Waste Heat Recovery through Organic Rankine Cycles in the Bioethanol Separation Process

The huge use of heating utilities is one of the main drawbacks associated with the azeotropic separation process for the bioethanol production. In this context, process integration through heat exchanger networks can be used to integrate the involved streams; however, the main problem in this scheme is that the streams that require cooling are at lower temperature that the ones that require heating, yielding very small opportunities for energy integration. Recently, the organic Rankine cycle has been proposed as an alternative for waste heat (i.e., heat at low temperature) recovery producing electric power. Therefore, in this paper is presented an optimization study for the energy integration in the azeotropic bioethanol separation process involving energy integration through heat exchanger networks incorporated into an organic Rankine cycle. A proper optimization approach is proposed to yield the solution with the minimum separation cost. Several separation sequences are used to demonstrate that incorporation of the organic Rankine cycle to energy integration in bioethanol production yields significant economic benefits. Furthermore, this integrated scheme improves the energy efficiency for the waste heat recovery, making more attractive the use of bioethanol.