Determining the flue gas recirculation effect on the verge of the gas-fired burners flame stabilization based on experimental industrial research. Methods. The studies were conducted on a circular heating furnace with a diameter of 30 m of the Interpipe NTRP wheelrolling workshop. The furnace for blanks heating to 625 ± 25°C with their isothermal holding has 5 zones with an adjustable and systematic supply of natural gas. To increase the thermal performance efficiency, the furnace has been equipped with an external exhaust gas recirculation system. When assessing the burners forcing ability of the after their ignition, the gas consumption, as well as recycled gas consumption was increased gradually in a predetermined ratio. Therewith, gas consumption was determined at the time of the flame-out, which was recorded visually. Findings. Based on a comprehensive analysis, the factors have been revealed, which affect the sustainability of the burner operating modes when exhaust flue gases are fed into the combustion zone. It is shown that the most rational for analyzing the recirculation influence on gas combustion stability is the use of criterion empirical models that take into account the complex of physical-chemical characteristics of the reagents, parameters of the combustion mode, gas-dynamic and design burner peculiarities. A criterion model has been obtained for the loss of a diffusion flame in combined "pipe-in-pipe" type burners when burning gas fuel in a medium of recycle flue gases with a temperature of 140-200°C and an oxygen composition of 15.4-19.6% in them. Dependences have been determined for assessing the expansion of combustion stability limits with a change in the coefficient of the oxidising agent consumption, its temperature, and the recirculation ratio. Originality. New computational models have been obtained for assessing the limits of the flame stabilization of straightflow gas burners during flue gas recirculation. The ratios have also been found of the recirculation ratio and the oxidising agents temperatures, that provide the conditions of their identical work for the flame-out and flame backflash when replacing the air with recycled gas for fuel combustion. Practical implications. The results make it possible to make a reasonable choice of burners and combustion standard parameters that ensure the safe unit operation during flue gas recirculation.

Purpose. To solve the task of assessing the components of the guaranteed atmosphere air quality P MPj , P MP depending the maximum pollutant concentrations for a point source of emissions at the stage of designing in various industries (mining, metallurgical, chemical, electric power and others).Methods. The distribution of pollutant concentrations is represented as a vector random field, which at a given point of the area is turned into a vector random variable of concentrations and is characterized by a multi-dimensional density of distribution. To determine the density, the mathematical Berland's model of the concentrations distribution is applicable in Ukraine, in which the concentration arguments (design parameters of the source and environmental characteristics) are considered as random variables. Having assumed that the distribution density follows the normal law, using the method of function linearization of the random arguments based on the limit theorems of probability theory, its numerical characteristics have been obtained: mathematical expectations of concentrations, its mean square deviations, and correlation coefficients between concentrations. Findings.A new concept has been introduced of guaranteed air quality for populated areas. Based on predictive assessment, the studies have been carried out to ensure it at the stage of designing the facilities that have a point source of pollutant emissions. In accordance with the methodology, a mathematical model of the task of assessing and ensuring the guaranteed quality of atmosphere air has been obtained. According to the determination of the guaranteed atmosphere air quality, its measure is presented as a multi-dimensional probability integral of non-exceedance by the concentrations of at least one pollutant of its maximum one-time permissible concentrations with obtaining the numerical characteristics.Originality. As a result of studies, a mathematical model has been developed for the first time of the task of assessing and ensuring the guaranteed quality of atmosphere air, characterized by the probability values P MP , P MPj , when it is polluted by emissions from a point source. The control of the probability value P MP is performed by selecting the design source parameters so that its value is close to 1. Practical implications.The implementation of the developed model in construction projects with high probability, close to 1, ensures that at least one pollutant by its concentration will not exceed its normative maximum one-time permissible concentration, that is not implemented now. According to the maximum permissible concentration MPC MPj , determination, it is guaranteed the absence of the pollution effect on a person and the occurrence of corresponding diseases.

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