JP6992905B2 - Manufacturing method of low sulfur coal - Google Patents

Description

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

When coal is used as a reducing material for iron ore in the iron-making process, a part of sulfur contained in the coal is solidly dissolved 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.
Further, when coal is used as a heat source, sulfur oxides are mixed in the exhaust gas, so that a great deal of effort is required to remove sulfur from the exhaust gas from the viewpoint of preventing air pollution.

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-sulfur 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 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 [16].
[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 acid.
[2] The method for producing low sulfur coal according to the above [1], wherein the molar ratio (acetic acid / hydrogen peroxide) of the acetic acid to the hydrogen peroxide is 1.2 or more and 60.0 or less.
[3] Before the chemical is brought into contact with the coal, the acetic acid and the hydrogen peroxide are mixed.
The method for producing low-sulfur coal according to the above [1] or [2], wherein the chemical is brought into contact with the coal after 30 minutes or more have passed after the mixing.
[4] A method for producing low-sulfur coal, which removes sulfur in the coal by contacting the coal with a chemical that is an aqueous solution of peracetic acid.
[5] The method for producing low-sulfur coal according to the above [4], wherein the content of peracetic acid in the drug is 10.0% by mass or more and 25.0% by mass or less.
[6] 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 formic acid.
[7] The method for producing low-sulfur coal according to the above [6], wherein the molar ratio (formic acid / hydrogen peroxide) of the formic acid to the hydrogen peroxide is 1.2 or more and 60.0 or less.
[8] The formic acid and the hydrogen peroxide are mixed before the chemical is brought into contact with the coal, and after 5 minutes or more have passed after the mixing, the formic acid is brought into contact with the coal. 6] or the method for producing low sulfur coal according to [7].
[9] The method for producing low-sulfur coal according to any one of the above [1] to [8], wherein the mass ratio (drug / coal) of the chemical to the coal is 1.0 or more.
[10] The method for producing low-sulfur coal according to any one of the above [1] to [9], wherein the temperature of the chemical when brought into contact with the coal is 10 ° C. or higher.
[11] The method for producing low-sulfur coal according to any one of [1] to [10] above, wherein the temperature of the chemical when brought into contact with the coal is 60 ° C. or lower.
[12] The method for producing low-sulfur coal according to any one of the above [1] to [11], wherein the coal contains subbituminous coal.
[13] The method for producing low-sulfur coal according to any one of the above [1] to [12], wherein the coal in contact with the chemical is heat-treated at a heat treatment temperature of 150 ° C. or higher.
[14] The method for producing low-sulfur coal according to the above [13], wherein the heating rate when raising the temperature of the coal in contact with the chemical to the heat treatment temperature is 10 ° C./min or more.
[15] The method for producing low-sulfur coal according to any one of the above [1] to [12], 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.
[16] 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 hydrogen solution / coal) is 1.0 or more. The method for producing low-hydrogen coal according to the above [15].

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 equipment 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-mentioned coal is removed by contacting the coal with a chemical which is a mixed solution of hydrogen peroxide and acetic acid. It is a method for producing low-sulfur coal to be removed.
Further, the method of the present invention is a method for producing low-sulfur coal, which removes sulfur in the coal by contacting the coal with a chemical which is an aqueous solution of peracetic acid.
Further, the method of the present invention is 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 formic acid.

<Primary treatment (drug treatment)>
In the following, first, the primary treatment (chemical treatment) in which coal is brought into contact with a specific chemical 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 the inorganic sulfur. Examples of the organic sulfur include aromatic sulfur compounds in which sulfur is present inside an aromatic ring such as dibenzothiophene; and aliphatic sulfur compounds such as mercaptan; Of these, it is known that sulfur existing inside the aromatic ring constituting coal is particularly difficult to remove.

The present inventors have investigated various agents (desulfurization agents). 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 have found that it is more efficient. It is presumed that due to the action of peracetic acid, thiophene sulfur is oxidized to, for example, sulfosulfur 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 (CH ₃ COO ₂ H) is generally used in a mixed solution of hydrogen peroxide (H ₂ O ₂ ) and acetic acid (CH ₃ COOH) (hereinafter, also simply referred to as “mixed solution”). It is produced by the reaction represented by the following formula (I).
H ₂ O ₂ + CH ₃ COOH ⇔ 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 details of the suitable conditions will be described later.

It is also practiced to accelerate the forward reaction of the above formula (I) using a catalyst to obtain an aqueous peracetic acid solution by means such as distillation. In this case, there is an optimum concentration of peracetic acid, which will be described in detail later.

That is, such a mixed solution or an aqueous solution of peracetic acid is used as a drug, and the drug is brought into contact with coal.
When the drug is brought into contact with coal, the easily removable inorganic sulfur dissolves and leaches into the drug 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 (that is, the sulfur in the coal is removed) to obtain a low-sulfurized coal (low-sulfur coal).

The present inventors have further found that performic acid has the same effect as peracetic acid.
Therefore, in the present invention, a mixed solution of hydrogen peroxide and formic acid (hereinafter, also simply referred to as “mixed solution”) is used as a drug. The mixed solution produces performic acid (HCOO ₂ H), which is a reaction product of hydrogen peroxide (H ₂ O ₂ ) and formic acid (HCOOH), by a reaction represented by the following formula (II). Such a mixture is brought into contact with coal.
H ₂ O ₂ + HCOOH ⇔ HCOO ₂ H + H ₂ O ... (II)

《Mole ratio (acetic acid / hydrogen peroxide)》
When a mixed solution of acetic acid and hydrogen peroxide is used as the drug, the molar ratio of acetic acid to hydrogen peroxide (acetic acid / hydrogen peroxide) in the drug is such that the reaction product peracetic acid is an appropriate amount and the desulfurization effect is more effective. For the reason of superiority, 1.2 or more is preferable, and 5.0 or more is more preferable.
Further, when the molar ratio (acetic acid / hydrogen peroxide) is in this range, acetic acid becomes excessive with respect to hydrogen peroxide, and it is possible to suppress the residual hydrogen peroxide in the mixed solution (as described later). Hydrogen peroxide reduces the carbon yield of coal).

The molar ratio (acetic acid / hydrogen peroxide) is preferably 60.0 or less, more preferably 20.0 or less. When the molar ratio (acetic acid / 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 acid.

The molar ratio (acetic acid / hydrogen peroxide) is calculated as follows.
First, the molar amount [mol] of each component (acetic acid or hydrogen peroxide) in the drug is represented by the following formula (a). Therefore, the molar ratio of acetic acid to hydrogen peroxide (acetic acid / hydrogen peroxide) in the drug is calculated by the following formula (b).
Mole amount = (Li × Ci) / (100 × Mi)… (a)
Mole 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 acid when it is 1, and hydrogen peroxide when it is 2.
The molecular weight of acetic acid is 60, and the molecular weight of hydrogen peroxide is 34. The amount Li of the aqueous solution is adjusted so that the desired molar ratio (acetic acid / hydrogen peroxide) is obtained.

《Mole ratio (formic acid / hydrogen peroxide)》
When a mixed solution of formic acid and hydrogen peroxide is used as the drug, the molar ratio of formic acid to hydrogen peroxide (formic acid / hydrogen peroxide) in the drug is preferably 1.2 or more, more preferably 5.0 or more. .. On the other hand, 60.0 or less is preferable, and 20.0 or less is more preferable. The reason is the same as when a mixed solution of acetic acid and hydrogen peroxide is used as a drug.
In the above formula (II), as in the above formula (I), the two substances that react with each other are 1 mol each. Therefore, the molar amount (molar ratio) of the reactant required for the production of performic acid is the same.
The method for determining the molar ratio (formic acid / hydrogen peroxide) is described in the above formulas (a) and (b).
Replace "acetic acid" with "formic acid". Formic acid has a molecular weight of 46.

<< Elapsed time after mixing acetic acid and hydrogen peroxide >>
The reaction of the above formula (I) (forward reaction) is slow. Therefore, immediately after mixing acetic acid and hydrogen peroxide, the production of peracetic acid may be insufficient.
The present inventors have quantified various reaction rates and clarified that it takes about 30 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 acid and hydrogen peroxide before bringing the drug into contact with coal, and after 30 minutes or more have passed after this mixing, bring the drug into contact with coal. As a result, peracetic acid is sufficiently generated, 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 acetic acid and hydrogen peroxide is more preferably 45 minutes or more, further preferably 60 minutes or more. On the other hand, 120 minutes or less is preferable, and 80 minutes or less is more preferable.

<< Elapsed time after mixing formic acid and hydrogen peroxide >>
The reaction of the above formula (II) (forward reaction) is faster than the reaction of the above formula (I). Therefore, the time elapsed after mixing and before contacting with coal may be shorter than that in the case of mixing acetic acid and hydrogen peroxide.
Specifically, the elapsed time after mixing formic acid and hydrogen peroxide is preferably 5 minutes or longer, more preferably 6 minutes or longer. On the other hand, 90 minutes or less is preferable, and 60 minutes or less is more preferable.

<< Concentration of peracetic acid aqueous solution (content of peracetic acid) >>
When a peracetic acid aqueous solution is used as a drug, the content of peracetic acid in the drug (peracetic acid aqueous solution) is preferably 1.0% by mass or more, preferably 5.0% by mass or more, because the desulfurization effect is more excellent. More preferably, 10.0% by mass or more.
On the other hand, the content of peracetic acid in the drug (peracetic acid aqueous solution) is preferably 25.0% by mass or less. Peracetic acid has a risk of ignition on the high concentration side, but within this range, it can be safely and sufficiently desulfurized.

《Mass ratio (drug / coal)
The present inventors examined the mass ratio of chemicals to coal (drugs / coal). In this study, a drug having a molar ratio of acetic acid to hydrogen peroxide (acetic acid / hydrogen peroxide) of 12.0 was used.
FIG. 1 is a graph showing the desulfurization rate with respect to the mass ratio (drug / coal) of chemicals and 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.

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.

When the molar ratio (acetic acid / hydrogen peroxide) is changed within the above range, the same as the graph in FIG. 1 is applied even when a different drug (peracetic acid aqueous solution or mixed solution of formic acid and hydrogen peroxide) is used. The tendency was seen.

The desulfurization rate [mass%] is such that the mass of the coal (solid content) before desulfurization is W ₁ [kg], the sulfur content of the coal (solid content) before desulfurization is% S ₁ [mass%], and after desulfurization. When the mass of the coal (solid content) is W ₂ [kg] and the sulfur content of the desulfurized coal (solid content) 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 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 acid to hydrogen peroxide (acetic acid / hydrogen peroxide) of 12.0 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 contributing substances (hydrogen peroxide and acetic acid) have completely reacted.

As shown in the graphs of FIG. 2 (lower and upper), when the temperature of the chemicals in contact 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 50 ° C. or higher.

On the other hand, as shown in the graph (upper part) of FIG. 2, in order to maintain a high carbon yield, it is preferable that the temperature of the drug does not become too high. Specifically, 65 ° C. or lower is preferable, 60 ° C. or lower is more preferable, and 55 ° C. or lower is further preferable, because the carbon yield is excellent.

When the molar ratio (acetic acid / hydrogen peroxide) is changed within the above range, the same as the graph in FIG. 2 is applied even when a different drug (peracetic acid aqueous solution or mixed solution of formic acid and hydrogen peroxide) is used. The tendency was seen.

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 for the decrease in carbon yield is presumed as follows.
Hydrogen peroxide and peracetic acid (or performic acid) can act as oxidants and destroy the skeleton of coal, which is thought to result in an unintended decrease in carbon yield at the same time as the removal of sulfur. As a result of the study 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 (or performic acid) and strong with hydrogen peroxide. This is especially noticeable with high temperature hydrogen peroxide.
Therefore, by appropriately controlling the conditions for contacting the drug with coal (for example, the mixing ratio of hydrogen peroxide in the mixed solution is appropriately adjusted so that the temperature of the drug does not become too high), carbon is used. 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 better than when coal with a high degree of calcification such as anthracite is used, and compared with the case where coal with a low degree of calcification 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-like sulfur, which is difficult to remove, changes to a form that is easily removed by the action of peracetic acid or performic acid, and can be removed by heat treatment at a relatively low temperature (about 150 ° C.).
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.

The hydrocarbon-containing hydrocarbon-containing gas produced by the heat treatment can be recovered and used as a part of the gaseous fuel in the iron-making 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 degrees Celsius is preferable.

As a furnace for heat-treating coal in the steelmaking process, there is a coke oven. 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 a heating agent (carbonizing material) used for raising the temperature in a converter, for example.

It is preferable that the heating rate (hereinafter, also simply referred to as “heating rate”) when raising the temperature of coal in contact with the chemical to the heat treatment temperature is high. This is because sulfur compounds that have been transformed into a form that is easy to desulfurize by the action of peracetic acid or performic acid may be resynthesized into thiophene-like sulfur, which is difficult to desulfurize under heating, and this resynthesis is suppressed. be. 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 used 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 diagram showing an example of a low-sulfur coal manufacturing facility (hereinafter, also simply referred to as “manufacturing facility”).
The manufacturing equipment shown in FIG. 3 has a hydrogen peroxide storage tank 1 for storing hydrogen peroxide and an acetic acid storage tank 3 for storing acetic acid.
The hydrogen peroxide inside the hydrogen peroxide storage tank 1 is supplied to the drug mixing tank 5 via the hydrogen peroxide transport pipe 2. The acetic acid inside the acetic acid storage tank 3 is supplied to the drug mixing tank 5 via the acetic acid 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 acid transport pipe 4, and the flow rates of hydrogen peroxide and acetic acid 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 acid supplied to the chemical mixing tank 5 are heated to a predetermined temperature by using the heating device 6 as needed, 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 to control the flow rate of the drug.
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 to control the flow rate of coal.
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 contacting 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 and acetic acid may remain in some of the chemicals used for desulfurization of coal. In that case, the chemical may be refluxed from the desulfurization treatment tank 9 to the chemical mixing tank 5 and reused.
However, sulfur may be leached out from the desulfurized chemicals. Reuse of sulfur-leached chemicals 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 charcoal transport pipe 16 is installed in another discharge hole of the desulfurization treatment tank 9. The chemical treatment charcoal transport pipe 16 is further branched into three. That is, there are three types: 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 charcoal discharge pipe 16a discharges the chemical-treated charcoal 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 charcoal 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 for reuse. The reflux destination may be a hydrogen peroxide storage tank (not shown) separately installed, or a chemical mixing tank 5.
However, sulfur may be leached out in 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 hydrogen peroxide solution after desulfurization 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 device 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 with reference to 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 waste heat as a heat source, or may be a furnace such as a semi-coke furnace or a coke oven.

When formic acid is used instead of acetic acid in the manufacturing equipment shown in FIG. 3, "acetic acid" is read as "formic acid" and "peracetic acid" is read as "peracetic acid".
In this case, the manufacturing equipment shown in FIG. 3 has a "formic acid storage tank 3" instead of the "acetic acid storage tank 3" and a "formic acid transport pipe 3" instead of the "acetic acid transport pipe 3".

When a peracetic acid aqueous solution is used as a chemical, the manufacturing facility shown in FIG. 3 replaces the "hydrogen peroxide storage tank 1" with the "peracetic acid storage tank 1" and replaces the "hydrogen peroxide transport pipe 2" with "hydrogen peroxide transport pipe 2". The "peracetic acid transport pipe 2" has a "diluted water storage tank 3" in place of the "acetic acid storage tank 3" and a "diluted water transport pipe 4" in place of the "acetic acid transport pipe 4".
In this case, the peracetic acid storage tank 1 stores peracetic acid. The diluted water storage tank 3 stores diluted water for diluting peracetic acid. The peracetic acid inside the peracetic acid storage tank 1 is supplied to the drug mixing tank 5 via the peracetic acid transport pipe 2. The diluted water inside the diluted water storage tank 3 is supplied to the drug mixing tank 5 via the diluted water transport pipe 4. An appropriate flow rate control device (not shown) is installed in each of the peracetic acid transport pipe 2 and the diluted water transport pipe 4, and the flow rates of the peracetic acid and the diluted water can be controlled.
In the drug mixing tank 5, the supplied peracetic acid and diluted water are mixed to prepare a peracetic acid aqueous solution.
Since the points other than these are the same as above, the description thereof will be omitted.

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 31 and Comparative Examples 1 to 2>
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 the 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, "d.af" indicates that it is based on dry ash free, and means the analytical value of net coal excluding water and ash.
"Db." Means that it is 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 are shown in Tables 2 to 4 below.
In Examples 1 to 8, 20 to 22 and 24 to 27, and Comparative Examples 1 to 2, 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 9 to 13, 23 and 28 to 29, the above-mentioned secondary treatment (heat treatment) 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 under a nitrogen atmosphere to determine the desulfurization rate and carbon yield after the heat treatment. ..
In Examples 14 to 19 and 30 to 31, the above-mentioned secondary treatment (hydrogen peroxide treatment) 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 acid, acetic acid having a purity of 99% by mass was used. As the peracetic acid, an aqueous solution having a peracetic acid concentration of 30% by mass was used. As formic acid, formic acid having a purity of 99% by mass was used.

<Summary of Table 2>
It was found that Examples 1 to 19 in which a mixed solution of hydrogen peroxide and acetic acid was used as a drug showed a higher desulfurization rate than Comparative Examples 1 and 2 in which this was not used, and a sufficient desulfurization effect was obtained. .. The carbon yield also tended to be good.

Comparing Example 1 and Example 5, Example 1 has a molar ratio (acetic acid / hydrogen peroxide) of 12.1 and Example 1 has a molar ratio (acetic acid / hydrogen peroxide) of 0.8. The desulfurization rate was higher than that, and the desulfurization effect was better.

Comparing Example 1 and Example 6, Example 1 in which the elapsed time after mixing acetic acid and hydrogen peroxide is 60 minutes has a higher desulfurization rate than Example 6 in which this time is 20 minutes. , The desulfurization effect was better.

Comparing Example 1 and Example 7, the desulfurization rate of Example 1 having a mass ratio (drug / coal) of 2.5 is higher than that of Example 7 having a mass ratio (drug / coal) of 0.9. Was high, and the desulfurization effect was better.

Comparing Example 1 and Example 8, Example 1 in which the temperature of the chemicals in contact with coal is 56 ° C. has a higher desulfurization rate than Example 8 in which this temperature is 9 ° C., and has a desulfurization effect. Was better.

The desulfurization rate of Examples 9 to 13 (after the secondary treatment) was equal to or higher than the desulfurization rate of Examples 1 to 8 (after the primary treatment).
Comparing Example 9 and Example 12, the desulfurization rate (after the secondary treatment) of Example 9 having a heat treatment temperature of 150 ° C. is higher than that of Example 12 having a heat treatment temperature of 135 ° C., and the desulfurization effect is higher. Was better.
Comparing Example 9 and Example 13, Example 9 in which the heating rate when raising the temperature to the heat treatment temperature is 20 ° C./min is higher than that in Example 13 in which the heating rate is 5 ° C./min. The desulfurization rate (after the secondary treatment) was high, and the desulfurization effect was more excellent.

The desulfurization rate of Examples 14 to 19 (after the secondary treatment) was equal to or higher than the desulfurization rate of Examples 1 to 8 (after the primary treatment).
Comparing Example 14 and Example 17, the desulfurization rate (after the secondary treatment) of Example 14 in which the temperature of the hydrogen peroxide solution is 20 ° C. is higher than that of Example 17 in which the temperature is 45 ° C. , The desulfurization effect was better.
Comparing Example 14 and Example 18, Example 14 having a concentration of hydrogen peroxide solution of 35.0% by mass has a desulfurization rate (2) higher than that of Example 18 having this concentration of 1.5% by mass. After the next treatment) was high, and the desulfurization effect was more excellent.
Comparing Example 14 and Example 19, the mass ratio (hydrogen peroxide solution / coal) of Example 14 is 2.5, and the mass ratio (hydrogen peroxide solution / coal) of Example 14 is 0.9. The desulfurization rate (after the secondary treatment) was higher than that of Example 19, and the desulfurization effect was more excellent.

<Summary of Table 3>
It was found that Examples 20 to 23 in which the peracetic acid aqueous solution was used as a drug showed a higher desulfurization rate than Comparative Examples 1 and 2 (see Table 2) in which the peracetic acid aqueous solution was not used, and a sufficient desulfurization effect was obtained. .. The carbon yield also tended to be good.
Comparing Example 20 and Example 22, the content of peracetic acid in the drug (aqueous solution of peracetic acid) is 12.7% by mass. In Example 20, this content is 7.8% by mass. The desulfurization rate was higher than that of Example 22, and the desulfurization effect was more excellent.
The desulfurization rate of Example 23 (after the secondary treatment) was equal to or higher than the desulfurization rate of Examples 20 to 22 (after the primary treatment).

<Summary of Table 4>
Examples 24 to 31 in which a mixed solution of hydrogen peroxide and formic acid was used as a drug showed a higher desulfurization rate than Comparative Examples 1 and 2 (see Table 2) in which this was not used, and a sufficient desulfurization effect was obtained. I found out. The carbon yield also tended to be good.
Comparing Example 24 and Example 27, Example 24, which has an elapsed time of 6 minutes after mixing formic acid and hydrogen peroxide, has a higher desulfurization rate than Example 27, which has a time of 3 minutes. , The desulfurization effect was better.

The desulfurization rates of Examples 28 to 29 (after the secondary treatment) were equal to or higher than the desulfurization rates of Examples 24 to 27 (after the primary treatment).
Comparing Example 28 and Example 29, Example 28, which has a temperature rise rate of 20 ° C./min when the temperature is raised to the heat treatment temperature, is higher than that of Example 29, which has a temperature rise rate of 5 ° C./min. The desulfurization rate (after the secondary treatment) was high, and the desulfurization effect was more excellent.

The desulfurization rates of Examples 30 to 31 (after the secondary treatment) were equal to or higher than the desulfurization rates of Examples 24 to 27 (after the primary treatment).
Comparing Example 30 and Example 31, the mass ratio (hydrogen peroxide solution / coal) of Example 30 is 2.5, and the mass ratio (hydrogen peroxide solution / coal) of Example 30 is 0.9. The desulfurization rate (after the secondary treatment) was higher than that of Example 31, and the desulfurization effect was more excellent.

1: Hydrogen peroxide storage tank (peracetic acid storage tank)
2: Hydrogen peroxide transport pipe (peracetic acid transport pipe)
3: Acetic acid storage tank (formic acid storage tank, diluted water storage tank)
4: Acetic acid transport pipe (formic acid transport pipe, diluted water 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-treated charcoal transport pipe 16a: Chemical-treated charcoal discharge pipe 16b: Heat treatment device connecting pipe 16c: Hydrogen peroxide treatment device connecting pipe 17: Heat treatment device 18: Heat-treated charcoal discharge pipe 19: Heat-treated gas discharge pipe 20: Peroxidation Hydrogen supply pipe 21: Diluting water tank 22: Diluting 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 (15)

Sulfur in the coal is removed by contacting the coal with a chemical that is a mixed solution of hydrogen peroxide and acetic acid.
A method for producing low-sulfur coal, in which 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 method for producing low-sulfur coal according to claim 1, wherein the molar ratio of acetic acid to hydrogen peroxide (acetic acid / hydrogen peroxide) is 1.2 or more and 60.0 or less. Prior to contacting the drug with the coal, the acetic acid and the hydrogen peroxide were mixed.
The method for producing low-sulfur coal according to claim 1 or 2, wherein the chemical is brought into contact with the coal after 30 minutes or more have elapsed after the mixing. Sulfur in the coal is removed by contacting the coal with a chemical that is an aqueous solution of peracetic acid.
A method for producing low-sulfur coal, in which 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 method for producing low-sulfur coal according to claim 4, wherein the content of peracetic acid in the drug is 10.0% by mass or more and 25.0% by mass or less. Sulfur in the coal is removed by contacting the coal with a chemical that is a mixed solution of hydrogen peroxide and formic acid.
A method for producing low-sulfur coal, in which 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 method for producing low-sulfur coal according to claim 6, wherein the molar ratio of formic acid to hydrogen peroxide (formic acid / hydrogen peroxide) is 1.2 or more and 60.0 or less. Prior to contacting the drug with the coal, the formic acid and the hydrogen peroxide were mixed.
The method for producing low-sulfur coal according to claim 6 or 7, wherein the chemical is brought into contact with the coal after a lapse of 5 minutes or more after the mixing. The method for producing low-sulfur coal according to any one of claims 1 to 8, 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 9, wherein the temperature of the chemical when brought into contact with the coal is 10 ° C. or higher. The method for producing low-sulfur coal according to any one of claims 1 to 10, wherein the temperature of the chemical when brought into contact with the coal is 60 ° C. or lower. The method for producing low-sulfur coal according to any one of claims 1 to 11, wherein the coal contains subbituminous coal. The method for producing low-sulfur coal according to any one of claims 1 to 12, 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 13, 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 concentration of the hydrogen peroxide solution is 2.0% by mass or more, and the concentration is 2.0% by mass or more.
The method for producing low-sulfur coal according to any one of claims 1 to 12, wherein the mass ratio of the hydrogen peroxide solution to the coal (hydrogen peroxide solution / coal) is 1.0 or more.

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