A novel process-level carbon contribution analysis (PCCA) method for carbon minimization of chemical processes: Exergy mapping to carbon emissions

Abstract

A well-known method for the environmental impact analysis of the chemical processes, life cycle assessment (LCA) has several limitations to apply to the process design and optimization stages. To overcome these limitations, this study proposed a novel carbon analysis and reduction method at the process level. The proposed LCA-free framework consists of four steps: process simulation, thermodynamic analysis, process-level carbon contribution analysis (PCCA), and carbon optimization. PCCA allows a detailed analysis of the CO2 contribution of each component by mapping exergy information to the CO2 emission. By applying the proposed method to the naphtha cracking center to minimize CO2 emissions, CO2 from utilities can be reduced by 8.72%. Compare to energy optimization, carbon optimization under the PCCA framework shows there is an optimal operating condition that emits less CO2 even though requires more utility duty. The proposed framework has four clear advantages: (i) it can estimate tailored emission factors for target processes at the process level, instead of relying on average values in conventional inventory, (ii) optimize the usage of utilities by type at the process design stage from a carbon perspective, (iii) provide a direction for economic optimization by giving information on the relationship between carbon emissions and energy consumption, and (iv) quantify the reduction in carbon emissions compared to existing processes when designing newly designed carbon reduction processes. Consequently, this study establishes a powerful methodology for the rigorous carbon emission analysis for chemical processes and offers guidelines for carbon reduction at the process level.