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Method and apparatus for uniformly injecting a fluid stream into a gas stream at elevated temperature by means of an injection nozzle comprising a nozzle head and a supply inner tube being concentrically surrounded with an outer casing tube spaced apart from the inner supply tube. It comprises passi

Method and apparatus for uniformly injecting a fluid stream into a gas stream at elevated temperature by means of an injection nozzle comprising a nozzle head and a supply inner tube being concentrically surrounded with an outer casing tube spaced apart from the inner supply tube. It comprises passing the fluid stream through the inner tube and the nozzle head and maintaining temperature of the fluid stream in the inner tube by providing thermal insulation in at least part of an annular space between the inner tube and the outer tube. Further it comprises maintaining a constant flow of the fluid inside the inner tube and nozzle head by plugging the nozzle head at outlet end and spraying the fluid stream through a number of nozzle holes provided in the nozzle head adjacent to the outlet end of the nozzle head.

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The invention claimed is: 1. Method of uniformly injecting a fluid stream into a gas stream at elevated temperature by means of an injection nozzle comprising a nozzle head and a supply inner tube being concentrically surrounded with an outer casing tube spaced apart from the inner supply tube, whi

The invention claimed is: 1. Method of uniformly injecting a fluid stream into a gas stream at elevated temperature by means of an injection nozzle comprising a nozzle head and a supply inner tube being concentrically surrounded with an outer casing tube spaced apart from the inner supply tube, which method comprises passing the fluid stream through the inner tube and the nozzle head and maintaining temperature of the fluid stream in the inner tube by providing thermal insulation in at least part of an annular space between the inner tube and the outer tube; maintaining a constant flow of the fluid inside the inner tube and nozzle head by plugging the nozzle head at outlet end and spraying the fluid stream through a number of nozzle holes provided in the nozzle head adjacent to the outlet end of the nozzle head; spraying the fluid stream through the nozzle holes in a direction being substantially at right angles to flow direction of the gas stream and adjacent to center axis of the gas stream channel; and uniformly distributing the sprayed fluid stream into the gas stream by conically narrowing the outer casing tube in region adjacent to the nozzle head. 2. Method of claim 1, wherein the gas stream is an exhaust gas stream from a Diesel engine and the fluid stream is an aqueous solution containing between 20% and 50% by weight, preferably between 30% and 35% by weight of urea. 3. Method of claim 2, wherein the aqueous solution is passed to the nozzle head by pressurized air. 4. Injection nozzle for use in a method according to anyone of the preceding claims comprising a nozzle head being connected to a fluid stream supply tube, wherein the supply tube is concentrically and spaced apart surrounded by an outer casing tube; space between the supply tube and the casing tube is at least partly filled with thermal insulation material; the outer casing tube is conically narrowed to adjacent to outer wall of the supply inner tube in region adjacent to the nozzle head; the nozzle head is plugged at outlet end with a plug; and the nozzle head is provided with a number of equally spaced nozzle holes in region adjacent to the plug of the nozzle head. 5. Injection nozzle of claim 4, wherein the sizes of outer diameter and inner diameter of the nozzle head are identical to sizes of outer diameter and inner diameter of the supply tube. 6. Injection nozzle of claim 4, wherein the nozzle head is a tube equipped with a 90째 bend between the supply tube and the nozzle holes. 7. Injection nozzle of claim 6, wherein the straight part of the nozzle head between the bend and the nozzle holes has a length of 5 mm. 8. Injection nozzle of claim 4, wherein the thermal insulation material is a ceramic compound. 9. Injection nozzle of claim 4, wherein the inner surface of the conically narrowed part of the outer casing tube has an angle of 30째. 10. Injection nozzle of claim 4, wherein the supply tube has an outer diameter of 6 mm and a wall thickness of 1.5 mm, the outer casing tube has an outer diameter of 25 mm and a wall thickness of 1.22 mm, and the nozzle head is equipped with four equally spaced holes each with a diameter of 0.55 mm or with eight equally spaced holes each with a diameter of 0.39 mm.