CN209511606U - A kind of multi-arm intelligence super-low liquid unloading unit - Google Patents

Abstract

The utility model discloses a multi-arm intelligent ultra-low temperature liquid unloading device, which includes a storage tank and a plurality of unloading units, each unloading unit includes a tank car, a cryogenic pump skid and a booster gasifier, and the tank car is provided with a tank car The liquid phase interface, the gas phase interface of the tanker and the pressurized liquid phase interface. The cryopump skid includes the liquid phase arm of the unloading crane tube, the unloading pipeline, the gas phase arm of the unloading crane tube and the gas phase pipeline. The liquid phase interface of the tanker passes through the liquid phase of the unloading crane tube. The phase arm is connected to one end of the unloading pipeline, the other end of the unloading pipeline is connected to the liquid phase main pipe of the storage tank, the gas phase interface of the tanker is connected to one end of the gas phase pipeline through the gas phase arm of the unloading crane pipe, and the other end of the gas phase pipeline is connected to the gas phase main pipe of the storage tank , a liquid phase branch is arranged on the unloading pipeline. By adopting the device and process of the utility model, a certain pressure difference can be maintained between the tank car and the storage tank during the unloading process, which not only ensures the normal operation conditions of the unloading pump, but also improves the unloading speed.

Description

A multi-arm intelligent ultra-low temperature liquid unloading device

technical field

The utility model belongs to the technical field of ultra-low temperature liquid unloading, in particular to a multi-arm intelligent ultra-low temperature liquid unloading device.

Background technique

At present, the unloading of ultra-low temperature liquid LNG tank trucks generally adopts the self-pressurized unloading or pump unloading mode. The self-pressurized unloading process is simple. Due to the low liquid level of the tank car, the pressurization time is long, and the unloading time is long. A 50 cubic tank tank needs unloading time 3 to 4 hours; if the pump is used to unload the truck, due to the limitation of the outlet diameter of the tank truck, the current domestic tank truck standard liquid outlet diameter is DN50, which limits the flow of LNG. Due to the special properties of ultra-low temperature liquid, It is easy to produce cavitation phenomenon, resulting in the use of unloading pump unloading can not greatly shorten the unloading time. At present, the scale of LNG peak-shaving stations built in China is getting larger and larger, and a large amount of LNG is transported by cars. The problem of how to quickly unload the trucks needs to be solved urgently.

Whether it is self-pressurized unloading or unloading pump unloading, the pressure difference between the tank car and the storage tank cannot be kept relatively constant during the unloading process, resulting in slow unloading speed, and the unloading pump fails due to cavitation and cannot play its due role.

Utility model content

The technical problem to be solved by the utility model is to provide a multi-arm intelligent ultra-low temperature liquid unloading device for the above-mentioned deficiencies in the prior art. The device has a short unloading time. A 50 cubic tank car needs to be unloaded within 1.5 hours, and the optimal unloading time can reach 50 minutes to 70 minutes, which shortens the traditional unloading time to about 1/3 and effectively improves the unloading efficiency.

In order to solve the above technical problems, the technical solution adopted by the utility model is: a multi-arm intelligent ultra-low temperature liquid unloading device, which is characterized in that it includes a storage tank and a plurality of unloading units, and each of the unloading units includes a tank car, a low-temperature Pump skid and booster vaporizer, the tank car is provided with a tank car liquid phase interface, a tank car gas phase interface and a pressurized liquid phase interface, the cryogenic pump skid includes a liquid phase arm of an unloading crane tube, an unloading pipeline, The gas phase arm of the unloading crane tube and the gas phase pipeline, the liquid phase interface of the tank car is connected to one end of the unloading pipeline through the liquid phase arm of the unloading crane tube, and the other end of the unloading pipeline is connected to the liquid phase main pipe of the storage tank. The gas phase interface is connected to one end of the gas phase pipeline through the gas phase arm of the unloading crane pipe, and the other end of the gas phase pipeline is connected to the gas phase main pipe of the storage tank. There are a first pressure sensor, an unloading pump, a first temperature sensor, a second pressure sensor and a first valve, and a liquid phase branch is arranged on the unloading pipeline between the second pressure sensor and the first valve, so One end of the liquid phase branch is connected to the unloading pipeline, the other end of the liquid phase branch is connected to the liquid inlet of the booster gasifier, and the gas outlet of the booster gasifier is connected to the gas phase pipe through the second pipeline. The pressurized liquid phase interface is connected to the liquid phase branch through the first pipeline, the second valve is set on the liquid phase branch, and the second valve is set on the gas phase pipeline close to the gas phase interface of the tanker. A temperature sensor and a third pressure sensor; a gas phase branch is arranged on the gas phase pipeline, one end of the gas phase branch is connected to the gas phase pipeline, and the other end of the gas phase branch is connected to the gas phase pipe of the tank car, and the gas phase of the tank car The pipe is connected to the gas phase interface of the tank car of each unloading unit, and a third valve is arranged on the gas phase branch road.

The above-mentioned multi-arm intelligent ultra-low temperature liquid unloading device is characterized in that a fourth valve is provided on the gas phase pipeline between the gas phase branch and the gas phase main pipe of the storage tank.

The above-mentioned multi-arm intelligent ultra-low temperature liquid unloading device is characterized in that it also includes a control system, the control system includes a PLC controller and a power supply for each power unit, and the first pressure sensor of each unloading unit , the first temperature sensor, the second pressure sensor, the second temperature sensor and the third pressure sensor are all connected to the input end of the PLC controller, the unloading pump, the first valve, the second valve, the third Both the valve and the fourth valve are connected to the output end of the PLC controller.

The above-mentioned multi-arm intelligent ultra-low temperature liquid unloading device is characterized in that a first check valve is provided on the unloading pipeline at a position close to the liquid phase main pipe of the storage tank.

The above-mentioned multi-arm intelligent ultra-low temperature liquid unloading device is characterized in that a second check valve is provided in the liquid phase branch and is located downstream of the second valve.

Compared with the prior art, the utility model has the following advantages:

1. Compared with the existing self-pressurized unloading truck, the utility model has a shorter unloading time. The unloading time for a 50-cubic tank truck is within 1.5 hours, and the optimal unloading time can reach 50 minutes to 70 minutes, making the traditional unloading time It is shortened to about 1/3, which effectively improves the unloading efficiency.

2. Compared with the traditional pump unloading, the utility model device can effectively avoid the occurrence of cavitation during the operation of the unloading pump and improve the unloading speed.

3. Compared with self-pressurized unloading and pump unloading, the utility model has the advantage that a certain pressure difference can be maintained between the tank car and the storage tank during the unloading process. By collecting the pressure and pressurized gasification of the tank car and the storage tank The temperature data at the outlet of the gasifier is fed back to the PLC controller. The PLC controller controls the opening of the valve and adjusts the flow rate of the ultra-low temperature liquid entering the booster vaporizer, thereby controlling the pressure difference between the tank car and the storage tank to ensure that the unloading pump is always at the optimum level. Optimum operating status, reducing cavitation and failure rate during unloading operation, thereby improving unloading efficiency.

4. The utility model is equipped with multiple unloading units, which can realize simultaneous unloading of multiple tank cars; the gas phase branch of each unloading unit is connected with the gas phase pipe of the tank car, and the gas phase pipe of the tank car is connected with the gas phase interface of the tank car of each unloading unit They are all connected. During the unloading process, the pressure balance between each tank car is controlled by detecting the tank car pressure of each unloading unit. The gas in the high-pressure tank car is sent to other low-pressure tank cars to pressurize them, shortening the pressurization time of the tank car and the pre-cooling time of the unloading pump, and improving the unloading speed and efficiency.

5. Compared with self-pressurized unloading and pump unloading, the utility model has the advantage of controlling the flow of ultra-low temperature gas entering the supercharged gasifier through the valve, so as to control the gasification temperature at the outlet of the supercharged gasifier, which not only realizes the low temperature The tank car is pressurized, while preventing overheated gas from entering the tank car, causing a large amount of gasification of ultra-low temperature liquid in the tank car, reducing the flash steam emission during the unloading process, achieving the effect of energy saving, and improving the operational safety of the unloading process.

The technical solutions of the present utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is the structural representation of the utility model device.

Fig. 2 is a structural schematic diagram of an unloading unit of the present invention.

Fig. 3 is a schematic diagram of the connection relationship between a truck unloading unit and a PLC controller of the present invention.

1—tank car; 2—cryogenic pump skid; 3—liquid phase arm of unloading crane tube;

4—unloading pipeline; 5—first pressure sensor; 6—PLC controller;

7—unloading pump; 8—first temperature sensor; 9—second pressure sensor;

10—the first valve; 11—the liquid phase main pipe of the storage tank; 12—the gas phase main pipe of the storage tank;

13—second valve; 14—gas phase branch; 15—third valve;

16—the fourth valve; 17—liquid phase branch; 18—gas phase pipeline;

19—the first pipeline; 20—the booster vaporizer; 21—the second pipeline;

22—the second temperature sensor; 23—the third pressure sensor; 24—the gas phase arm of the unloading crane pipe;

25—tank car gas phase pipe; 26—there is a first check valve; 27—the second check valve.

Detailed ways

Example 1

As shown in Figures 1 and 2, the multi-arm intelligent ultra-low temperature liquid unloading device of the present invention includes a storage tank and a plurality of unloading units, and each of the unloading units includes a tank car 1, a cryogenic pump skid 2 and a pressurized gas pump. A carburetor 20, the tank car is provided with a tank car liquid phase interface, a tank car gas phase interface and a pressurized liquid phase interface, and the cryopump skid 2 includes an unloading crane tube liquid phase arm 3, a truck unloading pipeline 4, an unloading crane The gas phase arm 24 and the gas phase pipeline 18, the liquid phase interface of the tank car is connected to one end of the unloading pipeline 4 through the liquid phase arm 3 of the unloading crane pipe, and the other end of the unloading pipeline 4 is connected to the liquid phase main pipe 11 of the storage tank, The gas phase interface of the tank car is connected to one end of the gas phase pipeline 18 through the gas phase arm 24 of the unloading crane pipe, and the other end of the gas phase pipeline 18 is connected to the gas phase main pipe 12 of the storage tank. A first pressure sensor 5, an unloading pump 7, a first temperature sensor 8, a second pressure sensor 9 and a first valve 10 are sequentially arranged between the liquid phase main pipe 11 of the storage tank, and the unloading pipeline 4 is located on the second The position between the pressure sensor 9 and the first valve 10 is provided with a liquid phase branch 17, one end of the liquid phase branch 17 is connected to the unloading pipeline 4, and the other end of the liquid phase branch 17 is connected to the pressurized vaporizer 20, the gas outlet of the booster vaporizer 20 is connected to the gas phase pipeline 18 through the second pipeline 21, and the boosted liquid phase interface is connected to the liquid phase branch 17 through the first pipeline 19 connected, the liquid phase branch 17 is provided with a second valve 13, and the gas phase pipeline 18 is provided with a second temperature sensor 22 and a third pressure sensor 23 near the gas phase interface of the tanker; the gas phase pipeline 18 is provided with a gas phase branch 14, one end of the gas phase branch 14 is connected to the gas phase pipeline 18, and the other end of the gas phase branch 14 is connected to the gas phase pipe 25 of the tank car, and the gas phase pipe 25 of the tank car is connected to each unloading car The tank car gas phase ports of the unit are all connected, and the gas phase branch 14 is provided with a third valve 15 .

In this embodiment, a fourth valve 16 is provided on the gas phase pipeline 18 at a position between the gas phase branch 14 and the gas phase main pipe 12 of the storage tank.

As shown in Fig. 3, in the present embodiment, also comprise control system, described control system comprises PLC controller 6 and the power supply that supplies power for each electric unit, the first pressure sensor 5 of each described unloading unit, the first The temperature sensor 8, the second pressure sensor 9, the second temperature sensor 22 and the third pressure sensor 23 are all connected to the input end of the PLC controller 6, and the unloading pump 7, the first valve 10, the second The valve 13 , the third valve 15 and the fourth valve 16 are all connected to the output end of the PLC controller 6 .

In this embodiment, a first check valve 26 is provided on the unloading pipeline 4 near the liquid phase main pipe 11 of the storage tank.

In this embodiment, the liquid phase branch 17 is provided with a second check valve 27 downstream of the second valve 13 .

The principle of the control system of the present utility model includes: the pressure of the tank car 1 detected by the first pressure sensor 5, the outlet temperature data of the pressurized gasifier 20 detected by the second temperature sensor 22 and the temperature data detected by the third pressure sensor 23. The pressure data at the outlet of the booster gasifier 20 is fed back to the PLC controller 6, and the PLC controller 6 controls the flow rate of the ultra-low temperature liquid entering the booster gasifier 20 through the opening of the second valve 13, and then controls the tank car 1 and the storage tank The pressure difference inside always ensures that the unloading pump 7 is in the best operating state, reduces the cavitation phenomenon and failure rate during the unloading operation process, and improves the unloading efficiency at the same time.

Example 2

When the storage tank is an atmospheric storage tank, that is, when the pressure P in the storage tank is 0.1 MPa, the process of unloading ultra-low temperature liquid using the device of the present utility model includes:

Step 1, nitrogen replacement is carried out to the air in each pipeline of the device;

Step 2: The ultra-low temperature liquid in the tank car 1 enters the liquid phase branch 17 through the unloading pipeline 4 and the first pipeline 19, and then is introduced into the booster gasifier 20 to pressurize the tank car 1. The opening and closing degree of the second valve 13 on the liquid phase branch 17 controls the flow rate of the ultra-low temperature liquid entering the supercharged vaporizer 20, and the pressure in the tank car 1 continues to rise. When the first pressure sensor 5 detects that the tank car 1 When the internal pressure P1 reaches 0.4MPa～0.8MPa and the dynamic quantity ΔP satisfies the following conditions, the _first valve 10 is opened to precool the unloading pump 7:

P _s =(λL/d)ρv ² /2;

ΔP=P ₁ -P=P _2-1 +P _s ;

In the formula:

P _2-1 ——Theoretical differential pressure, in MPa;

P——The pressure in the storage tank, the unit is MPa;

P _s ——pressure loss, in MPa;

ρ——fluid density, unit is kg/m ³ ;

ν ₁₂ ——The velocity of the fluid at the liquid outlet of the tanker, in m/s;

ν ₂₂ ——The velocity of the fluid at the inlet of the unloading pump, in m/s;

ν—pipe fluid velocity, in m/s;

gZ ₁ ——The potential energy of the liquid outlet of the tank car, the unit is m ² /s ² ;

gZ ₂ ——The potential energy of the liquid inlet of the unloading pump, the unit is m ² /s ² ;

λ——the resistance coefficient along the pipeline;

L—the length of the pipe, in m;

d - inner diameter of the pipe, in m;

When meeting the following two conditions simultaneously, start the unloading pump 7 to unload:

Dynamic quantity ΔP=P ₁ -P=P _2-1 +P _s ;

And the temperature T ₁ detected by the first temperature sensor 8 <-120°C;

During the unloading process, while the unloading pump 7 is unloading, by adjusting the degree of opening and closing of the second valve 13, part of the ultra-low temperature liquid flowing out of the tank car is introduced into the booster vaporizer 20 through the liquid phase branch 17 to increase the temperature of the tank car. pressure, and control the temperature detected by the second temperature sensor 22 at the outlet of the booster gasifier 20 to meet the following conditions:

P ₃ =∑y _i P _ci ;

T _c =∑y _i T _ci ;

ΔT=T ₂ -T _c ;

ΔT is 278K～298K;

In the formula: Ai, Bi, Ci, yi are all constants, check "Cryogenic Handbook";

P ₃ ——the pressure detected by the third pressure sensor, the unit is MPa;

P _{ci ——the} pressure produced by the steam of each component of natural gas in saturated state, the unit is MPa;

T _{ci ——the} temperature of each component of natural gas in saturated state, unit is K;

T _c ——the saturation temperature of ultra-low temperature liquid at P ₃ , in K;

T ₂ ——the temperature detected by the second temperature sensor;

At the same time, the dynamic quantity ΔP is maintained to meet the following conditions:

Dynamic quantity ΔP=P ₁ -P=P _2-1 +P _s ;

During the unloading process, the pressure balance between each tank car is controlled by detecting the tank car pressure of each unloading unit. When the tank car pressure of a certain unloading unit is too low, open the third part of the unloading unit where the tank car with higher pressure is located. Valve 15, so that part of the gas in the tank car with high pressure enters the tank car of other unloading units with too low pressure through the gas phase pipeline 18, gas phase branch 14 and tank car gas phase pipe 25. pressurize;

Step 3: After unloading, close the unloading pump 7 and corresponding valves, open the fourth valve 16, and balance the pressure of the tank truck 1 and the storage tank through the gas phase pipeline 18.

Example 3

When the storage tank is a pressurized storage tank, that is, when the pressure in the storage tank is 0.4MPa～1.0MPa, the process of using the device of the present utility model to unload ultra-low temperature liquid includes:

Step 1, nitrogen replacement is carried out to the air in each pipeline of the device;

Step 2. First judge the pressure difference between the storage tank and the tank car 1. When the pressure P in the storage tank is greater than the pressure P1 in the tank car ₁ detected by the first pressure sensor 5, open the fourth valve 16 and pass through the gas phase tube. Road 18 balances the pressure of the tank car 1 and the storage tank. After the pressure is balanced, close the fourth valve 16; the ultra-low temperature liquid in the tank car 1 enters the liquid phase branch 17 through the unloading pipeline 4 and the first pipeline 19, and then introduces The tank car 1 is pressurized in the booster gasifier 20, and the flow rate of the ultra-low temperature liquid entering the booster gasifier 20 is controlled by the opening and closing degree of the second valve 13 on the liquid phase branch 17 during the boosting process. The pressure inside 1 keeps rising. When the pressure P1 inside the tanker ₁ detected by the first pressure sensor 5 reaches 0.4MPa～0.8MPa, and the dynamic quantity ΔP satisfies the following conditions, the first valve 10 is opened, and the unloading pump 7 Pre-cooling:

P _s =(λL/d)ρv ² /2;

ΔP=P ₁ -P=P _2-1 +P _s ;

In the formula:

P _2-1 ——Theoretical differential pressure, in MPa;

P——The pressure in the storage tank, the unit is MPa;

P _s ——pressure loss, in MPa;

ρ——fluid density, unit is kg/m ³ ;

ν ₁₂ ——The velocity of the fluid at the liquid outlet of the tanker, in m/s;

ν ₂₂ ——The velocity of the fluid at the inlet of the unloading pump, in m/s;

ν—pipe fluid velocity, in m/s;

gZ ₁ ——The potential energy of the liquid outlet of the tanker, the unit is m ² /s ² ;

gZ ₂ ——The potential energy of the liquid inlet of the unloading pump, the unit is m ² /s ² ;

λ——the resistance coefficient along the pipeline;

L—the length of the pipe, in m;

d - inner diameter of the pipe, in m;

When meeting the following two conditions simultaneously, start the unloading pump 7 to unload:

Dynamic quantity ΔP=P ₁ -P=P _2-1 +P _s ;

And the temperature T ₁ detected by the first temperature sensor 8 <-120°C;

During the unloading process, while the unloading pump 7 is unloading, by adjusting the degree of opening and closing of the second valve 13, part of the ultra-low temperature liquid flowing out of the tank car is introduced into the booster vaporizer 20 through the liquid phase branch 17 to increase the temperature of the tank car. pressure, and control the temperature detected by the second temperature sensor 22 at the outlet of the booster gasifier 20 to meet the following conditions:

P ₃ =∑y _i P _ci ;

T _c =∑y _i T _ci ;

ΔT=T ₂ -T _c ;

ΔT is 278K～298K;

In the formula: Ai, Bi, Ci, yi are all constants, check "Cryogenic Handbook";

P ₃ ——the pressure detected by the third pressure sensor, the unit is MPa;

P _{ci ——the} pressure produced by the steam of each component of natural gas in saturated state, the unit is MPa;

T _{ci ——the} temperature of each component of natural gas in saturated state, unit is K;

T _c ——the saturation temperature of ultra-low temperature liquid at P ₃ , in K;

T ₂ ——the temperature detected by the second temperature sensor;

At the same time, the dynamic quantity ΔP is maintained to meet the following conditions:

Dynamic quantity ΔP=P ₁ -P=P _2-1 +P _s ;

During the unloading process, the pressure balance between each tank car is controlled by detecting the tank car pressure of each unloading unit. When the tank car pressure of a certain unloading unit is too low, open the third part of the unloading unit where the tank car with higher pressure is located. Valve 15, so that part of the gas in the tank car with high pressure enters the tank car of other unloading units with too low pressure through the gas phase pipeline 18, gas phase branch 14 and tank car gas phase pipe 25. pressurize;

Step 3: After unloading, close the unloading pump 7 and corresponding valves, open the fourth valve 16, and balance the pressure of the tank truck 1 and the storage tank through the gas phase pipeline 18.

Xi'an Qinhua Natural Gas LNG Emergency Peak Shaving Station adopts the device and process of the utility model to unload the tank car, strictly follows the process flow, monitors the pressure difference between the tank car and the storage tank in real time, the pressure and temperature at the outlet of the pressurized gasifier, and uses the increase The pressure gasifier pressurizes the tank car and ensures a certain pressure difference between the tank car and the storage tank, thereby ensuring the best operating state of the unloading pump; when the pressure of the tank car of a certain unloading unit is too low, the Part of the gas in the tank car with high pressure enters the tank car of other unloading units with too low pressure to pressurize it. The device of the utility model has highlighted its advantages in this project. After statistics of actual continuous operation data, the average unloading time is controlled at 60 minutes each time, and the unloading speed has reached the design standard.

The above are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any simple modifications, changes and equivalent changes made to the above embodiments according to the technical essence of the present utility model still belong to this utility model. Within the scope of protection of utility model technical solutions.

Claims (5)

1. A multi-arm intelligent ultra-low temperature liquid unloading device is characterized in that it includes a storage tank and a plurality of unloading units, and each of the unloading units includes a tank car (1), a cryogenic pump skid (2) and a pressurized gasification device (20), the tank car is provided with a tank car liquid phase interface, a tank car gas phase interface and a pressurized liquid phase interface, and the cryopump skid (2) includes an unloading crane tube liquid phase arm (3), an unloading tube Road (4), unloading crane pipe gas phase arm (24) and gas phase pipeline (18), the liquid phase interface of the tank car is connected with one end of the unloading pipeline (4) through the unloading crane pipe liquid phase arm (3), and the unloading The other end of the pipeline (4) is connected to the liquid phase main pipe (11) of the storage tank, and the gas phase interface of the tank car is connected to one end of the gas phase pipeline (18) through the gas phase arm (24) of the unloading crane pipe, and the gas phase pipeline (18 ) is connected to the gas phase main pipe (12) of the storage tank, and the first pressure sensor (5) is sequentially arranged on the unloading pipeline (4) from the liquid phase interface of the tank truck to the liquid phase main pipe (11) of the storage tank , the unloading pump (7), the first temperature sensor (8), the second pressure sensor (9) and the first valve (10), on the unloading pipeline (4) and located at the second pressure sensor (9) and the first A position between the valves (10) is provided with a liquid phase branch (17), one end of the liquid phase branch (17) is connected to the unloading pipeline (4), and the other end of the liquid phase branch (17) is connected to the The liquid inlet of the booster gasifier (20) is connected, and the gas outlet of the booster gasifier (20) is connected with the gas phase pipeline (18) through the second pipeline (21), and the booster liquid phase The interface is connected with the liquid phase branch (17) through the first pipeline (19), the second valve (13) is arranged on the liquid phase branch (17), and the gas phase pipeline (18) is close to the tanker The position of the gas phase interface is provided with a second temperature sensor (22) and a third pressure sensor (23); the gas phase pipeline (18) is provided with a gas phase branch (14), and one end of the gas phase branch (14) It is connected with the gas phase pipeline (18), and the other end of the gas phase branch (14) is connected with the gas phase pipe (25) of the tanker, and the gas phase pipe (25) of the tanker is connected with the gas phase interface of the tanker of each unloading unit , the gas phase branch (14) is provided with a third valve (15). 2. A multi-arm intelligent ultra-low temperature liquid unloading device according to claim 1, characterized in that, the gas phase pipeline (18) is located between the gas phase branch (14) and the gas phase main pipe (12) of the storage tank The position of is provided with a fourth valve (16). 3. A kind of multi-arm intelligent ultra-low temperature liquid truck unloading device according to claim 2, is characterized in that, also comprises control system, and described control system comprises PLC controller (6) and the power supply for each power consumption unit, every The first pressure sensor (5), the first temperature sensor (8), the second pressure sensor (9), the second temperature sensor (22) and the third pressure sensor (23) of each described unloading unit are all connected with the PLC controller The input end of (6) is connected, and the unloading pump (7), the first valve (10), the second valve (13), the third valve (15) and the fourth valve (16) of each described unloading unit are all connected with The output end of the PLC controller (6) is connected. 4. A multi-arm intelligent ultra-low temperature liquid unloading device according to claim 1, characterized in that a first check valve is provided on the unloading pipeline (4) near the liquid phase main pipe (11) of the storage tank (26). 5. A kind of multi-arm intelligent ultra-low temperature liquid unloading device according to claim 4, characterized in that, the liquid phase branch (17) and the downstream of the second valve (13) are provided with a second check valve ( 27).