阅读说明：本技术 煤混合物的制造方法和焦炭的制造方法 (Method for producing coal mixture and method for producing coke ) 是由 土肥勇介 松井贵 永山干也 于 2020-03-12 设计创作，主要内容包括：本发明提供通过简单的方法就能够比以往更好地抑制煤的流动性的降低的煤混合物的制造方法。一种煤混合物的制造方法,其是配合两种以上煤的煤混合物的制造方法,其中,所述煤混合物满足下述(1)式和下述(2)式。α-(calc)≤1.2×10～(-10)(mol/g-coal)…(2)在上述(1)式和上述(2)式中,α-(calc)是每单位质量的煤混合物的氢离子释放能力(mol/g-coal),α-(i)是每单位质量的煤i的氢离子释放能力(mol/g-coal),x-(i)是在煤混合物中配合的煤i的配合比率,N是煤混合物中所含的所有煤品种的数量。(The invention provides a method for producing a coal mixture, which can better inhibit the reduction of coal fluidity than the conventional method by a simple method. A method for producing a coal mixture in which two or more kinds of coals are blended, wherein the coal mixture satisfies the following formulae (1) and (2). α calc ≤1.2×10 ‑10 (mol/g-coal) … (2) in the above-mentioned formulae (1) and (2), α calc Is the hydrogen ion releasing capacity (mol/g-coal), alpha, per unit mass of the coal mixture i Is the hydrogen ion releasing ability (mol/g-coal), x, per unit mass of coal i i Is coal blended in a coal mixturei, and N is the number of all coal species contained in the coal mixture.)

1. A method for producing a coal mixture in which two or more kinds of coals are blended, wherein the coal mixture satisfies the following formulae (1) and (2),

α_calc≤1.2×10^-10(mol/g-coal)…(2)

in the formulae (1) and (2),

α_calcis the hydrogen ion releasing capacity (mol/g-coal) per unit mass of the coal mixture,

α_iis the hydrogen ion releasing ability (mol/g-coal) per unit mass of coal i,

x_iis the blending ratio of coal i blended in the coal mixture,

n is the number of all coal species contained in the coal mixture.

2. The method for producing a coal mixture according to claim 1, wherein the hydrogen ion releasing ability per unit mass of coal is calculated by dividing the mass of each coal by the product of the hydrogen ion concentration calculated from the pH of water in which each of the two or more kinds of coal is impregnated and the volume of the impregnated water.

3. The method for producing a coal mixture according to claim 1 or 2, wherein the coal mixture is produced before being transported to a coke plant provided with a coke oven.

4. A method for producing coke, comprising charging the coal mixture produced by the method for producing a coal mixture according to any one of claims 1 to 3 into a coking chamber of a coke oven, and subjecting the mixture to dry distillation to produce coke.

Technical Field

The present invention relates to a method for producing a coal mixture for producing coke, and more particularly to a method for producing a coal mixture capable of maintaining fluidity at a high level for a longer period of time than before, and a method for producing coke using the same.

Background

In order to produce pig iron in a blast furnace, it is necessary to first fill iron ores and cokes alternately into the blast furnace, fill them in layers, heat the iron ores and cokes with hot air at high temperature blown from tuyeres, and perform reduction melting of the iron ores mainly with CO gas generated from the cokes. In order to stably perform such blast furnace operation, it is effective to improve the air permeability and liquid permeability in the furnace, and for this reason, it is indispensable to use coke having excellent properties such as strength, particle size, and strength after reaction. Among these, strength is considered to be a particularly important property.

The cold strength of coke is generally controlled by using as an index the drum strength DI (150/15) measured by the rotational strength test prescribed in JIS K2151. The coal qualities that govern the drum strength include mainly the degree of coalification (Ro, JIS M8816) and the fluidity (MF, JIS M8801) (non-patent documents 1 and 2).

It is known that the fluidity of coal decreases over time due to degradation caused by oxidation in the atmosphere known as "efflorescence". Generally, coal is repeatedly transported and stored in an atmospheric atmosphere for a long period of time of several weeks or more from the time of mining in a coal mine to the time of charging into a coke oven. Therefore, it is generally difficult to avoid the deterioration of the fluidity of coal due to efflorescence. Therefore, development of a technique for controlling the efflorescence of coal is strongly desired.

In order to control the efflorescence of coal, it is effective to suppress the contact of coal with oxygen as much as possible. Patent document 1 discloses a technique of replacing carbon dioxide by flowing dry ice through a perforated pipe provided at the bottom of a coal pile. Patent document 2 discloses a technique of blowing an inert gas from the bottom. Patent document 3 discloses a technique of coating a surface layer for the purpose of suppressing diffusion of oxygen from the surface layer of a mound to the inside. Further, a method of storing coal in water, a method of storing coal using a closed coal storage tank, a method of consolidating the surface layer of a heap with heavy machinery, and the like are known (non-patent document 3).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 60-12405

Patent document 2: japanese laid-open patent publication No. 60-148830

Patent document 3: japanese laid-open patent publication No. 3-157492

Non-patent document

Non-patent document 1: uterus jin Long, four other people: "the multi-type blending allows なら to be more than に the raw material carbon permeability value (multi-type blending plan and evaluation of raw material coal)", and the japan steel pipe report, volume 67, 1975, and pages 125 to 137

Non-patent document 2: miyazu, et al, Nippon Kokan Technical Report-overreads, December 1975, page 1

Non-patent document 3: stored carbon (stored coal or efflorescence of coal) ", will be referred to in Meipu," char-shaped FENG-FENG およ ", journal of the Fuel Association, Vol.58, No. 622, 1979, pages 112 to 122

Disclosure of Invention

Problems to be solved by the invention

The techniques disclosed in patent documents 1 and 2 have a problem in that a dedicated facility for blowing an inert gas containing carbon dioxide from the bottom of a coal hill into a place where the coal hill is deposited and the cost of the gas used are high. Since the amount of coal stored in a coal yard used in the iron making industry is several hundred thousand tons or more, the size and the amount of dedicated facilities are increased, and the running cost is also increased. Therefore, the advantage of inhibiting efflorescence is offset, and a sufficient economic effect cannot be obtained. The technique of coating the surface layer disclosed in patent document 3 also has problems that a spreading operation of the coating agent is required and that material cost is required. In addition, the method of storing coal in water, the method of storing coal in a closed coal storage tank, and the method of consolidating the surface layer of a heap with heavy machinery also have the problem of equipment investment and running cost.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a coal mixture, which can suppress a decrease in coal fluidity more than before by a simple method without an excessive equipment investment or running cost.

Means for solving the problems

The present invention which solves the above problems is characterized as follows.

[1] A method for producing a coal mixture in which two or more kinds of coals are blended, wherein the coal mixture satisfies the following formulae (1) and (2).

α_calc≤1.2×10^-10(mol/g-coal)…(2)

In the above formulae (1) and (2), α is_calcIs the hydrogen ion releasing capacity (mol/g-coal), alpha, per unit mass of the coal mixture_iIs the hydrogen ion releasing ability (mol/g-coal), x, per unit mass of coal i_iIs the blending ratio of coal i blended in the coal mixture, and N is the number of all coal varieties contained in the coal mixture.

[2] The method for producing a coal mixture according to [1], wherein the hydrogen ion releasing ability per unit mass of the coal is calculated by dividing the mass of each coal by the product of the hydrogen ion concentration calculated from the pH of water in which each of the two or more kinds of coals is impregnated and the volume of the impregnated water.

[3] The method for producing a coal mixture according to [1] or [2], wherein the coal mixture is produced before being transported to a coke plant provided with a coke oven.

[4] A method for producing coke, wherein a coal mixture produced by the method for producing a coal mixture according to any one of [1] to [3] is charged into a coking chamber of a coke oven and carbonized to produce coke.

Effects of the invention

According to the present invention, a reduction in the fluidity of coal due to efflorescence can be suppressed by an extremely simple method of mixing two or more kinds of coal. Generally, in mines, coal centers, shipping ports, and coke plants that process coal, facilities for mixing coal are provided for the purpose of adjusting the amount and quality of coal products. Since the present invention can be implemented using such existing facilities, the efflorescence of coal can be suppressed without additional equipment investment.

Drawings

FIG. 1 is a graph showing the relationship between the reaction treatment time and the fluidity of coal.

Fig. 2 is a graph showing changes over time in pH of each coal variety.

Fig. 3 is a graph showing the relationship between the hydrogen ion releasing ability of the coal mixture and the fluidity "before treatment-after treatment".

Detailed Description

The present inventors have found that the weathering rate of coal differs depending on the pH of water adhering to the coal, i.e., the concentration of hydrogen ions, and the amount of hydrogen ions eluted into water differs depending on the type of coal, and it is considered that the weathering rate of coal can be controlled to a low level by adjusting the pH of the water adhering to the coal by blending different types of coal. In order to verify this hypothesis, intensive studies were carried out, and as a result, it was found that: transportation and storage of coal after being made into a coal mixture are the best conditions for suppressing the reduction in fluidity caused by weathering of coal, as compared with transportation and storage of coal alone.

First, the influence of the pH of the treated water on the weathering rate of coal will be described. The coal was immersed in treated water with a change in pH, and the change in the fluidity of the coal with time was examined. The pH of the treated water is prepared to be 2.0 to 5.6 by using hydrochloric acid and pure water. The properties of the coal used are shown in table 1.

[ Table 1]

FIG. 1 is a graph showing the relationship between the reaction treatment time and the fluidity of coal. In FIG. 1, the horizontal axis represents the reaction treatment time (hours) and the vertical axis represents the logMF (ddpm/log) of coal. As shown in fig. 1, it is understood that the lower the pH of the treated water, the faster the fluidity of the coal decreases, and the faster the weathering of the coal progresses. It is known that the lower the pH, the higher the oxidation-reduction potential, and the higher the oxidation-reduction potential, the more oxidizing aqueous solution is formed. From this result, it is considered that the oxidation of coal is promoted and the weathering of coal is accelerated as the treatment with the aqueous solution having a lower pH is performed.

Next, the pH of the water in which the coal is impregnated and the hydrogen ion release capacity per unit mass of the coal defined by the pH are described by immersing each coal variety in a predetermined amount of water. 50g of each coal was immersed in 400ml of purified water, and the change with time in pH of water heated to 60 ℃ was measured. The releasing ability of hydrogen ions was calculated by dividing the product of the hydrogen ion concentration determined from the pH of water and the volume of water in which the coal was impregnated by the mass of the impregnated coal. The hydrogen ion releasing ability of each coal variety is shown in table 2. When the hydrogen ion releasing ability is small, the pH of the water impregnated with coal becomes greater than 7 by receiving hydrogen ions from the water.

[ Table 2]

Fig. 2 is a graph showing changes over time in pH of each coal variety. In fig. 2, the horizontal axis represents the immersion time (minutes), and the vertical axis represents the pH of the water in which the coal is immersed. As shown in fig. 2, the pH of the coal-impregnated water greatly varies from acidic to basic depending on the kind of coal. It is considered that this result may be caused by the content of the water-soluble sulfate mineral contained in the coal and the difference in the kind and content of the organic acid. As described above, the pH of the water impregnated with the coal greatly varied depending on the kind of coal, and as a result, as shown in table 2, the hydrogen ion release capacity of the coal also greatly varied depending on the kind of coal.

From these results, the present inventors considered that by blending coals having different hydrogen ion releasing abilities and controlling the pH of the water attached to the coal, the efflorescence of the mixed coal can be suppressed. That is, it is considered that the amount of water (water content) attached to the coal during transportation and storage is about 10 mass%, and therefore, a reaction due to acid or alkali occurs between the coals constituting the coal mixture by the 10 mass% of the attached water, and this reaction affects the weathering rate of the coal, and it is found that the decrease in fluidity due to the weathering of the coal mixture can be suppressed by mixing two or more kinds of coals so as to increase the pH of the attached water, and the present invention has been completed. The present invention will be described below with reference to embodiments thereof.

In the method for producing a coal mixture of the present embodiment, α is calculated from the following formula (1)_calcIs 1.2X 10^-10(mol/g-coal) or less two or more kinds of coals are blended to produce a coal mixture. That is, a coal mixture satisfying both the following formula (1) and the following formula (2) is produced by mixing various kinds of coals.

α_calc≤1.2×10^-10(mol/g-coal)…(2)

In the above formulae (1) and (2), α is_calcIs the hydrogen ion releasing capacity (mol/g-coal), alpha, per unit mass of the coal mixture_iIs the hydrogen ion releasing ability (mol/g-coal), x, per unit mass of coal i_iIs the blending ratio of coal i blended in the coal mixture, and N is the number of all coal varieties contained in the coal mixture.

Herein, α is_iIs the hydrogen ion releasing ability (mol/g-coal) per unit mass of coal i blended in the coal mixture. The hydrogen ion releasing ability was determined by measuring the degree of impregnation into the coalThe pH of the water of the candidate coal blended in the mixture is calculated by dividing the product of the hydrogen ion concentration calculated from the pH and the volume of the impregnated water by the mass of the impregnated coal. When the amount of water used for impregnating the coal is too small, the hydrogen ion elution reaction does not reach equilibrium, and the hydrogen ion releasing ability is calculated to be low, which is not preferable. If the amount of water in the impregnated coal is too large, the change in the hydrogen ion concentration due to the impregnated coal is small, and the accuracy of the measurement of the hydrogen ion releasing ability is not preferable. Therefore, the mass ratio of coal to water when measuring the pH of the coal-impregnated water is preferably set to be coal: water 1: 1 or more and coal: water 1: 100 or less.

As shown in fig. 2, the pH of the coal-impregnated water changed slightly before the dissolution reaction reached equilibrium. Therefore, the pH measurement is preferably performed after the dissolution reaction reaches equilibrium. The temperature of the water in which the coal is impregnated is preferably high. By raising the temperature of water, the elution reaction is promoted, and the time until the elution reaction reaches equilibrium is shortened, so that the pH measurement can be performed quickly. Further, the time from the immersion of the coal in water to the measurement of the pH is preferably long.

On the other hand, too high temperature of the water for impregnating the coal or too long time before measuring pH is not preferable because the coal is weathered. From these viewpoints, the temperature of the water for coal impregnation is preferably set to be in the range of 0 ℃ to 80 ℃, and the time for coal impregnation is preferably set to be in the range of 1 hour to 2 hours. The finer the particle size of the coal, the shorter the time for the pH to reach equilibrium, but the weathering readily progresses, so fine pulverization is not necessary. If stirring is performed during coal impregnation, the time until the pH reaches equilibrium is shortened, and thus stirring is possible. However, even if stirring is not performed, if the coal is immersed for 1 hour or more, the pH is very close to the equilibrium value, and therefore, only the coal may be immersed in water without stirring.

Thus, if the hydrogen ion releasing ability of coal to be a candidate for blending in a coal mixture can be calculated, the product of the hydrogen ion releasing ability and the blending ratio of each coal blended in the coal mixture is calculated, and the sum of the products is 1.2X 10^-10(mol/g-coal) type and blending ratio of coal were determined in the following manner. Fitting ratio x_iCalculated by dividing the mass of blended coal i by the mass of the coal mixture.

For example, when two kinds of coals are blended to produce a coal mixture, the hydrogen ion releasing ability in one kind of coal exceeds 1.2X 10^-10(mol/g-coal) another coal having a selective hydrogen ion releasing ability of less than 1.2X 10^-10(mol/g-coal). Then, the sum of the products of the hydrogen ion releasing ability and the blending ratio of these coals was 1.2X 10^-10(mol/g-coal) the blending ratio of each coal was determined in the following manner. By determining the type and blending ratio of the coals blended in the coal mixture in this manner and blending the coals, it is possible to produce a coal mixture in which the reduction in fluidity due to efflorescence is suppressed.

The blending method of the blended coal can be a conventionally used blending method. For example, the coal may be mixed by a method of mixing at an adaptor portion of a belt conveyor, a method of mixing in a hopper, a method of mixing using heavy machinery, a method of using dedicated mixing equipment such as a yard mixer and a mixing tank, or a method of mixing using a mixer. Transportation and storage can be carried out by a conventionally used method. Two or more kinds of coals may be pulverized simultaneously and pulverized and mixed at the same time.

In this way, the method for producing a coal mixture of the present embodiment is performed only by using α calculated from the above formula (1)_calcIs 1.2X 10^-10(mol/g-coal) or less, and can be carried out by a simple method without an excessive investment in facilities or running costs. Further, by charging the coal mixture in which the decrease in the fluidity of the coal is suppressed into a carbonization chamber of a coke oven and performing carbonization, it is possible to produce coke having high strength.

Since the longer the transportation and storage time is, the more the fluidity is reduced by the efflorescence, it is preferable to carry out the method for producing a coal mixture of the present embodiment as soon as possible after the coal is mined, and it is preferable to carry out the method at least before the coal mixture is transported to a coke plant in which a coke oven is installed. This increases the effect of suppressing the decrease in fluidity.

Examples

Next, the evaluation results of the coal mixture produced by the method for producing a coal mixture of the present embodiment will be described. For the purpose of adjusting the weathering conditions, changes in the fluidity of the coal mixture were confirmed in the case where the coal mixture was prepared by blending two types of coals using a thermostatic bath and then stored in the thermostatic bath (before the thermostatic bath treatment) and in the case where the same two types of coals were blended after being stored in the thermostatic bath (after the thermostatic bath treatment). The properties, pH and hydrogen ion releasing ability of the coal used are shown in table 3. Regarding the hydrogen ion releasing ability of the coal, 50g of the coal was immersed in 400ml of pure water maintained at 60 ℃ and calculated from the pH of the water after 2 hours of immersion.

[ Table 3]

Each coal shown in table 3 was pulverized to a particle size of 9.6mm or less so that the mass ratio of the dry basis was 1: the two kinds of coals were mixed in the manner of 1 to prepare a coal mixture, and the moisture content was adjusted to 12 mass%. The coal mixture was filled into a closed container, and the closed container was stored in a constant temperature bath maintained at 50 ℃ for two weeks. Then, the fluidity of the coal mixture was measured.

On the other hand, coal of the same type was pulverized to a particle size of 9.6mm or less, the coal having a water content adjusted to 12% by mass was charged into a closed container, and the closed container was stored in a thermostatic bath maintained at 50 ℃ for two weeks. Then, the mass ratio of the dry base is 1: the method 1 was performed by blending two kinds of stored coals to prepare a coal mixture and measuring the fluidity of the coal mixture. The results are shown in Table 4.

[ Table 4]

TABLE 4 "Hydrogen ion ReleaseThe value listed in the column "capability" is the hydrogen ion release capability (α) per unit mass of the coal mixture calculated using the above formula (1)_calc). For example, in the case of level No.1 of Table 4, the hydrogen ion releasing ability of [ coal e ] (2.1X 10)^-6) X coordination ratio (0.5)]+ [ hydrogen ion releasing ability of coal c (2.0X 10)^-10) X coordination ratio (0.5)]And (6) calculating.

The value described in the column "before the thermostatic bath treatment" is a measured value of the fluidity of the coal mixture after the coal mixture is prepared by blending two kinds of coals before being stored in the thermostatic bath and then stored in the thermostatic bath. The value described in the column "after the constant temperature bath treatment" is a measured value of the fluidity of a coal mixture prepared by storing the same kind of coal in a constant temperature bath alone and blending the stored coal. The value described in the column "before treatment" and "after treatment" is the difference between the measured value "before treatment in the thermostatic bath" and the measured value "after treatment in the thermostatic bath".

Fig. 3 is a graph showing the relationship between the hydrogen ion releasing ability of the coal mixture and the fluidity "before treatment-after treatment". In fig. 3, the horizontal axis represents the hydrogen ion releasing capacity (mol/g-coral) of the coal mixture, and the vertical axis represents the fluidity (ddpm/l o g) of the coal mixture before and after the treatment. Here, the value of fluidity "before treatment-after treatment" means when positive: the decrease in fluidity when stored in the form of a coal mixture in the thermostatic bath is reduced as compared with when stored in the form of coal alone in the thermostatic bath. On the other hand, the fluidity value "before treatment-after treatment" is negative, and indicates that: the decrease in fluidity is increased when the coal mixture is stored in the oven as compared with when the coal mixture is stored in the oven as coal alone.

As shown in fig. 3, it was found that: the smaller the hydrogen ion releasing ability of the coal mixture, the more the value of "before-after-treatment" fluidity tends to be positive. Particularly, the hydrogen ion releasing ability is 1.2X 10^-10The fluidity values of the coal mixture "before treatment" and after treatment "are all positive, and the decrease in fluidity is smaller when the coal mixture is stored in the oven as a coal mixture than when the coal mixture is stored in the oven as a coal alone. Based on these results, it was confirmed thatThe hydrogen ion releasing ability of each individual coal blended in the coal mixture was made to be 1.2X 10^-10The coal mixture produced in the following manner can suppress the decrease in fluidity. Particularly, the hydrogen ion releasing ability is 1.0X 10^-10In the following, the value of "before treatment-after treatment" fluidity was more than 0.1. From these results, it is more preferable that the hydrogen ion releasing ability be 1.0X 10^-10The coal mixture was produced in the following manner.