A process for producing high-purity metallic silicon by cutting silicon powder

Abstract

The present invention discloses a process for producing high-purity metallic silicon by using cut silicon powder. The new process uses the cut silicon powder as raw material for drying, briquetting and sintering. Different from the traditional smelting process of medium frequency furnace, the new process has the characteristics of high efficiency, safety, no pollution and low cost.

Description

Technical Field

[0001] The invention relates to a new technology for producing high-purity metallic silicon by cutting silicon powder in the solar energy industry. Background Art

[0002] In recent years, with the rapid decline in the cost of solar power generation, the solar energy industry has flourished. The slicing process in the solar cell process has an annual production capacity of 500,000 tons of waste silicon powder. The traditional medium frequency furnace smelting process has the characteristics of high energy consumption, high cost, environmental pollution, and difficult to control production safety.

[0003] Patent document CN 106672977 A discloses a method for preparing metallic silicon using waste silicon material cut from solar silicon wafers, comprising the following steps: Step 1, the waste silicon material is filtered through a plate and frame to obtain a solid filter cake, and then the solid filter cake is crushed into silicon powder; Step 2, the silicon powder is placed in a double-cone rotary dryer for drying, and the moisture content is controlled within 0.5%; Step 3, the dried silicon powder is sent to a double-roll extrusion granulator for balling, and then placed in a double-roll extrusion granulator for balling again to obtain waste silicon material balls; Step 4, a metal silicon block is taken and placed in a smelting furnace for melting, and after the metal silicon block is dissolved, waste silicon material balls are added for smelting to obtain silicon liquid; Step 5, the silicon liquid is cooled and molded to obtain a silicon ingot; Step 6, the silicon ingot is crushed into the required particle size with a crusher to obtain metal silicon particles, which are dried and packaged to obtain a finished metal silicon product. This method still has the defects of high energy consumption and complicated steps.

[0004] Therefore, a new process of the present invention is proposed to solve the above problems. Summary of the invention

[0005] The invention adopts a briquetting and sintering process, and has the characteristics of low energy consumption, low cost, environmental friendliness, safety and good control.

[0006] To achieve the above object, the present invention provides a process for producing high-purity metallic silicon by cutting silicon powder, comprising the following steps:

[0007] 1) Drying: The cut powder from the plate and frame filter press is pre-treated and then enters the dryer for hot air drying. The moisture content of the dried product is less than 1%;

[0008] 2) Briquetting: The flash-evaporated silicon powder is in powder form, a binder is added, and the mixture is fully mixed in a high-speed mixer; the mixed silicon powder is loaded into a mold through an automatic loading device and isostatically pressed into briquettes;

[0009] 3) Sintering: After the briquetting, the cutting powder is dried and then sent to a vacuum sintering furnace for sintering, so that the crystal surface of the cutting powder is in a semi-molten state.

[0010] More preferably, the drying equipment used in step 1) is a flash dryer, the drying temperature is controlled between 200-500 degrees Celsius, and the drying time is 30-60 minutes.

[0011] More preferably, the binder added in step 2) is one or more of starch, water glass, silica sol, and epoxy resin; the addition ratio is 1-10%.

[0012] More preferably, the briquetting equipment used in step 2) is a static pressure equipment, the briquetting pressure used is 1-30 MPa, and the briquetting time is 10-30 minutes.

[0013] More preferably, the equipment used in step 3) is a continuous vacuum sintering equipment, the high sintering temperature is between 1300-1500 degrees, and the sintering time is 1-5 hours.

[0014] The above technical solution has the following beneficial effects:

[0015] The present invention adopts a preparation process of briquetting and sintering, which is different from traditional technical means and has the characteristics of low energy consumption, low cost, environmental friendliness, safety and good control, and has broad development prospects. DETAILED DESCRIPTION

[0016] In order to explain the technical content, structural features, achieved objectives and effects of the technical solution in detail, the following is a detailed description in conjunction with specific embodiments.

[0017] Embodiment 1

[0018] A process for producing high-purity metallic silicon by cutting silicon powder comprises the following steps:

[0019] 1) After pre-treating the cutting powder, add it to the preheated flash dryer through the electromagnetic feeder of the elevator; turn the material over and dry it with hot air, and the drying temperature is controlled at 280 degrees and the drying time is controlled at 50 minutes;

[0020] 2) Pour the cutting powder into a high-speed mixer, add 3% of the adhesive starch to quickly disperse it, and then add it into the mold through an automatic device. Put the mold into the briquetting equipment, adjust the equipment pressure to 10MPa, and the briquetting time is 15 minutes;

[0021] 3) The high temperature zone of the vacuum sintering furnace is first heated to 1400 degrees Celsius, and the vacuum is evacuated to below 0.1Pa. The pressed cutting powder blocks are added through the vacuum feeding device. The sintering temperature is 1400 degrees Celsius and the sintering is continued for 2 hours. The density analysis and chemical element analysis of the sintered silicon blocks are performed. The results are shown in Table 1:

[0022] element content Fe 0.05％ Al 0.012％ Ca 0.055％ B 0.0006％ P 0.0010％

[0023] Density: 1.91g / cm 3 .

[0024] Embodiment 2

[0025] A process for producing high-purity metallic silicon by cutting silicon powder comprises the following steps:

[0026] 1) After pre-treatment, the cutting powder is added to the preheated flash dryer through the elevator and electromagnetic feeder; the material is turned over and dried by hot air, and the drying temperature is controlled at 350 degrees and the time is controlled at 40 minutes.

[0027] 2) Pour the cutting powder into a high-speed mixer, add 6% epoxy resin as a binder and disperse it quickly, then add it into the mold through an automatic device. Put the mold into the briquetting equipment, adjust the equipment pressure to 20MPa, and the briquetting time is 20 minutes;

[0028] 3) The high temperature zone of the vacuum sintering furnace is first heated to 1450 degrees Celsius, and the vacuum is evacuated to below 0.1 Pa. The pressed cutting powder blocks are added through the vacuum feeding device. The sintering temperature is 1450 degrees Celsius and the sintering is continued for 3 hours. The density analysis and chemical element analysis of the sintered silicon blocks are performed, and the results are shown in Table 2:

[0029] element content Fe 0.04％ Al 0.02％ Ca 0.036％ B 0.0007％ P 0.0011％

[0030] Density: 2.16g / cm 3 .

[0031] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "include..." or "comprise..." do not exclude the existence of other elements in the process, method, article or terminal device including the elements. In addition, in this article, "greater than", "less than", "exceed" and the like are understood to exclude the number itself; "above", "below", "within" and the like are understood to include the number itself.

[0032] Although the above embodiments have been described, once those skilled in the art know the basic creative concepts, they can make additional changes and modifications to these embodiments. Therefore, the above description is only an embodiment of the present invention and does not limit the patent protection scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A process for producing high-purity metallic silicon by cutting silicon powder, characterized in that: The steps include: 1) Drying: The cut powder from the plate and frame filter press is pre-treated and then enters the dryer for hot air drying. The moisture content of the dried product is less than 1%; 2) Briquetting: The flash-evaporated silicon powder is in powder form, a binder is added, and the mixture is fully mixed in a high-speed mixer; The mixed silicon powder is loaded into the mold through an automatic loading device and isostatically pressed into blocks; 3) Sintering: After the briquetting, the cutting powder is dried and then sent to a vacuum sintering furnace for sintering, so that the crystal surface of the cutting powder is in a semi-molten state.

2. The process according to claim 1, characterized in that Step 1) The drying temperature is controlled between 200-500 degrees Celsius, and the drying time is 30-60 minutes.

3. The process according to claim 1, characterized in that The binder added in step 2) is one or more of starch, water glass, silica sol, and epoxy resin; the addition ratio is 1-10%.

4. The process according to claim 1, characterized in that The briquetting pressure used in step 2) is 1-30 MPa, and the briquetting time is 10-30 minutes.

5. The process according to claim 1, characterized in that Step 3) The high temperature of sintering is between 1300-1500 degrees, and the sintering time is 1-5 hours.