| 摘要 |
A continuous process for the multistage drying and postcondensation of polyamide pellets in the solid phase comprises 1) carrying out the predrying process in a continuous drying apparatus which is operated in countercurrent mode or in crossflow mode with inert gas or steam, or with a mixture of inert gas and steam, using a pellet temperature in the range from 70 to 200° C., and 2) Carrying out the subsequent continuous postcondensation process in a separate vertical duct with moving bed at a pellet temperature in the range from 120 to 210° C., where the duct is operated in countercurrent mode with inert gas or steam, or with a mixture of inert gas and steam, the inert gas is introduced at least two sites along the duct, and from 15 to 90% of the inert gas is introduced at the base of the vertical duct and from 10 to 85% of the inert gas is introduced in the upper half below the surface of the pellets. |
