Method for producing steel and associated plant complex

Abstract

The present invention concerns a method and a plant complex for steel production.

Description

[0001] METHOD FOR PRODUCING STEEL AND ASSOCIATED PLANT COMPLEX

[0002] The present invention concerns a method and a plant complex for steel production.

[0003] Steel production involves a first step of hot metal production, a second step of conversion of hot metal into liquid steel, and optionally the production of coke.

[0004] Hot metal is obtained in a blast furnace from iron ores, additives such as coke and other reducing agents such as coal, oil, gas, biomasses, recycled waste plastics or other substances containing carbon and / or hydrogen. CO, CO2, hydrogen and water vapour are inevitable products of the reduction reactions. Apart from the aforementioned constituents, a blast-furnace furnace top gas drawn off from the blast-furnace process often has a high content of nitrogen. The amount of gas and the composition of the blast-furnace top gas are dependent on the feedstock and the operating mode and are subjected to fluctuations. Typically, however, blast-furnace top gas contains 35 to 60% by volume N2, 20 to 30% by volume CO, 20 to 30% by volume CO2 and 2 to 15% by volume H2. Around 30 to 40% of the blast-furnace top gas produced in the production of hot metal is generally used for heating up the hot air for the blast-furnace process in air heaters; the remaining amount of top gas may also be used externally in other areas of the works for heating purposes or for electricity generation.

[0005] In the converter, which is arranged downstream of the blast-furnace process, hot metal is converted into liquid steel. By blowing oxygen onto hot metal, amounts of unwanted components such as carbon, silicon, sulphur and phosphorus are reduced. Since the oxidation processes are exothermic, scrap is often added in amounts of up to 25% with respect to the hot metal to increase the metal yield. Furthermore, lime is added as slag forming agent to remove unwanted impurities form the hot metal. A converter gas that has a high content of CO and also contains nitrogen, hydrogen and CO2 is drawn off from the steel converter. A typical converter gas composition has from 50 to 70% by volume of CO, from 10 to 20% by volume of N2, about 15% by volume of CO2 and about 2% by volume of H2. The converter gas is either burned off or, in the case of modern steel mills, captured and passed on to be used for energy supply.

[0006] The plant complex may optionally be operated in combination with a coking plant. In this case, the plant complex described at the beginning additionally comprises a coke-oven plant, in which coal is converted into coke by a coking process. In the coking of coal into coke, a coke-oven gas occurs, containing high hydrogen content and considerable amounts of CH4. Typically, coke-oven gas contains 55 to 70% by volume H2, 20 to 30% by volume CH4, 5 to 10% by volume N2 and 5 to 10% by volume CO. In addition, the coke-oven gas has fractions of CO2, NH3 and H2S. In practice, the coke-oven gas is used in various areas of the works for heating purposes and in the power-generating process for electricity generation. In addition, it is known to use coke-oven gas together with blast-furnace top gas or with converter gas for producing syngases.

[0007] In an integrated metallurgical plant that is operated in combination with a coking plant, approximately 40 to 50% of the raw gases that occur as blast-furnace top gas, converter gas and coke-oven gas are used for chemical or biotechnological engineering processes. Approximately 50 to 60% of the gases produced are fed to the power-generating plant and used for electricity generation. The electricity produced in the power-generating plant covers the electricity demand for the production of hot metal and liquid steel.

[0008] Ideally, the energy balance is closed, so that, apart from iron ores and carbon in the form of coal and coke as sources of energy, no further energy input is necessary and, apart from liquid steel and slag, no product leaves the plant complex.

[0009] EP3080309 discloses a plant complex for steel production comprising a blast furnace for producing hot metal, a converter for producing liquid steel, a gas-conducting system for gases that occur in at least one of the production of hot metal and liquid steel, and a biotechnological plant connected to the gas-conducting system.

[0010] This plant complex focuses on energy and cost optimization but is silent about the overall environmental impact and the management of co-products.

[0011] Thus, there is a need for a steelmaking plant complex in which the integration of the biotechnological plant is improved, and the global environmental footprint of the process is reduced.

[0012] There is also a need for a steelmaking plant complex that produces steel with an improved cost-effectiveness and with reduced costs.

[0013] The present invention solves these needs.

[0014] The present invention relates to a method for producing steel, comprising:

[0015] - producing hot metal and a blast furnace top gas in a blast furnace,

[0016] - producing liquid steel and a converter gas in a converter,

[0017] - capturing at least a partial amount of blast furnace top gas and / or a partial amount of converter gas,

[0018] - generating electricity in a power-generating plant, - producing at least one product and a residual gas in a a biotechnological plant, wherein :

[0019] - the captured blast furnace top gas and / or converter gas are divided into a first gas stream and a second gas stream, and a) the first gas stream is used for operating the power-generating plant, b) the second gas stream is fed to the biotechnological plant to produce the at least one product and the residual gas, and the residual gas is mixed with the first gas stream and the resulting mixture is fed to the power-generating plant for producing electricity.

[0020] Thanks to the invention, it is possible to use the residual gas from the biotechnological plant, thereby reducing the impact on the environment and without the need for additional installations.

[0021] The method of the invention may also comprise the following optional characteristics considered separately or according to all possible technical combinations:

[0022] - the second gas stream is fed after a gas-conditioning operation to the biotechnological plant to produce at least one product and a residual gas;

[0023] - the residual gas is directly mixed with the first gas stream before feeding the powergenerating plant, or the residual gas is first mixed with the tail gas stream produced by a gas-conditioning operation unit of the second gas stream and then mixed with the first gas stream;

[0024] - the power-generating plant is designed as a steam-turbine power-generating plant or as a gas-turbine power-generating plant or gas-turbine and steam-turbine power-generating plant;

[0025] - the first and second gas streams, and preferably the residual gas, are syngas;

[0026] - the gas-conditioning operation is a compression and / or a pressure swing adsorption (PSA) and / or a water-gas-shift reaction (WGS) and / or a compression and / or a Vacuum Pressure Swing Adsorption (VPSA);

[0027] - the biotechnological plant is a plant for the fermentation of the second gas stream and allows production of at least one product, preferably chosen from alcohols such as methanol, ethanol, propanol, butanol, isobutanol or 2,3-butanediol ; acetone ; and organic acids such as acetic acid, butyric acid, isobutyric acid, propionic acid, hexanoic acid or caproic acid;

[0028] - the fermentation is carried out by one of more strains of carboxydotrophic bacteria which are preferably anaerobic ; preferably the carboxydotrophic bacterium is selected from Clostridium, Moorella and Carboxydothermus, most preferably the carboxydotrophic bacterium is Clostridium autoethanogenum such as a Clostridium autoethanogenum having the identifying characteristics of DSMZ deposit number 19630 or having the identifying characteristics of DSMZ deposit number DSMZ 10061 ;

[0029] - coke and coke oven gas are produced in a coke oven and the coke oven gas is captured together with the blast furnace gas and / or the converter gas.

[0030] The present invention also relates to a plant complex for the production of steel for implementing a steel production method according to the invention, comprising: a blast furnace producing hot metal and a blast furnace top gas, a converter producing liquid steel and a converter gas, a gas-conducting system for capturing gases that occur in the production of hot metal and / or the production of liquid steel, a power-generating plant for electricity generation connected to the gas-conducting system and a biotechnological plant connected to the gas-conducting system, wherein: the power-generating plant is fed with a first gas stream that comprises at least a partial amount of the blast-furnace top gas and / or a partial amount of the converter gas, the biotechnological plant is operated with a second gas stream that comprises at least a partial amount of the blast-furnace top gas and / or a partial amount of the converter gas, the gas-conducting system has a switchable gas diverter for dividing the streams of gas that are fed to the power-generating plant and to the biotechnological plant, and the biotechnological plant produces a residual gas which is connected by a carrying line to the first gas stream.

[0031] The plant complex of the invention may also comprise the following optional characteristics considered separately or according to all possible technical combinations:

[0032] - the gas-conducting system further comprises, upstream of the switchable gas diverter in the direction flow, a cleaning device for producing a cleaned gas of blast-furnace top gas and / or converter gas ;

[0033] - at least one gas-conditioning operation unit is present in the gas-conducting system between the switchable gas diverter and the biotechnological plant;

[0034] - the carrying line connects the residual gas produced by the biotechnological plant directly to the first gas stream, or the carrying line connects the residual gas produced by the biotechnological plant to the tail gas stream produced by a gas-conditioning operation unit of the second gas stream, such as a PSA unit; - the power-generating plant is designed as a steam-turbine power-generating plant or as a gas-turbine power-generating plant or as a gas-turbine and steam-turbine powergenerating plant.

[0035] Thanks to the invention, it is possible to use the residual gas from the biotechnology plant, thereby reducing the impact on the environment and without the need for additional installations.

[0036] The method according to the invention makes it possible for the plant complex to be operated cost-effectively. Indeed, the conversion efficiency of the biotechnological plant is almost the double as compared to the power-generating plant efficiency. Typically the efficiency of the biotechnological plant is around 74%, whereas the existing powergenerating plant efficiencies range between 30% to 42%.

[0037] The product output of the power-generating plant can be controlled between 20% and 100%, in dependence on the amount of useful gas fed to the power-generating process. The product output of the biotechnological plant is controlled in dependence on the amount of mixed gas fed to this plant. The use of a biotechnological plant has the advantage that a biotechnological plant is more flexible with respect to load changes than a chemical plant.

[0038] Other characteristics and advantages of the invention will emerge clearly from the description of it that is given below by way of an indication, and which is in no way restrictive, with reference to the appended figure (Figure 1 ) which illustrates an embodiment of a method according to the invention.

[0039] It is noted that the figure represents mainly one embodiment of the object of the invention but other embodiments which correspond to the definition of the invention may exist. Elements in the figure are illustration and may not have been drawn to scale.

[0040] Figure 1 illustrates a plant complex for steel production according to one embodiment of the invention.

[0041] The plant complex for steel production that is represented in FIG. 1 comprises a blast furnace 1 for producing hot metal and / or a converter 2 for producing liquid steel, a powergenerating plant 3 for producing electricity and a biotechnological plant 11. The gasconducting system is also represented, but not linked to a specific number. In the blast furnace 1 , hot metal 33 is obtained substantially from iron ore 30 and reducing agents 31 , in particular coke and coal. Reduction reactions cause the production of a blast-furnace top gas 7 (BFG), which contains nitrogen, CO, CO2 and H2 as the main constituents. In the converter 2 that is arranged downstream of the blast-furnace process, hot metal is converted into liquid steel. By blowing oxygen onto the liquid hot metal, amount of unwanted component, in particular carbon, silicon and phosphorus, are reduced. Scrap may be added in amounts of up to 25% with respect to the amount of hot metal. Furthermore, lime is added for forming slag. At the top of the converter, a converter gas 9 that has a very high proportion of CO is drawn off.

[0042] The power-generating plant 3 is designed as a steam-turbine power-generating plant (such as a traditional gasfired steamboiler and a steam turbine driven generator to generate the electrical energy) or as a gas-turbine power-generating plant or as a gas-turbine and steam-turbine power-generating plant and is operated with a gas that comprises at least a partial amount of the blast-furnace top gas 7 that occurs in the production of hot metal in the blast furnace 1 and / or at least a partial amount of the converter gas 9 that occurs in the converter steel works 2. A gas-conducting system is provided for carrying the gases.

[0043] According to the overall balance represented in FIG. 1 , carbon 31 is fed to the plant complex as a reducing agent in the form of coal and coke together with iron ore 30. Occurring as products are liquid steel and raw gases 7, 9, which differ in amount, composition, calorific value and purity and are used again at various points in the plant complex. In an overall consideration, from 35 to 45%, usually approximately 45%, of the raw gases 7, 9 are reused into the metallurgical process for producing hot metal or producing liquid steel (not represented on FIG. 1 ). From 50 to 60%, usually approximately 55%, of the raw gases 7, 9 can be used for operating the power-generating plant 3 and the biotechnological plant 11.

[0044] A biotechnological plant 11 is provided, connected to the gas-conducting system and arranged in parallel with the power-generating plant 3 with respect to the gas supply. In other words, the power-generating plant 3 and the biotechnological plant 11 are arranged in a parallel setup with respect to the gas supply. The gas-conducting system has an operationally controllable gas diverter 12 for dividing the streams of gas that are fed on one hand 4.1 to the power-generating plant 3 and on the other hand 4.2 to the biotechnological plant 11. Provided upstream of the gas diverter 12 in the direction of flow is preferably a cleaning device 13 for producing a cleaned gas 4 of blast-furnace top gas 7 and / or converter gas 9. Typically, the cleaning devices 13 for each one of the blast-furnace top gas 7 and the converter gas 9 are water wash cleaning devices. Each gas has generally its own cleaning device, thus the washing step is not in common for both gases. The gasconducting system may further comprise, upstream of the switchable gas diverter 12 in the direction flow, a mixing device for producing a mixed gas comprising blast-furnace top gas 7 and converter gas 9.

[0045] In the case of the plant complex represented in FIG. 1 , at least a partial amount of the blast-furnace top gas 7 that occurs in the production of hot metal in the blast furnace 1 and / or a partial amount of the converter gas 9 that occurs in the production of liquid steel are used for operating the power-generating plant 3 and the biotechnological plant 11 in parallel. A first partial stream 4.1 of the useful gas (i.e. first gas stream) is used in the power-generating plant 3 for electricity generation. A second partial stream 4.2 of the useful gas (i.e. second gas stream) is fed to the biotechnological plant 11 and used after a gas-conditioning operation as syngas for fermentation. Thus, both the first and second gas streams 4.1 and 4.2 comprise at least a partial amount of the blast-furnace top gas 7 and / or a partial amount of the converter gas 9.

[0046] At least one gas-conditioning operation unit 14 is present in the gas-conducting system between the switchable gas diverter 12 and the biotechnological plant 11. The gasconditioning operation is performed in or or more gas conditioning units 14, such as for example a Pressure Swing Adsorption device (PSA) (for separating out and enriching H2), a compression, a Vacuum Pressure Swing Adsorption device (VPSA) or a water-gas-shift reaction (WGS) for converting CO into H2 and / or a steam reformer for converting the CH4 fraction into CO and H2 (in the case of the use of a coke oven gas). It aims notably to reduce the CO2 concentration of the gas. Typically, the gas-conditioning operation 14 comprises a compression and then PSA; the compression allows obtaining a required pressure that may be useful for the biotechnological plant 11 , especially for fermentation. PSA 14 aims to separate out and enrich the gas in H2 and / or CO. PSA 14 may further aim to remove from the gas any of the contaminants that are deleterious to the biotechnological plant 11. Said contaminant is especially HCN. Said contaminants are preferably sent to the PSA tail gas 6 that goes to the power-generating plant 3. Preferably, the PSA 14 comprises at least one pressure vessel, preferably at least six pressure vessels. The pressure vessel comprises an adsorbent material. At the exit of the gas conditioning units 14, the second partial stream 4.2 is split between a syngas 34 and a tail gas 6 that is rich in CO. Average compositions of those gases are provided in Table 1 . Table 1

[0047] The syngas 34 is then sent to the biotechnological plant 11 where it produces at least one biochemical product 16 and a residual gas 5. Said residual gas 5 produced by the biotechnological plant 11 may also be a syngas.

[0048] By « syngas » or « synthesis gas », it is meant a gas comprising at least a mixture of carbon monoxide (CO) and dihydrogen (H2). The syngas may further comprise other carbon-containing gases such as carbon dioxide (CO2), methane (CH4) and optionally nitrogen (N2).

[0049] The biotechnological plant 11 according to the invention is a plant for the fermentation of the second gas stream (syngas). The second gas stream 4.2 is used biochemically by way of a fermentation process. Thanks to fermentation, the biotechnological plant 11 allows production of at least one product 16. Said product 16 may be chosen from alcohols (such as methanol, ethanol, propanol, butanol, isobutanol or 2,3-butanediol), acetone and organic acids (such as acetic acid, butyric acid, isobutyric acid, propionic acid, hexanoic acid or caproic acid).

[0050] Preferably, the fermentation reaction is carried out by one of more strains of carboxydotrophic bacteria. By « carboxydotrophic bacteria », it is meant bacteria that have the ability to oxidize CO. Preferably, the carboxydotrophic bacteria are anaerobic. Preferably, the carboxydotrophic bacterium is selected from Clostridium, Moorella and Carboxydothermus. Clostridium autothenogenum DSMZ (German Resource Centre for Biological Material) 19630, Clostridium autothenogenum DSMZ 10061 , Clostridium ragsdahlei ATCC no. BAA-622, Clostridium autoethanogenum, Moorella sp HUC22-1 , Moorella thermoaceticum, Moorella thermoautotrophica, Carboxydothermus, Clostridium formicoaceticum, Clostridium butyricum, Clostridium aceticum, Clostridium ljungdahlii, Clostridium ATCC 29797 and Clostridium carboxidivorans, in particular ATCC BAA-624.

[0051] Most preferably, the carboxydotrophic bacterium is Clostridium autoethanogenum. Preferably, the Clostridium autoethanogenum is a Clostridium autoethanogenum having the identifying characteristics of DSMZ deposit number 19630. In another embodiment, the Clostridium autoethanogenum is a Clostridium autoethanogenum having the identifying characteristics of DSMZ deposit number DSMZ 10061 .

[0052] During the fermentation, typically the feed gas 34 which enters into the biotechnological plant 11 is rich in CO and H2. Indeed, the richer the feed gas is in CO and H2, the more product can be produced in the biotechnological plant.

[0053] The fermentation may be carried out in any suitable bioreactor. The term "bioreactor" includes a fermentation device consisting of one or more vessels and / or towers or piping arrangements, which can include the Continuous Stirred Tank Reactor (CSTR), Immobilized Cell Reactor (ICR), Trickle Bed Reactor (TBR), Bubble Column, Gas Lift Fermenter, Membrane Reactor such as Hollow Fibre Membrane Bioreactor (HFMBR), Static Mixer, or other vessel or other device suitable for gas-liquid contact. In some embodiments of the invention, the bioreactor may comprise a first growth reactor in which the bacteria are cultured, and a second fermentation reactor, to which fermentation broth from the growth reactor is fed and in which most of the fermentation product is produced.

[0054] The fermentation should desirably be carried out under appropriate conditions for the desired fermentation to occur (preferably CO-to-alcohol). Reaction conditions that should be considered include pressure, temperature, gas flow rate, liquid flow rate, media pH, media redox potential, agitation rate (if using a continuous stirred tank reactor), inoculum level, maximum gas substrate concentrations to ensure that CO in the liquid phase does not become limiting, and maximum product concentrations to avoid product inhibition.

[0055] The optimum reaction conditions will depend partly on the particular carboxydotrophic bacteria used. However, in general, it may be preferable that the fermentation be performed at a pressure higher than ambient pressure. Operating at increased pressures allows a significant increase in the rate of CO transfer from the gas phase to the liquid phase where it can be taken up by the carboxydotrophic bacteria as a carbon source for the production of alcohol. The products 16 of the fermentation reaction can be recovered using known methods. However, briefly and by way of example only, alcohol such as ethanol may be recovered from the fermentation broth by methods such as fractional distillation or evaporation, and extractive distillation. Distillation of ethanol from a fermentation broth yields an azeotropic mixture of ethanol and water (i.e. 95% ethanol and 5% water). Anhydrous ethanol can subsequently be obtained through the use of molecular sieve ethanol dehydration technology, which is also well-known in the art.

[0056] During fermentation, the biotechnological plant 11 produces, besides the product 16, a residual gas 5. Said residual gas 5 has typically a CO content that is lower than 5% and a H2 content that is lower than 1 %. However, the specific composition of the residual gas 5 can vary, depending on the composition of the feed gas given to the biotechnological plant 11 . Said residual gas 5 is connected by a carrying line to the first gas stream 4.1 . The powergenerating plant 3 is thus fed with a mixture 10 of the first gas stream 4.1 and the residual gas 5.

[0057] According to another embodiment, the carrying line connects the residual gas 5 produced by the biotechnological plant 11 to the tail gas stream 6 produced by a gasconditioning operation unit 14 of the second gas stream 4.2, such as a PSA unit.

[0058] The blast-furnace top gas 7 and the converter gas 9 may be combined with one another in any way desired. The combination of gas streams 7, 9 depends on the desired syngas, the availability of the different streams and / or on the product to be produced in the biotechnological plant 11.

[0059] Specifically, the power-generating plant 3 is operated with a mixed gas 10 comprising cleaned blast-furnace top gas and / or converter gas 4 mixed with the residual gas 5 emitted by the biotechnological plant 11. Indeed, the gas 10 corresponds to a mixture of a part of the cleaned blast-furnace top gas and / or converter gas 4 with the residual gas 5 emitted by the biotechnological plant 11. Preferably the gas 10 is a mixture of a part of the cleaned blast-furnace top gas and / or converter gas 4 with the tail gas 6 emitted by the PSA unit and the residual gas 5 emitted by the biotechnological plant 11. Electricity is produced by the power-generating plant 3 of the plant complex.

[0060] Externally obtained electricity and power-generating plant electricity, which is produced by the power-generating plant 3 of the plant complex, are used to cover the electricity demand of the plant complex. The externally obtained electricity is preferably obtained completely or at least partially from renewable energy and originates for example from wind turbine generator plants, solar plants, hydroelectric power-generating plants and the like. To achieve operation of the plant complex that is as cost-effective as possible, electricity is bought in as external electricity at times of low electricity prices and the powergenerating process for supplying electricity is cut back. At times of high electricity prices, the partial stream 4.1 of the useful gas that is used in the power-generating plant 3 for producing electricity is increased.

[0061] The plant complex can additionally comprise a coke-oven plant. In the coking of coal into coke, coke-oven gas occurs, containing a high proportion of hydrogen and CH4. Parts of the coke-oven gas may be used for the heating of the air heaters in the blast furnace 1. The gas-conducting system includes a gas distribution for the coke-oven gas. With the gas diverter 12, the streams of gas that are fed to the power-generating plant 3 and the biotechnological plant 11 can be controlled. In this embodiment, a partial amount of the blast-furnace top gas 7 and / or a partial amount of the converter gas 9 are mixed with a partial amount of the coke-oven gas that occurs in the coke-oven plant. The mixed gas may be used as the first and / or second gas streams. Preferably it is used as a useful gas for operating the power-generating plant 3 and the biotechnological plant 11 . The blast-furnace top gas 7, the converter gas 9 and the coke-oven gas may be combined with one another in any way desired. The combination of gas streams depends on the desired syngas or the product that is to be produced in the biotechnological plant 11 by using the syngas. The coke-oven gas may be conditioned in a conditioning unit, especially a cleaning unit to separate out troublesome contents, in particular tar, sulphur and sulphur compounds, aromatic hydrocarbons (BTX) and high-boiling hydrocarbons.

[0062] For example, it is possible within the scope of the invention that blast-furnace top gas 7 and converter gas 9 are mixed, that a syngas is produced from the mixed gas after a gas-conditioning operation and that conditioned coke-oven gas is additionally admixed with the syngas or the cleaned mixed gas before the further processing to form the syngas. Furthermore, there is the possibility that a syngas is produced from blast-furnace top gas 7 after a gas-conditioning operation and that conditioned coke-oven gas is additionally admixed with the syngas or the cleaned blast-furnace top gas before the further processing to form the syngas. Finally, there is the possibility that a syngas is produced from converter gas 9 after a gas-conditioning operation and that conditioned coke-oven gas is additionally admixed with the syngas or the cleaned converter gas before the further processing to form the syngas. Table 2 provides the gas compositions as an illustration of a plant complex wherein only blast furnace top gas 7 is captured, the biotechnological plant 11 is a fermentation plant that produces ethanol, the gas-conditioning operation unit 14 is a PSA unit, and the residual gas 5 from the fermentation plant is mixed with the tail gas of the PSA 6 before being mixed with the first stream 4.1 of BFG sent to the power-generating plant 3:

[0063] Table 2

[0064] Many different arrangements of the described invention are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention are described herein with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the disclosed improvements without departing from the scope of the present invention.

[0065] Further, it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. Not all steps listed in the various figures and description need to be carried out in the specific order described. The description should not be restricted to the specific described embodiments.

Claims

CLAIMS1 . Method for producing steel, comprising:- producing hot metal (33) and a blast furnace top gas (7) in a blast furnace (1 ),- producing liquid steel and a converter gas (9) in a converter (2),- capturing at least a partial amount of blast furnace top gas (7) and / or a partial amount of converter gas (9),- generating electricity in a power-generating plant (3),- producing at least one product (16) and a residual gas (5) in a a biotechnological plant (1 1 ), wherein :- the captured blast furnace top gas (7) and / or converter gas (9) are divided into a first gas stream (4.1 ) and a second gas stream (4.2), and a) the first gas stream (4.1 ) is used for operating the power-generating plant (3), b) the second gas stream (4.2) is fed to the biotechnological plant (11 ) to produce the at least one product (16) and the residual gas (5), and the residual gas (5) is mixed with the first gas stream (4.1 ) and the resulting mixture (10) is fed to the power-generating plant (3) for producing electricity.

2. Method according to claim 1 , wherein the second gas stream (4.2) is fed after a gasconditioning operation (14) to the biotechnological plant (11 ) to produce at least one product (16) and a residual gas (5).

3. Method according to any one of claims 1 or 2, wherein the residual gas (5) is directly mixed with the first gas stream (4.1 ) before feeding the power-generating plant (3), or the residual gas (5) is first mixed with the tail gas stream (6) produced by a gas-conditioning operation unit (14) of the second gas stream (4.2) and then mixed with the first gas stream(4.1 ).

4. Method according to any one of the preceding claims, wherein the first (4.1 ) and second(4.2) gas streams, and preferably the residual gas (5), are syngas.

5. Method according to any one of the preceding claims, wherein the gas-conditioning operation (14) is a compression and / or a pressure swing adsorption (PSA) and / or a watergas-shift reaction (WGS) and / or a Vacuum Pressure Swing Adsorption (VPSA).

6. Method according to any one of the preceding claims, wherein the biotechnological plant (11 ) is a plant for the fermentation of the second gas stream and allows production of at least one product, preferably chosen from alcohols such as methanol, ethanol, propanol, butanol, isobutanol or 2,3-butanediol ; acetone ; and organic acids such as acetic acid, butyric acid, isobutyric acid, propionic acid, hexanoic acid or caproic acid.

7. Method according to claim 6, wherein the fermentation is carried out by one of more strains of carboxydotrophic bacteria which are preferably anaerobic ; preferably the carboxydotrophic bacterium is selected from Clostridium, Moorella and Carboxydothermus, most preferably the carboxydotrophic bacterium is Clostridium autoethanogenum such as a Clostridium autoethanogenum having the identifying characteristics of DSMZ deposit number 19630 or having the identifying characteristics of DSMZ deposit number DSMZ 10061.

8. Method according to any one of the preceding claims, wherein coke and coke oven gas are produced in a coke oven and the coke oven gas is captured together with the blast furnace gas (7) and / or the converter gas (9).

9. Plant complex for the production of steel for implementing a steel production method according to any one of claims 1 to 8, comprising : a blast furnace (1 ) producing hot metal (33) and a blast furnace top gas (7), a converter (2) producing liquid steel and a converter gas (9), a gas-conducting system for capturing gases that occur in the production of hot metal (33) and / or the production of liquid steel, a power-generating plant (3) for electricity generation connected to the gas-conducting system and a biotechnological plant (1 1 ) connected to the gas-conducting system, wherein: the power-generating plant (1 1 ) is fed with a first gas stream (4.1 ) that comprises at least a partial amount of the blast-furnace top gas (7) and / or a partial amount of the converter gas (9), the biotechnological plant (11 ) is operated with a second gas stream (4.2) that comprises at least a partial amount of the blast-furnace top gas (7) and / or a partial amount of the converter gas (9),the gas-conducting system has a switchable gas diverter (12) for dividing the streams of gas that are fed to the power-generating plant (3) and to the biotechnological plant (11 ), and the biotechnological plant (11 ) produces a residual gas (5) which is connected by a carrying line to the first gas stream (4.1 ).

10. Plant complex according to claim 9, wherein the gas-conducting system further comprises, upstream of the switchable gas diverter (12) in the direction flow, a cleaning device (13) for producing a cleaned gas of blast-furnace top gas (7) and / or converter gas (9).1 1. Plant complex according to claim 9 or 10, wherein at least one gas-conditioning operation unit (14) is present in the gas-conducting system between the switchable gas diverter (12) and the biotechnological plant (11 ).

12. Plant complex according to any one of claims 9 to 11 , wherein the carrying line connects the residual gas (5) produced by the biotechnological plant (11 ) directly to the first gas stream (4.1 ), or the carrying line connects the residual gas (5) produced by the biotechnological plant to the tail gas stream (6) produced by a gas-conditioning operation unit of the second gas stream (4.2), such as a PSA unit.

13. Plant complex according to any one of claims 9 to 12, wherein the power-generating plant (3) is designed as a steam-turbine power-generating plant or as a gas-turbine powergenerating plant or as a gas-turbine and steam-turbine power-generating plant.

Images