Sep-2024

MellapakEvo and the evolution of structured packing (RI 2024)

Distillation has been the most prevalent separation technology in the chemical industry.

Shwu Tyng Goh
Sulzer

Article Summary

Distillation mass transfer components are categorised into three primary groups: trays, rings (random packing), and structured packing. Among the three groups of components, structured packing was the latest to be introduced and was initially applied mainly in vacuum and low liquid load applications.

As the understanding of structured packing performance deepens, leading to advanced product innovations, structured packing is now used in both vacuum and pressure distillation columns, high liquid load absorption columns, and extraction columns. Despite being a well-established technology, there remains significant potential for further research and development in structured packing and the associated column internals.

Every aspect of the packing, from the material to the geometric configuration and surface texture, must be carefully optimised to ensure uniform liquid distribution, minimal pressure drop, and enhanced phase interaction. This intricate balance between simplicity and precision holds the potential for further improvements in structured packings to achieve unprecedented efficiency in separation processes.

Since the first introduction of its structured packing, the Sulzer BX gauze packings, Sulzer has continued to drive excellence in this technology. The Sulzer MellapakTM product family launched in 1976 has since become synonymous with structured packing. The latest iteration of the technology, MellapakEvoTM, relies on the same fundamental principles but takes advantage of high effective interfacial area and optimised geometry to deliver a significant boost in performance.

Anatomy of structured packing
A structured packing solution consists of a carefully engineered arrangement of corrugated sheets, typically made from metal or other corrosion-resistant materials, stacked within a distillation column. These sheets are designed to maximise the surface area for contact between the liquid and vapour phases, which is crucial for efficient mass transfer.The key elements of a structured packing solution include:
• Material: Structured packing can be made from various materials, including stainless steel, alloys, and other corrosion-resistant materials. The choice of material depends on the specific application and the chemical compatibility requirements.
• Geometry: The sheets are arranged in a way that creates a large interfacial area, promoting efficient interaction between the liquid and vapour phases. The geometric configuration is designed to minimise pressure drop while maximising surface area.
• Surface texture: The texture of the corrugated sheets can be modified to enhance liquid spreading and improve wetting characteristics. This helps to ensure uniform distribution of the liquid phase across the packing surface.

A legacy of success
Sulzer Chemtech’s journey in structured packing technology began in 1964 with the introduction of Sulzer BX gauze packing. Twelve years later, the Mellapak product family was introduced and became a benchmark for distillation, absorption, and extraction applications under different operating conditions.

As industry demands for higher capacity and efficiency grew, Sulzer launched MellapakPlusTM in 1999. This second-generation packing featured an enhanced corrugation profile that reduced liquid holdup and significantly boosted column performance, setting new efficiency standards. Building on this success, Sulzer introduced BXPlusTM in 2003, applying similar advancements to gauze packing to further improve efficiency at lowest pressure drop.

In response to the increasingly specific needs of its expanding customer base, Sulzer developed diverse structured packings tailored to specialised processes. For example, MellaCarbonTM was designed to operate in corrosive environments without suffering a reduction in performance, while MellapakCCTM was tailored to meet the specific demands of carbon capture applications. The latest milestone in this evolutionary journey came with the launch of MellapakEvoTM in 2024.

Advancing structured packing
Sulzer’s new packing MellapakEvo represents the culmination of extensive research and development efforts, leveraging decades of expertise to push the boundaries of efficiency and performance in distillation processes. It marks the beginning of a new generation of structured packing, distinguished by its high effective interfacial or wetted area. It enhances mass transfer between the vapour and liquid phases for component separation in a distillation column. Simultaneously, the pressure drop is minimised due to the packing’s low gas flow resistance, thereby increasing the packing’s useful capacity. The efficiency is significantly influenced by the wettability of the packing surface. A superior surface texture ensures the creation, maintenance, and continuous renewal of the liquid film on the wetted surface, maximising the utilisation of the packing surface. The result is an enhanced performance of the distillation column while the useful capacity is extended.

These upgrades collectively result in up to 40% greater efficiency than the structured packing MellapakPlus 252.Y. Compared to MellapakPlus 452.Y, it offers similar separation efficiency with approximately 20% higher capacity. This makes it ideal for use in diverse applications in the chemical processing industry.

A look to the future
Sulzer remains dedicated to reducing the environmental impact of distillation columns. With our MellaTechTM column internals technology and applications know-how, we continue to focus on bringing optimum solutions with greater efficiencies and lower energy consumption to our customers. Sulzer is poised to lead these advancements and ensure Mellapak continues to set the standard for structured packing.

This short article originally appeared in the 2024 Refining India Newspaper, which you can VIEW HERE