Benedict-Webb-Rubin Equation of State for an alternative fuel, Dimethyl ether, and Estimation of Thermophysical Properties

The industrial production of dimethyl ether (DME) is now about 10,000 ton/year in Japan, and DME has been mainly used as an aerosol propellant. Recently, DME can be directly synthesized from water gas, carbon monoxide and hydrogen, by use of a new type catalyst dispersed in fluids. So, a large amount of DME will be supplied in future. Considering the molecular structure, the physical properties of DME are similar to those of light hydrocarbons in liquefied petroleum gas (LPG), propane or butane, and the combustion properties also similar to those of gas oil. Then, DME is expected to be an alternative energy for industrial, domestic and diesel fuels. However, comparing with propane and butane, there are few available data about p physical properties of DME. The members of research group, mainly organized by High Pressure Gas Safety Institute and Liquefied Petroleum Gas Center of Japan, have intensively investigated thermophysical properties to establish safety instructions for DME. This study is an activity of this project. Therefore, P-V-T relationship and vapor pressure were measured for DME. The eight constants, in Benedict-Webb-Rubin (BWR) equation of state, were optimized by applying Joffe’s corresponding state theory. The BWR equation well predicted experimental compressibility factor and vapor pressure of DME. Using the BWR eq., latent heat of vaporization, isochoric heat capacity, isobaric heat capacity and speed of sound were also calculated.