Filtration continuous operation

Because gravity is too weak to be used for removal of cakes in a gravity side filter (2), continuously operated gravity side filters are not practicable but an intermittent flow system is feasible in this arrangement the cake is first formed in a conventional way and the feed is then stopped to allow gravity removal of the cake. A system of pressure filtration of particles from 2.5 to 5 p.m in size, in neutralized acid mine drainage water, has been described (21). The filtration was in vertical permeable hoses, and a pressure shock associated with relaxing the hose pressure was used to aid the cake removal. 

The first filtration step should thus be carried out using a filter of at least F7 (EU7) quality, which should be changed after a maximum period of one year s continuous operation. The second filter of at least F7 (EU7) quality is not exposed to high RH, effectively stops microorganisms and particles, and can remain in place for about two years, provided the final pressure loss is not reached within this period. 

Membrane filtration using a polyaramide membrane [56] showed a retention of more than 99.8%. Application of this catalyst in a continuously operated membrane reactor showed conversion for more than 150 h. The ee dropped from 80% in the beginning (non-bonded analogue 97%) to about 20% after 150 h. The average ee for the first 80 h was 50%. 

The objective of the present study is to develop a cross-flow filtration module operated under low transmembrane pressure drop that can result in high permeate flux, and also to demonstrate the efficient use of such a module to continuously separate wax from ultrafine iron catalyst particles from simulated FTS catalyst/ wax slurry products from an SBCR pilot plant unit. An important goal of this research was to monitor and record cross-flow flux measurements over a longterm time-on-stream (TOS) period (500+ h). Two types (active and passive) of permeate flux maintenance procedures were developed and tested during this study. Depending on the efficiency of different flux maintenance or filter media cleaning procedures employed over the long-term test to stabilize the flux over time, the most efficient procedure can be selected for further development and cost optimization. The effect of mono-olefins and aliphatic alcohols on permeate flux and on the efficiency of the filter membrane for catalyst/wax separation was also studied. 

Application of cross-flow filtration for the removal of FT wax products can be a useful technique to maintain a constant catalyst loading in an FTS reactor in continuous operation. Addition of 1-dodecanol (at a concentration of 6 wt%) was found to decrease the permeation rate of the cross-flow filter used for the separation of simulated FT wax and activated iron catalyst slurry. However, additional... 

In the second type of filtration, depth or deep-bed filtration, the particles penetrate into the pores of the filter medium, where impacts between the particles and the surface of the medium are largely responsible for their removal and retention. This configuration is commonly used for the removal of fine particles from very dilute suspensions, where the recovery of the particles is not of primary importance. Typical examples here include air and water filtration. The filter bed gradually becomes clogged with particles, and its resistance to flow eventually reaches an unacceptably high level. For continued operation, it is therefore necessary to remove the accumulated solids, and it is important that this can be readily achieved. For this reason, the filter commonly consists of a bed of particulate solids, such as sand, which can be cleaned by back-flushing, often accompanied by... 

All of the membrane processes utilize an engineering design known as "cross-flow" or "tangential flow" filtration. in this mechanism, the bulk solution flows over and parallel to the membrane surface, and because the system is pressurized, water is forced through the membrane. The turbulent flow of the bulk solution across the surface minimizes the accumulati.on of particulate matter on the membrane and facilitates the continuous operation of the system. 

Example 5 Estimation of filtering area required for a plate-and-frame filtration operation. A plate-and-frame filter press is to be used for removing the solid material from a slurry containing 5 lb of dry solids per cubic foot of solid-free liquid. The viscosity of the liquid is 1 centipoise, and the filter must deliver at least 400 ft3 of solid-free filtrate over a continuous operating time of 2 h when the pressure-difference driving force over the filter unit is constant at 25 psi. On the basis of the following data obtained in a small plate-and-frame filter press, estimate the total area of filtering surface required. 

In continuous operations this can be done easily. In batch operations however, often filtration equipment cannot efficiently operate with extremely thin cakes. The long discharge times required to remove residual product in preparation for the next cycle, etc., make operation at a product s optimal... 

Kragl et al.100 described the retention of diaminopropyl-type metallodendrimers bearing palladium phosphine complexes on ultra- or nanofiltration membranes and their use as catalysts for allylic substitution in a continuously operating chemical membrane reactor. Their results demonstrated a viable procedure for catalyst recovery, because these metallodendrimers acting as catalyst supports offered an advantage in that the intrinsic viscosity of the solution is smaller, facilitating filtration. 

For a particulate application involving SLS, how to choose the best equipment, to use batch or continuous operation, which filter medium to select, and what is the optimum operating conditions are concerns of engineers. Although theories are available for some SLS operations, solutions for equipment selection, process design, and optimization are still very much dependent on test and experience, and are frequently qualitative or semi-qualitative. In this section, strategy and decision networks for selection of SLS equipment, introduction of filter media, centrifugal pumps for filtration operation, and selection of filter aids by cycle analysis will be discussed. 

Alternatively, membrane filtration can be used to separate soluble metal complexes, containing polymer-attached ligands, from reactants and products [43]. A major advantage of using soluble polymer-enlarged catalysts in conjunction with membrane separation is that it is readily amenable to continuous operation. A novel example of this concept is the use of dendritic ligands [44] in combination with membrane filtration. 

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