JPS5820858B2 - How to control the amount of powder cut out - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the amount of powder containing water, such as lime powder, used as a solvent in a blast furnace.

Since the amount of limestone in the sintering raw material is an important factor that influences the basicity of the sintered ore, the amount added must be accurately controlled.

Therefore, lime powder is cut out from the raw material hopper.
It is necessary to measure the lime powder value and correct the apparent cutting amount.

In the past, since moisture fluctuations in limestone were not so large, it was sufficient to correct the moisture value by intermittent measurements using the drying method, but recently limestone has been frequently sprinkled with water to prevent dust pollution. As a result, the moisture value in limestone fluctuates greatly, making it necessary to continuously measure the moisture value.

Therefore, in recent years, continuous measurement of moisture values using neutron moisture meters has been carried out, but this measurement method has drawbacks such as complicated safety management, difficult maintenance, and poor measurement accuracy. In addition, since the protective tube of the measuring device is inserted into the raw material powder, there are also other drawbacks such as the possibility of errors due to the material adhering to the protective tube or stagnation, and improvements to these drawbacks are required. Ta.

The present invention has been devised in view of the above circumstances, and the moisture value of powder containing moisture such as sintering raw lime, which is cut out from a hopper and continuously transferred by a belt conveyor, is measured by microwave transmission. This is a method for controlling the amount of powder to be cut out, characterized in that the amount of powder to be cut out is controlled based on the measurement result.

Hereinafter, the present invention will be described in detail with reference to the drawings showing an apparatus used in an embodiment of the present invention.

In FIG. 1, 1 is a hopper for powder 20 containing moisture;
3 is the cutting gate of the hopper 1; 4 is the microwave transmission antenna placed above the belt conveyor 2 immediately after the cutting gate 3; 5 is the belt conveyor 2 This is a microwave receiving antenna placed directly below the transmitting antenna 4.

The FM-modulated microwave (reference wave) oscillated from the micro oscillator 6 passes through a waveguide 9 provided with an isolator 8.
The signal is then sent to the transmitting antenna 4.

The microwaves emitted from the transmitting antenna 4 are cut out from the hopper 1 and are partially absorbed when passing through the powder 20 and the belt conveyor 2, which are continuously transported by the belt conveyor 2. Only the received microwaves are received by the receiving antenna 5.

The transmitted microwave (transmitted wave) received by the receiving antenna 5 is sent to a subsequent measuring circuit through a waveguide 11 provided with an isolator 10.

By the way, in this embodiment, as shown in the figure, the reference wave emitted from the microwave oscillator 6 passes through the coupler 7 and is sent to the waveguide 9 on the transmitting side as described above, and on the other hand, the reference wave is sent to the waveguide 1 on the receiving side.
The transmitted wave guided by 1 is sent through the coupler 12 to the subsequent measuring circuit as described above, but the coupler 7 on the transmitting side and the coupler 12 on the receiving side are connected by a delay line 13. Therefore, the reference wave and the transmitted wave are mixed to form a beat wave.

The amplitude Eb of the beat wave obtained in this way is proportional to the transmittance IT+, so after detecting it with the microwave detector 14, the beat wave is passed through the AC amplifier 15 and the detection smoothing circuit 16, so that its amplitude can be adjusted. It is processed into a signal proportional to Eb.

Then, the signal is transferred to the 10g amplifier 17 and the DC amplifier 18.
By processing this, a signal proportional to 10gIT+ is output.

The layer thickness d of the powder 20 immediately after the cutting gate 3 is kept almost constant, and the microwave absorption rate by the belt conveyor 2 is constant, so it is continuously measured as described above. A certain proportional relationship is established between the microwave transmittance measurement result and the moisture value of the powder 20 passing through this measurement point.

Therefore, 1 0 g obtained as above
The moisture value of the powder 20 is determined by the output signal proportional to IT+.

FIG. 2 shows the relationship between the moisture value and the transmittance, and it is clear from this figure that a linear proportional relationship exists between the two.

In the present invention, the powder 2 obtained continuously in this way
The cutting amount of the powder 20 is controlled based on the measurement result of the moisture value of 0, and the control is performed, for example, as follows.

That is, the signal outputted from the DC amplifier 18 as the measurement result of the powder 20 as described above is sent to the moisture correction circuit 21, and on the other hand, the signal output from the front end of the belt conveyor 2 to the conveyor 2 is sent to the moisture correction circuit 21.
The weight of the powder 20 transferred to No. 2 is continuously measured by a weighing machine 23 equipped with a detection unit 24 on the conveyor 22, and a weighing signal as a result of the measurement is also sent from the weighing machine 23 to the moisture correction circuit 21. sent to.

The 0-moisture correction circuit 21 corrects the weight of the powder 20 based on the moisture value based on both of the signals to determine the actual powder weight, and outputs the resulting signal to the comparator 25.

The comparator 25 compares the set value of the actual powder weight sent from the setting device 26 with the actual measured value of the actual powder weight obtained as described above, and then A belt speed control circuit 27 connected to the motor 19 controls the belt speed based on the output of the comparator 25 so as to eliminate the deviation between the actual measured value and the set value of the actual powder weight.

0 In the present invention, when the delay line 13 is used as shown in the above embodiment, several beat periods can be obtained per modulation period within the used band.

However, in the present invention, it is not essential to mix the reference wave and the transmitted wave as in case 5 of the above embodiment.

However, in the case where the reference wave and the transmitted wave are not mixed, the microwave detector 14 has a square-law characteristic and can only obtain an output proportional to the square IT2 of the transmittance. In terms of dB, twice the dynamic range is required.

Since a wide dynamic range is required to measure moisture values by the method of the present invention, the mixing method of the embodiment described above is advantageous in this respect because it provides an output proportional to a portion of the transmittance.

5 The present invention is constructed as described above, and according to the results of experiments using the method shown in the above embodiment, there is a linearity and reproducibility between the moisture value and the transmittance of approximately 0.2% moisture. In addition, the measurement error of the moisture value is approximately 0.25% in standard deviation, which is a sufficiently satisfactory result when the layer thickness of the hydrated powder is in the range of several tens of millimeters to over 100 millimeters. was gotten.

In addition, since the present invention uses microwaves to measure moisture levels, there are no safety management problems, there is no risk of exposure to radiation, and the measuring device is not connected to water-containing powder, so there is no risk of exposure to radiation. There is no adhesion or stagnation of powder, so errors are less likely to occur, and the moisture value measurement point is located on the belt conveyor, closer to the weighing machine, rather than inside the hopper as in the past, which improves controllability. The present invention has much better effects than the conventional method using a neutron moisture meter.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention, and FIG. 2 is a chart showing the relationship between moisture and microwave transmittance in the case of the present invention. 1...Hotsunojin 2...Belt conveyor, total...cutting gate, 4...Microwave transmitting antenna, 5...
・Microwave receiving antenna.

Claims (1)

[Claims] 1. When cutting out water-containing powder from a hopper, stacking the water-containing powder on a belt conveyor in a constant layer thickness, and continuously transporting it, the belt conveyor during transfer and the water-containing powder loaded thereon are The moisture value of the water-containing powder is measured based on the transmittance of microwaves transmitted through the layer, and the apparent cut-out amount of the water-containing powder is corrected by using the moisture value of the measurement result to determine the actual cut-out amount. A method for controlling the amount of cut-out powder, characterized in that the amount of water-containing powder to be cut out is controlled by controlling the moving speed of the belt conveyor based on the deviation from the set value of the actual cut-out amount.