer entsprechend der EP 0 508 335 A2 ausgebildeten zweikammerigen Vorrichtung,

Fig. 2

in einem schaltbildartigen Ablaufdiagramm die Einstellung der Wirbelschichthöhe für den mittels Korngrößenanalyse ermittelten Feinstsandmengenanteil in der Rohmaterialaufgabe bei der in Figur 1 dargestellten Vorrichtung,

Fig. 3

das Ablaufdiagramm gemäß Figur 2 für eine alternative Einstellung der Wirbelschichthöhe,

Fig. 4

in einem schaltbildartigen Ablaufdiagramm die Einstellung der Wirbelschichthöhe in Abhängigkeit von der durch Messung über Bandwaagen ermittelten Mengenströme,

Fig. 5

in einer schematischen Darstellung die Zuordnung der Massenbilanz bei einer mit einem Einkammerbehälter ausgebildeten Vorrichtung,

Fig. 6

das Ablaufdiagramm gemäß Figur 2 in Anwendung auf die in Figur 5 dargestellte Vorrichtung.

In the drawing, embodiments of the invention are shown, which are described below; show it:

Fig. 1

a schematic representation of the assignment of the mass balance in a two-chamber device designed in accordance with EP 0 508 335 A2,

Fig. 2

in a circuit diagram-like flow diagram, the setting of the fluidized bed height for the proportion of fine sand ascertained by means of grain size analysis in the raw material feed in the apparatus shown in FIG. 1,

Fig. 3

the flow diagram according to Figure 2 for an alternative setting of the fluidized bed height,

Fig. 4

in a circuit diagram-like flow diagram, the setting of the fluidized bed height as a function of the volume flows determined by measurement using belt scales,

Fig. 5

a schematic representation of the assignment of the mass balance in a device designed with a single-chamber container,

Fig. 6

the flow chart of Figure 2 applied to the device shown in Figure 5.

FIG. 1 partially shows the device described in detail in EP 0 508 335 A2; in this respect reference is made to EP 0 508 335 A2 with regard to the operation of the device.

In the device on which it is based, a mass flow ṁ _A flows through a feed arrangement 10 and reaches a coarse sand space 11, from which a coarse sand amount über _{GS is} removed via a discharge 12. The fine sand and ultra-fine constituents pass via the overflow 13 into the fine sand space 14, in which the fluidized bed 15 is present with a fluidized bed height h _FS . The fine sand flow rate ṁ _{FS is} drawn off via the discharge 16, while the fine sand constituents separated off, for example, with a cut of 0.25 mm, are carried away as a flow rate ṁ _FSS via the overflow 17. The corresponding solid mass balance is thus in the device $${\dot{\text{m}}}_{\text{A}}\text{=}{\dot{\text{m}}}_{\text{GS}}\text{+}{\dot{\text{m}}}_{\text{FS}}\text{+}{\dot{\text{m}}}_{\text{FSS}}$$ where the amount of sand product results $${\dot{\text{m}}}_{\text{Pr}}\text{=}{\dot{\text{m}}}_{\text{GS}}\text{+}{\dot{\text{m}}}_{\text{FS}}\text{=}{\dot{\text{m}}}_{\text{A}}\text{-}{\dot{\text{m}}}_{\text{FSS}}$$

As a requirement, the user of the device requires a fine sand concentration in the sand product quantity C _<Prsoll , which is derived from the ratio of Fine sand fraction ṁ _<Pr in the product to the total sand product quantity results in: $${\text{C.}}_{\text{<Pr}}\text{=}\frac{{\dot{\text{m}}}_{\text{<Pr}}}{{\dot{\text{m}}}_{\text{Pr}}}$$

The entire Feinstsandfraktion contained in the raw material feed ṁ _<A is divided into the M in the sand product mass _Pr micro particle contained ṁ _<Pr and the wegzuführenden via the overflow 17 micro particle ṁ _FSS (Figure 1). This fine grain fraction ṁ _FSS can also be defined as a loss of fine grain in the amount of sand product, and there is a dimensionless loss factor with $$\text{V =}\frac{{\dot{\text{m}}}_{\text{FSS}}}{{\dot{\text{m}}}_{\text{<A}}}$$

The method includes, as a method specification, the knowledge that the aforementioned loss factor V, that is to say corresponding to the fine sand quantity ṁ _FSS applied via the overflow 17, can be determined as a machine parameter as a function of the bed height h _{FS of} the fluidized bed 15 and then in the form of a calibration curve for machines comparable configuration can be specified. This dependency of the loss factor V on the fluidized bed height h _FS can be represented in the form of a curve which is identified in the flow diagrams according to FIGS. 2 to 4 with the reference symbol 18. This calibration curve can be used for all machines with geometric similarity and therefore does not have to be for every machine single machine can be determined, in which the geometry and the dimensions of the respective chambers are enlarged or reduced with a scaling factor.

In the exemplary embodiment of the method according to the invention shown in FIG. 2, the volume flow in the raw material feed ṁ _{A is} determined by means of a belt scale 19, and samples are also taken therefrom by the sampler 20, the grain size distribution of the raw material feed at a separating cut of 0 in a suitable device 21. 25 mm is determined so that the total amount of fine sand in the raw material feed ṁ _<A with a grain size smaller than 0.25 mm is known.

Likewise, the amount of very fine sand ṁ _FSS discharged via the overflow 17 is determined, and also the amount of sand product ṁ _Pr as the sum of the volume flows deducted from the fine sand area 14 and the coarse sand area 11. Finally, the layer height h _FS is measured using a suitable measurement as the actual value for the current machine status.

The relationships are shown in detail in the flowchart shown in FIG. 2, the sequence of the control steps being shown in the individual diagram 18.

An actual value for the loss factor V can be determined with the measured actual value for the layer height h _FS , the target value for the loss factor being calculable on the basis of the predetermined target concentration. With the setpoint for the loss factor is to determine the target value for the layer height h _FS , so that there is a Δ h _FS between the actual value and the target value. The actual value for the layer height can then be adjusted accordingly with this Δ h _FS .

The procedure shown in FIG. 3 is based in the same way on setpoints or actual values for the concentration C, a fixed Δ h _{FS being} specified in steps, which means that the setpoint for the fluidized bed height h _{FS is} approximated in a corresponding multiple comparison Fine sand room 14 can be determined.

FIG. 4 shows an alternative for the method according to the invention, in which it is possible to dispense with sampling and grain size determination; The quantity of the bed of the fluidized bed can be regulated solely by measuring the quantity, two influencing variables of the available quantity flows being measured via belt scales 19; In this respect, the flow chart according to FIG. 4 contains three possible exemplary embodiments with different combinations of two of the three possible influencing variables. By linking two measured flow rates ṁ _A and / or ṁ _FSS and / or ṁ _Pr , the setpoint for the loss factor, i.e. the spreading of the application rate, can be determined, and according to the setpoint for the loss factor V determined in this way, diagram 18 immediately shows that Read the setpoint for the fluidized bed height, which enables readjustment.

As shown in FIGS. 5 and 6, the embodiment of a device with a single-chamber fluidized bed space possible, with the entire amount of sand product ṁ _{Pr being} immediately available as discharge from the chamber.

5 shows the mass ratios in a device with a cylindrical single-chamber container, in which the coarse sand space 11 and the fine sand space 14 are combined in one chamber, in the lower region of which the fluidized bed 15 is present with a fluidized bed height h _FS . The amount of sand product ṁ _Pr containing the coarse sand fraction and the fine sand fraction is drawn off via the hood 12 formed at the bottom of the container.

FIG. 6 shows a representation corresponding to FIG. 2 for the situation that arises in a single-chamber container according to FIG. 5, the relationships between the individual influencing variables shown in FIG. 2 not changing because only the sand product quantity ṁ _{Pr is included} as a single variable, and this amount of sand product is immediately available in a single-chamber container as a single product stream from the trigger 12.

Claims (8)

1. Process for the control of the product composition in an apparatus for sizing and sorting mineral raw materials, in particular sand and gravel, comprising a feed means for the raw material feed and at least one chamber serving for the separation of low density materials from the sand product fraction, including a sand product removal means and an overflow for the low density materials, the chamber being designed to operate as a sorting region according to the fluidized bed process in order to sort the raw material feed, characterized in that in the chamber (14) by means of the level (h_FS) of the fluidized bed (15) present in the chamber additionally a sizing separation of the sand fraction into a sand product mass (ṁ_Pr) and into a micro particle sand fraction (ṁ_FSS), to be discharged via the overflow (17), takes place and that for the adjustment of a pre-set concentration of micro particle sand in the sand product mass (C_<Prsoll) the fluidized bed level (h_FS) is so controlled that the micro particle sand fraction (ṁ_<A) in the supplied raw material mass can be divided, by means of the fluidized bed (15), as a function of the pre-set admissible concentration (C_<Prsoll) into a micro particle sand fraction (ṁ_<PR) to be discharged into the sand product mass (ṁ_Pr) and a micro particle sand fraction (ṁ_FSS) to be discharged via the overflow (17), wherein, for all geometrically similar constructive designs of the apparatus, the fixed yield distribution (V), defined as a ratio of the micro particle sand fraction (ṁ_FSS) to be removed to mass, is predetermined as a function of the fluidized bed level (h_FS) in the form of a calibration curve as a parameter specific to the apparatus and that, based on the calibration curve, the fluidized bed level (h_FS), corresponding to the required yield distribution (V_soll) as a function of the determined micro particle sand content (ṁ_<A) in the supplied raw material mass, is derived as a set value for the level adjustment of the fluidized bed (15) present in the chamber (14).
2. Process according to claim 1 for an apparatus comprising an interior chamber serving as a coarse sand chamber for the separation of the coarse sand and an exterior chamber serving as a fine sand chamber for sorting the fine sand according to the fluidized bed process and connected to the coarse sand chamber via an overflow, designed as an inclined surface, and further comprising an overflow means for low-density materials associated with the exterior chamber, characterized in that additionally a sizing separation of the fine sand fraction into a micro particle sand fraction to be introduced into the fine sand product mass (ṁ_FS) and into a micro particle sand fraction (ṁ_FSS) to be discharged via the overflow (17) takes place in the fine sand chamber (14) via the fluidized bed level of the fluidized bed (15) present in the chamber, wherein the yield distribution (V) for the fine sand chamber (14) is pre-set as a parameter specific to the apparatus.
3. Process according to claim 1 or 2, characterized in that the micro particle sand content in the raw material feed (ṁ_A) is determined directly as a starting value by taking a sample and carrying out a particle size analysis of the sample taken.
4. Process according to claim 3, characterized in that the fluidized bed level (h_FS) is directly determined as the set value and the degree of the required readjustment (Δ h_FS) for the fluidized bed level is determined by comparison with the measured actual value.
5. Process according to claim 3, characterized in that by means of an appropriately set degree of the re-adjustment (Δ h_FS) for the fluidized bed level an approximation of the measured actual value of the fluidized bed level to the set value corresponding to the required yield distribution (V) is performed.
6. Process according to claim 1 or 2, characterized in that the yield distribution (V) is determined as a function of the amounts measured for the raw material being fed (ṁ_A) and/or the sand product mass (ṁ_Pr) and/or the micro particle sand mass (ṁ_FSS) discharged via the overflow and that the fluidized bed level (h_FS) is derived as the desired value as a function of the yield distribution (V).
7. Process according to claim 6, characterized in that the measurement of the amounts for the raw material feed and/or the sand product mass and/or the micro particle sand mass is carried out by means of in-line belt scales (19).
8. Process according to any one of claims 1 to 7, characterized In that the particle size limit between the micro particle sand fraction and the fine sand fraction is 0.25 mm.