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Estimation of Chemical Incompatibility (Other-Chemical Reactivity) By Copyright © 1980 Ohio Acad. Sci. 0030/0950/80/0004-0160/S2.00/0 ESTIMATION OF CHEMICAL INCOMPATIBILITY {OTHER-CHEMICAL REACTIVITY) BY COMPUTER1 DALE N. TREWEEK, 2626 Chartwell Road, Columbus, OH 43220 CARL A. ALEXANDER, JAMES R. HOYLAND, AL F. FENTIMAN, WILLIAM M. PARDUE, Battelle, Columbus Laboratories, 505 King Avenue, Columbus, OH 43201. Abstract. Two simple parameters—the National Academy of Science-National Re- search Council "Other Chemical" rating and a Lewis acid-base rating were combined in a linear discriminate model to predict the degree of hazard from binary mixtures as measured by Dow Chemical experimental tests. The observed error of 10% com- pares favorably with 40% error obtained using the NAS-NRC rating system. These results will be incorporated in the American Society for Testing and Materials com- puter program CHETAH (Chemical Thermodynamics and Energy Hazard Potential). OHIO J. SCI. 80(4): 160, 1980 The accidental mixing of industrial mishap make some type of model or chemicals during transportation, storage simplification highly desirable. Such a or processing poses a potential energy model might serve to reduce the potential hazard, denned in terms of both the hazard by identifying hazardous combi- relatively immediate release of heat nations, which can then be precluded by and/or gas as a result of chemical in- physical separation with relatively inert compatibility or "other chemical" re- chemicals. activity and the potential formation of an explosive mixture that can subse- Background quently be initiated by an appropriate A review of the more common hazard stimulus (mechanical impact, thermal or rating systems (over 30 have been physical shock). In some cases, the counted) resulted in the summary of circumstances of an accident (collision, reactivity definitions shown below. fire, etc.) causing the inadvertent mixing REACTIVITY DEFINITIONS of some unusual combination of chemicals USCG—(NAS-NRC)—Other Chemical- can also serve as the initiation stimulus Reactivity for a violent deflagration or detonation Based on possible reactivity with of such a mixture. members of other grades Water Presently, there are about 1000 chemi- Based on mixing with equal weight cals transported in bulk in the U.S. of water at ambient temperature Many thousands more are transported Self in smaller quantities. Statistically, the Usually based on polymerization number of combinations by which just 2 Fire Hazard of the bulk-shipped chemicals might be Based mostly on flash points but accidentally mixed is beyond experi- noxious gas production or air/ water spontaneous ignition con- mental evaluation. Chemical tankers, sidered for instance, may contain thousands of DOW—Binary Mixture kilograms of a half dozen or more dif- Based on temperature rise and gas ferent chemicals in relatively close prox- evolution imity. Therefore, the astronomical num- NFPA—Reactivity ber of unusual combinations that might Based on shock sensitivity, re- accidently arise during a transportation activity with water Flammability Based on ignition temperature and iManuscript received 28 March 1979 and in tendency to form explosive dusts revised form 21 January 1980 (#79-20). or mists 160 Ohio J. Sci. CHEMICAL COMPATIBILITY ESTIMATION 161 ASTM—Hazard Potential TABLE 3 Susceptibility to ignition or re- NFPA Reactivity {shock sensitivity and lease of energy under varying en- water reactivity). vironmental conditions Detailed study of these systems reveals a GRADE marked difference in the definition of 0 Stable and unreactive with water. 1 Unstable at high T and P or react terms like "reactivity," a vast difference slightly with water. in the degree of subjectivity required to Unstable, capable of violent chemi- assign a given chemical to a particular cal change but not detonation or re- hazard class, and in some cases, a lump- act violently with water. Shock sensitive but require strong ing of more than one type of hazard into initiating source or high T and P, or the same rating system to facilitate use react explosively with water. by a particular group. Shock sensitive at normal T and P. The diversity of these hazard rating systems relating to chemical compatibil- ity is exemplified by the U. S. Coast Addressing the chemical incompatibil- Guard (National Academy of Science ity or "other chemical" hazard exclu- 1973, Department of Transportation sively, the Dow Chemical binary mixture TABLE 1 Other Chemical Reactivity Hazard Rating System* {mixing results in overflow or rupture of tanks, ignition or evolution of noxious gases). GRADE 0 UNREACTIVE EXCEPT WITH GRADE 4 Saturated hydrocarbons 1 MILDLY REACTIVE WITH GRADE 4 Aromatic and olefinic hydrocarbons 2 MAY REACT WITH GRADES 3 OR 4 ONLY Alcohols, aldehydes, etc. 3 MAY REACT WITH GRADES 2, 3, OR 4 Organic acids, amines, etc. 4 MAY REACT WITH ALL OTHER GRADES Cone, mineral acids and bases "National Academy of Science-National Research Council (NAS 1973). 1975), which considers reactivity in 3 rating system (Flynn 1970) developed distinct rating systems: under contract to the National Academy Other chemical (see table 1) of Sciences Advisory Committee for the Coast Guard is very explicit about the Water and Compatibility criteria used to assign a chemical to a of Chemicals (see table 2) particular class (see table 4), whereas the whereas NFPA (National Fire Protec- TABLE 4 tion Assoc. 1973) lumps many of the Dow binary mixture {temperature rise and same considerations into its reactivity gas evolution). system: Reactivity shock sensitivity, de- HAZARD DEGREE composition or poly- 1 NONE AT max. <25 °C, no gas merization, reaction 2 LOW AT max. 25-50 °C, no gas with water (see table 3) 3 MEDIUM AT max 50-75 °C, no gas 4 HIGH AT max >75 °C or gas evolution TABLE 2 Water {mixing with equal weight of water at ambient temperature). NFPA and NAS-NRC systems use un- quantified descriptors like very, normal, GRADE moderate, mild, and vigorous. To quan- 0 No reaction. tify the NAS-NRC "Other Chemical" 1 Mild reaction. 2 Moderate reaction. system, a flow chart to assist in classify- 3 May be hazardous. ing an unknown was developed (figure 1). 4 Vigorous—hazardous. A computerized technique based on this flow chart would require a test for 162 D. N. TREWEEK, ET AL Vol. 80 was tested with a representative Grade 3 chemical (i.e., ammonia), no reaction START potential would be observed (Flynn 1970) and the unknown would pass the Grade 3 test. This same unknown, however, has been observed experimentally by Dow to be highly reactive with another Grade 3 chemical, ethylene diamine (A T-194C, A P-13.5 psi, High Hazard) (Flynn 1970). Herein lies the problem in simplifying binary or other chemical reactivity using the NAS-NRC rating system. The CG Guide to Compatibility of Chemicals (Circular No. NVIC 4-75) provides an ideal working document for field use, but the "GO/NO-GO" simpli- fication that makes this guide so attrac- tive for field use also makes it less suited for quantitative evaluation of a new model. Thermodynamic parameters were found to have little or no power in pre- dicting binary reaction tendency (Alex- ander el al 1975). Considering the low temperatures generally encountered, this finding is consistent with historical ob- servations on the power of such calcula- tions. Although the Dow rating system ap- pears to offer many advantages in terms FIGURE 1. Flow chart to classify an un- of reference utility to a research study known into the NAS-NRC Other Chemi- cal System. (0), (1), means test for re- (Flynn 1970), several irreconcilable dif- action with most reactive member of ferences have been encountered as a re- group 0, 1, etc. R—NAS other chemical sult of Dow's noble efforts to reduce the hazard rating (NAS 1973). amount of experimental data required. Specifically, Dow assigned 209 bulk- reactivity with the most reactive member shipped chemicals to 59 groups, each with of each grade (0 through 4). Some of a designated representative working the grades contain a variety of types of chemical. This reduced the amount of chemicals; therefore, to account for the binary experimental data required from possible wide spectrum of reactivity the 21,736 to 1711. unknown might exhibit because of its Ethylene glycol was selected by Dow own characteristics and because of those as the representative working chemical of the other reactant, the test with the for the alcohols as shown in table 5. In most reactive member of each grade Dow's experimental evaluation of this might conceivably also require testing chemical with 73% nitric acid (another with the most reactive member of each working chemical), no reactivity was ob- type of compound within each grade. served, and thus no reactivity is pre- Otherwise, the unknown might "fall dicted for any of the other alcohols of through" the flow chart with no estimated this group with nitric acid. Unpub- reaction potential (i.e., 0 grade) when in lished experimental data on similar 10 fact, one type of compound not tested ml quantities of several other alcohols might react quite vigorously with the un- of the same Dow group as ethylene glycol, known. For example, if ethylene chloro- however, resulted in no reactivity in 3 hydrin was the unknown (actual NAS- cases (glycerin, tertiary butyl alcohol NRC "other chemical" grade of 2) and and iso-butyl alcohol) and very high, al- Ohio J. Sci. CHEMICAL COMPATIBILITY ESTIMATION 163 TABLE 5 Comparison of binary mixture data with current ratings. Battelle DOW** Binary Mixture Experimental NAS-NRC* Rating USCG*** Data Guide System NVIC 4-75 Nitric acid (70%)/ethylene glycol Nt H N X Nitric acid (70%)/glycerin N H N X Nitric acid (70%)/butyl alcohol, tert- N H N X Nitric acid (70%)/butyl alcohol, iso- N H N X Nitric acid (70%)/butyl alcohol, sec- H H N X Nitric acid (70%)/isopropyl alcohol H H N X Nitric acid (70%)/cyclohexanol H H N X *NAS 1973 **Flynn 1970.
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