## 3 Results
### Thermochemical Transformation of Briquette cyanobacteria in Single Fluidized Bed
#### 3.3.2 Thermochemical Transformation with Hematite as Bed Materials  
In order to investigate the effect of hematite on thermochemical transformation of briquette cyanobacteria in CLC process, the tests with hematite were conducted in a single fluidized bed. The test condition was same as the previous quartz sand tests. The selected briquette cyanobacteria samples were the samples densified at the compressive load of 1 ton  
Figure 17: Carbon conversion of briquette cyanobacteria in a single fluidized bed at different temperatures: 750, 800, 850 and 900 \({}^{\circ}\)C.  
Figure 18: Carbon conversion rate of briquette cyanobacteria in a single fluidized bed at different temperatures: 750, 800, 850 and 900 \({}^{\circ}\)C.  
and the moisture content of 10%. The fluidizing agent was also the mixture of 1.5 L/min N\({}_{2}\) and 0.8 g/min steam. However, quartz sand of 30 g was replaced by hematite of the same mass (30 g). The mass of briquette cyanobacteria was still 0.5 g.  
Figure 19a-d shows the concentrations of product gases as a function of time with hematite as the oxygen carrier. Similar to the results from the quartz sand test, the concentrations of CO, CO\({}_{2}\), CH\({}_{4}\) and H\({}_{2}\) increased during the initial minute and then decreased. The initial increases were mainly caused by the release of volatiles and the gasification reaction by the steam. Meanwhile, the effect of the temperature on product gas concentrations was also the same. Based on the results in Figure 19a-d, the temperature is crucial for product gases from briquette cyanobacteria. By comparing the peaks, it is found that all of gas concentrations show an increasing trend with the temperature, which is ascribed to the enhanced devolatilization process by increasing temperature. However, the following concentration change in CO, H\({}_{2}\) and CH\({}_{4}\) shows a fast decrease with the temperature, while the decrease in CO\({}_{2}\) concentration is relatively slowly. The product gas concentrations were the result of a series of complex and competing reactions, gas/solid mixing and hydrodynamics in the reactor. Due to the presence of hematite, a series of combustion reactions proceeded by means of a reaction (Equation (9)-(14)). A series of cyanobacteria gasification reactions are an intensive endothermic process, and the reduction reactions (Equation (9)-(14)) are also endothermic reactions. Additionally, temperature would favor the products in the endothermic reactions. On the one hand, the products (CO and H\({}_{2}\)) from cyanobacteria gasification reactions would be increased due to the higher temperature. Then, the higher yields of CO and H\({}_{2}\) and higher temperature would together promote the reduction reaction (Equation (9)-(14)), increasing the CO\({}_{2}\) yield and the reactivity of hematite with briquette cyanobacteria-dried gas products. On the contrary, the consumption of CO and H\({}_{2}\) by hematite would accelerate the  
Figure 19: Concentrations of product gases as a function of time for tests using hematite oxygen carrier as the bed material at different temperatures: (**a**) 750 \({}^{\circ}\) C, (**b**) 800 \({}^{\circ}\) C, (**c**) 850 \({}^{\circ}\) C, (**d**) 900 \({}^{\circ}\) C.  
cyanobacteria gasification process, improving the total carbon conversion efficiency and rate, as shown in Figures 20 and 21. Additionally, compared with the results in Figure 17, the carbon conversion efficiency and rate due to the presence of hematite in CLC are evidently increased.