Patent Publication Number: US-2022213567-A1

Title: Ironmaking system and ironmaking process of two-section downdraft bed

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to the field of metal smelting technologies, and in particular, to an ironmaking process of a two-section downdraft bed. 
     Related Art 
     Information of the Related Art part is merely disclosed to increase the understanding of the overall background of the present invention, but is not necessarily regarded as acknowledging or suggesting, in any form, that the information constitutes the prior art known to a person of ordinary skill in the art. 
     Currently, blast furnace ironmaking is a main method for producing steel, and the predominance of the blast furnace ironmaking is unlikely to be changed in a short term. The method is a continuous metallurgical process for reducing iron ore into iron in a blast furnace, and a smelting process is as follows: Iron ore, coke, and a flux used for slagging are fed from a furnace top according to a prescribed ratio, and a charge level of a furnace throat is maintained at a certain height. The coke and the iron ore form an alternating layer structure in the furnace. The coke combusts with oxygen in blown hot air to generate carbon monoxide and hydrogen. Oxygen is removed from the iron ore in a rising process in the furnace, to obtain iron through reduction, and the iron becomes a liquid at a searing temperature of more than 2000° C. The refined liquid molten iron flows from a tapping hole, and forms cast iron ingots through solidification. Impurities in the iron ore and the flux are combined into slags, and discharged from a slag discharging hole. 
     It can be seen that a large amount of premium coke is required in the blast furnace ironmaking. However, coke resources are increasingly deficient, and prices of metallurgical coke are increasingly higher, but non-coke resources that are abundant in reserves and that are cheap cannot be fully utilized in ironmaking production. To change the dependency of ironmaking on the coke resources, researchers have discovered non-blast furnace ironmaking in different forms, and a modern non-blast furnace ironmaking industrial system with direct reduction and melting reduction as main parts is initially formed. The existing non-blast furnace ironmaking technologies include a direct reduction method of gas reduction, a direct reduction method using a solid reducing agent, and typical melting reduction processes, for example, a Corex process, a Finex process, and a HIsmelt process. However, the foregoing processes have different problems respectively, for example, low reduction efficiency, a low waste heat recovery rate, and that some metallurgical coke is still needed. An ironmaking process that has a simple process and low energy consumption is not achieved. 
     SUMMARY 
     To resolve the technical problem in the prior art, an objective of the present invention is to provide an ironmaking system and an ironmaking process of a two-section downdraft bed. 
     To achieve the objective, the present invention includes the following technical solutions: 
     An ironmaking system of a two-section downdraft bed is provided, including: 
     a melting furnace section, vertically downward disposed, where a basic combustor/gasifier is disposed at a top portion thereof, a first inlet and a second inlet are provided below the basic combustor/gasifier, both the first inlet and the second inlet are evenly provided along a side wall of the melting furnace section, and form a tangent circle in the melting furnace section, the second inlet is located below the first inlet, and the first inlet is connected to a coke powder/pulverized coal source, an air source, and a water vapor source; 
     a slag pool, disposed at a bottom portion of the melting furnace section, and equipped with a slag discharging device and a tapping device, where an outlet end is downstream of the slag pool; 
     a pre-reduction furnace section, vertically downward disposed, where a top portion thereof is connected to the outlet end of the melting furnace section, a third inlet and a fourth inlet are provided on an upper portion of the pre-reduction furnace section, an outlet is disposed at a bottom portion of the pre-reduction furnace section, the third inlet is connected to a temperature-adjusting and tempering medium source, and the fourth inlet is connected to an iron mineral powder source; and 
     a first separator, where an inlet of the first separator is connected to the outlet of the pre-reduction furnace section, and an outlet at a bottom portion of the first separator is connected to the second inlet through a conveying pipeline. 
     Carried by air and water vapor, coke powder/pulverized coal enters the melting furnace section from a side wall of the melting furnace section, to form a swirling flow in the melting furnace section, and rotationally moves downward. A combustor jets a flame to the swirling flow, to ignite or gasify the coke powder/pulverized coal, to generate a high-temperature flame. Carried by the swirling flow, the high-temperature flame flows through a pre-reduced mineral powder fluid that enters, and two strands of fluids with different movement velocities meet, collide, and further, are rapidly mixed evenly. 
     Because the fluids spirally move downward, a time during which pre-reduced iron mineral powder is in contact with a high-temperature reducing gas is prolonged, so that a reduction degree of the iron mineral powder can be effectively improved, thereby improving an ironmaking yield. In addition, the fluids spirally move downward, and play a sound role in carrying the iron mineral powder, to effectively prevent the iron mineral powder from sedimentation in the melting furnace section, so that the iron mineral powder and a gas flow are mixed evenly, which is relatively beneficial to improve an ironmaking rate of the iron mineral powder. 
     An iron oxide in the iron mineral powder is reduced to generate molten iron, and the molten iron and slags fall into the slag pool, and are discharged through the tapping device and the slag discharging device. 
     After being cooled to a proper temperature by a tempering medium that enters through the third inlet, the gas flow flowing out of the melting furnace section enters the pre-reduction furnace section, and comes into contact with the iron mineral powder fluid that enters, to pre-reduce the iron mineral powder. After the pre-reduction is completed, the iron oxide in the iron mineral powder mainly becomes FeO, and a part of the iron oxide is directly reduced into Fe. Separated by a separator, the pre-reduced iron mineral powder is conveyed to the melting furnace section for high-temperature reduction. Because a pre-reduction step has been performed, an ironmaking recovery rate of the iron mineral powder can be significantly improved. 
     In some embodiments, a funnel structure is disposed at the bottom portion of the melting furnace section, and the slag pool is disposed at an outlet end of the funnel structure. The molten iron generated in the melting furnace section converges at the funnel structure, and flows into the slag pool through the funnel structure, to ensure that the molten iron flows out smoothly. 
     In some embodiments, the first inlet includes 2 to 8 inlets, circumferentially arranged along the melting furnace section. 
     In some embodiments, the second inlet includes 2 to 8 inlets, circumferentially arranged along the melting furnace section. 
     In some embodiments, the pre-reduction furnace section is connected to the melting furnace section through an arc-shaped pipeline. The arc-shaped pipeline can gently change a flow direction of a reducing gas, and has relatively small impact on an inner flow field of the gas flow. Through the arc-shaped pipeline, when flowing through the pre-reduction furnace section, the gas flow flowing out of the melting furnace section can play relatively good role in disturbing and carrying the iron mineral powder added into the pre-reduction furnace section, to improve a pre-reduction effect on the iron mineral powder. 
     In some embodiments, the ironmaking system of a two-section downdraft bed further includes a second separator, where an inlet of the second separator is connected to a gas outlet of the first separator through a pipeline, a fifth inlet is provided on the pipeline, and the fifth inlet is connected to a cold iron mineral powder source. 
     A gas flow with a relatively high temperature that is separated from the first separator flows through the fifth inlet, comes into contact with cold iron mineral powder added from the fifth inlet, heats the cold iron mineral powder, and carries the cold iron mineral powder to the second separator for gas-solid separation in the second separator. The pre-heating of the cold iron mineral powder is relatively beneficial to subsequent reduction ironmaking of the iron mineral powder. 
     Further, a solid outlet of the second separator is connected to the fourth inlet through a conveying pipeline, and a gas outlet is connected to a first heat exchanger through a pipeline. 
     Because after the cold iron mineral powder is pre-heated, a temperature of the gas is still relatively high, waste heat recovery can be performed at a position of the first heat exchanger, to avoid heat waste. 
     In some embodiments, the ironmaking system of a two-section downdraft bed further includes a pulverized coal coking furnace section and a third separator, where the pulverized coal coking furnace section is vertically disposed, a bottom portion of the pulverized coal coking furnace section is connected to the gas outlet of the first separator, a sixth inlet is provided at a lower end of the pulverized coal coking furnace section, the sixth inlet is connected to a pulverized coal source, and a top portion of the pulverized coal coking furnace section is connected to an inlet of the third separator. 
     A hot gas flow separated from the first separator can be utilized for heating and coking the pulverized coal. 
     Further, a solid outlet end of the third separator is connected to the first inlet. The separated coke powder is conveyed to the melting furnace section to participate in a reaction. 
     Further, a gas outlet end of the third separator is connected to a second heat exchanger through a pipeline. 
     Waste heat recovery is performed through the second heat exchanger on the hot gas flow separated from the third separator, to avoid heat waste. 
     An ironmaking process of a two-section downdraft bed is provided, including the following steps: 
     entering, by coke powder/pulverized coal carried by air and water vapor, a melting furnace section from a side wall of the melting furnace section, to form a swirling flow in the melting furnace section; 
     jetting, by a basic combustor/gasifier at a top portion of the melting furnace section, a flame inward to ignite or gasify a fluid, to generate a reducing gas; 
     jetting pre-reduced iron mineral powder into the melting furnace section, to fully mix the pre-reduced iron mineral powder with a coke powder/pulverized coal gas flow; 
     under the action of high-temperature reduction, reducing an iron oxide in iron mineral powder into an iron element, and melting the iron element into molten iron at a high temperature; and 
     flowing, by a high-temperature reducing gas after the reaction, from the melting furnace section to a pre-reduction furnace section, and pre-reducing iron mineral powder jetted into the pre-reduction furnace section; and conveying the pre-reduced iron mineral powder to the melting furnace section. 
     In some embodiments, the ironmaking process of a two-section downdraft bed further includes a step of pre-heating cold iron mineral powder by using a high-temperature gas flow flowing out from the pre-reduction furnace section. 
     In some embodiments, the ironmaking process of a two-section downdraft bed further includes a step of coking pulverized coal by using a high-temperature gas flow flowing out from the pre-reduction furnace section. 
     In some embodiments, a temperature of a reaction in the melting furnace section ranges from 1300° C. to 1700° C. 
     In some embodiments, a temperature of the pre-reduction furnace section ranges from 700° C. to 1100° C. 
     In some embodiments, a circulating coal gas or a mixture of pulverized coal and a circulating coal gas is added into the pre-reduction furnace section as a cooling and temperature-adjusting medium, and a proportion of a reducing gas in tempered gases is increased. 
     A mineral powder pre-reduction furnace section cooperates with pulverized coal coking/gasification, and a pulverized coal/water vapor vaporization medium or a circulating coal gas, together with the pulverized coal/water vapor, adjusts a temperature and is gasified simultaneously. Cooling and pulverized coal gasification/coking are performed simultaneously, to achieve tempering of the coal gas, and provide more appropriate reduction conditions for subsequent mineral powder pre-reduction. In this case, the coke powder and the mineral powder are separated simultaneously, and are fed into the melting furnace section together. 
     The present invention has the following beneficial effects: 
     The present invention provides an ironmaking process of a two-section downdraft bed, applicable to a melting furnace section and a mineral powder pre-reduction furnace section. According to conditions required for reducing iron mineral powder into molten iron, temperature distribution in a two-section reactor is controlled, a high-temperature melting reduction reaction occurs in the melting furnace section, and molten iron is mainly generated from FeO. A pre-reduction reaction occurs in the mineral powder pre-reduction furnace section, FeO or a part of Fe is mainly generated from iron mineral powder. The process achieves pre-reduction and melting reduction of mineral powder. Both of the two reactions are achieved in the downdraft bed, which is beneficial to maintain a uniform suspension state for mineral powder particles, and is beneficial to improve reduction efficiency. A process that iron ore is transformed into molten iron is completed within a same set of devices, complexity of the system is decreased, and an occupied area is decreased. 
     Two temperature adjusting manners are provided for cooling and temperature adjusting of a coal gas at an inlet of the pre-reduction section. By using a circulating coal gas, the coal gas at an outlet of the melting furnace section enters the mineral powder pre-reduction furnace section after being cooled by a cooling medium. Pulverized coal, or together with a circulation coal gas, is used as a cooling and temperature-adjusting medium. A mineral powder pre-reduction furnace section cooperates with pulverized coal coking/gasification, and a pulverized coal/water vapor vaporization medium or a circulating coal gas, together with the pulverized coal/water vapor, adjusts a temperature and is gasified simultaneously. Cooling and pulverized coal gasification/coking are performed simultaneously, to provide more appropriate reduction conditions for subsequent mineral powder pre-reduction. In this case, the coke powder and the mineral powder are separated simultaneously, and are fed into the melting furnace section together. 
     Two distribution manners are provided for the coal gas after the pre-reduction. One is setting heat exchange of mineral powder in a pre-heating swirling flow separator, to increase a mineral powder temperature, which is beneficial to improve a pre-reduction level; and the other is setting coking of pulverized coal, to enhance adaptivity to coal types, and is particularly adapted to lignite or bituminous coal with high moisture. Short-process smelting of steel can be achieved, leading to a broad application prospect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary examples of the present invention and descriptions thereof are used to explain the present invention, and do not constitute an improper limitation of the present invention. 
         FIG. 1  is a structural schematic diagram of an ironmaking system of a two-section downdraft bed according to a first embodiment of the present invention; and 
         FIG. 2  is a structural schematic diagram of an ironmaking system of a two-section downdraft bed according to a second embodiment of the present invention. 
     
    
    
     In the figures:  1 . basic combustor/gasifier;  2 . first inlet;  3 . second inlet;  4 . melting furnace section;  5 . slag pool;  6 . third inlet;  7 . fourth inlet;  8 . pre-reduction furnace section;  9 . first separator;  10 . fifth inlet;  11 . second separator;  12 . first heat exchanger;  13 . coal gas outlet pipeline;  14 . sixth inlet;  15 . pulverized coal coking furnace section;  16 . third separator; and  17 . second heat exchanger. 
     DETAILED DESCRIPTION 
     It should be noted that, the following detailed descriptions are all exemplary, and are intended to provide further descriptions of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those usually understood by a person of ordinary skill in the art to which the present disclosure belongs. 
     It should be noted that the terms used herein are merely used for describing specific implementations, and are not intended to limit exemplary implementations of the present disclosure. As used herein, the singular form is also intended to include the plural form unless the context clearly dictates otherwise. In addition, it should further be understood that, terms “comprise” and/or “include” used in this specification indicate that there are features, steps, operations, devices, components, and/or combinations thereof. 
     Embodiment 1 
     As shown in  FIG. 1 , a structure of a device (arrangement manner  1 ) of an ironmaking process of a two-section downdraft bed includes a melting furnace section  4 , where the melting furnace section  4  is a downdraft bed, a basic combustor/gasifier  1  is disposed at a top portion of the melting furnace section  4 , a first inlet  2  of coke powder (pulverized coal) (air and water vapor) is provided on a side surface of an upper portion of the melting furnace section  4 , and a pre-reduced mineral powder inlet, that is, a second inlet  3 , is provided at a specific distance below the first inlet  2 ; and a mineral powder pre-reduction furnace section  8 , which is a downdraft bed, where a pre-heated mineral powder inlet, that is, a fourth inlet  7 , is provided on a side surface of an upper portion of the pre-reduction furnace section  8 , and a lower portion of the pre-reduction furnace section  8  is connected to an inlet of a pre-reduced mineral powder separator, that is, a first separator  9 . The melting furnace section  4  is connected to the mineral powder pre-reduction furnace section  8  through a slag pool  5 . A cooling, temperature-adjusting, and tempering medium inlet, that is, a third inlet  6 , is provided on a pipeline connecting the slag pool  5  and the mineral powder pre-reduction furnace section  8 . An upper outlet the first separator  9  is connected to an inlet of a pre-heating swirling flow separator, that is, a second separator  11 . A lower outlet of the first separator  9  is connected to the pre-reduced mineral powder inlet, that is, the second inlet  3 . A cold mineral powder inlet, that is, a fifth inlet  10 , is provided at the upper outlet of the pre-reduced mineral powder separator, that is, the first separator  9 . A lower outlet of the pre-heating swirling flow separator, that is, the second separator  11 , is connected to the pre-heated mineral powder inlet, that is, the fourth inlet  7 , and an upper outlet is connected to a coal gas heat exchanger, that is, a first heat exchanger  12  and a coal gas outlet pipeline  13  sequentially. 
     The foregoing method of the ironmaking process of a two-section downdraft bed (arrangement manner  1 ) includes the following specific steps: 
     1) High-Temperature Melting Reduction 
     A basic combustor/gasifier combusts/gasifies coke powder (pulverized coal) (air and water vapor) that is fed, generates a high temperature of around 1600° C. and a reducing atmosphere, pre-reduced iron mineral powder is mainly subject to a reaction in which FeO becomes molten iron in a melting reduction furnace, and the molten iron falls into a slag pool. The coke powder (pulverized coal) (air and water vapor) and the pre-reduced iron mineral powder are jetted in a four-corner tangential or a six-corner tangential manner, which is beneficial to even mixing. 
     2) Mineral Powder Pre-Reduction 
     A high-temperature coal gas generated in the melting furnace section enters the mineral powder pre-reduction furnace section after being cooled or tempered by a cooling/tempering medium, pre-heated mineral powder is fed from above the furnace section, and the coal gas and the pre-heated mineral powder are mainly subject to a pre-reduction reaction for generating FeO and a part of Fe from mineral powder. The cooling/tempering medium is a circulating coal gas, or a circulating coal gas together with pulverized coal. Both of the two sections are downdraft beds, which is beneficial to maintain a uniform suspension state for mineral powder particles, and improving reduction efficiency. 
     3) Pre-Reduced Mineral Powder Separation 
     The coal gas and the pre-reduced mineral powder enter an inlet of a pre-reduced mineral powder separator, the pre-reduced mineral powder is separated from below the separator, and enters the melting furnace section through a pre-reduced mineral powder inlet; and the coal gas is separated from above the separator. 
     4) Cold Mineral Powder Pre-Heating 
     The coal gas discharged from above the pre-reduced mineral powder separator carrying cold mineral powder enters an inlet of a pre-heating swirling flow separator, the coal gas exchanges heat with the cold mineral powder, and a temperature of the cold mineral powder is increased, which is beneficial to improve a pre-reduction level. The pre-heated mineral powder is separated from below the separator, and enters the mineral powder pre-reduction furnace section. The coal gas is discharged from above the separator, and is discharged from a coal gas outlet pipeline through a coal gas heat exchanger. 
     Embodiment 2 
       FIG. 2  is another implementation of this application. A structure of a device (arrangement manner  2 ) of an ironmaking process of a two-section downdraft bed includes a melting furnace section  4 , the melting furnace section  4  is a downdraft bed, a basic combustor/gasifier  1  is disposed at a top portion of the melting furnace section  4 , a coke powder (air and water vapor) inlet, that is, a first inlet  2 , is provided on a side surface of an upper portion of the melting furnace section  4 , and a pre-reduced mineral powder inlet, that is, a second inlet  3 , is provided at a certain distance below the first inlet  2 ; and a mineral powder pre-reduction furnace section  8 , which is a downdraft bed, where a mineral powder inlet, that is, a fourth inlet  7 , is provided on a side surface of an upper portion of the pre-reduction furnace section  8 , and a lower portion of the pre-reduction furnace section  8  is connected to an inlet of a pre-reduced mineral powder separator, that is, a first separator  9 . The melting furnace section  4  is connected to the mineral powder pre-reduction furnace section  8  through a slag pool  5 . A cooling, temperature-adjusting, and tempering medium inlet, that is, a third inlet  6 , is provided on a pipeline connecting the slag pool  5  and the mineral powder pre-reduction furnace section  8 . An upper outlet of the pre-reduced mineral powder separator, that is, the first separator  9 , is connected to a pulverized coal coking furnace section  15 , and a lower outlet of the first separator  9  is connected to the pre-reduced mineral powder inlet, that is, the second inlet  3 . A pulverized coal inlet, that is, a sixth inlet  14 , is provided on a lower portion of the pulverized coal coking furnace section  15 , and an upper portion of the pulverized coal coking furnace section  15  is connected to an inlet of a coke powder separator, that is, a third separator  16 . A lower outlet of the coke powder separator, that is, the third separator  16 , is connected to the coke powder (air and water vapor) inlet, that is, the first inlet  2 , and an upper outlet is connected to a coal gas outlet pipeline  13  and a second heat exchanger  17  sequentially. 
     The method of another ironmaking process of a two-section downdraft bed (arrangement manner  2 ) in this application includes the following specific steps: 
     1) High-Temperature Melting Reduction 
     A basic combustor/gasifier combusts/gasifies coke powder (air and water vapor) that is fed, generates a high temperature of around 1600° C. and a reducing atmosphere, pre-reduced iron mineral powder is mainly subject to a reaction in which FeO becomes molten iron in a melting reduction furnace, and the molten iron falls into a slag pool. The coke powder (air and water vapor) and the pre-reduced iron mineral powder are jetted in a four-corner tangential or a six-corner tangential manner, which is beneficial to even mixing. 
     2) Mineral Powder Pre-Reduction 
     A high-temperature coal gas generated in the melting furnace section enters the mineral powder pre-reduction furnace section after being cooled or tempered by a cooling/tempering medium, mineral powder is fed from above the furnace section, and the coal gas and the mineral powder are mainly subject to a pre-reduction reaction for generating FeO and a part of Fe from mineral powder. Both of the two sections are downdraft beds, which is beneficial to maintain a uniform suspension state for mineral powder particles, and improve reduction efficiency. 
     3) Pre-Reduced Mineral Powder Separation 
     The coal gas and the pre-reduced mineral powder enter an inlet of a pre-reduced mineral powder separator, the pre-reduced mineral powder is separated from below the separator, and enters the melting furnace section through a pre-reduced mineral powder inlet; and the coal gas is separated from above the separator. 
     4) Pulverized Coal Coking 
     The coal gas that is discharged from the upper portion of the pre-reduced mineral powder separator and that carries pulverized coal enters a pulverized coal coking furnace section, at a temperature and an atmosphere provided by the coal gas, coke powder is produced by using the pulverized coal, a pyrolysis gas and the coke powder move upward into a coke powder separator. Coking of the pulverized coal is set, to enhance adaptivity to coal types, and is particularly adapted to lignite or bituminous coal with high moisture. The coke powder is separated from below the separator, and enters the melting furnace section. The coal gas is discharged from above the separator, and enters a coal gas heat exchanger after flowing through a coal gas outlet pipeline. 
     The foregoing descriptions are merely preferred embodiments of the present invention, but are not intended to limit the present invention. A person skilled in the art may make various alterations and variations to the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.