PTQ Q3 2024 Issue

separation efficiency while maintaining the same through - put with a similar total pressure drop. The same column configuration can be retained, thereby saving the capital cost of the process revamp. For columns operating in the vacuum pressure range, an alternative strategy to reduce energy consumption is to minimise the column pressure drop. Advanced mass trans - fer components such as the structured packing described herein can provide the same required degree of separation at a lower pressure drop, thereby reducing the reboiler duty. This is an important factor to consider in energy-efficient process designs such as heat pump-assisted vacuum distil - lation, heat-integrated distillation process, and mechanical vapour recompression distillation unit designs. Pressure drop in a column is essentially energy loss. A lower pressure drop minimises the temperature gap between the top and bottom of the column and helps to improve the coefficient of efficiency of the heat pump or compressor. Importance of column internals As the operating conditions of the columns are pushed to higher capacity limits, uniform vapour and liquid distribu - tion must be achieved throughout the entire column. The design of column internals such as the liquid distributor, redistribution system between packed beds, feed inlet, and other gas or liquid inlet devices must be engineered to meet the demanding requirements. The negative effects of liquid maldistribution in a packed column have been investigated extensively.4 Maldistribution contributes to the loss of sepa - ration efficiency and must be avoided to ensure the packing can perform to its full potential. Well-engineered column internals are even more indis - pensable for challenging operating conditions, such as that of the ultra-low liquid load processes illustrated in the previ - ously mentioned AYPlus DC packing. A specially designed liquid distributor is essential to enable the performance of the packing. Extensive expertise is required to design a distribu - tion system that provides uniform liquid flow over all distrib - utor drip points onto the AYPlus DC packed bed under very low liquid load conditions. The performance of this packing with a MellaTech ultra-low liquid load distributor was tested at the Sulzer R&D Center under the supervision of an inde - pendent testing organisation in 2022. The test result with an N,N-dimethylformamide (DMF)-water mixture demon - strates that the packing outperforms equivalent metal sheet structured packings with up to three times more absorption efficiency at very low liquid load while meeting requirements in terms of capacity and pressure drop, as shown in Figure 4 . Another growing challenge is the increasing diameter of distillation columns. Designing mega columns requires extensive knowledge and adequate industry experience. Correcting liquid maldistribution becomes increasingly diffi - cult with larger column diameters, requiring advanced liquid distribution systems and meticulous liquid distributor test - ing. Gas phase distribution is equally critical for stable col - umn operation. Computational fluid dynamics (CFD) studies are often utilised to visualise and quantify gas distribution in the column and, subsequently, to optimise the design of the inlet configuration.

System: DMF absorption in water

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MellapakPlus 252.Y

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Notwithstanding these challenges, column internals can be confidently designed with a thorough understanding of the process, mechanical, and engineering aspects of the column. To date, Sulzer has delivered more than 200 ref - erences of packed columns with diameters exceeding 10 metres in various applications. Conclusion The primary function of structured packing is to provide an effective interfacial area for intimate and intensive contact of the vapour and liquid phases required to achieve the desired degree of separation. For structured packing to fully realise its benefits, column internals must be designed to provide uniform vapour and liquid distribution to the pack - ing. Distillation processes are inherently energy intensive. Innovative column internals, such as packings and distrib - utors, combined with application expertise and distillation process know-how, are critical to achieving greater produc - tivity and efficiency in the chemical separation industry. BXPlus, CYPlus, AYPlus DC, MellaCarbon, MellapackCC, Mellapak, Mellapak Plus, MellapakEvo, MellapakPlus 252.Y, MellapakPlus 452.Y, and MellaTech are trademarks of Sulzer Chemtech . References 1 M Y Lee, Mass Transfer Technology for Next-Generation Carbon Capture, GHGT-16 , 2022. 2 Sholl D, Lively R, Seven chemical separations to change the world. Nature 532 , pp435-437, 2016. 3 Pilling M, Be Smart about Column Design, AIChE , 2012. 4 Spiegel L, The Maldistribution Story – An Industrial Perspective. AIDIC, Vol. 69, 2018. Shwu Tyng Goh is global product manager of packings at Sulzer Chemtech, oversees research and development projects for packings products and leads packings product launch and marketing activities. She holds a Bachelor of Science in Chemical Engineering from National University of Singapore and a Master of Business Administration from Nanyang Business School, Singapore. Thomas Linder is head of mass transfer products at Sulzer Chemtech, manages the research and development for packings, internals, trays, mixers and separators. He holds a master’s degree in chemical- and bioengineering and a doctorate from the Friedrich Alexander University in Erlangen-Nuremberg, Germany. Figure 4 Pilot test results comparing number of transfer units per meter packing height of AYPlus DC and MellapakPlus 252.Y packings in a low liquid load system

PTQ Q3 2024