Dryer

Application example: Espey® WD500 for rotating reactor in the PET processing

Issue and challenge:

PET flakes with high vis­cos­ity are needed for the man­u­fac­ture of drink bottles out of PET. In the man­u­fac­ture of PET and the pro­cess­ing of recycled R-PET, the initial vis­cos­ity figures are too low for the re­quire­ment. The PET flakes there­fore undergo solid-phase con­den­sa­tion in a vac­uum-proof rotating reactor (length 80 m (3150 “), diameter 6.2 m (244 “)). After spending between 8 and 12 hours at defined tem­per­a­ture and pressure, they change from an amor­phous to a crys­talline con­di­tion. The poly­con­den­sa­tion starts at a set pressure/tem­per­a­ture level. The mol­e­c­u­lar chains lengthen while water is released, and the vis­cos­ity rises. The flow of inert gas (CO2) picks up unwanted, volatile con­t­a­m­i­nants. An easily fitted seal is needed for sealing the filling side of the reactor in order, for reasons of safety, to prevent the inert gas from escaping. It must be able to with­stand the move­ments of the reactor shaft (100 mm (3.94 “) axially, 25 mm (0.98 “) radially).

Solution from EagleBurgmann Espey:

For this purpose, Espey de­vel­oped the Espey® WD500. A shaft seal with barrier gas con­nec­tion and four seal rings, designed for a shaft diameter of 1190 mm (46.85 “), a tem­per­a­ture of 220 °C (428 °F) and a slight vacuum. Because it is very time con­sum­ing to dis­man­tle parts of the reactor shaft and its com­po­nents, Espey designed a 4-piece housing in order to meet the demand for the simplest possible assembly. In addition, the seal has to with­stand huge shaft move­ments (up to 25 mm (0.98 “) radially), and this is achieved through a special im­ple­men­ta­tion of the floating seal rings. Un­lim­ited axial shaft movement can be absorbed by the Espey sealing system. In order for the sur­round­ings of the reactor to be entirely safe for the op­er­at­ing staff, the seal of the reactor, which is filled with CO2, in­cor­po­rates a nitrogen barrier.