An oxygen compressor sealing gas supply device

Abstract

This utility model discloses an oxygen compressor sealing gas supply device. The device includes: an oxygen compressor sealing gas supply source that is liquid nitrogen vaporized from a liquid nitrogen storage tank; an additional oxygen compressor sealing nitrogen pipeline connected to the liquid nitrogen vaporization pipeline at the bottom of the liquid nitrogen storage tank, before the liquid nitrogen vaporization pump inlet valve; the oxygen compressor sealing nitrogen pipeline is connected sequentially from the gas source output direction to the liquid nitrogen storage tank, the liquid nitrogen pipeline inlet valve, the liquid nitrogen pipeline check valve, a pressure transmitter, a low-pressure liquid nitrogen vaporizer, the ambient temperature nitrogen pipeline inlet valve, the ambient temperature nitrogen pipeline check valve, and a flow meter, and is connected to the inlet valve of the original oxygen compressor sealing nitrogen main pipeline; this utility model solves the problem of oxygen compressor failure or substandard oxygen quality caused by high water content in the sealing nitrogen of the oxygen compressor in the prior art, and has a significant effect on ensuring safe production, avoiding equipment failure, and reducing energy consumption loss.

Description

Technical Field

[0001] This utility model belongs to the field of deep refrigeration air separation, and particularly relates to the sealing gas supply system for oxygen compressors in this field. Background Technology

[0002] Deep refrigeration air separation equipment (hereinafter referred to as air separation equipment) uses the principle of low temperature distillation to simultaneously produce oxygen and nitrogen. The principle of low temperature distillation is to input the raw material air into the low temperature distillation column, and in the low temperature distillation column, through heat and mass exchange of rising vapor and reflux liquid, the oxygen and nitrogen in the raw material air are separated by taking advantage of the different boiling points of oxygen and nitrogen in the raw material air, and low temperature gaseous and liquid oxygen and nitrogen products are extracted.

[0003] The air separation unit consists of a product production system, an ambient temperature gas product compression and conveying system, and a cryogenic liquid product storage and vaporization system. The product production system consists of an air compressor, an air pre-cooling and purification device, a refrigeration device, a heat exchange device, and a distillation device. The air pre-cooling and purification device consists of an air cooling tower, a water cooling tower, and a process water pump. The ambient temperature gas product compression and conveying system consists of an oxygen compressor and a nitrogen compressor. The cryogenic liquid product storage and vaporization system consists of a liquid oxygen and liquid nitrogen storage tank and a liquid oxygen and liquid nitrogen vaporization device.

[0004] Low-temperature gaseous oxygen and nitrogen products are heated to room temperature via the main heat exchanger and then compressed and pressurized by the oxygen compressor (hereinafter referred to as "oxygen compressor") and nitrogen compressor (hereinafter referred to as "nitrogen compressor") outside the cold box before being delivered to the user's oxygen and nitrogen pipeline network. Low-temperature liquid oxygen and nitrogen products are stored in liquid oxygen storage tanks and liquid nitrogen storage tanks respectively, and then loaded into liquid oxygen and liquid nitrogen tank trucks for sale. Alternatively, they are filled into liquid oxygen and liquid nitrogen vaporization devices, pressurized by low-temperature liquid oxygen pumps and liquid nitrogen pumps, vaporized and heated to room temperature in water bath or air bath vaporizers, and then delivered to the user's oxygen and nitrogen pipeline network.

[0005] The oxygen compressor consists of a rotor, stator, sealing gas, lubricating oil, and cooling system. The shaft seal is a labyrinth seal, composed of a sealing gas chamber, a mixing gas chamber, and an oxygen chamber. The pressure in each chamber decreases in a stepwise manner, creating a stepped differential pressure. The sealing gas enters the labyrinth seal's sealing gas chamber, where the pressure is higher than that of the oxygen chamber, forming a gas seal to prevent oxygen leakage and isolate external air or lubricating oil from seeping in. Simultaneously, the sealing gas enters the labyrinth seal's mixing gas chamber for safe venting to the atmosphere. Sealing gas is also introduced into the oxygen compressor's bearing housing, isolating lubricating oil vapor from oxygen, and then safely venting to the atmosphere through the isolation chamber.

[0006] When the nitrogen compressor is in operation, the following potential hazards can inevitably cause leakage in the interstage cooler of the nitrogen compressor, resulting in high moisture content in the sealed nitrogen of the oxygen compressor.

[0007] 1. The heat exchange tubes in the gas interstage cooler of the nitrogen compressor are designed to be made of stainless steel. During the circulating cooling on the water side of the interstage cooler, Cl⁻, O2, and pH value cause pitting / stress corrosion cracking of the stainless steel heat exchange tubes, resulting in leakage of the interstage cooler.

[0008] 2. The flow of compressed nitrogen on the gas side of the gas intercooler causes vibration of the stainless steel heat exchange tubes, leading to fatigue cracking of the tube walls and leakage of the intercooler.

[0009] 3. Production planning and scheduling led to an increase in the number of times the nitrogen compressor was started and stopped, causing thermal stress fatigue in the heat exchange tubes of the interstage cooler, resulting in the accumulation of plastic deformation at the tube expansion points and leakage in the interstage cooler.

[0010] 4. Changes in enterprise production load and nitrogen demand cause changes in nitrogen pipeline pressure, leading to interstage pressure fluctuations in nitrogen compressors, heat exchange tube impact in interstage coolers, and leakage in interstage coolers.

[0011] According to technical papers published in domestic oxygen production journals, in 2023, the average leakage rate of interstage coolers for nitrogen compressors in the domestic oxygen production industry was 0.8 to 1.2 times per year. Among them, the leakage rate of interstage coolers for nitrogen compressors with an operating life of more than 10 years was 3 times that of interstage coolers for nitrogen compressors with an operating life of less than 5 years. The main causes of leakage in interstage coolers for nitrogen compressors were vibration and corrosion.

[0012] High moisture content in the nitrogen gas used for oxygen compressor seals has the following impacts on the oxygen compressor and production:

[0013] 1. High moisture content in the sealed nitrogen gas can cause water to seep into the bearing cavity, mix with the lubricating oil, emulsify the lubricating oil, and cause bearing lubrication failure, resulting in the oxygen compressor seizing up and stopping. This can lead to the oxygen compressor being disassembled for repair or scrapped, stopping the supply of oxygen to the production line, reducing or stopping the production line; the lubricating oil film may fail, causing dry metal friction, generating sparks, and even causing the oxygen compressor to explode.

[0014] 2. High moisture content in the sealed nitrogen gas allows water to enter the labyrinth seal, causing the seal to oxidize and erode. This results in an oxygen leakage rate greater than 15%, leading to a reduction in the oxygen supply to the production line and reduced production.

[0015] 3. High moisture content in the sealed nitrogen gas leads to water entering the labyrinth seal, resulting in high moisture content in the oxygen. The droplets impact and erode the impeller, disrupting the rotor's dynamic balance and causing the oxygen compressor to shut down. The oxygen compressor needs to be disassembled and repaired, causing production line reduction or shutdown.

[0016] According to technical papers published in domestic oxygen production journals, an oxygen compressor exploded in a chemical plant in 2023. The cause was that the chemical plant was balancing the pressure of the nitrogen pipeline network, and the nitrogen compressor was frequently started and stopped. The expansion and plastic deformation of the heat exchange tubes in the interstage cooler of the nitrogen compressor exceeded the maximum design value, which led to leakage in the gas interstage cooler of the nitrogen compressor. The sealed nitrogen dew point was -10℃ (design value ≤ -65℃), and the nitrogen in the oxygen compressor had a high water content, which caused the oxygen compressor to explode.

[0017] Direct costs of the failure: replacement of bearings / sealing rings (80-120), impeller dynamic balancing, lubricant replacement, and expedited air freight of imported labyrinth sealing rings (Hastelloy C276), totaling 2 million RMB.

[0018] Indirect losses due to the malfunction: The chemical plant was forced to shut down, resulting in a production line shutdown loss of 24 million yuan.

[0019] Therefore, the existing air separation equipment oxygen compressor sealing nitrogen inlet process system has the following problem that needs to be improved, namely the high water content of the nitrogen in the oxygen compressor sealing.

[0020] The existing oxygen compressor sealing nitrogen supply process is as follows: the ambient temperature and low pressure product nitrogen at the outlet of the main heat exchanger of the air separation equipment is compressed by a nitrogen compressor and delivered to the user's nitrogen pipeline. The oxygen compressor sealing nitrogen is taken from the user's pipeline nitrogen. The pipeline nitrogen is depressurized by a pressure reducing valve and then input into the oxygen compressor sealing nitrogen pipeline.

[0021] Existing nitrogen compressors use multi-stage compression to compress nitrogen. An interstage gas cooler cools the high-temperature nitrogen gas exiting the volute or diffuser stage in each stage, completing the isothermal compression process. The interstage gas cooler is designed to exchange heat between circulating cooling water and the high-temperature compressed nitrogen gas at the volute or diffuser outlet, cooling the nitrogen gas to the design value before it is fed into the next stage of compression or into the user's nitrogen pipeline. If the interstage gas cooler leaks during operation, circulating cooling water can enter the compressed nitrogen, resulting in high moisture content in the user's nitrogen pipeline. This leads to high moisture content in the nitrogen gas sealing the oxygen compressor, causing high moisture content in the oxygen and lubricating oil, ultimately resulting in equipment failure, substandard oxygen quality, or production disruptions.

[0022] For example, the C40 centrifugal oxygen compressor in Maanshan Iron & Steel's 35,000 m³ / h air separation unit is designed and manufactured by MAN of Germany. The sealed nitrogen from the C40 oxygen compressor is compressed and transported to the Maanshan Iron & Steel's medium-pressure nitrogen pipeline network by the C60 centrifugal nitrogen compressor in the same air separation unit. The C60 centrifugal nitrogen compressor is designed as a 5-stage compression unit, equipped with 5 gas interstage coolers. Circulating cooling water is used to cool the compressed nitrogen at the outlet of the 5 gas interstage coolers to the design value of 40°C.

[0023] In September 2024, the centrifugal nitrogen compressor C60 was started, the fourth-stage cooler of the nitrogen compressor leaked, and the centrifugal oxygen compressor C40 was delayed in starting, which had a significant impact on the supply of medium-pressure oxygen to Maanshan Iron and Steel.

[0024] See Figure 1 Schematic diagram of the sealed nitrogen system of the oxygen compressor C70 in the 35000m3 / h air separation unit of Maanshan Iron and Steel. Utility Model Content

[0025] (a) Technical problems to be solved

[0026] To address the shortcomings of existing technologies, the purpose of this invention is to provide a sealing gas supply device for an oxygen compressor, ensuring that the sealing nitrogen gas for the oxygen compressor is dry and clean during operation. Furthermore, this invention achieves fully automated operation, realizing the technical goal of automatically starting, adjusting, and stopping the sealing nitrogen supply system for the oxygen compressor.

[0027] (II) Technical Solution

[0028] To achieve the above objectives, this utility model provides the following technical solution:

[0029] This utility model discloses an oxygen compressor sealing gas supply device, comprising an oxygen compressor of an air separation unit, a main nitrogen inlet pipe connected to the oxygen compressor and an inlet valve for the main nitrogen inlet pipe; a nitrogen discharge pipe for the oxygen compressor, and an online oxygen analyzer and a nitrogen discharge valve arranged sequentially from the nitrogen discharge direction; and a liquid nitrogen vaporization system for the air separation unit, comprising a liquid nitrogen storage tank and a vent pipe extending from the top of the liquid nitrogen storage tank and a vent valve installed on the pipe; and a liquid nitrogen storage tank. The self-pressurizing loop pipeline extends from the lower part of the liquid nitrogen storage tank, and is sequentially equipped with a liquid nitrogen storage tank booster inlet valve and a booster. The self-pressurizing loop pipeline connects to the top side of the liquid nitrogen storage tank from the booster outlet. It also includes a liquid nitrogen vaporization pipeline extending from the lower part of the liquid nitrogen storage tank and connecting to the nitrogen pipeline network. From the liquid nitrogen storage tank to the nitrogen pipeline network, the liquid nitrogen vaporization pipeline is sequentially equipped with a liquid nitrogen vaporization pump inlet valve, a liquid nitrogen vaporization pump, a liquid nitrogen vaporization pump outlet valve, a liquid nitrogen vaporization pump check valve, a medium-pressure liquid nitrogen vaporizer, a medium-pressure nitrogen pipeline delivery valve, and a medium-pressure nitrogen pipeline check valve, arranged in the direction of liquid nitrogen output.

[0030] The technical solution of this utility model is as follows: the air source for the oxygen compressor sealing gas supply is liquid nitrogen vaporized from liquid nitrogen storage tank; the oxygen compressor sealing gas supply device includes: an additional oxygen compressor sealing nitrogen pipeline connected to the inlet valve of the oxygen compressor sealing nitrogen main inlet pipe before the liquid nitrogen vaporization pump inlet valve on the liquid nitrogen vaporization pipeline, the oxygen compressor sealing nitrogen pipeline is divided into two sections, the front section is a cryogenic liquid nitrogen pipeline, the cryogenic liquid nitrogen pipeline is connected in sequence from the gas source output direction to the liquid nitrogen storage tank, the liquid nitrogen pipeline inlet valve, the liquid nitrogen pipeline check valve, the pressure transmitter, and the low-pressure liquid nitrogen vaporizer; the rear section is a normal temperature nitrogen pipeline, the normal temperature nitrogen pipeline is connected in sequence from the outlet end of the low-pressure liquid nitrogen vaporizer to the normal temperature nitrogen pipeline inlet valve, the normal temperature nitrogen pipeline check valve and the flow meter, and is connected to the inlet valve of the oxygen compressor sealing nitrogen main inlet pipe.

[0031] A further technical solution of this utility model is: a low-pressure liquid nitrogen ambient temperature vaporizer is used, which uses air convection to heat the liquid nitrogen in the heat exchange tube of the ambient temperature vaporizer. The liquid nitrogen is vaporized and heated, keeping the nitrogen dew point in the nitrogen inlet pipeline of the oxygen compressor less than -90°C. The water content in the liquid nitrogen is extremely low. After being vaporized by the ambient temperature vaporizer, the water content is maintained at a dew point of less than -90°C, which meets the drying requirements of the nitrogen sealing gas.

[0032] Because liquid nitrogen has an extremely low temperature, the inlet valve of the liquid nitrogen pipeline on the front-end cryogenic liquid nitrogen pipeline is a cryogenic pneumatic top-guided single-seat regulating valve resistant to ultra-low temperatures, and the one-way valve of the liquid nitrogen pipeline is a lift-type cryogenic check valve. On the rear-end ambient temperature nitrogen pipeline, the inlet valve of the ambient temperature nitrogen pipeline is a conventional air-opening ambient temperature sleeve regulating valve, and the one-way valve of the nitrogen pipeline is a spring-loaded check valve. The flow meter is an ultrasonic flow meter.

[0033] A further technical solution of this utility model is as follows: the liquid nitrogen pipeline inlet valve, pressure transmitter, ambient temperature nitrogen pipeline inlet valve, flow meter connected to the sealed nitrogen pipeline of the oxygen compressor, and the inlet valve of the main inlet pipe of the sealed nitrogen pipeline of the oxygen compressor are all electrically connected to the DCS control system of the air separation equipment. According to the set pressure and flow parameters, the data can be continuously detected online, and the nitrogen pressure and flow rate input to the inlet of the main inlet valve of the sealed nitrogen pipeline of the oxygen compressor can be automatically tracked and adjusted to maintain the sealed nitrogen in a stable state of constant pressure, constant flow and ambient temperature.

[0034] In the DCS control system of the air separation unit, when the oxygen compressor is turned on and running, a three-way control logic is set up for the automatic delivery, adjustment and shutdown of the sealing nitrogen of the oxygen compressor.

[0035] First, the pressure transmitter and flow meter installed on the oxygen compressor's sealed nitrogen pipeline are set to the sealed nitrogen pressure and flow rate set values. When the oxygen compressor of the air separation unit is running, the liquid nitrogen pipeline inlet valve, the ambient temperature nitrogen pipeline inlet valve, and the oxygen compressor sealed nitrogen inlet main pipe inlet valve are opened. At the same time, the liquid nitrogen storage tank booster inlet valve and the liquid nitrogen storage tank vent valve are opened and adjusted to increase the liquid nitrogen pressure to the pressure set value. The liquid nitrogen that reaches the pressure set value enters the low-pressure liquid nitrogen vaporizer and is vaporized to ambient temperature. Then, the ambient temperature and constant pressure nitrogen is adjusted to the set flow rate value through the ambient temperature nitrogen pipeline inlet valve. The ambient temperature, constant pressure, and constant flow nitrogen enters the oxygen compressor sealed nitrogen inlet main pipe from the ambient temperature nitrogen pipeline inlet valve outlet. At the same time, the oxygen compressor sealed nitrogen discharge valve is automatically opened.

[0036] During this period, the opening of the liquid nitrogen storage tank booster inlet valve and the liquid nitrogen storage tank vent valve are automatically adjusted according to the pressure transmitter setpoint, and the opening of the ambient temperature nitrogen pipeline inlet valve is automatically adjusted according to the flow meter setpoint. The sealed nitrogen discharged from the oxygen compressor enters the oxygen compressor sealed nitrogen discharge pipeline, and is automatically regulated by the sealed nitrogen discharge valve before being discharged into the atmosphere.

[0037] Finally, when the oxygen compressor stops operating and the oxygen compressor motor stops for 1 hour, the oxygen compressor sealing nitrogen shutdown switch is automatically activated, and the liquid nitrogen pipeline inlet valve, nitrogen pipeline inlet valve, and sealing nitrogen discharge valve are automatically fully closed.

[0038] The implementation of this utility model has a significant effect on ensuring the safe, stable and economical operation of oxygen compressors. It can be applied to various oxygen compressors in different industries. The field of deep refrigeration and air separation is a high-energy-consuming industry. In particular, centrifugal compressors such as oxygen compressors are high-power and high-energy-consuming equipment. Reducing or avoiding equipment failure rate can also reduce power consumption loss, which is of great significance for enterprises to save energy, reduce costs and reduce carbon emissions. Attached Figure Description

[0039] Figure 1 Schematic diagram of the nitrogen labyrinth seal structure of the centrifugal oxygen compressor in an air separation unit;

[0040] Figure 2 Schematic diagram of the C70 sealed nitrogen system of the oxygen compressor in the 35000m3 / h air separation unit of Maanshan Iron & Steel;

[0041] Figure 3 This utility model provides a schematic diagram of an oxygen compressor sealing gas supply device.

[0042] Figure 4 A simplified diagram of the self-starting adjustment logic control of this utility model embodiment.

[0043] Figure 5 A simplified diagram of the automatic shutdown logic control in this embodiment of the utility model.

[0044] Figure 1Explanation of symbols in the attached diagram: Y1, centrifugal oxygen compressor impeller; M2, labyrinth seal oxygen chamber; M3, labyrinth seal mixed gas chamber; M4, labyrinth seal sealed gas chamber; V1, sealed nitrogen inlet valve; V2, sealed nitrogen exhaust valve; M5, isolation chamber; Z6, bearing housing.

[0045] Figure 2 Explanation of symbols in the attached diagram: C70, oxygen compressor; C60, nitrogen compressor; AI2, online nitrogen dew point analyzer; V820, nitrogen compressor C60 check valve; V809, medium-pressure nitrogen pipeline delivery valve; V810, medium-pressure nitrogen pipeline check valve; V819, nitrogen delivery valve; V801, sealed nitrogen pressure reducing valve; V802, sealed nitrogen main inlet valve; AI1, sealed nitrogen online oxygen analyzer; V803, sealed nitrogen exhaust valve.

[0046] Figure 3 Explanation of symbols in the attached diagram: B70, liquid nitrogen storage tank; C70, oxygen compressor; L1, liquid nitrogen storage tank venting pipe; V818, liquid nitrogen storage tank venting valve; L2, liquid nitrogen storage tank self-pressurization pipe; E71, liquid nitrogen storage tank booster; V817, liquid nitrogen storage tank booster inlet valve; L3, liquid nitrogen storage tank liquid nitrogen vaporization pipe; V806, liquid nitrogen vaporization pump P50 inlet valve; P50, liquid nitrogen vaporization pump; V807, liquid nitrogen vaporization pump outlet valve; V808, liquid nitrogen vaporization pump check valve; E50, medium-pressure liquid nitrogen vaporizer; V809, medium-pressure nitrogen pipeline delivery valve; V810, medium-pressure nitrogen pipeline check valve; L4, oxygen compressor sealed nitrogen discharge pipe; AI1, sealed nitrogen online oxygen analyzer; V803, sealed... Nitrogen vent valve; L5, sealed nitrogen inlet manifold of oxygen compressor; V802, inlet valve of sealed nitrogen inlet manifold; L6, sealed nitrogen pipeline of oxygen compressor; V804, liquid nitrogen pipeline inlet valve; V805, liquid nitrogen pipeline check valve; P1, pressure transmitter; E70, low-pressure liquid nitrogen vaporizer; V811, inlet valve of ambient temperature nitrogen pipeline; V812, check valve of ambient temperature nitrogen pipeline; F1, flow meter.

[0047] Figure 4 , Figure 5 The attached diagram illustrates the following: AUTO ON means automatic start; AUTO STOP means automatic stop; PV: pressure setpoint; 0 indicates off, and 1 indicates on. Detailed Implementation

[0048] The following will be combined with the appendix of this utility model Figures 3-5 The technical solutions in the embodiments of this utility model will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0049] Example: Sealed nitrogen inlet device for C70 oxygen compressor in a 35000m3 / h air separation unit.

[0050] The 35000 m³ / h air separation unit's liquid nitrogen vaporization system includes: a liquid nitrogen storage tank B70 and a vent pipe L1 extending from the top of the liquid nitrogen storage tank, along with a vent valve V818 installed on the pipe; it also includes a self-pressurizing loop pipe L2 for the liquid nitrogen storage tank B70, which extends from the lower part of the liquid nitrogen storage tank B70, and sequentially includes a liquid nitrogen storage tank booster inlet valve V817 and a booster E71. The self-pressurizing loop pipe L2 connects to the top side of the liquid nitrogen storage tank from the booster outlet; it also includes a liquid nitrogen vaporization pipe L3 extending from the lower part of the liquid nitrogen storage tank B70 and connecting to the nitrogen pipeline network, which extends from the liquid nitrogen storage tank... From B70 to the nitrogen pipeline network, the following components are installed sequentially in the direction of liquid nitrogen output: liquid nitrogen vaporization pump inlet valve V806, liquid nitrogen vaporization pump P50, liquid nitrogen vaporization pump outlet valve V807, liquid nitrogen vaporization pump check valve V808, medium-pressure liquid nitrogen vaporizer E50, medium-pressure nitrogen pipeline delivery valve V809, and medium-pressure nitrogen pipeline check valve V810. Additionally, the system includes an oxygen compressor C70, an oxygen compressor sealed nitrogen inlet main pipe L5 and inlet valve V802; an oxygen compressor sealed nitrogen discharge pipe L4; and a sealed nitrogen online oxygen analyzer AI1 and a sealed nitrogen vent valve V803, installed sequentially in the direction of sealed nitrogen discharge. Vent valve V803 is connected to the atmosphere.

[0051] The technical solution of this utility model embodiment includes: 1. Design of sealed nitrogen inlet process for oxygen compressor C70; 2. Configuration of pipeline valves and instruments for sealed nitrogen inlet device; 3. Control logic (DCS control system) and operation of sealed nitrogen system.

[0052] I. Design of sealed nitrogen inlet process for oxygen compressor C70;

[0053] In this embodiment, the gas source for the sealing gas supply process of the oxygen compressor C70 is liquid nitrogen vaporized from the liquid nitrogen storage tank B70. The oxygen compressor sealing gas supply device includes: a new oxygen compressor sealing nitrogen pipeline L6 is added before the inlet valve V806 of the liquid nitrogen vaporization pump installed on the original liquid nitrogen vaporization pipeline L3, and connected to the inlet valve V802 of the original oxygen compressor C70 sealing nitrogen main pipeline L5. The oxygen compressor sealing nitrogen pipeline L6 is divided into two sections. The first section is a cryogenic liquid nitrogen pipeline. The warm liquid nitrogen pipeline is sequentially configured from the gas source output direction as follows: liquid nitrogen storage tank B70, liquid nitrogen pipeline inlet valve V804, liquid nitrogen pipeline check valve V805, pressure transmitter P1, and low-pressure liquid nitrogen vaporizer E70; the subsequent section is the ambient temperature nitrogen pipeline, which, from the outlet end of the low-pressure liquid nitrogen vaporizer E70, is sequentially configured as follows: ambient temperature nitrogen pipeline inlet valve V811, ambient temperature nitrogen pipeline check valve V812, flow meter F1, and connected to the oxygen compressor sealed nitrogen main pipeline L5 inlet valve V802.

[0054] The design values ​​for the sealed nitrogen pressure and flow rate of the C70 oxygen compressor are 450 kPa and 500 m³ / h, respectively.

[0055] The 35000 m³ / h air separation unit's liquid nitrogen storage tank B70 is designed to store 200 m³ of liquid nitrogen. 3 (Liquid) The equivalent gaseous nitrogen storage capacity is 648 × 200 m³. 3 =129600m 3 ;

[0056] The 35,000 m³ / h air separation unit is designed to produce 1,000 m³ / h of liquid nitrogen (gas state), and the oxygen compressor C70 is designed to produce 500 m³ / h of sealing nitrogen (gas state). When the oxygen compressor C70 is running, about half of the liquid nitrogen produced by the air separation unit is used to meet the nitrogen demand of the oxygen compressor sealing, and the other half is used for storage.

[0057] The liquid nitrogen storage tank B70 is an insulated vacuum type, and the pressure design value of the liquid nitrogen storage tank is 10~1000KPa. The pressure can be adjusted to meet the technical requirements of the sealing nitrogen pressure design value of 450KPa for the oxygen compressor C70.

[0058] When the oxygen compressor C70 of the 35000m3 / h air separation unit is running, open the liquid nitrogen pipeline inlet valve V804, adjust the liquid nitrogen storage tank B70 vent valve V818 and the booster E71 inlet valve V817 to increase the liquid nitrogen pressure to the design value of 450KPa. The liquid nitrogen enters the low-pressure liquid nitrogen vaporizer E70 and is vaporized to room temperature. The room temperature and constant pressure nitrogen gas is adjusted to the design value of 500m³ / h through the room temperature nitrogen pipeline inlet valve V811. Open the sealed nitrogen main inlet valve V802, and the room temperature, constant pressure and constant flow nitrogen gas is input into the sealed nitrogen inlet main of the oxygen compressor.

[0059] Oxygen compressor C70 exhaust process: Without changing the original design exhaust process, pipelines, valves, and online oxygen analyzer AI1 of oxygen compressor C70, the sealed nitrogen discharged from oxygen compressor C70 enters the sealed nitrogen exhaust pipeline L4 of oxygen compressor, and is regulated by the sealed nitrogen vent valve V803 before being discharged into the atmosphere.

[0060] II. Configuration of sealing nitrogen inlet device pipelines, valves, and instruments;

[0061] The liquid nitrogen storage tank B70 booster E71 is an ambient temperature tubular heat exchanger, model number DPL-206-1.38, made entirely of austenitic stainless steel. The liquid nitrogen storage tank B70 vent valve V818 is a cryogenic gas-closed diaphragm-type long-stem valve with a diameter of 50mm; the liquid nitrogen storage tank B70 booster E71 inlet valve V817 is a cryogenic gas-open diaphragm-type long-stem valve with a diameter of 20mm. The liquid nitrogen storage tank B70 vent valve V818 and the liquid nitrogen storage tank B70 booster E71 inlet valve V817 are electrically connected to the 35000m³ / h air separation unit's DCS control system.

[0062] Based on actual calculations and several field tests, the design specifications for the cryogenic liquid nitrogen pipeline upstream of L6 in the oxygen compressor sealing nitrogen pipeline are: diameter 40mm, pressure 1.6MPa, and material 316 stainless steel. The valves and instruments installed on the cryogenic liquid nitrogen pipeline upstream of L6 are as follows: Liquid nitrogen inlet valve V804 is a cryogenic pneumatic top-guided single-seat regulating valve with a diameter of 40mm; liquid nitrogen check valve V805 is a lift-type cryogenic check valve with a diameter of 40mm; pressure transmitter P1 is a pressure... An electric pressure transmitter is used; the low-pressure liquid nitrogen vaporizer E70 is an ambient temperature tube-fin heat exchanger, model VAN-1200-120. The design values ​​for the flow rate and pressure of the low-pressure liquid nitrogen vaporizer E70 are 600 m³ / h and 600 kPa, respectively, with redundancy. These values ​​are higher than the design values ​​for the sealing nitrogen pressure and flow rate of the oxygen compressor C70, which are 450 kPa and 500 m³ / h. The heat exchange tubes of the low-pressure liquid nitrogen vaporizer E70 are designed as star-shaped aluminum alloy finned tubes, with an outer diameter of 160 mm and a tube diameter of 24 mm × 2 mm. The liquid nitrogen pipeline inlet valve V804, the liquid nitrogen pipeline check valve V805, and the pressure transmitter P1 are all electrically connected to the DCS control system of the 35000 m³ / h air separation unit.

[0063] Based on actual calculations and several field tests, the designed diameter, pressure, and material of the ambient temperature nitrogen pipeline downstream of L6 in the oxygen compressor sealing pipeline are 80mm, 3.1MPa, and 304 stainless steel, respectively. The nitrogen pipeline inlet valve V811 is designed as an air-opening diaphragm-type ambient temperature sleeve regulating valve with a diameter of 80mm. The nitrogen pipeline check valve V812 is designed as a spring-loaded check valve with a diameter of 80mm. The flow meter is designed as an ultrasonic flow meter. The nitrogen pipeline inlet valve V811, nitrogen pipeline check valve V812, and flow meter F1 are all electrically connected to the DCS control system of the 35000m³ / h air separation unit.

[0064] III. Control Logic (DCS Control System) and Operation of Sealed Nitrogen System.

[0065] The automatic operation method of the gas supply device for the C70 sealed nitrogen system of the oxygen compressor in the 35000 m3 / h air separation unit of Maanshan Iron and Steel is as follows:

[0066] In the DCS control system of the 35000m3 / h air separation unit, a three-way control logic is designed for the automatic delivery, regulation, and shutdown of sealed nitrogen in the C70 oxygen compressor.

[0067] First, turn on the sealed nitrogen start switch of the oxygen compressor C70; the liquid nitrogen storage tank B70 booster E71 inlet valve V817 and the liquid nitrogen storage tank B70 vent valve V818 will automatically adjust, and the liquid nitrogen pipeline inlet valve V804, the nitrogen pipeline inlet valve V811, and the sealed nitrogen main inlet valve V802 will automatically open, adjusting the sealed nitrogen to the set pressure value of 450KPa and the flow rate value of 500m3 / h.

[0068] At the same time, the sealed nitrogen vent valve V803 opens automatically.

[0069] During this period, when the oxygen compressor C70 is running, the liquid nitrogen storage tank B70 booster E71 inlet valve V817 and the liquid nitrogen storage tank B70 vent valve V818 automatically adjust the valve opening according to the pressure transmitter P1 setting value of 450 kPa; the nitrogen pipeline inlet valve V811 automatically adjusts the valve opening according to the flow meter F1 setting value of 500 m3 / h.

[0070] Finally, when oxygen compressor C70 stops operating and the oxygen compressor motor stops operating for 1 hour, the sealing nitrogen shutdown switch of oxygen compressor C70 is automatically activated, and the liquid nitrogen pipeline inlet valve V804, the nitrogen pipeline inlet valve V811, and the sealing nitrogen vent valve V803 are automatically fully closed.

Claims

1. An oxygen compressor sealing gas supply device, comprising an oxygen compressor of an air separation unit, a main oxygen compressor sealing nitrogen inlet pipe connected to the oxygen compressor and an inlet valve for the main oxygen compressor sealing nitrogen inlet pipe installed thereon; a nitrogen discharge pipe for the oxygen compressor, and an online oxygen analyzer for sealing nitrogen and a nitrogen discharge valve for sealing nitrogen arranged sequentially from the nitrogen discharge direction of the oxygen compressor; further comprising a liquid nitrogen vaporization system for the air separation unit, the liquid nitrogen vaporization system comprising: The system includes a liquid nitrogen storage tank and a vent pipe extending from the top of the liquid nitrogen storage tank, along with a vent valve installed on the pipe. It also includes a self-pressurizing loop pipe for the liquid nitrogen storage tank, wherein a loop pipe extends from the lower part of the liquid nitrogen storage tank, and a liquid nitrogen storage tank booster inlet valve and a booster are sequentially installed thereon. The self-pressurizing loop pipe connects to the top side of the liquid nitrogen storage tank from the booster outlet. Furthermore, it includes a liquid nitrogen vaporization pipe extending from the lower part of the liquid nitrogen storage tank and connecting to a nitrogen pipeline network. The liquid nitrogen vaporization pipe, from the liquid nitrogen storage tank to the nitrogen pipeline network, sequentially includes a liquid nitrogen vaporization pump inlet valve, a liquid nitrogen vaporization pump, a liquid nitrogen vaporization pump outlet valve, a liquid nitrogen vaporization pump check valve, a medium-pressure liquid nitrogen vaporizer, a medium-pressure nitrogen pipeline delivery valve, and a medium-pressure nitrogen pipeline check valve, arranged in the direction of liquid nitrogen output. Its characteristic is that it supplies sealing gas from an oxygen compressor. The gas source is liquid nitrogen vaporized from liquid nitrogen storage tank; the oxygen compressor sealing gas supply device includes: an oxygen compressor sealing nitrogen pipeline leading out from the liquid nitrogen vaporization pump inlet valve on the liquid nitrogen vaporization pipeline and connected to the inlet valve inlet of the oxygen compressor sealing nitrogen main inlet pipe. The oxygen compressor sealing nitrogen pipeline is divided into two sections. The first section is a cryogenic liquid nitrogen pipeline, which is connected sequentially from the gas source output direction to the liquid nitrogen storage tank, the liquid nitrogen pipeline inlet valve, the liquid nitrogen pipeline check valve, the pressure transmitter, and the low-pressure liquid nitrogen vaporizer; the second section is a normal temperature nitrogen pipeline, which is connected sequentially from the outlet end of the low-pressure liquid nitrogen vaporizer to the normal temperature nitrogen pipeline inlet valve, the normal temperature nitrogen pipeline check valve, and the flow meter, and connected to the inlet valve inlet of the oxygen compressor sealing nitrogen main inlet pipe.

2. The oxygen compressor sealing gas supply device according to claim 1, characterized in that: The low-pressure liquid nitrogen vaporizer is an ambient temperature vaporizer.

3. The oxygen compressor sealing gas supply device according to claim 2, characterized in that: The liquid nitrogen pipeline inlet valve is a cryogenic pneumatic top-guided single-seat regulating valve; the liquid nitrogen pipeline check valve is a lift-type cryogenic check valve; the ambient temperature nitrogen pipeline inlet valve is an air-opening ambient temperature sleeve regulating valve; the nitrogen pipeline check valve is a spring-loaded check valve; and the flow meter is an ultrasonic flow meter.

4. The oxygen compressor sealing gas supply device according to claim 3, characterized in that: The liquid nitrogen pipeline inlet valve, pressure transmitter, ambient temperature nitrogen pipeline inlet valve, flow meter, and the inlet valve of the oxygen compressor sealing nitrogen main pipeline connected to the oxygen compressor sealing nitrogen pipeline are all electrically connected to the air separation equipment DCS control system. According to the set pressure and flow parameters, the nitrogen pressure and flow rate input to the inlet valve of the oxygen compressor sealing nitrogen main pipeline are automatically adjusted to maintain the sealing nitrogen in a stable state of constant pressure, constant flow, and ambient temperature.

Images