A method and apparatus for reducing the total sulfur content of furfural products

Abstract

The application discloses a method and device for reducing total sulfur content of furfural products, which comprises the following steps: detecting sulfur form of furfural raw materials to be treated to obtain sulfur form composition data including total sulfur content and one or more of sulfate, carbonyl sulfur, disulfide sulfur-containing components, hydrogen sulfide, mercaptan compounds and sulfur-containing high-boiling components; a control unit determines a processing route and / or processing intensity in water washing backflushing, catalytic hydrogenation, micro-nano bubble resolution, zinc oxide adsorption, rectification and reflux side line liquid phase fine desulfurization according to the sulfur form composition data; after water-soluble inorganic sulfur components are removed by water washing backflushing, furfural raw materials enter a temporary storage tank for distribution, and part of the materials enter a desulfurization reaction kettle for catalytic hydrogenation, so that carbonyl sulfur and / or disulfide sulfur-containing components are converted into hydrogen sulfide and / or mercaptan compounds. The application can perform segmented and cooperative desulfurization according to different sulfur forms, and improve stability and adaptability of total sulfur content control of furfural products.

Description

Technical Field

[0001] This invention relates to the field of furfural product refining technology, specifically to a method and apparatus for reducing the total sulfur content of furfural products. Background Technology

[0002] Furfural is a common basic chemical raw material used to produce furfuryl alcohol, furan compounds, and some fine chemical intermediates. In the production and sales of furfural products, conventional quality indicators such as furfural content, moisture, acidity, and color are typically the primary focus. While existing quality control systems address the detection and monitoring of total sulfur content in furfural products, the control requirements vary across different companies, batches, and applications.

[0003] In some downstream applications, sulfur-containing impurities in furfural can adversely affect subsequent reaction processes. For example, in the hydrogenation of furfural to furfuryl alcohol, sulfur-containing impurities in the feedstock may affect the activity and lifespan of the hydrogenation catalyst. Furthermore, in the further conversion of furfural to furans or other fine chemical products, if the downstream process uses precious metal catalysts or fixed-bed catalysts, sulfur-containing impurities may also affect catalyst stability and continuous operation of the equipment. Therefore, for some applications with high requirements for feedstock quality, it is necessary to further reduce the total sulfur content in furfural products and minimize fluctuations in the total sulfur content between different batches.

[0004] In actual production, sulfur in furfural does not necessarily exist in a single form. Depending on the source of raw materials, production process, acid catalysis conditions, purification conditions, and storage and transportation environment, furfural may contain sulfur-containing components in different forms, such as sulfate, carbonyl sulfide, carbon disulfide, organic disulfides, hydrogen sulfide, thiols, and high-boiling sulfur-containing components. These sulfur-containing components exhibit differences in physicochemical properties, including water solubility, volatility, reactivity, boiling point, and adsorption characteristics. For example, water-soluble inorganic sulfur components such as sulfate are relatively suitable for entering the aqueous phase through water washing; hydrogen sulfide has a certain degree of volatility and can be treated through gas stripping, desorption, and gas-phase adsorption; components such as carbonyl sulfide, carbon disulfide, or organic disulfides have limited effectiveness when directly removed by water washing or ordinary distillation, and usually need to be converted into more easily treated sulfur forms first; thiols and some high-boiling sulfur-containing components may accumulate on the bottom side of the distillation column during the distillation process.

[0005] In existing furfural refining processes, unit operations such as washing, dehydration, and distillation are common. These processes are effective in reducing acidic substances, moisture, or some high-boiling impurities, but their design purpose is usually not to remove sulfur in stages for different forms. When sulfur-containing components in furfural exist in multiple forms simultaneously, washing alone is often insufficient to effectively treat carbonyl sulfur, disulfide sulfur-containing components, and some high-boiling sulfur-containing components; distillation alone, while able to enrich some high-boiling components in the bottom of the distillation column, has limited stability in controlling water-soluble sulfur components, dissolved hydrogen sulfide, and some low-content sulfur-containing components; and adsorption alone is easily affected by changes in the sulfur form in the feed, which may lead to large fluctuations in adsorption load or increased consumption of adsorbent material.

[0006] Furthermore, the total sulfur content and sulfur speciation composition may vary between different batches of furfural products. If a fixed processing flow and operating intensity are used, on the one hand, insufficient desulfurization may occur when processing furfural with high sulfur content or complex sulfur speciation, making it difficult to meet the requirements for low-sulfur products; on the other hand, when processing furfural with low sulfur content or primarily composed of easily desulfurized speciation, unnecessary hydrogenation, gas consumption, adsorbent losses, energy consumption, and tower bottom losses may occur. Therefore, relying solely on a fixed route for furfural refining makes it difficult to simultaneously achieve both effective desulfurization and economical operation.

[0007] Therefore, it is necessary to provide a method and apparatus for reducing the total sulfur content in the refining process of furfural products. This allows for the acquisition of sulfur speciation data in the furfural raw material before treatment, and the selection of appropriate treatment routes and intensities based on the content or proportion of different sulfur-containing components. By employing treatment measures such as water washing and backflushing, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation separation, and liquid-phase desulfurization on water-soluble inorganic sulfur components, convertible organic sulfur components, volatile sulfur components, and high-boiling sulfur-containing components, respectively, it is beneficial to improve the stability of total sulfur content control in furfural products and enhance the process's adaptability to different batches of furfural raw materials. Summary of the Invention

[0008] The technical problem this invention aims to solve is: addressing the lack of methods for identifying and segmenting different sulfur forms in existing furfural refining processes, which makes it difficult to stably reduce the total sulfur content of furfural products using single methods such as water washing, single distillation, or single adsorption. This invention provides a method and apparatus for reducing the total sulfur content of furfural products. This method and apparatus can determine the processing route and intensity based on the sulfur form composition data of the furfural raw material. Through a combination of water washing backflushing, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation, and reflux side-stream liquid-phase desulfurization, different sulfur-containing components are removed in stages, thereby improving the stability and process adaptability of low-sulfur furfural product quality control and effectively solving the problems in the background technology.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for reducing the total sulfur content of furfural products, comprising the following steps: The furfural raw material to be treated is subjected to sulfur speciation detection by a sulfur speciation detection unit to obtain sulfur speciation composition data. The sulfur speciation composition data includes total sulfur content, as well as the content and / or proportion of one or more sulfur-containing components among sulfate, carbonyl sulfide, disulfide sulfur-containing components, hydrogen sulfide, mercaptans and sulfur-containing high-boiling components. Based on the sulfur speciation data, the control unit determines one or more treatment routes and / or treatment intensities among water washing backwash, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation, and reflux side-stream liquid phase fine desulfurization. After sulfur speciation detection, furfural raw material is sent to the water washing backflushing tower via the furfural raw material pipeline. Water is introduced into the water washing backflushing tower through the water inlet pipeline, and backflushing gas is introduced into the water washing backflushing tower through the backflushing gas inlet pipeline. This allows the furfural raw material to come into contact with water and be subjected to backflushing disturbance, so that the sulfate ions in the furfural raw material enter the aqueous phase, and the desulfated furfural is obtained. After desulfate removal, furfural is sent to a temporary storage tank. The outlet of the temporary storage tank is divided into a first line and a second line. The first line is connected to the distillation column via a bypass pipeline of furfural after desulfate removal, and the second line is connected to the desulfurization reactor. The control unit controls the on / off state and / or material distribution ratio of the first and second lines according to the sulfur composition data. After desulfurization, furfural is fed with catalyst through the catalyst inlet and hydrogen is introduced through the hydrogen inlet to convert carbonyl sulfur and / or disulfide sulfur-containing components in the desulfurized furfural into hydrogen sulfide and / or mercaptan compounds, thus obtaining hydrogenated furfural. After hydrogenation conversion, furfural is sent to a catalyst separation tank to separate the catalyst from the furfural liquid phase. The separated catalyst waste liquid is discharged through the catalyst waste liquid outlet. The furfural after catalyst separation is sent to a micro-nano bubble desorption tank through the hydrogenation conversion furfural pipeline. Desorption gas is introduced into the micro-nano bubble desorption tank through the desorption gas inlet and the microporous gas distributor, so that hydrogen sulfide dissolved in the furfural liquid phase enters the gas phase, and desorption gas and hydrogenated furfural are obtained. The desorbed gas is then combined with the overhead gas phase of the distillation column via the desorbed gas outlet pipeline and enters the zinc oxide adsorption column to remove hydrogen sulfide from the desorbed gas and the overhead gas phase. After hydrogenation and desorption, furfural is sent to a distillation column via the furfural pipeline for distillation, so that thiols and / or sulfur-containing high-boiling components are enriched in the bottom of the column and discharged from the bottom residue outlet. The gas phase treated by the zinc oxide adsorption column is condensed in the condenser, and the condensate is sent to the reflux tank. At least a portion of the condensate in the reflux tank is sent to the liquid phase desulfurization protector to further remove residual sulfur-containing components from the condensate. The condensate after being treated by the liquid phase desulfurization protector is partially returned to the distillation tower via the reflux pipeline, and the other part is extracted via the low-sulfur furfural product extraction pipeline to obtain the low-sulfur furfural product.

[0010] Furthermore, the sulfur speciation data include total sulfur content, sulfate sulfur content, carbonyl sulfur content, carbon disulfide content, organic disulfide content, hydrogen sulfide content, thiol compound content, sulfur-containing high-boiling component content, and one or more of the above sulfur-containing components in the total sulfur content. Sulfur speciation was detected using one or more of the following methods: total sulfur analysis, ion chromatography analysis, gas chromatography-chemiluminescence detection of sulfur, gas chromatography-mass spectrometry detection, electrochemical hydrogen sulfide detection, and ultraviolet fluorescence sulfur detection.

[0011] Furthermore, the control unit classifies the furfural raw material to be treated into inorganic sulfur-dominated, converted organic sulfur-dominated, volatile sulfur-dominated, high-boiling sulfur-containing component-dominated, or complex sulfur-dominated types based on the sulfur form composition data. When the furfural feedstock to be processed is dominated by inorganic sulfur, increase the washing intensity and / or backflushing intensity of the water washing backflushing tower, and allow at least part of the desulfated furfural to enter the distillation tower via the desulfated furfural bypass pipeline. When the furfural feedstock to be treated is dominated by convertible organic sulfur, the proportion of material entering the desulfurization reactor should be increased, and the catalytic hydrogenation intensity and micro-nano bubble desorption intensity should be improved. When the furfural raw material to be processed is dominated by volatile sulfur, the desorption intensity of the micro-nano bubble desorption tank and the adsorption intensity of the zinc oxide adsorption column should be increased. When the furfural feedstock to be treated is dominated by high-boiling sulfur-containing components, increase the proportion of residual liquid discharged from the bottom of the distillation column and / or the proportion of condensate entering the liquid phase desulfurization protector. When the furfural raw material to be treated is of the complex sulfur type, the following steps are performed in sequence: water washing backflushing, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation, and reflux side-stream liquid phase fine desulfurization.

[0012] Furthermore, the operating temperature of the water washing backflushing tower is 20℃~60℃, and the volume ratio of water to furfural raw material is 0.05:1~0.5:1; The backflush gas is compressed air, nitrogen, or an inert gas, and the pressure of the backflush gas is 0.05 MPa to 0.5 MPa. The bottom or side of the water washing backwash tower is equipped with an aqueous phase outlet for discharging the aqueous phase enriched with sulfate.

[0013] Furthermore, the catalyst is a nickel-based catalyst, and the amount of catalyst added is 0.05% to 0.30% of the mass of furfural; the reaction temperature for catalytic hydrogenation is 65℃ to 90℃, the hydrogen pressure is 1.0MPa to 2.5MPa, and the reaction time is 0.5h to 4h. Preferably, the amount of catalyst added is 0.1% to 0.15% of the mass of furfural, the reaction temperature of catalytic hydrogenation is 70°C to 85°C, and the hydrogen pressure is 1.5 MPa to 1.8 MPa.

[0014] The endpoint of catalytic hydrogenation is determined based on one or more of the following: carbonyl sulfur content, sulfur-containing disulfide content, hydrogen consumption per unit time, and change in furfural purity. When the carbonyl sulfur content is below 1 mg / L to 5 mg / L, the sulfur-containing disulfide content is below 1 mg / L to 5 mg / L, the hydrogen consumption per unit time is below 10% to 30% of the initial hydrogen consumption rate for 10 min to 30 min continuously, or the decrease in furfural purity does not exceed 0.1% to 1.0%, the catalytic hydrogenation reaction should be stopped or the catalytic hydrogenation intensity reduced.

[0015] Furthermore, the desorption gas is nitrogen, carbon dioxide, or an inert gas; the desorption temperature of the micro-nano bubble desorption vessel is 20℃~90℃, the desorption time is 5min~120min, the gas-liquid volume ratio is 0.5:1~100:1, and the pore size of the microporous gas distributor is 0.1μm~200μm; Preferably, the desorption temperature is 40℃~70℃, the desorption time is 20min~60min, the gas-liquid volume ratio is 1:1~50:1, and the pore size of the microporous gas distributor is 0.5μm~100μm.

[0016] Furthermore, there may be one, two, or more zinc oxide adsorption columns; when there are two or more zinc oxide adsorption columns, the multiple zinc oxide adsorption columns may be operated in series, in parallel, in a one-in-use-one-in-standby or series-parallel combination manner. A hydrogen sulfide detection point is set at the outlet of the zinc oxide adsorption column. When the hydrogen sulfide concentration at the outlet of the zinc oxide adsorption column reaches the set threshold, the control unit switches the operating mode of the zinc oxide adsorption column or prompts to replace the zinc oxide adsorbent.

[0017] Furthermore, the reflux ratio of the distillation column is 0.5:1 to 5:1, the temperature of the column bottom is 160℃ to 230℃, and the residue in the column bottom at the end of distillation accounts for 0.5% to 5% of the feed mass; the condensate sent to the liquid phase desulfurization protector is 5% to 100% of the total condensate in the reflux tank. The operating temperature of the liquid phase desulfurization protector is 20℃~90℃, and the liquid space velocity is 0.1h. -1 ~10h -1The liquid phase desulfurization protector is filled with liquid phase desulfurization material, which is one or more of the following: metal oxide adsorbent, supported metal oxide adsorbent, modified activated carbon, metal ion exchange resin, alkaline ion exchange resin, copper-loaded porous adsorbent, zinc-loaded porous adsorbent, iron-loaded porous adsorbent, nickel-loaded porous adsorbent, and silver-loaded porous adsorbent.

[0018] Furthermore, the control unit determines the removal rate, conversion rate, or residual rate of the corresponding sulfur-containing component by each processing unit based on the sulfur speciation data and at least one intermediate sulfur speciation detection data. Based on the removal rate, conversion rate, or residual rate, it performs closed-loop adjustment of one or more of the following treatment intensities: water washing backflushing, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation, and reflux side-stream liquid-phase fine desulfurization. The intermediate sulfur speciation detection data originates from one or more locations among the water washing backflushing tower outlet, desulfurization reactor outlet, micro-nano bubble desorption tank outlet, zinc oxide adsorption column outlet, reflux tank outlet, and low-sulfur furfural product collection pipeline.

[0019] Furthermore, an apparatus for reducing the total sulfur content of furfural products includes: a sulfur speciation detection unit, a furfural raw material pipeline, a water washing backflushing tower, a water inlet pipeline, a backflushing gas inlet pipeline, a temporary storage tank, a desulfurization reactor, a catalyst inlet, a hydrogen inlet, a catalyst separation tank, a catalyst waste liquid outlet, a micro-nano bubble desorption tank, a desorption gas inlet, a microporous gas distributor, a desorption gas outlet pipeline, a furfural pipeline after hydrogenation desorption, a distillation tower, a tower bottom, a tower bottom residual liquid outlet, a zinc oxide adsorption column, a condenser, a reflux tank, a liquid phase desulfurization protector, a reflux pipeline, a low-sulfur furfural product collection pipeline, a control unit, a signal line, a furfural bypass pipeline after desulfate removal, and a furfural pipeline after hydrogenation conversion. The sulfur speciation detection unit is connected to the water washing backflushing tower via the furfural feed pipeline. The water washing backflushing tower is connected to the water inlet pipeline, the backflushing gas inlet pipeline, and a temporary storage tank. The bottom or side of the water washing backflushing tower is equipped with an aqueous phase outlet for discharging the sulfate-enriched aqueous phase. The temporary storage tank is connected to the distillation tower via a furfural bypass pipeline after sulfate removal, and to the desulfurization reactor via another pipeline. The desulfurization reactor is connected to the catalyst inlet, the hydrogen inlet, and the catalyst separation tank. The catalyst separation tank is connected to the catalyst waste outlet and the furfural pipeline after hydrogenation conversion. The furfural pipeline after hydrogenation conversion is connected to the micro-nano bubble desorption tank. The desorption tank is connected to the desorption gas inlet, microporous gas distributor, desorption gas outlet pipeline, and the furfural pipeline after hydrogenation desorption, respectively. The furfural pipeline after hydrogenation desorption is connected to the distillation column. The desorption gas outlet pipeline merges with the top gas phase pipeline of the distillation column and is then connected to the zinc oxide adsorption column. The zinc oxide adsorption column is connected in sequence to the condenser, reflux tank, and liquid phase desulfurization protector. The distillation column is connected to the column bottom, column bottom residue outlet, furfural pipeline after hydrogenation desorption, furfural bypass pipeline after desulfate removal, and the top gas phase pipeline, respectively. The liquid phase desulfurization protector is connected to the distillation column through the reflux pipeline and to the product collection end through the low-sulfur furfural product collection pipeline. The control unit is connected to one or more of the following via signal lines: sulfur speciation detection unit, water washing backflushing tower, temporary storage tank, desulfurization reactor, micro-nano bubble desorption tank, zinc oxide adsorption column, reflux tank, and liquid phase desulfurization protector.

[0020] Furthermore, valve V1 is installed on the furfural bypass line after sulfate removal; valve V2 is installed between the temporary storage tank and the desulfurization reactor; valve V3 is installed between the catalyst separation tank and the micro-nano bubble desorption tank; valve V4 is installed on the furfural line after hydrogenation desorption between the micro-nano bubble desorption tank and the distillation column; valve V5 is installed on the reflux line between the liquid phase desulfurization protector and the distillation column; and valve V6 is installed at the outlet of the column bottom residue. The control unit controls the opening or closing state of one or more of valves V1, V2, V3, V4, V5 and V6 based on the sulfur composition data obtained by the sulfur form detection unit.

[0021] Among them, the water washing backflushing tower is a packed tower, plate tower, mixing clarifier or liquid-liquid contact equipment with backflushing structure; the catalyst separation tank is a settling tank, filter, centrifuge or solid-liquid separation equipment; the distillation tower is a packed tower or plate tower; the zinc oxide adsorption column is one, two or more molded adsorbent packed columns; the liquid phase desulfurization protector is a fixed bed liquid phase adsorber, ion exchange column or liquid phase processor filled with porous desulfurization material.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. Before the desulfurization treatment of furfural, the present invention first obtains the sulfur speciation data, and the control unit determines the treatment route and treatment intensity based on the total sulfur content and the content or proportion of sulfate, carbonyl sulfide, sulfur-containing components such as disulfides, hydrogen sulfide, mercaptans and sulfur-containing high-boiling components. Therefore, the present invention does not use a fixed single desulfurization process, but can carry out targeted treatment according to the actual composition of sulfur-containing components in different batches of furfural raw materials, reducing the problem of insufficient desulfurization or over-treatment caused by fluctuations in the sulfur speciation of raw materials, and improving the stability and adaptability of total sulfur content control of furfural products.

[0023] 2. This invention pretreats furfural feedstock using a water-washing backflushing tower, allowing water-soluble inorganic sulfur components such as sulfate to preferentially enter the aqueous phase and be discharged. Since the backflushing gas can enhance the disturbance and contact between the furfural phase and the aqueous phase, it is beneficial to improve the mass transfer efficiency of water-soluble sulfur components. This reduces the inorganic sulfur load before entering the subsequent catalytic hydrogenation, desorption, adsorption and distillation steps, creating more stable feed conditions for the subsequent treatment of organic sulfur, volatile sulfur and high-boiling sulfur-containing components.

[0024] 3. This invention sets up a temporary storage tank and forms a diversion route after water washing and backflushing, so that furfural after desulfurization can be directly fed into the distillation column or into the desulfurization reactor for catalytic hydrogenation treatment according to the sulfur form composition data. When the content of carbonyl sulfur and disulfide sulfur-containing components is low, the proportion of materials entering the hydrogenation route can be reduced, thereby reducing the consumption of hydrogen, catalyst and energy. When the content of the above-mentioned convertible organic sulfur is high, the proportion of materials entering the hydrogenation route is increased, so that the organic sulfur components that are difficult to be directly removed by water washing or ordinary distillation are converted into hydrogen sulfide and / or mercaptans, thereby facilitating subsequent desorption, adsorption or distillation separation.

[0025] 4. In this invention, furfural after catalytic hydrogenation is fed into a micro-nano bubble desorption tank. Fine bubbles are formed through a microporous gas distributor, transferring hydrogen sulfide dissolved in the furfural liquid phase to the gas phase. Simultaneously, the desorption gas is combined with the gas phase at the top of the distillation column and then enters a zinc oxide adsorption column for centralized treatment. This process can handle the hydrogen sulfide generated in the catalytic hydrogenation step, reducing its residue in the furfural liquid phase, the column top condensate, or the product. The zinc oxide adsorption column uniformly removes hydrogen sulfide from the desorption gas and the column top gas phase, improving the continuity and reliability of the treatment of sulfur-containing components in the gas phase.

[0026] 5. This invention uses a distillation column to enrich thiols and / or high-boiling sulfur-containing components in the column bottom and discharge them with the column bottom residue. Simultaneously, a liquid-phase desulfurization protector is installed after the reflux tank to supplement and finely desulfurize at least a portion of the column top condensate. This setup further reduces the trace sulfur-containing components remaining or entrained in the condensate, minimizing total sulfur fluctuations when low-sulfur furfural products are collected. Therefore, this invention forms a segmented synergistic desulfurization process that integrates sulfur speciation detection, water washing backflushing, split hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation enrichment, and liquid-phase protection, enabling more stable production of low-sulfur furfural products. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is a flowchart of the adaptive desulfurization control based on sulfur speciation data of the present invention.

[0028] The diagram shows: 1. Sulfur speciation detection unit; 2. Furfural raw material pipeline; 3. Water washing backflushing tower; 4. Water inlet pipeline; 5. Backflushing gas inlet pipeline; 6. Temporary storage tank; 7. Desulfurization reactor; 8. Catalyst inlet; 9. Hydrogen inlet; 10. Catalyst separation tank; 11. Catalyst waste liquid outlet; 12. Micro-nano bubble desorption tank; 13. Desorption gas inlet; 14. Microporous gas distributor; 15. Desorption gas outlet pipeline; 16. Furfural pipeline after hydrogenation desorption; 17. Distillation tower; 18. Tower bottom; 19. Tower bottom residual liquid outlet; 20. Zinc oxide adsorption column; 21. Condenser; 22. Reflux tank; 23. Liquid phase desulfurization protector; 24. Reflux pipeline; 25. Low-sulfur furfural product collection pipeline; 26. Control unit; 27. Signal line; 28. Furfural bypass pipeline after desulfate removal; 29. ​​Furfural pipeline after hydrogenation conversion. Detailed Implementation

[0029] The embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the following embodiments are used to illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make appropriate adjustments to the equipment type, pipeline connection method, detection method and process parameters according to the source of furfural raw materials, plant scale, total sulfur index of target product and on-site operating conditions.

[0030] like Figure 1As shown, this embodiment provides a method and apparatus for reducing the total sulfur content of furfural products; the apparatus includes a sulfur speciation detection unit 1, a furfural raw material pipeline 2, a water washing backflushing tower 3, a water inlet pipeline 4, a backflushing gas inlet pipeline 5, a temporary storage tank 6, a desulfurization reactor 7, a catalyst inlet 8, a hydrogen inlet 9, a catalyst separation tank 10, a catalyst waste liquid outlet 11, a micro-nano bubble desorption tank 12, a desorption gas inlet 13, a microporous gas distributor 14, a desorption gas outlet pipeline 15, a furfural pipeline after hydrogenation desorption 16, a distillation tower 17, a tower bottom 18, a tower bottom residual liquid outlet 19, a zinc oxide adsorption column 20, a condenser 21, a reflux tank 22, a liquid phase desulfurization protector 23, a reflux pipeline 24, a low-sulfur furfural product collection pipeline 25, a control unit 26, a signal line 27, a furfural bypass pipeline after sulfate removal 28, and a furfural pipeline after hydrogenation conversion 29.

[0031] The sulfur speciation detection unit 1 is connected to the water washing backflushing tower 3 via the furfural feed line 2. The water washing backflushing tower 3 is connected to the water inlet line 4, the backflushing gas inlet line 5, and the temporary storage tank 6. The bottom or side of the water washing backflushing tower 3 is equipped with an aqueous phase outlet for discharging the sulfate-enriched aqueous phase. The temporary storage tank 6 is connected to the distillation tower 17 via the desulfurization furfural bypass line 28 and to the desulfurization reactor 7 via another line. The desulfurization reactor 7 is connected to the catalyst inlet 8, the hydrogen inlet 9, and the catalyst separation tank 10. The catalyst separation tank 10 is connected to the catalyst waste liquid outlet 11 and the furfural pipeline 29 after hydrogenation conversion. Pipeline 29 is connected to the micro-nano bubble desorption tank 12; the micro-nano bubble desorption tank 12 is connected to the desorption gas inlet 13, the microporous gas distributor 14, the desorption gas outlet pipeline 15, and the furfural pipeline 16 after hydrogenation desorption; the furfural pipeline 16 after hydrogenation desorption is connected to the distillation column 17; the desorption gas outlet pipeline 15 merges with the top gas phase pipeline of the distillation column 17 and is then connected to the zinc oxide adsorption column 20; the zinc oxide adsorption column 20 is connected in sequence to the condenser 21, the reflux tank 22, and the liquid phase desulfurization protector 23; the liquid phase desulfurization protector 23 is connected to the distillation column 17 through the reflux pipeline 24 and to the product collection end through the low-sulfur furfural product collection pipeline 25.

[0032] In this embodiment, the sulfur speciation detection unit 1 can be an online detection unit or an offline detection unit after sampling. The detection items include total sulfur content, and the content and / or proportion of one or more sulfur-containing components among sulfate, carbonyl sulfide, carbon disulfide, organic disulfides, hydrogen sulfide, thiols, and high-boiling sulfur-containing components. The total sulfur content can be determined using a total sulfur analyzer or an ultraviolet fluorescence sulfur detection method. Sulfate can be determined using ion chromatography. Carbonyl sulfide, carbon disulfide, organic disulfides, hydrogen sulfide, and thiols can be determined using one or more of the following methods: gas chromatography-chemiluminescence detection of sulfur, gas chromatography-mass spectrometry detection, and electrochemical hydrogen sulfide detection. The above detection methods can be selected according to the site conditions, as long as the sulfur speciation composition data for subsequent control can be obtained.

[0033] In this invention, sulfur-containing disulfide components refer to sulfur-containing components in furfural feedstock that can be converted under catalytic hydrogenation conditions, including carbon disulfide, organic disulfides, and other sulfur-containing components that can be converted into hydrogen sulfide and / or thiols under catalytic hydrogenation conditions. High-boiling sulfur-containing components may include thiophene sulfides, thioether compounds, and other sulfur-containing organic components that are easily enriched in the bottom of the distillation column during furfural distillation. The above-mentioned sulfur-containing components can be used as detection targets in sulfur speciation data, and can also be used as the basis for the control unit to determine the treatment route, treatment intensity, material distribution ratio, and subsequent desulfurization unit operating conditions.

[0034] Based on the sulfur speciation data obtained by the sulfur speciation detection unit 1, the control unit 26 determines the subsequent processing route and processing intensity; such as Figure 2 As shown, the control unit 26 can classify furfural raw materials into inorganic sulfur-dominated, convertible organic sulfur-dominated, volatile sulfur-dominated, high-boiling sulfur-dominated, or complex sulfur-dominated types based on the proportion of different sulfur-containing components in the total sulfur. When the proportion of water-soluble inorganic sulfur components such as sulfate is high, the washing intensity and / or backflushing intensity of the water washing backflushing tower 3 is increased. When the proportion of convertible organic sulfur components such as carbonyl sulfur, carbon disulfide, or organic disulfides is high, the proportion of material entering the desulfurization reactor 7 is increased, and the... High catalytic hydrogenation intensity; when the proportion of volatile sulfur components such as hydrogen sulfide is high, increase the desorption intensity of the micro-nano bubble desorption tank 12 and the adsorption intensity of the zinc oxide adsorption column 20; when the proportion of mercaptans or sulfur-containing high-boiling components is high, increase the proportion of residual liquid discharged from the bottom of the distillation column 17 and / or the proportion of condensate entering the liquid phase desulfurization protector 23; when multiple sulfur-containing components are all high, perform water washing backflushing, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation and reflux side stream liquid phase fine desulfurization in sequence.

[0035] In this invention, different sulfur-containing components in furfural raw materials can be sequentially and segmented for processing based on their differences in water solubility, reactivity, volatility, and boiling point. Specifically, water-soluble inorganic sulfur components such as sulfate can be removed first by backwashing with water. Then, carbonyl sulfide and / or disulfide-like sulfur-containing components can be converted into hydrogen sulfide and / or thiols through catalytic hydrogenation. Next, hydrogen sulfide can be removed by micro-nano bubble desorption and zinc oxide adsorption. Finally, thiols can be reduced by distillation and reflux side-stream liquid-phase desulfurization. Residues of sulfur-containing compounds and high-boiling sulfur components; furthermore, the backwashing can be a single-stage or multi-stage backwashing; when the sulfate content in the furfural raw material is high, the amount of water used for washing can be increased, or the furfural raw material can be subjected to two or more stages of backwashing treatment; also, in the early dehydration stage of furfural refining, the system pressure, vacuum degree, or backwash gas introduction state can be periodically adjusted to allow the aqueous phase and furfural phase to undergo multiple miscibility and backwashing contacts, thereby improving the efficiency of sulfate entering the aqueous phase and being discharged with the aqueous phase.

[0036] After sulfur speciation detection, furfural raw material is fed into water washing backflushing tower 3 via furfural raw material pipeline 2. Water washing backflushing tower 3 can be a packed tower, plate tower, mixing clarifier, or liquid-liquid contact equipment with backflushing structure. Water enters water washing backflushing tower 3 through water inlet pipeline 4, and backflushing gas enters water washing backflushing tower 3 through backflushing gas inlet pipeline 5. Backflushing gas can be compressed air, nitrogen, or inert gas, preferably nitrogen or inert gas. The operating temperature of water washing backflushing tower 3 can be controlled at 20℃~60℃, the volume ratio of water to furfural raw material can be controlled at 0.05:1~0.5:1, and the backflushing gas pressure can be controlled at 0.05MPa~0.5MPa. Through the contact between the aqueous phase and the furfural phase and the disturbance of the backflushing gas, water-soluble inorganic sulfur components such as sulfate enter the aqueous phase and are discharged from the aqueous phase outlet of water washing backflushing tower 3, obtaining desulfated furfural. Furfural after sulfate removal is hereinafter referred to as desulfated furfural.

[0037] After desulfate removal, furfural enters temporary storage tank 6. Temporary storage tank 6 serves two purposes: firstly, to buffer the material after water washing, and secondly, to divert the material to subsequent routes according to the control instructions of control unit 26. The outlet of temporary storage tank 6 is divided into a first route and a second route. The first route enters the distillation column 17 via the desulfate removal furfural bypass pipeline 28, and the second route enters the desulfurization reactor 7. A valve V1 is installed on the desulfate removal furfural bypass pipeline 28, and a valve V2 is installed between temporary storage tank 6 and desulfurization reactor 7. Control unit 26 controls the opening and closing status or opening degree of valves V1 and V2 according to the sulfur composition data, thereby controlling the proportion of material entering the distillation route and the catalytic hydrogenation route.

[0038] After desulfurization, furfural enters the desulfurization reactor 7 and a catalyst is added through the catalyst inlet 8, while hydrogen is introduced through the hydrogen inlet 9. The catalyst can be a nickel-based catalyst, such as a supported nickel catalyst, a nickel-based composite catalyst, or a nickel-containing metal catalyst. The amount of catalyst added can be 0.05% to 0.30% of the mass of furfural, preferably 0.1% to 0.15%. The catalytic hydrogenation reaction temperature can be 65℃ to 90℃, preferably 70℃ to 85℃. The hydrogen pressure can be 1.0MPa to 2.5MPa, preferably 1.5MPa to 1.8MPa. The reaction time can be 0.5h to 4h. Through this step, carbonyl sulfur and / or disulfide sulfur-containing components are converted into hydrogen sulfide and / or thiols, yielding hydrogenated furfural. The disulfide sulfur-containing components include carbon disulfide, organic disulfides, and other convertible organic sulfur components.

[0039] In this invention, disulfide-type sulfur-containing components refer to sulfur-containing components in furfural raw materials that can be transformed under catalytic hydrogenation conditions, containing disulfide bonds or similar convertible sulfur structures. These include carbon disulfide, organic disulfides, and other sulfur-containing components that can be transformed into hydrogen sulfide and / or thiols under catalytic hydrogenation conditions. Disulfide-type sulfur-containing components can be used as detection targets in sulfur speciation data, and can also serve as the basis for the control unit to determine whether to increase the catalytic hydrogenation intensity, increase the proportion of materials entering the desulfurization reactor, and strengthen subsequent micro-nano bubble desorption and zinc oxide adsorption treatment.

[0040] During catalytic hydrogenation, one or more parameters can be monitored through intermittent sampling or online detection, including carbonyl sulfide content, sulfur-containing disulfide content, hydrogen consumption per unit time, and furfural purity changes. When the carbonyl sulfide content is below 1 mg / L to 5 mg / L, the sulfur-containing disulfide content is below 1 mg / L to 5 mg / L, the hydrogen consumption per unit time is below 10% to 30% of the initial hydrogen consumption rate for 10 min to 30 min continuously, or the furfural purity decreases by no more than 0.1% to 1.0%, the catalytic hydrogenation reaction can be stopped or the catalytic hydrogenation intensity can be reduced. This control method helps to reduce over-hydrogenation, allowing the catalytic hydrogenation step to be mainly used for the conversion of sulfur-containing components.

[0041] After hydrogenation conversion, furfural enters catalyst separation tank 10; catalyst separation tank 10 can be a settling tank, filter, centrifuge or other solid-liquid separation equipment; the separated catalyst can be reused according to its active state, or it can be discharged as catalyst waste liquid through catalyst waste liquid outlet 11; after catalyst separation, furfural is sent to micro-nano bubble desorption tank 12 through hydrogenation conversion furfural pipeline 29; a valve V3 can be installed between catalyst separation tank 10 and micro-nano bubble desorption tank 12, and control unit 26 can control the opening degree or opening and closing state of valve V3 according to the processing route requirements.

[0042] A microporous gas distributor 14 is installed inside the micro-nano bubble desorption vessel 12. The desorption gas enters the microporous gas distributor 14 through the desorption gas inlet 13 and forms tiny bubbles in the furfural liquid phase. The desorption gas can be nitrogen, carbon dioxide, or an inert gas, preferably nitrogen. The desorption temperature of the micro-nano bubble desorption vessel 12 can be 20℃~90℃, preferably 40℃~70℃. The desorption time can be 5min~120min, preferably 20min~60min. The gas-liquid volume ratio can be 0.5:1~100:1, preferably 1:1~50:1. The pore size of the microporous gas distributor 14 can be 0.1μm~200μm, preferably 0.5μm~100μm. Through micro-nano bubble desorption, hydrogen sulfide dissolved in the furfural liquid phase is transferred to the gas phase to form desorption gas. The liquid phase after desorption is the furfural after hydrogenation desorption.

[0043] The desorbed gas is discharged from the micro-nano bubble desorber 12 through the desorbed gas outlet pipeline 15 and merges with the top gas phase of the distillation column 17 before entering the zinc oxide adsorption column 20. The zinc oxide adsorption column 20 is filled with zinc oxide adsorbent to adsorb hydrogen sulfide in the desorbed gas and the top gas phase. One, two or more zinc oxide adsorption columns 20 can be set. When two or more zinc oxide adsorption columns 20 are set, each adsorption column can be connected in series, in parallel, in one-on-one standby, or in a series-parallel combination. A hydrogen sulfide detection point can be set at the outlet of the zinc oxide adsorption column 20. When the outlet hydrogen sulfide concentration reaches the set threshold, the control unit 26 switches the operating mode of the zinc oxide adsorption column 20 or prompts to replace the zinc oxide adsorbent.

[0044] After hydrotreating, furfural enters the distillation column 17 via the post-hydrotreating furfural pipeline 16. A valve V4 can be installed on the post-hydrotreating furfural pipeline 16, and the control unit 26 can control the opening degree or opening / closing state of the valve V4. The distillation column 17 can be a packed column, a plate column, or other equipment suitable for furfural distillation. The reflux ratio of the distillation column 17 can be controlled to be 0.5:1 to 5:1, and the temperature of the column bottom 18 can be controlled to be 160℃ to 230℃. The residual liquid in the column bottom can be controlled to be 0.5% to 5% of the feed mass at the end of distillation or during continuous operation. During the distillation process, mercaptans and / or sulfur-containing high-boiling components are enriched in the column bottom 18 and discharged through the column bottom residual liquid outlet 19. A valve V6 can be installed at the column bottom residual liquid outlet 19, and the control unit 26 can adjust the opening degree of the valve V6 according to the sulfur speciation data, the total sulfur content of the column bottom residual liquid, or the total sulfur content of the product.

[0045] The vapor phase from the top of distillation column 17 merges with the desorbed gas from micro-nano bubble desorption tank 12 and enters zinc oxide adsorption column 20. The vapor phase treated by zinc oxide adsorption column 20 enters condenser 21, and the resulting condensate enters reflux tank 22. At least a portion of the condensate in reflux tank 22 enters liquid phase desulfurization protector 23. The condensate entering liquid phase desulfurization protector 23 can be 5% to 100% of the total condensate in reflux tank 22. The operating temperature of liquid phase desulfurization protector 23 can be 20℃ to 90℃, and the liquid hourly space velocity can be 0.1 h⁻¹. -1 ~10h -1 The liquid phase desulfurization protector 23 is filled with liquid phase desulfurization material, which can be one or more of the following: metal oxide adsorbent, supported metal oxide adsorbent, modified activated carbon, metal ion exchange resin, alkaline ion exchange resin, copper-loaded porous adsorbent, zinc-loaded porous adsorbent, iron-loaded porous adsorbent, nickel-loaded porous adsorbent, and silver-loaded porous adsorbent. After being treated by the liquid phase desulfurization protector 23, part of the condensate is returned to the distillation column 17 via the reflux line 24, and the other part is collected via the low-sulfur furfural product collection line 25 to obtain the low-sulfur furfural product. A valve V5 can be installed on the reflux line 24, and the control unit 26 can control the opening degree or opening and closing state of the valve V5.

[0046] In one optional embodiment, the zinc oxide adsorption column can be set as an independent adsorption column between the top vapor line and the condenser of the distillation column; or it can be integrated as an adsorption section filled with zinc oxide solid adsorbent in the top region of the distillation column to remove hydrogen sulfide from the top vapor before condensation. The bottom liquid discharged from the bottom liquid outlet can be sent to the recovery column for furfural recovery. The recovered high-sulfur residue is centrally treated or utilized as a by-product residue. The sulfate-enriched aqueous phase discharged from the water washing backflushing column can be recovered or returned to a suitable water treatment unit in the furfural production system according to its furfural entrainment, so as to reduce wastewater discharge and reduce residue treatment costs.

[0047] The control unit 26 is connected to one or more of the following via signal line 27: sulfur speciation detection unit 1, water washing backflushing tower 3, temporary storage tank 6, desulfurization reactor 7, micro-nano bubble desorption tank 12, zinc oxide adsorption column 20, reflux tank 22, and liquid phase desulfurization protector 23. The control unit 26 can also be connected to valves V1, V2, V3, V4, V5, and V6, and adjust the opening or closing status of each valve according to data such as sulfur speciation composition, hydrogen sulfide concentration at the zinc oxide adsorption column outlet, total sulfur content in the reflux tank condensate, and total sulfur content in the product. In this way, the water washing intensity, hydrogenation intensity, desorption intensity, adsorption operation mode, reflux ratio, tower bottom residual liquid discharge ratio, and liquid phase desulfurization treatment ratio can be adjusted.

[0048] Example 1: Complete treatment of compound sulfur-type furfural A batch of complex sulfur-type furfural raw material was selected as the treatment target. The total sulfur content of this batch of furfural raw material was detected by sulfur speciation detection unit 1, which showed that the total sulfur content was 48.6 mg / kg, the furfural purity was 98.72%, the moisture content was 0.18%, the acidity was 0.043 mg KOH / g, and the color was 35 Hazen. The sulfur speciation detection results showed that this batch of furfural raw material contained sulfate sulfur, carbonyl sulfur, disulfide sulfur, hydrogen sulfide, mercaptan sulfur, and sulfur-containing high-boiling components. Control unit 26 determined that this batch of furfural was complex sulfur-type and executed the complete treatment route.

[0049] Furfural feedstock first enters water washing backflushing tower 3; the water washing temperature is controlled at 35℃, the volume ratio of water to furfural feedstock is 0.2:1, nitrogen is used for backflushing, and the backflushing gas pressure is 0.2MPa; after desulfate removal, furfural enters temporary storage tank 6. The control unit 26 controls the outlet diversion of temporary storage tank 6 according to the sulfur morphology data, so that most of the material enters desulfurization reactor 7, and a small portion of the material enters distillation tower 17 through furfural bypass pipeline 28 after desulfate removal.

[0050] The furfural entering the desulfurization reactor 7 is added with a nickel-based catalyst at a rate of 0.12% of the furfural mass. The hydrogen pressure is 1.6 MPa, the reaction temperature is 80°C, and the reaction time is 2 hours. After the reaction, the material enters the catalyst separation tank 10 for solid-liquid separation. The furfural after catalyst separation enters the micro-nano bubble desorption tank 12.

[0051] A microporous gas distributor 14 is disposed inside the micro-nano bubble desorption tank 12 and is connected to the desorption gas inlet 13. After the desorption gas enters the microporous gas distributor 14 through the desorption gas inlet 13, it is dispersed into the furfural liquid phase through multiple micropores of the microporous gas distributor 14, forming fine bubbles. During the rising process of the fine bubbles in the furfural liquid phase, they come into full contact with the furfural liquid phase, causing the hydrogen sulfide dissolved in the furfural liquid phase to transfer to the gas phase, thereby obtaining the desorption gas and the hydrogenated desorption furfural.

[0052] The microporous gas distributor 14 can be a sintered metal microporous tube, a sintered metal microporous plate, a ceramic microporous distributor, a porous polytetrafluoroethylene distributor, a porous titanium material distributor, a microporous aeration head, or other gas distribution components capable of dispersing the desorbed gas into fine bubbles; the pore size of the microporous gas distributor 14 can be 0.1μm to 200μm, preferably 0.5μm to 100μm; by setting the microporous gas distributor 14, the gas-liquid contact area between the desorbed gas and the furfural liquid phase can be increased, the efficiency of hydrogen sulfide transfer from the liquid phase to the gas phase can be improved, and the residue of hydrogen sulfide in the furfural liquid phase can be reduced.

[0053] Nitrogen is used as the desorption gas in the micro-nano bubble desorption tank 12. The desorption temperature is 55℃, the desorption time is 40 min, and the gas-liquid volume ratio is 10:1. The desorption gas enters the zinc oxide adsorption column 20 after merging with the gas phase at the top of the distillation column 17 through the desorption gas outlet pipeline 15. The zinc oxide adsorption column 20 adopts a two-column series operation mode.

[0054] After hydrogenation and desorption, furfural enters distillation column 17; the reflux ratio of distillation column 17 is 2:1, the temperature of the bottom 18 is controlled at 185℃, and the bottom residue accounts for 1.7% of the feed mass; the gas phase after treatment by zinc oxide adsorption column 20 enters condenser 21 for condensation, and the condensate enters reflux tank 22; 50% of the condensate in reflux tank 22 enters liquid phase desulfurization protector 23 for treatment, the operating temperature of liquid phase desulfurization protector 23 is 45℃, and the liquid hourly space velocity is 1.5 h⁻¹. -1 The packing material is a mixed packing material of zinc-modified activated carbon and metal oxide adsorbent; part of the condensate after treatment is returned to the distillation column 17 via reflux line 24, and the other part is collected via low-sulfur furfural product collection line 25 to obtain low-sulfur furfural product.

[0055] Under the above conditions, the total sulfur content of the obtained low-sulfur furfural product was 4.7 mg / kg, the furfural purity was 99.01%, the moisture content was 0.08%, the acidity was 0.016 mg KOH / g, and the color was 23 Hazen.

[0056] To compare the effects of different treatment routes on the total sulfur content of furfural, the same batch of furfural raw materials was used for treatment, and the results are shown in Table 1.

[0057] Table 1. Effects of different treatment routes on furfural product quality

[0058] As shown in Table 1, when only water washing and backflushing are used, the total sulfur content is reduced from 48.6 mg / kg to 37.0 mg / kg, mainly due to the reduction of water-soluble sulfur components; when only conventional distillation is used, the total sulfur content is reduced to 28.1 mg / kg, but there are still a lot of sulfur-containing components remaining; after adopting the complete treatment route of this invention, the total sulfur content of the product is reduced to 4.7 mg / kg, the total sulfur removal rate reaches 90.3%, and at the same time, the furfural purity, moisture, acidity and color do not show any adverse changes.

[0059] Further sulfur speciation analysis was performed on some of the above samples, and the results are shown in Table 2.

[0060] Table 2. Changes in sulfur speciation under different treatment methods

[0061] As shown in Table 2, water washing backflushing significantly reduces sulfate sulfur, but has little effect on carbonyl sulfur, disulfide sulfur, and thiol sulfur. Conventional distillation can reduce some thiol sulfur and high-boiling sulfur-containing components, but it is insufficient for treating convertible organic sulfur components such as carbonyl sulfur and disulfide sulfur. The complete treatment route of this invention can simultaneously reduce sulfate sulfur, carbonyl sulfur, disulfide sulfur, hydrogen sulfide, thiol sulfur, and high-boiling sulfur-containing components, indicating that each treatment unit has a corresponding effect on different sulfur forms.

[0062] Example 2: Treatment of furfural dominated by inorganic sulfur A batch of furfural raw material with a high sulfate sulfur content is taken. After being detected by the sulfur speciation detection unit 1, the control unit 26 determines that the batch of furfural raw material is dominated by inorganic sulfur. During processing, the control unit 26 increases the washing intensity and backflushing intensity of the water washing backflushing tower 3, controls the volume ratio of water to furfural raw material to 0.3:1, controls the water washing temperature to 40℃, uses nitrogen as the backflushing gas, and controls the backflushing gas pressure to 0.3MPa. After washing and desulfate removal, the furfural enters the temporary storage tank 6. The control unit 26 increases the opening of valve V1 and decreases the opening of valve V2, so that most of the desulfate removal furfural enters the distillation tower 17 through the desulfate removal furfural bypass pipeline 28.

[0063] The reflux ratio of distillation column 17 is controlled at 2:1, the bottom temperature is controlled at 180℃~190℃, and the bottom residue accounts for 1.5% of the feed mass. The gas phase at the top of the column is treated by zinc oxide adsorption column 20 and then enters condenser 21. The condensate enters reflux tank 22. 30%~50% of the condensate in reflux tank 22 is treated by liquid phase desulfurization protector 23 and then refluxed or collected as product. This treatment method reduces the amount of catalytic hydrogenation and is suitable for furfural feedstock with low carbonyl sulfur and disulfide sulfur content and mainly requires the removal of water-soluble inorganic sulfur.

[0064] Example 3: Treatment of furfural dominated by convertible organic sulfur A batch of furfural raw material with relatively high contents of carbonyl sulfur, carbon disulfide, and organic disulfides is taken. After sulfur speciation detection, the control unit 26 determines that the batch of furfural is dominated by convertible organic sulfur. The furfural raw material first enters the water washing backflushing tower 3 for pretreatment. The water washing temperature is controlled at 35℃, the volume ratio of water to furfural raw material is controlled at 0.15:1, and the backflushing gas pressure is controlled at 0.2MPa. After water washing, the furfural enters the temporary storage tank 6. The control unit 26 increases the opening of valve V2, so that most of the material enters the desulfurization reactor 7.

[0065] A nickel-based catalyst is added to desulfurization reactor 7 at a concentration of 0.15% of the furfural mass. The hydrogen pressure is controlled at 1.8 MPa, the reaction temperature at 85°C, and the reaction time at 2-3 hours. During the reaction, samples can be taken at intervals to detect the content of carbonyl sulfide and disulfide-containing sulfur components, or to monitor the hydrogen consumption per unit time. When the carbonyl sulfide and disulfide-containing sulfur components decrease to the set range, or when the hydrogen consumption per unit time is lower than 10%-30% of the initial hydrogen consumption rate for 10-30 minutes consecutively, hydrogen addition is stopped or the hydrogen addition intensity is reduced.

[0066] After hydrogenation, furfural is separated from the catalyst in catalyst separator 10 and then enters micro-nano bubble desorption tank 12. Nitrogen is used as the desorption gas in micro-nano bubble desorption tank 12, the desorption temperature is 60℃, the desorption time is 50 min, and the gas-liquid volume ratio is 20:1. The desorption gas merges with the top gas phase of distillation column 17 and then enters zinc oxide adsorption column 20. The desorbed furfural enters distillation column 17 for distillation. This embodiment utilizes catalytic hydrogenation to convert organic sulfur components that are difficult to remove directly by water washing or distillation into hydrogen sulfide and / or thiols, which are easier to process later.

[0067] Example 4: Treatment of furfural dominated by volatile sulfur A batch of furfural raw material with a relatively high hydrogen sulfide content is taken; after being detected by the sulfur speciation detection unit 1, the control unit 26 determines it to be dominated by volatile sulfur; after the furfural raw material is washed and backflushed by water washing tower 3 to remove water-soluble inorganic sulfur, it is selected whether to enter the desulfurization reactor 7 according to the content of carbonyl sulfur and disulfide sulfur; when the organic sulfur content is low, some material can be directly entered into the distillation tower 17 after desulfurization and furfural bypass pipeline 28; when it still contains a certain amount of convertible organic sulfur, the material enters the micro-nano bubble desorption tank 12 after passing through the desulfurization reactor 7 and catalyst separation tank 10.

[0068] In this embodiment, the control unit 26 increases the desorption intensity of the micro-nano bubble desorption tank 12. Nitrogen is used as the desorption gas, the desorption temperature is controlled at 50℃~65℃, the desorption time is controlled at 40min~60min, and the gas-liquid volume ratio is controlled at 20:1~40:1. The desorption gas enters the zinc oxide adsorption column 20 after merging with the top gas phase of the distillation column 17 through the desorption gas outlet pipeline 15. The zinc oxide adsorption column 20 adopts a two-column series operation mode. The first adsorption column is used to mainly adsorb hydrogen sulfide, and the second adsorption column is used for protective desulfurization. When the hydrogen sulfide concentration at the outlet of the zinc oxide adsorption column 20 reaches the set threshold, the control unit 26 switches the adsorption column operation mode or prompts to replace the adsorbent.

[0069] Example 5: Treatment of furfural dominated by high-boiling sulfur-containing components A batch of furfural raw material with a high proportion of thiol compounds and high-boiling sulfur components is taken. After sulfur speciation detection, the control unit 26 determines that the batch of furfural is dominated by high-boiling sulfur components. After water washing, backflushing and necessary hydrogenation treatment, the furfural enters the distillation column 17. The reflux ratio of the distillation column 17 is controlled at 2:1 to 3:1, the temperature of the column bottom 18 is controlled at 180℃ to 200℃, and the valve V6 is adjusted according to the enrichment of sulfur components in the column bottom residue so that the column bottom residue accounts for 1.5% to 3.0% of the feed mass.

[0070] Simultaneously, the control unit 26 increases the proportion of condensate entering the liquid phase desulfurization protector 23, so that 30% to 100% of the condensate in the return tank 22 enters the liquid phase desulfurization protector 23; the operating temperature of the liquid phase desulfurization protector 23 is controlled at 40℃ to 60℃, and the liquid hourly space velocity is controlled at 1.0 h⁻¹. -1 ~3.0h -1 The liquid phase desulfurization materials used are modified activated carbon, supported metal oxide adsorbents, or metal ion exchange resins. By combining distillation column bottom discharge with liquid phase protection treatment, the impact of mercaptans and high-boiling sulfur-containing components on the total sulfur content of the product can be reduced.

[0071] Example 6: Adaptation treatment of different types of furfural raw materials To illustrate the adaptability of this invention to different batches of furfural raw materials, five batches of furfural raw materials from different sources or different production batches were taken. First, the total sulfur content and main sulfur species composition were detected by the sulfur species detection unit 1. Then, the control unit 26 selected the processing route and processing intensity based on the sulfur species composition data. The processing results are shown in Table 3.

[0072] Table 3 Treatment effects of furfural feedstock with different sulfur forms

[0073] As shown in Table 3, there are differences in the total sulfur content and sulfur speciation of different batches of furfural raw materials. By selecting the appropriate treatment route and treatment intensity based on the sulfur speciation data, furfural products with lower total sulfur content can be obtained for different types of raw materials. For compound sulfur-type raw materials, the total sulfur content was reduced from 52.3 mg / kg to 5.0 mg / kg after adopting the complete treatment route. For inorganic sulfur-dominated or high-boiling sulfur-containing component-dominated raw materials, the total sulfur content can be reduced by strengthening the corresponding treatment units without having to adopt the highest intensity treatment conditions for all batches.

[0074] Example 7: The effect of the treatment ratio of the liquid phase desulfurization protector on the total sulfur content of the product. To investigate the effect of the liquid phase desulfurization protector 23 on the fluctuation of the total sulfur content of the product, under the same front-end treatment conditions, the proportion of the top condensate entering the liquid phase desulfurization protector 23 was adjusted, and the total sulfur content, mercaptan sulfur content, hydrogen sulfide content and furfural purity of the product were measured; the results are shown in Table 4.

[0075] Table 4. Effect of the treatment ratio of the liquid phase desulfurization protector on the total sulfur content of the product.

[0076] As shown in Table 4, the total sulfur content of the product gradually decreases as the proportion of condensate entering the liquid phase desulfurization protector 23 increases. When the treatment ratio increases from 0 to 50%, the total sulfur content of the product decreases from 8.8 mg / kg to 4.7 mg / kg. When the treatment ratio continues to increase to 100%, the total sulfur content further decreases to 4.1 mg / kg. This result indicates that the liquid phase desulfurization protector 23 can supplement and remove trace sulfur-containing components that are residual or entrained in the condensate at the top of the tower, which is beneficial to reducing the fluctuation of the total sulfur content of low-sulfur furfural products.

[0077] Furthermore, in a preferred embodiment of the present invention, the control unit 26 not only determines the treatment route and treatment intensity based on the initial sulfur form composition data of the furfural raw material to be treated, but also calculates the removal load, conversion load and residual load of different sulfur-containing components in each treatment unit based on the intermediate sulfur form detection data obtained before and after each treatment unit. Based on this, it performs closed-loop adjustment of the water washing backwash intensity, the proportion of material entering the desulfurization reactor 7, the catalytic hydrogenation intensity, the micro-nano bubble desorption intensity, the operation mode of the zinc oxide adsorption column 20, the proportion of residual liquid discharged from the tower bottom, and the proportion of condensate entering the liquid phase desulfurization protector 23.

[0078] Specifically, one or more sulfur speciation detection points or sampling points can be set at the outlet of the water washing backwash tower 3, the outlet of the desulfurization reactor 7, the outlet of the micro-nano bubble desorption tank 12, the outlet of the zinc oxide adsorption column 20, the outlet of the reflux tank 22, and the low-sulfur furfural product collection pipeline 25. The control unit 26 calculates the removal rate, conversion rate, or residual rate of each sulfur-containing component based on one or more of the following obtained from the above detection points: sulfate sulfur content, carbonyl sulfur content, disulfide sulfur-containing component content, hydrogen sulfide content, mercaptan compound content, high-boiling sulfur-containing component content, and total sulfur content.

[0079] When the sulfate residue rate at the outlet of the water washing backflushing tower 3 is higher than the set value, the control unit 26 increases the water inlet flow rate of the water inlet pipeline 4, increases the backflushing gas flow rate or pressure of the backflushing gas inlet pipeline 5, or reduces the proportion of material that directly enters the distillation tower 17 via the furfural bypass pipeline 28 after sulfate removal; when the conversion rate of carbonyl sulfur and / or disulfide sulfur-containing components at the outlet of the desulfurization reactor 7 is lower than the set value, the control unit 26 increases the proportion of material entering the desulfurization reactor 7, extends the catalytic hydrogenation time, increases the hydrogen pressure, or increases the catalyst addition amount; when the micro-nano... When the residual hydrogen sulfide rate at the outlet of the bubble desorption tank 12 is higher than the set value, the control unit 26 increases the desorption gas flow rate, extends the desorption time, or increases the desorption temperature; when the hydrogen sulfide concentration at the outlet of the zinc oxide adsorption column 20 reaches the warning threshold, the control unit 26 switches the series, parallel, or standby operation status of the zinc oxide adsorption column 20; when the total sulfur content at the outlet of the reflux tank 22 or at the low-sulfur furfural product collection pipeline 25 is higher than the target value, the control unit 26 increases the proportion of condensate entering the liquid phase desulfurization protector 23 and increases the discharge proportion of the tower bottom residual liquid outlet 19.

[0080] Through the above-mentioned closed-loop regulation method, the present invention can dynamically allocate the treatment load of sulfur-containing components with different sulfur forms according to the sulfur form composition of furfural raw materials and the actual desulfurization effect of each treatment unit, so as to avoid insufficient desulfurization or over-treatment caused by a single fixed treatment route, and can stably control the total sulfur content of low sulfur furfural products when the sulfur form of different batches of furfural raw materials fluctuates.

[0081] The above embodiments illustrate the application of the present invention in furfural raw materials with different sulfur forms. In actual production, the specific values ​​will vary depending on the source of furfural raw materials, sulfur form composition, equipment scale, and target product indicators. Those skilled in the art can adjust the values ​​within the parameter range disclosed in the present invention. Any technical solution that uses the method of determining the treatment route and / or treatment intensity based on the sulfur form composition data, and performs segmented treatment of different sulfur-containing components in furfural through corresponding steps in water washing backflushing, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation, and reflux side-stream liquid phase fine desulfurization, falls within the technical concept scope of the present invention.

Claims

1. A method and apparatus for reducing the total sulfur content of furfural products, characterized in that: Includes the following steps: The furfural raw material to be treated is subjected to sulfur form detection by sulfur form detection unit (1) to obtain sulfur form composition data. The sulfur form composition data includes total sulfur content, as well as the content and / or proportion of one or more sulfur-containing components among sulfate, carbonyl sulfur, disulfide sulfur-containing components, hydrogen sulfide, mercaptan compounds and sulfur-containing high-boiling components. The control unit (26) determines one or more treatment routes and / or treatment intensities among water washing backwash, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation and reflux side-stream liquid phase fine desulfurization based on sulfur speciation data. After sulfur speciation detection, furfural raw material is sent to water washing backflushing tower (3) through furfural raw material pipeline (2). Water is introduced into water washing backflushing tower (3) through water inlet pipeline (4), and backflushing gas is introduced into water washing backflushing tower (3) through backflushing gas inlet pipeline (5). This allows furfural raw material to come into contact with water and be subjected to backflushing disturbance, so that sulfate ions in furfural raw material enter the aqueous phase, and furfural after sulfate removal is obtained. After desulfate removal, furfural is sent to a temporary storage tank (6). The outlet of the temporary storage tank (6) is divided into a first path and a second path. The first path is connected to the distillation column (17) via the furfural bypass pipeline (28) after desulfate removal, and the second path is connected to the desulfurization reactor (7). The control unit (26) controls the on / off state of the first and second paths and / or the material distribution ratio according to the sulfur form composition data. After desulfurization, furfural entering the desulfurization reactor (7) is given a catalyst through the catalyst inlet (8) and hydrogen is introduced through the hydrogen inlet (9) to convert the carbonyl sulfur and / or disulfide sulfur-containing components in the desulfurized furfural into hydrogen sulfide and / or mercaptan compounds, thus obtaining hydrogenated furfural. After hydrogenation conversion, furfural is sent to a catalyst separation tank (10) to separate the catalyst from the furfural liquid phase. The separated catalyst waste liquid is discharged through the catalyst waste liquid outlet (11). After the catalyst is separated, the furfural after hydrogenation conversion is sent to a micro-nano bubble desorption tank (12) through the furfural pipeline (29). Desorption gas is introduced into the micro-nano bubble desorption tank (12) through the desorption gas inlet (13) and the microporous gas distributor (14), so that hydrogen sulfide dissolved in the furfural liquid phase enters the gas phase, and desorption gas and hydrogenated furfural are obtained. The desorbed gas is combined with the top gas phase of the distillation column (17) via the desorbed gas outlet pipeline (15) and then enters the zinc oxide adsorption column (20) to remove hydrogen sulfide from the desorbed gas and the top gas phase. After hydrogenation and analysis, furfural is sent to a distillation column (17) via the furfural pipeline (16) for distillation, so that thiol compounds and / or sulfur-containing high-boiling components are enriched in the bottom of the column (18) and discharged from the bottom residue outlet (19). The gas phase treated by the zinc oxide adsorption column (20) is condensed in the condenser (21), and the condensate is refluxed into the reflux tank (22). At least a portion of the condensate in the reflux tank (22) is sent to the liquid phase desulfurization protector (23) to further remove residual sulfur-containing components from the condensate; After being treated by the liquid phase desulfurization protector (23), part of the condensate is returned to the distillation tower (17) via the reflux line (24), and the other part is extracted via the low-sulfur furfural product extraction line (25) to obtain the low-sulfur furfural product.

2. The method and apparatus for reducing the total sulfur content of furfural products according to claim 1, characterized in that: The sulfur speciation data include total sulfur content, sulfate sulfur content, carbonyl sulfur content, carbon disulfide content, organic disulfide content, hydrogen sulfide content, mercaptan content, sulfur-containing high-boiling component content, and one or more of the above sulfur-containing components in the total sulfur content. Sulfur speciation was detected using one or more of the following methods: total sulfur analysis, ion chromatography analysis, gas chromatography-chemiluminescence detection of sulfur, gas chromatography-mass spectrometry detection, electrochemical hydrogen sulfide detection, and ultraviolet fluorescence sulfur detection.

3. The method and apparatus for reducing the total sulfur content of furfural products according to claim 1, characterized in that: The control unit (26) classifies the furfural raw material to be treated into inorganic sulfur-dominated, conversion-type organic sulfur-dominated, volatile sulfur-dominated, high-boiling sulfur-containing component-dominated, or composite sulfur-dominated types according to the sulfur form composition data. When the furfural raw material to be treated is inorganic sulfur-dominated, increase the water washing intensity and / or backflushing intensity of the water washing backflushing tower (3), and allow at least part of the desulfated furfural to enter the distillation tower (17) via the desulfated furfural bypass pipeline (28). When the furfural raw material to be treated is dominated by conversion-type organic sulfur, the proportion of material entering the desulfurization reactor (7) is increased, and the catalytic hydrogenation intensity and micro-nano bubble desorption intensity are increased. When the furfural raw material to be processed is dominated by volatile sulfur, the desorption intensity of the micro-nano bubble desorption tank (12) and the adsorption intensity of the zinc oxide adsorption column (20) are increased. When the furfural feedstock to be treated is dominated by high-boiling sulfur-containing components, increase the proportion of residual liquid discharged from the bottom of the distillation column (17) and / or the proportion of condensate entering the liquid phase desulfurization protector (23); When the furfural raw material to be treated is of the complex sulfur type, the following steps are performed in sequence: water washing backflushing, catalytic hydrogenation, micro-nano bubble desorption, zinc oxide adsorption, distillation, and reflux side-stream liquid phase fine desulfurization.

4. The method and apparatus for reducing the total sulfur content of furfural products according to claim 1, characterized in that: The operating temperature of the water washing backflushing tower (3) is 20℃~60℃, and the volume ratio of water to furfural raw material is 0.05:1~0.5:1; The backflush gas is compressed air, nitrogen, or an inert gas, and the pressure of the backflush gas is 0.05 MPa to 0.5 MPa. The bottom or side of the water washing backwash tower (3) is equipped with an aqueous phase outlet for discharging the aqueous phase enriched with sulfate.

5. The method and apparatus for reducing the total sulfur content of furfural products according to claim 1, characterized in that: The catalyst is a nickel-based catalyst, and the amount of catalyst added is 0.05% to 0.30% of the mass of furfural; the reaction temperature for catalytic hydrogenation is 65℃ to 90℃, the hydrogen pressure is 1.0MPa to 2.5MPa, and the reaction time is 0.5h to 4h. The endpoint of catalytic hydrogenation is determined based on one or more of the following: carbonyl sulfur content, sulfur content of disulfide components, hydrogen consumption per unit time, and change in furfural purity.

6. The method and apparatus for reducing the total sulfur content of furfural products according to claim 1, characterized in that: The desorption gas is nitrogen, carbon dioxide or inert gas; the desorption temperature of the micro-nano bubble desorption vessel (12) is 20℃~90℃, the desorption time is 5min~120min, the gas-liquid volume ratio is 0.5:1~100:1, and the pore size of the microporous gas distributor (14) is 0.1μm~200μm.

7. The method and apparatus for reducing the total sulfur content of furfural products according to claim 1, characterized in that: There are one, two or more zinc oxide adsorption columns (20); when there are two or more zinc oxide adsorption columns (20), the multiple zinc oxide adsorption columns (20) are operated in series, in parallel, in a one-in-use or series-parallel combination manner. A hydrogen sulfide detection point is set at the outlet of the zinc oxide adsorption column (20). When the hydrogen sulfide concentration at the outlet of the zinc oxide adsorption column (20) reaches the set threshold, the control unit (26) switches the operating mode of the zinc oxide adsorption column (20) or prompts to replace the zinc oxide adsorbent.

8. The method and apparatus for reducing the total sulfur content of furfural products according to claim 1, characterized in that: The reflux ratio of the distillation column (17) is 0.5:1 to 5:1, the temperature of the column bottom (18) is 160℃ to 230℃, and the residual liquid in the column bottom at the end of distillation accounts for 0.5% to 5% of the feed mass; the condensate sent to the liquid phase desulfurization protector (23) is 5% to 100% of the total condensate in the reflux tank (22); The operating temperature of the liquid phase desulfurization protector (23) is 20℃~90℃, and the liquid space velocity is 0.1h. -1 ~10h -1 ; The liquid phase desulfurization protector (23) is filled with liquid phase desulfurization material, which is one or more of the following: metal oxide adsorbent, supported metal oxide adsorbent, modified activated carbon, metal ion exchange resin, alkaline ion exchange resin, copper-loaded porous adsorbent, zinc-loaded porous adsorbent, iron-loaded porous adsorbent, nickel-loaded porous adsorbent, and silver-loaded porous adsorbent.

9. An apparatus for reducing the total sulfur content of furfural products by implementing the method according to any one of claims 1 to 8, characterized in that, include: Sulfur Speciation Detection Unit (1), Furfural Raw Material Pipeline (2), Water Washing Backflushing Tower (3), Water Inlet Pipeline (4), Backflushing Gas Inlet Pipeline (5), Temporary Storage Tank (6), Desulfurization Reactor (7), Catalyst Inlet (8), Hydrogen Inlet (9), Catalyst Separation Tank (10), Catalyst Waste Liquid Outlet (11), Micro-Nano Bubble Desorption Tank (12), Desorption Gas Inlet (13), Microporous Gas Distributor (14), Desorption Gas Outlet Pipeline (15), Furfural Pipeline After Hydrogenation Desorption (16), Distillation Tower (17), Tower Boiler (18), Tower Boiler Residual Liquid Outlet (19), Zinc Oxide Adsorption Column (20), Condenser (21), Reflux Tank (22), Liquid Phase Desulfurization Protector (23), Reflux Pipeline (24), Low-Sulfur Furfural Product Outlet Pipeline (25), Control Unit (26), Signal Line (27), Furfural Bypass Pipeline After Desulfate (28), and Furfural Pipeline After Hydrogenation Conversion (29); Among them, the sulfur speciation detection unit (1) is connected to the water washing backflushing tower (3) through the furfural raw material pipeline (2); the water washing backflushing tower (3) is connected to the water inlet pipeline (4), the backflushing gas inlet pipeline (5) and the temporary storage tank (6) respectively, and the bottom or side of the water washing backflushing tower (3) is provided with a water phase outlet for discharging the sulfate-enriched aqueous phase; the temporary storage tank (6) is connected to the distillation tower (17) through the desulfurization furfural bypass pipeline (28), and is connected to the desulfurization reactor (7) through another pipeline; the desulfurization reactor (7) is connected to the catalyst inlet (8), the hydrogen inlet (9) and the catalyst separation tank (10) respectively; the catalyst separation tank (10) is connected to the catalyst waste liquid outlet (11) and the furfural pipeline (29) after hydrogenation conversion respectively; the furfural pipeline (29) after hydrogenation conversion is connected to the micro-nano bubble desorption tank (12); the micro-nano bubble desorption tank (12) is connected to the water inlet pipeline (4), the backflushing gas inlet pipeline (5) and the temporary storage tank (6) respectively. The desorbed gas inlet (13), microporous gas distributor (14), desorbed gas outlet pipeline (15), and post-hydrogenated furfural pipeline (16) are connected; the post-hydrogenated furfural pipeline (16) is connected to the distillation column (17); the desorbed gas outlet pipeline (15) merges with the top gas phase pipeline of the distillation column (17) and is then connected to the zinc oxide adsorption column (20); the zinc oxide adsorption column (20) is connected in sequence to the condenser (21), the reflux tank (2), and the condenser (2), the microporous gas distributor (14), the desorbed gas outlet pipeline (15), and the top gas phase pipeline of the distillation column (17) and then to the zinc oxide adsorption column (20); the zinc oxide adsorption column (20) is connected in sequence to the condenser (21), the reflux tank (2), and the condenser (2), the microporous gas distributor (14), the desorbed gas outlet pipeline (15), and the top gas phase pipeline (16). 2) Connected to the liquid phase desulfurization protector (23); the distillation column (17) is connected to the column bottom (18), the column bottom residual liquid outlet (19), the furfural pipeline after hydrogenation and desorption (16), the furfural bypass pipeline after desulfurization (28), and the column top gas phase pipeline respectively; the liquid phase desulfurization protector (23) is connected to the distillation column (17) through the reflux pipeline (24) and connected to the product outlet end through the low sulfur furfural product outlet pipeline (25); The control unit (26) is connected via signal line (27) to one or more of the following: sulfur form detection unit (1), water washing backflushing tower (3), temporary storage tank (6), desulfurization reactor (7), micro-nano bubble desorption tank (12), zinc oxide adsorption column (20), reflux tank (22) and liquid phase desulfurization protector (23).

10. The apparatus according to claim 9, characterized in that: A valve V1 is installed on the furfural bypass line (28) after sulfate removal; a valve V2 is installed between the temporary storage tank (6) and the desulfurization reactor (7); a valve V3 is installed between the catalyst separation tank (10) and the micro-nano bubble desorption tank (12); a valve V4 is installed on the furfural line (16) after hydrogenation desorption between the micro-nano bubble desorption tank (12) and the distillation column (17); a valve V5 is installed on the reflux line (24) between the liquid phase desulfurization protector (23) and the distillation column (17); and a valve V6 is installed at the bottom residue outlet (19). The control unit (26) controls the opening or closing state of one or more of valves V1, V2, V3, V4, V5 and V6 based on the sulfur composition data obtained by the sulfur form detection unit (1).

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