Figure 2. SEM images of PPS-based bag filter materials with different loading units (All the bars are 10μm).
failure sample (5#) than partly failure sample (3# and 4#), showing that the cracks would extend with the increase of the content of SO2. In other words, the higher content of SO2 is, the larger depth of cracks is, the deeper damage of the fiber is. Besides, the service life of 5# is deeply destroyed below 200 MW is only 6 months, while that of 1# and 2# is more than 20 months, indicating that the structure transformation of fiber surface has nothing to do with the service life in factories.
The same trend of structural evolution on fiber surface was observed with the addition of SO2 content for samples loading units between 200 and 300 MW (sample 6#-10#) and above 300 MW (sample 11#-15#). This illustrates that the loading unit of coal-fired power plants is independent of the variation of fiber surface. It’s worth mentioning that the dust particles are attached to the fiber surface for all samples. Commonly, the dust particles would be removed from the network of bag filter by the cleaning operation, and the fiber surface should be smooth in accordance with the original morphology of PPS fibers. The appearance of particles on the fiber surface indicates that the roughness of fibers becomes obvious with the occurring of fiber degradation[9, 31], the interaction between the fiber and particles increases with absorbance of particles on the fiber surface, and thus above phenomenon can be explained. The absorbance of particles around the fiber is larger for sample 5#, 9#, 10# and 15#, whose SO2 content are higher as 4000 mg/m3 than other samples, and this is consistent with the degradation degree of PPS-fiber in the working conditions. The higher the content of SO2 is, the larger degradation degree is, the rougher of fiber surface is, and thus the easier of particle adsorption becomes. Besides, the trapped particles would increase the filtration resistance in the following cycling process of dust removal, thus the performance of bag filters becomes worse with the increase of SO2 content in the system.