Method for producing solution containing ammonium carbonate

Abstract

The invention discloses a production method of a solution containing ammonium carbonate, which comprises the following steps: 1) firing rare earth carbonate by using natural gas to obtain rare earth oxide and first tail gas; 2) performing heat exchange on the first tail gas through a tail gas cooler and recovering heat; introducing the cooled first tail gas into a quench tower, and circularly spraying with ammonia water to obtain second tail gas; and 3) absorbing the second tail gas with ammonia water in a stator-rotor reactor to obtain a solution containing ammonium carbonate, introducing the formed third tail gas into a tail gas absorption tower, removing residual ammonia with acid, and discharging the obtained fourth tail gas meeting the emission standard. According to the method, carbon recycling can be achieved through low-concentration ammonia water, and the ammonia utilization rate reaches 95% or above.

Description

Technical Field

[0001] The invention relates to a method for producing a solution containing ammonium carbonate. Background Art

[0002] Ammonium bicarbonate and ammonium bicarbonate mixed with ammonia water are commonly used in the smelting and separation process of rare earth minerals to prepare rare earth carbonates, and then the rare earth carbonates are burned and transformed into rare earth oxides. The advantages of the mixed precipitant system over single carbon precipitation are that it can reduce the amount of water used to prepare the precipitant, greatly reduce the carbon dioxide released by the decomposition of the precipitant, increase the concentration and utilization rate of the precipitant, reduce the cost of water treatment, and make the precipitation process system control more stable.

[0003] At present, in the process of preparing oxides by thermal decomposition of rare earth carbonates, for enterprises with large rare earth volumes, natural gas is mostly used to burn at about 1000°C in a burning kiln. In addition, the pyrolysis process of rare earth carbonates itself releases carbon dioxide. Therefore, a large amount of low-concentration carbon dioxide tail gas with waste heat will be emitted, which not only causes a large amount of carbon to be discharged, but also loses heat energy. In addition, during the rare earth smelting or carbon deposition process, a large amount of low-concentration ammonia water is recovered from ammonium chloride wastewater. Due to the low concentration of ammonia water and low market profit, most enterprises are self-sufficient, but there is still some excess ammonia water.

[0004] At present, the main technology for capturing carbon dioxide in flue gas is absorption method, and the absorption solvents include organic amines and ammonia water, etc. However, organic amines cannot directly convert and utilize carbon dioxide, which greatly limits the scale of production. The absorption of carbon dioxide by ammonia water is the most important method for the production and preparation of ammonium bicarbonate in industry. The industrial ammonium bicarbonate is prepared by strengthening the gas-liquid reaction process. Among them, the reactors mainly include bubbling towers, packed towers, microreactors, carbonization towers, etc., but the raw materials are mostly high-concentration carbon dioxide or liquid carbon dioxide.

[0005] CN102114383B discloses a carbon dioxide capture and conversion method based on ammonia chemical chain cycle, wherein an ammonia solution is used for gas-liquid contact in an absorption tower to absorb carbon dioxide in the flue gas generated in the steel production process, generate ammonium bicarbonate or ammonium carbonate, and then react it with the product of alkaline steel slag leaching to generate calcium carbonate and basic magnesium carbonate. The ammonia water used in the method is prepared ammonia water, and the ammonia utilization rate and carbon dioxide removal rate of the method are still low. In addition, although the method fixes carbon and recycles calcium and magnesium resources in ammonium chloride steelmaking waste slag, its products calcium carbonate and magnesium carbonate are still industrial by-products and cannot be directly recycled under the system.

[0006] CN112850775A discloses a method for recycling carbon-ammonia in the production process of rare earth oxides, which mainly proposes to use ammonia nitrogen wastewater produced in the process of extraction and precipitation to steam distill ammonia to obtain ammonia water; then the obtained ammonia water, water and carbon dioxide produced in the process of precipitation and calcination are mixed and contacted through a carbonization tower and carbonized multiple times to obtain an ammonium bicarbonate solution, and the obtained ammonium bicarbonate solution is returned to the precipitation step as a precipitant. The method does not provide a detailed description of the rare earth combustion tail gas composition and the tail gas after carbonization. If the obtained ammonium bicarbonate is directly used as a precipitant, it still leads to problems such as a large amount of carbon precipitation wastewater due to low alkalinity.

[0007] CN114180613B discloses a method for preparing rare earth oxides by recycling ammonia and carbon and the use of rare earth oxides, (1) a raw material including a first rare earth carbonate and a first rare earth oxide is heated by microwaves and calcined at 500-1000°C for 20-120 min to obtain a second rare earth oxide and carbon dioxide; (2) the carbon dioxide is reacted with the first ammonia water to obtain a precipitant; (3) the precipitant is reacted with a rare earth chloride to obtain a second rare earth carbonate and ammonium chloride wastewater. The second rare earth carbonate is returned to step (1) and used as a raw material. The ammonia resource utilization rate of this method still needs to be further improved. Moreover, the microwave heating method used in the method has high equipment cost in the rare earth calcination industry, and the processing capacity is limited relative to traditional rotary kiln and other equipment; in addition, the method does not mention the calcination tail gas absorption process and tail gas composition. Summary of the invention

[0008] In view of this, the object of the present invention is to provide a method for producing a solution containing ammonium carbonate. The production method has a high ammonia utilization rate and the obtained rare earth carbonate is easy to filter. The present invention adopts the following technical scheme to achieve the above object.

[0009] The present invention provides a method for producing a solution containing ammonium carbonate, comprising the following steps:

[0010] 1) burning rare earth carbonate with natural gas to obtain rare earth oxides and a first tail gas;

[0011] 2) exchanging heat of the first tail gas through a tail gas cooler and recovering heat; passing the cooled first tail gas into a quenching tower and spraying it with ammonia water to obtain a second tail gas;

[0012] 3) absorbing the second tail gas with aqueous ammonia in a stator-rotor reactor to obtain a solution containing ammonium carbonate, and simultaneously passing the formed third tail gas into a tail gas absorption tower to remove residual ammonia with acid, and discharging the obtained fourth tail gas that meets the emission standards;

[0013] Wherein, the concentration of the ammonia water in the above step is 8.0-9.6 mol / L, and the ammonia water is ammonia water recovered from ammonium chloride wastewater formed by rare earth smelting or carbon precipitation process.

[0014] According to the production method of the present invention, preferably, in step 1), the temperature of the first tail gas is 180-250° C., and the wet base flow rate of the first tail gas is 6500-7000 Nm 3 / h, and the carbon dioxide content is 4.0-5.0wt%.

[0015] According to the production method of the present invention, preferably, in step 2), the first tail gas is subjected to heat exchange and heat recovery through a tail gas cooler for use in a workshop heating system; the cooled first tail gas is pressurized by a fan and then passed into a quenching tower.

[0016] According to the production method of the present invention, preferably, in step 2) and step 3), the total amount of ammonia water used is 430-460 kg / h.

[0017] According to the production method of the present invention, preferably, in step 2), the temperature of the second tail gas is 40-45°C; the flow rate of the second tail gas is 4200-4700 Nm 3 / h.

[0018] According to the production method of the present invention, preferably, in step 3), the gas-liquid contact time during absorption is 5 to 15 seconds.

[0019] According to the production method of the present invention, preferably, in step 3), in the obtained ammonium carbonate-containing solution, the mass concentration of ammonium carbonate is ≥25wt%, and the content of rare earth oxide is 0.8-1.2wt%.

[0020] According to the production method of the present invention, preferably, in step 3), the temperature of the fourth tail gas is 30-40° C.; the concentration of rare earth oxide particles in the fourth tail gas is less than 5 mg / m 3 , ammonia concentration <20mg / m 3 , hydrogen chloride concentration <40mg / m 3 , the carbon dioxide content is 1.0~1.4wt%, and there is no visible white mist.

[0021] According to the production method of the present invention, preferably, in step 1), continuous dynamic burning is adopted.

[0022] According to the production method of the present invention, preferably, the following steps are further included: 4) reacting the obtained ammonium carbonate-containing solution with a rare earth chloride solution to prepare rare earth carbonate, and the obtained rare earth carbonate is further used in step 1) 。

[0023] The ammonia utilization rate of the present invention is relatively high, reaching more than 95%. The ammonium carbonate-containing solution obtained by the present invention contains an appropriate amount of rare earth oxides, so it is more helpful to induce the nucleation and growth of rare earth carbonates when used as a precipitant. The reaction slurry does not need to be aged and is easier to filter. In addition, the ammonium carbonate-containing solution obtained by the production method of the present invention can be directly used in the precipitation process of rare earth carbonates, and the waste heat and carbon dioxide in the tail gas of the rare earth carbonate burning process are effectively utilized. At the same time, the problem of excess ammonia water recovered from ammonium chloride wastewater is solved, achieving cost reduction and efficiency improvement while reducing carbon emissions and driving ammonia circulation. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0025] The ammonium carbonate-containing solution of the present invention means an aqueous solution containing ammonium carbonate, and may further contain ammonium bicarbonate and the like, and may further contain inevitable impurities and the like.

[0026] Based on the theme of "dual carbon background" and resource recycling, the inventors of the present invention use excess ammonia water recovered from ammonium chloride wastewater to absorb the carbon dioxide tail gas generated by the burning of rare earth carbonates, and then prepare a solution containing ammonium carbonate as a raw material for the rare earth carbon precipitation process. This can not only consume excess low-concentration ammonia water, greatly reduce tail gas carbon emissions, but also save the cost of purchasing precipitant ammonium bicarbonate. The present invention can further improve the utilization rate of ammonia and better achieve the goal of "ammonia cycle" driving "carbon emission reduction".

[0027] The present invention provides a method for producing a solution containing ammonium carbonate, comprising the following steps: (1) a step of burning a rare earth carbonate to form a first tail gas; (2) a step of forming a second tail gas; (3) a step of preparing a solution containing ammonium carbonate by absorption with low-concentration ammonia water. Optionally, the method further comprises: (4) a carbon precipitation step and a recycling step. The method is described in detail below.

[0028] <Step of burning rare earth carbonate to form first tail gas>

[0029] Rare earth carbonate is burned with natural gas to obtain rare earth oxides and the first tail gas, which is conducive to improving production efficiency.

[0030] In some embodiments, the rare earth carbonate may be a single rare earth carbonate. In other embodiments, the rare earth carbonate is a basic rare earth carbonate. In other embodiments, the rare earth carbonate is a mixture of a rare earth carbonate and a basic rare earth carbonate.

[0031] In the present invention, the obtained rare earth oxide may be a mixture of a very small amount of rare earth oxycarbonate and rare earth oxide.

[0032] In the present invention, the rare earth element in the rare earth carbonate can be selected from one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium or scandium. Preferably, the rare earth element in the rare earth carbonate is selected from one or more of lanthanum, cerium, praseodymium, neodymium, samarium, europium and gadolinium.

[0033] In certain embodiments, the present invention adopts continuous dynamic combustion, which is conducive to uniform heating of rare earth carbonate and / or basic rare earth carbonate and improves combustion efficiency.

[0034] In the present invention, the equipment, temperature and time required for burning the rare earth carbonate with natural gas can adopt those known in the art.

[0035] The temperature of the first tail gas obtained in the present invention can be 180-250°C, preferably 185-240°C, and more preferably 220-230°C. The wet base flow rate of the first tail gas is 6500-7000 Nm 3 / h, preferably 6500~6800Nm 3 / h, more preferably 6600-6800Nm 3 / h. The rare earth oxide particle content in the first tail gas is 15-25 mg / m 3 , preferably 15 to 22 mg / m 3 , more preferably 15 to 20 mg / m 3 The content of carbon dioxide in the first tail gas is 4.0 to 5.0 wt %, preferably 4.2 to 5.0 wt %, and more preferably 4.4 to 4.8 wt %.

[0036] <Second exhaust gas forming step>

[0037] The first tail gas is heat exchanged through the tail gas cooler to recover heat; the cooled first tail gas is passed into the quenching tower and sprayed with ammonia water to obtain the second tail gas. In this way, the heat exchange of the first tail gas is conducive to the effective utilization of the waste heat of the first tail gas. The pre-spraying of the first tail gas is conducive to providing the second tail gas with a suitable temperature for the next step of absorption and is conducive to improving the utilization rate of ammonia.

[0038] According to one embodiment of the present invention, the first exhaust gas is subjected to heat exchange via an exhaust gas cooler, and the recovered heat is used for a workshop heating system. The exhaust gas cooler may be any known one.

[0039] In certain embodiments, the cooled first tail gas is pressurized by a blower and then passed into a quenching tower, which is beneficial to improving production efficiency.

[0040] In the present invention, the ammonia water can be low-concentration ammonia water recovered from ammonium chloride wastewater formed in rare earth smelting or carbon precipitation process. The concentration of the ammonia water is less than 10 mol / L, preferably 8.0-9.6 mol / L, and more preferably 8.5-9.5 mol / L.

[0041] In this step, ammonia water is used for circulating spraying, which is beneficial to cool the first tail gas and pre-absorb to form an initial solution containing ammonium carbonate, which can be used for the next stage of stator and rotor absorption.

[0042] In the present invention, the temperature of the second tail gas is 40-45°C, and the flow rate of the second tail gas is 4100-4700 Nm 3 / h, preferably 4200~4700Nm 3 / h, more preferably 4300-4600Nm 3 / h.

[0043] <Step of preparing a solution containing ammonium carbonate by absorption of low concentration ammonia water>

[0044] The second tail gas is absorbed by ammonia water in a stator-rotor reactor to obtain a solution containing ammonium carbonate, and the third tail gas formed is introduced into a tail gas absorption tower to remove residual ammonia with acid, and the fourth tail gas obtained that meets the emission standards is discharged. The present invention is the first to use low-concentration ammonia in a stator-rotor reactor to treat tail gas containing carbon dioxide, and the effect is significant, which is not a conventional choice.

[0045] In the present invention, the stator-rotor reactor can adopt the stator-rotor reactor disclosed in the Chinese patent with application number 200410042631.6, which is introduced in full herein. The stator-rotor reactor is mainly composed of an end cap, a housing, a stator, a rotor, a motor, and a mechanical seal, one end of the housing is connected to the end cap, a gas channel is arranged on the housing, a discharge port is on the housing, the rotor is connected to the motor through a rotating shaft, a nozzle is arranged on the end cap, the other end of the housing is connected to the motor, the stator is composed of the end cap and multiple concentric rings or pins uniformly distributed on multiple concentric circles, the rotor is composed of a rotor seat and multiple concentric rings or pins uniformly distributed on multiple concentric circles, the rotor seat is connected to the motor shaft, the concentric rings or pins are fixed on the end cap or the rotor seat by threaded connection, the concentric rings have channels on the circumference, and the speed of the rotor is in the range of 100 to 3000 r / min.

[0046] The stator-rotor reactor can disperse and refine the liquid by the high-speed rotating rotor during the flow between the stator and the rotor, and redistribute it on each layer of the stator, thereby increasing the turbulence degree and surface renewal rate of the fluid. It is a combination of multiple end effect zones, and the gas-liquid mass transfer process is greatly enhanced. Secondly, there is no filler in the stator-rotor reactor. As a high-efficiency rotating mixing equipment, it avoids material blockage in high-viscosity systems or precipitation crystallization reactions, has the advantages of anti-scaling and anti-blocking, and can ensure the long-term stable operation of the system.

[0047] In the implementation process of the present invention, the second tail gas (the initial solution containing carbon dioxide and ammonium carbonate), ammonia water and related process water enter the stator-rotor reactor respectively, and the ammonia and carbon dioxide are reacted as completely as possible by controlling the gas-liquid countercurrent to strengthen the contact, so as to prepare a solution containing ammonium carbonate with a higher concentration, ensure that the ammonia utilization rate is greater than or equal to 95%, and make the carbon content carried by the rare earth carbonate itself fully recovered. The stator-rotor reactor has a higher gas-liquid mass transfer efficiency than conventional mass transfer and heat transfer equipment, a smaller equipment volume, and saves space.

[0048] In the present invention, the third tail gas can be subjected to deep removal of residual ammonia using dilute sulfuric acid in a tail gas absorption tower to form a fourth tail gas that can be discharged. The tail gas absorption tower can be known ones. The concentration of the dilute sulfuric acid can be 20-30wt%.

[0049] In the present invention, the ammonia water is low-concentration ammonia water, and the concentration of the ammonia water is less than 10 mol / L, preferably 8.0-9.6 mol / L, and more preferably 8.5-9.5 mol / L. In the process of circulating ammonia water spraying and stator-rotor absorption (i.e., the process of forming the second tail gas and the third tail gas), the total amount of ammonia water is 430-460 kg / h, preferably 440-460 kg / h, and more preferably 450-455 kg / h.

[0050] The second tail gas is absorbed by ammonia water in the stator-rotor reactor for 5 to 15 seconds, preferably 7 to 15 seconds, and more preferably 10 to 12 seconds. The obtained ammonium carbonate solution has a mass concentration of ammonium carbonate of greater than or equal to 25 wt %, and a rare earth oxide content of 0.8 to 1.2 wt %.

[0051] The temperature of the fourth tail gas is 30-40° C. The concentration of rare earth oxide particles in the fourth tail gas is less than 5 mg / m 3 , ammonia concentration <20mg / m 3 , the concentration of hydrogen chloride is less than 40mg / m 3 , the carbon dioxide content is 1.0-1.4wt%, no visible white mist. It can meet the emission standards.

[0052] In the present invention, the calculation method of ammonia utilization is as follows:

[0053] Ammonia utilization rate = NH4 in the solution containing ammonium carbonate + Content / NH4 in the raw ammonia water used + Content × 100%.

[0054] <Carbon Sedimentation and Recycling Steps>

[0055] The obtained ammonium carbonate-containing solution is reacted with rare earth chloride feed liquid to prepare rare earth carbonate. The rare earth carbonate can be further processed using the above steps. In this way, the ammonium carbonate-containing solution can be reused, the carbon element can be recycled, and the ammonia can be recycled.

[0056] In the present invention, the obtained ammonium carbonate-containing solution can also be compounded with ammonia water and then reacted with rare earth chloride solution to prepare rare earth carbonate.

[0057] In certain embodiments, the ammonium carbonate-containing solution and the rare earth chloride solution are added dropwise in parallel to form a slurry, which is then filtered to obtain rare earth carbonate.

[0058] In the present invention, after the reaction is completed, aging is not required and the filtration can be directly carried out, and the filtration is easy. The present invention finds that the use of the ammonium carbonate solution prepared as above is conducive to obtaining an easily filterable slurry. Although the principle is not clear, we believe that this may be because the ammonium carbonate solution contains 0.8 to 1.2 wt% of rare earth oxides, which act as seeds and help induce the nucleation and growth of rare earth carbonates. Therefore, the formed rare earth carbonate slurry does not need aging and is easier to filter.

[0059] <Analysis Method>

[0060] NH4 + The content was determined by neutralization titration.

[0061] Ammonia water: Ammonia water recovered from ammonium chloride wastewater formed in rare earth smelting or carbon precipitation process.

[0062] The following examples use the stator-rotor reactor disclosed in Chinese Patent Application No. 200410042631.6.

[0063] Example 1

[0064] 1) 25 tons of rare earth lanthanum carbonate are continuously burned with natural gas to obtain 12 tons of lanthanum oxide and generate the first tail gas. The wet base flow rate of the first tail gas is 6500-6510 Nm 3 / h.

[0065] 2) The first tail gas is passed into the tail gas cooler for heat exchange, and the recovered heat is used for workshop heating. The cooled first tail gas is pressurized by a fan and passed into a quenching tower. In the quenching tower, 8.3 mol / L low-concentration ammonia water is sprayed and externally cooled by circulating water to obtain the second tail gas.

[0066] 3) The second tail gas is fully contacted with 8.3 mol / L low-concentration ammonia water in a stator-rotor reactor by gas-liquid countercurrent strengthening to obtain a solution containing ammonium carbonate, and the formed third tail gas containing ammonia carbon is continuously introduced into a tail gas absorption tower, and finally residual ammonia is deeply removed by dilute sulfuric acid in the tail gas absorption tower, and the obtained fourth tail gas is discharged. Wherein, the content of ammonium carbonate in the solution containing ammonium carbonate is about 25wt%, and the content of rare earth oxide is 0.8wt%.

[0067] 4) The above ammonium carbonate-containing solution is used as a precipitant to carry out a co-current precipitation reaction with a rare earth chloride feed solution. After the reaction is completed, lanthanum carbonate is directly filtered without aging to obtain lanthanum carbonate. We found that since the ammonium carbonate-containing solution contains an appropriate amount of rare earth oxides, the crystallization of lanthanum carbonate is promoted, and therefore the obtained product is very easy to filter.

[0068] The raw material dosage and process parameters used in the above steps are shown in Table 1.

[0069] Repeat steps 1) to 4) to obtain a solution containing ammonium carbonate, and use the solution containing ammonium carbonate as a precipitant to obtain rare earth carbonate.

[0070] Example 2

[0071] 1) 28 tons of rare earth lanthanum cerium carbonate are continuously burned with natural gas to obtain 13 tons of lanthanum cerium oxide and generate the first tail gas. The wet basis flow rate of the first tail gas is 7000~7005Nm 3 / h.

[0072] 2) The first tail gas is passed into the tail gas cooler for heat exchange, and the recovered heat is used for workshop heating. The cooled first tail gas is pressurized by a fan and passed into a quenching tower. In the quenching tower, 9.5 mol / L low-concentration ammonia water is sprayed and externally cooled by circulating water to obtain the second tail gas.

[0073] 3) The second tail gas is fully contacted with 9.5 mol / L low-concentration ammonia water in a stator-rotor reactor by gas-liquid countercurrent strengthening to obtain a solution containing ammonium carbonate, and the formed third tail gas containing ammonia carbon is continuously introduced into a tail gas absorption tower, and finally ammonia is deeply removed by dilute sulfuric acid in the tail gas absorption tower, and the obtained fourth tail gas is discharged. Wherein, the content of ammonium carbonate in the solution containing ammonium carbonate is about 25wt%, and the content of rare earth oxide is about 1.0wt%.

[0074] 4) The ammonium carbonate-containing solution is used as a precipitant to carry out a co-current precipitation reaction with the rare earth chloride solution. After the reaction is completed, it is directly filtered without aging to obtain lanthanum cerium carbonate.

[0075] We have found that since the ammonium carbonate-containing solution contains an appropriate amount of rare earth oxide, the crystallization of lanthanum cerium carbonate is promoted, and therefore the resulting product is very easy to filter.

[0076] The raw material dosage and process parameters used in the above steps are shown in Table 1.

[0077] Continue to repeat step 1) to step 4) to obtain a solution containing ammonium carbonate, and use the solution containing ammonium carbonate as a precipitant to obtain rare earth carbonate.

[0078] Embodiment 3-4

[0079] Except for the specific parameters in Table 1, the rest is the same as Example 1.

[0080] Comparative Example 1

[0081] The first tail gas in the embodiment is replaced with pure carbon dioxide gas, and 9.0 mol / L ammonia water is used for conventional gas-liquid reaction absorption to prepare a 3 mol / L ammonium carbonate-containing solution as a precipitant, which is reacted in parallel with 220 g / L lanthanum cerium chloride solution, aged for 3 hours, and then filtered to obtain lanthanum cerium carbonate.

[0082] Table 1

[0083]

[0084] It can be seen from Table 1 that the ammonia utilization rate of the present invention is relatively high, and the fourth tail gas meets the emission standards.

[0085] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for producing a solution containing ammonium carbonate, characterized in that: The steps include: 1) burning rare earth carbonate with natural gas to obtain rare earth oxides and a first tail gas; 2) exchanging heat of the first tail gas through a tail gas cooler and recovering heat; passing the cooled first tail gas into a quenching tower and spraying it with ammonia water to obtain a second tail gas; 3) absorbing the second tail gas with aqueous ammonia in a stator-rotor reactor to obtain a solution containing ammonium carbonate, and simultaneously passing the formed third tail gas into a tail gas absorption tower to remove residual ammonia with acid, and discharging the obtained fourth tail gas that meets the emission standards; Wherein, the concentration of the ammonia water in the above step is 8.0-9.6 mol / L, and the ammonia water is ammonia water recovered from ammonium chloride wastewater formed by rare earth smelting or carbon precipitation process.

2. The production method according to claim 1, characterized in that In step 1), the temperature of the first tail gas is 180-250°C, and the wet base flow rate of the first tail gas is 6500-7000 Nm 3 / h, and the carbon dioxide content is 4.0-5.0wt%.

3. The production method according to claim 1, characterized in that In step 2), the first tail gas is subjected to heat exchange in a tail gas cooler and heat is recovered for use in a workshop heating system; the cooled first tail gas is pressurized by a fan and then passed into a quenching tower.

4. The production method according to claim 1, characterized in that In step 2) and step 3), the total amount of ammonia water used is 430-460 kg / h.

5. The production method according to claim 1, characterized in that: In step 2), the temperature of the second tail gas is 40-45°C; the flow rate of the second tail gas is 4200-4700 Nm 3 / h.

6. The production method according to claim 1, characterized in that: In step 3), the gas-liquid contact time during absorption is 5 to 15 seconds.

7. The production method according to claim 1, characterized in that: In step 3), the obtained ammonium carbonate solution has an ammonium carbonate mass concentration of ≥25wt% and a rare earth oxide content of 0.8-1.2wt%.

8. The production method according to claim 1, characterized in that: In step 3), the temperature of the fourth tail gas is 30-40°C; the concentration of rare earth oxide particles in the fourth tail gas is less than 5 mg / m 3 , ammonia concentration <20mg / m 3 , hydrogen chloride concentration <40mg / m 3 , the carbon dioxide content is 1.0~1.4wt%, and there is no visible white mist.

9. The production method according to any one of claims 1 to 8, characterized in that: In step 1), continuous dynamic burning is adopted.

10. The production method according to claim 9, characterized in that: The following steps are also included: 4) reacting the obtained ammonium carbonate-containing solution with rare earth chloride solution to prepare rare earth carbonate, and the obtained rare earth carbonate is further used in step 1) 。

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