Mixing purpose

This type unit [29] is used for a combination of pumping and mixing purposes. The unit has a closed disk on the top side. The feed flow into the unit comes from directly below the rotating impeller. The performance is dependent on the size of the unit and the physical location with respect to the distance up from the bottom of the vessel. As this clearance increases, the head decreases for constant flow and increases the pow er requirement. 

The entropy of a system can be interpreted in various ways. For mixing purposes, statistical mechanics provides the best conceptual under-... 

There are various purposes of using a stirred vessel, and the required mixing effect depends on the purpose. For any mixing purpose, rapid and homogeneous dispersion is required. In a stirred vessel, forced convection by the rotation of an impeller occurs, that is, each element of the fluid has an individual velocity finally, turbulent flow based on the shear stress accelerates the mixing. Therefore, the shape of the impeller has a very important effect on the mixing state. However, there are various types of impeller shapes, and traditional impellers are classified into three types ... 

From his detailed analysis, Cheng concludes that it cannot always be said that extensional flows are more effective for mixing purposes than simple shear flow. Care is needed, particularly for flows involving non-Newtonian liquids. The position is rather complicated and Cheng states that at small strains, extensional flows are on the whole more effective than simple shear, but only marginally so, at sufficiently large strains extensional flows are very much more effective. However, at some intermediate strains simple shear may be more effective particularly when the fluid is non-Newtonian. 

The entry point of the second phase can have a pronounced effect. For rate-of-mixing purposes and uniformity of drop-size distribution, it is claimed that entry close to the impeller tip is advantageous. This effect becomes particularly important where the temperatures of the two liquids are not equal. 

Bubble columns (BCs) belong to a family of pneumatic bioreactors. These bioreactors do not have any mechanical or otherwise moving parts. Compressed air, which is used for mixing purposes, is injected into the base of a cylindrical vessel. This approach provides a cheap and simple method to contact and mix different phases (Diaz et al., 2008). The liquid phase is delivered in batch or continuous mode, which can be either countercurrent or cocurrent. The batch BC is the more common form, but the cocurrent version, shown in Figure 7.1, is also encountered. Countercurrent liquid flow is rarely used in industry as it provides minor, if any, advantages and multiple complications (Deckwer, 1992), with separation by evaporation being one of the few exceptions (Ribeiro Jr. and Lage, 2005). 

Water storage and treatment facilities Generally treated water is required for both steam generation and mixing purpose Boiler may come in dangerand may affect the quality of product Keep a tank filled with treated watm always ready for the plant... 

Recall from Section 12.3.1 that a flow number of 0.5 indicates shear flow while a flow number of 1.0 indicates pure elongational flow. For mixing purposes, a flow number near 1.0 is preferred. Figures 12.10(a-c) illustrate that the co-rotating, double-flighted twin screw produces a flow that is mainly shear to elongation. 

Figure B2.5.1 schematically illustrates a typical flow-tube set-up. In gas-phase studies, it serves mainly two purposes. On the one hand it allows highly reactive shortlived reactant species, such as radicals or atoms, to be prepared at well-defined concentrations in an inert buffer gas. On the other hand, the flow replaces the time dependence, t, of a reaction by the dependence on the distance v from the point where the reactants are mixed by the simple transfomiation with the flow velocity vy...

Place 0 5 ml. of acetone, 20 ml. of 10% aqueous potassium iodide solution and 8 ml. of 10% aqueous sodium hydroxide solution in a 50 ml. conical flask, and then add 20 ml. of a freshly prepared molar solution of sodium hypochlorite. Well mix the contents of the flask, when the yellow iodoform will begin to separate almost immediately allow the mixture to stand at room temperature for 10 minutes, and then filter at the pump, wash with cold w ater, and drain thoroughly. Yield of Crude material, 1 4 g. Recrystallise the crude iodoform from methylated spirit. For this purpose, place the crude material in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, add a small quantity of methylated spirit, and heat to boiling on a water-bath then add more methylated spirit cautiously down the condenser until all the iodoform has dissolved. Filter the hot solution through a fluted filter-paper directly into a small beaker or conical flask, and then cool in ice-water. The iodoform rapidly crystallises. Filter at the pump, drain thoroughly and dry. 

Since formaldehyde solutions almost invariably contain formic acid, and amino-acids themselves are seldom exactly neutral, it is very important that both the formaldehyde solution and the glycine solution should before mixing be brought to the same pH (see footnote, p. 509), and for this purpose each solution is first madejWl alkaline to phenolphthalein by means of dilute sodium hydroxide solution. This preliminary neutralisation must not be confused with... 

What is the purpose of waiting 10 s after mixing the contents of the electrochemical cell before recording the voltammogram ... 

A schematic illustration of a typical inlet apparatus for separating volatile hydrides from the analyte solution, in which they are generated upon reduction with sodium tetrahydroborate. When the mixed analyte solution containing volatile hydrides enters the main part of the gas/liquid separator, the volatiles are released and mix with argon sweep and makeup gas, with which they are transported to the center of the plasma. The unwanted analyte solution drains from the end of the gas/liquid separator. The actual construction details of these gas/liquid separators can vary considerably, but all serve the same purpose. In some of them, there can be an intermediate stage for removal of air and hydrogen from the hydrides before the latter are sent to the plasma. 

Emulsion Process. The emulsion polymerization process utilizes water as a continuous phase with the reactants suspended as microscopic particles. This low viscosity system allows facile mixing and heat transfer for control purposes. An emulsifier is generally employed to stabilize the water insoluble monomers and other reactants, and to prevent reactor fouling. With SAN the system is composed of water, monomers, chain-transfer agents for molecular weight control, emulsifiers, and initiators. Both batch and semibatch processes are employed. Copolymerization is normally carried out at 60 to 100°C to conversions of - 97%. Lower temperature polymerization can be achieved with redox-initiator systems (51). 

---