阅读说明：本技术 一种硅熔体可控凝固去除杂质元素的方法 (Method for removing impurity elements by controllable solidification of silicon melt ) 是由 魏奎先 邓小聪 马文会 吕国强 于 2020-07-13 设计创作，主要内容包括：本发明涉及一种硅熔体可控凝固去除杂质元素的方法,属于工业硅冶炼技术领域。本发明将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元素的偏析富集,得到杂质元素含量梯级分布的硅锭产品,对硅锭产品进行取样检测,确定杂质元素含量梯级分布的节点,并对硅锭进行分级处理得到不同杂质元素总质量含量的各牌号等级的工业硅产品,其中杂质元素包括Al、Ca、Mn、Ti、Mg、P、B、S、V、Cr、Ni、Cu、Zn、Zr中的一种或多种。本发明可与现有的工业硅冶炼、硅熔体炉外精炼提纯的过程相结合,对硅熔体直接进行高效提纯,实现硅熔体中杂质元素的同步高效去除,精炼提纯后可将硅产品的等级提高2-3个等级。(The invention relates to a method for removing impurity elements by controllable solidification of silicon melt, belonging to the technical field of industrial silicon smelting. The method comprises the steps of continuously adding silicon melt into a directional solidification fixed casting device at a constant speed, controlling the temperature, the flow rate and the solidification speed of the silicon melt to realize segregation and enrichment of impurity elements, obtaining silicon ingot products with gradient distribution of the content of the impurity elements, sampling and detecting the silicon ingot products, determining nodes with the gradient distribution of the content of the impurity elements, and carrying out grading treatment on the silicon ingot to obtain industrial silicon products with grades of various brands and grades of the total mass content of different impurity elements, wherein the impurity elements comprise one or more of Al, Ca, Mn, Ti, Mg, P, B, S, V, Cr, Ni, Cu, Zn and Zr. The invention can be combined with the existing processes of industrial silicon smelting and external refining and purification of silicon melt, directly and efficiently purify the silicon melt, realize the synchronous and efficient removal of impurity elements in the silicon melt, and improve the grade of silicon products by 2-3 grades after refining and purification.)

1. A method for removing impurity elements by controllable solidification of silicon melt is characterized by comprising the following specific steps:

continuously and uniformly adding the silicon melt into a directional solidification fixed casting device, controlling the temperature, flow rate and solidification speed of the silicon melt to realize segregation and enrichment of impurity elements, obtaining silicon ingot products with gradient distribution of the content of the impurity elements, sampling and detecting the silicon ingot products, determining nodes of the gradient distribution of the content of the impurity elements, and carrying out grading treatment on the silicon ingot to obtain industrial silicon products with different grades of various grades of the total mass content of the impurity elements, wherein the impurity elements comprise one or more of Al, Ca, Mn, Ti, Mg, S, V, Cr, Ni, Cu, Zn and Zr.

2. The silicon melt controlled solidification impurity element removal method as set forth in claim 1, wherein: the 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 silicon melt controlled solidification impurity element removal method as set forth in claim 1, wherein: the temperature of the silicon melt is 1420-1650 ℃, the flow rate of the silicon melt is 0.1kg/s-7.5kg/s, and the directional solidification speed is 0.1cm/s-5 cm/s.

4. The silicon melt controlled solidification impurity element removal method as set forth in claim 3, wherein: the grades of the industrial silicon products comprise 1101#, 2202#, 3303#, 421#, 441#, and 553#, which are divided by the total mass content of different impurity elements.

5. The silicon melt controlled solidification impurity element removal method as set forth in claim 4, wherein: based on 100 percent of the total mass of the industrial silicon products, the 1101# grade industrial silicon product is not less than 30 percent, the 2202# grade industrial silicon product is not less than 20 percent, the 3303# grade industrial silicon product is not less than 20 percent, the sum of the 421# grade industrial silicon product and the 441# industrial silicon product is not less than 20 percent, and the 553# industrial silicon product is not more than 8 percent.

Technical Field

The invention relates to a method for removing impurity elements by controllable solidification of silicon melt, belonging to the technical field of industrial silicon smelting.

Background

Industrial silicon is used as a base material in the organosilicon industry and the photovoltaic industry, and the requirement on the impurity content is extremely strict. In the industrial silicon production industry, the method is generally adopted at present, and is the only impurity removal technology at present of enterprises, namely ladle blowing oxidation refining, and the technology can remove a large amount of oxygen-philic impurities Al and Ca in a crude silicon melt, but cannot remove non-oxygen-philic impurity elements and trace impurity elements. Meanwhile, the residual Al, Ca and other impurity elements remain in the oxidized and refined industrial silicon melt, and are finally left in the industrial silicon product after being formed by a rough die casting technology and generate obvious segregation phenomenon, so that the product is not uniform. Therefore, the quality of the industrial silicon is completely limited by the raw materials, and when the content of non-oxygen-philic impurity elements and trace impurities in the raw materials is high, the quality of the produced industrial silicon product is poor. Meanwhile, in order to meet the requirements of downstream industries, industrial silicon products must be subjected to secondary refining treatment. The improved siemens method, silane method and metallurgical method technology are effective intermediate processes for removing impurities in industrial silicon, but the processes all have a common problem of instability of raw material treatment components, which leads to the need of real-time regulation and control of technological parameters to achieve the aim of stable production. In addition, the change of the initial impurity content in the industrial silicon can greatly influence the efficiency of the secondary refining process. If the content of impurities in the industrial silicon product is low and stable, the technical route for purifying the industrial silicon by the metallurgical method can be greatly shortened, the production efficiency can be obviously improved, and the production benefit of enterprises can be further improved.

In conclusion, in the industrial silicon smelting process, refining and casting equipment is simple, so that the refining effect and the ingot casting uniformity are extremely rough, the improvement on the product quality is not obvious, and the value-added effect on the product is extremely low. Industrial silicon production has faced the problem of stable quality industrial silicon production, and the industrial silicon industry will face the technical problem of how to produce high quality industrial silicon from low quality raw materials. However, the existing refining and ingot casting technologies severely limit the progress of industrial silicon production technology and the stable production of high-quality industrial silicon products.

Disclosure of Invention

The invention provides a method for removing impurity elements stably by controllable solidification of silicon melt, aiming at the problem that most impurity elements are difficult to remove in the existing industrial silicon purification ingot casting technology. Based on the existing industrial silicon production process, the invention adopts a continuous casting mode, controls the segregation enrichment position of the impurity elements in the silicon melt through the continuously controllable melt cooling rate and the controllable ingot casting rate, and enables the impurity elements to be enriched into the uncrystallized tail melt in a reinforced segregation manner, thereby reducing the content of the impurity elements in the pre-solidified industrial silicon product and realizing the production target of the high-quality industrial silicon product with low impurities. The invention can ensure the stability of the production target of high-quality industrial silicon products.

As shown in Table 1, since the segregation coefficients of Al, Ca, Mn, Ti, Mg, P, B, S, V, Cr, Ni, Cu, Zn, Zr and other impurity elements in the industrial silicon are all less than 1, segregation can occur in the casting solidification process, and under the conventional ingot casting process conditions, the segregation phase can only be deposited in the industrial silicon product. On the basis of ensuring continuous solidification of the melt, the invention reduces the impurities such as Al, Ca, Mn, Ti, Mg, P, B, S, V, Cr, Ni, Cu, Zn, Zr and the like remained in the primary silicon part by adjusting the temperature of the melt, the flow rate of the melt and controlling the solidification rate of the melt, so that the impurities are enriched in the solidified melt, finally the segregation phase of the impurities is enriched at the tail end of the ingot, and finally the segregation occurrence phase of the impurities is cut and separated at a fixed point according to the detection and analysis result.

TABLE 1 segregation coefficient of impurity elements in silicon

A method for removing impurity elements by controllable solidification of silicon melt comprises the following specific steps:

(1) and continuously adding the silicon melt into the 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 elements so as to obtain a silicon ingot product with the content of the impurity elements distributed in a gradient manner.

(2) And (2) continuously sampling and detecting the silicon ingot product obtained in the step (1), determining the nodes with gradient distribution of the content of the impurity elements, and carrying out grading treatment on the silicon ingot to obtain the industrial silicon products with different grades of each grade of the total mass content of the impurity elements, wherein the impurity elements comprise one or more of Al, Ca, Mn, Ti, Mg, P, B, S, V, Cr, Ni, Cu, Zn and Zr.

The 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.

The temperature of the silicon melt is 1420-1650 ℃, the flow rate of the silicon melt is 0.1kg/s-7.5kg/s, and the directional solidification speed is 0.1cm/s-5 cm/s.

The grades of the industrial silicon products comprise 1101#, 2202#, 3303#, 421#, 441#, and 553#, which are divided by the mass content of different impurity elements.

And the sum of the 1101# grade industrial silicon product, the 2202# grade industrial silicon product, 3303# grade industrial silicon product, 421# and 441# grade industrial silicon product is not less than 20%, and the 553# grade industrial silicon product is not more than 8%, based on the total mass of the finally obtained industrial silicon product as 100%.

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, and the continuous segregation and enrichment of impurity elements with the condensation coefficient smaller than 1 in the silicon melt to be treated into the uncrystallized melt of the directional solidification continuous casting device are promoted, so that the content of the impurity elements in an industrial silicon product which is solidified firstly is reduced, the continuous silicon ingot with the impurity element content in step distribution is obtained, and the secondary refining and purification of the industrial silicon continuous casting are realized;

(2) by using the method, based on the total mass of the finally obtained industrial silicon product as 100%, the 1101# industrial silicon product is not less than 30%, the 2202# industrial silicon product is not less than 20%, the 3303# industrial silicon product is not less than 20%, the sum of 421# and 441# industrial silicon products is not less than 20%, and the 553# industrial silicon product is not more than 8%; therefore, the invention can be combined with the existing industrial silicon smelting and the process of external refining and purification of silicon melt, the silicon melt is directly and efficiently purified, the synchronous and efficient removal of impurity elements in the silicon melt is realized, and the grade of a silicon product can be improved by 2-3 grades after refining and purification.

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.