Weigh feeders

Figure 3.7. Solids feeders with variable speed drives, (a) Rotary vane (star) feeder with variable speed drive, (b) Horizontal screw feeder, (c) Belt feeder taking material from a bin with an adjustable underflow weir, (d) Rotary plate feeder Rate of discharge is controlled by the rotation speed, height of the collar, and the position of the plow, (e) Continuously weighing feeder with variable speed belt conveyor.

Digital blending systems pros ide the mosl accurate means (or automatic, continuous-control flow of bulk materials. They are dependent entirely on the accuracy of the digital pulses Irunsmilicd from the individual weigh feeders—with a control accuracy of plus or minus one pulse. 

To calculate the raw meal to clinker ratio, a clinker weighing test was carried out over 20 hours, while the kiln feed value was taken from weigh-feeder counters. The mass flow rate of raw meal 157.3 t/h and the clinker 97.42 t/h. 

British Materiais Handiing Board (1986) Guidelines for Specifying Weigh Feeder Systems (BMHB, Buckinghamshire, UK). 

SC-4 Me tering screiw W-5 Weigh feeder M-6 Cone mixer... 

SI-1 Urea bin W 2. W-8 Weigh feeders T-3 Sulfuric acid tank P-4, P-6, P-11 Pumps M-5 Mixing tank SI-7 Rock bin M-9 Rotary mixer X-10 Drum DEN... 

Gravimetric feeder gra-v3- me-trik- (weigh feeder). A device for feeding extruders that continuously meters, by weighing, the rate at which feedstock enters the feed port of the extruder. 

Concentrates and flnxes are mixed in a paddle mixer and fed via a weigh feeder directly into the slag bath reactor. Wet feed is satisfactory, eliminating any need for drying, but high moisture will consume more fuel and increase the volnme of smelter gases. 

The ideal way to mix continuously would be to have continuous weigh feeders which would continuously feed in the correct ratio to give the desired formula of rubber, chemicals and liquid directly into the continuous rubber mixing machine. However, most rubber formulas have on average 15 different chemicals to make the complete formula, so it is very difficult to do this weighing continuously due to the high cost and varied nature of the chemicals involved. 

Fig. 7.9. Schematic view of feeder control, lab control and melt sensor-based control. Keys 1, thermoplastic storage 2, weigh feeder 3, pigment storage 4, loss-in-weight feeder 5, extruder 6, vacuum system 7, strand die 8, water bath 9, air knife 10, strand pelletiser. After Sohl [9]. Reproduced by permission of C.H. Sohl, Experimental Station, Du Pont...

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