Method for producing microcrystalline cast stone by using nickel slag

Abstract

The invention belongs to the field of metallurgical and inorganic non-metallic materials, and particularly relates to a method for producing microcrystalline cast stone by using nickel slag. The tempering agent is added into the slag ladle, and the hot nickel slag is directly discharged into the slag ladle through the slag outlet; mixing and homogenizing the hot nickel slag in the slag ladle and a hardening and tempering agent to obtain homogenized nickel slag; and then pouring the homogeneous nickel slag into a mold, carrying out self-heating crystallization in air by utilizing the heat of the homogeneous nickel slag system, cooling after crystallization, and demolding to obtain the microcrystalline cast stone. The high-temperature hot nickel slag is directly mixed with the hardening and tempering agent, energy waste caused by reheating cold slag is avoided, the homogenizing process is carried out in the slag ladle, and heat loss is reduced; after the homogeneous nickel slag is poured into the mold, self-heating crystallization is carried out by utilizing heat of the homogeneous nickel slag and heat released by reaction of the homogeneous nickel slag and the hardening and tempering agent, a nucleating agent does not need to be additionally added, through a shrinkage-cavity-free pouring mode, the prepared cast stone is compact in material, the defect of large-size lock holes is avoided, the process is simple, and the method is suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy and inorganic non-metallic materials, and in particular relates to a method for producing microcrystalline cast stone by utilizing nickel slag. Background Art

[0002] Nickel slag is a metallurgical solid waste discharged during the smelting of nickel-iron alloys. Its iron content is typically over 10%. Currently, it is mainly recycled for metal, used as construction filler, or processed into microcrystalline cast stone through related processes.

[0003] Patent publication number CN116768496A proposes a method and production equipment for producing cast stone using titanium-containing blast furnace slag. This method utilizes titanium-containing high-aluminum slag solid waste resources, directly pours and seals and pressurizes in a molten state, and then crystallizes and insulates to form cast stone. The entire process does not require the addition of nucleating agents and tempering agents, but the crystallization process of this method requires a high-pressure environment, the equipment is complex, and the risk is increased.

[0004] Patent publication number CN103601377A proposes a temperature-controlled mold casting process and equipment for producing cast stone from blast furnace slag. The process involves directly transferring the high-temperature slag to a tempering tank, adding a tempering agent, and tempering it. After tempering, the slag is poured into a casting box through a slag outlet for crystallization. The casting box is placed in a semi-enclosed environment with a heating atmosphere to regulate the casting temperature, ensuring that the product can meet a temperature above 900°C during the demolding process before demolding. This method directly utilizes hot slag, saving heat consumption to a certain extent. However, the casting box structure required for this method is complex, and the temperature requirements for the crystallization and demolding processes are high. Furthermore, the cast stone produced by this method has many porosity defects, which greatly reduces the performance of the finished product. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the present invention provides a method for producing microcrystalline cast stone using nickel slag, which can simply and efficiently prepare dense microcrystalline cast stone without adding a crystal nucleating agent.

[0006] To achieve the above-mentioned purpose, the technical solution provided by the present invention is as follows:

[0007] The present application provides a method for producing microcrystalline cast stone using nickel slag, comprising:

[0008] Discharging hot nickel slag from the blast furnace tapping port into a slag bag containing a conditioning agent;

[0009] Mixing the hot nickel slag in the slag bag with the conditioning agent in a molten state to obtain a homogeneous nickel slag;

[0010] The homogeneous nickel slag is poured into a mold, and the self-heat of the homogeneous nickel slag system is utilized to self-crystallize in the air. After crystallization, the microcrystalline cast stone is obtained by cooling and demoulding.

[0011] Optionally, the hot nickel slag comprises, in percentage by mass: SiO2: 40%~60%, MgO: 20~40%, Al2O3: 1~15%, Fe: 0~1%, FeO: 0%~10%, Fe2O3: 0%~10%, CaO: 0%~5%, Cr2O3: 0%~5%, and others: 0~3%.

[0012] Optionally, the hot nickel slag is high-temperature slag produced by laterite nickel ore.

[0013] Optionally, the conditioning agent includes one or more of CaO, ZnO, CaF2, Na2CO3, and coke, and the fixed carbon content of the coke is ≥85%, the ash content is ≤10%, and the sulfur content is ≤1%.

[0014] Optionally, the viscosity of the homogeneous nickel slag is 0.5-10 Pa·s.

[0015] Optionally, the amount of the tempering agent is 5% of the mass of the hot nickel slag.

[0016] Optionally, the initial temperature of the hot nickel slag at the slag outlet is 1500-1600°C, and the temperature of the homogeneous nickel slag is 1400-1580°C.

[0017] Optionally, the crystallization temperature is 800-1100° C., and the crystallization time is 30 min-60 min.

[0018] Optionally, before pouring, the mold is preheated to 800-1100°C.

[0019] Optionally, the cooling method is natural cooling or air cooling.

[0020] Optionally, the mold adopts a detachable shrinkage-free mold, the mold cavity increases the height by at least 15% of the required cast stone height in the height direction, the mold cavity height is not less than 115% of the required cast stone height, the front and rear side walls of the mold are detachable, and the mold wall thickness is not less than 10 mm.

[0021] Compared with the prior art, this application has at least the following beneficial effects:

[0022] The present invention directly mixes high-temperature hot nickel slag with a conditioning agent, thereby avoiding energy waste caused by reheating cold slag, and the homogenization process is carried out in a slag bag, reducing heat loss. After the homogenous nickel slag is poured into a mold, the heat of the homogenous nickel slag system itself (the heat of the slag itself and the heat released by the reaction of the slag and the conditioning agent) is used for self-heating crystallization, without the need for external heating or the addition of an external crystal nucleating agent. Through the shrinkage-free casting method, the obtained cast stone material is dense, avoiding the formation of large shrinkage cavity defects, and the cast stone has the characteristics of high hardness, wear resistance, pressure resistance, low porosity, and acid and alkali resistance. At the same time, the production process is simplified and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of the preparation method of the present invention;

[0024] Figure 2 It is a schematic diagram of the production equipment structure of the present invention;

[0025] Figure 3 The simulation results of the crystallization process of the microcrystalline cast stone prepared by the present invention are analyzed; wherein 1 is the mold and 2 is the cast stone;

[0026] Figure 4 is the XRD pattern of cast stone samples at different crystallization times;

[0027] Figure 5 Thickening rate of slag poured into the mold (A) and temperature change of the steel mold side wall (B);

[0028] Figure 6 This is a picture of the microcrystalline cast stone sample obtained in Example 1, where A and B correspond to the top and bottom surfaces of the cast stone sample, respectively;

[0029] Figure 7 This is a picture of the microcrystalline cast stone sample obtained in Example 2, where A, B, and C correspond to crystallization times of 30 min, 90 min, and 180 min, respectively;

[0030] Figure 8 This is a sample of microcrystalline cast stone obtained in Example 3, wherein A represents a 3% amount of conditioning agent; B represents a 5% amount of conditioning agent; and C represents an 8% amount of conditioning agent.

[0031] 1. Pouring gate; 2. Side panel. DETAILED DESCRIPTION

[0032] The present invention is described in further detail below with reference to the accompanying drawings:

[0033] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are conventional methods.

[0034] The present application provides a method for producing microcrystalline cast stone using nickel slag, comprising:

[0035] Add the conditioning agent into the slag bag, and discharge the hot nickel slag directly into the slag bag through the slag outlet;

[0036] Mixing the hot nickel slag in the slag bag with a conditioning agent to obtain homogeneous nickel slag;

[0037] The homogeneous nickel slag is poured into a mold and crystallized in the air by self-heating using its own heat. After crystallization, it is cooled and demoulded to obtain microcrystalline cast stone. Figure 1 As shown, the crystallization process does not require any additional operations.

[0038] In certain embodiments of the present invention, the hot nickel slag comprises, by mass percentage, 40%-60% SiO2, 20%-40% MgO, 1%-15% Al2O3, 0%-1% Fe, 0%-10% FeO, 0%-10% Fe2O3, 0%-5% CaO, 0%-5% Cr2O3, and 0%-3% other components. These other components may vary slightly depending on the batch of laterite nickel ore, but their low content does not affect the production of cast stone. These other components generally include one or more of Li2O, PbO, and SrO. The hot nickel slag is the high-temperature slag produced by laterite nickel ore.

[0039] In certain embodiments of the present invention, the conditioning agent comprises one or more of CaO, ZnO, CaF2, Na2CO3, and coke. The conditioning agent reacts exothermically with magnesium powder or other components at high temperatures, releasing heat that supplements the heat required for autocrystallization. Only by adding the composite conditioning agent of the present invention to the slag system can homogenization and autocrystallization be achieved.

[0040] In certain embodiments of the present invention, the viscosity of the homogeneous nickel slag is 0.5-10 Pa·s.

[0041] In certain embodiments of the present invention, the amount of the conditioning agent is 5%.

[0042] In certain embodiments of the present invention, the temperature of the homogeneous nickel slag is 1400-1580°C.

[0043] In certain embodiments of the present invention, the crystallization temperature is 800-1100° C., and the crystallization time is 30 min-60 min.

[0044] In certain embodiments of the present invention, the mold is preheated to 800-1100° C. before casting. The mold is preheated at the crystallization temperature in advance to reduce heat loss during slag casting.

[0045] In certain embodiments of the present invention, the cooling method is natural cooling or air cooling.

[0046] The mold structure schematic diagram of the present invention is as follows Figure 2 As shown, an upper cover is provided on the top of the mold, a pouring port 1 is provided on the upper cover, the bottom wall of the mold is fixedly connected to the left and right side walls, and the front and rear side walls 2 are fixed to the left and right side walls by bolts.

[0047] To reduce shrinkage porosity in the finished product, the present invention employs a shrinkage-free casting method. Homogenized hot slag is poured through the designed pouring port 1. Shrinkage porosity is concentrated at the top, and the mold height is increased by 15% above the desired cast stone height. After annealing, the top portion with shrinkage porosity is removed. The remaining usable portion has a uniform composition and a dense structure.

[0048] The mold is designed so that the bottom surface and the left and right surfaces are fixed, and the remaining front and rear surfaces are fixed to the left and right surfaces by bolts. After complete crystallization, the fixing bolts are removed, and the front and rear side walls 2 are opened to take out the microcrystalline cast stone.

[0049] In certain embodiments of the present invention, to enhance the validity of experimental results, the present invention simulated the cooling process of autothermal crystallization after casting in a mold using Fluent software. In this example, the mold was made of Q345 heat-resistant steel with a wall thickness of 10 mm. The nickel slag solidus was 1132.33°C, and the liquidus was 1435.11°C.

[0050] In certain embodiments of the present invention, in order to verify that the nickel slag crystallization time can achieve the expected effect, the following is established on the result section by simulating the field working conditions: Figure 3 A coordinate system, according to Figure 3 B can be concluded that: when the wall thickness of the steel plate is not less than 2 cm, the cooling time of the nickel slag from 1130-800℃ after pouring is greater than 0.5h, which reaches the crystallization time required by the nickel slag.

[0051] Through simulation, we can further conclude that Figure 5 Conclusions shown: Figure 5 A shows the slag thickening rate. As time increases, the slag thickening rate shows a trend of first decreasing and then increasing until it is completely solidified. Figure 5 Figure B shows the temperature change inside the mold after the homogeneous nickel slag from Example 1 was added. The mold's inner wall temperature peaked at around 500°C, which is below the temperature limit of the steel plate used in structural mold production. The mold (made of Q345 heat-resistant steel) can function normally. The simulation results are generally consistent with the field test results.

[0052] Example 1:

[0053] This embodiment provides a method for producing microcrystalline cast stone using nickel slag, the steps of which are as follows:

[0054] (1) A tempering agent (CaO and coke in a mass ratio of 3:2, with the fixed carbon content of coke being 88%, the ash content being 8%, and the sulfur content being 0.5%) is pre-added to the bottom of the slag ladle in an amount of 5% of the mass of the hot nickel slag; the hot nickel slag discharged from the blast furnace at a temperature of about 1500°C is separated from the slag ditch and transferred to the slag ladle through the slag inlet. The insulation device of the slag ladle maintains the slag in a molten state, and the slag is mixed and homogenized to obtain a homogeneous nickel slag with a viscosity of 5 Pa•s and a homogeneous nickel slag temperature of 1400°C; the composition of the hot nickel slag used is: SiO2: 50.11%, MgO: 33.09%, Al2O3: 4.17%, Fe: 0.57%, FeO: 5.23%, Fe2O3: 4.10%, CaO: 1.08%, Cr2O3: 1.45%, and the remainder is other (PbO, SrO, etc.);

[0055] (2) The slag bag is transported to the designated location via relevant transportation equipment, and the slag is directly cast into the mold through the casting mouth (the mold is preheated to 1100℃ in advance). The ambient temperature of this process is 25℃. It is placed in the air for crystallization, then cooled to room temperature and demolded to obtain microcrystalline cast stone. The preparation process was tested and it was found that the temperature was maintained at the crystallization temperature of 800℃~1100℃ for 60 minutes.

[0056] (3) Cut and polish the demoulded microcrystalline cast stone to obtain samples. Figure 6 As shown, Figure 6 It shows that although the cast stone prepared by the present invention has some small holes inside before being cut off, it is relatively dense as a whole, without excessively large cavities or shrinkage cavities. After cutting off 15% of the top area, the whole is dense and uniform, with high hardness, low porosity, wear resistance, and acid and alkali resistance.

[0057] In step 2, air cooling is also used to control different crystallization times and produce cast stones with different crystallization times. Figure 4 2 is the XRD pattern of the cast stone samples obtained at different crystallization times. It can be seen from the figure that the optimal crystallization time of the hot nickel slag in this embodiment is 60 minutes.

[0058] Example 2:

[0059] The difference between this embodiment and embodiment 1 is that the hot nickel slag used has the following composition: SiO2: 51.13%, MgO: 30.83%, Al2O3: 4.66%, Fe: 0.63%, FeO: 4.23%, Fe2O3: 4.64%, CaO: 0.83%, Cr2O3: 2.06%, and the balance is other (PbO, SrO, etc.);

[0060] In this embodiment, the crystallization time is:

[0061] (1) Crystallization time 30 min; (2) Crystallization time 90 min; (3) Crystallization time 180 min;

[0062] The sample pictures obtained by each group are as follows Figure 7 As shown. Figure 7 As can be seen from A, when the crystallization time is 30 minutes, the sample is not completely crystallized due to the short crystallization time. Instead, solidification and crystallization will occur preferentially from the center of the surface. Since the lattice constants of amorphous (glass) and crystal (cast stone) are very different, if the liquid slag cannot enter the crystal gaps during crystallization, it will cause defects such as shrinkage cavities or voids, which will greatly reduce the performance of the cast stone product.

[0063] like Figure 7 As shown in Figure B, the crystallization time is 90 minutes, which allows the slag, which is still in a soft molten state during the cooling, forming and crystallization process, to enter the crystal gaps, thus avoiding shrinkage cavities caused by crystallization. At the same time, as the crystallization time increases, the crystal size becomes smaller, the grain arrangement tends to be denser, and the crystallization rate increases, making the cast stone obtained after crystallization more dense.

[0064] During the crystallization process, attention should be paid to the length of time. The crystallization time should be controlled within 60min~120min in order to ensure the structure and performance of the microcrystalline cast stone. If the sample crystallization time is too long, such as 180min, it will cause the crystals to grow abnormally, causing the block to expand, the shrinkage rate to decrease, and the porosity to increase, thus making it impossible to complete the preparation of the cast stone ( Figure 7 C).

[0065] Example 3:

[0066] The difference between this embodiment and embodiment 1 is that the hot nickel slag used has the following composition: SiO2: 52.26%, MgO: 29.11%, Al2O3: 4.03%, Fe: 0.86%, FeO: 5.33%, Fe2O3: 4.74%, CaO: 0.53%, Cr2O3: 2.96%, and the balance is other (PbO, SrO, etc.);

[0067] The amount of the conditioning agent used in this embodiment is (in mass percentage):

[0068] (1) The amount of conditioning agent is 3%; (2) The amount of conditioning agent is 5%; (3) The amount of conditioning agent is 8%;

[0069] The sample pictures obtained are as follows Figure 8 shown.

[0070] Depend on Figure 8As can be seen from A, when the amount of conditioning agent is 3%, the viscosity of the hot slag added is relatively high due to the small amount of conditioning agent, which leads to its homogenization and the appearance of defects such as voids in the finished product, making it fragile and prone to cracking, greatly reducing the performance of the finished cast stone product.

[0071] like Figure 8 As shown in Figure B, when the amount of the tempering agent is 5%, the slag, which is still in a soft molten state during the cooling, forming and crystallization process of the sample, will enter the crystal gaps, avoiding shrinkage cavities caused by crystallization. At the same time, as the crystallization time increases, the crystal size becomes smaller, the grain arrangement tends to be denser, and the crystallization rate increases, making the cast stone obtained after crystallization more dense.

[0072] like Figure 8 As shown in Figure C, when the dosage of the tempering agent is 8%, the degree of crystallization will increase, which will lead to further abnormal growth of the crystals, causing the block to expand, and further reducing the strength of the cast stone product.

Claims

1. A method for producing microcrystalline cast stone using nickel slag, characterized in that: include: Discharging hot nickel slag from the blast furnace tapping port into a slag bag containing a conditioning agent; Mixing the hot nickel slag in the slag bag with the conditioning agent in a molten state to obtain a homogeneous nickel slag; The homogeneous nickel slag is poured into a mold, and the self-heat of the homogeneous nickel slag system is utilized to self-crystallize in the air. After crystallization, the microcrystalline cast stone is obtained by cooling and demoulding.

2. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: Calculated in percentage by mass, the hot nickel slag comprises: SiO2: 40%~60%, MgO: 20~40%, Al2O3: 1~15%, Fe: 0~1%, FeO: 0%~10%, Fe2O3: 0%~10%, CaO: 0%~5%, Cr2O3: 0%~5%, and others: 0~3%.

3. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: The conditioning agent includes one or more of CaO, ZnO, CaF2, Na2CO3, and coke, wherein the fixed carbon content of the coke is ≥85%, the ash content is ≤10%, and the sulfur content is ≤1%.

4. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: The viscosity of the homogeneous nickel slag is 0.5-10 Pa·s.

5. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: The amount of the conditioning agent is 5% of the mass of the hot nickel slag.

6. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: The initial temperature of the hot nickel slag is 1500-1600°C, and the temperature of the homogeneous nickel slag is 1400-1580°C.

7. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: The crystallization temperature is 800-1100° C., and the crystallization time is 30 min-60 min.

8. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: Before pouring, the mold is preheated to 800-1100℃.

9. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: The cooling method is natural cooling or air cooling.

10. The method for producing microcrystalline cast stone using nickel slag according to claim 1, characterized in that: The mold is a detachable mold without shrinkage cavities, the front and rear side walls of the mold are detachable, and the wall thickness of the mold is not less than 10 mm.

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