Hopper structure, dehumidification plant and method for dehumidifying granular plastic material

A method of dehumidifying granular plastic material comprising the following steps:

• prearranging a hopper structure for the dehumidification of granular plastic material by means of a dehumidifying process fluid, including:
• a main body, bearing, at the top in use, a closure wall with loading opening or mouth for the granular plastic material to be treated;
• at least one discharge mouth or opening for the process fluid provided on said main body or on said closure wall,
• a tapered lower section terminating with a discharge opening for the dehumidified granular plastic material,
• an insert member fluid-sealed and positionable in the main body and in the tapered lower section so as to delimit an annular air space therewith, said insert member comprising at least one conical or frustoconical lower part, which tapers towards a bottom thereof, and an upper part, and
• at least one dehumidifying process fluid feed duct to said annular air space,
• the tapered lower section comprising at least one pair of walls or wall segments comprising:
• a wall or wall segment at least partially enclosing the other wall or wall segment, so as to delimit at least one chamber therewith that is outside said annular air space and in fluid communication therewith, said at least one chamber being feedable with dehumidifying process fluid from said at least one dehumidifying process fluid feed duct oriented tangentially or parallel to said enclosing wall or wall segment;
• feeding granular plastic material at said upper loading mouth;
• and
• feeding dehumidifying process fluid into said at least one dehumidifying process fluid feed duct and thus into said chamber, and subsequently into said annular air space,
• wherein said tapered lower section comprises an upper frustoconical segment, an intermediate segment, and a lower frustoconical segment, the upper frustoconical segment having conicity different from the conicity of said lower frustoconical segment and being extended therein to delimit said chamber, a top of the upper frustoconical segment having a greater radius than the intermediate segment.