Many proposed oxy-combustion concepts for carbon capture incorporate the recycling of flue gas which is used as a dilution gas to aid in the control of temperature and heat flux. Improvements in efficiency may be realized by significantly reducing the recycle flue gas (RFG), however, in application, care must be taken to avoid excessive radiant heat flux and gas temperature. One of the features oxy-combustion, unlike air-fired combustion, is that the oxygen and dilution gases are initially separated. RFG can, for example, be strategically blended with either the fuel stream, or oxidizer stream, or both, which affects the stoichiometric mixture fraction, Z_st. In this work, the effects of the amount of dilution, or RFG, and Z_st on soot fraction are experimentally investigated in a laminar coflow flame. Carbon dioxide is employed as the dilution gas to simulate the recycling of dry flue gas. Soot fraction and temperature are quantitatively determined by a flame image processing technique. In addition, the visible and near-IR emission spectra are given. When dilution, or RFG, is reduced, while holding Z_st constant, soot formation and thermal radiation increase due to higher temperature. However, high temperature flames with reduced or zero soot are achieved by increasing Z_st via the combination of fuel dilution and oxygen enrichment. This study highlights the inherent flexibility of oxy-fuel combustion, which offers the opportunity to control flame temperature and gas volume while independently controlling soot formation and radiant heat transfer.

许多提出的用于碳捕集的氧燃烧概念结合了烟气的再循环，该烟气被用作稀释气体以帮助控制温度和热通量。可以通过大大减少循环烟气（RFG）来实现效率的提高，但是，在应用中，必须注意避免过多的辐射热通量和气体温度。与空气燃烧不同，氧气燃烧的特征之一是氧气和稀释气体最初是分离的。RFG可以例如与燃料流或氧化剂流或两者策略性地混合，这会影响化学计量的混合物分数Z _st。在这项工作中，稀释量或RFG和Z _st的影响在层流同流火焰中对烟灰分率进行了实验研究。二氧化碳被用作稀释气体以模拟干烟气的再循环。烟灰分率和温度通过火焰图像处理技术定量确定。另外，给出了可见和近红外发射光谱。当降低稀释度或RFG时，在保持Z _st不变的情况下，由于温度升高，烟灰形成和热辐射增加。但是，通过增加Z _st可以实现烟灰降低或为零的高温火焰通过燃料稀释和富氧相结合。这项研究突出了氧燃料燃烧的固有灵活性，这为控制火焰温度和气体量同时独立控制烟灰形成和辐射热传递提供了机会。