Optimization purges

Grob, C. and Wortberg, J., Optimizing Purging Time at Product Change in Blown Film Extrusion by Selective Modification of Process Parameters, SPE ANTEC Tech. Papers, 50, 261 (2004)... 

The mother liquor containing impurities, phenol and dissolved BPA is recycled back to the BPA reactor. Part of the mother liquor is sent to the purge-recovery system, where impurities are partially decomposed and recombined to form BPA. Effluents are mixed with mother liquor and recycled to the BPA reactor. Undesirable impurities are condensed at the purge-recovery system and discharged as tarry materials, which can be used as fuels. The optimal purge ratio from the mother liquor controls product quality, while minimizing raw material consumption. 

Additionally, in Japan, the MTBE levels were analyzed in some rivers by using an improved P T-GC/MS (40 °C optimized purging temperature and - 180 °C cryo-focussing) allowing for a low limit of detection (0.003 xgL ) [19]. MTBE increases from the upper course of the rivers to its mouths as well as higher levels in winter than in srunmer were observed, which was consistent with other studies. 

Figure 4.9 shows a plot of Eq. (4.12). As the purge fraction a is increased, the flow rate of purge increases, but the concentration of methane in the purge and recycle decreases. This variation (along with reactor conversion) is an important degree of freedom in the optimization of reaction and separation systems, as we shall see later. 

After the purge activation time (which can be optimized), the split mode is turned on and the solvent vapors are purged out of the split vent. If possible, choose a sample solvent that has a boiling point that is at least 20° below the boiling point of the first sample component (if known). 

Now there are two variables in the optimization. These are the reactor conversion (as before) but now also the concentration of IMPURITY in the recycle. For each setting of the IMPURITY concentration in the recycle, a set of trade-offs can be produced analogous to those shown in Figures 13.17 and 13.18. Figure 13.19 shows the tradeoffs for the feed impurity case and a purge with fixed concentration of impurity in the recycle1213. 

Obviously, the use of purges is not restricted to dealing with impurities. Purges can also be used to deal with byproducts. As with the optimization of reactor conversion, changes in the recycle concentration of impurity might change the most appropriate separation sequence. 

Interactions between the reactor and the rest of the process are extremely important. Reactor conversion is the most significant optimization variable, since it tends to influence most operations through the process. When a purge is used to remove impurities from the process, the concentration in the recycle is another important optimization variable, again influencing operations throughout the process. 

The cost of a vertical Lasagna system was evaluated by DuPont using a cost optimization model. For remediation of TCE to a depth of 40 to 50 ft (12 to 15 m) in clay on a 1-acre (4047-m ) site, costs were estimated to range from 40 to 90/yd ( 52 to 117/m ). Soil properties, depth of contamination, cost of emplacing electrodes and treatment zones, required purge water volume, cleanup time, and cost of electrical power were all included in the estimate (D12500Y, p. 10). 

A series of complexometric extractions were performed to optimize the mobUiza-tion/purging of metallic ions from samples of processing condensate of chromated copper arsenate (CCA). Whereas Cr(VI) and Cu(II) were rapidly mobilized into isobu-tylmethyl ketone-amended SCCO2 after reaction with dithiocarbamate or alkylxan-... 

Sucan, M.K. and Russell, G.F. 1997. A novel system for purge-and-trap with thermal desorption Optimization using tomato juice volatile compounds. J. High. Resol. Chromatogr. 20 310-314. 

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