Liquid purification or separation – With alarm – indicator – register – recorder – signal or... – Responsive to fluid flow
Reexamination Certificate
2001-03-16
2004-01-06
Drodge, Joseph (Department: 1723)
Liquid purification or separation
With alarm, indicator, register, recorder, signal or...
Responsive to fluid flow
C210S086000, C210S090000, C210S097000, C210S143000, C210S519000, C210S540000, C700S273000
Reexamination Certificate
active
06673240
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to upflow clarification tanks, in which liquids are clarified by being directed in an upward helical path that causes the liquid to gradually decrease in velocity until precipitated or suspended solids separate from the rising water to create a rotating sludge blanket beneath a region of clarified water. More particularly, the invention is directed to feed control systems for such tanks.
An upflow clarification tank, such as those disclosed in Wyness U.S. Pat. Nos. 4,146,471 and 4,765,891, is a specific type of clarification tank that has a prominent conical portion with the larger diameter at the upper end. Typically, the walls of the clarification tank are angled at between about 40 degrees and 60 degrees with respect to the horizontal, although angles outside of this range can also be used. Contaminated water enters the tank at an inlet near the lower end, while clarified effluent is removed from an outlet near the upper end. Inside, the water is given a rotational movement, often in part by feeding it into the tank in a tangential direction, resulting in a generally upward helical flow of the water within the tank.
The increasing diameter of the tank toward its upper end causes a decrease in velocity of the flow of liquid as it moves upwardly. As the velocity decreases, suspended solids having a higher density than water agglomerate and separate from the water, forming a revolving sludge blanket that remains behind as clarified water continues upward until being withdrawn as clarified effluent.
In some conventional upflow clarification tanks, an increase in the flow rate into the clarifier can lead to increased velocities throughout the tank that could disturb the sludge blanket. Conversely, a decrease in the flow rate into the tank can lead to decreased velocities throughout the tank that may not be sufficient to keep the sludge blanket rotating and suspended in an optimal manner. Accordingly, some clarification tanks include a mechanism for controlling the entry of the liquid into the tank in order to help maintain the stability of the sludge blanket. For example, some tanks have been provided with a velocity baffle at or near the liquid inlet. The baffle can adjust the velocity of the flow in the lower sections by either changing the inlet direction or changing the cross-sectional area of the inlet. An operator can adjust the velocity baffle when he or she visually detects a disturbance or potential problem in the sludge blanket. More recently, some tanks have been provided with a pair of inlets having different cross-sectional areas. When an operator detects a disturbance or potential problem in the sludge blanket, he or she can use a valve to redistribute the entry of liquid between the two inlets in an effort to maintain desirable operating conditions.
SUMMARY OF THE INVENTION
The invention relates to a control system that enables automatic control over the entry of liquid into a clarification tank, permitting reduced reliance on the observations and or adjustments of a human operator. Like prior systems, the new system includes a regulator (such as a velocity baffle or pair of differently-configured inlets through which the flow can be controllably routed) for varying one or more objectively-determinable characteristics of the flow (such as the liquid level in a head tank, or the velocity, velocity head, momentum, or power of the liquid at some point in the system). Unlike prior systems, however, the new control system includes a sensor for measuring a value of one or more characteristics of the flow, and means for automatically adjusting the regulator based on the measured value.
The sensor may measure either pressure (or liquid level) or flow rate (or velocity) of the flow. Such sensor measurements may also be used to calculate other characteristics of the flow, such as velocity head, momentum, or power. Because many characteristics of a flow in a liquid clarification tank are mathematically interrelated, the sensor may be positioned so as to measure the pressure or flow rate at virtually any point in the supply line, an inlet line, or the tank itself. That measurement can then be used to adjust the regulator. This can be done directly through a mechanical connection, or indirectly by using a processor that uses a measured value to determine a desirable setting for the regulator. A desirable setting can be expressed either in terms of an incremental change in the setting of the regulator (for example, an opening or closing of a valve by 5%) or in terms of an absolute setting (for example, a valve being set at a 45% open position). The desirable setting can be effectuated through the use of a relay that communicates the setting to the regulator.
REFERENCES:
patent: 3227278 (1966-01-01), Johnson
patent: 3473665 (1969-10-01), Duff
patent: 4146471 (1979-03-01), Wyness
patent: 4765891 (1988-08-01), Wyness
patent: 5110458 (1992-05-01), Hechler et al.
patent: 5605636 (1997-02-01), Wyness
patent: 5695648 (1997-12-01), Fassbender et al.
patent: 5804062 (1998-09-01), Wyness
patent: 6224778 (2001-05-01), Peltzer
patent: 6408227 (2002-06-01), Singhvi et al.
patent: 637126 (1978-12-01), None
patent: 674760 (1979-08-01), None
patent: 916416 (1982-04-01), None
patent: 1011163 (1983-04-01), None
patent: 1255586 (1986-09-01), None
patent: 1318534 (1987-06-01), None
“Micro-Controller System for Water and Sewage Works”, Fuji Electric Review vol. 24, No. 1/1978, C. Fuji Electric Co. Ltd., Tokyo, Japan.*
CBI Walker, CLARICONE Operating Manual, Mar., 1999.
Fassbender John J.
Ruehrwein Donald Neil
Drodge Joseph
Marshall & Gerstein & Borun LLP
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