As a result of the global energy crisis, all countries around the world are resorting to burning using the solid, liquid, and gaseous fuels, whichever is available. However, because of the difficulty of solid fuel combustion, the global trend goes to liquid fuel combustion as it is easier than solid fuel combustion, then goes to the gaseous fuel according to its ease of combustion than the other two types. But, because of the gaseous fuel scarcity and high price, the tendency to co-fire liquid and gaseous fuels is gaining more attention to get Higher performance and solve problems related to liquid fuels. Double swirlers are used to improve the atomization of liquid fuel and improve the mixing of air with fuel to achieve the highest performance of combustion, thus obtaining clean combustion with low emissions. The goal of the current research is to use dual fuels, to increase the efficiency of the combustion and to solve the problem of fuel scarcity and the difficulty of liquid fuel combustion by using gaseous fuels, in addition, to figure out the effect of the recirculation zone and excess air on the combustion characteristics and NOx. The results showed that cofiring dual fuels increases the efficiency of burning liquid fuel as the gaseous fuel form a hot shield around the liquid flame that reduces evaporation time and fires falling droplets from liquid flame and increases soot oxidization, in addition cofiring raises the temperature inside the furnace which enhances convective heat transfer and reduces the visual and thermal flame lengths which decrease the heat flux from the flame. However, the overall cumulated heat transfer is better than the liquid case. Finally, cofiring gives the ability to efficiently burn biofuels in the future to generate thermal power for the industry especially for cement factories that need high power.