JP3385424B2 - Coal desulfurization and demineralization method using microorganisms - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to desulfurization and deashing of coal using microorganisms. More particularly, the present invention relates to a method for efficiently desulfurizing and deashing coal from a coal in the form of a pulverized coal-water mixture, and a pulverized coal-water mixture desulfurized and deashed by the method. It is a thing.

[0002]

2. Description of the Related Art Coal is attracting attention as a primary energy source to replace petroleum because of its rich reserves and stable supply. However, coal because it contains sulfur, SO _x this occurs by burning is one of the causes of acid rain. For this reason, at the time of coal consumption, low-sulfur coal with as low a sulfur content as possible is used and sulfur oxides are removed by a flue gas desulfurization method after combustion, but the flue gas desulfurization equipment and its operating cost are expensive. Considering the facts and utilization of high-sulfur coal when low-sulfur coal runs short in the future, it is necessary to develop a method for efficient desulfurization before coal combustion. On the other hand, it has been confirmed for some time that certain kinds of microorganisms propagate by utilizing the sulfur content in coal as an energy source, and a method of desulfurizing coal by utilizing this property is known. However, this method requires several weeks for desulfurization. Therefore, in order to shorten the desulfurization time, a method has been developed in which coal is placed in a microbial suspension and treated, and then flotation is carried out, and although the desulfurization time has been considerably shortened, this method requires fine coal treatment. However, the desulfurization effect is reduced, and there is still a problem that a large amount of microorganisms and flotation agents are required for the desulfurization treatment. Further, coal has a problem that it also contains ash content remaining after combustion, and it is preferable as a fuel to remove the ash content before combustion and make the combustible content per unit weight of coal as high as possible. further,
Coal has the disadvantage that it has poor transportation and storage properties compared to oil. Therefore, at present, a fuel in the form of fluidized pulverized coal mixed with water has been developed and partially put into practical use.
This pulverized coal-water mixture is promising as an important energy source in the future due to improved handling and high convenience. However, a method for efficiently desulfurizing and deashing a finely pulverized coal-water mixture before combustion has not been reported so far.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and efficiently desulfurizes and deashes finely pulverized coal-water mixture using microorganisms before combustion. It is an object to provide a method of doing.

[0004]

Means for Solving the Problems As a result of various studies conducted by the present inventors, a coal-water mixture (Coal Water Mixture, hereinafter also referred to as CWM) in which a certain kind of microorganism is pulverized
It was discovered that coal can be efficiently desulfurized and deashed by contacting with, and after further intensive studies, the present invention was completed.

That is, the present invention relates to the iron-oxidizing bacterium Thiobacillus ferrooxidan.
s) is desulfurized from coal by contacting it with a pulverized coal-water mixture and also to a pulverized coal-water mixture desulfurized by this method. Further, the present invention is an iron-oxidizing bacterium Thiobacillus ferrooxidans containing finely divided coal-
It also relates to a method of deashing coal by contacting it with a water mixture,
And to a pulverized coal-water mixture decalcified by this method.

In the present invention, the desulfurization and deashing of coal includes
By contacting the microorganisms with the pulverized coal-water mixture, to separate the sulfur and ash in the coal from the coal,
Next, the sulfur content and the ash content in the coal are sunk downward by flotation, while the desulfurized and deashed coal is floated upward to desulfurize and deash the coal.
At that time, it is preferable to promote the floating of the pulverized coal by supplying air from below or adding a foaming agent. In addition, desulfurization
Deashing is preferably performed in a cylindrical desulfurization / deashing tank, but this improves the efficiency of separation of coal from sulfur and ash, and desulfurization / deashing coal with a wider particle size range. Is possible.

The iron-oxidizing bacterium used in the desulfurization and deashing of coal of the present invention is Thiobacillus ferrooxidans as described above. Thiobacillus ferrooxidans ATCC2 from T-1 strain, T-9 strain, T-11 strain, and American Type Culture Collection
3270 strains can be mentioned. Among these, T-1
The strains, T-9 strain, and T-11 strain were isolated and purified by the present inventors, and all the soils collected from Takehara, Hiroshima prefecture were suspended in ferrous sulfate medium (Table 1) and shaken at 30 ° C. Culturing is carried out, and only the medium in which the medium turns red (the one in which iron hydroxide is produced) is subcultured every week to the medium having the same composition, and 2
After the enrichment culture for one month, pure culture was performed in a silica gel plate medium (Table 1) and separated. These isolates are preserved by subculturing every week. The bacteriological properties of these isolates are summarized in Table 2. The details of the isolation / purification and the mycological properties of the above-mentioned isolates are described in Omura et al., Central Research Institute of Electric Power Industry, Research Report, U91010 (May 1991). The above three isolates were deposited on July 27, 1992 at the Institute of Microbial Science and Technology of the Agency of Industrial Science and Technology and have the following deposit numbers: T-1 strain (Ministry of Microbiology Research No. 13090).
No.), T-9 strain (Microtechnology Research Institute, No. 13091) and T
-11 strains (Ministry of Industrial Research, No. 13092).

[Table 1] ───────────────────────────────── Ferrous Sulfate Silica Gel Plate Medium Medium ───── ──────────────────────────── (NH ₄ ) ₂ SO ₄ 1.0 g 0.75 g KCl 1.0 g 0.075 g K _{2 HPO 4 0.5g 0.375g MgSO 4 · 7H} 2 O 0.5g 0.375g Ca (NO 3) 2 · 4H 2 O 0.01g 0.0075g FeSO 4 · 7H 2 O 44.22g 44.2g distilled water 1000 ml 1000 ml Colloidal silica-800 ml 5 NH ₂ SO ₄ -10 ml pH 2.5 3.0 ─────────────────────────────── ───

[Table 2] ───────────────────────────── Nature Isolates ^{* 1} ───────────── ───────────────── Gram stain Negative cell shape Short rod-type motility Optimal for growth pH 2.5-3.5 Temperature (° C) 25-30 Various energies Growth on a medium using a source ^{* 2} Thiosulfate + thiolathionate + elemental sulfur + ferrous sulfate + pyrite + yeast extract − ────────────────────── ───────── (Footnote) * 1: T-1, T-9 and T-11 * 2: +,-indicates the presence or absence (+) of growth of the strain (-).

In the present invention, pulverized coal means a particle size of 75.
means less than or equal to μm, and the amount of pulverized coal in CWM varies variously in relation to the amount of iron-oxidizing bacteria to be contacted,
It can be selected so that a suitable desulfurization and deashing is carried out, but it is usually 5 to 25% by weight. Further, in the method for desulfurizing coal and the method for deashing coal of the present invention, the amount of iron-oxidizing bacteria to be brought into contact with CWM is determined by the sulfur and ash contents of the coal to be treated and the C content.
Depending on the concentration of pulverized coal in WM,
Normally, 5 × 10 ⁹ to 1 of iron-oxidizing bacteria per 1 g of coal
It is preferably 0 × 10 ⁹ (5 billion to 10 billion). The contact time between the iron-oxidizing bacterium and CWM is not particularly limited, but 1 to 10 minutes is sufficient, and the desulfurization / deashing of the present invention can provide a considerable desulfurization / deashing effect even in a short time of 1 to 2 minutes. Although it can be carried out batchwise, it is preferably carried out continuously in terms of workability and the like.

[0009]

The present invention will be described based on the following examples.
The invention is not limited to these examples. First, the flotation liquid for flotation, the pulverized coal-water mixture to be desulfurized and deashed, and the desulfurization and deashing experimental method used in this example will be described first. (A) Flotation liquid test strain (Thiobacillus ferrooxidans T-1
Strain, T-9 strain, T-11 strain, ATCC23270 strain) in 9K medium [MP Silverman et al., Appl. Micobiol., 9,
491 (1951)] at 30 ° C. for 3 days with aeration culture.
The cells were collected by centrifuging at 00 × g for 10 minutes, and then the cells were suspended in a dilute sulfuric acid aqueous solution (pH 2.0), washed 3 times with the same solution, and then adjusted to a bacterial suspension having a desired concentration. To make the flotation liquid. (B) Pulverized coal-water mixture coal is Pacific coal (total sulfur content: 0.23% by weight, ash content: 1
6.4% by weight, calorific value: 6140 / g), and pyrite from Dowa Kogyo Co., Ltd. and Yasuhara Mine was used.
Particle size adjusted to 0-300 mesh (particle size 50-75μ
m). A mixture of these in a weight ratio of coal: pyrite = 9: 1 is hereinafter referred to as high-sulfur coal. The desired amount of pyrite or high sulfur coal is added to the bacterial suspension to allow contact between the micronized coal-water mixture (CWM) and the bacteria. (C) Desulfurization / decalcification experiment method For desulfurization / decalcification experiment, diameter 5 cm and height 1 shown in FIG.
A flotation apparatus 1 having a diameter of 0 cm and a volume of 200 ml and equipped with a cylindrical glass column 2 in which a glass filter 3 was incorporated at the bottom was used. A desired amount of the flotation liquid 4 is put in the column 2 and a foaming agent (methylisobutylcarbinol) 150 μl
After adding and stirring, pyrite or high-sulfur coal (2 wt% in the case of pyrite and 10 wt% in the case of high-sulfur coal) is charged from above and stirred for a certain period of time. This stirring time is referred to as the microorganism contact time. After stirring, air was sent while adjusting the flow rate to 1.0 ml / min with an air pump 5 and washing water 8 was sent from a water supply unit 7 to perform floating coal preparation (in the figure, black circles represent fine powder). Fossil coal, black squares are sulfur
The ash content, and the white circles schematically represent the bubbles). At this time, the CWM overflowing from the upper part of the column was washed with floss 9 (floss recovery unit 10
CWM remaining in the column after flotation is used as tail 11 and each is collected by filtration with a 0.5 μm membrane filter and dried at 80 ° C. for 3 hours, after which sulfur content and ash content are respectively removed. It is measured according to JIS-M-8813 and M-9912, and the combustible content is calculated by subtracting the sulfur content and the ash content from the total amount of coal.

Example 1 Thiobacillus ferrooxidans ATC as a flotation liquid
The desulfurization experiment was carried out using a suspension of the C23270 strain at 5 × 10 ⁸ cells / ml, setting the microbial contact time to 10 minutes, and using only pyrite, which is the sulfur content in coal. The same treatment was used as a control except that no microbial treatment was performed. As a result, in the case of the control, 90% of the added pyrite was contained in the floss, whereas in the case of the present invention in which the cell suspension was added as a flotation solution, the content of pyrite in the floss was 35%. It was decreasing. That is, according to the present invention, it was shown that the pyrite contained in coal can be recovered in the tail and desulfurized.

Example 2 Thiobacillus ferrooxidans T-1 as a flotation liquid
Strain, T-9 strain, T-11 strain, and ATCC 23270 strain at a suspension of 10.0 × 10 ⁸ cells / ml, and the microbial contact time was set to 2 minutes, and only pyrite, which is a sulfur component in coal, was used. Was used to perform the desulfurization experiment. The one treated without the flotation liquid was used as a control. The results are shown in Table 3.

[Table 3] ─────────────────────────────────── T-1 T-9 T-11 ATCC stocks Control ─────────────────────────────────── Sulfur content in the floss (% by weight) 17 16 17 18 84 Desulfurization rate (%) 83 84 83 83 82 16 ─────────────────────────────────── According to this In the case of the control, 84 out of the input pyrite
% Was contained in the floss, whereas pyrite contained in the floss was reduced to 16 to 18% in the case of the present invention in which the cell suspension was added as a flotation solution. That is, in the case of the present invention, if a strain having a property such as Thiobacillus ferrooxidans is used, pyrite 82-
It was shown that 84% could be desulfurized.

Example 3 Thiobacillus ferrooxidans AT as a flotation liquid
The relationship between the cell concentration of the CC23270 strain and the desulfurization rate was determined according to the desulfurization experimental method described above by setting the microbial contact time to 5 minutes and using high sulfur coal as the pulverized coal. The results are shown in FIG. 2, which shows the relationship between the cell concentration, the sulfur content in the floss, and the recovery rate of the floss. According to this, it can be seen that the desulfurization effect begins to appear at a low concentration of 2 × 10 ⁸ cells / ml and becomes almost flat at 5 × 10 ⁸ cells / ml. Further, from the results of this test, it is clear that an excellent desulfurization effect is exhibited at a microorganism concentration of about 6 billion pieces per 1 g of coal.

Example 4 Thiobacillus ferrooxidans ATCC 23270
Using a flotation liquid adjusted to have a microbial concentration of 6 billion strains / g of coal 1 g, the microbial contact time was set to 1 minute according to the desulfurization / demineralization experiment method described above, and high sulfur coal was used as pulverized coal. It was used for desulfurization and deashing. The control is the one without microbial treatment. The results are summarized in Table 4. The distribution ratio represents the abundance ratio of each component in the CWM in the floss and tail.

[Table 4] ─────────────────────────────────── Content rate (%) Allocation rate (%) Recovery Rate ────────── ────────── (%) Ash content Sulfur content Combustible content Ash content Sulfur content Combustible content ──────────────── ─────────────────── Control floss 94 20.4 5.02 74.6 91 92 95 Tail 6.0 30.6 6.75 62.7 3 8 5 Invention floss 70 17.8 2.38 79.8 58 31 77 Tail 30 30.4 12.3 57.3 42 69 23 ─────────────────────────────────── As can be seen from these results, the method of the present invention According to the above, it is possible to desulfurize about 70% in one minute and 42% ash from a high-sulfur coal pulverized to a CWM-compatible particle size, which has been conventionally difficult to desulfurize.

[0014]

As described in detail above, the present invention is
It enables efficient desulfurization and deashing from a pulverized coal-water mixture before combustion. Further, according to the present invention, the flotation agent, which was necessary for desulfurization / deashing of coal by conventional microorganisms, is unnecessary, and desulfurization / deashing can be performed more reliably with a small amount of microorganisms. Therefore, the present invention provides for the first time a pulverized coal-water mixture desulfurized and deashed by microorganisms, and such treated coal has a small amount of SO _x that leads to acid rain and greatly contributes to environmental protection. It is a thing.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a deashing / desulfurization apparatus used in the present invention.

FIG. 2 is a graph showing the relationship between the cell concentration of the flotation liquid, the desulfurization rate and the coal recovery rate.

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-62-208270 (JP, A) JP-A-64-75590 (JP, A) JP-B-62-39636 (JP, B1) (58) Field (Int.Cl. ⁷ , DB name) C10L 1/32 C10L 9/00

Claims (5)

(57) [Claims] 1. An iron-oxidizing bacterium, Thiobacillus ferrooxidans, is contacted with a pulverized coal-water mixture containing coal pulverized to a particle size of 75 μm or less, and phases are formed in the mixture .
Contrary to this, the froth containing a large amount of combustibles (coal) is levitated, and the tee containing a relatively large amount of sulfur and ash mixed in the pulverized coal.
Method for coal desulfurization and deashing, which comprises depositing coal on the bottom of the mixed liquid. 2. An iron-oxidizing bacterium, Thiobacillus ferrooxidans, is T-1 (Microtechnical Laboratory No. 13090), T-9.
The method according to claim 1, wherein the bacterium is a bacterium selected from (Ministry of Industrial Science, No. 13091), T-11 (Ministry of Microbes, No. 13092) and ATCC23270 strain. 3. The method according to claim 1, wherein the amount of the pulverized coal dispersed in water is 5 to 25% by weight. 4. A cylindrical desulfurization tank in which iron-oxidizing bacteria are contained.
Air is supplied from the bottom of the tank while stirring the pulverized coal dispersed in water containing iron ,
Float containing a large amount of combustibles (coal) is levitated from the top of the tank
The method of claim 1 comprising flooding and depositing a relatively high sulfur and ash tail at the bottom of the vessel. 5. A pulverized coal-water mixture comprising coal desulfurized and deashed by the iron-oxidizing bacterium Thiobacillus ferrooxidans by the method according to claim 1.