Variable chamber filter

Mechanical Squeezing of Cakes. Mechanical squeesing of the cake in the so-called variable chamber filters has been used relatively recendy to lower moisture content of the final cake. This is appHcable only to cakes that are compressible. Many filters are available in which some form of mechanical expression of the cake is used either to foUow a conventional filtration process or to replace it. 

Comparisons are available on the relative performance and costs for dewatering municipal sludges (2). The relative performance of different filters and conditioners on waste sludges is shown in Table 3. The same sludge was treated on two belt-filter presses, two different centrifuges, and rotary vacuum filter (75). In another study, a variable chamber filter press, fixed-volume filter press, continuous belt-filter press, and rotary vacuum filter were compared for performance, capacity, and capital and operating costs (69). 

The variable Chamber filter has recaitly [Young, 1991] be demonstrated as the economic option in idudge dewatering, en conq>ared with c trifiiges and belt presses. Cake solids above the 24% DS autothermic incineration limit can be achieved, albeit at hi er flocculation doses than normally used in press operation. 

Cylindrical Variable-Chamber Filters. Cylindrical filtering sur ces are inhorent in the tube press. Figure 11.42, and the VC fibo . Figure 11.43. hr the latter, the filter is mounted on a... 

Cylindrica.1 Presses. Another group of filters that utili2e the variable chamber principle are those with a cylindrical filter surface. There are two designs in this category, both of which originate from the United Kingdom. 

Continuous Compression Filters. The variable chamber principle appHed to batch filtration, as described before, can also be used continuously in belt presses and screw presses. 

Significant improvements were made in the 1980s and early 1990s in high capacity, automated variable volume filters that incorporate automatic pressure filtration, expression, washing, and air displacement. Some of the large plate-and-frame automatic presses can operate at up to 2 MPa (ca 285 psig), with up to 100 chambers (25,26). 

The SU5 beamline [89] at the Super-ACO synchrotron (LURE, Paris ) employed an electromagnetic undulator to produce fully variable polarization in the VUV region [83, 90, 91]. This beamline was equipped with a gas filter for the suppression of unwanted higher order radiation [92] and had a VUV polarimeter [93] permanently installed just before the experimental chamber that could be rapidly lowered into the beam for polarization determinations. Full polarization analyses had been performed in commissioning, with 53 values ranging from 0.9 to 0.96 for rep and from 0.9 to 0.99 for Icp [93]. The remainder was determined... 

Fig. 2. Typical third-harmonic generation measurement. The beams from the laser source (here either a frequency shifted Nd YAG or a HoTmCnYAG laser) are split into a measurement and a reference beam. The polarization rotator and the polarizer serve as variable attenuator and yield the desired polarization of the input beam. The beam is focused on the sample in the vacuum chamber. The water filter removes the fundamental frequency and the attenuation filters limit the third-harmonic signal to the measurement range of the photomultiplier. The signal from the sample is divided by the reference signal and averaged with a boxcar gated integrator...

The bioassay chambers were constructed of 6.4 mm plexiglass, 0.60 X 0.60 X 2.4 meters in dimension. The air inlet end was fitted with a charcoal filter through which air was drawn through the chamber by a variable velocity fan. The formulations to be tested were applied to growing cotton plants and allowed to age for the desired length of time. The treated plants were positioned at the air inlet end of the ch lmber and the airflow adjusted to approximately 3-5 km/hr. Male pink bollworm moths were positioned at the opposite end of the chamber, downwind of the pheromone source. Moth mortality was recorded versus an untreated control plant to compensate for any natural mortality. Table I summarizes the data from the test designed to demonstrate the attracticide effect. As can be seen, significant mortality is obtained only in the case where pheromone and toxicant are both present. 

The basic principle on an RVF is a hollow rotating cylindrical drum driven by a variable speed drive at 0.1-10 revolutions per minute. One-third of the drum is submerged in a slurry trough. As it rotates, the mycelia suspension is drawn to the surface of the drum by an internal vacuum. The surface is the filter medium mounted on top of a grid support structure. Mother liquor and wash are pulled through the vacuum line to a large chamber and evacuated by a pump. 

The Boyden chamber is a simple apparatus used to test for chemotaxis, especially of leukocytes. It can also be used to assess tumor cell transmigration across an endo-thehal monolayer in vitro. It consists of two compartments separated by a MiUi-pore filter (3-8 pm pore size). A chemotac-tic factor is placed in one compartment, and a gradient develops across the thickness of the filter (ca. 150 pm). Cell movement into the filter is measured after an incubation period less than the time taken for the gradient to decay. Cell motility can be measured in Boyden chambers containing filters precoated with different materials, for example fibronectin or fibronectin fragments. The method, when apphed to malignant and non-mahgnant cell hnes, shows that the variable invasive potentials of these cells correlate with their abihty to disrupt the endothelial cell monolayer. 

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