Underwater pelletizer and heat exchanger die plate

In an underwater pelletizer apparatus for extruding molten material into a water bath to solidify the material, the improvement comprising:

• a solid die plate of substantial mass and having a plurality of spaced channels formed longitudinally therethrough, the channels extending completely through said die plate, solid portions of the die plate lying between the channels and defining walls of the channels, said solid portions being substantially continuous between adjacent channels, the die plate further having a plurality of passageways formed in said solid portions interconnecting the spaced channels;
• a tubular member disposed within each of the spaced channels, the outer walls of each of the tubular members being spaced at least over central portions thereof from the walls of the channel in which said tubular member is disposed, each tubular member having a longitudinal opening formed therein, the opening communicating at a first end of the member with the water bath, the first end of each tubular member having a first enlarged portion which is contiguous about perimetric portions thereof to portions of the walls of said channel at the end of said channel adjacent said first end of said tubular member, each tubular member further having a second enlarged portion of the other end thereof contiguous to the walls of said channel at the end of said channel opposite said first end of said tubular member:
• steam inlet means for directing a relatively heated fluent material into the portions of the spaced channels between the walls of said channels and the outer walls of the tubular members disposed therein, and through the passageways formed in the solid portions of the die plate to exchange heat with the tubular members and body portion of the die plate including said solid portions lying between the channels and defining the walls thereof;
• steam outlet means for directing the heated fluent material from the spaced channels;
• means for directing the molten material into and through the openings in the tubular members into the water bath;
• and,
• means for cutting the now-solidified molten material entering the water bath into substantially uniformally sized pellets, the molten material being maintained in a molten state throughout passage thereof through the tubular members due to heat exchange through walls of the tubular members including the first-mentioned enlarged portions thereof proximous to the water bath, the die plate including the solid portions lying between the channels and defining the walls thereof and the enlarged portions of the tubular members acting as means to retain heat for exchange with the molten material in heat sink fashion, and particularly to retain heat for transfer to the molten material at the first ends of the tubular members proximous to the water bath to present solidification of said molten material prior to entry thereof into the water bath.