The desulphurisation unit is mainly used to inject various chemicals such as desulphurising agents, neutralisers and defoamers into the single wells and gathering pipelines. Through the desulphurisation unit, defoamer is pumped into the residual acid in the high pressure zone upstream of the process to effectively remove the foam. A neutraliser is then added to the defoamer in the middle of the process via the desulphurisation unit to effectively neutralise the pH of the returning residual acid to make it neutral or weakly alkaline. Finally, downstream of the process a desulphurising agent is added to the neutralised liquid via the desulphurisation unit to achieve the ultimate goal of desulphurisation.