阅读说明：本技术 一种利用低品位硅石生产工业硅的方法 (Method for producing industrial silicon by using low-grade silica ) 是由 魏奎先 邓小聪 马文会 陈正杰 于 2020-07-13 设计创作，主要内容包括：本发明涉及一种利用低品位硅石生产工业硅的方法,属于工业硅冶炼技术领域。本发明将低品位硅石和碳质还原剂加入到矿热炉中进行冶炼得到低品质工业硅熔体；将低品质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质量含量的各级工业硅产品,其中杂质元素包括Fe、Al、Ca、Cu、V、Ti、Ni、Mn中的多种,工业硅产品包括化学级工业硅、冶金级工业硅和硅铁。本发明极大的降低了高质量工业硅产品对原料质量的依赖性。(The invention relates to a method for producing industrial silicon by using low-grade silica, belonging to the technical field of industrial silicon smelting. The method comprises the steps of adding low-grade silica and a carbonaceous reducing agent into an ore smelting furnace for smelting to obtain low-quality industrial silicon melt; continuously adding low-quality industrial 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 various levels of industrial silicon products with different mass contents of the impurity elements, wherein the impurity elements comprise various Fe, Al, Ca, Cu, V, Ti, Ni and Mn, and the industrial silicon products comprise chemical-level industrial silicon, metallurgical-level industrial silicon and ferrosilicon. The method greatly reduces the dependence of high-quality industrial silicon products on the quality of raw materials.)

1. A method for producing industrial silicon by using low-grade silica is characterized by comprising the following specific steps:

(1) adding low-grade silica and a carbonaceous reducing agent into an ore smelting furnace for smelting to obtain low-quality industrial silicon melt;

(2) continuously adding the low-quality industrial silicon melt obtained in the step (1) 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 elements to obtain 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, separating unqualified waste materials, and performing grading treatment on the silicon ingot to obtain various levels of industrial silicon products with different mass contents of the impurity elements, wherein the impurity elements comprise various Fe, Al, Ca, Cu, V, Ti, Ni and Mn, and the industrial silicon products comprise chemical-level industrial silicon, metallurgical-level industrial silicon and silicon iron.

2. The method for producing industrial silicon using low-grade silica according to claim 1, wherein: SiO in low-grade silica in step (1)₂The content is higher than 90%.

3. The method for producing industrial silicon using low-grade silica according to claim 1, wherein: step (1), adding an alloy additive into the low-quality industrial silicon melt to remove the non-metallic impurities B and/or P.

4. The method for producing industrial silicon using low-grade silica according to claim 1, wherein: the temperature of the silicon melt in the step (2) is 1450-1750 ℃, the flow rate of the silicon melt is 0.1-10 kg/s, and the directional solidification speed is 0.1-5 cm/s.

5. The method for producing industrial silicon using low-grade silica according to claim 1, wherein: in the industrial silicon product, the total amount of the chemical-grade industrial silicon and the metallurgical-grade industrial silicon is not less than 80 percent and the total amount of the ferrosilicon product is not more than 20 percent, calculated according to the total amount of the chemical-grade industrial silicon, the metallurgical-grade industrial silicon and the ferrosilicon being 100 percent.

Technical Field

The invention relates to a method for producing industrial silicon by using low-grade silica, belonging to the technical field of industrial silicon smelting.

Background

In order to improve the quality of industrial silicon products, most domestic and foreign industrial silicon production enterprises adopt external refining to remove impurities, particularly Al and Ca are well removed. But has no obvious removing effect on other non-oxophilic impurity elements, and the non-oxophilic impurity elements have obvious deposition phenomenon due to Si loss in the blowing refining process. Meanwhile, in the aspect of casting of industrial silicon melt, a die casting production process is always adopted, the silicon melt refined by blowing oxygen from the ladle is directly poured into an ingot mold, and a silicon ingot product is formed through natural cooling. In the casting process, due to the influence of factors such as ingot mold difference, melt component fluctuation, manual operation in the casting process and the like, component segregation with different degrees is generated in the industrial silicon melt die casting process, the uniformity of industrial silicon products is obviously influenced, the economic benefit of enterprises can be directly influenced by the difference between the product quality grade determined according to random sampling detection results and the actual product quality, and the quality dispute of downstream customers is also caused.

Therefore, industrial silicon production enterprises which depend on the quality of industrial silicon products for a long time have to start from the source and carry out layer-by-layer clearance in the industrial silicon smelting raw material link to strictly control the impurity content in the charging silica and the carbonaceous reducing agent, for example, the prior industrial silicon production process is used for SiO in the silica₂The content is required to be higher than 95%. In addition, due to the significant regional differences in silica composition from different origins, for example, the impurity content of the silica in the Shiwutai mountain is high and the impurity content of the silica in Liaoning Shimen is low. When selecting raw materials, industrial silicon companies often have some instability associated with the production area of the raw materials in order to obtain high-quality silica to ensure stable product quality. Further causing the fluctuation of the furnace condition in the industrial silicon smelting process. With the long-term consumption of high-quality silica, downstream enterprises do not decrease or increase the requirements on the quality of industrial silicon in order to obtain higher enterprise benefits, so that the improvement of the adaptability of raw materials in the industrial silicon smelting process is a problem which has to be paid attention to industrial development.

Disclosure of Invention

Aiming at the defects of producing industrial silicon by using low-grade silica in the prior art, the invention provides the method for producing the industrial silicon by using the low-grade silica, the method can obviously reduce the dependence of high-quality industrial silicon products on the quality of smelting raw materials such as the silica and the like, and effectively improve the production efficiency and the yield stability of the high-quality industrial silicon products by improving the refining and casting processes.

The principle of the invention is that the segregation coefficients of impurity elements such as Fe, Al, Ca, Cu, V, Ti, Ni, Mn and the like in the industrial silicon are all less than 1 (see table 1), and segregation can occur in the casting and solidification process, meanwhile, Fe impurities can not be effectively separated in the existing refining process, so that Fe becomes the key point for improving the quality of industrial silicon products, and the segregation coefficient of Fe is only 6.4 × 10 because the segregation coefficient of Fe is extremely small^-6Therefore, the segregation phase is very easy to occur in the process of solidification and is the main segregation phase composition 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. Therefore, the quality of silicon products fluctuates depending on the Fe content in the raw material, and the Fe content in silica needs to be strictly controlled. According to the invention, the deposition direction and position of impurities in the silicon melt are controlled through the controllable continuous melt cooling rate and the controllable ingot casting rate, so that the effective segregation of the metal impurities with the low segregation coefficient far less than 1 is realized, and the metal impurities are intensively precipitated into the uncrystallized tail melt. In the process, because of a large amount of metal impurities, such as Ca and Al, brought by the low-grade silica, the strengthening segregation process has a strong traction effect on the nonmetal impurities B, P with a large segregation coefficient, and further, the content of the nonmetal impurities in the industrial silicon product which is solidified first is favorably reduced. The synergistic precipitation separation of metal impurities and non-metal impurities realizes the purpose of refining and purifying the industrial silicon continuous ingot.

TABLE 1 segregation coefficient of each impurity element in silicon

A method for producing industrial silicon by using low-grade silica comprises the following specific steps:

(1) adding low-grade silica and a carbonaceous reducing agent into an ore smelting furnace for smelting to obtain low-quality industrial silicon melt, and selecting whether to carry out ladle oxygen blowing furnace external refining or add an alloy additive according to the component characteristics;

(2) continuously adding the low-quality industrial silicon melt obtained in the step (1) into a preheated directional solidification fixed casting device at a constant speed, adjusting the supercooling degree and the directional solidification speed of the directional solidification continuous casting device according to the size and the real-time temperature of the melt of the directional solidification continuous casting device, continuously feeding and continuously discharging ingots, and promoting the segregation of impurities such as Fe, Al, Ca, Mn, Cu, V, Ti, Ni and the like with the segregation coefficient of far less than 1 in the industrial silicon melt to be enriched in the uncrystallized melt at the upper part of a crystallization device to obtain a silicon ingot product with the impurity content in a step-shaped distribution;

(3) sampling and detecting the silicon ingot product obtained in the step (2), determining the nodes with gradient distribution of impurity content, and carrying out grading treatment on the silicon ingot to obtain chemical-grade industrial silicon, metallurgical-grade industrial silicon, ferrosilicon and intermediate products (waste materials) with different total impurity mass contents (see figure 2); returning the intermediate product (waste) to smelting and adding the intermediate product (waste) into the directional solidification and fixed casting device in the step (2) for continuous casting;

SiO in the low-grade silica in the step (1)₂The content is higher than 90%.

Before the low-quality industrial silicon melt in the step (1) enters the step (2), when the content of P is too high but the contents of Ca and Al which are P-philic metal impurities are not high, or the content of B is too high and the contents of Fe and Ti which are B-philic impurity elements are not enough, an alloy additive is added into the low-quality industrial silicon melt to increase the content of the alloy elements in the silicon melt, so that the non-metal impurities B and/or P are removed. The effect can also be obtained by selecting the smelting of industrial silicon production raw materials with high Al and Ca and assisting with controllable continuous ingot casting, or obtaining low-P products by using the process of smelting silica with high Fe and Ti.

And (2) selecting whether to carry out ladle oxygen blowing external refining or not according to the composition characteristics of the low-quality industrial silicon melt in the step (1), wherein when the B, P content in the melt is lower than 0.01 wt.%, and the contents of Ca and Al are higher, the oxidation refining can be selected. In other cases, ladle-to-ladle oxygen-blowing furnace external refining is not selected.

The temperature of the silicon melt in the step (2) is 1450-1750 ℃, the flow rate of the silicon melt is 0.1-10 kg/s, and the directional solidification speed is 0.1-5 cm/s.

The carbonaceous reducing agent is a conventional carbonaceous reducing agent sold in the market.

The alloy additive is Fe, Al, Ca, Sn, Ti, Zr or Na;

calculated by 100 percent of the total amount of the finally obtained chemical-grade industrial silicon, metallurgical-grade industrial silicon and ferrosilicon, the total amount of the chemical-grade industrial silicon and the metallurgical-grade industrial silicon is not less than 80 percent, and the ferrosilicon product is not more than 20 percent.

The invention has the beneficial effects that:

(1) the invention combines the existing industrial silicon production process, mixes the purification effect of the directional solidification technology and the controllable continuous crystallization ingot casting process in the continuous casting technology, realizes the concentration and removal of impurities with the segregation coefficients of Fe, Al, Ca, Cu, V, Ti, Ni, Mn and the like far less than 1 in the low-quality silica raw material silicon melt by changing the casting and solidification processes of the industrial silicon melt and replacing the ladle blowing refining and die casting technology with the controllable continuous crystallization technology, simultaneously has strong affinity between the metal impurities with extremely low segregation coefficients and the non-metal impurities in the silicon melt in the controllable and continuous process of industrial silicon melt solidification because the raw material quality is lower and the total content of the metal impurities is higher, and the silicon melt obtained by smelting the low-quality silica raw material carries out the continuous ingot casting process, thereby not only realizing the application of the directional solidification technology in the industrial silicon smelting process, meanwhile, grafting of an alloy refining technology in the industrial silicon smelting process is realized, and a high-quality silicon product with low metal impurities and low non-metal impurities can be obtained from the primary crystal part of the melt. The application and popularization of the technology can greatly improve the economic benefit of enterprises, and 3 types of industrial silicon products such as chemical-grade industrial silicon, metallurgical-grade industrial silicon, silicon iron and the like can be obtained by one-time continuous ingot casting;

(2) the method solves the problem that the high-quality industrial silicon product is controlled by the purity of the raw material, thereby realizing the purpose of preparing the high-quality industrial silicon product from the low-quality raw material.

(3) The yield ratio of the chemical grade industrial silicon, the metallurgical grade industrial silicon and the ferrosilicon can obtain stable production effect by selecting the raw material of the silica and adjusting the parameters of the continuous casting process.

(4) The method can adjust the supercooling degree and the ingot pulling-down rate of the directional solidification continuous casting device according to the size of the directional solidification continuous casting device and the real-time temperature of the melt, realize the control of the solidification rate of the low-quality industrial silicon melt, carry out the continuous ingot casting of the industrial silicon, realize the continuous feeding and the continuous ingot discharging, promote the segregation of impurities such as Fe, Al, Ca, Mn, Cu, V, Ti, Ni and the like with the solidification coefficient smaller than 1 in the low-quality industrial silicon melt to be enriched in the uncrystallized melt at the upper part of the crystallization device, and realize the continuous ingot casting of the low-quality industrial silicon melt with controllable quality.

Drawings

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

FIG. 2 is a schematic view of a low quality industrial silicon melt continuous ingot product staging.

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.