Novel pulp mill wastewater recovery process for CO₂ and SO_x utilization

Pulping industry has a pulp mill process that emits a significant amount of carbon dioxide (CO₂) and sulfur oxides (SO_x). The pulp mill wastewater has a high potential for reducing pollution caused by CO₂ and SO_x because it contains useful mineral ions in high concentrations, such as Ca²⁺, Mg²⁺, Na⁺, and K⁺ that react with carbonate and sulfate ions. In this study, we develop a novel pulp mill wastewater recovery process for CO₂ and SO_x utilization. To design the CO₂ and SO_x capture and utilization process using pulp mill wastewater, a process model is developed based on validated experimental data. The developed process model comprises the following three steps: (1) metal ion separation of pulp mill wastewater to produce KClO₄, Mg(OH)₂, and Ca(OH)₂; (2) SO_x capture and utilization using Ca(OH)₂ and SO_x, utilized as desulfurization gypsum; (3) CO₂ capture via generated KClO₄, and the captured CO₂ is utilized as carbonate using Mg(OH)₂ and Ca(OH)₂. Accordingly, the economic feasibility of the suggested process model is demonstrated by calculating the pay-back period in economic assessment. As a result, the desulfurization efficiency was 99% with high-purity gypsum production. In addition, ∼98.2% CO₂ was captured. Furthermore, the annual profit was increased by USD 94,469, and thus, the pay-back period was determined as 8.4 y.