Thermal effects of CO2 on the NOx formation behavior in the CH4 diffusion combustion system

Abstract

The objective of the present study is to numerically investigate the quantitative effects of CO2 replacement of N2 in the oxidizer side on NOx formation in CH4 diffusion flames established in counterflow configuration at atmospheric pressure. The mole fraction of O2 in the oxidizer was kept constant at 21%. Calculations were conducted at different stretch rates and different percentage of CO2 in the oxidizer. Calculations were also carried out with and without radiation to quantify the effects of radiation heat transfer. For this simulation, a modified CHEMKIN code and a radiation code developed at the Combustion Group of ICPET were used. Mainly due to its much higher specific heat, replacement of nitrogen in air by carbon dioxide significantly lowers the temperature of the flame, leading to much lower NO concentrations. For a specified stretch rate, there exists a maximum percentage of CO2 in the oxidizer beyond which flame extinction occurs. The value of the maximum percentage of CO2 in the oxidizer decreases as the stretch rate increases. Effect of radiation heat transfer becomes more important as the stretch rate decreases. Replacement of N2 by CO2 in the oxidizer is an effective way to control NOx formation in CH4 diffusion flames mainly due to its thermal effect and secondly due to its chemical and radiative effects.

Effects of strain rate and CO2 on no formation in CH4/N2/O2 counter-flow diffusion flames

“…The CO 2 has the heat and mass transfer in the combustion process. Thus, the effects of CO 2 addition on the fuels in combustion have been studied in recent years [1,4,5,8,11,17]. For this reason, the initial temperature of the fuel side is set to 300 K and the oxidant flow is 1200 K. The strain rate is kept at 100 s -1 and the oxidant side is oxygen-enriched O 2 / N 2 (0.8/0.2) CO 2 (0.1-0.59) (for convenience, molar fraction replaced by volume fraction).…”

“…With the continuous enrichment of experimental methods and the deepening application of numerical simulation in combustion research, related scholars have done a lot of research on opposed-jet diffusion flame [2][3][4][5]. Although the previous studies manifests sub-…”

Simulasi Numeris Karakteristik Pembakaran CH4/CO2/Udara dan CH4/CO2/O2 pada Counterflow Premixed Burner

“…Perhitungan dilakukan dengan menggunakan CHEMKIN dan kode perhitungan radiasi yang dikembangkan oleh ICPET. Dikarenakan oleh nilai kalor spesifik yang lebih tinggi, penggantian N2 menggunakan CO2 dapat menurunkan temperatur dari api secara signifikan, dan mengakibatkan turunnya konsentrasi NO yang terbentuk [7].…”

Adsorbed Natural Gas Storage for Onboard Applications

“…Among fossil fuels, natural gas (NG) is the best suited to satisfy the world's energy demand while minimizing environmental repercussions. [ 10–17 ] One advantage of NG is that its reserves could satisfy the global energy demand for the upcoming decades. [ 18,19 ] For instance, at the end of 2018, the world's proved NG reserves totaled about 197 trillion cubic meters.…”