Effects of Metal Additives (Fe, Zn, and Sn) on the Co-Pyrolysis of Rice Husk and Cow Manure

Co-pyrolysis characteristics of rice husk and cow manure using SnCl2, ZnCl2 and Fe3O4 as an additive were studied in a fixed tubular furnace. The effects of additive loading amount (0–20 wt.%) on the pyrolysis processes were investigated. The thermogravimetric-derivative thermogravimetric results showed that the weight loss rate was increased with the increase of additive content. There was no obvious shoulder peak appeared after the addition of Fe3O4, while the peak of weight loss was moved to the low-temperature region with the ZnCl2 addition. Gas yield was increased with the increase of Fe3O4 content while it was decreased after the addition of SnCl2 and ZnCl2. The highest gas yield (0.39 Nm3/kg) was obtained at 20% Fe3O4. At the same time, the additives could obviously improve the quality of syngas which promoted H2 content and reduced CO content. The H2 content was increased by 7.9%, 8.88%, and 4.44%, respectively, for SnCl2, ZnCl2, and Fe3O4. The results of GC/MS showed that the additives promoted hydrogen bond breaking and the cracking of macromolecules resulting in an increase of small polycyclic aromatic hydrocarbons production. Meanwhile, the additives made a great influence on the oxygen-containing functional groups in the biochar, which increased the content of O–H and O–C–O functional groups.