JPS6059277B2 - Underground gasification method for coal beds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to the underground gasification technology of coal beds, particularly to the coal bed gasification method that does not use a mine shaft. Methods are known and practiced to generate gas in situ, ie, gasify, from a coal bed by supplying an oxidizing agent to a coal bed and extracting gasified products from a discharge well system (e.g., PN. Skafa).
Author, Underground Gasification of Coal, P. 2lO, published in 1960).

1 To carry out this known gasification method, the coal bed is polled with an inclined injection well and the coal bed is polled with a discharge well. The disadvantage of known coal bed gasification methods is that when natural conditions change, such as the thickness of the coal bed, the quality of the coal and the amount of water flowing into the underground gas generating area, the efficiency factor, i.e. the amount of gas produced from a unit weight of coal The ratio of (calorific value of coal)/(calorific value of unit weight of coal) cannot be set to an appropriate energy level, at least 0.6.

Unless a method is developed to relate the blowing agent feed rate to the amount of water entering the underground gasification zone, the thickness of the coal bed, and the quality of the coal, no real control of the gasification process will be possible.

Therefore, in the Kuznetski coalfield, the coal 5;
The efficiency factor is at a high energy level of 0.6-0.7, which means that the combustion heat of gas is 1,000-1,100kc.
It is characterized in that it corresponds to the range of a1/bo.

But in other cases the combustion of the resulting gas. fever is 760k
Ca1/d may be less than 450 kca1/d, in which case the efficiency factor is about 0.5, and there are even cases where gasification is not performed satisfactorily (see table below). The main reason why the efficiency of gasification is not sufficient is that gasification is performed without changing the amount of blowing agent, that is, oxidizing agent, depending on the amount of inflow water and the thickness of the coal bed. .

The amount of water flowing into the gasification zone is 2 i/h on average in the first case, and 4 i/h in the second case.
d/h, but the gasification capacity (that is, gasification rate) is the same in both cases and is approximately equal to 2t/h.

Therefore, the main reason why the gasification efficiency factor is poor in the second case is that the gasification capacity is not sufficiently increased without considering the amount of inflow water and the thickness of the coal seam. As is clear from the table below,
When the amount of inflow water is 4 po/h, the gasification capacity increases to 4 t/h, and the combustion heat of the resulting gas is 1,100 kc.
High a1/d. The object of the invention is to eliminate the above-mentioned drawbacks, namely to provide a gasification process in which the heat of combustion of the gas can be increased as much as possible and controlled.

It is therefore an object of the present invention to clarify the relationship between the main parameters of the underground gasification process of coal beds, which can be obtained by gasification without rearranging or replacing the equipment. The goal is to increase the combustion heat of fuel gas.

The purpose is to supply blowing agent to the incandescent surface of the coal through an injection well system to generate gas from the coal bed, after previously draining the coal bed, and to release gasified products through a gas discharge well system. In the method of underground gasification of coal beds involving withdrawal, the following formula [
However, in the above equation, W is the amount of water flowing into the gasification zone per unit time, d/H. I is the amount of coal gasified per unit time (gasification capacity), t/h is the heat of combustion of gas, Kcal
/K,, VO is the yield of gas from 1k9 of coal, DlQ bone is the minimum heat of combustion of coal, Kcal/Dlm is the thickness of the coal bed,
This can be achieved by an underground coal bed gasification method characterized in that gasification is carried out by selecting the gasification capacity of the coal bed according to the following.

The above characteristics suggest the best operation for carrying out gasification in various conditions of coal mining and geology, without requiring additional investments in expensive new equipment and new technologies, and the above empirical formula Accordingly, by optimally controlling the gasification capacity and gasifying the coal bed underground, the combustion heat of the resulting fuel gas can be significantly increased.

In accordance with an embodiment of the invention, the specific inflow rate is reduced to at least 3.0 i/h, after which the rate of gas evolution from the coal bed is set and maintained in accordance with the empirical formula described above.

In this preferred embodiment of the invention, the extent of drainage operations prior to gasification is specified, thereby controlling the underground gasification process according to the above-described empirical formula, which is practical and convenient.

Embodiments of the coal bed gasification method disclosed herein will be described with reference to the accompanying drawings.

As shown in Figures 1 and 2, the vertical well 1 and the inclined well 2 are hole-linked through the coal bed 4 to carry out underground gasification of the coal bed 4, and the gas discharge well 3 is polled. . Before the start of gasification, the well 8 drains water, and during gasification, the gasification zone 6 is drained via the well 7. To control the underground gasification process, the position of the injection well gate valve can be varied to maintain a predetermined calculated gasification rate.

According to the present invention, this gasification rate is defined by the following equation. [In the formula, W is the amount of water flowing into the gasification zone per unit time, d/H, . I is the amount of coal gasified per unit time (gasification capacity), t/HQ is the combustion heat of gas,
Kcal/furrow VC is the gas yield of coal 1k9 force), A, Qbone is the minimum heat of combustion of coal, Kcal/K9, m is the thickness of the coal bed, expressed in m] According to the above formula, unit time The amount of water W that is obtained by subtracting the amount of inflow water per unit time or the amount of water discharged per unit time as necessary, the thickness of the coal seam m, and the minimum heat of combustion Q amount of coal are measured in advance, and the amount of water obtained from 1k9 of coal is measured in advance. By setting the gas yield ■0 and the combustion heat Q of the obtained gas in advance, the optimum value of the amount of coal gasified per unit time (gasification capacity) can be determined.

Therefore, it is possible to determine the amount of oxidizing agent blown that corresponds to this gasification capacity. However, the amount of inflow water is the allowable value (3d/
t), according to experience, it is very difficult to control the process so as to maintain the gasification rate of coal according to the above-mentioned empirical formula.

The relational expressions disclosed herein (see also Figure 3) were obtained as a result of conducting underground gasification of coal for several years with varying gasification rates under various mining and geological conditions.

In Figure 3, the horizontal axis shows the thickness of the coal seam (m), and the left vertical axis shows the amount of inflow water per unit time W (i/h)/weight of coal gasified per unit time 1 (t/h) (that is, gasification capacity) (d/t), and the right vertical axis shows the gasification efficiency factor. According to the disclosed relation, the thickness of the coal bed (m)
The optimal gasification capacity (1) for carrying out the underground gasification process is determined by matching the amount of water flowing into the gasification area (W) and the quality of the coal.
) can be set in advance.

The amount of water flowing into the underground gas generating area should be reduced by at least 3 d/m in advance.
Draining and reducing K9 creates an initial gasification channel in the underground gas generation section and then expands this channel to a size that allows gasification to be carried out at a high gasification capacity (rate). It is necessary to create water conditions to initiate and maintain the coal incandescence operation to produce high quality gas with the required energy rating.

When there is a large amount of specific inflow water in the underground gas generation area, the creation and expansion of the initial channel is prevented,
It is also often impossible to do so because the incandescent areas are flooded.

As an example of the relationships disclosed herein, the experience of carrying out an underground gasification process in one of the underground gasification mines operated by Bozem Gas will be described.

Here, the coal beds of Heshuan and Kato were gasified. After preliminary drainage of the gas generating section, the initial groundwater inflow into the gasification channel was approximately 5 i/h.

Using the above relational expression (1), the optimum gasification capacity was calculated for the thick and thick coal beds, that is, the optimum gasification capacity was calculated from the term of the blowing agent supply rate to the gasification zone. . In case of thick coal bed, the gasification efficiency factor is 0.6 and gasification capacity is 1.85 t/h, while in case of thick coal bed, gasification capacity is 3 t/h. /h was set.

In both cases, the heat of combustion of the gas produced by the gas generator was 1,000 kcal/77 t'. The combustion area was gradually expanded and the gas generation section was placed along the coal bed to a height of 100 r.
Expanding r1, the amount of water flowing into the gas generation part is approximately 2
Increases to 0 pa/h.

In this case, according to the relation (1) disclosed herein, the gasification capacity for the thick coal bed is 7.4 t/h, and for the thick coal bed it is 12.3 t/h. Become. When the gasification process is carried out at a specific gasification rate, the process is stable, the efficiency factor is 0.62, the heat of combustion of the gas is 1,000 kcal/i, and the energy level is high. Therefore, the underground coal gasification method disclosed herein produces gas with a higher heat of combustion and carries out a gasification process with a higher energy level, which requires additional equipment and new technology. No investment required.

In order to consider whether the method of underground gasification of coal beds disclosed here can be implemented in practice, i.e. to carry out the gasification process with a specified capacity, it is sufficient to determine the following parameters:

In other words, these are the quality of the coal (Q), the thickness of the coal bed (
m), the amount of water flowing into the gasification zone (W), the quality of the gas produced (Q) and the specific yield of this gas. Then, corresponding to the determined coal gasification capacity (1) Determine the blowing rate to the gas generation section. Substitute the last obtained value into the relational expression (1) disclosed herein to determine whether the gasification ability suggested by this invention can be maintained. You can decide whether or not to do so.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of underground gasification of a coal bed.
The figure is a cross-sectional view taken along the line ■-■ in Figure 1, and Figure 3 shows the relationship between the thickness of the coal seam (m), the ratio of inflow water volume W/gasification capacity 1, and the gasification efficiency factor. It is a line diagram. 1... Vertical injection well (also used to ignite coal bed)
, 2... Inclined injection well, 3... Gas discharge well, 4... Coal bed, 5... Surrounding rocks, 6... ... gasification area, 7... drainage well from the gasification area, 8... preliminary drainage well from the coal bed.

Claims (1)

[Claims] 1. After the coal bed has been drained in advance, a blowing agent is supplied to the incandescent surface of the coal through an injection well system to generate gas from the coal bed, and the gasification product is produced through the gas discharge well system. In underground gasification of coal beds, which involves drawing out the thickness of the coal bed (
m), coal quality and amount of water flowing into the gasification area (W)
The following formula I=W/[0
．． 506({Q^G_HV^G}/{Q^C_H})・
m^-^1^. ^9^(^0^.^7^0^2^-^0
^． ^6^5^9^lo^Q^^G^_^H^V^^G^
＾／＾Q＾＾C＾_＾H＾)〕Amount of water flowing into the area m
^/h, I is the amount of coal gasified per unit time (gasification capacity), t/hQ^G_H is the heat of combustion of gas, kcal/m
^2, V^G is the yield of gas obtained from 1 kg of coal, m
^3, Q^C_H is the minimum heat of combustion of coal, kcal/kg
A method for underground gasification of a coal bed, characterized in that gasification is carried out by selecting the gasification capacity of the coal bed according to the thickness of the coal bed, expressed in m. 2. The drainage is performed before gasification, and the gasification capacity (gasification rate) of the coal bed is then set so as to reduce the specific inflow water amount to at least 3.0 m^3/t. A method for underground gasification of a coal bed according to claim 1.