# Patent Analysis of the Development of Technologies Applied to the Combustion Process
## 3 Results and Discussion
Another strategy documented in the patents and also found in the literature is the use of O\({}_{2}\) to enhance the combustion process. First mentioned by [PERSON] (1998) [38], OEC is a process that involves enriching the intake air for combustion with O\({}_{2}\); it provides good results, including higher productivity, better thermal efficiency, a lower volume of exhaust gas, greater efficiency in heat transfer processes, reduction in fuel consumption, cost reduction in raw material, and greater flame characteristics, which promote stability and shape control [1; 39; 40]. Patent EP2284130A1 (2011) refers to a new method of producing mineral wool using a cupola furnace, where the combustion chamber is fed with fuel and O\({}_{2}\) gas. According to the invention, by increasing the O\({}_{2}\) concentration, the flame intensity and temperature increase significantly [41]. Another example, patent WO2000009945A1 (1998), refers to a combustion chamber device with burners of different geometric shapes, where each burner includes a supply for the flow of O\({}_{2}\)-containing gas. The main purpose of the invention was to reduce acoustic pressure oscillations without, at the same time, increasing the emissions of NOx [42]. [PERSON] et al. [43] evaluated the NOx reduction and burnout characteristics of pulverized coal in OEC with a drop-tube reactor, and their results showed the inhibition of thermal and fuel NOx formation with a rise in O\({}_{2}\) concentration under deep-staging parameters. [PERSON] and [PERSON] [44] explored the effect of OEC conditions on torrefied waste wood pellets with the main goal of optimizing the combustion efficiency. The results revealed improved data for both the total fluidized-bed combustion efficiency and volatile combustion ratio when using O\({}_{2}\) enrichment. [PERSON] et al. [1] evaluated the thermal radiation and formation of soot in flames of syngas using the OEC technique under the conditions of poor mixtures. The results demonstrated an influence of lean combustion and OEC on the formation of soot and the thermal radiation of the flame, indicating better control over the formation of soot without a reduction in thermal radiation. The enrichment of the combustion process with oxygen refers to concentrations ranging from 21 to 90%, where more than 90% O\({}_{2}\) is considered oxyfuel combustion [45]. In order to evaluate three different concentrations of O\({}_{2}\) (21, 25, and 30 volume fraction %) during methane combustion, [PERSON] and colleagues evaluated the stability of a methane\(-\)air flame and pollutant emissions, such as CO, CO\({}_{2}\), and NOx. The main results showed that oxygen enrichment promotes large CO conversion into CO\({}_{2}\). CO\({}_{2}\) increases linearly with oxygen addition; the concentration of NOx increases with oxygen addition, mostly because of the increase in the flame temperature; flame stability is enhanced with oxygen addition, even for low concentrations; and also, lift-off heights and their fluctuations largely decrease with oxygen addition [46]. [PERSON] et al. [47] searched for the effects of exhaust gases recirculation, water vapor, and CO\({}_{2}\), with and without O\({}_{2}\) addition, on non-premixed turbulent flames stabilized by a swirl burner. The O\({}_{2}\) enrichment varied from 21% to 30% (in vol.) and results demonstrated a significant decrease in the liftoff height enhancing the flame stability. They also observed a decrease in NOx emission and exhaust gas temperature and an increase in CO emissions that was directly related to the decreased flame temperature. The OEC technology can also be applied to others innovative fuel such as hyphae as describe by [PERSON] and colleagues [48]. The group has experimentally and numerically evaluated the combustion of hyphae generated in a coaxial burner to assess the efficiency of the process using an oxygen-enriched oxidizer.