EP0517022A2 - Pneumatic separator - Google Patents

Abstract

In a pneumatic separator (1), electronically controlled (5) air pressure is used to improve the mode of operation, i.e. chiefly the sharpness of separation in pneumatic separation processes having sharply fluctuating operating conditions, to reduce the energy requirement, and to avoid constant readjustment of mechanically operated reducing dampers. <IMAGE>

Description

The invention relates to an air-assisted separator.

In systems for processing solid mixtures or scrap used fans or blowers, such as in particular for air stoves or for air classifiers in metal and waste processing or for the air intake of separating plates in the processing of waste or existing materials, are used with very powerful drive motors and thus correspondingly high power consumption of the engine, ie large electricity consumption operated.

Air stoves known as heavy part readers are known for separating lighter from heavy good parts (light / heavy separation). In the machine housing of such air stoves there is usually a sieve inclined in the longitudinal direction, to which the solid mixture to be sorted is fed via a conveyor and a material feed which ensures a uniform loading of the sieve or read-out table. The air flowing through the sieve from bottom to top puts the specifically lighter constituents of the solid mixture in a flow-like state. The dust-free working air required for this is drawn in from the ambient air by a fan either external or arranged in the machine housing.

The specifically heavier constituents of the added solid mixture lie directly on the sieve and are conveyed to the higher end of the sieve due to the oscillating movement and the roughness of the sieve. So that a throwing movement can be achieved, for which purpose the air focus has to oscillate in a defined manner, the machine housing is supported on at least two pairs of links which introduce the drive power generated by a push-crank drive into the machine housing; alternatively, at least one unbalance motor can be provided on the machine housing. The light fraction (light goods) always flows to the lower end of the stove and the heavy fraction (heavy goods) always to the higher end of the hearth, from where the light and heavy goods are each conveyed to a subsequent conveyor for discharge.

Such an air cooker works best when the ratio of light to heavy goods and the air pressure are constant. It has been found that this cannot be guaranteed, above all, if the solid mixture given is material from electronic scrap, shredder debris, cable waste or other mixtures of non-ferrous metals, for example predominantly consisting of copper, zinc, brass, magnesium and aluminum with different grain size and shape. These solid mixtures intended for non-ferrous metal processing have a very heterogeneous grain shape, especially with grain sizes over 10 mm; in addition, their composition is constantly changing.

The separation success from the air sources is therefore insufficient and the discharge is often a coincidental product. The unsatisfactory Operating results of an air source, especially in non-ferrous metal processing, which is about separating a product (light or heavy goods), e.g. recovering the largest possible aluminum (light goods) portion, ie from heavy goods (copper, bronze, Separating brass, lead, etc.) deteriorate if the temperature changes during operation and, depending on this, the air density, which drops with increasing temperature. There is then no sufficient carrying pressure above the sieve which could prevent the light goods from being discharged together with the heavy goods. Because if there is no air pressure, the entire feed material moves upwards, since only the conveying component of the vibrating screen then has an effect; on the other hand, if the air pressure was extremely high, the heavy goods would also be discharged downwards, because the entire feed, depending on the inclination of the sieve, would flow downwards with the air cushion building up above the sieve or due to its carrying pressure.

In the case of air stoves, it is known to influence the air flow in the feed channel to the sieve by means of throttles or flaps that can be adjusted manually using a common handwheel or by an electric drive, but the throttle adjustments, which are mechanically very complex and are coupled to one another via lever linkages, eliminate the above difficulties Not. Despite the throttles or flaps, the air supplied by extraordinarily powerful, for example 10 to 15 KW fans or blowers, whirls above the sieve so strongly that light and heavy goods mix undesirably. In addition, there is an additional loss of friction at the throttle valves, which generates a heat that increases the ambient temperature again reduces the density of the air. Changing operating conditions due to a different nature and / or composition of the material to be processed also occur with a separating plate - for example influenced by wet or dry paper parts - and a shredder, in which, for example, the degree of filling and weather conditions are also decisive for the separation result. In order to obtain a clean product after the shredder dedusting and sifter, the system is usually supplied with a significantly excessive amount of air. This means not only appropriately large fans or blowers with associated powerful motors, but also high energy consumption.

The invention has for its object the operation, i.e. Above all to improve the selectivity in separation processes with strongly fluctuating operating conditions of an air-supported separator, in particular of air stoves, wind sifters and / or shredder dedusting and separating plates, to reduce the energy requirement and to avoid constant readjustment of mechanically operated throttle valves.

This object is achieved by electronically controlled air pressure. In this way, an exact, sensitive control of the air pressure and thus a controlled separation process can be achieved, in which, with regard to the amount of air supplied, there is a good adaptation to the particular composition and / or nature of the material supplied, which allows a high degree of selectivity to separate clean product. By means of, for example, a regulated air cooker, the aluminum contained in a solid mixture can be almost completely recovered, ie the aluminum losses can be kept below 3% and thus far lower than, for example, in a known swim-sink system. Finally, a uniform air speed can also be set in the separation zone. The respective actual value of the air pressure is determined by a sensor, which in a shredder system in the dedusting line between the shredder and a separator (cyclone) and / or the suction line between the classifier and a separator and in the case of an air source or a separating plate in the pressure line of the fan can be arranged.

It is recommended to use a fan that is speed-controlled by means of a frequency converter. In this case, a controller assigned to the frequency converter specifies a target value; decreases, e.g. With increasing operating and / or outside temperature, the air density, so that the air pressure drops, the controller causes a corresponding increase in the speed of the motor driving the fan via the frequency converter until the setpoint of the air pressure is reached. This means that fan speed control - the actual value of which can be specified using a potentiometer - can achieve constant air pressure using the frequency converter despite temperature differences.

If the current consumption of its drive motor is used as a reference variable for the target value of the air pressure in an air cooker, the air pressure can also be adapted to changing compositions of the solid mixture charged. It has been found that the drive motor which sets the air source in motion takes more current on when the heavy goods content increases and less when the light goods content, ie in particular aluminum in the solid mixture increases. Although the change in the motor current consumption is very small, a control component can be achieved with an electronic spread. Thus, if the proportion of heavy goods in the solid mixture decreases, the air pressure is increased by a correspondingly higher speed of the motor driving the fan, so that despite the lower heavy goods proportion, the light goods nevertheless reach the intended discharge; because of the then higher carrying pressure, it floats on the air cushion above the sieve and flows to the lower-lying light material discharge.

When operating with a - commercially available - frequency converter, less powerful fans or blowers and drive motors can be used, because tests with an air cooker have confirmed that when the air pressure is controlled, the power consumption of the drive motor can be reduced below 50%, which results in significantly lower power consumption and thus cost savings; It is therefore possible to install a correspondingly less powerful drive motor and fan from the outset.

With built-in components advantageously connected to the fan in the air cooker, e.g. Baffle and baffle plates, the air pressure can be changed over the length of the sieve and a desired air distribution can be achieved below the bed.

Advantageously, the end of the hearth having the heavy material discharge is ventilated less than the end of the hearth with the light material discharge, which can be achieved by a baffle located below the heavy material discharge. The lower layer of the solid mixture towards the heavy material discharge is thus less aerated than the higher, multilayered layer above the sieve in the area of the light material discharge. This measure supports the extraordinarily high degree of separation in an air cooker regulated according to the invention, because due to the lower air flow in the area of the heavy material discharge, a heavy part, for example a piece of copper, cannot be blown by the air into the conveying flow migrating to the light material discharge.

If the sieve tapers towards the heavy material discharge, the high separation accuracy achieved is supported. It has been shown that such a cross-sectional profile, preferably achieved by means of longitudinal wedges arranged on the sieve, in which the air has a passage cross section which becomes smaller towards the discharge end, prevents the constituents of the applied solid mixture from being released by the air stream into be rotated and thereby move to the wrong discharge side.

Fig. 1

einen erfindungsgemäßen, eine elektronische Luftdruckregelung aufweisenden Luftherd, in schematischer Seitenansicht;

Fig. 2

einen erfindungsgemäßen Luftherd mit in seinem Gehäuse angeordneten Luftleitblechen, in schemtischer Seitenansicht und ohne Regelung;

Fig. 3

den Luftherd gemäß Fig. 1 oder Fig. 2 mit sich zum Schwergutaustrag hin verjüngendem Sieb, in schematischer Draufsicht als Einzelheit; und

Fig. 4

eine andere Ausführung eines Luftherdes mit sich zum Schwergutaustrag hin verjüngendem Sieb, in schematischer Draufsicht.

Further features and advantages of the invention result from the claims and the following description, in which some exemplary embodiments of the subject matter of the invention are explained in more detail using an air source. Show it:

Fig. 1

an inventive air stove having an electronic air pressure control, in a schematic side view;

Fig. 2

an air cooker according to the invention with air baffles arranged in its housing, in a schematic side view and without control;

Fig. 3

1 or 2 with a sieve tapering toward the heavy material discharge, in a schematic plan view as a detail; and

Fig. 4

another embodiment of an air cooker with a sieve tapering towards the heavy material discharge, in a schematic plan view.

An air cooker 1 has a machine housing 2 which is set in vibration by means of a push-crank drive via handlebars 3 and a drive motor 4. The air cooker 1 is provided with an electronic control 5, which keeps the air pressure constant under a sieve 7 which is inclined towards the lower-lying light material discharge 6. The solid mixture to be separated, containing light goods and heavy goods, is placed on the sieve 7, as is illustrated in FIG. 2 by a material feed arrow 8. While the light material contained in the solid mixture floats due to the air flow supplied from below the sieve 7 by means of a fan 9 (cf. FIG. 1) via an air inlet 11 into the machine housing 2 and slides down according to the inclination of the sieve 7 towards the light material discharge 6 the heavy goods due to the vibrations of the machine housing 2 to the heavy goods discharge 12 at the higher end of the sieve 7.

The drive motor 4 which generates the vibrations of the air source 1 is electrically connected to a controller 13 which when the composition of the solid mixture 14 fed onto the sieve 7 changes (cf. FIG. 2), the current consumption of the drive motor 4, which is correspondingly greater or smaller, is tapped as a reference variable w for the setpoint value of the air pressure. If the ratio of light to heavy goods in the feed solid mixture 14 is no longer constant, for example the heavy goods content decreases, as in particular with feed goods consisting predominantly of comminuted railway wagons, the current consumption of the drive motor 4 drops. This value goes as the command variable w for the desired value of the air pressure in the controller 13, which forms a corresponding manipulated variable y for a frequency converter 15, via which the speed of a motor 16 driving the fan 9 is controlled. When the motor power consumption drops, a higher fan speed causes the air pressure to increase accordingly, so that despite the changed mixture composition, the light goods do not escape undesirably through the heavy goods discharge 12, but instead reach the light goods discharge 6 due to the higher air pressure below the sieve 7, because the carrying pressure of the air cushion increases.

If the proportion of heavy goods increases, e.g. B. by changing the feed material, the current consumption of the drive motor 4 increases to the same extent and a corresponding value is entered into the controller 13, so that the frequency converter 15 sets the speed of the fan motor 16 lower and thus the air pressure is reduced. In this case, the heavy goods predominantly present in the solid mixture prevent the light goods from migrating up to the heavy goods discharge 12. By means of the control 5, the air pressure can thus be dependent on the respective composition of the solid mixture 14 precisely and sensitively.

The control circuit 5 also has a controller 17, which is also connected to the frequency converter 15 and into which the actual value of the air pressure detected by a pressure sensor 18 is received as the control variable x. If the air pressure changes due to external influences, such as, in particular, the temperature, the controller 17 supplies a corresponding manipulated variable y for the frequency converter 15, which then either increases or decreases the speed of the drive motor 16 of the fan 9 until the air pressure under the sieve 7 also corresponds to the setpoint specified in the controller 17, so that a constant air pressure is maintained.

The fan 9 is followed in the machine housing 2 by baffles 19 designed as baffles or air baffles, which deflect and distribute the air flow entering through the air inlet 11 below the sieve 7. The layer of the solid mixture 14 which is lower in the direction of the heavy material discharge 12 becomes less and the layer of the solid mixture 14 which is higher towards the light material discharge 6 and contains the layer of solid material 14 floating on the air cushion and to be discharged. The sorting or separation of light and heavy goods is favored by longitudinal wedges 21 arranged on the sieve 7. which reduce the passage area of the sieve 7 towards the heavy material discharge 12 (see FIGS. 3 and 4), and in this way support a targeted delivery flow.

Claims (7)

Air-assisted separator, characterized by electronically controlled air pressure. Device according to Claim 1, characterized by a fan (9) which is speed-controlled by means of a frequency converter (15). Apparatus according to claim 1 or 2, characterized in that in the case of an air cooker (1) the current consumption of its drive motor (4) is used as a reference variable (w) for the desired value of the air pressure. Apparatus according to claim 3, characterized by internals (19) connected downstream of the fan (9) in the air cooker (1). Apparatus according to claim 4, characterized in that the end of the hearth having the heavy material discharge (12) is less aerated than the end of the hearth with the light material discharge (6). Device according to one or more of claims 3 to 5, characterized in that the screen (7) tapers towards the heavy material discharge (12). Device according to one or more of claims 3 to 6, characterized by longitudinal wedges (21) arranged on the sieve (7).

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