Filtration, continuous performance evaluation

A continuous cross-flow filtration process has been utilized to investigate the effectiveness in the separation of nano sized (3-5 nm) iron-based catalyst particles from simulated Fischer-Tropsch (FT) catalyst/wax slurry in a pilot-scale slurry bubble column reactor (SBCR). A prototype stainless steel cross-flow filtration module (nominal pore opening of 0.1 pm) was used. A series of cross-flow filtration experiments were initiated to study the effect of mono-olefins and aliphatic alcohol on the filtration flux and membrane performance. 1-hexadecene and 1-dodecanol were doped into activated iron catalyst slurry (with Polywax 500 and 655 as simulated FT wax) to evaluate the effect of their presence on filtration performance. The 1-hexadecene concentrations were varied from 5 to 25 wt% and 1-dodecanol concentrations were varied from 6 to 17 wt% to simulate a range of FT reactor slurries reported in literature. The addition of 1-dodecanol was found to decrease the permeation rate, while the addition of 1-hexadecene was found to have an insignificant or no effect on the permeation rate. 

The following three separation methods of product from the Ir-catalyst were evaluated distillation, extraction and filtration. For the last two options the preparation of new modified extractable or immobilized xyliphos ligands was necessary. However, lower activity and selectivity of these xyliphos derivatives and the additional development work that would have been required led to the decision to stay with the already well optimized soluble xyliphos system. After the hydrogenation step, a continuous aqueous extraction is performed to neutralize and eliminate the acid from the crude product. After flash distillation to remove residual water the catalyst is separated from (S)-NAA in a subsequent distillation on a thin film evaporator (see Fig. 13). From the organic distillation residue, Ir could in principle be recovered whereas the chiral ligand decomposes. Owing to the very low catalyst concentrations, Ir recovery is not economical. 

Since 2003, RO-based unit operation to remove the radionuclides C Cs, ° Ru, U, Pu) from delay tank is continued, and the performance of the system was found to be promising [49-51]. The final discharge of low-level active waste (i.e., a mixture of evaporator condensate, ADU filtrate, and waste generated from personnel contamination [like hand washing to remove contamination from hand]) is carried out from the delay tank, which temporarily holds low-active waste. We thus evaluated RO for the removal of alpha activity, beta activity, nitrates, and total dissolved salts (TDSs) from delay tank water at the pilot plant. The delay tank water composition is given in Table 26.4. The specification of the membrane module, which was supplied by the Desalination Division of the BARC (Mumbai), is listed in Table 26.5. The module was... 

Liithi and Luisi [44] have used a hoUow fiber membrane reactor for peptide synthesis catalyzed by a-chymotrypsin in microemulsion. Chang et al. [110] described the immobilization of lipase on liposomes, which, in turn, were solubilized in AOT/isooctane reversed micelles and used for the continuous glycerolysis of olive oil in an ultrafiltration cell. The half-Ufe of the Chromo. viscosum lipase was 7 weeks. The development of an ultrafiltration ceramic membrane bioreactor for the simultaneous lipolysis of olive oil and product separation in AOT/isooctane reversed micellar media has been also reported [106,107], Cutinase performance was also evaluated in a ceramic membrane reactor [9]. An attempt to minimize the surfactant contamination problem was based on the use of an electro-ultrafiltration method which can decrease the gel formation in the membrane surface, improving the filtration flux, achieving the separation of the AOT reverse micelles [187],... 

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