WO2020218248A1

WO2020218248A1 - Low-sulfur coal production method

Info

Publication number: WO2020218248A1
Application number: PCT/JP2020/017074
Authority: WO
Inventors: 村井　亮太; 鷲見　郁宏; 勝康菅原; 貴宏加藤
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2019-04-24
Filing date: 2020-04-20
Publication date: 2020-10-29
Also published as: AU2020260860A1; CA3134533A1; AU2020260860B2; JPWO2020218248A1; CA3134533C; CN113728076A; JP6795132B1; US20220220404A1

Abstract

Provided is a low-sulfur coal production method having an excellent desulfurization effect. The production method comprises bringing coal into contact with a chemical material that is a mixed solution of hydrogen peroxide and acetic anhydride to remove sulfur in the coal. It is preferred that the molar ratio of the acetic anhydride to the hydrogen peroxide (i.e., (acetic anhydride)/(hydrogen peroxide)) is 0.5 to 12.0 inclusive. It is preferred that the acetic anhydride is mixed with the hydrogen peroxide before the chemical material is brought into contact with the coal and the chemical material is brought into contact with the coal after 10 minutes or more has elapsed since the mixing.

Description

How to make low sulfur coal

The present invention relates to a method for producing low sulfur coal.

When coal is used as a reducing agent for iron ore in the steelmaking process, some sulfur contained in the coal dissolves in the iron obtained by reducing the iron ore. Since residual sulfur deteriorates the toughness and workability of steel materials, great efforts have been made to remove sulfur from iron.
In addition, when coal is used as a heat source, sulfur oxides are mixed in the exhaust gas, and therefore, from the viewpoint of preventing air pollution, great efforts are required to remove sulfur from the exhaust gas.

Against this background, if sulfur (sulfur content) in coal can be removed before the use of coal, the industrial value is high.

As a method for producing low-sulfurized coal (low-sulfur coal), the scope of the patent claim of Patent Document 1 is "Crushed coal is mixed with caustic soda or caustic potash alone or an aqueous solution of a mixture thereof, and oxygen gas is used. Alternatively, a method for chemically desulfurizing coal, which comprises removing sulfur in coal by heating at a high temperature in an atmosphere of air or a mixture thereof, is described.

Japanese Unexamined Patent Publication No. 3-275795

In producing low-sulfur coal by desulfurizing coal (removing sulfur in coal), the desulfurization effect may be insufficient by the conventional method.
Therefore, an object of the present invention is to provide a method for producing low-sulfur coal having an excellent desulfurization effect.

As a result of diligent studies, the present inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention.

That is, the present invention provides the following [1] to [11].
[1] A method for producing low-sulfur coal, which removes sulfur in the coal by contacting the coal with a chemical which is a mixed solution of hydrogen peroxide and acetic anhydride.
[2] The method for producing low-sulfur coal according to the above [1], wherein the molar ratio of the acetic anhydride to the hydrogen peroxide (acetic anhydride / hydrogen peroxide) is 0.5 or more and 12.0 or less.
[3] The acetic anhydride and the hydrogen peroxide are mixed before the chemical is brought into contact with the coal, and after 10 minutes or more have passed after the mixing, the chemical is brought into contact with the coal. The method for producing low sulfur coal according to [1] or [2].
[4] The method for producing low-sulfur coal according to any one of the above [1] to [3], wherein the mass ratio (drug / coal) of the chemical to the coal is 1.0 or more.
[5] The method for producing low-sulfur coal according to any one of the above [1] to [4], wherein the temperature of the chemical when contacting with the coal is 5 ° C. or higher.
[6] The method for producing low-sulfur coal according to any one of [1] to [5] above, wherein the temperature of the chemical when contacting with the coal is 30 ° C. or lower.
[7] The method for producing low-sulfur coal according to any one of [1] to [6] above, wherein the coal contains subbituminous coal.
[8] The method for producing low-sulfur coal according to any one of [1] to [7] above, wherein the coal in contact with the chemical is heat-treated at a heat treatment temperature of 150 ° C. or higher.
[9] The method for producing low-sulfur coal according to the above [8], wherein the rate of temperature rise when raising the temperature of the coal in contact with the chemical to the heat treatment temperature is 10 ° C./min or more.
[10] The method for producing low-sulfur coal according to any one of [1] to [7] above, wherein the coal in contact with the chemical is brought into contact with hydrogen peroxide solution at 40 ° C. or lower.
[11] The concentration of the hydrogen peroxide solution is 2.0% by mass or more, and the mass ratio of the hydrogen peroxide solution to the coal (hydrogen peroxide solution / coal) is 1.0 or more. The method for producing low sulfur coal according to the above [10].

According to the present invention, it is possible to provide a method for producing low-sulfur coal having an excellent desulfurization effect.

It is a graph which shows the desulfurization rate with respect to the mass ratio (drug / coal) of a drug and coal. It is a graph showing the amount of peracetic acid produced with respect to the temperature of the drug (lower), and the graph showing the desulfurization rate (solid line) and the carbon yield (broken line) with respect to the temperature of the drug (upper). It is a schematic diagram which shows an example of the manufacturing facility of low sulfur coal.

[Manufacturing method of low sulfur coal]
In the method for producing low-sulfur coal of the present invention (hereinafter, also simply referred to as "the method of the present invention"), sulfur in the above coal is obtained by contacting the coal with a chemical which is a mixed solution of hydrogen peroxide and anhydrous acetic acid. It is a method for producing low-sulfur coal that removes.

<Primary treatment (drug treatment)>
In the following, first, the primary treatment (chemical treatment) in which coal is brought into contact with a chemical which is a mixed solution of hydrogen peroxide and acetic anhydride will be described.

Sulfur in coal is roughly classified into inorganic sulfur (inorganic sulfur content) and organic sulfur (organic sulfur content).
FeS ₂ is a typical example of inorganic sulfur. Examples of the organic sulfur include aromatic sulfur compounds in which sulfur is present inside the aromatic ring such as dibenzothiophene; and aliphatic sulfur compounds such as mercaptan; Of these, sulfur existing inside the aromatic ring constituting coal is known to be particularly difficult to remove.

The present inventors examined various chemicals (desulfurization chemicals). As a result, peracetic acid effectively acts on thiophene-like sulfur, which is a particularly difficult component of organic sulfur in coal, thereby converting sulfur into a form that can or is easily removed from coal. We found that it would be more efficient. It is presumed that due to the action of peracetic acid, thiophene sulfur is oxidized to, for example, sulfone sulfur or sulfide sulfur, and the bond between carbon and sulfur is relatively weakened and the bond is easily broken, so that sulfur is easily desorbed. Will be done.

By the way, peracetic acid is easily decomposed. Therefore, in the present invention, a mixed solution of hydrogen peroxide and acetic anhydride (hereinafter, also simply referred to as “mixed solution”) is used as a drug. The mixed solution produces peracetic acid, which is the reaction product of hydrogen peroxide and acetic anhydride. Such a mixed solution is brought into contact with coal.

The reaction for obtaining peracetic acid (CH ₃ COO ₂ H) and water (H ₂ O) by the reaction of hydrogen peroxide (H ₂ O ₂ ) and acetic anhydride ((CH ₃ CO) ₂ O) is represented by the following formula (I). ).
2H ₂ O ₂ + (CH ₃ CO) ₂ O ⇔ ₂ CH ₃ COO ₂ H + H ₂ O ... (I)
In the above formula (I), the equilibrium state changes according to each condition such as temperature and mixing ratio of chemicals. Therefore, the concentration of each component varies depending on the combination of each condition. The preferred conditions will be described in detail later.

By bringing the chemical into contact with coal, the easily removable inorganic sulfur dissolves and leaches into the chemical in the form of, for example, sulfate ions. Similarly, some organic sulfur is also oxidized and leached into the drug in the form of sulfate ions and the like. In this way, the coal is desulfurized (ie, the sulfur in the coal is removed) to give a low sulfurized coal (low sulfur coal).

<< Mole ratio (acetic anhydride / hydrogen peroxide) >>
The molar ratio of acetic anhydride to hydrogen peroxide (acetic anhydride / hydrogen peroxide) in the drug is preferably 0.1 or more because the reaction product peracetic acid is an appropriate amount and the desulfurization effect is more excellent. 5 or more is more preferable.
Further, when the molar ratio (acetic anhydride / hydrogen peroxide) is in this range, it is possible to suppress the excess of acetic anhydride with respect to hydrogen peroxide and the residual hydrogen peroxide in the mixed solution (as described later). , Hydrogen peroxide reduces the carbon yield of coal).

The molar ratio (acetic anhydride / hydrogen peroxide) is preferably 15.0 or less, more preferably 12.0 or less. When the molar ratio (acetic anhydride / hydrogen peroxide) is in this range, the amount of peracetic acid, which is a reaction product, becomes appropriate as described above, and the desulfurization effect is more excellent. Furthermore, it is suppressed that the produced peracetic acid is diluted with excess acetic anhydride.

The molar ratio (acetic anhydride / hydrogen peroxide) is calculated as follows.
First, the molar amount [mol] of each component (acetic anhydride or hydrogen peroxide) in the drug is represented by the following formula (a). Therefore, the molar ratio of acetic anhydride to hydrogen peroxide (acetic anhydride / hydrogen peroxide) in the drug is calculated by the following formula (b).
Amount of mole = (Li × Ci) / (100 × Mi)… (a)
Molar ratio = (L1 x C1 x M2) / (L2 x C2 x M1) ... (b)
Li: Amount of i aqueous solution [g / h]
Ci: Concentration of i aqueous solution [mass%]
Mi: Molecular weight of i [g / mol]
Here, i represents acetic anhydride when it is 1, and hydrogen peroxide when it is 2.
Acetic anhydride has a molecular weight of 102 and hydrogen peroxide has a molecular weight of 34. The amount Li of the aqueous solution is adjusted so as to obtain a desired molar ratio (acetic anhydride / hydrogen peroxide).

《Elapsed time after mixing》
The reaction of the above formula (I) (forward reaction) is relatively slow. Therefore, immediately after mixing hydrogen peroxide and acetic anhydride, the production of peracetic acid may be insufficient.
The present inventors variously quantified the reaction rate and clarified that it takes about 10 minutes for the reaction of the above formula (I) to reach a steady state.
Therefore, in the present invention, it is preferable to mix acetic anhydride and hydrogen peroxide before bringing the drug into contact with coal, and after 10 minutes or more have passed after this mixing, bring the drug into contact with coal. As a result, peracetic acid is sufficiently produced, and the desulfurization effect of removing sulfur in coal is more excellent. Furthermore, since hydrogen peracetic acid is reduced, it is possible to suppress the reaction of hydrogen peroxide with coal to reduce the carbon yield.
The elapsed time after mixing is more preferably 20 minutes or more, and even more preferably 30 minutes or more. On the other hand, 120 minutes or less is preferable, 90 minutes or less is more preferable, and 60 minutes or less is further preferable.

《Mass ratio (drug / coal)》
The present inventors examined the mass ratio of drug to coal (drug / coal). In this study, a drug having a molar ratio of acetic anhydride to hydrogen peroxide (acetic anhydride / hydrogen peroxide) of 5.0 was used.
FIG. 1 is a graph showing the desulfurization rate with respect to the mass ratio of chemicals and coal (drugs / coal). As shown in the graph of FIG. 1, when the amount of the chemical is larger than the amount of coal, the desulfurization rate is high and the desulfurization effect is more excellent. Therefore, the mass ratio (drug / coal) is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 2.0 or more.

Further, as shown in the graph of FIG. 1, when the amount of the chemical is excessively large with respect to the amount of coal, the desulfurization rate hardly changes. From the viewpoint of reducing the amount of the drug used, the mass ratio (drug / coal) is preferably 100.0 or less, more preferably 50.0 or less.

The desulfurization rate [mass%] is W ₁ [kg] for the mass of coal (solid content) before desulfurization,% S ₁ [mass%] for the sulfur content of coal (solid content) before desulfurization, and after desulfurization. When the mass of coal (solid content) is W ₂ [kg] and the sulfur content of coal (solid content) after desulfurization is% S ₂ [mass%], it is defined by the following formula (1).
Desulfurization rate [mass%] = 100 × {1- (W ₂ ×% S ₂ ) / (W ₁ ×% S ₁ )}… (1)

《Drug temperature》
The present inventors have also examined the temperature of the drug when it comes into contact with coal (hereinafter, also simply referred to as “drug temperature”). In this study, a drug having a molar ratio of acetic anhydride to hydrogen peroxide (acetic anhydride / hydrogen peroxide) of 5.0 was used.
FIG. 2 is a graph (lower) showing the amount of peracetic acid produced with respect to the temperature of the drug, and a graph (upper) showing the desulfurization rate (solid line) and carbon yield (broken line) with respect to the temperature of the drug. The amount of peracetic acid produced is an index with the calculated value of 1.0 when the reaction contributors (hydrogen peroxide and acetic anhydride) have completely reacted.

As shown in the graphs of FIG. 2 (lower and upper), when the temperature of the chemical when contacting with coal is high, the amount of peracetic acid produced is large, the desulfurization rate is high, and the desulfurization effect is more excellent. From such a viewpoint, the temperature of the drug is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, further preferably 20 ° C. or higher, and particularly preferably 25 ° C. or higher.

On the other hand, as shown in the graph (upper part) of FIG. 2, it is preferable that the temperature of the drug does not become too high in order to maintain the carbon yield high. Specifically, 40 ° C. or lower is preferable, 35 ° C. or lower is more preferable, and 30 ° C. or lower is further preferable, because the carbon yield is excellent.

Regarding the carbon yield [mass%], the carbon content of coal (solid content) before desulfurization is% C1 [mass%], and the carbon content of coal (solid content) after desulfurization is% C2 [mass%]. Then, it is defined by the following equation (2).
Carbon yield [mass%] = 100 × (W ₂ ×% C ₂ ) / (W ₁ ×% C ₁ )… (2)

The reason why the carbon yield decreases is presumed as follows.
Hydrogen peroxide and peracetic acid can act as oxidants and destroy the skeleton of coal, in which case it is thought that at the same time as the removal of sulfur, an unintended decrease in carbon yield occurs. As a result of the examination by the present inventors, it was found that peracetic acid causes the cleavage of the sulfur-carbon bond of thiophene sulfur in advance, and the destruction of the carbon skeleton (carbon-carbon bond) occurs thereafter. .. Destruction of the carbon skeleton is weak with peracetic acid and strong with hydrogen peroxide. This is especially noticeable with high temperature hydrogen peroxide.
Therefore, by appropriately controlling the conditions for contacting the chemical with coal (for example, preventing the temperature of the chemical from becoming too high and adjusting the mixing ratio of hydrogen peroxide in the mixed solution appropriately), carbon Thiophene sulfur can be effectively removed while minimizing skeletal destruction.

<coal>
The coal used in the present invention is not particularly limited, and a wide variety of coals can be used, but it is preferable to include coal having a moderate degree of coalification such as subbituminous coal, more preferably to contain subbituminous coal, and subbituminous coal. Is more preferable.
When such coal is used, the desulfurization effect tends to be superior to that when coal with a high degree of coalification such as anthracite is used, and when coal with a low degree of coalification such as lignite is used. It tends to have excellent carbon yield.
The particle size (average particle size) of coal used in the present invention is not particularly limited. For example, even if the particle size of coal is about several millimeters, there is no significant change in desulfurization performance. If the grain size of the coal is larger than this, a light pulverization treatment may be performed, if necessary.

The primary treatment (chemical treatment) for desulfurizing coal has been described above.
Next, two types of secondary treatments will be described as treatments for further removing sulfur remaining in the coal desulfurized by the primary treatment.

<Secondary treatment (heat treatment)>
Thiophene sulfur, which is difficult to remove, changes to a form that is easy to remove by the action of peracetic acid, which is a reaction product of hydrogen peroxide and acetic anhydride, and is therefore removed by heat treatment at a relatively low temperature (about 150 ° C). it can.
That is, it is preferable to further heat-treat the coal in contact with the chemical because the desulfurization effect is more excellent. The heat treatment temperature is preferably 150 ° C. or higher, more preferably 250 ° C. or higher, and even more preferably 350 ° C. or higher.

It should be noted that the hydrocarbon-containing hydrocarbon-containing gas derived from coal generated by the heat treatment can be recovered and used as a part of the gaseous fuel in the steelmaking process. Considering heat treatment using waste heat generated in a factory such as a steel mill, heat treatment at a temperature of up to several hundred ° C. is preferable.

There is a coke oven as a furnace for heat-treating coal in the steelmaking process. The heat treatment temperature in the coke oven is about 1000 to 1200 ° C., and some operations are performed at 1200 ° C. or higher. Coal desulfurized in contact with a chemical may be introduced into a coke oven to produce low sulfur coke. At this time, a hydrocarbon gas and a sulfur-containing gas are generated, but the sulfur-containing gas may be removed separately. The generated gas after removing the sulfur-containing gas can be reused as a fuel gas.
Of the processes for heat-treating coal, the highest temperature is considered to be substantially the coke manufacturing process. As a result of experiments by the present inventors, it was confirmed that a sufficient desulfurization effect was exhibited even by the heat treatment temperature in the coke oven.
Therefore, the heat treatment temperature is, for example, 1300 ° C. or lower.

Coal heat-treated at about 600 ° C is generally called semi-coke. Coal desulfurized in contact with chemicals can also be used in the production of semi-coke. Semi-coke is generally inferior in strength to coke, so it is difficult to use as blast furnace coke, but it can be used for other purposes. In particular, semi-coke containing a small amount of sulfur is useful as, for example, a heating agent (carbonizing material) used for raising the temperature in a converter.

It is preferable that the rate of temperature rise when raising the temperature of coal in contact with the chemical to the heat treatment temperature (hereinafter, also simply referred to as “rate of temperature rise”) is high. This is because the sulfur compound, which has been transformed into a form that is easy to desulfurize by the action of a mixed solution of hydrogen peroxide and acetic anhydride, may be resynthesized into thiophene sulfur, which is difficult to desulfurize under heating. This is to suppress. Specifically, the rate of temperature rise is preferably 10 ° C./min or higher, more preferably 20 ° C./min or higher.

The upper limit of the temperature rise rate is not particularly limited, but it is technically and industrially (cost-wise) difficult to realize a temperature rise rate that is too fast. Therefore, the rate of temperature rise is, for example, 100 ° C./min or less.

<Secondary treatment (hydrogen peroxide treatment)>
According to the studies by the present inventors, it has been found that in further desulfurization of coal in contact with a chemical, a treatment using low-temperature hydrogen peroxide may be performed in addition to the above-mentioned heat treatment.
When hydrogen peroxide is allowed to act on coal that has not been subjected to the primary treatment (chemical treatment), the carbon skeleton is destroyed and the carbon yield is lowered as described above. However, the sulfur content remaining in the primary-treated coal is easily removed, and can be easily additionally desulfurized with hydrogen peroxide.
That is, it is preferable that the coal that has been brought into contact with the chemical is further brought into contact with the low-temperature hydrogen peroxide solution.

The temperature of the hydrogen peroxide solution is preferably 50 ° C. or lower, more preferably 40 ° C. or lower. Hydrogen peroxide gradually increases its oxidizing power as the temperature rises, and tends to reduce not only the desulfurization effect but also the carbon yield. When the temperature of the hydrogen peroxide solution is within the above range, the desulfurization effect is further excellent and the carbon yield is also good.
The lower limit is not particularly limited, and the temperature of the hydrogen peroxide solution is, for example, 5 ° C. or higher.

The concentration of the hydrogen peroxide solution (content of hydrogen peroxide in the hydrogen peroxide solution) is preferably 2.0% by mass or more, more preferably 3.0% by mass or more, because the desulfurization effect is further excellent.
When the concentration of the hydrogen peroxide solution is 3.0% by mass or more, the obtained effect is almost constant regardless of the concentration of the hydrogen peroxide solution. Therefore, the upper limit is not particularly limited, but for example, the concentration of the hydrogen peroxide solution is preferably 35.0% by mass or less.
Since hydrogen peroxide is easily decomposed on the high concentration side, it is often marketed as an aqueous solution of 30 to 35% by mass. In the present invention, such a commercially available aqueous solution may be appropriately diluted before use.

[Low sulfur coal manufacturing equipment]
Next, an example in which the present invention is carried out using specific equipment will be described with reference to FIG.

FIG. 3 is a schematic view showing an example of a low-sulfur coal manufacturing facility (hereinafter, also simply referred to as “manufacturing facility”).
The manufacturing facility shown in FIG. 3 has a hydrogen peroxide storage tank 1 for storing hydrogen peroxide and an acetic anhydride storage tank 3 for storing acetic anhydride.
The hydrogen peroxide inside the hydrogen peroxide storage tank 1 is supplied to the chemical mixing tank 5 via the hydrogen peroxide transport pipe 2. The acetic anhydride inside the acetic anhydride storage tank 3 is supplied to the drug mixing tank 5 via the acetic anhydride transport pipe 4. An appropriate flow rate control device (not shown) is installed in each of the hydrogen peroxide transport pipe 2 and the acetic anhydride transport pipe 4, and the flow rates of hydrogen peroxide and acetic anhydride can be controlled.
A heating device 6 and a mixing device 7 are installed in the chemical mixing tank 5. The hydrogen peroxide and acetic anhydride supplied to the chemical mixing tank 5 are heated to a predetermined temperature by using the heating device 6 as necessary, and are mixed by using the mixing device 7.
The drug, which is a mixed solution obtained by mixing in the drug mixing tank 5, is supplied to the desulfurization treatment tank 9 via the drug transport pipe 8. An appropriate flow rate control device (not shown) is installed in the drug transport pipe 8, and the flow rate of the drug can be controlled.
Further, coal is supplied to the desulfurization tank 9 from the coal storage tank 10 for storing coal via the coal transport pipe 11. An appropriate flow rate control device (not shown) is installed in the coal transport pipe 11, and the flow rate of coal can be controlled.
A heating device 12 is installed in the desulfurization treatment tank 9. The heating device 12 controls the chemicals supplied from the chemical mixing tank 5 and the coal supplied from the coal storage tank 10 to an appropriate temperature as needed. Further, a mixing device 13 is installed in the desulfurization treatment tank 9. The mixing device 13 mixes the drug and coal well, if necessary.
In this way, in the desulfurization tank 9, coal is desulfurized by coming into contact with a chemical to obtain low-sulfurized coal (low-sulfur coal) (hereinafter, also referred to as “chemical-treated coal”).

The desulfurization treatment tank 9 is provided with two discharge holes. A drug circulation pipe 14 is installed in one discharge hole. Peracetic acid may partially remain in the chemicals after being used for desulfurization of coal. In that case, the chemical may be refluxed from the desulfurization tank 9 to the chemical mixing tank 5 and reused.
However, sulfur may be leached into the chemical after desulfurization. Reusing chemicals that are leached with sulfur can adversely affect desulfurization. Therefore, the drug discharge pipe 15 is connected to the drug circulation pipe 14, and a part or all of the desulfurized drug can be discharged through the drug discharge pipe 15.

A chemical treatment coal transport pipe 16 is installed in another discharge hole of the desulfurization treatment tank 9. The chemical treatment coal transport pipe 16 is further branched into three. That is, there are three: a chemical treatment charcoal discharge pipe 16a, a heat treatment device connecting pipe 16b, and a hydrogen peroxide treatment device connecting pipe 16c.
The chemical-treated coal discharge pipe 16a discharges the chemical-treated coal obtained in the desulfurization treatment tank 9 without secondary treatment. The heat treatment device connecting pipe 16b transports the chemical-treated charcoal to the heat treatment device 17. The hydrogen peroxide treatment device connecting pipe 16c transports the chemical treatment charcoal to the hydrogen peroxide treatment device 23.

First, the heat treatment apparatus 17 will be described.
When low sulfur coal (chemically treated coal) is heat-treated in the heat treatment apparatus 17, sulfur is further volatilized, so that desulfurization further proceeds. The coal that has been heat-treated in the heat treatment apparatus 17 to further reduce sulfur (hereinafter, also referred to as “heat-treated coal”) is taken out through the heat-treated coal discharge pipe 18 and used for a predetermined purpose.
Further, the heat treatment apparatus 17 is provided with a heat treatment gas discharge pipe 19. The gas produced by the heat treatment may contain flammable gas. In that case, the gas can be taken out through the heat-treated gas discharge pipe 19 and used for a predetermined purpose.

Next, the hydrogen peroxide treatment apparatus 23 will be described.
Chemically treated charcoal is supplied to the hydrogen peroxide treatment device 23 via the hydrogen peroxide treatment device connecting pipe 16c. In the hydrogen peroxide treatment apparatus 23, the above-mentioned secondary treatment (hydrogen peroxide treatment) is applied to the chemical-treated charcoal.
Hydrogen peroxide is supplied to the hydrogen peroxide treatment device 23 via the hydrogen peroxide supply pipe 20. The hydrogen peroxide supply pipe 20 is connected to the hydrogen peroxide storage tank 1. When diluting hydrogen peroxide, water may be supplied from the diluted water tank 21 through the diluted water supply pipe 22. Another hydrogen peroxide storage tank (not shown) may be installed exclusively for the hydrogen peroxide treatment device 23.
A cooling device 24 is installed in the hydrogen peroxide treatment device 23. The cooling device 24 controls the temperature inside the hydrogen peroxide treatment device 23 to an appropriate temperature as needed.
Further, a mixing device 25 is installed in the hydrogen peroxide treatment device 23. The mixing device 25 mixes the hydrogen peroxide solution and the chemical-treated coal well, if necessary.

The hydrogen peroxide treatment device 23 is provided with two discharge holes.
A hydrogen peroxide circulation pipe 27 is installed in one discharge hole. A part of hydrogen peroxide may remain in the hydrogen peroxide solution after being used for desulfurization of coal (chemically treated coal). In that case, the hydrogen peroxide solution may be refluxed from the hydrogen peroxide treatment device 23 to the hydrogen peroxide storage tank 1 and reused. The reflux destination may be a hydrogen peroxide storage tank (not shown) installed separately, or a chemical mixing tank 5.
However, sulfur may be leached into the hydrogen peroxide solution after desulfurization. Reusing hydrogen peroxide with sulfur leaching can adversely affect desulfurization. Therefore, the hydrogen peroxide discharge pipe 28 is connected to the hydrogen peroxide circulation pipe 27, and a part or all of the desulfurized hydrogen peroxide solution can be discharged through the hydrogen peroxide discharge pipe 28.

A discharge pipe 26 is connected to another discharge hole of the hydrogen peroxide treatment device 23. Coal that has been further desulfurized inside the hydrogen peroxide treatment apparatus 23 (hereinafter, also referred to as “hydrogen peroxide treatment coal”) is taken out through the discharge pipe 26 and used for a predetermined purpose.

Since the chemical-treated charcoal transported to the heat treatment apparatus 17 or the hydrogen peroxide treatment apparatus 23 has already been reduced in sulfur, the heat-treated charcoal discharge pipe 18 does not undergo a secondary treatment (heat treatment or hydrogen peroxide treatment). Alternatively, it may be taken out through the discharge pipe 26.

Each part of the manufacturing equipment described based on FIG. 3 does not need to have special specifications, and existing equipment can be used as appropriate. For example, the heat treatment apparatus 17 may be a heat exchange apparatus using exhaust heat as a heat source, or may be a furnace such as a semi-coke furnace or a coke oven.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

<Examples 1 to 16 and Comparative Example 1>
Using the manufacturing equipment described with reference to FIG. 3, a test was conducted to produce low-sulfur coal by desulfurizing coal by the method of the present invention.
As coal, at least one selected from the group consisting of Coal A (subbituminous coal), Coal B (subbituminous coal) and Coal C (semi-smokeless coal) was used. Details of the coal used are shown in Table 1 below. The average particle size of the coal was about 300 μm. In all coals, the penetrating power of peracetic acid was strong, and the desulfurization performance did not change significantly depending on the particle size.

In Table 1 above, "daf" indicates that it is based on dry ash free, and means the analytical value of net coal excluding water and ash.
“Db” means a dry basis analytical value.
"VM" means the content of volatile matter in industrial analysis.
"Ash" means the ash content in the industrial analysis.

The test conditions such as the supply amount (flow rate) of coal, hydrogen peroxide and acetic anhydride are shown in Table 2 below.
In Examples 1 to 7 and Comparative Example 1, only the above-mentioned primary treatment (drug treatment) was performed. That is, the coal after contact with the chemical was taken out, and the desulfurization rate and the carbon yield were determined.
In Examples 8 to 11, the secondary treatment (heat treatment) described above was further performed. That is, after the primary treatment (chemical treatment), coal was further introduced into a heat treatment apparatus capable of raising the temperature to 1200 ° C. and heat-treated in a nitrogen atmosphere to determine the desulfurization rate and carbon yield after the heat treatment. ..
In Examples 12 to 16, the secondary treatment (hydrogen peroxide treatment) described above was further performed. That is, after the primary treatment (chemical treatment), coal was further introduced into a hydrogen peroxide treatment apparatus and subjected to hydrogen peroxide treatment, and the desulfurization rate and carbon yield after the hydrogen peroxide treatment were determined.

In the primary treatment, an aqueous solution having a hydrogen peroxide concentration of 35% by mass was used as the hydrogen peroxide. As acetic anhydride, acetic anhydride having a purity of 99% by mass was used.

<Summary of test results>
It was found that Examples 1 to 16 in which a mixed solution of hydrogen peroxide and acetic anhydride was used as a drug showed a higher desulfurization rate than Comparative Example 1 in which this was not used, and a sufficient desulfurization effect was obtained. The carbon yield was also good.

Comparing Example 1 and Example 4, the molar ratio (acetic anhydride / hydrogen peroxide) is 5.0, and Example 1 has a molar ratio (acetic anhydride / hydrogen peroxide) of 0.4. The desulfurization rate was higher than that of Example 4, and the desulfurization effect was more excellent.

Comparing Example 1 and Example 5, the desulfurization rate of Example 1 in which the elapsed time after mixing acetic anhydride and hydrogen peroxide is 30 minutes is higher than that in Example 5 in which this time is 8 minutes. It was high and had a better desulfurization effect.

Comparing Example 1 and Example 6, the desulfurization rate of Example 1 having a mass ratio (drug / coal) of 3.2 is higher than that of Example 6 having a mass ratio (drug / coal) of 0.9. Was high, and the desulfurization effect was better.

Comparing Example 1 and Example 7, Example 1 in which the temperature of the chemicals in contact with coal was 20 ° C. had a better carbon yield than Example 7 in which this temperature was 35 ° C. ..

The desulfurization rates of Examples 8 to 11 (after the secondary treatment) were equal to or higher than the desulfurization rates of Examples 1 to 7 (after the primary treatment).
Comparing Example 8 and Example 10, the desulfurization rate (after the secondary treatment) of Example 8 having a heat treatment temperature of 150 ° C. is higher than that of Example 10 having a heat treatment temperature of 100 ° C., and the desulfurization effect is higher. It was better.
Comparing Example 8 and Example 11, Example 8 in which the rate of temperature rise to the heat treatment temperature is 20 ° C./min is higher than that of Example 11 in which the rate of temperature rise is 5 ° C./min. The desulfurization rate (after the secondary treatment) was high, and the desulfurization effect was more excellent.

The desulfurization rates of Examples 12 to 16 (after the secondary treatment) were equal to or higher than the desulfurization rates of Examples 1 to 7 (after the primary treatment).
Comparing Example 12 and Example 14, the desulfurization rate (after the secondary treatment) of Example 12 in which the temperature of the hydrogen peroxide solution is 20 ° C. is higher than that of Example 14 in which the temperature is 45 ° C. , The desulfurization effect was better.
Comparing Example 12 and Example 15, the desulfurization rate (2) of Example 12 having a hydrogen peroxide solution concentration of 35.0% by mass is higher than that of Example 15 having this concentration of 1.5% by mass. After the next treatment), the desulfurization effect was more excellent.
Comparing Example 12 and Example 16, the mass ratio (hydrogen peroxide solution / coal) of Example 12 is 2.5, and the mass ratio (hydrogen peroxide solution / coal) of Example 12 is 0.9. The desulfurization rate (after the secondary treatment) was higher than that of Example 16, and the desulfurization effect was more excellent.

1: Hydrogen peroxide storage tank 2: Hydrogen peroxide transport pipe 3: Anhydrous acetic acid transport pipe 4: Anhydrous acetic acid transport pipe 5: Chemical mixing tank 6: Heating device 7: Mixing device 8: Chemical transport pipe 9: Desulfurization treatment tank 10 : Coal storage tank 11: Coal transport pipe 12: Heating device 13: Mixing device 14: Chemical circulation pipe 15: Chemical discharge pipe 16: Chemical treatment coal transport pipe 16a: Chemical treatment coal discharge pipe 16b: Heat treatment device connecting pipe 16c: Excessive Hydrogen oxide treatment device connection pipe 17: Heat treatment device 18: Heat treatment charcoal discharge pipe 19: Heat treatment gas discharge pipe 20: Hydrogen peroxide supply pipe 21: Diluted water tank 22: Diluted water supply pipe 23: Hydrogen peroxide treatment device 24: Cooling Device 25: Mixing device 26: Discharge pipe 27: Hydrogen peroxide circulation pipe 28: Hydrogen peroxide discharge pipe

Claims

A method for producing low-sulfur coal, which removes sulfur in the coal by contacting the coal with a chemical that is a mixed solution of hydrogen peroxide and acetic anhydride.
The method for producing low-sulfur coal according to claim 1, wherein the molar ratio of the acetic anhydride to the hydrogen peroxide (acetic anhydride / hydrogen peroxide) is 0.5 or more and 12.0 or less.
The acetic anhydride and the hydrogen peroxide are mixed before bringing the drug into contact with the coal.
The method for producing low-sulfur coal according to claim 1 or 2, wherein the chemical is brought into contact with the coal after a lapse of 10 minutes or more after the mixing.
The method for producing low-sulfur coal according to any one of claims 1 to 3, wherein the mass ratio (drug / coal) of the chemical to the coal is 1.0 or more.
The method for producing low-sulfur coal according to any one of claims 1 to 4, wherein the temperature of the chemical when brought into contact with the coal is 5 ° C. or higher.
The method for producing low-sulfur coal according to any one of claims 1 to 5, wherein the temperature of the chemical when brought into contact with the coal is 30 ° C. or lower.
The method for producing low-sulfur coal according to any one of claims 1 to 6, wherein the coal contains subbituminous coal.
The method for producing low-sulfur coal according to any one of claims 1 to 7, wherein the coal in contact with the chemical is heat-treated at a heat treatment temperature of 150 ° C. or higher.
The method for producing low-sulfur coal according to claim 8, wherein the rate of temperature rise when raising the temperature of the coal in contact with the chemical to the heat treatment temperature is 10 ° C./min or more.
The method for producing low-sulfur coal according to any one of claims 1 to 7, wherein the coal brought into contact with the chemical is brought into contact with a hydrogen peroxide solution having a temperature of 40 ° C. or lower.
The concentration of the hydrogen peroxide solution is 2.0% by mass or more,
The method for producing low-sulfur coal according to claim 10, wherein the mass ratio of the hydrogen peroxide solution to the coal (hydrogen peroxide solution / coal) is 1.0 or more.