4. Conclusions
The structural transformation and variation of mechanical properties of PPS-based bag filter materials collected from the coal-fired power plants with different loading units were investigated by SEM, FTIR and TG. As the SO2content increases in the flue gas, the oxidation degree of PPS fibers becomes deeper accompanying with transformation from oxidation of C-S bond to sulfonation of hydrogen in the benzene ring, and the surface evolution of above fibers from smooth to cracked occurs at the same time. But the melting point decreases with the addition of SO2 content, which is in accordance with the changing of crystalline of PPS-based bag filter materials. Thus, the reduction of crystalline and increasing of surface defeats of PPS fibers brings down the CD strength of bag filter. The major reason causing the failure of PPS-based bag filter is as follows: working temperature (T) is often passing through acid dew gas point (Ta), the SO3 would be produced from condensing of H2SO4 when T is lower than Ta. The SO3 with strong oxidation would attack the weak bonds of PPS, resulting in the oxidation or even sulfonation of PPS-based bag filters. Besides, the critical concentration of SO2 in the flue gas is lower than 1500 mg/m3, which is beneficial for the safety and long-time running of PPS-based bag filters in coal-fired power plants.
Supporting Information. Corresponding data summarized from FTIR patterns are included in supporting information.