Research into limits of gas-fired burners flame stabilization in the flue gas recirculation

Abstract

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.

Flue Gas Recirculation during Biomass Combustion: Implications on PM Release

“…Table summarizes the values of the different flue gases involved in the definition of FGR. The portion of recirculated gas was set to 30% to reduce the combustion disturbances that could negatively affect the plant behavior . Note that during the FGR experiments, the flue gas that entered through the plenum, m ̇ 1 , was maintained as a constant value, which affected the set point of the fresh air supplied by the primary fan.…”

“…In solid fuel combustion, the focus was laid on coal. ,− Most research has discovered significant CO and NO x reductions, such as Houshfar et al, who achieved a nearly 70% decrease. According to Ivanov, the feasibility of FGR is attributed to the low economic and technical effort needed to adapt it to existing facilities, although a proper adjustment of the recirculated gas needs to be assessed since it can cause a relevant disturbance in the flame front. Some studies have focused on the plant response to different FGR portions and have reported nearly 30% reduction values for CO and NO x concentrations with 10% to 20% FGR and even further effects when the recirculation rate was raised to 30%. , …”