A resource recovery system for produced gas from oilfield fire-driven combustion

Abstract

This invention belongs to the field of produced gas treatment technology for fire-driven oilfields, specifically relating to a resource utilization system for produced gas from fire-driven oilfields. The system includes a pretreatment unit and a resource utilization unit. The pretreatment unit includes a cooling device, a purification device, and a desulfurization device. The resource utilization unit includes a circulating fluidized bed boiler and a carbon dioxide capture device. The cooling device, purification device, desulfurization device, circulating fluidized bed boiler, and carbon dioxide capture device are connected sequentially. The pretreatment unit performs cooling, dehumidification, impurity removal, and desulfurization treatments on the produced gas from fire-driven oilfields. The pretreated gas is then mixed and combusted in the circulating fluidized bed boiler. The combusted mixture enters the carbon dioxide capture device for carbon dioxide capture and reuse. This invention achieves the combustion and utilization of combustible components such as methane and carbon monoxide in the produced gas, and the capture and recovery of carbon dioxide from the combusted mixture, fully realizing the resource utilization of produced gas from fire-driven oilfields.

Description

Technical Field

[0001] This invention belongs to the field of fire-driven produced gas treatment technology, specifically relating to an oilfield fire-driven produced gas resource utilization system. Background Technology

[0002] Fire flooding is an extraction method that involves injecting air into the formation through an injection well, igniting it to create a radially moving combustion zone. The heat from the combustion of crude oil and air increases the formation temperature, reduces crude oil viscosity, enhances crude oil flowability, and increases formation energy. During combustion, oxygen in the air is consumed, and the remaining nitrogen, cracked gases, and combustion products are discharged through the production well, forming fire flooding exhaust gas. Fire flooding exhaust gas has a complex composition and a high concentration of organic waste gases. Treatment methods are categorized into recovery methods and disposal methods based on whether the gas has recycling value. Recovery methods include absorption, adsorption, condensation, and membrane separation, while disposal methods include high-temperature incineration, catalytic combustion, and biological oxidation. Incineration, with its advantages of high adaptability, high treatment efficiency, and low input cost, is widely used in various emitting industries. However, this method fails to recover and reuse the usable components in the fire flooding produced gas, thus failing to achieve resource recovery.

[0003] Patent document CN113731098A discloses an environmentally friendly resource-based treatment system and process flow for fire-driven exhaust gas, mainly including two processes: dry desulfurization and pressure swing adsorption. The dry desulfurization process reduces the hydrogen sulfide content to less than 10 mg / m³. 3 The patented process enriches methane in the fire-driven tail gas through pressure swing adsorption (PSA) denitrification to obtain methane-rich gas, which is then exported to the pipeline network as fuel gas. However, the process fails to recover and utilize the approximately 15% carbon dioxide in the fire-driven produced gas, thus failing to achieve full resource utilization.

[0004] Patent document CN107725018A discloses a treatment system for fire-driven exhaust gas. This patent dries and desulfurizes the fire-driven exhaust gas, separates carbon dioxide and nitrogen, achieves the separation of the harmful gas hydrogen sulfide, and further separates and utilizes different components of the exhaust gas, such as carbon dioxide and nitrogen. However, the method of this patent does not utilize alkane components such as methane and carbon monoxide in the fire-driven exhaust gas, and the resource recovery rate needs to be further improved. Summary of the Invention

[0005] This invention aims to address the technical problems existing in the background art by providing a resource utilization system for oilfield fire-driven produced gas. The system introduces the produced gas into a coal-fired circulating fluidized bed boiler for thermal oxidation treatment, then mixes it with the boiler's primary and secondary air before combustion in the furnace. This achieves the recovery and utilization of components such as methane and carbon monoxide in the produced gas as fuel, allowing it to provide heat to the boiler after combustion. Simultaneously, a carbon dioxide capture device recovers carbon dioxide from the mixed gas after combustion, further maximizing the resource utilization of the produced gas.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] A resource utilization system for produced gas from oilfield fire-driven flooding includes a pretreatment unit and a resource utilization unit.

[0008] The pretreatment unit is used to sequentially pretreat the produced gas from the fire-driven combustion by cooling, removing impurities and desulfurizing. The resource utilization unit is used to mix the pretreated gas into a circulating fluidized bed boiler for mixed combustion, and to capture and reuse the mixed gas after combustion by carbon dioxide.

[0009] The pretreatment unit includes a cooling device, a purification device, and a desulfurization device; the resource utilization unit includes a circulating fluidized bed boiler and a carbon dioxide capture device; the cooling device, purification device, desulfurization device, circulating fluidized bed boiler, and carbon dioxide capture device are connected in sequence.

[0010] Furthermore, the carbon dioxide capture device includes an exhaust fan, a flue gas separator, and a gas recovery device connected in sequence;

[0011] The induced draft device is used to introduce the mixed gas after combustion in the circulating fluidized bed boiler into the flue gas separation device.

[0012] The flue gas separation device is used to separate carbon dioxide from the mixed gas and transport it to the gas recovery device, while the remaining exhaust gas meets emission standards.

[0013] Furthermore, a booster compressor is provided between the flue gas separation device and the gas recovery device to boost the separated carbon dioxide.

[0014] Furthermore, the gas recovery device is a gas storage device used to store pressurized carbon dioxide.

[0015] Furthermore, the gas recovery device is an injection compressor, used to re-pressurize the pressurized carbon dioxide and reinject it into the oil reservoir for oil displacement.

[0016] Furthermore, the flue gas separation device employs a chemical absorption method for carbon dioxide capture.

[0017] Furthermore, the flue gas separation device employs the alkanolamine method for carbon dioxide capture.

[0018] Furthermore, the flue gas separation device is equipped with an exhaust pipe, which is connected to an exhaust gas treatment unit. The exhaust gas treatment unit treats the exhaust gas to meet the standards and then discharges it into the air.

[0019] Furthermore, the cooling device is an air cooler; the purification device is a high-efficiency gas purification device; the desulfurization device is a wet desulfurization device; and the induced draft device is an induced draft fan.

[0020] Furthermore, the circulating fluidized bed boiler is a coal-fired boiler. The combustion of the fire-driven produced gas with coal involves introducing the fire-driven produced gas into the boiler's air supply duct, and then mixing it into the boiler's primary and secondary air ducts to enter the boiler furnace, where it undergoes an oxidation decomposition reaction.

[0021] Furthermore, when the produced gas from fire-driven combustion is blended with coal, the measures for controlling the amount of produced gas incorporated include:

[0022] The boiler flue gas flow rate is monitored online, and the total amount of fire-driven produced gas is adjusted in real time based on the monitored boiler flue gas flow rate, so that the total amount of fire-driven produced gas is ≤ 20% of the boiler flue gas flow rate.

[0023] The boiler furnace temperature is monitored online, and the amount of fire-driven produced gas mixed into the primary air duct is adjusted in real time based on the monitored boiler furnace temperature to ensure that the boiler furnace temperature is between 850℃ and 900℃.

[0024] The oxygen content of the boiler tail flue gas is monitored online, and the amount of gas produced by the fire drive mixed into the secondary air duct is adjusted in real time according to the monitored oxygen content of the boiler tail flue gas to ensure that the oxygen content of the boiler tail flue gas is 3%-5%.

[0025] Furthermore, when the produced gas from the fire-driven combustion is mixed and burned with the circulating fluidized bed boiler, the gas pipeline from the fire-driven combustion is connected to the primary air pipeline from the fire-driven combustion to the boiler and the secondary air pipeline from the fire-driven combustion to the boiler, respectively.

[0026] The gas extracted from the fire drive is transported to the boiler primary air pipeline and the primary air inlet pipeline. After being combined, the gas is transported to the common air preheater by the primary air fan, and then enters the boiler furnace for combustion through the mixed primary air inlet pipeline.

[0027] The gas extracted from the fire drive is transported to the boiler secondary air pipeline and the secondary air inlet pipeline. After being collected, the gas is transported to the common air preheater by the secondary air fan, and then enters the boiler furnace for combustion through the mixed secondary air inlet pipeline.

[0028] The gas pipeline from the fire-driven extraction is equipped with an electric regulating valve and a gas flow meter; both the gas pipeline from the fire-driven extraction to the boiler primary air pipeline and the gas pipeline from the fire-driven extraction to the boiler secondary air pipeline are equipped with electric regulating valves.

[0029] Furthermore, manual shut-off valves are installed on the gas supply pipeline of the fire-driven extraction gas, the gas supply pipeline from the fire-driven extraction gas to the boiler primary air pipeline, and the gas supply pipeline from the fire-driven extraction gas to the boiler secondary air pipeline, in order to promptly cut off the supply pipeline in the event of a fire-driven extraction gas leakage safety fault.

[0030] Furthermore, check valves are installed on the gas supply pipeline of the fire-driven extraction gas, the gas supply pipeline from the fire-driven extraction gas to the boiler primary air pipeline, and the gas supply pipeline from the fire-driven extraction gas to the boiler secondary air pipeline to prevent backflow of the combustion medium.

[0031] Furthermore, an alarm is also installed on the gas pipeline of the fire-driven gas production line. The alarm is located downstream of the electric regulating valve of the gas pipeline of the fire-driven gas production line and is used to monitor whether there is a leak of harmful gas in the working environment.

[0032] The alarm is linked to the MFT trip protection system of the fluidized bed boiler. When the alarm detects that the harmful gas exceeds the standard, it will trigger an alarm and simultaneously trigger the MFT trip protection system to trip, which will then cut off the electric regulating valve on the gas pipeline of the fire-driven gas extraction, thereby achieving safety protection for the entire system.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] (1) The oilfield fire-driven produced gas resource utilization system provided by the present invention first pre-treats and desulfurizes the fire-driven produced gas, and then mixes it into a coal-fired circulating fluidized bed boiler for mixed combustion. The combustible components such as methane and carbon monoxide in the produced gas are used to provide heat for the boiler, reducing the fuel consumption of the boiler and reducing the coal consumption of the boiler by about 100 tons / day. At the same time, carbon dioxide in the mixed gas is recovered and reused for storage or reinjection into the oil reservoir through a carbon dioxide capture device. Through the above methods, the resource utilization of oilfield fire-driven produced gas is fully realized, and the resource utilization rate is high.

[0035] (2) Because boiler flue gas contains dust and impurities, traditional membrane separation methods are prone to membrane fouling, which affects the separation effect and makes it difficult to obtain high-purity carbon dioxide, which cannot meet the requirements of subsequent carbon dioxide reinjection into the oil reservoir for oil displacement. However, the oilfield fire-driven produced gas resource utilization system provided by this invention uses a chemical absorption method (such as the alkanolamine method) to separate carbon dioxide in boiler flue gas. This method can better capture low concentrations of carbon dioxide in boiler flue gas and has a better capture effect than traditional membrane separation methods.

[0036] (3) The oilfield fire-driven produced gas resource utilization system provided by the present invention, when fire-driven produced gas is co-fired with coal, introduces the fire-driven produced gas into the boiler air duct, and enters the boiler furnace through the primary and secondary air ducts of the circulating fluidized bed boiler, and then undergoes an oxidation decomposition reaction in the furnace; during co-fired combustion, the total amount of fire-driven produced gas is adjusted in real time by monitoring the boiler flue gas flow rate online, the amount of fire-driven produced gas mixed into the primary air duct is adjusted in real time by monitoring the boiler furnace temperature online, and the amount of fire-driven produced gas mixed into the secondary air duct is adjusted in real time by monitoring the oxygen content of the flue gas at the tail of the boiler online, thereby improving the combustion efficiency and maximizing the amount of fire-driven produced gas co-fired while ensuring safe and stable combustion operation of the coal-fired fluidized bed boiler;

[0037] (4) The oilfield fire-driven produced gas resource utilization system provided by this invention, by adding manual shut-off valves to the fire-driven produced gas inlet pipeline before the primary and secondary air ducts of the coal-fired circulating fluidized bed boiler and to the fire-driven produced gas to the boiler's primary and secondary air pipelines, can promptly cut off the corresponding pipelines in the event of a fire-driven produced gas leak or other safety accident, ensuring system production safety; by adding check valves to the fire-driven produced gas inlet pipeline and to the fire-driven produced gas to the boiler's primary and secondary air pipelines, it can prevent backflow of the combustion medium and avoid primary air leakage. Secondary air is backflowed into the fire-driven gas production pipeline to further ensure the safe and stable operation of the system. An alarm is installed on the downstream pipeline of the electric regulating valve on the fire-driven gas production pipeline to monitor whether harmful gases are leaking or exceeding the standard. The alarm is linked to the MFT trip protection system of the fluidized bed boiler. When the alarm sounds, it triggers the MFT trip protection system to trip, which in turn shuts off the electric regulating valve on the fire-driven gas production pipeline, thereby preventing the leakage of toxic and harmful gases and preventing carbon monoxide and hydrogen sulfide poisoning of workers, thus achieving safety protection for the entire system. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the oilfield fire-driven produced gas resource utilization system in Embodiment 1 of the present invention;

[0039] Figure 2 This is a schematic diagram of the pipeline control structure for co-firing produced gas from fire-driven combustion into a coal-fired circulating fluidized bed boiler in Embodiment 2 of the present invention.

[0040] Figure 3 This is a schematic diagram of the oilfield fire-driven produced gas resource utilization system in Embodiment 3 of the present invention;

[0041] Explanation of markings in the diagram: 1-Air cooler; 2-High-efficiency gas purification device; 3-Desulfurization device; 4-Coal-fired circulating fluidized bed boiler; 5-Induced draft fan; 6-Flue gas separator; 7-Tail gas discharge pipe; 8-Booster compressor; 9-Gas storage device; 10-Injection compressor; 11-Gas pipeline from fire-driven production; 12-#1 electric regulating valve; 13-#1 manual shut-off valve; 14-#1 check valve; 15-Gas flow meter; 16-Gas pipeline from fire-driven production to boiler primary air. Delivery pipelines; 17-Fire-driven gas extraction to boiler secondary air pipeline; 18-2# electric regulating valve; 19-2# manual shut-off valve; 20-2# check valve; 21-3# electric regulating valve; 22-3# manual shut-off valve; 23-3# check valve; 24-primary air inlet pipeline; 25-secondary air inlet pipeline; 26-primary air fan; 27-secondary air fan; 28-air preheater; 29-mixed primary air to boiler pipeline; 30-mixed secondary air to boiler pipeline. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1

[0044] This invention provides an oilfield fire-driven produced gas resource utilization system, including a pretreatment unit and a resource utilization unit. The pretreatment unit is used to perform pretreatment such as cooling, impurity removal and desulfurization on the fire-driven produced gas. The resource utilization unit is used to mix the pretreated gas into a circulating fluidized bed boiler for mixed combustion, and to capture and reuse carbon dioxide in the mixed gas after combustion.

[0045] Reference Figure 1 As shown, the pretreatment unit includes an air cooler 1, a high-efficiency gas purification device 2, and a desulfurization device 3; the resource utilization unit includes a circulating fluidized bed boiler 4, an induced draft fan 5, a flue gas separation device 6, a booster compressor 8, and a gas storage device 9; the air cooler 1, the high-efficiency gas purification device 2, the desulfurization device 3, the circulating fluidized bed boiler 4, the induced draft fan 5, the flue gas separation device 6, the booster compressor 8, and the gas storage device 9 are connected in sequence.

[0046] Specifically, the gas produced by fire-driven oil recovery in the oil gathering area is first introduced into air cooler 1 through pipelines for cooling.

[0047] After cooling, the gas enters the high-efficiency gas purification device 2 for gas-liquid separation, removal of smoke / dust / impurities, etc., and removal of small particulate dust and liquid droplets (including water and oil droplets) ≥5μm.

[0048] The purified gas enters desulfurization unit 3 for desulfurization treatment. Desulfurization unit 3 is a wet desulfurization unit, and the H2S concentration after desulfurization is less than or equal to 15 mg / Nm³. 3 .

[0049] The outlet of the desulfurization device 3 is connected to the circulating fluidized bed boiler 4. The pretreated fire-driven produced gas enters the circulating fluidized bed boiler 4 and is mixed with coal for combustion. In the boiler furnace, the fire-driven produced gas uses the heat generated by coal combustion to oxidize and decompose the organic waste gas, generating carbon dioxide and water. The combustible components such as methane and carbon monoxide in the produced gas are burned in the furnace, serving as part of the fuel to provide heat. The produced gas after thermal oxidation treatment enters the boiler flue gas treatment and emission system along with the boiler flue gas for carbon dioxide capture, recovery, tail gas treatment, and emission.

[0050] The circulating fluidized bed boiler 4 is a coal-fired boiler. The co-firing of fire-driven produced gas and coal involves introducing the fire-driven produced gas into the boiler's air supply duct, mixing it into the primary and secondary air ducts of the circulating fluidized bed boiler, and then allowing it to enter the boiler furnace, where it undergoes an oxidation and decomposition reaction.

[0051] In some embodiments, the circulating fluidized bed boiler can also be configured as multiple units operating in parallel to increase the processing capacity of the produced gas from the fire-driven combustion process, depending on the actual engineering needs.

[0052] Connected to the circulating fluidized bed boiler 4 is an induced draft fan 5, which is used to introduce the mixed gas after combustion in the boiler furnace into the flue gas separation device 6.

[0053] Because boiler flue gas contains dust and impurities, traditional membrane separation methods are prone to membrane fouling, affecting the separation effect and making it difficult to obtain high-purity carbon dioxide, which cannot meet the requirements of subsequent carbon dioxide reinjection into the oil reservoir for oil displacement. Therefore, the flue gas separation device 6 in this embodiment of the invention uses chemical absorption to separate carbon dioxide from boiler flue gas, specifically the amine method. This method can better capture lower concentrations of carbon dioxide in boiler flue gas and has a better capture effect than traditional membrane separation methods.

[0054] The flue gas separation device 6 is equipped with a tail gas emission pipe 7. The flue gas separation device 6 is used to separate carbon dioxide in the mixed gas and transport it to the booster compressor 8. The remaining tail gas is transported to the tail gas treatment unit through the tail gas emission pipe 7 for treatment, so that the content of dust, SO2, NOx and other substances in the flue gas meets the local boiler flue gas environmental protection index requirements before being discharged into the atmosphere.

[0055] The booster compressor 8 is used to boost the carbon dioxide separated from the flue gas and then deliver the boosted carbon dioxide to the gas storage device 9 for storage.

[0056] Example 2

[0057] This invention is based on Example 1, which effectively controls the amount of fire-driven produced gas incorporated into a coal-fired fluidized bed boiler. Under the premise of ensuring the safe and stable operation of the circulating fluidized bed boiler, it improves combustion efficiency and maximizes the amount of fire-driven produced gas produced by co-firing.

[0058] like Figure 3 The diagram shows a flow chart of the oilfield fire-driven produced gas resource utilization system in an embodiment of the present invention. The fire-driven produced gas pipeline 11 is connected to the fire-driven produced gas to boiler primary air pipeline 16 and the fire-driven produced gas to boiler secondary air pipeline 17. The fire-driven produced gas to boiler primary air pipeline 16 and the primary air inlet pipeline 24 are combined and then transported to a shared air preheater 28 by the primary air fan 26, and then enter the boiler furnace for combustion through the mixed primary air inlet pipeline 29. The fire-driven produced gas to boiler secondary air pipeline 17 and the secondary air inlet pipeline 25 are combined and then transported to a shared air preheater 28 by the secondary air fan 27, and then enter the boiler furnace for combustion through the mixed secondary air inlet pipeline 30.

[0059] The gas pipeline 11 for the fire-driven gas extraction is equipped with a No. 1 electric regulating valve 12 and a gas flow meter 15; the gas pipeline 16 for the fire-driven gas extraction to the boiler primary air pipeline is equipped with a No. 2 electric regulating valve 18; and the gas pipeline 17 for the fire-driven gas extraction to the boiler secondary air pipeline is equipped with a No. 3 electric regulating valve 21.

[0060] The control of the amount of produced gas incorporated into a coal-fired fluidized bed boiler includes the following specific control measures:

[0061] (1) Online monitoring of boiler flue gas flow rate. Generally, the CEMS continuous emission monitoring system is used to detect flue gas flow rate, flue gas parameters, etc. online. Based on the online monitoring of boiler flue gas flow, the total amount of fire-driven gas mixed in is adjusted in real time. Specifically, the total amount of fire-driven gas mixed in is controlled by the No. 1 electric regulating valve 12 and the gas flow meter 15. The total amount of fire-driven gas mixed in is controlled to be ≤ 20% of the boiler flue gas flow rate, thereby reducing the impact of mixed combustion on boiler thermal efficiency and ensuring stable boiler combustion.

[0062] (2) Monitor the boiler furnace temperature online and adjust the amount of fire-driven gas mixed into the primary air duct in real time according to the monitored boiler furnace temperature. Specifically, adjust the amount of fire-driven gas mixed into the primary air duct through the No. 2 electric regulating valve 18 on the fire-driven gas to boiler primary air pipeline 16 to ensure that the boiler furnace temperature is between 850℃ and 900℃, so that the circulating fluidized bed boiler bed temperature distribution is within a suitable range, which is conducive to the efficient staged combustion of the circulating fluidized bed boiler.

[0063] (3) Monitor the oxygen content of the flue gas at the tail of the boiler online, and adjust the amount of fire-driven gas mixed into the secondary air duct in real time according to the oxygen content of the flue gas monitored online. Specifically, adjust the amount of fire-driven gas mixed into the secondary air duct through the No. 3 electric regulating valve 21 on the fire-driven gas to boiler secondary air pipeline 17 to ensure that the oxygen content of the flue gas at the tail of the boiler is 3%-5% to ensure a reasonable excess air coefficient in the boiler furnace and to ensure safe and economical operation of the boiler.

[0064] Meanwhile, to ensure the safety of co-firing and combustion of produced gas from fire-driven coal-fired fluidized bed boilers, the following measures are adopted:

[0065] (1) Manual shut-off valve 13, manual shut-off valve 19 and manual shut-off valve 22 are installed on the gas pipeline 11 from the fire-driven gas production line, the gas pipeline 16 from the fire-driven gas production line to the boiler primary air pipeline, and the gas pipeline 17 from the fire-driven gas production line to the boiler secondary air pipeline, respectively. These valves are used to cut off the corresponding pipelines in time and block the delivery of the fire-driven gas production line in the event of a fire-driven gas production leak or other safety accident, thereby ensuring the safety of system production.

[0066] (2) On the gas pipeline 11 from the fire-driven gas production line, the gas pipeline 16 from the fire-driven gas production line to the boiler primary air pipeline, and the gas pipeline 17 from the fire-driven gas production line to the boiler secondary air pipeline, respectively, check valve 14, check valve 20 and check valve 23 are installed. The check valves can prevent the combustion medium from flowing back and prevent the primary air and secondary air from flowing back into the gas pipeline from the fire-driven gas production line, thereby further ensuring the safe and stable operation of the system.

[0067] (2) An alarm is also installed on the gas pipeline 11 for the fire-driven gas production. The alarm is located downstream of the No. 1 electric regulating valve 12 of the gas pipeline 11 for the fire-driven gas production. It is used to monitor whether there is a leak of harmful gases such as carbon monoxide and hydrogen sulfide in the working environment. The alarm is linked to the MFT trip protection system of the fluidized bed boiler. When the alarm detects that the harmful gas exceeds the standard, it will issue an audible and visual alarm and trigger the MFT trip protection system to trip at the same time, and shut off the No. 1 electric regulating valve 12 on the gas pipeline 11 for the fire-driven gas production. This will prevent the leakage of toxic and harmful gases and prevent workers from being poisoned by carbon monoxide and hydrogen sulfide, thereby achieving safety protection for the entire system.

[0068] Example 3

[0069] The present invention is based on embodiment 1 or 2, in which the gas storage device 9 is replaced by the injection compressor 10.

[0070] The injection compressor 10 is used to re-pressurize the pressurized carbon dioxide and then reinject it into the reservoir for oil displacement.

[0071] Example 4

[0072] This embodiment of the invention is based on Example 3, and focuses on the processing of produced gas from fire-driven oilfields to further illustrate the overall process flow of the fire-driven produced gas resource utilization system in this invention.

[0073] Combination Figure 1 As shown in Figure 2, the system includes the following devices: an air cooler 1, a high-efficiency gas purification device 2, a desulfurization device 3, a circulating fluidized bed boiler 4, an induced draft fan 5, a flue gas separation device 6, a tail gas emission pipe 7, a booster compressor 8, a gas storage device 9, or an injection compressor 10.

[0074] The daily produced gas from the fire-driven oilfield is approximately 70 × 10⁻⁶. 4 Nm 3 / d, the composition of the produced gas from fire-driven flooding is shown in Table 1 below:

[0075] Table 1 Composition of Gas Produced by Fire Dredging

[0076]

[0077] The process flow of the fire-driven produced gas resource utilization system according to an embodiment of the present invention specifically includes the following steps:

[0078] The produced gas from the fire-driven oilfield (temperature T = 30-60℃) first enters air cooler 1 for cooling, reducing the temperature to 30-40℃.

[0079] The outlet of the air cooler 1 is connected to a high-efficiency gas purification device 2 through a pipeline for gas-liquid separation, dust removal, and solidification, removing small particles of dust and oil droplets ≥5μm.

[0080] The outlet of the high-efficiency gas purification device 2 is connected to the desulfurization device 3 via a pipeline. The desulfurization device 3 is a wet desulfurization device that removes H2S from the fire-driven produced gas to 15 mg / m³. 3 .

[0081] The outlet of the desulfurization unit 3 is connected to the circulating fluidized bed boiler 4 via a pipeline. In this embodiment of the invention, the circulating fluidized bed boiler 4 consists of two coal-fired circulating fluidized bed boilers, each handling half of the fire-driven produced gas flow rate. Half of the fire-driven produced gas flow rate is approximately 14583 Nm³. 3 / h. The total hydrocarbons in the produced gas from the fire-driven combustion are oxidized and decomposed in the furnace of the coal-fired circulating fluidized bed boiler, and then enter the flue gas treatment system of the coal-fired circulating fluidized bed boiler along with the flue gas generated by the boiler.

[0082] The composition of boiler flue gas before and after thermal oxidation treatment of the fire-driven produced gas in circulating fluidized bed boiler 4 is shown in Table 2 below. It can be seen that after the fire-driven produced gas is mixed into the coal-fired fluidized bed boiler 4 for thermal oxidation and dehydrocarbonization, the concentrations of CO2 and N2 increase slightly, while the concentrations of SO2 and O2 decrease slightly. The changes of the main gas components before and after mixing are not obvious.

[0083] Table 2. Composition of flue gas before and after produced gas from coal-fired circulating fluidized bed co-firing.

[0084] Components <![CDATA[CO2]]> <![CDATA[SO2]]> <![CDATA[H2O]]> <![CDATA[N2]]> <![CDATA[O2]]> Content before co-firing 11.8％ 0.04％ 9.00％ 73.59％ 5.57％ Content after blending 12.00％ 0.03％ 8.55％ 74.39％ 5.02％

[0085] The outlet of the flue gas treatment device of the circulating fluidized bed boiler 4 is connected to the induced draft fan 5 through a pipeline. The outlet of the induced draft fan 5 is connected to the flue gas separation device 6, which uses chemical absorption to separate carbon dioxide from the boiler flue gas.

[0086] The flue gas separation device 6 connects the separated carbon dioxide gas to the booster compressor 8, and the remaining exhaust gas is transported to the exhaust gas treatment unit through the exhaust gas discharge pipe 7 for treatment, so that the content of dust, SO2, NOx and other substances in the flue gas meets the local boiler flue gas environmental protection index requirements before being discharged into the atmosphere.

[0087] The booster compressor 8 pressurizes the carbon dioxide and delivers the pressurized carbon dioxide to the gas storage device 9 for storage. Alternatively, the booster compressor 8 is connected to the injection compressor 10, which pressurizes the pressurized carbon dioxide a second time and then reinjects it into the oil reservoir for oil displacement.

[0088] The system of this invention realizes the resource utilization of produced gas from fire-driven production. After pretreatment and desulfurization, the produced gas is thermally oxidized by a coal-fired circulating fluidized bed boiler, which can reduce the coal consumption of the boiler by about 100 tons / day. The carbon dioxide in the mixed gas after combustion is captured, recovered and utilized, thus fully realizing the resource utilization of produced gas from fire-driven production with a high resource utilization rate.

[0089] The above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for the resource utilization of produced gas from oilfield fire-driven flooding, characterized in that, Includes a pretreatment unit and a resource utilization unit; The pretreatment unit is used to sequentially pretreat the produced gas from the fire-driven combustion by cooling, removing impurities and desulfurizing. The resource utilization unit is used to mix the pretreated gas into a circulating fluidized bed boiler for mixed combustion, and to capture and reuse the mixed gas after combustion by carbon dioxide. The pretreatment unit includes a cooling device, a purification device, and a desulfurization device; the resource utilization unit includes a circulating fluidized bed boiler and a carbon dioxide capture device. The cooling device, purification device, desulfurization device, circulating fluidized bed boiler, and carbon dioxide capture device are connected in sequence. The circulating fluidized bed boiler is a coal-fired boiler. The combustion of fire-driven produced gas with coal involves introducing the fire-driven produced gas into the boiler's air supply duct, and then mixing it into the boiler's furnace through the primary and secondary air ducts of the circulating fluidized bed boiler, where it undergoes an oxidation decomposition reaction. When the produced gas from fire-driven combustion is blended with coal, the measures for controlling the amount of produced gas blended include: The boiler flue gas flow rate is monitored online, and the total amount of fire-driven produced gas is adjusted in real time based on the monitored boiler flue gas flow rate, ensuring that the total amount of fire-driven produced gas is ≤ 20% of the boiler flue gas flow rate; The boiler furnace temperature is monitored online, and the amount of fire-driven produced gas mixed into the primary air duct is adjusted in real time based on the monitored boiler furnace temperature to ensure that the boiler furnace temperature is between 850℃ and 900℃. The oxygen content of the boiler tail flue gas is monitored online, and the amount of gas mixed into the secondary air duct is adjusted in real time according to the monitored oxygen content to ensure that the oxygen content of the boiler tail flue gas is 3%-5%. The gas pipelines for fire-driven extraction are connected to the primary air pipeline of the fire-driven extraction and the secondary air pipeline of the fire-driven extraction to the boiler, respectively. The gas extracted from the fire drive is transported to the boiler primary air pipeline and the primary air inlet pipeline. After being combined, the gas is transported to the common air preheater by the primary air fan, and then enters the boiler furnace for combustion through the mixed primary air inlet pipeline. The gas extracted from the fire drive is transported to the boiler secondary air pipeline and the secondary air inlet pipeline. After being collected, the gas is transported to the common air preheater by the secondary air fan, and then enters the boiler furnace for combustion through the mixed secondary air inlet pipeline. The gas pipeline from the fire-driven extraction is equipped with an electric regulating valve and a gas flow meter; both the gas pipeline from the fire-driven extraction to the boiler primary air pipeline and the gas pipeline from the fire-driven extraction to the boiler secondary air pipeline are equipped with electric regulating valves. Manual shut-off valves are installed on the gas pipeline from the fire-driven extraction gas, the gas pipeline from the fire-driven extraction gas to the boiler primary air pipeline, and the gas pipeline from the fire-driven extraction gas to the boiler secondary air pipeline. These valves are used to cut off the pipeline in time in case of a fire-driven extraction gas leakage safety fault. Check valves are installed on the gas pipeline from the fire-driven extraction, the gas pipeline from the fire-driven extraction to the boiler primary air pipeline, and the gas pipeline from the fire-driven extraction to the boiler secondary air pipeline to prevent backflow of the combustion medium. An alarm is also installed on the gas pipeline of the fire-driven gas production line. The alarm is located downstream of the electric regulating valve of the gas pipeline of the fire-driven gas production line and is used to monitor whether there is a leak of harmful gas in the working environment. The alarm is linked to the MFT trip protection system of the fluidized bed boiler. When the alarm detects that the harmful gas exceeds the standard, it will issue an alarm prompt and simultaneously trigger the MFT trip protection system to trip, which will then cut off the electric regulating valve on the gas pipeline of the fire-driven gas extraction, thereby achieving safety protection for the entire system.

2. The system according to claim 1, characterized in that, The carbon dioxide capture device includes an exhaust fan, a flue gas separator, and a gas recovery device connected in sequence. The induced draft device is used to introduce the mixed gas after combustion in the circulating fluidized bed boiler into the flue gas separation device. The flue gas separation device is used to separate carbon dioxide from the mixed gas and transport it to the gas recovery device, while the remaining exhaust gas meets emission standards.

3. The system according to claim 2, characterized in that, A booster compressor is installed between the flue gas separation device and the gas recovery device to boost the pressure of the separated carbon dioxide.

4. The system according to claim 3, characterized in that, The gas recovery device is a gas storage device used to store pressurized carbon dioxide.

5. The system according to claim 3, characterized in that, The gas recovery device is an injection compressor, which is used to re-pressurize the pressurized carbon dioxide and reinject it into the oil reservoir for oil displacement.

6. The system according to claim 2, characterized in that, The flue gas separation device uses chemical absorption to capture carbon dioxide.

7. The system according to claim 6, characterized in that, The flue gas separation device uses the alkanolamine method for carbon dioxide capture.

8. The system according to claim 2, characterized in that, The flue gas separation device is equipped with an exhaust gas pipe, which is connected to an exhaust gas treatment unit. The exhaust gas treatment unit treats the exhaust gas to meet the standards and then discharges it into the air.

9. The system according to claim 2, characterized in that, The cooling device is an air cooler; the purification device is a high-efficiency gas purification device; the desulfurization device is a wet desulfurization device; and the induced draft device is an induced draft fan.

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