Process integration of a 1st and 2nd generation ethanol plant from wheat straw and wheat kernel

To reduce production cost for bioethanol from renewable and sustainable energy sources, such as lignocellulosic material, it is important to diminish the energy demand in the plant. One way of doing it is to employ pinch technology to investigate the possibility of decreasing hot and cold utilities by heat exchanging process streams. The technology can be applied already during the plant process design step and thereby reduce later investment cost.

Wheat, which is one of the most abundantly produced crops in Europe today, generates a major amount of lignocellulosic straw material. By combining a 1^st and 2^nd generation plant, bioethanol can be produced from both starch, found in the kernel, and cellulose, which is found in the straw. This can help to facilitate the introduction of 2^nd generation plants and any surplus energy from the 2^nd generation plant can be used to supply a 1^stgeneration plant with heat and power.

In this study pinch analysis has been applied on various scenarios comprising 1^st and 2^nd generation stand-alone plants or a 1^st and 2^nd generation plant where material streams are combined before distillation. This was made to investigate the effect of employing heat exchanger networks. The simulation program Aspen Energy Analyzer was utilized to create heat exchanger networks from process models, created in the flowsheeting program Aspen Plus, which were based on experimental data. Total direct costs for the heat exchanger networks were subsequently calculated using Aspen Process Economic Analyzer.