DE3905058C1 - Apparatus and process for smelting pig iron and for producing useful gas from fine ore and coal screenings (small coal) - Google Patents

Abstract

This invention relates to a process for smelting pig iron and for producing useful gas from fine ore and coal screenings and an apparatus therefor which is composed of three stages. Figure 1 shows this apparatus. The suspension gas heat exchanger with the cyclones 1, 2, and 3 forms the first stage and reduces fine ore 10 to preliminary sponge 9. The second stage is composed of the matched double turbulence chamber 20 and the hot cyclone 22, which stage prepares the reduction gas 11 for the first stage and delivers the fine sponge 23 which the third stage melts to give pig iron. The carbon dioxide 15 is scrubbed out of the exhaust gas 4 of the first stage and the pure gas 16 is obtained in a manner such that it divides into circulation gas 17 and useful gas 18. A gas circulation results which flows through the first and second stages, the volume of reduction gas 11 always remaining constant and, with this, the output of pig iron. If more useful gas 18 is taken off from the circulation it is necessary to supplement the absent portion of the circulation gas 17. This is achieved with carbon dioxide and/or steam with more coal for cracking and for additional heating. This invention makes sintering and coking superfluous and controls the gas production in desired ranges. For the reasons stated, it is economically superior to the blast furnace. <IMAGE>

Description

This invention relates to an apparatus and a method for melting pig iron and producing useful gas in selectable quantities of fine ore and fine coal according to the Preamble of claim 1.

More than 60 years ago it was proposed to use fine ore and blowing fine coal with oxygen into a melt and then the melted pig iron in the same vessel too fresh to steel. But it stayed the same for decades this suggestion. (German patent 5 08 966 dated June 1924, owner: Eisen- und Stahlwerke Hoesch AG, Dortmund)  

Forty years later, this thought was taken up again on, today a number of proposals are considered. Some of them provide for the required warmth to bring all or part of it into the bathroom as electricity, with With the help of an arc or a plasma. (Examples are the procedures according to Eketorp-Vallak, Elred, Inred and Plasma melt; see Steffen, Rolf: iron production outside of the blast furnace, in metallurgy, part I: iron production, volume 2, Verlag Stahleisen mbH, Düsseldorf 1982, pages 235 to 267, especially pictures 17, 20, 21 and 22.)

Soon you will have the work in one stage, i.e. H. Reduce and Melt in a jar, abandoned. Today you work only on processes with two separate stages. In the The ore is reduced in the first stage and the ore in the second Sponge iron melted down, the pre-reduction with the Exhaust gas from the melting stage is carried out. Fine ore is in the Fluid bed pre-reduced, or as a flight cloud in the so-called circulating fluidized bed, lumpy ore in the shaft ovens. Some procedures are sufficient with a pre-reduction to the desert, others strive for finished sponge iron. (Janke, Dieter and Steffen, Rolf: German-American Seminar on new metallurgical processes for the production of Iron and Steel, Steel and Iron 108 (1988) No. 23, page 24 to 28)

All suggestions provide for the product from the pre-reduction melt in a separate container in the bathroom itself ("Iron bath reactor"). This creates a lot of gas that you use for seeks to use the pre-reduction ("melter gasifier").

Coal with oxygen seems to hold its own for heating, Electricity plays a subordinate role.

So far, no process that provides fine ore has Reduce fine coal and then melt it down Found a way into the factories. Everyone is still struggling with big ones  Difficulties in both reducing and on melt. When pre-reducing, some fine ores tend to Baking ("sticking"). The extent of the pre-reduction, the one that best suits the subsequent melting is still controversial. All suggestions show that when melting a lot of gas leaves the bath, with the slag foaming heavily. The refractory delivery is at risk, especially if the Slag still contains iron oxide. Works particularly violently of if less metallized sponge iron is melted down. So far, you have not been able to do this mastering complex events sufficiently, even less, to control it satisfactorily.

In this situation, the invention is based on the object a process based on fine ore and fine coal To create smelting reduction, the shortcomings mentioned mastered options and at the same time useful gas in selectable Produces quantities.

This problem is solved with the features of Claim 1, further embodiments of the invention result from the subclaims.

An embodiment of the invention is explained using the system outlined in Figure 1.

It shows the three Stages of this process.

In the first stage, the fine ore is heated in a floating gas heat exchanger by the counter-flowing reducing gas and at the same time pre-reduced. This floating gas heat exchanger consists of the cyclones 1, 2 and 3 with their risers 4, 5 and 6 and their downpipes 7, 8 and 9 .

The fine ore 10 is fed to the riser 5 of the cyclone 2 , separated from the gas in the cyclone 1 and it leaves it in the down pipe 7 . The fine ore is heated during this mixing and separation. The warm fine ore from the downpipe 7 reaches ge in the hotter gas of the riser 6 of the cyclone 3 , with it in the cyclone 2 , in which it is separated. With the downpipe 8 and in the riser 11 it enters the cyclone 3 , which it leaves with the downpipe 9 .

When heating in risers 5, 6 and 11 and in cyclones 1, 2 and 3 , the fine ore is progressively reduced to the extent that it is predominantly metalized in the down pipe 9 ("pre-sponge"). The decomposition of carbon monoxide to soot and carbonic acid is also noticeable.

Figure 1 outlines a floating gas heat exchanger with only three cyclones. Equipped with four or five cyclones connected in series, these extend the heating and reduction of the fine ore over a longer distance, improve the metallization and reduce exhaust gas losses.

The used reducing gas in the riser 4 (the exhaust gas) is cleaned in the deduster 12 and reaches the carbon dioxide scrubber 14 , in which carbon dioxide 15 is separated off, as machine-fine gas 13 . The clean gas 16 is divided into circulating gas 17 and useful gas 18 . The circulating gas 17 is fed to the flame gasifier 20 , a characteristic gas circuit is created which flows through the first and the second stage.

In the second stage, the preliminary sponge from the downpipe 9 with the recycle gas 17 and with the oxygen 19 is introduced into the flame gasifier 20 . The hot reducing gas 26 is admixed with fine coal 29 before it enters the flame gasifier 20 , which carbonizes into fine coke in the heat of the gas 26 . In the riser 21 , fine sponge and fine coke with the reducing gas leave the flame gasifier 20 and enter the hot cyclone 22 . They are separated in it, fine sponge and non-gasified fine coke leave it in the downpipe 23 in order to enter the flame melter 25 mixed with the oxygen 24 .

The third stage, in the flame melter, is used for melting. Fine sponge and fine coke from the downpipe 23 are mixed with the oxygen 24 and fed to the flame melter 25 . Pig iron and slag 32 are tapped from it as usual. The hot exhaust gas 26 is fed to the second stage.

According to the invention, the pre-sponge from the downpipe 9 is completely reduced in a flame in which fine coke is gasified at the same time. According to the invention, the finished fine sponge from the downpipe 23 is also melted in a flame. After the partners have been properly mixed before and during the firing, local overheating is not possible because the heat from the combustion is distributed to all participants as soon as it is created. It has been found that the double vortex chamber known per se is very well suited for both of the above-mentioned works in that it keeps both the gasification with the finished reduction and the melting down stable.

Figure 2 shows the second stage.

It outlines the work of the flame gasifier 20 , which approximately has the shape of a truncated cone as a double swirl chamber. Vorschwamm from the downpipe 9 , circulating gas 17 and oxygen 19 are mixed and at the same time introduced tangentially into the flame gasifier 20 at its upper, narrow end. The momentum with which this mixture enters the chamber causes its vigorous rotation around the longitudinal axis. (This vortex is not outlined in Figure 2.) This creates a central backflow axially, which is amplified in it by the hot gas 26 coming from the flame 25 and the fine coke from the fine coal 29 . The interface between wall and backflow (between upstream and downstream flow) becomes an annular flame 27 , which quickly circles around the longitudinal axis. The turbulence is strongest within this ring flame, which is why all chemical reactions take place very quickly, especially the processes between the gases and the solids suspended in them.

According to the invention, the gas 11 required for the pre-reduction is prepared in this double swirl chamber, at the same time the reduction of the pre-sponge 9 to fine sponge is fully carried out in it, the ring flame 27 of the flame gasifier 20 completing both processes.

Figure 3 shows the third stage.

It outlines the work of the flame melter 25 , which is also a double swirl chamber. At the upper, narrow end, fine sponge with fine coke from the downpipe 23 , oxygen 24 and lime 33 are mixed and introduced tangentially with sufficient impulse, so that an annular flame 30 forms, in which iron and slag melt. With the lime 33 , other slag formers are given up to the flame melter 25 . A bath 31 , which always boils during the process, collects on the floor. Its bath level of different heights, even its occasional foaming, does not disturb the stability of the ring flame 30 . The tapping 32 delivers, in batches or continuously, pig iron and slag in the usual way. Little hot gas 26 is produced during the process. In its heat, the fine coal 29 is carbonized when it enters the flame gasifier 20 .

In the heat of flame melter 25 , alkalis (potassium and sodium), also zinc and lead, evaporate. Downstream of the gas flow, in the colder areas of the second and first stage, these pollutants condense and / or sublimate. With the pre-sponge from the downpipe 9 and the fine sponge from the downpipe 23 , condensate sat and / or sublimate return to the flame melter 25 , in which they evaporate again. A cycle is created in which all pollutants accumulate. After a short time, too much condensate and / or sublimate is formed, which leads to approaches that endanger operation.

According to the bypass ("by-pass") 34 reduces all the disadvantages that the cycle of pollutants causes to a tolerable level by taking part of the hot exhaust gas 26 , cleans it and uses it as a carrier gas for the fine coal 29 . At the same time, this procedure allows the residual dust 28 which arises in the gas cleaning 12 to be fed to the flame melter 25 . When cleaning the small amount of gas from the bypass 34 , you get a dust that contains a lot of zinc and a lot of lead in addition to alkalis and is therefore easier to work up.

This invention makes it possible to remove the useful gas 18 in varying amounts while the melt is running, without changing the output of pig iron. If more useful gas 18 is branched off, then the circulating gas 17 and with it the gas quantity 11 decrease. The first stage, however, requires that the amount of gas 11 remains unchanged. Consequently, fresh gas must be prepared in the flame gasifier 20 from the oxygen 19 , from the fine coal 29 and from carbon dioxide and / or water vapor (not sketched in Figure 1) in order to supplement the missing circulating gas 17 and to keep the gas quantity 11 the same. The remaining wustite in the pre-sponge from the downpipe 9, such as carbonic acid and / or water vapor, acts as an oxygen carrier for the gasification.

This process works advantageously with overpressure in all three levels. In the flame melter, 5.0 bar is still good dominate.

Fine ore under 0.2 mm can be processed well, little Oversize does not bother.

Fine coal should be dry ground to less than 0.2 mm, Varieties with a higher ash content should be finer. The lime should be ground to less than 0.2 mm, including that remaining slag generator.

A temperature between 800 and 1200 ° C. can be selected in the flame gasifier 20 .

Pig iron is smelted between 1300 and 1650 ° C in the flame melter 25 .

This invention offers a number of economical Advantages:

The cost of the plant is significantly lower than that conventional blast furnaces, mainly because of sintering and coking and because the throughput time of the raw materials is very low is short.

The operating costs are also lower, mainly because raw Fine ore and raw coal are processed.

Environmental protection is easier: there are no toxic wastewater to dispose of, no nitrogen oxides are generated.

All operating materials can be conveyed pneumatically and dose. The residual dust is recyclable.

Claims (5)

1. Device for melting pig iron and for producing useful gas in selectable quantities from fine ore and fine coal in three stages, the first stage being a floating gas heat exchanger for the pre-reduction, characterized in that both the second stage as a flame gasifier and the third stage as Flame melters are double swirl chambers. 2. Process for melting pig iron and for Production of useful gas in selectable quantities in three Stages, whereby in a first stage the fine ore in a suspended gas heat exchanger to a partial metal pre-reduced iron sponge, characterized in that in a second stage, which is also fine coal at the same time Converts reducing gas, the sponge iron reduced to fine sponge in a flame gasifier is adorned, and in a third stage the Fine sponge in a flame melter to cast iron is melted down.   3. The method according to claim 2, characterized in that carbon dioxide removed from the exhaust gas of the first stage and part of the reduction gas thus obtained is fed to the second stage. 4. The method according to claim 3, characterized in that within the gas cycle from the exhaust gas of the first Commercial gas level in selectable quantities is withdrawn, the amount of gas withdrawn in the second stage, in the flame gasifier, by gasifying additional fine coal with carbon dioxide and / or Water vapor is balanced. 5. The method according to claims 2 to 4, characterized in that the exhaust gas from the third stage, the flame melter, a part is removed, which after being removed from the Pollutants is cleaned as a conveying gas for the Fine coal is used.