Cascade pressurized adsorption oil gas recovery system and method thereof

Abstract

The invention relates to the technical field of oil gas recovery, and discloses a cascade pressurized adsorption oil gas recovery system which comprises an absorption and dehumidification device, a first-stage adsorption and desorption device and a second-stage adsorption and desorption device which are sequentially communicated through a pipeline, the absorption and dehumidification device comprises an oil gas feeding line, an oil gas buffer tank, a frequency conversion fan, an absorption tower, a demister and a dehumidification tank which are sequentially communicated through pipelines, the first-stage adsorption and desorption device comprises two first-stage adsorption towers which are arranged in parallel, and the second-stage adsorption and desorption device comprises two second-stage adsorption towers which are arranged in parallel. The invention also provides a cascade pressurization adsorption oil gas recovery method. The device has the beneficial effects that low-temperature absorption of diesel oil is performed firstly, then two-stage serial tower type pressurized adsorption is performed, adsorption of light hydrocarbon components is enhanced, negative-pressure desorption regeneration of hot nitrogen is performed, and the content of non-methane total hydrocarbon discharged from treated tail gas is less than or equal to 100mg / m < 3 >, so that ultralow up-to-standard discharge is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas recovery, and in particular relates to a cascade pressurized adsorption oil and gas recovery system and a method thereof. Background Art

[0002] During the storage and transportation of organic chemicals or oil products, some light components will inevitably volatilize, generating organic waste gas (VOCs), which can easily cause environmental and safety problems. With increasingly stringent air emission standards, oil and gas recovery methods have been severely challenged, and oil and gas recovery technology has gradually begun to develop towards multi-stage integrated oil and gas recovery processes.

[0003] Traditional absorption, condensation, membrane separation, adsorption and their combined treatment processes are difficult to achieve sustained and stable emission standards. The absorption method is to select a certain liquid absorbent and use its affinity for organic matter in organic waste gas to absorb organic matter from the waste gas. It is widely used in the production, storage and transportation of petrochemical products, but the absorption efficiency can generally only reach 70~85%, which cannot achieve standard emissions; the condensation method has high energy consumption, high equipment failure rate, and is difficult to treat light component waste gas, and cannot achieve ultra-low emissions; the core of the adsorption method is the selection of adsorbents. Typical adsorbents are activated carbon, zeolite molecular sieves, and silica gel For organic metal frameworks, although adsorption is relatively easy for heavy hydrocarbon components (components above C5), desorption and regeneration are difficult, and the adsorbent will be deactivated after a period of use. For light hydrocarbon components (components below C4), adsorption is difficult, but desorption is relatively easy. However, the components of organic waste gas are quite complex, and the presence of impurities and moisture will also cause the adsorbent to be deactivated, making it difficult to achieve stable emissions that meet standards by the adsorption method. Biological methods, photocatalytic oxidation methods, and low-temperature plasma methods are still technically immature. Destruction methods, such as catalytic combustion and high-temperature combustion, generally have problems such as large equipment investment, high operating costs, and poor overall performance. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the adsorbent in the prior art has poor adsorption effect and incomplete desorption and regeneration, which makes it difficult for oil and gas to achieve ultra-low emission standards in a continuous and stable manner. A cascade pressurized adsorption oil and gas recovery system and method are provided; according to the adsorption characteristics of light and heavy components of organic waste gas, the system firstly absorbs at low temperature, then conducts two-stage series tower adsorption and thermal nitrogen regeneration to achieve non-methane total hydrocarbons of organic waste gas ≤120mg / m 3 Ultra-low emissions.

[0005] In order to solve the above technical problems, the technical scheme adopted by the present invention is as follows: a cascade pressurized adsorption oil and gas recovery system, comprising an absorption + dehumidification device, a primary adsorption + desorption device and a secondary adsorption + desorption device connected in sequence by pipelines, the absorption + dehumidification device comprises an oil and gas feed line, an oil and gas buffer tank, a variable frequency fan, an absorption tower, a defoamer and a dehumidification tank connected in sequence by pipelines, the bottom of the absorption tower is connected to the absorbent tower outlet line, the upper section of the absorption tower is connected to the cooler outlet near the top side line, and the cooler inlet is connected to the absorbent tower inlet pipeline; the primary adsorption + desorption device is two primary adsorption towers arranged in parallel, the air outlets of the two primary adsorption towers are each connected to the middle buffer tank through a primary exhaust valve, and the air inlets of the two primary adsorption towers are each connected to the outlet of the dehumidification tank through a primary air inlet valve. The air ports are connected, and the air inlets of the two first-level adsorption towers are also connected to the inlet of the first-level vacuum pump through a first-level exhaust valve respectively, and the outlet of the first-level vacuum pump is connected to the oil and gas feed line in parallel and connected to the inlet of the oil and gas buffer tank; the second-level adsorption + desorption device is two second-level adsorption towers arranged in parallel, and the air outlets of the two second-level adsorption towers are connected to the atmosphere through a second-level exhaust valve respectively, and the air inlets of the two second-level adsorption towers are connected to the air outlet of the booster fan through a second-level air inlet valve respectively, and the inlet of the booster fan is connected to the air outlet of the intermediate buffer tank, and the air inlets of the two second-level adsorption towers are also connected to the inlet of the second-level vacuum pump through a second-level exhaust valve respectively, and the outlet of the second-level vacuum pump is connected to the second-level exhaust line, and the second-level exhaust line is connected to the low-pressure gas line outside the boundary or enters the incinerator for combustion.

[0006] Preferably, a first-level nitrogen replenishing valve is connected between the first-level adsorption tower top outlet and the first-level exhaust valve inlet, and a second-level nitrogen replenishing valve is connected between the second-level adsorption tower top outlet and the second-level exhaust valve inlet.

[0007] Preferably, the aspect ratio of the primary adsorption tower and the secondary adsorption tower is 6-15, preferably 9-12.

[0008] Preferably, the dehumidification tank is filled with solid sodium hydroxide particles with a filling porosity of 0.55-0.65.

[0009] Preferably, the absorption tower is a packed tower using structured packing.

[0010] Preferably, the first-level adsorption tower is filled with modified mesoporous activated carbon to remove heavy hydrocarbon components above C4 and C5, and the second-level adsorption tower is filled with modified mesoporous and microporous activated carbon to remove light hydrocarbon components of C4, C3, and C2.

[0011] The present invention further provides a cascade pressurized adsorption oil and gas recovery method, which is applied to any of the above-mentioned cascade pressurized adsorption oil and gas recovery systems, and comprises the following steps: Step 1: Pressurized absorption: The volatile oil and gas of the oil or chemical product is introduced into the oil and gas buffer tank through the oil and gas feed line together with the tail gas generated in the hot nitrogen vacuum desorption process of the first-level adsorption tower, and then the pressure is increased to above 800 Pa (gauge pressure) by the variable frequency fan, and then enters the absorption tower from the side line at the bottom of the absorption tower, and contacts with the absorbent cooled to 10-20°C by the cooler and entering from the side line at the top of the absorption tower in the absorption tower in countercurrent, and low-temperature absorption is carried out. The oil and gas components are partially dissolved in the absorbent according to the principle of like dissolves like, and the unabsorbed tail gas is discharged from the top of the absorption tower. The absorbent rich in oil and gas is pumped out from the bottom of the absorption tower through the absorption tower bottom pump (not marked) into the absorbent outlet line; Step 2: Defoaming and Dehumidification: The unabsorbed tail gas enters the defoamer to remove the carried absorbent, and passes through the dehumidification tank to remove trace moisture in the gas through solid sodium hydroxide particles; Step 3 Oil and gas adsorption For the first-level adsorption process, the gas from the dehumidification tank is introduced into the first-level adsorption tower through the first-level air inlet valve for adsorption. The organic gas molecules are adsorbed on the surface and micropores of the adsorbent, while methane and other components cannot be adsorbed and directly pass through the adsorbent bed of the first-level adsorption tower and are discharged to the intermediate buffer tank through the first-level exhaust valve. To prevent the adsorbent bed from being oversaturated, the adsorption time set by the program is 15 to 30 minutes. Once the set adsorption time is reached, the program will automatically close the first-level air inlet valve and the first-level exhaust valve of the current first-level adsorption tower, cut off the connection with the dehumidification tank and the intermediate buffer tank, and at the same time open the first-level air inlet valve and the first-level exhaust valve of the other adsorption tower for adsorption operation; At the same time, for the secondary adsorption process, the gas from the intermediate buffer tank is pressurized to above 200 kPa (gauge pressure) by the booster fan, and then introduced into the secondary adsorption tower through the secondary air inlet valve for adsorption. The organic gas molecules are adsorbed on the surface and micropores of the adsorbent, while methane and other components cannot be adsorbed and directly pass through the adsorbent bed of the secondary adsorption tower and are directly discharged into the atmosphere through the secondary exhaust valve. To prevent the adsorbent bed from being oversaturated, the adsorption time set by the program is 15 to 30 minutes. Once the set adsorption time is reached, the program will automatically close the secondary air inlet valve and secondary exhaust valve of the current secondary adsorption tower, cut off the connection with the booster fan and the atmosphere, and at the same time open the secondary air inlet valve and secondary exhaust valve of the other secondary adsorption tower for adsorption operation; the operation of the primary adsorption tower and the secondary adsorption tower is carried out simultaneously; Step 4 Negative pressure desorption For the first-level adsorption tower that has completed the oil and gas adsorption operation, the program automatically opens the first-level exhaust valve, connects the first-level vacuum pump, and evacuates the first-level adsorption tower to a pressure of -95kPa~-100kPa (gauge pressure) through the first-level vacuum pump. The organic gas components adsorbed in the activated carbon will be desorbed from the activated carbon micropores; the program is set to automatically open the first-level nitrogen replenishment valve, and nitrogen heated to 100~200℃ is intermittently injected. The pressure of the first-level adsorption tower changes in a wave-like manner between -65kPa~-100kPa (gauge pressure). The hot nitrogen regeneration time set by the program is synchronized with the negative pressure desorption time. Once the set hot nitrogen regeneration time is reached, the current first-level exhaust valve and the first-level nitrogen replenishment valve are closed, and the other-level air intake valve and the other-level exhaust valve are opened to enter the next round of oil and gas adsorption operation. The two first-level adsorption towers cycle alternately between oil and gas adsorption and negative pressure desorption; At the same time, for the secondary desorption process, for the secondary adsorption tower that completes the oil and gas adsorption operation, the program automatically opens the secondary exhaust valve, connects the secondary vacuum pump, and evacuates the secondary adsorption tower to a pressure of -95kPa~-100kPa (gauge pressure) through the secondary vacuum pump. The organic gas components adsorbed in the adsorbent will be desorbed from the adsorbent micropores; the program is set to automatically open the secondary nitrogen replenishment valve, and nitrogen heated to 100~200℃ is injected intermittently. The pressure of the secondary adsorption tower changes in a wave-like manner between -65kPa~-100kPa (gauge pressure). The hot nitrogen regeneration time set by the program is synchronized with the negative pressure desorption time. Once the set hot nitrogen regeneration time is reached, the secondary exhaust valve and the secondary nitrogen replenishment valve are closed, and another secondary air inlet valve and another secondary exhaust valve are opened to enter the next round of oil and gas adsorption operation. The two secondary adsorption towers cycle alternately between oil and gas adsorption and negative pressure desorption.

[0012] In certain embodiments of the present invention, the top pressure of the absorption tower is controlled at 600-800 Pa (gauge pressure), the absorbent temperature is controlled at 10-20° C., and the absorbent is preferably diesel.

[0013] In certain embodiments of the present invention, the pressure at the top of the secondary adsorption tower is controlled at 180-200 kPa (gauge pressure) to perform pressurized adsorption to remove light hydrocarbon components with smaller molecular weight.

[0014] Compared with the existing technology, the advantages are: (1) through diesel low-temperature absorption, more than 80% of the organic components in the exhaust gas are removed, and most of them are heavy hydrocarbon components, which can reduce the inlet concentration and adsorption load of the subsequent adsorption process, which is beneficial to improve the adsorption efficiency; (2) through coalescence defoaming and solid alkali dehumidification, the adsorption raw gas is purified, which can protect the adsorbent and avoid rapid deactivation, which is beneficial to continuous and stable compliance with the standard; (3) the two-stage tower adsorption is connected in series and uses a high aspect ratio adsorption tower, which can extend the adsorption stroke and target light and heavy hydrocarbon components. Two different adsorbents are loaded according to their adsorption characteristics. The first adsorption tower is loaded with modified mesoporous activated carbon to remove heavy hydrocarbon components above C4 and C5, and the second adsorption tower is loaded with modified meso-microporous activated carbon to remove light hydrocarbon components such as C4, C3, and C2. The second adsorption tower adopts pressurized adsorption, which is beneficial to the adsorption of light hydrocarbon components, thereby ensuring continuous and stable ultra-low emission compliance; (4) Hot nitrogen negative pressure desorption can ensure that the components in the adsorbent that are difficult to desorb are desorbed under the combined action of high vacuum and hot nitrogen, thereby ensuring the regeneration effect of the adsorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is a process flow chart of the cascade pressurized adsorption oil and gas recovery system of the present invention.

[0017] Explanation of symbols: 1. Oil and gas feed line; 2. Oil and gas buffer tank; 3. Variable frequency fan; 4. Absorption tower; 5. Absorbent inlet line; 6. Cooler; 7. Absorbent outlet line; 8. Defoamer; 9. Dehumidification tank; 10. Primary adsorption tower; 11. Primary exhaust valve; 12. Primary air inlet valve; 13. Primary exhaust valve; 14. Primary nitrogen replenishment valve; 15. Primary vacuum pump; 16. Intermediate buffer tank; 17. Pressurized fan; 18. Secondary adsorption tower; 19. Secondary exhaust valve; 20. Secondary air inlet valve; 21. Secondary exhaust valve; 22. Secondary nitrogen replenishment valve; 23. Secondary vacuum pump; 24. Secondary exhaust line.

[0018] Figure 2 It is the absorption efficiency of the absorbent on oil and gas components.

[0019] Figure 3 is the change of outlet concentration with adsorption time.

[0020] The present invention will be further described below by way of examples, but is not limited thereto. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, rather than all the embodiments, and the preferred embodiments of the present invention are given below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The appearance of the phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] See also Figure 1As shown, the cascade pressurized adsorption oil and gas recovery system comprises an absorption + dehumidification device, a primary adsorption + desorption device and a secondary adsorption + desorption device which are sequentially connected by pipelines. The absorption + dehumidification device comprises an oil and gas feed line (1), an oil and gas buffer tank (2), a variable frequency fan (3), an absorption tower (4), a defoamer (8) and a dehumidification tank (9) which are sequentially connected by pipelines. The bottom of the absorption tower (4) is connected to an absorbent outlet line (7). The upper section of the absorption tower (4) is connected to a cooler ( 6) outlet, the inlet of the cooler (6) is connected to the absorbent inlet pipeline (5); the first-stage adsorption + desorption device is two first-stage adsorption towers (10) arranged in parallel, the gas outlets of the two first-stage adsorption towers (10) are respectively connected to the intermediate buffer tank (16) through a first-stage exhaust valve (13), the gas inlets of the two first-stage adsorption towers (10) are respectively connected to the gas outlet of the dehydration tank (9) through a first-stage intake valve (12), and the two first-stage adsorption towers (10) are respectively connected to the gas outlet of the dehydration tank (9) through a first-stage intake valve (12). ) is also connected to the inlet of a primary vacuum pump (15) through a primary exhaust valve (11), and the outlet of the primary vacuum pump (15) is connected in parallel with the oil and gas feed line (1) and the inlet of the oil and gas buffer tank (2); the secondary adsorption + desorption device is two secondary adsorption towers (18) arranged in parallel, and the air outlets of the two secondary adsorption towers (18) are connected to the atmosphere through a secondary exhaust valve (21), and the air inlets of the two secondary adsorption towers (18) are connected to the atmosphere through a secondary exhaust valve (21). Each is connected to the air outlet of the pressurizing fan (17) through a secondary air inlet valve (20), the inlet of the pressurizing fan (17) is connected to the air outlet of the intermediate buffer tank (16), and the air inlets of the two secondary adsorption towers (18) are also connected to the inlet of the secondary vacuum pump (23) through a secondary air extraction valve (19), and the outlet of the secondary vacuum pump (23) is connected to the secondary air extraction line (24), and the secondary air extraction line (24) is connected to the low-pressure gas line outside the boundary or enters the incinerator for combustion.

[0024] According to a preferred technical solution, a first-level nitrogen replenishing valve (14) is connected between the top outlet of the first-level adsorption tower (10) and the inlet of the first-level exhaust valve (13), and a second-level nitrogen replenishing valve (22) is connected between the top outlet of the second-level adsorption tower (18) and the inlet of the second-level exhaust valve (21).

[0025] In a preferred technical solution, the aspect ratio of the primary adsorption tower (10) and the secondary adsorption tower (18) is 6 to 15, preferably 9 to 12.

[0026] According to a preferred technical solution, the dehumidification tank is filled with solid sodium hydroxide particles having a filling porosity of 0.55 to 0.65.

[0027] According to a preferred technical solution, the absorption tower (4) is a packed tower using structured packing, the first-level adsorption tower (10) is filled with modified mesoporous activated carbon to remove heavy hydrocarbon components above C4 and C5, and the second-level adsorption tower (18) is filled with modified mesoporous and microporous activated carbon to remove light hydrocarbon components such as C4, C3, and C2.

[0028] The present invention further provides a cascade pressurized adsorption oil and gas recovery method, which is applied to any of the above-mentioned cascade pressurized adsorption oil and gas recovery systems, and comprises the following steps: Step 1: Pressure absorption: The volatilized oil and gas of the oil or chemical product is introduced into the oil and gas buffer tank (2) through the oil and gas feed line (1) and the tail gas generated in the hot nitrogen vacuum desorption process of the first adsorption tower (10), and then the oil and gas is pressurized to above 800 Pa (gauge pressure) by the variable frequency fan (3), and then enters the absorption tower (4) from the side line at the bottom of the absorption tower (4), and enters from the side line at the top of the absorption tower (5) with the absorbent cooled by 10 to 20° C., and countercurrently contacts in the absorption tower (4) to perform low-temperature absorption. The oil and gas components are partially dissolved in the absorbent according to the principle of like dissolves like, and the unabsorbed tail gas is discharged from the top of the absorption tower (4). The absorbent rich in oil and gas is pumped out from the bottom of the absorption tower (5) through the absorption tower bottom pump and enters the absorbent outlet line (7); Step 2: Defoaming and Dehumidification: The unabsorbed tail gas enters the defoamer (8) to remove the carried absorbent, and passes through the dehydration tank (9) to remove trace moisture in the gas through the strong water absorption of solid sodium hydroxide particles, thereby purifying the gas entering the adsorption tower; Step 3 Oil and gas adsorption For the first-stage adsorption process, the gas from the dehumidification tank (9) is introduced into the first-stage adsorption tower (10) through the first-stage air inlet valve (12) for adsorption. The organic gas molecules are adsorbed on the surface and micropores of the adsorbent, while methane and other components cannot be adsorbed and directly pass through the adsorbent bed of the first-stage adsorption tower (10) and are directly discharged to the intermediate buffer tank (16) through the first-stage exhaust valve (13). To prevent the adsorbent bed from being oversaturated, the adsorption time set by the program is 15 to 30 minutes. Once the set adsorption time is reached, the program will automatically close the first-stage air inlet valve (11) and the first-stage exhaust valve (13) of the current first-stage adsorption tower (10), cut off the connection with the dehumidification tank (9) and the intermediate buffer tank (16), and at the same time open the first-stage air inlet valve (12) and the first-stage exhaust valve (13) of another stage adsorption tower (10) to perform the adsorption operation; At the same time, for the secondary adsorption process, the gas from the intermediate buffer tank (16) is pressurized to above 200 kPa (gauge pressure) by the booster fan (17), and then introduced into the secondary adsorption tower (18) through the secondary air inlet valve (20) for adsorption. The organic gas molecules are adsorbed on the surface and micropores of the adsorbent, while methane and other components cannot be adsorbed and directly pass through the adsorbent bed in the secondary adsorption tower (18) and are directly discharged to the atmosphere through the secondary exhaust valve (21). In order to prevent the adsorbent bed from being oversaturated, the adsorption time set by the program is 15 to 30 minutes. Once the set adsorption time is reached, the program will automatically close the secondary air inlet valve (20) and the secondary exhaust valve (21) of the current secondary adsorption tower (18), cut off the connection with the booster fan (17) and the atmosphere, and at the same time open the secondary air inlet valve (20) and the secondary exhaust valve (21) of the other secondary adsorption tower (18) for adsorption operation. The operation of the primary adsorption tower and the secondary adsorption tower is carried out synchronously; Step 4 Negative pressure desorption For the first-level adsorption tower (10) that has completed the oil and gas adsorption operation, the program automatically opens the first-level exhaust valve (11) and connects to the first-level vacuum pump (15). The first-level vacuum pump (15) evacuates the first-level adsorption tower (10) to a pressure of -95kPa to -100kPa (gauge pressure), and the organic gas components adsorbed in the activated carbon are desorbed from the micropores of the activated carbon; the program is set to automatically open the first-level nitrogen replenishment valve (20) to intermittently inject nitrogen heated to 100~200℃. The pressure of the adsorption tower (10) changes in a sawtooth wave-like manner between -65 kPa and -100 kPa (gauge pressure). The hot nitrogen regeneration time set by the program is synchronized with the negative pressure desorption time. Once the set hot nitrogen regeneration time is reached, the current first-stage exhaust valve (11) and the first-stage nitrogen replenishment valve (14) are closed, and the other-stage air intake valve (12) and the other-stage exhaust valve (13) are opened to enter the next round of oil and gas adsorption operation. The two first-stage adsorption towers (10) cycle alternately between oil and gas adsorption and negative pressure desorption in this way. At the same time, for the secondary desorption process, for the secondary adsorption tower (18) that has completed the oil and gas adsorption operation, the program automatically opens the secondary exhaust valve (19), connects to the secondary vacuum pump (23), and evacuates the secondary adsorption tower (18) to a pressure of -95 kPa to -100 kPa (gauge pressure) through the secondary vacuum pump (23), and the organic gas components adsorbed in the adsorbent are desorbed from the micropores of the adsorbent; the program is set to automatically open the secondary nitrogen replenishment valve (22), and intermittently inject nitrogen heated to 100~200°C into the secondary adsorption tower (18). The pressure of the secondary adsorption tower (18) rises and falls in a sawtooth wave-like manner between -65 kPa and -100 kPa (gauge pressure). The hot nitrogen regeneration time set by the program is synchronized with the negative pressure desorption time. Once the set hot nitrogen regeneration time is reached, the secondary exhaust valve (21) and the secondary nitrogen replenishment valve (22) are closed, and another secondary air inlet valve (20) and another secondary exhaust valve (21) are opened to enter the next round of oil and gas adsorption operation. The two secondary adsorption towers (18) cycle alternately between oil and gas adsorption and negative pressure desorption.

[0029] In certain embodiments of the present invention, the top pressure of the absorption tower (5) is controlled at 600-800 Pa (gauge pressure), the absorbent temperature is controlled at 10-20° C., and the absorbent is preferably diesel.

[0030] In certain embodiments of the present invention, the top pressure of the secondary adsorption tower (18) is controlled at 180-200 kPa (gauge pressure) to perform pressurized adsorption to remove hydrocarbon components with smaller molecular weight.

[0031] With diesel as the absorbent, under the conditions of absorption pressure of 600~800 Pa and absorption temperature of 15~20℃, the oil and gas removal rate of the absorption tower can reach more than 80%, and the heavy hydrocarbon components above C6 can be removed by more than 99.0%, greatly reducing the inlet concentration and adsorption load of the subsequent adsorption device; the subsequent stage of the secondary series tower pressurized adsorption adopts a high aspect ratio (9~10) adsorption tower, and the first adsorption tower is filled with modified mesoporous activated carbon, and the second adsorption tower is filled with modified meso-microporous activated carbon. The second adsorption tower adopts 200 kPa (gauge pressure) pressurized adsorption to strengthen the adsorption of light hydrocarbon components, and hot nitrogen negative pressure desorption. The components that are difficult to desorb in the adsorbent are desorbed under the combined action of high vacuum and hot nitrogen, ensuring the complete regeneration of the adsorbent. The total non-methane hydrocarbons in the tail gas after treatment are ≤100mg / m 3 , achieving ultra-low emission targets.

[0032] Figure 2is the absorption efficiency of the absorbent for oil and gas components. It can be seen that the absorption rate of C2 component is as low as 40.49%, the absorption rate of C3 component is only 72.43%, the absorption rate of C4 component is 89.24%, and the absorption rate of C5 and above components reaches more than 99.23%. The reason for this result is that the absorbent diesel and the oil and gas components show similar solubility differences, that is, there are certain differences between diesel and the oil and gas components, and diesel is mostly C8 components. Therefore, the closer the carbon atoms are, the better the solubility is, the stronger the interaction between the two, and the better the absorption effect is. Therefore, in different oil and gas systems, the absorption rate shows great differences.

[0033] Figure 3 (a) is the relationship between the oil and gas mole fraction at the outlet of the adsorption tower and the adsorption time. The adsorption tower bed breakthrough curve is obtained by recording the change of the oil and gas mole fraction at the outlet of the adsorption tower. The adsorption time is taken as the horizontal axis and the oil and gas concentration is taken as the vertical axis. Figure 3 (b) From Figure 3 (b) It can be seen that from the beginning of adsorption to 500 s, the oil and gas concentration in the outlet gas of the adsorption tower is close to 0. As the adsorption process proceeds, the adsorbent begins to gradually approach the saturated adsorption capacity. After the adsorption time exceeds 1010 s, the exhaust gas concentration at the top outlet of the tower reaches the restricted emission standard of 120 mg / m 3 In order to fully recover the oil and gas, the adsorption time should not be too short and the emission standards should be met. Therefore, the operation cycle of the adsorption section can be set to 990 s. At this time, the concentration of non-methane total hydrocarbons in the exhaust gas is 100 mg / m 3 .

[0034] The cascade pressurized adsorption oil and gas recovery system applied to the above-mentioned embodiment described in the above-mentioned embodiment can execute the cascade pressurized adsorption oil and gas recovery method applied to the above-mentioned cascade pressurized adsorption oil and gas recovery method provided in the embodiment of the present invention. The cascade pressurized adsorption oil and gas recovery method applied to the above-mentioned cascade pressurized adsorption oil and gas recovery method has the corresponding functional components and beneficial effects of the cascade pressurized adsorption oil and gas recovery system applied to the above-mentioned embodiment described in the above-mentioned embodiment. Please refer to the above-mentioned embodiment applied to the above-mentioned cascade pressurized adsorption oil and gas recovery system for details. The embodiment of the present invention will not be repeated here.

[0035] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field. The above are only embodiments of the present invention, but do not limit the patent scope of the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the aforementioned specific implementation methods, or make equivalent replacements for some of the technical features therein. Any equivalent replacement made using the contents of the specification of the present invention, directly or indirectly applied in other related technical fields, is also within the scope of patent protection of the present invention.

Claims

1. A cascade pressurized adsorption oil and gas recovery system, characterized in that: It includes an absorption + dehumidification device, a primary adsorption + desorption device and a secondary adsorption + desorption device which are connected in sequence through pipelines. The absorption + dehumidification device includes an oil and gas feed line, an oil and gas buffer tank, a variable frequency fan, an absorption tower, a defoamer and a dehumidification tank which are connected in sequence through pipelines. The bottom of the absorption tower is connected to an absorbent outlet line, the upper section of the absorption tower is connected to a cooler outlet near the top side line, and the cooler inlet is connected to an absorbent inlet pipeline; the primary adsorption + desorption device is two primary adsorption towers arranged in parallel, the air outlets of the two primary adsorption towers are each connected to the middle buffer tank through a primary exhaust valve, the air inlets of the two primary adsorption towers are each connected to the air outlet of the dehydration tank through a primary air inlet valve, and the air inlets of the two primary adsorption towers are connected to the air outlet of the dehydration tank through a primary air inlet valve. Each of them is also connected to the inlet of a first-level vacuum pump through a first-level exhaust valve, and the outlet of the first-level vacuum pump is connected to the oil and gas feed line in parallel and connected to the inlet of the oil and gas buffer tank; the second-level adsorption + desorption device is two second-level adsorption towers arranged in parallel, and the air outlets of the two second-level adsorption towers are connected to the atmosphere through a second-level exhaust valve respectively, and the air inlets of the two second-level adsorption towers are connected to the air outlet of the booster fan through a second-level intake valve respectively, and the inlet of the booster fan is connected to the air outlet of the intermediate buffer tank, and the air inlets of the two second-level adsorption towers are also connected to the inlet of the second-level vacuum pump through a second-level exhaust valve respectively, and the outlet of the second-level vacuum pump is connected to the second-level exhaust line, and the second-level exhaust line is connected to the low-pressure gas line outside the boundary or enters the incinerator for combustion.

2. The cascade pressurized adsorption oil and gas recovery system according to claim 1 is characterized in that A first-level nitrogen replenishing valve is connected between the top outlet of the first-level adsorption tower and the inlet of the first-level exhaust valve, and a second-level nitrogen replenishing valve is connected between the top outlet of the second-level adsorption tower and the inlet of the second-level exhaust valve.

3. The cascade pressurized adsorption oil and gas recovery system according to claim 1 is characterized in that The aspect ratio of the primary adsorption tower and the secondary adsorption tower is 6~15, preferably 9~12.

4. The cascade pressurized adsorption oil and gas recovery system according to claim 1 is characterized in that The dehumidification tank is filled with solid sodium hydroxide particles with a filling porosity of 0.55~0.

65.

5. The cascade pressurized adsorption oil and gas recovery system according to claim 1 is characterized in that ,The absorption tower is a packed tower, which adopts regular packing.

6. The cascade pressurized adsorption oil and gas recovery system according to claim 1 is characterized in that The first-level adsorption tower is filled with modified mesoporous activated carbon to remove heavy hydrocarbon components above C4 and C5, and the second-level adsorption tower is filled with modified mesoporous and microporous activated carbon to remove light hydrocarbon components such as C4, C3, and C2.

7. A cascade pressurized adsorption oil and gas recovery method, applied to the cascade pressurized adsorption oil and gas recovery system according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Pressurized absorption: The volatile oil and gas of the oil or chemical product is introduced into the oil and gas buffer tank through the oil and gas feed line together with the tail gas generated in the hot nitrogen vacuum desorption process of the first-level adsorption tower, and then the pressure is increased to above 800 Pa (gauge pressure) by the variable frequency fan, and then enters the absorption tower from the side line at the bottom of the absorption tower, and contacts with the absorbent cooled to 10-20°C by the cooler and entering from the side line at the top of the absorption tower in the absorption tower in countercurrent, and low-temperature absorption is carried out. The oil and gas components are partially dissolved in the absorbent according to the principle of like dissolves like, and the unabsorbed tail gas is discharged from the top of the absorption tower. The absorbent rich in oil and gas is pumped out from the bottom of the absorption tower through the absorption tower bottom pump (not marked) into the absorbent outlet line; Step 2: Defoaming and Dehumidification: The unabsorbed tail gas enters the defoamer to remove the carried absorbent, and passes through the dehumidification tank to remove trace moisture in the gas through solid sodium hydroxide particles; Step 3 Oil and gas adsorption For the first-level adsorption process, the gas from the dehumidification tank is introduced into the first-level adsorption tower through the first-level air inlet valve for adsorption. The organic gas molecules are adsorbed on the surface and micropores of the adsorbent, while methane and other components cannot be adsorbed and directly pass through the adsorbent bed of the first-level adsorption tower and are discharged to the intermediate buffer tank through the first-level exhaust valve. To prevent the adsorbent bed from being oversaturated, the adsorption time set by the program is 15 to 30 minutes. Once the set adsorption time is reached, the program will automatically close the first-level air inlet valve and the first-level exhaust valve of the current first-level adsorption tower, cut off the connection with the dehumidification tank and the intermediate buffer tank, and at the same time open the first-level air inlet valve and the first-level exhaust valve of the other adsorption tower for adsorption operation; At the same time, for the secondary adsorption process, the gas from the intermediate buffer tank is pressurized to above 200kPa (gauge pressure) by the booster fan, and then introduced into the secondary adsorption tower through the secondary air inlet valve for adsorption. The organic gas molecules are adsorbed on the surface and micropores of the adsorbent, while methane and other components cannot be adsorbed and directly pass through the adsorbent bed of the secondary adsorption tower and are directly discharged into the atmosphere through the secondary exhaust valve. In order to prevent the adsorbent bed from being oversaturated, the adsorption time set by the program is 15 to 30 minutes. Once the set adsorption time is reached, the program will automatically close the secondary air inlet valve and secondary exhaust valve of the current secondary adsorption tower, cut off the connection with the booster fan and the atmosphere, and at the same time open the secondary air inlet valve and secondary exhaust valve of the other secondary adsorption tower for adsorption operation; the operation of the primary adsorption tower and the secondary adsorption tower is carried out simultaneously; Step 4 Negative pressure desorption For the first-level adsorption tower that has completed the oil and gas adsorption operation, the program automatically opens the first-level exhaust valve, connects the first-level vacuum pump, and evacuates the first-level adsorption tower to a pressure of -95kPa~-100kPa (gauge pressure) through the first-level vacuum pump. The organic gas components adsorbed in the activated carbon will be desorbed from the activated carbon micropores; the program is set to automatically open the first-level nitrogen replenishment valve, and nitrogen heated to 100~200℃ is intermittently injected. The pressure of the first-level adsorption tower changes in a wave-like manner between -65kPa~-100kPa (gauge pressure). The hot nitrogen regeneration time set by the program is synchronized with the negative pressure desorption time. Once the set hot nitrogen regeneration time is reached, the current first-level exhaust valve and the first-level nitrogen replenishment valve are closed, and the other-level air intake valve and the other-level exhaust valve are opened to enter the next round of oil and gas adsorption operation. The two first-level adsorption towers cycle alternately between oil and gas adsorption and negative pressure desorption; At the same time, for the secondary desorption process, for the secondary adsorption tower that completes the oil and gas adsorption operation, the program automatically opens the secondary exhaust valve, connects the secondary vacuum pump, and evacuates the secondary adsorption tower to a pressure of -95kPa~-100kPa (gauge pressure) through the secondary vacuum pump. The organic gas components adsorbed in the adsorbent will be desorbed from the adsorbent micropores; the program is set to automatically open the secondary nitrogen replenishment valve, and nitrogen heated to 100~200℃ is injected intermittently. The pressure of the secondary adsorption tower changes in a wave-like manner between -65kPa~-100kPa (gauge pressure). The hot nitrogen regeneration time set by the program is synchronized with the negative pressure desorption time. Once the set hot nitrogen regeneration time is reached, the secondary exhaust valve and the secondary nitrogen replenishment valve are closed, and another secondary air inlet valve and another secondary exhaust valve are opened to enter the next round of oil and gas adsorption operation. The two secondary adsorption towers cycle alternately between oil and gas adsorption and negative pressure desorption.

8. The cascade pressure adsorption oil and gas recovery method according to claim 7, characterized in that The top pressure of the absorption tower is controlled at 600~800Pa (gauge pressure), the absorbent temperature is controlled at 10~20°C, and the absorbent is preferably diesel.

9. The cascade pressure adsorption oil and gas recovery method according to claim 7, characterized in that The top pressure of the secondary adsorption tower is controlled at 180~200kPa (gauge pressure) for pressurized adsorption to remove light hydrocarbon components with smaller molecular weight.

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