Published: June 1985
In this report, SRI considers versions of two general types of sulfuric acid plants: one with elemental sulfur as feed, and the other with pyrometallurgical sulfur dioxide as feed.
New sulfuric acid plants based on elemental sulfur as feed are designed to recover much more energy from the process than was heretofore economically feasible, because energy prices have risen much more rapidly than construction costs during the last decade. The retro-fitting of old (1970s) plants to increase energy recovery is also economically attractive in many cases. This report evaluates and compares typical new, old, and retrofitted plants.
In the United States and some other countries, for example, Canada, pollution control regulations have forced sulfide ore processors to modernize their production units. The modernization usually entails replacing air with oxygen or oxygen-enriched air; this change increases the sulfur dioxide concentration in the off-gas from the ore processing unit. Thus, in the modernized unit, the sulfuric acid plant uses a sulfur dioxide concentration of 10-13.5 mol% in the feed to the converter, whereas in older plants, the concentration is 4-9 mol%. The higher concentration lowers the capital cost of the plant and reduces the net energy usage. The report evaluates this type of sulfuric acid plant, and illustrates the effect of sulfur dioxide concentration on costs.