The flue gas of a sleeve kiln (lime kiln) is characterised by low pressure, high temperature, dust content, low CO₂ content and contains impurities such as NOx and SO₂.

Ionic liquids are substances composed of anions and cations that are liquid at or near room temperature. Unlike typical organic solvents, there are no electrically neutral molecules in ionic liquids, it is all anions and cations.

Ionic liquid flue gas desulphurisation technology is mainly used for the treatment and resource utilisation of sulphur dioxide in flue gas and other industrial waste gases. This technology can recover sulphur dioxide with purity as high as 99.5% for the production of chemical products such as sulphuric acid, liquid SO2 or sulphur at the same time of efficient desulphurisation, thus realising the resourceful use of sulphur pollutants.