Purification system for byproduct hydrogen chloride of electronic-grade polycrystalline silicon

Abstract

The utility model discloses a purification system for electronic-grade polycrystalline silicon by-product hydrogen chloride, belongs to the technical field of polycrystalline silicon, aims to solve the problem that hydrogen chloride in electronic-grade polycrystalline silicon by-product reduction tail gas cannot be directly purified, and is wider in raw material purity requirement range of the polycrystalline silicon by-product reduction tail gas. Under the mutual cooperation of all the units in the system, hydrogen chloride with the purity of 60% or above can be purified to the electronic grade or above, and the investment cost is reduced; hydrogen chloride is primarily purified under the action of a first hydrogen chloride desorption tower and a second hydrogen chloride desorption tower in the early-stage desorption unit, and then hydrogen chloride gas is further secondarily purified in sequence under the cooperation of a molecular sieve purification device, an activated carbon purification device and a separation device; and finally, purifying hydrogen chloride at an electronic grade or above under the action of the rectification unit. The system can meet the purification requirements of all kinds of hydrogen chloride processes, and is high in flexibility.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon, in particular to a purification system for by-product hydrogen chloride in electronic-grade polysilicon. Background Technique

[0002] In the electronic-grade polysilicon production industry, after trichlorosilane reacts in a reduction furnace, there are still a large amount of hydrogen chloride, chlorosilane, and hydrogen in the tail gas, and the impurity content includes trace amounts of nitrogen, oxygen, and hydrocarbons.

[0003] The existing patent CN201511031134.0, a method for purifying electronic-grade hydrogen chloride, includes: the first step: introducing industrial-grade liquid hydrogen chloride with a purity of 99% into the middle position of a first rectification column for rectification. The top of the first rectification column is connected to a first condenser, and the bottom is connected to a first reboiler. The hydrogen chloride gas generated by heating through the first reboiler is condensed by the first condenser and then fully refluxed into the first rectification column, and the uncondensed waste gas is discharged into the waste gas treatment system to remove light components; the second step: the liquid coming out from the bottom of the first rectification column reboiler is pumped into the middle position of a second rectification column for rectification. The top of the second rectification column is connected to a second condenser, and the bottom is connected to a second reboiler. The hydrogen chloride gas generated by heating through the second reboiler is condensed by the second condenser. The reflux ratio is controlled so that part of it is refluxed into the second rectification column, and the other part is transferred into an intermediate storage tank for storage. The residual liquid is pumped out from the bottom of the second reboiler into a waste liquid storage tank to remove heavy components; the third step: heating the liquid hydrogen chloride in the intermediate storage tank, and the generated hydrogen chloride gas is adsorbed and purified through at least one adsorption tower internally provided with molecular sieve, and high-purity hydrogen chloride with a purity of more than 99.9999% is obtained and collected by using a finished product storage tank placed in a liquid nitrogen cold trap.

[0004] The current technical problems of this patent are: the raw material requires a relatively high purity. Since the components contained in the by-product reduction tail gas of electronic-grade polysilicon include nitrogen, oxygen, hydrogen, hydrogen chloride, hydrocarbons, etc. in addition to chlorosilane, the current system cannot directly purify the hydrogen chloride in the by-product reduction tail gas of electronic-grade polysilicon; the packing cost of the rectification column used in this patent is relatively high, and the molecular sieve in the adsorption system adsorbs a single impurity and cannot meet the requirements of all types of hydrogen chloride process purification. Content of the Utility Model

[0005] The purpose of the utility model is to provide a purification system for by-product hydrogen chloride in electronic-grade polysilicon, aiming to solve the problem that the hydrogen chloride in the by-product reduction tail gas of electronic-grade polysilicon cannot be directly purified in the above-mentioned background technique.

[0006] The utility model is implemented by the following technical solutions: a purification system for by-product hydrogen chloride in electronic-grade polysilicon, which includes a condensation unit, an absorption unit, a desorption unit, an adsorption unit, a compression and cooling unit, and a rectification unit connected in sequence by pipelines;

[0007] The inlet of the air cooler in the condensation unit is connected with a tail gas inlet pipe;

[0008] The outlet of the final cooler in the condensation unit is connected with the inlet pipeline of the hydrogen chloride absorption tower in the absorption unit;

[0009] The outlet of the first heat exchange pipeline of the first pre-desorption tower heat exchanger in the absorption unit is connected with the inlet pipeline of the first hydrogen chloride desorption tower in the desorption unit;

[0010] The outlet of the second heat exchange pipeline of the hydrogen chloride heater in the desorption unit is connected with the inlet pipeline of the molecular sieve purification device in the adsorption unit;

[0011] The outlet of the activated carbon purification device in the adsorption unit is connected with the inlet pipeline of the compressor in the compression and cooling unit;

[0012] The outlet of the separation device in the compression and cooling unit is connected with the inlet pipeline of the first hydrogen chloride rectification tower in the rectification unit;

[0013] The hydrogen chloride outlet of the second hydrogen chloride rectification tower in the rectification unit is connected with the inlet pipeline of the hydrogen chloride storage tank.

[0014] Further, the condensation unit includes an air cooler, a circulating water cooler, a 7-degree water cooler, a chlorosilane storage tank, a plate heat exchanger, and a final cooler. The outlet of the air cooler is connected with the inlet pipeline of the circulating water cooler. The liquid outlet of the circulating water cooler is connected with the inlet pipeline of the chlorosilane storage tank. The gas outlet of the circulating water cooler is connected with the inlet pipeline of the final cooler through the first heat exchange pipeline of the plate heat exchanger. The outlet of the final cooler is connected with the inlet pipeline of the hydrogen chloride absorption tower.

[0015] Further, the absorption unit includes a hydrogen chloride absorption tower, a condenser at the top of the adsorption tower, a plate heat exchanger in the absorption tower, a hydrogen chloride heat exchanger, and a first pre-desorption tower heat exchanger. The top gas outlet of the hydrogen chloride absorption tower is connected with the inlet pipeline of the hydrogen recovery unit through the second heat exchange pipeline of the plate heat exchanger. The bottom liquid outlet of the hydrogen chloride absorption tower is connected with the inlet of the first heat exchange pipeline of the first pre-desorption tower heat exchanger through the first heat exchange pipeline of the plate heat exchanger in the absorption tower. The outlet of the first heat exchange pipeline of the first pre-desorption tower heat exchanger is connected with the inlet pipeline of the first hydrogen chloride desorption tower.

[0016] Further, the desorption unit includes a first hydrogen chloride desorption tower, a first desorption tower top condenser, a first desorption tower reflux drum, a second hydrogen chloride desorption tower, a second desorption tower top condenser, and a hydrogen chloride heater. The bottom liquid outlet of the first hydrogen chloride desorption tower is connected to the inlet pipeline of the second heat exchange pipeline of the heat exchanger in front of the first desorption tower. The outlet of the second heat exchange pipeline of the heat exchanger in front of the first desorption tower is connected to the inlet pipeline of the second heat exchange pipeline of the absorption tower plate heat exchanger through the hydrogen chloride heat exchanger. The outlet of the second heat exchange pipeline of the absorption tower plate heat exchanger is connected to the top inlet pipeline of the hydrogen chloride absorption tower through the absorption tower top condenser. The top gas outlet of the first hydrogen chloride desorption tower is connected to the inlet pipeline of the first desorption tower reflux drum through the first desorption tower top condenser. The gas outlet of the first desorption tower reflux drum is connected to the inlet pipeline of the second hydrogen chloride desorption tower. The liquid outlet of the first desorption tower reflux drum is respectively connected to the reflux port of the first hydrogen chloride desorption tower and the inlet pipeline of the first heat exchange pipeline of the hydrogen chloride heater. The bottom outlet of the second hydrogen chloride desorption tower is connected to the reflux port pipeline of the first hydrogen chloride desorption tower. The top gas outlet of the second hydrogen chloride desorption tower is connected to the inlet pipeline of the second desorption tower top condenser. The liquid outlet of the second desorption tower top condenser is connected to the reflux port pipeline of the second hydrogen chloride desorption tower. The gas outlet of the second desorption tower top condenser is connected to the inlet pipeline of the second heat exchange pipeline of the hydrogen chloride heater. The outlet of the second heat exchange pipeline of the hydrogen chloride heater is connected to the inlet pipeline of the molecular sieve purification device.

[0017] Further, the adsorption unit includes a molecular sieve purification device and an activated carbon purification device. The outlet of the molecular sieve purification device is connected to the inlet pipeline of the activated carbon purification device. The outlet of the activated carbon purification device is connected to the inlet pipeline of the compressor;

[0018] The molecular sieve purification device includes at least two molecular sieve purification towers;

[0019] The activated carbon purification device includes at least two activated carbon towers.

[0020] Further, the compression and cooling unit includes a compressor, a compressor after-cooler, and a separation device. The outlet of the compressor is connected to the inlet pipeline of the compressor after-cooler. The outlet of the compressor after-cooler is connected to the inlet pipeline of the separation device. The outlet of the separation device is connected to the inlet pipeline of the first hydrogen chloride rectification tower. The heavy component outlet of the separation device is connected to the inlet pipeline of the heavy component recovery unit;

[0021] The separation device includes at least two hollow fiber membranes.

[0022] Furthermore, the rectification unit includes a first hydrogen chloride rectification column, a second hydrogen chloride rectification column, a top condenser of the first rectification column, a top condenser of the second rectification column, and a hydrogen chloride storage tank. The light component outlet at the top of the first hydrogen chloride rectification column is connected to the inlet pipeline of the light component recovery unit through the top condenser of the first rectification column, and the heavy component outlet at the bottom of the first hydrogen chloride rectification column is connected to the inlet pipeline of the heavy component recovery unit.

[0023] The side outlet of the first hydrogen chloride rectification column is connected to the inlet pipeline of the second hydrogen chloride rectification column. The light component outlet at the top of the second hydrogen chloride rectification column is connected to the inlet pipeline of the light component recovery unit through the top condenser of the second rectification column, and the heavy component outlet at the bottom of the second hydrogen chloride rectification column is connected to the inlet pipeline of the heavy component recovery unit.

[0024] Advantages of the present utility model: The system has a wider range of requirements for the raw material purity of the by-product reduction tail gas of polysilicon. With the mutual cooperation of each unit in the system, hydrogen chloride with a purity of more than 60% can be purified to electronic grade and above, reducing the investment cost.

[0025] Through the action of the first hydrogen chloride desorption column and the second hydrogen chloride desorption column in the pre-desorption unit, the hydrogen chloride is preliminarily purified. Then, with the cooperation of the molecular sieve purification device, the activated carbon purification device, and the separation device, the hydrogen chloride gas is further purified secondary in sequence. Finally, under the action of the rectification unit, the hydrogen chloride is purified to electronic grade and above.

[0026] After detecting the components of the gas treated by the desorption unit, the packing type of the molecular sieve in the adsorption unit is selectively adjusted, and at the same time, impurities are removed by cooperating with the activated carbon purification device. The system can meet the requirements of all kinds of hydrogen chloride process purification, with high flexibility.

[0027] In the early stage, with the cooperation of the desorption unit, the adsorption unit, and the compression cooling unit, the first hydrogen chloride rectification column and the second hydrogen chloride rectification column of the rectification unit can meet the process requirements by using ordinary structured packing columns, reducing the production cost. Brief Description of the Drawings

[0028] Figure 1 It is a schematic connection diagram of the present utility model;

[0029] In the figure: tail gas inlet pipe 1, condensation unit 2, air cooler 2.1, circulating water cooler 2.2, 7-degree water cooler 2.3, chlorosilane storage tank 2.4, plate heat exchanger 2.5, final cooler 2.6, absorption unit 3, hydrogen chloride absorption tower 3.1, top condenser of absorption tower 3.2, plate heat exchanger of absorption tower 3.3, hydrogen chloride heat exchanger 3.4, pre-heat exchanger before the first desorption tower 3.5, desorption unit 4, first hydrogen chloride desorption tower 4.1, second hydrogen chloride desorption tower 4.2, top condenser of the first desorption tower 4.3, reflux drum of the first desorption tower 4.4, top condenser of the second desorption tower 4.5, hydrogen chloride heater 4.6, adsorption unit 5, molecular sieve purification device 5.1, molecular sieve purification tower 5.1.1, activated carbon purification device 5.2, activated carbon tower 5.2.1, compression cooling unit 6, compressor 6.1, after-cooler of compressor 6.2, separation device 6.3, hollow fiber membrane 6.3.1, rectification unit 7, first hydrogen chloride rectification tower 7.1, second hydrogen chloride rectification tower 7.2, top condenser of the first rectification tower 7.3, top condenser of the second rectification tower 7.4, hydrogen chloride storage tank 7.5, heavy component recovery unit 9, hydrogen recovery unit 8, light component recovery unit 10. Specific embodiments

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0031] As Figure 1 shown, a purification system for by-product hydrogen chloride of electronic-grade polysilicon includes a condensation unit 2, an absorption unit 3, a desorption unit 4, an adsorption unit 5, a compression cooling unit 6, and a rectification unit 7 that are connected in sequence by pipelines;

[0032] The inlet of the air cooler 2.1 of the condensation unit 2 is connected to the tail gas inlet pipe 1, and most of the chlorosilane in the tail gas is condensed by the condensation unit 2.

[0033] The outlet of the final cooler 2.6 of the condensation unit 2 is connected to the inlet pipeline of the hydrogen chloride absorption tower 3.1 of the absorption unit 3. The absorption unit 3 is used to separate hydrogen chloride and hydrogen. The main function of the hydrogen chloride absorption tower 3.1 is to adsorb hydrogen chloride in the mixed gas with low-temperature chlorosilane and store it in the tower kettle in a liquid state, and the remaining light components (mainly hydrogen) are discharged from the top of the tower.

[0034] The outlet of the first heat exchange pipeline of the first desorption tower pre-heat exchanger 3.5 of the absorption unit 3 is connected to the inlet pipeline of the first hydrogen chloride desorption tower 4.1 of the desorption unit 4. The desorption unit 4 further separates the impurities in the hydrogen chloride. The heavy components of the first hydrogen chloride desorption tower 4.1 are chlorosilane liquid, which also serves as the adsorption phase of the hydrogen chloride.

[0035] The hydrogen chloride with a purity of about 90% led out from the second hydrogen chloride desorption tower 4.2 of the desorption unit 4 enters the subsequent desorption unit 4.

[0036] The outlet of the second heat exchange pipeline of the hydrogen chloride heater 4.6 of the desorption unit 4 is connected to the inlet pipeline of the molecular sieve purification device 5.1 of the adsorption unit 5. The adsorption unit 5 adsorbs nitrogen, oxygen, and hydrocarbons contained in the hydrogen chloride.

[0037] The outlet of the activated carbon purification device 5.2 of the adsorption unit 5 is connected to the inlet pipeline of the compressor 6.1 of the compression and cooling unit 6. The compression and cooling unit 6 condenses the heavy components and uses the separation device 6.3 in the compression and cooling unit 6 to separate the suspension, hydrocarbons, nitrogen, oxygen, carbon monoxide, etc.

[0038] The outlet of the separation device 6.3 of the compression and cooling unit 6 is connected to the inlet pipeline of the first hydrogen chloride rectification tower 7.1 of the rectification unit 7.

[0039] The hydrogen chloride outlet of the second hydrogen chloride rectification tower 7.2 of the rectification unit 7 is connected to the inlet pipeline of the hydrogen chloride storage tank 7.5. The rectification unit 7 further separates the light and heavy components, and high-purity hydrogen chloride is side-drawn into the hydrogen chloride storage tank 7.5. The principle of rectification is to use the downward flowing liquid to exchange heat with the rising gas, and multiple partial vaporizations and partial condensations are required to achieve separation. Part of the reflux liquid must be returned to the tower as a cold source to participate in the rectification.

[0040] This system has a wider range of requirements for the raw material purity of the by-product reduction tail gas of polysilicon. With the mutual cooperation of each unit in this system, those with a purity above 60% can be purified to electronic grade and above, reducing the investment cost; due to the cooperation of the desorption unit 4, adsorption unit 5, and compression and cooling unit 6 in the early stage, for the first hydrogen chloride rectification tower 7.1 and the second hydrogen chloride rectification tower 7.2 of the rectification unit 7, an ordinary structured packing tower can meet the process requirements, reducing the production cost; after detecting the components of the gas treated by the desorption unit 4, the type of packing of the molecular sieve in the adsorption unit 5 is selectively adjusted, and at the same time, impurities are removed in cooperation with the activated carbon purification device 5.2. This system can meet the requirements for the purification of all types of hydrogen chloride processes.

[0041] The condensation unit 2 includes an air cooler 2.1, a circulating water cooler 2.2, a 7-degree water cooler 2.3, a chlorosilane storage tank 2.4, a plate heat exchanger 2.5, and a final cooler 2.6. The outlet of the air cooler 2.1 is connected to the inlet pipeline of the circulating water cooler 2.2. The liquid outlet of the circulating water cooler 2.2 is connected to the inlet pipeline of the chlorosilane storage tank 2.4. The gas outlet of the circulating water cooler 2.2 is connected to the inlet pipeline of the final cooler 2.6 through the first heat exchange pipeline of the plate heat exchanger 2.5. The outlet of the final cooler 2.6 is connected to the inlet pipeline of the hydrogen chloride absorption tower 3.1. The inlet temperature of the circulating water used by the circulating water cooler 2.2 is 30 degrees Celsius, and the inlet temperature of the 7-degree water cooler 2.3 is 7 degrees Celsius.

[0042] The absorption unit 3 includes a hydrogen chloride absorption tower 3.1, a condenser at the top of the absorption tower 3.2, a plate heat exchanger in the absorption tower 3.3, a hydrogen chloride heat exchanger 3.4, and a heat exchanger before the first desorption tower 3.5. The top gas outlet of the hydrogen chloride absorption tower 3.1 is connected to the inlet pipeline of the hydrogen recovery unit 8 through the second heat exchange pipeline of the plate heat exchanger 2.5. The bottom liquid outlet of the hydrogen chloride absorption tower 3.1 is connected to the inlet of the first heat exchange pipeline of the first heat exchanger before the desorption tower 3.5 through the first heat exchange pipeline of the plate heat exchanger 3.3 in the absorption tower. The outlet of the first heat exchange pipeline of the first heat exchanger before the desorption tower 3.5 is connected to the inlet pipeline of the first hydrogen chloride desorption tower 4.1.

[0043] The desorption unit 4 includes a first hydrogen chloride desorption tower 4.1, a first desorption tower top condenser 4.3, a first desorption tower reflux drum 4.4, a second hydrogen chloride desorption tower 4.2, a second desorption tower top condenser 4.5, and a hydrogen chloride heater 4.6. The bottom liquid outlet of the first hydrogen chloride desorption tower 4.1 is connected to the second heat exchange pipeline inlet pipeline of the heat exchanger 3.5 in front of the first desorption tower. The outlet of the second heat exchange pipeline of the heat exchanger 3.5 in front of the first desorption tower is connected to the second heat exchange pipeline inlet pipeline of the absorption tower plate heat exchanger 3.3 through the hydrogen chloride heat exchanger 3.4. The outlet of the second heat exchange pipeline of the absorption tower plate heat exchanger 3.3 is connected to the top inlet pipeline of the hydrogen chloride absorption tower 3.1 through the absorption tower top condenser 3.2. The top gas outlet of the first hydrogen chloride desorption tower 4.1 is connected to the inlet pipeline of the first desorption tower reflux drum 4.4 through the first desorption tower top condenser 4.3. The gas outlet of the first desorption tower reflux drum 4.4 is connected to the inlet pipeline of the second hydrogen chloride desorption tower 4.2. The liquid outlet of the first desorption tower reflux drum 4.4 is respectively connected to the reflux port of the first hydrogen chloride desorption tower 4.1 and the first heat exchange pipeline inlet pipeline of the hydrogen chloride heater 4.6. The bottom outlet of the second hydrogen chloride desorption tower 4.2 is connected to the reflux port pipeline of the first hydrogen chloride desorption tower 4.1. The top gas outlet of the second hydrogen chloride desorption tower 4.2 is connected to the inlet pipeline of the second desorption tower top condenser 4.5. The liquid outlet of the second desorption tower top condenser 4.5 is connected to the reflux port pipeline of the second hydrogen chloride desorption tower 4.2. The gas outlet of the second desorption tower top condenser 4.5 is connected to the second heat exchange pipeline inlet pipeline of the hydrogen chloride heater 4.6. The outlet of the second heat exchange pipeline of the hydrogen chloride heater 4.6 is connected to the inlet pipeline of the molecular sieve purification device 5.1.

[0044] The adsorption unit 5 includes a molecular sieve purification device 5.1 and an activated carbon purification device 5.2. The outlet of the molecular sieve purification device 5.1 is connected to the inlet pipeline of the activated carbon purification device 5.2. The outlet of the activated carbon purification device 5.2 is connected to the inlet pipeline of the compressor 6.1. The molecular sieve purification device 5.1 includes at least two molecular sieve purification towers 5.1.1. Specifically, there are two molecular sieve purification towers 5.1.1 in this embodiment, one in use and one in regeneration. The activated carbon purification device 5.2 includes at least two activated carbon towers 5.2.1. Specifically, there are two activated carbon towers 5.2.1 in this embodiment, one in use and one in regeneration. Nitrogen, oxygen, and incompletely adsorbed hydrocarbons in the mixed gas are adsorbed, and the remaining gas phase components are mainly hydrogen chloride. The impurities in the hydrogen chloride only include trace amounts of hydrocarbons, nitrogen, oxygen, and carbon monoxide. At this time, the content of the above substances in the discharged gas has dropped to the ppm level.

[0045] The compression cooling unit 6 includes a compressor 6.1, a post-cooler 6.2 of the compressor, and a separation device 6.3. The outlet of the compressor 6.1 is connected to the inlet pipeline of the post-cooler 6.2 of the compressor. Under the boosting of the compressor 6.1, the flow rate of the gas phase is accelerated. The outlet of the post-cooler 6.2 of the compressor is connected to the inlet pipeline of the separation device 6.3. The outlet of the separation device 6.3 is connected to the inlet pipeline of the first hydrogen chloride rectification column 7.1. The heavy component outlet of the separation device 6.3 is connected to the inlet pipeline of the heavy component recovery unit 9;

[0046] The separation device 6.3 includes at least two hollow fiber membranes 6.3.1. Specifically, there are two hollow fiber membranes 6.3.1 in this embodiment, one for use and one for regeneration (backwashing with dry hydrogen chloride gas). The hollow fiber membranes 6.3.1 further separate a very small amount of hydrocarbons, nitrogen, oxygen, carbon monoxide, and trace suspended droplets. Under the boosting of the compressor 6.1, the flow rate of hydrogen chloride is accelerated. The separation principle of the hollow fiber membranes 6.3.1 is to utilize the characteristics that impurities have slow penetration and hydrogen chloride has fast penetration, further reducing the content of impurities in hydrogen chloride per unit time. At the same time, the two hollow fiber membranes 6.3.1 are regularly backwashed with dry hydrogen chloride gas to clean the unpenetrated impurities. Therefore, with the cooperation of the molecular sieve purification tower 5.1.1, the activated carbon purification device 5.2, and the hollow fiber membranes 6.3.1 in the early stage, the hydrogen chloride gas is purified in sequence and then enters the rectification process for further purification.

[0047] The rectification unit 7 includes a first hydrogen chloride rectification column 7.1, a second hydrogen chloride rectification column 7.2, a top condenser 7.3 of the first rectification column, a top condenser 7.4 of the second rectification column, and a hydrogen chloride storage tank 7.5. The light component outlet at the top of the first hydrogen chloride rectification column 7.1 is connected to the inlet pipeline of the light component recovery unit 10 through the top condenser 7.3 of the first rectification column. The heavy component outlet at the bottom of the first hydrogen chloride rectification column 7.1 is connected to the inlet pipeline of the heavy component recovery unit 9;

[0048] The side outlet of the first hydrogen chloride rectification column 7.1 is connected to the inlet pipeline of the second hydrogen chloride rectification column 7.2. The light component outlet at the top of the second hydrogen chloride rectification column 7.2 is connected to the inlet pipeline of the light component recovery unit 10 through the top condenser 7.4 of the second rectification column. The heavy component outlet at the bottom of the second hydrogen chloride rectification column 7.2 is connected to the inlet pipeline of the heavy component recovery unit 9.

[0049] The specific operation process of this embodiment;

[0050] The reduction tail gas by-produced from electronic-grade polysilicon enters the condensation unit 2 through the tail gas inlet pipe 1. After being preliminarily cooled by the air cooler 2.1 in the condensation unit 2, it then passes through the circulating water cooler 2.2 and the 7-degree water cooler 2.3. Most of the chlorosilanes in the tail gas are condensed into the liquid phase and enter the chlorosilane storage tank 2.4. The uncondensed mixed gas phase enters the plate heat exchanger 2.5 to exchange heat with the hydrogen gas discharged from the top of the hydrogen chloride absorption tower 3.1. After heat exchange, the hydrogen gas is sent to the hydrogen recovery unit 8 for further treatment. The cooled mixed gas enters the final cooler 2.6, and after being cooled, it enters the hydrogen chloride absorption tower 3.1;

[0051] The liquid at the bottom of the hydrogen chloride absorption tower 3.1 passes through the absorption tower plate heat exchanger 3.3 and the pre-desorption tower heat exchanger 3.5 before entering the first hydrogen chloride desorption tower 4.1. The heavy components at the bottom of the first hydrogen chloride desorption tower 4.1 are led out, and after heat exchange through the pre-desorption tower heat exchanger 3.5, they enter the hydrogen chloride heat exchanger 3.4, the absorption tower plate heat exchanger 3.3, and the absorption tower top condenser 3.2 in sequence. After condensation, it serves as the reflux liquid for the hydrogen chloride absorption tower 3.1;

[0052] The gas phase at the top of the first hydrogen chloride desorption tower 4.1 enters the first desorption tower top condenser 4.3, is condensed, and then enters the first desorption tower reflux tank 4.4. Part of it returns to the first hydrogen chloride desorption tower 4.1 as the reflux liquid, and the other part serves as the heat source to enter the hydrogen chloride heater 4.6. After heat exchange, it enters the chlorosilane storage tank 2.4;

[0053] The uncondensed gas phase in the first desorption tower reflux tank 4.4 enters the second hydrogen chloride desorption tower 4.2. The liquid phase at the bottom of the tower (chlorosilane liquid) returns to the first hydrogen chloride desorption tower 4.1, and the gas phase at the top enters the second desorption tower top condenser 4.5. After being condensed by Freon, the liquid phase (hydrogen chloride liquid) returns to the second hydrogen chloride desorption tower 4.2, and the gas phase enters the hydrogen chloride heater 4.6 to be heated. At this time, the purity of the heated hydrogen chloride is about 90% or so, completing the primary purification;

[0054] The preliminarily purified hydrogen chloride gas enters the adsorption unit 5. First, it passes through the molecular sieve purification device 5.1 to adsorb CO, hydrocarbons, and trace water molecules in the mixed gas. The remaining gas phase components are hydrogen chloride, trace nitrogen, oxygen, hydrocarbons, and chlorosilane gas; then it enters the activated carbon purification device 5.2 to adsorb nitrogen, oxygen, and unadsorbed hydrocarbons in the mixed gas. The remaining gas phase components are mainly hydrogen chloride, and the impurities in the hydrogen chloride are only trace hydrocarbons, nitrogen, oxygen, and carbon monoxide. At this time, the contents of the above substances in the discharged gas have dropped to the ppm level;

[0055] Pressurized by the compressor 6.1 of the compression cooling unit 6, it enters the compressor aftercooler 6.2. The condensed heavy components enter the recovery, and the remaining gas phase enters the separation device 6.3. Under the pressurization of the compressor 6.1, the flow rate of the gas phase is accelerated;

[0056] The separation device 6.3 uses two hollow fiber membranes 6.3.1. Through the gas phase with increased speed under the pressurization of the compressor 6.1, the hollow fiber membranes 6.3.1 are used to further separate trace hydrocarbons, nitrogen, oxygen, carbon monoxide, and trace suspended droplets in the hydrogen chloride gas. The separation principle of the hollow fiber membranes 6.3.1 is to utilize the characteristic that impurities have slow penetration and hydrogen chloride has fast penetration, so that the passing rate of impurities in the hollow fiber membranes 6.3.1 is reduced, which further reduces the content of impurities in the hydrogen chloride entering the rectification process. At the same time, the hollow fiber membranes 6.3.1 are periodically backflushed with dry hydrogen chloride gas to clean the unpenetrated impurities. Therefore, with the cooperation of the molecular sieve purification device 5.1, the activated carbon purification device 5.2, and the separation device 6.3, the hydrogen chloride gas is purified in sequence to complete the secondary purification;

[0057] It enters the first hydrogen chloride rectification tower 7.1 and is heated by the reboiler at the bottom of the tower to separate the light and heavy substances in the separated components. The light components are discharged from the top of the tower and enter the first rectification tower top condenser 7.3. The liquid phase (the liquid phase is mainly hydrogen chloride liquid and contains trace amounts of chlorosilane substances) is refluxed into the first hydrogen chloride rectification tower 7.1 through the reflux pump. The uncondensed gas enters the light component recovery pipeline to the light component recovery unit 10. The heavy components are discharged from the bottom of the tower and enter the heavy component recovery pipeline to the heavy component recovery unit 9. The side draw of hydrogen chloride with a purity of about 99.99% enters the second hydrogen chloride rectification tower 7.2 and is heated by the reboiler at the bottom of the tower to separate the light and heavy components again. The light components are discharged from the top of the tower and enter the second rectification tower top condenser 7.4 at the top of the tower. The liquid phase is refluxed into the second hydrogen chloride rectification tower 7.2 through the reflux pump. The uncondensed gas enters the light component recovery pipeline to the light component recovery unit 10. The heavy components are discharged from the bottom of the tower and enter the heavy component recovery pipeline to the heavy component recovery unit 9 to complete the final purification. The side draw of high-purity hydrogen chloride with an electronic grade or above enters the hydrogen chloride storage tank 7.5.

[0058] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A purification system for hydrogen chloride produced as a byproduct of electronic grade polysilicon, characterized in that: It includes a condensation unit, an absorption unit, a desorption unit, an adsorption unit, a compression cooling unit, and a distillation unit which are sequentially connected by pipelines; The inlet of the air cooler of the condensing unit is connected to the exhaust gas intake pipe; The outlet of the final cooler of the condensing unit is connected to the inlet pipeline of the hydrogen chloride absorption tower of the absorption unit; The outlet of the first heat exchange pipeline of the heat exchanger before the first desorption tower of the absorption unit is connected to the inlet pipeline of the first hydrogen chloride desorption tower of the desorption unit; The outlet of the second heat exchange pipeline of the hydrogen chloride heater of the desorption unit is connected to the inlet pipeline of the molecular sieve purification device of the adsorption unit; The outlet of the activated carbon purification device of the adsorption unit is connected to the inlet pipeline of the compressor of the compression cooling unit; The outlet of the separation device of the compression cooling unit is connected to the inlet pipeline of the first hydrogen chloride distillation tower of the distillation unit; The hydrogen chloride outlet of the second hydrogen chloride distillation tower of the distillation unit is connected to the inlet pipeline of the hydrogen chloride storage tank.

2. The purification system for electronic grade polysilicon by-product hydrogen chloride according to claim 1, characterized in that: The condensing unit includes an air cooler, a circulating water cooler, a 7-degree water cooler, a chlorosilane storage tank, a plate heat exchanger, and a final-stage cooler. The outlet of the air cooler is connected to the inlet pipeline of the circulating water cooler, the liquid outlet of the circulating water cooler is connected to the inlet pipeline of the chlorosilane storage tank, the gas outlet of the circulating water cooler is connected to the inlet pipeline of the final-stage cooler through the first heat exchange pipeline of the plate heat exchanger, and the outlet of the final-stage cooler is connected to the inlet pipeline of the hydrogen chloride absorption tower.

3. The purification system for electronic grade polysilicon by-product hydrogen chloride according to claim 2, characterized in that: The absorption unit includes a hydrogen chloride absorption tower, an adsorption tower top condenser, an absorption tower plate heat exchanger, a hydrogen chloride heat exchanger, and a first desorption tower front heat exchanger. The top gas outlet of the hydrogen chloride absorption tower is connected to the air inlet pipeline of the hydrogen recovery unit through the second heat exchange pipeline of the plate heat exchanger, the bottom liquid outlet of the hydrogen chloride absorption tower is connected to the first heat exchange pipeline inlet of the first desorption tower front heat exchanger through the first heat exchange pipeline of the absorption tower plate heat exchanger, and the first heat exchange pipeline outlet of the first desorption tower front heat exchanger is connected to the inlet pipeline of the first hydrogen chloride desorption tower.

4. The purification system for electronic grade polysilicon by-product hydrogen chloride according to claim 3, characterized in that: The desorption unit includes a first hydrogen chloride desorption tower, a first desorption tower top condenser, a first desorption tower reflux tank, a second hydrogen chloride desorption tower, a second desorption tower top condenser, and a hydrogen chloride heater. The bottom liquid outlet of the first hydrogen chloride desorption tower is connected to the second heat exchange pipeline inlet pipeline of the first desorption tower front heat exchanger, the second heat exchange pipeline outlet of the first desorption tower front heat exchanger is connected to the second heat exchange pipeline inlet pipeline of the absorption tower plate heat exchanger through the hydrogen chloride heat exchanger, the second heat exchange pipeline outlet of the absorption tower plate heat exchanger is connected to the top inlet pipeline of the hydrogen chloride absorption tower through the absorption tower top condenser, the top gas outlet of the first hydrogen chloride desorption tower is connected to the inlet pipeline of the first desorption tower reflux tank through the first desorption tower top condenser, and the first desorption The gas outlet of the tower reflux tank is connected to the inlet pipeline of the second hydrogen chloride desorption tower, the liquid outlet of the first desorption tower reflux tank is respectively connected to the reflux port of the first hydrogen chloride desorption tower and the inlet pipeline of the first heat exchange pipeline of the hydrogen chloride heater, the bottom outlet of the second hydrogen chloride desorption tower is connected to the reflux port pipeline of the first hydrogen chloride desorption tower, the top gas outlet of the second hydrogen chloride desorption tower is connected to the inlet pipeline of the second desorption tower top condenser, the liquid outlet of the second desorption tower top condenser is connected to the reflux port pipeline of the second hydrogen chloride desorption tower, the gas outlet of the second desorption tower top condenser is connected to the inlet pipeline of the second heat exchange pipeline of the hydrogen chloride heater, and the second heat exchange pipeline outlet of the hydrogen chloride heater is connected to the inlet pipeline of the molecular sieve purification device.

5. The purification system for electronic grade polysilicon by-product hydrogen chloride according to claim 4, characterized in that: The adsorption unit comprises a molecular sieve purification device and an activated carbon purification device, the outlet of the molecular sieve purification device is connected to the inlet pipeline of the activated carbon purification device, and the outlet of the activated carbon purification device is connected to the inlet pipeline of the compressor; The molecular sieve purification device comprises at least two molecular sieve purification towers; The activated carbon purification device comprises at least two activated carbon towers.

6. The purification system for electronic grade polysilicon by-product hydrogen chloride according to claim 5, characterized in that: The compression cooling unit comprises a compressor, a compressor aftercooler, and a separation device, wherein the outlet of the compressor is connected to the inlet pipeline of the compressor aftercooler, the outlet of the compressor aftercooler is connected to the inlet pipeline of the separation device, the outlet of the separation device is connected to the inlet pipeline of the first hydrogen chloride rectification tower, and the heavy component outlet of the separation device is connected to the inlet pipeline of the heavy component recovery unit; The separation device comprises at least two hollow fiber membranes.

7. The purification system for electronic grade polysilicon by-product hydrogen chloride according to claim 6, characterized in that: The distillation unit comprises a first hydrogen chloride distillation tower, a second hydrogen chloride distillation tower, a first distillation tower top condenser, a second distillation tower top condenser, and a hydrogen chloride storage tank, wherein the top light component outlet of the first hydrogen chloride distillation tower is connected to the inlet pipeline of the light component recovery unit through the first distillation tower top condenser, and the bottom heavy component outlet of the first hydrogen chloride distillation tower is connected to the inlet pipeline of the heavy component recovery unit; The side outlet of the first hydrogen chloride distillation tower is connected to the inlet pipeline of the second hydrogen chloride distillation tower, the top light component outlet of the second hydrogen chloride distillation tower is connected to the inlet pipeline of the light component recovery unit through the top condenser of the second distillation tower, and the bottom heavy component outlet of the second hydrogen chloride distillation tower is connected to the inlet pipeline of the heavy component recovery unit.

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