A method for preparing ceramsite by using electrolytic manganese residue and synergistically recovering nitrogen and sulfur components in a step-by-step and directional manner

Abstract

This invention provides a method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner, relating to the field of solid waste resource utilization technology. The method includes batching, granulation, and roasting; the roasting process sequentially passes through a feeding section, a drying section, a deammoniation section, a preheating section, a desulfurization roasting section, and a cooling section, ultimately yielding shaped ceramsite. In the deammoniation section, the ceramsite temperature is 150℃-450℃, and the exhaust gas containing ammonia is 120-350℃, which is directly recovered to prepare ammonia water. In the desulfurization roasting section, the ceramsite temperature is 1050℃-1200℃, and the exhaust gas containing sulfur oxides has a sulfur oxide volume concentration of 5%-15%, which is directly recovered to prepare sulfuric acid. This invention, by constructing a multi-stage gradient roasting system of "simultaneous low-temperature deammoniation and high-temperature desulfurization of the roasted ceramsite product" and coordinating with an independent directional gas collection system, achieves high-purity, simultaneous, and full-component cascaded recovery and utilization of ammonia, sulfur, and tailings resources from electrolytic manganese slag.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, and in particular to a method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner. Background Technology

[0002] Electrolytic manganese is a key raw material for desulfurization, deoxidation, and the preparation of high-end alloys in the steel industry. Electrolytic manganese slag mainly originates from the leaching and purification processes during production. Leaching slag is obtained by filtering mineral powder after acidification with sulfuric acid, iron removal through oxidation, and pH adjustment with ammonia. It is rich in sulfates (CaSO4, MnSO4, etc.), silica, and unreacted mineral powder. Sulfide slag is a precipitate containing cobalt, nickel, copper, and other sulfides that emerge during heavy metal purification. Because electrolytic manganese slag contains high concentrations of ammonia nitrogen (mainly in the form of (NH4)2SO4) and soluble heavy metals, long-term open-air storage not only occupies a large amount of land but also causes severe soil acidification, groundwater ammonia nitrogen exceeding standards, and heavy metal pollution due to rainwater leaching, becoming a bottleneck restricting the green and sustainable development of the manganese industry. Therefore, realizing the large-scale, high-value utilization of electrolytic manganese slag, especially the simultaneous recovery of sulfur and ammonia resources, is of urgent practical significance.

[0003] Current research on the resource utilization of electrolytic manganese slag mainly focuses on two directions: high-temperature roasting desulfurization and building material utilization. Regarding high-temperature roasting desulfurization, multiple studies have confirmed that sulfur conversion and removal can be achieved by adding reducing agents. For example, Xiong Yulu et al. found that adding 4% coke and roasting at 1000℃ for 60 minutes under a nitrogen atmosphere could reduce the SO2 volume fraction in the flue gas to 7.6%. Zou Tingxin et al. reduced the sulfur content in the manganese slag to 0.62% by blending it with 3% coal and roasting it at 1050℃. Zeng Jun et al., under sealed conditions, achieved a desulfurization rate of 96.66% by roasting at 1050℃ for 1 hour with 2% carbon admixture. In addition, related patent technologies have also explored this area: Patent CN105217580B discloses a method for high-temperature calcination at 700℃-1350℃ in a rotary kiln after adding activators and reducing agents, achieving a desulfurization rate of over 85%; Patent CN110482612A proposes a high-temperature calcination process for producing manganese sulfate using SO2-containing flue gas; Patent CN118145672B discloses a synergistic acid production process that generates high-concentration SO2 flue gas through oxygen-enriched roasting and prepares the residue as building aggregate. Regarding the utilization of ceramsite and building materials, Patent CN118307296A discloses a method for preparing lightweight ceramsite by sintering electrolytic manganese slag as the main material, compounded with sludge, bentonite, etc.; Patent CN112029937A proposes a full-component recovery process combining melt desulfurization and reduction iron extraction.

[0004] Although the above technologies have made some progress in the recovery of single components or the utilization of residues, the following significant technical drawbacks still limit their large-scale industrial application:

[0005] (1) Most existing high-temperature roasting technologies focus primarily on the conversion of sulfur and the utilization of SO2 flue gas for acid production, often neglecting the ammonia nitrogen resources associated with the slag. Under high-temperature oxidizing or mixed atmospheres, ammonia nitrogen is readily oxidized to NO. x This results in secondary pollution, or the emissions are directly diluted with flue gas, failing to achieve "double harvest of ammonia and sulfur".

[0006] (2) Existing technologies mostly use rotary kilns or single-atmosphere roasting furnaces, and the airflow organization is mostly co-current or counter-current overall ventilation. In this mode, the ammonia gas volatilized in the low-temperature section and the SO2 gas generated in the high-temperature section are very easy to mix. This not only causes NH3 to react with SO2 to form ammonium sulfate and block the pipes, but also dilutes the SO2 concentration due to the entrainment of a large amount of cold air (some processes need to rely on oxygen enrichment or external fuel to maintain the temperature and further dilute the flue gas). This makes the flue gas composition complex and the concentration fluctuates greatly, making it difficult to directly meet the requirements of high-quality sulfuric acid and ammonia water co-production.

[0007] (3) Although some technologies have achieved harmlessness, the final products are mostly low-value cement admixtures or ordinary roadbed materials, which cannot cover the high treatment costs.

[0008] In summary, there are currently no reports on the simultaneous high-purity recovery of ammonia, high-concentration SO2 production, and high-performance ceramsite preparation using electrolytic manganese slag through a multi-stage roasting process. There is an urgent need to develop a new technology with a short process flow, no need for external fuel, and the ability to simultaneously achieve high-value recovery of both ammonia and sulfur while utilizing all components of the product. Summary of the Invention

[0009] To address the technical problems existing in the prior art, this invention provides a method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner. The technical solution is as follows:

[0010] This invention provides a method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner, comprising the following steps:

[0011] S1. Ingredients: Mix electrolytic manganese slag and auxiliary materials evenly to obtain a mixture with a calorific value of 300-600 kcal / kg and a sulfur content of 8%-15% by mass.

[0012] S2. Granulation: The mixture is put into a granulator for granulation to obtain ceramsite pellets;

[0013] S3. Calcination: The raw ceramsite pellets are conveyed to an exhaust-fired calcining furnace for calcination. This furnace includes a feeding section, a drying section, a deammoniation section, a preheating section, a desulfurization calcination section, and a cooling section. The raw ceramsite pellets sequentially pass through these sections to obtain shaped ceramsite pellets. In the deammoniation section, the ceramsite temperature is 150℃-450℃, and the exhaust gas containing ammonia is 120-350℃. This ammonia-containing gas is directly recovered to prepare ammonia water. In the desulfurization calcination section, the ceramsite temperature is 1050℃-1200℃, and the exhaust gas containing sulfur oxides has a sulfur oxide volume concentration of 5%-15%. This sulfur oxide-containing gas is directly recovered to prepare sulfuric acid.

[0014] Optionally, the exhaust-fired roasting furnace is one of the following: belt roaster, ceramsite roaster, sintering machine, exhaust-fired roasting tunnel kiln, or ceramsite flue gas circulating roasting furnace.

[0015] Optionally, the mass ratio of the auxiliary material to the electrolytic manganese slag is (5-25):(75-95).

[0016] Optionally, the auxiliary materials are one or more of the following: coal, coke, coal gangue, gasification slag, pyrite, sulfur, coal slime, biomass, and oil sludge.

[0017] Optionally, the batching process in step S1 can be as follows: wet-process electrolytic manganese slag slurry is directly mixed with auxiliary materials that have been ground to a particle size of no more than 20% on a 200-mesh sieve to obtain a mixed material; or the electrolytic manganese slag is dried and then mixed with auxiliary materials and ground to obtain powder with a particle size of no more than 20% on a 200-mesh sieve.

[0018] Optionally, the granulation process in step S2 can be performed by directly extruding the mixture obtained by wet mixing through pressure filtration, or by granulating the ground powder using a disc granulator.

[0019] Optionally, the maximum temperature at which the ceramsite is heated in the drying section is 130-160°C; the drying section includes a forced-air drying section and / or a forced-air drying section.

[0020] Optionally, the maximum temperature at which the ceramsite is heated in the deammoniation section is 300-450℃, the maximum temperature at which the ceramsite is heated in the desulfurization roasting section is 1100-1200℃, and the temperature at which the ceramsite is discharged from the cooling section is 50℃-100℃.

[0021] Optionally, the cooling section includes a high-temperature cooling section, a medium-temperature cooling section, and / or a low-temperature cooling section connected in sequence; the high-temperature cooling section cools the ceramsite to a temperature of 400℃-700℃, and the medium-temperature cooling section and / or the low-temperature cooling section cools the ceramsite to a temperature of 50-120℃.

[0022] Optionally, the shaped ceramsite is one of high-strength ceramsite, ordinary ceramsite, filter media ceramsite, or porous ceramsite; wherein, the highest temperature of the ceramsite material layer during the calcination process of high-strength ceramsite is 1120-1180℃; and the highest temperature of the ceramsite material layer during the calcination process of ordinary ceramsite, filter media ceramsite, or porous ceramsite is 1050-1150℃.

[0023] Optionally, the 200-400°C outlet flue gas from the preheating section or the 70-150°C tail gas from the ammonia removal section is directionally extracted and absorbed, and then transported to the high-temperature cooling section. The outlet flue gas is then heated to 700-900°C and transported to the desulfurization roasting section; or...

[0024] The 200-400℃ outlet flue gas from the preheating section is directionally extracted and first circulated to the ammonia removal section to heat the ceramsite. Then, the outlet flue gas from the ammonia removal section is directionally extracted and absorbed to prepare ammonia water. The exhaust gas at 70-150℃ is circulated to the high-temperature cooling section. After being heated to 700-900℃, the outlet flue gas is sent back to the desulfurization roasting section; or...

[0025] The 300-600℃ outlet flue gas discharged from the desulfurization roasting section is directionally extracted and sent to the preheating section. After the ceramsite is heated in the preheating section, the flue gas discharged at 200-400℃ is then transported to the desulfurization roasting section.

[0026] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0027] This invention achieves high-purity simultaneous recovery and high-value utilization of ammonia and sulfur resources from electrolytic manganese slag by constructing a multi-stage gradient roasting system of "low-temperature deammoniation-high-temperature desulfurization" and cooperating with an independent directional gas collection system. On the one hand, by utilizing a specific material ratio (calorific value 300-600 kcal / kg, sulfur content 8-15%), a weakly reducing atmosphere is formed in the low-temperature section (150℃-450℃) to inhibit ammonia nitrogen oxidation and separately recover and prepare high-quality ammonia water. At the same time, the roasting temperature in the high-temperature section is precisely controlled at 1050℃-1200℃. This range not only highly matches the decomposition temperature of sulfate in electrolytic manganese slag but is also significantly lower than the high temperature of over 1300℃ required for cement clinker firing. Under this temperature range, the process utilizes the material's own calorific value to achieve internal heating self-heating balance, and sulfate can be deeply decomposed without external fuel, producing high-purity SO2 flue gas with a concentration as high as 5%-15% for acid production. This completely solves the problems of product loss, secondary pollution, and difficulty in utilizing low-concentration flue gas caused by gas mixing in traditional processes. On the other hand, the final product of this process is high-value, high-strength, lightweight ceramsite with a compressive strength >5.0MPa, realizing the large-scale harmless treatment and resource utilization of electrolytic manganese slag, which has great industrial promotion value. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 (a) Figure 1 (b) is a process flow diagram of preparing ceramsite green pellets from electrolytic manganese slag according to an embodiment of the present invention;

[0030] Figure 2 , Figure 3 , Figure 4 , Figure 5 This is a flowchart of the roasting process of ceramsite pellets in an exhaust roasting furnace, as provided by the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0034] S1. Batching: The auxiliary materials, consisting of coal gangue and coal slime, are mixed into the electrolytic manganese slag slurry and stirred to form a mixture. The dry basis ratio of the auxiliary materials to the electrolytic manganese slag slurry is 25:75. The calorific value of the mixture is 590 kcal / kg, and the sulfur content is 8.1%. The particle size of the auxiliary materials is 200 mesh, with a sieve residue of 12%.

[0035] S2. Granulation: The mixture is put into a granulator, and after pressure filtration and extrusion, short cylindrical ceramic pellets with a cross-sectional diameter of 12mm and a length of 6-12mm are obtained.

[0036] S3. Calcination: The raw ceramsite pellets are conveyed to a ventilated calcining furnace for calcination. The calcination process involves six stages: feeding section, drying section, ammonia removal section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite (such as...). Figure 2(As shown); the drying section includes a forced-air drying section and an exhaust drying section; the average temperature of the ceramsite at the outlet of each process section is as follows: forced-air drying section 80℃, exhaust drying section 180℃, deammoniation section 420℃, preheating section 1030℃, desulfurization roasting section 1140℃, and cooling section 80℃.

[0037] The ammonia-rich gas emitted from the deammoniation section is separately discharged into the ammonia water absorption system to prepare ammonia water; the sulfur-rich gas emitted from the desulfurization roasting section has a volume concentration of 3.8%, which is separately discharged into the sulfuric acid production process to prepare sulfuric acid products; the cooled ceramsite product is ordinary ceramsite with a cylinder compressive strength of 5.9 MPa.

[0038] Example 2

[0039] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0040] S1. Batching: The auxiliary materials, consisting of pulverized coal and fly ash, are mixed into the electrolytic manganese slag slurry and stirred to form a mixture. The dry basis ratio of the auxiliary materials to the electrolytic manganese slag slurry is 10:90. The calorific value of the mixture is 418 kcal / kg, and the sulfur content is 12.3%. The particle size of the auxiliary materials is 200 mesh, with a sieve residue of 12%.

[0041] S2. Granulation: The mixture is put into a granulator, and after pressure filtration and extrusion, short cylindrical ceramic pellets with a cross-sectional diameter of 12mm and a length of 6-12mm are obtained.

[0042] S3. Calcination: The raw ceramsite pellets are conveyed to the blast furnace for calcination. The calcination process involves six stages: feeding section, drying section, deammoniation section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite pellets. The drying section includes a forced-air drying section and a forced-air drying section. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying section 80℃, forced-air drying section 185℃, deammoniation section 430℃, preheating section 980℃, desulfurization calcination section 1145℃, and cooling section 85℃.

[0043] The ammonia-rich gas emitted from the deammoniation section is separately discharged into the ammonia water absorption system to prepare ammonia water; the sulfur-rich gas emitted from the desulfurization roasting section has a volume concentration of 7.6%, which is separately discharged into the sulfuric acid production process to prepare sulfuric acid products; the cooled ceramsite product is ordinary ceramsite with a cylinder compressive strength of 5.1 MPa.

[0044] Example 3

[0045] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0046] S1. Batching: The auxiliary materials, consisting of gasification slag and clay powder, are mixed into the electrolytic manganese slag slurry and stirred to form a mixture. The dry basis ratio of the auxiliary materials to the electrolytic manganese slag slurry is 15:85. The calorific value of the mixture is 352 kcal / kg, and the sulfur content is 11.1%. The particle size of the auxiliary materials is 200 mesh, with a sieve residue of 10%.

[0047] S2. Granulation: The mixture is put into a granulator, and after pressure filtration and extrusion, short cylindrical ceramic pellets with a cross-sectional diameter of 12mm and a length of 6-12mm are obtained.

[0048] S3. Calcination: The raw ceramsite pellets are conveyed to the blast furnace for calcination. The calcination process involves six stages: feeding section, drying section, deammoniation section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite pellets. The drying section includes a forced-air drying section and a forced-air drying section. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying section 85℃, forced-air drying section 188℃, deammoniation section 450℃, preheating section 930℃, desulfurization calcination section 1130℃, and cooling section 55℃.

[0049] The ammonia-rich gas emitted from the deammoniation section is separately discharged into the ammonia water absorption system to prepare ammonia water; the sulfur-rich gas emitted from the desulfurization roasting section has a volume concentration of 6.8%, which is separately discharged into the sulfuric acid production process to prepare sulfuric acid products; the cooled ceramsite product is porous ceramsite with a cylinder compressive strength of 3.1 MPa.

[0050] Example 4

[0051] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0052] S1. Ingredients: The auxiliary materials, consisting of coal slime and fly ash, are mixed into the electrolytic manganese slag slurry and stirred to form a mixture. The dry basis ratio of the auxiliary materials to the electrolytic manganese slag slurry is 10:90. The calorific value of the mixture is 370 kcal / kg, and the sulfur content is 12.3%. The particle size of the auxiliary materials is 200 mesh, with a sieve residue of 9%.

[0053] S2. Granulation: The mixture is put into a granulator, and after pressure filtration and extrusion, short cylindrical ceramsite pellets with a cross-sectional diameter of 10mm and a length of 5-12mm are obtained.

[0054] S3. Calcination: The raw ceramsite pellets are conveyed to the blast furnace for calcination. The calcination process involves six stages: feeding section, drying section, deammoniation section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite pellets. The drying section includes a forced-air drying section and a forced-air drying section. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying section 80℃, forced-air drying section 182℃, deammoniation section 410℃, preheating section 980℃, desulfurization calcination section 1180℃, and cooling section 90℃.

[0055] The ammonia-rich gas emitted from the deammoniation section is separately discharged into the ammonia water absorption system to prepare ammonia water; the sulfur-rich gas emitted from the desulfurization roasting section has a volume concentration of 8.5%, which is separately discharged into the sulfuric acid production process to prepare sulfuric acid products; the cooled ceramsite product is high-strength ceramsite with a cylinder compressive strength of 7.5 MPa.

[0056] Example 5

[0057] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0058] S1. Batching: The auxiliary material composed of pulverized coal is mixed into the electrolytic manganese slag slurry and stirred to form a mixture; wherein, the dry basis ratio of the auxiliary material and the electrolytic manganese slag slurry is 5:95, the calorific value of the mixture is 302 kcal / kg, and the sulfur content is 13.1%; the particle size of the auxiliary material is 200 mesh, with a sieve residue of 7%;

[0059] S2. Granulation: The mixture is put into a granulator, and after pressure filtration and extrusion, short cylindrical ceramic pellets with a cross-sectional diameter of 12mm and a length of 6-12mm are obtained.

[0060] S3. Calcination: The raw ceramsite pellets are conveyed to the blast furnace for calcination. The calcination process involves six stages: feeding section, drying section, deammoniation section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite pellets. The drying section includes a forced-air drying section and a forced-air drying section. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying section 90℃, forced-air drying section 190℃, deammoniation section 480℃, preheating section 980℃, desulfurization calcination section 1150℃, and cooling section 90℃.

[0061] The ammonia-rich gas emitted from the deammoniation section is separately discharged into the ammonia water absorption system to prepare ammonia water; the sulfur-rich gas emitted from the desulfurization roasting section has a volume concentration of 9.6%, which is separately discharged into the sulfuric acid production process to prepare sulfuric acid products; the cooled ceramsite product is ordinary ceramsite with a cylinder compressive strength of 5.3 MPa.

[0062] Example 6

[0063] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0064] S1. Ingredients: The auxiliary materials consisting of coal powder and clay are mixed and ground with the dried electrolytic manganese slag filter cake at a dry basis ratio of 10:90 to form a mixture until the particle size passes through a 200-mesh sieve and the residue is 5%; the calorific value of the mixture is 325 kcal / kg and the sulfur content is 13.1%;

[0065] S2. Granulation: The mixture is granulated by a disc to obtain ceramsite pellets with a cross-sectional diameter of 8-16 mm;

[0066] S3. Calcination: The raw ceramsite pellets are conveyed to the blast furnace for calcination. The calcination process involves six stages: feeding section, drying section, deammoniation section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite pellets. The drying section includes a forced-air drying section and a forced-air drying section. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying section 85℃, forced-air drying section 180℃, deammoniation section 450℃, preheating section 1000℃, desulfurization calcination section 1120℃, and cooling section 75℃.

[0067] The ammonia-rich gas emitted from the deammoniation section is separately discharged into the ammonia water absorption system to prepare ammonia water; the sulfur-rich gas emitted from the desulfurization roasting section has a volume concentration of 8.3%, which is separately discharged into the sulfuric acid production process to prepare sulfuric acid products; the cooled ceramsite product is ceramsite filter media with a cylinder compressive strength of 5.2 MPa.

[0068] Example 7

[0069] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0070] S1. Ingredients: Biomass pellets and clay additives are mixed with dried electrolytic manganese slag filter cake at a dry basis ratio of 10:90 to form a mixture, until the particle size is such that the residue on a 200-mesh sieve is 5%; the calorific value of the mixture is 315 kcal / kg, and the sulfur content is 11.3%;

[0071] S2. Granulation: The mixture is granulated by a disc to obtain ceramsite pellets with a cross-sectional diameter of 8-20 mm;

[0072] S3. Calcination: The raw ceramsite pellets are conveyed to the blast furnace for calcination. The calcination process involves six stages: feeding section, drying section, deammoniation section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite pellets. The drying section includes a forced-air drying section and a forced-air drying section. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying section 85℃, forced-air drying section 180℃, deammoniation section 450℃, preheating section 760℃, desulfurization calcination section 1120℃, and cooling section 65℃.

[0073] The ammonia-rich gas emitted from the deammoniation section is separately discharged into an ammonia water absorption system to prepare ammonia water; the sulfur-rich flue gas from the desulfurization roasting section at 535℃ is directionally extracted and recycled to the preheating section (e.g., Figure 5 As shown in the figure, the sulfur-rich gas discharged after heating the ceramsite in the preheating section has a volume concentration of 7.8%, which is discharged separately into the sulfuric acid production process to obtain sulfuric acid products; the cooled ceramsite product is porous ceramsite with a cylinder compressive strength of 3.3 MPa.

[0074] Example 8

[0075] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0076] S1. Ingredients: The auxiliary materials consisting of coal gangue and pyrite are mixed and ground with the dried electrolytic manganese slag filter cake at a dry basis ratio of 15:85 to form a mixture until the particle size passes through a 200-mesh sieve and the residue is 5%; the calorific value of the mixture is 365 kcal / kg and the sulfur content is 14.8%;

[0077] S2. Granulation: The mixture is granulated by a disc to obtain ceramsite pellets with a cross-sectional diameter of 8-16 mm;

[0078] S3. Calcination: The raw ceramsite pellets are conveyed to an exhaust-fired calcining furnace for calcination. The calcination process involves six stages: feeding section, drying section, deammoniation section, preheating section, desulfurization calcination section, and cooling section, ultimately yielding shaped ceramsite pellets. The drying section includes a forced-air drying section and an exhaust-fired drying section. The cooling section includes a high-temperature cooling section, a medium-temperature cooling section, and a low-temperature cooling section. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying section 85℃, exhaust-fired drying section 180℃, deammoniation section 450℃, preheating section 1000℃, desulfurization calcination section 1165℃, high-temperature cooling section 735℃, medium-temperature cooling section 370℃, and low-temperature cooling section 87℃.

[0079] The ammonia-rich gas emitted from the ammonia removal section is separately discharged into an ammonia water absorption system to prepare ammonia water. The tail gas is then recirculated into a high-temperature cooling section, where the outlet air temperature is 850℃, and then recirculated into the desulfurization roasting section (e.g., Figure 4 (As shown); the sulfur-rich gas discharged from the desulfurization roasting section has a volume concentration of 11.8%, which is discharged separately into the sulfuric acid production process to obtain sulfuric acid products; the cooled ceramsite product is porous ceramsite with a cylinder compressive strength of 8.7 MPa.

[0080] Example 9

[0081] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and targeted manner includes the following steps:

[0082] S1. Ingredients: The auxiliary materials, consisting of pulverized coal and clay, are mixed into the electrolytic manganese slag slurry and stirred to form a mixture. The dry basis ratio of the auxiliary materials to the electrolytic manganese slag slurry is 10:90. The calorific value of the mixture is 390 kcal / kg, and the sulfur content is 12.8%. The particle size of the auxiliary materials is 200 mesh, with a sieve residue of 7%.

[0083] S2. Granulation: The mixture is put into a granulator, and after pressure filtration and extrusion, short cylindrical ceramsite pellets with a cross-sectional diameter of 10mm and a length of 5-15mm are obtained.

[0084] S3. Calcination: The raw ceramsite pellets are conveyed to the blast furnace for calcination. The calcination process involves six stages: feeding, drying, deammoniation, preheating, desulfurization, and cooling, ultimately yielding shaped ceramsite pellets. The drying stage includes a forced-air drying stage and a forced-air drying stage. The cooling stage includes a high-temperature cooling stage, a medium-temperature cooling stage, and a low-temperature cooling stage. The average temperature of the ceramsite pellets at the outlet of each stage is as follows: forced-air drying stage 90℃, forced-air drying stage 190℃, deammoniation stage 480℃, preheating stage 980℃, desulfurization, and calcination stage 1180℃, high-temperature cooling stage 810℃, medium-temperature cooling stage 430℃, and low-temperature cooling stage 98℃.

[0085] The ammonia-rich gas emitted from the deammoniation section is separately discharged into an ammonia water absorption system to prepare ammonia water; the gas emitted from the preheating section at 350°C contains sulfur oxides, which is circulated into the high-temperature cooling section, where the outlet air temperature is 905°C, and then circulated into the desulfurization roasting section (e.g., Figure 3 (As shown); the sulfur-rich gas discharged from the desulfurization roasting section has a volume concentration of 10.6%, which is discharged separately into the sulfuric acid production process to obtain sulfuric acid products; the cooled ceramsite product is high-strength ceramsite with a cylinder compressive strength of 8.1 MPa.

[0086] Comparative Example 1

[0087] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner is described. The preparation steps are the same as in Example 1, except that the calorific value of the mixture is 700 kcal / kg.

[0088] Due to the excessively high calorific value of the feed material, combustion was too intense in the high-temperature desulfurization roasting section, with local temperatures exceeding 1300℃. This caused excessive melting of the aluminosilicates in the electrolytic manganese slag, resulting in softening and adhesion of the material, leading to severe ring formation and blockage. To prevent overheating, excessive combustion air had to be blown in, causing the SO2 concentration to be drastically diluted to <1.5%. The intense combustion caused by the high calorific value not only resulted in high temperatures but also induced an unexpectedly strong oxidizing atmosphere in the low-temperature deammoniation section. This strong oxidizing atmosphere caused some ammonia nitrogen to be oxidized to NO in the low-temperature deammoniation section. x The experiment showed that the ammonia recovery rate decreased from over 90% in Example 1 to <40%, and the NO content in the exhaust gas decreased. x The content exceeds the standard.

[0089] Comparative Example 2

[0090] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner is described. The preparation steps are the same as in Example 1, except that the calorific value of the mixture is 250 kcal / kg.

[0091] Due to insufficient chemical energy (250 kcal / kg) carried by the material itself, the heat released by the oxidation of carbon during roasting could not offset the huge endothermic effect required for the decomposition of sulfate in the electrolytic manganese slag. Experimental monitoring showed that the temperature of the material bed in the high-temperature desulfurization roasting section could not rise to the critical temperature (1120℃) required for efficient sulfate decomposition, and the actual peak temperature was only maintained in the range of 950-1000℃. Under this low-temperature environment, the thermal decomposition reaction kinetics of calcium sulfate / magnesium sulfate were hindered, and the reaction rate decreased significantly, resulting in a sulfate decomposition rate of less than 60%. A large amount of sulfur remained in the ceramsite product in the form of solid sulfate and failed to be converted into the target product SO2.

[0092] The temperature of the high-temperature desulfurization roasting section cannot be maintained above 1100℃, and the sulfate decomposition rate is less than 60%. In order to maintain the temperature, additional pulverized coal needs to be continuously injected into the desulfurization roasting section. In order to ensure the full combustion of the externally added pulverized coal, a large amount of combustion air needs to be blown in simultaneously, which results in the total flue gas volume of the system increasing by about 30% compared with Example 1. The SO2 concentration is diluted to below 2.5%, which is not valuable for acid production.

[0093] Comparative Example 3

[0094] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner, the preparation steps are the same as in Example 1, except that the sulfur content of the mixture is 5%.

[0095] In the process system of this invention, sulfur is both the source of the target product (SO2) and an important chemical heat source for maintaining the thermal balance in the high-temperature section. Experimental data shows that when the sulfur content drops to 5%, the available sulfur source for reaction within the material is significantly reduced, resulting in insufficient chemical heat released by the reduction decomposition reaction to offset the huge endothermic effect required for sulfate decomposition. Consequently, the temperature of the desulfurization roasting section cannot be maintained above 1050℃. Within this temperature range, the decomposition kinetics of the difficult-to-decompose calcium sulfate and magnesium sulfate in the electrolytic manganese slag are severely hindered, the decomposition rate drops sharply, and a large amount of sulfur remains in solid form in the ceramsite matrix, failing to be converted into gaseous SO2. At the same time, to maintain the sintering temperature, additional pulverized coal or natural gas needs to be injected, and the combustion of external fuel produces a large amount of N2 and CO2, resulting in the SO2 flue gas concentration being diluted to < 2.5%. Low-concentration flue gas cannot be used to produce sulfuric acid using conventional processes, leading to a surge in tail gas treatment costs and eliminating the economic value of co-producing sulfuric acid.

[0096] Comparative Example 4

[0097] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner, the preparation steps are the same as in Example 1, except that the sulfur content of the mixture is 18%.

[0098] When the sulfur content reaches 18%, the excess sulfur reacts violently and exothermically under a reducing atmosphere, causing local temperatures to instantly exceed 1300℃ or even higher. Components such as silicon, aluminum, calcium, and magnesium in the electrolytic manganese slag rapidly form a large amount of low-viscosity liquid phase above 1300℃, leading to excessive melting of the material. This results in thick rings adhering to the walls of the calcining furnace or kiln, forcing shutdown for cleaning and disrupting continuous production. Normal ceramsite relies on a suitable amount of liquid phase to encapsulate gas and form closed micropores (closed pores). However, in the excessive liquid phase environment caused by high sulfur, the bubble wall strength is insufficient, adjacent pores merge and rupture, forming interconnected macropores or even through cracks. Experiments show that the water absorption rate of the finished ceramsite soars to >20%, and the cylinder compressive strength drops sharply to <2.6 MPa. The product fails to meet standards due to insufficient strength and excessive water absorption, becoming waste slag.

[0099] Comparative Example 5

[0100] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner is described. The preparation steps are the same as in Example 1, except that the temperature of the desulfurization roasting section is 1000℃.

[0101] The main sulfur-containing minerals in electrolytic manganese slag are calcium sulfate and magnesium sulfate. Their thermal decomposition reaction is a strongly endothermic process with a significant activation energy barrier. Experimental thermodynamic analysis shows that at a low temperature of 1000℃, the thermal energy provided by the system is insufficient to overcome the energy threshold required for sulfate lattice destruction, leading to an exponential decrease in the decomposition reaction rate. Monitoring data shows that at this temperature, the sulfate decomposition reaction is almost in a "semi-stagnant" state, with a large amount of sulfur failing to be converted into gaseous SO2, resulting in extremely low SO2 flue gas concentration (<1%). Due to incomplete decomposition, the semi-finished ceramsite raw material after roasting contains more than 5% active sulfur (mainly in the form of undecomposed sulfate and some intermediate products). When the finished ceramsite is put into use or cured, the residual sulfate undergoes a complex hydration reaction with moisture, resulting in expansion and cracking. Mechanical property test results show that the compressive strength of the ceramsite produced under these conditions is <2.4 MPa, far below the national standard limit for lightweight high-strength ceramsite.

[0102] Comparative Example 6

[0103] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner is described. The preparation steps are the same as in Example 1, except that the temperature of the desulfurization roasting section is 1300℃.

[0104] Electrolytic manganese slag belongs to a multi-component silicate system, with a softening point and melting flow temperature typically between 1150-1250℃. When the roasting temperature rises to 1300℃, a large amount of eutectic material is generated inside the material, and the liquid phase volume fraction far exceeds the optimal range required for ceramsite pelletizing. Excessive low-viscosity melt rapidly fills the interparticle gaps under the influence of gravity and capillary force, leading to severe "sintering densification" of the material layer and even localized melting and caking. This blocks the ventilation belt of the roaster, causing the negative pressure ventilation system to fail and making gas collection difficult. Due to the excessively high temperature, a large amount of additional cold air needs to be blown in to cool the material or the feed needs to be stopped, resulting in an SO2 concentration dropping to <2%, making acid production uneconomical.

[0105] Comparative Example 7

[0106] A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner is disclosed. The preparation steps are the same as in Example 1, except that in step S3, the raw ceramsite pellets are transported to an exhaust-fired roasting furnace for roasting. The roasting process only passes through three process sections: the feeding section, the desulfurization roasting section, and the cooling section. The average temperature of the ceramsite at the outlet of each process section is: 1150°C in the desulfurization roasting section and 90°C in the cooling section.

[0107] Because the material contains a high amount of organic matter (from high-calorific-value auxiliary materials), it burns violently at high temperatures, producing a large amount of volatile gases (CO2, H2O, NO). x (etc.) Because the sintering rate of the outer shell is faster than the escape rate of the internal gas, the enormous internal pressure cannot be released in time, causing large-scale physical disintegration of the green pellets in the high-temperature section, with a bursting rate as high as 40%. In this extreme environment of high temperature and rich oxygen, the ammonia gas released from the nitrogen-containing components in the material undergoes an irreversible thermal decomposition reaction within milliseconds before it enters the collection system. The test results show that almost no ammonia gas can be detected in the exhaust gas, and the ammonia recovery rate drops to 0%. The excessive combustion of organic matter not only consumes the limited oxygen in the material layer, but also produces a large amount of volatile gases, diluting the SO2 concentration that should have been enriched to 0.8%, making it uneconomical to produce acid.

[0108] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner, characterized in that, Includes the following steps: S1. Ingredients: Mix electrolytic manganese slag and auxiliary materials evenly to obtain a mixture with a calorific value of 300-600 kcal / kg and a sulfur content of 8%-15% by mass. S2. Granulation: The mixture is put into a granulator for granulation to obtain ceramsite pellets; S3. Calcination: The raw ceramsite pellets are conveyed to an exhaust-fired calcining furnace for calcination. This furnace includes a feeding section, a drying section, a deammoniation section, a preheating section, a desulfurization calcination section, and a cooling section. The raw ceramsite pellets sequentially pass through these sections to obtain shaped ceramsite pellets. In the deammoniation section, the ceramsite temperature is 150℃-450℃, and the exhaust gas containing ammonia is 120-350℃. This ammonia-containing gas is directly recovered to prepare ammonia water. In the desulfurization calcination section, the ceramsite temperature is 1050℃-1200℃, and the exhaust gas containing sulfur oxides has a sulfur oxide volume concentration of 5%-15%. This sulfur oxide-containing gas is directly recovered to prepare sulfuric acid.

2. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 1, characterized in that, The mass ratio of the auxiliary material to the electrolytic manganese slag is (5-25):(75-95).

3. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 1, characterized in that, The auxiliary materials are one or more of the following: coal, coke, coal gangue, gasification slag, pyrite, sulfur, coal slime, biomass, and oil sludge.

4. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 1, characterized in that, In step S1, the batching process involves directly wet-mixing the wet electrolytic manganese slag slurry with auxiliary materials that have been ground to a particle size of no more than 20% on a 200-mesh sieve to obtain a mixed material, or drying the electrolytic manganese slag and mixing it with auxiliary materials and grinding it to obtain powder with a particle size of no more than 20% on a 200-mesh sieve.

5. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 4, characterized in that, In step S2, the granulation process involves directly extruding the mixture obtained by wet mixing through pressure filtration, or granulating the ground powder using a disc granulator.

6. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 5, characterized in that, The maximum temperature at which the expanded clay particles are heated in the drying section is 130-160℃; the drying section includes a forced-air drying section and / or a forced-air drying section.

7. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 1, characterized in that, The maximum temperature at which the ceramsite is heated in the deammoniation section is 300-450℃, the maximum temperature at which the ceramsite is heated in the desulfurization roasting section is 1100-1200℃, and the temperature at which the ceramsite is discharged from the cooling section is 50℃-100℃.

8. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 7, characterized in that, The cooling section includes a high-temperature cooling section, a medium-temperature cooling section, and / or a low-temperature cooling section connected in sequence; the high-temperature cooling section cools the ceramsite to a temperature of 400℃-700℃, and the medium-temperature cooling section and / or the low-temperature cooling section cools the ceramsite to a temperature of 50-120℃.

9. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 1, characterized in that, The shaped ceramsite is one of high-strength ceramsite, ordinary ceramsite, filter media ceramsite, or porous ceramsite; wherein, the highest temperature of the ceramsite material layer during the calcination process of high-strength ceramsite is 1120-1180℃; and the highest temperature of the ceramsite material layer during the calcination process of ordinary ceramsite, filter media ceramsite, or porous ceramsite is 1050-1150℃.

10. The method for preparing ceramsite using electrolytic manganese slag and synergistically recovering nitrogen and sulfur components in a cascaded and directional manner according to claim 8, characterized in that, The 200-400℃ outlet flue gas from the preheating section is directionally extracted, or the 70-150℃ tail gas from the deammoniation section is directionally extracted and absorbed to prepare ammonia water and then transported to the high-temperature cooling section. The outlet flue gas is heated to 700-900℃ and then transported to the desulfurization roasting section. or, The 200-400℃ outlet flue gas from the preheating section is directionally extracted and first circulated to the ammonia removal section to heat the ceramsite. Then, the outlet flue gas from the ammonia removal section is directionally extracted and absorbed to prepare ammonia water. The exhaust gas at 70-150℃ is circulated to the high-temperature cooling section. After being heated to 700-900℃, the outlet flue gas is sent back to the desulfurization roasting section; or... The 300-600℃ outlet flue gas discharged from the desulfurization roasting section is directionally extracted and sent to the preheating section. After the ceramsite is heated in the preheating section, the flue gas discharged at 200-400℃ is then transported to the desulfurization roasting section.

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