A Reduced-Order Fluid Flow Model for Gas Injection into Porous Media: For Application in Carbon Sequestration in Mine Tailings

Abstract

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.

A techno-economic analysis of diesel exhaust injection into mine tailings for carbon sequestration

“…1 An illustration representing the proposed carbon sequestration approach tailored for off-grid mining sites (modified from Ref. [ 12 ]). …”

“…So far, a (1 + 1)D reduced-order model (ROM) was developed to predict the pressure profile for a perforated pipe embedded in a cylindrical block [ 12 ]. However, in practical scenarios, the tailings blocks will typically have a rectangular shape (illustrated in Fig.…”

“…For all the cases investigated here, the perforation scheme was selected based on the framework established and rigorously tested in Ref. [ 12 ]. In this configuration, the center-to-center distance of the perforations, known as pitch ( ), was the same in both axial (along the length of the pipe) and radial (along the circumference of the pipe) directions.…”

“…Due to their cold climatic locations, mines operating in remote areas depend heavily on fossil fuels, particularly diesel, for essential functions such as power generation and heating [ 11 ]. The injection of diesel flue gas from the power-generating units into mine tailings to capture and store holds the potential to reduce the carbon footprint of those operations significantly [ 12 ].…”

“…To bridge this knowledge gap, the present study further developed an existing framework (outlined in Ref. [ 12 ]) to devise an energy-optimal approach for flue gas injection into mine tailings for carbon sequestration. Drawing upon this framework, a comprehensive cost analysis was undertaken to assess the potential operational expenses linked with injecting diesel exhaust into mine waste for carbon capture.…”