Application of the fractal theory for evaluating effects of coal comminution by waterjet

Abstract

Comminution of coal to ultrafine sizes by high-pressure waterjet provides a novel method for preparation of coal-water fuels for next generation, near-zero emission electric power generation. The particle size distribution (PSD) of ground coal is a key parameter in the preparation of slurries as it determines the settling behavior of the particles and viscosity of the coal-water mixture. There are several methods available for representation and evaluation of particle size analysis data. However, fractal theory provides a means by which the entire PSD of comminuted materials can be quantified by using of a specific and exact value. In this paper, a volume-based fractal model was deduced to characterize the PSD of the coal which is ground in a specially designed comminution cell. During the size reduction process, the inlet pressures up to 276 MPa were used.

Micronization of Hard Coal with the Use of a High-Pressure Water Jet

“…The analyzed subsequent designs included equipment for ultra-pure coal micronization with the use of a high-pressure water jet [33] and of coal-water slurry flowing through a labyrinthshaped comminuting channel [34]. The review also covered other coal micronization devices [6,35], as well as a test rig developed for investigating cavitation-supported hydrojet comminution of coal for the production of ultrafine coal particles [36,37], together with its technical characteristics presented in [38]. Consideration was also given to [39], which offers a detailed and comprehensive description of the methods for the fabrication and processing of various fine particles.…”

“…On the other hand, the tests showed a limited usefulness of ultrasound treatment for coal comminution in an aqueous environment [42]. Still, the usefulness of a fractal model to characterize the degree of the particle size distribution of coal [37] comminuted in a hydro-jet mill was positively evaluated.…”

Comminution Theory of Superfine Pulverized Coal Based on Fractal Analysis of Aggregate Structures

“…For example, Tang et al adopted the single power law fractal dimension to evaluate the PSD and compactability of coal gangues. Li et al characterized the PSD of coal through a volume-based fractal model and found a bifractal performance of coal particles. Moreover, the effects of coal water slurry particle size on the rheological behavior and combustion dynamics have been characterized by the fractal theory .…”