Limestone long-term test

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. 

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. 

In summary, the objectives of this long-term test were met. High removal was consistently achieved at a good limestone utilization, and no fouling, scaling, or plugging occurred. 

Emphasis in the field tests of stone briquettes is on the long-term damage suffered by exposed marble and limestone. Because the pH variations for the existing test sites are principally variations between one rain and the next rather than from site to site, the separation of the pH effect cannot presently be achieved (except possibly in runoff chemistry on individual rains). The annual... 

This paper summarizes the results of tests conducted from July 1978 through March 1981 at the EPA, 10-MW equivalent, lime/limestone wet-scrubbing FGD test facility, during which adipic acid as an additive was tested and shown to be a powerful scrubber additive for improving SO2 removal. The optimum concentration of adipic acid is only 700 to 1500 ppm at a scrubber inlet pH of 5.2 or higher. SO2 removal efficiencies in excess of 90 percent and reliable operation were demonstrated in four long term, limestone/adipic acid runs. Factorial tests were also conducted to characterize SO2 removal as a function of gas and slurry flow rates, pH, and adipic acid concentration. Intermediate duration optimization runs and favorable economics are also reported. 

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