Increase of operating efficiency of mine energy complexes is an actual scientific and technical problem. Systems that utilize energy of low-potential sources and have freon-steam turbines are suggested to be included in mine energy complexes. Principles of selection of freons as working fluids in energy systems are suggested in the paper. Usage of some thermal equations of state for defining thermal and physical properties of freons is analyzed. Equation of isentropic process for the thermal Redlich–Kwong equation of state is obtained. Calculation of energy efficiency of a system with a freon-steam turbine for selected variants of usage of working fluids is performed. A calculation method of thermodynamic parameters that are necessary for energy conversion efficiency estimation of specific freons in a system of useful utilization of energy is developed. Analysis of results indicates that usage of ozone-safe and fire-safe freons in energy utilization systems of low-potential sources with a possibility of utilization of additional waste heat, which was not used in the past, allows increasing the operating efficiency of mine energy complexes.

Mining power complexes can significantly reduce the cost of production of mining enterprises and increase their competitive position in the relevant market. To solve the urgent problem of further improving the operation of mine energy complexes, it is proposed to include in their composition installations for the useful use of energy from low-potential sources with a freon-steam turbine, which implement the thermodynamic Rankine cycle. The article considers the features of the organization of the Rankine cycle depending on the properties of freons. When choosing freons, the emphasis is placed on the use of strictly ozone-safe freons that meet modern requirements for normalizing the value of the global warming potential. The previously proposed method for calculating the thermodynamic parameters necessary for evaluating useful action’s coefficient of using specific freons in a useful energy recovery equipment has been improved. The calculation of the energy efficiency of the equipment with a freon-steam turbine for the selected options for the use of freons is performed. The analysis of the obtained results showed that the use of ozone-safe freons with low values of the global warming potential in installations for the utilization of energy from low-potential sources will improve the operation of mine energy complexes.

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.