Integrated processes for nylon and polyester production were simulated. The polyester process includes four stages: esterification, prepolycondensation, finishing stage, and solid-state polycondensation. Three stages are involved in the nylon process: prepolycondensation, melt polycondensation, and the solid-state stage. The effect of beginning the solid-state stage at lower DP (compared to the value of the current process) was investigated for both nylon and polyester production. Reactors with either concurrent or countercurrent purge gas flow were applied to the finishing stage for polyester and to the melt stage for nylon. The performance of different reactors was compared. The effect of purge gas strongly depended on the mass-transfer capacity of reactors. In the nylon process, variations in purge gas conditions had a small effect on reactor performance. However, purge gas effects on the polyester process were considerable, and countercurrent flow was more effective than concurrent flow. The reactor operated at atmospheric pressure and, with countercurrent gas flow, can readily substitute for traditional high vacuum operation in the finishing stage of the polyester process.