CN112755734A

CN112755734A - Marine nitrogen informatization preparation device and control method thereof

Info

Publication number: CN112755734A
Application number: CN202011585070.XA
Authority: CN
Inventors: 曹学磊; 董磊; 刘晓翠; 高瑞侠; 刘炳言; 杜清华
Original assignee: Heideway Technology Group Qingdao Co ltd
Current assignee: Heideway Technology Group Qingdao Co ltd
Priority date: 2020-12-28
Filing date: 2020-12-28
Publication date: 2021-05-07

Abstract

The invention discloses a marine nitrogen informatization preparation device and a control method thereof, wherein the device consists of a mechanical system and an electrical control system; the mechanical system comprises a compressed air preparation unit, an air pretreatment unit, a nitrogen production unit (membrane air separation unit) and a nitrogen storage unit; the electrical control system consists of a power distribution unit and a control unit. The invention detects parameters such as O2 content, dew point temperature, membrane inlet and outlet pressure and the like in real time, detects the nitrogen quality in real time at each stage of equipment operation, realizes the optimized matching of process variables and membrane performance, and determines whether to vent or not in real time according to the detected conditions, thereby not only ensuring the nitrogen purity, but also improving the nitrogen production rate, simultaneously reducing the membrane loss and prolonging the service life of the whole machine. The quality of the nitrogen is ensured to meet the requirements, and the use safety of the nitrogen is ensured.

Description

Marine nitrogen informatization preparation device and control method thereof

Technical Field

The invention relates to a marine nitrogen informatization preparation device and a control method thereof.

Background

Nitrogen is used as the gas with the most abundant content in air (the content in air is 78.084 percent, the boiling point is-195.8 ℃, the condensation point is-210 ℃) and is inexhaustible, and is a sub-inert gas due to the characteristic, and is often used as a protective gas. The nitrogen-making device can be used in the fields of LNG storage tank inerting, pipeline purging, atmosphere replacement and the like, and along with the development and application of the existing LNG technology, the nitrogen-making device also gradually becomes a key component of an explosion-proof system of an LNG liquid cargo ship and a chemical ship.

Current several conventional nitrogen gas production systems state of the art, drawbacks and deficiencies

There are three methods commonly used in industry today for nitrogen production- -cryogenic air separation, molecular sieve air separation (PSA), and membrane air separation.

(1) The cryogenic air separation nitrogen production principle comprises the following steps: the nitrogen is obtained by compressing and purifying air as a raw material, liquefying the air into liquid air (mainly a mixture of liquid oxygen and liquid nitrogen) by heat exchange, and rectifying the liquid air by utilizing the difference of the boiling points of the liquid oxygen and the liquid nitrogen (the former boiling point is-183 ℃ and the latter boiling point is-196 ℃ under the standard atmospheric pressure) to separate the liquid oxygen and the liquid nitrogen.

The method has the disadvantages of complex cryogenic air separation nitrogen production equipment, large floor area, higher capital construction cost, more equipment one-time investment, higher running cost, slow gas production (12-24 h) and unsuitability for ships.

(2) The principle of molecular sieve air separation nitrogen production: a method for separating nitrogen from oxygen by using air as a raw material and a carbon molecular sieve as an adsorbent and utilizing the selective adsorption of the carbon molecular sieve on the oxygen and the nitrogen by applying a pressure swing adsorption principle is generally called PSA (pressure swing adsorption) nitrogen preparation. Compared with the traditional nitrogen preparation method, the method has the advantages of high automation degree, fast gas production (15-30 minutes), low energy consumption and capability of adjusting the product purity in a larger range according to the needs of users.

The defects that pressure swing adsorption requires frequent switching of devices such as valves and the like, the loss of equipment components is large, the failure rate is high, and the pressure swing adsorption is not suitable for ships.

(3) The principle of membrane air separation nitrogen production: air is used as a raw material, and under a certain pressure condition, gases with different properties, such as oxygen, nitrogen and the like, have different permeation rates in a membrane to separate the oxygen and the nitrogen. The equipment has the advantages of quick start, simple structure, less switching valves, small volume, quicker gas production (less than or equal to 3 minutes) and the like, and is particularly suitable for medium and small-sized nitrogen users with the nitrogen purity of less than or equal to 98 percent.

The device of the type is characterized in that the membrane component for producing nitrogen belongs to a consumable product and needs to be replaced regularly. The nitrogen quality (O2 content) and nitrogen productivity are influenced by a plurality of parameters such as membrane module performance, membrane inlet temperature, membrane inlet/outlet pressure, membrane inlet/outlet flow and the like, and if stable nitrogen quality and nitrogen productivity are obtained, the parameters have large mutual influence, a plurality of coupling factors and more complex control.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provided are a nitrogen preparation device for a ship and a control method thereof. Mainly solves the following problems:

a, in the case of a conventional membrane air separation nitrogen production device, the quality (mainly the content of O2) of nitrogen greatly fluctuates due to the influence of multiple external environments. Generally, within an allowable range, the higher the membrane inlet temperature is, the higher the membrane inlet pressure is, and the larger the nitrogen production flow is; likewise, at a given nitrogen production flow rate, the higher the membrane inlet temperature, the higher the membrane inlet pressure, and the higher the nitrogen production purity. The pressure (commonly called as 'back pressure') of a nitrogen storage device (nitrogen buffer tank) of the membrane air separation nitrogen production device also has a certain influence on the nitrogen production efficiency, and when the back pressure is increased, the nitrogen production purity is increased, but the nitrogen production flow is reduced, so that the nitrogen production capacity is influenced. The pressure, flow, temperature, etc. parameters collectively determine the efficiency and throughput of the nitrogen generation system.

For users, the content of O2 is high, and thus the nitrogen quality requirement cannot be met, especially in the LNG field, the increase of the content of O2 may cause serious safety hazard, while the too low content of O2 may cause the membrane air separation plant to be overloaded, shorten the service life of the device, and cause the waste of resources and the reduction of the nitrogen production efficiency, so that maintaining the nitrogen quality (the content of O2) within a certain range becomes a core task of the nitrogen production plant.

The device monitors parameters such as membrane inlet temperature, membrane inlet pressure, membrane outlet flow and the like in real time, dynamically adjusts the opening of the electric flow regulating valve arranged at the rear end of the membrane air-conditioning device according to a certain method according to the content of O2 detected by an O2 analyzer, solves the problem of nitrogen quality fluctuation of a nitrogen making device, enables the nitrogen making process to be stable and efficient, and ensures the nitrogen quality and the nitrogen yield.

The conventional nitrogen making device B usually needs manual analysis and judgment when equipment failure or production process abnormity occurs, is greatly influenced by human factors, particularly in a shipborne environment, is inconvenient in communication and is difficult to solve problems in time due to condition limitation when the abnormity occurs. The device predefines more than 20 system alarm/warning types, not only monitors the process parameters in the nitrogen production in real time, but also diagnoses the faults of equipment components (such as an O2 analyzer and a PLC module), is clear at a glance when the problems occur, and solves the problem of self-diagnosis of the faults of the marine nitrogen making device.

The information degree of the conventional membrane air separation nitrogen making device is not high, no record or less record is generated in the production process, the related information and operation cannot be effectively traced, and the device is difficult to integrate with a ship main control system. The invention adopts high-end HMI, uses SQL database to record and file the data in the production process according to a certain speed/mode, the filed data can be consulted on the spot through HMI, and can be output in the formats of XML, CSV, PDF and the like, thereby facilitating the subsequent production analysis, having the function of audit trail to a certain extent, and solving the informatization problem of the marine nitrogen making device.

The N2 buffer tank in the D nitrogen production system is used as a pressure container, and the overpressure is strictly forbidden in the production process.

In order to solve the technical problems, the invention adopts the technical scheme that:

a marine nitrogen preparation device is composed of a mechanical system and an electrical control system;

the mechanical system comprises a compressed air preparation unit, an air pretreatment unit, a nitrogen production unit (membrane air separation unit) and a nitrogen storage unit;

the electric control system consists of a power distribution unit (power control of a compressor and a cold dryer) and a control unit PLC.

Wherein:

the compressed air preparation unit generates compressed air using an air compressor, and stores the compressed air in an air storage tank as a raw material for nitrogen preparation.

The air pretreatment unit filters oil stains and micro particles in the compressed air through a three-stage filter.

The nitrogen production unit utilizes a membrane air separation device to separate compressed air into two parts of nitrogen and oxygen.

The nitrogen storage unit is used for storing the nitrogen produced by the nitrogen making unit.

Further, the preparation device comprises an air compressor (A1), a compressed air storage tank (A2), a freeze dryer (A3), a filter (A4), a membrane inlet flow transmitter (C1), a membrane inlet pressure transmitter (C2), a membrane inlet temperature transmitter (C3), a membrane inlet electromagnetic valve (B1), a membrane air separation device (A5), an oxygen analyzer (C4), a dew point temperature meter (C5), a membrane outlet pressure transmitter (C6), a membrane outlet flow transmitter (C7), a regulating valve (B3), a membrane outlet three-way valve (B2) and a nitrogen storage tank (A6) which are connected in sequence;

a nitrogen storage tank pressure transmitter (C8) and a nitrogen storage tank pressure switch (D3) are arranged on the nitrogen storage tank (A6);

an air compressor state switch (D1) is arranged on the air compressor (A1), and a cold dryer state switch (D2) is arranged on the cold dryer (A3);

an exhaust gas discharge pipeline (E1) is arranged on the membrane air separation device (A5); and a gas emptying pipeline (E2) is also arranged on the membrane outlet three-way valve (B2).

The electrical control system consists of a power distribution unit and a control unit PLC;

the power distribution unit in the electrical control system receives 440V power feed, and provides 440V power supply for the air compressor (A1) and the cold dryer (A3), and also provides 220V power supply for the control unit PLC.

The control unit PLC comprises HMI man-machine interaction, a man-machine interface dynamically displays the nitrogen preparation process flow, and the membrane inlet temperature, the membrane inlet pressure, the membrane inlet flow, the membrane outlet pressure, the membrane outlet flow, the dew point temperature, the nitrogen storage tank pressure and the O2 content in the preparation process are connected with the control unit and displayed in real time on the main interface.

The air compressor (A1), the freeze dryer (A3), the membrane inlet solenoid valve (B1), the membrane outlet three-way valve (B2) and the regulating valve (B3) are also connected with the control unit PLC.

The control unit PLC also comprises a remote monitoring interface and a nitrogen tank overpressure monitoring device.

The basic principle of the invention is as follows:

the function of the device is to produce nitrogen, the quality of the nitrogen is the core control target of the device, and the quality of the nitrogen is determined by several parameters such as nitrogen purity, dew point temperature and the like, wherein the nitrogen purity is the most important technical parameter of the nitrogen quality, and the nitrogen purity is related to the oxygen content in the nitrogen, so the index for measuring the nitrogen purity can be represented by the O2 content. In the actual nitrogen preparation process, the phenomenon that the nitrogen quality does not reach the standard can occur due to the membrane self-efficiency and the existence of various external objective factors.

In the dangerous chemical field such as LNG, use not up to standard nitrogen gas can have serious potential safety hazard.

It is known from process practice that the O2 content is mainly influenced by the following external factors, in addition to the membrane itself:

temperature factor A

The higher the membrane inlet temperature, the higher the efficiency of the membrane air separation plant, and the lower the membrane outlet O2 content. Changes in membrane inlet temperature, which can affect the O2 content;

factor of B pressure

The higher the membrane inlet pressure, the higher the efficiency of the membrane air separation unit. Changes in membrane inlet pressure, which can affect the O2 content;

factor of C flow

The greater the gas flow through the membrane air separation unit, the less O2 in the gas will be separated and the higher the content of membrane outlet O2. Changes in membrane inlet and outlet flow rates can affect the O2 content. In the nitrogen filling process, along with the pressure rise in the nitrogen buffer tank, the pressure difference (PT 1-PT 2) between the inlet and the outlet of the membrane air separation device is reduced, the air flow passing through the membrane air separation device is reduced, and the O2 content at the membrane outlet is also reduced (the nitrogen quality is improved).

From the above analysis, to adjust the O2 content, parameters such as temperature, pressure, flow rate, etc. are variables that can be used for adjustment. Considering the characteristic that the marine equipment is not too complex, the device selects the flow regulation mode with the most cost performance through the balance of cost and income.

Compared with the conventional nitrogen preparation system, the nitrogen preparation system has the following beneficial effects:

the device has the advantages of excellent performance, rich functions, simple operation, convenient maintenance and strong maneuverability, and completely accords with the national standard of the marine inert gas system. The use, operation and maintenance of the nitrogen making device accord with the principle of ergonomics, the nitrogen making process is stable, the pressure stability of a pipe network is ensured, the noise is low, and the nitrogen making device has the following characteristics:

1. basic Properties

Parameter(s)	Unit of	Range
			Purity of nitrogen gas	%	95.0-99.9 (optional)
Oil content	PPM	<0.001
			Dust content	PPM	<0.01
Pressure of nitrogen	Bar	2-10
			Dew point temperature	℃	<-40
Pressure of compressed air	Bar	10-12

2. Based on O₂Nitrogen quality self-adaptive control for real-time content detection (automatic emptying of unqualified nitrogen)

The system finds a set of unique self-adaptive control algorithm according to process practice and deep understanding of a control algorithm of a gas preparation device, and the basic principle is that the nitrogen quality is detected in real time at each stage of equipment operation by detecting parameters such as O2 content, dew point temperature, membrane inlet and outlet pressure and the like in real time, so that the optimization matching of process variables and membrane performance is realized, whether the air is emptied is determined in real time according to the detected condition, the nitrogen purity is ensured, the nitrogen production rate is improved, the membrane loss is reduced, and the service life of the whole machine is prolonged.

The quality of the nitrogen is ensured to meet the requirements, and the use safety of the nitrogen is ensured.

3. Safety redundancy

Aiming at the high-level requirements of the marine equipment on reliability and safety, the system adopts a unique safety redundancy design.

Is mainly embodied in

In the nitrogen preparation process, each process loop adopts a safety valve, a check valve and other components which are obtained by precise calculation according to process requirements, and is matched with a flow sensor, a temperature sensor, a pressure sensor and other components. The sampling position/static and dynamic characteristics of the sensing instruments of parameters such as flow, temperature, pressure and the like are subjected to precise calculation and long-term process practice.

The nitrogen buffer tank B is used as a pressure container, the selection of the nitrogen buffer tank meets the relevant national specifications, and the system adopts a unique overpressure monitoring and turn-off loop, so that the nitrogen buffer tank can also be quickly cut off the relevant loop after overpressure even if the master control PLC fails.

4. Fault self-diagnosis

The device has abundant fault self-diagnosis functions.

And A, aiming at conventional components (such as valves, air compressors and cold dryers) and the like, adopting logic analysis to prejudge faults.

And B, performing fault diagnosis on the operation condition of the membrane module by adopting a brand new method.

And C, monitoring faults between the CPU and the I/O module by the PLC, monitoring abnormal events such as disconnection, short circuit, power loss and the like between each module and a sensor of each station of the equipment, and monitoring the faults by the PLC and the HMI by adopting a heartbeat program.

And D, when a fault occurs, the system automatically outputs alarm information through the HMI, the acousto-optic device and other equipment, and the fault can be quickly positioned and eliminated through the alarm information.

5. Production process data recording (process value filing) and report output function

The production process data record has very important function on the control and retrospective analysis of the nitrogen quality. The device realizes accurate record of production process data by using the SQL database. The recording system has stable operation, no data loss, no data disorder and other conditions, and has the following specific functions,

(1) data recording the data recording of the present apparatus comprises three parts,

recording the A process: recording process data (membrane inlet temperature, membrane inlet pressure, membrane inlet flow, membrane outlet pressure, membrane outlet flow, nitrogen purity, dew point temperature, buffer tank pressure) of the process flow

B, alarm recording: alarm logging for abnormal events (such as valve failure, etc.).

C, recording operation: recording of operations on equipment and its components (e.g. equipment on/off, air compressor on/off, valve on/off), modification of key parameters, etc

(2) Data query and display browsing

By time, paging inquiry is carried out according to various retrieval modes such as ID numbers and the like, Trend browsing display is carried out according to time periods, and operations such as left shift, right shift, zooming, panoramic view and the like of data curves can be carried out.

(3) Data export

The device can output reports in different modes such as XML, PDF, CSV and the like according to the selected time range.

(4) Data verification

And according to the preset values of the process parameters, the data are checked for validity through a statistical method, and according to the development trend of the data, the situation that the data are found to be unqualified is early warned.

The historical data can be stored for up to 36 months

The production data recording function of the device thoroughly overcomes the defect of low informatization degree of the traditional nitrogen preparation system, and the nitrogen preparation system is incorporated into the automatic ship monitoring system.

6. Remote data interaction

The data related to the preparation system can be provided to a third party (such as a main control room) through a mainstream communication mode such as Prifinet, ModbusTCP, OPC UA and the like, and the control output of the third party is received.

7. Authority management

The management of rights is a very important content in information systems, and particularly in the field of LNG application, any operation should be performed by a right. The device groups the user authority, different groups have different operation authorities, and completely eradicates unauthorized behaviors of key process parameters and equipment operation from the use level of the equipment.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

FIG. 1 is a specific structure of a mechanical system of a nitrogen informatization preparation device for a ship.

Fig. 2 is a specific structure diagram of an electrical control system of the nitrogen informatization preparation device for the ship.

Fig. 3 is a flow chart of the operation of the apparatus.

Fig. 4 is a gas flow diagram of the present apparatus in operation.

FIG. 5 is a diagram of the gas flow apparatus when nitrogen quality is not acceptable.

FIG. 6 is a block diagram of gas flow for a nitrogen gas of unacceptable quality.

FIG. 7 is a diagram of the apparatus for gas flow when nitrogen gas is of acceptable quality.

FIG. 8 is a block diagram of gas flow for nitrogen quality.

Fig. 9 is a main monitoring screen of the present apparatus.

Fig. 10 is a real-time alarm screen.

FIG. 11 is a process value real-time/historical trend screen.

Fig. 12 is a process recording screen of data.

Fig. 13 is an alarm recording screen of data.

Fig. 14 is an operation recording screen of data.

FIG. 15 is a data report output screen.

In the drawings:

a1 air compressor, A2 compressed air storage tank, A3 refrigeration dryer, A4 filter, A5 membrane air separation plant, A6 nitrogen storage tank,

B1 membrane inlet electromagnetic valve, B2 membrane outlet three-way valve, B3 regulating valve

C1 membrane inlet flow transmitter, C2 membrane inlet pressure transmitter, C3 membrane inlet temperature transmitter, C4 oxygen analyzer, C5 dew point temperature meter, C6 membrane outlet pressure transmitter, C7 membrane outlet flow transmitter, C8 nitrogen storage tank pressure transmitter

D1 air compressor state switch, D2 cold dryer state switch, D3 nitrogen storage tank pressure switch.

E1: exhaust gas discharge pipe, E2: and (5) exhausting the pipeline by using gas.

Detailed Description

Example 1

The embodiment provides a marine nitrogen preparation device and a control method thereof, wherein the preparation device consists of a mechanical system and an electrical control system;

Wherein:

More specifically, as shown in fig. 1-2, the preparation device comprises an air compressor (a 1), a compressed air storage tank (a 2), a freeze dryer (A3), a filter (a 4), a membrane inlet flow transmitter (C1), a membrane inlet pressure transmitter (C2), a membrane inlet temperature transmitter (C3), a membrane inlet solenoid valve (B1), a membrane air separation device (a 5), an oxygen analyzer (C4), a dew point temperature meter (C5), a membrane outlet pressure transmitter (C6), a membrane outlet flow transmitter (C7), a regulating valve (B3), a membrane outlet three-way valve (B2) and a nitrogen storage tank (a 6) which are connected in sequence.

The nitrogen storage tank (A6) is provided with a nitrogen storage tank pressure transmitter (C8) and a nitrogen storage tank pressure switch (D3).

An air compressor state switch (D1) is arranged on the air compressor (A1), and a cold dryer state switch (D2) is arranged on the cold dryer (A3).

Wherein the regulating valve (B3) is an electric regulating valve.

The basic principle of the embodiment is as follows:

temperature factor A

factor of B pressure

factor of C flow

The invention realizes the basic principle of automatic adjustment of O2 content

The PLC system monitors the content of O2 after the membrane air separation device in real time, and the opening of the electric regulating valve is changed according to the content of O2, so that the gas flow passing through the membrane air separation is changed, and the purpose of regulating the content of O2 is achieved.

When the content of O2 increases (the quality of nitrogen decreases), the opening of the electric control valve is decreased to decrease the flow rate, so that the efficiency of the membrane air separation plant increases and the content of O2 decreases accordingly.

When the content of O2 decreases (the quality of nitrogen gas increases), the opening degree of the electric control valve increases to increase the flow rate, the efficiency of the membrane air separation plant decreases, and the content of O2 increases accordingly.

By the adjusting method, the content of O2 in the prepared nitrogen is stabilized at a set level, and the quality of the nitrogen entering the N2 buffer tank is ensured to be stable and reliable.

In addition, if the O2 content requirement cannot be met by means of adjusting an electric control valve and the like, the relevant electromagnetic valve is immediately closed, and nitrogen is exhausted.

In the specific adjusting process, in order to meet the practical requirement, the system adjusts the content of O2 and also considers the yield.

This example is illustrated in FIGS. 3-4, which are a flow chart and a gas flow chart during operation. After the system is powered on, the electrically operated valves B1 and B2 are both in a closed state, and the membrane air separation unit does not work.

After the system is started, the control method comprises the following steps:

(1) the method comprises the steps of preparing compressed air, enabling the compressed air generated by an air compressor to enter and be stored in an air buffer tank (the set pressure is 10-12 Bar), and judging whether the pressure of the air buffer tank meets the production requirements or not by a system according to the state of the air compressor.

(2) The system automatically opens the B1 solenoid valve after the pressure in the nitrogen buffer tank is less than the preset value and the pressure in the air buffer tank reaches the design requirement, the B2 solenoid valve is closed, the B3 electric control valve has 50% opening, and the membrane air separation device enters a working state to start the nitrogen making process. Upon entering the operating state, the nitrogen gas separated from the membrane air separation unit is in a non-qualified state and is evacuated through a B2 solenoid valve (see FIGS. 5-6).

(3) After 1-2 minutes, the quality of the nitrogen monitored by each detection instrument reaches a stable state, the B2 electromagnetic valve is opened, and the qualified nitrogen is not exhausted any more but enters a nitrogen buffer tank (see figures 7-8).

In the process of filling nitrogen gas into the nitrogen gas buffer tank, the system detects the quality of the nitrogen gas in real time, and automatically adjusts the opening of the electric regulating valve according to the regulating principle inside the system to ensure that the O is in contact with the nitrogen gas₂The content is maintained at a certain level.

(4) If the pressure in the nitrogen buffer tank is greater than the preset value, the system closes the B1 electromagnetic valve and the B2 electromagnetic valve in sequence, and the membrane air separation device stops working.

And (5) if the pressure in the nitrogen buffer tank is smaller than the preset value, re-executing the step (2) and entering another filling cycle.

(5) During the nitrogen production process, the system monitors the process parameters and equipment assembly units in real time and gives a response.

Aiming at the demand characteristics of marine equipment, the device of the embodiment provides a perfect monitoring function by combining a nitrogen making process. Referring specifically to fig. 9-15, the monitoring screens and measures are as follows.

Fig. 9 shows a main monitoring screen and a real-time dynamic display of the process flow (pipeline flow block indication, air compressor/freeze dryer power supply display, running state indication, valve state indication, data display of various parameter instruments, system state and the like).

Fig. 10 is a real-time alarm screen.

FIG. 11 is a process value real-time/historical trend:

the process parameters such as membrane inlet temperature, membrane inlet pressure, membrane inlet flow, membrane outlet pressure, O2 content, dew point temperature, nitrogen buffer tank pressure, electric control valve set opening, electric control valve actual opening, etc. can be browsed in a real-time/historical curve manner.

Fig. 12-14 are data logging screens, process log, alarm log, and operation log, respectively.

Fig. 15 shows data report output (USB device is used as a report receiving device), and data in all production processes can be output in XML, CSV, PDF, and other formats.

It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art should understand that they can make various changes, modifications, additions and substitutions within the spirit and scope of the present invention.

Claims

1. The informationized preparation device of the nitrogen for the ship is characterized by comprising a mechanical system, wherein the mechanical system comprises a compressed air preparation unit, an air pretreatment unit, a nitrogen preparation unit and a nitrogen storage unit;

wherein: the compressed air preparation unit comprises an air compressor (A1) and a compressed air storage tank (A2) which are connected in sequence,

the air pretreatment unit comprises a cold dryer (A3) and a filter (A4) which are connected in sequence;

the nitrogen production unit separates compressed air into two parts of nitrogen and oxygen by using a membrane air separation device (A5);

the nitrogen storage unit is a nitrogen storage tank (a 6).

2. The informationalized preparation device of nitrogen for a ship of claim 1, comprising an air compressor (A1), a compressed air storage tank (A2), a freeze dryer (A3), a filter (A4), a membrane inlet flow transmitter (C1), a membrane inlet pressure transmitter (C2), a membrane inlet temperature transmitter (C3), a membrane inlet solenoid valve (B1), a membrane air separation device (A5), an oxygen analyzer (C4), a dew point temperature meter (C5), a membrane outlet pressure transmitter (C6), a membrane outlet flow transmitter (C7), a regulating valve (B3), a membrane outlet three-way valve (B2), and a nitrogen storage tank (A6) which are connected in sequence;

3. The informationized preparation device of nitrogen for the ship according to claim 1 or 2, further comprising an electrical control system consisting of a power distribution unit and a control unit PLC;

a power distribution unit in the electrical control system receives 440V power feed, and provides 440V power supply for an air compressor (A1) and a cold dryer (A3) and 220V power supply for a control unit;

the control unit PLC comprises HMI human-computer interaction, a human-computer interface dynamically displays the nitrogen preparation process flow, and the membrane inlet temperature, the membrane inlet pressure, the membrane inlet flow, the membrane outlet pressure, the membrane outlet flow, the dew point temperature, the nitrogen storage tank pressure and the O2 content in the preparation process are connected with the control unit and displayed in real time on a main interface;

the air compressor (A1), the cold dryer (A3), the membrane inlet solenoid valve (B1), the membrane outlet three-way valve (B2) and the regulating valve (B3) are also connected with the control unit PLC,

4. The control method of the marine nitrogen informatization preparation device, according to claim 3, is characterized by comprising the following steps:

s1, preparing compressed air, namely, enabling the compressed air generated by the air compressor to enter and be stored in an air buffer tank (the set pressure is 10-12 Bar), and judging whether the pressure of the air buffer tank meets the production requirement or not by a system according to the state of the air compressor;

s2, after the pressure in the nitrogen buffer tank is smaller than a preset value and the pressure in the air buffer tank meets the design requirement, the system automatically opens the B1 electromagnetic valve, closes the B2 electromagnetic valve, and 50% of opening of the B3 electric regulating valve, so that the membrane air separation device enters a working state and starts a nitrogen making process; when the membrane air separation device is in a working state, the nitrogen separated from the membrane air separation device is in an unqualified state and is exhausted through a B2 electromagnetic valve;

s3, after 1-2 minutes, if the quality of the nitrogen monitored by each detection instrument reaches a stable state, the B2 electromagnetic valve is opened, and the qualified nitrogen is not emptied any more and enters a nitrogen buffer tank;

s4, in the process of filling nitrogen into the nitrogen buffer tank, the system detects the quality of the nitrogen in real time, and automatically adjusts the opening of the electric adjusting valve according to the adjusting principle inside the system to ensure that O₂The content is maintained at a certain level;

if the pressure in the nitrogen buffer tank is greater than the preset value, the system closes the B1 electromagnetic valve and the B2 electromagnetic valve in sequence, and the membrane air separation device stops working;

if the pressure in the nitrogen buffer tank is smaller than the preset value, the step S2 is executed again, and another filling cycle is started;

s5, in the nitrogen production process, the system monitors each process parameter and equipment component unit in real time and gives a response.

5. The control method according to claim 4, characterized in that the control unit PLC monitors the O2 content after the membrane air separation device in real time, and changes the opening of the electric regulating valve according to the O2 content, thereby changing the gas flow passing through the membrane air separation and further achieving the purpose of regulating the O2 content;

if the O2 content is increased (the quality of nitrogen is reduced), the opening degree of an electric regulating valve is reduced, the flow is reduced, the efficiency of the membrane air separation device is increased, and the O2 content is reduced;

if the O2 content is reduced (the quality of nitrogen is improved), the opening degree of an electric control valve is increased, the flow is increased, the efficiency of the membrane air separation device is reduced, and the O2 content is increased;

by the adjusting method, the content of O2 in the prepared nitrogen is stabilized at a set level, and the quality of the nitrogen entering the N2 buffer tank is ensured to be stable and reliable;