Research and implementation of instrument air syst

Research and implementation of instrument air system transformation of natural gas treatment station

reasons for transformation

before April 2004, there were 3 sets of oil screw air compressors with 3m3/min in the purification workshop of natural gas treatment station, and 1 set was in daily operation to provide instrument air for cryogenic device, deep processing device and boiler system in water truck room; There is one 6m3/min piston air compressor, which can provide air source for nitrogen generator and instrument air for cryogenic device; There is also one nitrogen generator, which is only started when the unit needs nitrogen replacement. According to the field observation and analysis, when a 3m3/min screw air compressor is operated to provide instrument air to the cryogenic device under daily conditions, the screw air compressor stops for 6 minutes every 15 minutes of operation, and then starts another cycle process. Such frequent startup and shutdown of the screw air compressor not only affects the service life of the screw air compressor, but also indicates that there is abundant instrument air available; In addition, the power and water consumption of the original 6m3/min piston air compressor in the purification workshop is also large. If it is necessary to start the nitrogen generator for nitrogen replacement, just start two screw air compressors to provide gas source for the nitrogen generator. The original 6m3/min piston air compressor can be completely removed

there are two piston air compressors in the oil workshop of the station, one of which is 6m3/min, and the specification and model are relatively backward. There were many faults at that time, and they can only be reluctantly used after overhaul, so they are generally out of service; The other is 10m3/min, which often works with diseases. The instrument air used for bottling in the oil workshop was provided by these two piston air compressors. In recent years, the LPG bottling volume in the oil workshop has decreased year by year, and the air volume of instruments used for bottling has also decreased. The displacement of the piston air compressor is large, and most of the remaining air can only be vented. Moreover, the power and water consumption of the piston air compressor are also large, resulting in a great waste of water and electric energy

after observation and analysis, calculate the loading and unloading time of the screw air compressor in the purification workshop, and analyze the compressed air surplus from the screw air compressor in the purification workshop. It is calculated that the screw air compressor in the purification workshop can supply instrument air for cryogenic and meet the instrument air for LPG bottling in the oil workshop and the instrument air for boiler system in the water truck room at the same time, which can save power and water consumption, It can also meet the requirements of nitrogen generator. In addition, the existing No.7 120m3 LPG spherical tank in the oil workshop was idle at that time. After process transformation, it can be used to store the compressed air left over by the purification workshop, so as to provide instrument air for LPG bottling in the oil workshop since 1035. In this way, the piston air compressor does not need to be started during LPG bottling in the oil workshop, which can save power and water consumption, It also saves the maintenance cost of the piston air compressor and solves the problem of operator tension. At the same time, it can also ensure the normal operation of other devices. This achieves the purpose of instrument air system transformation: under the condition of ensuring normal production, the transformation of instrument air system can reduce energy consumption, save costs and reduce the workload of operators

feasibility analysis study

first, the on-site data were collected, and the purification workshop collected the loading and unloading downtime of a screw air compressor. The instrument air pressure of the purification cryogenic device is set in DCS as the shutdown pressure of the whole plant is 0.85mpa, with a delay of 40 minutes after the alarm. The screw air compressor is set to have a loading pressure of 0.95mpa and a unloading pressure of 1.12mpa, with a total operation of 3890 hours and a loading of 3529 hours. Based on this, it is calculated that the instrument air consumption of the purification workshop is 2.72 m3/min, with a margin of 0.28 m3/min, and a margin of 4.3 m3 of instrument air per day. At the same time, the oil workshop installed a flowmeter at the exhaust port of the air buffer tank to calculate the instrument air consumption for LPG bottling to be 1m3/min

secondly, the minimum pressure of instrument air for LPG bottling in the oil workshop and instrument air for boiler system in the water truck room is 0.4MPa. Based on the 5-hour bottling time per day, the required air volume per day is 300m3120 m3 LPG spherical tank. When the pressure is 0.8MPa, the stored air volume is 960m3, even if the purification screw air compressor no longer supplies instrument air to oil, It can also provide instrument air for 8 hours (= 960/2/300) for LPG bottling in oil workshop and boiler in water truck room × 5）。 After the analysis and research of the members of the project team, the instrument air system can be transformed, and the transformation scheme has been formulated, and the instrument air process transformation flow chart of the natural gas treatment station has been drawn, as shown in the figure

figure auxiliary materials for packaging of instrument air process transformation in natural gas treatment station: bottle cap glove machine, mold, gasket, handle, gasket nozzle, closure cap, packaging film manufacturing flow chart

implementation of process transformation scheme

in April 2004, the removal of circulating water flow and foundation of piston air compressor and old air compressor in purification workshop was completed

in April 2004, the annual inspection of No. 7 LPG spherical tank in the oil workshop was carried out, and then the construction of sand blasting, rust removal and internal anti-corrosion spraying in No. 7 LPG spherical tank was completed

in April 2004, the construction of the process flow transformation of the air pipeline from the air compressor room of the purification workshop to the No. 7 liquefied petroleum gas spherical tank and the bottling room was completed, the redundant pipelines of the No. 7 liquefied petroleum gas spherical tank were removed, the old pipelines that had been idle were connected and utilized, and the pressure stabilizing valve was installed on the wind pressure pipeline before entering the liquefied petroleum gas bottling room

in May 2004, the process transformation of No. 3 screw air compressor in the purification workshop supplying air to the oil workshop alone was completed. Under the guidance of the production and operation Department and the process technology station of the company, the filter required by the nitrogen generator of the cryogenic unit was selected, the manufacturer was selected and inquired. One DD filter and one PD filter were purchased and installed in May 2004 (the installation position is at the outlet of No. 3 air buffer tank)

according to the production plan of screw air compressor supplying gas to oil product No. 7 LPG spherical tank prepared by the project team, the trial operation of screw air compressor supplying gas to oil product No. 7 LPG spherical tank was carried out in three stages:

the first stage (May 10 ~ May 20, 2004): two screw air compressors were carried out to supply instrument air to oil product No. 7 LPG spherical tank and cryogenic device at the same time

in order to ensure the normal operation of the devices in the purification workshop, first, the purification workshop starts the No. 3 screw air compressor to supply air to the No. 7 LPG spherical tank separately and pressurize it to 0.8MPa, avoiding the shutdown of the devices in the purification workshop due to the leakage at a connection; After the instrument air pressure of the cryogenic device and the pressure of the No. 7 LPG spherical tank in the oil workshop reach equilibrium, two screw air compressors supply air to the purification device and the No. 7 LPG spherical tank at the same time. During this period, pay close attention to the purification instrument air pressure. Once a large amount of air leakage occurs at the No. 7 LPG spherical tank in the oil workshop, resulting in a significant reduction in the purified cryogenic instrument air pressure or a wind pressure alarm, Quickly close the air supply valve of No.7 liquefied petroleum gas spherical tank to ensure that the instrument wind pressure of hard parts can be produced by injection molding of cryogenic equipment. According to the field data, the loading and unloading time of two screw air compressors is frequent

the second stage (from May 21 to June 9, 2004): a screw air compressor (No. 3 screw air compressor) was used to supply air to oil alone (without filtration, drying and other treatment), and a screw air compressor (No. 1 screw air compressor) was used to supply instrument air to the purification cryogenic device

the oil workshop adjusted the pressure stabilizing valve, and the data collected on site showed that the instrument air for bottling of No. 7 LPG spherical tank could meet the needs of bottling. However, after several days of tracking and observation of the operation, there are sundries at the regulating valve of the instrument air for LPG bottling in the oil workshop, which indicates that the supply of lithium salt as the upstream material of lithium battery in the purification workshop is in short supply. The instrument air supplied is dirty without filtration, drying and other treatment

the third stage (June 10 to July 10, 2004): a screw air compressor was carried out to supply instrument air to the purification cryogenic device and the LPG spherical tank in the oil workshop at the same time

after the trial operation observation in the first and second stages, the analysis shows that a screw air compressor is started, and its outlet compressed air is supplied to the instruments of the purification device and the No. 7 liquefied petroleum spherical tank in the oil workshop and the boiler system in the water truck room after being dried by the oil remover and the heatless regeneration drying tower, which can fully meet the requirements of using instrument air at the same time. Therefore, from June 10, 2004, a screw air compressor has been used to supply instrument air to the boiler system instruments in the purification workshop, oil product workshop and water vapor workshop at the same time. The data collected on site shows that this trial operation scheme is completely feasible, which indicates that the transformation of the instrument air system of the full treatment station is successful, and the goal of using screw air compressor to supply instrument air has been achieved and put into operation

operation results

under normal circumstances, starting a screw air compressor can meet the instrument air of the whole station. After two years and six months of operation, it will not affect the normal and stable operation of the purification plant, but also meet the needs of the air for bottling in the oil workshop and the instrument air of the boiler system in the water truck room

it solves the problem of abundant air waste in the purification workshop, reduces the frequent startup and shutdown times of screw air compressor, and extends the service life of screw air compressor; Two screw air compressors are used to produce nitrogen, which meets the requirements of the nitrogen generator system. It solves the problem of wasting water and electricity during the operation of piston air compressors in purification workshop and oil workshop, and cancels the operators of air compressors in oil workshop; After the screw air compressor is used for instrument air supply in the whole station, the cost of maintaining the piston air compressor in the purification workshop and the oil workshop is saved. (end)