JP2005530980A - Rotary furnace method and burner - Google Patents

Abstract

The present invention relates to a method and a burner for generating a flame in a combustion zone of a rotary furnace. The burner includes at least a burner pipe 4 extending from the outside of the rotary furnace into the rotary furnace, means 3 for introducing fuel into the burner pipe, and means for introducing primary air to the combustion zone of the rotary furnace via the burner pipe. . A unique feature of the present invention is that the burner is connected to the gas turbines 1 and 2 via the connecting pipe 7 in order to guide the combustion gas generated in the gas turbine as primary air to the burner pipe.

Description

  The present invention relates to a method and a burner for generating a flame with a burner in a combustion zone of a rotary furnace.

  A rotary furnace is typically used to process a variety of solid materials, particularly where high temperatures are required for processing. Also, typically, the treatment process is endothermic, i.e., requires external heat to be introduced into the furnace from outside the furnace. Some examples of this type of process include, for example, the reduction of oxide ores and oxide concentrates, and the firing of various compounds such as ingots and lime combustion. The processing material exiting the furnace is often hot and recovers its internal heat, for example by preheating the combustion air introduced into the furnace, in order to increase the economics of the heat.

  Heat sources utilized in the furnace include liquid, gaseous and solid fuels such as oil, natural gas and carbon dust. The burner is attached to the hot end of the furnace. Typically, the burner has a multi-channel tube configuration introduced from the end of the furnace through an opening disposed therein. The discharge end of the burner extends into the furnace and reaches a location that is optimal in terms of both fuel combustion and heat transfer and depends on the requirements set by the process performed in the furnace. In some cases, the burner tube extends only to the level of the inner surface of the furnace end, but may extend into the furnace over several meters. The burner tube is provided with flow paths for fuel and combustion air and possibly additives necessary for the operation of the process.

  In particular, in a processing process for producing high-temperature products (burned slag, lime, so-called lime mud), the internal heat is recovered by transferring it into the combustion air necessary for ignition of the fuel used in the process. . In such cases, this air (so-called secondary air) is usually routed around the burner and sent into the furnace, where it is called the primary required for ignition, stabilization (maintaining a constant ignition point), and flame formation. Only air is passed through the burner. The proportion of primary air varies depending on the individual burner and application, but is most typically 10% to 40% of the total volume of combustion air. Primary air is fed into the burner to control the ignition of the fuel, keep the ignition point constant (stabilize the flame), and control the formation of flame in the furnace. The primary air is directed to the burner by the burner's own fan.

  However, this primary air configuration does not always produce the desired results in terms of both flame control and furnace heat economy. Furthermore, the increasingly stringent environmental requirements set increasingly stringent constraints on nitrogen oxide emissions. For example, reducing the amount of primary air typically reduces nitrogen oxide emissions, but at the same time complicates the control of flame formation as well as the adjustment of the center of combustion. These are ultimately factors that affect, for example, the economics of process heat.

  It is an object of the present invention to provide a method and method for reducing the emission of harmful emissions, such as nitrogen oxides, as compared to prior art systems, while at the same time more efficiently controlling combustion in a rotary furnace such as a lime furnace. Is to provide a burner.

  The unique features of the invention are set forth in the appended claims. The present invention is basically based on using combustion gas from a gas turbine instead of air as the primary air source. Thus, the primary air fan has been replaced by a gas turbine.

  Known burners are either not preheated or slightly preheated and typically introduce primary air at a temperature of, for example, 150 ° C. to 200 ° C. with a pressure of several kPa. Air is known to contain oxygen in an amount of about 21% of its volume. In a new burner, the gas leaving the turbine and entering the burner tube is usually at an oxygen content of 15% to 16% and a temperature of 400 ° C to 800 ° C, depending on the turbine capacity and the pressure loss of the burner tube. is there.

  The gas turbine exhaust object is exactly the same as the air object introduced by the primary air fan, but with the burner arrangement according to the invention, the amount of air introduced for ignition is known. Clearly less than the burner being used, the flow rates of oxygen and gas are lower, typically only 4% to 10% of the total amount of combustion air. The fuel flow required for a gas turbine is very small compared to the main fuel flow, usually only a few percent.

  A unique feature of the burner is that a plurality of different fuels can be burned simultaneously in all three forms, even in the form of solids, liquids and gases.

  Preferably, the present invention can be applied to a lime mud furnace, a lime furnace and a cement furnace.

  Other air required for the furnace besides primary air, such as secondary air, bypasses the burner. Typically, the secondary air is heated by contacting the material combusted in the furnace.

  The present invention will be described in more detail with reference to the accompanying drawings.

  The construction and implementation principle of the burner is shown in FIG. The burner is formed by a tube 4 that extends into the furnace through an opening in the end wall 8 of the furnace. Exhaust gas from the gas turbine, i.e. primary air, is directed to the discharge end of the burner via the burner tube. Fuel, for example heavy oil, can be introduced in the conventional manner by directing from line 12 by its tube 3 (burner lance) to a nozzle located at the discharge end 13 of the burner tube 4. Conventional embodiments include concentric placement inside the burner tube so that it is surrounded by primary air, but other configurations are possible. Depending on the quality of the fuel, it can also be fed to the front end of the burner tube, in which case it will be entrained in the primary air flowing through the tube and burned in the formed mixture.

  According to the invention, the gas turbine is connected to a burner, said gas turbine comprising a compressor 1 and air is directed to the combustion chamber 2 and the turbine 11 connected thereto. Fuel in the line 9 such as natural gas or oil and air from the compressor are led to the combustion chamber 2 and combustion gas (ie primary air) is led from the combustion chamber through a turbine that rotates the compressor. Since the required power of the compressor 1 from the turbine 11 to generate the necessary pressure in the combustion chamber is small, the temperature drop of the gas in the turbine is only 50 to 100 ° C.

  A unique feature of the burner configuration is that the gas (primary air) produced in the combustion chamber 2 and exiting the gas turbine is supplied to the actual burner tube 4 through a short connecting tube 7. The connecting tube 7 is most preferably configured to be connected to the burner tube 4 outside the furnace burner end 8.

  A gas turbine unit with a combustion chamber is relatively light. The gas turbine unit can be arranged away from the burner tube if desired, but preferably the gas turbine unit is supported on the burner tube via a connecting tube, and if necessary further support The burner pipe, the gas turbine unit, and the connecting pipe therebetween are integrated. The advantage of this type of unit formed by a connected gas turbine and burner tube is that its position relative to the furnace can be changed. This also affects the operation of the furnace. The burner tubes are not necessarily arranged in the direction of the longitudinal axis of the furnace, but are typically inclined in the direction of the target material bed to be treated to enhance heat transfer from the flame to the floor. Because the connection between the gas turbine and the burner tube is made using a static connection tube that is required to withstand temperatures up to 800 ° C, if necessary, instead of using a flexible hose, A fixed connection is preferable in terms of structure. A cooling fan for the burner that is probably needed can be connected to the burner tube in a corresponding manner.

  According to FIG. 1, the gas from the turbine is supplied to the burner pipe 4 via the inclined connecting pipe 7. Basically, the gas may be supplied in a tangential direction from the side of the burner, or may be supplied in the axial direction via the end of the burner. The gas pressure loss in the burner pipe (back pressure of the gas turbine) depends on the gas supply direction, the loss due to the axial supply is minimized, and the loss due to the tangential supply is maximized. It must be decided for each case.

  2a and 2b are diagrams showing a burner configuration in which gas from the gas turbine is directed tangentially to the burner. According to FIG. 2 a, the burner comprises a burner lance 23, if necessary a burner lance casing tube 30, a burner tube 24 and a cooling air housing 25. In the present embodiment, the burner tube 24 includes a cyclone portion 32 connected to the straight portion 24 of the burner tube via a cone 26. Fuel is supplied from line 33 to burner lance 23. The gas from the gas turbine is introduced into the cyclone unit 32 via a connecting pipe 27 that connects the burner tube and the gas turbine and is attached to the cyclone unit 32 in a tangential direction. Reference numeral 28 is attached to the end wall of the furnace.

  FIG. 2b shows the connection between the burner tube and the gas turbine in a cross-sectional view along line AA in FIG. 2a. The gas turbine includes a compressor 21, a combustion chamber 22, and a turbine 31. The gas is led from the gas turbine to the cyclone section 32 of the burner pipe via a connecting pipe 27 tangentially connected to the cyclone 32. Fuel is introduced into the combustion chamber via line 29.

  If necessary, the amount of ignition energy at the discharge end of the burner can be increased by so-called intermediate combustion. Normally, the size of the burner tube is determined so that the fuel supplied to the burner tube cannot be combusted in the tube, but only when the mixture is discharged from the burner to the furnace. Intermediate combustion is enabled by providing a zone in the burner tube that locally increases the flow cross-sectional area of the primary air so that the primary air flow velocity is less than the propagation velocity of the flame front. A preferred method of achieving intermediate combustion is to place the zone at the front end of the burner tube so that a cyclonic intermediate burner is formed at the front end of the burner tube, as shown in FIGS. 2a and 2b. The exhaust gas from the turbine is guided tangentially to the burner pipe. Thus, if necessary, the temperature of the gas can be raised to a temperature higher than 1000 ° C. The fuel required for the temperature rise is usually supplied to the connecting pipe 7 between the gas turbine and the burner pipe via the line 10 in FIG. 1 and to the connecting pipe 27 in FIG. 2b. The space required for the intermediate combustion is not necessarily arranged at the front end of the burner pipe, and may be arranged at other locations inside the burner pipe.

  Since the exhaust gas from the gas turbine has a temperature of several hundred degrees (400 ° C. to 800 ° C.), the part of the burner placed in the furnace tends to be hotter than when using cooled primary air. For this reason, it is preferable to cool the burner tube in the arrangement according to the invention. According to the basic configuration illustrated in the figure, the burner is provided with a concentric outer casing 5, and cooling air is introduced between the casing and the actual burner pipe 4 by the fan 6. It is discharged into the furnace (flame) through an annular slot in between. A typical amount of cooling air is only 1% to 3% of the total combustion air flow. For individual purposes, insulation may be provided around the burner tube to enhance protection.

  The burner according to the invention makes it possible to reduce the amount of nitrogen oxides compared to the case of using an air-operated burner. The most important way to minimize emissions is to reduce the amount of primary air (primary oxygen) and increase the amount of ignition energy to promote the temperature rise of the flame after ignition . Fast combustion results in an oxygen deficit in the flame and furnace combustion zone, thereby producing almost thermal NO via OH radicals that react with NO much slower than free oxygen. The oxidation of nitrogen contained in the fuel to NO is reduced as the oxygen content is decreased, and the reduction of NO to nitrogen molecules is increased.

  Compared to current rotary furnace burners, the new means also improve the controllability of the flame in terms of both flame morphology and combustion rate. The latter is regulated by the ability of the gas turbine to affect the exhaust gas stream from the turbine and the temperature of the gas stream. The burning rate also affects the flame height and combustion temperature, as well as the heat transfer from the flame to the material being processed in the furnace.

  The burner also accommodates a power adjustment range that is larger than current rotary furnace burners. The amount of energy corresponding to the full capacity of the gas turbine can be introduced into the burner as ignition energy in the best case, so that stable combustion is possible even at very low power, and at the same time without turning off the burner The main supply of low amount of fuel is maintained.

FIG. 3 shows a preferred burner configuration according to the present invention. FIG. 4 shows a second preferred burner configuration according to the present invention. FIG. 4 shows a second preferred burner configuration according to the present invention.

Claims (12)

  At least a burner pipe extending from the outside of the rotary furnace into the rotary furnace, means for introducing fuel into the burner pipe, and means for guiding primary air to the combustion zone of the rotary furnace via the burner pipe A method of generating a flame in the combustion zone of the rotary furnace by a burner, wherein the combustion gas generated in a gas turbine connected to the burner is used as primary air.   The method according to claim 1, wherein the temperature of the combustion gas of the turbine is from 400 ° C. to 800 ° C.   The method according to claim 1, wherein the fuel is supplied to a discharge end of a burner pipe.   The method according to claim 1, wherein the fuel is supplied to a front end of the burner pipe to mix primary air flowing in from the gas turbine.   The primary air from the gas turbine is supplied through the connecting pipe so that the primary air is supplied to the burner pipe in a tangential direction, and fuel is supplied to the connecting pipe, so that a cyclone type intermediate burner is provided. The method of claim 1, wherein the method is formed in the burner tube.   In a burner for generating flames in a combustion zone of a rotary furnace, at least a burner pipe (4) extending from the outside of the rotary furnace into the rotary furnace, and means (3) for supplying fuel to the burner pipe, Means for directing primary air through the combustion zone of the rotary furnace to the combustion zone of the rotary furnace, connected to a gas turbine (1, 2) via a connecting pipe (7) Then, the fuel gas generated in the gas turbine is guided to the burner pipe as primary air.   The burner according to claim 6, wherein the connecting pipe (7) is inclined with respect to the burner pipe.   The burner according to claim 6, characterized in that the connecting pipe (7) is arranged axially with respect to the burner pipe.   The burner according to claim 6, characterized in that the connecting pipe (7) is tangential to the burner pipe.   The burner according to claim 6 or 9, further comprising means for introducing fuel into the connecting pipe in order to increase the temperature in the burner pipe.   The burner pipe (4), the connecting pipe (7) and the gas turbine (1, 2, 11) are configured as one unit and their position relative to the rotary furnace is adjustable. Burner in any one of 6-10.   12. Burner according to claim 11, characterized in that the unit further comprises a cooling air fan (6).

Images