The coal to ethylene glycol (CTEG) process has drawn much attention due to the serious conflict between supply and demand of ethylene glycol in China. However, it is inevitably accompanied by the problem of high CO₂ emissions. Carbon capture is one of the most promising potential effective ways to address this issue. However, the CTEG process, integrated with carbon capture technology, will lead to energy and economic penalties. Thus, a comprehensive evaluation of CTEG process with different CO₂ capture technologies is urgently needed. This study analyzed the technoeconomic performance of four CO₂ capture alternatives for the CTEG process: Rectisol, mono-ethanol amine (MEA), chilled ammonia process (CAP) and dimethyl carbonate (DMC) technologies. Results show the energy consumption of CO₂ capture of the Rectisol process is the lowest, 1.88 GJ/tCO₂, followed by the DMC process, 2.10 GJ/tCO₂, the CAP process, 3.64 GJ/tCO₂, and the MEA process, 5.20 GJ/tCO₂. The CO₂ capture cost of the Rectisol process is lowest, CNY 169.5/tCO₂, followed by the DMC process, CNY 193.2/tCO₂, the CAP process CNY 232.6/tCO₂, and the MEA process CNY 250.5/tCO₂. As the Rectisol technology has the best comprehensive performance, it is the best option for CTEG industry in comparison with the MEA, CAP, and DMC technologies.

The screening of high-efficiency and low-energy consumption absorbents is critical for capturing SO₂. In this study, absorbents with better performance are screened based on mechanism, model, calculation, verification, and analysis methods. The acidity coefficient (pK_a) values of ethylenediamine (EDA), piperazine (PZ), 1-(2-hydroxyethyl)piperazine (HEP), 1,4-bis(2-hydroxyethyl)piperazine (DIHEP), and 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)piperazine (HEHPP) are calculated by quantum chemical methods. A mathematical model of the SO₂ cyclic absorption capacity per amine (α_c) in the amine-based SO₂ capture process is built based on the electroneutrality of the solution. Another model of desorption reaction heat (Q_des) is also built based on the van’t Hoff equation. Correspondingly, α_c and Q_des of the above five diamines are calculated and verified with the experimental data. The results show that α_c of the diamine changes with the increase in the pK_a value, and the increase in the pK_a value directly leads to changes in Q_des. The order of α_c of the above five diamines is EDA > PZ > HEHPP > HEP > DIHEP, and the order of Q_des is EDA > PZ > HEHPP > DIHEP > HEP. The multiobjective analysis between α_c and Q_des suggests that it is not advisable to simply pursue a higher α_c while ignoring Q_des. The compound quaternary system absorbent has a wider range of α_c than the single ternary absorbent, which is the direction of absorbent development. This study is expected to strengthen absorbent screening for the amine-based SO₂ capture process from flue gas.