阅读说明：本技术 一种工业硅中杂质铁的去除方法 (Method for removing impurity iron in industrial silicon ) 是由 魏奎先 马文会 邓小聪 伍继君 于 2020-07-13 设计创作，主要内容包括：本发明涉及一种工业硅中杂质铁的去除方法,属于工业硅冶炼技术领域。本发明将工业硅熔体连续匀速加入到定向凝固连铸装置中,控制硅熔体的温度和流速、凝固速度以实现杂质铁的偏析富集,得到铁含量梯级分布的硅锭产品；对硅锭产品进行取样检测,确定Fe含量梯级分布的节点,并对硅锭进行分级处理得到不同铁质量含量的各级工业硅产品；以工业硅产品的总质量为100％计,微铁工业硅产品不低于60％、低铁工业硅产品不低于22％、中铁工业硅产品不高于10％、高铁工业硅产品不高于8％。本发明方法与现有的工业硅冶炼和炉外精炼过程相结合,将硅熔体直接进行高效除铁,可以将工业硅产品的等级提高2-3个等级,具有生产成本低、技术适应性广、应用前景广阔等特点。(The invention relates to a method for removing impurity iron in industrial silicon, and belongs to the technical field of industrial silicon smelting. The method comprises the steps of continuously adding industrial silicon melt into a directional solidification fixed casting device at a constant speed, and controlling the temperature, flow rate and solidification speed of the silicon melt to realize segregation and enrichment of impurity iron so as to obtain a silicon ingot product with iron content distributed in a step manner; sampling and detecting silicon ingot products, determining nodes of the gradient distribution of the Fe content, and carrying out grading treatment on the silicon ingots to obtain various levels of industrial silicon products with different iron mass contents; based on the total mass of the industrial silicon product as 100%, the micro-iron industrial silicon product is not less than 60%, the low-iron industrial silicon product is not less than 22%, the medium-iron industrial silicon product is not more than 10%, and the high-iron industrial silicon product is not more than 8%. The method is combined with the existing industrial silicon smelting and external refining processes, the silicon melt is directly subjected to high-efficiency iron removal, the grade of the industrial silicon product can be improved by 2-3 grades, and the method has the characteristics of low production cost, wide technical adaptability, wide application prospect and the like.)

1. A method for removing impurity iron in industrial silicon is characterized by comprising the following specific steps:

continuously adding industrial silicon melt to be deironized into a directional solidification fixed casting device at a constant speed, controlling the temperature, flow rate and solidification speed of the silicon melt to realize segregation and enrichment of impurity iron, obtaining silicon ingot products with iron content in step distribution, sampling and detecting the silicon ingot products, determining nodes with the Fe content in step distribution, and carrying out grading treatment on the silicon ingot to obtain all-grade industrial silicon products with different iron mass contents.

2. The method for removing impurity iron in industrial silicon according to claim 1, wherein: the industrial silicon melt includes, but is not limited to, a silicon melt directly smelted by a submerged arc furnace, a silicon melt refined outside the furnace, a silicon melt melted by heating massive industrial silicon, and a silicon melt melted by silicon-containing waste.

3. The method for removing impurity iron in industrial silicon according to claim 1, wherein: the temperature of the silicon melt is 1450-1750 ℃, the flow rate of the silicon melt is 0.1-15 kg/s, and the directional solidification speed is 0.1-10 cm/s.

4. The method for removing impurity iron in industrial silicon according to claim 3, wherein: the industrial silicon products comprise micro-iron industrial silicon products, low-iron industrial silicon products, medium-iron industrial silicon products and high-iron industrial silicon products which are divided by the mass content of iron.

5. The method for removing impurity iron in industrial silicon according to claim 4, wherein: the mass fraction of iron in the micro-iron industrial silicon product is less than 0.1%, the mass fraction of iron in the low-iron industrial silicon product is 0.1-0.3%, the mass fraction of iron in the medium-iron industrial silicon product is 0.3-0.5%, and the mass fraction of iron in the high-iron industrial silicon product is more than 0.5%.

6. The method for removing impurity iron in industrial silicon according to claim 4, wherein: based on the total mass of the industrial silicon product as 100%, the micro-iron industrial silicon product is not less than 60%, the low-iron industrial silicon product is not less than 22%, the medium-iron industrial silicon product is not more than 10%, and the high-iron industrial silicon product is not more than 8%.

Technical Field

The invention relates to a method for removing impurity iron in industrial silicon, and belongs to the technical field of industrial silicon smelting.

Background

The capacity and the yield of industrial silicon (metal silicon) in China exceed 2/3 of the world, in order to improve the quality of industrial silicon products, foreign impurities are removed by an external oxidation refining technology in industrial silicon production enterprises at home and abroad, and particularly, the impurities such as Al, Ca and the like in a crude silicon product can obtain a good removal effect. However, the limitation of the technology is that the main metal impurity Fe in the industrial silicon product cannot be effectively separated, so that the Fe impurity becomes a key impurity element which directly affects the grade of the industrial silicon, and a general method adopted for solving the problem is mainly to control the content of the impurity Fe in the industrial silicon product by controlling production raw materials and a smelting process. Meanwhile, along with the fluctuation of raw material components and furnace conditions, the quality regulation and control effect of the industrial silicon product realized by the method is unstable, so that the quality of the industrial silicon product has obvious instability, and the adverse effects of deterioration of supply and demand relationship between the industrial silicon production industry and the downstream industry, gliding of the industrial silicon enterprise benefit and the like are caused.

In the existing industrial silicon purification technology, based on a segregation theory, a directional solidification technology is that the purpose of enriching impurity Fe in a backward solidification liquid phase is realized through a controllable solidification process, so that the industrial silicon of a first solidification part obtains higher purity, but in the aspect of a casting process of melts in the industrial silicon industry, a natural air cooling type solidification technology of die casting is always adopted, silicon melts obtained by ladle oxygen blowing refining are directly poured into an ingot mould, and silicon ingot products are formed through natural cooling. The solidification mode is greatly influenced by factors such as ingot mold structure, melt component fluctuation, manual operation in the casting process and the like, so that component segregation with different degrees is generated in the industrial silicon melt die casting process, the uniformity of industrial silicon products is obviously influenced, and the product quality grade determined according to random sampling detection results and the real product quality are greatly different; therefore, the existing intermittent solidification forming technology cannot meet the continuous controllable requirement of the directional solidification Fe removing technology. The existing polycrystalline silicon ingot casting technology cannot be directly applied to the industrial silicon production process because the equipment cost and the equipment operation cost of polycrystalline silicon ingot casting are high, the intermittent production period is long, and the polycrystalline silicon ingot casting technology cannot be effectively grafted with the industrial silicon industry with low-cost space and a continuous production mode.

Disclosure of Invention

As the segregation coefficient of metallic impurity Fe element in industrial silicon is far less than 1, only 6.4 × 10^-6Can be sent during the casting solidification processEffective segregation occurs, Fe element is also a main segregation phase in the existing industrial silicon product, and under the condition of the conventional ingot casting process, the segregation phase can only be deposited in the industrial silicon product because the impurity Fe cannot be removed by blowing refining and the like. The quality of industrial silicon products can fluctuate significantly with the change of the Fe content in the raw materials. The invention provides a method for removing impurity iron in industrial silicon, aiming at the problem of removing impurity Fe in the existing industrial silicon purification technology, and based on the existing industrial silicon production technology, the method integrates the advantages of controllable solidification and segregation and impurity removal of the directional solidification technology and the characteristics of low cost and continuous production of the continuous casting technology, and controls the segregation and enrichment position of impurity Fe in silicon melt through the continuously controllable melt cooling rate and the controllable ingot casting rate, so that the impurity Fe is intensively segregated and enriched into the uncrystallized tail melt, the Fe content in the industrial silicon product which is solidified firstly is reduced, and the production target of the low-Fe high-quality industrial silicon product is realized. The invention can realize the low-cost production target of producing high-quality industrial silicon products from low-quality silicon products.

A method for removing impurity iron in industrial silicon comprises the following specific steps:

continuously adding industrial silicon melt to be deironized into a directional solidification fixed casting device at a constant speed, controlling the temperature, flow rate and solidification speed of the silicon melt to realize segregation and enrichment of impurity iron, obtaining silicon ingot products with iron content in step distribution, sampling and detecting the silicon ingot products, determining nodes with the Fe content in step distribution, and carrying out grading treatment on the silicon ingot to obtain all-grade industrial silicon products with different iron mass contents.

The industrial silicon melt includes, but is not limited to, a silicon melt directly smelted by a submerged arc furnace, a silicon melt refined outside the furnace, a silicon melt melted by heating massive industrial silicon, and a silicon melt melted by silicon-containing waste.

Furthermore, the temperature of the silicon melt is 1450-1750 ℃, the flow rate of the silicon melt is 0.1-15 kg/s, and the directional solidification speed is 0.1-10 cm/s.

The industrial silicon products comprise micro-iron industrial silicon products, low-iron industrial silicon products, medium-iron industrial silicon products and high-iron industrial silicon products according to the mass content of iron.

Further, the mass fraction of iron in the micro-iron industrial silicon product is less than 0.1%, the mass fraction of iron in the low-iron industrial silicon product is 0.1-0.3%, the mass fraction of iron in the medium-iron industrial silicon product is 0.3-0.5%, and the mass fraction of iron in the high-iron industrial silicon product is more than 0.5%.

The total mass of the industrial silicon product is 100%, the micro-iron industrial silicon product is not less than 60%, the low-iron industrial silicon product is not less than 22%, the medium-iron industrial silicon product is not more than 10%, and the high-iron industrial silicon product is not more than 8%.

The invention has the beneficial effects that:

(1) according to the method, the supercooling degree and the directional solidification speed of the directional solidification continuous casting device are adjusted according to the size of the directional solidification continuous casting device and the real-time temperature of a melt, continuous feeding and continuous ingot discharging are realized by continuous ingot casting of industrial silicon, Fe impurities with the segregation coefficient far smaller than 1 in the industrial silicon melt are promoted to be continuously segregated and enriched into the uncrystallized melt of the directional solidification continuous casting device, and a continuous silicon ingot with the Fe content in step distribution is obtained;

(2) by utilizing the method, the total mass of the industrial silicon product is 100 percent, the micro-iron industrial silicon product is not less than 60 percent, the low-iron industrial silicon product is not less than 22 percent, the medium-iron industrial silicon product is not higher than 10 percent, and the high-iron industrial silicon product is not higher than 8 percent, so the method is combined with the existing industrial silicon smelting and external refining processes, the silicon melt is directly subjected to high-efficiency iron removal, the grade of the industrial silicon product can be improved by 2-3 grades, and the method has the characteristics of low production cost, wide technical adaptability, wide application prospect and the like;

(3) the invention breaks through the control link of Fe content in the raw materials for industrial silicon enterprises, and solves the problem of the dependence of the industrial silicon production on the raw materials.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a schematic diagram of industrial silicon product grading.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.