Oxygen enrichment, roaster

The oxygen-enriched blast has been successfully tried in the zinc sulfide concentrates roasting in fluidized-bed, multiple-hearth, and suspension roasters. As early as 1956, Electrolytic Zinc Company of Australia improved calcine grade, increased oxidation rates, and facilitated use of cold blast to the hearth roasters for better temperature controls. Other nonferrous metals, such as molybdenum, copper, nickel, and lead, that use roasters to oxidize sulfide concentrates are technically and economically amenable to oxygen enrichment. 

Fluidized-bed roasting accounts for most of the world zinc production today. Over the last 15 years, several zinc roasters have augmented their calcine production capacities with oxygen enrichment. These roasters typically encounter production increase limitations due to existing blower capacities, requirements for fluidization characteristics of the bed, and downstream gas-handling capacities. Oxygen enrichment provides roaster operators with a tool to increase roaster capacity in a cost-effective way. Several roaster plants utilize oxygen enrichment to improve calcine... 

Oxygen Enrichment vs. Production Increase in Fluid-Bed Zinc Roasters... 

Oxygen Enrichment of Fluid-Bed Zinc Roasters — Plant Results... 

Use locally purchased liquid oxygen for the present expansion and then modify the roasters to operate without oxygen enrichment upon duplication. 

From the computer model, it was shown that oxygen enrichment of the fluidizing combustion air was a feasible option to increase roaster throughput without an increase in roaster air volume. 

Oxygen enrichment of the fluidizing air can alter the heat balance of the roaster operation. In essence the cooling effect of the nitrogen is reduced and roaster bed temperatures are increased, causing a corresponding increase in roaster quench water. However, there is a net reduction in off gas volume that permits either an increase in feed rate or a reduction in the upward velocity of the gases in the roaster. 

Oxygen enrichment of the roaster fluidizing air, the planned elimination/reduction of air ingress and targeted control of off-gas oxygen partial pressure has resulted in an increased SO2 partial pressure at the converter. On occasions dilution air is allowed into the gas stream under controlled conditions. Prior to 1996, Zincor did not require the use of dilution air for SO2 control at the converter. 

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