Limestone testing with forced oxidation

Tests without forced oxidation also demonstrated the efficacy of adipic acid. Operating a TCA scrubber with 2,000 ppm adipic acid and 6 inches H2O pressure drop, 92 percent SO2 removal was obtained at a limestone utilization level of 88 percent. By comparison, only 75 percent SO2 removal would be expected in the pilot plant at these test conditions without the additive. At this adipic acid level, the unoxidized sludge filtered to 49 percent solids at lower adipic acid levels (1,500 ppm or less), the... 

Limestone Long-Term Tests with Two Scrubber Loops and Forced Oxidation. The venturi/spray tower system was modified for two-scrubber-loop operation with forced oxidation as shown in Figure 2. Two tanks were used in the oxidation loop (venturi loop) air was injected to the first of these tanks through a simple 3-inch diameter pipe below the agitator. Adipic acid was dry-fed to the spray tower effluent hold tank. This was accomplished by manually adding one-pound increments hourly to maintain specified concentration, usually totaling only a few pounds per hour. A small screw feeder would serve the purpose in a full-scale plant. 

Adipic Acid-Enhanced Limestone Tests on the Two-Loop Venturi/Spray Tower System with Forced Oxidation... 

Limestone Tests with Bleed Stream Oxidation. A major advantage of the bleed stream oxidation is its simple flow configuration. In operation without forced oxidation, the scrubber bleed stream would be sent directly to the solids dewatering system. 

Limestone Long-Term Test with One Scrubber Loop and Without Forced Oxidation. Perhaps the most straightforward illustration of the effectiveness of adipic acid is demonstrated by a long-term limestone test conducted on the Shawnee TCA system, in which the additive was introduced without any system modifications. 

Limestone Long-Term Test with One Scrubber Loop and Forced Oxidation. A one-scrubber-loop system has an inherent advantage over a two-scrubber-loop system in its simple design and lower capital and operating costs. If a simple one-loop limestone (or lime) system is operated with adipic acid, which offers the advantage of lower operating pH, then both good SO2 removal and sulfite oxidation can be achieved with minimum cost. 

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