利用低溫精餾工藝分離空氣可制取氧氣、氮氣和氬氣。
空氣壓縮、冷卻和凈化
原料空氣經（空壓機配置有吸入空氣過濾器和中間/後冷卻器）多級離心式透平壓縮機壓縮，壓縮產生的熱量被中間冷卻器和後冷卻器帶走，而後在空氣冷卻塔中被污氮和冷凍水進一步冷卻到所需的溫度。采用除霧器來除去空氣中的水分，此外還設置瞭水分離器。
預冷後的空氣通過雙層床吸附器，由吸附器內充填的活性鋁和分子篩來清除空氣中的水分、二氧化碳和碳氫化合物。空氣穿過出床層後，進入濾塵器中去除空氣中可能含有的分子篩粉末。在濾塵器之後抽出一小股空氣，作為空分設備的機表空氣。
兩臺吸附器一臺使用，另一臺由來自冷箱的污氮進行再生。再生氣體（污氮）在再生加熱循環中由電加熱器加熱。
空氣離開凈化系統治後，乾凈的空氣被分成兩股。一股（5－6 kg/cm2 g的中壓空氣）進入冷箱內的主換熱器，另一股經多級離心空氣增壓機壓縮至高壓後送入冷箱。中壓空氣和高壓空氣經冷箱內的主換熱器與返流液氧換熱而被冷卻，制取產品氧氣，產品氮氣和污氮。
空氣精餾
空氣精餾在空分設備冷箱中進行。冷箱中設有主換熱器，氮加熱器，下塔，上塔，主冷凝器，氬冷凝器，氬塔，透平膨脹機，低溫泵等。
接近露點的中壓空氣（5－6 kg/cm2 g）進入下塔進行初次分離。
一部分高壓空氣從主換熱器的某一位置抽出，送入透平膨脹機中膨脹以獲得所需的冷量。膨脹後的空氣送入中壓塔（下塔的底部）。另一部分高壓空氣在與膨脹機聯軸的增壓機中進一步壓縮，提高瞭壓力，在主換熱器中使液氧蒸發，經膨脹閥膨脹後送入中壓塔（下塔的底部）。經冷箱內的低溫精餾，氧和氮從空氣中分離出來。為瞭制取氬氣，將上塔中部的氬餾分送入精氬塔中，去除其中的氮成分。把塔底部得到的純液氬送入儲罐。
所有的精餾塔都使用規整填料，以提高效率，減少能耗。
設備總體佈置時，控制室和冷箱要靠近壓縮機房，且通行方便
PROCESS DEscriptION
Oxygen, Nitrogen and Argon will be produced by air separation using cryogenic distillation process.
Air Compression, Cooling ＆ Purification
The atmospheric air will be compressed in a multistage centrifugal turbo air compressor (ATC) equipped with suction air filter and inter/ after coolers. The heat of compression will be rejected in the intercoolers, after coolers and further cooling upto desired temperature will be done in air water tower through waste nitrogen gas ＆ chilled water. A demister will be used to free water from the air stream. Moisture separator shall be provided.
The pre－cooled air will be passed through twin bed adsorber towers containing activated alumina and molecular sieve to remove moisture, carbon dioxide, as well as hydrocarbon impurities from air steam. After passing through the bed, the air passes through a dust filter that removes any molecular sieve fines that may be present. A small stream of air will be withdrawn downstream of the dust filter to meet the instrumentation air requirement of ASU.
One of the two vessels will be in operation while the other will be reactivated by waste Nitrogen coming form the cold box. The regeneration gas (waste Nitrogen) will be heated in electrical heater in the heating cycle of regeneration.
At the outlet of the air purification unit, the main stream of purified air will be divided into two streams. While the first stream of purified air (Medium pressure air at 5－6 kg/cm2 g) will enter the main exchanger in the cold box, the other stream of purified air will be further compressed to high pressure in a multistage centrifugal booster air compressor (BAC) and then it will enter the cold box. Both the medium MP (medium pressure)and HP air will be cooled down by heat exchange with the counter current liquid Oxygen to produce product gaseous Oxygen, product gaseous Nitrogen and waste gaseous Nitrogen steam in the main exchanger (inside the cold box).
Air Distillation
The air distillation takes place in the Air Separation Unit cold box consisting of main heat exchanger, nitrogen heaters, bottom column, top column, main condenser, argon condenser, argon columns, expansion turbine, cryogenic pumps etc.
The MP air (at 5－6 kg/cm2 g) which will be nearly to dew point, enters the bottom column which perform the first separation.
Part of the HP air will be used to produce required refrigeration by taking it out of the main exchanger at an appropriate point and expanding it in an expansion turbine. This expanded air will be fed to the MP column (at the bottom of the bottom distillation column). The other part of the HP air will be further compressed in the booster connected to the turbine to elevate the pressure level to vaporize liquid Oxygen in the main exchanger and then expanded through an expansion valve before it enters the MP column (i.e. at the bottom of the bottom distillation column). Oxygen and Nitrogen will be separated from the air by Cryogenic distillation from the cold box.
In order to produce Argon, the Argon rich stream of liquid from intermediate level of the top column will be fed into the pure Argon column wher it is stripped of its Nitrogen content. Pure liquid Argon product from the bottom of the column will be sent to the storage tank.
All distillation columns shall be with structured packing for high degree of efficiency with minimum energy consumption.
Layout of the Plant shall be such that control room and cold box are located near compressor building and easily approachable.
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