Although process retrofitting is essential for existing chemical plants to remain sustainable, studies on systematic retrofitting methodologies for chemical processes are limited and also do not focus on the possibility of replacing a few unit operations with an intensified unit. Hence, in this study, a heuristic-based systematic methodology is developed for process retrofitting via intensification/integration. Compared with the conventional method, it focuses on exploring integrated retrofit solutions. Fast screening with heuristics, process knowledge, and process simulation is used to avoid infeasible solutions in the early stage. The proposed methodology is applied to retrofitting the conventional isopropyl alcohol (IPA) process. An improved solution without capital investment is obtained by operation optimization; it results in reducing the manufacturing cost per unit product by 5.5%. Then, two retrofit solutions, both involving reactive distillation, are developed. One of them reduces the manufacturing cost per unit product by 23% and results in a reduction in the number of equipment in the process.