Sulfur recovering method and sulfur recycling system

Abstract

The purpose of the present invention is to provide a sulfur recovering method with which the amount of CO2 discharged can be reduced without requiring treatment in a high temperature environment.　In order to solve the abovementioned problem, the present invention provides a method for recovering sulfur from a used desulfurizing agent, the method being characterized in that sulfur is extracted from the desulfurizing agent by using a solvent comprising carbon disulfide, and then recovered.

Description

Sulfur recovery method and sulfur recycling system

[0001] The present invention relates to a method for recovering sulfur and a sulfur recycling system.

[0002] In response to environmental issues, there is a need to shift away from fossil fuels and towards non-renewable resources for the raw materials used in tires. The same is true for sulfur, one of the raw materials used in tires, and alternative technologies are needed. For example, sulfur recycling systems using biomass are being considered as a new energy source to replace fossil fuels, and sustainable sulfur can be obtained by using such technologies.

[0003] Among biomass fuels, gaseous fuels, i.e., biogas, are gases obtained by fermentation (methane fermentation), anaerobic digestion, and the like. Biogas is a non-exhaustible renewable resource, and the fuel components (e.g., methane) in the gas can be used directly or combusted to generate electricity, making it a promising energy source with high versatility. Typically, such biomass fuels contain sulfur compounds, particularly hydrogen sulfide, due to the raw materials and production process. Because this hydrogen sulfide has adverse effects such as corrosion of peripheral equipment, it is common to remove (desulfurize) it before using it as an energy source (see, for example, Patent Document 1).

[0004] Here, sulfur is known to undergo a vulcanization reaction with double-bond-containing polymers. Such vulcanization technology has been widely used, particularly in the rubber field, and has supported industrial development. Sulfur used for industrial purposes is mainly produced from hydrogen sulfide, a by-product of the hydrodesulfurization of crude oil, i.e., derived from fossil resources. From the perspective of preserving the global environment and realizing a sustainable society, it is essential to establish a recycling system for such sulfur. In this regard, for example, hydrogen sulfide contained in biogas is currently removed as described above, and technologies for recycling sulfur from such removed hydrogen sulfide are currently being developed and investigated.

[0005] JP 2012-101139 A JP 2003-514952 A

[0006] However, when the sulfur recycling technology as described above was examined, it was found that although biomass-derived sulfur could be obtained, conventional methods were used for the step of recovering sulfur from the removed hydrogen sulfide. As such a sulfur recovery method, for example, a technology disclosed in Patent Document 2 is known in which the Claus process is carried out in a high-temperature environment to recover sulfur. When the Claus process is used, energy can be used efficiently in the process of producing sulfur from crude oil, but when applied to the recovery of biomass-derived sulfur, a large amount of energy is required to achieve a high-temperature environment. As a result, CO ２ There were further environmental and operational challenges, such as increased emissions.

[0007] Therefore, no processing in a high-temperature environment is required, and CO ２ Another object of the present invention is to provide a sulfur recovery method that can reduce CO emissions by incorporating the sulfur recovery method of the present invention. ２ The present invention provides a sulfur recycling system using biomass that can reduce emissions and is constructed to be industrially applicable.

[0008] The present invention provides a method for recovering sulfur from a used desulfurizing agent, comprising extracting and recovering sulfur from the desulfurizing agent using a solvent comprising carbon disulfide. The sulfur recovery method having the above configuration does not require treatment in a high-temperature environment, and can recover sulfur by removing CO ２ Emissions can be reduced.

[0009] A sulfur recycling system using biomass, comprising: a desulfurization step of desulfurizing biomass or a biomass treatment product to remove sulfur-containing substances from the biomass or the biomass treatment product; a recovery step of recovering sulfur from the desulfurization residue generated in the desulfurization step; a processing step of processing the recovered sulfur into sulfur for vulcanization; a kneading step of kneading the sulfur for vulcanization with a double bond-containing polymer; and a vulcanization step of vulcanizing the double bond-containing polymer, wherein the recovery step of recovering sulfur comprises extracting and recovering sulfur from the desulfurizing agent using a solvent made of carbon disulfide. ２ This can be a sulfur recycling system using biomass that can reduce emissions and is constructed for industrial application.

[0010] According to the present invention, no treatment in a high temperature environment is required, and CO ２ Furthermore, according to the present invention, a sulfur recovery method can be provided that can reduce CO emissions by incorporating the sulfur recovery method of the present invention. ２ It is possible to provide a sulfur recycling system using biomass that can reduce emissions and is constructed for industrial application.

[0011] FIG. 1 is a flow diagram showing a process for recovering sulfur from a used desulfurizing agent according to one embodiment of the present invention.

[0012]

[0013] Hereinafter, one embodiment of the sulfur recovery method and sulfur recycling system (hereinafter, sometimes simply referred to as the "recovery method" and "recycle system") of the present invention will be specifically illustrated and described. Here, FIG. 1 is a schematic diagram showing the flow of the sulfur recovery method according to one embodiment of the present invention. <Sulfur Recovery Method> The sulfur recovery method of the present invention is a method for recovering sulfur from a used desulfurizing agent. As shown in FIG. 1, the present invention relates to a method for recovering sulfur from carbon disulfide (CS). ２ The method is characterized in that sulfur is extracted from the desulfurizing agent using a solvent consisting of

[0014] The inventors of the present invention have investigated a method for recovering sulfur from a used desulfurization agent, and have found that hydrogen sulfide (H ２ As a result of further intensive research, it was found that carbon disulfide (CS) was isolated into sulfur (S) over time. ２ As a result, the sulfur recovery method of the present invention does not require complicated processes or treatment in a high-temperature environment, and therefore, sulfur can be recovered by a relatively simple process, and CO ２ This makes it possible to reduce emissions.

[0015] The desulfurizing agent used for sulfur recovery is not particularly limited as long as it is a used one. From the viewpoint of sustainability, for example, a desulfurizing agent used for the purpose of removing hydrogen sulfide generated as a by-product and disposed of after use can be used, or a desulfurizing agent used for desulfurizing biomass or a biomass treatment product can be recovered and used.

[0016] Here, the solvent used for extracting sulfur is carbon disulfide (CS ２ Carbon disulfide is a sulfide of carbon and is a colorless, volatile liquid. By using carbon disulfide as the solvent, sulfur can be extracted simply by stirring in the solvent, and the solvent used can be reused, so CO ２ This is effective from the viewpoint of reducing emissions and minimizing the manufacturing process. Furthermore, since it does not contain any carcinogenic components like carbon tetrachloride, sulfur can be safely recovered. The conditions for carbon disulfide are not particularly limited, and any solvent conventionally used can be appropriately selected and used.

[0017] In addition, the conditions for extracting sulfur are also as follows: carbon disulfide (CS ２The method is not particularly limited except that a solvent such as carbon disulfide is used. For example, the desulfurizing agent is immersed in a solvent made of carbon disulfide and stirred. The temperature of the solvent is not particularly limited, but is preferably a temperature not exceeding the boiling point of carbon disulfide (46°C or lower). After the stirring, the sulfur precipitated in the solvent is extracted (preferably by filtration and drying, as described below), thereby extracting and recovering the sulfur.

[0018] Furthermore, in the sulfur recovery method of the present invention, it is preferable to dry the desulfurizing agent prior to the sulfur extraction, as shown in Fig. 1. By removing moisture from the desulfurizing agent by drying, the sulfur extraction is promoted, and therefore the amount and rate of sulfur extraction can be increased.

[0019] The drying conditions are not particularly limited as long as they can eliminate (reduce) the moisture content of the desulfurizing agent, and can be appropriately adjusted depending on the moisture content of the desulfurizing agent. For example, by carrying out a drying treatment at 70°C or higher for 50 hours or longer, the moisture content of the desulfurizing agent can be reduced, allowing the subsequent sulfur extraction treatment to be carried out effectively.

[0020] If necessary, a step of pulverizing (or crushing) the desulfurizing agent may be performed prior to the extraction of sulfur. ２ Since sulfur can be extracted without pre-treatment such as crushing using a solvent comprising carbon disulfide, a complicated process can be eliminated. Therefore, in the sulfur recovery method of the present invention, the desulfurizing agent can be immersed directly in the solvent comprising carbon disulfide. However, depending on the size of the container, the desulfurizing agent can be cut or broken to an appropriate size.

[0021] Furthermore, in the sulfur recovery method of the present invention, as shown in Figure 1, sulfur is extracted from the desulfurizing agent using the solvent composed of carbon disulfide, followed by filtration and drying. Since the extract from which the sulfur has been extracted contains a mixture of hydrogen disulfide and sulfur, the sulfur can be removed by filtration and then dried to obtain the recovered sulfur. The conditions for the filtration and drying are not particularly limited and can be selected appropriately depending on the required performance. For example, the drying can be performed by concentrating the extract under reduced pressure using an evaporator, followed by drying under reduced pressure at 40°C for 12 hours.

[0022] In the sulfur recovery method of the present invention, it is preferable to obtain insoluble sulfur using the extracted sulfur (recovered sulfur) that has been filtered and dried. This is because sulfur with higher purity and excellent industrial applicability can be obtained. Note that the step of obtaining the insoluble sulfur may, for example, involve heating the recovered sulfur to obtain liquid sulfur, dissolving the liquid sulfur in carbon disulfide, and heating, cooling, and drying the resulting solution.

[0023] Furthermore, in the sulfur recovery method of the present invention, as shown in Figure 1, sulfur is extracted from the desulfurizing agent using the solvent composed of carbon disulfide and sulfur, followed by filtration. The hydrogen disulfide obtained in this process, i.e., the hydrogen disulfide used in the sulfur extraction, can be recovered and used as a solvent for dissolving liquid sulfur in the subsequent step of obtaining the insoluble sulfur. This makes it possible to reuse the hydrogen disulfide, which is effective from the viewpoints of production cost and recycling.

[0024] In the sulfur recovery method of the present invention, in addition to the steps shown in FIG. 1, it is possible to appropriately carry out treatments that are usually carried out in sulfur recovery depending on the performance required of sulfur.

[0025] <Sulfur Recycling System> The sulfur recycling system of the present invention is a sulfur recycling system that uses biomass. The recycling system of the present invention includes a step of desulfurizing biomass or a treated biomass product and removing sulfur-containing substances from the biomass or the treated biomass product (desulfurization step), a step of recovering sulfur from the desulfurization residue generated in the desulfurization step (recovery step), a step of processing the recovered sulfur into sulfur for vulcanization (processing step), a step of kneading the sulfur for vulcanization with a double-bond-containing polymer (kneading step), and a step of vulcanizing the double-bond-containing polymer (vulcanization step). The recycling system of the present invention is a system that can be applied to the rubber field, including tires, which requires vulcanization using sulfur.

[0026] Although the present invention relates to the recycling of sulfur, the biomass used in the present invention often generates nitrogen-containing substances such as ammonia. Therefore, the recycling system of the present invention can also recycle nitrogen.

[0027] In this specification, "biomass" typically refers to organic resources derived from plants and animals, other than fossil resources (oil, coal, natural gas, etc.). Biomass is not particularly limited, but a wide range of materials can be used, including animal excreta, sewage, food waste, microalgae, black liquor, paper, sawmill residues, construction wood, inedible parts of agricultural crops, and forest residues.

[0028] Furthermore, the recycled raw material supplied to the recycling system of the present invention may be biomass itself, or a product obtained by subjecting the biomass to some kind of processing (defined herein as a "processed biomass product"), or a combination of these. Here, the processing preferably involves converting the biomass into a more usable form. For example, the processed biomass product may be biogas obtained by methane fermentation of biomass such as animal excrement, sewage, or food waste. The methane fermentation may be carried out by a known method. The biogas obtained by the methane fermentation typically contains sulfur-containing substances, primarily hydrogen sulfide, along with methane, a fuel component. Another example of the processed biomass product is oils and fats produced by microalgae such as Euglena. The oils and fats produced by microalgae typically contain sulfur-containing substances, primarily hydrogen sulfide, along with oils and fats such as wax esters.

[0029] In the recycling system of the present invention, the biomass or biomass treatment product as the recycling raw material (subject to treatment) may be one type alone or a combination of two or more types.

[0030] (Desulfurization process and recovery process) In the recycling system of the present invention, the desulfurization process is a process of desulfurizing biomass or a biomass treatment product to remove sulfur-containing substances from the biomass or the biomass treatment product. In the desulfurization process, a desulfurization treatment residue is usually generated. In addition, the recovery process is a process of recovering sulfur from the desulfurization treatment residue generated in the desulfurization process. That is, in the recovery process, sulfur is recovered as elemental sulfur.

[0031] The recycling system of the present invention is premised on the use of biomass or a biomass treatment product containing sulfur-containing substances as the recycling raw material. The sulfur-containing substances contained in the biomass or the biomass treatment product, or the sulfur-containing substances removed in the desulfurization step, are not particularly limited as long as they contain sulfur as a constituent element, and examples thereof include hydrogen sulfide and sulfur dioxide. The sulfur-containing substances removed in the desulfurization step may be one type alone or a combination of two or more types.

[0032] The desulfurization method in the desulfurization step is not particularly limited as long as it can remove sulfur-containing substances from the recycled raw material (biomass or treated biomass). As an example, desulfurization can be carried out by contacting the recycled raw material (biomass or treated biomass) with a contact medium selected from an adsorbent, a solvent, and bacteria. These contact media may be used alone or in combination of two or more. Hereinafter, embodiments of the desulfurization step and the recovery step will be described in detail for each contact medium used.

[0033] The adsorbent used in the contact medium may be any adsorbent capable of selectively treating (adsorbing) sulfur-containing substances, and specific examples thereof include iron oxide, zinc ferrite, zeolite, etc. The adsorbent may be used alone or in combination of two or more.

[0034] As an example, when iron oxide is used as an adsorbent, hydrogen sulfide can be converted to iron sulfide by contact with the adsorbent during the desulfurization process. In this case, the desulfurization residue corresponds to an adsorbent containing iron sulfide. Then, in the recovery process, the iron sulfide in the desulfurization residue is reacted with a strong acid to convert it back to hydrogen sulfide, and sulfur can be recovered from the hydrogen sulfide by a known method. Furthermore, in the desulfurization residue (adsorbent containing iron sulfide) in the above case, sulfur may be contained in the form of elemental sulfur in addition to iron sulfide. Sulfur can also be recovered from such an adsorbent containing elemental sulfur by a known method.

[0035] For example, when zeolite is used as an adsorbent, hydrogen sulfide can be brought into contact with the zeolite during the desulfurization step, allowing the hydrogen sulfide to be directly physically adsorbed onto the zeolite. In this case, the desulfurization residue corresponds to the adsorbent containing hydrogen sulfide. In the subsequent recovery step, the desulfurization residue is exposed to reduced pressure and high temperature conditions to recover hydrogen sulfide, and then sulfur can be recovered from the hydrogen sulfide by a known method.

[0036] Adsorbents such as iron oxide are advantageous in that they have a relatively high sulfur recovery efficiency.

[0037] The sulfur recovery method of the present invention is carried out as a method for recovering sulfur from hydrogen sulfide under the recovery conditions described above.

[0038] The solvent used in the contact medium may be any solvent capable of selectively treating (absorbing or extracting) sulfur-containing substances, and specific examples thereof include monoethanolamine, diethanolamine, methyldiethanolamine, etc. The solvent may be used alone or in combination of two or more. The solvent may also be diluted with water to form an aqueous solution.

[0039] For example, when monoethanolamine is used as the solvent, hydrogen sulfide can be absorbed by contacting the solvent during the desulfurization step. In this case, the desulfurization residue corresponds to the solvent that has absorbed hydrogen sulfide. Then, in the recovery step, the desulfurization residue is heated to separate the hydrogen sulfide, and sulfur can be recovered from the hydrogen sulfide by a known method (for example, the Claus process described above). The same applies when diethanolamine or methyldiethanolamine is used as the solvent.

[0040] The solvent such as monoethanolamine is advantageous in that it can be reused as a contact medium as it is after being heated in the recovery step.

[0041] The bacteria used in the contact medium may be any bacteria capable of selectively treating sulfur-containing substances, and specific examples thereof include sulfur-oxidizing bacteria. More specific examples of the bacteria include the sulfur-oxidizing bacteria described in "Biogas desulfurization in a microaerobic environment in a methane fermenter using sulfur-oxidizing bacteria" by Takuro Kobayashi et al. (Journal of the Japan Society of Civil Engineers, Vol. 65, No. 2, pp. 104-113, June 2009). Bacteria may be used singly or in combination of two or more.

[0042] For example, if sulfur-oxidizing bacteria are used as bacteria, they can oxidize hydrogen sulfide during the desulfurization process to produce sulfur. In this case, the desulfurization residue corresponds to the sulfur-containing bacteria. Then, in the recovery process, a cell lysis solution containing a surfactant or the like is used to lyse the desulfurization residue, and the sulfur can be extracted with a solvent to recover the sulfur. Examples of solvents used for the extraction include carbon disulfide and toluene.

[0043] Bacteria are advantageous in that they are relatively inexpensive to maintain.

[0044] (Processing Step) The processing step is a step of processing the recovered sulfur into sulfur for vulcanization. A known method can be used for the processing step. For example, in the processing step, the recovered sulfur (elemental sulfur) is dissolved in carbon disulfide, followed by heating, rapid cooling, separation, drying, and, if necessary, oil treatment to obtain insoluble sulfur (sulfur for vulcanization).

[0045] (Kneading Step) The kneading step is a step of kneading the sulfur for vulcanization with the double bond-containing polymer.

[0046] Examples of double bond-containing polymers include polymers that are widely used in the rubber field, including tires. Specific examples of double bond-containing polymers include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), halogenated butyl rubber, and ethylene-propylene-diene rubber (EPDM). The double bond-containing polymers may be used alone or in combination of two or more.

[0047] In the kneading step, in addition to the above-mentioned sulfur for vulcanization and double bond-containing polymer, various compounding agents such as a vulcanization aid such as stearic acid, a vulcanization accelerator, a vulcanization acceleration aid such as zinc oxide, an antioxidant, oil, a softener, a plasticizer, and a processability improver may be appropriately compounded and kneaded depending on the purpose.

[0048] The kneading method is not particularly limited, and kneading can be carried out using a kneading machine such as a roll, an internal mixer, or a Banbury rotor.

[0049] (Vulcanization Step) The vulcanization step is a step of vulcanizing the double bond-containing polymer kneaded with vulcanizing sulfur. In this step, the vulcanizing sulfur functions as a vulcanizing agent.

[0050] The vulcanization temperature is not particularly limited, and can usually be set to 130° C. or higher and 180° C. or lower. The vulcanization time is not particularly limited, and can usually be set to 5 minutes or higher and 120 minutes or lower.

[0051] Example 1 300 mL of carbon disulfide was added to 444.60 g of desulfurizing agent containing water (solid content: 300.41 g), and the mixture was stirred at room temperature for 2 hours. The mixture was then filtered using PTFE filter paper (pore size: 10 μm) to extract the solid, which was then dried under reduced pressure using an evaporator. The weight (g) of the extracted solid and the ratio (%) of the weight of the extracted solid to the weight of the solid content of the desulfurizing agent are shown in Table 1. The extracted solid was confirmed to be sulfur by XRD measurement, and the dried weight was quantitatively analyzed for trace metal components by IPC measurement.

[0052] [Example 2] 989.50 g of the desulfurizing agent containing water was dried under reduced pressure at 75°C for 5 hours to obtain a dried desulfurizing agent (weight 678.08 g). 300.26 g was extracted from the dried desulfurizing agent, and 300 mL of carbon disulfide was added and stirred at room temperature for 2 hours. Subsequently, filtration was performed using PTFE filter paper (pore size 10 μm) to extract the solid, and the extracted solid was then dried under reduced pressure using an evaporator. The weight (g) of the extracted solid and the ratio (%) of the weight of the extracted solid to the weight of the solid content of the desulfurizing agent are shown in Table 1. The obtained sulfur was confirmed to be sulfur by XRD measurement, and the dried weight was quantitatively analyzed for trace metal components by IPC measurement.

[0053]

[0054] The results in Table 1 show that sulfur can be recovered without treatment in a high-temperature environment in both the sulfur extraction methods of Examples 1 and 2. Furthermore, it was found that the sulfur extraction method of Example 2 can more efficiently remove sulfur by performing a drying treatment of the desulfurizing agent in advance.

[0055] According to the present invention, no treatment in a high temperature environment is required, and CO ２ Furthermore, according to the present invention, a sulfur recovery method can be provided that can reduce CO emissions by incorporating the sulfur recovery method of the present invention. ２ It is possible to provide a sulfur recycling system using biomass that can reduce emissions and is constructed for industrial application.

Claims

1. A method for recovering sulfur from a used desulfurizing agent, comprising extracting and recovering sulfur from the desulfurizing agent using a solvent comprising carbon disulfide.

2. The method for recovering sulfur according to claim 1, wherein the desulfurizing agent is dried prior to extraction of the sulfur.

3. A method for recovering sulfur according to claim 1 or 2, characterized in that the recovered sulfur is heated to form liquid sulfur, the liquid sulfur is dissolved in carbon disulfide, and the resulting solution is heated, cooled, and dried to obtain insoluble sulfur.

4. A method for recovering sulfur according to claim 3, characterized in that the carbon disulfide used in the extraction of sulfur is then used as a solvent for dissolving the liquid sulfur.

5. A method for recovering sulfur according to claim 1 or 2, characterized in that the extraction of sulfur does not include a step of pulverizing the desulfurization agent.

6. The method for recovering sulfur according to claim 1 or 2, wherein the used desulfurization agent is a desulfurization agent that has been used to desulfurize biomass or a biomass treatment product.

7. A sulfur recycling system using biomass, comprising: a desulfurization step of desulfurizing biomass or a biomass treatment product to remove sulfur-containing substances from the biomass or the biomass treatment product; a recovery step of recovering sulfur from a desulfurization residue generated in the desulfurization step; a processing step of processing the recovered sulfur into sulfur for vulcanization; a kneading step of kneading the sulfur for vulcanization with a double bond-containing polymer; and a vulcanization step of vulcanizing the double bond-containing polymer, wherein the recovery step of recovering sulfur comprises extracting and recovering sulfur from the desulfurizing agent using a solvent comprising carbon disulfide.

8. The sulfur recycling system according to claim 7, characterized in that the sulfur-containing substance is selected from hydrogen sulfide and sulfur dioxide.

9. The sulfur recycling system according to claim 7 or 8, characterized in that the biomass is selected from animal manure, sewage, food waste, and microalgae.

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