Limestone Fredonia

Figure 3. Dissolution rate at pH 5.8 vs. reciprocal temperature—Fredonia limestone.

Figure 4. Fredonia limestone dissolution rate vs. stirring rate, (50°C pH 5.8).

Stirring rate appeared to have little effect on the CaC03 and MgC03 dissolution rates for the Fredonia limestone at pH 5.8. 

Limestone Utilization. Two types of limestone were used for regenerating the spent scrubber liquor Fredonia limestone from Kentucky, ground to 96.A wt. % through 325 mesh, with a Ca content of 93.6 wt. % as CaCO and Mg content of A.2 wt. % as MgCO and Sylacauga limestone from Alabama, ground to 97.7 wt. % through 325 mesh, with a Ca content of 95.7 wt. %, and Mg of 1.3 wt. %. 

Although very limited information was collected while using Fredonia limestone during the startup and break-in period, all indications were that this limestone exhibited performance characteristics comparable to the Sylacauga limestone used during the testing period. 

Fifteen runs using three limestones are reported for various reactor conditions. A base case experiment was performed for each of three limestones 1) Fredonia, 2) Brassfield, and 3) Pfizer (see Tables II and III). Operating conditions were then varied to show the effect of stir rate, temperature, and pH as well as reactor feed composition. 

Each stone was ground and sized to 120-200 mesh in an attempt to minimize differences in surface area between the samples. Based upon optical counts of the three sized stones, each sample used in the experiments had approximately the same average particle diameter (Fredonia - 134 pm, Pfizer - 147 pm, Brassfield - 133 pm). However, no attempt was made to correct for any surface area differences due to different limestone porosities. 

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