Abstract: A process for condensing exhaust vapor comprises alternating modes of operation. In the first mode, the exhaust vapor contacts solid particles at a first temperature below the condensation temperature of the vapor and, simultaneously, solid particles at a second temperature above the first temperature are cooled to the first temperature. In the second mode, the exhaust vapor contacts the solid particles that were cooled in the first mode and, simultaneously, solid particles that were heated in the first mode are cooled to the first temperature. This cycle repeats continuously.