Dynamic feed

Figure 9. Comparative dynamic feed and liquid phage naphthalene in a continuous stirred soil slurry treatment reactor for contaminated Manufactured Gas Plant (MGP) soils.

Figure 10. Dynamic feed flow-rate profile in response to step change in monomer ratio in a controlled semi-batch reactor.

Serafim, L. S., Lemos, P. C., Oliveira, R-, Reis, M. A. M. (2004). Optimization of polyhydrox-ybutyrate production by mixed cultures submitted to aerobic dynamic feeding conditions. Biotechnology and Bioengineering, 87(1), 145-160. 

Gobi and Vadivelu [29] recently reported aerobic dynamic feeding as a strategy for the accumnlation of PHA. This is the first report... 

Reilly, J.F., Doyle, M., Kazmer, D., An assessment of dynamic feed control in modular tooling, /. Inject. Mold. Technol. 5 (1) (2001) 49-59. 

FIGURE 1.52 Melt pressure control system ( Dynamic Feed ) using a conical needle with position control... 

Dynamic feed-forward attempts to manage the Z2 goal by adding a filter to cancel disturbances to the desired Z2 = K02 resulting from changes in stack ciurent. Both of these methods are open loop feed-forward controllers hence, they are not very robust with respect to external disturbances, system parameter variations, or modeling errors. They are not guaranteed to eliminate any steady-state error of the y terms from desired values. For this feedback, controls are used where measurable values y are fed back to the... 

The added PI feedback controller to the dynamic feed-forward control gives better results. The controller input u for this is given as... 

The first term is an abstract representation of the dynamic feed-forward controller while the remaining terms are for PI control. The air mass flow rate is the output flow rate from the compressor. This controller provides air stoichiometry recovery that is twice as fast as the static feed-forward controller when I is changed in step increments. However, this controller suffers from a low bandwidth so it will not be able to reject rapid changes in I, the system disturbances. 

Dynamic Feed-Forward Neural Network (DFNN)... 

Dyna.micPerforma.nce, Most models do not attempt to separate the equiUbrium behavior from the mass-transfer behavior. Rather they treat adsorption as one dynamic process with an overall dynamic response of the adsorbent bed to the feed stream. Although numerical solutions can be attempted for the rigorous partial differential equations, simplifying assumptions are often made to yield more manageable calculating techniques. 

The American version of the dynamic filter, known as the Artisan continuous filter (Fig. 30), uses such nonfiltering rotors in the form of turbine-type elements. The cylindrical vessel is divided into a series of disk-type compartments, each housing one rotor, and the stationary surfaces are covered with filter cloth. The feed is pumped in at one end of the vessel, forced to pass through the compartments in series, and discharged as a thick paste at the other end. At low rotor speeds the cake thickness is controlled by the clearance between the scraper and the filter medium on the stationary plate, while at higher speeds part of the cake is swept away and only a thin layer remains and acts as the actual medium. 

Both control schemes react in a similar manner to disturbances in process fluid feed rate, feed temperature, feed composition, fuel gas heating value, etc. In fact, if the secondary controller is not properly tuned, the cascade control strategy can actually worsen control performance. Therefore, the key to an effective cascade control strategy is the proper selection of the secondary controlled variable considering the source and impact of particular disturbances and the associated process dynamics. 

Stea.dy-Sta.teFeedforwa.rd, The simplest form of feedforward (FF) control utilizes a steady-state energy or mass balance to determine the appropriate manipulated variable adjustment. This form of feedforward control does not account for the process dynamics of the disturbance or manipulated variables on the controlled variable. Consider the steam heater shown ia Figure 15. If a steady-state feedforward control is designed to compensate for feed rate disturbances, then a steady-state energy balance around the heater yields ... 

Pretreatment of membranes with dynamically formed polarization layers and enzyme precoats have been effective (12,13,39). Pretreatment with synthetic permeates prevents startup instabiUty with some feed dispersions. 

Another type of membrane is the dynamic membrane, formed by dynamically coating a selective membrane layer on a finely porous support. Advantages for these membranes are high water flux, generation and regeneration in situ abiUty to withstand elevated temperatures and corrosive feeds, and relatively low capital and operating costs. Several membrane materials are available, but most of the work has been done with composites of hydrous zirconium oxide and poly(acryhc acid) on porous stainless steel or ceramic tubes. 

A cocurrent evaporator train with its controls is illustrated in Fig. 8-54. The control system applies equally well to countercurrent or mixed-feed evaporators, the princip difference being the tuning of the dynamic compensator/(t), which must be done in the field to minimize the short-term effects of changes in feed flow on product quality. Solid concentration in the product is usually measured as density feedback trim is applied by the AC adjusting slope m of the density function, which is the only term related to x. This recahbrates the system whenever x must move to a new set point. 

FIG. 13-109a Resp onses after a 30 percent increase in the feed flow rate for the mnlticomponent-dynamic-distillation example of Fig. 13-100. Profiles of liquid mole fractions at several times. 

If the feed rate is decreased, the trends of curves in Fig. 13-109 are reversed. The disturbance of other variables such as feed composition, boil-up ratio, and recycle of water-rich effluent from the decanter produces similar shifts in the steep concentration fronts, indicating that azeotropic towers are among the most sensitive separation operations, for which dynamic studies are essential if reli-... 

Cyclone Separators Finer feed sohds, from 0.04 to 0.0005 m (1.5 in to 28 mesh), may be treated in dynamic separators of the Dutch State Mines cyclone type (Fig. 19-36). In cyclone separators, the medium and the feed enter the separator together tangentially at the feed inlet (1) the short cyhndiical section (2) carries the central vortex finder (3), which prevents short circuiting within the cyclone. Separation is made in the cone-shaped part of the cyclone (4) by the action of centrifugal and centripetal forces. The heavier portion of the feed leaves the cyclone at the apex opening (5), and the hghter portion leaves at the overflow top orifice (6). 

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