**2.1 Introduction**

The distillation is heating a liquid solution or mixture of liquid stream to produce steam, and then collecting and condensing that steam. In the simplest case, the products of the distillation process are limited to the upper distillate and the bottom, the composition of which differs from the feed. Thus, the major purpose of distillation is the separation or splitting into two or more products from a feed [32]. The distillation or rectification is one of the oldest and most common methods of chemical separation [33]. Historically, one of the most famous uses is the production of spirits from wine. More simply, in other words, the target of distillation is usually to remove the light component from the heavy component mixture, or viceversa, to separate the heavy product from the light component mixture [32]. One of the components of crude oil refining is distillation, therefore a stage of refining. Oil refining is a rather complex technological process that begins with the transportation of oil from the field to refineries. The fractionation or distillation column exists in practically all oil refining technologies through reforming, thermal cracking, hydrocracking, etc. [20]. Before receiving the petroleum products common to users, the oil goes through several stages before becoming a finished product. Some of these stages are [1, 9, 20, 21]:

