In this research, production planning for refinery production processes (multi-stage, multi-production) was modeled with two approaches: crisp and fuzzy. The purpose of this article was to answer this question that which approach (crisp or fuzzy) has a better answer for production planning. To answer this question, at first, one multi- stage multi- production crisp linear mathematical model for a 24-hour period was designed. Then its fuzzy model was organized and finally the models were tested in a research sample.
The results from fuzzy and crisp models showed the improvement of optimal answer in fuzzy model rather than crisp model. Also it should be mentioned that the presented model in this research can be applied in other refinery production processes (multi-stage,multi-production).So it is recommended that for mathematical modeling of production planning, Corresponding vague and ambiguous factors should be measured through fuzzy logic and this kind of modeling should be used as a base for production planning. Disregarding this subject is the shortcoming of the previous models (which are mentioned in Introduction).