Development of Energy-Efficient Modes of Installations for Heat Treatment of Concrete Products Using Numerical Calculation Methods

Abstract

Production of concrete and reinforced concrete products in the conditions of the Republic of Belarus and in the countries with similar climatic conditions requires heat treatment in heat-technological installations in order to achieve the desired strength of the products at the appointed time, which consumes a great amount of thermal energy. In this case, the purpose of equipment operating modes is associated with a number of difficulties when it comes to new products of complex spatial configuration and structure. The optimality criteria of such modes are, as a rule, the duration and temperature limits of processing, providing the required strength with minimal energy consumption. In the conditions of serial production in the case of structurally simple objects, the assignment of heat treatment modes is carried out empirically. As the analysis shows, the modes obtained in this way do not meet the above criteria, especially from the standpoint of energy saving. The paper, using a mathematical model previously developed by the authors, proposes dependencies for calculating the optimal modes of heat treatment of concrete products that are distinguished by a complex spatial shape and multi-component structure. The method is based on three-dimensional transfer equations, taking into account internal sources of heat release due to the ongoing hydration reaction of the active components of the cement clinker, and the boundary conditions corresponding to the structure of the processed product, as well as the type of heat technology device for accelerated hydration. Equations are proposed for calculating the amount of heat energy supplied to the processed product providing a given strength at a specified time. On the example of a manufactured industrial concrete product and for the conditions of an actually used device for accelerated hydration, a comparison has been made between two limiting modes of heat treatment: with isothermal exposure and in its absence. As a result of the performed calculations, the dependences of energy consumption, temperature fields and the degree of hydration in the product for both modes have been obtained and an energy-saving mode of heat treatment corresponding to the case under consideration has been developed. It is shown that the used numerical method allows to solve problems of this type and to achieve thermal energy savings.