Near-zero emission system for VOCs (Volatile Organic Compounds)-containing waste nitrogen respiratory gas in nitrogen-sealed tank area

Abstract

The utility model belongs to the technical field of oil storage and transportation, and relates to a near-zero emission system for VOCs (volatile organic compounds) waste nitrogen respiratory gas in a nitrogen-sealed tank area. The system comprises an oil product storage tank (1), a liquid nitrogen cryogenic oil gas recovery system (2), a condensate tank (3), a liquid nitrogen tank (4), a purified waste nitrogen temporary storage gas cabinet (5), a purified waste nitrogen compressor (6), an emergency discharge adsorption purification tank (7), a desorption vacuum pump (8), an exhaust funnel (9), a public nitrogen pipe network (10), an emergency discharge valve (11), a public nitrogen stop valve (12), a public nitrogen check valve (13) and a nitrogen supplementing valve (14). VOCs and nitrogen in the gas discharged by the nitrogen-sealed tank area are fully recycled, the nitrogen consumption of nitrogen sealing in the tank area and the VOCs treatment cost are greatly reduced, and remarkable economic benefits and environmental social benefits are achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of oil storage and transportation, and relates to a recovery and processing system for exhaust gas generated during the oil storage and transportation process, and in particular to a near-zero emission system for breathing gas containing VOCs and contaminated nitrogen in a nitrogen-sealed tank area. Background Art

[0002] The petrochemical storage tank area covers a large area, has a large number of storage tanks, and stores a wide variety of materials. The largest number of storage tanks are atmospheric pressure (micro internal pressure) fixed-roof tanks, including internal floating tanks, dome tanks, and other types. In order to avoid the deterioration of stored materials due to contact with oxygen and to avoid the occurrence of explosive gases, it is necessary to implement nitrogen sealing on atmospheric pressure tanks to maintain the oxygen concentration in the gas phase space of atmospheric pressure tanks below the limiting oxygen concentration (LOC), or even lower, to eliminate explosion conditions and prevent tank explosion accidents.

[0003] The large breathing exhaust formed when the storage tank is fed and the small breathing exhaust caused by the temperature rise in the morning lead to the emission of VOCs nitrogen (hereinafter referred to as dirty nitrogen) in the storage tank. This exhaust causes excessive emission of non-methane total hydrocarbons on the one hand, and also causes waste of protective nitrogen on the other hand. The large breathing inhalation formed when the storage tank is discharged and the small breathing inhalation caused by the temperature drop in the afternoon need to be supplemented with nitrogen. At present, the protective nitrogen for petrochemical storage tanks is generally produced by air separation units (liquefaction separation method or pressure swing adsorption method). According to the "Design Specifications for Nitrogen Oxygen Systems in Petrochemical Enterprises" (SH / T3106-2019), the nitrogen produced by air separation is divided into three levels: industrial nitrogen: its nitrogen content (volume fraction) is greater than or equal to 99.2%; pure nitrogen: its nitrogen content (volume fraction) is greater than or equal to 99.99%; high-purity nitrogen: its nitrogen content (volume fraction) is greater than or equal to 99.999%. In some cases, liquid nitrogen gasification is also used to prepare nitrogen. As far as the nitrogen sealing gas in the tank area is concerned, industrial nitrogen has fully met the requirements. The existing technology combination can treat VOC-containing nitrogen emissions from storage tanks, recover VOCs, and produce nitrogen for tank inerting.

[0004] In addition to nitrogen, the polluted nitrogen components discharged from various storage tanks in the petrochemical storage tank area also contain VOCs volatilized by various organic chemicals stored. VOCs can be converted into liquids for recycling by condensation and absorption methods, or various thermal oxidation methods can be used to destroy VOCs. Based on the stringency of the current VOCs emission standards, it is often required that non-methane total hydrocarbons be less than 60mg / m 3. Simple condensation and absorption methods of oil and gas recovery are difficult to meet emission standards. The end-of-pipe treatment of polluted nitrogen discharged from petrochemical storage and transportation tank areas mostly adopts combustion methods (such as thermal combustion, catalytic oxidation, thermal storage oxidation, etc.) to meet emission standards, making the nitrogen protection in the storage and transportation tank area a one-time gas with extremely high operating costs. At the same time, high-concentration nitrogen combustion treatment is very likely to generate thermal nitrogen oxides that pollute the atmosphere. Therefore, it is hoped that the purified nitrogen can be recycled to reduce nitrogen consumption and the cost of processing to meet emission standards.

[0005] Chinese patent CN 108380001 B discloses a storage tank area protective nitrogen recovery and recycling system, which adopts a combination of absorption desulfurization + cooling and drying dehydration + vacuum pressure swing adsorption dehydrogenation + pressure swing adsorption deoxygenation treatment technology, as well as segmented injection protective nitrogen safety control technology, to obtain high-concentration hydrocarbon organic matter and 99% (V%) pure industrial gaseous nitrogen, respectively. The high-concentration hydrocarbon organic matter is sent to the flare or collected into the fuel gas pipeline network for safe use, and the 99% (V%) pure nitrogen is recycled as the storage tank area protective nitrogen. This method has a long processing flow and complex operation. The high-concentration hydrocarbon organic matter exists in a gaseous state and cannot be used without a flare and a fuel gas pipeline network.

[0006] Chinese patent CN 213160077 U discloses a storage tank VOCs cycle emission-free treatment device, which includes a gas collection compression unit, a condensation unit, a condensate recovery unit, a separation membrane unit, an adsorption unit, and an analysis unit in sequence along the oil and gas travel path. The storage tank VOCs cycle emission-free treatment device increases the oil and gas pressure entering the condensation unit through the inlet oil and gas compressor, reduces the condensation point of the oil and gas, and greatly improves the recovery efficiency of the condensation unit for oil and gas; under normal operating conditions of the equipment, the tail gas has zero emission, the tail gas organic gas concentration after separation by the separation membrane is <0.1%, and the nitrogen purity is >99%, which can directly enter the N2 storage tank on site and enter the nitrogen-sealed storage tank after adjustment by the pressure regulating valve; under emergency conditions, such as overpressure of the N2 storage tank, the gas directly enters the emergency emission unit, and after adsorption by the emergency emission unit, it reaches the standard of oil and gas emission, and the organic matter treatment rate reaches more than 99%, and the non-methane total hydrocarbons are <120mg / m3. This solution has a long processing flow and complex operation. The N2 storage tank is a pressure tank with high cost and high control requirements.

[0007] Chinese patent CN 110420536 B discloses a tank top VOCs recovery and nitrogen reuse system, which includes a pressurizing subsystem, a condensing subsystem, a pressure swing adsorption subsystem and a nitrogen recovery subsystem. The pressurizing subsystem includes a pressurizing air pump and a flame arrester. The condensing subsystem includes a regenerative heat exchanger, a precooling heat exchanger, a shallow cooling heat exchanger, a deep cooling heat exchanger, an explosion-proof refrigeration compressor, a condensing heat exchanger, an evaporative condensing heat exchanger and a throttling element, etc. The pressure swing adsorption subsystem includes more than two sets of parallel pressure swing adsorption devices. The nitrogen recovery subsystem is composed of a nitrogen buffer tank and a one-way valve. It uses a pressurizing regenerative heat exchanger, a precooling heat exchanger, a shallow cooling heat exchanger, and a deep cooling heat exchanger to gradually cool down and condense, and recover and purify the tank top VOCs gas by pressure swing adsorption. Finally, the VOCs are recovered and the tank top nitrogen is reused after purification. This solution has a long processing flow and complex operation. Since the temperature of the mechanical refrigeration is not low enough, some difficult-to-condense components cannot be condensed into liquid and discharged. Gradually enriching the system will lead to system collapse.

[0008] Therefore, it is necessary to develop a solution with low condensation temperature, sufficient liquefaction and recovery of VOCs, and low cost of nitrogen buffer tank. Utility Model Content

[0009] The purpose of the utility model is to overcome the shortcomings of the prior art and provide a near-zero emission system for VOCs-containing contaminated nitrogen breathing gas in a nitrogen-sealed tank area, which fully recycles the VOCs and nitrogen in the gas emitted from the nitrogen-sealed tank area, greatly reduces the nitrogen consumption of the nitrogen sealing in the tank area and the cost of VOCs treatment, and has significant economic benefits and environmental and social benefits.

[0010] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0011] A near-zero emission system for VOCs-containing contaminated nitrogen breathing gas in a nitrogen-sealed tank area, comprising an oil storage tank, characterized in that it also comprises a liquid nitrogen cryogenic oil and gas recovery system, a condensate tank, a liquid nitrogen tank, a purified contaminated nitrogen temporary storage gas holder, a purified contaminated nitrogen compressor, an emergency discharge adsorption purification tank, a desorption vacuum pump, an exhaust pipe, a public nitrogen pipeline network, an emergency discharge valve, a public nitrogen stop valve, a public nitrogen check valve and a nitrogen replenishment valve, wherein the exhaust pipe of the oil storage tank is connected to the liquid nitrogen cryogenic oil and gas recovery system, the liquid nitrogen cryogenic oil and gas recovery system is connected to the purified contaminated nitrogen temporary storage gas holder, the liquid nitrogen tank, the condensate tank and the public nitrogen pipeline network, the purified contaminated nitrogen temporary storage gas holder is connected to the purified contaminated nitrogen compressor, the purified contaminated nitrogen compressor is connected to the nitrogen replenishment valve and the emergency discharge valve, the emergency discharge valve is connected to the emergency discharge adsorption purification tank, the emergency discharge adsorption purification tank is connected to the exhaust pipe and the desorption vacuum pump, and the desorption vacuum pump is connected to the liquid nitrogen cryogenic oil and gas recovery system.

[0012] Preferably, the purified nitrogen temporary storage gas cabinet is provided with a pressure sensor, an oxygen sensor and a VOCs sensor.

[0013] Compared with the prior art, the near-zero emission system of VOCs-containing contaminated nitrogen breathing gas in the nitrogen-sealed tank area of ​​the utility model has one or more of the following beneficial technical effects:

[0014] 1. The purpose of the utility model is to treat the polluted nitrogen discharged from the storage and transportation tank area and then recycle it as nitrogen for storage tank protection. For the polluted nitrogen components discharged from the storage and transportation tank area, liquid nitrogen deep cold treatment technology is adopted, which can obtain a very high VOCs recovery rate. The purified polluted nitrogen is stored in a normal pressure temporary storage gas cabinet, which reduces the cost of nitrogen pressure storage tanks and the difficulty of operation and management. For overpressure and unqualified polluted nitrogen, it is treated in an emergency discharge adsorption purification tank and then meets the emission standards, meeting strict VOCs emission standards. Compared with existing oil and gas processing technology, the near-zero emission technology provided by the utility model fully recovers VOCs and nitrogen, greatly reduces the amount of gas venting and pure nitrogen consumption after treatment, significantly reduces the comprehensive operating costs of owners, and has significant environmental and social benefits.

[0015] 2. The utility model adopts liquid nitrogen cryogenic oil and gas recovery technology, atmospheric pressure temporary storage gas cabinet technology, and adsorption emergency emission purification technology, which effectively prevents the occurrence of unsafe factors such as high temperature and explosion, and has inherent safety. Compared with the incineration method, it greatly reduces the safety distance requirements from the oil tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the composition of the near-zero emission system of VOCs-containing polluted nitrogen breathing gas in the nitrogen-sealed tank area of ​​the utility model.

[0017] In the figure: oil storage tank 1, liquid nitrogen deep-cold oil and gas recovery system 2, condensate tank 3, liquid nitrogen tank 4, purified contaminated nitrogen temporary storage gas cabinet 5, purified contaminated nitrogen compressor 6, emergency discharge adsorption purification tank 7, desorption vacuum pump 8, exhaust pipe 9, public nitrogen pipeline network 10, emergency discharge valve 11, public nitrogen stop valve 12, public nitrogen check valve 13, nitrogen replenishment valve 14; pressure sensor 5-1, oxygen sensor 5-2, VOCs sensor 5-3. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The utility model relates to a near-zero emission system for breathing gas containing VOCs polluted nitrogen in a nitrogen-sealed tank area, which processes polluted nitrogen containing VOCs discharged from oil storage tanks, recovers VOCs in a condensed liquid state, purifies polluted nitrogen and reuses it as nitrogen sealing gas for storage tanks, and recycles pure nitrogen formed by gasification of liquid nitrogen to a public nitrogen pipeline network. In normal operating conditions, zero emission is achieved, and in emergency emission conditions, emission standards can be met.

[0021] Figure 1 The schematic diagram of the composition of the near-zero emission system of VOCs-containing nitrogen breathing gas in the nitrogen-sealed tank area of ​​the utility model is shown. Figure 1 As shown, the near-zero emission system of VOCs-containing contaminated nitrogen breathing gas in the nitrogen-sealed tank area of ​​the utility model includes an oil storage tank 1, a liquid nitrogen deep-cold oil and gas recovery system, a condensate tank 3, a liquid nitrogen tank 4, a purified contaminated nitrogen temporary storage gas cabinet 5, a purified contaminated nitrogen compressor 6, an emergency emission adsorption purification tank 7, a desorption vacuum pump 8, an exhaust pipe 9, a public nitrogen pipeline network 10, an emergency discharge valve 11, a public nitrogen stop valve 12, a public nitrogen check valve 13 and a nitrogen replenishment valve 4.

[0022] Among them, the exhaust pipe of the oil storage tank 1 is connected to the liquid nitrogen deep-cold oil and gas recovery system 2. The liquid nitrogen deep-cold oil and gas recovery system 2 is connected to the purified dirty nitrogen temporary storage gas holder 5, the liquid nitrogen tank 4, the condensate tank 4 and the public nitrogen pipeline network 10. The purified dirty nitrogen temporary storage gas holder 5 is connected to the purified dirty nitrogen compressor 6. The purified dirty nitrogen compressor 6 is connected to the nitrogen replenishment valve 14 and the emergency discharge valve 11. The emergency discharge valve 11 is connected to the emergency discharge adsorption purification tank 7. The emergency discharge adsorption purification tank 7 is connected to the exhaust pipe 9 and the desorption vacuum pump 8. The desorption vacuum pump 8 is connected to the liquid nitrogen deep-cold oil and gas recovery system 2.

[0023] Preferably, the purified nitrogen temporary storage gas cabinet 5 is provided with a pressure sensor 5-1, an oxygen sensor 5-2 and a VOCs sensor 5-3.

[0024] When using the near-zero emission system of VOCs-containing contaminated nitrogen breathing gas in the nitrogen-sealed tank area of ​​the utility model, under normal operating conditions, first, when large breathing exhaust and small breathing exhaust occur in the oil storage tank 1, the VOCs-containing contaminated nitrogen exhaust gas is led to the liquid nitrogen deep-cold oil and gas recovery system 2, and liquid nitrogen is introduced from the liquid nitrogen tank 4 to the liquid nitrogen deep-cold oil and gas recovery system 2. The VOCs-containing contaminated nitrogen exhaust gas can drop to -70~-160°C under the endothermic effect of liquid nitrogen. At this temperature, almost all VOCs are condensed into condensate and collected in the condensate tank 3. The pure nitrogen after the liquid nitrogen endothermic vaporization is sent to the nitrogen public pipeline network 10, and the purified contaminated nitrogen after the VOCs are removed is sent to the purified contaminated nitrogen temporary storage gas cabinet 5.

[0025] At the same time, the purified nitrogen in the purified nitrogen temporary storage tank 5 is compressed to a common nitrogen public pipeline pressure of 0.4-0.8 MPa by the purified nitrogen compressor 6 , and then the purified nitrogen is sent to the nitrogen replenishment valve 14 .

[0026] When the oil storage tank 1 has large breathing and small breathing, the nitrogen replenishing valve 14 is opened, and the purified contaminated nitrogen enters the oil storage tank 1 to provide inert sealing gas.

[0027] Therefore, under normal operating conditions, the utility model achieves complete recovery of VOCs, polluted nitrogen and pure nitrogen, achieves zero emission, and does not consume nitrogen from the public nitrogen pipeline network.

[0028] In the emergency discharge state, that is, when the pressure sensor 5-1 provided in the purified nitrogen temporary storage gas tank 5 senses the high pressure in the gas tank, the oxygen sensor 5-2 senses the high oxygen content, and the VOCs sensor 5-3 senses the high VOCs content, the emergency discharge valve 11 is opened to discharge the unqualified purified nitrogen to the emergency discharge adsorption purification tank 7. The VOCs in the unqualified nitrogen are adsorbed by the adsorption material in the emergency discharge adsorption purification tank 7, and the exhaust gas meeting the emission standards is discharged through the exhaust pipe 9.

[0029] The nitrogen lost due to emergency discharge is replenished to the oil storage tank 1 from the public nitrogen pipeline network 10 through the public nitrogen stop valve 12 , the public nitrogen check valve 13 , and the nitrogen replenishment valve 14 .

[0030] In the desorption state of the emergency discharge adsorption purification tank, the emergency discharge adsorption purification tank 7, which is saturated with adsorption after use, performs vacuum desorption of VOCs under the action of the desorption vacuum pump 8, and the high-concentration VOCs desorbed gas enters the liquid nitrogen deep-cold oil and gas recovery system 2 for condensation recovery. The process of condensation and recovery of high-concentration VOCs desorbed gas is the same as that in normal operating state, that is, liquid nitrogen is introduced from the liquid nitrogen tank 4 to the liquid nitrogen deep-cold oil and gas recovery system 2, and the exhaust gas containing VOCs and contaminated nitrogen can drop to -70~-160℃ under the action of liquid nitrogen endothermic absorption. At this temperature, almost all VOCs are condensed into condensate and collected in the condensate tank 3, and the pure nitrogen after liquid nitrogen endothermic vaporization is sent to the nitrogen public pipeline network 10, and the desorbed gas after removing VOCs is sent to the purified contaminated nitrogen temporary storage gas cabinet 5.

[0031] The waste nitrogen discharged from the nitrogen-protected storage tanks in the storage and transportation tank area of ​​petrochemical enterprises is complex, containing high-concentration nitrogen and the air that inevitably enters, as well as VOCs volatilized by the stored materials. This utility model refers to the "Petrochemical Enterprise Nitrogen Oxygen System Design Specification" (SH / T3106-2019), and the purity of the recovered nitrogen is not less than 99% (V%) and the pressure is not less than 0.3M Pa. The requirements can fully meet the requirements of nitrogen sealing of storage tanks, ensure the safety of storage tanks, and ensure the quality of stored materials.

[0032] The above embodiments of the utility model are merely examples for clearly explaining the utility model, and are not intended to limit the implementation methods of the utility model. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the utility model are still within the scope of protection of the utility model.

Claims

1. A near-zero emission system for VOCs-containing nitrogen breathing gas in a nitrogen-sealed tank area, comprising an oil storage tank (1), characterized in that: The oil storage tank (1) also includes a liquid nitrogen cryogenic oil and gas recovery system (2), a condensate tank (3), a liquid nitrogen tank (4), a purified contaminated nitrogen temporary storage gas cabinet (5), a purified contaminated nitrogen compressor (6), an emergency discharge adsorption purification tank (7), a desorption vacuum pump (8), an exhaust pipe (9), a public nitrogen pipeline network (10), an emergency discharge valve (11), a public nitrogen stop valve (12), a public nitrogen check valve (13) and a nitrogen replenishment valve (14). The exhaust pipe of the oil storage tank (1) is connected to the liquid nitrogen cryogenic oil and gas recovery system (2), and the liquid nitrogen cryogenic oil and gas recovery system (2) is connected to the purified contaminated nitrogen temporary storage gas cabinet (5). A gas storage cabinet (5), a liquid nitrogen tank (4), a condensate tank (3) and a public nitrogen pipeline network (10), wherein the purified contaminated nitrogen temporary storage cabinet (5) is connected to the purified contaminated nitrogen compressor (6), the purified contaminated nitrogen compressor (6) is connected to the nitrogen replenishment valve (14) and the emergency discharge valve (11), the emergency discharge valve (11) is connected to the emergency discharge adsorption purification tank (7), the emergency discharge adsorption purification tank (7) is connected to the exhaust pipe (9) and the desorption vacuum pump (8), and the desorption vacuum pump (8) is connected to the liquid nitrogen deep-cold oil and gas recovery system (2).

2. The near-zero emission system for VOCs-containing nitrogen breathing gas in the nitrogen-sealed tank area according to claim 1 is characterized in that: The purified contaminated nitrogen temporary storage gas cabinet (5) is provided with a pressure sensor (5-1), an oxygen sensor (5-2) and a VOCs sensor (5-3).

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