Towards an electrochemical process for recovering sulphur dioxide

Research is reported on the development of a process to electrochemically o xidise sulphur dioxide gas, absorbed into sulphuric acid solutions. This pr ocess is aimed at the recovery of potentially valuable sulphur species, fro m waste and effluent gases, as sulphuric acid. A small pilot scale sieve-pl ate electrochemical reactor (SPER) is used for the oxidation of SO2. The SP ER is an undivided cell using, in this case, monopolar connected electrodes . The anode material was platinised titanium or lead dioxide and the cathod e material was zirconium metal or Ebonex(R), both materials do not form sul phur in the electrolysis of SO2 in solutions of sulphuric acid. Typical cur rent efficiencies are above 80% at current densities of 10-20 mA cm(-2). En ergy consumptions are between 1.8 and 2.4 kWh kg(-1). Production of sulphur ic acid at concentrations of 6 mol dm(-3) by anodic oxidation of SO2 is dem onstrated. The mass-transfer behaviour of the sieve-plate reactor is partic ularly good for this reaction involving relatively low concentrations of di ssolved SO2 concentration. The behaviour of the sieve-plate reactor is math ematically modelled. (C) 1999 Elsevier Science S.A. All rights reserved.