CH628972A5 - Tunnel furnace with direct firing - Google Patents

Tunnel furnace with direct firing Download PDF

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Publication number
CH628972A5
CH628972A5 CH1158377A CH1158377A CH628972A5 CH 628972 A5 CH628972 A5 CH 628972A5 CH 1158377 A CH1158377 A CH 1158377A CH 1158377 A CH1158377 A CH 1158377A CH 628972 A5 CH628972 A5 CH 628972A5
Authority
CH
Switzerland
Prior art keywords
furnace
gas
tunnel
outlet
tunnel furnace
Prior art date
Application number
CH1158377A
Other languages
German (de)
Inventor
Andreas Haessler
Wilhelm Jun Morgante
Original Assignee
Andreas Haessler
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE2643406A priority Critical patent/DE2643406C3/de
Application filed by Andreas Haessler filed Critical Andreas Haessler
Publication of CH628972A5 publication Critical patent/CH628972A5/en

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B33/00Clay-wares
    • C04B33/32Burning methods
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27FURNACES; KILNS; OVENS; RETORTS
    • F27BFURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/30Details, accessories, or equipment peculiar to furnaces of these types
    • F27B9/3005Details, accessories, or equipment peculiar to furnaces of these types arrangements for circulating gases
    • Y02P40/65

Description

The invention relates to a tunnel furnace with direct firing and furnace gas flowing in the longitudinal direction of the furnace, for firing ceramic products, in particular products containing combustible or gasifiable substances, which has a first outlet for withdrawing furnace gas at high temperature.
In a known tunnel kiln of this type (GB-PS 8 55 322), the exhaust gas is suctioned off essentially at the kiln entrance and led into the chimney. In the known tunnel kiln, the exhaust gas flow is enriched with pollutants by the gasification of polystyrene, sawdust, carbon or other substances on the way from the firing zone to the chimney, in the so-called warming zone. In the known tunnel furnace, the exhaust gas, which is enriched and contains pollutants and unburned but still combustible constituents, reaches the chimney and from there into the air. The exhaust gases loaded with these gasified components are released into the atmosphere. This not only creates a significant environmental impact, but also results in large heat losses in the known tunnel furnace, because large amounts of combustible gases escape unburned into the atmosphere.
A combustion process is also known (“brick industry”, issue 11, 1972, page 521) in which part of the furnace gas is removed from the heating zone and fed back into the tunnel furnace in the cooling zone. In the known method, the flue gas is finally removed at the end of the furnace, that is to say at the entry point of the fuel. The temperature of the furnace gas finally discharged into the atmosphere should be as low as possible in the known method according to the prevailing ideas of the professional world.
Even in a tunnel kiln that works according to this known method, the flue gases are always loaded with carbonization gases and flammable components, since all of the flue gas is discharged into the atmosphere at the end of the kiln. Since only a fraction of the furnace gas is removed from the heating zone and put back into the cooling zone, but the entire furnace gas on the route between the main combustion zone and the furnace outlet is loaded with gasifiable substances, the flue gas contains a considerable proportion of unburned pollutants.
A tunnel kiln is also known (DE-PS 12 02 706), which has circulation channels for the removal and circulation of still combustible gaseous decomposition products of the organic substances, via which the gas removed is fed to the burners. In this tunnel kiln, too, the flue gas extracted from the kiln exit is still loaded with pollutants.
Finally, an older, not previously published proposal (DE-OS 25 51 811) discloses a method and a device for the heat treatment of goods in which a flow of the furnace gas in the longitudinal direction of the furnace is to be eliminated. For this purpose, the combustion air is fed into the combustion zone and the flue gases are extracted in the combustion zone. Furthermore, an essentially stationary atmosphere in the longitudinal channel direction is set in the heating zone and in the cooling zone, which atmosphere is circulated in sections transverse to the longitudinal channel direction between a section of the cooling zone and a corresponding section of the heating zone. The tunnel furnace according to this older proposal requires the provision of ring lines with which the undesired movements of the furnace gas in the longitudinal direction of the furnace are to be avoided. The method according to the aforementioned older proposal already differs in approach from the method according to the application, in which a movement of the furnace gases in the longitudinal direction of the furnace is essential and desirable.
Based on the prior art shown, the object of the invention is to improve the exhaust gas quality in a tunnel kiln of the type mentioned at the outset in such a way that it withstands the critical provisions for keeping the air clean, while ensuring that the entire kiln system operates economically.
To achieve this object, it is proposed according to the invention that in a tunnel kiln of the type mentioned at the outset there is at least one further second outlet for withdrawing furnace gas, which is located in the product conveying direction before the first outlet, and that the furnace gas removed on the second outlet is behind or in the high-temperature range again is fed, wherein the first outlet is designed to discharge the furnace gas into the outside air.
In contrast to the previously known methods for operating tunnel furnaces, the flue gas is no longer removed from the tunnel furnace at the lowest possible temperature. The extraction of flue gas with a low temperature means that economic heat recovery from the flue gas is not possible. Heat recovery from flue gas at low temperatures is required
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eliminates complex and expensive heat exchangers that are not profitable and are also exposed to severe corrosion. In contrast, the flue gas is removed at high temperature in the tunnel furnace according to the invention.
This flue gas contains practically no more gasifiable or combustible substances. It already has a chemical composition that can withstand the critical requirements for keeping the air clean. In addition, the flue gas has a temperature level that enables the waste heat to be recovered economically.
It is also preferably proposed that a heat exchanger for cooling the exhaust gas be arranged behind the first outlet.
Furthermore, it has proven to be expedient for the first outlet to be arranged at the location of the tunnel furnace at which the temperature of the furnace gas is higher than the gasification temperature of the combustible or gasifiable substances contained in the moldings.
Further refinements of the invention are described in the subclaims. The invention is explained in detail below with reference to the drawings. It shows:
1 schematically shows a tunnel kiln operated according to a conventional method,
2 shows a temperature diagram for the tunnel furnace according to the invention,
FIG. 3 shows a schematic drawing of the tunnel furnace according to the invention corresponding to FIG. 2.
First of all to Fig. 1: In the tunnel furnace 1, the flue gas 6 symbolized by dashed lines flows in the direction of arrow 6a in counterflow to the trolleys 7, the conveying direction of which is symbolized by the arrow 7a. The flue gas leaves the furnace at 2 in front of the gate valve 3 and is conveyed to the chimney 5 by means of a fan 4. The known tunnel oven shown has a ceiling burner.
Now to FIGS. 2 and 3, which correspond to one another: Even in the tunnel furnace according to the invention, the kiln cars 7 run through the tunnel furnace from left to right in the direction of arrow 7a. The flue gas is discharged through the chimney 5. The fresh air supply can be regulated by a slide 19 arranged between the cooling zone E and the final cooling zone.
The movement of the kiln with the ceramic moldings takes place in countercurrent to the main gas flow, which is symbolized by arrow 10.
In principle, the tunnel kiln according to the invention can be divided into zones A to F. Zone A is the indifferent heating zone with temperatures below 200 ° C. In zone A there are no gasification processes. This is followed by Zone B with a temperature range of approx. 200 ° to 700 ° C, in which flammable substances degas from the ceramic moldings. The firing material is degassed within zone C, which is further connected, and is further heated, for example from 700 ° C to 1200 ° C. The main combustion zone D follows. The main part of the required fuel is fed into the tunnel furnace. In the subsequent cooling zone E, the firing material is cooled to approximately 850 ° C. and in the subsequent final cooling zone F, it is cooled down to the temperature at which the firing material leaves the tunnel furnace.
While in known tunnel ovens the flue gases are discharged from zone A or partially from zone B, there is no flue gas discharge in the tunnel oven shown. Instead, the flue gas provided for leaving the tunnel furnace is discharged from the fire zone or main combustion zone D at 14 or from zones adjacent to it, the flue gas having a high temperature. For example, it can be partially removed from the cooling zone E at a high temperature.
The main gas stream 10 is conducted in the combustion channel of the tunnel furnace through zones B and A, removed there through the double second outlet 110, returned via bypass lines 11, in which fans 12 are located, and fed back into the furnace in the cooling zone or in the main combustion zone. Several bypass lines connected in parallel can be provided. The main gas flow can be taken from several places in the heating zone and fed back into several places in the cooling zone and partly in the fire zone.
The exhaust gas stream 13, which is smaller than the main gas stream 10, is taken from the tunnel furnace in the high temperature range, at about 600 ° C. to 1200 ° C. smoke temperature. The exhaust gas can also be taken from several points in the high temperature range up to the cooling zone. The temperature at the tapping point or tapping points should be higher than the gasification temperature of the combustible substances in the moldings in the heating zone B serving as the degassing zone, so that no unburned carbonization gas gets into the exhaust gas chimney. Thus, the entire carbonization gas and volatile pollutants pass through the bypass lines 11 through the fire zone of the furnace and burn there completely at maximum temperature.
The exhaust gas stream or flue gas stream of high temperature (approx. 600 ° C to 1000 ° C) can be used for heating purposes. For example, heat exchangers 15 for hot air generation or steam generation can be operated with the flue gas stream removed at the first outlet 14. The cooled flue gas is conveyed into the chimney 5 by a fan 16.
In Fig. 3, 17 denotes a hot air flow which flows through the heat exchanger 15 and is used for drying purposes.
The tunnel furnace is heated via lateral or upper heating holes 18 with other conventional fuels with the addition of combustion air in a known manner. Since in the tunnel kiln according to the invention there is no complete cooling of the combustion material in the cooling zone E as a result of cooling with the main gas stream 10, an end cooling zone F is provided at the end of the tunnel kiln, which is controlled by the slide
19 is separated from the furnace chamber and from a cooling air flow
20 is applied to the residual cooling of the firing material.
The exhaust gas flow or the flue gas has a higher C02 content than the flue gas from tunnel kilns, which are operated according to the previously known methods. This already results in a significant improvement in thermal efficiency. By removing the gas flow immediately after passing through the high-temperature zone, all pollutants are completely burned, as are all combustible substances. The required air supply in the overall system is not limited to the firing zone, but can take place in all zones, depending on the requirements.
A reversing flow blower can be provided in the line connecting the second outlet to the feed, with the aid of which the main gas flow in the combustion channel of the tunnel furnace can be conveyed in a pulsating manner in the pilgrimage step.
Furthermore, a reversing flow blower can be connected downstream of the heat exchanger.
It can be expedient if the reversing flow fans for the main gas flow and for the exhaust gas flow are switched synchronously. The two gas flows are therefore coordinated.
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1 sheet of drawings

Claims (8)

628 972
1. Direct-firing tunnel kiln for firing ceramic products, which has a first outlet for withdrawing furnace gas at high temperature, characterized in that at least one further second outlet (110) is provided for withdrawing furnace gas, which is in the product conveying direction before the first outlet (14), and that the furnace gas withdrawn at the second outlet (110) is fed in again behind or in the high-temperature region, the first outlet (14) being designed to discharge the furnace gas into the outside air.
2. Tunnel furnace according to claim 1, characterized in that a heat exchanger (15) for cooling the exhaust gas is arranged in the gas discharge direction behind the first outlet (14).
2nd
PATENT CLAIMS
3. Tunnel furnace according to claim 1 or 2, for firing ceramic products which contain certain combustible or gasifiable substances, characterized in that the first outlet (14) is arranged at the location of the tunnel furnace at which the temperature of the furnace gas is higher than that Gasification temperature of the combustible or gasifiable substances contained in the moldings.
4. Tunnel furnace according to one of claims 1 to 3, characterized in that the outlets and feeds are each provided several times.
5. Tunnel furnace according to one of claims 1 to 4, characterized in that the cooling zone (E) is followed by a shut-off element (19) separated from the furnace space after-cooling zone (F), in which the firing material is supplied with fresh air.
6. Tunnel furnace according to one of claims 1 to 5, characterized in that a reversing flow blower (12) is provided in the line (11) connecting the feed (11), with the aid of which the main gas flow in the combustion channel in the pilgrimage step is pulsating.
7. Tunnel furnace according to claim 2, characterized in that the heat exchanger (15) is followed by a reverse flow fan (16).
8. Tunnel furnace according to claims 6 and 7, characterized in that the reversing flow blowers (12 and 16) for the main gas flow (10) and for the exhaust gas flow (13) are switched synchronously.
CH1158377A 1976-09-27 1977-09-22 Tunnel furnace with direct firing CH628972A5 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE2643406A DE2643406C3 (en) 1976-09-27 1976-09-27

Publications (1)

Publication Number Publication Date
CH628972A5 true CH628972A5 (en) 1982-03-31

Family

ID=5988948

Family Applications (1)

Application Number Title Priority Date Filing Date
CH1158377A CH628972A5 (en) 1976-09-27 1977-09-22 Tunnel furnace with direct firing

Country Status (7)

Country Link
AT (1) AT384101B (en)
CH (1) CH628972A5 (en)
DE (1) DE2643406C3 (en)
DK (1) DK151596C (en)
FR (1) FR2365766B1 (en)
NL (1) NL7710546A (en)
NO (1) NO147533C (en)

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1098416B (en) * 1978-09-04 1985-09-07 Salviati Impianti Spa Process for the production of bricks and plant for the implementation of said procedure
ATA312180A (en) * 1980-06-12 1986-03-15 Walter Ing Rieger Method for burning thin-walled ceramic moldings containing in particular core holes, and system for implementing the method
DE3042708C2 (en) * 1980-11-10 1986-07-17 Rudolf 2106 Bendestorf De Riedel
US4523907A (en) * 1981-03-11 1985-06-18 Haessler Andreas Holder and method of firing ceramic briquettes
AT376959B (en) * 1982-09-17 1985-01-25 Maerz Ofenbau Method for producing cement clinker
DE3324764C1 (en) * 1983-07-08 1985-02-14 Froehlich Air Ag Process for the operation of a throughflow kiln, especially a tunnel kiln, for the firing of ceramic mouldings and apparatus for the performance of this process
DE3516058C2 (en) * 1984-08-21 1986-07-17 Institut Fuer Ziegelforschung Essen E.V., 4300 Essen, De
DE3517866C2 (en) * 1985-05-17 1988-04-14 C. Keller Gmbh U. Co Kg, 4530 Ibbenbueren, De
DE3525771A1 (en) * 1985-07-19 1987-01-22 Haessler Andreas Tunnel furnace with waste gas flow which is low in harmful substances
AT383886B (en) * 1985-12-23 1987-09-10 Walter Ing Rieger Method for producing bricks from clay shapes and system for implementing the method
DE3605780C1 (en) * 1986-02-22 1987-06-19 Manfred Zimmermann Tunnel furnace for baking raw graphite electrodes
DE3627050C1 (en) * 1986-08-09 1991-11-28 Lingl Anlagenbau Tunnel kiln for the reducing firing of facing bricks
DE4023432C2 (en) * 1989-10-18 1995-05-24 Werner Ing Grad Strohmenger Tunnel kiln
AT401817B (en) * 1993-12-01 1996-12-27 Rieger Walter Method for burning ceramic moldings and system for implementing the method
DE4423221A1 (en) * 1994-07-01 1996-01-04 Lingl Anlagenbau Heat transfer in the tunnel oven
IT1309033B1 (en) * 1999-03-08 2002-01-15 Tecnochimica Sassolese S R L Continuous furnace improved for the heat treatment of materials
DE102011100736A1 (en) 2011-05-06 2012-11-08 Andreas Hässler Method for operating e.g. tunnel furnace used for firing brick, involves directing exhaust gas stream from tunnel furnace to waste heat boiler for generating electric power utilized for drying and heating processes of furnace

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1226477B (en) * 1962-02-05 1966-10-06 Kollergeneratoren Und Ofenbau Method for heating a kiln, in particular a tunnel kiln
FR1413674A (en) * 1964-11-09 1965-10-08 Robert Aebi A G Method of operating a tunnel kiln and device for implementing the method
DE1301436B (en) * 1965-03-01 1969-08-21 Andreas Haessler Process for operating tunnel ovens and the like for firing ceramic products
FR1470155A (en) * 1966-02-28 1967-02-17 Firing process and device for implementing this process for operating continuous circulation furnaces for ceramic products
DE1303473C2 (en) * 1966-04-06 1974-01-17 Process for the continuous firing of ceramic feedstock in tunnel ovens and tunnel ovens to carry out the process
FR2038592A5 (en) * 1969-03-19 1971-01-08 Koho Es Gepipari Miniszterium Tunnel kiln for the firing of refractory - ceramic products

Also Published As

Publication number Publication date
DK151596C (en) 1988-05-24
DK151596B (en) 1987-12-14
AT384101B (en) 1987-10-12
DE2643406A1 (en) 1978-04-06
DE2643406C3 (en) 1980-07-03
NL7710546A (en) 1978-03-29
FR2365766B1 (en) 1982-12-17
DE2643406B2 (en) 1979-10-11
DK425677A (en) 1978-03-28
NO147533B (en) 1983-01-17
ATA690077A (en) 1987-02-15
FR2365766A1 (en) 1978-04-21
NO147533C (en) 1983-04-27
NO773289L (en) 1978-03-29

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