Based on the analogy of a tubular heat exchanger with a structured heat-releasing granular bed, a technique has been developed that makes it possible to unify the simulation of heat transfer in heat exchangers with a tube bundle of different types and designs.

The laws governing the evolution of a shock wave moving along a granular bed are established. Using the methods of similarity theory, a criterion of shock wave stability is formulated, which includes the main characteristics of a granular bed. A generalization of this criterion to the case of a porous layer is proposed.

An experimental study of combustion processes in laboratory and pilot plants of various size equipped with cyclone-bed furnaces with a fixed and a fluidized bed and a wide range of solid biofuels was carried out. Numerical simulation of furnace processes in cyclone-bed furnaces was performed using the standard k–ε turbulence model and the Magnussen combustion model. A semiempirical method for calculating cyclone-bed furnaces has been developed.

The laws governing the thermomechanics of a granular bed in the case of nonuniform distribution of heat release have been studied. The bifurcation of a stationary solution of the equation of motion of gas with account for the temperature dependence of gas viscosity is described. The dependences of the critical pressure and critical gas flow rate on the determining factors have been established.

Modeling has been performed for the motion of burning fuel particles in the vortex zone of a cyclone-grate-fired furnace. It is shown that particles with a diameter that is larger than the hovering diameter, as a rule, have no time to burn in the swirled gas flow and burn down in the grate-fired zone.

Experimental and numerical studies have been made of the hydrodynamics of isothermal flows in a small-scale cyclone chamber (D = 0.21 m) with two-stage differently directed injection of tangentially blown air (with a cocurrent and countercurrent swirl). It has been established that the character of vortex flow with a countercurrent swire differs significantly from the structure of flow with a cocurrent swirl. The character of velocity and pressure distribution in the chamber′s volume has been revealed for the flows in question. Dimensionless dependences have been obtained for calculating the tangential velocity and pressure in the chamber. It has been shown that results of numerical modeling of vortex flows with the k–ω (SST) turbulence models for the concurrent and countercurrent air swirl are in satisfactory agreement with experimental data.

A study has been made of the effect of choking of a gas flow by isothermal and heat-releasing granular beds under the conditions of a viscous-inertial regime of flow. An asymptotic expression has been obtained for the gas velocity.

Within the framework of the model of ideal mixing of particles in a fluidized bed, the conditions needed for carrying out the continuous process of precarbonization (torrefaction) of biowaste in a fluidized bed reactor have been elucidated. The dependence of the degree of torrefaction on the average residence time of particles in the reactor and on the characteristic time of torrefaction has been established.

An investigation has been made into accelerated hydrothermal fluidized carbonization of sewage sludge in a superheated steam medium. It is shown that an increase in the process temperature has no effect on its duration but has a significant effect on the composition of noncondensable gases. Biochar activation has been investigated in potassium hydroxide at a temperature of 750°C and the biochar–KOH ratios of 1:1.5, 1:2, and 1:3. It is shown that the KOH concentration has no effect, in practice, on the sorption characteristics of the obtained product which is more suitable for the use as a soil improver.

Within the framework of a model of a heat-releasing structured granular bed, simulation has been conducted of the heat-transfer processes in a gas-tube heat exchanger in the presence of water vapor condensation in the vapor–gas mixture. A functional dependence of the heat flux used for heating water on the geometric and hydraulic parameters of the heat exchanger has been established.

An investigation has been made into the process of heating up the granular bed in two regimes: heating up a roomtemperature fluidized bed and heating it in conditions of thermal fluidization.

An experimental investigation has been conducted into combined hydrothermal fluidized carbonization of poultry litter and sawdust in a superheated steam medium. The effects of temperature on the duration of the process of hydrothermal carbonization have been identified, and the composition of the noncondensable gaseous products of carbonization has been established.

Furnace processes occurring in laboratory setups, pilot commercial facilities, and small-capacity boilers of various sized equipped with cyclone-bed furnaces containing fixed and fluidized beds burning solid biofuels (wood pellets, straw pellets, sunflower husk pellets, peat pellets, wood waste, wood chips, milled peat, and crushed peat bricks) are investigated. The distribution features of temperature and gas concentrations (CO, CO 2 , H 2 , O 2 , CH 4 ) in the combustion and secondary combustion chambers have been established in the course of experiments. With this information available, it becomes possible to determine the zones in which fuel actively reacts with the oxidant under the conditions of two-stage vortex combustion. Dependences of the carbon monoxide (CO) and nitrogen oxide (NO х ) concentrations in the flue gases on the excess air ratio, bottom blast share (primary air), furnace power, and the combustion chamber’s outlet hole diameter are obtained. The furnace processes in cyclone-bed furnaces are numerically simulated using the standard k –ε turbulence model and the Magnussen combustion model, and satisfactory agreement between the calculation and experimental results is shown. A semiempirical method for designing cyclone-bed furnaces has been developed, according to which their main geometrical and operating parameters are determined in two stages: a preliminary thermal design analysis is first carried out, after which the furnace process is numerically simulated. Based on extensive generalization of experimental data on the burning of solid biofuels in cyclone-bed furnaces having different diameters, the parameter М = 0.52, which appears in the well-known Gurvich formula for the thermal design of furnace chambers, has been determined. This parameter takes into account the temperature field structure and the heat transfer pattern over the furnace height, thus making it possible to use the standard method in carrying out thermal design computations of furnaces.

A numerical solution of a two-temperature problem on the thermal state of an aerated granular bed, constituting the thermal protection of the gas distributor of a high-temperature bubbling bed, is carried out. An equation is obtained for the coefficient of the efficiency of cooling the gas distributor. It is shown that on the side of the bubbling bed the surface temperature of the granular bed is independent of its thermal conductivity and thickness.

Russia faces an important environmental challenge associated with the accumulation of a large amount of biowaste due to the lack of technologies for their efficient processing. In particular, the intensive development of aviculture in Russia, including poultry farming, in the coming years will lead to the need of processing significant amounts of poultry manure and poultry litter. One of the options for litter disposal is its processing into biofuel suitable for the production of heat energy for the needs of poultry farms themselves and for outside consumers. However, with this option, the disposal of litter requires its disinfection, for example, by the method of torrefaction. However, the existing torrefaction technologies are characterized by a considerable process duration. A new method of torrefaction has been proposed and comparative studies have been carried out on the process of poultry litter torrefaction in a fixed bed under a nitrogen blanket (dry torrefaction) and in a fluidized manure bed pretreated in superheated steam (wet torrefaction). After both methods following heat treatment, manure samples are obtained, the mass of which is decreased twice due to an almost threefold decrease in the oxygen content, which, along with an increase in the carbon content and a decrease in the amount of moisture, causes the fuel efficiency of the manure. The manure torrefaction in a fluidized bed also makes it possible to significantly (four times) speed up the process. Technical solutions are proposed to solve the issues of full or partial recovery of energy costs related to the production of superheated steam due to the processing of gaseous torrefaction products into syngas using hot biochar thermal cracking.

Experimental investigation of the entrainment of quartz and olivine sand particles from a cyclone-bed chamber has been carried out. A generalized characteristic of the chamber is introduced that allows one to identify three different mechanisms of the entrainment.

Modeling of the process of thermal fluidization of a ventilated granular bed by means of a heat exchanger in the form of horizontal tubes positioned inside the bed is carried out.

Numerical simulation was carried out in three-dimensional and axisymmetric formulations for the hydrodynamics and mixing of bottom- and tangentially blown air with different temperatures in a cyclone chamber with local supply of tangentially blown air. To calculate vortex flows in the chamber, use was made of the most popular turbulence models k–ε, k–ω, and SA. It has been established that the best correspondence between the results of calculation and experimental data on hydrodynamic parameters (velocity and pressure) and air mixing under nonisothermal conditions is furnished by the k–ε and k–ω models of turbulence. Good agreement of the results of numerical simulation of vortex flows in the indicated chamber in three-dimensional and axisymmetric formulations has been obtained.