Feed ratio

DA Change in the vapor-feed ratio from one iteration to the next... 

DFA Partial derivative of the Rachford-Rice objective function (7-13) with respect to the vapor-feed ratio. 

Next to last iterative value of extract-feed ratio. 

DI Fractional change in extract-feed ratio during last two iterations. 

The fraction of sequences of the length indicated below have been measured t for a copolymer system at different feed ratios ... 

Numerous studies have probed how novolac microstmcture influences resist hthographic properties. In one example, a series of resists were formulated from novolacs prepared with varying feed ratios ofpara-jmeta-cmso. These researchers found that the dissolution rate decreased, and the resist contrast increased, as thepara-jmeta-cmso feed ratio increased (33). Condensation can only occur at the ortho position ofpara-cmso but can occur at both the ortho- and i ra-positions of meta-cmso. It is beheved that increased steric factors and chain rigidity that accompany increasedpara-cmso content modify the polymer solubihty. 

The Tatoray process was originally developed by Toray and is currendy Hcensed by UOP (53—57). A schematic of the process is shown in Figure 4. In this process, toluene or a mixture of toluene and Cg aromatics are reacted to form primarily xylenes and benzene. An equiUbrium distribution of xylenes is produced. As shown in Table 4, the ratio of xylenes to benzene can be adjusted by altering the feed ratio to toluene to aromatics. Trimethylbenzenes are the preferred aromatic compound. 

If the feed, solvent, and extract compositions are specified, and the ratio of solvent to feed is gradually reduced, the number of ideal stages required increases. In economic terms, the effect of reducing the solvent-to-feed ratio is to reduce the operating cost, but the capital cost is increased because of the increased number of stages required. At the minimum solvent-to-feed ratio, the number of ideal stages approaches infinity and the specified separation is impossible at any lower solvent-to-feed ratio. In practice the economically optimum solvent-to-feed ratio is usually 1.5 to 2 times the minimum value. 

Shell process. Universal Oil Pro-ducts sulfolane sulfolane selectivity and capacity insensitive to water content caused by steam-stripping during solvent recov-ery heavy paraffinic countersolvent use 120 rotating-disk contactor, up to 4 m in diameter the high selectivity and capacity of sulfolane leads to low solvent-feed ratios, and thus smaller equip-ment... 

MPa (15—20 atm), 300—400 kg benzene per kg catalyst per h, and a benzene ethylene feed ratio of about 30. ZSM-5 inhibits formation of polyalkjlated benzenes produced with nonshape-selective catalysts. With both ethylene sources, raw material efficiency exceeds 99%, and heat recovery efficiency is high (see Xylenes and ethylbenzene). 

The MTDP process, which is similar to the Tatoray process, produces an equilibrium composition of xylene isomers. A -xylene yield of 24% in the xylene product is formed at 42—48 wt % toluene conversion over the heterogeneous catalyst at 390—495°C, 4.2 MPa (600 psig), 1 2 Hquid hourly space velocity, and 4 H2/hydrocarbon molar feed ratio. A new ZSM-5 catalyst, which has higher activity and stability than the current catalyst, has been reported (93). 

FC and TC = flow and temperature controllers, respectively SP = setpoint S/F = steam/feed ratio x = multiplication of signals and + = sum of signals, (a) Additive (b) multiphcative and (c) combined additive and multiphcative. 

Maximum conversion to trichloroethylene (75% of dichloroethane feed) is achieved at a chlorine to dichloroethane ratio of 1.7 1. Tetrachloroethylene conversion reaches a maximum (86% conversion of dichloroethane) at a feed ratio of 3.0 1 (24). 

Fig. 1. Copolymer composition as a function of monomer feed ratio for various reactivity ratio combiaations, designated I—V and explained ia the text...

Fig. 9. Extractive distillation sequence cost as a function of the feed ratio for the production of anhydrous ethanol from azeotropic ethanol using ethylene glvcol at reflux ratios of A, 1.15 r O, 1.2 r and 1.3 r (39). Point A represents a previously pubhshed design for the same mixture (37).

Because there is no azeotrope, these mixtures could be separated without adding a solvent. This, however, would be a difficult and expensive separation. Thus there is no minimum feed ratio (minimum solvent flow) and the only way to determine the optimal solvent-to-process feed ratio is by determining the sequence cost over a range of feed ratios. The best reflux ratios are again 1.2—1.5 times the minimum. 

FIG. 13-75 Number of theoretical stages versus solvent-to-feed ratio for extractive distillation, a) Close-boiling vinyl acetate-etbyl acetate system with phenol solvent, (h) A2eotropic acetone-methanol system with water solvent. 

The response of solute concentration in the raffinate to the sol-vent-to-feed ratio S /F can be calculated by Eqs. (15-26) and (15-27) for a constant number of transfer units based on the overall raffinate phase N r-... 

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