Over the period of furnace life Sulphates and Batch carryover blocks the flow of the waste gases and combustion air inout in the checkers of the regenerators. These blockages can be clean by applying heat to melt sulphate to a liquid state. The high velocity burners are placed at the bottom of the regenerator under the rider arches. Normally there are two types of cone are being used for Firing , one with 45 Deg. extended  cone to clean  far side and other with 90 Deg. extended cone for nearer side of the regenerator. This cone can be move left and right side to cover entire rider arch area. The temperature increased between 40 Deg.C to 50 Deg.C up to maximum temperature 900 Deg.C depending upon the regenerator conditions.