Thermodynamic investigation of waste cooking oil based hydrogen generation system with chemical looping process

The thermodynamic features of hydrogen production via chemical looping reforming of waste cooking oil were studied at atmospheric pressure using Gibbs free energy minimization, accounting for the possibility of coke formation. The synthesis gas composition was determined as a function of reforming temperature (400–1000 °C), steam to carbon ratio (S/C, 1–14) and NiO to carbon ratio (NiO/C, 0–2). To evaluate the thermodynamically plausible products, the study started with an expanded product set of approximately 30 by-products. The results show that coke formation can be thermodynamically inhibited by increasing the S/C ratio and/or the NiO/C ratio. The conditions that maximize hydrogen production, minimize methane and carbon monoxide content as well as avoid coke formation at thermoneutral conditions were found to be S/C = 5, T = 600 °C and NiO/C = 0.493. Under these conditions, a hydrogen yield of 144.3 mol/kg of soybean waste cooking oil can be obtained, which appears to be an attractive result for starting experimental research.