CN113728076A

CN113728076A - Method for producing low-sulfur coal

Info

Publication number: CN113728076A
Application number: CN202080030636.4A
Authority: CN
Inventors: 村井亮太; 鹫见郁宏; 菅原胜康; 加藤贵宏
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2019-04-24
Filing date: 2020-04-20
Publication date: 2021-11-30
Also published as: JP6795132B1; US20220220404A1; CA3134533A1; JPWO2020218248A1; CA3134533C; AU2020260860B2; AU2020260860A1; WO2020218248A1

Abstract

Provided is a method for producing low-sulfur coal having excellent desulfurization effect. The above-mentioned production method removes sulfur in coal by bringing the coal into contact with a chemical agent which is a mixed solution of hydrogen peroxide and acetic anhydride. The molar ratio of the acetic anhydride to the hydrogen peroxide (acetic anhydride/hydrogen peroxide) is preferably 0.5 to 12.0. Preferably, the acetic anhydride and the hydrogen peroxide are mixed before the chemical reagent is brought into contact with the coal, and after the mixing, the chemical reagent is brought into contact with the coal after a lapse of 10 minutes or more.

Description

Method for producing low-sulfur coal

Technical Field

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

Background

In the case where coal is used as a reducing material of iron ore in the iron making process, a part of sulfur contained in the coal is dissolved in iron obtained by reducing the iron ore. Since the remaining sulfur deteriorates the toughness and workability of the steel, a lot of effort has been made to remove sulfur from iron.

In addition, when coal is used as a heat source, sulfur oxides are mixed into exhaust gas, and therefore, from the viewpoint of preventing air pollution, efforts to remove sulfur from exhaust gas are further required.

From such a background, if sulfur (sulfur content) in coal can be removed before the coal is used, the industrial value is high.

As a method for producing low-sulfur coal (low-sulfur coal), "a method for chemically desulfurizing coal, characterized in that an aqueous solution of caustic soda or caustic potash or an aqueous solution of a mixture of both is mixed with pulverized coal alone and heated to react at a high temperature in an atmosphere of oxygen, air or a mixture thereof to remove sulfur in coal", is described in claims of patent document 1.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 3-275795

Disclosure of Invention

Problems to be solved by the invention

When low-sulfur coal is produced by desulfurizing coal (removing sulfur in coal), the desulfurization effect of the conventional method may be insufficient.

Accordingly, an object of the present invention is to provide a method for producing low-sulfur coal having an excellent desulfurization effect.

Means for solving the problems

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

Namely, the present invention provides the following [1] to [11 ].

[1] A process for producing low-sulfur coal, wherein sulfur in coal is removed by bringing the coal into contact with a chemical agent which is a mixed solution of hydrogen peroxide and acetic anhydride.

[2] The process for producing low-sulfur coal according to [1], wherein a 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 method for producing low-sulfur coal according to [1] or [2], wherein the acetic anhydride and the hydrogen peroxide are mixed before the chemical reagent is brought into contact with the coal, and after the mixing, the chemical reagent is brought into contact with the coal after 10 minutes or more has elapsed.

[4] The method for producing low-sulfur coal according to any one of the above [1] to [3], wherein a mass ratio of the chemical agent to the coal (chemical agent/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 agent at the time of contact with the coal is 5 ℃ or higher.

[6] The method for producing low-sulfur coal according to any one of the above [1] to [5], wherein the temperature of the chemical agent at the time of contact with the coal is 30 ℃ or lower.

[7] The method for producing low-sulfur coal according to any one of the above [1] to [6], wherein the coal contains subbituminous coal.

[8] The method for producing low-sulfur coal according to any one of the above [1] to [7], wherein the coal after contact with the chemical agent is heat-treated at a heat treatment temperature of 150 ℃ or higher.

[9] The process according to [8] above, wherein the rate of temperature rise of the coal after contact with the chemical agent to the heat treatment temperature is 10 ℃/min or more.

[10] The method for producing low-sulfur coal according to any one of the above [1] to [7], wherein the coal after contact with the chemical agent is contacted with hydrogen peroxide at 40 ℃ or lower.

[11] The process for producing low-sulfur coal according to [10], wherein the concentration of the hydrogen peroxide is 2.0% by mass or more, and the mass ratio of the hydrogen peroxide to the coal (hydrogen peroxide/coal) is 1.0 or more.

Effects of the invention

According to the present invention, a method for producing low-sulfur coal having an excellent desulfurization effect can be provided.

Drawings

Fig. 1 is a graph showing the desulfurization rate with respect to the mass ratio of the chemical agent to the coal (chemical agent/coal).

Fig. 2 is a graph showing the amount of peracetic acid produced with respect to the temperature of the chemical agent (lower stage), and a graph showing the desulfurization degree (solid line) and the carbon yield (broken line) with respect to the temperature of the chemical agent (upper stage).

Fig. 3 is a schematic diagram showing an example of a low-sulfur coal production facility.

Detailed Description

[ Process for producing Low-Sulfur coal ]

The method for producing low-sulfur coal of the present invention (hereinafter, also simply referred to as "the method of the present invention") is a method for producing low-sulfur coal in which sulfur in coal is removed by bringing the coal into contact with a chemical agent which is a mixed solution of hydrogen peroxide and acetic anhydride.

(1 treatment (chemical treatment))

First, 1-time treatment (chemical treatment) in which coal is brought into contact with a chemical agent which is a mixed solution of hydrogen peroxide and acetic anhydride will be described below.

The sulfur in coal is roughly classified into inorganic sulfur (inorganic sulfur component) and organic sulfur (organic sulfur component)

The inorganic sulfur typically includes FeS₂. Examples of the organic sulfur include aromatic sulfur compounds in which sulfur is present inside an aromatic ring such as dibenzothiophene; aliphatic sulfur compounds such as mercaptans, and the like. Among these, it is known that sulfur existing inside an aromatic ring constituting coal is particularly difficult to remove.

The inventors of the present application studied various chemical agents (desulfation chemical agents). As a result, it has been found that peracetic acid effectively acts on thiophenic sulfur, which is a particularly difficult component to remove among organic sulfur in coal, thereby removing sulfur from coal or improving the efficiency of converting sulfur into a form that is easily removed. It is presumed that thiophene-state sulfur is oxidized to sulfone-state sulfur or thioether-state sulfur by the action of peracetic acid, and the carbon-sulfur bond is relatively weak and easily broken, whereby sulfur is easily released.

However, peracetic acid is easily decomposed. Therefore, a mixed solution of hydrogen peroxide and acetic anhydride (hereinafter, also simply referred to as "mixed solution") is used as the chemical reagent in the present invention. The mixed solution generates peracetic acid which is a reaction product of hydrogen peroxide and acetic anhydride. Such a mixed solution is brought into contact with coal.

By hydrogen peroxide (H)₂O₂) With acetic anhydride ((CH)₃CO)₂O) to obtain peracetic acid (CH)₃COO₂H) And water (H)₂O) is represented by the following formula (I).

In the formula (I), the equilibrium state changes depending on various conditions such as temperature and a mixing ratio of chemical agents. Therefore, the concentration of each component varies depending on the combination of the conditions. Preferable conditions will be described in detail later.

By bringing the chemical agent into contact with the coal, the inorganic sulfur that is easily removed is dissolved, and permeates the chemical agent in the form of, for example, sulfate ions. Similarly, a part of the organic sulfur is oxidized and permeates into the chemical agent in the form of sulfate ions or the like. In this way, the coal is desulfurized (i.e., sulfur in the coal is removed), and low-sulfur coal (low-sulfur coal) is obtained.

Molar ratio (acetic anhydride/hydrogen peroxide)

The molar ratio of acetic anhydride to hydrogen peroxide (acetic anhydride/hydrogen peroxide) in the chemical reagent is preferably 0.1 or more, more preferably 0.5 or more, from the viewpoint that peracetic acid as a reaction product becomes an appropriate amount and the desulfurization effect is more excellent.

When the molar ratio (acetic anhydride/hydrogen peroxide) is in this range, the acetic anhydride becomes excessive relative to the hydrogen peroxide, and the hydrogen peroxide can be prevented from remaining in the mixed solution (as described later, the hydrogen peroxide lowers the carbon yield of coal).

The molar ratio (acetic anhydride/hydrogen peroxide) is preferably 15.0 or less, and more preferably 12.0 or less. When the molar ratio (acetic anhydride/hydrogen peroxide) is in this range, peracetic acid as a reaction product becomes an appropriate amount as described above, and the desulfurization effect is more excellent. In addition, the formed peracetic acid can be inhibited from being diluted with excess acetic anhydride.

The molar ratio (acetic anhydride/hydrogen peroxide) was calculated as follows.

First, the molar amount [ mol ] of each component (acetic anhydride or hydrogen peroxide) in the chemical reagent is represented by the following formula (a). Therefore, the molar ratio of acetic anhydride to hydrogen peroxide (acetic anhydride/hydrogen peroxide) in the chemical reagent is calculated by the following formula (b).

Molar weight ═ Li × Ci)/(100 × Mi) … (a)

Molar ratio (L1 xc 1 xm 2)/(L2 xc 2 xm 1) … (b)

Li: i amount of aqueous solution [ g/h ]

Ci: i concentration of aqueous solution [% by mass ]

Mi: molecular weight of i [ g/mol ]

In this case, i represents acetic anhydride when it is 1, and hydrogen peroxide when it is 2.

The molecular weight of acetic anhydride was 102, and the molecular weight of hydrogen peroxide was 34. The amount of the aqueous solution Li is adjusted so as to become a desired molar ratio (acetic anhydride/hydrogen peroxide).

Elapsed time after mixing

The reaction (forward reaction) of the above formula (I) is slow. Therefore, immediately after mixing hydrogen peroxide and acetic anhydride, peracetic acid may not be sufficiently produced.

The inventors of the present application set various reaction rates, and found that it took about 10 minutes to find that the reaction of the formula (I) was in a steady state.

Therefore, in the present invention, it is preferable that acetic anhydride is mixed with hydrogen peroxide before the chemical reagent is brought into contact with coal, and after the mixture, the chemical reagent is brought into contact with coal after 10 minutes or more has elapsed. Thus, peracetic acid is sufficiently produced, and therefore, the desulfurization effect of removing sulfur in coal is more excellent. Further, since hydrogen peracetic acid is reduced, it is possible to suppress a decrease in carbon yield due to a reaction of hydrogen peroxide with coal.

The time elapsed after mixing is more preferably 20 minutes or more, and still more preferably 30 minutes or more. On the other hand, it is preferably 120 minutes or less, more preferably 90 minutes or less, and further preferably 60 minutes or less.

Angle of mass ratio (chemical reagent/coal)

The inventors of the present application studied the mass ratio of the chemical agent to the coal (chemical agent/coal). In this study, a chemical reagent 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 the chemical agent to the coal (chemical agent/coal). As shown in the graph of fig. 1, when the amount of the chemical agent is increased relative to the amount of the coal, the desulfurization rate is improved and the desulfurization effect is more excellent. Therefore, the mass ratio (chemical agent/coal) is preferably 0.5 or more, more preferably 1.0 or more, and still more preferably 2.0 or more.

As shown in the graph of fig. 1, when the amount of the chemical agent is too large relative to the amount of the coal, the desulfurization degree does not change substantially. From the viewpoint of reducing the amount of the chemical agent used, the mass ratio (chemical agent/coal) is preferably 100.0 or less, and more preferably 50.0 or less.

The mass of coal (solid content) before desulfurization was denoted as W₁[kg]The sulfur content of the coal (solid content) before desulfurization was defined as% S₁[ mass% ]]W represents the mass of the desulfurized coal (solid content)₂[kg]The sulfur content of the desulfurized coal (solid content) was defined as% S₂[ mass% ]]The desulfurization rate was [ mass% ]]Is defined by the following formula (1).

Desulfurization degree [ mass%]＝100×{1-(W₂×％S₂)/(W₁×％S₁)}…(1)

Temperature of chemical reagent

The inventors of the present application also studied the temperature of the chemical agent when contacting with the coal (hereinafter also simply referred to as "the temperature of the chemical agent"). In this study, a chemical reagent having a molar ratio of acetic anhydride to hydrogen peroxide (acetic anhydride/hydrogen peroxide) of 5.0 was used.

Fig. 2 is a graph showing the amount of peracetic acid produced with respect to the temperature of the chemical agent (lower stage), and a graph showing the desulfurization degree (solid line) and the carbon yield (broken line) with respect to the temperature of the chemical agent (upper stage). The amount of peracetic acid produced was an index obtained by setting a calculated value of 1.0 when the reaction-participating substances (hydrogen peroxide and acetic anhydride) were completely reacted.

As shown in the graphs (lower and upper stages) of fig. 2, when the temperature of the chemical agent at the time of contact with the coal is high, the amount of peracetic acid produced is large, the desulfurization rate is improved, and the desulfurization effect is more excellent. From such a viewpoint, the temperature of the chemical agent is preferably 5 ℃ or higher, more preferably 10 ℃ or higher, still more preferably 20 ℃ or higher, and particularly preferably 25 ℃ or higher.

On the other hand, as shown in the graph (upper stage) of fig. 2, in order to maintain the carbon yield high, it is preferable to avoid the temperature of the chemical agent from becoming excessively high. Specifically, from the viewpoint of excellent carbon yield, it is preferably 40 ℃ or lower, more preferably 35 ℃ or lower, and still more preferably 30 ℃ or lower.

When the carbon content of the coal (solid content) before desulfurization is% C1[ mass% ] and the carbon content of the coal (solid content) after desulfurization is% C2[ mass% ], the carbon yield [ mass% ] is defined by the following formula (2).

Carbon yield [ mass%]＝100×(W₂×％C₂)/(W₁×％C₁)…(2)

The reason why the decrease in carbon yield occurs is presumed as follows.

Hydrogen peroxide and peracetic acid may become oxidizing agents to destroy the coal skeleton, and in this case, it is considered that sulfur is removed and an undesirable decrease in carbon yield occurs. As a result of the studies by the inventors of the present application, it was found that peracetic acid firstly causes cleavage of a bond between sulfur and carbon of thiophenic sulfur, and then causes destruction of a carbon skeleton (carbon-carbon bond). The destruction of the carbon skeleton is weak in the case of peracetic acid and strong in the case of hydrogen peroxide. In particular, it is remarkable in the case of high-temperature hydrogen peroxide.

Therefore, by appropriately controlling the conditions when the chemical agent is brought into contact with the coal (for example, by appropriately adjusting the mixing ratio of hydrogen peroxide in the mixed solution while avoiding an excessively high temperature of the chemical agent), it is possible to efficiently remove the thiophenic sulfur while minimizing the destruction of the carbon skeleton.

Coal (coal)

The coal used in the present invention is not particularly limited, and various kinds of coal can be used in a wide range, and preferably includes coal having a medium degree of coalification such as subbituminous coal, more preferably includes subbituminous coal, and still more preferably subbituminous coal.

When such coal is used, the desulfurization effect tends to be more excellent than when coal having a high degree of coalification, such as anthracite coal, is used, and the carbon yield tends to be more excellent than when coal having a low degree of coalification, such as lignite coal, is used.

The particle size (average particle size) of the coal used in the present invention is not particularly limited. For example, even if the particle diameter of the coal is on the order of several millimeters, the desulfurization performance does not change greatly. If the particle size of the coal is larger, a slight pulverization treatment may be performed as necessary.

The above description has been made of 1 treatment (chemical agent treatment) for desulfurizing coal.

Next, two kinds of 2 treatments will be described as treatments for further removing sulfur remaining in the coal desulfurized by the 1-time treatment.

< 2 treatment (Heat treatment) >

Thiophene-like sulfur, which is difficult to remove, can be easily removed by a heat treatment at a relatively low temperature (about 150 ℃) because peracetic acid, which is a reaction product of hydrogen peroxide and acetic anhydride, acts on the thiophene-like sulfur.

That is, it is preferable to further heat-treat the coal after contact with the chemical agent, from the viewpoint of the better desulfurization effect. The heat treatment temperature is preferably 150 ℃ or higher, more preferably 250 ℃ or higher, and still more preferably 350 ℃ or higher.

The coal-derived hydrocarbon-containing gas generated by the heat treatment can be recovered and used as a part of the gas fuel in the iron-making process. When heat treatment is considered by utilizing waste heat generated in a plant such as an iron mill, heat treatment at a temperature of about several hundred degrees centigrade is preferable.

A coke oven is used as a furnace for heat treatment of coal in an iron making process. The heat treatment temperature in the coke oven is about 1000 to 1200 ℃, and the operation is also carried out at 1200 ℃ or above. The desulfurized coal obtained by contacting with the chemical agent may be introduced into a coke oven to produce low-sulfur coke. At this time, although a hydrocarbon gas and a sulfur-containing gas are generated, the sulfur-containing gas may be separately removed. The generated gas from which the sulfur-containing gas has been removed can be recycled as a fuel gas.

The process of heat-treating coal to the highest temperature is essentially considered to be a process of producing coke. As a result of experiments conducted by the inventors of the present application, it was confirmed that a sufficient desulfurization effect was exhibited even at the heat treatment temperature in the coke oven.

Therefore, the heat treatment temperature is, for example, 1300 ℃ or lower.

The material obtained by heat treating coal at around 600 c is commonly referred to as semicoke. The coal desulfurized by contact with the chemical agent can also be used for producing semicoke. Semicoke is inferior in strength to coke, and thus it is difficult to use it as blast furnace coke, but it can be used for other applications. In particular, the semicoke containing less sulfur is useful as a temperature raising agent (carbon additive) for raising the temperature in, for example, a converter.

The rate of temperature rise (hereinafter also simply referred to as "rate of temperature rise") when the coal contacted with the chemical agent is raised to the heat treatment temperature is preferably as high as possible. This is because the sulfur compound in a form that is easily desulfurized by the action of the mixed solution of hydrogen peroxide and acetic anhydride may be resynthesized to thiophenic sulfur that is difficult to be desulfurized under heating, and thus the resynthesizing is suppressed. Specifically, the temperature increase rate is preferably 10 ℃/min or more, more preferably 20 ℃/min or more.

The upper limit of the temperature increase rate is not particularly limited, but it is technically difficult and industrially (cost) to achieve an excessively high temperature increase rate. Therefore, the temperature increase rate is, for example, 100 ℃/min or less.

(2-pass treatment (Hydrogen peroxide treatment))

The inventors of the present application have found that, when the coal after contact with the chemical agent is further desulfurized, a treatment using hydrogen peroxide at a low temperature may be performed separately from the above-described heat treatment.

When hydrogen peroxide is allowed to act on coal which has not been subjected to 1 treatment (chemical treatment), the carbon skeleton is broken as described above, and the carbon yield is lowered. However, the sulfur content remaining in the coal after 1-time treatment was in a form that was easily removed, and further desulfurization was easily performed using hydrogen peroxide.

That is, it is preferable that the coal after contact with the chemical agent is further contacted with low-temperature hydrogen peroxide.

The temperature of the hydrogen peroxide is preferably 50 ℃ or lower, more preferably 40 ℃ or lower. The hydrogen peroxide is gradually increased in oxidizing power as it becomes high temperature, and not only has a desulfurization effect, but also easily decreases the carbon yield. When the temperature of the hydrogen peroxide solution is in the above range, the desulfurization effect is more 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 ℃ or higher.

From the viewpoint of further improving the desulfurization effect, the concentration of the hydrogen peroxide solution (the content of hydrogen peroxide in the hydrogen peroxide solution) is preferably 2.0 mass% or more, and more preferably 3.0 mass% or more.

If the concentration of the hydrogen peroxide is 3.0 mass% or more, the obtained effect is substantially constant regardless of the concentration of the hydrogen peroxide. Therefore, although the upper limit is not particularly limited, the concentration of hydrogen peroxide is preferably 35.0 mass% or less, for example.

Since hydrogen peroxide is easily decomposed at a high concentration, an aqueous solution of 30 to 35 mass% is often commercially available. In the present invention, such an aqueous solution of a commercially available product may be appropriately diluted and used.

[ Low-sulfur coal production facility ]

Next, an example of a case where the present invention is implemented using a specific apparatus will be described based on fig. 3.

Fig. 3 is a schematic diagram showing an example of a low-sulfur coal production facility (hereinafter, also simply referred to as "production facility").

The production 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 in the hydrogen peroxide storage tank 1 is supplied to the chemical agent mixing tank 5 through the hydrogen peroxide transport tube 2. The acetic anhydride in the acetic anhydride storage tank 3 is supplied to the chemical reagent mixing tank 5 through the acetic anhydride transfer pipe 4. The hydrogen peroxide transport pipe 2 and the acetic anhydride transport pipe 4 are provided with appropriate flow rate control devices (not shown), respectively, so that the flow rates of hydrogen peroxide and acetic anhydride can be controlled.

The chemical reagent mixing tank 5 is provided with a heating device 6 and a mixing device 7. The hydrogen peroxide and acetic anhydride supplied to the chemical reagent mixing tank 5 are heated to a predetermined temperature by a heating device 6 as needed, and are mixed by a mixing device 7.

The chemical agent of the mixed solution obtained by mixing in the chemical agent mixing tank 5 is supplied to the desulfurization treatment tank 9 via the chemical agent delivery pipe 8. The chemical reagent delivery pipe 8 is provided with an appropriate flow rate control device (not shown) to control the flow rate of the chemical reagent.

Further, coal is supplied from a coal storage tank 10 for storing coal to the desulfurization treatment tank 9 through a coal transfer pipe 11. The coal conveying pipe 11 is provided with an appropriate flow rate control device (not shown) to control the flow rate of coal.

The desulfurization treatment tank 9 is provided with a heating device 12. The heating device 12 controls the chemical agent supplied from the chemical agent mixing tank 5 and the coal supplied from the coal storage tank 10 to appropriate temperatures as needed. Further, a mixing device 13 is provided in the desulfurization treatment tank 9. The mixing device 13 mixes the chemical agent with the coal well as necessary.

In this manner, in the desulfurization treatment tank 9, the coal is desulfurized by contacting with the chemical agent, and low-sulfur coal (low-sulfur coal) (hereinafter, also referred to as "chemical agent-treated coal") is obtained.

The desulfurization treatment tank 9 was provided with 2 discharge holes. A chemical circulation pipe 14 is provided in the 1 discharge hole. Some peracetic acid may remain in the chemical agent used for desulfurization of coal. In this case, the chemical reagent may be returned from the desulfurization treatment tank 9 to the chemical reagent mixing tank 5 to be recycled.

In some cases, sulfur is permeated into the chemical agent after desulfurization. If the chemical agent impregnated with sulfur is recycled, there is a possibility that the chemical agent adversely affects desulfurization. Therefore, the chemical reagent circulation pipe 14 is connected to the chemical reagent discharge pipe 15, and a part or all of the desulfurized chemical reagent can be discharged through the chemical reagent discharge pipe 15.

A chemical agent treated coal conveying pipe 16 is provided in the other 1 discharge hole of the desulfurization treatment tank 9. The chemical agent-treated coal conveying pipe 16 is further branched into 3. That is, 3 pipes, i.e., the chemical agent treated coal discharge pipe 16a, the heat treatment device connecting pipe 16b, and the hydrogen peroxide treatment device connecting pipe 16 c.

The chemical agent treated coal discharge pipe 16a discharges the chemical agent treated coal obtained from the desulfurization treatment tank 9 without performing the treatment 2 times. The heat treatment device connecting pipe 16b conveys the chemical agent treated coal to the heat treatment device 17. The hydrogen peroxide treatment device connecting pipe 16c conveys the chemical agent treated coal to the hydrogen peroxide treatment device 23.

First, the heat treatment apparatus 17 is explained.

When the low-sulfur coal (chemical agent-treated coal) is subjected to the heat treatment in the heat treatment apparatus 17, sulfur is further volatilized, and thus desulfurization is further performed. The coal (hereinafter also referred to as "heat-treated coal") which has been subjected to the heat treatment in the heat treatment apparatus 17 and further low-sulfurized is taken out through the heat-treated coal discharge pipe 18 and used for a predetermined application.

The heat treatment apparatus 17 is provided with a heat treatment gas discharge pipe 19. There are cases where the gas generated by the heat treatment contains a combustible gas. In this case, the gas can be taken out through the heat treatment gas discharge pipe 19 and used for a predetermined application.

Next, the hydrogen peroxide treatment apparatus 23 will be explained.

The chemical agent-treated coal is supplied to the hydrogen peroxide treatment apparatus 23 through the hydrogen peroxide treatment apparatus connection pipe 16 c. In the hydrogen peroxide treatment apparatus 23, the chemical agent-treated coal was subjected to the above-described 2 treatments (hydrogen peroxide treatments).

Hydrogen peroxide is supplied to the hydrogen peroxide treatment apparatus 23 through the hydrogen peroxide supply pipe 20. The hydrogen peroxide supply pipe 20 is connected to the hydrogen peroxide storage tank 1. When hydrogen peroxide is diluted, water may be supplied from the dilution water tank 21 through the dilution water supply pipe 22. Another hydrogen peroxide storage tank (not shown) may be provided for exclusive use of the hydrogen peroxide treatment apparatus 23.

The hydrogen peroxide treatment apparatus 23 is provided with a cooling apparatus 24. The temperature inside the hydrogen peroxide treatment apparatus 23 is controlled to an appropriate temperature by the cooling apparatus 24 as necessary.

The hydrogen peroxide treatment apparatus 23 is provided with a mixing device 25. The mixing device 25 mixes the hydrogen peroxide solution and the chemical agent-treated coal well as necessary.

The hydrogen peroxide treatment apparatus 23 is provided with 2 discharge holes.

A hydrogen peroxide circulation pipe 27 is provided in 1 discharge hole. In some cases, hydrogen peroxide remains in hydrogen peroxide after desulfurization of coal (chemical agent-treated coal). In this case, the hydrogen peroxide solution may be returned from the hydrogen peroxide treatment apparatus 23 to the hydrogen peroxide storage tank 1 for recycling. The target of the back flow may be a hydrogen peroxide storage tank (not shown) provided separately or the chemical agent mixing tank 5.

In some cases, sulfur permeates into the desulfurized hydrogen peroxide. If the hydrogen peroxide into which sulfur has permeated is recycled, there is a possibility that the hydrogen peroxide adversely affects the desulfurization. Therefore, the hydrogen peroxide circulation pipe 27 is connected to a hydrogen peroxide discharge pipe 28, and a part or all of the desulfurized hydrogen peroxide is discharged through the hydrogen peroxide discharge pipe 28.

A discharge pipe 26 is connected to the other 1 discharge hole of the hydrogen peroxide treatment device 23. The coal further desulfurized in the hydrogen peroxide treatment device 23 (hereinafter also referred to as "hydrogen peroxide-treated coal") is taken out through the discharge pipe 26 and used for a predetermined application.

Since the chemical agent-treated coal fed to the heat treatment apparatus 17 or the hydrogen peroxide treatment apparatus 23 has been low-sulfurized, the chemical agent-treated coal may be taken out through the heat-treated coal discharge pipe 18 or the discharge pipe 26 without being subjected to the 2-time treatment (heat treatment or hydrogen peroxide treatment).

The manufacturing apparatus described with reference to fig. 3 does not require any special specification for each part, and can use existing equipment as appropriate. For example, the heat treatment device 17 may be a heat exchange device using waste heat as a heat source, or may be a furnace such as a semi-coke oven or a coke oven.

Examples

The present invention will be specifically described below with reference to examples. The present invention is not limited to the following examples.

EXAMPLES 1 to 16 AND COMPARATIVE EXAMPLE 1

A test for producing low-sulfur coal by desulfurizing coal by the method of the present invention was performed using the production apparatus described based on fig. 3.

As the Coal, at least 1 selected from the group consisting of Coal a (subbituminous Coal), Coal B (subbituminous Coal), and Coal C (semi-anthracite Coal) is used. Details of the coal used are shown in table 1 below. The coal had a particle size of about 300 μm in terms of the average particle size. All kinds of coal have strong infiltration capacity of peracetic acid, and the desulfurization performance has little change with the granularity.

[ Table 1]

TABLE 1

In table 1, the term "d.a.f" denotes dry ash free (dry ash free) and denotes an analysis value of pure coal excluding moisture and ash.

"d.b." represents the analytical value of dry mass (dry basis).

"V.M" indicates the content of Volatile Matter (volalite Matter) in the industrial analysis.

"Ash" represents the Ash content in the industrial analysis.

The test conditions such as the supply amounts (flow rates) 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-described treatment (chemical treatment) was performed 1 time. That is, the coal after contact with the chemical agent was taken out, and the desulfurization rate and the carbon yield were determined.

In examples 8 to 11, the above-mentioned 2 treatments (heat treatments) were further performed. That is, after 1 treatment (chemical treatment), the coal was further introduced into a heat treatment apparatus capable of raising the temperature to 1200 ℃.

In examples 12 to 16, the above-mentioned 2 treatments (hydrogen peroxide treatments) were further performed. That is, after 1 treatment (chemical treatment), the coal was further introduced into a hydrogen peroxide treatment apparatus to be subjected to hydrogen peroxide treatment, and the desulfurization rate and carbon yield after the hydrogen peroxide treatment were determined.

In the treatment 1, an aqueous solution having a hydrogen peroxide concentration of 35% by mass was used as hydrogen peroxide. Acetic anhydride having a purity of 99 mass% was used.

[ Table 2]

Summary of test results

In examples 1 to 16 in which a mixed solution of hydrogen peroxide and acetic anhydride was used as a chemical reagent, a high desulfurization rate was exhibited as compared with comparative example 1 in which the chemical reagent was not used, and it was found that a sufficient desulfurization effect was obtained. The carbon yield was also good.

Comparing example 1 with example 4, example 1 having a molar ratio (acetic anhydride/hydrogen peroxide) of 5.0, and example 4 having a molar ratio (acetic anhydride/hydrogen peroxide) of 0.4, the desulfurization rate was higher and the desulfurization effect was more excellent.

Comparing example 1 with example 5, example 1 in which the elapsed time after mixing of acetic anhydride and hydrogen peroxide was 30 minutes had a higher desulfurization rate and more excellent desulfurization effect than example 5 in which the elapsed time was 8 minutes.

Comparing example 1 with example 6, example 1 having a mass ratio (chemical agent/coal) of 3.2 has a higher desulfurization degree and more excellent desulfurization effect than example 6 having a mass ratio (chemical agent/coal) of 0.9.

Comparing example 1 with example 7, example 1, in which the temperature of the chemical reagent at the time of contact with coal was 20 ℃, was more excellent in carbon yield than example 7, in which the temperature was 35 ℃.

The desulfurization rates (after 2 treatments) of examples 8 to 11 were not less than the desulfurization rates (after 1 treatment) of examples 1 to 7.

Comparing example 8 with example 10, example 8 with a heat treatment temperature of 150 ℃ has a higher desulfurization rate (after 2 treatments) and more excellent desulfurization effect than example 10 with a heat treatment temperature of 100 ℃.

Comparing example 8 with example 11, example 8 in which the temperature raising rate at the time of raising the temperature to the heat treatment temperature was 20 ℃/min was higher in the desulfurization rate (after 2 treatments) and more excellent in the desulfurization effect than example 11 in which the temperature raising rate was 5 ℃/min.

The desulfurization rates of examples 12 to 16 (after 2 treatments) were not less than the desulfurization rates of examples 1 to 7 (after 1 treatment).

Comparing example 12 with example 14, example 12 in which the temperature of hydrogen peroxide was 20 ℃ was higher in desulfurization rate (after 2 treatments) and more excellent in desulfurization effect than example 14 in which the temperature was 45 ℃.

In comparison with example 12 and example 15, example 12 having a hydrogen peroxide concentration of 35.0 mass% had a higher desulfurization rate (after 2 treatments) and more excellent desulfurization effect than example 15 having a hydrogen peroxide concentration of 1.5 mass%.

Comparing example 12 with example 16, example 12 having a mass ratio (hydrogen peroxide/coal) of 2.5 showed a higher desulfurization rate (after 2 treatments) and more excellent desulfurization effect than example 16 having a mass ratio (hydrogen peroxide/coal) of 0.9.

Description of the reference numerals

1: hydrogen peroxide storage tank

2: hydrogen peroxide conveying pipe

3: acetic anhydride storage tank

4: acetic anhydride conveying pipe

5: chemical reagent mixing tank

6: heating device

7: mixing device

8: chemical reagent delivery pipe

9: desulfurization treatment tank

10: coal storage tank

11: coal conveying pipe

12: heating device

13: mixing device

14: chemical reagent circulating pipe

15: chemical reagent discharge pipe

16: chemical reagent treatment coal conveying pipe

16 a: chemical reagent treatment coal discharge pipe

16 b: connecting pipe of heat treatment device

16 c: connecting pipe of hydrogen peroxide treatment device

17: heat treatment apparatus

18: heat treatment coal discharge pipe

19: heat treatment gas discharge pipe

20: hydrogen peroxide supply pipe

21: dilution water tank

22: dilution water supply pipe

23: hydrogen peroxide treatment device

24: cooling device

25: mixing device

26: discharge pipe

27: hydrogen peroxide circulating pipe

28: hydrogen peroxide discharge pipe

Claims

1. A process for producing low-sulfur coal, wherein sulfur in coal is removed by bringing the coal into contact with a chemical agent which is a mixed solution of hydrogen peroxide and acetic anhydride.

2. The method for producing low-sulfur coal according to claim 1, wherein a 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 method for producing low-sulfur coal according to claim 1 or 2, wherein the acetic anhydride is mixed with the hydrogen peroxide before the chemical agent is brought into contact with the coal,

after the mixing, the chemical reagent is contacted with the coal after more than 10 minutes has elapsed.

4. The method for producing low-sulfur coal according to any one of claims 1 to 3, wherein the mass ratio of the chemical agent to the coal (chemical agent/coal) is 1.0 or more.

5. The method for producing low-sulfur coal according to any one of claims 1 to 4, wherein the temperature of the chemical agent at the time of contact with the coal is 5 ℃ or higher.

6. The method for producing low-sulfur coal according to any one of claims 1 to 5, wherein the temperature of the chemical agent at the time of contact with the coal is 30 ℃ or lower.

7. The method for producing low-sulfur coal according to any one of claims 1 to 6, wherein the coal contains subbituminous coal.

8. The method for producing low-sulfur coal according to any one of claims 1 to 7, wherein the coal after contact with the chemical agent is heat-treated at a heat treatment temperature of 150 ℃ or higher.

9. The method for producing low-sulfur coal according to claim 8, wherein a rate of temperature rise of the coal after contact with the chemical agent to the heat treatment temperature is 10 ℃/min or more.

10. The method for producing low-sulfur coal according to any one of claims 1 to 7, wherein the coal after being contacted with the chemical agent is contacted with hydrogen peroxide at 40 ℃ or lower.

11. The method for producing low-sulfur coal according to claim 10, wherein the concentration of hydrogen peroxide is 2.0% by mass or more,

the mass ratio of the hydrogen peroxide to the coal (hydrogen peroxide/coal) is more than 1.0.