Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2000-05-24
2003-09-02
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S321690, C210S321750, C210S321840, C210S360100, C210S380100
Reexamination Certificate
active
06613231
ABSTRACT:
This application is the U.S. national-phase application of PCT International Application No. PCT/FR98/02475.
TECHNICAL FIELD
Field of invention consists in treatment, separation and cleaning of liquids. Videlicet, the present invention relates to an apparatus for membrane separation that treats liquids by extracting suspended, emulsified and/or dissolved substances (mineral and organic ones) out of the said liquids. The same relates to a system and process of liquid separation.
The apparatus for membrane separation allows to obtain two flows of liquids such as:
a) flow of permeate or filtrate fully or partly free from suspended, emulsified and or dissolved substances (mineral and organic ones). This flow represents the major part of the liquid being treated;
b) flow of concentrate or retentate enriched with suspended, emulsified and or dissolved substances.
The present invention also relates to treatment of liquids containing chemicals, microbiological and pharmaceutical substances, foodstuffs that shall be efficiently removed or concentrated fully and/or selectively. In this field, the apparatus, system and process according to the present invention may have special advantages owing to a long-term serviceability without clogging membrane or with low clogging, maintaining a high permeability, not requiring a heavy pre-treatment of the said liquid being treated.
TERMS USED IN THE INVENTION
To avoid any misunderstanding of the present invention both itself and in comparison with the current state of the art, the following terms deserve explanation to be properly understood throughout this description.
“A liquid being treated”—a liquid mainly comprising water or organics, containing organic or inorganic substances in whatever condition: suspended and/or dissolved and/or emulsified. This liquid is introduced into system for treatment.
“A liquid”—a liquid in the process of treatment within apparatus for membrane separation. It is obtained from the liquid being treated during treatment stage that is referred to as “period of concentration”.
“A concentrate or retentate”—a part of liquid that, once failed to pass membrane, is enriched with substances retained on membrane until a required level of concentration is reached. As the required level of concentration is reached, the concentrate is let out whilst keeping its continuous level of concentration. Another stage of treatment referred to as “a separation period” would commence as from this moment.
“A permeate or filtrate”—a part of a liquid that, on passing a membrane, is fully or partly free from substances (colloidal, emulsified and/or dissolved ones).
“Concentration level T
c
” within the period of concentration of the liquid being treated is determined by the following formula:
T
c
=
V
p
V
p
+
V
cc
+
V
c
·
100
%
where
V
p
stands for the permeate volume;
V
cc
stands for the volume of a liquid in concentration tanks;
V
c
stands for the volume of a liquid in pipes.
Once the required level of concentration is reached (separation commencement moment), T
c
is determined by the following formula:
T
c
=
Permeate
flow
rate
Permeate
flow
rate
+
Flow
rate
of
concentrate
being
bled
down
·
100
%
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“A membrane or filtering medium”—a filtering or separating medium aimed at a more or less selective, partial or full extraction of substances contained in a liquid i.e. colloidal, emulsified and/or dissolved ones. A membrane would normally comprise the two following layers:
the first one is a selective layer containing fine pores facing a compartment filled with a liquid and playing a major part in the separation;
the second one is a supporting layer facing a compartment filled with a permeate or filtrate. It aims at supporting the thin selective layer by imparting mechanical stability to it.
The present invention may use various types of membranes:
from the viewpoint of their use: for micro-filtration, ultra-filtration, nano-filtration and/or hyperfiltration at low pressure;
from the viewpoint of their composition: polymer, metal, ceramic and/or metal-ceramic filters and/or filters made of other suitable materials;
from the viewpoint of their structure: symmetrical, asymmetrical and composite filters.
“An operating clearance”—a space between the main surface of a rotating body and the membrane surface.
“A cell”—a part of the apparatus for membrane separation, preferably of cylindrical shape, with a diameter longer than its length and representing a rotating body between two membranes with operating clearances on both its sides and bordered by a membrane on each side thereof.
“A permeate chamber”—a part of the apparatus for membrane separation, preferably of cylindrical shape, with a diameter significantly longer than its length and containing at least one substrate covered with a membrane on each of its main sides and used to support the membrane, to let in and out a permeate.
“Permeability” is determined by the ratio of permeate flow rate to the area of a membrane it has passed through.
“Oscillatory conditions”—a condition of a liquid characterized by transient and, if applicable, cyclic fluctuations of speed, flow rate and/or pressure of the said liquid under impact of controllable external forces.
“Clogging”—a phenomenon that restricts efficiency of any apparatus for membrane separation and reduces its permeability; this phenomenon consists in the following: deposition of a layer of substances on the membrane selective layer; plugging of membrane pores with the said substances; deposition of a polarization layer in the course of treatment of solutions containing salts and/or dissolved macromolecules.
“Coarse pre-filtration”—pre-treatment of a liquid being treated for the purpose of extracting large particle representing a part of a suspended substance and having a size no less than 20 micrometers with the use of the traditional filtration technique.
STATE OF THE ART
By present, certain engineering solutions have already been made. For example, well-known is [document 1: Nakao S.-I. “Current status of inorganic membrane in Japan”. Proc. 2nd Inter. Conf. Inorg. Membr. -ICIM2-91, Montpellier, France, Jul. 1-4, 1991. Eds.: A. J. Burggraaff, J. Charpin and L. Cot. Trans Tech Publications published in “Key Engineering Materials”, Vol. 61&62 (1991) pp. 219-228] a apparatus for membrane separation having flat rotating membranes. Soy-bean sauce micro-filtration does not result in filtration inferior of a certain minimum threshold of pressure due to centrifugal forces impacting on membrane permeability.
Apart from this, document 2: WO-A-95/09818 proposed a process of waste water treatment with the use of a complicated system including stages of physical-chemical deposition, micro-filtration and tangential nano-filtration. The above sequence of stages extends life of micro- and nano-filtration membranes owing to the sequence of various treatment processes: precipitation preceding micro-filtration, micro-filtration itself preceding nano-filtration. Apart from this, to avoid premature clogging of nano-filtration membranes, differential operating pressure of the above membranes was limited by 1.5 bar. However, it is well known that the micro-filtration stage that has to help avoid the nano-filtration membrane clogging will itself constitute a stage to cause a clogging problem.
Another invention (document 3: WO-A-96/09986) relates to processes and installation intended to treat liquids containing organic waste. The treatment chain includes stages of physical and chemical treatment, as well as ultra- or micro-filtration and then reverse osmosis. All stages of membrane-assisted treatment are of the classical type i.e. tangential stages. According to this invention, all stages of pre-treatment (pre-filtration, coagulation, flocculation, oxidation, filtration etc.) enable to extend the life of membranes at all s
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