One method to accelerate carbon sequestration within mine tailings from remote mines involves the injection of diesel generator exhaust into dry stack tailings. The techno-economic feasibility of this approach heavily depends on understanding the flow characteristics inside the perforated injection pipes embedded within the tailings. Two distinctive yet dynamically coupled transport phenomena were identified and evaluated: (i) gas transport inside the pipe and (ii) gas injection into the porous body of the tailings. This paper presents two models to investigate these transport phenomena, a three-dimensional (3D) and a one-plus-one-dimensional (1 + 1)D model. An experimental investigation of the pressure profile through the injection pipe was carried out to validate the models at the experimental scale. To apply the (1 + 1)D model to larger scales, the results were compared with those of the 3D model, as the (1 + 1)D model required significantly less computational resources and time. To include the effect of the perforations in the pipe on the pressure profile of the (1 + 1)D model, an analytical fluid velocity profile was developed in relation to geometric and physical parameters. The performance of the (1 + 1)D model with an impact factor was then evaluated against the 3D model results for the inlet pressure, pressure profile and gas outflow distribution under various conditions than those investigated experimentally. The developed (1 + 1)D model can be used to design an energy-efficient approach for large-scale implementation with a wide range of desired operating parameters.

Kimberlite residues mineralize CO 2 from the air into magnesium carbonate minerals [1]. These carbonation rates can be accelerated by increasing the supply of CO 2 into the tailings through injection of concentrated sources, such as diesel flue gas from mine power generation [2]. Successful injection requires careful management of physical properties (moisture content, particle size distribution, degree of compaction, and permeability) to optimize the chemical reactions and make largescale implementation feasible. These factors and their relationship to successful CO 2 injection were assessed through Proctor compaction and permeability testing and the findings were used to inform an experimental design. This experiment injected simulated flue gas into a 550 kg square meter pad of processed kimberlite from the Gahcho Kué Diamond Mine (NT, Canada), which represented a section of a larger mine-scale design. Injected CO 2 was removed from the gas phase into carbonate minerals in the solid phase as confirmed by increases in total inorganic carbon. The magnitude of carbon captured (1.4 kt CO 2 per Mt processed kimberlite) approached that attained from an idealized centimetre-scale injection experiment on the same material (2.1 kt CO 2 per Mt). This degree of reactivity implies Gahcho Kué could sequester 10 -15% of their power generation emissions in their mine waste, and the success of the experimental design proposes a manner to do so.[1] Subarctic weathering of mineral wastes provides a sink for atmospheric CO 2 , Wilson et al. (2011), Environmental Science and Technology 45, 7727-7736.[2] Strategies for enhancing carbon sequestration in Mg-rich mine tailings, Harrison et al. (2013b), Proceedings of International Mine Water Association, 593-598.

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