Abstract
The aim of this research is to evaluate the possibility to realize alkali-activated materials exploiting biochar, a secondary raw material coming from pyrolysis/gasification processes, for environmental benefits, such as improvement of soil fertility and reduction of CO2 emissions into the atmosphere thanks to the carbon sink process where carbon dioxide is subtracted from the cycle of carbon. For the matrix of the geopolymers, a waste material derived from incinerator bottom ash was used and compared to pure metakaolin matrix. The materials obtained are lightweight and porous, with high water absorption capacity and moisture adsorption/desorption. BET analysis shows an increase in specific surface by increasing the biochar content and the biochar acts as a filler in the pores. From porosimetry analysis it is possible to follow the evolution of the curing process of the geopolymer prepared: specimens containing 70 wt% biochar after 28 and 90 days showed an increase in total Hg intrusion volume, pore area and total porosity but a decrease in the dimensions of pores. Due to the technical properties of materials containing biochar, they can be used in the future for a cleaner design of products in the field of sustainable construction for insulating panels or lightweight materials for houses and gardens in terraces and balconies.
Highlights
Vegetable biomass can be treated by combustion, gasification or pyrolysis according to the scheme reported below (Figure 1): If the chemical oxidation between a fuel and a comburent is total, combustion takes place and thermal energy and new components are generated.For the biomass the combustion takes place in three steps: drying, pyrolysis-gasification, oxidation of coal and combustible gases If the oxidation of a liquid or solid material at temperatures between 800 and 1100 ◦ C is partial, gasification is realized and the products are gases (CO, H2, CO2 and CH4 ) with medium-low calorific value, a fraction of heavy hydrocarbons condensable at room temperature and a solid residue consisting of the inert fraction of the treated material
The second is a commercial product derived from the processing of municipal incinerator bottom ash (IBA) supplied by an authorized industrial plant located in Northern
The aim of this research was to evaluate the possibility of realizing lightweight alkaliactivated materials exploiting biochar
Summary
Vegetable biomass can be treated by combustion, gasification or pyrolysis according to the scheme reported below (Figure 1): If the chemical oxidation between a fuel and a comburent (generally oxygen) is total, combustion takes place and thermal energy and new components are generated. For the biomass the combustion takes place in three steps: drying (water evaporation), pyrolysis-gasification (biomass degradation in the absence or partial presence of oxygen), oxidation of coal and combustible gases If the oxidation of a liquid or solid material at temperatures between 800 and 1100 ◦ C is partial (i.e., with air in a quantity lower than the stoichiometric one), gasification is realized and the products are gases (CO, H2 , CO2 and CH4 ) with medium-low calorific value, a fraction of heavy hydrocarbons condensable at room temperature (tar) and a solid residue consisting of the inert fraction of the treated material (char). The products are: a low-medium calorific gas fraction containing CO; CO2 ; hydrocarbons (CH4 , C2 H4 , C3 H6 ); H2 O; H2 ; an oily liquid fraction containing tar, water and low molecular weight organic compounds such as aldehydes, acids, ketones, alcohols; and a solid product consisting of residues with a higher molecular weight such as carbonaceous portions (char), ashes, inert materials and metal species.
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