Simulation was performed to optimize a flue gas desulfurization (FGD) system, which removes sulfur dioxide (SO
2) from flue gas. Optimum conditions were sought by studying the influence of various parameters on desulfurization efficiency and CaCO
3 availability for the limestone-gypsum method (LGM) in comparison with the magnesium hydroxide method (MHM).
When an FGD system with a cross-sectional area of 30 m
2, an absorption tower of height 15 m and a water depth in the oxidation tank of 5 m was used to treat flue gas containing 1,000 ppm of SO
2 at a flow rate of 500,000 m
3 (STP)·h
−1, we obtained the following optimum values: dissolved SO
2 concentration: under 0.001 kmol·m
−3 (LGM), 0.05 kmol·m
−3 (MHM); diameter of droplet: 1.5 mm; pH: 6.5 (MHM), solid CaCO
3 concentration: 1.0 wt% (LGM), height of absorption tower: 15 m (LGM), 10 m (MHM); and liquid flow rate of recirculation: 6,000 m
3·h
−1 (LGM), 4,500 m
3·h
−1 (MHM).
Next, we studied the control system for temporary fluctuations of SO
2 gas concentration and the flue gas flow rate by using the above design and operating conditions obtained for LGM. As a result, it was indicated that the stable maintenance of desulfurization performance was possible by the feed-back control using a PID controller.
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