Method for inhibiting foaming of pig iron blocks in a ladle scrap preheating pig receiving process

Abstract

The application discloses a molten iron ladle scrap steel preheating molten iron foaming pig iron block inhibition method, belongs to the technical field of steel smelting, including the following steps: first, lay light scrap steel on the bottom of the molten iron ladle, then lay bulk scrap steel, when the total amount of light scrap steel and bulk scrap steel reaches about 3 / 4-4 / 5 of the planned total amount, add pig iron block; transport the molten iron ladle with scrap steel and pig iron block in step one to a scrap steel baking station for mixed gas combustion baking; after baking the scrap steel and pig iron block in the molten iron ladle in step two, transport to a blast furnace for molten iron receiving. The application delays the generation speed of foaming slag by adding pig iron block, effectively inhibits the occurrence probability of foaming slag, reduces the foaming slag occurrence ladle ratio from about 10% to below 2%, and basically ensures the molten iron discharge safety and transportation safety.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel smelting, and particularly relates to a molten iron ladle scrap steel preheating molten iron foaming pig iron block inhibition method. BACKGROUND

[0002] Generally, for steel metallurgy, scrap steel is a more energy-saving and environment-friendly renewable resource because it contains metallic iron >= 90%, compared with iron ore containing 56-65% of iron oxide. For each ton of scrap steel recovered and smelted, 1.7 tons of concentrate powder can be replaced, 350 kg of standard coal can be saved, 1.6 tons of CO2, 3 tons of solid waste, and various sulfides, nitrogen oxides, etc. can be reduced. In the traditional long process of blast furnace-converter process route, scrap steel is mostly used, which is added to the molten iron ladle and preheated, and the outlet temperature is controlled in the range of 700-800℃, and then the molten iron is discharged from the blast furnace. The kinetic energy (10-11m drop) and heat energy (1480-1520℃) of the blast furnace molten iron are used, so that the preheated scrap steel can be easily melted. However, these oxidized scrap steels, together with the iron oxide scale carried by themselves, react with C and Si in the molten iron to generate CO, CO2 gas and SiO2, which is easy to form foaming slag, which not only affects the loading capacity, but also threatens the safety of equipment and transportation. The existing technology is mostly concentrated in the four types of slag pressure forms of steelmaking converter, ladle, slag ladle and gas blowing.

[0003] Among them, the first type of converter slag is mostly used by various waste materials after reprocessing. The patent with publication number CN101487069A discloses a foaming slag inhibitor for converter, the main components of which are: 60-75% fiber pulp, 5-15% carbonized rice husk, 8-14% clay, additives and binders are added according to needs, which is mainly used to control the splashing in the converter blowing and to inhibit the foaming of the slag during tapping to prevent the slag from flowing down the furnace mouth. The patent with publication number CN1121114A discloses a slag pressure agent for oxygen top-blown converter and its production method, which contains 20-40% carbonized rice husk, 20-40% coke particles, 20-40% carbon, 3-5% fluorite, 0.5-55% acidified graphite, and auxiliary deoxidizer aluminum powder, slag and binder. The oxygen in the emulsified foaming slag is quickly absorbed by C, and the CO partial pressure in the furnace gas is close to the CO partial pressure in the steel slag emulsion, so that the CO gas in the furnace will not suddenly overflow. In addition, the FeO content in the slag is reduced, the viscosity of the slag is reduced, CO is easy to penetrate the slag layer, and the foaming of the slag is eliminated. The patent with publication number CN103540706A discloses a method for inhibiting foaming of slag, which contacts carbonaceous material with foaming slag on the surface of molten steel during the process of adopting converter tilting, and the carbonaceous material is 40-120g / m 2The carbonaceous material has a carbon content of C≥85 wt.%. The carbon element contained in the carbonaceous material reacts with FeO in the foamed slag after entering the foamed slag, thereby reducing the accumulated FeO, reducing the molten slag liquid phase ratio, increasing the tension, and making the slag dry, and further forming CO gas in the converter to better penetrate the slag layer, thereby further suppressing the foaming of the slag. Chinese Patent Publication No. CN103484595A discloses a production process of a magnesia slagging agent. The waste magnesia-carbon refractory material, industrial waste and iron-containing raw material are cooled to 25-30°C, crushed into 5-50mm particles, and ground into 3mm or less powder with a MgO content of 78%. The limestone powder with a CaCO3 content of 98% is mixed with the slagging agent at a mass ratio of 65:35, and stirred uniformly. The material is then placed in a steel slag ball press or a refractory ball press to press into 30±5mm balls, and dried at 30-50°C before use. Chinese Patent Publication No. CN111593162A discloses a converter slagging agent and its use method. The converter slagging agent is produced using corundum slag, converter steel slag and waste steel ladle brick. Chinese Patent Publication No. CN111100964A discloses a method for improving the foaming of converter final slag. During tapping, the waste probe after use in the converter is reused to quickly suppress the foamed slag and make the foamed slag stable, and then the slag pressing is assisted to better suppress the foamed slag. Chinese Patent Publication No. CN104531938A discloses a method for producing a slagging agent from waste blast furnace taphole mixture for converter steelmaking. The waste blast furnace taphole mixture is crushed and ground into powder particles with a particle size of 1mm or less, mixed with limestone powder with a particle size of 1mm or less at a mass ratio of 95:5, pressed into 30±5mm oval balls, and dried before being used in the converter for defoaming and slagging. Chinese Patent Publication No. CN104694690A discloses a high-efficiency slagging agent for the converter, which comprises the following components and has the following weight ratio: waste limestone powder 60-68%, waste steel slag 10-18%, waste magnesia-carbon refractory material 20-25%, and soil 2-5%. The slagging agent has the effects of cooling and thickening the slag. Chinese Patent Publication No. CN102212639A discloses a converter foamed slag slagging agent and its use method. The components of the converter foamed slag slagging agent include CaO 30-35 wt.%, MgO 20-25 wt.%, Al2O3 10-15 wt.%, SiO2 10-15 wt.%, FeO <1 wt.%, and B2O3 1.5-2.5 wt.%, with the balance being impurities. The use method is to add the converter foamed slag slagging agent into the converter during the carbon oxidation period of the converter blowing, and the addition amount is 2-3kg / t of molten steel.Chinese patent with publication number CN101824506A discloses a converter slagging agent and a converter slagging method. The converter slagging agent is composed of the following components in weight ratio: SiO2 8-15 parts, Al2O3 1-6 parts, Fe2O3 20-30 parts, MgO 10-20 parts, CaO 30-50 parts. The material used in the method is also waste product after production in the corresponding industry. The feature of helping to promote proper foaming in the converter may be beneficial to the converter, but for the ladle which has limited headroom, it is impossible to use this "helping to promote proper foaming" material to produce foaming slag. The first type of method is feasible for the converter with huge hearth space (70-80% of the hearth space of the converter is used for slagging, for a 200t converter, the distance from the molten steel surface to the converter mouth is 6000-7000mm), but it is impossible for the ladle with headroom (distance from the molten steel surface to the ladle side) of only 400-500mm, and it does not have the implementation space. In addition, for high oxidizing, high basicity converter slag and oxygen-containing molten steel, the above method can suppress foaming slag in the converter, but for reducing, low basicity, even slightly acidic blast furnace slag, these materials are difficult to melt (such as magnesite carbon brick, corundum with a melting point of more than 2000℃, and the temperature of molten iron is below 1500℃), or smoke and fire, or space limited and cannot be used in the molten iron ladle.

[0004] The second type is to slag in the ladle. Chinese patent with publication number CN102851452A discloses a slagging agent and a preparation method thereof. The slagging agent includes, in weight parts: silicon dioxide 10.0-15.0%, aluminum oxide 20.0-35.0%, calcium fluoride 10.0-15.0%, and elemental aluminum 7.00-10.00%. The slagging agent is made of fluorite, low-grade silicon-calcium alloy, and waste slag in the production of aluminum by electrolysis, and the density is controlled at 1.25-1.75g / cm3. The slagging agent reacts quickly with the original slag, and can form liquid slag within 3 seconds, eliminating the foaming slag generated by gas escape and oxidation during the molten steel pouring process. The technology uses the reducing property of aluminum in low-grade silicon-calcium alloy and waste slag to solve the foaming problem of high oxidizing, high basicity steel slag in the ladle. The technology has certain effect of reducing oxidizing property and modifying top slag for oxidizing slag, but it is powerless for the reducing, low basicity blast furnace slag in the ladle, and cannot modify and inhibit.

[0005] The third type is to carry out foam slag suppression in the slag tank. A Chinese patent with publication number CN105112580A discloses a production process of a multifunctional converter slag tank defoaming agent. Water bubble slag and gas ash with a mass percentage ratio of 65:35 are stirred and uniformly mixed to prepare a slag pressing agent. When the slag in the converter slag tank is seriously foamed, 100 kg of the slag pressing agent is manually added to achieve the purpose of slag pressing and defoaming. A Chinese patent with publication number CN104878161A discloses a slag pressing agent for a converter slag tank and a preparation method thereof. The weight percentage of the components of the slag pressing agent is as follows: carbon 75-95%, calcium carbonate 5-25%, and the rest is impurities in coke powder and limestone. The slag pressing agent is mainly used for pressing slag when the converter is smelted by the "double slag" process. The slag in the early stage of the converter is poured into the slag tank. The environment for using this technology is the molten steel slag tank. There is no molten steel, and the influence on the molten steel does not need to be considered. The implementation space is large, so the material added does not need to be considered to affect the quality of the molten steel. The main purpose is to suppress the foaming of the high-oxidizing and high-alkalinity converter steelmaking slag in the slag tank, to realize physical cooling and to destroy the development of the foamed slag, to prevent the overflow of the foamed slag, and to ensure safety. However, in the hot metal tank, not only is the implementation space limited, but also the material used needs to be considered whether it pollutes the hot metal. For example, the gas ash contains sulfur, which is not conducive to the quality of the hot metal. A large amount of gas is generated by the reaction of carbon and calcium carbonate, which only worsens the foamed slag in the hot metal tank.

[0006] The fourth type is to suppress the foamed slag by high-pressure gas. A Chinese patent with publication number CN103805732A discloses a converter smelting slag pressing method. High-pressure nitrogen gas is blown into the furnace by an oxygen lance. The high-pressure nitrogen gas jet is used to destroy the foamed slag, so as to achieve the purpose of smoothly pouring slag. This method has two advantages. One is to use the oxygen lance to blow high-pressure nitrogen gas to destroy the foamed slag. The other is that the space of the converter hearth is large enough to allow and contain a certain amount of splashing. These advantages are not possessed by the hot metal tank. The hot metal tank not only has a small clearance, but also the characteristics of the hot metal position and the hot metal of the blast furnace determine that it is difficult to install such a lance in the blast furnace. A Chinese patent with publication number CN202047090U discloses a slag pressing gun. The gun body, the gun head and the gun body are connected as a whole. The gun body is provided with a gas channel. The gas is sprayed out of the gun head. The gas is used to spray the part prone to slag overflow, so as to reduce the amount of overflow in the ladle. The environment for using this technology is in the VD. Even if there is a certain amount of slag splashing out of the tank, it can be handled because there is a professional working position. However, the hot metal tank is located on the train and is pulled by a locomotive or a special iron ox. There are a large number of auxiliary equipment nearby, so the technology cannot be transplanted.

[0007] None of the above four types of existing technologies involves the method and measures for suppressing the foaming of the hot metal tank blast furnace slag, especially the foaming caused by the addition of scrap steel and baking before hot charging. In view of the characteristics and limitations of the existing technologies, it is necessary to propose a method for suppressing the foaming of the pig iron block during the hot charging of the hot metal tank with preheated scrap steel. SUMMARY

[0008] The present application aims to provide a molten iron ladle scrap preheating ironing foaming pig iron block suppression method to solve the following technical problems: the existing slag method does not involve the foaming caused by adding scrap in the molten iron ladle after baking and then ironing, and the application to the molten iron ladle blast furnace slag foaming suppression is limited.

[0009] The purpose of the present application can be achieved by the following technical solutions:

[0010] A molten iron ladle scrap preheating ironing foaming pig iron block suppression method, comprising the following steps:

[0011] Step one: first lay light and thin scrap on the bottom of the molten iron ladle, then lay bulk scrap, when the total amount of light and thin scrap and bulk scrap reaches about 3 / 4-4 / 5 of the planned total amount, add pig iron block, the purpose is to reduce the impact of scrap on the bottom of the ladle and make the pig iron block placed on top to contact with the blast furnace molten iron first;

[0012] Step two: transport the molten iron ladle with scrap and pig iron block in step one to the scrap baking station for mixed gas combustion baking;

[0013] Step three: after the scrap and pig iron block in the molten iron ladle in step two are baked, transport them to the blast furnace for ironing.

[0014] As a further scheme of the present application, the laying amount of light and thin scrap is 2-3t, and the light and thin scrap includes leftover wire, edge, and sheet tail material generated in the machining process of steel material, easy-open can, iron sheet, and iron wire recyclables.

[0015] As a further scheme of the present application, the added amount of pig iron block is 3-5t.

[0016] As a further scheme of the present application, the total amount of light and thin scrap, bulk scrap, and pig iron block is 8-16% of the planned molten iron amount, and the amount of scrap is subject to the scrap type.

[0017] As a further scheme of the present application, no bulk scrap is added after the pig iron block is added to reach the planned molten iron amount, and bulk scrap is continuously added until the planned molten iron amount is reached after the pig iron block is added to be lower than the planned molten iron amount.

[0018] As a further scheme of the present application, the mixed gas is composed of mixed coal gas and oxygen in a flow ratio of 2:1.

[0019] As a further scheme of the present application, the flow of mixed coal gas is 2400-2600Nm 3 / h, and the flow of oxygen is 1200-1300Nm 3 / h.

[0020] As a further scheme of the present application, the mixed coal gas consumption is 20-30Nm 3 / t scrap steel.

[0021] The present application has the following advantages:

[0022] The present application delays the generation speed of foamed slag by adding pig iron blocks, effectively inhibits the probability of foamed slag, reduces the tank ratio of foamed slag from about 10% to below 2%, and basically ensures the safety of tapping and transportation; the present application does not need to reduce the probability of foamed slag by weakening the roasting intensity, and sufficient roasting intensity ensures that the outlet temperature of the scrap steel after roasting is above 700℃; the present application does not need to make higher requirements for the type and quality of scrap steel (the higher the requirements for the type and quality of scrap steel, the higher the cost), thereby reducing the production cost; the probability of foamed slag is controlled within 2%; the present application increases the total loading amount of scrap steel in the ladle due to the bulk density of pig iron blocks being much greater than that of ordinary scrap steel, thereby improving the production efficiency; the specific principle is as follows:

[0023] The melting point of pig iron blocks is much lower than that of scrap steel (the melting point of general pig iron blocks is 1160-1180℃, and the melting point of scrap steel is 1440-1480℃), when the molten iron of the blast furnace flows into the ladle, the pig iron is first melted, when the pig iron blocks begin to melt, low-temperature molten iron is formed together with the molten iron of the blast furnace, and at the beginning of the formation of these low-temperature molten iron, the C-FeO and Si-FeO reactions with the iron oxide in the scrap steel contacted by the low-temperature molten iron are slowly carried out, so that CO and CO2 can be slowly released, the blowing power of CO and CO2 on the slag when discharged is slowed down, and then the generation speed of foamed slag is weakened. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] Embodiment 1

[0026] A pig iron block inhibition method for foaming of scrap steel preheating of a molten iron ladle, comprising the following steps:

[0027] Step one: after the 210t molten iron ladle is tapped in the converter, it is hoisted to the scrap steel adding station, 2t thin scrap steel is first laid on the bottom of the molten iron ladle by using a scrap steel grabbing machine, then 18t bulk scrap steel is laid, and 4t pig iron blocks are added;

[0028] Step two: the molten iron ladle with the added scrap steel and pig iron blocks in step one is transported to the scrap steel roasting station, mixed coal gas and oxygen are introduced, the flow rate of the mixed coal gas is 2400Nm3 / h, oxygen flow 1200 Nm 3 / h, oxygen flow 1300 Nm

[0029] Step three: after the scrap steel and pig iron block in the ladle of molten iron in step two are roasted, they are transported to the blast furnace for iron receiving, and the tapping amount is 150 t.

[0030] In this example, the slag surface height in the ladle of molten iron can be controlled below 5.3 m (the height of the ladle opening is 5.8 m), and the phenomenon of exceeding the safety warning line of 5.5 m does not occur, and the foamed slag is effectively controlled.

[0031] Example 2

[0032] A method for inhibiting foaming of pig iron blocks in a ladle of molten iron during scrap steel preheating and iron receiving, comprising the following steps:

[0033] Step one: after the 210 t ladle of molten iron is tapped in the converter, it is hoisted to the scrap steel adding station, 3 t of thin scrap steel is first laid on the bottom of the ladle of molten iron using a magnetic disk, then 20 t of bulk scrap steel is laid, and 5 t of pig iron blocks are added.

[0034] Step two: the ladle of molten iron with scrap steel and pig iron blocks added in step one is transported to the scrap steel roasting station, mixed gas and oxygen are introduced, the flow rate of the mixed gas is 2600 Nm 3 / h, and the flow rate of oxygen is 1300 Nm 3 / h, and the preheating time is 16 min.

[0035] Step three: after the scrap steel and pig iron blocks in the ladle of molten iron in step two are roasted, they are transported to the blast furnace for iron receiving, and the tapping amount is 190 t.

[0036] In this example, the slag surface height in the ladle of molten iron can be controlled below 5.3 m (the height of the ladle opening is 5.8 m), and the phenomenon of exceeding the safety warning line of 5.5 m does not occur, and the foamed slag is effectively controlled.

[0037] Comparative Example 1

[0038] A method for inhibiting foaming of pig iron blocks in a ladle of molten iron during scrap steel preheating and iron receiving, comprising the following steps:

[0039] Step one: after the 210 t ladle of molten iron is tapped in the converter, it is hoisted to the scrap steel adding station, 2 t of thin scrap steel is first laid on the bottom of the ladle of molten iron using a scrap steel grabbing machine, then 18 t of bulk scrap steel is laid.

[0040] Step two: the ladle of molten iron with scrap steel added in step one is transported to the scrap steel roasting station, mixed gas and oxygen are introduced, the flow rate of the mixed gas is 2000 Nm 3 / h, and the flow rate of oxygen is 1000 Nm 3 / h, and the preheating time is 10 min.

[0041] Step three: after the scrap steel in the ladle of step two is roasted, it is transported to the blast furnace for iron receiving, and the tapping amount is 145 t.

[0042] The proportion of the molten iron ladle in the present comparative example whose slag surface height exceeds the safety warning line of 5.5 m is 10%.

[0043] It is to be noted that the relative terms such as first and second, and the like, are used herein solely to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0044] While embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, changes, and alterations can be made by those skilled in the art without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing the foaming of pig iron blocks caused by iron molten iron ladles during preheating of scrap steel, characterized in that, Includes the following steps: Step 1: First, lay light and thin scrap steel at the bottom of the molten iron ladle, then lay loose scrap steel. When the total amount of light and thin scrap steel and loose scrap steel reaches 3 / 4 to 4 / 5 of the planned total amount, add pig iron blocks. Step 2: Transport the molten iron ladle containing scrap steel and pig iron blocks from Step 1 to the scrap steel baking station for mixed gas combustion baking; Step 3: After baking the scrap steel and pig iron blocks in the molten iron ladle from Step 2, transport them to the blast furnace for iron receiving; The total amount of light and thin scrap steel, bulk scrap steel and pig iron blocks loaded is 8%-16% of the planned molten iron.

2. The method for suppressing the foaming of pig iron blocks caused by iron preheating of scrap steel in a molten iron ladle according to claim 1, characterized in that, The amount of light and thin scrap steel added is 2-3t. The light and thin scrap steel includes the wire, edge, and sheet material left over from cutting, turning, drilling and milling of steel materials during the machining process, as well as recycled materials such as beverage cans, iron sheets and iron wires.

3. The method for suppressing the foaming of pig iron blocks caused by iron foaming during the preheating of scrap steel in a molten iron ladle according to claim 1, characterized in that, The amount of pig iron blocks added is 3-5t.

4. A method for suppressing the foaming of pig iron blocks caused by iron foaming during the preheating of scrap steel in a molten iron ladle, as described in any one of claims 1-3, characterized in that... Once the planned amount of molten iron is reached after adding pig iron blocks, no more bulk scrap steel is added. If the amount of molten iron falls below the planned amount after adding pig iron blocks, bulk scrap steel is added until the planned amount of molten iron is reached.

5. The method for suppressing the foaming of pig iron blocks caused by iron foaming during the preheating of scrap steel in a molten iron ladle according to claim 1, characterized in that, The mixed gas is composed of mixed coal gas and oxygen at a flow rate ratio of 2:

1.

6. The method for suppressing the foaming of pig iron blocks caused by iron foaming during the preheating of scrap steel in a molten iron ladle according to claim 5, characterized in that, The flow rate of the mixed gas is 2400-2600 Nm³. 3 / h, oxygen flow rate 1200-1300 Nm 3 / h.

7. The method for inhibiting the foaming of pig iron blocks caused by iron foaming during the preheating of scrap steel in a molten iron ladle according to claim 5, characterized in that, The consumption of the mixed gas is 20-30 Nm³. 3 / t scrap steel.