TWI657857B - Gas treatment method and apparatus for ammonia-contained gas - Google Patents

Abstract

A method and device for treating ammonia-containing waste gas, the method includes: providing a mixed gas containing ammonia; contacting the mixed gas with an aqueous solution to form a pre-cleaned processing gas and an ammonia-rich aqueous solution; A phosphoric acid mixed solution is brought into contact to make the phosphoric acid mixed solution react with the pre-cleaned treatment gas to form an ammonium phosphate rich solution; the ammonia-rich aqueous solution and the ammonium phosphate rich solution are separately subjected to regeneration and recovery ammonia treatment procedures; the regenerated aqueous solution and The ammonium phosphate lean solution is returned to the exhaust treatment unit for recycling.

Description

Method and device for treating ammonia-containing exhaust gas

The invention relates to a method and a device for treating ammonia-containing exhaust gas, in particular to a two-stage method and device for removing ammonia-containing exhaust gas.

With the impact of the greenhouse effect, countries around the world have paid attention to carbon dioxide emissions. In order to reduce the carbon dioxide content in the exhaust gas, chemical absorption is the most commonly used carbon capture method. The process requires chemical absorption to capture carbon, and after regeneration, carbon dioxide is stored in various ways in specific environments (such as abandoned oil fields) Medium or underground brine layer), so that the content of carbon dioxide in the exhaust gas can be reduced. The current chemical methods to capture carbon dioxide mainly include the use of alkaline, ammonia, alcohol-amine aqueous solutions, ionic solutions, etc. to absorb carbon dioxide in the flue gas. Although carbon capture technology using alcohol amine chemical absorption liquid has a long history and mature technology, it has high energy consumption for regeneration, high chemical prices, easy degradation of alcohol amines during use, high corrosiveness and fugitive environmental protection concerns. Higher disadvantages, and because the alcohol-amine chemical absorption solution will react with sulfides in the gas, it must perform a deep desulfurization process before carbon capture, which also increases the cost of carbon capture and limits its applicability. In contrast, ammonia has the advantages of stable chemical properties, low price, low energy consumption for regeneration, and no unknown environmental protection concerns. In addition, the gas containing SOx sulfide can also be desulfurized with ammonia to generate ammonium sulfate. Ammonium sulfate can be recycled as fertilizer. However, technically, it is necessary to face the problems caused by the high volatility of ammonia water, and to establish a cost-effective process technology.

However, the above-mentioned existing ammonia water absorption method still has the following problems in practical use. The absorption of carbon dioxide in the flue gas by using ammonia water will cause ammonia in the exhaust gas, and the human body's odor threshold to ammonia gas is about 5 ppm. More than 5 ppm human body will feel the special smell of ammonia, and when the ammonia concentration is higher than about 20 ppm, it may cause eye, even respiratory irritation. Therefore, when the ammonia gas concentration in the discharged flue gas is too high, environmental protection problems will be caused. Among the current carbon capture technologies for ammonia, the chilled-NH ₃ process developed by ALSTOM is a process technology that has a large-scale industrial performance; its method is characterized by the use of a low-temperature absorption process (the temperature of the absorption tower is about 0 ° C to 10 ° C) ) To reduce ammonia emissions, but the investment costs and subsequent operating costs of low-temperature processes are expensive, which hinders industrial use. Therefore, many institutions in the world have developed room temperature ammonia carbon capture process technology; however, the results of Australian test plants show that high ammonia volatility will cause high ammonia concentration in the tail gas after carbon capture, and the tail gas must be further purified to meet environmental protection, and this procedure The cost is high, that is, the ammonia carbon capture method needs to establish a cost-effective exhaust gas purification technology.

Therefore, it is necessary to provide a method and a device for treating ammonia-containing exhaust gas to solve the problems existing in conventional technology.

The main purpose of the present invention is to provide a method and a device for purifying ammonia-containing exhaust gas, which use two stages to remove the ammonia gas contained in the exhaust gas in order to reduce the ammonia gas content in the exhaust gas, thereby improving the air quality and complying with environmental protection regulations.

A secondary object of the present invention is to provide a method and a device for treating ammonia-containing exhaust gas, which use an aqueous solution to first absorb a part of the ammonia content in the exhaust gas, and then use an ammonium phosphate solution for absorption in order to reduce the ammonia gas content in the exhaust gas. Further improve the efficiency of ammonia-containing waste gas treatment.

A secondary object of the present invention is to provide a method and a device for treating ammonia-containing exhaust gas, which use an aqueous solution to first absorb and remove most of the ammonia gas in the exhaust gas after carbon capture, and then use the ammonium phosphate aqueous solution to absorb the remaining ammonia gas in the exhaust gas. Removal to achieve environmentally efficient methods.

In order to achieve the above object, in one embodiment of the present invention, a method for treating ammonia-containing exhaust gas is provided, which includes the following steps: (a) providing a mixed gas containing ammonia; (b) combining the mixed gas with a The aqueous solution is contacted, so that the ammonia in the mixed gas is absorbed by the aqueous solution to form an ammonia-containing aqueous solution and a pretreatment gas, and the ammonia-containing aqueous solution is subjected to a recovery process, and the aqueous solution after ammonia removal is led back to absorb ammonia in the tail gas (C) contacting the pretreatment gas with a mixed solution of phosphoric acid, and reacting the mixed solution of phosphoric acid with the pretreatment gas to form an ammonium phosphate-rich solution; (d) performing a recovery treatment procedure on the ammonium phosphate-rich solution, Removing part of the ammonia in the ammonium phosphate rich solution to obtain an ammonium phosphate recovery solution; and (e) introducing the ammonium phosphate recovery solution back into the pretreatment gas formed in step (b), so that the ammonium phosphate recovery solution absorbs the The ammonia in the pretreatment gas of step (c) to form an ammonia water absorption liquid for recycling.

In one embodiment of the present invention, the aqueous solution absorbs one of the mixed gas. The temperature is from 0 ° C to 60 ° C.

In one embodiment of the present invention, the operating temperature of the phosphoric acid mixed solution to absorb the mixed gas is 10 ° C to 100 ° C.

In one embodiment of the present invention, the ammonium phosphate rich solution contains H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ and (NH ₄ ) ₃ PO ₄ , and the above compounds are total The weight accounts for 5% to 40% of the entire weight of the ammonium phosphate recovery solution.

In one embodiment of the present invention, after performing step (d), the NH ₃ / H ₃ PO ₄ molar ratio in the ammonium phosphate recovery solution is less than 1.4, and after performing step (c), the ammonium phosphate is rich. The molar ratio of NH ₃ / H ₃ PO ₄ in the liquid is less than 1.8.

In one embodiment of the present invention, an ammonia-containing exhaust gas treatment device is provided, including: a first processing unit for containing an aqueous solution and a mixed gas, the mixed gas including at least ammonia, wherein the aqueous solution and the mixed gas The gas reaction forms an ammonia-containing aqueous solution and a pretreatment gas, the ammonia-containing aqueous solution is led out through a first outlet pipe; a regeneration unit for collecting the led-out ammonia-containing aqueous solution and processing the ammonia-containing aqueous solution to generate a regeneration An aqueous solution and an ammonia gas, the regenerated aqueous solution is led back to the first processing unit through a first introduction pipe; a second processing unit is configured to contain a phosphoric acid mixed solution and the pretreatment gas, and the pretreatment gas contains at least Ammonia, wherein the phosphoric acid mixed solution reacts with the pretreatment gas to form an ammonium phosphate rich solution, the ammonium phosphate rich solution is led out through a second outlet pipe; and a recovery processing unit for collecting the led out ammonium phosphate rich solution And processing the ammonium phosphate rich solution to produce an ammonium phosphate recovery liquid and an ammonia gas, the ammonium phosphate recovery liquid is led back to the Second processing unit.

In one embodiment of the present invention, the regeneration unit and the recovery processing unit are each a distiller, and the first processing unit and the second processing unit are each a leaching tower.

In one embodiment of the present invention, the mixed gas is an ammonia-containing gas processed through a carbon dioxide absorption tower.

In an embodiment of the present invention, an operating temperature of one of the first processing units is 0 ° C to 60 ° C, and an operating temperature of one of the second processing units is 10 ° C to 100 ° C.

1‧‧‧ mixed gas

2‧‧‧ pretreatment gas

3‧‧‧ exhaust

11‧‧‧The first stage purification process

111‧‧‧ water solution

112‧‧‧Ammonia solution

12‧‧‧Second stage purification process

121‧‧‧ phosphoric acid mixed solution

122‧‧‧ ammonium phosphate rich solution

13‧‧‧ regeneration process

131‧‧‧ regeneration aqueous solution

14‧‧‧Recycling process

141‧‧‧Ammonium phosphate recovery liquid

41‧‧‧first processing unit

411‧‧‧water solution

412‧‧‧aqueous ammonia solution

413‧‧‧first outlet tube

414‧‧‧The first delivery pipe

415‧‧‧The first pump

42‧‧‧Second Processing Unit

421‧‧‧ phosphoric acid mixed solution

422‧‧‧ammonium phosphate rich solution

423‧‧‧Second outlet tube

43‧‧‧Regeneration unit

431‧‧‧Regenerated aqueous solution

432‧‧‧The first introduction tube

44‧‧‧Recycling unit

441‧‧‧Ammonium Phosphate Recovery Solution

442‧‧‧Second introduction pipe

45‧‧‧CO2 absorption tower

451‧‧‧second duct

452‧‧‧Second Pump

46‧‧‧Pure water storage tank

461‧‧‧Pure water delivery pipe

47‧‧‧Phosphoric acid storage tank

471‧‧‧ phosphoric acid delivery tube

FIG. 1 is a flow block diagram of an ammonia-containing exhaust gas treatment method according to an embodiment of the present invention.

FIG. 2 is a thermodynamic equilibrium characteristic diagram of ammonia gas at different temperatures according to an embodiment of the present invention.

FIG. 3 is a gas-liquid phase thermodynamic equilibrium diagram of an NH ₃ -H ₃ PO ₄ -H ₂ O system according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of an ammonia-containing exhaust gas treatment device according to an embodiment of the present invention.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, the following describes the preferred embodiments of the present invention and the accompanying drawings in detail, as follows. Furthermore, the directional terms mentioned in the present invention include, for example, top, bottom, top, bottom, front, back, left, right, inside, outside, side, periphery, center, horizontal, horizontal, vertical, vertical, axial, The radial direction, the uppermost layer, or the lowermost layer, etc., are only directions referring to the attached drawings. Therefore, the directional terms used are for explaining and understanding the present invention, but not for limiting the present invention.

Please refer to FIG. 1, an ammonia-containing exhaust gas treatment method according to an embodiment of the present invention mainly includes the following steps: providing a mixed gas 1 containing ammonia; and introducing the mixed gas 1 into a first-stage purification process 11 in contact with an aqueous solution 111, so that the ammonia in the mixed gas 1 is absorbed by the aqueous solution 111 to form an ammonia-containing aqueous solution 112 (also referred to as an ammonia-rich aqueous solution) and a pretreatment gas (also referred to as a pre-cleaning treatment) Gas) 2. The ammonia-containing aqueous solution may optionally be introduced into a regeneration processing program 13 to remove ammonia in the ammonia-containing aqueous solution 112 to obtain a regenerating aqueous solution 131. Alternatively, the regenerated aqueous solution 131 may be selectively returned to the first-stage purification procedure 11. The pre-treatment gas 2 is in contact with a phosphoric acid mixed solution 121 in a second-stage purification process 12 so that the phosphoric acid mixed solution 121 reacts with the pre-treated gas to form an ammonium phosphate rich solution 122; the ammonium phosphate rich solution is recovered A processing procedure 14 to remove a part of ammonia in the ammonium phosphate rich solution 122 to obtain an ammonium phosphate recovery solution 141; and returning the ammonium phosphate recovery solution 141 to the untreated pretreatment gas 2 to make the ammonium phosphate The recovery liquid 141 absorbs ammonia in the pretreatment gas 2 to form an ammonia water absorption liquid for recycling. The present invention will be described in detail below with reference to Figures 1 and 2 for the implementation details and principles of the above steps of an embodiment.

Referring to FIG. 1, an ammonia-containing exhaust gas treatment method according to an embodiment of the present invention is firstly: providing a continuous mixed gas 1, and the mixed gas 1 includes ammonia. In this step, the mixed gas 1 may be an ammonia-containing gas processed through a carbon dioxide absorption tower. Preferably, the mixed gas 1 is the tail gas after the carbon dioxide-containing gas generated by the ironmaking hot blast furnace exhaust gas or other process units absorbs the carbon dioxide through the ammonia water absorption liquid. The ammonia-containing gas usually contains 10,000 ppm to 50,000 ppm (5%) of ammonia.

Next, an ammonia-containing exhaust gas treatment method according to an embodiment of the present invention is to contact the mixed gas 1 with an aqueous solution 111 to perform a first-stage purification process 11 so that a part of the ammonia gas in the mixed gas 1 is removed. The ammonia in the mixed gas 1 is absorbed by the aqueous solution 111, so that the aqueous solution 111 absorbs the ammonia gas to form an ammonia-containing aqueous solution 112, and the mixed gas 1 removes a part of the ammonia gas to form a pretreatment gas 2. Preferably, in terms of volume (or weight) percentage, the ammonia gas removed by the mixed gas 1 accounts for 80 to 98% of the original total ammonia content in the mixed gas 1. The aqueous solution may be pure water or regenerated water containing ammonia after the regeneration treatment. After the aqueous solution treatment, part of the ammonia gas in the mixed gas 1 is dissolved in water to become ammonium ions. In this embodiment, the pre-treatment gas 2 after the first-stage purification process has been able to reduce the ammonia content in the pre-treatment gas 2 to 1000 to 5000 ppm initially; since the ammonia content is not required to be very low, Therefore, the cleanliness requirements of the aqueous solution used are low (for example, the content of ammonium in the aqueous solution) and the operating temperature can be higher, so the operating cost can be reduced. It should be understood that if better treatment efficiency is required, the first-stage purification process can be operated at a low temperature operating condition to alleviate the problem of ammonia gas escape.

An ammonia-containing exhaust gas treatment method according to an embodiment of the present invention is followed by a first-stage purification procedure 11 and then a second-stage purification procedure 12, which involves contacting the pretreatment gas 2 with a phosphoric acid mixed solution 121 to make the phosphoric acid mixed solution 121 reacts with the pretreatment gas 2 to form ammonium monophosphate rich liquid 122 (ie, the NH ₃ / H ₃ PO ₄ molar ratio is greater than 1.4). In this way, most of the ammonia gas in the treated pretreatment gas 2 reacts with the phosphoric acid mixed solution to form ammonium phosphate and is removed. Finally, the tail gas 3 after the treatment is discharged. In this embodiment, after the first-stage purification process 11 and the second-stage purification process 12, the ammonia gas concentration in the exhaust gas can be reduced to less than 50 ppm. The phosphoric acid mixed solution 121 may be a solution composed of phosphoric acid and water, or a mixed solution composed of phosphoric acid, ammonium phosphate, and water, for example, an aqueous phosphoric acid solution containing 5 to 40 wt% of phosphoric acid. Because phosphoric acid is a triprotic acid, it has more hydrogen groups that can be replaced by ammonium groups, so it can absorb more ammonia gas, and the produced ammonium phosphate rich solution 122 has H ₃ PO ₄ and (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ and (NH ₄ ) ₃ PO ₄ and other components can be used as fertilizer, can also be recycled and used. The ammonium phosphate rich liquid 122 contains, for example, 5 to 40% by weight of H ₃ PO ₄ . Generally, the molar ratio of the original NH ₃ to H ₃ PO ₄ in the solution is used as an absorption saturation index. The molar ratio of NH ₃ / H ₃ PO ₄ in the phosphoric acid mixed solution 141 is 1 to 1.4. _The molar ratio of ₃ / H ₃ PO ₄ is less than 1.8.

In this embodiment, the ammonium phosphate rich solution 122 after being absorbed is exported to a recovery processing program 14 to further remove a part of ammonia in the ammonium phosphate rich solution 122 to obtain an ammonium phosphate recovery solution 141. In this embodiment, the phosphoric acid mixed solution 121 and the ammonium phosphate recovery solution 141 are the same solution, and only the ammonium content of the two is different. In other embodiments, the phosphoric acid mixed solution 121 is a solution in which the phosphoric acid content is adjusted by adding phosphoric acid to the ammonium phosphate recovery solution 141. In this embodiment, the recovery process 14 may be to reduce ammonium in the ammonium phosphate rich solution 122 to gaseous ammonia by using a water vapor, and remove a part of the ammonia in the ammonium phosphate rich solution 122, wherein the phosphoric acid mixed solution the NH ₃ / H ₃ PO ₄ molar ratio of the number 141 is 1 to 1.4, the rich ammonium phosphate solution NH ₃ / H ₃ PO ₄ ratio of 122 moles of less than 1.8. In this embodiment, the water vapor can be generated by heating the water with waste heat generated from a steelmaking hot blast stove or a coke oven, so that the operating cost can be reduced. Other ways to remove ammonium from the ammonium phosphate rich solution 122 are also considered.

In this embodiment, the recovered ammonium phosphate recovery liquid 141 can be finally returned to another unprocessed pretreatment gas 2 after the recovery treatment, so that the ammonium phosphate recovery liquid absorbs ammonia in the other pretreatment gas, so An ammonia water absorbing solution is formed for recycling, for example, it is used to treat the exhaust gas generated by a steelmaking hot blast stove or a coke oven to absorb its carbon dioxide, and the exhaust gas remaining after the exhaust gas is absorbed by the carbon dioxide is also provided at the beginning of this embodiment. Mixed gas 1.

As described above, in one embodiment, after the first-stage purification process is performed, the ammonia in the mixed gas 1 is absorbed by the aqueous solution 111 to form an ammonia-containing aqueous solution 112, and the ammonia-containing aqueous solution may optionally be introduced into a regeneration processing program 13 In order to remove the ammonia in the ammonia-containing aqueous solution 112, a regenerated aqueous solution 131 is obtained. In this embodiment, the regeneration process 13 may be to reduce ammonium in the ammonia-containing aqueous solution 112 to gaseous ammonia by using a water vapor, and remove a part of the ammonia in the ammonia-containing aqueous solution 112. In this embodiment, the water vapor can be generated by heating the water with waste heat generated during the production process (for example, waste heat generated from a steelmaking hot air furnace or a coke oven), which can reduce operating costs. Other ways to remove ammonia from the ammonia-containing aqueous solution 112 are also considered.

Please refer to FIG. 2, which shows the thermodynamic equilibrium characteristics of ammonia gas at different temperatures. When the contact temperature between the aqueous solution and the ammonia gas is too high, the ammonia gas easily escapes from the aqueous solution, resulting in poor absorption efficiency. Therefore, in order to meet environmental protection requirements, in one embodiment, in the first stage purification process 11, the mixed gas 1 is contacted with the aqueous solution 111, and one of the aqueous solutions 111 may have an operating temperature of 0 ° C to 60 ° C. Cleanliness of 131 (i.e. allows higher ammonia Concentration) and increasing the temperature of the purification process 11 can greatly reduce the operating cost, although the ammonia concentration in the pretreatment gas 2 can be increased; the ammonia in the pretreatment gas 2 can be removed by the purification process 12 to environmental protection requirements. It should be understood that when the first-stage purification process 11 requires better ammonia gas removal efficiency, additional energy can be applied to make the operating temperature of the aqueous solution 111 lower than room temperature.

Please refer to FIG. 3, which shows the gas-liquid-phase thermodynamic equilibrium diagram of the NH ₃ -H ₃ PO ₄ -H ₂ O system calculated according to thermodynamics. In this embodiment, 7mole / L phosphoric acid is used. It can be understood in the figure that the use of phosphoric acid to absorb ammonia gas can also meet the expected purification effect at high temperatures without additional energy to reduce the operating temperature. Furthermore, the first-stage purification procedure 11 is first performed, and a part of the ammonia gas is absorbed by using the aqueous solution 111. In the second-stage purification procedure 12, a smaller amount of an ammonium phosphate aqueous solution can be used to reduce the operation cost and the operation danger. The ammonium phosphate rich solution 122 contains H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO _4, and (NH ₄ ) ₃ PO ₄ , and the preferred operating conditions are that the total weight of the compound accounts for the 5% to 40% of the entire weight of the ammonium phosphate recovery liquid 141. In order to obtain sufficient hydrogen group exchange with ammonium radical and have better operation efficiency, the NH ₃ / H ₃ PO ₄ Mole ratio in the ammonium phosphate recovery liquid 141 is controlled to be less than 1.4 (also called ammonium phosphate liquid). And in order to maintain better purification ability, the NH ₃ / H ₃ PO ₄ molar ratio in the ammonium phosphate rich liquid 122 is controlled to be less than 1.8.

Referring to FIG. 4, an ammonia-containing exhaust gas treatment device according to the present invention includes a first processing unit 41 for containing an aqueous solution and a mixed gas 1. The mixed gas 1 includes at least ammonia, and the aqueous solution 411 It comes into contact with the mixed gas 1 through rinsing. After the aqueous solution 411 and the mixed gas 1 react, the ammonia gas in the mixed gas 1 is absorbed to form an ammonia-containing aqueous solution 412 and a pretreatment gas 2. The ammonia-containing aqueous solution passes through a first A lead-out tube 413 leads out, and an ammonia-containing aqueous solution storage tank (not shown) can be optionally set in the equipment to store the ammonia-containing aqueous solution 412 or directly sent to a regeneration unit 43 for collecting the discharged The ammonia-containing aqueous solution 412 is processed to remove part of the ammonium ions to generate a regenerated aqueous solution 431 and an ammonia gas. The treated regenerated aqueous solution 431 is guided back to the first via a first introduction pipe 432. A processing unit 41. In this way, the regenerated aqueous solution 431 can be recycled to the first processing unit 41 to initially remove the ammonia gas in the mixed gas 1. In this embodiment, a pure water storage tank 46 may be provided to store pure water. When the purity of the regenerated aqueous solution 431 does not meet the requirements, the pure water storage tank 46 sends pure water to the regeneration through a pure water delivery pipe 461. The aqueous solution 431 improves the purity of the regenerated aqueous solution 431. In order to reduce the operation cost, the first processing unit 41 can be operated at Room temperature (for example, 20 ° C to 50 ° C).

The pretreatment gas 2 formed after the preliminary processing of the mixed gas 1 is transported to a second processing unit 42 through a first conveying pipe, and a first pump can be optionally set in the first conveying pipe to adjust the The flow rate of the pretreatment gas 2 entering the second processing unit 42. The second processing unit 42 is configured to contain a phosphoric acid mixed solution 421 and the pretreatment gas 2, and the pretreatment gas 2 includes at least ammonia. In this embodiment, the phosphoric acid mixed solution 421 rinses the pretreatment gas 2 so that the phosphoric acid mixed solution 421 and the pretreatment gas 2 react to form a purified mixed gas and an ammonium phosphate rich solution 422, wherein the ammonium phosphate is rich The liquid 422 absorbs the ammonia gas contained in the pretreatment gas 2 and the reacted ammonium phosphate rich liquid 422 is led out through a second outlet pipe 423. An ammonium phosphate rich liquid storage tank (not (Illustrated) to store the ammonium phosphate rich solution 422 or directly deliver it to a recovery processing unit 44. The recovery processing unit 44 is configured to collect the exported ammonium phosphate rich solution 422 and process the ammonium phosphate rich solution 422 to remove a part of ammonium ions to generate an ammonium phosphate recovery solution 441 and an ammonia gas. The ammonium phosphate recovery liquid 441 is returned to the second processing unit 42 through a second introduction pipe 442. In this way, the ammonium phosphate recovery liquid 441 can be recycled to the second processing unit 42 to remove the ammonia gas in the pretreatment gas 2 to a target value or less, and become the purified mixed gas to meet environmental protection requirements.

In one embodiment, the regeneration unit 43 and the recovery processing unit 44 are respectively a distiller, and the regeneration unit 43 and the recovery processing unit 44 are the ammonia-containing aqueous solution 412 and the ammonium phosphate rich solution 422 via water vapor. Removal of ammonium from the solution forms the regenerated aqueous solution 431 and the ammonium phosphate recovery solution 441. The water vapor can be generated by heating the water with the waste heat generated in the production process (for example, waste heat generated from a steelmaking hot blast stove or a coke oven), which can reduce operating costs. The first processing unit 41 and the second processing unit 42 may be a leaching tower, such as a packed washing tower or a Venturi washing tower. In this embodiment, the preferred operating conditions are H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ and (NH ₄ ) ₃ PO _4. The total weight of the above compounds accounts for the ammonium phosphate. 5% to 40% of the total weight of the recovery liquid 441. In this embodiment, a phosphoric acid storage tank 47 may be provided to store phosphoric acid. When H ₃ PO ₄ accounts for less than 5% of the total weight of the ammonium phosphate recovery solution 441, the phosphoric acid storage tank 47 transfers phosphoric acid to This ammonium phosphate recovery liquid 441. In order to obtain sufficient hydrogen group exchange with ammonium radicals and have better operation efficiency, the NH ₃ / H ₃ PO ₄ molar ratio in the ammonium phosphate recovery liquid 441 is controlled to be less than 1.4. In order to maintain a better purification ability, the NH ₃ / H ₃ PO ₄ molar ratio in the ammonium phosphate rich solution 422 is controlled to be less than 1.8.

In one embodiment, the mixed gas 1 is an ammonia-containing gas that has been carbon-treated by a carbon dioxide absorption tower 45 through an ammonia water absorption method, and is transported to the first processing unit 41 through a second conveying pipe 451. The second conveying pipe may be provided with a second pump 452 to convey the mixed gas 1 into the first processing unit 41.

In an embodiment, an operating temperature of one of the first processing units is 0 ° C to 60 ° C, and an operating temperature of one of the second processing units is 10 ° C to 100 ° C.

As described above, compared to conventional technology, the method and device for treating ammonia-containing exhaust gas of the present invention uses two stages to remove ammonia gas contained in the exhaust gas, which can indeed reduce the ammonia gas content of the exhaust gas, thereby improving air quality and conforming to Environmental protection regulations; and the method and device for treating ammonia-containing exhaust gas of the present invention use an aqueous solution to first absorb the ammonia content in the exhaust gas, and then use an ammonium phosphate solution to absorb, in addition to reducing the ammonia gas content in the exhaust gas, it can also Further improve the efficiency of ammonia-containing waste gas treatment and significantly reduce operating costs.

Although the present invention has been disclosed in a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. The scope of protection shall be determined by the scope of the attached patent application.

Claims (10)

A method for treating ammonia-containing exhaust gas, comprising the steps of: (a) providing a mixed gas containing ammonia; (b) contacting the mixed gas with an aqueous solution so that ammonia in the mixed gas is absorbed by the aqueous solution, To form an ammonia-containing aqueous solution and a pretreatment gas; (c) contacting the pretreatment gas with a phosphoric acid mixed solution, causing the phosphoric acid mixed solution to react with the pretreatment gas to form an ammonium phosphate rich solution; (d) the The ammonium phosphate rich solution is subjected to a recovery process to remove a portion of the ammonia in the ammonium phosphate rich solution to obtain an ammonium phosphate recovery solution; and (e) the ammonium phosphate recovery solution is returned to step (c) to cause the ammonium phosphate The recovery liquid absorbs ammonia in the pretreatment gas of step (b). The method for treating ammonia-containing exhaust gas according to item 1 of the scope of patent application, wherein after step (b), it further comprises: (b1) introducing the ammonia-containing aqueous solution into a regeneration treatment program to remove ammonia from the ammonia-containing aqueous solution; A regenerated aqueous solution was obtained. The method for treating ammonia-containing exhaust gas according to item 1 of the scope of patent application, wherein in step (b), an operating temperature of one of the aqueous solutions is 0 ° C to 60 ° C. The method for treating ammonia-containing exhaust gas as described in item 3 of the scope of patent application, wherein the operating temperature of the phosphoric acid mixture is 10 ° C to 100 ° C. The method for treating ammonia-containing exhaust gas according to item 1 of the scope of patent application, wherein in step (c), the ammonium phosphate rich solution contains H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ and (NH ₄ ) ₃ PO ₄ , and the total weight of the above compounds accounts for 5% to 40% of the total weight of the ammonium phosphate recovery solution. The method for treating ammonia-containing exhaust gas according to item 1 of the scope of patent application, wherein after step (d) is performed, the NH ₃ / H ₃ PO ₄ molar ratio in the ammonium phosphate recovery liquid is less than 1.4, and the step ( c), and the NH ₃ / H ₃ PO ₄ molar ratio in the ammonium phosphate rich solution is less than 1.8. An ammonia-containing exhaust gas treatment device includes: a first processing unit for containing an aqueous solution and a mixed gas, the mixed gas including at least ammonia, wherein the aqueous solution and the mixed gas react to form an ammonia-containing aqueous solution and a pretreatment A processing gas, the ammonia-containing aqueous solution is led through a first outlet pipe; a regeneration unit for collecting the led-out ammonia-containing aqueous solution and processing the ammonia-containing aqueous solution to generate a regenerating aqueous solution and an ammonia gas, and the regenerating aqueous solution passes through A first introduction pipe leads back to the first processing unit; a second processing unit is configured to contain a phosphoric acid mixed solution and the pretreatment gas, and the pretreatment gas contains at least ammonia, wherein the phosphoric acid mixed solution and the pretreatment gas The processing gas reacts to form an ammonium phosphate rich solution, which is discharged through a second outlet pipe; and a recovery processing unit for collecting the exported ammonium phosphate rich solution and processing the ammonium phosphate rich solution to produce An ammonium phosphate recovery liquid and an ammonia gas, the ammonium phosphate recovery liquid is led back to the second processing unit through a second introduction pipe. The ammonia-containing exhaust gas treatment device according to item 7 of the scope of the patent application, wherein the regeneration unit and the recovery treatment unit are each a distiller, and the first treatment unit and the second treatment unit are respectively a rinse tower. The ammonia-containing exhaust gas treatment device according to item 7 of the scope of the patent application, wherein the mixed gas is an ammonia-containing gas processed through a carbon dioxide absorption tower. The ammonia-containing exhaust gas treatment device according to item 7 of the scope of the patent application, wherein one of the first processing unit has an operating temperature of 0 ° C to 60 ° C, and one of the second processing unit has an operating temperature of 10 ° C to 100 ° C.