Flue gas mercury removal system

Abstract

The utility model discloses a flue gas mercury removal system. The flue gas mercury removal system comprises a first mercury removal device, a second mercury removal device and a sedimentation device, the first mercury removal device is provided with a first mercury-containing flue gas inlet, a first mercury-removed flue gas outlet, a first circulating washing liquid inlet and a first circulating washing liquid outlet; the second mercury removal device is provided with a second mercury-containing flue gas inlet, a second mercury-removed flue gas outlet, a demisting device, a mercuric chloride-containing second circulating washing liquid inlet and a mercuric chloride-containing circulating liquid outlet, and the second mercury-containing flue gas inlet is connected with the first mercury-removed flue gas outlet. According to the flue gas mercury removal system, two stages of mercury removal devices are adopted, mercury-containing flue gas can be used for removing mercury chloride in discharged mercurous chloride suspension liquid, zinc powder does not need to be added, hydrogen is effectively prevented from being generated, the risk of explosion is reduced, and therefore safe production of enterprises can be achieved easily, and the production cost is reduced. And the flue gas mercury removal efficiency can be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of environmental protection, in particular to a system for removing mercury from flue gas. Background Art

[0002] Entering the 21st century, my country's nonferrous smelting industry has developed rapidly. During the ore smelting and roasting process, the mercuric sulfide in the ore can be directly oxidized at high temperature in the furnace to generate mercury vapor and sulfur dioxide into the smelting flue gas without a reduction reaction. The smelting flue gas contains a large amount of SO2 gas, which is generally converted into SO3 under the action of a catalyst and then prepared into sulfuric acid. In the conventional flue gas acid production process, mercury is removed in the purification section, but the conventional acid production purification system can only remove part of the mercury in the flue gas. The remaining mercury is absorbed by the circulating acid in the drying tower and the absorption tower and enters the finished sulfuric acid, which increases the mercury content in the finished acid and causes the quality of sulfuric acid to decrease. On the other hand, the mercury that is not removed will eventually enter the atmospheric environment with the flue gas, which will cause harm to the environment and human health.

[0003] Due to the high temperature in the smelting furnace, mercury almost always stays in the flue gas in the form of gas, that is, in the form of elemental mercury Hg, and some divalent mercury Hg 2+ Among them, divalent mercury compounds are relatively stable and easily soluble in water, and can be removed by purifying dilute acid washing and capture. However, elemental mercury is highly volatile and less soluble in water, and its average residence time in the atmosphere is as long as six months to two years. It is one of the most difficult forms to control and remove.

[0004] The Boliden-norzink method, also known as the chlorination method, is a widely used method for removing mercury from smelting flue gas at home and abroad. The chlorination method uses mercuric chloride as a mercury removal agent. The mercuric chloride in the circulating washing liquid reacts with the elemental mercury in the flue gas in the mercury removal tower to generate mercurous chloride precipitate, thereby achieving the effect of removing mercury from the flue gas. After sedimentation, a part of the generated mercurous chloride is oxidized into mercuric chloride under the action of chlorine and returned to the flue gas mercury removal tower. In the secondary sedimentation of mercurous chloride, zinc powder needs to be added to further convert the unreacted mercuric chloride in the solution into mercurous chloride to ensure that the mercury ion concentration in the discharged waste liquid is within an acceptable range. The reaction equation of zinc powder and mercuric chloride is: 2HgCl2+Zn→Hg2Cl2↓+Zn 2+ +2Cl-, zinc powder will react with mercuric chloride and will also react with sulfuric acid in the solution to produce hydrogen, which may cause explosion if hydrogen overflows.

[0005] Based on this technology, many domestic and foreign companies have made technical improvements. In 2012, Outotec (Finland) Ltd. invented a continuous flue gas mercury removal method based on the Boliden-norzink method. Chlorine is used to oxidize mercurous chloride, and zinc powder still needs to be added in the secondary sedimentation, and the process production safety issues still exist. Utility Model Content

[0006] The utility model aims to solve one of the technical problems in the related art to a certain extent at least. To this end, one purpose of the utility model is to provide a flue gas mercury removal system, which can use mercury-containing flue gas to remove mercuric chloride from the exhausted mercurous chloride suspension (i.e., the concentrated liquid of the circulating liquid) by adopting a two-stage mercury removal device, without adding zinc powder, effectively avoiding the generation of hydrogen, reducing the risk of explosion, and thus facilitating the safe production of enterprises.

[0007] In one aspect of the utility model, the utility model proposes a system for removing mercury from flue gas. According to an embodiment of the utility model, the system for removing mercury from flue gas comprises: a first mercury removal device, the first mercury removal device having a first mercury-containing flue gas inlet, a first flue gas outlet after mercury removal, a first circulating washing liquid inlet and a first circulating washing liquid outlet; a second mercury removal device, the second mercury removal device having a second mercury-containing flue gas inlet, a second flue gas outlet after mercury removal, a demisting device, a second circulating washing liquid inlet containing mercuric chloride and a circulating liquid outlet containing mercuric chloride, the second mercury-containing flue gas inlet is connected to the first flue gas outlet after mercury removal, the demisting device is connected to the second flue gas outlet after mercury removal; a sedimentation device, the sedimentation device having a circulating liquid inlet containing mercuric chloride, a supernatant liquid outlet containing mercuric chloride and a concentrated liquid outlet containing mercuric chloride, the circulating liquid inlet containing mercuric chloride is connected to the circulating liquid outlet containing mercury chloride, the concentrated liquid outlet containing mercuric chloride is connected to the first circulating washing liquid inlet.

[0008] According to the system for removing mercury from flue gas in the above-mentioned embodiment of the utility model, it includes a first mercury removal device, a second mercury removal device and a sedimentation device. In the process of removing mercury from flue gas, a first circulating washing liquid containing mercuric chloride is supplied to the first mercury removal device and mixed with the mercury-containing flue gas, so that the mercuric chloride in the first circulating washing liquid reacts with the mercury in the mercury-containing flue gas to form mercurous chloride, thereby facilitating the removal of mercuric chloride in the first circulating washing liquid, and obtaining the first circulating washing liquid after the mercury chloride is removed and the first flue gas after mercury removal; the first flue gas after mercury removal is supplied to the second mercury removal device and mixed with the second circulating washing liquid containing mercury chloride, so that the mercury chloride in the second circulating washing liquid reacts with the mercury in the first flue gas after mercury removal to form mercurous chloride, thereby facilitating the removal of mercury in the first flue gas after mercury removal and obtaining the second flue gas after mercury removal and the circulating liquid containing mercury chloride, thereby facilitating the improvement of the efficiency of mercury removal from flue gas; and the second circulating washing liquid is set to be mixed with the second mercury removal device, so that the mercury in the second circulating washing liquid reacts with the mercury in the first flue gas after mercury removal to form mercurous chloride, thereby facilitating the removal of mercury in the second flue gas after mercury removal and obtaining the second flue gas after mercury removal and the circulating liquid containing mercury chloride, thereby facilitating the improvement of the efficiency of mercury removal from flue gas. The demisting device connected to the flue gas outlet after mercury removal is beneficial to reducing the pressure drop and the amount of mist entrainment in the second flue gas after mercury removal; the circulating liquid containing mercuric chloride is supplied to the sedimentation device for sedimentation, so as to obtain the supernatant of the circulating liquid containing mercuric chloride and the concentrated liquid of the circulating liquid containing mercuric chloride, which is beneficial to removing the mercurous chloride produced in the second mercury removal device and improving the efficiency of flue gas mercury removal; the concentrated liquid of the circulating liquid containing mercuric chloride is supplied to the first mercury removal device as the first circulating washing liquid containing mercuric chloride, and is mixed with the mercury-containing flue gas, and the mercuric chloride in the concentrated liquid of the circulating liquid reacts with the mercury in the mercury-containing flue gas to generate mercurous chloride, which is beneficial to removing the mercuric chloride in the concentrated liquid of the circulating liquid, that is, the mercuric chloride in the concentrated liquid of the circulating liquid is removed by using the mercury-containing flue gas, without the need to add zinc powder, effectively avoiding the generation of hydrogen, reducing the risk of explosion, and thus conducive to achieving safe production of the enterprise. Therefore, the flue gas mercury removal system of the utility model can utilize mercury chloride in the concentrated liquid of the liquid after the mercury removal cycle by adopting a two-stage mercury removal device, without the need to add zinc powder, effectively avoiding the generation of hydrogen and reducing the risk of explosion. By setting up a demisting device, it is helpful to reduce the pressure drop and the amount of mist entrainment in the flue gas after the second mercury removal, thereby facilitating the safe production of the enterprise and improving the efficiency of flue gas mercury removal.

[0009] In addition, the flue gas mercury removal system according to the above embodiment of the utility model may also have the following additional technical features:

[0010] In some embodiments of the utility model, the first mercury removal device includes a first circulation pump, the first circulation pump has a first liquid inlet and a first liquid outlet, the first mercury removal device defines a first spraying area and a first liquid storage area from top to bottom, the first spraying area is provided with a first nozzle, the first mercury-containing flue gas inlet, the first mercury-removed flue gas outlet and the first circulating washing liquid inlet, the first liquid storage area is provided with the first circulating washing liquid outlet, the first circulating washing liquid outlet is connected to the first liquid inlet, and the first liquid outlet is connected to the first nozzle. Thus, it is beneficial to remove mercuric chloride in the first circulating washing liquid.

[0011] In some embodiments of the utility model, the second mercury removal device includes a second circulating pump, the second circulating pump has a second liquid inlet and a second liquid outlet, the second mercury removal device defines a second spraying area and a second liquid storage area from top to bottom, the second spraying area is provided with a second nozzle, the second mercury-containing flue gas inlet, the second flue gas outlet after mercury removal and the second circulating washing liquid inlet containing mercuric chloride, the second liquid storage area is provided with the circulating liquid outlet containing mercuric chloride, the circulating liquid outlet containing mercuric chloride is connected to the second liquid inlet, and the second liquid outlet is connected to the second nozzle. Thus, it is beneficial to remove the mercury element in the flue gas after the first mercury removal.

[0012] In some embodiments of the utility model, the second mercury removal device further has an inlet for the supernatant containing mercuric chloride, and the inlet for the supernatant containing mercuric chloride is connected to the outlet for the supernatant containing mercuric chloride, thereby facilitating the improvement of the utilization rate of the circulating liquid.

[0013] In some embodiments of the utility model, the flue gas mercury removal system further comprises a circulating washing liquid regeneration unit, the circulating washing liquid regeneration unit having a first circulating washing liquid inlet and a regenerated circulating washing liquid outlet, the first circulating washing liquid inlet is connected to the first circulating washing liquid outlet, and the regenerated circulating washing liquid outlet is connected to the second circulating washing liquid inlet containing mercuric chloride, thereby helping to reduce the cost of flue gas mercury removal.

[0014] In some embodiments of the utility model, the circulating washing liquid regeneration unit includes: a first mixing device, the first mixing device has a gas inlet, the first circulating washing liquid inlet and a first mixed liquid outlet; a second mixing device, the second mixing device has a hypochlorite solution inlet, a first mixed liquid inlet and a second mixed liquid outlet, the first mixed liquid inlet is connected to the first mixed liquid outlet; a third mixing device, the third mixing device has an acid inlet, a second mixed liquid inlet and a third mixed liquid outlet, the second mixed liquid inlet is connected to the second mixed liquid outlet; a gas-liquid separation device, the gas-liquid separation device has a third mixed liquid inlet, a gas outlet and the regenerated circulating washing liquid outlet, the third mixed liquid inlet is connected to the third mixed liquid outlet, and the gas outlet is connected to the gas inlet. Thus, it is beneficial to improve the safety of the flue gas mercury removal process.

[0015] In some embodiments of the utility model, the circulating washing liquid regeneration unit further includes: a pH test device, the pH test device having a third liquid inlet and a third liquid outlet, the third liquid inlet being connected to the third mixed liquid outlet; a turbidity test device, the turbidity test device having a fourth liquid inlet and a fourth liquid outlet, the fourth liquid inlet being connected to the third liquid outlet, and the fourth liquid outlet being connected to the gas-liquid separation device. This is conducive to further strengthening the redox reaction of hypochlorite and mercurous chloride, and improving the removal efficiency of mercury in the flue gas after the first mercury removal.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 is a schematic diagram of a flue gas mercury removal system according to an embodiment of the utility model;

[0019] Figure 2 is a schematic diagram of a flue gas mercury removal system according to another embodiment of the utility model;

[0020] Figure 3 The figure is a schematic flow chart of a method for removing mercury from flue gas according to an embodiment of the utility model.

[0021] Reference numerals:

[0022] 100-first mercury removal device; 11-first mercury-containing flue gas inlet; 12-first mercury-removed flue gas outlet; 13-first circulating washing liquid inlet; 14-first circulating washing liquid outlet; 15-first circulating pump; 151-first liquid inlet; 152-first liquid outlet; 16-first spraying area; 17-first liquid storage area; 18-first nozzle; 200-second mercury removal device; 21-second mercury-containing flue gas inlet; 22-second mercury-removed flue gas outlet; 23 - inlet of the second circulating washing liquid containing mercuric chloride; 24- outlet of the circulating liquid containing mercuric chloride; 25- second circulating pump; 251- second liquid inlet; 252- second liquid outlet; 26- second spraying area; 261- filler; 27- second liquid storage area; 28- second nozzle; 29- demister; 291- baffle demister; 292- wire mesh demister; 210- flushing device; 211- inlet of the supernatant containing mercuric chloride; 300- sedimentation device; 31-inlet of post-circulation liquid containing mercuric chloride; 32-outlet of supernatant liquid containing mercuric chloride; 33-outlet of concentrated liquid containing mercuric chloride; 400-circulating washing liquid regeneration unit; 41-inlet of first circulating washing liquid; 42-outlet of regenerated circulating washing liquid; 43-first mixing device; 431-gas inlet; 432-outlet of first mixed liquid; 44-second mixing device; 441-inlet of hypochlorite solution; 442-inlet of first mixed liquid; 443-outlet of second mixed liquid; 45-third mixing device; 451-acid inlet; 452-inlet of second mixed liquid; 453-outlet of third mixed liquid; 46-gas-liquid separation device; 461-inlet of third mixed liquid; 462-gas outlet; 463-agitator; 47-pH testing device; 471-third liquid inlet; 472-third liquid outlet; 48-turbidity testing device; 481-fourth liquid inlet; 482-fourth liquid outlet; 49-delivery pump. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0025] 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, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0026] In 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 or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0028] In one aspect of the present invention, the present invention provides a system for removing mercury from flue gas. Figure 1 The flue gas may be flue gas containing mercury produced during ore smelting and roasting. The flue gas mercury removal system includes: a first mercury removal device 100, a second mercury removal device 200 and a sedimentation device 300.

[0029] According to an embodiment of the utility model, the first mercury removal device 100 has a first mercury-containing flue gas inlet 11, a first flue gas outlet 12 after mercury removal, a first circulating washing liquid inlet 13 and a first circulating washing liquid outlet 14. In the flue gas mercury removal process, the first circulating washing liquid containing mercuric chloride is supplied to the first mercury removal device 100 through the first circulating washing liquid inlet 13, and is mixed with the mercury-containing flue gas supplied to the first mercury removal device 100 through the first mercury-containing flue gas inlet 11. The mercuric chloride in the first circulating washing liquid reacts with the mercury in the mercury-containing flue gas to generate mercurous chloride, which is conducive to removing the mercuric chloride in the first circulating washing liquid, and obtaining the first circulating washing liquid after mercury chloride removal and the first flue gas after mercury removal. The first circulating washing liquid after mercury chloride removal can be discharged through the first circulating washing liquid outlet 14, and the first flue gas after mercury removal can be discharged through the first flue gas outlet 12 after mercury removal.

[0030] It should be noted that the specific type of the first mercury removal device 100 is not particularly limited, and those skilled in the art can select it according to actual needs, as long as the purpose of removing mercuric chloride in the first circulating washing liquid by using mercury-containing flue gas can be achieved. As a specific example, the first mercury removal device 100 can be an empty tower, that is, no filler is set in the first mercury removal device 100. This is conducive to reducing the cost of flue gas mercury removal.

[0031] According to a specific embodiment of the utility model, the first mercury removal device 100 may include a first circulating pump 15, the first circulating pump 15 has a first liquid inlet 151 and a first liquid outlet 152, and the first mercury removal device 100 defines a first spraying area 16 and a first liquid storage area 17 from top to bottom. The first spraying area 16 is provided with a first nozzle 18, a first mercury-containing flue gas inlet 11, a first flue gas outlet after mercury removal 12 and a first circulating washing liquid inlet 13, and the first liquid storage area 17 is provided with a first circulating washing liquid outlet 14, the first circulating washing liquid outlet 14 is connected to the first liquid inlet 151, and the first liquid outlet 152 is connected to the first nozzle 18. Specifically, the first circulating washing liquid containing mercuric chloride is supplied to the first liquid storage area 17 of the first mercury removal device 100 through the first circulating washing liquid inlet 13, and then supplied to the first nozzle 18 through the first circulating pump 15. The first nozzle 18 sprays the first circulating washing liquid containing mercuric chloride to the first spraying area 16. The mercury-containing flue gas is supplied to the first spraying area 16 through the first mercury-containing flue gas inlet 11 to mix with the first circulating washing liquid. The mercuric chloride in the first circulating washing liquid reacts with the mercury in the mercury-containing flue gas to generate mercurous chloride, which is beneficial to remove the mercuric chloride in the first circulating washing liquid.

[0032] According to a specific embodiment of the present invention, the bottom of the first mercury removal device 100 may be conical, so that the first mercury removal device 100 has not only a washing function but also a sedimentation function.

[0033] According to the specific embodiment of the utility model, the direction in which the mercury-containing flue gas enters the first mercury removal device 100 is not particularly limited, and those skilled in the art can select it according to actual needs. As a preferred solution, the mercury-containing flue gas can enter the lower part of the first mercury removal device 100 in a direction that is inclined downward and has an angle of 10°-45° with the horizontal direction, thereby facilitating the reasonable distribution of the mercury-containing flue gas in the first mercury removal device 100, thereby improving the removal efficiency of mercuric chloride in the first circulating washing liquid.

[0034] According to a specific embodiment of the present invention, the gas velocity in the first mercury removal device 100 can be 1.5m / s-2.9m / s, for example, it can be 1.5m / s, 1.7m / s, 1.9m / s, 2.1m / s, 2.3m / s, 2.5m / s, 2.7m / s, 2.9m / s, etc., which is beneficial to improve the removal efficiency of mercuric chloride in the first circulating washing liquid.

[0035] According to an embodiment of the utility model, the second mercury removal device 200 has a second mercury-containing flue gas inlet 21, a second mercury-removed flue gas outlet 22, a demisting device 29, a second circulating washing liquid inlet 23 containing mercuric chloride, and a circulating liquid outlet 24 containing mercuric chloride. The second mercury-containing flue gas inlet 21 is connected to the first mercury-removed flue gas outlet 12, and the demisting device 29 is connected to the second mercury-removed flue gas outlet 22. In the flue gas mercury removal process, the first mercury-removed flue gas is supplied to the second mercury removal device 200 through the second mercury-containing flue gas inlet 21, and is mixed with the second circulating washing liquid containing mercury chloride supplied to the second mercury removal device 200 through the second circulating washing liquid inlet 23 containing mercury chloride. The mercuric chloride in the second circulating washing liquid reacts with the mercury in the first mercury-removed flue gas to generate mercurous chloride, which is beneficial to remove the mercury in the first mercury-removed flue gas, obtain the second mercury-removed flue gas and the circulating liquid containing mercuric chloride, and thus is beneficial to improve the efficiency of flue gas mercury removal. Among them, the second flue gas after mercury removal can pass through the demisting device 29 and be discharged through the second flue gas outlet 22 after mercury removal, which is beneficial to reducing the pressure drop and the amount of mist entrainment in the second flue gas after mercury removal; the circulating liquid containing mercuric chloride can be discharged through the circulating liquid outlet 24 containing mercuric chloride.

[0036] It should be noted that the specific type of the second mercury removal device 200 is not particularly limited, and those skilled in the art can select it according to actual needs, as long as the purpose of removing the mercury element in the flue gas after the first mercury removal can be achieved. As a specific example, the second mercury removal device 200 can be a packed tower, that is, a packing 261 is provided in the second mercury removal device 200, thereby facilitating the increase of the contact surface between the flue gas after the first mercury removal and the second circulating washing liquid containing mercuric chloride, promoting the mass transfer between the flue gas after the first mercury removal and the second circulating washing liquid containing mercuric chloride, thereby further facilitating the removal of mercury element in the flue gas after the first mercury removal. Furthermore, the height of the packing 261 can be 2m-7m. Thus, it is beneficial for the flue gas after the first mercury removal to fully react with the second circulating washing liquid containing mercuric chloride, thereby further facilitating the removal of mercury element in the flue gas after the first mercury removal.

[0037] According to a specific embodiment of the utility model, the second mercury removal device 200 may include a second circulating pump 25, the second circulating pump 25 has a second liquid inlet 251 and a second liquid outlet 252, and the second mercury removal device 200 defines a second spraying area 26 and a second liquid storage area 27 from top to bottom. The second spraying area 26 is provided with a second nozzle 28, a second mercury-containing flue gas inlet 21, a second flue gas outlet after mercury removal 22 and a second circulating washing liquid inlet 23 containing mercuric chloride. The second liquid storage area 27 is provided with a circulating liquid outlet 24 containing mercuric chloride, the circulating liquid outlet 24 containing mercuric chloride is connected to the second liquid inlet 251, and the second liquid outlet 252 is connected to the second nozzle 28. Specifically, the second circulating washing liquid containing mercuric chloride is supplied to the second liquid storage area 27 of the second mercury removal device 200 through the second circulating washing liquid inlet 23 containing mercury chloride, and then supplied to the second nozzle 28 through the second circulating pump 25. The second nozzle 28 sprays the second circulating washing liquid containing mercuric chloride to the second spraying area 26. The flue gas after the first mercury removal is supplied to the second spraying area 26 through the second mercury-containing flue gas inlet 21 to mix with the second circulating washing liquid containing mercuric chloride. The mercuric chloride in the second circulating washing liquid reacts with the mercury in the flue gas after the first mercury removal to form mercurous chloride, which is beneficial to remove the mercury in the flue gas after the first mercury removal.

[0038] According to the specific embodiment of the utility model, the specific type of the demister 29 is not particularly limited, and those skilled in the art can select it according to actual needs. For example, the demister 29 can include a baffle demister 291 and / or a wire mesh demister 292. This is further conducive to reducing the pressure drop and the amount of mist entrainment in the flue gas after the second mercury removal.

[0039] According to a specific embodiment of the utility model, the second mercury removal device 200 may further include a flushing device 210. By providing the flushing device 210, the demisting device 29 may be flushed, thereby further facilitating the reduction of the pressure drop and the amount of mist entrainment in the flue gas after the second mercury removal. Specifically, the flushing device 210 may be a nozzle. In addition, the utility model has no particular limitation on the specific position of the flushing device 210. For example, the flushing device 210 may be provided below the demisting device 29.

[0040] It should be noted that the specific composition of the flushing liquid used by the flushing device 210 is not particularly limited. For example, the flushing device 210 can use water as the flushing liquid. This is helpful to reduce the cost of flue gas mercury removal.

[0041] According to the specific embodiment of the utility model, the direction in which the first flue gas after mercury removal enters the second mercury removal device 200 is not particularly limited, and those skilled in the art can select it according to actual needs. As a preferred solution, the first flue gas after mercury removal can enter the lower part of the second mercury removal device 200 in a direction inclined downward and with an angle of 10°-45° with the horizontal direction, thereby facilitating the reasonable distribution of the first flue gas after mercury removal in the second mercury removal device 200, thereby improving the removal efficiency of mercury in the first flue gas after mercury removal.

[0042] According to a specific embodiment of the present invention, the gas velocity in the second mercury removal device 200 may be 1.3 m / s-2.2 m / s, for example, 1.3 m / s, 1.5 m / s, 1.7 m / s, 1.9 m / s, 2.1 m / s, 2.2 m / s, etc. This is beneficial to improving the removal efficiency of mercury in the flue gas after the first mercury removal.

[0043] According to a specific embodiment of the utility model, the mercury ion concentration in the second circulating washing liquid containing mercuric chloride in the second mercury removal device 200 can be 2g / L-4g / L, for example, 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, etc. This is conducive to improving the removal efficiency of mercury in the flue gas after the first mercury removal.

[0044] According to an embodiment of the utility model, the sedimentation device 300 has an inlet 31 for the circulating liquid containing mercuric chloride, an outlet 32 ​​for the supernatant containing mercuric chloride and an outlet 33 for the concentrated liquid containing mercuric chloride. The inlet 31 for the circulating liquid containing mercuric chloride is connected to the outlet 24 for the circulating liquid containing mercuric chloride, and the outlet 33 for the concentrated liquid containing mercuric chloride is connected to the inlet 13 for the first circulating washing liquid. In the flue gas mercury removal process, the circulating liquid containing mercuric chloride is supplied to the sedimentation device 300 through the circulating liquid inlet 31 containing mercuric chloride for sedimentation, and the supernatant of the circulating liquid containing mercuric chloride and the concentrated liquid of the circulating liquid containing mercuric chloride can be obtained, which is beneficial to remove the mercurous chloride generated in the second mercury removal device 200 and improve the efficiency of flue gas mercury removal; the concentrated liquid of the circulating liquid containing mercuric chloride is supplied to the first mercury removal device 100 through the first circulating washing liquid inlet 13 as the first circulating washing liquid containing mercury chloride, and is mixed with the mercury-containing flue gas supplied to the first mercury removal device 100 through the first mercury-containing flue gas inlet 11. The mercuric chloride in the concentrated liquid of the circulating liquid reacts with the mercury in the mercury-containing flue gas to generate mercurous chloride, which is beneficial to remove the mercuric chloride in the concentrated liquid of the circulating liquid, that is, the mercuric chloride in the concentrated liquid of the circulating washing liquid is removed by using the mercury-containing flue gas, without the need to add zinc powder, effectively avoiding the generation of hydrogen, reducing the risk of explosion, and thus facilitating the safe production of the enterprise. As a specific example, the sedimentation device 300 may include a sedimentation tank with a conical bottom.

[0045] According to a specific embodiment of the utility model, the mercuric chloride-containing circulating liquid inlet 31 can be set at the top center of the sedimentation device 300, the mercuric chloride-containing supernatant liquid outlet 32 ​​can be set around the top of the sedimentation device 300, and the mercuric chloride-containing concentrated liquid outlet 33 can be set at the bottom of the sedimentation device 300. Specifically, the mercuric chloride-containing circulating liquid flowing out of the mercuric chloride-containing circulating liquid outlet 24 can enter the sedimentation device 300 from the mercuric chloride-containing circulating liquid inlet 31 at the top center of the sedimentation device 300 for sedimentation, and the supernatant of the mercuric chloride-containing circulating liquid and the concentrated liquid of the mercuric chloride-containing circulating liquid can be obtained. The supernatant of the mercuric chloride-containing circulating liquid overflows through the mercuric chloride-containing supernatant liquid outlet 32 ​​around the top of the sedimentation device 300, and the concentrated liquid of the mercuric chloride-containing circulating liquid flows out through the mercuric chloride-containing concentrated liquid outlet 33 at the bottom of the sedimentation device 300. Therefore, it is beneficial to remove the mercurous chloride generated in the second mercury removal device and improve the efficiency of flue gas mercury removal.

[0046] According to a specific embodiment of the utility model, the second mercury removal device 200 further has a supernatant liquid inlet 211 containing mercuric chloride, and the supernatant liquid inlet 211 containing mercuric chloride is connected to the supernatant liquid outlet 32 ​​containing mercuric chloride, thereby facilitating the improvement of the utilization rate of the circulating liquid.

[0047] Therefore, the flue gas mercury removal system of the utility model can utilize mercury chloride in the concentrated liquid of the liquid after the mercury removal cycle by adopting a two-stage mercury removal device, without the need to add zinc powder, effectively avoiding the generation of hydrogen and reducing the risk of explosion. By setting up a demisting device, it is helpful to reduce the pressure drop and the amount of mist entrainment in the flue gas after the second mercury removal, thereby facilitating the safe production of the enterprise and improving the efficiency of flue gas mercury removal.

[0048] According to the embodiment of the present utility model, referring to Figure 2 The above flue gas mercury removal system further includes a circulating washing liquid regeneration unit 400, which has a first circulating washing liquid inlet 41 and a regenerated circulating washing liquid outlet 42, wherein the first circulating washing liquid inlet 41 is connected to the first circulating washing liquid outlet 14, and the regenerated circulating washing liquid outlet 42 is connected to the second circulating washing liquid inlet 23 containing mercuric chloride. Specifically, the circulating washing liquid regeneration unit 400 can oxidize mercurous chloride in the first circulating washing liquid after mercuric chloride is removed into mercuric chloride to obtain a regenerated circulating washing liquid. This is conducive to reducing the cost of flue gas mercury removal.

[0049] According to a specific embodiment of the present invention, the circulating washing liquid regeneration unit 400 may include: a first mixing device 43 , a second mixing device 44 , a third mixing device 45 and a gas-liquid separation device 46 .

[0050] According to a specific embodiment of the utility model, the first mixing device 43 has a gas inlet 431, a first circulating washing liquid inlet 41 and a first mixed liquid outlet 432. Specifically, the first gas containing chlorine and the first circulating washing liquid after the mercuric chloride is removed are mixed in the first mixing device 43 to obtain a first mixed liquid, and the chlorine in the first gas can react with mercurous chloride in the first circulating washing liquid after the mercuric chloride is removed to generate mercuric chloride, which is conducive to removing the chlorine in the first gas.

[0051] According to a specific embodiment of the utility model, the first mixing device 43 may include a venturi gas-liquid mixer. When the first circulating washing liquid after removing mercuric chloride flows through the venturi gas-liquid mixer, negative pressure is generated, thereby facilitating the first gas containing chlorine to be sucked into the venturi gas-liquid mixer under the action of negative pressure and mixed with the first circulating washing liquid after removing mercuric chloride, thereby facilitating the prevention of chlorine pollution to the environment.

[0052] According to a specific embodiment of the utility model, the second mixing device 44 has a hypochlorite solution inlet 441, a first mixed liquid inlet 442 and a second mixed liquid outlet 443, and the first mixed liquid inlet 442 is connected to the first mixed liquid outlet 432. Specifically, the first mixed liquid obtained by the first mixing device 43 is mixed with the hypochlorite solution in the second mixing device 44 to obtain the second mixed liquid, which can be conducive to the hypochlorite solution and the mercurous chloride in the first mixed liquid to react to generate mercuric chloride. The traditional chlorination method is an intermittent production process, and the stability of the process depends largely on the workshop operators. Chlorine, as a highly toxic gas, will endanger the health of the operators once it leaks. Compared with chlorine, the utility model uses a relatively safe hypochlorite as an oxidant, which can be conducive to improving the safety of the flue gas mercury removal process from the source, and is conducive to improving the operating environment of the flue gas mercury removal process, and solving the operation safety problem of the chlorination method flue gas mercury removal equipment. As a specific example, the second mixing device 44 may include a liquid-liquid mixer.

[0053] It should be noted that the specific composition of the hypochlorite used in the present invention is not particularly limited, and those skilled in the art can select it according to actual needs. For example, sodium hypochlorite and / or potassium hypochlorite can be used.

[0054] According to a specific embodiment of the utility model, the third mixing device 45 has an acid inlet 451, a second mixed liquid inlet 452 and a third mixed liquid outlet 453, and the second mixed liquid inlet 452 is connected to the second mixed liquid outlet 443. Specifically, the second mixed liquid obtained by the second mixing device 44 is mixed with the acid in the third mixing device 45 to obtain a third mixed liquid, and the pH of the obtained third mixed liquid can be adjusted to further enhance the redox reaction of sodium hypochlorite and mercurous chloride. As a specific example, the third mixing device 45 can include a liquid-liquid mixer.

[0055] It should be noted that the specific composition of the acid used in the present invention is not particularly limited, and those skilled in the art can select it according to actual needs. For example, hydrochloric acid and / or sulfuric acid can be used.

[0056] According to a specific embodiment of the utility model, the gas-liquid separation device 46 has a third mixed liquid inlet 461, a gas outlet 462 and a regenerated circulating washing liquid outlet 42, the third mixed liquid inlet 461 is connected to the third mixed liquid outlet 453, and the gas outlet 462 is connected to the gas inlet 431. Specifically, the third mixed liquid is supplied to the gas-liquid separation device 46, and the gas-liquid separation device 46 can cause the chlorine gas generated by the side reaction of hypochlorite and acid to separate from the third mixed liquid and enter the gas phase, so as to obtain the regenerated circulating washing liquid and the chlorine-containing gas, and the obtained chlorine-containing gas is supplied to the first mixing device 43 through the gas inlet 431 as the first chlorine-containing gas, and mixed with the first circulating washing liquid after the mercuric chloride is removed. On the one hand, the chlorine gas in the gas generated by the gas-liquid separation device 46 can react with the mercurous chloride in the first circulating washing liquid after the mercuric chloride is removed to generate mercuric chloride, and on the other hand, it can effectively solve the problem that the chlorine gas enters the second mercury removal device 200 along with the circulating washing liquid and is finally discharged along with the flue gas tail after the second mercury removal, thereby avoiding the pollution of the environment by the chlorine gas. Therefore, the flue gas mercury removal system of the utility model has good environmental benefits and can achieve safe production of enterprises. As a specific example, the gas-liquid separation device 46 can adopt a gas-liquid separation tank.

[0057] According to a specific embodiment of the utility model, a stirrer 463 is provided in the gas-liquid separation device 46. The stirrer 463 can fully stir the liquid in the gas-liquid separation device 46, thereby improving the gas-liquid separation effect.

[0058] According to a specific embodiment of the present utility model, the circulating washing liquid regeneration unit 400 further includes: a pH testing device 47 and a turbidity testing device 48 .

[0059] According to a specific embodiment of the utility model, the pH testing device 47 has a third liquid inlet 471 and a third liquid outlet 472, and the third liquid inlet 471 is connected to the third mixed liquid outlet 453. By providing the pH testing device 47, the amount of acid added can be adjusted according to the test result of the pH testing device 47, so that the pH value of the third mixed liquid is controlled within the range of 3-6, thereby facilitating further strengthening the redox reaction of hypochlorite and mercurous chloride.

[0060] According to a specific embodiment of the utility model, the turbidity testing device 48 has a fourth liquid inlet 481 and a fourth liquid outlet 482, the fourth liquid inlet 481 is connected to the third liquid outlet 472, and the fourth liquid outlet 482 is connected to the gas-liquid separation device 46. By setting the turbidity testing device 48, the amount of hypochlorite solution added can be adjusted according to the test result of the turbidity testing device 48, so that the concentration of mercuric chloride in the third mixed solution is within the range of 25g / L-40g / L, thereby facilitating the control of the mercury ion concentration in the second circulating washing liquid containing mercuric chloride in the second mercury removal device 200, thereby facilitating the improvement of the removal efficiency of mercury in the flue gas after the first mercury removal.

[0061] It should be noted that the specific types of the pH test device 47 and the turbidity test device 48 are not particularly limited, and those skilled in the art can select them according to actual needs. As a preferred solution, the pH test device 47 can use a pH online analyzer, such as a pH meter flow cell, and the turbidity test device 48 can use a turbidity online analyzer, such as a turbidity flow cell. This is conducive to the continuous operation of the mercurous chloride oxidation process and the remote operation of the entire system, effectively reducing the frequency of operators contacting dangerous sources.

[0062] According to a specific embodiment of the utility model, the above flue gas mercury removal system further includes a delivery pump 49, the liquid inlet of the delivery pump 49 is connected to the first liquid storage area 17 of the first mercury removal device 100, and the liquid outlet of the delivery pump 49 is connected to the first circulating washing liquid inlet 41. Thus, it is beneficial to supply the first circulating washing liquid after the mercuric chloride is removed to the circulating washing liquid regeneration unit 400. Specifically, the delivery pump 49 can be a small flow and high head pump.

[0063] For ease of understanding, the following describes a method for implementing flue gas mercury removal using the above flue gas mercury removal system. Figure 3 , the method comprising:

[0064] S100: The mercury-containing flue gas and the first circulating washing liquid containing mercuric chloride are supplied to the first mercury removal device for mixing.

[0065] In this step, the flue gas containing mercury and the first circulating washing liquid containing mercuric chloride are supplied to the first mercury removal device for mixing, so as to obtain the flue gas after first mercury removal and the first circulating washing liquid after mercury chloride removal. Specifically, the first circulating washing liquid containing mercury chloride is supplied to the first mercury removal device and mixed with the flue gas containing mercury, and the mercuric chloride in the first circulating washing liquid reacts with the mercury in the flue gas containing mercury to generate mercurous chloride, thereby facilitating the removal of mercuric chloride in the first circulating washing liquid, and obtaining the first circulating washing liquid after mercury chloride removal and the flue gas after first mercury removal.

[0066] S200: The flue gas after the first mercury removal and the second circulating washing liquid containing mercuric chloride are supplied to the second mercury removal device for mixing.

[0067] In this step, the first flue gas after mercury removal and the second circulating washing liquid containing mercuric chloride are supplied to the second mercury removal device for mixing, so as to obtain the second flue gas after mercury removal and the circulating liquid containing mercuric chloride. Specifically, the first flue gas after mercury removal is supplied to the second mercury removal device and mixed with the second circulating washing liquid containing mercuric chloride (the main component is mercuric chloride, containing a small amount of mercurous chloride), and the mercuric chloride in the second circulating washing liquid reacts with the mercury in the first flue gas after mercury removal to generate mercurous chloride, thereby facilitating the removal of mercury in the first flue gas after mercury removal, obtaining the second flue gas after mercury removal and the circulating liquid containing mercuric chloride, and thus facilitating the improvement of the efficiency of flue gas mercury removal.

[0068] Furthermore, part of the mercury-containing flue gas can be supplied to the first mercury removal device, and the remaining part of the mercury-containing flue gas and the flue gas after the first mercury removal can be supplied to the second mercury removal device, thereby facilitating the improvement of the efficiency of mercury removal from flue gas.

[0069] S300: Supplying the circulating liquid containing mercuric chloride to the sedimentation device for sedimentation

[0070] In this step, the post-circulation liquid containing mercuric chloride is supplied to a sedimentation device for sedimentation to obtain a supernatant of the post-circulation liquid containing mercuric chloride and a concentrated liquid of the post-circulation liquid containing mercuric chloride. Specifically, supplying the post-circulation liquid containing mercuric chloride to a sedimentation device for sedimentation can be beneficial for removing mercurous chloride generated in the second mercury removal device and improving the efficiency of mercury removal from flue gas.

[0071] Furthermore, part of the circulating liquid containing mercuric chloride in the second mercury removal device can be transported back to the second mercury removal device, and the other part can be supplied to the sedimentation device, thereby facilitating the improvement of the utilization rate of the circulating liquid containing mercuric chloride.

[0072] S400: Supplying the concentrated liquid of the circulating liquid containing mercuric chloride to the first mercury removal device as the first circulating washing liquid containing mercuric chloride

[0073] In this step, the concentrated liquid of the post-circulation liquid containing mercuric chloride is supplied to the first mercury removal device as the first circulating washing liquid containing mercuric chloride and mixed with the mercury-containing flue gas to obtain the first flue gas after mercury removal and the first circulating washing liquid after mercury chloride removal. Specifically, the concentrated liquid of the post-circulation liquid containing mercuric chloride (the main component is mercurous chloride, containing a small amount of mercuric chloride) is supplied to the first mercury removal device as the first circulating washing liquid and mixed with the mercury-containing flue gas, and the mercuric chloride in the concentrated liquid of the post-circulation liquid reacts with the mercury in the mercury-containing flue gas to generate mercurous chloride, which is conducive to removing mercuric chloride in the concentrated liquid of the post-circulation liquid, that is, mercuric chloride in the concentrated liquid of the post-circulation liquid is removed by using the mercury-containing flue gas, without the need to add zinc powder, effectively avoiding the generation of hydrogen, reducing the risk of explosion, and thus facilitating the safe production of the enterprise.

[0074] The inventors found that by utilizing mercuric chloride in the concentrated liquid of the mercury-containing flue gas removal circulation liquid, there is no need to add zinc powder, which effectively avoids the generation of hydrogen and reduces the risk of explosion. Not only is the process simple, it is also conducive to achieving safe production of the enterprise and improving the efficiency of flue gas mercury removal.

[0075] It should be noted that the specific types and control parameters of the first mercury removal device and the second mercury removal device, as well as the specific type of the sedimentation device have been described in detail above and will not be repeated here.

[0076] Furthermore, the above-mentioned method for implementing flue gas mercury removal may also include: supplying the first circulating washing liquid after mercuric chloride is removed to a circulating washing liquid regeneration unit to obtain a regenerated circulating washing liquid; and supplying the regenerated circulating washing liquid to a second mercury removal device as a second circulating washing liquid containing mercuric chloride. This can help improve the utilization rate of raw materials and reduce the cost of flue gas mercury removal.

[0077] Furthermore, most of the first circulating washing liquid after mercuric chloride removal in the first mercury removal device can be transported back to the first mercury removal device, and one part of the remaining first circulating washing liquid after mercuric chloride removal is supplied to the circulating washing liquid regeneration unit, and the other part is discharged to the downstream process for treatment. This is conducive to improving the removal efficiency of mercuric chloride in the first circulating washing liquid and preventing other impurities from being enriched in the flue gas mercury removal system.

[0078] Furthermore, the first circulating washing liquid after the removal of mercuric chloride is supplied to the circulating washing liquid regeneration unit by adopting the following steps: the first gas containing chlorine and the first circulating washing liquid after the removal of mercuric chloride are supplied to a first mixing device for mixing to obtain a first mixed liquid; the first mixed liquid and the hypochlorite solution are supplied to a second mixing device for mixing to obtain a second mixed liquid; the second mixed liquid and the acid are supplied to a third mixing device for mixing to obtain a third mixed liquid; the third mixed liquid is supplied to a gas-liquid separation device to obtain a regenerated circulating washing liquid and a gas containing chlorine; and the gas containing chlorine is supplied to the first mixing device as the first gas containing chlorine.

[0079] Specifically, the first gas containing chlorine is mixed with the first circulating washing liquid after mercuric chloride is removed in the first mixing device, and the chlorine in the first gas can react with the mercurous chloride in the first circulating washing liquid after mercuric chloride is removed to generate mercuric chloride, which is beneficial to remove the chlorine in the first gas; the first mixed liquid obtained by the first mixing device is mixed with the hypochlorite solution in the second mixing device, which can be beneficial to the hypochlorite solution and the mercurous chloride in the first mixed liquid. The reaction generates mercuric chloride. Compared with chlorine, the use of a relatively safe hypochlorite as an oxidant can improve the safety of the flue gas mercury removal process from the source, and is beneficial to improving the operating environment of the flue gas mercury removal process, and solving the problem of operating safety of the chlorination method flue gas mercury removal equipment; the second mixed liquid obtained by the second mixing device is mixed with an acid in a third mixing device to obtain a third mixed liquid, which can be The pH of the obtained third mixed liquid is adjusted to further strengthen the redox reaction of sodium hypochlorite and mercurous chloride; the third mixed liquid is supplied to a gas-liquid separation device, and the gas-liquid separation device can cause the chlorine gas generated by the side reaction of hypochlorite and acid to separate from the third mixed liquid and enter the gas phase, thereby obtaining a regenerated circulating washing liquid and a chlorine-containing gas; the chlorine-containing gas generated by the gas-liquid separation device is supplied to the first mixing device as a chlorine-containing first gas, and is mixed with the first circulating washing liquid after the mercuric chloride is removed. On the one hand, the chlorine gas in the gas generated by the gas-liquid separation device can react with the mercurous chloride in the first circulating washing liquid after the mercuric chloride is removed to generate mercuric chloride. On the other hand, the problem that the chlorine gas enters the second mercury removal device along with the circulating washing liquid and is finally discharged along with the flue gas tail after the second mercury removal can be effectively solved, thereby avoiding the pollution of the environment by the chlorine gas.

[0080] Furthermore, the pH of the third mixed solution can be tested by a pH testing device, and the amount of acid added can be adjusted according to the test result of the pH testing device to control the pH value of the third mixed solution within the range of 3-6, thereby further strengthening the redox reaction of hypochlorite and mercurous chloride.

[0081] Furthermore, the turbidity of the third mixed liquid can be tested by a turbidity testing device, and the amount of hypochlorite solution added can be adjusted according to the test result of the turbidity testing device to keep the concentration of mercuric chloride in the third mixed liquid within the range of 25g / L-40g / L. This is beneficial for controlling the concentration of mercury ions in the second circulating washing liquid containing mercuric chloride in the second mercury removal device 200, thereby helping to improve the removal efficiency of mercury in the flue gas after the first mercury removal.

[0082] It should be noted that the specific types of the first mixing device, the second mixing device, the third mixing device, the gas-liquid separation device, the pH testing device and the turbidity testing device, as well as the specific composition of the hypochlorite and the acid have been described in detail above and will not be repeated here.

[0083] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0084] Example 1

[0085] This embodiment provides a system for removing mercury from flue gas. Figure 2 , including: a first mercury removal device 100 , a second mercury removal device 200 , a sedimentation device 300 , a circulating washing liquid regeneration unit 400 and a delivery pump 49 .

[0086] The first mercury removal device 100 is an empty tower with a conical bottom. The first mercury removal device 100 includes a first circulating pump 15, which has a first liquid inlet 151 and a first liquid outlet 152. The first mercury removal device 100 defines a first spraying area 16 and a first liquid storage area 17 from top to bottom. The first spraying area 16 is provided with a first nozzle 18, a first mercury-containing flue gas inlet 11, a first flue gas outlet after mercury removal 12 and a first circulating washing liquid inlet 13. The first liquid storage area 17 is provided with a first circulating washing liquid outlet 14, which is connected to the first liquid inlet 151 through a pipeline, and the first liquid outlet 152 is connected to the first nozzle 18 through a pipeline.

[0087] The second mercury removal device 200 is a packed tower, that is, a packing 261 is arranged in the second mercury removal device 200, and the height of the packing 261 is 4m. The second mercury removal device 200 includes a second circulating pump 25, and the second circulating pump 25 has a second liquid inlet 251 and a second liquid outlet 252. The second mercury removal device 200 defines a second spraying area 26 and a second liquid storage area 27 from top to bottom. The second spraying area 26 is provided with a second nozzle 28, a second mercury-containing flue gas inlet 21, a second flue gas outlet 22 after mercury removal, a second circulating washing liquid inlet 23 containing mercuric chloride, and a supernatant liquid inlet 211 containing mercuric chloride. The second liquid storage area 27 is provided with a circulating liquid outlet 24 containing mercuric chloride, and the circulating liquid outlet 24 containing mercuric chloride is connected to the second liquid inlet 251 through a pipeline, and the second liquid outlet 252 is connected to the second nozzle 28 through a pipeline. The second mercury removal device 200 also includes a demisting device 29 and a flushing device 210. The demisting device 29 is connected to the second mercury removal flue gas outlet 22. The demisting device 29 includes a flow plate demisting device 291 and a wire mesh demisting device 292. The wire mesh demisting device 292 is arranged above the baffle demisting device 291, and the flushing device 210 is arranged below the baffle demisting device 291.

[0088] The sedimentation device 300 is a sedimentation tank with a conical bottom, having a circulating liquid inlet 31 containing mercuric chloride, a supernatant liquid outlet 32 ​​containing mercuric chloride and a concentrated liquid outlet 33 containing mercuric chloride. The circulating liquid inlet 31 containing mercuric chloride is connected to the circulating liquid outlet 24 containing mercuric chloride through a pipeline, the concentrated liquid outlet 33 containing mercuric chloride is connected to the first circulating washing liquid inlet 13 through a pipeline, and the supernatant liquid inlet 211 containing mercuric chloride is connected to the supernatant liquid outlet 32 ​​containing mercuric chloride through a pipeline.

[0089] The circulating washing liquid regeneration unit 400 includes a first mixing device 43, a second mixing device 44, a third mixing device 45, a gas-liquid separation device 46, a pH testing device 47 and a turbidity testing device 48. The first mixing device 43 adopts a venturi gas-liquid mixer, having a gas inlet 431, a first circulating washing liquid inlet 41 and a first mixed liquid outlet 432, and the first circulating washing liquid inlet 41 is connected to the first circulating washing liquid outlet 14 through a pipeline. The second mixing device 44 adopts a liquid-liquid mixer, having a hypochlorite solution inlet 441, a first mixed liquid inlet 442 and a second mixed liquid outlet 443, and the first mixed liquid inlet 442 is connected to the first mixed liquid outlet 432 through a pipeline. The third mixing device 45 adopts a liquid-liquid mixer, having an acid inlet 451, a second mixed liquid inlet 452 and a third mixed liquid outlet 453, and the second mixed liquid inlet 452 is connected to the second mixed liquid outlet 443 through a pipeline. The gas-liquid separation device 46 adopts a gas-liquid separation tank, having a third mixed liquid inlet 461, a gas outlet 462 and a regenerated circulating washing liquid outlet 42. The third mixed liquid inlet 461 is connected to the third mixed liquid outlet 453 through a pipeline, and the gas outlet 462 is connected to the gas inlet 431 through a pipeline. An agitator 463 is arranged in the gas-liquid separation device 46, and the regenerated circulating washing liquid outlet 42 is connected to the second circulating washing liquid inlet 23 containing mercuric chloride through a pipeline. The pH testing device 47 adopts a pH meter circulation cell, having a third liquid inlet 471 and a third liquid outlet 472, and the third liquid inlet 471 is connected to the third mixed liquid outlet 453 through a pipeline. The turbidity testing device 48 adopts a turbidity circulation cell, having a fourth liquid inlet 481 and a fourth liquid outlet 482, and the fourth liquid inlet 481 is connected to the third liquid outlet 472 through a pipeline, and the fourth liquid outlet 482 is connected to the gas-liquid separation device 46 through a pipeline. The pipelines between the first mixing device 43, the second mixing device 44, the third mixing device 45 and the gas-liquid separation device 46 are arranged to have a sufficient length according to the site to ensure the reaction time of the solution in the pipeline.

[0090] The delivery pump 49 is a small flow and high lift pump. The liquid inlet of the delivery pump 49 is connected to the first liquid storage area 17 of the first mercury removal device 100 through a pipeline, and the liquid outlet of the delivery pump 49 is connected to the first circulating washing liquid inlet 41 through a pipeline.

[0091] The flue gas mercury removal system of this embodiment is used to implement flue gas mercury removal

[0092] A portion of mercury-containing flue gas from the upstream process of a smelter (gas volume: 60000Nm 3 / h, mercury content: 60mg / Nm 3) enters the first mercury removal device 100 (tower diameter 4.0m) from bottom to top along a downwardly inclined direction with an angle of 10° with the horizontal direction, and the gas velocity in the first mercury removal device 100 is 2.0m / s. It contacts and reacts with the first circulating washing liquid (mercurous chloride content is 36g / L, mercuric chloride content is 0.4g / L) from top to bottom in the first mercury removal device 100, and the mercury vapor in the mercury-containing flue gas continues to chemically react with the mercuric chloride in the first circulating washing liquid to generate mercurous chloride.

[0093] The first mercury-removed flue gas from the first mercury-removed flue gas outlet 12 and another part of the mercury-containing flue gas from the upstream process (gas volume: 60000Nm 3 / h, mercury content: 60mg / Nm 3 ) After mixing, the mixed flue gas enters the second mercury removal device 200 (tower diameter 6.0m) from bottom to top along a downwardly inclined direction with an angle of 10° with the horizontal direction. The gas velocity in the second mercury removal device 200 is 1.5m / s. It contacts and reacts with the second circulating washing liquid (mercurous chloride content of 1.0g / L and mercuric chloride content of 2.7g / L) from top to bottom in the second mercury removal device 200. The mercury vapor in the mixed flue gas reacts chemically with the mercuric chloride in the second circulating washing liquid to generate mercurous chloride, and the second flue gas after mercury removal and the circulating liquid containing mercuric chloride are obtained. The mercury content in the flue gas after the second mercury removal is 0.6mg / Nm 3 .

[0094] Most of the circulating liquid containing mercuric chloride in the second liquid storage area 27 is transported back to the second mercury removal device 200 through the second circulation pump 25, and the other part of the circulating liquid containing mercuric chloride is transported to the sedimentation device 300 through the branch pipe for sedimentation. The concentrated liquid of the circulating liquid containing mercuric chloride at the bottom of the sedimentation device 300 is discharged to the first mercury removal device 100 for use as the first circulating washing liquid, and the supernatant liquid of the circulating liquid containing mercuric chloride at the top is drained back to the second mercury removal device 200.

[0095] Most of the first circulating washing liquid in the first liquid storage area 17 is transported back to the first mercury removal device 100 through the first circulating pump 15. The remaining first circulating washing liquid is divided into two parts, one part of the first circulating washing liquid is transported by the transport pump 49, and enters the gas-liquid separation device 46 after passing through the first mixing device 43, the second mixing device 44, and the third mixing device 45 in sequence, and the other part of the first circulating washing liquid is discharged to the downstream process for treatment.

[0096] When the first circulating washing liquid passes through the first mixing device 43, negative pressure is generated, and the gas containing a small amount of chlorine in the gas-liquid separation device 46 is sucked into the first mixing device 43 to mix and react with the first circulating washing liquid to obtain a first mixed liquid. The first mixed liquid and the sodium hypochlorite solution are supplied to the second mixing device 44 for mixing, and the mercurous chloride in the system reacts with the sodium hypochlorite to form mercuric chloride to obtain a second mixed solution. The second mixed solution and hydrochloric acid are supplied to the third mixing device 45 for mixing to obtain a third mixed liquid, and the redox reaction of sodium hypochlorite and mercurous chloride is further strengthened. The pH value of the third mixed liquid is adjusted to 4 according to the test result of the pH test device 47, and the mercuric chloride concentration in the third mixed liquid is adjusted to 35.5 g / L according to the test result of the turbidity test device 48. The third mixed liquid is supplied to the gas-liquid separation device 46, and the gas at the top of the gas-liquid separation device 46 is sucked into the first mixing device 43 under the action of negative pressure. The regenerated circulating washing liquid at the bottom of the gas-liquid separation device 46 flows by gravity to the second mercury removal device 200 to replenish the mercuric chloride consumed by mercury in the second circulating washing liquid. The mercury ion concentration in the second circulating washing liquid is 2 g / L.

[0097] With the long-term operation of the first mercury removal device 100, other impurities are enriched in the flue gas mercury removal system. Waste liquid is discharged from one side of the conical bottom of the first mercury removal device 100 once a week. The mercury ion content in the discharged waste liquid is 40 mg / L.

[0098] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0099] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A system for removing mercury from flue gas, characterized in that: include: a first mercury removal device, the first mercury removal device having a first mercury-containing flue gas inlet, a first mercury-removed flue gas outlet, a first circulating washing liquid inlet and a first circulating washing liquid outlet; a second mercury removal device, the second mercury removal device comprising a second mercury-containing flue gas inlet, a second mercury-removed flue gas outlet, a demisting device, a second circulating washing liquid inlet containing mercuric chloride, and a mercury-chloride-containing circulating liquid outlet, the second mercury-containing flue gas inlet being connected to the first mercury-removed flue gas outlet, and the demisting device being connected to the second mercury-removed flue gas outlet; A sedimentation device, wherein the sedimentation device has an inlet for a circulating liquid containing mercuric chloride, an outlet for a supernatant liquid containing mercuric chloride and an outlet for a concentrated liquid containing mercuric chloride, wherein the inlet for the circulating liquid containing mercuric chloride is connected to the outlet for the circulating liquid containing mercuric chloride, and the outlet for the concentrated liquid containing mercuric chloride is connected to the inlet for the first circulating washing liquid.

2. The system for removing mercury from flue gas according to claim 1, characterized in that: The first mercury removal device includes a first circulation pump, which has a first liquid inlet and a first liquid outlet. The first mercury removal device defines a first spraying area and a first liquid storage area from top to bottom. The first spraying area is provided with a first nozzle, the first mercury-containing flue gas inlet, the first mercury-removed flue gas outlet and the first circulating washing liquid inlet. The first liquid storage area is provided with the first circulating washing liquid outlet, the first circulating washing liquid outlet is connected to the first liquid inlet, and the first liquid outlet is connected to the first nozzle.

3. The system for removing mercury from flue gas according to claim 1, characterized in that: The second mercury removal device includes a second circulation pump, which has a second liquid inlet and a second liquid outlet. The second mercury removal device defines a second spraying area and a second liquid storage area from top to bottom. The second spraying area is provided with a second nozzle, the second mercury-containing flue gas inlet, the second flue gas outlet after mercury removal and the second circulating washing liquid inlet containing mercuric chloride. The second liquid storage area is provided with an outlet for the circulating liquid containing mercuric chloride, and the outlet for the circulating liquid containing mercuric chloride is connected to the second liquid inlet, and the second liquid outlet is connected to the second nozzle.

4. The system for removing mercury from flue gas according to claim 1, characterized in that: The second mercury removal device further comprises an inlet for the supernatant liquid containing mercuric chloride, and the inlet for the supernatant liquid containing mercuric chloride is connected to the outlet for the supernatant liquid containing mercuric chloride.

5. The system for removing mercury from flue gas according to claim 1, characterized in that: It also includes a circulating washing liquid regeneration unit, which has a first circulating washing liquid inlet and a regenerated circulating washing liquid outlet, the first circulating washing liquid inlet is connected to the first circulating washing liquid outlet, and the regenerated circulating washing liquid outlet is connected to the second circulating washing liquid inlet containing mercuric chloride.

6. The system for removing mercury from flue gas according to claim 5, characterized in that: The circulating washing liquid regeneration unit comprises: a first mixing device, the first mixing device having a gas inlet, the first circulating washing liquid inlet and a first mixed liquid outlet; a second mixing device, the second mixing device having a hypochlorite solution inlet, a first mixed liquid inlet, and a second mixed liquid outlet, the first mixed liquid inlet being connected to the first mixed liquid outlet; a third mixing device, the third mixing device having an acid inlet, a second mixed liquid inlet and a third mixed liquid outlet, wherein the second mixed liquid inlet is connected to the second mixed liquid outlet; A gas-liquid separation device is provided, wherein the gas-liquid separation device has a third mixed liquid inlet, a gas outlet and the regenerated circulating washing liquid outlet, the third mixed liquid inlet is connected to the third mixed liquid outlet, and the gas outlet is connected to the gas inlet.

7. The system for removing mercury from flue gas according to claim 6, characterized in that: The circulating washing liquid regeneration unit also includes: A pH testing device, the pH testing device having a third liquid inlet and a third liquid outlet, the third liquid inlet being connected to the third mixed liquid outlet; The turbidity testing device comprises a fourth liquid inlet and a fourth liquid outlet, wherein the fourth liquid inlet is connected to the third liquid outlet, and the fourth liquid outlet is connected to the gas-liquid separation device.

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