Publication: Process simulation and multi-objective optimization of in-situ microalgae-based biodiesel plant
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Date
2022-09-01
Authors
Ahmed, Mukhtar
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Abstract
The scarcity of crude petroleum resources, environmental concerns and increasing energy consumption across the globe has gained the researcher’s attention to the search for renewable fuels such as biodiesel. Biodiesel is an alternative fuel to petroleum diesel. However, the main bottlenecks in the commercialisation of biodiesel are its production cost and industrial technique to process a pool of feedstocks. One-pot extraction-transesterification and utilization of cheap, low quality feedstocks could be used to eliminate bottlenecks in the development of biodiesel production. An alternative pathway for biodiesel production is the one-pot extraction-transesterification process. The present work aims at the simulation and multiobjective optimisation (MOO) of a dry microalgae-based in-situ biodiesel plant, modelled using the Aspen Plus V11. The process optimisation was carried out by
excel-based multiobjective optimisation (EMOO) considering the non-dominated sorting genetic algorithm-II (NSGA-II). Economic and environmental criteria were considered for constrained MOO with total annualised cost (TAC), organic wastes, and CO2 emissions as objectives. The statistical trade-offs were analysed by assessing the impacts of the decision variables on the chosen objectives. Firstly, bi-objective optimisation scenarios were studied, and finally, a tri-objective optimisation scenario was investigated. The results imply that the TAC increases with the decrease in organic waste generation and CO2 emissions. The decision-makers will be able to assess the Pareto-optimal front to find the preferred optimal solution to enhance plant performance. The first rank solution in the generated Pareto-optimal front was chosen by the net flow method (NFM). Compared to the base case study with a TAC of 69.31 million USD, Scenario 1, Scenario 2, and Scenario 3 resulted in an optimal plant operation with a TAC of 62.64 million USD, 61.52 million USD, and 60.23 million USD, respectively, with a saving of 6.67 million USD, 7.79 million USD, and 9.08 million USD respectively. Simultaneous optimisation of all three conflicting
objectives yielded significant reductions in TAC (13.1%), organic waste (55%), and CO2 emissions (41%), respectively.