Methodological aspects in synthesis of combined sugar and ethanol production plant

The synthesis problem, i.e. the definition of type, number and design parameters of system components and their interconnections, is one of the main research field of chemical and energy engineering. The present paper aims at clarifying some methodological aspects for the systematic synthesis of processes by suggesting an organized procedure which is applied here to a case study of a sugarcane mill. The procedure starts from the definition of a Basic Plant Configuration (BPC) that is built according to the original "concept" of the conversion process (e.g., "transform sugarcane into sugar" or "transform sugarcane into sugar and ethanol"). The BPC comprises the "basic components", i.e. those required to perform the main material and energy conversions, and considers the hot and cold thermal flows only instead of the heat exchangers. A design optimization of this configuration is then to be performed, in which the extreme temperature of the thermal streams are considered among the set of the decision variables. The original BPC is then progressively changed into new BPCs by means of structural modifications including component staging and addition of new material connections or subprocesses. Modifications to the original BPC are mainly derived from the interpretation of the process Grand Composite Curve (GCC), a graphical tool provided by Pinch Analysis, which helps identify the potential for process internal heat recovery. Although the development of an automated algorithm is the final goal of the research activities, this article aims at showing that the proposed approach can be used to systematically explore the most significant process synthesis options. In the light of the suggested procedure we investigate here three different process concepts for the conversion of sugarcane. Starting from the original concept of sugar production, process structural developments towards the combined sugar and ethanol production are proposed and discussed. (C) 2011 Elsevier Ltd. All rights reserved.