Mechanical Vapour Recompression Incorporated to the Ethanol Production from Sugarcane and Thermal Integration to the Overall Process Applying Pinch Analysis

Abstract

Vapour recompression is a means of upgrading energy by the compressing of a lower pressure vapour up to a higher pressure, thus making the energy more available to do useful work. There are two types of vapour recompression: thermo-compression and mechanical recompression. Thermo-compression uses high pressure steam through a nozzle to compress a lower pressure vapour to an intermediate pressure. On the other hand, in mechanical recompression “mechanical” means that the compression task is done through the expenditure of mechanical energy for instance a steam turbine driven a compressor. Other means of driving could be also include an electric motor or an internal combustion engine. In both of cases the main advantage of vapour recompression is that it is not necessary to supply the latent heat of vaporization to the vapour being compressed. The aim of this study is to evaluate the possibilities of the incorporation of mechanical vapour recompression in the ethanol production process from the energy point of view. Thus mechanical vapour recompression is integrated to the juice evaporation system which is composed by a multiple effect evaporator. Simulations in Aspen Plus were accomplished to perform the mass and energy balances. Results showed that the introduction of vapour recompression promoted a reduction in steam consumption of approximately 10 % in evaporation system and 4 % in overall process. In order to further reduce the steam consumption of the plant, Pinch Analysis was applied to integrate the vapour recompression process coupled to evaporation system to all available streams in ethanol production process.