SU1726739A1 - Method of underground coal gasification - Google Patents

Description

products endothermically reacts with hot carbon forming the walls of the second combustion zone, which results in the conversion of COg to CO.

The disadvantages of the method are: the presence of two combustion zones in one gas generator, which complicates the process control; the rapid burning of the reservoir and the formation of large gassed spaces, which leads to a drop in the caloric content of the exhaust gases; the impossibility of a method for the refinement of old, highly gassed underground gas generators, giving off-grade gas.

The closest to the proposed method is the method of converting coal and other carbonaceous solid material into liquid and gaseous products, in which several groups of wells are drilled into the coal seam, each of which contains at least 2 pairs of wells, inject gas into the first group of gas. containing oxygen to start the combustion process between the first pair of wells and the second pair of this group. Thereafter, the wells in which 08 was fed and the resulting mixture of pelvic and steam into the well of the first group, connected to the blocked well, are blocked, removing liquid and gaseous products from at least one and the neighboring well of the first group. Blocked wells are unblocked and gas is introduced into them containing Oj for gasification of coal and charred material. A mixture of gases is removed from the wells communicating with the wells into which O ,, is injected.

The disadvantages of the prototype are: the complexity of the process; high costs associated with a large volume of well drilling; high consumption of oxygen, spent not only for exothermic combustion reactions in the first stage, but also for direct gasification of coal in the future; the first-calorie low-calorie gas is not used for the gasification of coal and charred material; unacceptability of the method for the dogization of old, produced gas generators.

The purpose of the invention is to increase the efficiency of gasification due to the dogization of the produced gas generators while increasing the calorific value of the production gas of the existing gas generators.

This goal is achieved by the fact that in the method of underground gasification of coal, which includes opening the coal deposit by wells, conditional separation of the deposit into gas generators and sequential development of the latter by creating a source of combustion, supplying oxygen-containing blowing and pumping out production gas, each gas generator works in two stages: serves oxygen-containing

65% -75% oxygen content for intensive coal combustion, and the exhaust gas is fed into the produced gas generator for storing and dogization of the remaining coal reserves, and to the second stage the gas from the generated gas generator is supplied to the red-hot center of the existing gas generator, and the second stage is started when in the productive gas there is an excess content of carbon dioxide, and the flow rate to blow in the first stage supports it more to the second one by three and more times.

The drawing shows the method of gasification of brown coal.

The method is carried out as follows.

At the first stage, the coal deposit is opened by two groups of wells with inlet and outlet wells using known technology. By drilling wells, a coal deposit is conventionally divided into gas generators, which are coal blocks, the dimensions of which are dictated by the mining and geological and technological conditions of production.

In order to commission gas generators, wells are tamed by any of the known methods. After igniting a coal bed with hydrocarbon plumes using oxygen-containing blowing

You can begin the two-stage development of each gas generator.

In the first stage, an oxygen-rich blast (65-75%) is fed through the input wells of the gas generator,

established empirically, but sufficient for intensive burning of coal.

From the outlet well, gas containing a significant (up to 30%) amount of carbon dioxide is fed to the produced

a gas generator for storing and pre-gasifying the remaining coal reserves, while the outflow well of the produced gas generator is temporarily closed.

After a certain period of time, which corresponds to the achievement of an excessive content of carbon dioxide in the gas after the first stage, the wellbore of the developed gas generator is opened and the gas

Piping goes to the inlet well of the active gas generator to the hot hearth, moreover, with a flow rate three or more times less than in the first stage, to produce a high-calorific gas suitable for generating thermal energy.

After purging the entire gas volume in the second stage, the process is repeated again in a similar order.

Laboratory experiments were carried out on the current model of the gas generator given earlier.

PRI me R. A 40x20x20 cm sealed steel box 1, lined with refractory blocks of super lightweight from the inside, lays a piece of coal 2 about 35x15x15 cm in size with a drilled 1.5 cm diameter hole. The voids in the box are filled with asbestos crumb. A mixture of asbestos chips (70%) and liquid glass (30%) is used as putty in the refractory masonry. After the coal block has been laid down, 2 shchik 1 is closed with a steel lid 28 with a gasket made of heat-resistant rubber 27. The lid 28 is bolted to the cradle 1.

On the drawer 1 there are two nozzles (diameter 2 cm, length 15 cm): one 3 from the front end - blowing blow, the other 4 on the lid 28 - to remove the exhaust gases.

After closing the lid 28, the coal block 2 was ignited using a bookmark into the drilled hole of the coal block 2 of the burning wooden torch with a bundle moistened with fuel oil wound on it. The ignition was carried out for 15–20 min by blowing into a box, 40% enriched in oxygen as follows.

The compressor UK-1M5 was turned on to supply air to the AC system. The air from the compressor 5 through the hose-gas line 14 through the three-way valve 6 and the flow meter 7 to control its flow rate (10 l / min) enters the constant pressure vessel 8 to create a stable pressure in the system and to mix the components well. There, technical pressure oxygen 4 is supplied to the constant-pressure vessel 8 from the cylinder 9, which is opened simultaneously with the connection of the compressor 5.

Oxygen enters the constant-pressure vessel 8 via a hose-gas line 14 through a three-way valve 10 and a flow meter 11 (flow rate 2.5 l / min).

At the end of the ignition of the coal block 2, which is judged by the increase in temperature in the combustion zone, which is shown by the thermometer 22, the temperature reaches 1100-1200 ° C - the experiment is immediately started.

At the first stage, similarly to the above, during ignition, air is supplied to the combustion zone with a flow rate of 4 l / min and technical oxygen with a flow rate of 8 l / min. The oxygen content in the blast at the same time

is 73-75%. The first stage lasts for 10-15 minutes. The first 2-7 min. Exhaust gas from box 1 is discharged into the ventilation system. Then, flow meter 15 and gas tank 16 with a volume of 30 liters filled with an aqueous solution of NaCI (20%) are connected to rig 1 with a hose-gas pipeline 14 to collect waste gas for the remaining 2.5-3.0 minutes.

When collecting the gas, an aqueous solution of sodium chloride (20%), dissolving the minimum volume of the gas mixture, is drained from the gas tank 16 through valve 24 into an open glass vessel 25.

The gas collected in the gas-holder 16 is analyzed: firstly on its content C (by supplying gas to the GOU-1 gas analyzer 21. then to the CO content, N. g by supplying gas to the Tazokhrom 3101 chromatograph

23.

The gas is purified from impurities in a 25% potassium hydroxide solution (vessel 18), a 10% solution of calcium chloride solution (vessel 19), and sodium hydrosulfite solution (vessel 20) before entering chromatograph 23.

The analysis of the gas mixture is carried out according to the generally accepted method according to the instructions for the operation of the above-mentioned gas analyzers.

Test results: CO content 25.0%, - CO 7.5%; H23.9%.

Further, for the implementation of the second stage of the process, the gas tank 16 with the selected

gas of the first stage is transferred to a high level with respect to box 1.

Oxygen cylinder 9 and the compressor 5 is disconnected from the system, and the gas tank 16 through the flow meter 7 is connected. After filling the gas-holder bell 16 with an aqueous solution of sodium chloride, the gas-holder valve 16 is opened, the time and gas from the gas-holder 16 with a flow rate of 3–4 l / min, replaced by a solution of sodium chloride, are detected.

starts entering the reaction zone of the steel box 1 for 7-10 minutes. Exhaust gas is fed for analysis. The analysis is carried out similarly to the first stage. The results of the analysis: the content of C02 5,4%:

CO - 41.3%; H2 -4.4%; gas calorie - 5690 kJ / m3.

The pressure during the first stage of the inlet process is maintained at a level of 1.2 atm, and the pressure of technical rock from cylinder 9 is the same as the air pressure from compressor 5. The pressure during the second stage is 0.5 atm. at the entrance to the steel box 1. The temperature of the second stage is 1000-1100 ° С.

In order to obtain high-calorific gas, it is necessary to feed gas from the first stage, which is sufficiently rich in carbon dioxide, to the second stage of the process. From this point of view, the optimum flow rate and oxygen content for the blow supplied to the first stage were selected (Tables 1 and 2).

As can be seen from the data table. 1 and 2, the oxygen content in the blast is 65-75% optimal, and the flow rate is 12 l / min,

With an increase in the oxygen content in the blast, with its excess, the reaction of the complete carbon exothermic combustion of the carbon block occurs:

C + 02 - C02 + Q (1)

Consequently, the offgas is enriched with carbon dioxide the more, the greater the oxygen content in the blast. However, up to a certain limit - 65% 02. A further increase in the oxygen content in the blast only leads to an increase in its content in the exhaust gases, it remains chemically unoperated.

The CO content in the exhaust gases passes through a maximum (10.1%) with the oxygen content in the blast 49%, which is apparently caused by the reaction of incomplete oxidation of the carbon of the coal block under these conditions (oxygen deficiency)

С + 1/2 02- CO + Q (2)

then, with an increasing excess of oxygen, unspent, it oxidizes CO by the reaction

CO + 1/202 - C02 + Q, (3)

which leads to a drop in the CO content in the exhaust gases.

As the oxygen content in the blast increases, the process temperature also increases, which leads to an increase in the hydrogen content in the exhaust gases through endothermic reactions.

H20- H2 + 1/202-Q (4)

H20 + CO- H2 + C02-Q (5)

Н20 + С- Н2 + СО (6)

With an increase in the flow rate of blowing, the carbon dioxide content of C02 increases, and the CO content in the exhaust gases decreases. This is because the high flow rate of the blow, (for a given gas generator, taking into account the scale of the model) contributes to the rapid updating of gas mixtures in the reaction zone, provides a constant flow of excess amounts of free oxygen. However, at a flow rate of more than 12 l / min, there is almost no increase in the CO2 content in the exhaust gases, which is caused by the fact that reaction (1) passes from the diffusion to the kinetic region and is now limited only by the rate of the chemical reaction itself.

CO content continues to fall with increasing flow rate because. reaction (3) can also occur outside the immediate reaction zone, for example, at the outlet of the gas generator, and the greater the amount of unused oxygen (i.e., the greater the flow rate to blow), the lower the CO content in the blast.

In the second stage, the first stage waste gas is fed back to the coal block. Its optimum flow rate is selected taking into account the maximum content of the second stage in the exhaust gas, CO and H2, i.e. maximum calorific value of gas (Table 3). From these considerations, the optimal content of C02 in the gas supplied to the second stage is also selected (Table

four).

As can be seen from these tables, the optimum in the second stage is the flow rate of blowing 3–4 l / min, with a higher consumption, carbon dioxide does not have time to react with the carbon carbon and partially remains unused in the exhaust gas of the second stage and its amount increases with the consumption in the reaction zone, respectively, decreases the CO content in the exhaust gas.

The optimum content of carbon dioxide in the blast fed to the second stage is 25-30%. Below this content, low calorie gas is produced. Above it, the CO content of the incoming gas falls because carbon dioxide does not

5 it has time to be assimilated and, accordingly, the content of the latter in the exhaust gas increases.

Thus, the proposed method of coal gasification has several advantages: simplicity and low cost of the process; oxygen is consumed only for the exothermic reactions of burning carbon and coal in the first stage; low calorie gas of the first stage is used for gasification of coal.

The method is applicable for the dogification of produced gas generators that are not amenable to refinement by any of the known methods and which produce low-calorie gas.

Claims (1)

0 claims The method of underground gasification of coal, including the opening of coal deposits by wells, conditional separation of deposits into gas generators and sequential processing of the latter by creating a source of combustion, supplying oxygen-containing blowing and pumping out the produced gas, characterized in that while increasing the calorific value of the production gas of the existing gas generators, each gas generator is processed in two stages: in the first stage, oxygen-containing blast with an oxygen content of 65-75% is supplied for intensive burning of coal, and the exhaust gas is fed into the developed gas generator for storage and additional training 0 the remaining coal reserves, and in the second stage, the gas from the produced gas generator is supplied to the red-hot hearth of the existing gas generator, and the second stage starts when there is an excessive content of carbon dioxide in the production gas, and the flow rate blows in the first stage more more times. Table The dependence of the composition of the exhaust gas of the first stage of two-stage gasification on the oxygen content in the blast, t 1200 ° Cfr 10 min, V l / min The dependence of the composition of the exhaust gas of the first stage of a two-stage gasification on the flow rate to blow, t 1200 ° C. min,% Table 2 The dependence of the composition of the exhaust gas of the second stage of the two-stage gasification of the flow rate of the feed gas from the first stage t 1000-1100 ° C, g 10 min, the content of C ss, 25.5%, ,five % The dependence of the composition of the exhaust gas of the second stage of the two-stage gasification on the CO content in the gas supplied to the second stage t 1000-1100 ° С, g 10 min, l / min. Table3 Table4 Order 1260 Circulation: Subscription VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5 Raushsk nab.