A new improved Siemens polysilicon production process

Abstract

The present invention discloses a novel improved Siemens polysilicon production process, including a hydrochloric acid analysis unit, a cold hydrogenation unit, a slurry unit, a distillation unit, a reduction unit and a hydrogen production unit; the hydrochloric acid analysis unit is used to prepare high-purity hydrogen chloride gas, and is sent to the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to the distillation unit for impurity removal, and then sent to the reduction unit together with the hydrogen from the hydrogen production unit, and a vapor deposition reaction is carried out on the silicon core to obtain a polycrystalline silicon rod product; the slag slurry is sent to the slurry unit for further processing. The present invention uses a hydrochloric acid deep analysis device to supplement chlorine and hydrogen elements to the system, and compared with purchasing trichlorosilane and electrolyzing water to produce hydrogen, the production cost is significantly reduced. Hydrogen chloride gas is introduced into the inlet of the cold hydrogenation fluidized bed, and reacts with silicon powder in the fluidized bed to prepare trichlorosilane. The reaction process can utilize the existing cold hydrogenation device without the need for a new reactor.

Description

Technical Field

[0001] The invention belongs to the field of polysilicon production, and specifically relates to a novel improved Siemens method polysilicon production process. Background Art

[0002] At present, 90% of the polysilicon production processes at home and abroad are Siemens methods. This method places a silicon core in a reaction vessel in advance, uses SiHCl3 and H2 as raw materials, and makes the mixed gas of SiHCl3 and H2 entering the reduction furnace undergo a vapor deposition reaction on the surface of the silicon core under high temperature conditions of 1100-1200℃, so that the silicon core continues to grow and thicken into a silicon rod. At the same time, by-products such as SiCl4, SiH2Cl2, H2 and high-boiling substances are generated. The improved Siemens method realizes a closed cycle of the polysilicon production process by converting SiCl4, SiH2Cl2 and high-boiling substances into SiHCl3.

[0003] In the ideal state, the raw material of the modified Siemens polysilicon production process is only industrial silicon powder. In actual operation, process operations such as reduction furnace replacement, system maintenance replacement, tail gas venting, and cold hydrogenation by-product slag slurry treatment will cause the loss of hydrogen, chlorine and silicon in the system. At present, hydrogen is mostly supplemented by electrolysis of water, and chlorine and hydrogen are supplemented by purchasing finished SiHCl3.

[0004] The existing technologies at home and abroad remove impurities in chlorosilane through multi-stage distillation. Some impurities such as iron, copper, aluminum, calcium, manganese and other compounds can be easily removed through distillation. However, since the properties of boron and phosphorus compounds are similar to those of chlorosilane, it is necessary to increase the reflux ratio and reduce the extraction volume during multi-stage distillation to ensure the indicators. This operation process not only has high energy consumption and low output, but also unstable product quality.

[0005] At present, the production of hydrogen by electrolysis of water to supplement hydrogen has a production cost of 0.03 yuan per mole of hydrogen; the production cost of purchasing trichlorosilane to supplement hydrogen and chlorine is 2.95 yuan per mole of hydrogen and 0.98 yuan per mole of chlorine, which is a relatively high production cost. When purchasing trichlorosilane to supplement the chlorine element of the system, trichlorosilane is a flammable and explosive hazardous chemical, and the road transportation and loading and unloading safety risks are relatively high. The trichlorosilane distillation unit requires several large distillation towers to remove impurities in trichlorosilane, resulting in huge investment costs for the distillation unit, unstable product quality, and high energy consumption. Summary of the invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide an improved Siemens process for polysilicon production in view of the deficiencies in the prior art, so as to supplement chlorine and hydrogen elements and reduce costs.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A novel improved Siemens process for producing polysilicon comprises a hydrochloric acid analysis unit, a cold hydrogenation unit, a slag slurry unit, a distillation unit, a reduction unit and a hydrogen production unit; the hydrochloric acid analysis unit is used to prepare high-purity hydrogen chloride gas, which is sent to the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to the distillation unit for impurity removal, and then sent to the reduction unit together with the hydrogen from the hydrogen production unit to perform a vapor deposition reaction on the silicon core to obtain a polysilicon rod product; the slag slurry is sent to the slag slurry unit for further treatment.

[0009] Specifically, the cold hydrogenation unit mixes preheated silicon tetrachloride and hydrogen, and then mixes the mixture with hydrogen chloride from the hydrochloric acid analysis unit after electric heating and sends it into the cold hydrogenation fluidized bed to react with silicon powder in the fluidized bed to generate trichlorosilane, hydrogen and slag slurry; trichlorosilane, incompletely reacted hydrogen and silicon tetrachloride mixed gas are extracted from the top of the cold hydrogenation fluidized bed, sent to the dust removal and condensation separation after passing through the waste heat recovery heat exchanger to obtain crude trichlorosilane and hydrogen, and the hydrogen is pressurized by the circulating hydrogen compressor and re-preheated and sent to the cold hydrogenation fluidized bed as a raw material again.

[0010] Furthermore, part of the hydrogen chloride produced by the hydrochloric acid analysis unit is sent into the cold hydrogenation fluidized bed through pipe pass one, and the other part is mixed with the mixed gas produced from the top of the cold hydrogenation fluidized bed through pipe pass two to react with the silicon powder entrained in the gas phase at the outlet of the fluidized bed and the silicon powder attached to the inner wall of the waste heat recovery heat exchanger.

[0011] Specifically, the distillation unit comprises a partition distillation tower, a first adsorption tower, a dehydrogenation distillation tower and a deheaving distillation tower connected in sequence; the crude trichlorosilane from the cold hydrogenation unit first passes through the partition distillation tower to separate dichlorosilane and trace silicon tetrachloride therein, and then enters the first adsorption tower to remove the trace elements of boron and phosphorus in the trichlorosilane; then enters the delight distillation tower and the deheaving distillation tower in sequence, and the trichlorosilane with a higher impurity concentration is cut off from the top of the tower and the bottom of the tower respectively; finally, high-purity trichlorosilane is taken from the top of the deheaving distillation tower and sent to the reduction unit.

[0012] Furthermore, the cut materials in the partition distillation tower, the dehydrogenation distillation tower and the deheaving distillation tower are sent to the second adsorption tower for impurity removal, and then mixed with the crude trichlorosilane sent to the distillation unit, and re-enter the partition distillation tower for impurity removal.

[0013] Furthermore, the process also includes a tail gas recovery unit and a deproportionation unit; the reduced tail gas generated by the reduction unit is sent to the tail gas recovery unit to separate silicon tetrachloride, trichlorosilane, hydrogen, hydrogen chloride and high boiling points; wherein trichlorosilane is sent back to the reduction unit, the silicon tetrachloride, hydrogen, hydrogen chloride and a part of the silicon tetrachloride are sent to the cold hydrogenation unit, and the other part of the silicon tetrachloride is sent to the deproportionation unit; the high boiling points are sent to the slurry unit.

[0014] Furthermore, the dichlorosilane produced by the distillation unit is sent to the anti-disproportionation unit to react with silicon tetrachloride, and the produced trichlorosilane is returned to the distillation unit for impurity removal and then sent to the reduction unit.

[0015] Furthermore, the silicon tetrachloride and trichlorosilane produced by the slurry unit separation are sent to a cold hydrogenation unit for reaction.

[0016] Furthermore, part of the high-purity hydrogen chloride gas prepared by the hydrochloric acid analysis unit is sent to the slurry unit.

[0017] Furthermore, the first adsorption tower or the second adsorption tower is filled with a solid adsorbent, and the solid adsorbent is selected from any one of activated alumina, activated carbon, silica gel or ion exchange resin.

[0018] Beneficial effects:

[0019] (1) The present invention uses a hydrochloric acid analysis device to supplement chlorine and hydrogen elements to the system, which significantly reduces the production cost compared with purchasing trichlorosilane and producing hydrogen by electrolysis of water. Hydrogen chloride gas is introduced into the inlet of the cold hydrogenation fluidized bed, and reacts with silicon powder in the fluidized bed to prepare trichlorosilane. This reaction process can utilize the existing cold hydrogenation device without the need for a new reactor. At the same time, the above reaction is an exothermic reaction, which can reduce the operating load of the electric heater of the cold hydrogenation reaction device. Hydrogen chloride gas is introduced into the outlet pipe of the fluidized bed to react with silicon powder attached to the inner wall of the waste heat recovery heat exchanger, which can effectively ensure the heat transfer efficiency of the waste heat recovery heat exchanger and extend the service life of the equipment.

[0020] (2) The present invention adds a fixed-bed adsorption tower to the distillation device, which can greatly reduce the equipment investment of the distillation tower compared to the traditional distillation impurity removal process. The process indicators of the large distillation tower of the traditional distillation process can also be achieved with a smaller-scale distillation tower. The crude trichlorosilane is first separated into components to remove dichlorosilane and silicon tetrachloride, which can reduce the adverse effects of polar molecule dichlorosilane on the removal of trace impurities by the adsorption device. The impurities in trichlorosilane are concentrated by a light removal distillation tower and a heavy removal distillation tower, and then the impurities are removed by a fixed bed absorption device. This can not only efficiently remove the trace elements in trichlorosilane, but also recover trichlorosilane and reduce system losses. The use of solid adsorbents for impurity removal is more efficient and has higher product purity than traditional large-scale distillation towers, and the solid adsorbent can be replaced upon expiration, so that the product quality is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0022] Figure 1It is a schematic flow chart of the novel improved Siemens process for producing polysilicon of the present invention.

[0023] Figure 2 It is a schematic diagram of the process of the cold hydrogenation unit of the present invention.

[0024] Figure 3 It is a schematic diagram of the process of the distillation unit of the present invention. DETAILED DESCRIPTION

[0025] The present invention can be better understood with reference to the following examples.

[0026] like Figure 1 As shown, the novel improved Siemens process for polysilicon production of the present invention comprises a hydrochloric acid analysis unit, a cold hydrogenation unit, a slurry unit, a distillation unit, a reduction unit and a hydrogen production unit; the hydrochloric acid analysis unit is used to prepare high-purity hydrogen chloride gas, and is sent to the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to the distillation unit for impurity removal, and then sent to the reduction unit together with the hydrogen from the hydrogen production unit to perform a vapor deposition reaction on the silicon core to obtain a polysilicon rod product; the slag slurry is sent to the slag slurry unit for further treatment.

[0027] The invention uses a deep analysis process to prepare high-purity hydrogen chloride gas from purchased hydrochloric acid, which is pressurized to 3.2-3.5 MPa by a compressor and then sent to a cold hydrogenation fluidized bed to react Si+3HCl===SiHCl3+H2, thereby replenishing chlorine and hydrogen elements to the system.

[0028] Combination Figure 2 The cold hydrogenation unit mixes the preheated silicon tetrachloride and hydrogen, and then feeds them into the cold hydrogenation fluidized bed after electric heating. At the same time, the hydrogen chloride gas from the hydrochloric acid analysis unit is transported to the inlet of the cold hydrogenation fluidized bed through a pipeline, and reacts with silicon powder in the fluidized bed to generate trichlorosilane (TCS), hydrogen and slag slurry; trichlorosilane, unreacted hydrogen and silicon tetrachloride mixed gas are extracted from the top of the cold hydrogenation fluidized bed, and sent to the dust removal and condensation separation after the waste heat recovery heat exchanger to obtain crude trichlorosilane and hydrogen. The hydrogen is pressurized by the circulating hydrogen compressor and re-preheated as a raw material and then fed into the cold hydrogenation fluidized bed again.

[0029] In the present invention, a part of the hydrogen chloride generated by the hydrochloric acid analysis unit is sent into the cold hydrogenation fluidized bed through the pipe pass 1, and the other part is mixed with the mixed gas extracted from the top of the cold hydrogenation fluidized bed through the pipe pass 2, and reacts with the silicon powder entrained in the gas phase at the outlet of the fluidized bed and the silicon powder attached to the inner wall of the waste heat recovery heat exchanger, which can effectively reduce the production load of the dust removal system.

[0030] Combination Figure 3The distillation unit includes a partition distillation tower, a first adsorption tower, a dehydrogenation distillation tower and a deheaving distillation tower connected in sequence; the crude trichlorosilane (TCS) from the cold hydrogenation unit first passes through a partition distillation tower to separate dichlorosilane (DCS) and trace silicon tetrachloride (STC) therein, and then enters the first adsorption tower to remove trace elements such as boron and phosphorus in the trichlorosilane; then enters the de-light distillation tower and the de-heaving distillation tower in sequence, and cuts off part of the trichlorosilane (TCS) with a higher impurity concentration from the top and the bottom of the tower respectively; finally, high-purity trichlorosilane (TCS) is taken from the top of the de-heaving distillation tower and sent to the reduction unit.

[0031] The cut materials from the partition distillation tower, dehydrogenation distillation tower, and deheaving distillation tower are sent to the second adsorption tower for impurity removal, and then mixed with the crude trichlorosilane (TCS) sent to the distillation unit, and re-enter the partition distillation tower for impurity removal. The trichlorosilane (TCS) with concentrated impurity content is adsorbed and removed by solid adsorbent, and the trichlorosilane (TCS) after impurity removal is recovered.

[0032] The first adsorption tower or the second adsorption tower is filled with a solid adsorbent, and the solid adsorbent is selected from materials with a large specific surface area and a large surface activity, such as activated alumina, activated carbon, silica gel, ion exchange resin, etc.

[0033] Combination Figure 1 The process of the present invention also includes a tail gas recovery unit and a deproportionation unit; the reduction tail gas generated by the reduction unit is sent to the tail gas recovery unit to separate silicon tetrachloride, trichlorosilane, hydrogen, hydrogen chloride and high boiling points; wherein trichlorosilane is sent back to the reduction unit, the silicon tetrachloride, hydrogen, hydrogen chloride and a part of the silicon tetrachloride are sent to the cold hydrogenation unit, and the other part of the silicon tetrachloride is sent to the deproportionation unit; the high boiling points are sent to the slurry unit.

[0034] The dichlorosilane produced by the distillation unit is sent to the anti-disproportionation unit to react with silicon tetrachloride, and the produced trichlorosilane is returned to the distillation unit for impurity removal and then sent to the reduction unit.

[0035] Silicon tetrachloride and trichlorosilane produced by separation in the slurry unit are sent to the cold hydrogenation unit for reaction.

[0036] A portion of the high-purity hydrogen chloride gas prepared in the hydrochloric acid analysis unit is fed into the slurry unit.

[0037] The present invention uses a hydrochloric acid analysis device to supplement chlorine and hydrogen elements to the system, and compared with purchasing trichlorosilane and producing hydrogen by electrolysis of water, the production cost is significantly reduced. Hydrogen chloride gas is introduced into the inlet of the cold hydrogenation fluidized bed, and reacts with silicon powder in the fluidized bed to prepare trichlorosilane. The reaction process can utilize the existing cold hydrogenation device without adding a new reactor. At the same time, the above reaction is an exothermic reaction, which can reduce the operating load of the electric heater of the cold hydrogenation reaction device. Hydrogen chloride gas is introduced into the outlet pipe of the fluidized bed to react with silicon powder attached to the inner wall of the waste heat recovery heat exchanger, which can effectively ensure the heat transfer efficiency of the waste heat recovery heat exchanger and extend the service life of the equipment.

[0038] By adding a fixed-bed adsorption tower to the distillation device, the equipment investment of the distillation tower can be greatly reduced compared with the traditional distillation impurity removal process. The process indicators of the large distillation tower of the traditional distillation process can also be achieved with a smaller-scale distillation tower. The crude trichlorosilane is first separated into components to remove dichlorosilane and silicon tetrachloride, which can reduce the adverse effect of polar molecule dichlorosilane on the removal of trace impurities by the adsorption device. The impurities in trichlorosilane are concentrated by the light removal distillation tower and the heavy removal distillation tower, and then the impurities are removed by the fixed bed absorption device, which can not only efficiently remove the trace elements in trichlorosilane, but also recover trichlorosilane and reduce system losses. The use of solid adsorbents for impurity removal is more efficient and has higher product purity than traditional large-scale distillation towers, and the solid adsorbent can be replaced upon expiration, and the product quality is stable.

[0039] Example

[0040] The main raw materials of the present invention are industrial silicon powder, 30% hydrochloric acid and water, and the product is polysilicon. The product of the hydrochloric acid analysis unit is high-purity hydrogen chloride with a water content of less than 20ppm, which is used for the downstream preparation of trichlorosilane.

[0041] The process flow of preparing trichlorosilane by the traditional modified Siemens process cold hydrogenation unit is as follows: hydrogen and heated and vaporized silicon tetrachloride are mixed at a molar ratio of 2.5 to 2.8, and the mixture is heated to 540 to 550°C, and then introduced into a fluidized bed to react with silicon powder (reaction equation ②). The reaction product is subjected to waste heat recovery, washing and dust removal, cooling separation, and distillation separation to obtain crude trichlorosilane.

[0042] Combination Figure 1 and Figure 2 As shown, the cold hydrogenation process of the present invention is to introduce high-purity hydrogen chloride gas ( Figure 2 In the first stage of the process, silicon powder reacts with hydrogen chloride in the fluidized bed. The reaction generates trichlorosilane and hydrogen, while releasing a large amount of heat energy (reaction equation ①). Trichlorosilane is the product of the cold hydrogenation device, and hydrogen can be used as the raw material of the second stage of the reaction.

[0043] Si + 3HCL ==== SiHCl3 + H2 ①

[0044]

[0045] The present invention adds a hydrogen chloride pipeline ( Figure 2 In the second tube pass, the gas phase at the outlet of the fluidized bed carries some fine silicon powder particles with a particle size of less than 50μm, which will gradually adhere to the wall of the waste heat recovery heat exchanger tube, affecting the heat exchange efficiency. Figure 2 In the second process of the pipeline, hydrogen chloride is added into the pipeline to react with fine silicon powder particles, thereby reducing the impact of silicon powder adhesion on the heat exchange efficiency.

[0046] The crude trichlorosilane containing 98% trichlorosilane, 2% dichlorosilane, 50 ppbw phosphorus impurities and 150 ppbw boron impurities prepared by the cold hydrogenation unit is sent to the distillation unit ( Figure 3 ). Separation is carried out in a partition distillation tower, with a top temperature of 80°C and a pressure of 0.32MPa. Dichlorosilane and light impurities are produced from the top of the tower, and trichlorosilane carrying heavy impurities is produced from the bottom of the tower. The trichlorosilane produced from the side line is sent to the first adsorption tower, with an adsorption temperature of 0-25°C and an adsorption pressure of 0.55-0.6Mpa. The impurities of trichlorosilane produced from the first adsorption tower are less than: boron 20ppbw, phosphorus 5ppbw. After adsorption, trichlorosilane is sent to a light removal tower to remove some light impurities, and then to a heavy removal tower to remove heavy impurities, to obtain high-purity trichlorosilane with a boron impurity of less than 0.05ppbw and a phosphorus impurity of less than 0.03ppbw.

[0047] The cut materials from the bottom of the partition distillation tower, the top of the light removal tower, and the bottom of the heavy removal tower are pressurized by pump equipment and transported to the second adsorption tower. The boron and phosphorus impurities in trichlorosilane are concentrated by the partition distillation tower, the light removal tower, and the heavy removal tower. The impurity content is: 50ppbw for boron and 15ppbw for phosphorus. The high concentration of impurities is conducive to the adsorption of impurities. The adsorption temperature is 0-25℃, and the adsorption pressure is 0.55-0.6Mpa. After passing through the adsorption tower, the impurities of the product are less than 0.1ppbw for boron and 0.1ppbw for phosphorus. This part of the cut materials is returned to the inlet of the partition distillation tower.

[0048] The present invention provides a new improved Siemens polysilicon production process idea and method. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A novel improved Siemens polysilicon production process, characterized in that: It includes a hydrochloric acid analysis unit, a cold hydrogenation unit, a slag slurry unit, a distillation unit, a reduction unit and a hydrogen production unit; the hydrochloric acid analysis unit is used to prepare high-purity hydrogen chloride gas, and is sent to the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to the distillation unit to remove impurities, and then sent to the reduction unit together with the hydrogen from the hydrogen production unit to perform vapor deposition reaction on the silicon core to obtain polycrystalline silicon rod products; the slag slurry is sent to the slag slurry unit for further processing; A portion of the high-purity hydrogen chloride gas prepared by the hydrochloric acid analysis unit is sent to the slurry unit; The cold hydrogenation unit mixes the preheated silicon tetrachloride and hydrogen, and then mixes them with the hydrogen chloride from the hydrochloric acid analysis unit and feeds them into the fluidized bed of the cold hydrogenation unit to react with the silicon powder in the fluidized bed to generate trichlorosilane, hydrogen and slag slurry; trichlorosilane, unreacted hydrogen and silicon tetrachloride mixed gas are extracted from the top of the cold hydrogenation fluidized bed, and after passing through the waste heat recovery heat exchanger, they are fed into the dust removal condensation separation to obtain crude trichlorosilane and hydrogen, and the hydrogen is pressurized by the circulating hydrogen compressor and then re-preheated and fed into the cold hydrogenation fluidized bed as a raw material again; A part of the hydrogen chloride generated by the hydrochloric acid analysis unit is sent into the cold hydrogenation fluidized bed through pipe pass 1, and the other part is mixed with the mixed gas produced from the top of the cold hydrogenation fluidized bed through pipe pass 2 to react with the silicon powder entrained in the gas phase at the outlet of the fluidized bed and the silicon powder attached to the inner wall of the waste heat recovery heat exchanger.

2. The novel improved Siemens process for producing polysilicon according to claim 1, characterized in that: The distillation unit comprises a partition distillation tower, a first adsorption tower, a dehydrogenation distillation tower and a de-heaving distillation tower connected in sequence; the crude trichlorosilane from the cold hydrogenation unit first passes through the partition distillation tower to separate the dichlorosilane and trace silicon tetrachloride therein, and then enters the first adsorption tower to remove the trace elements of boron and phosphorus in the trichlorosilane; Then it enters the light removal distillation tower and the heavy removal distillation tower in turn, and some trichlorosilane with higher impurity concentration is removed from the top and bottom of the tower respectively; finally, high-purity trichlorosilane is taken from the top of the heavy removal distillation tower and sent to the reduction unit.

3. The novel improved Siemens process for producing polysilicon according to claim 2, characterized in that: The cut materials in the partition distillation tower, the dehydrogenation distillation tower and the deheaving distillation tower are sent to the second adsorption tower for impurity removal, and then mixed with the crude trichlorosilane sent to the distillation unit and re-entered the partition distillation tower for impurity removal.

4. The novel improved Siemens process for producing polysilicon according to claim 1, characterized in that: It also includes a tail gas recovery unit and a de-disproportionation unit; the reduced tail gas generated by the reduction unit is sent to the tail gas recovery unit to separate silicon tetrachloride, trichlorosilane, hydrogen, hydrogen chloride and high boiling points; wherein trichlorosilane is sent back to the reduction unit, the silicon tetrachloride, hydrogen, hydrogen chloride and a part of silicon tetrachloride are sent to the cold hydrogenation unit, and the other part of silicon tetrachloride is sent to the de-disproportionation unit; the high boiling points are sent to the slurry unit.

5. The novel improved Siemens process for producing polysilicon according to claim 1, characterized in that: The dichlorosilane produced by the distillation unit is sent to the anti-disproportionation unit to react with silicon tetrachloride, and the produced trichlorosilane is returned to the distillation unit for impurity removal and then sent to the reduction unit.

6. The novel improved Siemens process for producing polysilicon according to claim 1, characterized in that: The silicon tetrachloride and trichlorosilane produced by separation in the slurry unit are sent to the cold hydrogenation unit for reaction.

7. The novel improved Siemens process for producing polysilicon according to claim 2 or 3, characterized in that: The first adsorption tower or the second adsorption tower is filled with a solid adsorbent, and the solid adsorbent is selected from any one of activated alumina, activated carbon, silica gel or ion exchange resin.

Images