AU2705599A

AU2705599A - Process and apparatus for the thermal conversion of residues

Info

Publication number: AU2705599A
Application number: AU27055/99A
Authority: AU
Inventors: Dieter Dr Eidner; Alfred Escherle; Thomas Flick; Wolfgang Kadlubowski; Wilhelm Mottitschka; Andreas Schieber; Leo Seirlehner
Original assignee: Deutsches Brennstoffinstitut GmbH
Current assignee: Dbi Deutsches Brennstoffinstitut Rohstoff- & Anlagentechnik GmbH
Priority date: 1998-05-22
Filing date: 1999-05-07
Publication date: 1999-12-02
Also published as: CA2272495A1; EP0959049A1; JPH11351524A; CN1238247A

Description

I

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (Original) APPLICATION NO:

LODGED:

COMPLETE SPECIFICATION LODGED:

ACCEPTED:

PUBLISHED:

RELATED ART: NAME OF APPLICANT: ACTUAL INVENTORS: DBI Deutsches Brennstoffinstitut Rohstoff- Anlagentechnik GmbH EIDNER, Dieter (Dr) ofFriedeburger Str. 8b, D09599, Freiberg, Germany; ESCHERLE, Alfred (Dipl.-Math) of Freusburger Muhle 10, D-57548, Kirchen/Sieg, Germany; FLICK, Thomas (Dipl.-Ing) ofLeipziger Str 22, D-09599, Freiberg, Germany; KADLUBOWSKI, Wolfgang (Dipl.-Ing.) of Berthelsdorfer Str 16, D-09599, Freiberg, Germany; MOTTITSCHKA, Wilhelm (Dipl.-Ing) of Berthelsdorfer Str 203, D-09599, Freiberg, Germany; SCHIEBER, Andreas (Dipl-Wirtsch) of Richard Wagner-Str 6, D-73441, Bopfingen, Germany; and SEIRLEHNER, Leo (Dipl-Ing) of Jaegerstr 18, A-4040 Linz-Urfahr, Austria ADDRESS FOR SERVICE: INVENTION TITLE: LORD COMPANY, Patent Trade Mark Attorneys, of 4 Douro Place, West Perth, Western Australia, 6005, AUSTRALIA.

PROCESS AND APPARATUS FOR THE THERMAL CONVERSION OF RESIDUES The following Statement is a full description of this invention including the best method of performing it known to me/us: -la- Applicant: DBI Deutsches Brennstoffinstitut Rohstoff Anlagentechnik GmbH Frauensteiner Str. 81 09599 Freiberg Process and apparatus for the thermal conversion of residues to" The invention relates to a process for the thermal conversion of residues having varying particle sizes in S* the manner defined in more detail in the preamble of Claim 1. In addition, the invention relates to an apparatus for carrying out the process.

DE 44 39 939 Al discloses a generic process and an apparatus for carrying out the process described. In the process, gasification, combustion or mineralization of the residues takes place at temperatures above 1300 0 °C in a melting cyclone which is disposed above a lower furnace. The resultant reaction products are discharged into the lower furnace and the reaction products are separated into a liquid slag and an off gas.

In addition, there are a multiplicity of processes and apparatuses having the purpose of the thermal conversion of residues by gasification or combustion.

Whereas during combustion essentially only incombustible gases are formed, since the oxidizing atmosphere has the purpose of complete combustion, during gasification, owing to the incomplete _i 2 combustion, gaseous, liquid or solid substances are converted by a gasification agent, such as air, steam, carbon dioxide, oxygen or hydrogen, into a combustible gas and a solid residue, such as ash or slag. The incomplete combustion is accompanied by reducing conditions. For an adequate reaction, not only during the combustion but also during the gasification, a sufficiently high reaction temperature is necessary, for which reason all processes operate at temperatures above 9000C. An elevated pressure can additionally improve the reaction conditions.

For the safe disposal or utilization of hydrocarbon- :.-..containing residues, the generally known gasification 15 processes and apparatuses, such as the rotary-grate producer, fluidized-bed gasification or gasification in the airborne dust cloud, have been, and are being, modified and utilized.

In addition, there are processes and apparatuses from the nonferrous industry and metallurgy, such as the melting cyclone and the melting bath, which save on or replace fuel owing to the use of residues and simultaneously ensure the safe disposal or utilization 25 of these residues. Combustion and gasification likewise play a major role in these processes.

In particular, the use of solid residues in the fluidized bed, the airborne dust cloud (inter alia DD 267 880) and the melting cyclone inter alia the above cited DE 44 39 939 and DE 35 25 817 and DE 41 23 740 have a high conditioning requirement, since the particle size and moisture are there subject to severe limitations for utilization. For the particle sizes in this case, the upper limits are in a range between 0.1 and 5 mm and the moisture should be at most up to 10 percent by mass.

3 In contrast thereto, in particular the melting bath disclosed inter alia by DE 35 42 805 and DE 39 20 760 is essentially independent of particle size and moisture. However, there are disadvantages due to the inertia of reaction of such a system. With much effort and little success, attempts are being made to force melt circulation or agitation on the melting bath. Furthermore, efforts are made to achieve a high residence time which leads to a large size of the associated apparatuses. Finally, the manually laborious draining of the liquid and hot slag via the outlet holes of such melting baths is accompanied by disadvantages, which draining cannot be implemented mechanically in permanent operations until very high 15 throughputs of above 10 t/h are achieved.

The object therefore underlying the present invention is to provide a process and an apparatus using which residues of as high as possible a particle size band 20 width and moisture can be flexibly and economically converted into an inert, vitreous, environmentally neutral solid and into off gases. Process and apparatus in this case are to be operated continuously and permit as small a size as possible.

According to the invention, this object is achieved by the process steps mentioned in the characterizing part of Claim 1 and by the apparatus features mentioned in Claim 14.

The residue fed into the upper region of the hightemperature reactor having a maximal particle size of from 15 to 20 mm passes, via the feed apparatus, into the reactor together with a gasification agent or oxidizing agent, expediently oxygen. The gasification agent or oxidizing agent accelerates the residue here.

At the exit of the feed apparatus, the gas/residue suspension is ignited. The finely particulate residue fraction, approximately in a region of 0.5 mm, is 4 brought to reaction under reducing or oxidizing conditions. The resultant slag and the unreacted, generally coarse residue fraction falls, depending on density, onto or into the melting bath situated in the lower region of the high-temperature reactor. There, the further gasification or combustion reaction advantageously takes place up to the complete conversion of the introduced residues into a liquid, inert slag and an off gas.

The gas and slag are taken off from the lower part of the reactor according to the invention in such a manner that a brick retains or dams the slag, for which reason this brick is here termed a damming brick. Thus, advantageously, only material which is completely converted at the bottom can leave the reactor. The brick situated behind produces the desired slag bath height as overflow, is here termed overflow brick and is simultaneously designed as a detachment edge of the slag flow.

Using the apparatus according to the invention, the abovementioned advantages of the process according to the invention can be exploited in an ideal manner.

Advantageous embodiments and developments of the invention result from the subclaims and from the exemplary embodiments described in principle below with reference to the drawing.

In the drawings: Fig. 1 shows a first embodiment of the apparatus according to the invention for carrying out the process according to the invention; Fig. 2 shows three sectional views through the line II-II of Fig. 1 of different embodiments of a 5 burner device situated above the melting bath; and Fig. 3 shows a second embodiment of the apparatus according to the invention for carrying out the process according to the invention.

According to Fig. i, a high-temperature reactor 10 is depicted above an intermediate space 20, which in turn is disposed next to a quench apparatus or quench reactor The high-temperature reactor 10 is constructed as a straight upright cylinder, with its walls being able to taper toward the top or bottom, differently from that depicted here. The high-temperature reactor 10 has a refractory lining in the present case, but it can also be entirely or partially outfitted with a cooling jacket to protect the refractory lining from thermal overload, and has a feed apparatus 11 for the solids, a housing 12 having a refractory lining as mentioned above, a siphon part 15 which has a refractory lining and is extended to one side of the high-temperature reactor 10, one or more burner devices 13, whose function is described in more detail below, and, in its lower region, a melting bath 14 having a damming element constructed as a damming brick 16 and an overflow element constructed as an overflow brick 17.

The damming brick 16 and the overflow brick 17 are disposed in this case, as can be seen in Fig. 2, in the siphon part 15 of the high-temperature reactor Via the feed apparatus 11, which has, in a manner which is not shown, a metering apparatus and a burner device, and which is in turn provided with a solid burner, a gas or liquid auxiliary burner and an ignition and monitoring device, residues which are not shown and whose particle size is less than 20 mm, expediently less than 15 mm, are fed to the high-temperature 1 6 reactor 10. Any required comminution of the residues to the specified particle size prior to the feed into the high-temperature reactor 10 is performed in this case in devices of known type which are not shown.

In the high-temperature reactor 10, the residue is reacted at from 1200 to 20000C with air or oxygen, which is likewise fed via the feed apparatus 11, and with a combustible gas, such as natural gas, the residue being an energy-containing substance which is combustible per se. Natural gas is only fed in order to heat the reactor 10, in the heat-up mode, to the Srequired operating temperature 10000C, to initiate ignition of the solids and to maintain the necessary eo combustion temperature. A liquid fuel such as oil can equally take the place of the combustible gas, such as natural gas.

In a first part of the reaction, material of very small particle size already in flight from the upper region of the high-temperature reactor 10 to the melting bath 14 reacts with the offered atmospheric oxygen or oxygen and a fuel, e.g. natural gas or oil, under reducing or oxidizing conditions, depending on the amount of oxygen offered. Under a reducing' mode of operation, the reaction proceeds as gasification, and under an oxidizing operation the reaction proceeds as combustion of the residues. In this operation the residues form the reaction products gas and liquid slag.

Up to what particle size complete conversion of the feed stock is already accomplished here is essentially dependent on the residence time of the particles in flight and therefore on the size of the hightemperature reactor 10. With an approximately 3 m high high-temperature reactor 10, complete conversion proceeds up to a particle size of about 0.25 mm.

7 Residual unreacted solids and slag produced already form the melting bath 14, which, depending on the throughput rate of the entire reactor, is some centimeters to about 0.5 m deep. Depending on the mass and particle size, some of the as yet unreacted solids sinks into the melting bath 14 and is fused there. The floating part reacts with the melt and the surrounding gas atmosphere under reducing or oxidizing conditions and likewise melts.

To reinforce and accelerate these reactions, if needed, one or more of the burner devices 13 situated above the melting bath 14 are used. As fuel, use is made, in a similar manner to the feed apparatus 11, of atmospheric 15 oxygen or oxygen and a fuel, for example natural gas or ooo oil. As shown in Fig. 2, the burner devices 13 in this case are expediently slightly inclined toward the surface of the melting bath 14 between 5 and 400, extend over the entire melting bath surface and improve 20 the mass transfer at the reaction surfaces of the residues by introducing an impulse and a certain heat input into this area. In addition, the burner devices 13 are used when there is no material input and freezing or solidifying of the slag is to be prevented.

25 In reinforcement, in a manner which is not shown, an electrical heater can be used in the melting bath 14 or in the housing 12 with a refractory lining.

The burner devices 13 additionally offer gasification agent or oxidizing agent, produce an agitation of the bath and force unreacted, in particular coarse material to ignite and fuse by introducing additional heat of combustion.

In addition to the burner devices 13, in a manner which is not shown, it is further possible for gases and/or solids to be blasted in the form of bundled jets having high kinetic energy using blasting lances. The gas in this case can be mixed with oxygen and/or air, and _I 8 reducing gases, likewise neutral gases and/or oxidizing gases, can be blasted. The solids can consist of feedstock, additional fuel or else slag-forming materials or fluxes to improve the flow properties.

A further possibility for improving the melting and reducing work can be devices which are not shown and which introduce solids and/or gas into the bath beneath the surface of the melting bath 14 or from the bottom.

The predominant purpose in this case is always posttreatment of the liquid melt.

To prevent the floating, still unreacted residue from leaving the high-temperature reactor 10 laterally via *O0* 15 the extended siphon part 15, the damming brick 16 is situated at the height of the bath surface. The siphon S"part 15 thus formed guarantees that only liquid and completely converted slag can leave the reactor beneath the damming brick 16. The height of the melting bath 14 is set via the height of the overflow brick 17.

The hot gas is deflected by more than 900 from the reactor part into the extended part, flows past the surface of the draining slag and prevents solidification of same.

With a large size of the high-temperature reactor and with a low conversion rate within the same and therefore with a small slag flow, under some circumstances, solidification of the draining slag is possible in the area of the siphon part 15 having the damming brick 16 and overflow brick 17. In order to prevent this, a further burner device 41, as shown in Fig. 3, is used. The fuel which serves for the burner device 41 is likewise atmospheric oxygen or oxygen and a fuel, for example natural gas or oil.

To empty the slag bath 14 and in the removal of a heavy layer, for example ironstone, which has formed, a slag 9 taphole 42 which is likewise shown in Fig. 3, is additionally provided.

The gas and slag are removed downwards via an outflow hole 18 disposed in the lower area of the siphon part into an intermediate space 20, the outflow hole 18 being constructed so as to be conical.

On a wall on the inside of the intermediate space which does not have a refractory lining, are situated spray apparatuses 24, which are constructed in a manner known per se, e.g. as overflow or water nozzles, and which spray the wall with water over its entire periphery. This protects the wall of the intermediate oeoo S 15 space 20 against overheating and any slag particles arriving at the wall are flushed away.

Other embodiments are possible if they can safeguard "the protection of the intermediate space 20 against solidifying slag and thermal overload. Thus, e.g., designs having jacket cooling or externally mounted spraying are conceivable.

The liquid slag falls through the intermediate space into a water bath 21 which is situated beneath same and which seals the intermediate space 20 gas-tightly from the exterior. The liquid slag is there cooled, granulated, sedimented and transported via a discharge device 22, for example a drag chain, to further processing which is not shown. Cooling the liquid slag in the water bath represents a very simple and reliable method of obtaining an inert, vitreous, environmentally neutral and leaching-resistant solid as end product prepared from the slag, which end product is usable in the construction and ceramics industries.

The gas and the steam formed by the spray apparatus 24 flow essentially uncooled through the intermediate space 20 into a laterally disposed, slightly downward- 10 directed line 25 and from there into what is termed a quench apparatus 30. Already at the entry into the line 25 one or more pressure atomizing nozzles 32 are situated, which nozzles quench the gas in a first stage and protect the line 25 against overheating. Quenching is taken to mean here cooling within a very short time at a very high temperature difference.

Other embodiments are also possible for the line 25, if they safeguard the protection of the line 25 against thermal overload, e.g. as jacket cooling, refractory lining or externally applied spray. The line 25 here :should in all cases have as large an open diameter as :possible.

9 9@SS If the intermediate space 20 and/or the line 25 are provided with jacket cooling, these parts have cooling water feed lines and outlet lines and can be integrated into a cooling circuit, which is not shown, of the burner devices 11, 13 and 41.

*In the quench apparatus 30, pressure atomizating nozzles 33 are disposed over the entire periphery, possibly in a plurality of planes. Depending on the 25 size of the quench apparatus 30, obviously, a disposition of the pressure atomizing nozzles 33 other than that depicted is also conceivable. The water jets which depart from pressure atomizing nozzles 32 cool the gas to its water vapor dewpoint. A quench water tank 31 seals the quench apparatus 30 gas-tightly at its lower side.

Cooling the gas by injecting quench water into the quench apparatus 30 makes it possible to cool the gas very rapidly, but at the same time very simply and without great expenditure.

The water of the water bath 21 is expediently combined with the water of the quench water tank 31 by natural 11 overflow and is circulated, cleanup being required, and if appropriate neutralization and heat decoupling.

Combining the water bath 21 and the quench water tank 31 is not depicted in the figures, but it can be effected very simply by a somewhat higher water level in the water bath 21 than in the quench water tank 31.

As a result of the cleanup, the heavy metals and halogens transferred into the water of the quench water tank 31 are removed and can be fed as dust or salt to separate disposal.

The gas cooled as described above leaves the quench apparatus 30 via a line 34 on its upper side and can be fed to a dust retainer, such as a dust cyclone and/or to downstream energetic utilization, which is not shown, if the gas formed in the high-temperature reactor 10 under a reducing mode of operation is a combustible gas. Under an oxidizing mode of operation, an appropriate flue gas removal is required.

Alternatively, the gas cooling can also be implemented by evaporative coolers, which are not shown, and are of :ee conventional type having two-component nozzles. In this .0 case, a defined amount of water is injected, the completely evaporated amount of water absorbs the heat *and cools the gas. Downstream there is a dust retainer of customary type, e.g. as a dust filter.

A further possibility which is not shown is carrying out the gas cooling and slag solidification of the process jointly in a shared intermediate space 20. In this case, the liquid slag and the gas which exit from the outflow hole 18 are intensively cooled directly after exiting by means of pressure atomizating nozzles disposed in the intermediate space 20, which may be termed direct quenching. Below the intermediate space 20 is likewise situated a water bath 21 having a discharge device 22 for cooling, granulating, sedimenting and discharging the slag. The gas can exit 12 laterally from the intermediate space 20. The water in the water bath 21 is also circulated here and in a water treatment stage is subjected to a cleanup, and, if appropriate, a neutralization and a heat decoupling.

Again, the amount of water present in the circuit is so much that only partial evaporation occurs in the quench space or intermediate space This direct quenching represents a simplified possibility for rapidly cooling the gas, in this case the liquid slag also being cooled by the quench water injection, which is accompanied by a shortening of the process.

0* 00 0

Claims

2. Process according to Claim 1, characterised in that the gas and the liquid slag are fed together to an intermediate space (20) and the liquid slag is cooled and granulated in a water bath (21) situated beneath the intermediate space. 14
3. Process according to claim 1 or 2, characterised in that the gas is intensively cooled by quench water injection.
4. Process according to any one of the preceding claims, characterised in that, for conversion of the coarse-particle content of the residues, gases which partly comprise air and/or oxygen are additionally fed to the high-temperature reactor (10) in the area of the melting bath (14) above the melting bath surface. Process according to any one of the preceding claims, characterised in that, for post- treatment of the melt in the melting bath (14) gases are fed beneath the melting bath surface with high kinetic energy, which gases partly comprise air and/or oxygen.
6. Process according to any one of the preceding claims, characterised in that the thermal conversion of the residues into gas and liquid slag takes place in a temperature range 15 from 1000 to 1800'C.
7. Process according to any one of the preceding claims, characterised in that the residues having a heating value of 3000 kJ/kg are partially to completely burnt with oxygen and/or air to produce the necessary reaction temperature and conversion temperature, in the case of a reducing mode of operation, a combustible, energetic utilisable gas being formed and, under an oxidising mode of operation, an incombustible flue gas being formed.
8. Process according to any one of the preceding claims, characterised in that, if the heating value of the residues is too low, additional energy in the form of combustible gases or combustible liquid is fed to the high-temperature reactor
9. Process according to Claim 8, characterised in that, as additional energy, use is made of a high-heating value gas, a high-heating value liquid or a combustible energy- containing pyrolysis product.
10. Process according to any one of the preceding claims, characterised in that, for the post-treatment, and to improve the flow properties, of the melts, solids are fed in the form of slag-forming material or fluxes.
11. Apparatus for carrying out the process according to one or more of Claims 1 to 15 having a high-temperature reactor (10) which has a feed apparatus (11) for the residues and within which there is situated a melting bath (14) which is bounded on one side by an overflow element and in which is disposed a damming element (16).
12. Apparatus according to claim 11, characterised in that the high-temperature reactor is essentially constructed as an elongate upright cylinder having a lateral siphon part an outflow hold (18) for the joint outflow of gas and slag being provided on the lower side of the siphon part 16
13. Apparatus according to claim 11 or 12, characterised in that the overflow element is constructed as an overflow brick (17) disposed in the siphon part and in that the damming element is constructed as a damming brick (16) disposed between the siphon part (15) and the cylindrical part of the high-temperature reactor
14. Apparatus according to any one of claims 11 to 13, characterised in that the feed apparatus (11) has a metering apparatus and a burner device which is provided with a solids burner, a gas or liquid auxiliary burner and an ignition and monitoring device.
15. Apparatus according to any one of claims 11 to 14, characterised in that, to support the reaction in the high-temperature reactor at least one further burner device (13) is provided which is inclined toward the surface of the melting bath (14).
16. Apparatus according to any one of claims 11 to 15, characterised in that blasting lances 15 are provided in the high-temperature reactor through which blasting lances gases and/or solids can be blasted onto the melting bath (14).
17. Apparatus according to any one of claims 11 to 16, characterised in that devices are S provided below the melting bath through which devices gases and/or solids can be introduced into the melting bath (14).
18. Apparatus according to any one of claims 11 to 17, characterised in that at least one burner device (41) directed toward the melting bath (14) is provided in the high- temperature reactor (10) in the area of the siphon part M
19. Apparatus according to any one of claims 11 to 18, characterised in that at least one slag taphole (42) is provided in the high-temperature reactor (10) below the melting bath (14).
20. Apparatus according to any one of claims 11 5o 19, characterised in that an intermediate space (20) is disposed below the high-temperature reactor which intermediate space is provided on its side wall with spray apparatus (24) and on its underneath is provided with a water bath (21).
21. Apparatus according to Claim 20, characterised in that the intermediate space (20) is connected via a line (25) to a quench device (30) which, on its side wall, has pressure atomizating nozzles (33) and, on its underneath, a quench water tank (31).
22. A process substantially as hereinbefore described with reference to any one of the 15 accompanying drawings. S 23. Apparatus substantially as hereinbefore described with reference to any one of the accompanying drawings. Dated this 3 rd day of May 1999 DBI Deutsches Brennstoffinstitut Rohstoff- Anlagentechnik GmbH By their Patent Attorneys LORD COMPANY PERTH, WESTERN AUSTRALIA