Methods and systems for energy-efficient drying of co-products in biorefineries

Abstract

A method is disclosed for improving the energy efficiency of biorefinery drying operations through integration of a dryer that utilizes the heat of condensation of process vapors to dry material whose emissions are captured with energy recovery. The dryer separates clean process vapors (e.g., ethanol) and steam from vapors containing volatile organic compounds and entrained materials, to minimize the need for vapor cleanup. An indirect dryer condenses vapors in a tube dryer similar to a steam tube dryer, but utilizing compressed process vapors, transferring the heat to wet material undergoing drying. The resulting exhaust vapors are either directed to a process stage that requires heat (e.g., distillation) and minimizes the need for vapor cleanup or to an out-of-contact heat exchanger that produces vapors for process use, or to another dryer as an additional effect. Mechanical-vapor recompression or thermal-vapor recompression are employed to produce vapors that optimize overall energy recovery.