Abstract
Typical factors considered in industrial practice for process designs are material and energy efficiency, process economics and level of environmental burden caused by the new technology. In our work, we propose addition of process safety analysis into the decision-making. To overcome lack of process data known at early design stage, we have utilized safety index methods that are suitable to evaluate process safety level with minimum process knowledge required. Safety indices incorporated into the developed multiple-criteria decision analysis (MCDA) were Process Route Index and Comprehensive Inherent Safety Index. Material and energy efficiency was assessed through E factor and Specific Energy Consumption. Total Capital Cost and Total Production Cost were utilized to assess process economy. Finally, environmental impact was evaluated by C factor and Eco Indicator 99. The proposed MCDA methodology was tested on a case study of hydrogen production from natural gas and biogas. In total, sixteen different process design alternatives were generated and simulated in Aspen Plus. Utilizing Analytical Hierarchy Procedure (AHP) method, different weights were assigned to every calculated criterion to perform MCDA. After assignment of weights, final evaluation matrix for every process design alternative was generated. For easier interpretation of results, viability maps were constructed. Viability map is a 3D figure combining generated case studies, their score in individual criteria and importance of individual criteria represented by its weight. It was found out that natural gas as a feedstock was preferable if considering material and energy efficiency, process economics or process safety as the most important criterion. However, if environmental impact had the highest importance, biogas-based options were the highest rated options. Process safety factor was decisive in specific combination of other criteria. Hydrogen production from natural gas coupled with carbon capture technology for flue gas was identified as the overall best process route.
