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Sulfur Release and Migration Characteristics of Sewage Sludge Combustion under the Effect of Organic Calcium Compound Addition

Duan, Feng, Zhang, Lihui, Huang, Yaji
Energy & Fuels 2017 v.31 no.5 pp. 5525-5532
X-ray photoelectron spectroscopy, acetates, calcium, combustion, desulfurization, magnesium, sewage sludge, sulfates, sulfides, sulfur, temperature, thiophene
The effect of three organic calcium compound (OCC) addition on the sulfur release characteristics of sewage sludge (SS) combustion was studied using the KZDL-4A fast sulfur determination device. Results show that calcium magnesium acetate (CMA) has the highest desulfurization rate. Desulfurization rates of three OCCs significantly increase at a lower Ca/S molar ratio (R) stage while increase little as the R value reaches 4. Peak desulfurization rates both appear at 900 °C when the R value is 1 and 2. However, with increases of the temperature, no singular point is observed when the R value is 3. Meanwhile, the migration mechanisms of microscopic sulfur form during the combustion of SS, and its blends with CMA at different R values were investigate by an X-ray photoelectron spectroscopy (XPS) analyzer. Results showed that CMA impregnation has little effect on the SS sulfur functionalities. After combustion, mercaptan (S1), sulfide (S2), and thiophene (S3) decrease significantly, while sulfoxide (S4) and sulfate (S6) show inverse trends. Sulfone (S5) has the highest value. With an increasing R value, sulfoxide significantly decreases first and then increases little, while sulfate shows an inverse trend. The residual of SS/CMA-3 combustion has the highest value of sulfate. The first four kinds of sulfur are easier to release during the combustion, and these kinds of sulfur in SS are much easier to be captured using CMA.