Flue gas ammonia desulfurization recovery method and system

Abstract

The invention belongs to the field of waste gas treatment, and particularly relates to a flue gas ammonia process desulfurization recovery method and system.The method comprises the steps that flue gas enters the bottom of a desulfurization tower, is evenly distributed through a first gas distribution brick layer and then continues to rise, the flue gas and desulfurization liquid sent by primary tail absorption liquid circulation are subjected to countercurrent removal, and most SO2 is removed; and then the flue gas is removed from the reverse flow of the desulfurization liquid circularly sent by the second-stage tail absorption liquid, and SO2 in the flue gas is further removed, so that the flue gas meets the standard requirement. And the desulfurized flue gas enters a second gas distribution brick layer to uniformly distribute the gas again, the uniformly distributed gas is washed, the entrained desulfurization liquid is removed, washing and cooling are performed, and finally the gas is discharged into the atmosphere. According to the method, ammonium sulfite is directly utilized, a drying and concentrating facility is omitted, an oxidation process is omitted, investment is reduced, and processes are reduced.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment, specifically relating to a flue gas ammonia desulfurization and recovery method and system. Background Technology

[0002] Flue gas from coal-fired boilers contains high levels of sulfur dioxide. When this sulfur dioxide comes into contact with moisture in the atmosphere, it forms sulfuric acid (H₂SO₄), leading to acid rain. Acid rain has serious negative impacts on the environment and ecosystems, including corroding buildings, polluting water sources, and affecting crop growth. Furthermore, sulfur dioxide can harm human health; long-term exposure to high concentrations of sulfur dioxide can lead to respiratory diseases and other health problems. Therefore, the "Emission Standard of Air Pollutants for Boilers" (GB 13271-2014) specifies the sulfur dioxide content in boiler exhaust gas.

[0003] Therefore, most coal-fired boilers have desulfurization processes installed in their flue gas. Among all desulfurization processes, ammonia desulfurization is a widely used method. Ammonia desulfurization mainly consists of two steps: sulfur dioxide absorption and desulfurization liquid treatment. This desulfurization method has drawbacks such as a complex sulfur dioxide absorption system, a complex absorption process, large investment, high energy consumption, complex process, and increased environmental risks. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a flue gas ammonia-based desulfurization and recovery method and system. This allows for the direct utilization of ammonium sulfite, eliminating the need for drying and concentration facilities and oxidation processes, thereby reducing energy consumption and investment, streamlining the process, and lowering environmental risks. The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a flue gas ammonia desulfurization and recovery method, comprising: flue gas entering the bottom of a desulfurization tower, being evenly distributed through a first air distribution brick layer, and then continuing to rise, where it is counter-currently separated from the desulfurization liquid transported by a first-stage tail suction liquid circulation pump, thereby removing most of the SO2; and then being counter-currently separated from the desulfurization liquid transported by a second-stage tail suction liquid circulation pump, thereby further removing SO2 from the flue gas; wherein, circulation is carried out by a circulation pump, and the flow rate of the first-stage tail suction liquid circulation pump is greater than 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump is greater than 550 m³ / h. 3 / h; After desulfurization, the flue gas enters the second gas distribution brick layer to distribute the gas evenly again. The evenly distributed gas is then washed to remove the entrained desulfurization liquid, followed by washing and cooling, and finally discharged into the atmosphere.

[0005] The typical liquid-to-gas ratio for ammonia desulfurization is 2-3 L / m³. 3The method of this invention uses a large flow rate and a liquid-to-gas ratio of 3.9 to ensure that the sulfur content in the exhaust gas meets the standard. The gas distribution is carried out twice, and the resistance is minimized while ensuring uniform gas distribution and operation cycle. The ammonium sulfite produced by the method of this invention is directly utilized. When the concentration of the desulfurization liquid reaches the specified index, the ammonium sulfite-containing absorbent is used as an additive to recover nitrogen. In this way, nitrogen element is recovered and the drying and concentration facilities are eliminated, which greatly reduces investment.

[0006] The method of this invention eliminates the oxidation process, eliminating the need to oxidize ammonium sulfite to stable ammonium sulfate, thus further simplifying the process.

[0007] As an alternative, the desulfurization solution of the ammonium sulfide generated in the reaction is collected from the bottom of the tower and returned to the bottom of the tower by a multi-stage tail liquid circulation pump for recycling absorption, so as to further ensure that the sulfur content in the tail gas meets the standard.

[0008] As a preferred method, ammonia water with a concentration of 8-10% is added to the desulfurization tower to adjust the density and pH value of the desulfurization liquid. When the density of the desulfurization liquid reaches 1.15-1.16 kg / l and the pH value is 5.5-6.8, part of the desulfurization liquid containing ammonium sulfite is sent to the fertilizer plant as an additive to recover nitrogen and produce diammonium phosphate.

[0009] Nitrogen can be used as a source of nitrogen in final products such as diammonium phosphate and monoammonium phosphate. When the concentration of the absorbent reaches the specified index, the portion of the absorbent containing ammonium sulfite is sent to the fertilizer plant as an additive to recover the nitrogen.

[0010] As a preferred option, the liquid is returned for recirculation and absorption via a multi-stage tail-suction circulation pump. Specifically: The desulfurization liquid containing the ammonium sulfide generated in the reaction accumulates at the bottom of the tower, passes through the primary desulfurization liquid outlet, and returns to the primary desulfurization liquid inlet via the primary tail liquid circulation pump to circulate and absorb the flue gas. As the liquid level at the bottom of the tower gradually rises, it also flows through the secondary desulfurization liquid outlet above the primary desulfurization liquid outlet, and via the secondary tail liquid circulation pump, returns to the secondary desulfurization liquid inlet above the primary desulfurization liquid inlet, thus circulating and absorbing the absorbed flue gas. This two-stage circulation absorption ensures that the sulfur content in the tail gas meets standards and that the desulfurization liquid is fully recovered and reused.

[0011] As a preferred method, if the density of the desulfurization liquid is greater than 1.16 kg / l, increase the discharge rate of the desulfurization liquid; if the density is less than 1.15 kg / l, decrease the discharge rate of the desulfurization liquid. If the pH value of the desulfurization liquid is greater than 6.8, increase the amount of ammonia water; if the pH value is less than 5.5, decrease the amount of ammonia water. If the liquid level is lower than the preset value, increase the amount of washing water; if the liquid level is higher than the preset value, decrease the amount of washing water.

[0012] To avoid high levels of ammonium sulfite in the desulfurization solution affecting the desulfurization effect, and to prevent the solution level from being too low, which would result in insufficient circulation and thus affect the desulfurization effect, it is crucial to control the pH level to ensure optimal absorption of the desulfurization solution.

[0013] Secondly, the present invention also provides a flue gas ammonia desulfurization and recovery system, including a controller and a tower body. The tower body, from bottom to top, has a flue gas inlet, a process water makeup inlet, a first air distribution brick layer, a primary desulfurization liquid inlet, a secondary desulfurization liquid inlet, a second air distribution brick layer, a first flushing water inlet, a demister, and a second flushing water inlet. The primary and secondary desulfurization liquid inlets are connected to a plurality of nozzles evenly distributed within the tower for spray washing. The first and second flushing water inlets are connected to a plurality of nozzles evenly distributed within the tower for water washing. At the other end below the flue gas inlet, from top to bottom, there is a dilute ammonia water inlet, a secondary desulfurization liquid outlet, and a primary desulfurization liquid outlet. The primary desulfurization liquid outlet is connected to the primary desulfurization liquid inlet via a primary tail-suction circulation pump, and the secondary desulfurization liquid outlet is connected to the secondary desulfurization liquid inlet via a secondary tail-suction circulation pump. The flow rate of the primary tail-suction circulation pump is greater than 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump is greater than 550 m³ / h. 3 / h, the controller controls the opening and closing of the first-stage tail suction circulation pump and the second-stage tail suction circulation pump.

[0014] This invention optimizes the design of the desulfurization tower, integrating all processes such as washing and tail gas purification into a single tower. The primary tail liquid suction circulation pump uses a flow rate greater than 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump is selected as Q=550m³ / h. 3 With a liquid-to-gas ratio of 3.9, a high flow rate is used to ensure that the sulfur content in the exhaust gas meets the standard. Generally, the liquid-to-gas ratio for ammonia desulfurization is 2-3 L / m³. 3 .

[0015] By setting up two gas distribution brick layers, the resistance is minimized while ensuring uniform gas distribution and operating cycle. The ammonium sulfite produced by the system of this invention is directly utilized. When the concentration of the desulfurization liquid reaches the specified index, the ammonium sulfite-containing absorbent liquid is used as an additive to recover nitrogen. In this way, nitrogen element is recovered and the drying and concentration facilities are eliminated, which greatly reduces investment.

[0016] The system of this invention eliminates the oxidation process, eliminating the need to oxidize ammonium sulfite into stable ammonium sulfate, thus further simplifying the process.

[0017] Both the primary and secondary tail suction systems use evenly distributed nozzles for spraying and washing. The two water washes at the top of the tower also use evenly distributed nozzles, which reduces the tower's resistance while ensuring the absorption effect.

[0018] As a preferred option, a density meter, a pH meter, and a level gauge are installed at the lower end of the flue gas inlet, and the controller collects data from the density meter, pH meter, and level gauge.

[0019] A desulfurization liquid density meter is added to the desulfurization tower and data is collected in real time to detect the ammonium sulfite content in the desulfurization liquid. Based on the density meter data collected by the controller, it can be interlocked with the desulfurization liquid discharge valve to automatically discharge if the density is too high, preventing high ammonium sulfite levels from affecting the desulfurization effect. Based on the level gauge data collected by the controller, the washing water volume is increased when the liquid level is too low and decreased when the liquid level is too high, preventing insufficient circulation of desulfurization liquid due to low liquid levels, which would affect the desulfurization effect. Based on the real-time pH value of the desulfurization liquid collected by the controller, pH control can ensure that the desulfurization achieves the optimal absorption effect.

[0020] As a preferred configuration, the dilute ammonia water inlet is connected to the external pipe; the dilute ammonia water has a mass concentration of 8-10%. The first flushing water inlet, the second flushing water inlet, and the process water makeup water inlet are connected to the main process water pipe. The flue gas inlet is connected to the boiler. The secondary tail liquid circulation pump is also connected to the fertilizer unit. When the desulfurization liquid density reaches 1.15-1.16 kg / L and the pH value is 5.5-6.8, part of the desulfurization liquid containing ammonium sulfide is sent to the fertilizer unit as an additive to recover nitrogen. This recovers nitrogen and eliminates the need for drying and concentration facilities, greatly reducing investment and producing diammonium phosphate.

[0021] As a preferred embodiment, the pipeline connecting the secondary tail-end liquid circulation pump to the fertilizer unit is equipped with a self-regulating valve, and the external pipe connecting to the dilute ammonia inlet is also equipped with a self-regulating valve. Water inlet valves are installed at the first flushing water inlet, the second flushing water inlet, and the process water makeup water inlet. The controller controls the opening and closing of the self-regulating valves and water inlet valves based on data collected from the density meter, pH meter, and level gauge: when the desulfurization liquid density is greater than 1.16 kg / L, the controller increases the desulfurization liquid discharge rate through the self-regulating valve; when the density is less than 1.15 kg / L, the controller decreases the desulfurization liquid discharge rate through the self-regulating valve. When the desulfurization liquid pH value is greater than 6.8, the controller increases the ammonia water flow rate through the self-regulating valve; when the pH value is less than 5.5, the controller decreases the ammonia water flow rate through the self-regulating valve. When the liquid level is lower than the preset value, the controller increases the washing water flow rate through the water inlet valve at the process water makeup water inlet or all water inlet valves; when the liquid level is higher than the preset value, the controller decreases the washing water flow rate through the water inlet valve at the process water makeup water inlet or all water inlet valves. The controller collects data to control the self-regulating valve and water supply valve, thereby controlling the density and pH value of the desulfurization liquid, adjusting the liquid level, and discharging the desulfurization liquid. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the existing ammonium sulfate post-treatment technology; Figure 2 This is a schematic diagram of the structure of a desulfurization tower according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the lower structure of a desulfurization tower according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the middle (partial) structure of a desulfurization tower according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the upper (partial) structure of a desulfurization tower according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the first flushing water inlet, demister, and second flushing water inlet of a desulfurization tower according to an embodiment of the present invention; Figure 7 This is a process flow diagram of flue gas ammonia desulfurization and recovery according to an embodiment of the present invention; Among them, 1-flue gas inlet, 2-first air distribution brick layer, 3-first-stage desulfurization liquid inlet, 4-second-stage desulfurization liquid inlet, 5-second-stage air distribution brick layer, 6-first flushing water inlet, 7-demister, 8-second flushing water inlet, 9-flue gas sampling port, 10-dilute ammonia water inlet, 11-second-stage desulfurization liquid outlet, 12-first-stage desulfurization liquid outlet, 13-sewage outlet, 14-densitometer, 15-level gauge, 16-pH meter, 17-process water makeup inlet, 18-first-stage tail liquid circulation pump, 19-second-stage tail liquid circulation pump. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased.

[0024] Unless otherwise stated, all percentages in this invention represent mass fractions. Ratios are mass percentages, and concentrations are mass concentrations.

[0025] Unless otherwise specified, all materials, instruments, and equipment used below are conventional materials, instruments, and equipment or obtained through commercial channels; all testing methods used are existing methods unless otherwise specified.

[0026] Unless otherwise defined, the technical or scientific terms used in the embodiments of this application shall have the ordinary meaning understood by one of ordinary skill in the art. The terms "first," "second," and similar terms used in this embodiment do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Installed," "connected," and "linked" should be interpreted broadly; for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two elements. Terms such as "upper," "lower," "left," "right," "horizontal," and "vertical" are used only relative to the orientation of the components in the accompanying drawings. These directional terms are relative concepts used for relative description and clarification, and they may change accordingly depending on the orientation of the components in the accompanying drawings.

[0027] The existing technology involves two steps: sulfur dioxide absorption and desulfurization liquid treatment. The main process flow is described below: I. Absorption of Sulfur Dioxide The flue gas is first pre-washed, cooled, and absorbed before being released into the atmosphere. During this process, a circulating liquid containing ammonia absorbent absorbs sulfur dioxide from the flue gas, reacting to generate a desulfurization solution containing ammonium sulfite. The main processes are as follows: Cooling and pre-washing: The flue gas is cooled to about 100°C in the heat exchanger and then enters the desulfurization tower for absorption reaction.

[0028] Absorption reaction: Flue gas and ammonia water (or ammonia gas produced by the evaporation of liquid ammonia) come into countercurrent contact in the desulfurization tower to generate ammonium sulfite (NH4)2SO3. The desulfurized flue gas is discharged into the atmosphere after being dehydrated by a demister.

[0029] The above processes are combined in various ways. Most of them separate the cooling, washing and absorption processes, while some are combined, but the washing methods are relatively complicated.

[0030] II. Desulfurization liquid treatment This process mainly involves oxidizing the desulfurization liquid containing ammonium sulfite generated during absorption to produce an ammonium sulfate solution. The oxidized ammonium sulfate solution is then concentrated, cooled for crystallization, centrifuged, and dried to produce the finished ammonium sulfate product, which is sold as fertilizer. The main process is as follows: 1. Oxidation Reaction: The liquid containing ammonium sulfite undergoes an oxidation reaction with oxidizing air inside the desulfurization tower to form ammonium sulfate. This process typically takes place in the oxidation section of the desulfurization tower and is achieved by blowing in compressed air. 2. Concentration and Crystallization: The generated ammonium sulfate solution is further concentrated and crystallized in the desulfurization tower to form an ammonium sulfate slurry with a certain solid content. This slurry is then sent to the ammonium sulfate unit system for further processing. 3. Post-processing: The ammonium sulfate slurry undergoes hydrocyclone separation, centrifuge liquid-solid separation, fluidized bed dryer drying, and packaging to finally obtain the finished ammonium sulfate fertilizer. A simplified process diagram is shown below. Figure 1 As shown.

[0031] The above desulfurization methods have the following drawbacks: (1) The sulfur dioxide absorption system is relatively complex, including cooling facilities, desulfurization liquid storage facilities, etc.

[0032] (2) The absorption process is relatively complex, including steps such as absorption and oxygenation.

[0033] (3) The investment is large and it is not economical for equipment with small boiler capacity: the investment in ammonia desulfurization for a 50t / h boiler is more than RMB15 million, but the output value of the ammonium sulfate produced is only about RMB2.5 million.

[0034] (4) High energy consumption and high processing cost: According to statistics, the electricity consumption for converting ammonium sulfite solution into ammonium sulfate fertilizer is about 316 kW / h, the steam (0.5 MPa) consumption is 4.3 t / t, and the processing cost per ton is more than 100 yuan.

[0035] (5) The process is relatively complex and requires a lot of equipment: The above method consists of six main steps: oxidation, concentration, crystallization, centrifugal separation, drying and packaging. The process is relatively long, the process is relatively complex and requires a lot of equipment.

[0036] (6) Increased environmental risks: The above method adds an exhaust emission point, which increases environmental risks.

[0037] Furthermore, in a first aspect, embodiments of the present invention provide a flue gas ammonia desulfurization and recovery method, comprising: flue gas entering the bottom of the desulfurization tower, being evenly distributed through a first air distribution brick layer, and then continuing to rise, counter-currently separating from the desulfurization liquid transported by the primary tail suction liquid circulation, thereby removing most of the SO2; and then counter-currently separating from the desulfurization liquid transported by the secondary tail suction liquid circulation, thereby further removing SO2 from the flue gas; wherein, circulation is carried out by a circulation pump, and the flow rate of the primary tail suction liquid circulation pump is greater than 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump is greater than 550 m³ / h. 3 / h; After desulfurization, the flue gas enters the second gas distribution brick layer to distribute the gas evenly again. The evenly distributed gas is then washed to remove the entrained desulfurization liquid, followed by washing and cooling, and finally discharged into the atmosphere.

[0038] The typical liquid-to-gas ratio for ammonia desulfurization is 2–3 L / m³. 3 The method of this invention uses a large flow rate and a liquid-to-gas ratio of 3.9 to ensure that the sulfur content in the exhaust gas meets the standard. The gas distribution is carried out twice, ensuring uniform gas distribution and operation cycle while minimizing resistance. The ammonium sulfite produced by the method of this invention is directly utilized. When the concentration of the desulfurization liquid reaches the specified index, the ammonium sulfite-containing absorbent is used as an additive to recover nitrogen. In this way, nitrogen element is recovered and the drying and concentration facilities are eliminated, which greatly reduces investment.

[0039] The method in this embodiment of the invention eliminates the oxidation process, eliminating the need to oxidize ammonium sulfite to stable ammonium sulfate, thus further simplifying the process.

[0040] The desulfurization principle of this invention is as follows: The exhaust gas treatment adopts the ammonia-based desulfurization absorption process (i.e., using dilute ammonia water for desulfurization). The reaction mechanism of the ammonia-based flue gas desulfurization process is as follows: The absorption process utilizes the principle that sulfur dioxide reacts with ammonia at room temperature to produce ammonium sulfite, which is then oxidized to ammonium sulfate. The absorption process mainly takes place within the scrubbing absorption tower. The main reaction involves SO2 in the flue gas first dissolving in the desulfurization liquid, followed by thorough contact between the sulfur dioxide-containing flue gas and the desulfurization liquid, and the reaction proceeding according to the following formula: SO2 + H2O → H2SO3 (1) H2SO3+ NH4OH → NH4HSO3+H2O (2) H2SO3+ 2NH4OH → (NH4)2SO3 + 2H2O (3) H2SO3+(NH4)2SO3→ 2NH4HSO3 (4) The main reaction equation for the absorption process is (4). Regeneration process: The regeneration process mainly takes place in the tank of the washing absorption tower. To maintain a stable (NH4)2SO3 / NH4HSO3 ratio in the desulfurization liquid, ammonia water is added to the absorption tank and reacts according to the following formula to partially regenerate the desulfurization liquid: NH4HSO3+NH4OH → (NH4)2SO3+H2O The difficulties and technical obstacles of this invention are as follows: (1) How to achieve the best desulfurization effect under relatively high temperature conditions: Ammonia desulfurization is an exothermic reaction. At higher temperatures, the desulfurization effect is insufficient. Generally, the suitable desulfurization reaction temperature should not exceed 45℃, meaning the temperature of the desulfurization liquid should ideally not exceed 45℃. To ensure the desulfurization effect, this invention, after extensive experimentation, employs two methods: One approach was to remove the insulation from the outlet of the bag filter, the induced draft fan, and the pipelines before entering the desulfurization tower, in order to reduce the temperature of the flue gas entering the desulfurization tower as much as possible. After taking the above measures, the temperature of the flue gas entering the desulfurization tower was reduced from about 145℃ to about 120℃.

[0041] Secondly, the design incorporates a large circulation volume, with the primary tail suction circulation pump having a flow rate greater than 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump is selected as Q=550m³ / h. 3 With a liquid-to-gas ratio of 3.9 per hour, which is 30% higher than conventional methods, this design allows for increased spray density and mass and heat transfer area. While increasing SO2 absorption, it also removes a significant amount of heat, thereby lowering the desulfurization liquid temperature. In actual operation, the desulfurization liquid temperature remained stable at around 51℃. Although this exceeds the optimal reaction temperature, it did not significantly impact SO2 absorption.

[0042] (2) How to effectively consume desulfurization liquid with a density exceeding the target: Saturated desulfurization liquid contains substances such as ammonium sulfate and ammonium sulfite. Traditional treatment methods involve concentration, cooling crystallization, centrifugation, and drying to produce ammonium sulfate as a fertilizer product for sale. However, this method requires significant investment. For example, for a 50t / h boiler, the process of producing ammonium sulfate from saturated desulfurization liquid (excluding desulfurization absorption investment) requires approximately 10 million yuan. Furthermore, the energy consumption for producing the finished product is high, calculated to be as high as 414.14 kgce / h, equivalent to approximately 400 kgce / h of standard coal per ton of product. From an economic perspective, this is not cost-effective. Discharging the absorbed saturated desulfurization liquid, which contains sulfate, sulfite ions, and ammonia nitrogen, will inevitably increase wastewater treatment costs or cause environmental pollution.

[0043] In view of the above situation, considering that the fertilizer equipment used in the method of this invention mainly produces monoammonium phosphate (MAP) and diammonium phosphate (DAP), which are mainly obtained by the reaction of phosphoric acid and ammonium, and phosphoric acid is generated by the reaction of phosphate rock and sulfuric acid. According to the standard requirements of "Monoammonium Phosphate and Diammonium Phosphate" (GB / T 10205-2009): the total nutrient content of superior grade MAP should be 64% (12-52-0) and the nitrogen content should be 12%; the total nutrient content of superior grade DAP should be 64% (18-46-0) and the nitrogen content should be 18%. However, due to the current decline in the quality of phosphate rock, the produced MAP and DAP have a high impurity content, and the nitrogen content often fails to meet the requirements. The main components of saturated desulfurization liquid are ammonium sulfate and ammonium sulfite. The theoretical nitrogen content of ammonium sulfate is calculated to be 21%, and the nitrogen content of ammonium sulfite is calculated to be 24%, which exceeds the content requirements of MAP and DAP. Therefore, it was decided to send the saturated desulfurization liquid to the fertilizer equipment to participate in the reaction and produce fertilizer products. This brings three advantages: First, it consumes saturated desulfurization liquid without requiring large-scale investment, saving wastewater treatment costs and eliminating environmental pollution; second, the ammonia consumed in flue gas desulfurization is used in fertilizer products, effectively recovering the ammonia and turning waste into treasure; and third, the nitrogen content of fertilizer products (monoammonium phosphate and diammonium phosphate) can be increased.

[0044] As one implementation method, it also includes: the desulfurization solution of ammonium sulfide generated by the reaction is collected from the bottom of the tower and returned by a multi-stage tail liquid circulation pump for circulation absorption, so as to further ensure that the sulfur content in the tail gas meets the standard.

[0045] In one implementation method, ammonia water with a concentration of 8-10% is added to the desulfurization tower to adjust the density and pH value of the desulfurization liquid. When the density of the desulfurization liquid reaches 1.15-1.16 kg / l and the pH value is 5.5-6.8, part of the desulfurization liquid containing ammonium sulfite is sent to the fertilizer plant as an additive to recover nitrogen and produce diammonium phosphate.

[0046] Nitrogen can be used as a source of nitrogen in final products such as diammonium phosphate and monoammonium phosphate. When the concentration of the absorbent reaches the specified index, the portion of the absorbent containing ammonium sulfite is sent to the fertilizer plant as an additive to recover the nitrogen.

[0047] As one implementation method, the return of the liquid via a multi-stage tail suction circulation pump for recirculation absorption specifically involves: The desulfurization liquid containing the ammonium sulfide generated in the reaction accumulates at the bottom of the tower, passes through the primary desulfurization liquid outlet, and returns to the primary desulfurization liquid inlet via the primary tail liquid circulation pump to circulate and absorb the flue gas. As the liquid level at the bottom of the tower gradually rises, it also flows through the secondary desulfurization liquid outlet above the primary desulfurization liquid outlet, and via the secondary tail liquid circulation pump, returns to the secondary desulfurization liquid inlet above the primary desulfurization liquid inlet, thus circulating and absorbing the absorbed flue gas. This two-stage circulation absorption ensures that the sulfur content in the tail gas meets standards and that the desulfurization liquid is fully recovered and reused.

[0048] In one implementation method, if the density of the desulfurization liquid is greater than 1.16 kg / L, increase the discharge rate of the desulfurization liquid; if the density is less than 1.15 kg / L, decrease the discharge rate of the desulfurization liquid. If the pH value of the desulfurization liquid is greater than 6.8, increase the amount of ammonia water; if the pH value is less than 5.5, decrease the amount of ammonia water. If the liquid level is lower than the preset value, increase the amount of washing water; if the liquid level is higher than the preset value, decrease the amount of washing water.

[0049] To avoid high levels of ammonium sulfite in the desulfurization solution affecting the desulfurization effect, and to prevent the solution level from being too low, which would result in insufficient circulation and thus affect the desulfurization effect, it is crucial to control the pH level to ensure optimal absorption of the desulfurization solution.

[0050] Secondly, the present invention also provides a flue gas ammonia desulfurization and recovery system, including a controller and a tower body. The tower body, from bottom to top, has a flue gas inlet, a process water makeup inlet, a first air distribution brick layer, a primary desulfurization liquid inlet, a secondary desulfurization liquid inlet, a second air distribution brick layer, a first flushing water inlet, a demister, and a second flushing water inlet. The primary and secondary desulfurization liquid inlets are connected to a plurality of nozzles evenly distributed within the tower for spray washing. The first and second flushing water inlets are connected to a plurality of nozzles evenly distributed within the tower for water washing. At the other end below the flue gas inlet, from top to bottom, there is a dilute ammonia water inlet, a secondary desulfurization liquid outlet, and a primary desulfurization liquid outlet. The primary desulfurization liquid outlet is connected to the primary desulfurization liquid inlet via a primary tail-suction circulation pump, and the secondary desulfurization liquid outlet is connected to the secondary desulfurization liquid inlet via a secondary tail-suction circulation pump. The flow rate of the primary tail-suction circulation pump is greater than 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump is greater than 550 m³ / h. 3 / h, the controller controls the opening and closing of the first-stage tail suction circulation pump and the second-stage tail suction circulation pump.

[0051] This invention optimizes the design of the desulfurization tower, integrating all processes such as washing and tail gas purification into a single tower. The primary tail liquid suction circulation pump uses a flow rate greater than 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump is selected as Q=550m³ / h. 3 With a liquid-to-gas ratio of 3.9, a high flow rate is used to ensure that the sulfur content in the exhaust gas meets the standard. Generally, the liquid-to-gas ratio for ammonia desulfurization is 2-3 L / m³. 3 .

[0052] Two aeration brick layers are configured to minimize resistance while ensuring uniform gas distribution and operational cycles. The ammonium sulfite produced by this system is directly utilized. Since ammonium sulfite contains nitrogen during the desulfurization process, it can serve as a source of nitrogen for final products such as diammonium phosphate and monoammonium phosphate. Therefore, when the absorbent concentration reaches the specified parameters (1.15–1.16 kg / L, pH 5.5–6.8), the portion of the absorbent containing ammonium sulfite is pumped to the fertilizer unit via a tail-end pump to recover nitrogen as an additive. This recovers nitrogen and eliminates the need for drying and concentration facilities, significantly reducing investment. The aeration brick layers consist of two layers of corrosion-resistant 100mm ceramic packing.

[0053] The present invention eliminates the oxidation process because the method recovers nitrogen from ammonium sulfite during the desulfurization process, and the recovery is continuous. Therefore, it is not necessary to oxidize ammonium sulfite to stable ammonium sulfate, which further simplifies the process.

[0054] Both the primary and secondary tail suction stages employ uniformly distributed nozzles for spray washing. The two water washes at the top of the tower also utilize uniformly distributed nozzles, ensuring effective absorption while reducing tower resistance. Silicon carbide nozzles (up to 16) or PTFE nozzles (up to 12) can be used.

[0055] The controller can be a general-purpose processor, including a central processing unit, a network processor, etc.; it can also be a digital signal processor, an application-specific integrated circuit, a field-programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component.

[0056] In one implementation, a density meter, a pH meter, and a level gauge are installed at the lower end of the flue gas inlet, and the controller collects data from these gauges. The positions of the density meter, pH meter, and level gauge are determined by their ability to detect relevant data from the desulfurization liquid.

[0057] A desulfurization liquid density meter is added to the desulfurization tower and data is collected in real time to detect the ammonium sulfite content in the desulfurization liquid. Based on the density meter data collected by the controller, it can be interlocked with the desulfurization liquid discharge valve to automatically discharge if the density is too high, preventing high ammonium sulfite levels from affecting the desulfurization effect. Based on the level gauge data collected by the controller, the washing water volume is increased when the liquid level is too low and decreased when the liquid level is too high, preventing insufficient circulation of desulfurization liquid due to low liquid level, which would affect the desulfurization effect. Based on the real-time pH value of the desulfurization liquid collected by the controller, pH control can ensure that the desulfurization achieves the optimal absorption effect. The system has a high degree of automation, with unmanned control of concentration, absorbent pH value, and liquid level.

[0058] In one implementation method, the dilute ammonia water inlet is connected to the external pipe; the dilute ammonia water has a mass concentration of 8-10%. The first flushing water inlet, the second flushing water inlet, and the process water makeup water inlet are connected to the main process water pipe. The flue gas inlet is connected to the boiler. The secondary tail liquid circulation pump is also connected to the fertilizer unit. When the desulfurization liquid density reaches 1.16, part of the desulfurization liquid containing ammonium sulfite is sent to the fertilizer unit as an additive to recover nitrogen and produce diammonium phosphate. This method recovers nitrogen and eliminates the need for drying and concentration facilities, significantly reducing investment.

[0059] In one implementation, a self-regulating valve is installed on the pipeline connecting the secondary tail-end liquid circulation pump to the fertilizer unit, and a self-regulating valve is also installed on the external pipe connected to the dilute ammonia inlet. Water inlet valves are installed on the first flushing water inlet, the second flushing water inlet, and the process water makeup water inlet. The controller controls the opening and closing of the self-regulating valves and water inlet valves based on data collected from the density meter, pH meter, and level gauge: when the desulfurization liquid density is greater than 1.16 kg / L, the controller increases the desulfurization liquid discharge rate through the self-regulating valve; when the density is less than 1.15 kg / L, the controller decreases the desulfurization liquid discharge rate through the self-regulating valve. When the desulfurization liquid pH value is greater than 6.8, the controller increases the ammonia water flow rate through the self-regulating valve; when the pH value is less than 5.5, the controller decreases the ammonia water flow rate through the self-regulating valve. When the liquid level is lower than the preset value, the controller increases the washing water flow rate through the process water makeup water inlet water inlet valve or all water inlet valves; when the liquid level is higher than the preset value, the controller decreases the washing water flow rate through the process water makeup water inlet water inlet valve or all water inlet valves.

[0060] A desulfurization liquid density meter is added to the desulfurization tower to detect the ammonium sulfite content in the desulfurization liquid. The controller is interlocked with the valve controlling the discharge of desulfurization liquid. If the density is too high, it will automatically discharge the liquid to avoid the high ammonium sulfite content affecting the desulfurization effect. According to actual operation, the optimal desulfurization liquid density is controlled at 1.15-1.16 kg / l. When the density is greater than 1.16 kg / l, the opening degree of the desulfurization liquid discharge self-adjusting valve is increased to increase the discharge volume. When the density is less than 1.15 kg / l, the opening degree of the desulfurization liquid discharge self-adjusting valve is decreased to reduce the discharge volume, so as to achieve the purpose of automatic control of desulfurization liquid density.

[0061] To ensure optimal desulfurization absorption, the pH value of the desulfurization solution must be controlled. The optimal pH value is between 5.5 and 6.8. When the pH value is greater than 6.8, the controller opens the ammonia water self-regulating valve to increase the ammonia water volume. When the pH value is less than 5.5, the controller closes the ammonia water self-regulating valve to decrease the ammonia water volume, thus achieving automatic pH control.

[0062] The controller is interlocked with the water supply valve. When the liquid level is below the preset value, the controller adjusts the valve opening to increase the water flow. When the liquid level is above the preset value, the controller reduces the valve opening to decrease the water flow, preventing insufficient desulfurization liquid circulation due to excessively low liquid levels, which would affect the desulfurization effect. The preset value is set according to the actual tower height, etc.

[0063] During operation, controlling the density and pH value of the desulfurization solution is crucial. If the desulfurization liquid density is too low, too much desulfurization liquid needs to be discharged, leading to increased ammonia consumption; if the density is too high, the salt content in the desulfurization liquid will increase, making it easier for ammonium sulfate crystals to precipitate and clog equipment or pipelines. Furthermore, excessively high density can result in uneven liquid distribution, leading to higher SO2 concentrations in the flue gas. 2 The content increases. Therefore, the optimal desulfurization liquid density is controlled at 1.15–1.16 kg / L. To address this, this embodiment of the invention designs the valve delivering the desulfurization liquid to the fertilizer plant as a self-regulating valve and installs an online desulfurization liquid density detector. The self-regulating valve delivering the desulfurization liquid to the fertilizer plant is interlocked with the desulfurization liquid density.

[0064] pH control in the desulfurization solution is also crucial. If the pH is too low, the ammonia content in the solution will be low, resulting in poor desulfurization. If the pH is too high, it will lead to increased ammonia escape in the exhaust gas and increased ammonia consumption. Based on practical considerations, the desulfurization solution density should be controlled within a pH range of 5.5–6.8. Therefore, this invention designs the ammonia addition valve as a self-regulating valve and installs an online pH meter, interlocking the desulfurization solution pH value with the ammonia addition self-regulating valve.

[0065] To further illustrate the present invention, the following describes in detail a flue gas ammonia desulfurization and recovery method and system provided by the present invention with reference to embodiments.

[0066] Example 1 like Figure 2 , 3 As shown in 4, 5, 6, and 7, the desulfurization tower in this embodiment includes a controller and a tower body. The tower body is provided with a flue gas inlet 1, a process water makeup water inlet 17, a first air distribution brick layer 2, a primary desulfurization liquid inlet 3, a secondary desulfurization liquid inlet 4, a second air distribution brick layer 5, a first flushing water inlet 6, a demister 7, a second flushing water inlet 8, and a flue gas sampling port 9 from bottom to top.

[0067] A density meter 14, a level gauge 15, and a pH meter 16 are installed at one lower end of the flue gas inlet 1. The controller collects data from the density meter, pH meter, and level gauge. At the other lower end of the flue gas inlet 1, from top to bottom, there are a dilute ammonia water inlet 10, a secondary desulfurization liquid outlet 11, a primary desulfurization liquid outlet 12, and a sewage outlet 13.

[0068] Both air distribution brick layers and demister 7 adopt traditional structures. The air distribution brick layers are made of 100X type, 50mm thick ceramic corrugated structured packing, with a packing layer height of 300mm. Demister 7 uses 250Y type plastic plate corrugated structured packing. The primary desulfurization liquid inlet 3 and the secondary desulfurization liquid inlet 4 are fed from one side, using a ring pipe structure.

[0069] The primary desulfurization liquid outlet 12 is connected to the primary desulfurization liquid inlet 3 via the primary tail liquid circulation pump 18, and the secondary desulfurization liquid outlet 11 is connected to the secondary desulfurization liquid inlet 4 via the secondary tail liquid circulation pump 19; the flow rate of the primary tail liquid circulation pump 18 is 715 m³ / h. 3 / h, the flow rate of the secondary tail suction circulation pump 19 is 550m³ / h. 3 / h, the controller controls the opening and closing of the first-stage tail suction circulation pump 18 and the second-stage tail suction circulation pump 19.

[0070] The first flushing water inlet 6 and the second flushing water inlet 8 are respectively connected to 12 PTFE nozzles inside the tower.

[0071] The dilute ammonia water inlet 10 is connected to the external pipe. The dilute ammonia water is ammonia water with a mass concentration of 8%, and the usage rate is 1.678 m³ / h, with a maximum usage rate of 2.01 m³ / h.

[0072] The first flushing water inlet 6, the second flushing water inlet 8, and the process water makeup inlet 17 are connected to the main pipe, and the process water for flushing comes from the main pipe. The flue gas from flue gas inlet 1 comes from the 50t / h boiler and is connected to the 50t / h boiler.

[0073] The desulfurization liquid containing the generated ammonium sulfide accumulates at the bottom of the tower and returns to the primary desulfurization liquid inlet 3 via the primary desulfurization liquid outlet 12, the primary tail liquid circulation pump 18, and then for recirculation and absorption. As the liquid level at the bottom of the tower gradually rises, it also returns to the secondary desulfurization liquid inlet 4 via the secondary desulfurization liquid outlet 11, the secondary tail liquid circulation pump 19, and then for recirculation and absorption. The primary desulfurization liquid inlet 3 and the secondary desulfurization liquid inlet 4 can be connected to silicon carbide nozzles for spray washing; there are 16 silicon carbide nozzles.

[0074] A self-regulating valve is installed on the pipeline connecting the secondary tail liquid circulation pump 19 to the fertilizer unit, and a self-regulating valve is installed on the outer pipe connecting to the dilute ammonia water inlet 10; water filling valves are installed on the first flushing water inlet 6, the second flushing water inlet 8, and the process water makeup water inlet 17; the controller controls the opening and closing of the self-regulating valve and the water filling valve according to the collected data from the density meter, pH meter, and level meter.

[0075] The secondary tail liquid circulation pump 19 is also connected to the traditional fertilizer plant. When the absorption density reaches the specified index (density 1.15~1.16kg / l, pH value 5.5~6.8), the desulfurization liquid containing ammonium sulfide is sent by the secondary tail liquid transfer pump 19 to the traditional fertilizer plant as an additive to recover the nitrogen and produce diammonium phosphate.

[0076] Ammonia water with a mass concentration of 8% is added to the desulfurization tower to control the desulfurization liquid parameters. According to actual operation, the density of the desulfurization liquid is controlled between 1.15 and 1.16 kg / l. When the density is greater than 1.16 kg / l, the controller increases the opening degree of the desulfurization liquid discharge self-adjusting valve to increase the discharge volume. When the density is less than 1.15 kg / l, the controller decreases the opening degree of the desulfurization liquid discharge self-adjusting valve to reduce the discharge volume, thereby achieving the purpose of automatic control of the desulfurization liquid density.

[0077] To ensure optimal desulfurization absorption, the pH value of the desulfurization solution must be controlled. The pH value of the desulfurization solution should be controlled between 5.5 and 6.8. When the pH value is greater than 6.8, the controller will open the ammonia water self-regulating valve to increase the ammonia water volume. When the pH value is less than 5.5, the controller will close the ammonia water self-regulating valve to decrease the ammonia water volume, thereby achieving the purpose of automatic pH control.

[0078] When the liquid level is lower than the preset value, the controller increases the washing water volume through the process water replenishment inlet 17 water valve. When the liquid level is higher than the preset value, the controller reduces the washing water volume through the process water replenishment inlet 17 water valve.

[0079] Example 2 like Figure 7 As shown, this embodiment of the flue gas ammonia desulfurization and recovery method differs from Embodiment 1 in that, to accommodate the positions of process water, ammonia water, and fertilizer equipment, the desulfurization tower in this embodiment is slightly different from that in Embodiment 1 in that the liquid inlet, gas inlet, density meter 14, level gauge 15, and pH meter 16 are interchanged or slightly repositioned. A water tank is added below the drain outlet 13, which does not affect the desulfurization effect. The method includes: Flue gas from the induced draft fan enters the bottom of the desulfurization tower, where it is evenly distributed through the first air distribution brick layer 2. It then continues to rise, where it flows counter-currently with the desulfurization liquid delivered by the primary tail-suction liquid circulation pump 18, removing most of the SO2. It then flows counter-currently with the desulfurization liquid delivered by the secondary tail-suction liquid circulation pump 19, further removing SO2 from the flue gas to meet standard requirements. The primary tail-suction liquid circulation pump 18 and the secondary tail-suction liquid circulation pump 19 can be controlled by a controller and activated when needed.

[0080] To remove the ammonia entrained in the desulfurized flue gas, the desulfurized flue gas enters the second gas distribution brick layer 5 to distribute the gas evenly. The evenly distributed gas is then washed once with process water through the first flushing water inlet 6, and then the entrained desulfurization liquid is removed through the demister 7. The gas is then washed and cooled with a small amount of water through the second flushing water inlet 8, and finally discharged into the atmosphere. Samples are taken through the flue gas sampling port 9 for testing to see if the gas meets the standards.

[0081] The desulfurization solution containing the generated ammonium sulfide accumulates at the bottom of the tower and then enters the primary and secondary tail-suction circulation pumps. The desulfurization solution is returned to the spray nozzles for recirculation and absorption via the primary and secondary tail-suction circulation pumps. Ammonia water with a concentration of 8% is added through the dilute ammonia water inlet 10 inside the desulfurization tower to control the desulfurization solution parameters.

[0082] Ammonium sulfite contains nitrogen, which can be used as a source of nitrogen in final products such as diammonium phosphate and monoammonium phosphate. Therefore, when the absorption density reaches the specified index (density 1.15-1.16 kg / l, pH value 5.5-6.8), the desulfurization liquid containing ammonium sulfite is sent to the traditional fertilizer plant by the secondary tail liquid circulation pump 19 as an additive to recover the nitrogen. In this way, while utilizing the nitrogen in the ammonium sulfite produced by tail gas desulfurization, the oxidation, concentration, crystallization, centrifugation, and drying of sulfur liquid in the traditional ammonia desulfurization absorption process can be saved.

[0083] After the reaction is complete, drain outlet 13 is opened to discharge sewage.

[0084] Detection Examples Taking the 50t / h co-firing furnace of Honglin Chemical as an example, the 50t / h co-firing furnace of Honglin Chemical uses lignite as the main raw material, and simultaneously digests carbon-containing waste residue and CO-containing waste gas generated from the gasification process of the ammonia synthesis unit. The SO2 in the flue gas is 500-900 mg / Nm³. 3 The concentration exceeds the "Emission Standard for Air Pollutants from Boilers" (GB 13271-2014) by 400 mg / m³. 3 According to the requirements, after processing with the method and system of this invention, the SO2 content in the flue gas is reduced to 30 mg / m³. 3 The smoke and dust content also decreased significantly. See Table 1 below for details: Table 1 Comparison of processing results of the method in the embodiments of the present invention The investment, power consumption, steam consumption, and energy consumption of the prior art and the method of the present invention are shown in Table 2 below: Table 2 Comparison of different ammonia-based desulfurization methods for 50t / h boilers The invention has been verified and used, and its economic and quality benefits are quite good. Calculated solely from the recovered ammonia, a 50t / h boiler consumes approximately 200 tons of ammonia per year, and with an ammonia price of 3200 yuan per ton, the annual benefit is 640,000 yuan.

[0085] It is evident that the investment, electricity consumption, steam consumption, and energy consumption of the method in this embodiment are far lower than those of the prior art.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flue gas ammonia process desulphurization recovery method, characterized by: The flue gas after desulfurization enters the second gas distribution brick layer to uniformly distribute the gas again, the uniformly distributed gas is washed, then the entrained desulfurization solution is removed, and then the gas is washed and cooled, and finally discharged into the atmosphere. The flue gas enters the bottom of the desulfurization tower, is uniformly distributed through the first gas distribution brick layer, then continues to rise, is removed from the desulfurization liquid circulated and transported by a first tail gas absorption liquid, removes most of the SO2, then is removed from the desulfurization liquid circulated and transported by a second tail gas absorption liquid in countercurrent, further removes the SO2 in the flue gas, wherein the circulation is performed by a circulating pump, the flow of the first tail gas absorption liquid circulating pump is greater than 715 m 3 / h, and the flow of the second tail gas absorption liquid circulating pump is greater than 550 m 3 / h. Further comprising:

2. The flue gas ammonia process desulphurization recovery method according to claim 1, characterized in that: The desulfurization solution containing sulfurous acid amine generated by the reaction is collected from the tower to the bottom of the tower, and returned by the multi-stage tail suction liquid circulating pump for recycling. The desulfurization solution is added with ammonia water with a concentration of 8-10% to adjust the density and pH value of the desulfurization solution; 3. The flue gas ammonia process desulphurization recovery method according to claim 1, characterized in that: When the density of the desulfurization solution reaches 1.15-1.16 kg / l and the pH value is 5.5-6.8, part of the desulfurization solution containing sulfurous acid amine is sent to the chemical fertilizer device as an additive to recover nitrogen therein. The desulfurization solution containing sulfurous acid amine generated by the reaction is collected from the tower to the bottom of the tower, and returned by the multi-stage tail suction liquid circulating pump for recycling.

4. The flue gas ammonia process desulfurization recovery method according to claim 2, characterized in that: The desulfurization solution containing sulfurous acid amine generated by the reaction is collected from the tower to the bottom of the tower, and returned by the multi-stage tail suction liquid circulating pump for recycling. When the density of the desulfurization solution is greater than 1.16 kg / l, the desulfurization solution discharge is increased, and when the density is less than 1.15 kg / l, the desulfurization solution discharge is reduced; When the pH value of the desulfurization solution is greater than 6.8, the amount of ammonia water is increased, and when the pH value is less than 5.5, the amount of ammonia water is reduced; 5. The flue gas ammonia process desulphurization recovery method according to claim 3, characterized in that: When the liquid level is lower than the preset value, the amount of washing water is increased, and when the liquid level is higher than the preset value, the amount of washing water is reduced. The controller and the tower body are provided, the tower body is provided with a flue gas inlet, a process water supplement inlet, a first gas distribution brick layer, a first desulfurization solution inlet, a second desulfurization solution inlet, a second gas distribution brick layer, a first flushing water inlet, a demister, and a second flushing water inlet from bottom to top; the first desulfurization solution inlet and the second desulfurization solution inlet are communicated with a plurality of spray nozzles uniformly distributed in the tower for spraying and washing; the first flushing water inlet and the second flushing water inlet are communicated with a plurality of spray nozzles uniformly distributed in the tower for water washing; The other end of the lower side of the flue gas inlet is provided with a dilute ammonia water inlet, a second desulfurization solution outlet, and a first desulfurization solution outlet from top to bottom; 6. A flue gas ammonia process desulphurization recovery system characterized by: The first desulfurization solution outlet is connected with the first desulfurization solution inlet through a first tail suction liquid circulating pump, and the second desulfurization solution outlet is connected with the second desulfurization solution inlet through a second tail suction liquid circulating pump; The lower side of the flue gas inlet is provided with a density meter, a pH meter, and a liquid level meter, and the controller collects data of the density meter, the pH meter, and the liquid level meter.

8. The flue gas ammonia desulfurization recovery system according to claim 6, wherein: The flow of the primary tail liquid circulating pump is greater than 715 m 3 / h, and the flow of the secondary tail liquid circulating pump is greater than 550 m 3 / h, and the controller controls the opening and closing of the primary tail liquid circulating pump and the secondary tail liquid circulating pump.

7. The flue gas ammonia process desulphurization recovery system as claimed in claim 6, wherein: The dilute ammonia water inlet is connected with an outer pipe, and the dilute ammonia water is ammonia water with a mass concentration of 8-10%; the first flushing water inlet, the second flushing water inlet, and the process water supplement inlet are connected with a process water main pipe; and the flue gas inlet is connected with a boiler; The second tail suction liquid circulating pump is further connected with a chemical fertilizer device, and when the density of the desulfurization solution reaches 1.15-1.16 kg / l and the pH value is 5.5-6.8, part of the desulfurization solution containing sulfurous acid amine is sent to the chemical fertilizer device as an additive to recover nitrogen therein. ​ ​ 9. The flue gas ammonia process desulphurization recovery system as claimed in claim 8, wherein: The pipeline connected with the secondary tail suction liquid circulating pump and the chemical fertilizer device is provided with a self-adjusting valve, and the outer pipe connected with the dilute ammonia water inlet is provided with a self-adjusting valve; the first flushing water inlet, the second flushing water inlet and the process water supplement inlet are provided with water adding valves; the controller controls the opening and closing of the self-adjusting valves and the water adding valves according to the data collected by the density meter, the PH meter and the liquid level meter: When the density of the desulfurization liquid is greater than 1.16 kg / l, the controller increases the desulfurization liquid discharge amount through the self-adjusting valve, and when the density is less than 1.15 kg / l, the controller reduces the desulfurization liquid discharge amount through the self-adjusting valve; When the PH value of the desulfurization liquid is greater than 6.8, the controller increases the ammonia water amount through the self-adjusting valve, and when the PH value is less than 5.5, the controller reduces the ammonia water amount through the self-adjusting valve; When the liquid level is lower than the preset value, the controller increases the washing water amount through the water adding valve of the process water supplement inlet or all the water adding valves, and when the liquid level is higher than the preset value, the controller reduces the washing water amount through the water adding valve of the process water supplement inlet or all the water adding valves.

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