CN217972614U

CN217972614U - Energy cascade utilization system in polycrystalline silicon production tail gas recovery process

Info

Publication number: CN217972614U
Application number: CN202222024697.9U
Authority: CN
Inventors: 刘建明; 王鹏; 马鑫
Original assignee: Ningxia Runyang Silicon Material Technology Co ltd
Current assignee: Ningxia Runyang Silicon Material Technology Co ltd
Priority date: 2022-08-02
Filing date: 2022-08-02
Publication date: 2022-12-06
Anticipated expiration: 2032-08-02

Abstract

The utility model relates to an energy cascade utilization system in polycrystalline silicon production tail gas recovery process, the hydrogen storage tank links to each other with the tube side import of first heat exchanger, the tube side export of first heat exchanger is linked together with the desorption import of active carbon adsorption column, the desorption export of active carbon adsorption column links to each other with the shell side import of first heat exchanger, the shell side export of first heat exchanger links to each other with the shell side import of second heat exchanger, the shell side export of second heat exchanger links to each other with the shell side import of third heat exchanger, the rich liquid export of absorption tower links to each other with the tube side import of third heat exchanger, the liquid phase export of third heat exchanger links to each other with the tube side import of second heat exchanger. The heat in the 164 ℃ hydrogen is fully recycled by two stages, the heat in the 164 ℃ hydrogen is avoided being wasted, meanwhile, the cold in the low-temperature chlorosilane rich liquid discharged by the absorption tower is directly utilized to cool the hydrogen after pre-cooling, the waste of the cold is avoided, and therefore the recycling cost can be reduced.

Description

Energy cascade utilization system in polycrystalline silicon production tail gas recovery process

Technical Field

The application relates to the technical field of polycrystalline silicon tail gas recovery, in particular to an energy gradient utilization system in a polycrystalline silicon production tail gas recovery process.

Background

The method improves the process of producing polysilicon by reducing trichlorosilane by using a Siemens method, the reaction conversion rate is about 10 percent, unreacted hydrogen, trichlorosilane, reaction by-products silicon tetrachloride and hydrogen chloride jointly form production tail gas, and the production tail gas enters a dry recovery system for separation and recovery. The traditional dry recovery system consists of three parts, namely condensation separation of chlorosilane, absorption desorption separation of hydrogen chloride and absorption purification recovery of hydrogen. The specific process comprises the steps of firstly pressurizing and condensing production tail gas to recover liquid chlorosilane, then separating and recovering most of hydrogen chloride in non-condensable gas in a low-temperature chlorosilane absorption-high-temperature desorption mode, then adsorbing a small amount of chlorosilane, hydrogen chloride and other impurities in the noncondensable gas through activated carbon, returning most of the recovered hydrogen after adsorption to a silicon tetrachloride hydrogenation system, desorbing chlorosilane and hydrogen chloride adsorbed by the activated carbon through a small amount of recovered hydrogen serving as blowback gas, returning the mixed gas after desorption to a condensation process of a dry recovery system, and sending the separated hydrogen chloride to the silicon tetrachloride hydrogenation system to participate in reaction.

In the process of polysilicon dry recovery technology, purification and purification of hydrogen in production tail gas by adopting an activated carbon adsorption column are the mainstream treatment method for hydrogen recovery and utilization in 'improved Siemens' at present. The activated carbon adsorption column is the key equipment of the process method, and the equipment performance and the processing capacity directly determine the cost of hydrogen recovery. When the active carbon adsorption column works, the process is divided into three processes: the active carbon is used for adsorbing and purifying hydrogen, heating the active carbon to desorb impurity gas, reversely blowing the impurity gas by using the hydrogen and cooling to ensure that the active carbon continues to work. The latter two processes are combined into the regeneration process of the active carbon,

when the hydrogen is used for reversely purging the activated carbon adsorption column, the hydrogen is required to be heated to 182 ℃, then the activated carbon adsorption column is reversely purged, the purged mixed gas (such as the hydrogen, the hydrogen chloride and other impurity gases) returns to the condensation process of the dry recovery system again, because the temperature of the purged mixed gas is about 164 ℃, a large amount of heat is carried, if the purged mixed gas directly returns to the condensation process of the dry recovery system, the waste of the heat is bound to be caused, at present, the part of heat is not utilized, and the waste of energy and resources is caused.

SUMMERY OF THE UTILITY MODEL

Therefore, in the prior art, when the activated carbon adsorption column is desorbed and regenerated, the mixed gas after purging the activated carbon adsorption column needs to be directly returned to the condensation process of the dry recovery system, and the part of heat is not utilized, so that the waste of heat is caused, and the waste of energy and resources is caused. The utility model provides a polycrystalline silicon production tail gas recovery in-process energy cascade utilizes system, at first through the heat in the first heat exchanger recycle 164 ℃ hydrogen, secondly through the heat in the second heat exchanger recovery 92 ℃ hydrogen, through the heat in the two-stage recycle 164 ℃ hydrogen, heat in the abundant recycle 164 ℃ hydrogen, avoid the heat waste in the 164 ℃ hydrogen, and simultaneously, the hydrogen after the cold volume cooling precooling in the low temperature chlorosilane pregnant solution that directly utilizes the absorption tower to exhaust, avoid the waste of cold volume, reduce the consumption of cold volume, thereby can reduce the cost of recovery.

The energy cascade utilization system comprises an activated carbon adsorption column, an absorption tower, an analytic tower, a first heat exchanger, a second heat exchanger and a third heat exchanger, wherein an adsorption outlet of the activated carbon adsorption column is connected with a hydrogen storage tank, the hydrogen storage tank is connected with a tube side inlet of the first heat exchanger, a tube side outlet of the first heat exchanger is communicated with a desorption inlet of the activated carbon adsorption column, a desorption outlet of the activated carbon adsorption column is connected with a shell side inlet of the first heat exchanger, a shell side outlet of the first heat exchanger is connected with a shell side inlet of the second heat exchanger, a shell side outlet of the second heat exchanger is connected with a shell side inlet of the third heat exchanger, a gas phase outlet of the third heat exchanger is connected with a waste gas inlet of the absorption tower, a rich liquid outlet of the absorption tower is connected with a tube side inlet of the third heat exchanger, a liquid phase outlet of the third heat exchanger is connected with a tube side inlet of the second heat exchanger, and the tube side outlets of the second heat exchanger and the third heat exchanger are communicated with a rich liquid inlet of the analytic tower.

Preferably, the energy cascade utilization system further includes a fourth heat exchanger, tube-side outlets of the second heat exchanger and the third heat exchanger are both communicated with a tube-side inlet of the fourth heat exchanger, a tube-side outlet of the fourth heat exchanger is connected with a rich liquid inlet of the desorption tower, a lean liquid outlet of the desorption tower is connected with a shell-side inlet of the fourth heat exchanger, and a shell-side outlet of the fourth heat exchanger is communicated with a lean liquid inlet of the absorption tower.

Preferably, the energy cascade utilization system further includes a fifth heat exchanger, a tube-side outlet of the third heat exchanger is connected to a tube-side inlet of the fifth heat exchanger, a tube-side outlet of the fifth heat exchanger is connected to a tube-side inlet of the fourth heat exchanger, a shell-side outlet of the fourth heat exchanger is connected to a shell-side inlet of the fifth heat exchanger, and a shell-side outlet of the fifth heat exchanger is connected to a lean solution inlet of the absorption tower.

Preferably, in the energy cascade utilization system, a tube side outlet of the fifth heat exchanger is connected with a chlorosilane recovery pipeline, or a tube side inlet of the fifth heat exchanger is connected with a chlorosilane recovery pipeline.

Preferably, the energy cascade utilization system further comprises a first heater, a tube pass outlet of the first heat exchanger is connected with a heating inlet of the first heater, and a heating outlet of the first heater is connected with a desorption inlet of the activated carbon adsorption column.

Preferably, in the energy cascade utilization system, the number of the activated carbon adsorption columns is at least three, the at least three activated carbon adsorption columns are arranged in parallel, and the hydrogen storage tank is further connected with a hydrogen recovery pipeline.

Preferably, the energy cascade utilization system further comprises a reduction furnace and a cooling heat exchange system, a tail gas outlet of the reduction furnace is communicated with a tail gas inlet of the cooling heat exchange system, a gas phase outlet of the cooling heat exchange system is connected with a waste gas inlet of the absorption tower, a liquid phase outlet of the cooling heat exchange system is connected with a tube side inlet of the second heat exchanger, a cold hydrogen outlet of the absorption tower is connected with a refrigerant inlet of the cooling heat exchange system, and a refrigerant outlet of the cooling heat exchange system is connected with an adsorption inlet of the activated carbon adsorption column.

Preferably, the energy cascade utilization system further comprises a silicon powder dust removal device, a tail gas outlet of the reduction furnace is connected with an inlet of the silicon powder dust removal device, and an outlet of the silicon powder dust removal device is connected with a tail gas inlet of the cooling heat exchange system.

The technical scheme adopted by the application can achieve the following beneficial effects:

in the energy cascade utilization system in polycrystalline silicon production tail gas recovery process that this application embodiment discloses, at first preheat the hydrogen of-10 ℃ through the heat in the hydrogen of 164 ℃, through the heat in the first heat exchanger recycle 164 ℃ hydrogen, avoid the heat waste in the hydrogen of 164 ℃, secondly retrieve the heat in the hydrogen of 92 ℃ through the second heat exchanger, through preheating 92 ℃ hydrogen chlorosilane rich liquid, the heat in the recycle 92 ℃ hydrogen, avoid the heat waste in the 92 ℃ hydrogen, through the heat in the two-stage recycle 164 ℃ hydrogen, heat in the abundant recycle 164 ℃ hydrogen, avoid thermal waste, and can reduce the thermal consumption in the recovery process, thereby can reduce the recovery cost. Meanwhile, the cold energy in the low-temperature chlorosilane rich liquid discharged by the absorption tower is directly utilized to cool the hydrogen after pre-cooling, the extra cold energy is avoided from being additionally required to cool the hydrogen, the waste of the cold energy is avoided, the cold energy in the low-temperature chlorosilane rich liquid discharged by the absorption tower is fully recycled, the consumption of the cold energy is reduced, and therefore the recycling cost can be reduced.

Drawings

Fig. 1 is a schematic diagram of an energy cascade utilization system in a recovery process of tail gas from polysilicon production, disclosed in an embodiment of the present application.

Wherein: the system comprises an activated carbon adsorption column 100, a hydrogen storage tank 110, a hydrogen recovery pipeline 120, an absorption tower 200, a desorption tower 300, a first heat exchanger 410, a second heat exchanger 420, a third heat exchanger 430, a fourth heat exchanger 440, a fifth heat exchanger 450, a first heater 460, a chlorosilane recovery pipeline 500, a reduction furnace 600, a cooling and heat exchange system 700 and a silicon powder dust removal device 800.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are given in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. As used herein, the terms "vertical," "horizontal," "left," "right," "top," "bottom," "top," and the like are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, an embodiment of the present application discloses an energy cascade utilization system in a polysilicon production tail gas recovery process, including an activated carbon adsorption column 100, an absorption tower 200, an analytical tower 300, a first heat exchanger 410, a second heat exchanger 420, and a third heat exchanger 430, wherein:

the adsorption outlet of the activated carbon adsorption column 100 is connected with a hydrogen storage tank 110, so that the purified high-purity hydrogen adsorbed and purified by the activated carbon adsorption column 100 is stored in the hydrogen storage tank 110, the temperature of the purified high-purity hydrogen is lower and is about-10 ℃, the purified high-purity hydrogen needs to be heated to 182 ℃ and then is introduced into the activated carbon adsorption column 100 for reverse purging, and after the activated carbon adsorption column 100 is purged with the hydrogen at 182 ℃ in a reverse direction, the temperature of the hydrogen is reduced to 164 ℃, and the temperature of the part of the hydrogen is higher. The desorption outlet of the activated carbon adsorption column 100 is connected with the shell pass inlet of the first heat exchanger 410, so that the purged hydrogen at 164 ℃ is introduced into the shell pass of the first heat exchanger 410, the hydrogen storage tank 110 is connected with the tube pass inlet of the first heat exchanger 410, so that the hydrogen at-10 ℃ is firstly introduced into the tube pass of the first heat exchanger 410 and exchanges heat with the hydrogen at 164 ℃ in the shell pass, the heat in the hydrogen at 164 ℃ is recycled to preheat the hydrogen at-10 ℃, the waste of the heat in the hydrogen at 164 ℃ is avoided, the tube pass outlet of the first heat exchanger 410 is communicated with the desorption inlet of the activated carbon adsorption column 100, so that the preheated hydrogen is introduced into the activated carbon adsorption column 100 to be reversely purged, and the desorption and regeneration of the activated carbon adsorption column 100 are realized.

In the first heat exchanger 410, the hydrogen gas at 164 ℃ exchanges heat and preheats the hydrogen gas at-10 ℃, the temperature of the hydrogen gas at 164 ℃ is reduced to about 92 ℃ after heat exchange, the hydrogen gas is the hydrogen gas after purging the activated carbon adsorption column 100, impurities such as hydrogen chloride and the like are carried in the purged hydrogen gas, so chlorine needs to be recovered again, and the hydrogen gas after purging at the part has higher temperature and carries heat, so the hydrogen gas needs to be cooled before recovery. The shell pass outlet of the first heat exchanger 410 is connected with the shell pass inlet of the second heat exchanger 420, so that the 92 ℃ hydrogen is introduced into the shell pass of the second heat exchanger 420 for heat exchange and precooling, the heat in the 92 ℃ hydrogen is recovered through the second heat exchanger 420, and the cooling effect is achieved.

The shell side outlet of the second heat exchanger 420 is connected with the shell side inlet of the third heat exchanger 430, so that the pre-cooled hydrogen (the part of hydrogen carries impurities such as hydrogen chloride) is introduced into the shell side of the third heat exchanger 430 for cooling, the rich liquid outlet of the absorption tower 200 is connected with the tube side inlet of the third heat exchanger 430, because the temperature of the top of the tower in the absorption tower 200 is about-65 ℃, the temperature of the bottom of the tower is about-58 ℃, namely the temperature of the recovered hydrogen is about-65 ℃, the temperature of the chlorosilane poor liquid required to be introduced into the absorption tower 200 is about-65 ℃, the temperature of the chlorosilane rich liquid after absorbing the hydrogen chloride in the exhaust gas is about-58 ℃, so that the chlorosilane rich liquid at-58 ℃ is introduced into the shell side of the third heat exchanger 430, so that the chlorosilane rich liquid at-58 ℃ cools the pre-cooled hydrogen, and the pre-cooled hydrogen is subjected to gas-liquid separation to obtain the chlorosilane rich liquid (the liquid with a small amount of hydrogen chloride) and gaseous exhaust gas (mainly comprising hydrogen chloride and hydrogen). The cold energy in the low-temperature chlorosilane rich liquid discharged from the absorption tower 200 is directly utilized to cool the pre-cooled hydrogen, the extra cold energy is avoided from being additionally required to cool the hydrogen, the consumption of the cold energy is reduced, and the cold energy in the low-temperature chlorosilane rich liquid discharged from the absorption tower 200 is fully recycled.

The liquid phase outlet of the third heat exchanger 430 is connected with the tube pass inlet of the second heat exchanger 420, so that the chlorosilane rich liquid obtained by gas-liquid separation in the third heat exchanger 430 is introduced into the tube pass of the second heat exchanger 420, and exchanges heat with the 92 ℃ hydrogen in the shell pass of the second heat exchanger 420, the 92 ℃ hydrogen preheats the chlorosilane rich liquid, the heat in the 92 ℃ hydrogen is recycled, the waste of the heat in the 92 ℃ hydrogen is avoided, and the second heat exchanger 420 has the functions of preheating the chlorosilane rich liquid and also recovering the heat in the 92 ℃ hydrogen. The tube pass outlet of the second heat exchanger 420 is communicated with the rich liquid inlet of the desorption tower 300, so that the preheated chlorosilane rich liquid is introduced into the desorption tower 300 for desorption, hydrogen chloride in the chlorosilane rich liquid is desorbed, and the hydrogen chloride is recovered from the top of the desorption tower 300. Meanwhile, the tube pass outlet of the third heat exchanger 430 is communicated with the rich liquid inlet of the desorption tower 300, so that the chlorosilane rich liquid introduced into the tube pass of the third heat exchanger 430 from the rich liquid outlet of the absorption tower 200 is introduced into the desorption tower 300 for desorption, and in the desorption tower 300, the tower bottom temperature is about 110 ℃, the tower top temperature is about 60 ℃, namely, the temperature of the recovered hydrogen chloride gas is about 60 ℃, the temperature of the chlorosilane rich liquid required to be introduced into the desorption tower 300 is about 110 ℃, and the temperature of the desorbed chlorosilane poor liquid is about 110 ℃. Because chlorosilane rich solution exchanges heat in third heat exchanger 430, also can play the effect of preheating to chlorosilane rich solution, consequently, no matter let in the chlorosilane rich solution in desorption tower 300 through the tube side export of second heat exchanger 420 or through the tube side export of third heat exchanger 430, all through preheating to only need a small amount of extra heat just can heat chlorosilane rich solution to desorption tower 300's operating temperature, reduce thermal consumption.

The gas phase outlet of the third heat exchanger 430 is connected with the waste gas inlet of the absorption tower 200, the temperature of the waste gas after two-stage cooling through the second heat exchanger 420 and the third heat exchanger 430 is about-58 ℃, the working condition requirements of the absorption tower 200 on high pressure and low temperature are met, the waste gas is directly introduced into the absorption tower 200, hydrogen chloride in the waste gas is absorbed through chlorosilane poor liquid spraying, hydrogen chloride in the waste gas is dissolved into liquid phase chlorosilane poor liquid to obtain chlorosilane rich liquid, and hydrogen in the waste gas is recycled through the top of the absorption tower 200. Therefore, no external cold is introduced in the hydrogen cooling link at 164 ℃ after purging, and the consumption of cold in the recovery process can be greatly reduced.

The embodiment of the application discloses a polycrystalline silicon production tail gas recovery in-process energy cascade utilization system, at first preheat-10 ℃ hydrogen through the heat in 164 ℃ hydrogen, recycle the heat in 164 ℃ hydrogen through first heat exchanger 410, avoid the heat waste in 164 ℃ hydrogen, secondly retrieve the heat in 92 ℃ hydrogen through second heat exchanger 420, through preheating the rich liquid of chlorosilane with 92 ℃ hydrogen, recycle the heat in 92 ℃ hydrogen, avoid the heat waste in 92 ℃ hydrogen, recycle the heat in 164 ℃ hydrogen through the two-stage, fully recycle the heat in 164 ℃ hydrogen, avoid the waste of heat, and can reduce the thermal consumption in the recovery process, thereby can reduce the recovery cost. Meanwhile, the cold energy in the low-temperature chlorosilane rich liquid discharged from the absorption tower 200 is directly utilized to cool the pre-cooled hydrogen, the extra cold energy is avoided from being additionally required to cool the hydrogen, the waste of the cold energy is avoided, the cold energy in the low-temperature chlorosilane rich liquid discharged from the absorption tower 200 is fully recycled, the consumption of the cold energy is reduced, and the recycling cost can be reduced.

As described above, the temperature of the rich chlorosilane liquid to be fed into the desorption tower 300 is about 110 ℃, even after the rich chlorosilane liquid is preheated by the second heat exchanger 420 and the third heat exchanger 430, the temperature of the rich chlorosilane liquid cannot reach 110 ℃, and a small amount of extra heat is needed to heat the preheated rich chlorosilane liquid, based on this, in an optional embodiment, the energy cascade utilization system disclosed in the present application may further include a fourth heat exchanger 440, the tube-side outlets of the second heat exchanger 420 and the third heat exchanger 430 are both communicated with the tube-side inlet of the fourth heat exchanger 440, the lean chlorosilane liquid outlet of the desorption tower 300 is connected with the shell-side inlet of the fourth heat exchanger 440, the temperature of the lean chlorosilane liquid fed into the shell-side of the fourth heat exchanger 440 from the lean chlorosilane liquid outlet of the desorption tower 300 is higher, the rich chlorosilane liquid in the tube-side of the fourth heat exchanger 440 can be further heated, the heat of the rich chlorosilane liquid in the tube-side of the fourth heat exchanger 440 is recycled, this part of heat is avoided from being wasted, and the recycling cost is reduced.

A tube pass outlet of the fourth heat exchanger 440 is connected with a rich liquid inlet of the desorption tower 300 so as to introduce the heated chlorosilane rich liquid into the desorption tower 300 for desorption, a shell pass outlet of the fourth heat exchanger 440 is communicated with a lean liquid inlet of the absorption tower 200 so as to introduce the chlorosilane lean liquid discharged from the lean liquid outlet of the desorption tower 300 into the absorption tower 200 after heat exchange, so as to spray and absorb hydrogen chloride in the waste gas, and the hydrogen chloride in the waste gas is dissolved in the chlorosilane lean liquid to obtain the chlorosilane rich liquid.

In the application, the temperature of the rich chlorosilane solution discharged from the absorption tower 200 is about-58 ℃, after the rich chlorosilane solution at the temperature of-58 ℃ is cooled by hydrogen in the third heat exchanger 430, more cold energy still exists in the rich chlorosilane solution, if the gas is directly introduced into the desorption tower 300 for desorption, more heat is consumed, meanwhile, the temperature of the chlorosilane poor solution discharged from the desorption tower 300 is about 110 ℃, after the chlorosilane poor solution at 110 ℃ is heated in the fourth heat exchanger 440, more heat exists in the chlorosilane poor solution, if the absorption tower 200 is directly introduced to work, more cold is consumed, and based on this, in an alternative embodiment, the energy cascade utilization system disclosed herein can further comprise a fifth heat exchanger 450, the tube-side outlet of the third heat exchanger 430 is connected to the tube-side inlet of the fifth heat exchanger 450, so as to introduce the chlorosilane rich solution cooled by hydrogen in the third heat exchanger 430 into the tube side of the fifth heat exchanger 450, the shell side outlet of the fourth heat exchanger 440 is connected with the shell side inlet of the fifth heat exchanger 450, so that the chlorosilane poor solution after heating the chlorosilane rich solution in the fourth heat exchanger 440 is introduced into the shell side of the fifth heat exchanger 450, so that the chlorosilane poor solution with higher temperature exchanges heat with the chlorosilane rich solution with lower temperature in the fifth heat exchanger 450, the chlorosilane poor solution and the chlorosilane rich solution exchange heat sufficiently to heat the chlorosilane rich solution, meanwhile, the chlorosilane poor solution is cooled, heat and cold carried by the chlorosilane poor solution are fully recycled, the chlorosilane rich solution with lower temperature is heated to 110 ℃ only by additionally adding a small amount of heat after heat exchange, the working temperature requirement of the desorption tower 300 is met, the consumption of heat in the tail gas recycling process is reduced, and the heat in the high-temperature chlorosilane poor solution discharged by the desorption tower 300 is fully recycled.

Meanwhile, the temperature of the chlorosilane poor solution with higher temperature is reduced after heat exchange, and the chlorosilane poor solution can be cooled to meet the requirement of the working temperature of the absorption tower 200 only by additionally increasing a small amount of cold energy, so that the consumption of the cold energy in the tail gas recovery process can be reduced, and the cold energy in the low-temperature chlorosilane rich solution discharged by the absorption tower 200 can be fully recycled. Thereby avoiding the waste of heat in the liquid phase chlorosilane barren solution with higher temperature and the waste of cold in the liquid phase chlorosilane rich solution with lower temperature.

The tube pass outlet of the fifth heat exchanger 450 is connected with the tube pass inlet of the fourth heat exchanger 440, so that the chlorosilane rich solution after heat exchange is introduced into the fourth heat exchanger 440 for further heating and then introduced into the desorption tower 300 for desorption. The shell pass outlet of the fifth heat exchanger 450 is connected with the barren liquor inlet of the absorption tower 200, so that chlorosilane barren liquor discharged from the barren liquor outlet of the desorption tower 300 is subjected to two-stage heat exchange and then is introduced into the absorption tower 200 to be sprayed and absorbed for hydrogen chloride in waste gas, and the hydrogen chloride in the waste gas is dissolved in the chlorosilane barren liquor to obtain chlorosilane rich liquor.

Preferably, a chlorosilane recovery pipeline 500 may be connected to an outlet of a tube side of the fifth heat exchanger 450, so that all of the chlorosilane poor solution with a higher temperature exchanges heat in the fifth heat exchanger 450, and in the fifth heat exchanger 450, all of the chlorosilane poor solution may heat the chlorosilane rich solution to a higher temperature, thereby further reducing the amount of heat additionally required to be added, so that the chlorosilane rich solution may be heated to the operating temperature of the desorption tower 300 only by additionally adding a smaller amount of heat, thereby further reducing the amount of heat additionally required to be added, reducing the amount of heat used in a tail gas recovery process, further improving environmental protection performance of a system, and reducing energy consumption and cost of tail gas recovery.

Certainly, the tube side inlet of the fifth heat exchanger 450 may also be connected with a chlorosilane recovery pipeline 500, and a part of the chlorosilane poor solution with higher temperature is recovered to reduce the chlorosilane poor solution with higher temperature introduced into the fifth heat exchanger 450 for heat exchange, so that in the fifth heat exchanger 450, the chlorosilane rich solution with lower temperature can cool a smaller amount of the chlorosilane poor solution to a lower temperature, so that the chlorosilane poor solution can be cooled to the working temperature of the absorption tower 200 only by additionally increasing a smaller amount of cold energy, thereby further reducing the cold energy additionally required to be added, reducing the usage amount of the cold energy in the tail gas recovery process, further improving the environmental protection performance of the system, and reducing the energy consumption and cost of the tail gas recovery.

Because the temperature of the purge hydrogen required by desorption and regeneration of the activated carbon adsorption column 100 is 182 ℃, in the first heat exchanger 410, the hydrogen at 164 ℃ cannot heat the hydrogen at-10 ℃ to 182 ℃, and the heating hydrogen needs to be additionally added so as to enable the temperature of the hydrogen to reach 182 ℃, and then the hydrogen is introduced into the activated carbon adsorption column 100 for reverse purge. In an alternative embodiment, the energy cascade utilization system disclosed in the present application may further include a first heater 460, wherein the tube-side outlet of the first heat exchanger 410 is connected to the heating inlet of the first heater 460, and the heating outlet of the first heater 460 is connected to the desorption inlet of the activated carbon adsorption column 100. The first heat exchanger 410 can heat the hydrogen gas preheated in the first heat exchanger 410 to 182 ℃, and then the hydrogen gas is introduced into the activated carbon adsorption column 100 for reverse purging, and the hydrogen gas blows away impurities such as hydrogen chloride adsorbed on the activated carbon adsorption column 100 in the process of reversely purging the activated carbon adsorption column 100, so that the activated carbon adsorption column 100 is desorbed and regenerated, and the activated carbon adsorption column 100 can be recycled.

Further, the number of the activated carbon adsorption columns 100 may be at least three, and at least three activated carbon adsorption columns 100 are arranged in parallel, one or more of the at least three activated carbon adsorption columns 100 are used for adsorbing purified hydrogen, one of the at least three activated carbon adsorption columns is used for desorption regeneration, and one of the at least three activated carbon adsorption columns is used for standby, so that the whole tail gas recovery process can be continuous without interruption. The hydrogen storage tank 110 is further connected with a hydrogen recovery pipeline 120, and hydrogen is introduced into the reduction furnace 600 through the hydrogen recovery pipeline 120 and is used as a production raw material of the reduction furnace 600, so that waste of hydrogen in tail gas is prevented, and environmental protection and energy saving performance and resource recovery saving performance in the production process of polycrystalline silicon are improved.

Preferably, the energy cascade utilization system disclosed in the present application may further include a reduction furnace 600 and a cooling heat exchange system 700, wherein the temperature of the tail gas produced by the reduction furnace 600 is about 220 ℃, and the main components thereof are: hydrogen chloride, hydrogen and chlorosilane (trichlorosilane and silicon tetrachloride), wherein a tail gas outlet of the reduction furnace 600 is communicated with a tail gas inlet of the cooling heat exchange system 700 so as to introduce the tail gas of the reduction furnace 600 into the cooling heat exchange system 700 to cool the tail gas, and the tail gas is cooled to obtain liquid-phase chlorosilane rich liquid (a small amount of hydrogen chloride in the liquid) and gaseous waste gas (mainly hydrogen chloride and hydrogen). A gas phase outlet of the cooling heat exchange system 700 is connected with a waste gas inlet of the absorption tower 200, so that waste gas is introduced into the absorption tower 200, hydrogen chloride in the waste gas is absorbed by spraying liquid-phase chlorosilane poor liquid, the hydrogen chloride in the waste gas is dissolved into the chlorosilane poor liquid, hydrogen in the waste gas is recovered from the top of the absorption tower 200, in the absorption tower 200, the temperature of the top of the absorption tower is about-65 ℃, the temperature of the bottom of the absorption tower is about-58 ℃, namely the temperature of the recovered hydrogen is about-65 ℃, the temperature of liquid-phase chlorosilane poor liquid required to be introduced into the absorption tower 200 is about-65 ℃, and the temperature of liquid-phase chlorosilane rich liquid after the hydrogen chloride in the waste gas is absorbed is about-58 ℃. The temperature of the recovered hydrogen is about-65 ℃, the recovered low-temperature hydrogen can be used as a refrigerant for cooling the heat exchange system 700 to cool the tail gas, the cold hydrogen outlet of the absorption tower 200 is connected with the refrigerant inlet of the cooling heat exchange system 700, so that the recovered hydrogen is introduced into the cooling heat exchange system 700 to cool the tail gas, the temperature of the cooled waste gas is about-58 ℃, the recovered low-temperature hydrogen is directly used as the refrigerant for cooling the heat exchange system 700, the tail gas is prevented from being cooled by an extra cold source, and the cold energy in the hydrogen is fully recycled.

The liquid phase outlet of the cooling heat exchange system 700 is connected with the tube pass inlet of the second heat exchanger 420, so that the liquid phase chlorosilane rich solution is introduced into the tube pass of the second heat exchanger 420 to exchange heat with 92 ℃ hydrogen in the shell pass of the second heat exchanger 420, the 92 ℃ hydrogen preheats the chlorosilane rich solution, the heat in the 92 ℃ hydrogen is recycled, the waste of the heat in the 92 ℃ hydrogen is avoided, the second heat exchanger 420 has the function of preheating the chlorosilane rich solution and also has the function of recovering the heat in the 92 ℃ hydrogen.

As described above, the cold hydrogen outlet of the absorption tower 200 is connected to the coolant inlet of the cooling heat exchange system 700, the temperature of the hydrogen after cooling the tail gas in the cooling heat exchange system 700 is about-15 ℃, and then the hydrogen is recycled, but the hydrogen recovered here has more impurities (hydrogen chloride) and lower hydrogen purity, and needs to be further purified, and the coolant outlet of the cooling heat exchange system 700 is connected to the adsorption inlet of the activated carbon adsorption column 100, so that the hydrogen after heat exchange in the cooling heat exchange system 700 is introduced into the activated carbon adsorption column 100 for adsorption and purification, and the high-purity hydrogen is recovered, and the working environment for adsorption and purification by the activated carbon adsorption column 100 is high-pressure and low-temperature, therefore, the temperature of the hydrogen after heat exchange in the cooling heat exchange system 700 is about-15 ℃, and just meets the working temperature for adsorption and purification by the activated carbon adsorption column 100, and the purified hydrogen adsorbed in the activated carbon adsorption column 100 is recovered and stored by the hydrogen storage tank 110.

Based on that, in an optional embodiment, the energy cascade utilization system disclosed in the present application may further include a silicon powder dust removal device 800, a tail gas outlet of the reduction furnace 600 is connected to an inlet of the silicon powder dust removal device 800, and an outlet of the silicon powder dust removal device 800 is connected to a tail gas inlet of the second cooling heat exchange system 700, so that the high-temperature tail gas of the reduction furnace 600 first passes through the silicon powder dust removal device 800 to recover the silicon powder therein, and then the tail gas from which the silicon powder is removed is introduced into the subsequent system, thereby preventing the silicon powder from blocking the pipeline in the subsequent system, and improving the reliability and stability of the system. Specifically, the silicon powder dust removing device 800 may be a bag-type dust remover.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.

Claims

1. An energy cascade utilization system in the recovery process of tail gas in the production of polycrystalline silicon is characterized by comprising an activated carbon adsorption column (100), an absorption tower (200), a desorption tower (300), a first heat exchanger (410), a second heat exchanger (420) and a third heat exchanger (430), the adsorption outlet of the active carbon adsorption column (100) is connected with a hydrogen storage tank (110), the hydrogen storage tank (110) is connected with the tube side inlet of the first heat exchanger (410), the tube pass outlet of the first heat exchanger (410) is communicated with the desorption inlet of the activated carbon adsorption column (100), a desorption outlet of the activated carbon adsorption column (100) is connected with a shell side inlet of the first heat exchanger (410), the shell side outlet of the first heat exchanger (410) is connected with the shell side inlet of the second heat exchanger (420), the shell-side outlet of the second heat exchanger (420) is connected with the shell-side inlet of the third heat exchanger (430), the gas phase outlet of the third heat exchanger (430) is connected with the waste gas inlet of the absorption tower (200), the rich liquid outlet of the absorption tower (200) is connected with the tube side inlet of the third heat exchanger (430), the liquid phase outlet of the third heat exchanger (430) is connected with the tube side inlet of the second heat exchanger (420), tube side outlets of the second heat exchanger (420) and the third heat exchanger (430) are communicated with a rich liquid inlet of the desorption tower (300).

2. The energy cascade utilization system of claim 1, further comprising a fourth heat exchanger (440), wherein the tube-side outlets of the second heat exchanger (420) and the third heat exchanger (430) are both in communication with the tube-side inlet of the fourth heat exchanger (440), the tube-side outlet of the fourth heat exchanger (440) is in communication with the rich liquid inlet of the desorption tower (300), the lean liquid outlet of the desorption tower (300) is in communication with the shell-side inlet of the fourth heat exchanger (440), and the shell-side outlet of the fourth heat exchanger (440) is in communication with the lean liquid inlet of the absorption tower (200).

3. The energy cascade utilization system of claim 2, further comprising a fifth heat exchanger (450), wherein the tube-side outlet of the third heat exchanger (430) is connected to the tube-side inlet of the fifth heat exchanger (450), the tube-side outlet of the fifth heat exchanger (450) is connected to the tube-side inlet of the fourth heat exchanger (440), the shell-side outlet of the fourth heat exchanger (440) is connected to the shell-side inlet of the fifth heat exchanger (450), and the shell-side outlet of the fifth heat exchanger (450) is connected to the lean liquid inlet of the absorption tower (200).

4. The energy cascade utilization system according to claim 3, wherein a chlorosilane recovery line (500) is connected to a tube-side outlet of the fifth heat exchanger (450), or a chlorosilane recovery line (500) is connected to a tube-side inlet of the fifth heat exchanger (450).

5. The energy cascade utilization system of claim 1, further comprising a first heater (460), wherein the tube-side outlet of the first heat exchanger (410) is connected to the heating inlet of the first heater (460), and the heating outlet of the first heater (460) is connected to the desorption inlet of the activated carbon adsorption column (100).

6. The energy cascade utilization system according to claim 1, wherein the number of the activated carbon adsorption columns (100) is at least three, and at least three of the activated carbon adsorption columns (100) are arranged in parallel, and the hydrogen storage tank (110) is further connected with a hydrogen recovery pipeline (120).

7. The energy cascade utilization system according to claim 1, further comprising a reduction furnace (600) and a cooling heat exchange system (700), wherein a tail gas outlet of the reduction furnace (600) is communicated with a tail gas inlet of the cooling heat exchange system (700), a gas phase outlet of the cooling heat exchange system (700) is connected with a waste gas inlet of the absorption tower (200), a liquid phase outlet of the cooling heat exchange system (700) is connected with a tube pass inlet of the second heat exchanger (420), a cold hydrogen outlet of the absorption tower (200) is connected with a refrigerant inlet of the cooling heat exchange system (700), and a refrigerant outlet of the cooling heat exchange system (700) is connected with an adsorption inlet of the activated carbon adsorption column (100).

8. The energy cascade utilization system according to claim 7, further comprising a silicon powder dust removal device (800), wherein a tail gas outlet of the reduction furnace (600) is connected with an inlet of the silicon powder dust removal device (800), and an outlet of the silicon powder dust removal device (800) is connected with a tail gas inlet of the cooling heat exchange system (700).