Suppression of the HFO-1123 disproportionation reaction by adding R290

Abstract

Trifluoroethylene (HFO-1123) is a promising next-generation refrigerant candidate for refrigeration and air-conditioning applications owing to its low global warming potential (GWP) of less than one and zero ozone depletion potential. However, HFO-1123 may undergo a thermal decomposition reaction under high-temperature and high-pressure conditions. The refrigerant compressor is heated when glitches occur. Pressure and temperature inside the compressor are assumed to be approximately 6.0 MPa and 150 °C, respectively, in the worst practical situation. Subsequently, energy is input by short circuits between the enameled windings of the motor in the compressor. Consequently, a thermal decomposition reaction called disproportionation reaction propagates in the compressor, potentially causing the compressor to explode. From a safety perspective, it is mandatory to suppress this reaction under practical use. A previous study evaluated the suppression effect of inhibitors such as R32 and R13I1; herein, we explored an optimized inhibitor composition that simultaneously fulfills the requirements of excellent suppression of the disproportionation reaction under the worst practical condition and low GWP. R290 was selected as a new inhibitor owing to its extremely small thermal decomposition energy. Subsequently, suppression of the disproportionation reaction was investigated using mixtures of R290 and HFO-1123. The results revealed that the disproportionation reaction was suppressed at a critical concentration of R290. The suppression effect of R290 was confirmed by validation experiments using actual compressors.