Filtration cartridge filters

Several factors determine cartridge filter collection efficiency including gas filtration velocity, particle characteristics, filter media characteristics, and cleaning mechanism. In general, collection efficiency increases with increasing filtration velocity and particle size. 

Filter. A filter is used in some cases when coagulation and sedimentation do not completely separate the solids from the liquid waste in areas where sand and sandstone formations are susceptible to plugging. Filters with a series of metal screens coated with diatomaceous earth or cartridge filters are typically used.27 Where limestone formations with high solution porosity are used for injection, filtration is usually not required. 

A consideration in the design of a Recoflo system is adequate pre-filtration of the feed solution. The fine resin beds employed in the system will plug-up with any suspended material that is not filtered out prior to treatment. This is not a major issue for chlor-alkali brines, however, which are relatively clean. Disposable polypropylene cartridge filters should suffice in most cases. 

Both media filters and cartridge filters can be used in a pretreatment process. Granular media filters involve the filtration of large particles through different layers of fine particles, usually coal, pumice, sand or garnet (Bonnelye et al. 2004). Cartridge filters act as the final filtration step before the water passes through the membranes, and remove fine particles as small as 1 pm. 

However, the short lifetime of in-line cartridge filters makes them unsuitable for microfiltration of highly contaminated feed streams. Cross-flow filtration, which overlaps significantly with ultrafiltration technology, described in Chapter 6, is used in such applications. In cross-flow filtration, long filter life is achieved by sweeping the majority of the retained particles from the membrane surface before they enter the membrane. Screen filters are preferred for this application, and an ultrafiltration membrane can be used. The design of such membranes and modules is covered under ultrafiltration (Chapter 6) and will not be repeated here. 

Figure 7.13 Typical in-line filtration operation using two cartridge filters in series. The prefilter removes all of the large particles and some of the smaller ones. The final polishing filter removes the remaining small particles...

In the filtration process, a liquid containing suspended solids is passed through a porous medium. The solids are trapped against the medium, and the separation of solids from liquids results. For large solid particles, a thick barrier such as sand may be used for smaller particles, a fine filter such as a filter cloth is preferable. Fluid passage may be induced by gravity, positive pressure, or a r acuum. A few of the more popular filter fypes are the plate and frame filter press, and shell and leaf and cartridge filters. 

MEMBRANE FILTRATION. Membrane filter cartridges are seldom used in fruit juice technology, as hot-filling is the common practice and prior membrane filtration is therefore unnecessary. These filters can only be used after fine filtration, as otherwise the membrane is immediately clogged up. 

One of the possible configurations for the pharmaceutical water purification system is shown in Fig. 3. The first three stages in that system (multimedia filtration, softening, and carbon filtration) are considered pretreatment steps for the RO unit that conducts final purification. The cartridge filter shown before the RO is provided to protect the membranes from the fine carbon particles. There are many variations of the treatment systems sometimes carbon filter is placed before a softener, sometimes it is eliminated completely. 

In deep-bed filtration (Fig. ID), particles are caught inside the filter medium. Examples of deep-bed filters are granular beds and some cartridge filters. Deep-bed filtration is used for dilute suspensions (<100 ppm) containing fine particles that are not easy to be removed by sedimentation or cake filtration. 

The same cartridge filters with 2-4 sq. ft. surface area were employed in a pilot-scale production facility for semi-continuous growth of a murine lymphokine-producing cell line. This was done as dead-end filtrations, harvesting 80 to 85% of the 20-40 liter culture as cell-free filtrate and retaining 15 to 20% for inoculum to be regrown after volume restoration with fresh medium. No attempts were made to recirculate or back-flush the filter cartridges. 

Sterile air filtration is simple today with the commercial units readily available. However, some companies still design their own (see Aiba, Humphrey and Millisf ) to use a variety of filter media such as carbon, cotton, glass staple, etc. (For recent papers about industrial applications of cartridge filters, see BrunoPl and Perkowski.t )... 

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