Method for producing sulfur-containing compositions

Abstract

To provide a method for producing a sulfur-containing composition with a high content of a sulfur-containing compound.SOLUTION: A method for producing a sulfur-containing composition includes a mixing step for mixing a sulfur source with a carbon source to give a starting mixture; a granulating step for subjecting the starting mixture to rolling granulation, giving a granulated material; and a heating step for heating the granulated material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a sulfur-containing composition.

Background Art

[0002] A method of producing a sulfur-containing composition by heating a sulfur source containing sulfur and a carbon source containing carbon is known. For example, Patent Document 1 discloses a method of obtaining calcium sulfide by mixing gypsum and a pulverized carbon source and heating them in a reducing atmosphere. Further, Patent Document 2 discloses a method for producing a heavy metal elution inhibitor containing a sulfide by adding an oxide to a raw material containing a reducing agent and a metal sulfate, granulating, and heating and melting. Further, Patent Document 2 describes a method for producing a heavy metal elution inhibitor containing a metal sulfide by melting a raw material containing a reducing agent such as carbon and a metal sulfate at 1200 to 1600 ° C in an oxidizing atmosphere.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the production method disclosed in Patent Document 1 performs a heat treatment in a tubular electric furnace for 4 hours, and 20% or more of unreacted calcium sulfate remains in the product, and a more efficient production method is desired.

[0005] Furthermore, the manufacturing method described in Patent Document 2 required the inclusion of a mixture of two or more oxides or a complex oxide in the raw materials, which had to be melted by heating at a high temperature of 1200°C or higher. In other words, high-temperature heating of 1200°C or higher was required, and a large amount of oxides needed to be added for melting, resulting in the problem that the amount of active ingredients (sulfides) in the resulting heavy metal elution inhibitor was not necessarily large. Therefore, a method is desired that can obtain high-purity heavy metal elution inhibitors at lower temperatures.

[0006] The present invention has been made in accordance with the circumstances described above, and aims to provide a method for producing a sulfur-containing composition with a high content of sulfur-containing compounds. [Means for solving the problem]

[0007] The present invention provides a method for producing a sulfur-containing composition, comprising a mixing step of mixing a sulfur source and a carbon source to obtain a mixed raw material, a granulation step of tumbling the mixed raw material to obtain a granulated raw material, and a heating step of heating the granulated raw material.

[0008] The method for producing the sulfur-containing composition of the present invention may include a mixing step of mixing a sulfur source and a carbon source to obtain a mixed raw material, a granulation step of granulating the mixed raw material to obtain a granulated raw material containing substantially spherical raw material particles, and a heating step of heating the granulated raw material.

[0009] The above granulation process may be carried out by the rolling granulation method.

[0010] The particle size of the above-mentioned granulation raw material may be 3 mm or larger.

[0011] The above heating process may be carried out using a rotary kiln, with the heating temperature inside the rotary kiln being 1200°C or less and the oxygen concentration being 20% ​​by volume or less.

[0012] The above sulfur-containing composition may contain metal sulfides.

[0013] The sulfur source may contain gypsum, and the sulfur-containing composition may contain calcium sulfide.

[0014] The gypsum mentioned above is waste gypsum board containing paper, and the process may include a crushing step for crushing the waste gypsum board. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a method for producing a sulfur-containing composition with a high content of sulfur-containing compounds. [Modes for carrying out the invention]

[0016] A method for producing a sulfur-containing composition according to one embodiment of the present invention comprises a mixing step of mixing a sulfur source and a carbon source to obtain a mixed raw material, a granulation step of tumbling and granulating the mixed raw material to obtain a granulated raw material, and a heating step of heating the granulated raw material. Alternatively, the method for producing a sulfur-containing composition according to this embodiment may also comprise a mixing step of mixing a sulfur source and a carbon source to obtain a mixed raw material, a granulation step of granulating the mixed raw material to obtain a substantially spherical granulated raw material, and a heating step of heating the granulated raw material.

[0017] According to the manufacturing method of this embodiment, a sulfur-containing composition with a high content of sulfur-containing compounds can be obtained. The reason for this effect is that rolling granulation is performed on the mixed raw materials in the granulation process. Conventionally, when granulation is performed before heating the mixed raw materials, a method of compressing the raw materials, such as briquette granulation, has been employed. As a result, the granulated raw materials (particles) are compressed in a specific direction and have a flattened or columnar shape. Even when such raw materials are heated in a rotary kiln or the like, the granulated raw material particles do not roll properly, and heating proceeds only in a specific direction, resulting in uneven heating and inadequate reaction within the particles. As a result, a large amount of unreacted material remains. Furthermore, if the heating temperature is increased to promote the reaction, the combustion reaction of sulfur contained in the raw materials and sulfur-containing compounds progresses, generating oxides. As a result, the content of sulfur-containing compounds in the obtained sulfur-containing composition actually decreases. On the other hand, in the manufacturing method according to this embodiment, since the mixed raw materials are roll-granulated, it is easy to obtain granulated raw materials (raw material particles) that are roughly spherical. The roughly spherical raw material particles can easily change orientation by rolling during heating, allowing the reaction to proceed uniformly within the particles and reducing unreacted material. Furthermore, because the reaction proceeds uniformly, the heating temperature can be lowered, reducing costs and suppressing side reactions that would otherwise occur as sulfur-containing compounds react and produce oxides. Additionally, the heating time can be shortened.

[0018] (Mixing process) In the mixing process, the raw materials, the sulfur source and the carbon source, are first mixed. The mixing method is not particularly limited and may be done using a mixer or the like. The mixing may be carried out either wet or dry.

[0019] As a sulfur source, any raw material containing sulfur is acceptable. The sulfur source may contain a compound with a positive oxidation state of sulfur, and may be a compound containing sulfur oxoacids (such as sulfur oxoates). Examples of such compounds include sulfates, sulfites, and bisulfates (hydrogen sulfates). These salts may also be hydrates. The sulfur source may contain one or more sulfur-containing compounds.

[0020] Further, the sulfur source may contain a metal element. The metal element is not particularly limited and may be an alkali metal, an alkaline earth metal, or the like. Examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium, and the like. Examples of the alkaline earth metal include magnesium, calcium, barium, strontium, and the like, and may be magnesium or calcium. The metal element contained in the sulfur source may be one or more kinds.

[0021] Specifically, the sulfur source may contain gypsum. The sulfur source containing gypsum is not particularly limited, and examples include gypsum waste materials such as anhydrite, hemihydrate gypsum, dihydrate gypsum, waste gypsum board, gypsum mold for casting molding, and gypsum mold for industrial model. The waste gypsum board may contain paper. When using a waste gypsum board as the sulfur source, it may have a pulverizing step of pulverizing the waste gypsum board before the mixing step. The pulverizing step can be performed using an ordinary pulverizer. The particle size of the sulfur source may be 20 mm or less, 10 mm or less, or 1 mm or less. The particle size of the sulfur source can be measured by a metal sieve conforming to JIS Z 8801-1:2019.

[0022] Examples of the carbon source include carbon, coal, coke, charcoal, wood, etc. In addition, coal ash containing unburned carbon discharged from a coal-fired power plant, gasification slag discharged from a coal gasification furnace, pulp sludge, waste plastic, waste wood, harvested wood, and other biomass wastes discharged from a paper mill can be mentioned. The carbon contained in the carbon source can reduce the sulfur when the sulfur source contains a compound containing sulfur having a positive oxidation number during heating. For example, the ratio of the carbon source passing through a sieve having a predetermined nominal mesh size to the total amount of the carbon source used may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. The nominal mesh size of such a sieve may be 1.18 mm, 600 μm, 300 μm, or 150 μm.

[0023] <当該硫黄を含有する化合物を含む場合、加熱中に当該硫黄を還元することができる。例えば、使用する炭素源の全量に対して所定の公称目開きを有する篩を通過するものの割合が70質量%以上、80質量%以上、90質量%以上又は95質量%以上であってよい。かかる篩の公称目開きとしては、1.18mm、600μm、300μm又は150μmであってよい。 From the perspective of increasing the content of sulfur-containing compounds in the sulfur-containing composition as the product, the molar ratio of carbon contained in the carbon source to sulfur contained in the sulfur source in the mixed raw material may be 1.0 or more, 1.5 or more, 2.0 or more, or 2.2 or more. Further, from the perspective of reducing unreacted carbon and suppressing the generation of oxides due to excessive progress of the reaction, the molar ratio of carbon contained in the carbon source to sulfur contained in the sulfur source in the mixed raw material may be 10 or less, 5 or less, 3 or less, or 2.5 or less.

[0024] For example, when the sulfur source contains gypsum (CaSO4), the ratio of the carbon source to the sulfur source can be expressed as [C] / [CaSO4] as the molar ratio of carbon (C) contained in the carbon source to CaSO4.

[0025] The mixed raw material may contain a granulation accelerator in addition to the sulfur source and the carbon source. The granulation accelerator may be either inorganic or organic. Examples of the inorganic type include bentonite. Examples of the organic type include molasses, starch, alginic acid, polyvinyl alcohol, carboxymethyl cellulose, and the like.

[0026] The mixed raw material may contain ash (e.g., SiO2, Al2O3) derived from the carbon source.

[0027] (Granulation step) In the granulation process, the mixed raw materials obtained in the mixing process are granulated. The granulation process may be carried out by rolling granulation. The rolling granulation method is not particularly limited, but may be carried out using a pan-type granulator, drum-type granulator, vibrating granulator, high-speed mixer, etc. The size and particle size distribution of the granulated raw materials can be changed and adjusted by appropriately adjusting the granulation conditions according to the granulation method. For example, with a pan-type granulator, water may be sprayed in a mist onto the powdered raw materials placed in the pan, causing the particles to roll along the rotation direction of the granulation container and collide and bond with each other, thereby granulating particles of the required size. For other granulation methods, the granulation size and particle size distribution can be adjusted by appropriately adjusting the amount of water and binder added, the rotation speed of the drum and stirring screw, the motor vibration frequency, etc. Furthermore, the aspect ratio (=short axis length / long axis length) of the raw material particles after granulation may be 0.7 to 1, 0.8 to 1, or 0.9 to 1.

[0028] The particle size of the raw material particles may be 1 mm or larger, 3 mm or larger, greater than 3 mm, 5 mm or larger, or 10 mm or larger, from the viewpoint of reducing the purification of oxides, which are by-reaction products. In addition, the particle size of the raw material particles may be 50 mm or smaller, 30 mm or smaller, or 20 mm or smaller, from the viewpoint of allowing the reaction to proceed sufficiently to the interior of the particles.

[0029] The particle size of the raw material particles can be measured using a metal sieve in accordance with JIS Z 8801-1:2019. When measuring the particle size of the raw material particles by sieving, the particle size measured after granulation and drying of the raw material particles may be used. For example, the percentage of raw material particles that passed through a sieve with a nominal mesh size of 3.35 mm may be 5 to 50% by mass, or 5 to 20% by mass. Also, of the raw material particles that did not pass through the sieve with a nominal mesh size of 3.35 mm, the percentage that passed through a sieve with a nominal mesh size of 9.5 mm may be 5 to 80% by mass, or 20 to 80% by mass. Also, the percentage of raw material particles that did not pass through a sieve with a nominal mesh size of 9.5 mm may be 50 to 95% by mass, or 80 to 95% by mass. The percentage of raw material particles that failed to pass through a sieve with a nominal mesh size of 3.35 mm may be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. The percentage of raw material particles that failed to pass through a sieve with a nominal mesh size of 9.5 mm may be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0030] The moisture content of the granulation raw material may be 1 to 30% by mass, 3 to 25% by mass, or 5 to 20% by mass relative to the total amount of the granulation raw material.

[0031] (Heating process) The heating method is not particularly limited, but may be carried out in a heating furnace. The heating furnace is not particularly limited as long as it can heat to a predetermined temperature, such as an internal combustion burner rotary kiln, an external heating rotary kiln, a double-cylinder rotary kiln type carbonization furnace, a batch type carbonization furnace, etc.

[0032] The heating temperature may be 1200°C or lower, or 1100°C or lower. The oxygen concentration inside the heating furnace may be 20% by volume or lower, or 17% by volume or lower, 15% by volume or lower, 13% by volume or lower, or 10% by volume or lower. The oxygen concentration inside the heating furnace may be 3 to 20% by volume, or 5 to 15% by volume.

[0033] The resulting sulfur-containing composition may be subjected to classification. Classification can be carried out, for example, using a sieve in accordance with JIS Z 8801-1:2019.

[0034] Examples of sulfur-containing compounds included in the sulfur-containing composition obtained by the heating process include compounds containing sulfur with a lower oxidation state than the sulfur contained in the sulfur source of the raw material, such as metal sulfides and metal sulfites (i.e., compounds in which the sulfur has been reduced). Such sulfur-containing compounds containing sulfur with a lower oxidation state can be used as a reducing agent for hexavalent chromium. Examples of metal sulfides include calcium sulfide, calcium polysulfide, and magnesium sulfide. The metal sulfide may be calcium sulfide. Examples of metal sulfites include calcium sulfite and magnesium sulfite.

[0035] In the heating process, for example, if gypsum (CaSO4) is used as the sulfur source, the reaction represented by the following reaction equation (1) proceeds. Simultaneously, the reaction represented by the following reaction equation (2) may also proceed, and SO2 may be generated. CaSO4 + 2C → CaS + 2CO2 (1) CaSO4 + CaS → 2CaO + 2SO2(2)

[0036] In the heating process, it is preferable that the number of moles of gypsum (CaSO4) supplied to the heating section and the number of moles of the carbon source (C) satisfy the following formula (3), more preferably the following formula (4), and even more preferably the following formula (5). This makes the reaction between gypsum and the carbon source proceed more easily. C / CaSO4≧3 (3) C / CaSO4>4 (4) C / CaSO4>5 (5)

[0037] The sulfur-containing composition may contain components other than sulfides. Such components include calcium oxide, unreacted gypsum, and impurities derived from raw materials such as gypsum. By adding the sulfur-containing composition containing sulfides to the grinding process, which is one of the cement manufacturing processes for producing cement compositions, and grinding it together with cement clinker and gypsum, a cement composition capable of reducing the amount of hexavalent chromium leached can be produced. The sulfur-containing composition may also be added in the grinding process as a dry powder or alkaline slurry.

[0038] The calcium sulfide content of a sulfur-containing composition can be determined by analyzing the diffraction pattern obtained by powder X-ray diffraction measurement using the Rietveld method. The calcium sulfide content of the sulfur-containing composition is preferably 5% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more. From the viewpoint of ease of manufacture, the calcium sulfide content of the sulfur-containing composition may be 95% by mass or less.

[0039] The particle size of the sulfur-containing composition may be 1 mm or larger, 3 mm or larger, greater than 3 mm, 5 mm or larger, or 10 mm or larger, from the viewpoint of reducing the formation of oxides as by-reaction products. Furthermore, the particle size of the sulfur-containing composition may be 50 mm or smaller, 30 mm or smaller, or 20 mm or smaller, from the viewpoint of ensuring sufficient reaction within the particles.

[0040] The particle size of the sulfur-containing composition can be measured using a metal sieve in accordance with JIS Z 8801-1:2019. For example, the percentage of the sulfur-containing composition that passed through a sieve with a nominal mesh size of 3.35 mm may be 5 to 50% by mass, or 5 to 20% by mass. Also, of the sulfur-containing composition that did not pass through the sieve with a nominal mesh size of 3.35 mm, the percentage that passed through a sieve with a nominal mesh size of 9.5 mm may be 5 to 80% by mass, or 20 to 80% by mass. Also, the percentage of the sulfur-containing composition that did not pass through the sieve with a nominal mesh size of 9.5 mm may be 50 to 95% by mass, or 80 to 95% by mass. The percentage of the sulfur-containing composition that did not pass through the sieve with a nominal mesh size of 3.35 mm may be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. The proportion of the sulfur-containing composition that could not pass through a sieve with a nominal mesh size of 9.5 mm may be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. [Examples]

[0041] (Examples 1-4) A powdered mixed raw material was obtained by mixing crushed waste gypsum board (containing 94% dihydrate gypsum by mass, also containing paper) and a carbon source (coal gasification coarse slag, manufactured by Ube Industries, Ltd.) in a ratio of [C] / [CaSO4] = 2.4 (molar ratio). The obtained mixed raw material was granulated by rolling in a high-speed mixer (manufactured by Earth Technica Co., Ltd., FS100) to obtain a roughly spherical granulated raw material. Rolling granulation was performed by adding water to the mixed raw material placed in the granulation container. The obtained granulated raw material was then processed in a rotary kiln (total length approximately 3m, rotation speed 0.5min) -1The sulfur-containing compositions were obtained by heating under the conditions shown in Table 1. Since the obtained sulfur-containing compositions maintained their shape before heating, they were classified into appropriate particle sizes using a sieve, and their chemical composition was analyzed by powder X-ray diffraction. The classification by sieving was performed using metal mesh sieves with nominal mesh openings of 3.35 mm and 9.5 mm, in accordance with JIS Z 8801-1:2019. The obtained sulfur-containing compositions contained unreacted gypsum (CaSO4) and the products calcium sulfide (CaS) and calcium oxide (CaO). The amount of CaS and CaO produced was converted to the amount of CaSO4 used as raw material, and the content of these (gypsum equivalent %) relative to the total amount of unreacted CaSO4 and the converted CaS and CaO is shown in Table 1. In Table 1, the reaction rate is the ratio (%) of the total amount of converted CaS and CaO relative to the total amount in the obtained sulfur-containing composition. As shown in Table 1, the sulfur-containing compositions of each particle size that were classified are designated as Examples 1 to 4. Specifically, Example 1 is a sample that did not undergo classification; Example 2 is a sample that passed through a sieve with a nominal mesh size of 3.35 mm; Example 3 is a sample that did not pass through a sieve with a nominal mesh size of 3.35 mm but did pass through a sieve with a nominal mesh size of 9.5 mm; and Example 4 is a sample that did not pass through a sieve with a nominal mesh size of 9.5 mm.

[0042] (Comparative Examples 1 and 2) Except for not performing granulation and changing the kiln operating conditions as shown in Table 1, the raw materials were mixed and heated in the same manner as in the examples to obtain a sulfur-containing composition.

[0043] (Comparative Example 3) Except for granulating the mixed raw materials using a briquette machine (Furukawa Sangyo Co., Ltd., KP-102H) to obtain flat, almond-shaped granulated raw materials, and changing the kiln operating conditions as shown in Table 1, the raw materials were mixed and heated in the same manner as in the examples to obtain a sulfur-containing composition. The typical granulation size for Comparative Example 3 was 10mm x 24mm x 16mm (aspect ratio = 0.417), as measured with calipers.

[0044] [Table 1]

[0045] In Comparative Examples 1 and 2, where only gypsum and a carbon source were mixed and heated, most of the gypsum was converted to CaO, and the proportion obtained as CaS was small. Furthermore, the reaction rate of gypsum decreased as the temperature inside the kiln decreased. In Comparative Example 3, where raw materials granulated into almond shapes using a briquette machine, the reaction rate of gypsum was insufficient, and the proportion of CaS was also insufficient. On the other hand, in Examples 1 to 4, more than 90% of the gypsum reacted even at low kiln temperatures, and the proportion of CaS was also high. In particular, the proportion of CaS tended to increase as the size of the granulated raw materials increased.

Claims

1. A method for producing a sulfur-containing composition, A mixing process in which a sulfur source and a carbon source are mixed to obtain a mixed raw material, A granulation step is performed to obtain granulation material by tumbling the mixed raw materials, A heating step for heating the granulation raw material, It has, The sulfur-containing composition comprises a metal sulfide, A method for producing a sulfur-containing composition, wherein the heating temperature in the heating step is less than 1200°C.

2. A method for producing a sulfur-containing composition, A mixing process in which a sulfur source and a carbon source are mixed to obtain a mixed raw material, A granulation step is performed to obtain a granulated raw material containing roughly spherical raw material particles by granulating the aforementioned mixed raw materials, A heating step for heating the granulation raw material, It has, The sulfur-containing composition comprises a metal sulfide, A method for producing a sulfur-containing composition, wherein the heating temperature in the heating step is less than 1200°C.

3. A method for producing a sulfur-containing composition according to claim 2, wherein the granulation step is carried out by a rolling granulation method.

4. A method for producing a sulfur-containing composition according to any one of claims 1 to 3, wherein the particle size of the granulated raw material is 3 mm or more.

5. A method for producing a sulfur-containing composition according to any one of claims 1 to 4, wherein the heating step is performed by a rotary kiln, the heating temperature in the rotary kiln is 1200°C or less, and the oxygen concentration is 20% by volume or less.

6. A method for producing a sulfur-containing composition according to any one of claims 1 to 5, wherein the heating temperature in the heating step is 1040°C or less.

7. A method for producing a sulfur-containing composition according to any one of claims 1 to 6, wherein the sulfur source contains gypsum and the sulfur-containing composition contains calcium sulfide.

8. A method for producing a sulfur-containing composition according to claim 7, wherein the gypsum is waste gypsum board containing paper, and the method includes a grinding step of grinding the waste gypsum board.

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