From Heat Ingress to Financial Haemorrhage: Thermodynamic Characterization and Boil-Off Gas Economics of an LPG Storage Tank Under Tropical Ambient Conditions

Le-ol Anthony Kpegele^1*, Stanislaus Chinemerem Philip²

¹Sr. Lecturer, Department of Mechanical Engineering, Rivers State University, Port Harcourt, Nigeria.

²Student, Department of Mechanical Engineering, Rivers State University, Port Harcourt, Nigeria. 

Abstract

The generation of boil-off gas (BOG) in liquefied petroleum gas (LPG) storage tanks represents a simultaneous safety hazard and an escalating economic drain—especially within emerging tropical markets where ambient temperatures remain persistently elevated throughout the year. This study presents a comprehensive thermodynamic and heat-transfer analysis of a commercial 62.296 m³ double-containment, perlite-insulated LPG storage tank in Port Harcourt, Nigeria, characterized by a 12-month dataset of tank temperature and pressure. The Peng-Robinson equation of state is employed to compute monthly specific volume, density, compressibility factor, entropy, and enthalpy of butane LPG across ambient temperatures ranging from 297.1 K to 300.4 K. Thermal resistance analysis yields a total cylindrical wall resistance of 0.211 mK/W and a hemispherical end-cap resistance of 1.7738 m²K/W, confirming the dominant role of perlite insulation in impeding heat ingress. Monthly total heat leakage varies between 1,806.4 W (July) and 2,396.3 W (February), directly modulating BOG generation. The BOG rate ranges from 0.00666 kg/s to 0.00877 kg/s, with daily BOG quantities of 2.56%–3.26% of tank volume. At the prevailing LPG market price of ₦850/kg, the resulting financial losses span ₦5.66 to ₦7.45 per second of storage—equivalent to annual losses of up to ₦235 million per tank from heat-induced vapour generation alone. A strong positive linear correlation between ambient temperature and BOG generation is demonstrated, providing an analytical basis for targeted insulation upgrade and BOG recovery investment decisions in the Nigerian LPG sector. 

Keywords: Boil-off gas, Energy losses, LPG storage, Peng-Robinson EOS, Thermal resistance, Thermodynamic properties, Tropical climate. 

References

1. NLPGEP (2022) LPG Value Chain. National LPG Expansion Plan. Available at : http://dlpgovp.org/lpg-value-chain
2. Dobrota, D., Lalic, B. and Komar, I. (2013) ‘Problem of boil-off in LNG supply chain’, Trans. Marit. Sci., 2(2), pp. 91–100.
3. Amadi, H.N. (2018) ‘Wind energy potential assessment of coastal states in South-South Nigeria based on the Weibull distribution model’, Eur. J. Elect. Eng. Comput. Sci., 2(7), pp. 1–6.
4. Chen, Q.S., Wegrzyn, J. and Prasad, V. (2004) ‘Analysis of temperature and pressure changes in liquefied natural gas (LNG) cryogenic tanks’, Cryogenics, 44(10), pp. 701–709.
5. Khan, M.S., Qyyum, M.A., Ali, W., et al. (2020) ‘Energy saving through efficient BOG prediction and impact of static boil-off-rate in full containment-type LNG storage tank’, Energies, 13(7), pp. 1–14.
6. Khelifi, M.S., Benbrik, A., Lemonnier, D., et al. (2010) ‘Laminar natural convection flow in a cylindrical cavity application to the storage of LNG’, J. Pet. Sci. Eng., 71, pp. 126–132.
7. Zakaria, Z.B., Mustafa, A. and Mat, H. (2006) Heat and mass transfer studies in liquefied petroleum gas storage operations. Ph.D. dissertation, Univ. Technology Malaysia.
8. Shamekhi, S.S. and Ashouri, N. (2021) Minimize evaporation losses by calculating boiloff gas in LPG storage tanks. Gas Process. LNG. Available at: http://www.gasprocessingnews.com
9. Gbaarabe, B. and Sodiki, J.I. (2023) ‘Economic implication of boil-off gas generation in liquefied petroleum gas supply chain’, Int. J. Mod. Res. Eng. Technol., 8(4), pp. 8–18.
10. Adom, E., Zahidul, S.I. and Ji, X. (2010) ‘Modelling of boil-off gas in LNG tanks: A case study’, Int. J. Eng. Technol., 2(4), pp. 292–296.
11. Al Ghafri, S.Z.S., et al. (2021) ‘Advanced boil-off gas studies for liquefied natural gas’, Appl. Therm. Eng., 189, pp. 15–21.
12. Cengel, Y., Boles, M. and Kanoglu, M. (2019) Thermodynamics: An engineering approach. 9^th ed. New York: McGraw-Hill.
13. Usman, M.R. (2016) Advanced chemical engineering thermodynamics. Punjab: Inst. Chem. Eng. Technol.
14. Moran, M.J., Shapiro, H.N., Boettner, D.D., et al. (2011) Fundamentals of Engineering Thermodynamics. 7^th ed. Hoboken: Wiley.
15. Bergman, T.L., Lavine, A.S., Incropera, F.P., et al. (2011) Fundamentals of heat and mass transfer. 7^th ed. Hoboken: Wiley.
16. KTL (2019) Catalogues of aboveground storage tanks and accessories for LPG. Kada Technology Ltd. Available at: http://kadatec.cz