2.1.4: Chemical Engineering
- Page ID
- 113085
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Modular design is a primary consideration for chemical engineers. Factories and plants must be designed with modularity to facilitate maintenance and allow for future process expansions. In chemical plants, byproducts often require specialized machinery for handling and processing. Due to the nature of many chemical processes, this specialized equipment must be frequently replaced or maintained to address issues like corrosion, buildup, or compliance with safety standards.
In the next section, you will find two examples of modular design applied in chemical engineering. Please read through one example.
Practical Examples
Heat Exchanger
Modular design is critical in the design of heat exchangers. Shell and tube heat exchangers, which are widely standardized across the industry, minimize the number of fluid passes required while maximizing modularity and operability (1). Their modularity allows them to integrate seamlessly into various chemical processes. On the other hand, tubular heat exchangers are commonly used in the dairy industry because they limit milk stagnation, which helps prevent curdling and bacterial growth (2).
During pasteurization, milk must be heated to 72॰C for 15 seconds, enough to kill harmful pathogens while avoiding bacterial buildup. Afterward, the milk is run through a heat exchanger with chilled water to cool it down to 4॰C for packaging (2). However, even after pasteurization, issues within the heat exchanger can cause spoilage, unpleasant odors, and make the milk unsafe to consume. This can come from stagnant milk, bacterial buildup, or the temperature of the milk (3).
To prevent this, modular heat exchangers in the dairy industry are designed to be easily disassembled and flushed with water. This regular maintenance ensures both the internal and external pipes are clean and checked for leaks, keeping the milk safe for consumption. In addition to this, there are also “CIP” (clean in place) heat exchangers, which are designed to be flushed with water without needing to be disassembled (2).
In contrast, shell and tube heat exchangers are some of the most widely used heat exchangers in the world, commonly used in industrial settings to cool corrosive or hazardous materials, such as oil and its byproducts (4). Due to the widespread applications of the shell and tube design, as well as the potentially hazardous nature of the chemicals involved, modularity is essential. A failed component could have environmental and economical consequences, so these exchangers are disassembled for inspection every few months or every year. Their design allows the outer casing to be removed from the internal pipes for easy checks. Depending on the design, if any pipes are damaged, they can be replaced without replacing the entire unit, making maintenance more efficient (5).
Modular design is what keeps factories safe, cost-effective, and efficient. When a component fails, chemical plants must quickly and effectively address the issue. Modular design simplifies this process, making repairs faster and minimizing downtime.
Figure 3.3.5.1 A shell and tube heat exchanger with the external shell removed, showing how easy they are to disassemble and clean.
Distillation Column
Distillation columns are essential in the petroleum industry for refining crude oil into usable products like gasoline, jet fuel, and tar. The process also generates byproducts such as chlorine and sulfur, which are corrosive and contribute to the need for regular maintenance. This issue is further compounded by the high temperatures within the column, which often exceed 300 degrees Celsius. Distillation columns work by running superheated steam through petroleum, separating its components by boiling point into various solids, liquids, and gasses. The separation happens through a difference in volatility, which is a substance's capacity to vaporize and trays with valves that facilitate physical separation between liquids and gasses. These trays need periodic maintenance and replacement due to corrosion (6).
Distillation columns are built with standardized sections, which greatly simplifies their construction and makes expanding plants easier. The diverse byproducts of petroleum refinement each require specialized handling procedures (7). As technology advances, plants must be able to expand or adapt quickly to meet industry standards and improve byproduct management. The outer casings of distillation columns also need periodic replacement as the corrosive nature of the byproducts can weaken the structure over time (6). The ability to replace these components is critical for maintaining safety and functionality.
To facilitate maintenance, distillation columns are equipped with manhole covers that allow workers to enter and replace the trays. Allowing workers inside the column also makes it easier to inspect for corrosion and determine when parts need to be replaced (6).
The modular design of distillation columns enables chemical plants to operate continuously, as components can be monitored and replaced with minimal downtime. This ensures that plants run efficiently and cost-effectively, meeting the high demands of 24/7 operation.
Figure 3.3.5.2 A plant with several distillation columns with visible scaffolding.
References
(1) Yousef. 12 Different Types of Heat Exchangers & Their Application [PDF]. The Engineers Post. https://www.theengineerspost.com/typ...eat-exchanger/.
(2) HeatX. Dairy Heat Exchangers for Milk Pasteurization & Dairy Industry. Sanitary Exchangers. https://www.sanitaryexchangers.com/D...xchangers.html (accessed 2024-10-27).
(3) Fryer, M. Fouling in Heat Exchangers: Learn Causes, Detection, and Prevention. Central States Industrial. https://www.csidesigns.com/blog/arti...eat-exchangers.
(4) MechStudies. What are Shell and Tube Heat Exchangers? Definition, Parts, Types, Working. mechstudies.com. https://www.mechstudies.com/what-she...parts-working/.
(5) DASCO. OPERATING & MAINTENANCE MANUAL Shell & Tube Heat Exchanger; DASCO, 2022; pp. 1–24.
(6) Naik, S.; Schornak, B.; Seadeek, C.; Wesorick, S.; Robertson, M.; Nalbandian, A.; Cotton, S.; Hoffman, N.; Potter, A. Distillation Columns – Visual Encyclopedia of Chemical Engineering Equipment. encyclopedia.che.engin.umich.edu. https://encyclopedia.che.engin.umich...ation-columns/.
(7) OSHA. Process Safety Management for Petroleum Refineries Lessons Learned from the Petroleum Refinery Process Safety Management National Emphasis Program; 2017. https://www.osha.gov/sites/default/f...s/OSHA3918.pdf.