Feed composition, viscosity

Flux response to concentration, cross flow or shear rate, pressure, and temperature should be determined for the allowable plant excursions. Fouling must be quantified and cleaning procedures proven. The final design flux should reflect long-range variables such as feed-composition changes, reduction of membrane performance, long-term compaction, new foulants, and viscosity shifts. 

The simulator used was a DISMOL, described previously by Batistella and Maciel (2). All explanations of the equations used, the solution methods, and the routine of solution are described in Batistella and Maciel (5). DISMOL is a simulator that permits changes in feed composition, feed temperaturethe evaporation rate, as well as feed flow rate. The effective rate of surface evaporation is obtained from the kinetic theory of gases. The liquid film thickness is obtained by mass balance and geometry of the evaporator. The temperature in the liquid obeys the Fourier-Kirchhoff equation. The solution of the velocity profile requires knowledge of the viscosity and the liquid film thickness over the evaporator. The solution for the temperature and the concentration profiles requires knowledge of the velocity profiles, which determine the convective heat and mass fluxes. 

Liquid sulfur-dicyclopentadiene (DCP) solutions at 140°C undergo bulk copolymerization where the melt viscosity and surface tension of the solutions increase with time. A general melt viscosity equation rj == tj0 exp(aXH), at constant temperature, has been developed, where tj is the viscosity at time t for an S -DCP feed composition of DCP mole fraction X and rj0 (in viscosity units), a (in time 1), and b (a dimensionless number, -f- ve for X < 0.5 and —ve for X > 0.5) are empirical constants. The structure of the sul-furated products has been analyzed by NMR. Sulfur non-crystallizable copolymeric compositions have been obtained as shown by thermal analysis (DSC). Dodecyl polysulfide is a viscosity suppressor and a plasticizer for the S8-DCP system. 

Figure 11. A plot of the rate of increase of logarithmic viscosity vs. the feed composition in mole fractions of DCP at 140° C...

Figure 12. A double-logarithmic plot of the rate of increase of logarithmic viscosity vs. the feed composition in mole fractions of DCP (----------------------) at 140°C and (---) at 155°C...

A general exponential equation (see Appendix for detailed discussions) of the form tj = rj0 exp (aXbt), at constant temperature, has been developed to predict the viscosity (97, CP) as a function of feed composition (X, mol fraction of DCP) and time (t, hr) rj0, a, and b are empirical constants rj0 is the viscosity at t = 0, a is in units of reciprocal time, and b is dimensionless. The assumptions made here are ... 

C with two feed compositions are shown in Tables I and II. Surface tension has been measured as a function of time, and the viscosity of the solutions are shown along with surface tension. The data clearly show that as the viscosity increases with time, surface tension increases, and the higher the rate of increase of viscosity, the higher the rate of increase of surface tension. It has been shown for silicone polymers that as the viscosity increases from an increase in molecular weight, the surface tension increases (27). A step growth copolymerization mechanism, as mentioned earlier for the sulfur-DCP solutions, will have an increase of molecular weight with time, and the surface tension behavior appears to support this mechanism. 

As discussed in Section 7.3, the optimization in chromatography proceeds as follows. From the discovery experiments the mobile-phase composition, particle size (apparent or nominal), the thermodynamic parameters and the Knox parameters are known. From the mobile-phase composition, the feed composition (simplify to a binary mixture, one impurity and the product), the viscosity can be estimated from data in the literature. The void fraction can be measured from the retention of unretained component (Eq. (7.24)), or estimated based on vendor information. The packing density is typically known by... 

For fractionators the relative volatility and viscosity of the key components are taken at the average of the the top and bottom tray temperature and at the feed composition. For absorbers, separating hydrocarbons, the volatility is taken as ten times K, for the key component... 

The inherent viscosity of the DHA-NVP copolymer solutions varied with the feed composition (see Tables II and IV) the value was minimum for 80 mole % DHA in the monomer feed. Similar behavior, i.e. decrease in molecular weight with increase in DHA content in feed, was observed for the DHA-4VP systems. This is further evidence of DHA participation in lowering molecular weight by increased monomer-induced chain transfer reactions. 

According to the model, flux is directly proportional to the applied pressure and inversely proportional to the viscosity. For Newtonian fluids, viscosity is primarily controlled by two factors solids concentration (or feed composition) and temperature. Thus, increasing the temperature or increasing the pressure should increase the flux. This happens only under low pressure, low feed concentration, and high feed velocity. When the process deviates from any... 

In facilitated transport of metal ions through LM, the metal ions are transported through the membrane against their own concentration gradient, termed as the uphill transport. The driving force in such processes is provided by the chemical potential difference of the species other than the diffusing ones on either side of the membrane. The permeability of the transported species is decided by the parameters such as membrane thickness, pore structure, aqueous diffusion coefficient of the species, aqueous diffusion layer thickness, and distribution and diffusion coefficients of the transported species in the LM phase. The diffusion of the species in the carrier solvent depends on the membrane characteristics (viz., porosity and tortuosity) and viscosity of the solvent, while the aqueous diffusion of the metal ions depends upon the flow rate and diffusivity of metal species in the aqueous phase. On the other hand, the overall transport rates of the species can be controlled through various parameters such as feed composition, carrier concentration, and receiver phase composition. 

Polymer viscosity variations may be caused by changes in either the raw material or the feed composition. Additionally, we can see viscosity changes when there are variations in hardware temperature, such as may occur with an unstable temperature control circuit. 

Figure 8. Effect of feed composition on zero-shear intrinsic viscosity in 1.5% NaCl of Poly(l-amidoethylene-co-(l-(sodium 2-methylprop-2N-yl-l-sulfonate)amidoethylene)) ( ) and poly-((1-amidoethylene) -CO-(1-methyl-1-(sodium l-oxo-2-oxybutyl-4-sulfonate)) ethylene)) (A) copolymers at high conversion.

Feed stream characteristics (i.e., volumetric flow rate, temperature, pressure, humidity, composition, viscosity, density, reactivity, combustibility, corrosivity, toxicity, etc.)... 

An additional difficulty in the control of polymer properties is that in some cases the control problem is multivariable, in the sense that there are interactions between the molecular weight and composition loops and therefore when a manipulated variable is chosen to control molecular weight it may also affect composition. It is important to use process knowledge to validate the selection of manipulated variables. For example, for the polymerization reactor shown in Figure 12.33, process simulations showed that one way to decouple polymer quality control is to take advantage of the fact that polymer composition is naturally very sensitive to changes in reactor feed composition but inherent viscosity is relatively insensitive... 

Finally, it was investigated whether the atomization gas pressure influences the oil drop breakup. It would be expected that lower atomization gas pressure leads to lower stresses on the oil drops. In Fig. 21.49, the influence of the atomization gas pressure on the oil drop breakup for a viscosity ratio of 0.93 is displayed. Indeed, lower oil drop sizes could be achieved at higher gas pressure, meaning that at a lower pressure, a higher ALR is necessary to achieve identical results. It should be noted that the effect of atomization gas pressure is small compared to, e.g., that of the emulsion viscosity. Nonetheless, the gas pressure is a convenient process parameter in effervescent atomization, as varying the pressure is simple and inexpensive in comparison to modifying, e.g., the feed composition. Depending... 

Example 8.1.10 Consider the benzene-toulene distillation from Example 8.1.8. Calculate the overall efficiency using the correlations by Doherty and Malone (2001), Seader and Henley (1998) and Wankat (2007). You are given the following information feed mixture (50-50 benzene-toluene) viscosity, 0.278 cp separation factor, Obenzene-toiuene = 2.5 near the feed composition. 

Lube oil extraction plants often use phenol as solvent. Phenol is used because of its solvent power with a wide range of feed stocks and its ease of recovery. Phenol preferentially dissolves aromatic-type hydrocarbons from the feed stock and improves its oxidation stability and to some extent its color. Phenol extraction can be used over the entire viscosity range of lube distillates and deasphalted oils. The phenol solvent extraction separation is primarily by molecular type or composition. In order to accomplish a separation by solvent extraction, it is necessary that two liquid phases be present. In phenol solvent extraction of lubricating oils these two phases are an oil-rich phase and a phenol-rich phase. Tne oil-rich phase or raffinate solution consists of the "treated" oil from which undesirable naphthenic and aromatic components have been removed plus some dissolved phenol. The phenol-rich phase or extract solution consists mainly of the bulk of the phenol plus the undesirable components removed from the oil feed. The oil materials remaining... 

The composition of the feed to a debutaniser is given below. Make a preliminary design for a column to recover 98 per cent of the n-butane overhead and 95 per cent of the isopentane from the column base. The column will operate at 14 bar and the feed will be at its boiling point. Use the short-cut methods and follow the procedure set out below. Use the De Priester charts to determine the relative volatility. The liquid viscosity can be estimated using the data given in Appendix D. 

During operation, the owner/operator of an incinerator must conduct sufficient waste analyses to verify that the waste feed is within the physical and chemical composition limits specified in the permit. This analysis may include a determination of a waste s heat value, viscosity, and content of hazardous constituents, including POHCs. Waste analysis also comprises part of the trial burn permit application. U.S. EPA stresses the importance of proper waste analysis to ensure compliance with emission limits. 

The relative volatility between the key components is 1.57 and the viscosity of the feed is 0.1 mN-s-ur2. The physical properties for the distillate and bottoms compositions are given in Table 9.7. 

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