Acorn gasification char valorisation in the manufacture of alkali activated materials

Abstract

The use of biomass for energy production is becoming increasingly common. An energy source with good prospects for the future is the gasification process of biomass waste. This process is characterized by the partial oxidation of the raw material at high temperatures, which converts the raw material into a mixture of combustible gases. However, one of the problems when using biomass is the ash produced in the gasification process. This study investigates the effect of the incorporation of ash generated in the production of syngas from biomass residues from the acorn industry on the physical, mechanical and thermal performance of electric arc furnace slag (EAFS) based alkaline activated cements for industrial applications. Acorn gasification ash (AGA) after a calcination process were used to replace EAFS at different substitution ratios: 0, 25, 50, 75 and 100 wt%. The influence of the modulus of the activator (Ms = SiO2/K2O = 0.89; 1.38 and 1.84) was also studied. The specimens were evaluated for density, porosity, flexural and compressive strength, thermal conductivity, X-ray diffraction analysis, infrared spectroscopy, and microstructure development at 1, 7, 28 and 56 days of curing. The results showed that the inclusion of up to 50 wt% AGA gives rise to cements with similar or higher compressive strength than the control cement containing only EAFS. The optimum activator modulus depends on the proportion of precursors used, increasing with increasing AGA content. Therefore, the activator ratio and AGA content are factors that must be considered simultaneously to achieve the optimum compressive strength. The main reaction product was C-(A)-S-H gel, and to a lesser extent K-(A)-S-H gel and C-K-(A)-S-H hybrid gel. This work suggests the use of AGA improve alkali activated metallurgical slag binders, partially substituting the conventional Portland cement as structural material.