GB897923A - Dehydrating apparatus - Google Patents

Abstract

<PICT:0897923/III/1> <PICT:0897923/III/2> A dehydrating apparatus for gypsum comprises a rotatable chamber having an axial pipe bearing a hollow accordion-like structure serving to subdivide the gypsum mass, heating medium being passed into said axial pipe and the associated hollow structure, from which connecting pipes to the outside of the chamber may be provided. As shown in Figs. 1 and 2, a drum 6 is supported by, and rotates about, an axial pipe 21 which rests on rollers 5. Inside the drum the tube 21 carries a hollow accordian-like arrangement of annular dished members 26 peripherally joined to form a series of chambers communicating with the interior of pipe 21 through perforations 25. A gas burner 22 delivers a blast of hot combustion products into the pipe 21 from the left-hand side and these gases pass through perforations 25 into the chambers 33 formed by the annular dished members 26. The chambers 33 communicate with tubes 8 (Fig. 2) formed in the walls 7 of the drum, by means of pipes 30. Tubes 8 are provided with exhaust passages 31 having terminal elbows 32, whereby the hot combustion gases from chamber 33 pass through connections 30 into tubes 8 and out through exhausts 31 in contact with the exterior of the drum 6. Gypsum is fed to the drum through removable closures such as 11 and the steam formed by dehydration is vented through valve 13. As shown in Fig. 2, the valve 13 is operated by a lever 16 carrying a roller 18. The latter abuts a valve-operating cam 19 which is manually adjustable so as to release steam pressure as desired when the drum rotates. In operation for the dehydration of gypsum, gypsum pieces having a maximum dimension of an inch are fed to the drum in an amount sufficient to permit relative movement between the pieces of gypsum on rotation. The steam-tight closures 11 are sealed and the drum rotated. The pressure rises to about 35 p.s.i.g. as the gypsum becomes heated and thereafter rises to about 40 p.s.i.g. as dehydration commences. The cam 19 is thereupon adjusted to release the steam pressure and as dehydration proceeds, the valves 13 are progressively opened wider until at the end the pressure has dropped to atmospheric. The drum may be preheated before introducing gypsum, to a temperature of about 300 DEG F. During dehydration the temperature remains at about 250 DEG F. and may be raised to about 270 DEG F. at the end of the operation. Specifications 866,126, 897,924, 897,925, 897,926 and 897,927 are referred to.