Organic Rankine cycle(ORC) is one of the effective ways to improve energy utilization and develop renewable energy. R32/CO2 is a mixture working fluid with outstanding comprehensive performance in ORC. However, organic working fluids may undergo pyrolysis in ORC. Therefore, it is necessary to study the thermal stability and pyrolysis mechanism of mixture fluid R32/CO2. Firstly, the thermal stability of R32 and R32/CO2(70/30 mol%) was studied using high-temperature and high-pressure experiments. The results showed that the pyrolysis temperatures of both R32 and R32/CO2 were 270-290 degrees C, and the main gas product of R32 and R32/CO2 were HF. Then, the pyrolysis mechanism of R32 and R32/CO2 was investigated using ReaxFF MD. In ReaxFF MD, the pyrolysis mainly occurred in R32, CO2 mainly acted as an inert gas in the pyrolysis of R32/CO2, so the pyrolysis mechanism of R32 was mainly analyzed. The main fragments of pure R32 pyrolysis were HF, F, H, CH2F, CHF2, CF, CH and C2. The pyrolysis pathways of working fluids can be divided into two types: abstraction reaction and self-decomposition reaction. The self-decomposition reaction mainly occurred in the former stage, and the abstraction reaction mainly occurred in the latter stage of pyrolysis.
展开▼
