Nitrogen sealing gas recycling system for hazardous chemical substance normal-pressure liquid storage tank

Abstract

The utility model relates to a nitrogen sealing gas recycling system of a hazardous chemical substance normal-pressure liquid storage tank. The system comprises an air bag, a gas level meter, a hazardous chemical liquid storage tank and a flame arrester, wherein the air bag is connected with a nitrogen inlet / outlet in the top end of the hazardous chemical substance liquid normal-pressure storage tank through the nitrogen inlet / outlet valve and the flame arrester in sequence; the air bag is also connected with a gas level meter; an oxygen content analyzer is arranged on a pipeline between the nitrogen inlet and outlet valve and the flame arrester; the flame arrester is also connected with a tail gas treatment device through a valve and a discharge valve; the gas level meter is further provided with a signal transmitter, and the signal transmitter is connected with the drain valve through a line. According to the nitrogen sealing device, nitrogen discharged from a nitrogen sealing tank area can be fully recycled, the nitrogen consumption of nitrogen sealing of the tank area is greatly reduced, and the nitrogen sealing device has remarkable economic benefits and environmental social benefits.

Description

Technical Field

[0001] The utility model relates to the technical field of nitrogen sealing of hazardous chemical atmospheric pressure liquid storage tanks, in particular to a nitrogen sealing gas recovery and utilization system of hazardous chemical atmospheric pressure liquid storage tanks. Background Art

[0002] In the chemical and oil refining industries, there are numerous storage tanks, such as those used to store raw materials for hazardous chemicals, intermediate tanks containing hazardous chemicals, aromatic hydrocarbon tanks, and light oil tanks. Many of these materials naturally evaporate or, upon contact with oxygen in the air, form various compounds. Some of these volatile substances are toxic or have unpleasant odors, posing serious hazards and pollution to the atmospheric environment. In particular, the reaction between hazardous chemicals and air can produce other compounds, potentially leading to deflagration or explosion, posing a safety hazard. To address these issues, inert gas protection technology is currently the most widely used. This involves replacing the air in the tank with an inert gas (such as nitrogen) and sealing the tank to prevent the stored material from coming into contact with oxygen in the air to form an explosive mixture, which could result in combustion and explosion. This also prevents atmospheric pollution from emitted VOCs.

[0003] Chinese patent CN118594186A discloses a near-zero emission system and method for VOC-containing contaminated nitrogen breathing gas in a nitrogen-sealed tank area. This system utilizes liquid nitrogen cryogenic treatment technology to store purified contaminated nitrogen in a temporary atmospheric pressure storage tank. Overpressured and substandard contaminated nitrogen is treated in an emergency discharge adsorption purification tank before reaching emission standards. This method requires a cryogenic oil and gas recovery system, a purified contaminated nitrogen temporary storage tank, a purified contaminated nitrogen compressor, an emergency discharge adsorption purification tank, and a desorption vacuum pump. The process is lengthy, complex, and expensive.

[0004] Chinese patent CN202411116045.5 discloses a nitrogen-sealed gas recovery system for oil and gas recovery in a storage tank. The system sequentially connects a storage tank, a bombardment flame arrester, a variable-frequency induced draft fan, an oil and gas recovery device, a deoxygenation tank, a booster fan, an oxygen-containing control valve, a contaminated nitrogen storage tank, and a nitrogen-supplementing pressure control valve along a pipeline. This method introduces nitrogen-sealed gas into the oil and gas recovery device through the induced draft fan, and after deoxygenation, sends it into the contaminated nitrogen storage tank. Nitrogen is added to the tank by controlling the pressure of the contaminated nitrogen storage tank to achieve nitrogen sealing of the tank. This solution has a long processing flow and complex operation.

[0005] Therefore, it is necessary to develop a solution that can fully recover the nitrogen sealing gas in the storage tank, has a simple process, is easy to operate, and has a low cost. Utility Model Content

[0006] To address the aforementioned issues with existing processes, the present invention aims to provide a nitrogen blanketing gas recovery and utilization system for hazardous chemical atmospheric pressure liquid storage tanks. This system fully recycles nitrogen emitted from the nitrogen blanketing tank area, significantly reducing nitrogen consumption in the tank area and providing significant economic, environmental, and social benefits.

[0007] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0008] A nitrogen blanketing gas recovery and utilization system for a hazardous chemical atmospheric pressure liquid storage tank, the system comprising an air bag, a gas level gauge, a hazardous chemical liquid storage tank, and a flame arrester;

[0009] The airbag is connected to the nitrogen inlet and outlet valves, the flame arrester and the nitrogen inlet and outlet at the top of the atmospheric pressure storage tank for hazardous chemicals in sequence; the airbag is also connected to the gas level gauge;

[0010] An oxygen content analyzer is installed on the pipeline between the nitrogen inlet and outlet valves and the flame arrester;

[0011] The pipeline from the nitrogen inlet and outlet valves to the oxygen content analyzer is sequentially provided with three tees: the first tees, the second tees, and the third tees; the first tees are connected to the tail gas treatment device through a breathing valve; the second tees are connected to the main external pipe of the nitrogen source through a nitrogen supply valve and a pressure reducing valve; the third tees are connected to the tail gas treatment device through a nitrogen release valve;

[0012] The flame arrester is also connected to the exhaust gas treatment device through valves and discharge valves;

[0013] The gas level meter is also provided with a signal transmitter, which is connected to the discharge valve through a line.

[0014] Beneficial effects of the utility model:

[0015] 1. This utility model recycles the nitrogen sealing gas on the hazardous chemical liquid storage tank, greatly reducing the storage and transportation costs of hazardous chemicals. 3 Taking the nitrogen sealed storage tank as an example, the nitrogen volume can be saved by about 60,000 Nm per year. 3 .

[0016] 2. The equipment of this utility model has a simple structure. It only needs to set a nitrogen recovery air bag above the hazardous chemical storage tank. The nitrogen sealing gas of the hazardous chemical storage tank can be recovered and reused through valve control. It does not require a deep cooling system or an induced draft system. It has the characteristics of short process flow, simple equipment structure, easy operation and low cost.

[0017] 3. The utility model recycles the nitrogen sealing gas of the hazardous chemical liquid storage tank, and no longer discharges nitrogen containing VOCs into the environment, thus effectively protecting the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the utility model;

[0019] In the figure: 1-air bag, 2-gas level gauge, 3-nitrogen inlet and outlet valves, 4-pressure reducing valve, 5-nitrogen supply valve, 6-nitrogen release valve, 7-breathing valve, 8-hazardous chemical liquid atmospheric pressure storage tank, 9-discharge valve, 10-flame arrester. DETAILED DESCRIPTION

[0020] The present invention is further described below with reference to specific examples, but the protection scope of the present invention is not limited thereto.

[0021] Example 1:

[0022] A nitrogen blanketing gas recovery and utilization system for hazardous chemicals atmospheric pressure liquid storage tanks is composed of Figure 1 As shown, it includes an air bag (1), a gas level meter (2), a hazardous chemical liquid storage tank (8) and a flame arrester (10);

[0023] The air bag (1) is connected in sequence to the nitrogen inlet and outlet valve (3), the flame arrester (10) and the nitrogen inlet and outlet at the top of the hazardous chemical liquid atmospheric pressure storage tank (8); the air bag (1) is also connected to the gas level meter (2);

[0024] An oxygen content analyzer (11) is provided on the pipeline between the nitrogen inlet and outlet valve (3) and the flame arrester (10);

[0025] The pipeline from the nitrogen inlet and outlet valve (3) to the analyzer (11) is provided with a first tee, a second tee, and a third tee in sequence; the first tee is connected to the tail gas treatment device via a breathing valve (7); the second tee is connected to the main external pipe of the nitrogen source via a nitrogen supply valve (5) and a pressure reducing valve (4); the third tee is connected to the tail gas treatment device via a nitrogen release valve (6);

[0026] The flame arrester (10) is also connected to the exhaust gas treatment device through a valve and a discharge valve (9);

[0027] The gas level meter (2) is also provided with a signal transmitter, which is connected to the discharge valve (9) via a line;

[0028] The functions of the relevant components are:

[0029] The air bag (1) is used to recover nitrogen; the gas level meter (2) measures the gas height in the air bag; the gas level meter (2) is interlocked with the discharge valve (9) through a signal transmitter, and when the air bag is over-pressured, the discharge valve (9) is opened to release the pressure to the exhaust gas treatment system.

[0030] The nitrogen inlet and outlet of the hazardous chemical liquid storage tank (8) and the air bag (1) are connected to the pipeline, which is provided with a nitrogen supply valve (5), a nitrogen release valve (6), and a breathing valve (7) to provide protection against overpressure of the air bag and the storage tank. The nitrogen release valve (6) and the breathing valve (7) are respectively connected to the tail gas treatment system; when the gas phase pressure of the storage tank or the air bag is lower than the set value, the nitrogen supply valve (5) opens to add nitrogen to the storage tank or the air bag; when the gas phase pressure of the storage tank or the air bag is higher than the set value, the nitrogen release valve (6) opens to discharge nitrogen to the tail gas treatment system.

[0031] The setting of the pressure reducing valve (4) on the pipeline connecting the nitrogen supply valve (5) and the nitrogen source is to reduce the nitrogen pressure to 0.1-0.2 MPa and then provide the gas source for the nitrogen supply valve.

[0032] The function of the breathing valve (7) is: when the liquid storage tank (8) or the air bag (1) exceeds the set pressure and the nitrogen supply valve and the nitrogen release valve cannot provide effective protection, the breathing valve (7) opens to discharge nitrogen to the exhaust gas treatment system or inhale air to prevent the storage tank from being deflated.

[0033] The oxygen content analyzer (11) is used to measure the oxygen content in the system.

[0034] When the normal pressure liquid storage tank for storing hazardous chemicals is fed or discharged, or due to temperature effects, the pressure in the storage tank (8) will change with the change of the feed or discharge or temperature. When material enters the storage tank or the temperature rises, the pressure in the storage tank (8) increases, and the exhaust gas in the storage tank enters the air bag (1) for temporary storage. When the pressure exceeds the set limit (0.9kPa), the nitrogen release valve (6) automatically opens to discharge the nitrogen to the exhaust gas recovery system; when material is discharged from the storage tank or the temperature drops, the pressure in the storage tank (8) decreases, and the gas in the air bag (1) enters the storage tank (8) to maintain nitrogen sealing. When the pressure in the storage tank (8) drops to the set value (0.2kPa), the nitrogen supply valve (5) automatically opens to add nitrogen to the storage tank to maintain the nitrogen sealing pressure (0.2~0.9kPa).

[0035] As the tank is loaded and unloaded, the pressure inside the tank (8) changes, causing the air bag (1) to expand and contract as the pressure inside the tank changes, so as to maintain the nitrogen sealing pressure inside the tank within a certain range (0.2 to 0.9 kPa), thereby achieving nitrogen sealing of hazardous chemicals in the tank.

[0036] In an abnormal situation, if the pressure in the storage tank (8) exceeds the safety setting value (1.35kPa), the breathing valve (7) opens to release the pressure and discharge the nitrogen into the tail gas recovery system.

[0037] In an abnormal situation, if negative pressure is formed in the storage tank (8) and the pressure exceeds the safety setting value (-0.1kPa), the breathing valve (7) opens to inhale air to protect the storage tank from being damaged by the negative pressure.

[0038] The airbag is made of imported anti-static polymer material and its volume is variable, which is determined according to the volume of nitrogen sealing required for storing hazardous chemicals in normal pressure liquid storage tanks.

[0039] The utility model recycles the nitrogen sealing gas of the atmospheric pressure liquid storage tank for hazardous chemicals, which on the one hand reduces the amount of nitrogen used and lowers the nitrogen sealing cost; on the other hand, no longer discharges nitrogen containing VOCs into the atmosphere, thereby reducing air pollution and protecting the environment.

[0040] The contents described in this specification are merely an enumeration of implementation forms of the present utility model, and the protection scope of the present utility model should not be considered as being limited to the specific forms described in the embodiments.

[0041] Matters not covered in this utility model are known technologies.

Claims

1. A nitrogen blanketing gas recovery and utilization system for atmospheric pressure liquid storage tanks for hazardous chemicals, characterized in that the system comprises an air bag, a gas level gauge, a hazardous chemical liquid storage tank, and a flame arrester; in, The airbag is connected to the nitrogen inlet and outlet valves, flame arrester and the nitrogen inlet and outlet at the top of the atmospheric pressure storage tank for hazardous chemicals in sequence; the airbag is also connected to the gas level gauge; An oxygen content analyzer is installed on the pipeline between the nitrogen inlet and outlet valves and the flame arrester; The pipeline from the nitrogen inlet and outlet valves to the oxygen content analyzer is sequentially provided with three tees: the first tees, the second tees, and the third tees; the first tees are connected to the tail gas treatment device through a breathing valve; the second tees are connected to the main external pipe of the nitrogen source through a nitrogen supply valve and a pressure reducing valve; the third tees are connected to the tail gas treatment device through a nitrogen release valve; The flame arrester is also connected to the exhaust gas treatment device through valves and discharge valves; The gas level meter is also provided with a signal transmitter, which is connected to the discharge valve through a line.

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