# Biomass-Based Chemical Looping Gasification: Overview and Recent Developments
## 5 Progress in Biomass Chemical Looping Gasification
### Pilot-Scale Investigations  
Along with thermodynamic analysis and kinetic study, BCLG in experimental test rigs has been intensively investigated in the temperature range of 600-1300 \({}^{\circ}\)C using vari ous types of biomass, typically woody biomass to evaluate the feasibility of the process. Different pilot-scale configurations have been used in the BCLG studies, commonly fixed bed [42; 43; 45; 90] and fluidized bed reactors [25; 26; 32; 33]. One of the key performances in those studies is the reactivity of oxygen carriers in the BCLG process. Various oxygen carriers have been investigated including Fe-based [26; 32; 67; 68; 69; 70], Ni-based [25; 44], Cu-based [71; 72], Mn-based [28], Zn [73], bimetallic oxygen carriers (Fe-Ni [31; 74], Fe-Cu [71; 75], etc.). Additionally, the oxygen carriers were supported by supporting materials, such as SiO\({}_{2}\)[30], Al\({}_{2}\)O\({}_{3}\)[26; 33; 42], CaO [43; 85; 86], MgO [45], TiO\({}_{2}\)[69; 84], etc., to improve their reactivity and multifunctional properties, including catalytic function, tar decomposition and CO\({}_{2}\) adsorbent. A 25 kW\({}_{\text{th}}\) system was developed by [PERSON] et al. [30] to investigate the performance of rice husk gasification chemical looping using hematite as an oxygen carrier. The system mainly consists of a high-velocity fluidized bed as the AR and a bubble fluidized bed as the FR. The main components of hematite are Fe\({}_{2}\)O\({}_{3}\), SiO\({}_{2}\), and Al\({}_{2}\)O\({}_{3}\) with 83.21 wt.%, 7.06 wt.%, and 5.37 wt.%, respectively. The higher performance of BCLG with hematite, such as higher carbon could obtain at 860 \({}^{\circ}\)C, while carbon conversion efficiency reached a peak at oxygen carrier/biomass ratio of 1.0. [PERSON] et al. [31] experimentally investigated the performance of Fe-Ni bimetallic oxides as oxygen carriers that were applied for biomass chemical looping gasification. The experiments were performed in a 10 kW\({}_{\text{th}}\) interconnected circulating fluidized bed which mainly consists of a fast fluidized bed as the AR and a bubbling bed as the FR. Sawdust of pine was used as feedstock. The experimental results indicated that the content of CO, H\({}_{2}\), and CH\({}_{4}\), as well as process performance, increased with the rising gasification temperature. The Fe-Ni bimetallic oxygen carriers displayed a higher gasification efficiency of biomass and showed a stable reactivity and good sintering resistance. [PERSON] et al. [73] proposed a novel process for chemical looping gasification. The high-temperature solar-driven chemical looping gasification of lignocellulosic with ZnO/Zn redox pair was developed to evaluate the advantages and reliability of the combined process. Experiments were carried out in a lab-scale solar reactor at a range temperature from 1050 to 1300 \({}^{\circ}\)C with a biomass/solid ratio from 0.5 to 1. Biomass feedstock was been wood for the experiments. The experimental set-up mainly consists of the solar reactor, solar concentration system, gas injection, and particle feeding system, filtering unit, and gas analysis unit. A fixed ratio mixture of ZnO and biomass particles was placed in the hopper, and then the reactor was heated up to the required temperature by concentrated sunlight. During the study, the influence of temperature and reactant molar ratio on syngas production was analyzed. The result successfully demonstrated the feasibility of the process for the first time, and optimal operating conditions for the study were found at 1250 \({}^{\circ}\)C and a biomass/ZnO molar ratio of 0.75. Additionally, the temperature of Zn production was lower than that for ZnO thermal dissociation. A study was carried out to evaluate the multi-functional oxygen carrier for hydrogen-rich syngas production [129]. An iron-based oxygen carrier was developed from the Bauxite residual of the alumina industry (red mud).