Analysis Of Oxygen-Enriched Combustion Characteristics And NO_x Emission Of Natural Gas Under O₂/CO₂ Atmosphere

Since"coal to gas"was introduced,the unbalanced development of natural gas production,supply,storage and marketing system has gradually become prominent.With the increasing proportion of natural gas in China's energy consumption,the traditional boiler combustion mode has been unable to meet the needs of the existing energy structure reform because of its low combustion efficiency and high pollutant emissions.The technology of O₂/CO₂ combustion emerged at the historic moment.It abandoned the traditional O₂/N₂ combustion atmosphere,put fuel in O₂/CO₂ atmosphere for combustion,and controlled the ratio of O₂/CO₂ by adjusting the ratio of oxygen to flue gas recirculation.This technology can effectively reduce the emission of smoke and dust,improve fuel utilization efficiency,accelerate combustion rate,improve cycle heat efficiency and ultimately improve industrial production.The purpose of efficiency,energy saving and emission reduction.On this basis,the CO2/CO2 combustion technology is coupled with the CCUS technology,and the CO₂ generated by the flue gas circulation is injected into the oil and gas wells to improve the production of oil and gas wells and realize the benign cycle system of resource exploitation.After establishing the burner model,the maximum errors of temperature,CO concentration and OH concentration are 5.8%,4.7% and 5.3%respectively.Considering the difference between the two models and the difference of combustion mechanism,the errors are within a reasonable range,so the accuracy and reliability of the model are verified,and the simulation results of the model have guiding significance for industrial production.After verifying the accuracy of the model,the combustion of natural gas in the same oxygen concentration in the atmosphere of O₂/CO₂ and O₂/N₂ was simulated.The advantages of O2/CO2 combustion technology were demonstrated from the aspects of flow field distribution,component concentration distribution and pollutant emission level.The results show that the combustion efficiency of natural gas in O2/CO2 atmosphere is higher than that in O2/N2 atmosphere,and the generation of pollutants is less.In order to understand the combustion characteristics of natural gas in O2/CO2 atmosphere,the combustion temperature distribution,combustion velocity distribution,CH₄ concentration distribution,CO₂ concentration distribution,NO_x distribution and SOOT distribution were analyzed to change the oxygen concentration.The results showed that the combustion efficiency and combustion rate increased significantly with the increase of oxygen concentration,but with the increase of oxygen concentration,the combustion efficiency and combustion rate increased significantly.With the increase of NO_x content,the area of NO_x formation is ahead of schedule,and the volume fraction of carbon black increases sharply,and the peak volume fraction of carbon black also shows an exponential growth trend.In order to obtain the range of oxygen concentration which meets the national emission standard,the combustion characteristics of natural gas with 21%-36% oxygen concentration were further simulated.The concentration of NOx and Soot at the exit were obtained,and the oxygen concentration which meets the emission standard was 21%-35%.According to the combustion characteristics of natural gas in O₂/CO₂ atmosphere,this paper combines oxygen-enriched combustion technology with CCUS technology,and establishes a new scheme of oxygen-enriched combustion and flue gas recovery in O₂/CO₂ atmosphere.This scheme effectively improves the recovery rate of waste heat of flue gas and combustion efficiency of gas boiler,and reduces the emission level of pollutant NO_x and soot.Through flue gas circulation,the concentration of CO₂ in flue gas can be increased,the enrichment of CO₂ in combustion flue gas can be promoted,the recovery and utilization of CO₂ can be facilitated,and the final realization of low CO₂ emission is of great significance to energy saving and emission reduction and greenhouse effect reduction.On the basis of this scheme,the equipment is selected by calculation.Through economic regression analysis,the optimal oxygen concentration of the scheme is 29%,and the economic benefit of the scheme is calculated when the oxygen concentration is 29%.The cost recovery period of the equipment is 5 years,which verifies the rationality of the scheme.According to the optimum gas atmosphere of 29%O₂/71%CO₂,it is applied to natural gas boilers in power plants.The influence factors of excess air coefficient and preheating temperature on power plant boilers are mainly studied.The results show that the combustion efficiency increases with the increase of preheating temperature of combustion-supporting gas.The combustion efficiency increases rapidly from 300K to430K and slowly after 430K.At the same time,the production of NO_x also shows an exponential growth,and the preheating temperature which meets the national emission standards is less than 420K.Considering the cost and economic benefits,the preheating temperature of the gas should be controlled between 400K and 420K.With the increase of excess air coefficient,the combustion efficiency will increase.When the excess air coefficient is between 1.05 and 1.15,the increase will be faster,and when the excess air coefficient is greater than 1.15,the increase will be slower.At the same time,the production of NOx also shows an exponential growth,and the excess air coefficient which meets the national emission standards is less than 1.15.Considering the cost and economic benefits,the excess air coefficient should be controlled between 1.12 and 1.15.Through the simulation and economic analysis of this paper,considering the industrial applicability and economic benefits of power plant boilers,it is proposed that the preheating temperature of gas-assisted boilers should be controlled between 400 K and 420 K and the excess air coefficient between 1.12 and 1.15 when the atmosphere of gas-assisted gas is 29%O₂/71%CO₂,which can maximize combustion while ensuring that pollutants meet the national emission standards.Burning efficiency.Combined Edition...