Fouling processes particles, formation

For homogeneous catalysts, the process of polymer particle formation generally leads to porous, low-density polymer particles, which can cause significant increase in slurry viscosity and reactor fouling, leading to inadequate reactor temperature control. Additionally, polymer particles with poor powder properties are undesirable for postreactor polymer processing. These problems must be addressed before using soluble metallocene catalysts for industrial production of polyolefins. 

Owing to reduced salt solubility, the formation of metal oxides and, eventually, the presence of stable solid-matter particles, these are all present in the SCWO processes. These particles can cause equipment-fouling and erosion. However the reduced solubility of salts under supercritical conditions introduces the possibility of a solid fluid separation. 

Separation-layer micro mixers are specially tools for mixing solutions which react fast or tend to foul otherwise [39, 53, 135-138], The most prominent example of such processes is probably the generation of particles by immediate precipitation, as e.g. for calcium carbonate formation. Separation-layer mixers thus overcome the limits of normal micro mixers, which tend to clog under such conditions. 

With all polarization phenomena, the flux at a definite time is always less than the original value. When steady-state conditions have been attained a further decrease in flux will not be observed, i.e., the flux will become constant as a function of time. Polarization phenomena are reversible processes, but in practice, a continuous decline in flux can be observed. Such continuous decline is a result of membrane fouling, which may be defined as the irreversible deposition of retained particles, colloids, emulsions, suspensions, macro molecules, salts, etc. on or in the membrane. This includes adsorption, pore blocking, precipitation, and cake formation. 

Unlike in the case of the PMRs utilizing pressure driven membrane techniques, no membrane fouhng due to the presence of TiOj particles was observed in case of the hybrid photocatalysis-MD system. It was reported (Mozia and Morawski, 2009) that after more than 340 h of operation with a suspension of IIO2 in distilled water, the flux was equal to the maximum permeate flux (i.e., measured for distilled water) and amounted to about 0.16,0.26 and 0.39 m /m. day for the inlet feed temperatures (F, ) of 50,60, and 70°C, respectively. The observed lack of the influence of 1102 on the permeate flux could be explained by the mechanism of mass transport in MD which is due to a difference between the vapor pressure on the two sides of the membrane. Since the process can be conducted without application of pressure difference as a driving force, the main factor responsible for membrane fouling is excluded. In the absence of higher pressure, unlike in the case of pressure driven techniques, cake formation on the membrane surface could be avoided. 

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