JP3404614B2 - How to control the supply of powder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for controlling the supply amount of powder or granules for controlling the fuel supply amount to a combustion furnace which uses pulverized coal or pulverized plastic waste as a heat source.

[0002]

2. Description of the Related Art Generally, solid fuel such as pulverized coal or chip-like plastic waste, which has a large fluctuation in combustion calorific value, is placed in an air stream, sent to a combustion furnace, and used as a fuel for stabilizing the calorific value. Control is needed. Therefore, in the fuel supply system, the heat generation amount in the combustion furnace is measured, and the fuel supply amount F is obtained from this heat generation amount value and the preset required heat amount value.

In a conventional powder / particle supply amount control system, the VS motor is used as the set supply amount (flow rate setting value) on the side of the metering hopper for supplying fuel, which has been obtained. The volumetric feeder driven by means of (1) controls the cutting speed of the volumetric feeder when the powdery or granular material is supplied to the subsequent chemical equipment system, for example, the combustion furnace via the pneumatic tube.

That is, in this supply amount control system, FIG.
As shown in FIG. 10 and FIG. 10, the material such as the pulverized plastic waste is received in the receiving hopper 1, and the receiving valve 2 at the bottom is opened.
Is driven to supply a predetermined amount of material to the service hopper 4. Thereafter, the receiving valve 2 is closed, the rotary feeder 3 is stopped, and then pressurized air is supplied to the service hopper 4 via the pressurizing valve 5 (at this time, the service hopper 4
Exhaust valve 6 is closed), discharge valve 7 is opened,
Material is loaded from the service hopper 4 into the weighing hopper 8 (at this time, the exhaust valves 6 and 9 are opened in order to replace the internal air of the weighing hopper 8). Then, the VS motor 10A is driven from the weighing hopper 8 to cut out and supply the powdery particles to the pneumatic tube 11 via the volume feeder 10.

At this time, in this supply amount control system, the weight of the powder or granular material in the weighing hopper 8 is measured, and the continuous supply by the volume feeder 10 is started, while the receiving of the material from the service hopper 4 is started at the lower limit of the weight. However, at the upper limit of weight, acceptance will be stopped. The flow rate (weight) of the material at the time of cutting and supplying the powder and granules by the volume feeder 10 is
It is calculated by the following formula. F = ρ × S × V ………………………………………… (1) where ρ is the bulk specific gravity of the DUT (powder or granule), and S is the rotation speed of the volume feeder. (Operation amount of VS motor), V: Volume of volume feeder. Then, the flow rate control is performed by adjusting the rotational speed S described above.

[0006] However, when the volume feeder 10 cuts out the powder or granular material, a flash in the feeder (particularly, it tends to occur immediately after the start of receiving from the service hopper 4) or a sudden increase in the bulk specific gravity of the powder or granular material thereat. Since the fluctuation greatly influences, in order to measure the accurate flow rate in a timely manner, the weighing hopper 8 only discharges the powder or granules (cutting out by the volume feeder) to reduce the speed of the powder or granular material reduction (lower Formula) is required. F ₁ = δW / δt (2) where δW is the weight change and δt is the sampling time. Then, by using F ₁ , ρ in equation (1) is corrected,
The desired F is secured (see FIG. 11).

[0007]

However, in this control method, if .delta.t is made too small, the disturbance is amplified, so that it usually takes several tens of seconds, so that the flash and the sudden increase in bulk specific gravity are required. Even if fluctuations actually occur, they cannot respond immediately. Therefore, only when the powder or granular material which is the object to be measured does not cause a flash at the time of cutting and the material whose volume specific gravity fluctuates gently in the weighing hopper 8,
Only applicable. In addition, when the material is received from the service hopper 4, the discharge amount from the weighing hopper 8 cannot be measured, so that the hourly weighing cannot be accurately performed (see FIG. 12).

The present invention has been made based on the above-mentioned circumstances, and the amount of powder or granules to be supplied can be determined by the change in pressure in the pneumatic tube or from this change in pressure and the measured value of the bulk specific gravity in the service hopper. It is an object of the present invention to provide a method for controlling the supply amount of powder and granules, in which the cutting amount of the volume feeder is controlled to secure the set supply amount F.

[0009]

Therefore, in the present invention,
Set supply when supplying powder and granules from the weighing hopper to the subsequent chemical equipment system via the pneumatic tube by the volume feeder
The amount of air and the amount of carrier air and the measured bulk specific gravity of the granule
Since the constant pressure is calculated and the change in the internal pressure measured at the required location in the pneumatic tube is the main signal, the feed rate of the volumetric feeder is manipulated to indirectly control the feed amount of the granular material. is there.

In this case, according to the present invention, the bulk ratio of the powder or granular material is
The weight should be adjusted when the powder or granular material is supplied to the weighing hopper.
Therefore, the weight / volume of the receiving granules in the service hopper
It is given by the apparent bulk specific gravity measured by
To do. The control set pressure, the remaining amount of granular material of said metering hopper, the relationship between the emissions of particulate material from said volume feeders, to predict the bulk density varies with time
More, and correcting. Further, if necessary, control set pressure, the powder or granular material supply amount calculated from the weight change rate of the particulate material in the weighing hopper, may be corrected based on the deviation of the predetermined set amount .

Therefore, in such a structure, since the object to be measured is the internal pressure of the air feeding pipe, the supply amount control can be surely performed even in the process of supplying the granular material as the material from the service hopper to the weighing hopper. You can do it. Also, even if flushing is likely to occur depending on the particle size of the material and the bulk density of the volume feeder fluctuates, it is possible to correct the apparent bulk density by adjusting the apparent bulk density. The accuracy can be maintained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for controlling the supply amount of powdery or granular material according to the present invention will be specifically described with reference to the drawings. In addition, in the device according to the present invention shown in FIG. 1, basically the same components as those of the above-described conventional device (see FIG. 9) are
The same reference numerals are given and the description thereof is omitted. The main constituent parts added here are located on the downstream side of the pneumatic tube 11 from the level measuring device (volume measurement) 12 of the granular material provided in the service hopper 4 and the discharge port of the volume feeder 10. It is a pressure gauge (flow rate measurement) 13.

As shown in FIG. 2, the new measurement control flow according to the present invention is measured by the level measuring device 12 and the weight measuring device (load cell) 14 after the completion of receiving the powdery or granular material into the service hopper 4. Value, that is, volume V and weight W
_The apparent bulk specific gravity ρ (= W ₁ / V) is calculated from ₁ and is used as the bulk specific gravity at the preset supply amount (flow rate setting value) for the calculation of the pressure in the transportation pipe (air feeding pipe). .

The control set pressure here is calculated by the following equation. P _S = f (Q, ρ, F _S ) …………………… (3) Where, P _S : post-correction set pressure, Q: carrier air amount, ρ: apparent bulk specific gravity, F _S : Supply amount (feed) set value.

Further, in this embodiment, the apparent bulk specific gravity ρ is a constant value (for example, ± 10) as a method of correcting the pressure set value with respect to the change in bulk specific gravity of the granular material in the weighing hopper 8.
%) Service hopper 4 in preparation for changes above
After the material (powder or granules) is charged from the measuring hopper 8 into the weighing hopper 8, the relationship between the remaining amount of the material in the measuring hopper 8 and the discharge amount to the pneumatic tube 11 via the volume feeder 10 is changed by the bulk specific gravity. Time is predicted, and a table including the empirical rule is created from the previously measured (ρ-P) relational expression, and the pressure setting value is corrected. Note that P _S is a control set pressure of the transportation pipe (air feeding pipe 11) (see FIG. 3).

If necessary, the set pressure P described above is obtained by measuring the actual supply amount F = k × (δW / δt) by measuring the weight reduction curve in the weighing hopper 8 which is a conventional measuring method. Further, the correction process may be further performed based on the difference e from the set supply amount F _S (see FIG. 4).

The corrected set pressure P _SO at this time is expressed by the following equation. P _SO = P _S × k _S (F _S −F) (4) Here, k and k _S are constants in each relational expression.

The control system of the present invention as described above is used as a block configuration in the treatment of powdered plastic waste supplied as fuel, for example, as shown in FIG. Here, "the actual calculation of the supply amount from the rate of change in weight" is a correction based on the measurement of the above-mentioned weight loss curve, and the "pressure feeding pipe" is the transportation pipe (air feeding pipe 11).
That is. In this control method, the relational expression: P _S = f
In determining (Q, ρ, F _S ), Q is kept constant, P _S , ρ, and F _S data are collected in the conventional operation, and a simple statistical method is used.

In Table 1 below, the relationship between the amounts of plural kinds of plastic wastes (chips) and changes in the conveying air pressure for this purpose and the coefficient of the relational expression (regression to a linear function) are shown as data. It is shown. The air supply amount Q = 1,35
0 Nm ³ (constant), and the correlation coefficient (r) is 1
The closer the value is to, the more linearly related the coefficients A and B of the relational expression are.

[0020]

[Table 1] Further, the correction calculation of the control set pressure P _S is performed by correcting the coefficient of the relational expression when the difference of the bulk specific gravity ρ from the previous measured value exceeds ± 10% (see FIG. 6). In the control method, the setting of the coefficient in the relational expression between the bulk specific gravity and the amounts of plural kinds of plastic wastes (chips) is performed by the statistical method as described above. An example is shown in Table 2. Here, the relationship between the coefficients A and B and the bulk specific gravity ρ is approximated to the equations A = Aa + Ba × ρ and B = Ab + Bb × ρ.

[0021]

[Table 2] 7 and 8 show graphs of implementation data according to the control method of the present invention. In the graph of FIG. 7, the set supply amount F _S ,
The actual supply amount F and bulk specific gravity ρ are shown over time. Here, accurate control is possible even in the section t in which the material is received in the service hopper 4 (the opening and closing of the receiving valve 2) (the time cannot be measured by the conventional control method), and at the start of receiving ( The effect of flushing the discharge valve 7) and the effect of changes in the bulk specific gravity ρ (in the conventional control method, FIG.
As shown in 2, the actual supply amount F changes greatly.)
However, it turns out that there is almost no.

The graph of FIG. 8 shows the set supply amount F_STo
Transport setting pressure P_S, The corrected control set pressure P_SO,
And the relationship of the actual transport pressure P is shown. In addition, day
Type P _SAnd P_SOTo avoid overlapping
I am displaying it. Note that in these graphs
Each of the data shown in FIG.
The output locations of these data are indicated by the same symbols ~.
It

[0023]

Industrial Applicability The present invention has been described in detail above, and when the powdery or granular material is supplied from the weighing hopper to the subsequent chemical equipment system by the volumetric feeder via the pneumatic tube, the set supply amount is set.
And the control setting based on the amount of carrier air and the measured bulk specific gravity of the powder.
The pressure is calculated, and the change in the internal pressure measured at the required location in the pneumatic tube is used as the main signal to operate the feed rate of the volumetric feeder to indirectly control the feed amount of the granular material. .

Therefore, since the pressure change in the pneumatic tube is measured, continuous correction with good responsiveness can be performed without being affected by the flash at the time of receiving, and the cut amount of the volume feeder can be accurately measured. The actual supply amount with respect to the set supply amount can be controlled more accurately.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a powder / particle supply amount control device of the present invention.

FIG. 2 is likewise a measurement control flow.

FIG. 3 is likewise a block diagram of a measurement control system.

FIG. 4 is a conceptual graph showing flow rate calculation based on a weight loss curve in a weighing hopper.

FIG. 5 is likewise a block diagram of a measurement correction method according to the present invention.

FIG. 6 is a diagram showing a flow of calculation of control set pressure.

FIG. 7: Implementation data (supply amount) according to the control method of the present invention
It is a figure which shows the time progress of.

FIG. 8 is a diagram similarly showing a time course of implementation data (pressure).

FIG. 9 is a schematic configuration diagram of a powder supply amount control device of a conventional example.

FIG. 10 is likewise a measurement control flow.

FIG. 11 is likewise a block diagram of a measurement control method.

FIG. 12: Implementation data (supply amount) by the conventional control method
It is a figure which shows the time progress of.

[Explanation of symbols]

1 receiving hopper 2 Acceptance valve 3 Rotary feeder 4 Service hopper 5 Pressurizing valve 6, 7, 9 exhaust valve 8 Weighing hopper 10 volume feeder 10A VS motor 11 pneumatic tube 12 level measuring device (volume measurement) 13 Pressure gauge (flow rate measurement) 14 Weighing machine (load cell)

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G05D 7/00 G01F 13/00 341 B65G 65/34

Claims (4)

(57) [Claims] 1. When supplying a granular material from a weighing hopper to a subsequent chemical equipment system by a volume feeder via an air feeding pipe, a set supply amount and a carrier air amount and a measured bulk ratio of the granular material.
From the weight, the control set pressure is calculated, and the change in the internal pressure measured at the required location in the pneumatic tube is used as the main signal, and the feed rate of the volumetric feeder is operated to indirectly control the feed amount of the granular material. A method for controlling the supply amount of powder or granules, which is characterized in that: 2. The bulk specific gravity of the powder or granular material is given as an apparent bulk specific gravity measured as the weight / volume of the received powder or granular material in the service hopper when the powder or granular material is supplied to the weighing hopper. The method for controlling the supply amount of the powdery or granular material according to claim 1 , wherein the method is provided. Wherein the control set pressure, the remaining amount of granular material of said metering hopper, the relationship between the emissions of particulate material from said volume feeders, to predict the bulk density varies with time
The method for controlling the supply amount of the powder or granular material according to claim 1 or 2 , characterized in that 4. The control set pressure is compensated based on a deviation value between a powder and granular material supply amount calculated from a weight change rate of the powder and granular material in the weighing hopper and a preset set amount.
The method for controlling the supply amount of the powder or granular material according to any one of claims 1 to 3 , wherein the method is correct.