Novel process of hydrogen production from liquids of biomass origin

摘要

This thesis aims to investigate for the first time the chemical mechanism and efficiency of the process of unmixed steam reforming (also known as chemical looping reforming in a packed bed reactor) in producing hydrogen when utilising liquids of waste biomass origin as the feedstocks, in particular waste cooking oil. Moreover, the optimisation of unmixed steam reforming is investigated by incorporating a natural CO2 sorbent, calcined dolomite, in the reactor bed material, resulting in the process called Sorption Enhanced Unmixed Steam Reforming, which operates by shifting the reactions toward more favourable thermodynamics. The characteristic properties of three liquids of waste biomass origin (waste cooking oil, and fast pyrolysis oils from EFB -palm empty fruit bunches- and pinewood), are examined, including their decomposition kinetics by numerical modelling for the first time. The sorbent's efficiency, as expressed by its extent of C02 intake and release is examined at both 'micro'- and 'macro'-scales (i.e, from few mg to few g samples) through the kinetics of the carbonation and calcination reactions in conditions simulating sorption enhanced unmixed steam reforming, in addition to its durability in both set ups. These are compared to the sorbent's performance during the sorption enhanced unmixed steam reforming of the waste cooking oil throughout several chemical loops or cycles. The chemical looping (cyclic operation) of both processes is assessed using the Ni-NiO and CaO-CaC03 'loops', and compared against the equivalent process in thermodynamic equilibrium. The production from waste cooking oil of a nearly pure H2 stream (>96% vol), with a hydrogen yield enhancement of between 29 and 120%, with long periods of autothermality per cycle, at lower molar steam to carbon ratios (2.5 and 4) and lower temperatures (by 200°C) than the literature to date on steam reforming of equivalent virgin vegetable oils is shown. This investigation thus demonstrates the success in producing H2 from waste cooking oil using these advanced steam reforming processes, auguring promising results for similarly challenging organic waste liquid fuels.