Process for preparing silicon-calcium alloy by using magnesium smelting reduction slag and other industrial solid wastes

Abstract

The application discloses a process method for preparing silicon-calcium alloy by using magnesium smelting reduction slag and other industrial solid wastes, which comprises the following steps: a, magnesium smelting reduction slag, microsilica powder, ferrosilicon dust and calcium carbide slag are mixed according to a certain weight ratio, and then are ground to a 325 mesh passing rate of greater than or equal to 80%, and then are prepared into material balls with a diameter of 20-40 mm and a strength of 1000-3000 N by using a granulating device, and then are dried at 105 DEG C + / - 5 DEG C for 3-6 hours or are naturally dried for 3-10 days; b, the dehydrated material balls are mixed with carbonaceous reducing agents according to a certain weight ratio, the raw material ratio is adjusted according to the target silicon-calcium alloy grade, and then the mixture is smelted in a submerged arc furnace for 2-5 hours; and c, liquid silicon-calcium alloy is periodically discharged and is poured into fixed molds and then is cooled to obtain products with qualified chemical components. The application realizes the synergistic utilization of magnesium smelting reduction slag, ferrosilicon dust, calcium carbide slag and other industrial solid wastes, and has both environmental protection benefits and economic value.

Description

TECHNICAL FIELD

[0001] The present application relates to a silicon-calcium alloy preparation technology, in particular to a process for preparing silicon-calcium alloy by using magnesium smelting reduction slag and other industrial solid wastes. BACKGROUND

[0002] At present, the production of magnesium mainly adopts silicon-thermal method (Pidgeon method). For producing 1 ton of magnesium, more than 10 tons of dolomite and more than 1 ton of ferrosilicon are consumed, and more than 5 tons of magnesium smelting reduction slag is generated. Since the comprehensive utilization of magnesium slag in the prior art is less than 30%, a large amount of magnesium slag is forced to be stored and filled. The magnesium slag is easy to cause soil compaction and salinization due to its strong hygroscopicity, causing serious environmental pollution. Therefore, developing high-efficiency resource utilization technology of magnesium slag is the key to realize green development of magnesium smelting industry. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a process for producing silicon-calcium alloy by using magnesium smelting reduction slag as the core raw material, and cooperatively using silicon-iron dust, micro-silicon powder, carbide slag and other industrial solid wastes (among them, the silicon-iron dust and the micro-silicon powder can be used simultaneously or separately), to realize high-value conversion of waste slag.

[0004] The technical scheme of the present application is as follows:

[0005] A process for preparing silicon-calcium alloy by using magnesium smelting reduction slag and other industrial solid wastes, comprising the following steps:

[0006] a. Raw material pretreatment:

[0007] The magnesium smelting reduction slag, micro-silicon powder and / or silicon-iron dust, and carbide slag are mixed in a weight ratio of 1:1.5-8.0:0-4, then ground to a passing rate of 325 mesh of ≥80%, and then prepared into balls with a diameter of 20-40 mm and a strength of 1000-3000 N by using a granulating device, and then dried at 105℃±5℃ for 3-6 hours or naturally air-dried for 3-10 days;

[0008] b. Batch smelting:

[0009] The dehydrated balls are mixed with carbonaceous reducing agent in a weight ratio of 1:0.30-0.55, the raw material ratio is adjusted according to the target silicon-calcium alloy grade, and then smelted at 1500℃-1850℃ for 2-5 hours by using a submerged arc furnace;

[0010] c. Alloy forming: periodically discharging liquid silicon-calcium alloy and casting into fixed molds to cool, to obtain products with qualified chemical composition.

[0011] Furthermore, the magnesium reduction slag contains, by mass percentage, 4%–8% MgO, 22%–33% SiO2, 40%–60% CaO, and 1%–5% Al2O3.

[0012] Furthermore: the SiO2 content in the microsilica powder is 80%–97%, and the Al2O3 content is 0–1.5%; the SiO2 content in the ferrosilicon dust is 40%–90%, and the Al2O3 content is 1%–10%.

[0013] Furthermore, the calcium carbide slag contains 60% to 70% CaO, 3% to 5% SiO2, and 0.5% to 2.5% Al2O3.

[0014] Furthermore: the carbonaceous reducing agent is coke, semi-coke, or anthracite; the carbonaceous reducing agent has a fixed carbon content of ≥75%.

[0015] The beneficial effects of this invention are:

[0016] 1. The comprehensive utilization rate of magnesium smelting reduction slag of this invention can reach 95%, and it can simultaneously dispose of solid wastes such as ferrosilicon dust and calcium carbide slag, resulting in good environmental benefits.

[0017] 2. The silicon-calcium alloy (Ca16Si55 to Ca31Si60 series) of this invention can replace traditional deoxidizers and reduce steelmaking costs; at the same time, compared with the traditional method of producing silicon-calcium alloy using silica and lime, the raw material cost is lower and it has good economic benefits.

[0018] 3. By controlling the strength of the smelting balls (1000-3000N) and optimizing the melting parameters, this invention can stabilize the alloy composition and improve product quality.

[0019] 4. This invention develops a high-efficiency resource utilization technology for magnesium slag, realizing the green development of the magnesium smelting industry. The resulting silicon-calcium alloy can be used for steelmaking deoxidation, desulfurization, and cast iron production, etc. It has a wide range of applications and is easy to promote and implement. Attached Figure Description

[0020] Figure 1 A flowchart of a process for preparing silicon-calcium alloys using magnesium smelting reduction slag and other industrial solid wastes. Detailed Implementation

[0021] Example: See Figure 1 A process for preparing silicon-calcium alloys using magnesium smelting reduction slag and other industrial solid wastes includes the following steps:

[0022] a. Raw material pretreatment:

[0023] Magnesium smelting reducing slag, microsilica powder and ferrosilicon dust (total weight of both), and calcium carbide slag are mixed in a weight ratio of 1:1.5-8.0:0-4 and then ground to a 325-mesh pass rate of ≥80%. The mixture is then used to prepare pellets with a diameter of 20-40 mm and a strength of 1000-3000 N using granulation equipment. The pellets are then dried at 105℃±5℃ for 3-6 hours or air-dried naturally for 3-10 days.

[0024] b. Batching and smelting:

[0025] The dehydrated pellets and carbonaceous reducing agent are mixed at a weight ratio of 1:0.30 to 0.55. The raw material ratio is adjusted according to the target silicon-calcium alloy grade. The mixture is then smelted in a submerged arc furnace at 1500℃ to 1850℃ for 2 to 5 hours.

[0026] The core reduction reaction formula is as follows:

[0027] CaO + C = Ca + CO↑ (1);

[0028] SiO2 + 2C = Si + 2CO↑ (2);

[0029] c. Alloy forming: Liquid silicon-calcium alloy is periodically discharged and poured into a fixed mold for cooling to obtain a product with qualified chemical composition.

[0030] Preferred embodiment: The magnesium reduction slag contains, by mass percentage, 4%–8% MgO, 22%–33% SiO2, 40%–60% CaO, and 1%–5% Al2O3.

[0031] Preferred embodiment: The microsilica powder contains 80%–97% SiO2 and 0–1.5% Al2O3; the ferrosilicon dust contains 40%–90% SiO2 and 1%–10% Al2O3.

[0032] Preferred embodiment: The calcium carbide slag contains 60%~70% CaO, 3%~5% SiO2, and 0.5%~2.5% Al2O3.

[0033] Preferred embodiment: The carbonaceous reducing agent is coke, semi-coke, or anthracite; the fixed carbon content of the carbonaceous reducing agent is ≥75%.

[0034] Furthermore, the dosages of magnesium reducing slag, microsilica powder, ferrosilicon dust, carbide slag, and carbonaceous reducing agent are determined by calculation or experiment based on the chemical composition requirements of different grades in the industry standard YB / T5051 "Silicon-Calcium Alloys". The grades and chemical compositions of the silicon-calcium alloys comply with the requirements of the industry standard YB / T5051 "Silicon-Calcium Alloys".

[0035] The requirements for silicon-calcium alloy grades and chemical composition are as follows:

[0036] Example

[0037] A calcium-silicon alloy of grade Ca20Si55 was produced using 100 kg of magnesium smelting reducing slag, 450 kg of microsilica powder, 100 kg of calcium carbide slag, and 270 kg of carbonaceous reducing agent. The magnesium smelting reducing slag contained 5% MgO, 30% SiO2, 55% CaO, and 3% Al2O3. The microsilica powder contained 95% SiO2 and 1% Al2O3. The calcium carbide slag contained 65% CaO, 4% SiO2, and 1% Al2O3. The carbonaceous reducing agent was semi-coke with a fixed carbon content of 80%.

[0038] After mixing the above raw materials, they are ground using a ball mill. The fineness of the powder after grinding is 325 mesh with a passing rate of not less than 80%. Then, a pot granulator is used to granulate the powder. During the granulation process, an appropriate amount of water is added to the granulator and mixed. The granulation time meets the strength requirements of 1000-3000N. The pellets are taken out when the diameter reaches 20-40mm.

[0039] The removed pellets are dried at a temperature of 105℃ for 4 hours until the pellet strength reaches 1000-3000N.

[0040] After the dried pellets are mixed evenly with the carbonaceous reducing agent coke, they are added to an electric arc furnace for smelting. After smelting at 1700℃, a liquid silicon-calcium alloy is formed. The liquid silicon-calcium alloy is discharged from the bottom of the electric arc furnace and poured into an ingot casting machine to obtain a silicon-calcium alloy with the grade Ca20Si55 (alloy composition: Ca 22.1%, Si 55.4%, C 0.3%, Al 0.02%, P 0.03%, S 0.03%, O 1.26%, conforming to YB / T5051 standard).

[0041] Example 2:

[0042] A calcium-silicon alloy of grade Ca16Si55 was produced using 100 kg of magnesium smelting reducing slag, 660 kg of ferrosilicon dust, 110 kg of calcium carbide slag, and 336 kg of carbonaceous reducing agent. The magnesium smelting reducing slag contained 6% MgO, 31% SiO2, 59% CaO, and 1.38% Al2O3. The ferrosilicon dust contained 88% SiO2 and 3% Al2O3. The calcium carbide slag contained 68% CaO, 5% SiO2, and 1% Al2O3. The carbonaceous reducing agent was coke with a carbon content of 85%.

[0043] After mixing the above raw materials, they are ground using a ball mill. The fineness of the powder after grinding is 325 mesh with a passing rate of not less than 80%. Then, a pot granulator is used to granulate the powder. During the granulation process, an appropriate amount of water is added to the granulator and mixed. The granulation time meets the strength requirements of 1000-3000N. The pellets are taken out when the diameter reaches 20-40mm.

[0044] The removed material balls are air-dried naturally at an ambient temperature of 25℃ and a humidity of 50% for 7 days until the strength of the material balls reaches 1000-3000N.

[0045] After the dried pellets are mixed evenly with coke, they are added to an electric arc furnace for melting. After melting at 1650℃, a liquid silicon-calcium alloy is formed. The liquid silicon-calcium alloy is discharged from the bottom of the electric arc furnace and poured into an ingot casting machine to obtain a silicon-calcium alloy with the grade Ca16Si55 (alloy composition: Ca 18.3%, Si 55.9%, Al 0.03%, C 0.42%, P 0.03%, S 0.02%, O 1.93%, conforming to YB / T5051 standard).

[0046] Example 3:

[0047] The production of Ca16Si55 silicon-calcium alloy is achieved using magnesium smelting reducing slag, microsilica powder, ferrosilicon dust, and carbide slag. The raw materials used are: 100 kg of magnesium smelting reducing slag, with MgO content of 7%, SiO2 content of 28%, CaO content of 53%, and Al2O3 content of 5%; 100 kg of ferrosilicon dust with SiO2 content of 68% and Al2O3 content of 8%; 500 kg of microsilica powder with SiO2 content of 95% and Al2O3 content of 1.5%; 100 kg of carbide slag (CaO content of 60%, SiO2 content of 5%, and Al2O3 content of 2.5%); and 354 kg of anthracite with a fixed carbon content of 75%.

[0048] After mixing the above raw materials, they are ground using a ball mill. The fineness of the powder after grinding is 325 mesh with a passing rate of not less than 80%. Then, a pot granulator is used to granulate the powder. During the granulation process, an appropriate amount of water is added to the granulator and mixed. The granulation time meets the strength requirements of 1000-3000N. The pellets are taken out when the diameter reaches 20-40mm.

[0049] The extracted balls are air-dried naturally at an ambient temperature of 30℃ and a humidity of 45% for 5 days until the ball strength reaches 1000-3000N.

[0050] After the dried pellets are mixed evenly with coke, they are added to an electric arc furnace for melting. After melting at 1600℃, a liquid silicon-calcium alloy is formed. The liquid silicon-calcium alloy is discharged from the bottom of the electric arc furnace and poured into an ingot casting machine to obtain a silicon-calcium alloy with the grade Ca16Si55 (alloy composition: Ca 16.5%, Si 55.0%, Al 0.03%, C 0.38%, P 0.01%, S 0.01%, O 1.53%, conforming to YB / T5051 standard).

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications made based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A process for preparing silicon-calcium alloy using magnesium smelting reducing slag and other industrial solid waste, comprising the following steps: a. Raw material pretreatment: Magnesium smelting reducing slag, microsilica powder and / or ferrosilicon dust, and calcium carbide slag are mixed in a weight ratio of 1:1.5-8.0:0-4 and then ground to a 325-mesh pass rate of ≥80%. The mixture is then used to prepare pellets with a diameter of 20-40 mm and a strength of 1000-3000 N using granulation equipment. The pellets are then dried at 105℃±5℃ for 3-6 hours or air-dried naturally for 3-10 days. b. Batching and smelting: The dehydrated pellets and carbonaceous reducing agent are mixed at a weight ratio of 1:0.30 to 0.

55. The raw material ratio is adjusted according to the target silicon-calcium alloy grade. The mixture is then smelted in a submerged arc furnace at 1500℃ to 1850℃ for 2 to 5 hours. c. Alloy forming: Liquid silicon-calcium alloy is periodically discharged and poured into a fixed mold for cooling to obtain a product with qualified chemical composition.

2. The process for preparing silicon-calcium alloys using magnesium smelting reducing slag and other industrial solid wastes according to claim 1, characterized in that: The magnesium reduction slag contains, by mass percentage, 4%–8% MgO, 22%–33% SiO2, 40%–60% CaO, and 1%–5% Al2O3.

3. The process for preparing silicon-calcium alloys using magnesium reducing slag and other industrial solid wastes according to claim 1, characterized in that: The microsilica powder contains 80%–97% SiO2 and 0–1.5% Al2O3; the ferrosilicon dust contains 40%–90% SiO2 and 1%–10% Al2O3.

4. The process for preparing silicon-calcium alloys using magnesium reducing slag and other industrial solid wastes according to claim 1, characterized in that: The calcium carbide slag contains 60% to 70% CaO, 3% to 5% SiO2, and 0.5% to 2.5% Al2O3.

5. The process for preparing silicon-calcium alloys using magnesium smelting reducing slag and other industrial solid wastes according to claim 1, characterized in that: The carbonaceous reducing agent is coke, semi-coke, or anthracite; the carbonaceous reducing agent has a fixed carbon content of ≥75%.

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