BLACKGROUND The control of sulfur dioxide (SO2) emissions is vital for the treatment of flue gases of combustion. The wet flue gas desulfurization process using limestone‐gypsum is now used widely, due to its high efficiency and reliability. However, it has the disadvantages of high cost and production of hazardous by‐products. Ionic liquids are new green organic solvents that can absorb acidic gases selectively. Hydroxyl ammonium ionic liquids with different anions were synthesized by neutralization and used to separate SO2 from simulated flue gas at low partial pressure of SO2. RESULTS The absorption capacities of SO2 using ionic liquids were 1.02 mol/mol, 1.19 mol/mol, and 3.34 mol/mol for [TEOA][AC], [TEOA][LA] and [TEOA][CA], respectively, at the SO2 partial pressure of 4 kPa. Viscosity of ionic liquid affected the absorption process. A longer time was required to attain absorption equilibrium in the case of [TEOA][CA]. Low temperatures favoured absorption because the process was exothermic. Water in flue gas accumulated in the ionic liquids, causing a reduction in absorption of SO2. A mixture containing different ionic liquids could decrease the viscosity and achieve optimal absorption capacities. The ionic liquids could be recycled and regenerated by desorption at high temperature. A reduction of ≈2% in absorption capacities was found after four cycles of regeneration. Analysis of the absorption mechanism indicated that nitrogen atoms in the cationic part of ionic liquid molecules were the predominant site for combined chemical and physical absorption processes. CONCLUSION Hydroxyl ammonium ionic liquids exhibited excellent potential for absorption of SO2 at low partial pressure by combined chemical and physical absorption processes. © 2019 Society of Chemical Industry

Particle pollution has been a research topic attracting the attention of the researchers around the world because inhalable particles are hazardous to humans and the environment. The major resource of particle pollution is the combustion of coal and biomass. Dust collectors, electrostatic precipitators, and bag filters are required to remove particles from flue. Because of the large specific surface areas of inhalable particles, they easily agglomerate to form larger aggregates; therefore, improving the capture efficiency of dust collectors is of importance. Herein, chemical agglomeration agents were sprayed into a turbulent agglomeration chamber to improve the removal efficiency of inhalable particles. The results showed that the total removal efficiency of inhalable particles was 59.2% for the three-composition agglomeration agents of kappa carrageenans/Tween-80/NH 4 Cl (KC/TW/NH 4 Cl). The mean particle diameter increased from 2.8 μm before agglomeration to above 10.0 μm after agglomeration. In the agglomeration process, nonionic TW accelerates the wetting properties, in which the polymer, KC, or anion polyacrylamide, promotes prolongation of the contact time between droplets and particles. Two different removal mechanisms are proposed to explain the effect of chemical agglomeration agents. Immersion agglomeration described the agglomeration process of only fine particles, and distribution agglomeration supported the capture of large particles for fine ones in polydispersed aerosols.