Business process optimization has become a strategic aspect of companies' management due to the potential of cost reduction and throughput improvement. There are several ways to achieve process optimization, depending on the level of expressiveness of the processes at hand. In this paper, we focus on processes described using BPMN, but also including an explicit description of execution time and resources associated with tasks. We propose a refactoring procedure whose final goal is to reduce the total execution time of the process given as input. Such a procedure relies on refactoring operations that reorganize the tasks in the process by taking into account the resources used by those tasks. This process refactoring technique is fully automated by a tool that we implemented and applied on several examples for validation purposes.