Objective  The aim is to solve a series of problems such as the decrease of total conversion rate, selectivity and sulfur recovery rate of direct selection oxidation sulfur recovery unit and the high alkali consumption of downstream tail gas treatment unit, so as to ensure the efficient operation of the unit.

Methods  The operation status of isothermal and adiabatic two-stage reactors of direct selection oxidation sulfur recovery unit was analyzed, respectively, and the solution of replacing adiabatic catalysts was proposed. Through investigation and laboratory experiments, the silica-based catalyst was finally selected and the adiabatic catalyst was replaced.

Results  After replacing the adiabatic catalyst with a silica-based catalyst, both the adiabatic conversion rate and selectivity were greatly improved. Compared with the previous catalyst, the adiabatic conversion rate and selectivity were increased by more than 55 percentage points. Compared with the initial operation of the original titania-based catalyst, the adiabatic conversion rate was increased by 17.10 percentage points, the adiabatic selectivity was increased by 31.54 percentage points, and the adiabatic catalyst showed higher activity and anti-peroxidation ability during the reaction process. Compared with before replacing the catalyst, the total conversion rate, selectivity and sulfur recovery rate of the sulfur recovery unit were increased to more than 95%, and the alkali consumption was reduced by 16 m³/d. Compared with the initial operation of titania-based catalyst, the total conversion rate, selectivity and sulfur recovery rate increased by 1-3 percentage points, and the alkali consumption was reduced by 11 m³/d.

Conclusion  After the adiabatic catalyst was replaced by the silica-based catalyst, the mass concentration of SO₂ in the tail gas is significantly reduced, and it is stably maintained below 100 mg/m³, which has significant environmental benefits.