Screens shaking

Mechanical Picking. Many mechanical picking devices employ differences in physical picking dimensions of coal and impurities as a means of separation. Bituminous coal fractures into rough cubes, whereas slate and shale normally fracture as thin slabs. A slot-type flat picker can be installed on shaker screens, shaking conveyors, and chutes. 

Fig. 4. Malt mill with six rollers and shaking screens (1 = flour 2 = husks 3 = flue grits and, 4 = coarse grain).

Shaking screens, such as the mechanical-conveyor type made by Syntron Co., may be used for both screening and conveying. 

Once methanol-using organisms had been isolated they were screened in small-volume shake-flask cultures to determine their ability to grow in methanol-minimal-medium (such as Medium B described in the previous section) to produce high yields at high growth rates. Optimum growth temperatures and pHs were also determined. 

Figure 9. Procedure for the preparation of the test electrode for aqueous electrolytes (9 mol L 1 KOH or ZnCl2 solution). (1) the sample is mixed by shaking in a plastic container 20 mm (diam.) x 40 mm (height) (2) the mixture is made into a thin film by grinding with a pestle in a ceramic mortar (3) the metal screen is prepared (4) the three layers (A, B, C) are pressed between the steel blocks.

The sieving operation starts by mounting the sieves in a nest, the coarsest at the top. The sample is placed on the top screen, and the screens are shaken for several minutes. It is generally impossible to screen a sample completely the longer one shakes the screens, the more material comes thru, although to a continu-... 

For powders which may be classified dangerous, such as finely divided Ti and Zr and mixts containing these powders, the shaking machine should be grounded and wherever. possible the operation carried out behind a suitable barricade by remote control. Operators should observe all safety precautions, including the use of proper clothing, and a liq antistatic agent should be used to coat the screens and frames. 

It was concluded that approximately three minutes sieving time was adequate with the air-jet sieve even with waxlike materials such as cadmium stearate whereas, 20 minutes or longer was required for vibrating or shaking screens. The data presented (Refs 19 35) for AP by the Alpine, Tyler Ro-Tap, and Micromerograph agree remarkably well... 

Whereas roller bottles and shake flasks are used for screening tests or for the cultivation of precultures, on production scale mainly stirred tanks, bubble columns, and in a few cases, also loop reactors are used (see Table 5). The stress in these reactors is therefore also of special significance and should be given particular consideration. 

Shaker tube reactors are commonly used for the evaluation of catalysts at elevated pressure. The liquid reactant and powdered catalyst are introduced into a metal or glass ampoule, which is sealed and pressurized to a predetermined level with the gaseous reactant. The ampoule is immersed into a thermostatted liquid and maintained at this temperature for a certain period of time while shaking. Then the reactor is opened and the reaction mixture analysed. Ampoules of ca. 10-100 cm are typically used. The usefulness of data obtained using such reactors for process scale-up is nearly zero due to poor agitation and unknown hydrodynamics in the ampoule. These reactors are, however, very useful for fast screening of catalysts. 

Dynamic screening equipment can be categorised according to the type of motion used to shake-up and transport the material on the screen. The principal types used in the chemical process industries are described briefly below. 

Reciprocating screens operated with a shaking motion, a long stroke at low frequency (20-200 Hz). Used for conveying with size separation. 

Further miniaturization and lower-cost sensors will put an instrumented bioreactor in every scientist s reach. If this effort succeeds, it should be possible to instrument shake flasks at low cost. Since this is the most widely used bioreactor of any kind and the bulk of basic research as well as the annual screening of hundreds of thousands... 

Shake and vortex a Soil Volatile, semivolatile, nonvolatile Screening/ laboratory... 

Soxhlet, sonication, supercritical fluid, subcritical or accelerated solvent, and purge-and-trap extraction have been introduced into a variety of methods for the extraction of contaminated soil. Headspace is recommended as a screening method. Shaking/vortexing is adequate for the extraction of petroleum hydrocarbons in most environmental samples. For these extraction methods, the ability to extract petroleum hydrocarbons from soil and water samples depends on the solvent and the sample matrix. Surrogates (compounds of known identity and quantity) are frequently added to monitor extraction efficiency. Environmental laboratories also generally perform matrix spikes (addition of target analytes) to determine if the soil or water matrix retains analytes. 

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