DE2935466A1 - METHOD FOR REDUCING METAL OXIDES AND DEVICE FOR IMPLEMENTING THE METHOD - Google Patents

Description

16. The device according to claim 12, characterized in that the vacuum device is a suction device and a monitoring device for automatically influencing the suction device as a function of the Has pressure on the underside of the retort.

17. The device according to claim 16, characterized in that the suction device consists of a water jet pump consists.

18. The apparatus according to claim 12, characterized by a pressure relief valve in the gas exhaust pipe and by a Washing device for washing the gases flowing through the gas exhaust pipe and the washed-out sludge leads away.

030017/0613

LudwigshaΓen / Rhine, August 29, 1979 P 5 ^ 34 Dr. K. H / ber

-L 2335466

Representative:

Patent attorneys

Dipl.-Ing. Adolf H. Fischer Dipl.-Ing. Wolf-Dieter Fischer Kurfürstenstrasse 32 67OO Ludwigshafen / Ehein

Deposits:

Danieli & C.
Officine Meccaniche SpA 33042 Buttrio (Udine) Italy

030017/0613

Process for Eeduktion of metal oxides and before direction; for the implementation of the procedure

The invention relates to improvements in the reduction of metal oxides, particularly ores and pelletized Materials, with a solid reducing agent.

In the field of metallurgy there are a large number of processes for the reduction of minerals and pellets that consist largely of metal oxides and in particular of iron oxides. In different solutions these are oxides at a high temperature with reducing agents such as carbon monoxide, hydrogen (gaseous reducing agents) or coal (solid reducing agent) treated.

The common basis of all these processes is the creation of an atmosphere consisting of a suitable mixture of these gases (CO and H ₂ ), obtained from hydrocarbons of various compositions or from coal, and the treatment of the oxides with these gas mixtures at the highest possible temperatures which, due to the melting point of the oxides or the ashes or the gangue materials combined with the oxides, must not be exceeded. The reason for this is that agglomeration of the feed, which prevents discharge of the feed, must be avoided. Among the industrially used processes there are those which are operated with solid reducing agents (coal) and which are relatively simple, since coal is readily available in comparison to other energy sources and, in addition, since coal is in direct contact with the oxides to be reduced at high temperatures special reducing power unfolds.

In the processes described above, the reducing effect is achieved in two ways: directly through the intimate one Contact of the carbon with the oxide to be treated

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bound oxygen and indirectly between the carbon oxide gas that is produced in the direct reduction reaction with the in Oxides present oxygen is formed. Since in these processes there is always an excess of coal present and the temperature is always in the region of 1000 - 1200 ° C is, carbon dioxide, which can form from the carbon monoxide (indirect reduction), is again according to the known Formula CO- + C - * 2CO split into carbon monoxide. It follows that further carbon monoxide is formed in the indirect reaction.

Of course, the carbon dioxide is produced in the direct reduction reaction (between the carbon and the oxide oxygen) can also be formed to form a reducing Contribute carbon monoxide gas, as mentioned in the previous paragraph.

The reduction treatment which takes place in a known vertical retort furnace can be more easily understood with reference to FIG. 1, which shows a vertical section through such a furnace type. A feed consisting of a ^{mixture of} minerals and coal in the form of pellets and possibly a desulphurizer is fed via a chute 1. In an upper zone 2, the feed is dried with the formation of steam, the feed is preheated and the volatile constituents in the coal are distilled off. In this zone, the gas generated by the reduction reaction in the lower part of the retort flows through the feed.

In a lower zone 3, the actual reduction takes place through the direct action of the coal and indirect reaction by the action of carbon monoxide. Unless for special reasons hydrogen or hydrogen-containing Gas through a pipe 13 through the entire retort (zones 4

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and 3) there is only carbon monoxide gas. The carbon oxide concentration is determined by the kinetics of the reaction CC> 2 + C <± 2CO given. It should be noted that with the mentioned operating conditions at the bottom of the retort the gas has an almost constant composition and that its analysis depends on the reactivity of the oxides to be treated, while its pressure depends on the altitude and geometry of the retort, by the grain size of the feed and by the amount of gas expelled at the top, the is a function of the gas formation in the various retort sections is determined.

The movement of the reaction gases thus runs in countercurrent to the descending charge upwards, with their speed gets bigger and bigger as you ascend.

From the foregoing discussion it follows that the oxides are unchanged at the top of the neck and that they are in their descending order Movement give their oxygen to the solid reducing agent, with the reaction gases as a carrier between the Inside the mineral pieces or "pellets" and the reducing ones Coal, which is always present in the feed up to the bottom of the retort, has an effect. In other words that means in the upper zone the oxides are in intimate contact with a considerable amount of coal and a substantial amount of gas, that flows up from the retort stand, while at the bottom of the retort only a small amount Coal and are in contact with an almost stationary gas phase.

It should also be pointed out that the gas quantities involved in the process are relatively small and that their contribution to the preheating of the charge in the upper part of the retort is quantitatively negligible is.

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; t -

From a consideration of the known arrangement of Figure 1 it can be seen that the heating of the feed and the supply of heat occur for the reaction by the burner 9, so that during the discharge of the combustion products from the top of the post that is provided by the gases for heating, above is very high, but decreases downwards. The combustion products of all lower burner contribute to the heating of the retort? in addition to the thermal radiation emanating from the individual burners. The feed is cooled in a zone marked 4 in order to prevent new oxidation and to allow the excess coal to be separated off. Zone 5 is used for discharging the feed. This zone 5 is gas-tight. Through a suitable funnel 8 and a pusher 6, the load arrives on a conveyor belt 7. Arrows 14 show the descending movement of the load? and arrows 11 show the ascending movement of the reaction gases. The arrow 10 stands for the entirety of the reaction gases, the vapors emanating from the feed during drying and coal distillation. These gases are vented to the atmosphere or burned in a torch or otherwise used.

To understand the present invention, it is only necessary to examine the gases 10 released by the retort in more detail. Such an investigation must be based on theory and actual practice.

The most commonly used solid reducing agent for "such." Reduktxonsprozesse is the youngest coal, which has the highest percentage of volatile components. In addition, it must be considered that the overall analysis of the volatile components of such coals is the Presence of a large amount of hydrogen, methane and others Hydrocarbons results, which at high temperatures the

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Show tendency to split into hydrogen and active coal.

An examination of many known solutions in the past few years in this area has unequivocally a preference for the Properties of the above coal result, in particular because of their volatile constituents, since the The presence of hydrogen in the reducing gas significantly improves their effectiveness.

In view of the above facts, there are many known solutions in which the reaction gases in any one Way to be collected, this treated and then introduced under pressure to the bottom of the retort after they have been preheated if necessary. Even if this is technically possible, it must be very complicated arrangements are provided in the plant, with a view to the nature of the reduction process, its optimization operation at temperatures at the limit values of the Requires sintering temperature of the charge. In addition, it must be remembered that the feed losses and thus the pressure at the bottom of the retort in a square Relationship with the capacity. But in order not to increase this value too much and thus the gas tightness To impair the retort, it is opportune to make extensive use of the reducing gases.

On the basis of the known solutions to this problem and the above considerations, the main aim of the invention is to under Utilization of the simplest technology to fully and efficiently use the reducing power of the applied coal and to allow a free hand in the utilization of the reaction gases, whereby their reuse, if necessary. can be considered for heating the same system,

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The basic concept of the present invention is to provide a stream of distillation and reaction gases to create with the same flow direction as the feed, wherein the retort can be operated with a positive gas pressure or with a negative gas pressure.

If a retort with positive gas pressure is used, then the loading must be through a double chamber are introduced with gas-tight valves, the gas output being naturally due to a spontaneous equilibrium takes place, as is the case with the known systems, but with the outlet opening on the underside of the retort is in a conveniently selected location. If negative pressure retorts are used, then a will be generated Ventilate the necessary vacuum so that no gas escapes from the feed throat.

Another variant is to improve reliability and safety of the plant a gas-tight system in the loading zone by injecting a non-combustible Generated gas.

Carrying out the method according to the invention, wherein all rivers going in the same direction offers the following important advantages:

1. The water contained in the charge is even if the charge is not preheated, converted into steam and thus into water gas, and is water gas very flammable and is a particularly good reducing agent.

2. All coal distillation products consisting predominantly of hydrogen exist, contribute effectively to the reduction of oxides; the treatment is continued throughout the reduction cycle occur.

3. There will be an increase in "washing" to reduce the

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the minerals in proportion to the decrease in their reducibility.

4. There will be an increase in the reducing gas / coal exchange as a function of the smaller amount of coal that is in the descending order Loading 'is present.

5. An increase in heat exchange is obtained in the zones of greater reduction.

6. It is possible to have a gas at the bottom of the retort

to achieve which has a good calorific value and which falls in such an amount that all energy needs are the same Plant can be satisfied.

The invention will now be explained in more detail with reference to the accompanying drawings. In the drawings show: *

FIG. 1 shows a section through a known retort furnace for carrying out the known Reduk described above tion s procedure s;

FIG. 2 shows a section through a vertical retort furnace which can be used for carrying out the reduction process according to the invention;

- Figure 3 shows a section through a modified compared to Figure 2 vertical retort furnace; and

FIG. 4 shows a further section through a vertical retort furnace modified compared to FIG.

Figure 2 shows a retort furnace according to the invention, in which the gases in the same direction as the charge stream. The gases under pressure within the retort are withdrawn through a tube 20 which is in a cooling jacket 21 of a container 32 is arranged. From an upper one

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"- 15 -

In feed device 22, a batch K is admitted into a gas-tight space 24 via a slide 23. After the required amount in the space 24 is included-t _f is closed, the slide 23 and a slider 25 ,. which leads to a lower room 2β, open »The room 26 is equipped with walls 27 which have a fireproof lining. This process can take place with a timed or otherwise automatically functioning device as a function of the desired loading quantity.

On the way down, the load gradually enters a retort S. In a first part 28 of the retort, the load is gradually brought to a high temperature and completely dried. Volatile constituents of the coal are distilled off in the process. All gases and vapors, in the absence of any other vent, are led down, passing through the entire charge of the retort. Suitable temperatures are generated by a battery of burners 29, 30 _R 31 F in a furnace, comprising the various zones of the retort.

The retort has a - "Eleven tower ^11" profile so that the charge does not get stuck in the retort. The cross-section becomes larger and larger, as the gas flow and the compactness of the charge also increase. The increasing flow velocity of the gases through the charge improves the thermal conductivity of the mass considerably, especially in the zone where temperature homogeneity is more "" important,

At the bottom of the retort, the charge is cooled in the container 32 provided with the cooling jacket 21. A branch 33 leads away from the container, through which the gases pass into the pipe 20, from where they are guided to a predetermined point. The tapping of the finished product at the end of the process can be done in any way, for example with a screw conveyor 33a, which is a

030017/0613

gas-tight chamber 34 is charged with a slide 35, followed by a further gas-tight chamber 36 with a slide 37 connects. A conveyor belt 38 is periodically fed through the slide 37.

The above embodiment of a retort furnace that works with gas pressure requires, for obvious reasons, a retort with a good gas seal and good pressure resistance .

The gas exiting at the opening of the tube 20 has sufficient pressure that it can be used for various purposes can be. It contains all of the available sensible heat.

Figure 3, in which the same or corresponding parts Have the same reference numerals as in Figure 2, shows a variant with the same working scheme, with a rectified Flow of gases and feed is achieved by means of an exhaust fan 42 which is at the bottom the retort is arranged.

Compared to the solution shown in Figure 2, it can be observed that the charging with the charge K simply by gravity takes place, whereby the desired loading level in the retort S is maintained. Loading becomes easy inserted into an upper feed throat BC of the retort. In contrast, the reaction gases from the lower Exit tube 20, be cooled in a suitable heat exchanger 39, which is cooled by cooling liquid, the enters at 40 and exits at 41. The reason for this is loosing in that the exhaust fan 42 cannot withstand higher temperatures. It is also essential to have a throttle valve in the pipe 20 43 to be provided, which is regulated by a suitable device, so that the retort at the feed throat BC the pressure is kept near zero.

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In the embodiment described above, it is practically impossible for reducing gases to be lost in the flow to the combustion chamber unless the retort is completely sealed. The reducing gases are diluted by the combustion products of the burners 29 , 30, 31. The need to cool the exiting gases results in a loss of sensible heat and rather difficult control of the retort pressure. On the other hand, can the exhaust fan 42 give the gases a pressure? which is sufficient to lead the gases to consumers located further away.

The embodiment of Figure 4 aims at a gas flow in the same direction as the feed, without the need for mechanical slides, the sealing difficulties due to the formation of deposits and the risk of overpressure in the retort can bring. According to this embodiment, an artificial negative pressure is created in the upper zone of the retort, i.e. in the feed zone, caused by the injection of an appropriate amount of a non-combustible gas. At the same time, a small negative pressure is generated to prevent the reaction gases from flowing into the interior of the retort to facilitate.

The figure shows that the batch K is fed via a suitable metering conveyor 50 to a hopper 51 which is shaped so that the feed enters a sufficiently narrow vertical tube 52. The tube 52 is connected to the upper part of the retort S by a tight coupling G, which the? happy expansion of the retort without exerting a pressure !? on uen funnel 51 is permitted.

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Ensure delivery. The top of the retort is wider provided with a side exhaust gas burner 54, which in turn is equipped with a throttle and locking slide 54a which is controlled by an automatic oleodynamic system 54b. Small amounts of reaction gases can escape from the burner 54. For ecological reasons, they are in a Burned torch. After the batch K has entered the upper part of the retort S and dried and preheated it is preheated by the burners of oven F on its way down. The ascending combustion products are directed into a pipe 55 through valves 56 and 57, which can block and throttle to regulate the heating in the high zone of the retort. The products of combustion are then directed to a chimney 58.

After the treatment in the retort, the charge is cooled by means of a cooling jacket 59 and continuously passed through a snail discharged. The entire material collects on a slide 61 and is then with the help of a further slide 63 and a conveyor belt 64 removed.

A vertical tube 65 leads away via the slide 61, which is equipped with a pressure relief valve 65a. The tube is fed through an ejector 67, which is injected with water is operated via a trunk 68, kept at a slight negative pressure. The negative pressure is created by a special Control valve 69 regulated with great accuracy. The control valve 69 receives the signal from a probe 70, the at the bottom of the retort protrudes into it. The reaction gases are thus sucked off by the ejector 67 and washed through this. The dust is caught in a channel 66 and discharged as sludge. The gases flow to a pipe 71 and at 72 atiü serve out.

iJ Ί Ο U 1 7 M). 1 Ϊ

With the variant just described, the following advantages are obtained:

- The regulation of the pressure conditions at the top and bottom of the retort is relatively easy to obtain all or part of the flow rectified with the feed;

- Mechanical locking parts (slides) are missing on the top of the retort;

- it is extremely easy to switch from the usual gas flow direction to a direct current with the feed, by raising the level of the liquid in channel 66 and opening gate 54a;

- By shutting off the valves 56 and 57, the thermal load can be regulated.

030O17 / O613

Claims (15)

PATENT CLAIMS: 1. Process for the reduction of metal oxides, in which Pellets of the metal oxide are heated in a retort in the presence of a solid reducing agent, thereby characterized in that the gaseous reaction products are at least partially in cocurrent with the direction of flow the loading. 2. The method according to claim 1, characterized in that loading through a substantially gas-tight retort with a gas outlet on its underside at the bottom, the gas escaping due to a spontaneous equilibrium at the bottom the retort takes place. 3. The method according to claim 1, characterized in that the feed through a retort with a negative internal pressure down caused by an exhaust fan on the underside of the retort will. 4. The method according to claim 1, characterized in that a non-combustible gas in the charging zone at the Top of the retort is inserted to make the top of the retort gas-tight. 5. The method according to any one of claims 1 to 3, characterized in, that coal and / or reactive coke is used as a solid reducing agent. 6. The method according to claim 1, characterized in that the steam produced by drying the charge is passed in cocurrent through the entire feed in the retort, so that the steam in the reducing and combustible water gas is transferred. 030017/061 « _DL ^ f ^, 7. The method according to claim 1, characterized in that the high calorific value gas obtained from the retort is used as combustion gas for another purpose will. 8. Apparatus for performing the method according to claim 2, characterized in that it includes the following parts having: at least one retort; first and second loading chambers at the top of the retort; first and second gas tight barriers at the bottom of the first and second chambers, respectively; a gas discharge pipe on the underside of the retort for the discharge of the gas in co-current with the feed flowing gases; a heater for the retort; cooling means for cooling the charge exiting the retort; and a discharge device for the largely gas-tight Discharge of the charge. - 9. Apparatus according to claim 8, characterized in that the discharge device comprises the following: a screw conveyor; a first discharge chamber at the end of the screw conveyor; 030017/0613 a second discharge chamber at the outlet of the first Discharge cameraman; a first gas-tight barrier means between the first and second chambers; and a second gas-tight barrier at the outlet of the second Discharge chamber. 10. The device for "carrying out the method according to claim 3 _t characterized in that it has the following parts: at least one retort with an open feed throat at the top a loading device for direct loading by gravity into the loading throat of the retort? a gas discharge tube on the underside of the Retorteι an exhaust fan in the gas exhaust pipe; a heat exchanger in the gas exhaust pipe upstream " of the exhaust fan to cool the flowing through Gases? dine throttle device for regulating the pressure on the feed neck of the retort a retort heater; a cooling device for cooling the emerging from the retort. Feed; and 030017/0813 a discharge device for the largely gas-tight discharge of the charge. 11. The device according to claim 10, characterized in that that the discharge device comprises the following: a screw conveyor; a first discharge skairaner at the end of the screw conveyor; a second discharge chamber at the outlet of the first discharge chamber; a first gas-tight barrier means between the first and second chambers; and a second gas-tight locking device at the outlet of the second discharge chamber. 12. Apparatus for performing the method according to claim 4, characterized in that it is the following Has parts: at least one retort; a feed tube connected to the top of the retort by a tight expansion coupling; a feed hopper on the inlet side of the feed pipe; a tube that opens into the feed tube; an injector for injecting a non-combustible gas into the retort through this tube; 030017/0613 a heating device for the controlled heating of the retort; a cooling device attached to the bottom of the retort is connected in a gas-tight manner and is used to cool the charge emerging from the retort; a gas exhaust pipe which is arranged in the region of the cooling device; a negative pressure device in the gas suction roller for the Generating a controllable negative pressure in this pipe; and a discharge device for the gas-tight discharge of the charge. 13. The apparatus according to claim 12, characterized in that the discharge device has at least one screw conveyor, at least one collection and discharge chamber and a shut-off device at each collection and discharge chamber having. 14. The device according to claim 12, characterized in that it has at least one lateral reaction gas vent which is attached to the top of the retort and which in the event of overpressure in the retort can be used. 15. The device according to claim 14, characterized by a locking and throttle slide in the reaction gas vent for changing and regulating the amount of reaction gas that flows down in the retort. 3 0 0 17/0613