need for separate reboilers and condensers for each column, reducing equipment and energy demand. A DWC design represents the next level of improvement over the Petlyuk column, integrating the pre-fractionator column within the same shell as the main column. This arrangement (see Figure 2 ) involves placing a vertical baffle/wall inside the column, effectively dividing it into two functional sections: the pre- minimise the remixing phenomenon among different components, thereby enhancing the thermodynamic separation efficiency. The result is a significantly reduced energy requirement compared to a conventional distillation column separation scheme. The global refining and petrochemical industries are increasingly focused on energy efficiency to remain competitive and comply with regulations aimed at promoting greener energy and a reduced carbon footprint. DWC technology offers a simple, low-cost, and efficient solution that aligns with these goals and plays a vital role in enhancing energy efficiency efforts. Distill-Max DWC technology The DWC concept has been known for more than 50 years, with the first patent issued in 1949. However, its commercialisation was delayed due to historically low energy costs, a lack of established design procedures, and a general industry preference for conventional column designs. KBR developed its proprietary DWC technology, known as Distill-Max, in the late 1980s through pilot plant studies. The first industrial implementation was at bp’s Coryton Refinery in 1998, where it was used to revamp bp’s stabiliser column, which produced a special gasoline blend component. Since then, KBR has successfully licensed several grassroots and revamp DWC units globally. fractionator and the main-fractionator. This integration allows the DWC to Distill-Max DWC technology offers several key advantages over conventional distillation column schemes: • Capital cost savings : A DWC can reduce grassroots capital costs by ~25-30%, primarily due to a lower equipment count.
A
Liquid split
Main fractionator
Feed (ABC)
B
Dividing wall
Prefractionator
Vapour split
C
Figure 2 Dividing wall column
• Improved energy efficiency : Enables more than 25% energy savings compared to traditional sequential column operations. • Opex savings : Enables an increase in column throughput due to better separation efficiency and improved fractionation performance compared to conventional schemes. • Reduced plot space : A DWC system requires less plot space because it involves fewer pieces of equipment and fewer auxiliaries. opportunity to improve gross refinery margins with a short payback period. The advantages of this technology are clearly demonstrated by the recent revamp of the existing reformate splitter at Kochi Refinery of Bharat Petroleum Corporation Limited (BPCL) in India. Case study Distill-Max technology offers a valuable In 2014, the reformate splitter column was upgraded using Distill-Max technology to produce a stream concentrated in benzene, thereby optimising the operations of the existing downstream aromatic recovery unit (ARU). To achieve this objective, the reformate splitter was modified to provide an additional benzene-rich side draw product as ARU feed. An overhead fin fan cooler was replaced with a water cooler during the revamp, and a new water cooler was also installed for cooling the side stream. These changes helped minimise the ARU feed stream flow by concentrating benzene in the side
Refining India
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