New working fluids for the use of heat secondary sources in mining technologies

Abstract

Production cost of mining enterprises can be significantly reduced when using secondary heat. A large volume of secondary heat sources has a temperature potential of no higher than 50°C. To generate additional electricity using secondary heat it has been proposed to use installations with the Rankine thermodynamic cycle in mining enterprises. The paper aim is to study the thermodynamic efficiency of using R-1234yf and R-744 in the equipment, which uses the secondary heat of mining technologies for evaporation of these working fluids. R-1234yf is a freon that belongs to the class of hydrofluoroolefins and has a much lower level of global warming potential than other ozone-depleting substances. R-744 is carbon dioxide, which belongs to a natural, non-toxic and non-flammable working substance. It has been determined that the thermodynamic efficiencies of using R-1234yf and R-744 are 10% and 6.3%, respectively. The thermodynamic efficiency has been calculated for the temperature range from 50° to 20°C, which is typical for a large volume of secondary heat sources in mining technologies.

The use of secondary heat resources during the accumulation of compressed air in closed mining workings

“…By solving the equations of the system for the third stage using Newton's method [15], we find the relevant values of Lc3, T3 and n3. The solution of system ( 9), (12), and (13), which is obtained by the same method, gives us the air supply Ga, the required volume of mining working and the diameter of the air supply pipeline, according to the available capacity of secondary energy sources. Thus, a system of equations has been formed for determining the parameters of the secondary heat resource during three-stage air compression, as well as a system of equations for finding the air supply Ga, the required volume Va of the mining working and the diameter d of the pipeline in accordance with the available capacity of secondary energy sources.…”

“…It is to include in its composition of the equipment, which carries out gas dynamic and heat exchange processes in gas turbines to implement the Rankine thermodynamic cycle [9][10][11] with additional generation of electric energy. The main advantage of the Rankine thermodynamic cycle with a working substance from the class of freons is the possibility of its application for the use of secondary heat of various parameters and under different conditions due to the selection of the appropriate freon [12].…”