Ammonia desulfurization system and desulfurization method

Abstract

The invention relates to the technical field of gas impurity separation, in particular to an ammonia-process desulfurization system and method, and the ammonia-process desulfurization system comprises a desulfurization tower which comprises an oxidation section, a concentration section, an absorption section, a purification section and a demisting section which are sequentially arranged from bottom to top. The inside of the oxidation section is used for accommodating ammonia-containing desulfurization liquid, and the middle upper part of the oxidation section is provided with a reflux inlet and a first outlet lower than the reflux inlet. A second outlet and an oxygen inlet are formed in the bottom of the oxidation section. A flue gas inlet is formed in the middle of the concentration section, a concentration spraying layer is arranged on the upper portion of an inner cavity of the concentration section and communicated with the upper end of a concentration circulating tank through a liquid supply pipeline, the concentration circulating tank is communicated with the lower end of the concentration section through a liquid return pipe, and a concentration circulating pump is arranged on the liquid supply pipeline. A deamination spraying layer and two desulfurization spraying layers are sequentially arranged in the absorption section from top to bottom, the desulfurization spraying layers are communicated with the first outlet through a first pipeline, and the deamination spraying layer is communicated with the second outlet through a second pipeline.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas impurity separation, and particularly relates to an ammonia desulfurization system and a desulfurization method. BACKGROUND

[0002] The ammonia flue gas desulfurization is a wet flue gas desulfurization process in which an amino substance is used as an absorbent to remove sulfur dioxide in flue gas and recover by-products such as ammonium sulfate.

[0003] In the related technical solution, the desulfurization system comprises a desulfurization tower, the desulfurization tower comprises, from bottom to top, an oxidation section, a concentration section, an absorption section, a purification section and a demisting section, the oxidation section, the concentration section, the absorption section and the purification section are separated by partitions, and the partitions between the concentration section and the absorption section and between the absorption section and the purification section are respectively provided with gas lift caps. The oxidation section is pre-stored with ammonia-containing desulfurization liquid, the desulfurization tower is externally provided with a concentration circulating tank, the concentration circulating tank and the concentration section form a circulating loop, and the absorption section and the oxidation section form another circulating loop. The concentration section sprays the concentration liquid to cool the flue gas and part of the sulfur dioxide in the flue gas enters the desulfurization liquid to crystallize and precipitate. The absorption section sprays the ammonia-containing desulfurization liquid to remove the sulfur dioxide in the flue gas and part of the ammonium sulfate crystals.

[0004] However, in the above technical solution, in order to improve the absorption effect of the absorption section on the sulfur dioxide in the flue gas, the amino substance in the ammonia-containing desulfurization liquid is generally in a saturated or supersaturated state, which is prone to cause the amino substance in the ammonia-containing desulfurization liquid to escape in the form of ammonia gas in the absorption section, thereby causing the gas discharged from the upper end of the desulfurization tower to be lower than the emission standard.

[0005] In addition, the partitions and the gas lift caps arranged between the concentration section and the absorption section can realize the redistribution of the flue gas by the gas lift caps, improve the contact area and the reaction efficiency of the desulfurization liquid in the absorption section. However, the gas lift caps are prone to be blocked by impurities in the flue gas after long-term use, thereby affecting the redistribution and adjustment function of the gas lift caps on the flue gas. SUMMARY

[0006] The present application provides an ammonia desulfurization system and a desulfurization method, which can at least solve one of the above technical problems.

[0007] To solve the above technical problems, one or more embodiments of the present application provide an ammonia desulfurization system, which comprises a desulfurization tower including an oxidation section, a concentration section, an absorption section, a purification section and a demisting section arranged in sequence from bottom to top. The oxidation section is internally used for containing ammonia-containing desulfurization liquid, and the middle and upper part of the oxidation section is provided with a reflux port, an ammonia adding port and a first outlet lower than the reflux port. The bottom of the oxidation section is provided with a second outlet and an oxygen inlet. The middle part of the concentration section has a flue gas inlet, and the upper part of the inner cavity of the concentration section is provided with a concentration spray layer. The concentration spray layer is communicated with the middle and upper part of a concentration circulating tank through a liquid supply pipeline. The concentration circulating tank is communicated with the lower end of the concentration section through a liquid return pipe. The liquid supply pipeline is provided with a concentration circulating pump. The lower end of the concentration circulating tank is communicated with a post-processing device.

[0008] The absorption section internally has a deamination spray layer and two layers of desulfurization spray layers arranged in sequence from top to bottom. The lower end of the absorption section is communicated with the reflux port through a reflux pipe. The desulfurization spray layer is communicated with the first outlet through a first pipeline. The deamination spray layer is communicated with the second outlet through a second pipeline. The first pipeline and the second pipeline are respectively provided with absorption circulating pumps. The purification section has a water washing spray layer to wash the flue gas discharged from the absorption section with water. The demisting section is used for realizing demisting of the flue gas discharged from the purification section. The upper end of the demisting section is communicated with the flue gas outlet of the desulfurization tower.

[0009] Further, the concentration section and the oxidation section are separated by a first partition plate. The concentration section and the absorption section are separated by a second partition plate. The second partition plate is uniformly provided with a plurality of vertical gas lift caps with open lower ends.

[0010] Further, the second partition plate is provided below with a support fixed to the desulfurization tower. The support is provided with a plurality of vertical plugs. Each gas lift cap is provided below with a plug. The second partition plate is sealingly and slidably connected with the inner wall of the desulfurization tower. Springs are installed between the partition plate and the support. The partition plate can be vertically lifted to make the plug enter or leave the gas lift cap.

[0011] Further, the desulfurization tower is provided with a first inlet and a second inlet lower than the first inlet. The two inlets are respectively communicated with the reflux pipe through branch pipes. The branch pipes are provided with on-off valves. The height of the first inlet is equal to the height of the upper end of the second partition plate when the upper end of the second partition plate does not accumulate desulfurization liquid. The height of the second inlet is equal to the height of the upper end of the second partition plate when the upper end of the second partition plate accumulates desulfurization liquid.

[0012] One or more embodiments of the present application also provide a flue gas desulfurization method using the above-mentioned ammonia desulfurization system, which comprises the following steps: Step 1: The flue gas enters the concentration section from the flue gas inlet and is sprayed by the concentration spray layer to cool the flue gas to below 65℃. The concentrated liquid in the concentration section is evaporated by heat to realize concentration. The concentrated liquid enters the concentration circulating tank through the liquid return pipe. The upper layer of the concentrated liquid in the concentration circulating tank is sent into the concentration section by the concentration circulating pump for spraying. The crystalline body at the bottom of the concentration circulating tank is sent to the post-processing device.

[0013] Step 2, the flue gas rises to the absorption section, and the desulfurization spray layer and the deamination spray layer are used to spray the flue gas to absorb the sulfur dioxide in the flue gas and the ammonia gas escaping from the desulfurization solution. Then the flue gas rises from the absorption section to the water washing section.

[0014] Step 3, the water washing spray layer washes the residual sulfur dioxide, ammonium sulfate solution and ammonia gas in the flue gas, and then the flue gas is discharged to the outside of the desulfurization tower after demisting in the demisting section. The water in the water washing section flows back to the circulating water tank connected to the purification section.

[0015] The beneficial effects of one or more of the above technical solutions are: (1) In the present scheme, the upper part of the oxidation section is provided with a reflux port, an ammonia adding port and a first outlet, and the bottom is provided with a second outlet and an oxygen inlet. The absorption section is arranged from top to bottom with a deamination spray layer and two layers of desulfurization spray layer. The desulfurization spray layer is in communication with the first outlet, and the deamination spray layer is in communication with the second outlet. In this arrangement, the desulfurization solution in the absorption section reacts with the sulfur-containing flue gas to mainly generate ammonium sulfite and bisulfite. At this time, the ammonium sulfite and bisulfite flow back to the middle part of the oxidation section, and the slightly excessive ammonia water added in the middle part of the oxidation section converts the bisulfite into ammonium sulfite. That is, in the present scheme, the ammonium sulfite generated in the absorption section is reflowed to the desulfurization spray layer to spray the flue gas for desulfurization. Compared with the existing technology which uses ammonia water to absorb sulfur dioxide, the ammonium sulfite has higher capture efficiency and faster reaction speed for sulfur dioxide. Moreover, the present scheme is convenient for removing excess bisulfite using slightly excessive ammonia water, avoiding the influence of bisulfite on the capture of sulfur dioxide by the desulfurization solution.

[0016] At the same time, the above process of using slightly excessive ammonia water to remove bisulfite will cause a slight excess of ammonia water in the desulfurization solution, which will cause ammonia escape in the absorption section. In the present scheme, the oxidation air first enters the bottom of the oxidation section to oxidize the ammonium sulfite. The bottom of the oxidation section mainly forms ammonium sulfate and free hydrogen ions. The hydrogen ions have high capture efficiency and fast reaction speed for ammonia gas. At this time, it is convenient to use the deamination spray layer to spray the solution containing hydrogen ions to achieve the absorption and removal of escaped ammonia gas, thereby reducing the amount of ammonia gas escaping from the top of the desulfurization tower.

[0017] (2) In the present scheme, the concentration section and the absorption section are separated by a second partition plate. A plurality of gas lifting caps are uniformly arranged on the second partition plate, which facilitates the redistribution of flue gas in the absorption section by the gas lifting caps, thereby uniformly distributing the flue gas in the absorption section, increasing the contact area between the flue gas and the desulfurization solution, and improving the desulfurization efficiency of the flue gas.

[0018] (3) In the present scheme, the second partition plate is slidably and sealingly connected with the inner wall of the desulfurization tower, and springs are installed between the second partition plate and the support. The second partition plate can be vertically lifted so that the plug can scrape the inner wall of the gas lifting cap to achieve intermittent cleaning of the gas lifting cap.

[0019] Furthermore, due to the high-temperature operating environment inside the desulfurization tower (generally around 65 degrees Celsius in the concentration section) and the large overall size of the desulfurization tower, this solution does not include a hydraulic cylinder or other power source. Specifically, this solution utilizes a spring and the desulfurization liquid deposited above the second baffle as the power source for the raising and lowering of the second baffle. When the first inlet is closed, the desulfurization liquid deposited above the second baffle makes the weight of the second baffle greater than the spring force, causing the second baffle to descend. The plug is then inserted into the lifting cap to scrape and clean the inner wall of the lifting cap, preventing blockage. When the second inlet is opened, the accumulated desulfurization liquid is diverted to the oxidation section through the return pipe, thereby reducing the weight on the second baffle and the lifting cap, and the spring drives the second baffle to rise and reset.

[0020] In summary, this solution facilitates cleaning without shutting down the machine or using a power source such as a hydraulic cylinder, by raising and lowering the plug to scrape and clean the air ring, thus preventing blockage. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the desulfurization system in an embodiment of the present invention; Figure 2 This is a schematic diagram of the desulfurization tower with omitted pipelines in an embodiment of the present invention; Figure 3 This is a partial schematic diagram of the desulfurization tower when the second baffle has not descended in an embodiment of the present invention; Figure 4 This is a partial schematic diagram of the desulfurization tower when the second baffle descends in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the air-lifting cap in an embodiment of the present invention; Figure 6 This is a schematic diagram of the cleaning nozzles arranged below the second partition in an embodiment of the present invention; Figure 7 This is a schematic diagram of the cleaning nozzle below the second partition in an embodiment of the present invention rotating so that the opening faces horizontally.

[0022] In the figure, 1, desulfurization tower; 101, oxidation section; 102, concentration section; 103, absorption section; 104, purification section; 105, demisting section; 2, process water supply pipe; 3, water supply pipe; 4, first pipeline I; 5, first pipeline II; 6, second pipeline; 7, return water pipeline; 8, circulating water tank; 9, return liquid pipe; 10, liquid supply pipeline; 11, concentration circulating tank; 12, post-treatment discharge pipe; 14, first pipeline; 15, liquid discharge pipe; 16, oxygen supply pipeline; 17, ammonia addition pipe; 18, reflux pipe; 181, first branch pipe; 182, second branch pipe; 19, cooling flushing pipe; 20, flue gas pipe; 21, gas-liquid distributor; 22, ammonium sulfate distributor; 23, flue gas inlet; 24, second partition; 25, first filler layer; 26, deamination spray layer; 27, third partition; 28, first demister; 29, water washing spray layer; 30, second filler layer; 31, desulfurization spray layer; 32, gas lifting cap; 321, top plate; 322, main ring; 323, through hole; 33, flushing layer; 331, body; 332, spray head; 333, support frame; 34, concentration spray layer; 35, first partition; 36, spring; 37, plug; 38, bracket; 39, oxidation air distributor; 40, second demister; 41, backflushing layer. DETAILED DESCRIPTION

[0023] To clearly illustrate the technical features of the present application, the present application will be described in detail below with specific embodiments and in conjunction with the accompanying drawings.

[0024] Referring to Figures 1-7 , a typical embodiment of the present application provides an ammonia desulfurization system, which comprises a desulfurization tower 1. The desulfurization tower 1 is a tower structure as a whole. The inner cavity of the desulfurization tower 1 is divided into an oxidation section 101, a concentration section 102, an absorption section 103, a purification section 104 and a demisting section 105 from bottom to top by a first partition 35, a second partition 24 and a third partition 27. The oxidation section 101 is used to contain desulfurization liquid containing ammonia. The middle and upper part of the oxidation section 101 is provided with a reflux port, an ammonia addition port and a first outlet lower than the reflux port. The bottom of the oxidation section 101 is provided with a second outlet and an oxygen inlet. The concentration section 102 has a flue gas inlet 23 in the middle. The flue gas inlet 23 is inclined downward by 20°. The length of the flue gas in the concentration section 102 is extended to achieve the effect of sufficient cooling. The bottom of the flue gas inlet 23 is prevented from having accumulated material. The flue gas is prevented from horizontally entering to form hanging material on the opposite tower wall. The upper part of the inner cavity of the concentration section 102 is provided with a concentration spray layer 34. The concentration spray layer 34 is communicated with the middle and upper part of a concentration circulating tank 11 through a liquid supply pipeline 10. The concentration circulating tank 11 is communicated with the lower end of the concentration section 102 through a return liquid pipe 9. The liquid supply pipeline 10 is provided with a concentration circulating pump. The lower end of the concentration circulating tank 11 is communicated with a post-treatment device.

[0025] The ammonia-removing spray layer 26 and the two desulfurizing spray layers 31 are arranged in the absorption section 103 from top to bottom. The lower end of the absorption section 103 is communicated with the backflow port through the backflow pipe 18. The desulfurizing spray layers 31 are communicated with the first outlet through the first pipe 14. The ammonia-removing spray layer 26 is communicated with the second outlet through the second pipe 6. The absorption circulating pumps are arranged on the first pipe 14 and the second pipe 6 respectively. The purification section 104 has the water-washing spray layer 29 to wash the flue gas discharged from the absorption section 103 with water. The demisting section 105 is used to realize the demisting of the flue gas discharged from the purification section 104. The demisting section 105 has the first demister 28. The upper end of the demisting section 105 is communicated with the flue gas outlet of the desulfurizing tower 1.

[0026] Generally, the ammonia water is continuously added into the oxidation section 101. The products generated by the reaction between the ammonia water and the sulfur dioxide in the absorption section 103 mainly include ammonium sulfite, ammonium bisulfite and ammonium sulfate. In addition, the products also include part of hydrogen ions. That is, the above-mentioned desulfurizing solution containing ammonia is a mixed solution of ammonia water, ammonium sulfite, ammonium bisulfite, ammonium sulfate and hydrogen ions.

[0027] Specifically, the backflow port is communicated with the lower end of the absorption section 103 through the backflow pipe 18. The ammonia-adding port is communicated with the ammonia-adding pipe 17. One end of the first pipe 14 is communicated with the first outlet. The other end of the first pipe 14 is divided into the first pipe I 4 and the first pipe II 5. The first pipe I 4 and the first pipe II 5 are communicated with the two desulfurizing spray layers 31 respectively. The second outlet is communicated with the ammonia-removing spray layer 26 through the second pipe 6. The oxygen inlet is communicated with the oxygen supply pipe 16, so that the oxygen is introduced into the bottom of the desulfurizing solution in the oxidation section 101. The oxygen moves in the direction from bottom to top. The backflow solution containing ammonium sulfite and ammonium bisulfite in the absorption section 103 sprays and falls in the direction from top to bottom. Then, the oxygen reacts with the ammonium sulfite to oxidize the ammonium sulfite into ammonium sulfate, so as to be transported to the concentration circulating tank 11 to wait for crystallization after the concentration of the ammonium sulfate in the bottom of the oxidation section 101 exceeds the set threshold value.

[0028] Specifically, the flue gas inlet 23 is communicated with the flue gas to be desulfurized through the flue gas pipe 20. In order to realize the preliminary impurity removal and cooling of the flue gas, the cooling spray pipe 19 is connected to the flue gas pipe 20. The cooling spray pipe 19 can spray the process water to the flue gas in the flue gas pipe 20, so as to preliminarily cool and remove the impurities of the flue gas.

[0029] Specifically, the concentrated spray layer 34, the liquid supply pipeline 10, the concentrated circulating tank 11, the liquid return pipeline 9 and the concentration section 102 combine to form a circulating loop of concentrated solution, the main component of which is ammonium sulfite. The concentrated circulating tank 11 plays a role in stratifying the ammonium sulfite solution. The heavy liquid with high ammonium sulfite content, high density and easy to crystallize is at the lower end of the concentrated circulating tank 11, and the light liquid with low ammonium sulfite content, low density and not easy to crystallize is at the upper part of the concentrated circulating tank 11. At this time, the heavy liquid of the concentrated solution is transported to the post-processing equipment for centrifugal separation through the post-processing discharge pipe 12 at the lower end of the concentrated circulating tank 11 when it is about to precipitate or has precipitated part of the crystal. The light liquid of the centrifugal separation is returned to the concentrated circulating tank 11. Moreover, the light liquid in the concentrated circulating tank 11 is returned to the concentrated spray layer 34 of the concentration section 102 to continue to react with the flue gas, so as to realize the concentration of ammonium sulfate.

[0030] It is known that the temperature of the flue gas is reduced to about 65 degrees Celsius during the reaction of the flue gas with the spray liquid of the concentrated spray layer 34 in the concentration section 102. When the flue gas is at this temperature and rises to the absorption section 103, it reacts with the desulfurization solution at a relatively fast speed, and the reaction is relatively complete, which is conducive to the complete absorption and removal of sulfur dioxide in the flue gas.

[0031] Specifically, the number of the above-mentioned absorption circulating pumps is three, and the three absorption circulating pumps are respectively arranged on the first pipeline I 4 and the first pipeline II 5 and the second pipeline 6. The concentrated circulating pump is arranged on the liquid supply pipeline 10, so as to realize the circulation of the desulfurization solution between the absorption section 103 and the oxidation section 101, and the circulation of the concentrated solution between the concentration section 102 and the concentrated circulating tank 11. Similarly, the concentrated circulating tank 11 is also communicated with the lower end of the oxidation section 101 through the liquid discharge pipe 15 to receive the ammonium sulfate solution with high concentration in a saturated or supersaturated state discharged from the lower end of the oxidation section 101.

[0032] In this embodiment, the reflux pipe 18 is connected in series with a mixer, the mixer is communicated with the ammonia adding pipe 17, the upper part of the oxidation section 101 is provided with an air outlet, and the air outlet is communicated with the middle part of the concentration section 102 through an air discharge pipeline. The oxidation section 101 is sequentially provided with an oxidation air distributor 39, a plurality of gas-liquid distributors 21 and an ammonium sulfate distributor 22 from bottom to top, wherein the ammonium sulfate distributor 22 is communicated with the reflux port, and the oxidation air distributor 39 is communicated with the oxygen inlet.

[0033] Specifically, in the case of using the mixer, the ammonia adding port and the reflux port of the oxidation section 101 can be shared. At this time, the end of the ammonia adding pipe 17 and the lower end of the reflux pipe 18 are respectively communicated with the mixer, and the mixer is communicated with the reflux port. Generally, a pressure pump is arranged on the ammonia adding pipe 17 to pump the ammonia water into the mixer and mix with the reflux desulfurization solution.

[0034] As a specific structural form, see Figure 1 and Figure 2 In this embodiment, three layers of gas-liquid distributors 21 are provided. The main components of the reflux desulfurization liquid are ammonium sulfite and ammonium bisulfite, which are uniformly distributed in the horizontal direction by the ammonium sulfate distributor 22, and the desulfurization liquid containing ammonium sulfite is sprayed downward by the ammonium sulfate distributor 22. The oxidizing air entering from the oxygen inlet can be redistributed by the oxidizing air distributor 39 to achieve uniform distribution in the horizontal plane. The uniformly distributed oxidizing air moves upward to react with the downwardly sprayed desulfurization liquid, so that the ammonium sulfite is oxidized to ammonium sulfate for subsequent crystallization. In addition, the intermediate three layers of gas-liquid distributors 21 can improve the uniformity of the distribution of oxidizing air and ammonium sulfite in the oxidation section 101, increase the contact area between the two, and improve the reaction rate.

[0035] In this embodiment, the first partition plate 35 is provided between the concentration section 102 and the oxidation section 101, and the second partition plate 24 is provided between the concentration section 102 and the absorption section 103. A plurality of vertical and open-ended gas lift caps 32 are uniformly arranged on the second partition plate 24. The absorption section 103 and the purification section 104 are separated by the third partition plate 27. Specifically, the first partition plate 35 is arranged at the lower end of the concentration section 102. Specifically, the first partition plate 35 between the concentration section 102 and the oxidation section 101 can be a one-way inclined plate or a V-shaped plate inclined on both sides. This is convenient for using the inclined upper surface of the first partition plate 35 to completely discharge the concentrated liquid at the lower end of the concentration section 102 to the concentration circulating tank 11. This arrangement can avoid the accumulation of concentrated liquid at the bottom of the concentration section 102, thereby avoiding the crystallization of the concentrated liquid at the bottom of the concentration section 102, and eliminating the need for additional cleaning of the crystalline material in the concentration section 102.

[0036] Specifically, the second partition plate 24 and the third partition plate 27 are both flat plates, and the second gas lift cap 32 is arranged on the third partition plate 27. The structure of the second gas lift cap 32 can be the same as or different from the above-mentioned gas lift cap 32.

[0037] As a specific structural form, the lower end of the gas lift cap 32 on the second partition plate 24 is inserted into the concentration section 102, and the upper end is inserted into the absorption section 103, so that the flue gas in the concentration section 102 can enter the absorption section 103 only through the gas lift cap 32. In the case where a plurality of gas lift caps 32 are uniformly arranged on the second partition plate 24, the gas lift cap 32 can be used to redistribute the flue gas entering the absorption section 103, thereby increasing the contact area between the flue gas and the desulfurization liquid and the removal degree of sulfur dioxide.

[0038] Specifically, the gas lift cap 32 includes a main ring 322, and a top plate 321 with a diameter larger than the main ring 322 is arranged at the upper end of the main ring 322. The side wall of the main ring 322 is provided with a through hole 323 for the inlet and outlet of flue gas.

[0039] In the embodiment, the absorption section 103 and the purification section 104 are respectively provided with a filler layer, and the filler layer comprises two layers of grid nets arranged in an up-down manner, and the two layers of grid nets are filled with polypropylene fillers. Specifically, the absorption section 103 is provided with a first filler layer 25, and the purification section 104 is provided with a second filler layer 30. Through the structural arrangement of the first filler layer 25 and the second filler layer 30, the redistribution adjustment of the flue gas in the absorption section 103 or the purification section 104 can be further realized, so as to facilitate the increase of the contact area of the flue gas and the desulfurization liquid or the purification water.

[0040] In the embodiment, a second demister 40 and a backwashing layer 41 are arranged between the absorption section 103 and the purification section 104, and the second demister 40 is arranged below the third partition plate 27. The backwashing layer 41 is arranged below the second demister 40, and the second demister 40 is used to remove the entrainment of the absorption liquid in the flue gas. Here, the backwashing layer 41 and the water washing spray layer 29 are communicated on the same water supply pipe 3, and the water supply pipe 3 is connected to the middle part of the circulating water tank 8. The backwashing layer 41 can spray the cleaning liquid upward to indirectly clean the second demister 40. Generally, the circulating water tank 8 is communicated with the lower end of the purification section 104 through the backwater pipe 7 to recover the purification water sprayed by the water washing spray layer 29. In order to realize the water replenishment of the circulating water tank 8 and offset the part of the purification water evaporated and separated from the desulfurization tower 1, a process water replenishment pipe 2 is arranged in the embodiment, and the process water replenishment pipe 2 is communicated with the purification section 104, and the inlet of the process water replenishment pipe 2 is below the purification section 104.

[0041] In the process of long-time use, the structures such as the gas lifting cap 32 are easy to be blocked by the impurities in the flue gas. Especially, the impurities in the concentration section 102 are in a relatively large amount, and the gas lifting cap 32 on the second partition plate 24 between the concentration section 102 and the absorption section 103 is most easy to be blocked.

[0042] In the embodiment, a plurality of cleaning nozzles are arranged in the concentration section 102, so as to flush the gas lifting cap 32 on the second partition plate 24 by using the cleaning nozzles. It can be known that the spraying direction of the cleaning nozzles is upward when the cleaning nozzles clean the gas lifting cap 32. However, when the cleaning nozzles do not spray the cleaning water, the cleaning nozzles are easy to be blocked by the impurities flushed down by the spray liquid, and in the process of long-time use, the cleaning nozzles are easy to be blocked and cannot backwash the gas lifting cap 32.

[0043] Especially, the flushing layer 33 is arranged in the concentration section 102, and the flushing layer 33 has a plurality of the above-mentioned cleaning nozzles. The impurities in the concentration section 102 are relatively large, and the cleaning nozzles in the flushing layer 33 are more easy to be blocked.

[0044] In order to reduce the probability of the cleaning nozzle being blocked: in this embodiment, the cleaning nozzle comprises a body 331 and a spray head 332 connected by rotation, and the spray head 332 can be switched between a horizontal opening state and a vertical upward state. When in the upward state, the opening of the spray head 332 is directly below the lift cap 32 to be cleaned on the second baffle 24. The body 331 is supported by a support frame 333 which is fixed to the inner wall of the desulfurization tower 1.

[0045] That is, in the non-use state, the opening of the spray head 332 is horizontal, which can avoid being blocked by the downward flue gas impurities, thereby reducing the probability of being blocked. More specifically, the orientation of the spray head 332 here can be driven by a wire rope cooperating with a drum arranged outside the desulfurization tower 1. In other embodiments, the orientation of the spray head 332 can be adjusted by other rotary driving mechanisms, which can be arranged by those skilled in the art, and will not be described here. Alternatively, the rotation of the cleaning cap can also be driven manually, and when the entire desulfurization tower is shut down, the operator can enter the interior of the desulfurization tower to operate.

[0046] As another specific structure of this embodiment, in order to clean the lift cap 32 at the second baffle 24, it avoids the problem of flue gas impurities blocking the cleaning nozzle: a plug 37 capable of being inserted to scrape the inner wall of the lift cap 32 is arranged in the desulfurization tower 1.

[0047] Specifically, a support 38 fixed to the desulfurization tower 1 is arranged below the second baffle 24, and a plurality of vertical plugs 37 are arranged on the support 38, one plug 37 is arranged below each lift cap 32. The second baffle 24 is sealingly and slidably connected to the inner wall of the desulfurization tower 1, and a spring 36 is arranged between the second baffle 24 and the support 38. The baffle can be vertically lifted to make the plug 37 enter or leave the lift cap 32.

[0048] In order to realize the intermittent vertical lifting of the second baffle 24, a first inlet and a second inlet lower than the first inlet are arranged on the desulfurization tower 1, and the two are respectively communicated with the return pipe 18 through branch pipes, and on- off valves are arranged on the branch pipes. The height of the first inlet is equal to the height of the second baffle 24 when the upper end of the second baffle 24 does not accumulate desulfurization liquid, and the height of the second inlet is equal to the height of the second baffle 24 when the upper end of the second baffle 24 accumulates desulfurization liquid.

[0049] Specifically, the branch pipe here comprises a first branch pipe 181 and a second branch pipe 182, the first branch pipe 181 is communicated with the first inlet, and the second branch pipe 182 is communicated with the second inlet. The ends of the first branch pipe 181 and the second branch pipe 182 converge into the return pipe 18.

[0050] When the first inlet is closed, the desulfurization liquid can be deposited above the second partition 24 so that the second partition 24 is subjected to a gravity greater than the elastic force of the spring 36, and the second partition 24 is lowered, the plug 37 is inserted into the riser cap 32 to scrape the inner wall of the riser cap 32 to avoid blockage. When the second inlet is opened, the accumulated desulfurization liquid can be drained to the oxidation section 101 through the reflux pipe 18, thereby reducing the gravity borne by the second partition 24 and the riser cap 32, and the spring 36 drives the second partition 24 to rise to reset.

[0051] One or more embodiments of the present application also provide a flue gas desulfurization method using the ammonia desulfurization system described above, comprising the following steps: Step 1, the flue gas enters the concentration section 102 from the flue gas inlet 23, and is sprayed through the concentration spray layer 34 to cool the flue gas to below 65℃, and the concentrated liquid in the concentration section 102 is heated and evaporated to achieve concentration, and the concentrated liquid enters the concentration circulating tank 11 through the liquid return pipe 9, and the upper concentrated liquid in the concentration circulating tank 11 is sent into the concentration section 102 again by the concentration circulating pump for spraying, and the crystalline body at the bottom of the concentration circulating tank 11 is sent to a post-processing device.

[0052] Specifically, the concentrated liquid in the concentration section 102 and the concentration circulating tank 11 is mainly ammonium sulfate, and the concentrated liquid reacts with the flue gas entering the desulfurization tower 1 through the concentration spray layer 34, thereby reducing the temperature of the flue gas and reducing impurities. And in the process, the water vapor of the concentrated liquid is gradually evaporated, and the concentration of ammonium sulfate gradually increases. In the concentration circulating tank 11, the upper part forms a light liquid with low concentration, and the lower part forms a heavy liquid with high concentration which will gradually precipitate when the concentration is higher than the saturation state.

[0053] Step 2, the flue gas rises to the absorption section 103, and the desulfurization spray layer 31 and the deamination spray layer 26 are used to spray the flue gas to absorb the sulfur dioxide in the flue gas and the ammonia gas escaping from the desulfurization liquid. Subsequently, the flue gas rises from the absorption section 103 to the water washing section. Specifically, the desulfurization liquid in the absorption section 103 flows back to the upper part of the oxidation section 101, and the oxidation air enters the lower end of the oxidation section 101, and the oxidation air flows from bottom to top to gradually complete the oxidation of the desulfurization liquid in the oxidation section 101, and the ammonium sulfite is oxidized to ammonium sulfate. When the content of ammonium sulfate in the oxidation section 101 reaches a set threshold, the liquid at the lower end is sent into the concentration circulating tank 11.

[0054] Specifically, the desulfurization liquid taken out from the first outlet in the oxidation section 101 is mainly a mixed solution of ammonium sulfite, ammonium sulfate and ammonia water, and the desulfurization liquid generates ammonium sulfite, ammonium sulfate and ammonium bisulfite after reacting with the flue gas in the absorption section 103. The desulfurization liquid taken out from the second outlet is mainly ammonium sulfate and hydrogen acid solution, and this part of the solution is sprayed from the deamination spray layer 26 to capture the ammonia gas escaping in the absorption section 103.

[0055] Step 3, water washing spray layer 29 washes the residual sulfur dioxide, ammonium sulfate solution and ammonia gas in the flue gas, and then the flue gas is discharged to the desulfurization tower 1 after being demisted by the demisting section 105. The water in the water washing section is returned to the circulating water tank 8 connected with the purification section 104.

[0056] The above detailed description cannot be regarded as a limitation on the protection scope of the present application. Any alternative improvement or change made by those skilled in the art to the embodiments of the present application falls within the protection scope of the present application. The present application is not detailed, which is the known technology of those skilled in the art.

Claims

1. An ammonia-based desulfurization system, characterized in that, Including desulfurization towers, which consist of the following components arranged from bottom to top: The oxidation section contains ammonia-containing desulfurization liquid. The upper and middle parts of the oxidation section are equipped with a reflux port, an ammonia addition port, and a first outlet below the reflux port. The bottom of the oxidation section is equipped with a second outlet and an oxygen inlet. The concentration section has a flue gas inlet in the middle. The upper part of the inner cavity of the concentration section is equipped with a concentration spray layer. The concentration spray layer is connected to the upper middle part of the concentration circulation tank through a liquid supply pipeline. The concentration circulation tank is connected to the lower end of the concentration section through a liquid return pipeline. A concentration circulation pump is installed on the liquid supply pipeline. The lower end of the concentration circulation tank is connected to the post-treatment equipment. The absorption section has an ammonia removal spray layer and two desulfurization spray layers arranged sequentially from top to bottom. The lower end of the absorption section is connected to the return port through a return pipe. The desulfurization spray layer is connected to the first outlet through the first pipeline, and the ammonia removal spray layer is connected to the second outlet through the second pipeline. Absorption circulation pumps are respectively installed on the first pipeline and the second pipeline. The purification section has a water washing spray layer to wash the flue gas discharged from the absorption section with water; The demister section is used to remove mist from the flue gas discharged from the purification section. The upper end of the demister section is connected to the flue gas outlet of the desulfurization tower.

2. The ammonia desulfurization system according to claim 1, characterized in that, A mixer is connected in series in the reflux pipe, and the mixer is connected to the ammonia addition pipe. An air outlet is provided at the top of the oxidation section, and the air outlet is connected to the middle of the concentration section through an exhaust pipe. The oxidation section is provided with an oxidation air distributor, a multi-layer gas-liquid distributor and an ammonium sulfate distributor in sequence from bottom to top. The ammonium sulfate distributor is connected to the reflux port and the oxidation air distributor is connected to the oxygen inlet.

3. The ammonia desulfurization system according to claim 1, characterized in that, The concentration section and the oxidation section are separated by a first partition, the concentration section and the absorption section are separated by a second partition, and the absorption section and the purification section are separated by a third partition. The second partition is evenly provided with a plurality of vertical gas-lifting caps with open bottom ends.

4. The ammonia desulfurization system according to claim 3, characterized in that, It also includes a circulating water tank, a second demister is installed below the third partition, and a backwash cleaning layer is installed below the second demister. The circulating water tank supplies water to the backwash cleaning layer and the water washing spray layer through a water supply pipe. The concentration section has multiple cleaning nozzles, which are connected to a first or a second pipeline to facilitate flushing of the gas-lifting caps on the second baffle with desulfurization liquid.

5. The ammonia desulfurization system according to claim 4, characterized in that, The cleaning nozzle includes a body and a nozzle that are rotatably connected. The nozzle can switch between a horizontally open state and a vertically upward state. In the upward state, the opening of the nozzle is directly below the air cap to be cleaned on the second partition.

6. The ammonia desulfurization system according to claim 3, characterized in that, Below the second partition is a bracket fixed to the desulfurization tower. The bracket has multiple vertical plugs, and one plug is located directly below each gas lifting cap. The second partition is sealed and slidably connected to the inner wall of the desulfurization tower. A spring is installed between the partition and the bracket, and the partition can be raised and lowered vertically to allow the plugs to enter or leave the gas lifting caps.

7. The ammonia desulfurization system according to claim 6, characterized in that, The desulfurization tower is provided with a first inlet and a second inlet lower than the first inlet. The two inlets are connected to the return pipe through branch pipes, and the branch pipes are provided with on / off valves. The height of the first inlet is equal to the height of the upper part of the second baffle when no desulfurization liquid is accumulated, and the height of the second inlet is equal to the height of the upper part of the second baffle when desulfurization liquid is accumulated.

8. The ammonia desulfurization system according to claim 1, characterized in that, The absorption section and the purification section are respectively provided with a packing layer, which includes two layers of grid mesh arranged vertically, with polypropylene packing filling between the two layers of grid mesh.

9. A flue gas desulfurization method, utilizing the ammonia desulfurization system according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Flue gas enters the concentration section from the flue gas inlet and is sprayed through the concentration spray layer to cool the flue gas to below 65°C. The concentrate in the concentration section is heated and evaporated to achieve concentration. The concentrate enters the concentration circulation tank through the return pipe. The concentration circulation pump sends the upper layer of concentrate in the concentration circulation tank back into the concentration section for spraying. The crystals at the bottom of the concentration circulation tank are sent to the post-treatment equipment. Step 2: The flue gas rises to the absorption section, where it is sprayed with desulfurization and deammoniation spray layers to absorb sulfur dioxide and ammonia escaping from the desulfurization liquid; then the flue gas rises from the absorption section to the water washing section. Step 3: The water washing spray layer captures residual sulfur dioxide, ammonium sulfate solution and ammonia in the flue gas. Then, the flue gas is discharged outside the desulfurization tower after passing through the demisting section. The water in the water washing section is returned to the circulating water tank connected to the purification section.

10. The flue gas desulfurization method according to claim 9, characterized in that, In step 2, the desulfurization liquid in the absorption section is returned to the upper part of the oxidation section, and the oxidation air enters the lower end of the oxidation section. The oxidation air flows from bottom to top to gradually complete the oxidation of the desulfurization liquid in the oxidation section, and the ammonium sulfite is oxidized into ammonium sulfate. When the content of ammonium sulfate in the oxidation section reaches the set threshold, the liquid at the lower end is sent into the concentration circulation tank.

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