Biomass Chemical Looping Gasification for High-Quality Syngas: Performance Evaluation Using Industrial Waste-derived Oxygen Carrier and Benchmarking Against Conventional Gasification

Biomass Chemical Looping Gasification (BCLG) offers significant potential as it can convert biomass into high-quality, N₂-free syngas for producing base chemicals or liquid fuels. Despite this, BCLG faces several commercialization challenges and is in its early stages of development (Technology Readiness Level, 3-5).

Since BCLG is in its initial development phases, existing research was comprehensively reviewed to identify gaps and opportunities for further advancement. Consequently, the study evaluated eight different low-cost oxygen carrier (OC) materials to identify the most suitable option for BCLG. It assessed key parameters including reactivity, H2-selectivity, mechanical strength, and sintering behavior. Overall, nickel smelter slag calcined at 1100°C was identified as the most promising OC. It demonstrated optimal reactivity (3.1×10-4 moles H2-consumption/100g sample), high H2-selectivity (8.7), adequate material strength (25 MPa), and an acceptable sintering onset temperature (963°C). Subsequently, it was utilized as OC in BCLG experiments using a fluidized bed reactor to gasify pine forest residue and evaluate the performance. Additionally, the BCLG performance was benchmarked against conventional gasification methods. The assessment examined parameters such as reactor temperature, oxygen-carrier-to-biomass ratio (OCBR), and steam-to-biomass ratio (SBR). The optimal conditions were identified as a reactor temperature of 850°C, an OCBR of 10:1 and an SBR of 1.4. It displayed a balanced gas composition of 38.9vol% H2, 19.7vol% CO, 34.5vol% CO2, and 6.6vol% CH4. Furthermore, it achieved high product gas (1.2 Nm3/kg-bio) and syngas (0.7 Nm3/kg-bio) yields, high carbon conversion (77.9%) and cold gasification (58.7%) efficiencies. Nickel smelter slag demonstrated stability and consistent reactivity with limited sintering and structural changes. However, challenges related to the agglomeration of OC were identified at higher reactor temperatures and with the use of steam. BCLG (with steam), demonstrated superior performance, with improvements in the H2/CO ratio (~111%), product gas (~30%) yield, cold gasification efficiency (~14%), compared to air/steam gasification.

The primary contribution of this doctoral research is to advance the development of BCLG as a sustainable alternative to conventional gasification technologies. By investigating low-cost materials, evaluating performance using a fluidized bed reactor and performance benchmarking against conventional systems, this research supports its progression towards commercialization.