A high-pressure plate heat exchange system for air separation and a purging method

Abstract

The present invention discloses an air separation high-pressure plate heat exchange system and a purging method, the purging method comprising the following steps: draining the air channel of the high-pressure plate heat exchanger and reheating the air channel by positive blowing; temporary dummy connection of the liquid oxygen channel of the high-pressure plate heat exchanger; reheating of the high-pressure plate heat exchanger; blasting and purging of the liquid oxygen channel of the high-pressure plate heat exchanger; resetting the pipeline and flange. It is suitable for a single air separation operation or multiple air separations in parallel, and effectively solves the problem of continuous decrease in oxygen load caused by blockage of the high-pressure plate heat exchanger, deterioration of the heat exchange effect of the heat exchanger, etc. The air separation high-pressure plate heat exchange system comprises a high-pressure plate heat exchanger, and the high-pressure plate heat exchanger comprises an air channel, a nitrogen channel and an oxygen channel.

Description

Technical Field

[0001] The invention discloses an air separation high-pressure plate heat exchange system and a purge method, belonging to the technical field of air separation heat exchanger operation methods. Background Art

[0002] A heat exchanger is an energy-saving device that transfers heat between two or more fluids at different temperatures. It transfers heat from a higher temperature fluid to a lower temperature fluid, so that the fluid temperature reaches the specified index of the process to meet the needs of process conditions. It is also one of the main devices for improving energy utilization. A plate heat exchanger is composed of a series of stacked metal sheets with a certain corrugated shape.

[0003] When the air separation high-pressure plate heat exchanger runs for a long time, ice blockage or pearl sand residue may occur, resulting in poor heat exchange effect of the heat exchanger, which leads to lower and lower oxygen load and cannot meet the oxygen supply of the whole plant. The original solution was to stop the air separation system for comprehensive reheating and purging to completely solve the problem of low oxygen load. The shutdown and reheating time took about 7 days, which was too time-consuming and caused great economic losses. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention discloses an air separation high-pressure plate heat exchange system and a purging method, which is suitable for a single air separation operation or multiple air separation operations in parallel, and effectively solves the problem of continuous decrease in oxygen load caused by blockage of the high-pressure plate heat exchanger, deterioration of the heat exchange effect of the heat exchanger, etc.

[0005] The present invention is achieved through the following technical solutions:

[0006] An air separation high-pressure plate heat exchange system includes one or more sets of parallel air separation heat exchange systems, wherein the air separation heat exchange system includes a high-pressure plate heat exchanger, and the high-pressure plate heat exchanger includes an air channel, a nitrogen channel and an oxygen channel.

[0007] The inlet of the nitrogen channel is connected to the dirty nitrogen of the upper distillation tower, and the outlet of the nitrogen channel is used for venting the cooling tower;

[0008] The air channel comprises an air channel inlet and an air channel outlet, the air channel outlet is provided with a liquid air discharge guide port, and the liquid air discharge guide port is provided with an air deoxygenation pump outlet guide valve;

[0009] The oxygen channel comprises an oxygen channel inlet and an oxygen channel outlet, a detachable blind plate is arranged on the pipeline of the oxygen channel inlet, a liquid oxygen guide port and a liquid oxygen outlet pipeline are arranged on the oxygen channel outlet, a liquid oxygen guide port is provided with a liquid oxygen guide valve, an oxygen pump outlet valve and a liquid oxygen pump are arranged on the liquid oxygen outlet pipeline, a detachable blind plate is arranged on the liquid oxygen pump inlet, a detachable purge and blasting discharge port is also arranged on the liquid oxygen outlet pipeline, and temporary dummy parts are arranged on the purge and blasting discharge ports.

[0010] The temporary dummy is a cylindrical structure with flanges at both ends. One end is connected to a purge and blasting discharge port via the flange, and the other end is connected to a mounting ring via the flange. A removable asbestos plate is provided between the flange and the mounting ring.

[0011] The asbestos board is provided with shallow cuts.

[0012] A purging method for an air separation high-pressure plate heat exchange system comprises the following steps:

[0013] Step 1: drain the air channel of the high-pressure plate heat exchanger and perform positive blowing and reheating of the air channel, close the oxygen channel, open the air channel valve, and use heated air to perform positive blowing and reheating from the air channel;

[0014] Step 2, the liquid oxygen channel of the high-pressure plate heat exchanger is temporarily connected with a dummy, the liquid oxygen pump at the liquid oxygen outlet is turned off, and a blind plate is used to seal the inlet of the liquid oxygen pump; a burst discharge pipeline is set on the liquid oxygen outlet pipeline, a purge and burst discharge port are set on the burst discharge pipeline, temporary dummy parts are set for the purge and burst discharge ports, and a blind plate is set at the inlet of the oxygen channel at the same time;

[0015] The temporary dummy is a cylindrical structure with flanges at both ends. One end is connected to the purge and blasting discharge port through the flange, and the other end is connected to the mounting ring through the flange. An asbestos board can be detachably installed between the flange and the mounting ring.

[0016] Step 3: Reheat the high-pressure plate heat exchanger, close the air channel valve, and use heated air to repeatedly reheat and purge from the oxygen channel. During the reheating and purge process, the dew point analysis of the purge and blast discharge ports is continuously performed. Whether it is ice blockage is determined based on the dew point change. After the temperature and dew point are qualified, the oxygen channel of the high-pressure plate heat exchanger is blasted and purged;

[0017] Step 4, the liquid oxygen channel of the high-pressure plate heat exchanger is blasted and purged, and a 2-3 mm thick asbestos board is installed on the temporary dummy, and a shallow cut is made on the asbestos board;

[0018] Adjust the pressure in the oxygen channel from low to high, and perform multiple blasting and purging at different pressures;

[0019] The blasting and purging means that after the gas connection operation is performed to the specified pressure, the heated air is gradually introduced into the oxygen channel, and the pressure in the oxygen channel rises until the asbestos board explodes. The asbestos board must explode when the pressure in the channel exceeds the specified pressure by 10%-15%. The next blasting and purging operation is arranged according to the impurity content in the air after the explosion;

[0020] Step 5, reset the pipeline flange. After the blasting and purge is completed, remove the temporary fake parts and blind plates, and reset the removed pipelines and filters; reset the flange valves of the disassembled liquid oxygen pump; reset the safety valves of the oxygen channel.

[0021] Preferably, the process of step 1 is specifically as follows:

[0022] First, the oxygen channel of the system is closed and the valve of the air channel is opened;

[0023] Then, open the high-pressure liquid air discharge guide port at the outlet of the air channel to drain the liquid on the spot, and the drainage process is carried out slowly;

[0024] Finally, after confirming that no liquid is discharged from the high-pressure liquid air discharge guide port, heated air is introduced into the air channel entrance for positive blowing and reheating. The positive blowing and reheating should be carried out for at least 2 hours. After the positive blowing is completed, the air valve is closed and the reheating process should be carried out slowly.

[0025] Preferably, the overall process of step 3 is:

[0026] 1) Close the air channel valve, open the liquid oxygen drain port at the oxygen channel outlet, and drain the liquid oxygen slowly;

[0027] 2) After the drainage is completed, close the liquid oxygen drain port, connect the heated air from the oxygen channel inlet pipeline, fully open the oxygen pump outlet valve, and let the heated air pass through the oxygen channel and be discharged from the oxygen pump outlet purge and blast discharge port. Repeatedly reheat and purge the oxygen channel, and the reheating process is carried out slowly and multiple times;

[0028] 3) During the reheating process, always observe whether the valve has leakage. At the same time, continuously perform dew point analysis on the purge and blast discharge ports during the reheating process. Determine whether it is ice blockage based on the dew point change. After the temperature and dew point are qualified, perform blasting and purge on the oxygen channel of the high-pressure plate heat exchanger.

[0029] Preferably, the process of step 4 is specifically as follows:

[0030] 1) Install 2-3mm thick asbestos boards on the temporary fake parts. Install 1-2 more boards according to the pressure conditions and make shallow cuts;

[0031] 2) After the gas connection operation reaches 0.1MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.1-0.15Mpa. The next operation is arranged according to the content of impurities in the air after the explosion;

[0032] 3) After the gas connection operation reaches 0.2MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.2-0.25Mpa. The next operation is arranged according to the impurity content in the air after the explosion;

[0033] 4) After the gas connection operation reaches 0.3MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.3-0.35Mpa. The next operation is arranged according to the impurity content in the air after the explosion;

[0034] 5) After the gas connection operation reaches 0.4MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.35-0.4Mpa. According to the impurity content in the air after the explosion, the next operation is arranged until the impurity content in the air after the explosion reaches the requirement.

[0035] Preferably, the temperature and dew point analysis of the purge and blast exhaust ports are qualified if the temperature is below 10°C and the dew point is below -65°C.

[0036] This method is applicable to one or more air separation heat exchange systems in parallel. When used for multiple air separation heat exchange systems in parallel, when one system is in normal operation, another system is purged, and the heated air used for purging comes from the system in normal operation.

[0037] The multiple sets of air separation parallel heat exchange systems include a set A system and a set B system running in parallel, both of which include a high-pressure plate heat exchanger, and the high-pressure plate heat exchanger includes an air channel, a nitrogen channel and an oxygen channel. When the set B system is in normal operation, the set A system is purged, and the heated air used for purging comes from the set B system in normal operation. The heated air comes from the set B system in normal operation.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The system of the present invention is provided with temporary dummy parts and blind plates, which can effectively solve the problem of flammable and explosive oxygen in the air separation system. The use of temporary dummy parts can effectively ensure the safety of the operation and maintenance process of the air separation heat exchange system. Both the temporary dummy parts and the blind plates are detachable, which is convenient and effective, and reduces the economic losses caused by time-consuming maintenance.

[0040] The method of the present invention is applicable to the operation of a single air separation system or multiple air separation systems in parallel, and effectively solves the problem of continuous decrease in oxygen load caused by blockage of a high-pressure plate heat exchanger, deterioration of heat exchange effect of the heat exchanger, and the like.

[0041] This method introduces air to reheat and purge the high-pressure plate system alone without stopping the plant. The reheating and purge time is about 2 days, which is time-saving and has less economic losses. After three tests in September 2017, when the B set of high-pressure plates were replaced and purged, in November, and in October 2018, the oxygen production of the two air separation sets AB in our plant has returned to the designed output, meeting the oxygen demand of the entire plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the structure of system A in Example 1 of the present invention.

[0043] Figure 2 This is a schematic diagram of the temporary dummy structure. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to these embodiments, and any changes or equivalent substitutions that do not deviate from the concept of the present invention are included in the protection scope of the present invention.

[0045] An air separation high-pressure plate heat exchange system includes one or more sets of parallel air separation heat exchange systems, wherein the air separation heat exchange system includes a high-pressure plate heat exchanger, and the high-pressure plate heat exchanger includes an air channel 1, a nitrogen channel 3 and an oxygen channel 2.

[0046] The inlet of the nitrogen channel 3 is connected to the dirty nitrogen of the upper distillation tower 20, and the outlet of the nitrogen channel is used for venting the cooling tower 21;

[0047] The air channel 1 comprises an air channel inlet 4 and an air channel outlet 5, the air channel outlet 5 is provided with a liquid air discharge guide port 6, and the liquid air discharge guide port 6 is provided with an air deoxygenation pump outlet guide valve 8;

[0048] The oxygen channel 2 includes an oxygen channel inlet 15 and an oxygen channel outlet 9, a detachable blind plate 11 is arranged on the pipeline of the oxygen channel inlet 15, a liquid oxygen guide port 17 and a liquid oxygen outlet pipeline 12 are arranged on the oxygen channel outlet 9, a liquid oxygen guide port 17 is provided with a liquid oxygen guide valve 16, an oxygen pump outlet valve 18 and a liquid oxygen pump 10 are arranged on the liquid oxygen outlet pipeline 12, a detachable blind plate 11 is arranged at the inlet of the liquid oxygen pump 10, a detachable purge and blasting discharge port 13 is also arranged on the liquid oxygen outlet pipeline, and a temporary dummy 14 is arranged on the purge and blasting discharge port 13.

[0049] The temporary dummy 14 is a cylindrical structure, with flanges 22 at both ends of the cylindrical structure, one end of which is connected to the purge and blasting discharge port 13 through the flange 22, and the other end of which is connected to the mounting ring 23 through the flange 22, and a detachable asbestos board 24 is arranged between the flange and the mounting ring. The asbestos board 24 is provided with a shallow cut.

[0050] The purge and blast exhaust port 13 is installed or opened when needed, and the blind plate 11 in the system is installed when the purge and blast exhaust port 13 is installed or opened.

[0051] Example 1

[0052] This method is applicable to multiple sets of parallel air separation heat exchange systems. When used in multiple sets of parallel air separation heat exchange systems, when one system is in normal operation, another system is purged, and the heated air used for purging comes from the system in normal operation.

[0053] The multiple sets of parallel air separation heat exchange systems include a set A system and a set B system running in parallel, and the set A system and the set B system both include a high-pressure plate heat exchanger 25, and the high-pressure plate heat exchanger includes an air channel 1, a nitrogen channel 3 and an oxygen channel 2. When the set B system is in normal operation, the set A system is purged, and the heated air used for purging comes from the set B system in normal operation. The purging method for the air separation high-pressure plate heat exchange system includes the following steps:

[0054] Step 1, draining the air channel 1 of the high pressure plate heat exchanger and performing positive blowing and reheating of the air channel 1, closing the oxygen channel 2, opening the air channel valve, and using heated air to perform positive blowing and reheating from the air channel;

[0055] The process of step 1 is specifically as follows:

[0056] First, the system oxygen channel 2 is closed, and the valve at the air channel inlet 4 is opened;

[0057] Then, open the air channel outlet 5 and the high-pressure liquid air discharge guide 6 to drain the liquid on the spot, and the drainage process is carried out slowly;

[0058] Finally, after confirming that no liquid is discharged from the high-pressure liquid air discharge guide port 6, introduce heated air into the air channel inlet 4, adjust 1 / 5 turn of the B set system oxygen pump series air valve 7, adjust the heated air flow, perform positive blowing and reheating on the air channel 1, use the oxygen pump series air valve to control the pressure and reheating rate, and then open the heated air deoxygenation pump outlet guide valve 8 every 10 minutes, 1 / 5 turn each time, and perform positive blowing and reheating for at least 2 hours. The reheating process should be carried out slowly, and close the oxygen pump series air valve 7 after the positive blowing is completed.

[0059] Step 2, the liquid oxygen channel of the high-pressure plate heat exchanger is temporarily connected with a dummy, the liquid oxygen pump 10 of the liquid oxygen outlet at the oxygen channel outlet 9 is closed, and a blind plate 11 is used to seal the liquid oxygen pump inlet; a purge and burst discharge port 13 is set on the liquid oxygen outlet pipeline 12, and a temporary dummy 14 is set on the purge and burst discharge port 13, and a blind plate 11 is set at the oxygen channel inlet 15 at the same time;

[0060] Step 3, reheat the high-pressure plate heat exchanger, close the valve of the air channel 1, use heated air to repeatedly reheat and purge from the oxygen channel 2, and continuously perform dew point analysis on the purge and burst discharge port 13 during the reheat and purge process. Determine whether it is ice blockage based on the dew point change. After the temperature and dew point are qualified, perform burst purge on the oxygen channel 2 of the high-pressure plate heat exchanger;

[0061] The overall process of step 3 is:

[0062] 1) Close the valve of the air channel 1, open the liquid oxygen drain valve 16 on the oxygen channel outlet 9, and drain the liquid oxygen from the liquid oxygen drain port 17. The draining process is carried out slowly;

[0063] 2) After the drainage is completed, close the liquid oxygen inlet 17, connect the heated air from the oxygen channel inlet 15 pipeline, fully open the oxygen pump outlet valve 18, and the heated air passes through the oxygen channel 2 and is discharged from the purge and blasting discharge port 13. The oxygen channel 2 is repeatedly reheated and purged, and the reheating process is carried out slowly and multiple times; the oxygen pump outlet valve 18 adjusts the flow rate.

[0064] 3) During the reheating process, always observe whether there is any leakage in each valve on the oxygen channel, and judge whether there is a leakage based on the flow rate and temperature. If a leakage is found, a DN500 blind plate needs to be installed behind the valve. At the same time, during the reheating process, the dew point analysis of the purge and burst discharge port 13 is continuously carried out. If the dew point is below -65℃, it is judged to be qualified. According to the change of dew point, it is judged whether it is ice blockage. If the temperature is below 10℃ and the dew point is below -65℃, it is judged to be qualified. After the temperature and dew point are qualified, the oxygen channel of the high-pressure plate heat exchanger is burst purged.

[0065] Step 4, the liquid oxygen channel of the high-pressure plate heat exchanger is blasted and purged, and a 2-3 mm thick asbestos board 24 is installed on the temporary dummy 14, and a shallow cut is made on the asbestos board;

[0066] Adjust the pressure in the oxygen channel 2 from low to high, and perform multiple explosion and purge operations under different pressure conditions;

[0067] The blasting and purging means that after the gas connection operation is performed to the specified pressure, the heated air is gradually introduced into the oxygen channel 2, and the pressure in the oxygen channel 2 rises until the asbestos board explodes. The asbestos board must explode when the pressure in the channel exceeds the specified pressure by 10%-15%. The next blasting and purging operation is arranged according to the impurity content in the air after the explosion;

[0068] Preferably, the process of step 4 is specifically as follows:

[0069] 1) Install an asbestos board with a thickness of 2-3 mm on the temporary fake part 14. Install 1-2 asbestos boards according to the pressure situation, and make shallow cuts on the asbestos board;

[0070] 2) After the gas connection operation reaches 0.1MPa, the heated air is introduced into the oxygen channel 2, and the heated air of the B system is gradually opened to the oxygen channel of the A system. The pressure in the oxygen channel 2 gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.1-0.15Mpa. The next operation is arranged according to the content of impurities in the air after the explosion;

[0071] 3) After the gas connection operation reaches 0.2MPa, the heated air is introduced into the oxygen channel, and the heated air of the B system is gradually opened to the oxygen channel of the A system. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.2-0.25Mpa. The next operation is arranged according to the impurity content in the air after the explosion;

[0072] 4) After the gas connection operation reaches 0.3MPa, the heated air is introduced into the oxygen channel, and the heated air of the B system is gradually opened to the oxygen channel of the A system. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.3-0.35Mpa. The next operation is arranged according to the impurity content in the air after the explosion;

[0073] 5) After the gas connection operation reaches 0.4MPa, the heated air is introduced into the oxygen channel, and the heated air of the B system is gradually opened to the oxygen channel of the A system. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.35-0.4Mpa. According to the impurity content in the air after the explosion, the next operation is arranged until the impurity content in the air after the explosion meets the requirements.

[0074] Step 5, reset the pipeline flange. After the blasting and blowing is completed, remove the temporary dummy 14 and the blind plate 11, and reset the removed pipeline and filter; reset the flange valves of the disassembled liquid oxygen pump 10; reset the safety valves of the oxygen channel.

[0075] Preferably, the inlet of the nitrogen channel 3 is connected to the dirty nitrogen of the upper distillation tower 20, and the outlet of the nitrogen channel is used to vent the cold tower 21.

[0076] Preferably, the dew point analysis of the purge and blasting exhaust port 13 is below -65°C, which is a qualified state.

[0077] This technical solution is time-saving and can quickly restore oxygen production, effectively reducing the company's economic losses. For example, the results of the B set high-pressure plate replacement and purge in our factory in September 2017 are as follows:

[0078] (1) Through reheating explosion and purging, the oxygen volume was increased from 20000NM 3 / H increased to 26000NM 3 / H load is increased to achieve the expected effect of purging;

[0079] (2) By adjusting the original reheating explosion and purging plan, the entire treatment process took 2 days, saving 5 days compared to the previous treatment time of 7 days;

[0080] (3) Based on the original A single air separation operation and B treatment for 7 days, the single unit overhaul results in a loss of 150 tons of oil products per day, at RMB 4,000 per ton; 200 tons of liquid ammonia, at RMB 2,000 per ton; the company can reduce the loss of oil products by 150*4,000*5=3 million, and the loss of liquid ammonia by 200*2,000*5=2 million; the total loss is RMB 5 million;

[0081] (4) Based on the saving of 5 days, the original plan consumes 70 tons of steam per hour for reheating and purging. The company saves steam consumption costs at RMB 112 per ton of steam, RMB 112 / ton*70 tons / hour*24 hours*5=RMB 940,000

[0082] (5) The company’s total stop loss was RMB 5.94 million.

[0083] Example 2

[0084] A purging method for an air separation high-pressure plate heat exchange system, when applied to an independent air separation heat exchange system, the air separation high-pressure plate heat exchange system comprises a high-pressure plate heat exchanger, the high-pressure plate heat exchanger comprises an air channel, a nitrogen channel and an oxygen channel, the purging method comprises the following steps:

[0085] Step 1: drain the air channel of the high-pressure plate heat exchanger and perform positive blowing and reheating of the air channel, close the oxygen channel, open the air channel valve, and use heated air to perform positive blowing and reheating from the air channel;

[0086] Step 2, the liquid oxygen channel of the high-pressure plate heat exchanger is temporarily connected with a dummy, the liquid oxygen pump at the liquid oxygen outlet is turned off, and a blind plate is used to seal the inlet of the liquid oxygen pump; a burst discharge pipeline is set on the liquid oxygen outlet pipeline, and a purge and burst discharge port are set on the burst discharge pipeline, and temporary dummy parts are set on the purge and burst discharge port, and a blind plate is set at the inlet of the oxygen channel at the same time;

[0087] Step 3: Reheat the high-pressure plate heat exchanger, close the air channel valve, and use heated air to repeatedly reheat and purge from the oxygen channel. During the reheating and purge process, the dew point analysis of the purge and blast discharge ports is continuously performed. Whether it is ice blockage is determined based on the dew point change. After the temperature and dew point are qualified, the oxygen channel of the high-pressure plate heat exchanger is blasted and purged;

[0088] Step 4, the liquid oxygen channel of the high-pressure plate heat exchanger is blasted and purged, and a 2-3 mm thick asbestos board is installed on the temporary dummy, and a shallow cut is made on the asbestos board;

[0089] Adjust the pressure in the oxygen channel from low to high, and perform multiple blasting and purging at different pressures;

[0090] The blasting and purging means that after the gas connection operation is performed to the specified pressure, the heated air is gradually introduced into the oxygen channel, and the pressure in the oxygen channel rises until the asbestos board explodes. The asbestos board must explode when the pressure in the channel exceeds the specified pressure by 10%-15%. The next blasting and purging operation is arranged according to the impurity content in the air after the explosion;

[0091] Step 5, reset the pipeline flange. After the blasting and purge is completed, remove the temporary fake parts and blind plates, and reset the removed pipelines and filters; reset the flange valves of the disassembled liquid oxygen pump; reset the safety valves of the oxygen channel.

[0092] Preferably, the process of step 1 is specifically as follows:

[0093] First, the oxygen channel of the system is closed and the valve of the air channel is opened;

[0094] Then, open the high-pressure liquid air discharge guide port at the outlet of the air channel to drain the liquid on the spot, and the drainage process is carried out slowly;

[0095] Finally, after confirming that no liquid is discharged from the high-pressure liquid air discharge guide port, heated air is introduced into the air channel inlet for positive blowing and reheating. The heated air required for the heat exchange process is obtained by heating the heating equipment. A regulating valve is arranged between the heating equipment and the air channel inlet. The oxygen pump series air valve 7 of the B set system described in Example 2 is replaced by a regulating valve. The pressure and reheating rate are controlled by the regulating valve. Then, the heated air deoxygenation pump outlet guide valve is opened every 10 minutes (1 / 5 turn each time). The positive blowing and reheating are carried out for at least 2 hours. The reheating process should be carried out slowly. After the positive blowing is completed, the series air valve is closed.

[0096] Preferably, the overall process of step 3 is:

[0097] 1) Close the air channel valve, open the liquid oxygen drain port at the oxygen channel outlet, and drain the liquid oxygen slowly;

[0098] 2) After the drainage is completed, close the liquid oxygen drain port, connect the heated air from the oxygen channel inlet pipeline, fully open the oxygen pump outlet valve, and let the heated air pass through the oxygen channel and be discharged from the oxygen pump outlet purge and blast discharge port. Repeatedly reheat and purge the oxygen channel, and the reheating process is carried out slowly and multiple times;

[0099] 3) During the reheating process, always observe whether the valve has leakage, and judge whether it is leaking based on the flow rate and temperature. If leakage is found, install a DN500 blind plate after the valve. At the same time, during the reheating process, continue to perform dew point analysis on the purge and burst discharge ports (qualified below -65℃), and judge whether it is ice blockage based on the dew point change. After the temperature and dew point are qualified, perform burst purge on the oxygen channel of the high-pressure plate heat exchanger (temperature 10℃, dew point -65℃).

[0100] Preferably, the process of step 4 is specifically as follows:

[0101] 1) Install 2-3mm thick asbestos boards on the temporary fake parts. Install 1-2 more boards according to the pressure conditions and make shallow cuts;

[0102] 2) After the gas connection operation reaches 0.1MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.1-0.15Mpa. The next operation is arranged according to the content of impurities in the air after the explosion;

[0103] 3) After the gas connection operation reaches 0.2MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.2-0.25Mpa. The next operation is arranged according to the impurity content in the air after the explosion;

[0104] 4) After the gas connection operation reaches 0.3MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.3-0.35Mpa. The next operation is arranged according to the impurity content in the air after the explosion;

[0105] 5) After the gas connection operation reaches 0.4MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.35-0.4Mpa. According to the impurity content in the air after the explosion, the next operation is arranged until the impurity content in the air after the explosion reaches the requirement.

[0106] Preferably, the inlet of the nitrogen channel is connected to the dirty nitrogen of the upper distillation tower, and the outlet of the nitrogen channel is used for cooling tower venting.

[0107] Preferably, the dew point analysis of the purge and blast exhaust ports is below -65°C, which is a qualified state.

[0108] The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for purging an air separation high-pressure plate heat exchange system, characterized in that: When an air separation high-pressure plate heat exchange system is used, including one or more sets of parallel air separation heat exchange systems, the air separation heat exchange system includes a high-pressure plate heat exchanger, and the high-pressure plate heat exchanger includes an air channel, a nitrogen channel and an oxygen channel. The inlet of the nitrogen channel is connected to the dirty nitrogen of the upper distillation tower, and the outlet of the nitrogen channel is used for venting the cooling tower; The air channel comprises an air channel inlet and an air channel outlet, the air channel outlet is provided with a liquid air discharge guide port, and the liquid air discharge guide port is provided with an air deoxygenation pump outlet guide valve; The oxygen channel comprises an oxygen channel inlet and an oxygen channel outlet, a detachable blind plate is arranged on the pipeline of the oxygen channel inlet, a liquid oxygen guide port and a liquid oxygen outlet pipeline are arranged on the oxygen channel outlet, a liquid oxygen guide port is provided with a liquid oxygen guide valve, an oxygen pump outlet valve and a liquid oxygen pump are arranged on the liquid oxygen outlet pipeline, a detachable blind plate is arranged on the liquid oxygen pump inlet, a detachable purge and blasting discharge port is also arranged on the liquid oxygen outlet pipeline, and a temporary dummy is arranged on the purge and blasting discharge port; The purging method comprises the following steps: Step 1: drain the air channel of the high-pressure plate heat exchanger and perform positive blowing and reheating of the air channel, close the oxygen channel, open the air channel valve, and use heated air to perform positive blowing and reheating from the air channel; Step 2, the liquid oxygen channel of the high-pressure plate heat exchanger is temporarily connected with a dummy, the liquid oxygen pump at the liquid oxygen outlet is turned off, and a blind plate is used to seal the inlet of the liquid oxygen pump; a burst discharge pipeline is set on the liquid oxygen outlet pipeline, a purge and burst discharge port are set on the burst discharge pipeline, temporary dummy parts are set for the purge and burst discharge ports, and a blind plate is set at the inlet of the oxygen channel at the same time; Step 3: Reheat the high-pressure plate heat exchanger, close the air channel valve, and use heated air to repeatedly reheat and purge from the oxygen channel. During the reheating and purge process, the dew point analysis of the purge and blast discharge ports is continuously performed. Whether it is ice blockage is determined based on the dew point change. After the temperature and dew point are qualified, the oxygen channel of the high-pressure plate heat exchanger is blasted and purged; Step 4, the liquid oxygen channel of the high-pressure plate heat exchanger is blasted and purged, and a 2-3 mm thick asbestos board is installed on the temporary dummy, and a shallow cut is made on the asbestos board; Adjust the pressure in the oxygen channel from low to high, and perform multiple blasting and purging at different pressures; The blasting and purging means that after the gas connection operation is performed to the specified pressure, the heated air is gradually introduced into the oxygen channel, and the pressure in the oxygen channel rises until the asbestos board explodes. The asbestos board must explode when the pressure in the channel exceeds the specified pressure by 10%-15%. The next blasting and purging operation is arranged according to the impurity content in the air after the explosion; Step 5, reset the pipeline flange. After the blasting and purge is completed, remove the temporary fake parts and blind plates, and reset the removed pipelines and filters; reset the flange valves of the disassembled liquid oxygen pump; reset the safety valves of the oxygen channel.

2. The method for purging an air separation high-pressure plate heat exchange system according to claim 1, characterized in that: The temporary dummy is a cylindrical structure with flanges at both ends. One end is connected to a purge and blasting discharge port via the flange, and the other end is connected to a mounting ring via the flange. A removable asbestos plate is provided between the flange and the mounting ring.

3. A method for purging an air separation high-pressure plate heat exchange system according to claim 2, characterized in that: The asbestos board is provided with shallow cuts.

4. The method for purging an air separation high-pressure plate heat exchange system according to claim 1, characterized in that: The process of step 1 is specifically as follows: First, the oxygen channel of the system is closed and the valve of the air channel is opened; Then, open the high-pressure liquid air discharge guide port at the outlet of the air channel to drain the liquid on the spot, and the drainage process is carried out slowly; Finally, after confirming that no liquid is discharged from the high-pressure liquid air discharge guide port, heated air is introduced into the air channel entrance for positive blowing and reheating. The positive blowing and reheating should take at least 2 hours. After the positive blowing is completed, the air valve is closed and the reheating process is carried out slowly.

5. The method for purging an air separation high-pressure plate heat exchange system according to claim 1, characterized in that: The overall process of step 3 is: 1) Close the air channel valve, open the liquid oxygen drain port at the oxygen channel outlet, and drain the liquid oxygen slowly; 2) After the drainage is completed, close the liquid oxygen drain port, connect the heated air from the oxygen channel inlet pipeline, fully open the oxygen pump outlet valve, and let the heated air pass through the oxygen channel and be discharged from the oxygen pump outlet purge and blast discharge port. Repeatedly reheat and purge the oxygen channel, and the reheating process is carried out slowly and multiple times; 3) During the reheating process, always observe whether the valve has leakage. At the same time, continuously perform dew point analysis on the purge and blast discharge ports during the reheating process. Determine whether it is ice blockage based on the dew point change. After the temperature and dew point are qualified, perform blasting and purge on the oxygen channel of the high-pressure plate heat exchanger.

6. The method for purging an air separation high-pressure plate heat exchange system according to claim 1, characterized in that: The process of step 4 is specifically as follows: 1) Install 2-3mm thick asbestos boards on the temporary fake parts. Install 1-2 more boards according to the pressure conditions and make shallow cuts; 2) After the gas connection operation reaches 0.1MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.1-0.15Mpa. The next operation is arranged according to the impurity content in the air after the explosion; 3) After the gas connection operation reaches 0.2MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.2-0.25Mpa. The next operation is arranged according to the impurity content in the air after the explosion; 4) After the gas connection operation reaches 0.3MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.3-0.35Mpa. The next operation is arranged according to the impurity content in the air after the explosion; 5) After the gas connection operation reaches 0.4MPa, the heated air is introduced into the oxygen channel. The pressure in the oxygen channel gradually rises until the asbestos board explodes. The asbestos board must explode at a pressure between 0.35-0.4Mpa. According to the impurity content in the air after the explosion, the next operation is arranged until the impurity content in the air after the explosion reaches the requirement.

7. The method for purging an air separation high-pressure plate heat exchange system according to claim 1, characterized in that: The temperature and dew point analysis of the purge and blasting exhaust ports show that temperatures below 10°C and dew points below -65°C are acceptable.

8. The method for purging an air separation high-pressure plate heat exchange system according to claim 1, characterized in that: For multiple sets of parallel air separation heat exchange systems, when one set of air separation heat exchange systems is in normal operation, another set of air separation heat exchange systems is purged, and the heated air used for purging comes from the air separation heat exchange system in normal operation.

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