652 



CEMENTS, LIMES, AND PLASTERS. 



ratus dries from 7 to 8 metric tons of slag per day with a coal consump- 

 tion of about 5 per cent of the weight of slag dried. 



At Vitry, France, a simple and effective non-rotary drier, operated 

 by gravity, is employed, plan and section of which is given in Fig. 162. 

 It consists of drying compartments (each of which is lettered, a, 6, c, d, 

 in the plan), arranged about a central flue (c, d, c, d in plan), through 

 which passes the heated gases from a furnace. The central flue is 1 m. 



W/////////////////U 



SECTION ON A-B 



- FIG. 162. Vitiy slag-drier. 



square; the drying compartments 0.5X1 m. in area, and both are 

 7 m. in height. Each of the drying compartments contains 10 sheet- 

 iron plates (of which only six, E, are shown in each compartment of 

 the section). These plates are inclined and so arranged that the wet 

 slag, shoveled in at the top of each compartment, descends by gravity 

 and finally issues from the lowest plate in the heaps F, from which 

 it is shoveled and sent to the grinding mills. According to Prost, a 

 drier of this type and size will dry from 12 to 15 metric tons of slag 

 per working day. From 6 to 6.5 Ibs. of coke are necessary to dry each 

 100 Ibs. of slag. 



Tower driers, resembling those used at one or two American Portland 

 cement plants, could of course be used in drying slag. At present, 

 however, every slag-cement plant in the United States uses rotary 

 driers. 



