Feed stripping

The flow controllers are often used to set desired flows for the fresh feed, stripping steam, and dispersion steam. Each flow controller usually has three modes of control manual, auto, and cascade. In manual mode, the operator manually opens or closes a valve to the desired percent opening. In auto mode, the operator enters the desired flow rate as a set-point. In cascade mode, the controller set-point is an input from another controller. 

It is normal practice to have screws double flighted under the feed section. This is mainly because a single flight, working in conjunction with the feed roll, does not effectively pull in the feed strip in a consistent manner. In some extruder constructions the double flight continues down the length of... 

The main problem with a feed controlled condition is that throughput is determined entirely by what the feed end manages to pull in and this is very sensitive to the conditions in the feed area. For this reason it is better to keep the machine running full so that the conveying characteristics of the screw determine output rather than the combined characteristics of screw, feed roll, feed opening and feed strip. The compression designed into a screw should therefore be sufficient to achieve complete filling at the lowest likely head pressure. 

Element % in raffinate % in actinide strip % in solvent DF feed/strip... 

Urea 100 000 tonnes Reaction of ammonia and carbon (metric) dioxide at elevated temperature and pressure, using total-recycle process and C02-feed stripping. ... 

Process Feed/Strip Pore size Origin of Selectivity Pressure Gradient Operation C/) CO... 

Of course, during the transport process in the closed HLM system, the distribution ratio will change in accordance with changing feed and strip phase conditions (acidities, titanium concentration, etc.). At Kc = 1(Lf = Fr), concentration of titanium (IV) in the carrier solution should be [T1]r r (the system at equilibrium). Therefore, Lr may be denoted as an irreversible coefficient of the HLM for both, closed and open [78] systems (flowing feed, strip streams, buffered acidities, etc.). Kc is an uphill pumping border of the HLM system. 

FIGURE 13.8 Scheme of a rotating film contactor (1) body (2) stage wall (3) feed/stripping solution separating walls (4) rotating discs (5) common shaft. (From Zhivkova, S., Dimitrov, K., Kyuchoukov, G., and Boyadzhiev, L., Sep. Purif. TechnoL, 37, 9, 2004. With permission.)... 

The microporous membrane films (see Table 13.3) and one mesh spacers were spirally wound around acrylic resin pipes through which the feed, strip, and organic LM solutions were supplied to the module [34,36]. The outer surface and the top and bottom ends of the module were sealed with an adhesive. 

Metal Ion Carrier Feed Strip Cominents References... 

Although ELM technique is quite efficient essentially due to the thinness of the membrane, large-scale application of this technique is limited in view of the difficulties encountered in the demulsification step needed for the recovery of the trapped metal ion. On the other hand, promise of the SLM technique has been demonstrated in the lab scale experiments. Large-scale applications of SLM require additional work in the area of stability/reusability of the membranes. Apart from the selective extraction, there is a need to develop the membranes that are compatible with the diluent/solvent mixture with respect to physical properties such as surface tension and viscosity. In addition, chemical/radiation environment of the feed/strip solution to which these membranes are subjected over long duration is an area of particular concern. Additional stability can be obtained by developing chemically grafted membranes. 

FIGURE 39.8 (a) Concentration of Au(CN)2 in the feed, strip, and organic phase as a function of time in recycle mode, (h) % Transport of... 

This equation assumes that Ak < 1 and the fraction of liquid feed stripped is small. 

It is just as important to maintain a good control of the bottom liquid level in columns where the bottom feed, stripping steam, or reboiler return nozzle enters through a submerged sparger (Fig. 4.3a). Here the liquid level serves as a desuperheater, and its loss may overheat the column or its internals. One incident was reported (440) where plastic packings melted because this level was lost. 

As can be seen from Equation (9.5), in this case, the middle section had a significantly greater influence on the reboiler duty than did the top section, followed by the feed stripping location and the side product location. The quality of the polynomial model was expressed by the coefficient of determination, that is, R. Based on the analysis results from MINITAB, the model showed a high value of 0.93. The value of R is close to 1.0, which indicates a strong correlation between the simulated and predicted values. The relationship between the independent variables and the response is well explained by the regression model. 

Using this RSM model, the minimum reboiler duty was observed at the number of 1,40,1 and 1 tray in the top, middle, side product, and feed stripping sections, respectively, and was predicted to be 15.02 MW, which is equivalent to 25.83% in energy savings (Figure 9.13). Fy and Fl were then optimized to minimize the reboiler duty, whilst maintaining sufficient product purity and recovery. 

Carrier Membrane configuration Nature of feed Strip composition... 

High separation factors Higher flux compared to solid membranes Very high selectivity Uphill concentration and separation Possibility to use expensive extractants Minimization of chemical additives use High feed/strip volume ratios Ability to operate on very dilute solutions High flexibility and easy scale up Low capital and operating costs BLM small membrane surface area per unit volume ELM low emulsion stability SLM low system stability... 

Liquid membrane (LM) transport is a novel separation technique whose potential for application in effluent treatment in the nuclear industry is being explored (7). LM transport offers several advantages over other separation techniques, e.g., lower capital cost and space requirements, low energy consumption, and low solvent inventory which allows the use of expensive carrier molecules. High feed/strip solution volume ratios, the possibility of utilizing feed solutions which contain suspended solids, and high separation factors are other merits of the LM transport method. A prime requirement for a successful LM system is the selection of a selective and efficient carrier for the species to be separated. 

After mixing the rubber compound, it is strained to remove impurities and converted into either a feeding strip for an extruder or a calendered sheet for direct application. 

Number of Theoretical Stages = 5 Ethane remaining in bottoms = 10% of Ethane in feed Stripping factor =1.2... 

One could use the liquid inunobilized in the pores for separation of liquid mixtures as well, provided the feed liquid and the permeate (strip) liquid are immiscible with the liquid membrane in the pores (Figure 8.1.49(b)). Such membranes are called supported liquid membranes (SLMs). However, at the pore mouths, the two immiscible phases contact each other. The liquid membrane phase has some solubility, however small, in the feed/strip liquid phase. Therefore the life of the liquid membrane is limited (see Kowali and Sirkar (2003) for a brief review), and periodically it needs to be regenerated (Yang and Kocher-ginsky, 2006). The liquid membrane is most likely to have extractants used with the emulsion liquid membranes or solvent extraction in the case of chemically complexing extractants. 

---