Abstract Method for the expansion of granules of thermoplastic material, particularly polystyrene. The discrete granules are fed into the upper end of a tower or drum and allowed to descend by gravity while under agitation. While so descending they are insufflated with jets of saturated or superheated steam which surrounds each granule and causes it to expand to a final density as low as 4 kg/m3. The granules may be preheated before insufflation with steam, as by entraining them in a stream of heated air which also deposits them into the top of a tower. Or they may be preheated by moving them in a layer between confronting runs of upper and lower foraminous conveyor belts while directing heated air through the layer. When an inclined drum is used the discrete granules are introduced into the elevated end of the rotating drum and agitated while being insufflated with steam dispersed into the drum in a large number of jets distributed in and along its axis of rotation.
The method of claim 1, the flow of granules being verticallY downwardly in and along a tower defining said enclosed, confined space, insufflating steam being directed in a plurality of radial jets at each said level, from locations adjacent the peripheral walls of the tower.
Claim 2
Dependent Claim
46 words
The method of claim 1, and preheating the granules by entraining them in heated air, passing the heated air and entrained granules into said enclosed space, there separating the granules from the air, dispensing them into said space, and exhausting the heated air from the space.
Claim 3
Dependent Claim
12 words
The method of claim 3, and reheating and recirculating the exhausted air.
Claim 4
Dependent Claim
35 words
The method of claim 1, continuously forming the granules into a porous layer of uniform thickness, passing heated fluid through the layer to preheat the granules, and introducing the preheated granules continuously into said space.
Claim 5
Dependent Claim
59 words
The method of claim 1, said enclosed space having an axis of symmetry inclined downwardly to the vertical at less than 90* in the direction of flow of granules therethrough, and rotating the space about said inclined axis to agitate the granules while being insufflated with steam dispersed into the space in the form of a multiplicity of jets.
Claim 6
Dependent Claim
16 words
The method of claim 6, said jets being dispersed radially outwardly from and along said axis.