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This contribution addresses the optimal design of the heat exchanger network (HEN) for an integrated soybean biorefinery plant which encompasses six process areas: (i) beans preparation; (ii) oil extraction; (iii) miscella distillation; (iv) soy oil refining; (v) sodium methoxide production; and (vi) biodiesel production via homogeneous alkaline transesterification technology. For this purpose, a two-step methodology is employed, where a Total Site Analysis is first carried to estimate the energy targets for the whole process and assess the potential utility co-generation to be distributed to the process sites through the utility system. Subsequently, the HEN design of each site is performed using the Aspen Energy Analyzer, based on a sequential procedure employing Mixed Integer Linear Programming to minimize the HEN total cost. The results obtained reveal that the heat sources in the current process configuration limit the co-generation of utilities, and therefore the process heat waste needs to be preferentially recovered through stream matches within each site. A systematic design procedure is therefore used to identify an optimized HEN configuration, achieving lower utility consumption and lower total heat exchanger area, compared with a previous reference solution. The higher number of heat exchange units of this new design is compensated with the elimination of inter-site streams matches, resulting in a process alternative simpler to implement in practice.

In recent years, climate changes and fossil resources depletion prompted efforts on R&D of technologies associated with the production of biodiesel, among other biofuels. However, expensive refined vegetable oils and supply shortages of waste cooking oils are still major factors hindering biodiesel market growth to substitute petroleum diesel, due to lack of economic competitiveness and sustainability issues. We address in this paper the production of biodiesel coupled with soybean processing to study possible synergies leading to economic and sustainability gains. Simulations in Aspen Plus® were carried employing detailed thermodynamic and kinetic models from previous works; these were obtained fromexperimental and industrial data, to describe more rigorously the various unit operations. The simulation framework under analysis includes the soybeans preparation and extraction areas, the miscella distillation and physical soybean oil refining, the production of sodium methoxide and biodiesel using the homogeneous alkaline transesterification technology. A base case with a process structure and operating conditions similar to the ones reported in the literature is adopted, and several integration opportunities in the global process are identified. Results show that biodiesel production costs can be significantly reduced from 795 $/t to 584 $/t, by incorporating in the chemical supply chain soy meal, lecithins and soy deodorization distillate (SODD) products that have high commercial value. Moreover, the integration of these processes helps to further reduce the biodiesel production costs by 2.6 % and the amount of wastewater generated by almost 10 %.