Perspective directions of the development of hydrotransport gravity mixers installations in the light of existing industrial solutions

For fire prevention Polish hard coal mining has used mixtures of ash and water liquidshilts made on the basis of fine-grained energy wastes, which task is to fill free spaces by minimizing the possibility of oxygen access from mine air. The hydromixtures is prepared in surface mixer installations and gravitationally transported by a pipeline system to underground workings. Considering the availability of fine-grained energy waste in the immediate vicinity of hard coal mines, it should be assumed that this type of fire prevention will be successfully used in the future. The effectiveness of this method depends primarily on the efficiency and optimal operation of the mixing plant. The paper presents the evolution of mixing systems used in the last decades in hard coal mines with the division into generations, as well as the prospective directions of their development.