Technical field

Combined burner for injecting oxidizing gas and fuel is meant for blowing oxygen and fuel during the melting of scrap in melting furnaces.

State of the art

The burners presently used are at the same time used as nozzles and they are fixedly installed into the walls of the furnace. Injected oxidizing gas, which is oxygen or air enriched by oxygen, and injected fuel - e.g. natural gas, are blown into a given fixed place in the furnace. This means that the axis of blown oxygen and fuel doesn't move. This restricts the efficiency of transferring the heat of the flame into the charge and also the efficiency of the blown oxidizing gas, because the reaction happens in a relatively small volume in the space of the furnace, and heat flux decreases with growing temperature of the charge surface. The difference between the temperature of the heat source, which is the temperature of the burning of fuel and some chemical elements of the charge with oxygen, and the temperature of the material delivered to the furnace decreases.

The known movable solutions consist of moving the whole burner - nozzle, which is installed on a movable manipulator. The furnace thus has to have an aperture, in which the nozzle is moving, e.g. the working door of the furnace. The furnace thus isn't sealed, when the nozzle is working, which decreases the efficiency of the furnace. Another disadvantage of this solution are large dimensions and difficult installation. A version,: in which the burner - nozzle is tilted up and down in vertical axis, is also known. When tilted up, the efficiency of heat transfer decreases, because smaller layer of the charge is above the flame of the burner, which absorbs the heat. A rotational solution of the whole burner also exists, it is described in the US 5 630 713 patent, in which the whole burner, placed in a fixed block in the wall of the furnace, is moving. This solution has the substantial disadvantage that the gap between the fixed and movable part is inside the furnace. Hot gases from the furnace thus get into this gap and the furnace doesn't seal the materials in the furnace - parts of the charge, splashing liquid slag or metal. These particles then gradually fill this gap and the moving of the burner is blocked. Another disadvantage of this solution is that it is meant for installation into the cooled panel of the furnace wall and the face of the burner is in the same plane as the face of the furnace wall. This increases the risk of wear of the furnace wall by flame rebound from the charge.

Summary of the invention

These disadvantages mentioned above are removed by the combined burner for blowing oxidizing gas and fuel into the melting furnace, which is fixedly installed into the furnace and provided with outlet apertures for fuel and oxidizing gas according to the invention, which is based on the fact, that the burner consists of a fixed part of the burner and a movable nozzle, which is rotationally installed inside the body of the fixed part of the burner. Supply of oxidizing gas is connected to the nozzle and the nozzle motion is controlled using an actuator installed outside of the working space of the furnace. The axis x ₂ of the orifice of the movable nozzle is diverted from the axis xi of the rotation of the movable nozzle by an angle in the range of 5 to 60° and the movable nozzle is rotatable around the axis xi in any direction by the angle β in the range of 0 to 180°. The foundation is also that the burner is placed in a wall or ceiling of the furnace and that the body of the fixed part of the burner is arranged in the outside fixed housing cooled by liquid or gas, and it protrudes into the space of the furnace by the distance \ in the range of 0 to 2000 mm. It is also important that the movable nozzle is provided with at least one aperture for oxidizing gas and apertures for the fuel at the outlet.

The newly provided combined burner according to the invention is thus equipped with a movable nozzle inside, which allows directing blown gases into various places in the furnace. The whole burner is at the same time fixedly installed in the wall or ceiling, or the cover of the furnace, and the space of the furnace thus remains sealed. This solution has several basic advantages:

- the furnace remains sealed - air is not sucked in by the aperture for movement of the nozzle

- the movable part of the nozzle is built into the static part and movable mounting is protected from the impact of the atmosphere in the furnace, or splashes of the melted material in the furnace

- eccentric rotational movement moves the flame - the jet of blown gases in horizontal and vertical plane at the same time. Hot gases affect various places on the charge and this increases the heat flux into the material. Moving jet of oxidizing gas, e.g. oxygen, allows to cut the heated charge, similar to the cutting burner during splitting of the material. This causes faster splitting of the charge directly in the furnace and its falling into the melted bath in the furnace. Parts of the charge, which get thus into the liquid bath in the lower part of the furnace, are thus melted faster, which increases the efficiency of the whole process. After the charge is melted, the oxidizing gas is blown directly into the liquid bath in the furnace. We call this working mode the "oxygen lance mode". In the oxygen lance mode, it is possible to completely stop the fuel input and only oxidizing gas is thus blown into the furnace.

This combined burner can be used in any furnace for heating and/or melting of the charge. We mention typical applications as examples: melting of metal charge (scrap, additives, metallic charge) in electric arc furnace, melting the charge in chamber furnace, where the burners could be in the walls or ceiling of the furnace - e.g. melting of non-iron metals, glass, etc., also in heating furnaces for metal charge prior to further processing, e.g. prior to forging, rolling, etc. The applications mentioned are just examples of possible use, which could be broadened to other processes as well.

List of figures on the drawing

An example embodiment of the combined burner for blowing oxidizing gas and fuel into the melting furnace including actuator is depicted at fig. 1 , its detail D1 - fig. 2 - shows the orifice of the burner. Fig. 3 presents the turning of the internal movable nozzle. Fig 4 is a plan view showing the installation of the burner in the furnace and the positions of gas jets in three different situations. Fig. 5 shows the installation of the burner and positions of gas jets in three different situations in side section.

Examples of the invention

Combined burner 1 consists of a fixed part 2, whose main part consists of a body t Movable nozzle 4 is rotatably installed inside the body 2A_. Body 2J. is provided with protective outer housing 4, fixedly connected with wall 5 or cover 6 or the ceiling of the furnace. Outside fixed housing 2A is cooled by liquid or gas, which are forced into the channels 5, created in the outside housing 2A. The body 2J. of the burner is also provided with cooling channels 27 for cooling the face of the burner by liquid or gas. Wall 5 of the furnace can consist of cooled panels, or could be made of refractory material. Oxidizing gas is brought to the movable nozzle 4 by the inlet 7 and fuel is brought to the fixed part 2 of the burner by inlet 8. The burner is installed such that the orifice of the burner is in the distance ai from the wall 5 of the furnace. The distance ai is chosen so that the jet of gases from the burner doesn't collide with the lining of the furnace. The body 2A_ of the fixed part 2 of the burner is protruding into the space of the furnace from the wall 5 by the distance ai, in this case 800 mm long. Movable nozzle 4 is controlled by an actuator 3, installed outside of the working space of the furnace and it is rotatable around the rotation axis xi in any direction by the angle β, in this case 70°. Axis X2 of the orifice of the movable nozzle 4 is diverted from the rotation axis Xi of the movable nozzle 4 by the angle a, in this case 30°. Turned positions of the movable nozzle 4 are marked by working positions A, B and C. When the movable nozzle 4 is turned by the angle beta β, the jet of gases blown by the fixed part 2 of the burner into the furnace is moved to the position B, respective to the position C when turned in the other direction. The working range of the burner is thus anywhere between the positions B and C, middle position is marked as position A.

Outside cover 2A around the body 2 \ of the burner has a rugged design resistant to high temperature and mechanical damage by the charge of the furnace. Outside housing 2A is liquid cooled according to the example embodiment, or it could be manufactured from refractory material.

The movable nozzle 4 contains aperture 4J_, through which the oxidizing gas - e.g. oxygen - flows and the fuel - e.g. natural gas - flows through other apertures 4,2. The movable nozzle is installed in bearing 2J3 or rotatable housing with apertures for the flow of fuel. The fuel also flows through apertures 22, created in the body 2J. of the fixed part of burned 2. Fuel and oxidizing gas are mixed together in the mixing space 3 in the body 2Λ of the fixed part. The aperture 4J. of the movable nozzle 4 is in the shape of Laval's nozzle for obtaining supersonic speed of the oxidizing gas. Aperture 4J. with the axis Χ2 is inclined under angle g from the axis xi, which is the rotation axis of the movable nozzle 4.

When the movable nozzle 4 rotates around the axis Xi by the angle β, the jet of gases flowing through the aperture 4J. with axis X2 flows into various places of the furnace, depending on the angle β of diversion from the vertical plane. The angle β can be up to the range of 180°. For different types of applications, it is possible to interchange the apertures for the flows of fuel and oxidizing gas, for creating various types of flame. This means that the fuel could flow through the aperture 4J. and oxidizing gas through the apertures 42. The motion of the movable nozzle 4 is provided using actuator 3, which is installed on the furnace, or it could be connected to the fixed part 2 of the burner. Actuator 3 can be powered by an electric motor with gearing, hydraulically, pneumatically or in another way, it isn't important from the point of view of the function of the burner.