Aspen HYSYS: An Introduction to Chemical Engineering Simulations is intended for students who are using Aspen HYSYS for the first time and have little or no experience in computer simulation. It can be used as a textbook in freshmen chemical engineering courses, or workshops where Aspen HYSYS is being taught. The book can also serve as a reference in more advanced chemical engineering courses when Aspen HYSYS is used as a tool for simulation and solving problems. It also can be used for self study of Aspen HYSYS by students and practicing engineers. In addition, the book can be a supplement or a secondary book in courses where Aspen HYSYS is used, but the instructor does not have time to cover it extensively.