RU2490445C2 - Procedure for underground gasification of coal - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves drilling of an air injection hole and gas removal hole in a coal bed, including setting of pipe string, connection of holes in the bed by hydraulic fracturing with formation of a channel. Ferric oxide is loaded into a channel; at that quantity of ferric oxide is equal to 0.25-0.35 of the mass of gasifiable coal bed. Coal ignition is made by coal bed heating up to 300-500°C. Superheated steam of the same temperature is supplied to the channel and combustible gas with hydrogen content of 17-34% and calorific capacity of 6.5-15.2 MJ/m³ depending on the process temperature is removed through the gas removal hole.

EFFECT: increase of calorific capacity and hydrogen quantity for combustible gas, degree of coal conversion into combustible gas.

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Description

The invention relates to methods for underground gasification of coal seams by converting the coal mass at its location into combustible gas, which can be used in various power plants.

There is a method of downhole coal mining (RF patent No. 2177544, IPC ЕВВ 43/295, publ. 12/27/2001), which includes drilling at least two wells, creating an underground gas generator by forming a fault channel between the wells, igniting the coal in the channel and gasing the coal mass with supplying an underground gas generator with blast through one of the wells and the discharge of the gas formed in this case along the other. In the gasification process, oxygen and steam blasting are preferably used alternately, while the exhaust gas is rapidly cooled to a temperature that ensures equilibrium between the vapor and its dissociation products. In addition, the exhaust gas is cooled by means of liquefied nitrogen supplied to the sealed annulus of the exhaust gas well. In addition, the exhaust gas is cooled by means of liquefied carbon dioxide supplied to the sealed annulus of the exhaust gas well. In addition, the supply of the cooling agent is carried out directly to the lower end of the gas well.

The disadvantage of this method is that a low percentage of hydrogen is contained in coal gasification products, nitrogen is supplied to cool the resulting gas, which requires additional energy, and nitrogen oxides NO _x are formed in the underground gas generator due to oxygen blasting, which worsen the environmental situation.

A known method of gasification of coal to produce hydrogen and synthesis gas (RF patent No. 2354820, IPC ЕВВ 43/295, СВВ 3/00, publ. 05/10/2009), including the organization in the underground gas generator of the oxidation of coal material with oxygen, which is generated directly in the zone combustion as a result of thermal decomposition of water vapor and an exothermic reaction of the interaction of aluminum with water, which in the first embodiment of the method is fed into the combustion zone of an underground gas generator in the form of a prepared suspension of powdered aluminum in an aqueous medium with pH> 10 at elations Al: H2O = 1: 4-5 parts by weight and spray it into the water of the coal seam, providing a ratio of the supplied suspension to water of 1: 50-100 parts by weight In the second variant of the method, a prepared suspension of powdered aluminum in an aqueous medium is fed into the combustion zone of an underground gas generator at a ratio of Al: H2O = 1: 4-5 weight parts. with water in a ratio of 1: 50-100 parts by weight under pressure P in the supply well, which provides conditions for the supercritical state of water in the combustion zone, taking into account the depth H of the underground gas generator P≥23-10-5 · γ · H, where P is the pressure at H = 0 m, MPa; γ is the specific gravity of the supplied suspension, kg / m and N is the depth of the underground gas generator, m

The disadvantage of this method is the use of an expensive suspension of powdered aluminum as a catalyst.

The closest adopted for the prototype is the method (application for invention No. 95102723, IPC ЕВВ 43/295, publ. 12/20/1996), including the processing of coal in the reservoir, which is converted into water synthesis gas or occasionally transferred after the gasification channel by supply into the channel of dry saturated or superheated water vapor with a temperature below the temperature of the intensive formation of phenols and other high molecular weight toxic substances. And the heat content of steam supplied to the formation for coal gasification is maintained at a level that exceeds the thermal effect of the endothermic reaction of water vapor reduction with carbon.

The disadvantage of this method is the low hydrogen content in the combustible gas, the low degree of processing of coal.

The objective of the invention is to increase the calorific value of combustible gas and the amount of hydrogen in it, the degree of processing of coal into combustible gas.

The problem is solved as follows. Drilling of blast and gas outlet wells in a coal seam is carried out, pipe columns are installed, wells are connected along the formation by hydraulic fracturing, forming a channel. Iron oxide is loaded into the channel, the amount of iron oxide is 0.25-0.35 by weight of the gasified coal seam. The formation is ignited by heating it to temperatures of 300-500 ° C. Superheated steam of the same temperature is supplied to the channel, and combustible gas with a hydrogen concentration of 17-34% and a calorific value of 6.5-15.2 MJ / m ³ , depending on the process temperature, is diverted through a gas outlet. The upper limit of the temperature of the heat treatment is selected from the consideration of the use in the process of steam generators and steam pipelines made of cheap carbon steels that are not able to operate at temperatures above 500 ° C.

The figure 1 shows an experimental installation for implementing the method of underground gasification, which ensures the adequacy of laboratory conditions real, bearing in mind that the volume of the experimental reactor is insulated to the same extent as coal in the reservoir. As for the pressure inside the reactor, it does not need to be increased due to the fact that the proposed method is focused on the gasification of coal lying directly at the surface.

The installation consists of a reactor 1 placed in a furnace 2. A thermocouple 3 is installed in the reactor for monitoring the temperature of the coal placed in the reactor, as well as a pipe for introducing steam 4 from the steam generator 5. The reactor is connected to a gas analyzer using a heat-resistant hose 6 7. The installation is carried out in the following way.

Coal is placed in reactor 1, where it is heated up to 300-500 ° C without oxygen through a furnace 2, the temperature is controlled using a thermocouple 3. Then, superheated steam with the same temperature is supplied from the steam generator 5 through the steam inlet pipe 4. The resulting combustible gas enriched with hydrogen, through a heat-resistant hose 6 enters the gas analyzer 7.

The claimed invention is illustrated by examples.

Example 1

In the reactor 1, placed in the furnace 2, load brown coal with iron oxides in a ratio of 10: 3. The reactor is heated without oxygen, controlling the process temperature with thermocouple 3. When the temperature of lignite reaches 490 ° C, superheated steam with a temperature of 490 ° C is supplied from the steam generator 5 through the steam inlet 4. The combustible gas leaving the reactor through a heat-resistant hose 6 enters the gas analyzer 7. The hydrogen concentration in the resulting combustible gas is 34%, the calorific value of the combustible gas is 15.2 MJ / m ³ .

Example 2

In the reactor 1, placed in the furnace 2, load brown coal with iron oxides in a ratio of 10: 3. The reactor is heated without oxygen, controlling the temperature of the process with thermocouple 3. When the temperature of brown coal is reached 450 ° C, superheated steam with a temperature of 450 ° C is supplied from the steam generator 5 through the steam inlet 4. The combustible gas leaving the reactor, through the heat-resistant hose 6, enters the gas analyzer 7. The hydrogen concentration in the resulting combustible gas is 32%, the calorific value of the combustible gas is 14.5 MJ / m ³ .

Example 3

In the reactor 1, placed in the furnace 2, load brown coal with iron oxides in a ratio of 10: 3.5. The reactor is heated without oxygen, controlling the temperature of the process with thermocouple 3. When the temperature of brown coal is reached 400 ° C, superheated steam with a temperature of 400 ° C is supplied from the steam generator 5 through the steam inlet 4. The combustible gas leaving the reactor, through a heat-resistant hose 6, enters the gas analyzer 7. The hydrogen concentration in the resulting combustible gas is 30%, the calorific value of the combustible gas is 12.5 MJ / m ³ .

Example 4

In the reactor 1, placed in the furnace 2, load brown coal with iron oxides in a ratio of 10: 2.5. The reactor is heated without oxygen, controlling the temperature of the process with thermocouple 3. When the temperature of brown coal is reached 300 ° C, superheated steam with a temperature of 300 ° C is supplied from the steam generator 5 through the steam generator 4. The combustible gas leaving the reactor, through a heat-resistant hose 6, enters the gas analyzer 7. The hydrogen concentration in the resulting combustible gas is 15%, the calorific value of the combustible gas is 6.5 MJ / m ³ . Low calorific value and low content of H ₂ leads to the conclusion that the use of process temperature and superheated steam less than 300 ° C is impractical.

The method allows to solve the tasks, namely: the calorific value of combustible gas reaches 6.5-15.2 MJ / kg, the hydrogen concentration in it is 17-34% depending on the temperature of heating the coal seam and superheated steam. The degree of processing of coal into synthesis gas is given in table 1.

Table 1 Mass yield of gasification products. Gasified Raw Materials Gasification Products,% Carbon residue Flammable gas Moisture Resin Brown coal of Talovskoye deposit 20,0 25.0 50,0 5,0

Claims (1)

The method of underground coal gasification, including gasification of coal in a formation, supplying superheated steam to a channel, characterized in that a blast and a gas outlet are drilled in a coal seam, pipe columns are installed, wells are fractured along the formation to form a channel into which iron oxide is charged, amount iron oxide is 0.25-0.35 by weight of the gasified coal seam, ignite the seam by heating it to 300-500 ° C, superheated steam of the same temperature is fed into the channel, and combustible gas with a hydrogen concentration of 17-34% 6,5-15,2 calorific value MJ / m ³ depending on the temperature of the process is withdrawn through the vent hole.