CN112483062B - A method and system for in-situ gasification mining of underground interlayer coal - Google Patents

Abstract

The invention belongs to the technical field of underground coal gasification, and particularly relates to an underground interlayer type coal in-situ gasification mining method and system. The method aims to not directly treat the coal bed, reduce mining disturbance to the in-situ coal bed and improve the safety of the mining process; and the coal bed is heated more uniformly, and the gasification efficiency is higher.

Description

A method and system for in-situ gasification mining of underground interlayer coal

technical field

The invention belongs to the technical field of underground coal gasification, and in particular relates to an underground compartment type coal in-situ gasification mining method and system.

Background technique

The traditional underground coal gasification technology is a process of controlled combustion of underground coal to generate combustible gas through thermal and chemical effects on coal. It integrates the three major processes of well construction, coal mining and gasification, changes traditional physical coal mining into chemical coal mining, and changes traditional mechanized coal mining into unmanned gas extraction. It has the advantages of short mining flow, low cost, and low pollution The advantages of low emission and high resource recovery rate can improve the utilization value of coal, promote the mining of difficult-to-mining coal seams and low-grade coal seams, and drive the development of traditional industries such as coal, electric power, and chemical industry.

At present, the existing underground coal gasification technology solutions include three types: (1) long-wall airflow method underground coal gasification technology, the gasification channel of this technology is relatively long, and the channel is prone to blockage, which affects the The stability of the gasification process and the gas output are prone to safety accidents; and the movement of the working face relies on natural propulsion, which has poor controllability and low production capacity; (2) permeable underground coal gasification technology. The established underground gasifier has short gasification channels, small diameter, large air supply resistance, small gas production on a single working face, and cannot extract different pyrolysis gases by quality and classification, and the energy extraction rate is low; the service time is short, in order to achieve industrial production scale , many drill holes must be laid out in a checkerboard pattern, resulting in waste of land resources; industrial production gasifiers are expensive to build and operate, and are not suitable for large-scale gasification production in deep coal seams; (3) Underground coal gasification technology to control retreating gas injection points, The coal seam of this technology is generally located below 100 meters or even thousands of meters underground. It is generally necessary to convert solid coal with high carbon content into gasification energy with high hydrogen content. Usually, it is necessary to add a gasification agent. It is difficult for ordinary gasification agents to participate in the gasification after reaching the ground. The gasification reaction reduces the gasification efficiency; the gas injection nozzle is easily damaged at high temperature, and the gas production rate is low.

Contents of the invention

In order to solve the problems of large energy consumption in coal gasification, uneven heating of coal seams, poor airtightness, and as the gasification process continues to expand, the contact conditions between oxygen and coal become worse, resulting in a decrease in effective components in the outlet gas and poor gas quality. , the present invention provides an underground compartment type coal in-situ gasification mining method and system, the adopted technical scheme is:

An underground compartment type coal in-situ gasification mining method, comprising the following steps:

1) Evaluate the area of underground coal to be mined, determine the excavation position of the heating wells on the ground according to the assessment results, and drill several heating wells from the ground to the ground. The bottom of the heating wells is located in the rock formation below the coal layer. The area formed by the enclosure of the heating well covers the coal area to be mined;

2) Drill two production wells from the ground to the ground, the well bottom of the production wells is located above the coal seam, and the two production wells are located in the area surrounded by several heating wells;

3) Excavating a gas-gathering lane along the direction of the coal seam between the bottoms of the two production wells, and a plurality of gas-gathering holes connecting the coal seam are arranged in the gas-gathering lane;

4) Heating is carried out through the bottom of the heating well, and the heat is transferred to the coal layer through the floor rock layer around the heating well, and the heating temperature is controlled by the ground heat control system;

5) After the coal layer is heated by the interlayer, a pyrolysis reaction occurs, and the gaseous products generated after the reaction are collected in the gas-gathering lane through the gas-gathering hole;

6) Drainage gas is injected into one of the production wells on the ground, and the drainage gas flows through the gas-gathering lane, and the gaseous products after pyrolysis are brought to the separation system on the ground through another production well, and stored after separation.

Preferably, the vertical distance from the bottom of the heating well to the coal seam is 100-1000 meters.

Preferably, the number of the heating wells is four, and the four heating wells enclose to form a quadrilateral, and the distance between two adjacent heating wells is 100-500 meters.

Preferably, each of the production wells is located on the line connecting two adjacent heating wells, and the two production wells are symmetrically arranged around the center of a quadrilateral formed by four heating wells.

Preferably, the bottom of the production well is located at the elevation of the roof of the coal seam.

Preferably, before heating, a gasification catalyst is injected into the coal layer through the gas collection hole, and the catalyst is a composite catalyst of potassium-based catalyst, iron-based catalyst, 5% KOH and 3% CaO; the diversion gas is high-temperature water vapor , Supercritical carbon dioxide.

Preferably, the method of heating through the bottom of the heating well in step 4) is that the ground heat control system transports the combustible gas with high calorific value to the bottom of the heating well, and heats the floor rock layer around the heating well after igniting the combustible gas .

Preferably, the ground heat control system described in step 4) includes a monitoring center set on the ground, and the monitoring center controls the heating duration and heating temperature through thermocouples and pressure sensors set on the floor rock layer and coal layer.

Preferably, the thermocouples are respectively installed on the floor rock layer and the top plate of the coal layer.

An underground interlayer type coal in-situ gasification mining unit circulation system, including four heating wells, two production wells and a gas-gathering roadway, the well bottom of the heating wells is located in the floor rock layer below the underground coal bed, and the production The well bottom of the well is located above the coal seam, and the two production wells are connected to form a gas gathering lane, and the gas gathering lane is connected to the coal seam; among the two production wells, the wellhead of one production well is connected to the intake air of the diversion gas. The device is connected, and the wellhead of another production well is connected with the gas collection device.

The present invention has the following beneficial effects:

1) The disturbance to the in-situ coal seam is reduced, and the safety and airtightness are better. The method of the invention does not directly burn the coal seam, which reduces the mining disturbance of the in-situ coal seam, and has higher safety; heats the coal seam under a certain depth of rock, does not directly process the coal seam, and reduces the mining of the in-situ coal seam Disturbance improves the safety of the mining process; exerts the heat transfer efficiency of the floor rock layer, transports heat to the coal seam, and realizes the thermal carbonization and decomposition of the coal seam. The airtightness is better.

2) It can control the heating temperature of the floor rock layer, realize the temperature gradient change of the rock layer, and finally realize the classification and extraction of different pyrolysis gases in the coal seam, and the energy extraction rate is higher. The ground heating system controls the heating temperature in real time to realize the temperature gradient change of the rock formation, and finally realizes the extraction of different pyrolysis gases in the coal seam by quality and classification, and the energy extraction rate is higher.

3) The coal seam is heated more evenly and the gasification efficiency is higher. The method of the invention utilizes the good thermal conductivity of the rock in the tight rock layer and the characteristics that it is not easy to be cracked by heat to heat the rock layer to realize uniform heat transfer to the coal seam, the coal seam is heated more uniformly, and the gasification efficiency is higher.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are For some embodiments of the present invention, those skilled in the art can also obtain other drawings based on these drawings without creative work.

Figure 1 is a schematic diagram of an underground compartment type coal in-situ gasification unit;

Figure 2 is a schematic diagram of the layout of the underground compartment type coal in-situ gasification space;

Figure 3 is a schematic diagram of an underground compartment type coal in-situ gasification;

Figure 4 is the plan layout of underground compartment type coal in-situ gasification.

In the figure: 1-heating well; 2-production well; 3-gathering lane.

Detailed ways

The present invention is an underground interlayer type coal in-situ gasification mining method and system. Taking the coal seam in Northwest China as an example, the method of the present invention is suitable for the situation where the top, bottom, and floor rock layers of the coal seam are dense and not easily cracked or subsided by heat, especially It has broad application prospects in the mining and utilization of low-quality, steeply inclined coal seams.

An underground compartment type coal in-situ gasification mining method, comprising the following steps:

1) Evaluate the area of underground coal to be mined, determine the excavation position of the heating well 1 on the ground according to the assessment results, and drill several heating wells 1 from the ground to the ground. The bottom of the heating well 1 is located in the rock formation below the coal layer, The area formed by the enclosing of the several heating wells 1 covers the coal area to be mined; in a unit circulation system of the present invention, the quantity of the preferred heating wells 1 is four, and the enclosing of the four heating wells 1 forms a quadrilateral, and in the present invention The quadrilateral is a square, and the distance between adjacent two heating wells 1 is 100～500 (determined specifically according to local coal seam geology and coal occurrence conditions), preferably 250 meters in the present invention; The vertical distance from the bottom rock layer under the coal layer to the coal layer is L (by conducting laboratory experiments on factors such as the lithology and thermal conductivity of the coal layer bottom layer, according to the research on the optimal heat transfer efficiency of heated rocks and the pyrolysis effect of coal in the upper layer , determine the optimal L value), the preferred vertical distance L in the present invention is 100-1000 meters.

2) Two production wells 2 are drilled underground from the ground, the bottom of the production well 2 is located above the coal seam, and the two production wells 2 are located in the area surrounded by several heating wells 1; as shown in Figure 2, A total of four heating wells 1 form a square, and production wells 2 are respectively located on the line connecting the two heating wells 1, and are symmetrically arranged with the center of the quadrilateral formed by heating well 1 as the center; the bottom of production well 2 is located at the elevation of the coal seam roof Location.

3) Excavate a gas-gathering lane 3 between the bottoms of the two production wells 2 along the direction of the coal seam, the gas-gathering lane 3 is provided with a number of gas-gathering holes connected to the coal seam; when the system is not in operation, through the gas-gathering holes Inject the coal gasification catalyst, and the catalyst can be a potassium-based catalyst, an iron-based catalyst, a composite catalyst with a mass fraction of 5% KOH and a mass fraction of 3% CaO. The composite catalyst is preferred in the present invention, and the two will jointly promote the gasification reaction If it is carried out, the gasification efficiency will increase by 30%, and at the same time, the amount of CaO should not be added excessively, which will reduce the gasification activity; when the system starts to operate, the gas generated by thermal dry distillation of coal seams enters the gas-gathering lane 3 through the gas-gathering hole, and then passes through the production well 2 transported back to the ground.

4) Heating is carried out through the bottom of the heating well 1. The heating temperature range is 150°C to 300°C. The heating method can adopt existing electric heating or gas heating. The preferred method of heating the bottom of the heating well 1 in the present invention is , the surface heat control system transports combustible gas with high calorific value (mixed with an appropriate amount of oxygen) to the bottom of the four heating wells 1, and ignites the combustible gas to heat the floor rock around the heating well 1. It is better to use tight rock formations The heat generated by the heating well 1 is continuously transferred upwards through the floor rock layer as the medium, and the heat is transferred to the coal bed through the floor rock layer around the heating well 1, thereby achieving the effect of "thermal distillation and decomposition" of the coal bed The purpose is to control the heating temperature through the ground heat control system. By controlling different heating temperatures, the temperature gradient of the rock formation can be realized, and finally the different pyrolysis gases in the coal bed can be extracted by quality and classification, and the energy extraction rate can be improved.

The ground heat control system includes a monitoring center set on the ground, which controls the heating time and heating temperature through thermocouples and pressure sensors set on the floor rock layer and coal layer; For long-term safety, thermocouples are installed on the floor to be heated and the top of the coal bed to monitor the temperature near the two places. The monitoring center receives the temperature signal through the signal line, and uses the temperature to judge the status of the pyrolysis zone of the coal bed. In addition, temperature and pressure sensors are pre-embedded between the rock layers (between the floor rock layer and the coal layer) to monitor the underlying floor rock layer in real time, and to monitor the stability of the underlying floor rock layer after long-term heating and other related issues.

5) After the coal layer is heated by the interlayer, a pyrolysis reaction occurs, and the gaseous products generated after the reaction are collected in the gas-gathering lane 3 through the gas-gathering holes; The generated gas is collected in the gas gathering lane 3.

6) On the ground, inject drainage gas into one of the production wells 2, the density of the drainage gas is greater than the density of the pyrolysis gas produced after the pyrolysis of the coal bed, and the drainage gas can be selected from supercritical carbon dioxide and high-temperature water vapor, which is preferred in the present invention The drainage gas is high-temperature water vapor, which will not cause environmental pollution and can avoid heat loss during the process of transporting pyrolysis products back to the ground. Another production well 2 is brought to the separation system on the ground, and stored after separation. The effective separation of gas and other organic matter is completed in the ground separation system. The gas is stored in the ground gas storage tank, and the separated organic matter is in the form of organic liquid. Store in a liquid storage tank for other purposes.

The above method takes the mining of one unit circulation system as an example, and multiple unit circulation systems can also be combined for production to improve operational efficiency. For example, in Figure 4, the number of heating wells 1 is increased from four to six, and the number of production wells 2 is increased from two to three. , respectively numbered heating well No. 1, heating well No. 2, heating well No. 3, heating well No. 4, heating well No. 5, and heating well No. 6; Well C. Among them, heating well No. 1, heating well No. 2, heating well No. 3 and heating well No. 4 are a unit circulation system, and heating well No. 3, heating well No. 4, heating well No. 5 and heating well No. 6 are the second Unit circulation system; after the first unit circulation system is completed, switch to the second unit circulation system, that is: heating wells 3, 4, 5, and 6 to heat the coal bed, inject high-temperature steam from the production well C, and Gathering lane 3 is transported from production well B to the ground. When the second production cycle is in progress, the production well A is closed to prevent the pyrolysis gas from escaping from the well. Since heating well No. 3 and heating well No. 4 work in the previous cycle system, switch to the next cycle system to continue When working, it can continue to heat and work, realize self-circulation, improve efficiency and save costs.

An underground compartment type coal in-situ gasification mining unit circulation system, including four heating wells 1, two production wells 2 and a gas gathering lane 3, forming a unit circulation system, and multiple unit circulation systems can be superimposed for expansion Production, the well bottom of the heating well 1 is located in the floor rock layer below the underground coal bed, the well bottom of the production well 2 is located above the coal bed, and the two production wells 2 are connected to form a gas-gathering lane 3. The gas-gathering lane 3 is connected with the coal seam; among the two production wells 2, the wellhead of one production well 2 is connected to the air intake device, and the wellhead of the other production well 2 is connected to the gas collection device.

The invention and system of the present invention have the following advantages:

(1) Safe and reliable. This new type of underground interlayer coal in-situ gasification mining method has changed the traditional coal production method. During the mining process, unmanned underground coal mining can be realized, which makes coal production safer and more reliable, and greatly reduces the cost of mine coal production. The incidence of accidents and occupational diseases. At the same time, it can minimize the disturbance impact on the in-situ coal seam, and the safety and airtightness are better.

(2) Increased production capacity. This new underground compartment type coal in-situ gasification mining method can be implemented in new mining areas or new mining areas, and can also recover some coal resources that cannot be recovered by traditional methods in old mines, thereby improving resource utilization. At the same time, in the production process, the heating temperature of the floor rock can be controlled to realize the temperature gradient change of the rock layer, and finally realize the classification and extraction of different pyrolysis gases in the coal seam, and improve the energy extraction rate.

(3) Green and environmental protection. This new type of underground interlayer coal in-situ gasification mining method controls environmental pollution at the source, eliminates the pollution of smoke, dust, and ash emissions generated by traditional mining methods such as coal transportation and gas production, does not pollute the surface environment, and reduces conventional mining. Subsidence caused by coal.

(4) Promote employment. This new type of underground compartment type coal in-situ gasification mining method injects vitality into the development of local cities. The gasification project has a large number of needs in construction, transportation and other supporting industries and service industries and other tertiary industries during the construction and operation periods. It has driven the development of supporting industries related to underground coal gasification, and at the same time led to the employment of a large number of laborers, vigorously developed coal chemical industry and power generation and other related industries, and created more employment channels.

Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not used as a limitation of the present invention. Alterations and variations are within the scope of the claimed invention.

Claims (5)

1. An underground interlayer type coal in-situ gasification mining method is characterized in that: the method comprises the following steps:

1) Evaluating the area of underground coal to be mined, determining the digging position of a heating well (1) on the ground according to an evaluation result, and drilling a plurality of heating wells (1) from the ground to the underground, wherein the bottom of each heating well (1) is positioned below a coal bed, and the area formed by surrounding of the plurality of heating wells (1) covers the area of the coal to be mined;

2) Drilling two production wells (2) from the ground to the underground, wherein the bottoms of the production wells (2) are positioned above a coal layer, and the two production wells (2) are positioned in an area surrounded by a plurality of heating wells (1);

3) A gas collection lane (3) is excavated between the bottoms of the two production wells (2) along the direction of the coal layer, and a plurality of gas collection holes communicated with the coal layer are arranged in the gas collection lane (3);

4) The coal bed is heated through the bottom of the heating well (1), heat is transferred to the coal bed through a bottom rock stratum around the heating well (1), and the heating temperature is controlled through a ground heat control system;

5) The coal layer is heated by the interlayer and then undergoes a pyrolysis reaction, and gaseous products generated after the reaction are collected in the gas collection lane (3) through the gas collection holes;

6) Injecting drainage gas into one of the production wells (2) on the ground, enabling the drainage gas to flow through the gas collecting roadway (3), bringing the pyrolyzed gaseous product to a separation system on the ground through the other production well (2), and storing the gaseous product after separation;

the vertical distance from the bottom of the heating well (1) to the coal layer is 100 to 1000 meters;

the number of the heating wells (1) is four, the four heating wells (1) surround to form a quadrangle, and the distance between every two adjacent heating wells (1) is 100-500 m;

each production well (2) is positioned on the connecting line of two adjacent heating wells (1), and the two production wells (2) are symmetrically arranged by the center of a quadrangle formed by surrounding four heating wells (1);

the bottom of the production well (2) is positioned at the elevation position of the top plate of the coal layer;

in the step 4), the heating mode is carried out through the bottom of the heating well (1), the ground heat control system conveys the combustible gas with high heat value to the bottom of the heating well (1), and the bottom rock stratum around the heating well (1) is heated after the combustible gas is ignited.

2. An underground interlayer type coal in-situ gasification mining method according to claim 1, characterized in that: injecting a gasification catalyst into the coal bed through the gas collection holes before heating, wherein the catalyst is a potassium-based catalyst, an iron-based catalyst, a composite catalyst of 5% KOH and 3% CaO; the drainage gas is high-temperature steam and supercritical carbon dioxide.

3. An underground interlayer type coal in-situ gasification mining method according to claim 1, characterized in that: the ground heat control system in the step 4) comprises a monitoring center arranged on the ground, and the monitoring center controls the heating time and the heating temperature through thermocouples and pressure sensors arranged on the bottom plate rock stratum and the coal layer.

4. An underground interlayer type coal in-situ gasification mining method according to claim 3, characterized in that: the thermocouples are respectively arranged on the bottom plate rock stratum and the top plate of the coal layer.

5. A unit circulation system applying the underground interlayer type coal in-situ gasification mining method according to any one of claims 1 to 4, characterized in that: the coal-fired boiler comprises four heating wells (1), two production wells (2) and a gas-collecting lane (3), wherein the bottom of each heating well (1) is located on a bottom plate rock layer below an underground coal layer, the bottom of each production well (2) is located above a coal layer, the two production wells (2) are communicated to form the gas-collecting lane (3), and the gas-collecting lane (3) is communicated with the coal layer; and in the two production wells (2), the wellhead of one production well (2) is connected with a drainage gas inlet device, and the wellhead of the other production well (2) is connected with a gas collecting device.

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