Thermodynamic Evaluation of the Cross-Current Moving-Bed Chemical Looping Configuration for Efficient Conversion of Biomass to Syngas

Abstract

The rising chemical demand and its associated concern of climate change have put an impetus on converting diverse domestic sources to valuable products in a decarbonized manner. Lignocellulosic biomass, a viable feedstock, is garnering significant attention as a sustainable alternative to fossil fuels. However, challenges in handling biomass feed variability and effectively processing its char and tar contents have hampered its commercial deployment. However, the chemical looping-based biomass-to-syngas (BTS) technology being developed by The Ohio State University is among the most promising technologies for industrial biomass reforming. It utilizes proprietary iron oxide particles in a cocurrent moving-bed reactor, leveraging the flow dynamics to transform biomass to syngas, and has been proven to be more efficient than conventional processes. However, this cocurrent system suffers from a thermodynamic barrier, inhibiting the syngas yield. To overcome this barrier, a novel chemical looping crosscurrent system is developed and investigated through detailed thermodynamic ASPEN studies after accounting for practical constraints. The barrier in the cocurrent system can be attributed to the equilibrium between exiting syngas and solid streams, which limits the oxidation of oxygen carriers. The cross-current reactor system overcomes this issue by shifting the exit of the syngas stream to the middle of the reactor, thus not allowing the exiting syngas and solid streams to be in equilibrium and creating a cocurrent section above the syngas exit and a countercurrent section below it. Thermodynamic simulations conducted under autothermal conditions reveal that the cocurrent and cross-current systems perform similarly with steam and CO 2 co-injection. However, under an isothermal condition, which is now feasible with cheaper and sustainable heating methods, the cross-current system achieves ∼34% higher syngas yield over the cocurrent system (∼0.074 in cross-current compared to ∼0.055 in cocurrent) for both steam and CO 2 co-injection. The findings from this study justify the scale-up of the cross-current system and provide system-level insights into biomass valorization.

A Novel 2-Reactor Chemical Looping System for Hydrogen Production with Biogas as the Feedstock: Process Simulation and Comparison with Conventional Reforming Processes

“…When the H 2 O/CH 4 ratio increases to 3.9, the particles are completely oxidized into Fe 3 O 4 . Although the oxidation of Fe 3 O 4 to Fe 2 O 3 in the presence of steam is not greatly favored by thermodynamics, very high flow rates of steam can lead to the formation of Fe 2 O 3 in small amounts . Therefore, increasing the H 2 O/CH 4 ratio beyond 4.0 results in the formation of Fe 2 O 3 phase in the OC particles.…”

Hydrogen Production from Biomass-Based Chemical Looping: A Critical Review and Perspectives

“…Joshi's group 148 proposed the use of a lab-scale fixed bed reactor to evaluate the influence of Sr-, Mg-doped LaGaO 3−δ on the performance of Fe 2 O 3 , achieving high H 2 yield of 9.75 mmol g −1 . Similar work was also conducted by Zeng et al 149 using lab-scale fixed bed reactors for CLHP reactions.…”

“…Fluidized bed reactors are also widely utilized in CLHP processes. ,, Much research work has been done for the development of the reactors (Figure ). The results show that fluidized bed reactors offer significant advantages for use in chemical looping of H 2 production systems.…”

Chemical looping methanol oxidation using supported vanadium phosphorous oxide carriers for formaldehyde production

“…Chemical looping is a system involving redox reactions in two or more steps, facilitated by an oxygen carrier, and has been successfully applied for applications such as syngas and H 2 production. [21][22][23][24][25][26][27][28][29][30] Instead of co-feeding air with methanol, in the chemical looping approach, methanol reacts with the lattice oxygen of the carrier to form formaldehyde. The carrier provides the active site as well as the oxygen for executing the reaction.…”