EP0085833B1 - Process for the dry cooling of coke and apparatus for carrying out the process - Google Patents

Description

The invention relates to a method for dry coke cooling by means of a cooling gas containing water vapor and to an apparatus for performing this method.

Dry coke cooling has been a process that has been known for many decades, according to which the glowing coke expelled from the coke oven is filled into a cooling shaft, in which it is cooled by the inflowing inert gas. Consequently, such a shaft cooler works on the principle of a moving fixed bed in connection with the direct heat exchange between solid and gas in countercurrent. The hot inert gas is usually used to generate steam in a tubular boiler. From DE-A-2 853 299 z. B. a method and an apparatus for single-stage dry quenching of coke with an inert gas are known, in which the sensible heat of the coke resting in a prechamber preceding the quenching chamber is used to achieve a constant temperature at the cooling gas outlet at the quenching chamber, that the prechamber is flushed with the inert gas in cocurrent or countercurrent and the two cooling gas streams are then combined. - It is therefore not possible to do without expensive inert gas here.

More recently, it has been proposed to use the high-tension steam thus generated for preheating coking coal. Such a process coupling between coke dry cooling and. Preheating represents a sensible energy recovery; However, there are still no suitable methods and devices for this.

According to the generally prevailing opinion, the coke dry cooling and the preheating of coking coal cannot be carried out in direct heat exchange between the coking coal and the coke with one and the same circulating medium, because the vapors from a preheating system would cause inadmissibly high burn-up losses due to the water gas recession during the coking cooling. Therefore, a subdivision of the circulating medium is proposed, in which - as mentioned - inert gas is used for the dry coke cooling and this a z. B. steam-containing circulating medium for drying and preheating coking coal.

From DE-A-3 000 808 a two-stage countercurrent coke cooling process is known, in which a dry coke cooling is to be combined with the cleaning of the raw coking gas in such a way that an optimal cleaning of the raw coking gas takes place and a heat transfer gas of suitable, as uniform as possible, temperature is produced. For this purpose, in the first (hottest) stage, a raw coal degassing gas, which contains steam, is used in the coking process. This process necessarily leads to a not inconsiderable burn-off of the hottest coke, but this is consciously accepted in view of the cleaning of the raw coal degassing gas by conversion of the methane, higher hydrocarbons and the tar contained in the raw gas.

• 1. Zwei getrennte Wärmeübertragungs-Kreisläufe zwischen dem zu kühlenden Medium und dem zu erwärmenden Medium sind kostenintensiv und verringern das treibende Temperaturgefälle.
• 2. Indirekte Vorerhitzungsverfahren für Kokskohle haben nur eine geringe Leistung, weil der Wärmeübergang zwischen Heizfläche und dem Feststoff - der Kohle - gering ist. Würde ein indirekt arbeitender Kohle-Vorerhitzer auf der wärmeführenden Seite mit heißem Inertgas betrieben, müßte (zusätzlich zum schlechten Wärmeübergang auf der Kohleseite) noch ein schlechter Wärmeübergang auf der Gasseite in Kauf genommen werden.

All previously proposed methods have the disadvantage of high construction costs and / or poor heat transfer on the heat consumer side, with all the resulting consequences for the performance and economy of the methods:

• 1. Two separate heat transfer circuits between the medium to be cooled and the medium to be heated are costly and reduce the driving temperature gradient.
• 2. Indirect preheating processes for coking coal have a low output because the heat transfer between the heating surface and the solid - the coal - is low. If an indirectly operating coal preheater on the heat-carrying side were operated with hot inert gas, a poor heat transfer on the gas side would have to be accepted (in addition to the poor heat transfer on the coal side).

At most, it is possible according to DE-A-2 415 758 to condense out the water vapor from the drying process from a cycle gas subsequently used for coke cooling in a method for drying and for preheating coking coal by means of the heat obtained in dry coke cooling in countercurrent to the coke. This process is complex and requires two condensation stages.

It is therefore the object of the invention to provide a method and a device of the type mentioned, in which the sensible heat of the cooling gas can be given directly to a heat consumer containing water vapor, without the coke to be cooled burning off much more than in the case of the known coke dry cooling processes.

This object is achieved with regard to a method according to the features of patent claim 1 and, with regard to a device, according to the features of one of patent claims 9 to 11. Further developments of the invention result from the subclaims.

Surprisingly, in the process according to the invention, the water vapor contained in the cooling gas can hardly be felt with regard to the burning of the coke; Typical burns are about 1% of the coke fed compared to about 0.5% when dry countercurrent cooling with inert gas.

Regarding the type, quantity and temperature there are no special limits to the cooling gas; only at least a subset of the cooling gas contains water vapor and possibly similarly harmful gas components that promote the burning of coke.

A noticeable improvement in coke cooling is achieved according to the invention by a two-stage cooling process, whereby, according to a development of the invention, better use of the heat content of the coke is achieved by countercurrent cooling in the second stage; this means that the direct-current cooling in the first stage, which is more favorable in terms of burn-off, is coupled with the thermally more favorable counter-current cooling in the second stage. In the method according to the invention, however, the cooling gas - above all from the first cooling stage - can also be used for other purposes of providing energy beyond the thermal pretreatment of the coking coal (and of course also independently of it).

Due to the features of claim 8, the coke cooling is forced, but only such small and finely sprayed amounts of water are used that neither significant coke burn-off takes place nor that a so-called wet quenching comparable amount of water is used. Alternating in the sense of general usage means: alternating, i.e. repeated increasing and decreasing the spraying.

If with another development of the two-stage coke dry cooling only the cooling gas of the second stage contains water vapor, while the first stage z. B. is operated with inert gas, the coke burn is reduced even further - typically to 0.1% of the coke fed. Finally, the further proposed cooling in the first stage to coke temperatures of below about 800 ° C contributes to the fact that the temperature range, which is particularly sensitive to the water gas reaction, takes place exclusively in the first stage with direct current cooling, i. H. that this temperature range is run through extremely quickly; on the other hand, the cooling in the first stage will generally hardly be operated below 700 ° C in order to be able to use the thermally more favorable countercurrent cooling to the greatest extent possible in the second stage.

The use according to the invention of the cooling gas discharged from the cooling container is particularly advantageous for the thermal pretreatment of coking coal in direct contact, that is, above all for drying and preheating coking coal; this achieves the thermally most favorable temperature coupling of the two methods.

Since vapors obtained during the thermal pretreatment of coking coal contain water vapor and are at a temperature level suitable for dry coking, their use as cooling gas in the process according to the invention is recommended according to the invention; Accordingly, the separate provision of cooling gas is superfluous on the one hand and on the other hand the annoying problem of vapor removal is largely eliminated.

With the device proposed according to the invention for carrying out the method in question, all of the method proposals described above can be implemented. Here it is e.g. B. possible to realize through an interface in the cooling tank in the form of a coke lock separate cooling gas circuits for cocurrent and countercurrent cooling; Accordingly, two cooling gas discharge devices, namely above and below the interface, are required and the cooling gases used can have different temperatures and / or gas compositions. The coke lock can be realized by a constriction or special baffles within the cooling container, so that the coke can pass through it without too much hindrance, in particular no moving parts are necessary for this. A slight mixing of the two cooling gas circuits in the area of the interface will generally not be particularly damaging, especially since if necessary, the water vapor that may undesirably enter the first cooling stage (direct current cooling) can be condensed out before it is used again as cooling gas. In addition, with different directions of flow of the cooling gas in the first and second cooling stages in the area of the interface (coke lock), a gas build-up normally occurs, which naturally buffers the two circulating media against one another - especially if the respective cooling gas discharge devices are sufficiently far apart.

According to the two cooling stages, the cooling container is divided by the coke lock into an upper and a lower zone for coke cooling, the area of the coke lock being a separate zone - functioning as a gas buffer - and the cooling gas discharge devices for the two cooling stages at the ends of the buffer zone are provided.

The coke lock can be designed according to the features of claims 9, 10 and / or 11; Here, moving parts are avoided and the coke travels through such a lock, which is always open, without being mechanically loaded excessively, continuously and without the risk of blockages. - By arranging both types of built-in parts one above the other, a gas buffer space preventing mixing of the two cooling gas systems is automatically created; it does not matter which of the two installation parts is the upper or lower one.

The separation of the cooling gas circuits on the Lock can be done according to the invention in that the inlet openings of the gas discharge devices are assigned to the built-in parts in the claimed manner. So it is advisable for both types of built-in parts - if one of them forms the lock alone - to provide separate upper and lower inlet openings for the upper and lower cooling gas circuit. These inlet openings can, for. B. be provided nationwide in the form of a sieve; In the case of the upward-facing, conical installation part, it is particularly advisable to accommodate the inlet openings in the area of the cone tip (the cone can also be a hollow cone). For the downward-facing, truncated cone-shaped installation part, inlet openings above or below the outer edge of the installation part are recommended, in each case on the cooling container, on which an annular gas collecting line can be provided for this purpose (the truncated cone can also be designed as a hollow truncated cone).

If both installation parts together form the coke lock, they are preferably used as a hollow cone or truncated cone, in which - with respect to the cooling container on the undersides, the gas inlet openings for the lower cooling circuit and on the upper sides, the inlet openings for the upper cooling circuit are provided. - The internals can be double-walled or triple-walled, in order to implement area-wide inlet openings and to be able to conduct the gases which are collected in the spaces thus located within the internals separately.

A flushing gas device according to the invention for the coke lock improves its gaseous buffering effect; For this purpose, one or more gas inlet or gas outlet openings for purge gas, which can optionally be circulated, are provided in the area of the coke lock. Gas inlet or outlet openings, as described in connection with the built-in parts, are also fundamentally suitable for this. So z. B. the purge gas is not only passed across the coke stream through the coke lock, but also in or against the direction of the coke stream, for. B. between the opposite surfaces of the above-described installation parts.

Further objectives, features, advantages and possible uses of the present invention result from the following description of an exemplary embodiment with reference to the accompanying drawing.

• Fig. 1 eine Prinzipskizze der Kühlvorrichtung
• Fig. 2a einen Längsschnitt durch den Kühlbehälter gemäß Fig. 1
• Fig. 2b einen vergrößerten Ausschnitt eines Schleuseneinbauteiles gemäß Fig. 2a

The drawing shows:

• Fig. 1 is a schematic diagram of the cooling device
• 2a shows a longitudinal section through the cooling container according to FIG. 1st
• 2b shows an enlarged detail of a lock installation part according to FIG. 2a

In Fig. 1, 1 denotes a cooling container, with any upper coke feed device 2 and any lower coke extraction device 3, as well as an upper cooling gas feeding device 4 and a lower cooling gas feeding device 5 and a middle cooling gas discharge device 6 (the latter does not necessarily have to be in the middle of the vertical cooling container expansion located, but at the point where there is approximately the same temperature of the cooling gas fed in from above or below). The cooling gas discharge device 6 can, for. B. a ring line with several openings to the container wall.

The cooling container 1 has any cross-section and is traversed by the coke from top to bottom; the upper cooling zone is designated by 1a, the lower cooling zone by 1b and the zone in the area of the cooling gas discharge device is designated by 1.

2a, the coke feed device 2 is designed as a simple downpipe; the same applies to the coke extraction device 3 and to the upper and lower cooling gas supply devices 4 and 5. The cooling gas discharge device 6 comprises the pipes 6a and 6b with inlet openings 6c and 6d. A coke lock 7 comprises an upwardly directed, cone-shaped built-in part 10 fastened with a space 8 to the inner wall 9 of the cooling container 1 and a downwardly directed, frustoconical built-in part 11 attached to the inner wall 9 with a central opening 13.

In Fig. 2a, the inlet opening 6c is in the middle of the hollow-conical installation part 10 for the upward directed cooling gas flow of zone 1b; it is also possible to provide a plurality of openings 6c on the lower inner side of the built-in part 10 for a comprehensive cooling gas outflow, as indicated in FIG. 2b.

The inlet openings 6d are located on the outer edge 11 of the installation part 11, preferably in the cooling container wall. In this case, the gas discharge device is arranged as a ring line around the cooling container 1. A comprehensive cooling gas discharge is - according to that mentioned for the built-in part 10 - also possible in the manner of FIG. 2b by a double or triple-walled design of the hollow-cone-shaped built-in part 11.

A purge gas device 12 with a feed line 12a and a discharge line 12b in the area of the coke lock 7 can, according to FIG. B. operated in cross flow. However, it is also possible to carry out a flushing gas supply and disposal over the built-in parts 10 and 11.

2b shows how a comprehensive gas supply or disposal can be implemented on the built-in parts. Of course, such a gas supply or disposal device can also be provided only on the top and bottom of the installation part. Accordingly, one of the two perforated areas is missing (as not shown in FIG. 2b).

It goes without saying that the openings for the gas supply and disposal should be designed according to their size, shape and possibly also alignment so that no coke particles can penetrate or lay them.

Finally, it goes without saying that the built-in parts — as is not shown in more detail in FIG. 2a — need not necessarily be designed as a hollow cone or a hollow truncated cone, and they can be arranged in the cooling container 1 in different numbers and / or in succession.

Details of the device construction, especially the dimensioning, are left to the specialist - as are the throughputs and temperatures of coke, cooling gases and purge gas.

• Einem einzigen schachtförmigen Kühlbehälter wird aus einem Koksofen frisch ausgestoßener Koks oben aufgegeben. Der Koks durchwandert kontinuierlich den Kühlbehälter nach unten und wird dabei auf die gewünschte Endtemperatur in direktem Kontakt mit am oberen und unteren Ende des'Kühlbehälters aufgegebenem Kühlgas gekühlt, woraufhin der Koks unten am Kühlbehälter abgezogen wird. Dieser Vorgang kann kontinuierlich ablaufen. Das Kühlgas kann an beiden Aufgabestellen dieselbe Temperatur und chemische Zusammensetzung aufweisen. Es wird an einer geeigneten Stelle längs des Kühlbehälters insgesamt abgezogen. - Auf diese Weise wird der heiße Koks zunächst im Gleichstromverfahren, d. h. außerordentlich schnell, auf etwa unter 800°C abgekühlt, während die weitere Kühlung im Gegenstromverfahren erfolgt und die Kühlgase gemeinsam an der gewünschten Temperaturschnittstelle im Kühlbehälter aus diesem abgezogen werden (siehe Fig. 1). - Das schnelle Durchlaufen der hohen Temperaturzone (obere Kühlstufe) hat zur Folge, daß dort ebenfalls Wasserdampf enthaltendes Kühlgas, z. B. die Brüden einer Kohletrocknungs- und Vorerhitzungsanlage, eingesetzt werden können, und daß in der zweiten Stufe die bekannten Vorteile der Gegenstromkühlung voll genutzt werden, ohne daß ein anderes Kühlgas benutzt werden oder eine besondere Überführung des Kokses in eine zweite Stufe stattfinden muß. Somit entfällt auch eine gesonderte Weiterverwendung der aus den beiden Kühlstufen abgezogenen Kühlgase, da es sich hierbei um ein einheitliches Gas mit einer Mischtemperatur von etwa 750° C handelt. Der Koks erhält die gewünschte Endtemperatur von z. B. 250°C oder auch darunter.

The inventive method can, for. B. can be carried out as follows:

• A single shaft-shaped cooling container is charged with freshly expelled coke from the top of a coke oven. The coke continuously travels down the cooling container and is cooled to the desired end temperature in direct contact with the cooling gas introduced at the upper and lower ends of the cooling container, whereupon the coke is drawn off from the cooling container. This process can take place continuously. The cooling gas can have the same temperature and chemical composition at both feed points. It is pulled off at a suitable point along the cooling container as a whole. - In this way, the hot coke is first cooled to about below 800 ° C in the co-current process, ie extremely quickly, while the further cooling takes place in the counter-current process and the cooling gases are withdrawn from the cooling container at the desired temperature interface (see Fig. 1 ). - The rapid passage through the high temperature zone (upper cooling stage) has the result that there is also water vapor containing cooling gas, for. B. the vapors of a coal drying and preheating system can be used, and that in the second stage, the known advantages of countercurrent cooling can be fully exploited without the need to use another cooling gas or a special transfer of the coke to a second stage. A separate reuse of the cooling gases drawn from the two cooling stages is therefore also eliminated, since this is a uniform gas with a mixing temperature of approximately 750 ° C. The coke receives the desired final temperature of e.g. B. 250 ° C or below.

The two-stage procedure in a device according to FIG. 2a means that steam-free cooling gases can also be used in the upper cooling zone, as a result of which the coke burn-off is reduced even further without the coke lock to be recommended in this case being technically, procedurally and in terms of investment particularly expensive. - If you do not use the coke lock, you have to put up with different cooling gas in both stages that mixing occurs in the gas discharge device, which makes a recycle of the gases more expensive.

Claims (14)

1. A process for the dry cooling of coke by means of a cooling gas containing water vapour, characterized in that the coke and the cooling gas, containing water vapour at least in a partial cooling stage, are conveyed in direct contact in parallel at least through a first cooling container.

2. A process according to claim 1, characterized in that it is performed in two stages.

3. A process according to claim 2. characterized in that in the second stage the cooling gas is conveyed in counterflow to the coke.

4. A process according to claim 2 or 3, characterized in that only the cooling gas of the second stage contains water vapour.

5. A process according to one or more of claims 2 to 4, characterized in that the cooling in the first stage is carried out to coke temperatures of below about 800° C.

6. A process according to one or more of claims 1 to 5, characterized in that cooling gas removed from the cooling container is used in direct contact for the thermal pre-treatment of coking coal.

7. A process according to one or more of claims 1 to 6, characterized in that vapours occurring during the thermal pre-treatment of coking coal are used as cooling gas containing water vapour.

8. A process according to one or more of claims 1 to 7, characterized in that the cooling is forced in the first stage by alternately spraying a slight quantity of water, preferably between 5 and 12 kg water/t coke.

9. Apparatus for performing the process according to Claim 1, comprising a cooling container (1) with an upper coke charging device (2), a lower coke draw-off device (3), one upper (4) and one lower (5) cooling-gas charging device and at least one central cooling-gas removal device (6), a coke charging valve (7) disposed in one zone (1c) of cooling-gas removal devices (6a, 6b) being arranged between an upper zone (1 a) and a lower zone (1 b) of the cooling container (1), characterized by a flushing gas device (12a, b) for the coke charging valve (7).

10. Apparatus for performing the process according to Claim 1, comprising a cooling container (1) with an upper coke charging device (2), a lower coke draw-off device (3), one upper (4) and one lower (5) cooling-gas charging device and at least one central cooling-gas removal device (6), a coke charging valve (7) disposed in one zone (1c) of cooking-gas removal devices (6a, 6b) being arranged between an upper zone (1a), and a lower zone (1b) of the cooling container (1), characterized in that the coke charging valve (7) is formed at least in part by an upwardly orientated conical insert (10) with an interspace (8) towards the inner wall (9) of the cooling container (1) and situated in the latter.

11. Apparatus for performing the process according to Claim 1, comprising a cooling container (1) with an upper coke charging device (2), a lower coke draw-off device (3), one upper (4) and one lower (5) cooling-gas charging device and at least one central cooling-gas removal device (6), a coke charging valve (7) disposed in one zone (1c) of cooling-gas removal devices (6a, 6b) being arranged between an upper zone (1a) and a lower zone (1 b) of the cooling container (1), characterized in that the coke charging valve (7) is formed at least in part by a downwardly orientated frustoconical insert (11) disposed on the inner wall (9) of the cooling container (1) and having a central opening (13).

12. Apparatus according to claim 10, characterized in that at least one inlet opening (6c) of the gas removal device (6) is provided on the insert (10).

13. Apparatus according to claim 11, characterized in that at least one inlet opening (6d) of the gas removal device (6) is disposed on the outer edge (11a) of the insert (10).

14. Apparatus according to one or more of claims 10 to 13, characterized by a flushing gas device (12a, b) for the coke charging valve (7).

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