Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1995-05-22
1996-08-27
Spear, Frank
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210641, 21050023, B01D 6158
Patent
active
055498299
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus and process for producing a high solids content aqueous dispersion from a low solid content aqueous dispersion. The invention is particularly concerned with producing a high solids content dispersion from a low solids content dispersion or emulsion incorporating polymer latex.
Many products are manufactured in batches, and where such products are likely to undergo physical or chemical changes over time, or cross-contamination between batches is unacceptable, it is often necessary to clean the manufacturing equipment before working on a new batch. The cleaning operation usually involves the generation of a volume of waste water which must then be disposed of. The manufacture of emulsion paints is a typical example of such batch processes.
In the case of paint processing, valuable raw materials are lost in the waste water. Furthermore, the waste water has an extremely high polluting potential which precludes its discharge into waterways without appropriate treatment. Traditionally, it has been a common practice to transport such wastes to a landfill site for dumping. This in itself entails significant costs. Even this approach to the problem of waste water disposal is becoming unacceptable however as a result of concerns over the environment, particularly the conservation of water resources, and the growing scarcity of suitable landfill sites.
Ultrafiltration has been used in many industries for different applications, for example the concentration of milk, the clarification of fruit juices, the recovery of paint including resin from electrocoating paint tanks and the like. In the past, some paint manufacturers have investigated the use of membranes for the concentration of dilute emulsion paints. Their attempts largely failed, however, because they were only able to concentrate the waste water to about 25% total solids content on a dry weight basis. It would be necessary to use an evaporator to further concentrate the waste water to the desired solid content level of over 40%, that being the solid content level at which the retentate can be used for example in the manufacture of a subsequent batch of the same paint. In addition to the problem of obtaining adequate concentrations, it was also found that the membranes could not be maintained in a clean condition.
Membranes are thin polymeric films defining pores, the pore size determining the separation, that is which materials the membrane will pass and which materials the membrane will retain. Membranes are available in a variety of forms, for example spiral wound, hollow fibre, plate and frame and tubular. The present invention is concerned with the application of hollow fibre membranes and tubular membranes.
The term "hollow fibre membrane" is used in this document to denote a membrane comprising a relatively thick open-pored tubular support structure and a relatively thin surface layer defining pores which determine the pore size of the membrane, the support structure and surface layer being formed from the same material in a single manufacturing step. Hollow fibre membranes can be manufactured to have relatively small diameters, for example internal diameters as small as 1 mm, but cannot withstand large differentials between internal and external pressures.
The term "tubular membrane" is used in this document to denote a membrane comprising a porous tubular support structure of a first material on a surface of which is deposited a layer of a second material, the surface layer of the second material defining pores which determine the pore size of the membrane. The support structure of a tubular membrane can be manufactured from a material which gives high strength and can thus resist large pressure differentials, but it is difficult to manufacture tubular membranes of small internal diameter.
In the case of both hollow fibre and tubular membranes, in use the dispersion to be concentrated is passed at a relatively high velocity across the membrane surface so that any solid deposited on the membrane surface is
REFERENCES:
patent: 3457170 (1969-07-01), Havishs
patent: 4160726 (1979-07-01), DelPico
Concentration Polarization With Membrane Ultrafiltration; Ind. Eng. Chem. Prod. Res. Develop. vol. 11, No. 3. (1972).
Ultrafiltration Applications; Desalination, 77 (1990) 135-179; Elsevier Science Publishers B.V.
Northwest Water Group PLC
Spear Frank
LandOfFree
Membrane filtration system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Membrane filtration system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Membrane filtration system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1054329