Pyro-gasification of municipal solid waste for hydrogen production: A Sustainable Efficiency Analysis (SEA) from Norwegian perspective

Abstract

The sustainable management of Municipal solid waste (MSW) or Industrial Solid Waste (ISW) is a critical challenge, particularly in regions with surplus energy potential, such as Norway. The emissions from waste incineration plants and lack of energy efficiency drive to exploration of more efficient waste conversion technology. Chemical Looping Technology (CLT) is a new thermochemical technology gaining attraction due to its efficient waste-to-hydrogen conversion with combined heating and power. The study explores the potential hydrogen, and heat production with efficient carbon capture from ISW and MSW using Sorption Enhanced Chemical Looping Gasification (SE-CLG), and Sorption Enhanced Chemical Looping Gasification with Pyrolysis (Pyro-CLG). To achieve this, the ISW was characterized as it is a critical step for effective plant design. Three models were developed for model development and training using Aspen plus V11 software focusing on key parameters such as gasifier temperature and Oxygen Carrier (OC) selection. Out of three OCs, Ca2Fe2O5 was selected with 92.41% hydrogen production efficiency. However, the problem associated with using directly Ca2Fe2O5 in the gasifier was the formation of CaSiO3 with the interaction of ash formed in gasification which reduces its reproducibility for the looping. To solve this problem, a new model was developed combining Pyrolysis and Chemical Looping Gasification (Pyro-CLG) with acid leaching for the pretreatment of char and ash separation before char gasification with OC as the heavy metal trace presence was mentioned in ISW obtained from previous studies. 3-E (Energy, Exergy, and Environment) analysis was performed on the two models: SE-CLG2, and Pyro-CLG using OC: Ca2Fe2O5 and waste: ISW & MSW. The energy efficiency obtained for SE-CLG2 was 69.11% (ISW), 67.51%(MSW), and for Pyro-CLG 62.38%(ISW), and 59.143%(MSW). The exergy efficiency obtained for SE-CLG2 was 57.29% (ISW), and 55.16%(MSW), and for Pyro-CLG 52.59%(ISW), and 47.84%(MSW). The GWP and AP values obtained for SE-CLG2 were 2.74kgCO2-equiv. 19.031kgSO2-eqiv. (MSW), 13.94kgCO2-equiv. 57.32kgSO2-eqiv. (ISW), and for Pyro-CLG 33.62kgCO2-equiv. 19.017kgSO2-eqiv. (MSW), and 81.34kgCO2-equiv. 57.28kgSO2-eqiv. (ISW). 170 kg hydrogen with 4300litre 100OC hot water, and 142.8kg with 4000litre 100OC hot water were produced per ton MSW and ISW in SE-CLG2. Hydrogen production drops 16% and 20.17% when the Pyro-CLG model is used for MSW and ISW. For the Pyro-CLG model, the net product decreases by a moderate margin than SE-CLG2 for both MSW and ISW. So, if the production of more hydrogen and hot water can overtake the manufacturing cost of Ca2Fe2O5, then the SE-CLG2 model is recommended. Otherwise, the Pyro-CLG model is suitable for implications. The MSW was found more prone to hydrogen production ISW was more toward energy and exergy efficiency.