CN113738325B - A system for coupling in-situ pyrolysis of oil-rich coal with carbon capture - Google Patents

Abstract

The invention discloses a system for coupling oil-rich coal in-situ pyrolysis and carbon capture, including a power station oxygen-enriched combustion boiler, a compressor, an air separation device, a heat exchanger, a gas-liquid separation device and a boiler air preheater. Aiming at fuels with high tar yield such as oil-rich coal, which are easily decomposed to generate oil and gas when heated, the present invention uses the flue gas from the tail of the oxygen-enriched combustion power station boiler to heat the underground coal seam, realizes the in-situ pyrolysis of coal for oil extraction, and completes the in-situ coal heating. energy cascade utilization in the solution process. The oil produced during the pyrolysis process is extracted, the rest of the material is fully utilized, and carbon dioxide is captured. It realizes the input of fuel in the whole system and the output of processes including electricity and oil, without emitting pollutants and carbon dioxide. In the process of in-situ pyrolysis, the system realizes the clean and efficient utilization of oil-rich coal and promotes the goal of energy carbon neutrality.

Description

A system for coupling in-situ pyrolysis of oil-rich coal with carbon capture

technical field

The invention relates to a system for coupling oil-rich coal in-situ pyrolysis and carbon capture.

Background technique

The development of unconventional oil and gas resources provides another route for the supply of oil, which can be heated and pyrolyzed to produce a considerable amount of oil and gas products. Pyrolytic conversion of these coals can avoid direct combustion of coal, reduce air pollution, and enhance national energy security. The process of conventional mining to the ground and then refining oil in the refining furnace produces a lot of pollution, and the low-volatile pyrolysis residue after pyrolysis is also a huge amount of solid waste. produce pollution. As an emerging mode, underground in-situ pyrolysis can reduce the pollution to the atmosphere and soil. The process of heating and pyrolysis extraction is carried out underground. However, since the pyrolysis process requires a lot of thermal energy to heat the formation, the heating process requires a lot of heat. System heat utilization and heat recovery after heating are very important.

Oxygen-enriched combustion, also known as O ₂ /CO ₂ combustion, can efficiently capture CO ₂ and reduce carbon emissions to the atmosphere. Since the pyrolysis process requires thermal energy to enter the formation, the heating of the formation by the flue gas generated by the oxygen-enriched combustion can reduce the overall external carbon emissions of the pyrolysis system and help achieve the goal of carbon neutrality in the future. Therefore, it is of great significance to develop a system of oxy-fuel combustion and in-situ pyrolysis of underground coal for oil extraction.

SUMMARY OF THE INVENTION

For solid fuels with high volatile content such as oil-rich coal, the oil and gas can be extracted by pyrolysis, but a large amount of pollution will be generated due to the pyrolysis of above-ground coal. The present invention is a system for coupling oil-rich coal in-situ pyrolysis and carbon capture. The system heats underground coal seams by extracting tail flue gas from an oxygen-enriched combustion boiler in a power station, and performs in-situ pyrolysis of oil-rich coal to produce oil and gas. The method of fully utilizing the waste heat of the flue gas, thus realizing the efficient mixing of sludge in the power station boiler, which mainly includes the in-situ coal pyrolysis part, the waste heat utilization part of the product, the oxygen-enriched combustion power station boiler, the air separation device and other equipment .

The present invention adopts following technical scheme to realize:

A system for coupling oil-rich coal in-situ pyrolysis and carbon capture, comprising a power station oxygen-enriched combustion boiler, a compressor, an air separation device, a heat exchanger, a gas-liquid separation device and a boiler air preheater;

Oxygen-enriched combustion boilers in power stations are burned to generate high temperature CO ₂ , the heated boiler steam is used for power generation, and the high temperature CO ₂ flue gas produced by combustion in the flue is used for underground coal pyrolysis; the CO ₂ extracted from the flue is added to the gas by a compressor. Pressure, high temperature and pressurized supercritical CO ₂ can penetrate into the coal seam for sufficient pyrolysis and dissolve the organic matter produced by pyrolysis;

Using the cold energy of the air separation device in the oxygen-enriched combustion power station, the low-temperature pure oxygen from the air separation is introduced into the underground coal seam to create the freezing wall of the coal seam, isolating the pyrolysis zone and the non-pyrolysis zone, and the heat exchanger in the freezing wall. The pure oxygen after coming out is passed into the gas-liquid separator to exchange heat with the pyrolysis product, fully reducing the temperature in the pyrolysis product, and the pyrolysis product is condensed to form liquid oil for separation. The decomposed product is sent to a heat exchanger for heating feed water;

Then, the extracted gas is sent to the gas-liquid separator to cool down to normal temperature, the oil product is separated, and the water in the pyrolysis gas is also removed at the same time. The uncondensed gas in the pyrolysis product contains organic gas, which is sent to the boiler reburning zone. Continued combustion and the formation of a fuel-rich region can reduce part of the _NOx produced by the combustion;

Pure oxygen and circulating carbon dioxide are mixed to form primary air after heat exchange in the gas-liquid separator, which is sent to the air preheater of the boiler to continue heating the primary air, and the primary air carries fuel into the furnace for combustion;

When the first coal seam block is mined to the set value, the first valve is opened, and the high-temperature gas is passed into the second coal seam block to start preheating the second coal seam block, and the preheating time of the second coal seam block is advanced. So that after the oil production of the first coal seam block is completed, the second coal seam block can synchronously follow up the oil production; after the in-situ pyrolysis of the first coal seam block is completed to extract oil and gas, after the oil production is completed, the first valve and the second valve are closed. , open the third valve, pass the flue gas at the tail of the boiler into the coal seam, absorb the waste heat of the coal seam into the flue gas, and then send the flue gas back to the boiler furnace; a part of the _CO2 in the flue at the tail of the boiler is extracted to heat the coal seam, and can be recycled back In the furnace, excess carbon dioxide is captured.

A further improvement of the present invention is that the organic matter produced by solution pyrolysis is a mixture, including liquid oil and gas at normal temperature.

A further improvement of the present invention is that the organic gas contains small molecules such as CH ₄ and C ₂ H ₆ .

A further improvement of the present invention is that the high-temperature _CO2 flue gas generated by the oxyfuel combustion boiler of the power station is used to pass into the first coal seam block for pyrolysis, and the additional heating equipment is reduced by extracting part of the _CO2 from the tail flue of the oxyfuel combustion boiler of the power station. put in.

A further improvement of the present invention is that the product after coal pyrolysis is sent to a heat exchanger for heating feed water, and the temperature of the pyrolysis product can be lowered to 350°C.

The further improvement of the present invention is that after the oil extraction of the first coal seam block is completed, the low temperature flue gas at the end of the oxygen-enriched combustion boiler of the power station not higher than 120°C is passed into the coal seam, and the waste heat of 600°C in the coal seam is absorbed into the flue gas, The flue gas is then sent back to the oxy-fuel combustion boiler of the power station to realize flue gas recirculation.

A further improvement of the present invention is that the flow channel of the high temperature CO ₂ in the first coal seam block is serpentine.

The present invention at least has the following beneficial technical effects:

(1) By extracting the flue gas at the tail of the boiler of the oxy-fuel combustion power station to heat the underground coal seam for oil and gas production, additional energy input can be reduced, and the thermal energy of the flue gas of the boiler can be fully utilized, reducing the energy consumption of the overall system.

(2) Since the oxygen-enriched combustion technology requires a large amount of pure oxygen, there is a large amount of idle cold energy in the air separation device. The pure oxygen cold energy generated in the air separation device is used to freeze the freezing wall under the coal seam, which not only uses the air The cold energy of the sub-device is generated, and the freezing wall is generated, which reduces the pollution caused by the pyrolysis process to the ground.

(3) Each part of the waste heat generated in the in-situ pyrolysis process is utilized by various devices in the system, such as the power station oxygen-enriched combustion boiler (1), the heat exchanger for heating feed water (7) and the gas-liquid separation device (8) ), realizing the cascade utilization of energy.

(4) Only fuel is input in the system, oil products and electricity are output, and no additional pollutants are generated. At the same time, all carbon dioxide is recycled and captured, and carbon neutrality is realized externally.

(5) The system adopts the design of serpentine airflow channel and the method of preheating the second coal seam block in advance, which helps to shorten the time required for oil production and improve the oil production rate per unit time.

(6) The in-situ pyrolysis is carried out underground, which reduces the pollution to the ground and the atmosphere. Through the pyrolysis of coal with low added value, oil and gas with high added value and higher calorific value are produced, providing better economic Benefit, and the carbon emission per unit calorific value of oil and gas is lower than that of coal.

Description of drawings

FIG. 1 is a schematic structural diagram of a system for coupling in-situ pyrolysis of oil-rich coal with carbon capture according to the present invention.

Description of reference numbers:

1 is the oxygen-enriched combustion boiler of the power station, 2 is the compressor, 3 is the air separation device, 4 is the first coal seam block, 5 is the second coal seam block, 6 is the freezing wall, 7 is the heat exchanger for heating feed water, and 8 It is a gas-liquid separation device, 9 is oil product, 10 is circulating carbon dioxide, 11 is pure oxygen, 12 is primary air, 13 is organic gas, 14 is fuel, 15 is carbon dioxide capture, 16 is the first valve, and 17 is the first valve. Second valve, 18 is the third valve, 19 is the boiler air preheater.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

Referring to FIG. 1 , a system for coupling oil-rich coal in-situ pyrolysis and carbon capture provided by the present invention includes a power station oxy-fuel combustion boiler 1, a compressor 2, an air separation device 3, a first coal seam block 4, Second coal seam block 5, freezing wall 6, in-situ coal pyrolysis part composed of fuel 14; heat exchanger 7 for heating feed water, gas-liquid separation device 8, oil product 9, circulating carbon dioxide 10, pure oxygen 11, primary air 12. Organic gas 13, fuel 14, captured carbon dioxide 15, first valve 16, second valve 17, third valve 18, waste heat utilization part of boiler air preheater 19. The system comprehensively considers the optimization of the in-situ pyrolysis part, the waste heat utilization part and the carbon capture, and develops the process of flue gas pyrolysis coal seam, comprehensive utilization of waste heat after pyrolysis, separation of oil and gas, and carbon capture of the whole system.

A system for coupling oil-rich coal in-situ pyrolysis and carbon capture proposed by the present invention specifically refers to:

(1) The temperature of pure oxygen 11 produced by the air separation device 3 is low, and this part of low-temperature pure oxygen is sent into the coal seam for heat exchange, on the one hand, the coal seam is cooled to form a freezing wall 6, and on the other hand, the temperature of the pure oxygen 11 is increased, It is convenient to reach the temperature of the primary air 12 for the subsequent pure oxygen 11 to enter the oxygen-enriched combustion boiler 1 of the power station. The pure oxygen produced by the air separation device has a low temperature. This part of low-temperature pure oxygen is sent to the coal seam for heat exchange. On the one hand, the coal seam is cooled to form a freezing wall, which reduces problems such as water seepage and pollution. It is convenient to reach the temperature at which the subsequent pure oxygen enters the furnace and becomes primary air.

(2) The high-temperature flue gas (about 600°C) generated by the oxy-fuel combustion boiler 1 of the power station enters the first coal seam block 4 after being compressed. In actual operation, since the volatile content of the remaining products in the coal seam changes with time, it can be adjusted appropriately. Extracted flue gas content.

(3) The pyrolysis product enters the heat exchanger 7 for heating the feed water, which increases the temperature of the feed water, improves the power generation efficiency, and reduces the temperature of the pyrolysis product, which facilitates the subsequent separation of oil and gas. The heating and water supply process can reduce the pyrolysis product to about 350 °C. The gas-liquid separation device adopts the method of rotating while cooling to reduce the pyrolysis product to below the liquefaction temperature of the oil, so that the oil product in it is condensed. way to throw it out. The cold source gas for cooling the pyrolysis products in the gas-liquid separator is the circulating carbon dioxide and pure oxygen, which are preheated and mixed into primary air, which is sent to the furnace of the oxy-fuel combustion boiler of the power station.

(4) The pyrolysis product enters the gas-liquid separation device 8 to further reduce the temperature, condenses to generate oil, and is separated by the gas-liquid separation device to form an oil product.

(5) The organic gas 13 separated from the pyrolysis product is not easily separated from the flue gas in the pyrolysis process, so it is entered into the reburning zone of the oxy-fuel combustion boiler 1 of the power station for combustion, making full use of the calorific value of the gas, At the same time, a fuel-rich region is created in the furnace, reducing _NOx generation. The organic gases are small molecular hydrocarbons (such as CH ₄ , C ₂ H ₆ , etc.), and sending these gases into the reburning zone of the oxy-fuel combustion boiler in the power station is conducive to the formation of a reducing atmosphere in the furnace, reducing the production of NO _x , and using organic The calorific value of the gas reduces the supply of the original fuel.

(6) The working process of the second coal seam block 5 and the first coal seam block 4 is roughly the same, the only difference is that the second coal seam block 5 is preheated in advance to ensure uninterrupted oil production.

(7) The _CO2 generated by each part enters the oxy-fuel combustion boiler 1 of the power station after being circulated, and is finally collected in the flue at the end of the furnace. When the coal seam oil extraction is completed, the low-temperature flue gas (not higher than 120 ℃) at the end of the oxy-fuel combustion boiler of the power station is passed into the coal seam, and the waste heat of 600 ℃ of the coal seam is absorbed into the flue gas, and the flue gas from the coal seam is mixed with the incoming Compared with time, there is only more heat, and the composition is almost unchanged, and then the flue gas is sent back to the oxy-fuel combustion boiler of the power station to realize the recirculation of the flue gas, which is equivalent to treating the coal seam as a low-temperature furnace. The sequestered CO ₂ is all the CO ₂ produced by the whole system, and all the CO ₂ produced in part is circulated into the furnace of the oxy-fuel combustion boiler of the power station without being directly released into the atmosphere. Therefore, the CO ₂ produced at the tail of the sequestered boiler realizes the whole system. carbon capture.

Among them, a serpentine air flow channel is formed in the coal seam, which increases the heat exchange contact area when the flue gas passes through, strengthens the heat transfer, and facilitates the pyrolysis temperature to be reached in a shorter time, and the pyrolysis temperature distribution is more uniform. At the same time, the fracturing technology is used, and fracturing fluid is introduced to fract the coal layer into tiny cracks in all directions, which is convenient for the release of pyrolysis products.

In conjunction with accompanying drawing 1, the concrete working process of the present invention is as follows:

The process of pyrolysis occurs in many coal seam blocks underground. Since the working engineering in different coal seam blocks is similar, in order to simplify the drawings, only the first coal seam block 4 and the second coal seam block 5 are drawn to illustrate the system. work process. Oxygen-enriched combustion boiler 1 of the power station is burned to generate high temperature CO ₂ , the hot steam of the boiler heated by combustion can be used for power generation, and the high temperature CO ₂ flue gas generated by combustion in the flue is used for underground coal pyrolysis. The _CO2 extracted from the flue is pressurized by the compressor 2, and the high-temperature pressurized supercritical _CO2 can efficiently penetrate into the coal seam for sufficient pyrolysis and dissolve the organic matter produced by the pyrolysis. The pyrolyzed substance is a mixture, including liquid (oil) and gas at room temperature. Supercritical CO ₂ has good solubility and can dissolve oil and gas efficiently, which is equivalent to extracting pyrolysis products and avoids the solidification of organic matter with large molecular weight in the pipeline. , stick to the wall of the pipeline where the pyrolysis products are transported. Using the cold energy of the air separation unit 3 (ASU) in the oxygen-enriched combustion power station, the low-temperature pure oxygen 11 from the air separation is passed into the underground coal seam, and the freezing wall 6 of the coal seam is manufactured to isolate the pyrolysis zone and the non-pyrolysis zone, preventing the Water seepage, pollution, etc. The temperature of the pure oxygen 11 after coming out of the heat exchanger in the freezing wall is still low, which is not enough to meet the temperature requirements of the primary air 12 during combustion. Therefore, this part of the pure oxygen 11 is passed into the gas-liquid separator 8 to be separated from the pyrolysis system. The heat exchange of the product substantially lowers the temperature in the pyrolysis product, thereby condensing the pyrolysis product to form a liquid oil for separation, and at the same time increasing the temperature of the pure oxygen 11 . Open the second valve 17, close the first valve 16 and the third valve 18, the coal pyrolysis product is sent to the heat exchanger 7 for heating the feed water, the temperature of the feed water is generally above 300 ℃, and the pyrolysis product heat exchange After the end, the temperature can be kept above 350 °C to prevent the oil from the liquefaction of the pyrolysis gas from sticking to the heat exchanger. At the same time, after the water is heated up, the heat absorption of the furnace is reduced, the total power generation efficiency is improved, and the coal consumption is reduced. Then, the extracted gas below 350 ° C is sent to the gas-liquid separator 8 to cool down to normal temperature, and the liquid (oil product) is separated, and the water in the pyrolysis gas is also removed at the same time, and the uncondensed gas in the pyrolysis product contains CH. _4. Small molecule organic gas 13 such as C ₂ H ₆ can be sent to the reburning zone of the boiler for continuous combustion, which improves the fuel utilization efficiency, and forms a fuel-rich zone that can reduce part of the _NOx produced by the combustion. Pure oxygen and circulating CO ₂ are mixed to form primary air 12 after heat exchange by gas-liquid separator 8 , and the preheating temperature is still low, so the primary air 12 is continuously heated in the air preheater 19 of the boiler. When the first coal seam block 4 is mined to 60%, the first valve 16 is opened, and the high temperature gas is passed into the second coal seam block 5 to start preheating the second coal seam block 5, which can make the first coal seam block 4 The waste heat is utilized earlier, and the preheating time of the second coal seam block 5 is advanced, so that after the oil production of the first coal seam block 4 is completed, the second coal seam block 5 can synchronously follow up oil production (due to the second coal seam block 5). The working process of block 5 is the same as that of the first coal seam block 4, and the same working process is omitted in the figure and not shown).

After the in-situ pyrolysis extraction of oil and gas in the first coal seam block 4 is completed, after the oil production is completed, the first valve 16, the second valve 17 and the third valve 18 are closed, and the flue gas at the tail of the boiler is passed into the coal seam, and the coal seam 600 The waste heat of ℃ is absorbed into the flue gas, and the flue gas coming out of the coal seam has only more heat than when it enters, and the composition hardly changes, and then the flue gas is sent back to the boiler furnace 1, which can reduce the coal consumption. Only a part of CO ₂ is extracted from the boiler tail flue to heat the coal seam, and it will be recycled back to the furnace, so more and more CO ₂ will be produced by combustion, and the excess part will be captured by carbon _dioxide . Not released into the atmosphere, completely captured or sequestered. It realizes the functions of power generation, oil production, carbon dioxide capture, and carbon emission reduction.

The above content is a further detailed description of the present invention in conjunction with the specific preferred embodiments, and it cannot be considered that the specific embodiments of the present invention are limited to this. Below, some simple deductions or substitutions can also be made, all of which should be regarded as belonging to the invention and the scope of patent protection determined by the submitted claims.

Claims (7)

1. A system for coupling oil-rich coal in-situ pyrolysis and carbon capture, characterized in that it comprises a power station oxygen-enriched combustion boiler (1), a compressor (2), an air separation device (3), a heat exchanger ( 7), gas-liquid separation device (8) and boiler air preheater (19); The oxygen-enriched combustion boiler (1) of the power station is burned to generate high-temperature CO ₂ , the heated boiler steam is used for power generation, and the high-temperature CO ₂ flue gas generated by combustion in the flue is used for underground coal pyrolysis; The extracted CO ₂ is pressurized, and the high-temperature pressurized supercritical CO ₂ can penetrate into the coal seam for sufficient pyrolysis and dissolve the organic matter produced by the pyrolysis; Using the cold energy of the air separation device (3) in the oxygen-enriched combustion power station, the low-temperature pure oxygen (11) from the air separation is introduced into the underground coal seam to create a freezing wall (6) of the coal seam, isolating the pyrolysis zone and the non-pyrolysis zone. zone, the pure oxygen (11) coming out of the heat exchanger in the freezing wall is passed into the gas-liquid separation device (8) to exchange heat with the pyrolysis product, fully reducing the temperature in the pyrolysis product, and the pyrolysis product is thus condensed Liquid oil is formed to separate, and at the same time, the temperature of pure oxygen (11) is increased, and the product after coal pyrolysis is sent to a heat exchanger (7) for heating feed water; The extraction gas is then sent into the gas-liquid separation device (8) and cooled to normal temperature, the oil product (9) is separated, and the water in the pyrolysis gas is also removed simultaneously, and the uncondensed gas in the pyrolysis product contains organic gas ( 13), send it into the boiler reburning zone to continue burning, and form a fuel-rich zone that can reduce the _NOx produced by partial combustion; Pure oxygen and circulating carbon dioxide (10) are mixed to form primary air (12) after heat exchange by the gas-liquid separation device (8), and are sent to the air preheater (19) of the boiler to continue heating the primary air (12), once The wind (12) carries the fuel (14) into the furnace for combustion; When the first coal seam block (4) is mined to the set value, the first valve (16) is opened, and the high temperature gas is passed into the second coal seam block (5) to start preheating the second coal seam block (5), At the same time, the preheating time of the second coal seam block (5) is advanced, so that after the oil production of the first coal seam block (4) is completed, the second coal seam block (5) can synchronously follow up oil production; (4) After the extraction of oil and gas by in-situ pyrolysis is completed, after oil production is completed, close the first valve (16), the second valve (17), open the third valve (18), and pass the flue gas at the tail of the boiler into the coal seam. The waste heat of the coal seam is absorbed into the flue gas, and then the flue gas is sent back to the furnace of the boiler (1); a part of _CO2 from the flue at the tail of the boiler is extracted to heat the coal seam, and can be circulated back into the furnace, and the excess part is captured by carbon dioxide (15) . 2 . The system for coupling oil-rich coal in-situ pyrolysis and carbon capture according to claim 1 , wherein the organic matter produced by dissolution pyrolysis is a mixture, including liquid oil and gas at normal temperature. 3 . 3. A system for coupling oil-rich coal in-situ pyrolysis and carbon capture according to claim 1, wherein the organic gas ( ₁₃ ) contains small molecules such as _CH4 and _C2H6 . 4. A system for coupling oil-rich coal in-situ pyrolysis and carbon capture according to claim 1, characterized in that the high-temperature _CO2 flue gas generated by the oxy-fuel combustion boiler (1) of a power station is used to pass into the first The coal seam block (4) is pyrolyzed, and the additional heating equipment investment is reduced by extracting part of the _CO2 in the tail flue of the oxy-fuel combustion boiler (1) of the power station. 5. A system for coupling oil-rich coal in-situ pyrolysis and carbon capture according to claim 1, wherein the product after coal pyrolysis is sent into a heat exchanger (7) for heating feed water , the temperature of the pyrolysis product can be reduced to 350 °C. 6. A kind of oil-rich coal in-situ pyrolysis and carbon capture coupling system according to claim 1, it is characterized in that, after the first coal seam block (4) oil production is completed, the power station oxygen-enriched combustion boiler ( 1) The low-temperature flue gas at the end not higher than 120 °C is passed into the coal seam, the waste heat of 600 °C in the coal seam is absorbed into the flue gas, and then the flue gas is sent back to the oxy-fuel combustion boiler (1) of the power station to realize the flue gas recirculation. 7. A system for coupling oil-rich coal in-situ pyrolysis and carbon capture according to claim 1, wherein the flow channel of high temperature _CO2 in the first coal seam block (4) is serpentine.

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