Real-time Three-Dimensional In-Situ Imaging of Structural Evolution of Coal During Coke Making Process Using Adaptive Electrical Capacitance Volumetric Tomography

This project is concerned with the conversion of coking coal-to-coke with the primary aim of developing a deeper understanding of the evolution of the plastic (fluid) layer during the coking process using a new non-intrusive and non-optical imaging technique known as Adaptive Electrical Capacitance Volumetric Tomography (AECVT). Coke is an important industrial product that is made predominately by thermal decomposition of coking coal for use in the iron ore smelting process. The quality of coke largely depends on the evolution of its porous structure which is the result of a complex process. When coking coal is heated in a coke oven, it softens, coalesces into thermoplastic matter, and then resolidifies into the final porous structure. Transformation into thermoplastic matter corresponds to the formation of a thin foam-like plastic layer consisting of molten vitrinite and liptinite, inert coal components (i.e., inertinite macerals) and the volatile matter that is entrapped inside the layer.

Due to the transient nature of the plastic layer, imaging methods capable of capturing the temporal features of the layer during its initial formation and follow-on progress are highly sought after. Imaging techniques such as magnetic resonance imaging (MRI) and X-ray microfocus computed tomography (μ-CT), have been successfully employed to investigate the evolution of the plastic layer. However, by and large these methods are ex-situ requiring samples to be taken out of the coking process, quenched, and then tested for characterisation of structural properties and/or features. A truly in-situ imaging technique capable of monitoring the progress of the plastic layer uninterrupted and without the need for sample taking/quenching, is still lacking. This capability gap can be potentially narrowed down using the AECVT technique. Therefore, the main goal of this project is to assess the technical viability of the AECVT technique in imaging of selected coals during the coking process.

The project was undertaken in two parts:

• Adoption of the AECVT technique for coke characterisation studies.
• Focuss on the application of the AECVT technique to generate sufficiently detailed and quantitative data that accurately describe the temporal and spatial evolution of the plastic layer.

Outcomes:

• Adoption of the AECVT technique for coking characterisation studies was successful.
• A novel series of experiments were devised and carried out, aimed at assessing the capabilities of the AECVT sensors in detecting a range of materials, particularly coal and coke, under various conditions.
• Real-time volumetric tomographic imaging including cross sectional views (2D and 3D), isometric view, and volume fraction plots at different conditions were successfully conducted and the obtained images are presented.
• Valuable insights into the detectable flow range, bubble coalesces, and particles movement within the AECVT sensors by analysing real-time imaging data was obtained.
• The AECVT sensors have demonstrated great performance when employed for the analysis of multiphase flow for a broad range of applications beyond the coking process depending on the level of particle motion, bubble size and material properties such as dielectric constant.