Available online at www.sciencedirect.com
Procedia Engineering 45 (2012) 507 – 511
2012 International Symposium on Safety Science and Technology
Study of minimum flash-point behavior for ternary mixtures of flammable solvents Hao-Ying CHEN, Horng-Jang LIAW* Department of Occupational Safety and Health, China Medical University, Taichung, Taiwan, China
Abstract Flash point is one of the most important variables used to assess fire and explosion hazard of flammable liquids. Binary mixtures exhibiting minimum flash point behavior has been verified to be existed. In real processes, multi-component solutions are more frequently encounted than binary systems. However, the minimum flash point behavior of multi-component mixture is not discussed in literature. This study intended to study the minimum flash point behavior for ternary mixtures. The ternary solutions, IPA + ethanol + octane, 2butnaol + ethanol + octane, cyclohexanol + ethanol + octane, were selected as examples to investigate the minimum flash point behavior of ternary solutions in this study, The experimental data were compared with the simulation of flash point prediction model. Three different type of minimum flash point behavior were observed for the studied solutions, they provided the examples for the classification of minimum flash points solutions for ternary mixtures, and can be applied in hazard assessment and hazard reduction in the fire and explosion for flammable solvents.
© 2012 The Authors. Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Beijing Institute of Technology. Keywords: flash point; minimum flash point behavior; ternary solutions.
Nomenclature A, B, C P Psat Pi,satfp
Antoine coefficients ambient pressure, (kPa) saturated vapor pressure (kPa) saturated vapor pressure of component i at flash point,(kPa)
R gas constant 8.314 (J/mol) T temperature (K) x liquid-phase composition Greek symbols ¤activity coefficient 1. Introduction Safety in the usage and storage of flammable and combustible liquid mixtures is much needed as dramatic accidents regularly occur, such as a series of explosions of essential oils in 2003 and the Shengli illegal dumping event in 2000 in Taiwan [13]. In 2007, a gasoline tanker crashed and burst into flames near the San Francisco-Oakland Bay Bridge,
* Corresponding author. Tel.:886-4-220-53366 ext. 6209; fax: 886-4-220-30418. E-mail address:
[email protected] .
1877-7058 © 2012 Published by Elsevier Ltd. doi:10.1016/j.proeng.2012.08.194
508
Hao-Ying CHEN and Horng-Jang LIAW / Procedia Engineering 45 (2012) 507 – 511
resulting in a stretch of highway melted and collapsed [4,5], highlighting the importance of safe transportation for flammable and combustible liquids. One explosion resulting in the damage of waste water tank during hot work occurred in 2012 in Taiwan. The incident investigation indicated that flammable liquids which were partially miscible to water existed in the waste water. The fire and explosion hazard of liquids is primarily characterized by their flash point [6]. The flash point is defined as the temperature determined experimentally at which a liquid emits sufficient vapor to form a combustible mixture with air [7]. The United Nations encouraged the worldwide implementation of the GHS (Globally Harmonized System of Classification and Labeling of Chemicals) in 2008, and within it, the flash point of mixtures is the critical reference property in the classification of flammable liquids. We first demonstrated that the binary solution of ethanol and octane exhibits a minimum flash point behavior (i.e., below those of the pure components). A liquid solution demonstrating minimum flash-point behavior is more hazardous than the individual components of the combination because the flash point of the mixture, over a range of compositions, is lower compared to its constituents. This special behavior for a specific mixture, such as ethanol and octane, is attributable to the fact that a particular non-ideal solution reflects a highly positive deviation from the behavior of the ideal analogue, such that there is a substantial reduction in the solution’s flash point[1]. This phenomenon has also been demonstrated in mixtures of 1-butanol + octane, 2-butanol + octane, and methanol + methyl acrylate; with products exhibiting such a behavior termed minimum flash-point solutions [8] and such a behavior termed minimum flash-point behavior (MinFPB), respectively. In the real process, multi-component mixtures are much more frequently encountered than binary mixtures; however, the discussion of minimum flash-point behavior was limited to the binary mixtures. Several alternative models for predicting the flash points of different type of mixtures have been proposed. Models based on the assumption of ideal solutions[1,9-11] show limitations when applied to non-ideal mixtures, which are the most frequent ones. Models taking into account the non-ideality of the solution through liquid-phase activity coefficients have a wider application range and predicted efficiently the flash point of miscible mixtures[3-5,12,13,15,16]. Non-ideality of the liquid phase is in particular responsible for the occurrence of extreme flash-point behavior such as minimum and maximum flash-point behavior[14,17-20], with strong implications on the fire and explosion hazard assessment for the concerned mixtures. The general model for predicting the flash point of miscible mixtures proposed previously [3] , was verified to be able to predict the experimental data for ternary mixtures. 2. Experimental 2.1. Flash point experiment An HFP 362-Tag Flash Point Analyzer (Walter Herzog GmbH, Germany), which meets the requirements of the ASTM D56 standard, was used to measure the flash points for a variety of ternary minimum flash point solutions (IPA + ethanol + octane, 2-butnaol + ethanol + octane, and cyclohexanol + ethanol + octane) at different compositions. The apparatus consists of an external cooling system, test cup, heating block, electric igniter, sample thermometer, thermocouple (sensor for fire detection) and indicator/operating display. The apparatus incorporates control devices that program the instrument to heat the sample at a specified rate within a temperature range close to the expected flash point. The literature data and the estimated one of the flash point prediction model were used as the expected flash point for pure substance and mixture, respectively. The flash point is automatically tested using an igniter at specified temperature test intervals. If the expected flash point is lower than or equal to the change temperature, heat rate-1 is used and the igniter is fired at test interval-1. If the expected flash point is higher, heat rate-2 is adopted and the igniter is fired at test interval-2. In the standard method, the change temperature is laid down by the standard and cannot be changed. The first flash-point test series is initiated at a temperature equivalent to the expected flash point minus the start-test value. If the flash point is not determined when the test temperature exceeds the sum of the expected flash point plus the end-of-test value, the experimental iteration is terminated. The instrument operation was conducted according to the standard ASTM D56 test protocol [21] using the following parameters: start test 5ºC; end of test 20ºC; heat rate-1 1ºC/min; heat rate-2 3ºC/min; change temperature 60ºC; test interval-1 0.5ºC; and, test interval-2 1.0ºC. The liquid mole fraction was determined from the mass measured using a Setra digital balance (EL-410D: sensitivity 0.001 g, maximum load 100 g). The prepared mixtures were stirred by a magnetic stirrer for 30 minutes before the flash point test. Isopropanol (99.8%) was HPLC/Spectro grade reagents (Tedia Co. Inc.; USA). Ethanol (99.8%), octane (99%), 2-butanol (99%) and cyclohexanol (99%) were obtained from Panreac (Spain) 2.2. The general model for predicting the flash point of miscible mixtures The flash point for a miscible solution can be estimated by the modified equation of Le Chatelier, the Antoine equation,
Hao-Ying CHEN and Horng-Jang LIAW / Procedia Engineering 45 (2012) 507 – 511
509
and a model for estimating activity coefficients Ji [4]: 1
sat x J Pi ¦ i isat i z kl P i , fp
log Pi sat
Ai
(1)
Bi T Ci
(2)
where the summation runs over all flammable components, kl is the non-flammable components of the mixture. Pi ,satfp , the vapor pressure of the pure flammable component, i, at its flash point, Ti,fp, can be estimated using the Antoine equation. For a ternary liquid solution, Eq. (1) reduces to: xiJ i Pi sat x1J 1 P1sat x2J 2 P2sat x3J 3 P3sat (3) 1
¦ i z kl
Pi ,satfp
P1,satfp
P2,satfp
P3,satfp
Therefore, Equations (2), (3) and the equations to describe liquid phase activity coefficient constitute the flash pointprediction model for a ternary solution. The temperature from the solution of these equations is deemed to be the flash point of such a ternary solution. 3.
Results and discussion
3.1. Parameters used in this manuscript The general flash-point model for miscible mixtures was used for IPA + ethanol + octane, 2-butnaol + ethanol + octane, and cyclohexanol + ethanol + octane mixtures and compared with the corresponding experimental data. Liquid-phase activity coefficients were estimated by using the NRTL,[13] original UNIFAC and UNIFAC-Dortmund 93 models.[14] The group volume and surface area parameters, and the UNIFAC group interaction parameters for different UNIFAC-type models(Tables 2) were obtained from the literature [13, 17, 20, 22]. 3.2. The types of minimum flash point solution for ternary mixtures The IPA + ethanol + octane mixture exhibits two minimum flash-point binary mixtures, with ethanol + octane and IPA + octane behaving MinFPB (Fig.1). The flash point of IPA + octane are located at the minimum value, 5 oC, within a wide composition range. The similar behavior of flash point locating at the minimum value, 5 oC, within a wide composition range was also observed for ethanol + octane. This behavior reflected in the ternary mixture IPA + ethanol + octane was that the flash point within wide composition range located at a minimum value, 5 oC. Exhibition of two minimum flash-point binary mixtures, with ethanol + octane and 2-butanol + octane behaving MinFPB, was also observed for 2-butanol + ethanol + octane (Fig.2). The flash point within some composition range was located at the minimum value, 10 oC, for 2-butanol + octane. Combined with the flash point within wide composition range located at a minimum value, 5 oC, for ethanol + octane, the minimum value of flash point was located at the boundary of the ternary mixture, binary mixture of ethanol + octane, and its value was 5 oC within a wide composition range. The flash point value increased as the quantity of 2-butanol increased. However, the flash point of the mixture, 2-butanol + ethanol + octane was low within wide composition rage.
Fig.1. Comparison of the flash point curve with experimental data for ethanol (1) + octane (2) +IPA (3)
510
Hao-Ying CHEN and Horng-Jang LIAW / Procedia Engineering 45 (2012) 507 – 511
Fig.2. Comparison of the flash point curve with experimental data for ethanol (1) + octane (2) +2-butanol (3)
For cyclohexanol + ethanol + octane (Fig.3), only one minimum flash-point binary mixture, ethanol + octane, was observed. The minimum value of flash point was located at the boundary of the ternary mixture, binary mixture of ethanol + octane, and its value was 5 oC within a wide composition range. As the quantity of cyclohexanol increased, the flash point value of the ternary mixture increased.
Fig.3. Comparison of the flash point curve with experimental data for ethanol (1) + octane (2) + cyclohexanol (3)
4. Conclusions Three different type of the minimum flash point solution for ternary mixtures was presented in this study provide. One exhibits a minimum flash point binary mixture, and the other two minimum flash point binary mixtures the three mixtures are just some types of ternary mixtures exhibiting minimum flash point. The other kinds of the minimum flash point ternary mixtures are continuous investigated in one future studies. The results can be used in hazardous classification of ternary mixtures, and can be applied in process safety design and hazard reduction. References [1] Liaw, H.J., Lee, Y.H., Tang, C.L., Hsu, H.H., Liu,J. H., 2002, J. Loss Prev. Proc., 15: pp.429-438. [2] Liaw, H.J., Chiu, Y.Y., 2003, J. Hazard. Mater., 101: pp.83-106. [3] Liaw, H.J., Chiu, Y.Y., 2006, J. Hazard. Mater. , 137: pp.38-46. [4] Liaw, H.J., Gerbaud, V., Chiu, C.Y., 2010 , Flash point for ternary partially miscible mixtures of flammable solvents. J. Chem. Eng. Data, 55: pp.134146. [5] Liaw, H.-J., Gerbaud, V., Chen, C.C., Shu, C.M. 2010, J. Hazard. Mater., 177: pp.1093-1101.
Hao-Ying CHEN and Horng-Jang LIAW / Procedia Engineering 45 (2012) 507 – 511
511
[6] Crowl, D.A., Louvar, J.F. ,2002. Chemical Process Safety: Fundamentals with Applications, 2nd ed., Prentice Hall PTR, New Jersey, [7] CCPS/AIChE, Guidelines for Engineering Design for Process Safety, 1st ed., American Institute of Chemical Eng1993.ineers, New York, [8] Liaw H.J., Lee, T.P., Tsai, J.S., Hsiao, W.H., Chen, M.H. & ,Hsu ,T.T. 2003,Binary liquid solutions exhibiting minimum flash-pint behavior . Journal of Loss Prevention in Process Industries, 16 :pp.173-186. [9] Lee, S.J., Ha, D.M Korean 2003, J. Chem. Eng., 20: pp.799-802. [10] Liaw, H.J., Lu, W.H., Gerbaud, V., Chen, C.C., Flash-point prediction for binary partially miscible mixtures of flammable solvents. 2008,J. Hazard. Mater., 153: pp.1165-1175. [11] Liaw, H.J., Chen, C.T., Gerbaud, V. 2008,Flash-point prediction for binary partially miscible aqueousorganic mixtures. Chem. Eng. Sci., 63: pp.4543-4554. [12] Liaw, H.J., Gerbaud, V.,Wu, H.T., 2010,Flash point measurements and modeling for ternary partially miscible aqueousorganic mixtures. J. Chem. Eng. Data , 55: pp.3451-3461. [13] Fredenslund, A., Jones,R.L. , 1975,J.M. Prausnitz, AIChE J., 21: pp.1086-1099. [14] Fredenslund,A., Gmehling,J., Michelsen, M.L., Rasmussen,P., Prausnitz,J.M., 1977, Ind. Eng. Chem. Process Des Dev., 16: pp.450-462. [15] Vidal, M., Rogers, W.J., Mannan, M.S., 2006, Process Saf. Environ. Prot., 84:pp.1-9. [16] Weidlich, U., Gmehling, J., 1987, Ind. Eng. Chem. Res., 26: pp.1372-1381. [17] Gmehling, J., Li ,J., Schiller,M., 1993,Ind. Eng. Chem. Res., 32: pp.178-193. [18] Larsen, B.L., Rasmussen, P.,Fredenslund,A. 1987, Ind. Eng. Chem. Res., 26: pp.2274-2286. [19] Bastos, J.C., Soares, M.E., Medina, A.G., 1988, Ind. Eng. Chem. Res., 27: pp.1269-1277. [20] Magnussen, T., Rasmussen,P., Fredenslund,A., 1981, Ind. Eng. Chem. Process Des Dev., 20: pp.331-339. [21] ASTM D 56, Standard Test Method for Flash Point by Tag Closed Tester, American Society for Testing and Materials, West Conshohocken, PA, 1999. [22] Skjold-Jørgensen, S., Kolbe,B., Gmehling,J., Rasmussen,P., 1979, I
