Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1998-01-12
2000-06-20
Drodge, Joseph W.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
95 19, 95 23, 210108, 21032169, 210739, 210741, 73 38, B01D 6122, B01D 35143, G01N 1508
Patent
active
060774355
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to ultrafiltration and microfiltration systems and in particular to testing, monitoring and control systems for use with membrane filtering systems.
Although the invention is described with respect to its application to fibre membrane filtering systems, it will be appreciated that it is applicable to ultrafiltration/microfiltration systems in general and is not limited to the specific application described.
BACKGROUND ART
Fibre membrane filtration is a well developed method which involves the use of a large number of hollow tubular micro-porous fibres. Each fibre is adapted to allow filtrate to flow from the exterior of the fibre through micro-pores in the fibre wall to the interior of the fibre, while excluding impurities from the filtrate. The pores can be, for example, around 0.2 micrometers in diameter.
In practice, many thousands of fibres are bundled together and encased in a shell, the complete assembly being known as a module 5 (see FIG. 2). The shell 6 is usually cylindrical and the fibres 7 extend longitudinally therethrough. The ends of the shell are sealed, usually with a resin or the like known as the potting forming a plug 8 at each end. The ends of the hollow fibres 7 extend through, and are encased in the potting plug 8 so that the interior of each of the fibres 7 is in communication with the exterior of the module 5 at both ends, thereby allowing filtrate to be removed from two end locations. Alternatively, both ends of each fibre may extend through the potting and communicate with the exterior at one end of the module 5, or the fibres at one end may extend through the potting, the other fibre ends being sealed.
As shown in FIG. 1, the modules 5 are usually (but not necessarily) disposed in "banks" 9, each comprising a row of modules 5 sharing a manifold 10, the banks being arranged in an array.
In use, feed or influent is introduced to the space intermediate the exterior of the fibres and the interior of a module shell. Filtrate flows through the micro-porous membrane of the fibres 7 into the interior of the fibres and thereafter flows along the length of the fibres passing through the plug 8 to the exterior of the module 5, usually into a manifold.
The operation of the filtering system is normally controlled by a number of valves 11 which control the flow of feed to the system, the flow of filtrate, backwashing of the filters using gas and/or filtrate, and introduction of wetting agents and special chemical cleaning agents during backwashing. These valves 11 are typically pneumatically operated by compressed air, with the flow of compressed air to each valve being controlled by an electrically operated solenoid.
Operation of the system may be monitored by detectors which measure fluid flow, fluid pressure, temperature and other parameters at various points throughout the system. Feedback loops may be built into the system to ensure the system is operating according to preset control conditions.
During use the fibres become clogged with the filtered impurities and require "backwashing" at regular intervals to remove the impurities and maintain the efficiency of the filtering. The frequency and type of backwashing will be dependent on the state and type of feedstream being filtered. FIG. 3 illustrates flux decline with various types of feed. In many situations the state of the feedstream is dynamic and thus it is difficult to predict when and how often backwashing will be required. This can lead to the system being set to cope with a "worst case" situation, causing the system to be run inefficiently.
Furthermore, choosing the size, number and type of modules 5 required when designing a filtration plant for a particular purpose involves the consideration of a number of factors. For example, plant capacity, level of filtration required, backwashing requirements and type of feedstream to be filtered each need to be investigated. Whilst some of these factors are relatively easy to measure, quantifying the characteristics of the feedstream in pa
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Beck Thomas William
Drummond Humphrey John Jardine
Johnson Warren Thomas
Kensett-Smith Brett
Maxwell Ian Andrew
Drodge Joseph W.
USF Filtration and Separations Group Inc.
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