Decarbonisation Technology – August 2021

€200,000 annually vs the cost of a new APH and the associated revamping costs would call for a case-specific analysis, the results of which may be affected by geographical location, geopolitical factors, the prevailing carbon price and market conditions. Comparative results on a relative basis are shown in Figure 2 . Conclusion LNG has emerged as a clean source of energy, being a

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% of Base-Carbon emissions % of Base-APH area

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LNG-130

LNG-110

Figure 2 Relative heat recovery vs APH area analysis

where the refinery is ready to invest in augmenting the existing APH to one with a larger surface area for extracting more heat. The refinery may have to replace the existing APH with a new, larger one. The results are shown in Table 3. • Table 3 throws open another debate. It shows that additional investment in APH surface area can lead to CO 2 reduction; however, the magnitude of this additional saving of only 6 t/d is debatable, especially considering that it would call for a new APH with almost double the surface area. Notably, the carbon footprint would remain higher than the Min MW RFG. • Rather, it would be prudent to concentrate on Max MW RFG vs LNG, as covered in Table 2 , for a more practicable scenario and work out some basic economics. May 2021 has seen carbon prices in Europe breaching €50/ metric tonne of CO 2 . Thus, saving 23 metric tonnes of CO 2 per day through fuel shift from Max MW RFG to LNG equates to 7600 tonnes of CO 2 emissions reduced in an operating year (considering 333 operating days). Even if the price of carbon emissions remained constant at €50/metric tonne of CO 2 , an annual carbon reduction worth €380,000 can be realised on this route of LNG shift. • Further, if a revamping project is undertaken to increase APH capacity, an additional carbon saving of 6 t/d is feasible, which is equivalent to 2000 tonnes annually, amounting to a carbon revenue saving of approximately €100,000. Over and above this carbon reduction is a reduction in the annual fired duty of the order of 31,000 MMBtu. Considering concurrent LNG pricing of about $4/ MMBtu (equivalent to ~3.4€/MMBtu), this would lead to incremental savings of €100,000 more. Economic analysis of the combined savings of

dependable and stable source of supply. The role of LNG in curbing carbon emissions is well established in the power and steel industry, where coal is still the mainstay. For refinery furnaces, LNG’s role in reducing carbon emissions is a tough call. As shown in the case study, shifting from fuel oil to LNG can result in a 29% carbon footprint reduction so that LNG can become an obvious choice for fuel oil-based furnaces. However, for furnaces already being operated on fuel gas, shifting to LNG one-to-one might not lead to significant carbon reductions, and the figure can vary depending upon the molecular weight of the fuel gas. At this juncture, the clean nature of LNG can be taken advantage of, and the area of APH can be augmented. However, the gain in carbon reduction vis-à-vis the increase in APH heating surface area is not in proportion. Therefore, the decision in this regard needs to be evaluated depending upon various factors. To sum up, LNG holds promise. More assessment on a case-by-case basis and favourable conditions or stricter emission caps could lead to better results in all scenarios. The authors would like to thank Ms Shilpa Singh (DGM-EIL) for her encouragement and valuable guidance in preparing this article.

Ankur Saini ankur.saini@eil.co.in Akhil Gobind akhil.gobind@eil.co.in RupamMukherjee rupam.mukherjee@eil.co.in