Bead mills

Beach sands Beadboaid insulation Bead mills Beam... 

Recovery. The principal purpose of recovery is to remove nonproteinaceous material from the enzyme preparation. Enzyme yields vary, sometimes exceeding 75%. Most industrial enzymes are secreted by a microorganism, and the first recovery step is often the removal of whole cells and other particulate matter (19) by centrifugation (20) or filtration (21). In the case of ceU-bound enzymes, the harvested cells can be used as is or dismpted by physical (eg, bead mills, high pressure homogenizer) and/or chemical (eg, solvent, detergent, lysozyme [9001 -63-2] or other lytic enzyme) techniques (22). Enzymes can be extracted from dismpted microbial cells, and ground animal (trypsin) or plant (papain) material by dilute salt solutions or aqueous two-phase systems (23). 

The annular gap mill shown in Fig. 20-36 is avariation of the bead mill. It has a high-energy input as shown in Fig. 20-37. It may be lined with polyurethane and operated in multipass mode to narrow the residence-time distribution and to aid cooling. 

Performance of Bead Mills Materials processed in stirred-media mills are listed in Table 20-17. Variables affecting the milling process are listed below. 

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.)... 

A mathematical analysis of the action in Kady and other colloid mills checks well with experimental performance [Turner and McCarthy, Am. Inst. Chem. Eng. J., 12(4), 784 (1966)], Various models of the Kady mill have been described, and capacities and costs given by Zimmerman and Lavine [Co.st Eng., 12(1), 4-8 (1967)]. Energy requirements differ so much with the materials involved that other devices are often used to obtain the same end. These include high-speed stirrers, turbine mixers, bead mills, and vibratoiy mills. In some cases, sonic devices are effec tive. 

Only once in 15 years does a truly novel method of size reduction become successful. The roll press is a truly successful example of a novel mill, and stirred-bead mills are older mills that have reached a new state of development. Many more methods are proposed and studied some of these are described below The information may be useful to judge other novel methods that may be proposed. 

Among new mill developments, annular-gap bead mills and stirred bead mills are being used. These have a high cost, but result in a steep particle-size distribution when used in multipass mode [Kolb, Ceramic Forum International, 70(5), 212-216 (1993)]. Costs for fine grinding typically exceed the cost of raw materials. Produces are used for high-performance ceramics. 

For the purpose of paint formulation the most important units of equipment are the laboratory ball mill, bead mills and high speed dispersers. The most common, the ball mill, consists of a cylindrical porcelain vessel a little more than half filled with steel, porcelain balls or pebbles. Pigment, together with sufficient binder and solvent to make a free-flowing mix, is loaded into the mill until it is approximately two-thirds full. The mill is then closed and fixed into a device whereby it is made to rotate about its major axis. Normally, a period of about 16 hours is required for thorough dispersion of the pigment, whereupon the mill-base is emptied out and blended with the remainder of the ingredients. 

Baker s yeast suspension (20% ww/v original cells) was pumped to the bead mill at a flow rate of 280 cm h 1 within the BRG 4.5 cm inner diameter contactor. Then, the disruptate from the mill was directly introduced to the pre-equilibrated fluidised bed containing ZSA II-CB and Macrosorb K4AX-CB. 

The experimental rig and process configuration for integrated bead milling and fluidised bed adsorption is shown in Figure 17.5. 

Fig. 17.5. Experimental configuration for integrated bead milling and fluidised bed adsorption 1. Feedstock 2. peristaltic pump 3. bead mill 4. flow through/waste 5. fluidised bed contactor 6. elution buffer 7. fraction collector/ waste 8. loading buffer.

The primary purification of the enzyme G3PDH was exploited herein as a preliminary study to investigate and demonstrate the feasibility of the integrated operation of cell disruption by bead milling and immediate product capture by fluidised bed adsorption (panel A in Figure 17.6). Yeast G3PDH binds nicotinamide adenine dinucleotide (NAD) as a cofactor,... 

Fig. 17.7. Fluidised bed adsorption of G3PDH from milled yeast homogenate onto zirconia-silica Cibacron Blue. The feedstock (20% w/v) was fed to the bead mill at a rate 4.05 dm3-h 1, which corresponded to a linear flow velocity of 250 cm-h 1 within the BRG contactor with a settled bed height of 21 cm. The disrupted baker s yeast homogenate from the bead mill was applied to the integrated fluidised bed directly and terminated when C/Ca = 0.65.

Experiments investigated the integration of cell disruption by bead milling and product capmre by fluidised bed adsorption. By using fluidised bed adsorption, the clarification of the broth would be incorporated with the capture of the product which would result in a considerably... 

ZOZ continuous-fed horizontal mill, and other horizontal high-energy bead mills... 

Mechanical disruption methods include sonica-tion, high-speed homogenization using a French press, and bead milling, which is especially suitable... 

For fine grinding of limestone for paper and pottery manufaeturing, respectively, bead mills are widely used. The beads of steel, glass, or eeramic have a diameter of 0.2. 3mm and occupy up to 90% of the total mill volume (cp < 0.9). They are kept in motion by perforated stirrer dises while the liquid/solid suspension is pumped through the mill chamber. Mill types frequently used are the stirred disc mill, centrifugal fluidized bed mill, and ring gap mill. 

Karbstein et al. (26) pursued the question smallest size laboratory bead mill that would still deliver reliable data for scale-up. In differently sized rigs (F= 0.25-25 L), a sludge consisting of limestone (dsQ= 16 pm) and 10% aqueous Luviscol solution (mass portion of solids = 0.2) was treated. It was found that the minimum size of the mill chamber should be F= 1 L. An additional unexpected, but dramatic, result was that the validity of the process characteristics... 

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