WO1996028637A1

WO1996028637A1 - A two-stage of method for gasificating undergrounds coal in situ

Info

Publication number: WO1996028637A1
Application number: PCT/CN1995/000050
Authority: WO
Inventors: Li Yu; Jie Liang; Weilian Zhang; Feng Yu
Original assignee: China University Of Mining And Technology
Priority date: 1995-03-14
Filing date: 1995-06-14
Publication date: 1996-09-19
Also published as: CN1183507A; AU2731495A; CN1062329C

Abstract

It includes injection holes, a production hole and a gasification stove built up underground, into which the suppressed air is conveyed in the first stage, and in the second stage the steam is blasted, while coal gas including CO and CO2 is withdrawn. The two stages are in cycle, the second starts up when CO and CO2 content of lower-calorific coal gas is more than 26 %, and then first stage begins when CO content of high-calorific watercoal gas is less than 5 %.

Description

Two-stage coal underground gasification method Technical field

The present invention relates to a method for coal gasification, and more particularly to a method for underground coal gasification. Background technique

In recent decades, most domestic and foreign countries have used gas welling agents such as pitless underground gasifiers, continuous air supply, and water-rich steam to conduct research and development of underground coal gasification technology. Due to the limitation of the technical level of the gasification channel penetration, the gasification channel of the wellless gasifier has a small diameter and short length, so the air supply resistance is large, the stable gas production capacity is poor, the gas production is small, the service time is short, and the furnace construction and operating costs High gas cost; when using air or rich gas as gasifying agent, the N ₂ content in the gas is higher, so its calorific value is lower, which limits the range of gas use; when pure radon gasification is used, The cost of gas production is high, resulting in a substantial increase in gas costs. Due to the above reasons, it has been difficult for the wellless coal underground gasification technology to move towards commercial application.

In view of the shortcomings of the underground-less coal underground gasification technology in the prior art, the object of the present invention is to provide a coal underground gasification method that can inexpensively produce air gas and high-calorific groundwater gas and can achieve commercial production. Summary of the Invention

In order to achieve the above-mentioned object of the invention, the present invention provides a method for underground coal gasification. The method is to select a suitable coal seam in a mine, construct an air exhaust hole and an auxiliary air supply hole from the ground, dig a coal lane under the mine, and discharge it The air holes are connected to form a gasification channel, and an auxiliary air duct, a coal pile, and an igniter are arranged in the gasification channel to form an underground gasification furnace and isolate the gasification furnace from the mine. The characteristics are: After the furnace is ignited, air and water vapor are circulated and supplied to the underground gasification furnace. Each cycle consists of two stages. In the first stage, air is blown to produce low-heat-value blast gas until CO and C 0 in the low-heat-value blast gas obtained. the percentage amounts of _co-2 and more than 26% into the second stage, the second stage drum vapor producing high calorific value gas groundwater, until the heat value of the resulting CO binding amount less than 5% of underground coal gasification, re-entering the first stage .

Referring to FIG. 1, the present invention is implemented by the following method, selecting a suitable coal seam in a mine, and constructing air inlet and exhaust holes (11, 15) and auxiliary air supply holes (12, 1 3) from the ground. Coal tunnels are dug underground to connect the inlet and exhaust holes to form a gasification channel. An auxiliary air duct ( ²⁰ ), a coal pile (19), and an igniter are arranged in the gasification passage to form an underground gasification furnace. After taking certain sealing measures, isolate the gasifier (1) from the mine. An underground gasification station is formed on the ground by a fan room (1), a purification system [including air spray 珞 (6) and washing 珞 (5)], and an air supply pipeline. The total air supply system is composed of several air supply holes (1 1, 1 5, 1 2, 1 3), which are used in combination according to the blockage of the channel after the roof has risen. After the gasification furnace is ignited, air and water vapor are circulated to the underground gasification furnace. Each cycle consists of two stages. The first stage is the drum air heat storage stage and produces low-heat value blast gas. The second stage is the drum. In the steam phase, high-calorific underground ice gas is produced.

In this method, the air inlet and exhaust holes (11, 15) and the auxiliary air supply holes (12, 1 3) can be implemented by ordinary drilling technology. The entire drilling depth requires casing, and its diameter depends on the coal gas production. Inlet and exhaust holes (1 1, 1 5) —usually located at the bottom of the coal seam or drilling inclined holes to drill along the coal seam, if necessary, connect it to the gasification channel with a rock lane.

In this method, the gasification channel is excavated along the coal seam, and the support is taken from the looseness of the coal seam and the ground pressure. It can be supported by bolts, sheds, steel supports or hybrid support. The length of the passage depends on the coal seam occurrence conditions and the blast pressure, and should be greater than 150 meters. A coal pile is set up every 20 meters in the gasification channel.

In this method, the auxiliary channel is located in the middle of the bottom of the gasification channel, and is made of ordinary bricks into a square channel, with flower walls on both sides, and a steel pipe is placed under the air inlet, which is directly connected to the auxiliary channel to form a separate air supply system.

The igniter can be made by a common electric furnace of 2 KW, starting at 15 m from the air intake hole, one set is set every 10 m. Generally, 3 sets are required, and each set consists of 2 igniters. Place a layer of flammable briquettes on top of the igniter, then a layer of firewood, and a layer of high-quality large-sized coal on the top. The overall height is similar to the height of the coal pile.

After the gasification furnace is ignited, the gasification furnace is first subjected to air combustion and preheating. After the temperature field conditions of the gasification furnace are formed, it enters two-stage production.

In the first stage, air is blown in through the air inlet, and the gas component and heat value of the outlet gas are measured at any time. When the sum of the percentages of CO and C 0 ₂ reaches more than 26% (volume), the air supply is stopped, and then it is changed. Water supply steam enters the second stage.

In the second stage, steam is blown in through the air inlet. When water vapor is blown, the components and heat of the outlet gas are measured at any time. When the total amount of CO is less than 5% (volume), the water supply is stopped and the air is blown through the air inlet again. Into the air to achieve a cycle.

The first stage of this method can produce gas with a heating value of about 4 · 18 MJ / m ³ , which can be used as industrial fuel or used for power generation. The calorific value in the second stage is 1 2. A gas of 5 6 MJ / m ³ or more with a combustible component of 80% (vol.) Or more and a gas-gas content of less than 4% (vol.). Chemical raw materials. Overview of the drawings

FIG. 1 is a schematic diagram of an apparatus for implementing the two-stage underground coal gasification method of the present invention. Wherein, the description of each symbol is as follows:

1-fan room; 2-measurement and control room; 3-combustion radon;

4-cooling pond; 5-washing tower; 6-air spray;

7-vent tower; 8-flow meter; 9 a valve;

10-decoking plant; 11-air inlet; 12-temperature measuring hole;

13-steam hole; 14-fan; 15-air outlet;

16 a U-shaped tube; 17-underground gasification furnace; 18-gasification coal seam;

19-coal pile; 20-auxiliary passage; 21-dense wall;

22 A fan. Example 1 of the preferred embodiment of the present invention. The semi-industrial test of underground coal gasification in Xuzhou Xinhe No. 2 well. According to the device shown in FIG. Among them, the inlet and exhaust holes of the test gasifier have a diameter of 0.6 m and a depth of 83 m. Three auxiliary air supply holes are arranged in each of them. The gasification channel is 168 m in length and the net section of the channel is It is 2.5 m ² , with a concrete shed and a steel support mixed support. Three groups of igniters are arranged in the gasification channel. The front of the eight coal pile auxiliary channels is 1 1.3 m with bricks of 0.2 m. The square channel is 0.2 m 2, and the rear 3 5 m is connected with a ceramic tube of 0 3 5 X 7 0. There are two fans in the fan room, which can be used in series and parallel. There are air spray towers and scrubbers at the exit for preliminary purification of the gas. The test was ignited on March 23, 1994, and the gas was released on May 25, with stable gas production for 10 months. A two-stage test was carried out in the later stage, and the calorific value and composition of the gas in the second stage are shown in Table 1. 顼 Mesh gas composition (%) Gas calorific value Gas flow date Η ₂ CO CH ₄ C0 ₂ N ₂ kcal / m ³ J / m ³ m ³ / h

November 1 58.29 8.59 9.28 19.63 4.21 2919.37 12.22 1920

10th 53.03 18.59 15.08 13.16 0.13 3611.12 15.12 1900

11th 58.38 10.35 14.32 13.38 3.59 3450.33 14.45 1400

12th 57.10 11.66 14.89 13.81 2.50 3510.24 14.70 1500

28th 62.07 14.43 10.13 11.07 2.30 3292.10 13.73 1650

30th 54.25 15.72 10.65 15.26 4.23 3138.60 13.14 1810

December 3 67.94 14.97 6.30 11.69 0.00 3096.10 12.96 1450

6th 70.51 12.42 5.23 10.83 1.00 3024.00 12.66 1720

7th 64.07 11.31 9.94 11.13 3.56 3240.60 13.57 1900

8th 60.42 16.57 9.54 12.52 0.95 3250.20 13.61 1550

9th 72.95 6.07 8.30 12.17 0.51 3197.80 13.39 1520

100 69.16 10.32 9.10 10.94 0.49 3286.20 13.76 1750

11th 66.14 10.75 11.98 11.10 0.03 3481.30 14.58 1580

12th 64.63 12.47 9.65 11.70 1.55 3268.90 13.69 1850

13th 71.58 6.16 10.00 11.92 0.57 3287.80 13.77 1600

14th 67.56 9.47 9.50 12.92 0.57 3247.78 13.60 1830

Industrial applicability

The method of the present invention can effectively reduce the cost of underground coal gasification and commercialize the underground coal gasification method.

Claims

* Woo Wo ^ ^

1. A method for underground coal gasification is to select a suitable coal seam in a mine, construct air inlet and exhaust holes and auxiliary air supply holes from the ground, dig a coal roadway underground, and connect the air inlet and exhaust holes to form gasification. In the gasification channel, an auxiliary air duct, a coal pile, and an igniter are arranged in the gasification channel to form an underground gasification furnace, and the gasification furnace is isolated from the mine. The characteristics are:

After the underground gasification furnace is ignited, air and water vapor are circulated and supplied to the underground gasification furnace. Each cycle consists of two stages. In the first stage, air is blown to produce low-heat-value blast gas until the low-heat-value blast gas is obtained. The sum of the percentages of the percentages of C 0 and C 0 ₂ is more than 2%, and it enters the second stage. The second stage is to produce steam with a heating value of groundwater gas, until the CO content of the obtained high heating value underground gas is less than 5%. Re-enter the first stage.