An amine scrubber is used to treat the sour gas, which contains amine solution. By absorbing saur gas into this amine solution, tail gas and sweet sulphur free gas are produced. Tail gas also called as off gas, contains sulphur compounds including hydrogen sulfide.
sulphur recovery unit recovers the elemental sulphur from hydrogen sulfide (H2S) using claus process. sulphur recovered from this process in the range of 95-98%. Claus process was first invented by Carl Friedrich Claus in 1883, and later was modified by IG Farben, a German chemical company.
The basic claus process contains two parts- one thermal stage and two to three catalytic stage. The chemical reaction is shown as below-
2 H2S + SO2 ? 3 S + 2 H2O
Thermal stage consist thermal reaction furnace, heat removing boiler and mixing chamber. In this thermal reaction furnace H2S is heated at high temperature above 850 °C, in combustion and converted into the elemental sulphur. Basically, in this stage some of the hydrogen sulfide is converted in SO2. Left H2S is reacted with these SO2 in further thermal and catalytic stages, in order to produce elemental sulphur.
Later using the heat removing boiler, reaction furnace gases are cooled and passes through the Claus reactor and sulphur compounds are changed into sulphur in few stages. Claus reactors contain in-line heater upstream which are used to improve the efficiency of the process. Another further improvement in the efficiency of sulphur removal can be achieved by tail gas treatment. Tail gas which contains hydrogen sulfide and carbon dioxide, also called as off gas is treated in tail gas treating unit (TGT). H2S is removed from the Elemental sulphur through degassing process.