Background. Low-potential secondary energy resources are the majority of all types of thermal secondary energy resources. They include liquids with temperatures below 150 °C and gases with temperatures below 300 °C. The use of secondary energy resources in various processes makes it possible to reduce the consumption of organic fuels and, as a result, the number of emissions entering the atmosphere and having a negative impact on the environment. Since in thermal desalination plants about 40–50 % of the cost of desalinated water is the cost of thermal energy, it is advisable to use low-potential energy sources to reduce it. Application of low-potential secondary energy resources in gas-contact desalination plants is relevant, since the process of evaporation of water can be carried out at temperatures below the saturation temperature. In addition, direct utilization of gas secondary energy resources is possible in installations of this type, for example, combustion products. The use of combustion products allows not only to obtain fresh water suitable for technical needs, but also to purify flue gases. Several options for the utilization of secondary energy resources can be proposed depending on the requirements for desalinated water, as well as the parameters and type of heat carriers.
Materials and methods. The study has been conducted using the method of balance calculations of heat exchange processes in technological power plants.
Results. The authors have proposed several schemes for the utilization of low-potential secondary energy resources in desalination systems based on gas-contact desalination plants depending on the type and parameters of the low potential energy resources. The authors have evaluated the efficiency of the integration of heat transformers into the thermal circuits of gas-contact desalination plants for the disposal of secondary energy resources with a temperature less than 80 °C for various working agent: R600, R600a, R1234ze(Z), R142b, R717, R245fa, R134a. Nomograms have been constructed for the most efficient working agent. Depending on the temperature of secondary energy resources, it is possible to determine the energy consumption for the compressor drive, as well as the amount of energy taken from secondary energy resources. The required amount of flue gases has been determined to produce a cubic meter of fresh water in steam-air desalination plants, depending on the flue gas parameters and operating conditions.
Conclusions. It has been established that when disposing combustion products in surface heat exchangers of steam-air desalination plants, from 1,96 to 18,47 thousand kilograms of exhaust gases are required to produce 1 m3 of fresh water, depending on their parameters and the operating mode of the installation. When utilizing secondary energy resources using heat transformers, the most efficient and environmentally friendly is the use of working agents R1234ze(Z), R245fa and ammonia. Disposal of low-potential energy sources using of heat transformers at temperatures of the heat carrier less than 24 °C is impractical.