Mekhanobr Tekhnika Research and Engineering Corporation:

V. A. Arsentev, Director for R&D, Doctor of Engineering Sciences
L. A. Vaisberg, Research Manager, Corresponding Member of the Russian Academy of Sciences
I. D. Ustinov, Marketing Director, Doctor of Chemical Sciences
A. M. Gerasimov, Researcher, Candidate of Chemical Sciences, gornyi@mtspb.com

High-ash coal preparation employs mainly “wet” methods with water flow rate of 5–10 t per 1 t of coal. Recycling water supply lowers “fresh” water demand but it is still required to pump considerable volumes of water slurries, which needs much power. On the other hand, dry preparation of low-grade coal using modern technologies is low efficient. This study focuses on the supposition that it is expedient to precede dry preparation of high-ash coal by thermochemical treatment stage and, then, to employ physicomechanical methods aimed to produce low-ash high-energy product. The use of the mentioned chemical transformation opens up new possibilities of processing of heat-treated middlings, namely:
• Reduction in energy input of crushing and milling owing to decreased mechanical strength;
• Complete removal of ash using “dry” preparation methods only;
• Production of agglomeration semicoke using clean hydrocarbon fraction;
• Use of roasted mineral fraction to produce special binders, concrete admixtures and building units.
It is difficult to separate mineral powders less than 1 mm in size based on their magnetic and electric properties since internal friction forces in powders prevent from efficient separation of particles. It is possible to overcome these forces using the so-called vibro-combustion under certain vibrational impact. The application of this effect has allowed engineering of high-performance separators to recover individual finely dispersed mineral particles based on magnetic and electric properties. These separators have been employed in this study. Efficiency of thermochemical modification of coal and coal preparation products is evaluated using such index as the ash yield per unit calorific capacity. It has been found that cleaned semicoke 3 times exceeds original coal with respect to this index. It is proved that moderate temperature pyrolysis of both black coal and lignite improves disintegration of incombustile mineral fraction, which favors its recovery using dry preparation methods later on — combination of high-rate magnetic and triboelectric separation techniques. After such preparation process, semicoke as solid fuel has higher quality than conventionally dressed coal, and dry preparation tailings are disposable.
This study has been supported by the Russian Science Foundation, Project No. 15-17-300015.

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