DE102004037442A1 - Waste and/or compensation fuel thermal treatment method for combustion chamber, involves keeping direct heat exchange between exhaust gas and secondary air low through small dimensioned direct contact area within mantle nozzle - Google Patents

Abstract

method for the thermal treatment of waste and / or substitute fuel and / or other thermally treatable substances in a grate having combustion chamber of a thermal waste treatment plant, with feeders into the combustion chamber of primary air below the grate and from secondary air as well as from unpurified recirculated flue gas (Rezigas) above the grate, wherein the secondary air and the Rezigas is supplied by means of at least one Zweistromdüse, wherein the Rezigas through the central nozzle and the secondary air through the the central nozzle concentric comprehensive and forming a ring cross-section jacket nozzle is supplied and the secondary air jet issuing into the combustion chamber causes the jet of Rezig wrapped as well a thermal waste treatment plant for carrying out the Process.

Description

The The invention relates to a method for thermal treatment of waste and / or substitute fuel and / or other thermal treatable substances in a combustion chamber having a rust a thermal waste treatment plant and a thermal Waste treatment plant for carrying out the process.

Not decreasing amounts of waste and the fact that starting from the year 2005 in Germany according to current law no untreated waste more may be deposited on landfills, cause the erection and the operation of thermal waste treatment plants continues is forced. The deposited during the thermal treatment to be deposited Residues must be Comply with the provisions of the Waste Deposit Ordinance and the incurred emissions to those prescribed in the Federal Immission Control Ordinance Limits are reduced.

By the publication "Primary Measures to Reduce Emissions in Waste Incineration", VGB Kraftwerkstechnik 76 (1996), No. 8, pages 635 to 642 has become known that the use of a flue gas recirculation, ie the return of a subset of the flue gas or Rezigases in Flue gas recirculation is a proven method in fossil fuel burning to reduce combustion temperatures at high calorific values and therefore NO _x formation, and if recirculation with flue gases is carried out prior to gas purification, the flue gas purification plant can With the aid of the recirculated flue gas sprayed into the combustion chamber, the combustion exhaust gas coming from the grate and in some cases not yet completely burnt out can be thoroughly stirred and evenly distributed in the combustion chamber a better temperature distribution and a more uniform temperature profile within the combustion chamber leads.

At the Operation of thermal waste treatment plants using flue gas recirculation (The recirculated flue gas is also referred to as Rezigas) are equipped and partially recirculated flue gas recirculate (e.g., removal to electrostatic precipitator), show vulnerabilities the flue gas recirculation system in the form of corrosion in the flue-gas-contacted duct system or in the growth of the Rezigasdüsen in connection with a continuous decrease of the with the Rezisystem introduced Rezigasmassenstromes into the combustion chamber, so that ultimately the Rezigasdüsen or the Rezigassystem cleaned after a certain period of operation I'll have to. This has been due to non-probation in the past often to deactivate the flue gas recirculation system with the result being that the aforementioned advantages and effects of the flue gas recirculation in the thermal waste treatment plant no longer effective come. Compliance with the prescribed emissions is thus difficult or impossible.

By publication DE 41 03 025 A1 a method for controlling the temperature in waste incineration plants has become known in which 10 to 30% by volume of the total flue gas is recirculated and injected directly into the combustion chamber above the grate.

It is therefore an object of the present invention, a method for thermal treatment of waste and / or substitute fuel and / or other thermally treatable substances in a grate Combustion chamber of a thermal waste treatment plant and a to propose a thermal waste treatment plant for carrying out this process, in which the aforementioned disadvantages are largely avoided can.

The The above object is with respect to the method the characterizing features of claim 1 and in terms of thermal waste treatment plant by the characterizing features of claim 17.

advantageous Embodiments of the invention are the dependent claims remove.

• – Die Rauchgasrezirkulation kann ohne die sonst übliche Vorentstaubung sowie die sonst üblich auftretenden Probleme kontinuierlich betrieben werden.
• – Durch die Verwendung von nicht gereinigtem Rauchgas sinken die Investitionskosten für die Rauchgasreinigung erheblich, da die Menge bzw. das Rauchgasvolumen des rezirkulierten Rauchgases bei der Auslegung der Rauchgas-Reinigungsaggregate nicht berücksichtigt werden muss.
• – Der Einsatz der erfindungsgemäßen Rauchgasrezirkulation erlaubt es, den Verbrennungsprozess in der Brennkammer bei einer niedrigen Luftüberschusszahl durchzuführen und die Brennkammertemperaturen auf betrieblich beherrschbare Größen zu begrenzen.

The solution according to the invention provides a method and a device for the thermal treatment of waste and / or substitute fuel and / or other thermally treatable substances in a combustion chamber of a thermal waste treatment plant which has the following advantages:

• - The flue gas recirculation can be operated continuously without the usual dedusting and the usual problems occurring.
• - Through the use of non-purified flue gas, the investment costs for the flue gas cleaning decrease significantly, since the amount or the flue gas volume of the recirculated flue gas must not be considered in the design of the flue gas cleaning units.
• - The use of the flue gas according to the invention Recirculation allows the combustion process in the combustion chamber to be carried out at a low excess air ratio and to limit the combustion chamber temperatures to operationally controllable quantities.

A advantageous embodiment of the invention provides, the outlets of secondary air and Rezigas from the respective nozzles the twin-flow nozzle axially offset form, wherein the outlet of the secondary air the jacket nozzle downstream the exit of the Rezigases from the central nozzle takes place. This measure will the exit of the Rezigasdüse of slagging - caused by in the smoke or Rezigas contained particles - kept free. The dimension the axial offset of the two outlets is advantageously kept low to a low direct heat exchange between recirculated Flue gas and secondary air inside the twin-flow nozzle to achieve. A particularly advantageous embodiment has a dimension the axial offset of the two outlets of 60 to 80 mm.

By a minimum flow of Rezigas or secondary air through the respective nozzle is advantageously, the respective nozzle cooled and largely against Protected against corrosion.

By the removal of unpurified flue gas before the flue gas side Entry into the gas purification device and its recirculation within The thermal waste treatment plant can be a much smaller Gas cleaning device to be provided and installed, the inevitably and in a positive way lower investment costs. In a further advantageous embodiment, the Rezigasentnahme at a 180 ° gas deflection, which is designed as a gravity separation device and wherein the Rezigasentnahmebereich lies in a flow-calmed area.

Around Remove from the flue gas channel Rezigas with a uniform temperature and particle profile it is beneficial to over the Rezigas an opening, which are over extends the entire width of the flue gas duct, deduct.

By the possibility, in the method according to the invention To be able to use Rezigas, that no dedusting must be subjected, can in the flue gas path on a room and costly Pre-dedusting be waived and thus a cheaper Waste treatment plant to be created.

Around Deposits of ash and unburned particles within the Recco gas pipes and nozzles to avoid is the flow rate the Rezigases within the Rezigasleitungen and nozzles in an advantageous Way bigger than the sedimentation of the flue gas particles permitting flow velocity of the Rezigases. Reduced in a further advantageous embodiment the flow velocity the Rezigases between the sampling point and the exit point not in the combustion chamber, at no point a calm zone to get with deposits.

By the thermal treatment of waste and / or substitute fuel and / or other thermally treatable substances at low excess air in height of <1.6 can the combustion chamber temperature is limited to operationally controllable sizes become. To this excess air number It is advantageous to achieve 10 to 30% of that in the thermal waste treatment plant circulated Flue gas quantity recirculated as Rezigasmenge in the combustion chamber.

Around with every load case of the thermal waste treatment plant one uniform mixing the combustion gas within the combustion chamber for improvement to allow the combustion-related emissions, is introduced in a preferred embodiment of the introduced into the combustion chamber Reichenasmassenstrom over the load ranges kept substantially constant.

A advantageous training provides that in plan and unscheduled parking the thermal waste treatment plant by means of an automated Program the Rezigassystem after parking and / or before Start preheated and rinsed becomes. By this measure can in a safe way corrosion phenomena on the Rezigassystem (lines, nozzles) be avoided.

By the introduction of the Rezigases with the secondary air into the combustion chamber of one or more combustion chamber walls, for example of two walls from, the mixing with the flue gas in the combustion chamber can be optimized become.

Around a compactly penetrating into the combustion chamber secondary air / Rezigasstrahl To achieve it is advantageous, the cross section of the inner and outer nozzle of the two-flow nozzle circular train.

below are exemplary embodiments the invention with reference to the drawings and the description explained in more detail.

It shows:

1 a schematic longitudinal section through the combustion chamber of a thermal waste treatment plant,

2 the detail section "X" off 1 .

3 a schematic longitudinal section through the thermal waste treatment plant including flue gas path.

1 schematically shows the combustion chamber 3 a thermal waste treatment plant 1 on that with a rust 2 is trained. Waste, substitute fuel or other thermally treatable substance 11 is via a feed shaft 12 the combustion chamber 3 in which the waste, substitute fuel or other thermally treatable substance 11 on a mechanical grate 2 moved, usually dried, degassed and burned. Combustion residues are passed through the ash removal shaft 14 from the combustion chamber 3 deducted. As rust 2 Various known mechanical grates such as feed, recoil, counter-thrust or roller grates can be used. For substances that count as waste, reference may be made to the European Waste Catalog (EWC).

That for the thermal treatment, which is usually carried out as combustion and is also described as such, of the waste 11 in the combustion chamber 3 required oxygen is on the one hand from below through the grate 2 as primary air 8th and on the other above the grate 2 as secondary air 10 fed. According to the invention, the secondary air 10 by means of a twin-flow nozzle 4 according to 2 into the combustion chamber 3 introduced, wherein through the inner or central nozzle 4.1 the twin-flow nozzle 4 recirculated, unpurified flue gas 9 and through the outer nozzle or jacket nozzle 4.2 the twin-flow nozzle 4 secondary air 10 into the combustion chamber 3 is injected.

The inner nozzle 4.1 preferably has a circular cross section, which is also preferably a circular cross-section outer nozzle 4.2 with a radial distance concentrically, so that between the two nozzles 4.1 and 4.2 an annular cross-section 15 arises, through which the secondary air 10 is introduced while the through the inner nozzle 4.1 introduced recirculated flue gas 9 wrapped or sheathed. The inner and outer nozzle 4.1 . 4.2 may also have an elliptical or polygonal, for example, a rectangular, cross-section instead of a circular cross-section, so that the annular cross-section 15 correspondingly fails.

By this measure according to the invention is achieved that the issuing of a high pulse dual stream 9 . 10 deep into the combustion chamber 3 can penetrate and thereby the rust 2 ascending combustion or flue gases 13 can whirl and mix intensively. Due to the intensive mixing, there is an optimized combustion gas temperature distribution and a uniform temperature profile within the combustion chamber 3 one. This is achieved, among other things, that one over the combustion chamber 3 uniform afterburning of the combustion gases 13 and any unburned particles present; that due to the combustion gas temperature reduction caused by the injected recirculated flue gas 9 , the formation of NOx and thus the required to comply with the emission limit reducing agent requirements (for example, ammonia or uric acid) can be minimized and that a more uniform heat transfer from the hot combustion gas 13 to the wall heating surfaces of the combustion chamber wall 7 he follows.

Advantageous are the leaks 16 . 17 of secondary air 10 and Rezigas 9 from the respective two-stream nozzles 4 formed axially offset, wherein the outlet 17 the secondary air 10 from the jacket nozzle 4.2 downstream of the exit 16 of the Rezigases 9 from the central nozzle 4.1 he follows. In a further advantageous embodiment, the outlet 17 60 to 80 mm downstream of the exit 16 arranged, on the one hand to ensure that the Rezigasaustritt 16 not added as well as corroded and secondly, that the direct heat exchange between recirculated flue gas 9 and enveloping secondary air 10 inside the jacket nozzle 4.2 ie between exit 16 and 17 , is kept low. It is also advisable to have a minimum flow of Rezigas 9 and / or secondary air 10 through the central nozzle 4.1 or the ring cross section 15 between the central nozzle 4.1 and the jacket nozzle 4.2 upright to avoid corrosion on the respective nozzles. It is also advantageous, the length of the concentric pipe section in the Zweistromdüse 4 with 500 to 1000 mm form.

Characterized in that a subset of the superstoichiometric introduced secondary air 10 through the recirculated flue gas 9 is replaced, at the same time produced by the actual combustion process and from the combustion chamber 3 emerging and to be cleaned flue gas volume reduced and as a result, the facilities for the flue gas cleaning can be smaller. Advantageously, 10 to 30% of the thermal waste treatment plant 1 circulated flue gas amount of the combustion chamber 3 as Rezigas 9 supplied, wherein the recirculated flue gas mass flow over the load range of the thermal waste treatment plant 1 can remain substantially constant to the advantages of the injected Rezigases in all load ranges 9 to achieve. The above mentioned override The chiometric mode of operation, ie combustion with excess air, is advantageously used with an excess of air of <1.6, since the NOx emission can be kept low.

That from the combustion chamber 3 emerging flue gas 13 gives according 3 a large part of its heat to the Wandheizflächen the combustion chamber wall 7 as well as on secondary heating surfaces 19 before, by means of the flue gas duct 18 is passed into the flue gas cleaning device, not shown, or a partial flow of the flue gas 13 as Rezigas 9 via a supply line 5 the twin-flow nozzle 4 is supplied or recirculated. Thus, considerably cooled flue gas than Rezigas 9 the combustion chamber 3 supplied, which in turn required the process side temperature reduction in the combustion chamber 3 favored. The secondary air 10 is via supply lines 6 the two-stream nozzles 4 fed.

The recirculated flue gas 9 is advantageous before the flue gas inlet of the flue gas cleaning system, not shown, from the flue gas duct 18 taken, ie that it is substantially unpurified via the supply line 5 the combustion chamber 3 is forwarded. This results in the advantage that the capacity of the flue gas cleaning system can be lower by the volume of the previously recirculated recirculation and thus also cheaper. The removal of the Rezigases 9 before the flue gas cleaning system can from a gravitational separation device 20 take place and the Rezigasentnahmebereich in a flow-calm area of this separator device 20 lie. In order to save further costs, it is also possible to dispense with the preliminary dedusting of the flue gas, as practiced with U-Beams, for example.

To a concerning temperature or dust stranded removal of Rezigas 9 to avoid removal from the flue gas duct over its entire width is sought. Further, the dimensions of the Rezigasleitung 5 advantageously designed such that at the then applied passage rate of Rezigases 9 no sedimentation of the entrained dust particles (ash, unburned) and no speed reductions within the pipe 5 occurs between collection and delivery.

The Rezigassystem, ie the line 5 between the Reichenasentnahmestelle and combustion chamber entry point and other required components such as secondary air and Rezigas blower 21 . 22 , Secondary air and Rezigas valves 23 . 24 etc., the thermal waste treatment plant 1 can be preheated and flushed during scheduled and unscheduled shutdown by means of an automated program after stopping and / or before starting to avoid corrosion in the Rezigassystem.

Depending on the width or size of the combustion chamber 3 must be the number of twin streams 4 be adjusted. It may be necessary for the nozzles 4 be spaced apart at intervals of 200 to 500 mm seen across the combustion chamber width, to a complete mixing of the combustion gas 13 inside the combustion chamber 3 or to cause their width. 1 and 3 shows exemplary Zweistromdüsen 4 at the front and at the rear of the combustion chamber 3 arranged to ensure optimal mixing of the flue gas 13 with the secondary air 10 and the Rezigas 9 to achieve. However, there are also arrangements of the nozzles 4 on the side walls of the combustion chamber 3 or on only one wall 7 possible.

The inventive method and the system of the invention now allows the known per se recirculation of flue gas 9 into the combustion chamber 3 a thermal waste treatment plant 1 be applied so that the benefits of Rezigaszuführung in plant operation can be fully exploited.

1

thermal Waste treatment plant

2

rust

3

combustion chamber

4

Zweistromdüse

4.1

inner nozzle

4.2

outer nozzle

5

feed pipe recirculated flue gas

6

feed pipe secondary air

7

combustion chamber wall

8th

primary air

9

flue gas recirculated, Rezigas

10

secondary air

11

Waste, Replacement fuel or other thermally treatable substance

12

insertion slot

13

flue gas or combustion gas

14

Entaschungsschacht

15

Ring-shaped cross-section between outside and outside inner nozzle the twin-flow nozzle

16

exit Rezigas

17

exit secondary air

18

Flue

19

heat recovery area

20

gravity

21

Secondary air blower

22

Rezigasgebläse

23

Secondary air flap

24

Rezigasklappe

Claims (22)

Process for the thermal treatment of waste and / or substitute fuel and / or other thermally treatable substances in a combustion chamber having a grate of a thermal waste treatment plant, with feeds into the combustion chamber of primary air below the grate and of secondary air and of untreated recirculated flue gas (Rezigas) above the Grate, characterized in that the secondary air and the Rezigas is supplied by means of at least one Zweistromdüse, wherein the Rezigas through the central nozzle and the secondary air through the central nozzle concentrically comprehensive and forming a ring cross-section jacket nozzle is supplied and emerging into the combustion chamber secondary air jet Rezigasstrahl wrapped. Method according to claim 1, characterized in that that the outlets of secondary air and Rezigas from the respective nozzles are formed axially offset, the outlet of the secondary air from the jacket nozzle downstream the exit of the Rezigases from the central nozzle takes place. Method according to claim 1 or 2, characterized that the direct heat exchange between recirculated flue gas and enveloping secondary air within the jacket nozzle kept small by a small dimensioned direct contact area becomes. Method according to one of claims 1 to 3, characterized that given a minimum flow of Rezigas through the central nozzle is. Method according to one of claims 1 to 4, characterized that a minimum flow of secondary air through the ring cross-section between the central nozzle and the jacket nozzle given is. Method according to one of claims 1 to 5, characterized that the Rezigasentnahme before the smoke-gas entrance to the Gas cleaning device takes place. Method according to claim 6, characterized that the Rezigasentnahme on a gravitational separation device takes place, wherein the Rezigasentnahmebereich in a flow-calmed Area lies. Method according to one of claims 1 to 7, characterized that the removal of the Rezigases over one over the entire width of the flue gas channel reaching opening takes place. Method according to one of claims 1 to 8, characterized that the Rezigas extracted from the flue gas duct are not subjected to any dedusting becomes. Method according to one of claims 1 to 9, characterized that the flow velocity of the Rezigases within the Rezigasleitung is greater than the sedimentation the flue gas particles permitting flow velocity. Method according to one of claims 1 to 10, characterized that is the flow velocity the Rezigases between the Rezigasentnahmestelle and the exit point not reduced in the combustion chamber. Method according to one of claims 1 to 11, characterized that the thermal treatment of the waste and / or the substitute fuel and / or other thermally treatable substances within the Combustion chamber with an excess of air of <1.6. Method according to one of claims 1 to 12, characterized that 10 to 30% of the thermal waste treatment plant circulated Flue gas amount of the combustion chamber are supplied as Rezigas. Method according to one of claims 1 to 13, characterized that the recirculated flue gas mass flow over the load range of the thermal Waste treatment plant remains substantially constant. Method according to one of claims 1 to 14, characterized that at plan and unscheduled parking the thermal waste treatment plant by means of an automated program preheated the Rezigassystem after stopping and / or before starting and is rinsed. Method according to one of claims 1 to 15, characterized that Rezigas and secondary air through twin stream nozzles from one or more combustion chamber walls into the combustion chamber is registered. Waste treatment plant for carrying out the method according to claim 1, having a grate ( 2 ) having combustion chamber ( 3 ), with feeds into the combustion chamber ( 3 ) of primary air ( 8th ) from under the grate ( 2 ) and secondary air ( 10 ) and untreated recirculated flue gas (Rezigas) ( 9 ) above the grate, characterized in that the combustion chamber ( 3 ) with at least one central nozzle ( 4.1 ) and a jacket nozzle ( 4.2 ) having two-stream nozzle ( 4 ) for introducing the secondary air ( 10 ) and the Rezigases ( 9 ) is formed, the Rezigas ( 9 ) through the central nozzle ( 4.1 ) and the secondary air ( 10 ) through which the central nozzle ( 4.1 ) concentric and a ring cross-section ( 15 ) forming jacket nozzle ( 4.2 ) can be introduced. Waste treatment plant according to claim 17, characterized in that the outlet ( 16 ) of the central nozzle ( 4.1 ) opposite the exit ( 17 ) of the jacket nozzle ( 4.2 ) is offset. Waste treatment plant according to one of claims 17 or 18, characterized in that the outlet ( 16 ) of the central nozzle ( 4.1 ) 60 to 80 mm upstream of the outlet ( 17 ) of the jacket nozzle ( 4.2 ) lies. Waste treatment plant according to one of claims 17 to 19, characterized in that the concentric piece of pipe in the twin-flow nozzle ( 4 ) has a length of 500 to 1000 mm. Waste treatment plant according to one of claims 17 to 20, characterized in that at least one combustion chamber wall ( 7 ) with twin-flow nozzles ( 4 ) is trained. Waste treatment plant according to one of claims 17 to 21, characterized in that the inner nozzle ( 4.1 ) and the outer nozzle ( 4.2 ) is formed with a circular cross-section.