PROCESS UTILIZING SYNTHESIS GAS FOR IMPROVING THE ENVIRONMENTAL IMPACT OF THE REDUCTION OF IRON ORE IN BLAST FURNACES

Abstract

A BF iron-ore reduction process for the production of iron and/or iron-carbon compounds with low environmental impact is described, in which a synthesis gas produced from a hydrocarbon stream with a short contact time-catalytic partial oxidation (SCT-CPO) process integrated with the iron-ore reduction process is also used in the BF.

Claims

1-10. (canceled)

11. A method for reduction of iron ores in a blast furnace for production of iron and/or iron-carbon compounds, the method comprising: combustion of coke, wherein synthesis gas produced by a hydrocarbon stream with a short contact time-catalytic partial oxidation process (SCT-CPO) integrated with the method is also introduced into the blast furnace.

12. The method of claim 11, wherein the coke is produced in a coke oven upstream of the blast furnace, and wherein the SCT-CPO process produces synthesis gas using a gaseous hydrocarbon stream and an oxidizing agent selected from among oxygen, enriched air, air, and combinations thereof.

13. The method of claim 12, wherein the SCT-CPO process produces synthesis gas further using steam.

14. The method of claim 12, wherein the gaseous hydrocarbon stream comprises one or more gases selected from among natural gas, gases deriving from chemical processes, refinery gases, and gases produced by the fermentation of biomass.

15. The method of claim 11, wherein the hydrocarbon stream comprises blast furnace gas recycled from the blast furnace and coke oven gas recycled from the coke oven, thereby carrying out partial recycling of carbon atoms.

16. The method of claim 11, wherein the coke oven gas undergoes a desulphurization treatment before being used in the SCT-CPO process.

17. The method of claim 11, wherein the oxidizing agent fed to the SCT-CPO process comprises oxygen produced by a process of electrolysis of water in liquid or steam form.

18. The method of claim 11, wherein hydrogen produced by a process of electrolysis of water in liquid or steam form is added to the synthesis gas produced by the SCT-CPO process.

19. The method of claim 11, wherein the SCT-CPO process is carried out under the following operating conditions: a. pressure higher than an operating pressure of the blast furnace, preferably between 2 and 15 bar.sub.g, more preferably between 2.5 and 10 bar.sub.g, even more preferably between 3 and 8 bar.sub.g; b. temperature of reagent mixtures comprised between 100 and 600? C., preferably between 250 and 450? C.; c. O.sub.2/C ratio (v/v) expressed as moles of oxidant O.sub.2/moles of carbon C in the reagent mixture comprised between 0.30 and 0.70 v/v, preferably between 0.50 and 0.65 v/v; d. S/C ratio expressed as moles of steam/moles of carbon C in the reagent mixture between 0 and 1.5 v/v, preferably between 0 and 0.5 v/v.

20. The method of claim 19, wherein the SCT-CPO process is carried out under a pressure between 2 and 15 bar.sub.g.

21. The method of claim 20, wherein the SCT-CPO process is carried out under a pressure between 2.5 and 10 bar.sub.g.

22. The method of claim 21, wherein the SCT-CPO process is carried out under a pressure, even more preferably between 3 and 8 bar.sub.g.

23. The method of claim 19, wherein the temperature of the reagent mixtures is comprised between 250 and 450? C.

24. The method of claim 19, wherein the O.sub.2/C ratio (v/v) is expressed as moles of oxidant O.sub.2/moles of carbon C in the reagent mixture comprised between 0.50 and 0.65 v/v.

25. The method of claim 19, wherein the S/C ratio is expressed as moles of steam/moles of carbon C in the reagent mixture between 0 and 0.5 v/v.

26. The method of claim 11, wherein the SCT-CPO process is carried out with a percentage by volume of blast furnace gas in the hydrocarbon stream comprised between 0 and 60%.

27. The method of claim 26, wherein the SCT-CPO process is carried out with a percentage by volume of blast furnace gas in the hydrocarbon stream comprised between 15 and 50%.

28. The method of claim 11, wherein the SCT-CPO process is carried out with a percentage by volume of coke oven gas in the hydrocarbon stream comprised between 0 and 60%.

29. The method of claim 11, wherein the SCT-CPO process is carried out with a percentage by volume of coke oven gas in the hydrocarbon stream comprised between 15 and 50%.

Description

DESCRIPTION OF THE INVENTION

[0014] The invention is described below also with reference to the accompanying drawings, wherein:

[0015] FIG. 1 is a diagram of a process according to a first embodiment of the invention;

[0016] FIG. 2 is a diagram of a process according to a second embodiment of the invention; and

[0017] FIG. 3 is a diagram of a process according to a third embodiment of the invention.

[0018] Processes for the reduction of iron ore in blast furnaces typically produce pig iron, which is then converted into steel in oxygen converters.

[0019] With reference to FIG. 1, in the blast furnace 50, layers of crushed iron ore of different sizes are introduced into the unit 20, the smallest of which are agglomerated by sintering and pelletizing processes 30 and 40, together with particles of coke, which has a higher calorific value than coal and is mechanically more resistant in the moving beds of the blast furnace, so it is not crushed generating polluting dust. Coke is produced in a coke oven 10 integrated into the blast furnace steelmaking process and located upstream thereof. Coke production also produces a coke oven gas, the typical composition of which is indicated in Table 1:

TABLE-US-00001 TABLE 1 g/Nm3 % v/v H.sub.2 51.33 56.44% CH.sub.4 177.41 24.39% N.sub.2 68.52 5.38% CO 67.69 5.32% H.sub.2O 28.29 3.46% C.sub.2H.sub.2 25.58 2.16% CO.sub.2 27.47 1.37% C.sub.6H.sub.6 40.824 1.15% O2 2.75 0.19% H.sub.2S 0.37 0.02% HCN 0.98 0.07% C.sub.7H.sub.8 0.6566 0.02% SO.sub.2 0.3502 0.01% C.sub.10H.sub.8 0.0442 0.00% Tar 0.0002 0.00% COS 0.0008 0.00% CS.sub.2 0.0003 0.00% NH.sub.3 0.01 0.00% Ethylbenzene 0.0305 0.00% O-Xylene 0.0812 0.00% M-Xylene 0.073 0.00% P-Xylene 0.0539 0.00% 1-Methylnaphthalene 0.0453 0.00% 2-Methylnaphthalene 0.0394 0.00% Fluorene 0.0018 0.00% Phenanthrene 0.0001 0.00% Anthracene 0.0002 0.00% Acenaphthene 0.0331 0.00%

[0020] In the lower part of the blast furnace 50, air, or oxygen-enriched air, preheated in a unit 70 is blown through the line 72. This oxidizing current reacts with the coke produced in the coke oven 10 integrated with the blast furnace, producing a carbon monoxide-rich gas at a high temperature (approx. 1900? C.) that reduces iron ore. The iron separated from the other non-metallic species, typically alkali metals and silicon oxides, melts and is collected and tapped as molten iron from the lower part of the blast furnace.

[0021] Not all the reducing species in the gas produced by the combustion of coke are consumed in the reduction processes. Therefore, in the upper part of the furnace a spent blast furnace gas 80 at about 400? C. (BFG) is recovered, which has sufficient calorific value to be used for preheating the air or enriched air that is sent to the lower part of the blast furnace. The typical composition of blast furnace gas is indicated in Table 2 below:

TABLE-US-00002 TABLE 2 v/v CH.sub.4 0.00% CO 21.20% CO.sub.2 19.80% H.sub.2 3.70% H.sub.2O 8.00% N.sub.2 47.30%

[0022] According to one aspect of the invention, the process for the reduction of iron ore in a blast furnace for the production of iron and/or iron-carbon compounds by burning coke is implemented by replacing a portion of the coke produced in the coke oven upstream of the blast furnace with synthesis gas produced with a short contact time catalytic partial oxidation process that uses a hydrocarbon gas stream, an oxidizing agent selected from one or more of oxygen, enriched air and air and optionally hydrogen and/or steam.

[0023] According to another aspect of the invention, the process for the reduction of iron ores in a BF for the production of iron and/or iron-carbon compounds by coke combustion is implemented by replacing a portion of the coke produced in the coking plant upstream of the blast furnace with synthesis gas produced with a short contact time catalytic partial oxidation process using an oxidizing agent selected from oxygen, enriched air and air, and a gaseous hydrocarbon stream comprising BF gas and coke oven gas recycled from said BF and from said coke oven, respectively, thereby carrying out partial recycling of carbon atoms, and optionally from other hydrocarbon gases and steam.

[0024] Typically, synthesis gas is produced by various technologies, such as Steam Reforming (SR), Non-Catalytic Partial Oxidation (POx) and AutoThermal Reforming (ATR). A relatively recent variant of the Steam Reforming process is Gas Heated Reforming (GHR).

[0025] Synthesis gas is used in many chemical processes, such as the synthesis of methanol and its derivatives, the synthesis of ammonia and urea, the synthesis of liquid hydrocarbons using the Fischer-Tropsch process and the production of hydrogen.

[0026] The main industrial processes that use synthesis gas require it to be produced with very different compositions in order to improve the effectiveness of integration with the processes that use it. The synthesis gas production technologies mentioned above, in fact use catalysts that require relevant amounts of steam in the reagent mixture, expressed as a steam to carbon ratio (S/C) in the hydrocarbon feedstock, in order not to be deactivated. These technologies therefore produce wet synthesis gas mixtures, the composition of which would have a negative impact on the efficiency of the BF.

[0027] However, reducing this moisture would require the cooling of the synthesis gas to condense and remove the steam, and would thus require it to be subsequently heated to very high temperatures, typically between 800-1050? C., before it could be introduced into the BF. This leads to a considerable complication in plant engineering and a major loss of energy efficiency. Moreover, even the non-catalytic partial oxidation (POx) process, which is especially useful if heavy residues from oil processing are used as a hydrocarbon feedstock, would produce a high-temperature synthesis gas, typically above 1300? C., with a high quantity of impurities such as carbon residues, polyaromatic compounds and sulphur compounds, which would make its use in the BF complex and inefficient.

[0028] Producing synthesis gas using a short contact time catalytic partial oxidation (SCT-CPO) process is also known.

[0029] This technology is described in numerous documents, such as the following patent documents: WO 2020/058859 (A), WO 2016/016257 (A1), WO 2016/016256 (A1), WO 2016/016253 (A1), WO 2016/016251 (A1), WO 2011/151082, WO 2009/065559, WO 2011/072877, WO 2009/127512, WO 2007/045457, WO 2006/034868, WO 2005/211604, WO 2005/023710, WO 97/37929.

[0030] SCT-CPO technology is also described in the following scientific literature documents: [0031] a) Issues in H.sub.2 and synthesis gas technologies for refinery, GTL and small and distributed industrial needs; Basini, Luca, Catalysis Today, 106 (1-4), p. 34, October 2005; [0032] b) Fuel rich catalytic combustion: Principles and technological developments in short contact time (SCT) catalytic processes; Basini, L.; Catalysis Today, 117(4), 384-393; DOI: 10.1016/j.cattod.2006.06.043 Published: Oct. 15, 2006; [0033] c) Natural Gas Catalytic Partial Oxidation: A Way to Syngas and Bulk Chemicals Production/IntechOpen; G. Iaquaniello, E. Antonetti, B. Cucchiella, E. Palo, A. Salladini, A. Guarinoni, A. Lainati and L. Basini; http://dx.doi.org/10.5772/48708; [0034] d) Short Contact Time Catalytic Partial Oxidation (SCT-CPO) for Synthesis Gas Processes and Olefins Production; L. E. Basini, A. Guarinoni, Ind. Eng. Chem. Res. 2013, 52, 17023-17037; https://doi.org/10.1021/ie402463m.

[0035] The term short contact time catalytic partial oxidation (SCT-CPO) has a well-defined meaning in the scientific literature, as it appears clearly from the scientific articles a)-d) above. Table 3 below indicates the main reactions involved in synthesis gas production processes.

TABLE-US-00003 TABLE 3 ?H?.sub.298K Steam - CO.sub.2 Reforming CH.sub.4 + H.sub.2O = CO + 3 H.sub.2 206 CO + H.sub.2O = CO.sub.2 + H.sub.2 ?41 CH.sub.4 + CO.sub.2 = 2CO + 2 H.sub.2 247 Non-Catalytic Partial Oxidation (POx) CH.sub.4 + 3/2 O.sub.2 = CO + 2 H.sub.2O ?520 CO + H.sub.2O = CO.sub.2 + H.sub.2 ?41 Autothermal Reforming (ATR) CH.sub.4 + 3/2 O.sub.2 = CO + 2 H.sub.2O ?520 CH.sub.4 + H.sub.2O = CO + 3 H.sub.2 206 CO + H.sub.2O = CO.sub.2 + H.sub.2 ?41 Catalytic Partial Oxidation (CPO) CH.sub.4 + ? O.sub.2 = CO + H.sub.2 ?38 CO + H.sub.2O = CO.sub.2 + H.sub.2 ?41

[0036] It has now surprisingly been found that the use of synthesis gas produced by SCT-CPO process is particularly advantageous as it offers a solution to the problem of improving the energy efficiency of iron ore reduction processes in BFs, and also reducing the amount of CO.sub.2 emitted in such processes. In particular, the integration of SCT-CPO synthesis gas with the use of coke makes it possible to: [0037] a) produce a synthesis gas with a composition and temperature suitable for introduction into the BF, typically between 800 and 1050? C.; [0038] b) produce a synthesis gas that can be fed directly to the BF, preferably with a moisture content of less than 7% v/v; [0039] c) produce a synthesis gas with a reduction capacity defined as the ratio (H.sub.2+CO)/(H.sub.2 O+CO.sub.2)=R preferably above 7.5 v/v; [0040] d) reduce iron ore by decreasing CO.sub.2 emissions, making the process more energy efficient; e) achieve these goals by recycling significant amounts of coke oven and BF gas, and possibly other waste gases from industrial processes or from biomass such as biogas.

[0041] With reference to points b) and c) above, the production of synthesis gas must take into account the parameters of moisture content and reducing capacity. In particular, it must contain low percentages of steam, which inhibits the reduction processes of iron ores, and a clear prevalence of partial oxidation products (CO, H.sub.2) over the total oxidation products (CO.sub.2, H.sub.2O) of hydrocarbons.

[0042] The process of the invention thus constitutes an innovative solution suitable not only to reduce the production and use of coke with synthesis gas but also to use coke oven and BF gas to produce a synthesis gas with an optimal composition for the reduction of iron ore. This dual benefit is made possible by producing synthesis gas using the SCT-CPO process.

[0043] The SCT-CPO process makes it possible to produce a synthesis gas suitable for the reduction processes that take place in the BF using different hydrocarbon sources such as: i) natural gas, ii) purge gas from refining processes and some chemical and petrochemical processes, iii) biogas produced from biomass.

[0044] In particular, it is possible and advantageous to integrate the use of these hydrocarbon feedstocks with relevant quantities of COG and BFG produced in iron ore reduction processes.

[0045] FIG. 1 schematically shows an integrated iron ore reduction process according to a first embodiment of the invention.

[0046] The integrated process comprises a coking plant 10, an iron ore feed 20, coke and iron ore sintering 30 and pelletizing 40 units, a BF 50 and a CPO catalytic partial oxidation reactor 60 for the production of synthesis gas.

[0047] The SCT-CPO reactor 60 produces synthesis gas using hydrocarbon gases of various compositions, e.g. natural gas (NG), coke oven gas fed via the line 12, BF gas fed via the line 52 and one or more air streams, oxygen-enriched air and oxygen.

[0048] The SCT-CPO reactor produces synthesis gas which is introduced into the BF 50 through one or more tube lines 62 located above a line 72 feeding a high temperature oxidant mixture from a unit 70.

[0049] The use of synthesis gas produced in this way makes it possible to reduce the production and use of coke and related polluting emissions, to reduce polluting emissions containing nitrogen, sulphur and carbon compounds and to reduce CO.sub.2 emissions.

[0050] As the BF typically operates at pressures between 2 and 10 kg/cm.sup.2, the production of synthesis gas with the SCT-CPO process takes place at pressures higher than those of the BF, so that the synthesis gas can be sent directly, without undergoing cooling and purification processes, and therefore at high temperature, into the BF via the line 62.

[0051] The SCT-CPO process uses operating conditions characterized by low steam to carbon ratios (S/C) in the feed, which only the SCT-CPO catalytic technology allows the use of without promoting the formation of by-products consisting of unsaturated hydrocarbons, which could be transformed through radical reactions, giving rise to aromatic and polyaromatic compounds and possibly carbon residues.

[0052] In this regard, it should be emphasized that the presence of CO.sub.2 in the reagent mixture, particularly in the BFG but also to a lesser extent in the COG, just as the presence of steam, has a strong ability to inhibit the propagation of radical reactions in the gas phase and largely compensates for the reduction and, in borderline cases, the absence of steam in the reagent mixture (see Chemical Engineering Journal 165 (2010) 633-638).

[0053] The possibility of sending the synthesis gas produced at high temperature in the SCT-CPO reactor 60 directly into BF 50 (FIG. 1) is linked to the possibility of operating with a very low S/C ratio (v/v) in order to maintain a high reducing capacity of the synthesis gas. This condition in conventional systems such as SR and ATR leads to the formation of coal and carbonaceous residue precursors, contrary to what happens in the SCT-CPO reactor.

[0054] The operating conditions under which the SCT-CPO reactors will be used are as follows: [0055] pressures higher than those of the BF; preferably between 2 and 15 bar.sub.g, more preferably between 2.5 and 10 bar.sub.g, even more preferably between 3 and 8 bar.sub.g; [0056] temperatures of the reagent mixtures between 100 and 600? C. and preferably between 250 and 450? C.; [0057] ratio O.sub.2/C (v/v) (moles of oxidant O.sub.2/moles of carbon C) in the reagent mixture between 0.30 and 0.70 v/v and preferably between 0.50 and 0.65 v/v; [0058] S/C ratio between 0 and 1.5 v/v and preferably between 0 and 0.5 v/v.

[0059] The characteristics of the composition of the reagent mixture and the of operating conditions are combined to further produce a synthesis gas with a high reducing potential with respect to iron ore reduction reactions, and in particular lead to obtaining a synthesis gas with a steam fraction preferably less than 10% v/v, more preferably less than 7% v/v, and a ratio R=(H.sub.2+CO)/(H.sub.2 O+CO.sub.2) preferably greater than 5 v/v, more preferably greater than 7 v/v.

[0060] In addition, the SCT-CPO reactors used in this application allow low pressure drops of between 5 and 0.5 kg/cm.sup.2.

[0061] The v/v percentages of BFG in the mixture of hydrocarbon reagents used for the production of synthesis gas are between 0 and 60%, preferably between 15 and 50%.

[0062] The v/v percentages of COG in the mixture of hydrocarbon reagents are between 0 and 60%, preferably between 15 and 50%.

[0063] The sum of the v/v percentages of BFG and COG in the mixture of hydrocarbon reagents are between 0 and 80%, and preferably between 15 and 60%.

[0064] The moisture content of the synthesis gas produced is' less than 10% v/v, preferably less than 7% v/v, and wherein simultaneously the ratio R=(CO+H.sub.2)/(CO.sub.2+H.sub.2 O) is greater than 5 v/v and preferably greater than 7 v/v, more preferably 7.5 v/v.

[0065] It has also been observed, and constitutes an aspect of the present invention, that the presence of Hydrogen in the reagent mixture fed to the SCT-CPO reactor, in particular in the COG but also in the BFG, improves the operability of the SCT-CPO reactors since, with the same O.sub.2/C ratio v/v, the presence of hydrogen decreases the partial pressure of the oxidant, inhibits the radical combustion reactions of hydrocarbons in the homogeneous gaseous phase which generate unsaturated compounds and has a further hydrogenating effect on both unsaturated compounds fed into the reagent mixture, in particular those present in the COG but also to a lesser extent in the BFG. Furthermore, it has been observed, both experimentally and through theoretical analyses, that the presence of H.sub.2 together with the other hydrocarbons, CO.sub.2 and other inert molecules (e.g. N.sub.2) has a limited influence on the extent of the flammability limits of the reaction mixtures that can be readily used in SCT-CPO reactors.

[0066] In fact, the presence of hydrogen in the reagent mixture, in particular that contained in the COG and BFG, strongly inhibits all the radical reactions that lead to the formation of carbon residues, both in the areas of heat shielding and pre-heating of the reagents, which separate the reagent mixing zone from the catalytic reaction zone, and in the catalytic bed where the heterogeneous catalytic processes for the production of synthesis gas take place.

[0067] Furthermore, according to an aspect of the invention shown in FIG. 2, via the unit 75 the hydrogen contained in the coke oven gas is used to carry out hydrogenation and hydro-desulphurisation reactions of the coke oven gas stream before being fed to the SCT-CPO reactor.

[0068] The person skilled in the art is familiar with both the reactor solutions for the synthesis gas production process via SCT-CPO and the catalytic systems that can be used, as described in numerous literature documents. In particular, in addition to the documents already cited, mention is made of U.S. Pat. No. 5,856,585, WO 97/37929, WO 03/099712 A1, Journal of Catalysis, 138 (1) (1992) pp. 267-282, Fuel Processing Technology, 42(2-3) (1995) pp. 109-127, Science 271(5255) (1996) pp. 1560-1562.

[0069] According to a further embodiment, illustrated schematically in FIG. 3, the process of the invention provides for the integration, or replacement, of the processes used to produce oxygen by cryogenic distillation (Air Separation UnitASU) and Vacuum Pressure Swing Adsorption (VPSA) with an electrolysis process in which oxygen and hydrogen produced by water electrolysis are both used. Oxygen is fed to the SCT-CPO reactor and Hydrogen is added to the synthesis gas produced by the SCT-CPO reactor before being sent to the BF.

[0070] FIG. 3 shows the electrolyzer 90, which can either be of polymer electrolyte membrane (PEM) or alkaline water (AE) type. In these types of electrolyzer, the water is supplied in liquid form. If a SOEC (Solid Oxide Electrolyzer Cell) electrolyzer is used, water is fed into the steam phase and it is also possible to co-fuel CO.sub.2 in addition to steam and co-produce carbon monoxide, as well as hydrogen and oxygen. In this case, oxygen is fed to the SCT-CPO reactor while hydrogen and carbon monoxide are added to the synthesis gas produced before it is sent to the BF.

[0071] The use of electrolyzers in the iron ore reduction process is particularly advantageous when a surplus of electrical energy from various primary energy sources, including renewables, is available.

[0072] The following examples illustrate some embodiments of the invention and are provided by way of non-limiting example.

EXAMPLES

Example 1

[0073] This example describes an integrated synthesis gas production process using a SCT-CPO process fed with natural gas, oxygen and steam (with a steam/carbon ratio S/C=0.2 v/v) and its use in the reduction of iron ore in a BF.

[0074] Table 2 shows the input and output compositions to an CPO reactor operating at a Gas Hourly Space Velocity (GHSV) of 80,000 hours.sup.?1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of ?-Al.sub.2O.sub.3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of RhNi (0.5 and 2.5% by weight respectively) in the final part of the catalytic bed where the oxygen has been consumed by the hydrocarbon oxidation reactions. The SCT-CPO reactor produces from natural gas (NG), O.sub.2, and steam a synthesis gas suitable for use in a BF. This synthesis gas is produced at a pressure of 2.5 bar.sub.g and a temperature of 950? C. It has an R-value of ?7.5 v/v and a moisture content of approximately 8% v/v.

[0075] The process parameters and the composition of the reagents and the synthesis gas produced are shown in Table 4 below:

TABLE-US-00004 TABLE 4 SCT-CPO reactor Reactor Reactor operating conditions Units input output Temperature C. 375 950 Pressure barg 4 2.5 Media MW kg/kmol 23.34 12.34 Volume flow rate Nm3/h 23195 55952 Flow rate in moles kmol/h 1035 2496 CH4 % vol 45.46% 0.28% CO % vol 0.00% 30.28% CO2 % vol 1.10% 2.51% H2 % vol 0.00% 58.88% H2O % vol 12.28% 7.04% N2 % vol 1.78% 0.94% C2H6 % vol 4.54% 0.00% C3H8 % vol 1.23% 0.00% C4H10 % vol 0.53% 0.00% C5H12 % vol 0.15% 0.00% C6H14 % vol 0.05% 0.00% O2 % vol 32.76% 0.00% AR % vol 0.00% 0.00%

[0076] The introduction into the BF of 200 Nm.sup.3 of the synthesis gas produced in the SCT-CPO reactor per tonne of pig iron produced makes it possible to reduce the use of coke and coal dust by 43 to 49 kg per tonne of metal produced. The range depends on the composition of the solid fuels and solutions used for the synthesis gas inlet points in the BF. This saving, in a plant with a production of 2.35 million tonnes of metal per year, corresponds to a reduction in production and use of 101,000-116,200 tonnes of coke and coal dust per year and of the associated pollutant emissions of NOx, SOx, aromatics and poly-aromatics and particulates. As regards CO.sub.2 emissions, the reduction in the quantity of coke and coal dust used avoids the emission of 327,500-376,500 tonnes of CO.sub.2 per year, which is partly offset by CO.sub.2 emissions linked to the production and use of synthesis gas from natural gas (305,100 tonnes of CO.sub.2), which, however, does not contribute to NOx, SOx, aromatic and poly-aromatic and particulate emissions. Overall, therefore, the reduction in CO.sub.2 is between 22,300 and 71,400 tonnes per year.

Example 2

[0077] This example describes an integrated synthesis gas production process using a SCT-CPO process fed with natural gas, oxygen and hydrogen produced by water electrolysis, and steam (with a steam/carbon ratio S/C 0.2 v/v) and its use in the reduction of iron ore in a BF.

[0078] Table 5 shows the input and output compositions to a SCT-CPO reactor operating at a gas hourly space velocity (GHSV) of 80,000 hours.sup.?1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of ?-Al.sub.2O.sub.3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of RhNi (0.5 and 2.5% by weight respectively) in the final part of the catalytic bed where the oxygen has been consumed by the hydrocarbon oxidation reactions. The SCT-CPO reactor produces from NG, O.sub.2, steam a synthesis gas suitable for use in a BF. This synthesis gas is produced at a pressure of 2.5 bar.sub.g and a T of 950? C. It has an R value?7.5 v/v, a moisture content of approximately 800 v/v. Twice the amount of hydrogen is added to this synthesis gas with respect to the oxygen produced by the water electrolysis process.

TABLE-US-00005 TABLE 5 SCT-CPO reactor Reactor Reactor operating conditions Units input output Temperature C. 375 950 Pressure barg 4 2.5 Media MW kg/kmol 23.34 9.68 Volume flow rate Nm3/h 23195 55952 Flow rate in moles kmol/h 1035 2496 CH4 % vol 45.46% 0.21% CO % vol 0.00% 22.49% CO2 % vol 1.10% 1.86% H2 % vol 0.00% 69.47% H2O % vol 12.28% 5.23% N2 % vol 1.78% 0.70% C2H6 % vol 4.54% 0.00% C3H8 % vol 1.23% 0.00% C4H10 % vol 0.53% 0.00% C5H12 % vol 0.15% 0.00% C6H14 % vol 0.05% 0.00% O2 % vol 32.76% 0.00% AR % vol 0.00% 0.00% HE % vol 0.12% 0.04% HCN % vol 0.00% 0.00% C2H2 % vol 0.00% 0.00%

[0079] The introduction of 200 Nm.sup.3 of this synthesis gas produced in the SCT-CPO reactor, to which the hydrogen co-produced by the electrolyzer has been added, per tonne of pig iron produced allows a reduction of between 45 and 52 kg in the use of coke and coal dust per tonne of metal produced, depending on the composition of the solid fuels and the solutions that will be used for the synthesis gas inlet points. This saving, in a plant with a production of 2.35 million tonnes of metal per year, corresponds to a reduction in production and use of between 105,800 and 121,600 tonnes of coke and coal dust per year and of the associated pollutant emissions of NOx, SOx, aromatics and poly-aromatics and particulates. As regards CO.sub.2 emissions, the reduction of coke and coal dust use avoids the emission of between 342,600 and 393,000 tonnes of CO.sub.2 per year, which will be partly offset by CO.sub.2 emissions linked to the production and use of synthesis gas from natural gas (226,600 tonnes of CO.sub.2), which in any case does not contribute to NOx, SOx, aromatic and poly-aromatic and particulate emissions. Overall, therefore, the reduction in CO.sub.2 emissions is between 116,100 and 167,400 tonnes per year.

Example 3

[0080] This example describes an integrated synthesis gas production process using a SCT-CPO process fed with biogas and Oxygen and its use in the reduction of iron ore in a BF.

[0081] Table 6 shows the inlet and outlet compositions to a SCT-CPO reactor producing synthesis gas containing 45% v/v CO.sub.2, O.sub.2 in the absence of steam in the reagent mixture. The synthesis gas is suitable for use in a BF.

[0082] The reactor operates at a gas hourly space velocity (GHSV) of 80,000 hours.sup.?1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of ?-Al.sub.2 O.sub.3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of RhNi species (0.5 and 2.5% by weight respectively) in the final part of the catalytic bed where the oxygen has been consumed by the hydrocarbon oxidation reactions. The synthesis gas is produced at a pressure of 2.5 kg/cm.sup.2 at a temperature of 950? C. It has an R value=2.5 v/v and a moisture content of 16.7% v/v.

[0083] This example shows that it is possible to use a synthesis gas produced solely from biogas and achieve a reduction in the use of coke and coal dust and a large reduction in CO.sub.2 emissions. In other embodiments, biogas can clearly complement the use of other gaseous hydrocarbon sources such as natural gas and coke oven and BFG (see examples 5 and 6) and enable the production of a synthesis gas with a lower vapour content and higher reducing power R.

[0084] In fact, the introduction of 200 Nm.sup.3 of this synthesis gas per tonne of pig iron makes it possible to reduce the use of coke and coal dust by between 27 and 31 kg per tonne of metal produced, depending on the composition of the solid fuels and the solutions used for the synthesis gas inlet points. This saving, in a plant with a production of 2.35 million tonnes of metal per year, corresponds to a reduction in production and use of 63,500 to 73,000 tonnes of coke and coal dust per year and of the associated pollutant emissions of NOx, SOx, aromatics and poly-aromatics and particulates. As regards CO.sub.2 emissions.sub.2, the reduction in the amount of coke and coal dust used avoids the emission of 205,600-236,400 tonnes of CO.sub.2 per year.

[0085] Moreover, the use of biogas, does not contribute to NOx, SOx, aromatic and poly-aromatic and particulate emissions and to CO.sub.2 emissions.

TABLE-US-00006 TABLE 6 SCT-CPO reactor Reactor Reactor operating conditions Units inlet output Temperature C. 375 950 Pressure barg 4 2.5 Media MW kg/kmol 29.5 18.9 Volume flow rate Nm3/h 35924 55952 Flow rate in moles kmol/h 1603 2496 CH4 % vol 40.79% 0.03% CO % vol 0.00% 35.91% CO2 % vol 33.37% 11.71% H2 % vol 0.00% 35.59% H2O % vol 0.00% 16.76% N2 % vol 0.00% 0.00% C2H6 % vol 0.00% 0.00% C3H8 % vol 0.00% 0.00% C4H10 % vol 0.00% 0.00% C5H12 % vol 0.00% 0.00% C6H14 % vol 0.00% 0.00% O2 % vol 25.84% 0.00% AR % vol 0.00% 0.00% HE % vol 0.00% 0.00%

Example 4

[0086] This example describes an integrated process for producing synthesis gas using a catalytic partial oxidation (CPO) process fed with biogas with 45% v/v CO.sub.2, oxygen and hydrogen produced in an electrolysis process, and its use in the reduction of iron ore in a BF.

[0087] Table 7 shows the inlet and outlet compositions of a CPO reactor fed with biogas containing 45% v/v CO.sub.2, O.sub.2 and in the absence of steam in the reagent mixture. The synthesis gas produced is suitable for use in a BF.

[0088] The reactor operates at a gas hourly space velocity (GHSV) of 80,000 hours.sup.?1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of ?-Al.sub.2 O.sub.3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of RhNi, in quantities of 0.5 and 2.5% by weight respectively, in the final part of the catalytic bed, where the oxygen has been consumed by the hydrocarbon oxidation reactions. The synthesis gas is produced at a pressure of 2.5 kg/cm.sup.2 at a temperature of 950? C.

[0089] Twice as much hydrogen as oxygen is added to this synthesis gas, both of which are produced in an integrated water electrolysis process in the steel plant.

[0090] The synthesis gas obtained has an R value=3.7 v/v and a moisture content of 12.6% v/v. This example shows that it is possible to use a synthesis gas produced solely from biogas and achieve a reduction in the use of coke and coal dust and a large reduction in CO.sub.2 emissions. In other embodiments, biogas can clearly complement the use of other gaseous hydrocarbon sources such as natural gas and coke oven and BF gases (see examples 5 and 6) and allow the production of a synthesis gas with a lower steam content and a higher reducing power R.

TABLE-US-00007 TABLE 7 SCT-CPO reactor Reactor Reactor Reactor operating conditions Units inlet output output +H2 Temperature C. 375 950 950 Pressure barg 4 2.5 2.5 Media MW kg/kmol 29.5 19 14.7 Volume flow rate Nm3/h 27914 43340 55952 Flow rate in moles kmol/h 1245 1934 2496 CH4 % vol 40.79% 0.03% 0.02% CO % vol 0.00% 35.91% 26.96% CO2 % vol 33.37% 11.71% 8.79% H2 % vol 0.00% 35.59% 51.65% H2O % vol 0.00% 16.76% 12.58% N2 % vol 0.00% 0.00% 0.00% C2H6 % vol 0.00% 0.00% 0.00% C3H8 % vol 0.00% 0.00% 0.00% C4H10 % vol 0.00% 0.00% 0.00% C5H12 % vol 0.00% 0.00% 0.00% C6H14 % vol 0.00% 0.00% 0.00% O2 % vol 25.84% 0.00% 0.00% AR % vol 0.00% 0.00% 0.00% HE % vol 0.00% 0.00% 0.00% HCN % vol 0.00% 0.00% 0.00% C2H2 % vol 0.00% 0.00% 0.00% C6H6 % vol 0.00% 0.00% 0.00%

[0091] The use of 200 Nm.sup.3 of synthesis gas with the composition described in Table 7, per tonne of pig iron, allows a reduction of 44-51 kg in the use of coke and coal dust per tonne of metal produced, depending on the composition of the solid fuels and the solutions used for the synthesis gas inlet points. This saving, in a plant with a production of 2.35 million tonnes of metal per year, makes it possible to achieve a reduction in production and use of between 103,400 and 118,900 tonnes of coke and coal dust per year, and to reduce polluting emissions of NOx, SOx, aromatic hydrocarbons, polycondensed aromatic hydrocarbons and particulates. As regards CO.sub.2 emissions, the reduction of the amount of coke used, and of coal dust, avoids the emission of 335,000 to 385,300 tonnes of CO.sub.2 per year. Furthermore, the use of biogas does not contribute to NOx, SOx, aromatic hydrocarbons and polycondensed aromatic hydrocarbons emissions, or to CO.sub.2 emissions.

Example 5

[0092] This example describes an integrated synthesis gas production process using a SCT-CPO process fed with a hydrocarbon mixture consisting of natural gas (29% v/v), BFG (34% v/v), COG (37% v/v), Oxygen and Steam (S/C ratio=0.1 v/v), and its use in the reduction of iron ore in the BF.

[0093] Table 8 shows the inlet and outlet compositions for a SCT-CPO reactor fed with the mixture defined above, with a reduced amount of steam.

[0094] The synthesis gas produced is suitable for use in a BF.

[0095] The reactor operates at a gas hourly space velocity (GHSV) of 95,000 hours.sup.?1 (NL/hour of reagents/L of catalyst), using a catalyst consisting of spheroidal pellets of ?-Al.sub.2 O.sub.3 on which Rh species (0.8% by weight) are deposited in the upper part of the catalytic bed and RhNi species (0.5 and 3.5% by weight respectively) in the final part of the catalytic bed, where the oxygen has been consumed by the hydrocarbon oxidation reactions.

[0096] Synthesis gas is produced at a pressure of 2.5 kg/cm.sup.2 and a temperature of 950? C. It has an R-value of >7.5 v/v and a moisture content of less than 7% v/v.

[0097] The introduction of 200 Nm.sup.3 of this synthesis gas per tonne of pig iron makes it possible to reduce the use of coke and coal dust by 33 to 38 kg per tonne of metal produced, depending on the composition of the solid fuels and the solutions used for the synthesis gas inlet points.

[0098] This saving, in a steel plant with a production of 2.35 million tonnes of metal per year, makes it possible to reduce the quantity of coke and coal dust used per year by 77,600 to 89,200 tonnes, and consequently to reduce the associated polluting emissions of NOx, SOx, aromatic hydrocarbons, polycondensed aromatic hydrocarbons and particulates.

[0099] As regards CO.sub.2 emissions, the reduction of coke and coal dust used avoids emissions of between 251,300 and 289,000 tonnes of CO.sub.2 per year, which are however partly offset by CO.sub.2 emissions related to the production and use of synthesis gas from natural gas (135,600 tonnes of CO.sub.2). However, this does not contribute to emissions of NOx, SOx, aromatic hydrocarbons, polycondensed aromatic hydrocarbons and particulates.

[0100] Overall, therefore, the reduction in CO.sub.2 is between 115,700 and 153,340 tonnes per year.

TABLE-US-00008 TABLE 8 SCT-CPO reactor Reactor Reactor operating conditions Units inlet output Temperature C. 350 950 Pressure barg 3.5 2.5 Media MW kg/kmol 22.0 15.1 Volume flow rate Nm3/h 38416 55952 Flow rate in moles kmol/h 1714 2496 CH4 % vol 25.64% 0.14% CO % vol 6.96% 28.77% CO2 % vol 5.89% 2.99% H2 % vol 17.51% 48.51% H2O % vol 3.05% 7.30% N2 % vol 17.84% 12.25% C2H6 % vol 1.85% 0.00% C3H8 % vol 0.50% 0.00% C4H10 % vol 0.21% 0.00% C5H12 % vol 0.16% 0.00% C6H14 % vol 0.02% 0.00% O2 % vol 19.73% 0.00% AR % vol 0.00% 0.00% HE % vol 0.05% 0.06% HCN % vol 0.02% 0.00% C2H2 % vol 0.64% 0.00% C6H6 % vol 0.03% 0.00%

Example 6

[0101] This example describes an integrated synthesis gas production process using a SCT-CPO process fed with a hydrocarbon mixture consisting of natural gas (29% v/v), BFG (34% v/v), COG (37% v/v), Oxygen and Steam (S/C ratio=0.1 v/v), with the addition of a volume of hydrogen co-produced with oxygen in a water electrolysis process to the synthesis gas produced, and its use in the reduction of iron ore in the BF.

[0102] Table 9 shows the inlet and outlet compositions for a SCT-CPO reactor fed with the mixture defined above, with a reduced amount of steam.

[0103] The volume of hydrogen co-produced through the electrolysis of water with oxygen is added to the synthesis gas thus produced.

[0104] The synthesis gas produced is suitable for use in a BF.

[0105] The reactor operates at a gas hourly space velocity (GHSV) of 95,000 hours.sup.?1 (NL/hour of reagents/L of catalyst), using a catalyst consisting of spheroidal pellets of ?-Al.sub.2 O.sub.3 on which Rh (0.5% by weight) and Ir species (0.5% by weight) are deposited in the upper part of the catalytic bed and IrNi species (0.5 and 3.5% by weight respectively) in the final part of the catalytic bed, where the oxygen has been consumed by the hydrocarbon oxidation reactions.

[0106] The synthesis gas is produced at a pressure of 2.5 kg/cm.sup.2 at a temperature of 950? C., has an R-value >7.5 v/v and a moisture content of the order of 7% v/v.

[0107] The introduction of 200 Nm.sup.3 of this synthesis gas per tonne of pig iron makes it possible to reduce the use of coke and coal dust by 39 to 45 kg per tonne of metal produced, depending on the composition of the solid fuels and the solutions used for the synthesis gas inlet points.

[0108] This saving, in a plant with a production of 2.35 million tonnes of metal per year, corresponds to a reduction in production and use of between 91,700 and 105,400 tonnes of coke and coal dust per year and of the associated pollutant emissions of NOx, SOx, aromatic hydrocarbons, polycondensed aromatic hydrocarbons and particulates.

[0109] As regards CO.sub.2 emissions, the lower consumption of coke and coal dust avoids emissions of between 296,900 and 341,500 tonnes of CO.sub.2 per year, which are partly offset by CO.sub.2 emissions linked to the production and use of synthesis gas from natural gas (135,600 tonnes of CO.sub.2). This, however, does not contribute to emissions of NOx, SOx, aromatic hydrocarbons, polycondensed aromatic hydrocarbons and particulate matter.

[0110] Overall, therefore, the reduction in CO.sub.2 is between 161,400 and 205,900 tonnes per year.

TABLE-US-00009 TABLE 9 SCT-CPO reactor Reactor Reactor Reactor operating conditions Unit inlet output output +H.sub.2 Temperature C. 350 950 950 Pressure barg 3.5 2.5 2.5 Media MW kg/kmol 22 15 12.3 Volume flow rate Nm3/h 38416 45578 55952 Flow rate in moles kmol/h 1714 2033 2496 CH4 % vol 25.64% 0.14% 0.11% CO % vol 6.96% 28.77% 22.65% CO2 % vol 5.89% 2.99% 2.36% H2 % vol 17.51% 48.51% 59.46% H2O % vol 3.05% 7.30% 5.75% N2 % vol 17.84% 12.25% 9.64% C2H6 % vol 1.85% 0.00% 0.00% C3H8 % vol 0.50% 0.00% 0.00% C4H10 % vol 0.21% 0.00% 0.00% C5H12 % vol 0.16% 0.00% 0.00% C6H14 % vol 0.02% 0.00% 0.00% O2 % vol 19.73% 0.00% 0.00% AR % vol 0.00% 0.00% 0.00% HE % vol 0.05% 0.06% 0.06% HCN % vol 0.02% 0.00% 0.00% C2H2 % vol 0.64% 0.00% 0.00% C6H6 % vol 0.03% 0.00% 0.00%