IntroductionSoft computing techniques are popular and reliable numerical tools to solve real world optimization problems especially those involved in engineering applications. In particular, nature-inspired algorithms are a branch in the field of soft computing, which imitate processes in nature/inspired from nature. Nature-inspired computation can be classified into six categories [1]: swarm intelligence, natural evolution, biological neural network, molecular biology, immune system and biological cells. To date, several nature-inspired algorithms have been developed for solving difficult non-convex and multivariable optimization problems. In particular, the sophisticated decision making process that swarms of living organisms exhibit has inspired several of these meta-heuristics. Examples of these swarm intelligence optimization techniques are based on the decision making process of fireflies, ants, bees or birds. In general, the bio-inspired methods are quite simple to implement and use. They do not require any assumptions or transformation of the original optimization problems, do not require good starting points, can easily move out of local minima in their path to the global minimum, and can be applied with any model (i.e., black box model), yet provide a high probabilistic convergence to the global optimum. They can often locate the global optimum in modest computational time compared to deterministic optimization methods [2]. Therefore, these techniques are more advantageous compared to traditional local gradientbased and global deterministic optimization techniques.Recently, swarm intelligence optimization methods have been introduced for solving challenging global optimization problems involved in the thermodynamic modeling of phase equilibrium for chemical engineering applications [3][4][5][6][7][8]. In particular, the calculations of phase and chemical equilibrium are an essential component of all process simulators in chemical engineering. The prediction of phase behavior of a mixture involves the solution of two main thermodynamic problems: phase stability (PS) and phase equilibrium calculations (PEC). PS problems involve the determination of whether a system will remain in one phase at the given conditions or split into two or more phases. This type of problems usually precedes