GB423934A - Improvements in and relating to drying sludge and the like - Google Patents

Abstract

In the drying of sludgy material, e.g. cement slurry before delivery to a rotary kiln, china clay slip, sewage sludge, sludge from water-softening and paint plants &c., by heating balls of metal, stone, &c. coated with the sludge, the balls receive their full complement of sludge <PICT:0423934/III/1> <PICT:0423934/III/2> before being passed through the heating chamber, and the dried coating is removed in a second chamber from which the cleaned balls are returned to the drier. In the form shown in Fig. 1, a rotary drier 1, heated by hot air or flue gases, is formed internally, near its feed and discharge ends with annular flanges 7, 8, which provide a preliminary coating compartment 1<a> and a discharge compartment 1<b>. From the latter, the balls with their dried coatings, are delivered to a chamber 10 fitted with a rotary or oscillating screen, the dried material passing to the hopper 11 while the cleaned balls are returned to the compartment 1<a> of the drier by conveyers 12, 13, and a shoot 6. Screens may be provided at the discharge end of the drier 1 and at intermediate points in its length so that any of the coating which leaves the balls before their delivery to the chamber 10 may be collected separately from the fully dried material. Fig. 2 shows a modification in which the drying chamber is constituted by a vertical shaft 14 maintained full of balls, the coating being applied either before the balls are delivered to the hopper 21, in the hopper itself, or in the upper part of the shaft by means of nozzles 27. The heating gases are supplied through the hooded conical base 17, while the balls with their dried coatings are discharged through peripheral openings 16 covered by screens consisting of slowly driven endless belts 18. The discharged balls are received in an annular gutter 23 and pass to a screw 24 which conveys them to the separating screen 25, an elevator 26 being provided to return the cleaned balls to the hopper 21.