BOG compressor oil gas treatment system and method

Abstract

The invention discloses a BOG compressor oil gas treatment system and method, and relates to the technical field of petrochemical engineering, the BOG compressor oil gas treatment system comprises a cylindrical storage tank communicated with a plurality of BOG compressor oil gas output ports, and the side wall of the cylindrical storage tank is communicated with an oil gas inlet and a nitrogen inlet through a three-way connector with a Venturi effect; the nitrogen inlet is communicated with a nitrogen supply unit, and an oil gas outlet is formed in the upper end of the cylindrical storage tank; the cyclone generator is provided with a tangential inlet structure; the coalescence assembly is mounted on one side of the cyclone generator and is used for realizing adhesion and coalescence of the oil drops; an on-line calorific value instrument; the double-channel combustion assembly comprises a waste liquid furnace combustor and a torch system; through cooperation of the cylindrical storage tank, the three-way connector, the rotational flow generator, the coalescence assembly, the online calorific value instrument and the two-channel combustion assembly, oil gas is completely recycled and reused, meanwhile, the oil gas serves as a fuel supply source of the two-channel combustion assembly, the oil gas can be fully combusted, and the energy utilization rate is increased.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a BOG compressor oil and gas treatment system and method. Background Technology

[0002] During the storage and transportation of liquefied natural gas (LNG), the thermodynamic balance is disrupted, resulting in the continuous generation of boil-off gas (BOG). To maintain the pressure in the cryogenic storage tank within a safe range, the BOG compressor, as the core power unit, performs multi-stage compression of the boil-off gas, boosting the low-pressure gas to 1.0-3.0 MPa before delivering it to the condenser.

[0003] During the compression process, the high-speed rotating rotor and housing require a large amount of lubricating oil for sealing and cooling. When the temperature of the lubricating oil rises above 80°C, its light components continue to volatilize, forming an oil-gas mixture. Each compressor can produce a large amount of oil-gas per hour.

[0004] Currently, BOG compressor oil and gas are typically discharged directly into the atmosphere using an open oil tank design. However, the unorganized diffusion of this oil and gas leads to excessive VOC concentrations in the plant area, seriously endangering the health of operators and the surrounding environment. Furthermore, the oil and gas discharge pressure is generally at atmospheric pressure, lacking effective collection power and requiring significant collection verification. Therefore, we need to propose a BOG compressor oil and gas treatment system and method to solve the above-mentioned problems, enabling the complete recovery and reuse of oil and gas. At the same time, the oil and gas can be used as fuel to supply the combustion system, improving the thermal efficiency of the waste liquid furnace and thus increasing energy utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a BOG compressor oil and gas treatment system and method that can achieve complete recovery and reuse of oil and gas, while using oil and gas as fuel to supply the combustion system, thereby improving the thermal efficiency of the waste liquid furnace and thus improving energy utilization, in order to solve the problems mentioned in the background art.

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

[0007] A BOG compressor oil and gas treatment system includes: a cylindrical storage tank connected to multiple BOG compressor oil and gas outlets, the side wall of the cylindrical storage tank being connected to an oil and gas inlet and a nitrogen inlet via a tee interface with a Venturi effect, the nitrogen inlet being connected to a nitrogen supply unit, and an oil and gas outlet being provided at the upper end of the cylindrical storage tank.

[0008] A cyclone generator with a tangential inlet structure is fixed inside a cylindrical storage tank and connected to the oil and gas inlet, allowing the oil and gas mixture to enter tangentially at high speed and generate centrifugal force.

[0009] A coalescing assembly, mounted on one side of the cyclone generator, is used to achieve oil droplet adhesion and coalescence.

[0010] An online calorific value analyzer is installed at the oil and gas outlet of a cylindrical storage tank to detect the calorific value of oil and gas in real time and control the transmission rate of the mixed gas based on the detection results.

[0011] The dual-channel combustion assembly includes a waste liquid furnace burner and a flare system. Both the waste liquid furnace burner and the flare system are connected to the outlet of an online calorimeter via pipelines, and control valves are installed on the connecting pipelines between the online calorimeter and the waste liquid furnace burner and the flare system.

[0012] Preferably, the coalescing assembly includes corrugated coalescing plates, which are arranged alternately on one side of the swirl generator to form a corrugated channel.

[0013] Preferably, the three-way interface includes a tapered ejector chamber, a mixing throat of equal diameter, and a nitrogen annular distributor. The inner wall of the ejector chamber is provided with a spiral guide groove, the inner wall of the mixing throat is fitted with a porous sintered metal bushing, and the nitrogen annular distributor surrounds the outer wall of the mixing throat and is connected to the metal bushing.

[0014] Preferably, the nitrogen supply unit includes a nitrogen pipeline and a self-regulating valve, the self-regulating valve being used to control the nitrogen pressure to be maintained at 0.2-0.5 MPa, and the angle between the nitrogen inlet and the oil / gas inlet being 20-40°.

[0015] Preferably, one end of the cyclone generator is provided with a tangential inlet, which is connected to the end of the oil and gas inlet via a flange, and the cyclone generator is fixed to the upper side inside the cylindrical storage tank by a bracket.

[0016] Preferably, a first regulating valve is installed on the pipeline located at the outlet end of the online calorimeter, and the outlet end of the first regulating valve is connected to the waste liquid furnace burner and the flare system respectively through a three-way pipe.

[0017] Preferably, the control valve includes a manual valve and a shut-off valve, the manual valve being located on one side of the shut-off valve and close to the three-way pipe.

[0018] Preferably, the inner bottom of the cylindrical storage tank is provided with a liquid collection area, one side of which is connected to a bottom drain pipe, and a drain valve is installed on the bottom drain pipe.

[0019] Preferably, the cylindrical storage tank is equipped with a level gauge, which is a flap level gauge. When the level gauge level exceeds 30%, the drain valve is triggered to open.

[0020] Based on the above-described BOG compressor oil and gas treatment system, the present invention also provides a BOG compressor oil and gas treatment method, comprising the following steps:

[0021] S1. The oil and gas generated by the operation of multiple BOG compressors are connected to the oil and gas inlet through a series pipeline;

[0022] S2. Nitrogen source is provided to the three-way interface through the nitrogen supply unit, and the oil and gas are drawn into the cylindrical storage tank without compression.

[0023] S3. The oil and gas are separated by centrifugal force generated by the cyclone generator. The gas flow containing tiny droplets is coalesced by the coalescing component and then settles to the bottom of the cylindrical storage tank for collection.

[0024] S4. The oil and gas mixture after passing through the coalescing component enters the online calorific value meter to detect the calorific value of the mixture in real time, and the transmission rate of the mixture is controlled according to the detection results.

[0025] S5. The air-fuel mixture is fully combusted through a dual-channel combustion assembly.

[0026] The BOG compressor oil and gas treatment system and method proposed in this invention have the following advantages compared with the prior art:

[0027] 1. This invention achieves complete recovery and reuse of oil and gas through the combination of a cylindrical storage tank, a three-way interface, a cyclone generator, a coalescing component, an online calorimeter, and a dual-channel combustion component. At the same time, the oil and gas serve as the fuel supply source for the dual-channel combustion component, enabling the oil and gas to burn completely and improving energy utilization.

[0028] 2. This invention injects nitrogen into a cylindrical storage tank through a three-way interface with the Venturi effect. The Venturi effect creates a negative pressure at the oil and gas inlet, enabling uncompressed suction of oil and gas into the cylindrical storage tank. No additional pressurization equipment is required, reducing energy consumption. Furthermore, with real-time control by an online calorimeter and the optimal nitrogen injection angle, the calorific value of the mixture is ensured to be stable, avoiding the risk of explosion or incomplete combustion.

[0029] 3. The dual-channel combustion assembly of the present invention can switch to the flare system when the waste liquid furnace is shut down or under maintenance, ensuring safe combustion of oil and gas. The combination of the cyclone generator and the coalescing assembly improves the oil and gas separation efficiency and adapts to the oil and gas rate fluctuations caused by the compressor start-up and shutdown. Attached Figure Description

[0030] Figure 1 This is a system schematic diagram of the present invention;

[0031] Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0032] 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. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. 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.

[0033] This invention provides, for example Figure 1 The illustrated BOG compressor oil and gas handling system includes a cylindrical storage tank connected to multiple BOG compressor oil and gas outlets, a cyclone generator with a tangential inlet structure, a coalescing assembly, an online calorimeter, and a dual-channel combustion assembly. The BOG compressor is a screw-type BOG compressor. The side wall of the cylindrical storage tank is connected to an oil and gas inlet and a nitrogen inlet via a tee port with a Venturi effect. A nitrogen supply unit is connected to the nitrogen inlet. An oil and gas outlet is provided at the upper end of the cylindrical storage tank. The cyclone generator is fixed inside the cylindrical storage tank and connects to the oil and gas... The inlet connection allows the oil-gas mixture to enter tangentially at high speed, generating centrifugal force; the coalescing assembly is installed on one side of the cyclone generator to achieve oil droplet adhesion and coalescence; the online calorific value meter is installed at the oil-gas outlet of the cylindrical storage tank to detect the calorific value of the oil and gas in real time and control the gas-mixture transmission rate based on the detection results; the dual-channel combustion assembly includes a waste liquid furnace burner and a flare system, both of which are connected to the outlet end of the online calorific value meter via pipelines, and control valves are installed on the connecting pipelines between the online calorific value meter and the waste liquid furnace burner and the flare system;

[0034] By utilizing the Venturi effect of the three-way interface to create negative pressure at the oil and gas inlet to draw in oil and gas, the problem of insufficient power for collecting oil and gas at atmospheric pressure is solved. The cyclone generator and coalescing component form a two-stage separation structure, using centrifugal force and surface adsorption effect to achieve efficient gas-liquid separation. The online calorific value meter collects the calorific value data of the mixed gas in real time and dynamically adjusts the transmission rate of the mixed gas to ensure combustion stability. The dual-channel combustion component achieves safe connection between normal and fault conditions through branch switching, ultimately achieving the goal of full recovery, zero emissions and efficient utilization of oil and gas.

[0035] The coalescing assembly includes corrugated coalescing plates, which are staggered on one side of the vortex generator to form corrugated channels. The staggered arrangement of the corrugated coalescing plates forms irregular channels. When the airflow passes through, it undergoes a sudden change in channel opening and closing, resulting in a violent turn. The airflow carrying tiny oil droplets cannot follow the airflow turn in time due to inertia and collides with the surface of the corrugated coalescing plates. The corrugated coalescing plates are made of oleophilic material. After the oil droplets collide, they are adsorbed onto the surface of the plate, and different oil droplets merge with each other on the surface to form larger oil droplets. When the weight of the oil droplets exceeds the buoyancy of the airflow, they sink along the plate to the liquid collection area at the bottom of the tank, completing the deep separation of tiny oil droplets and reducing the risk of oil accumulation.

[0036] The three-way interface includes a tapered ejector chamber, a mixing throat of equal diameter, and a nitrogen annular distributor. The inner wall of the ejector chamber is provided with a spiral guide groove. The inner wall of the mixing throat is fitted with a porous sintered metal bushing. The nitrogen annular distributor surrounds the outer wall of the mixing throat and is connected to the metal bushing. The tapered ejector chamber gradually increases the oil and gas flow rate, and the spiral guide groove on the inner wall guides the oil and gas to generate a rotating flow field, enhancing the airflow disturbance. The mixing throat has a constant diameter structure, forming a throat with a Venturi effect, further increasing the flow rate and reducing the pressure, generating negative pressure to draw in the oil and gas. The nitrogen annular distributor evenly distributes nitrogen to the porous sintered metal bushing. The nitrogen permeates into the mixing throat in the form of tiny bubbles through the micropores of the bushing, fully contacting and mixing with the rotating oil and gas, avoiding local uneven concentration, and ensuring stable calorific value for subsequent combustion.

[0037] The nitrogen supply unit includes a nitrogen pipeline and a self-regulating valve. The self-regulating valve controls the nitrogen pressure to maintain it at 0.2-0.5 MPa. The angle between the nitrogen inlet and the oil / gas inlet is 20-40°. The self-regulating valve automatically adjusts its opening based on the nitrogen pipeline pressure via a spring and diaphragm mechanism, maintaining a stable nitrogen pressure of 0.2-0.5 MPa without external power. This ensures the continued effectiveness of the Venturi effect and prevents pressure fluctuations from interrupting the suction process. The 20-40° angle between the nitrogen inlet and the oil / gas inlet creates an optimal superimposed flow field between the nitrogen injection direction and the oil / gas flow direction, maximizing the negative pressure suction effect and promoting uniform mixing of oil / gas and nitrogen. A 30° angle results in the most reasonable flow field disturbance, with the mixed gas reaching its peak calorific value of 1625 kcal / Nm³. 3 .

[0038] One end of the cyclone generator is provided with a tangential inlet, which is connected to the end of the oil and gas inlet via a flange. The cyclone generator is fixed to the upper side of the cylindrical storage tank by a bracket. The cyclone generator adopts a tangential inlet design, and the oil and gas enter the generator at high speed in a tangential direction through the flange interface, forming a rotating airflow inside the tank. According to the centrifugal force formula F=mv² / r, where m is the mass of the oil droplet, v is the rotation speed, and r is the radius of rotation, large and medium-sized oil droplets, due to their large mass, generate a centrifugal force much greater than the centripetal force of the airflow and are thrown towards the inner wall of the storage tank, settling along the wall to the pre-separated liquid collection point. Small-sized oil droplets, due to their small mass, enter the subsequent coalescence assembly with the airflow. This structure can quickly separate most of the oil droplets, significantly reducing the subsequent processing load.

[0039] A first regulating valve is installed on the pipeline located at the outlet end of the online calorimeter. The outlet end of the first regulating valve is connected to the waste liquid furnace burner and the flare system respectively through a three-way pipe. The online calorimeter detects the calorific value of the mixed gas in real time and transmits the data to the control module. The control module compares the detected value with a preset threshold, such as 1200 kcal / Nm³. When the calorific value is lower than the threshold, it indicates that the concentration of the mixed gas is too low. The control module sends a signal to reduce the opening of the first regulating valve and reduce the transmission rate, so as to increase the concentration of the mixed gas in the combustion system. When the calorific value is higher than the threshold, the valve opening is increased to increase the transmission rate and avoid excessive concentration that may cause combustion explosion. Through continuous feedback adjustment, the calorific value of the mixed gas entering the combustion system is ensured to be stable within the safe combustion range.

[0040] The control valve includes a manual valve and a shut-off valve. The manual valve is located to one side of the shut-off valve and is close to the three-way pipe. The shut-off valve is a quick-opening and quick-closing type valve, used to quickly switch the branch circuit on and off. When a branch circuit fails, such as during waste liquid furnace maintenance, the branch circuit can be quickly shut off to prevent gas-liquid mixture leakage. The manual valve is a fine-tuning type valve, connected in series outside the shut-off valve, used to precisely adjust the branch circuit flow rate to assist in matching the combustion system requirements. The two work together: the shut-off valve is responsible for safety isolation, and the manual valve is responsible for fine-tuning the flow rate, ensuring no gas-liquid mixture leakage during branch switching and that the flow rate meets combustion requirements.

[0041] The cylindrical storage tank has a liquid collection area at its bottom. One side of the liquid collection area is connected to a bottom drain pipe, which is equipped with a drain valve. The bottom liquid collection area inside the tank has a low-lying structure. The oil, after being separated by cyclone separation and coalescence separation, has a density greater than that of gas and naturally settles into the liquid collection area under the action of gravity. The bottom drain pipe is connected to the lowest point of the liquid collection area. The drain valve is normally closed. When the oil in the liquid collection area reaches a certain amount, the valve is opened manually or triggered by an automatic control device. The oil is then discharged through the drain pipe to the collection bucket, preventing the oil from accumulating in the tank and causing system failure or contamination of the mixed gas.

[0042] The cylindrical storage tank is equipped with a level gauge, which is a flap level gauge. When the level gauge level exceeds 30%, it triggers the drain valve to open. The flap level gauge consists of a communicating vessel and a float-flap mechanism. The oil in the collection area is connected to the level gauge cavity through the communicating vessel. The float moves synchronously with the rise and fall of the oil level, causing the flap to flip and display the liquid level height intuitively. The level gauge has a built-in level sensor. When the level is detected to exceed the preset threshold of 30%, the sensor sends a signal to trigger the electric actuator of the drain valve to automatically open the valve and discharge the oil. When the level drops below the threshold, the valve automatically closes, realizing automated control of oil discharge and reducing manual intervention.

[0043] Based on the above description of a BOG compressor oil and gas treatment system, this invention also provides a BOG compressor oil and gas treatment method, such as... Figure 2 As shown, it includes the following steps:

[0044] S1. The oil and gas generated by the operation of multiple BOG compressors are connected to the oil and gas inlet through a series pipeline;

[0045] S2. Nitrogen source is provided to the three-way interface through the nitrogen supply unit, and the oil and gas are drawn into the cylindrical storage tank without compression.

[0046] S3. The oil and gas are separated by centrifugal force generated by the cyclone generator. The gas flow containing tiny droplets is coalesced by the coalescing component and then settles to the bottom of the cylindrical storage tank for collection.

[0047] S4. The oil and gas mixture after passing through the coalescing component enters the online calorific value meter to detect the calorific value of the mixture in real time, and the transmission rate of the mixture is controlled according to the detection results.

[0048] S5. The air-fuel mixture is fully combusted through a dual-channel combustion assembly.

[0049] Based on the BOG compressor oil and gas treatment system and method provided above, the following specific embodiments are provided:

[0050] First, the oil and gas generated during the operation of several BOG compressors are collected into the oil and gas recovery main pipe through DN50 carbon steel pipes;

[0051] Subsequently, nitrogen gas is controlled at a pressure of 0.4 MPa via a self-regulating valve and injected into the elliptical storage tank through a 30° acute-angle T-junction. Utilizing the Venturi effect, a negative pressure is created at the oil and gas inlet, achieving uncompressible oil and gas extraction.

[0052] The mixed gas entering the storage tank undergoes gas-liquid separation under normal operating conditions. The liquefied gas settles to the bottom of the tank by gravity. When the liquid level gauge exceeds 30%, the operator manually opens the DN25 drain valve to discharge the gas into the collection bucket.

[0053] The separated gaseous components are transported through the outlet and first undergo real-time monitoring of the calorific value of the oil and gas using an online calorific value analyzer. When the calorific value of the oil and gas is below 1200 kcal / Nm³, the oil and gas is considered to have a calorific value of 1200 kcal / Nm³. 3 When the oil and gas calorific value is higher than 1200 kcal / Nm³, the regulating valve will gradually decrease; when the calorific value of the oil and gas is higher than 1200 kcal / Nm³, the regulating valve will gradually decrease. 3 At this time, the regulating valve gradually increases, and the operator can also choose to burn the oil and gas in the waste liquid furnace or in the flare system according to the calorific value.

[0054] It should be noted that nitrogen gas was injected into the oil and gas inlet pipe from different angles to confirm its negative pressure suction effect at the oil and gas inlet. The test results are shown in Table 1 below:

[0055] Table 1

[0056]

[0057] Experiments have shown that a nitrogen incident angle of 20-40° is the optimal implementation case.

[0058] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A BOG compressor oil vapor treatment system, characterized in that: include: A cylindrical storage tank connected to multiple BOG compressor oil and gas outlets, the side wall of the cylindrical storage tank is connected to an oil and gas inlet and a nitrogen inlet through a tee interface with Venturi effect, the nitrogen inlet is connected to a nitrogen supply unit, and the upper end of the cylindrical storage tank is provided with an oil and gas outlet. A cyclone generator with a tangential inlet structure is fixed inside a cylindrical storage tank and connected to the oil and gas inlet, allowing the oil and gas mixture to enter tangentially at high speed and generate centrifugal force. A coalescing assembly, mounted on one side of the cyclone generator, is used to achieve oil droplet adhesion and coalescence. An online calorific value analyzer is installed at the oil and gas outlet of a cylindrical storage tank to detect the calorific value of oil and gas in real time and control the transmission rate of the mixed gas based on the detection results. The dual-channel combustion assembly includes a waste liquid furnace burner and a flare system. Both the waste liquid furnace burner and the flare system are connected to the outlet of an online calorimeter via pipelines, and control valves are installed on the connecting pipelines between the online calorimeter and the waste liquid furnace burner and the flare system.

2. The BOG compressor oil and gas treatment system according to claim 1, characterized in that: The coalescing assembly includes corrugated coalescing plates, which are arranged alternately on one side of the swirl generator to form a corrugated channel.

3. The BOG compressor oil and gas treatment system according to claim 2, characterized in that: The three-way interface includes a tapered ejector chamber, a mixing throat of equal diameter, and a nitrogen annular distributor. The inner wall of the ejector chamber is provided with a spiral guide groove. The inner wall of the mixing throat is fitted with a porous sintered metal bushing. The nitrogen annular distributor surrounds the outer wall of the mixing throat and is connected to the metal bushing.

4. The BOG compressor oil and gas treatment system according to claim 3, characterized in that: The nitrogen supply unit includes a nitrogen pipeline and a self-regulating valve. The self-regulating valve is used to control the nitrogen pressure to be maintained at 0.2-0.5 MPa. The angle between the nitrogen inlet and the oil / gas inlet is 20-40°.

5. The BOG compressor oil and gas treatment system according to claim 4, characterized in that: One end of the cyclone generator is provided with a tangential inlet, which is connected to the end of the oil and gas inlet through a flange, and the cyclone generator is fixed to the upper side of the inside of the cylindrical storage tank by a bracket.

6. The BOG compressor oil and gas treatment system according to claim 5, characterized in that: A first regulating valve is installed on the pipeline located at the outlet end of the online calorimeter. The outlet end of the first regulating valve is connected to the waste liquid furnace burner and the flare system respectively through a three-way pipe.

7. The BOG compressor oil and gas treatment system according to claim 6, characterized in that: The control valve includes a manual valve and a shut-off valve. The manual valve is located on one side of the shut-off valve and is close to the three-way pipe.

8. The BOG compressor oil and gas treatment system according to claim 7, characterized in that: The cylindrical storage tank has a liquid collection area at its inner bottom, and a bottom drain pipe is connected to one side of the liquid collection area. A drain valve is installed on the bottom drain pipe.

9. The BOG compressor oil and gas treatment system according to claim 8, characterized in that: The cylindrical storage tank is equipped with a level gauge, which is a flap level gauge. When the level gauge level exceeds 30%, it triggers the drain valve to open.

10. A method for treating oil and gas in a BOG compressor, based on the BOG compressor oil and gas treatment system according to any one of claims 1-9, characterized in that: Includes the following steps: S1. The oil and gas generated by the operation of multiple BOG compressors are connected to the oil and gas inlet through a series pipeline; S2. Nitrogen source is provided to the three-way interface through the nitrogen supply unit, and the oil and gas are drawn into the cylindrical storage tank without compression. S3. The oil and gas are separated by centrifugal force generated by the cyclone generator. The gas flow containing tiny droplets is coalesced by the coalescing component and then settles to the bottom of the cylindrical storage tank for collection. S4. The oil and gas mixture after passing through the coalescing component enters the online calorific value meter to detect the calorific value of the mixture in real time, and the transmission rate of the mixture is controlled according to the detection results. S5. The air-fuel mixture is fully combusted through a dual-channel combustion assembly.

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