A method and system of depressurizing a molecular sieve used in ethanol production is shown and described. The method and system utilizes a vapor mixing condenser that receives a vapor sieve feed from the molecular sieve during the depressurization cycle. The vapor from the molecular sieve during the pressurization cycle is used to heat the 190-proof product flow. The heated product flow is diverted directly to the 190-proof product vaporizer, which increases the input product flow temperature to the vaporizer, thereby reducing the amount of heat needed to vaporize the 190-proof product flow. The reduction in heat needed reduces energy costs and increases equipment life.