Ammonia-ammonium chloride catalytic method system for decarburization of steel slag solid waste and flue gas and process thereof

Abstract

The invention discloses an ammonia-ammonium chloride catalytic method system for decarburization of steel slag solid waste and flue gas and a process thereof, and belongs to the technical field of ferrous metallurgy. The ammonia-ammonium chloride catalysis system for steel slag solid waste and flue gas decarburization comprises a steel slag dissolving tank, an ammonia gas condensation cooler and a decarburization tower which are sequentially connected, the top of the decarburization tower is sequentially connected with an ammonia recovery system, an impurity filtering system and a calcium carbonate extraction system, and the bottom of the decarburization tower is connected with the calcium carbonate extraction system. The calcium carbonate extraction system is connected with the steel slag dissolving tank, and the steel slag dissolving tank is communicated with the ammonia recovery system. According to the technical scheme, by means of the system, the process of an ammonia-ammonium chloride catalysis method for decarburization of steel slag solid waste and flue gas is achieved, the purpose of carbon capture is achieved, and high-added-value resource reutilization of steel slag is achieved.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to an ammonia-ammonium chloride catalytic method system and process for decarbonizing steel slag solid waste and flue gas. Background Technology

[0002] In the field of iron and steel metallurgy, a large amount of steel slag is generated. Currently, the common method for disposing of solid waste steel slag is to first treat it simply and then mix it into cement clinker. However, because steel slag is highly alkaline, it reduces the performance of cement, making this method unsuitable. Meanwhile, with the increasing popularity of green production, steel mills and other industrial manufacturers face the task of carbon reduction and carbon neutrality.

[0003] In flue gas decarbonization technologies, most publicly disclosed techniques include the thermal potassium alkali method, the organic amine method, adsorption, and membrane separation. These technologies enrich carbon dioxide in flue gas to obtain carbon dioxide with a purity greater than 99%, which is then stored and treated. However, these carbon capture technologies are very energy-intensive and do not have the function of co-processing solid waste.

[0004] Meanwhile, ammonium chloride has the chemical property of dissolving steel slag. Dissolving steel slag with ammonium chloride yields products such as ammonia, calcium chloride, and magnesium chloride, which can be used to absorb carbon dioxide from flue gas. During the carbon dioxide absorption process, ammonium chloride is regenerated, achieving recycling.

[0005] Therefore, it is necessary to design an ammonia-ammonium chloride catalytic method system and process for decarbonizing steel slag solid waste and flue gas. Summary of the Invention

[0006] The purpose of this invention is to provide an ammonia-ammonium chloride catalytic method system and process for decarbonizing steel slag solid waste and flue gas, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A steel slag solid waste and flue gas decarbonization system using an ammonia-ammonium chloride catalytic method includes a steel slag dissolving tank, an ammonia condenser, and a decarbonization tower connected in sequence. The top of the decarbonization tower is connected in sequence to an ammonia recovery system, an impurity filtration system, and a calcium carbonate extraction system. The bottom of the decarbonization tower is connected to the calcium carbonate extraction system, which is connected to the steel slag dissolving tank. The steel slag dissolving tank is connected to the ammonia recovery system.

[0009] As a further aspect of the present invention: the ammonia recovery system includes an intermediate tank connected in sequence to the steel slag melting tank, an ammonia washing tower feed pump and an ammonia washing tower, wherein the ammonia washing tower is connected to the top of the decarbonization tower.

[0010] As a further embodiment of the present invention: the impurity filtration system includes a primary membrane separator connected to the bottom of the ammonia washing tower, the primary membrane separator being connected to a secondary membrane separator, and the secondary membrane separator being connected to a calcium carbonate extraction system.

[0011] As a further embodiment of the present invention: the calcium carbonate extraction system includes an acid gas decomposition tower connected to the bottom of the decarbonation tower, a carbon neutralization reactor connected to the top of the acid gas decomposition tower, and an ammonia water feed pump, an ammonia distillation tower and a carbon neutralization reactor connected in sequence to the bottom of the acid gas decomposition tower. The carbon neutralization reactor is connected in sequence to an ammonium chloride solution pump and a steel slag dissolving tank.

[0012] As a further embodiment of the present invention: a decarbonization tower circulation pump is provided between the bottom and top of the decarbonization tower.

[0013] As a further embodiment of the present invention, an ammonia water pump is installed between the ammonia condenser and the decarbonization tower.

[0014] As a further embodiment of the present invention: an ammonia scrubbing tower circulation pump is provided between the bottom and top of the ammonia scrubbing tower.

[0015] An ammonia-ammonium chloride catalytic decarbonization system and process for steel slag solid waste and flue gas decarbonization includes the following steps:

[0016] S1. Mix ammonium chloride solution with a certain amount of steel slag in a steel slag dissolving tank and heat to 90°C. The steel slag dissolves and releases ammonia gas, while producing an acidic suspension containing solid magnesium hydroxide, solid iron hydroxide, calcium chloride, and magnesium chloride.

[0017] S2. The generated ammonia gas is condensed, cooled, and washed in an ammonia condenser, converting it into ammonia water with a concentration of 20%.

[0018] S3. Ammonia water is pumped into the decarbonation tower, and flue gas is simultaneously introduced into the decarbonation tower. The carbon dioxide in the flue gas reacts with the ammonia water to generate ammonium bicarbonate, which then enters the acid decomposition tower.

[0019] S4. The acidic suspension is fed into the ammonia scrubbing tower by the ammonia scrubbing tower feed pump. The decarbonized flue gas enters the ammonia scrubbing tower, and the acidic suspension fully recovers the ammonia.

[0020] S5. The suspension after absorbing ammonia enters the first-stage membrane separator from the bottom of the ammonia washing tower. An appropriate amount of ammonia water is added to adjust the pH value to 6-8, and solid impurities such as silica, iron hydroxide, and aluminum hydroxide are filtered out.

[0021] S6. The filtrate from the primary membrane separator enters the secondary membrane separator, and an appropriate amount of ammonia is added to adjust the pH value to 9-11. The magnesium chloride in the filtrate undergoes a hydrolysis reaction to obtain high-purity magnesium hydroxide.

[0022] S7. Ammonium bicarbonate entering the acid gas decomposition tower decomposes into carbon dioxide gas and dilute ammonia solution. Carbon dioxide gas is released from the top of the acid gas decomposition tower and enters the carbon neutralization reactor. Dilute ammonia solution is discharged from the bottom of the acid gas decomposition tower and sent to the ammonia distillation tower by the ammonia feed pump.

[0023] S8. A dilute ammonia solution is heated at high temperature in an ammonia distillation tower, and ammonia gas is distilled off at the top of the tower and sent to a carbon neutralization reactor.

[0024] S9. In the carbon neutralization reactor, calcium chloride in the filtrate reacts with ammonia and carbon dioxide to obtain calcium carbonate and ammonium chloride solution. The ammonium chloride solution is then pumped back to the steel slag dissolving tank using an ammonium chloride solution pump.

[0025] As a further aspect of the present invention: the pH value of the acidic suspension in step S1 is less than or equal to 4.

[0026] As a further embodiment of the present invention, the acidic suspension at the bottom of the ammonia scrubbing tower can be transferred to the top of the tower by the ammonia scrubbing tower circulation pump.

[0027] In summary, the beneficial effects of this invention are as follows: by utilizing strongly alkaline steel slag, and with the assistance of ammonia and ammonium chloride as catalysts, the steel slag reacts with carbon dioxide to produce high-purity magnesium hydroxide and calcium carbonate products. This not only achieves the purpose of carbon capture, but also realizes the high-value-added resource reuse of steel slag. Attached Figure Description

[0028] Figure 1 A flowchart of an ammonia-ammonium chloride catalytic process system for decarbonizing steel slag solid waste and flue gas.

[0029] In the diagram: 1. Slag melting tank; 2. Ammonia condenser; 3. Ammonia water tank; 4. Ammonia water pump; 5. Decarbonization tower; 6. Decarbonization tower circulation pump; 7. Ammonia scrubbing tower; 8. Ammonia scrubbing tower circulation pump; 9. Acid gas decomposition tower; 10. Ammonia water feed pump; 11. Ammonia distillation tower; 12. Primary membrane separator; 13. Secondary membrane separator; 14. Carbon neutralization reactor; 15. Ammonium chloride solution pump; 16. Ammonia scrubbing tower feed pump; 17. Intermediate tank. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example

[0032] Please see Figure 1 ,like Figure 1 As shown, the ammonia-ammonium chloride catalytic decarbonization system for steel slag solid waste and flue gas includes a steel slag dissolving tank 1, an ammonia condenser 2, and a decarbonization tower 5 connected in sequence. An ammonia pump 4 is installed between the ammonia condenser 2 and the decarbonization tower 5. An ammonia recovery system, an impurity filtration system, and a calcium carbonate extraction system are connected in sequence to the top of the decarbonization tower 5. The bottom of the decarbonization tower 5 is connected to the calcium carbonate extraction system. A decarbonization tower circulation pump 6 is installed between the bottom and the top of the decarbonization tower 5. The calcium carbonate extraction system is connected to the steel slag dissolving tank 1, and the steel slag dissolving tank 1 is connected to the ammonia recovery system.

[0033] The ammonia recovery system includes an intermediate tank 17 connected in sequence to the steel slag melting tank 1, an ammonia washing tower feed pump 16, and an ammonia washing tower 7. An ammonia washing tower circulation pump 8 is installed between the bottom and top of the ammonia washing tower 7, and the ammonia washing tower 7 is connected to the top of the decarbonization tower 5.

[0034] The impurity filtration system includes a primary membrane separator 12 connected to the bottom of the ammonia scrubbing tower 7, the primary membrane separator 12 being connected to a secondary membrane separator 13, and the secondary membrane separator 13 being connected to the calcium carbonate extraction system.

[0035] The calcium carbonate extraction system includes an acid gas decomposition tower 9 connected to the bottom of the decarbonation tower 5. A carbon neutralization reactor 14 is connected to the top of the acid gas decomposition tower 9. An ammonia water feed pump 10, an ammonia distillation tower 11, and a carbon neutralization reactor 14 are connected in sequence to the bottom of the acid gas decomposition tower 9. The carbon neutralization reactor 14 is connected in sequence to an ammonium chloride solution pump 15 and a steel slag dissolving tank 1.

[0036] The process of the ammonia-ammonium chloride catalytic method system for decarbonizing steel slag solid waste and flue gas includes the following steps:

[0037] S1. An ammonium chloride solution is mixed with a certain amount of steel slag in a steel slag dissolving tank 1 and heated to 90°C. The steel slag dissolves and releases ammonia gas, while simultaneously producing an acidic suspension containing solid magnesium hydroxide, solid ferric hydroxide, calcium chloride, and magnesium chloride. The pH value of the acidic suspension is less than or equal to 4.

[0038] The following chemical reaction occurs in the steel slag melting tank:

[0039] ① Dissolution of steel slag:

[0040] CaO·SiO2+NH4Cl→CaCl2+NH3↑+SiO2↓

[0041] MgO·SiO2+NH4Cl→MgCl2+NH3↑+SiO2↓

[0042] Fe₂O₃ + NH₄Cl → FeCl₃ + NH₃↑

[0043] Al₂O₃ + NH₄Cl → AlCl₃ + NH₃↑

[0044] ② Hydrolysis reaction of ferric chloride and aluminum chloride:

[0045] FeCl3 + H2O → Fe(OH)3 + HCl (L)

[0046] AlCl3 + H2O → Al(OH)3 + HCl(L);

[0047] S2. The generated ammonia gas is condensed, cooled and washed in ammonia condenser 2, and converted into ammonia water with a concentration of 20%. The produced ammonia water is first transported to ammonia water tank 3.

[0048] S3. Ammonia water is pumped into decarbonation tower 5 using ammonia water pump 4. Simultaneously, flue gas is introduced into decarbonation tower 5. The carbon dioxide in the flue gas reacts with the ammonia water to produce ammonium bicarbonate, which then enters acid gas decomposition tower 9. The reaction formula for producing ammonium bicarbonate is:

[0049] CO2 + NH3 → NH4HCO3;

[0050] S4. The acidic suspension is fed into the ammonia scrubbing tower 7 via the ammonia scrubbing tower feed pump 16. The decarbonized flue gas enters the ammonia scrubbing tower 7, where the acidic suspension fully recovers the ammonia. The acidic suspension at the bottom of the ammonia scrubbing tower 7 can be transferred to the top of the tower via the ammonia scrubbing tower circulation pump 8 for complete absorption. The following reaction occurs inside the ammonia scrubbing tower:

[0051] HCl + NH3 → NH4Cl

[0052] MgCl2+NH3+H2O→Mg(OH)2↓+NH4Cl;

[0053] S5. The suspension after absorbing ammonia enters the first-stage membrane separator 12 from the bottom of the ammonia washing tower 7. An appropriate amount of ammonia water is added to adjust the pH value to 6-8, preferably 7, and the solid impurities of silicon dioxide, iron hydroxide, and aluminum hydroxide are filtered out.

[0054] S6. The filtrate from the primary membrane separator 12 enters the secondary membrane separator 13. At this point, the filtrate still contains a lot of soluble calcium and magnesium salts. An appropriate amount of ammonia is added to adjust the pH to 9-11. The magnesium chloride in the filtrate undergoes a hydrolysis reaction to obtain high-purity magnesium hydroxide. The following hydrolysis reaction occurs within the secondary membrane separator:

[0055] MgCl2+NH3+H2O→Mg(OH)2↓+NH4Cl;

[0056] S7. The ammonium bicarbonate entering the acid gas decomposition tower 9 decomposes into carbon dioxide gas and dilute ammonia solution. The carbon dioxide gas is released from the top of the acid gas decomposition tower 9 and enters the carbon neutralization reactor 14. The dilute ammonia solution is discharged from the bottom of the acid gas decomposition tower 9 and sent to the ammonia distillation tower 11 via the ammonia feed pump 10.

[0057] S8. The dilute ammonia solution is heated at high temperature in the ammonia distillation tower 11. Ammonia gas is distilled off at the top of the tower and sent to the carbon neutralization reactor 14. The wastewater at the bottom of the tower is sent to the wastewater treatment plant.

[0058] S9. In the carbon neutralization reactor, calcium chloride in the filtrate reacts with ammonia and carbon dioxide to obtain calcium carbonate and ammonium chloride solution. The ammonium chloride solution is also an ammonium salt solution. The ammonium chloride solution is sent back to the steel slag dissolving tank 1 by ammonium chloride solution pump 15. The following reaction occurs in the carbon neutralization reactor:

[0059] CO2+NH3+CaCl2→CaCO3↓+NH4Cl.

[0060] It should be noted that the above embodiments are only specific and clear descriptions of the technical solutions and features of this application. Solutions or features that are prior art or common knowledge to those skilled in the art will not be described in detail in the above embodiments.

[0061] Furthermore, the technical solutions of this application are not limited to the above embodiments. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. Steel slag solid waste and ammonia-ammonium chloride catalytic method system for flue gas decarburization, characterized in that, The system includes a steel slag dissolving tank (1), an ammonia condenser (2), and a decarbonation tower (5) connected in sequence. The top of the decarbonation tower (5) is connected to an ammonia recovery system, an impurity filtration system, and a calcium carbonate extraction system in sequence. The bottom of the decarbonation tower (5) is connected to the calcium carbonate extraction system. The calcium carbonate extraction system is connected to the steel slag dissolving tank (1). The steel slag dissolving tank (1) is connected to the ammonia recovery system.

2. The steel slag solid waste and flue gas decarburization system using ammonia-ammonium chloride catalysis method according to claim 1, characterized in that, The ammonia recovery system includes an intermediate tank (17) connected in sequence to the steel slag melting tank (1), an ammonia scrubbing tower feed pump (16), and an ammonia scrubbing tower (7), which is connected to the top of the decarbonization tower (5).

3. The ammonia-ammonium chloride catalytic method system for decarbonizing steel slag solid waste and flue gas according to claim 2, characterized in that, The impurity filtration system includes a primary membrane separator (12) connected to the bottom of an ammonia scrubbing tower (7), the primary membrane separator (12) being connected to a secondary membrane separator (13), and the secondary membrane separator (13) being connected to a calcium carbonate extraction system.

4. The ammonia-ammonium chloride catalytic method system for decarbonizing steel slag solid waste and flue gas according to claim 3, characterized in that, The calcium carbonate extraction system includes an acid gas decomposition tower (9) connected to the bottom of the decarbonization tower (5), a carbon neutralization reactor (14) connected to the top of the acid gas decomposition tower (9), an ammonia water feed pump (10), an ammonia distillation tower (11) and a carbon neutralization reactor (14) connected in sequence to the bottom of the acid gas decomposition tower (9), and an ammonium chloride solution pump (15) and a steel slag dissolving tank (1) connected in sequence to the carbon neutralization reactor (14).

5. The ammonia-ammonium chloride catalytic method system for decarbonizing steel slag solid waste and flue gas according to claim 4, characterized in that, An ammonia water pump (4) is installed between the ammonia condenser (2) and the decarbonization tower (5).

6. The ammonia-ammonium chloride catalytic method system for decarbonizing steel slag solid waste and flue gas according to claim 5, characterized in that, A decarbonization tower circulation pump (6) is installed between the bottom and top of the decarbonization tower (5).

7. The ammonia-ammonium chloride catalytic method system for decarbonizing steel slag solid waste and flue gas according to claim 6, characterized in that, An ammonia scrubbing tower circulation pump (8) is installed between the bottom and top of the ammonia scrubbing tower (7).

8. A process for decarbonizing steel slag solid waste and flue gas using an ammonia-ammonium chloride catalytic method, characterized in that, Includes the following steps: S1. Mix ammonium chloride solution with a certain amount of steel slag in a steel slag dissolving tank (1) and heat to 90°C. The steel slag dissolves and releases ammonia gas, while producing an acidic suspension containing solid magnesium hydroxide, solid iron hydroxide, calcium chloride and magnesium chloride. S2. The generated ammonia gas is condensed and cooled in the ammonia condenser (2) and washed to convert it into ammonia water with a concentration of 20%. S3. Ammonia water is pumped into the decarbonation tower (5) using an ammonia water pump (4). At the same time, flue gas is introduced into the decarbonation tower (5). The carbon dioxide in the flue gas reacts with the ammonia water to generate ammonium bicarbonate, which then enters the acid decomposition tower (9). S4. The acidic suspension is fed into the ammonia scrubbing tower (7) by the ammonia scrubbing tower feed pump (16). The decarbonized flue gas enters the ammonia scrubbing tower (7) and the acidic suspension fully recovers the ammonia. S5. The suspension after absorbing ammonia enters the first-stage membrane separator (12) from the bottom of the ammonia washing tower (7). Add an appropriate amount of ammonia water to adjust the pH value to 6-8, and filter out solid impurities such as silicon dioxide, iron hydroxide, and aluminum hydroxide. S6. The filtrate from the primary membrane separator (12) enters the secondary membrane separator (13). At the same time, an appropriate amount of ammonia is added to adjust the pH value to 9-11. The magnesium chloride in the filtrate undergoes a hydrolysis reaction to obtain high-purity magnesium hydroxide. S7. The ammonium bicarbonate entering the acid gas decomposition tower (9) decomposes into carbon dioxide gas and dilute ammonia solution. The carbon dioxide gas is released from the top of the acid gas decomposition tower (9) and enters the carbon neutralization reactor (14). The dilute ammonia solution is discharged from the bottom of the acid gas decomposition tower (9) and sent to the ammonia distillation tower (11) by the ammonia water feed pump (10). S8. Dilute ammonia solution is heated at high temperature in ammonia distillation tower (11), and ammonia gas is distilled off at the top of the tower and sent to carbon neutralization reactor (14). S9. In the carbon neutralization reactor (14), calcium chloride in the filtrate reacts with ammonia and carbon dioxide to obtain calcium carbonate and ammonium chloride solution. The ammonium chloride solution is sent back to the steel slag dissolving tank (1) by the ammonium chloride solution pump (15).

9. The process for decarbonizing steel slag solid waste and flue gas using the ammonia-ammonium chloride catalytic method according to claim 8, characterized in that, The pH value of the acidic suspension in step S1 is less than or equal to 4.

10. The process for decarbonizing steel slag solid waste and flue gas using the ammonia-ammonium chloride catalytic method according to claim 8, characterized in that, The acidic suspension at the bottom of the ammonia scrubbing tower (7) can be transferred to the top of the tower by the ammonia scrubbing tower circulation pump (8).

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