Discharge end constriction

Drum Without Lifters and Without Discharge End Constriction, 202 Drum Without Lifters and With Discharge End Constriction, 204 Drum With Lifters, 204... 

Drum Without Lifters and Without Discharge End Constriction... 

The variation of solids fractional hold-up with drum speed is shown in Figure 5 for the case of a drum without lifters and with discharge end constriction. The variation is similar to that reported by Abouzeid and Fuerstenau [11,29]. The solids hold-up is much higher with the end constriction than with a free drum opening as shown in Figure 3. 

Figure 7 displays the effect of the drum speed on the solids fractional hold-up for a drum fitted with lifters, but with no discharge end constriction. At the same solids feed rate and drum speed, the presence of the lifters increases the drum solids hold-up (Figures 3 and 7). 

C. Delivered solids concentration, volume fraction D Drum inside diameter, m D, Pipe diameter, m D Discharge end-constriction diameter, m... 

Qp Slurry feed flow rate, kg/s Solids mass flow rate, kg/s R Radius of rotating drum, m R Radius of discharge end-constriction, m... 

Berzelius A tin smelting process operated by Berzelius Metalhiitten at Duisberg-Wanheim, Germany. A mixture of oxide ore, coal, and sodium carbonate is fed continuously into a rotating tubular kiln having a constriction at the discharge end. The molten metal product collects in the sump at the end and the slag, which forms an upper layer, and flows off. 

Continuous screw extrusion is another way to form PVC plastisol propellant into the desired size and cross-sectional shape. Simultaneous curing of the propellant is also accomplished. This process has been described fully by Rossen and Rumbel (9) and is only summarized here. Mixed propellant is fed from a casting pot into the feed end of a continuous worm-screw extruder which is fitted at the discharge end of the screw with a device for constricting propellant flow. The action of the... 

Sympathetic discharge causes constriction of the renal resistance vessels and a fall in renal blood flow. This is the typical response in severe exercise or hypotension. The answer is (C). Each of these agents has a different mechanism of action, yet all but one act on the sympathetic postganglionic nerve terminal (site 5). Site 3 is a cholinergic nerve ending. The answer is (A). 

Most previous studies concentrated on the solution of Equation 3 by providing an approximate functional form for the term in the square brackets. Normally, the assumption is made that at the discharge end hj 0 for a drum with no end constriction, otherwise is the depth of the constriction lip, i.e., hj = (R - R ), where R is the radius of the constriction opening. The assumption for the values of h is particularly correct for lightly loaded drums, and it becomes less accurate as the drum loading is increased. Various approximate solutions to Equation 3 are given below for different authors using a unified nomenclature. 

In the previous section, the flow of a sand-water slurry in a horizontal drum with an open-end discharge was reviewed. Slurry hold-up was found to be a function of particle size, drum speed, feed flow rate, and composition. The experimental results also showed relatively low slurry hold-up and poor radial (transverse) mixing inside the drum. To overcome these problems for the case of dry solids, an end-constriction and lifters are normally used. The effects of such additions on the slurry hold-up and mean residence times of solids and fluid phases will be discussed in the next section. 

Ejfect of Drum Speed on Slurry Hold-up. It is instructive to discuss the effect of the end-constriction on the minimum slurry hold-up, before examining the effect of various parameters on the drum hold-up. In the case of a rotary drum with an end-constriction, material cannot flow out of the drum until it is filled to the height of the lip (R - R ). This means that a minimum slurry volume must be present in the drum before any material begins to flow over the discharge lip. The minimum slurry hold-up (percentage of the drum volume) can be calculated as ... 

For the flow of highly settling slurries through horizontal rotary drums with an end-constriction (overflow discharge), the following conclusions were obtained ... 

Nicholson (1996) found good agreement between such theoretical calculations and experimental data for cylinders with and without constrictions at the discharge end. 

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