CN108726481B - Treatment device for polycrystalline silicon reduction tail gas - Google Patents

Treatment device for polycrystalline silicon reduction tail gas Download PDF

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CN108726481B
CN108726481B CN201710240227.7A CN201710240227A CN108726481B CN 108726481 B CN108726481 B CN 108726481B CN 201710240227 A CN201710240227 A CN 201710240227A CN 108726481 B CN108726481 B CN 108726481B
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chlorosilane
washing tower
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gas
hydrogen
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CN108726481A (en
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陈世涛
王文
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Xinjiang Xinte Crystal Silicon High Tech Co.,Ltd.
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Xinte Energy Co Ltd
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    • C—CHEMISTRY; METALLURGY
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D50/00—Combinations of methods or devices for separating particles from gases or vapours
    • B01D50/60—Combinations of devices covered by groups B01D46/00 and B01D47/00
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • C01B33/035—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process
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    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/08—Compounds containing halogen
    • C01B33/107—Halogenated silanes
    • C01B33/1071—Tetrachloride, trichlorosilane or silicochloroform, dichlorosilane, monochlorosilane or mixtures thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2256/00—Main component in the product gas stream after treatment
    • B01D2256/16—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/20—Halogens or halogen compounds
    • B01D2257/204—Inorganic halogen compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0415—Purification by absorption in liquids
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/042—Purification by adsorption on solids

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Abstract

The invention provides a treatment device for polycrystalline silicon reduction tail gas, which comprises: the washing tower is used for carrying out leaching treatment on the reduction tail gas, outputting silicon powder-containing chlorosilane liquid from the tower bottom, and outputting noncondensable gas from the tower top; the circulating pump protection unit is used for removing silicon powder and impurities in the silicon powder-containing chlorosilane liquid and then outputting the chlorosilane liquid; the washing tower circulating pump is used for pressurizing the chlorosilane liquid and then sending the chlorosilane liquid back to the inside of the washing tower to participate in leaching work; the dust removal unit is used for removing silicon powder in the non-condensable gas to obtain the non-condensable gas after dust removal; the multistage cooling unit is used for sequentially carrying out multistage cooling treatment on the dedusted noncondensable gas, condensing all chlorosilane in the noncondensable gas, conveying the chlorosilane to the chlorosilane condensate collecting tank, and outputting hydrogen containing impurities; and the multistage activated carbon adsorption unit is used for enabling the hydrogen gas containing impurities output by the multistage cooling unit to sequentially undergo multistage adsorption treatment to obtain pure hydrogen gas and sending the pure hydrogen gas to the hydrogen buffer tank. The invention can effectively remove the silicon powder in the reduction tail gas.

Description

Treatment device for polycrystalline silicon reduction tail gas
Technical Field
The invention relates to the technical field of polycrystalline silicon production, in particular to a treatment device for 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 process polycrystalline silicon production process, the tail gas treatment process of the CDI device is characterized in that reduction tail gas is sequentially cooled by a circulating water cooler, a brine cooler and a Freon cooler, so that most of chlorosilane is condensed, hydrogen is separated from the chlorosilane, the separated hydrogen is compressed by a hydrogen compressor, the compressed hydrogen enters an absorption tower to be washed, and is washed by circulating chlorosilane at the temperature of-44 ℃ and then is sent into an activated carbon adsorption column to absorb a small amount of chlorosilane, HCl and PH which are mixed in the hydrogen3And then the mixture is sent into a reduction device to repeatedly participate in production. Sending the circulating chlorosilane after washing hydrogen in the absorption tower into an analysis tower, and adding HCl, dichlorosilane and PH in the circulating chlorosilane3And pressurizing and conveying part of the evaporated chlorosilane into an absorption tower through a pump for recycling, and meanwhile, conveying the rest part of the chlorosilane to a rectification process.
The inventor finds that the treatment of the reduction tail gas by using the CDI device has three defects:
firstly, silicon powder brought into a CDI device through tail gas after the silicon powder is recovered cannot be effectively removed. The entrained silica fume can clog and wear the towers, pumps, etc. of the CDI unit, causing equipment damage or system downtime and affecting downstream processes.
Secondly, the energy consumption of the CDI device is higher. Data statistics of some domestic polysilicon production enterprises show that in ten-thousand-ton polysilicon production enterprises, the average total power consumption of polysilicon production is 8.2 ten thousand degrees/ton silicon, and the power consumption of a CDI device accounts for 15% of the total power consumption of polysilicon production, and reaches 1.2 ten thousand degrees/ton silicon.
Thirdly, the system is huge, the equipment is numerous, and the overhaul and the maintenance are difficult. The occupation area of the CDI device of ten-thousand-ton grade polysilicon enterprises reaches 12000m2Above, the investment is more than 2 million yuan, the number of equipment such as various towers, pumps, heat exchangers, compressors, refrigerators, tanks and the like is as many as 200, and each set of equipment is damaged, which may cause partial or complete system shutdown of the polysilicon production line.
The cost is increased in the production process of the polycrystalline silicon due to the reasons, and the competitiveness of enterprises is reduced due to frequent system faults.
Disclosure of Invention
The invention aims to solve the technical problem of providing a treatment device for polycrystalline silicon reduction tail gas, which can effectively remove silicon powder in the reduction tail gas, greatly reduce the treatment energy consumption of the reduction tail gas and greatly reduce the equipment amount required by the reduction tail gas treatment.
The technical scheme adopted for solving the technical problem of the invention is as follows:
the invention provides a treatment device for polycrystalline silicon reduction tail gas, wherein the reduction tail gas comprises mixed gas of hydrogen, chlorosilane and a small amount of silicon powder, and the treatment device comprises:
the washing tower is used for carrying out leaching treatment on the reduction tail gas by using chlorosilane leacheate from top to bottom in the tower, outputting silicon powder-containing chlorosilane liquid from a tower kettle, and outputting non-condensable gas from the tower top, wherein the non-condensable gas comprises hydrogen, and a mixed gas of unabsorbed chlorosilane and silicon powder;
the circulating pump protection unit is used for removing silicon powder and impurities in the chlorosilane liquid containing silicon powder output by the tower kettle of the washing tower and then outputting the chlorosilane liquid;
the circulating pump of the washing tower is used for pressurizing chlorosilane liquid output by the circulating pump protection unit and then sending the pressurized chlorosilane liquid into the washing tower through a first-stage spraying port at the upper part of the washing tower to participate in leaching work;
the dust removal unit is used for removing silicon powder in the non-condensable gas output from the top of the washing tower to obtain the non-condensable gas after dust removal;
the multistage cooling unit is used for sequentially carrying out multistage cooling treatment on the dedusted noncondensable gas, completely condensing chlorosilane in the dedusted noncondensable gas, conveying the chlorosilane to the chlorosilane condensate collecting tank, and outputting hydrogen containing impurities;
and the multistage activated carbon adsorption unit is used for enabling the hydrogen gas containing impurities output by the multistage cooling unit to sequentially undergo multistage adsorption treatment to obtain pure hydrogen gas and sending the pure hydrogen gas to the hydrogen buffer tank.
Optionally, the circulation pump protection unit includes a first pressure difference meter, a first control unit and two ceramic filters, the two ceramic filters are connected in parallel, and one is on and one is standby, the first pressure difference meter is connected with the inlet and the outlet of the two ceramic filters respectively and is used for measuring the front-back pressure difference of the ceramic filter in the operating state, and the first control unit is used for cutting off the ceramic filter in the operating state when the measurement value of the first pressure difference meter is greater than 0.1MPa, and simultaneously switching the ceramic filter in the standby state to the operating state.
Optionally, the circulation pump protection unit further includes a liquid level switch tank, which is connected to outlets of the two ceramic filters and an inlet of the washing tower circulation pump, respectively, and a liquid level switch is disposed on the liquid level switch tank and used for measuring a liquid level in the liquid level switch tank, and the first control unit is further configured to stop the washing tower circulation pump in an interlocking manner when the liquid level in the liquid level switch tank is lower than 70%.
Optionally, a pressure gauge is further arranged on the liquid level switch tank and used for measuring the liquid pressure in the liquid level switch tank, and the first control unit is further used for enabling the washing tower circulating pump to stop in an interlocking manner when the liquid pressure in the liquid level switch tank is lower than 0.1 MPa.
Optionally, a vertical isolation filter screen is arranged at the bottom of the washing tower and used for dividing a bottom area in the washing tower into a spraying liquid area and a pumping liquid area, and a circulating pump of the washing tower pumps liquid from the pumping liquid area through a circulating pump protection unit; an inclined isolation baffle is arranged above the isolation filter screen, one end of the isolation baffle is fixed on the inner wall of the washing tower, the other end of the isolation baffle is a free end and inclines towards the spray liquid area, and the silicon-containing powder chlorosilane liquid leached from the washing tower is guided into the spray liquid area, and the silicon-containing powder chlorosilane liquid entering the spray liquid area enters the pump suction area after being filtered by the isolation filter screen.
Optionally, the upper portion of the isolation filter screen is provided with an overflow port for entering the pump liquid pumping area through the overflow port when the liquid level of the spray liquid area reaches a preset position.
Optionally, the outlet of the washing tower circulating pump is further connected with a pump pumping area at the bottom of the washing tower through an isolation filter screen backwashing pipeline, a control valve is arranged on the isolation filter screen backwashing pipeline and used for controlling the liquid level of the spraying liquid area to reach a preset position and controlling the liquid level of the pump pumping area to fall, and the washing tower circulating pump is opened when running normally so as to backwash the isolation filter screen by using the pressurized chlorosilane liquid output by the washing tower circulating pump.
Optionally, the dust removal unit includes a second pressure difference meter, a second control unit and two dust removers, the two dust removers are connected in parallel, and one dust remover is provided with one dust remover, the second pressure difference meter is respectively connected with the inlet and the outlet of the two dust removers and is used for measuring the front-back pressure difference of the dust remover in the operating state, the second control unit is used for cutting off the dust remover in the operating state when the measured value of the second pressure difference meter is greater than 0.1MPa, and simultaneously, the dust remover in the standby state is switched to the operating state.
Optionally, the multistage cooling unit comprises eight air coolers and a freon cooler, wherein the eight air coolers are used for cooling the dedusted noncondensable gas, condensing most of chlorosilane in the dedusted noncondensable gas and sending the condensed chlorosilane to a chlorosilane condensate collecting tank, and meanwhile, outputting the residual noncondensable gas to the freon cooler; and the freon cooler is used for cooling the residual non-condensable gas, condensing the rest chlorosilane in the residual non-condensable gas, conveying the condensed chlorosilane to a chlorosilane condensate collecting tank, and outputting hydrogen containing impurities.
Optionally, the multistage cooling unit further comprises a cold and hot medium heat exchanger located between the air cooler and the freon cooler, and the cold and hot medium heat exchanger is used for cooling the residual non-condensable gas output by the air cooler by using the cold energy containing the impurity hydrogen output by the freon cooler, and sending the chlorosilane condensed in the cooling process to the chlorosilane condensate collecting tank.
Optionally, the treatment device further comprises a first delivery pump, wherein the first delivery pump is used for pressurizing the chlorosilane condensate in the chlorosilane condensate collecting tank and then delivering the pressurized chlorosilane condensate to the inside of the washing tower through a secondary spraying port at the upper part of the washing tower to participate in the leaching work.
Has the advantages that:
the treatment device for the polycrystalline silicon reduction tail gas can effectively treat the silicon powder brought by the reduction tail gas under the condition of ensuring the quality of the separated hydrogen, greatly reduce the treatment energy consumption of the reduction tail gas, greatly reduce the equipment quantity of the reduction tail gas treatment device, reduce the difficulty of system maintenance, greatly reduce the investment amount during the construction of new enterprises, and create higher economic benefit for the enterprises.
Drawings
Fig. 1 is a schematic structural diagram of a device for treating polycrystalline silicon reduction tail gas according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the configuration of a circulation pump protection unit of the scrub column of FIG. 1;
FIG. 3 is a schematic diagram of the structure of the scrub column of FIG. 1;
fig. 4 is a schematic structural diagram of the activated carbon adsorption column in fig. 1.
In the figure: 1-reducing the tail gas; 2-a washing tower; 3-a washing tower slag discharge port; 4-a washing tower circulating pump; 5-a dust removal unit; 6-an air cooler; 7-cold and hot medium heat exchanger; 8-freon coolers; 9-liquid freon inlet; a 10-gaseous freon outlet; 11-a first delivery pump; a 12-chlorosilane condensate collection tank; a 13-chlorosilane storage tank; 14-a second delivery pump; 15-rectification process; 16-a hydrogen compressor; a water heat exchanger at the temperature of 17-7 ℃; a water inlet on water at 18-7 ℃; a water return port at the temperature of 19-7 ℃; 20-a first-stage activated carbon adsorption column; 21-a second-stage activated carbon adsorption column; 22-third-stage activated carbon adsorption column; 23-fourth stage active carbon adsorption column; 24-regenerating and purging a hydrogen inlet by the adsorption column; 25-regenerating and purging a hydrogen outlet by the adsorption column; a water inlet at 26-7 ℃; a water outlet at 27-7 ℃; a saturated steam inlet at 28-1.2 MPa; an outlet of 29-1.2 MPa saturated steam condensate; 30-steam trap; 31-a hydrogen buffer tank; 32-a reduction step; 33-chlorosilane liquid containing silicon powder; 34-a ceramic filter element; 35-a ceramic filter; 36-backwashing the ceramic filter element slag discharge port; 37-a first differential pressure gauge; 38-liquid level switch tank; 39-liquid level switch; 40-pressure gauge; 41-backwashing the ceramic filter element flushing line; 42-isolating the screen backwash line; 43-isolating a filter screen; 44-a separation baffle; 45-circulation pump protection unit; 46-first stage spray opening; 47-secondary spray port; 48-noncondensable gas; 49-non-condensable gas after dust removal; 50-non-condensable gas after air cooling; 51-cooling the cooled noncondensable gas after heat exchange; hydrogen containing impurities after the 52-Freon is cooled; 53-hydrogen containing impurities which is heated after heat exchange; 54-hydrogen containing impurities after pressure increase; 55-hydrogen containing impurities after cooling; 56-pure hydrogen.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.
The embodiment of the invention provides a treatment device for polycrystalline silicon reduction tail gas, and mainly relates to research on a polycrystalline silicon production technology process and application of the device in polycrystalline silicon production. The temperature of the reduction tail gas is about 130 ℃, the pressure is 0.45MPa, the reduction tail gas comprises mixed gas of hydrogen, chlorosilane and a small amount of silicon powder, and the chlorosilane comprises trichlorosilane, silicon tetrachloride and dichlorosilane. Wherein, the volume percentage of the silicon powder in the reduction tail gas is only 0.1 percent, although the percentage of the silicon powder is small, the influence on the production process of the polysilicon is large, and the silicon powder is removed; of course, the gas mixture will also contain small amounts of HCl (hydrogen chloride) and PH3(phosphine), and the like.
It should be noted that the term "minor amount" as used herein means an amount of HCl of less than 0.1% by volume and pH, which is generally understood in the art to be present in the composition3A volume percentage of less than 50PPM falls within the small category. "left and right" appearing in the present invention refers to addition or subtraction of a preset number of units on a base value, for example, about 130 ℃, and if the unit of the preset number is 5 units, it refers to 125 ℃ to 135 ℃, or, refers to 130 ℃ ± a first preset temperature value; for another example, about 85%, assuming that the unit of the predetermined number is 3 units, it means 82% to 88%, or 85% ± the first predetermined percentage. The unit of the preset quantity corresponding to each numerical value can be set by a person skilled in the art according to actual conditions.
As shown in fig. 1, the processing apparatus includes:
the washing tower 2 is used for carrying out leaching treatment on the reduction tail gas 1 by using chlorosilane leacheate from top to bottom in the tower, outputting a silicon powder-containing chlorosilane liquid 33 from a tower kettle, and outputting a non-condensable gas 48 from the tower top; the chlorosilane liquid 33 containing silicon powder comprises a mixed solution of silicon powder and chlorosilane, and a small amount of impurities (such as HCl and PH)3) (ii) a The non-condensable gases 48 include a mixture of hydrogen, unabsorbed chlorosilane and silicon powder, and small amounts of impurities (e.g., HCl, PH)3)；
The circulating pump protection unit 45 is used for removing silicon powder and impurities in the chlorosilane liquid 33 containing silicon powder output from the tower bottom of the washing tower 2 and then outputting the chlorosilane liquid, wherein the chlorosilane liquid almost does not contain silicon powder and impurities, and the chlorosilane liquid is relatively pure liquid chlorosilane;
the washing tower circulating pump 4 is used for pressurizing chlorosilane liquid output by the circulating pump protection unit 45 and then sending the pressurized chlorosilane liquid into the washing tower 2 through a first-stage spraying port 46 at the upper part of the washing tower 2 to be used as leacheate to participate in leaching work;
the dust removal unit 5 is used for removing silicon powder in the non-condensable gas 48 output from the top of the washing tower 2 to obtain the non-condensable gas 49 after dust removal; since the silicon powder is removed by the dust removal unit 5, the dust-removed noncondensable gas 49 includes a mixture of hydrogen and unabsorbed chlorosilane, and a small amount of impurities (e.g., HCl, PH)3)；
A multistage cooling unit for subjecting the dedusted non-condensable gas 49 to multistage cooling treatment in order to remove the dust in the non-condensable gas 49The chlorosilane is completely condensed and sent to a chlorosilane condensate collecting tank 12, and a small amount of impurities (such as HCl and PH) are output at the same time3Chlorosilane), hydrogen;
and the multistage activated carbon adsorption unit is used for sequentially subjecting the hydrogen gas containing a small amount of impurities output by the multistage cooling unit to multistage adsorption treatment, completely removing the impurities mixed in the hydrogen gas, obtaining pure hydrogen gas 56 and sending the pure hydrogen gas to the hydrogen buffer tank 31.
In this embodiment, in order to prevent the excessive amount of the chlorosilane leacheate entering the washing tower 2, the pressurized chlorosilane liquid output by the circulating pump 4 of the washing tower can be sent to the chlorosilane storage tank 13 except for the chlorosilane liquid sent into the washing tower through the primary spray port; meanwhile, the chlorosilane condensate in the chlorosilane condensate collecting tank 12 can also be sent to the chlorosilane storage tank 13. And the liquid chlorosilane in the chlorosilane storage tank 13 can be conveyed to a downstream rectification process 15 through a second conveying pump 14, and the dichlorosilane, the trichlorosilane and the silicon tetrachloride can be recycled after being separated by a rectification device. In addition, the pure hydrogen in the hydrogen buffer tank 31 can be delivered to the upstream reduction process 32, so that the pure hydrogen can take part in the reduction reaction in the reduction device to produce electronic grade polysilicon. Wherein the pressure range of the liquid chlorosilane output by the second conveying pump 14 is 1.0-1.5 MPa.
Therefore, by the treatment of the equipment, silicon powder in the reduction tail gas 1 can be effectively removed (realized by using the dust removal unit and the circulating pump protection unit), hydrogen and chlorosilane in the reduction tail gas can be well separated, and pure hydrogen obtained after the separated hydrogen is adsorbed and treated by the multistage activated carbon adsorption unit can be sent to an upstream reduction process to participate in a reduction reaction; the separated chlorosilane (comprising chlorosilane condensate and chlorosilane liquid) can be sent to a downstream rectification process and recycled after separation treatment. Moreover, the amount of equipment participating in the treatment is small, the energy consumption is low, and therefore the production cost and the overhaul and maintenance cost are low.
As shown in fig. 2, the circulation pump protection unit 45 includes a first pressure difference meter 37, a first control unit (not shown in the figure), and two ceramic filters 35, wherein the two ceramic filters 35 are connected in parallel, and one is on standby, that is, one is in an operating state, and the other is in a standby state.
The inside of the ceramic filter 35 is provided with a precise ceramic filter element, which can effectively filter more than 99% of silicon powder and impurities with the granularity larger than 1 μm (or larger than 1300 meshes) in the silicon powder-containing chlorosilane liquid 33 output from the tower kettle of the washing tower 2, the silicon powder-containing chlorosilane liquid 33 output from the tower kettle of the washing tower 2 enters from the lower part of the ceramic filter 35 in the running state, and after being filtered by the ceramic filter element 34 from bottom to top, purer chlorosilane liquid is output from the top of the ceramic filter 35 and then is sent to the circulating pump 4 of the washing tower for increasing treatment, thereby effectively protecting the stable running of the circulating pump 4 of the washing tower and avoiding the abrasion of the pump caused by the impurities.
The first pressure difference meter 37 is respectively connected with the inlet and the outlet of the two ceramic filters 35, namely is arranged in front of and behind the two ceramic filters 35 and is used for measuring the pressure difference between the front and the rear of the ceramic filters 35 in the running state, and the first control unit is used for cutting off the ceramic filters 35 in the running state when the measured value of the first pressure difference meter 37 is greater than 0.1MPa and switching the ceramic filters 35 in the standby state to the running state, so that the running ceramic filters 35 are switched in time, and the phenomena of low working medium throughput, triggering interlocking and causing the washing tower circulating pump 4 to jump and stop caused by overlarge resistance are avoided.
After the ceramic filter 35 in the operating state is cut off (i.e., switched and isolated), in order to meet the conditions required by the standby state and thus restore the standby state, as shown in fig. 2, a first delivery pump 11 may be used to enable a part of the chlorosilane condensate in the chlorosilane condensate collecting tank 12 to enter a top flushing port of the ceramic filter 35 through a backwashing ceramic filter element flushing pipeline 41, to backwash the ceramic filter element 34 from top to bottom, and the chlorosilane liquid rich in silicon powder formed after flushing is sent to a downstream slurry treatment process (not shown in the figure) through a backwashing ceramic filter element slag discharge port 36 at the bottom of the ceramic filter 35.
In addition, the circulation pump protection unit 45 further includes a liquid level switch tank 38, which is respectively connected to the outlets of the two ceramic filters 35 and the inlet of the washing tower circulation pump 4, i.e., located after the two ceramic filters 35 and before the washing tower circulation pump 4.
Liquid level interlock protection may be provided for the scrubber circulation pump 4 to interlock the scrubber circulation pump 4 with the low liquid level of the liquid level switch tank 38. Specifically, be provided with liquid level switch 39 on the liquid level switch jar 38 for measure the liquid level in the liquid level switch jar 38, first the control unit still is used for making scrubber circulating pump 4 interlocking when the liquid level in the liquid level switch jar 38 is less than 70% and stops to effectively protect the safe operation of pump, avoid leading to the pump overheat to burn out because of the liquid level is not enough.
Pressure interlocking protection can also be set for the washing tower circulating pump 4, so that the washing tower circulating pump 4 is interlocked with the liquid pressure in the liquid level switch tank 38 in a remote transmission manner. Specifically, still be provided with manometer 40 on the liquid level switch jar 38 for measure the liquid pressure in the liquid level switch jar 38, first the control unit still is used for making scrubber circulating pump 4 interlocking when the liquid pressure in the liquid level switch jar 38 is less than 0.1MPa and stops to effectively protect the safe operation of pump, avoid leading to the pump overheat to burn out because of the liquid level is not enough.
In this embodiment, the circulation pump protection unit 45 mainly aims at the condition that the working medium is a fluid rich in impurities and the pump body has a high requirement on the working medium, and since the washing tower circulation pump 4 generally adopts a shielding pump, the shielding pump is greatly abraded due to the high content of silicon powder, so that the equipment is suitable for use. Specifically, silicon powder and impurities in the chlorosilane liquid 33 containing silicon powder output from the tower bottom of the washing tower 2 are effectively removed through the ceramic filter 35 in the circulating pump protection unit 45, so that the circulating pump 4 of the washing tower is protected, and the liquid chlorosilane pump rich in silicon powder is prevented from being worn.
It is known that the density of silicon is 2.33g/cm3The average density of chlorosilane is 1.4g/cm3It can be seen that the density of silicon is greater than the average density of chlorosilanes. Therefore, after the reduction tail gas 1 is leached in the washing tower 2 by using the chlorosilane leaching solution from top to bottom, the chlorosilane liquid containing silicon powder quickly sinks to the bottom of the washing tower and is easier to separate from the non-condensable gas.
Moreover, chlorosilane liquid output by the circulating pump protection unit 45 is pressurized by the circulating pump 4 of the washing tower and then is sent into the washing tower 2 through the first-stage spray port 46 at the upper part of the washing tower 2 to be used as leacheate to participate in leaching work, about 80% of silicon powder in reduction tail gas can be sprayed and washed off, and the chlorosilane liquid rich in silicon powder accumulated at the bottom of the washing tower 2 can be conveyed to a downstream slurry process (not shown in the figure) for treatment through intermittent deslagging; when the chlorosilane leacheate leaches the reduction tail gas, cold energy is input into the reduction tail gas, so that the reduction tail gas is cooled in the leaching process.
As shown in fig. 3, the bottom of the washing tower 2 is provided with a vertical isolation screen 43 for dividing the bottom area in the washing tower into a spray liquid area (the area located at the left side of the isolation screen 43 in fig. 2) and a pump liquid area (the area located at the right side of the isolation screen 43 in fig. 2), and the washing tower circulation pump 4 pumps liquid from the pump liquid area through a circulation pump protection unit 45; an inclined isolation baffle 44 is arranged above the isolation filter screen 43, one end of the isolation baffle 44 is fixed on the inner wall of the washing tower 2, the other end of the isolation baffle 44 is a free end and inclines towards the spray liquid area, the inclination angle of the isolation baffle is 40 degrees from the horizontal plane, and the isolation baffle is used for guiding the silicon-containing chlorosilane liquid leached from the washing tower 2 into the spray liquid area, and the silicon-containing chlorosilane liquid entering the spray liquid area enters the pump liquid pumping area after being filtered by the isolation filter screen 43. The bottoms of the spraying liquid area and the pumping liquid area are provided with a washing tower slag discharge port 3, and the chlorosilane liquid rich in silicon powder accumulated in the two areas can be conveyed to a downstream slurry process by periodically discharging slag.
The isolating filter screen 43 is a multilayer 60-mesh filter screen, so that most silicon powder particles with the diameter larger than 0.3mm in the silicon powder-containing chlorosilane liquid in the spray liquid zone are filtered and then enter the pump liquid pumping zone, and the specific number of layers can be determined by a person skilled in the art according to actual conditions.
The upper part of the isolation filter screen 43 is provided with an overflow port (not shown in the figure) for entering the pumping area through the overflow port when the liquid level of the spraying area reaches a preset position, so as to avoid the pump evacuation caused by the liquid shortage of the pumping area. Of course, the height of the bottom of the overflow opening is flush with the height of the preset position. The preset position can be 80% of the height of the spray liquid area, namely, the liquid level of the spray liquid area reaches 80%, and then enters the pump liquid pumping area through an overflow port at the upper part of the isolation filter screen 43.
The outlet of the washing tower circulating pump 4 is also connected with a pump pumping area at the bottom of the washing tower 2 through an isolation filter screen backwashing pipeline 42, a control valve is arranged on the isolation filter screen backwashing pipeline 42, when the liquid level of the spray liquid area reaches a preset position (can be at a position which is 80% of the height of the spray liquid area), the liquid level of the pump pumping area is reduced, the washing tower circulating pump 4 operates normally, the silicon powder blockage phenomenon of the isolation filter screen 43 is indicated, at the moment, the control valve is opened to conduct the isolation filter screen backwashing pipeline 42, and pressurized chlorosilane liquid output by the washing tower circulating pump 4 can be used for backwashing the isolation filter screen 43 to flush silicon powder on the isolation filter screen 43.
As can be seen from the foregoing description, the pressurized chlorosilane liquid (with a pressure ranging from 1.0 to 1.5MPa) output by the circulating pump 4 of the scrubber tower can be divided into three parts, namely, a1 part, a2 part and A3 part (as shown in FIG. 1). Wherein, part A1 enters the pump liquid pumping area at the bottom of the washing tower 2 through the back flushing pipeline 42 of the isolation filter screen, the part is started to be put into use only when the isolation filter screen is blocked by silicon powder, the flow rate in use can be set to 10 tons/hour, and the part A1 can be closed once the blockage phenomenon of the isolation filter screen is eliminated; part A2 enters a chlorosilane storage tank 13, and the flow of the part A can be controlled to be 130 tons/hour; part A3 enters the washing tower 2 through the first-stage spray opening 46 at the upper part of the washing tower 2, the flow rate of the part A can be adjusted according to the production condition of the polysilicon, and can be set to 100 tons/hour under the conventional condition.
In this embodiment, the dust removal unit 5 is configured to further effectively remove silicon powder that is not washed down by the washing tower 2 in the reduction tail gas, and includes a second pressure difference meter, a second control unit, and two dust removers, where the two dust removers are connected in parallel, and one dust remover is on and standby, that is, one dust remover is in an operating state, and the other dust remover is in a standby state.
The dust remover is internally provided with a cylindrical stainless steel mesh filter element (namely a compact steel wire cylinder), can effectively filter more than 99.5 percent of silicon powder larger than 1000 meshes in the non-condensable gas 48 output from the top of the washing tower 2, simultaneously can block liquid drops carried in the non-condensable gas, the non-condensable gas 48 output from the top of the washing tower 2 enters from the lower part of the dust remover in a running state, and after being filtered by the dust remover from bottom to top, the non-condensable gas 49 subjected to dust removal is output from the top of the dust remover, wherein the silicon powder content is extremely low (less than 0.5 percent), the particle size is extremely small, and therefore, the normal production of subsequent processes can be guaranteed.
The second pressure difference meter is respectively connected with the inlet and the outlet of the two dust collectors and used for measuring the front-back pressure difference of the dust collector in the running state, and the second control unit is used for cutting off the dust collector in the running state when the measured value of the second pressure difference meter is larger than 0.1MPa and switching the dust collector in the standby state into the running state.
After the dust remover in the running state is cut off (i.e. switched and isolated), in order to meet the conditions required by the standby state and restore the standby state, a part of chlorosilane condensate in the chlorosilane condensate collecting tank 12 can enter a top flushing port of the dust remover by using the first delivery pump 11, a filter element of the dust remover is flushed from top to bottom, and chlorosilane liquid (which is less in silicon powder content compared with chlorosilane liquid 33 containing silicon powder output from a tower bottom of the washing tower 2) carrying silicon powder formed after flushing can be sent to the washing tower 2 for recycling.
As shown in fig. 1, the first transfer pump 11 may also be configured to pressurize the chlorosilane condensate in the chlorosilane condensate collecting tank 12, send the pressurized chlorosilane condensate to the interior of the washing tower through the secondary spray port 47 at the upper portion of the washing tower to participate in the leaching operation as a leaching solution, so as to prevent an excessive amount of the chlorosilane leaching solution entering the washing tower 2, a part of the chlorosilane condensate in the chlorosilane condensate collecting tank 12 may be sent to the interior of the washing tower 2, another part of the chlorosilane condensate may be sent to the chlorosilane storing tank 13, and the rest part of the chlorosilane condensate may be returned to the chlorosilane condensate collecting tank 12.
In this embodiment, the circulating pump 4 of the washing tower pressurizes (part of) chlorosilane liquid output by the circulating pump protection unit 45, and then the pressurized (part of) chlorosilane liquid is sent into the washing tower 2 through the first-stage spray opening 46 at the upper part of the washing tower 2, the first delivery pump 11 increases (part of) chlorosilane condensate output by the chlorosilane condensate collection tank 12, and then the increased (part of) chlorosilane condensate is sent into the washing tower 2 through the second-stage spray opening 47 at the upper part of the washing tower 2, so that the two parts of liquid chlorosilane are used as leacheate to participate in the leaching work, thereby about 95% of silicon powder in the reduction tail gas is sprayed and washed, only about 5% of silicon powder is output from the top of the washing tower 2 as noncondensable gas, and at the same time, 60% of chlorosilane in the reduction tail gas is. Furthermore, the leacheate entering the washing tower 2 from the first-stage spray port 46 and the second-stage spray port 47 leaches the reducing tail gas and simultaneously inputs cold energy to the reducing tail gas, so that the reducing tail gas is cooled to about 70 ℃ from about 130 ℃ in the washing tower, and therefore the temperature of the non-condensable gas 48 output from the top of the washing tower 2 and the temperature of the non-condensable gas 49 output from the dedusting unit 5 after dedusting are both about 70 ℃. It can be seen that the secondary spraying supplements the cold quantity of the reduction tail gas on the basis of the primary spraying, and if the secondary spraying is not arranged, the temperature of the non-condensable gas output from the top of the washing tower 2 can be relatively increased, so that the loads of the air cooler 6 and the Freon cooler 8 can be increased.
As shown in fig. 1, the multistage cooling unit includes an air cooler 6 and a freon cooler 8, eight air coolers 6 are adopted, a fan at the lower part of the air coolers provides power and air is used for providing cold energy, the air coolers 6 are used for cooling the dedusted noncondensable gas 49 at about 70 ℃, most of chlorosilane (about 85%) in the dedusted noncondensable gas 49 is condensed and sent to a chlorosilane condensate collecting tank 12, and meanwhile, the residual noncondensable gas at about 40 ℃ is output to the freon cooler 8, so that the air coolers 6 provide about 85% of cold energy for the condensation process of the dedusted noncondensable gas 49. The freon cooler 8 is used for cooling the residual non-condensable gas (namely cryogenic treatment), condensing the rest chlorosilane (about 15 percent) in the residual non-condensable gas and sending the condensed chlorosilane to a chlorosilane condensate collecting tank 12, and meanwhile, outputting hydrogen containing impurities, wherein about 99.8 percent of hydrogen only contains a small amount of chlorosilane, HCl and PH3And the like, so the Freon cooler 8 provides about 15 percent of cold energy for the condensation process of the non-condensable gas 49 after dust removal. As shown in the figure1 shows, still be equipped with liquid freon entry 9 and gaseous state freon export 10 on the freon cooler 8, cryogenic liquid freon passes through entry 9 gets into freon cooler 8 after, with surplus noncondensable gas carries out the heat transfer, cold volume quilt it becomes gaseous state freon and follows behind the utilization of surplus noncondensable gas export 10 output.
In order to fully recover the cold energy, save energy and reduce consumption, a cold and hot medium heat exchanger 7 is arranged behind the air cooler 6 and in front of the Freon cooler 8, and can exchange heat between the gas output by the air cooler 6 and the gas output by the Freon cooler 8. Therefore, preferably, the multistage cooling unit further comprises a cold and hot medium heat exchanger 7 positioned between the air cooler 6 and the freon cooler 8, and the cold and hot medium heat exchanger is used for cooling the air-cooled non-condensable gas output by the air cooler 6 by utilizing the cold energy containing the impurity hydrogen output by the freon cooler 8, and sending the chlorosilane condensed in the cooling process to a chlorosilane condensate collecting tank 12.
Specifically, the air cooler 6 cools the dedusted noncondensable gas 49 at about 70 ℃, outputs the air-cooled noncondensable gas 50 at about 40 ℃ to the tube side of the cold-hot medium heat exchanger 7, and condenses about 85% of chlorosilane; the cold and hot medium heat exchanger 7 carries out heat exchange (cooling) treatment on the non-condensable gas 50 after air cooling by utilizing the cold energy of the gas output by the Freon cooler 8, the non-condensable gas 51 with the temperature of about minus 10 ℃ and cooled after heat exchange is output to the Freon cooler 8 from the tube pass, and meanwhile, part of chlorosilane is condensed, and the chlorosilane condensed by the cold and hot medium heat exchanger 7 is much less than that condensed by the air cooler 6 and the Freon cooler 8; the freon cooler 8 carries out cryogenic treatment on the cooled noncondensable gas 51 after heat exchange, condenses about 15% of chlorosilane, condenses 99.8% of chlorosilane in the noncondensable gas 49 after dust removal, and outputs freon-cooled hydrogen 52 containing impurities at about minus 44 ℃ to the shell pass of the cold-hot medium heat exchanger 7; the hydrogen gas containing impurities 52 cooled by the freon is subjected to heat exchange in the cold and hot medium heat exchanger 7 to form hydrogen gas containing impurities 53 heated after heat exchange at about 10 ℃ and output from the shell side of the cold and hot medium heat exchanger 7. And chlorosilane condensate condensed by the air cooler 6, the cold and hot medium heat exchanger 7 and the Freon cooler 8 is sent into a chlorosilane condensate collecting tank 12.
As can be seen from the foregoing description, the chlorosilane condensate (with a pressure ranging from 1.0 to 1.5MPa) output from the chlorosilane condensate collecting tank 12 after being pressurized by the first transfer pump 11 can be divided into five parts, namely, part B1, part B2, part B3, part B4 and part B5 (as shown in FIG. 1). Wherein, the part B1 enters the chlorosilane storage tank 13, the part is used for liquid level balance of the chlorosilane storage tank 13, the flow rate is controlled to be 40 tons/hour, and the part can be closed in practice; part B2 enters the washing tower 2 through a secondary spray port 47 at the upper part of the washing tower 2 to realize secondary spray, and is also a second cold source (the first cold source is primary spray) brought into the washing tower 2, and the flow rate is controlled to be 40 tons/hour; part B3 returns to the chlorosilane condensate collecting tank 12, and the pipeline of the part is a spare pipeline which can not be used in general; part B4 enters the top flushing port of the dedusted deduster in the dedusting unit 5, the part is opened for use only after the deduster is cut, the flow rate during use can be set to 10 tons/hour, and the part B can be closed once the cut deduster is restored to the standby state; the portion B5 enters the top flushing port of the ceramic filter 35 which is cut off, and the portion is opened only after the ceramic filter is cut off, and the flow rate at the time of administration may be set to 10 tons/hr and closed once the cut-off ceramic filter is returned to a standby state.
As shown in fig. 1, before the hydrogen gas containing impurities (i.e. the aforementioned hydrogen gas containing impurities 53 heated after heat exchange) output by the multistage cooling unit enters the multistage activated carbon adsorption unit, in order to better meet the operating requirements of the activated carbon adsorption column to obtain a better adsorption effect, the hydrogen gas containing impurities may be first processed by the hydrogen compressor 16 and the liquid medium heat exchanger. Therefore, preferably, the processing apparatus further comprises a hydrogen compressor 16 and a liquid medium heat exchanger, wherein the hydrogen compressor 16 is configured to compress and boost the hydrogen containing impurities to obtain boosted hydrogen containing impurities 54; the liquid medium heat exchanger is used for cooling the hydrogen 54 containing the impurities after being boosted to obtain hydrogen 55 containing the impurities after being cooled, and then sending the hydrogen 55 containing the impurities after being cooled into a multi-stage active carbon adsorption unit for adsorption treatment.
Wherein, the liquid medium heat exchanger can adopt a 7 ℃ water heat exchanger 17. As shown in fig. 1, the 7 ℃ water heat exchanger 17 is further provided with a 7 ℃ water inlet 18 and a 7 ℃ water return port 19.
Specifically, the temperature of the impurity-containing hydrogen gas (i.e., the impurity-containing hydrogen gas 53 heated after the heat exchange) output from the shell side of the cold-hot medium heat exchanger 7 is about 10 ℃ and the pressure thereof is 0.45MPa, and the pressure thereof is increased to 1.8MPa by the compression and pressure increase of the hydrogen compressor 16, and the temperature thereof is also increased by the compression action, and at the same time, the hydrogen gas is cooled to about 30 ℃ by the circulating water heat exchanger provided in the hydrogen compressor 16, thereby obtaining the impurity-containing hydrogen gas 54 having a temperature of about 30 ℃ and a pressure of 1.8MPa after pressure increase. And cooling the hydrogen gas 54 containing the impurities after being pressurized by a water heat exchanger 17 at the temperature of 7 ℃ to obtain hydrogen gas 55 containing the impurities after being cooled at the temperature of about 10 ℃ and the pressure of 1.8 MPa.
As shown in fig. 1, in this embodiment, the multistage activated carbon adsorption unit includes four stages of activated carbon adsorption columns connected in series, namely a first stage activated carbon adsorption column 20, a second stage activated carbon adsorption column 21, a third stage activated carbon adsorption column 22, and a fourth stage activated carbon adsorption column 24. Wherein, each grade of active carbon adsorption column all includes two active carbon adsorption columns, and one is opened one and is equipped with, and one is in the running state, and another is in standby state. Specifically, processing apparatus still includes timing unit and third the control unit, the timing unit is used for measuring the active carbon adsorption post accumulative total operating time who is in the running state, the third the control unit is used for the active carbon adsorption post accumulative total work that is in the running state full 12 hours with its excision, will be in the active carbon adsorption post of standby state simultaneously and switch into the running state to realize that the active carbon adsorption post of automatic switch spare is operating condition, go on in order to guarantee that the adsorption process is high-efficient, continuous.
To the active carbon adsorption column that is in the running state, for guaranteeing adsorption effect, avoid making the active carbon temperature rise fast because of exothermic reaction that the adsorption process takes place releases heat in a large number, cause the adsorption effect variation, before the active carbon adsorption column gets into the working phase, usable 7 ℃ water falls the temperature of active carbon to about 10 ℃ (the temperature that contains impurity hydrogen 55 after the cooling that gets into multistage active carbon adsorption unit also is about 10 ℃), and continuously let in 7 ℃ water at the working phase of active carbon adsorption column, in order to take away the heat that the adsorption process produced. Specifically, the lower part of the activated carbon adsorption column is provided with a 7 ℃ water inlet 26, the upper part of the activated carbon adsorption column is provided with a 7 ℃ water outlet 27, valves on pipelines where the 7 ℃ water inlet 26 and the 7 ℃ water outlet 27 are located are opened, and 7 ℃ water is introduced into the activated carbon adsorption column from bottom to top, so that heat generated by adsorption reaction in the activated carbon adsorption column can be taken away, and the heat is sent out from the 7 ℃ water outlet 27 on the activated carbon adsorption column, and the activated carbon adsorption column is prevented from being heated too fast in the working process.
The cut-off activated carbon adsorption column needs to be regenerated in order to satisfy the conditions required for the standby state and to be restored to the standby state. Specifically, the top of the activated carbon adsorption column is provided with an adsorption column regeneration purging hydrogen inlet 24 connected with a hydrogen buffer tank 31, the bottom of the activated carbon adsorption column is provided with an adsorption column regeneration purging hydrogen outlet 25 connected with a downstream hydrogen recovery processing procedure (not shown in the figure), the upper part of the activated carbon adsorption column is provided with a 1.2MPa saturated steam inlet 28, the lower part of the activated carbon adsorption column is provided with a 1.2MPa saturated steam condensate outlet 29, when regeneration processing is needed, valves on pipelines on which a 7 ℃ water inlet 26 and a 7 ℃ water outlet 27 are positioned are closed, valves on pipelines on which a 1.2MPa saturated steam inlet 28 and a 1.2MPa saturated steam condensate outlet 29 are positioned are opened, 1.2MPa saturated steam is introduced into the activated carbon adsorption column in a regeneration state from top to bottom, the pressure of the activated carbon adsorption column is changed from 1.8MPa to 0.05MPa, and the activated carbon adsorption column is heated and regenerated by the heat of the decompressed saturated steam, so that a small amount of impurities (, HCl, PH3) When the heated active carbon adsorption column is heated, the impurities can be separated from the active carbon adsorption column after sufficient heat is absorbed, meanwhile, a valve on a pipeline from the hydrogen buffer tank 31 to the adsorption column regeneration purging hydrogen inlet 24 and a valve on a pipeline from the adsorption column regeneration purging hydrogen outlet 25 to the hydrogen recovery processing procedure are required to be opened, and the active carbon adsorption column is blown by the hydrogen stored in the hydrogen buffer tank 31 from top to bottomSweeping, and the purge amount is controlled at 500Nm3And h, leading the impurities separated from the activated carbon adsorption column to enter a downstream hydrogen recovery treatment process along with the purging hydrogen.
The four-stage active carbon adsorption column is sequentially used for adsorption treatment, so that a small amount of chlorosilane and HCl in the hydrogen (namely the hydrogen 55 containing impurities after cooling) and the PH value which is very similar to the HCl in physical property and can cause the quality reduction of the produced polysilicon are effectively removed3And pure hydrogen 56 is obtained, so that the quality of the hydrogen is ensured, and the requirement of the downstream reduction process 32 for producing the electronic grade polysilicon is met.
The process flow of the reduction tail gas treatment device of the present embodiment is described in detail below, taking a polycrystal production device with an annual output of 3 ten thousand tons as an example:
reducing tail gas washing tower part
The reduction tail gas with the pressure of 0.5MPa and the temperature of about 130 ℃ output from the reduction device contains 9.4 tons/hour of hydrogen, 68 tons/hour of silicon tetrachloride, 88.4 tons/hour of trichlorosilane and 13.6 tons/hour of mixed gas of dichlorosilane, and the total amount is 179.4 tons/hour.
The reducing tail gas enters from the lower part of the washing tower 2, is subjected to primary spray washing by a circulating pump 4 of the washing tower and secondary spray washing by a first conveying pump 11, 95% of silicon powder in the reducing tail gas is removed in the washing tower 2, 60% of chlorosilane in the reducing tail gas is leached out and mixed into spray liquid, meanwhile, the temperature of the reducing tail gas is reduced to about 70 ℃, noncondensable gas 48 is output from the top of the tower, and the noncondensable gas enters a dust removal unit 5.
The noncondensable gas 48 with the temperature of about 70 ℃ output from the top of the washing tower 2 enters a dust removal unit, silicon powder which is not washed in the noncondensable gas 48 is further effectively removed in a dust remover of the dust removal unit, and more than 99.5 percent of the silicon powder with the mesh of more than 1000 is removed.
A circulating pump 4 of the washing tower extracts silicon powder-containing chlorosilane liquid 33 from the bottom of the washing tower 2, the silicon powder-containing chlorosilane liquid 33 firstly enters a ceramic filter 35, and the ceramic filter 34 which is precise is used, so that more than 99% of impurities with the granularity larger than 1 mu m (or larger than 1300 meshes) can be effectively filtered; the filtered chlorosilane liquid enters the liquid level switch tank 38 after coming out of the ceramic filter 35, then enters the washing tower circulating pump 4, is pressurized by the pump, and enters the washing tower 2 through the primary spray port 46 at the upper part of the washing tower 2 to carry out primary spray washing on the reduction tail gas. According to the liquid level condition in the washing tower 2, about 130 tons/hour of chlorosilane liquid output by a circulating pump 4 of the washing tower is controlled to be extracted to a chlorosilane storage tank 13.
The chlorosilane condensate collecting tank 12 outputs 40 tons/hour of chlorosilane condensate through the first conveying pump 11, and the chlorosilane condensate enters the washing tower 2 through a secondary spraying port 47 at the upper part of the washing tower 2 to carry out secondary spraying washing on the reduction tail gas. And according to the liquid level condition of the chlorosilane condensate collecting tank, the surplus chlorosilane condensate of about 40 tons/hour is extracted to the chlorosilane storage tank 13. And the chlorosilane liquid in the chlorosilane storage tank 13 is treated by a subsequent rectification process 15 to separate and recycle dichlorosilane, trichlorosilane and silicon tetrachloride.
Two dust removers in the dust removal unit 5 are opened and prepared, when the front-back pressure difference of the dust removers is larger than 0.1MPa, the dust removers are switched in time, after the dust removers are switched and isolated, chlorosilane condensate is led from a chlorosilane condensate collecting tank 12 through a first conveying pump 11 to carry out backwashing on filter elements of the dust removers, and chlorosilane liquid carrying silicon powder obtained after flushing is conveyed to a washing tower 2 to be recycled.
And a spray liquid area at the bottom of the washing tower 2 and a washing tower slag discharge port 3 at the bottom of a pump liquid pumping area are opened periodically, chlorosilane rich in silicon slag is discharged to remove deposited silicon powder, and the silicon powder is conveyed to a downstream slag slurry treatment process.
An isolation filter screen 43 is fixed at the bottom of the washing tower 2, the bottom area in the washing tower is divided into a spray liquid area and a pump liquid pumping area, an isolation baffle 44 inclined by 40 degrees is arranged above the isolation filter screen 43, the silicon powder-containing chlorosilane liquid leached from the washing tower 2 is guided to flow into the spray liquid area, and then most silicon powder particles with the diameter larger than 0.3mm are filtered by the multilayer 60-mesh isolation filter screen 43 and then enter the pump liquid pumping area. When the liquid level of the spraying liquid area reaches 80%, the liquid level exceeds the overflow port at the upper part of the isolation filter screen 43 and overflows to the liquid pumping area, so that the pump evacuation caused by the liquid shortage of the liquid pumping area is avoided. When the liquid level of the spraying liquid area reaches 80%, the liquid level of the pumping liquid area is reduced, and the pump runs normally, the phenomenon that the isolation filter screen 43 is blocked by silicon powder is indicated, at the moment, a control valve on the back flushing pipeline 42 of the isolation filter screen can be opened, and the isolation filter screen 43 is back flushed by pressurized chlorosilane liquid output by the circulating pump 4 of the washing tower.
Second, cooling and deep cooling part
The dedusted noncondensable gas 49 which is output from the dedusting unit 5 and has the temperature of about 70 ℃ enters eight air coolers 6, the temperature of the dedusted noncondensable gas 49 is reduced to below 40 ℃ by a fan, and the chlorosilane condensed in the air coolers 6 is sent to a chlorosilane condensate collecting tank 12.
The air-cooled noncondensable gas 50 output from the air cooler 6 enters the cold and hot medium heat exchanger 7 to exchange heat with the gas output from the Freon cooler 8, the noncondensable gas 51 cooled after heat exchange at about-10 ℃ is output from the tube side, and the chlorosilane condensed in the cold and hot medium heat exchanger 7 is also sent to the chlorosilane condensate collecting tank 12.
The noncondensable gas 51 of cooling down after the heat transfer of the output of cold and hot medium heat exchanger 7 tube side enters into freon cooler 8, the freon through the shell side evaporates and absorbs the heat, with gaseous 51 temperature drop to about-44 ℃, thereby condense 99.8% chlorosilane, and export the impurity-containing hydrogen 52 of freon cooling back to the shell side of cold and hot medium heat exchanger 7, then export the impurity-containing hydrogen 53 that heaies up after the heat transfer from the shell side of cold and hot medium heat exchanger 7, the chlorosilane that condenses down in freon cooler 8 also sends to chlorosilane condensate collection tank 12. The gas 53 now has a composition of about 99.8% hydrogen and contains only small amounts of chlorosilane, HCl and pH3。
Third, compressing and cooling part
The temperature of the impurity-containing hydrogen 53 which is heated up after heat exchange and output from the shell side of the cold and hot medium heat exchanger 7 is about 10 ℃ and the pressure is 0.45MPa, then the hydrogen enters the hydrogen compressor 16, the hydrogen 53 is compressed and pressurized by the hydrogen compressor 16 to increase the pressure of the hydrogen 53 to 1.8MPa, the hydrogen 53 is cooled to about 30 ℃ by a circulating water heat exchanger carried by the compressor due to the temperature rise of the compression action, and therefore the impurity-containing hydrogen 54 is output after the pressure rise of the temperature of about 30 ℃ and the pressure of 1.8 MPa.
The hydrogen 54 with impurities after being pressurized and output from the hydrogen compressor 16 enters a 7 ℃ water heat exchanger 17, and the hydrogen 54 is cooled to about 10 ℃.
Four, four stage active carbon pressure swing adsorption
The hydrogen 55 containing impurities enters from the bottom of a first-stage active carbon adsorption column 20 after being cooled at the temperature of about 10 ℃ and the output pressure of 1.8MPa from a 7 ℃ water heat exchanger 17, and almost all chlorosilane, HCl and PH in the hydrogen 55 are adsorbed by utilizing the adsorption function of active carbon under the environment of the pressure of 1.8MPa and the temperature of 10 DEG C3Adsorbing impurities, and sequentially entering a second-stage, a third-stage and a fourth-stage activated carbon adsorption columns. Hydrogen from the four-stage active carbon adsorption column basically contains chlorosilane, HCl and PH3And the impurities are removed by almost 100 percent, so that the quality of the hydrogen can be effectively guaranteed, and the production of electronic grade polycrystalline silicon is met.
The pure hydrogen 56 output from the four-stage activated carbon adsorption column enters the hydrogen buffer tank 31 and then is sent to the reduction device of the upstream reduction process for reuse.
The inventor finds that the invention brings the following beneficial effects in the production of polycrystalline silicon:
1) 99.5 percent of silicon powder brought by reduction tail gas generated by the reduction device can be removed, and the silicon powder is prevented from wearing a pump or causing the blockage of equipment and devices, thereby causing the partial or complete shutdown of the system.
2) The power consumption for reducing tail gas treatment can be reduced from 1.2 ten thousand DEG/ton silicon to 0.6 ten thousand DEG/ton silicon, 0.6 ten thousand DEG/ton silicon is saved, and the annual average power saving of ten thousand-ton polysilicon production enterprises is more than 6000 ten thousand DEG.
3) The investment of newly-built polysilicon enterprises in the reduction tail gas treatment device is reduced from 2 million yuan to less than 1 million yuan, and the total equipment amount of the device is reduced from 200 to less than 100. The floor area of the device is 12000m2Down to 6000m2The following.
4) The operation, maintenance, overhaul and management personnel of the reduction tail gas treatment device can be reduced to below 35 persons from the original average 60 persons.
5) The method adopts 1.2MPa saturated steam to heat and regenerate the adsorption column, has higher thermal efficiency and higher heating speed, can improve the temperature by 15 ℃ compared with the traditional method which uses hot water with the temperature of about 170 ℃ for heating and regeneration, has better regeneration effect, and ensures the PH value in the hydrogen3Impurities are effectively removed, and the quality of the obtained hydrogen can meet the requirement of electronic grade polycrystalline silicon production. Meanwhile, because saturated steam is directly used, the arrangement of a heat exchanger, a hot water tank and a water delivery pump is reduced, the equipment investment is reduced by about 1000 ten thousand yuan, the maintenance cost is saved by more than 100 ten thousand yuan every year, and the number of operating operators is reduced by 4 persons.
6) In the process of treating the reduction tail gas, the invention does not need to use a circulating water heat exchanger, 85 percent of cold energy is provided by an air cooler, 100 tons of water per hour can be saved, 80 ten thousand tons of water can be saved all the year round, and the invention has great advantages in areas with deficient water resources.
7) Can be with reduction tail gas processing apparatus by the general annual 1 major overhaul of adopting, prolong to 2 ~ 3 years major overhaul 1 times, practice thrift maintenance cost 200 ten thousand yuan/year.
In summary, the invention provides a novel treatment device applied to polycrystalline silicon production reduction tail gas aiming at the defects of a CDI device in the existing process for producing polycrystalline silicon by an improved Siemens method, which can effectively treat silicon powder brought in by the reduction tail gas under the condition of ensuring that the quality of separated hydrogen meets the requirement of producing electronic grade polycrystalline silicon, greatly reduce the treatment energy consumption of the reduction tail gas, greatly reduce the equipment quantity required by the reduction tail gas treatment, reduce the difficulty of system maintenance, greatly reduce the investment amount when a new enterprise is built, and create higher economic benefit for the enterprise.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims (10)

1. A processing apparatus of polycrystalline silicon reduction tail gas, the reduction tail gas includes the mist of hydrogen, chlorosilane and a small amount of silica flour, its characterized in that, processing apparatus includes:
the washing tower is used for carrying out leaching treatment on the reduction tail gas by using chlorosilane leacheate from top to bottom in the tower, outputting silicon powder-containing chlorosilane liquid from a tower kettle, and outputting non-condensable gas from the tower top, wherein the non-condensable gas comprises hydrogen, and a mixed gas of unabsorbed chlorosilane and silicon powder;
the circulating pump protection unit is used for removing silicon powder and impurities in the chlorosilane liquid containing silicon powder output by the tower kettle of the washing tower and then outputting the chlorosilane liquid;
the circulating pump of the washing tower is used for pressurizing chlorosilane liquid output by the circulating pump protection unit and then sending the pressurized chlorosilane liquid into the washing tower through a first-stage spraying port at the upper part of the washing tower to participate in leaching work;
the dust removal unit is used for removing silicon powder in the non-condensable gas output from the top of the washing tower to obtain the non-condensable gas after dust removal;
the multistage cooling unit is used for sequentially carrying out multistage cooling treatment on the dedusted noncondensable gas, completely condensing chlorosilane in the dedusted noncondensable gas, conveying the chlorosilane to the chlorosilane condensate collecting tank, and outputting hydrogen containing impurities;
the multistage activated carbon adsorption unit is used for enabling the hydrogen gas containing impurities output by the multistage cooling unit to be subjected to multistage adsorption treatment in sequence to obtain pure hydrogen gas and sending the pure hydrogen gas to the hydrogen gas buffer tank;
the circulating pump protection unit comprises two ceramic filters which are connected in parallel, and one ceramic filter is provided for each other;
the dust removal unit comprises two dust removers which are connected in parallel, and one dust remover is on and the other dust remover is on;
the treatment device also comprises a first delivery pump, a second delivery pump and a third delivery pump, wherein the first delivery pump is used for pressurizing the chlorosilane condensate in the chlorosilane condensate collecting tank and then delivering the pressurized chlorosilane condensate into the washing tower through a second-level spray port at the upper part of the washing tower to participate in leaching work;
the chlorosilane condensate collecting tank is pressurized by the first conveying pump, and then the output chlorosilane condensate is divided into five parts, namely a part B1, a part B2, a part B3, a part B4 and a part B5, wherein a part B1 enters the chlorosilane storage tank, and the part is used for liquid level balance of the chlorosilane storage tank; b2 part enters the washing tower through the second level spray mouth on the upper part of the washing tower to realize the second level spray, which is also the second cold source brought into the washing tower; part B3 returns to the chlorosilane condensate collecting tank; part B4 enters the top flush port of the excised duster in a dust removal unit; part B5 enters the top flush port of the cut ceramic filter.
2. The processing apparatus according to claim 1, wherein the circulation pump protection unit further comprises a first pressure difference meter connected to an inlet and an outlet of the two ceramic filters, respectively, for measuring a pressure difference across the ceramic filters in an operating state, and a first control unit for cutting off the ceramic filters in the operating state when the measured value of the first pressure difference meter is greater than 0.1MPa, and simultaneously switching the ceramic filters in a standby state to the operating state.
3. The processing apparatus according to claim 2, wherein the circulation pump protection unit further comprises a liquid level switch tank connected to the outlets of the two ceramic filters and the inlet of the washing tower circulation pump, respectively, and a liquid level switch is disposed on the liquid level switch tank for measuring the liquid level in the liquid level switch tank, and the first control unit is further configured to stop the washing tower circulation pump in an interlocking manner when the liquid level in the liquid level switch tank is lower than 70%.
4. The processing device according to claim 3, wherein the liquid level switch tank is further provided with a pressure gauge for measuring the liquid pressure in the liquid level switch tank, and the first control unit is further used for interlockingly stopping the washing tower circulating pump when the liquid pressure in the liquid level switch tank is lower than 0.1 MPa.
5. The treatment apparatus according to any one of claims 1 to 4, wherein the bottom of the washing tower is provided with a vertical separation screen for separating a bottom region in the washing tower into a spray liquid zone and a pump liquid zone, and the washing tower circulation pump draws liquid from the pump liquid zone through the circulation pump protection unit; an inclined isolation baffle is arranged above the isolation filter screen, one end of the isolation baffle is fixed on the inner wall of the washing tower, the other end of the isolation baffle is a free end and inclines towards the spray liquid area, and the silicon-containing powder chlorosilane liquid leached from the washing tower is guided into the spray liquid area, and the silicon-containing powder chlorosilane liquid entering the spray liquid area enters the pump suction area after being filtered by the isolation filter screen.
6. The processing device as claimed in claim 5, wherein the upper part of the isolation filter screen is provided with an overflow port for entering the pumping region through the overflow port when the liquid level in the spray region reaches a preset position.
7. The processing apparatus as claimed in claim 6, wherein the outlet of the circulation pump of the washing tower is further connected to a pumping area at the bottom of the washing tower through a back-flushing pipeline of the isolation filter screen, the back-flushing pipeline of the isolation filter screen is provided with a control valve for controlling the liquid level of the pumping area to drop when the liquid level of the spraying area reaches a preset position, and the circulation pump of the washing tower is opened when the circulation pump of the washing tower is running normally, so as to back-flush the isolation filter screen by using the pressurized chlorosilane liquid output by the circulation pump of the washing tower.
8. The processing apparatus according to any one of claims 1 to 4, wherein the dust removing unit further comprises a second differential pressure gauge connected to an inlet and an outlet of the two dust removers, respectively, for measuring a differential pressure before and after the dust remover in the operating state, and a second control unit for cutting off the dust remover in the operating state when the measured value of the second differential pressure gauge is greater than 0.1MPa, and simultaneously switching the dust remover in the standby state to the operating state.
9. The processing device according to any one of claims 1 to 4, wherein the multistage cooling unit comprises eight air coolers and a Freon cooler, the eight air coolers are used for cooling the dedusted noncondensable gas, most of the chlorosilane in the dedusted noncondensable gas is condensed and sent to a chlorosilane condensate collecting tank, and the residual noncondensable gas is output to the Freon cooler; and the freon cooler is used for cooling the residual non-condensable gas, condensing the rest chlorosilane in the residual non-condensable gas, conveying the condensed chlorosilane to a chlorosilane condensate collecting tank, and outputting hydrogen containing impurities.
10. The processing device as claimed in claim 9, wherein the multistage cooling unit further comprises a cold and hot medium heat exchanger which is arranged between the air cooler and the freon cooler and is used for cooling the residual non-condensable gas output by the air cooler by utilizing the cold energy containing the hydrogen with impurities output by the freon cooler and sending the chlorosilane condensed in the cooling process to the chlorosilane condensate collecting tank.
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CN109835904A (en) * 2019-04-12 2019-06-04 四川永祥多晶硅有限公司 Restore the treatment process of amorphous silicon in tail gas
CN111661827A (en) * 2020-06-22 2020-09-15 四川永祥多晶硅有限公司 System and method for recycling silicon powder in polycrystalline silicon reduction tail gas
CN112944205B (en) * 2021-03-12 2023-03-14 中国恩菲工程技术有限公司 Chlorosilane filling system and chlorosilane filling method
CN113426245B (en) * 2021-07-05 2022-11-22 四川炳辉环保科技有限责任公司 High-purity gas preparation method based on pressure swing adsorption
CN115804992B (en) * 2023-02-10 2023-06-13 山东东岳有机硅材料股份有限公司 Device and process for purifying methyl chlorosilane synthesis gas

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