## 3 Results
### Thermochemical Transformation of Briquette cyanobacteria in Single Fluidized Bed
#### 3.3.2 Thermochemical Transformation with Hematite as Bed Materials
\[\text{CO}+3\text{ Fe}_{2}\text{O}_{3}\to 2\text{ Fe}_{3}\text{O}_{4}+\text{CO}_{2} \tag{9}\] \[\text{CO}+\text{Fe}_{2}\text{O}_{3}\to 2\text{ FeO}+\text{CO}_{2}\] (10) \[\text{H}_{2}+3\text{ Fe}_{2}\text{O}_{3}\to 2\text{ Fe}_{3}\text{O}_{4}+\text{H}_{2}\text{O}\] (11) \[\text{H}_{2}+\text{Fe}_{2}\text{O}_{3}\to 2\text{ FeO}+\text{H}_{2}\text{O}\] (12) \[\text{CH}_{4}+3\text{ Fe}_{2}\text{O}_{3}\to 2\text{ Fe}_{3}\text{O}_{4}+\text{CO}+2\text{ H}_{2}\text{O}\] (13) \[\text{CH}_{4}+4\text{ Fe}_{2}\text{O}_{3}\to 8\text{ FeO}+\text{CO}_{2}+2\text{ H}_{2}\text{O} \tag{14}\]  
For a more intuitive understanding of the effect of hematite on the CLC of briquette cyanobacteria, Figure 22 shows the gas yield comparison between quartz sand and hematite. For quartz sand, CO yield decreases from the maximum (53.1%) at 750 \({}^{\circ}\)C to about the minimum (43.9%) at 850 \({}^{\circ}\)C, and then increases slightly at 900 \({}^{\circ}\)C. However, the changing  
Figure 21: Carbon conversion rate of briquette cyanobacteria with hematite in single fluidized bed at different temperatures: 750 \({}^{\circ}\)C, 800 \({}^{\circ}\)C, 850 \({}^{\circ}\)C, 900 \({}^{\circ}\)C.  
Figure 18:0 Carbon conversion of briquette cyanobacteria with hematite in single fluidized bed at different temperatures: 750 \({}^{\circ}\)C, 800 \({}^{\circ}\)C, 850 \({}^{\circ}\)C, 900 \({}^{\circ}\)C.  
trend of CO yield for hematite is completely the opposite. CO yield at 750 \({}^{\circ}\)C with hematite is evidently lower than that with quartz sand, and CO yield at 800 \({}^{\circ}\)C with hematite is higher than that with quartz sand, while the two groups of data are close at 850 or 900 \({}^{\circ}\)C. Due to the presence of hematite, part of CO would be oxidized by Fe\({}_{2}\)O\({}_{3}\) based on the reaction (Equations (9) and (10)). At the same time, the presence of hematite would enhance the carbon conversion of cyanobacteria and catalyzed crack liquid products (tar) from cyanobacteria. In addition, the stronger impact force of hematite during the fluidization process would accelerate the fragmentation of briquette cyanobacteria, which is also advantageous to the carbon conversion of cyanobacteria. Combined with the above factors, the difference in CO yield between quartz sand and hematite is not so much, especially at a higher temperature (850 and 900 \({}^{\circ}\)C). CO\({}_{2}\) yields both with quartz sand and hematite decrease to the minimum at 800 \({}^{\circ}\)C and then increase and maintain lastly with temperature. It is found that CO\({}_{2}\) yield with the presence of hematite is evidently higher, which is ascribed to the reactions (Equations (9), (10), (13) and (14)). The combustion reactions between hematite and cyanobacteria-derived gaseous products are the dominated reactions, which generate a large amount of CO\({}_{2}\). Additionally, the effect is more evident with the increase in temperature. With regard to CH\({}_{4}\) yield, less CH\({}_{4}\) is generated during the CLC process due to the redox reactions between CH\({}_{4}\) and Fe\({}_{2}\)O\({}_{3}\). At 750 \({}^{\circ}\)C, CH\({}_{4}\) yields with two bed materials are close. It is inferred that although CH\({}_{4}\) is consumed by Fe\({}_{2}\)O\({}_{3}\), the pyrolysis or gasification of cyanobacteria is enhanced by hematite.