JPS5818400B2 - Coal gasification slag processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for harmlessly treating slag generated when coal is gasified in an iron bath gasifier.

The method of gasifying coal using an iron bath gasifier is a method in which the heat necessary for the gasification reaction is supplied by molten iron, and the coal is kept in a molten state together with a gasifying agent (oxygen, steam, etc.). This method involves blowing into a high-temperature molten iron bath to gasify it.

An example of a gasification apparatus for carrying out this method is shown in Fig. 1 (a gasification furnace 2 having a slag discharge port 1 on the side wall of the furnace, a lance for injecting coal and a gasification agent, It consists of a gas recovery hood 3, and the gasification furnace 2
An apparatus is known in which coal is gasified by blowing it together with a gasifying agent using a lance 5 into a molten iron bath (1,300 to 1,500°C) 4 stored in a molten iron bath (1300 to 1500°C).

In such an iron bath coal gas system, slag 6 derived from the ash in the coal is generated on the surface of the molten iron bath during gasification as gas is generated.

The components of this coal gasification slag are shown in Table 1.

That is, during coal gasification, the temperature of the molten iron bath rises due to heat generated by oxidation, but the atmosphere is reducing, and S in the coal is fixed and concentrated in the slag as FeS, CaS, and MnS.

For this reason, usually a large amount of CaO is added to perform desulfurization using slag, and when the amount of slag increases, the slag is periodically discharged.

This discharged slag contains mainly CaS, FeS,
Contained as MnS, when in contact with air and water, 2CaS+02+2H20→2Ca(OH)2
+28・=(1) Formula CaS+(X-1)S→CaSx
・---゛Polysulfide is produced by the reaction of formula (2), and when this polysulfide dissolves in water, yellow water is generated.

Also, CaS+2H20→Ca(OH)2+2H2S
-------Hydrogen sulfide is generated by the reaction of formula (3), which causes a bad odor.

By the way, coal gasification slag, like blast furnace slag, has excellent properties as a material for reclamation of rivers, roads, etc., and is a powerful resource from the standpoint of protecting the natural environment. Therefore, in order to use it effectively, it is necessary to It is necessary to solve the problem of yellow water and bad odor, and since the amount of gasification produced will naturally be enormous if coal gasification is carried out on an industrial scale, some effective countermeasure must be taken. .

: In order to effectively utilize the coal gasification slag, this invention provides a method that prevents yellow water and also eliminates the bad odor of hydrogen sulfide gas by adding and mixing sulfites such as CaSO3 to the coal gasification slag. This is what we propose.

Sulfite is converted into coal gasified slag (hereinafter abbreviated as slag)
When mixing with sulfite, the slag discharged from the coal gasifier is crushed into an appropriate size depending on the intended use, and then the necessary amount of sulfite is added and mixed.

At this time, CaS in the slag is 2 Ca S + 4
Ca5Oa + 3 H20→3 Ca S 203+
3 Ca (OH)'2 -・”-・(
4) The formula changes to thiohydrochloric acid.

This reaction is a competitive reaction with the front 1) and (3) equation (3), but in the presence of sulfite, the reaction of equation (4) is dominant.

Calcium sulfite is a sulfite. (CaS03・2H20) is optimal.

CaSO3.2H20 can be obtained in large quantities and at low cost as a byproduct of flue gas desulfurization equipment used to prevent recent air pollution.

The amount of sulfite required to be added to the slag varies depending on the form of the additive (liquid, powder, etc.), the method of addition, the particle size of the slag, and the components.

Figure 2 shows the results of an experiment showing the relationship between the generation of yellow water and the amount of calcium sulfite added.

That is, if the slag containing the components shown in Table 2 has a particle size of 0,
．． Grind it to 5 mm or less and add powdered CaSO3 to it.
A liquid material containing 50% 2H20 was added and left to stand for about one day and night, and the generation of yellow water was observed.

Yellow water generation test is 300rn for 100g of slag.
1 of distilled water and display the water level in the beaker, heat to 100℃ in about 10 minutes, boil for 60 minutes from the start of heating, cool to room temperature after boiling, and return to the bottom of the beaker. The amount of water was adjusted by adding water up to the water level, and the yellowness index was determined after filtration and plotted against the addition rate of CaSO3.2H20.

In this case, the yellowness index was determined using a spectrophotometer using quartz 10Cr.
It refers to the absorbance at a wavelength of 350 mm using a /l cell.

As is clear from the figure, in the above test, the generation of yellow water can be almost completely prevented by adding 0.5% or more of CaSOs.2H20.

However, the amount added is not particularly limited, and is adjusted depending on the particle size of the slag and the content of CaS, and to the extent that the strength of the slag body does not decrease.

Sulfite can be added and mixed in any process from the crushing process after the slag is discharged to the process where it is used for the intended purpose, but it can be added in powder form during crushing, or in slurry form after laying roadbed material, etc. The spraying method is easy to implement.

As mentioned above, according to the method of this invention, it is possible to effectively utilize coal gasification slag by an extremely simple method of adding and mixing sulfite, and it is useful not only for the development of coal gas but also for civil engineering and construction. There are other major contributions as well.

Next, embodiments of the invention will be described.

Example: A slag having the components shown in Table 2 above was ground, and the particle size was 5.
Calcium sulfite ('CaSO3.2H2Q') is added to 100f of particles with a particle size of 0.251.0.5 mm or less.
Add and mix 2 grams of each separately, and mix each with IB.

After leaving it for 2 or 3 days, a yellow water elution test was conducted.

In the elution test, slag to water was mixed at a ratio of 1:3, boiled for 1 hour, filtered, and the absorbance of the filtrate was measured at a wavelength of 350 m.
Measured in m.

The results are shown in Table 3.

For comparison, Table 3 also shows the results of an elution test conducted on slag with distilled water added.

As is clear from the results in Table 3, in the case of the slag to which calcium sulfite was added, the absorbance was lower than that of the slag to which distilled water was added, and no tendency to generate yellow water was observed.

In addition, while distilled water-added slag produced a bad odor due to hydrogen sulfide, no odor was observed in calcium sulfite-added slag.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of an iron bath gasifier, and FIG. 2 is a chart showing the relationship between CaSO3.2H20 addition rate and yellowness index in this invention. 1-----Slag outlet, 2... Gasifier, 3...
...-Gas recovery hood, 4... Molten iron bath, 5
...Lance, 6...Slag.

Claims (1)

[Claims] 1. Blowing coal into a high-temperature molten iron bath together with a gasifying agent: A method for treating coal gasification slag, which is characterized by adding and mixing sulfite to the slag generated when the coal is poured into a hot molten iron bath and gasified.