Furnace installation for burning liquid or gaseous fuel, in particular for a boiler

Claim 1

A furnace installation for burning liquid or gaseous fuel with recycling of the flue gases, in particular for a boiler, comprising a combustion chamber; a furnace wall enclosing said combustion chamber and having at least one flame hole; a burner mounted in line with said flame hole for directing fuel through said hole to be burned in said combustion chamber; a source of secondary combustion air; duct means for conducting said secondary combustion air to said flame hole; means for conducting recycled flue gas to said flame hole, said means opening circumferentially into said duct means adjacent to said flame hole whereby said flue gas flowing through said flame hole forms a mantle of flue gas enveloping the flame of said burning fuel; a flue gas box mounted on the outside of said furnace wall around the flame hole, said box having a back wall opposite said furnace wall and provided with an aperture in line with said flame hole; a flue gas conduit opening into said box; sleeve means extending through said box and coaxially enclosing said burner, said sleeve means having a forward end joining the periphery of said flame hole and having a rear end attached to the edge of the aperture in said box rear wall whereby a ring-shaped duct for said secondary combustion air is formed between said sleeve and said burner and passing through said flue gas box and communicating with said source of secondary combustion air, said sleeve having outflow apertures for the flue gas uniformally distributed around its circumference and opening into said duct.