Carbon emission reduction strategy planning and scheduling for transitioning process plants towards net-zero emissions

In recent years, the imperative to minimise carbon dioxide (CO2) emissions has become a central concern for both government and business organisations. To address this challenge, process integration tools such as pinch analysis have been widely applied for carbon management. However, existing tools do not consider CO2 emissions, operating costs, and capital costs alongside optimal scheduling for decarbonisation strategies. To address this gap, this paper aims to present a methodology for screening cost-effective decarbonisation strategies and planning these strategies to achieve net-zero emissions in chemical process plants. The effectiveness of the methodology is demonstrated through two case studies on refinery and methanol processes. In the refinery case study, the average carbon intensity was 18.81 t CO2 per k USD of operating cost, with a total CO2 emission of 3722.97 t CO2. Three main CO2 emissions reduction strategies were deployed to achieve a 32% reduction in CO2 emissions which include biomass combined heat and power, hydrogen recycling, and water electrolysis. In the methanol case study, the average carbon intensity was 0.72 t CO2 per k USD, with a total CO2 emission of 19 678 t CO2 per day. To achieve a 49% reduction in emissions, strategies such as heat integration, compressor ratio adjustments, and recycle ratio adjustments were employed. The scheduling of these decarbonisation strategies was conducted to evaluate the respective economic feasibility of the payback period and loan required. The results indicate that implementing all strategies simultaneously results in the shortest payback period but incurs a high investment cost, leading to high financial risk. In order to lower the financial risk, the strategies are scheduled one by one by dispersing the investment costs.