Method and device for processing slag occurring in a combustion chamber of a refuse incineration plant

Abstract

A method processes slag occurring in a combustion chamber. An incineration grate is formed at least in its end region that is facing the slag-removing device as a separating grate, which has openings, via which the chamber is connected to a fine-slag discharge chamber, and at least one fine fraction of the slag is ejected through the openings into the discharge chamber and discharged in a substantially dry state, and the remaining coarse fraction is fed to the slag-removing device and discharged. In this case, the average particle size of the at least one fine fraction is smaller than the average particle size of the coarse fraction. The separating grate has at least in certain regions air feeds that are distributed over its entire width and via which air is fed in a controlled manner to the slag, and the air feeds are isolated from the openings and formed separately.

Claims

1. A method comprising processing slag occurring in a combustion chamber of a refuse incineration plant that is produced by the refuse that is burned on an incineration grate and at the same time conveyed in the direction of a slag removal device, wherein: the slag comprises a fine fraction and a coarse fraction, the incineration grate is formed at least in its end region that is facing the slag removal device as a separating grate, which has openings, via which the combustion chamber is connected to a fine-slag discharge chamber, and the fine fraction of the slag is separated from the course fraction and ejected through the openings into the fine-slag discharge chamber and discharged to the outside in a substantially dry state, the remaining coarse fraction is fed to the slag removal device and discharged to the outside, and the separating grate has at least in certain regions air feeds that are distributed over its entire width and via which air is fed in a controlled manner to the slag, and the air feeds are isolated from the openings and formed separately.

2. The method as claimed in claim 1, wherein the fine-slag discharge chamber is assigned a fine-slag discharger that discharges the fine fraction of the slag to the outside substantially in an airtight manner.

3. The method as claimed in claim 2, wherein the fine-slag discharger forms a lock.

4. The method as claimed in claim 1, wherein the fine fraction contains only particles, the maximum particle size of which is at most 12 mm.

5. The method as claimed in claim 1, wherein the incineration grate is designed as a separating grate only in its end region facing the slag removal device.

6. The method as claimed in claim 1, wherein the separating grate has openings of different cross-sectional areas, wherein the extent of the cross-sectional area of the openings increases when viewed in the conveying direction.

7. An incineration grate, comprising a plurality of grate elements, which rest one upon the other in the manner of steps in a conveying direction of refuse to be burned and thus form grate steps, wherein the incineration grate is designed as a separating grate, at least in the end region thereof situated downstream in the conveying direction, which separating grate has openings configured to separate a fine fraction of the slag from a course fraction of the slag and eject the fine fraction, wherein the separating grate has at least in certain regions air feeds that are distributed over its entire width for the controlled supply of air to the slag, and the air feeds are isolated from the openings and formed separately.

8. The incineration grate as claimed in claim 7, wherein at least some of the grate elements comprise a body which has an upper wall, which forms a supporting surface, and a wall at the front when viewed in the conveying direction of the incineration grate.

9. The incineration grate as claimed in claim 7, wherein the openings are in the form of gaps between the grate elements.

10. The incineration grate as claimed in claim 9, wherein the gaps between the grate elements are each formed by two grate elements spaced apart in the transverse direction.

11. The incineration grate as claimed in claim 7, wherein the grate elements are designed in such a way as to turn over and/or convey the slag by means of feed movements performed relative to one another.

12. The incineration grate as claimed in claim 11, wherein a cross section of the openings is varied during a feed movement.

13. The incineration grate as claimed in claim 11, wherein a cross section of gaps forming the openings is varied during a feed movement.

14. The incineration grate as claimed in claim 7, wherein the grate elements are grate blocks and a plurality of grate blocks arranged adjacent to one another across the width of the grate in each case forms a grate step.

15. The incineration grate as claimed in claim 7, wherein the openings of the separating grate are designed in such a way as to allow through only particles with a maximum particle size of at most 12 mm.

16. The incineration grate as claimed in claim 7, wherein the proportion of the sum of the cross-sectional area of the openings and the air feeds to the total area of the separating grate facing the slag is more than 5%.

17. A combustion chamber for a refuse incineration plant comprising an incineration grate, wherein: the incineration grate comprises a plurality of grate elements, which rest one upon the other in the manner of steps in a conveying direction of refuse to be burned and thus form grate steps, the incineration grate is designed as a separating grate, at least in the end region thereof situated downstream in the conveying direction, which separating grate has openings configured to separate a fine fraction of the slag from a course fraction of the slag and eject the fine fraction, and the separating grate has at least in certain regions air feeds that are distributed over its entire width for the controlled supply of air to the slag, and the air feeds are isolated from the openings and formed separately.

18. The combustion chamber as claimed in claim 17, wherein the openings of the separating grate are designed in such a way as to allow through only particles with a maximum particle size of 12 mm.

Description

(1) The invention is illustrated further by means of attached figures, of which:

(2) FIG. 1 shows a technical drawing of an incineration furnace of a refuse incineration plant comprising a combustion chamber, an incineration grate, a refuse feed and a primary air feed, a slag removal device and a fine slag discharge chamber, divided into two fine slag discharge chamber compartments, for carrying out the method according to the invention;

(3) FIG. 2 shows a technical drawing of another incineration furnace for carrying out the method according to the invention;

(4) FIG. 3 shows a technical drawing of part of an incineration grate according to the present invention in a perspective view with several options for the design of the openings;

(5) FIG. 4 shows an enlarged view of a grate segment, comprising three grate steps, of the incineration grate shown in FIG. 3, with openings which are formed by holes in the grate bars, said holes varying in their respective geometry from grate stage to grate stage;

(6) FIG. 5 shows an enlarged view of the forwardmost grate segment of the incineration grate shown in FIG. 3, with openings formed by gaps between the grate bars;

(7) FIG. 6 shows a technical drawing of a separating grate in the form of a disk screen for an incineration grate according to the invention; and

(8) FIG. 7 shows a technical drawing of a separating grate of another incineration grate according to the invention, wherein the grate elements are in the form of grate blocks and grate beams.

(9) As shown in FIG. 1, the refuse incineration plant comprises a combustion chamber 2, arranged upstream of which is a refuse feed hopper 4 with a refuse chute 6 connected thereto, which is connected to the combustion chamber 2 via an inlet 8.

(10) The combustion chamber 2 comprises an incineration grate 10 in the form of a forward-feed grate forming the lower boundary of said chamber. In the embodiment shown, the incineration grate 10 is divided into six incineration grate sections 10a, 10b, 10c, 10d, 10e, 10f, to each of which two drives 12a, 12b, 12c, 12d, 12e, 12f that can be operated in phase opposition are assigned. (Of these two drives, only a single drive is shown in each case in FIG. 1.)

(11) Arranged below each of the first four incineration grate sections 10a, 10b, 10c, 10d is an undergrate air chamber 14a, 14b, 14c, 14d, into each of which a separate primary air line 16a, 16b, 16c, 16d opens and which is intended to feed primary air to the combustion bed via corresponding primary air ducts in the incineration grate sections 10a-d.

(12) At the downstream end of the incineration grate 10, when viewed in the conveying direction F, there is an adjoining slag removal device 17. This comprises a coarse slag ejection chute 66 and a coarse slag collecting trough 70.

(13) In the embodiment shown in FIG. 1, the incineration grate 10 in the forwardmost incineration grate sections when viewed in the conveying direction F, i.e. the fifth and sixth incineration grate sections 10e, 10ffacing the slag removal device 17, is in the form of a separating grate 11. This separating grate has openings, via which the combustion chamber 2 is connected to a fine slag discharge chamber 34. (The openings are not visible in FIG. 1.)

(14) In the embodiment shown in FIG. 1, the fine slag discharge chamber 34 is divided into two fine slag discharge chamber compartments 34e, 34f, which are in the form of hoppers 52, which are each arranged below the corresponding incineration grate sections 10e, 10f. In the embodiment shown, there is no separation into several fine fractions; after passing through the fine slag discharge chamber compartments 34e, 34f, the fine fractions from the fine slag discharge chambers are carried away jointly by means of a conveyor belt 58.

(15) The fifth and sixth incineration grate sections 10e, 10f are furthermore assigned air feeds 36e, 36f for feeding in air in a controlled manner. The air feeds 36e and 36f respectively allocated to an incineration grate section 10e and 10f are each connected to an air blower 38e and 38f, respectively. As shown in FIG. 3, the connection between the air blower 38 and the air feeds 36 or 36a, 36b is generally made via corresponding air lines 40a, 40b and air distributor rails 42a, 42b.

(16) The embodiment according to FIG. 2 differs from that according to FIG. 1 in that the entire incineration grate 10 is designed as a separating grate 11. Consequently, it has openings in all its incineration grate sections 10a-f, via which the combustion chamber is connected to fine slag discharge chamber compartments 34a-f. Here, the fine slag discharge chamber compartments 34a, 34b, 34c and 34d arranged beneath the first four incineration grate sections 10a-d are formed by the respective undergrate air chambers 14a, 14b, 14c and 14d. In the embodiment shown, there is no separation into several fine fractions; after passing through the fine slag discharge chamber compartments 34a-f, the fine fractions from the fine slag discharge chambers are carried away jointly by means of a conveyor belt 58.

(17) As mentioned, the fine slag discharge chamber 34 in the embodiment shown in FIGS. 1 and 2 is divided into fine slag discharge compartments 34e-f and 34a-f respectively, which are each in the form of a hopper 52. In the hopper neck 54, i.e. the narrowest region of the hopper 52, there are fine slag discharge means 50 in the form of two fine slag shutoff slides 51a, 51b arranged one above the other, which each alternately open and airtightly close the passage 56 defined by the hopper neck 54 and in this way form a lock. Arranged underneath the lower fine slag shutoff slide 51b and as an extension of the hopper neck 54 is a conveyor belt 58, which, in FIG. 2, is of significantly longer configuration than the conveyor belt 58 according to FIG. 1 owing to the fact that the entire incineration grate is designed as a separating grate.

(18) The openings which, according to the invention, are present in that region of the incineration grate 10 which is designed as separating grate 11, as well as the air feeds, are illustrated in greater detail by means of FIG. 3.

(19) That part of an incineration grate 10 which is shown in FIG. 3 has a first grate segment 10i, in which the incineration grate 10 has air feeds 36 distributed over its entire width.

(20) Adjoining the first grate segment 10i in the conveying direction F in the embodiment shown in FIG. 3 is a second grate segment 10ii. In the embodiment shown, this does not have any air feeds butas illustrated schematically in the figureis cooled by means of water. Here, the water is circulated in a circuit, in which there is a heat exchanger 43 and a fan 45 associated therewith for cooling the water and in which the cooled water is passed through corresponding cavities in the incineration grate and passed back from the latter to the heat exchanger 43 by means of a pump 47.

(21) Although it is not shown explicitly in the figure, it is preferred thatin addition to the second grate segment 10iiother grate segments, in particular the first grade segment 10a, also have water-cooled grate elements. It is furthermore conceivable thatin addition to the first grate segment 10ithere are air feeds also in other grate segments, in particular in the second grate segment 10ii.

(22) In the embodiment shown in FIG. 3, the incineration grate 10 in the first and second grate segments 10i, 10ii is formed by grate plates 44, which extend over the entire width of the incineration grate 10. Of course, it is also conceivable for these grate segments to be constructed from grate blocks.

(23) The grate plates 44 have an upper wall 53, which forms a supporting surface, and a wall 55 at the front when viewed in the conveying direction F of the grate, wherein the air feeds 36 in the embodiment shown are arranged in the upper wall 53 or open via the upper wall into the combustion chamber 2. However, it is also conceivable that the air feeds 36 are arranged in the front wall 55 or open into the combustion chamber 2 via the front wall.

(24) The second grate segment 10ii has openings 46, which have different cross-sectional geometries in each of the three grate plates of this segment in the embodiment shown, as can furthermore also be seen from FIG. 4. Of course, it is also conceivable to choose the same cross-sectional geometry for each grate step. To this extent, FIGS. 3 and 4 serve merely to indicate possible openings without the need for all of these to be implemented in one and the same embodiment of the incineration grate.

(25) In the specific case, in the purely illustrative illustration in FIGS. 3 and 4, the openings 46a of that grate plate 44a of the second incineration grate segment 10ii which is the first when viewed in the conveying direction F are in the form of holes or slots, which, in the specific case, have the shape of a rectangle with rounded corners in cross section. The openings 46b of the second grate plate 44b of the second incineration grate segment 10ii, in contrast, are in the form of holes of circular cross section, while the openings 46c of the third grate plate 44c of the second incineration grate segment 10ii are in the form of holes with a square cross section. Of course, any other geometries ire conceivable apart from those shown.

(26) Adjoining the second grate segment 10ii in the conveying direction F is a third grate segment 10iii, which is shown on an enlarged scale in FIG. 5. In this third grate segment 10iii, the individual grate elements are in the form of grate blocks 49 (each likewise having an upper wall 53 and a front wall 55), which are arranged spaced apart in the transverse direction, i.e. transversely to the conveying direction F, with the result that there is in each case a gap between two grate blocks, as can also be seen especially from FIG. 5. These gaps form further openings 46d, via which the combustion chamber 2 is connected to the fine slag discharge chamber 34.

(27) In the embodiment shown, the gap widths are of larger design in a first grate step 48a than the gap widths of a second grate step 48b arranged downstream of the first grate step in the conveying direction F. Of course, it is also conceivable that at least some of the gaps forming the openings are formed by merely omitting part of the respective grate block.

(28) By virtue of the presence of corresponding openings 46a-d, the second and third grate segments 10ii and 10iii form a separating grate 11 for ejecting a fine fraction of the slag.

(29) As mentioned, the arrangement of the openings which is shown in FIG. 3 is used merely to illustrate the fact that any geometries of the openings in any arrangement are possible. In particular, it is conceivable to provide only holes 46a-c or only gaps 46d as openings in all of the grate segments formed as a separating grate 11.

(30) It is furthermore conceivable to design at least part of the separating grate as a disk screen 64, as illustrated in FIG. 6. In this case, the openings 46 are formed by the interspaces between the disks 65. Of course, other types of screen are also conceivable.

(31) During operation, the refuse to be burned is discharged into the refuse feed hopper 4 and the adjoining refuse chute 6 by means of a crane, of which only the refuse grab 76 is shown in FIG. 1 and FIG. 2.

(32) At the outlet of the refuse chute 6, the refuse is pushed by means of corresponding charging rams 9 through the inlet 8 into the combustion chamber 2 or onto the incineration grate 10, from where the refuse is conveyed in the form of a combustion bed in the direction of the slag removal device 17. In this case, the refuse passes through several combustion phases, namely a drying phase, an ignition phase, a main combustion phase and a burnout phase. These phases are assigned to corresponding zones on the incineration grate 10, i.e. drying zone, an ignition zone, a main combustion zone and a burnout zone.

(33) As soon as the refuse or slag is conveyed over the separating grate 11, slag components of appropriate size, i.e. the fine fraction or fine slag, fall out of the combustion chamber 2 into the fine slag discharge chamber 34 through the openings 46. The remaining coarse fraction or coarse slag, which comprises slag components of relatively large dimensions, passes via a coarse slag ejection edge 60 into the coarse slag discharge chute 66 and, via the latter, into the coarse slag collecting trough 70 of the slag removal device 17, from where it is discharged to the outside.

(34) Consequently, bulky slag constituents are separated from the fine constituents for further separation, and can thus be fed directly to the corresponding separation devices in order to recover from the slag materials that can be reused.

(35) The method is explained in greater detail below with reference to FIG. 7:

(36) In the separating grate 11 shown in FIG. 7, a first set of grate elements is in the form of grate blocks 49 with corresponding air feeds 36, and a second set of grate elements is in the form of grate beams 78. In this case, the grate beams 78 have a longitudinal axis L extending in the conveying direction F and they extend over the entire length of the separating grate 11.

(37) In the specific embodiment shown, the separating grate 11 is bounded laterally by respective fixed grate beams 78b and 78b, wherein four movable grate beams 78a and three fixed grate beams 78b are arranged alternately in the transverse direction between the lateral grate beams 78b, 78b. Eight grate blocks 49 are arranged one above the other in the manner of steps between the grate beams in the embodiment shown.

(38) In the specific case, grate blocks 491a are secured laterally on in each case one first movable grate beam 781a in such a way that they are spaced apart on the side facing away from the first grate beams 781a from an adjacent second fixed grate beam 782b, with the result that a gap 461 is formed, through which the fine fraction constituents of the slag are ejected into the fine slag discharge chamber.

(39) The grate blocks 49 arranged one above the other in the manner of steps in the conveying direction F are secured alternately on a movable grate beam 78a and on a fixed grate beam 78b adjacent thereto.

(40) During operation, the movable grate beams 78a are moved backward and forward in the conveying direction, as a result of which the grate blocks 49a secured on said grate beams are pushed backward and forward by the respective fixed grate beam 49b following in the conveying direction. In this case, the cross section of the gap 461 formed between grate block 49 and grate beam 78 is also varied continuously, i.e. the gap length is either reduced or increased during a forward movement and correspondingly increased or reduced during a reverse movement. On the one hand, this results in an optimum screening effect and, on the other hand, jamming of bulky slag constituents is counteracted in an effective manner.

(41) On their upper side facing the slag, the grate beams 78 furthermore have wedge-shaped deflection elements 80.

(42) In this case, the deflection elements 80 of grate beams 78 that follow one another in the transverse direction are arranged offset relative to one another in respect of the conveying direction F and describe a zigzag line.

(43) By means of the deflection elements 80, a meandering course of different subsidiary slag flows is obtained during operation, this being particularly advantageous in respect of a good screening effect.

(44) It is furthermore conceivable for the grate beams 78 to assume the function of the distribution device for the air feeds of the grate blocks 49 arranged on the respective grate beam.

LIST OF REFERENCE SIGNS

(45) 2 combustion chamber 4 refuse feed hopper 6 refuse chute 8 inlet 9 charging ram 10 incineration grate 10a-f incineration grate sections 10i-iii incineration grate segments 11 separating grate 12a-d drives of the incineration grate 14a-d undergrate air chamber 16a-d primary air feed 17 slag removal device 34 fine slag discharge chamber 36 air feeds of the incineration grate 36a, b first and second group of air feeds 38; 38e-f air blower 40a, b air lines 42a, b air distributor rails 43 heat exchanger 44 grate plate 45 fan 46; 46a-d openings 461 gap 47 pump 48a, b grate step 49 grate block 50 fine slag discharge means 51a, 51b fine slag shutoff slide 52 hopper 53, 53 upper wall (supporting surface) of the 54 grate element 54 hopper neck 55, 55 front wall of the grate element 56 passage of the hopper neck 58 conveyor belt 60 coarse slag ejection edge 64 disk screen 66 coarse slag ejection chute 70 coarse slag collecting trough 76 refuse grab 78 grate beams 80 deflection elements F conveying direction L longitudinal axis of the grate beams