Designing and integrating NO_x, SO₂ and CO₂ capture and utilization process using desalination wastewater

Numerous industries are facing serious environmental contamination, because of the significant emission of nitrogen oxide (NO_x), sulfur dioxides (SO₂), and carbon dioxide (CO₂) and it has become imperative to reduce these gaseous emissions. To reduce pollution caused by gaseous emissions, desalination wastewater is possible to be used because it contains highly concentrated useful mineral ions such as Ca²⁺, Mg²⁺, and Na⁺ which react with carbonate, nitrogen, and sulfate ions. This work designed and integrated NO_x, SO₂, and CO₂ capture and utilization processes using desalination wastewater for cleaner production. To design and integrate the NO_x, SO₂, and CO₂ capture and utilization process, a process model is developed based on validated experimental data. The proposed process model comprises the following three steps: (1) electrolysis and metal ion separation of desalination wastewater to produce NaOH, Mg(OH)₂, and Ca(OH)₂; (2) NO_x and SO₂ capture and utilization via Ca(OH)₂; (3) CO₂ capture and utilization using NaOH, Mg(OH)₂ and Ca(OH)₂. Then the economic feasibility of the suggested process is demonstrated compared to conventional process by economic assessment. As a result, the NO_x and SO₂ are captured and utilized at about 90% and 99% respectively. In addition, the CO₂ is captured at about 91% and the conversion yields of each carbonate are 99% and 63% respectively. To demonstrate the economic feasibility of the proposed process, two cases are set. Case 1 is the case that employs selective catalytic reduction (SCR), wet flue gas desulfurization (WFGD), and a CO₂ capture process that uses amine as a CO₂ absorbent with an electrodialysis reclaiming unit. Case 2 is the case that employs SCR, WFGD, and the CO₂ capture process that uses amines with an ion-exchange resin reclaiming unit. As a result, the total annualized cost of the proposed process was ∼7.9% and 14% lower than those of Case 1 and Case 2, respectively.