Start-up plan for the air separation unit in the oxygen production plant

Thread Content

Start-up plan for the air separation unit at the oxygen production station: As the resumption of operations is scheduled according to the plant’s arrangements, and to ensure the smooth start-up of our station’s air separation unit, we will carry out all preparatory work prior to startup in strict accordance with the operating procedures for each piece of equipment in the air separation unit. The following plan is therefore formulated. 1. Due to the long shutdown period of the air separation unit, it is necessary to strengthen maintenance during startup; dedicated personnel should be assigned to oversee the processes, equipment, and electrical systems in order to address any potential faults that may arise during startup promptly. II. Preparations and inspections before starting up 2.1 The air separation unit at this site completed all equipment maintenance by June 20, 2007, and underwent trial operations prior to startup, meeting the conditions for resuming operation. However, during the testing of the air compressor, the online shaft vibration monitoring system showed that the vibration levels of bearings level 1 and level 2 were between 45μm and 60μm – values that are on the high side. The impellers of rotor assemblies level 1 and level 2 had rust spots to varying degrees, and the same was true for rotor assemblies level 3 and level 4. Since the air compressor is a key component for the continuous, safe, and stable operation of the air separation unit, responsible for supplying raw air to this system, the workshop and equipment management staff decided that it would be best to conduct a dynamic balance check on the rotor assemblies before starting up, in order to ensure smooth resumption of operations. 2.2 Two days before startup, all automatic control valves associated with the instrument transmitters should be brought into a quasi-operational state, and these valves should be calibrated again. 2.3 Conduct another trial run for each individual piece of equipment. (To be carried out 2 days in advance) 2.4. Inspect all lubricating oil equipment and top up the lubricating oil. 2.5. Check all motor instruments, electronic control systems, lighting signals, and other instrumentation and control devices. 2.6、Clean the circulating cooling water tank. (To be carried out 2 days before driving) 2.7 All personnel in the various driving-related positions shall receive training on the rules and regulations regarding the operation of various equipment as well as the standard operating procedures for their respective positions. 2.8 Since the oxygen production unit has been shut down for nearly 9 months, it is appropriate to determine the time of restart based on the need of the smelting workshop for oxygen supply, seven days in advance. 2.9. Check and calibrate the CO2 analyzer. III. Resume production and start up in strict accordance with the operating standards for each position. 3.1 Start the air compressor, following the operating standards specific to that position; 30 minutes after it starts, increase the pressure to 0.5 MPa. If there are no abnormalities after 8 hours of operation under load, begin supplying air to the air separation system. 3.2 Start the pre-cooling system, adjust the cooling water flow rates of each water pump, and flush the air guide in the air-cooled tower; make sure that the water level in the air-cooled tower is not at “0” before starting the air guide. 3.3 After gas introduction is complete, pressurize the purification system and start it up. Once pressurization is finished, adjust the amount of regeneration gas to 2500 m3/h, and carry out periodic regeneration of the two molecular sieve purifiers one by one. (Due to the prolonged parking time, it is necessary to thoroughly humidify and regenerate the molecular sieve in order to ensure the quality of the air entering the distillation tower; once the entire system becomes stable, the various switch butterfly valves are set to automatic mode. The entire process takes 24 hours.) 3.4 After the molecular sieve in the purification system has been regenerated, slowly open the main inlet valve V1101 of the distillation tower to introduce gas into it. To prevent overpressure in the tower, open all low-pressure purge valves while introducing gas. 3.5 After gas introduction is complete, adjust the various purge valves as well as the product gas and liquid throttle valves to purge the pipelines in each flow path within the tower; the entire process takes approximately 12 hours, with the purge sequence following①. 3.6 After the purging of each flow path is completed, close the respective purge valves and start the expansion unit to cool each flow path within the tower. (Each cooling circuit follows procedure ②.) 3.7 When frosting occurs in the various purge valves, close those valves, adjust the expansion unit so that its cooling capacity is fully utilized to introduce liquid into the air separation system. 3.8 Once the liquid air level reaches the normal value, valve V1 is set to automatic operation; when the liquid oxygen level reaches 2200, the oxygen and nitrogen gases are gradually purified until the required standards are met. IV. After the air separation unit has been adjusted during operation and the output and purity of oxygen and nitrogen products meet the specified standards, the product gas compressor is started to supply gas to the melting workshop. 4.1 Before supplying gas, start the nitrogen compressor and run it at light load for half an hour, then increase the pressure to 1.6 MPa. After running it under load for one hour with no abnormalities, supply nitrogen to the melting workshop and purge the oxygen delivery pipelines and valve components until no impurities are detected at the pipeline outlets when inspected with a damp white cloth. 4.2 After the nitrogen pipeline has been purged, the smelting workshop shall cooperate to connect the nitrogen pipeline with the oxygen pipeline, and then purge the oxygen pipeline until no impurities are detected in the gas exiting the pipeline when inspected with a damp white cloth. 4.3 After the oxygen pipeline has been purged, start the oxygen compressor and run it at light load for 30 minutes, gradually increasing the pressure to the operating pressure of 1.6 MPa. After running for 1 hour, supply oxygen to the melting workshop. 4.4 Once the product gas compressor starts operating properly, it enters the normal production phase. V. Oxygen production station startup schedule. Note: In the \"Time arrangement\" column of the \"Oxygen production startup schedule\", T denotes the startup time of the bottom-blown furnace; the numbers in the \"Time arrangement\" column represent hours ； “+”Indicates before driving ； “-”It means after driving. “＞” indicates before the time point ； “＜” indicates after the time point. Schedule, Work Content, Remarks:
>T+216: Rotor dynamic balance testing; staff receive training. Equipment is ready for operation.
T+216: Preparation of instruments, individual unit testing, cleaning of the cooling tank. Total time: two days.
T+168: Startup of the oxygen plant. Air compressors are started, and the pressure is increased to 0.5 MPa after 8 hours.
T+140: Introduction of air into the air separation system; molecular sieve regeneration begins, enabling system purification.
T+116: Purification process completed; transition to the purging phase. The purpose of purification is to ensure the quality of air entering the distillation tower.
T+104: Purging completed; accumulation of liquid begins. Flow path purging takes 12 hours.
T+32: Liquid accumulation completed; purification of oxygen and nitrogen gases finished.
T+8: Purging of pipes connecting to the bottom-blown furnace completed. System preparation takes 8 hours; pipe purging lasts 24 hours.
T+1: Air compressors are started, and the pressure is increased to 1.6 MPa. Oxygen and nitrogen are supplied to the bottom-blown furnace.
<T: Normal production begins.
Production Technology Department, July 23, 2007