Abstract: A method of applying a hot composite on top of the refractory lining of steel making and processing vessels is disclosed. The composite may be applied to the refractory wall in more than one layer, including a dense intermediate layer for adhesion, and a less dense layer on top that is designed to be consumed as a slag-forming component during steel making and refining. The composite is applied by discharging a carrier gas containing a mixture of small particles, including particles of silica, particles of at least one high-temperature oxide based material and particles of solid carbonaceous fuel, through a carrier gas discharge nozzle. Additional substances may be added to the mixture to enhance the slag-forming process. A controllable flow of oxidizing gas is charged at high and preferably supersonic speed through an essentially crescent-shaped nozzle partially surrounding the carrier gas discharge nozzle.