Hydrodynamic problems of a three-phase fluidized bed are considered. The main attention is paid to experimental studies into the process of cooling industrial circulating water in a three-phase layer. An experimental setup was developed and assembled, and its brief description and operating principle are given. Adjustment experiments and experiments with a two-phase fluidized bed were carried out, the main task of which was to determine the dependence on the air velocity in the apparatus of the hydraulic resistance of a dry grate without a nozzle. A series of experiments is described that made it possible to establish the optimal cooling mode for circulating water in an apparatus with a three-phase fluidized bed. The experiment was carried out at both constant and variable irrigation density, and the experiments were repeated at different air velocities. The following parameters of the three-phase fluidized bed were recorded: hydraulic resistance, the rate of onset of fluidization, the rate of entrainment, and the height of the dynamic bed. The results of experimental studies into the fluidization rate and entrainment rate at various ball nozzles and the dependence of the dynamic height of a three-phase fluidized bed on the rate and density of irrigation are presented. Experimental data have been obtained on the pressure drop in a three-phase fluidized bed depending on the air velocity, the rate of the beginning of fluidization of the irrigated bed of the packing, and the rate of flooding of the three-phase fluidized bed as a function of the irrigation density. The analysis of hydrodynamic and thermal processes occurring in a three-phase fluidized bed is carried out, and the main technological parameters for the optimal operation of installations with the specified bed are obtained in relation to solving the problem of cooling the circulating water. The dependence of the expansion of a three-phase fluidized bed on air velocity and irrigation density has been investigated. On the basis of the performed experimental studies, empirical formulas for calculations are derived.