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

Journal article, 2026

High-temperature heating processes that are transitioning towards low-carbon operations are emphasizing work on gas radiation modeling. The formation of CO from CO2-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 CO2-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 CO2-plasma plumes, where CO2-dissociation and the formation of CO are significant, the chemical timescales are sufficient to approximate equilibrium. Within this thermochemical and optical regime, CO2 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/CO2 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 CO2 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-CO2 mixtures, thereby simplifying the treatment of CO in radiation models within the identified thermochemical and optical regime relevant for novel applications such as CO2-based thermal plasmas.