Abstract

Tobacco particles, particularly Burley tobacco, which form a continuous stream are conditioned during transport by a series of vibratory conveyors. The foremost conveyor receives tobacco particles from a unit which contacts the particles with an atomized liquid, especially casing, and the conveyors thereupon transport the particles seriatim through preconditioning, heating, cooling and moisturizing units. The preconditioning unit has a housing consisting of one or more coiled steam pipes having orifices which discharge currents of steam against the underside of the tobacco stream at a pressure which suffices to enable the currents to form a cushion for the moving tobacco particles. The currents condense on contact with the relatively cool tobacco particles whereby the particles entrain the condensate into the heating unit wherein the particles are relieved of nitrogen and the casing is caused to penetrate into the fibrous structure of each particle with attendant roasting of the casing. The moisturizing unit may be similar to the preconditioning unit but is then further provided with one or more nozzles serving to sprinkle finely atomized water onto the particles which are supported by the cushion of steam in the housing of the moisturizing unit. The temperature of tobacco particles is measured immediately downstream of the heating unit and, if the measured temperature deviates from a desired temperature, a control circuit automatically changes the temperature and/or moisture content of hot air which is used for heating, the rate of tobacco feed to the vibratory conveyor(s) or the length of intervals of dwell of tobacco particles in the heating unit.