JP2013023653A - Method for producing coal gas and method for producing methane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method in which coal gas having a low tar content can be produced and coal can be gasified with high production efficiency.SOLUTION: The method uses a coal gasification reactor 4 including: a lower part reaction container 11 inside which a containing space 11a is formed; and an upper part reaction container 13 which is provided above the lower part reaction container 11 and in which a vertically extending through-hole 12 in communication with the containing space 11a of the lower part reaction container 11 is formed. In the method, hot gas is generated by a partial oxidation reaction by supplying coal, oxygen, and water vapor into the lower part reaction container 11, and the coal gas including hydrogen gas and carbon monoxide gas is produced by supplying new coal into the upper part reaction container 13 while introducing the hot gas thereinto and by performing pyrolysis of the newly supplied coal, wherein temperature of the coal gas flowing from the exit of the upper part reaction container 13 is controlled to be 1,000°C or more by increasing and decreasing the supplied amount of the new coal which is supplied into the upper part reaction container 13.

Description

  The present invention relates to a method for producing combustible gas or the like by gasifying coal with an oxidizing agent such as oxygen or steam, and in particular, a method for producing coal gas containing hydrogen gas and carbon monoxide gas, and production of methane. Regarding the method.

  Conventionally, gasification furnaces having various configurations such as a fixed bed type, a fluidized bed type, and an airflow bed (spouted bed) type have been studied in order to gasify coal and efficiently produce combustible gas and the like. One of the gas bed type gasification furnaces is one of the recent gasification furnaces because of its large capacity, high load followability, etc., especially when considering applications for power generation. It has become mainstream.

In a gas bed type gasifier, a high temperature gas of 1300 to 1800 ° C. mainly composed of hydrogen and carbon monoxide is produced by a partial oxidation reaction of coal using an oxidizing agent such as oxygen or air, and gas Heat is generally recovered with steam or the like.
Utilizing this high-temperature gas sensible heat for the pyrolysis reaction of coal, as a gasification furnace that produces more gas, tar and BTX (benzene, toluene, xylene) and char, partial oxidation reaction of coal in the lower chamber, A double two-stage coal pyrolysis gasification furnace that performs coal pyrolysis in the upper chamber has been proposed (see Patent Document 1).

  In the gasification furnace described in Patent Document 1, in the upper chamber, hydrogen and carbon monoxide are obtained by a pyrolysis reaction of coal that occurs by mixing hydrogen gas and coal with high-temperature coal partial oxidation gas generated in the lower chamber. A pyrolysis gas composed of methane or the like, tar / BTX, and char are generated, and tar is reformed by reaction of tar and hydrogen gas to further generate BTX.

Japanese Patent No. 4088363

However, the gasification furnace described in Patent Document 1 has the following problems because a large amount of tar is generated by the thermal decomposition reaction of coal.
In the method of Patent Document 1, a facility for recycling a part of the product gas as hydrogen gas is required in order to reduce the weight of the generated tar. In addition, a part of the product gas is consumed, resulting in a quantitative loss of the final product.
Moreover, when preparing product gas, since pyrolysis gas and tar are isolate | separated by a cooler, the equipment which collect | recovers tar is also needed. Furthermore, since the cooling is performed when the pyrolysis gas and tar are separated, the loss of the heat amount of the pyrolysis gas occurs, and the sensible heat of the generated gas is not effectively used, resulting in a reduction in production efficiency.

  This invention is made | formed in order to solve said problem, Comprising: It aims at providing the method which can manufacture coal gas with little tar content, and can gasify coal with high manufacturing efficiency.

In order to solve the above problems, the present invention proposes the following means.
The method for producing coal gas according to the present invention includes a lower reaction vessel in which an accommodation space is formed, and a through-hole that is provided above the lower reaction vessel and communicates with the accommodation space of the lower reaction vessel and extends in the vertical direction. Using a coal gasification reactor having an upper reaction vessel formed with, supplying coal, oxygen and water vapor to the lower reaction vessel, generating a high temperature gas by a partial oxidation reaction, and supplying the high temperature gas to the upper reaction vessel In the method for producing coal gas containing hydrogen gas and carbon monoxide gas by thermally decomposing the newly supplied coal while introducing the coal, the newly supplied coal is supplied to the upper reaction vessel. The amount of coal supplied is increased or decreased, and the temperature of coal gas flowing out from the outlet of the upper reaction vessel is controlled to 1000 ° C. or higher.

  Moreover, the method for producing methane of the present invention is characterized in that the coal gas produced by the method for producing coal gas of the present invention is methanated.

According to the method for producing coal gas of the present invention, coal gas having a small tar content can be produced.
According to the method for producing methane of the present invention, methane can be produced with higher production efficiency than before by applying the coal gas having a low tar content to the methane production process.

It is a block diagram showing one embodiment of a coal gasification system in which the method for producing coal gas of the present invention is used. It is a longitudinal section showing one embodiment of a coal gasification reaction furnace in the present invention. It is a graph which shows the relationship between the temperature (degreeC) of the coal gas which flows out from the exit of the thermal decomposition part in a coal gasification reactor, and the conversion rate (mass%) of the carbon in coal into tar. It is a figure which shows the calculation result which compared the manufacturing method of this invention, and the conventional manufacturing method about the manufacturing efficiency at the time of manufacturing methane from coal.

<Method for producing coal gas>
The method for producing coal gas of the present invention uses a specific coal gasification reactor equipped with a lower reaction vessel and an upper reaction vessel, supplies coal, oxygen and water vapor to the lower reaction vessel, and performs a high temperature gas by partial oxidation reaction. The coal is newly supplied while introducing the high temperature gas into the upper reaction vessel, and the newly supplied coal is pyrolyzed to produce a coal gas containing hydrogen gas and carbon monoxide gas. It is.
This production method is characterized in that the temperature of the coal gas flowing out from the outlet of the upper reaction vessel is controlled to 1000 ° C. or higher, and a known method for producing coal gas can be applied as appropriate for other configurations.
Hereinafter, the manufacturing method of the coal gas of this invention is demonstrated, referring FIG. 1 and FIG.

FIG. 1 is a block diagram showing an embodiment of a coal gasification system in which the method for producing coal gas of the present invention is used.
The coal gasification system 1 of the present embodiment uses a coal gasification reaction furnace 4 to generate coal gas mainly composed of hydrogen gas and carbon monoxide gas using coal as a raw material, and finally produces methane from the coal gas. Plant equipment for producing products such as methanol or ammonia.
The coal gasification system 1 includes a coal pulverization / drying facility 2, a coal supply facility 3, a coal gasification reaction furnace 4, a heat recovery facility 5, a char recovery facility 6, a shift reaction facility 7, and a gas purification facility. 8, a chemical synthesis facility 9, and an air separation facility 10.

In general, the outer diameter of coal is not uniform, and depending on the type, coal may contain more water than desired.
Therefore, first, in the coal pulverization / drying facility 2, the coal is pulverized so that the outer diameter is, for example, about 0.01 mm or more and 0.15 mm or less, and further dried to have a predetermined water content. Later, it is supplied to the coal supply facility 3.
In addition, after the coal pulverization / drying facility 2 to the coal gasification reactor 4, the pulverized coal moves in a sealed space so that the moisture content in the dried coal does not change.
Subsequently, the coal is pressurized to a predetermined pressure by a carrier gas or the like in the coal supply facility 3 so that the coal can be supplied into the coal gasification reactor 4, and is then transported to the coal gasification reactor 4. The
On the other hand, the air separation facility 10 separates dried oxygen gas, nitrogen gas, and the like from the air that has been compressed and liquefied and changed into liquid by the difference in boiling point. The oxygen gas separated by the air separation facility 10 is supplied to the coal gasification reactor 4.

The coal gasification reactor 4 is used by being incorporated in a part of the coal gasification system 1, and includes coal gas containing hydrogen gas and carbon monoxide gas as main components by causing a partial oxidation reaction of coal in the reactor. Is a device for manufacturing.
FIG. 2 is a longitudinal sectional view showing an embodiment of a coal gasification reactor in the present invention.
The coal gasification reactor 4 of the present embodiment is provided in a partial oxidation part (lower reaction vessel) 11 in which an accommodation space 11a is formed, and an upper space D1 above the partial oxidation part 11, and the accommodation space of the partial oxidation part 11 The thermal decomposition part (upper reaction container) 13 in which the through-hole 12 which was connected to 11a and extended in the up-down direction D was formed is provided. The coal gasification reactor 4 is formed of heat-resistant bricks or the like.
In the coal gasification reaction furnace 4, a preheating part 14 is provided below the partial oxidation part 11. The partial oxidation unit 11 and the preheating unit 14 communicate with each other in the vertical direction D, and the connection portion between the thermal decomposition unit 13 and the partial oxidation unit 11 and the connection portion between the partial oxidation unit 11 and the preheating unit 14 are Each is configured to be thinner than the continuous portion.

As shown in FIG. 2, the partial oxidation portion 11 is formed in a substantially cylindrical shape extending in the vertical direction D, and is formed on the inner peripheral surface of the partial oxidation portion 11 in a cylindrical shape extending along a predetermined axis C <b> 1. A plurality of gasification burners 17 are provided.
The gasification burner 17 is connected to the coal supply facility 3, the air separation facility 10, and the heat recovery facility 5 that generates water vapor by a method described later. Collectively referred to as “carbon etc.”) at a predetermined rate. The plurality of gasification burners 17 are installed horizontally so as to be twisted with respect to the central axis C <b> 2 of the partial oxidation unit 11.
Moreover, a cooling means (not shown) is provided on the outer peripheral surface of the partial oxidation unit 11 so that the wall surface of the partial oxidation unit 11 heated by the partial oxidation reaction of coal can be cooled.

The thermal decomposition part 13 is formed in a substantially cylindrical shape extending in the vertical direction D.
In the thermal decomposition part 13, a plurality of coal nozzles 18 for supplying coal to the thermal decomposition part 13 are provided in the middle part in the vertical direction D. The coal nozzle 18 is connected to the coal supply facility 3.
The number of coal nozzles 18 is not limited and may be any number. Moreover, you may provide the water vapor | steam nozzle which supplies water vapor | steam to the thermal decomposition part 13 below the coal nozzle 18, for example as needed. This water vapor nozzle can be provided connected to the heat recovery equipment 5, for example.

An end (exit) 12 a at the upper side D <b> 1 of the through hole 12 of the thermal decomposition unit 13 is connected to the heat recovery facility 5.
And the temperature measuring apparatus 20 which measures the temperature of the coal gas which flows out out of the edge part 12a is provided in the edge part 12a.

  A predetermined amount of water W is accommodated in the preheating unit 14 of the present embodiment, and the slag flowing down from the partial oxidation unit 11 can be cooled as will be described later.

When the coal gasification reactor 4 configured as described above is operated, granular carbon or the like is supplied from the gasification burner 17 into the partial oxidation unit 11 at a predetermined flow rate. Since each gasification burner 17 is arranged as described above, carbon or the like supplied from each gasification burner 17 swirls around the central axis C <b> 2 of the partial oxidation unit 11.
At this time, the inside of the partial oxidation unit 11 is at a high temperature and a high pressure. The temperature and pressure in the partial oxidation part 11 are preferably 1300 to 1600 ° C., more preferably 1300 to 1400 ° C., and more preferably 2 to 4 MPa because the partial oxidation reaction proceeds well. Preferably, it is more preferable to set it as 2-3 Mpa.
Under this environment, the coal becomes high temperature and is thermally decomposed to separate char and volatile gas containing tar, water vapor and the like, and the coal is combusted (partial oxidation reaction). ) To (4), carbon monoxide gas, carbon dioxide gas and hydrogen gas, and slag (ash) are generated.

2C + O ₂ → 2CO (2)
C + O ₂ → CO ₂ (3)
C + H ₂ O → CO + H ₂ (4)

Although the slag generated in the partial oxidation part 11 is in a molten state, a part of the slag is cooled on the inner peripheral surface of the partial oxidation part 11 by the above-mentioned cooling means and adheres to this inner peripheral surface, and other parts Falls into the water W in the preheating unit 14 provided below the partial oxidation unit 11 and is cooled and recovered.
On the other hand, high-temperature gas (gas containing carbon monoxide gas, carbon dioxide gas, hydrogen gas, water vapor, etc.), tar, char, etc. generated in the partial oxidation part 11 rises in the partial oxidation part 11 while turning, It moves from the partial oxidation part 11 and rises in the thermal decomposition part 13.

In the pyrolysis unit 13, new coal is supplied from the coal nozzle 18 into the high-temperature gas rising from the partial oxidation unit 11, and pyrolysis gas, tar, char, and the like are generated by the pyrolysis reaction of coal.
Part of the carbon in the new coal supplied to the pyrolysis unit 13 reacts with the carbon dioxide gas in the pyrolysis unit 13 to become carbon monoxide gas according to the following chemical reaction formula (5).
Since the above-described pyrolysis reaction of coal and the gasification reaction of carbon with carbon dioxide gas are endothermic reactions, the high-temperature gas rising from the partial oxidation unit 11 is cooled.

C + CO ₂ → 2CO (5)

In that case, in this invention, the supply amount of the said new coal supplied to the thermal decomposition part 13 is increased / decreased, and the temperature of the coal gas which flows out from the edge part 12a is controlled to 1000 degreeC or more. The upper limit of the temperature of the coal gas flowing out from the end 12a is preferably controlled to 1200 ° C. or less, and particularly preferably controlled to the range of 1050 to 1150 ° C.
By controlling the temperature of coal gas to 1000 ° C. or higher, coal gas with a small tar content can be produced. When the temperature of the coal gas is controlled to 1200 ° C. or less, the coal gasification reactor 4 is hardly damaged.

  The temperature of the coal gas flowing out from the end portion 12a is controlled by increasing or decreasing the supply amount of the new coal supplied to the thermal decomposition unit 13. Since the pyrolysis of coal in the pyrolysis section 13 is an endothermic reaction, the temperature of the coal gas flowing out from the end portion 12a can be lowered or raised by increasing or decreasing the supply amount of coal.

  Moreover, since the pressure in the pyrolysis part 13 and gas residence time can reduce tar content in coal gas more, it is preferable to make a pressure into 2-4 Mpa, and it is more preferable to set it as 2-3 Mpa, The residence time is preferably 1 to 5 seconds, and more preferably 2 to 3 seconds.

Then, as shown in FIG. 1, high-temperature coal gas containing hydrogen gas and carbon monoxide gas is transported together with char from the outlet of the thermal decomposition unit 13 and supplied to the heat recovery facility 5.
In the heat recovery facility 5, steam is generated by heat exchange between the coal gas conveyed from the thermal decomposition unit 13 and water. This steam is supplied for the purpose of raw materials used in the above-described coal pulverization / drying equipment 2 and shift reaction equipment 7.
The coal gas cooled by the heat recovery facility 5 is supplied from the heat recovery facility 5 to the char recovery facility 6, and the char contained in the coal gas is recovered by the char recovery facility 6.
Coal gas that has passed through the char recovery facility 6 is supplied to the shift reaction facility 7. And in order to raise the ratio of the hydrogen gas to the carbon monoxide gas in the coal gas to a certain value, water vapor is supplied into the shift reaction facility 7, and by the shift reaction shown by the following chemical reaction formula (6), Carbon monoxide gas in the coal gas is consumed, and hydrogen gas is generated instead.

CO + H ₂ O → CO ₂ + H ₂ (6)

The coal gas whose gas component content ratio is adjusted in the shift reaction facility 7 is supplied to the gas purification facility 8, and carbon dioxide gas or sulfur-containing gas contained in the coal gas is recovered.
Coal gas refined in the gas purification facility 8 is supplied to the chemical synthesis facility 9, and products such as methane and methanol are produced by various chemical reactions.

As described above, according to the method for producing coal gas of the present invention, coal gas that hardly generates tar and has a small tar content (for example, synthesis gas mainly composed of H ₂ , CO, and CH ₄ ). Can be produced.
Tar is generated by an initial thermal decomposition reaction of coal that reacts instantaneously, and is decomposed and disappeared by H ₂ , H ₂ O, CO _{2 and the} like in the atmospheric gas. Therefore, the tar content in the coal gas is determined by the balance between the generation and the decomposition disappearance. Factors affecting the decomposition / disappearance reaction include the composition of the atmospheric gas and, in addition, the temperature that affects the reaction rate.
On the other hand, in the production of coal gas using a coal gasification reactor, the amount of tar produced depends on the amount of coal used as a raw material.
From these, the present inventors can control the amount of tar produced by increasing or decreasing the amount of coal supplied to the upper reaction vessel when producing coal gas using a coal gasification reactor, In addition, the present inventors completed the present invention by finding that the temperature of coal gas flowing out from the outlet of the upper reaction vessel changes and that the tar temperature is hardly generated by controlling the temperature of the coal gas to 1000 ° C. or higher. It came to do.

  Moreover, since the manufacturing method of this invention can manufacture coal gas with little tar content, like the method described in patent document 1 mentioned above, the facilities for lightening of produced | generated tar, For tar collection | recovery No equipment is required, there is no quantitative loss of the final product due to consumption of product gas, and there is no loss of heat due to cooling of the pyrolysis gas, resulting in excellent production efficiency.

<Methane production method>
The method for producing methane of the present invention is a method for methanating coal gas produced by the method for producing coal gas of the present invention. As one embodiment, there is a method of combining a shift reaction process and a methanation process in the coal gasification system 1 shown in FIG.
By methanating the coal gas with a small tar content produced by the method for producing coal gas according to the present invention, heat loss is reduced, and methane can be produced with higher production efficiency than before.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to these embodiment, The change of the structure of the range which does not deviate from the summary of this invention, etc. are included.

Methane was produced by the coal gasification system of the same embodiment as in FIG. 1 except that the coal gasification reactor of the same embodiment as in FIG. 2 was used and methanation was performed in a chemical synthesis facility. Hereinafter, the same reference numerals as those in FIGS. 1 and 2 are used for explanation.
In the coal gasification reactor 4, the end 12a is provided with a temperature measuring device 20 for measuring the temperature of coal gas flowing out from the outlet (end 12a) of the thermal decomposition unit 13 as shown in FIG. Was manufactured.

As a raw material, coal having an outer diameter of 0.15 mm or less, a water content of 5% by mass, and carbon containing 70% by mass in dried coal was used.
Coal, oxygen gas and water vapor supplied from the total gasification burner 17 to the partial oxidation unit 11 are coal 500 (kg / h), oxygen gas 300 (Nm ³ / h) and water vapor 40 (kg / h), respectively. Time supplied.
The temperature and pressure in the partial oxidation unit 11 were set to a temperature of 1350 ° C. and a pressure of 2.45 MPa, the pressure in the thermal decomposition unit 13 was set to 2.45 MPa, and the gas residence time was set to 2 seconds.
Furthermore, the coal supplied to the thermal decomposition part 13 from all the coal nozzles 18 was adjusted as follows.

The tar content contained in coal gas flowing out from the outlet (end portion 12a) of the thermal decomposition unit 13 was measured.
For the tar content, a predetermined amount of the generated coal gas is extracted from a sampling nozzle installed at the outlet (end portion 12a) of the thermal decomposition unit 13, and after absorbing the tar in the absorption liquid, the absorption liquid is removed. It was measured by.
The temperature of coal gas was controlled at 800 degreeC by supplying coal supplied to the thermal decomposition part 13 from all the coal nozzles 18 at 500 (kg / h) for 24 hours.
Similarly, the temperature of coal gas was controlled to about 1050 degreeC by supplying coal at 200 (kg / h) for 24 hours.
Similarly, the temperature of coal gas was controlled to about 1150 degreeC by supplying coal at 150 (kg / h) for 24 hours.

Methanation at the chemical synthesis facility 9 is carried out by using the shift reaction facility 7 and the gas refining facility 8 as upstream processes to increase the volume ratio of hydrogen and carbon monoxide in the coal gas to 3: 1 or more by the following formula. Reaction was performed to produce methane. CO + 3H ₂ → CH ₄ + H ₂ O

FIG. 3 shows the temperature (° C.) of coal gas flowing out from the outlet (end portion 12a) of the thermal decomposition unit 13 in the coal gasification reactor 4 and the conversion rate (mass%) of carbon in the coal into tar. It is a graph which shows a relationship.
From the results of FIG. 3, when the temperature of the coal gas was changed from 800 ° C. to 1150 ° C., the conversion rate of carbon in the coal into tar (the tar content contained in the coal gas) was reduced from 6.9% by mass to 0%. It can be seen that the content is significantly reduced to 3% by mass. That is, according to the method for producing coal gas of the present invention, it was confirmed that coal gas having a small tar content can be produced.

FIG. 4 is a calculation result comparing the production method of the present invention and a conventional production method (a general method for producing a gas-bed gasifier with only a partial oxidation reaction) for production efficiency when producing methane from coal. FIG.
As a general gas-bed gasification furnace, coal gasification efficiency is 80% (the amount of heat) with reference to the Shell process, which is said to have the highest coal gasification efficiency as a currently commercialized gas-bed gasification furnace. Base).
In the production method of the present invention, methane was produced by controlling the temperature of coal gas flowing out from the outlet (end portion 12a) of the thermal decomposition unit 13 to 1100 ° C.
In FIG. 4, “pyrolysis gasification” includes both partial oxidation in the partial oxidation unit 11 of the coal gasification reactor 4 and thermal decomposition in the thermal decomposition unit 13.
The number shown below the compound indicates the calorific value, and when the calorific value of the raw material coal is 1.00, for example, in the present invention, the reaction efficiency (η) of pyrolysis gasification is 85%, that is, 15% min. Means that a loss of heat has occurred, 73% of which has been converted to CO + H ₂ and the remaining 12% has been converted to CH ₄ .

In FIG. 4, in the production method of the present invention, when coal is pyrolyzed and gasified, the reaction efficiency (η) is 85% from coal (1.00), and CO + H ₂ (0.73) and CH ₄ as coal gas. (0.12) was produced.
Then, when the methanation of coal gas _from the CO + H 2 (0.73), the reaction efficiency _{(η) 74%, CH 4} (0.54) is manufactured, CH ₄ obtained by the pyrolysis gasification Combined with (0.12), a total of CH ₄ (0.66) was produced from coal (1.00).

In the conventional production method, when coal is gasified (partial oxidation), CO + H ₂ (0.80) is produced as coal gas from coal (1.00) with a reaction efficiency (η) of 80%.
Next, when coal gas is methanated, CH ₄ (0.60) is produced from CO + H ₂ (0.80) with a reaction efficiency (η) of 74%, and from coal (1.00), CH ₄ (0.60) was produced.

  From the comparison between the manufacturing method of the present invention and the conventional manufacturing method (the manufacturing method of a general gas-bed gasification furnace with only partial oxidation reaction), the manufacturing method of the present invention has a calorific value compared to the conventional manufacturing method. Since the loss is reduced and methane produced by pyrolysis gasification is not subject to production loss in chemical synthesis, it can be seen that the efficiency of producing methane from coal is 10% higher (the present invention) However, the calorific value is larger than that of a method of producing methane using a general gas-bed gasifier (difference 0.06)). That is, from the result of FIG. 4, according to the method for producing methane of the present invention, it was confirmed that methane can be produced with higher production efficiency than the method for producing methane using a general air-bed gasification furnace.

4 Coal gasification reactor 11 Partial oxidation section (lower reaction vessel)
12 Through-hole 12a End 13 Pyrolysis part (upper reaction vessel)
17 Gasification burner 18 Coal nozzle 20 Temperature measuring device

Claims (2)

A lower reaction vessel having an accommodation space formed therein, and an upper reaction vessel provided above the lower reaction vessel and having a through-hole extending in the vertical direction communicating with the accommodation space of the lower reaction vessel. Using a coal gasification reactor,
Supplying coal, oxygen and water vapor to the lower reaction vessel, generating high temperature gas by partial oxidation reaction, supplying new coal while introducing the high temperature gas into the upper reaction vessel, In a method for producing coal gas containing hydrogen gas and carbon monoxide gas by pyrolysis,
The method for producing coal gas, wherein the supply amount of the new coal supplied to the upper reaction vessel is increased or decreased, and the temperature of coal gas flowing out from the outlet of the upper reaction vessel is controlled to 1000 ° C. or more. .   A method for producing methane, comprising methanating the coal gas produced by the method for producing coal gas according to claim 1.

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