In-depth experimental study of pyrolysis characteristics of raw and cooking treated shrimp shell samples

Shrimp shells discharged in large quantities causes serious environmental pollution. Pyrolysis is a promising method to achieve the resource utilization of discarded shrimp shells as renewable energy. However, the distribution and the characteristics of pyrolysis products are strongly determined by the volatile-char interactions. On the other hand, cooking treatment changes the properties of shrimp shells, making the pyrolysis process more complicated. The focus of this study is to explore the pyrolysis mechanism of both raw and cooked shrimp shells by observing the interactions among volatiles as well as the reactions between volatiles and char. The results showed that char accounted for 60–70 wt% in the pyrolysis products, tar occupied about 20 wt%, and the rest was gases. In the volatile-char interactions, H radicals combined with the special sites to promote the volatilization of the N-containing components and aromatic compounds. Interestingly, a large amount of carbon was stabilized in CaCO3, which was tightly doped with organic carbon in char. Meanwhile, the secondary reactions among volatiles caused the cyclization and dehydrogenation of the N-containing compounds. After cooking treatment, the partial structures of organics became more easily cracked, and more H radicals went deep into the carbon matrix to generate more volatiles.