A method and system for utilizing waste heat from polysilicon reduction tail gas

Abstract

The present invention discloses a method for utilizing the waste heat of polysilicon reduction tail gas, comprising: using the coldness of the first feed gas in a first tail gas heat exchanger to cool the first reduction tail gas from the first reduction furnace, and allowing the first feed gas after the coldness has been utilized by the first tail gas heat exchanger to enter the second reduction furnace; using the coldness of the second feed gas in a second tail gas heat exchanger to cool the second reduction tail gas from the second reduction furnace, and allowing the second feed gas after the coldness has been utilized by the second tail gas heat exchanger to enter the first reduction furnace. The present invention also discloses a system for utilizing the waste heat of polysilicon reduction tail gas. The present invention can realize the recycling of the waste heat of the reduction tail gas, so that the reduction furnace maintains a relatively high deposition rate in each operation stage, and the conversion rate in each operation stage is always maintained at a high level.

Description

Technical Field

[0001] The present invention belongs to the technical field of polysilicon, and in particular relates to a method and system for utilizing waste heat of polysilicon reduction tail gas. Background Art

[0002] Polysilicon is the basic material of the solar photovoltaic industry. At present, the production of polysilicon mainly adopts the modified Siemens method (i.e., trichlorosilane reduction method). The basic principle is to use trichlorosilane and H2 in a certain proportion to carry out vapor deposition reaction in a reduction furnace, so that the polysilicon crystal particles produced by the reaction are deposited and grown on the silicon core, thereby obtaining rod-shaped polysilicon. The reaction temperature is 1080℃~1100℃, and the tail gas (reduction tail gas) after the reaction contains a large amount of waste heat, which is very wasteful to discharge directly.

[0003] Chinese patent CN 107512719 A discloses a method and system for utilizing waste heat from polysilicon reduction tail gas, which can reduce the power consumption of polysilicon production, improve the primary conversion rate of trichlorosilane, and effectively reduce the temperature of the reduction tail gas to a certain extent. However, this method and system still have at least the following deficiencies:

[0004] In the process of producing polysilicon in a reduction furnace, due to the low initial furnace atmosphere temperature and the small diameter of the silicon rod, the temperature radiated to the wall of the reduction furnace is also relatively low, resulting in a low gas phase temperature in the furnace and a slow gas phase deposition rate. If you want to obtain a faster gas phase deposition rate in the early stage, you need to increase the gas phase temperature. However, the above-mentioned polysilicon reduction tail gas waste heat utilization method and system, due to the low initial furnace gas phase temperature, the initial waste heat recovery amount is relatively limited, so it is impossible to provide a sufficient gas phase temperature field for the initial silicon rod growth in the reduction furnace, resulting in a relatively low initial gas phase deposition rate.

[0005] In the middle stage of silicon rod growth, the silicon rod gradually grows and thickens from the initial thin diameter, and its external radiation, furnace wall, etc. gradually heat up, and the gas phase temperature in the furnace is relatively high. The waste heat recovery amount of the above-mentioned polysilicon reduction exhaust waste heat utilization method and system can basically meet the silicon rod growth to provide a sufficient gas phase temperature field, which can promote the growth of silicon rods, improve the conversion rate, and reduce the energy consumption of the reduction process; however, after the middle stage of silicon rod growth, due to the further increase in the diameter of the silicon rod, the external radiation energy of the silicon rod further increases, resulting in a further increase in the temperature of the reduction furnace wall surface, etc., and a further increase in the gas phase temperature in the reduction furnace. At this time, if the above-mentioned polysilicon reduction exhaust waste heat utilization method and system are continued to be used for waste heat recovery, the temperature of the feed gas will be higher, further increasing the gas phase temperature field in the furnace, and then causing atomization in the furnace. Atomization will cause the sight glass of the reduction furnace to be contaminated, increase the cleaning cost, increase the proportion of surface cauliflower material, and other problems. In order to reduce atomization, it is generally regulated by reducing the current. The reduction of current will reduce the surface temperature of the silicon rod. However, the reduction of the surface temperature of the silicon rod will cause the vapor deposition reaction process to deviate from the optimal deposition temperature, resulting in a decrease in conversion rate and an increase in energy consumption, which is not conducive to the production of polysilicon. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method and system for utilizing the waste heat of polysilicon reduction tail gas in view of the above-mentioned deficiencies in the prior art, which can realize the recovery and utilization of the waste heat of the reduction tail gas, so that the reduction furnace maintains a relatively high deposition rate in each operation stage, thereby maintaining the conversion rate in each operation stage at a high level, avoiding appearance problems of polysilicon products, and achieving the purpose of reducing the unit electricity consumption of polysilicon production; at the same time, the temperature of the reduction tail gas is greatly reduced, which can not only avoid large heat load fluctuations in subsequent tail gas treatment, but also reduce the cooling load of the downstream reduction tail gas recovery process, thereby reducing the production cost of the downstream reduction tail gas recovery process.

[0007] According to one aspect of the present invention, a method for utilizing waste heat from polysilicon reduction tail gas is provided, and the technical solution is as follows:

[0008] A method for utilizing waste heat from polysilicon reduction tail gas, comprising:

[0009] Combining and connecting two or more reduction furnaces into a polysilicon reduction tail gas waste heat utilization system;

[0010] In the first tail gas heat exchanger, the first reduction tail gas from the first reduction furnace is cooled by using the cold energy of the first feed gas, and the first feed gas after the cold energy has been used by the first tail gas heat exchanger enters the second reduction furnace;

[0011] The second reduction tail gas from the second reduction furnace is cooled in the second tail gas heat exchanger using the cold energy of the second feed gas, and the second feed gas whose cold energy has been used by the second tail gas heat exchanger enters the first reduction furnace.

[0012] Preferably, before cooling the first reduced tail gas output from the first reduction furnace in the first tail gas heat exchanger, the method further comprises:

[0013] In the first Liebig condenser, the first reduced tail gas from the first tail gas heat exchanger is cooled again by using the cold energy of the first feed gas and the first circulating water, and the first feed gas whose cold energy has been used by the first Liebig condenser enters the first tail gas heat exchanger, and the first circulating water whose cold energy has been used by the first Liebig condenser enters the first reduction furnace;

[0014] And / or, before cooling the second reduced tail gas output from the second reduction furnace in the second tail gas heat exchanger, the method further comprises:

[0015] In the second Liebig condenser, the second reduction tail gas from the second tail gas heat exchanger is cooled again using the cold energy of the second feed gas and the second circulating water, and the second feed gas whose cold energy has been used by the second Liebig condenser enters the second tail gas heat exchanger, and the second circulating water whose cold energy has been used by the second Liebig condenser enters the second reduction furnace.

[0016] Preferably, after cooling the first reduced tail gas outputted from the first reduction furnace in the first tail gas heat exchanger and before cooling the first reduced tail gas from the first tail gas heat exchanger again in the first Liebig condenser, the method further comprises:

[0017] In the second tube, the first reduced tail gas from the first tail gas heat exchanger is cooled again by using the cold energy of the first circulating water from the first Liebig condenser, and the first reduced tail gas cooled by the second tube enters the first Liebig condenser, and the first circulating water whose cold energy has been used by the second tube enters the first reduction furnace;

[0018] And / or, after cooling the second reduced tail gas output from the second reduction furnace in the second tail gas heat exchanger and before cooling the second reduced tail gas from the second tail gas heat exchanger again in the second Liebig condenser, the method further includes:

[0019] In the fourth tube, the cold energy of the second circulating water from the second Liebig condenser is used to cool the second reducing exhaust gas from the second exhaust gas heat exchanger again, and the second reducing exhaust gas cooled by the fourth tube enters the second Liebig condenser, and the first circulating water whose cold energy has been utilized by the fourth tube enters the second reduction furnace.

[0020] Preferably, before cooling the first reduced tail gas output from the first reduction furnace in the first tail gas heat exchanger, the method further comprises:

[0021] In the first casing, the first reduction tail gas output from the first reduction furnace is first cooled by using the cold energy of the first circulating water from the second casing, and the first reduction tail gas cooled by the first casing enters the first tail gas heat exchanger, and the first circulating water whose cold energy has been used by the first casing enters the first reduction furnace;

[0022] And / or, before cooling the second reduced tail gas output from the second reduction furnace in the second tail gas heat exchanger, the method further comprises:

[0023] In the third casing, the second reduction tail gas output from the second reduction furnace is first cooled using the cold energy of the second circulating water from the fourth casing, and the second reduction tail gas cooled by the third casing enters the second tail gas heat exchanger, and the second circulating water whose cold energy has been utilized by the third casing enters the second reduction furnace.

[0024] Preferably, the first reduction furnace is in the initial operation stage and the second reduction furnace is in the middle and late operation stage, or the second reduction furnace is in the initial operation stage and the first reduction furnace is in the middle and late operation stage; the start-up interval between the first reduction furnace and the second reduction furnace is ≥20h.

[0025] Preferably, the method further comprises:

[0026] The first feed gas after the cooling capacity has been utilized by the first tail gas heat exchanger enters the first reduction furnace;

[0027] The second feed gas after its cooling capacity has been utilized by the second tail gas heat exchanger enters the second reduction furnace.

[0028] Preferably, the method further comprises:

[0029] Real-time monitoring of the temperature of the feed gas before entering the first reduction furnace;

[0030] Monitor the temperature of the feed gas before entering the second reduction furnace in real time.

[0031] According to another aspect of the present invention, a waste heat utilization system for polysilicon reduction tail gas is provided, and its technical solution is as follows:

[0032] A polysilicon reduction tail gas waste heat utilization system, characterized in that it comprises a first reduction furnace, a first heat exchange unit, a second reduction furnace, and a second heat exchange unit, wherein the first heat exchange unit comprises a first tail gas heat exchanger, and the second heat exchange unit comprises a second tail gas heat exchanger.

[0033] The first reduction furnace and the second reduction furnace are both used for performing vapor deposition reaction to produce polysilicon, the first reduction furnace outputs a first reduction tail gas, and the second reduction furnace outputs a second reduction tail gas;

[0034] The first tail gas heat exchanger is connected to the first reduction furnace and is used to cool the first reduction tail gas from the first reduction furnace using the cold energy of the first feed gas, and can pass the first feed gas into the first reduction furnace.

[0035] The first tail gas heat exchanger is also connected to the second reduction furnace, and can be used to pass the first feed gas after the cooling energy has been utilized by the first tail gas heat exchanger into the second reduction furnace;

[0036] The second tail gas heat exchanger is connected to the second reduction furnace and is used to cool the second reduction tail gas from the second reduction furnace using the cold energy of the second feed gas, and can pass the second feed gas into the first reduction furnace.

[0037] The second tail gas heat exchanger is also connected to the first reduction furnace, and can be used to pass the second feed gas whose coldness has been utilized by the second tail gas heat exchanger into the first reduction furnace.

[0038] Preferably, the first heat exchange unit further comprises a first Liebig condenser, and / or the second heat exchange unit further comprises a second Liebig condenser, wherein:

[0039] The first Liebig condenser is connected to the first tail gas heat exchanger, and is used to use the cold energy of the first feed gas and the first circulating water to cool the first reduced tail gas from the first tail gas heat exchanger again, and pass the first feed gas whose cold energy has been used by the first Liebig condenser into the first tail gas heat exchanger, and pass the first circulating water whose cold energy has been used by the first Liebig condenser into the first reduction furnace;

[0040] The second Liebig condenser is connected to the second tail gas heat exchanger, and is used for utilizing the cold energy of the second feed gas and the second circulating water to cool the second reduced tail gas from the second tail gas heat exchanger again, and passing the second feed gas whose cold energy has been utilized by the second Liebig condenser into the second tail gas heat exchanger, and passing the second circulating water whose cold energy has been utilized by the second Liebig condenser into the second reduction furnace.

[0041] Preferably, the first heat exchange unit further includes a second sleeve, and / or the second heat exchange unit further includes a fourth sleeve, wherein:

[0042] The second sleeve is connected to the first Liebig condenser and the first tail gas heat exchanger, and is used to use the cold energy of the first circulating water from the first Liebig condenser to cool the first reduced tail gas from the first tail gas heat exchanger again, and pass the first reduced tail gas cooled by the second sleeve into the first Liebig condenser, and pass the first circulating water whose cold energy has been used by the second sleeve into the first reduction furnace;

[0043] The fourth sleeve is connected to the second Liebig condenser and the second exhaust gas heat exchanger, and is used to utilize the cold energy of the second circulating water from the second Liebig condenser to cool the second reduced exhaust gas from the second exhaust gas heat exchanger again, and to pass the second reduced exhaust gas cooled by the fourth sleeve into the second Liebig condenser, and to pass the second circulating water whose cold energy has been utilized by the fourth sleeve into the second reduction furnace.

[0044] Preferably, in the method, the first heat exchange unit further comprises a first casing, and / or the second heat exchange unit further comprises a third casing, wherein:

[0045] The first sleeve is connected to the second sleeve and the first reduction furnace, and is used to use the cold energy of the first circulating water from the second sleeve to first cool the first reduction tail gas output from the first reduction furnace, and pass the first circulating water whose cold energy has been used by the first sleeve into the first reduction furnace, and the first sleeve is also connected to the first tail gas heat exchanger, and is used to pass the first reduction tail gas cooled by the first sleeve into the first tail gas heat exchanger;

[0046] The third sleeve is connected to the fourth sleeve and the second reduction furnace, and is used to utilize the cold energy of the second circulating water from the fourth sleeve to first cool the second reduction exhaust gas output from the second reduction furnace, and pass the second circulating water whose cold energy has been utilized by the fourth sleeve into the second reduction furnace. The third sleeve is also connected to the second exhaust gas heat exchanger, and is used to pass the second reduction exhaust gas cooled by the third sleeve into the second exhaust gas heat exchanger.

[0047] Preferably, the system further comprises a first control component and a second control component, wherein the first control component is connected to the first tail gas heat exchanger and the first reduction furnace, the second control component is connected to the second tail gas heat exchanger and the second reduction furnace, and the second control component is also connected to the first control component, wherein:

[0048] The first control component is used to distribute the first feed gas after the cooling capacity has been utilized by the first tail gas heat exchanger to the first reduction furnace and the second reduction furnace;

[0049] The second control component is used to distribute the second feed gas after the cooling capacity has been utilized by the second tail gas heat exchanger to the second reduction furnace and the first reduction furnace.

[0050] Preferably, the system further comprises a first control valve and a fourth control valve, wherein:

[0051] The first control valve is connected to the first Liebig condenser, the cold source inlet of the first tail gas heat exchanger, and is also connected to the cold source outlet of the first tail gas heat exchanger, and is used to adjust the amount of the first feed gas that has been used by the first Liebig condenser and has been introduced into the first tail gas heat exchanger;

[0052] The fourth control valve is connected to the second Liebig condenser, the cold source inlet of the second tail gas heat exchanger, and is also connected to the cold source outlet of the second tail gas heat exchanger, and is used to adjust the amount of the second feed gas introduced into the second tail gas heat exchanger whose cold energy has been utilized by the second Liebig condenser.

[0053] Preferably, the system further comprises a first temperature measuring instrument and a second temperature measuring instrument.

[0054] The first temperature measuring instrument is used to monitor the temperature of the feed gas before entering the first reduction furnace in real time;

[0055] The second temperature measuring instrument is used to monitor in real time the temperature of the feed gas before entering the second reduction furnace.

[0056] The method and system for utilizing the waste heat of polysilicon reduction tail gas of the present invention cool the reduction tail gas output by each reduction furnace so that the feed gas absorbs heat to collect the waste heat of the reduction tail gas and raises the temperature. Moreover, according to the operation stage of each reduction furnace, each reduction furnace can be operated in a cross-operation, a single operation, or a combination of the cross-operation and the single operation, so that the temperature of the feed gas before entering each reduction furnace can be adjusted to ensure that the feed gas entering each reduction furnace can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace, that is, the waste heat of the reduction tail gas is recycled and utilized, so that each reduction furnace maintains a relatively high deposition rate at different production times and different growth states (that is, each operation stage), improves the level of refined control, and thus maintains the conversion rate at each operation stage at a high level, avoids appearance problems of polysilicon products, and reduces the unit power consumption of polysilicon production; at the same time, the temperature of the reduction tail gas after the cooling treatment is greatly reduced, which not only avoids a large heat load fluctuation for subsequent tail gas treatment, but also reduces the cooling load of the downstream reduction tail gas recovery process of the reduction furnace, and reduces the production cost of the downstream reduction tail gas recovery process. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the structure of the waste heat utilization system of polysilicon reduction tail gas in an embodiment of the present invention.

[0058] In the figure: 101-first reduction furnace; 102-second reduction furnace; 11-chassis; 12-furnace drum; 201-first casing; 202-second casing; 203-third casing; 204-fourth casing; 21-inner tube; 22-outer tube; 31-first tail gas heat exchanger; 32-second tail gas heat exchanger; 501-first Liebig condenser; 502-second Liebig condenser; 51-inner straight tube; 52-outer casing; 53-inner coil; 61-first temperature measuring instrument; 62-second temperature measuring instrument; 71-first control valve; 72-second control valve; 73-third control valve; 81-fourth control valve; 82-fifth control valve; 83-sixth control valve; a11, a12, a13, a21, a22, a23, b11, b12, b21, b22, c1, c2-pipeline. DETAILED DESCRIPTION

[0059] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0060] In the description of the present invention, it should be noted that the directions or positional relationships indicated by “upper” and the like are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience and simplification of the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0061] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0062] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connect", "set", "install", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] Example 1

[0064] like Figure 1 As shown, this embodiment discloses a method for utilizing waste heat of polysilicon reduction tail gas, comprising:

[0065] Two or more reduction furnaces are combined and connected to form a polysilicon reduction tail gas waste heat utilization system. In this embodiment, two reduction furnaces are preferably combined and connected to form a polysilicon reduction tail gas waste heat utilization system;

[0066] In the first tail gas heat exchanger 31, the first reduction tail gas from the first reduction furnace 101 is cooled by using the cold energy of the first feed gas, and the first feed gas after the cold energy has been used by the first tail gas heat exchanger 31 enters the second reduction furnace 102;

[0067] The second reduction tail gas from the second reduction furnace 102 is cooled in the second tail gas heat exchanger 32 using the cold energy of the second feed gas, and the second feed gas whose cold energy has been used by the second tail gas heat exchanger 32 enters the first reduction furnace 101 .

[0068] In this embodiment, the first reduction tail gas outputted from the first reduction furnace 101 and the second reduction tail gas outputted from the second reduction furnace 102 are both mixed gases including hydrogen, hydrogen chloride and chlorosilane, wherein chlorosilane is a mixed gas including trichlorosilane, silicon tetrachloride and dichlorosilane.

[0069] In this embodiment, the first feed gas and the second feed gas are both mixed gases including hydrogen and trichlorosilane. Specifically, hydrogen and trichlorosilane are introduced into a static mixer (not shown) and fully mixed to form the first feed gas and the second feed gas.

[0070] Depend on Figure 1It can be seen that the first feed gas absorbs the heat of the first reducing tail gas in the first tail gas heat exchanger 31, and its own temperature increases, and then it can enter the second reduction furnace 102. After the first feed gas with increased temperature enters the second reduction furnace 102, the reaction temperature in the second reduction furnace 102 is increased, thereby increasing the primary conversion rate of trichlorosilane (TCS) in the second reduction furnace 102 and reducing the unit power consumption of polysilicon production. The first reducing tail gas output by the first reduction furnace 101 absorbs the cold of the first feed gas in the first tail gas heat exchanger 31, and its own temperature decreases, thereby reducing the cold load of the downstream reducing tail gas recovery process of the first reduction furnace 101 (the function of this process is: according to their different boiling points, the hydrogen and hydrogen chloride in the reducing tail gas are separated from the chlorosilane through a refrigerator to obtain pure chlorosilane), thereby reducing the production cost of the downstream reducing tail gas recovery process. Similarly, the second feed gas absorbs the heat of the second reducing exhaust gas in the second exhaust gas heat exchanger 32, and its own temperature increases, and then it can enter the first reduction furnace 101. After the second reducing exhaust gas with increased temperature enters the first reduction furnace 101, the reaction temperature in the first reduction furnace 101 is increased, thereby increasing the primary conversion rate of trichlorosilane (TCS) in the first reduction furnace 101 and reducing the unit electricity consumption of polysilicon production. The second reducing exhaust gas output from the second reduction furnace 102 absorbs the cold of the second feed gas in the second exhaust gas heat exchanger 32, and its own temperature is reduced, thereby reducing the cold load of the downstream reducing exhaust gas recovery process of the second reduction furnace 102, and further reducing the production cost of the downstream reducing exhaust gas recovery process.

[0071] In some embodiments, Figure 1 As shown, it is preferred that the first reduction furnace 101 and the second reduction furnace 102 in the present method are in different operating stages, for example, the first reduction furnace 101 is in the initial stage of operation, while the second reduction furnace 102 is in the middle and late stages of operation, or the second reduction furnace 102 is in the initial stage of operation, while the first reduction furnace 101 is in the middle and late stages of operation.

[0072] By using the reduction tail gas generated by the reduction furnace in the late stage of operation to heat the feed gas of the reduction furnace in the early stage of operation, the waste heat of the reduction tail gas of the reduction furnace in the late stage of operation can be fully recovered. Compared with the prior art, the temperature of the feed gas entering the reduction furnace in the early stage of operation can be increased, and the reduction furnace in the early stage of operation can be provided with a gas phase temperature field sufficient for the initial growth of silicon rods, so that the silicon rods can quickly reach the optimal deposition rate at the initial stage of the reduction furnace operation, thereby improving the conversion rate and reducing the power consumption at the initial stage of the reduction furnace operation. By using the reducing tail gas generated by the reducing furnace in the early stage of operation to heat the feed gas of the reducing furnace in the middle and late stages of operation, the waste heat of the reducing tail gas of the reducing furnace in the early stage of operation can be fully recovered, and the temperature rise of the feed gas after absorbing heat is limited, compared with the relatively existing technology (using the reducing tail gas generated by the reducing furnace itself to heat its feed gas, when the reducing furnace is in the middle and late stages of operation, the temperature of its reducing tail gas is relatively high, and the feed gas can be heated to a relatively high temperature, and at this time the temperature in the reducing furnace has reached a relatively high level, and the higher temperature feed gas will further increase the gas phase temperature field in the reducing furnace, which may cause adverse phenomena such as atomization), the temperature of the feed gas entering the reducing furnace in the middle and late stages of operation can be relatively reduced, so that the gas phase temperature field in the reducing furnace in the middle and late stages of operation will not be too high, avoiding the occurrence of atomization in the furnace, thereby avoiding the need to reduce the current in order to reduce the atomization in the furnace, and then avoiding the surface temperature of the silicon rod from decreasing and deviating from the optimal deposition temperature, effectively maintaining the surface temperature of the silicon rod, keeping the silicon rod in a growth state with a relatively high deposition rate, and ensuring that the conversion rate is maintained at a high level.

[0073] In some embodiments, the start-up interval between the first reduction furnace 101 and the second reduction furnace 102 is ≥20 hours, preferably 60-100 hours, to ensure that one reduction furnace is in the early stage of operation and the other reduction furnace is in the middle and late stages of operation.

[0074] In some embodiments, Figure 1 As shown, before cooling the first reduction tail gas output from the first reduction furnace 101 in the first tail gas heat exchanger 31, the method may further include: using the cold energy of the first feed gas and the first circulating water in the first Liebig condenser 501 to cool the first reduction tail gas from the first tail gas heat exchanger 31 again, and allowing the first feed gas whose cold energy has been used by the first Liebig condenser 501 to enter the first tail gas heat exchanger 31, and allowing the first circulating water whose cold energy has been used by the first Liebig condenser 501 to enter the first reduction furnace 101;

[0075] And / or, before cooling the second reduced tail gas output from the second reduction furnace 102 in the second tail gas heat exchanger 32, the method may further include: using the cold energy of the second feed gas and the second circulating water in the second Liebig condenser 502 to cool the second reduced tail gas from the second tail gas heat exchanger 32 again, and allowing the second feed gas whose cold energy has been utilized by the second Liebig condenser 502 to enter the second tail gas heat exchanger 32, and allowing the second circulating water whose cold energy has been utilized by the second Liebig condenser 502 to enter the second reduction furnace 102.

[0076] In this embodiment, the first Liebig condenser 501 and the second Liebig condenser 502 both include an inner straight tube 51, an outer sleeve 52, and an inner coil 53, and the inner coil 53 is coiled outside the inner straight tube 51, and the outer sleeve 52 is sleeved on the outside of the inner straight tube 51 and the inner coil 53, wherein the corresponding first reduction tail gas / second reduction tail gas flows in the inner straight tube 51, the corresponding first feed gas / second feed gas flows in the inner coil 53, and the corresponding first circulating water / second circulating water flows in the outer sleeve 52.

[0077] In some embodiments, Figure 1 As shown, after cooling the first reduction tail gas output from the first reduction furnace 101 in the first tail gas heat exchanger 31, and before cooling the first reduction tail gas from the first tail gas heat exchanger 31 again in the first Liebig condenser 501, the method may further include: using the cold energy of the first circulating water from the first Liebig condenser 501 in the second sleeve 202 to cool the first reduction tail gas from the first tail gas heat exchanger 31 again, and allowing the first reduction tail gas after cooling in the second sleeve 202 to enter the first Liebig condenser 501, and allowing the first circulating water (through the b12 pipeline and the first sleeve 201) whose cold energy has been used by the second sleeve 202 to enter the first reduction furnace 101;

[0078] And / or, after the second reduction exhaust gas output from the second reduction furnace 102 is cooled in the second exhaust gas heat exchanger 32, and before the second reduction exhaust gas from the second exhaust heat exchanger 32 is cooled again in the second Liebig condenser 502, the method may also include: in the fourth sleeve 204, using the cold energy of the second circulating water from the second Liebig condenser 502 to cool the second reduction exhaust gas from the second exhaust heat exchanger 32 again, and allowing the second reduction exhaust gas after cooling by the fourth sleeve 204 to enter the second Liebig condenser 502, and allowing the first circulating water (through the b22 pipeline and the third sleeve 203) whose cold energy has been utilized by the fourth sleeve 204 to enter the second reduction furnace 102.

[0079] In some embodiments, Figure 1As shown, before cooling the first reduction tail gas outputted from the first reduction furnace 101 in the first tail gas heat exchanger 31, the method may further include: using the cold energy of the first circulating water from the second casing 202 to cool the first reduction tail gas outputted from the first reduction furnace 101 in the first casing 201, and allowing the first reduction tail gas cooled by the first casing 201 to enter the first tail gas heat exchanger 31, and allowing the first circulating water whose cold energy has been used by the first casing 201 to enter the first reduction furnace 101;

[0080] And / or, before cooling the second reduction exhaust gas output from the second reduction furnace 102 in the second exhaust gas heat exchanger 32, the method may further include: first cooling the second reduction exhaust gas output from the second reduction furnace 102 in the third casing 203 using the cold energy of the second circulating water from the fourth casing 204, and allowing the second reduction exhaust gas after cooling by the third casing 203 to enter the second exhaust gas heat exchanger 32, and allowing the second circulating water whose cold energy has been utilized by the third casing 203 to enter the second reduction furnace 102.

[0081] In this embodiment, the first sleeve 201, the second sleeve 202, the third sleeve 203, and the fourth sleeve 204 all include an inner layer tube 21 and an outer layer tube 22, and the outer layer tube 22 is sleeved on the outside of the inner layer tube 21, wherein the corresponding first reduction exhaust gas / second reduction exhaust gas flows in the inner layer tube 21, and the corresponding first circulating water / second circulating water flows in the outer layer tube 22.

[0082] In some embodiments, Figure 1 As shown, the method may further include: passing the first feed gas whose cooling capacity has been utilized by the first tail gas heat exchanger 31 into the first reduction furnace 101 ; passing the second feed gas whose cooling capacity has been utilized by the second tail gas heat exchanger 32 into the second reduction furnace 102 .

[0083] That is to say, in the present method, the first reduction furnace 101 and the second reduction furnace 102 can be cross-operated (i.e., after the first feed gas absorbs the waste heat of the first reduction tail gas generated by the first reduction furnace 101, all or part of it enters the second reduction furnace 102, and after the second feed gas absorbs the waste heat of the second reduction tail gas generated by the second reduction furnace 102, all or part of it enters the first reduction furnace 101) to produce polycrystalline silicon, and can also be operated separately (i.e., after the first feed gas absorbs the waste heat of the first reduction tail gas generated by the first reduction furnace 101, all of it enters the first reduction furnace 101, and after the second feed gas absorbs the waste heat of the second reduction tail gas generated by the second reduction furnace 102, all of it enters the second reduction furnace 102) to produce polycrystalline silicon. Compared with the prior art in which each reduction furnace can only operate separately, the present method can adjust the temperature of the feed gas entering the reduction furnace according to the operating stage of each reduction furnace, to ensure that the feed gas temperature entering the reduction furnaces at different operating stages can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace at that stage.

[0084] In some embodiments, the method further includes: real-time monitoring of the temperature of the feed gas before entering the first reduction furnace 101; real-time monitoring of the temperature of the feed gas before entering the second reduction furnace 102, so as to adjust the temperature of the feed gas before entering each reduction furnace, and ensure that the feed gas can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace after entering the reduction furnace, with stronger adjustability, which is conducive to achieving refined control.

[0085] Specifically, by setting the first control valve 71, a part of the first feed gas after the cooling capacity has been utilized by the first Liebig condenser 501 is passed into the first tail gas heat exchanger 31 for heat exchange with the first reducing tail gas from the first sleeve 201, and this part of the first feed gas absorbs the waste heat of the first reducing tail gas and then heats up, and the other part does not pass through the first tail gas heat exchanger 31 but is directly mixed with the first feed gas output after heat exchange in the first tail gas heat exchanger 31, and the ratio of these two parts of the first feed gas is controlled by adjusting the first control valve 71 to adjust the temperature of the first feed gas before entering the second reduction furnace 102 or the first reduction furnace 101; similarly, by setting the fourth control valve 81, a part of the second feed gas after the cooling capacity has been utilized by the second Liebig condenser 502 is passed into the second tail gas heat exchanger 32 for heat exchange with the second reducing tail gas from the third sleeve 203, and this part of the second feed gas absorbs the waste heat of the second reducing tail gas and then heats up. The temperature of the second feed gas before entering the first reduction furnace 101 or the second reduction furnace 102 is adjusted by adjusting the ratio of the two parts of the second feed gas by adjusting the fourth control valve 81. In addition, the ratio of the first feed gas and the second feed gas entering the first reduction furnace 101 and the ratio of the first feed gas and the second feed gas entering the second reduction furnace 102 can be adjusted by setting the first control component and the second control component, so as to adjust the temperature of the feed gas entering each reduction furnace, ensure that the temperature of the feed gas entering the reduction furnace at different operating stages can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace at this stage, so that each reduction furnace maintains a relatively high deposition rate in each operating stage, thereby maintaining the conversion rate at each operating stage at a high level.

[0086] The method for utilizing the waste heat of polysilicon reduction tail gas of the present embodiment is to cool the reduction tail gas output by each reduction furnace through a casing (including a first casing 201, a second casing 202, a third casing 203, and a fourth casing 204), a tail gas heat exchanger (including a first tail gas heat exchanger 31, a second tail gas heat exchanger 32), and a Liebig condenser (including a first Liebig condenser 501, a second Liebig condenser 502), so that the feed gas absorbs the waste heat of the hot reduction tail gas and the temperature is increased. In addition, according to the operation stage of each reduction furnace, the temperature of the feed gas before entering each reduction furnace can be controlled by performing cross-operation, single operation, or a combination of cross-operation and single operation on each reduction furnace. The degree is adjusted to ensure that the feed gas can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace, that is, the waste heat of the reduction tail gas is recycled, so that each reduction furnace maintains a relatively high deposition rate at different production times and different growth states (that is, each operation stage), improves the level of refined control, and thus keeps the conversion rate at a high level at each operation stage, avoids appearance problems of polysilicon products, and achieves the purpose of reducing the unit electricity consumption of polysilicon production; at the same time, the temperature of the reduction tail gas after cooling treatment is greatly reduced, which not only avoids large heat load fluctuations in subsequent tail gas treatment, but also reduces the cooling load of the downstream reduction tail gas recovery process of the reduction furnace, and reduces the production cost of the downstream reduction tail gas recovery process.

[0087] Example 2

[0088] like Figure 1 As shown, this embodiment discloses a polysilicon reduction tail gas waste heat utilization system, including a first reduction furnace 101, a first heat exchange unit, a second reduction furnace 102, and a second heat exchange unit, the first heat exchange unit includes a first tail gas heat exchanger 31, and the second heat exchange unit includes a second tail gas heat exchanger 32, wherein:

[0089] The first reduction furnace 101 and the second reduction furnace 102 are both used for performing vapor deposition reaction to produce polysilicon, the first reduction furnace 101 outputs a first reduction tail gas, and the second reduction furnace 102 outputs a second reduction tail gas;

[0090] The first tail gas heat exchanger 31 is connected to the first reduction furnace 101, and is used to cool the first reduction tail gas from the first reduction furnace 101 using the cold energy of the first feed gas, and can pass the first feed gas into the first reduction furnace. The first tail gas heat exchanger 31 is also connected to the second reduction furnace 102, and is used to pass the first feed gas after the cold energy has been used by the first tail gas heat exchanger 31 into the second reduction furnace 102;

[0091] The second exhaust gas heat exchanger 32 is connected to the second reduction furnace 102, and is used to utilize the cold energy of the second feed gas to cool the second reduction exhaust gas from the second reduction furnace 102. The second exhaust gas heat exchanger 32 is also connected to the first reduction furnace 101, and is used to pass the second feed gas after its cold energy has been utilized by the second exhaust gas heat exchanger 32 into the first reduction furnace 101.

[0092] It should be noted that the first exhaust gas heat exchanger 31 is also connected to the first reduction furnace 101, and can be used to pass the first feed gas after the cooling energy has been utilized by the first exhaust gas heat exchanger 31 into the first reduction furnace 101; and / or, the second exhaust gas heat exchanger 32 is also connected to the second reduction furnace 102, and can be used to pass the second feed gas after the cooling energy has been utilized by the second exhaust gas heat exchanger 32 into the second reduction furnace 102.

[0093] In this embodiment, the first reduction furnace 101 and the second reduction furnace 102 can be cross-operated (i.e., after the first feed gas absorbs the waste heat of the first reduction exhaust gas generated by the first reduction furnace 101, it can enter the second reduction furnace 102 in whole or in part, and after the second feed gas absorbs the waste heat of the second reduction exhaust gas generated by the second reduction furnace 102, it can enter the first reduction furnace 101 in whole or in part) to produce polycrystalline silicon, and can also be operated separately (i.e., after the first feed gas absorbs the waste heat of the first reduction exhaust gas generated by the first reduction furnace 101, it can enter the first reduction furnace 101 in whole, and after the second feed gas absorbs the waste heat of the second reduction exhaust gas generated by the second reduction furnace 102, it can enter the second reduction furnace 102 in whole) to produce polycrystalline silicon. In addition, since the temperature of the reduction tail gas output by the reduction furnaces at different operation stages is different, the temperature of the first feed gas and the second feed gas after the waste heat recovery is also different. Therefore, the ratio of the first feed gas and the second feed gas in the feed gas entering the reduction furnace can be adjusted according to the operation stage of each reduction furnace, so as to ensure that the temperature of the feed gas entering each reduction furnace can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace at this stage. Compared with the prior art in which each reduction furnace can only operate independently, this system has stronger adjustability and can achieve refined control.

[0094] In this embodiment, Figure 1 As shown, the first tail gas heat exchanger 31 and the second tail gas heat exchanger 32 can both be shell and tube heat exchangers, the first feed gas / the second feed gas respectively enter the shell side of the corresponding first tail gas heat exchanger 31 / the second tail gas heat exchanger 32, and the first reduction gas / the second reduction gas respectively enter the tube side of the corresponding first tail gas heat exchanger 31 / the second tail gas heat exchanger 32. The first reduction tail gas output by the first reduction furnace 101 and the second reduction tail gas output by the second reduction furnace 102 are both mixed gases including hydrogen, hydrogen chloride and chlorosilane, wherein the chlorosilane includes a mixed gas of trichlorosilane, silicon tetrachloride and dichlorosilane.

[0095] In some embodiments, the first heat exchange unit further includes a first Liebig condenser 501, and / or the second heat exchange unit further includes a second Liebig condenser 502, wherein:

[0096] The first Liebig condenser 501 is connected to the first tail gas heat exchanger 31, and is used to use the cold energy of the first feed gas and the first circulating water to cool the first reduced tail gas from the first tail gas heat exchanger 31 again, and pass the first feed gas whose cold energy has been used by the first Liebig condenser 501 into the first tail gas heat exchanger 31, and pass the first circulating water whose cold energy has been used by the first Liebig condenser 501 into the first reduction furnace 101;

[0097] The second Liebig condenser 502 is connected to the second exhaust gas heat exchanger 32, and is used for utilizing the cold energy of the second feed gas and the second circulating water to cool the second reduced exhaust gas from the second exhaust gas heat exchanger 32 again, and passing the second feed gas whose cold energy has been utilized by the second Liebig condenser 502 into the second exhaust gas heat exchanger 32, and passing the second circulating water whose cold energy has been utilized by the second Liebig condenser 502 into the second reduction furnace 102.

[0098] In this embodiment, Figure 1 As shown, the first Liebig condenser 501 and the second Liebig condenser 502 both include an inner straight tube 51, an outer sleeve 52, and an inner coil 53, and the inner coil 53 is coiled outside the inner straight tube 51, and the outer sleeve 52 is sleeved on the outside of the inner straight tube 51 and the inner coil 53, wherein the inner straight tube 51 is used to circulate the first reduction tail gas / second reduction tail gas from the static mixer (not shown in the figure), the corresponding first feed gas / second feed gas circulates in the inner coil 53, and the outer sleeve 52 is used to circulate the first circulating water / second circulating water from the circulating water system (not shown in the figure).

[0099] In some embodiments, the first heat exchange unit further includes a second casing 202, and / or the second heat exchange unit further includes a fourth casing 204, wherein:

[0100] The second sleeve 202 is connected to the first Liebig condenser 501 and the first tail gas heat exchanger 31, and is used to use the cold energy of the first circulating water from the first Liebig condenser 501 to cool the first reduced tail gas from the first tail gas heat exchanger 31 again, and pass the first reduced tail gas cooled by the second sleeve 202 into the first Liebig condenser 501, and pass the first circulating water whose cold energy has been used by the second sleeve 202 into the first reduction furnace 101;

[0101] The fourth sleeve 204 is connected to the second Liebig condenser 502 and the second exhaust gas heat exchanger 32, and is used to use the cold energy of the second circulating water from the second Liebig condenser 502 to cool the second reduced exhaust gas from the second exhaust heat exchanger 32 again, and pass the second reduced exhaust gas cooled by the fourth sleeve 204 into the second Liebig condenser 502, and pass the second circulating water whose cold energy has been used by the fourth sleeve 204 into the second reduction furnace 102.

[0102] In some embodiments, the first heat exchange unit further includes a first sleeve 201, and / or the second heat exchange unit further includes a third sleeve 203, wherein:

[0103] The first sleeve 201 is connected to the second sleeve 202 and the first reduction furnace 101, and is used to use the cold energy of the first circulating water from the second sleeve 202 to first cool the first reduction tail gas output from the first reduction furnace 101, and pass the first circulating water whose cold energy has been used by the first sleeve 201 into the first reduction furnace 101. The first sleeve 201 is also connected to the first tail gas heat exchanger 31, and is used to pass the first reduction tail gas cooled by the first sleeve 201 into the first tail gas heat exchanger 31;

[0104] The third sleeve 203 is connected to the fourth sleeve 204 and the second reduction furnace 102, and is used to use the cold energy of the second circulating water from the fourth sleeve 204 to first cool the second reduction exhaust gas output from the second reduction furnace 102, and pass the second circulating water whose cold energy has been used by the fourth sleeve 204 into the second reduction furnace 102. The third sleeve 203 is also connected to the second exhaust gas heat exchanger 32, and is used to pass the second reduction exhaust gas cooled by the third sleeve 203 into the second exhaust gas heat exchanger 32.

[0105] In this embodiment, Figure 1 As shown, the first sleeve 201, the second sleeve 202, the third sleeve 203, and the fourth sleeve 204 all include an inner tube 21 and an outer tube 22, and the outer tube 22 is sleeved on the outside of the inner tube 21, wherein the inner tube 21 is used to circulate the corresponding first reduction exhaust gas / second reduction exhaust gas, and the outer tube 22 is used to circulate the corresponding first circulating water / second circulating water.

[0106] In some embodiments, the system further includes a first control component and a second control component, the first control component being connected to the first exhaust gas heat exchanger 31 and the first reduction furnace 101, the second control component being connected to the second exhaust gas heat exchanger 32 and the second reduction furnace 102, and the second control component being also connected to the first control component, the first control component being used to distribute the first feed gas after the cooling energy has been utilized by the first exhaust gas heat exchanger 31 to the first reduction furnace 101 and the second reduction furnace 102, the second control component being used to distribute the second feed gas after the cooling energy has been utilized by the second exhaust gas heat exchanger 32 to the second reduction furnace 102 and the first reduction furnace 101.

[0107] Specifically, the first control component includes a second control valve 72 and a third control valve 73, and the second control component includes a fifth control valve 82 and a sixth control valve 83, wherein: the second control valve 72 is connected in series with the third control valve 73, the second control valve 72 is also connected to the first reduction furnace 101, and the third control valve 73 is also connected to the first exhaust gas heat exchanger 31; the fifth control valve 82 is connected in series with the sixth control valve 83, the fifth control valve 82 is connected to the second reduction furnace 102, the sixth control valve 83 is also connected to the second exhaust gas heat exchanger 32, and the fifth control valve 82 is also connected to the third control valve 73, and the sixth control valve 83 is also connected to the second control valve 72. By adjusting and coordinating the second control valve 72, the third control valve 73, the fifth control valve 82, and the sixth control valve 83, the ratio of the first feed gas to the second feed gas entering the first reduction furnace 101 can be adjusted, and the ratio of the first feed gas to the second feed gas entering the second reduction furnace 102 can be adjusted, thereby adjusting the temperature of the feed gas entering each reduction furnace, ensuring that the temperature of the feed gas entering the reduction furnace at different operating stages can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace at this stage, so that each reduction furnace maintains a relatively high deposition rate at each operating stage, thereby maintaining the conversion rate at each operating stage at a high level. In this embodiment, the second control valve 72, the third control valve 73, the fifth control valve 82, and the sixth control valve 83 are all three-way valves.

[0108] In some embodiments, the system also includes a first control valve 71 and a fourth control valve 81, wherein: the first control valve 71 is connected to the first Liebig condenser 501 and the cold source inlet of the first exhaust heat exchanger 31, and is also connected to the cold source outlet of the first exhaust heat exchanger 31, and is used to adjust the amount of the first feed gas introduced into the first exhaust heat exchanger 31 and the cold energy has been utilized by the first Liebig condenser 501; the fourth control valve 81 is connected to the second Liebig condenser 502 and the cold source inlet of the second exhaust heat exchanger 32, and is also connected to the cold source outlet of the second exhaust heat exchanger 32, and is used to adjust the amount of the second feed gas introduced into the second exhaust heat exchanger 32 and the cold energy has been utilized by the second Liebig condenser 502.

[0109] Specifically, by adjusting the first control valve 71, a portion of the first feed gas after the cooling capacity has been utilized by the first Liebig condenser 501 is introduced into the first tail gas heat exchanger 31 to exchange heat with the first reduction tail gas from the first sleeve 201. This portion of the first feed gas absorbs the waste heat of the first reduction tail gas and heats up. The other portion does not pass through the first tail gas heat exchanger 31 but is directly mixed with the first feed gas output after heat exchange in the first tail gas heat exchanger 31. The first control valve 71 is adjusted to control the ratio of the two portions of the first feed gas to adjust the temperature of the first feed gas before entering the second reduction furnace 102 or the first reduction furnace 101. Similarly, by adjusting the fourth control valve 81, a portion of the second feed gas whose coldness has been utilized by the second Liebig condenser 502 is passed into the second tail gas heat exchanger 32 to exchange heat with the second reduction tail gas from the third sleeve 203. This portion of the second feed gas absorbs the waste heat of the second reduction tail gas and heats up, and the other portion does not pass through the second tail gas heat exchanger 32 but directly mixes with the second feed gas output after heat exchange in the second tail gas heat exchanger 32. The ratio of these two portions of the second feed gas is controlled by adjusting the fourth control valve 81 to adjust the temperature of the second feed gas before entering the first reduction furnace 101 or the second reduction furnace 102. In this embodiment, the first control valve 71 and the fourth control valve 81 are both three-way valves.

[0110] It should be noted that the first control valve 71, the second control valve 72, the third control valve 73, the fourth control valve 81, the fifth control valve 82, and the sixth control valve 83 can be controlled manually or automatically. In this embodiment, automatic control is preferred, which is conducive to realizing automatic operation and reducing labor costs. In addition, in actual production, the various heat exchange cooling devices used for cooling the reduction tail gas can be appropriately centrally arranged to reduce the length of the pipelines between the heat exchange cooling devices, and only switch through valves.

[0111] In some embodiments, the system further includes a temperature measuring instrument for real-time monitoring of the temperature of the feed gas (which may be the first feed gas, the second feed gas, or a mixture of the first feed gas and the second feed gas) before the feed gas enters the reduction furnace. Specifically, the temperature measuring instrument includes a first temperature measuring instrument 61 and a second temperature measuring instrument 62, wherein the first temperature measuring instrument 61 is used to monitor in real time the temperature of the feed gas (which may be the first feed gas, the second feed gas, or a mixture of the first feed gas and the second feed gas) before entering the first reduction furnace 101; the second temperature measuring instrument 62 is used to monitor in real time the temperature of the feed gas (which may be the first feed gas, the second feed gas, or a mixture of the first feed gas and the second feed gas) before entering the second reduction furnace 102.

[0112] like Figure 1As shown, the following is an example of the different operating modes of the polysilicon reduction tail gas waste heat utilization system, as follows:

[0113] (1) Each reduction furnace operates independently

[0114] Feed gas route: The first feed gas from the static mixer first enters the first Liebig condenser 501 through the pipeline a11, and exchanges heat with the tail gas of the first reduction furnace 101 output from the first tail gas heat exchanger 31 in the first Liebig condenser 501. After the heat exchange, the first feed gas enters the pipeline a12, and enters the first tail gas heat exchanger 31 in whole or in part under the regulation of the first control valve 71, and exchanges heat with the first reduction gas from the first sleeve 201 in the first tail gas heat exchanger 31. The first feed gas after the heat exchange and the first feed gas that has not entered the first tail gas heat exchanger 31 are merged, and then, under the cooperation of the third control valve 73 and the second control valve 72, all enter the first reduction furnace 101 through the pipeline a13, and are used for silicon rod production in the first reduction furnace 101. long; similarly, the second feed gas from the static mixer first enters the second Liebig condenser 502 through the pipeline a21, exchanges heat with the second reduction furnace 102 tail gas output from the second tail gas heat exchanger 32 in the second Liebig condenser 502, and the second feed gas after heat exchange enters the pipeline a22, and enters the second tail gas heat exchanger 32 in whole or in part under the regulation of the fourth control valve 81, and exchanges heat with the second reduction gas from the third sleeve 203 in the second tail gas heat exchanger 32, the second feed gas after heat exchange and the second feed gas that has not entered the second tail gas heat exchanger 32 merge, and then, with the cooperation of the sixth control valve 83 and the fifth control valve 82, all enter the second reduction furnace 102 through the pipeline a23, and are used for the growth of silicon rods in the second reduction furnace 102.

[0115] Reduction tail gas route: the first reduction tail gas outputted from the first reduction furnace 101 first enters the first sleeve 201 for cooling, then successively enters the first tail gas heat exchanger 31 and the second sleeve 202 for cooling again, and finally after further cooling through the first Liebig condenser 501, the temperature of the tail gas of the first reduction furnace 101 outputted from the first Liebig condenser 501 is greatly reduced, and then enters the downstream process (such as the CDI process) through the pipeline c1; similarly, the second reduction tail gas outputted from the second reduction furnace 102 first enters the third sleeve 203 for cooling, then successively enters the second tail gas heat exchanger 32 and the fourth sleeve 204 for cooling again, and finally after further cooling through the second Liebig condenser 502, the temperature of the tail gas of the second reduction furnace 102 outputted from the second Liebig condenser 502 is greatly reduced, and then enters the downstream process (such as the CDI process) through the pipeline c2.

[0116] Circulating water route: The first circulating water from the circulating water system first enters the first Liebig condenser 501 through the pipeline b11, then passes through the second sleeve 202, enters the first sleeve 201 through the pipeline b12, and then enters the first reduction furnace 101 to cool the first reduction furnace 101. Specifically, the first circulating water first enters the chassis 11 of the first reduction furnace 101 to cool the chassis 11 of the first reduction furnace 101, then enters the furnace drum 12 of the first reduction furnace 101 to cool the furnace drum 12 of the first reduction furnace 101, and finally returns to the circulating water system. system; similarly, the second circulating water from the circulating water system first enters the second Liebig condenser 502 through the pipeline b21, then passes through the fourth sleeve 204, enters the third sleeve 203 through the pipeline b22, and then enters the second reduction furnace 102 to cool the second reduction furnace 102. Specifically, the second circulating water first enters the chassis 11 of the second reduction furnace 102 to cool the chassis 11 of the second reduction furnace 102, and then enters the furnace drum 12 of the second reduction furnace 102 to cool the furnace drum 12 of the second reduction furnace 102, and finally, returns to the circulating water system.

[0117] (2) Cross-operation of each reduction furnace

[0118] Compared with (1) when each reduction furnace operates independently, the difference is:

[0119] The first feed gas from the static mixer first passes through the first Liebig condenser 501, and exchanges heat with the first reduction furnace 101 tail gas output from the first tail gas heat exchanger 31 in the first Liebig condenser 501. The first feed gas after heat exchange enters the first tail gas heat exchanger 31 in whole or in part under the regulation of the first control valve 71, and exchanges heat with the first reduction gas from the first sleeve 201 in the first tail gas heat exchanger 31. The first feed gas after heat exchange and the first feed gas that has not entered the first tail gas heat exchanger 31 are merged. The merged first feed gas passes through the third control valve 73 and the fifth control valve 82 in turn, and is Under the guidance of the control valve 73 and the fifth control valve 82, the first feed gas after merging enters the second reduction furnace 102 (for example, the second reduction furnace 102 is in the middle and late stages of operation) for the growth of silicon rods in the second reduction furnace 102. In addition, before entering the second reduction furnace 102, the temperature of the feed gas (herein, the first feed gas after merging) in front of the second reduction furnace 102 is monitored in real time by the second temperature measuring instrument 62, and the proportion of the first feed gas entering the first tail gas heat exchanger 31 is adjusted by the first control valve 71, so as to achieve accurate control of the temperature of the feed gas entering the second reduction furnace 102.

[0120] Similarly, the second feed gas from the static mixer first passes through the second Liebig condenser 502, and exchanges heat with the second reduction furnace 102 tail gas output from the second tail gas heat exchanger 32 in the second Liebig condenser 502. The second feed gas after heat exchange enters the second tail gas heat exchanger 32 in whole or in part under the regulation of the fourth control valve 81, and exchanges heat with the second reduction gas from the third sleeve 203 in the second tail gas heat exchanger 32. The second feed gas after heat exchange and the second feed gas that has not entered the second tail gas heat exchanger 32 are merged. The merged second feed gas passes through the sixth control valve 83 and the second control valve 72 in turn, and then passes through the sixth control valve 83 and the second control valve 72. Under the coordinated guidance of the sixth control valve 83 and the second control valve 72, the merged second feed gas enters the first reduction furnace 101 (correspondingly, the first reduction furnace 101 is in the initial operation stage) for the growth of silicon rods in the first reduction furnace 101. In addition, before entering the first reduction furnace 101, the temperature of the feed gas in front of the first reduction furnace 101 (here refers to the merged first feed gas) is monitored in real time by the first temperature measuring instrument 61, and the proportion of the second feed gas entering the second exhaust gas heat exchanger 32 is adjusted by the fourth control valve 81, so as to achieve precise control of the temperature of the feed gas entering the first reduction furnace 101.

[0121] It should be noted that when the reduction furnaces are operated crosswise, the operation mode of the reduction furnaces may be different from the above-mentioned cross-operation mode of the reduction furnaces in that:

[0122] Under the guidance of the third control valve 73 and the fifth control valve 82, a part of the merged first feed gas enters the second reduction furnace 102. At the same time, under the guidance of the sixth control valve 83 and the fifth control valve 82, a part of the merged second feed gas enters the second reduction furnace 102, that is, a part of the merged first feed gas and a part of the merged second feed gas are simultaneously used for the growth of silicon rods in the second reduction furnace 102, and, before entering the second reduction furnace 102, the temperature of the feed gas in front of the second reduction furnace 102 (here, it refers to a mixed gas of a part of the merged first feed gas and a part of the merged second feed gas) is monitored in real time by the second temperature measuring instrument 62, and the proportion of the first feed gas entering the first tail gas heat exchanger 31 through the first control valve 71, and / or the proportion of the second feed gas entering the second tail gas heat exchanger 32 is adjusted by the fourth control valve 81, so as to achieve accurate control of the temperature of the feed gas entering the second reduction furnace 102;

[0123] Similarly, under the coordinated guidance of the sixth control valve 83 and the second control valve 72, another part of the merged second feed gas enters the first reduction furnace 101. At the same time, under the coordinated guidance of the third control valve 73 and the second control valve 72, another part of the merged first feed gas enters the first reduction furnace 101, that is, another part of the merged second feed gas and another part of the merged first feed gas are simultaneously used for the growth of silicon rods in the first reduction furnace 101, and, before entering the first reduction furnace 101, the temperature of the feed gas in front of the first reduction furnace 101 (here refers to the mixed gas of the other part of the merged first feed gas and the other part of the merged second feed gas) is monitored in real time by the first temperature measuring instrument 61, and the proportion of the second feed gas entering the second exhaust gas heat exchanger 32 is adjusted by the fourth control valve 81, and / or the proportion of the first feed gas entering the first exhaust gas heat exchanger 31 is adjusted by the first control valve 71, so as to achieve precise control of the temperature of the feed gas entering the first reduction furnace 101.

[0124] (3) Cross-operation + individual operation of each reduction furnace

[0125] Considering that each reduction furnace is operated independently, taking the first reduction furnace 101 as an example, at the initial stage of operation of the first reduction furnace 101, the gas phase temperature in the first reduction furnace 101 is low, the temperature of the output first reduction tail gas is low, and the first feed gas absorbs limited residual heat from the first reduction tail gas. The first feed gas entering the first reduction furnace 101 cannot provide a sufficient gas phase temperature field for the growth of silicon rods at the initial stage of operation of the first reduction furnace 101, resulting in a relatively low initial deposition rate. At this time, the feed gas temperature of the first reduction furnace 101 at the initial stage of operation should be increased as much as possible, so that the silicon rods in the first reduction furnace 101 can quickly reach the optimal deposition rate, thereby improving the conversion rate and realizing the operation of the reduction furnace. The initial power consumption is reduced; and in the middle and late stages of the operation of the first reduction furnace 101, the first feed gas has sufficient waste heat recovery from the first reduction tail gas, and the first feed gas entering the first reduction furnace 101 can provide a sufficient gas phase temperature field for the growth of silicon rods in the middle and late stages of the operation of the first reduction furnace 101, and can maintain a better silicon rod deposition rate when operated alone, and even the feed gas after recovering its own waste heat exceeds the gas phase temperature field required for the growth of silicon rods in the middle and late stages of the operation of the first reduction furnace 101, thereby causing atomization in the furnace. At this time, the feed gas temperature of the first reduction furnace 101 in the middle and late stages of the operation should be appropriately lowered, and the reduction furnace in the middle and late stages of the operation can be cross-operated with the reduction furnace in the early stages of the operation.

[0126] Therefore, the system optimizes the operation mode of each reduction furnace. For example, the first reduction furnace 101 and the second reduction furnace 102 are operated alternately for a period of time, and then they are operated separately, as follows:

[0127] At this time, the start-up interval time of the two furnaces is ≥20h. For example, the first reduction furnace 101 is in the initial stage of operation (such as running for 15-30h), and the second reduction furnace 102 is in the middle and late stages (such as running for 60-100h). The intake amount of the second feed gas is appropriately increased. At the same time, according to the temperature of the feed gas (second feed gas) in front of the second reduction furnace 102 monitored in real time by the second temperature measuring instrument 62, the ratio of the second feed gas entering the second tail gas heat exchanger 32 and the second feed gas not entering the second tail gas heat exchanger 32 (that is, the second feed gas in the bypass connected in parallel with the second tail gas heat exchanger 32) is adjusted through the fourth control valve 81 to ensure that the temperature of the feed gas entering the second reduction furnace 102 remains basically unchanged, that is, the second reduction furnace 102 is maintained at the optimal feed temperature; most of the second feed gas is introduced into the second reduction furnace 102 itself through the fifth control valve 82, and a small part of the second feed gas is introduced into the first stage of operation through the sixth control valve 83 through the fifth control valve 82. The first reduction furnace 101 ensures that the feed gas of the first reduction furnace 101 is maintained at an optimal feed temperature, and gradually increases the amount of the first feed gas entering the first Liebig condenser 501 from zero, and then all the first feed gas output from the first Liebig condenser 501 is passed into the first tail gas heat exchanger 31 through the first control valve 71 for heat exchange with the first reduction tail gas output from the first reduction furnace 101. As the operating time of the first reduction furnace 101 increases, the temperature of the first feed gas output after heat exchange in the first tail gas heat exchanger 31 gradually increases, increasing the amount of the first feed gas entering the first Liebig condenser 501, and gradually increasing the amount of the first feed gas output after heat exchange in the first tail gas heat exchanger 31 entering the first reduction furnace 101 and gradually reducing the amount of the second feed gas entering the first reduction furnace 101, until the second feed gas entering the first reduction furnace 101 is completely closed, that is, the first reduction furnace 101 and the second reduction furnace 102 are changed from cross operation to separate operation.

[0128] The polysilicon reduction tail gas waste heat utilization system of the present embodiment can make the feed gas absorb the waste heat of the hot reduction tail gas and increase the temperature by cooling the reduction tail gas output by each reduction furnace in the casing (including the first casing 201, the second casing 202, the third casing 203, and the fourth casing 204), the tail gas heat exchanger (including the first tail gas heat exchanger 31, the second tail gas heat exchanger 32), and the Liebig condenser (including the first Liebig condenser 501, the second Liebig condenser 502). In addition, the operation mode is diverse and the temperature is highly adjustable. According to the operation stage of each reduction furnace, the reduction furnaces can be cross-operated, operated separately, or a combination of cross-operation and separate operation to adjust the temperature of the feed gas entering each reduction furnace. The temperature of the feed gas in front of the furnace is adjusted to ensure that the feed gas can provide a suitable gas phase temperature field for the growth of silicon rods in the reduction furnace, that is, the waste heat of the reduction tail gas is recycled, so that each reduction furnace maintains a relatively high deposition rate at different production times and different growth states (that is, each operation stage), and improves the level of refined control, so that the conversion rate of each operation stage is always maintained at a high level, avoiding appearance problems of polysilicon products and achieving the purpose of reducing the unit electricity consumption of polysilicon production; at the same time, the temperature of the reduction tail gas after cooling treatment is greatly reduced, which not only avoids large heat load fluctuations in subsequent tail gas treatment, but also reduces the cooling load of the downstream reduction tail gas recovery process of the reduction furnace, and reduces the production cost of the downstream reduction tail gas recovery process.

[0129] Example 3

[0130] This embodiment discloses a polysilicon reduction tail gas waste heat utilization system, the principle of which is the same as that of the polysilicon reduction tail gas waste heat utilization system in Example 2, and the difference from the polysilicon reduction tail gas waste heat utilization system in Example 2 is:

[0131] At the same time, more than three reduction furnaces are connected and combined, and any two reduction furnaces are connected in the same manner as the first reduction furnace and the second reduction furnace in Example 2, which will not be repeated here.

[0132] Specifically, taking the polysilicon reduction exhaust gas waste heat utilization system formed by connecting three reduction furnaces as an example, this system includes a first reduction furnace, a second reduction furnace, and a third reduction furnace. In addition to exchanging heat with the feed gas of its own reduction furnace, the reduction exhaust gas of the first reduction furnace can also exchange heat with the feed gas of the second reduction furnace, the reduction exhaust gas of the second reduction furnace can exchange heat with the feed gas of the third reduction furnace, and the reduction exhaust gas of the third reduction furnace can exchange heat with the feed gas of the first reduction furnace. When the system is running, during the heat exchange process, at least one of the reduction furnace providing the reduction exhaust gas and the reduction furnace providing the feed gas is in the early stage of operation and the other is in the middle and late stages of operation.

[0133] It is to be understood that the above is only a preferred embodiment of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered as the protection scope of the present invention.

Claims

1. A method for utilizing waste heat from polysilicon reduction tail gas, comprising: Combining and connecting two or more reduction furnaces into a polysilicon reduction tail gas waste heat utilization system; In the first tail gas heat exchanger (31), the first reduction tail gas from the first reduction furnace (101) is cooled by using the cold energy of the first feed gas, the first feed gas absorbs the heat of the first reduction tail gas, and its own temperature is increased, and the first feed gas whose cold energy has been used by the first tail gas heat exchanger enters the second reduction furnace (102), and after the first feed gas with increased temperature enters the second reduction furnace, the reaction temperature in the second reduction furnace is increased; In the second tail gas heat exchanger (32), the second reduction tail gas from the second reduction furnace (102) is cooled by using the cold energy of the second feed gas, the second feed gas absorbs the heat of the second reduction tail gas, and its own temperature is increased, and the second feed gas whose cold energy has been used by the second tail gas heat exchanger enters the first reduction furnace (101), and after the second feed gas with increased temperature enters the first reduction furnace, the reaction temperature in the first reduction furnace is increased; The first reduction furnace is in an initial stage of operation, and the second reduction furnace is in a middle or late stage of operation, or the second reduction furnace is in an initial stage of operation, and the first reduction furnace is in a middle or late stage of operation.

2. The method for utilizing waste heat from polysilicon reduction tail gas according to claim 1, characterized in that: Before cooling the first reduced tail gas output from the first reduction furnace in the first tail gas heat exchanger, the method further includes: In the first Liebig condenser (501), the first reduced tail gas from the first tail gas heat exchanger is cooled again by using the cold energy of the first feed gas and the first circulating water, and the first feed gas whose cold energy has been used by the first Liebig condenser enters the first tail gas heat exchanger, and the first circulating water whose cold energy has been used by the first Liebig condenser enters the first reduction furnace; And / or, before cooling the second reduced tail gas output from the second reduction furnace in the second tail gas heat exchanger, the method further comprises: In the second Liebig condenser (502), the second reduction exhaust gas from the second exhaust gas heat exchanger is cooled again using the cold energy of the second feed gas and the second circulating water, and the second feed gas whose cold energy has been used by the second Liebig condenser enters the second exhaust gas heat exchanger, and the second circulating water whose cold energy has been used by the second Liebig condenser enters the second reduction furnace.

3. The method for utilizing waste heat from polysilicon reduction tail gas according to claim 2, characterized in that: After cooling the first reduced tail gas outputted from the first reduction furnace in the first tail gas heat exchanger and before cooling the first reduced tail gas from the first tail gas heat exchanger again in the first Liebig condenser, the method further includes: In the second tube (202), the first reduced tail gas from the first tail gas heat exchanger is cooled again using the cold energy of the first circulating water from the first Liebig condenser, and the first reduced tail gas after cooling in the second tube enters the first Liebig condenser, and the first circulating water after the cold energy has been used in the second tube enters the first reduction furnace; And / or, after cooling the second reduced tail gas output from the second reduction furnace in the second tail gas heat exchanger and before cooling the second reduced tail gas from the second tail gas heat exchanger again in the second Liebig condenser, the method further includes: In the fourth tube (204), the second reducing exhaust gas from the second exhaust gas heat exchanger is cooled again using the cold energy of the second circulating water from the second Liebig condenser, and the second reducing exhaust gas cooled by the fourth tube enters the second Liebig condenser, and the first circulating water whose cold energy has been utilized by the fourth tube enters the second reduction furnace.

4. The method for utilizing waste heat from polysilicon reduction tail gas according to claim 3, characterized in that: Before cooling the first reduced tail gas output from the first reduction furnace in the first tail gas heat exchanger, the method further includes: In the first casing (201), the first reduction tail gas output from the first reduction furnace is first cooled using the cold energy of the first circulating water from the second casing, and the first reduction tail gas cooled by the first casing enters the first tail gas heat exchanger, and the first circulating water whose cold energy has been used by the first casing enters the first reduction furnace; And / or, before cooling the second reduced tail gas output from the second reduction furnace in the second tail gas heat exchanger, the method further comprises: In the third casing (203), the second reduction exhaust gas output from the second reduction furnace is first cooled using the cold energy of the second circulating water from the fourth casing, and the second reduction exhaust gas cooled by the third casing enters the second exhaust gas heat exchanger, and the second circulating water whose cold energy has been utilized by the third casing enters the second reduction furnace.

5. The method for utilizing waste heat from polysilicon reduction tail gas according to any one of claims 1 to 4, characterized in that: The start-up interval between the first reduction furnace and the second reduction furnace is ≥20h.

6. The method for utilizing waste heat from polysilicon reduction tail gas according to any one of claims 1 to 4, characterized in that: Also includes: The first feed gas after the cooling capacity has been utilized by the first tail gas heat exchanger enters the first reduction furnace; The second feed gas after its cooling capacity has been utilized by the second tail gas heat exchanger enters the second reduction furnace.

7. The method for utilizing waste heat from polysilicon reduction tail gas according to any one of claims 1 to 4, characterized in that: Also includes: Real-time monitoring of the temperature of the feed gas before entering the first reduction furnace; Monitor the temperature of the feed gas before entering the second reduction furnace in real time.

8. A polysilicon reduction tail gas waste heat utilization system, characterized in that: The invention comprises a first reduction furnace (101), a first heat exchange unit, a second reduction furnace (102), and a second heat exchange unit, wherein the first heat exchange unit comprises a first tail gas heat exchanger (31), and the second heat exchange unit comprises a second tail gas heat exchanger (32); the first reduction furnace and the second reduction furnace are both used for performing a vapor deposition reaction to produce polysilicon; the first reduction furnace outputs a first reduction tail gas, and the second reduction furnace outputs a second reduction tail gas; The first tail gas heat exchanger (31) is connected to the first reduction furnace (101) and is used to utilize the cold energy of the first feed gas to cool the first reduction tail gas from the first reduction furnace. The first feed gas absorbs the heat of the first reduction tail gas, and its own temperature increases. The first feed gas can be introduced into the first reduction furnace. The first tail gas heat exchanger (31) is also connected to the second reduction furnace (102) and can be used to pass the first feed gas after the cooling energy has been utilized by the first tail gas heat exchanger into the second reduction furnace. After the first feed gas with increased temperature enters the second reduction furnace, the reaction temperature in the second reduction furnace is increased. The second tail gas heat exchanger (32) is connected to the second reduction furnace (102) and is used to utilize the coldness of the second feed gas to cool the second reduction tail gas from the second reduction furnace. The second feed gas absorbs the heat of the second reduction tail gas, and its own temperature increases. The second feed gas can be introduced into the second reduction furnace. The second tail gas heat exchanger (32) is also connected to the first reduction furnace (101) and can be used to pass the second feed gas after the cooling capacity has been utilized by the second tail gas heat exchanger into the first reduction furnace. After the second feed gas with increased temperature enters the first reduction furnace, the reaction temperature in the first reduction furnace is increased; The first reduction furnace is in an initial stage of operation, and the second reduction furnace is in a middle or late stage of operation, or the second reduction furnace is in an initial stage of operation, and the first reduction furnace is in a middle or late stage of operation.

9. The polysilicon reduction tail gas waste heat utilization system according to claim 8, characterized in that: The first heat exchange unit further comprises a first Liebig condenser (501), and / or the second heat exchange unit further comprises a second Liebig condenser (502), wherein: The first Liebig condenser is connected to the first tail gas heat exchanger (31) and is used to use the cold energy of the first feed gas and the first circulating water to cool the first reduced tail gas from the first tail gas heat exchanger again, and to pass the first feed gas whose cold energy has been used by the first Liebig condenser into the first tail gas heat exchanger, and to pass the first circulating water whose cold energy has been used by the first Liebig condenser into the first reduction furnace (101); The second Liebig condenser is connected to the second tail gas heat exchanger (32) and is used to utilize the cold energy of the second feed gas and the second circulating water to cool the second reduced tail gas from the second tail gas heat exchanger again, and to pass the second feed gas whose cold energy has been utilized by the second Liebig condenser into the second tail gas heat exchanger, and to pass the second circulating water whose cold energy has been utilized by the second Liebig condenser into the second reduction furnace (102).

10. The polysilicon reduction tail gas waste heat utilization system according to claim 9, characterized in that: The first heat exchange unit further includes a second casing (202), and / or the second heat exchange unit further includes a fourth casing (204), wherein: The second sleeve is connected to the first Liebig condenser (501) and the first tail gas heat exchanger (31), and is used to utilize the cold energy of the first circulating water from the first Liebig condenser to cool the first reduced tail gas from the first tail gas heat exchanger again, and to pass the first reduced tail gas cooled by the second sleeve into the first Liebig condenser, and to pass the first circulating water whose cold energy has been utilized by the second sleeve into the first reduction furnace; The fourth sleeve is connected to the second Liebig condenser (502) and the second exhaust gas heat exchanger (32), and is used to utilize the cold energy of the second circulating water from the second Liebig condenser to cool the second reduced exhaust gas from the second exhaust heat exchanger again, and to pass the second reduced exhaust gas cooled by the fourth sleeve into the second Liebig condenser, and to pass the second circulating water whose cold energy has been utilized by the fourth sleeve into the second reduction furnace.

11. The polysilicon reduction tail gas waste heat utilization system according to claim 10, characterized in that: The first heat exchange unit further comprises a first casing (201), and / or the second heat exchange unit further comprises a third casing (203), wherein: The first sleeve is connected to the second sleeve (202) and the first reduction furnace (101) and is used to utilize the cold energy of the first circulating water from the second sleeve to first cool the first reduction tail gas output from the first reduction furnace, and to pass the first circulating water whose cold energy has been utilized by the first sleeve into the first reduction furnace; the first sleeve is also connected to the first tail gas heat exchanger (31) and is used to pass the first reduction tail gas cooled by the first sleeve into the first tail gas heat exchanger; The third sleeve is connected to the fourth sleeve (204) and the second reduction furnace (102), and is used to utilize the cold energy of the second circulating water from the fourth sleeve to first cool the second reduction exhaust gas output from the second reduction furnace, and then pass the second circulating water whose cold energy has been utilized by the fourth sleeve into the second reduction furnace. The third sleeve is also connected to the second exhaust gas heat exchanger (32), and is used to pass the second reduction exhaust gas cooled by the third sleeve into the second exhaust gas heat exchanger.

12. The polysilicon reduction tail gas waste heat utilization system according to any one of claims 9 to 11, characterized in that: It also includes a first control component and a second control component. The first control component is connected to the first tail gas heat exchanger (31) and the first reduction furnace (101). The second control component is connected to the second tail gas heat exchanger (32) and the second reduction furnace (102), and the second control component is also connected to the first control component. The first control component is used to distribute the first feed gas after the cooling capacity has been utilized by the first tail gas heat exchanger to the first reduction furnace and the second reduction furnace; The second control component is used to distribute the second feed gas after the cooling capacity has been utilized by the second tail gas heat exchanger to the second reduction furnace and the first reduction furnace.

13. The polysilicon reduction tail gas waste heat utilization system according to claim 12, characterized in that: It also includes a first control valve (71), a fourth control valve (81), The first control valve is connected to the first Liebig condenser (501) and the cold source inlet of the first tail gas heat exchanger (31), and is also connected to the cold source outlet of the first tail gas heat exchanger (31), and is used to adjust the amount of the first feed gas whose cold energy introduced into the first tail gas heat exchanger has been utilized by the first Liebig condenser; The fourth control valve is connected to the second Liebig condenser (502) and the cold source inlet of the second exhaust gas heat exchanger (32), and is also connected to the cold source outlet of the second exhaust gas heat exchanger (32), and is used to adjust the amount of the second feed gas that has been used by the second Liebig condenser after being introduced into the second exhaust gas heat exchanger.

14. The polysilicon reduction tail gas waste heat utilization system according to claim 12, characterized in that: It also includes a first temperature measuring instrument (61) and a second temperature measuring instrument (62). The first temperature measuring instrument is used to monitor in real time the temperature of the feed gas before entering the first reduction furnace (101); The second temperature measuring instrument is used to monitor in real time the temperature of the feed gas before entering the second reduction furnace (102).

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