Using the flammability potential and the exergy indicator to assess the fire hazard of the rail transportation of cargoes
Introduction. Problems of fire safety of dangerous goods (DG) in the process of their rail transportation have not been fully resolved. The flammability assessment of substances and materials is insufficiently impartial; an integrated indicator, that allows to apply a consolidated methodological standpoint to improve their energy efficiency and environmental/fire safety is unavailable. The purpose of this work is to substantiate the feasibility and advantages of the exergy approach to assessing the fire hazard of the exhaust gas emitted from railroad transport. Materials and methods. The use of the flammability potential as an integrated indicator of the fire hazard of cargoes has a number of limitations. The exergy approach has a strong potential if applied to the assessment and prediction of fire hazards. Present-day and potential railroad cargoes serve as examples that substantiate the feasibility of this approach. Results and its discussion. Dependences between fire hazard indicators (flash points, flame propagation limits, auto-ignition points, heat of combustion) demonstrated by the components of liquid and gaseous fuels and the chemical exergy were identified.A study of changes in the physical exergy triggered by spills and combustion were illustrated by liquefied natural gas and liquefied hydrocarbon gases having various compositions. Physical exergy change patterns depending on the temperature and pressure of the above products were developed.For self-ignitable cargoes, dependences between the physical exergy and activation energy, critical ambient temperature, and heat capacity of self-heating materials were identified. The influence of thermal conductivity and humidity coefficients on the exergy value is established. Exergy changes were determined depending on the elemental composition of solid municipal waste, ash, volatile matter and fixed carbon content. Polymers and rubbers have the highest values of this indicator. An exergy indicator was introduced to assess fire and environmental hazards of substances and materials; it serves as the basis for the classification of cargoes. Conclusions. The use of the exergy indicator allows to increase the objectivity of assessments and take account of technical, economic, environmental criteria and indicators of fire hazards within an integrated system.