1、STD-API/PETRO PUBL 4b4b-ENGL L79b 0732270 05b3L04 2b0 = documenting performance; and communicating with the public. API ENVIRONMENTAL MISSION AND GUIDING ENVIRONMENTAL PRINCIPLES The members of the American Petroleum Institute are dedicated to continuous efforts to improve the compatibility of our o
2、perations with the environment while economically developing energy resources and supplying high quality products and services to consumers. We recognize our responsibility to work with the public, the government, and others to develop and to use natural resources in an environmentally sound manner
3、while protecting the health and safety of our employees and the public. To meet these responsibilities, API members pledge to manage our businesses according to the following principles using sound science to prioritize risks and to implement cost-effective management practices: 9 To recognize and t
4、o respond to community concerns about our raw materials, products and operations. 4 To operate our plants and facilities, and to handle our raw materials and products in a manner that protects the environment, and the safety and health of our employees and the public. 9 To make safety, health and en
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9、le, use, transport or dispose of similar raw materials, petroleum products and wastes. STD.API/PETRO PUBL 4bLib-ENGL 177b 0732290 05b31Ob 033 Evaluation of Fuel Tank Flammability of Low RVP Gasolines Health and Environmental Sciences Department API PUBLICATION NUMBER 4646 PREPARED UNDER CONTRACT BY:
10、 DAVID W. NAEGELI SOUTHWEST RESEARCH INSTITUTE US. ARMY TARDEC FUELS AND LUBRICANTS RESEARCH FACILITY (SwRI) P.O. Box DRAWER 28510 SAN ANTONIO, TEXAS 78228-051 O DECEMBER 1996 American Petroleum Institute STD.API/PETRO PUBL 4bqb-ENGL L77b 0732270 05b3L07 T7T FOREWORD API PUBLICATIONS NECESSARILY ADD
11、RESS PROBLEMS OF A GENERAL NATURE. WITH RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE, AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED. API IS NOT UNDERTAKING TO MEET THE DUTIES OF EMPLOYERS, MANUFAC- TURERS, OR SUPPLIERS TO WARN AND PROPERLY TRAIN AND EQUIP THEIR EMPLOYEES, AND OTHERS EXPOS
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13、 OR PRODUCT COV- ERED BY LETTERS PATENT. NEITHER SHOULD ANYTHING CONTAINED IN ITY FOR INFRINGEMENT OF LETERS PATENT. THE PUBLICATION BE CONSTRUED AS INSURING ANYONE AGAINST LIABIL- Copyright O 1996 American Petroleum Institute iii STD.API/PETRO PUBL qbllb-ENGL L99b 0732270 O5b3108 70b E ACKNOWLEDGME
14、NTS THE FOLLOWING PEOPLE ARE RECOGNIZED FOR THEIR CONTRIBUTIONS OF TIME AND EXPERTISE DURING THIS STUDY AND IN THE PREPARATION OF THIS REPORT API STAFF CONTACT David Lax, Health and Environmental Sciences Department MEMBERS OF J. Steve Welstand, Chairperson, Chevron Research and Technology Bill Band
15、y, Amoco Research Center Helen Doherty, Sun Refining and Marketing Company John Eckstrom, Amoco Research Center King Eng, Texaco, Inc. Dennis Feist, Shell Development Company Ana Rodriguez Forker, Arco Products Company Frank S. Gerry, BP America, Inc. Peter Jessup, Unocal Corporation George S. Musse
16、r, Exxon Research and Engineering Company Mani Natarajan, Marathon Oil Michael Payne, Arco Products Company Robert M. Reuter, Texaco, Inc. Rick Riley, Phillips Petroleum Charles Schleyer, Mobil Research and Development James P. Uihlein, Unocal Corporation iv STD.API/PETRO PUBL 4blib-ENGL L77b = 0732
17、270 05b3L07 842 ABSTRACT The changes in fuel properties brought on by the reformulation of gasoline to reduce VOC emissions in urban areas with severe ozone problems have raised concerns about potential impacts on the flammability of hydrocarbon vapors in closed storage vessels such as automobile fu
18、el tanks. A desire to define the effects of reformulated gasoline (RFG) on flammability temperature limits prompted this study. Several experiments were performed to evaluate the conditions under which the vapors from reformulated gasoline (RFG) contained in automobile fuel tanks become flammable. T
19、he program was conducted with 22 test fuels that had been systematically varied with respect to Rei vapor pressure (RVP), pentane-to-butane ratio, and addition of ethanol and MTBE. In Phase I, vapor pressures were measured for each test fuel over a 15 to 130F temperature range. In addition, the uppe
20、r and lower temperature limits of flammability were measured for each fuel. Phase II involved measurements of the concentrations of hydrocarbons in the vapor phase and an assessment of stratification. The results show that temperature limits of flammability correlate with RVP. The upper flammability
21、 temperature limits increase as RVP is reduced. The addition of either MTBE or ethanol or both to gasoline indicates a moderate increase in upper flammability limits. Gasoline blends containing ethanol, including those commingled with MTBE, elevate the upper flammability limits more substantially th
22、an do gasoline blends containing MTBE. The lower temperature limits of flammability also increase as RVP is reduced, although less markedly than the upper limits. The flammable concentration limits of the gasolines containing ethanol are substantially greater than those containing MTBE or no oxygena
23、tes. The flammable concentration limits of gasolines containing MTBE are only slightly higher than those of the test gasolines with no oxygenates. The ratio of C,-to-C, hydrocarbons in the fuel has no consistent effect on either the upper temperature limits of flammability or the upper concentration
24、 limits of flammability when comparing fuels at similar RVP levels. STD.API/PETRO PUBL 4b4b-ENGL L99b m 0732270 05b3LLO 5b4 m TABLE OF CONTENTS Section Paqe EXECUTIVESUMMARY . e5-1 1 . INTRODUCTION . 1-1 2 . TESTFUELS . 2-1 FUELS PROCUREMENT AND FORMULATION 2-1 FUEL ANALYSIS 2-2 FUELMATRIX 2-5 3 . P
25、HASE I STUDY 3-1 VAPOR PRESSURE MEASUREMENTS 3-1 Apparatus and Procedure . 3-1 Results 3-1 TEMPERATURE LIMITS OF FLAMMABILITY . 3-6 Apparatus 3-6 Procedure . 3-7 Results . 3-8 4 . PHASE II STUDY 4-1 VAPOR PHASE SPECIATION 4-1 Apparatus and Procedures 4-1 Analytical Method 4-2 Speciation Results 4-3
26、STRATIFICATION . 4-8 General Approach 4-8 Experiment I . 4-9 Experiment II 4-10 Fuel Tank Test . 4-15 Procedure . 4-16 Results . 4-16 REFERENCES . R-I 5 . SUMMARY OF KEY FINDINGS 5-1 TABLE OF CONTENTS (continued) Section Page Appendix A VAPOR PRESSURE DATA . A-1 Appendix B CORRELATIONS OF VAPOR PRES
27、SURE WITH TEMPERATURE AND RVP B-1 Appendix C TEMPERATURE LIMITS OF FLAMMABILITY DATA C-1 Appendix D Appendix E FLAMMABILITY LIMITS OF HYDROCARBONS . D-1 REGRESSION COEFFICIENTS FOR UPPER TEMPERATURE FLAMMABILITY LIMIT DATA IN FIGURE 5 . E-1 Appendix F VAPOR PHASE SPECIATION OF TEST FUELS. . F-1 Appe
28、ndix G Appendix H STRATIFICATION EXPERIMENTS G-1 FUEL TANK TEST H-1 STD.API/PETRO PUBL 4b4b-ENGL L99b E 0732290 05b3112 337 W Fiqure 3- 1 3-2 3-3 3-4 3-5 3-6 4- 1 4-2 4-3 4-4 4-5 4-6 4-7 LIST OF ILLUSTRATIONS Paqe Clausius-Clapeyron plots for ethanol and MTBE showing the effect of temperature on vap
29、or pressure . 3-2 Comparison of vapor pressures predicted by Eq. 2 with measured values . . 3-5 Temperature limit of flammability test apparatus 3-7 The effect of RVP on the upper and lower temperature limits The effect of RVP on the upper temperature limits Calculated upper concentration flammabili
30、ty limits of the test fuels 3-15 The effect of fuel RVP on the vapor phase concentrations of ethanol and MTBE . 4-5 Measured upper concentration flammability limits of the Fuel temperature and vapor concentration history in a vessel that has been pre-cooled to 45F and allowed to warm to room tempera
31、ture . 4-1 1 The time dependencies of the fuel temperature and the percent of vapor-liquid equilibrium in a vessel that has been pre-cooled to 45OF and allowed to warm to room temperature . 4-12 The time dependence of the percent of vapor-liquid equilibrium in a vessel at constant temperature (75F)
32、. 4-13 The effect of molecular weight on the rate of diffusion of species into the vapor space . 4-14 Fuel tank test results . 4-18 of flammability of all the test fuels 3-12 of flammability of the gasoline test fuels . 3-13 gasoline test fuels . 4-7 LIST OF TABLES Table Page 1-1 Fuel Parameters for
33、 Conventional Gasoline and “Simple Model“ RFG 1-2 2-1 Composition of Baseline Gasolines Prepared at SwRI 2-2 2-2 Baseline Gasoline Properties and Compositions 2-3 2-3 2-4 2-4 Test Fuel Descriptions . 2-6 3-1 Coefficients for the Expression Log(P. ) = A + B/T+ C/F. . 3-3 3-2 Correlation Coefficients
34、for the Expression P = RVP exp(a + b/T+ cnp). 3-3 Limits of Flammability . 3-9 4-1 Temperature and Concentration Limits of Flammability . 4-4 4-2 Fuel Vapor/Air Mixture Analysis in a Fuel Tank Over a Diurnal Cycle in the 60 to 84F Range 4-17 ASTM D 86 Boiling Point Distributions of Baseline Gasoline
35、s. OF Where Pvap is in psia and Tis in OR Where P is in psia. RVP is Reid vapor pressure in psia. and T is in OR 3-5 STD.API/PETRO PUBL LIbLib-ENGL L79b 0732290 05b31LLI LOT GLOSSARY OF TERMS Lower Concentration Limit of Flammability (LCLF) - The lowest concentration of vapor in dry air which will p
36、ropagate a flame away from an ignition source. (The lean flammability limit of the fuel vapor.) Upper Concentration Limit of Flammability (UCLF) - The highest concentration of vapor in dry air which will propagate a flame away from an ignition source. (The rich flammability limit of the fuel vapor.)
37、 Lower Temperature Limit of Flammability (LTLF) - Temperature at which the lower concentration limit of flammability (LCLF) exists in dry air under conditions of vapor-liquid equilibrium. Temperatures below the LTLF result in gasoline vapor concentrations that are too low to propagate a flame away f
38、rom an ignition source. Upper Temperature Limit of Flammability (UTLF) - Temperature at which the upper concentration limit of flammability (UCLF) exists in dry air under conditions of vapor-liquid equilibrium. Temperatures above the UTLF result in gasoline vapor concentrations that are too high to
39、propagate a flame away from an ignition source. - STD.API/PETRO PUBL LibLib-ENGL L79b 0732290 05b3335 OLib EXECUTIVE SUMMARY The changes in fuel properties brought on by the reformulation of gasoline to reduce emissions in urban areas with severe ozone problems have raised concerns about potential i
40、mpacts on the flammability of hydrocarbon vapors in closed storage vessels such as automobile fuel tanks. Recent changes to gasoline which are needed to meet the federal requirements for reformulated gasoline (RFG) include the addition of ethanol and/or methyl t-butyl ether (MTBE), reduction in the
41、benzene content, and lower Reid vapor pressure (RVP). The primary means for lowering RVP is to reduce the amount of butane in the gasoline. Lowering the RVP results in a decrease in the concentration of hydrocarbon vapors in the vapor space above the fuel. For gasoline, this decrease would tend to r
42、aise the upper temperature limit of flammability (UTLF). Oxygenates also could increase the upper temperature limit of flammability of fuel vapors as these compounds generally have wider flammability limits than hydrocarbons. At temperatures below the upper temperature limit of flammability, the con
43、centration of vapors in a fuel tank can fall to the point where there is sufficient air or oxygen to sustain combustion or an explosion if an adequate ignition source is present. In 1995, the American Petroleum Institute (API) sponsored a study to define the effects of reformulated gasoline (RFG) on
44、 flammability temperature limits. The study was conducted on 22 test fuels that had been systematically varied with respect to RVP, pentane-to-butane ratio, and concentrations of ethanol and MTBE. In Phase I, vapor pressures of each of these test fuels were measured over temperatures ranging from 15
45、 to 130F. Correlations were developed to predict vapor pressures as functions of temperature for the various fuels. Upper and lower temperature limits of flammability were determined and correlated with vapor pressure and differences in composition. Phase II involved measurements of the concentratio
46、ns of hydrocarbons in the vapor phase at the upper temperature limit of flammability (UTLF) of each test fuel and correlation of these results with the predicted upper concentration limits of flammability ES-1 STD.API/PETRO PUBL 4b4b-ENGL L77b m 0732290 05b3Llb T82 m reported in Phase I. Phase II al
47、so entailed an assessment of stratification in an automobile fuel tank. Experiments were performed to study the interaction of temperature change, air dilution and mass diffusion rate with respect to changes in vapor-liquid equilibrium in fuel tanks. The reader should be aware that this study is an
48、assessment of the “risk“ of igniting vapors from low RVP and oxygenated fuels in a fuel tank. Such an assessment would have required both a detailed technical analysis of potential sources of ignition and the determination of the probabilities of igniting flammable fuel tank vapors by the various so
49、urces. That type of analysis was beyond the scope and level of resources available for this effort. The following key findings result from the experiments conducted in this study: The temperature limits of flammability correlate with RVP. The upper flammability temperature limits increase as RVP is reduced. The temperature limits for non- oxygenated fuels correlate well with prior studies. The addition of either MTBE or ethanol or both to gasoline yields a moderate increase in upper flammability limits. Gasoline blends containing ethanol, includ
