Design and multi-objective optimization of a biomass based multi-generation energy system

In this paper, a novel multi-generation system(MGS) comprising a biomass gasification process, a supercritical( S-CO2) cycle and a Multi effect distillation forward feed (MED-FF) unit is proposed and investigated, to produce power, pasteurized milk, H2, O2and distillate water production. The system is modeled and developed, using Exergy and exergoeconomic analysis, in EES (engineering equation solver) software. The effects of key parameters as (main compressor inlet temperature (T1), turbines inlet temperature (T5), main compressor inlet pressure (P1), intermediate pressure between HP and LP turbines (P6), producer gas mass fraction (MF) and equivalence ratio(ER) on the energy and exergy efficiencies, as well as distillate flow and total product cost rate, is investigated. Moreover, the total cost rate of the proposed system and the system efficiencies are selected as three objective functions in anon-dominated sorting genetic algorithm(NSGA-II). Three decision makers as LINMAP, TOPSIS and SHANNON ENTROPY are applied to select the optimum performance of the system. The results show that at the base point the energy and exergy efficiencies of the system are 65.51% and 43.61% respectively and the total product cost rate is 0.02268($/s). TOPSIS method with the deviation indexof 0.2686 indicates a more reliable solution than what is obtained from other methods. The TOPSIS methodindicates a more reliable solution, than the other method’s solutions, and the improvements for energy and exergy efficiencies and total product cost rate within TOPSIS method are 3.61%, 4% and 3.1%, respectively

Keywords:

Biomass gasification , Multi-generation energy system , Desalination , thermoeconomic , Optimization