JPH0114604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate regulating device in which fluid supplied to a filter press or the like is controlled by two regulating valves whose opening and closing directions operate in opposite directions.

Generally, the supply of processing liquid to a filter press needs to be controlled at a predetermined amount depending on the press capacity, etc., but the resistance of the cloth gradually increases depending on the liquid supply time, and the flow rate changes accordingly. While measuring the actual flow rate and the flow surface level of the relay tank, the opening degree of the flow rate control valve is increased or decreased to obtain a predetermined flow rate.

This state is shown in FIG. 1, in which the treatment liquid quantitatively supplied to the relay tank 1 is sent to the filter press 6 via the pipes 3, 4, and 5 by the pump 2. A flow control valve 7 is provided between the pipes 4 and 5, and the opening degree of the control valve 7 is automatically adjusted via a control device 9 based on the output of a liquid level detector 8 that detects the liquid level in the relay tank 1. It increases and decreases, and constantly supplies fluid equal to the inflow amount to the filter press 6.

In other words, if the supplied liquid becomes difficult to flow due to clogging of the filter press 6, the liquid level in the relay tank 1 will rise above the set value, and this will be detected and the opening degree of the control valve 7 will be increased to increase the flow rate. It is.

In this way, the flow rate supplied to the filter press 6 is always kept equal to the flow rate into the relay tank 1, but in reality, sediment adheres to the cloth approximately in proportion to the time of liquid supply to the filter press 6. Since the pressure loss fluctuates widely, for example from 0.5 to 4.0 Kg/cm ² , a considerably large capacity is required for the flow rate control valve 7, and as is well known, in the region where the valve opening is large, , since the range of flow rate change with respect to the unit valve opening becomes relatively large (close to on/off control characteristics), especially for filter press 6.
When there is a large pressure loss in There were also problems such as damage to equipment, making smooth operations impossible.

The present invention solves this problem by returning a portion of the liquid supplied from the pump and adjusting the amount of this return and the amount of liquid sent to the main piping using two reversibly operated control valves. By controlling
It is an object of the present invention to provide a flow rate adjustment device that can provide accurate quantitative control despite pressure fluctuations.

Hereinafter, an embodiment of the present invention will be described based on FIG. 2, in which the same parts as in FIG. 1 are denoted by the same reference numerals.

A control valve 7A is provided between the main pipes 4 and 5 for supplying the processing liquid from the relay tank 1 to the filter press 6 to adjust the processing flow rate.
A branch pipe 10 is branched from a point in front of A.

The branch pipe 10 returns a part of the liquid sent from the main pipe 4 to the relay tank 1, and a control valve 7B for controlling the amount of return is provided in the middle thereof.

These control valves 7A and 7B are feedback-controlled by signals from the control device 9 so that the liquid level is always constant while the valve opening degrees operate in an opposite relationship.

In other words, when the liquid level in the relay tank 1 becomes higher than the set value, the opening degree of the control valve 7A of the main pipe 4 is decreased and at the same time the opening degree of the control valve 7B of the branch pipe 10 is decreased.

Note that the control valves 7A and 7B can be used with either an electrical control method or a pneumatic control method.

Next, the overall effect will be explained.

A processing liquid flows continuously and quantitatively into the relay tank 1 from the outside, and the same amount as this inflow is supplied to the filter press 6.

For this purpose, the liquid level detector 8 detects the liquid level in the relay tank 1, and based on this, the opening degrees of the control valves 7A and 7B are controlled by a signal from the control device 9, and the pump 2 pumps out the liquid. The liquid is fed from the main pipes 4 and 5 to the filter press 6, and part of it is returned to the relay tank 1 via a branch pipe 10.

In this state, as cake gradually adheres to the cloth of the filter press 6 and pressure loss increases, the flow rate to the main pipe 5 decreases, and at the same time, the pump discharge pressure increases and the return flow rate to the branch pipe 10 increases. Therefore, the liquid level in the relay tank 1 rises.

However, this rise in the liquid level can be detected by the liquid level detector 8.
is detected, the control device 9 increases the opening degree of the main side control valve 7A, and also increases the opening degree of the return side control valve 7A.
By reducing the opening degree of B, the liquid level is kept constant. Thereby, a decrease in the amount of liquid fed to the filter press 6 can be prevented despite an increase in pressure loss. Furthermore, this control reduces the liquid feeding resistance to the main side and at the same time increases the resistance on the return side, so even when the pressure loss in the filter press 6 is extremely large (close to the cleaning process), the control valves 7A and 7B It is not necessary to change the opening degree so much, and therefore extremely good control accuracy and quick response can be obtained.

In other words, the present invention can reliably prevent the control hunting phenomenon that occurs in the apparatus shown in FIG. 1 because a fairly large-capacity flow control valve is used in a large opening range.

In the above explanation, an example is shown in which a single filter press 6 is connected to the relay tank 1, but it is also possible to connect a plurality of filter presses 6 in parallel and set a timer corresponding to the required operation time of each. According to
It is also possible to supply the processing liquid by switching sequentially.

As described above, in the present invention, control valves are provided on the main side and the return side, and both control valves are operated in opposite directions so that the liquid level in the relay tank remains constant. Constant flow control with extremely high accuracy and excellent responsiveness is possible despite fluctuations.

[Brief explanation of drawings]

FIG. 1 is a piping diagram of a conventional device, and FIG. 2 is a piping diagram of an embodiment of the present invention. 1... Relay tank, 2... Pump, 3, 4, 5... Main piping, 6... Filter press, 7A, 7B... Control valve, 8... Liquid level detector, 10... Branch pipe.

Claims (1)

[Claims] 1. A first control valve is provided in the middle of the main piping that sends liquid to the demand part from a relay tank that is continuously supplied with liquid from the outside, and a part of the liquid is returned to the relay tank from before this control valve. A second control valve is provided in the branch pipe, and a detector is provided to detect the liquid level in the relay tank, and both control valves are arranged so that the liquid level measured by the detector is constant. 1. A flow rate adjustment device characterized in that the opening degree of the flow control device is controlled by feedback.