EP1606553B1 - Method and device for feeding industrial combustion plants with wastes, in particular with secondary fuels - Google Patents

Abstract

The invention relates to a method and device for feeding industrial combustion plants with wastes, in particular with secondary fuels, and to the thus produced fuel, in order to better use, in particular a secondary fuel and to obtain a low-cost usable product which can be introduced into a combustion chamber in an improved manner, especially in order to reliably avoid obstructions in ducts leading to a boiler. The inventive method consists in crushing wastes in a crushing unit, extracting crushed wastes from said crushing unit practically just prior to the introduction thereof into the boiler by means of a conveyer which is arranged in an extracting device, on a pneumatic conveyer and in transporting said wastes to the combustion chamber by means of the pneumatic conveyer.

Description

The invention relates to a method and a device for feeding industrial furnaces, in particular power plant boilers and rotary kilns, with waste material, in particular with secondary fuel, as well as a fuel produced therewith.

In particular, when using secondary fuels from waste and / or waste mixtures when used in power boilers, the shape and surface of the material of considerable importance. In particular, the inadequate burnout behavior of the solid secondary fuels proves to be problematic to this day. If the consistency is too firm or too large pieces of waste incomplete combustion takes place, so that z. still get significant amounts of unburned material in the boiler slag. This in turn leads to difficult conditions in the disposal of such ashes, or the utilization of slags.

Secondary fuels are used in addition to their use in power boilers for a long time in cement and lime production as substitution fuel. Again, however, a complete combustion of considerable importance, since in particular the finished product cement does not allow incompletely burned residues, which, not least due to a possible browning of the clinker, would make the respective product useless.

The substitution rate of the secondary fuel is up to 25% for lignite-fired power plants, while in cement and lime production it even reaches up to 50% of the original primary or standard fuel.

In the production of secondary fuels has already been attempted to subordinate waste products after crushing a shaping in order to transport the fuel better. Out DE 196 39 330 C1 a method and a device for producing a substitute fuel from waste are known in which a waste material is first finely crushed and then punched by means of a ring die and pressing organs in loose and substantially disc-shaped piece goods. It is also already known to pellet shredded waste material.

In any case, an intermediate storage and the transport of the pretreated waste material leads to an influence on its physical properties. For example, moisture absorbed by the waste material can lead to problems in feeding the product into the actual boiler room due to caking in the delivery units. This applies in particular to the use of screw conveyors. For a transport by means of augers it comes to Verhakelungen the secondary fuel with each other, so that not only the risk of constipation, but in particular form larger units secondary fuel, which after injection via a lance or similar. do not completely burn into a combustion chamber.

In addition, the surface of the comminuted material is reduced by storage and under the additional influence of various environmental and material parameters, in particular by moisture, which is absorbed from the ambient air, and by the weight of the secondary fuel, which adversely affects not only the transport but also the burning behavior becomes. In order to achieve a problem-free combustion of secondary fuels, they must completely burn off within the first few seconds after they have been introduced into the combustion chamber.

EP 0 175 407 A1 discloses a device for transporting fuel into an oven, which has a crushing unit immediately upstream of a pneumatic conveyor, wherein there via a conveyor belt without any ensiling or storage always the fuel is moved.

US 4,995,324 discloses a method for recovering heat from waste materials, wherein the collected bales of waste material are passed through a bale breaker to release the waste material so that it is transferred in a free flowing stream to a conveyor-like storage unit for subsequent movement into a mill, the the mixture of waste material reduces to a substantially uniform particle size before the waste material is transferred by air into an oven.

US 4,638,952 Finally, an apparatus and method for reducing spherically-engineered pellets to a powdered state for use as fuel is disclosed. In this case, the material is first ground and pulverized by means of a mill, wherein subsequently the pre-shredded material is transported to a second crushing mill, in which the spherical configuration of the material is changed so that it is easier to pulverize. Subsequently, the thus further crushed material is fed back to the first crushing mill for finally pulverizing the waste material before adding it to a furnace, etc.

A disadvantage of the prior art is that on the one hand two individual successive process steps to produce a useful substitute fuel are necessary because the waste material must first be crushed and then subjected to shaping such as pelleting, and on the other hand, the pretreated waste material must be stored and transported consuming , Insufficient Digested material is not economically usable as a secondary fuel.

The invention is therefore based on the object, the above-mentioned method and the corresponding device for charging of industrial furnaces with waste materials, especially with secondary fuel, so design and further that better handling and ultimately complete combustion of the waste material, especially secondary fuel is achieved. It should be produced with the least possible effort an operational product. In addition, an improved introduction of the material is desired, in particular to reliably prevent blockages in the conveyor line leading to the boiler and to achieve complete combustion of the secondary fuel. A corresponding device should also be inexpensive and build small.

According to the invention the object is achieved by a method according to claim 1 and by a device according to claim 5.

The solid secondary fuel preferably used as waste material is contaminated with metal and Störstoff, was spotted, then vor- and usually also nachzerkleinert and optionally pelletized. The secondary fuel consists predominantly of shredded plastic in the form of films, molded articles such as bottles or the like. He may also have shares in textiles, especially cords, etc., as well as papers. In particular, it does not contain organic waste and other liquid or similar components, as well as glass and metals. The material can be supplied to the combustion chamber alone, or else together with, for example, coal, secondary air, etc.

The process according to the present invention eliminates the final pelletization in secondary fuel production, as in the prior art, for example from US Pat DE 196 39 330 C1 known method was required, as well as storage / ensiling of the secondary fuel. By taking place immediately after the production of the shredded waste material discharge and promotion of the same in the combustion chamber a closed process chain is achieved in which the shredded waste material does not get in contact with moisture and blockages of the device and dust developments are achieved at the same time best Ausbrandergebnissen. The proportion of unburned waste material in the ash when it is fired is drastically reduced.

The delivery device comprises not only a conveyor, but in the context of the invention, other components, in particular a discharge shoe, in particular Seitenaustragsschuh. As a conveying device is preferably a screw conveyor / screw conveyor, preferably provided with a short conveyor line, but other possible delivery units can apply, such as gear locks, rotary blower o. The like. By the provision of a conveyor ensures that coming from the crushing unit crushed waste material itself does not accumulate in Ecken / angles of the Austragsschuhs and there it comes to blockages. Preferably, the conveying distance of the screw conveyor is not more than 2 m, more preferably not more than 1.50 m or not more than 1 m.

Essentially immediately the discharge before abandonment in the combustion vessel in the context of the present invention, when no storage / ensiling is interposed, the shredded waste material is thus always moved over the entire conveying path. Between the discharge from the comminution unit and the task via the pneumatic conveyor into the combustion chamber is preferably a period of less than about 1 min., Preferably less than about 30 sec.

With regard to the device according to the invention, the solution of the object is that it comprises a crushing unit for crushing the waste material and a discharge device in which a conveyor device is arranged, which discharges the shredded waste material to a pneumatic conveyor out, the crushing unit substantially directly the pneumatic Conveying device is connected upstream, and wherein in the conveyor a cyclone, preferably after the blower, is arranged, via which a subset of the conveyed air is removed and fed into the circulation of the crushing unit.

The pneumatic conveying according to the invention is optimally adapted to the shredded and shredded fuel material. Instead of the commonly used delivery units such as screw conveyors, rotary valves, rotary blower o. The like. By means of at least one immediately behind the conveyor of the discharge device of the crushing unit arranged blower, in particular Saugzuggebläses / suction pressure blower achieved that achieved by the changed surface and grain texture of the reinforced Constipation tendency in the delivery line is reliably countered. The suction capacity of the suction pressure blower is preferably in a range of about 2,000 to about 4,000 m ³ / h, more preferably about 2,500 to about 3,500 m ³ / h, the pressure side, the power is preferably in a range of about 1,300 to about 3,300 m ³ / h, more preferably about 1700 to about 2400 m ³ / h. The ratio of the power on the suction side to the pressure side is in a range of about 1 to 0.3 to about 1 to 0.85. The comminuted waste material is fed into the combustion chamber at a speed in a range of about 20 to 30 m / sec, preferably about 20 to about 25 m / sec, preferably via a lance. This ensures that it burns completely within a few seconds. The intake manifold of the pneumatic conveyor in front of the blower has an approximately 30 to 50% larger diameter than the subsequently arranged the blower balancing nozzle, whereby an optimal flow rate is achieved.

In a further embodiment of the invention, a mill is provided as comminution unit, wherein the mill is preferably a high-speed hammer mill. The hammer mill is preferably designed as a hammer mill and has about 80 to about 150 hammers, which can be up to four times changeable. The shredded waste material taken from the crushing unit has a geometrically determined diameter in a range of about 0.001 to 25 mm, preferably 0.01 to 10 mm. It has a cotton consistency. The hammer mill operates at a speed in a range of about 2,000 to about 4,000 rpm, preferably in a range of about 2,500 to about 3,000 rpm. Such with the hammer mill shredded waste material, especially secondary fuel is burned in connection with the provision of a pneumatic conveyor and the total very short overall conveying distance in the device according to the invention as well as completely after blowing it into a combustion chamber.

In a further embodiment of the invention, the discharge of the crushing unit is designed as Seitenaustragsschuh. This may have one or more lateral discharge openings, wherein two opposite discharge openings may be provided.

A further embodiment of the invention provides that between perforating unit and Seitenaustragsschuh a perforated plate is arranged. The perforated plate preferably has regularly distributed round holes, through which a screening of the crushed material to a maximum of about 25 mm, preferably a maximum of 20 mm occurs.

According to a further embodiment of the invention, the pneumatic conveyor downstream of the fan in a leading into the boiler conveyor line supply pipe, which preferably forms an acute angle with the feed line. An influence on the ratio of conveying air and fuel can be realized according to a further embodiment of the invention preferably characterized in that the supply pipe is designed to be axially displaceable in the feed line. The pressure difference (increase) between the end of the feed tube and immediately before the combustion chamber is in a range of about 5 to about 25 mbar, preferably in a range of about 6 to about 15 mbar. Due to the axial displaceability of the delivery line, the burning behavior of the fuel can be optimally adapted to different furnaces or power plants. Especially with longer delivery lines, a further blower can be provided in the delivery line. This can be configured as a radial fan, but preferably a positive displacement blower is used.

Upstream of the actual device is expediently a feed device, which preferably has a weighfeeder and a screw conveyor to ensure a metered task. The with the device according to the invention produced fuel is so well digested that its complete combustion can be reliably guaranteed.

Particularly preferably, in particular, the cyclone is arranged behind the fan in the conveyor. The usually removable via the overflow of the cyclone subset of the delivered air is returned to the crushing unit in the circulation system. This has the great advantage that a pressure drop across the conveyor can be avoided. The amount of air is the metering unit preferably metered supplied so that in the circuit substantially no pressure drop, especially in the area between crushing unit and cyclone, occurs, or only a very low-particularly advantageous is such an embodiment, especially in conveyors, which has a length of 20 or more meters, preferably 50 or more meters, more preferably 100 or more meters.

The fuel obtained by the process according to the invention preferably has a dry residue according to DIN EN 12 880 (S2) in a range from about 75 to about 90% by weight, a water content according to DIN EN 12 880 (S2) in a range from about 12 to about 25 wt.%, An ash content according to DIN 51 719 in a range of about 4 to about 10 wt.%, Each based on the total amount of fuel on. Preferably, the fuel according to DIN 51 900 has a calorific value in a range of about 21,000 to about 24,000 kJ / kg and a calorific value in a range of about 19,000 to about 22,000 kJ / kg calculated according to the formula Hu = Ho x F.

Fig. 1:

die erfindungsgemäße Vorrichtung in schematischer Darstellung;

Fig. 2:

den Austrag des Zerkleinerungsaggregats der erfindungsgemäßen Vorrichtung im Querschnitt; und

Fig. 3:

den Austrag des Zerkleinerungsaggregats der erfindungsgemäßen Vorrichtung im Längsschnitt entlang der Linie III - III in Fig. 2.

The invention will be explained in more detail with reference to a preferred embodiment, but is by no means limited to the embodiment shown there. The figures show in detail:

Fig. 1:

the device according to the invention in a schematic representation;

Fig. 2:

the discharge of the crushing unit of the device according to the invention in cross section; and

3:

the discharge of the crushing unit of the device according to the invention in a longitudinal section along the line III - III in Fig. 2 ,

In the in Fig. 1 schematically illustrated embodiment, a feeder 1 a feeder 2 and a screw conveyor 3. About this feeding device 1, the optionally pre-shredded waste material is a crushing unit, in the illustrated and insofar preferred embodiment of a mill 4, preferably a high-speed percussion hammer supplied. Therein, the supplied material is comminuted to a defined grain size (geometrically determined diameter of the waste material) and surface texture. The task of the waste product on the mill 4 is carried out in bulk from above. The discharge below the mill 4 is designed as Seitenaustragsschuh 5, in the FIGS. 2 and 3 will be described in more detail below. From the Seitenaustragsschuh 5, the crushed material is transported via a arranged in this conveyor, in particular a screw conveyor 14, on the pneumatic conveyor 15, which in particular has a Saugzuggebläse 6.

In the mill 4, the material supplied by the crushing effect gets a fibrous, watty consistency with a large surface. This fuel can be completely removed from the Seitenaustragsschuh by means of the Seitenaustragsschuh 5 downstream induced draft fan 6 and the screw conveyor 14 5 and pneumatically feed the combustion chamber / combustion chamber, not shown. This is done in an advantageous embodiment of the invention via a feed pipe 7, which opens into a leading into the combustion chamber conveying line 8.

In the in Fig. 1 A cyclone 17 is arranged downstream of the fan 6 via this cyclone 17. Via this cyclone 17, a subset of the conveyed air is again supplied via the overflow via a schematically drawn return line 19 to the mill 4. In this case, a control device, not shown here, such as a valve, for metering the amount of air to be supplied in the return line 19 may be provided. A entrainment small particles in the air flow can be taken into account, but preferably the cyclone 17 is set so that this does not occur.

The feed tube 7 is preferably axially freely displaceable in an unspecified receiving tube of the delivery line 8, so that an optimum chimney effect at the end of the feed tube 7 can be adjusted, but can also be fixed. The chimney effect arises as a function of the position of the end of the feed tube 7 in the cross section of the delivery line 8 and reliably prevents blockages in the delivery line eighth

For longer delivery routes, the delivery line 8 can be acted upon on its side facing away from the boiler via a further blower 9 with conveying air. The conveying air flows past the end of the acute angle feed tube 7 and carries the kettled material with it. This embodiment allows a very accurate metering of the conveying air, the amount of which can be adjusted to an optimal level with the conveying air of the supplied primary fuel.

The blower 9 is designed as a rotary piston blower, which works in the direction of a combustion chamber upstream rotary feeder 18. If necessary, the rotary feeder 18 can be omitted in particular in the case of a continuous supply of the material into the combustion chamber.

The FIGS. 2 and 3 finally show the aforementioned Seitenaustragsschuh 5 in more detail. The Seitenaustragsschuh 5 has internally disposed inclined plates 10 a funnel shape and has a single lateral outlet opening 11. The dimensioning of the Seitenaustragsschuhs 5 depends on the nature of the waste material and the furnace. Such a design is ensured in connection with the screw conveyor 14 that no material remains in the shoe 5 and thus optionally leads to blockages.

Between the mill 4 and Seitenaustragsschuh 5 is a perforated plate 12, preferably with round holes 13, respectively. The perforated plate 12 is, as in Fig. 2 seen adapted to the outer shape of the mill. It has holes with a diameter of for example 16 mm. It is understood that while the dimensions of the openings (diameter or edge length) correspond to the selected for the particular purpose of the secondary fuel upper grain size.

The sufficiently digested waste material is discharged through the perforated plate 12, fed via the screw conveyor 14 to the pneumatic conveyor 15 and pneumatically the firing space. Due to the suction effect and the very light fuel it comes in the behind Delivery line 7 or 8 not to blockages. Furthermore, dust is prevented by the short and closed conveying path of the device according to the invention.

The invention proposes a device which generates a conditioned fuel in situ, which has significantly improved burnout properties compared with secondary fuel produced at a different location, stored and transported for firing. The device is extremely compact and can therefore be assembled optimally for the respective application.

Without prior treatment, a complete combustion takes place, so that minimized in the power plant combustion, the proportion of unburned material in the boiler slag and the disposal of such ashes, or the utilization of slags is facilitated. In cement production can be adjusted with the device according to the invention an optimum temperature profile in the rotary kiln.

Claims (19)

1. A method for feeding industrial furnace systems, in particular power station boilers or rotary furnaces, with waste material, in particular with secondary fuel, characterised by the following steps:

   - comminuting the waste material in a comminution unit;

   - discharging the comminuted waste material from the comminution unit substantially immediately before charging into the boiler by means of a conveying device arranged in the discharging device on to a pneumatic conveying means; and

   - conveying the waste material by means of the pneumatic conveying means into the combustion chamber, with a portion of the conveyed air being removed via a cyclone and being recirculated to the comminution unit.
2. A method according to Claim 1, characterised in that the comminution unit is matched to the waste material such that the waste material after comminution has a fibrous consistency with large surface area.
3. A method according to one of the preceding claims, characterised in that the conveying means has a conveying line which can be supplied with air and is designed such that the waste material is supplied in metered amounts to the combustion chamber by the action of suction via the conveying line.
4. A method according to one of the preceding claims, characterised in that the waste material is supplied to the comminution unit in metered amounts via a metering device.
5. A device for feeding industrial furnace systems, in particular power station boilers or rotary furnaces, with waste material, in particular with secondary fuel, comprising a comminution unit (4) for comminuting the waste material and a discharging device, in which a conveying device (14) is arranged which discharges the comminuted waste material on to a pneumatic conveying means (15), the comminution unit (4) substantially immediately preceding the pneumatic conveying means (15), and a cyclone being arranged in the conveying means (15), preferably after the fan (6), via which cyclone a portion of the conveyed air is removed and is recirculated to the comminution unit (4).
6. A device according to Claim 5, characterised in that a mill (4) is provided as comminution unit.
7. A device according to Claim 6, characterised in that the mill (4) is a high-speed hammer mill.
8. A device according to one of Claims 5 to 7, characterised in that the discharge device has a lateral discharge shoe (5).
9. A device according to Claim 8, characterised in that the lateral discharge shoe (5) has opposing discharge openings (11).
10. A device according to one of Claims 8 or 9, characterised in that a perforated plate (12) is arranged between the comminution unit (4) and the lateral discharge shoe (5) of the discharging device.
11. A device according to Claim 10, characterised in that the perforated plate (12) has round holes (13) distributed in a regular arrangement.
12. A device according to one of Claims 5 to 11, characterised in that the pneumatic conveying means (15) comprises at least one fan (6), in particular an induced-draught fan, arranged immediately after the conveying device (14) of the discharging device.
13. A device according to one of Claims 5 to 12, characterised in that the pneumatic conveying means (15) after the fan (6) comprises a supply tube (7) opening into a conveying line (8) leading into the boiler.
14. A device according to Claim 13, characterised in that the supply tube (7) forms an acute angle with the conveying line (8).
15. A device according to Claim 13 or 14, characterised in that the supply tube (7) is designed to be axially displaceable in the conveying line (8).
16. A device according to one of Claims 13 to 15, characterised in that an additional fan (9) is provided in the conveying line (8).
17. A device according to one of Claims 5 to 16, characterised in that the comminuting unit (4) is preceded by a charging device (1).
18. A device according to Claim 17, characterised in that the charging device (1) has a weigh feeder (2).
19. A device according to Claim 17 or 18, characterised in that the charging device (1) has a worm conveyor (3).

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