Ironmaking equipment suitable for low-grade iron ore

Abstract

The utility model relates to the technical field of iron-making equipment, and provides iron-making equipment suitable for low-grade iron ore, which comprises a mixing device for mixing low-grade iron ore powder, pulverized coal and an adhesive; the ball press machine is used for cold-pressing the mixture into cold-pressed balls, and the mixing device is connected with the ball press machine; the rotary kiln is used for reducing iron oxide in the cold-pressed balls, the ball press machine is connected with the rotary kiln, and the cold-pressed balls are reduced in the rotary kiln to generate iron shots; the heat preserving furnace is used for preserving heat of the cold-pressed balls and is connected with the rotary kiln; the crushing furnace is used for cooling the cold-pressed balls, the heat preservation furnace is connected with the crushing furnace, iron beads are stripped from generated impurity powder in the cooling process of the cold-pressed balls in the crushing furnace, and a screen used for separating the iron beads from the impurity powder is arranged in the crushing furnace. According to the utility model, the problem that the existing direct reduction ironmaking technology has high dependence on high-grade iron ore can be solved, and high-quality utilization of low-grade iron ore is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of metal smelting, especially to a smelting equipment suitable for low-grade iron ore. BACKGROUND

[0002] Under the background of promoting industrial upgrading and environmental protection and emission reduction, the steel industry is facing severe opportunities and challenges. In order to realize high-quality development, steel enterprises should pay attention to energy saving and emission reduction and clean production, comprehensively reduce the emission of SOx, NOx, CO2 and smoke dust in the sintering and coking link, and thus build a green and sustainable industrial system. Compared with the traditional blast furnace ironmaking method, the non-blast furnace direct reduction ironmaking technology has obvious advantages in environmental protection and energy saving, greatly reduces the dependence on main coking coal in the ironmaking process, reduces energy consumption and pollutant emission, and provides a solid cornerstone for the steel industry to realize sustainable development.

[0003] The direct reduction ironmaking technology using non-coking coal and high-grade iron ore powder as raw materials has high metalization rate pellets as its terminal product, which is pure in chemical composition and extremely low in impurity content. These pellets are not only the main raw material for electric furnace steelmaking, but also can be used in converter steelmaking. The direct reduction ironmaking process mainly includes gas-based and coal-based two categories. The mainstream process of gas-based direct reduction includes MIDREX (typical shaft furnace method) and HYL (typical reaction tank method). The coal-based direct reduction ironmaking process mainly includes rotary kiln and rotary hearth furnace. Compared with the traditional blast furnace ironmaking, the method of using non-coking coal saves the high-energy consumption and high-pollution links such as coking and sintering, and shows the advantages of high quality, low consumption and environmental protection. However, due to the high gangue content in the steelmaking process, the power consumption and refractory material consumption of the steelmaking furnace increase, so the iron ore grade requirement is relatively high.

[0004] In recent years, the direct reduction ironmaking technology has made significant progress, but the existing process has high requirements for the iron-containing ore powder charged into the furnace, and the ore grade requirement is more than 66%. The direct reduced iron produced by low-grade ore cannot be used in the steelmaking furnace due to the high content of gangue and impurities, so the direct reduction process depends on high-grade ore to a large extent, which greatly increases the production cost. The development of direct reduction process and high-grade iron ore resources is in sharp conflict. Under this condition, developing a new ironmaking process with strong adaptability of raw materials and furnace charge, high energy utilization rate, low investment cost and flexible operation has become one of the topics concerned by steel enterprises. UTILITY MODEL CONTENT

[0005] The utility model aims to provide a smelting equipment suitable for low-grade iron ore, solve the problem that the current direct reduction ironmaking technology depends on high-grade iron ore to a large extent, and realize high-quality utilization of low-grade iron ore.

[0006] The above technical purpose of the utility model is mainly realized through the following technical scheme.

[0007] The utility model provides a kind of suitable for low-grade iron ore's iron-making equipment, it includes:

[0008] Mixing device for low-grade iron ore powder, coal powder and binder mixing;

[0009] Pelletizer for cold pressing into cold pressed ball, the mixing device is connected with the pelletizer;

[0010] Rotary kiln for reducing iron oxide in the cold pressed ball, the pelletizer is connected with the rotary kiln, and the cold pressed ball is reduced to generate iron beads in the rotary kiln;

[0011] Heat preservation furnace for heat preservation of the cold pressed ball, the rotary kiln is connected with the heat preservation furnace;

[0012] Crushing furnace for cooling the cold pressed ball, the heat preservation furnace is connected with the crushing furnace, and in the cooling process of the cold pressed ball in the crushing furnace, the iron beads are stripped from the impurity powder generated from the cold pressed ball, and the crushing furnace is provided with a screen for separating the iron beads and the impurity powder.

[0013] The iron-making equipment suitable for low-grade iron ore comprises a reduction-slag iron separation system composed of a rotary kiln, a heat preservation furnace and a crushing furnace, realizes high-quality utilization of low-grade iron ore resources, realizes iron slag separation of terminal product, the metallization rate of obtained metal iron beads is high, and the metal iron beads can be directly used in electric furnace or converter, realizes near-zero content of furnace slag, and improves purity in steelmaking process.

[0014] In a preferred embodiment of the utility model, the kiln head of the rotary kiln is connected with the pelletizer, and the kiln tail of the rotary kiln is connected with a gas supply pipeline, and the gas supply pipeline can introduce fuel gas into the rotary kiln.

[0015] The rotary kiln is inclined to make the kiln head higher than the kiln tail, and the movement direction of the cold pressed ball in the rotary kiln is opposite to the movement direction of the fuel gas.

[0016] In the embodiment, the cold pressed ball slowly moves forward in the kiln by the slope and rotation of the rotary kiln cylinder, and is gradually heated by the reverse hot air flow, to complete reduction and carburizing reaction processes, and the cold pressed ball generated after reduction is discharged from the kiln tail end.

[0017] In a preferred embodiment of the utility model, the rotary kiln is provided with an angle adjusting mechanism capable of adjusting the inclination angle thereof, and the time for the cold pressed ball to move from the kiln head to the kiln tail is controlled by the angle adjusting mechanism.

[0018] In the embodiment, the reaction time of the cold-pressed ball in the rotary kiln is strictly controlled by the angle adjusting mechanism, and the reduction is not complete if the reduction time is too short, thereby reducing the iron generation rate, and the metallic iron is melted to wrap the slag if the reduction time is too long, thereby making it difficult to separate the iron slag in the subsequent process.

[0019] In a preferred embodiment of the present application, an oxygen tank, a gas tank and a blowing mechanism are arranged on the gas supply pipeline, and the gas supply pipeline is connected with a gas injection gun at the end in the rotary kiln.

[0020] In the embodiment, the gas tank on the gas supply pipeline contains natural gas, and the raw materials for the rotary kiln are natural gas and oxygen, and the high nitrogen content in the air will affect the calorific value of the gas and the utilization efficiency of the nitrogen enrichment in the reforming cycle, so oxygen is selected as the combustion-supporting agent; and the temperature in the rotary kiln is strictly controlled by the blowing mechanism on the gas supply pipeline, and the reduction is not complete if the reduction temperature is too low, thereby reducing the iron generation rate, and the metallic iron is melted to wrap the slag if the reduction temperature is too high, thereby making it difficult to separate the iron slag in the subsequent process.

[0021] In a preferred embodiment of the present application, a recovery pipeline is connected with the flue gas outlet of the rotary kiln, and the outlet end of the recovery pipeline is connected with the gas supply pipeline.

[0022] In the flow direction of the flue gas in the recovery pipeline, the recovery pipeline is sequentially provided with:

[0023] A reforming furnace for reducing CO2 and H2O in the reduction flue gas, the reforming furnace is provided with CH4, and in the reforming furnace, CO2 and H2O react with CH4 to produce CO and H2.

[0024] A dust remover for filtering dust in the flue gas.

[0025] In the embodiment, the low-quality waste flue gas generated in the rotary kiln is reformed into high-quality gas by the reforming and regeneration of the reforming furnace on the recovery pipeline, and the carbon emission is reduced by 30%-40% compared with the existing process by the reforming conversion of CO2 in the flue gas.

[0026] In a preferred embodiment of the present application, the nitrogen tank is connected with the heat preservation furnace and the crushing furnace by pipelines, and the nitrogen tank can respectively introduce nitrogen into the heat preservation furnace and the crushing furnace.

[0027] In the embodiment, nitrogen is introduced into the heat preservation furnace by the nitrogen tank to prevent the reduced iron in the cold-pressed ball from being re-oxidized during the heat preservation process; and nitrogen is introduced into the crushing furnace by the nitrogen tank to blow and cool the high-temperature furnace charge in the crushing furnace.

[0028] In a preferable embodiment of the utility model, nitrogen circulation pipeline is connected between the heat preservation furnace and the crushing furnace, the nitrogen circulation pipeline includes first nitrogen pipeline and second nitrogen pipeline; the high-temperature nitrogen generated in the crushing furnace can enter the heat preservation furnace through the first nitrogen pipeline; the high-temperature nitrogen in the heat preservation furnace can enter the crushing furnace through the second nitrogen pipeline, and a power generation mechanism is arranged on the second nitrogen pipeline.

[0029] In the embodiment, nitrogen preheating and waste heat recovery of the furnace charge are simultaneously completed in the crushing furnace, then high-temperature nitrogen is passed into the bottom of the heat preservation furnace as protective gas through the first nitrogen pipeline, thereby reducing temperature fluctuation in the heat preservation furnace; meanwhile, the high-temperature nitrogen in the heat preservation furnace is subjected to waste heat recovery through the power generation mechanism.

[0030] In a preferable embodiment of the utility model, a ball valve is arranged in the heat preservation furnace, and the residence time of the cold-pressed ball in the heat preservation furnace is controlled through the ball valve.

[0031] In the embodiment, the residence time of the cold-pressed ball in the heat preservation furnace is strictly controlled through the ball valve, so that the tricalcium silicate in the slag phase can fully undergo crystal type transformation.

[0032] In a preferable embodiment of the utility model, a water cooling pipe is arranged at the bottom of the crushing furnace.

[0033] In the embodiment, the cooling water in the water cooling pipe can water cool the furnace charge in the crushing furnace, and cooperate with the air cooling of nitrogen to realize rapid cooling of the furnace charge.

[0034] In a preferable embodiment of the utility model, a vibrating mechanism connected with the screen is arranged in the crushing furnace, the vibrating mechanism can drive the screen to vibrate so as to separate the iron beads and the impurity powder, and simultaneously move the iron beads towards the outlet direction of the crushing furnace.

[0035] In the embodiment, the screen is vibrated through the vibrating mechanism, which can separate the iron beads and the impurity powder on one hand, and move the iron beads towards the outlet direction of the crushing furnace on the other hand.

[0036] In a preferable embodiment of the utility model, a coal powder spraying mechanism is arranged in the ball presser, the coal powder spraying mechanism can spray coal powder to the cold-pressed ball to form the cold-pressed ball wrapped with coal powder.

[0037] In the embodiment, in the process of reduction of the cold-pressed ball to generate metal iron in the rotary kiln, the coal powder sprayed on the surface of the cold-pressed ball is first involved in the reaction, and a solid iron shell is generated on the outer surface of the cold-pressed ball, which can effectively inhibit the adhesion between the furnace charges. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

[0039] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present application in any way. In addition, the shapes and proportions of the components in the drawings are only illustrative, used to help understand the present application, and are not specific limitations on the shapes and proportions of the components of the present application. Those skilled in the art can choose various possible shapes and proportions to implement the present application according to specific circumstances under the guidance of the present application.

[0040] Figure 1 Process flow chart of the ironmaking equipment suitable for low-grade iron ore of the present application;

[0041] Figure 2 Structure schematic diagram of the ironmaking equipment suitable for low-grade iron ore of the present application.

[0042] Explanation of reference signs:

[0043] 1, mixing device; 2, ball press; 3, rotary kiln; 4, coal gas lance; 5, injection mechanism; 6, coal gas tank; 7, oxygen tank; 8, flue gas outlet; 9, reformer; 10, dust collector; 11, fan; 12, heat preservation furnace; 13, ball valve; 14, nitrogen sealing mechanism; 15, crushing furnace; 16, power generation mechanism; 17, nitrogen lance; 18, nitrogen tank; 19, slag inlet; 20, tapping hole; 21, gas supply pipeline; 22, recovery pipeline; 23, first nitrogen pipeline; 24, second nitrogen pipeline. DETAILED DESCRIPTION

[0044] In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

[0045] It is to be understood that when an element such as a layer, region or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. In addition, it is to be understood that when a layer is referred to as being "connected", "coupled" or "supported" to another layer, it can be directly connected, coupled or supported to the other layer, or intervening layers can also be present. Also, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety for the purpose of describing and disclosing

[0047] As shown in Figure 1 and Figure 2 The utility model provides a kind of ironmaking equipment suitable for low-grade iron ore, it includes: for low-grade iron ore powder, coal powder and binder mixing mixing device 1;For the cold balling machine 2 of mixed material cold pressing into cold pressure ball, mixing device 1 is connected with cold balling machine 2;For the reduction of iron oxide in cold pressure ball rotary kiln 3, cold balling machine 2 is connected with rotary kiln 3, and iron bead is generated in the reduction of cold pressure ball in rotary kiln 3;For the heat preservation furnace 12 of cold pressure ball heat preservation, rotary kiln 3 is connected with heat preservation furnace 12;For the crushing furnace 15 of cold pressure ball cooling, heat preservation furnace 12 is connected with crushing furnace 15, and iron bead and impurity powder are generated in the cooling process of cold pressure ball in crushing furnace 15, and screen mesh for separating iron bead and impurity powder is provided in crushing furnace 15.

[0048] The ironmaking equipment suitable for low-grade iron ore, through the reduction-slag iron separation system of rotary kiln 3, heat preservation furnace 12 and crushing furnace 15, realize the high-quality use of low-grade iron ore resources, and the end product realizes iron slag separation, the metallization rate of obtained metal iron bead is high, can be directly used for electric furnace steelmaking or converter steelmaking, realizes nearly zero content of furnace slag, improves the purity in the process of steelmaking.

[0049] The specific structure of each part of the ironmaking equipment suitable for low-grade iron ore and the position and connection relationship between each part will be described below.

[0050] As shown in Figure 2As shown in the figure, the iron smelting device has a mixing device 1 which can realize mixing of multiple materials. The mixing device 1 is provided with multiple material boxes, each of which can contain one kind of material; in this embodiment, three material boxes are used to contain low-grade iron ore powder, coal powder and adhesive respectively. The outlets at the bottom of the material boxes are connected with a mixing box, and by controlling the opening degree of the outlets at the bottom of each material box, the mixing ratio of various materials can be controlled.

[0051] Further, in the mixing process, the mixing ratio of each raw material is calculated according to the components in each raw material, and then the low-grade iron ore powder, coal powder and adhesive are mixed together by the mixing device 1. The main component of the low-grade iron ore powder is iron oxide, and the main impurity is gangue. The content of the gangue impurity in the low-grade iron ore powder is relatively high, and the iron grade in the low-grade iron ore powder is usually below 50%. The low-grade iron ore powder can be used as the main raw material for producing reduced iron, and high-quality utilization is realized. The main component of the coal powder is carbon, which is used as a reducing agent to reduce the iron oxide in the iron ore powder into iron under high temperature conditions. The adhesive is used as an auxiliary material for adhesion before the reaction of the iron ore powder and the coal powder, and the adhesive can be clay minerals, bentonite and the like.

[0052] Preferably, the mass percentage of the coal powder in the mixture is y;

[0053] y = (0.11x + 0.76z) / d

[0054] Wherein, x is the mass percentage of Fe2O3 in the iron ore powder; z is the mass percentage of total iron (Fe) in the iron ore powder; and d is the mass percentage of fixed carbon (C) in the coal powder.

[0055] As shown in the figure, Figure 1 and Figure 2 The iron smelting device has a ball press 2 which can realize cold pressing of the mixture. The ball press 2 is arranged below the mixing device 1, and the mixture enters the ball press 2 between two counter-rollers and is pressed into cold pressed balls.

[0056] As shown in the figure, Figure 1 and Figure 2 The iron smelting device has a rotary kiln 3 which can realize reduction of iron oxide under high temperature conditions. The kiln head of the rotary kiln 3 is connected with the ball press 2, and the cold pressed balls generated by the ball press 2 can enter the cylinder of the rotary kiln 3 through the kiln head. The kiln tail of the rotary kiln 3 is connected with a gas supply pipeline 21 which can introduce fuel gas into the rotary kiln 3. The cylinder of the rotary kiln 3 is arranged obliquely so that the kiln head is higher than the kiln tail, and the movement direction of the cold pressed balls in the rotary kiln 3 is opposite to the movement direction of the fuel gas. The cold pressed balls slowly move forward in the kiln by relying on the slope and rotation of the cylinder of the rotary kiln 3, and are gradually heated by the counter-flow of hot gas, so that reduction reaction and carburizing reaction and other processes are completed. The reduced cold pressed balls are discharged from the kiln tail.

[0057] Under the above temperature and time conditions, in the rotary kiln 3, after the iron oxide in the iron ore powder in the cold-pressed ball is reduced and carburized, it partially melts and agglomerates into iron beads. The iron beads are distributed in the internal voids and surface of the cold-pressed ball. At the same time, CaO and SiO2 in the gangue phase in the cold-pressed ball react to generate tricalcium silicate (3CaO·SiO2) and dicalcium silicate (2CaO·SiO2), which in turn form a slag phase mainly composed of calcium silicate.

[0058] like Figure 2 As shown, the ironmaking equipment includes a holding furnace 12, which is used to maintain the temperature of the cold-pressed briquettes. The inlet of the holding furnace 12 is connected to the tail of the rotary kiln 3. After reduction, the cold-pressed briquettes directly enter the holding furnace 12 through the outlet of the kiln tail for heat preservation. The holding furnace 12 is electrically heated, with heating rods on both sides of the furnace body. The heating effect of the heating rods maintains the temperature inside the furnace within the range of 1100℃-1150℃.

[0059] Under the above temperature and time conditions, in the holding furnace 12, tricalcium silicate (3CaO·SiO2) in the slag phase undergoes a crystal transformation to α-2CaO·SiO2.

[0060] like Figure 2 As shown, the ironmaking equipment also includes a pulverizing furnace 15, which enables rapid cooling and slag-iron separation of the cold-pressed briquettes. The inlet of the pulverizing furnace 15 is connected to the outlet of the holding furnace 12. After being held in the heat, the cold-pressed briquettes directly enter the pulverizing furnace 15 through the outlet of the holding furnace 12. The pulverizing furnace 15 can cool the cold-pressed briquettes by air cooling and / or water cooling, decomposing them into metallic iron beads and impurity powder. The pulverizing furnace 15 is equipped with a 3mm aperture screen. Fine impurity powder is screened off and recovered through the slag receiving port 19, while the metallic iron beads with a diameter greater than 3mm enter the iron tapping port 20, achieving slag-iron separation and ultimately obtaining metallic iron beads with a metallization rate greater than or equal to 95%, realizing the high-quality utilization of low-grade ore.

[0061] The cooling rate of the cold-pressed balls in the pulverizing furnace 15 needs to be strictly controlled to ensure that the calcium silicate in the cold-pressed balls undergoes rapid crystal transformation. Therefore, the cooling rate of the cold-pressed balls in the pulverizing furnace 15 is controlled to be 50℃ / min-60℃ / min.

[0062] Under the aforementioned cooling rate conditions, within the pulverizing furnace 15, calcium silicate in the slag phase undergoes a rapid crystal transformation, changing from α-2CaO·SiO2 to β-2CaO·SiO2, and then from β-2CaO·SiO2 to γ-2CaO·SiO2. The slag phase is broken into fine powder, simultaneously producing iron beads with a diameter greater than 3 mm. The metallization rate of the iron beads (the percentage of elemental iron in the iron beads relative to the total iron content in the iron beads) is greater than or equal to 95%.

[0063] The structure and technical effects of the preferred embodiment of the iron smelting equipment suitable for low-grade iron ore will be further described below.

[0064] According to one embodiment of the present application, the ball press 2 is provided with a coal powder injection mechanism 5, which can spray coal powder on the cold-pressed ball to form a cold-pressed ball wrapped with coal powder.

[0065] During the process of reducing the cold-pressed ball to generate metallic iron in the rotary kiln 3, the coal powder sprayed on the surface of the cold-pressed ball first participates in the reaction, and a solid iron shell is formed on the outer surface of the cold-pressed ball, which can effectively inhibit the adhesion between the furnace charges.

[0066] According to one embodiment of the present application, the rotary kiln 3 is provided with an angle adjusting mechanism capable of adjusting the inclination angle thereof, and the time for the cold-pressed ball to move from the kiln head to the kiln tail is controlled by the angle adjusting mechanism.

[0067] If the reduction time is too short, the reduction will not be complete, and the iron generation rate will be reduced; if the reduction time is too long, the metallic iron will be melted and wrapped with slag, and the separation of iron slag in the subsequent process will be difficult, so the angle adjusting mechanism is provided to control the reaction time of the cold-pressed ball in the rotary kiln 3 to be between 65 min and 75 min.

[0068] According to one embodiment of the present application, as shown in Figure 2 The gas supply pipeline 21 is connected with the coal gas injection gun 4 at the end portion located in the rotary kiln 3.

[0069] The coal gas cabinet 6 on the gas supply pipeline 21 contains natural gas, and the raw materials used in the rotary kiln 3 are CH4 in the natural gas and oxygen in the oxygen cabinet 7; the high nitrogen content in the air will affect the calorific value of the coal gas, and the enrichment of nitrogen in the reforming and recycling process will affect the utilization efficiency, so oxygen is selected as the combustion-supporting agent.

[0070] If the reduction temperature is too low, the reduction will not be complete, and the iron generation rate will be reduced; if the reduction temperature is too high, the metallic iron will be melted and wrapped with slag, and the separation of iron slag in the subsequent process will be difficult, so the injection rate of the coal gas injection gun 4 is controlled by the injection mechanism 5 on the gas supply pipeline 21, so that the temperature in the rotary kiln 3 is between 1227°C and 1250°C.

[0071] According to one embodiment of the present application, as shown in Figure 2As shown, the flue gas outlet 8 of the rotary kiln 3 is connected with a recovery pipeline 22, the outlet end of the recovery pipeline 22 is connected with the gas supply pipeline 21; along the flow direction of the flue gas in the recovery pipeline 22, the recovery pipeline 22 is sequentially provided with: a reforming furnace 9 for reducing CO2 and H2O in the flue gas, the reforming furnace 9 is communicated with CH4, in the reforming furnace 9, CO2 and H2O react with CH4 to produce CO and H2; and a dust remover 10 for filtering dust in the flue gas.

[0072] By the reforming regeneration of the reforming furnace 9 on the recovery pipeline 22, the low-quality waste flue gas generated in the rotary kiln 3 is reformed into high-quality coal gas, the re-conversion of CO2 in the flue gas reduces carbon emission, and compared with the existing process, CO2 emission is reduced by 30%-40%.

[0073] Specifically, as shown in the figure, Figure 2 the inlet end of the recovery pipeline 22 is connected to the kiln head of the rotary kiln 3, the high-temperature flue gas generated in the rotary kiln 3 enters the recovery pipeline 22; the outlet end of the recovery pipeline 22 is connected to the gas supply pipeline 21, the coal gas generated by the reforming and dust removal of the flue gas enters the gas supply pipeline 21.

[0074] The flue gas first enters the reforming furnace 9, and at the same time, the gas tank 6 is connected with the reforming furnace 9 through a pipeline for introducing CH4 into the reforming furnace 9; the high-temperature flue gas and CH4 enter the reforming furnace 9 from the inlet at the bottom of the reforming furnace 9, the reforming furnace 9 is provided with a spiral upward pipeline and filled with porous gas resistance balls to slow down the flow speed of the gas and ensure that the flue gas and natural gas are fully mixed. Because the flue gas has a high temperature (≥1200℃), the CO2 and H2O in the flue gas and the CH4 in the natural gas react to generate CO and H2 (CH4+CO2=2CO+2H2; CH4+H2O=CO+3H2) under high-temperature conditions.

[0075] The mixing ratio of the flue gas and the natural gas is maintained at 0.5-0.6, at which time the conversion rate is the highest, about 65%-70%; in addition, Fe and CaO in the flue gas dust also promote the increase of the conversion rate to a certain extent, based on which the low-quality flue gas is converted into high-quality coal gas. The flue gas dust rises to a certain height with the gas flow, and under the conditions of pipeline obstruction and reduced coal gas flow rate, it falls downward to the bottom of the reforming furnace 9 under the action of gravity, completing the rough dust removal of the flue gas.

[0076] After that, the coal gas after the reforming and rough dust removal enters the dust remover 10 for further dust removal, and then enters the gas supply pipeline 21, and enters the coal gas injection lance 4 through the injection mechanism 5 to be injected into the rotary kiln 3 for re-combustion and utilization.

[0077] The flue gas is reformed to produce coal gas, which reduces CO2 emissions from the flue gas. On the other hand, since CH4 absorbs heat during cracking at high temperatures (1 mol of CH4 absorbs 1760 kJ of heat), directly injecting CH4 into the rotary kiln 3 through the coal gas injector 4 will partially crack it, resulting in heat loss in the kiln. Through the reforming process, the waste heat of the flue gas is used to convert some of the CH4 into CO and H2 for direct combustion and heat release, thus completing the recovery of waste heat resources from the flue gas while reducing heat loss in the kiln.

[0078] Furthermore, such as Figure 2 As shown, a blower 11 for driving gas flow is provided on the recovery pipeline 22; a blower 11 for driving natural gas flow toward the reformer 9 is also provided on the pipeline between the reformer 9 and the gas holder 6.

[0079] According to one embodiment of the present invention, such as Figure 2 As shown, both the holding furnace 12 and the pulverizing furnace 15 are connected to nitrogen tanks 18 via pipes, allowing nitrogen gas to be introduced into both the holding furnace 12 and the pulverizing furnace 15. The nitrogen gas introduced into the holding furnace 12 via the nitrogen tank 18 prevents the reduced iron in the cold-pressed briquette from re-oxidizing during the holding process; the nitrogen gas introduced into the pulverizing furnace 15 via the nitrogen tank 18 purges and cools the high-temperature furnace material within the pulverizing furnace 15.

[0080] Specifically, the nitrogen tank 18 is connected to the top of the holding furnace 12 via a pipe. To prevent gas from entering the holding furnace 12 during the feeding process, a nitrogen sealing mechanism 14 is provided on the upper part of the furnace body of the holding furnace 12. The nitrogen tank 18 is connected to the nitrogen spray gun 17 in the crushing furnace 15 via a pipe. Low-temperature nitrogen is sprayed onto the furnace material in the crushing furnace 15 through the nitrogen spray gun 17.

[0081] According to one embodiment of the present invention, such as Figure 2 As shown, a nitrogen circulation pipeline connects the heat preservation furnace 12 and the pulverizing furnace 15. The nitrogen circulation pipeline includes a first nitrogen pipeline 23 and a second nitrogen pipeline 24. The high-temperature nitrogen generated in the pulverizing furnace 15 can enter the heat preservation furnace 12 through the first nitrogen pipeline 23. The high-temperature nitrogen in the heat preservation furnace 12 can enter the pulverizing furnace 15 through the second nitrogen pipeline 24. A power generation mechanism 16 is provided on the second nitrogen pipeline 24.

[0082] Nitrogen preheating and waste heat recovery of the furnace charge are completed simultaneously in the pulverizing furnace 15. Then, high-temperature nitrogen is introduced into the bottom of the holding furnace 12 as a protective gas through the first nitrogen pipeline 23, thereby reducing the temperature fluctuation in the holding furnace 12. At the same time, the high-temperature nitrogen in the holding furnace 12 is recycled for waste heat through the power generation mechanism 16. The low-temperature nitrogen generated after waste heat recovery is then introduced into the pulverizing furnace 15 to cool the furnace charge.

[0083] According to one embodiment of the present invention, such as​ As shown, the holding furnace 12 is provided with a ball valve 13, the residence time of the cold-pressed ball in the holding furnace 12 is controlled through the ball valve 13, and the full crystalline transformation of tricalcium silicate in the slag phase is ensured. In the embodiment, the residence time of the cold-pressed ball in the holding furnace 12 is controlled through the ball valve 13 and is between 30 min and 40 min.

[0084] According to an embodiment of the present application, the bottom of the crushing furnace 15 is provided with a water cooling pipe; the cooling water in the water cooling pipe can water cool the furnace charge in the crushing furnace 15, and cooperate with the air cooling of nitrogen to realize the rapid cooling of the furnace charge.

[0085] According to an embodiment of the present application, the crushing furnace 15 is provided with a vibrating mechanism connected with the screen mesh, the vibrating mechanism can drive the screen mesh to vibrate to separate the iron beads and the impurity powder, and simultaneously make the iron beads move towards the outlet direction of the crushing furnace 15. The vibrating mechanism drives the screen mesh to vibrate, which can separate the iron beads and the impurity powder quickly on the one hand, and make the iron beads move towards the outlet direction of the crushing furnace 15 on the other hand. In the embodiment, the diameter of the mesh hole in the screen mesh is 3 mm, the fine impurity powder is screened out and recycled through the slag outlet 19, and the metal iron beads with a diameter greater than 3 mm enter the iron outlet 20 to realize the separation of slag and iron.

[0086] The above-described specific embodiments further specifically describe the purpose, technical scheme and beneficial effects of the present application, and it should be understood that the above-described specific embodiments are only specific embodiments of the present application and are not used to limit the protection scope of the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An iron-making plant suitable for low-grade iron ore, characterized by, The application relates to a mixing device (1) for mixing low-grade iron ore powder, coal powder and a binding agent; a ball press (2) for cold pressing the mixture into cold pressed balls, the mixing device (1) being connected to the ball press (2); a rotary kiln (3) for reducing iron oxides in the cold pressed balls, the ball press (2) being connected to the rotary kiln (3), and the cold pressed balls being reduced into iron beads in the rotary kiln (3); a holding furnace (12) for holding the cold pressed balls, the rotary kiln (3) being connected to the holding furnace (12); and a crushing furnace (15) for cooling the cold pressed balls, the holding furnace (12) being connected to the crushing furnace (15), and the iron beads being separated from impurity powder during the cooling process of the cold pressed balls in the crushing furnace (15), and a screen being arranged in the crushing furnace (15) for separating the iron beads and the impurity powder. The kiln head of the rotary kiln (3) is connected to the ball press (2), the kiln tail of the rotary kiln (3) is connected to a gas supply pipeline (21), and the gas supply pipeline (21) can supply fuel gas into the rotary kiln (3). The rotary kiln (3) is arranged in an inclined manner so that the kiln head is higher than the kiln tail, and the movement direction of the cold pressed balls in the rotary kiln (3) is opposite to the movement direction of the fuel gas. An angle adjusting mechanism is arranged on the rotary kiln (3) to adjust the inclination angle of the rotary kiln (3), and the time for the cold pressed balls to move from the kiln head to the kiln tail is controlled by the angle adjusting mechanism. An oxygen tank (7), a coal gas tank (6) and a blowing mechanism (5) are arranged on the gas supply pipeline (21), and a coal gas injection gun (4) is arranged at the end of the gas supply pipeline (21) in the rotary kiln (3). A recovery pipeline (22) is connected to the flue gas outlet (8) of the rotary kiln (3), and the outlet end of the recovery pipeline (22) is connected to the gas supply pipeline (21).

2. The ironmaking plant suitable for low-grade iron ore according to claim 1, characterized in that, In the flow direction of the flue gas in the recovery pipeline (22), a reforming furnace (9) for reducing CO2 and H2O in the flue gas is arranged on the recovery pipeline (22), CH4 is supplied into the reforming furnace (9), and CO2 and H2O react with CH4 in the reforming furnace (9) to generate CO and H2; and a dust remover (10) for filtering dust in the flue gas is arranged on the recovery pipeline (22). Nitrogen tanks (18) are connected to the holding furnace (12) and the crushing furnace (15) through pipelines, and the nitrogen tanks (18) can respectively supply nitrogen into the holding furnace (12) and the crushing furnace (15).

3. The ironmaking plant suitable for low-grade iron ore according to claim 2, characterized in that, A nitrogen circulation pipeline is connected between the holding furnace (12) and the crushing furnace (15), and the nitrogen circulation pipeline comprises a first nitrogen pipeline (23) and a second nitrogen pipeline (24).

4. The ironmaking plant suitable for low-grade iron ore according to claim 2, characterized in that, High-temperature nitrogen generated in the crushing furnace (15) can enter the holding furnace (12) through the first nitrogen pipeline (23).

5. The ironmaking plant suitable for low-grade iron ore according to claim 2, characterized in that, High-temperature nitrogen in the holding furnace (12) can enter the crushing furnace (15) through the second nitrogen pipeline (24), and a power generation mechanism (16) is arranged on the second nitrogen pipeline (24). ​ ​ ​ 6. The ironmaking plant suitable for low-grade iron ore according to claim 1, characterized in that, ​ 7. The ironmaking plant suitable for low-grade iron ore according to claim 6, characterized in that, ​ ​ ​ 8. The ironmaking plant suitable for low-grade iron ore according to claim 1, characterized in that, The heat preservation furnace (12) is provided with a ball valve (13), and the residence time of the cold-pressed ball in the heat preservation furnace (12) is controlled through the ball valve (13).

9. The ironmaking plant suitable for low-grade iron ore according to claim 1 or 6, characterized in that, The bottom of the crushing furnace (15) is provided with a water cooling pipe.

10. The ironmaking plant suitable for low-grade iron ore according to claim 1, characterized in that, The crushing furnace (15) is provided with a vibrating mechanism connected with the screen, the vibrating mechanism can drive the screen to vibrate to separate the iron beads and the impurity powder, and simultaneously move the iron beads towards the outlet direction of the crushing furnace (15).

11. The ironmaking plant suitable for low-grade iron ore according to claim 1, characterized in that, The ball press (2) is provided with a pulverized coal spraying mechanism (5), and the pulverized coal spraying mechanism (5) can spray pulverized coal to the cold-pressed ball to form a layer of pulverized coal on the surface of the cold-pressed ball.

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