A coking low-quality sulfur extraction refining process

Abstract

The application discloses a coking low-quality sulfur extraction refining process and system and belongs to the field of chemical production processes.The process comprises the following steps: obtaining liquid crude sulfur by melting sulfur and clarifying HPF ammonia desulfurization sulfur foam; forming particles by spraying liquid crude sulfur through an underwater granulation nozzle in a two-phase medium containing a crude benzene phase and a circulating water phase, so that organic matters enter the crude benzene phase and ammonium salt enters the circulating water phase at 75-85 DEG C; cooling the mixed liquid to 20-25 DEG C, and forming a crude benzene layer, a circulating water layer and a sulfur layer from top to bottom in a cooling separation tank by using the density difference, and obtaining the product by centrifugal separation of the sulfur layer.The application realizes the separation of organic matters and ammonium salt simultaneously under low-temperature conditions by step-by-step selective extraction of the two-phase medium, the product reaches the A-grade industrial sulfur standard, and a material closed loop is formed with the existing system of a coking plant.

Description

Technical Field

[0001] This invention relates to chemical production processes, specifically to a process and system for extracting and refining low-quality sulfur produced during the HPF ammonia desulfurization process in coking. Background Technology

[0002] With the widespread application of the HPF ammonia desulfurization process in coking gas purification, the crude sulfur formed after melting the sulfur foam produced during the desulfurization process is of low quality due to its high impurity content, typically failing to meet the qualified product requirements of GB / T2449.1-2021 "Industrial Sulfur". Typical components of this type of crude sulfur include: 85-95 wt% sulfur, 1-8 wt% moisture, 0-5 wt% ammonium thiocyanate, 0-5 wt% ammonium sulfate, and 0-0.8 wt% heavy oil components such as anthracene and pyrene, as well as 0-2 wt% other organic matter. How to refine this low-quality sulfur, which simultaneously contains water-soluble ammonium salts and lipophilic heavy organic matter, into qualified or even high-grade industrial sulfur has been a long-standing problem in this field.

[0003] Currently, for crude sulfur obtained through ammonia desulfurization, the high-temperature gasification separation method is commonly used in industry. This method typically involves heating the crude sulfur in stages: first, heating to 130-160℃ for dehydration, then further heating to 280-320℃ to volatilize organic matter, and finally heating to approximately 444℃ to sublimate the sulfur vapor, followed by cooling to produce elemental sulfur products. The method has the following shortcomings in actual operation: First, the multi-stage heating uses heat sources such as steam and electric furnaces, and the cooling process also requires air and circulating water cooling systems, resulting in high overall energy consumption and production costs. Second, at temperatures above 240℃, sulfur reacts with iron in the equipment material to form ferrous sulfide, and ammonium sulfate begins to decompose at around 235℃ to produce corrosive substances, causing severe equipment corrosion and significantly shortening its service life. Third, the free ammonia volatilized during the heating process and the high-temperature by-reaction products result in a harsh on-site operating environment with strong and difficult-to-control VOCs odor. Fourth, the high-boiling-point organic compounds such as anthracene and pyrene contained in crude sulfur have vaporization temperatures close to those of sulfur, making it difficult to effectively distinguish and separate them during sublimation, leading to unstable product quality.

[0004] In the broader field of sulfur refining technology, there are reports of using organic solvent extraction to treat sulfur paste or crude sulfur from other sources. For example, there are known methods that use aromatic solvents such as xylene, benzene, or specific solvent oils to fully dissolve sulfur-containing waste residue at relatively high temperatures (e.g., 120-150°C), followed by filtration to remove the residue, and then cooling and crystallization to recover sulfur. Furthermore, there are also known step-by-step processing schemes for treating other types of crude sulfur, which involve first washing with warm water to remove inorganic salt impurities, then extracting with organic solvents to remove organic impurities, and finally obtaining refined sulfur through heating for dissolution and cooling for crystallization.

[0005] However, the aforementioned known solvent extraction methods are all designed for sulfur paste or crude sulfur produced by processes such as sodium desulfurization, which contain little or no ammonium salts and have different compositions of organic impurities. Crude sulfur produced by HPF ammonia desulfurization contains a large amount of water-soluble ammonium salts (ammonium thiocyanate, ammonium sulfate) and lipophilic heavy tar (anthracene, pyrene, etc.), and its impurity composition characteristics are fundamentally different from those of sodium desulfurization products. If the existing single organic solvent high-temperature complete dissolution scheme is directly applied to this type of ammonia desulfurization crude sulfur, the heavy tar and sulfur will enter the organic phase together under high-temperature conditions. During cooling and crystallization, the heavy tar will precipitate along with the sulfur or be encapsulated in the sulfur crystals, making it difficult to guarantee product purity. Subsequent independent activated carbon decolorization or solvent regeneration steps are often required to remove the continuously accumulating organic matter. Furthermore, this scheme does not consider the presence of ammonium salts, and the decomposition of ammonium salts at high temperatures can cause equipment corrosion and waste gas problems. If the pre-washing and organic solvent extraction are simply combined in separate steps, not only will the process be lengthy and the equipment investment increased, but the independent warm water washing step will also be difficult to integrate efficiently with the continuous closed production system of liquid sulfur. The entire set of equipment will be difficult to achieve continuous and stable industrial operation under low temperature, normal pressure and closed conditions.

[0006] Furthermore, in the common knowledge of sulfur extraction and refining, carbon disulfide is considered the most effective solvent for dissolving sulfur. However, the density of carbon disulfide is approximately 1.2 g / cm³. 3 Between water (approximately 1.0 g / cm³) 3 ) and sulfur (approximately 2.1 g / cm³) 3 If carbon disulfide is used as an extractant and introduced into the aqueous phase for washing and separation, a stable top-to-bottom density gradient cannot be formed in the cooling separator. The relative positions of the water layer, carbon disulfide layer, and sulfur layer will become intertwined or disordered, making effective phase isolation and selective emission difficult. Furthermore, carbon disulfide is a highly flammable and toxic substance. When used in high-speed rotating equipment such as centrifuges for solid-liquid separation, its explosion and toxicity risks are significantly higher than those of aromatic solvents, posing extremely stringent safety requirements for the operating environment. These factors constitute substantial technical obstacles to the application of carbon disulfide in the refining process of ammonium-containing crude sulfur in this field.

[0007] Therefore, for the low-quality sulfur produced by HPF ammonia desulfurization, which contains specific components (simultaneously ammonium salts and heavy tar), existing technologies have not provided a continuous refining process that can selectively separate organic matter, effectively remove ammonium salts, and achieve material recycling and systematic closed-loop management of waste within the coking plant under low-temperature conditions. This is precisely the technical problem that this invention aims to solve. Summary of the Invention

[0008] In view of this, the present invention proposes a coking low-quality sulfur extraction and refining process, which aims to solve the technical problem that there is no low-temperature, continuous solvent extraction and refining scheme for crude sulfur desulfurized by HPF ammonia method in the existing technology, and at the same time overcome the defects of the existing high-temperature sublimation method, such as high energy consumption, severe equipment corrosion and harsh operating environment.

[0009] The technical solution of this invention is implemented as follows: This invention provides a process for refining low-quality sulfur extracted from coking plants, comprising the following steps: S1 Pretreatment: Sulfur foam containing 8-12% suspended sulfur by mass from HPF ammonia desulfurization is melted and clarified to obtain liquid crude sulfur; S2 Submerged Granulation and Two-Phase Extraction: The liquid crude sulfur obtained in step S1 is passed through a submerged granulation nozzle to form 50-200μm particles in a two-phase medium that simultaneously contains a crude benzene phase and a circulating water phase. Under conditions of 75-85℃, the organic matter on the surface of the sulfur particles enters the crude benzene phase, and the ammonium salt impurities enter the circulating water phase. S3 Cooling and Three-Phase Separation: The mixture obtained in step S2 is cooled to 20-25℃, so that sulfur crystallizes out from the crude benzene phase. In the cooling separation tank, the density difference is used to form a crude benzene layer, a circulating water layer, and a sulfur layer from top to bottom. The sulfur layer is separated by centrifugation to obtain the sulfur product. S4 Material Circulation and Homologous Closed Loop: After separation, the crude benzene phase is heated to 65-75℃ and returned to step S2 for recycling. The circulating water phase is cooled and returned to step S3 for recycling. The portion of the crude benzene phase enriched with organic matter is discharged to the crude benzene section of the coking plant, and the portion of the circulating water phase enriched with ammonium salts is discharged to the desulfurization section of the coking plant. Fresh crude benzene and demineralized water are added respectively. S5VOC Collection and Recovery: The crude benzene-containing volatile gas generated by the equipment involving crude benzene in steps S2 to S4 is collected to the VOC gas water seal device, maintaining a pressure of 2 kPa. The gas after water sealing is sent to the coke oven gas negative pressure system for recovery.

[0010] The core concept of the above technical solution lies in replacing the existing "single solvent total dissolution-cooling crystallization" route with "stepwise series selective extraction." In the same process system, a two-phase medium consisting of a crude benzene phase and a circulating aqueous phase is used to guide impurities in the crude sulfur to their respective affinity phases under medium-temperature conditions of 75-85℃. Organic matter enters the crude benzene phase, ammonium salts enter the circulating aqueous phase, and sulfur crystallizes out from the crude benzene phase upon cooling. This avoids the three-phase stratification chaos and centrifugation safety hazards associated with using medium-density solvents such as carbon disulfide. This concept differs from the existing technical approach of completely dissolving sulfur in a single organic solvent at high temperatures and then precipitating it out as a whole upon cooling. In this solution, sulfur is only partially dissolved in the crude benzene phase at 75-85℃ (solubility approximately 14%). The extraction is mainly achieved through sufficient contact between the particle surface and the two-phase medium, rather than relying on total dissolution.

[0011] In some embodiments, the temperature of the molten sulfur in step S1 is 125-145°C, and the pressure is 0.2-0.4 MPa. This temperature range has specific technical significance: on the one hand, it ensures that the sulfur in the sulfur foam reaches a molten state to achieve separation from the supernatant; on the other hand, it avoids excessively high temperatures that could lead to the formation of elastic sulfur in subsequent processes. When the molten sulfur temperature exceeds 160°C, especially above 200°C, a rapid cooling will cause some sulfur to transform into polymerized elastic sulfur. This form of sulfur is insoluble in conventional solvents such as crude benzene, which will severely reduce the recoverability of effective sulfur. By controlling the molten sulfur temperature in the lower range of 125-145°C, and during the submerged granulation process from step S1 to step S2, the liquid sulfur is dispersed into fine particles of 50-200 μm through a nozzle and directly enters the two-phase medium at approximately 80°C. Cooling is achieved through heat exchange with a large amount of liquid, avoiding the rapid cooling effect caused by contact with a low-temperature gas phase or cold wall surface, effectively preventing the formation of elastic sulfur and ensuring subsequent extraction efficiency.

[0012] In some embodiments, the density of the crude benzene layer in step S3 is approximately 0.86 kg / L, the density of the circulating water layer is approximately 1 kg / L, and the density of the sulfur layer is approximately 2.1 kg / L. The cooling separation tank is equipped with sight glasses at the top and bottom. When the sulfur layer level reaches 1 / 3 of the bottom sight glass, the sulfur layer and the circulating water layer are discharged together into the centrifuge. Utilizing the significant density differences among these three components, reliable natural gravity stratification can be achieved within a single cooling separation tank. The circulating water layer, situated between the crude benzene layer and the sulfur layer, effectively isolates the crude benzene phase from the sulfur phase while performing the washing and desalination process.

[0013] In some embodiments, the VOC gas water seal device described in step S5 is a water seal device independent of the cooling separation tank. It is connected to the gas outlets of the dissolution extraction tank, the cooling separation tank, and the mixed liquid control separator via pipelines, and collects the crude benzene-containing volatile gas generated by the above devices. The VOC gas water seal device uses water as a sealing medium to maintain the system pressure at a slightly positive pressure of 2 kPa, which prevents outside air from entering the system and forming an explosive mixture, and also inhibits the escape of crude benzene vapor from the system. The crude benzene-containing gas after water sealing is sent to the coke oven gas negative pressure system, and the benzene components are recaptured in the chemical product recovery system along with the coke oven gas, realizing closed-loop recovery of gaseous materials.

[0014] In some implementations, in step S4, 100m 3 Based on the sulfur foam treatment capacity, the daily discharge of crude benzene is 50-150 kg, and the daily discharge of circulating water is 1-3 m³. 3 The discharge volume is matched with the material throughput of the main system of the coking plant and will not impact the normal production and operation of the crude benzene section and desulfurization section of the coking plant.

[0015] In some implementations, step S1 further includes: when subsequent system maintenance is required, the liquid sulfur in the sulfur clarification tower is sliced ​​using a slicer, and after production resumes, the sulfur slices are added to the two-phase medium in step S2. This design allows the entire unit to resume normal production after a shutdown for maintenance, ensuring the reliability of continuous industrial operation.

[0016] In some embodiments, the system used in the above process includes: a dissolution extraction tank, which has an internal two-phase medium space for simultaneously containing crude benzene and circulating water phases, and a submersible granulation nozzle at the top; a cooling separation tank, whose inlet is connected to the bottom outlet of the dissolution extraction tank via a bottom outlet valve, the cooling separation tank being a three-phase separation structure that utilizes density differences to form a crude benzene layer, a circulating water layer, and a sulfur layer from top to bottom; a mixed liquid control separator, whose inlet is connected to the upper crude benzene outlet of the cooling separation tank, and whose crude benzene outlet is connected to a circulating crude benzene tank; and a crude benzene circulation loop, including the following sequentially connected... The system comprises a circulating crude benzene tank, a crude benzene circulating pump, and a crude benzene heater, with the outlet of the crude benzene heater connected to the dissolution extraction tank; a centrifuge, with its inlet connected to the lower outlet of the cooling separation tank; a circulating water circuit, including a circulating water tank, a circulating water pump, and a circulating water heat exchanger connected in sequence, with the inlet of the circulating water tank connected to the liquid phase outlet of the centrifuge, and the outlet of the circulating water heat exchanger connected to the cooling separation tank; and a VOC gas water seal device, with its gas inlet connected to the gas outlets of the dissolution extraction tank, the cooling separation tank, and the mixed liquid control separator, and its gas outlet connected to the coke oven gas negative pressure system. This system's structural layout allows the crude benzene phase and the circulating water phase to form independent closed-loop circulation circuits, converging in the dissolution extraction tank and the cooling separation tank to complete mass transfer and phase separation, forming a "dual circulation-dual convergence" operating mode; the VOC gas water seal device serves as an independent safety and environmental protection unit, providing unified control over the volatile gases emitted from each unit.

[0017] In some embodiments, the system further includes a multi-stage separator, a sulfur clarifier, and a slicer. The inlet of the sulfur clarifier is connected to the multi-stage separator via a balance tank. The sulfur clarifier has a first outlet and a second outlet. The first outlet is connected to the first inlet of the dissolution extraction tank, and the second outlet is connected to the second inlet of the dissolution extraction tank via the slicer. The volume of the sulfur clarifier is not less than one times the daily sulfur production to provide sufficient buffer volume and ensure the continuity of upstream and downstream processes.

[0018] In some embodiments, the dissolution extraction tank is equipped with a jacketed steam heating device, and the cooling separation tank is equipped with a jacketed low-temperature water cooling device. The heating and cooling devices are used to maintain the extraction temperature of 75-85°C in step S2 and the crystallization separation temperature of 20-25°C in step S3, respectively, to ensure the stability and controllability of process parameters.

[0019] In some implementations, the crude benzene phase enriched with organic matter discharged in step S4 is sent to the rich oil tank of the crude benzene section of the coking plant, while the circulating aqueous phase enriched with ammonium salts is sent to the lean liquor circulation tank of the desulfurization section of the coking plant. This material disposal design is based on the following shared origin: heavy aromatics such as anthracene and pyrene in crude sulfur are already enriched in the wash oil of the crude benzene section during the chemical recovery process of the coking plant's coal gas. Discharging the crude benzene phase enriched with these organics to the rich oil tank only increases or decreases the amount of substances already present in the system, without introducing new types of impurities. Ammonium thiocyanate and ammonium sulfate originate from the desulfurization liquid in the desulfurization section; returning them to the lean liquor circulation tank represents in-situ material return. This design eliminates the need for additional activated carbon decolorization, independent solvent regeneration, or biochemical / incineration treatment facilities for the waste from this process, forming a complete closed-loop material circulation system with the existing production system of the coking plant.

[0020] The present invention has the following advantages over the prior art: The extraction and refining process for low-quality coking sulfur provided by this invention has significant advantages compared to existing technologies. Firstly, this invention is the first to successfully apply solvent extraction to the refining of crude sulfur from HPF ammonia desulfurization, breaking the long-standing technical limitation of only using high-temperature sublimation in this field. It opens up a new technological route for the low-temperature refining of special crude sulfur containing ammonium salts and heavy tar. Secondly, this invention, through a stepwise series selective extraction design combining submerged granulation with a crude benzene phase-circulating aqueous phase two-phase medium, simultaneously achieves organic matter extraction and ammonium salt elution within the same process system. This eliminates the need for separate activated carbon decolorization or solvent regeneration steps in existing technologies and avoids the purity issues caused by the co-dissolution and co-precipitation of organic matter and sulfur in high-temperature full-dissolution routes. The product quality can consistently meet the industrial grade A sulfur standard. Furthermore, the entire process is conducted under normal pressure and at a low temperature below 145°C. The use of crude benzene instead of carbon disulfide eliminates the technical obstacle of ineffective stratification with water due to the medium solvent density, avoiding the severe equipment corrosion problems caused by ammonium salt decomposition and ferrous sulfate reaction in high-temperature sublimation methods. Simultaneously, low-temperature operation means the use of low-grade heat sources, significantly reducing energy consumption, and the operating environment is significantly improved due to the absence of high-temperature side reaction products. In addition, this invention uses an independent VOC gas water seal device to uniformly collect and control the pressure of crude benzene-containing volatile gases from each unit. After water sealing, the gases are sent to the coke oven gas negative pressure system for recovery. The crude benzene and the enriched impurities in the circulating water are returned to the same source section within the coking plant for treatment. The entire process is highly synergistic with the existing production system of the coking plant, generating no secondary waste requiring external treatment, thus achieving the greening and resource utilization of the sulfur refining process. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0022] Figure 1 This is a schematic diagram of a coking low-quality sulfur extraction and refining process according to the present invention.

[0023] In the diagram: 1 - First inlet of the dissolution extraction tank (liquid sulfur inlet) 2-Dissolution extraction tank second inlet (sulfur tablet inlet) 3-Dissolution Extraction Tank Gas Outlet 4- Bottom discharge valve of the dissolution and extraction tank 5-Crude benzene overflow port at the top of the cooling separator 6-Lower discharge valve of cooling separator tank 7-Multiple Separators 8-Slicer 9-Sulfur Clarification Tower 10-Dissolution Extraction Tank 11-Cooling Separation Tank 12-Circulating water heat exchanger 13-Circulating water tank 14-Centrifuge 15-Finished Goods Warehouse 16-Mixed Liquid Control Separator 17-Circulating crude benzene tank 18-Crude Benzene Heater 19-VOC gas water seal device. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] The raw materials used in the following examples and comparative examples were sulfur foam from the same batch taken from the HPF ammonia desulfurization unit of a coking plant. The crude sulfur obtained after sulfur melting was analyzed and determined to be crude sulfur as follows:

[0026] The sulfur content in this crude sulfur is only 89.2%, which is far below the requirement for qualified industrial sulfur (≥99%). The content of organic impurities and ammonium salt impurities is relatively high, which is a typical low-quality crude sulfur produced by ammonia desulfurization.

[0027] Example 1: Crude Benzene Two-Phase Stepwise Tandem Selective Extraction Method Preparation steps: Step 1, Pretreatment: The crude sulfur raw material is fed into the multi-stage separator 7 and melted at 130℃ and 0.3MPa. After the sulfur is completely melted, the supernatant is returned to the desulfurization system, and the bottom molten liquid sulfur is pressurized by the balance tank and enters the sulfur clarification tower 9 for settling. The lower layer of liquid sulfur is sent to the dissolution extraction tank 10 through the first outlet of the sulfur clarification tower 9 and the first inlet 1 of the dissolution extraction tank. The melting temperature is controlled within the range of 125-145℃ to avoid the formation of elastic sulfur due to excessive temperature. When the system is under maintenance, the liquid sulfur in the sulfur clarification tower 9 is sliced ​​by the slicer 8, and the sulfur slices enter the dissolution extraction tank 10 through the second inlet 2 of the dissolution extraction tank. After production is resumed, it will be used in the subsequent steps.

[0028] Step 2, Submerged Granulation and Two-Phase Extraction: The dissolution extraction tank 10 is preheated to 80°C. It contains a crude benzene phase and a circulating water phase, forming a two-phase medium with a volume ratio of approximately 3:1. The liquid sulfur obtained in Step 1 is dispersed into fine particles of 50-200 μm below the surface of the two-phase medium through a submerged granulation nozzle at the top of the dissolution extraction tank 10. The small liquid sulfur droplets enter the 80°C two-phase medium directly from approximately 130°C, cooling through heat exchange with a large volume of liquid. Within minutes, the temperature of the dispersed droplets matches that of the two-phase medium, avoiding the rapid cooling effect caused by contact with the low-temperature gas phase or cold wall surfaces, effectively preventing the formation of insoluble elastic sulfur. The temperature inside the dissolution extraction tank 10 is maintained at 80±2°C by jacketed steam. The stirring device at the top of the dissolution extraction tank 10 operates at an appropriate speed to promote sufficient contact between the particles and the two-phase medium. At this temperature, the anthracene, pyrene, and other organic compounds on the surface of the sulfur particles enter the crude benzene phase due to their good similarity and compatibility with crude benzene. The ammonium thiocyanate and ammonium sulfate entrained in the particles enter the circulating aqueous phase due to their high solubility in water. After continuous stirring and contact for 30 minutes, the mixture in the tank is discharged through the bottom outlet valve 4 of the dissolution extraction tank at a rate of 3m... 3 A flow rate of / h is delivered to the cooling separation tank 11. At the same time, fresh crude benzene is replenished to the dissolution extraction tank 10 through the circulating crude benzene tank 17 to maintain a stable liquid level.

[0029] Step 3, Cooling and Three-Phase Separation: The cooling separation tank 11 gradually reduces the temperature of the mixture to 23±2℃ through a jacketed low-temperature water and circulating water heat exchanger 12. At this temperature, the solubility of sulfur in crude benzene approaches 0%, and sulfur crystals precipitate out in large quantities from the crude benzene phase. In the cooling separation tank 11, utilizing the density differences between the phases—crude benzene phase approximately 0.86 kg / L, circulating water phase approximately 1 kg / L, and sulfur approximately 2.1 kg / L—the mixture naturally separates into a crude benzene layer, a circulating water layer, and a sulfur layer from top to bottom. The circulating water layer is located between the crude benzene layer and the sulfur layer, effectively isolating them. The upper crude benzene layer overflows through the upper crude benzene overflow port 5 of the cooling separation tank into the mixture control separator 16 for further separation. The separated crude benzene enters the circulating crude benzene tank 17, and after being heated to 70℃ by the crude benzene heater 18, it is returned to the dissolution extraction tank 10 of Step 2 for recycling. The liquid levels of each phase are observed through the sight glasses at the top and bottom of the cooling separation tank 11. When the liquid level of the sulfur layer reaches about 1 / 3 of the bottom sight glass, the discharge valve 6 at the bottom of the cooling separation tank is opened to discharge the sulfur layer and the circulating water layer together into the centrifuge 14 for solid-liquid separation.

[0030] Step 4, Centrifugal Separation and Product Collection: Centrifuge 14 separates sulfur from circulating water. The resulting solid sulfur enters the finished product silo 15, which is the refined sulfur product. The separated circulating water enters the circulating water tank 13, and after being cooled by the circulating water heat exchanger 12, it returns to the cooling separation tank 11 for recycling.

[0031] Step 5, Material Discharge and Replenishment: Approximately 100g (in 100m³) of crude benzene is discharged and replenished daily via a crude benzene circulation pump. 3 The crude benzene phase enriched with organic matter (corresponding to the laboratory scale of the sulfur foam scale) is discharged to the oil-rich tank of the crude benzene section of the coking plant, and an equal amount of fresh crude benzene is added from the crude benzene finished product tank in the plant to the circulating crude benzene tank 17; about 2L of circulating water phase enriched with ammonium salt is discharged to the lean liquor circulating tank of the desulfurization section of the coking plant every day through the circulating water pump, and an equal amount of demineralized water is added to the circulating water tank 13.

[0032] Step 6, VOC Collection and Recovery: The crude benzene-containing volatile gas generated by the dissolution extraction tank 10, through the gas outlet 3 of the dissolution extraction tank, and the gas generated by the cooling separation tank 11 and the mixed liquid control separator 16, respectively, flows through their respective gas outlets and into the VOC gas water seal device 19 via pipelines. The VOC gas water seal device 19 uses water as the sealing medium to maintain a slightly positive pressure of 2 kPa within the system, preventing outside air from entering the system and simultaneously suppressing the escape of crude benzene vapor. After being sealed by water, the crude benzene-containing gas is released at approximately 10 Nm³. 3 A flow rate of / h is fed into the coke oven gas negative pressure system, and the coke oven gas enters the chemical product recovery process, where the benzene components are recaptured and recovered.

[0033] Comparative Example 1: Xylene Total Dissolution Extraction Method Preparation steps: Step 1, Pretreatment: The same batch of crude sulfur raw materials was melted at 130℃, cooled, crushed, and sieved to a particle size range of 100-200μm to obtain solid sulfur powder.

[0034] Step 2, Heating and Dissolving: The sulfur powder obtained in Step 1 is added to a reaction vessel, and xylene, in the same amount as in Example 1, is added as a solvent. The reaction vessel is heated to 125°C under stirring and stirred at a constant temperature for 60 minutes to ensure that the sulfur and soluble organic matter are fully dissolved in the xylene.

[0035] Step 3, hot filtration to remove slag: Pass the high-temperature solution obtained in step 2 through a filtration device while it is still hot to remove insoluble impurities.

[0036] Step 4, Cooling and Crystallization: The filtrate obtained in Step 3 is introduced into a crystallizer and cooled to 25°C to allow sulfur to crystallize out.

[0037] Step 5, solid-liquid separation: The slurry obtained in step 4 is subjected to solid-liquid separation. The resulting solid sulfur is the refined product, and the separated xylene mother liquor is returned to step 2 for recycling.

[0038] Comparative Example 2: Pre-washing combined with xylene total dissolution extraction method Preparation steps: Step 1, Water washing and desalination: Put the same batch of crude sulfur raw materials into a water washing tank, add deionized water, and stir and wash at 80°C for 30 minutes to dissolve ammonium salt impurities in the water. Then perform solid-liquid separation and collect solid sulfur.

[0039] Step 2, Drying and Crushing: The solid sulfur obtained in Step 1 is dried at 105℃ to constant weight, and then crushed and sieved to a particle size range of 100-200μm.

[0040] Step 3, Heating and Dissolving: The sulfur powder obtained in Step 2 is added to the reaction vessel, and xylene, in an amount equal to that in Comparative Example 1, is added as a solvent. The reaction vessel is heated to 125°C under stirring and stirred at a constant temperature for 60 minutes.

[0041] Step 4, activated carbon decolorization: Add activated carbon to the solution obtained in step 3, stir for 30 minutes, and then filter while hot to remove activated carbon and adsorbed organic matter.

[0042] Step 5, Cooling and Crystallization: The filtrate obtained in Step 4 is introduced into a crystallizer and cooled to 25°C to allow sulfur to crystallize out.

[0043] Step 6, Solid-liquid separation: The slurry obtained in step 5 is subjected to solid-liquid separation. The resulting solid sulfur is the refined product, and the separated xylene mother liquor is returned to step 3 for recycling.

[0044] Comparative Example 3: Total Dissolution Extraction Method Preparation steps: Step 1, Pretreatment: The same batch of crude sulfur raw materials was melted at 130℃, cooled, crushed, and sieved to a particle size range of 100-200μm to obtain solid sulfur powder.

[0045] Step 2, Heating and Dissolving: The sulfur powder obtained in Step 1 is added to the reaction vessel, along with an equal amount of heavy benzene as a solvent as in Example 1. The reaction vessel is heated to 125°C under stirring and stirred at a constant temperature for 60 minutes to ensure that the sulfur and soluble organic matter are fully dissolved in the heavy benzene.

[0046] Step 3, hot filtration to remove slag: Pass the high-temperature solution obtained in step 2 through a filtration device while it is still hot to remove insoluble impurities.

[0047] Step 4, Cooling and Crystallization: The filtrate obtained in Step 3 is introduced into a crystallizer and cooled to 25°C to allow sulfur to crystallize out.

[0048] Step 5, solid-liquid separation: The slurry obtained in step 4 is subjected to solid-liquid separation. The resulting solid sulfur is the refined product, and the separated heavy benzene mother liquor is returned to step 2 for recycling.

[0049] Performance verification Comparison of product purity and impurity content The refined sulfur products obtained from Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were tested according to the methods specified in GB / T 2449.1-2021 "Industrial Sulfur" for sulfur content (on a dry basis), organic matter content (on a dry basis), and ash content (on a dry basis). The quality grade achieved by each product was then determined. The test results are shown in the table below:

[0050] Comparison of the removal effects of different methods on ammonium salts The refined sulfur products obtained in Example 1, Comparative Example 1, and Comparative Example 3 were analyzed by ion chromatography to determine the residual total amounts of ammonium thiocyanate and ammonium sulfate in the products (using NH4+). + (Calculation). The test results are shown in the table below:

[0051] Effects of different melting temperatures on sulfur speciation and effective solubility Crude sulfur from the same batch, obtained through ammonia desulfurization, was melted and held at three temperatures—140℃, 180℃, and 220℃—for 30 minutes each. It was then cooled to 80℃ at the same rate (approximately 5℃ / min) and added to an equal amount of crude benzene at 80℃. The mixture was stirred for 30 minutes, filtered, and the insoluble content was determined. The effective solubility of sulfur in crude benzene was calculated (based on the total amount of sulfur added minus the insoluble content). The results are shown in the table below.

[0052] Continuous operation stability verification Based on the process conditions described in Example 1, a small-scale continuous operation unit was built and operated continuously for 30 days. The sulfur content of the product, the concentration of anthracene / pyrene organic matter in the crude benzene phase, and the concentration of ammonium salts in the circulating water phase were monitored every 5 days to examine the long-term stability of the system. The results are shown in the table below:

[0053] In the above test data, the values ​​in Example 1 are based on the inventor's measured solubility parameters (sulfur solubility in crude benzene is approximately 14% at 83℃ and approaches 0% at 23℃) and continuous operation verification results; the values ​​in Comparative Examples 1-3 are engineering extrapolations based on the component characteristics of the same batch of raw materials, the physical properties of each solvent, and the mass-quantity balance of the chemical separation process. The purpose of the above data is to help understand the technical solution of the present invention and compare the technical effects of various solutions. The scope of protection of the present invention is defined by the claims.

[0054] The performance verification data above shows that: 1. Comparative Example 1 uses a single organic phase high-temperature complete dissolution method with xylene as the solvent. Because it lacks a water washing step and anthracene, pyrene, and sulfur are co-soluble at high temperatures, organic matter and sulfur co-precipitate during cooling. Furthermore, ammonium salts cannot be removed, resulting in a product sulfur content of only 99.1%, with both organic matter and ash residue exceeding the standards. Comparative Example 3 uses heavy benzene as the solvent. Although it shares the same origin as crude benzene, the problem of heavy tar co-dissolving and co-precipitating with sulfur still exists under high-temperature operation at 125℃, resulting in a product sulfur content of only 99.2%, similar to Comparative Example 1. This is consistent with the analysis in the background section that "the complete dissolution route cannot effectively separate high-boiling-point tar."

[0055] 2. Comparative Example 2 added an activated carbon decolorization step to the water washing desalination process, increasing the product's sulfur content to 99.4% and improving ash content, but still failing to meet the Grade A standard, and the organic residue remained high. This indicates that pre-washing alone is insufficient to completely remove ammonium salts, and while activated carbon can adsorb some organic matter, its removal effect on complex tar components is limited.

[0056] 3. A comparative study on ammonium salt removal showed that in single organic solvent solutions without a water washing step (Comparative Examples 1 and 3), almost all ammonium salts remained in the product, with a removal rate of only about 76-78%. However, in Example 1, through in-situ synchronous washing with circulating aqueous phase in a two-phase medium, the ammonium salt removal rate exceeded 99%, fully demonstrating the technical advantages of the "stepwise series selective extraction" method of this solution.

[0057] 4. The effect of different sulfur melting temperatures was verified. The results showed that when the sulfur melting temperature exceeded 180℃, some sulfur was converted into elastic sulfur, which is insoluble in crude benzene, during the rapid cooling process, significantly reducing the effective solubility and thus the sulfur recovery rate. This method controls the sulfur melting temperature within the lower range of 125-145℃ and uses submerged granulation to allow small droplets of liquid sulfur to enter the two-phase medium for heat exchange with a large amount of liquid, avoiding the rapid cooling effect, effectively preventing the formation of elastic sulfur, and ensuring a high sulfur recovery rate.

[0058] 5. 30 days of continuous operation verification showed that, under the daily quantitative discharge of crude benzene and the adjustment of circulating water, the concentration of organic matter in the crude benzene phase did not show a continuous accumulation trend during the operation of the unit, the fluctuation of ammonium salt concentration in the circulating water phase was controlled within ±6%, the sulfur content of the product remained stable, the overall material balance of the system was achieved, and the operation was stable and reliable.

[0059] In summary, Example 1, without the need for activated carbon decolorization, achieved a sulfur content that meets the industrial sulfur grade A standard (GB / T 2449.1-2021), with organic matter and ash residues controlled at extremely low levels. Its technical advantages stem from: submersible granulation ensures that sulfur particles are in full contact with the two-phase medium at the moment of formation; the crude benzene phase selectively extracts organic matter, while the aqueous phase simultaneously washes ammonium salts, avoiding co-dissolution and co-precipitation of organic matter and sulfur at high temperatures; and the VOCs gas water seal device provides unified collection and pressure control of volatile gases from various devices, ensuring a safe and environmentally friendly operating environment. This results in a significantly improved quality and simplified process compared to existing technologies.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for refining low-quality sulfur from coking processes, characterized in that, Includes the following steps: S1 Pretreatment: Sulfur foam containing 8-12% suspended sulfur by mass from HPF ammonia desulfurization is melted and clarified to obtain liquid crude sulfur; S2 Submerged Granulation and Two-Phase Extraction: The liquid crude sulfur obtained in step S1 is passed through a submerged granulation nozzle to form 50-200μm particles in a two-phase medium that simultaneously contains a crude benzene phase and a circulating water phase. Under conditions of 75-85℃, the organic matter on the surface of the sulfur particles enters the crude benzene phase, and the ammonium salt impurities enter the circulating water phase. S3 Cooling and Three-Phase Separation: The mixture obtained in step S2 is cooled to 20-25℃, so that sulfur crystallizes out from the crude benzene phase. In the cooling separation tank, the density difference is used to form a crude benzene layer, a circulating water layer, and a sulfur layer from top to bottom. The sulfur layer is separated by centrifugation to obtain the sulfur product. S4 Material Circulation and Homologous Closed Loop: After separation, the crude benzene phase is heated to 65-75℃ and returned to step S2 for recycling. The circulating water phase is cooled and returned to step S3 for recycling. The portion of the crude benzene phase enriched with organic matter is discharged to the crude benzene section of the coking plant, and the portion of the circulating water phase enriched with ammonium salts is discharged to the desulfurization section of the coking plant. Fresh crude benzene and demineralized water are added respectively. S5VOC Collection and Recovery: The crude benzene-containing volatile gas generated by the equipment involving crude benzene in steps S2 to S4 is collected to the VOC gas water seal device, maintaining a pressure of 2 kPa. The gas after water sealing is sent to the coke oven gas negative pressure system for recovery.

2. The process according to claim 1, characterized in that, The temperature of the molten sulfur in step S1 is 125-145℃ and the pressure is 0.2-0.4MPa.

3. The process according to claim 1, characterized in that, In step S3, the density of the crude benzene layer is approximately 0.86 kg / L, the density of the circulating water layer is approximately 1 kg / L, and the density of the sulfur layer is approximately 2.1 kg / L. The cooling separation tank is equipped with sight glasses at the top and bottom. When the sulfur layer reaches 1 / 3 of the bottom sight glass position, the sulfur layer and the circulating water layer are discharged together into the centrifuge.

4. The process according to claim 1, characterized in that, In step S4, the daily discharge of crude benzene is 0.5%-1.5% of the total mass of suspended sulfur contained in the sulfur foam in step S1, and the daily discharge of circulating water is 0.5%-3% of the total mass of suspended sulfur contained in the sulfur foam in step S1.

5. The process according to claim 1, characterized in that, Step S1 also includes: when the system is under maintenance, the liquid sulfur in the sulfur clarification tower is sliced ​​by a slicer, and after production is resumed, the sulfur slices are put into the two-phase medium in step S2.

6. A coking low-quality sulfur extraction and refining system for implementing the process according to any one of claims 1 to 5, characterized in that, include: The dissolution extraction tank (10) has a two-phase medium space inside for simultaneously containing the crude benzene phase and the circulating water phase, and a submerged granulation nozzle is provided on the top. The cooling separation tank (11) has its inlet connected to the bottom outlet of the dissolution extraction tank (10) via the bottom outlet valve (4) of the dissolution extraction tank. The cooling separation tank (11) is a three-phase separation structure that uses density difference to form a crude benzene layer, a circulating water layer and a sulfur layer from top to bottom. The mixing liquid control separator (16) has its inlet connected to the upper crude benzene outlet of the cooling separator (11), and its crude benzene outlet connected to the circulating crude benzene tank (17). The crude benzene circulation loop includes the circulating crude benzene tank (17), the crude benzene circulation pump and the crude benzene heater (18) connected in sequence, and the outlet of the crude benzene heater (18) is connected to the dissolution extraction tank (10). Centrifuge (14), whose inlet is connected to the lower outlet of the cooling separation tank (11); The circulating water circuit includes a circulating water tank (13), a circulating water pump and a circulating water heat exchanger (12) connected in sequence. The inlet of the circulating water tank (13) is connected to the liquid phase outlet of the centrifuge (14), and the outlet of the circulating water heat exchanger (12) is connected to the cooling separation tank (11). The VOC gas water seal device (19) has its gas inlet connected to the gas outlet of the dissolution extraction tank (10), the cooling separation tank (11) and the mixed liquid control separator (16), respectively, and its gas outlet is used to connect to the coke oven gas negative pressure system.

7. The system according to claim 6, characterized in that, It also includes a multi-stage separator (7), a sulfur clarifier (9) and a slicer (8). The feed inlet of the sulfur clarifier (9) is connected to the multi-stage separator (7) through a balance tank. The sulfur clarifier (9) is provided with a first outlet and a second outlet. The first outlet is connected to the first inlet (1) of the dissolution extraction tank (10), and the second outlet is connected to the second inlet (2) of the dissolution extraction tank (10) through the slicer (8).

8. The system according to claim 6, characterized in that, The dissolution extraction tank (10) is equipped with a jacketed steam heating device, and the cooling separation tank (11) is equipped with a jacketed low-temperature water cooling device.

9. The system according to claim 6, characterized in that, The VOC gas water seal device (19) maintains the system pressure at 2 kPa.

10. The system according to claim 7, characterized in that, The volume of the sulfur clarification tower (9) is not less than 1 times the daily sulfur production.

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