WO2001032940A1

WO2001032940A1 - Method and devices used in the production of iron for increasing output and reducing fuel consumption

Info

Publication number: WO2001032940A1
Application number: PCT/EP2000/010245
Authority: WO
Inventors: Bodo Wolf
Original assignee: Crg Kohlenstoffrecycling Ges.Mbh
Priority date: 1999-11-05
Filing date: 2000-10-18
Publication date: 2001-05-10
Also published as: DE19953298C2; DE19953298A1; AU1139801A

Abstract

The invention relates to a method and to devices for producing iron by fluid bed and entrained flow gasification using fossil and regenerative fuels. According to the inventive method, wuestite is reduced to iron in a largely separate process step to which wuestite and a reducing gas is continuously added from an internal or external gasification process and iron or iron carbide and a reducing gas are removed after completion of the reduction of wuestite to iron at temperatures of 750 °C ? 150 K. A partial flow of the removed gases is returned to the external or internal gasification of the fuels as the gasification agent via special gas collection chambers or the tuyeres of a blast furnace without washing out the carbon dioxide. The invention is particularly characterized by the independent design of the temperature profile in shaft furnaces due to the partial oxidation of the gases in the top part of the shaft and the equipment of the tuyeres of the blast furnaces with burners for the gasification of substitute fuels with hot air and/or oxygen.

Description

Methods and devices for increasing performance and saving fuel in the production of iron

The invention relates to a method for increasing performance and saving fuel in the production of iron from iron ore or oxides, which are left in their natural state or pelletized, as fine ore or concentrate, preferably of pig iron in blast furnaces, but also of sponge iron and iron carbide in shaft furnaces, in the fluidized bed and in the entrained flow, with the help of fossil and renewable fuels, in particular hard coal and brown coal or other organic fuels such as waste and sewage sludge.

The invention can be used in all iron smelting processes in which the iron undergoes at least its oxidation states magnetite and wustite.

Most of the iron, the base material for steel production, is obtained from iron ore and with the help of blast furnaces, even if the reuse of scrap secures a large part of the steel production. The production process is basically divided into two steps, the reduction of the mostly processed, hematitic ore to iron via the oxidation levels hematite, magnetite and wustite and the melting of the iron in direct combination with the reduction as with the blast furnace or externally in cupola, SM -, electric oven etc.

Fundamental knowledge of iron metallurgy is that only the decay and gasification products of the fuels are suitable for the decomposition of oxygen from the ore, never the fuels themselves, not even the gaseous methane, whereby of the decay product carbon is little involved in the reduction due to inertia.

The predominant method of producing iron worldwide is the production of pig iron in blast furnaces. In this process, the necessary process steps are optimally combined in such a way that the fuels are gasified in the melting zone with hot wind, the resulting high-temperature heat melts the slag and the iron, and enables the Boudouar reaction, technically referred to as "direct reduction", and that above that Shaft of gas rising from the melting zone reduces the ore.

The process control in the production of pig iron with the help of shaft furnaces has remained largely unchanged for decades, although a large number of measures to increase performance, e.g. by increasing the furnace dimensions and increasing the process pressure, and to reduce coke consumption, e.g. by blowing in other fuels such as coal, heating oil, natural gas, coke oven gas, waste, sewage sludge, ore and the use of oxygen etc. have become known.

Results are shared by Gudenau in the journal "Stahl und Eisen" 117 (1997) No. 6 under the title "Experiments for the combined blowing of coal dust and fine-grained ore into the blast furnace" and at the 1 ^tn TIMS / IEHK Metallurgical Symposium, 28/29 September 1997 in Cairo under the title "Environmental and economical benefits by injecting iron containing recyclings and steel plant residues into the blast furnace" and the VDI with the handbook "Recovery by melting, secondary metal extraction and energy use in the thermal treatment of waste" for the seminar of September 22 and 23, 1997 in Düsseldorf. A basic description of the blast furnace process is given, among other things, by Textbook by Ost, H .; Rassow, B .: "Textbook of chemical technology", 26th edition, Leipzig, Barth-Verlag, 1955.

Characteristic of the state of the art of process control in blast furnaces is the gasification of coke and other organic fuels and the reduction of the ore in counterflow to the bulk material, so that the process heat demand the flow rate of the gas and the respective oxidation level of the ore, the gas composition and thus the fuel utilization in the Determine the blast furnace. With regard to the oxidation potential of the fuels, approximately 65% of the fuels are used in the practical operation of the blast furnace.

An indispensable part of the blast furnace process is therefore the regenerative preheating of the process air, which uses part of the chemical enthalpy of the blast furnace gas outside the blast furnace and thus leads it back into the process. Good blast furnace systems already achieve a fuel utilization of 75 to 80% when using a high proportion of expensive and scarce metallurgical coke as fuel.

Nevertheless, a variety of efforts are known to further improve pig iron production and blast furnace operation. This applies in particular to the substitution of metallurgical coke with alternative fuels, the lowering of fuel consumption through better utilization of the gas in the furnace, the increase in the space-time yield of existing plants and the better external utilization of the blast furnace gas.

It has been proposed several times to process blast furnace gas by washing out carbon dioxide into reducing gas and to recycle it to the blast furnace. Austin, PR and others in ISIJ Int. 38 (1998), No. 3, pp. 239-245 results from Studies on recirculation of blast furnace gas in the blast furnace process are published. In comparison to the conventional driving style without recycle gas recirculation, the recirculation of top gas without scrubbing out carbon dioxide with and without oxygen enrichment of the wind and the recirculation with scrubbing out carbon dioxide and simultaneous enrichment of the wind with oxygen was investigated. Only the variant with carbon dioxide leaching and simultaneous oxygen enrichment led to fuel savings and increased performance.

An essential part of the state of the art are furthermore insights into advantages which result from the use of oxygen instead of hot wind as a gasifying agent in the vortex chambers of the blast furnaces.

When reducing in shaft furnaces, e.g. in blast furnaces or in the Corex process, the gas flows through the bed in counterflow. The result of this is that the ore passes through its oxidation stages one after the other, the gas first taking up the oxygen from the wustite and the resulting gas being suitable for the reduction of magnetite and the gas present thereafter again for the reduction of hematite. The inflowing gas also has the task of ensuring the temperature level necessary for the chemical reactions taking place in the furnace by transporting heat from the mold level into the shaft. Reduction potential and heat capacity are therefore forcibly coupled. In the prior art, the reduction of hematite to iron in the countercurrent of the shaft achieves a carbon monoxide / hydrogen utilization of approximately only 50%.

In contrast, when iron ore is reduced in the fluidized bed and in the flight cloud with the continuous addition of ore and the continuous removal of iron, the reduction stages take place at the same time. Determination of the lowest oxidation level of the ore as the "soil body" in the fluidized bed, ie at a fluidized bed temperature of 800 ° C, the carbon monoxide / hydrogen mixture can only be used to about 35% under normal pressure. However, since the reactions from hematite to magnetite and magnetite to wustite take place primarily in the fluidized bed and at the same time to reduce wustite to iron, the reducing gas is already contaminated with carbon dioxide and water vapor via these reactions and thus in its effectiveness for the reduction of wustite to iron so reduced. The reduction gas requirement thus increases to approx. 170%, based on the amount of gas required for the reduction of wustite to iron. The amount of gas actually to be circulated is usually significantly higher because the gas is used to introduce the kinetic energy required for fluidization into the process.

In the state of the art, this is counteracted by gas cycles, for example in the circular process, in which the ore passes through a circulating and a stationary fluidized bed in succession and is reduced there by two parallel hydrogen flows. This parallel operation of the gas flows does not allow the gas utilization that can be achieved with the counterflow operation from the outset. This is countered by using hydrogen as a reducing gas and a gas cycle, as a result of which the water formed during the reduction of the ore is thawed by cooling the entire cycle gas and the used hydrogen is replaced by feeding. The cycle mode thus ensures a high level of fuel utilization, but with a high expenditure for the conversion of the fuels into hydrogen and for energy for the recirculation of the gas and the fluidization of the solids. The process heat requirement is covered by recuperative heating of the cycle gas and additional firing as part of the preheating of solids (Paper presented at the METEC Congress 99 in Düsseldorf, Germany, from June 13-15, 1999). The recuperative heat input requires a lot of equipment. The same paper presents the Circofer process, in which the reducing components of the cycle gas are renewed by a partial oxidation of a coal / ore mixture integrated in the cycle process, carried out in a fluidized bed fluidized by cycle gas. The generation of the reduction gas by gasification of fossil fuels, preferably coal, is thus integrated into the process. As in the Circored process, the ore is reduced in two fluidized beds connected in parallel on the gas side. The carbon dioxide and water formed are removed from the circuit by cooling and MEA washing. In addition to partial oxidation, the process heat requirement is also covered here by recuperative heat supply. The lower expenditure for the generation of reducing gas compared to the circored process is offset by the increased expenditure for washing out the carbon dioxide in the circofer process.

The good mass transfer which is claimed for both processes and is achieved by high relative velocities between gas and solid is subordinate, since in both cases the chemical reaction of ore reduction is the rate-determining step.

If, in addition to the reduction of hematite to iron, carbonization of the iron to iron carbide is also to be carried out in the fluidized bed, then the formation of iron carbide ultimately decides on the gas utilization. Under the process conditions selected in the Trinidad der Nucor iron carbide plant, this means that more than 100 times the required amount of gas is circulated compared to thermodynamically optimal process management (Paper presented at the ISS 56th Ironmaking Conference in April 1997 in Chicago, IL).

The state of the art is therefore characterized by two extremes: the system-technically perfected, thermodynamically advantageous multi-stage smelting of ore to pig iron in countercurrent between the bed and gas in a heat in the blast furnace with the double function of the reducing gas generated in the mold plane and the resulting, insufficient fuel utilization and

the one-stage reduction of the ore in the fluidized bed with recycle gas, which is decoupled from the melting process, and thus full use of fuel with high equipment and energy expenditure.

With regard to the advanced state of the smelting of iron ore in the blast furnace, it must first be noted that the gradual reduction of the ore via the oxidation levels hematite, magnetite, wustite, iron in the blast furnace shaft is thermodynamically advantageous for fuel utilization compared to the one-stage reduction in the fluidized bed. The extent to which these thermodynamic advantages are actually being used in the management of the technical process is to be shown in the following evaluation of practical indicators of a blast furnace operation, based on 1 t of pig iron.

Fuel use: coke 311 kg

Hard coal 185 kg

Air: volume 976 m3

24% oxygen content

Temperature 1,228 ° C

ad. Flammentemp. 2,150 ° C Molding gas volume: 1,338 m ³

Blast furnace gas: proportions in volume% CO ₂ 20.8 corrected ^* 20.3

CO 25.1 25.3

H ₂ 3.5 3.5

H ₂ O 2.5 2.0

N ₂ 48.1 48.9

Volume m ³ / t RE

(from nitrogen balance) 1,541 1,515

The material balance shows that 286.5 m ^{3 was introduced} with the ore and 235 m ³ with the air, a total of 521.5 m ³ oxygen / t RE, and 533 m ³ were discharged with the blast furnace gas. The oxygen volume of 26 m ³ additionally introduced with the blast furnace gas was entered with the additives as carbon dioxide and with the bulk material as water.

^* For subsequent calculations corrected for carbon dioxide and moisture from aggregates or fill.

With the blast furnace gas, 338 m ^{3 of} carbon dioxide and water are discharged, which were created in the course of iron reduction. The formation of carbon dioxide and water from carbon monoxide and hydrogen during the reduction from hematite to magnetite and from magnetite to wustite is calculated to be 191 m ³ , that is to say only 147 m ^{3 of} carbon dioxide and water were formed during the reduction of wustite to iron, which means a reduction gas utilization corresponds to 19%.

The thermodynamic calculations of the reduction of haematitic ore to iron for a reaction temperature of 800 ° C and a partial pressure of the reacting gas components of 1 bar show that regardless of whether the The process is carried out in shaft furnaces, e.g. blast furnaces, in stationary or circulating fluidized beds or with entrained-flow processes, only 33 m ³ with complete reduction of hematite to magnetite, 67 m ³ from magnetite to wustite, but 200 m ³ with the reduction of wustite to iron Oxygen per t of iron are to be mined, whereby, based on the oxygen absorption capacity of a carbon monoxide / hydrogen mixture as a reducing gas, the gas is thermodynamically limited in the reduction of wustite to iron by only 35%, and in the reduction of magnetite to wustite by approx. 75% and can only be used almost completely when reducing hematite to magnetite.

For the blast furnace process, it is assumed that the direct reduction is of secondary importance in the reduction of hematite to magnetite and magnetite to wustite, and the oxygen in the blast furnace gas is reduced by that with the additions and during the reduction of hematite and reduced taken magnetite, is then calculated for the process from the stage of "reduction of wustite to iron" gas exiting a bound oxygen volume of 421, 5 m ^3, of 186.5 m ³ from the ore and 235 m ³ from the wind.

The invention is therefore based on the object, from the thermodynamic system iron-carbon-hydrogen-oxygen-sulfur (Fe-CHOS) derivable technical possibilities for increasing performance and fuel savings in the smelting of iron ore with fossil fuels process engineering and suitable for implementation Propose devices and measures accompanying the process to optimize the application.

The task is solved by the characteristic features of independent claims, which can also be used technically independently of each other enable a gradual conversion of existing devices to the method according to the invention. The subclaims represent advantageous embodiments of the invention.

The object is achieved according to the invention with a method in which the reduction of wustite to iron in fixed beds or in fluidized beds or flying clouds is carried out largely independently of the upstream reduction of hematite and magnetite and the subsequent melt as a process step which is separate in terms of process technology, by this process step on the one hand Wustite and reducing gas, preferably generated externally by gasification and / or degassing of fuels, or gaseous, liquid or solid fuels which are gasified in the process stage even by partial oxidation with air and / or oxygen to form a reducing gas, with a temperature sufficient for the reduction supplied and on the other hand iron sponge and by the absorption of oxygen from the wüstite carbon dioxide and water vapor enriched reduction residual gas, regardless of the physical enthalpy of this gas.

It is according to the invention that the iron produced in the process technology separate process stage from wustite mostly in the form of sponge iron of an internal one, as in the blast furnace, or an external melting stage, preferably an electric furnace, or also a carbonization to iron carbide, and the reduction residual gas partly partly of the internal one or external gasification of the fuels as an endothermic gasification agent, for the reduction of hematitic or magnetitic ore to wustite, as fuel gas for preheating the bulk material fed into the process or for a coke-free iron melt, similar to the Siemens Martin furnaces, or for other external use , The application of the invention in the smelting of iron ore in the blast furnace takes place according to the invention with a process control, in which the furnace the gas rising from the mold level and the lower part of the furnace at the beginning of the reduction of wustite, preferably at a temperature level of 750 ° C ± 150 K. is partially or completely removed via a lower gas collection channel, of which such a portion is fed back to the furnace via the mold level without removal of carbon dioxide, such as for setting the desired temperature in the melting zone of preferably 2,000 to 2,150 ° C. depending on the conditions there the gasification of available fuels, the temperature and oxygen concentration of the wind, up to pure oxygen, is required, whereby at least as much gas remains in the furnace during the partial withdrawal and continues to flow in countercurrent to the bulk material up to an upper gas collection channel as for the Reduction of magnetite to desert it is necessary, while with complete gas extraction a further partial flow, sufficient for the reduction of hematite to wustite and to ensure the required reaction temperature by partial oxidation with air via the upper gas collection duct, is returned to the upper part of the furnace shaft and via a medium gas extraction, the in the height between the upper and lower gas collection channels, is removed again from the furnace after this partial gas flow has flowed through the bulk material in cocurrent, preheated it to the reaction temperature and reduced the haematitic ore to wustite.

The separation of the gases ascending and descending in the furnace required for carrying out the method according to the invention with complete gas removal is achieved by adjusting the pressure of the gas guided in the upper part of the furnace in cocurrent with the bulk material when it is fed to the furnace such that do not mix the gases to be discharged via the first and second gas extraction in the bed or mix them only to the intended extent. According to the invention, the gas utilization in the furnace and the effectiveness of the gas recirculations in the furnace are increased by dedusting the gas removed from the furnace via the first gas extraction before cooling, cooling the pressure, preferably to the operating pressure of the wind heating, and recuperatively and / or regeneratively up to temperatures above 1,000 ° C is increased.

It is also according to the invention to partially oxidize the gas in the furnace without removing gas via the lower gas extraction before starting the reduction of hematite to magnetite by supplying air in the furnace, or preferably to completely burn it with partial gas extraction via the lower gas extraction and to use the oxidized gas or the resulting combustion gas for preheating the bulk material to 600 to 700 ° C. in the furnace itself, and preferably to cool it to 150 to 250 ° C.

The process temperature in the reduction of hematite to magnetite or wustite by the gas passed through the bulk material in cocurrent is adjusted according to the invention by the heat input with the recirculated, regeneratively and / or recuperatively heated gas and optionally by admixing air and thus partial oxidation in the upper shaft area of the blast furnace.

It is also according to the invention to supply gas from the lower gas extraction to an external process for the gasification of substitute fuel to reducing gas for blowing into the blast furnace in the production of pig iron, the production of sponge iron and carbide as a gasification agent or to use it directly for the production of iron carbide under increased process pressure.

The recycling of the gas that is not returned as a gasifying agent to the partial extraction of gas from the lower gas extraction or that from the Upper gas extraction of extracted gas takes place after its dedusting and cleaning, as well as pressure increase, preferably to hot wind pressure outside the furnace, by burning it under pressure in the hot water heaters for the purpose of regenerative air or gas heating and in additional combustion chambers to work tools for preferably turbochargers, which are used for the in-process Air and gas compression and compressed air generation are used for air separation, but also for expansion turbine systems for power generation.

A further measure for improving fuel utilization is, according to the invention, the injection of the substitute fuel instead of the usual injection lances via burners which are preferably integrated in the wind molds, which burn the substitute fuel with as much hot wind and / or oxygen during the injection, optionally with the addition of recirculated gas from the first Extract gas, blast furnace gas or externally generated reducing gas, mix as required for the complete gasification of the substitute fuel in the swirl chambers even at high injection rates and for the reduction of carbon dioxide and water vapor of the recirculated gas to carbon monoxide and hydrogen at predetermined temperatures in the mold level.

A maximum increase in performance of the blast furnace is achieved according to the invention in that the substitute fuel is blown in via the burners in addition to the oxygen required for the gasification of the substitute fuels and also the oxygen required for the proportionate gasification of the coke in the bulk material, the transition to " Nitrogen-free operation "by completely replacing the hot air with oxygen, the temperature level in the mold level is adjusted with gas recirculated from the first gas extraction, blast furnace gas or with externally generated reducing gas. According to the invention, when the nitrogen-free process is implemented in blast furnaces, the wind heaters are used for regenerative preheating of the gas withdrawn from the furnace via the lower gas extraction and the hot wind system for returning the gas to the furnace.

The application of the invention with the aid of fluidized bed or entrained flow technology is carried out according to the invention in that the stationary or circulating fluidized beds forming the process stage or the entrained flow are predominantly formed from eddy or blowable iron, to which wustite is continuously fed to and from which iron is continuously removed, whereby the gas supplying the fluidized bed or the entrained flow to the process stage is preferably generated externally by gasification and has a volume ratio of the reducing components carbon monoxide and hydrogen to the oxidizing components carbon dioxide and water vapor which is smaller than that of the gas removed from the process stage.

However, it is also in accordance with the invention to increase the pressure of the gas to be removed from the process stage formed by fluidized bed or flight cloud and to return it to the process, fuel or air and / or oxygen being supplied at the same time or carbon dioxide and water being removed from the gas before the return ,

In addition to recirculation, the gas to be removed from the process stage formed by fluidized beds or entrained flow is also used proportionately as an endothermic gasification agent in external reduction gas production, for reducing haematitic or magnetitic ore to wustite, and as a fuel for ore preheating and production of work equipment for power processes. The production of iron carbide is a particularly economical application of the invention. Carbon, preferably in the form of carbon monoxide, is indispensable for the carbonization of iron to iron carbide. The formation of iron carbide from iron and carbon monoxide is a pressure- and temperature-dependent chemical reaction, which requires a minimum content of carbon monoxide in this regard with the lowest possible proportions of carbon dioxide and water, but also of hydrogen.

According to the invention, therefore, the production of iron carbide under normal pressure from sponge iron in a debris or fluidized bed, circulating fluidized bed or by entrained flow, etc. The process step formed is carried out by adding sponge, swirlable or blowable iron sponge and reducing gas generated by gasification of carbonaceous fuels, the carbon monoxide content of which may be obtained through the use of coal, coke, e.g. Petroleum coke, as a fuel and possibly carbon dioxide as an endothermic gasification agent and / or separation of hydrogen was raised to at least one third of the sum of carbon monoxide and hydrogen, the proportion of the oxidizing gas components carbon dioxide and water vapor together not to exceed 3% by volume, in one Partial pressure of the reacting gas components of at least 1 bar and a process temperature <750 ° C.

The gas to be removed from the process step of carbonization of iron to iron carbide and the hydrogen which may occur in the production of the gas required for this purpose are used according to the invention as a reducing gas in the reduction of wustite to iron preceding carbonization.

According to the invention, iron carbide from Wüstit is produced with gasification gas generated from fossil or renewable fuels that is generated internally or externally Fuels at process pressures> 10 bar and magnetite> 25 bar, each at process temperatures from 600 to 800 ° C.

For the implementation of the method according to the invention in stationary and circulating fluidized beds and in the entrained flow, the known devices corresponding to the state of the art can be used with a slight modification, since the features of the invention are achieved by the requirements according to the invention regarding the quality of the substances supplied and removed as well as the type of energy supply.

The implementation of the invention in fixed bed fillings in shaft furnaces, e.g. Blast furnaces, however, sometimes require a fundamental further development of the devices and their peripheral systems, which are characterized below according to the invention.

A device for decoupling the chemical reactions of iron ore reduction from heat transport by the gas rising in the furnace according to the invention corresponds to a shaft furnace, e.g. Blast furnace of the prior art, which according to the invention is equipped with a device, preferably a hollow cone or a tubular grate, which distributes the air supplied via one or more channels for the partial oxidation in the bulk material, preferably before the ore reduction begins.

A device according to the invention for using a further feature of the method according to the invention is characterized in addition to the device for the partial oxidation of the gas rising in the furnace in the bulk material by air before the start of the ore reduction by burners for gasifying the substitute fuels in the mold plane with hot air and / or oxygen, which are preferably are integrated in the wind molds and are controlled by pneumatic dense phase conveying Spray the driven, blowable substitute fuel with the hot air and / or oxygen so that the substitute fuel largely gasifies even at high blowing rates in the swirl chambers.

The device for realizing all the features of the method according to the invention in a solid bed in combination with the pig iron production corresponds in its lower part to a medium height to a blast furnace with the measures according to the invention described above for improving the introduction of substitute fuel, while the upper part of the device according to the invention a filling shaft and a gas-tight cylinder or truncated cone, which together with the bed form the upper gas collection duct, from which the gas is completely discharged from the furnace in a continuous countercurrent mode with or without partial gas extraction, the upper and lower part of the device with the bulk material being the lower one Form a gas collecting duct, through which the gas rising in the lower part of the furnace can be partially or completely discharged from the furnace and fed to the recycling and recycling according to the invention.

In a preferred embodiment, the device has a hot gas injection device which corresponds in its external design to a conventional wind form which, according to the invention, is equipped with oxygen with a burner for gasifying substitute fuel, preferably coal fuel dust or blowable fine coke, with either hot wind via this injection device or hot, recirculated and / or hot reducing gas from external production, which is recirculated from the first gas extraction, is introduced into the mold level of the furnace and the recirculated or supplied gas, the substitute fuel and air and / or oxygen are introduced into the mold level with the aid of the burner, that a vortex chamber is blown in the furnace in which recirculated gas Convert substitute fuel, air and / or oxygen to reducing gas at temperatures above 1,900 ° C.

For the production of sponge iron or iron carbide from granular, lumpy or pelletized iron ore, a device for implementing the method according to the invention in the solid bed is preferably proposed, which, similar to that for the production of pig iron, consists of a filling shaft and a gas-tight upper part, which together with the bed is an upper gas collection channel form, via which the combustion gas is discharged from the bulk material preheating, while, as with the device for pig iron production, the furnace upper part with the lower part and the solid bed form the lower gas collecting duct, through which the gas escaping from the bed reduced to wustite is partially removed and the one according to the invention Recovery can be supplied. The lower part of the furnace is preferably closed off by a grate, via which cold reducing gas can be introduced into the furnace for the purpose of cooling the bed and, depending on the CO partial pressure in the reducing gas and the process pressure, either iron sponge or carbide can be discharged. As with the device for pig iron production according to the invention, there is a device in the upper part of the furnace, preferably a cone or tubular grate with bores, to which air is fed via a feed line for the combustion of the gas flowing in the shaft after the reduction of hematite to magnetite.

A special device for the production of iron carbide is also equipped with an additional gas supply, which is arranged between the grate and the lower gas collection duct, via which the separated hydrogen can be fed to the reduction process in the event of an upstream enrichment of carbon monoxide in the reducing gas. embodiments

Example 1 The method according to the invention for improving the use of blast furnace gas is described with the aid of FIG. 1

The blast furnace gas present after the cleaning is passed through a cold gas line 1 to the compression stage 2 of a turbocharger 3, where it is compressed to the permissible operating pressure of the hot air heater, partially fed to the hot air heater II 4 under operating conditions and burned there with compressed air. The combustion gas cools down in the blast heater II 4, is then passed to a pressure combustion chamber 5 at a temperature of 300 to 600 ° C, where the temperature of the other part of the compressed blast furnace gas is increased to the input level of the expansion stage 6 of the turbocharger 3 with compressed air raised and relaxed while handing over the technical work required for top gas compression. The turbocharger exhaust gas is cooled in the recuperator 7 and then released into the environment.

The air required for the blast furnace operation and the combustion of the blast furnace gas is sucked in by the compression stage of a second turbocharger 9 and compressed to the operating pressure of the existing hot wind system and preheated in the recuperator 7 by turbocharger exhaust gas. The partial flow of preheated air required for the blast furnace is fed to a second blow heater 10, where it is heated to the required hot wind temperature and made available to the blast furnace via the existing hot wind system 11, while the other partial flow of compressed air is fed to the combustion chamber 5. The pressure combustion gas from the combustion chamber 5, which is not required for driving the turbochargers 3 and 9, is expanded in the expansion turbine 12 by submitting technical work for the generation of electrical energy. The turbine exhaust gas is discharged from the turbochargers 3 and 9 to the environment via the recuperator 7. The inlets and outlets of the hot air heaters for compressed air and blast furnace gas are equipped with shut-off devices and throttle valves in such a way that the hot air heaters 4 and 10 are cyclically heated by blast furnace gas combustion under pressure and cooled by hot air heating.

Example 2 The invention is used to describe FIG. 2

Device for the production of pig iron as follows:

Extension stage 1

According to the invention, a blast furnace of the prior art is equipped in the upper shaft section with a device (hollow cone, pipe grate, etc.) 9 for introducing and distributing air 7, preferably preheated. The air 7 is fed to the device 9 and the gas space 10 formed by it and the bulk material via one or more channels 8 of the bed, mixed with blast furnace gas and reacted. The heat of reaction that arises raises the temperature of the bulk material, so that the reduction temperature is reached regardless of the temperature and the mass flow of the blast furnace gas.

This measure makes it possible to reduce the reduction gas generation in the level of the forms and the direct reduction to the mass flow required for the reduction of wustite to iron and to use the reducing gas approximately up to the thermodynamic gas equilibrium of the phase boundary iron / wustite. Compared to the blast furnace described in the prior art, the following economic advantages can be achieved by this measure according to the invention: Reduction of the reduction gas production in the mold level from 1,338 to 1,170 m ³ / t pig iron and thus an increase in the pig iron output up to 114%

Reduction of specific fuel consumption by 14%, d a v o n

Coke consumption reduced by 30 from 311 to 281 kg / t of pig iron

Coal injection reduced by 42 from 185 to 143 kg / t pig iron.

Extension stage 2

The second stage of expansion can be characterized by the installation of burners 19, preferably in the wind molds 14, suitable for the gasification of substitute fuel 20, in particular coal fuel dust, with oxygen 23 and / or hot air 24.

With this measure it is possible to largely gasify the substitute fuel in the swirl chambers to reducing gas, to reduce the influence of the substitute fuel on the gas permeability of the bulk material, to increase the blowing rate for substitute fuel and to further increase the coke rate, possibly to a technologically related minimum reduce.

Stage 3

The device 1 consists of the filling shaft 12, to which the bulk material 6 consisting of iron ore, coke and aggregates is fed via the lock 15. The Filling shaft 12 protrudes into the upper part 5 of the furnace and forms the upper gas collecting duct 16 with this and the bulk material 6. This arrangement prevents the lock 15 from coming into direct contact with hot gas which is discharged from the furnace via the gas collecting duct 12 or supplied to the latter. The gas discharge from the upper collecting duct 16, which is required in a continuous countercurrent mode, takes place via the hot gas line 13. When the gas is completely removed via the lower gas collecting duct 3, the gas is recirculated via the hot gas line 13 for the reduction of the hematite via magnetite to wustite in the furnace top 5 with direct current to the bulk material , Upper furnace part 5 or its refractory lining and lower furnace part 4 form with the bulk material 6 the lower gas collecting duct 3, from which the gas rising in the lower furnace part 4 is partially or completely removed via the hot gas line 2, depending on the selected mode of operation.

A device 9 is anchored in the cylindrical upper furnace part 5, in the example a cone, which forms a gas space 10 with the bulk material 6, to which combustion air 7 is supplied via the hot gas line 8 for the purpose of partial oxidation and thus raising the bulk material temperature in a continuous countercurrent mode of operation. In the case of a direct current mode of operation in the upper furnace part 5, the gas which is fed in via the upper gas collecting chamber 16 is discharged again from the device 1 via the gas chamber 10, the device 9 and the hot gas line 8. According to the invention, the device is operated in such a way that the reduction of magnetite to wustite is largely completed in the upper furnace part 5, so that mainly wustite is supplied to the lower furnace part 4, which reduces the reducing gas rising from the mold plane 11 and the direct reduction zone 17 to sponge iron.

While, according to the invention, the temperature level in the upper furnace part 5 can be designed by partial oxidation independently of the process control in the lower furnace part 4, the mold level 11 must be used for melting, preheating the bulk material to the melting temperature and direct reduction. released heat and the reducing gas for the gas reduction supplementary to the direct reduction are generated.

For this purpose, the furnace lower part via the wind molds 14 either, as in the prior art, hot wind supplied via the hot wind pipes 18, possibly oxygen-enriched, and substitute fuel provided via a dense flow conveyor 20 via blowing lances or, according to the invention, hot wind and substitute fuel supplied by hot wind and / or oxygen is mixed in the swirl chambers in front of the wind molds 14 by burners 19 which are preferably integrated in the wind molds 14 in such a way that an intensive material distribution which accelerates the gasification reaction is ensured. The melt is withdrawn separately from the device 1, as in the prior art of pig iron production, as pig iron 21 and slag 22.

The economic advantage of this expansion stage is that the furnace can be switched to "nitrogen-free operation" and its output can be increased to 135 to 150%.

Example 3 The method according to the invention and the interaction of the method-carrying devices proposed with the invention are described using the example of pig iron production with the aid of FIG. 3:

Iron ore and pellets, coke and aggregates are fed via the locks 15 of the device according to the invention to a furnace for the pig iron production 1 as bulk material 6. The bulk material 6 sinks in the device 1 in countercurrent to the reducing gas produced in the lower part 4 of the furnace, which is partly discharged from the device 1 via the lower gas collecting space 3 and the hot gas line 8. The gas remaining in the furnace top 5 is after the reduction of magnetite to wustite and from hematite to magnetite in the furnace top 5 with over the hot gas line 8 and the distributor cone 9 of air supplied to the gas space 10 are largely burned. The combustion gas preheats the bulk material 6, cools down in the process, and is then released at a temperature of approximately 200 ° C. via the upper gas collection duct 16 from the device 1 to the environment via a gas cleaning device 25.

The reduction gas is generated in the level of the wind molds 11 by gasifying coke and coal fuel dust introduced with the bulk material 6 as a substitute fuel, with oxygen and gas removed from the lower gas collecting duct 3 and returned as an endothermic gasification agent, with the aid of gas into the wind molds 14 integrated burner 19 and by direct reduction in the bed above the melting zone 17. The gas removed from the lower gas collection channel 3 is cooled before use as an endothermic gasification agent in the recuperator 26, then washed in 27 and with the turbocharger 28 for the return to the Windforms 14 required pressure increased. The gas is returned after reheating in the recuperator 26 and overheating in the hot-air generators 29, which according to the invention have been switched to continuous pressure operation, via the hot-gas system 18.

The part of the gas removed from the furnace via the gas collection space 3, which is not required for the pressure firing in the hot air heaters 29 and not as an endothermic gasification agent for the reduction gas generation in the mold plane 11, is fed to a combustion chamber 30 in which the pressure exhaust gas from the firing of the Wind heater 31 is raised to the inlet temperature of the expansion stages 32 of the turbocharger 28 by combustion with compressed air. In this way, the combustion chamber 30 produces, according to the invention, working means for the turbocharger 28, which in turn expands the technical work for the compression of the gas removed from the gas collection space 3 and the generation of compressed air for the pressure firing in the hot water heaters 31 during the expansion 32 Combustion chamber 30 and in the furnace top 10 and for the air separation 33 and thus the oxygen generation, but also for the electrical power generation 34. The air compressed for pressure combustion in 31, 30 and 10 is preheated in the recuperator 35 in counterflow to the turbocharger exhaust gas.

The main advantage of the third stage of expansion, in addition to the advantages already achieved with the stages of expansion, is that the "useful gas volume" to be removed from the furnace is reduced to almost half compared to the usual top gas volumes, of which almost 30% is returned to the furnace as a gasifying agent be used while the remaining gas is used for hot gas and electrical power generation. The metallurgical plant, which is so energetically optimized, works with full fuel utilization including oxygen generation in an energy-self-sufficient manner.

Example 4 The application of the invention for the production of sponge iron and iron carbide in coupling with external coal gasification is described here using the example of FIG. 4:

When using the invention for the production of sponges and iron carbide, it should be noted that the formation of iron carbide is a chemical reaction which is strongly dependent on process temperature and pressure. In addition to the requirements for the partial pressures of the reducing and oxidizing components that apply to reducing gas, the carbon monoxide concentration ultimately determines the carbonization of iron.

It thus emerges that gasification gas from coal has better preconditions for the carbonization of iron than that from methane, the carbon monoxide concentration of which in the prior art is caused by thawing out water, washing of carbon dioxide and separation of hydrogen is raised, which is not necessary when applying the invention as described below.

Blown coal is fed via a pneumatic conveyor system 1 to the endothermic part 2 of a two-stage gasification reactor 3, where it is partially gasified endothermically to reducing gas with the gas 5 containing steam and carbon dioxide coming out of the melting chamber 4. It is advantageous to add lime, calcium hydroxide or limestone powder to the coal before it is blown in, which converts to calcium sulfide in the temperature range from 800 to 1,100 ° C. with the sulfur introduced with the coal. The residual coke from the gasification and the calcium sulfide are fed with the 700 to 1000 ° C reducing gas via the hot gas line 6 of the hot gas dedusting 7 and dedusted there. The mixture of residual coke and calcium sulfide obtained in the dedusting unit 7 is discharged from the dedusting unit 7 via the lock 8, pneumatically conveyed to the combustion chamber 4 and gasified there with air or oxygen preheated in the recuperator 9 above the melting temperature of the coal ash. The calcium sulfide is largely melted into the slag so that it is resistant to elution. The reducing gas derived from the dedusting 7 is fed via a further hot gas line 10 to a hot gas fine desulfurization 11, which preferably works with iron, and is largely desulfurized there. Approximately 70% of the reducing gas cleaned in this way is introduced into the reduction reactor 13 at a temperature of 700 to 900 ° C. via the gas collection chamber 12 and is distributed there into the bulk material 14 consisting of sponge iron. The other part of the reducing gas is cooled in the recuperator 9 and passed as a cooling medium through a grate 15 through the bulk material 14.

The composition of the reducing gas is determined by the fuel and the gasification agent, so it is possible to regulate the carbon monoxide partial pressure by mixing air and oxygen in such a way that effect of pressure and temperature in the middle process stage 16, iron sponge from wustite is reduced, while in the cooling zone 18 above the grate 15, iron sponge is carbonized to iron carbide with the same gas composition. It is thus possible to obtain iron sponge from the same process in addition to iron carbide, which can be drawn off from the reactor 13 via a lock 19 from the upper region of the cooling zone 18.

The formation of iron carbide can also be prevented by reducing the proportion of oxidizing gas components in the cooling gas, e.g. by admixing 20 of residual reduction gas from the reduction of wustite to iron. The reduction of hematitic and magnetitic ore to wustite takes place in the upper process stage 21 before the gas present thereafter is completely burned for the purpose of preheating the bulk material to the reaction temperature by supplying combustion air 22. The resulting combustion gas cools down in the bulk material and is then released to the environment via gas cleaning 25.

According to the invention, this device also has a central gas collection channel 23, via which the residual reduction gas present after the “reduction to iron” process stage, which is not required for the reduction of magnetite to wustite and the bulk material preheating in the upper process stage 21, is discharged from the reactor 13 becomes. This gas is used as an endothermic gasifying agent in coal gasification in the combustion chamber 4, for preheating the combustion air in the recuperator 24 and for external tasks, e.g. for covering the electrical energy requirement of the process and, if necessary, for admixing to the cooling gas 20.

The advantage of this application of the invention lies in particular in the use of coal as fuel and in the high utilization of the fuels with little energy expenditure for gas recirculation. The technical implementation of the invention can be optimally designed depending on the respective application. The exemplary embodiments describe only selected variants for this.

Claims

claims

1. A process for the production of iron from iron ore or oxides, natural or pelletized, fine ore or ore concentrate, preferably pig iron in blast furnaces, but also iron sponge and iron carbide in shaft furnaces, in the fluidized bed and in the entrained flow with the help of fossil and renewable fuels, In particular of hard coal and lignite or organic fuels such as waste and sewage sludge, characterized in that the reduction of wustite to iron is carried out as a process-related separate process stage independently of the upstream reduction of hematite and magnetite and the subsequent process stages, such as melting, carbide formation or cooling is by this process stage on the one hand wüstite and reducing gas, externally by gasification of fuels, and / or gaseous, liquid or solid fuels, which are gasified in the process stage itself by partial oxidation with air and / or oxygen to reduce gas, for the reduction sufficient temperature and, on the other hand, sponge iron and, through the absorption of oxygen from the wüstite, carbon dioxide and water vapor-enriched reducing gas are removed, regardless of the physical enthalpy of the gas.

2. A process for the production of iron according to claim 1, characterized in that the iron produced is internal, such as in the blast furnace, or an external melting stage, an electric melting furnace or carbonization to iron carbide and the gas formed in the reduction of wustite is partly in each case internal or external gasification of the fuels as an endothermic gasification agent, for the reduction of hematitic or magnetitic ore to wustite, as fuel gas for preheating the bulk material supplied to the process or for a coke-free molten iron, similar to the Siemens Martin furnaces, or another external use.

3. A process for the production of iron in the blast furnace according to claims 1 and 2, characterized by a process control in which the furnace, the gas rising from the mold level and possibly the lower part of the furnace at the start of the reduction of wustite, preferably at a temperature level of 750 ° C ± 150 K is partially or completely removed via a lower gas collection duct, of which such a portion is fed back to the furnace via the mold level without removal of carbon dioxide, such as for setting the desired temperature in the melting zone from 1,800 to 2,100 ° C, Depending on the fuels available for gasification, the temperature and oxygen concentration of the wind, up to pure oxygen is required, with at least as much gas remaining in the furnace during the partial withdrawal and further in counterflow to the bulk material up to an upper gas collection duct flows as required for the reduction of magnetite to wustite ch is, while with complete gas extraction, a further partial flow, sufficient for the reduction of hematite to wustite and to ensure the required reaction temperature by partial oxidation with air, is returned to the upper part of the furnace shaft via the upper gas collection duct and via a medium gas extraction, the in the height between the upper and lower gas collection channels, is removed again from the furnace after this partial gas flow has flowed through the bulk material in cocurrent, preheated it to the reaction temperature and reduced the haematitic ore to wustite.

4. A process for the production of iron in the blast furnace according to claim 3, characterized in that the separation of the gases ascending and descending in the furnace, which is required for complete gas removal, is carried out by the pressure of the gas conducted in the upper part of the furnace in cocurrent with the bulk material its supply to the furnace is set so that the gases to be discharged via the lower and middle gas extraction do not mix in the bed or only mix to the intended extent.

5. A process for the production of iron in the blast furnace according to claim 3 or 4, characterized in that the gas removed from the furnace via the first gas extraction is dedusted before cooling, cooled, in pressure to the operating pressure of the wind heating and recuperative and / or regenerative to temperatures is raised above 1,000 ° C.

6. A process for producing iron in the blast furnace according to claim 3 to 5, characterized in that the gas in the furnace, regardless of whether no or only partial gas is removed from the furnace via the lower gas extraction, before the reduction of hematite Magnetite is partially oxidized by supplying air in the furnace to raise the temperature, is completely burned when gas is partially removed and the oxidized gas or the combustion gas is used to preheat the bulk material to 600 to 700 ° C in the furnace itself and is thereby cooled to 150 to 250 ° C ,

7. A process for producing iron in the blast furnace according to claims 3 to 5, characterized in that the process temperature in the reduction of hematite to magnetite or wustite by the recirculated, regeneratively and / or recuperatively heated gas and by admixing air and so that partial oxidation is set in the upper shaft area of the blast furnace.

8. A process for the production of iron in the blast furnace according to claim 3 to 7, characterized in that the gas from the lower gas extraction an external process for the gasification of substitute fuel to reducing gas for blowing into the blast furnace, the sponge and carbide production as a gasifying agent or supplied is used directly for the production of iron carbide under increased process pressure.

9. A process for producing iron in the blast furnace according to claim 3 to 8, characterized in that the blast furnace gas or gas discharged from the furnace, which was partially or completely removed from the furnace according to claim 3 via the lower gas extraction or via the upper gas extraction, on hot wind pressure Compressed and burned under pressure in the hot air heaters and in additional combustion chambers to work equipment for preferably turbochargers, which are used for the internal air and gas compression and compressed air generation for air separation, but also for expansion turbine systems for power generation.

10. A process for the production of iron in the blast furnace according to claim 1 to 9, characterized in that the injection of the substitute fuel instead of blowing lances over burners integrated in the wind molds, which the substitute fuel during the injection with so much hot wind and / or oxygen, if appropriate with the addition of recirculated gas from the first gas extraction, blast furnace gas or externally generated reducing gas, mix as for the complete gasification of the substitute fuel in the swirl chambers even at high blowing rates and for the reduction of carbon dioxide and water vapor of the recirculated gas Carbon monoxide and hydrogen are required at predetermined temperatures in the mold plane.

11. A process for the production of iron in the blast furnace according to claim 1 to 10, characterized in that with the substitute fuel via the burner in addition to that required for the gasification of the substitute fuels and also the oxygen required for the proportionate gasification of the coke in the bulk material is blown in, wherein the temperature level in the mold plane is adjusted with gas recirculated from the furnace, blast furnace gas or with externally generated reducing gas.

12. A process for the production of iron in blast furnaces according to claims 3 and 11, characterized in that the hot heater is used for regenerative preheating of the gas removed from the furnace via the lower gas extraction and the hot wind system for the return of the gas to the furnace.

13. A process for the production of iron according to claim 1, characterized in that the process is carried out with the aid of fluidized bed or entrained flow technology, in that the stationary or circulating fluidized beds which implement the process stage or the entrained flow are predominantly formed from eddy or blowable iron, which continuously wustite to and from which iron is continuously discharged, the gas which drives the fluidized bed or the entrained flow and which is fed to the process stage is generated externally by gasification and has a volume ratio of the reducing constituents carbon monoxide and hydrogen to the oxidizing constituents carbon dioxide and water vapor which is smaller , preferably at most half as large as that of the gas removed from the process stage.

14. A process for the production of iron according to claims 1 and 13, characterized in that the gas to be removed from the process stage formed by a fluidized bed or flying cloud is increased in pressure and returned to the process, fuel, air and / or oxygen being fed in at the same time or carbon dioxide and water are removed from the gas before recycling.

15. A process for the production of iron according to claims 1 and 13 to 14, characterized in that the gas to be removed from the process step formed by fluidized beds or entrained flow is also used in part in addition to the recirculation as an endothermic gasifying agent in the external reduction gas production, for the reduction of haematitic or magnetitic ore to wustite and as a fuel for ore preheating and production of tools for power processes.

16. A process for producing iron carbide according to claims 1 and 13 to 15, characterized in that the process is carried out in a process stage formed by stationary debris or fluidized bed, circulating fluidized bed or by entrained flow and others, and by stoking the process stage, vortex- or blowing iron sponge and reducing gas produced by gasifying carbon-containing fuels is supplied, the carbon monoxide content of which is at least one third of the sum of carbon monoxide and. by using coke, preferably petroikoks, or coal as a fuel and optionally carbon dioxide as an endothermic gasifying agent and / or separation of hydrogen Hydrogen was raised, the proportion of the oxidizing gas components carbon dioxide and water vapor should not exceed 3% by volume a partial pressure of the reacting gas components of at least 1 bar and a process temperature <750 ° C.

17. A process for the production of iron carbide according to claim 16, characterized in that the gas to be removed from the process step of carbonization of iron to iron carbide and the hydrogen which may occur in the production of the gas required for this purpose is used as the reducing gas in the carbonization preceding the reduction of wustite to iron.

18. A process for the production of iron carbide according to claims 16 and 17, characterized in that the production of iron carbide from wustite takes place with gasification gas generated internally or externally from fossil or renewable fuels at process pressures> 10 bar and from magnetite> 25 bar, each at process temperatures of 600 to 800 ° C.

19. Blast furnace for carrying out the method according to claim 1 to 12, characterized by a device, preferably a hollow cone or a pipe grate, which the air supplied via one or more channels for partial oxidation in the bulk material, preferably before the start of ore reduction, across the shaft cross-section distributed.

20. Blast furnace for the production of iron according to claim 19, characterized by burners for the gasification of the substitute fuels in the mold plane with hot air and / or oxygen, which atomize the blown substitute fuels supplied via pneumatic dense phase conveyance with hot air and / or oxygen.

21. Device for carrying out the process in a solid bed in combination with the pig iron production according to claims 1 to 12, characterized in that this corresponds in its lower part to a middle height of a blast furnace with the features of claims 19 and 20, while the upper Part of the device consists of a filling shaft and a gas-tight cylinder or truncated cone, which together with the bed form the upper gas collection duct, from which the gas is completely discharged from the furnace in a continuous countercurrent mode with or without partial gas extraction, with the upper and lower part of the device also form the bulk gas the lower gas collection channel, through which the gas rising in the lower part of the furnace is partially or completely discharged from the furnace.

22. The apparatus according to claim 21, characterized by a hot gas injection device, which corresponds in its outer design to a conventional wind form, but is equipped with a burner for the gasification of substitute fuel, preferably coal fuel dust or blowable fine coke, with oxygen, with this blowing device either hot wind or hot, recirculated and / or hot reducing gas from external production, which is recirculated from the first gas extraction, is introduced into the mold level of the furnace and the recirculated or supplied gas, the substitute fuel and air and / or oxygen are introduced into the mold level with the aid of the burner, that a vortex chamber is blown in the furnace, in which recirculated gas, substitute fuel, air and / or oxygen are converted to reducing gas at temperatures of over 1,900 ° C.

23. Device for producing sponge iron or iron carbide from granular, lumpy or pelletized iron ore in the solid bed, preferably for the implementation of claims 16 to 18, characterized in that their gas-tight upper part with a filling shaft and the bulk material form an upper gas collection channel, via the the combustion gas is removed from the bulk material preheater, the upper part of the device with the lower part and the solid bed form the lower gas collecting duct, via which the gas escaping from the bed reduced to wustite can be partially removed and recycled, the lower part of the furnace preferably by a Rust is completed, via which cold reducing gas is introduced into the furnace for the purpose of cooling the bed and, depending on the CO partial pressure in the reducing gas and the process pressure, either iron sponge or carbide can be discharged, the upper part of the furnace a device, preferably a cone or tubular grate with holes, which is supplied with air via a feed line for the combustion of the gas flowing in the shaft after the reduction of hematite to magnetite.