Life cycle assessment and exergoeconomic analysis of the multi-generation system based on fuel cell for methanol, power, and heat production

Abstract

The main purpose of present investigation is to evaluate a multi-generation process by Life Cycle Assessment (LCA) and exergoeconomic analysis methods. This integrated system is composed of Methanol Synthesis Process, Molten Carbonate Fuel Cell (MCFC), and Combined Heat and Power system.This exergy – based evaluation is comprised of three items: (1) exergy evaluation to assess the efficiency and performance of the multi-generation system, (2) exergoeconomic evaluation to express a relationship between overall costs and the performance of the hybrid system, (3) exergoenvironmental evaluation to present useful information about the mutual impact of the process’s performance and environmental conditions. By applying the exergoeconomic and exergoenvironmental analyses, The process simulation and exergetic evaluation are conducted by the Aspen HYSYS V 11 and MATLAB software, respectively.This configuration provides 271.7 kgmole/h pure methanol, 110,544 kW net power, and 65398.7 kgmole/h hot water (at 80 °C). The total exergy efficiency and destroyed exergy rate of this multi-generation configuration are obtained to be 58.4% and 128549 kW, respectively. About 41.28% of the total exergy destruction rate occurred in the MCFC. The results of exergoeconomic assessment illustrate that the highest overall cost is associated with MCFC (4836.87 $/h). In addition, the burner has the least value of exergoeconomic factor (1.47%). So, to improve the cost-effectivity of the system, the burner should be re-designed. According to the exergoenvironmental analysis, the greatest values of overall environmental impacts belonged to MCFC (4033.13 Pt/h) and burner (1501.99 Pt/h), respectively. Accordingly, to decline the negative environmental impacts of the system, the operating conditions of selected devices must be modified. Finally, the 3D sensitivity analyses for four main devices are implemented. By using this sensitivity evaluation, the thermodynamic parameters that need to be optimized are specified.