The objective of this paper is to present the results of a study to simulate, cost, and optimize a large scale chemical plant using as many of the built-in features of AspenPlus as possible. This paper presents the results of the study as well as present our findings with respect to the use of AspenPlus. A large scale, complex chemical process was simulated, costed and optimized using the process simulator AspenPlus. The process studied is a Modified High Temperature Ethylene Polymerization process which produces alpha olefin products ranging from octene to octadecene. A base flowsheet was developed for comparison purposes, the base case flowsheet was then costed using AspenPlus costing modules and optimized using the Complex Method. The optimizations were driven to reduce utility and capital costs giving improvements in the objective value over that of the base case value. However, because of the complex nature of the process (i.e., discontinuities caused by the switching of sizing and costing models and nonlinearities) the optimizer had difficulty converging properly resulting in suboptimal solutions. AspenPlus is capable of simulating, costing, and optimizing large processes. However, the use of user defined cost factors and good initial optimization starting points should be used to get reasonable results.