Improving filtration performance

As discussed above, sterile filtration is capable of producing beer of high quality. However, because the process is multistage the costs become significant. Some opportunities for optimisation have already been outlined. However, ultimately the limiting factor for performance of a filtration step is the characteristics of the beer requiring filtration. Therefore, there is scope for the introduction of technologies upstream of the filtration steps that improve the filterability of the beer. 

Exogenous enzymes are those that are added by the brewer rather than those that occur naturally from the malted cereals and yeast. Enzymes are available that exhibit proteolytic, cytolytic (plant cell wall material) and carbohydrase activity. Cost-effective enzyme preparations are not in general pure enzymes, however, a blend is often an advantage, enabling more than one activity to occur. 

Enzymes may be employed throughout the process from brewhouse through to cold storage to eliminate problematic components or in some cases significantly 

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Cutting edge technologies include as nanofibre nonwoven filtration media and electret-charged media. These electrostatic effects directly increase the efficiency of capture of submicron particles, resulting in improved filtration performance. 

Another feature of an extruder is the presence of a gauze filter after the screw and before the die. This effectively filters out any inhomogeneous material which might otherwise clog the die. These screen packs as they are called, will normally filter the melt to 120-150 fim. However, there is conclusive evidence to show that even smaller particles than this can initiate cracks in plastics extrudates e.g. polyethylene pressure pipes. In such cases it has been found that fine melt filtration ( 45 p.m) can significantly improve the performance of the extrudate. 

Often, these fuels respond poorly to treatment with a wax crystal modifier or may require high rates of a wax crystal modifier to improve filtration and pumpability performance. This problem seems to occur whenever two situations exist ... 

Another set of applications includes those aimed at improving the performance of physicochemical unit operations such as coagulation-sedimentation or biological carbon filtration [18,212]. A few examples of scale-up and actual applications of 03/H202/UV systems are briefly discussed in the following two sections. 

Kamoshita Y, Ohashi R, and Suuzuki T. Improvement of filtration performance of stirred ceramic membrane reactor and its application to rapid fermentation of lactic acid by dense cell culture of Lactoccus lactis. J. Ferment. Bioeng. 1998 85(4) 422 27. 

Dean vortex improves the filtration performance. A highly concentrated solution is obtained, and it is highly energy saving... 

In the kidney, dihydropyridines have been reported to reduce vasoconstriction on the afferent arterioles without affecting efferent resistance (Loutzenhiser and Epstein, 1985). This profile appears to be unique to the dihydropyridine class since members of the other classes did not have preferential effects on the afferent side. The resulting increase in renal perfusion and glomerular filtration rates leads to improved kidney function. In humans with induced renal insufficiency, nifedipine was shown to improve renal performance (Neumayer et al., 1989 Russo et al., 1990). 

Increasing the velocity gradient in the flocculation tank improves the performance of subsequent settling and filtration facilities. This effect is as expected. The integral analysis presented here describes the causes of these improvements and relates improved solid-liquid separation to... 

A unique interaction between fluid mechanics and transport exists for filtration processes. Such processes perform better than expected based on the predicted impact of concentration boundary layers. The improvement in performance, a rare occurrence for membrane processes, arises from a combination of hydrodynamic diffusion and inertial lift [51]. Hydrodynamic interactions between particles or colloids that accumulate in the concentration boundary layer lead to shear-induced diffusion away from the membrane surface. Shear-induced diffusion can be significantly larger than molecular diffusion and thereby reduce surface concentrations. For sufficiently large particles at high shear rates, inertial lift becomes the dominant mechanism for particle movement away from the membrane. 

There are some commercially available electrospinning processes, such as the Nanospider electrospun nanofibres, which can provide thin coatings on traditional filtration substrates and enhance the filtration performance of these materials many fold. This technology can yield nanofibres with a narrow diameter distribution and distinct diameter size that can be used to optimise the filtration behaviour of the filter substrates for many applications, where particle retention efficiency is a critical requirement. These suhmicron fibres can significantly improve the air filtration efficiency of a variety of media and filters. The submicron fibres provide improved filter efficiency in the interception and inertial impaction regimes. ... 

The electrode materials in thin conductive sheets or bucky-paper forms are more suitable for industrial supercapacitor applications. Oh et al. prepared the highly porous sheets comprised of SWNT and doped PPy (SWNT-PPy) by vacuum filtration of SWNT-PPy methanol dispersions [35]. The nanotube network provided mechanical strength and improved electrochemical performance of the nanocomposites. The highest SC of 131 F/g was obtained for nanocomposite with 1 1 SWNTiPPy ratio. 

Data recorded under both low (15%) and high (80%) relative humidity conditions show that the H-ZSM-5 (0.4N) sample yields improved EtO filtration performance relative to the nntreated material. The H-ZSM-5 (LON) sample prodnces similar breakthrongh curves to the untreated sample while the ethylene oxide filtration performance of the H-ZSM-5 (1.5N) sample is significantly rednced as compared to the imtreated sample. 

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