CN111979376B - Lime-based molten iron desulfurizing agent and preparation method thereof - Google Patents
Lime-based molten iron desulfurizing agent and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
- C21C7/0645—Agents used for dephosphorising or desulfurising
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Abstract
The embodiment of the invention relates to a lime-based molten iron desulfurizer and a preparation method thereof. The desulfurizer comprises 60 to 90 weight percent of lime and 8 to 40 weight percent of desulfurization additive, wherein the desulfurization additive comprises 45 to 75 weight percent of Al 2 O 3 、8～30％Al, 2-8% of simple substance Si, 2-14% of MgO and 3-14% of SiO 2 . The molten iron desulfurizer of the invention adopts common metallurgical lime and also adds materials adopting renewable resources, which contain metallic aluminum, silicon and active alumina, and can completely replace fluorite. The desulfurization effect of the molten iron desulfurizer of the invention is not different from that of fluorite, and the molten iron desulfurizer has lower cost and is more environment-friendly.
Description
Technical Field
The invention relates to the technical field of external desulphurization in the ferrous metallurgy process flow, in particular to a fluorine-free desulfurizer material for desulphurization of blast furnace molten iron or molten steel and a preparation method thereof.
Background
The modern traditional steel production process mainly comprises the procedures of blast furnace-converter-continuous casting-rolling and the like. Sulfur is a harmful impurity in steel, and the performance and the internal quality of steel are seriously influenced, so that the removal of sulfur in steel is one of important tasks in the steel production process. As the society has higher and higher requirements on the quality and performance of various steel products, the external desulfurization, desiliconization and dephosphorization of blast furnace molten iron are generally adopted process flows in consideration of the sulfur load of blast furnace iron making ingredients and the burden of desulfurization on raw material molten iron in the converter steelmaking process.
The existing external desulfurization method for blast furnace molten iron mainly comprises a blowing desulfurization method and a stirring desulfurization method. The blowing desulfurization method is a Ukrainian technology, and takes passivated lime and passivated magnesium powder as desulfurizing agents. The agitation desulfurization method is a KR (Kambara Reactor) method of Japanese invention, in which fluorite and CaC are added to lime base 2 、Na 2 CO 3 And the like are desulfurizing agents. The blowing desulfurization method has high cost of using the passivated metal magnesium powder, and the desulfurized furnace slag is difficult to remove and easy to generate the resulfurization phenomenon. At present, the KR desulfurization method is mainly used due to the great improvement of the service life of refractory materials of a stirring head in the KR desulfurization method and the reduction of comprehensive desulfurization cost. The KR method external desulfurization has the main operation cost of selection and application of a molten iron desulfurizing agent except equipment investment and consumption of refractory materials of a ladle lining and a stirring head.
However, the KR method pollutes air and circulating water due to the use of fluorite; erosion of refractory material inside the ladle lining; and the desulfurization slag has high fluorine content, and can pollute soil and surface water when being stacked in the open air, and can not be used as a building material raw material or a paving material, so that the problems of limited desulfurization slag discharge, storage and reutilization exist.
Disclosure of Invention
In view of the above, the invention provides a lime-based fluorine-free molten iron desulfurizer and a preparation method thereof. The molten iron desulfurizer of the invention adopts common metallurgical lime and also adds materials adopting renewable resources, containing metal aluminum, silicon, active alumina and the like, and can completely replace fluorite. The molten iron desulfurizer of the invention has no difference in desulfurization effect from fluorite, and has the advantages of lower cost and more environment-friendly property.
The temperature of molten iron produced by blast furnace ironmaking is 1400-1500 ℃, the sulfur content is generally controlled to be more than 0.01% and less than 0.1%, the sulfur content of raw material molten iron required by most steelmaking converters is about less than 0.01-0.005%, and the sulfur content of molten iron required to be treated by individual steel grades is lower. Therefore, the process of molten iron desulphurization outside the furnace is required to meet the requirements of steel making and steel products on sulphur.
The currently applied desulfurizing agents are mainly lime, metal magnesium and the like, and because the lime has a high melting point (2570 ℃), about 10-20% of fluorite needs to be added to form a low-melting-point eutectic body so as to be close to the temperature of molten iron, and the desulfurizing effect of the lime can be exerted. The basic chemical reaction of desulfurization with lime-based desulfurizing agent and blast furnace molten iron is as follows (1):
[S]+(CaO)＝(CaS)+[O] ①
brackets refer to elements in the iron bath. In order to carry out chemical reaction and realize deep desulfurization, the oxygen level in the molten iron must be reduced, and the effective CaO content of lime is required to be more than 80-85%, and the lime has higher activity and small granularity. Therefore, desulfurization of molten iron requires high CaO activity and a low oxygen level of molten iron. The main participating deoxidation reaction in the molten iron are C, si, al and the like, and the chemical reaction formulas of the main participating deoxidation reaction in the molten iron are respectively (2), (3) and (4) as follows:
[C]+[O]＝CO ②
1/2[Si]+[O]＝1/2 SiO 2 (S) ③
2/3[Al]+[O]＝1/3 Al 2 O 3 (S) ④
theoretically, at blast furnace molten iron temperatures around 1500 ℃, carbon does not substantially participate in the deoxidation reaction. And silicon and aluminum in the molten iron can participate in a deoxidation reaction, wherein the aluminum is preferentially deoxidized. However, since the amount of aluminum contained in the blast furnace molten iron is small and is about 1ppm or less, a small amount of (Al) is added. With the advancement of the desulfurization process and the change of element concentration, the two deoxidation reactions of Si and Al are simultaneously carried out and exist. Promote the desulfurization reaction to proceed in the forward direction, and realize deep desulfurization.
In the actual blast furnace molten iron desulphurization process, lime is excessive, and Si in the molten iron is reduced by about 10%, so that the addition of the metal aluminum can maintain a certain content of aluminum in the molten iron, realize the acceleration of the desulphurization reaction and the deep desulphurization, and realize the target of the end point sulfur below 10 ppm.
Molten iron desulphurization is a liquid phase chemical reaction. Since lime has a melting point of 2570 ℃ and the molten iron is far from being melted and cannot be subjected to desulfurization reaction by lime, fluorite is usually added to promote lime slagging to produce (CaO. CaF) 2 ) A low melting eutectic of (a). The use of fluorite, although allowing the desulfurization of lime to be carried out, as described in the background of the invention, the hazard of fluorite has been a recognized fact: including erosion to ladle lining and stirring head refractory material, and damage to air, circulating water and personnel after fluorite volatilizes and decomposes at high temperature. On the other hand, because fluorite is used for slagging, the desulphurization slag is stacked outdoors in the open air, which causes serious harm to soil and surface water. According to national regulations, the surface water fluoride is less than or equal to 1.0mg/L according to the GB 3838-2002 standard, and is very strict; and the fluorine-containing slag can not be used as a raw material of building materials. In addition, the state stipulates that the fluoride content in the outdoor waste slag is less than 4000ppm. Therefore, developed countries in the world have long legislated and the application of fluorite is cancelled. In recent years, fluorite has become a scarce raw material, and the price has been increasing year by year.
In view of the above, an object of the present invention is to provide a lime-based molten iron desulfurizing agent, which comprises, by weight, 60 to 90% of lime, such as 60 to 70%, 71 to 85%, 65 to 75%, 86 to 90%, 64%, 68%, 72%, 77%, 81%, 86%, etc., and 8 to 40% of desulfurizing additive, such as 9 to 15%, 16 to 25%, 30 to 36%, 20 to 30%, 10%, 14%, 18%, 22%, 26%, 32%, 37%, etc., and the mass percentages of the lime and the desulfurizing additiveThe sum of the percentages is 100%. Wherein the desulfurization additive comprises 45-75% of Al in percentage by weight 2 O 3 8 to 30 percent of Al, 2 to 8 percent of simple substance Si, 2 to 14 percent of MgO and 3 to 14 percent of SiO 2 And the rest substances are inevitable impurities, such as oxides of iron, manganese, zinc, titanium and the like.
Al in desulfurizing additive 2 O 3 For example, 45-55%, 50-60%, 54-61%, 62-70%, 66-75%, 48%, 53%, 57%, 63.5%, 67%, 71%, 74%, etc.
The amount of Al in the desulfurization additive is, for example, 8 to 12%, 10 to 15%, 16 to 22%, 20 to 27%, 9%, 11%, 14%, 18%, 23.6%, 26%, 28%, etc. in percentage by weight.
The amount of elemental Si in the desulfurization additive is, for example, 2 to 5%, 3 to 7%, 5 to 8%, 4.5%, 6%, etc. in weight percent. Silicon deoxidization and heat release are beneficial to desulfurization. Si can improve the activity coefficient of S, which is beneficial to the transfer of S to slag, thereby promoting desulfurization.
The amount of MgO in the desulfurization additive is, for example, 2 to 5%, 6 to 10%, 11 to 15%, 3.5%, 7%, 9.5%, 13%, etc. in percentage by weight.
SiO in desulfurizing additive 2 The amount of (b) is, for example, 3-6%, 5-10%, 11-14%, 5.5%, 8%, 12%, 14%, etc.
Preferably, the lime-based molten iron desulfurizer comprises 75-85% of lime and 12-31% of desulfurization additive by weight, the desulfurization additive in the range ensures desulfurization effect and simultaneously controls production cost within a proper level, the desulfurization effect of 15-30% of desulfurization additive content is better, wherein the desulfurization additive comprises 55-65% of Al by weight 2 O 3 12 to 21 percent of Al, 3 to 5 percent of simple substance Si, 4 to 10 percent of MgO and 5 to 10 percent of SiO 2 。
The molten iron fluorine-free desulfurizer of the invention is a new measure benefiting the nation, the people and the enterprises, the application of the desulfurizer can not increase the desulfurization cost of the molten iron in the blast furnace, and the desulfurization cost can be reduced compared with the prior art of adding fluorite into lime.
The lime-based molten iron desulphurization process is mainly a heterogeneous reaction between solid lime and sulfur in molten iron, and comprises a complex mass transfer process and an interfacial chemical reaction. The outward diffusion of the desulfurization reaction product at the lime interface and the diffusion of the desulfurization reaction product to the lime interface are restrictive links of the kinetics of the desulfurization chemical reaction. Because the desulfurizer of the invention is added with the additive containing metallic aluminum, silicon and oxide thereof instead of fluorite, the oxygen level in the molten iron can be greatly reduced, and the desulfurization reaction and deep desulfurization are promoted. Wherein aluminum and silicon participate in deoxidation to generate alumina and silicon oxide, and simultaneously generate calcium aluminate and calcium silicate series compounds with lime, the added aluminum oxide and free lime also generate calcium aluminate, so that the molten iron desulphurization slag becomes mixed slag composed of multiple elements, and the process can refer to the following reaction formula (5)
CaO (S) +xAl 2 O 3(S) +ySiO 2(S) ＝CaO·xAl 2 O 3 ·ySiO 2 ⑤
In particular alumina and lime can form low melting eutectic, i.e. the following series of calcium aluminate phases: 3 CaO. Al 2 O 3 、CaO·6Al 2 O 3 、12CaO·7Al 2 O 3 、CaO·Al 2 O 3 、CaO·2Al 2 O 3 Promotes the slagging of lime and replaces fluorite. According to CaO-Al 2 O 3 The first two substances are different melting point compounds, and the last three substances are same melting point compounds. The generation of the substances reduces the melting temperature of the slag, improves the slagging rate and the utilization rate of the lime, and plays a role of replacing fluorite. In addition, due to Al generated 2 O 3 And added Al 2 O 3 The calcium aluminate with different components is generated with the same CaO, and the CaO and the SiO can be reduced 2 To produce 2CaO SiO 2 (this substance has a high melting point (2130 ℃ C.), and is unfavorable for desulfurization reaction, so that the desulfurization reaction is facilitated.
A large number of practical experiences show that the fluorine-free calcium aluminate slag greatly increases the sulfur capacity of the slag, and the distribution ratio of sulfur in metal and slag is increased from about 500 to over 1800, so that the requirements of quick and deep desulfurization can be met.
The invention is particularly pointed out from theory and practice, since Al 2 O 3 May exhibit acidic or basic properties in different phases, too high of Al generated and added from Al 2 O 3 The effective basicity of the slag is lowered, which is not favorable for desulfurization, and therefore the amount of the additive in the desulfurizing agent is controlled.
The desulfurizer of the invention avoids a series of pollution problems caused by using fluorite, and the like, and the cost is lower than that of the fluorite because of the selection of valuable materials comprehensively utilizing renewable resources. The invention is suitable for KR desulfurization method and blowing desulfurization method, and replaces passivated magnesium powder. The invention is also suitable for the desulfurization of molten steel.
Preferably, the desulfurization additive further comprises 1.5 to 10 weight percent of carbonate material, and preferably 3 to 5 weight percent of carbonate material.
Preferably, the carbonate material is BaCO 3 、MgCO 3 、NaHCO 3 、CaCO 3 A mixture of one or more of them.
BaCO 3 、MgCO 3 、NaHCO 3 、CaCO 3 Such carbonates will rapidly decompose at the temperature of the molten iron into BaO, mgO and Na which have high activity and are beneficial to desulphurization 2 O and CaO directly participate in molten iron desulphurization reaction; CO produced by decomposition 2 、H 2 O gas, which promotes the diffusion of substances that accelerate the kinetics of the desulfurization reaction zone; in addition, due to the low melting point and the low decomposition temperature, the slagging and the utilization rate of the lime are promoted; and the carbonate can desorb heat and reduce the temperature, which is beneficial to the desulfurization reaction. However, when molten iron is desulfurized and then supplied to converter steelmaking, the temperature drop is not too large, and the temperature drop is favorable for the thermodynamics of the desulfurization reaction but unfavorable for the kinetics of the desulfurization reaction, so that the carbonate content in the desulfurization additive is controlled within the above-mentioned suitable range. One, two or a combination of the above substances, although in small amounts, can act like a catalyst for a desulfurization chemical reaction.
Preferably, the carbonate is powdery material with the granularity less than or equal to 0.8mm. Preferably, the particle size is less than or equal to 0.6mm. The finer the particle size of the carbonate, the more favorable the chemical reaction (the larger the specific surface area). However, too thin leads to the increase of processing cost, and in addition, the powder is easy to be sucked away by negative pressure during the desulfurization blanking, and more than 15% of the powder is lost in some cases. Therefore, the granularity is preferably 0.35-0.5 mm, and the carbonate in the granularity range is favorable for quick decomposition and diffusion, promotes and directly participates in the desulfurization chemical reaction, and simultaneously reduces the processing cost and material loss.
Preferably, the lime contains CaO at 85.0% or more, e.g., 87%, 90%, 92%, 95%, etc., mgO < 5.0%, and SiO 2 Less than or equal to 3.5 percent. The effective CaO in the lime is more than or equal to 85 percent, so that the dosage of the desulfurized lime of molten iron per ton can be reduced. Preferably, the lime has an S content of 0.050% or less and a scorch of 5% or less, the smaller the value in this range, the smaller the value of the equilibrium value of the desulfurization chemical reaction is, the better the S content in the molten iron is transferred to the slag.
Preferably, the lime has an activity of not less than 280, for example, 290, 305, 320, 345, 360, etc., at 4mol/ml under the conditions of 40. + -. 1 ℃ and 10 min. The lime has high activity, i.e. the lime is hydrolyzed into Ca (OH) 2 The amount of the lime is low, so that the forward desulfurization reaction is more favorably carried out, and the lime consumption is reduced.
Preferably, caO in the lime is more than or equal to 90 percent, the dosage of the lime per ton of molten iron desulfurizer can be reduced, and more preferably more than or equal to 95 percent.
Preferably, the particle size of the lime is less than or equal to 1mm. The small lime granularity and the increased specific surface area are favorable for the thermodynamics and the kinetics of desulfurization chemical reaction and the effective utilization of lime.
Preferably, the Al, the simple substance Si, and the Al 2 O 3 、SiO 2 MgO, etc. are powdery materials after high-temperature firing, the particle size of Al, simple substance Si is less than or equal to 3mm, such as 1.5-3mm, 0.5-1.4mm, 0.8-1.2mm, etc., preferably 1-2mm 2 O 3 MgO and SiO 2 The particle size of (B) is 60 to 100 mesh, for example, 65 mesh, 70 mesh, 80 mesh, 90 mesh, etc. The Al and the simple substance Si have moderate particle sizes, are favorable for fully utilizing the deoxidation of the Al and the simple substance Si, and avoid the phenomenon that the particle sizes are too small and the loss due to burning of the Al and the Si is easy to lose at high temperature.
Preferably, the water content of the desulfurization additive is less than or equal to 0.5%, and the desulfurization additive has high water content, so that the activity of lime is reduced, the desulfurization reaction is not facilitated, and the dosage of the desulfurization additive or the lime is increased. The water content of the desulfurization additive is controlled to be less than or equal to 0.5 percent, so that the actual influence on the lime activity is avoided, and the desulfurization reaction is favorably carried out.
Preferably, the desulfurization additive at least comprises metal Al, simple substance Si and Al 2 O 3 The aluminum industrial byproduct is taken as a main raw material and is prepared by grinding, grading, adjusting the granularity and adding corresponding raw materials according to the limitation of the components. The industrial by-product of aluminium used in this invention is waste aluminium and aluminium alloy recovered from society, and the residue and metal left in the process of recovering metal by pyrogenic process (the metal can not be recovered completely, and its content is about 30%), also called valuable by-product. The invention adopts a method that at least contains metal Al, simple substance Si and Al 2 O 3 Is used as main raw material, and the corresponding components in the desulfurization additive, such as Al, are adjusted by adding proper components 2 O 3 Al, simple substance Si, mgO, siO 2 The content of the additive is used for obtaining the desulfurization additive with a specific composition, so that on one hand, resources are fully utilized, the product cost is reduced, and meanwhile, a good desulfurization effect is obtained.
One of the contents of the present invention is also to provide a method for preparing the lime-based molten iron desulfurizing agent according to the present invention, comprising the steps of: and (3) selecting, crushing, grinding and screening all the components, weighing and proportioning according to respective granularity and weight percentage, and mixing to obtain the lime-based molten iron desulfurizer.
The application of the desulfurizer of the invention can adjust the optimal granularity of materials and is beneficial to promoting the chemical reaction of desulfurization.
Compared with the existing desulfurizer, such as the desulfurizer containing passivated lime and passivated magnesium powder and the desulfurizer added with fluorite, the desulfurizer of the invention can achieve the same effect and low cost under the same addition amount, and the fluoride content in the desulfurized slag is far lower than the 4000ppm amount required by the national standard. The desulfurizer of the invention can reduce the material cost of the molten iron desulphurization process. More specifically, the desulfurizing agent of the present invention has the following advantageous effects:
(1) the same amount of iron desulfurizer per ton (such as 5 kg/ton iron to 8.5 kg/ton iron) has the same desulfurization effect as the conventional process;
(2) the desulfurization slag conditions are the same, the desulfurization slag is easy to remove and is not sticky, and the content of iron beads is slightly lower than that of the traditional process; the desulphurization slag contains no fluorine, so that the desulphurization slag can be comprehensively utilized;
(3) because of the exothermic reaction of the deoxidation of the metal aluminum and the silicon, the temperature reduction in the molten iron desulphurization process is smaller than that of the traditional process;
(4) because the additive adopts raw materials comprehensively utilized by industrial cycle, and has high activity without moisture after high-temperature calcination, the cost is lower than that of the added fluorite desulfurizer;
(5) the desulfurizer of the invention is applicable to the stirring method (KR method) and is also applicable to refining and desulfurization of other molten iron or molten steel. The desulfurizer of the invention can replace magnesium powder in a blowing method, and can greatly reduce the desulfurization cost. The principle of applying the desulfurizer of the invention in the blowing method is the same as that of the KR method, and the effect is the same as that of using Mg in the blowing method, so that the end point S can be reached. When the desulfurizer of the invention is used in a blowing method, the amount of the desulfurization additive can be properly increased, such as 18-21%, so as to obtain better desulfurization effect, the temperature is reduced to about 30 ℃, and the slag condition is good, no resulfurization is caused, and slag skimming is good.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
Detailed Description
The present invention will be described in detail below by way of examples. The relevant properties of the lime referred to in the following examples were measured according to the method specified in YB/T042-2004.
Example 1
Lime-based ironThe water desulfurizer comprises 90 percent of lime and 10 percent of desulfurization additive by weight percentage, wherein the desulfurization additive at least comprises metal Al, simple substance Si and Al 2 O 3 The aluminum industrial byproduct is taken as a raw material, is prepared by grinding, grading, adjusting the granularity and adding corresponding raw materials according to the limitation of the components, and the desulfurization additive comprises the following components in percentage by weight:
CaO 87%, mgO 1.9%, siO in lime 2 1.6 percent of the total weight of the steel, 0.046 percent of S and less than or equal to 5.0 percent of ignition loss. The activity of lime is 285 at 40 + -1 deg.C for 10min at a concentration of 4 mol/ml. The granularity of the lime is 0.64mm.
Al and simple substance Si are powdery materials after high-temperature firing, the granularity is 2mm 2 O 3 MgO and SiO 2 Is 80 meshes and is also a material which is fired at high temperature. The water content of the additive was 0.38%. The carbonate particle size was 0.56mm.
Example 2
The lime-based molten iron desulfurizing agent according to this embodiment is different from embodiment 1 in that it includes 85% of lime and 15% of a desulfurization additive by weight and MgCO powder in the desulfurization additive 3 The content of (B) is 4%, the particle size of carbonate is 0.4mm, and the rest is the same as example 1.
Example 3
The lime-based molten iron desulfurizing agent according to this embodiment is different from embodiment 1 in that 80% of lime and 20% of a desulfurization additive are included by weight and powder of MgCO in the desulfurization additive is MgCO 3 The content of (B) is 5%, and the rest is the same as in example 1.
Comparative example 1
This comparative example replaces the desulfurization additive of example 1 with fluorite (where CaF 2 75% or more) of the above-mentioned components, and the rest is the same as in example 1.
Comparative example 2
This comparative example replaces the devulcanization additive of example 2 with fluorite, the remainder being identical to example 2.
Comparative example 3
This comparative example replaces the desulfurization additive of example 3 with fluorite, and is otherwise the same as example 3.
Comparative example 4
The lime-based molten iron desulfurizing agent of the comparative example, which comprises 93% by weight of lime and 7% by weight of a desulfurizing additive, is the same as example 2.
Comparative example 5
The lime-based molten iron desulfurizer of this comparative example is the same as example 2 except that the CaO content in lime is not more than 80%.
Comparative example 6
The lime-based molten iron desulfurizing agent of this comparative example was the same as example 2 except that the particle size of the carbonate was 1mm.
Comparative example 7
The lime-based molten iron desulfurizing agent of this comparative example was the same as example 2 except that the particle size of lime was 1.5mm. The granularity of Al and simple substance Si is 5mm 2 O 3 MgO and SiO 2 Has a particle size of 120 meshes.
Desulfurization examples
The process parameters in the KR hot metal desulfurization are generally as shown in Table 1 below.
TABLE 1
The capacity of the blast furnace ladle is 300 tons, 6 times of tests are totally carried out, and the serial numbers 1, 2 and 3 are lime and fluorite processes (respectively corresponding to comparative examples 1, 2 and 3 in the table); numbers 4, 5 and 6 represent the number of times of applying the desulfurizing agent (corresponding to examples 1, 2 and 3 in the following table, respectively), wherein the mass percentages of one, two or more than two other substances in the additive are 3%, 4% and 5% in sequence. Specific parameters and results are shown in tables 2 and 3.
TABLE 2
TABLE 3
Embodiments and effects thereof
Basically, the operation of the desulfurization process of the raw lime and the fluorite is not changed, and the molten iron desulfurizer is prepared by mechanically and uniformly mixing the materials in advance according to the composition and the proportion of the materials in the embodiment of the invention. And then conveying the prepared molten iron desulfurizer to a high-position desulfurizer bin by using gas for later use. The dosage of the molten iron per ton of the desulfurized molten iron is controlled to be 6-8 kg; the addition amount of the materials in the desulfurizer can be properly adjusted according to the requirements of the sulfur of the original molten iron and the end point sulfur so as to achieve the optimal process parameters and meet the requirements of the steel-making production process.
The time used by the desulfurization procedure is in the range of 8min to 25min, and the procedure matching connection is preferred, so that the end-point sulfur requirement is met on the premise, and the turnover time is shortened as much as possible.
In the KR desulfurization process, the revolution of the stirring head is controlled to be between 70 and 120rpm, and when the temperature of molten iron is lower than 1260 ℃, 120 to 125rpm is preferably adopted. In general, the number of revolutions should be increased by 10 to 20% at a stage when the life of the stirring head is close to replacement, but the maximum number of revolutions is not more than 150rpm.
For steel types with special requirements, such as silicon steel (including oriented and non-oriented silicon steel), deep drawing thin plates and other steel types, the end point sulfur is required to reach less than or equal to 10ppm, by adopting the technical scheme of the invention and properly adjusting the revolution of the stirring head and the desulfurization stirring time, the upper limit of 8.5 kg/ton of iron is adopted for the amount of a desulfurizing agent in each ton of molten iron, wherein 15-31% of an additive accounts for realizing a better desulfurization purpose.
As can be seen from the results of tables 2-3: compared with the traditional fluorite, the molten iron desulfurizer of the invention has the following advantages:
(1) the influence on the content of C, si and Mn in the molten iron is almost the same.
(2) If the dosage of the desulfurization additive is increased, the desulfurization rate of the molten iron can be improved, and more deep desulfurization can be realized.
(3) The dosage of the desulfurization additive reaches about 15 percent, thus meeting the requirements of most steel types on molten iron S in the steel making furnace.
(4) The difference of the desulfurization time is within the allowable range of the process.
(5) Comparison of comparative example 4 with example 2 shows that the desulfurization effect of the desulfurization agent prepared when the contents of lime and desulfurization additive are not in the present invention is significantly inferior to that of the desulfurization agent prepared when they are within the ranges of 60 to 90% and 8 to 40% as defined in the present invention.
(6) Comparison between comparative example 5 and example 2 shows that the desulfurization effect of the desulfurizer obtained when the CaO in lime is 80% is significantly inferior to that of the desulfurizer obtained when the CaO in lime is 85.0% or more.
(7) Comparison of comparative example 6 with example 2 shows that the desulfurization effect of the desulfurizing agent obtained when the particle size of the carbonate is not in the range of 0.8mm or less of the present invention is inferior to that of the desulfurizing agent obtained when the particle size of the carbonate is in the range defined by the present invention.
(8) Comparison of comparative example 7 with example 2 shows lime, al, elemental Si, al 2 O 3 MgO and SiO 2 When the particle size of the raw materials is not within the range defined by the present invention, the desulfurization effect of the obtained desulfurization agent is significantly inferior to that of the desulfurization agent obtained when the particle size of the raw materials is within the range defined by the present invention.
From the above, the desulfurization additive of the present invention can completely replace fluorite. The invention meets the requirement of molten iron desulphurization by the mutual matching and synergistic action of proper components and contents thereof, and can also realize the goal of molten iron desulphurization by properly adjusting the dosage and the composition of the additive. In addition, through a great deal of research, better desulfurization effect can be realized through further limiting the granularity of the components, the content of the effective components and the like. And the temperature drop and the burning loss of C, si and Mn in the desulfurization process of the molten iron desulfurizer are also superior to those of the case of using fluorite.
The technical scheme of the invention mainly has the following effects:
1. the corrosion of fluorite used in the original desulfurizer to refractory material lining and a stirring head is improved and eliminated, and the harm to human bodies caused by the fluorite volatilized at high temperature and decomposed in the air is avoided, so that the fluorine pollution in the cooling circulating water of a factory is prevented from exceeding the national specified standard. Meanwhile, the desulphurization slag is stacked in the open air, so that the polluted soil and underground water can not be caused; on the other hand, the waste desulfurized slag contains far lower fluorine content than the national standard, and therefore can be used as a raw material for building materials. Therefore, the invention brings great long-term economic and social benefits for eliminating the fluorine pollution in advance and protecting the environment for enterprises.
2. The invention replaces fluorite material, mostly adopts industrial cycle comprehensive utilization raw materials, wherein the main additive containing Al, simple substance Si, alumina and the like is calcined at high temperature, has no water and high reaction activity, is easy to deoxidize and form slag, and the cost of the desulfurizer is lower than that of fluorite, so the cost of the blast furnace molten iron desulfurizer can be reduced by more than 20 percent by applying the technical scheme of the invention.
3. The metal aluminum and silicon in the raw materials of the additive are mainly subjected to the replacement oxidation reaction during CaO desulfurization in the desulfurization process and are partially combined with oxygen in the air to release heat, and the temperature of the discharged desulfurization waste gas is measured to be 40-50 ℃ higher than that of fluorite materials in practice, and meanwhile, the reduction of the molten iron temperature in the desulfurization process is less than that of the fluorite materials.
4. By applying the technical scheme of the invention, the properties and the fluidity of the desulfurized slag after the molten iron is desulfurized are basically the same as those of fluorite, and the desulfurized slag is easy to remove slag and is not sticky.
It should also be understood that, in the embodiments of the present invention, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.
While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (9)
1. The lime-based molten iron fluorine-free desulfurizer is characterized by comprising 60 to 72 weight percent of lime and 26 to 40 weight percent of desulfurization additive; caO in the lime is more than or equal to 85.0 percent, mgO is less than 5.0 percent, and SiO is contained in the lime 2 Less than or equal to 3.5 percent, less than or equal to 0.050 percent of S and less than or equal to 5 percent of ignition loss;
wherein the desulfurization additive comprises 45-63.5 percent of Al in percentage by weight 2 O 3 18 to 30 percent of Al, 2 to 8 percent of simple substance Si, 7 to 14 percent of MgO and 11 to 14 percent of SiO 2 ；
The desulfurization additive also comprises 1.5 to 10 weight percent of carbonate substances which are used as catalysts for desulfurization chemical reaction;
the carbonate material is BaCO 3 、MgCO 3 、NaHCO 3 A mixture of (a);
the carbonate is a powdery material, and the granularity is less than or equal to 0.8mm;
the aluminum and the silicon participate in deoxidation to generate alumina and silicon oxide, and simultaneously generate calcium aluminate and calcium silicate series compounds with lime; the added aluminum oxide and free lime also generate calcium aluminate, so that the molten iron desulphurization slag becomes mixed slag composed of multiple elements, and the corresponding reaction formula (5):
CaO(S)+xAl 2 O 3 (S)+ySiO 2 (S)＝CaO·xAl 2 O 3 ·ySiO 2 ⑤
the Al and the simple substance Si are used for reducing oxygen level in molten iron to generate alumina and silicon oxide, and the Al 2 O 3 And the alumina produced is used to produce with lime a low melting eutectic, i.e. a calcium aluminate phase of the following series: 3 CaO-Al 2 O 3 、CaO·6Al 2 O 3 、12CaO·7Al 2 O 3 、CaO·Al 2 O 3 、CaO·2Al 2 O 3 ；
The generated Al 2 O 3 And added Al 2 O 3 With generation of CaOThe calcium fluoroaluminate slag with different components can reduce CaO and SiO 2 2CaO SiO with a melting point of 2130 ℃ is formed 2 The desulfurization reaction is facilitated to be carried out;
the fluorine-free calcium aluminate slag increases the sulfur capacity of the slag, so that the distribution ratio of sulfur in metal and slag is increased from 500 to 1800 or above;
the Al is 2 O 3 Al, simple substance Si, mgO, siO 2 Is a powdery material which is fired at high temperature, the granularity of Al and simple substance Si is less than or equal to 3mm 2 O 3 MgO and SiO 2 The particle size of (A) is 60-100 meshes.
2. The fluorine-free desulfurizer for lime-based molten iron according to claim 1, wherein the content of carbonate material is 3 to 5%.
3. The lime-based molten iron fluorine-free desulfurizing agent according to claim 2, wherein the particle size of the carbonate substance is less than or equal to 0.6mm.
4. The lime-based molten iron fluorine-free desulfurizer as claimed in claim 2, wherein CaO in the lime is more than or equal to 90.0%, mgO is less than 5.0%, siO is 2 Less than or equal to 3.5 percent, less than or equal to 0.050 percent and less than or equal to 5 percent of scorching.
5. The fluorine-free desulfurizer for lime-based molten iron according to claim 4, wherein the activity of lime is not less than 320 at 40 ± 1 ℃ for 10min at 4 mol/ml.
The particle size of the lime is less than or equal to 1mm.
6. The lime-based molten iron fluorine-free desulfurizing agent according to claim 5, characterized in that,
the water content of the desulfurization additive is less than or equal to 0.5 percent.
7. The fluorine-free desulfurizing agent for lime-based molten iron according to any one of claims 1 to 6, wherein the desulfurizing additive utilizes a sulfur containing at least metallic Al,Elemental Si, al 2 O 3 The aluminum industrial byproduct is taken as a main raw material and is prepared by grinding, grading, adjusting the granularity and adding corresponding raw materials according to the limitation of the components.
8. The fluorine-free desulfurizer for lime-based molten iron according to claim 3, wherein the particle size of the carbonate material is 0.35 to 0.5mm.
9. A method for preparing the lime-based molten iron fluorine-free desulfurizing agent according to any one of claims 1 to 7, wherein the method comprises the following steps: and (2) selecting, crushing, grinding and screening all the components, weighing and proportioning according to respective granularity and weight percentage, and mixing to obtain the lime-based molten iron fluorine-free desulfurizer.
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| CN113403451A (en) * | 2021-05-24 | 2021-09-17 | 鞍钢股份有限公司 | Fluorine-free spherical slag for molten iron desulphurization and preparation method thereof |
| CN113481343A (en) * | 2021-07-05 | 2021-10-08 | 马鞍山钢铁股份有限公司 | High-efficiency KR desulfurizer as well as preparation method and use method thereof |
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| CN114875194B (en) * | 2022-04-25 | 2023-11-14 | 武汉钢铁有限公司 | Molten iron lime-based KR efficient desulfurizing agent and preparation method thereof |
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