Method for constructing phase envelope of multicomponent mixtures

Two methods for constructing phase envelope of multicomponent mixtures (hydrocarbon+non-hydrocarbon gas) are compared. A single variable (T or P) iteration method for constructing the entire phase envelope is developed. The critical point and points of maximum pressure and maximum temperature can be determined simultaneously during the phase envelope construction. This method has been successfully applied to nine multicomponent mixtures including gas-condensate. As compared with the more sophisticated Newton-Raphson method, the proposed single variable iteration method is simple and reliable.