## 3 Results
### Cyclical Performance and Phosphorus Transformation  
The variation in the mechanical strength of briquette cyanobacteria and the advantage of carbon conversion in the CLC process with hematite were studied. In order to further study the characteristics of briquette cyanobacteria as fuel in CLC with hematite, the redox cycle experiments were conducted to investigate the stability of hematite reactivity in terms of gas yields. A 10-cycle experiment on the reactivity of hematite in the CLC of briquette cyanobacteria was carried out in the single fluidized bed. Figure 24 shows the variation in relative gas yields of carbonaceous gas during 10 cycles at 900 \({}^{\circ}\)C. It is clear that CO gas yield is relatively high, which has been maintained at about 45% for eight cycles. CO\({}_{2}\) gas  
Figure 23: Comparison of NO concentration between (**a**) conventional combustion and (**b**) CLC at 750, 800, 850, 900 \({}^{\circ}\)C.  
yield during eight cycles also maintains at about 45%, which is relatively lower in the combustion process. CH4 gas yield is the lowest, which is stable at 10%. It is difficult for the internal carbon components of briquette cyanobacteria to react with steam or hematite OC rapidly. Therefore, some reacted carbonaceous gases escape from the outlet of the reactor before reacting with the hematite OC. However, CO2 gas yield exhibits an evident increase and CO gas yield decreases sharply. It is inferred that the reactivity between briquette cyanobacteria and hematite increases after eight cycles. The fresh calcinated and reacted hematite particles after three and 10 cycles were characterized by scanning electron microscopy (SEM) to achieve morphological feature, as shown in Figure 25. The fresh calcinated hematite particle (Figure 25a) was the original preparation OC, which had a visible sintering pattern in some parts on account of the high-temperature calcination process. As for the reacted hematite particle after three cycles, there was no evident change regarding the morphological feature. However, after 10 cycles, a distinct porous structure with many irregular small granules adhered to the surface was performed, which is propitious to the diffusion of reactant gases into the interior part of hematite particles. Therefore, CO2 gas yield or carbon conversion efficiency would increase and maintain at higher values after 10 cycles. In addition, the phosphorus transformation in the CLC of briquette cyanobacteria may vary substantially compared to the conventional combustion process. The incineration ash from conventional combustion and CLC ash collected from a 10-cycle test were analyzed by an X-ray diffractometer (XRD, Rigaku Co., Neu-Isenburg, Germany) and the qualitative results are shown in Table 4. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Composition**} \\ \hline Incineration ash & SiO2(major), CaAl2 Si2O8(major), Ca2P2O7(trace) \\ CLC fly ash & Fe3O4(major), SiO2(major), CaAl2 Si2O8(major), CaH2P2O7(trace), CaHPO4(trace) \\ \hline \hline \end{tabular}  
* The markings trace, minor and major give a comparative measure of the amount of each compound. Trace means less than approximately 3%, minor approximately 10% and major more than 10%.  
\end{table} 
Table 4: XRD results for main compositions. Figure 24: Variations in carbonaceous gas yield during a 10-cycle test at 900 \({}^{\circ}\)C.  
SiO\({}_{2}\) and CaAl\({}_{2}\)Si\({}_{2}\)O\({}_{8}\) are two main phases in incineration ash of briquette cyanobacteria. Phosphorus species in incineration ash exist mainly in the form of Ca\({}_{2}\)P\({}_{2}\)O\({}_{7}\). There are three main phases, i.e., Fe\({}_{3}\)O\({}_{4}\), SiO\({}_{2}\), CaAl\({}_{2}\)Si\({}_{2}\)O\({}_{8}\), in the CLC ash of briquette cyanobacteria. The Fe\({}_{3}\)O\({}_{4}\) is mainly from hematite OC. In addition, the phosphorus combines with hydrogen to form CaH\({}_{2}\)P\({}_{2}\)O\({}_{7}\) and CaHPO\({}_{4}\) in CLC fly ash.