L04 Desulphurisation of smoke

Aim: To show how sulphur is removed from smoke

Ideally, fuel should be made sulphur-free before burning, as occurs with some of the gas from the gas fields in the Netherlands. If this is not possible, the sulphur can be removed from the exhaust gases of large furnaces in a number of ways. The wet desulphurisation process is shown in a simplified form on illustration L4.
The sulphur-containing exhaust gas is passed through a reaction chamber. Water is sprayed into the top of the chamber and the water droplets as they fall absorb sulphur dioxide :

 

   The resulting mixture of sulphur dioxide, sulphurous acid and water is collected and transported to a second chamber containing limestone chip (CaCO3). The calcium carbonate reacts with the sulphur dioxide forming calcium sulphite.


This calcium sulphite is further oxidised with oxygen from the air in an oxidation reactor to calcium sulphate.


The product can be used in the manufacture of plaster, but the quantities are such that most of it is dumped.