| In the face of increasing demand for natural gas,the pollutants emitted by its combustion have become an unfavorable factor for the sustainable development of the oil and gas industry.Compared with traditional air combustion,natural gas oxy-fuel humidified combustion technology can significantly improve the combustion speed and combustion efficiency,improve the thermal efficiency of the cycle,promote the complete combustion reaction,and effectively reduce the concentration of pollutant emissions.At present,the research on the combustion reaction mechanism of natural gas oxy-fuel humidified combustion technology is not clear,and further research on the combustion characteristics and pollutant generation mechanism under this condition is needed.Based on the combined technical route of oxy-fuel combustion,humidified combustion,and low-nitrogen combustion,a co-production scheme of natural gas oxy-fuel humidified combustion and replacement of NGH with flue gas is proposed.This article uses numerical simulation methods to study the characteristics of premixed natural gas oxy-fuel humidified combustion to achieve the effects of improving combustion thermal efficiency and controlling pollutant emissions.The comparative literature with the same burner structure as this paper is selected and the simulation is performed using the same combustion conditions.The simulation results obtained are basically consistent with the measured data results of the comparative literature,and the maximum errors are within a reasonable range,which validates the model in this paper.The accuracy and reliability ensure the accuracy of subsequent simulations.Under the condition that the natural gas mass flow rate at the inlet of the burner is constant,the influence of a single variable R_fon the oxy-fuel humidified combustion of natural gas is studied.The results show that under the condition of oxy-fuel humidified combustion,the convection and radiant heat transfer effects in the burner are enhanced,the combustion efficiency is improved,the combustion reaction is more complete,the pollutant emission concentration is significantly reduced,and the combustion performance is improved.However,as the amount of steam injected increases,the decrease in combustion temperature will affect the combustion efficiency,and a large increase in water vapor will easily cause the boiler to stall.Therefore,the amount of steam injected to reach the emission standard is selected as the limit,that is R_f=0.33.On this basis,the influence rule of humidified combustion characteristics of natural gas is analyzed,including the influence rule of FGR ratio,αand preheating temperature of combustion gas on combustion characteristics.The max combustion temperature gradually decreases,and the high-temperature region gradually shrinks with the increase of the FGR ratio.The injection of the recirculated flue gas has a positive effect on the improvement of the combustion efficiency and the reduction of the pollutant emission.With the increase ofα,the combustion reaction rate of natural gas is accelerated,the combustion efficiency is increased,and the pollutant emissions at the burner outlet are reduced.With the rise of the preheating temperature of the combustion-supporting gas,the temperature distribution area is more uniform.But the NO_xshows an exponential explosion trend and Soot emissions decreased slightly.Through a comprehensive analysis of the simulation results and considering economic benefits and industrial applicability,it is proposed that under the condition of natural gas oxy-fuel humidified combustion,the FGR ratio should be controlled between 5%and 10%,the excess air coefficient should be controlled between 1.05 and 1.1,and the combustion supporting gas should be preheated to within 420k,which can effectively improve the combustion thermal efficiency and subsequent carbon capture efficiency of the gas boiler and minimize the carbon capture efficiency Emission level of pollutants.In order to realize the industrialized application of natural gas oxy-fuel humidified combustion,this technology is introduced into the field of gas-fired steam boilers in power plants.Based on the above research results,a set of natural gas oxy-fuel humidified combustion and replacement of NGH with flue gas co-production process was proposed,and linear regression analysis was performed on the economics of the oxy-fuel humidification combustion technology to verify its industrial feasibility and evaluate its Economical,to obtain its optimal working conditions,provide a certain theoretical basis for the future industrial application of natural gas oxy-fuel humidified combustion technology,and create a win-win situation of energy optimization-clean environmental protection-increase production and income. |
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