Process for the preparation of sulphur dioxide

In a process for the preparation of sulphur dioxide comprising thermally decomposing a metal sulphate and/or a metal hydrogen sulphate in a fluidized bed reactor having a fluidized layer and being supplied with fluidizing air, with a sulphurcontaining reducing agent selected from the group consisting of sulphur, iron pyrites and a mixture thereof, the improvement which comprises

• (a) controlling the amount of reducing agent to sulphate in a manner such that there is an sufficient amount of reducing agent to convert the sulphate to sulphur dioxide, "said amount being insufficient to provide all the necessary heat for the process",
• (b) supplying 75 to 99% of the balance of the necessary energy to convert the sulphate to sulfur dioxide by a first energy supplier, said first energy supplier being a fuel selected from the group consisting of coal, coke, heavy fuel oils and mixtures thereof, said first energy supplier being fed into the fluidized bed reactor along with the metal sulphate and the sulphur containing reducing agent,
• (c) supplying the remainder of the balance of the necessary energy to convert the sulphate to sulphur dioxide by a second energy supplier selected from the group consisting of fuel oil, natural gas and finely divided coal, the second energy supplier being introduced separately into the fluidized layer of the fluidized bed reactor and the second energy supplier being introduced into the reactor by mixing the fluidization air and
• (d) controlling the amount of the second energy supplier so that a reaction temperature of 800.degree. C. to 1100.degree. C. is maintained in the reactor.