Radiative effects of carbon monoxide in high-temperature carbon dioxide plumes and implications for modeling thermal plasmas

High-temperature heating processes that are transitioning towards low-carbon operations are emphasizing work on gas radiation modeling. The formation of CO from CO 2 -dissociation is significant at high temperatures, raising questions about the relative importance of CO in broadband gas radiation models. This work focuses on the radiative effect of CO in high-temperature CO 2 -plumes. The analysis combines speciation in these zones with the construction of a framework to evaluate the radiative contribution of gases. It is shown that under peak temperature conditions associated with thermal CO 2 -plasma plumes, where CO 2 -dissociation and the formation of CO are significant, the chemical timescales are sufficient to approximate equilibrium. Within this thermochemical and optical regime, CO 2 dominates the radiative contribution, as compared to CO . The reason for this is the extensive spectral overlap in the relevant infrared bands between the two species. For temperatures of approximately 1200–3000 K and CO / CO 2 ratios of 1 or below, treating CO as transparent results in less than 6% error in the peak radiative source term and about 7% error in gas-mixture emissivity. The radiative contribution of CO becomes more pronounced under CO -rich conditions, and at temperatures above approximately 3800 K, where CO 2 dissociation increases the relative importance of CO . Thus, the results provide a quantitative basis for effectively modeling CO as a transparent gas in broadband representations of CO - CO 2 mixtures, thereby simplifying the treatment of CO in radiation models within the identified thermochemical and optical regime relevant for novel applications such as CO 2 -based thermal plasmas.