Stirring speed

The stirring speed and time influence the size of the precipitate s particles, as well as their suspension in solution. 

FIG. 20-38 Newton number as a Function of Reynolds number for a horizontal stirred bead mill, with fluid alone and with various filling fractious of 1-mm glass beads [Weit and Schwedes, Chemical Engineering and Technology, 10(6), 398 04 (1987)]. (N = power input, W d = stirrer disk diameter, m n = stirring speed, 1/s i = liquid viscosity, Pa-s Qj = feed rate, mVs.)... 

The most important feature of o/w suspension polymerization is the formation of an oil droplet suspension of the monomer in the water and the maintenance of the individual droplets throughout the polymerization process. Droplet formation in an oil-in-water mixture is accomplished and controlled by two major factors mechanical stirring and the volume ratio of the monomer phase to water. The stirring speed is a key factor in controlling the size of oil droplets and the final size of the polymers. The stirring speed usually needs to be over... 

An important aspect of nitrating toluene to nitrotoluene is the very low solubility of toluene and nitroioluenes in nitrating mix Is. Therefore the nitration proceeds in a two-phase system and the rate of nitration depends greatly on dispersion, which in turn depends on keeping the two phases efficiently stirred. This is emphasized in Fig 4, which gives the yield of MNT for a 11/64/25% nitric acid/sulfuric acid/water MA and a nitration time of 30 minutes as a function of stirring speed... 

Model predictions are caipared with experimental data In the case of the ternary system acrylonitrlle-styrene-methyl methacrylate. Ihe experimental runs have been performed with the same recipe, but monomer feed composition. A glass, thermostat ted, well mixed reactor, equipped with an anchor stirrer and four baffles, has been used. The reactor operates under nitrogen atmosphere and a standard degassing procedure is performed Just before each reaction. The same operating conditions have been maintained in all runs tenperature = 50°C, pressure = 1 atm, stirring speed = 500 rpm, initiator (KgSgOg) 0. 395 gr, enulsifier (SLS) r 2.0 gr, deionized water = 600 gr, total amount of monomers = 100 gr. 

KLa varies with stirring speed (N) and aeration rate (G) according to... 

The equations used to calculate permeability coefficients depend on the design of the in vitro assay to measure the transport of molecules across membrane barriers. It is important to take into account factors such as pH conditions (e.g., pH gradients), buffer capacity, acceptor sink conditions (physical or chemical), any precipitate of the solute in the donor well, presence of cosolvent in the donor compartment, geometry of the compartments, stirring speeds, filter thickness, porosity, pore size, and tortuosity. 

Determination of UWL Permeabilities using Stirring Speed Dependence... 

Caco-2 assay permeabilities corrected for the UWL usually include Pu determined as a function of the stirring speed (since the cells are not stable over a wide pH range), as in Eq. (7.57) [511-514,552,578]... 

Measurements of Pe in fixed-pH solutions but at various different stirring speeds need to be made. The double-reciprocal analysis, HPe versus 1/v , for Caco-2 permeability measurements in the Transwell (Corning Costar) system produced a linear plot for x- 0.8 [514]. The intercept yields the membrane permeability for the particular pH value in the study the slope determines the k constant. From the analysis of testosterone transport, for the stirring speed of 25 rpm (planar rotating shaker), the thickness of each UWL (assuming symmetric geometry) was calculated to be 465 pm at 150 rpm, haq= 110 pm [514], Karlsson and Artursson [512] found x = 1.0 to best represent their stirring-based analysis of the UWL permeability. 

Recently, nonliving biomass of S. cucullata has been described as a low-cost absorbent of Cr(VI).106 Optimum conditions for the Cr(VI) adsorption by acid-treated S. cucullata were found out using a full factorial design. The Cr(VI) removal efficiency of the adsorbent was found to increase with the increase in time, temperature, adsorbate concentration, and stirring speed, and to decrease with increase in pH and adsorbent dose. The Fourier transform infrared spectroscopy (FT-IR) analysis revealed that in addition to electrostatic force, the adsorption may be due to... 

Flow in stirred vessels was also investigated by Holmes et al. (H5), who simulated mass transfer in a diaphragm diffusion cell stirred by magnetic stirrer bars. This is a good example of a simple model study with a direct practical purpose. A minimum stirring speed in such cells is necessary to avoid appreciable errors in the cell constant. The experiment permits this stirring speed to be related to the solution properties. 

Figure 1 Effect of stirring speed on the rate of hydrogenation of DMIT over AHC-2. 5000 TON each reaction, ee s = 95-97%. Reactions run at 50° and 50 psig.

Response time to >90% new sulfide level 10s (stirring speed 500 rpm)... 

---