Wet process nickel extraction and tailing recovery ironmaking coupling method and system and pellets prepared by using method

Abstract

The invention relates to a coupling method and system for wet nickel extraction and tailing recovery ironmaking and pellets prepared through the method, and belongs to the technical field of metallurgy. The method comprises the four steps of wet-process nickel extraction, tailing agglomeration, blast furnace smelting and molten iron treatment, specifically, after the wet-process nickel extraction tailings are dried and smashed, pelletizing is conducted on the wet-process nickel extraction tailings, quick lime and dolomite according to the specific alkalinity and the MgO content ratio, and high-strength low-sulfur pellets are prepared through high-temperature roasting; and the pellets are matched with high-alkalinity sinter to be smelted in a blast furnace, efficient output of molten iron is achieved through slag component optimization control, and cement is prepared from blast furnace slag. The system comprises a nickel extraction unit, an agglomeration unit, a smelting unit and a product treatment unit. According to the method, the agglomeration problem caused by low grade, high sulfur and fine granularity of the wet tailings is solved, the synergistic utilization of nickel and iron resources is realized, the solid waste stockpiling pollution is greatly reduced, and the method has remarkable environmental and economic benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and relates to a coupling method and system for wet nickel extraction and iron smelting from tailings, and a pellet prepared by using the method. Background Art

[0002] Due to its high nickel extraction rate and the ability to recover associated valuable metals, the wet nickel extraction process has become the mainstream technology for nickel resource development. However, the wet nickel extraction tailings produced by this process have long faced the problem of large-scale resource utilization due to their low iron grade (30%-55%), high sulfur content (>1%), high water content (about 30%) and fine particle size. In the prior art, such tailings are usually stored in tailing ponds, which not only occupy land but also easily cause environmental pollution, and at the same time cause serious waste of iron resources. Although the blast furnace iron smelting process can theoretically process iron-containing materials, the physical properties of wet tailings are significantly different from those of traditional iron ore powder: their low grade, high sulfur and fine particle size characteristics make it difficult for conventional pelletizing processes to prepare pellets or sintered ores that meet the requirements of blast furnace smelting. If the existing pelletizing process is directly applied to wet tailings, problems such as insufficient green ball strength, high roasting powdering rate and difficult sulfur removal are likely to occur, and adding binders such as bentonite will further increase costs and introduce impurities. In addition, non-blast furnace iron smelting processes (such as direct reduction methods) cannot achieve efficient treatment of wet tailings due to scale limitations and cost disadvantages. Therefore, developing a pelletizing process adapted to the characteristics of wet nickel extraction tailings and coupling it with the blast furnace smelting system has become the key to solving the problems of solid waste resource utilization and environmental pollution in wet nickel-iron production. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a coupling method and system for wet nickel extraction and iron smelting from tailings, and a pellet prepared by using the method, to provide a pelletizing process adapted to the characteristics of wet nickel extraction tailings, and couple it with the blast furnace smelting system to synchronously solve the problems of solid waste resource utilization and environmental pollution in wet nickel-iron production.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A coupling method for wet nickel extraction and iron smelting from tailings, comprising the following steps:

[0006] Wet nickel extraction process: The nickel ore is successively subjected to pretreatment, acid leaching, separation, purification, precipitation, filtration and drying to obtain a nickel product and wet nickel extraction tailings;

[0007] Tailings treatment process: The wet nickel extraction tailings produced by the "wet nickel extraction process" are dried and prepared into fine powder. The fine powder is used alone or mixed with ordinary iron ore powder, and then mixed with quicklime and dolomite, and water is added to prepare green balls; The green balls are preheated and roasted to obtain pellets.

[0008] Blast furnace smelting process: Pellets prepared by the "tailings treatment process" are added to the blast furnace together with at least one of high-alkali sinter, limestone, and dolomite for smelting to obtain molten iron.

[0009] Subsequent treatment of molten iron: The molten iron obtained from the "blast furnace smelting process" is used to produce steel products through steelmaking and rolling processes, and the blast furnace slag is used to prepare cement.

[0010] Optionally, the iron content of the wet nickel extraction tailings used in the "tailings treatment process" is ≥ 45%; if the iron content is lower than 45%, the tailings need to be magnetically reduced roasted and separated by magnetic separation to increase the iron content to more than 45%.

[0011] Optionally, the green balls prepared in the "tailings treatment process" meet the following performance indicators:

[0012] Drop strength at 0.5 m > 10 times, compressive strength of green balls > 20 N, bursting temperature of green balls > 400 °C;

[0013] The compressive strength of the pellets ≥ 2000 N, the low-temperature reduction degradation index RDI +3.15 ≥ 85%, and the reduction index ≥ 55%.

[0014] Optionally, the roasting temperature range of the pellets in the "tailings treatment process" is 1220 °C - 1280 °C, and the sulfur removal rate during roasting is ≥ 95%.

[0015] Optionally, the blast furnace smelting process in the "blast furnace smelting process" also includes adding one or more of ordinary sinter, ordinary lump ore, or ordinary pellets to improve the in-furnace grade.

[0016] Optionally, the Cr content in the molten iron in the "blast furnace smelting process" is 1.75% - 2.65%, which is preferably used to produce stainless steel products; if other steel products need to be produced, the Cr in the molten iron needs to be removed in the steelmaking refining process.

[0017] A system for implementing the above coupling method includes:

[0018] Wet nickel extraction unit: including an ore pretreatment device, an acid leaching tank, a separation device, a purification device, a sedimentation tank, a filter press, and a drying equipment connected in sequence;

[0019] Tailings treatment unit: A drying kiln connected to the wet nickel extraction unit for drying and crushing the tailings; a mixing device for mixing the dried tailings with quicklime and dolomite in proportion; a pelletizing machine for adding water to the mixture to form pellets; a preheating device and a roasting kiln for preheating and roasting the green balls;

[0020] Blast furnace smelting unit: It includes a blast furnace, a batching device and a slag treatment device. The feed inlet of the blast furnace is connected to the roasting kiln of the tail slag treatment unit, and is used to receive pellet ore and add limestone, dolomite or high-alkalinity sintered ore;

[0021] Hot metal treatment unit: A steelmaking furnace and rolling equipment connected to the blast furnace, and a cement production device for treating blast furnace slag.

[0022] Optionally, a water addition device is provided between the mixing device and the pelletizer to control the water addition amount of 15%-22%; the temperature control system of the roasting kiln is set at 1220°C - 1280°C.

[0023] Optionally, the tail slag treatment unit further includes a magnetic separator, which is used for magnetization reduction roasting and magnetic separation treatment of tail slag with an iron grade lower than 45%.

[0024] A pellet ore prepared according to the above method, and its composition meets:

[0025] Alkalinity ≤ 1, MgO content ≤ 2%, sulfur content ≤ 0.12%, and compressive strength ≥ 2000N, low-temperature reduction degradation index RDI +3.15 ≥ 85%.

[0026] The beneficial effects of the present invention are as follows:

[0027] Technological innovation:

[0028] Pelletizing process breakthrough: By limiting the tail slag fineness (-200 mesh > 80%), alkalinity (≤ 1) and MgO content (≤ 2%), combined with the addition of no bentonite and a specific roasting temperature (1220°C - 1280°C), the technical bottlenecks such as low green ball strength, difficult sulfur removal and high roasting powdering rate of wet tail slag are solved, and high-quality pellets with a compressive strength ≥ 2000N and RDI + 3.15 ≥ 85% are prepared to meet the requirements of blast furnace smelting.

[0029] Precise control of slag composition: By controlling the slag alkalinity (1 - 1.15) and MgO / Al 2 O 3 ratio (0.45 - 0.65), the slag fluidity and desulfurization efficiency are optimized, and the problems of large slag volume and high smelting difficulty caused by low grade of wet tail slag are overcome, ensuring the smooth operation of the blast furnace.

[0030] Comprehensive utilization of resources:

[0031] Efficient extraction of nickel and iron dual resources is realized. The iron recovery rate in wet tail slag is > 90%, and at the same time, the pellet roasting desulfurization rate is > 95%, significantly reducing sulfur pollution.

[0032] All the blast furnace slag is used for cement production, forming an "extracting nickel - iron smelting - building materials" industrial chain, and the comprehensive utilization rate of solid waste reaches 100%.

[0033] Environmental benefits:

[0034] It completely replaces the storage of tailings ponds, reduces land occupation and the risk of heavy metal leaching. It can process wet tailings in the scale of millions of tons per year, and reduce emissions of harmful gases such as SO 2 etc.

[0035] Improved economy:

[0036] Using waste slag to replace part of iron ore powder reduces raw material costs; the molten iron is preferentially used for stainless steel production to increase the added value of products.

[0037] Examples show that after adopting this process, the theoretical coke ratio of the blast furnace only increases by 10% - 15% compared with the conventional process. However, combined with the zero - cost advantage of tailings slag, the overall economic benefits are significant.

[0038] Process compatibility:

[0039] The system design is flexible, which can adapt to tailings slags with different grades (a magnetic separator needs to be added when magnetic separation and purification are required), and can be mixed with ordinary iron ore powder to adjust the properties of pellets, expanding the application scope of the process.

[0040] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Description of the drawings

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, where:

[0042] Figure 1 is the process flow chart of one of the embodiments of this solution. Specific implementation manners

[0043] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.

[0044] Among them, the attached drawings are only for illustrative purposes, showing only schematic diagrams rather than physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the attached drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0045] In the attached drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the attached drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the attached drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0046] Please refer to Figure 1 , the purpose of the present invention is to provide a coupling method for wet nickel extraction and efficient recovery of iron from tailings. The coupling method for wet nickel extraction and efficient recovery of iron from tailings is as follows:

[0047] The technological process of wet nickel extraction includes ore pretreatment, acid leaching, separation, purification, precipitation, filtration and drying, and nickel products can be obtained. The tailings after wet nickel extraction are a kind of metallurgical solid waste containing iron, with low iron grade, high sulfur content and high water content. After drying in a drying kiln, it needs to be prepared into fine powder with a particle size of -200 mesh accounting for more than 80%. The prepared pellet ore is mixed with high-alkali sinter ore or limestone and dolomite and fed into the blast furnace for smelting. The alkalinity of the high-alkali sinter ore or the addition amount of blast furnace dolomite and limestone is controlled according to the slag alkalinity of 1-1.15 and the MgO / Al 2 O 3 ratio of 0.45-0.65 to ensure the smooth operation of blast furnace production and produce qualified hot metal. The blast furnace slag produced can be used to prepare cement, and then qualified steel products are produced through the steelmaking and rolling processes.

[0048] In the process of efficient recovery of iron from the tailings, it is necessary to prepare pellet ore that meets the requirements of blast furnace smelting from the wet nickel extraction tailings. The method for preparing the pellet ore is to mix the wet nickel extraction tailings with quicklime and dolomite, without adding bentonite, and control the addition amount of quicklime and dolomite according to the alkalinity ≤1 and the MgO ratio ≤2%. After the prepared raw materials are mixed evenly, 15%-22% of water is added to prepare green pellets. The prepared green pellets are preheated and then roasted at 1220℃-1280℃ to become finished pellet ore that meets the requirements of blast furnace smelting.

[0049] For the nickel-extracting wet tailings described above, the iron grade of the tailings should be ≥ 45%. If it is lower than 45%, magnetization reduction roasting and magnetic separation treatment are required to increase the tailings grade to more than 45%. In the blast furnace smelting process described above, part of ordinary sinter, ordinary lump ore or ordinary pellet can be added to improve the grade of the charge entering the blast furnace and optimize the blast furnace smelting indexes. In the blast furnace smelting process described above, the purpose of adding limestone and dolomite during the blast furnace smelting process is to control the appropriate composition of the blast furnace slag. Since the nickel-extracting wet tailings have a low grade and a large amount of blast furnace slag is produced, the slag basicity can be controlled at 1 - 1.15 and the ratio of MgO / Al 2 O 3 ratio at 0.45 - 0.65, and the addition amounts of limestone and dolomite are controlled according to this slag composition.

[0050] The nickel-extracting wet slag contains a certain amount of Cr 2 O 3 . When recovering iron by the method described above, part of the Cr will also enter the hot metal. Therefore, the iron recovered by the method described above is preferentially used for producing stainless steel products. If other steel products need to be produced, the Cr in the hot metal needs to be removed in the steelmaking refining process. Different from the pellet preparation process of ordinary iron ore concentrate, the nickel-extracting wet tailings have a fine particle size and good adhesion effect. No bentonite is added additionally during the preparation process. The 0.5m drop strength of the green pellets is > 10 times, the compressive strength of the green pellets is > 20N, and the bursting temperature of the green pellets is > 400℃. The properties of the green pellets meet the requirements of the grate-kiln-cooler and traveling grate processes for the properties of green pellets.

[0051] The reason for controlling the pellet basicity ≤ 1 is that if the basicity is higher than 1, due to excessive addition of limestone or dolomite, the green pellets are extremely easy to powder during the drying process, affecting the pellet yield. The reason for controlling the MgO content of the pellets ≤ 2% is that if the MgO content is higher than 2%, the low-temperature reduction powdering performance of the pellets after roasting is poor and cannot meet the requirements of blast furnace smelting. 15% - 22% of water is added during the preparation process of the green pellets, which is more than the water added during the preparation of pellet ore from ordinary iron ore concentrate. The reason is that the nickel-extracting wet tailings have a fine particle size and strong water absorption, and more water needs to be added during the pelletizing process. The roasting temperature of the pellet ore is controlled at 1220℃ - 1280℃. On the one hand, if the roasting temperature is higher than 1220℃, the strength of the pellets after roasting will be lower than 1500N. On the other hand, if the roasting temperature is higher than 1280℃, the pellets are prone to adhesion during the roasting process.

[0052] The compressive strength of the pellets prepared according to this method is ≥ 2000N, and the low-temperature reduction degradation index RDI of the pellets +3.15≥85%, the reducibility index of the pellet ore ≥55%, meeting the requirements of blast furnace smelting. In the preparation process of the pellet ore, a part of ordinary iron ore powder can be added to improve the grade of the pellet ore and optimize the performance parameters of the pellet ore. The sulfur content in the wet nickel extraction tailings is relatively high, usually greater than 1%, mainly existing in the form of sulfate. Through the preparation method of the pellet ore described above, the sulfur therein can be effectively removed, and the sulfur removal rate of the wet slag raw material reaches more than 95%.

[0053] Example 1

[0054] As Figure 1 shown, it is the specific implementation process of the present invention. The coupling utilization of wet nickel extraction and efficient recovery of iron from tailings is realized according to this process, and the specific process is as follows:

[0055] First, the wet nickel extraction process is carried out. The process flow is ore pretreatment, acid leaching, separation, purification, precipitation, filtration and drying, and nickel products can be obtained.

[0056] After wet nickel extraction, tailings with about 30% water content are obtained, with an iron grade of 50% and a sulfur content of 2%. The composition is shown in Table 1.

[0057] Table 1 Composition of wet slag

[0058] Element TFe <![CDATA[SiO 2 > CaO MgO <![CDATA[Al 2 O 3 > P S <![CDATA[Cr 2 O 3 > <![CDATA[H 2 O]]> Ig Content / % 50 7.90 0.07 0.08 4.30 0.01 2 2.86 30.00 7.00

[0059] According to the pellet basicity of 0.8 and the MgO content of 1.5%, after the prepared raw materials are mixed evenly, 18% water is added to prepare green pellets. After the prepared green pellets are preheated, they are roasted at 1250°C to become finished pellets. The pellet composition is shown in Table 2. After roasting, the S content of the pellets is 0.1%, and the desulfurization rate during the roasting process is 95%.

[0060] Table 2 Pellet composition

[0061] Element TFe <![CDATA[SiO 2 > CaO MgO <![CDATA[Al 2 O 3 > <![CDATA[Cr 2 O 3 > P S R Content / % 50.08 8.13 6.48 1.50 4.32 2.85 0.010 0.1 0.80

[0062] The performance indicators of the roasted pellets are shown in Table 3.

[0063] Table 3 Pellet performance

[0064]

[0065] It can be seen from Table 3 that the performance of the pellets prepared by the method provided by the present invention can meet the requirements of blast furnace smelting.

[0066] Using these pellets for blast furnace smelting, after calculation, the blast furnace needs to additionally charge 5% limestone and 5% dolomite to meet the requirements of the blast furnace slag composition. The blast furnace burden structure and main production technical indicators are shown in Table 4.

[0067] Table 4 Blast furnace burden structure and main production technical indicators

[0068]

[0069] The composition of the blast furnace slag is shown in Table 5 below.

[0070] Table 5 Composition of the blast furnace slag

[0071]

[0072] As can be seen from Tables 4 and 5, the pellets prepared from the nickel-extracting wet slag are smelted using the blast furnace process. The indexes such as the theoretical coke ratio, theoretical coal ratio, and theoretical slag ratio of the blast furnace are all worse than those of a conventional blast furnace. However, considering that this nickel-extracting wet slag belongs to metallurgical solid waste with a very low composition, this process is technically and economically feasible.

[0073] In addition, the theoretical slag composition of the blast furnace is similar to that of a conventional blast furnace, and blast furnace smelting is feasible. The produced blast furnace slag can adopt the water granulation process, and the granulated slag produced can be used to prepare cement, realizing the full resource utilization of this tail slag.

[0074] The composition of the blast furnace hot metal is shown in Table 6 below.

[0075] Table 6 Composition of the blast furnace hot metal

[0076]

[0077] The Cr content in the blast furnace hot metal is relatively high, and it is suitable for subsequent production of stainless steel products. If producing ordinary steel products with a relatively low Cr content, Cr can be removed in the steelmaking refining process. The contents of other impurities in the hot metal are not much different from those of ordinary hot metal.

[0078] The produced hot metal is processed through the steelmaking and rolling processes to produce qualified steel products.

[0079] Example 2

[0080] The nickel hydrometallurgy process and the composition of the wet slag are the same as those in Example 1. According to a pellet basicity of 1.0 and an MgO content of 2%, after the prepared raw materials are mixed evenly, 20% water is added to prepare green pellets. After the prepared green pellets are preheated, they are roasted at 1250 °C to become finished pellets. The composition of the pellets is shown in Table 2. After roasting, the S content of the pellets is 0.12%, and the desulfurization rate during the roasting process is 94%.

[0081] Table 1 Composition of the pellets

[0082] Element TFe <![CDATA[SiO 2 > CaO MgO <![CDATA[Al 2 O 3 > <![CDATA[Cr 2 O 3 > P S R Content / % 48.86 8.00 8.00 2.00 4.22 2.78 0.010 0.12 1.0

[0083] The performance indexes of the roasted pellets are shown in Table 2.

[0084] Table 2 Pellet properties

[0085]

[0086]

[0087] Using ordinary hematite powder, magnetite powder and limonite to produce high-alkali sinter, the composition is shown in Table 3.

[0088] Table 3 Pellet Composition

[0089] Element TFe <![CDATA[SiO 2 > CaO MgO <![CDATA[Al 2 O 3 > <![CDATA[Cr 2 O 3 > P S R Content / % 56.39 4.23 9.52 2.88 2.47 0.001 0.092 0.02 2.25

[0090] Using this pellet and sinter for blast furnace smelting, the blast furnace burden structure and main production technical indexes are shown in Table 4.

[0091] Table 4 Blast Furnace Burden Structure and Main Production Technical Indexes

[0092]

[0093] The blast furnace slag composition is shown in Table 5.

[0094] Table 5 Blast Furnace Slag Composition

[0095]

[0096] It can be seen from Table 4 and Table 5 that the pellet prepared from this nickel extraction hydrometallurgical slag and the sinter prepared from ordinary ore form a blast furnace burden structure of 70% pellet + 30% sinter. When smelted by the blast furnace process, indexes such as the theoretical coke ratio, theoretical coal ratio, and theoretical slag ratio of the blast furnace are all significantly reduced compared with Example 1. However, a certain proportion of ordinary ore powder is used to produce sinter in Example 2, and the use ratio of the nickel extraction hydrometallurgical tailings is relatively reduced.

[0097] In addition, the theoretical slag composition of the blast furnace is similar to that of a conventional blast furnace, and blast furnace smelting is feasible. The produced blast furnace slag can adopt the water granulation process, and the produced granulated slag can be used to prepare cement, realizing the full resource utilization of this tailings.

[0098] The blast furnace hot metal composition is shown in Table 6.

[0099] Table 6 Blast Furnace Hot Metal Composition

[0100]

[0101] The Cr content in the blast furnace hot metal is slightly reduced compared with Example 1, but it is still higher than the Cr content in the hot metal produced from ordinary ore powder. It is also suitable for producing stainless steel products in the follow-up. If producing ordinary steel products with a lower Cr content, Cr can be removed in the steelmaking refining process. The other impurity contents in the hot metal are not much different from those of ordinary hot metal.

[0102] The produced hot metal passes through the steelmaking and rolling processes to produce qualified steel products.

[0103] Example 3

[0104] The wet nickel extraction process and the composition of the wet slag are the same as those in Example 1. The raw materials are proportioned according to 20% of ordinary iron concentrate powder and 80% of wet slag, and the pellet basicity is 1.0 and the MgO content is 2%. After the prepared raw materials are mixed evenly, 16% water is added to prepare green pellets. After the prepared green pellets are preheated, they are roasted at 1230 °C to become finished pellets. The composition of the ordinary iron concentrate powder is shown in Table 1. The composition of the pellets is shown in Table 2. After roasting, the S content of the pellets is 0.08%, and the desulfurization rate during the roasting process is 95%.

[0105] Table 1 Composition of ordinary iron concentrate

[0106] Element TFe <![CDATA[SiO 2 > CaO MgO <![CDATA[Al 2 O 3 > <![CDATA[Cr 2 O 3 > P S Content / % 65.00 4.00 1.60 0.60 1.20 0.01 0.060 0.01

[0107] Table 2 Composition of pellets

[0108] Element TFe <![CDATA[SiO 2 > CaO MgO <![CDATA[Al 2 O 3 > <![CDATA[Cr 2 O 3 > P S R Content / % 52.12 6.99 6.99 2.00 3.46 2.09 0.022 0.08 1.0

[0109] The performance indexes of the roasted pellets are shown in Table 3. Since a part of ordinary iron concentrate powder is incorporated, the overall performance of the pellet ore has a certain degree of improvement compared with the pellets in the example, except for the reduction swelling index. The performance of the pellets can meet the requirements of blast furnace smelting.

[0110] Table 3 Pellet performance

[0111]

[0112] Using these pellets for blast furnace smelting, after calculation, the blast furnace needs to additionally incorporate 3% limestone and 2% dolomite to meet the requirements of the blast furnace production slag composition. The blast furnace burden structure and main production technical indexes are shown in Table 4.

[0113] Table 4 Blast furnace burden structure and main production technical indexes

[0114]

[0115]

[0116] The blast furnace slag composition is shown in Table 5.

[0117] Table 5 Blast furnace slag composition

[0118]

[0119] It can be seen from Table 4 and Table 5 that when the pellets prepared from the wet nickel extraction slag are smelted by the blast furnace process, the theoretical coke ratio, theoretical coal ratio, theoretical slag ratio, etc. of the blast furnace all have a certain degree of decrease compared with those in Example 1. However, this scheme incorporates a certain proportion of ordinary iron concentrate powder, which will increase the cost of some raw materials.

[0120] The theoretical slag composition of the blast furnace is similar to that of a conventional blast furnace, and blast furnace smelting is feasible. The blast furnace slag produced can adopt the water granulation process, and the granulated slag produced can be used to prepare cement, realizing the full resource utilization of the tail slag.

[0121] The composition of the hot metal in the blast furnace is shown in Table 6.

[0122] Table 6 Composition of the hot metal in the blast furnace

[0123]

[0124] The Cr content in the hot metal of the blast furnace is slightly lower compared with that in Example 1, but it is still higher than the Cr content in the hot metal produced from ordinary ore powder. It is also suitable for the subsequent production of stainless steel products. If ordinary steel products with a lower Cr content are to be produced, Cr can be removed in the steelmaking refining process. The contents of other impurities in the hot metal are not much different from those of ordinary hot metal.

[0125] The hot metal produced is processed through the steelmaking and rolling processes to produce qualified steel products.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A coupling method for wet nickel extraction and tailings recovery and ironmaking, characterized in that: The following steps are involved: Wet nickel extraction process: nickel ore is pretreated, acid-leached, separated, purified, precipitated, filtered and dried in sequence to obtain nickel products and wet nickel extraction tailings; Tailings treatment process: The wet nickel extraction tailings produced by the "wet nickel extraction process" are dried and prepared into fine powder, which is used alone or mixed with ordinary iron ore powder, and then mixed with quicklime and dolomite, and water is added to prepare green balls; the green balls are preheated and roasted to obtain pellets; Blast furnace smelting process: the pellets prepared by the "tailings treatment process" are added to the blast furnace with at least one of high-basicity sintered ore, limestone and dolomite to obtain molten iron; Subsequent processing of molten iron: The molten iron obtained from the "blast furnace smelting process" is used to produce steel products through steelmaking and steel rolling processes, and the blast furnace slag is used to prepare cement.

2. The coupling method according to claim 1, characterized in that: The iron content of the wet nickel extraction tailings used in the "tailings treatment process" is ≥45%; if the iron content is lower than 45%, the tailings need to be subjected to magnetic reduction roasting and magnetic separation treatment to increase the iron content to above 45%.

3. The coupling method according to claim 1, characterized in that: The green balls prepared in the "tailings treatment process" meet the following performance indicators: 0.5m drop strength>10 times, green ball compressive strength>20N, green ball burst temperature>400℃; The compressive strength of the pellets is ≥2000N, and the low temperature reduction powder index RDI+ 3.15 ≥85%, reduction index ≥55%.

4. The coupling method according to claim 1, characterized in that: The roasting temperature range of the pellets described in the "tailings treatment process" is 1220°C-1280°C, and the sulfur removal rate during the roasting process is ≥95%.

5. The coupling method according to claim 1, characterized in that: The blast furnace smelting process described in the "blast furnace smelting process" also includes adding one or more of ordinary sintered ore, ordinary lump ore or ordinary pelletized ore to improve the grade of the ore entering the furnace.

6. The coupling method according to claim 1, characterized in that: The Cr content in molten iron described in the "Blast Furnace Smelting Process" is 1.75%-2.65%, which is preferentially used for the production of stainless steel products. If other steel products are to be produced, the Cr in the molten iron must be removed during the steelmaking and refining process.

7. A system for implementing the coupling method according to any one of claims 1 to 6, characterized in that: include: Wet nickel extraction unit: including ore pretreatment device, acid leaching tank, separation device, purification device, sedimentation tank, filter and drying equipment connected in sequence; Tailings treatment unit: a drying kiln connected to the wet nickel extraction unit, used to dry and crush the tailings; a mixing device, used to mix the dried tailings with quicklime and dolomite in proportion; a pelletizing machine, used to add water to the mixture to make pellets; Preheating device and roasting kiln, used for preheating and roasting of green balls; Blast furnace smelting unit: including a blast furnace, a batching device and a slag treatment device. The feed port of the blast furnace is connected to the roasting kiln of the tailings treatment unit, which is used to receive pellets and add limestone, dolomite or high-basicity sintered ore; Hot metal processing units: steelmaking furnaces and steel rolling equipment connected to blast furnaces, and cement production units for processing blast furnace slag.

8. The system according to claim 7, characterized in that A water adding device is arranged between the mixing device and the pelletizing machine, which is used to control the water addition amount to 15%-22%; the temperature control system of the roasting kiln is set to 1220℃-1280℃.

9. The system according to claim 7, characterized in that The tailings processing unit also includes a magnetic separator for performing magnetic reduction roasting and magnetic separation treatment on tailings with an iron content of less than 45%.

10. A pellet prepared according to the method according to any one of claims 1 to 6, characterized in that: Its ingredients meet the following requirements: Basicity ≤1, MgO content ≤2%, sulfur content ≤0.12%, compressive strength ≥2000N, low temperature reduction powder index RDI+ 3.15 ≥85%.

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