阅读说明：本技术 一种硅粉的回收方法及其制备的硅锭 (Recovery method of silicon powder and silicon ingot prepared by same ) 是由 王贯勇 高志国 于 2018-08-06 设计创作，主要内容包括：本发明实施例提供一种硅粉的回收方法及其制备的硅锭,涉及二次资源再利用技术领域,用于回收硅粉,实现资源的二次利用。该硅粉的回收方法包括准备原料；利用碳棒对原料进行加热至熔融状态形成硅液,熔炼的温度为A,1450℃≤A≤1850℃；取出所述碳棒,再次加入与碳棒同等体积的原料；在硅液内至少加入一次造渣剂,造渣剂用于将硅液中的杂质吸附在硅液表面,造渣剂占硅液的重量百分百为H1,0.2％≤H1≤0.3％；扒除吸附到所述硅液表面的杂质；将硅液与沉淀在硅液底部的沉淀渣分离；将所述硅液冷凝形成硅锭。本发明实现了硅粉到硅锭的转化,避免了粉状硅进入废料浆,进而一方面保护了环境,另一方面资源得到了二次利用,也为下一步的提纯工作做出来相应的准备。(The embodiment of the invention provides a silicon powder recovery method and a silicon ingot prepared by the same, relates to the technical field of secondary resource recycling, and is used for recovering silicon powder and realizing secondary utilization of resources. The recovery method of the silicon powder comprises the steps of preparing a raw material; heating the raw materials to a molten state by using a carbon rod to form silicon liquid, wherein the smelting temperature is A, and A is more than or equal to 1450 ℃ and less than or equal to 1850 ℃; taking out the carbon rod, and adding the raw material with the same volume as the carbon rod again; adding a slagging agent into the silicon liquid at least once, wherein the slagging agent is used for adsorbing impurities in the silicon liquid on the surface of the silicon liquid, and the slagging agent accounts for H1 in percentage by weight of the silicon liquid, and H1 is more than or equal to 0.2% and less than or equal to 0.3%; removing impurities adsorbed to the surface of the silicon liquid; separating the silicon liquid from the precipitation slag precipitated at the bottom of the silicon liquid; and condensing the silicon liquid to form silicon ingots. The invention realizes the conversion from silicon powder to silicon ingot, avoids the powdery silicon from entering the waste slurry, thereby protecting the environment on the one hand, and making corresponding preparation for the next purification on the other hand, the resources are recycled.)

1. A method for recovering silicon powder is characterized by comprising the following steps: the method comprises the following steps:

preparing raw materials;

heating the raw materials to a molten state by using a carbon rod to form silicon liquid, wherein the smelting temperature is A, and A is more than or equal to 1450 ℃ and less than or equal to 1850 ℃;

taking out the carbon rod, and adding the raw material with the same volume as the carbon rod again;

adding a slagging agent into the silicon liquid at least once, wherein the slagging agent is used for adsorbing impurities in the silicon liquid to the surface of the silicon liquid, and the slagging agent accounts for H1 in percentage by weight of the silicon liquid, and H1 is more than or equal to 0.2% and less than or equal to 0.3%;

removing impurities adsorbed on the surface of the silicon liquid;

separating the silicon liquid from the precipitation slag precipitated at the bottom of the silicon liquid;

and condensing the silicon liquid to form silicon ingots.

2. The method for recovering silicon powder according to claim 1, wherein the preparing raw material includes:

collecting silicon powder;

adding an additive into the silicon powder, wherein the additive is used for reducing the melting point of the impurities in the silicon powder, the additive accounts for H2 in percentage by weight of the silicon powder, and H2 is more than or equal to 4% and less than or equal to 5%;

extruding the silicon powder added with the additive to generate silicon particles;

and drying the silicon particles, wherein the drying temperature is B, and B is less than or equal to 200 ℃.

3. The method for recovering silicon powder according to claim 2, wherein,

the additive includes at least one calcification compound for reducing the melting point of the impurities in the silicon powder.

4. The method for recovering silicon powder according to claim 3, wherein,

the calcification is calcium fluoride.

5. The method for recovering silicon powder according to claim 2, wherein,

the additive comprises a binder, wherein the binder accounts for H3 in percentage by weight of the additive, and H3 is more than or equal to 3% and less than or equal to 5%.

6. A silicon ingot, characterized in that the silicon ingot is suitable for use in the method for recovering silicon powder according to any one of claims 1 to 5.

7. The silicon ingot of claim 6 wherein the recovery of the silicon ingot is C, wherein 55% C80%.

Technical Field

The invention relates to the technical field of secondary resource recycling, in particular to a silicon powder recovery method and a silicon ingot prepared by the same.

Background

No matter the silicon is monocrystalline silicon or polycrystalline silicon, semiconductor silicon or crystalline silicon for solar energy, the silicon must be cut before flowing into the next step for use, but in the existing cutting technology, linear cutting is the best choice, and the method has the advantages of high precision, high yield, high efficiency, small loss and the like.

The principle of wire cutting is as follows: the cutting edge material attached to the steel wire is driven by a high-speed moving gold steel wire to rub the silicon rod, so that the cutting effect is achieved.

The content of silicon in the waste mortar is 88 to 92 percent, which shows that the waste mortar has very high recovery value.

Therefore, how to recycle the high-purity silicon powder in the cutting mortar is a major technical problem currently faced in the industry.

Disclosure of Invention

In view of this, the embodiment of the invention provides a method for recovering silicon powder and a silicon ingot prepared by the method, which are used for recovering silicon powder and realizing secondary utilization of resources.

The embodiment of the invention provides a method for recovering silicon powder, which comprises the following steps:

preparing raw materials;

heating the raw materials to a molten state by using a carbon rod to form silicon liquid, wherein the smelting temperature is A, and A is more than or equal to 1450 ℃ and less than or equal to 1850 ℃;

taking out the carbon rod, and adding the raw material with the same volume as the carbon rod again;

adding a slagging agent into the silicon liquid at least once, wherein the slagging agent is used for adsorbing impurities in the silicon liquid to the surface of the silicon liquid, and the slagging agent accounts for H1 in percentage by weight of the silicon liquid, and H1 is more than or equal to 0.2% and less than or equal to 0.3%;

removing impurities adsorbed on the surface of the silicon liquid;

separating the silicon liquid from the precipitation slag precipitated at the bottom of the silicon liquid;

and condensing the silicon liquid to form silicon ingots.

Optionally, the preparing raw materials include:

collecting silicon powder;

adding an additive into the silicon powder, wherein the additive is used for reducing the melting point of the impurities in the silicon powder, the additive accounts for H2 in percentage by weight of the silicon powder, and H2 is more than or equal to 4% and less than or equal to 5%;

extruding the silicon powder added with the additive to generate silicon particles;

and drying the silicon particles, wherein the drying temperature is B, and B is less than or equal to 200 ℃.

Optionally, the additive includes at least one calcification for reducing the melting point of the impurities in the silicon powder.

Optionally, the calcification is calcium fluoride.

Optionally, the additive comprises a binder, wherein the binder accounts for H3 in percentage by weight of the additive, and H3 is equal to or more than 3% and equal to or less than 5%.

In another aspect, the invention provides a silicon ingot suitable for the preparation of the silicon powder recovery method of the previous aspect.

Optionally, the recovery rate of the silicon ingot is C, wherein C is more than or equal to 55% and less than or equal to 80%.

The beneficial effects of the aspects and any possible implementation described above are as follows:

in this embodiment, through forming silicon liquid to the raw materials heating, impurity in the rethread slagging constituent adsorbs the silicon liquid surface and then takes off it, has improved the purity of silicon liquid, and further, separates silicon liquid and sediment, condenses silicon liquid and obtains the silicon ingot. The conversion from the powdery silicon to the massive silicon is realized, the powdery silicon is prevented from entering the waste slurry, so that the environment is protected on the one hand, resources are secondarily utilized on the other hand, and corresponding preparation is made for the next purification work. In addition, in the embodiment, the silicon powder is physically recycled, so that secondary environmental pollution is not caused.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive labor.

FIG. 1 is a schematic flow chart of a method for recovering silicon powder according to an embodiment of the present invention;

fig. 2 is another schematic flow chart of the method for recovering silicon powder according to the embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be noted that the terms "upper", "lower", "left", "right", and the like used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element.

Before the present invention is described in detail, the technical context of the present technical solution is briefly described:

at present, the cutting technology of crystalline silicon mainly comprises mortar SiC cutting and diamond wire cutting, and no matter the mortar SiC cutting or the diamond wire cutting is carried out, because the difference between the diameter of a cutting wire and the thickness of a required silicon wafer is not large, 40 to 50 percent of crystalline silicon is cut and ground into powder to enter waste slurry by the two cutting modes, on one hand, the waste of resources is caused, and on the other hand, the pollution to the environment is caused.

In order to solve the problems, the inventor develops the following technical scheme, which can realize the reformation of the powdery silicon into the silicon ingot, and is convenient for further purification and use, thereby avoiding the environmental pollution and the resource waste caused by the mortar entering the waste slurry.

The present embodiment provides a method for recovering silicon powder, as shown in fig. 1, which is a schematic flow chart of the method for recovering silicon powder provided in the embodiment of the present invention, and the method for recovering silicon powder includes:

s101, preparing raw materials.

In this embodiment, after the mortar is processed by the filter press, moisture is filtered out to form powdery polysilicon, and the powdery polysilicon needs to be processed by a series of processes to be prepared into granular polysilicon. On one hand, because the powdery polycrystalline silicon has light weight, the loss in the subsequent process is large, the recovery rate is low, and on the contrary, the granular polycrystalline silicon has large weight and cannot float on the surface of silicon liquid in a high-temperature furnace, thereby being beneficial to recovery; on the other hand, the powdery polycrystalline silicon has larger water content, the energy consumption in the subsequent process is higher, the cost is not favorably saved, and the granular polycrystalline silicon does not generate redundant energy consumption in a high-temperature furnace because the water content is smaller, so the cost can be effectively saved.

Although the process step is increased by changing the powdered polysilicon into the granular polysilicon, the cost and energy consumption for preparing the powdered polysilicon into the granular polysilicon are far lower than the cost and energy consumption for directly using the powdered polysilicon as the raw material, therefore, the preferred raw material in this embodiment is granular silicon, and the granular silicon may include granular polysilicon or granular monocrystalline silicon, or a combination of the two.

S102, heating the raw materials to a molten state by using a carbon rod to form silicon liquid, wherein the melting temperature is A, and A is more than or equal to 1450 ℃ and less than or equal to 1850 ℃.

In this embodiment, the raw material can be collected by using a dry crucible made of SiO₂Can avoid the pollution to the raw materialsThereby ensuring the purity of the raw materials.

In the embodiment, the carbon rod can be placed in the dry forging crucible, and the heat of the carbon rod is transferred to the raw material, so that the granular silicon is melted into silicon liquid.

Under the high temperature state, the impurities in the raw materials can float on the surface of the silicon liquid after being treated, and then are easily separated and removed from the silicon liquid, thereby being beneficial to the recovery of the polycrystalline silicon.

It should be added that the higher the temperature, the higher the energy consumption, but the lower the temperature, the raw material is not heated sufficiently, and part of the raw material can not be melted, so the recovery rate is reduced, and in this embodiment, after the energy consumption and the recovery rate are both considered, the melting temperature can be set between 1450 ℃ and 1850 ℃.

S103, taking out the carbon rod, and adding the raw material with the same volume as the carbon rod again.

It is supplementary to need, does benefit to intermediate frequency induction furnace and heats the raw materials in this embodiment, because silicon liquid is the semiconductor, after heating temperature reaches 800 ℃, silicon liquid accessible magnetic induction and spontaneous heating to electromagnetic induction can make silicon liquid roll from top to bottom, plays the effect of stirring, and then can stir the top with the raw materials of deposit in the bottom, obtains sufficient heat, forms recoverable silicon liquid.

Therefore, in order to further save energy consumption, raw materials with the same volume as the carbon rod are added into the dry forging crucible. On one hand, the silicon liquid is heated by magnetic induction, and on the other hand, the whole temperature of the silicon liquid cannot be influenced due to the fact that the added raw materials are small in size.

The silicon liquid is heated by using the medium-frequency direct current generated by the carbon rod, so that the heating efficiency is higher, and the aim of saving energy is fulfilled; the heating temperature is higher, and the melting temperature of the raw materials can be reached; after the carbon rod is taken out, the silicon liquid is continuously heated through magnetic induction, heat is uniformly distributed in the silicon liquid, the quality of the silicon liquid is guaranteed, and the recovery efficiency can be further improved.

S104, adding a slag former into the silicon liquid at least once, wherein the slag former is used for adsorbing impurities in the silicon liquid to the surface of the silicon liquid, and the slag former accounts for H1 in percentage by weight of the silicon liquid, and H1 is more than or equal to 0.2% and less than or equal to 0.3%;

because the silicon liquid contains impurities, the recovery of the silicon liquid is not facilitated, and at the moment, the impurities in the silicon liquid need to be removed, so that the purity of the silicon liquid is improved.

In this embodiment, a slag former may be added to the silicon liquid, and for example, the slag former may be a carbide, which is beneficial to adsorbing impurities in the silicon liquid onto the surface of the silicon liquid and removing the impurities.

When the content of the slag former is large, although the generated impurities are favorably adsorbed to the surface of the silicon liquid, a certain amount of silicon liquid is inevitably lost in the subsequent process of separating the impurities from the silicon liquid, and the recovery efficiency is reduced. When the content of the slag former is low, the impurity removal is not facilitated, and the purity of the silicon liquid is influenced. Therefore, in this embodiment, the weight percentage of the slag former is set to be between 0.2% and 0.3% after the above consideration is taken into consideration.

S105, removing impurities adsorbed on the surface of the silicon liquid.

The slag former can float impurities in the silicon liquid on the surface of the silicon liquid, and in this case, the impurities floating on the surface of the silicon liquid can be removed so as not to affect the purity of the silicon liquid.

If the slagging agent is added for a plurality of times, the amount of generated impurities is increased, and part of silicon liquid is lost in the process of removing the impurities each time. Therefore, in the present embodiment, whether or not the slag former is added a plurality of times can be determined based on the surface temperature of the silicon melt and the amount of impurities at each time.

And S106, separating the silicon liquid from the precipitation slag precipitated at the bottom of the silicon liquid.

Although partial impurities can be adsorbed to the surface of the silicon liquid by using the slagging agent, the density of the partial impurities is similar to that of the silicon liquid, and the partial impurities are not easily adsorbed to the surface of the silicon liquid. Because the cooling temperature of the precipitated slag is different from that of the silicon liquid, the silicon liquid can be separated from the precipitated slag in a cooling mode. In this embodiment, after considering both the difficulty of separating the silicon liquid from the precipitated slag and the recovery efficiency of the silicon liquid, the silicon liquid and the precipitated slag may be separated after removing at least one impurity.

And S107, condensing the silicon liquid to form a silicon ingot.

In this embodiment, through forming silicon liquid to the raw materials heating, impurity in the rethread slagging constituent adsorbs the silicon liquid surface and then takes off it, has improved the purity of silicon liquid, and further, separates silicon liquid and sediment, condenses silicon liquid and obtains the silicon ingot. The conversion from the powdery silicon to the massive silicon is realized, the powdery silicon is prevented from entering the waste slurry, so that the environment is protected on the one hand, resources are secondarily utilized on the other hand, and corresponding preparation is made for the next purification work.

In addition, in the embodiment, the silicon powder is physically recycled, so that secondary environmental pollution is not caused.

Further, the raw materials in this example are briefly described:

as shown in fig. 2, which is another schematic flow chart of the method for recovering silicon powder according to the embodiment of the present invention, S101, preparing raw materials includes:

s1011, collecting the silicon powder. The silicon powder in the embodiment is about 800 to 1000 meshes, and the particle size of the silicon powder is very small, so that the silicon powder is not beneficial to direct smelting, and therefore the silicon powder needs to be treated.

It should be noted that the raw material in this embodiment is not waste mortar generated during the cutting process, and this embodiment requires a plurality of treatments on the waste mortar to obtain a raw material suitable for smelting.

After the waste mortar is subjected to a filter press, silicon powder, i.e., the silicon powder referred to in this example, is obtained. Silica powder can be understood as mortar after simple dehydration, and because the water content of the powder silicon is still higher, the energy consumption in the process of heating to melting is relatively high, so that further treatment is needed, specifically:

s1012, adding an additive into the silicon powder, wherein the additive accounts for 5% of the silicon powder by weight. And the additive is used for reducing the melting point of impurities in the silicon powder, so that the energy consumption can be reduced in the subsequent heating process, and the cost is further reduced.

In addition, because the melting point of the impurities in the silicon powder is lower, the impurities are changed into molten state from solid state after being heated to a certain temperature, the liquidity of the impurities is improved, and the flow property of the raw materials in the smelting process is further improved.

If the amount of the additive is too large, although the flowability of the impurities is good, the energy consumption of the next process is increased, so that the weight percentage of the additive is set to about 5% in the embodiment, and the energy consumption is reduced as much as possible on the premise of ensuring that the impurities have certain flowability.

In addition, the additive is added into the silicon powder, so that the silicon powder is relatively uniform and is prepared for subsequent granulation; because the additive is added in the smelting process, the additive can be scattered along with hot gas, and a part of additive can be wasted, the additive is added in the silicon powder, the additive is prevented from being added in the subsequent smelting process, and the cost can be saved.

Further, in one embodiment, the additive includes at least one calcification compound for reducing the melting point of impurities in the silicon powder.

In this embodiment, reducing the melting point of the impurities in the silicon powder can reduce energy consumption in the subsequent smelting process, and can improve the flowability of the impurities in the smelting process, thereby improving the flowability of the whole raw material.

The higher the water content of the silicon powder is, the higher the possibility of oxidation is, so that the water content of the silicon powder is removed as much as possible, and the purity of the silicon powder is kept. In this embodiment, the calcification can absorb excess moisture in the silicon powder, so that the purity of the silicon powder can be effectively maintained.

Still further, the calcification of this embodiment can be calcium fluoride. After considering the cost, the preferred calcification of this embodiment is calcium fluoride.

Further, in another embodiment, the additive may further include a binder, wherein the binder accounts for 3 to 5 weight percent of the additive.

Since the powder silicon is light in weight and is not easy to sink into the crucible in a molten state, and the powder silicon drifts away with hot air, so that raw materials are lost, and the recovery rate is reduced, in this embodiment, the silicon powder is bonded by the binder to form silicon particles with a large diameter.

In the embodiment, the amount of the binder may be determined according to the amount of the raw material, and may be, for example, between 3% and 5% by weight of the additive.

And S1013, extruding the silicon powder added with the additive to generate silicon particles.

As can be seen from the above embodiments, before the raw materials are heated to a molten state, the silicon powder needs to be treated to form granular silicon having a large weight.

Because the weight of granular silicon, namely silicon granules, is larger, the granular silicon is easy to sink into a dry forging crucible in a molten state, so that the loss of raw materials is avoided, and the recovery rate is further improved.

S1014, drying the silicon particles, wherein the drying temperature is B, and B is less than or equal to 200 ℃.

After the silicon particles are obtained, on one hand, in order to avoid that the monocrystalline silicon in the silicon particles is oxidized when meeting water, the moisture in the silicon particles needs to be further removed; on the other hand, the excessive moisture also increases the energy consumption of heating, so that the silicon particles can be dried in the embodiment. The drying temperature is lower than 200 ℃, the moisture in the silicon particles can be removed at a lower temperature, the temperature is low, the energy consumption is low, and the cost is saved.

The embodiment also provides a silicon ingot which is suitable for being prepared by the silicon powder recovery method in the embodiment.

In this embodiment, form silicon liquid through heating the raw materials, impurity in rethread slagging constituent adsorbs the silicon liquid surface and then takes off it with silicon liquid surface, has improved the purity of silicon liquid, and further, separates silicon liquid and sediment, and then condenses the silicon liquid and obtain the silicon ingot. The conversion from the powdery silicon to the massive silicon is realized, the powdery silicon is prevented from entering the waste slurry, so that the environment is protected on the one hand, resources are secondarily utilized on the other hand, and corresponding preparation is made for the next purification work.

In addition, in the embodiment, the silicon powder is physically recycled, so that secondary environmental pollution is not caused.

In one embodiment, the above process is facilitated, and a silicon ingot of 550 kg to 800 kg is obtained from 1 ton of feedstock, with a recovery rate of 55% to 80%.

The silicon ingot prepared by the method has low energy consumption and high recovery rate, and is beneficial to industrial production.

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on at least two network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.