阅读说明：本技术 一种多晶硅还原尾气中硅粉的回收利用系统及方法 (System and method for recycling silicon powder in polycrystalline silicon reduction tail gas ) 是由 冉祎 王琴 罗轩 *** 于 2020-06-22 设计创作，主要内容包括：本发明公开了一种多晶硅还原尾气中硅粉的回收利用系统及方法,该回收利用系统包括依次连接的主过滤器和残液过滤器,所述残液过滤器的硅粉出口连接有氮化炉,氮化炉的出口连接研磨器。本发明通过主过滤器和残液过滤器的配合过滤,提高残液过滤器内烘干液体的固含量,不仅可以减少烘干能耗,而且可以加强烘干效果。相对现有的硅渣回收方法,本发明方法中分离出的硅粉表面基本无硅烷残留,活性高,可直接入氮化炉用于氮化硅粉的制作,回收利用价值高。本发明能耗低,烘干效果好,出过滤器的硅粉活性高,可直接回用,同时将价值低的硅粉变成了附加值更高的氮化硅产品,提高了多晶硅还原反应副产物的经济价值。(The invention discloses a system and a method for recycling silicon powder in polycrystalline silicon reduction tail gas, wherein the system comprises a main filter and a residual liquid filter which are sequentially connected, a silicon powder outlet of the residual liquid filter is connected with a nitriding furnace, and an outlet of the nitriding furnace is connected with a grinder. The invention improves the solid content of the drying liquid in the residual liquid filter by the matched filtration of the main filter and the residual liquid filter, thereby not only reducing the drying energy consumption, but also strengthening the drying effect. Compared with the existing silicon slag recovery method, the silicon powder separated by the method has the advantages of no silane residue on the surface, high activity, high recovery value and the like, and can be directly fed into a nitriding furnace for manufacturing silicon nitride powder. The invention has low energy consumption and good drying effect, the silicon powder discharged from the filter has high activity and can be directly recycled, and meanwhile, the silicon powder with low value is changed into a silicon nitride product with higher added value, thereby improving the economic value of the byproduct of the reduction reaction of the polysilicon.)

1. A recycle system of silica flour in polycrystalline silicon reduction tail gas which characterized in that: the filter comprises a main filter and a residual liquid filter which are sequentially connected, wherein the main filter comprises a cylindrical main filtering cylinder, a conical discharging cylinder connected with the main filtering cylinder and an arc-shaped sealing plate for sealing the top of the main filtering cylinder; the residual liquid filter comprises a cylindrical residual liquid filtering barrel, a conical residual liquid discharging barrel connected with the residual liquid filtering barrel and an arc-shaped cover plate used for sealing the top of the residual liquid filtering barrel, wherein jackets are arranged outside the residual liquid filtering barrel and the conical residual liquid discharging barrel, a residual liquid feeding hole is formed in the barrel wall of the conical residual liquid discharging barrel, a silicon powder outlet is formed in the bottom of the conical residual liquid discharging barrel, a plurality of filter bags are arranged in the residual liquid filtering barrel, each filter bag outlet is communicated with a filter liquid pipe, a filter liquid pipe outlet is connected with a discharging pipe, two ends of the discharging pipe are provided with a filter liquid outlet and a back flushing port, an overflow vent is formed in the upper part of the residual liquid filtering barrel;

and a silicon powder outlet of the residual liquid filter is connected with a nitriding furnace, and an outlet of the nitriding furnace is connected with a grinder.

2. The system for recycling silicon powder in polycrystalline silicon reduction tail gas as set forth in claim 1, characterized in that: and a standby port is arranged on the arc-shaped sealing plate of the main filter.

3. The system for recycling silicon powder in polycrystalline silicon reduction tail gas as set forth in claim 1, characterized in that: and a nitrogen inlet is formed in the silicon powder outlet of the residual liquid filter.

4. The system for recycling silicon powder in polycrystalline silicon reduction tail gas as set forth in claim 1, characterized in that: the filter element of the main filter adopts a 316L metal powder sintered filter element, and the filtering precision is 1 mu m.

5. The method for recycling silicon powder in polycrystalline silicon reduction tail gas by using the system according to any one of claims 1 to 4, characterized by comprising the following steps: the method comprises the following steps:

(1) filtering the chlorosilane liquid containing fine silicon powder through a main filter to obtain pure liquid-phase chlorosilane and a first solid-liquid mixture;

(2) blowing the first solid-liquid mixture into a residual liquid filter to filter chlorosilane residual liquid, and obtaining a second solid-liquid mixture in the residual liquid filter;

(3) starting a jacket drying function in the residual liquid filter, and heating and drying the second solid-liquid mixture for 92-96 hours to obtain silicon powder;

(4) sending the silicon powder obtained in the step (3) into a nitriding furnace for reaction to obtain a silicon nitride block;

(5) and (4) sending the silicon nitride block obtained in the step (4) into a grinder to grind to obtain silicon nitride powder with the particle size of 0.2-1.5 microns.

6. The method for recycling silicon powder in polycrystalline silicon reduction tail gas as claimed in claim 5, wherein the method comprises the following steps: and (4) introducing 130-135 ℃ steam into the jacket in the step (3) for heating.

7. The method for recycling silicon powder in polycrystalline silicon reduction tail gas as claimed in claim 5, wherein the method comprises the following steps: in the step (4), the reaction temperature in the nitriding furnace is 1400 ℃, the reaction pressure is 90KPa, and the nitriding time is 140 h.

8. The method for recycling silicon powder in polycrystalline silicon reduction tail gas as claimed in claim 5, wherein the method comprises the following steps: the silicon nitride powder obtained in the step (5) can be used for manufacturing silicon nitride ceramic parts.

Technical Field

The invention relates to the technical field of polycrystalline silicon production, in particular to a system and a method for recycling silicon powder in polycrystalline silicon reduction tail gas.

Background

Polycrystalline silicon is a key raw material adopted by integrated circuits and photovoltaic power generation and is a necessary raw material for national new energy development. In the age of the present increasing shortage of fossil energy, the rise of new energy has become a necessary trend.

In the production process of polycrystalline silicon in China, 90% of polycrystalline silicon production enterprises adopt the improved Siemens method polycrystalline silicon production process to produce polycrystalline silicon, and meanwhile, a CDI device (namely a tail gas dry recovery device) is adopted to recover and treat tail gas (namely reduction tail gas) generated by a reduction device. Specifically, hydrogen and chlorosilane in the reduction tail gas are separated, impurities in the hydrogen separated by the CDI device are removed, and the hydrogen repeatedly enters the reduction device for production and use; conveying chlorosilane separated from the CDI device to a rectifying device to separate silicon tetrachloride, conveying the silicon tetrachloride to a cold hydrogenation or hot hydrogenation device to be used as a raw material, producing trichlorosilane again, conveying the trichlorosilane to a reduction device to participate in a reduction reaction, and directly conveying the trichlorosilane and dichlorosilane separated from the rectifying device to the reduction device to participate in the reduction reaction to produce polycrystalline silicon.

In the improved siemens method, in the process of reducing trichlorosilane by hydrogen, because the temperature, the proportion and the amount of dichlorosilane carried by trichlorosilane are not well controlled, fine silicon powder (the granularity is about 3 μm) is often generated and entrained in the reduction tail gas, the reduction tail gas containing the fine silicon powder is recovered by the tail gas of a CDI device, the fine silicon powder enters chlorosilane liquid, if the fine silicon powder brought into the CDI device by the tail gas after the trichlorosilane is still produced cannot be effectively removed, the brought fine silicon powder can block and wear a tower and a pump of the CDI device, so that equipment is damaged or a system is stopped, and the downstream process is influenced. The existing operation method is to directly put chlorosilane liquid containing fine silicon powder into a heating tank with a jacket for steam heating and dry silicon slag, so that not only is much heat energy needed and the drying effect poor, but also silane residue is always left in the center of the heating tank, and the recycling of the silicon powder is influenced.

Disclosure of Invention

In view of the above, aiming at the defects of the prior art, the invention aims to provide a system and a method for recycling silicon powder in polycrystalline silicon reduction tail gas, so as to solve the adverse effect of the silicon powder on a CDI device and improve the economic value of by-products of polycrystalline silicon reduction reaction.

In order to achieve the purpose, the invention provides a system for recycling silicon powder in polycrystalline silicon reduction tail gas, which comprises a main filter and a residual liquid filter which are sequentially connected, wherein the main filter comprises a cylindrical main filtering cylinder, a conical discharging cylinder connected with the main filtering cylinder and an arc-shaped sealing plate for sealing the top of the main filtering cylinder; the residual liquid filter comprises a cylindrical residual liquid filtering barrel, a conical residual liquid discharging barrel connected with the residual liquid filtering barrel and an arc-shaped cover plate used for sealing the top of the residual liquid filtering barrel, wherein jackets are arranged outside the residual liquid filtering barrel and the conical residual liquid discharging barrel, a residual liquid feeding hole is formed in the barrel wall of the conical residual liquid discharging barrel, a silicon powder outlet is formed in the bottom of the conical residual liquid discharging barrel, a plurality of filter bags are arranged in the residual liquid filtering barrel, each filter bag outlet is communicated with a filter liquid pipe, a filter liquid pipe outlet is connected with a discharging pipe, two ends of the discharging pipe are provided with a filter liquid outlet and a back flushing port, an overflow vent is formed in the upper part of the residual liquid filtering barrel;

and a silicon powder outlet of the residual liquid filter is connected with a nitriding furnace, and an outlet of the nitriding furnace is connected with a grinder.

Further, be provided with reserve mouth on the arc shrouding of main filter, substitute when can not having a problem other mouths on the arc shrouding and use, avoid influencing the system operation.

Furthermore, a nitrogen inlet is formed in a silicon powder outlet of the residual liquid filter, so that heating of a solid-liquid mixture in the residual liquid filter can be enhanced.

Preferably, the filter element of the main filter adopts a 316L metal powder sintered filter element, the filtering precision is 1 micron, the strength is high, the filtering performance is good, the fine silicon powder particles can be effectively intercepted, and the service life is long.

Meanwhile, according to the recycling system, the invention also provides a recycling method of silicon powder in the polycrystalline silicon reduction tail gas, which comprises the following steps:

(1) filtering the chlorosilane liquid containing fine silicon powder through a main filter to obtain pure liquid-phase chlorosilane and a first solid-liquid mixture;

(2) blowing the first solid-liquid mixture into a residual liquid filter to filter chlorosilane residual liquid, and obtaining a second solid-liquid mixture in the residual liquid filter;

(3) starting a jacket drying function in the residual liquid filter, and heating and drying the second solid-liquid mixture for 92-96 hours to obtain silicon powder;

(4) sending the silicon powder obtained in the step (3) into a nitriding furnace for reaction to obtain a silicon nitride block;

(5) and (4) sending the silicon nitride block obtained in the step (4) into a grinder to grind to obtain silicon nitride powder with the particle size of 0.2-1.5 microns.

Further, steam with the temperature of 130-135 ℃ is introduced into the jacket in the step (3) for heating.

Further, in the step (4), the reaction temperature in the nitriding furnace is 1400 ℃, the reaction pressure is 90KPa, and the nitriding time is 140 h.

Further, the silicon nitride powder obtained in the step (5) can be used for manufacturing silicon nitride ceramic parts. Mixing silicon nitride fine powder and a forming assistant according to a certain proportion, and forming to prepare a silicon nitride ceramic blank; and (4) the silicon nitride blank enters a sintering furnace, is sintered, is discharged and is polished, and the production of the silicon nitride ceramic piece is completed.

Compared with the prior art, the system and the method for recycling the silicon powder in the polycrystalline silicon reduction tail gas improve the solid content of drying liquid in the residual liquid filter through the matched filtering of the main filter and the residual liquid filter, can reduce drying energy consumption and enhance the drying effect, and through detection, the content of chlorosilane in the dried silicon powder is less than 0.02 percent, silane residue is basically avoided, the activity of the silicon powder is high, and meanwhile, the dried silicon powder has the granularity of about 2-3 mu m, does not need to be ground and can be directly fed into a nitriding furnace to be used for manufacturing silicon nitride powder. The existing one-time filtering method for the silicon slag only filters once, filter residues contain a large amount of chlorosilane, solid content of silicon powder is low, drying is carried out at the moment, drying time is long, energy consumption is high, the drying effect of the center of the tank body is poor, discharged silicon powder also contains the chlorosilane, the chlorosilane generates silicon dioxide after encountering air, the silicon dioxide can wrap the surface of the fine silicon powder, and therefore activity of the fine silicon powder is reduced, and recycling value of the fine silicon powder after activity reduction is also low.

Compared with the existing silicon slag recovery method, the method has the advantages that the main filtration and the residual liquid filtration are carried out for secondary filtration, the recovery of chlorosilane in the reduction tail gas is realized by the liquid-phase silicon chloride through the CDI recovery device, the surface of the separated silicon powder basically has no silane residue, the activity is high, the silicon powder can be directly fed into a nitriding furnace for manufacturing silicon nitride powder, and the recovery and utilization value is high. The invention has low energy consumption and good drying effect, the silicon powder discharged from the filter has high activity and can be directly recycled, and meanwhile, the silicon powder with low value is changed into a silicon nitride product with higher added value, thereby improving the economic value of the byproduct of the reduction reaction of the polysilicon.

Drawings

FIG. 1 is a schematic flow diagram of a recycling system according to the present invention;

FIG. 2 is a schematic perspective view of the primary filter of the present invention;

FIG. 3 is a schematic top view of the primary filter of the present invention;

FIG. 4 is a schematic perspective view of a raffinate filter according to the present invention;

FIG. 5 is a schematic top view of a raffinate filter according to the present invention.

Illustration of the drawings:

1, a main filter, 2 a residual liquid filter, 3 a nitriding furnace and 4 a grinder;

101 main filtering cylinder body, 102 conical discharging cylinder, 103 arc-shaped closing plate, 104 filter element, 105 feeding hole, 106 discharging hole, 107 back flushing hole, 108 emptying hole, 109 standby hole and 110 deslagging hole;

201 raffinate filter tube body, 202 toper raffinate play feed cylinder, 203 arc apron, 204 presss from both sides the cover, 205 raffinate feed inlet, 206 silica flour export, 207 filter bag, 208 filter liquor pipe, 209 discharging pipes, 210 filter liquor export, 211 blowback mouth, 212 overflow drain, 213 nitrogen gas import, 214 steam inlet, 215 steam outlet.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the 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 application.

Referring to fig. 1 to 5, the application provides a system for recycling silicon powder in polysilicon reduction tail gas, which comprises a main filter 1 and a residual liquid filter 2 which are connected in sequence, wherein a silicon powder outlet of the residual liquid filter is connected with a nitriding furnace 3, and an outlet of the nitriding furnace is connected with a grinder 4.

The main filter 1 comprises a cylindrical main filter cylinder 101, a conical discharge cylinder 102 connected with the main filter cylinder and an arc-shaped sealing plate 103 used for sealing the top of the main filter cylinder, wherein a plurality of groups of filter elements 104 are arranged in the main filter cylinder, the filter elements 104 preferably adopt 316L metal powder sintered filter elements, the filtering precision is 1 mu m, the strength is high, the filtering performance is good, the superfine silicon powder particles can be effectively intercepted, and the service time is long; the lower part of the main filtering cylinder body 101 is provided with a feeding hole 105, the arc-shaped sealing plate 103 is provided with a discharging hole 106, a back flushing hole 107 and a drainage hole 108, and the bottom of the conical discharging cylinder 102 is provided with a slag discharging hole 110; the residual liquid filter 2 comprises a cylindrical residual liquid filtering cylinder 201, a conical residual liquid discharging cylinder 202 connected with the residual liquid filtering cylinder and an arc-shaped cover plate 203 used for sealing the top of the residual liquid filtering cylinder, a jacket 204 is arranged outside the residual liquid filtering cylinder and the conical residual liquid discharging cylinder, a residual liquid feeding hole 205 is arranged on the wall of the conical residual liquid discharging cylinder, a silicon powder outlet 206 is arranged at the bottom of the conical residual liquid discharging cylinder, a plurality of filter bags 207 are arranged in the residual liquid filtering cylinder, the outlet of each filter bag is communicated with a filter liquor pipe 208, the outlet of the filter liquor pipe is connected with a discharging pipe 209, two ends of the discharging pipe are provided with a filter liquor outlet 210 and a back flushing hole 211, an overflow vent 212 is arranged at the upper part of the residual liquid filtering;

further, be provided with reserve mouth 109 on the arc shrouding of main filter, substitute when can not having a problem other mouths on the arc shrouding and use, avoid influencing the system operation.

Furthermore, a nitrogen inlet 213 is arranged on the silicon powder outlet of the raffinate filter, so that the heating of the solid-liquid mixture in the raffinate filter can be enhanced.

Referring to the above structural description, the method of using the system of the present invention is:

chlorosilane liquid containing fine silicon powder enters the main filter 1 through the feeding hole 105, and under the action of the filter element 104, a filtrate (pure liquid-phase silicon chloride) with the silicon powder filtered out is discharged through the discharging hole 106 and can directly enter a CDI recovery device for recovery, and a first solid-liquid mixture (with low solid content) containing the silicon powder at the lower part of the filter element of the main filter is blown into the residual liquid filter 2 for secondary filtration by introducing nitrogen into the back flushing hole 107; the first solid-liquid mixture enters the residual liquid filter 2 through the slag discharge port 110 and the residual liquid feed port 205 of the main filter, silicon powder is collected again under the action of the filter bag 207, so that the solid content of the second solid-liquid mixture is increased, a filtrate (chlorosilane residual liquid) is discharged through the filtrate pipe 208 and the filtrate outlet 210 of the discharge pipe 209, and steam at 130-135 ℃ is introduced into the steam inlet 214 of the jacket 204 for 92-96 hours, so that the second solid-liquid mixture can be dried to obtain the silicon powder, in the process, nitrogen is continuously introduced into the nitrogen inlet 213, the mixture at the bottom of the conical residual liquid discharge cylinder can be in a 'surging' state, and the phenomenon that the mixture at the bottom cannot contact the jacket and is heated unevenly is avoided. After drying, the filter bag is still attached with dried silicon powder, the silicon powder can be shaken by introducing nitrogen into the back blowing port 211, and the nitrogen is discharged from the overflow vent 212. The dried silicon powder can directly enter a nitriding furnace 3 from a silicon powder outlet 206 for nitriding reaction (the reaction temperature is 1400 ℃, the reaction pressure is 90KPa, and the nitriding time is 140h) to obtain a silicon nitride block, and the silicon nitride block is sent into a grinder 4 for grinding to obtain the silicon nitride powder with the granularity of 0.2-1.5 mu m. The silicon nitride powder can be used for manufacturing silicon nitride ceramic parts. Mixing silicon nitride fine powder and a forming assistant according to a certain proportion, and forming to prepare a silicon nitride ceramic blank; and (4) the silicon nitride blank enters a sintering furnace, is sintered, is discharged and is polished, and the production of the silicon nitride ceramic piece is completed.