System for slowing the rise in pressure of a tank during the unloading of cryogenic liquid ammonia

Abstract

This utility model discloses a system for mitigating the pressure rise in a storage tank during the unloading of cryogenic liquid ammonia. The system includes a cryogenic liquid ammonia tank, an unloading pipeline, and a tank group boundary ball valve. One end of the unloading pipeline is connected to a liquid ammonia unloading tanker, which has a built-in temperature detection unit. The other end of the unloading pipeline is connected to the interior of the cryogenic liquid ammonia tank, which includes an outer tank and an inner tank. The tank group boundary ball valve is installed on the unloading pipeline, and one end of the valve is connected in parallel to a first unloading branch pipe and a second unloading branch pipe. A regulating valve is installed on the first unloading branch pipe, which is connected to a lower inlet pipe extending from the inner tank via a flange. The outlet end of the lower inlet pipe is close to the bottom of the inner tank. This system for mitigating the pressure rise in a storage tank during the unloading of cryogenic liquid ammonia utilizes different inlet methods to slow down the pressure rise inside the tank, significantly improving unloading efficiency.

Description

Technical Field

[0001] This utility model relates to the field of petrochemical oil storage and transportation technology, specifically a system for mitigating the pressure rise in storage tanks during the unloading of cryogenic liquid ammonia. Background Technology

[0002] Liquid ammonia, also known as anhydrous ammonia, is a colorless liquid that readily vaporizes into gaseous ammonia. For ease of transportation and storage, gaseous ammonia is typically converted into liquid ammonia through pressurization or cooling. When liquid ammonia is stored in cryogenic tanks, the minimum operating temperature of the inner tank is usually set to -40°C to account for extreme environmental temperatures. Cryogenic liquid ammonia is typically transported by truck.

[0003] Because the liquid ammonia to be unloaded is a cryogenic liquid, two problems often occur during the unloading process. First, the liquid ammonia may vaporize after flowing in the pipeline or entering the cryogenic storage tank, and the generated gas will also enter the storage tank, causing the pressure inside the storage tank to rise and hinder unloading. Second, as liquid ammonia enters, the liquid level in the storage tank rises, and the gas phase space is continuously compressed, causing the pressure inside the storage tank to rise, resulting in a significant decrease in the unloading flow rate of liquid ammonia. These problems reduce the efficiency of unloading cryogenic liquid ammonia. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to overcome the existing defects and provide a system for slowing down the rise in tank pressure during the unloading of cryogenic liquid ammonia. This system solves the problem of increased tank pressure during the unloading of cryogenic liquid ammonia and effectively improves the efficiency of unloading cryogenic liquid ammonia.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a system for mitigating the pressure rise of a storage tank during the unloading of cryogenic liquid ammonia, comprising a cryogenic liquid ammonia tank, an unloading pipeline, and a tank group boundary ball valve. One end of the unloading pipeline is connected to a liquid ammonia unloading tanker, which has a built-in temperature detection unit. The other end of the unloading pipeline is connected to the interior of the cryogenic liquid ammonia tank, which includes an outer tank and an inner tank. The tank group boundary ball valve is installed on the unloading pipeline, and one end of the tank group boundary ball valve is connected in parallel to a first unloading branch pipe and a second unloading branch pipe.

[0006] The first unloading branch pipe is equipped with a regulating valve. The first unloading branch pipe is connected to the lower liquid inlet pipe extending from the inner tank of the storage tank through a flange. The outlet end of the lower liquid inlet pipe is close to the bottom of the inner tank of the storage tank.

[0007] The second unloading branch pipe is sequentially equipped with a stop valve for the unloading pipe and a ball valve for the unloading pipe. The second unloading branch pipe is connected to the upper liquid inlet pipe extending from the inner tank of the storage tank through a flange. The outlet end of the upper liquid inlet pipe is equipped with multiple annular nozzles, and the annular nozzles are close to the upper end of the inner tank of the storage tank.

[0008] The bottom of the inner tank of the storage tank is provided with an inner tank bottom temperature measuring element, which is connected to the inner tank bottom temperature indication signal provided outside the cryogenic liquid ammonia tank. The side wall of the inner tank of the storage tank is provided with an inner tank wall temperature measuring element, which is connected to the inner tank wall temperature indication signal provided outside the cryogenic liquid ammonia tank.

[0009] As a preferred embodiment of this utility model, a front shut-off ball valve and a rear shut-off ball valve are respectively provided at the front and rear positions of the regulating valve on the first unloading branch pipe. A regulating valve bypass pipe is provided between the inlet end of the front shut-off ball valve and the outlet end of the rear shut-off ball valve, and a regulating valve bypass ball valve is provided on the regulating valve bypass pipe.

[0010] As a preferred technical solution of this utility model, the unloading pipe stop valve on the second unloading branch pipe is provided with an orifice plate, a flow transmitter and a flow measurement indicator for controlling the flow rate.

[0011] As a preferred embodiment of this utility model, a gasket is provided between the flanges connecting the first unloading branch pipe and the lower liquid inlet pipe, and the second unloading branch pipe and the upper liquid inlet pipe.

[0012] As a preferred embodiment of this invention, the input end of the regulating valve is connected to the output end of the valve remote manual positioner.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows: This system for mitigating the pressure rise in the storage tank during the unloading of cryogenic liquid ammonia adopts different liquid inlet methods based on the difference in liquid temperature between the unloading tanker and the cryogenic liquid ammonia tank. When the liquid temperature in the unloading tanker is lower than that in the cryogenic liquid ammonia tank, the upper liquid inlet method is selected to enter the cryogenic liquid ammonia tank. The upper liquid inlet uses a spray method to reduce the pressure in the cryogenic liquid ammonia tank, which can speed up the unloading speed. When the liquid temperature in the unloading tanker is higher than that in the cryogenic liquid ammonia tank, the lower liquid inlet method is selected to enter the cryogenic liquid ammonia tank. The liquid entering the tank hydraulically first contacts the relatively cooler liquid in the cryogenic liquid ammonia tank, thus slowing down the pressure rise in the cryogenic liquid ammonia tank, reducing the impact on unloading, and greatly improving the unloading efficiency. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the system of this utility model.

[0015] In the diagram: 1. Cryogenic liquid ammonia tank; 2. Outer tank; 3. Inner tank; 4. Unloading pipeline; 5. Tank group boundary ball valve; 6. First unloading branch pipe; 7. Regulating valve bypass pipe; 8. Regulating valve bypass ball valve; 9. Regulating valve pre-shut-off ball valve; 10. Regulating valve; 11. Valve remote manual positioner; 12. Regulating valve post-shut-off ball valve; 13. Orifice plate; 14. Flow measurement indicator; 15. Flow transmitter; 16. Unloading pipeline shut-off valve; 17. Unloading pipeline ball valve; 18. Second unloading branch pipe; 19. Gasket; 20. Lower inlet pipe; 21. Upper inlet pipe; 22. Inner tank wall temperature measuring element; 23. Inner tank wall temperature indicator; 24. Inner tank bottom temperature measuring element; 25. Inner tank bottom temperature indicator; 26. Annular nozzle. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0017] Please see Figure 1 This utility model provides a technical solution: a system for mitigating the pressure rise of a storage tank during the unloading of cryogenic liquid ammonia, comprising a cryogenic liquid ammonia tank 1, an unloading pipeline 4, and a tank group boundary ball valve 5. One end of the unloading pipeline 4 is connected to a liquid ammonia unloading tank truck. The liquid ammonia unloading tank truck is equipped with a temperature detection unit for monitoring the temperature inside the liquid ammonia unloading tank truck. The cryogenic liquid ammonia tank 1 includes an outer tank 2 and an inner tank 3. The tank group boundary ball valve 5 is installed on the unloading pipeline 4. One end of the tank group boundary ball valve 5 is connected in parallel to a first unloading branch pipe 6 and a second unloading branch pipe 18.

[0018] A regulating valve 10 is installed on the first unloading branch pipe 6. The first unloading branch pipe 6 is connected to the lower liquid inlet pipe 20 extending from the inner tank 3 of the storage tank through a flange. The outlet end of the lower liquid inlet pipe 20 is close to the bottom of the inner tank 3 of the storage tank. In order to facilitate remote control of the opening and closing of the regulating valve 10, the input end of the regulating valve 10 is connected to the output end of the valve remote manual positioner 11.

[0019] The second unloading branch pipe 18 is sequentially equipped with a stop valve 16 for the unloading pipe and a ball valve 17 for the unloading pipe. The second unloading branch pipe 18 is connected to the upper liquid inlet pipe 21 extending from the inner tank 3 of the storage tank through a flange. The outlet end of the upper liquid inlet pipe 21 is equipped with multiple annular nozzles 26, which are close to the upper end of the inner tank 3 of the storage tank.

[0020] The bottom of the inner tank 3 is equipped with an inner tank bottom temperature measuring element 24. The inner tank bottom temperature measuring element 24 is connected to the inner tank bottom temperature indicator 25 located outside the cryogenic liquid ammonia tank 1. The temperature of the bottom of the inner tank 3 can be detected by the inner tank bottom temperature measuring element 24, and the real-time temperature of the bottom of the inner tank 3 can be displayed by the inner tank bottom temperature indicator 25, which is convenient for comparison with the liquid temperature inside the liquid ammonia unloading tanker.

[0021] An inner tank wall temperature measuring element 22 is installed on the side wall of the inner tank 3 of the storage tank. The inner tank wall temperature measuring element 22 is connected to the inner tank wall temperature indicator 23 located outside the cryogenic liquid ammonia tank 1. The temperature on the side wall of the inner tank 3 of the storage tank can be detected by the inner tank wall temperature measuring element 22, and the real-time temperature of the side wall of the inner tank 3 of the storage tank can be displayed by the inner tank wall temperature indicator 23, which is convenient for comparison with the liquid temperature inside the liquid ammonia unloading tank truck.

[0022] To prevent damage to the regulating valve 10 from affecting the liquid ammonia transport, or to ensure that the liquid ammonia transport in the first unloading branch pipe 6 is not affected during maintenance, a regulating valve front shut-off ball valve 9 and a regulating valve rear shut-off ball valve 12 are respectively installed before and after the regulating valve 10 on the first unloading branch pipe 6. A regulating valve bypass pipe 7 is installed between the inlet end of the regulating valve front shut-off ball valve 9 and the outlet end of the regulating valve rear shut-off ball valve 12, and a regulating valve bypass ball valve 8 is installed on the regulating valve bypass pipe 7.

[0023] To facilitate the adjustment of the liquid ammonia flow rate in the second unloading branch pipe 18, the unloading pipe stop valve 16 on the second unloading branch pipe 18 is equipped with an orifice plate 13, a flow transmitter 15, and a flow measurement indicator 14 for controlling the flow rate. The orifice plate 13 is located inside the second unloading branch pipe 18. When the liquid passes through the orifice plate 13, a pressure difference is generated before and after the orifice plate 13. The generated pressure difference is transmitted to the flow transmitter 15. The flow measurement indicator 14 is used to display the real-time flow rate. The flow transmitter 15 sends the signal to the control system, and the control system realizes the function of limiting the fluid flow rate.

[0024] To prevent liquid ammonia leakage and to distribute the pressure entering the cryogenic liquid ammonia tank 1, a gasket 19 is provided between the flanges connecting the first unloading branch pipe 6 and the lower inlet pipe 20, and between the second unloading branch pipe 18 and the upper inlet pipe 21.

[0025] When the liquid temperature inside the liquid ammonia unloading tanker is lower than the liquid temperature inside the receiving cryogenic liquid ammonia tank 1, the liquid enters the cryogenic liquid ammonia tank 1 via the top-inlet method. At this time, the tank group boundary ball valve 5, the regulating valve pre-shutdown ball valve 9, the regulating valve 10, and the regulating valve post-shutdown ball valve 12 are opened, and the regulating valve bypass ball valve 8, the unloading pipe stop valve 16, and the unloading pipe ball valve 17 are closed. The liquid inside the liquid ammonia unloading tanker passes through the gas phase space of the cryogenic liquid ammonia tank 1 via the first unloading branch pipe 6 in a spray manner. The supercooled droplets inside the liquid ammonia unloading tanker will absorb the gas in the storage tank. The spray method increases the space for convection between the gas and liquid phases in the storage tank, increases the heat exchange area between the gas and liquid, accelerates the depressurization process of the storage tank, and causes the pressure inside the storage tank to drop continuously, thereby speeding up the unloading speed.

[0026] When the liquid temperature inside the liquid ammonia unloading tanker is higher than the liquid temperature inside the receiving cryogenic liquid ammonia tank 1, the liquid enters the cryogenic liquid ammonia tank 1 via the bottom inlet method. At this time, the pre-closing ball valve 9, regulating valve 10, post-closing ball valve 12, and regulating valve bypass ball valve 8 are closed, and the tank group boundary ball valve 5, unloading pipe shut-off valve 16, and unloading pipe ball valve 17 are opened. The liquid inside the liquid ammonia unloading tanker enters the cryogenic liquid ammonia tank 1 at a relatively high temperature through the second unloading branch pipe 18. It first mixes with the relatively low-temperature liquid in the cryogenic liquid ammonia tank 1. The liquid ammonia unloaded from the liquid ammonia unloading tanker is rapidly cooled and does not have time to vaporize. This can reduce the tendency of the liquid inside the liquid ammonia unloading tanker to vaporize, slow down the increase in pressure inside the cryogenic liquid ammonia tank 1, and thus speed up the unloading speed.

[0027] When the liquid temperature inside the liquid ammonia unloading tanker is the same as the liquid temperature inside the receiving cryogenic liquid ammonia tank 1, the liquid inlet method can be determined according to the actual situation.

[0028] In addition, when using top-inlet unloading, when the total amount of liquid ammonia in the liquid ammonia unloading tanker is reduced to less than three tons, the valve on the first unloading branch pipe 6 should be closed immediately, and the unloading should be switched to the second unloading branch pipe 18 for bottom-inlet unloading. Since the gas-liquid mixture will be converted into liquid under the cooling effect of a large amount of liquid ammonia in the cryogenic liquid ammonia tank 1, the method of switching the inlet can prevent the cryogenic liquid ammonia tank 1 from pressurizing rapidly and ensure that the unloading task is completely completed.

[0029] The parts of the utility model not described in detail are prior art. Although embodiments of the utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the utility model. The scope of the utility model is defined by the appended claims and their equivalents.

Claims

1. A system for slowing down the pressure rise of a storage tank during low-temperature liquid ammonia unloading, comprising a low-temperature liquid ammonia tank (1), an unloading pipeline (4), and a tank group boundary ball valve (5), one end of the unloading pipeline (4) being connected with a liquid ammonia unloading tank truck, the liquid ammonia unloading tank truck being provided with a temperature detection unit therein, the other end of the unloading pipeline (4) being in communication with the inside of the low-temperature liquid ammonia tank (1), the low-temperature liquid ammonia tank (1) comprising a storage tank outer tank (2) and a storage tank inner tank (3), the tank group boundary ball valve (5) being arranged on the unloading pipeline (4), characterized in that: One end of the tank group boundary ball valve (5) is connected in parallel to the first unloading branch pipe (6) and the second unloading branch pipe (18); A regulating valve (10) is provided on the first unloading branch pipe (6). The first unloading branch pipe (6) is connected to the lower liquid inlet pipe (20) extending from the inner tank (3) of the storage tank through a flange. The outlet end of the lower liquid inlet pipe (20) is close to the bottom of the inner tank (3). The second unloading branch pipe (18) is sequentially equipped with a stop valve (16) for unloading pipe and a ball valve (17) for unloading pipe. The second unloading branch pipe (18) is connected to the upper liquid inlet pipe (21) extending from the inner tank (3) of the storage tank through a flange. The outlet end of the upper liquid inlet pipe (21) is equipped with multiple annular nozzles (26). The annular nozzles (26) are close to the upper end of the inner tank (3). The bottom of the inner tank (3) of the storage tank is provided with an inner tank bottom temperature measuring element (24), which is connected to the inner tank bottom temperature indicator (25) located outside the cryogenic liquid ammonia tank (1). The side wall of the inner tank (3) of the storage tank is provided with an inner tank wall temperature measuring element (22), which is connected to the inner tank wall temperature indicator (23) located outside the cryogenic liquid ammonia tank (1).

2. The system for mitigating the pressure rise in a storage tank during the unloading of cryogenic liquid ammonia according to claim 1, characterized in that: A regulating valve front shut-off ball valve (9) and a regulating valve rear shut-off ball valve (12) are respectively installed in front of and behind the regulating valve (10) on the first unloading branch pipe (6). A regulating valve bypass pipe (7) is provided between the inlet end of the regulating valve front shut-off ball valve (9) and the outlet end of the regulating valve rear shut-off ball valve (12). A regulating valve bypass ball valve (8) is provided on the regulating valve bypass pipe (7).

3. The system for mitigating the pressure rise in a storage tank during the unloading of cryogenic liquid ammonia according to claim 1, characterized in that: The unloading pipe stop valve (16) on the second unloading branch pipe (18) is equipped with an orifice plate (13), a flow transmitter (15) and a flow measurement indicator (14) for controlling the flow rate.

4. A system for mitigating the pressure rise in a storage tank during the unloading of cryogenic liquid ammonia according to claim 1, characterized in that: A gasket (19) is provided between the flanges connecting the first unloading branch pipe (6) and the lower liquid inlet pipe (20), and the second unloading branch pipe (18) and the upper liquid inlet pipe (21).

5. A system for mitigating the pressure rise in a storage tank during the unloading of cryogenic liquid ammonia according to claim 1, characterized in that: The input end of the regulating valve (10) is connected to the output end of the valve remote manual positioner (11).

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