Solids suspension mechanism

The overall superficial fluid velocity, mentioned earlier, should be proportional to the settling velocity o the sohds if that were the main mechanism for solid suspension. If this were the case, the requirement for power if the setthng velocity were doubled should be eight times. Experimentally, it is found that the increase in power is more nearly four times, so that some effect of the shear rate in macro-scale turbulence is effec tive in providing uphft and motion in the system. 

Stable solids suspensions in water- The mechanisms involved in keeping solids suspended in water,... 

Szekely and Carr 58 have studied the heat transfer between the walls of a cyclone and a gas-solid suspension, and have shown that the mechanism of heat transfer is quite different from that occurring in a fluidised bed. There is a high rate of heat transfer directly from the wall to the particles, but the transfer direct to the gas is actually reduced. Overall, the heat transfer rate at the walls is slightly greater than that obtained in the absence of the particles. 

Charge transfer occurs when particles collide with each other or with a solid wall. For monodispersed dilute suspensions of gas-solid flows, Cheng and Soo (1970) presented a simple model for the charge transfer in a single scattering collision between two elastic particles. They developed an electrostatic theory based on this mechanism, to illustrate the interrelationship between the charging current on a ball probe and the particle mass flux in a dilute gas-solid suspension. This electrostatic ball probe theory was modified to account for the multiple scattering effect in a dense particle suspension [Zhu and Soo, 1992]. 

In general, at least six mechanisms, which are not independent of each other, contribute to turbulence modulation in gas-solid suspension flows ... 

A 50% w/v solution of sodium hydroxide in water (12.5 ml, 0.32 mol) was added to a mechanically stirred suspension of diphenylacetonitrile (15.0 g,0.08 mol) and dibenzo-18-crown-6 (0.5 g, cat.) in dimethylsulphoxide (12.5 ml). The color rapidly deepened to an orange/brown. R-(-)-l-Dimethylamino-2-chloropropane (30.0 g, 0.095 mol) was added in portions over 30 min, this caused the temperature to rise to 30°C. After the addition was complete the mixture was warmed to 45°-50°C (water bath) and stirred for a further hour. The reaction mixture was then allowed to cool to room temperature and was poured into ice/water (250 ml) and extracted with ethyl acetate (3 times 150 ml). The combined extracts were dried (MgS04) and filtered and evaporated down to -100 ml. The product was extracted into IN HCI (100 ml+50 ml) and this was back washed with ethyl acetate. The aqueous was basified with 2 M sodium hydroxide and extracted into ethyl acetate (3 times 100 ml). The extracts were washed with brine (70 ml), dried (MgS04), and evaporated down to a yellow oil. This was chilled and triturated with cold hexane (50 ml) to give a white solid which was collected by filtration and washed thoroughly with a further portion of cold hexane (100 ml). 14.65 g (33%) of S-(+)-2,2-diphenyl-4-dimethylaminopentanenitrile were obtained, melting point 100°-101°C (recrystallised from hexane). 

A mechanically stirred suspension of crude amino-sulfonamide hydrochloride salt (26.4 g, 73 mmol) in water (70 mL) was heated at 90°-95°C until all of the solid dissolved. To the hot solution was added activated carbon (Darco KB, 0.26 g), and the mixture stirred for 15 min at 90°-95°C. The mixture was filtered hot (85°-90°C) through a well-washed bed of filter aid (SuperCel). The filter cake was washed with boiling water (9 mL). The filtrate and cake wash were combined, and the product allowed to crystalize as well-stirred solution was cooled to 60°C. The mixture was stirred for 1 h at 60°C, or until the product had convened to the thermodynamically more stable hemihydrate crystal form. The mixture was then slowly cooled to 3°C, and then stirred for 1 h at this temperature. The mixture was filtered cold, using the mother liquors to rinse the cake. The product was air-dried, then dried in vacuo (100 mBar, nitrogen sweep, 45°-50°C) to constant weight. Yield 24.2 g (92% yield 59% overall yield from hydroxysulfone) of pure aminosulfonamide hydrochloride salt (dorsolamide) as a white crystalline solid. HPLC 99.9 area % (254 nm), 99.6 wt % vs an external standard, >99% (4S,6S) as the N-TFA derivative. Specific Rotation a589 =-17.1° (c=1.00, H20). MP 238°C. 

Solid-solid Adhesion Solid suspension, adhesion, cohesion, corrosion, passivation, epitaxial growth, wear, friction, diffusion, thin films, delamination, creep, mechanical stability, durability, solid state devices, blend and alloy, charge transfer, nucleation and growth abrasion... 

A solution of 2-bromo-3-dodecylthiophene (34.92 mmol) dissolved in 40 ml of anhydrous THF was slowly added over a period of 20 minutes to a mechanically stirred suspension of magnesium turnings (51.83 mmol) in 10 ml of THF under an inert argon atmosphere. The mixture was stirred at ambient temperature for 2 hours and then at 50°C for 20 minutes before cooling down to ambient temperature. This mixture was added by cannula to 5,5 -dibromo-2,2 -dithiophene (13.88 mmol) and l,3-bis(diphenylphosphino)dichloronickel (II) (0.35 mmol) in 80ml of THF and refluxed for 48 hours. The reaction mixture was then diluted with 200 ml of EtOAc, washed twice with water and 5% HCl, dried with Na2S04, and concentrated. The dark brown syrupy residue was purified by column chromatography on silica gel, and the product was isolated in 55% yield as a yellow crystalline solid, MP = 58.9°C. 

MJ/kWh (10,400 Btu/kWh), mechanical vapor recompression can vaporize 1 kg of water for less than 0.46 MJ (1.0 lb for less than 200 Btu). The Carver-Greenfield process is based on combining mechanical vapor recompression with multiple-effect evaporation to dry high-water-content biomass and other solid suspensions. Many full-scale units have been placed in operation since the first facility was installed in 1961. One unit was used at the Hyperion wastewater treatment plant in Los Angeles from 1987 to early 1995 to dry 40 t/day of biosolids wetcake to 99+% total solids content (Haug, Moore, and Harrison, 1995). The process has since been replaced by rotary steam dryers because it was not possible to reach the design capacity of the unit. 

Pachuca Tanks Air-agitated Pachuca tanks were widely used in mineral processing until the 1960s when the industry concluded that mechanical agitation was more economical and more effective for solids suspension. A description of Pachuca tanks can be found in previous editions of Perry s Handbook. 

Solids suspension is usually carried out in mechanically agitated vessels with or without draft tubes, as shown in Figs. 5 and Dished heads (ASME dished, elliptical, or torispherical heads) are preferred. A single impeller is usually sufficient for off-bottom solids suspension in vessels with dished heads and 7 < 1.3. Dual impellers are recommended for vessels with 13 < H/T < 2.5, which are used for uniform suspension of fast-settling solids. Three or more impellers... 

Choudhury, N.H., W.R. Penney, K. Meyers, and J.B. Fasano (1995). An experimental investigation of solids suspension at high solids loadings in mechanically agitated vessels. AIChE Symp. Ser. 305(91), 131-138. 

Solid inorganic soils, such as dust particles, are removed through a wetting and suspension mechanism. Solid organic soils, such as greases, are broken up and... 

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