Thermal Stability Of N-pentane

With the aggravation of the global energy crisis,and the extensive consumption of fossil fuels and serious environmental pollution,the consciousness of energy conservation and environmental protection have gradually increased in the world.The researches and development of low-grade energy such as industrial waste heat,geothermal energy and solar energy have become a hotspot in recent decades.Organic Rankine cycle(ORC)is proved to be a reliable technology that can efficiently convert these low grade heat sources into mechanical energy.However,the organic working fluid may decompose under high temperature conditions.If the decomposition occurs,decomposition products may be non-condensable gases,liquids or solids which may affect system performance and destroy components.Therefore the thermal stability of organic fluid is an important consideration in working fluids selection and application studies.N-pentane is widely used in the study and application of medium-high temperature ORC system.Therefore,it is necessary to investigate the thermal stability of n-pentane.The thermal stability test system of organic working fluids was designed by oneself,and the thermal stability of n-pentane was studied by using a reactor method to investigate the thermal decomposition temperature of n-pentane.The thermal decomposition products were analyzed by Fourier Transform Infrared Spectroscopy(FTIR)method and Gas Chromatography-Mass Spectrometer(GCMS)method.The analysis model for the thermal stability of n-pentane,isopentane,n-butane,and isobutene was built and the thermal stability of these four working fluids are investigated through the Gibbs free energy,chemical equilibrium and chain reaction theory by introducing the cofunction.The results showed that n-pentane was stable up to 300°C and the decompose temperature range is 300 ~ 310°C.The thermal decomposition products include propylene,and the butene was formed at a higher reaction temperature.Air has a great influence on the thermal stability of n-pentane.When the reactor contains a small amount of air,the pyrolysis temperature of n-pentane will drop to 225~250°C,the n-pentane will be completely decomposed at 275 °C,and there will have carbon deposit in the reactor.The thermodynamics decomposition temperature difference for the different pathways of n-pentane,isopentane,n-butane,and isobutene are relatively large.The temperature difference between experiment and theory is become smaller by introducing of the cofunction.