Enhanced SO2 and CO2 synergistic capture with reduced NH3 emissions using multi-stage solvent circulation process

Abstract

NH₃-based SO₂ and CO₂ synergistic capture technology shows promise in reducing the costs associated with current flue gas desulfurization and CO₂ capture systems. However, it faces challenges such as NH₃ slip and high energy consumption. In this study, we proposed an advanced Multi-Stage Solvent Circulation (MSC) process that incorporates a desulfurization-washing solution circulation, which involved partitioned absorption according to different functions of SO₂ capture, CO₂ capture, and NH₃ emission control. The experimental results demonstrated that using desulfurization solution in place of water for washing reduced the NH₃ emissions from the absorber and desorber by 10.6 % and 7.9 %, respectively. Additionally, the recovered NH₃ enhanced SO₂ capture, resulting in a 61.8 % decrease in SO₂ emission concentration. A pilot-plant trial model for SO₂ and CO₂ synergistic capture was further developed using Aspen Plus. The impact of operational time and parameters on capture efficiency and energy consumption were analyzed. Under typical flue gas conditions, the process achieved SO₂ capture efficiency of > 99 %, regeneration energy consumption of 2.42 GJ/t CO₂, NH₃ emissions of < 5 ppm. This study presents a novel approach for designing a SO₂ and CO₂ synergistic capture system, which has the potential to facilitate the economic and effective implementation of post-combustion flue gas pollutant control management and carbon emission reduction.