Liquid purification or separation – Constituent mixture variation responsive
Patent
1986-02-07
1986-12-09
Adee, John
Liquid purification or separation
Constituent mixture variation responsive
210108, 210138, B01D 2512
Patent
active
046279148
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to control of suspension filtration processes and, in particular, to devices for automatic control of pressure filters.
BACKGROUND ART
Known in the art is a method of automatic control of a chamber filter press (cf., for example, the USSR Inventor's Certificate No. 442 812, Class B 01 D 37/04, J 05 D 27/00, published in 1974). The automatic controlling device realizing the known method is provided with a unit for determination of the termination of the suspension dehydration process when the filter cake reaches a specific water content which is continuously monitored by means of a sensor extending through the rubber membrane and located inside a top control chamber of the horizontal chamber filter press. This sensor is connected to an amplifying device connected to an actuating device of the filter press. The amplifying device is equipped with a sensor in order to set a specific water content level of the filter cake and is provided with a scale for visual control. Continuous monitoring of the water content level of the filter cake, which is the function of the electrical conductivity of the liquid phase in the filter cake, is effected by means of the sensor located in the chamber of the filter press and the amplifying device. The water content of the filter cake is shown on the scale of the amplifier sensor, calibrated to read the percentage ratio of the liquid and solid phases.
When a specific water content of the filter cake is obtained, the amplifier sensor generates a signal to indicate termination of the filtering process, which is delivered, after amplification, to the actuating device of the filter press.
A gland seal in the membrane is to be provided to install the sensor in the filter press chamber. If the membrane is made movable along the sensor, the chamber cannot be hermetically sealed.
The known device is deficient in that the sensor is installed in the upper chamber on the filter press whose chambers are arranged horizontally. The water content of the cake in the upper chamber can substantially differ from that of other chambers and cannot, therefore, be accurately controlled. Moreover, the conductivity of the liquid phase of the filter cake varies with the amount of coagulating agents and soluble salts used, also affecting the accuracy of the water content determination.
To summarize, the known device cannot be used for accurate determination of the average water content of the filter cake in all chambers of the filter press. It is certainly not applicable to filter presses having a vertical arrangement of chambers.
Also known in the art is a device for automatic control of the cake water content in a horizontal chamber filter press (cf., for example, the USSR Inventor's Certificate No. 683 784, Cl. B 01 D 37/04, B 01 D 25/12, published in 1979), which comprises a unit for monitoring the water content of the filter cake in the chambers of the filter press, a measuring vessel for filterate collection, a pipe connecting one of the chambers to the measuring vessel, a filtrate level detector comprising an electrode vertically movable by a hand drive, a scale calibrated in percent of the initial water content, and a locking valve equipped with an electromagnetic drive, and an amplifying-converting unit. The amplifier-converter comprises a step-down transformer, a resistor, a rectifier built around diodes, a semiconductor amplifier, and sound and light indicators.
For effective use of the known device, the content of the solid phase in the suspension has to be determined. It is done in a laboratory and the process takes more time than the actual dehydration of the suspension. Moreover, the water content of the cake is monitored in one chamber only, where it can substantially differ from the average water content of the cake in other chambers of the filter press. The efficiency of the filter press is therefore seriously affected.
Also known in the art is a method for controlling a chamber filter press (cf., for example, the USSR Inventor's Certificate No
REFERENCES:
patent: 4151080 (1979-04-01), Zuckerman
patent: 4439325 (1984-03-01), Blais
patent: 4544489 (1985-10-01), Campbell et al.
"Radio", No. 1, 1977, pp. 43-44.
"V Pomoshch Radioliubiteliu", ISSN 0130-0830, Issue 72, pp. 62-64, 69-73.
"V Pomoshch Radioliubiteliu", ISSN 0130-0830, Issue 77, pp. 47-51.
"V Pomoshch Radioliubiteliu", ISSN 0130-0830, Issue 76, pp. 52-54.
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