JP5389335B2 - Gasifier - Google Patents

Description

  The present invention relates to a gasification furnace used in a coal gasification process for producing a fuel gas such as carbon monoxide, hydrogen, methane from a solid hydrocarbon fuel such as coal.

  As a process used for coal gasification, there is a two-stage gasification method. With regard to this two-stage gasification method, for example, Japanese Patent Publication No. 5-47595 (hereinafter sometimes referred to as a prior invention) discloses a two-stage gasification furnace.

FIG. 1 shows an example of such a two-stage gasifier. As shown in FIG. 1A, the two-stage gasification furnace 1 includes a furnace body 2, an upper burner group 3 provided at the upper part of the furnace body 2, and a lower part provided at the lower part of the furnace body 2. The burner group 4 is schematically configured.
The furnace main body 2 has a cylindrical shape having a substantially constant cross-sectional area, and a gas outlet 5 through which a product gas such as carbon monoxide, hydrogen, and methane generated in the furnace main body 2 is led opens at the top. ing. The diameter (Dout) of the gas outlet 5 is made smaller than the diameter (D) of the furnace body 2 and is connected to the subsequent apparatus.

  An annular slag stack 6 is attached to the inner surface of the lower part of the furnace body 2, and a central opening of the slag stack 6 serves as a molten slag outlet 7 through which the molten slag flows down. The diameter of the molten slag outlet 7 is also made smaller than the diameter of the furnace body 2 so that the heat radiation from the molten slag outlet 7 is reduced.

  The upper burner group 3 is disposed at the upper part of the furnace body 2 and four burners 31, 32, 33, and 34 are each equally distributed and attached to the peripheral wall of the furnace body 2 as shown in FIG. ing. These burners 31... Are not directed toward the central axis of the furnace body 2 but are directed outward from the central axis as shown in the figure, and are ejected from the respective ejection openings. Combustion gas flows in the circumferential direction of the furnace body 2 to form a swirl flow in the furnace body 2.

The diameter of the virtual circle of the swirl flow formed by the upper burner group 3 is called “virtual swirl flow circle diameter”, and this diameter is hereinafter referred to as Du.
In the present invention, the “virtual swirl flow circle diameter” does not refer to a swirl flow caused by an actual gas flow, but four virtual lines in which the nozzles of the burner 31, 32. It is defined as the diameter of the circle inscribed in the line. Thereby, by determining the “virtual swirl flow circle diameter”, the arrangement of the burners 31, 32,... Is determined.

  The individual burners constituting the upper burner group 3 are supplied with a fine powder of a solid hydrocarbon fuel such as coal and an oxidizer composed of an oxygen-containing gas such as air or oxygen gas, and this is injected from each injection port. It is like that. Hereinafter, the mixing ratio of oxidant and solid hydrocarbon fuel (oxidant supply amount / solid hydrocarbon fuel supply amount: weight ratio) is defined as the oxidant amount ratio.

The lower burner group 4 is disposed above the slag stack 6 at the lower part of the furnace body 2, and the four burners 41, 42, 43, 44 are evenly arranged on the peripheral wall of the furnace body 2 as shown in FIG. It is arranged and attached to. These burners 41 are also not directed to the central axis of the furnace body 2 but directed to the outside of the central axis as shown in the figure, and are injected from the respective injection holes. Similarly, the combustion gas forms a swirl flow in the furnace body 2.
The diameter of the virtual circle of the swirl flow formed by the lower burner group 4 is also called “virtual swirl flow circle diameter”, and this diameter is hereinafter referred to as Dl. The definition of the “virtual swirl flow circle diameter” here is the same as that in the upper burner group 3.

As with the upper burner group 3, the individual burners constituting the lower burner group 4 are supplied with fine powder of solid hydrocarbon fuel and an oxidant composed of an oxygen-containing gas such as air or oxygen gas. It comes to be injected from the mouth.
The virtual swirl flow circle diameter Du by the upper burner group 3 is larger than the virtual swirl flow circle diameter Dl by the lower burner group 4, and the virtual swirl flow circle diameter Dl by the lower burner group 4 is the diameter of the gas outlet 5. It is configured to be larger than Dout (Du>Dl> Dout).

  A molten slag cooling chamber 8 is provided below the slag stack 6 of the furnace body 2. The molten slag cooling chamber 8 is formed integrally and continuously with the furnace body 2 and has a cylindrical shape having substantially the same diameter as the furnace body 2 so that the molten slag dropped from the molten slag outlet 7 is cooled and solidified. It has become.

  In the two-stage gasification furnace 1 configured as described above, combustion is performed by reducing the oxidant amount ratio in the upper burner group 3 and increasing the oxidant amount ratio in the lower burner group 4 to cause combustion. At the same time as the swirling flow is formed, a temperature distribution in the furnace main body 2 as shown in FIG. 2 is formed, and the ash content in the lower region is melted at a temperature at which the ash content in the solid hydrocarbon fuel does not melt in the upper region. Operated at temperature.

Thereby, in a region near the upper burner group 3, a gas such as hydrogen, carbon monoxide, and methane is generated by a chemical reaction in the high-temperature swirling flow, and is derived as a high-temperature product gas from the upper gas outlet 5. The The temperature of this product gas is lower than the melting temperature of the ash content in the solid hydrocarbon fuel.
On the other hand, in the area near the lower burner group 4, gases such as carbon dioxide and moisture are generated, and this gas rises to the area of the upper burner group 3 and is used for the reaction here. Further, the ash content in the solid hydrocarbon fuel is melted together with the ash content that is generated and descends in the upper burner group 3, and this molten ash content as a molten slag adheres to the wall surface of the furnace body 2 on the swirling flow, Then, it flows down from the lower molten slag outlet 7 and is discharged into the molten slag cooling chamber 8.

  And in the said prior invention, the diameter (D) of the furnace main body 2 is larger than the diameter (Dout) of the gas outlet 5, Dout / D is about 0.2-0.35, and the virtual swirl by the upper burner group 3 is carried out. The flow circle diameter Du is larger than the virtual swirl flow circle diameter Dl by the lower burner group 4, and the virtual swirl flow circle diameter Dl by the lower burner group 4 is larger than the diameter Dout of the gas outlet 5 (Du> Dl> It is said that the gasification efficiency can be improved by Dout).

By the way, when the gasification furnace is scaled up (increasing the processing capacity) while maintaining the operating conditions of the gas furnace in this prior invention, minimizing the increase in the dimensions of the furnace body 2 itself can reduce equipment costs, This is important from the viewpoint of reducing heat loss.
For this reason, when the diameter of the furnace body 2 is increased, it is necessary to make the increase amount as small as possible. There is a method of increasing the gas flow rate in the furnace body 2 as a measure for increasing the processing capacity while suppressing an increase in the diameter of the furnace body 2.

However, when the gas flow rate in the furnace body 2 is increased, a part of the molten slag is scattered along with the product gas from the gas outlet 5, and this molten slag adheres to the inner wall of equipment such as a heat recovery boiler at the subsequent stage, It has been found that it causes fouling problems that cause various problems.
FIG. 3 is a diagram for explaining the fouling failure, and is a schematic diagram showing a gas flow in the furnace main body 2. The same reference numerals are given to the same components as those in FIG.

With the operation of the gasification furnace, the molten slag travels along the furnace wall of the furnace body 2 and falls from the molten slag outlet 7 to the slag cooling chamber 8. On the other hand, as the gas flow, there is a swirling descending flow 20 that descends while swirling on the furnace wall side. A part of this swirling downward flow flows into the slag cooling chamber 8 through the molten slag outlet 7, and forms a molten slag outlet reversal flow 21 that is reversed and passes again through the molten slag outlet 7 and returns into the furnace body 2.
The gas flow in the center of the furnace body 2 is basically an upward flow 22. At this time, a phenomenon occurs in which a part of the molten slag 13 flowing down the molten slag outlet 7 is blown off into the reverse flow 21 and is transported to the furnace body 2 again.

Furthermore, the blown-off molten slag rides on the upward flow 22 and may scatter as a scattered slag toward the gas outlet 5 of the furnace body 2. Thus, the molten slag adheres to the inner wall of a device such as a heat recovery boiler installed at the rear stage of the gas outlet 5 and causes a fouling failure.
Thus, increasing the gas flow rate in the furnace body 2 increases the scattering of molten slag that causes fouling failures.
Japanese Patent Publication No. 5-47595

  Therefore, the object of the present invention is based on the premise of scaling up the two-stage gasification furnace, and in order to achieve this object while minimizing the increase in the diameter of the furnace body, the average gas flow rate in the furnace body is set. When the size is increased, molten slag is scattered from the gas outlet of the furnace body to prevent fouling failure.

To solve this problem,
According to the first aspect of the present invention, a cylindrical furnace body that generates gas by a reaction between a solid hydrocarbon fuel powder and an oxidant, and an upper part of the furnace body, the solid hydrocarbon fuel powder and the oxidant are provided. An upper burner group for injecting a mixed fluid into the furnace body, and a lower burner group disposed in the lower part of the furnace body and injecting a mixed fluid of solid hydrocarbon fuel powder and oxidant into the furnace body;
A gas outlet from which product gas is discharged is formed at the upper end of the furnace body, and a molten slag outlet from which molten slag is discharged is formed at the lower end of the furnace body,
The ratio Dout / D between the diameter (Dout) of the gas outlet and the diameter (D) of the furnace body is 1> Dout / D ≧ 0.4 ,
The upper burner group and the lower burner group are each composed of three or more burners, and these burners are arranged on the peripheral wall of the furnace body,
When the diameter of the virtual swirl flow formed by each burner of the upper burner group is Du and the diameter of the virtual swirl flow formed by each burner of the lower burner group is D1, D> Du ≧ Dout> Both burner groups are arranged to be Dl,
When the pressure in the furnace is 2.5 to 3.0 MPa and the operation is performed for 8000 hours per year, the pressure difference (ΔPout) at the gas outlet is a value obtained by gradually declining the pressure in the furnace (Pg). The gasification furnace is characterized in that the integrated value of increase (ΔPout / Pg) is 1% or less of the pressure in the furnace.

According to the present invention, the ratio of the gas outlet diameter (Dout) to the furnace body diameter (D) is 1> Dout / D ≧ 0.4, thereby increasing the average gas flow velocity in the furnace body. Even if the processing capacity of the furnace itself is increased, a part of the molten slag does not scatter from the gas outlet of the furnace body to cause a fouling failure.
Further, when the diameter of the swirling flow formed by the upper burner group is Du and the diameter of the swirling flow formed by the lower burner group is D1, both burner groups are arranged so that D> Du ≧ Dout> Dl. As a result, part of the solid hydrocarbon fuel powder ejected from the upper burner group does not flow directly toward the gas outlet, and the gasification efficiency does not decrease.

Hereinafter, the present invention will be described with reference to FIG.
According to the study by the present inventor, it is found that the scattering of molten slag from the gas outlet 5 depends on the upward flow velocity at the center of the gasifier, and this velocity is strongly influenced by the diameter of the gas outlet 5. It was.
Based on this finding, the relationship between the diameter of the gas outlet 5 and fouling was further examined, and the results are shown in Table 1.

The degree of fouling failure was evaluated by the rate of increase ΔPout / Δt (kPa / h) of the pressure loss at the gas outlet 5 (ΔPout in FIG. 3) over time.
The average gas velocity (Ugas) in the furnace main body 2 is a value obtained by dividing the amount of generated gas per unit time by the cross-sectional area of the furnace main body 2 and is a relative value where the value in Test No = 1 is 1. .
In addition, the examination example of Table 1 is in a gasification furnace having a processing capacity of solid hydrocarbon fuel of 50 to 150 tons / day and a furnace pressure of 2.5 to 3.0 MPa.

The “conventional method” in Table 1 is based on the prior invention disclosed in the above-mentioned Japanese Patent Publication No. 5-47595.
[Test 1] of the conventional method has a small gas outlet diameter / furnace body diameter (Dout / D), so the gas rising speed at the center of the furnace body 2 is fast, and the amount of molten slag scattered increases, and ΔPout /Δt=0.166 kPa / h, and adhesion and growth of molten slag at the gas outlet 5 was observed.
Similarly, in [Test 2] of the conventional method, as a result of increasing Dout / D from [Test 1], [Delta] Pout / [Delta] t was reduced, which was effective in preventing the molten slag from scattering.

[Test 3] of the present invention is a case where the gas average velocity Ugas is increased 1.43 times that of the conventional method, but ΔPout / Δt is further reduced. This is because Dout / D is a conventional method test no. This is because the slag scattering is remarkably suppressed by the effect larger than 2.
In [Test 4], the average gas velocity Ugas was increased more than in [Test 3], but ΔPout / Δt was comparable.
From the above, it was found that fouling failure can be prevented by increasing Dout / D to some extent even if the gas average velocity Ugas is increased to twice that of the conventional method.
From Table 1, the appropriate Dout / D is 0.4 or more.

  On the other hand, the gas outlet diameter Dout cannot be larger than the furnace body 2 diameter D in terms of the apparatus configuration, and thus Dout / D is less than 1. Therefore, 1> Dout / D ≧ 0.4, and in practice 0.7 ≧ Dout / D ≧ 0.4 is preferable, and 0.6 ≧ Dout / D ≧ 0.5 is the most preferable value. Become.

FIG. 4 shows the relationship between the integrated value of pressure loss ΔPout / Δt and Dout / D in Table 1 when the operation is performed for 8000 hours per year in consideration of the practical use of the gasifier. In the graph of FIG. 4, Dout / D is taken on the horizontal axis, and ΔPout (ΔPout / Δt × 8000) after 8000 hours is taken on the vertical axis by the furnace pressure Pg.
In practical gasification furnaces, it is necessary that there be as few operational obstacles as possible, and the annual differential pressure increase (ΔPout / Pg) is preferably 1% or less of the pressure in the furnace. Therefore, from the graph of FIG. 4, Dout / D is 0.4 or more.

As for the upper limit of Dout, it is preferable not to exceed the virtual swirl flow circle diameter Du in the upper burner group 2, that is, Du ≧ Dout. If this is exceeded, the solid hydrocarbon fuel powder ejected from the product gas outlet burner will flow directly toward the product gas outlet, leading to a decrease in the gasification rate.
Therefore, the relationship D> Du ≧ Dout> Dl is preferable. This relationship is 1> Du / D ≧ Dout / D> Dl / D. Du / D is determined by the arrangement position of the upper burner group 3 as shown in FIG. When this ratio is close to 1, the burner flame hits the furnace wall directly and causes damage. Considering this point, 0.9> Du / D.

As a result, the virtual swirl flow circle diameter in the lower burner group 3 which was Dl> Dout in the conventional method (the above-described prior invention) is, on the contrary, excellent in Dout> Dl in the present invention.
And it is preferable to set the arrangement of the burners 31, 32,.., 41, 42,... In the upper burner group 3 and the lower burner group 4 so that the relationship D> Du ≧ Dout> Dl is satisfied. It is.

By adopting such a configuration, slag scattering can be suppressed even if the gas velocity in the furnace body 2 is increased by a factor of two. As shown in Table 1, as a result, the diameter D of the furnace body 2 can be reduced to at least 1 / √2≈0.7, which is scaled up while satisfying the conditions described in the conventional method, which is useful for downsizing. That is, from Table 1, the gas average flow velocity Ugas can be at least twice that of the conventional one, and the gas average flow velocity Ugas is the product gas amount divided by the cross-sectional area of the furnace body 2, in other words, the furnace Since it corresponds to the value obtained by dividing the main body 2 by the square of the diameter, it is 1 / √2.
For example, the diameter of a gasification furnace used for a 500 MW power generation facility is 5 m in the conventional method, but can be reduced to about 3.5 m in the method of the present invention, thereby reducing facility costs and heat transfer loss from the furnace wall.

In the above description, four examples of the burners constituting each of the burner groups 3 and 4 are shown, but the present invention is not limited to this, and it may be two or more.
Further, as the solid hydrocarbon fuel in the present invention, a solid hydrocarbon fuel containing an inorganic substance that becomes ash such as oil coke in addition to coal is used, and further, a plastic to which an inorganic substance that becomes ash is added can be used.
Furthermore, air, pure oxygen gas, oxygen-containing gas, water, water vapor or the like is used as the oxidant.

It is a schematic block diagram which shows the example of the two-stage gasifier in this invention. It is a graph which shows the temperature distribution in the furnace main body of the two-stage gasifier in this invention. It is drawing which shows the flow of the gas in the two-stage gasifier in this invention. It is a graph which shows the relationship between the pressure loss integrated value in this invention, and Dout / D.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Two-stage gasification furnace, 2 ... Furnace main body, 3 ... Upper burner group, 4 ... Lower burner group, 5 ... Gas outlet, 7 ... Molten slag outlet, 8 ... Molten slag cooling room, 20 ... Swirling downward flow, 21 ... Reverse flow of molten slag outlet, 22 ... Upflow

Claims (1)

A cylindrical furnace body that generates gas by the reaction of the solid hydrocarbon fuel powder and the oxidant, and a fluid mixture of the solid hydrocarbon fuel powder and the oxidant that is disposed in the upper part of the furnace body is injected into the furnace body. An upper burner group, and a lower burner group disposed in the lower part of the furnace body and injecting a mixed fluid of solid hydrocarbon fuel powder and oxidant into the furnace body,
A gas outlet from which product gas is discharged is formed at the upper end of the furnace body, and a molten slag outlet from which molten slag is discharged is formed at the lower end of the furnace body,
The ratio Dout / D between the diameter (Dout) of the gas outlet and the diameter (D) of the furnace body is 1> Dout / D ≧ 0.4 ,
The upper burner group and the lower burner group are each composed of three or more burners, and these burners are arranged on the peripheral wall of the furnace body,
When the diameter of the virtual swirl flow formed by each burner of the upper burner group is Du and the diameter of the virtual swirl flow formed by each burner of the lower burner group is D1, D> Du ≧ Dout> Both burner groups are arranged to be Dl,
When the pressure in the furnace is 2.5 to 3.0 MPa and the operation is performed for 8000 hours per year, the pressure difference (ΔPout) at the gas outlet is a value obtained by gradually declining the pressure in the furnace (Pg). A gasification furnace characterized in that an integrated value of increase (ΔPout / Pg) is 1% or less of the pressure in the furnace.

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