Reconsidering the CAPEX/OPEX compromise for chemical plants design optimization under emissions-oriented operation scheduling

• Chemical plants economics need to be revised to account for the current energy landscape • Operation and plant flexibility are required to optimize renewables-assisted chemical processes • For large operating windows, more restrictive feasibility constraints should be considered • With the increasing cost of energy and concern for sustainability OPEX play the most critical role • Distillation columns sizing heuristics are provided to manage variable capacity scheduling In order to meet the duty availability from the energy-mix-fed grid and minimize the consumption of fossil fuel, the concept of steady state is undergoing a substantial reconsideration. Flexible scheduling has indeed become the priority of next generation chemical plants which should be able to operate over a wide window. In addition, the increasing cost of energy and the carbon taxes have shifted the predominance from investment to operating costs and new heuristics should be then conceived. In this research, a biogas-to-methanol case study was set up to quantify the impact of bio-feedstock and emissions-oriented operations on process design. A particular focus was dedicated on the reactor and distillation columns. The study quantifies the best CAPEX/OPEX balance and design decisions for flexible operations at variable capacity. In addition, the economic analysis prove that, for a system designed with an oversizing factor up to 2.5 times with respect to the nominal value, the mitigation of carbon emissions is able to compensate the investment gap with respect to the fossil-based route. This promising outcome could be the starting point for a set of revised heuristics for both new process design and existing plants revamping.