Low drum

Equations (30.32) and (30.33) apply both to continuous vacuum filters and to continuous pressure filters. When R is negligible, Eq. (30.33) predicts that the filtrate flow rate varies inversely with the square root of the viscosity and of the cycle time. This has been observed experimentally with thick cakes and long cycle times with short cycle times, however, this is not true and the more complicated relationship shown in Eq. (30.32) must be used. In general, the filtration rate increases as the drum speed increases and the cycle time diminishes, because the cake formed on the drum face is thinner than at low drum speeds. At speeds above a certain critical value, however, the filtration rate no longer increases with speed but remains constant, and the cake tends to become wet and difficult to discharge. 

Figure 3 illustrates the effect of the drum speed on the solids fractional hold-up in the drum. At a low drum speed the solids hold-up is relatively high and decreases with the drum speed. According to Abouzeid and Fuerstenau, this trend is due to the variation of the thickness of the shear zone of the cascading bed with the drum speed [29]. 

Figures 11 and 12 depict the effect of the drum speed on the slurry hold-up and its solids volumetric concentration, respectively. The slurry feed rate is 20 g/s, and the solids particle size is d = 2.0 mm. For a given slurry feed solids concentration. Figure 11 displays that the drum slurry hold-up decreased with the drum speed. Also, at a given drum rotational speed, the drum slurry hold-up was higher for a slurry feed having a higher solids concentration. At low drum speeds, say 7 rpm, the drum slurry hold-up for a feed slurry solids concentration of Cp = 46.1 vol.% was twice that for a Cp = 7.6 vol.%.

Figure 23 also shows that the model predicts the frequency of oscillation increases at low drum speeds and becomes constant at higher values of N. It is interesting to note that the model predicts an oscillation frequency independent of the solids hold-up, i.e., solids mass in the drum. The experimental data shown in Figure 23 are for various feed slurry solids concentrations and represent different solids holdup in the drum (Figures 24 and 25). The experimental data also indicate that the frequency of oscillation is not sensitive to the solids mass hold-up as predicted by the model. In general, the frequency of oscillation is a function of and p. Increasing the drum speed results in a decrease in the value of p, which is reflected... 

Slurry Hold-up and Mean Solids Concentration. Figure 30 depicts the influence of the drum rotational speed on the slurry hold-up for slurry feed concentrations of 7.8%, 21.0%, and 45.9%. The slurry hold-up-drum speed relationship exhibited a minimum for all the feed solids concentrations examined. At low drum speeds, the slurry hold-up increased with the feed solids concentration. However, at high drum speeds the effect of the slurry feed solids concentration on the slurry holdup was less significant. The most important aspect of Figure 30 is that the lifters eliminated the abrupt changes in the slurry hold-up observed for the drum without lifters. 

Figure 35b displays the variation of the average hold-up solids volumetric concentration with the drum speed for the same conditions as in Figure 35a. For the case of 10% feed solids concentration, the hold-up solids concentration decreased sharply with the drum speed. The dependence of C on the drum speed decreased for the higher feed solids concentration. In all cases, at a drum speed of about 2.62 s", the hold-up solids concentration approached its respective feed solids concentration. This result indicated that at drum speeds > 2.62 s" both the solids and the water moved in the drum with the same forward velocity. At low drum speeds, the average hold-up solids concentration approached 45%, irrespective of the feed solids concentration.

Figure 36a is similar to Figure 35a, but for a slurry feed rate of 0.04 kg/s. The percent slurry hold-up behavior was similar to that for = 0.02 kg/s. The variation of the hold-up solids concentration ratio, C/Cp, is shown in Figure 36b. It is clear that for drum speeds > 2.62 s, all the curves for the various Cp values approached a limiting value of C/Cp = 1.0. This result is, once again, indicative that both the water and the solids move with the same axial velocity similar to a homogeneous slurry. The maximum deviation of C/Cp from unity occurs at low drum speeds, signifying a large relative velocity for the water and the solids. This case is that of a stratified slurry flow.

High and low drum water level alarms provided... 

Difficulties in steam dmm water level control at this juncture led the operators to override the reactor trip signals generated by low drum level. They then topped up the drum water level under manual control, with relatively cold feedwater. This caused a fall in reactor temperature and therefore a reduction in the amount of steam voidage inside the reactor core hence (via the positive steam voidage coefficient) the control rods had to be withdrawn yet further to maintain reactor power level at 200 MW. 

Drum dryers are shown in Fig. 3.15c. his consists of a heated metal roll. As the roll rotates, a layer of liquid or slurry is dried. The final dry solid is scraped off the roll. The product comes ofiF in flaked form. Drum dryers are suitable for handling slurries or pastes of solids in fine suspension and are limited to low and moderate throughput. 

Beside all technical reasons the big advantage of a pneumatic test is, that the steam drums can remain within the line because first we have no additional load for the bearing and only small adjustments (for the connection with the pressurisation unit and the tightening of the man ways for the applied low temperature gas test) have to be done to make the drum ready for a pneumatic loading. The pressurised air is available in every paper mill and even if the maximum pressure does not fit, the use of a compressor or pressure bottles produce no problems. 

Fig. 15. Wet drum low intensity magnetic separator tank designs (a) concurrent, (b) counter-rotation, and (c) countercurrent (6) (d) shows the operating...

The value of the coefficient of heat transfer from steam to sheet is determined by the conditions prevailiug on the inside and on the surface of the dryers. Low coefficients may be caused by (1) poor removal of air or other noncoudeusables from the steam in the cyhn-ders, (2) poor removal of condensate, (3) accumulation of oil or rust on the interior of the drums, and (4) accumulation of a fiber lint on the outer surface of the drums. In a test reported by Lewis et al. [Pulp Pap. Mag. Can., 22 (Februaiy 1927)] on a sulfite-paper diyer, in which the actual sheet temperatures were measured, a value of 187 W/(m °C) [33 Btu/(h ft" °F)j was obtained for the coefficient of heat flow between the steam and the paper sheet. 

Direct-expansions are more appropriate for smaller systems which should be compact, and where there are just one or few evaporators. Overfeed (recirculation) systems should be considered for aU applications where first cost for additional equipment (surge drums, low-pressure receivers, refrigerant pumps, and accessories) is lower than the savings for the evaporator surface. 

Derivatives or rates of change of tray and condenser-reflux drum hquid holdup with respecl to time are sufficiently small compared with total flow rates that these derivatives can be approximated by incremental changes over the previous time step. Derivatives of liquid enthalpy with respect to time eveiywhere can oe approximated in the same way. The derivative of the liquid holdup in the reboiler can likewise be approximated in the same way except when reflux ratios are low. 

High-speed, low-intensity drum magnetic separator. This device is designed to handle very fine material (minus 0.15 mm and finer) to produce a high-grade magnetic concentrate. 

Low sbepf mixers Fluid-beds Pans Drums... 

Other advantages claimed for the disc graniilator include low equipment cost, sensitivity to operating controls, and easy observation of the granulation/classification action, all of which lend versatility in agglomerating many different materials. Dusty materials and Chernies reactions such as the ammoniation of fertilizer are handled less readily in the disc granulator than in the drum. 

Boxes Bulk boxes (Fig. 21-40) of corrugated kraft paper for dry bulk products fall into hvo broad categories large, for 0.5- to 2-ton loads, and small, for loads of 23 to 68 kg (50 to 150 lb). Large boxes are used extensively for resin shipment small ones, for certain regulated materials (such as caustic soda) and for low-bulk-density products that are assessed excessive freight rates if packed in drums. 

Hence, copper heat exchanger tubes handling acetic acid can he more seriously corroded at low temperatures than at high temperatures. Sulfuric acid at room temperature is handled routinely in carbon steel drums and tanks when water concentration is low, but it becomes extremely corrosive as water concentration increases. As ferric-ion concentration increases during acid cleaning of industrial systems, the corrosion rate of steel increases rapidly. 

Contact with Drum at temperatures low enough to protect operator due to operator against thermal injury spill, over flow, hot drum, etc. CCPS G-15 CCPS G-22 CCPS G-29... 

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