Patent ID: 6083862
Filing Date: 2000-07-04
Classification: C01B,C01F

Abstract:
A process for oxidizing calcium sulfide, said process comprising the steps of:exposing particles contained in waste solids produced by coal gasification comprising calcium sulfide and a source of carbon in a fluidized bed reactor having an upper part, a lower part, a middle part, and a bottom, to a treatment cycle conducted at a temperature within a temperature range greater than 900.degree. C. by circulating said particles freely between the lower part of the fluidized bed reactor maintained in a reducing state and the upper part of the fluidized bed reactor maintained in an oxidizing state so that said particles are treated repeatedly to oxidation and reduction;creating reducing conditions of said reducing state in the lower part of the fluidized bed reactor by supplying oxygen in a fluidizing gas to the bottom of the fluidized bed reactor in an amount less than 50% of the stoichiometric amount required for complete combustion of the carbon in feed particles comprising calcium sulfide and carbon, wherein incomplete combustion of the carbon supplies carbon monoxide and hydrogen reducing gases, and wherein the concentration of oxygen in said fluidizing gas is less than 10 volume %; andcreating oxidizing conditions of said oxidizing state in the upper part of the fluidized bed by introducing additional air in the middle of the fluidized bed in an amount such that oxygen supplied to the fluidized bed reactor exceeds the sum of a stoichiometric amount required for complete combustion of the carbon in the feed particles and a stoichiometric amount required for complete conversion of calcium sulfide to calcium oxide and sulfur dioxide.