Power feed profiles

Normalized plots of several power feed profiles are shown in Figure 2. For the special case where x = 1,(Wi=W2,R]=2R2), the feed profile is linear with time. Curvature is introduced by suitable changes of the initial monomer weights in the two tanks when x > 1, the curve is concave to the abscissa when x < 1, the curve is convex. With proper mixing in the near tank, these feed profiles can be verified experimentally. 

In Figure 9, the polymer was prepared via a linear power feed profile in which the near tank contained only ethyl acrylate and the far tank contained only styrene. In Figure 10, the polymer was prepared with the tanks reversed the monomer feed began with styrene and ended with ethyl acrylate. In both cases, the transition regions are much broader than those observed with the uniform feed or staged feed examples. 

The toughness parameter q is defined by Equation 13. The effect of nonuniform polymerization is shown for a 50/50 copolymer in which the power feed profile involved a decreasing ethyl acrylate concentration (0 1), with x = 1 (linear). (( ) power feed, q = 0.19)... 

Figure 4. The 13C NMR spectrum of a 50/50—styrene/ethyl acrylate copolymer prepared using a linear power feed profile with ethyl acrylate increasing 0—> 1.0, and styrene decreasing 1.0 —> 0 with time...

Figure 5. Linear power feed profile for a 50/50—styrene/ethyl acrylate copolymer in which ethyl acrylate decreases 1.0 -> 0 and styrene increases 0 -> 1.0 with...

Figure 9. Correlation of calculated and measured triad fractions for a model 50/50—styrene/ethyl acrylate copolymer prepared with a linear power feed profile in which ethyl acrylate increases 0—> 1.0 and styrene decreases 1.0 — 0 with time (n = 0.16 r2 = 0.82 (A) EA-EA-EA EA-EA-STY = STY-EA-EA ...

Figure 4. Power feed profiles of a single monomer in the feed stream entering the reactor as a function of time. (Bassett and Hoy, Ref. 22)...

Figure 7. Development of triad fractions as observed by carbon-13 NMR for a model 25/75-styrene/ethyl acrylate latex prepared by a linear power feed profile. (Johnston, Bassett, MacRury, Ref. 24)...

The addition of a third monomer tank to the basic power-feed arrangement expands the possible feed profiles available for investigation. As illustrated in Figure 3, one such arrangement involves a stirred middle tank which receives a monomer mix from the far tank and pumps a varying mixture to the near tank. The arrangement is essentially a power feed on top of a power feed and can be analyzed in the same manner as carried out with the two tank systems, except that C2, the concentration of monomer A in the second (middle) tank is not constant but is given by... 

Whereas the two-tank arrangement permits monomer feed profiles which vary smoothly in one direction, the three-tank scheme leads to inflections and concentration reversals as illustrated in Figure 4. Such reversals are useful in preparing hard-soft-hard, hydrophilic-hydrophobic-hydrophilic polymer variations and the like. In addition, three tank power feed has been useful as a means of calculating monomer inventory in copolymerization experiments (4). 

The power feed example utilized a feed profile with increasing butyl acrylate, 0 — 0.65, decreasing methyl methacrylate concentration, 1.0— 0.35, and x = 1.3. 

Figure 6. Stress relaxation comparison of two emulsion polymers having the same overall composition. The power feed example utilized a feed profile with increasing butyl acrylate (0-> 0.65), decreasing methyl methacrylate (1.0 -> 0.35), and x = 1.3. The time axis has been shifted to a reference temperature of 26°C.

Figure 12. Monomer feed profile using a linear power feed. Overall polymer composition 47.5/47.5/5—styrene/ethyl acrylate/methacrylic acid.

Figure 13. The effect of nonuniform polymerization on the expansion behavior of carboxylic emulsion polymers. The power feed example was prepared using the monomer feed profile illustrated in Figure 12 ((%) uniform feed power feed).

In order to design experiments to test the influence of process variables on polymer infrastructure, a simple but general process design is needed. For these studies a new sequential feed polymerization process called "power-feed" was chosen (7 -8, 9). The advantage of this technique is that almost any conventional monomer feed profile can be simulated and described by an equation containing only three independent variables. In addition, a number of novel monomer composition profiles can also be constructed with this approach. The composition of the monomer feed to the reactor can be described by ... 

The power exponent, x determines what the monomer feed profile will look like as a function of of. Some examples of more common feed profiles are shown in Figure 1. If the polymerization is carried out under monomer-starved conditions, the composition of the polymer being formed at any instant is the same as the feed composition, C-. Therefore, the cumulative polymer composition at any timeef may be obtained from ... 

C nuclear magnetic resonance spectroscopy can be employed to study changes in copolymer sequence distribution brought about by differences in monomer feed profiles. Sequence distributions characteristic of conventional, staged, and power-feed copolymers are easily distinguishable in a model system of the type described here. 

Adjustments were made in several parameters in order to increase the fresh feed. The exit temperature from the first reactor was reduced from 277 to 245°C. The exit temperature from the heater HX3 was reduced from 150 to 110°C. These two changes increased the fresh feed from 4990 to 7415 kmol/h. The feed was further increased to 9288 kmol/h by increasing the power to the recycle compressor K3 from 1884 to 4000 kW. The recycle flowrate increased from 34,880 to 46,380 kmol/h. Figure 6.106 gives flowsheet conditions with these adjusted parameters. This flowsheet is used for exploring dynamic controllability. Figure 6.107 gives the temperature profiles in the two reactors under these adjusted conditions. 

Roughly 5000 full load hours per year of the fuel-cell heating appliances could cover the electrical demand of a household. Unfortunately, the load profiles of electrical demand and production by the fuel-cell heating appliances are different. So there are times the fuel-cell heating appliance could not cover the electrical demand of the household. In this case the needed peak load will be covered by the power grid. If the fuel-cell heating produces more electrical power than needed by the household the excess electrical power will feed into the power grid. 

Most servo feeds manufactured today utilize a trapezoidal move profile with its four distinct jerk points that can cause slippage but some are also available with controls that can execute s-curve move profiles. Systems that are electronically synchronized to press rotation are available as well. These units require a special controls package and feedback device, either a resolver or encoder, that are attached to the press crank to track press rotation. Their top speeds are still limited by the available drive power as opposed to press-driven feeds which can run as fast as the press and tooling are capable of handling. 

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