Optimal retrofit planning of pulp and paper industrial integrated energy system for enhancing flexibilities and carbon reduction capabilities

Pulp and paper industry (PPI) is a traditional energy-intensive sector with a high carbon footprint. Promising carbon reduction and energy storage technologies have endowed PPI with a certain level of environmental sustainability. However, considering these technologies in the retrofit planning of pulp and paper industrial integrated energy system (PPIIES) is challenged by the currently oversimplified energy flow and equipment models as well as the lack of consideration of carbon trading mechanism and production process scheduling. To address this, this paper proposes an optimal planning framework for PPIIES characterized by detailed carbon trading, carbon reduction equipment, and heat storage model with in-depth exploration of production flexibilities. Specifically, we first propose the improved Carbon Capture (CC), Steam Accumulator (SA), and Pressurized Unit (PU) models for retrofitted PPIIES with high, medium, and low steam pressure levels. Then, a European Union Allowance (EUA) and Certified Emission Reduction (CER) embedded optimal planning model for PPIIES is established. Ultimately, we examine the planned capacity and economic performance of PPIIES across various carbon market periods with typical technology combinations and process scheduling options. Results demonstrate that the proposed model can reduce the integrated costs by 13 % and the carbon emission by 36 %.