Device for effecting continuous gravimetric dosing

p0001The invention relates to a device for the continuous, gravimetric metering and mass flow determination of flowable goods, comprising a metering device, in particular a metering rotor, with the instantaneous mass flow being determined.

p0002Such a system for the continuous, gravimetric conveying and / or dosing of bulk materials is excluded <patcit id="pcit0001" dnum="WO9913302A"><text>WO 99/13302</text></patcit>, <patcit id="pcit0002" dnum="DE3926038A1"><text>DE 3926038 A1</text></patcit> or <patcit id="pcit0003" dnum="DE3721186A1"><text>DE 3721186 A1</text></patcit> , With a metering rotor weighing preferably being used. The metering device following a bulk material feed is arranged in a closed pneumatic conveying path and is supported on force measuring cells. A computer-controlled, central dosing control system is used for corresponding control of the desired flow rate per time unit (delivery rate), the weighing signal from load cells serving as an input signal, and the rotational speed of the dosing rotor and, if appropriate, the rotary valve slide being controlled for the bulk material feed.

p0003In this control system, the bulk material which is currently active in the rotor weaving section is thus detected in the metering rotor weight, from which the bulk material mass throughput results from multiplication by the angular velocity of the metering rotor. In this case, the weighing electronics delays the transfer of the respective weight value of the bulk material mass (loading) present momentarily on the rotor weighing section (measuring section) to a certain pilot control point; the angular speed or the feed speed, The rotational speed can be varied, ie the metering rotor is accelerated or decelerated. This results in a relatively high metering accuracy, which has been generally used for the metering of dust-like bulk materials, for example in the case of pulverized dust metering in cement rotary kilns or for metering additives in flue gas purification.

p0004For controlling such gravimetric, continuous metering devices, such as metering belt weighers, metering rotor weighers or gravimetric charge systems, a separate metering computer has so far been used. This is where the weight and speed measurement or similar parameters are evaluated. A separate frequency converter is usually used to control the speed of the drive. The frequency converter controls the speed of the dosing drive, whereby the preset speed is set by the dosing computer. The reference speed is transmitted to the frequency converter by means of serial or parallel data lines in an analog or binary manner. This configuration corresponds to that of a distributed control system for communication, which means that the installation and commissioning expenditure is correspondingly high due to the cabling, interfaces, etc.

p0005Accordingly, the invention is based on the object of providing a device for continuous, gravimetric metering and mass flow determination, in particular bulk goods, with which the installation and commissioning expense can be substantially reduced.

p0006This object is achieved by a device according to the features of claim 1.

p0007In contrast to the conventional dosing electronics construction, the function of the dosing computer or the dosing control is now shifted into the motor control (frequency converter or thyristor control unit). The evaluation of the process-relevant measured values, calculation of the desired rotational speeds of the metering drive and control of the metering drive is thus advantageously carried out in a single subassembly. This considerably reduces the complexity of the cabling, as well as interfaces or seals on the individual housings, since such dosing devices are usually used in very dust-laden environments.

p0008The following configurations are possible for the module from dosing control and motor control in one device. For example, this structure can be implemented in a common control cabinet, whereby the measured value detection communicates with the combined motor-dosing control with a separate measuring amplifier. The assembly or mounting of the assembly from the metering controller and the motor controller is preferably carried out directly on the metering device, wherein the measured value detection can also communicate there with a separate measuring amplifier with the combined motor metering controller. The module of the combined motor dosing control is preferably integrated directly in the drive motor, whereby the measured value detection communicates there with a separate measuring amplifier with the motor dosing control. The measured value detection can also be integrated into the motor dosing control. In this case, the cultivation is again preferably effected directly on the dosing device.

p0009Further preferred embodiments are the subject matter of the dependent claims, wherein in particular the possibility for simplified construction is particularly advantageous.

p0010In the following, an exemplary embodiment is explained and described in more detail with reference to the drawings. Here,<dl id="dl0001" compact="compact"><dt>FIG</dt><dd>6 shows a schematic representation of a device for continuous, gravimetric bulk material metering with a metering rotor as a metering device;</dd><dt>FIG</dt><dd>3 shows a schematic representation of a metering belt scale as a metering device;</dd><dt>FIG</dt><dd>2 shows a modified embodiment of the metering belt scale according to FIG. 2; FIG. and</dd><dt>FIG</dt><dd>6 shows a further embodiment of the dosing device.</dd></dl>

p0011DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a device 1 for continuous gravimetric dosing and mass flow determination. The feed material to be dosed according to an adjustable target flow rate, in particular a free-flowing bulk material, is fed from a bunker or silo 2 by means of a feed 3. In this case, the material to be conveyed reaches a metering device 4, which is arranged within a housing 5 and thus defines a weighing range of approximately 300 ° to a delivery point 8. The metering device 4 is preferred as the metering rotor 4a sold out here ildet.

p0012This metering rotor 4a is thereby mounted on a pivot axis AA guided laterally from the housing 5 and is driven by a speed-controlled electric motor as drive 6, which is designed as an asynchronous, synchronous, vector or reluctance motor. The housing 5 of the metering rotor 4a is limitedly pivotally supported on a force measuring cell 7. The supporting moment on the force measuring cell 7 spaced apart from the pivot axis AA is directly proportional to the mass current which is transported via the weighing section of the metering rotor 4a from the feed 3 to the dispensing point 8.

p0013At the lower end of the housing 5, a discharge line 9 opens out towards the delivery point 8. The force measuring cell 7 and a tachogenerator 6a of the drive 6 are connected to an electronic dosing controller 10 which thus determines the instantaneous mass flow X by multiplication from instantaneous loading and rotational speed / The drive motor 6 of the metering rotor 4a is controlled by a PI controller, a control line 15 and a motor controller 20, in particular a frequency converter, in order to vary the rotational speed or angular speed. This control or regulation is generally used to keep the set flow rate constant. If a negative deviation (eg -0.2%) is present at the metering device 4, then the angular speed of the metering rotor 4a is increased by the corresponding value, that is, by +0.2% as shown in FIG 1 is known per se. A similar dosing control 10 is also provided in the subsequent, novel embodiments according to FIGS. 2 to 4, but this dosing control 10 is, according to the invention, directly connected directly to the motor controller 20 to form an assembly G.

p0014It is of great importance that, as a result of the connection or coupling of the metering control unit 10 with the motor controller 20 (usually a frequency converter), the cabling and sealing effort can be substantially reduced so that overall the construction expenditure of the metering device 4, here in FIGS 4 for a schematically illustrated dosing balance can be considerably reduced. In addition, the data exchange on the dosing device 4, in particular the signal flow with the parameters such as the rotational speed, speed, weighing signals from the force measuring cell 7, etc., can also be accelerated. Thus, by means of the metering controller 10, which is coupled to a module, with motor controller 20, the speed regulation can be made possible virtually without a dead time, virtually without the signal line 15 shown in FIG. To this end, (as is known), the comparator components or integration circuits indicated in FIG. 1 are also provided for the purpose of largely minimizing control deviations. If, for example, the position corresponding to the pilot control point P (see FIG<patcit id="pcit0004" dnum="WO9913302A"><text>WO 99/13302</text></patcit> The required time interval for accelerating / decelerating the metering device 4 can be achieved by means of the forward movement of the controlled speed at the delivery point 8 by means of a time advance of the pilot control point P relative to the delivery point 8 And thus the desired mass flow W can be controlled with the dosing device 4. The pilot control point P should be as close as possible to the output point 8 so that accelerating / braking-strength drives 6 and fast-response frequency converters as motor control 20 are expedient.

p0015FIG. 3 shows a preferred embodiment of the device for continuous gravimetric dosing and mass flow determination. The assembly G with combined dosing control / motor control 10/20 with a construction similar to that in FIGS. 1 and 2 directly with the drive motor 6 of the dosing device 4 is connected. Depending on the instantaneous loading of the metering belt, the start or start point of the speed regulation of the drive motor 6 can thus also be varied taking into account the respective moment of inertia in order to maintain the desired feedrate W. In the metering controller 10 geometrical parameters, such as the inherent mass and the length of the metering belt, can also be stored in the metering controller 10, so that accurate statements can be made as to the actual angular speed measured by the metering device 4 by means of the actual angular speed measured by the tachogenerator 6a or a pulse generator Load measuring cell 7 arrives at the delivery point 8 and thus a corresponding re-regulation can be carried out by acceleration / reduction of the conveying speed.

p0016Although a dosing rotor and a dosing belt weighing device have been described as a dosing device 4, the described control and regulating device can also be used in a dosing screw conveyor or similar dosing devices for increasing the short-term dosing accuracy at the delivery or discharge point since considerable moments of inertia can also be present here . In this case, the assembly G can also be installed or mounted within the metering device 4, as is indicated in FIG. 4 by way of the example of the strand gap of the metering belt scale. This makes it possible to realize a particularly compact design.