Patent Application
20240279756
The present invention relates to a process for the reduction of iron ore in a blast furnace using synthesis gases produced by Catalytic Partial Oxidation (CPO), in order to reduce CO2 emissions.
More than 90% of steel production is currently obtained through the reduction of iron ores in blast furnaces (BF) with a process that makes extensive use of coke whose combustion allows the achievement of the temperatures and of the gaseous mixture required for reduction process. Typically, the product obtained in the BF is a pig iron with a high carbon content which is subsequently converted into steel in the Basic Oxygen Furnace (BOF).
However, this production technology has a relevant environmental impact due to the CO2 and other pollutant emissions.
The reduction of iron ores in the BF typically requires a coke consumption of 450-700 kg per ton of produced hot metal (Ton of Hot Metal—THM), an amount that by burning provides approximately the 75% of the total energy consumption required for the conversion of iron ores into steel with the combined BF and BOF processes. However, coke amount can also be reduced below 400 kg/THM if its use is combined with the use of pulverized and/or micronized coal, as occurs in the most recent steelmaking technologies.
The coke oven that produces the coke from coal also produces a coke oven gas (COG), which contains hydrogen, light hydrocarbons but also pollutants such as polyaromatic hydrocarbons, various nitrogen and sulphur compounds as well as liquid and/or solid particles that can be dispersed into the atmosphere if not properly captured, and that are usually referred to as particulate matter.
In addition, the processes for the reduction of iron ore in the BF produce a blast furnace gas (BFG), whose main components are CH4, CO, CO2, H2, H2O, N2 as well as smaller amounts of aromatic hydrocarbons, sulphur compounds, particulate matter, ammonia compounds and NOx.
Moreover, as mentioned above, the process for the reduction of iron ore in the BF produces large amounts of CO2, e.g. 1.7 tonnes of CO2/THM.
There is therefore the need of improving the energy efficiency of iron ore reduction processes in BF and of reducing the amount of the emitted CO2.
Therefore, an object of the present invention is to provide a process solution for the reduction of iron ore in a BF that improves its energy efficiency and reduces the carbon dioxide emissions.
Therefore, an aspect of the present invention relates to an environmentally friendly process for the reduction of iron ores in a BF for the production of iron and/or iron-carbon compounds, comprising the combustion of coke, and the utilization into said BF of synthesis gas produced from a hydrocarbon stream by means of a short contact time catalytic partial oxidation process. According to an aspect of the invention, the process for the reduction of iron ore in a BF furnace for the production of iron and/or iron-carbon compounds is carried out by combustion of coke produced in a coke oven upstream of the blast furnace, and is characterized in that synthesis gas produced with a short contact time catalytic partial oxidation process (SCT-CPO) integrated with said process for the reduction of iron ore is also introduced into said blast furnace, wherein said SCT-CPO process uses a gaseous hydrocarbon stream, an oxidizing agent selected from one or more of oxygen, enriched air and air, and optionally hydrogen and/or steam.
According to another aspect of the invention, the hydrocarbon stream comprises BFG and COG recycled from said blast furnace and said coke oven, respectively.
The term ‘hydrocarbon gases’ is meant as natural gas, gases from chemical processes, refinery gases and gases produced by the fermentation of biomass, also known as ‘biogas’.
The use of synthesis gas in the process for the reduction of iron ore in the blast furnace allows a reduction in the amount of coke used in the blast furnace. Moreover, the use of coke oven gas and blast furnace gas to produce synthesis gas allows a further reduction in pollutant emissions related to the production and use of coke, as well as an improvement in the overall energy efficiency of the process for the reduction of iron ore and the reduction of CO2 emissions.
The invention is described below also with reference to the accompanying drawings, wherein:
Processes for the reduction of iron ore in blast furnaces typically produce pig iron, which is then converted into steel in oxygen converters.
With reference to
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.
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:
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.
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.
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).
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.
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.
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.
Producing synthesis gas using a short contact time catalytic partial oxidation (SCT-CPO) process is also known.
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.
SCT-CPO technology is also described in the following scientific literature documents:
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.
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 CO2 emitted in such processes. In particular, the integration of SCT-CPO synthesis gas with the use of coke makes it possible to:
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, H2) over the total oxidation products (CO2, H2O) of hydrocarbons.
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.
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.
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.
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.
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.
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.
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 CO2 emissions.
As the BF typically operates at pressures between 2 and 10 kg/cm2, 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.
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.
In this regard, it should be emphasized that the presence of CO2 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).
The possibility of sending the synthesis gas produced at high temperature in the SCT-CPO reactor 60 directly into BF 50 (
The operating conditions under which the SCT-CPO reactors will be used are as follows:
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=(H2+CO)/(H2 O+CO2) preferably greater than 5 v/v, more preferably greater than 7 v/v.
In addition, the SCT-CPO reactors used in this application allow low pressure drops of between 5 and 0.5 kg/cm2.
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%.
The v/v percentages of COG in the mixture of hydrocarbon reagents are between 0 and 60%, preferably between 15 and 50%.
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%.
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+H2)/(CO2+H2 O) is greater than 5 v/v and preferably greater than 7 v/v, more preferably 7.5 v/v.
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 O2/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 H2 together with the other hydrocarbons, CO2 and other inert molecules (e.g. N2) has a limited influence on the extent of the flammability limits of the reaction mixtures that can be readily used in SCT-CPO reactors.
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.
Furthermore, according to an aspect of the invention shown in
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.
According to a further embodiment, illustrated schematically in
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.
The following examples illustrate some embodiments of the invention and are provided by way of non-limiting example.
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.
Table 2 shows the input and output compositions to an CPO reactor operating at a Gas Hourly Space Velocity (GHSV) of 80,000 hours−1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of α-Al2O3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of Rh—Ni (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), O2, and steam a synthesis gas suitable for use in a BF. This synthesis gas is produced at a pressure of 2.5 barg 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.
The process parameters and the composition of the reagents and the synthesis gas produced are shown in Table 4 below:
The introduction into the BF of 200 Nm3 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 CO2 emissions, the reduction in the quantity of coke and coal dust used avoids the emission of 327,500-376,500 tonnes of CO2 per year, which is partly offset by CO2 emissions linked to the production and use of synthesis gas from natural gas (305,100 tonnes of CO2), which, however, does not contribute to NOx, SOx, aromatic and poly-aromatic and particulate emissions. Overall, therefore, the reduction in CO2 is between 22,300 and 71,400 tonnes per year.
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.
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−1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of α-Al2O3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of Rh—Ni (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, O2, steam a synthesis gas suitable for use in a BF. This synthesis gas is produced at a pressure of 2.5 barg 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.
The introduction of 200 Nm3 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 CO2 emissions, the reduction of coke and coal dust use avoids the emission of between 342,600 and 393,000 tonnes of CO2 per year, which will be partly offset by CO2 emissions linked to the production and use of synthesis gas from natural gas (226,600 tonnes of CO2), which in any case does not contribute to NOx, SOx, aromatic and poly-aromatic and particulate emissions. Overall, therefore, the reduction in CO2 emissions is between 116,100 and 167,400 tonnes per year.
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.
Table 6 shows the inlet and outlet compositions to a SCT-CPO reactor producing synthesis gas containing 45% v/v CO2, O2 in the absence of steam in the reagent mixture. The synthesis gas is suitable for use in a BF.
The reactor operates at a gas hourly space velocity (GHSV) of 80,000 hours−1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of α-Al2 O3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of Rh—Ni 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/cm2 at a temperature of 950° C. It has an R value=2.5 v/v and a moisture content of 16.7% 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 CO2 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.
In fact, the introduction of 200 Nm3 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 CO2 emissions2, the reduction in the amount of coke and coal dust used avoids the emission of 205,600-236,400 tonnes of CO2 per year.
Moreover, the use of biogas, does not contribute to NOx, SOx, aromatic and poly-aromatic and particulate emissions and to CO2 emissions.
This example describes an integrated process for producing synthesis gas using a catalytic partial oxidation (CPO) process fed with biogas with 45% v/v CO2, oxygen and hydrogen produced in an electrolysis process, and its use in the reduction of iron ore in a BF.
Table 7 shows the inlet and outlet compositions of a CPO reactor fed with biogas containing 45% v/v CO2, O2 and in the absence of steam in the reagent mixture. The synthesis gas produced is suitable for use in a BF.
The reactor operates at a gas hourly space velocity (GHSV) of 80,000 hours−1 (NL/hour of reagents/L of catalyst) using a catalyst consisting of spheroidal pellets of α-Al2 O3 on which species of Rh (0.5% by weight) are deposited in the upper part of the catalytic bed and of Rh—Ni, 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/cm2 at a temperature of 950° C.
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.
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 CO2 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.
The use of 200 Nm3 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 CO2 emissions, the reduction of the amount of coke used, and of coal dust, avoids the emission of 335,000 to 385,300 tonnes of CO2 per year. Furthermore, the use of biogas does not contribute to NOx, SOx, aromatic hydrocarbons and polycondensed aromatic hydrocarbons emissions, or to CO2 emissions.
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.
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.
The synthesis gas produced is suitable for use in a BF.
The reactor operates at a gas hourly space velocity (GHSV) of 95,000 hours−1 (NL/hour of reagents/L of catalyst), using a catalyst consisting of spheroidal pellets of α-Al2 O3 on which Rh species (0.8% by weight) are deposited in the upper part of the catalytic bed and Rh—Ni 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.
Synthesis gas is produced at a pressure of 2.5 kg/cm2 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.
The introduction of 200 Nm3 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.
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.
As regards CO2 emissions, the reduction of coke and coal dust used avoids emissions of between 251,300 and 289,000 tonnes of CO2 per year, which are however partly offset by CO2 emissions related to the production and use of synthesis gas from natural gas (135,600 tonnes of CO2). However, this does not contribute to emissions of NOx, SOx, aromatic hydrocarbons, polycondensed aromatic hydrocarbons and particulates.
Overall, therefore, the reduction in CO2 is between 115,700 and 153,340 tonnes per year.
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.
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.
The volume of hydrogen co-produced through the electrolysis of water with oxygen is added to the synthesis gas thus produced.
The synthesis gas produced is suitable for use in a BF.
The reactor operates at a gas hourly space velocity (GHSV) of 95,000 hours−1 (NL/hour of reagents/L of catalyst), using a catalyst consisting of spheroidal pellets of α-Al2 O3 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 Ir—Ni 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.
The synthesis gas is produced at a pressure of 2.5 kg/cm2 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.
The introduction of 200 Nm3 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.
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.
As regards CO2 emissions, the lower consumption of coke and coal dust avoids emissions of between 296,900 and 341,500 tonnes of CO2 per year, which are partly offset by CO2 emissions linked to the production and use of synthesis gas from natural gas (135,600 tonnes of CO2). This, however, does not contribute to emissions of NOx, SOx, aromatic hydrocarbons, polycondensed aromatic hydrocarbons and particulate matter.
Overall, therefore, the reduction in CO2 is between 161,400 and 205,900 tonnes per year.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021000011189 | May 2021 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/061672 | 5/2/2022 | WO |
