JPH112695A - Flow rate control method of waste liquid supply tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the flow rate control method of a waste liquid supply tank capable of accurately calculating the fluctuation quantity of a liquid level and properly performing constant supply control even in the case where disturbance of the liquid level by a stirrer is received. SOLUTION: A waste liquid supply tank 1 supplying high level radioactive waste liquid to a glass melting furnace is provided with an air purge type liquid level meter 2 and an air lift pump 3 transmitting its waste liquid. The flow rate of the waste liquid is repeatingly sampled by dividing into a constant time, and flow rate average per constant time is calculated. Newly calculated flow rate average and therebefore-calculated primary delay flow rate average are compared with a set flow rate value respectively, their differences are found, and only in the case where their differences are a same mark, a driving amount of the air lift pump 3 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste liquid supply tank for storing a high-level radioactive waste liquid generated in a nuclear fuel reprocessing facility or the like, and more particularly to a flow rate control for quantitatively supplying the high-level radioactive waste liquid to a glass melting furnace. It is about the method.

[0002]

2. Description of the Related Art In general, high-level radioactive liquid waste generated in a nuclear fuel reprocessing facility or the like is difficult to handle in a liquid state. Therefore, it is sent to a glass melting furnace together with a glass raw material, where it is mixed at a high temperature. After being processed into a stable form as a vitrified body, it is planned to be buried deep underground for a long time.

[0003] When the high-level radioactive liquid waste is vitrified, it is necessary to mix the high-level radioactive liquid with the glass raw material at a predetermined ratio. Must always be constant.

Therefore, conventionally, an air purge type liquid level meter for detecting the liquid level of a waste liquid supply tank for supplying a high level radioactive waste liquid to the glass melting furnace side, and an air lift pump for discharging the high level radioactive waste liquid are provided. Comprising, detected by the air purge type liquid level meter, for example, to calculate the average flow rate per minute of the waste liquid supplied to the glass melting furnace from the difference between the liquid level 10 minutes ago and the current liquid level, By adjusting the driving amount of the air lift pump according to the average flow rate,
PI so that the flow rate of waste liquid does not deviate from the preset flow rate
(Proportional integration) was controlled.

[0005]

Incidentally, since the above-mentioned high-level radioactive liquid waste contains components having different specific gravities, the high-level radioactive liquid waste is supplied to a waste liquid supply tank for storing the high-level radioactive liquid waste in order to make its properties uniform. It is necessary to always stir high-level radioactive liquid waste by providing a stirrer.

[0006] However, assuming that the fixed amount of waste liquid supplied to the glass melting furnace is, for example, 1 L / min, the change in liquid level of the current waste liquid supply tank is -1 mm.
However, when the stirrer is provided, the air purge type liquid level signal is disadvantageously affected by a disturbance corresponding to a liquid level of about ± 10 mm. As a result, if the PI control is performed by using the liquid level signal as an input, the control signal of the air lift drive hunts, and in some cases, diverges, causing a problem, and it is difficult to perform appropriate quantitative supply control.

Therefore, the present invention has been devised in order to effectively solve such a problem, and an object of the present invention is to accurately measure the fluctuation amount of the liquid level even when the liquid level is disturbed by the stirrer. It is an object of the present invention to provide a novel method for controlling the flow rate of a waste liquid supply tank that can perform appropriate quantitative supply control by performing calculations.

[0008]

To solve the above-mentioned problems, the present invention provides an air purge type liquid level meter for detecting a liquid level in a waste liquid supply tank for supplying a high level radioactive waste liquid to a glass melting furnace, An air lift pump for discharging high-level radioactive waste liquid is provided, and the flow rate of the waste liquid supplied to the glass melting furnace is calculated from the decrease in the liquid level detected by the air purge type liquid level meter, and the flow rate is set in advance. In the flow control method for the waste liquid supply tank, wherein the drive amount of the air lift pump is adjusted so that the flow rate becomes a predetermined flow rate, the flow rate of the waste liquid is divided into a certain period of time, and the flow rate is repeatedly sampled, and an average of the flow rate for each certain period is obtained. Calculate and compare the latest calculated flow average with the previously calculated first-order lag flow average with the set flow value to determine the difference between them. Only when the same numerals is obtained so as to adjust the drive amount of the air lift pump.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a waste liquid supply tank 1 according to the method of the present invention.
FIG. 2 shows an embodiment of a flow control chart of the waste liquid, and FIG. 2 shows an air purge type liquid level detecting a liquid level from a pressure difference between a liquid phase and a gas phase in the waste liquid supply tank 1. 3 is an air lift pump for discharging the liquid from the waste liquid supply tank 1, 4 is an air pump for supplying air to the air lift pump 3, 5 is an air lift pump drive valve for adjusting the driving amount of the air lift pump 3, Reference numeral 6 denotes a stirrer including a stirring blade for stirring the liquid in the waste liquid supply tank 1 and a motor for driving the stirring blade.

As shown in the figure, a high-level radioactive waste liquid to be vitrified is stored in the waste liquid supply tank 1 so that a constant amount of the waste liquid can be supplied to a glass melting furnace (not shown) by an air lift pump 3. It has become.
The high-level radioactive waste liquid in the waste liquid supply tank 1 is:
When the amount falls below a certain level, the waste liquid is supplied from the waste liquid supply line 7 in a batch manner as needed.

The air purge type liquid level meter 2 and the air lift pump 3 are provided with flow rate control means 8 incorporating flow rate control logic.
Calculates the flow rate by inputting the value detected in step (1), and drives the air lift pump (3) according to the calculated value.
And the air lift pump drive valve 5 is controlled.

Next, a method of controlling the flow rate of the waste liquid supply tank 1 configured as described above will be described.

First, the air lift pump 3 is driven while the stirrer 6 is driven, and the high-level radioactive waste liquid in the waste liquid supply tank 1 is discharged at a predetermined drive amount, and a fixed amount (1 L) is discharged to the glass melting furnace side. / Min).

Then, the liquid level gradually decreases (-1 mm / min) with the supply of the waste liquid, and the fluctuation amount of the liquid level is measured by the air purge type liquid level meter 2 for a predetermined time (10 mm / min). ), And the amount of fluctuation is extracted as sampling and input to the flow control means 8.

The flow control means 8 first averages the liquid level from the sampling (F) inputted first, calculates the flow rate by the flow rate calculating section (E), and then calculates the average flow rate per 10 minutes. Is temporarily stored as the first-order lag (A). Next, similarly, the liquid level is averaged and the flow rate is calculated from the latest sampling (F) input immediately after that, and the flow rate average (B) for 10 minutes is obtained.

Next, the latest flow rate average (B) calculated in this way and the previously calculated primary delay flow average (A) are compared with preset flow rates respectively.
After obtaining the respective differences as e1 and e2, these e
1 and e2 are compared (C).

If e1 and e2 have the same sign, the average value is used as the two-position control unit (D) and integrator (G).
To determine the driving direction of the air lift pump.
A signal for changing the drive amount of the V amount air lift pump is output. On the other hand, when the signs of e1 and e2 are different,
In any case, the flow rate value calculated by the flow rate calculation unit (E) is determined to be uncertain and is not adopted, and sampling (F) is performed again.

That is, according to the present invention, sampling is repeated at staggered times, and the differences e1 and e2 between the set flow rate and the latest 10 minute flow rate calculated by the flow rate calculating section (E) are calculated from the previous flow rate calculated value. If these e1 and e2 have the same sign, it is determined that accurate control can be performed, and the control is performed.

Therefore, with the accurate control information, the air lift pump drive valve 5 for driving the air lift pump 3 does not move unnecessarily, so that appropriate operation, that is, appropriate quantitative supply control can be performed. Becomes

The various numerical values shown in this embodiment are, for example, the flow rate of the air lift pump 3, the fluctuation amount of the liquid level in the waste liquid supply tank 1, the fluctuation amount of the liquid level by the stirrer 6, the sampling time, and the like. However, it is needless to say that the technical scope of the present invention is not limited at all.

[0022]

In summary, according to the present invention, instead of PI control based on one-time sampling as in the prior art,
Since the air lift pump is controlled only when the operation code matches when sampling is performed twice with a shift in time, the amount of fluctuation in the liquid level can be accurately measured even when the liquid level is disturbed by the stirrer. It is possible to exhibit excellent effects such as performing appropriate quantitative supply control by performing calculations.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 waste liquid supply tank 2 air purge type liquid level meter 3 air lift pump 4 air pump 5 air lift pump drive valve 6 stirrer 7 waste liquid supply line 8 flow rate control unit

Claims (1)

[Claims] 1. A waste liquid supply tank for supplying a high-level radioactive liquid waste to a glass melting furnace, comprising an air purge type liquid level meter for detecting the liquid level, and an air lift pump for discharging the high-level radioactive liquid waste. The flow rate of the waste liquid supplied to the glass melting furnace is calculated from the decrease amount of the liquid level detected by the air purge type liquid level meter, and the driving amount of the air lift pump is adjusted so that the flow rate becomes a preset flow rate. In the method for controlling the flow rate of the waste liquid supply tank, the flow rate of the waste liquid is repeatedly sampled by dividing the flow rate into a certain time period, and the flow rate average is calculated for each fixed time. The calculated average of the first-order lag is compared with the set flow rate value to determine each difference, and the air lift pump is used only when the difference value has the same sign. A method for controlling a flow rate of a waste liquid supply tank, wherein a driving amount of a pump is adjusted.