Cyclic process for oxidation of calcium sulfide

A process for oxidizing calcium sulfide, comprising the steps of:

• exposing particles comprising calcium sulfide to a treatment cycle consisting essentially of an oxidizing phase comprising oxidizing conditions and a reducing phase comprising reducing conditions, and a temperature within a temperature range of about 900.degree. C. to about 1200.degree. C. in a reactor;
• repeating said treatment cycle at least three times in the reactor whereby substantially all the calcium sulfide is converted to calcium oxide;
• removing excess heat of reaction, above heat required to maintain said temperature, from the reactor, wherein the oxidizing conditions and reducing conditions are provided in a moving bed reactor by supplying gas of varying compositions to the reactor in a periodic manner so that gas flowing through the reactor is alternately oxidizing and reducing;
• and
• treating fluidized bed reactor off-gas to remove sulfur dioxide and result in tail gas;
• and recycling tail gas to dilute the reducing gas supplied to the reactor.

A process for oxidizing calcium sulfide, comprising the steps of:

• exposing particles comprising calcium sulfide to a treatment cycle consisting essentially of an oxidizing phase comprising oxidizing conditions and a reducing phase comprising reducing conditions and, a temperature within a temperature range of about 900.degree. C. to about 1200.degree. C. in a reactor;
• repeating said treatment cycle at least three times in the reactor whereby substantially all the calcium sulfide is converted to calcium oxide;
• removing excess heat of reaction, above heat required to maintain said temperature, from the reactor, wherein the oxidizing conditions and the reducing conditions are provided in a fluidized bed reactor having a fluidized bed comprising an oxidizing zone in one part and a reducing zone in another part such that the particles circulate freely between the two zones, wherein a reducing zone is provided in a lower part of the fluidized bed by introducing a reducing gas mixture comprising from about 1 to about 50% reducing gas in the reducing zone, and an oxidizing zone is provided in an upper part of the fluidized bed by introducing an oxidizing gas mixture comprising from about 10 to about 90% oxygen;
• and
• treating fluidized bed reactor off-gas to remove sulfur dioxide and result in tail gas;
• and recycling tail gas to the reducing zone to dilute reducing gas in the fluidized bed.

A process for oxidizing calcium sulfide, comprising the steps of:

• exposing particles comprising calcium sulfide to a treatment cycle consisting essentially of an oxidizing phase comprising oxidizing conditions and a reducing phase comprising reducing conditions and, a temperature within a temperature range of about 900.degree. C. to about 1200.degree. C. in a reactor;
• repeating said treatment cycle at least three times in the reactor whereby substantially all the calcium sulfide is converted to calcium oxide;
• removing excess heat of reaction, above heat required to maintain said temperature, from the reactor, wherein the oxidizing conditions and the reducing conditions are provided in a fluidized bed reactor having a fluidized bed comprising an oxidizing zone in one part and a reducing zone in another part such that the particles circulate freely between the two zones, wherein a reducing zone is provided in a lower part of the fluidized bed by introducing a reducing gas mixture comprising from about 1 to about 50% reducing gas in the reducing zone, and an oxidizing zone is provided in an upper part of the fluidized bed by introducing an oxidizing gas mixture comprising from about 10 to about 90% oxygen;
• and
• introducing water into the fluidized bed to absorb heat and control bed temperature.

A process for oxidizing calcium sulfide, comprising the steps of:

• exposing particles comprising calcium sulfide to a treatment cycle consisting essentially of an oxidizing phase comprising oxidizing conditions and a reducing phase comprising reducing conditions and, a temperature within a temperature range of about 900.degree. C. to about 1200.degree. C. in a reactor;
• repeating said treatment cycle at least three times in the reactor whereby substantially all the calcium sulfide is converted to calcium oxide;
• removing excess heat of reaction, above heat required to maintain said temperature, from the reactor, wherein the oxidizing conditions and reducing conditions are provided in a fluidized bed reactor by supplying gas of varying compositions to the fluidized bed reactor in a periodic manner so that the gas throughout the reactor is alternately oxidizing and reducing;
• and
• treating fluidized bed reactor off-gas to remove sulfur dioxide and result in tail gas;
• and recycling tail gas to dilute reducing gas supplied to the fluidized bed.