Method for improving purity and yield of crude argon of air separation system

Abstract

The invention discloses a method for improving the purity and yield of crude argon of an air separation system, belongs to the technical field of air separation systems, and aims to solve the four core technical problems of extensive measurement, frequent nitrogen plug generation, yield limitation and poor stability in the traditional argon production process of a crude argon tower. The invention aims to provide a crude argon tower high-efficiency argon production method based on precise metering and closed-loop regulation and control. The method comprises the following steps: constructing a data linkage mechanism with a DCS (Distributed Control System) by deploying precise detection equipment such as a low-temperature Coriolis mass flowmeter and an online nitrogen content analyzer and combining a Siemens S7-1200 PLC (Programmable Logic Controller); the whole-process closed-loop control of initial material balance quantification establishment, backflow liquid air volume precise regulation and control, nitrogen plug active prevention and argon yield steady-state improvement is achieved, finally the problems that nitrogen plug prevention, yield improvement and parameter stability are difficult in the traditional technology are solved, and the argon production process is precise, efficient and steady.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of air separation system, and particularly relates to a method for improving the purity and yield of crude argon of an air separation system. BACKGROUND

[0002] The main process of the argon system is to separate oxygen components through rectification of crude argon towers 1 and 2, and then separate nitrogen components through a refined argon tower to obtain high-purity liquid argon. The liquid argon flow process pump is a key device for transporting liquid argon from the crude argon tower to the crude argon tower 1, and the sealing gas used in the design is normal-temperature nitrogen. However, it is found during the debugging stage that the Ar content in the crude argon is always low during the commissioning of the argon system, which causes the rectification condition of the refined argon tower to be abnormal and the production load to be affected. The reason is that the nitrogen used as the sealing gas leaks into the medium through the seal of the liquid argon flow process pump, and enters the crude argon tower, which causes the nitrogen content in the crude argon to increase, and mainly affects the following aspects: 1) The purity of the crude argon gas is low, and is maintained at about 95% for a long time, which directly affects the rectification load of the refined argon tower. When the flow rate of the refined argon tower is 1950 Nm3 / h, the vent valve of the refined argon tower is in a full-venting state, and the amount of nitrogen has exceeded the processing range of the refined argon tower.

[0003] 2) The stability of the system is affected. The long-term nitrogen leakage accumulates in the crude argon tower, which increases the risk of nitrogen plugging of the argon system and affects the stability of the system. SUMMARY

[0004] The purpose of the present application is to provide a method for improving the purity and yield of crude argon of an air separation system. In view of the four core technical pain points of the traditional crude argon tower argon production process, namely, extensive metering, frequent nitrogen plugging, limited yield, and poor stability, the present application aims to provide a high-efficiency crude argon tower argon production method based on precise metering and closed-loop control. By deploying low-temperature Coriolis mass flow meters, online nitrogen content analyzers and other precise detection equipment, and combining with the data linkage mechanism of the Siemens S7-1200 PLC and the DCS system, the initial material balance quantization establishment, the precise control of the reflux liquid air volume, the active prevention of nitrogen plugging, and the stable improvement of the argon yield are realized, and the problems of difficult prevention of nitrogen plugging, difficult increase of yield, and difficult stability of parameters in the traditional process are solved, and the precision, efficiency and stability of the argon production process are achieved.

[0005] The purpose of the present application can be achieved by the following technical solutions: The method for improving the purity and yield of crude argon of an air separation system comprises the following steps: Step 1: A low-temperature Coriolis mass flow meter is installed on the liquid air reflux pipeline of the crude argon tower, an online nitrogen content analyzer is installed on the argon fraction pipeline, and a platinum resistance thermometer is installed on the shell side of the crude argon condenser. The PID controller is selected as a Siemens S7-1200 PLC, which is communicated with the original DCS system to realize data linkage.

[0006] Step two: initial material balance establishment.

[0007] Step three: precise control of reflux liquid volume and prevention of nitrogen blockage.

[0008] Step four: argon yield improvement and steady state confirmation.

[0009] Further, the specific steps of initial material balance establishment are as follows: The initial argon fraction extraction amount is 1200m 3 / h, the argon fraction value is gradually reduced to 20-22% Ar, the nitrogen content is monitored by a nitrogen content analyzer to make the nitrogen content stable, after running for 1h, the crude argon tower liquid level is stable at 50-51.2%, the pressure is stable at 0.32-0.34MPa, and the initial material balance is established.

[0010] Further, the process argon yield is controlled at 38400-43200m 3 / h.

[0011] Further, the nitrogen content is stable at 0.08-0.09%.

[0012] Further, the specific steps of precise control of reflux liquid volume and prevention of nitrogen blockage are as follows: The purity of the lower tower liquid volume is monitored by an oxygen content analyzer, the oxygen content is 36.5%, the measurement module shows that the initial reflux liquid volume is 6.2%, the PID controller automatically closes the reflux valve opening, and the opening is adjusted by 0.5-1.52% every 3-4min, and finally the reflux liquid volume is stable, the argon fraction value is gradually increased to 13-14% Ar, the nitrogen content is monitored by a nitrogen content analyzer, the nitrogen content is 0.07-0.09%, the heat exchange temperature difference of the crude argon condenser is 6.5-7.2℃, the liquid level of the crude argon tower is stable at 52-53%, and the system runs continuously for 2-3h without any abnormality, and the high fraction value is determined to be stable without nitrogen blockage.

[0013] Further, the reflux liquid volume is stable at 4.8-4.9%.

[0014] Further, the specific steps of argon yield improvement and steady state confirmation are as follows: Under the premise of reflux liquid volume ≤4.8% and no liquid level rising, the argon fraction extraction flow is gradually increased to 1300m 3 / h, the process argon temperature is monitored at -186.2℃, the air bypass nitrogen pipeline valve is gradually opened to 35-37% opening, the temperature is stable at -186.5℃, the oxygen content of the crude argon I tower is monitored at 4.2-4.4%, the process argon yield is gradually increased to 41600m 3 / h, and finally stabilized at 42900m 3 / h, continuously monitor 24h, argon distillate value 12-13% Ar, nitrogen content 0.06-0.08%, crude argon I tower oxygen content 3.8-4.5%, process argon temperature -186.3 to -186.8℃, no large fluctuations in each parameter.

[0015] Further, the circulating pump outlet pressure is 0.83-0.85 MPa.

[0016] The beneficial effects of the present application are: 1. The present application realizes the transformation of the backflow liquid air volume from traditional qualitative experience adjustment to quantitative and accurate control through the closed-loop control of the low-temperature Coriolis mass flowmeter and the Siemens PLC, avoids the enrichment of the nitrogen component of the argon distillate due to the uncontrolled backflow liquid air volume, and simultaneously identifies the nitrogen plug risk in advance by combining the collaborative monitoring of the online nitrogen content analyzer and the platinum resistance thermometer, reduces the working condition fluctuations caused by the nitrogen plug in the traditional process, and ensures the stable operation of the crude argon tower under high distillate conditions.

[0017] 2. The liquid argon vaporization sealing and double gas source switching design are adopted to replace the traditional single nitrogen sealing, eliminate the influence of nitrogen pressure fluctuations on the sealing effect of the liquid argon pump, avoid the liquid level disturbance of the crude argon tower caused by sealing failure; at the same time, through the standardized switching process, the sealing gas medium switching operation is simplified, the disturbance of manual operation to the system stability is reduced, and the adaptability of the auxiliary system to the main process is improved.

[0018] 3. The parameter linkage mechanism of the crude argon tower main process and the liquid argon pump auxiliary system is established, the main process argon yield is adjusted by the feedback of the liquid argon pump pressure signal, the sealing gas switching is triggered by the stable signal of the main process, forming a closed loop of main process control and stable and auxiliary system adaptation, avoiding the disconnection problem caused by single system optimization, and significantly improving the continuous operation stability of the whole argon production system. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor belong to the scope of protection of the present application.

[0020] Embodiment 1: a method for improving the purity and yield of the crude argon air separation system, comprising the following steps: S1: system installation: install a low-temperature Coriolis mass flowmeter on the crude argon tower liquid air backflow pipeline, install an online nitrogen content analyzer on the argon distillate pipeline, install a platinum resistance thermometer in the shell of the crude argon condenser, and select a Siemens S7-1200 PLC as the PID controller, communicate with the original DCS system, and realize data linkage.

[0021] S2: Initial material balance establishment: The initial argon fraction extraction amount is 1200 m 3 / h, and the process argon production is controlled at 38400 m 3 / h, and the argon fraction value is gradually reduced to 20% Ar. The nitrogen content is monitored by a nitrogen content analyzer and is stabilized at 0.08%. After running for 1 h, the crude argon column liquid level is stabilized at 50%, and the pressure is stabilized at 0.32 MPa. It is determined that the initial material balance is established.

[0022] S3: Precise control of reflux liquid volume and prevention of nitrogen blockage: The oxygen content in the lower column liquid is monitored by an oxygen content analyzer, and the oxygen content is 36.5%. The initial reflux liquid volume is 6.2% as shown by the metering module. The PID controller automatically closes the reflux valve opening. The opening is adjusted by 0.5% every 3 min. The final reflux liquid volume is stabilized at 4.8%. The argon fraction value is gradually increased to 13% Ar. The nitrogen content is monitored by a nitrogen content analyzer and is 0.07%. The heat exchange temperature difference of the crude argon condenser is 6.5°C. The crude argon column liquid level is stabilized at 52% for 2 h without any abnormality. It is determined that the high fraction value is not blocked and the steady state is established.

[0023] S4: Argon production improvement and steady state confirmation: Under the premise of reflux liquid volume ≤ 4.8% and no liquid level rise, the argon fraction extraction flow is gradually increased to 1300 m 3 / h, the process argon temperature is monitored at -186.2°C, the air bypass nitrogen pipeline valve is gradually opened to 35% opening, the temperature is stabilized at -186.5°C, the crude argon I column oxygen content is monitored at 4.2%, the circulating pump outlet pressure is 0.83 MPa, the process argon production is gradually increased to 41600 m 3 / h, and finally stabilized at 42900 m 3 / h, and continuously monitored for 24 h. The argon fraction value is 12% Ar, the nitrogen content is 0.06%, the crude argon I column oxygen content is 3.8%, the process argon temperature is -186.3°C, and there is no large fluctuation in each parameter.

[0024] Example 2: A method for improving the purity and yield of a crude argon air separation system, comprising the following steps: S1: System installation: A low-temperature Coriolis mass flowmeter is installed on the crude argon column liquid reflux pipeline, an online nitrogen content analyzer is installed on the argon fraction pipeline, and a platinum resistance thermometer is installed on the shell side of the crude argon condenser. The PID controller is selected as Siemens S7-1200 PLC, which communicates with the original DCS system to realize data linkage.

[0025] S2: Initial material balance establishment: The initial argon fraction extraction amount is 1200 m 3 / h, and the process argon production is controlled at 40800 m 3 / h, the nitrogen content was monitored by the nitrogen content analyzer to be stable at 0.085%, after running for 1 h, the liquid level of the crude argon tower was stable at 50.6%, and the pressure was stable at 0.33 MPa, and it was determined that the initial material balance was established.

[0026] S3: Precise control of reflux liquid volume and prevention of nitrogen plug: The oxygen content in the lower tower liquid was monitored by the oxygen content analyzer to be 36.5%, the initial reflux liquid volume was measured by the metering module to be 6.2%, the PID controller automatically closed the reflux valve opening, and every adjustment of 1.01% opening was stable for 3.5 min, and finally the reflux liquid volume was stable at 4.85%, the argon fraction value was gradually increased to 13.5% Ar, the nitrogen content analyzer monitored the nitrogen content to be 0.08%, the heat exchange temperature difference of the crude argon condenser was 6.85°C, the liquid level of the crude argon tower was stable at 52.5%, and there was no abnormality during continuous operation for 2.5 h, and it was determined that the high fraction value was not nitrogen plug stable state.

[0027] S4: Argon yield improvement and stable state confirmation: Under the premise of reflux liquid volume ≤4.8% and no liquid level rise, the argon fraction extraction flow was gradually increased to 1300 m 3 / h, the process argon temperature was monitored to be -186.2°C, the expansion air bypass nitrogen pipeline valve was gradually opened to 36% opening, the temperature was stable at -186.5°C, the oxygen content in the crude argon I tower was monitored to be 4.3%, the circulating pump outlet pressure was 0.84 MPa, the process argon yield was gradually increased to 41600 m 3 / h, and finally stabilized at 42900 m 3 / h, and continuously monitored for 24 h, the argon fraction value was 12.5% Ar, the nitrogen content was 0.07%, the oxygen content in the crude argon I tower was 4.15%, the process argon temperature was -186.55°C, and there was no large fluctuation in each parameter.

[0028] Example 3: A method for improving the purity and yield of a crude argon air separation system, comprising the following steps: S1: System installation: A low-temperature Coriolis mass flowmeter is installed on the liquid reflux pipeline of the crude argon tower, an online nitrogen content analyzer is installed on the argon fraction pipeline, and a platinum resistance thermometer is installed on the shell side of the crude argon condenser. The PID controller is selected as Siemens S7-1200 PLC, which communicates with the original DCS system to realize data linkage.

[0029] S2: Initial material balance establishment: The initial argon fraction extraction amount is 1200 m 3 / h, and the process argon yield is controlled at 43200 m 3 / h, the argon fraction value is gradually reduced to 22% Ar, the nitrogen content is monitored by the nitrogen content analyzer to be stable at 0.09%, after running for 1 h, the liquid level of the crude argon tower is stable at 51.2%, and the pressure is stable at 0.34 MPa, and it is determined that the initial material balance is established.

[0030] S3: precise control of reflux liquid volume and prevention of nitrogen plug: the purity of the liquid in the lower column was monitored by an oxygen content analyzer, which showed that the oxygen content was 36.5%. The initial reflux liquid volume was 6.2% as shown by the metering module. The PID controller automatically reduced the opening degree of the reflux valve. The opening degree was adjusted by 1.52% every 4 minutes, and the final reflux liquid volume was stabilized at 4.9%. The argon fraction value was gradually increased to 14% Ar. The nitrogen content analyzer showed that the nitrogen content was 0.09%. The heat exchange temperature difference of the crude argon condenser was 7.2°C. The liquid level of the crude argon column was stabilized at 53% for 3 hours without any abnormality. It was determined that the high fraction value was not nitrogen-plugged and the steady state was established.

[0031] S4: argon yield improvement and steady state confirmation: under the premise of reflux liquid volume ≤4.8% and no liquid level rise, the argon fraction extraction flow was gradually increased to 1300 m 3 / h. The process argon temperature was monitored to be -186.2°C. The valve of the dilution air bypass nitrogen pipeline was gradually opened to 37% opening degree. The temperature was stabilized at -186.5°C. The oxygen content in the crude argon I column was monitored to be 4.4%. The circulating pump outlet pressure was 0.85 MPa. The process argon yield was gradually increased to 41600 m 3 / h. The final stable value was 42900 m 3 / h. The argon fraction value was 13% Ar, the nitrogen content was 0.08%, the oxygen content in the crude argon I column was 4.5%, and the process argon temperature was -186.8°C. The parameters did not fluctuate greatly. Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made without departing from the principles and spirit of the present application.

Claims

1. A method for improving the purity and yield of crude argon in an air separation system, characterized in that, Includes the following steps: Step 1: Install a low-temperature Coriolis mass flow meter on the liquid air reflux pipeline of the crude argon tower, install an online nitrogen content analyzer on the argon fraction pipeline, install a platinum resistance thermometer on the shell side of the crude argon condenser, and select a Siemens S7-1200 PLC as the PID controller to communicate with the existing DCS system and realize data linkage. Step 2: Establishing initial material balance; Step 3: Precise control of reflux liquid air volume and prevention of nitrogen blockage; Step 4: Increase argon production and confirm steady state.

2. The method for improving the purity and yield of crude argon in an air separation system according to claim 1, characterized in that, The specific steps for establishing the initial material balance are as follows: The initial argon fraction extraction volume was 1200m. 3 The argon fraction was gradually reduced to 20-22%Ar per hour. The nitrogen content was stabilized by monitoring with a nitrogen content analyzer. After 1 hour of operation, the crude argon column liquid level stabilized at 50-51.2%, and the pressure stabilized at 0.32-0.34MPa, indicating that the initial material balance was established.

3. The method for improving the purity and yield of crude argon in an air separation system according to claim 2, characterized in that, The argon production rate of the process is controlled at 38400-43200 m³ / h. 3 / h.

4. The method for improving the purity and yield of crude argon in an air separation system according to claim 2, characterized in that, The nitrogen content is stable at 0.08-0.09%.

5. The method for improving the purity and yield of crude argon in an air separation system according to claim 1, characterized in that, The specific steps for precise control of reflux liquid air volume and prevention of nitrogen blockage are as follows: The purity of the liquid air in the lower column was monitored by an oxygen content analyzer, showing an oxygen content of 36.5%. The metering module displayed an initial reflux liquid air volume of 6.2%. The PID controller automatically reduced the opening of the reflux valve, stabilizing it for 3-4 minutes with each adjustment of 0.5-1.52%, eventually stabilizing the reflux liquid air volume. The argon fraction was gradually increased to 13-14%Ar. The nitrogen content was monitored by a nitrogen content analyzer, showing a nitrogen content of 0.07-0.09%. The heat exchange temperature difference of the crude argon condenser was 6.5-7.2℃, and the liquid level in the crude argon column was stable at 52-53%. After continuous operation for 2-3 hours without any abnormalities, it was determined that a steady state without nitrogen blockage had been established at the high fraction value.

6. The method for improving the purity and yield of crude argon in an air separation system according to claim 5, characterized in that, The reflux liquid air volume was stabilized at 4.8-4.9%.

7. The method for improving the purity and yield of crude argon in an air separation system according to claim 1, characterized in that, The specific steps for increasing argon production and confirming steady state are as follows: With the premise that the reflux liquid air volume is ≤4.8% and the liquid level does not rise, the argon fraction extraction flow rate is gradually increased to 1300 m³ / h. 3 The process argon temperature was monitored at -186.2℃. The expansion air bypass nitrogen pipeline valve was gradually opened to 35-37% of its opening, and the temperature stabilized at -186.5℃. The oxygen content in the crude argon I tower was monitored at 4.2-4.4%. The process argon production was gradually increased to 41600 m³ / h. 3 / h, eventually stabilizing at 42900m 3 / h, continuously monitored for 24h, argon fraction value 12-13%Ar, nitrogen content 0.06-0.08%, oxygen content in crude argon I tower 3.8-4.5%, process argon temperature -186.3 to -186.8℃, and no significant fluctuations in any parameters.

8. The method for improving the purity and yield of crude argon in an air separation system according to claim 7, characterized in that, The outlet pressure of the circulating pump is 0.83-0.85 MPa.