AU2007222784A1

AU2007222784A1 - Round burner

Info

Publication number: AU2007222784A1
Application number: AU2007222784A
Authority: AU
Inventors: Bernd Krohmer; Michael Weisenburger
Original assignee: Alstom Technology AG
Current assignee: General Electric Technology GmbH
Priority date: 2006-03-09
Filing date: 2007-03-02
Publication date: 2007-09-13
Anticipated expiration: 2027-03-02
Also published as: DE102006011326B4; DE102006011326C5; CN101400947B; CN101400947A; DE102006011326A1; AU2007222784B2; WO2007101427A1; EP1991810A1

Description

CERTIFICATION OF TRANSLATION I, Rosamund Durham, c/o Technical Translation Agency GmbH, Fasangarten 8, A-2136 Laa/Thaya, Austria, am the translator of the documents attached and certify that the following is a true translation to the best of my knowledge and belief. Signature of translator dated this C41 day of 2008 p.1 ROUND BURNER The invention relates to a round burner for burning fossil fuels as well as a method for operating such a round burner. In addition to jet burners which usually have rectangular cross-sections, round burners are the mostly frequently used burners in combustion chambers of large power plants in which fossil fuels are burned. They are frequently also designated as vortex or swirl burners since the oxidising agent introduced and/or the fuel introduced is usually swirled or vortexed by means of swirling devices to carry out the combustion more efficiently. Such round burners which have become known, for example, from the document "Development of low-pollutant dust firing systems" from VGB Kraftwerkstechnik 76 (1996), Issue 5 usually comprise a primary air tube (or primary air nozzle) which is surrounded externally by a fuel tube (or nozzle) and this in turn is surrounded externally by a secondary air tube (or nozzle). The secondary air tube can be surrounded externally by a tertiary air tube (or nozzle), wherein all the tubes or nozzles are coaxially aligned and therefore each form annular cross-sections to the adjacent tubes or nozzles. The medium passed through the respective tubes or nozzles according to the designation of the tube or nozzle is introduced into the combustion chamber for burning the fossil fuel, e.g. secondary air is introduced through the secondary nozzle. The fuel is introduced through the fuel nozzle together with its carrier medium, the primary air. As it is known that CO 2 containing flue gas is emitted into the atmosphere during the combustion of fossil fuels by means of air as oxidising agent and CO 2 as a presumed main cause of the climate-changing greenhouse effect is attracting increasing public criticism, the oxy-fuel process has already been proposed in which pure oxygen is used as the oxidising agent during combustion instead of air. By using pure oxygen or 02 obtained from the air, a high-purity CO 2 stream can be produced instead of the emission of flue gases -2 p. 2 and this can be separated and disposed of without affecting the climate. Such an oxy-fuel process or such an oxy-fuel combustion process has become known, for example from document DE 103 56 703 Al. For power plant or burner suppliers and operators, the aforesaid facts of the matter have the result that on the one hand, with regard to the different fossil fuels used, different round burner cross-sections result as a consequence of the different oxidising agent requirement and on the other hand, with regard to the oxidising agent used, i.e. either air or 02, different and deviating round burner cross-sections as well gas streams differing in respect of the type of gas result, e.g. instead of an air stream in conventional operation, a recirculated gas stream (recirculated flue gas) in oxy-fuel operation. Thus, if the power plant or burner supplier, when designing a round burner, commits to a fossil fuel and an oxidising agent, during a subsequent change of the fuel or a change from air to pure oxygen as oxidising agent, said power plant operator has no option but to convert the round burner or burners (a combustion chamber of a power plant usually has a plurality of such round burners) to the new situation or the new fuel. Such required conversion is very disadvantageous from many aspects since the entire power plant must be put out of operation due to the conversion and in this phase a high drop in income must be registered, for example, due to loss of the power generation. Furthermore, considerable material and assembly costs are incurred for the new round burners. It is now the object of the invention to provide a round burner which is capable of burning different fossil fuels as required such as, for example - dry brown coal with air or - dry brown coal with an 02 carrier wherein different 02 volume shares can be present or - bituminous coal with air or -3 p.

3 - bituminous coal with an 02 carrier wherein different 02 volume shares can be present or - oil/gas with air or - oil/gas with an 02 carrier wherein different 02 volume shares can be present and thereby has a large control range. At the new round burners to be provided, furthermore the outlet velocities of the various gas streams or the fuel stream must not exceed or fall below certain velocity ranges since otherwise, stable ignition of the introduced fossil fuel is no longer ensured or the required fans for the various gas streams would need to be uneconomically large. It is further an object of the present invention to provide a method for operating such a round burner. The aforesaid object is achieved with regard to the round burner by the features of claims 1 or 2 and with regard to the method for operating a round burner by the features of claim 11. Advantageous embodiments of the invention can be deduced from the dependent claims. The solution according to the invention provides a round burner and a method for operating a round burner which has the following advantages: Great flexibility in the quantity of the 02 carrier stream therefore - degrees of freedom in the choice of fuel, - degrees of freedom in the choice of 02 content of the 02 carrier stream, possibly even in the individual cross-sections of the various gas nozzles, - possibility of adding the oxygen required for combustion directly at the burner, large control range.

-4 p.

4 In an advantageous embodiment of the invention, one of the gas nozzles I, II or III or the gas nozzles II.1 in their entirety is or are configured in such a manner that through their cross-section in oxy-fuel operation, the total amount of oxygen required for combustion of the fuel introduced at the round burner can be introduced via this one cross section or in the case of the gas nozzles II.1, via their total cross-section. In order to achieve secure and stable ignition of the fossil fuel, it is advantageous if the first nozzle and/or the fuel nozzle and/or the gas nozzle I and/or the gas nozzle II or gas nozzles II.1 and/or the gas nozzle III is configured with a baffle ring and/or with a deflection throat. In an advantageous embodiment of the invention, the first nozzle and/or the fuel nozzle and/or the gas nozzle I and/or the gas nozzle II or gas nozzles II.1 and/or the gas nozzle III comprises swirl elements. By means of this measure, the combustion of the fossil fuel can be made more intensive and optimised. At the same time, it is advantageous if the respective swirl elements of the first nozzle and the fuel nozzle are swirled in the same direction or opposite directions with respect to one another, i.e. the swirl elements are aligned in such a manner that a swirl in the same direction or in the opposite direction is produced on the gas or fuel stream passed therethrough. An appropriate embodiment of the invention provides that on the gas nozzle I and/or the gas nozzle II or gas nozzles II.1 and/or the gas nozzle III the swirl elements are configured to be adjustable in burner operation. As a result, the firing system can be influenced at any time during operation of the power plant. An appropriate embodiment of the invention provides that the width(s) of the annular gap of the annular cross section of the fuel nozzle is at least 20 mm. By this measure, the pressure loss caused by the burner nozzle can be kept low and the geometries of the other nozzles of the round burner can advantageously be influenced.

-5 p. 5 A further advantageous embodiment provides that the longitudinal axes of the gas nozzles II.1 are arranged parallel or inclined towards the longitudinal axis of the first nozzle. Exemplary embodiments of the invention are explained in detail hereinafter with reference to the drawings and the description. In the figures: Fig. 1 shows schematically a longitudinal section through a round burner according to the invention, Fig. 2 shows schematically a cross-section according to section A-A in Figure 1, Fig. 3 as Fig. 1 but an alternative embodiment, Fig. 4 shows schematically a cross-section according to section B-B in Figure 3, Fig. 5 as Fig. 4 but an alternative embodiment, Fig. 6 shows the allocation or switching of the respective round burner nozzle cross-sections in operation as a function of the 02 carrier volume flow and the gas velocity by means of a diagram. Figure 1 shows a round burner 1 in longitudinal section which is suitable for the combustion of various fossil fuels. The round burner 1 is designed in this case such that as required, pulverized dry brown coal or pulverized bituminous coal or oil or gas (for the use of the round burner according to the invention for the combustion of oil or gas, an oil or gas lance not shown is required to introduce the fuel, p. 6 this being disposed centrally in the burner) can be burned either by means of air or by means of 02 which is introduced by the 02 carrier. The 02 carrier can have various 02 volume shares, wherein the 02 carrier is usually a recirculated flue gas or recirculated gas from the rear flue gas passes of the power plant. Therefore, the round burner 1 according to the invention is not only suitable for burning different fuels but also for the use of different oxidising media, i.e. air or 02, i.e. pure oxygen can be added in a conventional manner in oxy-fuel operation in order to form highly pure CO 2 which can be separated and disposed of without affecting the climate. As stated above, the oxygen is added as a mixture with pure recirculated flue gas wherein the proportion of oxygen in the mixture can be varied. The recirculated flue gas used as 02 carrier gas is removed, for example from the flue gas path downstream of the combustion chamber and supplied to the round burner 1 at a temperature of 150 0 C to 300 0 C. For this purpose it must optionally be heated again by heat exchange with a hotter medium. The recirculated flue gas can have a low residual oxygen content. According to Figures 1 and 2, the round burner 1 according to the invention comprises a first nozzle 2 having a cross section 10 which is surrounded or encased by a fuel nozzle 3 aligned coaxially to the first nozzle 2 and an annular cross-section 11 is formed between first nozzle 2 and fuel nozzle 3, its annular gap having a width s in the radial direction. The fuel nozzle 3 is surrounded or encased by the gas nozzle I 4, this is surrounded or encased by the gas nozzle II 5 and the latter is surrounded or encased by the gas nozzle III 6. The gas nozzles I, II and III 4, 5, 6 are all coaxially aligned to the first nozzle 2, wherein the annular cross-sections 12, 13 and 14 are formed within the gas nozzles I, II and III 4, 5, 6. Adjoining the outlet-side end of the gas nozzle 1II 6 when viewed on the gas flow side, is the burner throat 18 which forms the transition to the combustion chamber not shown. Figures 3 and 4 show another round burner 1 according to the invention. In contrast to the round burner according to Figures 1 and 2, this has no coaxially p. 7 aligned gas nozzle II 5 surrounding the gas nozzle I 4 but, for example, eight gas nozzles 11.1 5.1 whose longitudinal axes 16 are parallel to the longitudinal axis 15 of the first nozzle 2 or the round burner 1 and the gas nozzles 11.1 5.1 are arranged inside the annular cross-section 12 of the gas nozzle I 4. Instead of the parallel alignment of the longitudinal axes 16 to the longitudinal axis 15, the longitudinal axes 16 of the gas nozzles 11.1 5.1 can also be inclined i.e. at an angle to the longitudinal axis 15 of the first nozzle 2 (not shown). In this case, the gas nozzles 11.1 5.1 can either be directed towards the longitudinal axis 15 or away from said axis. Alternatively to this and as shown in Figure 5, the gas nozzles 11.1 5.1 can also be arranged inside the annular cross-section 14 of the gas nozzle III 6. The gas nozzles 11.1 5.1 in total have a total cross-section 13.1. The mid points of all the gas nozzles II.1 5.1 in this case advantageously lie on a pitch circle and are preferably an equal distance apart from one another. According to the invention, the cross-sections 10, 12, 13 or 13.1 and 14 of the first nozzle 2 and the gas nozzles I, II or II.1 and III 4, 5, or 5.1 and 6 are in certain relationships to one another in the gas nozzle outlet region 17. In detail, the surface area of the annular cross-section 13 of the gas nozzle II 5 is in a ratio of 1.2-2.0:1 to the surface area of the annular cross-section 12 of the gas nozzle I 4 and the surface area of the annular cross-section 14 of the gas nozzle III 6 is in a ratio of 0.2-0.8:1 to the surface area of the annular cross-section 12 of the gas nozzle I 4 and the surface area of the cross-section 10 of the first nozzle 2 is in a ratio of 0.01-0.1:1 to the surface area of the annular cross-section 12 of the gas nozzle I 4. By means of the different cross-sectional areas of the nozzles 2, 4, 5 or 5.1 and 6, it is possible for the round burner 1 to have maximum flexibility with regard to the supply of the oxidising agent required for the combustion, i.e. due to the different-sized cross-sectional areas 10, 12, 13 or 13.1 and 14, a wide range of cross-sectional areas for different burner operating modes can be supplied by suitable combination of the nozzles 2, 4, 5 or 5.1 and 6 or their cross sections 10, 12, 13 or 13.1 and 14. All the cross-sections 10, 11, 12, 13 or 13.1 and 14 are thereby designed such that the minimum required or maximum permissible flow velocities of the gas or fuel passing therethrough are maintained within the respective cross-sections. The p. 8 gas velocities in the nozzles 2, 4, 5 or 5.1 and 6 in this case are between 15 and 80 m/s. The gas nozzle outlet region 17 defines the region in which, when viewed over a respective cross-section, all the cross sections 10, 11, 12, 13 or 13.1 and 14 of the nozzles 2, 3, 4, 5 or 5.1, 6 are present and through which the various gas streams as well as the fuel stream ultimately flow in the respective nozzles 2, 3, 4, 5 or 5.1, 6 before they exit into the combustion chamber. The annular cross-section 11 of the fuel nozzle 3 is on the one hand dependent on the carrier medium volume flow carrying the fuel and on the other hand on the speed of the carrier medium inside the fuel nozzle 3 which is usually 10 to 35 m/s. In order that firstly the pressure losses caused by the fuel nozzle 3 remain within a usual framework or are low and secondly the geometries of the remaining nozzles 2, 4, 5 or 5.1 and 6, in particular those of the first nozzle 2, likewise remain within a realistic and practicable size, the width s of the annular gap of the annular cross-section 11 of the fuel nozzle 3 in the radial direction is advantageously configured as at least 20 mm. Figure 6 comprises a diagram from which it can be seen, for example, which nozzle combinations are possible as a function of the 02 carrier volume flow introduced by the round burner 1. Between 0 and about 20% of the 02 carrier volume flow is introduced only through the cross-section 13 or 13.1 of the gas nozzle II 5 or the gas nozzles 11.1 5.1. With increasing 02 carrier volume flow, this is introduced through the gas nozzle I 4 instead of through the gas nozzle(n) II 5 or 11.1 5.1. If the 02 carrier volume flow increases further, the gas nozzle(s) II 5 or 11.1 5.1 are added to the gas nozzle I 4 having the cross-section 13 or 13.1. With further increasing 02 carrier volume flow, a transition is made to the cross-sections 13 or 13.1 and 14 of the gas nozzles II 5 or 11.1 5.1 and III 6, then to the cross-sections 12 and 14 of the gas nozzles I 4 and III 6, and lastly to all the available cross-sections 12, 13 or 13.1 and 14 of the gas nozzles I, II or II.1 and III 4, 5 or 5.1 and 6 for introduction of the respective gas streams. With the last combination, the maximum 02 p. 9 carrier volume flow can be introduced through the round burner 1. In cases in which one or two of the gas nozzles have no throughput of an 02 carrier volume flow, this gas nozzle or these gas nozzles can be supplied with a small quantity of gas for cooling purposes. This applies particularly if the outer gas nozzle III 6 has no throughput of 02 carrier volume flow. For oxy-fuel operation the round burner 1 can be configured in such a manner that one of the cross-sectional areas 12, 13 or 13.1 or 14 of the gas nozzles I, II or II.1 or III 4, 5 or 5.1 or 6 is suitable for introducing the total required quantity of oxygen through this one cross-section, wherein the required quantity of oxygen can be introduced in this case as a pure 02 gas stream. For reducing peak temperatures in the combustion chamber at least one further gas nozzle I, II or II.1, III 4, 5 or 5.1, 6 must be supplied with recirculated flue gas. When using the round burner 1 according to the invention for burning a fossil fuel, for example, dry brown coal, bituminous coal, oil or gas in oxy-fuel operation, i.e. the oxidising agent for combustion is pure oxygen, the introduction at the burner 1 can appear as follows, for example: introduction of the fossil fuel through fuel nozzle 3, introduction of 02 through the gas nozzle IT 5 or gas nozzles 11.1 5.1 and introduction of recirculated gas, i.e. recirculated flue gas, through the first nozzle 2 and as carrier gas through the fuel nozzle 3 and through the gas nozzles I and III 4, 6. Alternatively, an oxygen stream fraction can be allocated to the recirculated flue gas streams within the first nozzle 2, the fuel nozzle 3 and the gas nozzles I and ITT 4, 6 and a recirculated flue gas stream fraction can be allocated to the 02 stream inside the gas nozzle II 5 or the gas nozzles II.1 5.1. The exemplary information relates to a 100% gas volume flow throughput through the round burner 1, at lower throughputs, as described above the throughput through individual gas nozzles can be omitted (see Figure 6). If required, however a small amount of cooling gas can be passed through. In conventional operation of the round burner 1, i.e. during combustion of fossil fuels with air as oxidising agent, for example at 100% p. 10 gas volume flow throughput, i.e. when the firing system is operating at full load, air can be introduced through all the nozzles 2, 3, 4, 5 or 5.1 and 6. In the fuel nozzle 3, the air then serves as carrier medium for the fuel. Alternatively, the air can also be added to the recirculated flue gas in the respective nozzles 2, 4, 5 or 5.1 and 6. At lower gas volume flow throughputs, i.e. when the firing system is operating at partial load, as mentioned above, individual gas nozzles can be shut off by flaps and the throughput can thus be controlled or adjusted to a very low coolant throughput almost to zero. In order to stabilise or guide the flame at the round burner 1, baffle rings 7 and/or deflection throats 8 can be used in a tried and tested manner. These can each be attached to each of the nozzles 2, 3, 4, 5 or 5.1 and 6. Furthermore, individual or all the gas partial streams or the fuel stream can be swirled by means of swirl elements 9 arranged in the respective nozzle cross-sections 10, 11, 12, 13 or 13.1 and 14, wherein the gas stream in the first gas nozzle 2 and the fuel nozzle 3 (as carrier stream) can either be swirled in the same direction or in the opposite direction to one another. The swirling elements 9 at the gas nozzles I, II or 11.1 or III 4, 5 or 5.1 or 6 can be configured to be adjustable during burner operation to influence the firing system during operation. The selection of the said devices is dependent on the preferred operating states (i.e. full-load air operation or operation with a specific 02 fraction etc.) and the associated combinations of burner cross-sections of the round burner 1. The flame guidance can thus be favourably influenced in these cases of operation.

-2 p.

11 Reference list 1 Round burner 2 First nozzle 3 Fuel nozzle 4 Gas nozzle I 5 Gas nozzle II 5.1 Gas nozzle II.1 6 Gas nozzle III 7 Baffle ring 8 Deflection throat 9 Swirling element 10 Cross-section first nozzle 11 Annular cross-section fuel nozzle 12 Annular cross-section gas nozzle I 13 Annular cross-section gas nozzle II 13.1 Sum of cross-sections gas nozzle II.1 14 Annular cross-section gas nozzle III 15 Longitudinal axis of round burner or first nozzle 16 Longitudinal axis of gas nozzle II.1 17 Gas nozzle outlet region 18 Burner throat

Claims

1. A round burner for burning fossil fuels, comprising the following: a first nozzle (2) for introducing a stream of air or recirculated flue gas or a mixed stream of 02 or air and recirculated flue gas, a fuel nozzle (3) for injecting fuel, arranged coaxially in relation to the first nozzle (2), enclosing the latter and forming an annular cross-section (11), a gas nozzle I (4) for introducing a stream of air or recirculated flue gas or a mixed stream of 02 or air and recirculated flue gas, arranged coaxially in relation to the first nozzle (2), enclosing the fuel nozzle (3) and forming an annular cross-section (12), a gas nozzle II (5) for introducing a stream of air or 02 or a mixed stream of 02 or air and recirculated flue gas, arranged coaxially in relation to the first nozzle (2), enclosing the gas nozzle I (4) and forming an annular cross-section (13), a gas nozzle III (6) for introducing a stream of air or recirculated flue gas or a mixed stream of 02 or air and recirculated flue gas, arranged coaxially in relation to the first nozzle (2), enclosing the gas nozzle II (5) and forming an annular cross-section (14), wherein, in the gas nozzle outlet region (17), the surface area of the annular cross-section (13) of the gas nozzle II (5) is in a ratio of 1.2 to 2.0:1 to the surface area of the annular cross-section (12) of the gas nozzle I (4) and the surface area of the annular cross section (14) of the gas nozzle III (6) is in a ratio of 0.2 to 0.8:1 to the surface area of the annular cross section (12) of the gas nozzle I (4) and the surface area of the cross-section (10) of the first nozzle (2) is in a ratio of 0.01 to 0.1:1 to the surface area of the annular cross-section (12) of the gas nozzle I (4).

2. Round burner for burning fossil fuels, comprising: a first nozzle (2) for introducing a stream of air or recirculated flue gas or a mixed stream of 02 or air and recirculated flue gas, p. 13 a fuel nozzle (3) for injecting fuel, arranged coaxially in relation to the first nozzle (2), enclosing the latter and forming an annular cross-section (11), a gas nozzle I (4) for introducing a stream of air or recirculated flue gas or a mixed stream of 02 or air and recirculated flue gas, arranged coaxially in relation to the first nozzle (2), enclosing the fuel nozzle (3) and forming an annular cross-section (12), a gas nozzle III (6) for introducing a stream of air or recirculated flue gas or a mixed stream of 02 or air and recirculated flue gas, arranged coaxially in relation to the first nozzle (2), enclosing the gas nozzle I (4) and forming an annular cross-section (14), at least three gas nozzles 11.1 (5.1) for introducing a stream of air or 02 or a mixed stream of 02 or air and recirculated flue gas, arranged within the annular cross section (12, 14) of the gas nozzle I (4) or the gas nozzle III (6), wherein, in the gas nozzle outlet region (17), the surface area of the cross-sections (13.1) of all the gas nozzles

11.1 (5.1) is in a ratio of 1.2 to 2.0:1 to the surface area of the annular cross-section (12) of the gas nozzle I (4) and the surface area of the annular cross-section (14) of the gas nozzle III (6) minus the total cross-sectional area (13.1) of the gas nozzles 11.1 (5.1) is in a ratio of 0.2 to 0.8:1 to the surface area of the annular cross section (12) of the gas nozzle I (4) and the surface area of the cross-section (10) of the first nozzle (2) is in a ratio of 0.01 to 0.1:1 to the surface area of the annular cross-section (12) of the gas nozzle I (4). 3. The round burner according to claim 1 or 2, characterised in that one of the gas nozzles I, II or III (4, 5, 6) or the gas nozzles 11.1 (5.1) in their entirety is or are configured in such a manner that through their cross section (12, 13, 14) in oxy-fuel operation, the total amount of oxygen required for combustion of the fuel introduced at the round burner (1) can be introduced via this one cross-section (12, 13, 14) or in the case of the gas nozzles 11.1 (5.1) via their total cross-section (13.1). p. 14 4. The round burner according to one of claims 1 to 3, characterised in that at least one of the nozzles from the first nozzle (2) , the fuel nozzle (3) , the gas nozzle I (4), the gas nozzle II (5) or the gas nozzle III (6) is configured with a baffle ring (7). 5. The round burner according to one of claims 1 to 3, characterised in that at least one of the nozzles from the first nozzle (2), the fuel nozzle (3), the gas nozzle I (4), the gas nozzle II (5) or the gas nozzle III (6) is configured with a deflection throat (8). 6. The round burner according to one of claims 1 to 5, characterised in that at least one of the nozzles from the first nozzle (2) , the fuel nozzle (3) , the gas nozzle I (4), the gas nozzle II (5) or the gas nozzle III (6) is configured with swirl elements (9). 7. The round burner according to claim 6, characterised in that the respective swirl elements (9) of the first nozzle (2) and the fuel nozzle (3) are swirled in the same direction or opposite directions with respect to one another. 8. The round burner according to claim 6, characterised in that at least on one of the gas nozzles I, II or II.1 or III (4, 5, 5.1, 6) the swirl elements (9) are configured to be adjustable in burner operation. 9. The round burner according to one of claims 1 to 8, characterised in that the width(s) of the annular gap of the annular cross-section (11) of the fuel nozzle (3) is at least 20 mm. 10. The round burner according to claim 2, characterised in that the longitudinal axes (16) of the gas nozzles 11.1 (5.1) are arranged parallel or inclined towards the longitudinal axis (15) of the first nozzle (2). p. 15 11. A method for operating a round burner according to the features of claims 1 or 2.