Waste Gasification for Hydrogen Production

Abstract

The vision for hydrogen being at the forefront of the energy transition is already in existence, due to its high energy density and its zero greenhouse gas emissions during use. Current production methods include steam-methane reforming and coal gasification, which lead to high CO2 emissions that will amplify climate change with increasing demand. Opposite to this is waste gasification, which provides a sustainable gateway for clean hydrogen production as waste contains biogenic carbon and can attain negative carbon emissions when coupled with carbon capture and sequestration (CCS). This study concentrates on the development of a novel approach to predict the pyrolysis yields of diverse waste based on its components of cellulose, hemicellulose, lignin, polyethylene and polypropylene. The work demonstrates that the flexibility and predictive capability of an air-steam bubbling fluidised bed (BFB) gasification model for a wide array of waste types is improved. The model was rigorously validated against pilot plant data through comparison of the outlet syngas composition, the tar content, the heating value and the temperature profile across the fluidised bed gasifier at a range of conditions. The effects of the feedstock type, equivalence ratio (ER) and the steam-to-waste ratio (STWR) are investigated to determine the optimal conditions for achieving a high H2 yield, while maintaining medium heating values. It was found that a H2/CO ratio of 2.37 is achieved with an ER of 0.30 and a STWR of 1.2 using sugarcane bagasse.