Method for treating converter slag by using CO2 gas

Abstract

The invention provides a method for treating converter slag by using CO2 gas, and the principle of the method is as follows: CO2 with weak oxidizability is used for reacting with steel slag, weak magnetic FeO in the steel slag is converted into strong magnetic Fe3O4, and the strong magnetic Fe3O4 is not oxidized into weak magnetic Fe2O3; meanwhile, metal sulfide in the steel slag is converted into metal oxide, and then crushing and magnetic separation are conducted; and the screened iron component is returned for steelmaking, and the residual low-sulfur high-alkalinity slag is used as a substitute of quick lime for secondary utilization. According to the method, iron-containing components in the steel slag are oxidized into high-magnetism Fe3O4, so that the yield of iron reaches 94% or above, and iron-containing substances obtained through magnetic separation are directly sent to the rotary furnace to participate in smelting; meanwhile, metal sulfide in the steel slag is converted into metal oxide, sulfur is removed from the slag in the form of sulfur dioxide, the sulfur content of the high-alkalinity slag obtained after magnetic separation is extremely low, and the high-alkalinity slag can serve as a substitute of quick lime to act on the whole process of steel production to be secondarily utilized.

Description

Technical Field

[0001] The present invention relates to the technical field of converter steelmaking, in particular to a method of utilizing CO 2 A method for gas treatment of converter slag. Background Art

[0002] Converter slag, commonly known as steel slag, is the main solid waste in the steelmaking process. It contains oxides and sulfides of various elements. The slag has a high sulfur content and strong magnetite Fe 3 O 4 The low proportion leads to a low amount of iron that can be magnetically separated and recycled under low magnetic fields. Therefore, how to reduce the pollution of steel slag and improve the full utilization of steel slag is an urgent problem to be solved.

[0003] At present, the domestic method of processing steel slag is usually: after slagging, adopt the steel slag processing technology such as hot stuffing method, hot pouring method, drum method, etc., and after the steel slag is fully cooled and granulated, magnetic separation, classification and other operations are carried out to recover the iron in the slag, and the remaining slag is used for other purposes, such as recycling desulfurization slag for converters, or as building materials, etc. Chinese patent CN117654902A discloses a multi-stage sorting and recovery method for steel slag, which screens the steel slag at multiple levels according to the size of the steel slag particles and magnetically separates them, and according to the block size and quality of the steel slag, they are recycled into the converter, blast furnace and sintering process respectively. However, this method only separates the strong magnetic Fe in the slag. 3 O 4 The total iron content in converter slag, especially low carbon steel slag, is very high, a large part of which is Fe 2 O 3 Exist in the form of FeO and Fe 2 O 3 The magnetism is weak, which is not conducive to magnetic separation; and during the high-temperature transportation of steel slag, the strong magnetic Fe 3 O 4 It is also easily oxidized by oxygen to Fe 2 O 3 , a large amount of FeO and Fe 2 O 3 It needs a strong magnetic field to be recovered, and the iron recovery rate is lower than Fe 3 O 4 Low.

[0004] Converter slag is usually high-alkalinity slag, and the content of alkaline CaO+MgO in the slag is very high. If the steel plant adopts slag desulfurization, the S in the slag is mostly in the form of CaS. The S content in the slag is high, and directly reusing the slag will cause resulfurization, resulting in an increase in the sulfur content in the steel. For most types of steel, sulfur is a harmful element. Its distribution coefficient between solid and liquid is small, and it is easy to segregate during the solidification process. After solidification, it mainly exists in the steel in the form of aggregated FeS. It is easy to become "hot brittle" during high-temperature rolling, thereby deteriorating the plasticity, processability and weldability of the steel. Therefore, steel slag cannot be reused directly, and the S content in the slag needs to be strictly controlled during reuse. Chinese patent CN112899428A discloses a method for recycling and desulfurizing KR desulfurized slag. In the process of pouring the KR desulfurized slag out of the slag pot, CO is sprayed into the slag. 2 gas, which rapidly cools the KR desulfurization slag and 2 After the gas reaction, it fully expands and splits into small particles. The desulfurized slag after desulfurization is recycled and mixed with the desulfurizer as the desulfurizer of the KR desulfurization method. However, this method ignores the thermodynamic conditions in the desulfurization process. 2 When the reaction temperature is lower than 1000°C, the sulfur removal rate in the slag is only 40%.

[0005] In summary, a method to extract as much iron as possible from steel slag and make other substances in the steel slag available for secondary use has always been the goal of domestic scientific researchers. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of low utilization rate of domestic steel slag, high content of weak magnetite in slag that has not been magnetically separated, and environmental and economic benefits caused by accumulation of large amount of steel slag in China, and propose a method of utilizing CO 2 A method for gas treatment of converter slag.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A method of utilizing CO 2 The method of treating converter slag with gas is based on the principle of using weakly oxidizing CO 2 React with steel slag to convert the weakly magnetic Fe 2 O 3 Transformed into strong magnetic Fe 3 O 4 At the same time, the metal sulfides in the steel slag are converted into metal oxides, and then crushed and magnetically separated; the screened iron components are returned to steelmaking, and the remaining low-sulfur and high-basicity slag is used in steel production as a substitute for quicklime.

[0009] The use of CO 2 The method for treating converter slag with gas comprises the following steps:

[0010] S1. Transfer the converter slag to a high temperature atmosphere furnace and introduce CO into the high temperature atmosphere furnace. 2 gas, making slag and CO 2 to respond adequately;

[0011] S2, cooling the high temperature liquid slag;

[0012] S3. Crushing the steel slag and subjecting it to multi-stage magnetic separation as required; the magnetic material can be used as raw material for converter smelting, and the remaining material that has not been magnetically separated is high-basicity slag, which can be used as a substitute for quicklime.

[0013] In the step S1, hot slag from the converter is mixed with cold slag stored in the steel plant as a processing raw material to fully utilize the waste heat of the hot slag.

[0014] The step S1 specifically includes the following steps:

[0015] S11, pouring the converter slag into a slag pot, transporting the hot slag and the cold slag to a high-temperature atmosphere furnace, mixing and heating them to 1200±50°C in the high-temperature atmosphere furnace;

[0016] S12, introduce CO into the high temperature atmosphere furnace 2 After the gas is introduced, the atmosphere furnace is turned over regularly to make the slag and CO 2 The steel slag is obtained by sufficient reaction; the reaction time is not less than 40 minutes.

[0017] In the step S11, the mass ratio of the hot slag to the cold slag is 2 to 4:1, preferably 3:1.

[0018] In step S12, CO 2 The gas flow rate is 1.0NM 3 / (t·min)~1.5NM 3 / (t·min), preferably 1.2NM 3 / (t·min).

[0019] In actual production, pct CO can be used 2 / pct CO>200、SO 2 Flue gas with a content of less than 0.2% and an oxygen content of <1% replaces CO 2 Pass it into the atmosphere furnace to react with the slag.

[0020] The crushing and magnetic separation in step S3 is arranged in multiple stages. As the crushing particle size gradually decreases, the magnetism of the magnetic separation gradually increases. The iron recovery rate after magnetic separation is not less than 94%.

[0021] Generally speaking, after the steel slag is crushed to -75mm and then magnetically separated, there is about 4% to 6% of metallic iron in the tailings; after crushing to -35mm and then magnetically separated, there is about 3% to 5% of metallic iron in the tailings; when crushed to -10mm and then magnetically separated, the metallic iron content in the tailings can be reduced to about 1%. Steel slag is usually crushed to 75mm to 5mm and subjected to multi-stage magnetic separation.

[0022] The high basicity slag has a basicity of not less than 3.0 and can be used in sintering batching, molten iron desulfurization, steelmaking, refining and other processes.

[0023] Through the above technical solution, the beneficial effects obtained by the present invention are:

[0024] The invention discloses a method for utilizing CO 2 A method for treating converter slag with gas to oxidize the weakly magnetic FeO component in the slag into highly magnetic Fe 3 O 4 , making it easy to magnetically separate and control the strong magnetic Fe 3 O 4 Will not be oxidized to weakly magnetic Fe 2 O 3 , effectively improving the iron recovery rate, the iron recovery rate after magnetic separation is not less than 94%. At the same time, the metal sulfides in the steel slag are converted into metal oxides, and sulfur is removed from the slag in the form of sulfur dioxide, so that the sulfur content of the high-basicity slag after magnetic separation is extremely low, not exceeding 0.08wt%. After being treated by the method of the present invention, a large amount of iron in the steel slag is magnetically separated and can be directly sent back to the converter for smelting; the remaining high-basicity slag can be used as a substitute for quicklime and act on the whole process of steel production for secondary use, so that waste solids do not leave the factory, the purchase of quicklime / limestone is reduced, and the production cost is greatly reduced.

[0025] The present invention adopts CO 2 As a treatment gas, the gas has moderate oxidizing property, low cost and is environmentally friendly. 2 / pct CO ratio is greater than 200, SO 2 The content is lower than 0.2% and the oxygen content is <1%, so it can also be used as treatment gas, which not only realizes the effective treatment of converter slag, but also makes full use of the composition and waste heat of flue gas, greatly reducing the pressure of environmental protection treatment.

[0026] The method of the present invention adopts a mixture of hot slag and cold slag as raw materials, which can fully utilize the waste heat of the hot slag, reduce heating energy consumption, and shorten the heating time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The main components of steel slag and CO calculated by Factsage8.1 2 Plot of the actual Gibbs free energy change ΔG for a reaction. DETAILED DESCRIPTION

[0028] The present invention is described in further detail below.

[0029] The main components of converter slag include oxides and sulfides of various elements such as Fe, Ca, Mg, and Si. Among them, Fe is mostly in the form of FeO, Fe 2 O 3 , FeS, etc., and a small amount exists in the form of Fe 3 O 4 forms; Ca and Mg mostly exist in the form of CaO, CaS, MgO, and MgS, and a small amount exists in the form of other compounds. The slag is directly crushed and magnetically separated, and a large amount of weakly magnetic Fe cannot be screened and remains in the slag. The magnetic field strength needs to be increased to ensure the magnetic separation rate of iron-containing materials; and the remaining slag cannot be used in steel smelting due to its high S content and harmful to steel. It can only be piled up or sold as construction materials. Therefore, how to extract the iron component in the slag as much as possible, return it to smelting and avoid waste, and at the same time, improve the remaining slag composition so that it can be fully reused in the factory as much as possible, reduce environmental pressure and production costs, and achieve no waste solid out of the factory, is a difficulty in current research.

[0030] Based on the above problems, the present invention provides a method for utilizing CO 2 Gas treatment method for converter slag. The principle is to use weakly oxidizing CO 2 Reacts with steel slag to convert the weakly magnetic FeO in the steel slag into strongly magnetic Fe 3 O 4 , and strong magnetic Fe 3 O 4 Will not be oxidized to weakly magnetic Fe 2 O 3 ; At the same time, the metal sulfides in the steel slag are converted into metal oxides, which are then crushed and magnetically separated; the screened iron components are returned to steelmaking, and the remaining low-sulfur and high-basicity slag is used as a substitute for quicklime in various steel production processes.

[0031] The main reaction equation is:

[0032] Fe+CO 2 →FeO+CO

[0033] FeS+3CO 2 →FeO+3CO+SO 2

[0034] CO 2 +3FeO→Fe 3 O 4 +CO

[0035] CaS+CO2 →CaO+SO 2

[0036] MgS+CO 2 →MgO+SO 2

[0037] The recovery of Fe in slag mainly relies on magnetic separation. Therefore, Fe oxides / sulfides are converted into Fe with stronger magnetic properties. 3 O 4 , and prevent strong magnetic Fe 3 O 4 Will not be oxidized to weakly magnetic Fe 2 O 3 It becomes a key factor affecting the recovery rate of slag iron. If the oxidizing property is too low, the conversion cannot be completed; if the oxidizing property is too high (such as oxygen), Fe 3 O 4 Further oxidation to Fe 2 O 3 , the magnetic property becomes lower and is more unfavorable for magnetic separation; the present invention selects CO 2 As an oxidant, its oxidizing property is moderate. At 1200℃±50℃, it can only oxidize Fe, FeO, etc. into Fe 3 O 4 Since all Fe is in the form of strong magnetic Fe 3 O 4 The majority of Fe 3 O 4 After screening, the iron recovery rate can be as high as over 94%.

[0038] pass Figure 1 From the Gibbs free energy change ΔG diagram, it can be seen that the S in the slag is mainly in the form of CaS, with a small amount of FeS and MgS. It can be seen that when the temperature is greater than 1100°C, CaS, FeS, MgS and CO 2 The ΔG of the reaction to form oxides is negative, CO 2 Can S 2- Oxidized to SO 2 Gas, thereby reducing the S content in the slag. 2 The reaction generates FeO, FeO and CO 2 The reaction generates Fe 3 O 4 The ΔG of the reactions is also negative, but Fe 3 O 4 With CO 2 The reaction generates Fe 2 O 3The ΔG of the reaction is greater than 40 kJ / mol, indicating that under this reaction condition, most of the Fe and FeO will be oxidized to Fe 3 O 4 , while Fe 3 O 4 Will not be oxidized to weakly magnetic Fe 2 O 3 .

[0039] The use of CO 2 The method for treating converter slag with gas comprises the following steps:

[0040] S1. Transfer the converter slag to a high temperature atmosphere furnace and introduce CO into the high temperature atmosphere furnace. 2 gas, making slag and CO 2 to respond adequately;

[0041] S2, cooling the high temperature liquid slag to below 100°C;

[0042] S3. Crushing the steel slag and subjecting it to multi-stage magnetic separation as required; the magnetic material can be used as raw material for converter smelting, and the remaining material that has not been magnetically separated is high-basicity slag, which can be used as a substitute for quicklime.

[0043] In step S1, in order to make full use of the waste heat resources of hot slag and reduce energy consumption, hot slag from converter (about 1400°C) and cold slag stored in steel mill are mixed as processing raw materials. After the liquid hot slag is mixed with the solid cold slag, it turns into a relatively viscous liquid, which is easy to stir and turn.

[0044] The step S1 specifically includes the following steps:

[0045] S11, pouring the converter slag into the slag pot, transporting the hot slag and the cold slag to the high temperature atmosphere furnace, mixing them evenly in the high temperature atmosphere furnace, and heating them to 1200±50℃;

[0046] S12, introduce CO into the high temperature atmosphere furnace 2 After the gas is introduced, the atmosphere furnace is turned over regularly to make the slag and CO 2 The steel slag is obtained by sufficient reaction; the reaction time is not less than 40 minutes.

[0047] In the step S11, the mass ratio of the hot slag to the cold slag is 2 to 4:1, preferably 3:1, and the reaction temperature can be basically reached after mixing without excessive additional heating consumption.

[0048] In step S12, CO 2 The gas flow rate is 1.0NM 3 / (t·min)~1.5NM 3 / (t·min), preferably 1.2NM 3 / (t·min). During the reaction process, the high-temperature atmosphere in the furnace is a carbon dioxide atmosphere, and carbon dioxide is introduced continuously and stably to reduce the contact between slag and oxygen and avoid excessive oxidation.

[0049] The turning frequency of the high temperature atmosphere furnace can be adjusted according to the slag processing amount, usually not less than 5r / min, preferably 5r / min, to ensure sufficient contact between the slag and carbon dioxide. In addition, after the introduction of carbon dioxide, the slag may expand and break, and timely turning can control the slag breakage and improve safety.

[0050] It should be noted that in actual production, pct CO 2 / pct CO>200、SO 2 Flue gas with oxygen content less than 0.2% and oxygen content <1% replaces CO 2 It is used as an oxidant to react with the slag. These flue gases can come from coke ovens, hot furnaces, boilers and other facilities. While oxidizing the slag, it can also make full use of the components and waste heat of the flue gas, reduce heat consumption and reduce costs.

[0051] In step S2, after the high-temperature liquid slag is cooled to room temperature, a slag sample is taken to determine the slag desulfurization rate. The desulfurization rate calculation formula is:

[0052] R=(S 0 -S) / S 0 *100%

[0053] In the formula, S 0 is the initial sulfur content in the slag, expressed in mass fraction;

[0054] S is the sulfur content in the slag after desulfurization, expressed in mass fraction;

[0055] R is the desulfurization rate, in %.

[0056] Generally speaking, the desulfurization rate of the slag after the reaction is not less than 92%.

[0057] During the cooling process of liquid slag, it is best to maintain a carbon dioxide atmosphere or nitrogen atmosphere to minimize the contact between slag and oxygen and avoid Fe 3 O 4 If it is impossible to isolate the slag from oxygen, the slag can be placed in a slag pot and left to cool so that the oxidation reaction only occurs on the surface of the liquid slag.

[0058] The crushing and magnetic separation in step S3 is set in multiple stages. As the crushing particle size gradually decreases, the magnetism of the magnetic separation gradually increases, so as to fully recover the iron components in the slag. The recovered magnetic iron material can be directly recovered as a converter smelting raw material.

[0059] After magnetic separation, the iron recovery rate is calculated as follows:

[0060] H=(T.Fe 0 -T.Fe) / T.Fe 0 *100%.

[0061] In the formula, T.Fe 0 is the initial total iron content in the slag, expressed in mass fraction;

[0062] T.Fe is the total iron content in the slag after the reaction is completed and magnetic separation is performed, in mass fraction;

[0063] H is the iron recovery rate after magnetic separation, in %.

[0064] Generally speaking, the recovery rate of iron in the slag is not less than 94% when the method of the present invention is used for treatment.

[0065] The high-basicity slag remaining after magnetic separation usually has a basicity of no less than 3.0, and its main components are CaO, MgO, etc., with extremely low sulfur content. It can be used as a substitute for quicklime or limestone in the entire process of steel smelting. Specifically, it includes but is not limited to the following:

[0066] 1. Used as sintering ingredients to adjust the pH of sintering materials and enhance the strength of sintering materials;

[0067] 2. Used as a desulfurizer to desulfurize molten iron during ironmaking;

[0068] 3. Used as slag-making material in converter steelmaking and refining;

[0069] 4. Used as slag regulating agent in slag splashing furnace protection section;

[0070] etc.

[0071] It should be noted that, since there is Si component in the slag itself, during the reaction process, Ca not only exists as a single phase of CaO, but also reacts with Si to generate multiple complex phases, such as calcium silicate, dicalcium silicate, tricalcium silicate, etc. These complex phase components are very fusible, and compared with adding quicklime, the melting time after using the high basicity slag of the present invention is significantly shortened.

[0072] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] Example 1

[0074] In this embodiment, a method of using CO 2 The method of gas treatment of converter slag is carried out in a high-temperature atmosphere rotary furnace. The specific experimental steps are as follows:

[0075] S1. After the converter is finished tapping, pour the converter slag into the slag pot, and use the slag pot car to transport the converter slag to the high-temperature atmosphere furnace.

[0076] S2. Prepare cold blast furnace slag in a ratio of 3:1 between high temperature slag and cold slag. First, put the cold slag into the high temperature atmosphere furnace, and then pour in the hot slag. At this time, the hot slag is hot and will wash the cold slag during the pouring process, which is conducive to faster mixing of the two slags. After mixing, measure the S content and T.Fe content in the slag.

[0077] S3, after the hot slag and the cold slag are fully mixed, the temperature is raised to 1200℃. When the temperature rises to 1200℃, 3 / (t·min) gas flow rate into CO 2 The atmosphere furnace is turned over at 5r / min while blowing in the gas for 40 minutes. The atmosphere furnace is stirred during the blowing process to desulfurize the slag and oxidize FeO to Fe 3 O 4 It provides good kinetic conditions, which can make the reaction more complete and the sulfur in the slag more completely removed, and can also increase the magnetic separation yield of iron in the slag.

[0078] S4. Rapidly cool the high-temperature liquid slag. After the slag temperature reaches room temperature, take a sample to measure the sulfur content in the slag, and then calculate the desulfurization rate.

[0079] S5. Crushing the steel slag to 75mm-5mm and multi-stage magnetic separation as needed, and calculating the iron recovery rate. The magnetic material can be used as raw material for converter smelting, and the remaining material that has not been magnetically separated is high-basicity slag, which can be used as converter slag for secondary use.

[0080] Using the above method, three batches of experiments were carried out in parallel, which were marked as Example 1-1, Example 1-2, and Example 1-3 respectively.

[0081] Comparative Example 1

[0082] This comparative example is a comparative example of Example 1, except that the gas blown into the high temperature atmosphere furnace is O 2 , the specific steps are:

[0083] S1. After the converter is finished tapping, pour the converter slag into the slag pot, and use the slag pot car to transport the converter slag to the high-temperature atmosphere furnace.

[0084] S2. Prepare cold blast furnace slag in a ratio of 3:1 between high temperature slag and cold slag. First, put the cold slag into the high temperature atmosphere furnace, and then pour in the hot slag. At this time, the hot slag is hot and will wash the cold slag during the pouring process, which is conducive to faster mixing of the two slags. After mixing, measure the S content and T.Fe content in the slag.

[0085] S3, during the mixing of hot slag and cold slag, open the high temperature atmosphere furnace and raise the temperature to 1200℃. When the temperature rises to 1200℃, 3 / (t·min) gas flow rate into O 2 The gas was blown in, and the atmosphere furnace was turned at 5 r / min for 40 minutes.

[0086] S4. Rapidly cool the high-temperature liquid slag. After the slag temperature reaches room temperature, take samples to determine the sulfur content in the slag, and then calculate the desulfurization rate.

[0087] S5. Crushing the steel slag and performing multi-stage magnetic separation as required, and calculating the iron recovery rate. The magnetic material can be used as raw material for converter smelting, and the remaining material that has not been magnetically separated is high-basicity slag, which can be used as converter slag for secondary use.

[0088] Using the above method, three batches of experiments were carried out in parallel, which were marked as Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3, respectively.

[0089] The three batches of experiments in Example 1 were compared with the three batches of experiments in Comparative Example 1. The reaction parameters were compared in Table 1, and the slag components before and after the reaction were compared in Table 2.

[0090] Table 1 Condition parameters

[0091] Heat <![CDATA[CO 2 Air flow]]> <![CDATA[O 2 Air flow]]> Slag Desulfurization rate Iron recovery rate Example 1-1 <![CDATA[1.2NM 3 / t·min]]> 0 Mixed slag 92.10％ 95.0％ Example 1-2 <![CDATA[1.2NM 3 / t·min]]> 0 Mixed slag 92.95％ 95.4％ Examples 1-3 <![CDATA[1.2NM 3 / t·min]]> 0 Mixed slag 91.89％ 94.7％ Example average value --- --- --- 92.31％ 95.03％ Comparative Example 1-1 0 <![CDATA[1.2NM 3 / t·min]]> Mixed slag 93.68％ 72.0％ Comparative Example 1-2 0 <![CDATA[1.2NM 3 / t·min]]> Mixed slag 95.05％ 70.8％ Comparative Examples 1-3 0 <![CDATA[1.2NM 3 / t·min]]> Mixed slag 93.89％ 71.4％ Comparison ratio average --- --- --- 94.21％ 71.4％

[0092] Table 2 Slag composition before and after reaction of Comparative Example 1 and Example 1 is as follows (unit, wt%)

[0093]

[0094]

[0095] As can be seen from the table above, the T.Fe content of the original converter slag is as high as 18.23%, and the basicity is also as high as 3.46. If the converter slag can be effectively recycled, the economic benefits of the enterprise will be greatly improved. 3 O 4 The mass fraction of FeO·Fe 2 O 3 Although the converter slag has a high content of valuable components, it cannot be directly returned to the furnace for secondary use because it contains 0.95% S by mass.

[0096] It can be seen from the data in Table 1 that the average desulfurization rate of the three parallel tests of Example 1-1, Example 1-2, and Example 1-3 is 92.31%, and the average iron recovery rate is 95.03%; the average desulfurization rate of the three parallel tests of Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3 is 94.21%, and the average iron recovery rate is 71.4%. Compared with the comparative example, although the average desulfurization rate of the embodiment is slightly lower than that of the comparative example, the average iron recovery rate of the embodiment is as high as 95.03%, which is much higher than that of the comparative example, which fully verifies that the oxygen oxidizing property is too strong and the Fe in the slag after the reaction is mainly in the form of weakly magnetic Fe 2 O 3 The presence of Fe in the carbon dioxide oxidation reaction results in a large amount of iron-containing substances being unable to be recovered by magnetic separation. 3 O 4 Most of the iron-containing substances are successfully magnetically separated and recovered, and the iron recovery rate is greatly improved.

[0097] It can be seen from the data in Table 2 that after the reaction, the S content in the slag of the embodiment and the comparative example is reduced to less than 0.08wt%. Generally speaking, the sulfur content in the quicklime purchased by the steel plant is controlled within 0.2%. When the S content in the slag after treatment is lower than 0.08%, it can replace lime in the sintering ironmaking or steelmaking process to adjust the basicity, desulfurize and remove inclusions.

[0098] However, it should be noted that the treated slag can, to a certain extent, replace quicklime to adjust alkalinity, desulfurize, and remove inclusions. At the same time, it can improve the utilization rate of steel slag in steel mills and reduce the environmental pressure caused by solid waste stacking.

[0099] Comparative Example 2

[0100] This comparative example is a comparative example of Example 1, and the difference is that the slag sample added to the high-temperature atmosphere furnace is cold slag, and the main comparison is the utilization of the slag waste heat and the heating time of the high-temperature atmosphere furnace after the cold slag is placed at high temperature. The specific steps are:

[0101] S1. After the converter is finished tapping, pour the converter slag into the slag pot, and use the slag pot car to transport the converter slag to the high-temperature atmosphere furnace.

[0102] S2. Put the cold steel slag into a high-temperature atmosphere furnace, take a slag sample, and determine the S content and T.Fe content in the slag.

[0103] S3, raise the temperature to 1200℃, when the temperature rises to 1200℃, at 1.2NM 3 / (t·min) gas flow rate into CO 2 The gas was blown in, and the atmosphere furnace was turned at 5 r / min for 40 minutes.

[0104] S4. Rapidly cool the high-temperature liquid slag. When the slag reaches room temperature, take a sample to measure the sulfur content in the slag, and then calculate the desulfurization rate.

[0105] S5. Crushing the steel slag and performing multi-stage magnetic separation as required, and calculating the iron recovery rate. The magnetic material can be used as raw material for converter smelting, and the remaining material that has not been magnetically separated is high-basicity slag, which can be used as converter slag for secondary use.

[0106] The reaction parameters of Comparative Example 2 and Example 1 are shown in Table 3.

[0107] Table 3 Experimental control parameters of Example 1 and Comparative Example 2

[0108]

[0109] Compared with Example 1, Comparative Example 2 selects two different slag samples. Example 1 uses mixed slag, which can recycle the waste heat of steel slag and is assisted by heating in a high-temperature atmosphere furnace; Comparative Example 2 uses cold slag and completely relies on heating in a high-temperature atmosphere furnace.

[0110] The slag tapping temperature of converter slag is about 1400℃. The specific heat capacities of solid and liquid slags are similar. The heat loss of the two slags is 10% after they are fully mixed. The temperature of the two slags after they are fully mixed is about 845℃. The specific heat capacity of converter slag is about 1.25KJ / (kg·℃). Therefore, assuming that the mixed mass of slag is 1000kg, the slag heat that can be saved is Q=c*m 总 *(tt 0 )=1.025*10 6 J;

[0111] Where, Q is the saved heat, in joules;

[0112] m is the total slag mass in kilograms;

[0113] t is the temperature of the two slags after mixing, in °C;

[0114] t 0This is the temperature of the cold slag before mixing, which can be regarded as 25℃.

[0115] Therefore, the slag heat utilization of Example 1 is 1.025*10 3 kJ / kg, the time for the high temperature atmosphere furnace to heat up to 1200℃ is only 10min; while the time for the high temperature atmosphere furnace in comparative example 2 to heat up to 1200℃ is 30min. Compared with the two, the use of mixed slag can save 20min of heating time, which can improve the rhythm of converter slag recovery in steel plants; at the same time, it also greatly reduces the heating energy consumption of the high temperature atmosphere furnace, and realizes the full utilization of the waste heat of slag.

[0116] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for treating converter slag using CO2 gas, characterized in that: Weakly oxidizing CO2 is used to react with steel slag to convert the weakly magnetic FeO in the steel slag into strongly magnetic Fe3O4, and the strongly magnetic Fe3O4 will not be oxidized to weakly magnetic Fe2O3; at the same time, the metal sulfides in the steel slag are converted into metal oxides, which are then crushed and magnetically separated; the screened iron components are returned to steelmaking, and the remaining low-sulfur and high-alkalinity slag is reused as a substitute for quicklime.

2. The method for treating converter slag using CO2 gas according to claim 1, characterized in that The following steps are involved: S1. Transfer the converter slag to a high temperature atmosphere furnace, and introduce CO2 gas into the high temperature atmosphere furnace to allow the slag and CO2 to react fully; S2, cooling the high temperature liquid slag; S3. Crushing the steel slag and subjecting it to multi-stage magnetic separation as required; the magnetic material can be used as raw material for converter smelting, and the remaining material that has not been magnetically separated is high-basicity slag, which can be used as a substitute for quicklime.

3. The method for treating converter slag using CO2 gas according to claim 2, characterized in that: In the step S1, hot slag from the converter is mixed with cold slag stored in the steel plant as a processing raw material to fully utilize the waste heat of the hot slag.

4. The method for treating converter slag using CO2 gas according to claim 3, characterized in that: The step S1 specifically includes the following steps: S11, pouring the converter slag into a slag pot, transporting the hot slag and the cold slag to a high-temperature atmosphere furnace, mixing and heating them to 1200±50°C in the high-temperature atmosphere furnace; S12. Introduce CO2 gas into the high-temperature atmosphere furnace. After the gas is introduced, turn the atmosphere furnace over regularly to allow the steel slag to fully react with CO2; the reaction time shall not be less than 40 minutes.

5. The method for treating converter slag using CO2 gas according to claim 4, characterized in that: In the step S11, the mass ratio of the hot slag to the cold slag is 2-4:

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6. The method for treating converter slag using CO2 gas according to claim 4, characterized in that: In step S12, the flow rate of CO2 gas is 1.0 NM 3 / (t·min)~1.5 NM 3 / (t·min).

7. The method for treating converter slag using CO2 gas according to claim 2, characterized in that: Flue gas with pctCO2 / pct CO>200, SO2 content less than 0.2%, and oxygen content less than 1% can be introduced into the atmosphere furnace instead of CO2 to react with the slag.

8. The method for treating converter slag using CO2 gas according to claim 2, characterized in that: The crushing and magnetic separation in step S3 are arranged in multiple stages. As the crushing particle size gradually decreases, the magnetism of the magnetic separation gradually increases; the iron recovery rate after magnetic separation is not less than 94%.

9. The method for treating converter slag using CO2 gas according to claim 2, characterized in that: The high-basicity slag has a basicity of not less than 3.0 and a sulfur content of less than 0.1%, and can be used in sintering batching, molten iron desulfurization, steelmaking, refining and other processes.

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