Device for effecting continuous gravimetric dosing

Metering device for continuous gravity measurement

The invention relates to a device that uses a metering device, in particular a metering rotor with the function of determining the instantaneous mass flow rate, to continuously measure and determine the mass flow rate of a flowable substance.

This type of equipment for conveying and/or metering bulk materials for continuous gravimetric measurement has been disclosed in WO99/13302, in which a metering rotor scale is advantageously used. The metering device immediately following a bulk material conveying device is arranged in a closed pneumatic conveying line and supported on a force measuring unit. In order to adjust the desired delivery volume per time unit (delivery intensity) accordingly, a computer-controlled central metering control system is used here, in which the weighing signal of the weighing unit is used as the input signal and the speed of the metering rotor is adjusted and sometimes adjusted. Impeller gate for bulk material conveying device.

Therefore, the adjustment system detects the amount of bulk material that acts instantaneously within the weighing stroke of the rotor in the metering rotor scale, and obtains the throughput of the bulk material through the product of the angular velocity of the metering rotor. Here, the weighing electronics delay the transmission of the current weight value of the bulk material amount (loading amount) currently in the rotor weighing stroke until a certain pre-control point, thus making it possible to send the bulk material to the pneumatic conveying pipe The angular velocity or the rotation speed is changed in accordance with the predetermined rated conveying intensity before in the road, that is, the metering rotor is accelerated or decelerated. As a result, a relatively high metering accuracy is obtained, which is generally suitable for metering dust-like bulk materials, such as metering coal powder in a cement rotary tube kiln, or metering additives when purifying exhaust gas.

In order to control this type of continuous metering device for gravity measurement, such as a metering belt scale, a metering rotor scale or a charging system for gravity measurement, an independent batching calculator has been used so far. Analyze weight measurement value and rotational speed measurement value or similar parameters in the batching calculator. In most cases, a separate frequency converter is used to control the speed of the drive device. The frequency converter controls the rotation speed of the metering drive device, wherein the rated rotation speed is specified by the batching calculator. The transmission of the rated speed to the inverter is done by means of series or parallel data wires in the form of analog signals or binary digital signals. This structure is equivalent to a distributed control system for communication, which increases installation and operation costs due to laying cables and interfaces.

Therefore, the purpose of the present invention is to create a device for measuring and determining the mass flow rate of bulk materials, especially bulk materials, by continuous gravimetric measurement, which can greatly reduce installation and operating costs.

The above object is achieved by a device according to the characterizing part of claim 1.

Contrary to the structure of the usual metering electronics, the metering calculator or metering control device is now moved to the motor control device (frequency converter). Therefore, the analysis of the process-important measurement values, the calculation of the rated speed of the metering drive and the control of the metering drive are advantageously carried out in a single component. As a result, the cost for laying cables is greatly reduced, and the cost for interfaces or sealing on the housings is also reduced. In particular, such metering devices are mostly used in environments that are extremely dust-bearing.

Here, the components composed of the metering control device and the motor control device can be configured in one device as follows, for example, the combined structure can be completed in a common switch cabinet, wherein a separate measuring amplifier is used to detect the measured value The device is connected in communication with the combined motor-metering-control device. Preferably, the assembly composed of the metering control device and the motor control device is directly constructed or added to the metering equipment. Here, the measured value detection device and the combined motor can also be connected through a separate measuring amplifier. -Metering-control device is connected in communication. It is also preferable to directly integrate the combined motor-metering-control assembly into the drive motor, wherein the measurement value detection device is also connected to the motor-metering-control device in communication through an independent measurement amplifier. . Here too, the measurement value detection device can be integrated in the motor-metering-control device. Here again, this addition can advantageously be done directly on the metering device.

Other advantageous embodiments are the content of the dependent claims, in which in particular those technical solutions for simplified construction have particular advantages.

An embodiment will be described and described in detail below with the aid of the drawings. In the drawings: Figure 1 shows a schematic diagram of a device for continuous gravimetric measurement of bulk materials with a metering rotor as a metering device; Figure 2 shows a schematic diagram of a metering belt scale as a metering device; Fig. 3 shows a modified embodiment of the measuring belt scale shown in Fig. 2; Fig. 4 shows another embodiment of the measuring device.

Figure 1 shows a device for continuous gravimetric measurement and determination of the mass flow of materials, in which the conveying material to be measured according to an adjustable rated conveying strength, especially the dripping bulk material, is aided by a conveying device 3 is transported out of a storage room or a circular silo 2. The conveyed material here reaches a metering device 4 which is arranged in a housing 5 and thus determines a weighing path which leads to an output position 8 at an angle of approximately 300°. The metering device 4 is here preferably designed as a metering rotor 4a. Wherein, the metering rotor 4a is supported on a rotating shaft AA guided by the casing 5 along the side, and is driven by an electric motor with an adjustable speed as a driving device 6. The housing 5 of the metering rotor 4a can be supported on a force measuring unit 7 with a limited rotational movement. The supporting torque acting on the force measuring unit 7 arranged at a distance from the rotation axis AA is directly proportional to the mass flow of the material transported from the conveying device 3 to the output position 8 through the weighing stroke of the metering rotor 4a.

An exhaust pipe 9 leads to the lower end of the housing 5 in the direction of the output position 8. The force measuring unit 7 of the driving device 6 and a tachogenerator 6a are connected to an electronic metering control device 10, which determines the instantaneous material flow rate X through the product of the instantaneous load and the rotational speed/angular speed And link the material flow X with the adjusted rated conveying intensity W, and control the metering rotor 4a through a proportional integral (PI) regulator, a control wire 15 and a motor control device 20, especially a frequency converter. The drive motor 6 in order to change the rotational speed and angular velocity. Usually this control or adjustment is used to keep the adjusted delivery intensity constant. If there is a negative deviation (for example -0.2%) on the metering device 4, in order to keep the conveying intensity X constant, the angular velocity of the metering rotor 4a is increased by a corresponding value, specifically +0.2% here. , As is already known in the adjusting circuit shown in Figure 1. In the following innovative embodiments shown in FIGS. 2 to 4, a similar metering control device 10 is also provided, but the metering control device 10 is innovatively directly connected to the motor control device 20 Combine into a component G.

It is of great significance here that by connecting or coupling the metering control device 10 and the motor control device 20 (in most cases a frequency converter), the cable laying cost and sealing cost can be greatly reduced. Therefore, in general, , It is possible to significantly reduce the construction cost of the measuring device 4 of the measuring scale shown briefly in FIGS. 2 to 4. In addition, this also speeds up the data exchange on the metering device 4, especially the signal flux of parameters such as the rotation speed, the number of revolutions, and the weighing signal of the force measuring unit 7. Therefore, by coupling the metering control device 10 and the motor control device 20 into a component, it is actually possible to adjust the rotation speed with almost no delay time without the signal wire 15 shown in FIG. 1. For this reason, as is known, in order to minimize the adjustment deviation to the greatest extent in this inventive embodiment, the comparison function module or the integration circuit shown in FIG. 1 is also provided. When, for example, at the pre-control point P (refer to Figure 1 and the applicant's another patent application WO mentioned earlier) 99/13302) When the adjustment value sent to the drive motor 6 is not enough for the desired conveying intensity based on the overall inertia, the pre-control point P can be moved forward relative to the output position 8 to achieve the required The time interval for accelerating or braking the metering device 4, while reaching the control speed in time at the output position 8, and therefore the metering device 4 can be used to control or adjust to the rated material flow. Wherein, the pre-control point P should be as close to the output position 8 as possible, so that the drive motor 6 with strong acceleration/braking characteristics and the fast response frequency converter as the motor control device 20 can be suitably used.

A preferred embodiment of the device for measuring and determining mass flow for continuous gravimetric measurement is shown in FIG. 3, wherein the assembly G combining the metering control device 10 and the motor control device 20 is directly connected to the metering device The driving motor 6 of 4 is connected, and in other respects, it is similar to the structure shown in FIG. 1 and FIG. 2. Therefore, the start or start time of the rotation speed adjustment of the drive motor 6 can be changed according to the instantaneous charging situation of the metering belt and the moment of inertia at that time, so as to maintain the rated conveying strength W. Among them, the metering control device 10 can also store geometric parameters predetermined in terms of structural design, such as the quality and length of the metering belt itself, so that it can be accurately judged when the actual angular velocity is measured by the tachogenerator 6a or by a pulse transmitter. The metering device 4 combined with the force measuring unit 7 determines when the charge arrives at the output position 8 and thus can be adjusted accordingly by increasing/decreasing the conveying speed.

Although a metering rotor and a metering belt scale are described here as the metering device 4, the above-mentioned control and adjustment device can also be used in a metering screw conveyor or similar metering instrument to improve the output position or the delivery. Short-term measurement accuracy at the location, because significant moments of inertia may also occur here. Wherein, the component G can also be installed or additionally installed in the metering device 4, which can be installed in the belt gap of the metering belt scale as shown in FIG. 4, for example. As a result, a particularly compact design can be achieved.