A loading dock oil vapor recovery apparatus

Abstract

This invention belongs to the field of environmental protection and resource recycling technology, and relates to an oil and gas recovery device for a loading platform. It includes an oil and gas collection unit, a pretreatment unit, a multi-stage condensation unit, a gas-liquid separation unit, a liquid nitrogen supply and cold energy recovery unit, a recovered oil processing unit, and an intelligent control system. The liquid nitrogen supply and cold energy recovery unit transfers the cooling energy of liquid nitrogen to the multi-stage condensation unit in stages, fully utilizing the cold energy of liquid nitrogen for deep condensation of the oil and gas, avoiding waste of cooling energy. The pretreatment unit removes impurities and some heavy components from the oil and gas, preventing impurities from clogging subsequent pipelines and affecting the condensation and separation effect, and also reducing the cooling energy loss caused by heavy components directly entering the low-temperature condensation unit. The multi-stage condensation unit progressively lowers the condensation temperature along the oil and gas transport direction, allowing oil and gas components with different boiling points to be condensed and separated sequentially, ensuring recovery efficiency while avoiding excessive cooling energy consumption caused by one-time deep condensation.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and resource recycling technology, specifically a loading platform oil and gas recovery device. Targeting the oil and gas volatilized and emitted during the loading process at loading platforms in the petrochemical industry, this device can achieve efficient recovery. While ensuring that the concentration of non-methane total hydrocarbons in the exhaust gas meets the requirements of current environmental protection standards, it fully recovers the cold energy of liquid nitrogen, reducing the overall energy consumption of the equipment and avoiding the problems of low cold energy utilization and high operating costs of traditional condensation recovery processes. Background Technology

[0002] During the loading of oil products onto tank trucks, a large amount of oil vapor is released from the tankers. Its main components are low-carbon hydrocarbons, which are not only a significant source of VOCs pollution but also have extremely high recovery value. Currently, commonly used oil vapor recovery technologies mainly include adsorption, absorption, membrane separation, and condensation.

[0003] Adsorption methods separate oil and gas using adsorbents, but they suffer from drawbacks such as adsorbent failure, high replacement costs, safety risks, and high energy consumption. Absorption methods recover oil and gas using absorbents, but suffer from absorbent loss, low recovery rates for light components, large equipment size, and high energy consumption. Membrane separation relies on the selective permeability of membranes, but it is sensitive to inlet gas conditions, prone to membrane fouling, has a short lifespan, and single-stage separation is incomplete. Condensation methods liquefy oil and gas through cooling; shallow / medium cooling (-35℃ to -70℃) has insufficient capacity for recovering light hydrocarbons, while traditional cryogenic (below -100℃) technologies are complex, with extremely high equipment investment and operating energy consumption, making them unaffordable for most companies.

[0004] To balance efficiency and economy, combined processes such as "adsorption + condensation" and "membrane + condensation" have emerged. However, these processes significantly increase system complexity, energy consumption, and floor space, and still do not fundamentally solve the problem of efficient recovery of light components (such as C2 components). Therefore, the current field of vehicle-mounted oil and gas recovery faces common challenges, including the difficulty in achieving both efficiency and economy, poor adaptability to intermittent fluctuations in operating conditions, and high total life-cycle costs.

[0005] Liquid nitrogen, as an readily available, low-temperature (boiling point at atmospheric pressure -196℃), and inert industrial product, holds promise for oil and gas recovery. However, key challenges remain, including how to achieve efficient, stable, and economical coupling, and address issues such as antifreeze, energy cascade utilization, and system integration control. In recent years, some patented technologies have attempted to apply cryogenic liquid nitrogen to oil and gas recovery, but many limitations still exist. Chinese patent CN222317372U discloses an adsorption-desorption and liquid nitrogen cryogenic system for oil and gas recovery. This technical solution connects a shallow cooling unit, an adsorption-desorption unit, and a liquid nitrogen cryogenic recovery unit in series. Liquid nitrogen is used for cryogenic cooling to reduce energy consumption, and the vaporized nitrogen is recovered to the plant's nitrogen pipeline network for reuse. However, this system still relies on the adsorption-desorption unit, resulting in a complex process flow, high equipment investment and operation and maintenance costs, and it does not achieve efficient cascade utilization of liquid nitrogen cooling energy; therefore, there is still room for improvement in overall energy efficiency.

[0006] Chinese patent CN213327463U discloses a liquid nitrogen condensate oil and gas recovery and treatment system with high cold energy recovery. This system utilizes a multi-stage cold box and a gas-liquid separator to provide cooling to the multi-stage cold boxes using purified low-temperature oil and gas and low-temperature liquid nitrogen, achieving partial cold energy recovery. However, its cold energy recovery network is relatively simple, mainly relying on the oil and gas's own circulation heat exchange. It fails to fully utilize the cold energy of the low-temperature nitrogen gas after liquid nitrogen vaporization for systematic cascade utilization, and it does not address the frosting problem in the cryogenic section, resulting in insufficient reliability for continuous operation.

[0007] Chinese patent CN212320161U discloses a non-stop, self-defrosting, dual-channel oil-gas recovery condensing unit. This unit employs a dual-channel oil-gas switching system, achieving an alternating operating mode where one channel operates while the other defrosts, ensuring long-term continuous operation. However, this technology is mainly applied to mechanical refrigeration condensing units, whose defrosting process typically relies on high-temperature refrigerant discharged from the compressor or electric heating, resulting in high energy consumption. Furthermore, it is not combined with liquid nitrogen cryogenic technology, making it unable to achieve deep condensation below -100℃, thus limiting the recovery efficiency of light hydrocarbon components.

[0008] In summary, existing technologies either fail to organically integrate key technologies such as deep cryogenic liquid nitrogen, efficient cascade recovery of cold energy, reuse of nitrogen working fluid, and non-stop defrosting; or they are complex, energy-intensive, and have poor adaptability. Therefore, there is an urgent need for a high-efficiency loading platform oil and gas recovery device that can deeply utilize liquid nitrogen cold energy, achieve a closed-loop nitrogen resource system, and adapt to continuous and stable operation under intermittent loading conditions. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art, solve the problems of difficulty in balancing efficiency and economy in cryogenic recovery and poor adaptability to intermittent loading conditions, and seek to design and provide a loading platform, especially a recovery device.

[0010] To achieve the above-mentioned objective, the present invention provides a loading platform oil and gas recovery device, comprising: [the following components are connected sequentially via pipelines] The oil and gas collection unit is used to collect volatile organic compounds (VOCs) oil and gas generated at the loading platform. Specifically, it includes a gas collection branch pipe connected to the loading arm, a main collection pipe, a pressure balancing valve, and safety devices (such as flame arresters). The pressure balancing valve ensures that the internal pressure of the tanker is stable during the oil loading process, and the safety device is used to prevent backfire and other safety hazards. Its function is to effectively collect the escaping oil and gas at the source and provide a stable gas source for subsequent processing. The pretreatment unit is used to filter and stabilize the oil and gas; it typically includes a filter and a buffer tank. The filter removes particulate matter, droplets, and other impurities entrained in the oil and gas, preventing them from damaging or clogging subsequent equipment; the buffer tank buffers the drastic fluctuations in oil and gas flow and pressure caused by the intermittent loading operation, providing relatively stable and continuous air intake conditions for the subsequent condensation unit and improving the stability of system operation. The multi-stage condensation unit includes a primary precooling module and a secondary cryogenic module. The primary precooling module precools the oil and gas to a first temperature range (e.g., 0°C to -5°C), at which temperature most of the water and high-boiling-point heavy hydrocarbon components (such as C5 and above) in the oil and gas are condensed and precipitated. The secondary cryogenic module includes a liquid nitrogen cryogenic heat exchanger, which uses the heat absorption of liquid nitrogen vaporization to further cool the precooled oil and gas to a lower second temperature range (e.g., -110°C to -180°C). At this cryogenic temperature, the dew points of most hydrocarbon components, including light components (C1-C4) such as methane, ethane, and ethylene, are also crossed, thus being liquefied and precipitated. The multi-stage condensation design achieves the cascade utilization of cooling capacity, first removing water and high-boiling-point substances to prevent them from freezing and clogging in the cryogenic section, and then selectively and deeply condensing light components, significantly improving the overall recovery efficiency and energy efficiency. The gas-liquid separation unit is connected to the outlets of the primary precooling module and the secondary cryogenic module. It is used to separate the liquid substances (including condensate and liquid hydrocarbons) obtained from condensation. It is usually a separation tank that uses gravity settling and / or cyclone separation principles to separate the denser droplets from the gas phase and discharge them separately, ensuring the purity of the purified exhaust gas and the quality of the recovered oil. The liquid nitrogen supply and cold energy recovery unit includes a liquid nitrogen storage tank and a cold energy recovery network. The liquid nitrogen storage tank and pressure regulating conveying system are used to store liquid nitrogen and stably supply it to the liquid nitrogen cryogenic heat exchanger as needed. The cold energy recovery network is the key to achieving high efficiency and energy saving in this invention. It guides and recovers the nitrogen gas (referred to as cryogenic nitrogen gas) generated by the vaporization of liquid nitrogen in the cryogenic heat exchanger, which is still at an extremely low temperature (e.g., below -100°C). This network guides at least a portion of this cryogenic nitrogen gas to the first-stage precooling module as part of its precooling cold source, replacing or assisting traditional mechanical refrigeration, thereby significantly reducing the energy consumption of the precooling section. Its function is to maximize the utilization of the cold energy of liquid nitrogen and realize the circulation and optimization of energy within the system. The oil recovery processing unit is used to collect and transport the liquid oil separated by the gas-liquid separation unit; it typically includes a condensate storage tank and a transfer pump to pump the recovered liquid hydrocarbons back to the raw material storage tank or a dedicated collection tank for resource recycling. In addition, an intelligent control system is used to adjust the operating parameters of the liquid nitrogen supply and cold energy recovery unit and the opening degree of valves on each pipeline in real time according to the system operating parameters. Its core function is to automatically adjust the liquid nitrogen injection volume and control the opening, closing and switching of each valve through a programmable logic controller (PLC) or distributed control system (DCS) based on real-time data fed back by sensors (such as temperature, pressure, flow and liquid level sensors) to adapt to changes in loading flow and oil and gas concentration, realize on-demand cooling, safety interlock and minimum energy consumption operation, and improve the automation level and operating economy of the system. The volatile oil and gas generated at the loading platform involved in this invention are first centrally extracted and collected by an oil and gas collection unit, and then sent to a pretreatment unit to filter out impurities mixed in the oil and gas, and adjust the oil and gas pressure in the pipeline to a stable range to avoid pressure fluctuations affecting separation efficiency during subsequent condensation. The pretreated oil and gas first enters the primary precooling module, where it is cooled to the first temperature range by low-temperature nitrogen from the cold energy recovery network, causing the water and large molecular weight components contained in the oil and gas to condense first, and then initially separating liquid impurities after entering the gas-liquid separation unit. The oil and gas that has been precooled and removed of heavy components is then sent to the liquid nitrogen cryogenic heat exchanger of the secondary cryogenic module, where it exchanges heat directly or indirectly with liquid nitrogen. The liquid nitrogen rapidly vaporizes and absorbs a large amount of heat, cooling the oil and gas to a lower second temperature range, allowing almost all the remaining light hydrocarbon components in the oil and gas to condense and liquefy. The condensed mixture is sent to a gas-liquid separation unit to separate liquid oil and non-condensable gas. The liquid oil is temporarily stored in a recovery oil treatment unit before being transferred, while the non-condensable gas can be connected to subsequent treatment devices as needed for discharge after meeting emission standards. The low-temperature nitrogen generated by liquid nitrogen vaporization is not directly discharged but is transported to the primary pre-cooling module through a cold energy recovery network to pre-cool the incoming high-temperature oil and gas, fully recovering and utilizing the cold energy of liquid nitrogen, significantly reducing liquid nitrogen consumption and operating costs. At the same time, the intelligent control system collects the temperature, pressure, and flow parameters of each unit in real time, automatically adjusting the output flow of the liquid nitrogen storage tank and the opening of valves in each pipeline to ensure stable operation of the entire oil and gas recovery process and ensure that the oil and gas recovery efficiency meets emission standards.

[0011] The secondary cryogenic module of this invention adopts a skid-mounted structure, including a first cryogenic branch and a second cryogenic branch connected in parallel and switchable in operation. Each cryogenic branch includes a pre-cooling condenser, a cryogenic condenser, and a corresponding gas-liquid separator and control valve group connected in series. The intelligent control system is configured to control the switching between the first and second cryogenic branches, so that when one branch is running, the other branch can be defrosted or kept on standby. When the operating branch experiences internal frost buildup due to prolonged low-temperature operation, affecting heat exchange efficiency, the intelligent control system automatically switches to the other branch to continue operation. Workers can then defrost and de-ice the frosted branch without shutting down the entire machine, ensuring continuous and uninterrupted oil and gas recovery operations. Loading operations are not interrupted due to equipment defrosting, thus improving the continuity and efficiency of the entire equipment operation.

[0012] The defrosting process described in this invention is achieved by introducing room temperature or heated nitrogen gas into the heat exchanger tubes of the cryogenic branch to be defrosted. The nitrogen gas exchanges heat with the frost layer adhering to the shell side, melting it. The melted liquid flows into a condensate collection tank. Room temperature nitrogen gas can be directly obtained from the vaporized nitrogen in the cold energy recovery network, eliminating the need for an additional defrosting heat source. After defrosting, to further utilize the cold energy absorbed by the nitrogen during defrosting, the nitrogen gas carrying the absorbed cold energy is sent to the primary pre-cooling module to continue participating in heat exchange, improving the overall cold energy utilization rate. This also eliminates the need to introduce impurities, avoiding pollution of the original oil and gas system. The defrosted liquid is collected and treated in a condensate collection tank, preventing on-site environmental pollution.

[0013] The cold energy recovery network described in this invention also includes an exhaust gas reheater. The purified exhaust gas after treatment by the secondary cryogenic module has an extremely low temperature (down to -150℃). If directly emitted, it would cause frost formation at the exhaust port and surrounding area, generating a large amount of white water mist ("white smoke"), affecting the environment and potentially causing cold damage. Through the exhaust gas reheater, the low-temperature purified exhaust gas exchanges heat with low-temperature nitrogen from the liquid nitrogen cryogenic heat exchanger, and the exhaust gas is reheated to ambient temperature before being emitted. This design has three advantages: first, it recovers the residual cold energy in the exhaust gas, further improving system energy efficiency; second, it completely solves the visual pollution and frost problems of low-temperature emissions, making it environmentally friendly; and third, it provides stable temperature conditions for possible subsequent online monitoring of the exhaust gas. After absorbing the cold energy of the exhaust gas, the temperature of the low-temperature nitrogen is further reduced, and it is then sent to the primary pre-cooling module to pre-cool the oil and gas entering the tower. This avoids freezing damage to the exhaust pipe caused by direct emission of low-temperature exhaust gas, further recovers the residual cold energy carried by the exhaust gas, improves the overall system's cold energy utilization efficiency, and avoids cold energy waste.

[0014] The liquid nitrogen supply and cold energy recovery unit of this invention also includes a nitrogen recovery subsystem. After liquid nitrogen vaporizes in the cryogenic heat exchanger, it generates a large amount of low-temperature nitrogen gas. After the cold energy recovery network recovers the cold energy, its temperature rises to near room temperature, and it is itself a clean, pressurized, inert gas. The nitrogen recovery subsystem is used to collect this nitrogen gas and adjust its pressure to slightly higher than the plant's nitrogen pipeline pressure through a buffer tank and pressure regulating valve group, and then injects it into the pipeline for reuse. It can be used in process steps such as nitrogen sealing of storage tanks, inerting of ship compartments, and pipeline purging. This design realizes the closed-loop utilization of the working fluid, transforming liquid nitrogen consumption from a purely "cost" component into a reusable "resource," significantly reducing the overall operating cost of the system. It is used for nitrogen sealing of storage tanks, pipeline purging, or process inerting. The vaporized nitrogen is pure industrial nitrogen, free of impurities. After pressurization, it can be directly fed back into the plant's nitrogen pipeline network, replacing part of the purchased nitrogen to meet the plant's nitrogen needs for production. By fully recovering the cold energy, the resource recovery of nitrogen itself is further realized, avoiding the waste of nitrogen resources, reducing the overall operating cost of the entire oil and gas recovery process, and reducing the energy waste caused by direct venting, thus improving the environmental and economic benefits of the equipment operation.

[0015] The nitrogen recovery subsystem of this invention includes a nitrogen buffer tank and a pressure regulating valve assembly. The intelligent control system is configured to adjust the opening of the pressure regulating valve assembly according to the pressure inside the nitrogen buffer tank to maintain the output pressure of the nitrogen recovery subsystem within a preset range. When the pressure inside the nitrogen buffer tank is higher than the preset range, the intelligent control system controls the pressure regulating valve assembly to increase the output opening, thereby increasing the nitrogen output to the plant's nitrogen pipeline network and reducing the pressure inside the tank. When the pressure inside the tank is lower than the preset range, the output valve is closed to reduce nitrogen output and stabilize the pressure inside the tank. This ensures that the nitrogen pressure delivered to the plant's pipeline network is stable, preventing pressure fluctuations in the plant's nitrogen pipeline network and not affecting the nitrogen demand of other production units in the plant, thus ensuring the stable operation of the entire system and plant production.

[0016] The intelligent control system described in this invention is configured to execute at least one of the following control logics: (a) Based on the feedback from the temperature sensor installed at the nitrogen outlet of the liquid nitrogen cryogenic heat exchanger, the opening of the liquid nitrogen injection valve is controlled by the PID control algorithm to stabilize the oil and gas temperature within the set range of -110°C to -180°C. (b) Based on the cumulative operating time or the pressure difference signal across the heat exchanger, automatically control the switching between the first cryogenic branch and the second cryogenic branch; (c) The start and stop of the drain pump are automatically controlled according to the liquid level in the condensate tank of the gas-liquid separation unit.

[0017] By precisely controlling the liquid nitrogen injection volume through PID regulation, the oil and gas temperature can be stably maintained within the set cryogenic range. This avoids both excessively high temperatures that lead to incomplete condensation of light components and reduced recovery efficiency, and excessively low temperatures that cause unnecessary liquid nitrogen waste, effectively balancing recovery performance and operating costs. The cryogenic branch is automatically switched based on accumulated operating time or the pressure difference signal across the heat exchanger, allowing for pre-frosting before it affects heat exchange efficiency, thus preventing a decline in heat exchange efficiency and impacting recovery performance. This eliminates the need for manual monitoring of the switching timing, reducing manual maintenance costs. The automatic control of the drain pump's start and stop based on the condensate tank level ensures timely condensate discharge, preventing condensate accumulation from occupying space in the gas-liquid separation unit and affecting separation performance, and also preventing excessively high condensate levels from entering subsequent pipelines with the gas phase, ensuring stable operation of the entire process.

[0018] The first temperature range described in this invention is 0°C to -5°C, and the second temperature range is -110°C to -180°C. This temperature range design ensures that moisture and heavy components are fully condensed and separated during the primary pre-cooling stage, preventing heavy components from condensing and clogging the heat exchanger channels at low temperatures after entering the secondary cryogenic module. Simultaneously, controlling the secondary cryogenic temperature within this range ensures that the vast majority of light hydrocarbon components are condensed and recovered, meeting environmental standards for oil and gas emissions and avoiding excessive cooling that could lead to liquid nitrogen waste.

[0019] The oil and gas recovery method of the oil and gas recovery equipment of the present invention includes the following steps: S1: Collect the oil and gas generated at the loading platform and perform filtration and pressure stabilization pretreatment; S2: The pretreated oil and gas are passed into the first-stage precooling module for precooling, and water and some high-boiling-point hydrocarbons are initially separated. S3: The pre-cooled oil and gas are introduced into the liquid nitrogen cryogenic heat exchanger of the secondary cryogenic module. By precisely controlling the liquid nitrogen flow rate, the oil and gas temperature drops sharply to the cryogenic temperature, and most of the hydrocarbon components are liquefied. S4: Separate the gas-liquid mixture generated after each stage of condensation to obtain liquid oil and purified exhaust gas; S5: The low-temperature nitrogen gas generated by the liquid nitrogen cryogenic heat exchanger is introduced into the cold energy recovery network to pre-cool the oil and gas of the first-stage pre-cooling module, so as to realize the cascade utilization of cold energy. S6: The separated liquid oil is transported back for reuse, and the purified exhaust gas is reheated before being discharged in compliance with standards.

[0020] This invention fully utilizes the cooling value of liquid nitrogen through cascaded cold energy utilization. Compared with the process of directly using liquid nitrogen for deep cryogenics without recovering cold energy, it significantly reduces liquid nitrogen consumption and equipment operating costs. At the same time, the staged condensation and separation design can remove moisture and heavy components first, preventing heavy components from condensing and clogging the equipment in the cryogenic section, ensuring long-term stable operation of the equipment, reducing maintenance frequency, and ultimately achieving efficient recovery of oil and gas at the loading platform. This not only yields reusable liquid oil but also ensures that the content of pollutants such as non-methane total hydrocarbons in the exhaust gas meets environmental emission standards, thus achieving both environmental and economic benefits.

[0021] In step S5 of this invention, some or all of the cryogenic nitrogen is used to reheat the purified exhaust gas generated in step S4, and then it is recycled back to the factory's nitrogen pipeline network. After absorbing the heat from the purified exhaust gas, the cryogenic nitrogen not only raises the exhaust gas temperature to near ambient temperature, preventing the cryogenic exhaust gas from freezing and damaging the emission pipeline, but also further improves its own cold energy utilization efficiency. No additional reheating heat source is needed, reducing system energy consumption. The pure nitrogen recycled back to the factory's nitrogen pipeline network can also be directly used in other production processes in the factory, realizing the full value utilization of liquid nitrogen from cold energy utilization to medium recovery, further reducing the operating cost of the entire oil and gas recovery process and improving resource utilization.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: First, the liquid nitrogen supply and cold energy recovery unit transfers its cooling capacity to the multi-stage condensation unit in stages, fully utilizing the cold energy of the liquid nitrogen for deep condensation of the oil and gas, thus avoiding waste of cooling capacity. Second, the pretreatment unit removes impurities and some heavy components from the oil and gas, preventing impurities from clogging subsequent pipelines and affecting the condensation and separation effect, and also reducing the cooling capacity loss caused by heavy components directly entering the low-temperature condensation unit. Third, the multi-stage condensation unit progressively lowers the condensation temperature along the oil and gas transport direction, allowing oil and gas components with different boiling points to be condensed and separated sequentially, ensuring recovery efficiency while avoiding primary condensation. The excessive cooling energy consumption caused by deep condensation is mitigated. A liquid nitrogen supply and cooling energy recovery unit enables the cascade utilization of liquid nitrogen cooling energy, recovering oil for resource recovery. The vaporized nitrogen, after cooling energy recovery, can be returned to the factory's nitrogen pipeline for reuse, achieving full resource utilization of the liquid nitrogen working fluid without additional waste emissions, significantly reducing overall operating costs. Simultaneously, an intelligent control system matches the intermittent fluctuations of the loading platform, dynamically adjusting the liquid nitrogen supply based on real-time conditions to achieve on-demand cooling, avoiding energy waste during idling or low loads, and improving the system's adaptability to intermittent operations.

[0023] Secondly, the parallel switchable dual cryogenic branch design enables defrosting of the frosting branch without interrupting system operation, solving the pain points of easy icing and blockage in cryogenic processes and the need to stop the machine for defrosting, which affects continuous operation and ensures long-term stable operation of the system. At the same time, through the exhaust gas reheating design, the residual cold energy in the purified exhaust gas is recovered, and the problems of frosting and visual pollution caused by direct emission of low-temperature exhaust gas are avoided, thus improving the environmental friendliness of the equipment.

[0024] Third, it adopts direct condensation using liquid nitrogen cryogenics, which greatly simplifies the system structure compared to traditional combined processes, reducing equipment footprint and initial investment; it eliminates the need for regular replacement of adsorbents, absorbents, and special separation membranes, reducing operating and maintenance costs and offering better economic performance throughout its entire life cycle. At the same time, it can also achieve efficient recovery of light hydrocarbon components, with a high overall hydrocarbon recovery rate that is far higher than that of traditional processes, combining environmental and economic benefits. Attached Figure Description

[0025] Figure 1 This is a schematic block diagram of the overall logic of the loading platform oil and gas recovery equipment involved in this invention.

[0026] Figure 2 This is a logic block diagram illustrating the dual-branch switching of the secondary cryogenic module involved in this invention.

[0027] Figure 3 This is a schematic block diagram of the cold energy recovery and nitrogen recovery involved in the present invention.

[0028] Figure 4 This is a schematic block diagram of the control process for defrosting in a cryogenic branch, which relates to the present invention.

[0029] Figure 5 This is a schematic block diagram of the pressure regulation and control of the nitrogen recovery subsystem involved in this invention.

[0030] Figure 6 This is a schematic block diagram of the control process for the drainage of the gas-liquid separation unit involved in the present invention.

[0031] Figure 7 This is a schematic diagram of the parameters for temperature control of the multi-stage condensing unit involved in this invention.

[0032] Figure 8 This invention relates to a schematic block diagram illustrating the complete workflow of oil and gas recovery at the loading platform.

[0033] Figure 9 This is the logic diagram of the loading platform oil and gas recovery equipment involved in this invention. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings.

[0035] Example 1: This implementation example Figure 1 and Figure 9 As shown, a loading platform oil and gas recovery device is disclosed, including an oil and gas collection unit, a pretreatment unit, a multi-stage condensation unit, a gas-liquid separation unit, a liquid nitrogen supply and cold energy recovery unit, a recovered oil processing unit, and an intelligent control system.

[0036] The oil and gas collection unit includes collection branch pipes and a main collection pipe connected to multiple loading arms. The main collection pipe is equipped with a pressure sensor and a pressure balancing valve to maintain a slight negative pressure in the collection system, ensuring that oil and gas do not escape. Flame arresters are installed at key locations such as the fan inlet and outlet to prevent potential backfire risks. The collected oil and gas are transported to the pretreatment unit via a fan, which can be frequency-controlled to automatically adjust the airflow according to the main collection pipe pressure, adapting to load changes.

[0037] Pretreatment unit: Includes a fine filter and a buffer tank. Oil and gas first enter the filter to remove solid particles and droplets larger than 5μm. They then enter the buffer tank, whose volume is designed based on the peak flow rate at the loading site to smooth flow fluctuations and provide relatively stable intake conditions for the subsequent condensation unit. A drain valve is located at the bottom of the buffer tank to periodically drain any condensate that may accumulate.

[0038] Multi-stage condensation unit: including a first-stage precooling module and a second-stage cryogenic module.

[0039] In this embodiment, the primary precooling module is a plate-fin heat exchanger. Its hot side (tube side) carries pretreated oil and gas, while its cold side (shell side) carries low-temperature nitrogen from the cold energy recovery network. Through heat exchange, the oil and gas are cooled from ambient temperature to approximately -3°C, at which point most of the water vapor and some high-boiling-point gasoline components (such as pentane and hexane) in the oil and gas are condensed.

[0040] like Figure 2 and Figure 7As shown, the secondary cryogenic module is the core of this invention, employing a skid-mounted design and comprising a first cryogenic branch and a second cryogenic branch connected in parallel. Taking the first cryogenic branch as an example, it includes a pre-cooling condenser and a cryogenic condenser connected in series. The pre-cooling condenser is used to further cool the oil and gas from the primary pre-cooling stage (e.g., to -30°C). The pre-cooling condenser utilizes low-temperature nitrogen from the cold energy recovery network as a cold source to further cool the oil and gas. The cryogenic condenser is a liquid nitrogen cryogenic heat exchanger, with a shell-and-tube structure. The oil and gas flow through the tubes, while liquid nitrogen vaporizes and absorbs heat in the shell side. By precisely controlling the opening of the liquid nitrogen injection valve TV-70105, the oil and gas temperature can be reduced to -140°C (which can be set within the range of -110°C to -180°C). At this ultra-low temperature, most of the light hydrocarbon components in the oil and gas, such as methane, ethane, ethylene, propane, and propylene, are liquefied. The equipment composition of the second cryogenic branch is exactly the same as that of the first cryogenic branch. The inlet and outlet of the two branch lines are connected to the main pipe through a series of pneumatic shut-off valves, and their switching is controlled by an intelligent control system.

[0041] The gas-liquid separation unit includes a primary separation tank connected to the outlet of the precooling condenser and a secondary separation tank connected to the outlet of the cryogenic condenser. The separation tanks are equipped with high-efficiency wire mesh demisters or cyclone separators, utilizing the density difference between gas and liquid and inertia to efficiently separate the condensed liquid droplets from the gas phase. The separated liquid is temporarily stored at the bottom of the tank, while the gas enters the next stage. A level gauge is installed on the separation tank to monitor the liquid level.

[0042] Example 2: This implementation example Figure 3 As shown, the liquid nitrogen supply and cold energy recovery unit involved includes a liquid nitrogen storage tank, a cryogenic transfer pump, a vaporizer, a cold energy recovery network, and a nitrogen recovery subsystem.

[0043] The liquid nitrogen storage tank is a vacuum-insulated tank used to store cryogenic liquid nitrogen. After being pressurized by a cryogenic pump, the liquid nitrogen is transported through pipelines to the cryogenic condenser of the secondary cryogenic module.

[0044] The cold energy recovery network is one of the key innovations of this invention. The gas flowing out of the shell-side outlet of the cryogenic condenser (during operation) is cryogenic nitrogen gas (after liquid nitrogen vaporization) at a temperature of approximately -100°C. This cryogenic nitrogen gas is divided into two streams (the ratio can be adjusted via valves): like Figure 4 As shown, the first path is led back to the shell side of the primary precooling module as its cold source, and its temperature rises to about -20°C after exchanging heat with the hot oil and gas.

[0045] The second path either merges with the first path or enters the shell side of the exhaust gas reheater independently. The deeply purified exhaust gas from the secondary separator, at approximately -140°C, enters the tube side of the exhaust gas reheater, where it undergoes counter-current heat exchange with the low-temperature nitrogen gas (approximately -20°C to -30°C) in the shell side. As a result, the purified exhaust gas is reheated to ambient temperature (e.g., above 15°C) before being emitted through the chimney, completely resolving the white fog problem; while the low-temperature nitrogen gas is heated to near room temperature.

[0046] like Figure 5 As shown, the nitrogen recovery subsystem includes a nitrogen buffer tank and a pressure regulating valve assembly. Clean nitrogen gas at near-room temperature (approximately 0.6 MPa) from the exhaust gas reheater enters the nitrogen buffer tank for pressure stabilization. Then, the pressure is precisely controlled by the pressure regulating valve assembly to be slightly higher than the plant's nitrogen pipeline pressure (e.g., 0.65 MPa), before being connected to the plant's nitrogen pipeline network for other uses. When the nitrogen pressure in the system is too high, the safety release valve automatically opens to relieve pressure.

[0047] Recycled oil processing unit: Condensate discharged from the bottom of the primary and secondary separation tanks flows by gravity through insulated pipes into a shared condensate storage tank. The condensate storage tank is equipped with coils that can be heated with warm water to prevent the cryogenic condensate from freezing. When the liquid level in the tank reaches a high set value, the intelligent control system activates a cryogenic explosion-proof transfer pump to transport the mixed condensate (mainly light oil and a small amount of water) to a designated recycled oil tank or return it to the raw material storage tank. The transfer pump is interlocked with the level gauge for automatic start and stop.

[0048] Example 3: The intelligent control system involved in this embodiment uses an explosion-proof PLC (such as the Siemens S7-1500 series) as the main controller, which is installed in an explosion-proof cabinet on site. The controller communicates with the central control room via Ethernet to realize remote monitoring and emergency shutdown.

[0049] Sensor configuration: Install PT100 platinum resistance thermometers (e.g., TT70105 for measuring the cryogenic temperature of the first cryogenic branch, TT70108 for measuring the cryogenic temperature of the second cryogenic branch), pressure transmitters (e.g., PT70105 / PT70106 for measuring the differential pressure of the first / second cryogenic branch), vortex flow meters, radar level gauges, etc. at key points. All instruments have an IP65 protection rating and an ExdIIBT4 explosion-proof rating.

[0050] Control logic implementation: Temperature control: Taking the operation of the first cryogenic branch as an example, the PLC reads the value of the temperature sensor TT70105 and compares it with the set value SPTT70105 (such as -140℃). The PLC calculates the output through the built-in PID algorithm and controls the opening of the liquid nitrogen regulating valve TV-70105 to stabilize the cryogenic temperature at the set value.

[0051] First cryogenic branch / Second cryogenic branch switching control: Timed switching: Set the continuous operating time for a single cryogenic branch (e.g., 4 hours). When the operating time of the first cryogenic branch reaches the set value, the PLC automatically executes the switching program: closes the oil and gas inlet valve XV-70101 and outlet valve XV-70102 of the first cryogenic branch, and opens the corresponding valves XV-70111 and XV-70112 of the second cryogenic branch, switching the system to operation of the second cryogenic branch. Subsequently, the first cryogenic branch enters the defrosting program.

[0052] Differential pressure switching: Real-time monitoring of the differential pressure ΔPA across the cryogenic heat exchanger in the first cryogenic branch. When ΔPA exceeds the set value (e.g., 15 kPa), indicating severe frost buildup leading to increased flow resistance, the PLC immediately forces a switch to the second cryogenic branch, regardless of whether the timer has been reached.

[0053] Defrosting Control: After the first cryogenic branch switches off, the PLC first opens its drain valves XV-70101 / XV-70102 to return residual hydraulic fluid from the separator to the condensate main pipe. Then, it opens the defrosting nitrogen valve XV-70108 to introduce ambient temperature nitrogen (or nitrogen slightly heated to 50°C by an electric heater) from the nitrogen recovery subsystem into the tube side of the cryogenic condenser to heat the frost layer on the shell side. After defrosting continues for a certain period of time (e.g., 20 minutes) or when the heat exchanger outlet temperature reaches the set value, the defrosting nitrogen valve is closed. The first cryogenic branch is then defrosted and enters standby mode to await switching.

[0054] Liquid drainage and nitrogen pressure control: such as Figure 6 As shown, the condensate storage tank automatically starts the drain pump when the liquid level reaches a high level and automatically stops the pump when the liquid level drops to a low level. The pressure of the nitrogen buffer tank is automatically controlled by a pressure regulating valve to maintain stable pipeline pressure.

[0055] Safety Interlocks: The system is equipped with multiple safety protection measures, including fan and main pipe pressure interlocks, heat exchanger overpressure alarm shutdown, cryogenic equipment leakage alarm, and motor overload protection.

[0056] The workflow involved in this embodiment is as follows: like Figure 8As shown, loading begins, and oil and gas are collected. The system starts, and the intelligent control system defaults to activating the first cryogenic branch. After pretreatment, the oil and gas first enter the primary precooling module, where they are precooled to approximately -3°C by low-temperature nitrogen from the first cryogenic branch. Some water and high-boiling-point oil condense and are separated in the primary separator. The gas then enters the precooling condenser of the first cryogenic branch for further cooling, and then enters the cryogenic condenser of the first cryogenic branch, where it is deeply cooled to -140°C under the action of liquid nitrogen. Most of the hydrocarbons are liquefied, and gas-liquid separation is achieved in the secondary separator. The purified low-temperature exhaust gas enters the exhaust gas reheater, is reheated, and then discharged. The low-temperature nitrogen generated by the vaporization of liquid nitrogen is used sequentially for precooling and exhaust gas reheating, and is ultimately recovered. The separated oil is collected and pumped for recovery. After 4 hours of operation (or when the pressure difference exceeds the limit), the system automatically switches to the second cryogenic branch, and the first cryogenic branch automatically defrosts, thus repeating the cycle.

Claims

1. A loading platform oil and gas recovery device, characterized in that, Including those connected sequentially via pipes: The oil and gas collection unit is used to collect volatile organic compound oil and gas generated at the loading platform; A pretreatment unit is used to filter and stabilize the oil and gas; The multi-stage condensation unit includes a first-stage precooling module and a second-stage cryogenic module. The first-stage precooling module is used to precool the oil and gas to a first temperature range to condense and separate water and heavy components. The second-stage cryogenic module includes a liquid nitrogen cryogenic heat exchanger, which uses liquid nitrogen vaporization to absorb heat and cool the oil and gas to a second temperature range to liquefy hydrocarbons, including light components. The second temperature range is lower than the first temperature range. A gas-liquid separation unit is connected to the outlets of the primary precooling module and the secondary cryogenic module, and is used to separate the liquid substances obtained by condensation. The liquid nitrogen supply and cold energy recovery unit includes a liquid nitrogen storage tank and a cold energy recovery network; the liquid nitrogen storage tank supplies liquid nitrogen to the liquid nitrogen cryogenic heat exchanger; the cold energy recovery network guides the low-temperature nitrogen gas generated by the vaporization of the liquid nitrogen cryogenic heat exchanger, with a temperature not higher than -100°C, to the primary precooling module as part of its precooling cold source; An oil recovery processing unit is used to collect and transport the liquid oil separated by the gas-liquid separation unit; as well as, The intelligent control system is used to adjust the operating parameters of the liquid nitrogen supply and cold energy recovery unit and the opening degree of valves on each pipeline in real time according to the system operating parameters.

2. The oil and gas recovery equipment for a loading platform according to claim 1, characterized in that, The secondary cryogenic module adopts a skid-mounted structure, including a first cryogenic branch and a second cryogenic branch that are connected in parallel and can be switched. Each cryogenic branch includes a pre-cooling condenser, a cryogenic condenser, and a corresponding gas-liquid separator and control valve group connected in series. The intelligent control system is configured to control the switching between the first cryogenic branch and the second cryogenic branch, so that when one branch is running, the other branch can be defrosted or standby.

3. The oil and gas recovery equipment for a loading platform according to claim 2, characterized in that, The defrosting process is achieved by introducing nitrogen gas at room temperature or heated gas into the heat exchanger tube side of the cryogenic branch to be defrosted. The nitrogen gas exchanges heat with the frost layer attached to the shell side, causing it to melt. The melted liquid flows into the condensate collection tank.

4. The oil and gas recovery equipment for a loading platform according to claim 1, characterized in that, The cold energy recovery network also includes an exhaust gas reheater; the purified exhaust gas after being processed by the secondary cryogenic module first undergoes heat exchange with the low-temperature nitrogen in the exhaust gas reheater, and is then discharged after being reheated to the ambient temperature.

5. The oil and gas recovery equipment for a loading platform according to claim 4, characterized in that, The liquid nitrogen supply and cold energy recovery unit also includes a nitrogen recovery subsystem, which is used to collect and pressurize the nitrogen generated by the vaporization of the liquid nitrogen cryogenic heat exchanger and reuse it in the factory's nitrogen pipeline network.

6. The oil and gas recovery equipment for a loading platform according to claim 5, characterized in that, The nitrogen recovery subsystem includes a nitrogen buffer tank and a pressure regulating valve group. The intelligent control system is configured to adjust the opening of the pressure regulating valve group according to the pressure in the nitrogen buffer tank, so as to maintain the output pressure of the nitrogen recovery subsystem within a preset range.

7. The oil and gas recovery equipment for a loading platform according to claim 1, characterized in that, The intelligent control system is configured to execute at least one of the following control logics: (a) Based on the feedback from the temperature sensor installed at the nitrogen outlet of the liquid nitrogen cryogenic heat exchanger, the opening of the liquid nitrogen injection valve is controlled by the PID control algorithm to stabilize the oil and gas temperature within the set range of -110°C to -180°C. (b) Based on the cumulative operating time or the pressure difference signal across the heat exchanger, automatically control the switching between the first cryogenic branch and the second cryogenic branch; (c) The start and stop of the drain pump are automatically controlled according to the liquid level in the condensate tank of the gas-liquid separation unit.

8. The oil and gas recovery equipment for a loading platform according to claim 1, characterized in that, The first temperature range is 0°C to -5°C, and the second temperature range is -110°C to -180°C.

9. A loading platform oil and gas recovery device according to any one of claims 1-8, characterized in that, The oil and gas recovery method of this oil and gas recovery equipment includes the following steps: S1: Collect the oil and gas generated at the loading platform and perform filtration and pressure stabilization pretreatment; S2: The pretreated oil and gas are passed into the first-stage precooling module for precooling, and water and some high-boiling-point hydrocarbons are initially separated. S3: The pre-cooled oil and gas are introduced into the liquid nitrogen cryogenic heat exchanger of the secondary cryogenic module. By precisely controlling the liquid nitrogen flow rate, the oil and gas temperature drops sharply to the cryogenic temperature, and most of the hydrocarbon components are liquefied. S4: Separate the gas-liquid mixture generated after each stage of condensation to obtain liquid oil and purified exhaust gas; S5: Introduce the low-temperature nitrogen gas generated by the liquid nitrogen cryogenic heat exchanger into the cold energy recovery network for precooling the oil and gas of the first-stage precooling module; S6: The separated liquid oil is transported back for reuse, and the purified exhaust gas is reheated before being discharged in compliance with standards.

10. The oil and gas recovery equipment for a loading platform according to claim 9, characterized in that, In step S5, some or all of the low-temperature nitrogen gas is used to reheat the purified exhaust gas generated in step S4, and then it is recycled back to the factory's nitrogen pipeline network.

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