Chemical engineering design and petroleum refining design

Excluding differences in manufacturing processes, their design principles are essentially the same; however, petrochemical products require higher precision, which means greater attention to details, such as in distillation. The processing volume in refinery engineering is generally much larger than that in petrochemical industries, and its energy consumption is high; therefore, comprehensive energy utilization is even more important. Furthermore, due to long-standing *conventional issues among design firms, there are differences in the design of the same units between refining and petrochemical industries.

Let’s discuss a few different points; they may not be correct, but please use them as reference: 1) The basic data for chemical engineering design is quite comprehensive, and the parameters used in the design process are also specific – values such as temperature and pressure are relatively accurate. However, this is not the case in oil refining. For example, the distillation columns used in catalytic cracking are much more complex than those used in chemical engineering, mainly because it’s difficult to determine the appropriate parameters. 2) The requirements for chemical plant design are quite strict, whereas those for oil refining are relatively more flexible. 3) Once a chemical plant is built, there is little room for modification, whereas most oil refining plants require renovation. 4) The raw materials for chemical processing units are relatively stable, while those for refining units vary more and require greater adaptability (as the type of crude oil can change). In short, each has its advantages, its own benefits, as well as its own challenges.

In fact, the differences between the two are mainly determined by their raw material and product requirements. In chemical engineering design, the products are single pure components, whereas in petroleum refining design, the products are multi-range mixtures that are not pure components. Therefore, there is a significant gap in simulation and design. People in the chemical industry often say that those involved in oil refining design are too rough in their approach; for example, when it comes to selecting equipment, oil refining projects allow for a large degree of flexibility, while the chemical industry can achieve greater precision in such selections. In chemical processing towers, the diameter and plate spacing are generally 500 mm, or even 600 mm; in contrast, the maximum value in this sector is 450 mm, with some cases having even lower values. This is related to the distillation of pure components, as such processes require high standards for the product quality, often necessitating a large number of theoretical plates and thus a tall tower. To reduce the tower height, it is necessary to decrease the plate spacing. Towers in oil refining plants, on the other hand, are not very tall. A comparison between ethylene distillation units and atmospheric/ vacuum distillation units in oil refineries makes this clear: for example, in the propylene distillation units used in gas separation plants, around 180 plates are required to obtain pure propylene. Oil refining engineers typically design these units as two connected towers, whereas propylene distillation units in ethylene plants are usually single towers.

It seems that oil refining design is more challenging than chemical engineering design. But it’s really tiring. Just doing chemical engineering design already feels so exhausting.