| 摘要 |
Tobacco containing solid carbon dioxide is fed into an expansion chamber (14) in which it is expanded by hot gas; the solid carbon dioxide thereby being sublimed and moisture and organic material in the tobacco being volatalised. The gas and expanded tobacco enter a separator (15) from which the tobacco is discharged through a rotary valve (17). Gas is withdrawn from the separator (15), a portion of it vented, and the remainder heated by heater (27) and then returned to the expansion chamber (14). In order substantially to preclude air flowing through the rotary valve (17) into the separator (15) the pressures below and above the rotary valve are equalised. Alternatively, some of the gas withdrawn from the chamber (15) my be used to isolate the valve (17) from the atmosphere. By precluding air flow into the separator (15) the tobacco may be expanded without using steam (other than that evolved from the tobacco) or excessive temperatures. |
