## 2 Literature Review
The effect on the fluid dynamics of a fluidized bed of various parameters was studied: gas injection time into the bed, gas flow velocity and bubbling regime [25], bubble dynamics during nonspherical particles fluidization [26], continuous injection of the central air jet into the bed [27], and features of the pseudo-two-dimensional two-zone gas-solid fluidized bed [28], from the features of solid particles and gas bubbles [29]. Researchers also paid attention to the study of the interphase heat transfer intensity between particles and the gas flow [30] and heat transfer to heat exchange surfaces located in the layer [31; 32; 33; 34]. The research in [31] studied the effect on the heat transfer of the gas flow uneven distribution, which led to the heat transfer intensification due to the higher packet updating frequency. The research in [32] considered the influence of the rate of contact renewal between solid particles and a vertical heat tube placed in a fluidized bed. In [33], the influence of the bubble frequency and gas retention on heat transfer with vertical tubes dipped into a fluidized bed was studied. Since the coefficients of heat transfer between particles and heat transfer surfaces are higher in the center of the layer than at its periphery, it is proposed in [34] to use a gas distributor with an inhomogeneous nozzle array to overcome the unevenly distributed heat transfer. Thus, the above review of scientific articles showed that researchers direct their efforts to a detailed study of the hydrodynamic and structural features of the fluidized bed to increase the operating efficiency of the device. However, at the same time, one of the significant drawbacks of fluidized beds consists of rather high energy costs to weigh a significant amount of material on a gas distribution grid (more than 1-2 m\({}^{3}\) of gas/kg of product). The separation of small particles of less than 500 um in size from the fluidized bed leads to the formation of large volumes of dusty exhaust gas with a low dust concentration in it. Purification of such gases from dust requires powerful gas cleaning systems. The fluidized bed devices for organizing the motion of gas-dispersed flows are between shaft-type devices (with particles of material falling downward and moving countercurrent of gas) [35; 36] and pneumatic transportation devices (with direct ascending flow motion) [37]. Both types have disadvantages--insignificant contact of phases and, accordingly, low heat transfer coefficients between particles and gas flow, as well as the short residence time of particles in a flow. Therefore, such devices are not so effective and are very high-priced. One of the solutions that allow stabilizing the operation of a fluidized bed apparatus is the swirling of flows, which has found application, for example, in the granulation devices [38]. The data of theoretical [39] and computer [40] modeling of the operation of such devices as applied to the production of porous ammonium nitrate [41] is confirmed by the successful testing of product samples [42]. The authors of this article have chosen another way to improve the fluid dynamics of the fluidized beds--namely, a method to weigh solid particles on a gas distribution grid. The gas distribution grid (shelf) is installed in a vertical channel at an angle of 25-45\({}^{\circ}\) to the horizon forming the outloading space between the end of the shelf and the channel wall. There can be several shelves throughout the height of the device. This feature enables to create various gas-dispersed flow modes in shelf units, in which not only the basic features of the flow are quantitatively changed (concentration of solid particles in the gas flow, velocities, heat-mass transfer coefficients), but there are qualitative changes in flow structure, phase motion mechanism, and heat-mass transfer conditions under certain critical conditions.