Mega Columns: Challenges and Solutions

Mega columns will play an increasing role as refining and petrochemical facilities look to meet carbon-neutral goals and implement post-combustion carbon capture.

Mega columns have very large diameters and/or heights that provide unique challenges in column design, construction, and operation. These types of columns are not particularly new; many large-diameter petroleum refinery vacuum columns and tall chemical plant “superfractionators” have been in operation for decades. However, with the construction of world-scale refineries and petrochemical complexes — capable of processing many hundreds of thousands of barrels of crude oil per day — mega columns are at the forefront of mass transfer technology and continue to grow in size and complexity. As limits on carbon emissions become stricter to meet carbon-neutrality goals, hundreds of mega columns may be constructed for post-combustion carbon dioxide (CO₂) capture. Regardless of the application, distillation columns require massive investments for construction and subsequent operation. This is especially true for mega columns.

In this article, a “mega column” refers to a column with large enough dimensions to require special mechanical, hydraulic, or process designs and likely special operation. Mega columns are those that have a large diameter (e.g., greater than 10 m), tall height (e.g., greater than 70 m), or a combination of both. Diameter is driven by column internal flows (i.e., feed throughput, vapor rate, and liquid rate) and height is driven by mass transfer stages (i.e., difficulty of separation).

This article describes challenges in the design and operation of mega columns and discusses the important role of high-performance tower internals...