CA2770947C - Method for reducing the carbon dioxide emissions of a blast furnace, and associated device - Google Patents
Method for reducing the carbon dioxide emissions of a blast furnace, and associated device Download PDFInfo
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- CA2770947C CA2770947C CA2770947A CA2770947A CA2770947C CA 2770947 C CA2770947 C CA 2770947C CA 2770947 A CA2770947 A CA 2770947A CA 2770947 A CA2770947 A CA 2770947A CA 2770947 C CA2770947 C CA 2770947C
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B5/00—Making pig-iron in the blast furnace
- C21B5/001—Injecting additional fuel or reducing agents
- C21B5/003—Injection of pulverulent coal
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B5/00—Making pig-iron in the blast furnace
- C21B5/008—Composition or distribution of the charge
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Abstract
The present disclosure relates mainly to a method for reducing the carbon dioxide emissions of a blast furnace, in which reducing agents are charged into the throat and auxiliary fuels in pulverized form are injected into the tuyeres, and which is essentially characterized in that the reducing agents charged into the throat comprise charcoal. According to a preferred aspect of the disclosure, the specific consumption of charcoal charged into the throat is more than 0% and less than 20% of the total quantity of reducing agents charged into the throat. By proceeding in this matter, a significant reduction in carbon dioxide emissions is obtained, and also substantial beneficiation of the charcoal relative to the reduction in carbon dioxide emissions. The present disclosure also relates to a device for implementing this method.
Description
Method for reducing the carbon dioxide emissions of a blast furnace, and associated device The invention relates to a method for reducing the carbon dioxide emissions of a blast furnace. The invention also relates to a device implementing said method.
A blast furnace is a gas-liquid-solid countercurrent chemical reactor whose main objective is to produce pig iron, which is then converted to steel by reducing its carbon content.
The blast furnace is conventionally supplied with solid materials, mainly sinter, pellets, iron ore and carbonaceous material, generally coke, charged into its upper part, called throat of the blast fumace. The liquids consisting of pig iron and slag are tapped from the crucible in the bottom of the blast furnace.
The iron-containing burden (sinter, pellets and iron ore) is converted to pig iron conventionally by reducing the iron oxides with a reducing gas (containing CO, H2 and N2 in particular), which is formed by combustion of the carbonaceous material in the tuyeres located in the lower part of the blast furnace, where air, preheated to a temperature of between '1000 and 1300 C, called hot blast, is injected.
This process of converting the iron-containing burden takes place in two distinct zones of the apparatus, separated by an intermediate zone called a thermal reserve zone. The latter Is characterized by an interruption of the heat exchanges associated with the fact that the gas and the solids are practically at the same temperature, called the reserve zone temperature. This also causes an interruption of the chemical reactions between gases and solids, thus defining a chemical reserve zone.
The two zones where the iron-containing materials are converted are:
- the lower part of the apparatus, called the production zone, which sets the energy requirements of the blast furnace and serves to carry out the conversion of the iron oxides from the wustite state to iron metal. It also serves to heat and melt the materials from the reserve zone temperature to the final pig iron temperature;
- the upper part of the apparatus, called the preparation zone, which acts as a recuperator of the thermal and chemical potential of the gas. It serves to heat the materials from the ambient temperature to the reserve zone temperature, and
A blast furnace is a gas-liquid-solid countercurrent chemical reactor whose main objective is to produce pig iron, which is then converted to steel by reducing its carbon content.
The blast furnace is conventionally supplied with solid materials, mainly sinter, pellets, iron ore and carbonaceous material, generally coke, charged into its upper part, called throat of the blast fumace. The liquids consisting of pig iron and slag are tapped from the crucible in the bottom of the blast furnace.
The iron-containing burden (sinter, pellets and iron ore) is converted to pig iron conventionally by reducing the iron oxides with a reducing gas (containing CO, H2 and N2 in particular), which is formed by combustion of the carbonaceous material in the tuyeres located in the lower part of the blast furnace, where air, preheated to a temperature of between '1000 and 1300 C, called hot blast, is injected.
This process of converting the iron-containing burden takes place in two distinct zones of the apparatus, separated by an intermediate zone called a thermal reserve zone. The latter Is characterized by an interruption of the heat exchanges associated with the fact that the gas and the solids are practically at the same temperature, called the reserve zone temperature. This also causes an interruption of the chemical reactions between gases and solids, thus defining a chemical reserve zone.
The two zones where the iron-containing materials are converted are:
- the lower part of the apparatus, called the production zone, which sets the energy requirements of the blast furnace and serves to carry out the conversion of the iron oxides from the wustite state to iron metal. It also serves to heat and melt the materials from the reserve zone temperature to the final pig iron temperature;
- the upper part of the apparatus, called the preparation zone, which acts as a recuperator of the thermal and chemical potential of the gas. It serves to heat the materials from the ambient temperature to the reserve zone temperature, and
2 to carry out the reduction of the Iron oxides charged (hematite and magnetite) to the wustite state.
To Increase productivity and reduce costs, auxiliary fuels are also injected Into the tuyeres, such as pulverized coal, fuel oil, natural gas or other fuels, combined with oxygen which enriches the hot blast.
The gases recovered in the upper part of the blast furnace, called top gases, mainly consist of CO, CO2, H2 and N2 in proportions of about 22%, 22%, 3% and 53%, respectively. These gases are generally used as fuel In other parts of the plant. Blast furnaces are therefore large producers of CO2.
In fact, faced with the considerable increase in the CO2 concentration in the atmosphere since the onset of the last century, it is essential to reduce the emissions where they are produced in large quantities, and therefore in blast furnaces In particular.
In this context, during the last 50 years, the consumption of reducing agents, and mainly of the carbonaceous materials used, has been reduced by half, so that today, In blast furnaces of a conventional configuration, the carbon consumption has reached a low limit, dependent, on the one hand, on the laws of thermodynamics, and, on the other hand, on the type and intrinsic properties of the carbonaceous materials charged into the throat of the installation.
According to various aspects, the present disclosure relates to a method for reducing carbon dioxide emissions in top gases of a blast furnace, wherein reducing agents are charged into the throat of said blast furnace and auxiliary fuels in pulverized form are injected into tuyeres, characterized in that the reducing agents charged into the throat comprise charcoal and in that specific consumption of the charcoal charged into the throat is more than 0% and less than 20% of the total quantity of the reducing agents charged into the throat.
According to various aspects, the present disclosure relates to a device implementing the method as defined herein, comprising means for charging the charcoal into the throat of the blast furnace so that the consumption of the charcoal charged into the throat is more than 0% and less than 20% of the total quantity of the reducing agents charged into the throat.
2a In this context, the invention proposes a method that significantly limits the carbon dioxide emissions, without entailing any major changes to the Installations.
For this purpose, the inventive method for reducing the carbon dioxide emissions of a blast furnace, in which reducing agents are charged into the throat and auxiliary fuels in pulverized form are injected into the tuyeres, is essentially characterized in that the reducing agents charged into the throat comprise charcoal.
The inventive method may also comprise the following optional features, considered separately or in combination:
- the specific consumption of charcoal charged into the throat is less than 20% of the total quantity of reducing agents charged into the throat;
- the specific consumption of charcoal charged Into the throat is less than 10% of the total quantity of reducing agents charged into the throat;
- the remainder of the reducing agents charged into the throat is mineral carbon;
To Increase productivity and reduce costs, auxiliary fuels are also injected Into the tuyeres, such as pulverized coal, fuel oil, natural gas or other fuels, combined with oxygen which enriches the hot blast.
The gases recovered in the upper part of the blast furnace, called top gases, mainly consist of CO, CO2, H2 and N2 in proportions of about 22%, 22%, 3% and 53%, respectively. These gases are generally used as fuel In other parts of the plant. Blast furnaces are therefore large producers of CO2.
In fact, faced with the considerable increase in the CO2 concentration in the atmosphere since the onset of the last century, it is essential to reduce the emissions where they are produced in large quantities, and therefore in blast furnaces In particular.
In this context, during the last 50 years, the consumption of reducing agents, and mainly of the carbonaceous materials used, has been reduced by half, so that today, In blast furnaces of a conventional configuration, the carbon consumption has reached a low limit, dependent, on the one hand, on the laws of thermodynamics, and, on the other hand, on the type and intrinsic properties of the carbonaceous materials charged into the throat of the installation.
According to various aspects, the present disclosure relates to a method for reducing carbon dioxide emissions in top gases of a blast furnace, wherein reducing agents are charged into the throat of said blast furnace and auxiliary fuels in pulverized form are injected into tuyeres, characterized in that the reducing agents charged into the throat comprise charcoal and in that specific consumption of the charcoal charged into the throat is more than 0% and less than 20% of the total quantity of the reducing agents charged into the throat.
According to various aspects, the present disclosure relates to a device implementing the method as defined herein, comprising means for charging the charcoal into the throat of the blast furnace so that the consumption of the charcoal charged into the throat is more than 0% and less than 20% of the total quantity of the reducing agents charged into the throat.
2a In this context, the invention proposes a method that significantly limits the carbon dioxide emissions, without entailing any major changes to the Installations.
For this purpose, the inventive method for reducing the carbon dioxide emissions of a blast furnace, in which reducing agents are charged into the throat and auxiliary fuels in pulverized form are injected into the tuyeres, is essentially characterized in that the reducing agents charged into the throat comprise charcoal.
The inventive method may also comprise the following optional features, considered separately or in combination:
- the specific consumption of charcoal charged into the throat is less than 20% of the total quantity of reducing agents charged into the throat;
- the specific consumption of charcoal charged Into the throat is less than 10% of the total quantity of reducing agents charged into the throat;
- the remainder of the reducing agents charged into the throat is mineral carbon;
3 - the charcoal charged into the throat is in the form of pieces having a diameter larger than 20 millimeters;
- the method comprises a screening step which separates the charcoal pieces charged into the throat from the fine charcoal fraction;
- the fine charcoal fraction is injected in pulverized form into the tuyeres, in addition to and/or as replacement of the corresponding quantity of auxiliary fuel normally injected in pulverized form into the tuyeres;
- the auxiliary fuel is either mineral coal or charcoal.
The invention also relates to a device for implementing the method defined above. Said device is essentially characterized in that it comprises means for charging the charcoal into the throat of the blast furnace.
The inventive device may also comprise the following optional features, considered separately or in combination:
- the device comprises a screen for separating the charcoal pieces intended to be charged into the throat from the fine charcoal fraction;
- the device comprises a coal mill in which the fine charcoal fraction is mixed with carbonaceous material, the combination formed by the charcoal and the carbonaceous material being intended to be injected into the tuyeres;
- the corresponding carbonaceous material is either mineral coal or charcoal.
The invention will be better understood from a reading of the description that follows, provided with reference to the appended figures in which:
- Figure 1 is a schematic representation of the inventive device according to a first alternative, in which the fine charcoal fraction obtained from the screening operation is not re-used in the method, and - - Figure 2 is a schematic representation of the inventive device according to a second alternative, in which the fine charcoal fraction obtained from the screening operation is re-used in the method.
In the context of the invention, a particular and essential property of these carbonaceous materials used as reducing agent is their gasification threshold or gasification start temperature. This is the temperature at which the carbon that they contain starts to react with the CO2 in the gas passing through the stack of the blast furnace to produce carbon monoxide by the chemical reaction:
C + CO2 --> 2 CO
- the method comprises a screening step which separates the charcoal pieces charged into the throat from the fine charcoal fraction;
- the fine charcoal fraction is injected in pulverized form into the tuyeres, in addition to and/or as replacement of the corresponding quantity of auxiliary fuel normally injected in pulverized form into the tuyeres;
- the auxiliary fuel is either mineral coal or charcoal.
The invention also relates to a device for implementing the method defined above. Said device is essentially characterized in that it comprises means for charging the charcoal into the throat of the blast furnace.
The inventive device may also comprise the following optional features, considered separately or in combination:
- the device comprises a screen for separating the charcoal pieces intended to be charged into the throat from the fine charcoal fraction;
- the device comprises a coal mill in which the fine charcoal fraction is mixed with carbonaceous material, the combination formed by the charcoal and the carbonaceous material being intended to be injected into the tuyeres;
- the corresponding carbonaceous material is either mineral coal or charcoal.
The invention will be better understood from a reading of the description that follows, provided with reference to the appended figures in which:
- Figure 1 is a schematic representation of the inventive device according to a first alternative, in which the fine charcoal fraction obtained from the screening operation is not re-used in the method, and - - Figure 2 is a schematic representation of the inventive device according to a second alternative, in which the fine charcoal fraction obtained from the screening operation is re-used in the method.
In the context of the invention, a particular and essential property of these carbonaceous materials used as reducing agent is their gasification threshold or gasification start temperature. This is the temperature at which the carbon that they contain starts to react with the CO2 in the gas passing through the stack of the blast furnace to produce carbon monoxide by the chemical reaction:
C + CO2 --> 2 CO
4 This gasification threshold sets the reserve zone temperature of the blast furnace. In a conventional blast fumace, this gasification start temperature is about 950 C.
The inventive method is based on the fact that, by lowering the temperature of the blast furnace reserve zone, the specific consumption of reducing agents decreases, along with the carbon dioxide emissions.
The Applicant has thus estimated that the decrease in coke consumption would be approximately 20 kilograms per tonne of liquid metal for a 100 C
decrease in the reserve zone temperature.
While it is known to lower the reserve zone temperature by substituting the reactive coke for the coke conventionally used, this reactive coke requires time-consuming and costly preparation. Furthermore, to the knowledge of the Applicant, no link has so far been established between the lowering of the reserve zone temperature and the reduction of the CO2 emissions.
In this context, the Applicant has discovered that the addition of a small amount of charcoal charged into the throat, instead of the corresponding quantity of conventional coke, serves to lower and to control this reserve zone temperature to the level of the charcoal gasification threshold.
In fact, charcoal has a reactivity threshold of about, or lower than, 850 C, which Is therefore considerably lower than that of the metallurgical coke conventionally used in a blast furnace.
Moreover, charcoal is a source of mineral carbon that is neutral in carbon dioxide production, or even negative. In fact, in the blast furnace burden, it can replace coke which has an impact on the carbon dioxide emissions of about 3 kilograms of CO2 emitted per kilogram of coke used.
These combined effects (decrease in the quantity of coke used associated with the lowering of the reserve zone temperature and replacement of mineral carbon (coke) by carbon coming from biomass (charcoal)) give rise to a substantial decrease in the quantity of coke consumed, and therefore of mineral carbon injected or charged into the blast fumace, and subsequently a significant reduction of the carbon dioxide emissions.
With reference to Figure 1, the blast furnace 1 is supplied with coke, sinter, pellets, and iron ore 2 via the line 3 into the throat 4. The pig iron and slag 5 are recovered at point 6 at the crucible via the line 7. The hot blast and additional oxygen 8 are introduced into the tuyeres 9 via the line 10. The coal and/or other auxiliary reducing agents are also introduced into the tuyeres 9 via the line 10.
The top gases are recovered at point 11 in the upper part of the blast furnace 1.
According to the invention, charcoal as received 12 is sent to a screen 13 in which the fine fraction 14 is separated from the charcoal pieces 15 charged into the throat 4 by means of a charging device 16. These pieces 15 have a diameter larger than the screen cut-off point, i.e. at least 20 millimeters.
The charcoal pieces 15 can be charged either at the same time as the coke, or at the same time as the iron ore.
The quantity of charcoal charged into the throat is 20 kilograms per tonne of pig iron.
With reference to Figure 2, the charcoal pieces 15 are charged into the throat 4 under the same conditions as those described with reference to Figure 1.
According to this alternative, the fine coal fraction 14 obtained from the screening of the charcoal as received 12 is mixed with coal 17 and pulverized in the coal mill 18 to form carbonaceous material 18a intended to be introduced into the tuyeres 9 via the line 10a. This coal 17 may either be mineral coal, or charcoal, as will be described in detail below. Also introduced into the tuyeres are the auxiliary reducing agents other than coal schematically shown injected into the tuyeres 9 via the line 10a.
The specific consumption of carbonaceous material injected into the tuyeres is 200 kilograms per tonne of pig iron. This consumption comprises the fine charcoal fraction 14 from the screening operation, which is estimated to be equal to the specific consumption of charcoal charged into the throat, or 20 kilograms per tonne of pig iron, assuming a screening efficiency of 50%.
For example, Table I below shows the main operating characteristics of a blast furnace producing 6000 tonnes of pig iron per day, and their variation when, according to the second alternative, 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat, and when the fine charcoal fraction 14 produced during the screening operation is injected in the form of pulverized charcoal into the tuyeres of the blast furnace, as replacement of an identical quantity of pulverized auxiliary fuel normally injected into said blast furnace.
The characteristics mentioned in Table l are as follows:
- the maximum productivity that can be achieved by this blast furnace under the conditions considered, expressed in tonnes of molten pig iron per day (t/d), - the flow rate of the natural dry blast blown into the tuyeres, expressed in kilo-Normal cubic meters per hour (kNm3/h), - the specific consumption, or yield, of coke charged into the throat, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of charcoal charged into the throat, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of pulverized mineral coal injected into the tuyeres, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of pulverized charcoal injected into the tuyeres, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of fine pulverized charcoal fraction injected into the tuyeres, expressed in kilograms per tonne of pig iron (kg/tp), said fine fraction 14 being that one, recovered after screening the charcoal 12 during the production of the charcoal, charged into the throat 15, - the flame temperature expressed In degrees Celsius ( C), - the reserve zone temperature expressed in degrees Celsius ( C), - the top gas temperature expressed in degrees Celsius ( C), and - the top gas flow rate expressed in normal cubic meters per hour (Nrn3/h).
Every blast furnace has a given operating range, in which its operation remains optimal. To make the calculations given in Table I, operational limits were therefore set, mainly associated with the temperatures reached in certain specific zones of the apparatus, and with the flow rate of gas streams entering and/or passing through the blast furnace. These limits are as follows:
- the top gas temperature is between 120 and 200 C;
- the flame temperature is between 2000 and 2200 C;
- the top gas flow rate must be lower than or equal to 400 000 Nm3/h (limitation of the method);
- the natural dry blast flow rate is lower than or equal to 225 kNm3/h (technological limitation).
Reference 1 corresponds to the charging of coke into the throat and to an injection of pulverized mineral coal into the tuyeres.
Reference 2 corresponds to the charging of coke into the throat and to an injection of pulverized charcoal into the tuyeres. The flame temperature is controlled at its maximum threshold of 2200 C.
Example 1 corresponds to the charging of 20 kilograms of charcoal pieces 15 per tonne of pig iron into the throat, the remainder of the carbonaceous material charged into the throat consisting of coke. Assuming a screening efficiency of 50%, 20 kilograms of fine charcoal fraction 14 obtained from the screening per tonne of molten metal is pulverized for injection into the tuyeres, as replacement of 20 kilograms of mineral coal per tonne of pig iron, the remainder of the pulverized carbonaceous material injected into the tuyeres being mineral coal. It is assumed In this Example 1 that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is 850 C.
Example 2 is identical to Example 1, except that the reserve zone temperature obtained, due to the intrinsic properties of the charcoal, is assumed to be 750 C.
Example 3 corresponds to the charging into the throat of 20 kilograms of charcoal pieces 15 per tonne of pig iron, the remainder of the carbonaceous material charged into the throat consisting of coke. Assuming a screening efficiency of 50%, 20 kilograms of fine charcoal fraction 14 from the screening per tonne of molten metal is pulverized for injection into the tuyeres, as replacement of 20 kilograms of injection charcoal obtained independently per tonne of pig iron.
The remainder of the carbonaceous material pulverized into the tuyeres consists of this independently obtained charcoal. In this Example 3, it is assumed that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is 850 C.
Example 4 is identical to Example 3, except that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is assumed to be 750 C. It is found that if the operating conditions of reference 1 are preserved, the blast fumace can no longer operate under the conditions selected for this Example 4. Only a less efficient blast furnace can operate under these conditions.
So-called less efficient operation may be said to mean a lower efficiency of reduction of the materials in the upper part of the blast furnace or higher heat losses from the apparatus. Reference 3 falls into the latter case, and Example must therefore be compared to this reference 3 and not to references 1 and 2.
In other words, the results obtained in Example 4 correspond to the operating modification of reference 3 when 20 kilograms of charcoal pieces 15 per tonne of pig iron are charged into the throat and when the corresponding fine charcoal fraction 14 is injected in pulverized form into the tuyeres of the blast furnace.
It is found for Example 1 that all the operating conditions defined above are satisfied. Moreover, the maximum possible productivity for the blast furnace under these conditions is significantly higher than the nominal production of said blast furnace. The blast furnace is therefore suitable for operating with a charging of 20 kilograms of charcoal pieces 15 per tonne of pig iron into the throat and an injection of 20 kilograms of fine charcoal fraction 14 obtained from the screening of the charcoal as received 13 per tonne of pig iron.
For Example 2, assuming that the reserve zone temperature is 750 C, a number of reaction conditions are no longer satisfied, particularly the flame temperature, which is substantially lower than 2000 C. The value obtained nevertheless appears to be sufficiently close to this limit for the blast furnace to operate. Moreover, the maximum productivity permitted under these conditions is lower than the nominal production of the installation. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel industry.
It should nevertheless be observed that this result depends on the assumption concerning the capacities of the installations. In particular, a blower having a capacity higher than the limit capacity considered here would help to maintain the blast furnace productivity at its nominal level of 6000 t/d.
For Example 3, as for Example 1, all the operating conditions are satisfied.
In consequence, the blast fumace can therefore operate with a reserve zone temperature of 850 C, when 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat, 20 kilograms of fine charcoal fraction 14 obtained from the screening operation are injected in pulverized form into the tuyeres per tonne of molten metal, the remainder of the coal injected into the tuyeres possibly being mineral coal such as charcoal.
In Example 4, if all the operating conditions are satisfied, the productivity, as for Example 2, is lower than 6000 tonnes/day. In consequence, whether the remainder of the carbonaceous material injected into the tuyeres is mineral coal or charcoal, when the reserve zone temperature is 750 C, the blast fumace does not operate optimally. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel industry.
As for Example 2, this result depends on the assumption concerning the capacities of the installations.
Table II resumes references 1, 2 and 3 and Examples 1 to 4, and demonstrates the advantages of the Inventive method according to this second alternative in terms of reduction of coke consumption, decrease in carbon dioxide emissions and beneficiation of charcoal relative to the reduction of the carbon dioxide emissions.
Reference 2, which corresponds to a coke injection into the throat and an injection of pulverized fine charcoal fraction into the tuyeres, is presented in comparison with reference 1. In fact, it constitutes an easy-to-implement solution for reducing the CO2 emissions. This solution nevertheless has the disadvantage of being the least effective of all the solutions presented in terms of kilograms of CO2 avoided per kilogram of charcoal used, as shown by the overall results in said Table II.
For the configuration of Example 1, a 12% reduction in carbon dioxide emissions is obtained, for Example 2, a 16% reduction, and for Examples 3 and 4, reductions of 46 and 48% in the carbon dioxide emissions, respectively.
Coke consumption has been reduced by 13.5% for Example 1, 19.4% for Example 2, 11.4% for Example 3 and 16.5% for Example 4, whereas it is 2.7%
higher for reference 2.
The ratio of the reduction in carbon dioxide emissions expressed in kilograms per tonne of pig iron to the charcoal consumption expressed in the same units illustrates the beneficiation of charcoal for reducing the carbon dioxide emissions.
It is found that the addition of a small quantity of charcoal into the throat and the tuyeres, when the remainder of the carbonaceous materials charged into the throat and injected into the tuyeres is mineral carbon, provides greater beneficiation of the charcoal than when the remainder of the carbonaceous material injected into the tuyeres is charcoal. In fact, this ratio is 4.65 and 6.00 for Examples 1 and 2, respectively, whereas it is only 3.18 and 3.43 for Examples and 4, and 2.83 for reference 2. In practice, this means that for the same charcoal availability, the configurations of Examples 1 and 2 serve to maximize the overall reduction of CO2 emissions.
According to the first alternative, Table III shows the main operating characteristics of a blast furnace producing 6000 tonnes of pig iron per day, and their variation when 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat without injecting the fine charcoal fraction 14 obtained from the screening operation into the tuyeres.
The characteristics mentioned in Table III and the operational limits set are the same as those associated with Table I.
Table III also shows references 1, 2 and 3 already explained for Tables I and Example 5 corresponds to the charging of 20 kilograms of charcoal pieces 15 into the throat per tonne of pig iron, the remainder of the carbonaceous material charged into the throat consisting of coke. 200 kilograms of mineral coal are injected in pulverized form into the tuyeres per tonne of pig iron. The fine charcoal fraction 14 obtained from the screening operation is not injected into the tuyeres.
Example 6 is identical to Example 5, except that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is assumed to be 750 C.
Example 7 corresponds to the charging of 20 kilograms of charcoal pieces 15 into the throat per tonne of pig iron, the remainder of the carbonaceous material charged into the throat consisting of coke. 200 kilograms of charcoal obtained separately are injected in pulverized form into the tuyeres per tonne of pig iron.
The fine charcoal fraction 14 obtained from the screening operation is not injected into the tuyeres.
Example 8 is identical to Example 7, except that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is assumed to be 750 C. It is found that if the operating conditions of reference 1 are preserved, the blast furnace can no longer operate under the conditions selected for this Example 8. Only a less efficient blast furnace can operate under these conditions.
So-called less efficient operation can be said to mean a lower efficiency of the reduction of the materials in the upper part of the blast furnace or higher heat losses from the apparatus. Reference 3 falls into the latter case, and Example must therefore be compared to this reference 3 and not to references 1 and 2.
in other words, the results obtained in Example 8 correspond to the operating modification of reference 3 when 20 kilograms of charcoal pieces 15 are charged into the throat per tonne of pig iron without injecting the corresponding fine charcoal fraction 14 in pulverized form into the tuyeres of the blast furnace.
It is found for Example 5 that all the operating conditions defined above are satisfied. Moreover, the maximum possible productivity for the blast furnace under these conditions is significantly higher than the nominal production of this blast furnace. The blast furnace therefore appears suitable for operating with a charging of 20 kilograms of charcoal pieces into the throat per tonne of molten metal, without injecting the fine charcoal fraction 14 obtained from the screening into the tuyeres.
For Example 6, assuming that the reserve zone temperature is 750 C, a number of reaction conditions are no longer satisfied, particularly the flame temperature, which is slightly lower than 2000 C. The value obtained nevertheless appears to be sufficiently close to this limit for the blast furnace to operate. Moreover, the maximum productivity permitted under these conditions is lower than the nominal production of the installation. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel industry. As for Examples 2 and 4, this result depends on the assumption concerning the capacities of the installations.
For Example 7, as for Example 5, all the operating conditions are satisfied.
In consequence, the blast furnace can therefore operate with a reserve zone temperature of 850 C, when 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat, without injecting the fine charcoal fraction 14 obtained from the screening into the tuyeres as a mixture with the pulverized charcoal normally injected.
In Example 8, if all the operating conditions are satisfied, the productivity, as for Example 6, is lower than 6000 tonnes/day. In consequence, whether the remainder of the carbonaceous material injected into the tuyeres is mineral coal or charcoal, when the reserve zone temperature is 750 C, the blast furnace does not operate optimally. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel Industry.
As for Example 6, this result depends on the assumption concerning the capacities of the installations.
Table IV resumes references 1, 2 and 3 and Examples 5 to 8, and demonstrates the advantages of the inventive method according to the first alternative in terms of reduction in coke consumption, decrease in carbon dioxide emissions and beneficiation of the charcoal relative to the reduction in carbon dioxide emissions.
For the configuration of Example 5, an 8% reduction in carbon dioxide emissions is obtained, and for Example 6, a 12% reduction in carbon dioxide emissions.
For the configuration of Example 7, a 46% reduction in carbon dioxide emissions is obtained, and for Example 8, a 48% reduction in carbon dioxide emissions in relation to reference 3.
Coke consumption has been reduced by 13.5% for Example 5 and 19.1% for Example 6.
it has been reduced by 10.9% for Example 7, and 15.9% for Example 8 in comparison with reference 3.
The ratio of the reduction in carbon dioxide emissions expressed in kilograms per tonne of pig iron to the Charcoal consumption expressed in the same units illustrates the beneficiation of charcoal for reducing the carbon dioxide emissions.
The impact of not injecting the fine fraction obtained from the screening of the charcoal as received into the tuyeres of the blast furnace can be evaluated by comparing Example 1 to Example 5, Example 2 to Example 6, Example 3 to Example 7, and Example 4 to Example 8. This shows that the beneficiation of charcoal relative to the total quantity of charcoal as received is significantly lower in Example 5 (3.11) in comparison with Example 1 (4.65), and also in Example 6 (4.37) in comparison with Example 2 (6.00). This is also the case to a lesser degree when Example 7 (2.87) is compared to Example 3 (3.18) and Example 8 (3.09) to Example 4 (3.43).
On the other hand, if only the charcoal used in the blast furnace is taken into account, that is to say the case in which the fine fraction obtained from the screening can be utilized elsewhere, the beneficiation of charcoal relative to the quantity of charcoal actually introduced into the blast furnace is significantly higher in Example 5 (6.21) in comparison with Example 1 (4.65), and also in Example 6 (8.74) in comparison with Example 2 (6.00).
However, this is not true in the case in which pulverized charcoal is injected into the tuyeres, because the total quantities of charcoal actually used in the blast furnace in Examples 7 and 8 are identical to those used in Examples 3 and 4, respectively. The beneficiation of charcoal relative to the quantity of charcoal actually introduced into the blast furnace in Example 7 (3,16) is thus virtually identical to that obtained in Example 3 (3.18), and that of Example 8 (3.41) is very close to that of Example 4 (3.43). The differenc,es observed are associated with the difference in chemical composition between the charcoal as received 13 and the charcoal normally injected into the tuyeres.
All the results given above reveal that the charging of a small amount of charcoal into the throat, whether the fine fraction is or is not injected into the tuyeres, serves to considerably decrease the coke consumption thanks to the dual effect of the replacement of the coke by the charcoal and the lowering of the reserve zone temperature. Moreover, the carbon dioxide emissions are significantly reduced, in general with substantial beneficiation of the charcoal, particularly in the case in which the carbonaceous material injected into the tuyeres is mineral coal.
Table I
Units Reference 1 Reference 2 Example 1 Example 2 Example 3 Reference 3 Example 4 Maximum possible productivity t/d 6 818 6 131 6 540
The inventive method is based on the fact that, by lowering the temperature of the blast furnace reserve zone, the specific consumption of reducing agents decreases, along with the carbon dioxide emissions.
The Applicant has thus estimated that the decrease in coke consumption would be approximately 20 kilograms per tonne of liquid metal for a 100 C
decrease in the reserve zone temperature.
While it is known to lower the reserve zone temperature by substituting the reactive coke for the coke conventionally used, this reactive coke requires time-consuming and costly preparation. Furthermore, to the knowledge of the Applicant, no link has so far been established between the lowering of the reserve zone temperature and the reduction of the CO2 emissions.
In this context, the Applicant has discovered that the addition of a small amount of charcoal charged into the throat, instead of the corresponding quantity of conventional coke, serves to lower and to control this reserve zone temperature to the level of the charcoal gasification threshold.
In fact, charcoal has a reactivity threshold of about, or lower than, 850 C, which Is therefore considerably lower than that of the metallurgical coke conventionally used in a blast furnace.
Moreover, charcoal is a source of mineral carbon that is neutral in carbon dioxide production, or even negative. In fact, in the blast furnace burden, it can replace coke which has an impact on the carbon dioxide emissions of about 3 kilograms of CO2 emitted per kilogram of coke used.
These combined effects (decrease in the quantity of coke used associated with the lowering of the reserve zone temperature and replacement of mineral carbon (coke) by carbon coming from biomass (charcoal)) give rise to a substantial decrease in the quantity of coke consumed, and therefore of mineral carbon injected or charged into the blast fumace, and subsequently a significant reduction of the carbon dioxide emissions.
With reference to Figure 1, the blast furnace 1 is supplied with coke, sinter, pellets, and iron ore 2 via the line 3 into the throat 4. The pig iron and slag 5 are recovered at point 6 at the crucible via the line 7. The hot blast and additional oxygen 8 are introduced into the tuyeres 9 via the line 10. The coal and/or other auxiliary reducing agents are also introduced into the tuyeres 9 via the line 10.
The top gases are recovered at point 11 in the upper part of the blast furnace 1.
According to the invention, charcoal as received 12 is sent to a screen 13 in which the fine fraction 14 is separated from the charcoal pieces 15 charged into the throat 4 by means of a charging device 16. These pieces 15 have a diameter larger than the screen cut-off point, i.e. at least 20 millimeters.
The charcoal pieces 15 can be charged either at the same time as the coke, or at the same time as the iron ore.
The quantity of charcoal charged into the throat is 20 kilograms per tonne of pig iron.
With reference to Figure 2, the charcoal pieces 15 are charged into the throat 4 under the same conditions as those described with reference to Figure 1.
According to this alternative, the fine coal fraction 14 obtained from the screening of the charcoal as received 12 is mixed with coal 17 and pulverized in the coal mill 18 to form carbonaceous material 18a intended to be introduced into the tuyeres 9 via the line 10a. This coal 17 may either be mineral coal, or charcoal, as will be described in detail below. Also introduced into the tuyeres are the auxiliary reducing agents other than coal schematically shown injected into the tuyeres 9 via the line 10a.
The specific consumption of carbonaceous material injected into the tuyeres is 200 kilograms per tonne of pig iron. This consumption comprises the fine charcoal fraction 14 from the screening operation, which is estimated to be equal to the specific consumption of charcoal charged into the throat, or 20 kilograms per tonne of pig iron, assuming a screening efficiency of 50%.
For example, Table I below shows the main operating characteristics of a blast furnace producing 6000 tonnes of pig iron per day, and their variation when, according to the second alternative, 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat, and when the fine charcoal fraction 14 produced during the screening operation is injected in the form of pulverized charcoal into the tuyeres of the blast furnace, as replacement of an identical quantity of pulverized auxiliary fuel normally injected into said blast furnace.
The characteristics mentioned in Table l are as follows:
- the maximum productivity that can be achieved by this blast furnace under the conditions considered, expressed in tonnes of molten pig iron per day (t/d), - the flow rate of the natural dry blast blown into the tuyeres, expressed in kilo-Normal cubic meters per hour (kNm3/h), - the specific consumption, or yield, of coke charged into the throat, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of charcoal charged into the throat, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of pulverized mineral coal injected into the tuyeres, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of pulverized charcoal injected into the tuyeres, expressed in kilograms per tonne of pig iron (kg/tp), - the specific consumption of fine pulverized charcoal fraction injected into the tuyeres, expressed in kilograms per tonne of pig iron (kg/tp), said fine fraction 14 being that one, recovered after screening the charcoal 12 during the production of the charcoal, charged into the throat 15, - the flame temperature expressed In degrees Celsius ( C), - the reserve zone temperature expressed in degrees Celsius ( C), - the top gas temperature expressed in degrees Celsius ( C), and - the top gas flow rate expressed in normal cubic meters per hour (Nrn3/h).
Every blast furnace has a given operating range, in which its operation remains optimal. To make the calculations given in Table I, operational limits were therefore set, mainly associated with the temperatures reached in certain specific zones of the apparatus, and with the flow rate of gas streams entering and/or passing through the blast furnace. These limits are as follows:
- the top gas temperature is between 120 and 200 C;
- the flame temperature is between 2000 and 2200 C;
- the top gas flow rate must be lower than or equal to 400 000 Nm3/h (limitation of the method);
- the natural dry blast flow rate is lower than or equal to 225 kNm3/h (technological limitation).
Reference 1 corresponds to the charging of coke into the throat and to an injection of pulverized mineral coal into the tuyeres.
Reference 2 corresponds to the charging of coke into the throat and to an injection of pulverized charcoal into the tuyeres. The flame temperature is controlled at its maximum threshold of 2200 C.
Example 1 corresponds to the charging of 20 kilograms of charcoal pieces 15 per tonne of pig iron into the throat, the remainder of the carbonaceous material charged into the throat consisting of coke. Assuming a screening efficiency of 50%, 20 kilograms of fine charcoal fraction 14 obtained from the screening per tonne of molten metal is pulverized for injection into the tuyeres, as replacement of 20 kilograms of mineral coal per tonne of pig iron, the remainder of the pulverized carbonaceous material injected into the tuyeres being mineral coal. It is assumed In this Example 1 that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is 850 C.
Example 2 is identical to Example 1, except that the reserve zone temperature obtained, due to the intrinsic properties of the charcoal, is assumed to be 750 C.
Example 3 corresponds to the charging into the throat of 20 kilograms of charcoal pieces 15 per tonne of pig iron, the remainder of the carbonaceous material charged into the throat consisting of coke. Assuming a screening efficiency of 50%, 20 kilograms of fine charcoal fraction 14 from the screening per tonne of molten metal is pulverized for injection into the tuyeres, as replacement of 20 kilograms of injection charcoal obtained independently per tonne of pig iron.
The remainder of the carbonaceous material pulverized into the tuyeres consists of this independently obtained charcoal. In this Example 3, it is assumed that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is 850 C.
Example 4 is identical to Example 3, except that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is assumed to be 750 C. It is found that if the operating conditions of reference 1 are preserved, the blast fumace can no longer operate under the conditions selected for this Example 4. Only a less efficient blast furnace can operate under these conditions.
So-called less efficient operation may be said to mean a lower efficiency of reduction of the materials in the upper part of the blast furnace or higher heat losses from the apparatus. Reference 3 falls into the latter case, and Example must therefore be compared to this reference 3 and not to references 1 and 2.
In other words, the results obtained in Example 4 correspond to the operating modification of reference 3 when 20 kilograms of charcoal pieces 15 per tonne of pig iron are charged into the throat and when the corresponding fine charcoal fraction 14 is injected in pulverized form into the tuyeres of the blast furnace.
It is found for Example 1 that all the operating conditions defined above are satisfied. Moreover, the maximum possible productivity for the blast furnace under these conditions is significantly higher than the nominal production of said blast furnace. The blast furnace is therefore suitable for operating with a charging of 20 kilograms of charcoal pieces 15 per tonne of pig iron into the throat and an injection of 20 kilograms of fine charcoal fraction 14 obtained from the screening of the charcoal as received 13 per tonne of pig iron.
For Example 2, assuming that the reserve zone temperature is 750 C, a number of reaction conditions are no longer satisfied, particularly the flame temperature, which is substantially lower than 2000 C. The value obtained nevertheless appears to be sufficiently close to this limit for the blast furnace to operate. Moreover, the maximum productivity permitted under these conditions is lower than the nominal production of the installation. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel industry.
It should nevertheless be observed that this result depends on the assumption concerning the capacities of the installations. In particular, a blower having a capacity higher than the limit capacity considered here would help to maintain the blast furnace productivity at its nominal level of 6000 t/d.
For Example 3, as for Example 1, all the operating conditions are satisfied.
In consequence, the blast fumace can therefore operate with a reserve zone temperature of 850 C, when 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat, 20 kilograms of fine charcoal fraction 14 obtained from the screening operation are injected in pulverized form into the tuyeres per tonne of molten metal, the remainder of the coal injected into the tuyeres possibly being mineral coal such as charcoal.
In Example 4, if all the operating conditions are satisfied, the productivity, as for Example 2, is lower than 6000 tonnes/day. In consequence, whether the remainder of the carbonaceous material injected into the tuyeres is mineral coal or charcoal, when the reserve zone temperature is 750 C, the blast fumace does not operate optimally. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel industry.
As for Example 2, this result depends on the assumption concerning the capacities of the installations.
Table II resumes references 1, 2 and 3 and Examples 1 to 4, and demonstrates the advantages of the Inventive method according to this second alternative in terms of reduction of coke consumption, decrease in carbon dioxide emissions and beneficiation of charcoal relative to the reduction of the carbon dioxide emissions.
Reference 2, which corresponds to a coke injection into the throat and an injection of pulverized fine charcoal fraction into the tuyeres, is presented in comparison with reference 1. In fact, it constitutes an easy-to-implement solution for reducing the CO2 emissions. This solution nevertheless has the disadvantage of being the least effective of all the solutions presented in terms of kilograms of CO2 avoided per kilogram of charcoal used, as shown by the overall results in said Table II.
For the configuration of Example 1, a 12% reduction in carbon dioxide emissions is obtained, for Example 2, a 16% reduction, and for Examples 3 and 4, reductions of 46 and 48% in the carbon dioxide emissions, respectively.
Coke consumption has been reduced by 13.5% for Example 1, 19.4% for Example 2, 11.4% for Example 3 and 16.5% for Example 4, whereas it is 2.7%
higher for reference 2.
The ratio of the reduction in carbon dioxide emissions expressed in kilograms per tonne of pig iron to the charcoal consumption expressed in the same units illustrates the beneficiation of charcoal for reducing the carbon dioxide emissions.
It is found that the addition of a small quantity of charcoal into the throat and the tuyeres, when the remainder of the carbonaceous materials charged into the throat and injected into the tuyeres is mineral carbon, provides greater beneficiation of the charcoal than when the remainder of the carbonaceous material injected into the tuyeres is charcoal. In fact, this ratio is 4.65 and 6.00 for Examples 1 and 2, respectively, whereas it is only 3.18 and 3.43 for Examples and 4, and 2.83 for reference 2. In practice, this means that for the same charcoal availability, the configurations of Examples 1 and 2 serve to maximize the overall reduction of CO2 emissions.
According to the first alternative, Table III shows the main operating characteristics of a blast furnace producing 6000 tonnes of pig iron per day, and their variation when 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat without injecting the fine charcoal fraction 14 obtained from the screening operation into the tuyeres.
The characteristics mentioned in Table III and the operational limits set are the same as those associated with Table I.
Table III also shows references 1, 2 and 3 already explained for Tables I and Example 5 corresponds to the charging of 20 kilograms of charcoal pieces 15 into the throat per tonne of pig iron, the remainder of the carbonaceous material charged into the throat consisting of coke. 200 kilograms of mineral coal are injected in pulverized form into the tuyeres per tonne of pig iron. The fine charcoal fraction 14 obtained from the screening operation is not injected into the tuyeres.
Example 6 is identical to Example 5, except that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is assumed to be 750 C.
Example 7 corresponds to the charging of 20 kilograms of charcoal pieces 15 into the throat per tonne of pig iron, the remainder of the carbonaceous material charged into the throat consisting of coke. 200 kilograms of charcoal obtained separately are injected in pulverized form into the tuyeres per tonne of pig iron.
The fine charcoal fraction 14 obtained from the screening operation is not injected into the tuyeres.
Example 8 is identical to Example 7, except that the reserve zone temperature obtained due to the intrinsic properties of the charcoal is assumed to be 750 C. It is found that if the operating conditions of reference 1 are preserved, the blast furnace can no longer operate under the conditions selected for this Example 8. Only a less efficient blast furnace can operate under these conditions.
So-called less efficient operation can be said to mean a lower efficiency of the reduction of the materials in the upper part of the blast furnace or higher heat losses from the apparatus. Reference 3 falls into the latter case, and Example must therefore be compared to this reference 3 and not to references 1 and 2.
in other words, the results obtained in Example 8 correspond to the operating modification of reference 3 when 20 kilograms of charcoal pieces 15 are charged into the throat per tonne of pig iron without injecting the corresponding fine charcoal fraction 14 in pulverized form into the tuyeres of the blast furnace.
It is found for Example 5 that all the operating conditions defined above are satisfied. Moreover, the maximum possible productivity for the blast furnace under these conditions is significantly higher than the nominal production of this blast furnace. The blast furnace therefore appears suitable for operating with a charging of 20 kilograms of charcoal pieces into the throat per tonne of molten metal, without injecting the fine charcoal fraction 14 obtained from the screening into the tuyeres.
For Example 6, assuming that the reserve zone temperature is 750 C, a number of reaction conditions are no longer satisfied, particularly the flame temperature, which is slightly lower than 2000 C. The value obtained nevertheless appears to be sufficiently close to this limit for the blast furnace to operate. Moreover, the maximum productivity permitted under these conditions is lower than the nominal production of the installation. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel industry. As for Examples 2 and 4, this result depends on the assumption concerning the capacities of the installations.
For Example 7, as for Example 5, all the operating conditions are satisfied.
In consequence, the blast furnace can therefore operate with a reserve zone temperature of 850 C, when 20 kilograms of charcoal pieces 15 per tonne of molten metal are charged into the throat, without injecting the fine charcoal fraction 14 obtained from the screening into the tuyeres as a mixture with the pulverized charcoal normally injected.
In Example 8, if all the operating conditions are satisfied, the productivity, as for Example 6, is lower than 6000 tonnes/day. In consequence, whether the remainder of the carbonaceous material injected into the tuyeres is mineral coal or charcoal, when the reserve zone temperature is 750 C, the blast furnace does not operate optimally. This type of operation may nevertheless be advantageous for low-productivity operation, for example in a less favorable economic situation for the steel Industry.
As for Example 6, this result depends on the assumption concerning the capacities of the installations.
Table IV resumes references 1, 2 and 3 and Examples 5 to 8, and demonstrates the advantages of the inventive method according to the first alternative in terms of reduction in coke consumption, decrease in carbon dioxide emissions and beneficiation of the charcoal relative to the reduction in carbon dioxide emissions.
For the configuration of Example 5, an 8% reduction in carbon dioxide emissions is obtained, and for Example 6, a 12% reduction in carbon dioxide emissions.
For the configuration of Example 7, a 46% reduction in carbon dioxide emissions is obtained, and for Example 8, a 48% reduction in carbon dioxide emissions in relation to reference 3.
Coke consumption has been reduced by 13.5% for Example 5 and 19.1% for Example 6.
it has been reduced by 10.9% for Example 7, and 15.9% for Example 8 in comparison with reference 3.
The ratio of the reduction in carbon dioxide emissions expressed in kilograms per tonne of pig iron to the Charcoal consumption expressed in the same units illustrates the beneficiation of charcoal for reducing the carbon dioxide emissions.
The impact of not injecting the fine fraction obtained from the screening of the charcoal as received into the tuyeres of the blast furnace can be evaluated by comparing Example 1 to Example 5, Example 2 to Example 6, Example 3 to Example 7, and Example 4 to Example 8. This shows that the beneficiation of charcoal relative to the total quantity of charcoal as received is significantly lower in Example 5 (3.11) in comparison with Example 1 (4.65), and also in Example 6 (4.37) in comparison with Example 2 (6.00). This is also the case to a lesser degree when Example 7 (2.87) is compared to Example 3 (3.18) and Example 8 (3.09) to Example 4 (3.43).
On the other hand, if only the charcoal used in the blast furnace is taken into account, that is to say the case in which the fine fraction obtained from the screening can be utilized elsewhere, the beneficiation of charcoal relative to the quantity of charcoal actually introduced into the blast furnace is significantly higher in Example 5 (6.21) in comparison with Example 1 (4.65), and also in Example 6 (8.74) in comparison with Example 2 (6.00).
However, this is not true in the case in which pulverized charcoal is injected into the tuyeres, because the total quantities of charcoal actually used in the blast furnace in Examples 7 and 8 are identical to those used in Examples 3 and 4, respectively. The beneficiation of charcoal relative to the quantity of charcoal actually introduced into the blast furnace in Example 7 (3,16) is thus virtually identical to that obtained in Example 3 (3.18), and that of Example 8 (3.41) is very close to that of Example 4 (3.43). The differenc,es observed are associated with the difference in chemical composition between the charcoal as received 13 and the charcoal normally injected into the tuyeres.
All the results given above reveal that the charging of a small amount of charcoal into the throat, whether the fine fraction is or is not injected into the tuyeres, serves to considerably decrease the coke consumption thanks to the dual effect of the replacement of the coke by the charcoal and the lowering of the reserve zone temperature. Moreover, the carbon dioxide emissions are significantly reduced, in general with substantial beneficiation of the charcoal, particularly in the case in which the carbonaceous material injected into the tuyeres is mineral coal.
Table I
Units Reference 1 Reference 2 Example 1 Example 2 Example 3 Reference 3 Example 4 Maximum possible productivity t/d 6 818 6 131 6 540
5 832 6 098 6 326 5 690 Natural dry blast flow rate kNe/h 204 221 209 Specific consumption of dry kg/tp 284 292 246 coke charged into throat Specific consumption of dry kg/tp - - 20 20 20 - 20 (-) charcoal charged into throat .
Specific consumption of I.) -I
pulverized mineral coal injected kg/tP 200 - 180 (wet) into the tuyeres ko Specific consumption of pulverized charcoal injected kgitP - 200 - -180 200 180 N) H
(wet) into the tuyeres N) i Specific consumption of fine charcoal fraction injected (dry) kgliP - - 20 , into the tuyeres Flame temperature oc 2 147 2 200 2 088 1 987 Reserve zone temperature oc 950 950 850 750 Top gas temperature C 150 151 120 120 _ Top gas flow rate Nreih 368 432 370 170 365 306 Table II
= Units Reference 1 Reference 2 Example 1 Example 2 Example 3 Reference 3 Example 4 Reserve zone temperature .0 950 950 850 750 ' ' Maximum possible productivity t/d ' 6 818 6 131 6 540 5 Flame temperature C 2 147 - 2 200 2 088 1 987 ' Specific consumption of dry kg/tp 284.5 292.2 246.0 229.4 252.0 301.9 = 252.5 coke charged into throat n -Reduction of ooke consumption % - -2.7 115 19.4 11.4 - 16.5 0 I.), Decrease in CO2 emissions % - 37 12 16 Decrease in CO2 emissions kg/tp - 560 186 240 693 - - 748 ko a, _ ' Total charcoal consumption !cop _ 198 40 40 218 198 218 I.) (dry) _ H
I.) Reduction in CO2 emissions/total - - 2.83 4.66
Specific consumption of I.) -I
pulverized mineral coal injected kg/tP 200 - 180 (wet) into the tuyeres ko Specific consumption of pulverized charcoal injected kgitP - 200 - -180 200 180 N) H
(wet) into the tuyeres N) i Specific consumption of fine charcoal fraction injected (dry) kgliP - - 20 , into the tuyeres Flame temperature oc 2 147 2 200 2 088 1 987 Reserve zone temperature oc 950 950 850 750 Top gas temperature C 150 151 120 120 _ Top gas flow rate Nreih 368 432 370 170 365 306 Table II
= Units Reference 1 Reference 2 Example 1 Example 2 Example 3 Reference 3 Example 4 Reserve zone temperature .0 950 950 850 750 ' ' Maximum possible productivity t/d ' 6 818 6 131 6 540 5 Flame temperature C 2 147 - 2 200 2 088 1 987 ' Specific consumption of dry kg/tp 284.5 292.2 246.0 229.4 252.0 301.9 = 252.5 coke charged into throat n -Reduction of ooke consumption % - -2.7 115 19.4 11.4 - 16.5 0 I.), Decrease in CO2 emissions % - 37 12 16 Decrease in CO2 emissions kg/tp - 560 186 240 693 - - 748 ko a, _ ' Total charcoal consumption !cop _ 198 40 40 218 198 218 I.) (dry) _ H
I.) Reduction in CO2 emissions/total - - 2.83 4.66
6.00 3.18 - 3.43 0 I.) charcoal consumption = H
Table 111 Units Reference 1 Reference 2 Example 5 Example 6 Example 7 Reference 3 Example 8 , Maximum possible productivity Yid 6 818 6 131 6 569 , 5 854 6 078 6 326 5 677 -' Natural dry blast flow rate kNr-n3/h 204 221 _ Specific consumption of dry kgitp 284 292 247 coke charged into throat Specific consumption of dry !cop _ - 20 charcoal charged into throat , Specific consumption of pulverized mineral coal injected kgitto 200- 200 200 - - - n (wet) into the tuyeres _ Specific consumption of I.) pulverized charcoal injected kg/tP - 200 - -(wet) into the tuyeres ko -.1,.
Specific consumption of fine charcoal fraction in - jected (dry) kgitP - -- _ - - I.) H
into the tuyeres N) .
Flame temperature C 2 147 2 200 2 086 1 985 2 142 . 2 200 2 140 0 I.) I
Reserve zone temperature C 950 950 850 750 Top gas temperature C 150 151 120 120 Top gas flow rate Neill 368 432 370 170 365 388 367 509 Table IV
Units Reference 1 Reference 2 Example 5 Example 6 Example 7 Reference 3 Example 8 Reserve zone temperature C 950 950 850 750 Maximum possible productivity t/d 6 818 ' 6 131 6 569 ' Flame temperature oc 2 147 2 200 2 086 1 985 _ , Specific consumption of dry kg/fp 284.5 292.2 246.8 230.3 253.6 301.9 254.0 n coke charged into throat 1 Reduction of coke consumption % - -2.7 13.5 19.1 , 10.9 - 15.9 ="
, , Decrease in CO2 emissions % - 37 8 12 46 - 48 ko .1,.
Decrease in CO2 emissions kg/tp - 560 124 175 688 - 743 I.) H
Consumption of charcoal as kop . 198 40 40 238 198 238 I.) I
received (dry) I.) Consumption of charcoal in kop _ 198 20 20 blast furnace (dry) 0 _ Reduction in CO2 emissions/
consumption of charcoal as - - 2.83 3.11 4.37 2.87 - 3.09 received Reduction in CO2 emissions/
consumption of charcoal in - - 2.83 821 8/4 3.16 - 3.41 blast furnace
Table 111 Units Reference 1 Reference 2 Example 5 Example 6 Example 7 Reference 3 Example 8 , Maximum possible productivity Yid 6 818 6 131 6 569 , 5 854 6 078 6 326 5 677 -' Natural dry blast flow rate kNr-n3/h 204 221 _ Specific consumption of dry kgitp 284 292 247 coke charged into throat Specific consumption of dry !cop _ - 20 charcoal charged into throat , Specific consumption of pulverized mineral coal injected kgitto 200- 200 200 - - - n (wet) into the tuyeres _ Specific consumption of I.) pulverized charcoal injected kg/tP - 200 - -(wet) into the tuyeres ko -.1,.
Specific consumption of fine charcoal fraction in - jected (dry) kgitP - -- _ - - I.) H
into the tuyeres N) .
Flame temperature C 2 147 2 200 2 086 1 985 2 142 . 2 200 2 140 0 I.) I
Reserve zone temperature C 950 950 850 750 Top gas temperature C 150 151 120 120 Top gas flow rate Neill 368 432 370 170 365 388 367 509 Table IV
Units Reference 1 Reference 2 Example 5 Example 6 Example 7 Reference 3 Example 8 Reserve zone temperature C 950 950 850 750 Maximum possible productivity t/d 6 818 ' 6 131 6 569 ' Flame temperature oc 2 147 2 200 2 086 1 985 _ , Specific consumption of dry kg/fp 284.5 292.2 246.8 230.3 253.6 301.9 254.0 n coke charged into throat 1 Reduction of coke consumption % - -2.7 13.5 19.1 , 10.9 - 15.9 ="
, , Decrease in CO2 emissions % - 37 8 12 46 - 48 ko .1,.
Decrease in CO2 emissions kg/tp - 560 124 175 688 - 743 I.) H
Consumption of charcoal as kop . 198 40 40 238 198 238 I.) I
received (dry) I.) Consumption of charcoal in kop _ 198 20 20 blast furnace (dry) 0 _ Reduction in CO2 emissions/
consumption of charcoal as - - 2.83 3.11 4.37 2.87 - 3.09 received Reduction in CO2 emissions/
consumption of charcoal in - - 2.83 821 8/4 3.16 - 3.41 blast furnace
Claims (11)
1. A method for reducing carbon dioxide emissions in top gases of a blast furnace, wherein reducing agents are charged into the throat of said blast furnace and auxiliary fuels in pulverized form are injected into tuyeres, wherein the reducing agents charged into the throat comprise charcoal and in that specific consumption of the charcoal charged into the throat is more than 0% and less than 20% of the total quantity of the reducing agents charged into the throat.
2. The method as defined in claim 1, wherein the specific consumption of the charcoal charged into the throat is more than 0% and less than 10% of the total quantity of the reducing agents charged into the throat.
3. The method as defined in claim 1 or 2, wherein the reducing agents charged into the throat consist of charcoal and mineral carbon in the form of coke.
4. The method as defined in any one of claims 1 to 3, wherein the charcoal charged into the throat is in the form of pieces having a diameter larger than millimeters.
5. The method as defined in claim 4, comprising a screening step which separates the charcoal pieces charged into the throat from a fine charcoal fraction having a diameter smaller than 20 millimeters.
6. The method as defined in claim 5, wherein the fine charcoal fraction is injected in pulverized form into the tuyeres, in addition to and/or as replacement of a corresponding quantity of the auxiliary fuel normally injected in pulverized form into the tuyeres.
7. The method as defined in claim 6, wherein the auxiliary fuel is either mineral coal or charcoal.
8. A device implementing the method as defined in any one of claims 1 to 7, comprising means for charging the charcoal into the throat of the blast furnace so that the consumption of the charcoal charged into the throat is more than 0%
and less than 20% of the total quantity of the reducing agents charged into the throat.
and less than 20% of the total quantity of the reducing agents charged into the throat.
9. The device as defined in claim 8, comprising a screen for separating the charcoal pieces charged into the throat from a fine charcoal fraction having a diameter smaller than 20 millimeters.
10. The device as defined in claim 9, comprising a coal mill in which the fine charcoal fraction is mixed with carbonaceous material, the combination formed by the fine charcoal fraction and the carbonaceous material is injected into the tuyeres.
11. The device as defined in claim 10, wherein the carbonaceous material is either mineral coal or charcoal.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/FR2009/001052 WO2011027038A1 (en) | 2009-09-02 | 2009-09-02 | Method for reducing the carbon dioxide emissions of a blast furnace, and associated device |
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| GB218647A (en) * | 1923-07-03 | 1925-09-25 | Commentry Fourchambault Et Dec | Process of treatment of ore in blast furnaces by the injection of powdered combustible concurrently with the use of a charge of coke |
| AT399724B (en) * | 1992-10-08 | 1995-07-25 | Voest Alpine Stahl | Process for producing pig iron making optimum use of the coal seam |
| JPH08157914A (en) * | 1994-12-06 | 1996-06-18 | Kawasaki Steel Corp | Blowing of charcoal powder into blast furnace |
| JPH10306303A (en) * | 1997-04-30 | 1998-11-17 | Kawasaki Steel Corp | Operation of vertical type melting furnace |
| JP4383075B2 (en) * | 2003-03-28 | 2009-12-16 | 新日本製鐵株式会社 | Method for producing highly reactive molded coke for blast furnace |
| AU2005265480B2 (en) * | 2004-07-30 | 2008-06-12 | Posco | Apparatus for manufacturing molten irons by injecting fine coals into a melter-gasifier and the method using the same |
-
2009
- 2009-09-02 CA CA2770947A patent/CA2770947C/en active Active
- 2009-09-02 WO PCT/FR2009/001052 patent/WO2011027038A1/en active Application Filing
- 2009-09-02 BR BR112012004763-9A patent/BR112012004763B1/en active IP Right Grant
- 2009-09-02 CN CN201610674500.2A patent/CN106282451A/en active Pending
- 2009-09-02 CN CN2009801612252A patent/CN102482723A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| WO2011027038A1 (en) | 2011-03-10 |
| BR112012004763A2 (en) | 2020-12-08 |
| CN106282451A (en) | 2017-01-04 |
| BR112012004763B1 (en) | 2022-08-16 |
| CN102482723A (en) | 2012-05-30 |
| CA2770947A1 (en) | 2011-03-10 |
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