Lamella settling

The lamellar thickening proceeds through many metastable states, each metastable state corresponding to a particular number of folds per chain, as illustrated in Fig. 8. In the original simulations of [22], Kg was monitored. Rg is actually very close to the lamellar thickness due to the asymmetric shape of the lamella. The number of folds indicated in Fig. 8 were identified by inspection of the coordinates of the united atoms. This quantization of the number of folds has been observed in experiments [50], as already mentioned. The process by which a state with p folds changes into a state with p - 1 folds is highly cooperative. The precursor lives in a quiescent state for a substantial time and suddenly it converts into the next state. By a succession of such processes, crystals thicken. If the simulation is run for a reasonably long time, the lamella settles down to the equilibrium number of folds per chain. 

Tilted-Plate Clarifiers Lamella or tilted-plate separators have achieved increased use for clarification. They contain a multiplicity of plates inchned at 45 to 60° from the horizontal. Various feed methods are employed so that the influent passes into each inchned channel at about one-third of the vertical height from the bottom. This results in the solids having to settle only a short distance in each channel before sliding down the base to the collection zone beneath the plates. The clarified liquid passes in the opposite direction beneath the ceiling of each channel to the overflow connection. 

Lamella settlers are gravity settlers that use a large number of inclined flat plates, closely packed, so that the distance between the plates is small. The gravitational action makes the cells move in the direction of the lower surface of the individual separating space between two plates. Once settled, the particles slide down in a layer towards the plate periphery and then into the sludge hopper. For the same required sedimentation area, lamella settlers are much more compact than vertical ones. Theoretically, their total sedimentation area is the sum of the horizontally projected areas of all plates. In practice, however, only 50% of this total area is effective [137]. The main problem with inclined settlers is that the cells tend to adhere to the plates. Special coating of the plate surface and vibration of the whole lamella pack may alleviate this problem. 

Thompson and Wilson [78] operated a 21-L air-lift perfusion reactor coupled to an external lamella settler. The sedimentation device bearing an angle of inclination of 30° to the vertical was maintained at 37°C. They found a reasonable agreement between the theoretical and experimental values of breakthrough for viable and nonviable cells in the harvest stream. As expected (see Eq. 8), the maximum perfusion rates increased with an increasing settling area. 

A process for phase separation based on density differences. A commercial lamella settler for suspensions or emulsions comprises a stack of parallel plates spaced apart from each other and inclined from the horizontal. The space between each set of plates forms a separate settling zone. The feed is pumped into these spaces, at a point near the longitudinal middle of the plates. The less dense phases rise to the underside of the upper plates... 

Inclined plate clarifiers, also known as Lamella clarifiers, use several inclined plates (or sometimes tubes) to maximize the settling area for a given floor area (Lamella is a registered trademark of Parkson Corporation, Ft. Lauderdale, FL). Figure 8.5 shows a diagram of an inclined-plate clarifier. 

The s> stem receives effluent horn the customers existing bag filter system, w hich comprises of a lamella separator, from w heie settled solids drop into bags. Overflow ing settled waste w ater then flows into a dedicated feed buffer tank w heie it is pressure boosted and Fibra filtered before passing through into either of tw o pH batch reactor tanks, operating consecutively. Tlie filtration cycle is ten minutes of filtration foUow ed by ten seconds of air ei haiKed toiw ard flush, to w ash the collected fine solids back... 

Washing of effluent treatment units like lamella clarifiers, tube settlers, settling tanks, filter press ... 

If A is in the range lo -io and in the range 0-10, then the Nakanmra-Kuroda equation can be e ected to predict adequately file settling rate for both batdi and continuous lamella separators provided steady state condifions can be maintained and separator dimensions chosen so that flow instabilities are avoided. 

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