High purity H2 by sorption-enhanced chemical looping reforming of waste cooking oil in a packed bed reactor.

High purity hydrogen (>95%) was produced at 600 degrees C and 1 atm by steam reforming of waste cooking oil at a molar steam to carbon ratio of 4 using chemical looping, a process that features redox cycles of a Ni catalyst with the in-situ carbonation/calcination of a CO(2) sorbent (dolomite) in a packed bed reactor under alternated feedstreams of fuel-steam and air. The fuel and steam conversion were higher with the sorbent present than without it. Initially, the dolomite carbonation was very efficient (100%), and 98% purity hydrogen was produced, but the carbonation decreased to around 56% with a purity of 95% respectively in the following cycles. Reduction of the nickel catalyst occurred alongside steam reforming, water gas shift and carbonation, with H(2) produced continuously under fuel-steam feeds. Catalyst and CO(2)-sorbent regeneration was observed, and long periods of autothermal operation within each cycle were demonstrated

Autothermal reforming of palm empty fruit bunch bio-oil: thermodynamic modelling

This work focuses on thermodynamic analysis of the autothermal reforming of palm empty fruit bunch (PEFB) bio-oil for the production of hydrogen and syngas. PEFB bio-oil composition was simulated using bio-oil surrogates generated from a mixture of acetic acid, phenol, levoglucosan, palmitic acid and furfural. A sensitivity analysis revealed that the hydrogen and syngas yields were not sensitive to actual bio-oil composition, but were determined by a good match of molar elemental composition between real bio-oil and surrogate mixture. The maximum hydrogen yield obtained under constant reaction enthalpy and pressure was about 12 wt% at S/C = 1 and increased to about 18 wt% at S/C = 4; both yields occurring at equivalence ratio Φ of 0.31. The possibility of generating syngas with varying H2 and CO content using autothermal reforming was analysed and application of this process to fuel cells and Fischer-Tropsch synthesis is discussed. Using a novel simple modelling methodology, reaction mechanisms were proposed which were able to account for equilibrium product distribution. It was evident that different combinations of reactions could be used to obtain the same equilibrium product concentrations. One proposed reaction mechanism, referred to as the ‘partial oxidation based mechanism’ involved the partial oxidation reaction of the bio-oil to produce hydrogen, with the extent of steam reforming and water gas shift reactions varying depending on the amount of oxygen used. Another proposed mechanism, referred to as the ‘complete oxidation based mechanism’ was represented by thermal decomposition of about 30% of bio-oil and hydrogen production obtained by decomposition, steam reforming, water gas shift and carbon gasification reactions. The importance of these mechanisms in assisting in the eventual choice of catalyst to be used in a real ATR of PEFB bio-oil process was discussed

Chemical looping reforming of waste cooking oil in packed bed reactor.

Chemical looping steam reforming for hydrogen production from waste cooking oil was investigated using a packed bed reactor. The steam to carbon ratio of 4 and temperatures between 600 and 700 degrees C yielded the best results of the range of conditions tested. Six cycles at two weighted hourly space velocities (WHSV of 2.64 and 5.28 h(-1)) yielded high (>0.74) and low (<0.2) oil conversion fractions, respectively, representing low and high coking conditions. The WHSV of 2.64 h(-1) yielded product concentrations closest to equilibrium values calculated assuming a fresh rapeseed oil composition. Repeated cycling revealed some output oscillations in reactant conversion and in the extent of Ni-NiO conversion, but did not exhibit deterioration by the 6th cycle. The selectivity of CO, CO(2) and CH(4) were remarkably constant over the performed cycles, resulting in a repeatable syngas composition with H(2) selectivity very close to the optimum

Characterisation of palm empty fruit bunch (PEFB) and pinewood bio-oils and kinetics of their thermal degradation

Ultimate and proximate analyses and thermal degradation of bio-oils from pinewood and palm empty fruit bunches (PEFB) were carried out to evaluate the oils' potential for production of fuels for transport, heat and power generation, and of hydrogen via the calculation of performance indicators. The pinewood and PEFB oils indicated good theoretical hydrogen yields of 13.7 and 15.9wt.% via steam reforming, but their hydrogen to carbon effective ratios were close to zero, and their propensity for fouling and slagging heat exchanger surfaces via combustion was high. Both oils exhibited two phases during mass loss under nitrogen flow at heating rates of 3-9Kmin , but the kinetics of their thermal degradation from TGA-FTIR analysis indicated different degradation mechanisms that were well reproduced by a nth order reaction model for pinewood and Jander's 3D-diffusion model for PEFB. These findings lead to recommendations on pretreatments prior to the oils' utilisation

Durability of CaO–CaZrO₃ Sorbents for High-Temperature CO₂ Capture Prepared by a Wet Chemical Method

Powders of CaO sorbent modified with CaZrO have been synthesized by a wet chemical route. For carbonation and calcination conditions relevant to sorbent-enhanced steam reforming applications, a powder of composition 10 wt % CaZrO/90 wt % CaO showed an initial rise in CO uptake capacity in the first 10 carbonation-decarbonation cycles, increasing from 0.31 g of CO/g of sorbent in cycle 1 to 0.37 g of CO/g of sorbent in cycle 10 and stabilizing at this value for the remainder of the 30 cycles tested, with carbonation at 650 C in 15% CO and calcination at 800 C in air. Under more severe conditions of calcination at 950 C in 100% CO, following carbonation at 650 C in 100% CO, the best overall performance was for a sorbent with 30 wt % CaZrO/70 wt % CaO (the highest Zr ratio studied), with an initial uptake of 0.36 g of CO/g of sorbent, decreasing to 0.31 g of CO /g of sorbent at the 30th cycle. Electron microscopy revealed that CaZrO was present in the form of ≤0.5 μm cuboid and 20-80 nm particles dispersed within a porous matrix of CaO/CaCO; the nanoparticles are considered to be the principal reason for promoting multicycle durability