Patent GB-944667-A (GB)
Title: Improvements relating to methods and apparatus for drying animal waste products
Inventor: COLLINS LIONEL GEORGE
IPC: F26B3/00
Filed: 1961-10-11
Abstract: 944,667. Drying poultry &c. waste products. WILLIAM DOUGLAS & SON (ENGINEERING) Ltd. Oct. 29, 1962 [Oct. 11, 1961], No. 36514/61. Heading A2B. [Also in Division F2] Poultry or other animal waste products which yield little or no fat on heating are dried to a moisture content of 8% or below by loading the waste products into a chamber in which they are stirred or otherwise agitated and are dried by the conduction to them of heat from the walls of the chamber, after which they are further dried in the same chamber by passing heated air through the chamber whilst continuing the heating of the walls of the chamber and the stirring or other agitation of the contents. When the waste products include wet poultry feathers and blood, these may be pressure-cooked in the chamber before the other waste products such as heads and offal are loaded into it, or the waste products including the feathers and blood may be loaded into the chamber, and, after the initial drying with conduction of heat from the walls of the chamber, the chamber is sealed and heated to pressurecook the feathers and blood; thereafter the chamber is unsealed and the further drying takes place with the passage of heated air through the chamber. The first drying step takes place for between 4 and 5 hours; the second drying with the passage of hot air takes 1-1¢ hours when it immediately follows the first drying or from 3 to 4 hours when it follows the pressure cooking. The drying drum 1, Fig. 3, is mounted on pedestals 2 and 3, and is heated by the circulation of steam in a jacket 24; the contents of the drum are stirred by paddles 35 mounted on a rotating shaft 29 and giving only a small clearance from the inside wall of the drum. According to an example, the cover 28 was opened to enable the drum to be completely filled with feathers and blood of slaughtered fowls and was then closed. With the valve 9 of the fume outlet pipe 8 closed, a gauge pressure of about 40 1bs. per square inch was produced and maintained in the drum for 35 minutes by steam heat in the jacket 24. During the next 45 minutes the steam supply to the jacket was cut off and the valve 9 was cracked open so that the pressure within the drum was gradually reduced to atmospheric. The cover was again temporarily opened for charging the remaining poultry waste into the drum. With the valve 9 fully open, steam was supplied to the jacket for 4 hours to dry the whole contents of the drum to a coarse meal of moisture content about 30%. Next the valve 9 was closed, the cover 28 was opened and a hot air outlet pipe was connected to the top of the pipe 27. Hot air at a temperature of 230‹ F. was then supplied for U¢ hours from a centrifugal blower at a rate of 375 cubic feet. per minute through valve inlets 38 to 40 to reduce the moisture content of the meal to 8% or below. The waste products and meal were continuously stirred by the paddles 35 throughout the drying operations. Finally the dried meal was discharged by the paddles through an opening 14 into a hopper for transference by a conveyer and air hoist to a bagging plant, Fig. 1 (not shown.