INVESTIGATION INTO FIRE SPREAD IN PETROLEUM TANK FARM USING CFD SIMULATIONS- Joseph Adoghe

The casualties arising from fire and explosions in tank farm operations are alarming and heartbreaking and thus call for urgent remedy. In achieving this, the effect of wind on fire spread was critically investigated using CFD Simulations. The wind effect is crucial for safe tank farm operations and this depends largely on the chemicals stored and the tank capacity and the wind speed of Nigeria was employed for this research project. An explicit work of wind effect showed that as the wind speed increases, the heat release rate (HRR) decreases and the flame height decreases thereby reducing the safe tank distance (1), (2) and (3).

Transcript

1. INVESTIGATION INTO FIRE SPREAD IN PETROLEUM TANK FARM USING CFD SIMULATIONS BY JOSEPH OWEDE ADOGHE UNIVERSITY OF CENTRAL LANCASHIRE PRESTON, LANCASHIRE, UK. MSc Fire Safety Engineering 15th June 2014 1
2. ABBREVIATIONS 2 CFD: “Computational Fluid Dynamics” FDS: “Fire Dynamics Simulations” HRR: “Heat Release Rate(kw)”
3. AN OUTLINE OF THIS PRESENTATION 3  Introduction  Background knowledge.  Significance of research  Aim & Objectives of research  Methodology  Results  Summary/Conclusion  Recommendation  References  The End
4. PREAMBLE 4 CFD is a fluid flow simulation frequently used in Engineering designs e.g. Considering a room or a lecture theatre with cubes as units of cells and there is interaction of fluid flow. Then the computational fluid flow is measured. CFD has many tools and among them is FDS used to measure low speed thermally driven transportation of heat and combustion. FDS is best for simulating fires. For example: CFD is used for: 1) Car manufacture- to simulate the aerodynamics surrounding the car. 2) Weather forecast –divide the world into small areas and find the resolution step by step. FDS can do the following: 1) Low speed thermally driven transportation of heat and combustion products from fires 2) Chemical reaction 3) Heat transfer between one wall and the other etc.
5. The casualties arising from fire and explosions in tank farm operations are alarming and heartbreaking and thus call for urgent remedy. In achieving this, the effect of wind and tank diameter on fire spread were critically investigated using CFD/FDS Simulations. The wind effect is crucial for safe tank farm operations and this depends largely on the chemicals stored and the tank diameter/capacity and the wind speed of Nigeria was employed for this research project. The result showed that the heat release rate (HRR) decreases with increase in wind velocity and thus reducing the safe tank distance (1), (2) and (3). INTRODUCTION
6. Background Knowledge To This Presentation 6 Table 1: Tank Farm Incidents (4) Incidents Causes Cost Effects Buncefield fire, Hertfordshire, UK. 11/12/2005. Human Failure/ Instrumental Failure (i) £1 million materials burnt. (ii) 630 nearby homes burnt. (iii) Nearby businesses burnt. Oil Field fire, Mississippi, USA. 05/06/2006. Fire Explosion (i) 500 deaths. (ii) 3 contractors killed (iii) 1 person injured. Amuay Refinery fires, Venezuela. 25/08/2012. Sabotage (i) 48 deaths. (ii) 86 persons injured. (iii) 500 nearby homes burnt. (iv) 956,000 bbl/day lost. Chevron Oil Tank fire, Escravos, Nigeria. 20/07/2002. Lightning 180,000 bbl/day lost.
7. Background contd. 7 Fig I :Amuay Refinery fires, Venezuela (5)
8. TANK FARM LAYOUT 8 Fig.2: Chevron Tank Farm, Escravos, Nigeria (4).
9. SIGNIFICANCE 9 Gave insight into the fire challenges in tank farm design and construction especially in areas of tank diameter and wind velocity.
10. AIM 10 To identify the relationship between wind velocity, tank diameter and their effect on fire spread due to radiation.
11. OBJECTIVES 11 1. To set up a CFD modeling of petroleum tank farm design. 2. To identify the relationship between tank diameter and fire spread. 3. To identify the effect of wind parameters on fire spread.
12. METHODOLOGY 12 Despite previous researchers have employed other techniques such as the Zone models and hand-calculation models which consist of: (I) point-source model, (ii) Shore and Beyler’s method, and (iii) Mudan’s method to predict safe separation distance between tanks, but no accurate results have been obtained because fire incidents are still on the increase. Today, fire modeling tool is used primarily to predict the spread of fire and smoke. However, CFD/FDS research tools are employed to predict accurately the effect of tank diameter and wind velocity on fire spread in storage tank farms. In this research work, six scenarios are analysed for each tank diameter of 7.5m and 9.6m respectively to investigate the effect of wind velocity and tank diameter on fire spread using CFD/FDS (1) and (3).
13. RESULTS 13 Fuel was modeled as jet fuel and was allowed to burn as liquid fuel. Varied Wind velocity and tank diameter were examined as variables and they had significant effect on fire spread(3). The result showed that as the tank diameter was varied and wind velocity increases, the height of flame decreases and the more the fire spread from one tank to another. This implies that as the wind velocity increase, the HRR decreases. Hence, for 7.5m and 9.6m tank diameters at 0m/s, the peak HRR was 68,250.17KW, and 186,821.51KW respectively, but for that of 7.5m and 9.6m at 10m/s, it was 49,164.55KW and 46,072.96KW respectively. From figures 3 and 4 below for 7.5 diameter, only NFPA and Taiwan and for 9.6m diameter only P21 and P27 that did not satisfy the critical value of heat flux of 4.732 KW/m2. If the diameter is smaller, the fire area is smaller, then the firepower and the HRR are smaller (5).
14. CFD SET UP OF TANK FARM LAYOUT 14 Figure 3: CFD set up of 7.5 m tank diameter in a Tank Farm illustrating tank farm Layout.
15. FDS SETUP Figure 4: Simulated FDS of 7.5m tank diameter in a Tank Farm illustrating tank farm Layout
16. SET UP OF TANK FARM LAYOUT 16 Figure 5: Sketch of 9.6m tank diameter in a Tank Farm illustrating tank farm Layout.
17. CFD SETUP OF 9.6m TANK DIAMETER Figure 6: CFD set up of 9.6m tank diameter in a Tank Farm illustrating tank farm Layout.
18. FDS SETUP Figure 7: Simulated FDS of 9.6m tank diameter in a Tank Farm illustrating tank farm Layout
19. RESULTS 19 0 1 2 3 4 5 6 0 2 4 6 8 10 12 Heat Flux (KW/m2) Wind Velocity (m/s) Heat Flux (KW/m2) against Wind Velocity (m/s) at 7.5m tank diameter Point Source Shokri Mudan NFPA API Taiwan Linear (Critical Value) 4.732 KW/m2 Figure 8: Heat flux (KW/m2) against Wind velocity (m/s) at 7.5m tank diameter.
20. RESULTS CONTD. 20 0 1 2 3 4 5 6 0 2 4 6 8 10 Heat Flux (KW/m2) Wind Velocity (m/s) Heat Flux (KW/m2) against Wind Velocity (m/s) at 7.5m tank diameter Point source Shokri Mudan NFPA API Taiwan Linear (Critical value) 4.732 KW/m2 Figure 9: Heat flux (KW/m2) against Wind velocity (m/s) at 7.5m tank diameter.
21. RESULTS CONTD. 21 0 1 2 3 4 5 6 7 8 9 10 0 2 4 6 8 10 12 Heat Flux (KW/m2) Wind Velocity (m/s) Heat Flux (KW/m2) against Wind Velocity (m/s) at 9.6m diameter P11 P21 P31 P12 P22 P32 P13 P23 P33 P24 P26 P15 P25 P35 P17 P27 P37 P18 P28 P38 Linear (Critical Value) 4.732 KW/m2 Figure 10: Heat Flux (KW/m2) against Wind Velocity (m/s) at 9.6m tank diameter
22. RESULTS CONTD.. 0 1 2 3 4 5 6 7 8 9 10 0 2 4 6 8 10 Heat Flux (KW/m2) Wind Velocity (m/s) Heat Flux (KW/m2) against Wind Velocity (m/s) at 9.6m tank diameter P11 P21 P31 P12 P22 P32 P13 P23 P33 P24 P26 P15 P25 P35 P17 P27 P37 P18 P28 P38 Linear (Critical Value) 4.732 KW/m2 Fig. 11: Heat flux (KW/m2) versus Wind velocity (m/s) at 9.6m tank diameter.
23. RESULTS CONTD. 0.00 20,000.00 40,000.00 60,000.00 80,000.00 100,000.00 120,000.00 140,000.00 160,000.00 180,000.00 200,000.00 0 2 4 6 8 10 12 Peak HRR (KW) Wind Velocity (m/s) Peak HRR (KW) against Wind Velocity (m/s) at 7.5m and 9.6m tank diameter. Peak HRR at 7.5m Peak HRR at 9.6m Figure 12: Peak HRR (KW) against Wind velocity (m/s) at 7.5m and 9.6m tank diameters.
24. RESULTS CONTD. 0.00 20,000.00 40,000.00 60,000.00 80,000.00 100,000.00 120,000.00 140,000.00 160,000.00 180,000.00 200,000.00 0 2 4 6 8 10 Peak HRR (KW) Wind Velocity (m/s) Peak HRR (KW) against Wind Velocity (m/s) at 7.5m and 9.6m diameters Peak HRR at 7.5m diameter Peak HRR at 9.6m diameter Figure 13: Peak HRR (KW) against Wind velocity (m/s) at 7.5m and 9.6m tank diameters.
25. Twelve scenarios were analysed for this research work involving tank diameters of 7.5m and 9.6m respectively. It was observed that as the wind velocity increases and the tank diameter increased, the flame height decreases with wind velocity increase and this consequently brings about decrease in safe distance between adjacent storage tanks in Petroleum storage tank farms. Moreover, it was discovered that the NFPA and Taiwan standards did not put into consideration the effect of wind velocity say at 8m/s for the 7.5m tank diameter and for P21 and P27 devices for 9.6m tank diameter did not satisfy the critical value of Heat flux of 4.732KW/m2. The smaller the diameter, the smaller the fire area and invariably the smaller the firepower and the heat release rate (HRR). Therefore, the results obtained from the CFD/FDS analyses were very accurate, ideal and adequate for safe tank farm operations (1) and (4). SUMMARY/CONCLUSION
26. For further researchers, to consider:  Other natural factors such as hurricane, earthquake etc. Smoke visibility. Tank height. RECOMMENDATION
27. (1) Meng, Y., Zhoo, D. and Wong, W. (2012) “Study on performance-based safety spacing between ultra large Oil tanks”, Process safety progress, 31(4), pp 398-400. (2) Adaramola, M. S. and Oyewola, O. M. (2011) “Wind speed distribution and Characteristics in Nigeria”, Journal of Engineering and Applied Sciences, 6(2), p.82. (3) Bahmann, A., Vahid, B., Davood, R. and Genserik, R. (2013) “Fire dynamics Simulation of multiple ethanol pool fires”, Research journal of Chemistry and Environment, 17,PP 3-9. (4) Chang, J. I. and Cheng-Chung, L. (2006) “A study of storage tank incidents”, Journal of Loss prevention in the Process Industries, 19, pp 51- 59. (5) Sengupta, A. and Mishra, I. M. (2011) “Engineering layout of fuel tanks in a tank farm”, Journal of Loss Prevention in the process Industries, 24, pp 568-574. (6) Drysdale, Dougal (2012) “An Introduction to Fire Dynamics”, 3rd edition, United Kingdom, John Wiley & Sons Ltd. Pp130, 163-165. REFERENCES