Carbonation of industrial calcium silicate slags for the production of a drought resistance increasing soil additive

The goal of this research is to investigate whether it is technically feasible to produce a material that can help reduce the effects of global warming on global crop yields by making the soil more drought resistant. This material should be produced in a sustainable and economic way starting from calcium silicate slags from the steel industry by contacting them with carbon dioxide (carbonation) during or after a milling process. Through the carbonation, Si and Ca are set free and made more available for the plant, resulting primarily in lower drought stress in addition to higher crop yield and more nutritional value. This way, climate mitigation by carbon dioxide capture and climate adaptation through increased drought resistance are combined. The first step in the investigation consists of a full parametric study of the effect of milling parameters (like milling time, ball size, ball-to-powder ratio …) on the one hand and other process conditions (like temperature and carbon dioxide partial pressure) on the other hand on the eventual characteristics of the produced material. The product’s chemical and physical properties (particle size distribution, present chemical bonds, morphology …) are determined using a wide range of analytical techniques to fully grasp the carbonation process. Using basalt as a benchmark starting material followed by the slags of both the carbon steel and the stainless steel industry, products at different levels of carbonation are produced. These are subsequently delivered to another researcher who will test the effect of these materials on plants when applied to the soil. Next, a more fundamental understanding of the forces at play during the milling process and their effect on the reaction rate and yield of the carbonation process is necessary if this technique is to be scaled up at a later stage. Therefore, experiments are carried out in apparatuses that focus on (a combination of) shear, impact or compression forces. Additionally, a tool is developed that can be used to benchmark different milling equipment using both X-ray peak broadening analysis and self-sustaining reactions. Finally, the applicability of organic solvents to increase the carbonation yield during the milling experiment is examined as well.