SE439535B - PROCEDURE FOR REDUCING NO NO 71X EMISSION IN BURNING - Google Patents

Description

80Û1.l§8U-6 sub-stoichiometric range which also the thermal NOX formation can be considerably reduced. In experiments, through the use of two-stage combustion, a reduction of the NOX emission value in relation to non-step combustion of up to about 70% has been achieved.

A process according to the preamble of the claim is unknown from U.S. Pat. No. 4,025,921. This process is used to reduce NOK recirculation of cold flue gas. Admittedly, this gives a certain step division of the combustion by dividing the combustion air into a primary stream and a secondary stream, which are also mixed into the flame one after the other, but the primary stream only amounts to 2 to 10%. However, this small percentage of air mixture is not sufficient to pyrolyze a significant part of the fuel in the primary zone. Only when one has a fuel pyrolysis in the primary zone with oxygen deficiency, the formation of fuel NOX can be suppressed. Therefore, with this procedure, only a reduction of thermal NOK is achieved.

It has further been established that even by slowing down the mixture between the air and fuel stream, a significant reduction in NOX emissions can be obtained.

In a known carbon powder burner (DE Gebrauchsmuster 1 868 0O31) the jacket-shaped secondary air stream is supplied in two adjacent, annularly arranged and separately controllable tubes, for example to allow the inner, immediately adjacent to the powder jet to flow out with lower and the outer secondary air. The disadvantage of this arrangement is that the flame is elongated, which leads to a larger fireplace, and that in the case of load-dependent lowering of the secondary air, its speed is reduced, thereby changing the character and shape of the flame.In certain circumstances, ignition can be negatively affected.

Furthermore, it is previously known from DE Offenlegungsschrift 2 129 357 to allow a primary combustion to take place under subchiometric conditions in an antechamber, and to mix the air required for complete combustion into the flue gases leaving the antechamber. Furthermore, flue gases are sucked out of the fireplace through a device mounted on the burner.

The object of the present invention is thus to provide a process of the kind mentioned in the introduction, which further reduces the formation of NOK.

This task is solved by giving the procedure according to the preamble of the claim the features according to the characterizing part of the claim. 8001480-6 The advantages obtained by the process according to the invention, namely reduced NOX emissions, are achieved by the special division of the secondary air stream in connection with a direct intake of flue gases in the fireplace.

While one part of the secondary air, which is immediately supplied to the burner, with respect to vortex motion and speed, it can be affected that an intense ignition is guaranteed over the entire load range, the other part of the secondary air stream is supplied as step air stream outside the burner to the flame, so that after ignition and primary combustion through the mixed energy flow of the step air stream and complete combustion in the secondary zone, the objective described in connection with the task is realized. The process according to the invention is described in more detail in the following with reference to the attached principle sketch of a burner and the flame emanating from the mouth of the burner.

With the burner consisting of nuclear air pipe 2, fuel and carrier air part 1 and in jacket air part 5, a partial combustion zone (primary zone) 6 is created, the air number of which is between 0.9 and 0.5 - times the stoichiometric value. g The burner is designed so that by certain measures (grouting for the jacket air, conically expanded burner mouth, closed core air) in the flame's interior a zone of intense backflow is achieved from an area of already advanced combustion.

As a result, the fuel-air mixture is quickly heated and ignited.

Heating and ignition can be affected by the supply of nuclear air. Thus, the best ignition is ensured, when the core air is closed; The air required for the final complete combustion is blown in as step air 4 over some nozzles on the circumference so; that it only after the formation of the primary flame supplies the secondary flame with oxygen or even the afterburning zone 7. The step air flow 4 is arranged for the purpose in a dividing circle corresponding to double the mantle air cross-section, thereby ensuring that the step air 4 only after a distance of approx. two jacket air tube diameters when the actual flame is downstream of the burner mouth.

In the sections of the circumferential surface of the flame which are not in to the step air flow 4, flue gases from the fireplace are sucked in by impulse exchange. This lowers the low temperature.

Claims (1)

1. 8001480-6 4. A method for reducing NOX emissions during the combustion of nitrogen-containing fuels via burners in a closed fireplace, the combustion taking place with the addition of flue gases in a sub-stoichiometric primary combustion zone (6) with direct supply of a fuel stream surrounding the mantle air stream. and in an overstoichiometric secondary combustion zone (7), which is supplied with the residual air (4) over the periphery of the primary combustion zone, characterized in that the residual air (4) is supplied regulated by the load coaxially around the burner in question to the fireplace in at least two substreams the flame at a distance in front of the orifice of the burner, which corresponds to approximately one to two times the diameter of the jacket air pipe, and that flue gases are sucked in from the fireplace into the primary combustion zone by the flame impulse via the free space between the partial streams, the mantle air flow being so large that in the primary zone gets an air number between n = 0.9 and n = 0.5. ”X