PTQ Q1 2023 Issue

With this configuration in place, RFU Splitters I and II are sufficient to split the entire quantity of stabilised naphtha from the CDUs. Major modifications during reconfiguration No modifications were envisaged in the Splitter I and II reboilers, which are fired heaters. Four new heat exchanger shells were added by replacing three existing ones to meet the revised cooling requirement of various process streams. Further, seven new pumps with LT motors replaced five existing pumps. Major modifications during the reconfigu - ration are listed in Table 2 . Post-reconfiguration product specifications are provided in Table 3 . Divided wall column technology The reconfiguration of naphtha splitters is based on opti - mised DWC, which maximises product yields. The added benefit of lower capital investment combined with lower operational cost has helped DWCs gain popularity over conventional columns. When applied to sequential multi- component separation, DWCs can separate the feed into two or more purified streams within a single tower, thus eliminating the need for a second tower. DWCs offer the following benefits: • Suitable for separating multi-component mixture into three or more high-purity product streams in a single column • Ideal alternative for revamp of side-cut columns when high purity is required from the three product streams • Lower footprint as equipment count is reduced by half • Equipment turnaround time and other miscellaneous expenditure are reduced • Operational and capital expenditure are reduced by approximately 20-50%. The following are the salient features of reconfiguring the naphtha splitters: • Integration between Splitters I and II: the side-cut from Splitter I substantially overlaps C5 components. The side- cut from Splitter I is fed to Splitter II on the feed side of the dividing wall. This leads to a considerable reduction in the overall side-cut rate from the two columns. The new pack - ings in both columns are high-efficiency packings, which are capable of handling high vapour liquid traffic • Flexibility has also been provided to operate Splitter I and II columns in a series configuration. In addition to the product quality improvement post- reconfiguration, the yield of top and bottom cuts has been

Post-reconfiguration product specifications

Parameter

Top

Mid-cut

Bottom product

product

IBP, ºC

- -

- - - - - - -

>95 >98

D86 5%V, ºC D86 95%V, ºC

<80 <85

- - - - - -

FBP, ºC

Benzene, %w

C₆ naphthenes, %w C7 hydrocarbons, %w

<10

Toluene, %w

Table 3

increased considerably, thereby reducing the mid-cut, which goes to the naphtha pool. Mid-cut generation has decreased significantly, and mid-cut quality has improved, with less overlap of the stream with top and bottom cuts. Thanks to the ISOM naphtha splitter shutdown, MR could achieve huge energy consumption savings, contributing to a reduction in emission of approximately 29,000 tons/annum of GHG. Optimisation of process parameters, digital transformation, and use of DWCs can deliver increased energy efficiency and minimise the carbon footprint of the industry Conclusion Oil and gas will remain part of the energy mix until renew - able energy sources adequately replace them. For the world to meet ambitious emissions reduction targets, a premium value needs to be associated with the lowest carbon-intensity oil and gas assets. Optimisation of pro - cess parameters, digital transformation, and use of DWCs can deliver increased energy efficiency and minimise the carbon footprint of the industry. With the latest advances in process simulators and design methods, DWCs have emerged as a viable technology that can also be integrated into existing refining technologies to reduce operating cost. BPCL refineries are embarking on the journey to meet the net-zero target by 2040. With the reconfiguration of naph - tha splitters, BPCL MR has two DWCs: a middle DWC with structured packings in the RFU and a top DWC with trays, a deisohexaniser, in the ISOM unit, with huge savings in terms of energy. Our third DWC, a dearomatised solvent splitter in the lubricating oil base stock (LOBS) unit, will be operational in another couple of months. Ratheesh S is Manager, Process Technology, Bharat Petroleum Corpo - ration Limited Mumbai refinery. He has over 12 years of experience in front-end engineering design, detailed engineering, pre-commission - ing and commissioning, start-ups, turnarounds and technical services for refineries in India and abroad. He holds a B. Tech in chemical en - gineering from Thangal Kunju Musaliar College of Engineering, Kollam affiliated to University of Kerala. Email: ratheeshs@bharatpetroleum.in

Figure 3 New dividing wall inside Splitter II

PTQ Q1 2023