System and method for absorbing sulfur dioxide in boiler flue gas

Abstract

The invention discloses a system and a method for absorbing sulfur dioxide in boiler flue gas. The system comprises a boiler induced draft fan outlet flue, a sulfur dioxide spraying and absorbing device and a flue gas discharging device, an outlet of the boiler induced draft fan outlet flue is connected with a first inlet of the sulfur dioxide spraying and absorbing device, and a first outlet of the sulfur dioxide spraying and absorbing device is connected with an inlet of the flue gas discharging device; the sulfur dioxide spraying absorption device is provided with a filler layer, a demisting device is arranged at a first outlet of the sulfur dioxide spraying absorption device, absorption liquid adopted by the sulfur dioxide spraying absorption device is a mixed solution of sulfuric acid, hydrogen iodide and iodine, and the mixed solution is located at the lower part of the sulfur dioxide spraying absorption device; a first inlet of the sulfur dioxide spraying and absorbing device is formed between the position above the liquid level of the mixed liquid and the filler layer; and flue gas from an outlet flue of the boiler induced draft fan passes through the filler layer and the demisting device to enter the flue gas emission device. The iodine solution is adopted to absorb sulfur dioxide in the boiler flue gas, and the atmospheric pollution gas sulfur dioxide is recycled.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of boiler flue gas and hydrogen production, and specifically relates to a system and method for absorbing sulfur dioxide in boiler flue gas. Background Art

[0002] Sulfur dioxide in boiler flue gas is an air pollutant gas that must be removed when discharged into the atmosphere. Currently, limestone wet desulfurization is mainly used for boiler flue gas desulfurization. This desulfurization method has the following disadvantages:

[0003] (1) The calcium hydroxide used for desulfurization is produced by pyrolysis of calcium carbonate, and carbon dioxide will be generated during this process, increasing the carbon emissions of coal-fired boilers;

[0004] (2) The gypsum produced by desulfurization has low industrial value;

[0005] (3) The power consumption during the desulfurization process is relatively large. Summary of the Invention

[0006] Aiming at the problems existing in the current boiler flue gas desulfurization, the present invention provides a system and method for absorbing sulfur dioxide in boiler flue gas.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A system for absorbing sulfur dioxide in boiler flue gas includes an outlet flue of a boiler induced draft fan, a sulfur dioxide spray absorption device, and a flue gas emission device;

[0009] The outlet of the outlet flue of the boiler induced draft fan is connected to the first inlet of the sulfur dioxide spray absorption device, and the first outlet of the sulfur dioxide spray absorption device is connected to the inlet of the flue gas emission device;

[0010] The sulfur dioxide spray absorption device is provided with a packing layer, and the first outlet of the sulfur dioxide spray absorption device is provided with a demisting device. The absorption liquid used in the sulfur dioxide spray absorption device is a mixed solution of sulfuric acid, hydrogen iodide, and iodine. The mixed solution is located at the lower part of the sulfur dioxide spray absorption device, and the first inlet of the sulfur dioxide spray absorption device is located between the liquid level of the mixed liquid and the packing layer.

[0011] A further improvement of the present invention is that it further includes a mixed liquid collection device, a circulation pump, and an iodine addition and water replenishment device;

[0012] The second outlet of the sulfur dioxide spray absorption device is connected to the first inlet of the mixed liquid collection device, the outlet of the iodine addition and water replenishment device is connected to the second inlet of the mixed liquid collection device, the first outlet of the mixed liquid collection device is connected to the inlet of the circulation pump, and the outlet of the circulation pump is connected to the second inlet of the sulfur dioxide spray absorption device;

[0013] A second inlet of the sulfur dioxide spray absorption device is provided with an atomizing nozzle, and the atomizing nozzle is located between the packing layer and the demisting device.

[0014] A further improvement of the present invention is that the iodine addition and water replenishment device adds iodine and replenishes water to the system at the initial stage of the system startup and operation. After the system operates normally, the water required for the system operation mainly comes from the water vapor carried by the boiler flue gas itself, and the iodine required mainly comes from the iodine returned to the mixed liquid collection device in the subsequent link.

[0015] A further improvement of the present invention is that it further includes a hydrogen iodide collection device, a sulfuric acid purification device, a vacuum pump, and a hydrogen iodide decomposition device;

[0016] The second outlet of the mixed liquid collection device is connected to the inlet of the hydrogen iodide collection device, the first outlet of the hydrogen iodide collection device is connected to the inlet of the vacuum pump, the second outlet of the hydrogen iodide collection device is connected to the first inlet of the sulfuric acid purification device, and the outlet of the vacuum pump is connected to the inlet of the hydrogen iodide decomposition device;

[0017] The lower part of the hydrogen iodide collection device is a mixed liquid, in which a heating device is arranged, which can heat the mixed liquid to above 90 °C. A packing layer is arranged above the mixed liquid, and the upper part is a space. The mixed liquid maintains a certain liquid level. The mixed liquid from the mixed liquid collection device passes through a pipeline through the packing layer and is inserted below the liquid level of the mixed liquid. The first outlet of the hydrogen iodide collection device is located in the upper space of the packing layer. The vacuum pump is used to maintain the internal vacuum degree of the hydrogen iodide collection device above 95 Kpa.

[0018] A further improvement of the present invention is that it further includes a sulfuric acid purification device, an iodine filtration device, a sulfuric acid concentration device, a sulfuric acid storage device, a sulfur dioxide suction device, an iodine circulation device, and a concentrated sulfuric acid circulation pump;

[0019] The second outlet of the hydrogen iodide collection device is connected to the first inlet of the sulfuric acid purification device, the first outlet of the sulfuric acid purification device is connected to the inlet of the iodine filtration device, the second outlet of the sulfuric acid purification device is connected to the inlet of the sulfur dioxide suction device, the outlet of the sulfur dioxide suction device is connected to the third inlet of the sulfur dioxide spray absorption device, the first outlet of the iodine filtration device is connected to the inlet of the sulfuric acid concentration device, the second outlet of the iodine filtration device is connected to the inlet of the iodine circulation device, the outlet of the iodine circulation device is connected to the second inlet of the mixed liquid collection device, the outlet of the sulfuric acid concentration device is connected to the inlet of the sulfuric acid storage device, the outlet of the sulfuric acid storage device is connected to the inlet of the concentrated sulfuric acid circulation pump, and the outlet of the concentrated sulfuric acid circulation pump is connected to the second inlet of the sulfuric acid purification device.

[0020] A further improvement of the present invention is that it further includes a hydrogen iodide decomposition device, a condensation device, a condensate circulation pump, and a hydrogen storage device;

[0021] The outlet of the vacuum pump is connected to the inlet of the hydrogen iodide decomposition device, the outlet of the hydrogen iodide decomposition device is connected to the inlet of the condensation device, the first outlet of the condensation device is connected to the inlet of the condensate circulation pump, the outlet of the condensate circulation pump is connected to the fourth inlet of the mixed liquid collection device, and the second outlet of the condensation device is connected to the inlet of the hydrogen storage device.

[0022] A method for absorbing sulfur dioxide from boiler flue gas, which is based on a system for absorbing sulfur dioxide from boiler flue gas, including:

[0023] The flue gas coming from the outlet flue of the boiler induced draft fan passes through the packing layer and the demisting device and enters the flue gas discharge device.

[0024] A further improvement of the present invention lies in that it further includes: the mixed solution of the sulfur dioxide spray absorption device, after being boosted by the circulation pump, passes through the atomizing nozzle at the second inlet of the sulfur dioxide spray absorption device, and enters the upper part of the packing layer of the sulfur dioxide spray absorption device in the form of spray droplets. The droplets fall and mix with the rising flue gas. Iodine, water and sulfur dioxide in it react to form sulfuric acid and hydrogen iodide, so as to achieve the purpose of absorbing sulfur dioxide. The packing layer increases the contact surface between sulfur dioxide and iodine and strengthens the absorption.

[0025] A further improvement of the present invention lies in that it further includes: after the sulfuric acid concentration at the outlet of the sulfuric acid concentration device reaches more than 98%, it enters the sulfuric acid storage device. A part of the concentrated sulfuric acid in the sulfuric acid storage device returns to the sulfuric acid purification device through the concentrated sulfuric acid circulation pump. The concentrated sulfuric acid reacts with hydrogen iodide in the sulfuric acid purification device to generate water, iodine and sulfur dioxide. Among them, sulfur dioxide, part of the water vapor and iodine vapor are transported back to the sulfur dioxide spray absorption device by the sulfur dioxide suction device. The solution in the sulfuric acid purification device after removing hydrogen iodide, after removing iodine by the iodine filtration device, the remaining sulfuric acid solution enters the sulfuric acid concentration device. The iodine filtered out by the iodine filtration device is transported to the mixed liquid collection device by the iodine circulation device.

[0026] A further improvement of the present invention lies in that it further includes: after the vacuum pump sucks hydrogen iodide gas and a small amount of water vapor in the hydrogen iodide collection device, a certain vacuum degree is formed in the hydrogen iodide collection device. The sucked hydrogen iodide gas and a small amount of water vapor enter the hydrogen iodide decomposition device and are heated to more than 450 °C. Part of the hydrogen iodide is catalytically decomposed to generate iodine vapor and hydrogen. The mixed gas composed of hydrogen iodide gas, water vapor, hydrogen and iodine vapor in the hydrogen iodide decomposition device enters the condensation device and is cooled to below 30 °C. The water vapor in the mixed gas is condensed into water, and the water dissolves hydrogen iodide to form a hydrogen iodide solution. The hydrogen iodide solution dissolves iodine again to form a mixed solution of hydrogen iodide and iodine. The mixed solution is transported to the mixed liquid collection device by the condensate circulation pump, and the non-condensable hydrogen is discharged to the hydrogen storage device for storage.

[0027] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0028] A system and method for absorbing sulfur dioxide from boiler flue gas provided by the present invention uses an iodine solution to absorb sulfur dioxide in the boiler flue gas, producing hydrogen and sulfuric acid with relatively high industrial value, and resourcefully utilizing the air-polluting gas sulfur dioxide; during the sulfur dioxide absorption process, no carbon emissions are increased, but hydrogen is produced instead, which is a green hydrogen production method; the iodine used during the sulfur dioxide absorption process is recycled, and the sulfur dioxide and water used come from the boiler flue gas, without consuming other raw materials, and the heat of the boiler itself is used for thermochemical hydrogen production, so the hydrogen production thermal efficiency is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a structural block diagram of a system for absorbing sulfur dioxide from boiler flue gas according to the present invention.

[0031] Description of the reference numerals:

[0032] 1. Outlet flue of boiler induced draft fan; 2. Sulfur dioxide spray absorption device; 3. Flue gas emission device; 4. Mixed liquid collection device; 5. Circulation pump; 6. Hydrogen iodide collection device; 7. Sulfuric acid purification device; 8. Iodine filtration device; 9. Sulfuric acid concentration device; 10. Sulfuric acid storage device; 11. Sulfur dioxide suction device; 12. Iodine circulation device; 13. Vacuum pump; 14. Condensation device; 15. Iodine addition and water replenishment device; 16. Hydrogen storage device; 17. Concentrated sulfuric acid circulation pump; 18. Hydrogen iodide decomposition device; 19. Condensate circulation pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] In the following text, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0034] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing 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 should not be construed as a limitation of the present invention.

[0035] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0036] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or a communication connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly defined and limited, the fact that the first feature is "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the fact that the first feature is "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The fact that the first feature is "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0038] It should be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0039] It should also be understood that the term "and / or" used in the specification and appended claims of the present invention refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0040] Various schematic structural diagrams according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, where for the purpose of clear expression, certain details are enlarged and certain details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual requirements.

[0041] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0042] Embodiment 1

[0043] As Figure 1 shown, a system for absorbing sulfur dioxide from boiler flue gas provided by the present invention includes an outlet flue 1 of a boiler induced draft fan, a sulfur dioxide spray absorption device 2, and a flue gas emission device 3; the outlet of the outlet flue 1 of the boiler induced draft fan is connected to the first inlet of the sulfur dioxide spray absorption device 2, and the first outlet of the sulfur dioxide spray absorption device 2 is connected to the inlet of the flue gas emission device 3; the sulfur dioxide spray absorption device 2 is provided with a packing layer, and a demisting device is arranged at the first outlet of the sulfur dioxide spray absorption device 2. The absorption liquid used in the sulfur dioxide spray absorption device 2 is a mixed solution of sulfuric acid, hydrogen iodide, and iodine. The mixed solution is located at the lower part of the sulfur dioxide spray absorption device 2, and the first inlet of the sulfur dioxide spray absorption device 2 is located between the liquid level of the mixed liquid and the packing layer.

[0044] In this embodiment, it further includes a mixed liquid collection device 4, a circulation pump 5, and an iodine addition and water replenishment device 15; the second outlet of the sulfur dioxide spray absorption device 2 is connected to the first inlet of the mixed liquid collection device 4, the outlet of the iodine addition and water replenishment device 15 is connected to the second inlet of the mixed liquid collection device 4, the first outlet of the mixed liquid collection device 4 is connected to the inlet of the circulation pump 5, and the outlet of the circulation pump 5 is connected to the second inlet of the sulfur dioxide spray absorption device 2; a spray nozzle is arranged at the second inlet of the sulfur dioxide spray absorption device 2, and the spray nozzle is located between the packing layer and the demisting device; the iodine addition and water replenishment device 15 adds iodine and water to the system at the initial stage of system startup and operation. After the system operates normally, the water required for system operation mainly comes from the water vapor carried by the boiler flue gas itself, and the iodine required mainly comes from the iodine returned to the mixed liquid collection device 4 in the subsequent link.

[0045] In this embodiment, it further includes a hydrogen iodide collection device 6, a sulfuric acid purification device 7, a vacuum pump 13, and a hydrogen iodide decomposition device 18; the second outlet of the mixed liquid collection device 4 is connected to the inlet of the hydrogen iodide collection device 6, the first outlet of the hydrogen iodide collection device 6 is connected to the inlet of the vacuum pump 13, the second outlet of the hydrogen iodide collection device 6 is connected to the first inlet of the sulfuric acid purification device 7, and the outlet of the vacuum pump 13 is connected to the inlet of the hydrogen iodide decomposition device 18; the lower part of the hydrogen iodide collection device 6 is a mixed liquid, in which a heating device is arranged, which can heat the mixed liquid to above 90°C. A packing layer is arranged above the mixed liquid, and the upper part is a space. The mixed liquid maintains a certain liquid level. The mixed liquid coming from the mixed liquid collection device 4 passes through a pipeline and penetrates through the packing layer and is inserted below the liquid surface of the mixed liquid. The first outlet of the hydrogen iodide collection device 6 is located in the upper space of the packing layer, and the vacuum pump 13 can keep the internal vacuum degree of the hydrogen iodide collection device 6 above 95 Kpa.

[0046] In this embodiment, it further includes a sulfuric acid purification device 7, an iodine filtration device 8, a sulfuric acid concentration device 9, a sulfuric acid storage device 10, a sulfur dioxide suction device 11, an iodine circulation device 12, and a concentrated sulfuric acid circulation pump 17; the second outlet of the hydrogen iodide collection device 6 is connected to the first inlet of the sulfuric acid purification device 7, the first outlet of the sulfuric acid purification device 7 is connected to the inlet of the iodine filtration device 8, the second outlet of the sulfuric acid purification device 7 is connected to the inlet of the sulfur dioxide suction device 11, the outlet of the sulfur dioxide suction device 11 is connected to the third inlet of the sulfur dioxide spray absorption device 2, the first outlet of the iodine filtration device 8 is connected to the inlet of the sulfuric acid concentration device 9, the second outlet of the iodine filtration device 8 is connected to the inlet of the iodine circulation device 12, the outlet of the iodine circulation device 12 is connected to the second inlet of the mixed liquid collection device 4, the outlet of the sulfuric acid concentration device 9 is connected to the inlet of the sulfuric acid storage device 10, the outlet of the sulfuric acid storage device 10 is connected to the inlet of the concentrated sulfuric acid circulation pump 17, and the outlet of the concentrated sulfuric acid circulation pump 17 is connected to the second inlet of the sulfuric acid purification device 7.

[0047] In this embodiment, it further includes a hydrogen iodide decomposition device 18, a condensation device 14, a condensate circulation pump 19, and a hydrogen storage device 16; the outlet of the vacuum pump 13 is connected to the inlet of the hydrogen iodide decomposition device 18, the outlet of the hydrogen iodide decomposition device 18 is connected to the inlet of the condensation device 14, the first outlet of the condensation device 14 is connected to the inlet of the condensate circulation pump 19, the outlet of the condensate circulation pump 19 is connected to the fourth inlet of the mixed liquid collection device 4, and the second outlet of the condensation device 14 is connected to the inlet of the hydrogen storage device 16.

[0048] Embodiment 2

[0049] As Figure 1 shown, a method for absorbing sulfur dioxide from boiler flue gas provided by the present invention includes: the flue gas coming from the outlet flue 1 of the boiler induced draft fan passes through the packing layer and the demisting device and enters the flue gas discharge device 3.

[0050] In this embodiment, it further includes: the mixed solution of the sulfur dioxide spray absorption device 2, which is pressurized by the circulation pump 5 and enters above the packing layer of the sulfur dioxide spray absorption device 2 through the atomizing nozzle at the second inlet of the sulfur dioxide spray absorption device 2 in the form of spray droplets. The droplets fall and mix with the rising flue gas. The iodine, water and sulfur dioxide therein react to generate sulfuric acid and hydrogen iodide, so as to achieve the purpose of absorbing sulfur dioxide. The packing layer increases the contact surface between sulfur dioxide and iodine and strengthens the absorption.

[0051] In this embodiment, it further includes: after the sulfuric acid concentration at the outlet of the sulfuric acid concentration device 9 reaches more than 98%, it enters the sulfuric acid storage device 10. Part of the concentrated sulfuric acid in the sulfuric acid storage device 10 is returned to the sulfuric acid purification device 7 through the concentrated sulfuric acid circulation pump 17. The concentrated sulfuric acid reacts with hydrogen iodide in the sulfuric acid purification device 7 to generate water, iodine and sulfur dioxide. Among them, sulfur dioxide, part of the water vapor and iodine vapor are transported back to the sulfur dioxide spray absorption device 2 by the sulfur dioxide suction device 11. The solution in the sulfuric acid purification device 7 except hydrogen iodide enters the sulfuric acid concentration device 9 after iodine is removed by the iodine filtration device 8. The iodine filtered out by the iodine filtration device 8 is transported to the mixed liquid collection device 4 by the iodine circulation device 12.

[0052] In this embodiment, it further includes: after the vacuum pump 13 sucks the hydrogen iodide gas and a small amount of water vapor in the hydrogen iodide collection device 6, a certain vacuum degree is formed in the hydrogen iodide collection device 6. The sucked hydrogen iodide gas and a small amount of water vapor enter the hydrogen iodide decomposition device 18 and are heated to more than 450 °C. Part of the hydrogen iodide is catalytically decomposed to generate iodine vapor and hydrogen. The mixed gas composed of hydrogen iodide gas, water vapor, hydrogen and iodine vapor in the hydrogen iodide decomposition device 18 enters the condensation device 14 and is cooled to below 30 °C. The water vapor in the mixed gas is condensed into water, and the water dissolves hydrogen iodide to form a hydrogen iodide solution. The hydrogen iodide solution dissolves iodine again to form a mixed solution of hydrogen iodide and iodine. The mixed solution is transported to the mixed liquid collection device 4 by the condensate circulation pump 19. The non-condensable hydrogen is discharged to the hydrogen storage device 16 for storage.

[0053] Embodiment 3

[0054] As Figure 1 shown, for a method for absorbing sulfur dioxide from boiler flue gas provided by the present invention, the sulfur dioxide content in the flue gas from the outlet flue 1 of the boiler induced draft fan is 5000 mg / Nm3, and the flue gas flow rate is 130,000 Nm3 / h. After the flue gas passes through the sulfur dioxide spray absorption device 2 to absorb sulfur dioxide, the sulfur dioxide content in the flue gas entering the flue gas emission device 3 is lower than 10 mg / Nm3, meeting the requirement that the sulfur dioxide content in the flue gas emission is lower than 50 mg / Nm3.

[0055] 224 Nm3 / h of hydrogen can be obtained from the hydrogen storage device 16, and 1 t / h of concentrated sulfuric acid can be obtained from the sulfuric acid storage device 10.

[0056] In the whole process, iodine is recycled, and the iodine supplement amount of the iodine and water supplement device 15 is less than 0.1 kg / h; due to the certain moisture in the flue gas, the water supplement amount is less than 10 kg / h.

[0057] The above shows and describes the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0058] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A system for absorbing sulfur dioxide from boiler flue gas, characterized in that, It includes the outlet flue of the boiler induced draft fan (1), the sulfur dioxide spray absorption device (2) and the flue gas emission device (3); The outlet of the outlet flue of the boiler induced draft fan (1) is connected to the first inlet of the sulfur dioxide spray absorption device (2), and the first outlet of the sulfur dioxide spray absorption device (2) is connected to the inlet of the flue gas emission device (3); The sulfur dioxide spray absorption device (2) is provided with a packing layer, and a demisting device is arranged at the first outlet of the sulfur dioxide spray absorption device (2). The absorption liquid used in the sulfur dioxide spray absorption device (2) is a mixed solution of sulfuric acid, hydrogen iodide and iodine. The mixed solution is located at the lower part of the sulfur dioxide spray absorption device (2), and the first inlet of the sulfur dioxide spray absorption device (2) is located between the liquid level of the mixed liquid and the packing layer.

2. The system for absorbing sulfur dioxide in boiler flue gas according to claim 1, characterized in that, It also includes a mixed liquid collection device (4), a circulation pump (5) and an iodine addition and water supply device (15); The second outlet of the sulfur dioxide spray absorption device (2) is connected to the first inlet of the mixed liquid collection device (4), the outlet of the iodine addition and water supply device (15) is connected to the second inlet of the mixed liquid collection device (4), the first outlet of the mixed liquid collection device (4) is connected to the inlet of the circulation pump (5), and the outlet of the circulation pump (5) is connected to the second inlet of the sulfur dioxide spray absorption device (2); The second inlet of the sulfur dioxide spray absorption device (2) is provided with an atomizing nozzle, and the atomizing nozzle is located between the packing layer and the demisting device.

3. The system for absorbing sulfur dioxide in boiler flue gas according to claim 2, characterized in that, The iodine addition and water supply device (15) adds iodine and water to the system at the initial stage of system startup and operation. After the system operates normally, the water required for system operation mainly comes from the water vapor carried by the boiler flue gas itself, and the iodine required mainly comes from the iodine returned to the mixed liquid collection device (4) in the subsequent link.

4. A system for absorbing sulfur dioxide in boiler flue gas according to claim 2, characterized in that, It also includes a hydrogen iodide collection device (6), a sulfuric acid purification device (7), a vacuum pump (13) and a hydrogen iodide decomposition device (18); The second outlet of the mixed liquid collection device (4) is connected to the inlet of the hydrogen iodide collection device (6), the first outlet of the hydrogen iodide collection device (6) is connected to the inlet of the vacuum pump (13), the second outlet of the hydrogen iodide collection device (6) is connected to the first inlet of the sulfuric acid purification device (7), and the outlet of the vacuum pump (13) is connected to the inlet of the hydrogen iodide decomposition device (18); The lower part of the hydrogen iodide collection device (6) is a mixed liquid. A heating device is arranged in the mixed liquid, which can heat the mixed liquid to above 90 °C. A packing layer is arranged in the upper part of the mixed liquid, and the upper part is a space. The mixed liquid maintains a certain liquid level. The mixed liquid coming from the mixed liquid collection device (4) passes through the pipeline through the packing layer and is inserted below the liquid level of the mixed liquid. The first outlet of the hydrogen iodide collection device (6) is located in the upper space of the packing layer. The vacuum pump (13) is used to keep the internal vacuum degree of the hydrogen iodide collection device (6) above 95 Kpa.

5. The system for absorbing sulfur dioxide in boiler flue gas according to claim 4, wherein It also includes a sulfuric acid purification device (7), an iodine filtration device (8), a sulfuric acid concentration device (9), a sulfuric acid storage device (10), a sulfur dioxide suction device (11), an iodine circulation device (12) and a concentrated sulfuric acid circulation pump (17); The second outlet of the hydrogen iodide collection device (6) is connected to the first inlet of the sulfuric acid purification device (7), the first outlet of the sulfuric acid purification device (7) is connected to the inlet of the iodine filtration device (8), the second outlet of the sulfuric acid purification device (7) is connected to the inlet of the sulfur dioxide suction device (11), the outlet of the sulfur dioxide suction device (11) is connected to the third inlet of the sulfur dioxide spray absorption device (2), the first outlet of the iodine filtration device (8) is connected to the inlet of the sulfuric acid concentration device (9), the second outlet of the iodine filtration device (8) is connected to the inlet of the iodine circulation device (12), the outlet of the iodine circulation device (12) is connected to the second inlet of the mixed liquid collection device (4), the outlet of the sulfuric acid concentration device (9) is connected to the inlet of the sulfuric acid storage device (10), the outlet of the sulfuric acid storage device (10) is connected to the inlet of the concentrated sulfuric acid circulation pump (17), and the outlet of the concentrated sulfuric acid circulation pump (17) is connected to the second inlet of the sulfuric acid purification device (7).

6. The system for absorbing sulfur dioxide in boiler flue gas according to claim 5, wherein, It further includes a hydrogen iodide decomposition device (18), a condensation device (14), a condensate circulation pump (19) and a hydrogen storage device (16); The outlet of the vacuum pump (13) is connected to the inlet of the hydrogen iodide decomposition device (18), the outlet of the hydrogen iodide decomposition device (18) is connected to the inlet of the condensation device (14), the first outlet of the condensation device (14) is connected to the inlet of the condensate circulation pump (19), the outlet of the condensate circulation pump (19) is connected to the fourth inlet of the mixed liquid collection device (4), and the second outlet of the condensation device (14) is connected to the inlet of the hydrogen storage device (16).

7. A method for absorbing sulfur dioxide in boiler flue gas, characterized in that, This method is based on a system for absorbing sulfur dioxide in boiler flue gas according to claim 6, characterized in that it includes: The flue gas coming from the outlet flue (1) of the boiler induced draft fan passes through the packing layer and the demisting device and enters the flue gas discharge device (3).

8. A method for absorbing sulfur dioxide in boiler flue gas according to claim 7, characterized in that, It further includes: The mixed solution of the sulfur dioxide spray absorption device (2), after being boosted by the circulation pump (5), passes through the atomizing nozzle at the second inlet of the sulfur dioxide spray absorption device (2) and enters above the packing layer of the sulfur dioxide spray absorption device (2) in the form of spray droplets. The droplets fall and mix with the rising flue gas, and iodine, water and sulfur dioxide in it react to form sulfuric acid and hydrogen iodide, thereby achieving the purpose of absorbing sulfur dioxide. The packing layer increases the contact area between sulfur dioxide and iodine and strengthens the absorption.

9. A method for absorbing sulfur dioxide in boiler flue gas according to claim 8, characterized in that, It further includes: After the sulfuric acid concentration at the outlet of the sulfuric acid concentration device (9) reaches more than 98%, it enters the sulfuric acid storage device (10). A part of the concentrated sulfuric acid in the sulfuric acid storage device (10) is returned to the sulfuric acid purification device (7) through the concentrated sulfuric acid circulation pump (17). The concentrated sulfuric acid reacts with hydrogen iodide in the sulfuric acid purification device (7) to generate water, iodine and sulfur dioxide. Among them, sulfur dioxide, part of the water vapor and iodine vapor are transported back to the sulfur dioxide spray absorption device (2) by the sulfur dioxide suction device (11). The solution in the sulfuric acid purification device (7) after removing hydrogen iodide, after removing iodine by the iodine filtration device (8), the remaining sulfuric acid solution enters the sulfuric acid concentration device (9), and the iodine filtered out by the iodine filtration device (8) is transported to the mixed liquid collection device (4) by the iodine circulation device (12).

10. A method for absorbing sulfur dioxide in boiler flue gas according to claim 9, characterized in that, It further includes: After the vacuum pump (13) sucks the hydrogen iodide gas and a small amount of water vapor in the hydrogen iodide collection device (6), a certain degree of vacuum is formed in the hydrogen iodide collection device (6). The sucked hydrogen iodide gas and a small amount of water vapor enter the hydrogen iodide decomposition device (18) and are heated to above 450 °C. Part of the hydrogen iodide is catalytically decomposed to produce iodine vapor and hydrogen. The mixed gas composed of hydrogen iodide gas, water vapor, hydrogen and iodine vapor in the hydrogen iodide decomposition device (18) enters the condensation device (14) and is cooled to below 30 °C. The water vapor in the mixed gas is condensed into water, and the water dissolves hydrogen iodide to form a hydrogen iodide solution. The hydrogen iodide solution dissolves iodine again to form a mixed solution of hydrogen iodide and iodine. The mixed solution is transported to the mixed liquid collection device (4) by the condensate circulation pump (19), and the non-condensable hydrogen is discharged to the hydrogen storage device (16) for storage.

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