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

Abstract

This paper presents an original method for the micronization of coal particles in a hydro-jet mill, which allows effective comminuting of coal in the pressure range of 100–250 MPa, at a variable water flow rate of 0.2–0.5 dm3/s. The discussed high-pressure water jet mill (HPWJM) allows the comminution of standard fines, with a grain size up to 2 mm, and at a relatively high comminuting efficiency of 8 to 55 g/s. In addition, the paper presents energy-consumption ratios, and indicates the advantage of this method over mechanical grinding in a planetary ball-mill. At optimum conditions, coal comminution at an efficiency of Qc = 38.4 g/s and at an energy input of EH = 1.1 MJ/kg provides an average particle size of about 40 µm. The degree of comminution was further improved by applying roto-turbulent micronization, which resulted in an average size of comminuted coal particles of only 17 µm. As an additional result, the actual surface area of the particles increased by 10–30 thousand times when compared to ground fines—this fact is of significance for the application of micronized particles in quasi-liquid coal-water fuel.

Comminution of Polymetallic Nodules with a High-Pressure Water Jet

“…The concretions were crushed in two passes, initially using a jaw crusher to obtain feed particles with the grain size of less than 2 mm. They were subjected to final comminution in a hydro-jet mill [44] of our own design, constructed as a result of analyzing many similar designs included in the most relevant US patents [45,46] as well as in publications [47,48] from China and other countries. The hydro-jet mill uses the energy of a high-pressure water jet by following an operating principle similar to that of an abrasive water jet in a cutting head [49,50].…”

“…The percentage composition of the size of particles formed from ground polymetallic concretions is shown in Figure 7. All such particles are the feed for their final comminution performed in a hydro-jet mill [44] under the action of a high-pressure water jet. Such a method of preliminary crushing of polymetallic concretions provides approximately 23.8% by weight of particles with dimensions exceeding 1 mm, approximately 18.1% by weight of particles with dimensions of 0.7-1 mm, approximately 14.4% by weight of particles with dimensions of 0.43-0.7 mm, and approximately 43.7% by weight of the finest particles, with dimensions below 0.43 mm.…”

“…The percentage composition of the size of particles formed from ground polymetallic concretions is shown in Figure 7. All such particles are the feed for their final comminution performed in a hydro-jet mill [44] under the action of a high-pressure water jet.…”

“…The most effective comminution of concretion particles occurs when a distance of s = 10 mm is ensured in all ranges of the applied water pressures. Such a distance has already been optimized for identical comminution of brittle materials of similar dynamic strength [44]. Increasing the distance further leads to unnecessary dissipation of the water jet energy and to a gradual increase in the size of the comminuted particles.…”

Design and Experiment of Hydraulic Scouring System of Wide-Width Lotus Root Digging Machine

“…The cutting application of water jets was first introduced by Professor N FRANZ in the USA in 1968 [11,12]. Borkowski et al carried out research and discussion on the mechanism of impact crushing of coal blocks, concrete and rock hard objects by high-pressure water jets [13][14][15][16]. With the progress of technology, it is now widely used in the field of material cutting, machine and agricultural product cleaning.…”