Liquid purification or separation – Casing divided by membrane into sections having inlet – Energy recovery from treated liquid
Reexamination Certificate
2000-11-15
2003-07-08
Kim, John (Department: 1723)
Liquid purification or separation
Casing divided by membrane into sections having inlet
Energy recovery from treated liquid
C210S258000, C210S323100, C210S416100, C210S433100
Reexamination Certificate
active
06589423
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is filtration systems.
BACKGROUND OF THE INVENTION
Filtration systems often require substantial pressure to drive a fluid through a membrane or other filter. In the case of reverse osmosis systems, this pressure requirement can translate into a substantial energy cost or “penalty.”
It is known to mitigate the energy cost of filtration pumping by employing a work exchange pump such as that described in U.S. Pat. No. 3,489,159 to Cheng et al. (January 1970) which is incorporated herein by reference. In such systems, pressure in the “waste” fluid that flows past the filter elements is used to pressurize the feed fluid. Unfortunately, known work exchange pumps employ relatively complicated piping, and in any event are discontinuous in their operation. These factors add greatly to the overall cost of installation and operation.
It is also known to mitigate the energy cost of filtration pumping on a continuous basis by employing one or more turbines to recover energy contained in the “waste” fluid. A typical example is included as FIG. 3 in PCT/ES96/00078 to Vanquez-Figueroa (publ. October 1996), which is also incorporated herein by reference. In that example, a feed fluid is pumped up a mountainside, allowed to flow into a filtration unit partway down the mountain, and the waste fluid is run through a turbine to recover some of the pumping energy.
A more generalized schematic of a prior art filtration system employing an energy recovery turbine is shown in FIG.
1
. There a filtration system
10
generally comprises a pump
20
, a plurality of parallel permeators
30
, an energy recovery turbine
40
, and a permeate or filtered fluid holding tank
50
. The fluid feed lines are straightforward, with an intake line (not shown) carrying a feed fluid from a pretreatment subsystem (not shown) to the pump
20
; a feed fluid line
22
conveying pressurized feed fluid from the pump
20
to the permeators
30
; a permeate collection line
32
conveying depressurized permeate from the permeators
30
to the holding tank
50
; a waste fluid collection line
34
conveying pressurized waste fluid from the permeators
30
to the energy recovery turbine
40
; and a waste fluid discharge line
42
conveying depressurized waste fluid from the energy recovery turbine
40
away from the system
10
.
A system according to
FIG. 1
may be relatively energy efficient, but is still somewhat complicated from a piping standpoint. Among other things, each permeator
30
has at least three high pressure fluid connections—one for the feed fluid, one for the waste fluid, and one for the permeate. In a large system such fluid connections may be expensive to maintain, especially where filtration elements in the permeators need to be replaced every few years.
Thus, there is a continuing need for a simplified approach to recovering energy costs employed in pressurizing a filtration system.
SUMMARY OF THE INVENTION
The present invention is directed to filtration systems in which a plurality of filtration modules disposed within an outer casing produce both a low pressure filtrate and a high pressure waste fluid from a feed fluid, and energy in the high pressure waste fluid is used to pressurize the feed fluid.
In preferred embodiments the feed fluid is pressurized using a pressurization subsystem, the energy in the waste fluid is recovered using an energy recovery subsystem, and the pressurization and energy recover subsystems are mechanically coupled such that energy derived from the energy recovery subsystem is used to drive the pressurization subsystem. In more preferred embodiments at least one of the pressurization and energy recovery subsystems utilize a turbine. In still more preferred embodiments the pressurization and energy recovery subsystems are coupled using a common drive shaft.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.
REFERENCES:
patent: 4125463 (1978-11-01), Chenoweth
patent: 4321137 (1982-03-01), Kohler
patent: 4973408 (1990-11-01), Keefer
patent: 4983305 (1991-01-01), Oklejas et al.
patent: 5914041 (1999-06-01), Chancellor
patent: 5944999 (1999-08-01), Chancellor et al.
patent: 5980751 (1999-11-01), Chancellor
Kim John
Nate International
Rutan & Tucker LLP
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