The article features an experimental study of thermally thin biomass samples (beech wood particles 17×8×6 mm) pyrolysis in a laboratory scale batch reactor. The reactor was a cylindrical steel body with internal diameter of 200 mm and height of 500 mm. The temperature of a lateral surface of the cylinder during the experiment was being kept constant (550 °C) due to electrical heating. The initial loading of the apparatus was about 4 kg with moisture content of about 14 % by weight. During the experiment, the temperature values of the material being pyrolyzed were recorded at two points of the radial coordinate, viz. at the wall of the apparatus and on its axis. A one-dimensional numerical model of the nonstationary process of biomass conversion (heat and mass transfer in combination with the Avrami – Erofeev reaction model) has been proposed and verified. The reactor is represented as a set of a countable number of cylindrical layers, considered as cells (representative meso-volumes) with an ideal mixing of the properties inside. The cylindrical surfaces that form cells are considered to be isothermal. The size of the cells is chosen to be sufficiently large in comparison with the individual particles of the layer, which makes it possible to consider the temperature field inside the cell volume as monotonic. The evolution of the temperature distribution over the radius of a cylindrical reactor is determined on the basis of a difference approximation of the process of non-stationary thermal conductivity. The calculated forecasts and experimental data showed a good agreement, which indicates the adequacy of the developed mathematical model of pyrolysis and makes it possible to recommend it for engineering calculations of biomass pyrolysis. This model can also be useful in improving the understanding of the basic physical and chemical processes occurring in the conditions of biomass pyrolysis.

The article presents the results of computational and experimental studies of the distribution of a model material (plastic spherical particles with a size of 6 mm) along the height of a laboratory two-dimensional apparatus of the fluidized bed of the periodic principle of action. To experimentally determine the distribution of the solid phase over the height of the apparatus, digital photographs of the fluidized bed were taken, which were then analyzed using an algorithm that had been specially developed for this purpose. The algorithm involved splitting the image by height into separate rectangular areas, identifying the particles and counting their number in each of these areas. Numerical experiments were performed using the previously proposed one-dimensional cell model of the fluidization process, constructed on the basis of the mathematical apparatus of the theory of Markov chains with discrete space and time. The design scheme of the model assumes the spatial decomposition of the layer in height into individual elements of small finite sizes. Thus, the numerically obtained results qualitatively corresponded to the full-scale field experiment that had been set up. To ensure the quantitative reliability of the calculated forecasts, a parametric identification of the model was performed using known empirical dependencies to calculate the particle resistance coefficient and estimate the coefficient of their macrodiffusion. A comparison of the results of numerical and field experiments made us possible to identify the most productive empirical dependencies that correspond to the cellular scheme of modeling the process. The resulting physical and mathematical model has a high predictive efficiency and can be used for engineering calculations of devices with a fluidized bed, as well as for setting and solving problems of optimal control of technological processes in these devices for various target functions.