Rotary kiln installation forms a very complex system, as it consists of various components which affect cement production. However, some problems with particle settling are encountered during operation of tertiary air installation. This paper reports on the results of a study into gas-particle flow in a tertiary air duct installation. This flow was calculated using Euler method for air motion and Lagrange method for particle motion. The results in this paper demonstrate that study focus on the tertiary air installation is a practical measure without the analysis of other processes in the rotary kiln. A solution to this problem offers several alternatives of modifying the inlet to the tertiary air duct. As a result of numerical calculations, we demonstrate the influence of geometry of a rotary kiln modification on the number of large particles transported in the tertiary air duct. The results indicate that in order to reduce large particles, rotary kiln head geometry needs to be modified, and a particle settler should be installed at its outlet.

Clinker burning process has a decisive influence on energy consumption and the cost of cement production. A new problem is to use the process of decarbonization of alternative fuels from waste. These issues are particularly important in the introduction of a two-stage combustion of fuel in a rotary kiln without the typical reactor-decarbonizator. This work presents results of numerical studies on thermal-hydraulic phenomena in the riser chamber, which will be designed to burn fuel in the system where combustion air is supplied separately from the clinker cooler. The mathematical model is based on a combination of two methods of motion description: Euler description for the gas phase and Lagrange description for particles. Heat transfer between particles of raw material and gas was added to the numerical calculations. The main aim of the research was finding the correct fractional distribution of particles. For assumed particle distribution on the first stage of work, authors noted that all particles were carried away by the upper outlet to the preheater tower, what is not corresponding to the results of experimental studies. The obtained results of calculations can be the basis for further optimization of the design and operating conditions in the riser chamber with the implementation of the system. Keywords: Two-phase flow; Precalcination; Particle distribution; CFD

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Abstract. The subject of the study is to analyze the phenomena of thermal flow in the precalcinator chamber of the exchanger's furnace tower including the combustion of coal dust and decarbonisation of raw lime powder. During the research were provided development of a mathematical model of particulate solid fuels combustion, calcining the raw material, NO x and CO x formation. Moreover conducting the number for the current and the upgraded design of the precalcinator and analysis of the results. In this study, a mathematical model based on Euler's method to describe the motion of the gas phase and the Lagrange method to describe the motion of particles [1][2][3][4]. In the calculations there were assumed fractional particles raw material and fuel, and the following processes: flow of exhaust gases from the rotary kiln through the precalcinator chamber, heat exchange between the particles of raw material and exhaust gases, the additional fuel combustion in the precalcinator, the process of raw material calcination, transformation of gaseous substances, effect of the additional (tertiary) air delivery on the processes in the chamber.

The main topic of the study is to evaluate the effect of particle concentration and fractional composition on the differential pressure in the Venturi tube during the measurement of flow rate of the gasparticle mixture. Gas phase flow was described by Euler method, while particles movement by Lagrange method. Calculations were performed using ANSYS Fluent Package. A series of numerical calculations were carried out on the particle loading ratio Y ≤ 2 and their diameters of 10 µm ≤ d p ≤ 200 µm. It has been found that, except for the Y concentration loading ratio, the increase in the differential pressure in the venturi tube also affects the Stokes number. It depends on the flow conditions and particles diameter. A correction function has been proposed to determine the effect of particles diameter on the results of the mixture flow measurement. The results of the calculations were compared with the Lee and Crowe experimental data. A good comparison of calculation results to measurement results was found.