Process method for preparing sulfur from mirabilite

Abstract

The invention provides a process method for preparing sulfur from mirabilite, and relates to the technical field of sulfur production and carbon emission reduction, and the process method comprises the following steps: with C or CO as a fuel, preheating mirabilite, adding the preheated mirabilite into a three-blade closed reduction rotary kiln, and calcining at 900-1050 DEG C to obtain liquid Na2S; enabling the liquid or solid Na2S calcined in the step S1 and solid CaCO3 to enter a multi-phase reactor for reaction; performing solid-liquid separation on the slurry after the reaction in the step S2, wherein the filter residue is CaS and the filtrate is a Na2CO3 solution; the gas phase obtained after calcination in the step S1 enters a CO2 trapping system, and then flue gas is discharged after being subjected to desulfurization, denitrification and dust removal; the filter residues obtained in the step S3 and the CO2 captured in the step S4 are fed into a supergravity carbonization reactor, the obtained solid phase is CaCO3, and the obtained gas phase is H2S; the solid-phase CaCO3 is returned to the multi-phase reactor of S2 for recycling; h2S enters a Claus reaction system, and finally a sulfur product is obtained. According to the method, sulfur in the low-quality mirabilite is converted into sulfur; in the production process, CaCO3 can be recycled only through one-time feeding, and resources are saved.

Description

Technical Field

[0001] This invention relates to the field of sulfur production and carbon emission reduction technology, specifically a process for preparing sulfur using sodium sulfate. Background Technology

[0002] my country is a country with extremely scarce sulfur resources. Sulfur, as an important basic chemical raw material, is widely used in fertilizers (such as potassium sulfate and superphosphate), pesticides, rubber, pharmaceuticals, and food processing. The stability of its resource supply is directly related to my country's agricultural security and the development of its chemical industry. my country's sulfur resources have long been in a state of "extreme shortage," a situation determined by multiple factors including resource endowment, demand structure, and dependence on imports. Therefore, using abundant solid waste containing Na2SO4 as raw materials, such as mirabilite, SDS desulfurization ash, and industrial waste sodium sulfate, to produce lime-sulfur co-production can provide an innovative technological path to alleviate this predicament, possessing significant strategic and economic value.

[0003] Currently, the main methods of sulfur production can be divided into three categories: traditional resource extraction methods, industrial by-product recovery methods, and new co-production processes. The specific classifications and technical details are as follows: (a) Traditional resource extraction methods: relying on natural sulfur mines and fossil fuels Traditional sulfur production mainly relies on the mining of natural sulfur mines and the processing of fossil fuels (oil and gas), which has been the mainstream path for global sulfur supply throughout history. The core of this approach is the direct or indirect extraction of sulfur from natural resources.

[0004] 1. Natural sulfur mining method Technical principle: The "underground melting method" (Flash method) involves injecting high-temperature and high-pressure water (160℃~170℃) into underground sulfur mines to melt solid sulfur into liquid. The liquid sulfur is then pumped to the surface through pipelines and cooled to form solid sulfur.

[0005] Application scenarios: This method is suitable for high-grade natural sulfur mines (such as large sulfur mines in Texas, USA and Poland). However, my country has limited natural sulfur reserves (accounting for only 0.1% of the global total), so its application is extremely rare.

[0006] Features: High product purity (≥99.5%), but it relies on scarce natural sulfur resources, and the mining cost increases with the depth of the vein.

[0007] 2. Oil and gas associated sulfur recovery method Technical principle: Petroleum and natural gas usually contain H2S (acid gas). The H2S is first separated from the oil and gas through "amine desulfurization". Then the H2S is sent to the Claus reaction system and the sulfur is recovered through two steps: "H2S is oxidized to SO2 → SO2 reacts with H2S to produce sulfur".

[0008] Application scenarios: More than 70% of the world's sulfur is produced using this method. This technology is used in large oil and gas fields in my country (such as Sichuan Gas Field and Xinjiang Oil Field) and in the processing of imported oil and gas.

[0009] Features: It is tied to the oil and gas processing industry chain and has stable output, but it is greatly affected by international oil prices and oil and gas imports, and requires desulfurization equipment to control environmental emissions.

[0010] (ii) Industrial by-product recycling method: recycling industrial waste This method uses sulfur-containing byproducts generated in industrial production as raw materials, and has the dual attributes of "environmental protection and emission reduction" and "resource recycling", making it an important supplementary path for my country's sulfur supply.

[0011] 1. Sulfur recovery from coal chemical byproducts Technical principle: In coal chemical processes such as coal-to-methanol and coal-to-olefins, sulfur in coal is converted into H2S. After H2S is separated by "low-temperature methanol washing", sulfur is recovered through the Claus reaction system.

[0012] Application scenarios: This equipment is used in coal chemical industry clusters in my country (such as Inner Mongolia and Shaanxi), and typical enterprises such as Shenhua Group and Yitai Group have equipped their coal chemical projects with this equipment.

[0013] Features: Relying on coal chemical production capacity, the cost of by-product sulfur is low, but the output is affected by the operating rate of coal chemical plants, and the purity is slightly lower than that of sulfur associated with oil and gas (about 98% to 99%).

[0014] 2. Sulfur recovery from by-products of metal smelting Technical principle: When smelting sulfide ores such as copper, lead, and zinc, SO2-containing flue gas is generated. SO2 is converted into sulfuric acid through the "flue gas to acid" process, or SO2 is reduced to sulfur through the "reduction method" (such as the "activated carbon adsorption-desorption" technology).

[0015] Application scenarios: Non-ferrous metal smelting bases in my country (such as Jiangxi and Yunnan), for example, the smelters of Jiangxi Copper can produce sulfur or sulfuric acid as by-products (sulfuric acid can be further converted into sulfur).

[0016] Features: Solves the problem of smelting flue gas pollution; products can be flexibly selected from sulfur or sulfuric acid, but are greatly affected by the grade of metal ore and smelting process.

[0017] 3. Recovery of sulfur-containing resources from solid waste Technical principle: Using industrial solid waste (such as SDS sodium-based desulfurization ash, mirabilite, industrial waste sodium sulfate) and high-sulfur fuels such as high-sulfur coal as raw materials, the sulfur element in the solid waste is converted into H2S through high-temperature reduction, and then sulfur is recovered through Claus reaction.

[0018] Application scenarios: Suitable for areas where solid waste is generated in large quantities (such as power plant desulfurization ash and chemical waste sodium sulfate). It has been validated in the laboratory and has the potential for large-scale production.

[0019] Features: It realizes the transformation of "solid waste into resources", has significant strategic value (alleviating my country's dependence on sulfur imports), and can be used in conjunction with soda ash production to improve the profitability of the industrial chain.

[0020] 4. Other novel co-production processes Examples of successful projects include "sulfur produced as a byproduct of soda ash production via the ammonia-soda process" and "lithium extraction and sulfur co-production from salt lakes." These projects integrate regional resources (such as Na2SO4 and LiCl from salt lakes) to achieve multi-product synergistic production. Currently, these projects are in the pilot or small-scale application stage and have not yet been widely promoted.

[0021]

[0022] In summary, my country's current sulfur production is mainly based on "sulfur recovery from associated oil and gas" and "sulfur recovery from coal chemical by-products," accounting for over 90% combined. However, due to the shortage of natural sulfur ore and high dependence on oil and gas imports (over 70%), supply stability is at risk. The document mentions new technologies such as the "sulfur co-production process from mirabilite to soda ash," which, by utilizing my country's abundant mirabilite reserves and industrial solid waste, can achieve self-sufficiency in sulfur production. This has both economic and strategic value and is expected to become one of the core technological pathways to alleviate my country's sulfur shortage in the future. Summary of the Invention

[0023] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a process for preparing sulfur using sodium sulfate, thus solving the problems mentioned in the background section.

[0024] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a process for preparing sulfur using sodium sulfate, comprising the following steps: S1. Using C or CO as fuel, preheated sodium sulfate is added to a three-lobe closed rotary kiln for calcination at 900℃~1050℃ to obtain liquid Na2S; the main reaction formula is: Na₂SO₄ + 2C → Na₂S + 2CO₂↑ Na₂SO₄ + 4CO → Na₂S + 4CO₂↑ S2. The liquid or solid Na2S obtained after calcination of S1 is reacted with solid CaCO3 in a multiphase reactor. The main reaction formula is as follows: Na₂S + CaCO₃ → Na₂CO₃ + CaS S3. The slurry after the reaction in S2 is subjected to solid-liquid separation. The filter residue is CaS and the filtrate is a Na2CO3 solution. S4. The gas phase after S1 calcination is introduced into the CO2 capture system, and then the flue gas is discharged after desulfurization, denitrification and dust removal. S5. The filter residue from S3 and the CO2 captured in S4 are fed into a high-gravity carbonization reactor, yielding a solid phase of CaCO3 and a gas phase of H2S. The solid CaCO3 is then returned to the multiphase reactor in S2 for recycling. The main reaction formula is: CaS + CO2 → H2S↑ + CaCO3 S6. Introduce H2S into the Claus reaction system to ultimately obtain sulfur products. The main reaction formula is as follows: H₂S + O₂ → SO₂ + H₂O SO2 + H2S → 3S↓ + H2O S7. The Na2CO3 filtrate in S3 is evaporated, concentrated, crystallized, and dried to obtain the by-product solid Na2CO3 product.

[0025] Preferably, the C or CO used in S1 is one of coal, coke, biomass and natural gas, and high-sulfur fuels are preferred; in addition to sodium sulfate, the raw materials used also include solid waste raw materials with Na2SO4 as the main component, such as sodium desulfurization ash of SDS.

[0026] Preferably, the oxygen content during combustion in S1 is controlled to be above 30%. When using a conventional rotary kiln, the kiln's sealing function should be strengthened to avoid reducing the oxygen content.

[0027] Preferably, the total length of the three-lobe closed reduction rotary kiln used in S1 should be 66 meters or more. To meet the requirements of calcination efficiency and material properties, the kiln should have the basic characteristics of gravity-driven semi-suspended closed heating, and its material filling rate should be 15% to 30% or more. When using a conventional rotary kiln, the material filling rate inside the kiln should be improved, and should be no less than 10% as much as possible.

[0028] Preferably, the reaction conditions in the three-lobe closed rotary kiln of S1 are atmospheric pressure, the temperature should be controlled between 900℃ and 1050℃, and the reaction time is 60min ± 10min. If natural gas or other CO carbon sources are used, the temperature should not be lower than 700℃, and the reaction time needs to be extended to 80min or more. To avoid reactants sticking to the kiln wall and forming rings, the combustion temperature of the CO carbon source should also be kept stable above 900℃.

[0029] Preferably, in step S1, when the three-lobe closed reduction rotary kiln has a good sealing effect, the purity of sodium sulfate is high, and pure fuels such as natural gas are used, the obtained liquid Na2S can be cooled again to produce solid Na2S, or further produced into products such as Na2S solution.

[0030] Preferably, the stirring, flow, or filling structure within the multiphase reactor in S2 should facilitate the breaking down of interphase interface resistance, enhance the mass transfer rate between different phases (gas-liquid, liquid-solid, etc.), and simultaneously strengthen heat transfer to avoid localized overheating or incomplete reaction. Furthermore, it should enable precise control of reaction conditions to reduce side reactions, thereby improving the selectivity of the target product and the conversion rate of raw materials.

[0031] Preferably, the solid-liquid separation in S3 should be well-sealed to control the length of CaS entering the supergravity carbonization reactor, so as to prevent CaS decomposition and the generation of H2S odor.

[0032] Preferably, the carbonization temperature of the supergravity carbonization reactor in S5 is typically controlled between 30°C and 55°C, with the optimal range being 35°C to 45°C.

[0033] (III) Beneficial Effects This invention provides a process for preparing sulfur using sodium sulfate, which has the following beneficial effects: 1. Sulfur production from mirabilite can treat solid wastes such as mirabilite and SDS desulfurization ash. Processing one million tons of mirabilite annually can co-produce 250,000 tons of sulfur, reducing my country's sulfur import dependence by approximately 8 percentage points. If projects are implemented in resource-rich areas such as Qinghai (with mirabilite reserves exceeding 10 billion tons), large-scale supply can be achieved. For regions rich in mirabilite resources (such as Qinghai and Sichuan in China), this technology can reduce dependence on salt, revitalize low-value mineral resources, form a closed-loop industrial chain of "resources-products-by-products," and enhance regional economic competitiveness. This invention converts the sulfur content in low-quality mirabilite into sulfur, which is scarce in my country and heavily reliant on imports, possessing significant economic and strategic importance.

[0034] 2. The Glauber's salt raw material used in this invention does not require pretreatment (such as dehydration or purification), which greatly reduces the energy consumption of the process.

[0035] 3. This technology has a shorter process flow, lower energy consumption, and lower production costs, thus requiring less equipment investment.

[0036] 4. It saves electricity and energy, with its energy consumption being about 50% of that of conventional alkali production methods.

[0037] 5. No waste is generated, allowing for mass production.

[0038] 6. In the production process, CaCO3 can be recycled after only one feeding, thus eliminating the dependence of the soda ash industry on the large consumption of natural limestone.

[0039] 7. This invention captures and recycles most of the CO2 generated during the production process, resulting in a significant carbon emission reduction effect. Attached Figure Description

[0040] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0041] 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.

[0042] Example 1: like Figure 1 As shown, this embodiment of the invention provides a process for preparing sulfur using sodium sulfate, comprising the following steps: S1. Using C or CO as fuel, preheated sodium sulfate is added to a three-lobe closed rotary kiln for calcination at 900℃~1050℃ to obtain liquid Na2S; the main reaction formula is: Na₂SO₄ + 2C → Na₂S + 2CO₂↑ Na₂SO₄ + 4CO → Na₂S + 4CO₂↑ S2. The liquid or solid Na2S obtained after calcination of S1 is reacted with solid CaCO3 in a multiphase reactor. The main reaction formula is as follows: Na₂S + CaCO₃ → Na₂CO₃ + CaS S3. The slurry after the reaction in S2 is subjected to solid-liquid separation. The filter residue is CaS and the filtrate is a Na2CO3 solution. S4. The gas phase after S1 calcination is introduced into the CO2 capture system, and then the flue gas is discharged after desulfurization, denitrification and dust removal. S5. The filter residue from S3 and the CO2 captured in S4 are fed into a high-gravity carbonization reactor, yielding a solid phase of CaCO3 and a gas phase of H2S. The solid CaCO3 is then returned to the multiphase reactor in S2 for recycling. The main reaction formula is: CaS + CO2 → H2S↑ + CaCO3 S6. Introduce H2S into the Claus reaction system to ultimately obtain sulfur products. The main reaction formula is as follows: H₂S + O₂ → SO₂ + H₂O SO2 + H2S → 3S↓ + H2O S7. The Na2CO3 filtrate in S3 is evaporated, concentrated, crystallized, and dried to obtain the by-product solid Na2CO3 product.

[0043] Example 2: like Figure 1 As shown, this embodiment of the invention provides a process for preparing sulfur using sodium sulfate, comprising the following steps: S1. Using high-sulfur coal as fuel, under oxygen enrichment conditions of 30% or higher, Glauber's salt is preheated in a preheater. The preheating source is CO generated in a three-lobe closed reduction rotary kiln. The preheated Glauber's salt does not require pretreatment (such as dehydration or purification) and is directly fed into the atmospheric pressure three-lobe closed reduction rotary kiln. The total length of the three-lobe closed reduction rotary kiln is 66 meters or more. To meet the requirements of calcination efficiency and material characteristics, the kiln should have the basic characteristics of gravity semi-suspended closed heating, and maintain a material filling rate of 15% to 30% or more. Calcination is carried out at 900℃ to 1050℃ for a reaction time of 60 min ± 10 min to obtain liquid Na2S. The main reaction formula is: Na₂SO₄ + 2C → Na₂S + 2CO₂↑ Na₂SO₄ + 4CO → Na₂S + 4CO₂↑ Among them, when the three-lobe closed reduction rotary kiln has a good sealing effect, the purity of sodium sulfate is high and pure fuels such as natural gas are used, the obtained liquid Na2S can be cooled again to make solid Na2S, or further made into Na2S solution and other products. S2. The liquid or solid Na2S obtained after calcination of S1 is reacted with solid CaCO3 in a multiphase reactor. The main reaction formula is as follows: Na₂S + CaCO₃ → Na₂CO₃ + CaS The stirring, flow, or packing structure within the multiphase reactor should facilitate the breaking down of interphase interface resistance, enhance the mass transfer rate between different phases (gas-liquid, liquid-solid, etc.), and simultaneously strengthen heat transfer to prevent localized overheating or incomplete reaction. Furthermore, it should enable precise control of reaction conditions to reduce side reactions and improve the selectivity of the target product and the conversion rate of raw materials. S3. The slurry after the reaction in S2 is subjected to solid-liquid separation. The filter residue is CaS and the filtrate is Na2CO3 solution. During solid-liquid separation, proper sealing management should be implemented to control the travel distance of CaS into the high gravity carbonization reactor to prevent CaS decomposition and the generation of H2S odor. S4. The gas phase after S1 calcination is introduced into the CO2 capture system. After the flue gas is desulfurized, denitrified and dust removed, it is discharged. The captured CO2 enters the supergravity carbonization reactor. S5. The filter residue from S3 and the CO2 captured in S4 are fed into a high-gravity carbonization reactor for a complete carbonization reaction at 35–45°C. The resulting solid phase is CaCO3, and the gas phase is H2S. The solid CaCO3 is then returned to the multiphase reactor in S2 for recycling. The main reaction formula is: CaS + CO2 → H2S↑ + CaCO3 S6. Introduce H2S into the Claus reaction system to ultimately obtain sulfur products. The main reaction formula is as follows: H₂S + O₂ → SO₂ + H₂O SO2 + H2S → 3S↓ + H2O S7. The Na2CO3 filtrate in S3 is evaporated, concentrated, crystallized, and dried to obtain the by-product solid Na2CO3 product.

[0044] Example 3: The difference between Example 3 and Example 2 is that in S1, if a CO carbon source such as natural gas is used, the temperature should not be lower than 700°C, and the reaction time needs to be extended to more than 80 minutes. To avoid the reactants sticking to the kiln wall and forming rings, the combustion temperature of the CO carbon source should also be kept stable above 900°C.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the preparation of sulphur from Glauber's salt, characterized in that: It comprises the following steps: S1, using C or CO as fuel, preheat mirabilite and then add it into a three-leaf closed reduction rotary kiln, calcine at 900-1050℃ to obtain liquid Na2S; the main reaction formula is: Na2SO4+2C→Na2S+2CO2↑ Na2SO4+4CO→Na2S+4CO2↑ S2, react liquid or solid Na2S after S1 calcination with solid CaCO3 in a multi-phase reactor, the main reaction formula is: Na2S+CaCO3→Na2CO3+CaS S3, solid-liquid separation is performed on the slurry after S2 reaction, the filter residue is CaS and the filtrate is Na2CO3 solution; S4, gas phase after S1 calcination is sent into a CO2 capture system, then the flue gas is discharged after desulfurization, denitrification and dust removal; S5, send the filter residue of S3 and the captured CO2 of S4 into a supergravity carbonization reactor, the obtained solid phase is CaCO3 and the gas phase is H2S; the solid phase CaCO3 is returned to the multi-phase reactor of S2 for recycling, the main reaction formula is: CaS+CO2→H2S↑+CaCO3 S6, send H2S into a Claus reaction system to obtain sulfur product, the main reaction formula is: H2S+O2→SO2+H2O SO2+H2S→3S↓+H2O S7, evaporate, concentrate, crystallize and dry the Na2CO3 filtrate of S3 to obtain by-product solid Na2CO3 product.

2. A process for the preparation of sulphur from Glauber's salt as claimed in claim 1, wherein: The C or CO used in S1 is one of coal, coke, biomass and natural gas, and high-sulfur fuel is preferred.

3. A process for the preparation of sulphur from Glauber's salt as claimed in claim 1, wherein: The oxygen content during combustion in S1 is controlled to be above 30%.

4. A process for the preparation of sulphur from Glauber's salt as claimed in claim 1, wherein: The total length of the three-leaf closed reduction rotary kiln used in S1 is 66 meters or more, and the material filling rate thereof is 15%-30% or more.

5. A process for the preparation of sulphur from Glauber's salt as claimed in claim 1, wherein: The reaction conditions of the three-leaf closed reduction rotary kiln in S1 are normal pressure, the temperature is controlled to be 900-1050℃, and the reaction time is 60 min±10 min.

6. A process for the preparation of sulphur from Glauber's salt as claimed in claim 1 or 5, wherein the process comprises the steps of: When the CO carbon source is natural gas, the temperature cannot be lower than 700℃, and the reaction time is extended to 80 min or more.

7. The process for preparing sulfur from sodium sulfate according to claim 1, characterized in that: The carbonization temperature of the supergravity carbonization reactor in S5 is usually controlled to be 30-55℃.

8. A process for the preparation of sulphur from Glauber's salt as claimed in claim 7, wherein: The carbonization temperature of the supergravity carbonization reactor is 35-45℃.

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