Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for recovering waste gas in the production process of polycrystalline silicon, aiming at the defects in the prior art, and the method is used for separating impurities adsorbed by an adsorption column through segmented analysis and separating chlorosilane adsorbed by the adsorption column from other impurities.
The technical scheme adopted for solving the technical problem of the invention is to provide a method for recovering waste gas in the production process of polycrystalline silicon, the method uses an adsorption device to recover the waste gas, the adsorption device comprises an adsorption column, and the method comprises the following steps:
1) introducing waste gas in the production process of polycrystalline silicon into an adsorption column of an adsorption device, filling an adsorbent in the adsorption column, and adsorbing chlorosilane, boron, phosphorus and metal chloride in the waste gas by the adsorbent;
2) and (3) carrying out segmented analysis on the adsorption column, firstly analyzing the adsorbed chlorosilane, and then analyzing the other adsorbed impurities.
The invention is suitable for treating the waste gas in the production process of the polycrystalline silicon, and the waste gas comprises the following components: tail gas containing low-boiling-point substances discharged from a rectification process, tail gas containing iron chloride, calcium chloride and aluminum chloride discharged from a cold hydrogenation process, and replacement gas for starting and stopping a reduction furnace.
Preferably, the adsorbent in step 1) adsorbs chlorosilane in the exhaust gas through physical adsorption, and adsorbs boron, phosphorus and metal chloride in the exhaust gas through chemical adsorption.
Preferably, the adsorbent packed in the adsorption column in step 1) is a resin containing a functional group that selectively adsorbs boron, phosphorus, and metal chloride.
Preferably, the adsorbent in step 1) is one or more of modified styrene resin, divinylbenzene resin, acrylic resin and vinyl chloride resin.
Preferably, the functional group selectively adsorbing boron, phosphorus and metal chloride in the step 1) is one or more of a sulfonic acid group, a hydroxyl group and an amine group.
Preferably, the pore diameter of the adsorbent filled in the adsorption column in the step 1) is 30-80 nm.
Preferably, the adsorption conditions in step 1) are as follows: not more than 60 ℃ and 0-50 KpaG.
Preferably, the resolving process in step 2) is specifically: firstly, resolving for 10-60 minutes at the temperature of 20-60 ℃ and under the pressure of not higher than-90 KpaG to obtain chlorosilane; then heating to 70-90 ℃, and resolving for 10-60 minutes under the pressure of not less than-95 KpaG to resolve the adsorbed other impurities.
Preferably, the adsorption device comprises at least three adsorption columns, wherein at least two adsorption columns are connected in series for performing the steps 1) and 2), at least one adsorption column is reserved, and the number of reserved adsorption columns is at least 1 less than that of the working adsorption columns.
Preferably, the off-gas in the production process of polycrystalline silicon comprises: the total content of trichlorosilane, silicon tetrachloride and dichlorosilane is 40-90 mas%, the total content of hydrogen and nitrogen is 9-60 mas%, and the total content of chlorides of boron, phosphorus and iron, chlorides of calcium and chlorides of aluminum is 0.01-1 mas%.
According to the method for recovering the waste gas in the production process of the polycrystalline silicon, the impurities adsorbed by the adsorption column are separated through segmented analysis, and the chlorosilane adsorbed by the adsorption column is separated from the rest impurities, so that the chlorosilane can be fully and effectively recycled, a large amount of impurities in the chlorosilane can be removed, the purity of the chlorosilane is improved, the recovery method is high in recovery efficiency and low in energy consumption, the content of the impurities in the chlorosilane can be reduced through selective recovery, and the quality of raw materials and products is improved.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Example 1
The embodiment provides a method for recovering waste gas in a polycrystalline silicon production process, which uses an adsorption device to recover the waste gas, wherein the adsorption device comprises an adsorption column and comprises the following steps:
1) introducing waste gas in the production process of polycrystalline silicon into an adsorption column of an adsorption device to adsorb chlorosilane, boron, phosphorus and metal chloride in the waste gas;
2) and (3) carrying out segmented analysis on the adsorption column, firstly analyzing the adsorbed chlorosilane, and then analyzing the other adsorbed impurities.
In the method for recovering the waste gas in the production process of the polycrystalline silicon, the impurities adsorbed by the adsorption column are separated through segmented analysis, and the chlorosilane adsorbed by the adsorption column is separated from the rest impurities, so that the chlorosilane can be fully and effectively recycled, a large amount of impurities in the chlorosilane can be removed, the purity of the chlorosilane is improved, the recovery method is high in recovery efficiency and low in energy consumption, the impurity content in the recycled chlorosilane can be reduced through selective recovery, and the quality of raw materials and products is improved.
Example 2
As shown in fig. 1, the present embodiment provides an adsorption apparatus for use in a method of recovering exhaust gas from a polycrystalline silicon production process, comprising: at least three adsorption columns, wherein at least two adsorption columns are connected in series and used for performing adsorption in a working mode, at least one adsorption column is reserved, and the number of the reserved adsorption columns is at least 1 less than that of the working adsorption columns.
Specifically, adsorption equipment includes three adsorption columns in this embodiment, and wherein, two adsorption columns are established ties and are used for work execution to adsorb, and another adsorption column is reserve.
Specifically, the adsorption device used in the method for recovering exhaust gas in the polycrystalline silicon production process in the embodiment includes: a first adsorption column 1, a second adsorption column 2 and a third adsorption column 3,
the embodiment is suitable for treating the waste gas in the production process of polycrystalline silicon and comprises the following steps: tail gas containing low-boiling-point substances discharged from a rectification process, tail gas containing iron chloride, calcium chloride and aluminum chloride discharged from a cold hydrogenation process, and replacement gas for starting and stopping a reduction furnace.
Specifically, the exhaust gas in the production process of polycrystalline silicon in the present embodiment includes: the total content of trichlorosilane, silicon tetrachloride and dichlorosilane is 40-90 mas%, the total content of hydrogen and nitrogen is 9-60 mas%, and the total content of chlorides of boron, phosphorus and iron, chlorides of calcium and chlorides of aluminum is 0.01-1 mas%.
The embodiment provides a method for recovering waste gas in a polycrystalline silicon production process, which uses the adsorption device to recover the waste gas and comprises the following steps:
1) in the production process of polycrystalline silicon, waste gas enters a first adsorption column 1 from an upper pipe orifice of the first adsorption column 1 (an adsorbent is filled in the adsorption column), the first adsorption column 1 is used as a first-stage adsorption column to perform first-stage adsorption, then the waste gas enters a second adsorption column 2, the second adsorption column 2 is used as a second-stage adsorption column to perform second-stage adsorption, and two-stage adsorption is performed at 60 ℃ and 50 KpaG. The adsorbent adsorbs chlorosilane, boron, phosphorus and metal chloride in the waste gas. The lower the temperature, the more favorable the adsorption process, wherein, the adsorbent packed in the adsorption column is resin containing functional groups for selectively adsorbing boron, phosphorus and metal chloride, the functional groups are hydroxyl groups, and the functional groups can combine B, P and the metal chloride to play a role in separating impurities. Specifically, the adsorbent is a modified styrene resin. The aperture of the adsorbent is 30-80 nm, the adsorbent has the advantage of a porous structure, and chlorosilane can be adsorbed by utilizing intermolecular force, so that the chlorosilane can be recovered. The types and the quantity of the adsorbents filled in the two-stage adsorption columns are the same, and the two-stage adsorption mainly has the effects of improving the utilization rate of the adsorption device and reducing the construction investment of the adsorption device; meanwhile, the waste gas purification degree is improved, and the recovery rate is improved.
2) After an adsorption period, the first adsorption column 1 is first saturated, the first adsorption column 1 is cut out, and the second adsorption column 2 and the regenerated third adsorption column 3 are used as a first-stage adsorption column for first-stage adsorption and a second-stage adsorption column for second-stage adsorption.
3) In order to recover the desorbed chlorosilane without recovering the desorbed impurities, according to the properties of the adsorbent, the bond energy of N-, S-, OH-and boron, phosphorus and metal chloride after the combination of hydroxyl, amino and sulfonic acid groups on the adsorbent can be destroyed at a higher temperature, so that the boron, phosphorus and metal chloride can be released. Therefore, the segmented analysis is carried out on the cut first adsorption column 1 under the controlled analysis condition, the chlorosilane physically adsorbed and adsorbed in the resin pores as the adsorbent is analyzed and recovered under the pressure of-50 KpaG at the temperature of 20 ℃ for 10 minutes; and (3) heating to 90 ℃, resolving for 60 minutes under the pressure of-95 KpaG, resolving out the other adsorbed impurities and a small amount of chlorosilane by destroying the combination of chemical bonds and impurities, thereby completing the regeneration of the cut-out first adsorption column 1, cooling the regenerated adsorption column to the condition of having the re-investment, and leaching and discharging the other resolved impurities and a small amount of chlorosilane.
Specifically, three adsorption columns of the adsorption device are switched and alternately used, two adsorption columns are in an adsorption state in each adsorption period to perform two-stage adsorption, and one adsorption column is in a regeneration state.
Specifically, the adsorption device used in the method for recovering exhaust gas in the polycrystalline silicon production process in the embodiment includes: a first adsorption column 1, a second adsorption column 2 and a third adsorption column 3,
and in the production process of the polycrystalline silicon, the waste gas is discharged through a main discharge waste gas pipeline.
A first inlet valve 4 is arranged between the inlet of the first adsorption column 1 and the outward exhaust gas main pipeline, a second inlet valve 5 is arranged between the inlet of the second adsorption column 2 and the outward exhaust gas main pipeline, and a third inlet valve 6 is arranged between the inlet of the third adsorption column 3 and the outward exhaust gas main pipeline.
A first communicating valve 7 is arranged on a pipeline between the outlet of the first adsorption column 1 and the inlet of the second adsorption column 2, a second communicating valve 8 is arranged on a pipeline between the outlet of the second adsorption column 2 and the inlet of the third adsorption column 3, and a third communicating valve 9 is arranged on a pipeline between the outlet of the third adsorption column 3 and the inlet of the first adsorption column 1.
An outlet of the first adsorption column 1 is connected with a first outer discharge pipeline for discharging waste gas, and a first outlet valve 10 is arranged on the first outer discharge pipeline; the outlet of the second adsorption column 2 is connected with a second external exhaust pipeline for discharging waste gas, and a second outlet valve 11 is arranged on the second external exhaust pipeline; an outlet of the third adsorption column 3 is connected with a third outer discharge pipeline for discharging waste gas, and a third outlet valve 12 is arranged on the third outer discharge pipeline.
The outlet of the first adsorption column 1 is connected with a first vacuumizing pipeline for vacuumizing, and a first vacuumizing valve 13 is arranged on the first vacuumizing pipeline; the outlet of the second adsorption column 2 is connected with a second vacuum-pumping pipeline for vacuum-pumping, and a second vacuum-pumping valve 14 is arranged on the second vacuum-pumping pipeline; the outlet of the third adsorption column 3 is connected with a third vacuum-pumping pipeline for vacuum-pumping, and a third vacuum-pumping valve 15 is arranged on the third vacuum-pumping pipeline. The first vacuum-pumping pipeline, the second vacuum-pumping pipeline and the third vacuum-pumping pipeline in the embodiment are all connected with a vacuum-pumping device, and vacuum pumping is carried out through the vacuum-pumping device.
Condensation valves 16 are arranged on the pipelines between the outlet of the first vacuum-pumping pipeline, the outlet of the second vacuum-pumping pipeline, the outlet of the third vacuum-pumping pipeline and the condensing device 18 for condensation; and leaching valves 17 are arranged on the pipelines between the outlet of the first vacuum-pumping pipeline, the outlet of the second vacuum-pumping pipeline, the outlet of the third vacuum-pumping pipeline and the leaching device 19 for leaching.
The operation method of the adsorption device in this embodiment is as follows:
in the using process, the discharged waste gas in the polycrystalline silicon production process enters the adsorption device from the discharged waste gas main pipeline, the first inlet valve 4, the first communicating valve 7, the second outlet valve 11 and the leaching valve 17 are opened,
the waste gas enters the first adsorption column 1 and the second adsorption column 2 from top to bottom in sequence, chlorosilane is adsorbed and impurities are combined in the contact process of the waste gas with the first adsorbent and the second adsorbent, the main component of the adsorbed gas is hydrogen, and the hydrogen enters the leaching device 19 from the outlet of the second adsorption column 2 for leaching.
After one adsorption period expires, the first adsorbent in the first adsorption column 1 first reaches adsorption saturation, the first adsorbent needs to be regenerated, the first inlet valve 4 and the first communication valve 7 are closed, the first vacuumizing valve 13 is opened, and chlorosilane and impurities adsorbed in the first adsorption column 1 are analyzed and separated in a heating and negative-pressure pumping mode. At this time, the second adsorption column 2 is not saturated to be adsorbed and can be used continuously, and the second adsorption column 2 and the third adsorption column 3 are communicated and put into use. And opening a second inlet valve, opening a second communication valve 8, opening a third outlet valve 12 and closing a second outlet valve 11, and enabling the waste gas to sequentially enter the second adsorption column 2 and the third adsorption column 3 from top to bottom. The first adsorption column 1, the second adsorption column 2 and the third adsorption column 3 are sequentially put into use in the system in this order.
Vacuumizing the first adsorption column 1 under the condition of no heating, opening a condensation valve 16, pumping the pressure in the first adsorption column 1 to-50 KPaG, maintaining the pressure for 10min at the temperature control range of 20 ℃, sending the pumped chlorosilane gas into a condensing device 18 for condensation and recovery, and storing the recovered chlorosilane as a polycrystalline silicon production raw material; and when the pressure in the first adsorption column 1 reaches-50 KPaG and is maintained for 10min, closing the condensation valve 16, heating the first adsorption column 1 to 90 ℃, opening the leaching valve 17, pumping the pressure in the first adsorption column 1 to-95 KPaG, and sending the pumped impurities and a small amount of chlorosilane gas into the leaching device 19 for discharging, wherein the content of the impurities in the chlorosilane is high, and the chlorosilane is not recycled.
When the pressure in the first adsorption column 1 is pumped to-95 KPaG, the first vacuumizing valve 13 is closed to cool the first adsorption column 1, and when the temperature is reduced to below 30 ℃, the first adsorption column 1 is put into use again.
In the operation process, adopt online chromatograph and spectrum appearance to the waste gas of the import of first adsorption column 1, the waste gas of the 2 exports of second adsorption column respectively and monitor gas composition, and the import waste gas of first adsorption column 1 includes: 60 mas% of trichlorosilane, 20 mas% of silicon tetrachloride, 8 mas% of dichlorosilane, 6 mas% of hydrogen, 5 mas% of nitrogen and 0.3 mas% of chlorides of boron, phosphorus and metal. The waste gas at the outlet of the second adsorption column 2 comprises: 3mas percent of trichlorosilane, 1mas percent of silicon tetrachloride, 1mas percent of dichlorosilane, 48mas percent of hydrogen, 42mas percent of nitrogen and 0.01mas percent of chlorides of boron, phosphorus and metal. The adsorption rate of chlorosilane can reach about 95%.
In the regeneration process of the adsorption column, the materials of the condensation system and the leaching system are respectively subjected to impurity detection at the outlet of the vacuum pumping system, and the impurity content of the materials recovered by the condensation system is as follows: p-100ppb, B-50ppb, Fe-500ppb, Al-200ppb, Ca-300 ppb; the impurity content of the discharged materials of the leaching system is as follows: p-1500ppb, B-1000ppb, Fe-20000ppb, Al-2000ppb, Ca-3500 ppb; the removal rate of impurities can reach about 96%.
In the method for recovering the waste gas in the production process of the polycrystalline silicon, the impurities adsorbed by the adsorption column are separated through segmented analysis, and the chlorosilane adsorbed by the adsorption column is separated from the rest impurities, so that the chlorosilane can be fully and effectively recycled, a large amount of impurities in the chlorosilane can be removed, the purity of the chlorosilane is improved, the recovery method is high in recovery efficiency and low in energy consumption, the impurity content in the recycled chlorosilane can be reduced through selective recovery, and the quality of raw materials and products is improved.
In the embodiment, modified resin with a selective adsorption function is used as an adsorbent, and macromolecular chlorosilane in waste gas is adsorbed by utilizing the porous structural characteristics of the resin, so that the chlorosilane can be recovered; specific functional groups on a resin macromolecular chain are utilized, impurity molecules in the waste gas are combined through chemical bonds to play a role in separating impurities, under the combined action of physical adsorption and chemical adsorption, chlorosilane in the waste gas is recycled, a large amount of impurities in the chlorosilane are removed, the chlorosilane with high purity is obtained, and the chlorosilane with high purity can be directly used as a production raw material.
Two adsorption columns of the adsorption device used in the method in the embodiment are used in series, namely, the waste gas is firstly subjected to first-stage adsorption through the first adsorption column 1 and then enters the second adsorption column 2 for second-stage adsorption, the adsorption recovery rate is improved through the two-stage adsorption, the chlorosilane recovery rate can reach more than 90%, and the purity of the recovered product is also greatly improved. The method adopted by the embodiment has high recovery efficiency and low energy consumption, and can reduce the content of impurities in the recovered chlorosilane and improve the quality of raw materials and products through selective recovery.
Example 3
This example provides a method for recovering exhaust gas from a polycrystalline silicon production process, which uses the adsorption apparatus of example 2 to recover the exhaust gas, and differs from the method of example 2 in that:
1) two-stage adsorption was carried out at 30 ℃ and 0 KpaG. The adsorbent filled in the adsorption column is resin containing functional groups for selectively adsorbing boron, phosphorus and metal chloride, the functional groups are sulfonic groups, and the adsorbent is divinylbenzene resin.
2) Analyzing the cut first adsorption column in segments at 40 ℃ and-20 KpaG for 40 minutes to analyze chlorosilane physically adsorbed in the resin pores serving as the adsorbent and recover the chlorosilane; heating to 80 deg.C, and desorbing at a pressure of not less than-135 KpaG for 10min to desorb the adsorbed impurities and small amount of chlorosilane by breaking the bonds between the chemical bonds and the impurities.
Example 4
This example provides a method for recovering exhaust gas from a polycrystalline silicon production process, which uses the adsorption apparatus of example 2 to recover the exhaust gas, and differs from the method of example 2 in that:
1) two stages of adsorption were carried out at 0 ℃ and 25 KpaG. The adsorbent filled in the adsorption column is resin containing functional groups for selectively adsorbing boron, phosphorus and metal chloride, the functional groups are hydroxyl and amino (the molar ratio is 1:1), and the adsorbent is acrylic resin and vinyl chloride resin (the mass ratio is 2: 1).
2) Analyzing the cut first adsorption column in segments at 60 ℃ under the pressure of-90 KpaG for 60 minutes to analyze chlorosilane physically adsorbed in the resin pores serving as the adsorbent and recover the chlorosilane; then heated to 70 ℃, and the mixture is resolved for 30 minutes under the pressure of not less than-115 KpaG, and the other adsorbed impurities and a small amount of chlorosilane are resolved out by breaking the combination of chemical bonds and impurities.
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.