Deep arsenic removal system and method

Abstract

The invention provides a deep arsenic removal system and method, the system comprises an arsenic removal tank and a reaction tank, a reactor is additionally arranged between the arsenic removal tank and the reaction tank, and a flue gas pipe is arranged at an exhaust port of the arsenic removal tank; a pressurizing device is arranged on the flue gas pipe, a branch is arranged on the flue gas pipe, the flue gas pipe is communicated with the arsenic removal tank, and the branch is communicated with the reactor; after hydrogen sulfide gas at the exhaust port of the arsenic removal tank is collected and pressurized through the arranged pressurizing device, one part of the hydrogen sulfide gas enters the arsenic removal tank, the other part of the hydrogen sulfide gas enters the reactor, and the hydrogen sulfide gas entering the reactor fully reacts with materials conveyed by the reaction tank and then enters the arsenic removal tank for pressurized reaction. According to the invention, the technical difficulties of high cost, low efficiency and high safety risk of the current arsenic removal process can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphoric acid dearsenication, and in particular to a deep dearsenication system and method. Background Art

[0002] The current wet-process phosphoric acid arsenic removal process mainly adopts the method of adding sodium sulfide to the front-end pre-treatment arsenic removal tank and adding sodium sulfide to the purification fine desulfurization system to remove arsenic ions from phosphoric acid. This arsenic removal process is not efficient enough in pre-treatment arsenic removal, does not meet the product acid requirements, and has a high safety risk. The addition of sodium sulfide to the purification process increases the safety risk points, makes safety and process control more difficult, and the introduction of sodium sulfide leads to solvent contamination.

[0003] At the same time, the production control requirement for the arsenic index of wet-process purified phosphoric acid products is below 1ppm. The current process requires the addition of sodium sulfide to the pretreatment reaction arsenic removal tank to remove arsenic, so that the pretreatment acid arsenic ions are reduced to below 4ppm. Since the index has not yet reached the product acid control requirement, it is necessary to add sodium sulfide to the purification fine desulfurization system to further remove arsenic to meet the product acid index requirement, and the dearsenicization process produces toxic hydrogen sulfide gas. This dearsenication process has high requirements for safety and environmental protection, and has many risk points, is difficult to manage, and also involves the removal of flue gas pipes, which has high operational risks.

[0004] The invention with announcement number: CN114455558B discloses a deep arsenic removal system for arsenic-containing phosphoric acid, comprising a arsenic removal agent configuration tank, a primary reactor, a arsenic removal reaction tank and a washing tower; the top inlet of the arsenic removal agent configuration tank is connected to the arsenic removal agent feed pipe, the bottom outlet of the arsenic removal agent configuration tank is connected to the liquid inlet pipe of the primary reactor through a delivery pump and a first flow regulating valve pipeline, the upper side inlet of the primary reactor is connected to the arsenic-containing phosphoric acid feed pipe through a second flow regulating valve pipeline, the bottom outlet pipeline of the primary reactor is connected to the top side inlet of the arsenic removal reaction tank, the top side inlet of the arsenic removal reaction tank is connected to the lower part of the washing tower through a pipeline, one pipeline of the washing tower outlet is connected to the upper spray pipe of the washing tower, and the other pipeline is connected to the top of the arsenic removal agent configuration tank.

[0005] The current arsenic removal process in the arsenic removal tank has the following disadvantages:

[0006] First, the arsenic removal tank is in a negative pressure state, and when the flue gas pipe is blocked, hydrogen sulfide gas overflows;

[0007] Second, the existing system has low solubility of hydrogen sulfide and cannot remove arsenic deeply;

[0008] Third, the sodium sulfide is added by inserting a tube under the liquid, and the overflow port of the dearsenicization tank is located at the bottom, which cannot fully react and has low reaction efficiency;

[0009] Fourth, the existing flue gas pipelines are unreasonable and pose great safety risks. Summary of the invention

[0010] The purpose of the present invention is to provide a deep arsenic removal system and method, which can effectively solve the technical difficulties of high cost, low efficiency and high safety risks in the current arsenic removal process.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0012] A deep arsenic removal system comprises an arsenic removal tank and a reaction tank, a reactor is additionally provided between the arsenic removal tank and the reaction tank, a flue gas pipe is provided at the exhaust port of the arsenic removal tank; a booster device is provided on the flue gas pipe, a branch is provided on the flue gas pipe, the flue gas pipe is connected to the arsenic removal tank, and the branch is connected to the reactor;

[0013] The hydrogen sulfide gas at the exhaust port of the arsenic removal tank is collected and pressurized by the booster device, and a part of it enters the arsenic removal tank, and the other part enters the reactor. The hydrogen sulfide gas entering the reactor fully reacts with the material transported by the reaction tank and then enters the arsenic removal tank for pressurized reaction.

[0014] Furthermore, the reactor is connected to a steam pipe of a first reaction tank, and the steam pipe of the first reaction tank is used to heat the reactor.

[0015] Among them, the boosting device is a boosting fan.

[0016] Furthermore, a self-regulating valve is provided at the outlet end of the boosting device.

[0017] Preferably, the pressure entering the reactor from the outlet of the self-regulating valve is 88 KPa-100 KPa.

[0018] The arsenic removal tank further comprises a tank body and a stirring device arranged on the tank body, wherein a sealing structure is arranged between a stirring shaft of the stirring device and the tank body.

[0019] Among them, the sealing structure includes a sealing cover, a fixed end cover, a spring and a plurality of fillers. The sealing cover is fixedly arranged on the slot body, and the rotating shaft passes through the slot body and the sealing cover. The filler is sleeved on the rotating shaft and is located inside the sealing cover. The spring is located in the sealing cover and contacts with the filler at the uppermost end. The fixed end cover is installed on the sealing cover, and the extrusion part of the fixed end cover contacts with the spring. Under the action of the fixed end cover and the spring, the filler contacts with the rotating shaft in a sealed manner.

[0020] Furthermore, the sealing structure also includes a pressure plate, which is sleeved on the rotating shaft, with an upper end of the pressure plate in contact with the spring and a lower end in contact with the packing.

[0021] The filler has a cavity inside.

[0022] The present invention also discloses a deep arsenic removal method, which includes using the above-mentioned deep arsenic removal system, and specifically includes the following steps:

[0023] After the hydrogen sulfide gas in the arsenic removal tank is pressurized by a booster device, a portion of it is sent to the reactor to react with the material in the first reaction tank, and the other portion is sent to the arsenic removal tank, so that the interior of the arsenic removal tank is in a positive pressure state, so that the internal pressure of the arsenic removal tank is 103KPa-105KPa.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] In actual use, the present invention maintains a positive pressure inside the dearsenication tank by setting a booster device, and the excess hydrogen sulfide gas is recycled for secondary use and sent to the reactor under the action of the booster device; at the same time, the reactor is heated and heated by the steam pipe of the first reaction tank, and the increase in reaction temperature can increase the solubility of hydrogen sulfide in the acid to a certain extent, thereby promoting the dearsenication efficiency. The purpose of efficient dearsenication is achieved by collecting the undissolved hydrogen sulfide gas, pressurizing the dearsenication tank and the reactor, and reacting with phosphoric acid under pressure. After the process is optimized, the dearsenication effect is as expected, and the arsenic content is reduced to below 1ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 It is the overall principle diagram of the present invention.

[0028] Figure 2 This is one of the overall structural schematic diagrams of the sealing structure of the present invention.

[0029] Figure 3 This is the second schematic diagram of the overall structure of the sealing structure of the present invention.

[0030] Figure 4 It is a schematic diagram of the matching relationship between the rotating shaft and the sealing cylinder of the present invention.

[0031] Reference numerals:

[0032] 101 arsenic removal tank, 102 reaction tank, 103 reactor, 104 flue gas pipe, 105 pressurizing device, 106 branch, 107 first reaction tank, 108 steam pipe, 109 stirring device, 110 sealing structure, 111 sealing cover, 112 fixed end cover, 113 spring, 114 filler, 115 pressure plate, 116 first cavity, 117 base, 118 pressure cylinder, 119 sealing cylinder, 120 upper extrusion part, 121 lower extrusion part, 122 connecting part, 123 sealing cavity, 124 charging valve, 125 detection sensor, 126 tank body, 127 rotating shaft, 128 limiting ring, 129 sealing pad. DETAILED DESCRIPTION

[0033] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0034] In the description of the embodiments of the present invention, it should be understood that the terms "length", "vertical", "horizontal", "top" and "bottom" etc. indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present invention.

[0035] In addition, 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] 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 connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, and 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.

[0037] In the embodiments of the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0038] The disclosure below provides many different embodiments or examples to implement different structures of the embodiments of the present invention. In order to simplify the disclosure of the embodiments of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the embodiments of the present invention. In addition, the embodiments of the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0039] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0040] See also Figure 1-Figure 3 This embodiment discloses a deep arsenic removal system, including an arsenic removal tank 101 and a reaction tank 102, a reactor 103 is additionally provided between the arsenic removal tank 101 and the reaction tank 102, a flue gas pipe 104 is provided at the exhaust port of the arsenic removal tank 101; a booster device 105 is provided on the flue gas pipe 104, a branch 106 is provided on the flue gas pipe 104, the flue gas pipe 104 is connected to the arsenic removal tank 101, and the branch 106 is connected to the reactor 103;

[0041] The hydrogen sulfide gas at the exhaust port of the arsenic removal tank 101 is collected and pressurized by the booster 105, and a portion of the gas enters the arsenic removal tank 101, and the other portion enters the reactor 103. The hydrogen sulfide gas entering the reactor 103 reacts with the material transported by the reaction tank 102 and then enters the arsenic removal tank 101 for a pressurized reaction.

[0042] Furthermore, the reactor 103 is connected to a steam pipe 108 of a first reaction tank 107 , and the steam pipe 108 of the first reaction tank 107 is used to heat the reactor 103 .

[0043] In actual use, the present invention maintains a positive pressure inside the arsenic removal tank 101 through the provided booster equipment, and the excess hydrogen sulfide gas is recycled for secondary use and sent to the reactor 103 under the action of the booster device 105; at the same time, the reactor 103 is heated and heated through the steam pipe 108 of the first reaction tank 107, the reaction temperature is increased to increase the solubility of hydrogen sulfide in the acid, and the arsenic removal efficiency is promoted. The purpose of efficient arsenic removal is achieved by collecting the undissolved hydrogen sulfide gas, pressurizing the arsenic removal tank 101 and the reactor 103, and reacting with phosphoric acid under pressure. After the process is optimized, the arsenic removal effect is as expected, and the arsenic content is reduced to below 1ppm.

[0044] In actual use, the boosting device 105 is a boosting fan.

[0045] Furthermore, a self-regulating valve is provided at the outlet of the pressure boosting device 105. The pressure of the gas entering the reactor 103 at the outlet of the self-regulating valve is 88KPa-100KPa.

[0046] The arsenic removal tank 101 includes a tank body 126 and a stirring device 109 disposed on the tank body 126 , and a sealing structure 110 is disposed between a stirring shaft in the stirring device 109 and the tank body 126 .

[0047] In this embodiment, the sealing structure 110 includes a sealing cover 111, a fixed end cover 112, a spring 113 and a plurality of fillers 114. The sealing cover 111 is fixedly arranged on the groove body 126. The rotating shaft 127 passes through the groove body 126 and the sealing cover 111. The filler 114 is sleeved on the rotating shaft 127 and is located inside the sealing cover 111. The spring 113 is located in the sealing cover 111 and contacts with the uppermost filler 114. The fixed end cover 112 is installed on the sealing cover 111. The extrusion portion of the fixed end cover 112 contacts with the spring 113. Under the action of the fixed end cover 112 and the spring 113, the filler 114 is in sealing contact with the rotating shaft 127.

[0048] Since the interior of the arsenic removal tank 101 is in a positive pressure state, the seal at the rotating shaft 127 in the stirring device 109 needs to be further strengthened. Therefore, in this embodiment, the spring 113 is provided to squeeze the filler 114, so that the filler 114 is always in a deformed state to improve the sealing performance between the rotating shaft 127 and the tank body 126. In the present application, the spring 113 is a strong spring 113 with a large elastic coefficient, so that the spring 113 has a large elastic force after being compressed to ensure that the filler 114 can be in a better deformation state.

[0049] Furthermore, in actual use, the sealing structure 110 further includes a pressure plate 115, which is sleeved on the rotating shaft 127, and the upper end of the pressure plate 115 contacts the spring 113, and the lower end contacts the packing 114. The pressure applied by the spring 113 to the packing 114 can be made more uniform by the provision of the pressure plate 115, so as to ensure that the packing 114 is more evenly stressed and has a better deformation effect, thereby improving the contact sealing effect with the rotating shaft 127.

[0050] Furthermore, the filler 114 has a cavity inside, which makes it easier for the filler 114 to deform after being compressed, and the cavity can better contact the rotating shaft 127 after being compressed.

[0051] The present invention also discloses a deep arsenic removal method, which includes using the above-mentioned deep arsenic removal system, and specifically includes the following steps:

[0052] After the hydrogen sulfide gas in the arsenic removal tank 101 is pressurized by the booster 105, a portion of it is sent to the reactor 103 so that the hydrogen sulfide gas reacts with the material in the first reaction tank 107, and the other portion is sent to the arsenic removal tank 101, so that the interior of the arsenic removal tank 101 is in a positive pressure state, so that the internal pressure of the arsenic removal tank 101 is 103KPa-105KPa.

[0053] The reactor 103 is a tubular reactor 103 .

[0054] In actual use, in the arsenic removal tank 101, hydrogen sulfide gas generated by the reaction of sodium sulfide and acid escapes from the acid, there is a risk of hydrogen sulfide gas overflowing from the top of the arsenic removal tank 101, and arsenic removal is not efficient enough.

[0055] The first embodiment of the present invention is to modify the existing flue gas pipe 104, and use the above-mentioned sealing structure 110 to seal the dearsenication tank 101 and the rotating shaft 127. When the equipment is running, the pressure and friction in the packing 114 make the shaft form a reliable seal. The dearsenication tank 101 is kept at a positive pressure, and the opening of the self-adjusting valve of the flue gas pipe 104 is remotely adjusted, and the pressure is controlled to be 103KPa-105KPa.

[0056] The second aspect of the present invention is that the sodium sulfide is added in the prior art by a submerged insertion tube, that is, the sodium sulfide is sent from the side of the tank body 126 into the dearsenication tank 101 at a height of about 20% of the liquid level through the insertion tube, and the height is flush with the blade of the stirring device 109 in the tank, and the rotation of the blade drives it to contact and react with phosphoric acid. Since the overflow port of the dearsenication tank 101 in the prior art is located at the bottom, it cannot fully react. The present invention first adds a tubular reactor 103 to the overflow pipe from the reaction tank 102 to the dearsenication tank 101, and at the same time, the unreacted hydrogen sulfide gas is collected through the modified flue gas pipe 104, and the air volume is controlled by the pressure fan P-197A / B through the outlet self-regulating valve opening, and the air volume pressure is controlled at 88KPa to 100KPa, and it is pressurized and added to the tubular reactor 103 and the dearsenication tank 101, so that it is further dearsenicated and the reaction efficiency is improved.

[0057] This not only reduces the safety and environmental risks on site, but also allows the unreacted hydrogen sulfide gas in the arsenic removal tank 101 to be safely and effectively reused for arsenic removal.

[0058] The third method of the present invention is to heat the tubular reactor 103 to 85° C. through the low-pressure steam pipe 108 of the first reaction tank 107 to promote the arsenic removal efficiency.

[0059] In the existing process, the atmosphere of the arsenic removal tank 101 is negative pressure, and the overflow method is bottom overflow. Sodium sulfide is sent into the arsenic removal tank 101 from the side of the tank body 126 through an insertion tube to react at about 20% of the liquid level. The arsenic removal of this process is not efficient enough, and the safety risk of hydrogen sulfide overflow is high. It is planned to optimize the arsenic removal process mode, from negative pressure reaction conditions to positive pressure reaction conditions, and the arsenic content of the arsenic removal tank 101 drops below 1ppm. When the system is running, the test data are as follows:

[0060] date load Reaction temperature Arsenic content index September 2, 2024 <![CDATA[80m 3 / h]]> 86℃ 0.8ppm September 3, 2024 <![CDATA[80m 3 / h]]> 85℃ 0.9ppm September 4, 2024 <![CDATA[85m 3 / h]]> 84℃ 0.8ppm September 5, 2024 <![CDATA[85m 3 / h]]> 85℃ 0.7ppm September 6, 2024 <![CDATA[90m 3 / h]]> 86℃ 0.8ppm September 7, 2024 <![CDATA[90m 3 / h]]> 86℃ 0.6ppm September 8, 2024 <![CDATA[95m 3 / h]]> 85℃ 0.8ppm September 9, 2024 <![CDATA[95m 3 / h]]> 86℃ 0.7ppm September 10, 2024 <![CDATA[100m 3 / h]]> 85℃ 0.9ppm September 11, 2024 <![CDATA[100m 3 / h]]> 85℃ 0.8ppm

[0061] After the process was optimized, the arsenic removal tank 101 did not overflow hydrogen sulfide, and the amount of hydrogen sulfide gas discharged to the chimney was reduced. The undissolved hydrogen sulfide gas was collected, pressurized into the reactor 103 and the arsenic removal tank 101, reacted with phosphoric acid under pressure, and the tubular reactor 103 was heated through the steam pipe 108 of the first reaction tank 107, so as to achieve the purpose of efficient arsenic removal. After the process was optimized, the arsenic removal effect reached the expected level, and the arsenic content dropped to below 1 ppm.

[0062] In actual use, when the above structure is used for sealing, it is not easy to set a detection device at the rotating pair position, and the detection of hydrogen sulfide gas cannot be realized. Therefore, in actual use, the following sealing structure 110 is used.

[0063] See also Figure 1-Figure 4The sealing structure 110 includes a base 117, a pressing cylinder 118 and a sealing cylinder 119. The base 117 is used to be fixedly mounted on the tank body 126 of the dearsenicization tank 101. The pressing cylinder 118 is movably mounted on the base 117 so that the pressing cylinder 118 can move vertically on the base 117. The sealing cylinder 119 includes an upper extrusion portion 120, a lower extrusion portion 121 and a connecting portion 122. The connecting portion 122 is an arc-shaped structure, and the two ends of the connecting portion 122 are respectively connected to the upper extrusion portion 120 and the lower extrusion portion 121;

[0064] The base 117 is installed on the groove body 126 . After the pressing cylinder 118 contacts the base 117 , the pressing cylinder 118 fixes the sealing cylinder 119 in the pressing cylinder 118 so that the arc portion contacts the rotating shaft 127 .

[0065] In this way, the connection portion 122 and the rotating shaft 127 can be in close contact with each other. The sealing cylinder 119 is made of wear-resistant material. Since the pressing cylinder 118 is movably connected to the base 117, the sealing cylinder 119 can also serve as a support.

[0066] Furthermore, in actual use, the upper extrusion part 120 and the lower extrusion part 121 form a sealed cavity 123 after contacting with the inside of the cylinder, and an inflation valve 124 is provided on the side of the pressure cylinder 118. The sealed cavity 123 is filled with gas or liquid. After the sealing cylinder 119 is deformed under pressure, it contacts with the base 117 and the pressure cylinder 118 to form a sealing pair, and no leakage will occur. At this time, the high-pressure gas and liquid will act on the lower connecting part 122, so that the connecting part 122 is deformed and fits more closely with the rotating shaft 127, thereby increasing the fitting area, and when the rotating shaft 127 undergoes radial runout, the connecting part 122 and the rotating shaft 127 can still effectively contact each other to ensure the sealing effect.

[0067] In actual use, since the connecting part 122 is an arc-shaped structure, the connecting part 122, the upper extrusion part 120 and the pressing cylinder 118 can form a first cavity 116. A detection sensor 125 is arranged in the first cavity 116. When leakage occurs between the connecting part 122 and the rotating shaft 127, the detection sensor 125 can detect the gas in the first cavity 116, thereby realizing real-time monitoring of hydrogen sulfide gas and improving safety performance during use.

[0068] In actual use, a sealing gasket 129 is provided between the base 117 and the tank body 126 .

[0069] A limiting ring 128 is provided on the base 117 , and the limiting ring 128 is coaxially matched with the pressing cylinder 118 .

[0070] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A deep arsenic removal system, comprising a arsenic removal tank and a reaction tank, characterized in that: A reactor is added between the arsenic removal tank and the reaction tank, and a flue gas pipe is provided at the exhaust port of the arsenic removal tank; a booster device is provided on the flue gas pipe, a branch is provided on the flue gas pipe, the flue gas pipe is connected to the arsenic removal tank, and the branch is connected to the reactor; The hydrogen sulfide gas at the exhaust port of the arsenic removal tank is collected and pressurized by the booster device, and a part of it enters the arsenic removal tank, and the other part enters the reactor. The hydrogen sulfide gas entering the reactor fully reacts with the material transported by the reaction tank and then enters the arsenic removal tank for pressurized reaction.

2. A deep arsenic removal system according to claim 1, characterized in that: The reactor is connected to a steam pipe of a first reaction tank, and the steam pipe of the first reaction tank is used to heat the reactor.

3. A deep arsenic removal system according to claim 1, characterized in that: The boosting device is a booster fan.

4. A deep arsenic removal system according to claim 1, characterized in that: A self-regulating valve is provided at the air outlet of the booster device.

5. A deep arsenic removal system according to claim 4, characterized in that: The pressure entering the reactor from the outlet of the self-regulating valve is 88KPa-100KPa.

6. A deep arsenic removal system according to any one of claims 1 to 5, characterized in that: The arsenic removal tank comprises a tank body and a stirring device arranged on the tank body, wherein a sealing structure is arranged between a stirring shaft of the stirring device and the tank body.

7. A deep arsenic removal system according to claim 6, characterized in that: The sealing structure includes a sealing cover, a fixed end cover, a spring and a plurality of fillers. The sealing cover is fixedly arranged on the slot body. The rotating shaft passes through the slot body and the sealing cover. The filler is sleeved on the rotating shaft and is located inside the sealing cover. The spring is located in the sealing cover and contacts with the filler at the uppermost end. The fixed end cover is installed on the sealing cover. The extrusion part of the fixed end cover contacts with the spring. Under the action of the fixed end cover and the spring, the filler contacts with the rotating shaft in a sealed manner.

8. A deep arsenic removal system according to claim 7, characterized in that: The sealing structure also includes a pressing plate, which is sleeved on the rotating shaft, with the upper end of the pressing plate in contact with the spring and the lower end in contact with the packing.

9. A deep arsenic removal method, characterized in that: The method comprises using the deep arsenic removal system according to any one of claims 1 to 8, and specifically comprises the following steps: After the hydrogen sulfide gas in the arsenic removal tank is pressurized by a booster device, a portion of it is sent to the reactor to react with the material in the first reaction tank, and the other portion is sent to the arsenic removal tank, so that the interior of the arsenic removal tank is in a positive pressure state, so that the internal pressure of the arsenic removal tank is 103KPa-105KPa.

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