阅读说明：本技术 一种取之于精炼镁废固渣而用之于镁的方法 (Method for extracting magnesium from refined magnesium waste solid slag ) 是由 张伟 张嘉洋 于 2021-09-17 设计创作，主要内容包括：本发明一种取之于精炼镁废固渣而用之于镁的方法属于工业制造技术和环境保护资源综合利用领域,是一种从精炼镁及合金废固渣干选提粗镁粒,水溶解剩余物的母液制熔剂,过滤固渣再制金属镁的方法。此方法既能解决增加耗能、浪费资源、不能彻底消灭含剧毒废渣的问题;又能达到资源综合利用保护环境,还能生产出高附加值金属镁和熔剂产品,为镁业的可持续发展打下基础。破碎精炼镁渣,筛选、风选出粗镁粒。可作制镁原料。剩余物溶解、过滤,母液蒸发、浓缩、脱水、熔融、冷却、破碎,制得生产金属镁及镁合金熔剂。过滤下的固渣烘干,含氧化镁80%以上,制的生产金属镁的极品原料。(The invention relates to a method for preparing magnesium from refined magnesium waste solid slag, belongs to the field of industrial manufacturing technology and environment-friendly resource comprehensive utilization, and is a method for preparing magnesium metal by dry separation and extraction of coarse magnesium particles from refined magnesium and alloy waste solid slag, dissolution of residual mother liquor by water, and filtration of solid slag. The method can solve the problems of increasing energy consumption, wasting resources and not thoroughly eliminating waste residues containing high toxicity, can achieve the comprehensive utilization of resources to protect the environment, can produce metal magnesium and flux products with high added values, and lays a foundation for the sustainable development of the magnesium industry. Crushing the refined magnesium slag, screening and winnowing to obtain coarse magnesium particles. Can be used as raw material for preparing magnesium. Dissolving and filtering the remainder, evaporating, concentrating, dehydrating, melting, cooling and crushing the mother liquor to prepare the flux for producing the magnesium metal and the magnesium alloy. Drying the filtered solid slag containing more than 80% of magnesium oxide to prepare the best raw material for producing the metal magnesium.)

1. The method for preparing magnesium from refined magnesium waste solid slag is characterized in that the method is prepared by taking refined magnesium and magnesium alloy waste solid slag as raw materials through the following processing technology:

(1) crushing the refined magnesium slag to obtain particles with the particle size of less than 5mm, screening, milling, and separating out 15-2.5% of coarse magnesium particles by air separation;

(2) adding appropriate amount of SO-free residue to the residue_４ ^２－Stirring and dissolving the solution to make the solution in a saturated state, filtering, evaporating the mother liquor, concentrating, cooling, crystallizing, and centrifugally dewatering to extract the water-containing carnallite;

(3) adding MgCl with purity of more than 95 percent into the carnallite containing water according to the proportion which can produce barium flux standard shown in the table 1 after the test_２、KCl、BaCl_２Heating to 750 deg.C in a crucible, dewatering and melting completely, cooling the melt to 30-50 deg.C, crushing to obtain dewatered carnallite, also called flux finished product, whose index is regulated to the barium flux standard shown in Table 1, if no pure MgCl is added_２、KCl、BaCl_２The products shown in Table 2 were obtained;

table 1: barium flux reference standard table

Index name Index (I) Index name Index (I) MgCl_２Content (%) 38～46 Water-insoluble matter, ash content (%) ≤O.5 KCl content (%) 32～40 Ignition loss (%) ≤2.0 MgO content (%) ≤1.5 Total content of sodium chloride and calcium chloride (%) ≤8.0 BaCl₂Content (%) 5.0～8.0

Table 2: index table for natural dehydration product

Index name Index (I) Index name Index (I) MgCl_２Content (%) 47～54 Water-insoluble matter, ash content (%) ≤O.5 KCl content (%) 30～42 Ignition loss (%) ≤1.5 BaC1₂Content (%) 1～3 Total content of sodium chloride and calcium chloride (%) ≤8.0 MgO content (%) ≤1.5

(4) Hydrogen chloride gas and water vapor generated in the processes of dehydration and melting are absorbed and condensed to generate diluted hydrochloric acid which is received into a glass fiber reinforced plastic vessel, and then a proper amount of filtered solid slag with the main component of magnesium oxide is added to prepare MgCl_２The product is also a raw material for producing the fusing agent, and then the fusing agent is repeatedly produced;

(5) and thoroughly cleaning the filtered solid slag again to ensure that soluble salt does not remain in the slag, filtering for the second time, returning unsaturated mother liquor to the dissolving process for repeated use, drying the filtered solid slag to obtain the raw material for producing the metal magnesium, wherein the content of magnesium oxide is more than 80%.

Technical Field

The invention belongs to the field of industrial manufacturing technology and comprehensive utilization of environmental protection resources, and relates to a method for preparing magnesium metal by dry separation and extraction of coarse magnesium particles from waste solid slag of refined magnesium and magnesium alloy, dissolution of a mother solution of residues by water, filtration of the solid slag and further preparation of magnesium metal.

Background

At home and abroad, the metal magnesium and magnesium alloy are not only widely applied to the fields of aerospace, military, traffic (including automobile, airplane, motorcycle, bicycle industry and the like), and the like, but also are further applied to the fields of electronic technology, optical equipment and other precision machinery along with the increasing refinement of the electronic technology. The reserve and the yield of magnesium resources in China are at the top of the world; the yield is above 2/3 worldwide. The built productivity of magnesium and magnesium alloy breaks through million tons, wherein the productivity is mainly distributed in 60 million T/year in Shaanxi, 20 million T/year in Shanxi and 20 million T/year in Ningxia. The rapid rise of the magnesium industry has great significance for integrally improving the national economic level. And a huge environmental burden is generated during production and utilization. The defects of low technical level, high pollution and high energy consumption still exist in part of the current magnesium metal industry in China. And the refined waste slag is about 200 KG-300 KG when one ton of magnesium is produced, and the total amount of magnesium-smelting waste slag discharged every year in China is more than 20 ten thousand tons. At present, most enterprises of the refining waste residues can not recycle and are generally discharged to remote places. Over time, on the one hand, these residues undergo weathering to form dust which drifts around to pollute the environment. On the other hand, the waste residues contain a large amount of alkaline substances, and can be dissolved and taken away by water under the driving action of rainwater, so that the surrounding soil is alkalized, and underground water sources are polluted. If the water is not hard, the underground water source is changed into hard water due to the increase of calcium and magnesium ions; the waste residue contains barium chloride which is very soluble in water to form highly toxic pollution. Some enterprises construct leakage-free waste solid discharge fields [1] by huge capital consumption, but cannot ensure that the waste materials cannot leak after being continuously accumulated and moved geologically. Finally, hidden troubles are buried for later people, and the problem of pollution sources cannot be thoroughly solved once and for all. This problem cannot be solved and eventually limits the development of the magnesium industry. Therefore, it is very important to effectively utilize the waste solid slag of magnesium smelting to avoid secondary discharge. The existing methods for treating refined magnesium slag basically comprise the following two methods:

1. the flux consumption is increased and then the refining is carried out to extract the metal magnesium, so that the energy consumption is increased, and the waste residue containing the high toxicity is continuously generated.

2. The dilute hydrochloric acid is used to dissolve refined magnesium slag to prepare carnallite and magnesium chloride [2], and this process needs to consume a lot of hydrochloric acid and sodium carbonate, but rather the magnesium grains with high value are produced into low-value magnesium chloride, and the waste slag is still produced secondarily.

The two methods increase energy consumption, waste resources and cannot thoroughly eliminate waste residues. The only method for producing the flux in China at present is to dehydrate and prepare the raw material of the water-containing carnallite which is unique in the Carlo salt lake in the Guermu area of Qinghai province in China. The raw material of the water-containing carnallite is extremely expensive, is mainly used as a raw material of potash fertilizer, and can be used as a raw material of electrolytic magnesium metal. Therefore, a method which is completely beautiful, saves energy, thoroughly decomposes and comprehensively utilizes resources, protects the environment and can produce high-quality products must be developed.

Disclosure of Invention

In order to solve the problems of increasing energy consumption, wasting resources and recycling waste residues, achieve the purposes of protecting the environment and thoroughly and comprehensively utilizing resources, lay the foundation for the sustainable development of the magnesium industry, and provide high-quality products, the following manufacturing method is developed:

1. collecting the waste refined magnesium slag of the magnesium metal and magnesium alloy plant, and separating 15-2.5% of coarse magnesium particles by crushing (the particle size is less than 5 mm), screening, pulverizing and winnowing. The product can be refined to purify the magnesium metal. Namely a semi-finished product raw material for producing the metal magnesium.

2. The residue, as shown in Table 1, was added with an appropriate amount of SO-free water_４ ^２－Water, stirring, dissolving (MgCl)₂、KCl、BaCl₂、CaC1₂And NaC1 are all dissolved in water, and MgO and the like are not dissolved in water) to make the solution saturated, filtering, evaporating the mother liquor, concentrating, cooling, crystallizing, and centrifugally dewatering to extract the hydrous carnallite, the standard of which is shown in Table 2. The main component of the filtered solid slag is magnesium oxide. And (4) cooling and recycling the water vapor generated by evaporating the mother liquor.

Table 1: composition table of residual refined magnesium slag

Composition (I)	MgCl２	KCl	BaC12	NaC1	MgO
						Content (%)	53.0	30.0	1.5	6.0	5.28
Composition (I)	CaC12	CaF2	Dust	Fe２＋+Cu２＋	Mn２＋
						Content (%)	3.0	0.5	0.5	0.2	0.02

Table 2: composition table of hydrous carnallite

3. The hydrous carnallite is added with MgCl with purity of more than 95 percent according to the proportion of the hydrous carnallite which can produce barium flux standard shown in the table 3 after the test₂、KCl、BaCl₂Heating to 750 deg.C in stainless steel pot, dewatering and melting, cooling to 30-50 deg.C, and crushing to obtain dewatered carnallite, also called flux, whose index is regulated to the barium flux standard shown in Table 3. If no pure MgCl is added₂、KCl、BaCl₂Products as shown in Table 4 were produced. The product is a necessary flux for producing metal magnesium and magnesium alloy, and at least 120 kg of barium flux is used for producing one ton of metal magnesium.

Table 3: barium flux reference standard table

Index name	Index (I)	Index name	Index (I)
				MgCl２Content (%)	38～46	Water-insoluble matter, ash content (%)	≤O.5
KCl content (%)	32～40	Ignition loss (%)	≤2.0
				MgO content (%)	≤1.5	Total content of sodium chloride and calcium chloride (%)	≤8.0
BaC12Content (%)	5.0～8.0

Table 4: index table for natural dehydration product

Index name	Index (I)	Index name	Index (I)
				MgCl２Content (%)	47～54	Water-insoluble matter, ash content (%)	≤O.5
KCl content (%)	30～42	Ignition loss (%)	≤1.5
				BaC12Content (%)	1～3	Total content of sodium chloride and calcium chloride (%)	≤8.0
MgO content (%)	≤1.5

4. Hydrogen chloride gas and water vapor generated in the dehydration and melting process are absorbed and condensed to generate diluted hydrochloric acid which is received into a glass fiber reinforced plastic vessel, and then a proper amount of filtered solid slag with the main component of magnesium oxide is added to prepare MgCl₂. The product is also a raw material for producing the fusing agent, and then the fusing agent is repeatedly produced.

5. And thoroughly cleaning the filtered solid slag again to ensure that soluble salt does not remain in the slag, filtering for the second time, returning unsaturated mother liquor to the dissolving process for repeated use, drying the filtered solid slag to obtain the magnesium oxide with the content of more than 80 percent, and preparing the best-quality raw material for producing the metal magnesium. Referred to herein as the magnesia feedstock.

The most widely used Pidgeon process for smelting magnesium in domestic magnesium smelting industry, and the most representative silicothermic process for smelting magnesium, is to calcine dolomite (MgCO)₃CaCO₃= MgO•CaO+2CO₂℃. (w) (Si) =75%) and fluorite powder (w (CaF) =95%) are ground and mixed with the ferrosilicon powder to prepare balls (the ball preparation pressure is 9.8-29.4 MPa), the balls are conveyed into a heat-resistant steel reduction tank, and the balls are reduced into crude magnesium under the vacuum conditions of l 190-l 210 ℃ and 1.33-10 Pa, wherein the reaction process is that 2(MgOCaO) Si =2Mg ℃ = 2CaOSiO₂And refining by using a flux to produce the magnesium metal. The general calcined dolomite component is CaO 32.50%; 20.58 percent of MgO; fe₂O₃2.18%；SiO₂0.96 percent; loss on ignition (CO)₂) 43.78% of the magnesium oxide raw material is added according to a certain proportion before the mixing and ball making stage in the process of producing the magnesium metal by adopting the silicothermic Pidgeon magnesium smelting process. 4 tons of dolomite can be used instead of 1 ton of the raw material, and the carbon dioxide emission of calcining 4 tons of dolomite is correspondingly reduced. And can also reduce the dosage of a large amount of ferrosilicon. The raw material cost is remarkably reduced.

In the whole process of treating the metal magnesium and magnesium alloy refining waste solid slag, the produced gas, liquid and solid are all comprehensively utilized in the production of magnesium.

Reference to the literature

[1] Influence of Liu Feng, magnesium salt/mineralized refuse modification on gas production performance of sewage and sludge [ J ]. Sichuan environment, 2013,32(04):28-32.

[2] Sea lake salt and chemical industry, stage 1 in 2006.