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Cryogenic ASU Air Pre Purification
Gas Treatment & Drying

Cryogenic ASU Air Pre Purification

Pre purifying air feed to cryogenic air separation units by removing water, carbon dioxide, and trace hydrocarbons on a graded molecular sieve and activated alumina bed.

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The Challenge
Cryogenic ASU cold boxes operate at minus 180 °C in the main heat exchanger. Trace water freezes against the exchanger surface and progressively blocks gas passages; trace CO₂ does the same. Trace hydrocarbons accumulate in the liquid oxygen and pose an explosion risk. Without effective pre purification the operator faces a costly defrost campaign within…
Quick Answer

Cryogenic ASU air pre purification removes water, carbon dioxide, and trace hydrocarbons from the air feed to a cryogenic air separation unit. A graded bed of activated alumina at the inlet and 13X molecular sieve in the main layer delivers outlet water below 0.1 ppmv and outlet CO₂ below 1.0 ppmv on a TSA cycle regenerated with waste nitrogen.

Cryogenic ASU Air Pre Purification

Cold Box Contamination Is the Operator’s Biggest Risk

A cryogenic air separation unit produces oxygen, nitrogen, and argon by distilling liquefied air at minus 180 °C in the cold box. The main heat exchanger and the distillation column are exquisitely sensitive to feed gas contamination: trace water freezes against the exchanger and blocks gas passages; trace carbon dioxide does the same; trace hydrocarbons (acetylene from urban air, ethane from neighbouring industrial sites) accumulate in the liquid oxygen sump and pose an explosion risk. The SorbiTech pre purification package eliminates all three risks.

Graded Bed With Alumina Inlet and 13X Main Layer

The standard configuration is a graded bed. Activated alumina drying grade at the inlet handles the bulk water removal at near isothermal conditions; the alumina protects the more expensive 13X from hydrothermal damage during an upset and extends the campaign life. SorbiTech 13X molecular sieve in the main layer holds the residual water, the carbon dioxide, and the trace C2 and C3 hydrocarbons; outlet H₂O is below 0.1 ppmv and outlet CO₂ is below 1.0 ppmv at end of cycle.

Cryogenic ASU Air Pre Purification process equipment

TSA Cycle With Waste Nitrogen Regeneration

The cycle is temperature swing adsorption regenerated with dry waste nitrogen returned from the cold box. The waste nitrogen is heated to 180 to 250 °C, passed through the off line vessel in counter flow, and vented after recovering the captured water and carbon dioxide. The integration with the ASU heat recovery loop makes the parasitic energy of pre purification a small fraction of total plant energy.

Defrost Interval and Operator Economics

A correctly sized SorbiTech pre purification bed extends the campaign between defrosts from 1 to 3 years (poorly engineered front end) to 4 to 7 years (well engineered SorbiTech package). The reduction in defrost frequency is the single largest operating saving available to an ASU owner. Delivered as a complete cryogenic ASU pre purification package by SorbiTech. Sector coverage is industrial gas and air separation.

Selection Guidance

Graded bed: inlet layer of activated alumina drying grade for bulk water removal at isothermal conditions, main layer of 13X molecular sieve for residual water plus CO₂ plus trace hydrocarbons. TSA cycle regenerated with hot waste nitrogen from the cold box.

How SorbiTech Solves It

A Specified, Verified Solution

Define the duty

We capture your process conditions: flow, composition, pressure, temperature, and the target outlet specification.

Select media & configuration

Our engineers recommend the adsorbent grade and system type that meet the duty with margin.

Size & engineer

Bed sizing, vessel design, and cycle parameters are engineered to your case and documented for approval.

Commission & verify

We support loading, start up, and performance verification against the guarantee.

Recommended Products & Systems

Media

Adsorbents & Media

  1. 01 SorbiTech Activated Alumina Drying Grade Compressed Air Desiccant ISO 8573 Adsorbent Activated Alumina Drying Grade High capacity activated alumina for compressed air dryers, gas dehydration, and heatless desiccant systems. Water Cap. ≥ 20 %
  2. 02 Molecular Sieve 13x Adsorbent Molecular Sieve 13X Sodium form 13X zeolite for cryogenic air pre purification and combined drying and sweetening. Pore Ø 10 Å
  3. 03 CMS 450hp Adsorbent Carbon Molecular Sieve CMS 450HP Ultra high purity carbon molecular sieve. 99.99999 percent (7N) N2, selective O2 and CO2 capture, 1.0 to 1.6 mm pellets, minimal fines, deoxo polishing… Water Cap. Feed must reach ISO 8573 class 1.4.1, deoxo polishing recommended for 7N %
  4. 04 CMS 420kt Adsorbent Carbon Molecular Sieve CMS 420KT High efficiency carbon molecular sieve. Higher oxygen affinity under 7 to 12 barg, 1.2 to 1.8 mm pellets, Snowstorm Filling compatible, ASTM D4058 attrition… Water Cap. Feed must reach ISO 8573 class 1.4.1 %
  5. 05 CMS 350kt Adsorbent Carbon Molecular Sieve CMS 350KT Rapid adsorption carbon molecular sieve. 40 to 90 second cycle at 7 to 10 barg, up to 99.99 percent N2, 1.0 to 2.2 mm… Water Cap. Moisture at supply below 1.0 percent, feed must reach ISO 8573 class 1.4.1 %
  6. 06 Activated Alumina Aa 201 Adsorbent Activated Alumina Impregnated Promoter loaded activated alumina for hydrogen sulphide, chloride, and Claus tail gas guard duty. Form 3–5 mm spheres · 1.6–3.2 mm spheres
Equipment

Engineered Systems

  1. 01 SorbiTech Cryogenic ASU Pre Purification Package ASU Front End 13x Alumina TSA Towers Equipment Cryogenic ASU Pre Purification Package Front end TSA pre purification package for cryogenic air separation units removing water, carbon dioxide, and trace hydrocarbons before the cold box. Capacity 5,000–500,000 Nm³/h air
  2. 02 SorbiTech Transformer Breather Cartridge System Silica Gel Grid Utility Breather Equipment Transformer Breather Cartridge System Pre packaged stainless steel transformer breather cartridge with indicating silica gel for grid transformer moisture protection across the high voltage transmission and distribution network. Capacity 0.5–25 kVA transformer to 800 kV substation
  3. 03 SorbiTech Biogas Upgrading Unit Biomethane PSA Carbon Molecular Sieve Equipment Biogas Upgrading Unit PSA biogas upgrading unit using carbon molecular sieve to separate carbon dioxide from methane and deliver grid quality bio methane from anaerobic digester biogas… Capacity 50–2,000 Nm³/h raw biogas
  4. 04 SorbiTech Oxygen Vpsa Package Industrial Oxygen Vpsa Steel Mill Blast Furnace Equipment Oxygen VPSA Package On site vacuum pressure swing adsorption (VPSA) oxygen generation package delivering 90 to 95 percent oxygen for medical, aquaculture, ozone generation, and metals applications. Capacity 50–2,500 Nm³/h O₂ (90–95 % purity)
  5. 05 SorbiTech Heatless Desiccant Air Dryer Compressed Air ISO 8573 Twin Tower Dryer Equipment Heatless Desiccant Air Dryer Twin tower heatless desiccant compressed air dryer using activated alumina or silica gel for instrument and process air to pressure dew points below minus… Capacity 50–10,000 Nm³/h
  6. 06 SorbiTech Gas Sweetening Unit H2S CO2 Removal 13x Mol Sieve Equipment Gas Sweetening Unit Molecular sieve and impregnated carbon gas sweetening unit for H₂S, CO₂, and mercaptan removal from natural gas, refinery gas, and LPG streams. Capacity 0.5–500 MMSCFD
Industries

Industries Using This Application

  1. 01 SorbiTech Industrial Gas Air Separation ASU Cryogenic Distillation Cold Box Sector Industrial Gas & Air Separation Molecular sieves and carbon molecular sieve plus PSA/TSA systems for nitrogen and oxygen generation and cryogenic air separation pre purification.

Specify a Solution for This Application

Provide your process conditions and our team will recommend the grade, configuration, and sizing.

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