Method, CHETAH program

Batch reactor, typical, DACSL kinetic and reactor modeling, 94 Benefits, HAZOP study, 37 Benson s second-order group additivity method, CHETAH program, 82 Benzoyl peroxide (BPO), effect of dilution with xylene, CHETAH program, 87... 

Approximate heats of formation can be estimated by other methods, such as calculations that sum average bond energies. Computer programs such as the ASTM CHETAH program (Balaraju et al. 2002) use these types of calculations. Such programs may require expertise to understand and interpret. 

Other methods such as oxygen balance are available that point to chemicals likely to show self-reactivity. These methods are described in CCPS (1995b) and elsewhere. The ASTM CHETAH program (Balaraju et al. 2002) is useful for this purpose, if both the program and the expertise to use it are available to you. 

In summary, we would like to emphasize the two current capabilities of the CHETAH program. The first is the estimation of gas phase thermodynamic data over the range of 25-1200°C, using Benson s second order group contribution method. The second capability of CHETAH is a hazard appraisal. This uses thermodynamic data to... 

Discussions have also been held with ASTM E27 Committee (On The Hazard Potential of Chemicals) members regarding the use of the CHETAH (Chemical Thermodynamics and Hazards Estimation Program) software to aid in the classification process. Work is proceeding (by E27.07 Estimation Methods) on both a PC version of the existing CHETAH program (with considerable updating) and a new mainframe (and possible PC) version with expanded capabilities. CHETAH is described in detail in references 43a, b, c. 

Copies of the TNO peroxide test databases have been provided to E27.07 and the new versions of CHETAH are expected to contain an extensive database as well as pattern-recognition techniques for estimating the hazard of new materials. The CHETAH software will continue to rely on bond energy data and group contribution calculations to estimate energy release potential. Hopefully, the new versions will also incorporate natural language expert system-type front ends so that the CHETAH program(s) will see expanded use in both analytical and tutorial modes. Copies of the LEILA (8) dissertation have also been provided to E27.07 as an example of an expert system approach to selection and use of appropriate theories and computational methods for the solution of problems in chemical kinetics. 

Two standard estimation methods for heat of reaction and CART are Chetah 7.2 and NASA CET 89. Chetah Version 7.2 is a computer program capable of predicting both thermochemical properties and certain reactive chemical hazards of pure chemicals, mixtures or reactions. Available from ASTM, Chetah 7.2 uses Benson s method of group additivity to estimate ideal gas heat of formation and heat of decomposition. NASA CET 89 is a computer program that calculates the adiabatic decomposition temperature (maximum attainable temperature in a chemical system) and the equilibrium decomposition products formed at that temperature. It is capable of calculating CART values for any combination of materials, including reactants, products, solvents, etc. Melhem and Shanley (1997) describe the use of CART values in thermal hazard analysis. 

This computer program calculates the thermodynamic data of molecules, of free radicals and of radical reactions in the gas phase between 300 and 5000 K by BENSON S methods. It also determines the CHETAH safety criteria. 

CHETAH or any other calculation method is not intended to replace physical testing of materials and should never be used in this manner. Responsible use of such programs means using them only as screening tools in an overall scheme involving both physical testing and other predictive tools. 

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