Production of syngas via gasification using optimum blends of biomass

Considering changes in the global climate, there is an impetus to diversify away from fossil fuels as part of efforts to reduce greenhouse gas emissions. Biomass, as a source of energy, has the potential to generate sustainable power and fuels and contribute towards a cleaner future. In fact, the utilisation of biomass as a carbon dioxide neutral organic source in an integrated system generates valuable products, and reduces waste and the consumption of non-renewable resources. Gasification, the preferred option for converting biomass to combustible gas, provides higher electrical efficiencies than combustion, whereby the syngas generated from the gasification process can be utilised to generate clean energy. In addition, syngas can be utilised for the production of ammonia and methanol thus reducing their respective dependencies on natural gas. This study will detail an optimised biomass gasification process considering multiple parameters, including the thermodynamic operating conditions, the type of gasifier (gasifying agent) and feedstock. Fundamentally, this study considers the process pathways for the recycling of multiple sources of biomass to generate high energy syngas from the available biomass options when used in combination as blends or individually. To achieve this aim, an Aspen Plus simulation model is developed for four different biomass agent-based gasification techniques using the biomass characteristics of certain Qatar biomass materials, which include date pits, manure and sewage sludge. Outcomes of the study included an optimisation of the gasification processes to yield different blending options of the biomass feedstock satisfying the downstream operations of power and fuels production. The results demonstrate the domination of date pits for two of the considered configurations with over 99% w/w date pit feed composition. Moreover, the sensitivity analysis conducted on the different configurations highlighted specific optimum operation points in terms of temperature, pressure, and oxygen and steam feed ratios. The hydrogen content in the generated syngas, considered important for the downstream production, yields a peak at approximately 850 °C and 1 bar with a modified equivalence ratio of approximately 2.5, and a ratio of oxygen supplied by an air-steam combination of approximately 0.6. The process can be further optimised by considering trade-offs between product purity or yield, profit, operating efficiency, quality of raw materials blends, and carbon footprint.