Flammability Limits of Binary Mixtures of 1,2-Ethanediol + Steam

1,2-Ethanediol and 1,2-propanediol are important chemical materials in the .... p0 = 101.3 kPa is the standard pressure, p is the pressure of vapor in...
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Flammability Limits of Binary Mixtures of 1,2-Ethanediol + Steam and 1,2-Propanediol + Steam Ke Zhang, Xianyang Meng,* and Jiangtao Wu Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, 710049, China ABSTRACT: Flammability limits of binary vapor mixtures of 1,2-ethanediol + steam and 1,2-propanediol + steam were measured by the ASHRAE method. The test temperatures were 473 K for 1,2-ethanediol + steam and 463 K for 1,2propanediol + steam. The observed values were analyzed by the extended Le Chatelier’s formula. It was found that the experimental results were excellently reproduced by the formula. In addition, the experimental results were compared with the estimated values based on the adiabatic flame temperature method. The observed values of lower flammability limits were in good agreement with the estimated values, and those of upper flammability limits were within acceptable deviations.

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INTRODUCTION 1,2-Ethanediol and 1,2-propanediol are important chemical materials in the syntheses of plasticizers, resin, explosives, cosmetics, and so forth.1,2 With relatively high boiling points and low freezing points, the aqueous solutions of 1,2-ethanediol and 1,2-propanediol are widely used as engine coolants and heat transfer agents.3 Knowledge of the combustion potential of chemicals is crucial when designing safe chemical processes. The flammability limit is one of the most important properties to consider when dealing with gases or liquids. However, flammability limits of binary mixtures of the two diols with steam could not be found in published literature. Thus, this work reports flammability limits of binary mixtures of 1,2ethanediol + steam and 1,2-propanediol + steam.

Table 1. Specification of Chemical Samples chemical

supplier

1,2ethanediol 1,2propanediol methanol

Tianjin Zhiyuan Chemical Reagent Co., Ltd., China Tianjin Zhiyuan Chemical Reagent Co., Ltd., China Tianjin Fuyu Chemical Reagent Co., Ltd., China Tianjin Fuyu Chemical Reagent Co., Ltd., China Tianjin Fuyu Chemical Reagent Co., Ltd., China

ethanol n-butanol

mass fraction purity

purification method

0.99

none

0.99

none

0.995

none

0.997

none

0.995

none

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EXPERIMENTAL METHODS Fluid Samples. All of the chemical samples used in this work were analytical grade. The methanol, ethanol, and nbutanol with a mass fraction purity of 99.5 %, 99.7 %, and 99.5 %, respectively, were provided by Tianjin Fuyu Chemical Reagent Co., Ltd., China. The 1,2-ethanediol and 1,2propanediol with a mass fraction purity of 99 % were provided by Tianjin Zhiyuan Chemical Reagent Co., Ltd., China. Complete specification of chemical samples is listed in Table 1. Deionized and redistilled water was used throughout all of the experiments. All sample materials were used without further purification. Apparatus. The measurements of flammability limits were done essentially by the ASHRAE method, which is a revised version of ASTM E681.4 Figure 1 is a schematic of the present apparatus. A 12-L spherical glass flask was placed in an oven, and the vessel cover held in place by two spring loaded clamps was outside the oven. Because of the high operating © 2013 American Chemical Society

Figure 1. Schematic of the experimental apparatus: A, oven; B, aluminum stopper; C, air inlet; D, silicon rubber liquid inlet; E, electrode; F, thermocouples; G, magnetic stir mechanism.

Received: June 30, 2013 Accepted: July 27, 2013 Published: August 13, 2013 2681

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temperature, an aluminum cover instead of rubber stopper was used. A silicon rubber seal ring between the cover and flask was designed to obtain vacuum inside the flask. The oven was heated to the regulated temperature by an electric heating blower. To maintain a uniform temperature inside the flask and avoid the condensation of vapor on the surface of aluminum cover, the neck of the flask and the cover were heated by two loop-shape heaters. Two K-type thermocouples, one was placed just below the neck of the flask and the other near the center of the flask, were used to measure the temperature and verify the thermal equilibrium within the flask. The stability and uniformity of the temperature inside the flask were better than ± 2 K. In the experiments, the vessel was evacuated below 1 kPa. A specified amount of prepared liquid sample was injected into the flask by a syringe. The consumed amount of sample was determined through weighing the syringe before and after injecting. An analytical balance (FA1004, Shanghai Shang Tian Precision Instrument Co., Ltd., China) with an accuracy of ± 0.0001 g was used to weigh the sample. Once the sample was completely evaporated, the preheated air was slowly introduced into the flask until the flask reached atmospheric pressure. The pressure was measured using a pressure transducer MPM 4730 (Micro Sensor Co., Ltd., China, ± 0.1 % FS). The accuracy of pressure measurement was ± 0.1 kPa. The mixture was agitated with a magnetic stirrer for at least 5 min to obtain complete mixing and attainment of thermal equilibrium. Shortly before ignition, the stirrer was turned off, and the mixture was left for 1 min to eliminate turbulence. After releasing the clamps on the cover, ignition was attempted by a 15 kV neon transform attached to a pair of tungsten electrodes 6.4 mm apart, with a spark duration limited to 0.4 s. The electrodes were positioned one-third the diameter of the flask from the bottom of the flask. Whether the mixture was flammable or not was determined by the ASHRAE 90° flame propagation criterion.5,6 This process was repeated, varying the sample injection mass until a flame fulfilled the flame propagation criterion. The flammability limits of fuel in the mixture of fuel + diluent and air were calculated as the ideal gas behavior which was assumed:4 FL =

m 1 ·100 MW (V /22.4)(p /p0 )(T0/T )

Table 2. Comparison between the Observed Results and Literature Values of Flammability Limits of Methanol, Ethanol and n-Butanol at Different Temperaturesa sample

T/K

methanol methanol ethanol ethanol ethanol n-butanol

373 423 373 423 423 373

obsb/vol % 6.49 6.08 3.17 3.10 18.5 1.65

± ± ± ± ± ±

lit.c/vol %

0.02 (LFL) 0.02 (LFL) 0.01 (LFL) 0.01 (LFL) 0.1 (UFL) 0.01 (LFL)

6.43 6.08 3.20 3.05 18.8 1.57

± 0.046 ± 0.056 (curve)8 (curve)8 (curve)8 ± 0.026

deviationd/ vol % 0.06 0.00 −0.03 0.05 −0.3 0.08

The temperature uncertainty is ± 2 K. The expanded uncertainty of LFL and UFL with a level of confidence of 0.95 (k = 2) is attached to the observed values. b“obs” is the observed results. c“lit.” is the literature values. dDeviation = obs − lit.

a

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RESULTS Flammability limits for pure 1,2-ethanediol and 1,2-propanediol are investigated and listed in Table 3. The values of (3.2 to Table 3. Literature Values of Flammability Limits for Pure 1,2-Ethanediol and 1,2-Propanediol 1,2-ethanediol LFL/vol %

3.2 3.2 3.2

1,2-propanediol

UFL/vol %

LFL/vol %

21.6 15.3

2.6 2.62 2.6 2.6 2.6

UFL/vol %

ref

12.55 12.5 12.5 12.5

10 11 12 13 14, 15

15.3) % for 1,2-ethanediol and (2.6 to 12.5) % for 1,2propanediol are the most common data in various handbooks and Material Safety Data Sheets from manufacturers of chemical reagents, and some handbooks declare that their values are sourced from National Fire Protection Association (NFPA). NFPA-HAZ01 explained that the low flammability limit of 2.6 % for 1,2-propanediol was corresponding to the temperature of 369 K.9 Coward and Jones reported that the flammability range for 1,2-propanediol were (2.62 to 12.55) %, with upward propagation of flame in a tube with 1 in. in diameter and 18 in. in length, at a temperature sufficient to vaporize the substance.10 The test temperature for 1,2propanediol was not specified in other literature, and no measured temperature was referred to 1,2-ethanediol. In view of the present situation, the flammability limits of pure 1,2ethanediol and 1,2-propanediol were measured first. To avoid the condensation of the vapor, the test temperatures were 473 K for 1,2-ethanediol and 463 K for 1,2-propanediol, respectively, which were a little higher than their normal boiling points. The experimental flammability ranges are (3.45 to 24.5) % for 1,2-ethanediol and (2.26 to 16.2) % for 1,2propanediol, which were not in accordance with literature values. For 1,2-propanediol the measurement temperature is 369 K in NFPA-HAZ01 and 463 K in this work, so the flammability limit results should be different. The dependence of lower flammability limit on temperature was simply estimated by the modified Burgess and Wheeler law,11 the experimental results of 2.26 % at 463 K would be corresponding to a value of 2.45 % at 369 K, which was a little smaller than the value of 2.6 % from NFPA-HAZ01. No

(1)

where FL is the lower flammability limit (LFL) or upper flammability limit (UFL) in mol % or vol %, MW is the molecular weight of pure sample in g·mol−1, m is the mass of pure 1,2-ethanediol or 1,2-propanediol in g, V is the volume of flask with a value of 12.68 ± 0.01 L calibrated by pure water, p0 = 101.3 kPa is the standard pressure, p is the pressure of vapor in kPa, T0 = 273 K is the standard temperature, and T is the test temperature in K. According to eq 1, the combined standard uncertainty of the flammability limits was calculated for each measurement using the law of propagation of uncertainty outlined on the NIST Web site7 as listed in Tables 2, 4, and 5. Performance of the apparatus was validated by determining the flammability limits of three alcohols at different temperatures, and the experimental results were compared with the reference values.6,8 The maximum deviation is −0.3 vol % for the upper flammability limits of n-butanol, which shows good agreement between the experimental results and reference values as listed in Table 2. 2682

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comparison is done for 1,2-ethanediol because of lack of measuring conditions. Flammability limits of binary vapor mixtures of 1,2ethanediol + steam and 1,2-propanediol + steam were measured at different mole fractions. The experimental results and the corresponding flame colors are listed in Tables 4 and 5, respectively. The critical flammability ratio is 0.910 for 1,2ethanediol + steam and 0.935 for 1,2-propanediol + steam.

n1 =

0 0.200 0.400 0.600 0.800 0.850 0.900 0.905 0.910

Lf/vol %

flame color

± ± ± ± ± ± ± ± ±

whitish blue whitish blue whitish blue orange + blue orange + blue orange red orange red orange red orange red

3.45 3.47 3.48 3.48 3.61 3.71 4.02 4.17 4.31

0.01 0.01 0.01 0.01 0.02 0.03 0.04 0.04 0.05

Uf/vol %

flame color

± ± ± ± ± ± ± ± ±

pale blue pale blue pale blue orange + blue orange red orange red orange red orange red orange red

24.5 20.8 18.3 13.9 8.34 6.86 4.95 4.72 4.31

0.1 0.1 0.1 0.1 0.05 0.05 0.05 0.05 0.05

Uf,pure

(4)

p, q, and r in eq 2 and s, t, and u in eq 3 are adjustable parameters determined by regression with the measured results. The resulting values of parameters are shown in Table 6. Table 6. Parameter Values Resulting from Regression Calculation to Flammability Limits

Table 4. Flammability Limits of 1,2-Ethanediol + Steam at 473 Ka cH 2 O

0.21(100 − Uf,pure)

parameter values p

q

r

s

t

u

−1.85·10−2 5.74·10−4 −1.88·10−2 −3.45·10−4

5.47·10−2 1.99·10−3 5.83·10−2 4.46·10−3

−4.39·10−2 −2.35·10−3 −4.66·10−2 −3.74·10−3

case 1,2-ethanediol + steam 1,2-proponediol + steam

LFL UFL LFL UFL

The observed values of flammability limits of 1,2-ethanediol + steam and 1,2-propanediol + steam together with the calculated values from eqs 2 and 3 are shown in Figures 2 and

a

The expanded uncertainty of Lf and Uf with a level of confidence of 0.95 (k = 2) is attached to the observed values.

Table 5. Flammability Limits of 1,2-Propanediol + Steam at 463 Ka cH 2 O 0 0.200 0.400 0.600 0.800 0.900 0.920 0.930 0.935

Lf/vol %

flame color

± ± ± ± ± ± ± ± ±

whitish blue whitish blue whitish blue orange + blue orange + blue orange red orange red orange red orange red

2.26 2.27 2.27 2.27 2.30 2.41 2.49 2.60 2.97

0.01 0.01 0.01 0.01 0.01 0.02 0.03 0.03 0.04

Uf/vol %

flame color

± ± ± ± ± ± ± ± ±

pale blue pale blue orange + blue orange red orange red orange red orange red orange red orange red

16.2 13.5 11.9 9.68 6.72 4.35 3.66 3.21 2.97

0.1 0.1 0.1 0.04 0.04 0.04 0.04 0.04 0.04

Figure 2. Comparison between the observed and calculated values of flammability limits of 1,2-ethanediol + steam at 473 K: □, observed values; , values calculated from the extended Le Chatelier’s formula; - - -, estimated values obtained by the adiabatic flame temperature method.

a

The expanded uncertainty of Lf and Uf with a level of confidence of 0.95 (k = 2) is attached to the observed values.

■

DISCUSSION The results of flammability limits were correlated with the extended Le Chatelier’s formula proposed by Kondo et al.16,17 The lower and upper flammability limits can be explained by cf cf = + p(1 − c f ) + q(1 − c f )2 + r(1 − c f )3 Lf Lf,pure

3, respectively. As shown in Figures 2 and 3, it is clear that the experimental data are excellently fitted by the extended Le Chatelier’s formula. Deviations between the observed values and the results from eqs 2 and 3 are shown in Figure 4. The average absolute deviation between the observed and calculated values of the lower flammability limit for the two binary mixtures is 0.04 vol %, and for the upper flammability limit is 0.11 vol %. Shrestha et al.18 and Wierzba et al.19,20 proposed a method based on adiabatic flame temperature to predict the flammability limits. In the present work, flammability limits of 1,2-ethanediol + steam and 1,2-propanediol + steam were also estimated using their method. The lower and upper flammability limits of fuel + diluent in air can be estimated by

(2)

c f n1 c f n1 = + s(1 − c f ) + t(1 − c f )2 100 − (Uf /c f ) 100 − Uf,pure + u(1 − c f )3

(3)

where Lf and Uf are the lower and upper flammability limit of fuel in the mixture of fuel + diluent and air, respectively, in vol %, Lf,pure and Uf,pure are the lower and upper flammability limit of pure fuel in air under the same corresponding conditions, respectively, in vol %, cf is the fuel volume fraction in the fuel + diluent, and the value of n1 is obtained from the following equation:

cf 1 = + αL(1 − c f ) Lm Lf,pure 2683

(5)

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a4 = (Δh|TTad0 )diluent

(12)

the parameters b1 to b5 in eq 8 are calculated using the following equations b1 = (Hf,fuel)Tref + (Δh|TT0ref )fuel

(13)

b2 = 0.21(Δh|TT0ref )O2 + 0.79(Δh|TT0ref )N2

(14)

b3 = n(Hf + Δh|TTadref )CO + (l − n)(Hf + Δh|TTadref )H2O m + (n + − l)(Δh|TTadref )H2 2

(15)

b4 = 0.42(Δh|TTadref )H2 − 0.42(Hf + Δh|TTadref )H2O − 0.79(Δh|TTadref )N2

Figure 3. Comparison between the observed and calculated values of flammability limits of 1,2-propanediol + steam at 463 K: □, observed values; , values calculated from the extended Le Chatelier’s formula; - - -, estimated values obtained by the adiabatic flame temperature method.

(16)

b5 = (Δh|TTad0 )diluent

(17)

in eqs 9 to 17, n, m, and l are the number of carbon, hydrogen, and oxygen atoms in fuel CnHmOl, respectively, Hf is the enthalpy of formation of compounds in kJ·mol−1, Δh is the enthalpy of chemicals in kJ·mol−1, and Tref, T0, and Tad are the reference temperature, the initial reactant temperature, and the adiabatic flame temperature in Kelvin, respectively. The chemistry and physical properties of 1,2-ethanediol and 1,2-propanediol used in the calculation are listed in Table 7, Table 7. Basic Chemical and Physical Properties of 1,2Ethanediol and 1,2-Propanediola

Figure 4. Deviations of results fitted from eqs 2 and 3 “fit” of flammability limits for the two diols from the observed values “obs”: □, LFL of 1,2-ethanediol; ○, UFL of 1,2-ethanediol; △, LFL of 1,2propanediol; ▽, UFL of 1,2-propanediol.

cf 1 = + αR (1 − c f ) Um Uf,pure

b2 + b4 + b5 Uf,pure(b2 + b3 + b4 − b1)

a 2 = 0.21(Δh|TTad0 )O2 + 0.79(Δh|TTad0 )N2

a3 = n(Hf + Δh|TTadref )CO2 +

and all of the properties were directly taken from CHEMCAD Data Bank.21 The adiabatic flame temperature was calculated by GASEQ software.22 The values of Tref, T0, and Tad are listed in Table 8. The enthalpies of the reactants and products were calculated by NIST REFPROP 9.0 software.23 Because 1,2ethanediol and 1,2-propanediol are not included in REFPROP software, a Peng−Robinson equation of state together with the ideal gas heat capacity equation were selected to calculate the enthalpies of the two diols. The calculated results of αL, αR, and the critical flammability ratios for 1,2-ethanediol + steam and 1,2-propanediol + steam were acquired and are listed in Table 8. The estimated critical flammability ratios are close to the experimental results. The observed values and the estimated results of 1,2ethanediol + steam and 1,2-propanediol + steam are shown in Figures 2 and 3, respectively. Deviations between the observed values and the results from eqs 4 and 5 are shown in Figure 5. The average absolute deviation between the observed and calculated values of the two binary mixtures for the lower

(8)

(9) (10)

m (Hf + Δh|TTadref )H2O 2

⎛ m l⎞ − ⎜n + − ⎟(Δh|TTadref )O2 ⎝ 4 2⎠

57-55-6 1,2-propanediol C3H8O2 76.095 626 6.1 213.15 460.75 1.1065 −421.5

All of the values in the table were taken from CHEMCAD Data Bank.21

the parameters a1 to a4 in eq 7 are calculated by a1 = (Hf,fuel)Tref + (Δh|TT0ref )fuel

107-21-1 1,2-ethanediol C2H6O2 62.068 720 8.2 260.15 470.45 0.5068 −392.2

a

(6)

where Lm and Um are the lower flammability limits and upper flammability limits of fuel + diluent in air, respectively, in vol %, and αL and αR are constants, which depend on the types of fuel and diluent, given by a4 − a 2 αL = Lf,pure(a3 − a1 − a 2) (7) αR =

CAS no. name formula molar mass/g·mol−1 critical temperature/K critical pressure/MPa triple point temperature/K normal boiling point/K acentric factor enthalpy of formation/kJ·mol−1

(11) 2684

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0.935 for 1,2-propanediol + steam. The experimental results were correlated with the extended Le Chatelier’s formula. Excellent agreements were obtained. The dilution effect was analyzed based on the method of adiabatic flame temperature. The observed values of lower flammability limits are in good agreement with the estimated values, and the critical flammability ratios of the two binary mixtures were close to the experimental values. The agreement between the observed and the calculated values of upper flammability limits is not as good as for the lower flammability limits, but the deviations are still reasonably acceptable.

Table 8. Parameters and Results in the Calculation of the Flammability Limits for 1,2-Ethanediol + Steam and 1,2Propanediol + Steam case

1,2-ethanediol + steam

1,2-propanediol + steam

T0/K Tref/K Tad/K (LFL) Tad/K (UFL) αL αR CFRexpa/vol % CFRcalb/vol %

473 300 1520 1105 −0.002730 0.01311 0.910 0.940

463 300 1531 1044 −0.002713 0.01355 0.935 0.959

■

CFRexp is the experimental results of critical flammability ratio. b CFRcal is the calculated values of critical flammability ratio. a

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +86-29-82663737. Funding

The authors acknowledge the financial support of National Natural Science Foundation of China (No. 51076128) and Natural Science Foundation of Jiangsu Province, China (No. SBK201122327). Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Yin, A. Y.; Guo, X. Y.; Dai, W. L.; Fan, K. N. The Synthesis of Propylene Glycol and Ethylene Glycol from Glycerol Using Raney Ni as a Versatile Catalyst. Green Chem. 2009, 11, 1514−1516. (2) Sun, J.; Liu, H. Selective Hydrogenolysis of Biomass-Derived Xylitol to Ethylene Glycol and Propylene Glycol on Supported Ru Catalysts. Green Chem. 2011, 13, 135−142. (3) Kim, K. N.; Hoffmann, M. R. Heterogeneous Photocatalytic Degradation of Ethylene Glycol and Propylene Glycol. Korean J. Chem. Eng. 2008, 25, 89−94. (4) American Society of Testing and Materials, Designation: E681-04; ASTM: Philadelphia, 2004. (5) Kondo, S.; Takizawa, K.; Takahashi, A.; Tokuhashi, K.; Sekiya, A. Flammability Limits of Isobutane and its Mixtures with Various Gases. J. Hazard. Mater. 2007, 148, 640−647. (6) Rowley, J. R.; Rowley, R. L.; Wilding, W. V. Experimental Determination and Re-examination of the Effect of Initial Temperature on the Lower Flammability Limit of Pure Liquids. J. Chem. Eng. Data 2010, 55, 3063−3067. (7) NIST Physical Measurement Laborary Homepage. http://www. nist.gov/pml/pubs/tn1297/index.cfm (accessed June 8, 2013). (8) Coronado, C. J. R.; Carvalho, J. A.; Andrade, J. C.; Cortez, E. V.; Carvalho, F. S.; Santos, J. C.; Mendiburu, A. Z. Flammability Limits: A Review with Emphasis on Ethanol for Aeronautical Applications and Description of the Experimental Procedure. J. Hazard. Mater. 2012, 241, 32−54. (9) NFPA-HAZ01. Fire Protection Guide to Hazardous Materials, 13th ed.; National Fire Protection Association: Quincy, MA, 2002. (10) Coward, H. F.; Jones, G. W. Limits of Flammability of Gases and Vapors, Bureau of Mines Bulletin: U.S. Bureau of Mines: Washington, DC, 1952; No. 503. (11) Zabetacis, M. G. Flammability Characteristics of Combustible Gases and Vapors, Bureau of Mines Bulletin: U.S. Bureau of Mines: Washington, DC, 1965; No. 627. (12) NFPA 325. Guide to Fire Hazard Properties of Flammable Liquids, Gases, and Volatile Solids; National Fire Protection Association: Quincy, MA, 1994. (13) Vallero, D. Environmental Contaminants: Assessment and Control; Elsevier Academic Press: New York, 2010. (14) Kuchta, J. M. Investigation of Fire and Explosion Accidents in the Chemical, Mining, and Fuel-related Industries - A Manual, Bureau of Mines Bulletin: U.S. Bureau of Mines: Washington, DC, 1985; No. 380.

Figure 5. Deviations of the estimated results given by eqs 5 and 6 “esti” of flammability limits for the two diols from the observed values “obs”: □, LFL of 1,2-ethanediol; ○, UFL of 1,2-ethanediol; △, LFL of 1,2-propanediol; ▽, UFL of 1,2-propanediol.

flammability limit is 0.10 vol % and for the upper flammability limit is 1.48 vol%. The observed values of lower flammability limits are in good agreement with the estimated values. However, agreements between the observed and calculated values of upper flammability limits are not as good as for the lower flammability limits. From Tables 4 and 5, we can get that the flame colors are blue when the steam mole fractions are not exceeding 0.4, which indicated the existence of the effect of cool flame upon the upper flammability limits.24 So the accuracy of estimated values may be affected by cool flame to some extent. Considering the factors the estimated method can be used to reasonably estimate the flammability limits of binary mixtures of 1,2-ethanediol + steam and 1,2-propanediol + steam. From the deviations of the estimated results from the observed values described in Figure 5, it is concluded that the dilution effects of steam on 1,2-ethanediol and 1,2-propanediol are similar at various volume fractions. The flammable ranges of 1,2-ethanediol and 1,2-propanediol narrow with the increasing of steam concentration. However, the critical flammability ratios of the two mixtures are relatively high, which indicates that the dilution effects of steam on the flammability limits of 1,2-ethanediol and 1,2-propanediol are not prominent.

■

CONCLUSION Flammability limits of binary mixtures of 1,2-ethanediol + steam and 1,2-propanediol + steam were measured at the temperatures of 473 K and 463 K, respectively. The critical flammability ratios were 0.910 for 1,2-ethanediol + steam and 2685

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(15) Davletshina, T. A.; Cheremisinoff, N. P. Fire and Explosion Hazards Handbook of Industrial Chemicals; Noyes Publications: Westwood, NJ, 1998. (16) Kondo, S.; Takizawa, K.; Takahashi, A.; Tokuhashi, K. Extended Le Chatelier’s Formula and Nitrogen Dilution Effect on the Flammability Limits. Fire Safety J. 2006, 41, 406−417. (17) Kondo, S.; Takizawa, K.; Takahashi, A.; Tokuhashi, K. Extended Le Chatelier’s Formula for Carbon Dioxide Dilution Effect on Flammability Limits. J. Hazard. Mater. 2006, 138, 1−8. (18) Shrestha, S. O. B.; Wierzba, I.; Karim, G. A. A Thermodynamic Analysis of the Rich Flammability Limits of Fuel-Diluent Mixtures in Air. J. Energy Resour.: ASME 1995, 117, 239−242. (19) Wierzba, I.; Shrestha, S. O. B.; Karim, G. A. A Thermodynamic Analysis of the Lean Flammability Limits of Fuel-Diluent Mixtures in Air. J. Energy Resour.: ASME. 1994, 116, 181−185. (20) Wierzba, I.; Karim, G. A.; Cheng, H. Correlating the Flammability Limits of Fuel-Diluent Mixtures. J. Energy Resour.: ASME 1988, 110, 157−160. (21) CHEMCAD Software, Version 5.1; Chemstations Inc.: Houston, 2001. (22) Morley, C. GASEQ: A Chemical Equilibrium Program for Windows, Version 0.79; 2005. (23) Lemmon, E. W.; Huber, M. L.; McLinden, M. O. NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties (REFPROP), Version 9.0; National Institute of Standards and Technology: Gaithersburg, MD, 2010. (24) Kondo, S.; Takahashi, A.; Tokuhashi, K. Experimental Exploration of Discrepancies in F-number Correlation of Flammability Limits. J. Hazard. Mater. 2003, 100, 27−36.

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