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Cracked Gas Drying (Ethylene)
Gas Treatment & Drying

Cracked Gas Drying (Ethylene)

Drying ethylene cracked gas using 3A molecular sieve to protect downstream low temperature distillation and polymerisation catalysts from water poisoning and coke laydown.

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The Challenge
Ethylene cracker downstream distillation and polymerisation catalysts are water sensitive. A 4A sieve would dry the gas but would also adsorb the cracked olefins, lose ethylene to the regeneration vent, and laydown coke inside the crystal during regeneration that progressively destroys the sieve.
Quick Answer

Cracked gas drying removes water from ethylene plant cracked gas using 3A molecular sieve in a TSA cycle. The 3 Å pore size excludes ethylene, propylene, and butadiene from the sieve, which prevents coke laydown inside the crystal during regeneration and gives 5 to 7 year media life versus 12 to 18 months for a 4A bed in the same service.

Cracked Gas Drying (Ethylene)

Why 4A Fails and 3A Succeeds in Olefin Service

Steam cracker cracked gas at the ethylene plant outlet carries ethylene, propylene, butadiene, hydrogen, methane, and saturation water. Downstream low temperature distillation (the demethaniser and the C2 splitter) demands dry gas; water freezes in the cold column and disables the plant. A 4A sieve would dry the gas, but the 4 Å pore admits the C2 and C3 olefins along with the water, the olefins adsorb, vent with regeneration purge (lost ethylene revenue), and laydown carbonaceous coke inside the crystal during the hot regeneration. Within 12 to 18 months the sieve loses water capacity and the cycle collapses.

3A Pore Size Excludes Olefins by Geometry

SorbiTech 3A molecular sieve has a 3 Å pore opening, narrow enough to admit water (2.6 Å kinetic diameter) and ammonia but to exclude ethylene (4.2 Å), propylene (4.5 Å), and butadiene (5.1 Å) at the pore mouth. The olefins never enter the crystal, so no coke laydown occurs during regeneration. The 3A bed holds its water capacity for 5 to 7 years in this duty, compared to 12 to 18 months for the wrong grade.

Cracked Gas Drying (Ethylene) process equipment

Bed Configuration and Cycle Design

Twin or triple adsorber vessels run TSA cycle at the cracked gas pressure (typically 35 to 40 barg). Adsorption half cycle is 8 to 16 hours; regeneration uses hot purge gas at 250 to 300 °C. The regeneration off gas returns to the front end of the plant where the released water is removed by the inlet chilling train. SorbiTech sizes the vessel and the cycle for the cracker design.

Delivery as Media or Complete Package

SorbiTech delivers cracked gas drying either as a SorbiTech 3A media supply contract for an existing dryer or as a complete twin tower TSA dehydration unit for a new plant. Sector coverage is petrochemicals and refining.

Selection Guidance

3A molecular sieve is the only correct grade. The 3 Å pore admits water alone; ethylene, propylene, and butadiene cannot enter the crystal, so no coke laydown occurs. Bed sized for the contracted regeneration interval, typically 8 to 16 hours adsorption.

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 Molecular Sieve 3a Adsorbent Molecular Sieve 3A Potassium form 3A zeolite, the size selective desiccant for streams that must not lose hydrocarbons to the bed. Pore Ø 3 Å
  2. 02 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 %
  3. 03 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 %
  4. 04 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 %
  5. 05 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
  6. 06 CMS 260l Adsorbent Carbon Molecular Sieve CMS 260L Affordable carbon molecular sieve. 1.2 to 1.8 mm pellets, sub 10 Angstrom pore, 95 to 99.9 percent N2 from compressed air at 7 to… Water Cap. Intolerant of liquid water, feed must reach ISO 8573 class 1.4.1 %
Equipment

Engineered Systems

  1. 01 Twin Tower TSA Gas Dehydration Unit Sorbitech Equipment Twin Tower TSA Gas Dehydration Unit Continuous duty temperature swing adsorption dehydration package for natural gas, engineered by SorbiTech to ASME VIII and PED, with an integrated regeneration heater and… Capacity 0.5–200 MMSCFD (custom engineered)
  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 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
  4. 04 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
  5. 05 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)
  6. 06 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
Industries

Industries Using This Application

  1. 01 SorbiTech Petrochemicals Refining Integrated Cracker Complex Distillation Columns Sector Petrochemicals & Refining Adsorbents and separation systems for feedstock drying, process gas conditioning, solvent recovery, and refinery effluent treatment.

Specify a Solution for This Application

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

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