The present invention discloses a reactor (100) for manufacturing carbon black, said reactor (100) comprising flow guide means (110) provided between a fuel burner (106) and an air inlet (108) for altering the flow path of combustion air entering at the air inlet (108) to result in a better mixing between the fuel and the combustion air, thereby, producing higher temperature hot combustion gases which are subsequently received in a reaction chamber (104) where they react with a carbonaceous feedstock to produce carbon black. The reactor (100) of the present invention increases the carbon black production by 5-20%. Further, the positioning of the flow guide means (110) stabilizes the flame from the fuel burner (106) to maintain it along the reactor axis, thus, increasing the life of the refractory lining (114).