chemical mechanism
　　1）absorption theory
　　Limestone-gypsum FGD process adopts lime slurry as a sorbent which reacts with SO2 in the flue gas to form CaSO3,and CaSO3 reacts with oxygen to form CaSO4, and further crystallizes into gypsum(CaSO4 •2H2O). This FGD process is applied most popular with high removal efficiency and reliability.

　　2）Chemical equation
　　CaCO3 + SO2 + ½ O2+2H2O =CaSO4.2H2O+CO2

　　Features
　　-- Limestone as a sorbent, that is abundant, cheap non-toxic and harmless.
　　-- Utilization of the sorbent can be over 90%.
　　-- Gypsum as a by-product can be used widely.
　　-- Forced oxidation.
　　-- High SO2 removal efficiency is over 95%.
　　-- Rate of auxiliary power is lower than 1.5%.
　　-- Capacity for single tower can be 600mw or above.
　　-- Flexible auxiliary system
　　-- Reliability is as high as 99%
　　-- Both one boiler with one tower and several boilers with one tower are available. Synchronous inspection with the boiler is available.
　　-- All FGD process can be monitored by central monitoring system of the power plant.