Study of the thermodynamic efficiency of solid fuel preparation systems of a thermal power plant based on an exergy analysis of the operation of subsystems

¹ Department of Industrial Heat Technology, Almaty University of Power Engineering and Telecommunications, Almaty, Kazakhstan
² Department of Power Engineering and Power Machines, Technical University of Sofia, 8 Kliment Ohridski blvd., 1000 Sofia, Bulgaria

^* Corresponding author: aterziev@tu-sofia.bg

Abstract

Own energy consumption needs at combined heat and power plant depends on the type and installed capacity of the main and auxiliary equipment installed on-site, as well as the type of the fuel and combustion method used. The coal dust preparation system, in turn, is the most energy- intensive part of coal mining. Therefore, methods for improving the operation of the fuel path of a combined heat and power plant and the technology for producing coal dust are very relevant. The present study proposes a comprehensive methodology for determining the thermodynamic efficiency of solid fuel preparation systems at combined heat and power plant 2 (CHP-2) in the city of Temirtau of the Republic of Kazakhstan. Outdated equipment is operated at the CHP and there is virtually no automation of technological processes related with the solid fuel preparation system. The scientific novelty of the work is the theoretical study and analysis of the thermodynamic efficiency of an individual dust preparation system with an intermediate hopper when grinding coal. The thermal and thermodynamic calculations based on the determination of exergy efficiency for individual units of the dust system and the system as a whole allow to propose means to increase the efficiency of the coal industry and give recommendations to reduce energy costs for the plant’s own needs. As a recommendation to reduce energy costs for the preparation of coal dust, the installation of a crushing press with a studded surface is proposed, which allows grinding large pieces of coal to optimal sizes (25 mm) in the absence of preliminary crushing of the material on-site. An automation scheme for the entire dust preparation system is proposed, including automation of the operation of the intermediate coal dust bin. Automatic control of the supply of coal dust from the intermediate hopper allows to determine the exact fuel consumption of the steam boiler, which were not permissible under the previous conditions of the dust system due to the use of a semi-mechanical method of regulating the supply of coal dust to the boiler.