Modern approach to the problem of fossil gas fuels replacement by alternative fuels

New scientific and engineering fundamentals of fuels substitution have been developed instead of obsolete methodology "Interchangeability of Fuel Gases" developed in USA and existing from the middle of XXth century. To perform the complex prediction of total or partial substitution of given flow rate of natural gas NG for alternative gases AG the following parameters are to be predicted: plant utilization efficiencies – regarding fuel and energy utilization, the last in form of heat ȘH and exergy Șeff efficiencies, saving or overexpenditure of the NG flow rate in the gas mixture with AG, specific fuel consumption b f and specific issue of harmful substances Ct – pollutants in the combustion products (CNOx ) and greenhouse gases (C CO2 ). Certification of alternative gas fuels and fuel mixtures as a commodity products is carried out in frame of our approach with necessary set of characteristics, similar to those accepted in the world practice. Key words: alternative fuel, fuel replacement (substitution), natural gas, process gases, theoretical combustion temperature, thermodynamic equilibrium computations, total enthalpy