Hydrocarbon-containing tail gas treatment method and treatment system

Abstract

The embodiment of the invention provides a treatment method and a treatment system for hydrocarbon-containing tail gas, and belongs to the technical field of tail gas treatment of an oil field air injection technology. The treatment method comprises the following steps: carrying out shallow cold oil adsorption on hydrocarbon-containing tail gas to separate out non-methane light hydrocarbon and first tail gas; detecting tail gas components of the first tail gas; and conveying the first tail gas or second tail gas containing the first tail gas to the internal combustion engine according to the tail gas component of the first tail gas, so that the internal combustion engine generates power. According to the technical scheme, the non-methane light hydrocarbon component in the low-concentration hydrocarbon-containing tail gas is recycled, the content of the non-methane light hydrocarbon in the low-concentration hydrocarbon-containing tail gas is reduced, and stable operation of an internal combustion engine is facilitated. And meanwhile, the hydrocarbon-containing tail gas without the non-methane light hydrocarbon is introduced into the internal combustion engine for power generation, low-concentration hydrocarbon-containing tail gas treatment is converted into a link of generating economic benefits from a link of purely putting into negative value, and high-efficiency echelon utilization of the low-concentration hydrocarbon-containing tail gas is realized.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas treatment of oil field air injection technology, and in particular to a method and system for treating hydrocarbon-containing tail gas. Background Art

[0002] In the context of implementing the country’s and the company’s “dual carbon” goals, research on oilfield exhaust gas treatment will inevitably become an important research direction for reducing carbon emissions.

[0003] In the treatment of oilfield tail gas, the low-concentration hydrocarbon-containing tail gas produced by air injection technology has the characteristics of large gas volume and complex hydrocarbon composition. Usually, hydrocarbon-containing tail gas includes methane, ethane, propane, isobutane, n-butane, isopentane, n-pentane and other alkane gases, and sometimes also includes ethylene, carbon monoxide and other gases. At the same time, hydrocarbon-containing tail gas has the characteristics of large hydrocarbon concentration changes and high CO2 content. At present, different treatment methods are used for tail gas with different hydrocarbon concentrations: for hydrocarbon tail gas with hydrocarbon concentration greater than 35%, direct discharge after combustion can be adopted; for hydrocarbon tail gas with concentration less than 35%, since it cannot be burned or directly discharged, thermal oxidation combustion (RTO) or thermal oxidation catalytic method (RCO) is usually used for treatment. However, this treatment method has large equipment investment, high operating cost, and does not generate economic benefits. Therefore, it is urgent to explore low-cost and high-efficiency tail gas treatment and recovery technology. Summary of the invention

[0004] In view of the above problems, the purpose of the embodiments of the present invention is to provide a method and system for treating hydrocarbon-containing exhaust gas, which proposes a technology of shallow cooling oil recovery of hydrocarbon-containing exhaust gas + comprehensive utilization of internal combustion engine power generation exhaust gas, to achieve the cascade utilization of low-concentration hydrocarbon-containing exhaust gas generated by air injection technology, and solve the problem that hydrocarbon-containing exhaust gas is difficult to effectively utilize as a resource.

[0005] In order to achieve the above-mentioned purpose, an embodiment of the present invention provides a method for treating hydrocarbon-containing exhaust gas, which comprises: performing shallow cold oil adsorption on the hydrocarbon-containing exhaust gas to separate non-methane light hydrocarbons and a first exhaust gas; detecting the exhaust gas components of the first exhaust gas; and according to the exhaust gas components of the first exhaust gas, transporting the first exhaust gas or a second exhaust gas containing the first exhaust gas to an internal combustion engine so that the internal combustion engine can generate electricity.

[0006] Optionally, delivering the first exhaust gas or the second exhaust gas containing the first exhaust gas to the internal combustion engine includes: when the exhaust gas components of the first exhaust gas meet the set requirements, directly delivering the first exhaust gas to the internal combustion engine; or when the exhaust gas components of the first exhaust gas do not meet the set requirements, mixing natural gas or associated gas with the first exhaust gas to obtain a second exhaust gas, and delivering the second exhaust gas to the internal combustion engine.

[0007] Optionally, the setting requirement is that the concentration of methane in the exhaust gas component of the first exhaust gas is greater than or equal to a first preset value.

[0008] Optionally, the associated gas is associated gas produced by air injection technology in one or more of a heavy oil reservoir, a light oil reservoir, a low permeability reservoir, a condensate gas reservoir, shale oil, shale gas, and oil shale; and

[0009] The concentration of methane in the associated gas is greater than or equal to a second preset value, wherein the second preset value is greater than the first preset value.

[0010] Optionally, the shallow cold oil adsorption of the hydrocarbon-containing tail gas to separate the non-methane light hydrocarbons and the first tail gas includes: passing the hydrocarbon-containing tail gas into an absorption tower; spraying an absorbent from the top of the absorption tower to produce a mixed liquid including the absorbent and non-methane light hydrocarbons at the bottom of the absorption tower and the first tail gas at the top of the absorption tower; and desorbing the mixed liquid to separate the non-methane light hydrocarbons.

[0011] Optionally, the absorbent is a C5 fraction comprising one or more of the following: n-pentane, isopentene, n-pentene and isopentene.

[0012] Optionally, before the shallow cold oil adsorption is performed on the hydrocarbon-containing tail gas, the treatment method further comprises: pre-treating the hydrocarbon-containing tail gas, wherein the pre-treatment comprises one or more of the following: filtration, desulfurization and drying.

[0013] Optionally, before detecting the exhaust gas components of the first exhaust gas, the processing method further includes: recovering cold energy from the first exhaust gas.

[0014] On the other hand, the present invention provides a treatment system for hydrocarbon-containing exhaust gas, the treatment system comprising: an adsorption device for performing shallow cold oil adsorption on the hydrocarbon-containing exhaust gas to separate non-methane light hydrocarbons and a first exhaust gas; an exhaust gas detection control device for detecting the exhaust gas components of the first exhaust gas; and an exhaust gas conveying device for conveying the first exhaust gas or a second exhaust gas containing the first exhaust gas to an internal combustion engine according to the exhaust gas components of the first exhaust gas, so that the internal combustion engine can generate electricity.

[0015] In another aspect, the present invention provides an internal combustion engine, which generates electricity using the first exhaust gas or the second exhaust gas obtained by the hydrocarbon-containing exhaust gas treatment system.

[0016] Optionally, the internal combustion engine is connected to the processing system for transmitting the generated electrical energy to the processing system.

[0017] Through the above technical scheme, the beneficial effects of the present invention are as follows: non-methane light hydrocarbon components in low-concentration hydrocarbon-containing tail gas are recovered to reduce the content of non-methane light hydrocarbons therein, thereby recovering non-methane light hydrocarbons of high economic value while overcoming the detonation and misfire problems of non-methane light hydrocarbons burning in an internal combustion engine, which is beneficial to the stable operation of the internal combustion engine. Then, the hydrocarbon-containing tail gas separated from the non-methane light hydrocarbons is passed into the internal combustion engine for power generation, thereby turning the low-concentration hydrocarbon-containing tail gas into treasure and reducing the treatment cost of the low-concentration hydrocarbon-containing tail gas. By transforming the treatment of low-concentration hydrocarbon-containing tail gas from a pure input negative value link to a link that generates economic benefits, a high-efficiency cascade utilization of low-concentration hydrocarbon-containing tail gas is achieved.

[0018] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0020] Figure 1 is a schematic diagram of a method for treating hydrocarbon-containing tail gas according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of a method for separating non-methane light hydrocarbons according to an embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of a system for treating hydrocarbon-containing tail gas according to an embodiment of the present invention;

[0023] Figure 4a is a schematic diagram of the connection relationship between a hydrocarbon-containing tail gas treatment system and an internal combustion engine according to an embodiment of the present invention;

[0024] Figure 4b It is a schematic diagram of the connection relationship between a hydrocarbon-containing tail gas treatment system and an internal combustion engine according to another embodiment of the present invention. DETAILED DESCRIPTION

[0025] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0026] In view of the problem that the hydrocarbon-containing tail gas of air injection technology is difficult to effectively utilize as resources, the present invention proposes a technology of shallow cooling oil recovery of low-concentration hydrocarbon-containing tail gas by air injection technology + comprehensive utilization of tail gas from internal combustion engine power generation. First, the non-methane light hydrocarbon components in the hydrocarbon-containing tail gas are efficiently recovered to reduce the concentration of non-methane light hydrocarbons, thereby reducing the impact on the internal combustion engine. Then, the treated hydrocarbon-containing tail gas is transported to the internal combustion engine for high-efficiency power generation, realizing the cascade utilization of low-concentration hydrocarbon-containing tail gas.

[0027] Specifically, in a first aspect, the present invention provides a method for treating hydrocarbon-containing tail gas using air injection technology, such as Figure 1 As shown, steps S110-S130 may be included.

[0028] Step S110, performing shallow cold oil adsorption on the hydrocarbon-containing tail gas to separate non-methane light hydrocarbons and the first tail gas.

[0029] Among them, before the hydrocarbon-containing tail gas is subjected to shallow cold oil adsorption, the hydrocarbon-containing tail gas can also be pretreated. Specifically, the hydrocarbon-containing tail gas from the air injection production well can be filtered (dust and impurity removal), desulfurized and dried to form dust-free, dry and sulfur-free hydrocarbon-containing tail gas. For example, dust and other impurities in the hydrocarbon-containing tail gas can be removed by a precision filter; the sulfur in the hydrocarbon-containing tail gas can be removed by a desulfurization tank; and the moisture in the hydrocarbon-containing tail gas can be removed by a cyclone gravity dehydrator. It is worth noting that this step is to pretreat the hydrocarbon-containing tail gas containing impurities, but if it is a relatively clean or pure hydrocarbon-containing tail gas, some or all of the steps in the pretreatment step can be omitted according to actual conditions.

[0030] Then, the obtained dust-free, dry, and sulfur-free hydrocarbon-containing tail gas can be subjected to shallow cold oil adsorption to recover the non-methane light hydrocarbon components in the hydrocarbon-containing tail gas and reduce the content of non-methane light hydrocarbons in the hydrocarbon-containing tail gas. Figure 2 As shown, the specific method of performing shallow cold oil adsorption on hydrocarbon-containing tail gas may include S111-S113.

[0031] In step S111, the hydrocarbon-containing tail gas may be introduced into an absorption tower. Preferably, the hydrocarbon-containing tail gas may be introduced from the bottom of the absorption tower.

[0032] In addition, before the hydrocarbon-containing tail gas is passed into the absorption tower, the hydrocarbon-containing tail gas can be compressed and cooled. For example, after the compression treatment, the pressure of the hydrocarbon-containing tail gas can be increased to 2 to 2.6 MPa. After the cooling treatment, the temperature of the hydrocarbon-containing tail gas can be cooled to -20 to 10 degrees Celsius. Then, the compressed and cooled hydrocarbon-containing tail gas is passed into the absorption tower.

[0033] In step S112, an absorbent may be sprayed from the top of the absorption tower to generate a mixed liquid including the absorbent and non-methane light hydrocarbons at the bottom of the absorption tower, and a first tail gas may be generated at the top of the absorption tower.

[0034] The absorbent is sprayed from the top of the absorption tower, so that the absorbent can be easily diffused in the absorption tower. Moreover, this spraying method can make the absorbent contact more fully with the hydrocarbon-containing tail gas introduced from the bottom of the absorption tower, so as to increase the absorption effect of the absorbent.

[0035] In one embodiment, a C5 fraction containing one or more of n-pentane, isopentene, n-pentene and isopentene can be used as an absorbent, so that non-methane light hydrocarbons above C2 in the hydrocarbon-containing tail gas can be absorbed. For example, the non-methane light hydrocarbons can be various alkane gases such as ethane, propane, isobutane, n-butane, isopentane, and n-pentane. The inventors found in the implementation of the present invention that these components have a great influence on the stable operation of the internal combustion engine power generation, which can cause problems such as knocking and misfire of the internal combustion engine, affecting the normal operation of the internal combustion engine. At the same time, these non-methane light hydrocarbon components also have extremely high economic value. Therefore, the present invention selects a C5 fraction, which can better absorb the high-carbon components in the hydrocarbon-containing tail gas according to the principle of like dissolves like, so that the high-carbon components that affect the combustion of the internal combustion gas can be removed.

[0036] After the absorbent absorbs the non-methane light hydrocarbons, a mixed liquid including the absorbent and the non-methane light hydrocarbons will be produced at the bottom of the absorbent tower. At the same time, a first tail gas will be produced at the top of the absorbent tower. The first tail gas is the part of the hydrocarbon-containing tail gas that has been separated from the non-methane light hydrocarbons, thereby avoiding the effects of knocking during subsequent combustion in the internal combustion engine.

[0037] In step S113, the mixed liquid may be desorbed to separate non-methane light hydrocarbons.

[0038] Specifically, the mixed liquid produced at the bottom of the absorption tower is transported to the desorption tower for heating treatment, so that the non-methane light hydrocarbons can be recovered at the top of the desorption tower, and the separated absorbent can be obtained at the bottom of the desorption tower.

[0039] In one embodiment, the separated absorbent can be cooled step by step and returned to the absorption tower for recycling. This recyclable absorbent can save resources in the treatment process of hydrocarbon tail gas. In actual implementation, only a small amount of volatile absorbent needs to be regularly added to achieve long-term stable operation.

[0040] Through the above steps S111-S113, the non-methane light hydrocarbon components in the hydrocarbon-containing tail gas can be separated and efficiently recovered. On the one hand, the concentration of non-methane light hydrocarbons in the hydrocarbon-containing tail gas can be reduced, thereby reducing the impact on the internal combustion engine. On the other hand, the recovered non-methane light hydrocarbons also have extremely high economic value, which can increase economic benefits.

[0041] In addition, before the first tail gas is processed in the next step, the first tail gas can also be subjected to cold recovery. That is, after the hydrocarbon-containing tail gas is cooled and introduced into the shallow cold oil for adsorption, the temperature of the first tail gas obtained is in the range of -20 to 10 degrees Celsius, which contains a large amount of cold. If the first tail gas is directly discharged into the internal combustion engine for combustion, it will not only cause a waste of cold, but also affect the combustion efficiency of the internal combustion engine. Therefore, it is necessary to recover the cold of the first tail gas.

[0042] Specifically, the first tail gas (including the unabsorbed gas and part of the absorbent in the hydrocarbon tail gas) generated from the top of the absorption tower is passed into a system composed of an expander and a cold box, and then the pressure of the first tail gas itself is used for expansion and refrigeration, and flashed in a flash tank, thereby releasing the cold in the first tail gas. Next, the recovered cold can be further used to cool the hydrocarbon tail gas, thereby saving the energy consumed in the original cooling link. Then, the unabsorbed non-methane light hydrocarbon fraction and the entrained absorbent in the hydrocarbon tail gas can be recovered from the top of the flash tank, and the first tail gas after the cold is recovered is pressurized by a compressor and enters the internal combustion engine to generate electricity.

[0043] Step S120, detecting exhaust gas components of the first exhaust gas.

[0044] After the non-methane light hydrocarbons in the hydrocarbon-containing tail gas are absorbed through the shallow cold oil adsorption step, the tail gas components of the first tail gas obtained can be analyzed through the tail gas online monitoring system.

[0045] In one embodiment, the flow rate, pressure and gas composition data of the first tail gas can be obtained through a pressure measuring instrument, a gas composition chromatographic analyzer and a flow meter.

[0046] The purpose of step S120 is to obtain the flow rate, pressure and gas composition data of the first exhaust gas before the first exhaust gas is introduced into the internal combustion engine, so as to determine the control parameters matching the internal combustion engine, such as the intake mode, boost matching, air-fuel ratio control and ignition mode, etc., according to the above data and the required power generation.

[0047] Step S130 , according to the exhaust gas components of the first exhaust gas, delivering the first exhaust gas or the second exhaust gas including the first exhaust gas to the internal combustion engine, so that the internal combustion engine generates electricity.

[0048] In one embodiment, the above-mentioned delivering the first exhaust gas or the second exhaust gas containing the first exhaust gas to the internal combustion engine may include the following step S131 or S132.

[0049] Step S131, when the exhaust gas components of the first exhaust gas meet the set requirements, the first exhaust gas is directly delivered to the internal combustion engine.

[0050] Step S132, when the exhaust gas components of the first exhaust gas do not meet the set requirements, natural gas or associated gas is mixed into the first exhaust gas to obtain a second exhaust gas, and the second exhaust gas is delivered to the internal combustion engine.

[0051] In one embodiment, the setting requirement may be specifically: the concentration of methane in the exhaust gas component of the first exhaust gas is greater than or equal to a first preset value. This is because a methane concentration less than the first preset value may cause the internal combustion engine to fail to burn, so the concentration of methane in the exhaust gas component of the first exhaust gas needs to be limited to not less than the first preset value. Preferably, the first preset value is 10-15%, more preferably 15%.

[0052] Therefore, when the exhaust gas components of the first exhaust gas meet the set requirements, that is, when the concentration of methane in the exhaust gas components of the first exhaust gas is greater than or equal to the first preset value, the first exhaust gas can be directly delivered to the internal combustion engine.

[0053] When the exhaust gas components of the first exhaust gas do not meet the set requirements, that is, when the concentration of methane in the exhaust gas components of the first exhaust gas is less than the first preset value, it is necessary to mix natural gas or associated gas into the first exhaust gas to obtain a second exhaust gas, and transport the second exhaust gas to the internal combustion engine.

[0054] Specifically, when the concentration of methane in the exhaust gas component of the first exhaust gas is less than the first preset value, the internal combustion engine may not be able to burn due to the low concentration of the combustible gas. In this case, natural gas or associated gas containing a high concentration of methane may be mixed into the first exhaust gas to obtain a second exhaust gas that meets the set requirements, and the second exhaust gas can avoid causing the problem of the internal combustion engine not being able to burn.

[0055] The concentration of methane in the associated gas should be greater than or equal to the second preset value. The second preset value should be greater than the first preset value, so that after the first tail gas with a methane concentration less than the first preset value is mixed with the associated gas with a methane concentration greater than the second preset value, the second tail gas with a methane concentration greater than the first preset value can be obtained, thereby meeting the set requirements. Preferably, the second preset value is 30-45%, and more preferably 30%.

[0056] It is worth noting that when the inventor studied the tail gas law of air injection technology, he found that the tail gas produced by air injection technology in the oil field varies greatly from well to well. The proportion of hydrocarbons in some wells is more than 70% all year round, some are gradually decreasing, and some are even increasing. For wells where the proportion of hydrocarbons remains unchanged or even increases, there is no need for mixing to meet the set requirements. For wells with poor conditions (that is, their hydrocarbon content will show a decreasing concentration over time. That is to say, in the early stage of air injection technology, the hydrocarbon content in hydrocarbon-containing tail gas is high, and can even reach 80-90%. In the later stage of air injection technology, the hydrocarbon content in hydrocarbon-containing tail gas decreases and will gradually drop to less than 10%), it is necessary to take mixing treatment measures. Based on this law, the mixing system of high-concentration alkane tail gas stage and low-concentration hydrocarbon tail gas can be comprehensively coordinated to meet the intake composition and component requirements of the internal combustion engine.

[0057] For example, in the later stage of using air injection technology in a certain oil field, when the concentration of hydrocarbon-containing tail gas produced by it no longer meets the set requirements, it is possible to mix and utilize the wells with high methane content in the tail gas associated gas in the adjacent area of ​​the well, so that local materials can be used to mix the higher concentration associated gas of the adjacent area wells with the low concentration associated gas of the well to generate electricity. In another embodiment, the high concentration hydrocarbon tail gas produced by another oil field in the early stage of air injection technology can also be mixed with it as associated gas, so that the high concentration alkane tail gas and low concentration hydrocarbon tail gas produced by the oil field at different stages can be comprehensively utilized. Or multiple wells can be mixed together to generate electricity. Since many oil fields are generally concentrated with production wells, such an operation can effectively reduce the combustion instability caused by the rapid change of hydrocarbon concentration in a certain well. Through the above treatment, the hydrocarbon tail gas of both wells can meet the set requirements of internal combustion engine combustion power generation, thereby realizing the high-efficiency cascade utilization of low-concentration hydrocarbon tail gas.

[0058] In one embodiment, the associated gas may be associated gas generated using air injection technology in one or more oil and gas reservoirs such as heavy oil reservoirs, light oil reservoirs, low permeability reservoirs, condensate gas reservoirs, shale oil, shale gas, and oil shale.

[0059] In one embodiment, in the absence of available associated gas, other hydrocarbon-containing combustible gases may be used for mixing. For example, natural gas, such as bottled natural gas, may be used to mix the first tail gas to obtain a second tail gas that meets the set requirements.

[0060] It is worth noting that the higher the methane concentration of the associated gas, the smaller the required blending amount. The lower the methane concentration of the associated gas, the larger the required blending amount. Therefore, according to the measured gas composition of the first tail gas, a flow controller can be used to blend an appropriate amount of natural gas or high-concentration methane associated gas, so as to meet the intake composition and flow requirements of the internal combustion engine, and then transport it to the internal combustion engine for power generation.

[0061] In summary, the present invention first recovers the non-methane light hydrocarbon components in the low-concentration hydrocarbon-containing tail gas, and reduces the content of non-methane light hydrocarbons therein, thereby recovering the non-methane light hydrocarbons of high economic value while overcoming the detonation and misfire problems of the non-methane light hydrocarbons burning in the internal combustion engine, which is beneficial to the stable operation of the internal combustion engine. Then, the hydrocarbon-containing tail gas separated from the non-methane light hydrocarbons is passed into the internal combustion engine for power generation, thereby turning the low-concentration hydrocarbon-containing tail gas into treasure and reducing the processing cost of the low-concentration hydrocarbon-containing tail gas. By transforming the treatment of low-concentration hydrocarbon-containing tail gas from a pure input negative value link to a link that generates economic benefits, a high-efficiency cascade utilization of low-concentration hydrocarbon-containing tail gas is achieved.

[0062] On the other hand, the present invention also provides a system 200 for treating hydrocarbon-containing tail gas, such as Figure 3 As shown, it may include an adsorption device 210 , an exhaust gas detection and control device 220 , and an exhaust gas delivery device 230 .

[0063] The adsorption device 210 is used to perform shallow cold oil adsorption on the hydrocarbon-containing tail gas to separate non-methane light hydrocarbons and the first tail gas.

[0064] The treatment system 200 may also include a pretreatment device for pretreatment of the hydrocarbon-containing tail gas before shallow cold oil adsorption. Specifically, the pretreatment device may include filtering equipment, desulfurization equipment and drying equipment, which are respectively used to filter (dust removal and impurity removal), desulfurize and dry the hydrocarbon-containing tail gas of the air injection production well, so as to form dust-free, dry and sulfur-free hydrocarbon-containing tail gas. It is worth noting that the pretreatment device is used to pretreatment the hydrocarbon-containing tail gas containing impurities, but if it is a relatively clean or pure hydrocarbon-containing tail gas, some or all of the equipment in the pretreatment device can be discarded according to actual conditions.

[0065] Then, the obtained dust-free, dry, and sulfur-free hydrocarbon-containing tail gas can be subjected to shallow cold oil adsorption by the adsorption device 210 to recover the non-methane light hydrocarbon components in the hydrocarbon-containing tail gas and reduce the content of non-methane light hydrocarbons in the hydrocarbon-containing tail gas. The adsorption device 210 can also include a compression device, a cooling device, an absorption tower, and a desorption tower.

[0066] The compression equipment is used to compress the hydrocarbon-containing tail gas, and the cooling equipment is used to cool the hydrocarbon-containing tail gas. For example, the compression equipment can increase the pressure of the hydrocarbon-containing tail gas to 2-2.6 MPa. The cooling equipment can cool the temperature of the hydrocarbon-containing tail gas to -20-10 degrees Celsius.

[0067] The absorption tower is used to absorb the hydrocarbon-containing tail gas after compression and cooling.

[0068] Specifically, first, the hydrocarbon-containing tail gas is introduced into the absorption tower. Preferably, the hydrocarbon-containing tail gas can be introduced from the bottom of the absorption tower.

[0069] Secondly, the absorbent may be sprayed from the top of the absorption tower to generate a mixed liquid including the absorbent and non-methane light hydrocarbons at the bottom of the absorption tower, and to generate a first tail gas at the top of the absorption tower.

[0070] The absorbent is sprayed from the top of the absorption tower, so that the absorbent can be easily diffused in the absorption tower. Moreover, this spraying method can make the absorbent contact more fully with the hydrocarbon-containing tail gas introduced from the bottom of the absorption tower, so as to increase the absorption effect of the absorbent.

[0071] In one embodiment, a C5 fraction containing one or more of n-pentane, isopentene, n-pentene and isopentene can be used as an absorbent, so that non-methane light hydrocarbons above C2 in the hydrocarbon-containing tail gas can be absorbed. For example, the non-methane light hydrocarbons can be various alkane gases such as ethane, propane, isobutane, n-butane, isopentane, and n-pentane. The inventors found in the implementation of the present invention that these components have a great influence on the stable operation of the internal combustion engine power generation, which can cause problems such as knocking and misfire of the internal combustion engine, affecting the normal operation of the internal combustion engine. At the same time, these non-methane light hydrocarbon components also have extremely high economic value. Therefore, the present invention selects a C5 fraction, which can better absorb the high-carbon components in the hydrocarbon-containing tail gas according to the principle of like dissolves like, so that the high-carbon components that affect the combustion of the internal combustion gas can be removed.

[0072] After the absorbent absorbs the non-methane light hydrocarbons, a mixed liquid including the absorbent and the non-methane light hydrocarbons will be produced at the bottom of the absorbent tower. At the same time, a first tail gas will be produced at the top of the absorbent tower. The first tail gas is the part of the hydrocarbon-containing tail gas that has been separated from the non-methane light hydrocarbons, thereby avoiding the effects of knocking during subsequent combustion in the internal combustion engine.

[0073] The desorber is used to desorb the mixed liquid to separate non-methane light hydrocarbons.

[0074] Specifically, the desorption tower is used to heat the mixed liquid produced at the bottom of the absorption tower, so that non-methane light hydrocarbons can be recovered at the top of the desorption tower, and separated absorbent can be obtained at the bottom of the desorption tower.

[0075] In one embodiment, the desorption tower can also be used to cool the separated absorbent step by step and return it to the absorption tower for recycling. This recyclable absorbent can make the hydrocarbon tail gas treatment process more resource-saving. In the actual implementation process, only a small amount of volatile absorbent needs to be regularly added to achieve long-term stable operation.

[0076] The non-methane light hydrocarbon components in the hydrocarbon-containing tail gas can be separated and efficiently recovered by the above-mentioned compression equipment, cooling equipment, absorption tower and desorption tower. On the one hand, the concentration of non-methane light hydrocarbons in the hydrocarbon-containing tail gas can be reduced, thereby reducing the impact on the internal combustion engine. On the other hand, the recovered non-methane light hydrocarbons also have extremely high economic value, increasing economic benefits.

[0077] In addition, the adsorption device 210 may also include a cold recovery device for recovering cold from the first tail gas. That is, after the hydrocarbon-containing tail gas is cooled and introduced into the shallow cold oil for adsorption, the temperature of the first tail gas obtained is in the range of -20 to 10 degrees Celsius, which contains a large amount of cold. If the first tail gas is directly discharged into the internal combustion engine for combustion, it will not only cause a waste of cold, but also affect the combustion efficiency of the internal combustion engine. Therefore, it is necessary to recover the cold of the first tail gas through a cold recovery device.

[0078] Specifically, the cold recovery equipment may include an expander, a cold box, and a flash tank. First, the first tail gas (including the unabsorbed gas and part of the absorbent in the hydrocarbon tail gas) generated from the top of the absorption tower is passed into a system composed of an expander and a cold box, and then the pressure of the first tail gas itself is used for expansion refrigeration, and flashed in a flash tank, thereby releasing the cold in the first tail gas. Next, the recovered cold can be further used to cool the hydrocarbon tail gas, thereby saving the energy consumed in the original cooling link. Then, the unabsorbed non-methane light hydrocarbon fraction and the entrained absorbent in the hydrocarbon tail gas can be recovered from the top of the flash tank, and the first tail gas after the cold is recovered is pressurized by a compressor and enters the internal combustion engine to generate electricity.

[0079] The exhaust gas detection control device 220 is used to detect the exhaust gas components of the first exhaust gas.

[0080] Specifically, the exhaust gas detection control device 220 is used to obtain the flow rate, pressure and gas composition data of the first exhaust gas before the first exhaust gas is introduced into the internal combustion engine, so as to determine the control parameters matching the internal combustion engine, such as the intake mode, boost matching, air-fuel ratio control and ignition mode, etc., according to the above data and the corresponding power generation.

[0081] In one embodiment, the flow rate, pressure and gas composition data of the first tail gas can be obtained through a pressure measuring instrument, a gas composition chromatographic analyzer and a flow meter.

[0082] The exhaust gas delivery device 230 is used to deliver the first exhaust gas or the second exhaust gas including the first exhaust gas to the internal combustion engine according to the exhaust gas components of the first exhaust gas, so that the internal combustion engine can generate electricity.

[0083] In one embodiment, the above-mentioned delivery of the first exhaust gas or the second exhaust gas containing the first exhaust gas to the internal combustion engine may include: when the exhaust gas components of the first exhaust gas meet the set requirements, the first exhaust gas is directly delivered to the internal combustion engine; or when the exhaust gas components of the first exhaust gas do not meet the set requirements, natural gas or associated gas is mixed into the first exhaust gas to obtain the second exhaust gas, and the second exhaust gas is delivered to the internal combustion engine.

[0084] In one embodiment, the setting requirement may be specifically: the concentration of methane in the exhaust gas component of the first exhaust gas is greater than or equal to a first preset value. This is because a methane concentration less than the first preset value may cause the internal combustion engine to fail to burn, so the concentration of methane in the exhaust gas component of the first exhaust gas needs to be limited to not less than the first preset value. Preferably, the first preset value is 10-15%, more preferably 15%.

[0085] Therefore, when the exhaust gas components of the first exhaust gas meet the set requirements, that is, when the concentration of methane in the exhaust gas components of the first exhaust gas is greater than or equal to the first preset value, the first exhaust gas can be directly delivered to the internal combustion engine.

[0086] When the exhaust gas components of the first exhaust gas do not meet the set requirements, that is, when the concentration of methane in the exhaust gas components of the first exhaust gas is less than the first preset value, it is necessary to mix natural gas or associated gas into the first exhaust gas to obtain a second exhaust gas, and transport the second exhaust gas to the internal combustion engine.

[0087] Specifically, when the concentration of methane in the exhaust gas component of the first exhaust gas is less than the first preset value, the internal combustion engine may not be able to burn due to the low concentration of the combustible gas. In this case, natural gas or associated gas containing a high concentration of methane may be mixed into the first exhaust gas to obtain a second exhaust gas that meets the set requirements, and the second exhaust gas can avoid causing the problem of the internal combustion engine not being able to burn.

[0088] The concentration of methane in the associated gas should be greater than or equal to the second preset value. The second preset value should be greater than the first preset value, so that after the first tail gas with a methane concentration less than the first preset value is mixed with the associated gas with a methane concentration greater than the second preset value, the second tail gas with a methane concentration greater than the first preset value can be obtained, thereby meeting the set requirements. Preferably, the second preset value is 30-45%, and more preferably 30%.

[0089] It is worth noting that when the inventor studied the tail gas law of air injection technology, he found that the tail gas produced by air injection technology in the oil field showed a decreasing concentration law over time. That is to say, in the early stage of air injection technology, the hydrocarbon content in the hydrocarbon-containing tail gas is relatively high, and can even reach 80-90%. In the later stage of air injection technology, the hydrocarbon content in the hydrocarbon-containing tail gas decreases and gradually drops to below 10%. Based on this law, the mixing system of high-concentration alkane tail gas stage and low-concentration hydrocarbon tail gas can be comprehensively coordinated to meet the intake composition and component requirements of the internal combustion engine. For example, in the later stage of air injection technology in a certain oil field, when the concentration of the hydrocarbon tail gas produced by it no longer meets the set requirements, the high-concentration hydrocarbon tail gas produced in the early stage of air injection technology in another oil field can be mixed with it as associated gas, so as to coordinate the use of high-concentration alkane tail gas and low-concentration hydrocarbon tail gas produced in the oil field at different stages. Through the above treatment, the hydrocarbon-containing exhaust gases of both can meet the set requirements of internal combustion engine combustion power generation, thereby realizing the high-efficiency cascade utilization of low-concentration hydrocarbon-containing exhaust gases.

[0090] In one embodiment, the associated gas may be associated gas generated using air injection technology in one or more oil and gas reservoirs such as heavy oil reservoirs, light oil reservoirs, low permeability reservoirs, condensate gas reservoirs, shale oil, shale gas, and oil shale.

[0091] In one embodiment, when there is no available associated gas, other hydrocarbon-containing combustible gases may be used for mixing. For example, bottled natural gas available on the market may be used to mix the first tail gas to obtain a second tail gas that meets the set requirements.

[0092] It is worth noting that the higher the methane concentration of the associated gas, the smaller the required blending amount. The lower the methane concentration of the associated gas, the larger the required blending amount. Therefore, according to the measured gas composition of the first tail gas, a flow controller can be used to blend an appropriate amount of natural gas or high-concentration methane associated gas, so as to meet the intake composition and flow requirements of the internal combustion engine, and then transport it to the internal combustion engine for power generation.

[0093] In summary, the present invention first recovers the non-methane light hydrocarbon components in the low-concentration hydrocarbon-containing tail gas, and reduces the content of non-methane light hydrocarbons therein, thereby recovering the non-methane light hydrocarbons of high economic value while overcoming the detonation and misfire problems of the non-methane light hydrocarbons burning in the internal combustion engine, which is beneficial to the stable operation of the internal combustion engine. Then, the hydrocarbon-containing tail gas separated from the non-methane light hydrocarbons is passed into the internal combustion engine for power generation, thereby turning the low-concentration hydrocarbon-containing tail gas into treasure and reducing the processing cost of the low-concentration hydrocarbon-containing tail gas. By transforming the treatment of low-concentration hydrocarbon-containing tail gas from a pure input negative value link to a link that generates economic benefits, a high-efficiency cascade utilization of low-concentration hydrocarbon-containing tail gas is achieved.

[0094] On the other hand, the present invention also provides an internal combustion engine 300, which can generate electricity using the first exhaust gas or the second exhaust gas obtained by the above-mentioned hydrocarbon-containing exhaust gas treatment system 200. The internal combustion engine 300 can determine the control parameters that match the internal combustion engine, such as the intake mode, boost matching, air-fuel ratio control, and ignition mode, based on the flow rate, pressure, and gas component data of the first exhaust gas obtained by the exhaust gas detection control device 220 in the treatment system 200, combined with the required power generation, so as to achieve stable power generation of the exhaust gas.

[0095] In one embodiment, if Figure 4a As shown, the internal combustion engine 300 can be connected to the processing system 200 and can be used to transmit the generated electric energy to the processing system 200. For example, the internal combustion engine 300 can use the electric energy to directly electrically heat the desorption process of non-methane light hydrocarbons in the processing system 200.

[0096] In another embodiment, if Figure 4b As shown, the internal combustion engine 300 can also output electric energy to the power grid or supply it to the oil field for internal use. For example, the electric energy can be used to directly power the compressor used in the air injection technology.

[0097] The present invention passes hydrocarbon-containing tail gas separated from non-methane light hydrocarbons into an internal combustion engine for power generation, thereby turning low-concentration hydrocarbon-containing tail gas into valuables, and reducing the cost of treating low-concentration hydrocarbon-containing tail gas. At the same time, by transmitting the electric energy generated by the internal combustion engine to the treatment system of the hydrocarbon-containing tail gas for internal circulation, and converting the treatment of low-concentration hydrocarbon-containing tail gas from a pure input negative value link to a link that generates economic benefits, high-efficiency cascade utilization of low-concentration hydrocarbon-containing tail gas is achieved.

[0098] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0099] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for treating hydrocarbon-containing tail gas, characterized in that: The processing method comprises: The hydrocarbon-containing tail gas is subjected to shallow cold oil adsorption to separate non-methane light hydrocarbons and the first tail gas; detecting exhaust gas components of the first exhaust gas; and According to the exhaust gas component of the first exhaust gas, the first exhaust gas or the second exhaust gas containing the first exhaust gas is delivered to an internal combustion engine, so as to generate electricity by the internal combustion engine.

2. The processing method according to claim 1, characterized in that: The delivering the first exhaust gas or the second exhaust gas containing the first exhaust gas to the internal combustion engine comprises: When the exhaust gas components of the first exhaust gas meet the set requirements, directly delivering the first exhaust gas to the internal combustion engine; or When the exhaust gas components of the first exhaust gas do not meet the set requirements, natural gas or associated gas is mixed into the first exhaust gas to obtain a second exhaust gas, and the second exhaust gas is delivered to the internal combustion engine.

3. The processing method according to claim 2, characterized in that: The setting requirement is that the concentration of methane in the exhaust gas component of the first exhaust gas is greater than or equal to a first preset value.

4. The processing method according to claim 2, characterized in that: The associated gas is associated gas generated by air injection technology in one or more of a heavy oil reservoir, a light oil reservoir, a low permeability reservoir, a condensate gas reservoir, shale oil, shale gas, and oil shale; and The concentration of methane in the associated gas is greater than or equal to a second preset value, wherein the second preset value is greater than the first preset value.

5. The processing method according to claim 1, characterized in that: The step of subjecting the hydrocarbon-containing tail gas to shallow cold oil adsorption to separate non-methane light hydrocarbons and the first tail gas comprises: Passing the hydrocarbon-containing tail gas into an absorption tower; Spraying an absorbent from the top of the absorption tower to produce a mixed liquid including the absorbent and non-methane light hydrocarbons at the bottom of the absorption tower and the first tail gas at the top of the absorption tower; and The mixed liquid is desorbed to separate the non-methane light hydrocarbons.

6. The processing method according to claim 5, characterized in that: The absorbent is a C5 fraction comprising one or more of the following: n-pentane, isopentene, n-pentene and isopentene.

7. The processing method according to claim 1, characterized in that: Before the shallow cold oil adsorption is performed on the hydrocarbon-containing tail gas, the treatment method further comprises: pre-treating the hydrocarbon-containing tail gas, wherein the pre-treatment comprises one or more of the following: filtering, desulfurization and drying.

8. The processing method according to claim 1, characterized in that: Before detecting the exhaust gas components of the first exhaust gas, the processing method further includes: recovering cold energy from the first exhaust gas.

9. A system for treating hydrocarbon-containing tail gas, characterized in that: The processing system comprises: An adsorption device, used for performing shallow cold oil adsorption on the hydrocarbon-containing tail gas to separate non-methane light hydrocarbons and the first tail gas; an exhaust gas detection control device, used to detect exhaust gas components of the first exhaust gas; and The exhaust gas conveying device is used to convey the first exhaust gas or the second exhaust gas containing the first exhaust gas to the internal combustion engine according to the exhaust gas components of the first exhaust gas, so that the internal combustion engine can generate electricity.

10. An internal combustion engine, characterized in that: The internal combustion engine generates electricity using the first exhaust gas or the second exhaust gas obtained by the system for treating hydrocarbon-containing exhaust gas according to claim 9.

11. The internal combustion engine according to claim 10, characterized in that The internal combustion engine is connected to the processing system for transmitting the generated electrical energy to the processing system.

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