CN1064084C - Method and apparatus for producing reducing gas for reducing metal ore - Google Patents

Abstract

Production of a gas containing CO and H for reducing lumpy metal ores, especially iron ores₂By gasification of carbon carriers, in particular coal, under oxygen supply conditions, a reducing gas is formed in the gasifier (8) and subsequently cooled to a reducing gas temperature which is favorable for the reduction process. For producing a thermodynamically more stable reducing gas by adding H₂O and/or CO₂The reducing gas is converted into a more thermodynamically stable reducing gas at the reducing gas temperature in order to prevent the Bowden and multiphase water-gas reaction and the resulting heating of the reducing gas.

Description

Method and apparatus for producing reducing gas for reducing metal ore

The invention relates to a method for the production of a reducing gas for the reduction of massive metal ores, especially iron ores, wherein, in a gasification zone, gasification of a carbon carrier, especially coal, takes place in the presence of oxygen to form The reducing gas is then cooled to a reducing gas temperature convenient for use in the reduction process. The invention also relates to apparatus for carrying out the method.

Processes of the type mentioned at the outset are known, for example, from DE-C-3034539 and EP-B-0114040. With these known methods, pig iron or steel pre-products are obtained from at least partly pre-reduced sponge iron by smelting in a melter-gasification zone with a supply of carbon carriers and an oxygen-containing gas, and also produce CO-containing and _H2 as reducing gas. The temperature of the reducing gas formed in the melter-gasification zone is in the range of 1000-1200°C. At this temperature, the released hydrocarbons decompose. At the same time, based on this temperature, _CO2 and _H2O are transformed into CO and _H2 , so their content drops to below 6% _CO2 and 4% _H2O .

To be usable in the reduction reactor, this very hot reducing gas must be cooled before it is introduced into the reduction reactor. According to DE-C-3034539, for example, a spray cooler which is connected to the subsequent dedusting tower is provided for this purpose. Part of the reducing gas thus cooled is mixed into the reducing gas coming out of the melter-gasification zone. This cooling of the reducing gas to about 700-900°C, which is carried out in a conventional manner with the same kind of cooled reducing gas, prevents the ore particles from being reduced to the primary melt in the reduction zone during its reduction, but The reducing potential of the reducing gas is not lowered.

Disadvantageously, such cooled reducing gas is thermodynamically unstable; just as the reaction of CO and _H2 to generate _H2O and C occurs in heterogeneous water-gas equilibrium, CO is generated from CO in Bowers equilibrium ₂ and C, this reaction is also exothermic like the reaction described at the beginning. This increases the temperature of the reducing gas and thus also the temperature of the shaft furnace charge. Clumping will also form. Thus, not only the reduction process is disturbed, but also the yield of the shaft furnace charge from the reduction zone is affected.

A method is known from FR-A-2236951, wherein the hot reducing gas formed in an electric furnace is introduced into a reduction shaft furnace directly above the Cooling with steam, carbon dioxide, hydrocarbons or other cooling media in order to prevent agglomeration of the material containing metal oxides in the reduction shaft furnace. The CO ₂ - and H ₂ O contents of the reducing gas thus cooled are relatively high.

A method is described in FR-A-766167, wherein the hot reducing gas formed in a melting device is directly introduced into a reduction chamber, wherein in the vault area of the reduction device, ie before being introduced into the reduction chamber , or by introducing spent reducing gas from which carbonic acid has been removed, or by introducing a mixture of carbonic acid or water vapor and carbon, the hot reducing gas is cooled in order to avoid agglomeration of the charge in the reduction chamber.

The present invention aims to avoid these disadvantages and difficulties, and its object is to provide a method of the type mentioned at the outset and an apparatus for implementing the method, which can produce a reducing gas whose temperature is in a range favorable for the reduction of metal ores, thereby also It is to keep the temperature of the reducing gas below the temperature at which incipient melting and clogging (agglomeration formation) etc. occur in the at least partially reduced metal ore. Furthermore, chemical attack on metallic materials in the gas delivery system, ie reactors and gas pipelines, internals etc. will be avoided.

This object is achieved by means of the type mentioned at the outset: To prevent the Bowman reaction and the heterogeneous water-gas reaction, and the resulting heating of the reducing gas and thus of the metal ore, by adding H ₂ O and/or CO ₂ converts a reducing gas that has undergone cooling not caused by adding H ₂ O/CO ₂ to the reducing gas to a reducing gas that is thermodynamically stable at the temperature of the reducing gas.

By purposely adding H ₂ O and/or CO ₂ , the thermodynamically induced decomposition of the reducing agents CO and H ₂ is influenced or prevented in a targeted manner. The concentration range of the reducing gas is adjusted, under which the strongly exothermic Bowman reaction and the heterogeneous water-gas reaction can be suppressed, so that the temperature of the reducing gas does not increase excessively. At the same time, the oxidation degree of the reducing gas is controlled by this method, and the chemical attack on the metal material is suppressed.

Advantageously, the amount of _H2O and/or _CO2 added is such that Bowman and heterogeneous water-gas equilibrium of the reducing gas is almost reached at a temperature favorable for the reduction reaction.

Cooling of the reducing gas may be advisable by adding similar cooling gases, top gas and/or _H2O and/or _CO2 .

It is suitable to add _H2O by adding steam and add _CO2 by adding _CO2 -containing gas.

According to a preferred embodiment, the feeding of CO ₂ into the reducing gas can be carried out at least in part by feeding the reducing gas reacted during the reduction of the metal ore, the so-called top gas, into the reducing gas. Other CO ₂ -containing gases, such as gases from CO ₂ purification processes, may also be used.

In order to achieve an intensive cooling of the reducing gas, it is advantageous to mix into the reducing gas a cooled reducing gas of the same kind, as known from the prior art, while H ₂ O and/or CO ₂ are added to the cooled reducing gas gas and/or the hot reducing gas from the gasification reactor.

The equipment for carrying out the method comprises at least one reduction reactor with a metal ore delivery pipe extending therein and a reducing gas conduit extending therein, and a gasification reactor with a gasification reactor extending therein The carbon carrier delivery pipe and the oxygen-containing gas delivery pipe and a reducing gas conduit leading therefrom, with a reducing gas conduit that is not cooled by adding H ₂ O/CO ₂ to the reducing gas Cooling device, the device is characterized in that a source of CO ₂ and/or H ₂ O is connected in flow communication with the reducing gas pipe for conveying reducing gas which has undergone a cooling.

The reduction reactor is advantageously provided with a top gas discharge pipe for carrying away the reacted reducing gas, from which branch a branch pipe is connected in flow communication with the reducing gas pipe.

Another preferred embodiment is characterized in that there is a reducing gas recirculation pipe starting from the reducing gas pipe, passing through a scrubber and a compressor and then extending into the reducing gas conduit, but viewed along the flow direction of the gas, it is in the reducing The upstream part of the branching point of the gas recirculation pipe, in particular upstream of the dedusting device arranged in the reducing gas pipe, is also characterized in that the source of _CO2 and/or the source of _H2O communicates with the reducing gas conduit connected.

The invention will now be described in detail with reference to the embodiment shown schematically in the drawing, which schematically shows an advantageous embodiment of the device according to the invention.

Lumped iron ore and/or pelletized iron ore are subjected to moving bed conditions from above, via conveying means such as conveying pipe 2, via a ram system (not shown), optionally together with flux material The stone is added to the first shaft furnace forming the reduction reactor 1.

The term "moving bed" is understood to mean a continuously moving stream, the moving particles of which are in contact with the reducing gas stream. It is desirable to utilize a material flow that is continuously moving downward due to gravity.

Instead of the shaft furnace 1, it is also feasible to use a reactor with a moving grate or a rotary tubular kiln as a reduction reactor.

The shaft furnace 1 communicates with a melter-gasifier 3 in which a reducing gas is formed from a solid carbon carrier such as coal and an oxygen-containing gas, which passes through a line 4 and a gas cleaning device 4 optionally provided in the line 4 ' is supplied to the shaft furnace 1, and the device 4' is used for dry dust removal.

The melter-gasifier 3 has means 5 for supplying a solid carbon carrier, an oxygen-containing gas delivery pipe 6 and optionally a pipeline 7 for supplying a carbon carrier that is liquid or gaseous at room temperature, such as hydrocarbons and calcined flux. Inside the melter-gasifier 3 , molten pig iron 9 and molten slag 10 are collected under the melter-gasifier 8 and discharged through a discharge port 11 .

Together with the flux calcined in the reduction zone 12, the iron ore that has been reduced to sponge iron in the reduction zone 12 passes through the conveying pipe 13 connecting the shaft furnace 1 to the melter-gasifier 3, e.g. by means of a screw feeder. wait to be introduced. A top gas discharge pipe 14 for discharging top gas formed from reducing gas in the reduction zone 12 is connected to the upper part of the shaft furnace 1 .

The top gas drawn off via the top gas discharge line 14 is firstly cleaned in a scrubber 15 in order to render it as completely free of dust particles as possible and to reduce its water vapor content for subsequent further utilization.

A part of the reducing gas is recirculated back to the pipeline 4 through the deduster 16, and then through the recirculation pipeline 17 provided with a compressor 18, so that the reducing gas in a very hot state from the melter-gasifier 3 is recirculated in its Before entering the gas cleaning device 4' it is conditioned, in particular cooled to a temperature range favorable for the reduction process in the shaft furnace 1 (approximately 700-900° C.).

Reference number 19 designates the most important points of the above-mentioned equipment, where it is possible in a particularly advantageous manner to connect to a _CO2 source and/or a _H2O source, in particular to feed in a _CO2- and/or _H2O -containing gas, Their action will be fully explained hereinafter with reference to Examples II-IV. The feed point 19 can be located either on the line 4 connecting the melter-gasifier 3 to the reduction reactor 1 or in the reducing gas cooling loop 16 , 17 , 18 . If the feed point 19 is located downstream of the compressor 18 in the cooling loop 16, 17, 18, then some advantages arise, as the compressor 18 can be smaller and the gas which has been heated due to compression can be fed in _H2O and/or _CO2 cooling.

The effects of the above-mentioned measures in the present invention are illustrated with reference to Examples I-IV. Example 1 only describes the prior art. All values listed in Gas Analysis are expressed in percent by volume. Embodiment I:

The analytical values of the reducing gases produced according to the prior art, e.g. according to EP-B-0114040, are listed in Table I. The reducing gas leaves the melter-gasifier 3 at a temperature of 1050° C. and a pressure of 4.5×10 ⁵ Pascal (absolute). It will be used to reduce iron ore.

Table I

CO 65%

_H2 30%

CO ₂ 1%

_H2O 1%

_CH4 1%

N ₂ 2%

In order to achieve a reducing gas temperature of approximately 850° C., a cooling gas must be mixed into the reducing gas. According to Example I, the temperature is 70 ℃, the pressure is also 4.5 × 10 ⁵ Pascal (absolute) of the same type of cooling gas mixed therein. To achieve a temperature of 850°C, 27.8% of cooling gas must be mixed. As a result, the following disadvantages are produced:

• Large quantities of cooling gas are required, that is to say, a relatively large portion of the hot reducing gas has to be separated and subjected to a cooling process, which involves considerable costs in terms of energy and equipment.

The total content of CO ₂ and H ₂ O does not fit the equation, so after mixing, CO and H ₂ respectively on the way to the shaft furnace 1 according to the reaction formula (Bowman's reaction) and (Heterogeneous Water-Gas Reaction) decomposition, which is highly exothermic. This thus raises the temperature and further cooling gas must be supplied. This temperature rise causes the shaft furnace charge to form agglomerates. There is also chemical attack on internal components made of metal, such as pipes for further conveying the reducing gas. Furthermore, due to this reaction of CO and _H2 , the effective amount of gas used for reduction drops.

Embodiment II:

To the reducing gas whose chemical composition is shown in Table I, a gas rich in CO ₂ at a temperature of 70°C and a pressure of 4.5×10 ⁵ Pa (absolute) was supplied. The analytical values of the _CO2 -enriched gas are shown in Table II

Table II

CO 13%

H2 ₂ %

CO ₂ 77%

_H2O 5%

_CH4 1%

N ₂ 2%

By adding 12.3% of the same kind of gas and 10.7% of the rich CO shown in Table II by Example I In the _reducing gas in Table I, the result is that the temperature is 850 ° C and the pressure is 4.5 × 10 ⁵ Pa (absolute), the reducing gas whose chemical composition is shown in Table III.

Table III

CO 60.5%

_H2 27.5%

CO ₂ 7.6%

H ₂ O 1.4%

_CH4 1.0%

N ₂ 2.0%

In this reducing gas, the total content of _CO2 and _H2O is close to the equilibrium value at 850 °C, so that the decomposition of CO and _H2 can be almost completely avoided. According to the figure, this CO ₂ -enriched gas is fed into the cooling gas loop, eg into the recirculation line 17 . It can be seen that it is possible to greatly reduce the size of the cooling loop, such as adding only 12.3% of cooling gas instead of 27.8% according to Example I. According to Example II, it is feasible to properly utilize gas with low calorific value, such as gas rich in CO ₂ . During the reduction of iron ore with the reducing gas adjusted in this way, overheating of the shaft furnace charge is reliably avoided, and the reduced charge can be passed continuously to the melter-gasifier 3 without difficulty.

Embodiment III:

According to this example, suitably purified, cooled and compressed top gas at 70°C and 4.5×10 ⁵ Pa (absolute) extracted from the shaft furnace I is mixed into the reducing gas from the melter-gasifier 3 . The chemical analysis of the top gas is shown in Table IV.

Table IV

CO 42%

_H2 19%

CO ₂ 34%

_H2O 2%

_CH4 1%

N ₂ 2%

By mixing 23.3% top gas into the reducing gas, a gas mixture with a temperature of 850°C and a pressure of 4.5×10 ⁵ Pa (absolute) was formed, the chemical analysis of which is shown in Table V. At this time, the total amount of CO ₂ and H ₂ O is also close to equilibrium, so Bowman and heterogeneous water-gas reactions are almost completely avoided at this time as well.

Table V

CO 60.6%

H ₂ 27.9%

CO ₂ 7.3%

H ₂ O 1.2%

_CH4 1.0%

N ₂ 2.0%

In Example III, too, the amount of gas required to cool the reducing gas from the melter-gasifier 3 is smaller than that required in Example 1. The top gas is mixed into the pipe 4 or 17 via a branch 20 extending from the top gas discharge pipe 14 to the pipe 4 and optionally via the feed point 19, said branch flowing through a compressor 21 and a suitable cooling device .

Embodiment IV:

According to Example IV, _H₂O vapor is mixed with the same type of cooling gas. The chemical composition of the reducing gas and the cooling gas from the melter-gasifier 3 is the same as that given in Example 1.

Steam (100% water) is mixed in at a temperature of 250°C and a pressure of 12 x 10 ⁵ Pa (absolute). When 18% cooling gas is mixed with 8.5% water vapor, a reducing gas with a temperature of 850°C and a pressure of 4.5×10 ⁵ Pa (absolute) is formed. The results of chemical analysis of the reducing gas are shown in Table VI.

Table VI

CO 60.7%

H ₂ 28.0%

CO ₂ 0.9%

_H2O 7.6%

_CH4 0.9%

N ₂ 1.9%

This variant also has the advantage that the cooling gas loop can be built on a small scale, since the total content of _CO2 and _H2O is roughly close to equilibrium. An additional advantage resulting from this change is that the amount of reducing agent changes slightly.

Claims (11)

1. produce be used to reduce block metallic ore, contain CO and H ₂The method of thermal reduction gas, wherein, in gasification zone (8), by under the condition of oxygen supply, making the carbon support generating gasification form reducing gas, then this reducing gas is cooled to the reducing gas temperature that helps reduction process, it is characterized in that, for preventing Bao Shi reaction and heterogeneous water-solid/liquid/gas reactions and the heating that produces therefrom, by adding H reducing gas ₂O and/or CO ₂, be not by in reducing gas, adding H with a kind of the experience ₂O/CO ₂The refrigerative reducing gas that is caused is transformed under this reducing gas temperature comparatively stable reducing gas on the thermodynamics.

2. the method for claim 1 is characterized in that, said reguline metal ore is an iron ore.

3. the method for claim 1 is characterized in that, said carbon support is a coal.

4. the method for claim 1 is characterized in that, H ₂O and/or CO ₂Add-on will under helping the temperature of reduction process, almost reach Bao Shi-and heterogeneous water-gas balance the time till.

5. the method for claim 1 is characterized in that, steam adds H by watering ₂O.

6. each method among the claim 1-5 is characterized in that, by being provided with containing CO ₂Gas adds CO ₂

7. the method for claim 6 is characterized in that, the reducing gas that will react in the reduction process of metallic ore (for example stock gas) infeeds in this reducing gas.

8. each method among the claim 1-5 is characterized in that, will sneak in this reducing gas through chilled similar reducing gas, and with H ₂O and/or CO ₂Add this in chilled similar reducing gas.

9. be used for implementing each the equipment of method of claim 1-8, it comprises at least one reduction reactor (1), reactor (1) has the pipeline (4) of stretching in pipeline wherein, the transferring metal ore (2) and carrying reducing gas, and comprise gasifying reactor (3), reactor (3) has stretches in supply pipe wherein, that be used for carbon support and oxygen-containing gas (5,6), and from (3), draw reducing gas pipe (4), and have one be located in the reducing gas conduit (4), be not by in reducing gas, adding H ₂O/CO ₂And cause the refrigerative refrigerating unit, it is characterized in that CO ₂Source and/or H ₂The O source links to each other with being used to carry reducing gas pipe (4) circulation of having experienced a kind of refrigerative reducing gas.

10. the equipment of claim 9 is characterized in that, reduction reactor (1) is provided with the stock gas delivery pipe (14) of the reducing gas discharge that will react, draws an arm (20) that flows and link to each other with reducing gas pipe (4) from pipe (14).

11. the equipment of claim 10, it is characterized in that, reducing gas recirculation pipe (17) is from reducing gas pipe (4), through a washer (16) and compressor (18), stretching in the reducing gas pipe (4) again, but see along gas flow direction, is that a upstream section in the upstream section of the branching-point of reducing gas recirculation pipe (17), especially being located at the cleaning apparatus (4 ＇) in the reducing gas pipe (4) stretches into pipe (4), its feature also is, CO ₂Source and or H ₂Flow with reducing gas recirculation pipe (17) and link to each other in the O source.