Tail gas pre-washing pressurizing cryogenic system

Abstract

The utility model provides a tail gas pre-washing, pressurizing and cryogenic system, which relates to the technical field of polycrystalline silicon production and comprises a tail gas pre-washing device and a tail gas pressurizing and cryogenic device, the tail gas pre-washing device is used for removing dust from dust-containing tail gas; the tail gas pressurizing and copious cooling device comprises a compressor, an air cooler, a tail gas condensate tank, a second heat exchanger and a tail gas copious cooler which are connected in sequence; after a stream of a gas phase outlet of the tail gas condensate tank enters the second heat exchanger, a first condensed stream and a first gas phase stream are obtained; the first gas-phase stream enters a tail gas deep freezer to obtain a second condensation stream and a second gas-phase stream; and the second gas-phase stream flows through the second heat exchanger and then enters a tail gas leaching system at the rear end. And the problems of abrasion of the compressor and blockage of the interstage cooler are solved by dedusting the dust-containing tail gas. An air cooler, a tail gas condensate tank, a second heat exchanger and a tail gas deep freezer are additionally arranged on the basis of a compressor, chlorosilane can be recycled, and the load of a tail gas leaching system can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon production, in particular to a tail gas pre-washing pressurized deep cooling system. Background Art

[0002] Most of the exhaust gas from polysilicon enterprises is directly discharged into the exhaust gas washing tower for hydrolysis treatment. There are many white hydrolyzates in the water pool at the bottom of the exhaust gas washing tower, and the exhaust gas discharged from the top exceeds the emission standard, polluting the atmosphere. After process optimization, some enterprises add compressors to pressurize and condense the exhaust gas from the entire plant before entering the exhaust gas washing tower for hydrolysis treatment. In this way, there are relatively fewer hydrolyzates in the water pool at the bottom of the exhaust gas washing tower, and the exhaust gas emissions at the top are reduced.

[0003] However, the current solution of adding compressors still has some technical problems:

[0004] 1. A certain amount of chlorosilane gas in the exhaust gas of the whole plant directly enters the exhaust gas washing tower for hydrolysis (the existing exhaust gas washing tower uses water to wash the exhaust gas of the whole plant), which will cause waste of chlorosilane (there are a lot of white hydrolyzates in the water pool at the bottom of the exhaust gas washing tower), the exhaust gas washing system has a large load (a lot of gas needs to be treated), the exhaust gas treatment cost is high, the exhaust gas discharged from the top exceeds the standard, and the air pollution is serious.

[0005] 2. Since the exhaust gas from the entire plant contains solid impurities such as silicon dioxide and silicon powder, the filter at the compressor inlet is often blocked, resulting in frequent maintenance. At the same time, it will also cause the compressor interstage cooler to be blocked, resulting in poor heat exchange effect, making the compressor (two-stage compression) second-stage inlet temperature high, which in turn leads to high compressor second-stage exhaust temperature.

[0006] 3. Due to the presence of solid impurities such as silicon dioxide and silicon powder in the exhaust gas of the entire plant, the compressor is worn. Utility Model Content

[0007] In view of the above situation, the utility model provides an exhaust gas pre-washing pressurized deep cooling system, aiming to solve the technical problems pointed out in the above background technology.

[0008] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0009] The utility model provides a tail gas pre-washing pressurized deep cooling system, comprising a tail gas pre-washing device and a tail gas pressurized deep cooling device connected in sequence;

[0010] The tail gas pre-scrubber is used to remove dust from the dusty tail gas;

[0011] The tail gas pressurized cryogenic device comprises a compressor, an air cooler, a tail gas condensate tank, a second heat exchanger and a tail gas cryogenic cooler which are connected in sequence;

[0012] The inlet of the compressor is connected to the end of the tail gas pre-scrubber;

[0013] After the stream at the gas phase outlet of the tail gas condensate tank enters the second heat exchanger, a first condensed stream and a first gas phase stream are obtained;

[0014] The first condensate stream is returned to the tail gas condensate tank;

[0015] The first gas phase stream enters the tail gas cryogenic cooler to obtain a second condensed stream and a second gas phase stream;

[0016] The second condensate stream is returned to the tail gas condensate tank;

[0017] The second gas phase stream flows through the second heat exchanger and enters the tail gas washing system at the rear end.

[0018] In some embodiments of the present invention, the exhaust gas pressurized cryogenic device further includes a circulating water cooler, and the air cooler, the circulating water cooler and the exhaust gas condensate tank are connected in sequence.

[0019] In some embodiments of the present invention, the tail gas pre-scrubbing device comprises:

[0020] Filters for separating the gas phase and the solid phase in the dusty exhaust gas;

[0021] The tail gas pre-wash tower has a to-be-washed gas inlet, a washing liquid inlet, a pre-wash tower gas phase outlet and a pre-wash tower liquid phase outlet;

[0022] The inlet of the gas to be scrubbed is connected to the gas phase outlet of the filter;

[0023] The eluent inlet is located above the inlet of the gas to be washed;

[0024] The eluent inlet is used to introduce silicon tetrachloride into the tail gas pre-wash tower; and the stream at the gas phase outlet of the pre-wash tower flows to the compressor.

[0025] In some embodiments of the present invention, the tail gas pre-scrubbing device further comprises a heat exchanger; the flow stream at the gas phase outlet of the pre-scrubbing tower and the flow stream at the gas phase outlet of the filter are heat exchanged in the heat exchanger.

[0026] In some embodiments of the present invention, the tail gas pre-washing device also includes a chlorosilane circulation pump and a chlorosilane cryogenic cooler; the flow stream at the liquid phase outlet of the pre-washing tower is transported by the chlorosilane circulation pump, first passes through the chlorosilane cryogenic cooler, and then enters the upper part of the tail gas pre-washing tower.

[0027] In some embodiments of the present invention, the chlorosilane circulation pump is a slurry pump.

[0028] In some embodiments of the present invention, the exhaust gas pre-scrubbing device further includes a dust collection tank, and the inlet of the dust collection tank is connected to the solid phase outlet of the filter.

[0029] In some embodiments of the present invention, the top of the dust collection tank is connected to the inlet of the air to be cleaned.

[0030] In some embodiments of the present invention, the exhaust gas pre-washing device further comprises a dust-free exhaust gas inlet pipe, and the flow stream in the dust-free exhaust gas inlet pipe merges with the flow stream at the gas phase outlet of the filter and enters the exhaust gas pre-washing tower together.

[0031] In some embodiments of the present invention, an exhaust gas buffer tank is provided on the path of the dust-free exhaust gas input pipe.

[0032] The embodiments of the present invention have at least the following advantages or beneficial effects:

[0033] 1. The problems of compressor wear and interstage cooler blockage are solved by removing dust from dusty exhaust gas.

[0034] 2. An air cooler, an exhaust gas condensate tank, a second heat exchanger and an exhaust gas deep cooler are added on the basis of the compressor, which can recover chlorosilane and reduce the amount of gas entering the rear-end exhaust gas elution system, thereby reducing the load of the exhaust gas elution system.

[0035] Other features and advantages of the present invention will be set forth in the following description, and in part will become apparent from the description, or may be understood by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 This is a schematic diagram of the structure of the exhaust gas pre-washing pressurized deep cooling system.

[0038] icon:

[0039] 11-dust-free exhaust gas inlet pipe, 12-exhaust gas buffer tank,

[0040] 13-filter, 131-filter gas phase outlet, 132-filter solid phase outlet,

[0041] 14-dust collection tank, 15-heat exchanger,

[0042] 16- tail gas pre-wash tower, 161- gas inlet to be washed, 162- eluent inlet, 163- gas phase outlet of pre-wash tower, 164- liquid phase outlet of pre-wash tower, 165- liquid level meter, 166- flow meter, 167- flow regulating valve,

[0043] 17-Chlorosilane circulation pump, 18-Chlorosilane cryocooler,

[0044] 21-Compressor,

[0045] 22- air cooler, 23- circulating water cooler, 24- tail gas condensate tank, 25- second heat exchanger, 26- tail gas deep cooler. DETAILED DESCRIPTION

[0046] In the following, only some exemplary embodiments are briefly described. As those skilled in the art can appreciate, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present invention.

[0047] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0048] The embodiments of the present utility model are described in detail below with reference to the accompanying drawings.

[0049] Example

[0050] See also Figure 1 This embodiment provides an exhaust gas pre-washing pressurized deep cooling system, including an exhaust gas pre-washing device and an exhaust gas pressurized deep cooling device connected in sequence.

[0051] The tail gas pre-washing device comprises a dust-free tail gas inlet pipe 11 , a tail gas buffer tank 12 , a filter 13 , a dust collection tank 14 , a first heat exchanger 15 , a tail gas pre-washing tower 16 and a chlorosilane circulation pump 17 .

[0052] The dust-free exhaust gas inlet pipe 11 is used to transport the dust-free exhaust gas.

[0053] The tail gas buffer tank 12 is arranged on the path of the dust-free tail gas inlet pipe 11 , and the tail gas buffer tank 12 plays a buffering role for the dust-free tail gas.

[0054] The filter 13 has a filter gas phase outlet 131 and a filter solid phase outlet 132 for separating the gas phase and the solid phase in the dust-containing tail gas.

[0055] The inlet of the dust collection tank 14 is connected to the solid phase outlet 132 of the filter; the top of the dust collection tank 14 is connected to the inlet of the tail gas buffer tank 12 to collect and process the exhaust gas generated in the dust collection tank 14.

[0056] After the flow stream of the filter gas phase outlet 131 merges with the flow stream in the dust-free tail gas inlet pipe 11 , they first flow through the first heat exchanger 15 together and then enter the tail gas pre-wash tower 16 .

[0057] The tail gas pre-wash tower 16 has a to-be-washed gas inlet 161 , an eluent inlet 162 , a pre-wash tower gas phase outlet 163 and a pre-wash tower liquid phase outlet 164 .

[0058] The inlet 161 for the gas to be cleaned is used to introduce the flow stream of the gas phase outlet 131 of the filter and the flow stream in the dust-free exhaust gas inlet pipe 11 .

[0059] The eluent inlet 162 is located above the inlet 161 of the gas to be washed; the eluent inlet 162 is used to introduce silicon tetrachloride into the tail gas pre-wash tower 16, that is, the eluent of the tail gas pre-wash tower 16 is silicon tetrachloride.

[0060] The stream from the gas phase outlet 163 of the pre-wash tower flows through the first heat exchanger 15, enters the compressor 21, and then enters the tail gas washing system at the rear end; the tail gas washing system includes the tail gas washing tower described in the background technology.

[0061] The liquid phase outlet 164 of the pre-wash tower is connected to the downstream waste liquid treatment device, and the absorbed chlorosilane is sent to the downstream waste liquid treatment device to filter and separate the particulate impurities in the chlorosilane, thereby separating the chlorosilane.

[0062] The stream of the pre-wash tower liquid phase outlet 164 can be transported by the chlorosilane circulation pump 17 and first pass through the chlorosilane cryogenic cooler 18, and then enter the upper part of the tail gas pre-wash tower 16, thereby realizing circulation.

[0063] In a specific implementation scenario, the chlorosilane circulation pump 17 adopts a slurry pump to prevent the chlorosilane circulation pump 17 from being blocked.

[0064] In order to adjust the liquid level at the bottom of the exhaust gas pre-wash tower 16, the liquid phase outlet 164 of the pre-wash tower is connected to a flow meter 166 and a flow regulating valve 167, and a liquid level meter 165 is provided at the bottom of the exhaust gas pre-wash tower 16; the liquid level meter 165, the flow meter 166 and the flow regulating valve 167 are associated with each other, and the liquid level stability at the bottom of the exhaust gas pre-wash tower 16 is controlled by the liquid level meter 165, the flow meter 166 and the flow regulating valve 167.

[0065] The working principle of the above tail gas pre-scrubbing device is:

[0066] The tail gas of the whole plant is divided into dust-containing tail gas (containing solid impurities, such as silicon powder) and dust-free tail gas. The dust-containing tail gas first passes through the filter 13 to filter out solid impurities, and then enters the first heat exchanger 15 together with the dust-free tail gas after passing through the tail gas buffer tank 12 to exchange heat to a lower temperature, and then enters the tail gas washing tower to recover the chlorosilane gas in the tail gas of the whole plant through silicon tetrachloride elution. At the same time, it can also absorb solid impurities in the tail gas, thereby solving the problems of wear of the compressor 21 and blockage of the interstage cooler. The absorbed chlorosilane can be sent to the downstream waste liquid treatment device to filter and separate the particulate impurities in the chlorosilane, so as to separate the chlorosilane therein.

[0067] The reason for using silicon tetrachloride as the eluent of the tail gas pre-wash tower 16 is that the tail gas of the whole plant is mainly a mixture of solid dioxide impurity dust, trichlorosilane, silicon tetrachloride, etc. When the silicon tetrachloride eluent is used as an absorbent for chlorosilane, other impurities will not be introduced. At the same time, silicon tetrachloride can also be recycled and reused (silicon tetrachloride has a higher boiling point than trichlorosilane, which makes it easy for trichlorosilane to liquefy first and be separated from the tail gas of the whole plant).

[0068] It should be noted that, in other embodiments, the exhaust gas pre-washing device may not include the dust-free exhaust gas inlet pipe 11, that is, it does not distinguish whether the exhaust gas of the entire polysilicon enterprise contains solid impurities.

[0069] In combination with the above content, the tail gas pre-scrubbing device has at least the following beneficial effects:

[0070] 1. Through the setting of the filter 13 and the tail gas pre-washing tower 16, the dust-containing tail gas in the tail gas of the whole plant of the polysilicon enterprise is filtered by the filter 13 to remove solid impurities, and then washed and dusted by the tail gas pre-washing tower 16, and then pressurized and condensed by the compressor 21 and enters the rear-end tail gas washing system for further purification. In this way, the wear of the compressor 21 and the blockage of the interstage cooler are solved.

[0071] 2. Using silicon tetrachloride as the eluent of the tail gas pre-wash tower 16 can absorb chlorosilane without introducing other impurities, reducing the waste of chlorosilane and the load of the rear tail gas washing system. At the same time, silicon tetrachloride can also be recycled and reused, further reducing waste.

[0072] 3. Through the setting of the first heat exchanger 15, the flow stream of the pre-wash tower gas phase outlet 163 is heat exchanged with the intake air of the exhaust gas pre-wash tower 16 (the flow stream of the filter gas phase outlet 131 and the flow stream in the dust-free exhaust gas inlet pipe 11) and then enters the compressor 21 for pressure boosting, thereby recovering the cold energy of the flow stream of the pre-wash tower gas phase outlet 163 (the temperature of the top gas phase of the exhaust gas pre-wash tower 16 is lower after washing), reducing the intake temperature of the exhaust gas pre-wash tower 16, and realizing low-temperature elution.

[0073] 4. The inlet of the dust collection tank 14 is connected to the solid phase outlet 132 of the filter, which is convenient for bagging and loading the dust (such as silicon powder) separated by the filter 13 for recycling; the top of the dust collection tank 14 is connected to the exhaust buffer tank 12, which is convenient for collecting and processing the exhaust gas generated at the dust collection tank 14.

[0074] 5. Through the arrangement of the chlorosilane circulation pump 17 and the chlorosilane cryocooler 18, the stream of the pre-wash tower liquid phase outlet 164 can be transported by the chlorosilane circulation pump 17 and can first pass through the chlorosilane cryocooler 18 and then enter the upper part of the tail gas pre-wash tower 16, thereby realizing circulation. The chlorosilane circulation pump 17 adopts a slurry pump, which effectively prevents the chlorosilane circulation pump 17 from being blocked.

[0075] 6. The liquid level meter 165 , the flow meter 166 and the flow regulating valve 167 are associated with each other, and the liquid level stability at the bottom of the tail gas pre-wash tower 16 is controlled by the liquid level meter 165 , the flow meter 166 and the flow regulating valve 167 .

[0076] 7. The exhaust gas buffer tank 12 can provide a buffer for dust-free exhaust gas.

[0077] The exhaust gas pressurization and cryogenic device comprises a compressor 21, an air cooler 22, a circulating water cooler 23, an exhaust gas condensate tank 24, a second heat exchanger 2515 and an exhaust gas cryogenic cooler 26 which are connected in sequence.

[0078] The inlet of the compressor 21 is connected to the pre-cleaning tower gas phase outlet 163 , and the outlet of the compressor 21 is connected to the inlet of the air cooler 22 .

[0079] The outlet of the air cooler 22 is connected to the inlet of the circulating water cooler 23 .

[0080] The outlet of the circulating water cooler 23 is connected to the inlet of the tail gas condensate tank 24 .

[0081] After the stream at the gas phase outlet of the tail gas condensate tank 24 enters the second heat exchanger 2515 , a first condensate stream and a first gas phase stream are obtained. The first condensate stream returns to the tail gas condensate tank 24 .

[0082] The first gas phase stream enters the tail gas cryogenic cooler 26 to obtain the second condensed stream and the second gas phase stream. The second condensed stream returns to the tail gas condensate tank 24. After the second gas phase stream flows through the second heat exchanger 2515, it enters the tail gas washing system at the rear end; the tail gas washing system includes the tail gas washing tower described in the background technology.

[0083] The working principle of the above tail gas pressurization cryogenic device is:

[0084] The stream from the gas phase outlet 163 of the pre-wash tower enters the compressor 21 for pressure increase, and then enters the tail gas condensate tank 24 to separate the liquid phase after being cooled by the air cooler 22 + circulating water cooler 23. The gas phase is further condensed by the second heat exchanger 2515 and the tail gas deep cooler 26 in sequence, and the condensed chlorosilane is returned to the tail gas condensate tank 24. The liquid phase in the tail gas condensate tank 24 is pumped to the rear-end distillation system. The gas phase that is not condensed by the tail gas deep cooler 26 is sent to the rear-end tail gas washing system for treatment.

[0085] The above tail gas pressurization cryogenic device has at least the following beneficial effects:

[0086] 1. An air cooler 22, a circulating water cooler 23, an exhaust condensate tank 24, a second heat exchanger 2515 and an exhaust deep cooler 26 are added on the basis of the compressor 21, which can recover chlorosilane and reduce the amount of gas entering the rear-end exhaust gas washing system, thereby reducing the load of the exhaust gas washing system.

[0087] 2. When the temperature is high in summer, the air cooler 22 alone may not meet the cooling requirements, so a circulating water cooler 23 is provided. This embodiment adopts a solution of using the air cooler 22 + the circulating water cooler 23. In other embodiments (such as winter), the air cooler 22 alone may meet the requirements, thereby saving the amount of circulating water and reducing energy consumption.

[0088] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. In the absence of conflicts, the embodiments of the present application and the features in the embodiments may be combined with each other at will. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An exhaust gas pre-washing pressurized cryogenic system, characterized in that: It includes an exhaust gas pre-scrubbing device and an exhaust gas pressurizing and deep cooling device connected in sequence; The tail gas pre-washing device is used to remove dust from the dust-containing tail gas; The tail gas pressurized cryogenic device comprises a compressor, an air cooler, a tail gas condensate tank, a second heat exchanger and a tail gas cryogenic cooler which are connected in sequence; The inlet of the compressor is connected to the end of the tail gas pre-washing device; After the stream at the gas phase outlet of the tail gas condensate tank enters the second heat exchanger, a first condensed stream and a first gas phase stream are obtained; The first condensate stream is returned to the tail gas condensate tank; The first gas phase stream enters the tail gas cryogenic cooler to obtain a second condensed stream and a second gas phase stream; The second condensate stream is returned to the tail gas condensate tank; The second gas phase stream flows through the second heat exchanger and then enters the tail gas washing system at the rear end.

2. The tail gas pre-washing pressurized cryogenic system according to claim 1, characterized in that: The tail gas pressurized deep cooling device also includes a circulating water cooler, and the air cooler, the circulating water cooler and the tail gas condensate tank are connected in sequence.

3. The tail gas pre-washing pressurized cryogenic system according to claim 1 or 2, characterized in that: The tail gas pre-scrubbing device comprises: Filters for separating the gas phase and the solid phase in the dusty exhaust gas; The tail gas pre-wash tower has a to-be-washed gas inlet, a washing liquid inlet, a pre-wash tower gas phase outlet and a pre-wash tower liquid phase outlet; The inlet of the gas to be washed is connected to the gas phase outlet of the filter; The eluent inlet is located above the inlet of the gas to be washed; The eluent inlet is used to introduce silicon tetrachloride into the tail gas pre-wash tower; and the stream at the gas phase outlet of the pre-wash tower flows to the compressor.

4. The tail gas pre-washing pressurized cryogenic system according to claim 3, characterized in that: The tail gas pre-washing device also includes a heat exchanger; the stream at the gas phase outlet of the pre-washing tower and the stream at the gas phase outlet of the filter are heat exchanged in the heat exchanger.

5. The tail gas pre-washing pressurized cryogenic system according to claim 3, characterized in that: The tail gas pre-washing device also includes a chlorosilane circulation pump and a chlorosilane cryocooler; the stream at the liquid phase outlet of the pre-washing tower is transported by the chlorosilane circulation pump, first passes through the chlorosilane cryocooler, and then enters the upper part of the tail gas pre-washing tower.

6. The tail gas pre-washing pressurized cryogenic system according to claim 5, characterized in that: The chlorosilane circulation pump is a slurry pump.

7. The tail gas pre-washing pressurized cryogenic system according to claim 3, characterized in that: The tail gas pre-washing device also includes a dust collection tank, the inlet of which is connected to the solid phase outlet of the filter.

8. The tail gas pre-washing pressurized cryogenic system according to claim 7, characterized in that: The top of the dust collection tank is connected to the inlet of the air to be cleaned.

9. The tail gas pre-washing pressurized cryogenic system according to claim 3, characterized in that: The exhaust gas pre-washing device also includes a dust-free exhaust gas inlet pipe. After the flow stream in the dust-free exhaust gas inlet pipe merges with the flow stream at the gas phase outlet of the filter, they enter the exhaust gas pre-washing tower together.

10. The tail gas pre-washing pressurized cryogenic system according to claim 9, characterized in that: An exhaust gas buffer tank is arranged on the path of the dust-free exhaust gas input pipe.

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