DE1263792C2 - Continuous kiln - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

PATENT LETTERING

Int. Cl .:

C 21b

German class: 18 a -13/00

Number:

File number:

Registration date:

Display day:

Issue date:

A30912VIa / 18a
December 9, 1958
March 21, 1968
November 14, 1968

The patent specification matches the original fibenia font

The invention relates to continuous kilns, in particular tunnel kilns, for the reduction of Iron ore to sponge iron. Continuous kilns of this type consist of tunnel-like lined up and in open communication with each other S sections for preheating, firing and cooling. The goods are passed through these ovens on kiln cars.

Oven of this type are known with different cooling zones, the zones against one another can be separated, or it can be a continuous furnace space. It is also known to cool indirectly, for example through pipe systems through which coolant flows immediately by introducing air.

These known ovens do not take into account the particular problems that arise in the construction of such ovens that are used to treat oxidation-sensitive substances, such. B. the production of sponge iron by reducing ore below μ the melting point, which takes place in capsules or similar containers. Difficulties arise especially in the cooling section, because cooling with air easily leads to reoxidation of the already reduced iron due to the large and highly active surface of the sponge. The cooling has therefore hitherto been carried out as indirect cooling in various recuperator arrangements. At the same time, however, direct cooling took place to a lesser extent by secondary air for the combustion in the combustion or reduction section, this secondary air being introduced through inlets at the furnace outlet end and flowing countercurrent to the material through the cooling zones of the furnace. The risk of reoxidation has considerably limited the extent of such cooling. A further limiting factor is the fact that there is a maximum amount of secondary air that can be introduced into the combustion or reduction zone from an economic point of view. These conditions have resulted in the cooling sections of the ovens in question being required to be of considerable length, thereby increasing the cost of the ovens.

The aim of the invention is to enable more effective cooling in a shorter cooling section and thereby considerably reducing the construction costs of the ovens.

This object is achieved according to the invention by dividing the cooling section into one Recuperator zone for indirect cooling, which is adjacent to the burning section, as well as in a zone Continuous kiln

Patented for

AB Höganäsmetoder, Höganäs (Sweden)
Representative:

Dr.-Ing. H. v. Blacks, patent attorney,
8000 Munich 5, Müllerstr. 31

Named as inventor:
Per Egon Gummeson,
Mihkel Mathiesen, Höganäs (Sweden)

Claimed priority:

Sweden December 13, 1957 (11329)

for direct cooling takes place. The last-mentioned zone is adjacent to the furnace outlet end . Like the other zones , the two zones are also in open communication with one another. At the hot end of the zone for direct cooling, outlet channels for the direct cooling air are provided above and below.

The outlets are expediently provided with control devices such as slides or the like , in order to monitor the amount of air circulating through this direct cooling zone and the part that is passed through the indirect cooling zone as secondary air to the combustion or reduction section, depending on the temperature is desired, and for the purpose of equalizing the pressure in the cross section of the cooling zone to be watched, and. The length of the indirect Kfihfaone is limited in order to only cool the product down to a temperature which is not harmful to the product when it comes into contact with the cooling air in the direct cooling zone.

In the recuperator or indirect cooling zone, too, it is desirable to compensate for pressure and temperature differences between the upper and lower part of the tunnel furnace in order to make the heating front steeper. For this purpose, fans are advantageously seen in the recuperator in order to circulate the furnace atmosphere between the top and bottom in the transverse direction to the longitudinal extension of the furnace.

The recuperator is expediently made of pipes made of heat and oxidation-resistant steel formed, wherein the pipe sections run perpendicular Kngs of the side walls. Under the vault of the

mouun

Claims (5)

Oven chamber they are telescopically inserted in sleeves so that they can be easily exchanged from a channel below the oven during operation. If very high temperatures are used in the combustion section and for safety in the event of an interruption of the electrical current, which can lead to a standstill of the high temperature kiln cars, which in turn could cause overheating of the recuperator tubes, the part of the recuperator adjacent to the Brennabscfanitt is preferred made of refractory ceramic material. However, this section should be made as short as possible in order to be able to achieve short furnace lengths, because the heat exchange in a metallic recuperator is more effective than in a ceramic recuperator. The invention is explained in more detail below with reference to the drawings which illustrate an exemplary embodiment of the invention. However, the concept of the invention is not restricted to this exemplary embodiment. 1 is a horizontal and FIG. 2 a vertical longitudinal section through a continuous furnace with cooling sections according to the invention; 3 and 4 show, on an enlarged scale, a vertical and a horizontal longitudinal section through the cooling section; F i g. 5,6,7 and 8 are sections along the lines V, VL, VII and Vni of FIG. 3. In the figures, A denotes the preheating section, B denotes the burning or reduction section and C denotes the cooling section. The Brennwagen are marked with D. They are pushed through the furnace on rails E. In the vicinity of the inlet end of the preheating section, ducts F are provided for the exhaust gases, and the burning or reducing section is equipped with burners G. According to the invention, the cooling section of the continuous furnace consists of a zone for indirect and a zone for direct cooling. In the example chosen, the indirect cooling zone is divided into a ceramic recuperator 10 and a metallic recuperator 12. The zone of direct cooling is denoted by 14. The cooling air for the direct cooling is blown directly into the cooling zone 14, through the inlets 16 by means of a fan 15. The main amount of cooling air is discharged through the lines 18, which with the upper part of the direct cooling zone by means of channels 17 and with the lower part are connected by channels 19. In these channels 17 and 19 control devices 17a and 19a are provided, which serve to monitor and equalize the pressure and temperature differences over the cross-section of the KShteone. Suitable control devices 18 β are also provided in the collecting lines 18 to monitor the proportions of the air which has been used for direct cooling and which are to be removed as heated air in order to draw it through the furnace as secondary combustion air. Cooling air is fed into the metallic recuperator 12 through channels 20 attached below and fed to the metallic recuperator tubes 24. The air is evacuated through ducts or conduits 22 outside the oven. In the example shown, these lines 22 are directly connected to the duct for the heated air that is emitted from the ceramic recuperator zone. As can be seen from FIG. 2, heated air is fed from the recuperator zones to the burners G through line 23. The air supply for direct cooling can be seen particularly clearly in FIG. 7, while the air outlet can be seen in FIG. A suitable design of the metallic recuperator is shown in detail in FIG. The metallic recuperator consists of a series of tubes 24 which are inserted telescopically into sleeves or sleeves 26 of the collecting line 22. With their opposite ends they rest on covers 28 at the end of the inlet channels 20 for the cooling air. This arrangement makes it possible to replace damaged pipes in a simple manner as follows: ao The kiln carriages are pushed apart at the point at which a replacement is to take place, so that the pipes are accessible from the inspection passage 1 below the furnace. The tube to be replaced is lifted off its cover 28, with its upper end being pushed further into the socket 26. The pipe is then twisted so that it can be lowered into the control room, and a new pipe is inserted in a corresponding manner. In order to even out the temperature and pressure of the furnace atmosphere in the recuperator or indirect cooling zone, special means for circulating this atmosphere can be provided between the upper and lower part of the furnace. These means are particularly shown in the section of FIG. 8. The fans 30 suck in the atmosphere from the lower part of the furnace through channels 32 and press it through pipes 34, channels 36 and openings 38 in the vault of the furnace into the upper part of the furnace chamber. In this case, the pipes, ducts and fans are of course made of high-temperature-resistant material. Patent claims: 1. Continuous kiln, in particular tunnel kiln, for reducing iron ore to sponge iron, lined up in a tunnel-like manner and sections in open communication with each other for preheating, firing and cooling, through which the goods are passed on kiln trolleys by dividing the cooling section (C) into a recuperator zone (10 '; 12) for indirect cooling to the burning section is adjacent, and a zone for direct cooling (14), which is adjacent to the furnace discharge end is, which two zones are also in open communication with each other, with the hot end of the direct cooling zone above and below outlet channels (17; 19) are arranged for the direct cooling air. 2. Continuous furnace according to claim 1, characterized by inlet openings (16) on the Oven discharge end with a fan (15) for blowing cooling air into the zone more directly Cooling and by arranged in the hottest part of the direct cooling zone above and below Outlet openings (17; 19) with control devices (17 α; 19 α) for controlling the temperature and pressure between the zone upper and lower part compensating flow are provided in these channels, the channels being connected to a collecting duct (18) for the air heated in the direct cooling zone and this collecting duct is provided with control devices (18 a) for monitoring the total amount of air flowing through the direct cooling zone. 3. Continuous furnace according to claim 1 or 2, characterized in that the Recuperator zone at least partially built as a metallic recuperator (12) and perpendicular to the lower part of the furnace wall In the middle of the vault, the pipes (24) are provided, which are loosely inserted into sleeves (26) of the collecting duct (22) arranged on the vault, and with their other ends loosely sit in the lids of the channels, which are used to supply fresh cooling air, while the rest, the Burning section adjacent part is designed as a ceramic recuperator (10). 4. Continuous furnace according to claims 1 to 3, the furnace atmosphere between the upper and lower part of the recuperator zone to compensate for temperature and Differences in pressure are to be circulated, characterized by ducts (32, 34, 36) provided on both sides, each equipped with a fan (SO), the suction openings of which are located near the upper edge of the kiln carriage (D) and their common openings (38) in the furnace vault are arranged. 5. A method for operating a continuous kiln according to claims 1 to 4, characterized in that the main part of Cooling air withdrawn from the direct cooling zone and only a small proportion of this air required as secondary air in the combustion section through the Recuperator zone is passed to the combustion section. Considered publications: German patent specifications No. 228432, 407247, 537 For this purpose 2 sheets of drawings