Start-up of argon production by full rectification
In the total distillation argon production, the crude argon Tower is just a distillation section without distillation section, and the argon Tower is a typical tower with distillation section and distillation section of intermediate feed, because the raw materials come from the air separation upper tower. Pass argon Tower cold and hot source are also from context Tower and back up the tower each other auxiliary fiber, can say with argon distillation air separation Tower distillation with comprehensive change and awareness.
Air separation distillation lower tower for extraction argon device, its task is to try to argon from pure liquid nitrogen washing down, so heavy key components becomes nitrogen and argon, and requires a higher reflux ratio, therefore, Air Liquide purity low some, is generally 33% O2, This can moderate reduction waste nitrogen including argon amount, to rich argon area down, improve argon fraction in including argon amount, on the other hand, bottom Air Liquide most used crude argon tower condensation evaporator, to maintain enough temperature difference, guarantee crude argon Tower have enough reflux ratio can be achieved anaerobic argon, this temperature difference may need Air Liquide composition. Undercooling of adjustment to keep, so lower tower back to flow and pure liquid nitrogen quantity proportion for good distribution. Thus it can be seen that argon rectification and high extraction rate of argon are firstly guaranteed from the lower tower, and argon rectification directly occurs in the lower tower.
The change of air separation rectification in the upper tower not only has its own requirement of air separation rectification, but also meets the requirement of crude argon tower. The requirement of air separation rectification itself is to improve the purity of oxygen and nitrogen, waste nitrogen empty loss reduction start, oxygen and argon extraction rate of increase, meet crude argon Tower need is to use packed tower to tower pressure reduce that not only reduce air pressure energy saving, and low pressure to relative volatility increase, oxygen argon distillation easier and to select good taking argon fraction pressure to ensure argon tower top condensing the required temperature difference, on the other hand, and make argon fraction argon content High, nitrogen content is low. Argon rectification actually starts from the top Tower, otherwise oxygen-free argon rectification can not achieve the best extraction rate. Note that the entire main tower load cannot too low, otherwise coarse argon Tower conditions easy fluctuation, while argon distillate component not too big, so as not to affect the main tower.
The start-up time of total rectification argon production is relatively long, about 40 h, mainly because the boiling points of oxygen and argon in the crude argon rectification system are relatively close (oxygen: 88.87 K, nitrogen: 77.09 K, argon: 87.02 K), and during the creation process must also exclude nitrogen interference, full distillation argon system start two stages.
The first stage: crude argon system start
Crude argon Tower operation must have certain conditions, if in crude argon tower not pre-cooling good, main tower instability or cold quantity under inadequate input, the result is that the resistance of the crude argon tower can't go up, and the working condition of the main tower is unstable. In the main tower main condenser after operation, can open a little crude argon condenser backflow V702 (previously should V701 Will Air Liquide import crude argon Ⅱ in the condenser),, air Liquide Hengtong valve V704 according to the valve rear regulate the temperature of the keep in TE for-185.1 ℃, meanwhile, side adjusting main tower oxygen, nitrogen distillation conditions, looking at crude argon Ⅱ at the bottom of the liquid level. When the liquid level reaches 30%, the crude liquid argon pump can be precooled. When the liquid level exceeds 60%, the crude liquid argon pump can be started. Pay attention to opening all the bypass valve V703 at the beginning, liquid all from bypass backflow back to crude argon Tower Ⅱ, otherwise a large amount of liquid into crude argon Tower Ⅰ back to main tower, will inevitably cause the tower conditions volatility, and then gradually hallway V703 bypass valve, while slowly open V713 to crude argon Tower I conveying liquid, and turn up the V702 to put into operation crude argon Tower Ⅱ condenser, open crude argon drain valve V712 emissions air, depending on the situation gradually turn up V702, will argon fraction and crude argon vent traffic adjustment to normal flow of 2/3, (argon fraction: 7500 m3/H, crude argon vent 221.3 m3/H), at the same time, the bypass valve of crude liquid argon pump is put into operation automatically, and the automatic setting of liquid level can slowly decrease to about 60%. In the precooling and starting of crude liquid argon pump, first of all, the precooling of the pump must be thorough for about 40 minutes, and it can be started only when the front and back blow-off valves of the pump can blow out the liquid continuously, start when full open backflow, slightly open export chui chu fa, start normal after adjustment V713 valve and hallway chui chu fa, then according to the crude argon Tower Ⅱ bottom liquid height and pump rear pressure corresponding adjustment submit valve and backflow, pump normal operation, both avoid start due exit pressure high caused relief valve take-off, and ensure crude argon Tower Ⅱ bottom level stability.
Crude argon Condenser Heat load depends on argon fraction purity, also depends on Air Liquide purity and liquid air volume size, is based on coarse argon Tower Ⅱ resistance PdI-702 indicator, by adjusting the crude argon Tower Ⅱ condenser Air Liquide liquid level to achieve, it will affect crude argon yield and purity, turn up the V701 Air Liquide liquid level lifting, Condenser Heat load increased, whereas decreased, therefore, guarantee argon fraction components meet the design value, and stable conditions appropriate increase condensing heat load, conducive to crude argon purity improved.
In the whole crude argon system in the startup of, must make argon fraction oxygen content control in 93-95% (required for 90-92%), mainly avoid excessive nitrogen, because liquid argon severe relatively liquid oxygen liquid nitrogen large (liquid oxygen: 1.24, liquid argon 1.41, liquid nitrogen: 0.81 ), the increase of argon content in crude argon tower is positively proportional to the increase of outlet pressure of liquid argon pump, so the argon content in the column fraction can be judged by observing the outlet pressure of crude argon pump.
In guarantee argon fraction oxygen content 93-95% (AI-701, create oxygen and argon distillation conditions of process by observing crude argon Tower I exit the oxygen content of AIA-702 changes to regulate secondary crude argon Tower exit the displacement to control and implementation, just started, no argon gathered, and with a lot of nitrogen exists, since nitrogen is the boiling point of than argon low boiling point more, in crude argon Tower first the vaporization of nitrogen, necessarily so hinder oxygen and argon distillation conditions of formation, only through crude argon drain valve V712 a lot of drain nitrogen while slowly gathered argon, with nitrogen emissions, the reduction of nitrogen content in the crude argon Tower, the gradual increase of argon content, and participation in oxygen rectification, this process generally needs more than 24 hours, with the accumulation of argon and the removal of nitrogen, can see crude argon I top oxygen content AIA-702 (reference AIA-705) in slowly declining, when to about 20% when, showed that crude argon Tazhong gathered have more argon, can also from crude argon Tower outlet pressure rise and judgment outlet, the can reduce secondary crude argon tower the displacement, hallway small V712 valve, Drain flow adjustable to the original 1/3, although nitrogen must be discharged, the content of argon in the discharged gas is relatively high and cannot be discharged in vain, But it should be gathered in the crude argon tower, so as to improve the speed of subaggregation and shorten the start-up time of the crude argon system.
When the oxygen content (relative to AI-705) on the top of the first-class crude argon Tower AI-702 to decrease to 5%, it indicates that the content of argon in the crude argon tower is close to its normal value. The one hand turn up the secondary crude argon tower the displacement that turn up V712, continue to exclude crude argon Tower nitrogen content, and keep main tower and crude argon Tower distillation conditions of balance, because once crude argon Tazhong argon content more than its normal value AE-716, too much argon will pass crude argon Tower I return the tower, is bound to cause oxygen purity falling and the tower by distillate conditions deterioration; on the other hand, slowly turn up crude argon column condenser backflow V702 to increase argon fraction of the flow to normal, crude argon displacement also enlargement to normal, the argon fraction the purity of appropriate to reduce, but must ensure that its oxygen content shall be not less than 91%, to prevent excessive nitrogen into crude argon tower.
When level crude argon tower at the top of the oxygen drop stop normal (AIA-702) at 2%, showed that crude argon tower start basic end, can be secondary crude argon Tower outlet AIAS-704 of trace oxygen analyzer put into operation, to detect coarse argon body of content, the whole process see figure.
Crude argon I top oxygen content change crude argon tower top crude argon emissions crude argon pump exit pressure change
The second stage: fine argon system start
Compared with the start-up of the crude argon Tower, the start-up of the distillation tower is much simpler, and it only establishes the simple argon nitrogen rectifying working condition of removing trace nitrogen, in crude argon Tower Ⅱ export coarse argon oxygen content to 100ppm left and right when you are ready to fine argon system cold and hot source., open V711, V710. When AIAS-704 ≤ 10ppmO2, slowly turn up V705 will crude argon import crude argon liquefier in, while gradually turn up V711, V710, turn up the V710, make PI-703 Control in 70-90KPa, to prevent liquid argon curing (hereafter make appears supercooling, liquid argon gelatinized, continue cooling turn snow-shaped, pure argon column resistance increases, residual gas emission reduction until zero, Argon flow gradually decrease ), stay liquefier nitrogen side PICA-703 to 95KPa vote automatic, adjustment crude argon liquefier liquid nitrogen imported control valve V711, prompted liquefier K704 work, stay PIC-702 reaches a certain value (17.9KPa) vote automatic.
Quilt liquefaction of crude argon Inlet and pure argon Tower, and turn up the V706 introduced liquid nitrogen as cold source, turn up the V715 evaporation liquid nitrogen returns, cold source establish certain level, heat source establish certain gas flow, ajar V714, pair pure argon column cooling, gathered at the bottom of the liquid, adjustment pure argon column pressure to normal (the pressure control of coarse argon system important ), formation preliminary small amount of argon nitrogen distillation conditions, when crude argon in the micro content to set 2 ppmo2Condition value, turn up the V705 valve, total import crude argon, also close crude argon exhaust valve, and then adjust the fine argon distillation, in evaporator LIC-704 liquid level reached 10% after all emissions liquid, open V757 to ensure argon purity.
When evaporator liquid level LIC704 rose to rating (1000-1350) when, turn up the V707, to Tanei resistance PdI-703 proximity design value (~ 7.5KPa), Tanei pressure stability after V707 vote automatic, if nitrogen content excessive, can turn up V707 enlargement fine argon system evaporator heat source nitrogen amount, to pure argon column bottom nitrogen try to evaporation, and then through the top V751 drain, meanwhile, emissions non-qualified liquid argon (open V757 valve ). When pure argon nitrogen in the metals content meet the requirements, and level up to 1200mm when open V708, to PV702 liquid argon balancer, open V717 to liquid nitrogen tank (V716 open greatly pure argon column bottom increase steam, further improve argon content ).
When PICAS-704 more than normal, LIC-703 low, turn up the V706, liquid nitrogen level LIC-703 rise, increase condenser back to flow (or ajar V714), recovery Tower pressure, turn up the V751 can be low liquid argon nitrogen content in.
